JP3091276B2 - 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 type displacement measuring device which focuses reflected light from a measuring object on a position sensor and measures the displacement of the measuring object by an electric signal obtained by moving the light spot. It concerns the device.

[0002]

2. Description of the Related Art FIG. 7 illustrates the basic structure of a non-contact displacement measuring device. The light emitted from the laser diode 100 is narrowed down by the light projecting lens 101 and enters the measurement object 102. The reflected light from the measurement target 102 is the imaging lens 1
The light is condensed by the light source 03 and forms an image of a light spot on the position sensor 104. This image moves on the position sensor 104 in the direction of the arrow when the measurement object 102 moves in the direction of the arrow y in the figure. Position sensor 1
Since an electric signal corresponding to the movement of the light spot is taken out from 04, by processing this signal by the processing system 105, a displacement signal of the measuring object 102 can be obtained.

According to the above apparatus, the displacement of the surface can be measured by relatively moving the measuring object 102 in the direction X intersecting with the displacement direction y. In this case, the X-direction edge of the measurement target 102 can be detected by increasing or decreasing the received light level of the position sensor 104.

[0004] For example, a measurement object 102 is set in a measurement range of the apparatus.
When entering along the X direction, as shown in FIG.
Since the level of the amount of light received by the position sensor 104 due to the reflected light of the light spot gradually increases at the boundary of the edge of the measurement target 102, the processing system 105 has a certain threshold level with respect to the level of the received light of the position sensor 104. Is set, the edge of the measurement target 102 can be detected.

[0005]

The light from the device is in the form of a spot narrowed by the light projecting lens 101 as described above. Therefore, the diameter of the light spot is not constant within the measurement range in the y direction. For this reason, as shown in FIG. 8, the level of the received light received by the position sensor 104 differs depending on whether the measurement target 102 is at the center of the measurement range or at the end of the measurement range, and the edge signal has an error of Δt. There was a problem that would occur. Also, the reflected light may increase or decrease irregularly depending on the surface condition of the measurement object, which also causes an error in the edge signal.

An object of the present invention is to enable an optical displacement measuring device to accurately detect an edge portion of an object to be measured based on a level of a received light amount of reflected light.

[0007]

According to a first aspect of the present invention, there is provided a displacement measuring apparatus which receives reflected light from a light spot on a measurement object and moves the image of the light spot formed on the position sensor to detect the position of the measurement object. In a displacement measuring device for detecting displacement, four light receiving elements are arranged, one diagonal line of two opposing light receiving elements is juxtaposed on a parallel straight line, and the other of the other two opposing light receiving elements The diagonal lines are arranged side by side on a straight line orthogonal to the edge direction, and the four light receiving elements are arranged in a point symmetry with respect to the intersection of the two orthogonal straight lines, and the four detectors are: When the signals to be output are A, B, C, and D, respectively, a difference AB between the signals from the two detectors located along the moving direction is calculated, and the two detectors located along the moving direction are calculated. A of the signal from The sum C + D of the signals from the two detectors positioned along a direction perpendicular the moving direction and B
The difference (A + B)-(C + D) is calculated, and the above-mentioned AB shaped at a predetermined level and the above-mentioned (A) shaped at a 0 level are calculated.
Signal processing means for calculating an AND signal of (+ B)-(C + D) and detecting an edge portion in the moving direction of the measurement target from the AND signal.

[0008]

The object to be measured moves relatively to the displacement measuring device, and the light spot reflected near the edge is detected by each detector in the detector. The signals output from the respective detectors are processed by the signal processing means in accordance with the arrangement of the respective detectors and the relative movement direction of the measurement target, whereby a detection signal indicating the edge portion of the measurement target is obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The displacement measuring device 1 of the present embodiment shown in FIG. 1 has the same configuration as that of the related art for displacement measurement, and the same portions are denoted by the same reference numerals as in FIG. 7 and description thereof is omitted.

Laser diode 100 and light projecting lens 10
A lens 2 is provided between the light source 1 and the lens 2 for converting the light from the laser diode 100 into a parallel light beam and giving the light to the light projecting lens 101. A half mirror 3 is provided between the lens 2 and the light projecting lens 101 at an angle of 45 ° with respect to the optical axis. The half mirror 3 reflects the reflected light from the measurement target 102 to the left in the figure and inputs the reflected light to the detector unit 4.

As shown in FIG. 2, the detector section 4 has four square detectors A, B, C and D which are independent of each other and have the same light receiving area. The detector unit 4 is arranged in a direction in which one of the diagonal lines coincides with the moving direction X of the measuring object 102. That is, when the light spot 5 is reflected from the vicinity of the edge 6 of the measurement object 102 due to the relative movement of the measurement object 102 and the light spot 5 in the X direction, the reflected light first enters the detector A, And detectors D and C
And finally the detector B.

Next, detection of the light spot 5 by the detector unit 4 and processing of signals output from the detectors A to D of the detector unit 4 will be described. As shown in FIG. 2, the light spot 5 reflected near the edge 6 of the measurement target 102 is input to each of the detectors A to D at a timing as shown in FIG. That is, first, detector A rises,
While the light receiving level of the detector A is increasing, the detectors C and D rise. Next, while the light receiving levels of the detectors C and D are increasing, the light receiving level of the detector A is saturated, and subsequently the detector B rises. Then, after the detectors C and D are saturated, the detector B is also saturated.

The output signals of the detectors A to D are processed by signal processing means (not shown) as follows. First, (AB) is obtained from each output of the detectors A and B in order to know the moving direction of the edge portion 6, and a signal E is obtained. Further, since the edge portions 6 are determined by comparing the light amounts, the detectors A, B,
From the outputs of C and D, (A + B)-(C + D) is obtained to obtain a signal F.

Next, when the waveform shaping level of the comparator in the signal processing means is set to + R, the signal E is set to + R
And + R and -R respectively.
Get.

Next, the signal F is shaped at the O level to obtain a signal H. Then, from the AND of the signals + G and H, the signal +
I is obtained, and the signal -I is obtained from the inversion of the signal -G and the AND of H. The falling of the signal + I and the signal −
The rising edge of I indicates the edge portion 6 of the measurement target 102. If the detection times are t ₁ and t ₂ and the moving speed of the measurement target 102 is v, the edge portion of the measurement target 102 measured in the movement direction X The width W from 6 to the edge 6a is as follows.

[0016]

(Equation 1)

The conditions for determining an edge portion by the above-described signal processing are expressed by a logical expression, assuming that the reference level is L, as follows.

[0018]

(Equation 2)

In the embodiment described above, the detector section 4 is constituted by four detectors A to D.
Even with the three detectors A, B, C or A, B, D, the edge portion can be detected by substantially the same signal processing.

In the case where a detector section including three detectors as described above is formed, the shape of each detector does not necessarily have to be a square. For example, as shown in FIG. 4, each of the three detectors A, B, and C has a sector shape with a central angle of 120 °, and may be circular as a whole.
Further, as shown in FIG. 5, the detectors A and B may be square and the detector C may be a rectangular parallelepiped. However, in any case, the detector A,
B are arranged so as to sandwich the boundary line, and the detector C is arranged inside the detectors A and B in the same direction, straddling the boundary between them.

If the three detectors A, B, and C are arranged as described above, the detector A first rises, and then the detector C rises in the light receiving level signal from the light spot from the edge. Next, after the detector A falls, the detector B rises. Then, after the detector C falls, the detector B falls. If such a signal is obtained,
By processing these signals in the same manner as described above, an edge portion to be measured can be detected.

In this embodiment, since the reflected light in the direction orthogonal to the moving direction of the object to be measured is detected, the detection accuracy of the edge portion is high. However, the reflected light for detecting the edge portion does not necessarily need to be taken from the direction as in the present embodiment. For example, as shown in FIG.
The reflected light may be guided to the detector unit 4 by placing the half mirror 7 between the position sensor 3 and the position sensor 104. Further, as shown in FIG. 6B, the scattered light from the measurement object 102 may be spread separately from the position sensor 104 side and guided to the detector unit 4 by the condenser lens 8.

If the detector section 4 is composed of four detectors A to D as in the above-described embodiment,
The edge part can be detected also in the Z direction in FIG.

[0024]

According to the present invention, the light spot from the moving edge of the measuring object is detected by three or more detectors arranged in a predetermined arrangement in the moving direction. By processing the signal from the detector, it is possible to obtain a signal that accurately indicates the edge portion of the measurement target.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of one embodiment.

FIG. 2 is a diagram illustrating a positional relationship between a detector unit, a light spot, and a measurement target in the embodiment.

FIG. 3 is a waveform diagram showing an output signal, an edge signal, and the like of a detector in the embodiment.

FIG. 4 is a diagram illustrating another configuration example of the detector unit.

FIG. 5 is a diagram illustrating another configuration example of the detector unit.

FIG. 6 is an overall configuration diagram showing another embodiment.

FIG. 7 is an overall configuration diagram of a conventional displacement measuring device.

FIG. 8 is a graph illustrating an edge detection method in a conventional displacement measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Displacement measuring device 4 Detector part 5 Light spot 6 Edge part 102 Measurement object 104 Position sensor A, B, C, D Detector

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-63402 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30

Claims (1)

(57) [Claims] 1. A displacement measuring device which receives reflected light from a light spot on a measurement target and detects displacement of the measurement target from movement of an image of the light spot formed on a position sensor, comprising four light receiving elements. And one diagonal of the two opposing light receiving elements is juxtaposed on a parallel straight line, the other diagonal of the other two opposing light receiving elements is juxtaposed on a straight line orthogonal to the edge direction, and An edge detector in which the four light-receiving elements are arranged point-symmetrically with respect to the intersection of the two orthogonal straight lines; and signals A and A output by the four detectors, respectively.
When B, C, and D are set, 2 located along the moving direction
The difference A−B between the signals from the two detectors is calculated, and the sum A + B of the signals from the two detectors located along the moving direction and the signal from the two detectors located along the direction orthogonal to the moving direction are calculated. Difference from the sum C + D (A +
B)-(C + D) is calculated, and the AB shaped at a predetermined level and the (A + B)-(C shaped at a 0 level
+ D) and a signal processing means for calculating an AND signal with respect to the moving direction of the object to be measured from the AND signal.