JPS59228633A - Optical modulating element - Google Patents

Abstract

PURPOSE:To allow one driving circuit to drive plural optical modulation parts on time-division basis and simplify a driving means by utilizing positively the long attenuation time of a thermo-optic effect optical modulating element. CONSTITUTION:Conductors 19-1-19-N are connected to electrodes 18-1-18-N of N sets of heating resistors, and rectifying elements 20-1-20-N are connected to their halfway points and further connected to conductors 21-1-21-n so that every three elements are parallel. Further, the conductors are connected to switch elements 22-1-22-n respectively, and only when a signal generated by a switch driving signal generation system is inputted to one of the switch elements, the switch becomes conductive with a conductor 23 which is grounded or held at a specific potential. On the other hand, the signal is inputted from the switch driving signal generation system 24 to a series-parallel converting element 25 and video signals from a video signal generator 26 which are as many as simultaneously driven resistors are outputted in parallel and inputted to heating resistors 18-1- in prallel.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light modulation element that can be used in display devices, recording devices, switching devices, and the like.

Conventional light modulation elements that utilize the electro-optic effect or the acousto-optic effect often use optical crystals, and the response speed of the original modulation to the electrical signal input thereto is fast and the decay time is short.

For example, the decay time of a light modulation element using an electro-optic effect or an acousto-optic effect is often 1 μsec or less.

Therefore, an optical modulation element that utilizes the electro-optic effect or acousto-optic effect can exhibit the advantage of high-speed response as a flying spot scan type modulation element. When used as a shutter array, as mentioned above, since the element has a fast response, the time during which the incident light beam can be modulated is short, so in order to obtain a sufficient amount of light, a high-intensity light source is required. have to use something. Furthermore, if the brightness of the light source cannot be made that high, it is necessary to increase the input time by increasing the width of the input signal for driving the line and light modulation elements.

On the other hand, the present applicant filed a patent application No. 57-179265.
The light modulation element disclosed in Japanese Patent Application No. 58-35077 generates a refractive index distribution by locally applying heat to a thermal effect medium whose refractive index is easily changed by heat, thereby modulating the luminous flux. The modulation characteristics of this thermo-optic effect light modulator are different from those of the electro-optic and acousto-optic light modulators mentioned above, and the most notable difference is that the decay time is several tens of microseconds.
(It is a long time, about several tens of meters5ec.

When forming or displaying an image using a light modulation element such as the one described above, one light modulation section that can independently perform light modulation corresponds to one dot of light modulation on the projection surface. Since there are approximately 210 dots in the width direction, in order to modulate the width direction of an A4 sheet at once, 2100 light modulation sections must be arranged in a row. In order to drive these optical modulators, the same number of drive circuits are required, leading to an increase in size and complexity of the optical modulator.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light modulation element with a simplified driving mechanism in a light modulation element including a plurality of modulation sections.

In the light modulation device according to the present invention, the above object is achieved by paying attention to the long decay time of the above-mentioned thermo-optic effect light modulation device and actively utilizing this phenomenon. In other words, since a thermo-optic effect light modulation element has a long decay time, even if the width of the input signal that drives the light modulation element is short, the light modulation section can perform light modulation over a long period of time. , the total amount of light modulated reaches a sufficient amount. Therefore, since the driving time for driving one modulation part of the light modulation element is short, in other words, the duration of the drive pulse is short, so one drive circuit can drive multiple light modulation parts in a time-sharing manner. I can do it. Therefore, the number of drive circuits can be reduced relative to the number of light modulation sections, and the drive means can be simplified. Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a diagram illustrating the relationship between the input voltage signal and the optical output response characteristic of the thermo-optic effect light modulator used in the present invention, (a)
is a voltage pulse that is an input signal, and (b) is the output response characteristic of light modulated by the refractive index distribution generated in the medium by the voltage pulse. Both horizontal axes are time.

In FIG. 1(a), (a)-1 to (a)-5 are
The case where the voltage value is changed and inputted according to each voltage pulse is shown. In FIG. 1(b), (b)-1 to (b)
-! 1 is a schematic diagram showing the response of light output according to each of the above-mentioned voltage type covers. Here, if the input voltage value is kept constant and the duration of the voltage pulse is shortened, the light intensity ratio between the modulated light and the unmodulated light of the thermo-optic effect light modulation element will decrease, so in Fig. 1, this is done as much as possible. In order to avoid this problem, the voltage value is increased as the duration of the input voltage pulse is shortened. In FIG. 1(b), tDiCi=
1, 2. ...) indicates the decay time of the optical output, and in the case of a thermo-optic effect light modulation element, the characteristics vary depending on the medium and structure used, but generally the decay time iDi is several tens of μs.
Many range from ec to several tens of m5ec. On the other hand, during the pulse of the voltage pulse that is the input signal, τ1 (z=
1.2.・The shorter the length, the greater the effect. The details are described below.

FIG. 2 is a diagram explaining the modulation principle of the thermo-optic effect light modulation element used in the present invention, in which 1 is a transparent retaining plate, 2 is a thermal effect medium that generates a change in refractive index in response to temperature change, and 6 is a light reflecting layer, 4 and 7 are insulators, and 5 is a conductor, which are connected to a heating resistor 6 and a conductive wire 9, and a voltage is applied to the heating resistor 6 by a voltage applying means 10. There is.

8 is a support plate. When a voltage is applied by the voltage applying means 10 to the thermo-optic effect light modulation element having the above configuration, heat is generated in the heat generating resistor B, and the heat propagates into the heat effect medium 2 to change the refractive index. A distribution 21 is formed. Its distribution 2
When the light beam 11 is incident on the / portion, its wavefront is converted and the light is emitted from the light modulation element as a light beam 12 indicated by the broken line in FIG.

When no voltage is applied to the heating resistor 6 by the voltage applying means 10, no refractive index distribution is generated in the medium 2, and therefore the incident light beam is not wavefront-converted and becomes the 16 light beams shown in FIG. It emits as. A light-shielding plate 1 that forms an image of the emitted light beam with an imaging lens 14 and sets an imaging spot of the light beam whose wavefront is not converted at that position.
5 to block light. On the other hand, the light beam whose wavefront has been converted is imaged at a position different from the position of the light shielding plate, a light receiving medium (photosensitive medium, screen, or original sensor) is placed at that position, and the light shielding plate is set to a predetermined size. By selecting the desired wavelength, the light flux having the converted wavefront can be caused to reach the light-receiving medium.

With the above configuration and method, light modulation can be confirmed on the light receiving medium 16 according to the voltage signal applied from the stain pressure applying means 10.

FIG. 6 is a plan view of the thermo-optic effect light modulation element shown in FIG. 2, and a diagram showing a method of driving a voltage signal applied to the heating resistor used in the present invention. In FIG. 6, 17-1.
17-2. ---, 17-N is a conductor, and 18-
1.18-2.・・e・.

It is connected as an electrode of N heating resistors indicated by 18-N.

Each electrode has a conductive wire 19-1, 19-2. ....

19-N is connected, and a rectifying element 20-N is connected in the middle.
1.20-2, -----. Connect conductive wires 21-1 so that 20-N is connected, and three rectifying elements are connected in parallel (hereinafter, this number is referred to as the number of simultaneous drives, and this number is arbitrary, but here it is set to six).゜21-2. -・Fist, 21-n
It is connected to the. Furthermore, conductive wire 21-1.21-2
．． ..., 21-n are switch elements 22-1, respectively.
．． 22-2.

..., 22-n, and each of them is connected to the switch drive signal generation system 24, and the signal generated by the switch drive signal generation system is transmitted to the switch elements 22-1, 22-2, 22-n, and 22-n. -----.

22-n, the switch becomes conductive with the conductor 26 connected to ground or a constant potential. On the other hand, a signal is also inputted from the switch drive signal generation system 24 to the serial-parallel conversion element 25, and the video signal from the video signal generation device 26 is converted into the number of simultaneous drives (
In this case, as mentioned above, the design is such that 6) are simultaneously output in parallel. The parallel signals of the number of simultaneous drives are the heating resistors 18-1. , 18-2, . . . traps are input in parallel. The switch drive signal generation system 24
When the signals inputted from to switch elements 22-1, 22-2, . This results in input to the heating resistor corresponding to the switch element. One of the parallel input signals is a voltage signal with a pulse width τi shown in Fig. 1. At any given time, the parallel signals of the number of simultaneous drives are applied only to the heating resistors corresponding to that number, and are sequentially applied n times. By applying , each video signal is distributed to N heating resistors.

As described above, by utilizing the long decay time, it is not necessary to apply a signal to all N heating resistors at the same time (it is possible to drive the signal divided into n (< N ) times). It is.

The number of heating resistors to be driven simultaneously may be Vn.

