JPH10300630A - Scanning line measuring equipment and inspection method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the curvature of a moving stage accurately without causing any error on the scanning plane of a calibration light source by disposing the calibration light source on the extension of the moving stage in a scanning line measuring equipment having a sensor for detecting laser light at a plurality of point on the moving stage. SOLUTION: A light source 11 having a collimator lens is disposed on the extension of a moving stage 1 and a slit 12 is arranged in a parallel luminous flux. The slit 12 has a shape symmetrical to the optical axis and extends vertically to the optical axis and orthogonally to the paper plane thus focusing the image of the slit 12 on a line sensor 4. At the time of measuring the curvature of the moving stage 1, measuring range thereof is determined and the level of the light source 11 is adjusted finely such that the output of a slit image 12' comes on a same element at the starting and ending points. Subsequently, a carrier 2 is moved and the line sensor 4 disposed at each measuring point focuses the slit image 12' and then the curvature of the moving stage 1 is measured from focal position of the line sensor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring the curvature of a scanning line of a scanning optical system used in an image forming apparatus such as a facsimile or a copying machine, and more particularly, to a technique for measuring the curvature of a scanning line itself. The present invention relates to a technique capable of accurately grasping an error.

[0002]

2. Description of the Related Art Scanning optical systems using a combination of a polygon mirror and an fθ lens are used in facsimile machines and copiers. Then, the laser beam from the light source is reflected by a polygon mirror, formed into an image on a photosensitive drum or the like via an fθ lens, and this image is scanned by rotating the polygon mirror to form an electrostatic image of the original on the photosensitive body. To form.

In such a scanning optical system, for example, if the f-theta lens has a defect and the scanning line is bent, the image of the finally formed original will be distorted. Therefore, it is necessary to accurately evaluate the bending of the scanning line in the scanning optical system.

FIG. 3 is a diagram showing a basic configuration of a scanning line measuring apparatus conventionally used to achieve this object. In the figure, 1 is a linear moving stage,
It is arranged horizontally. A carrier 2 is provided on the moving stage 1, and the carrier 2 can freely move on the moving stage 1. A camera 3 is fixed to the carrier 2, and a line sensor 4 extending in a vertical direction is attached to an imaging surface of the camera 3.
Reference numeral 5 denotes a fixed base on which the scanning optical system 6 is mounted.

The measurement of the bending of the scanning line of the scanning optical system 6 is performed as follows. First, a laser beam is emitted from a light source 6a of a scanning optical system, and a polygon mirror 6b that rotates this light beam is used.
And is incident on the fθ lens 6c. The horizontal scanning light transmitted through the fθ lens 6c forms an image on a line sensor 4 provided on an image forming surface of the camera 3. The line sensor 4 is disposed in a vertical direction (a direction perpendicular to the paper surface), and a light image of a laser beam is formed thereon.

The carrier 2 is moved on the moving stage 1,
If the position of the line sensor 4 is moved from the position indicated by the solid line to the position indicated by the dotted line in FIG. 3 to determine the imaging position of the scanning light at each position, the bending of the scanning line can be measured as shown in FIG. Can be.

However, the above measurement requires two assumptions. First, it is necessary that the moving stage 1 is accurately set horizontally. If the moving stage is not horizontal, the scanning line is measured as being inclined, and a non-defective product is determined as a defective product.

Second, when the moving stage 1 itself is completely straight or has a bend, the bend must be accurately grasped. If there is a bend in the moving stage itself, the bend will naturally be added to the scanning line of the scanning optical system measured, so if the bend is accurately grasped and subtracted from the measured value, it can not be judged correctly. become.

Therefore, the above-mentioned two problems have been solved in the above-mentioned scanning line measuring apparatus as follows. As shown in FIG. 5, first, a rotary table 7 is installed in place of the fixed table 5, and H is provided thereon as a light source for calibration.
A light source 8 using an e-Ne laser is arranged. Turntable 7
Can rotate around the central axis O as indicated by the arrow, the upper surface of the table is accurately set horizontally, and the luminous flux from the light source 8 is also
Make sure it is fired horizontally.

Next, the measurement range of the moving stage 1 is determined, and the line sensor 4 is moved to both ends (shown by a solid line and a dotted line in the figure) so that the laser beam is focused on the same position of the line sensor 4. The horizontal of the moving stage 1 is adjusted. The position of the laser beam on the line sensor 4 is determined by obtaining the center position of the image (light image). Thus, the premise that the first moving stage is horizontal can be achieved.

Next, the line sensor 4 is moved to a plurality of measurement positions within the measurement range, and a laser beam is emitted from the light source 8 while rotating the turntable 7 to obtain an image formation position on the line sensor. Also at this time, the center position of the light image and the line sensor 4
Is defined as the image forming position. If this is plotted, FIG.
As shown in (1), the bending of the moving stage 1 can be measured, and the above second premise can be achieved.

In the above description, the fixed base 5 is replaced by the rotary base 7. However, when the rotary base 7 is installed from the beginning without using the fixed base 5 and the scanning optical system 6 is measured, Alternatively, it may be performed in a state where the turntable 7 is fixed without rotating.

[0013]

However, in the above measurement, the scanning surface on which the laser light of the light source 8 on the turntable 7 scans is used as a reference. Therefore, if the scanning plane itself is bent, accurate measurement cannot be performed.

However, even if the conventional rotary table 6 is of a high precision, the horizontal runout is as large as 5 to 10 μm, and deformation due to handling is apt to occur, and these are enlarged on the line sensor 4. This was included as an error in the measurement of the scanning optical system, and high-precision measurement could not be performed.

In addition, the reproducibility of the output position on the line sensor 4 when the image forming center of the laser beam is adjusted to the line sensor 4 is poor, and an error of about ± 2 to 3 μm occurs. The present invention has been conceived based on such a fact, and there is no error in the scanning surface of the light source for calibration, and a scanning line measuring device capable of accurately measuring the bending of the moving stage, and the bending of the moving stage thereby. It is intended to provide a measuring method. Another object of the present invention is to provide a measurement method and a measurement apparatus with good reproducibility.

[0016]

In order to achieve the above object, a scanning line measuring apparatus according to the present invention measures a curvature of a scanning line on an image plane of a scanning optical system which performs writing or reading by scanning a laser beam. A moving stage extending in the direction of the scanning line, and one or more sensors for detecting laser light at a plurality of positions on the moving stage; The laser light source for calibration is provided on the extension.

Further, the laser light source has a collimator lens and a slit provided in a parallel light beam of the collimator lens, and the sensor is a line sensor provided in a direction orthogonal to an image of the slit. It is desirable to have a configuration.

Further, the method for measuring the bending of the moving stage of the scanning line measuring device is characterized in that one or two or more sensors arranged on the moving stage of the scanning line measuring device are provided with the laser for calibration. The method is characterized by irradiating a light beam to form an image of the laser beam on the sensor at a plurality of positions on the moving stage, and measuring a bending of the moving stage from an image forming position on each sensor.

Further, a slit image is formed on the line sensor of the scanning line measuring apparatus, and a graph of the output of each pixel of the line sensor in the slit image is obtained.
It is desirable that the position of the line sensor on the line that bisects the area exceeding the value of is set as the intersection of the slit and the line sensor, and that the intersection be determined for a plurality of points on the moving stage.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a state in which the bending of a moving stage of the measuring device is measured by the scanning line measuring device of the present invention. The moving stage 1, the carrier 2, the camera 3, and the line sensor 4 are the same as those described in the conventional example.
In this measuring device, a light source 11 is provided at an extended position of the moving stage 1. The light source 11 is not shown,
It has a collimator lens and makes the laser beam of the light source parallel and horizontal. Further, a slit 12 is arranged in the parallel light beam. The slit 12 has a shape symmetrical with respect to the optical axis, and extends in a direction perpendicular to the optical axis and perpendicular to the plane of the drawing. The image of the slit 12 is formed on the line sensor 4. On the other hand, the line sensor 4 is in a plane orthogonal to the optical axis and has a length in the vertical direction in the figure.

Accordingly, as shown in FIG. 1B, the line sensor 4 and the slit image 12 'are orthogonal to each other. Therefore, the personal computer 1 is connected between the line sensor 4 and the slit image 12 ′ via the image input device 13.
4 is displayed on the monitor screen 15 of FIG.

First, when measuring the bending of the moving stage 1, the measuring range of the moving stage 1 is determined, and the horizontal position of the light source 11 is finely adjusted so that the output of the slit image 12 'is on the same element at the start point and the end point. . Alternatively, moving stage 1
May be finely adjusted.

Next, the carrier 2 is moved, and the line sensor 4 is set at each measurement point. The slit image 12 'is formed there, and the slit image 1
It measures whether 2 'forms an image.

Since the slit image 12 'has a certain width, the slit image 12'
(Or the position where the slit image cuts the line sensor) with the point of intersection is a problem. Therefore, the intersection is determined as follows.

The width d of the slit image 12 'is much larger than the width p of the elements of the line sensor 4 (pixel pitch = approximately 7 .mu.m). Therefore, there are many elements of the line sensor 4 which cross the slit image 12'. Will be.

FIG. 2 is an enlarged view of the monitor screen of FIG.
It is the figure rotated 0 degrees. The output of each element of the line sensor 4 has a step-like mountain-shaped distribution with the pixel pitch p as a unit. The width of the foot of the mountain is wider than the width d of the slit image.

At this time, the line sensor 4 and the slit image 1
The intersection with 2 'is determined not as the peak output position of the line sensor 4 but as follows. First, the area of a portion exceeding 1 / e2 (13.5%) of the peak output (100%) of the line sensor 4 is obtained, and the intersection of the line a passing through the center of gravity G and the line sensor 4 is determined by the slit image 12 '. Intersection. In other words, when the area of the oblique lines in FIG.
It can be said that the position of the line a where the areas of 1 and S2 are equal.

According to such a measuring method, since the turntable is not used, the influence of the runout of the turntable is eliminated.
It is possible to completely eliminate errors due to surface runout. Also,
Since the slit light is used, the output position of the sensor does not change due to a slight positional difference in the horizontal direction of the light source, the reproducibility of repetition is improved, and the amount of bending of the moving stage can be measured accurately. Further, since the position at which the area of the portion exceeding 1 / e2 (13.5%) of the peak output of the line sensor 4 is bisected is determined, the sensitivity variation and the influence of noise are reduced, and the bending with high precision is achieved. Measurement becomes possible.

Next, a method of fixing a plurality of line sensors on a moving stage and measuring the bending of the moving stage will be described. A small rotary stage is provided below the line sensor camera, the line sensor is set on the rotation axis, fixed to a carrier mounted on a moving stage, and can be freely moved on the stage. The structure can be changed to the axis center.

As the light source, the same light source 11 as in FIG. 1 is used, and the line sensor is set at the first setting position. The position of the slit image on the line sensor is read on the monitor screen, the next line sensor (the same structure as the first) is set at a predetermined setting position, and the output on the line sensor is read in the same manner. The same operation is sequentially repeated, and the setting of a predetermined number of line sensors is completed.

If the intersection between the line sensor and the slit image is determined for each line sensor as described with reference to FIG. 2, the bending of the moving stage can be measured with high accuracy. At this time, the line sensor is supported by the small rotary stage, but is not on the light source side. Therefore, the bending measurement of the moving stage can be performed with high accuracy.

When the bending of the moving stage can be grasped as described above, the bending of the scanning line of the scanning optical system is measured. However, since the bending of the moving stage has been accurately measured, this bending is subtracted. And accurate measurement becomes possible.

[0033]

According to the present invention as described above,
An apparatus for measuring the curvature of a scanning line on an image plane of a scanning optical system that performs writing or reading by scanning a laser beam, comprising: a moving stage extending in the direction of the scanning line; 1 or 2 for detecting light
In the scanning line measuring device having the above-described sensor, the laser light source for calibration is provided on the extension of the moving stage, so that the influence of the surface deflection of the turntable is eliminated at a plurality of positions on the moving stage. An image formed by a laser beam is formed on the sensor, and a bend for measuring a bend of the moving stage can be measured from an image formation position on each sensor.

Further, the laser light source has a collimator lens and a slit in a parallel light beam of the collimator lens, and the sensor is a line sensor provided in a direction orthogonal to an image of the slit. For example, the output position of the sensor does not change due to a slight positional difference in the horizontal direction of the light source, the reproducibility of the repetition is improved, and the bending amount of the moving stage can be measured accurately.

A slit image is formed on the line sensor, a graph of the output of each pixel of the line sensor in the slit image is obtained, and a line on a line bisecting an area exceeding 1 / e2 of the maximum value If the position of the sensor is defined as the intersection between the slit and the line sensor, and the intersection is determined for a plurality of points on the moving stage, highly accurate measurement with good reproducibility can be performed.

[Brief description of the drawings]

FIG. 1A is a diagram illustrating a configuration of a main part of a scanning line measuring apparatus according to the present invention, and FIG. 1B is a diagram illustrating a relationship between a line sensor and a slit image.

FIG. 2 is a diagram illustrating an output of each pixel of a line sensor.

FIG. 3 is a plan view showing a configuration of a conventional scanning line measuring device.

FIG. 4 is a diagram illustrating a state where a scanning line of a scanning optical system is bent.

FIG. 5 is a diagram showing a state in which the bending of a moving stage is measured by a conventional scanning line measuring device.

[Explanation of symbols]

 Reference Signs List 1 moving stage 4 line sensor 6 scanning optical system 11 light source 12 slit 12 'slit image

Claims (4)

[Claims] 1. An apparatus for measuring a curvature of a scanning line on an image plane of a scanning optical system for writing or reading by scanning a laser beam, comprising: a moving stage extending in the direction of the scanning line; A scanning line measuring apparatus having one or more sensors for detecting laser light at a plurality of locations, wherein a laser light source for calibration is provided on an extension of the moving stage. apparatus. 2. A line sensor wherein the laser light source has a collimator lens and a slit provided in a parallel light beam of the collimator lens, and the sensor is provided in a direction orthogonal to an image of the slit. The scanning line measuring device according to claim 1, wherein: 3. The scanning line measuring apparatus according to claim 1, wherein one or two or more sensors arranged on the moving stage are irradiated with the laser beam for the calibration so that a plurality of sensors are arranged on the moving stage. An image formed by a laser beam on the sensor at the position (1), and measuring the bending of the moving stage from the image forming position on each sensor. 4. An image of the slit is formed on the line sensor of the scanning line measuring device according to claim 2, and a graph of an output of each pixel of the line sensor in the slit image is obtained.
A scanning line measurement, wherein a position of a line sensor on a line bisecting an area exceeding a value of 1 / e2 of a maximum value is defined as an intersection of a slit and a line sensor, and the intersection is obtained for a plurality of points on a moving stage. Equipment inspection method.