JPH0451018A - Spatial optical modulator - Google Patents

Abstract

PURPOSE:To perform image processing with an optional gray scale and to shorten a convergence time by causing a lamp drop of a voltage, which is applied to the back electrode of an electrooptic crystal plate in threshold mode, at the time of writing operation and controlling the lamp drop speed according to input/output characteristics. CONSTITUTION:In the threshold mode wherein a lock-out area is used for the setting of the voltage applied to the crystal back electrode at the time of writing to the secondary electron collecting electrode 5 of an electrooptic crystal plate 6, the voltage applied to the back electrode of the electrooptic crystal plate 6 is made to lamp dropped where the lamp drop speed is controlled by a controller 16 etc., according to the input/output characteristics of the spatial optical modulator to be found. Therefore, the input/output characteristics in hard clip mode can be selected optionally without making operation astable. Consequently, the image processing is performed with an optional gray scale and an input/ output function is set to shorten the convergence time.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an electron tube that converts incoherent light into coherent light, and relates to a spatial light modulation device used in coherent parallel optical information processing and the like.

[Conventional technology]

In a conventional spatial light modulator, its input/output characteristics are determined by setting the back voltage at which the crystal surface potential becomes a negative voltage when writing an optical image, and selecting the speed at which the crystal surface potential of the electro-optic crystal drops by a threshold operating point. This can be changed by selecting the hard clip mode, which sets the voltage applied to the back electrode so that the crystal surface voltage does not become a negative voltage (hereinafter referred to as back voltage), and the normal mode, which lowers the crystal surface potential drop in a step function manner. It was hot. Therefore, in the conventional spatial light modulator, the input/output characteristic (γ
Characteristics) have two types of γ: linear in normal mode (sin2 characteristic) and B value in hard clip mode.
Only values could be selected. Further, in the spatial light modulation device, in the input/output characteristic variable device that selects the voltage of the secondary electron collecting electrode in the hard clip mode according to the desired input/output characteristics, the voltage VC applied to the secondary electron collecting electrode is selected. must be changed, and the crystal back voltage Vb of the electro-optic crystal must be changed accordingly. In order to obtain equivalent operation, the value of Vc must be decreased.

[Problem to be solved by the invention]

In the conventional spatial light modulation device, only two types of γ values can be selected as described above, so there is a problem that image processing cannot be performed with an arbitrary gray scale. In addition, when trying to use a spatial light modulator as a unit of a neural network, there is a problem that it is not easy to adjust the convergence time until the network becomes stable because the selection range of input/output characteristics is small as described above. There was a point. In addition, as mentioned above, when equipped with an input pressure characteristic variable device,
Reducing Vc in order to obtain threshold operation corresponds to decreasing the sensitivity of the spatial light modulation tube, which poses the problem of unstable operation. This invention was made in view of the above-mentioned conventional problems, and it is possible to arbitrarily select the input/output characteristics in hard rip mode without making the operation unstable, and therefore it is stable at any gray scale. An object of the present invention is to provide a spatial light modulation device that can perform image processing using a neural network and shorten the convergence time in a neural network. [Means for Solving the Problems] The present invention includes an electron image generating means and an electro-optic crystal plate, and a secondary electron collecting electrode is provided between the electron image generating means and an electro-optic crystal plate so as not to interfere with the formation of a charge image on the electro-optic crystal plate. a spatial light modulator,
In a threshold mode in which a lockout region is used to set the voltage applied to the back electrode of the crystal during writing to the secondary electron collecting electrode of the electro-optic crystal plate, the voltage applied to the back electrode of the electro-optic crystal plate is set during the write operation. The above object is achieved by having a control device that lowers the ramp and controls the ramp lowering speed in accordance with the input/output characteristics required by the spatial light modulator.

[Action and effect]

In this invention, the back voltage of the electro-optic crystal plate is changed in a ramp-like manner in the threshold mode of the spatial light modulator, and the writing time is controlled according to the input/output characteristics required by the spatial light modulator. Therefore, the input/output characteristics in hard clip mode can be arbitrarily selected without making the operation unstable. Therefore, image processing can be performed at any gray scale, and when used in a neural network, By setting input/output functions suitable for the system, it has the excellent effect of shortening the convergence time.

【Example】

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining the configuration and operation of the spatial light modulator W110 according to the present invention, where 1 is an input image, 2 is a lens, and 3
is the photocathode, 4 is the microchannel plate, 5 is 2
Mesh electrode for collecting secondary electrons, 6 is an electro-optic crystal plate, 6A
is a surface having a charge storage function and a secondary electron emission function, 7
The half mirror 8 is a continuous beam of light whose polarization direction is not random (the polarization direction is adjusted to linear, circular, or elliptically polarized light),
9 is an analyzer, 1A is an output image, and IOA is a spatial light modulator. A variable ND filter 12 is provided between the lens 2 and the photocathode 3 in the spatial light modulator 10 shown in FIG.
is provided, and the voltage of the mesh electrode 5 is changed, and the electro-optic crystal plate 6 is changed according to the voltage change of the mesh electrode 5.
A voltage supply means (control device) 14 is provided for changing the back voltage Vb of the sensor and changing the back voltage Vb in a ramp-like manner. The ramp time of the back voltage Vb by the voltage supply means 14 is:
The ramp time controller 16 adjusts the desired input cuff M into the ramp time controller 16. The variable ND filter 12 is an ND filter 12A.
is driven by the motor 12B via the gear 12C, and the rotation angle of the motor 12B at this time is adjusted by the motor rotation surface controller 12D, so that the light input intensity incident on the optical N cathode 3 can be adjusted as shown in FIG. In this way, the input/output characteristic curves are aligned. In the figure, an input image 1 projected onto a photocathode 3 of a spatial light modulator 10A through a lens 2 is converted into a photoelectron image. After this photoelectron image is multiplied by the microchannel plate 4, a charge pattern is formed on the surface 6A of the electro-optic crystal plate 6. The electro-optic crystal plate 6
The electric field across the crystal changes, and the refractive index of the electro-optic crystal plate 6 changes due to the Pockels effect. A voltage VC is applied to the mesh electrode 5 for collecting secondary electrons, and a crystal back surface voltage Vb is applied to the back surface of the electro-optic crystal plate 6 from the voltage supply means 14, respectively. Here, when the electro-optic crystal plate 6 is uniformly irradiated with the linearly polarized readout light 8, the polarization state of the reflected light from the surface 6A changes due to the birefringence of the electro-optic crystal plate 6, so that
When the light passes through the analyzer 9, an output image 1A having a light intensity corresponding to the light intensity of the input image 1 is obtained. Next, the main functions of the spatial light modulator 10 related to the present invention will be explained. The spatial light modulator 10A can selectively form a positive or negative charge distribution on the surface 68 of the electro-optic crystal plate 6. FIG. 2 is a graph showing the secondary electron emission characteristics of the electro-optic crystal plate 6. Here, an electrode (conductive surface) is formed on the back surface of the electro-optic crystal plate 6 opposite to the surface 6A, and a negative voltage Vb can be applied thereto. As shown in the figure, if the primary electron energy E incident on the surface 6A is smaller than the first crossover point E1 or larger than the second crossover point E2, the number of primary electrons is emitted at the crystal surface. Since the number of secondary electrons is larger than the number of secondary electrons (δ×1), the crystal surface 6A is negatively charged. When the energy of the primary electrons is between El and El, the number of secondary electrons is greater than the number of primary electrons (δ>1), so the crystal surface 6A is positively charged. When accumulating charges in the electro-optic crystal plate 6, whether to write with positive charges or negative charges is carried out by controlling the mesh potential Vc and crystal back voltage Vb shown in FIG. Ru. The writing and erasing methods are well known, and will be explained using a positive charge image as an example with reference to FIGS. 2 and 3. Note that the first crossover point E1 is determined by the physical properties of the surface 6A of the electro-optic crystal plate 6, and the voltage Vc applied to the secondary electron collecting mesh electrode 5 is determined by the second crossover point E2. When the crystal back voltage Vb is set higher than the potential corresponding to the second crossover point E2, the crystal surface potential Vs at the surface 6A becomes secondary electron emission ratio δ×1 because the energy of the incident primary electron is 82 or more. , the surface potential is El
Negative charge is accumulated until . When the potential reaches El, δ=1, an equilibrium state is reached, and the charge on the surface 6A becomes zero. Bring the crystal back voltage Vb to the first crossover point E. If the voltage E' is set to a value that provides a sufficient dynamic range between E1 and the second crossover point E2, the crystal surface potential Vs will also be approximately E', so the energy of the incident primary electron will be equal to the energy of El and El. It is between. Therefore, since the secondary electron emission ratio δ>1, a positive charge image is formed. When the potential reaches El, it becomes δ-1 and becomes an equilibrium state, and the charge on the surface 6A becomes zero. The emitted secondary electron is Vs
The secondary electrons are collected by the secondary electron collecting electrode, which is at a higher potential Vc. Next, the real-time threshold operation function (hard clip operation) will be explained. The spatial light modulator 10A can perform real-time threshold operation according to the setting conditions of Vc and crystal backside voltage shown in FIG. The mesh electrode 5 is provided near the crystal surface, and when it is set to a predetermined potential, the crystal surface potential Vs
becomes the potential Vc of the mesh electrode 5, and this potential becomes the second crossover point E2. That is, the crystal surface potential Vs is higher than the mesh electrode 5 (
In the case of VbE (erasure), the potential of the crystal surface decreases because the number of secondary electrons emitted from the crystal surface is smaller than the incident electrons, and conversely, the crystal surface potential Vs is lower than the mesh electrode potential Vc. In the case of FIG. VbW: writing), the number of secondary electrons exceeds the incident electrons, and the crystal surface potential Vs rises. Eventually, when the crystal surface potential VS becomes equal to the mesh electrode potential Vc, the potential becomes constant. That is, when there is a sufficient amount of incident light, the mesh potential Vc and the crystal surface potential Vb are always the same potential. Regarding the voltage setting of Vc, the relative voltage between Vc and Vb is due to the birefringence caused by the thickness of the electro-optic crystal plate 6 (that is, the relative relationship between the voltages of Vbw to VbE and the voltage of Vc is (depending on the thickness of the optical crystal plate 6), use something like a phase compensation tube to apply a constant voltage of 1, for example, Vc = 1.1.
(KV>, Vb=1.0~2.7 (KV)(: I
I value mode), the surface 6A of the electro-optic crystal 6 becomes a negative potential (-0.6 KV) as shown in FIG. 3, and electrons no longer reach it (lockout state). However, when V is slowly lowered by the voltage supply means 14, electrons are supplied to the crystal surface in areas where the intensity of the incident light is high and a large amount of electrons are supplied, increasing secondary electron emission. In areas where the potential is not negative, the intensity of the incident light is low, and the amount of supplied electrons is small, the supply of electrons cannot keep up with the lower potential, and therefore the crystal surface becomes a negative potential and electrons are transferred to the crystal surface. It will not reach you. Therefore, in response to the intensity of light incident on the photocathode 3, there are areas where the crystal surface becomes negative potential and no writing is performed, and areas where electrons reach the crystal surface and writing is performed without the surface becoming negative potential. As a result, a threshold operation is performed depending on the intensity of the incident light. For example, as shown in FIG. 4, only the areas where enough electrons can be supplied to allow the movement of the surface voltage Vs of the electro-optic crystal plate 6 (>) to follow the rate of fall (→ direction) of the back voltage Vb of the crystal It enters the writing state. In other words, the input light intensity that can be written (more than that can be written, less than that cannot be written) can be determined by the rate of fall of the crystal back surface voltage Vb. A variable7 mode (variable γ mode) can be obtained by changing the value of Vc in the hard clip mode. For example, assuming the unit is KV, the voltage supply device 14 calculates: (1) Vc=1. I Vb-1.0~2.7■Vc-0
,6Vb-0,5~2.2 ■Vc=0.3 Vb=0.2~1.9■Vc=0
．． 1 When Vc is varied and Vb is ramped down at the same time as Vb-0 to 1.7, and the rate of decline is set constant, multiple characteristic curves with different γ (with large γ) as shown in Figure 5 are created. (the slope is smaller) is obtained. However, as mentioned above, as Vc is changed, V
b must be changed accordingly, and in order to obtain threshold operation, Vc must be decreased, which corresponds to decreasing the sensitivity of the spatial light modulator 10A, and the operation may become unstable. It becomes stable. Here, for example, VC-1.0, V = 0.9 to 2°9 (kilovolt K V ) V b ramp writing time TH
When W is set to 38, the input/output characteristics have a value close to γ=2 in the normal mode, as shown in FIG. As shown in FIG. 6, as the write time Tow is increased, the input/output characteristics gradually change to a threshold value operation. At this time, the set voltages of V c and V b are fixed. That is, as mentioned above, the input/output characteristics shift to the left as the threshold value operation is reached, so when trying to obtain the input/output characteristics as shown in FIG. 7, for example, the variable ND filter 12 in FIG. 1 must be operated. to adjust the intensity of light input to the spatial light modulator 10A. Alternatively, the voltage applied to the microchannel plate 4 may be adjusted. Correspondingly, the ramp time controller 16 adjusts the ramp time of Vb according to the desired γ value. Therefore, in this case, the input/output characteristics can be arbitrarily changed in the hard clip mode without reducing Vc and Vb, that is, without making the operation unstable. More specifically, compared to the aforementioned variable γ in the Vc control mode, the direction from the value of γ = 2 to the threshold operation is the direction of increasing the writing time Tow, and this is due to the spatial light modulation. This is equivalent to increasing the sensitivity of the device 10A, and the light intensity of the reading light source can be lower than in the VC control mode, so the system operation becomes stable. As described above, by varying the input/output characteristic γ of the spatial light modulator 10, halftone processing becomes possible. That is, image processing at arbitrary gray scale, image processing that changes γ, function conversion in linear operation, and linear operation,
Nonlinear operations become possible. Moreover, the spatial light modulator 10 can be used as a unit of a neutral network. The convergence time can be shortened by changing the slope of the input/output characteristics of the unit (spatial light modulator) until the network becomes stable and setting an input/output function suitable for the system.

[Brief explanation of drawings]

FIG. 1 shows the spatial luminous intensity Wj! according to the present invention. A schematic cross-sectional view showing an embodiment of the device, and FIG. 2 is a diagram showing the relationship between the primary electron energy E incident on the surface of the electro-optic crystal plate and the secondary electron emission ratio in the spatial light modulation device. Fig. 3 is a block diagram showing the relationship between erasing and writing in the spatial light modulator, and Fig. 4 shows the movement of the back voltage of the electro-optic crystal plate during ramping and the crystal surface voltage of the spatial light modulator and the writing. A diagram showing the relationship; FIG. 5 is a diagram showing the input/output characteristics in the variable T mode; FIG. 6 is a diagram showing the input/output characteristics of the spatial light modulator in the write time control mode;
FIG. 7 is a diagram showing the input/output characteristics in the above embodiment. 3...Charging cathode, 4...Micro channel plate (MCP), 5...
...Mesh electrode (secondary electron collecting electrode), 6...Electro-optic crystal plate, 6A...Surface, 10...Spatial luminosity m device, 10A...Spatial light modulator, 12... Variable NO filter 14... Voltage supply means. Figure 1

Claims (1)

[Claims] (1) A spatial light modulator comprising an electron image generating means and an electro-optic crystal plate, with a secondary electron collecting electrode placed between them so as not to interfere with the formation of a charge image on the electro-optic crystal plate; In a threshold mode in which a lockout region is used to set the voltage applied to the back electrode of the crystal during writing to the secondary electron collecting electrode of the electro-optic crystal plate, the voltage applied to the back electrode of the electro-optic crystal plate is set during the writing operation. A spatial light modulator comprising: a control device for lowering a ramp and controlling the ramp lowering speed according to input/output characteristics determined by the spatial light modulator.