JPH02931A - Optical scanning recorder - Google Patents

Abstract

PURPOSE:To stabilize the quantity of recording light and to increase the modulation speed by using an electrooptic modulator which modulates a light beam incident on a surface acoustic wave. CONSTITUTION:An optical deflector 10 has a slab type optical waveguide 11 formed on a transparent substrate 16, an interdigital electrode couple (IDT) 15 provided to a side end part of the optical waveguide 11, an electrooptic grating (EOF) 14 as the electrooptic modulator, a linear diffraction grating (LGC) 20 for light incidence, and an LGC 21 for light projection. Consequently, variation in the wavelength of the recording light due to direct modulation on a semiconductor laser 18 as a recording light source can be prevented, so the variation in the quantity of the recording light caused by this wavelength variation is prevented to record a highly fine image of high picture quality. Further, the state of voltage application to the optical modulator is changed and then the modulation state of the light beam changes instantaneously, so the modulating speed can be increased.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an optical scanning recording device, and more particularly, to a method for guiding a light beam as recording light into an optical waveguide, and propagating this light beam in the optical waveguide. The present invention relates to an optical scanning recording device in which the surface acoustic waves are deflected and taken out from the optical waveguide.

(Prior Art) As an optical deflection device for deflecting a light beam in an optical scanning recording device, mechanical optical deflectors such as galvanometer mirrors and polygon mirrors, EOD (electro-optic optical deflector), and AOD (acousto-optical optical deflector) have conventionally been used. optical deflectors) are often used. However, mechanical optical deflectors have problems such as poor durability and tendency to increase in size.
In D and AOD, since the optical deflection angle cannot be large, the beam optical path becomes long, leading to an increase in the size of the optical scanning recording device, etc., which is a problem.

Recently, as an optical deflection device that can solve the above-mentioned problems,
Optical deflection devices using optical waveguides are attracting attention. This optical deflection device consists of a slab-shaped optical waveguide made of a material that allows surface acoustic waves to propagate, and a surface whose frequency changes continuously as it travels in the direction intersecting the optical beam guided inside the optical waveguide. It has means for generating elastic waves in the optical waveguide (for example, composed of a pair of crossed comb-shaped electrodes and a driver that applies an alternating voltage whose frequency changes continuously to the pair of interdigitated electrodes). In this optical deflection device, the light beam guided in the optical waveguide undergoes Bragg diffraction due to acousto-optic interaction with the surface acoustic wave, and this diffraction angle changes depending on the surface acoustic wave frequency, so the surface acoustic wave By varying the frequency as described above, the light beam can be continuously deflected within the optical waveguide.

The light beam thus deflected can be emitted out of the optical waveguide by, for example, a diffraction grating (grating coupler) formed on the surface of the optical waveguide, a prism coupler, or the like. In order to configure an optical scanning recording device using this optical deflection device, a light source that generates a light beam as recording light and a photosensitive material placed at a position to be irradiated with the light beam emitted from the optical waveguide are required. A sub-scanning means for moving the light beam relatively in a direction substantially perpendicular to the direction of deflection thereof is provided, and a modulation means for modulating the light beam based on an image signal (intensity modulation or pulse modulation) is provided. Bye.

The above-mentioned optical deflection device is described in detail in, for example, Japanese Patent Application Laid-open No. 77761/1983.

(Problem to be Solved by the Invention) By the way, in order to modulate the light beam as described above, conventional methods have been to directly modulate the semiconductor laser that emits the light beam as the recording light, or to change the intensity of the surface acoustic wave. This was done to change the diffraction efficiency of the guided light, that is, the amount of light beam to be deflected. Note that as means for generating surface acoustic waves, a pair of crossed comb-shaped electrodes and a driver as described above are generally used, and in this case, the intensity of the surface acoustic waves can be controlled by changing the value of the voltage applied to the pair of electrodes. It can be changed.

However, when directly modulating a semiconductor laser as described above, fluctuations in the optical wavelength, especially wavelength jumps due to mode hopping, are likely to occur, which causes the diffraction efficiency of the guided light by the surface acoustic wave to fluctuate, resulting in a decrease in the recording light. There is a problem that the amount of light tends to become unstable.

Furthermore, when changing the intensity of the surface acoustic wave, the modulation frequency The problem is that it is difficult to increase the This will be explained in detail below. When the beam width of the guided light is D1 and the speed of the surface acoustic wave is V, the time τ required for the surface acoustic wave to cross the guided light is τ - D
/V. The above beam width is generally set large in order to obtain a large number of resolution points, for example, D-1.
mm and v = 3500m/S,
τ-0,28 [iμs. Since the modulation frequency fM is at most fM-1/τ, in the above case, at most f
H=3.5 MHz, which is quite low. If the modulation frequency is low in this way, high-speed recording will naturally become difficult.

