JPS6355641B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a shape measuring device that measures the one-dimensional surface shape of an object using the principle of measuring the distance to the object by irradiating the object with a scanning light beam. .

When measuring the shape of an object, the simplest method is to use a ruler to measure the distance from a certain reference plane to each point on the object, and the mechanical probe method is a precise way to do this. As is well known, this mechanical probe method involves directly contacting the probe with the object and measuring its shape, so there are limitations to the nature of the object, and it takes a considerable amount of time to measure. Continuous measurement was difficult. In addition, a non-contact method for measuring displacement is to irradiate a light beam to measure the distance to the object, but when the object is stationary, it is necessary to move the measuring device to avoid irregularities and other shapes. was difficult to measure.

This invention was made in order to eliminate the above-mentioned drawbacks, and is a non-contact, continuous, and high-speed method for
The present invention provides a shape measuring device that is capable of measuring shapes such as dimensional unevenness.

Before explaining the apparatus of the present invention, the basic configuration when one light source is used and the relationship between the reflected light from the object surface and the light receiving position will be explained with reference to FIGS. 1 to 3. FIG. 1 is a diagram showing the configuration of an apparatus for measuring the displacement of an object to be measured. In the figure, 21 is a light source, and 22 is a lens that converges the light beam from the light source 21 into a narrow irradiation light beam 23. Reference numeral 24 denotes an object to be measured, the surface of which is displaced in the directions of arrows A and B. 25 is a condensing lens that converges the reflected light from the object to be measured 24.
Reference numeral 26 denotes a position detector, which is composed of a light receiving element 27, an arithmetic unit 28, and the like. 9 is a correction circuit.

However, in the above device, the light source 21
The light beam outputted from the lens 22 is converged into a narrow irradiation light beam 23 and directed to the object to be measured 24.
irradiated onto the surface of At this time, as shown in FIG. 2, when the surface displacement x of the object to be measured 24, that is, each point on the x-axis changes by -a, +a from the center 0, the reflected light 23' from the object to be measured 24 is projected onto the light receiving element 27 through the condenser lens 25 at points -b and +b from the center 0' on the y-axis. Since the position of the image formed by the condenser lens 25 differs depending on the distance and angle between the object to be measured 24 and the condenser lens 25, the light-receiving element surface is adjusted so that the locus of the image-forming position and the light-receiving element surface coincide. Determine the position. If the locus of the imaging position and the light receiving element surface do not match, the light spot on the object to be measured will not be imaged on the light receiving surface, and the light spot on the light receiving surface will become large, causing an error. . Regarding errors other than those mentioned above, please refer to the division circuit 1 shown in FIG.
1 ₁ and 11 ₂ to correct errors caused by differences in light intensity on the light receiving element surface due to differences in reflectance of the object to be measured 24, and linear correction circuits 12 ₁ and 12 ₂ shown in FIG. Nonlinearity in the movement of the measurement object 24 in the x-axis direction and the movement of the light spot on the light receiving surface is corrected.

Therefore, the device of the present invention measures the one-dimensional shape of the object to be measured using two light sources based on the above-mentioned principle configuration. Refer to and explain. In Figure 4, 1 ₁ is a first light source that outputs light modulated at a frequency of ₁ , 1 ₂ is a second light source that outputs light that is modulated at a frequency of ₂ , and 2 is a first and second light source that outputs light modulated at a frequency of 2. Scanner 3 ₁ , consisting of a rotating mirror, etc. for scanning the light from the light sources 1 ₁ , 1 _{2 of 2} ;
3 ₂ is this scanner 2 and the first and second light sources 1 ₁ , 1
This lens is installed on the optical axis of the light sources 1 ₁ and 1 ₂ and converts the light beams from the light sources 1 1 and 1 ₂ into a narrow irradiation beam. Reference numeral 4 denotes an object to be measured whose surface to be measured in the y direction is displaced in the x-axis direction. 5 ₁ and 5 ₂ are irradiation lenses installed on the optical axis between the object to be measured 4 and the scanner 2. 6 is a light-receiving element (detailed configuration is shown in FIG. 5), and the light-receiving area of this light-receiving element 6 is determined by the deflection width of the rotating mirror 2 toward the object to be measured 4, the magnification of the condensing lens 7, etc. It is determined. A condenser lens 7 is installed on the optical axis between the light receiving element 6 and the object to be measured 4 and focuses the reflected light from the object to be measured 4.

The light receiving element 6 is such that the ratio of photocurrents i ₁ and i ₂ obtained from each terminal changes depending on the image position of the light spot on the light receiving surface, and a diffused PIN diode or the like is used.

In addition, 8 ₁ and 8 ₂ are filters that allow only one frequency component to pass from the photocurrents i ₁ and i ₂ , and 8 ₃ and 8 ₄ are filters that allow only _one frequency component to pass from the photocurrents i 1 and i 2 .
This is a filter that allows only _two frequency components from i ₁ and i ₂ to pass through. 9 ₁ is a subtraction circuit that calculates the difference (i ₁ - i ₂ ) between photocurrents i ₁ and i ₂ that have passed through filters 8 ₁ and 8 ₂ ; 10 ₁
is an addition circuit that calculates the sum (i 1 + i ₂ ) of photocurrents i ₁ and i ₂ that have passed through filters _{8 1} and 8 2 , and 9 2 is an addition circuit that calculates the sum (i ₁ + i ₂ ) of photocurrents i 1 and i ₂ that have passed through filters 8 ₁ and 8 2 ,
₁₀₂ is the sum of the photocurrents _{i1 + i2} that have passed through _{filters 83} and _{84 ( i1} + _{i2 ) .} ).
11 ₁ and 11 ₂ are division circuits that divide (i ₁ −i ₂ ) by (i ₁ +i ₂ ), 12 ₁ and 12 ₂ are linear correction circuits, and 13 is a displacement calculator.

A configuration diagram of the diffused PIN diode used as the light receiving element 6 is shown in FIG. In FIG. 5, 61 is an n-type semiconductor substrate, 62 is a p-type semiconductor region, 63 is an electrode attached to the n-type semiconductor substrate 61, and 64 and 65 are electrodes attached to the p-type semiconductor region 62. Also, 66 is a power supply, 67,
68 is a load resistor. In such a configuration, a photocurrent i ₁ flowing through the load resistor 67 and a photocurrent i ₂ flowing through the load resistor 68 depend on the irradiation position of the reflected light.
The results are different. Therefore, this photocurrent i ₁ ,
i ₂ through the filters 8 ₁ , 8 ₄ , subtraction circuits 9 ₁ , 9 ₂ ,
By performing arithmetic processing in the adder circuits 10 ₁ , 10 ₂ and the divider circuits 11 ₁ , 11 ₂ , the irradiation positions y ₁ , y ₂ from the center O of the light receiving element 6 are calculated as follows: y ₁ =K ₁・(i ₁ −i ₂ )/(i ₁ + i ₂ )… (1) y ₂ = K ₂・(i ₁ − i ₂ )/(i ₁ + i ₂ )… (2) However, K ₁ and K ₂ are constants.

Further, the linear correction circuits 11 ₁ and 11 ₂ are arranged so that the y ₁ and y ₂ are linearly proportional to the change in the x-axis direction of the illustrated xy two-dimensional coordinates of the object to be measured 4 (with the condensing lens 7 as the origin). This is to compensate for the fact that the signal does not match, and uses a polygonal approximation circuit, an exponential function circuit, etc. Therefore, y ₁ and y ₂ linearly corrected and outputted by these linear correction circuits 11 ₁ and 11 ₂ correspond to changes in the object to be measured 4 in the x-axis direction. From y ₁ and y ₂ obtained in this way, the measured object 4
When considered in two-dimensional coordinates with the condensing lens 7 as the origin, the displacement x _a is expressed as xa=Δyh·xc/y ₁ +y ₂ (3). x _a in the above equation (3) is the distance variation in the x-axis direction from the condensing lens.
x _a is the distance corresponding to the unevenness. Therefore, if the displacement calculator 13 calculates the above equation (3) and the output signal is displayed on an XY recorder or the like, a shape corresponding to the surface shape of the object to be measured 4 will be drawn.

