JPS632396B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical scanning device that is effective for use in devices that record and display signals, images, etc. using optical signals.

Conventionally, various optical scanning devices that deflect the direction of a light beam at high speed have been proposed, such as those that utilize light diffraction due to the electro-optic effect, those that use a hologram scanner, and those that use galvano mirrors or polygon mirrors. There is. Among these things,
Since those using polygon mirrors have better deflection characteristics than other mirrors, they are widely put into practical use.

FIG. 1 is a configuration diagram showing an example of a conventional device using a polygon mirror. This device converges light from a laser light source 1 to a predetermined beam diameter using a converging lens 2, projects it onto a polygon mirror 3, and transmits reflected light from there through an fθ lens 4 to a photosensitive drum 5, which is a projection surface. I try to project it to The fθ lens serves to correct scanning distortion by ensuring that the diameter of the light spot on the projection plane is constant and the light scanning speed is equal.

However, since such a device uses a polygon mirror, processing accuracy such as inclination of the reflecting surface with respect to the rotation axis, angle division accuracy, flatness, etc. is important, and the processing cost is high and the overall configuration is complicated. There are drawbacks. Furthermore, the fθ lens is a combination of various lenses, and has the disadvantage that the design of the lens system is complicated and expensive.

In addition, as described in Japanese Patent Application Laid-Open No. 52-27645, a parabolic mirror is used as a reflector to reflect the light beam deflected by a deflector to correct scanning distortion. There is something that I tried to do. However, this device requires the deflection surface to be accurately placed at the focal point of the parabolic mirror, and has the disadvantage that distortion errors will increase unless the parabolic mirror is constructed with high precision.

Here, the present invention uses polygon mirrors and fθ
The present invention aims to realize an optical scanning device that does not use lenses or parabolic mirrors, has a simple configuration, can effectively utilize optical power, and can perform linear plane scanning.

The optical scanning device according to the present invention is characterized in that the light source itself is rotated or vibrated, and the position of the light source in the optical axis direction is moved in relation to the deflection angle of the light source. Here, the term "light source" refers to a light source such as a semiconductor laser, and may include a lens in some cases.

FIG. 2 is a diagram illustrating a main part of an embodiment of an optical scanning device according to the present invention. In the figure, 1 is a light source such as a semiconductor laser, and 6 is a rotation drive means for rotating or vibrating the light source 1 in the directions of arrows a and b, such as a motor, a scanning galvanizer, or the like. 7 is an actuator that moves the light source 1 in the optical axis direction (in the direction of arrow c), and for example, a force coil motor or a piezoelectric element such as PZT is used. 6
Reference numeral 1 denotes a motor control section of the rotation drive means 6, 71 a light source position control section for driving the actuator 7, and 8 a control circuit for controlling the motor control section 61 and the light source position control section 71, for example, a microprocessor is used. . Reference numerals 62 and 63 denote light receiving elements for detecting light spots installed near both ends of the photosensitive drum 5, and their output signals are applied to the control circuit 6.

In the device configured in this way, the control circuit 8 controls the rotational drive means 6 via the motor control section 61.
A drive signal is applied to alternately rotate forward and reverse. As a result, the light source 1 itself is swung alternately at a deflection angle of ±θ, and the light beam from it horizontally scans the surface (photosensitive surface) of the photosensitive drum 5. In this device, the control circuit 8 inputs signals from the light receiving elements 62 and 63, and controls forward and reverse rotation based on these timing signals, so that the light beam accurately covers the entire width of the photosensitive drum 5. However, this is not necessarily necessary.

Here, if the position of the light source 1 is fixed and the imaging point is exactly on the surface of the photosensitive drum 5 when the deflection angle θ of the light beam is 0, its trajectory is shown by the broken line _lB. The deviation f of the imaging point from the surface of the photosensitive drum 5 at the deflection angle θ is expressed by the following equation.

Δr=L(1/cosθ−1) (1) Where, L: Shortest distance from the center of rotation of the light source 1 to the surface of the photosensitive drum 5 For this reason, the light spot projected on the surface of the photosensitive drum 5 is: Not only is scanning not performed at a constant speed near the center and near both ends, but the intensity and size of the light spot are not uniform.

In the device according to the present invention, the actuator 7 drives the position of the light source 1 in the optical axis direction according to the deflection angle θ of the light beam so that Δr in equation (1) becomes 0. That is, the light source position control section 71 inputs a signal related to the deflection angle θ of the light source 1 from the control circuit 8, generates an actuator drive signal such that Δr becomes 0, and the actuator 7 responds to this drive signal. Therefore, the position of the light source 1 in the optical axis direction is changed.

In this way, the light spot is placed on the photosensitive drum 5.
The surface of the plane is always scanned in a straight line.

In the above embodiment, the light source itself is moved in the optical axis direction, but a lens is provided in front of the light source 1, and the position of this lens in the optical axis direction is
It may be moved in synchronization with the deflection angle θ. In addition,
The above assumes that the light source 1 is modulated on and off in accordance with recorded or displayed information, but this drive signal is supplied to the light source 1 via, for example, a slip ring, flexible wire, electromagnetic coupling means, etc. shall be carried out.

As explained above, the optical scanning device of the present invention includes:
Linear plane scanning of a light spot can be achieved without using a polygon mirror or f-theta lens, and the overall configuration is simple and inexpensive. Furthermore, since the light beam from the light source is projected onto the surface of the linear photoreceptor, the optical power can be used effectively.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional device, and FIG. 2 is a block diagram of main parts showing an example of a device according to the present invention. DESCRIPTION OF SYMBOLS 1... Light source, 5... Photoreceptor, 6... Rotation drive means, 7... Actuator, 61... Motor control section, 71... Light source position control section, 8... Control circuit.

Claims (1)

[Claims] 1. In an optical scanning device that scans a projection surface with light modulated according to recorded or displayed information, a light source is mounted and the light source itself is rotated or vibrated to emit light from the light source. 1. An optical scanning device comprising: a rotation drive means for changing the direction of a light beam; and a light source position control means for moving the position of the light source in the optical axis direction according to a rotation angle or a vibration angle of the light source.