JPH06281453A - Optical displacement sensor - Google Patents

Abstract

PURPOSE:To reduce the number of connecting cables in a separate type optical displacement measuring device in which a sensor member and an amplifier member are separated. CONSTITUTION:A square wave generating circuit 11 and a current source 37 driven by the output of the circuit 11 are provided to an amplifier member 32. A pulse signal is fed from the current source 37 to a sensor member 31. In the sensor member 31, the pulse signal is used as the power source of each block. A projection element 13 is driven to make the adding value of the outputs at both ends of a photodetector 15 constant. When the adding value (VA+VB) of the light receiving level is made constant, the distance signal to an object body is obtained from one side output (VB). Consequently, in the amplifier member 32, the distance signal is output depending on the above output. When the current value fed from the current source 37 is small or large excessively, a warning signal is output by using a comparison circuit 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement sensor which projects light onto a light measuring area and measures the distance to an object based on the light receiving position.

[0002]

2. Description of the Related Art A conventional optical displacement sensor is a sensor section having a light projecting section and a light receiving section for irradiating light to an object detection area, and an amplifier for giving a light projecting pulse signal to the light projecting section and processing the light receiving signal. An amplifier-separated optical displacement sensor in which a part is separated is generally used. FIG. 3 is a block diagram showing a configuration of such a conventional amplifier-separated optical displacement sensor, in which a sensor unit 1 and an amplifier unit 2 are connected by a cable 3. The cable 3 is a cable having at least five cores, that is, a power supply line 3a, a line 3b for transmitting a transmission pulse signal, lines 3c and 3d for transmitting a light receiving signal, and a ground line 3e. The amplifier section 2 has a square wave generating circuit 11 that oscillates a square wave signal having a predetermined period, and its output is given to a differential amplifier 12. The output of the differential amplifier 12 is input to the sensor unit 1 as a light emitting pulse signal via the line 3b of the cable 3.

The sensor section 1 is provided with a drive circuit 14 for driving the light projecting element 13 based on the light projecting pulse signal. The light projecting element 13 irradiates a parallel light beam toward the object detection area. Then, the light receiving element 15 that receives the reflected light of the light beam is arranged at a predetermined angle from the light projection axis (not shown). The light receiving element 15 is an element that can obtain different signals at a pair of output ends according to the distance to the object, and is, for example, a two-division photodiode or a position detecting element (P
SD). The current outputs at both ends of the light receiving element 15 are converted into voltage signals by the amplifier circuits 16 and 17, respectively, and input to the amplifier unit 2 side via the lines 3c and 3d. In the amplifier unit 2, an adder circuit 1 that adds these outputs
8 and sample and hold circuits 19 and 20 for sampling the output of the amplifier 17 and the addition output, respectively.
The output of the square wave generation circuit 11 is given to the timing circuit 21. The timing circuit 21 generates a timing signal immediately before the falling edge of the square wave pulse and supplies it to the sample hold circuits 19 and 20. The sample hold circuits 19 and 20 are sampled and held based on the timing signal of the timing circuit 21. The output of the sample hold circuit 19 is output as a displacement output to the object via the correction circuit 22. The output of the sample hold circuit 20 is input to the comparison circuit 23. The comparison circuit 23 compares predetermined threshold values Vref1 and Vref2 with the output of the sample hold circuit 20. If the held output is outside the predetermined range, normal position detection cannot be performed and an alarm signal is output. .

[0004]

However, such a conventional optical displacement sensor requires a cable having at least five core lines as the cable 3 for electrically connecting the sensor section and the amplifier section. Therefore, there is a drawback that the wiring is troublesome, and even when the connector is used to facilitate the wiring, it takes time to disconnect and connect when the user freely selects the length, which is expensive. It was

The present invention has been made in view of the above conventional problems, and it is technically possible to reduce the number of connecting cables between the sensor section and the amplifier section without complicating the structure. It is an issue.

