JP4022621B2 - Array type holographic code recognition device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hologram recording apparatus having a strip-like transparent electrode on both sides of a phase hologram material having an electro-optic effect and an optical damage effect, and voltage control for selecting a cross region of the crossing electrodes on both sides during hologram recording The present invention relates to an array-type holographic code recognition device that recognizes an input code depending on which detector detects a reference light by placing a detector corresponding to each cross region during reproduction with a detector and diffusion code light. .
[0002]
[Prior art]
The code recognition apparatus proposed conventionally is a method using an optical deflector. In this method, in order to realize the code recognition device holographically, an input angle is deflected by an optical deflector at the time of code recording instead of applying a voltage. However, in this case, a beam deflector is required, the optical system becomes complicated, and power loss of the input code is inevitable. In addition, the diffraction angle dependency of the diffracted light intensity has a full width at half maximum for a certain reproduction angle, so that the separation of the diffraction angle is deteriorated.
Patent Document 1 discloses a hologram recording apparatus having a strip-shaped transparent electrode on both sides of a phase hologram material having an electro-optic effect and an optical damage effect, and a voltage for selecting a cross region of cross electrodes on both sides during hologram recording. We propose a photoelectric storage display device equipped with a controller.
[0003]
With respect to the photoelectric storage display element described in Patent Document 1, the characteristics of the photodamage effect as an operation principle will be described with reference to FIG. That is, the relationship between the amount of incident light and the refractive index change caused by the optical damage effect under each applied electric field is shown in FIG. 6A. Therefore, it can be seen that the sensitivity to the amount of incident light is increased by the applied voltage. FIG. 6B shows a linear relationship between the refractive index change and the phase change with respect to the reproduced plane wave.
As a result, by applying a high applied electric field during recording, the refractive index change with respect to a constant incident light quantity becomes larger (that is, the sensitivity of the refractive index change with respect to the incident light quantity increases), and further the refractive index change. It can be seen that the refractive index can be modulated by the amount of incident light up to the point where is saturated. Furthermore, it can be seen that the phase of transmitted light changes linearly with respect to the refractive index by irradiating uniform incident light during reproduction.
[0004]
[Patent Document 1]
Japanese Patent Publication No.57-29796
[Problems to be solved by the invention]
In view of these points, the present invention uses a photoelectric storage display element, does not require the use of a deflector, and has a full width at half maximum with respect to one reproduction angle when multiple recording is performed with different recording angles. You can overcome the poor angle separation caused by things. Therefore, a holographic recognition apparatus that utilizes the fact that a large number of code information can be recorded (that is, the size of one cross area can be reduced to a point where the reproduction and detection of the hologram is not hindered) should be provided. It is what.
Compared to the case where an optical deflector is used, the present invention has no loss, is not complicated, is extremely simple, and has a low angle separation property because the diffraction angle has a full width at half maximum for a certain reproduction angle. It is an object of the present invention to provide a code recognition device that can recognize a large number of codes since it can be overcome.
[0006]
[Means for Solving the Problems]
The hologram recording apparatus of the present invention has a strip-shaped transparent electrode on both sides of a phase-type volume hologram material (KTN (K (Ta, Nb) O3, LiNbO3, high-density photorefractive Quantum Well, etc.)) having an electro-optic effect and an optical damage effect. A diffusion pattern (diffused light obtained by passing through a diffusion plate) in a state where the spatial information of the input code is equally concentrated at any one point at a certain angle from one surface of the transparent electrode In addition, by entering a reference light from another surface at a certain angle, selecting one of the strip-shaped transparent electrodes and applying an electric field, a single cross region to which a voltage is applied is selected and the cross region is selected. The hologram is selectively recorded only there by increasing the sensitivity of the material.
In addition, the hologram recording apparatus of the present invention irradiates the entire cross region with a diffusion pattern of a specific input code without an electric field, and the reference light is reproduced only from the hologram of the cross region where the input diffusion pattern is recorded. Thus, the input code is recognized depending on which detector is entered by placing the detector at the reproduction position from each cross region.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on examples. FIG. 1 illustrates the configuration of an array type holographic code recognition device. The exemplary configuration itself is known as shown in the above-mentioned Patent Document 1, and a photoelectric storage display element having a photodamage effect in which a strip-like transparent electrode is pasted in a cross shape on both sides, and to this element. Voltage control device for controlling voltage application, light source and code light generation device, optical device for guiding a reference beam for holographic recording of code information on this element, and reproduction without voltage Sometimes the angle to be reproduced is determined, and it consists of a group of detectors (see FIG. 2) installed in that angle direction. This photoelectric storage display element has a strip-shaped transparent electrode on both sides of a phase-type volume hologram material (KTN (K (Ta, Nb) O3, LiNbO3, high-density photorefractive Quantum Well, etc.)) that has an electro-optic effect and an optical damage effect. Provided in a cross shape.
[0008]
The present invention is characterized in that a code is recognized using such a configuration of the code recognition device. The present invention is different from Patent Document 1 in the usage of the photoelectric storage display element. In Patent Document 1, a computer generated hologram is a method of recording a computer generated hologram in the form of a refractive index change while changing the sensitivity of each cross region depending on the applied voltage. However, the present invention has the same element configuration. However, the diffusion pattern of each code is recorded holographically in each cross area, and the code is recognized by detecting from which cross area it is reproduced.
[0009]
The present invention provides a pattern in which the spatial information of the input code is equally concentrated on any one point at a certain angle from one surface of the transparent electrode (diffused light obtained by passing through the diffusion plate), Reference light is incident at a certain angle from another surface, and one of the strip-shaped transparent electrodes is selected and an electric field is applied. Thus, by selecting one cross region to which a voltage is applied and increasing the sensitivity of the material of the cross region, a hologram is selectively recorded only there.
[0010]
In addition, by irradiating the entire cross area with a diffusion pattern of a specific input code without an electric field, the reference light is reproduced only from the cross area recorded in the holographic manner by irradiating the input diffusion pattern. The input code is recognized depending on which of the detectors placed at the reproduction positions from the cross area.
[0011]
First, the principle of diffused light will be described. As shown in FIG. 3, after passing the input light through the code information board, the light at all the points on the diffusion board is spread evenly by passing through the diffusion board. Therefore, when viewed from the irradiation surface shared among the equal spreads from all points on the diffusion plate, the information on the entire code is concentrated on all the points on the irradiation surface. Therefore, it is possible to record the entire code information spread spatially in a minute area (for example, an area where the vertical and horizontal transparent electrodes cross each other).
[0012]
Hereinafter, an operation for code recognition will be described. The action consists of two. One is the creation of an element in which a diffusion code is arranged and recorded by holographic multiplex recording and enhancing the sensitivity of each cross region. The second is code recognition using this code array corresponding element (this corresponds to the conventional photoelectric storage display element).
[0013]
First, the creation of the code arrangement corresponding element will be described. In the configuration shown in the code holographic recording apparatus of FIG. 1, the correspondence table is determined by associating the code Ci, j with the array (i, j) of the cross areas Ri, j. Next, when the hologram is recorded with the diffusion light of the code light Ci, j and the reference light based on this correspondence table, the voltage Vi, j is applied to the cross region Ri, j corresponding to each code Ci, j. Thus, the double-sided strip-like transparent electrodes Ti and Tj are selected. In this way, the transparent electrodes Ti, Tj on both sides are selected so that all the codes are applied to the cross regions Ri, j corresponding to the codes Ci, j, and the code diffusion light and reference light are used to Multiple records on graphics. Then, this becomes a code arrangement corresponding element.
[0014]
Next, code recognition using this code arrangement corresponding element will be described with reference to FIG. This hologram multiplex recording (This is a holographic multiplex recording method. Actually, however, the diffusion pattern of each code Ci, j is recorded for each cross region with increased sensitivity, and each hologram is recorded in an array. When the code light is incident on the photoelectric storage display element without voltage, the reproduction angle is shifted in accordance with the voltage applied during recording. In this case, since the applied voltage is constant, the shifted reproduction angle is constant in any arrangement. Therefore, by arranging the detector groups Deti, j according to the respective arrays Ri, j in the shifted reproduction angle direction, the arrays Ri, j and the detectors Deti, j can be made to correspond to each other. Thus, the reference light from which sequence is detected can be determined depending on whether the signal is detected, and therefore the code can be recognized from the correspondence between the code and the sequence.
[0015]
FIG. 4 shows a configuration example of the element when a transparent electrode is attached to the Fe-added LiNbO ₃ crystal. FIG. 5 shows a configuration example of the element in the case where a transparent electrode is attached to the refraction type quantum well. In the case of a ferroelectric material having a photodamage effect such as Fe-doped LiNbO ₃ crystal, there is C-axis anisotropy, and the photoexcited carrier drifts in the C-axis direction, and the refractive index through the electro-optic effect by the internal electric field. Since a change occurs, a change in refractive index can be obtained efficiently if a change in light intensity occurs in the C-axis direction. On the other hand, in the case of a refraction type quantum well, either direction is possible.
[0016]
【The invention's effect】
The present invention does not require the use of a deflector, and does not require the use of a high voltage in order to improve angle separation. Therefore, a large number of code information can be recorded.
The present invention is less complicated than the case of using an optical deflector, and as a very simple code recognition device, and overcomes the poor angle separation due to the diffraction angle dependence of diffraction efficiency having full width at half maximum. Thus, it can be used as a large number of code recognition devices.
[Brief description of the drawings]
FIG. 1 shows a code holographic recording device.
FIG. 2 shows a code holographic recognition device.
FIG. 3 is a diagram illustrating the principle of diffused light.
FIG. 4 is a diagram showing a configuration of an element in the case where a cross-shaped band-like transparent electrode is attached to an Fe-added LiNbO ₃ crystal.
FIG. 5 is a diagram showing a configuration of an element when a cross-type band-like transparent electrode is attached to a refraction type quantum well.
6 is a known characteristic diagram disclosed in Patent Document 1. FIG.
[Explanation of symbols]
Ti: (i) th strip-shaped transparent electrode on the code light incident surface of the photoelectric storage display element
Tj: (j) -th transparent electrode on the reference light incident surface of the photoelectric storage display element
Ri, j: Cross region located in array (i, j)
Vi, j: Applied voltage in the cross region Ri, j
Ci, j: Code pattern
Difi, j: Diffracted light from cross region Ri, j
Deti, j: Detector that receives diffracted light from cross-region Ri, j

Claims (2)

A photoelectric storage display element having a photodamage effect in which strip-shaped transparent electrodes are pasted on both sides in a cross shape, a voltage control device for controlling voltage application to the device, a light source, a code light generation device, and the code light Diffusion code generator for creating a state in which all spatially distributed code information is concentrated at an arbitrary point on the irradiation surface of the photoelectric storage display element, for recording the diffusion code light in a holographic manner In a holographic code recognition device comprising an optical device for guiding the reference light and a detector group installed in an angular direction for reproduction when reproduced with no voltage,
In the code light generation device, the diffused code light generation device, and the reference light generation optical device, the spatial information of the input code is substantially equally concentrated at any one point at a certain angle from one surface of the transparent electrode. The diffusion code light in the state and the reference light are incident at a certain angle from another surface
The voltage control device selects one of each of the strip-shaped transparent electrodes and applies a voltage to increase the sensitivity of the material in the cross region, thereby selectively recording a hologram there. Holographic code recognition device. By irradiating the entire cross area with a specific input code diffusion pattern in the absence of an electric field and reproducing the reference beam from the hologram only in the cross area where the input diffusion pattern is recorded, the reproduction position from each cross area is 2. The array type holographic code recognition device according to claim 1, wherein the input code is recognized depending on which of the placed detectors is entered.

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