JPS5918673B2 - distance detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a distance detector that can be effectively used in robot systems and the like.

Various kinds of distance detectors have been proposed in the past, including electromagnetic detectors, pneumatic detectors, and optical detectors.

However, electromagnetic detectors have the disadvantage that the target objects for distance detection are limited to electromagnetic induction objects, and the range of detection distance is up to several III meters, while pneumatic detectors have the disadvantage of being large in size and , has the disadvantage that the detectable distance is extremely short.

Furthermore, optical detectors detect distance by combining a pair of light-emitting elements and light-receiving elements with a lens system, but the equipment is complicated, the detection operations are troublesome, and short distances cannot be detected. There are drawbacks.

Therefore, it is an object of the present invention to provide a distance detector with a simple structure that does not have the above-mentioned drawbacks.

This invention will be explained below.

The present invention relates to a distance detector that uses phase information, and the present invention relates to a distance detector that uses phase information.
A light emitting device is provided, and a light receiving device is located on the same straight line as these two light emitting devices and receives the light emitted from the two light emitting devices by reflecting it on the surface of the target object, and the power of the light received by the light receiving device is The distance between the light receiving device and the surface of the target object can be detected from the phase difference between the signal (the light receiving device outputs an output signal in proportion to the power of the light hitting the light receiving surface) and the above repetitive signal. be.

FIG. 1 shows an embodiment of the present invention, in which numerals 1 and 2 are light emitting diodes (for example, GaAs-LED) that emit highly diffused and uniformly spreading light, each with a phase difference of 90°. It is driven by two repetitive signals that are shifted from each other.

A phototransistor 4 as a light-receiving element with strong directivity is provided in the middle of the mounting plate 3 where these light emitting diodes 1 and 2 are attached, and in front of the phototransistor 4 is a target whose distance X is to be detected. There is object 5.

Here, among the irradiated lights from the light emitting diodes 1 and 2, only the light that is diffusely reflected by the surface P of the target object 5 is received by the phototransistor 4, and in consideration of filtering in the signal processing stage, the fundamental frequency Considering only the components, it is sufficient to consider that the brightness of the light emitting diodes 1 and 2 changes periodically with a sine wave and a cosine wave.

Therefore, the brightnesses G1 and G2 of the light emitting diodes 1 and 2 can be expressed as if A and B are constants, and the contributions L1 and L2 by the light emitting diodes 1 and 2 at point P on the surface of the target object 5 are If the reflectance of the object 5 is C, then the above equation 2) becomes the following equation.

Here, the brightness LP of point P is LP=L1+L2...
- Since it is expressed as (6), if we substitute equation (5) into this, we end up with the following.

However, D=CX7 and ;7E5777-43-1...
(8) Ba2+x2-L ψ=tan "" 1 () 2...
...(9) A b2+X2.

As is clear from equations (7) to (9), the phase ψ is a function of only the distance X (A, B, a, and b are constants) and is influenced by the reflectance C of the surface of the target object 5. do not have.

Therefore, if the brightness LP at point P is detected by the photodiode 4 and the phase difference ψ between the two lights is determined, the distance X can be measured conversely from this.

Note that the brightness L at eight points of the photodiode 4 that receives light is proportional to the brightness LP at point P, and if the proportionality constant is K, then L, 1 diode·LP...・((埒), and does not affect the phase ψ of the above η equation.

Regarding the sizes of a and b in FIG. 1, distance measurement cannot be performed in principle when a=b holds.

Also, to measure the distance to a nearby object, the size of b is a
However, in order to measure the distance to a distant object, it is desirable that the size of b be as far away from the size of a as possible.

However, there will be problems with light intensity and noise, so there is no point in placing them too far apart.

Therefore, in principle, it is possible to measure distances between a and b.

In addition, in practical terms, 115≦ga≦3 It is desirable that , and the optimal value is 1/4≦%≦false It will be about.

Here, a specific circuit example is shown in FIG. 2 and explained.
The output of an oscillator 10 that oscillates a 50 Hz rectangular wave is input to a light emitting diode 1 and also to a light emitting diode 2 via a phase shifter 11.

In the phase shifter 11, the phase is advanced (or delayed) by 90 degrees, and the light emitting diodes 1 and 2 are driven to emit light using rectangular wave repetition signals corresponding to sine and cosine, respectively.

3A shows an example of the brightness at point P due to light emitting diode 1, and FIG. 3B shows an example of the brightness at point P due to light emitting diode 2.
This shows an example of the brightness of a point, and in this case P
The brightness of the points is combined and becomes stepwise as shown in Figure 3C.

Such step-like brightness is photoelectrically detected by a phototransistor 4, amplified by an amplifier 12, harmonics and subharmonics are removed by a bandpass filter 13, and the resulting sine wave is converted into a sine wave by an automatic gain circuit (AGC) 14. The signal maintained at a predetermined level is input to the phase difference detection circuit 20.

A reference rectangular wave from the oscillator 10 is input to the phase difference detection circuit 20, and a phase shift with respect to this reference rectangular wave is detected.

Specifically, the sine wave output of the automatic gain circuit 14 is converted into a rectangular wave with the O level as a threshold by a rectangular wave conversion circuit (for example, a comparator) 21, and this rectangular wave signal is multiplied by the reference rectangular wave from the oscillator 10. A circuit 22 performs multiplication and obtains a phase difference from the product signal.

The phase difference signal obtained in this way is sent to the display device 30, where the phase difference is converted into a distance and the distance is displayed, and the distance signal is separately processed as required.

Here, the calculated value of the phase shift when the distance X is changed from 1 cIrL to 10 cIrL is shown in FIG. 4.

The figure shows that constants A and B in equation 1) above are equal, and a=
In the case of 1cIIL, the characteristic ■ is b = 1 crt
t.

Characteristic ■ is b = 2 crrL, characteristic ■ is b = 3
crn, characteristic ■ is b = 4 cm, characteristic V is b = 5c
The case of IrL is shown respectively.

Furthermore, when the actual phase shift is compared with the calculated value, the result is as shown in FIG.

In the figure, the characteristics marked with ○ are a-1crIL, b=3crf
In the case of L, the characteristic X mark is a=IC7FL, b=4c
This is the case with F71.

Furthermore, the distance X was calculated using the phase shift and compared with the actual distance X, as shown in FIG. 6.

Here, the circle mark in Fig. 6 indicates a=1cIIL, b=3
In the case of cIIL, the X mark is a=1cIIL, b=4
This is the case for cIIL.

In the case of the embodiment shown in FIG. 1, vertical reflected light may not be obtained depending on the inclination of the surface of the target object 5, which may affect the detection accuracy.

However, if the light emitting diodes 1 and 2 and the phototransistor 4 are arranged vertically as shown in FIG.
Since the reflected light can always be received in the right angle direction from the surface of the target object 5, the above-mentioned problems are solved.

Note that the distance in this case can also be easily converted into the position of the phototransistor 4.

As described above, according to the distance detector of the present invention, the measured value does not depend on the surface reflectance of the target object, and the device is small, lightweight, and inexpensive, and signal processing is easy.

Therefore, in addition to being applicable as a proximity sensor for a robot band, it can also be used as a three-dimensional information detector in object recognition.

Note that although a light emitting diode is used as the light emitting element and a phototransistor as the light receiving element in the above description, it is also possible to use other elements, and the repetitive signal for driving the light emitting element may be a triangular wave or the like in addition to a rectangular wave. is also possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a specific example of the circuit, FIGS. 3A, B, and C are diagrams showing the phase relationship between light emission and light reception, and FIG. The figure shows the calculated value of the phase shift with respect to the distance 1.2...Light emitting diode, 3...Mounting plate, 4...Phototransistor, 5...・
...Target object, 10... Oscillator, 11...
...Phase shifter, 12...Amplifier, 13...
・Band pass filter, 14... Flow gain circuit,
20... Phase difference detection circuit, 21... Rectangular wave conversion circuit, 22... Multiplication circuit, 3'0...
...Display device.

Claims (1)

[Claims] 1. A light-receiving device; and 2. A light-receiving device, which is provided at asymmetrical positions on the same straight line with respect to the light-receiving device, and emits light with two repetitive signals that are 90° out of phase, and illuminates the surface of the target object. a distance between the light receiving device and the surface of the target object based on the phase difference between the reflected light from the surface of the target object received by the light receiving device and the repetitive signal for the light emission; A distance detector characterized in that it is capable of detecting.