JPH09133887A - Light beam deflecting optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light beam deflector which is simple in structure, easy to assemble, and small in size and low in cost and responds fast and enables arbitrary positioning by optically expanding the angle of deflection of a beam. SOLUTION: The light beam deflecting optical device is composed of a laser diode LD as a light source, a beam shaping lens 51 which converges the laser beam LB emitted by the laser diode LD after collimating it, a light beam deflector 52 which deflects the laser beam LB passed through the beam shaping lens 51 in two dimensions, and an aspherical lens 53 which operates as a deflection angle expanding mechanism that bends and expands the deflected laser beam LB. Namely, this aspherical lens 53 is provided between the light beam deflector 52 and an exposure surface 54 and then the laser beam LB is bent increasing in the angle of deflection, so that this laser deflecting operation device 50 functions equally to the case wherein the light beam deflector 52 is equipped mechanically with a displacement expanding mechanism.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning device, and more particularly, it is applied to an optical scanning device such as an image forming device or an optical device for performing recording by converging and scanning a light beam on an optical recording medium. The present invention relates to a possible light beam deflector and its optical device.

[0002]

2. Description of the Related Art Various devices to which an optical system is applied, such as an optical scanning recording device such as an electrophotographic copying machine and a laser beam printer, or an optical scanning reading device and an optical communication device, are widely used in various fields. As the scanning method, there are two types of scanning methods, that is, raster scanning and vector scanning, depending on the application. For each scanning method,
In the above equipment, as a means for scanning (also referred to as deflecting or sweeping) a light beam, a mechanical light beam deflector such as a polygon scanner or a galvanometer, or other electro-optical element (abbreviation EOD) or acousto-optical element (abbreviation) Electric deflectors such as AOD) are often used. However, in the former mechanical light beam deflector, the polygon scanner, which is a rotating polygon mirror, is allowed to perform raster scanning at a constant speed only, and a galvanometer capable of vector scanning is difficult to miniaturize and it is difficult to increase the deflection speed. There is a problem. Further, in the latter electric light beam deflector, since the deflection angle of the light beam cannot be made large, the device itself has to be increased in order to increase the movement amount of the light beam by lengthening the optical path length. There is a problem that it becomes large. Furthermore, there is a problem that the optical attenuation becomes (relatively) large and is not suitable for practical use as a two-dimensional deflector.

In recent years, in order to realize the miniaturization of the light beam deflector and the extension of the life of the deflector, it is possible to realize a high-speed response without the need for a movable part and a small piezoelectric loss as a method with a small insertion loss. A light beam deflector using an actuator is drawing attention. As the piezoelectric actuator in this case, there are a piezoelectric bimorph, a unimorph, a laminated piezoelectric element applying a sliding vibration, a piezo element, and the like. In many of these application examples, a method of deflecting the direct reflection mirror by the displacement amount of the piezoelectric element (hereinafter referred to as "direct drive method") is used. Generally, the amount of displacement of the piezoelectric element is as small as several microns to several tens of microns. Therefore, in the case of this direct drive system, it is inevitable to obtain a large deflection angle as compared with the conventional technique. This will lead to a further increase in size.

Therefore, there has been proposed a small-sized deflector having a structure which does not generate a beam shift and which is provided with a displacement amount expanding mechanism for obtaining a relatively large deflection angle using a piezoelectric element and having a small shape dimension. An example of this is a light beam having a ball screw as disclosed in Japanese Patent Laid-Open No. 11287/1990, which converts a linear displacement of a piezoelectric actuator into a rotational displacement and has a conversion / amplification mechanism for amplifying the displacement. There is a deflector. Further, as another prior art, as shown in Japanese Patent Application Laid-Open No. 4-255919, there are provided two arms having different displacement enlargement ratios, and the arms, the piezoelectric element and the arms are connected by an elastic hinge. There is.

Further, as another conventional technique other than these, there is one disclosed in Japanese Patent Application No. 6-236470. That is, as shown in FIG. 4B, the deflection unit 11 includes the table 18,
The displacement magnifying / transmitting mechanism unit 12 includes the elastic hinge portions 9a and 9b and the reflection plate 4, and the support base 13, the transmitting portion 14, the elastic hinge portions 9c and 9d, and the arm 15. The reflection mirror 1 for reflecting the laser beam LB (not shown) is
It is fixed on the reflection plate 4 which is connected to the base 18 of the deflecting portion 11 via elastic hinge portions 9a and 9b. Here, an arm 15 rotatably connected to a support base 13 via an elastic hinge portion 9c at one end (right end in the figure) of the reflection plate 4 to which the reflection mirror 1 is fixed is supported at a support point A. The reflecting mirror 1 is displaced by driving the arm 15, and the reflecting mirror 1 is rotated about the elastic hinge portions 9a and 9b as fulcrums.

The tip of the arm 15 is shaped into an L shape. The transmission portion 14, the arm 15, and the elastic hinge portions 9c and 9d are integrated with the support base 13,
This constitutes the displacement magnifying / transmitting mechanism 12. A piezo element 5, which is a piezoelectric actuator that expands and contracts in the longitudinal direction when a voltage is applied, is provided between the base 18 of the deflection unit 11 and the support base 13 of the displacement magnifying / transmitting mechanism unit 12. At the upper end, the arm 15
The transmission portion 14 connected to the via the elastic hinge portion 9d,
The piezo elements 5 are connected so as to be displaced according to the deformation of expansion or contraction.

When a voltage is applied to the piezo element 5 and the piezo element 5 expands and contracts in the longitudinal direction, the displacement is transmitted from the transmission section 14 to the arm 15 via the elastic hinge section 9d. Then, the displacement due to the expansion and contraction of the piezo element 5 is enlarged in proportion to the lengths of the arms on both sides of the elastic hinge portion 9c, and the arm 15 rotates around the elastic hinge portion 9c as a fulcrum and is connected at the support point A. The reflection mirror 1 to which the reflection plate 4 is fixed rotates about the elastic hinges 9a and 9b as a fulcrum to deflect the laser beam LB. The deflection table 11, the displacement magnifying / transmitting mechanism section 12,
The deflector 10 is formed by fixing the piezo element.

Similarly, as shown in FIG. 5, in order to solve the problem of the beam shift which is the defect of the deflector shown in FIG. 4, the deflector 10 is provided with a reflection mirror 1 for reflecting the laser beam LB. The deflection table 2 and the deflection table 2 are fixed to a reflection plate 4 connected to the deflection table 2 via elastic hinges 3a and 3b of a rotary shaft 20 having both ends fastened. The reflector 4 is the reflector 4
The torsion elastic hinge portions 3a, 3 connected to the rotary shaft 19 integrally manufactured with
b is formed. The piezo element 5, which is a piezoelectric actuator that expands and contracts in the longitudinal direction when a voltage is applied, is attached to the deflection table 2
It is provided inside the piezo element frame 19 on the table 18. The fine adjustment screw 21 is used to fix the piezo element 5 and adjust the rotation angle of the reflection mirror 1. The upper end portion of the piezo element 5 is connected by a transmission portion 14 which is a force point provided near one of the rotary shafts 20. It has been proposed that the transmission portion 14 which is a force point provided for transmitting the displacement of the piezo element 5 to the rotating shaft 20 and the rotating shaft 20 are connected by an elastic hinge 3c.

Further, as a conventional example having a displacement magnifying mechanism which does not use an elastic hinge, there is one disclosed in Japanese Patent Laid-Open No. 4-199116. A piezoelectric element is used as the light beam reflector driving device, and the light beam reflector has a curvature, or a diffraction grating plate in which the light beam reflector is a flat surface and the reflected light is incorporated in the beam traveling path is used. The purpose is to amplify the emission angle of the light beam.

[0010]

However, the light beam deflector disclosed in Japanese Patent Application Laid-Open No. 2-128787 has a large number of parts and includes a sliding portion, so that parts made with high precision cannot be obtained. The cost is increased because it becomes necessary. Further, since these light beam deflectors are mechanical type, the improvement of the response speed is inevitably limited to 2 to 3 times as compared with the conventional technique, and the response speed performance is improved. It's a problem.

Then, the above-mentioned JP-A-4-255919.
Since the optical head actuator including the elastic hinge and the arm for displacement enlargement shown in FIG. 3 and FIG. 3 has the displacement enlargement transmission mechanism having the movable portion, its fabrication requires high-precision finishing. It Therefore, as the required quality of these optical head actuators becomes more accurate, the period required for manufacturing gradually increases, and the production of non-defective products also becomes more difficult. As a result, there is a problem that the cost is increased. Also, these optical head actuators are not suitable for equipment that requires high-speed response because it is not easy to manufacture the part that supports and fixes the mirror at the support point, and the displacement magnifying mechanism with arms does not have excellent start-stop characteristics. There are also problems. Therefore, FIG.
However, as a result of making the mirror surface and the center of rotation the same in order to eliminate the beam shift, this optical beam deflector is miniaturized because the rotation operation mechanism is provided outside the mirror surface. However, there are drawbacks in that there are limitations and the structure is not simple.

In the conventional example disclosed in Japanese Patent Application Laid-Open No. 4-199116, a light beam reflector driving device is a reciprocating piezoelectric element and is intended only for one-dimensional scanning.
The configuration is not such that two-dimensional scanning is possible for vector drawing. Further, since the light beam reflector is directly attached to the piezoelectric element, there are problems that a beam shift occurs and the size of the reflector is restricted.

The present invention has been made in view of the above problems, and its purpose is to have a simple structure, easy assembling, small size and low cost. It is an object of the present invention to provide a two-dimensional light beam deflector capable of drawing on a relatively large area by a vector scanning method capable of realizing high-speed response.

[0014]

[Means for Solving the Problems] Means provided by the present invention for solving the above problems are as follows. First, as described in claim 1, a reflection mirror for arbitrarily changing the direction of a light beam and its driving. In a two-dimensional light beam deflection optical device including a section, (a) a laser diode as a light source, (b)
Shape the laser beam emitted from the laser diode,
An optical system for condensing, (c) a light beam deflector for rotating a reflection mirror to reflect and deflect the laser beam,
(D) A deflection angle expansion mechanism for expanding the deflection angle of a light beam deflected separately from the light beam deflector, and a light beam deflection optical device including each of the above (a) to (d). .

According to a second aspect of the present invention, there is provided a light beam deflection optical device characterized in that the deflection angle enlarging mechanism is a concave lens.

Further, as described in claim 3, there is provided a light beam deflecting optical device, wherein the deflection angle expanding mechanism is a convex mirror.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A light beam scanning system in an optical drawing apparatus includes raster scanning and vector scanning.

The raster scanning method adopted in a general-purpose laser printer or the like is a scanning means for generating a drawing beam which is one-dimensionally moved at a constant speed called main scanning for forming a two-dimensional image. It is composed of scanning means called sub-scanning for step-feeding one scanning line for each main scanning. An image is formed line by line by modulating the light beam emitted during one main scan. At this time, the sub-scanning means is not limited to the step feed, and is allowed to move continuously at a speed sufficiently lower than the main scanning speed. Therefore, in the raster scanning method, a rotating polygon mirror driving device that rotates at a constant speed or a resonant mirror driving device that continuously reciprocates can be used as the main scanning means. In these deflecting means, since it is important that the driving device always rotates at a constant speed after the drive device is started until the drawing is completed, the response characteristic related to the start and stop does not matter so much. On the contrary, there is an advantage that the one having a large inertia and a low response frequency is less likely to be affected by the fluctuation of the scanning speed due to the external disturbance.

On the other hand, the light beam deflection optical apparatus according to the present invention is a vector scanning type drawing apparatus capable of arbitrary positioning, and in this vector scanning, a deflection mirror driving apparatus having two equivalent operation characteristics is required. Is. In vector scanning, XY from a point (x0, y0) having an XY coordinate which is a drawing area to another point (x1, y1)
Drawing is performed by the movement of the light beam deflected by the deflector. In this method, the light beam is continuously irradiated from the start of the movement of the light beam (start of the deflector) to the stop of movement of the light beam (stop of the deflector). Therefore, the drawing performance is greatly affected by the positioning characteristics of the deflector, and the deflector is repeatedly started and stopped for each vector.
The response characteristic related to the start and stop of the deflector is greatly related to the drawing time. The longer the start and stop time, the longer the drawing time. Moment of inertia and motion amplitude are factors that limit this response characteristic.

In mechanical vibration caused by inertial force, if the operation amplitude is increased, a correspondingly larger force acts, and as a result, a large amount of energy is required for driving, and the device and the driving source are increased in size. . Further, the time required for starting and stopping also increases, and the response speed decreases. In order to improve the response speed, it is important to reduce the size and weight to reduce the moment of inertia, and it is also effective to reduce the operation amplitude. However, in the conventional beam deflector using the piezoelectric actuator, as described in the prior art, since the displacement amount of the piezoelectric actuator is small, a mechanism for mechanically expanding and transmitting the displacement in order to increase the deflection angle is provided. I had many things. Further, the provision of the mechanical displacement magnifying transmission mechanism causes a problem that the response frequency of the displacement transmitting system becomes low.

In view of the decrease in the response speed of the deflector due to the provision of the displacement magnifying mechanism in the present invention, the configuration of the drive unit for deflecting the beam, that is, the piezoelectric actuator and the reflection mirror rotationally driven by the actuator is provided. By simplifying as much as possible, driving with a small amplitude, and optically expanding the deflection angle of the beam, the response frequency is improved. As a specific embodiment, the light beam deflected in a two-dimensional minute angle by the mirror of the deflector is incident on an aspherical concave lens or convex mirror to bend the light beam in the direction of expanding the deflection angle. With such a configuration, it is not necessary to mechanically provide the beam deflector with a displacement magnifying mechanism, and a practical drawing size can be obtained with a slight displacement of the actuator.

[0022]

Next, an embodiment of the present invention will be described. <Embodiment 1> FIG. 1 is a schematic configuration diagram of a first embodiment of a light beam deflecting optical device according to the present invention. The optical beam deflecting optical device 50 of this embodiment includes a laser diode LD as a light source, a beam forming lens 51 for collimating and converging the laser beam LB emitted from the laser diode LD, and a laser beam L passing through the beam forming lens 51.
A light beam deflector 52 that two-dimensionally deflects B, and an aspherical concave lens 5 that is an important component of the present invention that functions as a deflection angle expanding mechanism that bends and expands the deflected laser beam LB.
Consists of three.

When the rotation operation of the light beam deflector 52 is started by the drawing position signal converted into an electric signal in synchronization with the start of energization of the laser diode LD, the laser beam LB is deflected within a range of several milliradians at the maximum. To be done. Laser beam LB deflected by the light beam deflector 52
Is incident on the aspherical concave lens 53, is bent so as to enlarge the deflection angle, and is irradiated onto the exposure surface 54. The solid line extending from the light beam deflector 52 to the aspherical concave lens 53 shown in FIG. 1 schematically represents the optical axis of the beam deflected by the light beam deflector 52, and the center line corresponds to the deflection angle of 0 °. . That is, it means the laser beam LB passing through the center of the aspherical concave lens 53. Two lines drawn on both sides of the central line show two states in which the laser beam LB is deflected by the operation of the light beam deflector 52. The laser beam LB that has passed through the aspherical concave lens 53 has the aspherical concave lens 5
A solid line extending from 3 to the exposure surface 54 is shown. The dotted line extending from the aspherical concave lens 53 to the exposure surface 54 indicates the aspherical concave lens 5
3 shows the optical axis of the laser beam LB deflected only by the light beam deflector 52 when the light beam deflector 52 is not provided between the light beam deflector 52 and the exposure surface 54. By providing the aspherical concave lens 53 between the light beam deflector 52 and the exposure surface 54, the laser beam LB is bent in the direction of increasing the deflection angle, and in the laser deflection optical device 50 of the present invention, It functions in the same manner as when the light beam deflector 52 is mechanically provided with a displacement magnifying mechanism. Further, since the deflection angle of the laser beam LB is optically increased, the response characteristic of the light beam deflector 52 is not impaired. At this time, the curvature of the aspherical lens 53 is optimally designed according to the focal length so as not to cause image distortion on the exposure surface 54 due to the incident position of the aspherical concave lens 53 of the laser beam LB. That is, it has the f-θ characteristic and is adapted to obtain an optimum beam spot on the exposure surface 54.

<Embodiment 2> FIG. 2 is a schematic structural diagram of a second embodiment of the present invention. The enlargement of the deflection angle of the laser beam LB of the first embodiment is replaced with the aspherical convex mirror 55. By optimally designing the aspherical convex mirror 55 with this configuration, the same function as that of the first embodiment is provided.

Next, the schematic structure of the light beam deflector according to the present invention will be described with reference to FIG. 3A is a plan view of the light beam deflector, and FIG. 3B is a side view.
For the sake of explanation, a part of the internal structure is transparently shown by a dotted line.

As shown in FIG. 3, the light beam deflector 52
Is one reflection mirror 60, two piezoelectric actuators 61a, 61b and piezoelectric actuators 61a, 61
It is composed of elastic hinges 62a and 62b which are displacement transmitting mechanism portions which respectively convert the displacement of b into a rotational motion. 2
The piezoelectric actuators 61a and 61b and the reflection mirror 6
0 is rigidly coupled to the coupling portions 63a and 63b, respectively. The reflecting mirror 60 that reflects the laser beam LB (not shown) is a plane reflecting mirror, and since the incident laser beam LB has a cross-sectional diameter of several millimeters, the mirror diameter can be 10 mm or less.

Next, the operation of the deflector according to the present invention will be briefly described. One-axis deflection drive is performed by the piezoelectric actuator 61a and the elastic hinge 62a. The piezoelectric actuator 61b and the elastic hinge 62b drive the deflection of the other axis. The piezoelectric actuator 61a is linearly displaced by a displacement amount control signal converted into an electric signal to bend the elastic hinge 62a and rotate the reflection mirror 60 in one rotation direction. On the other hand, the piezoelectric actuator 61b
Is linearly displaced by a displacement amount control signal converted into an electric signal to bend the elastic hinge 62b and rotate the reflection mirror 60 in another rotation direction. By simultaneously driving the two piezoelectric actuators 61a and 61b, the reflection mirror is deflected in an arbitrary direction. FIG. 3 (b)
As shown in FIG. 7, the elastic hinges 62a and 62b of the light beam deflector 52 according to this embodiment are aligned in the height direction from the surface of the reflection mirror 60. With this structure, the centers of rotation of the two axes can be made coincident with each other, so that a deflection error between the axes does not occur.

In this embodiment, the piezoelectric actuator is used to drive the reflection mirror 60, but the piezoelectric element is not limited to a piezoelectric element as long as it can generate a linear displacement, and it can be driven by a voice coil or a giant magnetostrictive actuator. Good. Further, if the system is capable of high-speed response, the X-axis is not the two-dimensional integrated deflector having one reflection mirror as shown in the present embodiment.
A method of driving two axes of −Y by separate mirrors may be used. In this case, a small galvanometer or a DC servomotor that can be directly driven to rotate is effective as a drive device. Other electric or magnetic actuators may be used.

[0029]

According to the present invention, the drive unit for deflecting the beam, that is, the structure of the piezoelectric actuator and the reflection mirror rotationally driven by the same is simplified as much as possible, and driven with a small amplitude. As a result, there is an effect that the response frequency is improved by optically expanding the deflection angle of the beam. A light beam is deflected in a two-dimensional minute angle by a mirror of a deflector and is incident on an aspherical concave lens or convex mirror to bend the light beam in the direction of expanding the deflection angle. It is not necessary to provide a displacement magnifying mechanism, and a practical drawing dimension can be obtained with a slight displacement of the actuator without impairing the response characteristics. Further, since the aspherical concave lens and the aspherical convex mirror are adopted, the degree of freedom in design is increased, and a large displacement magnification ratio can be achieved as compared with a mechanical displacement magnification mechanism. Moreover, since the size of the beam deflector main body can be easily reduced, cost reduction can be realized.

From the above, according to the present invention, it is possible to provide an optical beam deflector which has a simple structure, is easy to assemble, is small in size, low in cost, and capable of achieving high-speed response, and which can be arbitrarily positioned. I was able to.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a light beam deflection optical device according to a first embodiment of the invention.

FIG. 2 is a schematic configuration diagram of a light beam deflection optical device according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a light beam deflector according to an embodiment of the present invention. FIG. 3A is a plan view of the light beam deflector, and FIG. 3B is a side view of the light beam deflector.

FIG. 4 is an explanatory diagram showing an outline of a mechanical portion of a first example of a light beam deflector according to a conventional technique. FIG. 4 (a) shows the first
FIG. 4B is a plan view of the conventional light beam deflector of FIG.
FIG. 4 is a side view of a light beam deflector of a first conventional example.

FIG. 5 is an explanatory diagram showing an outline of a mechanical portion of a second example of a light beam deflector according to a conventional technique. FIG. 5A shows the second
FIG. 5B is a plan view of the conventional light beam deflector of FIG.
FIG. 6 is a side view of a light beam deflector of a second conventional example.

[Description of sign]

 1 ... Reflective mirror 2 ... Deflection base 3a ... Elastic hinge part 3b ... Elastic hinge part 3c ... Elastic hinge part 4 ... Reflector plate 5 ... Piezo element 6a ... Damper 6b ... Damper 6c ... Damper 7 ... Fixed base 8 Strain gauge 9a Elastic hinge part 9b Elastic hinge part 9c Elastic hinge part 9d Elastic hinge part 10 Deflection device 11 Deflection part 12 Displacement expansion / transmission mechanism part 13 Support base 14 Transmission unit 15 Arm 16a Damper 16b Damper 17 Board 17 Base 19 Frame 20 Rotation axis 21 Fine adjustment screw 50 Light beam deflection optical device 51 Beam forming lens 52 Light beam deflector 53 Aspherical concave lens 54 Exposure surface 55 Aspherical convex mirror 60 Reflective mirror 61a Piezoelectric actuator 61b Piezoelectric actuator Eta 62a. Elastic hinge 62b. Elastic hinge 63a. Coupling part 63b .. Coupling part A .. Support point LD .. Laser diode LB ..... Laser beam

Claims (3)

[Claims] 1. A two-dimensional light beam deflecting optical device comprising a reflecting mirror for arbitrarily changing the direction of a light beam and a drive unit therefor, (a) a laser diode as a light source,
(B) An optical system that shapes and focuses the laser beam emitted from the laser diode, (c) a light beam deflector that rotates a reflection mirror to reflect and deflect the laser beam, and (d) deflected light A light beam deflecting optical device comprising: a deflection angle expanding mechanism for expanding a beam deflection angle; and each of the above (a) to (d). 2. The light beam deflecting optical device according to claim 1, wherein the deflection angle enlarging mechanism is a concave lens. 3. The light beam deflecting optical device according to claim 1, wherein the deflection angle enlarging mechanism is a convex mirror.