JPH036419A - Noncontact method for measuring displacement - Google Patents

Abstract

PURPOSE:To measure displacement with high precision by a method wherein the displacement of a measured distance between an optical fiber for sensing light and the surface of a substance to be measured, from a reference distance, is led out on the basis of a difference between the quantity of light sensed by the optical fiber for sensing light and the quantity of light sensed by an auxiliary optical fiber for sensing light. CONSTITUTION:Displacement of a measured distance between an optical fiber 6 for sensing light and the surface of a substance 11 to be measured, from a reference distance, is led out on the basis of a difference between the quantity of light sensed by the fiber 6 and the quantity of light sensed by an auxiliary optical fiber 7 for sensing light. Therefore, it is unnecessary to provide an additional circuit such as an attenuation processing circuit afresh, deterioration S/N and the lowering of reliability consequent thereon are prevented and thus measurement of the displacement can be executed with high precision. By calculating the difference between the quantity of light sensed by the fiber 6 and that by the fiber 7 and the ratio between them, besides, the displacement of the measured distance to the surface of the substance 11 to be measured, from the reference distance, can be led out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a non-contact displacement measuring method for non-contactly measuring the displacement of the distance between an object to be measured and the tips of optical fibers for projecting and receiving light.

[Conventional technology]

Conventionally, as a non-contact method for measuring the distance between the object to be measured and the tips of the light emitting and light receiving optical fibers, there has been a method described in the specification and drawings of Japanese Patent Application No. 1983-259464 previously proposed by the applicant. There is a way.

As shown in FIG.
) and the tip of the receiving optical fiber (2) are at the same distance from the surface of the object to be measured (3).
i+, (2+) are disposed, and a light-emitting optical fiber is partially branched to form a light-receiving auxiliary optical fiber (4).

Optical fiber for receiving emitted light and auxiliary optical fiber for receiving light R4
], derive 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), and based on the ratio, the light emitting optical fiber (1) and the light receiving The distance between the tip of the optical fiber (2) and the surface of the object to be measured (3) is measured.

By the way, when the distance between the tips of both optical fibers fl+ and (21) and the surface of the object to be measured (3) is small, the projection spot of light on the surface of the object to be measured (3) by the light projection optical fiber (1) and the light receiving field of view on the surface of the object to be measured (3) by the light receiving optical fiber (2) do not overlap, and as the distance increases, the overlap between the projection spot and the light receiving field of view gradually increases. However, the relationship between the distance and the amount of light received by the light-receiving optical fiber (2) φ1 is as shown in FIG.

At this time, the amount of light received by the light-receiving optical fiber (2) φ1 gradually increases due to the increase in overlap between the projection spot and the light-receiving field of view as the distance increases, but when the distance exceeds a certain level, the reflected light The amount of light received by the light-receiving optical fiber (2) gradually decreases as the attenuation of the light increases.

On the other hand, since the light-receiving auxiliary optical fiber (4) is formed by partially branching the light-emitting optical fiber (1), the optical fiber (4)
The light receiving field of view almost completely overlaps the projection spot, the reflected light is attenuated as the distance increases, and the light receiving amount φ2 of the light receiving auxiliary optical fiber (4) is as shown in Fig. 11. As the distance increases, the amount of received light φ2 gradually decreases.

Note that when the reflectance of the object to be measured (3) is high, the amount of received light φ1. φ2 increases overall as shown by the broken line in FIG. 11, and conversely decreases overall when the reflectance is low.

The ratio φ1/φ2 of the amount of light received by the light-receiving optical fiber (2) φ1 and the amount of light received by the auxiliary light-receiving optical fiber (4) φ2 changes with distance as shown in FIG. 12.

Therefore, if the relationship curve between the distance to the test piece with the same reflectance as the object to be measured (3) and the ratio of the amount of received light is obtained in advance, the ratio of the amount of received light to the actual object to be measured (3) φ1/φ
From the point on the above-mentioned relationship curve corresponding to 2, the distance between the tips of both optical fibers fil, [2+ and the surface of the object to be measured (3) can be calculated.

By the way, by this method, both optical fibers (1).

For example, the distance ■) between (2) and the surface of the object to be measured (3) is D
Displacement δD (-D2-1) with respect to the reference distance DI when the distance changes to 1) 2 when
], ), the distance D2 and DI obtained based on the ratio φ1/φ2 of the amount of received light from the relationship curve determined in advance.
Additional circuits such as a subtraction processing circuit and a voltage amplification circuit are required to calculate the difference between the two.

[Problem to be solved by the invention]

In the conventional case, an additional circuit is required to determine the displacement relative to the reference distance, which complicates the subsequent circuit configuration.
Furthermore, there are problems in that the SN ratio deteriorates, the reliability is lacking, and highly accurate displacement measurement cannot be performed.

The present invention has been made with the above-mentioned points in mind, and makes it possible to measure the displacement of the distance between the tips of optical fibers for transmitting and receiving light and the surface of an object to be measured without providing an additional circuit as in the conventional method. The purpose is to

[Failure to solve the problem]

In order to achieve the above object, in the present invention, 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, branching a part of the optical fiber for use [7] to form an auxiliary optical fiber for light reception, irradiating light onto the surface of the object to be measured using the optical fiber for projecting light, and converting light reflected from the surface of the object to light into the light reception light. Receive light with the auxiliary optical fiber for light reception, calculate the difference between the amount of light received by the auxiliary optical fiber for light reception, and calculate the difference between the amount of light received by the auxiliary optical fiber for light reception, and when the difference is zero, the optical fiber for light reception The measurement distance between the tip of the object and the surface of the object to be measured is taken as a reference distance, and the displacement of the measurement distance at the time of measurement with respect to the reference distance is derived based on the calculated difference.

In addition, the above-mentioned optical fibers are arranged so that the tip of the optical fiber for light emission and the tip of the optical fiber for light reception are the same distance from the surface of the object to be measured, and the optical fiber for light emission described in III is branched. forming an auxiliary light-receiving optical fiber; irradiating light onto the surface of the object to be measured using the light-emitting optical fiber; and transmitting light reflected from the surface of the object to the light-receiving optical fiber and the auxiliary light-receiving optical fiber. receive light, calculate the difference between the amount of light received by the light receiving optical fiber and the amount of light received by the auxiliary light receiving optical fiber, and calculate the difference between the tip of the light receiving optical fiber and the surface of the measured object when the difference is zero. Using the measurement distance as a reference distance, calculating a ratio between the calculated difference and the amount of light received by the auxiliary optical fiber for light reception, and deriving a displacement of the measurement distance at the time of measurement with respect to the reference distance based on the calculated ratio. You can do it like this.

[Effect]

In the above configuration, the displacement of the measurement distance between the light-receiving optical fiber and the surface of the object to be measured with respect to the reference distance is derived based on the difference between the amount of light received by the light-receiving optical fiber and the amount of light received by the auxiliary light-receiving optical fiber. Therefore, there is no need to newly install additional circuits such as conventional subtraction processing circuits and voltage amplification circuits, and the deterioration of the 8N ratio and the accompanying decrease in reliability are prevented.
Highly accurate displacement measurement can be performed.

In addition, by calculating the ratio of the difference between the amount of light received by the light-receiving optical fiber and the amount of light received by the auxiliary light-receiving optical fiber, and the amount of light received by the auxiliary light-receiving optical fiber, it is possible to ensure that the surface texture of the object to be measured is uniform. Even if the reflectance of the surface of the object to be measured is not uniform, the displacement of the measured distance between the light receiving optical fiber and the surface of the object to be measured with respect to the reference distance can be derived.

〔Example〕

Examples will be described with reference to FIGS. 1 to 9.

(Example 1) First, Example 1 will be described with reference to FIGS. 1 to 4.

The basic schematic configuration of the optical fiber is the same as that shown in FIG. 10 above, and the detailed configuration is shown in FIG. 1. In FIG. (7) is a light receiving auxiliary optical fiber formed by partially branching the light emitting optical fiber C51, (8) is a monitoring optical fiber, and (5) is the light emitting optical fiber. The incident side is bundled and used for monitoring the amount of incident light in order to keep the amount of incident light to the projection optical fiber C5) constant.

At this time, the tips of the fiber bodies of the light emitting optical fibers (51) are distributed and bundled as shown in FIG. 2(a), and connected to the optical fiber east GO via the glass rod (9). The tip of the fiber body 0Q of the optical fiber bundle αO and the receiving optical fiber (61) is shown in FIG.
As shown in b), the optical fibers C5) are dispersed and bundled, so that the optical fibers C5) are substantially used for light emission and light reception.

The distance between the tip of (6) and the surface of the object to be measured OD is kept the same.

Furthermore, in FIG. 1, 02 is an optical fiber for light projection (5
A light emitting element such as a light emitting diode provided on the incident side of 1,
0.1 to α average is a light receiving element such as a photodiode,
Each of them is provided on the output side of the optical fibers (6) to (8).

Next, in FIG. 3 showing the signal processing circuit, αQ is an operational amplifier, and light receiving elements a'i,
(14) are connected in antiparallel, and the output signal of the light-receiving element α3 is proportional to the amount of light received by the light-receiving optical fiber (6), and the output signal is proportional to the amount of light received by the auxiliary light-receiving optical fiber (7). is subtracted and input to the operational amplifier Oe, and a signal proportional to the difference in the amount of light received by the optical fibers (61 and (7)) is output from the output terminal 07 of the operational amplifier OQ.

For tenutopis with the same reflectance as the measured object 0]), the light-receiving optical fiber (6) and the light-receiving auxiliary optical fiber when the measurement distance between the tip of the optical fiber bundle 00 and the measured object circle is changed. (7) A change in the output of the operational amplifier OQ is derived in proportion to the difference in the amount of received light, and a relationship curve of the output of the operational amplifier Oe with respect to the measurement distance is determined in advance.

At this time, the amount of light received by the light-receiving optical fiber (6) φ1 and the amount of light received by the auxiliary light-receiving optical fiber (7) φ2 change with respect to the measurement distance in the same manner as shown in FIG. , (7) is proportional to the difference in the amount of received light (φ1-φ2).
f, the output of the operational amplifier 0 is positive when the measured distance is greater than the reference distance Dr, and negative when it is smaller, and the output changes approximately in proportion to the displacement from the reference distance Df in the vicinity of the reference distance Df.

Next, the operational amplifier qQ for the actual object under test Ql)
Based on the output of , the displacement ΔD of the measured distance between the tip of the optical fiber bundle aO and the surface of the object to be measured with respect to the reference distance Df is determined from the relational curve determined in advance.

For example, when the output of the operational amplifier 00 is Va, from this output Va, as shown in FIG. can get.

In this way, the displacement of the measurement distance with respect to the reference distance Df is derived based on the output of the operational amplifier OQ which is proportional to the difference between the amount of light received by the light receiving optical fiber (6) and the amount of light received by the auxiliary light receiving optical fiber (7). As a result, there is no need to provide additional circuits such as conventional subtraction processing circuits and voltage amplification circuits to derive the displacement, and it is possible to prevent deterioration of the S/N ratio and the accompanying decrease in reliability, improving reliability. can perform high displacement measurements.

(Example 2) Next, Example 2 will be described with reference to FIGS. 5 to 9.

In FIG. 5 showing the overall schematic configuration, the same symbols as in FIG. This is an auxiliary optical fiber for use.

On the other hand, the detailed configuration is shown in FIG. 6, in which the same symbols as in FIG. 1 indicate the same or equivalent parts, and the difference from FIG. 5) is further branched into another auxiliary optical fiber α for receiving light.
(f) is formed, and a light receiving element (1!lft) such as a photodiode is provided on the output side of this optical fiber 08).

Next, in FIG. 7 showing the signal processing circuit, the same symbols as in FIG. Divide the output of the amplifier α by the output of the amplifier (a), and calculate from the output terminal (a) the difference in the amount of light received by the light receiving optical fiber (6) and the auxiliary light receiving optical fiber (7), and the amount of light received by the auxiliary optical fiber. α
8) A signal proportional to the amount of received light is output.

As in the case of Example 1, for a test piece made of the same material as the object to be measured 01), the divider ( 21) is derived, and a relationship curve between the output of the divider (2]) and the measured distance is determined in advance.

At this time, the auxiliary optical fiber for both light reception (7), Q8)
If the number of fiber elements is the same, the changes in the amount of light received by both light receiving auxiliary optical fibers (7) and Q8) with respect to the measurement distance will be almost the same, and the output of operational amplifier 0. By dividing by the output, the time when the output of the operational amplifier θ0 becomes zero is set as the reference distance Df, and the divider (21)
The output is positive when the measured distance is greater than the reference distance Df, and negative when it is smaller than the reference distance Df.In the vicinity of the reference distance Df, the output changes approximately in proportion to the displacement from the reference distance Df.

Next, based on the output of the divider Q1) for the actual object to be measured OB, the optical fiber bundle QO
For example, the measurement distance between the tip of the object 011 and the surface of the object to be measured 011 is
When the output of the divider (21J is Vb, this output vb
As shown in FIG. 8, the displacement Δ between the distance corresponding to the output vb on the relational curve determined in advance and the reference distance Df
D is obtained.

