JPH04307308A - Displacement measuring instrument - Google Patents

Abstract

PURPOSE:To obtain a reflection type displacement measuring instrument which can highly accurately measure the displacement of an object in the direction perpendicular to the projecting axis of an optical beam emitted from a light projecting section over a wide range. CONSTITUTION:An optical beam having a spread which is larger than the dimension of an object 6 is emitted from a light projecting section 1. The image of the light spot of the optical beam on the object 6 is formed on the light receiving surface of the position detecting element 9 of a light receiving section 7. An arithmetic processing section 10 calculates the position or displacement of the object 6 in the direction perpendicular to the projecting axis C of the optical beam from the image forming position of the element 9.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement measuring device. In particular, the present invention relates to a displacement measuring device that can detect the displacement of an object in a direction perpendicular to the projection axis of a light beam projected from a light projecting section.

0002

2. Description of the Related Art FIG. 6 shows a conventional displacement measuring device 51. The light receiving section includes a light emitting source 52 such as a light emitting diode or a semiconductor laser element, and a projection for focusing the light beam α emitted from the light emitting source 52 into a very small spot compared to the surface dimension of the object to be measured 54. It is composed of a light lens 53, and irradiates the surface of the object to be measured 54 with a light beam α projected from a light projector in a spot shape. On the other hand, the light receiving section includes a light receiving lens 55 and a position detecting element (PSD) 56, and the light receiving lens 55 forms an image of a light spot on the surface of the object to be measured 54 on the light receiving surface of the position detecting element 56. Based on the photocurrent obtained from the position detection element 56 according to the position, the displacement of the object to be measured 54 in the direction of the projection axis of the light beam α is determined in the arithmetic processing section.

However, although conventional displacement measuring devices can measure the displacement of the object to be measured in the direction of the projection axis of the light beam projected from the light projector, they cannot measure the displacement of the object to be measured in the direction perpendicular to the projection axis of the light beam. The displacement of the measurement object could not be measured. In other words, even if the object to be measured is moved in a direction perpendicular to the projection axis, the spot of the light beam is small compared to the dimensions of the object to be measured, so the position of the light spot does not move, and as a result, the position of the light beam from the position detection element The current did not change either, and the displacement of the object to be measured in the direction perpendicular to the projection axis could not be detected.

[0004]Furthermore, conventional displacement measuring devices can measure the displacement of an object that is displaced in the direction of the projection axis within a certain range in front of the displacement measuring device; In the case of an object to be measured that moves continuously, the displacement measuring device will prevent the object from moving and the object will collide with the displacement measuring device, so it cannot be used to measure the displacement of the object in such cases. Ta. For example, when measuring the displacement of an object being conveyed in one direction by a conveyor, conventional displacement measuring devices cannot be used because they must be installed on the conveyor, which obstructs the conveyance of the object to be measured. .

For this reason, conventionally, as shown in FIG. 7, a photoelectric switch 58 is installed next to a conveyor path 57, and a slit light is projected from the photoelectric switch 58 toward an object 59. The passage of the object 59 was confirmed by turning the switch 58 on and off. However, the photoelectric switch 58 merely determines the presence or absence of the object 59 within a certain area by turning it on or off.
Since it is not possible to track the displacement of the sensor, highly accurate position detection is impossible.

[0006]

[Problems to be Solved by the Invention] The present invention has been made in view of the drawbacks of the conventional examples described above, and its object is to provide a light beam that is perpendicular to the projection axis of the light beam emitted from the light projector. An object of the present invention is to provide a displacement measuring device capable of measuring the displacement or distance of an object in a direction.

[0007]

[Means for Solving the Problems] The displacement measuring device of the present invention includes a light projecting section that projects a light beam having a spread larger than the surface dimension of the object to be measured, and a condensing light beam reflected from the surface of the object to be measured. a light-receiving unit having a light-receiving lens, a position detection element placed near the imaging position of the condensed reflected light; It is characterized by comprising a calculation processing means for calculating the displacement of the object or the distance to the object to be measured.

Further, the displacement measuring device of the present invention has a first light receiving section and a second light receiving section disposed on both sides of the light projecting section, and
The displacement of the object to be measured in the direction orthogonal to the projection axis may be determined based on the outputs from the first and second light receiving sections.

Further, the displacement measuring device of the present invention has a first light receiving section and a second light receiving section disposed on both sides of the light projecting section, respectively.
The displacement of the object in the direction of the projection axis and the displacement of the object in the direction orthogonal to the projection axis may be simultaneously measured by the outputs from the first and second light receiving sections.

0010

[Operation] In the present invention, since the light beam having a spread larger than the surface dimension of the object to be measured is projected from the light projecting section, when the object moves in a direction perpendicular to the projection axis of the light beam, The light spot on the object surface moves in a direction perpendicular to the projection axis. Therefore, by focusing this light spot on the light receiving surface of the position detection element, the displacement or position of the object in the direction orthogonal to the projection axis can be detected through calculation in the calculation processing means.

[0011] Therefore, the displacement of the object to be measured can be measured not from the direction of movement of the object but from the lateral direction of the movement path, so that the displacement of an object crossing in front of the displacement measuring device can be measured without interfering with the movement of the object. Moreover, the displacement of the object to be measured can be measured with high precision over a wide range.

Furthermore, by arranging the first and second light receiving sections on both sides of the light projecting section, the influence of displacement of the object to be measured in the direction of the projection axis can be removed, and the effect of displacement of the object to be measured in the direction perpendicular to the projection axis can be removed. The amount of displacement can be accurately measured. Alternatively, displacement of the object to be measured in two directions, ie, the direction of the projection axis and the direction perpendicular to the projection axis, can be measured simultaneously.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of a displacement measuring device 1 according to an embodiment of the present invention. The light projecting unit 2 includes a light emitting source 3 such as a light emitting diode or a semiconductor laser element, a driving circuit 4 for driving the light emitting source 3 to cause the light beam α to be emitted from the light emitting source 3, and a light beam α emitted from the light emitting source 3. It consists of a light projection lens 5 for converting the light beam α into parallel light or diffused light with an appropriate spread. The light beam α projected from the light projecting unit 2 is not focused into a spot shape as in the conventional example, but has a large spread compared to the surface dimension of the object to be measured 6. Therefore, within the projection area of this light beam α,
When the measured object 6 moves in a direction perpendicular to the projection axis C,
A light spot on the surface of the object to be measured 6 moves together with the object to be measured 6. The light receiving unit 7 includes a light receiving lens 8 for condensing the reflected light β reflected from the surface of the object to be measured 6, and a position detection element (PSD) 9.

This displacement measuring device 1 has an origin O that is the intersection of the extension of the straight line connecting the center Q0 of the light-receiving surface of the position detection element 9 and the principal point R of the light-receiving lens 8 and the projection axis C of the light beam α. , the object to be measured 6 is arranged and used so as to move along a movement path V passing through the origin O and perpendicular to the projection axis C. Now, suppose that the object to be measured 6 is located at a position P on the moving path V, which is a distance x away from the origin O, and its image is formed at a position Q1, which is a distance ρ from a point Q0 on the position detection element 9. do. Further, if the distance between the moving path V of the object to be measured 6 and the principal point R of the light receiving lens 8 is a, and the distance between the light receiving surface of the position detection element 9 and the principal point R of the light receiving lens 8 is b, then FIG. From the geometrical relationship shown in , the following equation 1 can be obtained.

[0015]

[Math 1]

Photocurrents Ia and Ib are obtained from the position detection element 9 in accordance with the imaging position, and these photocurrents Ia and Ib are processed by an arithmetic processing circuit 10. In the arithmetic processing circuit 10, the photocurrents Ia and Ib are converted into currents and voltages by the light receiving amplifiers 11a and 11b, and the voltage signals A and B converted by the light receiving amplifiers 11a and 11b are converted by the adding circuit 12 as a signal A+B corresponding to the amount of light received. At the same time, the subtraction circuit 13 outputs the signal A-B. moreover,
Output A-B of subtraction circuit 13 and output A+B of addition circuit 12
is input to the division circuit 14, and from the division circuit 14 the signal (
A-B)/(A+B) is output.

Now, the length of the light receiving surface of the position detection element 9 is L.
When the image is formed at the center Q0 of the light receiving surface, A=B,
Assuming that A=0 or B=0 when the image is formed at the end of the light receiving surface, the distance ρ of the image forming position Q1 on the position detection element 9 is expressed by the following equation 2.

[0018]

[Math 2]

Therefore, from equations 1 and 2, the following equation 3 can be obtained, so the output of the arithmetic processing circuit 10 (A-B)/(
By multiplying A+B) by a constant, the position P of the object to be measured 6 can be calculated.
The displacement x of the measured object 6 from the origin 0 can be known, and by observing the change in the output of the arithmetic processing circuit 10, the amount of displacement of the measured object 6 can be known.

[0020]

[Math 3]

In the above embodiment, the light receiving surface of the position detecting element 9 is arranged perpendicular to the projection axis C, but the light receiving surface of the position detecting element 9 and the projection axis C may be arranged parallel to each other. Further, when the perpendicular line erected on the light receiving surface is inclined by φ with respect to the projection axis C, the above equation 3 is modified as shown in the following equation 4.

[0022]

[Math 4]

FIG. 2 is a schematic diagram showing a displacement measuring device 21 according to another embodiment of the present invention. In the example of FIG.
Although it is assumed that the object to be measured 6 is on a fixed movement path V perpendicular to the projection axis C, in this displacement measuring device 21, even if the object to be measured 6 is displaced in the direction of the projection axis, it will not move in the direction perpendicular to the projection axis C. The displacement of can be determined accurately. In the example of FIG.
A light projecting unit 2 is arranged in the center, and light receiving lenses 23 are arranged on both sides of the light projecting unit 2.
A first light receiving section 22 consisting of a position detecting element 24 and a second light receiving section 27 consisting of a light receiving lens 28 and a position detecting element 29 are arranged symmetrically with respect to the projection axis C.

FIG. 3 is an explanatory diagram for explaining the principle of the embodiment shown in FIG. Now, let the distances between the principal points R1, R2 of both the light receiving lenses 23, 28 and the projection axis C be d, and the projections of the centers Q10, Q20 of the light receiving surfaces of both the principal points R1, R2 and the position detecting elements 24, 29 The distance in the direction perpendicular to the axis C is g, and the center Q1 of the light receiving surfaces of both position detection elements 24 and 29 is
The coordinates (the direction of the projection axis is the y-axis, and the orthogonal direction is the x-axis) that represents the position of the object to be measured 6 are at the intersection of the projection axis C of the extension line connecting the principal points R1 and R2 with 0, Q20. Suppose there is an origin O. Further, let the coordinates representing the position of the object to be measured 6 be P (x1, y1), and the coordinates of the imaging positions Q11, Q21 on both position detection elements 24, 29 are ρ1, ρ2 (right (The direction is the positive direction.)
Then, the following equation 5 can be obtained from the geometrical relationship shown in FIG.

[0025]

[Math 5]

When this number 5 is rearranged with respect to x1, the following number 6 is obtained.

[0027]

[Math 6]

Therefore, even if the object to be measured 6 is displaced in the y-axis direction, the left and right position detection elements 24 and 29
The position of the object to be measured 6 in the x-axis direction can be accurately determined from the coordinates ρ1 and ρ2 of the imaging positions Q11 and Q21.

FIG. 4 is a block diagram showing an arithmetic processing circuit 31 for determining the coordinate x1 of the object to be measured 6 according to Equation 6 above. The photocurrent of the position detection element 24 is transmitted to the light receiving amplifier 32.
a and 32b into voltage signals A1 and B1, and an addition circuit 33, a subtraction circuit 34, and a division circuit 35 convert the imaging position on the position detection element 24 to ρ1=(L/2)×[(A1-B1)/(
A1+B1)] is obtained and output from the division circuit 35. Similarly, the photocurrent of the position detection element 29 is
2a and 42b into voltage signals A2 and B2,
The addition circuit 43, the subtraction circuit 44, and the division circuit 45 calculate the imaging position on the position detection element 29 ρ2=(L/2)×[(A2-B2)/(
A2+B2)] is obtained and output from the division circuit 45. The outputs ρ1 and ρ2 of both the division circuits 35 and 45 are added in an adder circuit 36 to output a signal (ρ1+ρ2). Further, the outputs ρ1 and ρ2 of both the division circuits 35 and 45 and the known value 2g are input to the subtraction circuit 46, and the subtraction circuit 46 outputs a signal (ρ2-ρ1-2g). Further, the signal (ρ1+ρ2) and the signal (ρ2-ρ1-2g) are input to the division circuit 37, and as is clear from the above equation 6, the coordinate x1
Signal proportional to (ρ1+ρ2)/(ρ1-ρ2-2g)
is output from the division circuit 37. Therefore, the x-coordinate can be accurately determined regardless of the y-coordinate value y1 of the object to be measured 6.

FIG. 5 is a block diagram showing a displacement measuring device 47 according to yet another embodiment of the present invention. The configuration of this displacement measuring device 47 other than the arithmetic processing circuit 48 is the same as that of the embodiment shown in FIGS. 2 and 3. From Figure 3,
Although the x-coordinate of the object to be measured 6 can be determined as shown in Equation 6, the y-coordinate of the object to be measured 6 can also be determined as follows. In other words, from number 5, the following number 7
is obtained.

[0031]

[Math 7]

When x1 of equation 6 is substituted for x1 of equation 7, the following equation 8 is obtained.

[0033]

[Math. 8]

Therefore, the position of the object to be measured 6 in the direction of the projection axis and in the direction orthogonal to the projection axis C can be determined by performing and outputting the calculations of Equations 6 and 8 using the arithmetic processing circuit 48 that performs arithmetic processing using a microcomputer. P(x1,y
1) Or displacement can be determined.

[0035]

According to the present invention, the displacement of an object to be detected moving in a direction perpendicular to the projection axis of the light beam can be detected. Therefore, the displacement of the object to be measured can be measured not in the direction of movement of the object but in the lateral direction of the movement path, and the displacement of an object passing in one direction in front of the displacement measuring device can be measured without interfering with the movement of the object. Measurements can be made over a wide range and with high precision.

Furthermore, by arranging the first and second light receiving sections on both sides of the light projecting section, the influence of displacement of the object to be measured in the direction of the projection axis can be removed, and the effect of displacement of the object to be measured in the direction perpendicular to the projection axis can be removed. The amount of displacement can be accurately measured. Alternatively, displacement of the object to be measured in two directions, ie, the direction of the projection axis and the direction perpendicular to the projection axis, can be measured simultaneously.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 3 is a diagram illustrating the principle for determining the position of an object to be measured in the above embodiment.

FIG. 4 is a block diagram showing an arithmetic processing circuit similar to the above.

FIG. 5 is a schematic configuration diagram showing still another embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing a conventional displacement measuring device.

FIG. 7 is a schematic diagram showing a measurement method using a photoelectric switch.

[Explanation of symbols]

2　　　　Light projection part 3. Luminous source 5　　　　　Light projection lens 6 Object to be measured 7, 22, 27 Light receiving section 8, 23, 28 Light receiving lens 9, 24, 29 Position detection element 10, 31, 48 Arithmetic processing circuit

Claims (3)

[Claims] Claim 1: A light projector that projects a light beam having a spread larger than the surface dimension of the object to be measured; a light receiving lens that collects reflected light from the surface of the object to be measured; Calculates the displacement of the object to be measured or the distance to the object to be measured in the direction orthogonal to the projection axis of the light beam based on the light receiving section that has a position detection element placed near the imaging position and the output from the light receiving section. A displacement measuring device comprising: arithmetic processing means; 2. A light projecting unit that projects a light beam having a spread larger than the surface dimension of the object to be measured, a first light receiving lens that collects reflected light from the surface of the object to be measured, a first position detection element placed near the image formation position of the reflected light; a first light receiving part placed on the side of the light projecting part; and a first light receiving part placed on the side of the light projecting part; a second light-receiving lens that emits light; and a second position detection element placed near the imaging position of the condensed reflected light; The displacement of the object to be measured in the direction orthogonal to the projection axis of the light beam or the distance to the object to be measured is calculated based on the output from the first and second light receiving sections and the second light receiving section placed on the side. arithmetic processing means for
Displacement measuring device consisting of. 3. A light projector that projects a light beam having a spread larger than the surface dimension of the object to be measured, a first light receiving lens that collects the reflected light from the surface of the object to be measured, a first position detection element placed near the image formation position of the reflected light; a first light receiving part placed on the side of the light projecting part; and a first light receiving part placed on the side of the light projecting part; a second light-receiving lens that emits light; and a second position detection element placed near the imaging position of the condensed reflected light; A second light-receiving section disposed in the direction of the light beam, and a displacement of the object to be measured in the direction of the projection axis of the light beam and a direction orthogonal to the projection axis based on the outputs from the first and second light-receiving sections. A displacement measuring device comprising: arithmetic processing means for calculating the distance to.