JPS5912146B2 - distance detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention emits sinusoidally modulated light toward a moving body, receives a combined signal light of the reflected signal light and a reference signal light obtained from a part of the transmitted signal light, The present invention relates to a distance detection device that measures the distance to a moving object from changes in the received amplitude.

Conventionally, devices that measure distance using sinusoidal modulated light,
It transmits modulated light toward a reflective object, receives a portion of the modulated light that is reflected from the reflective object, and detects the phase difference between the transmitted and received signals to determine the distance to the reflective object. However, when calculating the phase difference, the reference signal that serves as the reference signal phase and the above received signal were processed in separate electronic circuits and the phases were compared, so phase fluctuations such as phase drift that occur in each electronic circuit part This caused poor measurement accuracy.

These drawbacks are due to the measurement principle whether the reflecting object is stationary or moving.

As a system that eliminates these drawbacks, there is a distance detection device that receives a composite signal light of a reference signal light and a reflected signal light from a reflecting object.

FIG. 1 is a block diagram showing the configuration of a conventional device for measuring the distance of a moving object using this method.

In FIG. 1, a light emitting element 2, a light receiving element 8, a moving body 4, and a reflecting mirror 5 are installed at positions forming an angle of 90 degrees to each other with a beam splitter 1 in between.

When the optical system is configured in this way, the light emitting element 2 is intensity-modulated using the drive circuit 7 based on the signal from the sine wave oscillator 6.
A part of the emitted light is reflected by a reflecting mirror 5 provided opposite to the light receiving element 3, and enters the light receiving element 3 as a reference signal light serving as a reference for the signal phase.

Further, in the above optical system, the light receiving element 3 receives a composite signal light of the reference signal light and the reflected signal light from the moving object 4, and the received composite signal is amplified by the amplifier 8. After that, the signal is detected by a wave detector 9, and the level meter 10 reads the signal level.

In this case, the combined received signal light R8 is the reference signal light fi
is the vector sum of and the amount of reflected signal light from the moving object 4,
As shown in FIG. 2a, the amplitude R8 of the combined received signal light moves on the circumference α in the figure in response to changes in the distance to the moving object.

Further, since the phase fluctuation occurring in the receiving circuit portion contributes equally to both Ri and Rr, R8 only moves on the circumference β in the figure and no amplitude fluctuation occurs.

In other words, this shows that the influence of phase fluctuations occurring in the electronic circuit section can be automatically removed, and in this case, the relationship between the distance l to the moving object 4 and the amplitude R8 of the combined received signal light is shown in Fig. 2b. The amount of change Δl in distance can be determined by measuring the amount of change ΔR8 from the calibrated reference amplitude as shown in FIG.

However, in the distance detection device described above, since the light intensity of the reference signal light is kept constant, it is inevitable that the light intensity of the reflected signal light will fluctuate, especially in the case of a moving object, and the received amplitude of the composite signal light will be the true value. Therefore, there was a drawback that the measurement accuracy could not be increased in principle.

That is, as shown in FIG. 2c, the reflected signal light Rr moves on the circumference α from point P to point Q as the distance changes, but at this time, the amount of reflected signal light received by the light receiving element changes. Then, the reflected signal light changes to Ri or 1pRr''.

Therefore, the received amplitude R8// of the composite signal light is the true value R8//
deviate from

Such changes in the amount of reflected signal light always occur due to changes in the reflectance of the moving object and changes in light transmittance due to the conditions of the space in which the signal light propagates, such as fog, rain, and atmospheric fluctuations. Therefore, conventional devices using this method had poor measurement accuracy.

In order to eliminate these drawbacks, the present invention detects the amount of reflected signal light from a moving body, and based on the detected signal, a beam splitter is installed to face the light receiving element. The amount of reference signal light incident on the light receiving element is controlled by changing the position of a ring-shaped reflecting mirror, and will be described in detail below with reference to the drawings.

FIG. 3 is a vector diagram showing the measurement principle of this invention.

In FIG. 3, it is assumed that a point P on the circumference α is used as a distance reference, and that the moving object moves from that position to a point Q, and the reflected signal light changes from Rr to Ri.

At this time, it is assumed that the reflected signal light changes from Ri to Rr'' as the amount of reflected signal light changes.

In this case, when the light intensity of the reference signal light is changed from Ri' to Ri by the amount of change in the light intensity of the reflected signal light Rr', the phase of the combined signal light R8 at that time is Since the phase matches the phase of the composite signal light RSl when there is no change in the light amount, the influence of the light amount fluctuation of the reflected signal light can be removed.

At this time, multiplying the Rr' reception amplitude R8// of the combined signal light by (Ri,) yields R8', which is equivalent to directly reading the reception amplitude R8/.

The amount of change in distance can be determined from the difference between the amplitude R8 of the composite signal light and the distance reference.

FIG. 4 is a conceptual diagram for explaining the principle of detecting the amount of reflected signal light in this invention.

In FIG. 4, in order to simplify the explanation, it is assumed that the distance is constant and the amplitude Rr of the reflected signal light changes as shown in FIG. 4a.

At this time, the reference signal light (1, ~
When the light-receiving element is repeatedly turned on and off so that it is in the OFF state between t2) and the ON state between t2 and t3, the fourth light-receiving element
As shown in FIG. c, in the ON state, the combined signal light of the reference signal light and the reflected signal light is received, and in the OFF state, only the reflected signal light is received.

Therefore, in order to detect the amount of reflected signal light, the fourth d
As shown in the figure, the received light level in the OFF state may be selectively extracted.

FIG. 5a shows a ring-shaped reflecting mirror as a reflecting mirror for adjusting the amount of reference signal light in the present invention, and this reflecting mirror is simply a plane mirror with a hole.

When this ring-shaped reflecting mirror is moved in a direction perpendicular to the optical axis of the incident light, the amount of reflected light Ri changes as shown in FIG. 5b.

Therefore, by moving the installation position of the reflecting mirror, the light intensity of the reference signal light can be easily adjusted.

FIG. 6 is a block diagram of an apparatus configuration according to an embodiment of the present invention based on the above measurement principle.

In FIG. 6, 1 to 10 are the same as in FIG. 4
The light receiving element 3 receives a combined signal light of the reflected signal light from the moving body 4 and the reference signal light reflected by the ring-shaped reflecting mirror 5'.

At this time, the beam splitter 1 and the ring-shaped reflecting mirror 5'
An optical chopper inserted between
) When the light beam is repeatedly interrupted in step 11, the light receiving element 3 receives only the reflected signal light while the light beam is interrupted, and receives the reflected signal light and the reference signal light while the light beam is passing through. The combined signal light is repeatedly received.

The received signal obtained in this way is input to the analog switch circuit 12, separated into each component based on the synchronization signal from the optical chopper 11, and each signal is sent to the detectors q and 9".
Detect each wave.

Detector 9' taken out in synchronization with the cutoff state of the optical beam
The detected output signal is inputted to the arithmetic circuit 13, and compared with the reference signal generated by the reference signal generation circuit 14. Based on the signal, a ring-shaped The light intensity of the reference signal light is adjusted by moving the position of the reflecting mirror 51.

At the same time, the gain of the AGC amplifier 16 is controlled in proportion to the comparison signal from the arithmetic circuit 13, and the detection signal from the detector 9'' when the light beam enters the passing state is detected by the AGC amplifier 16. By inputting the signal to the amplifier 16 and reading its output signal level using the level meter 10, the amount of change in distance can be easily determined from the difference between the signal level and the signal level set as the distance reference value.

As described above, according to the present invention, it is possible to eliminate the influence of variations in the amount of reflected signal light caused by variations in the reflectance of a moving body, variations in reception efficiency due to spatial propagation, etc., thereby reducing measurement errors and increasing measurement accuracy. can do.

Another advantage is that the optical system has a simple configuration in which an optical chopper is inserted into a conventional device, and the amount of reflected signal light can be detected simultaneously.

Although the above description has been given of the case where the device according to the present invention is stationary and the distance is measured, the present invention is not limited to this. Needless to say, this method can also be applied to measuring the distance to a reflective object.

As described above, the distance detection device according to the present invention has an optical system that receives the reference signal light and the reflected signal light with one light receiving element, and uses an optical chopper to detect the transmitted signal light. The device configuration detects the amount of reflected signal light from the moving object by intermittent reference signal light taken out from a part of the moving object, and changes the amount of reference signal light based on the detected signal. The measurement accuracy is high because it eliminates the effects of fluctuations in the amount of reflected signal light that occur due to changes in reflectance, and the device can be easily operated and maintained because the amount of reflected signal light can be detected simultaneously. There are advantages.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of a conventional device that measures distance from the amplitude change of a combined received signal of a reference signal light and a reflected signal light from a moving object, and Fig. 2a shows a distance change of the combined received signal light. Figure 2b is a characteristic diagram showing the relationship between reception amplitude and distance, Figure 2c is a vector diagram showing the effect of variation in the amount of reflected signal light, and Figure 3 is a diagram showing the measurement principle of this invention. 4 is a conceptual diagram for explaining the principle of detecting the amount of reflected signal light, FIG. 5a is an outline diagram of the ring-shaped reflector, and FIG. 5b is the moving distance of the ring-shaped reflector and the amount of reflected light. FIG. 6 is a block diagram of the device configuration of an embodiment of the device of the present invention. In the figure, 1 is a beam splitter, 2 is a light emitting element, 3 is a light receiving element, 4 is a moving body, 5 is a reflecting mirror, C is a ring-shaped reflecting mirror, 6
7 is a sine wave oscillator, 7 is a drive circuit, 8 is an amplifier, 9. γ,
9" is a detector, 10 is a level meter, 11 is an optical chopper, 1
2 is an analog switch circuit, 13 is an arithmetic circuit, 14 is a reference signal generation circuit, 15 is a reflector moving device, and 16 is an AG
It is an amplifier with C. Note that the same or corresponding parts in the figures are indicated by the same reference numerals.

Claims (1)

[Claims] 1. Sine wave modulated transmission signal light emitted from a light emitting element is emitted toward a moving object, and the signal light reflected from the moving object is combined with a reference signal light obtained by extracting a part of the above transmission signal light. In a distance detection device that receives signal light and measures the distance to a moving object from changes in the reception double width,
A light emitting element, a light receiving element, a moving body, and a ring-shaped reflecting mirror are arranged through a splitter so as to make an angle of 90 degrees to each other, and an optical chopper is installed between the beam splitter and the ring-shaped reflecting mirror. The optical system is configured to detect the amount of reflected signal light from the moving body by inserting the ring-shaped reflector, and use the detected signal to move the installation position of the ring-shaped reflector to change the amount of the reference signal light. A distance detection device featuring: