JPH0575051B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a laser displacement meter for measuring the displacement of the surface of an object, and particularly to a laser displacement meter used for measuring the outline and cross-sectional profile of a turbine blade. [Prior Art] Conventionally, a laser displacement meter used for this type of application includes a semiconductor laser 1, a detector (light receiver) 2, and first and second condensing lenses 3, 4, as shown in FIG.
is housed in the laser head 7.
In this laser displacement meter, a laser beam 5 from a semiconductor laser 1 is focused by a first condensing lens 3 and irradiated onto a workpiece (object to be detected) 8 . Work 8
The reflected light 6 is collected by the second condensing lens 4 and is made to be incident on the detector 2. Then, the displacement of the workpiece 8 is measured based on the movement of the position of the reflected light spot on the detector 2. The principle by which the displacement of the workpiece 8 can be measured is as follows. That is, when a displacement corresponding to the measurement range l occurs, and if W is the displacement of the center of gravity of the reflected light spot on the detector 2, then l∝W is obtained by trigonometry. Therefore, the actual displacement is calculated from the displacement of the spot light on the detector 2. [Problems to be Solved by the Invention] However, this type of displacement meter has the following problems. That is, the diffuse reflection mode (intensity of reflected light) when a laser beam hits a workpiece differs greatly depending on whether the workpiece is metal or non-metallic. Figure 3 shows an example of the diffuse reflection mode when a laser beam is applied from directly above the workpiece.
According to this, there is a relatively uniform diffuse reflection mode from the incident position of the laser beam (in this case, if it is perpendicular to the workpiece, it is the same as a mirror and the peak of the reflected light is also the same as the incident position) to the angle β. However, beyond the angle β, the reflected light intensity decreases rapidly. That is, looking at FIG. 2, if the reflected light 6 from the laser beam 5 at an angle α and the detector 2 located on the extension of the reflected light 6 are replaced with the angle β in FIG. 3, the laser beam of the semiconductor laser 1 The intersection angle between the axis of 5 and the axis connecting the reflected light 6 and the detector 2 is β
When the value exceeds , the amount of light received by the detector 2 (reflected light) decreases rapidly. This change in the amount of received light is related to the accuracy of the laser displacement meter, as described below, and causes data variation, that is, a decrease in measurement accuracy. The reason why changes in the amount of received light affect accuracy is as follows. As shown in Fig. 4, when detecting the displacement of the workpiece 8, the reflected light intensity at the A-A' cross section in the figure is 5th.
Suppose the situation is as shown in the figure. In this case, as shown in FIG. 5, the amount of light received by the detector 2 (reflected light) is a,
When the light changes as shown in b, the center of gravity of the light also changes. That is, the center of gravity of the light at the light level a of diffuse reflection is B, and the center of gravity of the light at the light level b of diffuse reflection is B. When the center of gravity of the light changes, it is detected as a displacement of the workpiece 8 on the detector 2. In other words, variations in data will occur. The present invention was made in consideration of the above circumstances, and
The purpose is to provide a laser displacement meter that can detect displacement of a metal workpiece with high precision as an object to be detected, and is suitable for detecting displacement of a turbine blade or the like. [Means for solving the problem] The gist of the present invention is to obtain in advance an angular range in which the diffuse reflection mode for incident light is uniform, and to align the optical axis of the incident light from the semiconductor laser with the reflected light to the detector. The purpose is to set the angle with the optical axis to fall within the above angle range. Non-metals (ceramics), metals (stainless steel)
A 0.2φ laser beam is irradiated onto the surface of the
The diffuse reflection mode at each angle was measured from the incident position (reflected light peak) at that time. The results are shown in FIGS. 6 and 7. For ceramics, the angle at which the diffuse reflection mode is approximately uniform is β = 70°, and for stainless steel, β = 30°. Therefore, considering the measurement of the turbine blade (stainless steel), a good mounting angle between the semiconductor laser and the detector is 30 degrees. The present invention has been made with attention to such points, and the present invention irradiates the surface of an object to be detected with laser light from a semiconductor laser through a first condensing lens, and collects the reflected light from the surface of the object. In the laser displacement meter, the displacement of the surface of the object to be detected is measured by making the spot light enter a light receiver through a second condensing lens and detecting the displacement of the position of the spot light on the light receiver. When the angle range in which the diffuse reflection mode is approximately uniform when light is irradiated perpendicularly to the surface of The semiconductor laser, the light receiver, and the first and second condenser lenses are arranged in the laser head at a position where the optical axis connecting the second condenser lens intersects at the angle θ. [Operation] If the mounting angle of the semiconductor laser and the detector is set so that the angle between the optical axis of the laser beam from the semiconductor laser and the optical axis of the reflected light incident on the detector is 30 degrees, it will be possible to attach the laser beam to the metal workpiece. On the other hand, when a laser beam is irradiated from directly above it, a consistent detection output can be obtained. Further, even if the workpiece is tilted by 0 to 30 degrees, the relative angle between the laser reflected light peak and the detector is always within the range of 0 to 30 degrees.
In other words, data variations can be eliminated before they occur. [Example] Hereinafter, details of the present invention will be explained with reference to illustrated examples. FIG. 1 is a schematic configuration diagram showing a laser displacement meter according to an embodiment of the present invention. A semiconductor laser 1, a detector 2, and first and second condensing lenses 3 and 4 are housed and fixed in a laser head 7. The laser beam 5 emitted from the semiconductor laser 1 is focused by the first condenser lens 3 and then irradiated onto the surface of the workpiece 8 . The reflected light reflected from the surface of the workpiece 8 is focused by the second condensing lens 4 and then enters the detector 2 . The displacement of the workpiece 8 is then measured based on the position of the reflected light spot on the detector 2. Here, the semiconductor laser 1, the detector 2, and the lenses 3 and 4 are arranged so that the intersection angle between the optical axis of the laser beam 5 from the semiconductor laser 1 and the optical axis of the reflected light 6 incident on the detector 2 is 30 degrees. is fixed to the laser head 7. In addition, the measured distance L at this time
is determined by the size of the laser head 7, that is, the distance m between the semiconductor laser 1 and the detector 2, and the focal lengths of the condensing lenses 3 and 4 are changed accordingly.
Further, the semiconductor laser 1, the detector 2, and the focusing lenses 3 and 4 are adjusted so that the optical axis of the laser beam 5 and the optical axis of the reflected light 6 intersect on the same plane,
must be set. In such a configuration, when the workpiece 8 is tilted as shown in FIG. 8, the angle between the diffusely reflected light peak and the detector is as shown in the table below.

