JPS6262208A - Range-finding apparatuws and method - Google Patents

Abstract

PURPOSE:To guarantee high-accuracy measurement regardless of a possible break and a dent on a specimen, by throwing a beam of light onto the specimen surface and conducting range finding by a means of issuing out the data of a distance from the obtained reflected beam to the specimen and that of correcting a distance signal by conceding fluctuations of the coefficient of reflection. CONSTITUTION:An output beam from a luminous element 1 of a limited light spot diameter, such as a laser beam, etc. is thrown onto a specimen through projecting lens 2 and half-mirror 7 and the reflecting beam from there is directed the No.1 light- receiving elements 3 through a light-receving lens 4. Here, to the elements 3 is allowed to face reflecting positions C, B, and A from the depth of the specimen, using a position sensitive detector and these reflected beams of light are allowed to be developed on the element 3. Further, a beam of light passing through the mirror 7 is directed the No.2 light-receiving element 6 which develops images in the same position through a light-receiving lens 5 and after is is amplified by an amplifier 8 located in the rear of the lens 3 and the element 6, it is transmitted as a signal to a corrector 9 and corresponding position to those C, B and A are obtained by a distance converting apparatus 10.

Description

[Detailed description of the invention] A device and a measuring method for measuring distance by measuring light, especially when the object to be measured is a metal surface as in a laser processing machine, and measurement accuracy due to uneven reflection of the projected light etc. The present invention relates to a distance measuring device and a distance measuring method in which deterioration of the distance is a problem.

(Prior Art) A conventional distance measuring device and measuring method will be described with reference to FIGS. 7 and 8.

FIG. 7 is a diagram showing a conventional distance measuring device, and FIG. 8 is a block diagram showing a conventional measuring method. In Figure 7, %A
, B, and C indicate the positions of the objects to be measured, respectively, and a, b, and c
% indicates the image position on the light receiving element (3) of the reflected light from the measured object when the measured object is at position A, %B, and C, respectively.

In general, such distance measuring devices and distance measuring methods based on triangulation using light have been put into practical use as distance detecting means for autofocus cameras and are well known, but they are also widely used in laser processing machines, etc., as in the technical field to which this invention pertains. In order to be used as a distance detecting means, it cannot be used with rough detection accuracy such as that used in the above-mentioned autofocus camera. Therefore, in the conventional example in this field shown in FIG. 7, a laser oscillator is used as the light emitting element (1) in order to improve the directivity of the light projected onto the object to be measured. The light projecting lens (2) is arranged so that the light source of the light emitting element (1) is located at its focal position, and projects a spot light as a parallel light beam onto the surface of the object to be measured. The light receiving element (3) is a light receiving element called PSD (Photo, Sensitive, Detector).

It has a characteristic that signals such as the amount of current change depending on the position where the spot light is received. Since the output of this light receiving element (3) is weak, it is amplified by a signal amplifier (8).

The distance converter a1 converts it into a distance signal. Next, the measurement method will be explained. The light emitted from the light emitting element (1) is projected onto the surface of the object as a spot light by the projection lens (2) (step l). The projected spot light is diffusely reflected on the surface of the object to be measured and reflected in random directions.

The light receiving lens (4) forms an image of the spot light on the surface of the object to be measured on the light receiving surface of the light receiving element (3) (step 2).

The current value of the light receiving element changes depending on the position where it receives light.
A signal uniquely corresponding to the distance to the object to be measured is output according to the position where the image of the spot light is formed (Step 8)
.

This signal is amplified and further converted into a distance signal (step 4).

[Problem that the invention seeks to solve]

Conventional distance measuring devices and measuring methods are as described above, but in reality, reflectance unevenness occurs even in minute areas due to surface roughness of metal surfaces (irregularities) and scratches, as shown in Figure 8. As shown, the image of the spot light formed on the light receiving element is chipped.

The light-receiving element outputs a signal by regarding the position of the center of gravity of the spot light imaged on the light-receiving surface as the distance to the object being measured, so if a chip occurs in the spot light as described above, the center of gravity changes and the center of gravity changes. The amount of movement is expressed as an error in the measured distance to the object to be measured.

This invention has been made in view of the above points.

It is an object of the present invention to provide a device and a measuring method for correcting the lack of spot light and correctly measuring the position of an object to be measured.

[Means for Solving the Problems] A distance measuring device and a distance measuring method according to the present invention will be explained using FIGS. 1 and 2, which correspond to embodiments.

Compared to conventional devices, the distance measuring device shown in FIG. Second
The outputs of the light receiving elements are combined.

It is characterized by having a corrector for correction.

In addition, compared to the conventional measurement method, the distance measurement method shown in Fig. The method is characterized by comprising a step of inverting, and a step of synthesizing the signal corresponding to the distance and the horizontally inverted signal.

[Effect]

Next, we will discuss the effect. In the distance measuring device shown in FIG. 1, a spot light image similar to that of the first light receiving element is formed on the second light receiving element, as shown in FIG. 8. As shown in the figure, the second light-receiving element is installed on the light projection path from the light-emitting element, so if there are no gaps in the spot light, the image is always formed at the same position, that is, at the center of the light-receiving element, and the output is also constant. However, when the spot light is chipped, the center of gravity of the spot light moves, and the amount of change in the output of the second light receiving element becomes a distance measurement error caused by the spot light chip. The corrector horizontally inverts the output of the second light-receiving element and combines it with the output of the first light-receiving element to correct the lack of spot light and measure the correct position of the object.

[Embodiments of the invention]

A preferred embodiment of the distance measuring device according to the present invention will be described below with reference to FIG. In Figure 1, one light emitting element (
For 1), a laser light source is used because the diameter of the spot light needs to be small and it also needs to have sufficient power to improve the accuracy of light reception. A light projection lens (2) is provided to project the output light from the light emitting element (1) onto the object to be measured as a parallel light beam. The first light receiving element (
3) is an element called, for example, a PSD (position sensitive detector), which is installed at the focal point of the light receiving lens (4), and is located at the position where the image of the spot light is formed, as shown in the figure. Outputs the corresponding signal (change in current value, etc.). As described above, the light receiving lens (4) collects the reflected light from the object to be measured and forms an image on the first light receiving element (3). A, B, and C indicate the position of the object to be measured.ha
@ b I C is the image position on the light receiving element (3) of the reflected light from the measured object when the measured object is at position A, position B, and position C, respectively. shows. A light emitting system consisting of a light emitting element (1) and a light emitting lens (2), a first light receiving element (3) and a light receiving lens (
Although the light receiving system consisting of 4) is fixed, the image position of the reflected light from the object to be measured differs depending on the position of the object to be measured, as shown in the figure. The position of the object to be measured is uniquely determined when the position where the reflected light from the object to be measured is imaged is determined based on the preset positional relationship between the light projecting system and the light receiving system. The light projection system is provided with a half mirror (7), which reflects the reflected light from the object to be measured toward the second light receiving element (6). Light receiving lens (
5) forms an image of the spot light reflected by the surface of the object to be measured on the surface of the second light receiving element (6).

In this case, unlike the first light receiving element (8) described above.

Of the light projected onto the object to be measured, the reflected light that follows the same optical path is received, so the spot light images are always formed at the same position. In addition, a laser beam is used as the light source of the 1 light emitting element (1), but since laser light is generally coherent (coherent), if the emitting optical path and the receiving optical path coincide, interference may occur and the actual The intensity distribution of the reflected light on the surface of the object to be measured may not match the intensity distribution of the spot light image on the second light receiving element (6). If the coherency of the laser light is a problem, a Faraday element or the like should be installed in the light path of the light emitting element (1).
It is also possible to solve this problem by rotating the vibration planes of the light emitted from the object and the light reflected from the object to be measured so that they do not interfere with each other.

Next, the distance measuring method according to the present invention will be explained using FIGS. 1 to 8.

In Fig. 1, the light emitted from the light emitting element is projected onto the surface of the object as a spot light consisting of a parallel beam (
Step 10). The projected light causes diffuse reflection on the surface of the object to be measured and is scattered in random directions. Next, only the light reflected toward the first light receiving element (3) is focused by the light receiving lens (4).

An image of the spot light is formed on the surface of the first light receiving element (3) (step 11). FIG. 8 shows the relationship between the images of spot light formed on the surfaces of the light receiving elements (3) and (6) and the light receiving elements. If there is no chipping in the spot light, the first light receiving element (3) regards the center of gravity of the spot light, that is, the center of the spot in this case, as the position of the object to be measured, and outputs a signal corresponding to the distance (step 12). ).

In addition, since the projection optical path from the light emitting element (1) and the receiving optical path of the second light receiving element (6) coincide with each other, unless there is a chip in the spot light, the light is always received at the same position. The center of gravity of the light coincides with the center of the spot,
A constant signal is output regardless of the position of the object to be measured (step 15). However, if the surface of the object to be measured has variations in reflectance due to scratches or other irregularities, and the spot light is missing as shown in FIG. 8, the first and second light receiving elements (3) and (6) is to output a signal corresponding to the center of gravity of each spot light.

Compared to the case where there is no chipping in the spot light, each of the output signals includes an error due to the chipping in the spot light. First light receiving element (3) and second light receiving element (6)
Although the images of the spot light formed on the surface of the surface will not exactly match because the reflection directions are different, they have roughly similar shapes. Therefore, the amount of error included in the signal corresponding to the distance, which is the output of the first light receiving element (3), is the same when there is a chip in the spot light of the second light receiving element (6) and when there is no chipping. It can be considered that the difference between the output and the

Therefore, the corrector (9) combines the output of the second light receiving element (6) with the signal corresponding to the distance from the @1 light receiving element (3) as a correction amount (step 16). The resulting distance measurement error can be resolved. However, in this case, since the error components included in the bamboo bending force signals of the first light receiving element (3) and the second light receiving element occur in the same direction, the output characteristics of the second light receiving element (6) are Invert. That is, a procedure (step 14) for horizontally inverting the signal is required.

The center of gravity position of the spot light (the peak position of the signal) is detected from the signal corrected so that the error component becomes zero in this way.Step 16) (step 18).

In the embodiment described above, the first and @2 light receiving elements (3
) and (6) use an element that outputs analog signals called PSD, so signals corresponding to distance and signals corresponding to spot light are all processed using analog signals. 2 light receiving elements (3) and (6
), it is also possible to use an image sensor in which a minute light-receiving element such as a MOS or CCD is arranged on line L. In this case, the relationship between the spot light image on the surface of the light receiving element and the light receiving element is as shown in FIG. Further, the output of each light receiving element is as shown in FIG. 5(a) when no spot light is missing, and as shown in FIG. 6(b) when spot light is missing. In this case as well, since the outputs of the first light receiving element (3) and the second light receiving element (6) are almost the same, the output signal (solid line) of the first light receiving element is horizontally inverted as shown in Fig. 6. By combining the output signals (dashed line) of the second light-receiving element (dotted line), the error component due to the missing spot light is corrected, and the signal at the peak position corresponding to the center of gravity of the spot light is amplified. 1 position detection accuracy can be improved.

Furthermore, in the case of an image sensor using 1MO8 or CCD, the output signal is digitized, so the corrector (9) is omitted, and the output signal is directly input to an arithmetic processing unit consisting of a microcomputer, etc., and the left and right of the signal is adjusted by a software program. It is also possible to perform error correction by performing inversion or the like.

〔Effect of the invention〕

As explained above, by using the distance measuring device and the distance measuring method according to the present invention, even if the surface of the object to be measured has uneven reversal due to scratches or unevenness, the error can be corrected and distance measurement can be performed with high accuracy. can be done.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of a distance measuring device according to the present invention, FIG. 2 is a block diagram showing a distance measuring method according to the present invention, and FIG. 8 is a spot imaged on the surface of a light receiving element. FIG. 4 is a diagram showing the light image and the chipping of the spot light, and FIG. 4 is a diagram showing the relationship between the spot light image and each pixel when the light receiving element is an image sensor such as a CCD.
) is a diagram showing the output characteristics when the light-receiving element is an image sensor such as a CCD, and the diagram shows the signal of the first light-receiving element when the light-receiving element is an image sensor such as a CCD. FIG. 2 is a diagram showing characteristics of signals of two light receiving elements and a signal corresponding to a combined and corrected distance. FIG. 7 is a diagram showing a conventional distance measuring device, and FIG. 8 is a block diagram showing a conventional distance measuring method. In the figure, (1) is a light emitting element, (3) is a first light receiving element, (
6) is a second light receiving element, and (9) is a corrector.

Claims (2)

[Claims] (1) Light projecting means for projecting a spot light onto the surface of the object to be measured; first light receiving means for receiving the reflected light from the object to be measured and outputting a distance signal corresponding to the distance to the object to be measured; , a second light receiving means for receiving reflected light from the object to be measured and outputting a correction signal for correcting variations in reflectance of the spot light; A distance measuring device comprising: a correction means for correcting the distance signal by applying it to the distance signal from the first light receiving means. (2) Projecting a spot light onto the surface of the object to be measured, receiving the reflected light from the object to be measured, outputting a first signal corresponding to the distance, and receiving the light reflected from the object to be measured. outputting a second signal for correcting variations in the reflectance of the spot light, inverting the output characteristics of the second signal, and converting the output of the inverted second signal into the first signal. A distance measuring method characterized by applying the signal to the signal and correcting the error.