2ちゃんねるの管理人である西村博之氏のインタビュー記事「Meet Hiroyuki Nishimura, the Bad Boy of the Japanese Internet」がWIREDに掲載されている。記事は2ちゃんねるの成り立ちや問題点、ニコニコ動画の紹介や西村氏の考え方を扱った内容だが、本家/.では2ちゃんねるがユーザ登録やハンドル名、モデレーションが無い上、炎上や荒しをフィルタする仕組みもなく、Web2.0からかけ離れた形態であるにも関わらず毎月5億ページビューを稼いでいる点が取り上げられ、話題を呼んでいる。中には掲示板の内容をモデレーションできるサードパーティを仲介する提案や、携帯電話からのインターネット閲覧が多い日本ではWeb1.0の形態のほうがより好まれるという指摘、さらに携帯電話での日本語入力はどのように行われているのかといったコメントが寄せられている。
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A distance between Betelgeuse and our solar system was considerably changed from about 430 light years to about 640 light years in 2008 .
※ By the way, a national order called Ming (明) was started by Chu Yuan-chang ( 1328 〜 1398 ) in China ( the eastern part of the Eu-r-asian continent to which the head of a large-scale snake called 'Fer-de-lance' is oriented ) 640 years before from 2008 namely in 1368 .
>>391
Chu Yuan-chang had two extremely different phases, one is a feature as a hero who pushed up oneself from the worst situation, another is a feature as an insane person who was driven by strong suspicions and persecution complexes and successively spoiled & broke many people including mates with which joys and sorrows were shared for many years.
Accordingly, his character is regarded a typical character having affinity with schizophrenia, his personality is categorized into a remarkable ambivalent pattern in psychology.
In the sense, he is very similar to cases of Robespierre, Stalin and the Pol Pot faction, etc.
一
This is a typical case of 'symmetry-detection or grouping' .
Namely, the same as psychic photographs, a fact that a spilled stain of ink often looks like an order-ed pattern is applied to Rorschach tests.
・ Liquid Crystal Materials
A common way to categorize the aggregate states of matter is by translational symmetry into ‘crystalline’ and ‘amorphous’ states.
In crystals translations by a discrete set of lattice vectors transform the solid into itself.
In amorphous materials ( gases, liquids and glasses ) this symmetry is not present.
>>399
The fact that there are three space co-ordinates and in case of molecules without rotational symmetry three angles of orientation makes it possible that states of matter exists where the discrete translational symmetry is only present in some of these co-ordinates in the case of the smectic phase in one space co-ordinate and two angles.
一
>>400
Such states are called ‘liquid crystalline’ because they show properties of both liquids and crystals.
In most of them the molecules are directionally ordered.
Therefore, they show crystal-like anisotropy of susceptibilities. Meanwhile, they don’t form rigid bodies but appear mechanically as viscous liquids.
>>402
The physical properties of liquid crystals are largerly determined by their molecular anisotropy. The molecules are rod- or disk-like shaped, similar to ellipsoids with one axis strongly differing from the other two. This anisotropy causes a tendency of the molecules to arrange in parallel which is often enhanced by electrical dipolar interactions. In the most simple approximation of the molecules as uniaxial ellipsoids the average orientation is described by a vector ｎ called ‘director’ . The degree of orientation is expressed by the order-parameter,
S ＝ 1/2 （3・cos＾2θ’ - 1）with cos＾2θ’
＝ 1/2 0∫π p( θ ) cos＾2( θ ) sin ( θ ) dθ
( 1 )
where θ is the angle between the molecule axes and the director and p ( θ ) its distribution. In addition to the directional ordering one often finds positional order. This ordering concerns one or more co-ordinate in space, i.e. the molecules are arranged in layers, columns or macrocrystalline structures.
>>403
The type of symmetry characterizing the liquid crystalline order is the ( nowadays used ) basic classification property. The lowest symmetry is that of the nematic ( N ) phase. In this phase a ( long-range ) order exists only for the orientation of the molecules. Their positions only show a local order similar to that of liquids but are uncorrelated over large distances.
一
>>404
The next higher symmetry is that of smectic ( Sm ) liquid crystals in which also one spatial co-ordinate is ordered. This means that the molecules arrange in layers. The smectic class of liquid crystals is divided into many subclasses SmA-SmO which differ in the order of molecules within the layers. Especially, it’s not necessary that the director is identical to the layer normal. The molecules may be tilted resulting in the SmC phase. Higher spatial symmetries are e.g. columnar ( Col ) or cubic ( Cub ). But those materials are not technologically important ( about 2003 ).
>>406
An important variation of these phases results from the use of chiral molecules. These are molecules which are not mirror symmetrical. They are intrinsically optically active. Such molecules build chiral phases, i.e. phases in which the arrangement of molecules is not identical to its mirror image.
Due to its widespread occurrence it was considered a class of its own in the old Friedel nomenclature, the cholesteric phase.
※ The director rotates if one proceeds in one spatial direction perpendicular to the molecules.
By this rotation a helicity is defined which corresponds to the chirality of the molecule.
If one would build the same structure from mirrored molecules the director would spiral in the opposite way.
>>407
Another chiral phase of technological interest is the SmC’ . Each of the layers is identical to a SmC layer but the directors of different layers are not the same. Rather the director rotates around the layer normal when proceeding from one to the next layer.
The spiral of directors again defines a helicity of the phase.
>>408
Sometimes different phases may be observed for the same material. In the case of the materials discussed here the phase state depends on the temperature.
For this reason they are called ‘thermotropic’ liquid crystals. As one would expect from the principles of thermodynamics the sequence of phases goes from most ordered to least ordered when raising the temperature ; crystalline → smectic ( H → A ) → nematic → isotropic liquid.
It has been often pointed out since 6 〜 7 years ago that the moon is a hologram.
By the way, both liquid crystalline phase and plasma phase are called the fourth state of matter.
>>409
The anisotropy of the molecules combined with their ordering causes an anisotropy of many macroscopic physical properties, e.g. index of refraction ( birefringence ), dielectric constant, and elastic constants.
All these observable reflect in their temperature dependence the underlying order parameter which in the nematic phase usually can be described by
S ( T ) ＝ （ 1−yT/Tni ）＾b
( 2 )
>>411
Where Tni is the nematic isotropic phase transition temperature and y and b are empirical parameters.
This means that in the liquid crystalline phase the order decreases when the temperature is raised causing the anisotropy to reduce.
At the phase transition it still has a final value before it vanishes upon entering the liquid isotropic phase.
This temperature dependence has consequences for technical applications : often the desired properties of a liquid crystal cell degrade when the temperature is raised.
一
>>412
The different indices of refraction for the ordinary beam and the extra-ordinary beam. The behavior of the indices of refraction can be calculated using the Lorentz-Lorenz equation,
n i＾2 − 1 / n＾−2 ＋ 2 ＝ N / 3 ε0 ・〈 α ii 〉
( 3 )
>>413
Where ni is the index of refraction for a specific polarization, with subscript 1 ( or e )) for the extra-ordinary beam and 2 or 3 ( or o ) for the ordinary beam.
n’ is its directional average. 〈 α ii 〉are the averaged molecular anisotropic polarizabilities.
N is the number of molecules per unit volume.
>>415
Here, we assume that the minor axes 2 and 3 of the molecule are randomly distributed.
If we compare the last expression with the definition of the order-parameter, equation ( 1 ), we obtain
〈 α11 〉
＝ 2S ＋ 1 / 3・α11 ＋ 1 − S / 3・α22 ＋ 1 − S / 3・α33
＝ α’ ＋ 2/3 ｛ α11 − 1/2 ( α22 ＋ α33 )｝S( T )
( 5 )
with α’ ＝ ( α11 ＋ α22 ＋ α33 ) / 3 being the average polarizability.
>>416
In a similar way one obtains,
〈α22〉
＝ α’ − 1/3 ｛ α11 − 1/2 ( α22 ＋ α33 ) ｝S ( T )
( 6 )
From formula ( 5 ) and ( 6 ) it becomes clear that the bi-refringence expressed by Δn ＝ n1 − n2 is a monotonous function of the order-parameter.
It decreases with temperature and vanishes in the liquid isotropic phase.
>>418
The importance of bi-refringence for the technical application is immediately clear because it allows to control light transmission through an liquid crystal cell via the change of polarization.
The second important physical quantity is the dielectric anisotropy which is related to the possibility to orient liquid crystal molecules by an external field.
In a nematic phase it’s usually defined by the difference of dielectric constants parallel and perpendicular to the liquid crystal director ;
ε‖ − ε⊥
＝ NFh ｛Δα ＋ Pe＾2 F / 2 kB T ( 3 cos ＾2 β − 1 ) ｝S ( T )
( 7 )
>>419
In the large parenthesis one can recognize two terms ; Δα ＝ α11 − ( α22 ＋ α33 ) / 2 describes the influence of the anisotropic polarizability on the dielectric constants.
Here, F and h are reaction field and cavity field factor which account for the field dependent interaction of a molecule with its environment.
>>420
In the large parenthesis one can recognize two terms : Δα ＝ α11 − ( α22 ＋ α33 ) / 2 describes the influence of the anisotropic polarizability on the dielectric constants.
The second term where Pe is the electric dipole moment of the molecule and β its angle with the molecule’s long axis describes the effect of rotation of the molecules by imposing an external electrical field.
Again the total value is proportional to the order-parameter.
>>422
・ Chemistry of Liquid Crystals
The liquid crystal molecules which form the technologically important phases mentioned in the last section are invariably rod-shaped, I.e. their extension in one spatial direction is significantly larger than in the other two.
They usually consist of a central part connected to two ( possibly substituted ) hydro-carbon chains.
The central part is a concatenation of ring-shaped groups ; these can by aliphatic, aromatic, or hetero-cyclic.
>>423
The rings are either linked directly or by short functional groups as either or ester bridges.
The cyclic groups may also have substituents, mostly halogen atoms.
The hydrocarbon chain can differ in length and can be either saturated or unsaturated.
They are if at all substituted in the end position by halogens in order to increase the dipole moment.
It’s clear that there is a vast number of possible chemical structures for liquid crystal molecules even under these ‘construction rules’ . This allows to vary the physical properties of liquid crystals over a wide range.
>>424
The difference in polarizability Δα is mostly a consequence of the presence of conjugated electron systems, i.e. alternating sequences of single and double bonds.
In the topmost structure the central part consists only of cyclohexane rings, there is no aromatic character.
>>425
Therefore, the polarizability is low arising from displacements of electrons in the restriction of σ bonds only.
The lowest molecule in contrast has a π electron system which extends over three benzene rings and the connecting triple bond.
In this structure, the electrons can move over a much larger distance if an electrical field is applied. Therefore, the polarizability is about six times higher.
>>426
Orientation of polar molecules in an external field leads to an additional contribution to the dielectric constant.
The effect can be enhanced by substitution of an aromatic group. The electro-negativity shifts the electron distribution in the π electron system creating a large permanent dipole moment.
The dielectric constant of this liquid crystal in parallel direction is larger than that of water.
>>428
Although the effect of the anisotropy of the dielectric constant expressed by eq ( 7 ) 〈 >>419 〉is similar , the variations of chemical structure on the physical properties of liquid crystals have different effects for application.
Increasing the number of conjugated double bonds enhances the electronic polarizability and thus only affects the optical properties ( bi-refringence ).
Increase of the dipole moment by introduction of polar groups enhances the polarizability by re-orientation of the molecules. The re-orientation process is too slow to play a role at optical frequencies.
But it’s desired to control the molecular orientation by an electrical field which is the method by which most of the liquid crystal displays are addressed.
>>429
Quantum mechanical simulation has become an important technique for the design of such molecules.
By this method it’s possible to calculate dipole moment and polarizabilities with high precision.
By using formulae as ( 3 ) 〜 ( 7 ) 〈 >>413>>415>>416>>417>>419 〉, the macroscopic properties can be predicted without need to synthesize the molecules.
Besides, the electrical properties several other features are of importance for application.
For example, the elastic constants determine the dynamical behavior of a cell, i.e. the speed of its response to a change of the electrical field.
>>430
Finally, it’s important to have the properties stable over a large temperature range.
This requires a large nematic phase region. One way to achieve this is as before the modification of the molecular structure.
Here the length of the hydrocarbon chains is an important factor. Because the phase behavior ( as well as the viscosity mentioned above ) is a multi-particle property it can currently not be predicted by computer simulation.
In lengthy experiment series homologues have to be synthesized and compared that respect.
>>431
Another way to obtain a large nematic range is by mixing different liquid crystal species.
Similar to the eutectic range in the phase diagram of an alloy it’s thus possible to have a lower crystal-nematic phase transition than in s pure liquid crystal.
>>432
Another reason why mixtures are preferred in technical applications is that by varying the composition it’s easy to continuously control the physical parameters.
By mixing a polar liquid crystal with a less polar one, any desired anisotropy of the dielectric constant in between the Δε values of the pure components can be obtained.
By using a larger number of components multiple properties can be controlled simultaneously.
For this purpose, the chemical industry provides so-called ‘multi-bottle kits’ of miscible liquid crystals.
>>433
・ Twisted Nematic Cell
Next, we explain about a kind of liquid crystal having a similar structure to that of the chiral nematic ( cholesteric ) phase.
The main difference is that the structure is not self-assembled but maintained by minute forces exerted by the upper and lower cell walls.
The cell walls are coated with polyimide which is ‘brushed’ or ‘buffed’ namely rubbed along one direction with a piece of fabric.
>>436
By this rubbing process, the polymer chains are microscopically aligned.
Liquid crystal molecules close to these surface order parallel to the polymer molecules.
By having the rubbing direction of the top and bottom plate perpendicular to each other, one can force the liquid crystal into a twisted structure.
一
>>437
The cell walls are made from glass so that light will be transmitted through the cell.
If this light is initially polarized parallel to the molecular director, the polarization will be turned with the twist of the structure.
From the parallel change of molecule and polarization direction, this is called the ‘waveguide mode’ of a liquid crystal cell.
The emerging light will be polarized at an angle of about 90° with respect to the incoming light.
>>438
Therefore, if we put the cell between two parallel polarizers, no light will be transmitted because at the second polarizer the light will just have the wrong polarization to be transmitted.
Conversely, if the polarizers are crossed, light will be transmitted through the arrangement which otherwise would be blocked by the second polarizer.
一
>>439
The point of this arrangement is now that one can switch off the polarization-rotation by applying an electric field.
This is done by coating the glass walls of the cell with indium-tin-oxide ( ITO ). ITO is an electrically conducting compound which in thin layers is nearly transparent.
If a voltage is applied to these electrodes, there will be a torque on the liquid crystal molecules trying to orient them parallel to the field, i.e. perpendicular to the cell walls.
一
>>440
Although the molecules close to the wall will retain their parallel order the majority of the molecules in the center will turn parallel to the light path.
This means that a large part of the polarization-rotation will vanish and the cell will go to the opposite transmission state, i.e. black for an NW cell, clear for an NB cell.
一
>>441
In order to calculate the change of polarization of light going through a liquid crystal cell exactly, it’s necessary to take into account the birefringence which changes the incoming linear polarized light into elliptically polarized.
Elliptically polarized light can in general be described by the time-dependent field in the direction parallel to the long axis of the molecule and perpendicular to it :
Ex’ ( z ) ＝ A ( z ) sin ωt ＋ B ( z ) cos ωt
Ey’ ( z ) ＝ C ( z ) sin ωt ＋ D ( z ) cos ωt
( 8 )
>>443
The twisted nematic liquid crystal is now considered as composed of infinitesimal layers of thickness dz .
If the total twist of the structure is ξ on a thickness d each layer causes a trivial rotation of dξ ＝ − ( ξ / d ) dz in the molecules’ co-ordinate system.
In addition, the bi-refringence causes a phase shift dψ ＝ ( 2πΔn / λ ) dz for a wavelength λ .
Expanding the trigonometric functions of ( 8 ) and those arising from the rotation by dξ , we obtain a set of linear differential equations for the amplitude factors A − D :
dA / dz ＝ − ξ / d・C dB / dz ＝ − ξ / d・D
dC / dz ＝ ξ / d・A − 2π Δn / λ・D
dD / dz ＝ ξ / d・B ＋ 2π Δn / λ・C
( 9 )
>>444
These differential equations can be combined into one fourth order differential equation for each amplitude, e.g. for A :
d＾4A / dz＾4 ＋ ［ 2ξ＾2 / d＾2 ＋ 4π＾2・Δn＾2 / λ＾2 ］・d＾2A / dz＾2 ＋ ξ＾4 / d＾4 ＝ 0
( 10 )
As boundary conditions one has the four amplitudes upon entry into the cell at z ＝ 0 .
In the case of the TN cell, the light enters polarized parallel to the molecules : A ( 0 ) ＝ 1 , B ( 0 ) ＝ C ( 0 ) ＝ D ( 0 ) ＝ 0 .
>>445
The respective solutions for the z dependence of the amplitudes are ;
A ＝ q＾2 / 1+q＾2 cos ξz / qd ＋ 1 / 1+q＾2 cos qξz / d
B ＝ −q＾2 / 1+q＾2 sin ξz / qd ＋ 1 / 1+q＾2 sin qξz / d
C ＝ q / 1+q＾2 sin ξz / qd ＋ q / 1+q＾2 sin qξz / d
D ＝ q / 1+q＾2 cos ξz / qd − q / 1+q＾2 cos qξz / d
( 11 )
with
q ＝ √ 1 ＋ 2u＾2 ＋ 2u√1+u＾2 and u ＝ πdΔn / θλ
( 12 )
>>446
From eq ( 11 ), one can see that in general, the polarization will be elliptic when the light leaves the cell at z ＝ d .
Only in the case of very thick cells, λ ≪ dΔn , the hand-waving argument that the polarization of the light stays parallel to the molecule axis is approximately correct.
>>447
This is usually called the Mauguin limit. But also for special values dΔn / λ ＝ √ m＾2 − ( ξ / π )＾2 with integer m the polarization will be elliptic only within the cell but linear ( and perpendicular to the initial polarization ) upon exit.
For economic reasons, cells are normally not built in the Mauguin limit but at one of the transmission minima.
>>448
The problem is reduced for normally-white cells because then it just means a slight nuance of white which is more tolerable.
In addition, the normally-white state offers theoretically unlimited contrast.
High extinctions can be achieved by raising the voltage arbitrarily.
一
>>449
Unfortunately, these advantages of the normally-white state are more than compensated by its smaller viewing angle.
The range of viewing angles is a common weak point of liquid crystal displays.
The problem arises from the different action of the bi-refringence on rays with oblique incidence.
一
>>450
The calculation done above is only valid if the light direction is vertical to the molecules. This is not true for a beam which is tilted with respect to the cell normal.
Therefore, the contrast may be lower or even inverted when a display is observed under an angle.
一
>>451
§ Addressing of Liquid Crystal Displays
For simple devices, each segment is represented by an individual electrode on one cell wall and the other cell wall is completely coated by ITO ( Indium-Tin-Oxide ).
This is called ‘static’ addressing because in principle, DC voltages would be sufficient to control the display. For static addressing, the number of lines contracting the segments and the number of drivers controlling the voltages are equal to the number of segments.
>>452
§. 1 Dynamic Addressing
It’s evident that for a laptop PC display with 768 × 1024 〜 800,000 pixels, it’s impossible to realize such a number of leads and drivers.
Clearly, the pixels have to be addressed as a matrix through rows and columns. Front and back wall bear electrodes formed as stripes whose intersections define the pixels.
>>453
This kind of adressing is only possible because the voltage-transmission characteristics shows a threshold voltage Vth below which the cell stays in the off-state.
If we want to address a single pixel we can put a voltage −V to the row electrode and +V to the column.
>>455
Then, only at the part of the cell in between the selected row and column electrode, a voltage 2V occurs.
For all pixels where only one electrode is activated, the voltage is V , for the rest of the panel, it’s zero.
If we chose V ＜ Vth ＜ 2V , only one panel will go into the on state.
>>456
In order to create an arbitrary pattern of on-states, it’s now necessary to scan the display row by row similar to a cathode ray tube.
That is why this form of matrix addressing is usually called ‘dynamic’ .
All dynamic addressing schemes rely on the fact that only the root-mean-square voltage V rms ＝ √V＾2’ determines the state of the cell, if the frequency is sufficiently high.
>>457
It can be seen that during the first three time intervals, the three rows are addressed one after the other by a voltage +2V .
When a row is selected, the desired on-state pixels get a voltage −V on the column electrode, those which should be off a voltage +V .
In this way only for the selected pixels, a voltage difference of 2V − (−V) ＝ 3V lies across the cell.
For all other pixels, it’s |0 − (+V)| ＝ |0 − (−V)| ＝ |2V − (+V)| ＝ V .
>>458
Because a pixel is selected only during one time interval of three, the rms voltage on the once-selected pixel is √（V＾2 + V＾2 + (3V)＾2）/ 3 ＝ √11 / 3V ＝ 1.91・V .
For all pixels which are never selected, the rms voltage is simply V . After the first three time intervals, the sequence is repeated invertedly to ensure a zero DC component and then periodically continued.
>>459
So, by using the 3:1 scheme, it’s possible to put a.r.m.s (≒ arms) voltage which is 91% higher than the ‘off’ voltage onto an optional pattern of selected pixels for a three row panel.
It’s easy to see that for a panel having n rows, the ‘selected’ voltage Vs decreases with n as
Vs ＝ √1 + 8 / n ・V
( 13 )
>>460
Therefore, the relative voltage difference ΔV / V becomes smaller if the number of rows increases.
This makes dynamic addressing finally impossible because the effected contrast becomes too small.
A significant improvement above the 3:1 scheme was introduced by Alt & Pleshko.
They simply suggested to change the levels of the row & column voltages to values which optimize ΔV / V :
2V → n＾3/4 / √2( √n−1 ) ・V ( 14 )
>>461
These values now depend on the row number n ; only for n = 4 , this scheme is identical to the 3:1 .
But, there are still only three distinguished voltages to be set by the driver circuit, so it’s electronically easy to realize.
By this simple modification leaving the principle of row-wise addressing unchanged, the select voltage can be raised to
Vs ＝ √ √n+1 / √n−1 ・V
( 16 )
>>462
Interestingly, it could be proven that the absolute limit for matrix addressing schemes is not much higher than what can be achieved by the Alt-Pleshko scheme. That is why ( 16 ) is still called the ‘iron law’ of dynamic addressing.
>>463
The select and unselect voltages can not be placed far enough to produce a sufficient constant.
To make it worse, the characteristics depend on the viewing angle and the operation temperature.
一
>>464
Therefore, an optimal setting of V and Vs may be bad for oblique observation or at different ambient temperature.
This usually makes a ‘contrast control knob’ necessary with which the user manually adjusts the voltages to the optimum.
Here, the situation can be improved substantially only by the use of super-twisted nematic liquid crystals or an ‘active matrix’ which will be described below.
>>465
Another problem related to dynamic addressing results from the response time of the liquid crystal.
If the liquid crystal reacts too fast scanning, the rows will become visible as a flicker.
If it’s too slow the display of motions ( for example, a mouse cursor dragged across the screen ) will smear out.
This problem can nowadays be solved by multi-line addressing ( in 2003 ).
>>466
The dynamic addressing schemes shown here can be generalized in a way that the row voltages activate several rows at the same time.
Then, the column voltages don’t depend on the intended pattern in a single row but a linear combination of several rows.
The calculations of the column voltages are more complicated but can be done by state-of-the-art display controller circuits.
>>467
Up to here, only addressing schemes were discussed which generate a pattern of black & white pixels.
Of course, for video or computer applications also grey levels are necessary. Different principles have been exploited to achieve this ;
The most straightforward way is to use analog voltages instead of the finite number of voltage levels described before.
一
>>468
Because the voltage differences between ‘black’ and ‘white’ are already very low in highly multiplexed displays, the accuracy of voltage generation becomes a problem here.
Also a deeper analysis shows that if one uses interpolated voltages between the positive and negative value of ( 15 ), the voltages on the non-select pixels are not equal among each other.
>>469
This means that addressing one pixel causes others in the same row or column to change their grey levels.
This phenomenon is called ‘cross-talk’ and is one of the major problems of liquid crystal displays.
>>470
This can be avoided by switching between the select and unselect voltage during the time interval a pixel is addressed.
In principle, this resolves also the problem to generate exact-valued analog voltages. Meanwhile, pulses can be very short for ‘light grey’ or ‘dark grey’ situations.
This means that the limiting frequency of the driver circuit has to be high and due to capacity between the electrodes that new cross-talk can emerge.
>>471
A similar possibility is the frame rate modulation where a pixel is addressed as black in one period and white in the next.
Provided that the slow response of the liquid crystal and/or the averaging by the cognitive system of the user is sufficient, an impression of ‘grey’ will result.
Otherwise, frame modulation leads to a flickering display.
>>472
Finally, a pixel can be divided into sub-pixels of different area.
Even if black and white pixels are put together within a distance, they can’t be resolved by the eye which creates the impression of one grey pixel.
The technical disadvantage is here that the number of addressing lines increases.
>>473
In general, different principles will be combined. One can get three grey levels by a frame rate modulation over two refresh periods.
If these are distributed onto four sub-pixels with the area ratio 1:3:9:27 , a total of 81 grey levels can be synthesized which is sufficient for standard applications.
一
>>474
Similar problems are caused by the demand for colour displays. Here, the approach is in nearly all applications spatial dithering as it’s for colour cathode ray tubes.
Three very small sub-pixels (≒ 100 μm) are combined for each pixel of the display.
Each sub-pixel is equipped with a colour filter when ch can be made of dye or be an interference filter.
Interference filters are preferred for projection devices where the energy of the absorbed light would lead to excessive heating of the device.
>>475
Because each of the sub-pixels only uses a narrow wavelength band, the problem of incomplete blocking of light in the off-state can be solved in a simple way here.
One can go exactly to the minimum positions by matching the gap of the cell to the wavelength of light for each pixel.
一
>>476
The disadvantage of such arrangements is that the colour filters reject about 80% of the white light.
For reflective applications, where the light goes twice through the cell this isn’t tolerable.
Therefore, current colour liquid crystal displays for PC and mobile terminals have to be operated with back-lighting as if ambient light is present ( about 2003 ).
>>477
In a few cases, a cell isn’t operated at a transmission minimum, and the birefringence colours of the cell are directly used as the display colours.
In applications, where only a limited number of colours have to be represented, this principle has been successfully used.
>>478
It offers the possibility to build ‘transflective’ displays, which can be operated with ambient light and/or backlight.
But if one wants to address the whole colour space 〜 what is expected from a PC display 〜 it’s necessary to stack several such devices to create colours by subtractive mixing.
This principle has never been realized in commercial PC display applications due to high cost ( in 2003 ), though it would offer a higher transparency than common colour liquid crystal displays.
>>479
§ 5 Cell for High-Resolution Displays
5.1 Super-twisted Nematic Cells
As already pointed out, the problem of losing contrast in highly multiplexed displays can’t be solved satisfactory with 90° twisted nematic liquid crystals.
Fortunately, the situation can be improved by increasing the twist angle ( about 2003 ).
>>480
According to some investigations, up to a certain threshold voltage, all molecules remain more or less parallel to the cell walls, above it the tilt rises continuously.
But for higher twist, the dependence becomes steeper and finally, beyond about 240° , even a bi-stable situation happens.
From this microscopic action of the molecules, it’s evident that also the electro-optic characteristics improve with increasing twist.
>>481
In practice, additional efforts are necessary to maintain the ‘supertwisted’ structure with a twist angle θ ＞ 90° .
An ordinary nematic liquid crystal would optimize its elastic energy by ‘flipping back’ to ξ − 180° which has the smaller absolute value.
Therefore, it’s necessary to ‘pre-twist’ the material. This is done by admixing a small amount of a chiral nematic ( cholesteric ) liquid crystal.
>>482
In this way, an intrinsic twist with optional pitch between that of the chiral component and infinity can be created.
The only limitation arises from the following fact. That is, for too small pitch, the structure may change to one which is periodic in a direction parallel to the cell walls.
This ‘stripe structure’ was discovered earlier by Chigrinov. This effect limits the twist to 〜 240° , the bi-stable situation can’t be used. The twist angles in commercial displays are in the range 180 〜 240° .
>>483
By the way, the order parameter of liquid crystal has a RP＾2 ( real projective plane ) -like structure, we must ‘4-dimensionally’ paste a punctured ball with a Mobius-band to realize such a projective plane.
It’s told that people in Jyoumon-period (縄文時代) have an ability to 4-dimensionally perceive various objects, in the sense, their abilities is suitable for dealing with such an order parameter.
>>483
Another major difference of super-twisted displays is that the polarizers on both sides are placed in a non-standard way.
They are not parallel to the respective liquid crystal molecule orientations as in the twisted nematic cell. This becomes necessary because of the residual twist in the select state which makes the standard way of operation impossible.
一
>>486
Instead the ‘interference mode’ is used where one has to accept a highly coloured off-state.
According to some experiments, they show periodic zeros for the different colours as before but not the general decaying envelope.
Therefore, the transmission for ‘wrong’ colours is much higher than in the waveguide mode.
The resulting colour is chosen in a way that the subjective contrast is still acceptable ー usually yellow or blue.
Therefore, in the context of super-twisted nematic displays one speaks about normally-yellow and normally-blue displays.
>>487
Several principles are used to improve this situation.
In using coloured backlight, one can achieve colours of the transmitted light.
Replacing the polarizers by dichroitic devices, one can let the opposite colour of the off-state through so that additive mixing results approximately in white.
Extremely thin cells don’t show this coloration but have a low transmission even in the ‘white’ state.
>>488
The best but also most expensive solution is the optical compensation. This principle is most easily explained from the double super-twisted nematic cell which was used as a standard laptop display application for a long time.
There, one combines two layers of STN liquid crystal with opposite twist.
一
>>489
This is done by mirroring the direction of the orienting coatings on the cell walls and using the enantiometric chiral component in the liquid crystal mixture.
Without any calculation symmetry tells that a light beam crossing both structures will remain unchanged in its polarization.
一
>>490
All effects bi-refringence of the first layer are identically compensated by the second.
This means one can get a white off-state by parallel polarizers and a black one by perpendicular polarizers.
The ‘active’ layer, a voltage is applied to get the device into the on-state only on one of the liquid crystals. In this way, the symmetry is destroyed and the cell switches to the opposite colour.
>>491
As the construction of the second mirrored liquid crystal layer is very expensive, the compensation of developed devices has been accomplished with a solid foil ( about 2003 ). Such a foil is made from a polymer containing liquid crystalline side-groups.
Here, the demerit with respect to the DSTN ( double super-twisted nematic ) principle is that the optical compensation (≒ optical correction) will reach the complete condition only for one wavelength and one temperature.
Therefore, a slight coloration of the off-state is resulted from rise in ‘abnormal’ ambient temperatures.
>>492
5.2 Active Matrix Displays
The current standard for PC display mainly adopts AM ( active matrix ) or TFT ( thin film transistor ).
Instead of solving a problem of highly multiplexed addressing by chemical methods, we used an electronic one for that.
Each display pixel is equipped with its own driver. This is only possible by putting the driving transistor close to the pixel into the display’s matrix.