〔Effect of the invention〕

According to the present invention, even if the workpiece is tilted within a range of 0 to 30 degrees, the intensity of reflected light detected by the detector remains unchanged, making it possible to prevent data variations. Therefore, displacement measurement accuracy can be significantly improved. Therefore, it is extremely effective for measuring the displacement (measuring the contour and cross-sectional profile) of metal workpieces, especially turbine blades.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing a laser displacement meter according to an embodiment of the present invention, Fig. 2 is a schematic configuration diagram showing a conventional laser displacement meter, and Fig. 3 is a schematic configuration diagram showing a laser displacement meter according to an embodiment of the present invention. A schematic diagram showing an example of the diffuse reflection mode from a workpiece. Figure 4 is a schematic diagram showing the mechanism in which a laser beam hits a workpiece and the reflected light is detected by a detector. Figure 5 is a diagram showing the center of gravity of light with respect to changes in the level of diffusely reflected light. Schematic diagram for explaining changes, No. 6
The figure is a characteristic diagram showing the diffuse reflection mode when a laser beam is applied to ceramics, Figure 7 is a characteristic diagram showing the diffuse reflection mode when a laser beam is applied to stainless steel, and Figure 8 is a characteristic diagram showing the diffuse reflection mode when a laser beam is applied to stainless steel. FIG. 3 is a schematic diagram for explaining the relative angle between a reflected light peak and a detector. DESCRIPTION OF SYMBOLS 1... Semiconductor laser, 2... Detector (light receiver), 3... First condensing lens, 4... Second condensing lens, 5... Laser beam, 6... Reflected light,
7... Laser head, 8... Work (object to be detected).

Claims (1)

[Claims] 1. Irradiating the surface of an object to be detected with laser light from a semiconductor laser through a first condensing lens, and causing reflected light from the surface of the object to enter a light receiver through a second condensing lens, In a laser displacement meter that measures the displacement of the surface of the object to be detected by detecting the displacement of the spot light position on the light receiver, the diffuse reflection mode when light is irradiated perpendicularly to the surface of the object to be detected is approximately When the uniform angle range is -θ to +θ, the optical axis connecting the semiconductor laser and the first condensing lens and the optical axis connecting the light receiver and the second condensing lens are at the above angle. A laser displacement meter characterized in that the semiconductor laser, the light receiver, and the first and second condensing lenses are arranged in a laser head at positions where they intersect at θ.