JP2001208512A - Measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measuring apparatus capable of measuring whether an apparatus for performing work repeatedly is accurately stopped at a predetermined position and whether a position where the apparatus moves on an X-Y plane to stop is accurate with good accuracy (about ±0.1 μm) by one sensor. SOLUTION: A measuring apparatus is equipped with at least the concave mirror mounted on an object to be measured, a laser beam source for irradiating the concave mirror with laser beam, a half mirror for transmitting and reflecting laser beam and an imaging element for imaging the laser beam reflected by the concave mirror to be incident and the moving quantity of the object to be measured is operated from the moving quantity of the laser beam imaged by the imaging element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device.

[0002]

2. Description of the Related Art In general, in order to specify the position of an object moving on a plane (XY plane), the position is indicated by coordinate positions on an X axis and a Y axis. In order to display the position at which the moving object has stopped, the position of the stopped object must be detected and compared with the X-axis and Y-axis coordinate positions to determine the coordinates.

The center point of an object at a certain point on a plane is represented by XY
The origin O of the coordinates is set, and the position where the object moves on the first quadrant and stops (point Z) can be detected. The distance L from the origin O to Z, the straight line connecting the origin O and the point Z, and the X axis Is known, the position of the stopped object is X = Lcosθ, Y = Ls
can be displayed in inθ. The same can be displayed in the second to fourth quadrants. Generally, as L increases, the measurement error increases. However, sometimes it is desired to move the object regardless of the origin O and always stop at the Z point. In addition, although it is desired to stop accurately, it is often impossible to accurately measure how far the stopped position is shifted.

FIG. 1 is a perspective view of an XY table used in a precision processing device or precision assembly device according to the prior art. A base 7 having a table 6 which is moved in a Y-axis direction by a feed screw 5 rotated by a stepping motor 4 is mounted on a table 3 which is moved in an X-axis direction by a feed screw 2 rotated by a stepping motor 1. The table 6 moves on the XY plane according to the rotation amounts of the two stepping motors.

[0005]

The stop position of the table 6 is determined by the number of stepping pulses.
The machine origin is detected and the X axis direction is
In the Y-axis direction, the stop position is determined by rotating the xxx pulse stepping motors 1 and 4, and the stop position may deviate from a predetermined position due to a small or large number of rotations due to some trouble. In the work of repeatedly performing the same movement, there occurs a problem that the same positional deviation continues until the correction is made once the deviation is made.
This is caused by replacing the position measurement with the number of pulses that determines the rotation amount of the stepping motors 1 and 4.
This is very dangerous in continuous precision machining and precision assembly.

[0006] In order to detect the stop position of an object moving in the X-Y2 direction on a plane, two sensors are required because detection sensors must be arranged on each moving axis. Since the detection method is direct, the detection accuracy is ± 1μ
m. It is an object of the present invention to accurately determine whether or not a device that performs repetitive operations is accurately stopped at a predetermined position, and whether or not the position to stop by moving on the XY plane is one. It is an object of the present invention to obtain a measuring device that can accurately measure (about ± 0.1 μm) with a sensor.

[0007]

At least a concave mirror attached to an object to be measured, a laser light source for irradiating the concave mirror with laser light, a half mirror for transmitting and reflecting the laser light, and an image of the laser light reflected and incident on the concave mirror are imaged. A measurement device includes an imaging device and calculates a movement amount of a device under test from a movement amount of laser light captured by the imaging device.

[0008] A measuring apparatus having a convex lens between a laser light source and a half mirror is provided.

The spot image of the imaged laser light is represented by X
Recognized by the Y coordinate, the midpoint of the maximum length on the X axis and Y axis of the spot image is set as the coordinate origin, and the X
It is assumed that the measuring device displays the intermediate point of the maximum length on the XY axis as the movement amount from the origin on the XY coordinates.

[0010]

FIG. 2 is a schematic diagram for explaining the measuring principle of the measuring apparatus according to the present invention. The measuring device includes at least a laser emitter 10, a half mirror 11, and a concave mirror 1.
2. It has an image sensor 13 and is arranged by positioning and fixing means. The concave mirror 12 is fixed to an object to be measured (for example, the table 6).

As an initial position, the center of the concave mirror 12 is located directly below the laser emitter 10. Half mirror 11 is arranged between laser emitter 10 and concave mirror. The laser light emitted from the laser emitter 10 is partially reflected by the half mirror 11 and partially transmitted through the half mirror 11 and projected on the concave mirror 12. The laser light is reflected at right angles by the concave mirror 12, returns along the projected path as it is, is reflected by the half mirror 11, and reaches a point of the image sensor 13. This point is the origin O on the image sensor 13.

The concave mirror 12 moves by .DELTA.Z. Since the concave mirror 12 has a curvature C, the laser light is reflected at an angle of θ with respect to the initially reflected light, is reflected by the half mirror 11, and reaches a point of the image sensor. Assuming that the distance between the half mirror 11 and the concave mirror 12 is A and the distance between the half mirror 11 and the image sensor 13 is B, the distance X between points on the image sensor 13
Is (A + B) sin θ. θ = 2 sin-1 (ΔZ
/ C), X = (A + B) sin (2sin−
1 (ΔZ / C)). (However, A, B, C≫ΔZ)

A = 100 mm, B = 50 mm, C = 10
mm, ΔZ = 10 μm, X = 300 μm,
It can be measured as a 30 times movement amount. A, B, and C can be appropriately set in consideration of ΔZ, the size of the imaging element 13, and the like.

Although the above-mentioned principle is based on the premise that the laser light does not change in a sufficiently small spot, the laser light is actually diffused, so that it is necessary to interpose a convex lens for focusing. It is preferable that the focal length of the convex lens is selected in consideration of the distance between the convex lens and the concave mirror, the focal length at which the laser light is focused on the concave mirror, and disposed between the laser emitter and the half mirror. The laser light reflected by the concave mirror is imaged as a spot of a certain size on the image sensor.

FIG. 3 is a schematic diagram for explaining a method of measuring the moving amount of the laser light by imaging the laser light with the image pickup device. For the sake of explanation, the image pickup device is a charge-coupled semiconductor device (hereinafter referred to as CCD) and has 500 × 500 pixels. First, in order to determine the outline to be imaged by the laser beam, 0, 1 is determined by the brightness of each pixel imaged by the CCD.
A determination is made (assuming that a pixel receiving laser light is 1 and a pixel not receiving laser light is 0). An origin O of a point is defined as an intermediate point of one determination pixel of a line having the largest number of one pixel on each of lines in the X-axis direction and the Y-axis direction of the CCD. Next, the point at which the line having the largest number of 1 pixels on the line in the X-axis direction intersects with the Y axis is Y1. Assuming that the point is X1, a center point O 'of the point is obtained.

If the resolution of one pixel is clear, the resolution of the measuring device of the present invention is determined. In the example of [0013], when ΔZ = 10 μm and X = 300 μm, if the movement amount on the CCD is 300 pixels, the measurement resolution is 10
/300=0.033 μm. Resolution is A, B, C
And the number of pixels of the image sensor.

[0017]

According to the first aspect of the present invention, the amount of deviation from the initial setting position can be measured while being enlarged. The apparatus using this measuring instrument can easily measure the displacement and control the repetitive moving operation with high accuracy.

According to the second aspect of the present invention, the image spot on the image sensor can be clearly defined, and the accuracy of the measuring device can be improved.

According to the third aspect of the present invention, the movement amount in the X-Y2 direction can be measured by one sensor.
Further, since the movement amount is measured with the center of the laser light spot image taken out, the influence of the laser light spot distortion can be minimized.

[Brief description of the drawings]

FIG. 1 is a perspective view of an XY table used in a precision processing device or precision assembly device according to the related art.

FIG. 2 is a schematic diagram for explaining the measurement principle of the measurement device of the present invention.

FIG. 3 is a schematic diagram for explaining a method of measuring a moving amount of the laser light by imaging the laser light with an imaging device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 stepping motor 2 feed screw 3 table 4 stepping motor 5 feed screw 6 table 7 base 10 laser light emitter 11 half mirror 12 concave mirror 13 image sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA03 AA19 BB15 CC00 FF43 GG04 HH04 HH13 JJ03 JJ09 JJ26 LL19 LL46

Claims (3)

[Claims] At least a concave mirror attached to an object to be measured, a laser light source for irradiating the concave mirror with laser light, a half mirror for transmitting and reflecting the laser light, and an imaging device for imaging the laser light reflected and incident on the concave mirror are provided. A measuring device for calculating a moving amount of the object to be measured from a moving amount of the laser light imaged by the image sensor. 2. The measuring apparatus according to claim 1, further comprising a convex lens between the laser light source and the half mirror. 3. A spot image of a captured laser beam is recognized by XY coordinates, an intermediate point of the maximum length on the X axis and the Y axis of the spot image is set as a coordinate origin, and the X axis of the spot image after the movement is determined. 2. The method according to claim 1, wherein an intermediate point of the maximum length on the Y axis is displayed as XY coordinates as a movement amount from the origin.
Or the measuring device according to 2.