[0006]

The invention according to claim 1 of the present application is an optical displacement sensor in which a sensor section and an amplifier section are separated, and these are connected via a cable. An element and a light projecting unit that has a drive circuit that drives the light projecting element so that the light quantity level is based on the light projecting control signal at the timing when the light projecting pulse signal is obtained, and projects a light beam toward a detection region. And a light receiving section having light receiving elements which are arranged so as to intersect at a constant angle from the optical axis of the light projecting section and which receive reflected light from an object and give different outputs to both ends depending on the irradiation position, and both ends of the light receiving section. And a differential circuit that takes the difference between the output of the adding circuit and the input pulse signal and gives it to the light projecting section as a light projecting control signal. Power source of The amplifier unit includes a pulse generation circuit that generates a light emission pulse signal and a current source that is driven by the pulse generation circuit and that supplies the light emission pulse signal to the amplifier unit via a cable. It is characterized in that the distance to the object is measured based on one of the outputs obtained from the section via the cable.

The invention of claim 2 of the present application is characterized in that the amplifier section is further provided with alarm output means for outputting an alarm output when the current output value of the current source is out of a predetermined range.

[0008]

According to the present invention having such a feature, the light emitting pulse is periodically generated by the pulse generating circuit of the amplifier unit, and the light emitting pulse is generated as the power source and light emitting timing signal to the sensor unit via the current source. Providing a signal. In the sensor section, the light projecting element is driven at the timing of this signal.
When the light projecting element is driven so that the added value of the outputs of both ends of the light receiving element becomes constant, the output of either one of the light receiving elements becomes the distance signal as it is. Therefore, the amplifier section determines the distance based on this signal. Further, according to the invention of claim 2 of the present application, since an accurate distance signal cannot be obtained when the current value of the current source in the amplifier is out of the predetermined value range, an alarm signal is output.

[0009]

1 is a block diagram showing the structure of an optical displacement sensor according to an embodiment of the present invention. The same parts as those in the conventional example described above are designated by the same reference numerals and detailed description thereof will be omitted. Also in this embodiment, the sensor unit 31 and the amplifier unit 32 are separated, and the line 33a of the cable 33 is provided between them.
~ 33c connect. The line 33 a is a line that supplies a light emitting pulse signal that also serves as a power source from the amplifier unit 32, and is connected to the power source terminal P of each unit of the sensor unit 31. The sensor unit 31 has a differential circuit 34 as illustrated. The differential circuit 34 takes the difference between this pulse signal and the addition output of the addition circuit 35, and outputs the difference signal to the drive circuit 36.
To give to. The drive circuit 36 drives the light projecting element 13 at a level based on this difference signal. Here, the light projecting element 13 and the drive circuit 36 are a light projecting unit that drives the light projecting element so as to reach the light projecting control signal level of the differential circuit 34 at the timing of the light projecting pulse signal. A light receiving element 15 such as a position detecting element is arranged at a position separated from the axis of the light beam emitted from the light projecting element 13 by a predetermined angle, and both ends thereof are connected to the amplifiers 16 and 17. Amplifiers 16 and 17
Are added by the adder circuit 35, and the added output is given to the differential circuit 34. The output of the one amplifier 17 is given to the amplifier section 32 via the cable 33b.

The amplifier section 32 has a square wave generating circuit 11 for generating a pulse signal of a square wave at a constant cycle, sample hold circuits 19 and 20 operated by its output, and a timing circuit 21 as in the conventional example. . The square wave output of the square wave generating circuit 11 is given to the current source 37.
The current source 37 is driven based on a square wave pulse, and supplies a pulse signal to the sensor unit 31 via the line 33a. The current value supplied from the current source 37 to the sensor unit 31 is converted into a voltage signal by the I / V converter 38. The I / V converter 38 gives a voltage signal corresponding to the current to the sample hold circuit 20.
The output of the square wave generation circuit 11 is given to the timing circuit 21. The timing circuit 21 generates a timing signal immediately before the falling edge of the square wave pulse, and the sample hold circuits 19 and 20 hold the voltage values input at this timing, and the correction circuit 22 and the comparison circuit 23 respectively.
Is given to. The signal held by the sample hold circuit 19 is converted into a signal proportional to the displacement to the object by the correction circuit 22 as in the conventional example. Comparison circuit 23
In the same manner as in the conventional example, an alarm signal is output by comparing with predetermined threshold values Vref1 and Vref2. I / V here
Converter 38, sample hold circuit 20, comparator 23
Constitutes an alarm output means for outputting an alarm signal when the current output value of the current source 37 is out of a predetermined range.

Next, the operation of this embodiment will be described with reference to a time chart. FIG. 2A shows the voltage waveform of the square wave oscillation signal of the square wave generating circuit 11, which drives the current source 37. FIG. 2B shows a current source 3
7 shows a pulse current waveform supplied from 7 to the sensor circuit 31, a solid line indicates a normal state in which the amount of received light is large, and a broken line indicates a state in which the amount of received light is small. Then, a differential value with respect to the addition output is calculated by the differential circuit 34, and the light projecting element 13 is driven by the drive circuit 36 so that the light amount level corresponds to this differential value. FIG. 2C shows the light amount level of the light projecting element. If the object is present in the detection area, the light receiving element 15 can obtain outputs having different levels at both ends according to the distance to the object. This current output is converted into a voltage signal by the amplifiers 16 and 17 and output. FIG. 2D shows the output of one amplifier 17. Then, these outputs are added by the adder circuit 35 and supplied to the differential circuit 34. Therefore, the light projecting element 13 is driven so that the added output becomes constant.

Here, the outputs of the amplifiers 16 and 17 are respectively set to V
Assuming _A and V _B , the displacement output to the object is V _B / (V
It is represented by _A + V _B ). However, in this embodiment, since the addition output V _A + V _B is controlled by the adder circuit 35 and the differential circuit 34 to be always constant, the output V _B of the amplifier 17 is directly used as a signal indicating the displacement to the object. Has become. This signal V _B is sent to the amplifier 32 through the line 33b.
Is input to the sample hold circuit 19. Figure 2 (e)
Is an S / H timing signal output from the timing circuit 21, and based on this signal, the displacement signal is continuously output from the sample hold circuit 19 as shown in FIG. 2 (f). This signal is converted into a signal proportional to the displacement by the correction circuit 22 and output as a displacement signal.

On the other hand, if the current value supplied from the current source 37 is too large or too small, sufficient control cannot be performed and a correct displacement signal cannot be obtained. Therefore, when the output of the sample hold circuit 20 is not within the range of the predetermined threshold value, the comparison circuit 23 outputs an alarm signal. In this way, the warning signal can be output when the amount of received light is small and the pulse current is too large, and when the amount of received light is large and the pulse current is too small. In this case, since it is only necessary to connect the sensor section and the amplifier section with a three-core cable, the configuration can be simplified.

[0014]

As described in detail above, according to the present invention, the number of lines of the cable connecting the sensor section and the amplifier section can be greatly reduced to three timings.
Therefore, there is an effect that the connection work becomes easy and the work of changing the length of the cable can be performed very easily.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical displacement sensor according to an embodiment of the present invention.

FIG. 2 is a time chart showing the operation of this embodiment.

FIG. 3 is a block diagram showing a configuration of a conventional optical displacement sensor.

[Explanation of symbols]

 11 Square Wave Generating Circuit 13 Light Emitting Element 15 Light Receiving Element 19, 20 Sample Hold Circuit 21 Timing Circuit 22 Correction Circuit 23 Comparison Circuit 31 Sensor Section 32 Amplifier Section 33 Cable 34 Differential Circuit 35 Addition Circuit 36 Driving Circuit 37 Current Source 38 I / V converter

Claims (2)

[Claims] 1. An optical displacement sensor, in which a sensor section and an amplifier section are separated and connected via a cable, wherein the sensor section is a light projecting element and a timing at which a light projecting pulse signal is obtained. A light projecting unit that has a drive circuit that drives the light projecting element so as to have a light amount level based on a light projecting control signal, and projects a light beam toward a detection region; and a constant angle from the optical axis of the light projecting unit. A light receiving unit having a light receiving element that receives reflected light from an object and gives different outputs to both ends depending on the irradiation position, and an adder circuit that adds outputs from both ends of the light receiving unit, A differential circuit that takes the difference between the output of the adder circuit and the input pulse signal, and gives it to the light projecting section as a light projecting control signal, and uses the light projecting pulse signal as the power supply for each section, The amplifier section Includes a pulse generating circuit that generates a light emitting pulse signal, and a current source that is driven by the pulse generating circuit and supplies a light emitting pulse signal to the amplifier unit via the cable. An optical displacement sensor, characterized in that the distance to an object is measured based on one of the outputs obtained from the light receiving section via the cable. 2. The optical system according to claim 1, wherein the amplifier section includes alarm output means for outputting an alarm output when the current output value of the current source is out of a predetermined range. Displacement sensor.