JPH035736A - Optical flip-flop array - Google Patents

Abstract

PURPOSE:To shorten the response time and to providing the optical flip-flop array with static memory ability and to simplify the constitution by utilizing ferroelectric liquid crystal for a spatial optical modulator. CONSTITUTION:The optical flip-flop array consists of the spatial optical modulator (a), a write optical system 2a, a read optical system 3a, and a pulse generator 4a and the spatial optical modulator (a) is constituted by laminating transparent electrodes 16a and 16b, a photoconductive film 12, a dielectric mirror 13, a liquid crystal orienting film 15, ferroelectric liquid crystal 14, and a liquid crystal orienting film 15 in order between two glass substrates 11a and 11b. Then the pulse generator 4a feeds electricity to between the transparent electrodes 16a and 16b in response to the detection of a light signal by a photodetector 21a to vary the deflection direction of the ferroelectric liquid crystal 14. Consequently, the response time is shortened, the static memory ability is obtained, and the constitution can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application> The present invention relates to an optical flip-flop array capable of optically loading and reading data in parallel.

<Prior art> Conventionally, as this type of optical flip-flop array, the fifth
As shown in Figure (1), a liquid crystal light valve array 01,
02, polarizer 11! By combining the polarizers 03 and 04, polarizers os and os, and 07 and 08, and reading the optical signal as set manual S or reset manual R, the optical signal is read out as Q output and q output. Known (Applied 0pties, Vol.

23, to N13. pp2183-2171 (1984
)).

Here, as the electrical equivalent circuit is shown in FIG. 5 (2), since the liquid crystal light valves 01 and 02 do not have a memory function, the liquid crystal light valves 01 and 02 are connected to the NOR gate 0.
9,010, and the output of both games) 09,010 is returned to the input of the other, achieving memory performance.

Note that q indicates negation in pool algebra.

<Problems to be Solved by the Invention> However, conventional optical flip-flop arrays have a slow response (approximately 10
m s ), and since it requires an optical feedback configuration, it has the disadvantage of requiring a complicated optical system.

The present invention was made against the above-mentioned background, and an object of the present invention is to provide an optical flip-flop array that has a short response time, has static memory properties, and is simple in configuration.

<Means for Solving the Problems> The configuration of the present invention to achieve such an object is to write optical signals in parallel as set inputs or reset inputs,
The optical flip-flop array reads optical signals in parallel as a Q output and a q output, and includes a spatial light modulator, a writing optical system, a reading optical system, and a pulse generator, and the spatial light modulator includes two pieces. A transparent electrode, a photoconductive film, a dielectric mirror, a liquid crystal alignment film, a ferroelectric liquid crystal, and a liquid crystal alignment film are laminated in order between the glass substrates of the writing optical system. one or more beam splitters that split an optical signal input as an input or a reset input to the photodetector and the photoconductive film side of the spatial light modulator; comprising a laser diode that makes predetermined polarized light enter the spatial light modulator from the ferroelectric liquid crystal side, and a polarization splitting mirror that branches the polarized light reflected by the dielectric mirror as a Q output and a rotation output depending on the polarization direction, Moreover, the pulse generator is characterized in that it applies current between the transparent electrodes to vary the deflection direction of the ferroelectric liquid crystal in response to the detection of the optical signal by the photodetector.

Further, in the above invention, the dielectric mirror is omitted from the spatial light modulator, and predetermined polarized light from the laser diode is made incident on the photoconductive film side of the spatial light modulator, and then on the ferroelectric liquid crystal side. The above object can also be achieved by splitting the passed polarized light by the polarization separation mirror as Q output and q depending on the polarization direction.

For example, when an optical signal input as a set input is split into a photodetector and a photoconductive film side of a spatial light modulator using a beam splitter, only the light irradiated part of the photoconductive film has a low resistance. The non-irradiated area has high resistance. Therefore, even if an optical signal is detected by a photodetector and current is applied between the transparent electrodes by a pulse generator, no voltage is applied to the part of the ferroelectric liquid crystal that corresponds to the high-resistance part of the photoconductive film. Not done.

