JP2816257B2 - Non-contact displacement measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact displacement measuring device capable of measuring a displacement of a measuring object in a non-contact manner, and particularly to an accurate non-contact displacement measuring device irrespective of the surface condition of the measuring object. The present invention relates to a non-contact displacement measuring device capable of measuring a displacement amount.

[0002]

2. Description of the Related Art Displacement such as size, shape, vibration, etc. of a measurement object can be measured with high accuracy by a non-contact displacement measuring device using an optical system. FIG. 4 is a block diagram showing a configuration of a conventional non-contact displacement measuring device 39. The operation of measuring displacement will be described with reference to FIG. 4. Light emitted from a semiconductor laser 40 is narrowed down through an illumination lens 41. , L1
A light spot is formed at the position of b1 of the measurement target when the measurement target B at the position is irradiated. When a part of the light reflected and scattered on the surface of the measurement target B is captured by the imaging lens 43 and the image of the light spot is projected on the light receiving surface of the light detection element 44,
An image of the light spot is formed on c1.

The image of the reflection point formed by the imaging lens 43 is
When the measurement target B moves back and forth, it moves on the photodetector 44 accordingly. When the measurement object B moves to the position of L2, the light spot moves to the position of b2, and the image of the light spot formed by the imaging lens 43 accordingly changes to the light detecting element 44.
Move to c2 above. Terminals 44 on both sides of photodetector 44
Currents depending on the light quantity and the position of the image of the light spot are generated from a and 44b. The currents i1 and i2 are voltage-converted to V1 and V2, respectively.
When the sum and difference signals of 1, V2 are formed and divided, a displacement output determined only by the position of the light spot is obtained irrespective of the change in the light amount of the image. Since the position of the light spot (the position of the measurement target B) and the position of the image of the light spot have a fixed relationship, the position of the measurement target B can be known from the displacement output.

[0004]

By the way, the allowable value of the measurement error generated when the position of the measurement object B is changed within the measurement range is defined as the linearity. It depends on the surface condition of B.
An object having a mirror surface as a standard sample of the measurement object B,
Alternatively, any of white scatterers is used. Therefore, in the above-described conventional non-contact displacement measuring device, when the surface state of the measurement target B varies depending on the location and the reflectance changes, linearity cannot be obtained, and a measurement error occurs, and accurate displacement measurement can be performed. could not. The above drawbacks are caused by the measurement object B
This is also due to the fact that a sensor for detecting the surface condition of the above is not provided.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and constantly monitors the surface state of a measurement object, and can always obtain linearity regardless of the surface state of the measurement object, thereby achieving high-precision displacement. An object of the present invention is to provide a non-contact displacement measuring device capable of performing measurement.

[0006]

In order to achieve the above object, a non-contact displacement measuring apparatus according to the present invention is a non-contact displacement measuring apparatus for measuring a displacement of a measurement object B in a non-contact manner using an optical system. A main optical system 2 provided with a light projecting unit 3 for emitting outgoing light N1 to a measurement target, and a light receiving unit 4 for receiving reflected light N2 from the measurement target, and a measurement unit provided near the main optical system; A scattered light detection optical system 15 provided with a polarization filter 17 for transmitting the scattered light W of the target 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 A processing unit 10 for outputting a signal S1, and a linear correction unit 20 for correcting and outputting the displacement output signal S1 based on the detection output of the optical system for detecting scattered light, using correction data S4 corresponding to the surface state of the object to be measured.
And the following.

[0007]

The linearity of the object to be measured B differs due to the different surface conditions. The main optical system 2 and the processing unit 10 obtain a displacement output signal S1 of the measurement target B. Further, the scattered light detection optical system 15 detects the surface state based on the scattered light of the measurement target B. Further, the linearity correction unit 20 obtains linearity correction data S4 corresponding to the surface state. As a result, the surface state of the measurement target B can be automatically detected, and the displacement output signal S1 corrected according to the surface state can be obtained.

[0008]

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 unit 3 and a light receiving unit 4 as a main optical system 2.
The light projecting unit 3 is provided with a semiconductor laser 5 that emits light of a predetermined wavelength (for example, 780 nm). This semiconductor laser 5
Outgoing light N1 passes through the illumination lens 6 and is narrowed down narrowly so that the measurement target B is irradiated with the light spot b. The light receiving section 4 includes an imaging lens 7 and a light detection element 8, and the imaging lens 7
Part of the reflected light N2 reflected on the surface of the measurement target B is captured,
The image of the light spot b is projected on a portion c on the light receiving surface of the light detecting element 8. Here, the outgoing light N1 and the reflected light N2 have a predetermined angle R with respect to the measurement target B and have a regular reflection relationship. Therefore, the light projecting unit 3 and the light receiving unit 4 are arranged along the predetermined angle R. ing.

The image of the reflection point formed by the imaging lens 7 moves on the light detecting element 8 in accordance with the movement of the light spot b1-b2 corresponding to the displacement of the measuring object B in the L1-L2 direction.
Move in the 1-c2 direction. The light detecting element 8 is constituted by a position sensor, and has two terminals 8a and 8b.
From the current i depending on the light quantity and the position of the image of the light spot b.
1, i2 are output. This output is output to the processing unit 10 after being converted into voltage signals V1 and V2 by the current-voltage conversion units 9a and 9b, respectively.

The processing section 10 calculates a difference between the voltage signals V1 and V2 based on the voltage signals V1 and V2.
1. An adder 12 for calculating the sum is provided at the preceding stage. Further, the outputs of the subtraction unit 11 and the addition unit 12 are input to a division unit 13, where the division operation is performed, and output via a linear correction unit 14 for linearizing. Thus, a displacement output signal S1 determined only by the position of the light spot b is obtained irrespective of a change in the light amount of the image of the measurement target 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 unit 3 and the light receiving unit 4. The scattered light detection optical system 15 includes:
The scattered light W of the emitted light N1 applied to the measurement target B is detected. Interference filter 16 provided facing measurement object B
Transmits only light having the wavelength of the outgoing light N1. A polarization filter 17 is provided adjacent to the interference filter 16, and polarized light enters the light receiving element 18. Thereby, the light receiving element 18 obtains the scattered light output signal S2 according to the light receiving level of the scattered light W of the measurement target B, that is, the surface state of the measurement target B.

The scattered light output S2 is input to the straight line correction unit 20. The straight line correction unit 20 is output to the discrimination circuit 25 via the amplification unit 24 that amplifies the scattered light output S2. A detection unit may be provided in a stage preceding the amplification unit 24. Determination circuit 25
Determines the measurement target B based on the scattered light output signal S2. The measurement target B to be determined is of three types: a glossy object B1, a scatterer B2, and an object B3 into which light enters.

FIG. 3 is a graph showing the linearity of each of the objects to be measured B1, B2, and B3 having different surface states. 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 the measurement target B1, B
The linearity differs depending on the displacement amount of B2 and B3. The surface state of the glossy object B1 is close to the total reflection, and the linearity has a gentle slope and a small change over the entire fixed range. On the other hand, the object B3 into which light enters has a linearity with a steeper right-down slope where the error increases as the distance becomes shorter due to absorption. The scatterer B2 exhibits these intermediate characteristics due to the reflection action.

By the way, the scatterer B2 and the object B3 into which light enters usually have almost the same level when viewed only at the light receiving level, and are difficult to distinguish. However, the present inventor has found that the scattered light B of the scatterer B2 and the scattered light W of the object B3 into which the light enters have different polarization states. The detection circuit 25 detects the object B1, B2, and B3, and outputs a scattered light output signal S2.

The determination 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 result of the determination. The correction data section 26 stores correction data corresponding to the expected linearity (see FIG. 3) for each of the measurement objects B1, B2, and B3 in advance. The correction data S4 corresponding to the linearity of each measurement target B is input to the linear correction unit
Output to Accordingly, the linear correction unit 14 corrects and outputs the displacement output signal S1 so as to correspond to the linearity of each of the measurement objects B1, B2, and B3.

With the above structure, for example, a glossy object B1 and a scatterer B2 are placed on an object B3 into which light enters.
When measuring the thickness of the object provided with each, the main optical system 2 measures any one of the measurement objects B1, B2,
The emitted light N1 is emitted to B3, and the processing unit 10 outputs a displacement output signal S1 based on the reflected light N2. At the same time, the scattered light detection optical system 15 and the linear
The object to be measured at this measurement point is determined using the scattered light W, and the displacement output signal S1 is corrected and output in accordance with the linearity of the measurement object B at the measurement point by the generated correction data S4. . Thus, when continuously measuring the measurement objects B having different linearities, this measurement can be accurately performed 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 straight line correction unit 20 is modified. The correction signal S3 output from the discriminating circuit 25 is supplied to the first and second constant selecting circuits 27a,
27b. These first and second constant selection circuits 27a and 27b are connected to the respective measurement objects B (B
1, B2, B3) linear equation y = Bax + d
(Y; displacement output signals S1, B; each measurement object, x; displacement of the measurement object, a; constant (inclination of a straight line for each measurement object), d;
The parameters B and d in the offset value for the error 0 when the displacement of the measurement target B is 0 are stored.

The output of the linear correction section 14 is input to a sensitivity correction circuit 28, which receives a signal of a first constant selection circuit 27a and corrects the linearity gradient. Then, it is output to the offset circuit 29. The offset circuit 29 receives the signal of the second constant selection circuit 27b, corrects the linearity offset value, and outputs the final displacement output signal S1. Thus, a displacement output signal S1 having linearity corresponding to each of the measurement objects B1, B2, and B3 can be obtained by the correction signal S3.

[0019]

According to the present invention, the displacement of the object to be measured corresponds to the scattered light detecting optical system for detecting the surface state of the object to be measured, and further to the surface state based on the output of the scattered light detecting optical system. The system is equipped with a linear correction unit that corrects and outputs with linearity, and automatically detects the surface state of the measurement target and always obtains the optimum linearity, thereby enabling displacement measurement with high accuracy. Can be.

[Brief description of the drawings]

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

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

FIG. 3 is a graph showing linearity of measurement objects having different surface states.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sensor head, 2 ... Main optical system, 3 ... Light emitting part, 4 ... Light receiving part, 5 ... Semiconductor laser, 6 ... Illumination lens, 7 ... Imaging lens, 8 ... Photodetector, 9a, 9b ... Current- Voltage conversion unit, 10 processing unit, 11 subtraction unit, 12 addition unit, 13
... Division section, 14 ... Linear correction section, 15 ... Scattered light detection optical system, 16 ... Interference filter, 17 ... Polarization filter, 18
... Light receiving element, 20 ... Linear correction part, 24 ... Amplification part, 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 ... Correction data.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-25710 (JP, A) JP-A-4-252915 (JP, A) JP-A-63-108218 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) G01C 3/00-3/32 G01B 11/00-11/30

Claims (1)

(57) [Claims] 1. A non-contact displacement measuring device for measuring a displacement of a measurement target (B) in a non-contact manner using an optical system, wherein a light projecting unit (3) for emitting outgoing light (N1) to the measurement target.
A main optical system (2) provided with a light receiving section (4) for receiving the reflected light (N2) from the measurement target; and a polarized light, which is provided near the main optical system and scattered light (W) of the measurement target. A scattered light detecting optical system (15) provided with a polarizing filter (17) and a light receiving element (18) that are transmitted in a state, and a displacement output signal corresponding to the displacement of the measurement object based on the detection output of the main optical system A processing unit (10) for outputting (S1) and a correction output of the displacement output signal (S1) by correction data (S4) corresponding to the surface state of the measurement object based on the detection output of the scattered light detection optical system. A non-contact displacement measuring device, comprising: