JP4191953B2 - Calibration method of laser scanning dimension measuring machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for calibrating a laser scanning measuring machine, in particular, Oite laser scanning measuring machine using a laser beam, a precise correction laser scanning capable of performing the characteristic measuring machine The present invention relates to a calibration method for a dimension measuring machine.
[0002]
[Prior art]
In recent years, a laser scanning type size measuring machine that performs non-contact measurement at high speed using a laser beam has been put into practical use (Japanese Patent Publication No. 6-54214, Japanese Patent Laid-Open No. 2000-88528).
[0003]
In such a laser scanning type dimension measuring machine, conventionally, as shown in FIG. 1, a moving pin 80 moved by a moving mechanism 82 is arranged in the optical path of the parallel scanning beam 32 formed by the collimator lens 30. , The end face positions L0 to L (n) are measured, and the moving pin 80 is moved by the precision scale 84 using the fact that the change amount of the measured value generated when the moving pin 80 is moved is an error component of the measuring machine. The moving pin 80 is moved while detecting the position of the lens, and data for correcting the lens characteristics of the measuring machine is obtained from the measured values at various places.
[0004]
That is, in the measuring machine that measures the dimension from the end face of the moving pin 80 to the reset signal light receiving element 44, first, the moving amount (L 1 -L 0) of the moving pin 80 is measured by the scale 84.
[0005]
Next, as shown in the following equation, the difference between the movement amount (L1−L0) detected by the measuring instrument and the value S indicated by the scale 84 is defined as an error E (L) of the measuring instrument.
[0006]
E (L) = (L1-L0) -S (1)
[0007]
[Problems to be solved by the invention]
However, the value S indicated by the scale 84 includes an error of the scale 84 itself and an error due to deformation of a structure that couples the scale 84 and the moving pin 80, and it is difficult to separate these errors from the error of the measuring machine. It had the problem that.
[0008]
The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to enable high-precision calibration without using a separate scale.
[0009]
[Means for Solving the Problems]
According to the present invention, when calibrating a laser scanning type dimension measuring machine using a laser beam, the calibration measuring body is positioned at a predetermined position within the measurement range, and the dimensions LS0 and L0 to the entrance side and exit side end faces are set. Measure, move the calibration measuring body until the position of the entry side end face coincides with the position of the exit end face, measure the dimension L1 to the exit end face, And measurement of the dimensions to the exit end face are repeated to obtain measured values LS0, L0 to L (n) of the respective dimensions. From the measured dimension values LS0, L0 to L (n), the following equation is obtained. Obtain each dimension D (n) of the calibration measuring body at each measurement position,
D0 = L0-LS0
D (n) = L (n) -L (n-1)
The error E (n) of each dimension measurement value L (n) is obtained by the following equation,
E (n) = Σ (D (n) −D0)
The above-described problems are solved by calibrating each dimension measurement value L (n) .
[0010]
In addition, a plurality of sets of calibration measurement values are obtained by changing the dimensions of the calibration measurement body , and the overall error is calibrated with the measurement result of the large calibration measurement body , thereby measuring the small calibration measurement body. As a result, the error of the large-sized calibration measuring body is interpolated and calibrated.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
A laser scanning type size measuring machine to which the present invention is applied is configured as shown in FIG. That is, the laser beam 22 generated from the beam generator 20 is reflected by the mirror 24, then enters the polygon mirror 26, is converted into a fan-shaped scanning beam 28, and then is converted into a parallel scanning beam 32 by the collimator lens 30. Converted. The parallel scanning beam 32 partially shielded by the DUT 10 placed in the optical path of the parallel scanning beam 32 is collected by the condenser lens 34 and is incident on the measurement light receiving element 36 for detecting the brightness. The The scan signal output from the measurement light-receiving element 36 is amplified by an amplifier 38, and then an edge signal indicating a light / dark boundary is extracted by a shaping circuit 40 and input to a segment selection circuit 42 for selecting a measurement target portion.
[0013]
A reset light receiving element 44 is provided in the vicinity of the collimator lens 30 of the fan-shaped scanning beam 28. The reference signal indicating the start of scanning obtained by the reset light receiving element 44 is input to the segment selection circuit 42 via the amplifier 46, and is used to select a necessary measurement segment.
[0014]
The clock pulse output from the clock pulse transmitter 50 is input to the motor of the polygon mirror 26 through the frequency dividing circuit 52, synchronized with the rotation of the motor and input to the AND gate 60, and the segment selection circuit. The AND gate 60 passes only while the AND gate 60 is opened by the output of 42. The clock pulse passing through the AND gate 60 is input to the counting circuit 62, and the dimension of the device under test 10 can be obtained from the number of clock pulses corresponding to the shadow length of the device under test 10.
[0015]
In the figure, 70 is a CPU, 72 is a main bus, 74 is a memory for measurement data and correction data, and 76 is a display / key / input / output interface.
[0016]
The correction according to the present invention in such a laser scanning type dimension measuring machine is performed by sequentially moving the calibration moving pins (here, cylindrical gauges) 80 to positions adjacent to each other as shown in FIG. Is done by obtaining
[0017]
That is, (1) the measuring machine measures the dimension from the both end faces of the moving pin 80 to the light receiving element for reset 44 as shown in FIG.
[0018]
Then determined by calculating the (2) from the dimensions of the end surfaces (L0-LS0, L1-L 0), the mobile pin diameter (D0, D1). Here, it is assumed that the error of the first term L0 as the starting point of the calculation is zero.
[0019]
(3) If the true value of the diameter of the moving pin is defined as Ds and the error of L (n) is defined as E (n), it is expressed by the following equation.
[0020]
D (n) = L (n) −L (n−1) (2)
Ds = (L (n) -E (n))-(L (n-1) -E (n-1)) (3)
[0021]
(4) From the above relationship, the following equation is established.
[0022]
D (n) -Ds = E (n) -E (n-1) (4)
[0023]
Therefore, the following equations (5) and (6) are obtained.
[0024]
E (n) = D (n) -Ds + E (n-1) (5)
D (n) = Ds + E (n) −E (n−1) (6)
[0025]
(5) When D0 = Ds + E (0) −E (−1) and C = E (0) −E (−1), the following equation is established.
[0026]
E (n) = D (n) -D0 + E (n-1) + C (7)
[0027]
(6) Therefore,
E (n) = Σ (D (n) −D0) + C × n (8)
[0028]
Here, since C × n is a linear component (proportional to the measurement size), it corresponds to the inclination, and can be corrected separately by the calibration function of the measuring instrument, so that the lens characteristic error to be calibrated here is ignored. be able to.
[0029]
In this way, by obtaining the calibration measurement values while sequentially moving the calibration moving pins 80 to positions adjacent to each other, a scale is not required, and errors due to deformation of the scale and the measurement structure are not included. Correction is possible.
[0030]
In the correction according to the present invention, correction (error) data can be obtained only for each size (diameter) of the moving pin 80. Therefore, the correction is also performed in units of the size of the moving pin 80, and fine correction in the middle is difficult. It is. On the other hand, if the moving pin has a small size, an error can be obtained with a fine pitch, but the detection sensitivity of the error decreases, and a quantization error or the like generated during calculation accumulates. A second embodiment of the present invention that solves such problems will now be described.
[0031]
In the second embodiment, as shown in FIG. 5, more accurate correction data can be obtained by synthesizing data using two or several types of moving pins (here, two types of 80A and 80B). it can.
[0032]
That is, the total error is obtained from the measurement result of the large-sized pin 80A.
[0033]
Then, the error of the large-sized pin 80A is interpolated based on the measurement result of the small-sized pin 80B. The small size error to be interpolated is proportionally calculated to match the error of the large size pin.
[0034]
Specifically, (1) The pin is moved at a sufficiently fine pitch, and L on the upper and lower end surfaces of the pin is measured.
[0035]
(2) Perform this measurement for large and small pins.
[0036]
(3) From the data in the vicinity of the adjacent condition shown in FIG. 3, the measurement value of the adjacent condition is obtained by interpolation calculation.
[0037]
(4) The error is calculated at a pitch for each diameter of the large-sized pin 80A.
[0038]
(5) For each large calculation pitch, interpolation is performed using an error due to the measurement value of the small pin 80B.
[0039]
Here, in order to simplify the calculation, it is desirable that the diameter of the small-sized pin 80B is set to 1 / integer (¼ in the second embodiment) of the diameter of the large-sized pin 80A. It is not limited to this relationship. Although the number is not limited to two, two to three are preferable in practice.
[0040]
In the present invention, data satisfying the adjacency condition is required. However, in actual processing, the value of the adjacency condition can be obtained by complementary calculation from adjacent neighboring data, and the size ratio and movement pitch can be calculated. Precision is not required.
[0041]
The shape of the calibration moving pins is not limited to cylindrical.
[0042]
【The invention's effect】
According to the present invention, precise calibration can be performed without using a scale.
[Brief description of the drawings]
FIG. 1 is an essential optical path diagram showing an example of a conventional calibration method. FIG. 2 is a block diagram including a partial optical path diagram showing the overall configuration of a laser scanning dimension measuring machine to which the present invention is applied. FIG. 4 is an optical path diagram showing a measured value in the first embodiment. FIG. 5 shows a pin moving position in the second embodiment of the present invention. Diagram [Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... To-be-measured object 20 ... Beam generator 26 ... Polygon mirror 30 ... Collimator lens 32 ... Parallel scanning beam 34 ... Condensing lens 36 ... Measurement light receiving element 44 ... Reset light receiving element 70 ... CPU
74: Memory 80, 80A, 80B ... Moving pin (calibration measuring object)

Claims (2)

When calibrating a laser scanning dimension measuring machine using a laser beam,
The calibration measurement body is positioned at a predetermined position within the measurement range, and the dimensions LS0 and L0 to the entrance and exit end faces thereof are measured.
The calibration measuring body is moved until the position of the input side end surface coincides with the position of the output side end surface, and the dimension L1 to the output side end surface is measured,
By repeating the movement of the measurement body for calibration and the measurement of the dimensions to the exit end face, the measurement values LS0, L0 to L (n) of the respective dimensions are obtained,
From each dimension measurement value LS0, L0-L (n), obtain each dimension D (n) of the calibration measuring body at each measurement position by the following equation:
D0 = L0-LS0
D (n) = L (n) -L (n-1)
The error E (n) of each dimension measurement value L (n) is obtained by the following equation,
E (n) = Σ (D (n) −D0)
A calibration method of a laser scanning type dimension measuring machine, wherein each dimension measurement value L (n) is calibrated . Change the dimensions of the calibration measurement object to obtain multiple sets of calibration measurement values , calibrate the overall error with the measurement result of the large calibration measurement object , and use the measurement result of the small calibration measurement object. 2. The method of calibrating a laser scanning dimension measuring machine according to claim 1, wherein the calibration is performed by interpolating an error of a large-sized calibration measuring body .

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