JPS60152928A - Divided-angle-error measuring apparatus of polygon mirror - Google Patents

Abstract

PURPOSE:To make the price of an apparatus low, by providing a means, which inputs parallel luminous flux into mirror surfaces with a polygon mirror being rotated, a means, which converges the reflected luminous fluxes by a converging optical system, and luminous-flux detecting means, which are provided at a converging point. CONSTITUTION:Diverging luminous flux emitted from a semiconductor laser 1 is made to be parallel luminous flux by a collimate lens 2. The parallel luminous flux is inputted to two neighboring mirror surfaces of a polygon mirror 3. The parallel luminous fluxes reflected by the two mirror surfaces are converged by converging lenses 4 and inputted to photo-detectors 5. Based on the rotation of the polygon mirror 5, the reflected luminous fluxes are detected by the two photo-detectors 5 as pulses A and B. The time difference DELTAt between the pulses A and B is caused by the divided-angle errors and the rotation irregularity of the mirror 3. The arrangement of the detectors 5 are adjusted by utilizing the reference polygon mirror, the rotation irregularity is made sufficiently small, and the error in the divided angle is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a division angle error measuring device that can measure the division angle error of a polygon mirror used in a laser printer or the like at low cost and in a short time.

(Prior art) To measure the error in the division angle of a conventional polygon mirror, the polygon mirror for measuring the 9-division angle error is set on a highly accurate and rotatable index table, and while rotating the teniple, the polygon mirror is adjusted to the mirror surface of the polygon mirror. Light enters from the light source.

This is done by receiving the reflected light and reading the reflection angle of the received light. For example, if a six-sided mirror is manufactured accurately, the incident light from the light source should be able to be identified as reflected light every 60 degrees of rotation, but if there is an angular error in the polygon mirrors, This results in a deviation in the rotation angle of °.

However, the conventional split angle error measuring device.

It uses a high-precision index table,
Therefore, the price is high, and each side of the polygon mirror is
Since the index table is rotated and errors are measured individually, there is a drawback that the measurement time is extremely long.

(Objects and Structure of the Invention) The present invention has been made in view of the above, and is an object of the present invention to measure the division angle error of a polygon mirror in a short time using a low-cost device. While rotating, light from the light source is incident on the polygonal mirror surfaces.

The reflected light beams from at least two adjacent mirror surfaces are detected by a photodetector, and the 9-division angle error is converted into a time difference for measurement. The present invention provides a division angle error measuring device for a polygon mirror.

(Example) The polygon mirror division angle error measuring device according to the present invention will be described in detail below. A polygon mirror, which is the object of error measurement, is set on a table that is rotated at a constant speed by a motor or the like. Light emitted from one or more light sources is made to enter two or more mirror surfaces of a polygon mirror as a parallel light beam by a collimating optical system. When the light beam that enters the mirror surface and is reflected once is focused by a focusing optical system and a photodetector is placed at the focusing point to detect the light, if there is a division angle error on the mirror surface, the mirror surface is rotating and the corresponding mirror surface is detected. By measuring the time the light beam reaches the photodetector, the two-division angle error can be measured as the difference in the time the light beam reaches the photodetector. In the polygon mirror division angle error measuring device of the present invention, there may be one or more light sources, and the division angle error of the plurality of mirror surfaces can be measured by making the light source simultaneously enter two or more corresponding mirror surfaces of the polygon mirror. Simultaneous measurements are possible. In FIG. 1, a case will be described as an example in which there is one light source and a light beam is incident on two adjacent mirror surfaces of a polygon mirror in the object to be measured. There is a semiconductor laser 1 that emits light, and a collimator lens 2 that converts a diverging beam emitted from the semiconductor laser into a parallel light beam. It can be rotated. There is a polygon mirror 3 to be measured, and the light beam from the collimating lens 2 is made to enter two adjacent mirror surfaces of the polygon mirror 3 without being split. There is a focusing optical system 4 that focuses the parallel light beams reflected by the two mirror surfaces. A photodetector 5 is placed so as to cross this focused light beam by rotating the multifaceted surface [3. Since each photodetector 5 generates a pulse output due to the passage of the light beam, a time interval counter 6 is provided to measure this output.

In the above configuration, the operation of measuring the division angle error of the polygon mirror will be explained. The diverging light beam emitted from the semiconductor laser 1 is turned into a parallel light beam by the collimating lens 2 and enters two adjacent mirror surfaces of the polygon mirror 3 which is rotating once. The parallel light beams reflected from the two mirror surfaces are focused by a focusing lens 4 and enter a photodetector 5. By rotating the polygon mirror 3.

The passage of the light beam is obtained as a pulse by a photodetector 5 and measured by a time interval counter 6. Third
The figure shows outputs from two photodetectors 5, A and B.
, the change in the time difference Δt between A and B measured by the time interval counter 6 is shown as C. t represents the transit time for one surface, and the variation in its value depends on the rotation speed unevenness of the polygon mirror 3 and the division angle error.

Although the variation in Δt depends on the rotation unevenness of the polygon mirror 3 and the division angle error, the two photodetectors 5 are arranged so that it is sufficiently small compared to Δtt−t using a reference polygon mirror that is accurately manufactured in advance. (still.

The configuration in which two photodetectors 5 are arranged symmetrically with respect to the polygon mirror 3 is a configuration that makes Δt sufficiently smaller than t, but furthermore, as shown by the broken line in FIG. 7) when the light beam moves, the influence of uneven rotation of the polygon mirror 3 can be sufficiently reduced.

After adjustment, the division angle error of the polygon mirror can be calculated by measuring Δt.

In Figure 2, there are two light sources, and the light beam from the light source enters two adjacent mirror surfaces of the polygon mirror that is the object to be measured, and is reflected by 9 and 1
This shows the case where the light is focused on one photodetector. There is a semiconductor laser 1 that emits light, and a collimating optical system 2 that converts the diverging light beam emitted from the semiconductor laser 1 into a parallel light beam.
There is. There is a rotatable polygon mirror 3 which is the object to be measured.
A parallel light beam from the collimating optical system 2 is made to be incident on two mirror surfaces of the polygon mirror 3 that are adjacent to each other.

There is a condensing system 4 for converging the parallel light beams reflected by the two mirror surfaces, and a photodetector 5 installed so that the focused light beams are traversed by the rotation of the polygon mirror 3. The operation for measuring the angular error of a polygon mirror is the same as that shown in FIG. 2 adjacent to each other in mirror 3
The light is reflected from two mirror surfaces, is focused by a focusing lens 4, and enters a photodetector 5. By rotating the polygon mirror 3, the passage of the light beam is obtained by the photodetector 5 as a corresponding pulse. By measuring the interval Δt between two pulses output from the photodetector 5, the division angle error of the polygon mirror can be determined.

(Effects of the Invention) As explained above, according to the device for measuring division angle error of a polygon mirror used in a laser printer or the like according to the present invention, a light beam from a light source is incident on the mirror surface of the polygon mirror while rotating the polygon mirror, Since the reflected light beam is detected by a photodetector and the 1-division angle error is converted into a time difference for measurement, the division angle error of the polygon mirror can be measured in a short time using a low-cost device.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing an example in which there is one light source and two photodetectors, Figure 2 is an explanatory diagram showing an example in which there are two light sources and one photodetector, and Figure 3 is an explanatory diagram showing an example in which there are two light sources and one photodetector. FIG. 3 is an explanatory diagram of pulses in an interval counter. Explanation of symbols 1: Semiconductor laser. 2...Collimating optical system. 3... Polygonal mirror. 4...Focusing optical system. 5...Photodetector. 6...Time interval counter. 7...Photodetector. Patent Applicant Fuji Xerox Co., Ltd. Figure 1 Narrow Z2.7 Figure 2 Figure 3

Claims (1)

[Claims] In a dividing angle error measuring device for a polygon mirror used in a laser printer or the like. Means for turning the light emitted from the light source into a parallel beam of light by a collimating optical system and making it incident on the mirror surface of the polygon mirror while rotating the polygon mirror. means for converging the light beam incident on the mirror surface and reflected by a convergence optical system; What is claimed is: 1. A polygon mirror division angle error measuring device, comprising: a light beam detection means provided at the convergence point of the polygon mirror.