JPH03264918A - Reflection type phase modulating element and optical information processor - Google Patents

Abstract

PURPOSE:To allow the control of the refractive index of each picture element by the voltages which switching elements impress to a liquid crystal layer by forming a 1st oriented film and a 2nd oriented film in such a manner that the respective orientation directions are approximately paralleled with each other. CONSTITUTION:The voltages are impressed to the liquid crystal layer 208 by plural pieces of the switching elements 202 formed on a substrate 201, by which the refractive index of the liquid crystal molecules of each picture element is controlled and, therefore, the number of the picture elements constituting the liquid crystal 208 is effectively utilized. Since this element is of a reflection type, the phases of the incident light are modulated by double paths and, therefore, the modulation of the phases is larger than a transmission type and the phase modulation with the good efficiency of light utilization is executed. The phases of the incident light are modulated by controlling the refractive index of the liquid crystals of each picture element in such a manner and, therefore, the phase modulation with the good utilization efficiency of the picture elements is executed.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a spatial light modulation element used in optical information processing, particularly a reflective phase modulation element that spatially modulates the phase of incident light and reflects it. be.

The present invention also provides filtering in the spatial frequency domain of human-powered images in visual devices such as industrial robots.
The present invention relates to an optical information processing device that performs image processing such as feature extraction, or identifies patterns that match a specific standard pattern from a plurality of input patterns.

10 to 1, the configuration of an optical information processing device previously proposed by the present inventors (Japanese Patent Application No. 1987-287016) is explained below.
This will be explained using FIG. 3, and FIG. 10 shows the configuration of the above-mentioned optical information processing device, in which 20 is a television camera (hereinafter referred to as TV camera), and 21 is an image captured by the TV camera 20. 22 is a semiconductor laser beam 23 is a collimator lens that collimates the light from the semiconductor laser 22, and 24 is a first lens. A second TN type liquid crystal display 25 is disposed on the focal plane on the light source side of the first lens 24 (hereinafter referred to as the front focal plane).
The lens 26 is arranged on the focal plane opposite to the light source (hereinafter referred to as the back focal plane) of the lens 24. The lens 26 uses each pixel on the second TN liquid crystal display as a sampling point for a plurality of standard patterns. A read-only memory (hereinafter referred to as R) is written with the data of the Fourier transform computer hologram calculated in advance, that is, the data of the applied voltage corresponding to the transmittance of each pixel of the second TN liquid crystal display 25.
(referred to as OM), 27 is a second lens, and a second TN type liquid crystal display 25 is arranged on its front focal plane, and 28 is a photoelectric converter arranged on the back focal plane of the second lens 27. As for the apparatus, FIG. 11C shows the configuration of the second TN type liquid crystal display 25 for displaying a computer generated hologram in FIG.

121 is a polarizer, 122 is a first glass substrate 123 is a pixel type, 14 and 124 are drive TPT (Thin
It is connected to the gate and drain of the film transistor. 125 is the first alignment [126 is the second alignment film 127 is the liquid crystal disposed between the first alignment film 125 and the second alignment film 126] 128 is the counter electrode K 129 is the black matrix input 130 is the liquid crystal disposed between the first alignment film 125 and the second alignment film 126 The second glass substrate 131 represents an analyzer, as shown in FIG. 12. This second TN type liquid crystal display 25
This shows the liquid crystal alignment state in the absence of an electric field.

132 indicates the liquid crystal molecules in the liquid crystal layer 127.
90° from the alignment film 125 to the second alignment film 126
It is twisted and oriented. On the other hand, the transmission axis of the polarizer 121 (
Even if the transmission axis of the analyzer 131 is arranged so as to substantially match the alignment direction of the first alignment film 125 and to be substantially orthogonal to the alignment direction of the second alignment film 126,
The TN type liquid crystal display 25 is a twisted nematic type liquid crystal device. Fig. 13 shows a computer generated hologram image displayed on a part of the second liquid crystal display 25, which is a transmission type amplitude modulation element.

151 is one picture element on the second liquid crystal display 25, and 152 indicated by a bold line is a cell consisting of several picture elements 151, even though they correspond one-to-one to the sampling points of the standard pattern. ΔP is a group of picture elements 151a to 151d that transmit selected light from the center C of one cell 152.
It represents the amount of offset up to.

Next, the operation of the conventional optical information processing device configured as described above will be explained below using FIGS. 10 to 13. In FIG. The pattern of the target object is the collimator lens 23.
Even if the first TN type liquid crystal display 21 is irradiated with coherent light from the semiconductor laser 22 which is parallelized by the ! Y Since it is arranged on the front focal plane of the first lens 24, the image of the object to be measured is optically converted by the first lens 24, which is the rear focal plane of the first lens 24. A Fourier transformed image of the object to be measured is formed on the display 25. At this time, the data written in the U ROM 26 becomes an input signal to the second TN type liquid crystal display 25, and the T and F T shown in Figure il1 are input.
Although a Fourier transform image of a standard pattern is formed by applying a gate-source voltage of 124, liquid crystal molecules change from the first alignment film 125 to the second alignment in the absence of an electric field (as shown in FIG. 12). It is oriented with a 90° twist toward the membrane 126.

-X In FIG. 11, the transmission axis of the polarizer 121 is set so that it approximately coincides with the orientation direction of the first orientation M125, and the transmission axis C of the analyzer 131 is set approximately orthogonal to the orientation direction of the second orientation film 126. Therefore, the linearly polarized light transmitted through the polarizer 121 is twisted by the liquid crystal which is twisted and oriented by 90" so that the polarization direction of the linearly polarized light is twisted in a direction approximately perpendicular to the transmission axis of the analyzer 131. As a result, the emitted light is However, when the data written in the ROM 26 becomes an input signal and the voltage between the gate and source of the TFT 124 is applied, the twist angle of the liquid crystal molecules is canceled according to the applied voltage, and the amount of emitted light increases. In order to modulate the phase component of the incident light (as shown in FIG.
This is possible by selecting the position of d and by controlling the transmittance of the selected pixel group by the gate-source voltage of i:LTFT124 in order to modulate the amplitude component of the incident light. The second liquid crystal display 25 can be used as a display medium for computer generated holograms, and can perform optical information processing such as pattern matching. Problems to be Solved by the Invention As described above, in the case of conventional transmissive amplitude modulation elements, the phase component of incident light is modulated by changing the spatial position of the picture element group that transmits the light. Also
Therefore, the cell corresponding to one sampling point must be composed of a plurality of picture elements. Therefore, the number of picture elements constituting one cell is set to mxn. On the other hand, the number of picture elements constituting the second liquid crystal display 25 is Assuming MXN pieces,
Only (M/m) x (N/n) sampling images can be handled. In other words, the board has the disadvantage of low efficiency in using the number of picture elements.

Furthermore, as shown in FIG. 11, in the conventional transmissive amplitude modulation element, there is a black matrix 129 for blocking light from T F T 124. Therefore, the aperture ratio of one picture element 151, that is, the light utilization efficiency within one picture element Although the present invention has the disadvantage of low amplitude modulation, the present invention is capable of producing a TN-type liquid crystal display, which is a conventional transmissive amplitude modulation element, by using a reflection type phase modulation element that uses active matrix liquid crystal and modulates the phase of input light. A means for solving the problem is aimed at improving the disadvantages of the optical information processing device using the same, such as the low utilization efficiency of the number of picture elements and the low efficiency of light utilization within one picture element. In order to solve the above problems, the present invention has a configuration in which a liquid crystal layer is filled between a substrate and a transparent substrate, and a switching element is installed on the surface of the substrate on the liquid crystal layer side. A reflective screen and a first alignment film are provided, and a transparent electrode and a second alignment film are provided on the transparent substrate.The alignment directions of the two alignment films are made to be approximately parallel to each other, and the switching element is a liquid crystal. A reflective phase modulation element is provided in which the refractive index of each picture element is controlled by a voltage applied to a layer.

The method of the present invention also provides an optical information processing device characterized in that a phase-type computer generated hologram or a phase filter is displayed by spatially modulating the phase of light incident on the above-mentioned reflective phase modulation element.

Function The reflective phase modulation element of the present invention controls the refractive index of liquid crystal molecules for each picture element by applying voltage to the liquid crystal layer using a plurality of switching elements formed on the substrate, so it is different from conventional picture elements. Compared to the method of modulating the phase by selecting a group and changing the position of the window that transmits the light, it is possible to use the number of picture elements that make up the liquid crystal more effectively.Also, since it is a reflective type, the phase of the incident light is double-passed. Since it is modulated by
The phase modulation is larger than that of the transmission type, and phase modulation with high light utilization efficiency can be performed.

In addition, the optical information processing device of the present invention (above) displays a phase-type computer hologram (kinoform) or a phase filter on the above-mentioned reflective phase modulation element, and by using this, the number of picture elements constituting the liquid crystal can be effectively utilized, EMBODIMENT OF THE INVENTION An embodiment of the reflective phase modulation element of the present invention will be described with reference to the drawings.

FIG. 1 shows a cross section of the same embodiment.

In the figure, 201 is a TFT, and 202 is a source which is a driving switching element provided for each picture element.
A TFT consisting of a gate and a drain, 203 is a TFT
Conductive to supply current to T 202! 204 is a reflection Fj formed on the conductive film 203; 205 is a first orientation WL formed on the reflection layer 204; 206 is a transparent counter electrode 207 is a second orientation formed on the transparent counter electrode 206; First alignment film 205 and second alignment film 20
A liquid crystal layer 209 disposed between 7 represents a glass substrate. Furthermore, even if the alignment direction of the first alignment film 205 and the alignment direction of the second alignment film 207 are configured to be substantially the same, as shown in FIG. In this example, the first alignment film 205
Since the orientation directions of the second orientation M2O7 and the second orientation M2O7 are substantially the same, no twist occurs in the liquid crystal molecules (1. shows the relationship between the polarization direction of the incident light and the polarization direction of the incident light.

FIG. 3 shows the alignment state of liquid crystal molecules when there is no electric field in the liquid crystal layer 208. The arrow xX indicates the direction of linearly polarized light incident on the liquid crystal layer 208. As shown in the figure, the polarization direction of this incident light is approximately coincident with the long molecular axis of the liquid crystal molecules in the absence of an electric field. Even if the signal voltage is set in the direction of It is tilted by θ in the XZ plane with respect to the polarization direction XX.

When the applied voltage is further increased, the liquid crystal molecules become parallel to the incident optical axis ZZ, as shown in FIG.

The relationship between the tilt of the liquid crystal molecules with respect to the incident optical axis, that is, the applied voltage and the refractive index of the liquid crystal layer 208 will be explained using FIGS. 3 to 7.

FIG. 6 shows the index ellipsoid of liquid crystal molecules.

As is well known, liquid crystal is a substance that has birefringence, that is, refractive index anisotropy, and the axis showing the refractive index nE for extraordinary light coincides with the long molecular axis of the liquid crystal molecule, and the refractive index no for ordinary light
Therefore, in the no-electric field state shown in FIG. 3, the polarization direction of the incident light coincides with the direction of the long molecular axis of the liquid crystal molecule, so the refraction of the liquid crystal layer 208 The index indicates the refractive index nε for extraordinary light.

Furthermore, when the long molecular axis of the liquid crystal molecules becomes parallel to the incident optical axis ZZ as shown in FIG. Indicates no.

On the other hand, the refractive index when the liquid crystal molecules are tilted or in an intermediate state as shown in Fig. 4 is explained using Fig. 7. Fig. 7 shows a refractive index ellipsoid cut along a plane perpendicular to the incident optical axis. The cut plane of the case is shown. The fact that the liquid crystal molecules are tilted with respect to the incident optical axis is equivalent to the fact that the cut plane of the refractive index ellipsoid is tilted, as shown in the same figure.
The refractive index at this time is expressed as n (no<n<nt), and as described above, the incident optical axis of the liquid crystal molecules is The inclination with respect to ZZ changes, and as a result, the refractive index n of the liquid crystal layer 208 for incident light having linear polarization properties
The force changes up to (no=nE. Therefore, the light incident on the reflective phase modulation element passes through the 2nd pass (d is the liquid crystal layer 2).
The reflective phase modulation element of the present invention can also receive phase modulation with a thickness of 0.08 mm! Phase information is not expressed by the spatial position of a selected group of picture elements, but by directly controlling the refractive index of each picture element with the voltage applied to the liquid crystal layer.Also, there is a T for controlling the applied voltage. Since it has a reflective structure in which the F T 202 is placed under the reflective layer 205, there is no need for a black matrix, and the aperture ratio of one picture element is high.As a result, compared to conventional transmissive amplitude modulation elements, , it is possible to improve the light utilization efficiency within one picture element of the spatial light modulation element and the utilization efficiency of the number of picture elements.
This figure shows the configuration of the first embodiment of the optical information processing device of the present invention using the above-mentioned reflective phase modulation element.
An input display liquid crystal display that displays an image captured by a camera 301; 303 is a semiconductor laser;
04 is a collimator lens X that collimates the laser light emitted from this semiconductor laser 303. 305 is a first lens whose focal plane on the light source side is the surface where the input display liquid crystal display 302 is located (hereinafter referred to as the front focal plane). Ren, ;(
Reference numeral 306 denotes the above-mentioned reflective phase modulation element, which is disposed on the focal plane of the first lens 305 opposite to the light source (hereinafter referred to as the back focal plane).
The reflective phase modulating element 306 is a beam splitter placed in the optical path between the beam splitter 307 and the first lens 30.
A lens 308 is a second lens located at the rear focal plane of the first lens 305. A lens 308 is a second lens located at the rear focal plane of the first lens 305.
The CCD element disposed on the rear focal plane and 310 indicate a ROM that stores a phase-type computer-generated hologram (kinoform) of a standard pattern calculated in advance to be displayed on the reflection-type phase modulation element 306. The operation of the constructed optical information processing apparatus of the present invention will be explained using FIGS. 1 to 8.

The pattern of the target object displayed on the liquid crystal display 302 for human power display is irradiated with coherent light from the semiconductor laser 303 that is collimated by the collimator lens 304. Since it is placed in the focal plane, the image of the object to be measured is optically converted by the first lens 305.The reflective phase modulator is located in the back focal plane of the first lens 305 and on the transmission side of the beam splitter 307. A Fourier transform image is formed on element 306. At this time,
When the data written in the ROM 310 becomes an input signal and the transmittance of each picture element of the reflective phase modulation element 306 is spatially transformed, the reflective phase modulation element 306 receives the Fourier transform image power of the standard pattern\Fourier transform The light incident on the reflective phase modulation element 306 is displayed in the form of a phase computer generated hologram. A phase type computer hologram (Kinohome) stored in the ROM 310 is displayed at 306, and a Fourier transformed image obtained by optically converting the pattern of the target object displayed on the input display liquid crystal display 302 by the first lens 305, and a standard pattern. The Fourier transform image of is superimposed on the reflective phase modulation element 306.
, and reflective phase modulation element 3061; L second
A beam splitter 307 is placed on the front focal plane of the lens 308.
of the target object because it is placed through the reflective surface of the!
Even if the optical product of the two Fourier transform images of the pattern and the standard pattern is inversely Fourier transformed by the second lens 308, if the Fourier transform images of the target object pattern and the standard pattern on the reflective phase modulation element 306 match In other words, when both objects are the same object, a bright spot is generated on the back focal plane of the second lens 308. Although it is possible to realize an optical information processing device in which an optical filter based on a hologram acts as a matched filter and performs optical correlation processing, in this embodiment, a reflection type phase modulation element 306 is used as a spatial light modulation element for displaying a phase type computer generated hologram. Since phase modulation is performed not by selecting the spatial position of a group of picture elements, but by applying a voltage to the liquid crystal layer and directly controlling the refractive index of each picture element. Since it has a reflective structure in which the TFT 202 for voltage control is placed under the reflective layer 205, there is no need for a black matrix, and the aperture ratio of each pixel is increased.As a result, compared to conventional transmissive amplitude modulation elements, The configuration of a second embodiment of the optical information processing device of the present invention is shown in FIG. 9. show.

401 is a semiconductor laser, 402 is a collimator lens X403 that converts the light from the semiconductor laser 401 into parallel light, the human-powered graphic display medium 404 is a reflective phase modulation element having the configuration shown in FIG. 1, 405 is a beam splitter, and 406 is a lens. , 407 is a CCD element, 408 is a reflective phase modulation element 4
This is a ROM that stores data to be displayed on 04.

The input figure displayed on the input figure display medium 403 is irradiated with laser light from the semiconductor laser 401 via the collimator lens 402 . At this time, the reflective phase modulation element 404 is a phase filter having a coordinate conversion function etc. stored in the ROM 408! J<, as in the first embodiment, the signal voltage applied between the source and drain of the TPT of the reflective phase modulation element 404 changes the inclination of the liquid crystal molecules with respect to the incident optical axis ZZ.As a result, the linear polarization property is changed. The refractive index of the liquid crystal layer changes from nO to nE with respect to the incident light. Therefore, the light beam incident on the reflective phase modulation element
The phase modulation of 2nd (d is the thickness of the liquid crystal layer) is received by the double bus and displayed on the reflective phase modulation element 408.As a result, the Fourier transform image of the optical product of the G1 human figure and the phase filter is displayed on the focal plane of the lens 406. is formatted and it is CC
Even when optical information processing such as coordinate transformation is performed by the D element 407, the second embodiment of the present invention has the same fineness as the first embodiment. It is possible to improve the light usage efficiency within one picture element of the light modulation element and the usage efficiency of the number of picture elements.Furthermore, the Fourier transform image of the black matrix of the spatial light modulation element is superimposed on the Fourier transform image by the lens 406. Moreover, the reflective phase modulation element of the present invention is compatible with the well-known Schlieren optical system (an optical system consisting of a lens and a knife) or the optical system used in C& phase contrast microscopes. It goes without saying that when combined with a system, it can also be used as an amplitude modulation element by modulating the phase. By applying a voltage to the layer, the refractive index of liquid crystal molecules for each picture element is controlled and the phase of incident light is modulated, allowing for phase modulation with high picture element usage efficiency.

In addition, since it has a reflective structure, phase modulation is performed using a double bus, and a round black matrix is not required, resulting in high light utilization efficiency. By displaying a computer-generated hologram (kinoform) or a phase filter, it is possible to perform optical information processing with high efficiency in the use of moving plates and light of the picture elements that make up the liquid crystal.Furthermore, black matrix power patterns and Fourier transform images can be performed. can be prevented from being superimposed on
It becomes possible to improve signal quality.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the structure of a reflective phase modulation element according to an embodiment of the present invention; Figure 2 is a cross-sectional view showing the alignment state of liquid crystal molecules in the element; Relationship between the alignment state of liquid crystal molecules and the polarization direction of incident light due to voltage
Figures 6 and 7 are explanations of the refractive index ellipsoid of liquid crystal molecules @
FIGS. 8 and 9 show the configuration of each embodiment of the optical information processing device of the present invention. FIG. 10 shows the configuration of a conventional optical information processing device. FIG. Figure 12 shows the liquid crystal alignment state of the same display & Figure 13
The figure shows a computer generated hologram image displayed on the same display. 201...TFT base cage 202...TPT, 2
03... Conductivity! 204...Reflection #205
...First orientation blow 206...Transparent opposing electric wire 20
7...Second alignment method 208...Liquid crystal FL 3
01...TV camera, 302...Liquid crystal display for human power display, 303...Semiconductor laser, 304
...Collimator lens, 305...First lens X306...Reflection type phase modulation element, 307...
Beam split 308...Second lens X309
...CCD element, 310...-ROM,.

Claims (3)

[Claims] (1) A substrate and a transparent substrate arranged at a predetermined interval,
a liquid crystal layer disposed between the two substrates, a conductive film on the surface of the substrate on the liquid crystal layer side, and a current supplied by the conductive film provided on the conductive film. a plurality of switching elements, a reflective layer provided on the switching element, and a first liquid crystal alignment film provided on the reflective layer; A transparent electrode and a second alignment film provided on the transparent electrode are formed on the side surface, and the alignment directions of the first and second alignment films are substantially parallel, and the switching element A reflective phase modulation element characterized by controlling the refractive index of each picture element. (2) a spatial light modulator that displays an image captured by a television camera; a light source that illuminates the spatial light modulator; and a light source whose focal plane is the surface on which the spatial light modulator is placed. 1; and a reflective phase modulation element according to claim 1, which is disposed on a focal plane opposite to the focal plane of the first lens; and a focal plane opposite to the light source of the first lens as a light source. a second lens having a side focal plane;
includes a photoelectric conversion device placed on the focal plane opposite to the light source of the lens, and expresses a phase computer hologram or a phase filter by spatially modulating the phase of light incident on the reflective phase modulation element. An optical information processing device characterized by: (3) A spatial light modulation element that displays an image, a reflective phase modulation element according to claim 1 arranged in parallel with the spatial light modulation element, and irradiation of the spatial light modulation element and the reflective phase modulation element. a light source, a lens whose focal plane on the light source side is the position of the reflective phase modulating element, and a photoelectric conversion device disposed on the focal plane of the lens on the opposite side to the light source, An optical information processing device characterized by expressing a phase-type computer generated hologram or a phase filter by spatially modulating the phase of incident light.