JPS62245110A - Displacement measuring apparatus - Google Patents

Abstract

PURPOSE:To accurately measure the positional change of a matter to be measured and to enhance the response speed of measurement, by preliminarily storing the signal of a position sensor at the time of non-irradiation of laser beam and subtracting the value at said time from the value at the time of the irradiation of laser beam. CONSTITUTION:The laser beam 12 emitted from a laser beam source 11 forms a beam spot on an article 14 to be measured through an irradiation lens 13 and the reflected beam 17 thereof forms the image of a beam spot by a condensing lens 16 to be received by a position sensor 18 and the output signal of the sensor 18 on the basis of the reception of beam is inputted to the positive side of a substraction means 21. The output signal of the sensor 18 at the non-output time of the beam source 11, that is, the signal caused by ambient light and the signal caused by the dark current of the sensor 18 are stored in a memory means 20 and inputted to the negative side of the subtraction means 21. Therefore, the signal obtained by subtracting the stored signal of ambient light from the output signal of the sensor 18 due to the laser beam 12 is outputted from the subtraction means 21 to be inputted to a position detection means 22. By this method, the beam receiving position on the sensor 18 is calculated to be converted to the positional displacement of the matter 14 and, therefore, displacement can be measured with high accuracy and high speed response.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention irradiates a measured object with a light beam and uses the reflected light to measure the distance to the measured object or its displacement in a non-contact manner. The present invention relates to a displacement measuring device.

[Prior Art] Some displacement measuring devices that measure the distance to an object to be measured or the displacement of the object to be measured by a device that irradiates the object to be measured with a light beam and then emit light from a direction different from the direction of the irradiated light beam. When observing this measured object, there is a method that detects the positional displacement of the measured object as a movement of a light reflection point, and calculates the positional displacement of the measured object from the movement of the detected reflection point.

A displacement measuring device using such a light beam is, for example, the fifth
It is constructed as shown in the figure (Special Publication Publication No. 59-762).
. That is, numeral 1 in the figure is a light source that outputs a light beam with good directionality, such as a laser beam, and a light beam 2 output from this light source 1 is irradiated onto an object to be measured 4 via an irradiation lens 3. The object to be measured 4 is displaced in the direction of the arrow, which is the same as the irradiation direction of the light beam 2. Reference numeral 5 denotes a condensing lens, which condenses reflected light 6 from the object 4 to be measured. A position sensor 7 is disposed on the imaging plane (focal position) of the condensing lens 5. This position sensor 7 has, for example, a P-type semiconductor region 7a formed on the light-receiving surface side, and an n-type semiconductor region 7a on the side opposite to the light-receiving surface.
A type semiconductor region 7b is formed. A predetermined DC voltage VD is applied to the center position on the side opposite to the light-receiving surface, and a load resistor is connected to both ends of the p-type semiconductor region 7a on the light-receiving surface side. When the light receiving position on the light receiving surface changes, the value of each current 11+12 flowing through each load resistor changes. Then, using the value of this current 'L+'2, the irradiation position y from the center position is calculated by the calculation unit 8 at the next stage. Further, the irradiation position y on the light receiving surface of the position sensor 7 determined by the calculator 8 is converted into a displacement X of the object to be measured 4 in the direction of the arrow by the correction circuit 9.

[Problems to be Solved by the Invention] However, the displacement A11l fixing device configured as described above also has the following problems. That is, according to this measuring device, ambient light such as a light in the room that is not directly related to displacement measurement is also received by the light receiving surface of the position sensor 7. As a result, the currents tl and t2 taken out from both ends of the p-type semiconductor region 7a of the position sensor 7 always include the current and dark current due to this ambient light. As a result, the error component included in the irradiation position y obtained by the calculator 8 increases. Therefore, the measurement accuracy of the entire device ultimately decreases.

In order to solve this problem, it is necessary to
2, a light beam 2 output from a light source 1 is modulated at a constant frequency, and the modulated light beam is irradiated onto an object 4 to be measured. Then, the current 11+12 modulated at the constant frequency obtained by the position sensor 7
demodulates and returns it to a DC value. By using modulated light in this manner, it is possible to completely separate the measurement light beam from the surrounding light and extract it, thereby significantly improving measurement accuracy.

However, if the light beam is once modulated in this way and the detection current modulated according to the light beam is demodulated and returned to a DC value, the response speed of measurement to the displacement speed of the object to be measured is Since the modulation frequency is limited to the modulation frequency, when the object to be measured fluctuates at high speed, a problem arises in that the measurement cannot follow the fluctuations.

Furthermore, a circuit for modulation and demodulation is required, which not only increases the size and complexity of the entire measuring device, but also increases manufacturing costs.

The present invention has been made based on the above circumstances, and its purpose is to store the output signal of the position sensor when the light beam is not being irradiated, so that it can be used when the light beam is irradiated. It is an object of the present invention to provide a displacement measuring device that can accurately determine a light receiving position, can accurately measure changes in the position of an object to be measured, and can improve measurement response speed.

[Means for Solving the Problems] As shown in FIG.
4 to form a light spot 15 on the object to be measured 14, and a condenser lens 16 disposed so that the optical axis is not parallel to the optical axis of the irradiation lens 13, The reflected light 17 is focused to form an image of a light spot, the light spot imaged by the condenser lens 16 is received on the light receiving surface of the position sensor 18, and the position sensor 18 further focuses on the object to be measured 14. The light-receiving position of the light spot on the light-receiving surface, which changes in response to a change in the position of In the displacement measuring device configured to calculate the displacement, the calculating means 19 is combined with a storage means 20 for storing a signal output from the position sensor 18 when the light source 11 is not outputting, and a signal output from the position sensor 18 when the light source 11 is outputting. The subtraction means 21 subtracts the signal stored in the storage means 20 from the light reception position obtained by the subtraction means 21, and the position calculation means 22 calculates the position of the object to be measured 14 from the light reception position obtained by the subtraction means 21. It is something.

[Function] With the displacement measuring device configured in this way, the signal output from the position sensor in a state in which the light source does not output a light beam, that is, the signal caused by ambient light and the dark current of the position sensor. The signal to be used is temporarily stored. Then, the previously stored ambient light signal is subtracted from the signal output from the position sensor when a light beam is normally output from the light source. Therefore, a correct light receiving position can be obtained using only the light beam that excludes the influence of ambient light. Then, the correct position of the object to be measured is calculated from this correct light receiving position.

[Example code] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing the displacement measuring device of the embodiment. In the figure, reference numeral 31 denotes a laser light source that outputs a light beam of a laser beam, and a light beam 32 output from this laser light source 31 is irradiated onto an object to be measured 34 via an irradiation lens 33. The object to be measured 34 is displaced in the same arrow direction as the irradiation direction of the light beam 32. A condensing lens 35 condenses reflected light 36 from the object to be measured 34. A position sensor 3 is placed on the imaging plane (focal position) of this condensing lens 35.
7 are arranged. This position sensor 37 has the same configuration as the position sensor shown in FIG. 5, with a P-type semiconductor region 37a formed on the light-receiving surface side and an N-type semiconductor region 37b formed on the side opposite to the light-receiving surface. There is. A predetermined DC voltage VD is applied to the center position on the side opposite to the light-receiving surface, and a load resistor (not shown) is connected to both ends of the p-type semiconductor region 37a on the light-receiving surface side. Then, when the light receiving position on the light receiving surface changes, each current i! flows through each load resistor! .

12 values change.

Then, each of these type currents 11+12 is input to current-voltage converters 38a and 38b, and the voltage value Vl+
Converted to v2. Each voltage v1+v2 output from each current-voltage converter 38a, 38b is input to a subtracter 39 and an adder 40. The output signal of the subtracter 39 (VI
V2) is input to the (+) input terminals of the subtracter 41a at the next stage, and is also input to the A/D converter 42a where it is converted into a digital value. Furthermore, this A/D converter 4
The data converted into digital values at 2a is sent to the D/A converter 4.
3a, it is converted back into an analog signal and sent to the subtracter 41a.
is input to the (-) input terminals.

Similarly, the output signal (vl +V2) of the adder 40 is input to the (+) input terminals of the subtracter 41b at the next stage, and is also input to the A/D converter 42b where it is converted into a digital value. Further, the data converted into a digital value by the A/D converter 42b is again converted into an analog signal by a D/A converter 43b, and is inputted to the (-) input terminals of the subtracter 41b.

When the A/D converters 42a and 42b receive the data storage command signal 46 from the operation unit 45 via the delay circuit 44, they convert the voltage (vl-v2) input from the subtracter 39 and adder 40, respectively. ), (Vl +V2
) into digital values and converts them into digital values and converts them into digital values.
Output to 3b. Thereafter, the output value is held until a new storage command signal 46 is input. Therefore, the above A
The /D converters 42a and 42b constitute storage means for storing the light receiving position output from the position sensor 37.

A storage command signal 46 outputted from the operation section 45 is inputted to each A/D converter 42a, 42b via a delay circuit 44, and is also inputted to a laser drive circuit 47 that drives the laser light source 31. Furthermore, a measurement command signal 48 is outputted from the operation section 45 to the laser drive circuit 47 . When the storage command signal 46 is input, the laser drive circuit 47 stops outputting the light beam 32 from the laser light source 31 and outputs the measurement command signal 4.
When 8 is input, a light beam 32 is output from the laser light source 31.

