JPH0240506A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To improve resolution in distance measurement and linearity by constituting an apparatus by using three condenser lenses so as to satisfy Scheinpflug conditions, and specifying the positions of a photodetector and the three condenser lenses. CONSTITUTION:A position detector 6 is composed of the following parts: a light source 1 which emits a light beam; a light projecting lens 2 which projects the light beam on a body to be measured 4; first - third condenser lenses 51 - 53; a photodetector 7; and an operator 8. Said second condenser lens 52 is arranged so that the central surface of the lens 52 agrees with the (x) axis that is perpendicular to the (y) axis which is the path of the light beam from the light source 1 to the body 4. The photodetector 7 is arranged so that the light receiving surface of the photodetector agrees with the (y) axis. The body 4, the first condenser lens 51 and the second condenser lens 52 satisfy the first Shine Pruge conditions. The second condenser lens 52, the third condenser lens 53 and the photodetector 7 satisfy the second Scheinpflug conditions. The first condenser lens and the third condenser lens are arranged so that the (x) coordinates of the lenses are the same when the (x) axis and the (y) axis are made to be the coordinate axes.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a measurement method in which a light beam such as a laser beam is irradiated onto an object to be measured, and the reflected light is used to measure the distance to the object or its displacement. Concerning distance devices.

[Conventional technology]

As this type of distance measuring device, for example, Japanese Patent Application Laid-Open No. 55-409
One is based on the triangulation method disclosed in Japanese Patent Publication No. 119006/1983.

There is known an optical system arrangement that satisfies the Scheimpflug condition as disclosed in Japanese Patent Application Laid-Open No. 57-67815. In both of these devices, a light spot projected onto the object to be measured from a light projection optical system is imaged onto a light receiving element by a light receiving optical system iζ arranged obliquely to the light projection axis.
For example, the amount of displacement of the object to be measured along the light projection axis of the object to be measured is measured by detecting the change in the position of the image of the light spot on the light receiving element.

FIG. 3 shows the configuration of the optical system disclosed in the above-mentioned Japanese Unexamined Patent Publication No. 55-119006. An irradiation light beam I from a light source I is irradiated onto an object to be measured 4 via a projection lens 2 . The reflected light 31 reflected by the object to be measured 4 is passed through the condenser lens 5.
PAD (Position
5intensive Detector ) 7 (
Hereinafter, it will simply be referred to as a light receiving element 7. ). Reference numeral 6 denotes a position detector, which is composed of the light receiving element 7 and an arithmetic unit 8.

The position of the light spot on the light receiving element 7 is determined by a subtracter that calculates the difference between the two output currents I, , I2 of the light receiving element 7.

The following (1
It can be found by calculating Equation 1.

However, here dy: Displacement of the position of the light spot on the light receiving element 7.

I,,I2: 2Illtl force current of the light receiving element 7.

Ko: Constant Furthermore, signal processing is performed by a nonlinearity correction circuit 9 such as a polygonal line approximation circuit, an exponential function circuit, or a digital calculation circuit in order to make the calculation result of equation (1) proportional to the displacement of the measured object 4. The displacement is measured.

In the configuration of FIG. 3, the Scheimpflug condition is satisfied as described above. Here, this Scheimpflug condition will be briefly explained. In FIG. 3, a surface 501 including the central plane of the condenser lens and a surface 7 including the light receiving element 7 are shown.
1 (corresponding to the imaging plane) intersect at any point 75 on the irradiated light beam, all arbitrary points on the irradiated light beam will be in focus and will form an image on the light receiving element 7. It is known that This is called the Scheimpflug condition.

Now, the above-mentioned distance measuring device that uses a laser beam or the like to measure the position or displacement of an object in a non-contact manner is capable of measuring objects such as soft plastic without damaging them, and can be used at the factory. The contact-type position i* can also be used as a distance detector for automated equipment such as internal robots.
++It has several advantages that foot devices do not have.

[Problem to be solved by the invention]

Problems with conventional distance measuring devices of this type are as follows. That is, as described above, in order to make the calculation result of equation (1) proportional to the displacement of the object to be measured.

A non-linearity correction circuit such as a polygonal line approximation circuit is required, which poses a problem in that the electrical circuit for signal processing becomes complicated and expensive. Furthermore, when this Scheimpflug condition is used, due to the configuration of the optical system, the reflected light is irradiated obliquely onto the photodetector, which causes an error in the distance measurement output from the photodetector, which causes the distance measurement device to There were also problems such as deterioration of orthogonality and resolution.An object of the present invention is to eliminate the above-mentioned conventional problems.

It is an object of the present invention to provide an inexpensive distance measuring device that does not require a special nonlinearity correction circuit, has excellent resolution, and has good linearity.

[Means to solve the problem]

In order to achieve the above object, according to the present invention, in a distance measuring device that measures the distance to an object to be measured or the displacement of the object to be measured in a non-contact manner by irradiating a light beam, the light beam is emitted. a light source; a light projection lens that projects the beam onto the object to be measured; Second. The second condenser lens includes a third condensing lens and a position detector including a light receiving element and a computing unit, and the second condensing lens has the path of the light beam from the light source to the object to be measured as the y-axis. When the central plane of the lens is arranged to coincide with the y-axis orthogonal to the y-axis,
The light-receiving element is arranged so that its light-receiving surface coincides with the y-axis,
The object to be measured, the first condensing lens, and the second condensing lens satisfy the first Scheimpflug condition, and the second condensing lens, the third condensing lens, and the light receiving and the first condensing lens and the third condensing lens have the same X coordinate when the y-axis and the y-axis are the coordinate axes. shall be.

[Effect]

In this way, the original school that satisfies the Scheimpflug condition is
It is constructed in two stages using three condensing lenses.

In addition, by specifying the positions for arranging the light receiving element and three condensing lenses, it is possible to simply focus the image of the object on the light receiving element, unlike when using a simple single-stage Scheimpflug condition. Not only can the image be formed in the same state, but also the displacement of the object to be measured can be made proportional to the displacement of the light spot on the light receiving element.

As a result, the position or displacement of the object to be measured can be determined simply by calculating the ratio of the sum and difference of the two output currents of the light receiving element, without using a nonlinearity correction circuit such as a conventional broken line approximation circuit. It becomes possible to measure. In addition, the reflected light is directed onto the light receiving element at an angle close to perpendicular (with a deviation from vertical of 10° to 2°).
Since the irradiation can be performed at an angle of 0°, it is possible to perform measurements with excellent linearity and resolution.

〔Example〕

FIG. 1 shows the configuration of a distance measuring device that satisfies the two-stage Scheimpflug condition, which is an embodiment of the present invention.

The same members as in FIG. 3 are denoted by the same reference numerals, and explanations thereof will be omitted. 51, 52, and 53 are the first. Second. The third condensing lens 1 reflected light 32 is the second condensing lens 52.
The light beam is refracted by the light beam and becomes a single reflection source to form a light spot on the light receiving element 7. In the light receiving element 7, the center plane of the irradiation beam coincides with the X axis. Furthermore, the first. Third condensing lens 51
, 53 are arranged so that their X coordinates are the same. The first Scheimpflug condition is that the object to be measured 4 and the first
is filled with a condenser lens 51 and a second condenser lens 52. Further, the second Scheimpflug condition is that the second condenser lens 52, the third condenser lens, and the light receiving element 7
It is filled with. The major difference between FIG. 1 and FIG. 3 is that the number of condensing lenses has increased to three, but the nonlinearity correction circuit has been eliminated. Next, according to Figure 2,
The operation of the embodiment of the present invention shown in FIG. 1 will be explained geometrically.

In FIG. 2, X@ corresponds to the center plane of the second condensing lens 52, and the y-axis corresponds to the original axis of the irradiation light beam I. For convenience of explanation, in FIG. 2, the positive direction of the y-axis is represented by y, and the negative direction of the y-axis is represented by Y. Equation 1 representing the reflected light 32 Equations representing the reflected light 32 are expressed by the following equations (2) and (3), respectively.

Y Yo=M(x xo) (
2) Y Yo = m (X-Xo)
(3) However, here.

M: Inclination of reflected light 32.

m: That tilt of reflected light.

xo: first condensing lens 51. X coordinate of the third condensing lens 53.

Yo: Y coordinate of the first condensing lens 51.

yo: X coordinate of the third condenser lens x53.

It is. The position (Y-intercept) of the light spot on the object to be measured 4 is (2
) From the formula.

Y −Yo = −Mxo (
4), and the point where the reflection source is incident on the second condensing lens 52, that is, the intersection of the reflected light 32 and the X axis (X). Therefore, from equations (4) and (5), .

(Y-Yo) m (x-XO)=xoYo
(6) becomes. Next, the image position (X-intercept) of the light spot on the light-receiving element 7 is determined from equation (3), y −yo = −mXQ
+'7), and the reflected light is reflected by the second condensing lens 52.
The point where the reflected light is irradiated from, that is, the intersection of the reflected light and the X axis (
Intercept) is from equation (3).

O x −x6 = −−(8) becomes. Therefore, from equations (13) and (14).

(yyo)・(x-xo)=xo yo
(9) On the other hand, the reflected light 32 and the reflected light on the X axis become as follows. Here, when the measured object 4 is displaced from Y to Y2, and the light spot on the light receiving element 7 changes from 'fs to y2, then from equation (10).

O YI　　　Y2=　　　　　()'t　Y2).

This equation (11) shows that the displacement dY of the object to be measured 4 is yo/Yo
This means that it is multiplied and displaced on the light receiving element 7.

Therefore, equation (11) is.

Y.

dY = -ay (12)
Y.

It can be expressed as

As is clear from the above explanation, since the positions of the light receiving element and the three condensing lenses are specified and the two-stage Scheimpflug condition is satisfied, the displacement ay on the light receiving element 7
is proportional to the displacement dY on the object to be measured 4, and the image point on the surface of the object to be measured 4 is always focused on the surface of the light receiving element 7 II. Therefore, by determining the position of the light spot on the light receiving element 7, the displacement of the object to be measured 4 can be directly measured. Furthermore, the light spot on the light receiving element 7 is extremely small and has excellent linearity. Furthermore, a second condensing lens 52
The reflected light 132 is refracted at a angle close to perpendicular to the light receiving element 7 arranged parallel to the optical axis of the irradiated light beam, that is, at an angle in which the deviation from the vertical is in the range of 10° to 200°. Since the structure is configured to irradiate light with

The distance measurement resolution as a distance measurement device is also very excellent. The reason for this is that it is better for the light receiving element to be irradiated with light at an angle close to that on duty due to mechanical misalignment of the light receiving element (0.1°) that may occur after the rangefinder is assembled.
This is because even if a small rotational deviation of about 1° occurs, the % output error can be suppressed to about several pm.

From the above, the displacement dY to be found can be calculated using equation (1) as Y.

By substituting =-.KO into equation (12), we get (where K is a constant).

〔Effect of the invention〕

As described above, according to the present invention, the optical system of the distance measuring device is configured to satisfy the Scheimpflug condition of 2 steps using three condenser lenses, and the optical system of the distance measuring device is configured using three condenser lenses, and Now that we have determined the position to place the condenser lens, we can determine the position or displacement of the object to be measured.

It is possible to directly output the signal as the output of the arithmetic unit at low cost without complicating the signal processing electric circuit due to the nonlinearity correction circuit. In addition, since the reflected light is refracted by the second condensing lens and irradiated onto the light receiving element at an angle close to perpendicular, that is, at an angle with a deviation from the vertical in the range of 10' to 20', the output error at the light receiving element is reduced. is small V)
It will also be possible to improve the linearity and distance measurement resolution of the distance measurement device.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention. FIG. 2 is a configuration diagram of a distance measuring device that satisfies two-stage Scheimpflug conditions. FIG. 2 is a diagram for geometrically explaining the operation of the embodiment shown in FIG. 1, and FIG. 3 is a block diagram of a conventional distance measuring device using Scheimpflug conditions. 1: Light source, 2: Projection lens% 4: Object to be measured. 6: position g1 detector, 7: light receiving element, 8: arithmetic unit, 9: nonlinearity correction circuit, 31, 32, 33: reflected light. 50 = condenser lens, 51: first condenser lens % 52: second MK lens, 53: third condenser lens. 1st mouth

Claims (1)

[Claims] A distance measuring device that non-contactly measures the distance to an object to be measured or the displacement of the object by irradiating a light beam, including a light source that emits the light beam, and a light source that projects the light beam onto the object to be measured. A position detector including a light projecting lens, first, second, and third condensing lenses, a light receiving element, and an arithmetic unit, and the second condensing lens moves from the light source to the object to be measured. When the path of the light beam reaching the y-axis is set as the y-axis, the center plane of the lens is arranged to coincide with the x-axis orthogonal to the y-axis, and the light-receiving element is arranged so that its light-receiving surface coincides with the y-axis, The object to be measured, the first condensing lens, and the second condensing lens satisfy the first Scheimpflug condition, and the second condensing lens, the third condensing lens, and the light receiving satisfies the second Scheimpflug condition with the element,
The distance measuring device is characterized in that the first condenser lens and the third condenser lens have the same x-coordinate when the x-axis and the y-axis are used as coordinate axes.