JPH08122072A - Level sensor - Google Patents

Abstract

PURPOSE: To accurately and easily measure the distance from a laser beam emitting unit to a level sensor. CONSTITUTION: The time intervals of the output of three photoreceiving means 9A, 9B, 9C corresponding to three edges 9a, 9b, 9c detected by the means 9A, 9B, 9C, the distances to a laser beam emitting unit are calculated based on the measured intervals, the rotary angle of a triangle formed by the three edges 9a, 9b, 9c in the plane of the laser beams is obtained based on the comparison of the measured plurality of the intervals, and the distances are corrected based on the obtained angle. Even if the sensor body is inclined and the apparent intervals of the three edges 9a, 9b, 9c as seen from the unit are varied, the distance to the unit can be accurately obtained without regulating the inclination of the body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a level sensor,
In particular, the present invention relates to a level sensor that performs leveling and distance measurement using a laser beam that is rotationally projected.

[0002]

2. Description of the Related Art A conventional level sensor of this type is shown in FIG. 5 (Japanese Patent Laid-Open No. 4-307320).

FIG. 5 is a block diagram of a conventional level sensor. This level sensor includes a wedge-shaped light receiving element 107A, 107B that receives a laser beam rotatively projected from a laser beam projector (not shown), and a height position detection circuit 1 including an amplification circuit, a peak hold circuit, a comparison circuit, and the like.
08 and the light receiving elements 109A and 109B, which are arranged so as to sandwich the wedge-shaped light receiving elements 107A and 107B and receive the laser beam rotatively projected from the laser projecting device, and waveforms for shaping the signals from the light receiving elements 109A and 109B. Shaping circuits 110A and 110B and waveform shaping circuit 110
A time detection circuit 111 for detecting the time from the output time of the light receiving element 110A to the output time of the light receiving element 110B based on the signals from A and 110B, and time information and height position detection from the time detection circuit 111. Circuit 10
A CPU 112 that calculates the distance from the laser beam projecting device to the sensor body and the height position of the laser beam based on the height position information from 8, and a display 104 that displays the calculation result of the CPU 112. .

The operation of this level sensor will be described with reference to the flowchart of FIG.

First, the wedge type light receiving elements 107A and 107
The analog outputs of B are compared (step S61). Next, when there is an output difference, an arrow is displayed on the display 104 (step S62). This arrow mark is an instruction to move the sensor body up or down with respect to the laser beam. Then move the sensor body up and down as indicated by the arrow,
It is determined whether or not the difference between the analog outputs of the wedge-shaped light receiving elements 107A and 107B has disappeared (step S63), and when the output difference has disappeared, a bar is displayed to indicate that the center of the laser beam has been detected (step S64). At this time, marking work is performed.

Further, the time detection circuit 111 includes the light receiving element 10
The time when the laser beam scans the interval L between 9A and 109B is detected, and the CPU 112 calculates the distance R to the laser beam projecting device by the following equation based on the time information t detected by the time detection circuit 111 ( Step S
65).

R = TL / 2πt Equation (1) In Equation (1) above, the time T required for the laser beam to make one rotation and the time t required to traverse the light receiving elements 109A and 109B are t.
And an arbitrary radial distance from the beam rotation center of the laser beam projector and the distance L between the light receiving elements 109A and 109B.
Since there is a relation of t / T = L / 2πR, the radial distance R to be obtained from this is summarized in the equation (1). The distance R thus obtained holds the minimum value and is digitally displayed on the display 104 (step S66). As a result, the distance R can be easily read.

[0008]

However, the apparent distance between the light receiving elements 109A and 109B as seen from the laser beam projecting device changes due to the inclination of the sensor body.
The distance R cannot be obtained accurately. In order to accurately obtain the distance R, the level sensor for the laser beam projecting device must be tilted in the left-right direction, which causes a problem that the measurement work is complicated.

The present invention has been made in view of such circumstances, and an object thereof is to provide a level sensor capable of accurately and easily measuring a distance from a laser beam projecting device to a sensor body. .

[0010]

In order to solve the above-mentioned problems, a level sensor according to the present invention is a plane of light formed by a laser beam rotatably projected from a laser beam projecting device installed away from a sensor body. Placed on top and having at least three edges, in the plane of the light
A plurality of light receiving means for receiving the laser beam, the triangle being formed by the edges of the places, and a time measuring means for measuring the time intervals of the outputs corresponding to the three edges detected by the plurality of light receiving means, Distance calculation means for calculating the distance to the laser beam projecting device based on the time interval measured by the time measuring means, and a comparison of a plurality of time intervals measured by the time measuring means A rotation angle detecting means for obtaining the rotation angle of the triangle in the plane and a distance correcting means for correcting the distance calculated by the distance calculating means based on the rotation angle obtained by the rotation angle detecting means.

[0011]

As described above, the time intervals of the outputs corresponding to the three edges detected by the plurality of light receiving means are measured, and the distance to the laser beam projecting device is calculated based on the measured time intervals. Is calculated and the rotation angle of the triangle formed by the three edges in the plane of the laser beam is calculated based on the comparison of the measured time intervals, and the distance calculation means is calculated based on the calculated rotation angle. Since the distance calculated by is corrected, even if the sensor body is tilted and the apparent intervals of the three edges seen from the laser beam projector are changed, the tilt of the sensor body is not adjusted. The distance to the laser beam projector can be accurately obtained.

[0012]

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

FIG. 1 is a block diagram showing the overall structure of a level sensor according to an embodiment of the present invention, and FIG. 2 is a perspective view showing the appearance of the level sensor of FIG.

As shown in FIG. 2, on the outer wall surface of the sensor body 1, a switch group 2 such as a power switch and a sensor body 1 are provided.
3 for horizontally installing the laser beam at the measurement point, and a display 4 for displaying the distance from the laser beam projector 13 (FIG. 3) to the sensor body 1 and the height position of the laser beam LB.
And the laser beam L rotatably projected from the laser projector.
A light receiving portion 5 for receiving B and a notch 6 for marking are respectively provided. The display unit 4 has a height position display unit 4A for displaying the height position of the laser beam LB, and a distance display unit 4B for displaying the distance from the laser beam projecting device 13 to the sensor body 1 as a number. There is.

This level sensor, as shown in FIG.
Wedge type light receiving elements 7A, 7B for receiving the laser beam LB rotatably projected from the laser beam projecting device 13, a height position detection circuit 8 including an amplifier circuit, a peak hold circuit, a comparison circuit, etc., and a wedge type light receiving element. Light receiving elements 9A, 9 arranged so as to sandwich 7A, 7B to receive the laser beam LB rotatively projected from the laser beam projecting device 13.
B, the light receiving elements 9C, 9A, 9B, which are arranged on a different plane from the light receiving elements 9A, 9B and receive the laser beam LB rotatively projected from the laser beam projector 13.
Waveform shaping circuit 10A, 1 for shaping the signal from 9C
0B, 10C, a time detection circuit 11 for detecting the time from the output time of the light receiving element 9A to the output time of the light receiving element 9B and the time from the output time of the light receiving element 9A to the output time of the light receiving element 9C, and a time detection circuit. A CPU 12 for calculating the distance from the laser beam projector 13 to the sensor body 1 and the height position of the laser beam LB based on the time information from 11 and the height position information from the height position detection circuit 8;
And a display unit 4 for displaying the calculation result of the CPU 12. The light receiving section 5 is composed of wedge-shaped light receiving elements 7A, 7B and light receiving elements 9A, 9B, 9C.

As shown in FIG. 1, the light receiving elements 9A and 9B are arranged on the same plane, and the front edge 9a of the light receiving element 9A in the laser beam rotating direction and the front edge 9b of the light receiving element 9B in the laser beam rotating direction. The light receiving element 9C is arranged on a different plane with respect to the light receiving elements 9A and 9B, and the edge 9a of the light receiving element 9A and the front edge 9c of the light receiving element 9C on the front side in the laser beam rotation direction are spaced apart from each other by a distance L1. L2 apart. On the horizontal plane of the light formed by the rotational projection of the laser beam LB, as shown in FIG. 3, an imaginary triangle is formed between the edge 9a of the light receiving element 9A, the edge 9b of the light receiving element 9B, and the edge 9c of the light receiving element 9C. The straight line connecting the edges 9a and 9b and the straight line connecting the edges 9a and 9c form an angle θ.
1 is formed.

FIG. 3 is a diagram showing the principle of the present invention. C
The distance calculation executed by the PU 12 will be described with reference to FIG.

Edge 9a of light receiving element 9A and light receiving element 9B
Of the laser beam LB across the distance L1 from the edge 9b of the light receiving element 9b, the edge 9a of the light receiving element 9A
If the laser beam LB crosses the distance L2 from the edge 9c of the laser beam LB at t2 and the laser beam LB is scanning from the laser beam projector 13 at one rotation time = T, the laser beam projector 13 detects the sensor. The distance R to the main body 1 can be obtained by the equation R = L1 · T / 2πt1 (1) as in the conventional example.

However, if the sensor body 1 is tilted by an angle θ2 as shown in FIG. 3, ΔL1 = L1 (1-Co
An error of sθ2) occurs, and an accurate distance cannot be obtained.

Therefore, the apparent distances L1 'and L2' from the laser projecting device are expressed by L1 '= L1.Cos.theta.2 (2) and L2' = L2.Cos (.theta.1 + .theta.2) (3).

However, since the lengths of the intervals L1 'and L2' cannot be actually measured, the intervals L1 'and L2' are replaced with the time when the laser beam LB crosses. That is, L1 ': L
Since 2 '= t1: t2, θ2 = Tan ⁻¹ {(1 / Sinθ1) · (L1 · t2 / L2 · t1) − (Cosθ1 / Sinθ1)} (4) By substituting the equation (4) into the equation (2), the apparent distance L1 ′ corresponding to the inclination of the sensor body 1 can be obtained.

L1 ′ = L1 · Cos {Tan ⁻¹ [(1 · Sinθ1) · (L1 · t2 / L2 · t1) − (Cosθ1 / Sinθ1)]} (5) Expression Therefore, the correction expression R ′ = L1 ′ · T / 2πt1 Equation (6) is obtained.

When actually inputting a numerical value, L1 = 100
mm, L2 = 130 mm, θ1 = 9 °, number of revolutions of laser beam projector 13 = 300 rpm, distance R = 100 m, θ
When 2 = 45 °, t1 = 22.51 μs, t2 = 2
Assuming that the time is measured with an accuracy of 4.32 μs, L1 ′ = 70.6722 mm is calculated from the equation (5),
Further, from the equation (6), R '= 99.94 m is calculated. If the same numerical value is calculated using equation (1) without correction, R =
It becomes 141.4 m, and an error of about 41 m occurs.

Next, the operation of this level sensor will be described with reference to the flowchart of FIG.

First, the analog outputs of the wedge type light receiving elements 7A and 7B are compared (step S1). Next, when there is an output difference, an arrow is displayed on the display device 4 (step S
2). This arrow mark indicates that the sensor body 1 is the laser beam LB.
Is an instruction to move up or down. Then, the sensor body 1 is moved up and down as indicated by the arrow, and it is determined whether or not the difference between the analog outputs of the wedge-shaped light receiving elements 7A and 7B is eliminated (step S3). When there is no difference between the outputs, the laser beam LB A bar is displayed to indicate that the center has been detected (step S4). At this time, the marking work is performed using the notch 6.

Further, the time detection circuit 11 uses the edges 9a, 9
The CPU 12 detects the time when the laser beam LB scans the interval L1 of b and the interval L2 of the edges 9a and 9c, and the CPU 12 detects the time information t1 and t2 detected by the time detection circuit 11.
Based on the above, the apparent interval L1 'is calculated by the equation (5) (step S5).

Further, the CPU 12 calculates the distance R to the laser beam projecting device 13 by the following equation based on the one rotation time T detected by the time detection circuit 11 (step S6).

R = TL1 ′ / 2πt1 (7) Equation (7) The distance R thus obtained is digitally displayed on the display unit 4.

According to the level sensor of this embodiment, even if the sensor body 1 is tilted, the distance to the laser beam projecting device 13 can be accurately obtained without adjusting the tilt of the sensor body 1. Measurement work becomes easy.

In the above embodiment, the case where three light receiving elements 7A to 71C are used as a plurality of light receiving means has been described, but instead of this, two light receiving elements are used and the same as in the above embodiment. Are arranged on different planes, and the width of one light receiving element (the distance between the front edge and the rear edge in the laser beam rotation direction) is set to L1, and the front edge of one light receiving element and the other edge are set to L1. The distance from the rear edge of the light receiving element is set to L2, and the front edge and the rear edge of one light receiving element and the rear edge of the other light receiving element form a triangle similar to the above-described embodiment. You may

[0031]

As described above, according to the level sensor of the present invention, even if the sensor body is tilted and the apparent intervals of the three edges seen from the laser projector are changed, the tilt of the sensor body is increased. The distance to the laser beam projecting device can be accurately obtained without adjusting, and the measurement operation becomes easy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a level sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the appearance of the level sensor shown in FIG.

FIG. 3 is a diagram for explaining the principle of the present invention.

FIG. 4 is a flow chart for explaining the operation of the level sensor.

FIG. 5 is a block diagram of a conventional level sensor.

FIG. 6 is a flowchart for explaining the operation of the level sensor.

[Explanation of symbols]

 5 Light receiving section 9A, 9B, 9C Light receiving element 9a, 9b, 9c Edge 11 Time detection circuit 12 CPU

Claims (1)

[Claims] 1. A laser beam projecting device installed away from a sensor body is arranged on a plane of light formed by a laser beam rotatively projected, and has at least three edges, and the Triangles are formed on the plane by the three edges, and a plurality of light receiving means for receiving the laser beam, and time intervals of outputs corresponding to the three edges detected by the plurality of light receiving means are measured. A time measuring means, a distance calculating means for calculating a distance to the laser beam projector based on the time interval measured by the time measuring means, and a comparison of a plurality of time intervals measured by the time measuring means. A rotation angle detecting means for obtaining a rotation angle of the triangle in the plane of the light based on the distance, and a distance calculated by the distance calculating means on the basis of the rotation angle obtained by the rotation angle detecting means. Level sensor, characterized in that and a distance correction means for correcting.