In other words, the alignment direction of the liquid crystal does not change in the portions of the ferroelectric liquid crystal corresponding to the high resistance of the photoconductive film, and changes only in the portions of the photoconductive film corresponding to the low resistance. on the other hand,
When the predetermined polarized light output from the laser diode is made incident from the ferroelectric liquid crystal side of the spatial light modulator, it is reflected by the dielectric mirror and passes back and forth through the ferroelectric liquid crystal.
The deflection direction changes only in the portion where the voltage is applied and the alignment direction of the liquid crystal changes. Therefore, this reflected light is split by the polarization splitting mirror according to its polarization direction and output as Q output and Mo output.

On the other hand, in the case of a reset input, the voltage applied between the transparent electrodes by the pulse generator is reversed, the polarization direction of the ferroelectric liquid crystal is reversed, and furthermore, the polarization direction of the polarized light passing through it is reversed. is the same as above.

Embodiments Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

An embodiment of the present invention is shown in FIGS. 1 and 2. FIG. As shown in FIG. 1, the optical flip-flop array of the present invention includes a spatial light modulator 1a, a writing optical system 2a, and a reading optical system 3a.
and pulse generation i4a. Here, the writing optical system 2a includes photodetectors 21a and 2lb such as silicon photodiodes, and a lens 22a.

22b1 Mirror unit 23a, half mirror 231
, 232, 233. Further, the reading optical system 3a includes a lens 22C.

Mirror unit 23b1 half mirror 234, polarization separation mirror 235, visible light 1nGaA with a starting wavelength of 670nm
J! 5) with a Plz-the diode 31a. Regarding the spatial light modulator 1a, as its cross-sectional view is shown in FIG. 2, a transparent electrode 16a, a photoconductive film 12, a dielectric mirror 13, a liquid crystal alignment film 15, a ferroelectric A liquid crystal 14, a liquid crystal alignment film 15, and a transparent electrode 16b are laminated in this order. A spacer 17 is interposed between the liquid crystal alignment films 15 to set the thickness of the ferroelectric liquid crystal.

A sealing material 18 is formed in close contact around the glass substrates 11a and llb. A transparent electrode 1 is placed on the glass substrate 1a.
A transparent electrode 16c is formed which is insulated from the transparent electrode 6a, and is electrically connected to the transparent electrode 16b through a Buddhist altar paste 19.

The photoconductive film 12 is a-3i:H, is formed to a thickness of 5 μm by plasma CVD, and has type 1 conductivity. The dielectric mirror 13 has an optical length nd of a quarter wavelength, that is, 1 wavelength, so as to reflect the readout light (670 nm).
A total of 15 films of titanium oxide and silicon oxide are alternately formed at a wavelength of 68 nm, and the reflectance is 99% or more at that wavelength. The refractive index anisotropy of the ferroelectric liquid crystal 14 was Δn=0.13, and the thickness was set to 1.5 μm by the spacer 17. The tilt angle of the ferroelectric liquid crystal 14 is 22
．． At 5 degrees, the spontaneous polarization was 10 nc/cj. The liquid crystal alignment film 15 uses a polyvinyl alcohol film, as shown in FIG.
), the glass substrate 11a.

The rubbing process was performed at an angle of 22.5 degrees with respect to the longitudinal direction (y-axis) of 11b. Transparent electric tEF+16a.

Tin-doped indium oxide (ITO) films were used as 16b and 16c.

Next, the operating principle of such a spatial light modulator 1a will be explained with reference to FIG.

Figure 3 (11 (21), light irradiation from the photoconductive film 12 side (P
L, 1=P0), and f31 in the same figure.
(41 is the non-irradiated (Pu=0) part.

In addition, (1) and (3) in the same figure are transparent electrodes 16 a, 16
Applying a positive voltage (v=+v0) to b-oka, +2)
f4) is a voltage applied with a negative voltage (V=-Vo).

That is, as shown in FIG. 3(1), the photoconductive film 12 that has been irradiated with light becomes in a low resistance state, so that most of the positive voltage is applied to the ferroelectric liquid crystal 14, and the molecular axis (like Tilt at 45 degrees to the y-axis.

Due to the inherent properties of the ferroelectric liquid crystal 14, this alignment state is maintained even when voltage application and light irradiation are removed. Here, when S-polarized light is incident from the ferroelectric liquid crystal 14 side, it is reflected by the dielectric mirror 13, and the
Due to the birefringence effect of 4, the reflected light is read out as P-polarized light.

Next, in FIG. 3(2), since most of the negative voltage is applied to the ferroelectric liquid crystal 14, the molecular axis of the liquid crystal 14 is parallel to the y-axis. Therefore, from the ferroelectric liquid crystal 14 side, the sg
When light is incident, it is reflected by the dielectric mirror 13, passes directly through the ferroelectric liquid crystal 14, and is read out as S-polarized light. Note that this alignment state is also a stable state for the ferroelectric liquid crystal 14, so even if voltage application and light irradiation are removed, this state is maintained.

On the other hand, in FIG. 3 (3) and (4), the photoconductive film 12
Since it is not irradiated with light, it is in a high resistance state, and even if a positive voltage or a negative voltage is applied between the transparent electrodes 16a and 16b, almost no voltage is applied to the ferroelectric liquid crystal 14. Therefore, the light distribution of the liquid crystal molecules does not change, and the state before voltage application is maintained. For example, if the molecular axis of the liquid crystal is inclined at 45 degrees with respect to the y-axis as shown in Figure 3 (1) before voltage application, the IP
The polarized light is read out as reflected light, but if it is parallel to the y-axis as shown in (2) of the figure, the S-polarized light will be read out as reflected light.

The operation of the optical flip-flop array of this embodiment using such a spatial luminous intensity device 1a will now be described with reference to FIG.

First, when an optical signal is input as a set input, this optical signal is split into two at the half mirror 231, one goes straight and enters the spatial light modulator 1a, and the other is reflected and condensed by the lens 22b. The light is incident on the photodetector 21b.

Here, since the set input consists of a pattern of light rays, a light irradiated part and a non-irradiated part are generated in the photoconductive film 12 in the spatial light modulator 1a.

As described above, only the light irradiated portions of the photoconductive film 12 are in a low resistance state, but the non-irradiated portions remain in a high resistance state. On the other hand, when a set input is detected by the photodetector 21b, the pulse generator 4a outputs the set pulse shown in FIG. 1 between the transparent electrodes 16a and 16b of the spatial light modulator 1a. The set pulse is a bipolar pulse to avoid shortening the life of the ferroelectric liquid crystal 14 due to charging, but since the rear pulse is a positive voltage, it is applied as a positive voltage to the ferroelectric liquid crystal 14. work. Therefore, the liquid crystal molecules in the photoconductive film 129 and the part of the ferroelectric liquid crystal 14 corresponding to the light irradiation part are tilted at 45 degrees with respect to the y-axis, and the part of the ferroelectric liquid crystal 14 corresponding to the non-irradiation part is tilted at 45 degrees with respect to the y-axis. , the state before voltage application is maintained (see Figure 3 (1) (3)).

On the other hand, the S-polarized red light output as readout light from the laser diode 31a passes through the lens 22C1 half mirror 234 and enters the spatial light modulator 1a as a parallel beam.

This S-polarized/red light is reflected by the dielectric mirror 13, and when it passes through the ferroelectric liquid crystal 14, it partially becomes PM light, or passes through as SLF light, and is sent to the half mirror 23.
The light (p-polarized light) whose direction is changed at 4 and passes through the polarization splitting mirror 235 is read out as a Q output, and the light reflected by the polarization splitting mirror 235 (5g light) is read out as a ma output.

Similarly, the optical signal input as a reset input is split into two by the half mirror 232, one goes straight, is reflected by the half mirror 233, and enters the spatial light modulator 1a, and the other is reflected and enters the lens 22a. The light is focused on the photodetector 21
incident on a. When the reset input is detected by the photodetector #21a, the pulse generator 4a applies a reset pulse to the spatial light modulator 1a as shown in FIG. The reset pulse is a pulse with the polarity of the set pulse reversed. For this reason,
In the ferroelectric liquid crystal 14, a negative voltage is applied only to the portion of the photoconductive film 12 corresponding to the light irradiation portion, and the liquid crystal molecules are aligned parallel to the y-axis (see FIG. 3 (2) (see 41)). The operation of the readout light output from the laser diode 31a is read out in the same manner as in the case of set input.Such results are summarized as a truth table in FIG.

In this example, the effective stone of the spatial light modulator is IXle.
wr, the wavelength of set input, reset input, and read light is 670 nm, and the write light power is 0.1 mw.
/cd, readout optical power 1 mw/c4 Check the voltage applied to the modulator. = ±20v1 When the pulse width (both positive and negative electrodes) is 300μS, the resolution (number of arrays) is 100X
100, ON10 F F ratio 20: 1 characteristic,
The written data could be retained for one day.

Next, another embodiment of the present invention will be described with reference to FIG.

In this embodiment, the wavelengths of the write light and the read light are set to different wavelengths, the dielectric mirror is omitted from the spatial light modulator 1b, and the read light output from the laser diode 31b is used within the spatial modulator 1b. It is designed to allow light to pass through without being reflected. That is, in the optical flip-flop of this embodiment, the spatial light modulator is the spatial light modulator 1b.

A writing optical system 2b and a reading optical system 3b.

It is composed of a pulse generator 4b. Spatial light modulator 1b
is the same as the above spatial light modulator 1 except that the dielectric mirror is omitted.
It has the same structure as c, but since it is a transmissive type rather than a reflective type, the long axis of the spacer was set to 3 μm in order to double the optical length of the ferroelectric liquid crystal. The writing optical system 2b includes a silicon photodiode photodetector 521c.

It is equipped with a 21d lens 22d1 half mirror 236° wavelength separation mirror 237, and an E sea unit 23c. The readout optical system 3b includes a mirror unit 23d1, an information/light separation mirror 238, and a GaAJAs laser diode 31b with an oscillation wavelength of 830 nm.

The operation of this embodiment is as follows. When an optical signal (wavelength 633 nm) is input as a set input, this optical signal is reflected by the half mirror 236, passes through the wavelength separation mirror 237, and enters the spatial light modulator 1b. The wavelength separation mirror 237 is a dichroic mirror that transmits wavelengths from 750 nm and reflects wavelengths shorter than 750 nm. Set input is to the pulse generator 4b in the same light beam pattern as in the above embodiment.
It includes a set clock light for starting the.

The set clock light utilizes a part of the light beam pattern, and is incident on the set photodetector 21c. When the set clock light is detected, the set pulse shown in the figure is generated from the pulse generator 94b and applied to the spatial light modulator 1b. Since the resistance of the photoconductive film in the modulator 1b decreases only in the light beam pattern irradiation part of the set input, the ferroelectric M
The product molecule is tilted at 45 degrees to the y-axis and stabilized. The readout light uses Sgs light/infrared light from the laser diode 31b, and is connected to the lens 22d and the wavelength lll! mirror 237
It is reflected as a parallel beam through the photoconductive film and ferroelectric liquid crystal of the spatial light modulator 1b, and the polarizing molecules aZ Schiller 3
The light (p-polarized light) transmitted through the polarization filter 238 is read out as the Q output of the flip-flora, and the light (5g light) reflected by the polarization separation mirror 238 is read out as the output power. Since the wavelength of the set input is shorter than the absorption edge of H-3i:H, it is absorbed by the photoconductive film and is not transmitted to the readout side. Since the wavelength of the readout light is longer than the absorption edge of a-3i=H, the readout light beam passes through the spatial light modulator 1b and has an output of 92 beams.

Regarding the reset input, when an optical signal (wavelength 633 nm) is input as the reset input, this light beam pattern is transmitted through the half mirror 236, passes through the wavelength separation mirror 237, and enters the spatial light modulator 1b. Similarly to the set input, the reset input is a light beam pattern that includes a reset clock light, and the reset clock light is a part of the light beam pattern and enters the reset photodetector 21d. When the reset clock light is detected, a reset pulse is generated from the pulse generator 4b and applied to the spatial light modulator 1b.

Since the resistance of the photoconductive film in the modulator 1b decreases only in the irradiated part of the light beam pattern of the reset input, the ferroelectric liquid crystal molecules become oriented parallel to the y-axis and become unstable. Outputs Q and F are read out in the same manner as when they are set.

In this example, the effective surface of the spatial light modulator is lX1c
d, and the wavelength of the set input and reset input is 633n.
m, readout light wavelength 830 nm.

Right input optical power 0.1 mw/cnr, readout optical power 1 mw/d, voltage applied to the modulator v0 = ±2
When 0V and pulse width (both positive and negative) are 300μs, resolution (number of arrays) 100X100, ON10
Characteristics similar to those of the previous example were obtained with a FF ratio of 20:1.

<Effects of the Invention> As described above, the present invention uses a ferroelectric liquid crystal, has a short response time, has a static memory property, and has no feedback. Since no circuit is required, the configuration can be simplified.

Therefore, the optical flip-flop array of the present invention can be applied to processing devices such as image processing and optical measurement that require high-speed and parallel access, as well as broadcasting and display devices such as video display devices.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
Figure (1) F21 is a cross-sectional view and a plan view of the spatial light modulator in the above embodiment, and Figure 3 (1) (2) F31 (
41 is an explanatory diagram showing the operation of the spatial light modulator in the above embodiment, FIG. 4 is a configuration diagram showing another embodiment of the present invention, and FIG. 5 (1) is a diagram showing the operation of the spatial light modulator in the above embodiment. FIG. 5(2) is an electrical equivalent circuit of FIG. 5(1), and FIG. 6 is an operation and logic table of the present invention. In the drawings, la and lb are spatial light modulators, 2a and 2b are writing optical systems, 3a and 3b are reading optical systems, 4a and 4b are pulse generators, 11a and Ilb are glass substrates, 12 is a photoconductive film, 13 Dielectric mirror 4 is a ferroelectric liquid crystal, 5 is an alignment film, 6a, 16b are transparent electrodes, 7 is a spacer 8 is a sealing material, 9 is a conductive paste, la, 21d are photodetectors, 2a, 22d 3a and 23d are mirror units; 31, 234 and 236 are half mirrors; and 35 and 238 are polarization separation mirrors 37 are wavelength separation mirrors.

Claims (2)

[Claims] (1) In an optical flip-flop array that writes optical signals in parallel as set input or reset input and reads out optical signals in parallel as Q output and ,
The spatial light modulator is composed of a transparent electrode, a photoconductive film, a dielectric mirror, a liquid crystal alignment film, a ferroelectric liquid crystal, and a liquid crystal alignment film stacked in this order between two glass substrates. On the other hand, the writing optical system includes a photodetector and one or more components that split an optical signal input as a set input or a reset input into the photodetector and the photoconductive film side of the spatial light modulator. Further, the readout optical system includes a beam splitter for splitting the polarized light reflected by the ferroelectric liquid auto into the spatial light modulator and the dielectric mirror into a Q output and a (2) output depending on the polarization direction. a separation mirror, and the pulse generator is configured to apply current between the transparent electrodes to vary the deflection direction of the ferroelectric liquid crystal in response to the detection of the optical signal by the photodetector. flip-flop array. (2) In claim (1), the dielectric mirror is omitted from the spatial light modulator, and a predetermined polarized light is made incident on the photoconductive film side of the spatial light modulator from the laser diode, and the ferroelectric An optical flip-flop array characterized in that the polarized light that has passed toward the liquid crystal side is split by the polarization splitting mirror into Q output and (2) depending on the polarization direction.