JPH04130239A - Apparatus for measuring outward position and inward position of dynamic surface - Google Patents

Abstract

PURPOSE:To make it possible to measure the outward position and the inward position of a surface highly accurately without the effect of the state of the reflecting surface of a polariscope by focusing an image which is conjugate with the focal point on a mirror on a reflected- light-position detector. CONSTITUTION:When the light from a light source 5 enters, a trigger detector 8 transmits a trigger signal. The light emitted from a light source 1 is reflected from the mirror surface of a polariscope 9. The reflected light is condensed on a beam-position detector 4 through an optical system 3. At the time of the trigger generation, the direction of the mirror surface is constant. Therefore, the fluctuation of the output from the detector 4 is caused by the outward and inward movements of the surface. Thus the outward and inward positions of the surface are measured. Namely, a focal point F1 of the incident light L1 is focused on the detector 4 through the optical system 3. When the surface is moved outward or inward, the reflected light is moved to a light path L3. The focal point on the detector which is conjugate with the apparent movement of the focal point is moved to F2. Therefore, the incident point becomes S1. The amount of the outward or inward movement (d) is obtained based on the distance X1 between F1 and S1. Even if an angular error occurs in the reflected light under the state of the mirror surface, the deviation of the optical incident point on the detector 4 is very small, and the highly accurate measurement can be performed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a rotating polygon mirror used in a laser printer, etc.
This invention relates to an evaluation device for an optical deflector such as a vibrating mirror.

(Prior art) Conventionally, in optical deflectors, the rotational accuracy and the inclination of the surface have been considered important characteristics, but the position of the reflective surface from the center of rotation fluctuates (hereinafter referred to as surface entry and exit). and,
Since these characteristics are affected, as a method of measuring this in-plane entry and exit during rotation, the incident and reflected optical paths are configured to be in a plane containing the rotation axis of the optical deflector 28, as shown in FIG. A light source 24, an optical system 25, a beam splitter 26, a trigger detector 27, and a light source 21, an optical system 22, which are configured so that the light enters and reflects on the mirror at an angle when a trigger is generated. A surface entry/exit measuring device has been proposed that includes a surface position detection system including a beam position detector 23 and measures the entry/exit from the surface based on the output of the detector 23 at the time when a trigger is generated.

(Problems to be Solved by the Invention) In conventionally proposed surface entry and exit measuring devices, the light emitted from the light source 21 is directly focused on the detector 23. In such a configuration, when the mirror surface moves by a distance d from 28a to 28b as shown in Fig. 4, the chief ray of the light emitted from the mirror moves from L22 to L23, and the focal point moves from F21 to F22. And the point of incidence on the detector is F
It moved from 21 to 521, and the amount of surface entry and exit was calculated from the amount of movement X2. However, since the surface of the mirror surface cannot be a perfect plane, L2
If an angular error occurs in the light emitted from the mirror as shown in No. 4, the incident point becomes S22, resulting in an error Y2, which poses a problem in that accurate measurement cannot be performed.

(Means for Solving the Problems) The present invention has been made to solve the above problems, and will be explained with reference to FIGS. 1 and 2, which correspond to embodiments. Trigger detection systems 5, 6, and 7 that include incident and reflected optical paths in a plane that includes the rotation center axis of the optical deflector 9 that scans the light by rotating a mirror, and that detect the passing point of the reflected light and generate a trigger signal. , 8, and has incident and reflected optical paths that are not perpendicular to the mirror surface, and detects the position of the reflected light in a direction substantially perpendicular to the reflected light within a plane that includes the incident and reflected light at the time when the trigger signal is generated by the trigger detection system. In the dynamic surface entrance/exit measuring device equipped with surface position detection systems 1, 2, 3.4, the optical system 3 of the surface position detection system is such that the incident light LX has a focus on the mirror surface 9a, and the reflected light The optical system 3 is a dynamic surface entry/exit measuring device characterized in that it is an optical system that focuses an image F1 conjugate with the focal point o1 on the mirror 9a onto the reflected light position detector 4.

(Function) In this case, the focal point 01 on the mirror surface 9a and the image point F1 on the detector 4 are conjugate, so even if the angle of the reflected light changes depending on the surface condition of the mirror surface 9a, the reflected light L2 is always detected. The light is focused on an image point on the vessel 4. Furthermore, when the surface moves in and out, the reflection point on the mirror surface moves, so the image point also moves, so the surface movement can be detected based on the amount of movement.

(Embodiment) FIG. 1 shows an embodiment of the present invention, in which 1 and 5 are light sources, 2
3 is an optical system that focuses the incident light on a mirror surface, 3 is an optical system that focuses the output light on a detector, 4 is a beam position detector, and 6 is an optical system that focuses the incident light on a mirror surface.
is an optical system that focuses the emitted light onto a trigger detector 8, 7 is a beam splitter, 8 is a trigger detector, and 9 is a rotating polygon mirror. Since the light emitted from the light source 5 and entering the trigger detector 8 is within a plane that includes the rotation axis of the rotating polygon mirror 9, the trigger detector 8 generates a trigger signal without being affected by entering or exiting the plane. At this time, the light emitted from the light source 1 is configured to enter the beam position detector 4. Light emitted from a light source 1 is focused onto a mirror surface by an optical system 2, and its reflected light is focused by an optical system 3 onto a beam position detector 4 and enters the beam position detector 4. Since the direction of the mirror surface at the time of trigger generation is constant, the fluctuation in the output of the beam position detector at that time is considered to be due to the movement in and out of the surface.

From this, you can measure the surface entrance and exit.

Next, the optical path will be explained in detail using FIG. 2.

The incident light L1 has a focal point 01 on the mirror surface 9a.

The reflected light L2 is brought to a focus F1 on the detector 4 by the optical system 3. Here, when entry and exit from the surface occurs as shown on the mirror surface 9b, the reflection moves to the optical path L3, and the apparent focus moves from 01 to 02. The focal point on the detector 4 conjugate thereto moves from Fl to F2. As a result, the light incident point on the detector 4 becomes Sl.

The surface inflow/outflow amount d is determined from the distance x1 between Fl and Sl.

Furthermore, even if the reflected light causes an angular error like L4 due to the condition of the mirror surface, the light incident point on the detector 4 at that time is S2, and the difference Y1 between Sl and S2 is equal to Y in the conventional method.
Compared to 2, it is extremely small and can perform highly accurate measurements.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to construct a highly accurate surface entry/exit measuring instrument that is less affected by the state of the reflecting surface of an optical deflector than conventional methods.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a principle diagram of the present invention, FIG. 3 is a block diagram of a conventional example, and FIG. 4 is a principle diagram of a conventional example. 1.2, 21, 24... Light source 2.3, 6, 22, 25... Condensing optical system 4.23...
・Beam position detector 7, 26... Beam splitter 8.27... Trigger detector 9.28... Optical deflector (rotating polygon mirror) 9 a, 9
b, 28 a, 28 b - mirror surfaces LL, L
2. L3. L4. L21. L22°L23. L24...
・Light path

Claims (1)

[Claims] A trigger detection system includes an incident and reflected optical path in a plane that includes the rotation center axis of an optical deflector that scans light by rotating a mirror, and a trigger detection system that generates a trigger signal by detecting the point at which the reflected light passes; It has non-perpendicular incident and reflected optical paths and the incident and reflected light paths at the time when the trigger signal is generated by the trigger detection system.
In a dynamic surface entry/exit measurement device equipped with a surface position detection system that detects the position of the reflected light in a direction substantially perpendicular to the reflected light within a plane containing the reflected light, the optical system of the surface position detection system detects the position of the reflected light in a direction substantially perpendicular to the reflected light. A dynamic surface entrance/exit measuring device having a focal point on a mirror surface, and a reflected light optical system that focuses an image conjugate with the focal point on the mirror onto a reflected light position detector.