JP3927064B2 - Non-contact displacement meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-contact type displacement meter that optically measures the amount of displacement of a measurement object, and more particularly to a non-contact type displacement meter effective for long-term displacement measurement of a diffuse reflection surface.
[0002]
[Prior art]
As a displacement meter for optically measuring the amount of displacement of a measurement object, one based on the principle of a triangulation method has been proposed. This displacement meter, for example, irradiates a measurement object with a laser beam through a light projecting lens, and connects the light reflected by the measurement object as a spot light on a light receiving portion of the detection element through a light receiving lens. The amount of displacement from the light receiving position of the light receiving unit to the measurement object is calculated.
[0003]
That is, the reflection angle of the laser beam varies depending on the distance to the measurement object, and the spot light receiving position changes accordingly, so that the amount of displacement of the measurement object can be detected from the change position.
[0004]
[Problems to be solved by the invention]
By the way, in the conventional optical displacement meter as described above, when measuring in a short time, or when using it with initialization (fixed point correction) at regular time intervals, it is possible to measure with high accuracy. When the displacement amount is measured continuously over a long period of time, the measurement output changes due to changes in the ambient temperature, the output fluctuation of the light source itself, etc., and thus the reliability of the measurement value cannot be obtained.
[0005]
In addition, since the measurement resolution is fixed by the optical arrangement, it is necessary to use a separate product for each of several types of resolution in order to match the measurement application.
[0006]
The present invention has been made in view of the above-described problems, and can reduce output changes due to fluctuations in the output of the light source and fluctuations in the ambient temperature, so that the stability and reliability of the measured value can be obtained. An object of the present invention is to provide a non-contact displacement meter that can cope with various resolutions with a single sensor (displacement meter).
[0007]
[Means for Solving the Problems]
A non-contact displacement meter according to the present invention is a non-contact displacement meter that optically measures the amount of displacement of a measurement object, and includes a light source, a light source control circuit that controls the amount of light emitted from the light source, A polarization beam splitter that divides the reflected light projected from the light source and reflected by the measurement object into P-wave and S-wave polarizations, and polarized light that has been split into P-waves and S-waves by the polarization beam splitter. Each having a light receiving element that receives light, and a position adjusting unit that adjusts the position of at least one of the light receiving elements, and calculating a displacement amount of the measurement object from a difference or ratio of outputs of the light receiving elements, A position adjusting means for adjusting the position of at least one of the light receiving elements and arbitrarily setting the resolution is provided.
[0009]
In the above-described configuration, the light source control circuit includes a polarization beam splitter that divides the light emitted from the light source for each polarization of P wave and S wave, and a light receiving element that receives the divided polarized light. The amount of light emitted from the light source is controlled based on the output of the element.
[0010]
Further, in the above configuration, an amplifier that amplifies the output of at least one of the light receiving elements that receive the polarized light obtained by dividing the reflected light from the measurement object by the polarization beam splitter, and adjusts the amplification factor of the amplifier. Thus, the calculation output of the difference between the respective light receiving element outputs becomes the reference potential.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0012]
FIG. 1 is a diagram schematically showing the configuration of an LED displacement meter according to an embodiment of the present invention. In the figure, 1 is an LED (light emitting diode) as a light source, 2 is a polarization beam splitter (hereinafter referred to as PBS) that divides the light projected from the LED 1 into P-wave and S-wave polarized light, and 3 is projected from the LED 1. It is PBS which divides | segments the reflected light reflected by the measuring object 4 for every polarization of P wave and S wave.
[0013]
In FIG. 1, reference numerals 5 and 6 denote PDs (photodiodes), which are light receiving elements that receive the polarized light divided into the P wave and the S wave by the PBS 3, respectively. Position adjustment means for adjusting the position in the directions of arrows A and B in the figure is provided in at least one PD (PD5 in the figure) of PD6. Reference numeral 7 denotes a PD, which is a light receiving element that receives polarized light divided by the PBS 2, and is provided for monitoring to control the amount of light emitted.
[0014]
FIG. 2 is a block diagram showing a circuit configuration of this embodiment. In the figure, 11, 12, 13 are amplifiers that amplify the outputs of the PDs 5, 6, and 7, and 14 calculates the displacement amount of the measurement object 4 from the difference or ratio of the outputs of the PDs 5, 6, and outputs the result. The arithmetic circuit adjusts the amplification factor of at least one of the amplifiers 11 and 12 to correct the sensitivity variation of each light receiving element and adjust the balance of the received light output in accordance with the reflection characteristic of the measurement object. Reference numeral 15 denotes a light source control circuit that controls the amount of light emitted from the LED 1 based on the output of the PD 7, reference numeral 16 denotes a constant voltage circuit that applies a constant voltage to the PDs 5, 6, and 7, and reference numeral 17 denotes a variable resistor for adjustment.
[0015]
In the non-contact type LED displacement meter configured as described above, single polarized light from the LED 1 is projected onto the measurement object 4 through the PBS 2. This projection light is reflected on the surface of the measurement object 4 and guided to the PBS 3 and input to the PDs 5 and 6 as detection light. Then, the outputs of the PDs 5 and 6 are input to the arithmetic circuit 14 through the amplifiers 11 and 12, where the displacement amount of the object 4 is calculated and output.
[0016]
At that time, P wave and S wave components are generated as detection light according to the reflection characteristics of the measurement object 4, and the sensor output (output ratio) of the calculation result of the polarized light of each component is the light receiving element. When the PDs 5 and 6 are not deviated from the optical design center position, the change is small with respect to the distance change to the measurement object 4. The degree of change in the sensor output increases as the amount of deviation of the light receiving position of the P wave or S wave from the center increases.
[0017]
That is, by controlling the relative positional relationship between PD5 and PD6, the change rate of the sensor output with respect to the distance displacement to the measurement object 4 is arbitrarily selected, and the distance displacement to the measurement object 4 is detected. Is possible. Therefore, a displacement meter capable of arbitrarily setting the sensor resolution can be realized.
[0018]
FIG. 3 is a diagram showing the rate of change in sensor output with respect to the element position (mm) from the center of the PDs 5 and 6 that receive the P wave and S wave. The solid line in the figure indicates data when the displacement amount is ± 1.0 mm, and the broken line indicates data when the displacement amount is ± 0.5 mm.
[0019]
In addition, since the light source control circuit 15 that can stabilize the amount of light emitted from the LED 1 by the monitor light reception output of the PD 7 is built in, the sensor output is highly stable, the ambient temperature changes, and the LED 1 itself that is the light source generates heat. The output fluctuation due to can be suppressed to an extremely small one.
[0020]
Furthermore, even when the output calculation is the output difference between the P wave and the S wave, if the measurement object 4 has a strong diffuse reflection, the amplification factor of the output of the PD 5 or PD 6 is adjusted, and the sensor output becomes the reference potential V 1. By setting so as to be, it is possible to obtain a sensor output that is not affected by fluctuations in the light source output.
[0021]
Also, when the measurement object has a reflection characteristic with many specular reflection components, the output difference calculation is affected by fluctuations in the light source output, but by correcting the light amount so that the output of PD5 or PD6 is constant The effect can be eliminated.
[0022]
FIG. 4 is a diagram showing the change of the sensor output with time, and shows data of the sensor output Vout (V) when energized continuously for one week as compared with the conventional example. (A) of the same figure is the data of a present Example, (b) is the data of the prior art example mentioned above.
[0023]
Thus, in the present embodiment, the light source control circuit 15 that controls the amount of light emitted from the light source is provided, and the change in the sensor output due to the output fluctuation of the LED 1 that is the light source and the fluctuation in the ambient temperature can be reduced. Stability and reliability of the measured value can be obtained. Further, by changing the position of PD5 which is a light receiving element for P wave or PD6 which is a light receiving element for S wave, it is possible to change the output change width with respect to the displacement amount of the measuring object 4, and one unit This sensor (displacement meter) can cope with various resolutions.
[0024]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the output change due to the output fluctuation of the light source and the fluctuation of the ambient temperature, and the stability and reliability of the measurement value can be obtained. In addition, there is an effect that it is possible to cope with various resolutions with a single sensor (displacement meter).
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a configuration of an embodiment of the present invention. FIG. 2 is a block diagram showing a circuit configuration of the embodiment. FIG. 3 is a diagram showing a relationship between an element position and an output change rate. Figure showing changes over time 【Explanation of symbols】
1 LED (light source)
2 Polarizing beam splitter 3 Polarizing beam splitter 4 Measurement object 5 PD (light receiving element)
6 PD (light receiving element)
7 PD (light receiving element)