>>493
One of the glass substrates contains a matrix of thin film transistors whose gates are connected to the row lines and source electrodes are connected to the column lines.
The pixels are not directly constructed as the intersection of row and column lines.
They are rather created by individual electrode patches connected to the drains of the TFTs. The counter-electrode extends over the whole area of the opposed glass substrate.
一
>>494
This integration of a transistor onto the glass matrix was based on a way devised by Lilienfeld in 1933 ( amazing ! ).
In principle, it’s a field-effect transistor similar to the well-known MOS ( Metal-Oxide-Silicon ) FET.
But, instead of the conventional way to make the transistor from bulk material, here it’s made by coating a glass cell wall with semiconductor, conductor layers and etching.
>>495
The source and drain electrodes are connected by a layer of n-type amorphous hydrogen-doped silicon.
The metal gate electrode is placed below the semiconductor layer insulated by silicon nitride.
Because the carriers in the semiconductor correspond to electrons rather than holes, a positive voltage on the gate enhances source-drain conductivity and a negative voltage suppresses the conductivity.
So, the TFT can be viewed as an electronically controllable switch.
一
>>496
The TFTs simply act as switches. The thin-film transistors of rows are sequentially opened by applying row-by-row a positive voltage.
When the source-drain line is opened, the voltage on the column lines is forwarded to the liquid crystal cell.
After a row is addressed, the TFT will close again and shield the pixel from the voltage applied to the next row.
The electric field on the liquid crystal is kept by own capacity, and it (＝ the electric field) is kept by an additional capacitor in most cases.
>>497
TFT active matrix displays are currently ( about 2003 ) the best solution for high resolution displays.
Cross-talk can be avoided except for capacitive effects. There is no limits in the selective / non-selective voltages.
Therefore, normal TN liquid crystals can be used, and analog grey scale addressing is possible.
一
>>498
Meanwhile, TFT displays are three times more expensive than DSTN displays. Therefore, though applications of this technology have been widely circulated over PC & video displays, they are already high in cost.
The market fraction of TFT displays was 74 % in 1999 . It’s expected to further be increased.
Because they are more expensive than DSTN devices, they will sooner or later disappear from the market of high-resolution displays ( in 2003 ).
>>499
During the year since its discovery TFT technology has made an enormous progress. The image resolution is already approaching that of printers a decade ago.
※ one of the TFT displays was manufactured by IBM .
It boasts a so-called QUXGA resolution of 3,840 × 2,400 pixels. This type at a diagonal size of 22.2′′ ( 564 mm ) corresponds to a pixel distance of 0. 1245 mm or a pixel density of 204 per inch. The retail price of the monitor based on this display is well above 15,000 US$ ( in 2003 ).
>>499
More precisely, it’s expected that though TFT displays are more expansive than DSTN displays, the former technology is more popular than the latter one because of good performance, accordingly devices at the expense of DSTN will disappear from the market in display at that time.
>>500
§ 6 Backlihhting
As indicated previously, some LCD display principles require backlihhting. In other cases, the applications forces to adopt backlight in addition to the ambient light.
Therefore, design of the light source is often important for the construction of a LCD display module.
Because about 90% of the electrical power is consumed by a backlight for now.
Accordingly, its power consumption is the major factor determining an operation time of battery powered device.
>>502
By the way, a cold cathode fluorescent lamp is the best available source with respect to power consumption. Namely, the low power consumption enables use of the light source for notebook PCs without exception.
The filament lamp and electro-luminiscent foil are used in small scale applications as wristwatches and cellular phone displays.
Because the display lighting is only inter-mittently activated, the lifespan isn’t a subject to be solved so much, rather the cost for production is more important.
If a coloured backlighting is requested, light emitting diodes have a limited application.
>>503
Because of its widespread application, a cold cathode fluorescent lamp ( CCFL ) must be taken into consideration in detail.
CCFLs are commonly called ‘neon’ lamps. They had been utilized since 1910, that is, those ‘neon’ lamps were first adopted in advertising signs.
Because a high voltage required for use of CCFLs was mostly restricted to this ‘neon sign’ application until the appearance of LCD backlighting.
>>504
A CCFL consists of a tube filled with a mixture of mercury vapour and ‘penning gas’ at about 7 hPa pressure.
The gas discharge mainly produces a 253.7 nm ultraviolet radiation from mercury atoms. Meanwhile, the penning gas enhances the ionization of mercury at lower voltage.
The interior of the tube is covered with a mixture of phosphorus to convert ultraviolet into visible light.
A broad range of colours can be obtained by an appropriate choice of phosphorus.
>>505
Furthermore, high voltage is required for the major drawback of CCFLs. Because electrical emission is only based on electrical voltage,
And, CCFLs have no heating of the cathode to facilitate emission.
※ Then, the voltage amounts is 25 〜 50 V/ cm.
This means that CCFLs need a power supply of 800 〜 1000 V for notebook PC applications.
So that, so-called ‘inverters’ is needed, this circuit can convert the DC power from a battery into a sinusoidal AC voltage.
※ The voltage is transformed up to the optionally desired voltage.
>>506
§ 7 Reflective Liquid Crystal Displays
Reflective liquid crystal displays offer some competitive merits over the transmissive ones in low power consumption, sunlight readability and film-like image quality. The readout light comes from ambient.
As backlight isn’t used in this case, both its power consumption and panel weight are reduced.
>>507
In a bright outdoor environment, the images of a transmissive display could be washed out by sunlight. Since reflective displays utilize ambient light as reading source. The brighter the ambient light is, the more vivid the displayed image gets.
In most reflective LCDs, the thin-film-transistor ( TFT ) are imbedded under-neath a reflector.
Therefore, the aperture ratio is as large as 90 %, it can still be obtained even for a high-resolution device ( 1024 × 768 ).
High aperture ratio makes the displayed images like film quality.
※ But, the screen door effect in some types of transmissive LCDs no longer exists.
>>508
Besides, several reflective display technologies for LCD have been developed such as digital micro-mirror device, grating light valve, inter-ferometric modulation, electrophoretic display and rotating ball display.
Each technology has both merits and demerits. Some devices are more suitable for direct-view and others are preferred for projection displays.
一
>>509
Within the liquid crystal family, several light modulation mechanisms have been discovered. Theee include phase retardation, polarization rotation, absorption, light scattering and Bragg reflection.
Phase retardation and polarization effects need to incorporate at least one polarizer.
一
>>510
A reflective direct-view display adopting a polarizer can achieve 30 - 40 : 1 contrast ratio and good color saturation, except that the light throughput is sacrificed.
Meanwhile, the display mechanisms including absorption, light scattering and Bragg reflection don’t require any polarizer.
High brightness and wide view angle are necessary requirements for such displays. But their contrast ratio is usually limiited to 5 - 10 : 1 .
>>511
Several types of reflective direct-view liquid crystal displays have been developed.
They can be roughly categorized by the number of adopted polarizers. The benchmark for these types of reflective displays is at white paper.
A white paper and newspaper respectively has reflectivity of 80 and 55 % and contrast ratio of 12 : 1 and 6 : 1 .
All electronic displays developed until now still can’t match the performance of a white paper in reflectivity and viewing angle.
>>512
§ 7.1 Two-polarizer R-LCDs
Wristwatch displays use two polarizers. A LC cell is sandwiched between two crossed linear polarizers. The 90° twisted nematic ( TN ) cell is used as light switch.
Behind the second polarizer, a diffusive reflector reflects the incident light back to the viewer.
The 90° TN cell has been widely used for transmissive display due to its high efficiency, weak color dispersion, high contrast ratio and low operation voltage.
>>513
But, when a 90° TN cell cell is used for reflective display, two crossed polarizers are required to achieve high contrast ratio.
The second polarizer put between the back substrate and diffuse reflector not only reduces brightness but also causes parallax ( double image ) to bring limits on resolution.
Thus, the two-polarizer R-LCD isn’t suitable for high resolution displays.
>>514
As yesterday was 08/12 , I abruptly turn a topic into an other content.
