JPS6298211A - Displacement measuring method by laser displacement gage - Google Patents

Abstract

PURPOSE:To obtain optimum measuring accuracy by setting a diameter of a spot to 1.3-1.6mm. CONSTITUTION:Laser beam 5 emitted from a semiconductor laser 1 is condensed by a condenser lens 3 and the spot 7 is formed on a work 8 of a measuring distance L. At this time, the distance (l) between the laser 1 and the lens 3 is adjusted and the diameter of the spot 7 (beam diameter) is made 1.3-1.6mm at the measuring distance L. Further, the distance L, an angle alpha of reflection, the distance (m) between the laser 1 and a detector 2 and the focal distances of the condenser lenses 3 and 4 are set according to the design specifications. In other words, an optical axis 9 connecting the laser beam 1 with the center of the lens 3 and an optical axis 10 connecting the detector 2 with the lens 4 are crossed at an angle of alpha deg. at the distance L from a laser head. At that time, the diameter of the spot 7 can be selected to 1.3-1.6mm by selecting the distance (l) between the laser 1 and the lens 3 and the proper focal distance of the lens 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a displacement measuring method using a laser displacement meter, which is applied to measuring the profile of a turbine blade.

[Conventional technology]

FIG. 2 is a diagram for explaining a method of measuring displacement using a conventional laser displacement meter. Create a spot with a beam diameter of φA. Then, the detector 2 is set at a location α0 with respect to the laser beam 5, and only the reflected light 6 at this angle passes through the condensing lens 4 and forms an image on the detector 2, thereby measuring the displacement. However, the beam diameter φA on the workpiece 8 varies depending on the manufacturer, and the optimum value has not been determined depending on the material, rough surface, etc.

[Problem that the invention seeks to solve]

As mentioned above, the beam diameter φA of the spot on the workpiece 8 of the conventional laser displacement meter differs depending on the manufacturer, and these beam diameters φA are optimal depending on the material of the workpiece 8, rough surface, etc. For example, non-metals (ceramics), metals (stainless steel, steel, etc.)
If all materials are measured with the same beam diameter (φA),
The accuracy varies greatly. For example, when measuring with a semiconductor laser (GaAs) with a beam diameter of 0.2φ, the accuracy is ±130 on stainless steel (surface roughness 6).
μm1 ceramic AI, O8 (surface roughness 6) ±3
It is 0 μm. (See Figure 3). Therefore, it is necessary to determine a beam diameter that satisfies both stainless steel and ceramics.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a method for measuring displacement using a laser displacement meter, which allows the precision of plane displacement measurement and the precision of width measurement to be selected to optimal values.

Note that width measurement is performed by scanning the laser beam 5 by sliding the laser beam in the horizontal direction, and when the laser beam 5 hits one end of the surface of the workpiece 8, the diffusely reflected light 6 is detected by the detector 2. The purpose is to read the sliding distance of the laser head from one end to the time when it comes off from the other end using a linear inductor. The amount of received light and the detection accuracy of the detector 2 at the time of starting and coming off are issues.

[Failure to solve the problem]

The method of measuring displacement using a laser displacement meter according to the present invention is to apply a beam from a laser light source onto a workpiece through a condenser lens, connect the spots, and condense the diffusely reflected light with a condenser lens and apply it to a detector. In the displacement measurement method using a laser displacement meter that detects the displacement of the upper spot,
The diameter of the spot applied to the workpiece is 1.31~
It is characterized in that measurement is performed by setting the distance to 1.6 mm, and the accuracy of displacement measurement on a flat surface of stainless steel (surface roughness 6), for example, can be maintained at 50 μm.

[Effect]

Generally, as the beam diameter increases, the accuracy of flat measurement improves, but on the other hand, the accuracy of width measurement decreases in inverse proportion to this. According to the present invention, for example, in the case of stainless steel, the optimum beam diameter is 1.3-1.6 m.
m and the accuracy at that time is ±50 μm. Also, in the case of ceramics, accuracy of ±50 μm or less is guaranteed.

〔Example〕

FIG. 1 is a diagram for explaining the present invention, and 1 is a diagram for explaining the present invention.
2 is a detector, 3° and 4 are condensing lenses, 5 is a laser beam, 6 is a reflected light, 7 is a spot, 8 is a workpiece, and 9° and 10 are optical axes, respectively.

The laser beam 5 emitted from the semiconductor laser 1 is condensed by a condenser lens 3 to form a spot 7 on a workpiece 8 at a measurement distance. At this time, the distance j between the semiconductor laser 1 and the condensing lens 3
The diameter of the spot 7 (beam diameter) at the measurement distance is adjusted to be 1.3 mm to 1.6 u.

Note that the measurement distance L, the reflection angle α, the distance m between the semiconductor laser 1 and the detector 2, and the focal length of the condenser lens 3.4 depend on the design specifications.

To explain the details, the optical axis 9 connects the centers of the semiconductor laser 1 and the condenser lens 3, and the optical axis 1 connects the detector 2 and the condenser lens 4.
0 intersect at an angle α0 at a measurement distance from the laser head.

At that time, the distance between the semiconductor laser 1 and the condenser lens 3! By selecting an appropriate focal length of the condenser lens 3, the diameter of the spot 7 can be selected from 1.3 u to 1.6 mm.

According to the present invention, the most accurate measurement accuracy can be obtained by setting the diameter of the spot 7 applied to the workpiece 8 to be 1.3 to 1.6 mm.

Figure 3 is a diagram showing the relationship between measurement accuracy and laser beam diameter, where A is the flat displacement measurement characteristic of stainless steel (surface roughness 65), and B is the displacement measurement characteristic of ceramics (AAzOs, surface roughness 65).
) shows the plane displacement measurement characteristics, and C shows the width measurement characteristics of stainless steel.

Note that plane displacement measurement means measuring the distance to each point on the workpiece surface by moving the laser head horizontally and scanning the workpiece with laser light.

〔Effect of the invention〕

For both nonmetals (ceramics) and metals (stainless steel), when measuring plane displacement, the accuracy improves as the laser beam diameter increases, but when measuring width, the accuracy deteriorates.

According to Tomei, the diameter of the spot is 1.3u to 1.6m.
The optimum measurement accuracy can be obtained by setting the value to m. For example, in the case of stainless steel, excellent effects such as being able to ensure accuracy of ±50 μm can be achieved.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining one embodiment of the present invention, FIG. 2 is a diagram showing a conventional example, and FIG. 3 is a diagram showing the relationship between measurement accuracy and laser beam diameter. 1... Semiconductor laser, 2... Detector, 3, 4...
...Condensing lens, 5...Laser beam, 6...Reflected light, 7...Spot, 8...Work. Applicant Sub-Agent Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] Displacement by a laser displacement meter that shines the light beam from a laser light source onto the workpiece through a condensing lens, connects the spots, condenses the diffusely reflected light with the condensing lens and hits a detector, and detects the displacement of the spot on the detector. In the measurement method, the diameter of the spot applied to the workpiece is 1.3 m.
A method for measuring displacement using a laser displacement meter, characterized in that measurement is performed by setting the distance between m and 1.6 mm.