The analog signals output from each of the subtracters 41a and 41b are input to a divider 49. The divider 49 is the subtracter 41
The light receiving position y of the reflected light 36 on the light receiving surface of the position sensor 37 is calculated by dividing the output signal of the signal a by the output signal of the other subtractor 41b, and dividing the quotient by 1 by a predetermined constant. The light receiving position y calculated by the divider 49 is converted into a positional displacement X of the object to be measured 34 by a correction circuit 50 at the next stage.

Thus, the divider 49 and the correction circuit 50 constitute a position calculation means.

In the displacement measuring device configured in this way, the operating section 4
When the storage command signal 46 is output from 5, if the light beam 32 is being output from the laser light source 31, the output of the light beam 32 is immediately stopped. Then, after the storage command signal 46 is output and is delayed by a predetermined time Δt in the delay circuit 44, each A/D converter 42a, 42b operates. This delay time Δt turns off the laser light source 31 and the light beam 3
2 completely disappears until the influence of the afterimage of the light beam 32 from the position sensor 37 and the current-voltage converters 38a, 38b completely disappears.

When the laser light source 31 is turned off and the delay time Δt has elapsed, the p-type semiconductor region 37a of the position sensor 37
An image is formed on the light-receiving surface of the sensor due to ambient light, which is not equally involved in the measurement. Then, currents t,, tz, that is, dark currents due to reception of this ambient light are input to the current-voltage conversion circuits 38a, 38b, and the corresponding voltage values V1. V
Converted to 2. Then, a subtracter 39 and an adder 40
The voltage value (Vt −v2), (VL +V2
) are calculated, and the A/D converters 42a, 42
Human power is applied to b.

Therefore, at this point, the A/D converter 42a.

When the storage command signal 46 is input to 42b, the light beam 32
is not output, the voltage value (Vl-V2) of the information indicating the light receiving position in the position sensor 37, (
v1+v2) is converted into a digital value and stored.

This digital value (VI V2)l (Vl +V2
) are respectively converted to the original analog values by the D/A converters 43a and 43b and input to the (-) input terminals of the subtracters 41a and 41b, but in this state, the (+) input terminals are Since the value input to the subtracters 41a and 41b is equal to the value input to the (-) input terminals, the output value of each subtractor 41a, 41b is zero.

Next, when the measurement command signal 48 is output from the operation unit 45,
The laser light source 31 is turned on and a light beam 32 is output. This light beam 32 is then imaged into a light spot on the object to be measured 34 by the irradiation lens 33. The reflected light 36 from the object to be measured 34 is focused onto the light receiving surface of the position sensor 37 by the condensing lens 35 . That is, an image of a light spot formed by the light beam 32 on the object to be measured 34 is formed on the position sensor 37.

Therefore, the current 'l+12 corresponding to the light receiving position of the light spot on the position sensor 37 is detected and converted into voltage values Vl and V2 by the current-voltage conversion circuits 38a and 38b. Then, as described above, the subtracter 39 and the adder 40
It is converted into a voltage value (vl-V2)+(v1+v2) at . These values are (
+) input terminals. In addition, the above multi-value is A/D
These values are also input to the converters 42a and 42b, but since no new storage command signal 46 is input, these values are not A/D converted. Each subtractor 41a24
Since the multiple values of the ambient light when the light beam 32 is turned off are input to the (-) input terminals of 1b, the influence of the ambient light can be calculated by subtracting the value due to the ambient light from the value when the light beam 32 is irradiated. can be removed. Therefore, each subtractor 41a.

Each voltage value (vt V2 ) + (v, +v2 ) resulting from the positional displacement of the object to be measured 34 is output from 41b, and the light receiving position y on the position sensor 37 is calculated by the divider 49 using the following equation.

Y-Kx (VI V2)/ (Ml +V2
) Then, the determined light receiving position y is converted into a positional displacement X of the object to be measured 34 in the next stage correction circuit 50.

With the displacement measuring device configured in this way, once the storage command signal 46 is output from the operation unit 45, the light beam 3
2. Information on the light receiving position on the position sensor 37 due to ambient light when the lights are off is stored in the A/D converter 42 as a storage means.
a, 42b. Then, the information is subtracted from the information on the light receiving position of the position sensor 37 at the time of regular measurement by irradiating the light beam 32. Therefore, the influence of ambient light can be removed, and the accuracy of displacement measurement of the object to be measured 34 can be improved.

Further, information on the light receiving position due to ambient light is always obtained from the A/D converters 42a and 42b to each subtractor 41a.

Since the signal is input to the (-) input terminal of 41b, the measurement response characteristics are affected only by the response characteristics of the position sensor 37, etc., and are not subject to limitations due to modulation and demodulation as in conventional devices. Therefore, it is possible to respond to high-speed changes in the object to be measured 34 while maintaining high measurement accuracy.

