JPH0240505A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to measure a distance to an objective body highly accurately all the time by providing an area sensor, an optical-center-of-gravity computing means and a measured-value correcting means. CONSTITUTION:An area sensor 7 receives reflected light from an objective body 5 along the axis of the projected light spot at a specified position. A microcomputer 8 performs the functions of the following means: a computing means of a distance utilizing the amount of displacement of the receiving position of the reflected light f2 at a semiconductor position detector 2; an optical-center-of-gravity computing means which computes the optical center of gravity from the distribution of the detected signals in correspondence with the amount of incident light in the area sensor 7; and a measured-value correcting means which corrects the amount of displacement of the light receiving position detected with the detector 2 or the distance value that is computed from the amount of displacement, in correspondence with the amount of position deviation of the optical-center-of-gravity with respect to the predetermined center of the received light. In this constitution, even if there are parts where colors and reflectivities are different on the surface to be measured of the objective body 5, errors in measurement which occur at a boundary part can be corrected without fail. Therefore, the distance to the objective body 5 can be measured highly accurately all the time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distance measuring device that measures the distance to a target object in a non-contact manner with high precision and high speed response.

[Conventional technology]

Conventionally, distances have been used in various industrial fields, such as shape recognition of high-temperature, high-speed moving objects in steel plants, and measurement of the dimensions and displacement of easily damaged objects in the mechanical and electrical industries, allowing for non-contact, high-precision, and high-speed response. Measuring equipment is required.

As a distance measuring device that meets these demands, a triangulation type laser distance sensor using laser light has been put into practical use, and various measuring devices using it have been developed.

As shown in FIG. 7, the laser distance sensor includes, for example, a small, high-output semiconductor laser 1 and a semiconductor device detector (Positio
nS sensitive device:hereinafter r
A combination of the two (abbreviated as P S DJ) is known.

To explain this simply, a laser beam from a semiconductor laser 1 as a light source is focused by a projection lens 3 and irradiated onto a target object 5 to be measured as a small light spot f1. Reflected light f by light spot f1
2 is condensed and received at one point on the light receiving surface of the PSD 2 by a light receiving lens 4 disposed at a predetermined distance from a light projecting lens 3.

Since the angle θ of the reflected light f2 focused by the light-receiving lens 4 changes due to the displacement of the target object 5 in the direction of the arrow Q, the position of the focused spot on the PSD 2, that is, the light-receiving position Displace. This light receiving position 1x can be easily detected by the PSD 2.

Therefore, if the distance between the optical axes between the light projecting lens 3 and the light receiving lens 4 is calculated, and the distance between the light receiving lens 4 and the PSD 2 is F, then the distance to the target object 5 can be determined by the following equation.

L = D - F / Since the reflected light of the light spot irradiated on the target object 5 is collected and received by the PSD 2, and the distance is calculated by detecting the displacement of the light receiving position, the color and reflectance state of the surface of the target object 5 can be calculated. This causes a difference in the reflection and absorption of light, which poses a problem in that errors may occur in the distance measurement results.

For example, as shown in Fig. 8 (a), the surface of the target object 5 is made up of alternating whitish parts (displayed as white) and dark parts (displayed as black). In such a case, when measuring the distance by moving the sensor head 10 of the laser distance sensor shown in Fig. 7 in parallel in the direction of the arrow instead of facing the surface, the PSD is shown in Fig. 8 (b).
As shown in the figure, the output of the PSD varies at the boundary between the whitish portion and the dark portion even if the distance ML is constant, resulting in a measurement error.

The size of this error changes depending on the contrast difference,
The direction (positive or negative) that occurs changes depending on how the shading changes.

This is because, as shown in Figure 9, when the light spot f1 hits the boundary between a whitish part and a dark part, the light is reflected in the whitish part and absorbed in the dark part. Although the center PO is supposed to be the point where the reflected light is strongest, the point where the reflected light is strongest is shifted to the center P1, which is where the whitish part of the light spot hits.

As a result, as shown in FIG. 10, the point P1 where the reflected light f2 is strongest is shifted by ΔS from the center Pa of the light spot, and the light receiving point by the PSD 2 is also shifted by ΔX.

Such errors occur not only in black and white, but also in all colors and at boundaries between parts with different surface conditions (specularity, etc.), and the distance measurement values calculated based on these errors also include errors.

This invention was made to solve such problems, and even if the distance measuring device described above measures an object whose measurement surface has parts of different colors or reflectances, measurement errors may occur. The purpose of the present invention is to make it possible to always measure the distance to an object with high accuracy without causing errors.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a light source and a light projecting lens that irradiates a light spot onto a target object, a light receiving lens that collects light reflected by the light spot from the target object, and a light receiving lens that collects the light reflected by the light spot from the target object. Semiconductor device detector that receives light (P
SD and D) are arranged at a predetermined interval, and the PSD
The amount of displacement of the light receiving position detected by the triangle ig
In a distance measuring device that measures the distance to a target object using a quantitative method.

an area sensor that receives reflected light along an irradiation optical axis of a light spot from a target object at a predetermined position; a light center of gravity calculation means that calculates a light center of gravity based on the distribution of a detection signal according to the amount of incident light by the area sensor; Measured value correction means for correcting the amount of displacement of the light receiving position detected by the PSD or the distance value calculated based on the displacement amount of the light receiving position detected by the PSD according to the positional deviation amount of the light gravity center with respect to a predetermined light receiving center calculated by. It has been established.

Further, it is preferable to provide a half mirror on the irradiation optical axis of the light spot, which separates the reflected light from the target object from the irradiation light and guides it to the area sensor.

[For production]

The distance measuring device according to the present invention configured in this way can detect the object using the area sensor, even if the measurement surface of the target object has parts with different colors or reflectances, and the boundary part is irradiated with a light spot for measurement. Since the reflected light along the irradiation optical axis of the light spot from the object is received at a predetermined position, even if the position of the target object changes, the receiving center of the reflected light received by the area sensor (the original light spot explained in Figure 9) center P of
) corresponding to o does not change.

Then, by the distribution of detection signals according to the distribution of the amount of reflected light received by this area sensor.

The optical center of gravity of the reflected light (corresponding to the point P1 where the reflected light is actually the strongest explained in FIG. 9) is calculated.

P
Since the amount of displacement of the light receiving position detected by the SD (causing an error) or the distance value calculated based on it is corrected, the relationship between the amount of positional deviation of the light center of gravity and the amount of error that occurs is simulated in advance. If you do this and memorize it, you can reliably correct the error.

Further, if the reflected light along the irradiation optical axis of the light spot from the target object is separated from the irradiated light by a half mirror and guided to the area sensor, the arrangement position of the area sensor can be arbitrarily selected.

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a block diagram of the optical system and its control section of a sensor head constituting a distance measuring device showing an embodiment of the present invention, and parts corresponding to those in FIG. 7 described above are given the same reference numerals. It is.

First, the optical system constituting the sensor head of this embodiment will be explained. Laser light from a semiconductor laser 1 as a light source is focused by a projection lens 3, and a small light spot f1 is formed on a target object 5 to be measured. The reflected light f2 from the light spot f1 from the target object 5 is received by the semiconductor device detector (PSD) 2 by the light receiving lens 4 disposed at a predetermined distance from the light projecting lens 3. The structure is different from the conventional one explained in FIG. 7 in that the light is focused on one point on the surface and is received, and the distance to the target object 5 is calculated based on the displacement of the light receiving position of the focused spot. It is similar to the device.

Furthermore, in this embodiment, on the optical axis of the light projecting lens 3, that is, on the irradiation optical axis of the light spot f1, 45"
A half mirror 6 is arranged at an angle, and this half mirror
6, the reflected light f3 along the irradiation optical axis of the light spot from the target object is separated from the irradiation light and guided to the area sensor 7.

The area sensor 7 is a two-dimensional optical sensor such as a CCD image sensor or a color sensor that can detect the distribution of colors and the distribution of brightness.
1 is fixed to a fixed part of a sensor head (not shown) so that light can be received at a predetermined position.

Next, the configuration of the control section of this distance measuring device will be explained.
Central processing unit (cpu)11. ROM12 which is a program memory. RAM l which is data memory 3. A microcomputer 8 composed of a large number of input/output ports (■/○) 14 to 18 collectively controls the entire apparatus.

The microcomputer 8 includes distance calculation means based on the amount of displacement of the light reception position of the reflected light f2 by the PSD 2, and light center of gravity calculation means for calculating the light center of gravity based on the distribution of the detection signal according to the amount of incident light by the area sensor 7. and each function of the measured value correction means that corrects the amount of displacement of the light receiving position detected by the PSD 2 or the distance value calculated based on the displacement amount of the light receiving position detected by the PSD 2 according to the positional deviation amount of the light gravity center with respect to the predetermined light receiving center. Also accomplish.

Furthermore, this control section includes an operation display section 20.1 connected to each input/output port 18, 14. Semiconductor laser removal circuit 21. and the area sensor late-acting circuit 22 and the output currents IA and I of the PSD2.
Preamplifiers 23 and 24 that amplify each of B, an analog switch 25 that alternately switches each output, and a sample hold circuit 26 that samples and holds the output.
, an A/D conversion circuit 27 that converts the hold value into a digital signal and inputs it to the input/output port 15, and a detection signal (video signal) sequentially output from the area sensor 7 according to the distribution state of the amount of received light. The A/D conversion circuit 28 converts the digital signal into a digital signal and inputs the digital signal to the input/output port 17.

The operation display unit 20 is provided with various switches or a keyboard for setting measurement modes and conditions, and a display for displaying the status of the apparatus and measurement results.

Here, the action of the PSD 2 will be explained with reference to FIG.

FIG. 2 is a cross-sectional explanatory diagram of the PSD, and this PSD2 is
Uniform resistance layers 2b, 2 on both sides of high resistance silicon substrate 2a
c is formed, and the high-resistance silicon base 12a is a layer
The resistance layer 2b constitutes pH, and the resistance layer 2c constitutes NM, and has a photoelectric effect.

The surface of one resistance layer 2a serves as a light receiving surface, and a pair of electrodes A and B for signal extraction are provided at both ends thereof, and a bias electrode C is provided on the other resistance layer 2c.

Therefore, if the distance between electrodes A and B is Q, their resistance is RQ, the distance from electrode A to the light incident position is X, and the resistance of that part is Rx, then the photogenerated current generated at the light incident position is Since Io is divided inversely proportional to the resistance value up to each electrode A, B, the current I taken out from each electrode A, B is
A, IB are I A = I o (RQ - Rx) / Rn I B = I o - Rx / RQ ... group (
2) Since the resistance N2b is uniform, the length and resistance value are proportional, so the formula (2) is IA"Io(Q-X)/12 IB = Io-X/Q ・-=C
3>(I O =: I A + I B). Therefore, taking the ratio of IA and IB, I
A/ I B = CD-X)/X = -Q/X-1 X=U・I B/(I A+ I B) ・Old...
(4) From the values of IA and IB, the light incident position X can be known regardless of the incident energy.

Therefore, in the embodiment shown in FIG.
The currents IA and IB drawn from A and B.

The signals are amplified and detected by preamplifiers 23 and 24, respectively, and alternately held in a sample and hold circuit 26 via an analog switch 25.

The A/D conversion circuit 27 converts the hold value into a digital signal, which is sequentially taken in by the microcomputer 8, and calculates the distance to the light incident position, that is, the displacement amount X of the light receiving position by calculating the above equation (4). calculate.

On the other hand, the area sensor 7 receives the reflected light f3 from the light spot from the target object 5 in a light receiving area as shown in FIG.
A detection signal (video signal) corresponding to the amount of received light is sequentially output for each coordinate (different coordinates).

The detection signal from the area sensor 7 is converted into a digital signal by the A/D conversion circuit 28 as shown in FIG. 1, and the microcomputer 8 takes in the digital signal to calculate the optical center of gravity.

Here, the calculation of the optical center of gravity will be explained.

For example, in the light receiving area of the area sensor 7, a and b are shown in FIG.
, if there are parts with different brightness and darkness as shown in c,
With respect to the center O of this light-receiving area, the light center of gravity G is shifted toward the bright portion.

The brightness of these parts a, b, and Q depends on the reflectance on the target object 5, so the detection signal from each light receiving element of the area sensor 7 also has a value according to this light reflectance, and this is m Then, Z+t/coordinate of the light center of gravity G (x g
+ q g ) is calculated as follows.

xg=Σmx/Σm yg”Σmy/Σm −′° (5) For example, if the value of m is distributed as shown in Figure 4, calculate the coordinates (x g v y g ) of the optical center of gravity G. When I tried it,
It will look like this:

Σm = 6 + 5 + 2+・・・・・・・・・
・・+6+6=99Σmχ= (6+4+4+6)X3 +(5+ 2 +2 + 6)X 4+・・・・・・・・・
・・+(4+2+4+6)x9=576 Σm y=(6+6+6+6+6
+ 6 + 6 ) X 3+ (4+2+2+2+2+
2+4)
8yg”Σmv/Σm=416/9944.2 In this case, the coordinates of the center O of the light receiving area (xo.

vo) is xo=6. Since yo=4.5, the optical center of gravity G is shifted by 0.2 in the X-axis direction + -0.3 in the q-axis direction.

Next, the processing operation of the microcomputer 8 during distance measurement according to the embodiment shown in FIG. 1 will be explained according to the flowchart shown in FIG.

First, the semiconductor diode (LD) 1 is made to emit light, and the PSD
The data based on the currents IA and I from 2] are read, and the reflected light f2 effective incident position X is calculated using the above-mentioned equation (4).

Thereafter, a detection value m (x *
q).

Then, it is determined whether or not correction is necessary, for example, based on the presence or absence of an input by the operator using a correction instruction key from the operation display section 20. If correction is not necessary, the previously calculated value of The distance is calculated by the calculation.

If correction is necessary, the coordinates (x g * q g ) of the optical center of gravity are calculated from the data of m (Z + q) read from the area sensor 7 using the above-mentioned equation (5).

Then, from the calculated value of Xg+t/g,
Correct the value of. This correction value can be calculated by, for example, storing the correction coefficient value in the ROM 12 in the microcomputer 8 with xg+''/g as the address, reading it out, and multiplying it by the previously calculated X.

Further, the corrected value of X is used to calculate the distance WIL by calculating the equation (1), and the result is output to the operation display section 20 for display. If no correction is required, the distance calculated using the uncorrected value of X is output.

Thereafter, if the measurement is to be continued, the process returns to reading data from the PSD 2 and the above-described process is repeated; if the measurement is not to be continued, the semiconductor laser (LD) 1 is turned off and the process is completed.

FIG. 6 is a flowchart showing other processing operations by the microcomputer 8.

In this example, only the differences from the above case will be explained. After reading the detection value m (χ, t/) from the area sensor 7, the coordinates (χg, vg) of the light center of gravity are calculated.

Furthermore, the coordinates of the center of the light receiving area (zo, tlo)
Deviation from! (Δχ, ΔV) is calculated.

Then, it is automatically determined whether or not correction is necessary based on the magnitude of the amount of deviation, and if it is determined that correction is necessary, the amount of deviation ΔX, Δy, and the value of X calculated previously are stored in the ROM 12. Look up the distance table, read the distance, and print it out.

In this way, even if the operator does not check the surface condition of the target object and input whether or not correction is necessary, if correction is necessary, it will be automatically performed.

In addition, as the area sensor 7, for example, P for distance measurement is used.
By using a two-dimensional PSD having the same spectral sensitivity characteristics as SD2, it is possible to more reliably correct errors caused by color unevenness on the light spot irradiation surface of the target object.

In addition, a semiconductor laser (laser diode) is used as a light source.
However, it is also possible to use not only other laser generators but also light emitting diodes, lamps, etc.

〔Effect of the invention〕

As explained above, according to the present invention, even if there are parts with different colors or reflectances on the surface of the target object to be measured by a distance measuring device that uses a light spot, the difference in color and reflectance will occur, especially at the boundaries. Since measurement errors can be reliably corrected,
The distance to the target object can always be measured with high precision.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a distance measuring device showing an embodiment of the present invention, FIG. 2 is a cross-sectional explanatory diagram showing the principle of the semiconductor device detector 2 in FIG. 1, and FIG. 6 is an area sensor in FIG. 1. Fig. 4 is an explanatory diagram of the light receiving area according to No. 7, and Fig. 4 also shows the detected value m by each light receiving element.
An explanatory diagram showing an example of the distribution of (x + q), and FIGS. 5 and 6 are flowcharts showing different examples of processing operations of the microcomputer 8 during distance measurement according to the embodiment of FIG. FIG. 7 is an explanatory diagram showing the configuration of a conventional optical system of a distance measuring device to which the present invention is applied, and FIGS. 8 to 10 explain the occurrence of measurement errors and their causes in the conventional distance measuring device. FIG. 1... Semiconductor laser (LD) 2... Semiconductor device detector (PSD) 3... Light emitting lens 4... Light receiving lens 5... Target object 6... Half mirror 7... Area sensor 8 . . . Microcomputer 20 . . . Operation display section 21 . . . Semiconductor laser opening circuit 22 . . . Area sensor activation circuit Fig. 2 Fig. 3 Fig. 4 Fig. 7 Fig. 8

Claims (1)

[Scope of Claims] 1. A light source and a light projection lens that irradiate a light spot onto a target object, a light receiving lens that collects light reflected by the light spot from the target object, and a semiconductor device that receives the focused light. A distance measuring device that measures the distance to the target object by a triangulation method based on the amount of displacement of the light receiving position detected by the semiconductor device detector, with a detector arranged at a predetermined interval, an area sensor that receives reflected light along the irradiation optical axis of the light spot from the target object at a predetermined position; and an optical center of gravity calculation means that calculates the optical center of gravity based on the distribution of detection signals according to the amount of incident light by the area sensor. and a displacement amount of the light receiving position detected by the semiconductor device detector or based on the displacement amount of the light receiving position detected by the semiconductor device detector according to the positional deviation amount of the light center of gravity with respect to a predetermined light receiving center calculated by the light center of gravity calculating means. A distance measuring device comprising: a measured value correcting means for correcting a calculated distance value. 2. A half mirror is provided on the irradiation optical axis of the light spot, further comprising a half mirror that separates the reflected light along the irradiation optical axis of the light spot from the target object from the irradiation light and guides it to the area sensor. distance measuring device.