JPH01125791A - Solid-state optical memory device - Google Patents

Abstract

PURPOSE:To make an image into high resolution and high contrast by using a solid-state optical memory device and providing an optical means for recording and an optical means for reproduction for the solid-state optical memory device. CONSTITUTION:The solid-state optical memory device 1 is provided, and an image-forming lens 3 that is the optical means for recording to record the image of an original image 2 on the solid-state optical memory device 1 is provided oppositely to the solid-state optical memory device 1, and for the solid-state optical memory device 1, the optical means 4 for reproduction is also provided. And the image information of the original image 2 is recorded on the solid-state optical memory device 1 by the image-forming lens 3. In such a case, it is assumed that an optical image from the original image 2 is projected almost perpendicularly to the solid-state optical memory device 1. Meanwhile, the readout reproduction of the image recorded on the solid-state optical memory device 1 is performed in such a way that the image is reproduced by making incident readout light from an irradiation light source 5 at an angle theta for the normal of the solid-state optical memory device 1. In such a way, it is possible to obtain the image with high resolution and high contrast.

Description

TECHNICAL FIELD The present invention relates to a solid-state optical memory device for recording/reproducing two-dimensional images using the memory effect of ferroelectric materials.

Prior Art Conventionally, solid-state optical memory devices using crystals include Pockels effect crystal elements (Bi, SiO,...), ferroelectric crystals (Bi, Ti, O,..., PLZT), and photoconductive films. and MC with secondary electron multiplication effect.
P (micro channel plate) and LiNb0.
An MSLM based on a combination of the following is known.

However, the Pockels effect crystal element cannot be used in applications that use strong readout light because it is difficult to produce a large-diameter single crystal and the readout light causes image deterioration. Furthermore, a combination element of a ferroelectric crystal and a photoconductive film has memory characteristics by controlling the polarization direction.
Difficult to create crystals. In particular, B 14 T 1301
! It is difficult to increase the diameter of the crystal. Furthermore, processing and polishing are required to make the device extremely thin. Furthermore, MSLM is not practical because it increases the size, complexity, and cost of the device.

Purpose The present invention was made in view of the above points, and provides a method for optically recording a two-dimensional image, retaining the recorded image for a long time, and performing non-destructive readout without image deterioration during readout and reproduction. The objective is to obtain a high-resolution, high-contrast, and inexpensive solid-state optical memory device.

Structure In order to achieve the above object, the present invention provides a first layer on a transparent substrate.
a solid-state optical memory element formed by sequentially laminating a transparent conductive film, a ferroelectric film, a photoconductive film, and a second transparent conductive film; a recording optical means for recording an image on the solid-state optical memory element; It is characterized by comprising a reproducing optical means for irradiating an optical memory element with light and reading an image recorded in the solid-state optical memory.

A first embodiment of the present invention will be described below with reference to FIGS. 1 to 5. First, a solid-state optical memory element 1 is provided, and an imaging lens 3 serving as a recording optical means for recording an image of an original image 2 on the solid-state optical memory element 1 is provided to face the solid-state optical memory element 1. There is. The solid-state optical memory device 1 is also provided with optical means 4 for reproduction. This reproducing optical means 4 consists of an irradiation light source 5, an irradiation lens 6, a polarizer 7, an analyzer 8, an imaging lens 9, and a screen 10, and a solid-state optical memory element l is placed between the polarizer 7 and the analyzer 8. I will arrange it.

Here, image information of the original image 2 is recorded in the solid-state optical memory element 1 by the imaging lens 3. When recording in this manner, it is assumed that the optical image from the original image 2 is irradiated onto the solid-state optical memory element 1 almost perpendicularly.

On the other hand, to read and reproduce an image recorded on the solid-state optical memory element 1, the image is reproduced by making the read-out light from the irradiation light source 5 incident at an angle θ with respect to the normal line of the solid-state optical memory element 1.

At this time, the polarizer 7 and the analyzer 8 are set to be orthogonal to each other.

Here, the structure of the solid-state optical memory device 1 is shown in FIG. This solid-state optical memory element 1 has a transparent substrate 10 such as a glass plate.
First, on this transparent substrate 10, In, O,
: The first transparent conductive film 11 made of Sn is formed by vacuum evaporation. A ferroelectric film 12 is formed on this first transparent conductive film ll. This ferroelectric film 12 is a thin film of B 14Ti, O□ which is a ferroelectric material, and is formed by an ion blating method under the condition that the temperature of the transparent substrate 10 is 300°C. On the ferroelectric film 12, a photoconductive film 13 is formed by vacuum-depositing 5e-Te (4 wt%).

Note that the photoconductive film 13 is made of amorphous silicon, As, S.
e, OPC etc. may be used.Furthermore, this photoconductive film 1
A second transparent conductive film 14 is formed by vapor-depositing In and 03:Sn on the second transparent conductive film 14 . Note that the thin film B L 4 T l s C)+z constituting the ferroelectric film 12 is grown so that the C axis is perpendicular to the growth plane, and the one used as a memory is a-b. It is a surface.

Here, a recording power supply 1 is connected between the transparent conductive films 11 and 14.
5. The switching element 17 is connected so that the voltage from the erasing power supply 16 can be selectively applied. In addition,
Since no voltage is applied during playback, the switching element 17
A switching terminal for playback is also provided.

In such a configuration, the recording/reproducing/erasing operations of the solid-state optical memory device 1 of this embodiment will be explained with reference to FIG. 3. In FIG. 3, (a) shows the time of writing and recording, (b) shows the time of reading and reproducing, and (C) shows the time of erasing.

First, before writing, the polarization direction of the ferroelectric film 12 is set as shown in the figure (
As shown in a), the electric field applied by the recording power source 15 aligns them in a certain direction as shown by arrow A. In this state, the optical image f8 corresponding to the image from the original image 2 is transferred to the photoconductive film 1.
3.

At the same time, the resistance value of the photoconductive film 13 in the area irradiated with light by the optical image 18 decreases and most of the applied voltage is applied to the ferroelectric film 12, so the polarization direction of this area 12a rotates. The direction is indicated by arrow B. However, in a portion not irradiated with light, the polarization direction of the region 12b corresponding thereto remains in the initial direction A without rotation. In other words, ferroelectric film 1
Image information will be recorded according to the polarization direction in 2. Here, such a state is caused by an electric field (recording power supply 15
The polarization direction does not change even when the applied voltage (applied voltage) is turned off, and the polarization direction is maintained for a long time, ensuring memory function. This property is due to the hysteresis characteristic specific to ferroelectric materials.

Next, when reading and reproducing the image recorded on the solid-state optical memory device 1, the solid-state optical memory device 1 is placed between the polarizer 7 and the analyzer 8 at orthogonal positions, as shown in FIG. 3(b). The image is reproduced by irradiating the readout light 19 based on the irradiation light source 5. At this time, the readout light 19 is transmitted to the solid-state optical memory element 1.
Since it is not possible to read out the difference in the polarization direction in the ferroelectric film 12 if the light is incident perpendicularly to (See Figure 4). Further, the switching element 17 is switched to a state in which no voltage is applied between the transparent conductive gills and 14. Note that if the incident angle 0 is too small, the contrast of the readout image will be low, so it is necessary to increase it to some extent. In reality, due to the law of refraction, ferroelectric film ■2
The angle of incidence on the second transparent conductive film 14 is the angle of incidence θ
Therefore, it is desirable to set the incident angle θ to 20° or more. Further, the incident polarization direction of the readout light 19 is set at 456 degrees with respect to the b-axis as shown in FIG.

By the way, there are actually two regions 12a with different polarization directions,
The refractive index ellipsoid 12b is as shown in FIG. FIG. 5 shows a refractive index ellipsoid in the a-c plane. The readout light 19 incident at an angle θ is transmitted to the ferroelectric film 1
2 is incident at an angle β. At this time, retardation (phase difference) in each region 12a, 12b
r becomes. Here, Q is the thickness of the ferroelectric film 12, and Δ
n1. Δn2 is the birefringence difference between the respective regions 12a and 12b, and is a function dependent on the angle β. And polarizer 7
, when the analyzer 8 is in the orthogonal position, the light off state (dark state) is r,=Nλ or r,='Nλ...
It is given by (3) (where N is an integer). Therefore, the conditional expression that gives the maximum contrast of the readout image is: 1 r', -r, 1 = λ/2...
......(4). Here, it is easy to set the values of β and Q so as to satisfy such a formula.

Furthermore, when erasing the image recorded on the solid-state optical memory element 1, the switching element 1 is activated as shown in FIG. 3(c).
7 is switched to the erasing power supply 16 side, and a voltage opposite to that during recording is applied to the solid-state optical memory element 1. In this state, the entire surface of the solid-state optical memory element 1 is uniformly irradiated with erasing light 20. As a result, the polarization direction of the ferroelectric film 12 is changed to arrow A.
The images are aligned in a certain direction as shown by and the recorded image is erased. If an image is to be recorded again, the applied voltage may be reversed and a light image 18 corresponding to the image may be made incident as shown in FIG. 3(a).

As described above, according to this embodiment, first, by making the solid-state optical memory element 1 thinner, it becomes unnecessary to create a crystal. In addition, in the case of a crystal, it is necessary to process and polish it into an extremely thin film, but in the case of a thin film as in this example, the processing and polishing steps can be omitted, making it easier to create a memory element. Become. Furthermore,
Such a thin film makes it possible to realize a solid-state memory device with high resolution and high contrast. Furthermore, since the polarization direction of the ferroelectric film 12 is switched, it is possible to perform non-destructive reading without destroying the memory no matter how strong the image is read out, and it is expected to be widely applicable. Furthermore, there is no need to use expensive crystals, and costs can be reduced.

In addition, in the case of the arrangement shown in FIG. 1, the solid-state optical memory element 1
Since the optical axis of the reproducing optical means 4 is tilted at an angle θ, the read and reproduced image is reproduced as a somewhat distorted image.

In order to correct such distortion, for example, as shown in FIG. 6, the optical axis of the imaging lens 3, which is the writing system, is tilted by an angle θ' from the perpendicular state with respect to the solid-state optical memory element 1, and the original image 2 is If writing and recording is performed on the solid-state optical memory element 1 while tilted by an angle θ", and this is reproduced,
The original painting can be faithfully reproduced without distortion.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the first transparent conductive film 11 and the ferroelectric film 12 are
A solid-state optical memory element 1 is formed by forming a transparent crystal axis alignment film 21 between the two. This crystal axis orientation film 21
is made of ZnO with C-axis orientation, and ZnO
It is formed by RF sputtering using a sintered target.

The ZnO thin film is oriented with its C axis perpendicular to the substrate, facilitating the formation of the ferroelectric film 12. That is, the C-axis of the ferroelectric film 12 follows the C-axis of the crystal axis orientation film 21 and is perpendicular to the transparent substrate 10, resulting in an advantage that the crystallinity of the ferroelectric film 12 is improved.

Furthermore, a third embodiment of the present invention will be explained with reference to FIG.

In this example, the solid-state optical memory element 1 is provided with a crystal axis-oriented first transparent conductive film 22 made of ZnO:AQ in place of the first transparent conductive film 11 made of Ingos:Sn. Here, this first transparent conductive film 22 is a film with crystal axis orientation, and the C axis is oriented perpendicularly to the transparent substrate 10. This film is formed on the transparent substrate 10 by RF sputtering using a sintered target containing ZnO containing several mol% of AQ. As described above, the ferroelectric film 12 is formed on this film. According to this embodiment, by providing the first transparent conductive film 22 with the functions of a transparent electrode and a crystal axis alignment film at the same time, it is possible to omit the step of forming a separate transparent conductive film.

Effects As described above, the present invention uses a solid-state optical memory element in which a first transparent conductive film, a ferroelectric film, a photoconductive film, and a second transparent conductive film are sequentially laminated on a transparent substrate. Since the element is equipped with an optical means for recording and an optical means for reproducing, the solid-state optical memory element itself does not require the creation of crystals by making it a thin film, and it also eliminates the need for processing and polishing processes to make it ultra-thin. The device can be manufactured easily and at low cost, and by making the film thinner, higher resolution and higher contrast can be achieved.Also, since switching of the polarization direction of the ferroelectric film is used, two A device that optically records a dimensional image, can retain the recorded image for a long time, and can perform non-destructive readout without image deterioration regardless of the intensity of the playback light during readout and playback, and has a wide range of applications. It is something that can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing a first embodiment of the present invention, and FIG.
The figure is a structural diagram of a solid-state optical memory element, and Figure 3 is a recording/reproducing/
An explanatory diagram of the erasing operation, FIG. 4 is a schematic perspective view of the reproduction system, and FIG.
6 is a schematic side view showing a modified example, FIG. 7 is a structural diagram showing a second embodiment of the present invention, and FIG.
The figure is a structural diagram showing a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Solid-state optical memory element, 3... Imaging lens (optical means for recording), 4... Optical means for reproduction, 10...
・Transparent substrate, 11... First transparent conductive film, 12... Ferroelectric film, 13... Photoconductive film, 14... Second transparent conductive film, 22... First transparent conductive film Applicant Ricoh Co., Ltd. - Ju Figure, %6 Figure, %7 Figure 30 Countries''

Claims (1)

[Claims] A solid-state optical memory element formed by successively laminating a first transparent conductive film, a ferroelectric film, a photoconductive film, and a second transparent conductive film on a transparent substrate, and recording optics for recording an image on the solid-state optical memory element. 1. A solid-state optical memory device comprising: optical means for irradiating the solid-state optical memory element with light and reading an image recorded in the solid-state optical memory element.