Further, there is no need to use complicated circuit configurations such as modulation of light beams and demodulation of signals. Therefore, the manufacturing cost of the entire device can be reduced.

Furthermore, the storage command signal 4 is sent from the operation unit 45 at regular intervals.
6, the current-voltage converter 32a, 3
2b, measurement errors due to zero point fluctuations of the subtracter 39 and adder 40 can be suppressed to a minimum.

FIG. 3 is a block diagram showing a displacement measuring device according to another embodiment of the present invention. The same parts as in FIG. 2 are given the same reference numerals. In this embodiment, each current-voltage converter 38 a, due to the ambient light when the light beam 32 is turned off,
The output voltage v1 +v2 of 38b is input to each A/D converter 51a, 51b as a voltage storage means, and each A/D converter 51a, 51b is
D converter 51a.

51b, it is converted into a digital value and stored.

The signals are then input to (-) input terminals of each subtractor 53a, 53b via D/A converters 52a, 52b. The (+) input terminals of each subtractor 53a, 53b are connected to the light beam 3.
The voltage values Vl and V2 outputted from the current-voltage converters 38a and 38b during measurement during one irradiation are input. A subtracter 30 shown in FIG. 2 is provided after each subtractor 53a, 53b. An adder 40 is connected.

Even with the displacement measuring device configured in this way, the influence of ambient light and dark current of the position sensor is removed by each subtractor 53a, 53b, and the influence of the dark current of the position sensor is removed by the subtractor 39 of the next stage.
And from the adder 40, the correct voltage value (V+ -V2
), (vl +V2) are obtained. Therefore, it is possible to obtain substantially the same effects as in the previous embodiment.

FIG. 4 is a block diagram showing a displacement measuring device according to yet another embodiment of the present invention. The same parts as in the embodiment of FIG. 2 are given the same reference numerals. In this embodiment, sample and hold circuits 61a and 61b are connected to a subtracter 39 and an adder 40 as storage means. That is,
When the storage command signal 46 is input from the control unit 45, each sample-hold circuit 61a, 61b receives analog voltage values (vl - V2), (Vt +v2) output from the subtracter 39 and adder 40 due to ambient light. hold. Then, this multi-value is input to (-) input terminals of each subtractor 41a, 41b.

Even with a displacement measuring device configured in this way, the influence of ambient light and dark current of the position sensor is limited to each subtractor 4.
1a and 41b, it is possible to obtain substantially the same effect as the embodiment shown in FIG.

[Effects of the Invention] As explained above, according to the present invention, signals caused by the ambient light and the dark current of the position sensor when the light beam is not irradiated are stored, and the value of this signal is used when the light beam is irradiated. I am trying to subtract it from the value of . Therefore, the light receiving position at the time of irradiation with the light beam can be accurately determined, and changes in the position of the object to be measured can be accurately measured, and the response speed of measurement can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a displacement measuring device according to the present invention, FIG. 2 is a block diagram showing a displacement measuring device according to an embodiment of the present invention, and FIG. 3 is a diagram showing a displacement measuring device according to another embodiment of the present invention. FIG. 4 is a block diagram showing a displacement measuring device according to yet another embodiment of the present invention, and FIG. 5 is a block diagram showing a conventional displacement measuring device. 31... Laser light source, 32... Light beam, 33...
- Irradiation lens, 34... Object to be measured, 35... Condensing lens, 37... Position sensor, 38a, 38b
...Current voltage converter, 39...Subtractor, 40...
Adders, 41a, 41b, 53a, 53b---Subtractor, 42a. 42 b, 51 a, 5 l b/A/D converter, 43a. 43 b, 52 a, 52 b-D/A converter, 44...delay circuit, 45... operating unit, 49...
- Divider, 5o... Correction circuit, 61a, 61b...
Sample and hold circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (1)

[Claims] A light source that irradiates a light beam, an irradiation lens that projects the light beam onto an object to be measured to form a light spot on the object, and is arranged so that its optical axis is not parallel to the optical axis of the irradiation lens. a condenser lens that condenses reflected light from the object to be measured to form the light spot image; and a condenser lens that receives the light spot imaged by the condenser lens on a light receiving surface, and a position sensor that detects the light receiving position of the light spot on the light receiving surface that changes in response to a change in the position of the object; and a position sensor that detects the light receiving position of the light spot on the light receiving surface, which changes in response to a change in the position of the object. A displacement measuring device comprising a calculation means for calculating a change, wherein the calculation means includes a storage means for storing a signal output from the position sensor when the light source is not outputting, and a storage means for storing a signal output from the position sensor when the light source is not outputting, subtraction means for subtracting the signal stored in the storage means from the signal output from the sensor;
A displacement measuring device comprising: position calculating means for calculating the position of the object to be measured from the light receiving position obtained by the subtracting means.