「The plasticity of brain」was planned as one of the prior researches in the second half of the 1980’s by the ministry of education ( the ministry of education & science at present ) in Japan.
Unfortunately, Nobuaki.Tsukahara who would get the chief of the research died in a plane accident on 1985/08/12 .
>>515
・ Memorization, learning and neuro-computing
Neurons mainly bear learning, memorization, those processes are based on variations of synapse ( plasticity of synapse ).
If a learning newly holds, the number of synapses, the quantity of secreted neurotransmitters increase. So that, the electric potential of synapse rises and the nerve cell gets easy to be excited.
>>516
In case of forgetting, the change of synapse turns to be reverse of the above case.
Brain has remarkable flexibility, its neural circuits are modified and reformed by various internal and external factors.
And, functions of neural circuit often continue to vary.
一
>>517
The visual system is a typical example to show the plasticity of brain.
If a kitten is put in a visual environment of only vertical stripes for 3 〜 14 weeks after the birth,
it will get difficult for the cat to see horizontal contours.
And, most of visual fields become put in the range of ±30° in the vertical direction.
※ Then, simple type cells selectively react to segmental stimuli in some azimuth ( direction ).
>>518
Namely, in this case, neurons of the visual field to react to horizontal segments almost disappear.
※ Such a change doesn’t happen over three months after the birth.
The neural circuit of brain isn’t completed just after the birth, it will be remarkably modified according to given stimuli.
※ For example, Lorenz made clear special learnings found out in the beginning after the birth called ‘imprinting’ from the viewpoint of ethology.
>>519
・ The plasticity of brain in the mature step
It has been regarded that a formed nerve net once can never be varied again after the formation.
But, it has been made clear that a completed neural circuit of brain once also can be changed in its functionality, shape according to environmental variations.
→ the plasticity of brain in the mature step
>>520
As an example, a clinical case of ‘replacement of nerves’ to a patient whose nerve from the spinal cord to the brachial muscle is cut off because of an accidental injury of spinal cord is known.
Then, a part of intercostal nerves ( governed by a respiratory muscle ) was transplanted into the musculo-cutaneous nerve of the brachial muscle.
First, the arm moved together with the respiration, soon the person could voluntarily move the arm namely bend the elbow independently of respiration.
>>521
・ Foundations of plasticity of synapse
Plasticity of synapse is roughly divided into two types as follows.
① Plasticity on the conjunction among synapses
② Plasticity of transmission on a synapse
In a case to manage increased works in an office, following two ways are presented.
( a ) Increasing a number of members in the office (≒ a number of synapses )
( b ) Improving the ability for managing of each member (≒ raising the transmitting efficiency over each synapse )
Then, ( a ) , ( b ) correspond to ①, ② respectively.
>>522
As an example of ① , a phenomenon called ‘germination’ is found out over nerve, muscular system, red nucleus and hippocampus, etc.
Synapses are newly formed from healthy ( sound ) nerve fibers in this phenomenon.
There are two types of ② namely increasing & decreasing in transmitting efficiency,
The former is found out in a hippocampus, a sea-hare ( one of the mollusks ). Meanwhile, the latter is found out over a cerebellum.
>>523
◎ Examples of synaptic plasticity
・ The plasticity of conjunction among synapses (≒ the plasticity of coupling synapses)
A cross-sewing operation was performed on a foreleg of a cat to replace the nerve for bending muscle of peripheral nerves with the nerve for stretching muscle.
After 2 〜 8 months since the operation, first the foreleg of the cat moves oppositely to the intention ( namely, when the cat tries to bend the arm, it’s stretched. Inversely, when the cat tries to stretch the arm, it’s bent ), soon the cat gets to be able to perform usual behavior such as catching a bait in the way before the operation.
A synapse is formed of fibers from the motor area of a cerebrum at a red nucleus.
→ the cerebral red nuclear synapse
>>524
Synaptic potentials from red nuclear cells governing both front & rear legs were measured.
As the result, it was found out that cerebral red nuclear synapses were newly formed on red nuclear cells governing the foreleg in the above case.
※ N.Tsukahara and others made clear the plasticity of brain in the cellular level to variations on peripheral function.
>>525
・ The plasticity of transmission on synapses
If a temporal lobe including the hippocampus in a deep part of a cerebrum is damaged,
the patient will fall in a serious defect of memory.
Namely, a hippocampus plays important role for formation, maintenance and control of memory.
A typical example of improved transmission on synapses has been found out on a hippocampus.
T.Bliss and others reported that if impulses successively pass through a synapse between perforated path and granule cell, the improvement in transmission efficiency is maintained for about several hours.
※ Such a phenomenon is called ‘long-term potentiation’ .
>>526
If a subject is put in an environment which is seeable oppositely in right & left, the adaptive mechanism of the vestibular oculomotor reflection works and the cerebellum plays important role.
In such a case, in the cerebellar cortex, an input-system is formed of climbing fibers and mossy fibers, neuraxons from Purkinje cells behave as output-systems.
Furthermore, an excitatory synaptic junction of a Purkinje cell with a climbing fiber can be found out in this case.
一
>>527
Then, signals from a mossy fiber are relayed to parallel fibers through granule cells, parallel fibers as the output system form an excitatory synaptic junction with a Purkinje cell.
一
>>528
And, informations from about 6000 separate mossy fibers converge on a Purkinje cell.
But, if a Purkinje cell almost-simultaneously and successively receives signals from both parallel fibers and climbing fibers, the transmission efficiency on synapses between the Purkinje cell and parallel fibers falls.
一
>>529
By the way, J.S.Albus and D.Marr presented it as a hypothesis about 1970 that information-processing on a cerebellum may be same as the principle of percep-tron.
Ito and others have investigated variations over synaptic junctions with a Purkinje cell to physiologically check the hypothesis.
〈 A reference 〉
「The cerebellum as a neuronal machine」
J.C.Eccles, M.Ito and J.Szentagothai, ed.
( Springer, 1967 )
>>531
PDLC and LC gels are used to prepare light scattering devices. Ch-LCD utilizes Bragg reflection. And, GH display takes merits of the anisotropic absorption of dichroic dyes.
Ch-LCD and GH displays of them are better than PDLC and LC gels in momentum.
一
>>532
A main advantage of the Ch-LCD is that the reflected light is already colored.
Therefore, it’s possible to realize a color display without using color filters.
Because it’s unnecessary for polarizer in the case, the reflectivity of a Ch-LCD is at least 6 times higher than a reflective display adopting a polarizer and color filters.
>>533
The viewing cone of a Ch-LCD without polarizers is wider than 60° except that its contrast ratio is in the 5 - 10 : 1 range.
2 or 3 RGB panels are stacked together as one approach to achieve multiple colors.
Accordingly, ‘parallax’ can be regarded as a potential problem of the stacking method. For example, an incident light & a reflected light pass through different pixels.
>>535
Mixed color is induced by ‘parallax’ . This subject is serious for preparing a high-resolution LCD .
The operation voltage of a Ch-LCD is inversely proportional to the pitch length. The operation voltage of a Ch-LCD is in the vicinity of 20 V rms due to the short pitch involved for visible displays.
Besides, as Ch-LCD is bi-stable, its low power consumption is particularly suitable for electronic books.
>>536
The guest-host ( GH ) display can be driven by TFT arrays. But, its contrast ratio is limited to 〜 5 : 1.
Because the operation principle of a GH display is based on utilization of absorption anisotropy of dichroic dye molecules doped in an aligned LC host.
Normally, a GH display system consists of 1 〜 5 % of absorbing dye molecules dissolved in a LC host.
The host LC is highly transparent in a visible spectral region and the guest dyes strongly absorb one polarization of an incoming light and transmit other polarization.
>>537
Special device configurations have been developed to avoid use of any polarizer in a GH display.
For example, the Coke-Kashow cell uses a homogenous GH cell with a quarter-wave film put between the rear substrate and the reflector.
The White-Taylor cell uses chiral dopant to form twisted GH layers. So that, both polarization of an incident light can be absorbed while traversing through the GH LC layer twice.
一
>>538
The double cell uses two orthogonal homogenous cells, the first GH layer is responsible for one polarization and the second layer for the other polarization.
All the three cells in the above have their own pros and cons. The typical performance of a GH LCD is 50 〜 60 % reflectivity, 5:1 contrast ratio, 〜 ± 60° viewing angle and 50 〜 80 ms response time.
Low power consumption is an main attractive character of a GH display.
>>539
§ Single-polarizer R-LCD
For a reflective LCD with one polarizer, the light still traverses the polarizer twice, so that the maximum light throughput is limited to 〜40 %.
But, as compared with two-polarizer LCD, two merits are brought by a single-polarizer LCD.
>>540
Fiirst, parallax is eliminated by removing the second polarizer put between a back glass substrate and a reflector, next, the reflectiivity is raised by 25 % with removing the second polarizer.
Meanwhile, though its reflectivity is lower, the single-polarizer LCD exhibits a higher contrast ratio than a non-polarizer LCD.
In this case, contrast ratio is necessary for color displays.
一
>>541
If the contrast ratio is 5 〜 10 : 1 , light is leaked out of a color pixel and relatively larger mixed colors are brought.
If contrast ratio exceeds 30 : 1 , light leakage in a color pixel is remarkably improved however that state is still far from the perfect condition.
>>542
In case of reflective display, it’s not easy to get contrast ratio higher than 50 : 1 under ambient light condition due to surfacial reflections.
A compromise between display brightness and contrast ratio is brought by the single-polarizer LCD and it has become the mainstream in approach ( about 2003 ).
>>543
Several cell configurations have been devoloped for single-polarizer reflective LCDs.
For example, the mixed-mode TN cell, super-twist TN cell, homotropic cell, film-compensated homogeneous cell and π-cell all have their own merits.
544
For passive matrix display, STN with 220° 〜 240° twist angle has been considered for achieving high duty ratio.
Meanwhile, for active matrix display, a large cell gap tolerance to accomodate the bumpy reflector surfaces is brought by MTN cells, so that, a good contrast ratio can still be obtained.
Furthermore, for reflection type projection display, MTN and homotropic cells are favored choices due to their high contrast ratio.
>>545
The viewing angle of a reflective cell is equivalent to a two-domain transmissive cell. Because the mirror image effect is realized by the incident and reflected beams. For computer monitor, such ± 45° viewing angle is in-sufficient.
But, for handheld displays, the panel can be conventionally adjusted to fit the viewer’s position. Therefore, viewing angle isn’t a critical issue for most handheld reflective LCDs.
>>546
For reflective direct-view displays, design and fabrication for a reflector is probably the most critical concern. An ideal reflector reaches two criteria : 1 .
If the requirement is satisfied, displayed images will be run to viewers without overlapping with surfacial reflection.
一
>>548
If images are mixed with glares, the contrast ratio will be considerably reduced.
Accordingly, we must prepare sufficiently wide viewing cone and optical gain for avoiding that. A specular mirror has too narrow viewing angle and can’t be used alone for reflective display.
A Lambertian reflector has uniform scanning all over the angles by contrast, so that the light intensity in the preferred viewing cone is reduced.
>>549
Extensive efforts have been put into design & fabrication for reflector with acceptable viewing angle while providing optical gain preserving good contrast ratio.
So far, four types of reflectors have been investigated :
( 1 ) light control films,
( 2 ) rough surfacial reflectors,
( 3 ) holographic reflectors,
( 4 ) cholesteric reflectors
一
>>550
A light control film is designed so as to guide images to the observer at approximately normal viewing direction, the viewing direction is well separated from the specular angle.
This film has been applied to STN, PDLC and cholesteric displays. The display brightness and contrast ratio are remarkably improved.
一
>>551
Meanwhile, the bumpy reflector gets higher and it diffuses the incident light to a preferred viewing cone to avoid overlapping with the specular reflection.
In fact, a structural change is incorporated into it.
The holographic reflector can be either laminated to the backside of the display or integrated with color filters.
一
>>551
Meanwhile, the bumpy reflector gets higher and it diffuses the incident light to a preferred viewing cone to avoid overlapping with the specular reflection.
In fact, a structural change is incorporated into it.
The holographic reflector can be either laminated to the backside of the display or integrated with color filters.
一
>>552>>553
Though the former approach is simple, its usefulness is limited to low resolution because undesirable parallax is caused by the simpleness.
Surely, designs for internal holographic reflector is under improvement, but they hold promise for displays with high brightness, high contrast and excellent chromaticity.
Finally, cholesteric liquid crystal layer has also been utilized as diffusive reflector for some bi-refringence color reflective LCDs.
一
>>554
§ ‘Transflective’ Displays
A reflective LCD relies on ambient light to read out displayed informations. When the ambient light is dim, the display isn’t readable whether built-in light is available or not.
We must develop a trans-flective display to overcome such a problem.
In a trans-flective LCD, each pixel is split into reflective sub-pixels ( R ) and transmissive sub-pixels ( T ). Usually, the R & T area ratio is 4 : 1 in favor of reflection.
The backlight is used for dark ambient only for conserving power.
>>555
In the single cell gap approach, the cell gap for R modes is equal to that for T modes and it’s optimized for R-mode.
As a result, the light transmittance for T-mode gets lower than 50% because the light only passes the LC layer once.
Meanwhile, in the double cell gap approach, the cell gap for T-pixels is twice that for R-pixels.
Besids, both R and T have high light efficiency. But, the response of T mode is four times slower than that of R mode.
>>556
A common problem for most transflective displays is that both R & T pixels have different color saturation.
For R pixels, the ambient light passes a color filter twice, on the other hand, for T pixels, the backlight only passes the color filter once.
The pigment concentration or the color filter thickness of the transmissive pixels should be twice that of the reflective ones to realize equal color saturation. For simplicity, this problem is ignored in most trans-flective displays.
一
>>557
According to existing technologies ( in 2003 ), it’s possible to realize 40-inch direct-view LCDs. But, high cost is needed for producing them. To overcome such a problem, projection is prepared so as to be alternative way for achieving large-sized display ( for example, high definition TV, boardroom presentation and electronic cinema ).
Two types of projection displays have been often proposed : front & rear projections. In case of front projection configuration, a distant screen is utilized to view a magnified image. Meanwhile, in case of rear projection configuration, the magnification optics is enclosed in back of an imaging screen to produce a self-contained system.
Both transmissive and reflective LCDs have been considered for projection displays ( about 2003 ).
>>557
According to existing technologies ( in 2003 ), it’s possible to realize 40-inch direct-view LCDs. But, high cost is needed for producing them. To overcome such a problem, projection is prepared so as to be alternative way for achieving large-sized display ( for example, high definition TV, boardroom presentation and electronic cinema ).
Two types of projection displays have been often proposed : front & rear projections. In case of front projection configuration, a distant screen is utilized to view a magnified image. Meanwhile, in case of rear projection configuration, the magnification optics is enclosed in back of an imaging screen to produce a self-contained system.
Both transmissive and reflective LCDs have been considered for projection displays ( about 2003 ).
>>557
According to existing technologies ( in 2003 ), it’s possible to realize 40-inch direct-view LCDs. But, high cost is needed for producing them. To overcome such a problem, projection is prepared so as to be alternative way for achieving large-sized display ( for example, high definition TV, boardroom presentation and electronic cinema ).
Two types of projection displays have been often proposed : front & rear projections. In case of front projection configuration, a distant screen is utilized to view a magnified image. Meanwhile, in case of rear projection configuration, the magnification optics is enclosed in back of an imaging screen to produce a self-contained system.
Both transmissive and reflective LCDs have been considered for projection displays ( about 2003 ).
>>557
According to existing technologies ( in 2003 ), it’s possible to realize 40-inch direct-view LCDs. But, high cost is needed for producing them. To overcome such a problem, projection is prepared so as to be alternative way for achieving large-sized display ( for example, high definition TV, boardroom presentation and electronic cinema ).
Two types of projection displays have been often proposed : front & rear projections. In case of front projection configuration, a distant screen is utilized to view a magnified image. Meanwhile, in case of rear projection configuration, the magnification optics is enclosed in back of an imaging screen to produce a self-contained system.
Both transmissive and reflective LCDs have been considered for projection displays ( about 2003 ).
>>558 〜
§ Transmissive Displays
We briefly show a LCD projector using three transmissive poly-silicon thin-film-transistor ( TFT ) panels.
The incoming white light from a lamp is divided into three channels by dichroic mirrors. In each channel, a LCD panel is sandwiched between two linear polarizers.
The 90°-TN and Vertical Aligned ( VA ) cells are popular in choice, because TN cell has weak wavelength dependency, meanwhile VA cell has an un-precedented contrast ratio ( ＞ 1000 : 1 ).
In case of the X-cube, RGB beams are re-combined, the reflective lens is projected into the images on a screen.
>>558 〜
§ Transmissive Displays
We briefly show a LCD projector using three transmissive poly-silicon thin-film-transistor ( TFT ) panels.
The incoming white light from a lamp is divided into three channels by dichroic mirrors. In each channel, a LCD panel is sandwiched between two linear polarizers.
The 90°-TN and Vertical Aligned ( VA ) cells are popular in choice, because TN cell has weak wavelength dependency, meanwhile VA cell has an un-precedented contrast ratio ( ＞ 1000 : 1 ).
In case of the X-cube, RGB beams are re-combined, the reflective lens is projected into the images on a screen.
>>563 〜
Linearly polarized light is required for most LC devices. A few polarization conversion devices have been invented to convert unpolarized light into linear one.
So that, the conversion efficiency reaches 70 〜 80 % . Furthermore, an array of microlenses is utilized to raise aperture ratio of a high resolution TFT-LCD panel.
The effective aperture ratio was improved to 〜 80 % for a XGA device.
In many cases, the power efficiency of 10 〜 15 lm / watt in a projection system with three transmissive LCD panels has been routinely obtained.
Under such circumstance, 1000 〜 1500 lumens can be produced on a screen with a 100 W short-arc lamp.
>>563 〜
Linearly polarized light is required for most LC devices. A few polarization conversion devices have been invented to convert unpolarized light into linear one.
So that, the conversion efficiency reaches 70 〜 80 % . Furthermore, an array of microlenses is utilized to raise aperture ratio of a high resolution TFT-LCD panel.
The effective aperture ratio was improved to 〜 80 % for a XGA device.
In many cases, the power efficiency of 10 〜 15 lm / watt in a projection system with three transmissive LCD panels has been routinely obtained.
Under such circumstance, 1000 〜 1500 lumens can be produced on a screen with a 100 W short-arc lamp.
>>563 〜
Linearly polarized light is required for most LC devices. A few polarization conversion devices have been invented to convert unpolarized light into linear one.
So that, the conversion efficiency reaches 70 〜 80 % . Furthermore, an array of microlenses is utilized to raise aperture ratio of a high resolution TFT-LCD panel.
The effective aperture ratio was improved to 〜 80 % for a XGA device.
In many cases, the power efficiency of 10 〜 15 lm / watt in a projection system with three transmissive LCD panels has been routinely obtained.
Under such circumstance, 1000 〜 1500 lumens can be produced on a screen with a 100 W short-arc lamp.
>>563 〜
Linearly polarized light is required for most LC devices. A few polarization conversion devices have been invented to convert unpolarized light into linear one.
So that, the conversion efficiency reaches 70 〜 80 % . Furthermore, an array of microlenses is utilized to raise aperture ratio of a high resolution TFT-LCD panel.
The effective aperture ratio was improved to 〜 80 % for a XGA device.
In many cases, the power efficiency of 10 〜 15 lm / watt in a projection system with three transmissive LCD panels has been routinely obtained.
Under such circumstance, 1000 〜 1500 lumens can be produced on a screen with a 100 W short-arc lamp.
>>563 〜
Linearly polarized light is required for most LC devices. A few polarization conversion devices have been invented to convert unpolarized light into linear one.
So that, the conversion efficiency reaches 70 〜 80 % . Furthermore, an array of microlenses is utilized to raise aperture ratio of a high resolution TFT-LCD panel.
The effective aperture ratio was improved to 〜 80 % for a XGA device.
In many cases, the power efficiency of 10 〜 15 lm / watt in a projection system with three transmissive LCD panels has been routinely obtained.
Under such circumstance, 1000 〜 1500 lumens can be produced on a screen with a 100 W short-arc lamp.
At that time ( 2003 〜 2004 ), as I worked in a certain company located in Fukaya-city of Saitama-prefecture in Japan ( ※ ) , I also had heard of the methodology.
※ TMD ;
a company which was founded on a joint investment of T and P
Strangely, though there are many research fruits about influences of light through liquid crystalline molecules on sub-consciousness, those results have been scarcely known.
>>576
If a laser-beam is applied to a compression wave inter-vertically, the compression wave plays the same role as a dif-fraction grating.
※ In these cases, ‘dif-fraction’ means the abbreviation of a different (≒ unusual) fraction’ implicating fractal dimensions or a rather unusual rate as a novel combination.
>>577
Namely, a certain fundamental experiment had been performed with a rather dated method,
so that an explosive accident was caused by the experiment and plural members who took part in the experiment were killed due to the explosive accident.
а
>>576>>577>>578
That is, those accidental cases show that basic experiments including acoustic-optical spectrometry were carried out around the region the end of the 1970’s 〜 the beginning of the 1980’s .
Indeed, we also heard that the fellows habitually undesirable advertisements including unreliable ones on the net would fight against the world as their enemies from now.
一
>>580
Besides, it’s probable that bad influences called Kodoku (蠱毒) brought through an obscure assassin such as 酒乱・大西共産党 ( the Great Western Communist Party as a Hopeless Alcoholic ) have considerably affected those fellows so as to make them misbehave.
According to many reports, we also heard that most of the hopeless alcoholics and the chaps habitually presenting undesirable advertisements such as e×tremely erotic & vulgar ones and posters to sell fakes on the net would fight against the world as their enemies from now.
>>585
Besides, such an excessive bias or a group of the hopeless alcoholics or the chaps habitually presenting undesirable advertisements on the net can turn to be a very massive attractor to divide a country or a ‘world’ into two states like gravitational lensing.
>>586
Furthermore, we should pay attention that people at a something-dependent state such as the alcoholics and the chaps are easily operated through ‘Kodoku (蠱毒)’ .
>>586
「1984 ≒ 2 ＋ 2 ＝ 5」by George.Orwell,
For example, 「田」of the Kan-characters implies the above cryptic meaning.
Namely, 「田」can be diagrammatically realized by surrounding a cross with two horizontal bars and two vertical bars ( 2 ＋ 2 ＝ 田 ).
>>588
Besides, 「田」is composed of four smaller square rooms and the biggest square room surrounding a cross.
Accordingly, if we bear 「田」in mind independently of sizes of rooms, 「2 ＋ 2 ＝ 5」holds as the number of rooms in such a rather visual context.
>>587>>589
However, if these edges of 「田」are regarded as wavelengths and amplitudes, it’s possible to deform and/or break the 「田」by modifying lengths of those edges.
※ This is an auditory operation.
A nostalgic home song has come from four directions today too ( 四面楚歌 ).
According to many reliable informations, it’s highly probable that the people habitually presenting undesirable advertisements such as those of defective products on the net would fight against the world as their enemies from now.
>>599
According to many reliable informations, it’s highly probable that the people frequently making big noises so as to threaten persons with vehicles also would fight against the world as their enemies from now.
>>600
The anomalous adhesiveness is just same as that of the people habitually pasting undesirable advertisements such as ones to sell fakes and defective products on the net.
Probably, they are operated by Kodoku (蠱毒) called 「酒乱・大西共産党」( The Great Western Communist Party as a Hopeless Alcoholic ) come from Sikoku (死国 and/or 尸国).
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