By the way, if the reflectance changes due to a change in the surface properties of the object to be measured 011, the change in the output of the operational amplifier αQ due to the change in reflectance will be equal to the change in the output of the amplifier (e), and therefore the change in the output of the operational amplifier OQ output and amplifier (
The ratio to the output of (a) does not depend on changes in reflectance, but only changes depending on the measurement distance, so even if the measured object OD has uneven reflectance due to changes in surface texture, the displacement can be derived.

Note that the fiber body ot of the optical fiber bundle 00 and the tip of the fiber body (6) of the light-receiving optical fiber (6) are the ninth
The cross section may be divided into two as shown in Figure (a), or the cross section may be concentrically bound as shown in Figure (b).

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

Based on the difference between the amount of light received by the light-receiving optical fiber and the amount of light received by the auxiliary light-receiving optical fiber, conventional subtraction is used to derive the displacement of the measurement distance between the light-receiving optical fiber and the surface of the object to be measured relative to the reference distance. There is no need to newly install additional circuits such as processing circuits and voltage amplification circuits, and it is possible to prevent deterioration of the S/N ratio and associated reliability, and it is possible to perform highly accurate displacement measurements. High resolution measurement becomes possible.

In addition, the difference between the amount of light received by the light-receiving optical fiber and the amount of light received by the auxiliary light-receiving optical fiber, and the ratio of the amount of light received by the auxiliary light-receiving optical fiber are calculated. Even if the reflectance is not uniform, the displacement of the measurement distance between the light-receiving optical fiber and the surface of the object to be measured relative to the reference distance can be derived with high accuracy.

[Brief explanation of drawings]

1 to 9 show embodiments of the non-contact displacement measuring method of the present invention, and FIGS. 1 to 4 show embodiment I.
Figure 1 is a schematic diagram of the measuring device, Figures 2 (a) and (b) are partial cross-sectional views at different positions, Figure 3 is a wiring diagram of the signal processing circuit, and Figure 4 is the distance and operational amplifier. FIGS. 5 to 9 show Example 2, FIGS. 5 and 6 are a schematic diagram and a schematic diagram of the measuring device, respectively, and FIG. 7 is a wiring diagram of the signal processing circuit. Fig. 8 is a diagram showing the relationship between distance and the output of the divider, Fig. 9 fa) and Fig. 9 (b) are cross-sectional views of some different states, Figs. 11 is a diagram showing the relationship between the distance and the amount of received light, and FIG. 12 is a diagram showing the relationship between the distance and the ratio of the amount of received light. (5) Optical fiber for light emission, (6) Optical fiber for light reception, (
7), 0.8)...Auxiliary optical fiber for light reception, 0]
)...Object to be measured.

Claims (2)

[Claims] (1) Both 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 part of the light-emitting optical fiber is branched to receive light. forming an auxiliary optical fiber for light reception, irradiating light onto the surface of the object to be measured using the optical fiber for projecting light, and receiving reflected light from the surface of the object to be measured by the optical fiber for light reception and the auxiliary optical fiber for light reception. and calculating the difference between the amount of light received by the light-receiving optical fiber and the light amount received by the auxiliary light-receiving optical fiber, and measuring the distance between the tip of the light-receiving optical fiber and the surface of the measured object when the difference is zero. A non-contact displacement measuring method, characterized in that the distance is used as a reference distance, and a displacement of the measured distance at the time of measurement with respect to the reference distance is derived based on the calculated difference. (2) Both 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 part of the light-emitting optical fiber is branched to receive light. forming an auxiliary optical fiber for light reception, irradiating light onto the surface of the object to be measured using the optical fiber for projecting light, and receiving reflected light from the surface of the object to be measured by the optical fiber for light reception and the auxiliary optical fiber for light reception. and calculating the difference between the amount of light received by the light-receiving optical fiber and the light amount received by the auxiliary light-receiving optical fiber, and measuring the distance between the tip of the light-receiving optical fiber and the surface of the measured object when the difference is zero. Using the distance as a reference distance, calculating a ratio between the calculated difference and the amount of light received by the light receiving auxiliary optical fiber, and deriving a displacement of the measured distance at the time of measurement with respect to the reference distance based on the calculated ratio. A non-contact displacement measurement method characterized by: