JPS62127612A - Surface displacement measuring method by laser light - Google Patents

Abstract

PURPOSE:To measure surface displacement accurately while suppressing variance of data by applying particulates over the surface of a body to be measured and processing detection data at respective irradiation points by a moving average method. CONSTITUTION:A work 4 is irradiated with laser light L while a laser displacement gauge 11 is moved in an X-axial direction. The surface of the work 4 is coated with alumina powder 14 to stabilize its surface roughness, so the reflected light R of the laser light L is detected by a detector 16 without any variance. The detected value of the detector 16 is led to a smoothing process circuit 17 at specific sampling timing and then the circuit adds, for example, the input data to data at a past point 29 to calculate the mean value. This calculation is carried out shifting, point by point, to find the moving average value of all data. Consequently, even when data with a large error is inputted, the data does not have large variance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a surface displacement measurement method using a laser beam, which is applied, for example, to turbine blade profile measurement.

[Conventional technology]

In the field of turbine blade profile measurement, etc.
A known technique is to irradiate a turbine surface with a laser beam and measure a profile based on changes in the reflected light.

For example, a laser displacement meter 1 as shown in FIG. 5 is used in this technique. This laser displacement meter 1 irradiates a laser beam L from a semiconductor laser 2 serving as a laser light source through a focusing lens 3 onto the surface of a workpiece 4, which is an object to be measured, and transmits the reflected light R through a focusing lens 5. An image is formed on the detector 6. Then, by moving the laser displacement meter 1 configured in this way in the X-axis direction as shown, the laser beam is scanned over the workpiece, and the displacement of the surface of the workpiece 4, that is, the profile of the turbine blade, etc., is measured. I try to do that.

[Problem that the invention seeks to solve]

However, in this measurement method using a laser displacement cylinder, the intensity of the reflected light changes depending on the surface roughness of the workpiece, so as shown in Figure 6, data as large as 0.6 m may be affected by the surface roughness. This results in variations in the

Therefore, when attempting to obtain the coordinates of a certain point on the profile, there is a problem in that this variation affects the measurement accuracy and causes a decrease in measurement accuracy.

The present invention was made based on such problems, and an object of the present invention is to provide a surface displacement measurement method using a laser beam that suppresses data variation and enables highly accurate surface displacement measurement.

[Means for solving problems]

The present invention provides a method of measuring the displacement of the surface of the object to be measured by scanning the laser beam while irradiating the surface of the object to be measured, and collecting and detecting the diffusely reflected light at each irradiation point. In this method, the displacement of the surface of the object to be measured is determined by applying fine powder to the surface of the object to be measured in advance, and processing the detection data of each of the irradiation points using a moving average method (smoothing processing). It is characterized by

[Function] When a powder such as alumina is applied to the surface of the workpiece, the surface roughness of the workpiece becomes constant, thereby stabilizing the reflected light, thereby suppressing data variations.

Further, the data obtained by scanning with the laser beam is converted into a moving average value of several pieces of data obtained previously. This smoothing process suppresses data variations.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing the configuration of a laser displacement meter 11 for implementing the present invention. The output of the semiconductor laser 12 is controlled by a laser drive circuit (not shown). The laser beam from the semiconductor laser 12 is focused by a focusing lens 13, and is irradiated onto a workpiece 4, which is an object to be measured, with a predetermined beam spot diameter. Alumina (Ag2O3) powder 14 having a particle size of about 11Bn is applied to the workpiece 4 in advance.

The reflected light R from the workpiece 4, which forms a predetermined angle with respect to the incident light, is focused by a focusing lens 15, and is sent to a detector 16.
Detected in The light reception signal from the detector 16 is input to a smoothing processing circuit 17.

Laser light is irradiated onto the workpiece 4 while the laser displacement meter 11 configured as described above is moved in the X-axis direction in the figure. Since the surface of the workpiece 4 is coated with alumina powder 14 to stabilize its surface roughness, the reflected light R of the laser beam is detected by the detector 16 without large variations. When the detected value from the detector 16 is guided to the smoothing processing circuit 17 at a predetermined sampling timing, the input data and the data for the past 29 points are added together to calculate the average value. The moving average value of all data is obtained by shifting this calculation one point at a time. As a result, even if data with a large error is input, the data will not vary greatly.

2 to 4 show the effect of the present invention by irradiating a turbine blade with a laser beam having a beam diameter of 0.7 mm. FIG. 2 is a plot of the blade profile when smoothing processing is performed. Compared to the conventional variation (0.6M), the variation has been reduced to 0.09m.

Moreover, FIG. 3 is a diagram plotting the profile of the blade in the case of alumina surface treatment. In this case, the variation has been reduced to 0.15 m. moreover,
FIG. 4 is a plot of the blade profile when both smoothing treatment and alumina surface treatment were performed.

In this example, the variation could be suppressed to 0.05tta.

〔Effect of the invention〕

As described above, according to the present invention, variations in measurement data can be suppressed, and surface displacement can be measured with high precision laser light.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a laser displacement meter according to an embodiment of the present invention, FIGS. 2 to 4 are diagrams showing turbine blade profiles determined by the present invention, and FIG. 5 is a block diagram of a laser displacement meter according to an embodiment of the present invention. FIG. 6 is a block diagram showing the configuration of the turbine, and FIG. 6 is a diagram showing the profile of a 6-turbine blade obtained by a conventional method. 1.11...Laser displacement meter, 2,12...Semiconductor laser, 3,5,13.15...Focusing lens, 4...
Workpiece, 6.16...Detector, 14...Alumina powder, 17...Smoothing processing circuit, L...Laser light, R...Reflected light. Applicant Sub-Agent Patent Attorney Takehiko Suzue Figure 1X Figure 6

Claims (1)

[Claims] In the method of measuring the displacement of the surface of the object to be measured by scanning the laser beam while irradiating the surface of the object to be measured and collecting and detecting the diffusely reflected light at each irradiation point, Using a laser beam, the displacement of the surface of the object to be measured is determined by coating the surface of the object to be measured with fine powder and processing the detection data of each irradiation point using a moving average method. Surface displacement measurement method.