The present invention has been made in view of the above circumstances, and is an object of the present invention to stabilize the amount of recording light and increase the modulation speed in an optical scanning recording device that uses an optical waveguide to deflect a light beam. With the goal.

(Means for Solving the Problems) An optical scanning recording device according to the present invention is an optical scanning recording device equipped with a light source, an optical waveguide, a surface acoustic wave generating means, and a sub-scanning means as described above. , the optical waveguide is formed from a material having an electro-optic effect, and an optical modulator for modulating the optical beam is disposed in the optical path of the optical beam guided in the optical waveguide, and an electric field is applied to the optical waveguide. The present invention is characterized by using an electro-optic light modulator that modulates the light beam incident on the surface acoustic wave by changing the diffraction efficiency of the light beam by changing the .

(Function) If the optical modulator described above is used, it becomes unnecessary to directly modulate the semiconductor laser as the recording light source, and by changing the voltage application state to the optical modulator, the modulation state of the light beam can be changed instantaneously. , the modulation speed can be increased.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

1 and 2 show an optical scanning recording apparatus according to an embodiment of the present invention. The optical deflector 10 includes a slab-shaped optical waveguide 11 formed on a transparent substrate IB, and a pair of crossed comb-shaped electrodes (I
inter D Igltal Transdue
(hereinafter referred to as IDT) 15, and an electro-optic grating (E IDT) as an electro-optic light modulator.
optlcG ratings (hereinafter referred to as EOG)
14, and a linear diffraction grating for light incidence (L 1 near G
ratlng couple" (hereinafter referred to as LGC) 20 and a light output LGC 21. Also, on the surface lea of the substrate 16 opposite to the optical waveguide 11, a light input prism 30 and a light output prism 30 are provided. 31 is attached.The light entrance prism 30 has a triangular cross section, and has a first light passing surface 30a and a second light passing surface 3.
0b, and the first light passing surface 30a is on the substrate surface te.
It is tightly fixed to the surface 16a by being strongly pressed against the surface 16a or by using an adhesive with a high refractive index.

The light emitting prism 31 has the same shape as the light entering prism 30, has a first light passing surface 31a and a second light passing surface 31b, and is fixed to the substrate lea in the same manner as described above. .

In this embodiment, as an example, LiNb0 is used on the substrate 1B.
．． The optical waveguide 11 is formed by using a wafer and providing a Ti diffusion film on the surface of the wafer. Note that substrate 1
As the material 6, a crystalline substrate made of sapphire, Si, etc. may also be used. Furthermore, the optical waveguide 11 is not limited to the above-mentioned Ti diffusion, but may also be formed by sputtering, vapor depositing, or the like other materials on the substrate 16. Regarding optical waveguides, for example, T, Tal1lr
) ed. “Ingrated Obtics (Inte
gratcdOptIcs)J(Topics in Applied Physics(Topics in Ap)
plied Physics) Volume 7) Springer-Verlag
Published (1975); Co-authored by Nishihara, Haruna, and Suhara, "Optical Integrated Circuits"
There is a detailed description of the success or failure of Ohm columns (19g5), etc.
In the present invention, any of these known optical waveguides can be used as the optical waveguide 11. However, this optical waveguide 11 is formed of a material, such as the above-mentioned Ti diffusion film, that allows surface acoustic waves (described later) to propagate and exhibits an electro-optic effect. Further, the optical waveguide may have a laminated structure of two or more layers.

The semiconductor laser 18 that emits recording light emits a light beam (
It is arranged so as to emit a laser beam (laser beam) 13.

This light beam 13, which is a diverging beam, is made into a parallel beam by the collimator lens 27, and then enters the light incidence prism 30 from the second light passing surface 30b, and passes through the first light passing surface 30a. The light passes through the substrate 16, passes through the optical waveguide 11, and enters the LGC 20 formed on the surface thereof. Thereby the light beam 13
is diffracted by this LGC 20 and enters the optical waveguide ll,
The light beam propagates in the direction of arrow A within the optical waveguide 11 in a waveguide mode.

When recording an image, the photoreceptor 23 is set on a transport means 22 such as an endless belt.

The semiconductor laser 18 is driven by a laser drive circuit I9.
The IDT 15 is driven to emit a laser beam 13, and at the same time, an alternating voltage whose frequency changes continuously is applied from a drive circuit 17 to the IDT 15. On the other hand, a voltage V is applied from the drive circuit 24 to the E OG 14 arranged in the optical path of the guided light (parallel beam) 13. The value of this voltage ■ is
The modulation circuit 25 that receives the image signal S changes the intensity of the light beam 13 according to the signal S (in other words, it changes continuously when the intensity is modulated on the light beam 13, and when it performs 0N-OFF modulation, it changes the intensity of the light beam 13 between two values). (to selectively take one of the two).