FIG. 4 is a diagram showing an optical printer device as an example using the light modulation element of the present invention.
2 are a switch element system, a switch drive system, a serial-to-parallel conversion system, and a video signal generator, each having the same functions as the members shown in FIG. 6, and 27 is a rectifier element 20 shown in FIG. -1 to 20-n, light is modulated according to the principle shown in FIG. Reference numeral 28 denotes a light source device having a light source such as a laser, a light emitting diode, or a halogen.
The light modulation element 27 is illuminated with the light beam emitted from the light modulation element 27. 5
Reference numeral 0 denotes an S source plate that blocks as much of the unmodulated light beam as possible out of the illumination light, and is arranged so as to allow as much of the modulated light beam indicated by the broken line as possible to pass through. The above-mentioned modulated light beam forms an imaging spot by an imaging lens 61 on a cylindrical body 62 provided with an electrophotographic photoreceptor. At this time, the light modulation element 27 has a one-dimensional play of the heating resistor in a direction perpendicular to the plane of the paper, and forms modulated light from the array as a one-dimensional array spot parallel to the generatrix of the cylindrical body 32. It was designed that way.

In FIG. 4, the light source device may be a light source device using a halogen lamp having a linear filament or a halogen lamp having a slit opening, and the illumination optical system 29 may be a cylindrical lens or a multi-lens array.

The number of heating resistors in the light modulation element 270 is 2,000 to 5,000.
00 pieces are arranged and projected onto the electrophotographic photoreceptor 32 with a length of 200 to 300 ff1m by the imaging lens 61.

At this time, the imaging lens may be one that projects with magnification or one that projects at the same magnification.

Particularly in the case of full-scale projection, there is an advantage that the entire apparatus can be made into a shed. Further, in this case, it is highly effective to use a halogen lamp having a linear filament or a light source device having a slit-like opening as described above. That is,
2 as described above using coherent light such as a laser.
If you try to illuminate a heating resistor section with a length of 00 mm to 300 mm, the illumination system will become complicated or large, but if you use a light source device like the one above, the illumination system will be a cylindrical one. It may be a general lens or a multi-lens array.

The light modulation element used in this embodiment is shown in FIG. 2, and although distilled water or ethyl alcohol is used as the thermal effect medium, plastic, polymeric material, liquid crystal, etc. may also be used. 1 during the voltage pulse applied to each heating resistor.
It is 0 μsec to 50 μsec, and the decay time of the modulated light is 100 μsec to 500 μsec. Therefore, the number of driving divisions can be up to about 50.

Further, the modulated light by the light modulation element of the present invention is due to refraction of light due to the refractive index distribution within the thermal effect medium, and the degree of wavefront conversion is greater than that due to diffraction.

This action also has the effect of realizing the above-mentioned divided drive without reducing the exposure amount.

On the other hand, when using the optical modulation element of USP 4,281,904, the incident light beam used needs to have polarization characteristics, and the decay time of the modulated light is also short, so split drive is not necessary. In order to realize K, it is difficult to use a light source like the one of the present invention.

As described above, in the light modulation element according to the present invention, the drive system is simplified by effectively utilizing the modulation characteristics of the thermo-optic effect light modulation element, and it has excellent effects.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are diagrams showing the relationship between signal pulses and modulation characteristics of the thermo-optic effect light modulator used in the present invention, and FIG. 2 is a diagram showing the relationship between the signal pulse and modulation characteristics of the thermo-optic effect light modulator used in the present invention. A diagram for explaining the operation, FIG. 6 is a diagram showing an embodiment of the drive circuit of the light modulation element of the present invention, and FIG. 4 is a diagram showing an embodiment of the optical printer device using the light modulation element of the present invention. Figure shown. 1... Transparent protection plate, 2... Thermal effect medium, 3...
...Light reflecting layer, 4, 7... Insulator, 5 Pot... Conductor, 6... Heat generating resistor, 8-... Support plate, 10...
... Voltage application means, 11... Incident light, 12-...
-Modulated light, 16...Unmodulated light, 14...Imaging lens, 15...-light shielding plate, 16...-light receiving medium, 17
...Fist conductor, 18...Heating resistor, 20...
Fist rectifier element, 2211@@11 switch element, 24...
...Switch drive system, 25... - Direct/load/parallel conversion system, 2
6...Video signal generator, 28...ψ light source device, 27...Light modulation element, 32--Cylindrical body having Φ-electrophotographic photoreceptor. Applicant: Canon Co., Ltd. Page 1 continued 0 Inventor: Yuko Mochizuki, Canon Co., Ltd., 3-30-2 Shimomaruko, Ota-ku, Tokyo

Claims (1)

[Claims] (1) A thermal effect medium whose refractive index changes with heat, a plurality of independent light modulation sections that apply heat to the medium, the light modulation sections are divided into a plurality of predetermined groups, and each group has a 1. A light modulation element comprising a single drive means for driving light modulation sections included in a group, each drive means sequentially driving the light modulation sections included in one group over time.