JPH0778414B2 - Laser thickness gauge - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laser thickness meter for measuring the thickness of an object to be measured that moves from the state of an image of light reflected by laser light irradiation.

[Prior Art] For example, when measuring the thickness of an object to be measured such as a moving plate material, a laser displacement meter using a laser beam shown in FIG. 3 has been used.

This laser displacement meter is provided with two detection heads 24 and 25 having a light emitting element 20, a light projecting lens 21, an imaging lens 22, and a position sensor 23 built in, and each detection head 24, 25 passes through an object to be measured W. The light emitted from the light emitting element 20 is applied to the object to be measured W through the light projecting lens 21, and the light reflected from the object to be measured W is stored in the imaging lens 22. The position sensor 23 detects the light, and the detected light is arithmetically processed for each of the detection heads 24 and 25, and the thickness of the moving object W to be measured is measured from the result.

[Problems to be Solved by the Invention] However, in the above-described conventional laser displacement meter, since the detection heads 24 and 25 having the same structure are arranged to face each other with the object to be measured W interposed therebetween, When measuring the thickness of a translucent member such as glass, the light emitted from the light emitting element 20 (20a) of one detection head 24 passes through the object to be measured W and the other detection head 25 emits light. Element 20 (20
This light-emitting element 20b detects the light that has been transmitted through the object to be measured W, and as a result, the power of the light emitted from the light-emitting element 20b is reduced and sufficient light is transmitted to the object to be measured W. However, it was not possible to irradiate it, and an error was introduced, which made it impossible to perform accurate thickness measurement.

Therefore, the present invention has been made in view of the above-mentioned problems, and an object thereof is to perform highly accurate thickness measurement of an object to be measured without being affected by light from a light emitting element of a partner. The present invention is to provide a laser thickness gauge.

[Means for Solving the Problems] In order to achieve the above object, a laser thickness meter according to the present invention includes a projection system for irradiating a laser beam from an oblique direction with respect to a normal line of a measurement surface of an object to be measured, The detection heads of two sets of laser displacement meters, each of which has a light receiving system arranged in a direction of regular reflection with respect to the incident angle of the laser light, are arranged opposite to each other on both sides of the object to be measured, and the object to be measured is detected. In a laser thickness meter that passes between the heads and measures the thickness of the object to be measured by simultaneously irradiating the object to be measured from each of the light projecting systems, the object to be measured is a transparent member. The light-projecting system and the light-receiving system of the detection head, which are opposed to each other on both sides, are arranged in a direction excluding the extension line of the laser light to be irradiated, and the measurement points of two sets of laser displacement meters are the measurement planes of the object to be measured. It is characterized by being on the same normal line.

[Operation] When measuring the thickness of the object to be measured, the light from the projection system of each detection head is measured on the normal line of the measuring surface of the object to be measured.
Due to the extension of this light, the light from the light projecting system on the other side is applied to the object to be measured so as not to overlap. Then, the thickness of the measured object is measured based on the detection result of the reflected light from the measured object due to the irradiation of the light.

[Embodiment] FIG. 1 is a perspective view showing an embodiment of a laser thickness gauge according to the present invention, and FIG. 2 is a block diagram of the laser thickness gauge.

In the laser thickness gauge according to this embodiment, each laser displacement gauge 1, 2 has a detection head 5, 6 having a detection system 3, 4, a light emitting element driver 7, and a signal processing circuit 8. 6
The detection heads 5 and 6 are arranged so as to face each other with the object to be measured W in a state in which their light emitting and receiving surfaces are orthogonal to each other. The measurement object W is irradiated with light at the same time to measure the thickness.

In the detection heads 5 and 6, one unit 5 detects the position of the upper surface of the measured object W, and the other unit 6 detects the position of the lower surface of the measured object W. The detection systems 3 and 4 in the detection heads 5 and 6 are light emitting elements 3a and 4a, light projecting lenses 3b and 4b, and an imaging lens 3
c, 4c, position sensors 3d, 4d, and light emitting element 3
a and 4a emit light of a predetermined wavelength, and the projection lenses 3b and 4b
Collects the light from the light emitting elements 3a and 4a and irradiates the object to be measured W. The imaging lenses 3c and 4c image the light reflected from the object W to be measured at the positions of the position sensors 3d and 4d.
The position sensors 3d and 4d convert the imaged light into an electric signal and output it as a detection signal to the signal processing circuit 8.
The detection systems 3 and 4 include light emitting elements 3a and 4a and light projecting lenses 3b and 4b.
An imaging lens 3c arranged in a direction of regular reflection with respect to the incident angle of the laser light, which constitutes a light projecting system for irradiating the laser light obliquely with respect to the normal to the measurement surface of the object to be measured W. Four
The position sensors 3d and 4d form a light receiving system. As shown in FIGS. 1 and 2, the light projecting systems and the light receiving systems are located on the same optical axis, and the measurement point is located on the normal line of the surface of the object W to be measured. The objects W are arranged so as to face each other on both sides.

Here, the detection head 5 for detecting the position of the upper surface of the object to be measured W has an optical path formed by the light emitting element 3a and the position sensor 3d.
L ₁ is arranged so as to be orthogonal to the traveling direction of the object to be measured W indicated by arrow A in the figure. Further, in the detection head 6 for detecting the position of the lower surface of the object to be measured W, the optical path L ₂ formed by the light emitting element 4a and the position sensor 4d is arranged parallel to the traveling direction of the object to be measured W. That is, the light emitting / receiving surfaces 5a, 6a of the respective detection heads 5, 6 are arranged above and below the object to be measured W orthogonal to each other, and the optical paths L ₁ , L ₂ of the respective detection heads 5, 6 are orthogonal to each other. The light from the other side is prevented from entering through the measured object W.

The light emitting element driver 7 drives the light emitting elements 3a and 4a based on a control signal from the control circuit 9, and causes the light emitting elements 3a and 4a to emit light of a predetermined wavelength toward the object to be measured W.

The signal processing circuit 8 measures the position from the detection signal indicating the image state of the light of the object to be measured W obtained by the position sensors 3d and 4d, and outputs the result to the addition circuit 10, and the addition circuit 10 detects each detection. With the position data from the signal processing circuit 8 in the heads 5 and 6 aligned, two data are added to calculate the thickness and the result is output.

The control circuit 9 outputs a control signal for synchronously driving the light emitting element driver 7 and the signal processing circuit 8 in each of the detection heads 5 and 6.

Next, the operation of the laser thickness gauge configured as described above will be described.

When measuring the thickness l of the measured object W, first, the measured object W
Regarding the detection of the position of the upper surface in the above, the control circuit 9 outputs a control signal indicating the driving to the light emitting element driver 7a and the signal processing circuit 8a of the detection head 6 provided above the object to be measured W to operate. It becomes a state. At this time, the light emitting element driver 7b and the signal processing circuit 8b in the detection head 5 for detecting the position of the lower surface of the object to be measured W are also controlled by the control circuit 9.
The control signal indicating the driving is output and the system is in the operating state. As a result, when the light emitting element driver 7a drives the light emitting element 3a, light having a predetermined wavelength is emitted from the light emitting element 3a.
It is irradiated to the measured object W side via. The reflected light from the object to be measured W that moves due to this irradiation of light is imaged at the position of the position sensor 3d by the imaging lens 3c, converted into an electric signal by this position sensor 3d, and output to the signal processing circuit 8a as a detection signal. To be done.

The signal processing circuit 8a measures the upper surface position of the object to be measured W from the detection signal indicating the light image state of the object to be measured W of the position sensor 3d, and outputs the result to the adding circuit 10.

On the other hand, regarding the detection of the position of the lower surface of the object to be measured W, a control signal indicating that the light emitting element driver 7b and the signal processing circuit 8b of the detection head 6 provided below the object to be measured W are driven by the control circuit. It is output from 9 and becomes an operating state. At this time, the control signal indicating the driving is output from the control circuit 9 to the light emitting element driver 7a and the signal processing circuit 8a in the detection head 5 which has detected the position of the upper surface of the object to be measured W and is in the operating state. Light will be irradiated to the measurement object at the same time, but the light emitting and receiving surfaces 5a of the detection heads 5 and 6,
Since 6a are orthogonal to each other, the power of light is not reduced by the influence of light from the other side. After this, as described above, the light emitting element driver 7b is driven and the light is emitted from the light emitting element 4a to the object to be measured W, and the position sensor 4d detects the reflected light from the object to be measured W and the signal processing circuit. Output to 8b. And the signal output circuit 8b
Then, the lower surface position of the object to be measured W is measured from the detection signal indicating the light image state of the object to be measured W of the position sensor 4d, and the result is output to the adding circuit 10. Further, the adder circuit 10 adds the position data on the upper and lower surfaces of the object to be measured W by the detection heads 5 and 6 to calculate the thickness, and outputs the result as a display.

Therefore, in the above-mentioned embodiment, the optical path between the light emitting elements 3a, 4a of the respective detection heads 5, 6 and the position sensors 3d, 4d, that is, the light emitting / receiving surfaces 5a, 6a are orthogonal to each other, the object to be measured W is measured. Since the light is simultaneously emitted to the other side and unnecessary light is not directly detected from the other side, it is possible to prevent the output power of the light emitting elements 3a, 4a from being lowered by the light from the other side as in the conventional case. Accurate displacement measurement can be performed without being affected by the error.

By the way, in the above-described embodiment, the detection heads 5 and 6 are arranged such that the light paths between the light emitting elements 3a and 4a and the position sensors 3d and 4d are orthogonal to each other, and the detection heads 5 and 6 are arranged so as not to be affected by light. However, as long as the light from the other side is not directly incident, a sufficient effect can be obtained by arranging the detection heads 5 and 6 with their optical paths deviated from each other.

As described above, according to the laser thickness meter of the present invention,
The light-projecting system and the light-receiving system of the detection head, which are opposed to both sides of the object to be measured, have their light-transmitting and light-receiving surfaces arranged at positions where they do not overlap each other on the extension line of the laser light to be irradiated, and the measurement surfaces of the two sets of laser displacement gauges are the above-mentioned. Since the configuration is on the normal to the measurement surface of the DUT, sufficient light is emitted to the DUT without being affected by the light transmitted from the projection system of the detection head on the other side. Therefore, highly accurate thickness measurement can be performed.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a laser thickness gauge according to the present invention, FIG. 2 is a block diagram of the same laser thickness gauge, and FIG.
FIG. 1 is a perspective view showing a configuration of thickness measurement by a conventional laser displacement meter. 1,2 …… Laser displacement meter, 3,4 …… Detection system, 5,6 …… Detection head, 5a, 6a …… Projector / receiver surface, 7 …… Light emitting element driver,
8 ...... signal processing circuit, 9 ...... control circuit, 10 ...... adder circuit, W ...... DUT, L _1, L ₂ ...... optical path, l ...... thickness (displacement).

Claims (1)

[Claims] 1. A light projecting system for irradiating a laser beam from an oblique direction with respect to a normal line of a measurement surface of an object to be measured, and a light receiving system arranged in a direction of regular reflection with respect to an incident angle of the laser beam. The detection heads of two sets of laser displacement gauges provided with are arranged opposite to each other on both sides of the object to be measured, the object to be measured is passed between the detection heads, and each of the light projecting systems moves the object to the object to be measured. In the laser thickness meter that simultaneously irradiates light to measure the thickness of the object to be measured, when the object to be measured is a transmissive member, the light projecting system and the light receiving system of the detection heads facing the both sides irradiate. A laser thickness meter, which is arranged in a direction other than an extension line of laser light, and wherein the measurement points of two sets of laser displacement meters are on the same normal line to the measurement surface of the object to be measured.