The above EOG 14 forms a diffraction grating, and the guided light 13 is diffracted by this EOG 14, and the diffracted light 1
3° travels in the direction indicated by the solid line in FIG. The refractive index of E OG 1 changes, and the diffraction efficiency changes.The rate of change of this diffraction efficiency is E OG 1
4, the diffracted light 13' is modulated in accordance with the image signal S.

In addition, EOG 14 in the above example has an electrode finger line width of 3.75 μm, an electrode finger period of 15 μm, an effective length of each electrode finger of t, a mm, 514, a number of pole finger pairs of 100, and a maximum diffraction efficiency η- 93%, modulation frequency fM-25
MHz was achieved. Such an EOG 14 can be formed by a known photolithography method or the like.

On the other hand, by applying the aforementioned voltage to the IDT 15, the surface acoustic wave 12 travels on the surface of the optical waveguide 11 in the direction of arrow B in FIG. The IDT 15 is arranged so that the surface acoustic wave 12 travels in a direction intersecting the optical path of the guided light (the diffracted light) 13'. Therefore, the guided light 13° travels across the surface acoustic wave 12, but
At this time, the guided light 13° undergoes Bragg diffraction due to acousto-optic interaction with the surface acoustic wave 12. As is well known, the deflection angle of the guided light 13' due to this diffraction is approximately proportional to the frequency of the surface acoustic wave 12. As described above, the drive circuit 17 applies an alternating voltage whose frequency changes continuously to the IDT 15, so that the frequency of the surface acoustic wave 12 changes continuously and the deflection angle changes continuously.

Therefore, as shown by arrow C, this guided light 13' is diffracted and deflected so that the diffraction angle changes continuously.

The guided light 13° deflected in this way is
The light is diffracted and emitted from the optical waveguide 11 to the substrate 16 side. In this way, the light beam 13' that has been emitted from the optical waveguide 11 and has become external light passes through the first light passing surface 31a of the light emitting prism 31, enters the prism 31, and enters the second prism 31.
The light passes vertically through the light passing surface 31b and exits from the prism.

The light beam 1 emitted to the outside of the optical deflector 10 as described above
3' passes through a scanning lens 26 consisting of, for example, an fθ lens, is focused to a small beam spot Q, and is focused on a photoreceptor 23.
Scan the top in the direction of arrow U (main scan).

At the same time, the photoreceptor 23 is transferred by the transfer means 22 in the direction of arrow V, which is substantially perpendicular to the main scanning direction, to perform sub-scanning, so that the photoreceptor 23 is two-dimensionally scanned by the light beam 13'. . As mentioned above, this light beam is 13°
is modulated based on the image signal S, so the photoreceptor 2
3, an image carried by this image signal S is recorded.

Note that the image signal S for one main scanning line and the light beam 13'
In order to synchronize with the main scanning, the blanking signal sb included in the image signal S may be used as a trigger signal to control the timing of voltage application to the IDT 15. Furthermore, by controlling the driving timing of the transfer means 22 using this blanking signal sb, the main scanning and sub-scanning can be synchronized.

(Effects of the Invention) As explained above in detail, in the optical scanning recording device of the present invention, the light beam guided in the optical waveguide is modulated by the electro-optic optical modulator, so that the semiconductor It is possible to prevent fluctuations in the wavelength of the recording light caused by direct modulation of the laser, thereby preventing fluctuations in the amount of recording light due to the wavelength fluctuations, making it possible to record high-quality, high-definition images. Furthermore, if the above electro-optic light modulator is used,
By controlling the intensity of the surface acoustic waves, the modulation speed can be significantly increased compared to when optical modulation is performed, so the present apparatus enables high-speed recording.

[Brief explanation of the drawing]

1 and 2 are a perspective view and a side view, respectively, showing an optical scanning recording apparatus according to an embodiment of the present invention.

Claims (1)

[Claims] A slab-shaped optical waveguide formed of a material that allows surface acoustic waves to propagate and exhibits an electro-optic effect, a light source that generates a light beam as recording light, and a light beam that enters the optical waveguide. means for generating in the optical waveguide a surface acoustic wave that propagates in a direction that intersects the optical beam guided in the optical waveguide and whose frequency changes continuously; a sub-scanning means for moving a photosensitive material placed at a position to be irradiated with the light beam emitted from the waveguide relative to the light beam in a direction substantially perpendicular to the direction of deflection of the light beam; Electro-optic light modulation, which is disposed in the optical path of the guided light beam and modulates the light beam incident on the surface acoustic wave by changing the diffraction efficiency of the light beam by changing the electric field application state to the optical waveguide. An optical scanning recording device consisting of a container.