JPH0335113A - Distance measuring instrument - Google Patents

Abstract

PURPOSE:To improve the distance measurement accuracy and to speed up its response by outputting a gain adjustment signal to a light projecting means or photodetecting means according to the result of fuzzy inference. CONSTITUTION:A light projecting element 12 is driven in response to the input of a pulse output to a light projecting circuit 40, and consequently the element 12 projects a light beam 16 toward an object 18 of detection. Then the photodetecting means and a position detecting element 22 receive the reflected light 24 of the beam 16 from the object 18 and sends a photodetection output corresponding to the photodetection position. Further, a differentiation circuit 50 differentiates the photodetection output of the photodetecting means 22 directly or indirectly. Further, a fuzzy control part 46 performs fuzzy inference by using the direct or indirect photodetection output of the photodetecting means 22 and the output of the means 50 to find the gain of the projecting means or photodetecting means for preventing the saturation of the photodetection output. The gain adjustment signal is outputted to the projecting means or photodetecting means according to the result to improve the distance measurement accuracy and speed up its response.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a light projecting means for driving a light projecting element in response to input of a pulse output to project a light beam toward a detection target;
Relating to a distance measuring device that measures the distance to the detection target based on the light reception output, including a light receiving means that receives reflected light of the light beam from the detection target and outputs a light reception output according to the light reception position. .

(Prior Art) FIG. 8 is a circuit diagram of a distance measuring device configured to measure the distance to a detection target based on a triangulation method according to a conventional example although it is not publicly known, and FIG. 3 is a timing chart of signals of various parts for explaining the operation of the distance measuring device.

This triangulation method is described in Japanese Patent Application Laid-Open No. 57-448.
Since it is also publicly known in No. 09, detailed explanation thereof will be omitted.

As shown in FIG. 8, the pulse oscillation circuit 2 to FIG. 9(a)
A trapezoidal signal S1 such as
and are given respectively. Based on the trapezoidal signal St from the pulse oscillation circuit 2, the comparison circuit 6 outputs a signal having a waveform as shown in FIG.
The gate signal S2 is generated and output as the gate signal S2. Further, the light projection control circuit 4 generates and outputs a triangular wave signal as shown in FIG. 9(C) as a light projection control signal S3 based on the trapezoidal signal Sl from the pulse oscillation circuit 2, and controls the light projection of this triangular wave. Signal S
3 to drive and control the light emitting element drive circuit 10.

The light projecting element drive circuit 10 drives the light projecting element 12 in response to the input of the light projecting control signal S3. The driven light projecting element 12 irradiates a light beam 16 toward a detection target 18 via a focusing lens 14 . The position detection element 22 detects the detection target via the condenser lens 20 which is placed at a predetermined distance from the condenser lens 14! The reflected light 24 of the light beam at 8 is received. The position detection element 22, which has received the reflected light 24, outputs different current outputs to both ends thereof depending on the receiving position of the reflected light with respect to the power supplied from the bias power supply 25.

In this case, as the receiving position of the reflected light 24 at the position detecting element 22 changes according to the distance from the focusing lens 14 to the detection target 18, the position detecting element 22 changes to the receiving position of the reflected light 24. Two different analog current outputs are output from both ends according to the voltage.

The I/V converters 26 and 28 convert the current outputs from both ends of the position detection element 22 into triangular wave position detection signals S5. After converting into S6 (voltage signal), each position detection signal S5. S6 is applied to a subtraction circuit 30 and an addition circuit 32, respectively. The output of the subtraction circuit 30 is applied to a comparison circuit 36 via a sample and hold circuit 34. A predetermined level Vrefl set by the user within the distance measurement range is set in the comparator circuit 36, and samples and samples exceeding the level Vrefl are set.
When the hold circuit 34 output is given, the sample
The output of the hold circuit 34 is applied to the AND gate 8a of the signal processing circuit 8, where it is processed as a distance measurement signal and then output to the output circuit 38. In the signal processing circuit 8, 8b is an integration circuit, and 8c is a comparison circuit set to a threshold level Vref3.

On the other hand, the output S6 of the adder circuit 32 which adds the respective outputs of both I/V converters 26 and 28 has a waveform as shown in FIG. 9(f), and its level is the threshold level V.
When ref2 is exceeded, the comparator circuit 40 outputs the signal from the comparison circuit 40 as shown in FIG. 9(g).
A light projection stop signal S7 as shown in is output.

That is, in this conventional example, since the output of the adding circuit 32 is kept constant, the output of the subtracting circuit 30 corresponds to the distance to the detection target 18. By processing the signal in the signal processing circuit 8 and outputting it to the output circuit 38, the distance to the detection target 18 can be measured.

(Problem to be Solved by the Invention) In the conventional distance measuring device having the above configuration and operation, when the reflective surface of the general detection target 18 has a reflective surface that diffusely reflects light, , the subtraction circuit 30 outputs each output S4. of both I/V converters 26, 28. The distance to the detection target 18 can be measured by performing the subtraction in S5, but when the reflective surface of the detection target 18 is a mirror surface, the position detection element 22
The current output of S4. of both 1/V converters 26.28 rises rapidly and saturates, resulting in the output S4.
As shown by the virtual lines in FIG. 9(d) and (e), S5 becomes sharply rising and saturated signals S4' and S5', and even if both signals 94' and S5' are subtracted, the detection target 1
Since it becomes impossible to obtain a subtraction value that accurately corresponds to the distance of 8, highly accurate distance measurement becomes impossible.

Furthermore, when the detection target 18 is far away, the amount of light received by the position detection element 22 is small, so in that case it is possible to increase the gain of the output of the position detection element 22. When the reflective surface is an oblique surface, the output from the position detection element 22 reaches saturation as described above, making it impossible to measure distance with high accuracy.

Furthermore, even if such a situation could be avoided, it would be difficult to improve the responsiveness of the circuit operation so as to quickly avoid it, for example, within one pulse output from the pulse oscillation circuit 2.

The present invention was made in view of these problems, and it is possible to prevent saturation of the light receiving output even if the reflective surface of the detection target is a mirror surface or even if the detection target is located at a long distance. The purpose of this invention is to make it possible to quickly measure the distance to a detection target with high accuracy and high responsiveness.

(Means for Achieving the Problem) In order to achieve such an object, in the distance measuring device of the present invention, a light beam is directed toward a detection target by driving a light projecting element in response to input of a pulse output. and a light receiving means that receives the reflected light of the light beam from the detection target and outputs a light reception output according to the light reception position, and the detection target is detected based on the light reception output. , a differentiating means for directly or indirectly differentiating the light receiving output from the light receiving means, and the direct or indirect light receiving output from the light receiving means and the output of the differentiating means according to a fuzzy rule. A gain of the light emitting means or a gain of the light receiving means that can prevent the saturation of the light receiving output of the light receiving means is fuzzy inferred, and a gain adjustment signal is provided to the light emitting means or the light receiving means based on the result of the fuzzy inference. It is characterized by comprising a fuzzy control means for outputting.

(Function) In response to human power outputting pulses to the light projecting means, the light projecting means drives the light projecting element, whereby a light beam is projected from the light projecting element toward the detection target.

The light-receiving means receives the reflected light of the light beam from the detection target and outputs a light-receiving output according to the light-receiving position. The differentiating means directly or indirectly differentiates the received light output from the light receiving means.

F. The agile control means uses the direct or indirect light reception output from the light reception means and the output of the differentiating means to control the gain of the light projecting means or the gain of the light reception means that can prevent saturation of the light reception output of the light reception means according to fuzzy rules. is fuzzy inferred, and a gain adjustment signal is output to the light projecting means or the light receiving means based on the result of the fuzzy inference.

As a result, in the present invention, when the detection target has a mirror reflective surface and the light receiving output from the light receiving means is saturated, the light is immediately emitted while applying one pulse output to the light emitting means. A gain adjustment signal for adjusting the gain of the means or the light receiving means can be outputted to prevent saturation of the light receiving output of the light receiving means,
As a result, it is possible to improve the accuracy of distance measurement and speed up its response.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram of a distance measuring device according to an embodiment of the present invention, in which parts that are the same as or corresponding to those of the conventional distance measuring device according to FIG. A detailed explanation of the portions indicated by the reference numerals will be omitted.

In FIG. 1, 2 is a pulse oscillation circuit, 12 is a light projecting element, 14 is a focusing lens, 16 is a light beam, 18 is a detection target, 20 is a focusing lens, 22 is a position detection element, 24 is reflected light, 25 is a bias power supply, 26.28 is an I/V converter, 30 is a subtraction circuit, 32 is an addition circuit, 40 is a light projection circuit consisting of the light projection control circuit 4 and the light projection element drive circuit 10 shown in FIG. 42 is the sample/hold circuit 34 in FIG.
Sample and hold circuit 34' described later, comparison circuit 36 in FIG. 8, comparison circuit 36' described later, signal processing circuit 8 in FIG. 8
and an output circuit 38.

However, in this embodiment, a sample-and-hold circuit 34' (not shown) similar to the sample-and-hold circuit 34 connected to the output stage of the subtraction circuit 30 is also connected to the output stage of the addition circuit 32. A comparison circuit 36' (not shown) is connected to the output stage of the sample-and-hold circuit 34', and both comparison circuits 36 and 36' are connected to an AND gate (8a) of the signal processing circuit 8, which performs calculations. It is provided within the output circuit 42.

In this embodiment, a comparison output circuit 44 is provided which compares the outputs from both [/V converters 26 and 28, respectively, selects one output having a higher level, and outputs it as Va. This comparison output circuit 44 has a circuit configuration as shown in FIG.
is the (-) terminal.

A first comparison circuit 44a to which the output VI2 of the other I/V converter 9 is applied to the (+) terminal, and one of the ■/V converters 8
A second comparator circuit 44 in which the output Vll of the 1/V converter 9 is given to the (+) terminal, and the output VI2 of the other 1/V converter 9 is given to the (-) terminal.
b, a first field effect transistor 44C1 whose gate is supplied with the output of the first comparison circuit 44a, and a second field effect transistor 44d whose gate is supplied with the output of the second comparison circuit 44C1. That is, of the outputs VII and VI2 of the I/V converters 8.9 applied to the comparison output circuit 44, for example, VIf is higher than VI2.
When it is larger than , the output of the first comparison circuit 44a decreases, so the first field effect transistor 44c turns on, and as a result, the output VII of the I/V converter 8 is output from the comparison output circuit 44. Of both outputs VI2,
The higher level one is output from the comparison output circuit 44 as Va.

Returning to FIG. 1, 46 is a fuzzy control unit to which the output Va of the comparison output circuit 44 and the output vb of the amplifier circuit 52, which will be described later, are respectively given, and 48 is the output V of the comparison output circuit 44.
50 is a differentiation circuit for differentiating the output of the sample and hold circuit 48, 52
is the fuzzy system 61114 by amplifying the output of the differentiating circuit 50.
6 as an output Vb.

The fuzzy control unit 46 uses the membership functions of the Ryokawa force Va and Vb shown in the fuzzy rules ≈ to ① in FIG. 3 and in FIGS. 4(a) and (b), respectively, and the fuzzy control unit 46 in FIG. The membership function of the output Vr (gain adjustment signal of the light projecting circuit 40) is stored, respectively. To explain the fuzzy rule in Figure 3, this fuzzy rule is if (antecedent part) ~ then (consequent part)
It is composed of multiple types of formats, five types in this example.

Va and Vb are the antecedent variables given from the comparison output circuit 44 and the amplifier circuit 52, respectively, V'' is the consequent variable, N L , NM, . . . P S , P M, P L
are the fuzzy label names of the fuzzy sets to which the antecedent variable and the consequent variable belong, respectively, NL is a negative small, and N
M is a fuzzy label name indicating negative medium, NL is negative large, PS is positive small, PM is positive medium, and PL is positive large.

The fuzzy control unit 46 stores membership functions in the membership function coordinate system of each of the antecedent variables Va and Vb, as shown in FIGS. 4(a) and 4(b). FIG. 4(a) shows the membership function 1k for the antecedent variable Va, and FIG. 4(b) shows the membership function for the antecedent variable vb. Furthermore, in FIGS. 4(a) and 4(b), the numerical values of the antecedent variables shown on the horizontal axis indicate voltages, respectively, NL, NM, . . .
Ps.

PM and PL each correspond to the membership functions illustrated below. Figure 5 shows the membership function for the consequent change vf, and the consequent variables shown on the horizontal axis each indicate voltage, NL, NM
, . . . PS, PM, and PL respectively correspond to the membership functions illustrated below.

The operation will be explained with reference to FIGS. 6(a), (b), and (c). 6(a) shows the output waveform of the light projecting circuit 40, and FIG. 6(b) shows the I/V conversion 1i526.2817) corresponding to the output of the light projecting circuit 40. The waveform of the output Va of the larger I/V converter 26 and 28 selected by the comparison output circuit 44 and FIG. 6(c) show the waveform of the output vb of the amplifier circuit 52, respectively.

In FIG. 6, during the period TI, the reflective surface of the detection target T8 is mirror-like and has an extremely high light reflectance, so the output Va is saturated (saturation voltage value 5V), and the output Vb also has a peak value of 6V. , the output Va is not saturated during the period T2 because the reflectance of the reflective surface of the detection target 18 is lower than in the case T1, but the target output value (for example, the voltage value of 3) is not saturated. ), and the output vb has a small peak value of 4V, in the period T3, the detection target 18 is far away, so the output Va is less than the desired value, and the output vb is almost zero. Each case is shown below.

Now, since the gain of the light projecting circuit 40 is large, the light projecting circuit 40 outputs a waveform with a large peak value as shown in the period TI in FIG.
4 outputs a peak value of output Va as shown in the period Tl in FIG. 6(b) and is saturated, while the amplifier circuit 52 outputs the output Va as shown in the period TI in FIG. 6(C). A peak value output vb is output. Then, in order to adjust the gain of the light projecting circuit 40 within this TI period (within one pulse output from the pulse oscillation circuit 2), the fuzzy control unit 46 adjusts the timing at an appropriate number of times within this TI period. Therefore, according to the input of each output Va, Vb, the membership function that matches the membership function corresponding to each fuzzy rule from FIGS. 4(a) and (b), respectively. Variable Va
, select the one with the smaller membership value of Vb MI
N operation), the fifth membership value is determined by this selected membership value.
yl of each fuzzy rule from the figure.

NL, NS, ...PS, PM for each of y2
.

Cut each membership function of PL. NL, NS, regarding Vf of all these cut fuzzy rules,
...The membership functions of PS, PM, and PL are superimposed (MAX operation) to obtain the final V' superposed membership functions.

By determining, for example, the center of gravity of this superposition membership function, Vf as a gain adjustment signal of the light projecting circuit 40 released from the mold is outputted from the fuzzy control section 46 to the light projecting circuit 40. And the same MIN-M as above for the second time.
AX calculation is performed, and the gain of the light projecting circuit 40 is adjusted so that the output Va is not saturated until the TI period ends. As a result, the gain-adjusted light projecting circuit 40 drives the light projecting element 12, the position detecting element 22 receives the reflected light 24 of the light beam 16 from the light projecting element 12, and the position detecting element 22 outputs The saturation of the output Va of the comparison output circuit 44 corresponding to the above is eliminated during the first pulse output period, and the distance to the detection target 18 can be measured accurately and quickly.

Incidentally, since the same applies to each period T2 and T3 in FIG. 6, the explanation thereof will be omitted. As a result, the light projecting circuit 40 adjusts the gain of the pulse output to the light projecting element 12, thereby preventing saturation of the light receiving output from the position detecting element 22 during one pulse output.

In this embodiment, the gain adjustment signal is transmitted to the light projecting circuit 40.
However, the same effect can be achieved by outputting the signal to the light receiving section side such as the position detection element 2 or I/V converter and adjusting its gain.

FIG. 7 is a circuit diagram of a distance measuring device according to another embodiment of the present invention, in which parts that are the same as or correspond to those in FIG. Explanation will be omitted.

A characteristic feature of the embodiment shown in FIG. 7 is that the comparison output circuit 44 is not provided, and the fuzzy control section 46 is supplied with the output Va from the addition circuit 32. The operation of the fuzzy control unit 46 in the distance measuring device shown in FIG. 7 is the same as that shown in FIG. 1, and therefore its explanation will be omitted.

Note that in the present invention, the outputs Va and Vb are compared and outputted by the output circuit 44.
Although it is obtained indirectly through the position detection element 22, it may also be obtained directly from the position detection element 22.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, even if the reflective surface of the detection target is a mirror surface, and even if the detection target is located at a long distance, the received light output does not saturate. It is now possible to quickly measure the distance to a detection target with high precision and high responsiveness without causing any damage.

[Brief explanation of drawings]

The figures relate to embodiments of the present invention; FIG. 1 is a circuit diagram of a distance measuring device according to an embodiment of the present invention; FIG. 2 is a specific circuit diagram of the comparison output circuit of FIG. 1; and FIG. FIG. 4(a) is a diagram showing the fuzzy rules stored in the fuzzy control unit shown in FIG.
(b) is a diagram showing the membership functions for the antecedent variables stored in the fuzzy control unit of FIG. 1, respectively;
FIG. 5 is a diagram showing membership functions for consequent variables stored in the fuzzy control unit, FIG. 6 is a timing chart for explaining the operation of the above embodiment, and FIG.
The figure is a circuit diagram of another embodiment of the present invention. FIG. 8 is a circuit diagram of a conventional distance measuring device, and FIG. 9 is a timing chart of signals of various parts to explain the operation of the conventional example. 2... Pulse oscillation circuit, 12... Light projecting element, 14.
... Focusing lens, 16... Light beam, 18... Detection target, 20... Condensing lens, 22... Position detection element, 24... Reflected light, 26.28... I/ V converter,
30... Subtraction circuit, 32... Addition circuit, 44...
Comparison output circuit, 46...Fuzzy control section, 48...
Sample/hold circuit, 50...Differential circuit, 52...
...Amplification circuit.

Claims (1)

[Claims] (1) A light projecting means that drives a light projecting element in response to input of a pulse output to project a light beam toward a detection target, and a light projector that receives reflected light of the light beam from the detection target; and a light receiving means that outputs a light receiving output according to the light receiving position,
A distance measuring device that measures the distance of the detection target based on the light receiving output, comprising: a differentiating means for directly or indirectly differentiating the light receiving output from the light receiving means; a direct or indirect light receiving output from the light receiving means; Using the output of the differentiating means, perform fuzzy inference on the gain of the light emitting means or the gain of the light receiving means that can prevent the saturation of the light receiving output of the light receiving means according to fuzzy rules, and calculate the light emitting means based on the result of the fuzzy inference. A distance measuring device comprising: fuzzy control means for outputting a gain adjustment signal to the means or the light receiving means.