By the way, the above equation (3) can be obtained as follows. That is, y ₁ (light point of the light beam from the first light source 1 ₁ ) and y ₂ (light point of the light beam from the second light source 1 ₂ ) on the light receiving element 6 are y ₁ =y _h /x _a・x _c … (4) y ₂ =−y _h +Δy _h ／x _a・x _c … (5) From equations (4) and (5), y ₂ =−(−xa/xc) y ₁ +Δyh/xa・xc… (6) From this, xa becomes xa=−Δyh・xc/y ₂ −y ₁ =Δyh・xc/y ₁ −y ₂ .

With the above configuration, when the scanner 2 is irradiated with light modulated at frequencies ₁ and ₂ from the first and second light sources 1 ₁ and 1 ₂ , those lights scan the object to be measured 4 . , the reflected beam passes through the condenser lens 7 and is irradiated onto the light receiving element 6 . This light receiving element 6
outputs photocurrents i ₁ and i ₂ corresponding to the position of the light spot of the reflected beam. The photocurrents i ₁ and i ₂ are separated by filters 8 ₁ to 8 ₄ at frequencies of 5 ₁ and 5 ₂ , respectively. Therefore, filters 8 ₁ , 8 ₂
are the photocurrents i ₁ , i ₂ due to the light from the first light source 1 ₁
are output, and photocurrents i ₁ and _i 2 due to the light from the second light source 1 ₂ are output from the filters 8 ₃ and 8 ₄ . Then, the photocurrents i ₁ , i ₂ due to the light from the first light source 1 ₁ and the photocurrents i 1 , i ₂ due to the light from the second light source 1 ₂ are converted to i _{1 −i} by the subtraction circuits 9 ₁ , 9 ₂ , respectively. ₂ is subtracted, addition circuits 10 ₁ and 10 ₂ add i ₁ + i ₂ , and division circuits 11 ₁ and 11 ₂ divide (i ₁ − i ₂ )/(i ₁ + i ₂ ). After that, linear correction is performed in linear correction circuits 12 ₁ and 12 ₂ .
The y 1 and y ₂ of the above equations (1) and (2) that have been linearly corrected by the linear correction circuits 12 ₁ and _{12 2 are} input to the displacement calculator 13, where the above equation (3) is calculated and output. be done. As mentioned above, the output x _a from the displacement calculator 13 is the distance to the unevenness of the surface shape of the object to be measured 4, that is, in this embodiment, the center of the condenser lens 7 is the origin. It shows the displacement of the x coordinate from . Therefore, by inputting the output of the displacement calculator 13 into, for example, an XY recorder, a shape corresponding to the surface shape of the object to be measured 4 can be picked up.

As explained above, according to the present invention, one-dimensional shapes such as unevenness of an object can be measured non-contact, with high precision, and at high speed while the object is stationary, regardless of whether the object is moving or not. A shape measuring device can be provided.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle configuration of the device of the present invention when one light source is used, and Figures 2 and 3 are the relationship between the displacement of the object to be measured and the light receiving position when the device shown in Figure 1 is used. FIG. 4 is a block diagram showing an embodiment of the apparatus of the present invention, and FIG. 5 is a block diagram showing a specific example of a light receiving element used in the same embodiment. 1 ₁ ...first light source, 1 ₂ ...second light source, 2...scanner, 4...object to be measured, 6...light receiving element, 8 ₁ ...8 ₄
...Filter, 9 ₁ , 9 ₂ ...Subtraction circuit, 10 ₁ , 10 ₂
... Addition circuit, 11 ₁ , 11 ₂ ... Division circuit, 12 ... Linear correction circuit, 13 ... Displacement calculator.

Claims (1)

[Claims] 1 First and second light sources 1 ₁ and 1 ₂ that output highly directional light beams modulated at different frequencies, a scanner 2 that scans the light from these first and second light sources, and this scanner an irradiation lens 5 ₁ that projects the images of the first and second light sources scanned by onto the object to be measured and forms light spots at different points, respectively;
5 ₂ , a condensing lens 7 arranged in a direction different from the optical axis of the irradiation lens and condensing reflected light from each light point of the object to be measured, and at least two lights formed on the object to be measured. a position detector 6 having a light-receiving surface in a direction connecting the points, receiving light at different positions depending on the displacement of the object to be measured that enters through the condenser lens, and obtaining a position output of an image of the light point; Calculating means 8 ₁ to 8 ₄ , to 13 which separates the position output from the position detector for each frequency and calculates the displacement of the object to be measured using the separated position outputs.
A shape measuring device characterized by comprising: