JP2668663B2 - 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 a shape measuring apparatus for measuring a three-dimensional shape of an object to be measured in a non-contact manner by using optical means, and more specifically, it is stable by using a rotating mirror rotating at high speed. The present invention relates to a shape measuring device configured to perform measurement.

[0002]

2. Description of the Related Art Conventionally, a spatial coding method is known as one of typical optical shape measuring methods. The spatial coding method is one of active measurement methods that include a light projecting device on a measuring device side and measure reflected light of a projected light by a measurement target.
FIG. 5 shows an example of a shape measuring apparatus based on the space coding method disclosed in Japanese Patent Application Laid-Open No. 5-332737.
This will be described with reference to FIG. 5 includes a laser light source 87 and a lens system 8 for shaping a laser beam into a slit shape.
8, a polygon mirror 89 for irradiating the measured object Q with a shaped laser beam, a CCD camera 81 for detecting light reflected by the object Q to be measured, and a control section 82 for controlling these. I have.

A laser light source 87 is controlled so as to blink according to a predetermined rule, and a polygon mirror 89 rotates to scan the laser light. Therefore, on the surface of the measurement object Q, a stripe pattern of a part irradiated with the laser light and a part not irradiated is generated. Here, 1 of the CCD camera 81
Since the laser beam is scanned once within the accumulation time for one frame, the striped pattern data of the measurement object Q is accumulated in the image data for one frame. Then, when scanning is performed a plurality of times by different blinking patterns, a plurality of different stripe data are stored for each space code.

On the basis of these stripe data, an arithmetic unit built in the control unit 82 calculates the coordinates of a point on the measurement object Q corresponding to each pixel using the principle of triangulation, and measures the shape. Is done. This shape measuring device is intended to realize the downsizing of the device and quick measurement by making the laser light source 87 blink, thereby eliminating the need for a mechanical pattern mask and its replacement operation.

[0005]

However, there is a problem which cannot be solved by this shape measuring device. That is, in this shape measuring apparatus, the laser beam is scanned by rotating the polygon mirror 89, but stable rotation cannot be obtained because the rotation speed is slow. This is because the polygon mirror 89 scans the laser light once within the accumulation time of one frame of the CCD camera 81.
The scanning is performed by one rotation of the polygon mirror 89 (for example, in the case of 12 surfaces, 1/12 rotation, 30 °). On the other hand, the storage time for one frame is determined by the video rate and is usually 1/60 second. Therefore, in this case, the rotation speed of the polygon mirror 89 is 300 rpm,
This is much slower than the speed range where stable rotation can be obtained with a normal motor.

Therefore, fluctuations in the rotational speed of the motor, such as wow and flutter and jittering, cannot be ignored, and good measurement accuracy cannot be obtained. It is conceivable that a reduction gear is interposed between the motor and the polygon mirror 89, but it is unavoidable to increase the size of the device, and other problems such as machining accuracy of the reduction gear and backlash occur.

The rotation of the polygon mirror 89 is 1/6.
It must be completely synchronized with the video rate of 0 seconds, but if this is to be realized by attaching an encoder to the polygon mirror 89 and controlling it while reading angle information, a resolution of about 5000 divisions per screen is required. Is necessary and there are 12 faces, so 1 rotation is 60000
You need something to split. For this reason, the price becomes extremely high, and it is difficult to reduce the size of the device.

Alternatively, there is a method in which a galvano mirror having two front and back surfaces is used instead of the polygon mirror 89 and the laser beam is scanned by reciprocating rotation instead of continuous rotation. However, in this case, non-constant velocity motion control is required, while it is susceptible to external factors such as temperature changes and external vibrations.
Highly accurate reciprocating rotary motion is very difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to perform deflection scanning using high-speed rotation capable of obtaining a stable rotation and to provide an encoder. An object of the present invention is to provide a small-sized and low-cost shape measuring device by enabling measurement without performing the measurement. Therefore, for that purpose, the polygon mirror is rotated at high speed so that the scanning is performed a plurality of times within the imaging time of one screen, the phase of the deflection scanning is detected, and the flashing of the laser beam is performed based on this phase to perform the high-speed deflection scanning. It is an object of the present invention to provide a shape measuring apparatus which acquires measurement data by integrating images obtained by the above method. Further, it is another object of the present invention to provide a shape measuring device capable of measuring both bright and dark places by making it possible to select the number of times of flashing and emitting a laser beam among a plurality of scans during image storage. .

[0010]

In order to achieve this object, a shape measuring apparatus of the present invention comprises a laser light source for flashing a laser beam, a pattern memory storing a plurality of flashing patterns of the laser beam, and the laser. A polygon mirror that deflects and scans light toward an object to be measured, an image pickup unit that picks up an image generated on the surface of the object to be measured by the irradiation of the laser beam, and a shape of the object to be measured based on image pickup data by the image pickup unit. A shape measuring device having a shape calculating means for calculating, wherein a driving means for rotationally driving the polygon mirror to deflect and scan, and a phase reference signal when a phase of rotation of the polygon mirror is detected and a specific phase is detected. A phase reference signal generating means for generating, and the laser based on one of the blinking patterns stored in the pattern memory based on the phase reference signal. And lighting control means for lighting control sources,
Pattern changing means for changing a blinking pattern followed by the blinking control means when the imaging means completes imaging of one screen, wherein the driving means performs a plurality of scans within an imaging time of one screen of the imaging means. The gist of the invention is to rotate and drive the polygon mirror so as to perform the operation.

Further, the shape measuring apparatus of the present invention is the above-mentioned shape measuring apparatus, wherein the laser light is actually blinked and emitted among a plurality of scans performed within the image pickup time of one screen by the image pickup means. The gist of the invention is that light amount adjusting means for setting the number of scans is provided.

[0012]

In the shape measuring apparatus of the present invention having such a configuration, the polygon mirror is rotationally driven by the driving means, and is rotated at a high speed such that the laser light is scanned a plurality of times within one imaging time of one screen of the imaging means. I do. Then, the phase of this rotation is detected by the phase reference signal generating means, and a phase reference signal is generated at the time of a specific phase. This phase reference signal is sent to the blinking control means, and the blinking control means causes the laser light source to blink with the phase reference signal as a reference. At that time, it follows one of the blinking patterns stored in the pattern memory.
Since this laser light is deflected and scanned by the rotating polygon mirror toward the object to be measured, an image is produced on the surface of the object to be measured, and this image is captured by the image capturing means.

When the deflection scanning of the laser beam is performed once by the rotation of the polygon mirror and the phase becomes a specific phase again, the phase reference signal generating means generates the second phase reference signal. Therefore, even in the second deflection scanning, the laser light source blinks and emits light according to the same blinking pattern as in the first deflection scanning. Then, when the imaging of one screen by the imaging means is completed, the blinking pattern followed by the blinking control means is changed by the pattern changing means, and the imaging is performed by the new blinking pattern. Thus, the shape calculation means calculates the shape of the object to be measured based on the image data obtained by the imaging means, and the shape is measured.

In the shape measuring apparatus of the present invention, the light quantity adjusting means sets the number of scans in which the laser light is actually blinked and emitted among a plurality of scans performed within the image pickup time of one screen by the image pickup means. Is done. For this reason, since the measurement can be performed with the light amount corresponding to the brightness of the object to be measured, both the bright place and the dark place can be measured.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a shape measuring apparatus according to the present invention. A shape measuring apparatus according to the present embodiment, which is schematically illustrated in FIG. 1, includes a laser light source 1 that generates laser light, a lens system 2 that shapes the laser light generated by the laser light source 1 into a slit shape, and a slit shape that is formed into a slit shape. The polygon mirror 3 that reflects the laser light and irradiates the object to be measured Q by the rotational motion so as to scan the object to be measured Q, and the image C generated by irradiating the object Q to be measured with the laser light
It has a CD camera 6.

The laser light source 1 may be any known laser light source such as a semiconductor laser, a gas laser, a solid-state laser, and a liquid laser. However, from the viewpoint of miniaturization of the apparatus and high-speed switching, the semiconductor laser is preferred. Is most suitable. The laser light source 1 has a control unit 5
Flashing light.

The control unit 5 is a microcomputer for controlling the shape measuring device, and includes a known CPU, ROM,
It is a combination of RAM and the like. This ROM stores various programs required for control. The control unit 5 includes a main clock 16 and a pattern memory 17 for controlling blinking of the laser light source 1.
And 8 shown in Table 1 in the pattern memory 17
The gray code of the digit is stored. The data "0" of this code means dark, and the data "1" means bright. According to one of the memory bits 0 to 7, the memory address of 0 to 255 is sequentially changed for each pulse of the main clock 16. The state is changed to a blinking pattern. The main clock 16 has a frequency of about several MHz.

