JPH02176517A - Optical system position measuring device - Google Patents

Abstract

PURPOSE:To accurately measure the position and the thickness of an object to be measured by correcting the position of the centroid of light quantity based on reflectance and transmittivity inside and outside the object to be measured and the thickness of the object to be measured by means of a correction operation part. CONSTITUTION:In the case that the object to be measured 1A is a light- transmissive one, the position of the centroid of the light quantity of scattered light on a light position detecting element 6 is corrected by the correction operation part 15 based on the reflectance on the surface of the object 1A, the reflectance and transmittivity inside the object 1a and the thickness of the object 1A. At such a time, a signal in proportion to the position of the centroid of the light quantity from a signal processing part 3 calculates the actual position of the centroid of the light quantity and the apparent position of the centroid of the light quantity is corrected by the correction operation part 15 based on several values inputted from a numeric value input device 14 and stored 16. Thus, the position and the thickness of the object to be measured 1A is accurately measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an optical position measuring device suitable for non-contact measurement of the position and thickness of a translucent and transparent object. It is.

[Prior Art] Fig. 3 is a block diagram of an optical position measuring device disclosed in, for example, Japanese Patent Publication No. 56-10561, in which 1 is an object to be measured, 2 is a detection section, and 3 is a signal processing section. Department.

The detection unit 2 includes a lens 4a.

4b, a light source 5 such as an LED that irradiates a light beam onto the object to be measured 1, and a photoelectric converter.
It is composed of an optical position detection element 6 called an optical position detection element 6. Also,
The signal processing unit 3 includes a light source drive circuit 7 that pulse-drives the light source 5 and an output current Il+1 from both ends of the optical position detection element 6.
amplifiers 8a and 8b for respectively amplifying .2, and a subtracter 9. for performing arithmetic processing to be described later. Adder 10. It is composed of sample and hold circuits 11a, llb, and a divider 12.

Next, the operation will be explained. The light source 5 is driven by pulses from the drive circuit 7, and repeatedly turns on and off at appropriate time intervals to generate light. The light beam emitted from the light source 5 is focused by the lens 4a and projected onto the surface of the object to be measured 1 perpendicularly to the surface. At this time, if the surface of the object to be measured 1 is a general object surface other than an ideal mirror surface, the projected light will be scattered, and from various angles, a bright spot of light due to reflected and scattered light, that is, a light Points can be observed.

In the detection unit 3, the light beam is placed on the optical axis forming a predetermined angle θ with the irradiation beam emitted through the lens 4a.

Another lens 4b is installed, and the image of the above-mentioned light spot is formed on the light receiving surface of the optical position detection element 6 by the lens 4b. When the optical position detection element 6 receives light, it performs photoelectric conversion and generates two currents from both ends depending on the imaging position of the light spot.

Outputs 12. After these currents x1t 12 are amplified by amplifiers 8a and 8b, they are converted to (xt 12) and (i +
iz) are taken out and input to sample and hold circuits 11a and llb, respectively.

The sample and hold circuits 11a and llb sample the input signal in synchronization with the drive pulse from the light source drive circuit 7, and the pulse waveform light reception signal is converted into a DC signal and output. Then, by the divider 12, (il-i,)
/(i + 12)) is calculated and output, and a signal proportional to the light intensity gravity center position of the spot light imaged on the light receiving surface of the optical position detection element 6 is obtained. Based on this signal, the optical triangular The position of the object to be measured 1 is calculated and measured using the surveying method.

[Problems to be Solved by the Invention] Since the conventional optical position measuring device is configured as described above, it has the following problems.

When the object to be measured 1 is translucent and translucent, as shown in FIG. 4, in addition to the reflected light component 13a from the surface of the object to be measured 1, as shown in FIG. book reflected rays 13
As shown in FIGS. b and 13c, the reflected light from the light that has penetrated into the inside of the object to be measured 1 is also incident on the optical position detection element 6.

The center of gravity of the entire reflected light from the object to be measured 1 is:
It moves to a position deeper inside the object to be measured 1 than the surface position, and an error is included in the measurement position.

In other words, since the optical position detection element 6 converts the center of gravity position of the entire received light into an electrical signal as described above,
In this case, the output signal corresponds to the position inside the object to be measured 1 rather than the surface position of the object to be measured (the position to be measured). Therefore, when measuring the position of a translucent and light-transmitting object to be measured, a measurement result that appears as if the object is far away from its true position can be obtained.

There is also a device that measures the thickness of the object to be measured 1 by using two such position measuring devices and adding the values obtained by measuring the position from both sides of the object to be measured.
When measuring the thickness of a translucent and translucent object with such a device, for the same reason as mentioned above, the values from both sides will be as if they were far away. The thickness will be thinner than the actual size.

The measurement error that occurs in this way is affected by the transmittance and reflectance of light inside the object to be measured 1, so when measuring the position of objects of different types and properties, there will be a certain offset in the measurement result. It is not possible to measure the true surface position or thickness simply by adding the values as follows.

This invention was made to solve the above-mentioned problems, and provides an optical position measuring device that can accurately measure the position and thickness of a translucent and translucent object. With the goal.

[Means for Solving the Problems] When the object to be measured is translucent, the optical position measuring device according to the present invention is capable of determining the reflectance of the surface of the object to the light beam and the The device is equipped with a correction calculating section that corrects the light quantity gravity center position based on the reflectance and transmittance inside the object to be measured and the thickness of the object to be measured.

[Function] In the optical position measuring device according to the present invention, when the object to be measured is translucent, the center of gravity of the amount of scattered light on the photodetecting element is determined by the reflectance on the surface of the object to be measured, The correction is performed by the correction calculation unit based on the reflectance and transmittance inside the object to be measured and the thickness of the object to be measured, and the true center of gravity position of the light quantity that is not affected by the translucent material is measured.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
The figure is a block diagram showing an optical position measuring device according to an embodiment of the present invention. In the figure, the same reference numerals as those already described indicate the same parts, and the explanation thereof will be omitted.

In FIG. 1, LA is a translucent and transparent object to be measured, and here, the reflection coefficient (reflectance) on the surface of the object IA is the coefficient related to the amount of reflection inside the object IA. It is assumed that (reflectance) b, attenuation constant (transmittance) it per unit length inside the object to be measured IA, and thickness X of the object to be measured IA are known. And 14 are these coefficients a/b etc.

Numerical input device such as a keyboard for inputting ε and xo, 15 is a calculation device, which calculates the actual light amount gravity position (apparent It has a function as a correction calculation unit that calculates the gravity center position) and also corrects the apparent light intensity gravity center position based on various values input from the numerical input device 14 using an arithmetic formula described later. It is configured using Further, 16 is a storage device for storing input values a/b, a, and xo.

Next, the correction calculation process performed by the calculation device 15 will be explained with reference to FIG. In FIG. 2, 10 is the amount of irradiation of the light beam from the light source 5, and 11 is the amount of scattered light that is reflected by the surface of the object to be measured IA and reaches the lens 4b. In addition, dix is the depth X from the surface of the object to be measured IA
This is the amount of reflected light that is reflected from the layer with the minute thickness dx at the location and finally reaches the lens 4b. At this time,
11=a-10...(1) = b-1o, e-'("tJg)" -(
The relational expression 2) holds true.

Then, the depth x o of the object to be measured IA (i.e., the object to be measured I
If the center position of the light intensity of the entire reflected light from the range up to the thickness of
), and by substituting equation (2), we obtain. The true position of the surface of the object to be measured IA is obtained by subtracting the above measured value from the apparent value of xg. Based on this formula (4), <x
The g calculation and the correction calculation using the obtained xg are performed by the calculation device 1.
This will be done in 5.

In this way, according to the apparatus of this embodiment, the influence of reflected light inside the object to be measured IA is corrected, so even if the object to be measured IA whose position is to be measured is translucent, The surface position can be measured accurately.

In the above embodiment, the thickness xo of the object to be measured IA is known and the surface position is measured. However, by using two devices having the same configuration as in FIG. The thickness X of the object to be measured IA is determined as follows. can also be measured.

In other words, x
Surface position measurement (apparent position measurement) without correction by g is performed to measure the positions of both sides of the object IA, and the apparent thickness X of the object IA. ′, and this thickness
. ', X in equation (4). Find the xg value using formula (4), and calculate the thickness (apparent thickness) before correction x0'
By adding the xg value for two cars, that is, 2xg, to
Accurate thickness measurements can be obtained.

In addition, in the above embodiment, the transmission coefficient and reflection coefficient (a/b,
ε) is entered from a numerical input device 14 such as a keyboard, but at least two objects to be measured of the same material and different thickness are prepared, and the measured value before xg correction and the measured value by a micrometer etc. are input. The xgO value for each sample is determined as an actual value from the difference with the thickness measurement result, and (
4) It may be configured such that the simultaneous equations are solved by substituting a/b and ε into the equations, and the values of a/b and ε are calculated by the arithmetic unit 15 and stored in the storage device 16. In this case, there is no need to check the transmission coefficient and reflection coefficient (a/b, 1) in advance.

[Effects of the Invention] As described above, according to the present invention, when the object to be measured is translucent, the center of gravity of the amount of scattered light on the photodetecting element is determined by the reflection on the surface of the object. The correction calculation unit performs correction based on the reflectance and transmittance inside the object to be measured, the thickness of the object to be measured, and the influence of reflected light inside the object to be measured is corrected. This has the effect of accurately measuring the position and thickness of a photosensitive object.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an optical position measuring device according to an embodiment of the present invention, Fig. 2 is a diagram for explaining the operation of the above embodiment device, and Fig. 3 is a diagram showing a conventional optical position measuring device. The block diagram shown in FIG. 4 is a diagram for explaining the operation of the above-mentioned conventional device. In the figure, IA...-object to be measured, 3--signal processing section, 5--light source, 6--optical position detection element, 15--
Arithmetic device (correction arithmetic unit). In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A light source that irradiates a light beam onto an object to be measured, and an optical position detection element that receives scattered light of the light beam from the object to be measured at a predetermined angle, and forms an image on the light receiving surface of the optical position detection element. In an optical position measuring device that measures the position of the object to be measured by triangulation based on the light amount and gravity center position of the scattered light, when the object to be measured is translucent, A correction calculation unit is provided for correcting the light amount gravity center position based on the reflectance on the surface of the object to be measured, the reflectance and transmittance inside the object to be measured, and the thickness of the object to be measured. An optical position measuring device characterized by: