JPH0577241B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a non-contact displacement measuring method for measuring the distance to an object to be measured in a non-contact manner.

[Conventional technology]

Generally, when measuring the distance to the object to be measured without contact, measurement is carried out using an optical fiber as shown in FIG. so that the tip of 2 is at the same distance from the surface of the object to be measured 3.
Both optical fibers 1 and 2 are arranged, the light emitting optical fiber 1 projects light onto the surface of the object to be measured 3, the light reflected from the surface of the object to be measured 3 is received by the light receiving optical fiber 2, Based on the amount of light received by the light-receiving optical fiber 2, the distance D between the tips of both optical fibers 1 and 2 and the surface of the object to be measured 3 is derived.

At this time, if the distance D between the tips of both optical fibers 1 and 2 and the surface of the object to be measured 3 is small, as shown in FIG. The projection spot S and the light receiving field R on the surface of the object to be measured 3 by the light receiving optical fiber 2 do not overlap, and as shown in FIGS. As the overlap between S and the light-receiving field of view R gradually increases, the relationship between the distance D and the amount of light received by the light-receiving optical fiber 2 becomes as shown by the solid line in FIG. The amount of light received by the light receiving optical fiber 2 gradually increases due to the increase in the overlap between It gradually decreases.

Therefore, if the relationship between the distance and the amount of received light as described above is determined in advance for a test piece having the same reflectance as the object to be measured 3, the actual reception of reflected light from the object to be measured 3 on the relationship curve can be determined in advance. From the point corresponding to the amount, the distance D between the tips of both optical fibers 1 and 2 and the surface of the object to be measured 3 can be easily derived.

An advantage of such a measurement method using an optical fiber is that, for example, when a coherent light source with a single wavelength such as a visible laser is used as the light source for projection light, the resolution is on the order of the wavelength (0.1 μm). Distance detection accuracy is extremely high, and the device is small and lightweight, making it easy to handle.

[Problem that the invention seeks to solve]

However, in this case, if the reflectance of the object to be measured 3 differs, the relationship between the distance and the amount of received light will change as described above. For example, if the reflectance is larger than the solid line in FIG. The relationship curve with the amount of received light is generally shifted in the positive direction of the amount of received light on the vertical axis compared to the solid line in the same figure, as shown by the dashed-dotted line in the same figure, and the reflectance is as shown by the solid line in the same figure. If the relationship between the distance and the amount of light received is smaller than the case of When the reflectance changes midway through the distance, when the amount of light received changes due to the change in reflectance, it is actually a change in the amount of light received due to the change in reflectance without changing the distance. However, this method can only be detected as a change in distance, and cannot be applied to measuring the distance to the object 3 whose surface texture is not uniform, resulting in a lack of applicability.

Therefore, a technical problem of the present invention is to enable the method to be applied to measurement of distance to an object to be measured whose surface properties are not uniform.

[Means for solving problems]

This invention has been made with the above points in mind, and the optical fibers are arranged so that the tip of the light-emitting optical fiber and the tip of the light-receiving optical fiber are at the same distance from the surface of the object to be measured. and irradiate the surface of the object to be measured with light using the light emitting optical fiber,
Non-contact displacement, in which the reflected light from the surface of the object to be measured is received by the optical fiber for light reception, and the distance between the tips of the optical fibers and the surface of the object to be measured is measured based on the amount of light received by the optical fiber for light reception. In the measuring method, a part of the light emitting optical fiber is branched to form a light receiving auxiliary optical fiber, and the light emitting and receiving auxiliary optical fibers are determined based on the ratio of the amount of light received by the light receiving optical fiber and the light receiving amount of the light receiving auxiliary optical fiber. This is a non-contact displacement measuring method characterized by measuring the distance between the tips of the optical fiber for light and the optical fiber for light reception and the surface of the object to be measured.

[Effect]

Therefore, according to the present invention, for example, when the surface properties of the object to be measured change after a certain position and the reflectance changes, the relationship between the tips of the light emitting and receiving optical fibers and the surface of the object to be measured changes. If the distance is constant, the rate of change in the amount of light received by the light-receiving optical fiber and the rate of change in the amount of light received by the auxiliary light-receiving optical fiber are equal, and the amount of light received by the light-receiving optical fiber and the amount of light received by the auxiliary light-receiving optical fiber are equal. The ratio to the measured object changes depending only on the distance, not on changes in reflectance due to changes in the surface texture of the object to be measured, making it possible to measure distances to objects whose surface texture is not uniform. becomes possible.

〔Example〕

Next, the present invention will be explained in detail with reference to FIGS. 1 to 3 showing one embodiment thereof.

In Fig. 1, the same symbols as in Fig. 4 indicate the same or equivalent parts, and the difference from Fig. 4 is that a part of the light emitting optical fiber 1 is branched and a light receiving auxiliary optical fiber 4 is and measure the distance D between the tips of both optical fibers 1 and 2 and the surface of the object to be measured 3 based on the ratio of the amount of light received by the light-receiving optical fiber 2 and the amount of light received by the auxiliary light-receiving optical fiber 4. This is the point I made.

By the way, using a test object 3 with uniform surface properties and a constant reflectance, the relationship between the distance D and the amount of light received by the light receiving optical fiber 2 φ1 and the amount of light received by the auxiliary light receiving fiber 4 φ2 is calculated. As a result of my investigation,
In the case of the light-receiving optical fiber 2, the pattern is similar to each curve in FIG. 6 described above, as shown by the dashed-dotted line in FIG. Distance D as shown in the middle two-dot chain line
The pattern is such that the amount of light received gradually decreases as
φ2 gradually increases as the distance D increases, as shown in FIG. 2b.

At this time, if the surface texture of the object to be measured 3 changes after a certain position and the reflectance changes, then if the distance between the tips of both optical fibers 1 and 2 and the surface of the object to be measured 3 is constant, then Amount of light received by optical fiber 2 for light reception φ1
Since the rate of change in the amount of light received by the auxiliary light receiving fiber 4 is equal to the rate of change in the amount of light received by the auxiliary optical fiber 4, the ratio φ1/φ2 of the amount of light received by both fibers 2 and 4 does not change, and can be calculated from the ratio of the amount of received light. There is no change in the distance traveled,
The light receiving ratio φ1/φ2 of both fibers 2 and 4 does not depend on changes in reflectance due to changes in surface properties of the object to be measured, but changes depending only on distance D.

Therefore, using a test object to be measured, FIG.
The ratio of the light receiving fiber 2 and the light receiving auxiliary optical fiber 4 to the distance D as shown in φ1/
If the relationship of φ2 is determined in advance, as shown in FIG. and the ratio of received light amount φ1/φ2, and both fibers 2 and 4 obtained by moving both fibers 1 and 2 in the direction of the arrow in FIG.
Based on the ratio φ1/φ2 of the amount of received light, the distance D between the tips of both optical fibers 1 and 2 and the surface of the object to be measured 3 can be continuously derived and measured.

[Effects of the Invention] As described above, according to the non-contact displacement measurement method of the present invention, even if the surface of the object is uneven, the tips of the light emitting and light receiving optical fibers can be easily connected to the object. The distance to the surface can be measured continuously and easily using a small and lightweight measuring device, making it possible to eliminate the drawbacks of conventional methods and expanding the range of applications, with extremely effective results. big.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the non-contact displacement measuring method of the present invention, FIG. 1 is a sectional view, and FIG.
Figures a and b are relationship diagrams between distance, received light amount, and received light amount ratio, respectively, Figure 3 is a cross-sectional view during measurement, and Figure 4
The figure is a perspective view during measurement using the conventional non-contact displacement measurement method, Figures 5a, b, and c are diagrams showing the projection spot and light receiving field of view on the surface of the object to be measured in different states, and Figure 6 is a diagram showing the distance and field of view. It is a relationship diagram with the amount of light received. DESCRIPTION OF SYMBOLS 1... Optical fiber for light emission, 2... Optical fiber for light reception, 3... Object to be measured, 4... Auxiliary optical fiber for light reception.

Claims (1)

[Scope of Claims] 1. Both the optical fibers are arranged so that the tip of the light-emitting optical fiber and the tip of the light-receiving optical fiber are the same distance from the surface of the object to be measured, and the light-emitting optical fiber The surface of the object to be measured is irradiated with light, the reflected light from the surface of the object to be measured is received by the optical fiber for light reception, and the tips of the optical fibers and the object to be measured are connected based on the amount of light received by the optical fiber for light reception. In a non-contact displacement measurement method for measuring a distance to an object surface, a portion of the light emitting optical fiber is branched to form a light receiving auxiliary optical fiber, and the amount of light received by the light receiving optical fiber and the light receiving auxiliary optical fiber are A non-contact displacement measuring method, characterized in that the distance between the tip of the light emitting optical fiber and the light receiving optical fiber and the surface of the object to be measured is measured based on the ratio of the amount of light received to the amount of light received.