JPH06117852A - Optical displacement gauge - Google Patents

Abstract

PURPOSE:To improve the measurement accuracy of the title gauge by reducing an error caused by the inclination of the surface to be measured of an object. CONSTITUTION:An object is irradiated with light by using a light emitting element having two light emitting points which can be independently driven and are arranged at a short interval as the light emitting element 11' for emitting the irradiating light. The measurement accuracy of the title displacement gauge is improved by detecting the inclined angle of the surface to be measured of the object 1 from two output signals obtained from a light receiving section 30 by means of an inclination correcting circuit 53 and correcting the distance to the object 1 from a light projecting section 10 in accordance with the magnitude of the detected inclined angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement meter for measuring a distance to an object based on a triangulation method, and particularly to an improvement thereof.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a conventional example of this type of optical displacement meter. In the figure, 10 is a light emitting element 11.
And a light projecting section including the light projecting lens 12, 30 a light receiving section including a light receiving lens 31, a position detecting element 32, and the like, 50 a position detecting circuit 51 and a linearization correcting circuit 52.
A signal processing unit including That is, the light projecting unit 10
The projection beam 2 emitted from the optical axis along the optical axis is applied to the surface of the object 1 whose distance from the light projecting unit 10 along the optical axis is to be measured. The reflected light 3 from the object 1 is incident on the light receiving unit 30 and a current signal 33 (A
1, A2) and output. This current signal 33
Is input to the signal processing unit 50, subjected to processing such as linearization correction, and then output as a distance signal 55 to the outside.

The light emitting element 11 of the light projecting section 10 is composed of, for example, a semiconductor laser, and the light projecting lens 12 converges the light emitted by the light emitting element 11. The light receiving unit 30 mainly includes the light receiving lens 3
1 and a position detection element 32 capable of detecting the light receiving position, and an image of the position of the surface of the object 1 illuminated by the projection beam is received by the position detection element 32 according to the distance of the object 1. It is tied in place on the surface. The signal processing unit 50 mainly uses the current signal 33 from the light receiving unit 30 to detect the position detecting element 32.
It comprises a position detection circuit 51 for calculating the upper light receiving position and a linearization circuit 52 for converting a signal representing the light receiving position into a signal 55 proportional to the distance or displacement to the object to be measured. The respective optical components are arranged so as to satisfy the so-called Scheimpflug condition, and as a result, the main surface of the light receiving lens 31 and the light receiving surface of the position detecting element 32 are arranged so that the light projecting section 1
The point S on the optical axis of the projection lens 12 of 0 intersects.

A specific example of the position detecting element is shown in FIG. This is because the P-type resistance layer 6 is formed on one surface of the plate-shaped high resistance semiconductor 5.
However, an N-type layer 7 is formed on the other surface, and a PN junction is formed by both surfaces. Generally, PSD (Pos
edition Sensitive Detector)
Is called. The photocurrent generated by the photoelectric effect in the resistance layer 6 having the length L is output from the pair of electrodes P1 and P2 provided at both ends of the P-type resistance layer 6.
When the respective current outputs at this time are A1 and A2, the magnitudes thereof vary depending on the distribution of the amount of received light on the resistance layer 6 which is the light receiving surface. Letting the incident light on the light receiving surface be spot-like, and letting the distance from the center of gravity of the power distribution of this light spot to the center of the resistance layer 6 be X, the following relationship is established between them. X = L / 2 · (A1−A2) / (A1 + A2) (1) The position detection circuit 51 performs the calculation according to the equation (1).

FIG. 5 shows the characteristic of the position detecting element. This shows the relationship between the distance D from the light projecting unit 10 to the object 1 and the light receiving position X on the light receiving surface of the position detecting element 32. It is shown that D and X have a non-proportional non-linear relationship due to the arrangement of the optical system utilizing triangulation, and a linearization correction circuit 52 is provided to correct this to a linear relationship. That is why

[0006]

However, in the optical displacement meter as described above, when the surface to be measured of the object is tilted and the angle with respect to the projection beam is changed, the incident light on the light receiving surface of the position detecting element is changed. The power distribution may be different, and the position of the center of gravity of this power distribution may be different. Since the position detection element detects the position of the center of gravity of the power distribution of the incident light,
When this movement of the center of gravity occurs in the longitudinal direction of the position detecting element, that is, in the direction in which the distance to the electrode changes, even if the distance to the object to be measured is the same, it depends on the inclination of the surface to be measured as described above. The light receiving element detects different positions, which causes a measurement error. In general, in the application of the displacement meter, the tilted state of the measured surface of the object is not always constant, and from this point as well, there is a problem that it is difficult to avoid a measurement error. Therefore, an object of the present invention is to make it possible to reduce the measurement error due to the change of the tilted state of the measured surface of the object, and to improve the measurement accuracy.

[0007]

In order to solve such a problem, according to the present invention, a light projecting unit for irradiating an object with a light beam, and a light beam reflected from the object for receiving a light beam on the position detecting element. In the optical displacement gage, which comprises a light receiving unit that detects the irradiation position by irradiating the object and a signal processing unit that receives the output signal from the light receiving unit and obtains the distance to the object, A light emitting element having two light emitting points adjacent to each other, which can be individually driven, and
A light projecting lens for converging any of the light emitted from each of the two light emitting points to form a light projecting beam is provided, and when these two light projecting beams illuminate an object, the light is obtained via the light receiving unit. From the two output signals, the magnitude of the tilt angle in the plane formed by the principal rays of the two projected beams of the object at that time and the optical axis of the light receiving unit is detected, and the detected object is detected. It is characterized in that an error due to the inclination of the object included in the separately obtained distance information from the light projecting unit to the object can be corrected according to the size of the inclination angle of the object.

[0008]

The object is irradiated with each of the light emitting elements having two adjacent light emitting points which can be individually driven, and the inclination angle of the object is detected from the two output signals from the light receiving section obtained at that time. By correcting the distance from the light projecting unit to the object according to the size of the tilt angle, the measurement accuracy is improved.

[0009]

1 is a block diagram showing an embodiment of the present invention, in which the same components as those shown in FIG. 3 are designated by the same reference numerals.
That is, this embodiment also largely includes the light projecting unit 10 and the light receiving unit 3.
0 and the signal processing unit 50, the reflected light 3 from the object 1 is imaged on the light receiving element 32 via the light receiving lens 31 as in the case of FIG. The light projecting unit 10 includes a light emitting element 11 ′ and a light projecting lens 12. The light emitting element 11 ′ has two light emitting points as represented by a two-beam LD (Laser Diode) used as a light source for high-speed recording on an optical disc,
Light emitted from each light-emitting point is converged by the same light-projecting lens 12 to form light-projected beams 21 and 22, respectively. Therefore, a dash is added to distinguish it from the light-emitting element 11 in FIG. Is shown.

The principal surface of the light receiving lens 31 and the position detecting element 32
The respective optical components are arranged so as to intersect with the light receiving surface of the projection lens 12 at a point S on the optical axis of the projection lens 12, satisfy the so-called Shine-Plug condition, and the principal rays of the projection beams 21 and 22 are projected. It passes near the optical axis of the optical lens 12. Since the respective chief rays are arranged so as to be in the same plane as the optical axis of the light receiving section 30, the position of the object irradiated by the projection beams 21 and 22 on the measured surface is determined by the position detecting element 32. The images are formed at different positions on the light receiving surface of, and the positional relationship is such that they are separated in the longitudinal direction of the position detecting element 32, that is, in the direction in which the distance from the electrode is different.

FIG. 2 shows an image formation state on the light receiving surface by the two projection beams in the case of the above-mentioned structure. here,
Only the chief rays 71 and 72 of the reflected light from the projected beams 21 and 22 are shown, and the others are omitted. FIG. 9A shows the case where the surface to be measured is perpendicular to the optical axis 2 ′ of the light projecting lens, and the distance between the images on the light receiving surface at this time is w. On the other hand, when the surface to be measured is inclined by θ with respect to the optical axis 2 ′ as shown in FIG. 6B, the distance between the images on the light receiving surface at that time changes from w to w ′. w> w '. This is because the surface to be measured is tilted counterclockwise, and if the surface to be measured is tilted clockwise, then w <w '.

Since the signal processing circuit 50 has a position detection circuit 51 and a linearization correction circuit 52 as in FIG. 3,
The reflected light of each projected beam is detected by the light receiving unit 30 and its current signal 33 is introduced into the signal processing circuit 50, so that the object 1 is emitted from the projected unit 10 as in the case of FIG.
The distance to can be detected. Further, here, the output of the linearization correction circuit 52 is input to the inclination correction circuit 53. That is, the light emitting element 1 of the light projecting unit 10
The two light emitting points 1'are driven so as to alternately emit the light emitting beams 21 and 22, and which light emitting beam is being emitted is determined by the tilt correction circuit 53 based on the light source determination signal 54.
Be transmitted to.

The tilt correction circuit 53 is, for example, the projection beam 21.
The output from the linearization correction circuit 52 when is emitted is temporarily stored as a distance signal including a measurement error signal due to the inclination of the surface to be measured. Next, the inclination correction circuit 53 receives the output from the linearization correction circuit 52 when the projection beam 22 is emitted, and obtains the difference between this output and the previously stored value. Finally, the inclination correction circuit 53 detects the magnitude of the inclination of the surface to be measured by comparing the magnitude of this difference with a reference value, and uses this to correct the previously stored distance signal, The correct distance signal 55 is output to the outside. In this way, by repeating the above-described operation while alternately emitting the projection beams, it is possible to reduce the measurement error due to the inclination of the measured surface of the object under measurement.

In the above, the two projected beams are alternately emitted to perform the tilt correction for each measurement. However, when the change in the tilt of the surface to be measured is slow compared with the measurement cycle, the tilt detection is performed. It is also possible to reduce the emission frequency of the light projection beam (22) as compared with the light projection beam (21) for distance measurement, and to update the tilt correction amount in the tilt correction circuit 53 every multiple distance measurements. Needless to say. In this case, it is possible to shorten the distance measurement cycle as compared with the case where the tilt correction amount is updated every time.

[0015]

According to the present invention, the two projection beams are used to detect the inclination of the surface to be measured which gives an error to the measurement result and correct the error. Therefore, the measurement accuracy and reliability can be improved. The advantage is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining an image formation state on a light receiving surface by two projection beams according to the present invention.

FIG. 3 is a configuration diagram showing a conventional example of an optical displacement meter.

FIG. 4 is a schematic diagram showing a specific example of a position detection element.

FIG. 5 is a characteristic diagram showing characteristics of a position detection element.

[Explanation of symbols]

1 ... Object, 2, 21, 22 ... Projection beam, 2 '... Optical axis of projection lens, 3 ... Reflected light, 5 ... High resistance semiconductor, 6 ... P
-Type resistance layer, 7 ... N-type layer, 10 ... Projector, 11, 11 '...
Light emitting element, 12 ... Projecting lens, 30 ... Light receiving part, 31 ... Light receiving lens, 32 ... Position detecting element, 33 ... Current signal, 50
... Signal processing unit, 51 ... Position detection circuit, 52 ... Linearization correction circuit, 53 ... Inclination correction circuit, 55 ... Distance signal, 71, 7
2 ... The chief ray of reflected light.

Claims (1)

[Claims] 1. A light projecting unit for irradiating an object with a light beam,
A light receiving unit for detecting the irradiation position by receiving the light beam reflected from the object and irradiating it on the position detecting element, and a signal for receiving the output signal from the light receiving unit and obtaining the distance to the object. In an optical displacement meter including a processing unit, the light projecting unit emits light from a light emitting element having two light emitting points adjacent to each other, which can be individually driven, and two light emitting points of the light emitting element. A light projecting lens for converging any of the light beams to form a light projecting beam is provided, and two output signals obtained through the light receiving unit when the object is irradiated with these two light projecting beams 2 of the object
The magnitude of the tilt angle in the plane formed by the principal rays of the two projected beams and the optical axis of the light receiving unit is detected, and separately determined according to the magnitude of the tilt angle of the detected object. An optical displacement gage capable of correcting an error due to the inclination of an object included in the distance information from the light projecting unit to the object.