JPH0792486A - Spatial light modulator and driving method thereof - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a spatial light modulator adapted to an optical neurocomputing system and a driving method thereof. [Structure] FIG. 1 shows the structure of a ferroelectric liquid crystal spatial light modulator. In the present invention, corresponding to the surface charge of the alignment film due to the drift of the ions generated in the ferroelectric liquid crystal layer, the charge is generated in the photoconductive layer at the interface between the alignment film layer and the photoconductive layer (or mirror layer). Photo carriers are trapped. The sensitivity was changed by the electric field generated by the trapped charges. In addition, the single-shot mode continuously and repeatedly outputs a bipolar or tri-continuous pulse voltage and a drive voltage consisting of a rest period to control the voltage and pulse width of each pulse, or to apply an alternating electric field superposed with direct current. The sensitivity fluctuation is controlled by a driving method of the ferroelectric liquid crystal spatial light modulator in which the DC voltage to be superimposed is controlled by controlling the bias voltage or the bias light irradiation means other than the writing light or the reading light is provided to control the bias light amount. Made possible

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical writing type liquid crystal spatial light modulator applied to an optical information processing apparatus, an image processing apparatus and the like and a driving method thereof.

[0002]

2. Description of the Related Art Conventionally, a spatial light modulator using a liquid crystal has been used as an element for intensity-modulating and outputting input image information in real time. Generally, a binarization device using a surface-stabilized ferroelectric liquid crystal as a modulation material is known. However, in the conventional device using the surface-stabilized ferroelectric liquid crystal, when the ferroelectric liquid crystal is in a stable state, charges are accumulated particularly in the alignment film layer to cancel the spontaneous polarization, and an electric field is generated. When removed, this may act as an anti-electric field and impair the memory property. This phenomenon causes the so-called burn-in phenomenon in the optical writing type ferroelectric liquid crystal spatial light modulator in which the sensitivity changes in the region where writing is continuously performed. For this reason, the authors, in Japanese Patent Application No. 02-239594 and the like, are of an optical writing type using an alignment film having a thin vertical film in which an oxide is vapor-deposited at an angle of 80 degrees or more from the normal line direction of the substrate. We demonstrated a ferroelectric liquid crystal spatial light modulator and succeeded in providing good memory properties and bistability.

[0003]

However, recently, as neuro-computing using light has been studied, the spatial light modulator may be required to have characteristics other than the conventional simple bistability. Came. For example, in reproducing the memory and forgetting mechanism of the brain, when the same information is continuously given, that information is gradually accumulated, that is, optical information is stored in the spatial light modulator, and when the presentation of information is interrupted. With the passage of time, the information accumulated becomes faint, that is, the function of forgetting the information stored in the spatial light modulator is required.

In optical neurocomputing, for example, in the case where the Hopfield model is optically realized (reference: NH Farhat et. Al., "0p").
rical implementation of the Hopfield model "Applie
d Optics, Vol.24, No.10, pp.1469-1475, 1985), etc., it may be necessary to add a negative value when updating the coupling load. There is a problem that the system becomes complicated because there is no way to realize and there is no choice but to allocate different memories to the positive and negative coupling weight matrices.

[0005]

Therefore, according to the present invention, in order to solve the above problems, the alignment film layer is made thicker than before.
Alternatively, by using a material with a high insulating property, we have realized a spatial light modulator that is susceptible to sensitivity fluctuations due to charge accumulation. further,
It has become possible to control the displacement amount of the sensitivity by a driving method in which the pulse width or voltage of each pulse is controlled using a bipolar pulse or three continuous pulses.

Further, by controlling the amount of light including the bias light, it has become possible to shift the sensitivity in both positive and negative directions.

[0007]

By using the above method, when the ferroelectric liquid crystal spatial light modulator is applied to optical computing such as an optical neural network, characteristics similar to those of the human brain, such as memory and forgetting, can be obtained. The device can be made to function as a device including, and the range of application can be increased accordingly.

Further, since the sensitivity can be shifted in both positive and negative directions by controlling the amount of light including the bias light, the coupling weight can be increased when optically trying to realize the neural network model. In the case of updating (1), it is possible to update both positive and negative in one device, thereby simplifying the optical system of the optical neurocomputing system and improving its feasibility.

[0009]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic view showing the structure of a photo-writing type ferroelectric liquid crystal spatial light modulator according to the present invention.

Substrates 11a, 1 for sandwiching liquid crystal molecules
As 1b, a transparent glass substrate having a thickness of 5 mm was used, both surfaces of which were polished to a parallel flatness of λ / 5 or less at a He-Ne laser wavelength. The ITO transparent electrode layer 12 is formed on the surface of both substrates.
a and 12b are provided. A hydrogenated amorphous silicon (a-Si: H) photoconductive layer 15 having a thickness of 3.0 μm was formed on the transparent electrode layer 12a on the light writing side.

Depending on the application of the spatial light modulator, a dielectric multilayer mirror may be formed as a mirror layer on the photoconductive layer. There is no problem even if the mirror layer has a structure in which metal films insulated from each other are arranged. The total thickness of the mirror layer is determined by the requirement for the reflectance at the wavelength used, but an increase in the total thickness affects the resolution of the device, so it cannot be excessively increased.

It should be noted that the photoconductive layer 15 can be made of other materials such as cadmium sulfide without any problem, and the optimum layer thickness varies depending on the thicknesses of the mirror layer and the liquid crystal layer. It is set in the range of 5 to 10 μm in consideration of the electrical characteristics and film thickness of each of the above films.

Further, on the surfaces of both substrates, alignment film layers 13a and 13b formed by oblique vapor deposition of silicon monoxide at an angle of 82.5 degrees from the substrate normal direction were provided. The film thickness is 100 as a direct reading of the film thickness meter installed toward the evaporation source during vapor deposition.
It was set to 0 angstrom. Alignment film layers 13a and 13b
In the case where both substrates were combined, the incident directions of vapor deposition were the same.

The alignment film layer may be a rubbing film using a polymer film such as polyimide. This is because in the ferroelectric liquid crystal spatial light modulator according to the present invention, accumulation of charges in the alignment film layer does not hinder. By the way, if stable bistability in normal operation is required, the above charge accumulation will be an obstacle, so sufficient characteristics cannot be obtained using a rubbing film made of a polymer film such as polyimide. .

Further, in the oblique deposition, there is no problem even if a method such as ion assisted deposition is used, and there is no problem in the oblique sputtering. Furthermore, when the material is formed by vapor deposition or sputtering, silicon oxide containing silicon dioxide other than silicon monoxide, or an oxide such as titanium oxide, zirconium oxide, tantalum oxide, germanium oxide, or aluminum oxide, or magnesium fluoride, etc. No problem if it is a fluoride or a mixture of any two or more thereof. This is because the requirements for the formed alignment film are the tilted columnar structure generated by oblique vapor deposition for orienting the ferroelectric liquid crystal molecules with a certain degree of pretilt and the capacity for causing charge accumulation. Because it has

As described above, the material and film thickness of the alignment film layer have an important influence on the sensitivity change characteristic imparted to the ferroelectric liquid crystal spatial light modulator according to the present invention. Here, the cause of the sensitivity variation will be described with reference to FIGS. The structure of the ferroelectric liquid crystal spatial light modulator according to the present invention is schematically shown in FIG. 2-A. A schematic equivalent circuit corresponding to FIG. 2-A is shown in FIG. 2-B. The driving voltage applied between the transparent electrodes 22a and 22b carried on the substrates 21a and 21b is applied to the photoconductive layer 23, the ferroelectric liquid crystal layer 24 and the alignment film layer 2.
The pressure is divided into 5a and 25b. Writing by light is performed by decreasing the resistance of the photoconductive layer in a portion of the photoconductive layer irradiated with the writing light and increasing the electric field divided into the liquid crystal layer.

Here, in order to explain the cause of the sensitivity fluctuation,
The state of potential during operation of the alignment film layer and the ferroelectric liquid crystal layer excluding the transparent electrode and the photoconductive layer is shown in FIG. This is the behavior of the ferroelectric liquid crystal layer as a general electro-writing type display. If no electric field is applied, the whole is equipotential. However, since the liquid crystal molecules are aligned in one stable state in the ferroelectric liquid crystal layer, the direction of spontaneous polarization is constant, and the ferroelectric liquid crystal layer is macroscopically polarized. In the writing state, this is the case where the writing voltage is applied and the writing light is applied, but the potential becomes as shown in FIG. 3-A, and an electric field is applied to the ferroelectric liquid crystal layer to cause spontaneous polarization. Torque is generated by the coupling with and polarization inversion occurs. In this state, if an attempt is made to store the voltage by excluding the voltage, both ends of the alignment film layer will be equipotential to ground, but since the spontaneous polarization of the ferroelectric liquid crystal layer is canceled, the alignment as shown in FIG. A potential difference occurs in the membrane layer. It is generally considered that this is caused by the drift of ions existing in the ferroelectric liquid crystal layer. If this potential difference is very large, a so-called switchback phenomenon may occur in which the ferroelectric liquid crystal molecules are inverted in the opposite direction due to the reverse electric field generated thereby. Further, when the impedance of the alignment film layer is small, the time constant becomes small, and the charges flow without accumulating in a short time.

In the case of the ferroelectric liquid crystal spatial light modulator according to the present invention, a photoconductive layer is added to the structure shown in FIG.
Also, a mirror layer may be formed between the photoconductive layer and the alignment film layer. In this case, in response to the surface charge of the alignment film due to the drift of the ions generated in the ferroelectric liquid crystal layer, the photo-generated layer in the photoconductive layer is formed at the interface between the alignment film layer and the photoconductive layer (or mirror layer). Carriers are trapped. The electric field generated by the trapped charges is considered to be the cause of sensitivity fluctuation. When the writing state is continued, the electric charge accumulated in the interface gradually increases,
The sensitivity is apparently improved from the initial state.

As described above, the impedance of the alignment film layer has an important influence on the sensitivity change characteristic. The manufacturing parameters that control the impedance of the alignment film layer are, of course, the alignment film material (its volume resistance and dielectric constant) and the film thickness, and in the ferroelectric liquid crystal spatial light modulator according to the present invention. Specifies the alignment film material and film thickness that satisfy the necessary requirements.

The relationship between the write parameter and the change in sensitivity, its controllability, saturation and relaxation characteristics will be described later on the basis of actual measurement data. Next, silica spheres having an average particle diameter of 1.0 μm are mixed and dispersed in a peripheral sealing material, the sealing material is applied by printing using a letterpress printing method, and then two substrates are adhered to each other to hold a liquid crystal. A gap was formed. Here, in this example, since the hydrogenated amorphous silicon photoconductive layer having a thickness of 3.0 μm was used, the liquid crystal layer thickness was set to 1.0 μm. However, the liquid crystal layer thickness is the condition of the photoconductive layer and the mirror layer as described above. Since the optimum value fluctuates depending on the value, it is set within the range of 1 to 5 μm.

As the liquid crystal composition 14, a smectic liquid crystal composition SCE-13 manufactured by BDH was used. FIG. 4 is a system diagram of an optical system in which writing and reading experiments were performed. A halogen lamp was used as the writing light source 41, and the wavelength distribution was controlled through the interference filter 42a. The writing light is applied to the liquid crystal spatial light modulator 44 according to the present invention. When writing an image, a mask was placed at 45 in the drawing, and an image was formed on the input surface of the spatial light modulator 44 by the lens 46. The reading light source 47 uses a halogen lamp, and a liquid crystal spatial light modulator 44 according to the present invention passes through a diaphragm 48 for adjusting the amount of light, an interference filter 42b for controlling the wavelength distribution, a polarizer 49, and a beam splitter 50. Is reflected by the interface between the liquid crystal layer and the hydrogenated amorphous silicon photoconductive layer while being modulated by the liquid crystal layer, and then enters the beam splitter 50 again. Here, the light transmitted by the beam splitter surface is detected by the analyzer 51 and observed by the CCD camera 52. Alternatively, a photograph camera is installed at the position of the CCD camera 52 to photograph the read image. The polarizer 49 and the analyzer 51 are arranged in crossed Nicols, and the reading is set to be in the dark state when there is no writing light at the wavelength used. For the observation, the image captured by the CCD 52 was displayed on the CRT. Moreover, the photodetector 53 was installed and the optical response was also measured. The driving was performed using a self-made driver 54.

The light source used for writing is a halogen lamp, He-Ne laser, Ar laser, semiconductor laser, LED, etc., and the light source used for reading light is a halogen lamp, He-Ne laser, Ar laser, semiconductor laser. , LEDs, etc.

It is possible to adjust the sensitivity characteristics by providing a bias light source separately from the writing and reading light sources and applying bias light to the device. Writing experiments were performed using the above system.
FIG. 5 shows the writing light intensity of 2 under the same writing condition.
00 μW / cm ² , 400 μW / cm ² , 600 μW /
6 is a graph showing a change in sensitivity with operating time when the sensitivity is changed to cm ² . The writing conditions are as follows: write light center wavelength 550 nm (half-value width 40 nm), read light wavelength 600 nm (half-value width 40 nm), read light intensity 1
00μW / cm ^2, the driving waveforms in a bipolar pulse, the erase pulse 10V2ms, write pulse -10V1ms, readout period 7 ms, the frequency 100 Hz. The sensitivity was defined as the threshold light sensitivity, which is the writing light intensity that causes complete inversion under standard writing conditions. The data corresponding to each writing light intensity is standardized with an initial value of 1.

As can be seen from FIG. 5, the fluctuation of the sensitivity fluctuates depending on the writing light intensity and is saturated by continuous writing for about 450 seconds at the maximum. In addition to the writing light and the reading light, bias light can be considered as the light to be irradiated in the writing state, and these all act in the same manner as the writing light in FIG. From this, it can be seen that the variation amount of the sensitivity can be controlled by the bias light.

FIG. 6 shows the standard conditions (writing light intensity is 4
The intensity of the erase pulse at 12.00 μW / cm ² is 12.
It is a graph which shows the sensitivity change with operation time when changing to 5V, 10V, and 7.5V. Further, FIG. 7 shows the erase pulse widths of 1.5 ms, 2 ms, and 3 ms under the standard conditions (writing light intensity is 400 μW / cm ² ).
7 is a graph showing a change in sensitivity depending on the operating time when the value is changed.

It can be seen from FIGS. 6 and 7 that the fluctuation amount of the sensitivity can be controlled by the voltage or pulse width of each pulse. Here, with respect to the write pulse, the sensitivity change can be similarly controlled, but since the write pulse must be set within a range in which an image can be written, the control range is very narrow in an actual system.

Similarly, when driving is performed using three continuous pulses, it is possible to control the sensitivity variation by any of the erase pulse, the write pulse, and the third pulse. Here, in the Japanese Patent Application No. 02-239594, the authors have shown a method of expressing continuous gradation in a ferroelectric liquid crystal spatial light modulator by using a rectangular wave on which a DC bias is superimposed. It should be noted that this driving method also has a similar sensitivity variation and is practical. In this driving method, the reading light amount continuously changes according to the writing light amount. Therefore, a clear threshold value for the writing light intensity cannot be defined. However, when the ferroelectric liquid crystal spatial light modulator according to the present invention is used, a DC bias is superposed on the alternating electric field in this driving method, so that the photoconductive layer and the alignment film layer are similar to the case of pulse driving. Accumulation of electric charges occurs at the interface of the, and sensitivity changes. However, the change in sensitivity appears in the form of a shift in the γ characteristic. This means that the sensitivity can be controlled even in analog optical information processing.

From these, it is possible to control the sensitivity fluctuation of the ferroelectric liquid crystal spatial light modulator according to the present invention by using the driving method of the ferroelectric liquid crystal spatial light modulator according to the present invention. I understand.

FIG. 8 is a graph showing the relaxation of the sensitivity fluctuation when the continuous writing is performed for 10 minutes under the standard writing condition and then left without applying the driving voltage, the writing light and the reading light. Even if the sensitivity fluctuation is saturated from the figure,
It can be seen that if it is left without writing for about 10 minutes, it returns to the initial state.

From the above, it was found that in the ferroelectric liquid crystal spatial light modulator according to the present invention, the sensitivity of the written portion changes as the written state continues, and relaxes to the initial state when left standing. This means that when the ferroelectric liquid crystal spatial light modulator according to the present invention is continuously supplied with the write information, the sensitivity changes according to the write information as if the memory of the human being becomes stronger by repeated writing. ,
In addition, if it is left without writing, human memory gradually fades, and it approaches the initial state as if it were forgotten. If this characteristic is applied to an optical neural network, it will function as a memory closer to the function of the human brain.

FIG. 9 is a graph showing a change in sensitivity with operating time when only a driving electric field under standard conditions is applied without applying writing light and reading light. In this case, the saturation occurs relatively quickly and its value (normalized value) is about 0.87. Here, comparing this data with the data in FIG. 5,
It can be seen that the sensitivity change when the writing light intensity is as strong as 600 μW / cm ² is almost the same as the sensitivity change in the dark state. On the other hand, 200μW / cm ² or 400μ
At W / cm ² , a much larger sensitivity change occurs. From these, for example, the ferroelectric liquid crystal spatial light modulator according to the present invention is used as a memory mask of a coupling weight matrix in an optical neurocomputing system, and uniform light of 300 μW / cm ² is applied to the entire surface as bias light,
If the writing light is given as a binary value of 0 or 300 μW / cm ² , it is possible to cause sensitivity variations in the opposite directions between the writing light off and the writing light on. That is, it can be seen that the coupling weight matrix can be updated to either positive or negative.

If this characteristic is applied, the optical system in optical neurocomputing can be remarkably simplified, and it will greatly contribute to its realization.

[0033]

Industrial Applicability By using the present invention, it is possible to increase the range of application of ferroelectric liquid crystal spatial light modulators in optical computing including optical neural networks. Further, in the case of optically realizing the neural network model, when the coupling weight is updated, it is possible to update to positive or negative in one device, and thus the optical system of the optical neurocomputing system can be simplified. Can be realized and its feasibility can be enhanced.

[Brief description of drawings]

FIG. 1 is a schematic view showing a structure of an optical writing type ferroelectric liquid crystal spatial light modulator according to the present invention.

FIG. 2A is a diagram schematically showing a configuration of a ferroelectric liquid crystal spatial light modulator according to the present invention, and 2-B is a diagram showing a corresponding equivalent equivalent circuit. .

FIG. 3 is a diagram showing potential states during operation of an alignment film layer and a ferroelectric liquid crystal layer, excluding a transparent electrode and a photoconductive layer, in order to explain a cause of sensitivity fluctuation of the present invention.

FIG. 4 is a system diagram of an optical system in which the writing and reading experiments of the present invention were performed.

FIG. 5 is a graph showing a change in sensitivity with operating time when the writing light intensity is changed under the same writing condition of the present invention.

FIG. 6 is a graph showing a change in sensitivity with operating time when the voltage of the erase pulse is changed under the standard conditions of the present invention.

FIG. 7 is a graph showing a change in sensitivity with operating time when the pulse width of an erase pulse is changed under the standard conditions of the present invention.

FIG. 8 is a graph showing the relaxation of sensitivity fluctuations when a continuous write is performed for 10 minutes under the standard write condition of the present invention and then left without applying a drive voltage, write light and read light.

FIG. 9 is a graph showing a change in sensitivity with operating time when only a driving electric field under standard conditions is applied without applying writing light and reading light according to the present invention.

[Explanation of symbols]

 11a, 11b Transparent substrate 12a, 12b Transparent electrode 13a, 13b Alignment film layer 14 Liquid crystal layer 15 Photoconductive layer 21a, 21b Substrate 22a, 22b Transparent electrode 23 Photoconductive layer 24 Ferroelectric liquid crystal layer 25a, 25b Alignment film layer 41 Writing Light source 42a, 42b Interference filter 44 Ferroelectric liquid crystal spatial light modulator 45 Mask 46 Lens 47 Readout light source 48 Aperture 49 Polarizer 50 Beam splitter 51 Analyzer 52 CCD camera 53 Photodetector 54 Driver

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Rieko Sekura 6-31-1, Kameido, Koto-ku, Tokyo Seiko Electronics Co., Ltd. (72) Nobuyuki Kasama 6-31-1, Kameido, Koto-ku, Tokyo No. Seiko Electronics Industry Co., Ltd.

Claims (13)

[Claims] 1. A glass substrate on which a photoconductive film is formed on a transparent electrode and a glass substrate on which a transparent electrode is formed, each of which is provided with a light writing device, a light reading device, and a voltage applying device. In a liquid crystal spatial light modulator in which a pair of glass substrates having a liquid crystal alignment film formed on the surface thereof are arranged to face each other, and a liquid crystal composition is sealed in the gap,
The liquid crystal composition is a liquid crystal composition exhibiting a chiral smectic phase at room temperature, the liquid crystal alignment film has a film thickness of 200 angstroms or more, and the liquid crystal spatial light modulator changes sensitivity due to continuation of a writing state. , A spatial light modulator characterized in that fluctuations in sensitivity are alleviated over time in a non-written state. 2. The liquid crystal alignment film is formed by performing vacuum deposition or sputtering from a direction in which a dielectric is inclined from the normal line direction of the substrate.
The liquid crystal spatial light modulator described. 3. The liquid crystal spatial light modulator according to claim 1, wherein
The liquid crystal spatial light modulator according to claim 1, wherein the liquid crystal alignment film is formed by rubbing a polymer film. 4. The voltage applying means continuously and repeatedly outputs a driving voltage consisting of a pulse voltage of single-pole bipolar or three continuous pulse and a rest period, and independently outputs a voltage and a pulse width for each pulse. A method for driving a liquid crystal spatial light modulator, characterized in that the liquid crystal spatial light modulator is controlled by controlling the light quantity. 5. The write side of the spatial light modulator is biased to the read side separately from the writing means by the light or the reading means by the light in order to control the sensitivity variation of the liquid crystal spatial light modulator. 5. The method for driving a liquid crystal spatial light modulator according to claim 4, further comprising means for irradiating light, and controlling the light quantity of the bias light to control the fluctuation amount of the sensitivity. 6. The voltage applying means continuously and repeatedly outputs a continuous bipolar pulse voltage and a driving voltage composed of a rest period to control the voltage and pulse width of the second pulse,
6. The method for driving a liquid crystal spatial light modulator according to claim 5, wherein the variation amount of sensitivity is controlled by this. 7. The voltage applying means continuously and repeatedly outputs a driving voltage composed of three consecutive pulse voltages and a rest period, and controls the voltage and pulse width of the second pulse, thereby The method for driving a liquid crystal spatial light modulator according to claim 5, wherein the amount of fluctuation in sensitivity is controlled. 8. The voltage applying means continuously and repeatedly outputs a driving voltage consisting of three consecutive pulse voltages and a rest period, and controls the voltage and pulse width of the third pulse, thereby The method for driving a liquid crystal spatial light modulator according to claim 5, wherein the amount of fluctuation in sensitivity is controlled. 9. The voltage applying means outputs an alternating electric field on which a DC bias is superimposed, and the frequency of the alternating electric field controls the DC bias voltage, thereby controlling the variation amount of the sensitivity. Driving method for liquid crystal spatial light modulator. 10. The liquid crystal spatial light modulator is controlled by a write side of the spatial light modulator biased to the read side, separately from the light writing means or the light reading means, in order to control the sensitivity variation amount. 10. The method for driving a liquid crystal spatial light modulator according to claim 9, further comprising: a means for irradiating light, and controlling the light quantity of the bias light to control the fluctuation amount of the sensitivity. 11. The liquid crystal alignment film comprises silicon oxide containing silicon monoxide and silicon dioxide, an oxide such as titanium oxide, zirconium oxide, tantalum oxide, germanium oxide or aluminum oxide, or a fluoride such as magnesium fluoride, or 3. The liquid crystal spatial light modulator according to claim 2, wherein any one of a plurality of these mixtures is obliquely vapor-deposited by resistance heating or electron beam heating in vacuum. 12. The liquid crystal alignment film comprises silicon oxide containing silicon monoxide and silicon dioxide, an oxide such as titanium oxide, zirconium oxide, tantalum oxide, germanium oxide or aluminum oxide, or a fluoride such as magnesium fluoride, or The liquid crystal spatial light modulator according to claim 2, wherein any one of a plurality of these mixtures is obliquely vapor-deposited by ion-assisted vapor deposition. 13. The liquid crystal alignment film comprises silicon oxide containing silicon monoxide and silicon dioxide, titanium oxide, zirconium oxide, tantalum oxide, germanium oxide, aluminum oxide or a fluoride such as magnesium fluoride, or any of these. 3. The liquid crystal spatial light modulator according to claim 2, wherein the plurality of mixtures are formed by oblique sputtering.