JP3356321B2 - Object shape measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object for measuring a three-dimensional position and a shape of a moving object by irradiating a moving object by two-dimensionally spatially scanning light emitted from a distance / speed meter using light. Related to a shape measuring device.

[0002]

2. Description of the Related Art As a conventional active method for measuring the shape of an object, there is a triangulation method. However, in an apparatus using the triangulation method for three-dimensional measurement, the size of the apparatus is increased and the measurable distance range is limited. Is a disadvantage. As other methods, there are an illuminance type stereo method, a moiré method, an interference method, and the like, but it is difficult to measure the shape of a moving object by three-dimensional measurement by these methods. On the other hand, in the optical radar method, a three-dimensional image can be obtained by optical scanning, but there is no example applied to a moving object.

FIG. 13 is a view showing a conventional example of a light beam scanning device of a laser distance meter for shape measurement. As an example of an apparatus for measuring the shape of a stationary three-dimensional object by triangulation, a paper by Mark Lieu "Laser range finder based on synchronized sca"
nners "Author: Marc Rioux 1 November 1984 Vol. 23, p
With reference to p.3837-3844 APPLIED OPTICS), a light beam scanning device of a range finder will be briefly described with reference to FIG.

In FIG. 13, light (laser) emitted from a light source S is applied to a surface of a polygonal pyramid mirror 61, and further to plane mirrors M1, M3.
Then, the light is reflected by the surface of the measured object 62.
This light is reflected by the plane mirrors M3 and M2 and another surface of the polygon mirror 61 and is incident on the position detector D. At this time, if the plane mirrors M1 and M2 are set to an appropriate angle and fixed, the light is scanned in the left-right direction by rotating the polygon mirror 61 at high speed. On the other hand, by slowly changing the angle of the plane mirror M3, light is scanned in the forward direction. As described above, the distance, that is, the “depth” is measured by the triangulation method while the measurement light is two-dimensionally scanned by the rotation of the polygon mirror 61 and the angle change of the plane mirror M3, so that a three-dimensional shape can be obtained. .

[0005]

However, the object shape measuring apparatus using the above-mentioned conventional laser rangefinder has the following problems.

(1) The range of the measurable distance (the range of the depth) is limited due to the restriction of the performance of the position detector.

(2) Since the plane mirrors M1 and M2 are set apart, the size of the optical system becomes large.

(3) Since only the distance is detected, it is not possible to correct the apparent change in the shape due to the movement of the object within the measurement time.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an object shape measuring apparatus capable of reducing the size of an optical system and measuring the position and shape of a moving object.

[0010]

SUMMARY OF THE INVENTION To this end, the present invention relates to an object shape measuring apparatus for measuring the shape of a moving object by optical scanning, wherein the apparatus uses a light source and a light receiver to receive reflected light from the measured object. Distance / speed meter for detecting the distance and speed to the object to be measured by the detector, optical scanning means for two-dimensionally scanning light emitted from the distance / speed meter, and each scanning time by the optical scanning means. It is characterized by comprising a time measuring means for measuring, and a calculating means for calculating the shape and position of the object to be measured from the measured value by the distance / speed meter, the scanning point by the optical scanning means, and the time by the time measuring means.

[0011]

In the object shape measuring apparatus according to the present invention, a distance / velocity meter for measuring a distance and a speed to the object to be measured by detecting the reflected light from the object to be measured by using the light source and the optical receiver, and Optical scanning means for two-dimensionally scanning the light emitted from the distance / speed meter, timing means for measuring each scanning time by the optical scanning means, measurement values by the distance / speed meter, scanning points by the optical scanning means, and timing Since the calculating means for calculating the shape and position of the object to be measured from the time by the means is provided, the shape of the moving object to be measured can be measured by performing distance correction by speed at each time.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an object shape measuring apparatus according to the present invention.

In FIG. 1, a distance / speed meter A measures the distance and the speed to an object simultaneously using light.
At least one light source 1, a light receiver 2 close to the light source 1, a distance detector 3 for detecting a distance based on a signal from the light receiver 2, a speed detector 4 for detecting a speed, and a distance detector 3
And speed calculating section 5 for calculating distance and speed using output signals from speed and speed detecting section 4, power supply 6 for exciting light source 1, and lens system 7 for converting light emitted from light source 1 into parallel light. Using a self-mixing type semiconductor laser (for example, Japanese Patent Application No. 63-26558).
No. 5). In the distance / velocimeter A of FIG. 1, the case of a self-mixing type light source configured so that a part of the light emitted from the light source 1 is coupled to the light receiver is shown, but the reflected light is guided to the light receiver 2. For this purpose, another lens system may be added. The plane mirrors 8 and 9 are for two-dimensionally scanning the light (laser beam) emitted from the distance / velocity meter A, and for driving these are step motors 1.
0, 11, the motor drive circuits 12, 13, and the motor control circuit 14. The clock circuit 15 is for measuring the measurement time of each scanning point (measurement point) on the measured object 18, and the computer 16 calculates the distance from the distance / speed meter A,
This is for calculating the shape of the measured object 18 based on the measured value of the speed, the measurement time from the timing circuit 15, and the angle information of the optical scanning, and for outputting a control signal for controlling the scanning device. The display device 17 is for displaying a three-dimensional image of the shape of the measured object.

Next, the principle of shape measurement by the object shape measuring apparatus will be described. 2 is a diagram for explaining a coordinate system in shape measurement, FIG. 3 is a diagram for explaining a distance / velocity measurement order on a shape measurement surface, and FIG. 4 is a diagram for explaining a principle of a distance image restoration of a moving object. FIG. 5 is a flowchart showing the procedure of measuring the shape of the moving object. The scanning of the laser beam is performed by the two plane mirrors 8 and 9 as shown in FIG.
In the X and Y directions, the origin of the coordinates in the shape measurement is determined by the plane mirror 9 for vertical scanning as shown in FIG.
For example, a right-handed system in which the direction away from the apparatus to the front is the positive direction of z, the vertical direction is the Y axis, and the horizontal direction is the X axis.

In the above coordinate system, data directly obtainable by the apparatus is based on a plane having a distance L _r Y = 0, X = 0 on the optical path from the light source 1 to a coordinate P of a certain point on the object surface. a laser beam scanning angle theta _x that is the speed V _r felt theta _y direction of the optical axis. In addition, necessary parameters and the like are defined as shown in FIG. That is, the distance from the light source 1 to the plane mirror 8 for scanning in the X direction is L ′, and the plane mirror 8 for scanning in the X direction is Y
The distance to the plane mirror 9 for scanning in the direction is L ₀ , the reflection point of the laser beam on the plane mirror 9 for scanning in the Y direction is X _p , the distance from the reflection point X _p to the coordinates P on the object surface is L, and the distance L is L. Is Y
= Length projected onto the XZ plane 0 and L _1. As a result, the coordinates P = (x, y, z) on the surface of the object are as follows due to the geometric relationship.

[0016]

L = L _r −L′−L ₀ sec θ _x (1) L ₁ = L / (1 + cos ² θ _x tan ² θ _y ) ^1/2 (2) x = L ₀ tan θ _x + L ₁ sin θ _x (3) y = L ₁ cos θ _x tan θ _y (4) z = L ₁ cos θ _x (5) The object shape measuring apparatus according to the present invention scans one laser beam and FIG. 3 shows one example of the order in which information on the distance and speed in the direction is sequentially acquired. The order is, for example, 1 in the figure.
Start measurement from the lower right corner to the left from
3. Perform through m until m. Of course, as shown in the figure, instead of return scanning in which scanning is performed to the left and then slightly shifted upward and then scanning is performed in the opposite right direction, returning from the left end to the right end and slightly shifting upward and repeatedly scanning in the same left direction is performed. Needless to say, it is good. In the measurement of the shape of a stationary object, the coordinates of the surface of the object at that scanning point need only be obtained from the distance data at each scanning point, but in the case of a moving object, the coordinates obtained from each scanning point are calculated based on the moving speed of the object. Must be corrected. The speed is measured from a beat signal obtained using the Doppler effect or the self-mixing effect. Therefore, in order to simplify the processing after the measurement, it is assumed that the velocity vector V of the object does not change from the start of the first measurement to the end of the m-th measurement.

[0017] Under this assumption, one point of a surface of an object to the coordinates P at time T _p would have moved to the coordinate P 'at time T _m to finish m-th measurement. FIG. 4 shows this state. Therefore, the coordinates P 'are given as follows.

[0018]

P ′ = P + V (T _m −T _p ) (6) Further, if the moving direction of the object is limited to only the z-axis direction for simplicity,

[0019]

P ′ = P + V _z (T _m −T _p ) (7) Here, the V _z vector in the Z-axis direction, its magnitude is the velocity V _r when measured coordinate in the Z direction.

Next, the procedure of shape measurement will be described. In the case of shape measurement, as shown in FIG. 5 or after the start, measurement conditions such as a scanning range and the average number of measurements at one measurement point are input (step S1). At this point, since the laser beam is directed toward the origin on the measurement surface, that is, in the Z-axis direction, the beam is first moved to the measurement start point (step S2). The measurement start point is at the lower right corner of the measurement plane, that is, at the minimum value of each of X and Y. Here, after the first distance measurement is performed, the counter of the timing circuit is started (steps S3 to S4). Thereafter, the optical scanning and the distance / velocity measurement are sequentially repeated (step S5). After the measurement at the last measurement point is completed, the counter is stopped (step S6).

Thereafter, it is assumed that the time at each measurement point is uniform, and based on the time taken for measurement and the total number of measurement points, the measurement time at each measurement point is determined based on the time when the measurement of the first measurement point is completed. It is determined (step S7). Based on this time and the speed obtained by the measurement, the position vector obtained by the measurement is corrected by using the equation (7) to obtain the distance image of the object at the time when the measurement of the final measurement point is completed (step S8). ). This is graphically displayed on the display of the computer (step S9). Finally, the laser beam is returned to the origin (step S10), and the measurement is completed.

FIG. 6 is a diagram showing a configuration of a laser beam scanner according to the present invention, FIG. 7 is a diagram showing a configuration example of a motor control circuit, FIG. 8 is a diagram for explaining driving of a step motor,
FIG. 9 is a timing chart for explaining the operation of the motor drive circuit, and FIG. 10 is a diagram for explaining the resolution of the laser beam scanner in the X and Y directions.

The laser beam scanner has plane mirrors 8 (M1) and 9 (M) for scanning in the X and Y directions as shown in FIG.
2) and having independent step motors 10, 1
FIG. 6 shows a portion of the optical scanning system which is driven by the optical scanning system 1. In the light scanning by the plane mirrors 8 and 9, the light scanning angle is twice the rotation angle of the mirror. The axes of the step motors 10 and 11 rotate by an angle determined by the rise of the input time-series pulse. In order to operate the step motors 10 and 11 by a computer, it is possible to directly output a time-series pulse from the computer, but it is necessary to convert the bus output of the computer into a time-series pulse by an external circuit. You may comprise. FIG. 7 shows an example of the latter.

The motor control circuit 14 includes a computer 16
And generates a time-series pulse for driving the motor in response to a command from the controller. Each step motor rotates by a predetermined minimum angle θ _{min at} each rising edge of one pulse of the input time-series pulse, and when the number of time-series pulses is p, the step motor rotates by an angle of pθ _min and its position To stop.
In FIG. 7, the output of an oscillator 21 is divided by a frequency dividing circuit 23 through a gate circuit 22, and the pulse is divided by the gate circuit 2.
The motor 8 and the motor 8 are arranged so as to be distributed in the respective rotation directions and output. The binary counter 24 counts the number of pulses output to the motor. The control circuit 25 sets the number of pulses to be output to the motor, resets the binary counter 24, allocates the X and Y axis motors, and indicates the direction of rotation. The control circuit 25 sets the number of pulses from the A port. In response to a command from the port C, the binary counter 24 is reset, the X and Y axis motors are distributed, and the rotation direction is specified. The comparator 26 compares the output value of the binary counter 24 with the set value of the control circuit 25. The gate control circuit 27 controls the gate circuit 22 based on the comparison result.
It is.

In the driving of the step motor, for example, in the step motor 10 for rotating the plane mirror 8, the output terminal M1CW of the motor control circuit 14 outputs an output signal for rotating clockwise, and the output terminal M1CCW outputs an output signal for rotating counterclockwise. Similarly, in the step motor 11 for rotating the plane mirror 9, the output signal of the output terminal M2CW of the motor control circuit 14 to rotate clockwise and the output signal of the output terminal M2CCW to rotate counterclockwise are If so, it operates as follows. First, as shown in FIG. 8, the number of drive pulses corresponding to the rotation angle of the motor to be rotated in one step scan of the plane mirror is set in the control circuit 25, and 2
The data is output in a base number (step S11). The control circuit 25 determines the direction of rotation for each of the step motors 10 and 11, outputs each gate control signal of the gate circuit 28 from the C port (step S12), and outputs a counter reset command from the C port. Then, the binary counter 24 is reset (step S13). Then, a start command is generated at the falling edge of the reset signal, the gate control circuit 27 is cleared, the gate circuit 22 is turned on (step S15), and a pulse is output to each motor through the gate circuit 28 to drive it (step S16).
A pulse is output to the motor until the count value of the binary counter 24 matches the set value of the control circuit 25, and the gate control circuit 27 is operated by the match output of the comparator 26 to turn off the gate circuit 22 and stop the pulse to the motor. (Step S18). This series of operations is performed according to an instruction from the computer 16. FIG. 9 is a time chart showing the waveform. This operation may be continuous, or the scanning beam may be moved at equal time intervals, and a short stop time may be inserted after the movement until the next movement.

In such a laser beam scanner, since the scanning angles are equally spaced, the displacement distance of the measuring point in one scanning step differs depending on the distance from the origin of the scanner to the point to be measured. One scanning step is performed by motor 1, 2, 3
FIG. 10 shows the relationship between the scanning interval and the distance Z in the case of steps. Therefore, in order to finely measure a distant object, one scanning step must be reduced.

In the above laser beam scanner, in order to prevent transmission of a pulse for a short time exceeding the maximum self-starting frequency f _max of the step motor, 2f _max is selected as a reference clock, and the frequency dividing circuit 23 divides the frequency by 2 minutes. It is reported to the motor around. This way the motor, pulse frequencies above f _max is not input. In the above example, the pulse frequency supplied to the motor is set to 5 kHz.

Next, the timing circuit will be described. FIG. 11 is a diagram illustrating a configuration example of a timing circuit, and FIG. 12 is a diagram for describing an operation of the timing circuit. In measuring the shape of a moving object, if it is not known when each measurement point was measured, the shape of the object cannot be restored when all the measurements are completed, even if the speed of the object is known. Therefore, a timing circuit 15 is needed to know when each measurement point was measured. This timing circuit 1
5 is 10 MHz of the crystal oscillator 31 as shown in FIG.
Is divided by a frequency dividing circuit 32 to, for example, 100 Hz, and this is counted by 16-bit binary counters 33 and 34. And the connection to the computer is
The binary counters 33 and 34 are also reset via the interface circuit 35 and through this.

Next, the operation will be described. The clock pulse from the crystal oscillator 31 is divided by the frequency dividing circuit 32,
Input to the binary counters 33 and 34. As shown in FIG. 12, first, in response to a start command from the computer 16, the interface circuit 35 resets the binary counters 33 and 34 (step S21), and then starts measuring the frequency-divided pulse (step S22).
When the beam scanning is completed, the computer 1
When the measurement end signal is received from 6, the values of the binary counters 33 and 34 at that time are read by the interface circuit 35 (steps S23 and S24) and transmitted to the data bus of the computer 16. By multiplying the output values of the binary counters 33 and 34 by the period of one divided pulse, the time required to measure all the measurement points can be obtained. Is divided by (m-1), the time τ required for measuring one measurement point can be obtained. Therefore, in this case, since the scanner scans at equal time intervals, if the measurement time start time is set to zero, the measurement time of the Nth measurement point can be obtained as (N-1) τ.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above-described embodiment, the two-dimensional optical scanning mechanism is constituted by two plane mirrors. However, the scanning differs from the above according to the shape, size, speed, distance to the existing position, and the like of the measurement object. May be employed.

[0031]

As is apparent from the above description, according to the present invention, the reflected light from the object to be measured is measured by using the light source and the light receiver while scanning the light emitted from the distance / speed meter two-dimensionally. Since the distance and speed to the object to be measured are detected by the light receiver and each scanning time is measured, the distance and the speed of each scanning point are corrected from the time and speed to accurately determine the shape and position of the moving object to be measured. Can be sought.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an object shape measuring apparatus according to the present invention.

FIG. 2 is a diagram for explaining a coordinate system in shape measurement.

FIG. 3 is a diagram for explaining a distance / velocity measurement order on a shape measurement surface.

FIG. 4 is a diagram for explaining the principle of distance image restoration of a moving object.

FIG. 5 is a flowchart illustrating a procedure of measuring a shape of a moving object.

FIG. 6 is a diagram illustrating a configuration of a laser beam scanner.

FIG. 7 is a diagram illustrating a configuration example of a motor control circuit.

FIG. 8 is a diagram for explaining driving of a step motor.

FIG. 9 is a timing chart for explaining the operation of the motor drive circuit.

FIG. 10 is a diagram for explaining the resolution in the X and Y directions of a laser beam scanner.

FIG. 11 is a diagram illustrating a configuration example of a timing circuit.

FIG. 12 is a diagram for explaining the operation of the timing circuit.

FIG. 13 is a diagram illustrating a conventional example of a light beam scanning device of a laser distance meter for shape measurement.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 light source, 2 light receiver, 3 distance detector, 4 speed detector, 5 distance / speed calculator, 6 power supply, 7 lens system,
8, 9 ... plane mirror, 10, 11 ... step motor, 12,
13 ... motor drive circuit, 14 ... motor control circuit, 15 ...
Clock circuit, 16: Computer, 17: Display device, A:
Distance / speedometer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masao Kado 2-325-8 Kobe, Higashiyamato-shi, Tokyo (56) References JP-A-5-60523 (JP, A) JP-A-4-155204 (JP) JP-A-2-112784 (JP, A) JP-A-62-194413 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102

Claims (3)

(57) [Claims] An object shape measuring device for measuring the shape of a moving object by optical scanning, comprising detecting a reflected light from an object to be measured by using a light source and a light receiving device and detecting the reflected light from the object to be measured. A distance / speed meter for measuring distance and speed, an optical scanning means for two-dimensionally scanning light emitted from the distance / speed meter, a time measuring means for measuring each scanning time by the optical scanning means, and a distance / speed meter An object shape measuring device, comprising: an arithmetic means for calculating a shape and a position of an object to be measured from a measured value, a scanning point by an optical scanning means, and a time by a timing means. 2. The optical scanning means comprises two plane mirrors for scanning light emitted from a distance / velocity meter in X and Y directions, a step motor for driving the plane mirror, and a control circuit for controlling the step motor. The apparatus for measuring the shape of an object according to claim 1, wherein: 3. The object shape measuring apparatus according to claim 1, wherein the calculating means corrects the distance to the measured object at each scanning point by time and speed.