JPS6031115A - Optical modulating device - Google Patents

Abstract

PURPOSE:To obtain a good light extinction ratio by shielding a luminous flux which is not modulated by a luminous flux generated from each light emitting part at a position optically conjugate to plural light emitting parts placed along an optical modulating part in order to illuminate an optical modulating element. CONSTITUTION:A luminous flux from a light source 20 is condensed to a pin hole part of a pin hole plate 22 by a condensing lens 21. As for the luminous flux for which each pin hole is used as the secondary light source, a component in the in hole array direction is collimated by a collimator lens 23 and made incident to an optical modulating element 24. A luminous flux L1 whose wave surface is not converted by the optical modulating element 24 is made to form an image on a light shielding part 31b of a light shielding filter 30 by a multi-lens array 30. On the other hand, a luminous flux L2 whose wave surface has been converted by the optical modulating element 24 is condensed by the multi-lens array 30, passes through a light transmitting part 31b of the light shielding filter 31, and is made to form an image on a photosensitive drum. In this way, a modulating device of a high extinction ratio is obtained by a simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light modulation device that can be widely used in recording devices, display devices, optical communication devices, etc. Conventionally, recording or displaying using a light beam has been widely used. It is being done. A typical example of this is a laser beam printer, which uses a mechanical deflector to deflect a light beam, modulates the light beam, and records information on a photosensitive drum. On the other hand, in recent years, it has been proposed to cause a physical change locally and to modulate the luminous flux by this physical change. For example, in Japanese Patent Application Laid-Open No. 56-5523, an electric field is locally applied to a crystal made of an electro-optic material,
It has been shown that optical modulation is performed by changing the refractive index of the portion to which this electric field is applied. Furthermore, Japanese Patent Application No. 57-128566 filed by the present applicant discloses a method of generating vapor bubbles locally in a liquid and modulating the luminous flux by the vapor bubbles. The paper describes a method of modulating the luminous flux by thermally generating a refractive index distribution locally in a liquid. In such a light modulation device,
Since the light modulation section has a fine structure, the number of light modulation sections corresponding to the number of resolution points necessary to form a scanning line, for example, approximately 2,000 in the width direction of an A4 sheet, is provided in a straight line. , it is possible to simultaneously form an image corresponding to one scanning line.

An object of the present invention is to provide a light modulation device that uses the above-mentioned light modulation element and can obtain a good extinction ratio.

The light modulation device according to the present invention includes a light modulation element in which a plurality of light modulation parts that cause a local physical change in a medium and enable light modulation are arranged in a predetermined direction; A plurality of light emitting sections arranged along the light modulating section for illumination, and a light shielding section that blocks light beams that are not modulated by the light beams emitted from each light emitting section at positions optically conjugate with the light emitting sections. It has a member. Note that the light emitting part and the light shielding member have an optically conjugate relationship at least in a plane that includes the optical axis of the optical member and is determined by the arrangement direction of the light modulating part with respect to the optical member disposed between them. Further features of the present invention will become clear from the description of the present invention shown below. In the following description, a type of light modulation element that changes the refractive index distribution in a heat-generating medium will be used as the light modulation element, but the light modulation element according to the present invention may be of the various types described above. It goes without saying that the following light modulation elements can be used.

1 to 4 are diagrams showing one embodiment of a light modulation element applied to a light modulation device according to the present invention. In Figure 1, 1 is a transparent protective plate, 2 is a thin layer of a thermal effect medium whose refractive index is easily changed by heat, 3 is a thermally conductive insulating layer, and 4
is 6a.

6b16c, 6d... is a heat generating resistor layer in which heat generating resistors are arranged; 5 is a support for the insulating layer 3 and the heat generating resistors 6a) 6bl 6c, 6d... . When the heating resistor generates heat, this heat is transmitted through the insulating layer 3 to the thin thermal effect medium layer 2, creating a temperature distribution within the thin liquid layer and forming a refractive index distribution. for example,
As shown in FIG. 1, when the heat-generating resistor 6b is selected and generates heat, this heat is transmitted to the heat effect medium thin layer 2 through the insulating layer 3 adjacent to the resistor 6b, and the heat is transferred to the heat effect medium thin layer 2 facing the resistor 6b. The liquid in the area of the thin thermal effect medium layer 2 is heated to form a refractive index profile 7 in this area. This refractive index distribution 7 disappears after a predetermined period of time as the thermal effect medium in this region cools. 1 from the formation of this refractive index distribution to its extinction
The cycles are very short (j) and can be performed on the order of KHz. The above heating resistor is ■・C
It is formed on the support 5 by the manufacturing technique of
The spacing between adjacent heating resistors is on the order of mμ. As for the thermal effect medium, liquids are water, alcohol, and others are -4.0X 10 . In addition, solid materials include plastic materials such as acrylic and polycarbonate, and epoxy resins used as adhesives.
^n High polymer materials such as fat are good. c, kT is approximately -1.0X10. in the case of acrylic. Approximately - for polycarbonate
1,3X 10 is 0 FIG. 2 is a schematic perspective view showing the configuration of the light modulation element shown in FIG. 1, and numbered 1 to 6 are the same as shown in FIG. 1. 8 is a conductive wire and heat generating resistor (6a, 6b,...
...) are connected to the drive voltage of each machine that 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 resistor 6
a.

When a voltage signal is applied to each of 6b, . . . , a refractive index distribution is generated in the thin layer of the thermal effect medium 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. 3 is a diagram showing a transmission type light modulation element. The structure of the light modulation element itself is the same as that shown in FIG. ) and the insulating layer 3' are made of a transparent medium.

FIG. 4 shows a reflective light modulation element L- based on the refractive index distribution.
FIG. 2 is a diagram showing an example of a light modulation device using M, and is an example in which a light beam whose wavefront is modified by a refractive index distribution is used as information light. When the light beam 10 is incident on the light modulation element LM and any heating resistor 6c among the heating resistors (6a, 6b, . . . ) is driven by the voltage Vi, a refractive index distribution 7 is generated. The light beam incident on the heating resistor 6c becomes a light beam 12 with a deformed wavefront and exits. The light beam 11 that is specularly reflected on the surface of the heating resistor and whose wavefront is not deformed by the refractive index distribution 7 is imaged by the lens 13a,
The light beam 12 whose wavefront is deformed is partially blocked by the light-shielding filter 15a placed at the image forming position. By making the imaging spot of
It is possible to irradiate on 4.

As described above, by applying the voltage pulse Vi corresponding to the image signal to the heating resistor 6c through the conductive wire 8 or making it zero, the refractive index distribution 7 is repeatedly generated or eliminated accordingly.

In that case, a blinking light spot is generated on the light receiving medium 14. By creating a conjugate relationship between a point on the heating resistor and a point on the light-receiving medium 14 using the lens 13a,
An image of a portion where a refractive index distribution occurs near the heating resistor (6a16b, . . . ) is formed as a spot on the light receiving medium 14.

FIG. 5(4), ω) is a diagram showing an embodiment of a recording device using a light modulation element according to the present invention, FIG. 5(2) is a perspective view, and FIG. 5(B) is a A schematic plan view is shown.

In FIG. A pinhole plate having a plurality of pinholes arranged at an optical position and arranged at equal intervals on a straight line, 23
Before! A collimating lens that has a function of collimating at least a luminous flux component in the pinhole arrangement direction of each luminous flux emitted from each pinhole of the pinhole plate 22 as a point light source, and the lens is constituted by a single normal optical axis. It may be constructed as a system, or as shown in the figure, it may be constructed as a multi-lens array such as a bar lens or a gradient index lens.

24 is the above-mentioned light modulation element, and a plurality of heating resistors (25a, 25b) are arranged in the direction in which the pinholes are arranged.
, 25cb-...) 026 is a video signal source, 2
7 is a voltage applying means for converting the electric signal from the video signal source 26 into a voltage, and 28 is a means for applying the voltage from the voltage applying means 27 to each heating resistor (25a, 25b, 25c).
, -...) is a conductive wire whose one end is connected to the heating resistor (25a, 25bs25c1...) and the other end is grounded. Reference numeral 30 denotes a lens system for condensing the light beam passing through the light modulation element 24. This lens system may be composed of a lens system having one optical axis, or it may be composed of a multi-lens array as shown in the figure. Reference numeral 031, which may be configured, is a light-shielding filter disposed on the focal plane of the lens system 30, with a pitch proportional to the pitch of the pinholes disposed on the pinhole plate 22, or a pitch equal to this pitch. Light blocking portions 31m and light transmitting portions 31b are provided alternately. Therefore, the collimated light beam that is not subjected to wavefront conversion by the light modulation element 24 is imaged by the lens system 30 on the light-shielding portion of the light-shielding filter 31 . 32 is a heating resistor (25&, 25
b% 25c1"...") is a photosensitive drum arranged at a position that is almost optically conjugate.

The light beam from the light source 20 is focused onto a pinhole portion of a pinhole plate 22 by a condenser lens 21 .

At least a component of the light flux using each pinhole as a secondary light source in the pinhole arrangement direction is collimated by the collimator lens 23 and enters the light modulation element 24 . The light beam L1 whose wavefront is not converted by the light modulation element 24 is routed to the multi-lens array 30 and passes through the light shielding portion 31b of the light filter 30.
is imaged. On the other hand, the light beam L2 whose wavefront has been converted by the light modulation element 24 is focused by the multi-lens array 30, passes through the transparent portion 31b of the light-blocking filter 31, and is imaged on the photosensitive drum.

In this embodiment, a pinhole plate is used to form a plurality of linear point light sources, but an array of laser diodes may be provided instead of the pinhole plate.

Each light emitting part of this laser diode array is made to have an optically conjugate relationship with the light shielding part 31 of the light shielding filter 31 by the lens system (23, 24).〇Figure 6 (4) 5 is a diagram showing the shape of the heating resistor of the light modulation element 24 for effectively utilizing the luminous flux from the light source in the recording apparatus shown in FIG.

4xt (t=t~N) is a heating resistor, 42(i) is an electrode for voltage applied by the voltage applying means, and 43 is a ground electrode. It will be explained in FIG. 6) that the shape of the heating resistor can efficiently guide the light beam deflected in the direction in which it is arranged.

Figure 6 @) shows one heating resistor 4 shown in Figure 6 (2).
1(i) shows an equal refractive index distribution curve in a thermal effect medium formed when a voltage is applied. Figure 6 (4)
As shown in , the length tY of the heating resistor in the arrangement direction is shorter than the length 1x in the direction perpendicular to it (tY < tx
), the equirefractive index curve becomes an elongated ellipsoidal distribution with the major axis in the tx direction, as shown in 44. This means that the refractive index change becomes steep in the direction of t, and the light flux incident on the part of the refractive index distribution has a strong wavefront transformation in the direction of tx and tY. This is because it is acted upon. Therefore, a large amount of light beam is deflected in the direction in which the heating resistors are arranged, and the light beam can be efficiently utilized by separating the modulated light beam and the non-modulated light beam using an optical system as shown in FIG. 5(4).

As described above, in the optical modulation device according to the present invention, a modulation device with a high extinction ratio can be obtained with a simple configuration.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 are diagrams for explaining an example of a light modulation element applicable to the light modulation device of the present invention,
FIG. 5 (B) is a diagram showing an embodiment of a recording device to which the optical modulation device of the present invention is applied; FIG.
FIG. 4 is a diagram showing an example of the shape of the heating resistor of the light modulation element shown in FIGS. (4) and (B). 2o... Light source, 21... Curved condensing lens, 22...
...Pinhole plate, 24...Tune modulation element, 25a
. 25b, 25c...Heating resistor, 23.30.
...Multi-lens array, 31° curved light tracing filter, 32...Photosensitive drum, Ll...
Non-modulated light flux, L...Modulated light flux. −= (old name is ■) ) sleep

Claims (3)

[Claims] (1) A light modulation element in which a plurality of light modulation parts are arranged to modulate light by locally applying physical changes to a medium, and a light modulation element arranged along the arrangement direction of the light modulation parts to illuminate the light modulation element. A light modulation device comprising a plurality of light emitting sections and a light shielding member provided at a position optically conjugate with each of the light emitting sections. (2) The light modulation device according to claim 1, wherein the light emitting section comprises a light source that emits a luminous flux and a pinhole array that regulates the luminous flux from the light source. (3) The light modulation device according to claim 1, wherein the light emitting section is a light emitting diode array.