JPH06258075A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To accurately measure a distance to an object to be measured irrespective of a quantity of a reflected light to be condensed by lighting a light emitting unit until an integrated output from a position detecting photoreceiver becomes a predetermined value or more, and calculating the distance to the object to be measured based on the integrated output becoming the predetermined value or more. CONSTITUTION:After an integration of an integrator 15 is initialized, an LED 5 is pulse-lit by a command from a light emission controller 11, and when an output of an adder 16 obtained through an A/D converter 18 is judged to be lower than IV, the LED 5 is again pulse-lit. When the output of the adder 16 is judged to be larger than the IV, a distance L to an object 2 to be measured from a distance measuring apparatus 1 is calculated based on digital voltage values of a sum (I1+I2) and a difference (I2-I1) of output currents I1, I2 obtained from the converter 18 and a numeric value of a distance stored in a ROM 12. Accordingly, it is integrated by an integrator 15 until an output of the adder 16 obtained through the converter 18 becomes 1V or more, and the distance L to the object 2 to be measured is calculated based on values of the currents I1, I2 becoming the predetermined value or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for measuring a distance to an object, and more particularly to a distance measuring device using a position detecting light receiving element.

[0002]

2. Description of the Related Art Conventionally, a light receiving element for position detection is used to
An apparatus for measuring the distance to an object based on the principle of angular measurement is proposed in Japanese Patent Laid-Open No. 2-276908.

FIG. 4 shows the principle of a distance measuring device of this type. Infrared light emitted from a light source 41 such as an LED is a projection lens
The object to be measured 45 is condensed and irradiated by the object 42, and the reflected light is condensed by the light receiving lens 43 onto the position detecting light receiving element 44.

Here, the distance from the light projecting lens 42 to the measuring object 45 is L, and the distance between the light projecting lens 42 and the light receiving lens 43 corresponding to the base line in the principle of triangulation is d, and the light receiving lens 43.
The distance px from the center of the optical axis of the light-receiving lens 43 to the position P of the spot light focused on the position-detecting light-receiving element 44 is given by the following equation. It

[0005]

[Equation 1]

Therefore, the position detection light receiving element 44 is used to calculate
The distance L to the measurement object 45 can be obtained by obtaining the displacement amount px of. Usually, the position-detecting light-receiving element 44 is provided with output electrodes 47 and 48 at both ends in the position-detecting direction of the image pickup surface 46 on which the spot light is imaged, and the position-detecting light-receiving element 44 is provided with the output electrodes 47 and 48 by the spot-light imaging. since the output current I _1, I ₂ from the output electrode 47, 48 generated in response to the imaging position, the current I _1, the light receiving position detection from the relationship I ₂ elements 44
The position of the upper spot light can be detected, and the distance L can be calculated from Equation 1.

However, in the above distance measuring device, when the distance to the measuring object 45 is long or the reflectance of the measuring object 45 is low, the amount of spot light reaching the light receiving element 44 for position detection is small. However, since the output currents I ₁ and I ₂ are both small, there is a possibility that the measurement error in detecting the image-forming position becomes large.

Therefore, recently, the light receiving element 44 for position detection is used.
Light source 41 so that the amount of spot light reaching
There has been proposed a method of controlling the amount of emitted light.

[0009]

However, in the above-mentioned light emission amount control, it is necessary to irradiate a high-intensity spot light with a high-output light source in order to accurately perform long distance measurement. This has led to an increase in the size of the distance device.

Further, when the object to be measured is a human, there is a possibility that high-intensity spot light directly enters the eyes of the human and causes a functional disorder of the eyes.

The present invention has been made in view of the above problems, and accurately measures the distance to a measuring object by a low-output light source regardless of the distance measuring distance and the reflectance of the measuring object. It is an object of the present invention to provide a distance measuring device that can do the above.

[0012]

According to the present invention, a light emitting means for irradiating an object to be measured with a constant output light beam, and a position detecting light receiving element arranged at a fixed distance from the light emitting means are provided. Condensing means for condensing the reflected light from the measurement object on the light receiving element for position detection, light emission control means for controlling lighting of the light emitting means, and integration for integrating outputs from the light receiving element for position detection Means and the integrated output from the integrating means becomes equal to or more than a predetermined value, the light emission control means performs the lighting operation of the light emitting means, and the integrated output from the integrating means is equal to or more than the predetermined value. And a control means for calculating the distance to the object to be measured.

[0013]

According to the present invention, the lighting operation of the light emitting means is performed until the integrated output from the position detecting light receiving element becomes a predetermined value or more, and the object to be measured is measured based on the integrated output which becomes the predetermined value or more. Since the distance is calculated, it is possible to accurately measure the distance to the object to be measured regardless of the amount of the reflected light focused on the position detecting light receiving element.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A distance measuring device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the distance measuring device of the present invention. In the figure, the distance measuring device 1 is provided with a light emitting unit 3 which outputs a light beam for irradiating the measuring object 2 and a light emitting unit 3 which are spaced apart from the measuring object 2 by a certain distance. The light receiving unit 4 receives light. Here, the light emitting unit 3 is a light emitting diode (LE that outputs a light beam of 10 mW).
D) 5 and a light projecting lens 6 that collects the light beam from the LED 5 on the measurement target 2, and the light receiving unit 4 collects the reflected light from the measurement target 2 and a collecting lens 7. A one-dimensional semiconductor position detecting element (one-dimensional PS) as a position detecting light receiving element on which the spot light from the optical lens 7 is imaged on the surface.
D) 8. Then, the light projecting lens 6 and the condensing lens 7 are arranged with a base line length d apart in the base line direction,
The image pickup surface of the one-dimensional PSD 8 is arranged at a position separated from the center of the condenser lens 7 by the focal length f thereof so as to be parallel to the base line direction.

As shown in FIG. 2, the one-dimensional PSD 8 has an image pickup surface 21 in the shape of a square with a length 2a, and output electrodes 22 and 23 are provided at both ends of the image pickup surface 21 in the position detecting direction. Then, due to the image formation of the spot light, the one-dimensional PSD 8 outputs the output current I ₁ from the output electrodes 22 and 23 in accordance with the image formation position.
Since I ₂ is generated, if the distance from the position B (center position) of the one-dimensional PSD 8 on the optical axis center of the condenser lens 7 to the image forming position P of the spot light in the position detection direction is px, then px is It is calculated by the formula. Here, when px is positive, the position in the direction of the output electrode 22 is set, and when px is negative, the output electrode 23 is set.
It represents the position in the direction.

[0017]

[Equation 2]

The output currents I ₁ and I ₂ generated in the one-dimensional PSD 8 by the image formation of the spot light on the image pickup surface 21 are the sum of the output currents I ₁ and I ₂ (I
₁ + I ₂ ) and a digital voltage of a predetermined level or higher corresponding to the difference (I ₂ −I ₁ ) and then the control circuit (CPU)
Entered in 10. Then, in the CPU 10, the digital voltage of a predetermined level or higher corresponding to the sum (I ₁ + I ₂ ) of the output currents and the difference (I ₂ −I ₁ ) is substituted into the above equation 2 and the distance p is substituted.
The distance x from the distance measuring device 1 to the measuring object 2 is calculated by calculating x and substituting the calculated result into the above mathematical expression 1.

Connected to the CPU 10 are a light emission control circuit 11 for controlling the lighting of the LED 5, an ROM 12 for storing the execution program of the CPU 10 and the numerical values of the distances a, f and d in advance. In this embodiment, the LED 5 is controlled by the light emission control circuit 11.
Is subjected to pulse lighting control for a lighting time of 100 μs, and changes in the current generated in the one-dimensional PSD 8 during the lighting are taken into the output processing circuit 9 as output currents I ₁ and I ₂ .

Here, the LED 5 is turned on in a pulsed manner, and the change in the current generated in the one-dimensional PSD 8 is output as the output currents I ₁ and I _2.
As a result, the current component generated in the one-dimensional PSD 8 due to the ambient light can be removed by taking it into the output processing circuit 9. Therefore, it is possible to accurately detect the image formation position on the imaging surface 21 by the reflected light from the measurement target 2 regardless of the presence or absence of ambient light.

The output processing circuit 9 has a one-dimensional P
A pulse current detection circuit 13, 13 for detecting a change in the output currents I ₁ , I ₂ generated in SD8, and a pulse current detection circuit 13,
Current-voltage conversion circuits 14 and 14 for converting the current signals from 13 into voltage signals, respectively, and an integration circuit for integrating and outputting the voltage signals from these current-voltage conversion circuits 14 and 14 for a predetermined period according to a command from the CPU 10. 15 and 15 and output signals from the integrator circuits 15 and 15 are input to the adder 16 and the subtracter 17, which perform addition or subtraction, and the analog voltage signals from the adder 16 and the subtractor 17, respectively. It is composed of A / D converters 18, 18 which convert the digital voltage signal and input the converted output to the CPU 10.

Here, the CPU 10 is an integrating circuit at the start of distance measurement.
When a reset signal for initializing the integrating operation (output = 0) is sent to 14 and 14 and the output of the adder 15 obtained via the A / D converter 18 becomes 1 V or more, the integrating circuit 1
A stop signal is sent to 5 and 15 to end the integration operation. The output 1V of the adder 16 in the present embodiment means the output value of the adder 16 when a spot light having an output of 10 mW is applied to the measuring object 2 having a reflectance of 100% 1 m ahead from the distance measuring device 1. Is represented.

Next, the operation of the distance measuring device having the above structure will be described with reference to the flowchart of FIG.

First, after the integrating operation of the integrating circuits 15 and 15 is initialized (S1), the LED 5 is pulse-lighted (100 μs) by a command from the light emission control circuit 11 (S3), and A / D conversion at that time is performed. It is judged whether or not the output of the adder 16 obtained through the device 18 is 1 V or more (S5).

Then, in step S5, the adder 16
If it is determined that the output of is less than 1V, the process returns to step S3 and the LED 5 is pulse-lit again.

On the other hand, if it is determined in step S5 that the output of the adder 16 is 1 V or higher, then the next step S5.
Proceed to 7.

In the next step S7, the A / D converter 18,
The digital voltage value of the sum (I ₁ + I ₂ ) and the difference (I ₂ −I ₁ ) of the output currents I ₁ and I ₂ obtained from 18 and the numerical values of the distances a, f and d stored in the ROM 12. Based on the above, the distance L from the distance measuring device 1 to the measuring object 2 is calculated by the above-mentioned formulas 1 and 2, and the operation is ended.

Therefore, until the output of the adder 16 obtained via the A / D converter 18 is 1 V or more, that is, the values of the output currents I ₁ and I ₂ are above a predetermined level, the integrating circuits 15 and 15 are used. Output current I ₁ , which has exceeded the predetermined level,
The distance L to the measurement object 2 is calculated based on the value of I ₂ .

In the above embodiments, the case where the one-dimensional semiconductor position detecting element is used as the position detecting light receiving element has been described, but the same effect can be obtained when the two-dimensional semiconductor position detecting element is used. it can.

Further, in the above embodiment, the case where the light emitting means is pulse-lighted has been described, but the light emitting means may be continuously lighted in a place where the influence of ambient light is small.

[0031]

As described above, according to the present invention, the lighting operation of the light emitting means is performed until the integrated output from the position detecting light receiving element becomes equal to or more than a predetermined value, and the integrated output exceeding the predetermined value is obtained. Since the distance to the object to be measured is calculated based on the distance, the distance to the object to be measured can be accurately measured regardless of the amount of reflected light focused on the light receiving element for position detection.

Therefore, the distance to the object to be measured can be accurately measured by the low output light emitting means regardless of the distance to be measured and the reflectance of the object to be measured, and the distance measuring device can be downsized and It is possible to improve safety.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a distance measuring device of the present invention.

FIG. 2 is a schematic perspective view of a one-dimensional semiconductor detection element in the embodiment of FIG.

FIG. 3 is a flowchart for explaining the operation of the distance measuring device of the present invention.

FIG. 4 is a schematic cross-sectional view illustrating the principle of a distance measuring device using a position detecting light receiving element.

[Explanation of symbols]

 1 distance measuring device 2 measuring object 3 light emitting part 4 light receiving part 5 LED 6 light emitting lens 7 condensing lens 8 one-dimensional semiconductor position detecting element 9 output processing circuit 10 control circuit (CPU) 11 light emitting control circuit 12 ROM 13 pulse current Detection circuit 14 Current-voltage conversion circuit 15 Integration circuit 16 Adder 17 Subtractor 18 A / D converter 21 Imaging surface 22, 23 Output electrode

Claims (2)

[Claims] 1. A light emitting means for irradiating a light beam having a constant output to a measuring object, a position detecting light receiving element arranged at a constant distance from the light emitting means, and reflected light from the measuring object. Light-collecting means for collecting light on the position-detecting light-receiving element, light-emission control means for controlling lighting of the light-emitting means, integrating means for integrating outputs from the position-detecting light-receiving element, and the integrating means. Until the integrated output of exceeds the specified value,
And a control means for causing the light emission control means to perform a lighting operation of the light emission means, and for calculating a distance to the measurement object based on an integrated output of a predetermined value or more from the integration means. Characteristic distance measuring device. 2. The distance measuring apparatus according to claim 1, wherein the light emission control means turns on the light emission means in pulses.