JPH0718981B2 - Optical deflector evaluation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a rotary polygon mirror used in a laser printer or the like,
The present invention relates to an evaluation device for an optical deflector such as a vibrating mirror.

(Prior Art) As the evaluation characteristics of the deflection performance of a conventional optical deflector,
Various evaluation methods and evaluation devices have been disclosed in consideration of the importance of jitter due to fluctuations in the tilt angle of the reflecting surface, uneven rotation, etc. (for example, Japanese Patent Laid-Open No. 64-63916). , JP-A-64-28535).

Further, apart from the above-mentioned one, there has been proposed an apparatus for measuring the surface entrance / exit, in consideration of the fact that the surface entrance / exit, that is, the fluctuation of the surface position affects the jitter measurement value.
No. 26 bulletin).

(Problems to be Solved by the Invention) Generally, in an optical system for measuring surface tilt and jitter, the mirror surface position is an important measurement factor. However, in the above-mentioned conventional example, the optical deflector to be measured has various shapes, therefore, the accurate position of the mirror surface is measured, and effective means for comparing this is not disclosed, Therefore, there is a problem that the reproducibility of measurement is poor.

Also, especially in the measurement of jitter, if the mirror surface goes in and out, the measured value of jitter fluctuates, and it is impossible to distinguish whether the cause of this fluctuation is due to sudden surface entry or exit or rotation fluctuation. There was a problem.

(Means for Solving the Problems) The present invention has been made to solve the above problems, and the means will be described with reference to the accompanying drawings corresponding to the embodiments. The optical deflector evaluation device according to the present invention is as follows. On the street.

In an optical deflector that deflects and scans a laser beam by using the rotation of the deflecting / reflecting surface, it is detected that the incident light on the deflecting surface and the light emitted from the deflecting surface match when viewed from the rotation axis direction, and a trigger signal is generated. A first light source 1 and a first light source arranged to generate
When the first light detector 6 emits a trigger signal from the second light source 2 which makes a light beam incident on the deflecting surface of the rotary polygon mirror 9 from a direction different from that of the first light source 1. A first light beam position detector 7 for detecting the position in the rotation axis direction of the light beam emitted from the second light source 2 and reflected by the deflecting surface.
A third light source 3 for injecting a light beam onto the deflecting surface of the rotary polygon mirror 9 from a direction different from that of the respective light sources 1, 2, and the first light detector 6 when the first light detector 6 issues a trigger signal. Second light beam position detector 10 for detecting the position in the scanning direction of the light beam emitted from the light source 3 of No. 3 and reflected by the deflecting surface.
And the first light source 1 according to the deflection scanning of the rotary polygon mirror 9.
The rotary polygon mirror 9 is provided with second and third photodetectors 4 and 8 which are arranged so as to sequentially detect the light beams deflected and scanned by the rotary polygon mirror 9 and generate trigger signals. An optical deflector evaluation device characterized by measuring a tilt angle of a deflecting surface, a distance from a rotation center of the surface, and uneven rotation of the surface.

(Operation) In the present invention, since it is possible to simultaneously obtain data regarding the jitter and the entrance / exit of the surface, it is possible to clearly know whether or not the measured value of the jitter changes due to the entrance / exit of the surface. .

Further, since the surface position can be specified without fail, it is possible to reduce the error in the measurement value due to the surface position error when measuring the surface tilt and the jitter.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

Reference numerals 1, 2, and 3 in the figure denote light sources, 10 denotes a one-dimensional optical sensor (hereinafter, referred to as a second optical beam position detector) that detects the beam position in the scanning direction, and 4 and 8 denote jitter measurement trigger sensors. Hereinafter, they are referred to as a second photodetector and a third photodetector, respectively.
Reference numeral 5 is a beam splitter, 6 is a surface entrance / exit detection trigger sensor, and is hereinafter referred to as a first photodetector. Reference numeral 7 is a one-dimensional optical sensor that detects the beam position in the direction parallel to the rotation axis, and is hereinafter referred to as the first optical beam position detector. Reference numeral 9 is a rotary polygon mirror.

When the rotary polygon mirror 9 rotates in a predetermined direction, first, the light from the light source 1 is reflected by the rotary polygon mirror 9 and enters the trigger sensor 8 which is a third photodetector to generate a trigger signal. Next light source 1
Is transmitted through the beam splitter 5, reflected by the beam splitter 5 again through the rotating polygon mirror 9, enters the surface entrance / exit detection trigger sensor 6 which is the first photodetector, and enters the surface entrance / exit detection trigger signal. Occurs. At this time, the light emitted from the light source 3 is incident on the one-dimensional optical sensor 10 which is the second light beam position detector for detecting the beam position in the scanning direction, and the primary light at the moment when the surface entrance / exit trigger signal is generated. The beam position on the original photosensor 10 is measured. Since the incident light and the reflected light are in the same optical path of the light from the light source 1 when the surface entrance / exit detection trigger signal is generated, there is no influence by the position of the surface of the rotary polygon mirror. However, the light emitted from the light source 3 is affected by the surface position of the rotary polygon mirror, so that the second position depends on the position of the surface.
Since the beam position incident on the one-dimensional optical sensor 10, which is a light beam position detector, changes, it is possible to measure the entrance and exit of the surface by this. At the same time, the light from the light source 2 is reflected by the rotary polygon mirror 9 and enters the one-dimensional optical sensor 7 which is the first light beam position detector. Here, since the position of the reflected light in the direction parallel to the rotation axis is measured, the surface tilt is measured.

Next, the light emitted from the light source 1 is reflected by the rotary polygon mirror 9 and is incident on the trigger sensor 4 which is the second photodetector to generate a trigger signal. Here, the time from the trigger signal generated by the third photodetector 8 to the generation of the trigger signal generated by the second photodetector 4 is measured by a counter (not shown) to measure the jitter. Is done.

In this way, it is possible to simultaneously measure the surface coming-in, the face-up, and the jitter phenomenon.

Furthermore, although the three light sources 1, 2 and 3 are separately employed in this embodiment, it is possible to employ a single light source and divide the light from this light source by using a beam splitter or the like. Of course.

(Effect) According to the present invention, since it is possible to simultaneously measure the surface entrance / exit and the jitter, it is possible to remove the component due to the surface entrance / exit from the element that causes the jitter. Furthermore, since the position of the reflective surface can be accurately specified during surface entry / exit measurement,
Even if the shape of the adopted optical deflector changes, there is an effect that stable measurement work can be performed under the same conditions.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are plan views of an optical deflector evaluation device according to the present invention. 1,2,3 ... Light source, 4,6 ... Trigger sensor, 5 ... Beam splitter, 7 ... One-dimensional optical sensor, 8 ... Trigger sensor, 9 ... Rotating polygon mirror, 10 ... One-dimensional optical sensor

Claims (1)

[Claims] 1. An optical deflector for deflecting and scanning a laser beam by utilizing the rotation of a deflecting / reflecting surface, the incident light on the deflecting surface,
The first light source and the first photodetector arranged so as to generate a trigger signal by detecting that the light emitted from the deflecting surface coincides with each other when viewed from the direction of the rotation axis, and from the different direction from the first light source. A second light source for making a light beam incident on the deflection surface of the rotating polygon mirror, and a light beam emitted from the second light source when the first photodetector emits a trigger signal and reflected by the deflection surface. A first light beam position detector for detecting a position in the direction of the rotation axis; a third light source for making a light beam incident on the deflecting surface of the rotary polygon mirror from a different direction from the respective light sources; and the first light detection A second light beam position detector for detecting the position in the scanning direction of the light beam emitted from the third light source and reflected by the deflecting surface when the device emits a trigger signal, and according to the deflection scanning of the rotary polygon mirror, The light was emitted from the first light source and deflected and scanned by the rotary polygon mirror. A second and a third photodetector arranged to sequentially detect the beams and generate a trigger signal. The tilt angle of the deflection surface of the rotary polygon mirror, the distance from the center of rotation of the surface, and the unevenness of rotation of the surface. An optical deflector evaluation device characterized by measuring.