JPS63290907A - Distance measuring instrument - Google Patents

Abstract

PURPOSE:To prevent an error in measurement originating from temperature characteristics of a photodetector and the drift of a processing circuit by photodetecting reflected light beams form a body to be measured by a linear scanning type photodetection array and processing its photodetection signal digitally. CONSTITUTION:Spot beam light B from a light projecting means 2 is projected on the body 18 to be measured and its reflected light beams R is photodetected on a CCD 8 through a lens 7. Its photodetection signal is converted by comparators 10 and 11 into pulse trains. Counters 12 and 13 driven with the output of the comparator 10 and counters 14 and 15 are driven with the output of the comparator 11. An arithmetic circuit 16 calculates peak correspondence timing from inputs the counters 12, 13, 14 and 15. The arithmetic circuit 16 determines the triangle system consisting of the spot beam light B and lenses 5 and 7 according to the photodetection position and calculates and outputs the distance of the body 18 to be measured.

Description

[Detailed Description of the Invention] (a) Industrial Application Field This invention relates to the improvement of a distance measurement device using a one-dimensional scanning type light receiving device such as a CCD or BBD, and more specifically, to the improvement of distance measurement accuracy. The present invention relates to a distance measuring device equipped with a circuit configuration that enables dualization.

(B) Conventional technology Conventionally, the object to be measured is irradiated with a beam of light, the reflected light from the object is received by a light-receiving element, the light-receiving signal of the light-receiving element is processed, and trigonometry is applied to the object to be measured. As a distance measuring device for measuring the distance to an object, a device to which a one-dimensional scanning type light receiving array such as a CCD or BBD is applied (for example, Japanese Patent Laid-Open No. 57-2
11008) or a device to which a semiconductor device detection element (PSD) is applied (for example, Japanese Patent Laid-Open No. 57-44
(Refer to Publication No. 809 and Japanese Patent Application Laid-Open No. 175904/1983)
It has been known.

An example of a conventional distance measuring device to which a one-dimensional scanning type light receiving array is applied will be explained with reference to FIGS. 3 and 4. Reference numeral 22 denotes a light projecting means, which includes a light projecting element 24 such as an LED, and a lens 25 that converts the light of the light projecting element 24 into a beam and irradiates it onto the object to be measured 38 .

A part of the reflected light from the surface of the object to be measured 38 is transmitted through the lens 27, focused, and received on the CCD 2B. CCD2
After the light reception signal No. 8 is amplified by two amplifier circuits, it is input to a comparator 30 and converted into a pulse train. This pulse train is further counted by counters 32 and 33, and the distance to the object to be measured 38 is calculated based on the count result. CCD2B, counter 32.33,
A clock pulse from an oscillator 37 is input.

To explain in more detail the processing of the light reception signal of the CCD 28, the light reception signal of the CCD 2B has a mountain shape as shown in FIG. The comparator 30 has a threshold Th,
This light reception signal is converted into a pulse train as shown in FIG. The counter 31 counts the timing indicated by the solid line in FIG. 6, and the counter 32 counts the timing N2 (counts the number of clock pulses). Each pulse of the pulse train corresponds to each pixel in the light receiving state of the CCD 2B.

The arithmetic circuit 36 calculates the arithmetic mean N, (= (N, 1-N2)/2) of the quimmings N, , N,.

The pixels of the CCD 28 corresponding to this quimming N are:
This means that it is located at the center of the reflected light.

Furthermore, the arithmetic circuit 36 uses the lens 25, 27 and the light projecting device 22 based on the position of this pixel on the CCD 28.
The triangle formed by the beam light is determined, and the distance to the object to be measured 38 is determined.

FIG. 5 is a block diagram showing an example of processing of another CCD light reception signal. The light reception signal of the CCD 48 is sent to an amplifier circuit 49.
After being amplified by the sample and hold circuit 50, the light reception signal of each pixel is stubbornly held. This held light reception signal is sent to an analog/digital (A/D) converter 51
The signal is converted into a digital signal and input to the signal processing circuit 52. The signal processing circuit 52 processes these digital signals to determine the peak, and from the position of the 18 pixels of the CCD corresponding to the peak, applies trigonometry as before to determine the object to be measured. It measures distance. In addition,
As before, CCD4B, sample hold circuit 50, A/
The D converter 51 and the signal processing circuit 52 include an oscillator 5.
3 clock pulses are input.

(c) Description of problems to be solved by the invention In the case of the distance measuring device shown in FIG.
There is no problem if the received light signals of No. 8 are symmetrical as shown in FIG. However, in reality, due to the coma aberration of the lens 27, the received light signal of CC028 becomes left-right asymmetrical as shown by the solid line in FIG. 6 (in addition, in FIG. 6, the received light signal of each pixel is shown by the envelope line). Therefore, there is a problem that the value of N does not match the actual bead position P, resulting in an error in distance measurement, and in order to correct this, the arithmetic circuit becomes complicated.

On the other hand, in the case of the distance measuring device shown in FIG.
Since the /D converter 51 is used, the frequency of the clock pulse cannot be increased, resulting in a slow response. In addition, as shown by the broken line in FIG.
When the 4B light reception signal becomes saturated, it becomes difficult to determine the peak, and there is a problem that the distance measurement accuracy decreases.

On the other hand, in a distance measuring device using PSD, since the PSD light reception signal is an analog signal, the PSD
Due to the temperature characteristics of itself and the drift of the light receiving signal processing circuit,
There was a problem that caused errors in distance measurement.

The present invention has been made in view of the above, and aims to provide a distance measuring device with a simple circuit configuration, high distance measuring accuracy, and excellent responsiveness.

(d) Means for Solving the Problems The configuration of the distance measuring device of the present invention will be explained with reference to FIG. 1 corresponding to the embodiment. a light projection means 2 for projecting beam light B;
An optical system 7 focuses the reflected light R of the beam B on the object to be measured 18 and causes each pixel of the one-dimensional scanning light-receiving array 8 to receive the light, and converts the light reception signal of the one-dimensional scanning light-receiving array 8 into a pulse train. , at least a first comparator 10 and a second comparator 11 having different threshold values, , L2;
Start timing T1, TPI and end timing TP, T of the pulse train output from these comparators 10, 11
A plurality of counters each counting 4 12.13.
14.15, a coordinate system (TPL) whose coordinates are the level L and timing T of the light reception signal of the one-dimensional scanning light reception array 8.
Points (TI, L,) and ('r1, , r1, ) in
The T coordinate of the intersection of the straight line connecting points (Tz, L,) and (T4, L2) is defined as peak corresponding timing TP, and this peak corresponding timing T1. an arithmetic circuit 16 that determines the light receiving position of the one-dimensional scanning light-receiving array 8 and calculates the distance to the object to be measured 18 by trigonometric calculation;
15, and a synchronization signal generation circuit 17 that sends a synchronization signal to 15.

(E) Function The 34-distance measurement device of the present invention uses a one-dimensional scanning light receiving array to scan and receive the reflected light from the object to be measured, and digitally processes the received light signal, so the temperature characteristics of the light receiving element and There is no risk of measurement errors occurring due to drift in the processing circuit for the received light signal.

Further, the distance measuring device of the present invention will be explained using FIG. 2 corresponding to the embodiment. In the coordinate system (TPL),
The envelope line of the light reception signal of the one-dimensional scanning type light reception array 8 is the second
This is represented by curve C in the figure.

When %C is cut in this song by two thresholds LI and L2, a straight line L connecting points (TP1, L,), (T3, L2) and points (T2, r-1), ( T4, L.

) and the intersection point ('rp, LP) with the straight line 12.
P substantially matches the peak P of the curve C even if the curve C is asymmetrical. Therefore, if this TP is used as the peak corresponding timing, it becomes possible to measure distance with higher accuracy than before.

