JPH11248430A - Three-dimensional measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the three-dimensional measurement at a higher resolution than that of a two-dimensional light receiving device, by providing the light receiving device for outputting a photoelectric conversion signal according to the incident angle in a subscanning direction of a reference light, and subscanning mechanism for relatively moving it in a main scanning direction. SOLUTION: A light projection system 10 is composed of a semiconductor laser 11 to be a light source, projection lens 13 for making a laser beam into a slit light (reference light) L, etc. A light receiving system 20 is composed of an image forming lens 21, light receiving device 25 for detecting the incident angle of the slight light L and, subscanning mechanism 26 for inching it in a main scanning direction. The light receiving system 20 are located with a distance from the light projection system 10 to measure the incident angle of the slit light incident on the light receiving device 5 in the subscanning direction, to obtain the distance between the irradiated part of an object Q to be measured by the slit light L and reference position in the apparatus. The output of the receiving device 25 is periodically sampled and the depth of the object Q is measured every sampling section SP of finely divided virtual plane VS to obtain a distance image with SP as a pixel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional measuring apparatus for projecting reference light to measure an object shape in a non-contact manner.

[0002]

2. Description of the Related Art A non-contact type three-dimensional measuring device (three-dimensional camera) called a range finder can perform higher-speed measurement than a contact-type three-dimensional measuring device.
It is used for data input to the D system, body measurement, visual recognition of robots, and the like.

[0003] As a measuring method suitable for a range finder, a slit light projection method (also called a light cutting method) is widely known. This method is a kind of active measurement method that optically scans an object to obtain a distance image (three-dimensional image) based on the principle of triangulation. Since the line scanning is performed by projecting the slit-like reference light having a length corresponding to the main scanning range, the scanning time of one frame is shorter than that of performing the point scanning by projecting the beam-like reference light.

Conventionally, a technique has been proposed in which a PSD (position detection type photodetector) is used instead of a general CCD image sensor as a photoelectric conversion device for receiving reference light. That is, this is a method in which a large number (for example, 128) of one-dimensional PSDs having a band-shaped light receiving surface are arranged in the main scanning direction to form a pseudo two-dimensional light receiving surface. Each P
The SD outputs an analog signal corresponding to the position of the light incident on the band-shaped light receiving surface. According to the PSD, since charge accumulation is not required, scanning at a higher speed than that of the CCD can be performed.
In addition, the resolution (resolution) in the sub-scanning direction is greatly improved (it becomes infinite in principle).

[0005]

However, the above-mentioned PSD
In the measurement using an array, the resolution in the main scanning direction is defined by the number of PSD arrays. The higher the number of arrays, the higher the price. In addition, since a head amplifier is required for each PSD, the number of arrays is limited in terms of circuit scale.

An object of the present invention is to realize three-dimensional measurement with a higher resolution than that of a light receiving device constituting a two-dimensional light receiving surface.

[0007]

According to the present invention, by slightly displacing a light receiving device with respect to incident light,
Or, conversely, the incident light is slightly deflected with respect to the light receiving surface, thereby increasing the apparent resolution. For example, when a light receiving surface is formed by arranging a plurality of photodetectors, the displacement is intermittently displaced at a pitch of 1 / m of the arrangement pitch, and the photoelectric conversion signal is sampled at each time, so that the resolution is increased by a factor of m. Become.

The apparatus according to the first aspect of the present invention projects reference light so as to linearly scan a virtual plane, and passes through each sampling section obtained by subdividing the virtual plane in a main scanning direction and a sub-scanning direction. What is claimed is: 1. A three-dimensional measuring apparatus for outputting a signal corresponding to an incident angle of said reference light reflected by a measurement target at a point in time, wherein said light receiving device outputs a photoelectric conversion signal corresponding to an incident angle of said reference light in a sub-scanning direction. And an auxiliary scanning mechanism for relatively moving the light receiving device and the reference light toward the light receiving surface in the main scanning direction.

The apparatus according to a second aspect of the present invention has a data processing means for calculating distance data for each of the sampling sections based on the photoelectric conversion signal. 4. The apparatus according to claim 3, wherein the light receiving device is composed of two or more n one-dimensional position detection type photodetectors arranged in a main scanning direction, and the auxiliary scanning mechanism includes a photodetector of the photodetector. The light receiving device and the reference light are relatively moved at a pitch smaller than the arrangement pitch.

[0010]

FIG. 1 is a diagram showing an outline of a three-dimensional measuring apparatus 1 according to the present invention. The three-dimensional measuring apparatus 1 includes a light projecting system 10 that projects slit light L so as to perform a line scan toward a virtual plane VS set as a reference plane for measurement, and receives the slit light L reflected by an object Q to be measured. A light receiving system 20, a signal processing circuit 90 for quantizing a received light signal, and a CPU 51 as control means.

A light projecting system 10 includes a semiconductor laser (LD) 11 as a light source, a light projecting lens 13 for converting a laser beam into slit light L, and a galvano mirror 12 as a sub-scanning means.
It is composed of The galvanometer mirror 12 includes a mirror that reflects the slit light L and an electromagnetic mechanism that rotates the mirror. A drive signal for changing the rotation angle of the mirror is provided to the electromagnetic mechanism so that the sub-scanning speed on the virtual plane VS is constant. The sub-scan is performed intermittently every main scan of one line. For example, the main scanning direction (X direction) is a horizontal direction, and the sub scanning direction (Y direction) is a vertical direction.

The light receiving system 20 includes an imaging lens 21, a light receiving device 25 for detecting an incident angle of the slit light L, and an auxiliary scanning mechanism 26 for slightly moving the light receiving device 25 in the main scanning direction. The auxiliary scanning mechanism 26 includes, for example, a piezoelectric element and a driving circuit thereof.

The light receiving system 20 and the above-mentioned light projecting system 10 are arranged at a fixed distance (base length) in the Y direction, and the mutual arrangement relationship is known. Therefore, the light receiving device 25
If the incident angle in the Y direction of the slit light L incident on
The distance between the part of the object Q irradiated with the slit light L and the reference position in the apparatus can be obtained by applying a well-known triangulation method. The incident angle of the slit light L in the Y direction is
This corresponds to the distance between the center of the light receiving surface of the light receiving device 25 and the light receiving spot. The CPU 51 performs data processing for performing a triangulation calculation for obtaining a distance image and performing correction based on calibration on the result. The calibration measures, for example, a plane. If the output of the light receiving device 25 is periodically sampled during the scanning period, the depth (virtual plane VS) of the object Q is obtained for each sampling section (in principle, a point) sp obtained by subdividing the virtual plane VS in the X and Y directions. (A position in a direction perpendicular to the direction of the arrow). That is, a distance image having the sampling section sp as a pixel can be obtained.

FIG. 2 is a configuration diagram of the light receiving device 25.
The number of the light receiving devices 25 is n (0 to n−1) (for example, 1
This is a PSD array in which PSDs 251 are closely arranged and arranged so that the arrangement direction of the PSDs 251 is the main scanning direction. Each PSD 251 is a one-dimensional detector having a band-shaped light receiving surface, and includes first and second detection signals (photocurrent) Y1, indicating a spot position (part of the slit light image SG) in the sub-scanning direction. Y2 is output. The suffixes (0 to n-1) of the reference numerals in the figure represent the corresponding PSD251 array element numbers. All the PSDs 251 are moved simultaneously with respect to the slit light image SG by the auxiliary scanning mechanism 26 as described later. In addition, by using PSD, CCD
Scanning can be sped up as much as charge accumulation is unnecessary as compared with the case where an imaging device is used.

FIG. 3 is a schematic diagram of the step movement of the light receiving device 25. The light receiving device 25 moves stepwise in the main scanning direction during the scanning period of one line. The moving width is 1 / m of the width w of one PSD 251 (m is an integer of 2 or more;
For example, 8), and the number of steps per line is m−
It is one. Here, the detection signal output from the j-th PSD 251 at the time of performing the k-th step movement is represented by Y1 _{j, k} , Y2 _{j, k} (j = 0 to n−1, k = 0 to m−).
1).

FIG. 4 is a block diagram of the signal processing circuit 90, and FIG. 5 is a schematic diagram of improving the resolution of the light receiving surface. The signal processing circuit 90 includes head amplifiers (preamplifiers) 91 and 92 for converting the detection signals Y1 and Y2 from each PSD 251 into voltage signals of a predetermined level, and a total of 2n head amplifiers 91 and 9
An analog switch 93 for selecting the output of the analog switch 93 and an A / D converter 94 for quantizing the detection signals Y1 and Y2 selected by the analog switch 93. In each of a total of m stages from the stage before the start of movement of the PSD 251 (step 0) to the stage after the (m−1) th movement (step m−1), the detection signals Y1 _{j, k} , Y2 _{j , k} are simultaneously input to the signal processing circuit 90, and are sequentially selected by the analog switch 93. Then, the detection signal Y
1 _{j, k} and Y2 _{j, k} are sequentially quantized and sent to the CPU 51. The CPU 51 outputs m × n data DY1 corresponding to the detection signals Y1 _{j, k} in steps 0 to m−1.
_P (p = 0 to m × n−1) and n × m data DY2 _p corresponding to the detection signal Y2 _{j, k} are stored as measurement data for one line.

Here, the data DY1 _P , DY2 _p of the area of width w / m obtained by dividing the light receiving surface of the PSD 251 into m are actually the detection signals Y1 _{j, k} , Y2 _{j, k of} the m adjacent areas.
Is the photoelectric conversion information corresponding to the sum of. That is, FIG.
Assuming that the detection signals are assumed to be y1 _p and y2 _p when each area e is assumed to be an independent light receiving surface as in (B), the detection signal Y1 _{j, k} is represented by the following equation. The same applies to the detection signal Y2 _{j, k} .

[0018]

(Equation 1)

This relationship can be expressed as a matrix Y = Ay. Y is an (m × n) × 1 matrix (j = 0 to n−1, k = 0 to m−) in which the (m × j + k) -th element is Y1 _{j, k}
1), y is a first p element is _{y p (m × n) ×} 1 matrix (p = 0~m × n-1 ). A is a _ij (i, j)
Assuming that the elements are (m × n) × (m × n) square matrix, Becomes If the (i, j) element of the left inverse matrix A ′ of A is a ′ _ij , Becomes

When A 'is used, each PS is obtained from y = A'Y.
The signal component of each area obtained by dividing D251 into m can be obtained, and the resolution in the main scanning direction can be increased. A 'is a one-dimensional P
Since it is uniquely determined by the number n of arrays of SD 251 and the number m of movement steps, it is determined in advance and Y1 at each sub-scanning position is determined.
_{j, k,,} Y2 j, k for each of (j = 0~n-1, k = 0~m-1) is inputted, the CPU 51 y1 _p, y2 _p [p =
0-mx (n-1)]. For each set of _{y1 p, y2 p, d p} = Request _{(y1 p -y2 p) / (} y1 p + y2 p). d _p is the amount of deviation between the incident position of the slit light in the PSD 251 and the center of the light receiving surface, and the distance to the target object Q is determined from this value and the control signal of the galvanomirror 12 (or the monitor signal of the rotation angle position). .

FIG. 6 is a configuration diagram of another light receiving device 25b. In the above example, n PDSs 251 have a width w without any gap.
The light receiving device 25 shown in FIG.
In b, n PDSs 251 are arranged at regular intervals. The resolution of the light receiving device 25b having this configuration can be improved by the step movement.

FIG. 7 is a schematic diagram of the step movement corresponding to FIG.
FIG. Step moving width is the array pitch of PSD251
V is 1 / m, and the number of steps per line is m
It is -1. Like the above example, the k-th step movement
Output from the j-th PSD 251
The detection signal is Y1_{j, k}, Y2 _{j, k}(J = 0 to n-1, k =
0 to m-1).

In the case of this example, since Y1 _{j, k} and Y2 _{j, k} represent the position of the slit light image SG in the sub-scanning direction at each step movement position, the matrix operation performed in the above example is unnecessary. is there. For each set of Y1 _{j, k and} Y2 _{j, k} , d _{j, k} = (Y1 _{j, k} -Y2 _{j, k} ) / (Y1 _{j, k} + Y2
_{j, k} ) to obtain the slit light image S at each main scanning position.
The shift amount of G from the center of the light receiving surface is obtained. The distance to the target object Q is obtained from this value and the control signal of the galvanometer mirror 12 (or the monitor signal of the rotation angle position).

In the above embodiment, the light receiving devices 25, 2
5b is displaced by a predetermined amount with respect to the slit light image SG by moving the light receiving device 2b.
Alternatively, the slit light image SG and the light receiving surface may be relatively moved by arranging the fixed positions 5 and 25b and deflecting the incident light on the rear side or the front side of the imaging lens 21. For example, by arranging the glass plate 22 in the incident light path as shown in FIG. 8 and rotating it by a small angle, the incident optical axis can be shifted in the main scanning direction with respect to the light receiving surface.

Although the slit light is exemplified as the reference light, the spot light may be deflected in the main scanning direction. In this case, the signal processing system may be configured to repeatedly scan the same line during a period in which the light receiving device is moved.

[0026]

According to the first to third aspects of the present invention,
It is possible to realize three-dimensional measurement with a higher resolution than the resolution of the light receiving device forming the two-dimensional light receiving surface.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a three-dimensional measuring apparatus according to the present invention.

FIG. 2 is a configuration diagram of a light receiving device.

FIG. 3 is a schematic diagram of a step movement of a light receiving device.

FIG. 4 is a block diagram of a signal processing circuit.

FIG. 5 is a schematic diagram of improvement in resolution of a light receiving surface.

FIG. 6 is a configuration diagram of another light receiving device.

FIG. 7 is a schematic diagram of a step movement corresponding to FIG. 6;

FIG. 8 is a diagram showing a modification of the relative movement between the incident light and the light receiving surface.

[Explanation of symbols]

 Reference Signs List 1 3D measuring device VS virtual plane L slit light (reference light) sp sampling section Q measurement target 25 light receiving device Y1, Y2 detection signal (photoelectric conversion signal) 26 auxiliary scanning mechanism 51 CPU (data processing means) 251 PSD (1D) (Position detection type photodetector) w Width (array pitch) v Array pitch

Claims (3)

[Claims] A reference light is projected so as to perform a line scan toward a virtual plane, and is reflected by a measurement target at a point in time when the virtual plane passes through each sampling section subdivided in a main scanning direction and a sub-scanning direction. A three-dimensional measuring device that outputs a signal corresponding to the incident angle of the reference light, wherein the light receiving device outputs a photoelectric conversion signal according to the incident angle of the reference light in a sub-scanning direction; An auxiliary scanning mechanism for relatively moving the reference light toward the light receiving surface in the main scanning direction. 2. The three-dimensional measuring apparatus according to claim 1, further comprising data processing means for calculating distance data for each of said sampling sections based on said photoelectric conversion signal. 3. The light-receiving device comprises two or more n one-dimensional position detection type photodetectors arranged in a main scanning direction, and the auxiliary scanning mechanism is smaller than an arrangement pitch of the photodetectors. The three-dimensional measurement apparatus according to claim 1, wherein the light receiving device and the reference light are relatively moved at a pitch.