Claims (4)

A non-contact displacement meter that optically measures the amount of displacement of a measurement object, the light source, a light source control circuit for controlling the amount of light emitted from the light source, and the measurement object projected from the light source A polarization beam splitter that divides the reflected light reflected by P for each polarization of the P wave and S wave, and a light receiving element that receives the polarized light divided into the P wave and the S wave by the polarization beam splitter, It has position adjustment means for calculating the displacement amount of the measurement object from the difference or ratio of the outputs of the respective light receiving elements, adjusting at least one of the positions of the light receiving elements , and arbitrarily setting the resolution . Non-contact displacement meter. A polarization beam splitter that divides the light emitted from the light source into P-wave and S-wave polarizations; and a light receiving element that receives the divided polarized light. The light source control circuit is based on the output of the light receiving element. non-contact type displacement meter according to claim 1 Symbol placement and controls the projection light amount of the light source. It has an amplifier that amplifies the output of at least one of the light receiving elements that receive the polarized light obtained by dividing the reflected light from the measurement object by the polarization beam splitter, and adjusts the amplification factor of the amplifier to obtain a difference between the outputs of the light receiving elements. non-contact type displacement meter according to claim 1 or 2, wherein computing output is characterized in that as a reference potential. The light source non-contact type displacement meter 3 according claim 1, characterized in that an LED.

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