These points ('r1, Ll), (T3, Lz), (
The determination of T2, L+), (T4, Lz) and TP can be obtained using at least two comparators, a plurality of counters, and an arithmetic circuit as described above, and the circuit configuration of the distance measuring device can be simplified. It can be done.

Further, in the distance measuring device of the present invention, there is no need to convert the light reception signal of each pixel of the one-dimensional scanning optical array into a digital signal, making it possible to speed up the processing time.

(F) Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram illustrating the optical system and circuit configuration of the distance measuring device according to the embodiment. Reference numeral 2 denotes a light projection means for projecting the spot beam B onto the object 18 to be measured. This light projecting means 2 is composed of a light projecting element 3 made of a light emitting diode or the like, a drive circuit 4 that drives the light projecting element 3, and a lens 5 that converts the light from the light projecting element 3 into a spot beam B. ing.

Note that the design of the light projecting means can be changed as appropriate, such as a laser diode or a gas laser light source.

A lens (optical system) 7 is provided adjacent to the lens 5. The lens 7 focuses the reflected light R from the object to be measured 18 and causes each pixel of a CCD (one-dimensional scanning type light receiving array) 8 to receive the light. That is, a spot image of the light on the object to be measured 18 is formed on the CCDB. Note that a pinhole can be used instead of the lens 7, and the design can be changed as appropriate.

The light reception signal of the CCD 8 is amplified by an amplifier circuit 9 and then input to comparators 10 and 11, respectively. Comparator 10 uses threshold value L1 to
The light reception signal of D8 is converted into bulk and column data (see also FIG. 2). On the other hand, the comparator 11 has a threshold r-2 (>r
-1) converts the light reception signal of the CCD 8 into a pulse train.

The output pulse train of the comparator 10 is sent to the counter 12.1.
3 will be done manually. Further, the output pulse train of the comparator 11 is input to counters 14 and 15. Clock pulses from an oscillator (synchronizing signal generating circuit) are input to these counters 12, 13, 14, 15 and CCD 8.

The count results at counters 12, 13, 14, and 15 are:
The signal is input to the arithmetic circuit 16. This arithmetic circuit 16 performs arithmetic processing, which will be described later, to calculate and output the distance of the object to be measured.

Next, the operation of this embodiment distance measuring device will be explained.

Spot beam light B from the light projecting means 2 is projected onto the object to be measured on the 1st. The reflected light R from the object to be measured 18 is
The light is focused by the lens 7 and received on the CCDB. C
As shown in FIG. 2, the light reception signal of CD8 is represented by a curve C in the orthogonal coordinate system (TPL) of timing T and light reception signal level I7. This curve C is an envelope of light reception signals of individual pixels of the CCD 8, and in this case, it has a left-right asymmetric shape due to coma aberration of the lens 7.

The comparator 10 converts the received light signal of the CCD 8 into a pulse train based on the threshold value. Figure 2 shows the envelope of this pulse train, but of course individual pixels (
The level of the received light signal is equal to or higher than the threshold value L2. The converter 11 similarly converts the light reception signal of the CCD 8 into a pulse train. Since the threshold L2 is larger than the threshold L1, the convergence rate 1
The length of the pulse train of the comparator 10 is shorter than that of the comparator 10.

The counter 12 counts the start timing T1 of the pulse train of the comparator 10, and the counter 13 counts the end timing T2 of the pulse train. On the other hand, counter 14.1
5 counts the start timing T3 and end timing T4 of the pulse train of the comparator 11, respectively.

Note that the starting end and the ending end are concepts for identifying one end and the other end of a pulse train.

Counter result T1 at counter 12.13.14.15
, T2, T3, T4 and the threshold value of comparator 10.11, , L2, four points are determined in the orthogonal coordinate system (TPL). That is, the point (TP, L,
), (T3, L2), (T2, Ll), (T4, L,
). TP of the intersection point ('rp, +, r) of the straight line p, 1 that connects the points (T1, Ll) and (T4, L2), and the straight line P2 that connects the points (T2, L,) and ('r4, L2) is This is the timing for peak response.

The straight line ρ1 is L = a T -1-b -・-
---(Ia) TP-TJ TP-T.

It is expressed as -, the straight line C2 is L--r, T + d ・--
- (2a) Represented by TP-T4. The peak-corresponding timing TP is denoted by -C.

The arithmetic circuit 16 calculates -1- (1b), (1c
), (2b), (2c), and (3), the peak corresponding timing T1 is calculated.

Furthermore, the arithmetic circuit 16 calculates this peak corresponding timing T.
From P, the center position of the light receiving spot on CCDa is determined.

Even if the light reception signal of the CCD 8 is a horizontally asymmetrical curve C, the peak corresponding quimming TP substantially coincides with the peak P of the curve C.

Of course, if the curve C is symmetrical, the peak corresponding timing TP coincides with the peak P of the curve C. Therefore, the light receiving position on the CCDB can be determined more accurately than before. In addition, as shown by the broken line C″ in FIG.
Even when the light reception signal of D8 is saturated, the peak corresponding quimming TP can be calculated and the light reception position can be accurately determined.

The arithmetic circuit 16 generates a spot beam B from the light receiving position.
, a diagonal system constituted by lenses 5 and 7 is determined, the distance to the object to be measured 18 is calculated, and this is output.

In the above embodiment, two converters are used, but three or more converters each have a threshold value. ! It is possible to use a configuration using two comparators. In this case, if an output pulse train is obtained, it is preferable to count the respective output pulse trains of the comparator having the highest threshold value and the comparator having the lowest threshold value, and calculate the peak-corresponding quimming TP. because,
This is because the larger the difference between the threshold values of the two comparators, the closer the obtained peak-corresponding timing TP can be to the beat P of the received light signal.

(g) Effects of the invention As explained above, the distance measuring device of the present invention has the following advantages:
This method has the advantage that the peak of the light reception signal of the dimensional scanning type light reception array can be accurately determined, and the accuracy of distance measurement can be improved. Further, there is no need to digitally change and process the light reception signals of each pixel of the one-dimensional scanning light receiving array, and there is an advantage that excellent responsiveness can be achieved. Furthermore, it has the advantage that the circuit configuration can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the optical system and circuit configuration of a distance measuring device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of the distance measuring device, and FIG. 3 is a block diagram for explaining the operation of the distance measuring device. , a block diagram for explaining the optical system and circuit configuration of a conventional distance measuring device, FIG. 4 is a diagram for explaining the operation of the conventional distance measuring device, and FIG. 5 is a diagram for explaining the operation of the conventional distance measuring device. FIG. 6, a block diagram for explaining the circuit configuration, is a diagram for explaining problems with the conventional distance measuring device. 2: Light projection means, 7: Optical system. 8: CCD, 10・11: Comparator 12・
13/14/15: Counter. 16: Arithmetic circuit, 17: Oscillator. 18: Object to be measured, B Nisbon) Beam light. OR: Reflected light.

Claims (1)

[Claims] (1) A one-dimensional scanning light receiving array, a light projecting means for projecting a beam of light onto an object to be measured, and each pixel of the one-dimensional scanning light receiving array by concentrating the reflected light of the beam light on the object to be measured. an optical system for receiving light; at least a first comparator and a second comparator having different threshold values L_1 and L_2, respectively, for converting the light reception signal of the one-dimensional scanning light receiving array into a pulse train; a plurality of counters that calculate start timings T_1, T_3 and end timings T_2, T_4 of the pulse train output from the comparator and the second comparator, respectively; and the level L and timing of the light reception signal of the one-dimensional scanning light reception array. A point (
A straight line connecting T_1, L_1) and (T_3, L_2),
The T coordinate of the intersection of the straight line connecting the points (T_2, L_1) and (T_4, L_2) is set as the peak corresponding timing T_P,
an arithmetic circuit that determines the light receiving position of the one-dimensional scanning light-receiving array from this peak corresponding timing T_P and calculating the distance to the object to be measured by trigonometry; A distance measuring device comprising a synchronization signal generation circuit that sends a synchronization signal.