JPS62284323A - optical scanning device - Google Patents

Abstract

PURPOSE:To obtain the titled scanner which generates no noise and whose mechanical accuracy is excellent, by allowing a light beam which is deflected by a resonance type scanner, to pass through a correcting optical lens, a collimation lens and a diffraction grating. CONSTITUTION:A light beam 2 from a laser light source 1 is reflected by the surface of a reflecting mirror 3 consisting of a bimorph piezoelectric element, etc., and as for its light, its scanning speed is made uniform by using an ftheta lens being a correcting optical lens 4, etc. Subsequently, the light beam 2 becomes parallel rays by a collimation lens 5, formed to a spot shape by an unequal interval diffraction grating 6, and also, deflected, and reaches on a scanning surface. When said beam is displaced to a position 3a by vibrating the piezoelectric element 3, a displacement point of an incidence to the collimation lens surface and the diffraction grating surface of the light beam 2 also moves to 5a and 6a, and a scanning point is displaced to 7a on the scanning surface, as well. When a recording material is placed on the scanning surface 7 and the piezoelectric element 3 is vibrated by driving a voltage, a spot of the light beam 2 moves on the recording material and recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to an optical scanning device used for scanning a light beam in a laser printer, a liquid crystal display, etc. The present invention relates to an optical scanning device that obtains a desired scanning length without using.

2. Description of the Related Art Conventionally, polygon scanners using rotating polygon mirrors have been generally used in laser printers and the like, and hologram scanners using holograms (diffraction gratings) are also known. However, the polygon scanner is a mechanical optical scanning device driven by an electric motor.
Since the number of revolutions is very high, the noise is high, and in order to eliminate the effects of surface runout, it is necessary to have high mechanical precision, and therefore, the major disadvantage is that it is expensive.

In addition, hologram scanners that use holograms, or diffraction gratings, have advantages over polygon scanners in terms of noise, surface vibration accuracy, price, and the use of cylindrical optical systems, but there are problems associated with the use of electric motors. Although there are differences in degree, it is essentially the same as a polygon scanner, and the technology for attaching multiple holograms on a disk is
It has a very difficult drawback in terms of accuracy. On the other hand, non-mechanical optical scanning devices that use electro-optic effects and acousto-optic effects are known, but both have small deflection angles and therefore short scanning lengths. In addition, there were drawbacks such as poor light efficiency.

Problems to be Solved by the Invention Conventional scanners using rotating polygon mirrors or holograms are driven by electric motors, making them noisy, expensive, and requiring extremely high mechanical precision. Scanners that use the electro-optic effect or acousto-optic effect, which are mechanical scanners, have a small deflection angle and therefore a short scanning length.
In addition, there were drawbacks such as poor light efficiency. The present invention
Taking this point into consideration, by using a resonant scanner, an f-theta lens, a collimation lens, and a diffraction grating, it is possible to reduce noise, reduce mechanical precision, and achieve a scan length without using an electric motor. is long (
The present invention provides an optical scanning device with high light efficiency.

Means for Solving the Problems In order to solve the above problems, the present invention provides a resonant scanner, such as a piezoelectric scanner using a piezoelectric vibrator, or a piezoelectric scanner in which a reflecting mirror is installed on the piezoelectric vibrator as necessary. is used to deflect the light beam by driving it, and then input this light beam into a correction optical lens,
By correcting aberrations, making the beam incident on a collimation lens to make it parallel, and then making it incident on an unevenly spaced diffraction grating to achieve the desired scanning length, it does not involve rotating parts such as electric motors. This provides an efficient optical scanning device.

Operation The present invention, with the above-described configuration, does not include a rotating part such as an electric motor, and therefore can efficiently deflect a light beam over a desired scanning length with a relatively simple configuration.

Embodiment An optical scanning device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram showing an embodiment of an optical scanning device of the present invention. A light beam 2 emitted from a laser light source 1 is reflected on the surface of a reflecting mirror 3 made of a piezoelectric element, such as a bimorph piezoelectric element, and the light is reflected at a scanning speed using a correction optical lens 4, such as a spherical lens, or an fθ lens. Make it constant. A toric lens may also be used as the optical lens 4 when correction of surface blur of the reflecting mirror 3 is required. The light beam that has passed through the optical lens is incident on a collimation lens 5 to become parallel light beams, and then is incident on a diffraction grating 6.

If an unevenly spaced diffraction grating is used as the diffraction grating 6, the light beam passing through the diffraction grating 6 will be
It forms a spot and is deflected by the deflection action of the diffraction grating, reaching the scanning surface 7. When the piezoelectric element 3 is vibrated and displaced to the dotted line 3a, the displacement points of the light beam incident on the collimation lens surface and the diffraction grating surface also move to 5a and 6a, and as a result, the scanning point also changes on the scanning plane. Displaced to 73. When a recording material is placed on a scanning surface and the piezoelectric element is vibrated by voltage driving, the spot of the light beam moves on the scanning surface, that is, on the recording material, and recording can be performed.

As the laser light source 1, an H6-Me laser or a semiconductor laser is useful. A piezoelectric element reflecting mirror uses a PZT element or the like as a piezoelectric element, and the surface that is hit by the laser beam is
Mirror polishing is performed, and a reflective film of gold or aluminum is formed. Gold films and the like are also used as drive electrodes for piezoelectric elements.

Piezoelectric elements require hot pressing to create a dense element. Furthermore, a bimorph structure is also useful. Further, as shown in FIGS. 2 and 3 as an example of a bimorph piezoelectric element reflecting mirror, a phosphor bronze plate 9 is adhered to the bimorph piezoelectric element 8, and a gold reflective film 10 is formed on the phosphor bronze plate. It is also possible to use a structure with a Also, if necessary, a thin glass plate can be used instead of the phosphor bronze plate.
Soricon thin plates can also be used. The scanning speed can be changed by changing the driving frequency of the bimorph piezoelectric element. The driving frequency can be made from several tens of hertz to several tens of kilohertz.

A hologram created by interference between a plane wave and a spherical wave or an interference between a spherical wave and a spherical wave of laser light is useful as the nonuniformly spaced diffraction grating.

FIG. 4 shows the incident angle θ1 and the diffraction grating θ6 when a light beam consisting of a laser beam is incident on the diffraction grating 11 and diffracted.
The zero diffraction angle θ, which shows the relationship diagram, is expressed by the following equation.

fλ=sinθa-sine.

f: Spatial frequency of the diffraction grating λ: Wavelength of the laser beam When the laser beam is incident perpendicularly to the diffraction grating surface, θ, =
Since it is 0, fλ=sinad.

Figure 5 shows the change in the diffraction angle due to the change in spatial frequency when a laser beam with a wavelength λ = 0.78μ is incident perpendicularly to the grating plane of an unevenly spaced diffraction grating whose spatial frequency varies depending on the location. show. As shown in the figure, by setting appropriate conditions, the diffraction angle, that is, the deflection angle, and therefore the scanning length can be expanded.

Effects of the Invention The present invention uses a resonant scanner to convert a deflected light beam into a correction optical lens and a collimation lens.

By passing the light through a diffraction grating, it is possible to create an optical scanning device that does not use an electric motor and is therefore superior in terms of noise, mechanical performance, etc.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing an embodiment of the optical scanning device of the present invention, FIGS. 2 and 3 are conceptual diagrams of a bimorph piezoelectric element reflecting mirror, and FIG. 4 is: A light beam is directed onto a diffraction grating. FIG. 5 is a conceptual diagram showing the relationship between the incident angle and the diffraction angle when the light is incident, and is a graph showing the relationship between the spatial frequency and the diffraction angle when the incident angle is perpendicular to the diffraction grating surface. 1... Laser light source, 2... Light beam,
3...Piezoelectric element reflecting mirror, 4...Correction optical lens, 5...Collimation lens, 5a
...Displacement point of the incident light on the collimation lens, 6...Diffraction grating, 6a...Displacement point of the incident light on the diffraction grating, 7... Scanning plane, 7a...
... Displacement point of scanning point, 8 ... Bimorph piezoelectric element, 9 ... Phosphor bronze plate, 10 ... Gold reflective film, 11 ... Diffraction grating. Name of agent: Patent attorney Toshio Nakao 1 person Figure 4 Figure 5
Tsuju 8

Claims (5)

[Claims] (1) An optical scanning device characterized by comprising a resonant scanner, a correction optical lens, a collimation lens, and a diffraction grating. (2) The optical scanning device according to claim (1), wherein the correction optical lens is an fθ lens. (3) The optical scanning device according to claim (1), wherein the resonance type scanner uses a piezoelectric vibrator. (4) The optical scanning device according to claim (1), wherein the diffraction grating is an unevenly spaced diffraction grating. (5) The optical scanning device according to claim (1), wherein the resonant scanner includes a light beam reflecting mirror.