JPH04276514A - Noncontact displacement measuring apparatus - Google Patents

Abstract

PURPOSE:To measure displacement highly accurately by obtaining the output of the displacement corresponding to the state of the surface regardless of the surface state of an object to be measured. CONSTITUTION:A displacement output signal S1 corresponding to displacement is obtained without contact with a main optical system 2 and a processing part 10 with respect to an object to be measured B. A scattered light detecting optical system 15 for detecting the scattered light W of the main optical system 2 is provided in the vicinity of the main optical system 2. The state of the surface of the object to be measured B is detected and outputted into a linear correcting part 20. The linear correcting part 20 generates correcting data S4 corresponding to the surface state of the object to be measured B and corrects the output of the displacement output signal S1. Thus, the highly accurate displacement measurement can be performed automatically regardless of the surface state of the object to be measured B.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a non-contact displacement measuring device capable of non-contactly measuring the amount of displacement of an object to be measured. The present invention relates to a non-contact displacement measuring device that can measure the amount of displacement.

0002

BACKGROUND OF THE INVENTION Displacement measurements of dimensions, shapes, vibrations, etc. of objects to be measured can be performed with high accuracy by non-contact displacement measuring devices using optical systems. FIG. 4 is a block diagram showing the configuration of a conventional non-contact displacement measurement device 39. Using this diagram to explain the displacement measurement operation, light emitted from a semiconductor laser 40 passes through an illumination lens 41 and is narrowed down. ,L1
The light beam is irradiated onto the measurement object B at the position , and a light spot is formed at the measurement object position b1. When a part of the light reflected and scattered by the surface of the measurement object B is captured by the imaging lens 43 and an image of the light spot is projected onto the light receiving surface of the photodetector element 44, an image of the light spot is formed at c1.

The image of the reflection point created by the imaging lens 43 is
When the measurement target B moves back and forth, it moves on the photodetecting element 44 accordingly. When the measurement target B moves to the position L2, the light spot moves to the position b2, and accordingly, the image of the light spot created by the imaging lens 43 also changes to the light detection element 44.
Move to c2 above. Terminals 44 on both sides of the photodetector element 44
A and 44b generate currents that depend on the amount of light and the position of the image of the light spot. These currents i1 and i2 are converted into voltages and set to V1 and V2, respectively.
, V2 and are divided, a displacement output determined only by the position of the light spot without depending on the change in the light amount of the image is obtained. Light spot position (position of measurement target B)
Since there is a certain relationship between the position of the image of the light spot and the position of the image of the light spot, the position of the object B to be measured can be known from this displacement output.

0004

[Problem to be Solved by the Invention] By the way, linearity is defined as the allowable value of measurement error that occurs when the position of measurement object B is changed within the measurement range. It varies depending on the surface condition of B. Note that the standard sample for measurement target B is an object with a mirror surface,
Alternatively, either a white scatterer is used. Therefore, in the conventional non-contact displacement measuring device described above, if the surface condition of the measurement object B varies depending on the location and the reflectance changes, linearity cannot be obtained, measurement errors occur, and accurate displacement measurement cannot be performed. could not. The above drawback is that the measurement target B
Another factor is that there are no sensors available to detect the surface condition of the surface.

The present invention has been made to solve the above-mentioned problems, and is capable of constantly monitoring the surface condition of the object to be measured, and achieving highly accurate displacement that can always obtain linearity regardless of the surface condition of the object to be measured. It is an object of the present invention to provide a non-contact displacement measuring device that can perform measurements.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the non-contact displacement measuring device of the present invention is a non-contact displacement measuring device that non-contactly measures displacement of a measurement object B using an optical system. A main optical system 2 is provided with a light projecting section 3 that emits the output light N1 to the measurement object, and a light receiving section 4 that receives the reflected light N2 from the measurement object; A polarizing filter 17 that transmits the scattered light W of the object in a polarized state, a scattered light detection optical system 15 provided with a light receiving element 18, and a displacement output corresponding to the displacement of the measurement object based on the detection output of the main optical system. a processing unit 10 that outputs a signal S1; a linear correction unit 20 that corrects and outputs the displacement output signal S1 using correction data S4 corresponding to the surface state of the measurement target based on the detection output of the scattered light detection optical system; It is characterized by having the following.

[0007]

[Operation] The measurement object B has different linearity due to different surface conditions. A displacement output signal S1 of the measurement object B is obtained by the main optical system 2 and the processing section 10. Furthermore, the scattered light detection optical system 15 detects the surface state of the object B based on the scattered light. Further, the linearity correction section 20 obtains linearity correction data S4 corresponding to this surface condition. Thereby, the surface condition of the measurement object B can be automatically detected, and the displacement output signal S1 corrected in accordance with this surface condition can be obtained.

[0008]

Embodiment FIG. 1 is a block diagram showing an embodiment of the non-contact displacement measuring device of the present invention. The sensor head 1 is provided with a light projecting section 3 as a main optical system 2 and a light receiving section 4. The light projection unit 3 is provided with a semiconductor laser 5 that emits light of a predetermined wavelength (for example, 780 nm). The emitted light N1 of the semiconductor laser 5 passes through an illumination lens 6 and is narrowed down to a narrow beam spot b to be irradiated onto the object B to be measured. The light receiving unit 4 is composed of an imaging lens 7 and a photodetecting element 8. The imaging lens 7 captures a part of the reflected light N2 reflected on the surface of the measurement object B, and transmits the image of the light spot b to the photodetecting element. The image is projected onto part c on the light-receiving surface of No.8. Here, the emitted light N1 and the reflected light N2 have a predetermined angle R with respect to the measurement target B, and are in a regular reflection relationship, and therefore the light projecting section 3 and the light receiving section 4 are arranged along this predetermined angle R. ing.

The image of the reflection point formed by the imaging lens 7 moves over the photodetector element 8 according to the movement of the light spot b1-b2 corresponding to the displacement of the object B in the L1-L2 direction.
Move in the 1-c2 direction. The photodetection element 8 is composed of a position sensor, and has two terminals 8a and 8b.
is a current i that depends on the light intensity and position of the image of light spot b.
1, i2 is output. These outputs are converted into voltage signals V1 and V2 by current-voltage conversion units 9a and 9b, respectively, and then output to a processing unit 10.

The processing section 10 includes a subtraction section 11 that calculates the difference between the voltage signals V1 and V2 based on the voltage signals V1 and V2.
, an adder 12 that calculates the sum is provided at the front stage. Further, the outputs of the subtraction section 11 and the addition section 12 are inputted to a division section 13, subjected to a division operation, and outputted via a linear correction section 14 for linearization. As a result, a displacement output signal S1 determined only by the position of the light spot b is obtained regardless of changes in the light amount of the image of the measurement object B.

An optical system 15 for detecting scattered light is provided in an intermediate portion of the main optical system 2 of the sensor head 1, that is, between the light projecting section 3 and the light receiving section 4. The scattered light detection optical system 15 is
The scattered light W of the emitted light N1 irradiated onto the measurement object B is detected. The interference filter 16 provided facing the measurement target B transmits only the light having the wavelength of the emitted light N1. A polarizing filter 17 is provided adjacent to the interference filter 16, and polarized light enters the light receiving element 18. As a result, the light receiving element 18 detects the light receiving level of the scattered light W of the measurement object B,
That is, a scattered light output signal S2 corresponding to the surface condition of the measurement object B is obtained.

This scattered light output S2 is input to the straight line correction section 20. The linear correction section 20 outputs the scattered light output S2 to the discrimination circuit 25 via the amplification section 24 that amplifies the scattered light output S2. A detection section may be provided before the amplification section 24. Discrimination circuit 25
determines the measurement target B based on the scattered light output signal S2. There are three types of measurement objects B to be determined: a shiny object B1, a scattering object B2, and an object B3 into which light enters.

FIG. 3 is a graph showing the linearity of the measurement objects B1, B2, and B3 having different surface conditions. The displacement output signal S1 within the measurement range (L1-L2; where L1 is the longest measurement position, L2 is the shortest measurement position, and L0 is the center of the measurement range) is
, B3, the linearity differs depending on the amount of displacement. The surface state of the glossy object B1 is close to total reflection, and the linearity has a gentle slope over the entire fixed range with little variation. On the other hand, the object B3 into which light enters has linearity with a steeper downward slope to the right, where the error increases as the distance is measured due to the absorption effect. Scatterer B2 exhibits these intermediate characteristics due to the reflection effect.

By the way, the scatterer B2 and the object B3 into which light enters are usually at almost the same level when viewed only in terms of the light reception level, making it difficult to distinguish between them. However, the inventor discovered that the scattered light W of the scatterer B2 and the scattered light W of the object B3 into which the light enters have different polarization states, and by using the polarizing filter 17, it is possible to eliminate the difference in the level of received light. Detection is performed by the leaning light receiving element 18, and a scattered light output signal S2 is output, so that the discrimination circuit 25 can discriminate whether each object to be measured is B1, B2, or B3.

The discrimination circuit 25 outputs a correction signal S3 corresponding to each of the measurement objects B1, B2, and B3 to the correction data section 26 based on the discrimination result. The correction data section 26 stores the expected linearity (
(see FIG. 3) is stored. Then, by inputting the correction signal S3, correction data S4 corresponding to the linearity of each measurement object B is output to the linear correction section 14. Thereby, the linear correction unit 14 corrects the displacement output signal S1 so as to correspond to the linearity of each of the measurement objects B1, B2, and B3, and outputs the corrected displacement output signal S1.

With the above configuration, for example, a shiny object B1 and a scattering object B2 are placed on an object B3 into which light enters.
When measuring the thickness of an object provided with B1, B2,
Output light N1 is emitted to B3, and processing section 10 outputs displacement output signal S1 using this reflected light N2. At the same time, the scattered light detection optical system 15 and the straight line correction unit 20
The measurement object at this measurement point is determined using the scattered light W of 1, and the displacement output signal S1 is corrected and outputted in accordance with the linearity of the measurement object B at the measurement point using the generated correction data S4. . Thereby, when measuring objects B having different linearities are successively measured, this measurement can be performed accurately with the same characteristics.

Next, FIG. 2 is a block diagram showing a modification of the above embodiment. In this embodiment, the configuration of the linear correction section 20 is modified. The correction signal S3 outputted by the discrimination circuit 25 is transmitted to the first and second constant selection circuits 27a,
27b, respectively. These first and second constant selection circuits 27a and 27b are connected to each measurement object B (B1
, B2, B3) of the linear straight line y=Bax+d(y;
Displacement output signal S1, B: each measurement object, x: displacement of the measurement object, a: constant (slope of straight line for each measurement object), d: offset value for error 0 when displacement of measurement object B is 0). B and d are memorized.

The output of the linear correction section 14 is input to a sensitivity correction circuit 28, and the signal from the first constant selection circuit 27a is input to this sensitivity correction circuit 28, and the slope of the linearity is corrected. and output to the offset circuit 29. The offset circuit 29 includes a second constant selection circuit 2.
The signal 7b is input, the linearity offset value is corrected, and the final displacement output signal S1 is output. Thereby, it is possible to obtain a displacement output signal S1 having linearity corresponding to each of the measurement objects B1, B2, and B3 using the correction signal S3.

[0019]

According to the present invention, the displacement of the object to be measured corresponds to the surface condition based on the scattered light detection optical system that detects the surface condition of the object to be measured, and the output of the scattered light detection optical system. It is equipped with a linear correction section that corrects and outputs linearity, and automatically detects the surface condition of the measurement target and always obtains optimal linearity.This allows displacement measurement to be performed with high precision. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a non-contact displacement measuring device of the present invention.

FIG. 2 is a block diagram showing another embodiment of the device.

FIG. 3 is a graph showing the linearity of measurement objects with different surface conditions.

FIG. 4 is a block diagram showing the configuration of a conventional non-contact displacement measuring device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...Sensor head, 2...Main optical system, 3...Light emitter, 4...Light receiving part, 5...Semiconductor laser, 6...Illumination lens, 7...Imaging lens, 8...Photodetection element, 9a, 9b...Current - Voltage conversion section, 10... Processing section, 11... Subtraction section, 12... Addition section, 13...
Dividing unit, 14... Linear correction unit, 15... Optical system for detecting scattered light, 16... Interference filter, 17... Polarizing filter, 18...
Light receiving element, 20... Linear correction section, 24... Amplification section, 25... Discrimination circuit, 26... Correction data section, 27a... First constant selection circuit, 27b... Second constant selection circuit, 28... Sensitivity correction circuit, 29 ...Offset circuit, B (B1, B2, B3)...
Measurement object, b...light spot, N1...outgoing light, N2...reflected light, W...scattered light, S1...displacement output signal, S2...scattered light output signal, S3...correction signal, S4...data for correction.

Claims (1)

[Claims] Claim 1: A non-contact displacement measurement device that non-contactly measures displacement of a measurement object (B) using an optical system, comprising:
Light projection unit (3) that emits the output light (N1) to the measurement target
, and a main optical system (2) provided with a light receiving section (4) that receives the reflected light (N2) from the measurement target, and a main optical system (2) that is provided near the main optical system and receives the scattered light (W) of the measurement target. a scattered light detection optical system (15) provided with a polarizing filter (17) that transmits in a polarized state and a light receiving element (18); and a displacement output corresponding to the displacement of the measurement target based on the detection output of the main optical system. The displacement output signal (S1) is corrected by a processing unit (10) that outputs a signal (S1) and correction data (S4) corresponding to the surface condition of the measurement target based on the detection output of the scattered light detection optical system. A non-contact displacement measuring device, comprising: a straight line correction section (20) that outputs an output.