JPS6050518A - Optical modulating device - Google Patents

Abstract

PURPOSE:To converge satisfactorily a modulated luminous flux by setting an image forming point of a luminous flux which is made incident on a refractive index distributing part, and a photodetecting medium, to an optically conjugate relation with regard to an optical system. CONSTITUTION:A titled device is provided with a transparent protecting plate 1, a liquid thin layer 2, an insulating layer 3 having a heat conductivity, a heating resistor layer 4 on which heating resistors 6a, 6b- are arranged, and a supporting body 5 of the insulating layer 3 and the heating resistors 6a, 6b-. The heating resistors 6a, 6b- are connected to each driving voltage by a conductive line 9 so as to be driven independently, respectively, and the other end of the heating resistors 6a, 6b- is grounded or set to a common voltage. When a voltage signal is applied to the heating resistors 6a, 6b- through the conductive line 9, a refractive index distribution is generated in a medium thin layer in the vicinity of each heating resistor, and this refractive index distribution is returned again to its original state that there is no refractive index distribution, after setting the voltage signal to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical modulation device suitable for optical recording devices, optical display devices, optical switches, optical shutter devices, and the like.

2. Description of the Related Art Recording, displaying, etc. using a luminous flux has been widely practiced. For this purpose, various techniques for providing light beam modulation are known;
It has been shown that modulation is achieved by changing the electric field distribution within a crystal that has an electro-optic effect, and diffracting the light beam incident on the portion of the crystal where the refractive index that occurs with this electric field distribution changes. There is.

On the other hand, in recent years, attention has been focused on modulating light by utilizing the refractive index distribution due to thermal effects.

Regarding light modulation using the refractive index distribution caused by this thermal effect, "light is deflected due to a change in the refractive index due to heat" (
Nikkei Electronics August 16, 1982 issue) or “Response speed of TO glass waveguide optical switch” (Showa 5
It was introduced at the 7th Annual National Conference of the Institute of Electronics and Communication Engineers (IEICE).

The applicant proposed an optical modulation element based on this principle of optical modulation in Japanese Patent Application No. 179265/1983. Due to the characteristics of the refractive index distribution, the light modulation element using this refractive index distribution has
It has been found that the apparent origin of the light beam modulated by the refractive index distribution section does not match the position where the refractive index distribution exists.

An object of the present invention is to provide a light modulation device using an element that modulates a light beam with the above-mentioned refractive index distribution, which can converge a modulated light beam well onto a light receiving medium.

In the light modulation device according to the present invention, the apparent origin of the light flux modulated by the refractive index distribution section, in other words, the imaging point of the light flux incident on the refractive index distribution section and the light receiving medium is determined by the distribution section. The above object is achieved by creating an optical system that condenses the light beam from the light modulation element into an optically conjugate relationship.

The present invention will be explained in detail below using the drawings.

FIG. 1 is a diagram showing an embodiment of a light modulation element applied to the light modulation device of the present invention. In Figure 1, 1 is a transparent protective plate, 2 is a thin liquid layer, 6 is a thermally conductive insulating layer, and 4 is 6
ELH6bg 6Q, 6 (1@II @ A heating resistor layer in which heating resistors are arranged, 5 is an insulating layer 6 and heating resistors 6a, 6b, 6C16d... support for the fist. And the heating resistor When the body generates heat, this heat is transmitted through the insulating layer 3 to the thin liquid layer 2, creating a temperature distribution within the thin liquid layer and forming a refractive index distribution.For example, as shown in FIG. When the resistor 6b is selected and generates heat, this heat is transferred to the thin liquid layer 2 through the insulating layer 6 that is in contact with the resistor 6b, and the thin liquid layer 2 facing the resistor 6b is transferred to the thin liquid layer 2 facing the resistor 6b.
The liquid in the region is heated to form the refractive index distribution 7 in this region.

This refractive index distribution 7 disappears after a predetermined period of time as the liquid in this region cools. One cycle from the formation of this refractive index distribution to its extinction is a very short time, and can be performed on the order of KHz. The heating resistors described above are formed on the support body 5 using Eri manufacturing technology, and the spacing between adjacent heating resistors is on the order of μm.

In addition to the above-mentioned liquid, polymeric materials such as acrylic resin and polycarbonate can be used as the thermal effect medium for forming the refractive index distribution. The temperature dependence of the refractive index is -L OX 10-' for water, -4,OX 10""' for T ethyl alcohol, and -5,8X 10-' for tetracarbon. Also, 7cryl is about -1,OX and 10-polycarbonate is about -1,3X
10-'.

FIG. 2 is a schematic perspective view showing the structure of the light modulation element shown in FIG. 1, and the numbers 1 to 6 are the same as those shown in FIG. 1. 8 is a conductive wire, and a heating resistor (6 &, <Sb...
) are connected to individual drive voltages so that they can be driven independently, while the other end of the heating resistor is grounded or set to a common voltage. From the conductive wire 8, the heating resistors 6a and 6b
When a voltage signal is applied to each of the heating resistors, a refractive index distribution is generated in the thin medium layer in the vicinity of each heating resistor. When the voltage signal is reduced to zero, this refractive index distribution is cooled and returns to the original state without refractive index distribution.

FIG. 6 is a diagram showing an embodiment of the light modulation device according to the present invention using the light modulation element LM with the refractive index distribution, in which a light beam whose wavefront is modified by the refractive index distribution is used as the pre-information light. Indicates when to do so. A light beam 10 is incident on the variable Δ adjustment element L6M, and the heating resistor (6a)

When any heating resistor 6o among the heating resistors 6b. do. A light beam 11 that is specularly reflected on the surface of the heat generating resistor and whose wavefront is not deformed by the refractive index distribution 7 is imaged by the lens tea, and is blocked by a light blocking filter 15a disposed at the image forming position. The light beam 12 whose wavefront has been deformed is partially blocked by the light blocking filter 15a, but the size of the light blocking filter 15a is set to the minimum size that blocks the imaging spot of the light beam 11 whose wavefront is not deformed. By doing so, it is possible to irradiate most of the wavefront-converted light beam 12' onto the light-receiving medium 14. In FIG. 3, a point P is the origin of divergence of a light beam 12 having a distorted wavefront created by the incident light beam 10 passing through the refractive index distribution 7. That is, the refractive index distribution 7 can be considered as one microlens, and the point P can be considered as the imaging point of the incident light beam 10 formed by the lens. The lens 15a is arranged so that a conjugate image P' of the point P is formed on the light receiving medium 14, thereby making it possible to receive an imaging spot with the highest brightness on the light receiving medium 14. That is, the heating resistor 6c
When a voltage is applied, a light beam with the maximum contrast is obtained with respect to the case where no voltage is applied.

As described above, by applying the voltage pulse v1 corresponding to the image signal to the heating resistor 6o through the conductive wire 8 or making it zero, the refractive index distribution 7 is repeatedly generated or eliminated accordingly. In that case, a flashing light spot with maximum brightness is generated on the light receiving medium 14.

Figure 4 shows a light modulation element L-M for improving the blinking contrast of light on the light-receiving medium, that is, for maximizing the light utilization efficiency.
This is a diagram for showing the state of the luminous flux incident on the
) is light change? FIG. 4B is a view of the Fi element viewed from the direction in which the heating resistors are arranged, and FIG. In the refractive index distribution, the gradient of the refractive index becomes steeper near the heating resistor, and the divergence efficiency is highest when the luminous flux 16 is incident thereon in a concentrated manner. Also, the support 5
Or heating resistor (6&, 6b...) or,
Depending on the flatness or roughness of the surface of the insulator m3, light beams other than the diverging light due to the refractive index distribution will enter, the light blocking efficiency of the light blocking filter 15 will deteriorate, and the light will be irradiated onto the light receiving body 14 as noise light. . Since this noise light is irradiated onto the light-receiving medium 14 regardless of the input signal voltage pulse v1 applied from the conductive line 8, the contrast is reduced. In order to eliminate such inconveniences, it is desirable to converge the incident light beam 16 linearly near the heating resistor, as shown in FIG. 4(A). 17 is a specularly reflected light beam (light that is not subject to divergence due to the refractive index distribution) of the incident light beam 16, and 1st indicated by a broken line is a divergent light beam due to the refractive index distribution. FIG. 4(B) is a cross-sectional view taken along the line AA' of the 41st fi(A), where 17 is a specularly reflected light beam of the incident light beam 16, and 18 is the vicinity of the heating resistor 6c to which the image signal is input. This is a diverging light beam due to the refractive index distribution generated in the above-mentioned period, and is scattered in a different direction with respect to the specularly reflected light beam 17 with the point P as the origin of divergence, as described above.

Figure 5 shows how to increase the light utilization efficiency explained in Figure 4 and
FIG. 2 is a layout diagram of an embodiment of a light modulation device for improving the stability of blinking light on the JJ& body 14; A light beam emitted from a light source 19 such as a semiconductor laser or a light emitting diode is passed through a line image forming optical system 2o composed of a spherical lens 20a and an anamorphic lens 20b to the heating resistors (6a, 6b*
...) is formed linearly in the direction of arrangement. A component of this linearly formed light flux in a plane perpendicular to the arrangement direction of the heat generating resistors is a heat generating resistor light flux. Therefore, the light beam 17 that is not diverged by the heating resistor takes a triangular prism-shaped optical path and enters the positive cylindrical lens 221L. The cylindrical lens 22& has its generatrix in the direction in which the heating resistors are arranged, and is provided so that its focal line coincides with the position of the heating resistors. Therefore, after the light beam 17 passes through the cylindrical lens 22&, it becomes an afocal light beam and enters the spherical lens 22b.

The light beam 17 is then focused by a spherical lens 22b on the focal plane of this lens. At this focal plane, the light beam 1
A rectangular filter 2'5 large enough to block 7.
Therefore, the light beam that has not been diverged by the heating resistor is blocked by the filter 23. On the other hand, the light beam 18 diverged by the heating resistor becomes parallel light only in a plane perpendicular to the arrangement direction of the heating resistor by the cylindrical lens 22.
2b, a linear image is formed near the rectangular filter 26. Therefore, a part of the diverging light beam 1B is blocked by this rectangular filter 26, but most of the light beam is not blocked by this light blocking filter, and is transmitted through the positive cylindrical lens 22a, which has a generatrix in the same direction as the cylindrical lens 22a. The light enters the lens 22c and is formed as a dot image (24&, 241)...@) on the light receiving medium 14.

The filter 23 and the light-receiving medium 14 are located in an optically conjugate focal plane of the cylindrical lens 220, and the heating resistor and the light-receiving medium are located in an optically conjugate position with respect to the spherical lens system 22b. be. Or, to put it another way,
In the cylindrical lenses 22 & 220 and the spherical lens system 22b, the heating resistors (6 to 6b...) and the light receiving medium 14 are arranged in an optically conjugate focal plane, and the light of the anamorphic lens system 22 is The light-receiving medium 14 is located on the focal line plane of the anamorphic lens system 22 within a region b defined by the axis and the direction in which the heating resistors are arranged. still,
In FIG. 5, only the heating resistor portion of the light modulation element LM is shown.

In the embodiments described above, the heating resistor is made of a reflective member, and both the diverging light flux and the non-diverging light flux are
Although the case where both light beams are reflected by a resistor is shown, FIG. 6 shows the case where both light beams pass through a light modulation element. 6th
The configuration itself of the light modulation element shown in the figure is the same as that shown in FIG.
b'...) and the insulating layer 6' are made of a transparent medium. In this case as well, sufficient practical effects can be obtained using the optical system described above. In other words, in FIG. 6, point P is considered to be an image forming point formed when the incident light beam 16 passes through the refractive index distribution 7, and there is a conjugate relationship with this point P as explained in FIG. By arranging the lenses and the light-receiving medium in the same manner, the same effect as the structure shown in FIG. 6 can be obtained.

FIGS. 7(A) and 7(B) are diagrams showing other embodiments of the light modulation device according to the present invention, in which the heating resistor in the light modulation element LM is similar to the optical system shown in FIG. A linear image is formed in the arrangement direction of 6a, 6b, . . . . FIG. 7(A) is a developed view seen from a direction perpendicular to the line image. FIG. 7(B) is a side view of FIG. 7(A). The difference from the optical system shown in FIG. 5 is that the light beam emitted from the light source is
As shown in FIG. 7(A), the light modulator L-M
A conjugate image of the light source is formed between the lens 25 and the lens 25, as shown in FIG.
), the lens 20a, ! =7t% A line image is formed in the vicinity of the heating resistor of the light modulation element LM by the line image forming optical system 20 which is a combination system of the Fick lens 20b. In FIG. 7(A), by arranging a rectangular light shielding filter 23 having long sides in a direction perpendicular to the arrangement direction of the heat generating resistors 6a, 6b, . . . at the conjugate image position of the light source, the refractive index distribution is improved. The luminous flux that is not diverged by the refractive index distribution is blocked, and the luminous flux that is diverged by the refractive index distribution passes around the light shielding filter 23 and passes through the heating resistor (6a
, 6b... enters the lens 25 that keeps the light-receiving medium 14 in a conjugate position, and forms an image on the light-receiving medium 14) 24
5Ll 24b@... is formed. In this way, the configuration of the optical system as shown in FIG. 5 can be simplified.

As described above, in the light modulation device according to the present invention, by keeping the origin of the light beam modulated by the refractive index distribution generated in the thermal effect medium and the light-receiving medium in an optically conjugate ratio of 1, It can form a sharp point image with high brightness.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing an embodiment of the light modulation element applied to the light modulation device according to the present invention, and FIG.
FIG. 4 is a diagram showing an embodiment of the light modulation device according to the present invention.
A) and (B) are diagrams showing a preferred embodiment of illuminating a light modulation element according to the present invention, FIG. 5 is a diagram showing another embodiment of the light modulation device according to the present invention, and FIG. FIGS. 7(A) and 7(B) are diagrams showing other embodiments of the light modulation element applied to the light modulation device according to the present invention, respectively. 1...Fist transparent preservation plate, 6a, 6b, 6Q, 6dφ...Heating resistor, 2...Medium thin layer, LM...Light modulation element, 6.0 Insulating layer, 7... Refractive index distribution 4...Heating resistor layer, 11...Non-divergent light flux 5・ψ・
Support, 12...Divergent light flux P...Divergent origin, 14...Light-receiving medium 15a--Light shielding filter Applicant Canon Corporation

Claims (1)

[Scope of Claims] 0) An optical modulator comprising an element that modulates an incident light beam by generating a refractive index distribution in a medium using heat, and an optical system that focuses the light beam from the element onto a light-receiving medium. . A light modulation device, characterized in that an imaging point of a light beam incident on the refractive index distribution section and a light receiving medium are in an optically conjugate relationship with respect to the optical system.