[0018]

[Table 1]

Further, the control unit 5 includes a CCD camera 6
To supply a video vertical synchronization signal (hereinafter, referred to as a “VD signal”). This VD signal is also used to change the memory bits (0 to 7) actually used for blink control in the bright and dark data stored in the pattern memory 17, and the motor drive circuit 10 to be described later.
It is also sent to.

The CCD camera 6 is provided with a capture circuit 14 and an arithmetic circuit 15. The capture circuit 14 digitizes and captures an image captured by the CCD camera 6 according to the VD signal captured from the control unit 5, and the arithmetic circuit 15 uses the digitized data to perform the triangulation method on the object to be measured. The shape of Q is calculated. The video rate of the CCD camera 6 is 1/60 second, and 60 screens are imaged per second.

Although the polygon mirror 3 is shown as having six faces in FIG. 1, it is not limited to six faces, and any of four faces to 24 faces can be used. Where N
Is related to the irradiation angle θ for scanning the laser light as follows:
It is sufficient that the irradiation angle θ is about 45 ° to 90 °, so that the number of faces within the range of 8 to 16 is suitable. θ = 720 / N (°) Further, considering the ease of manufacturing the polygon mirror 3 itself, any of the eight, twelve, and sixteen surfaces is realistic. In this case, the irradiation angles .theta. Are 90.degree., 60.degree. And 45.degree., Respectively, and the polygon mirror 3 is rotated 360 / N.degree.

The polygon mirror 3 is provided with a motor 9 which is a driving source for the rotational movement. The polygon mirror 3 and the motor 9 are connected at a 1: 1 rotation ratio without intervening reduction gears such as gears. ing. The motor 9 is controlled by a motor drive circuit 10 including a PLL synchronization circuit 11 and a motor clock generation circuit 12 so as to rotate at a constant speed.

The motor clock generating circuit 12 receives the supply of the VD signal from the control section 5 and generates a motor clock completely synchronized with the VD signal, and the PLL synchronizing circuit 11 uses the motor clock to generate the motor clock. Is designed to drive. This motor clock has a much lower frequency than the main clock. In this embodiment, the polygon mirror 3 is rotated at a high speed and at a constant speed so that the laser beam is scanned many times within the accumulation time of one frame of the CCD camera 6.

The polygon mirror 3 is provided with a photodetector 18. The photo detector 18 is
It has a light emitter, an optical sensor, and a pulse transmitter, and the pulse transmitter emits a pulse when the light from the light emitter is reflected by the polygon mirror 3 and enters the optical sensor. Thereby, the surface phase of the polygon mirror 3 is detected. This pulse signal is transmitted to the control unit 5 and is hereinafter referred to as a “PD signal”. The PD signal is transmitted when each reflection surface of the polygon mirror 3 is at a specific angle with respect to the photodetector 18, and is transmitted as many times as the number of surfaces during one rotation of the polygon mirror 3. This signal is used to reset the blinking pattern when one scan of the laser beam is completed.

Next, the operation of the shape measuring device will be described. In this shape measuring device, the laser light source 1 is controlled by the control unit 5 to emit blinking light. The blinking pattern is based on the gray code pattern stored in the pattern memory 17. That is, according to one of the memory bits 0 to 7 shown in Table 1, a light and dark pattern is generated by the data of "0" and "1" in the order of the memory address of 0 to 255. “0” is dark and “1” is light. For example, when the memory bit is “0”, dark, bright, bright, dark, dark, bright,
Light, dark, dark,...

The blinking laser light is shaped into a slit by the lens system 2 and reaches the polygon mirror 3.
It is reflected toward the object to be measured Q. Since the polygon mirror 3 is rotated by the drive of the motor 9, the reflected laser light scans the object to be measured Q and forms a stripe pattern on the object to be measured Q with a blinking pattern. Then, the CCD camera 6 captures the stripe pattern as an image, and the image is digitized and captured by the capture circuit 14, and the arithmetic circuit 15 calculates the shape of the DUT based on the digitized data. .

Here, the relationship between the imaging time of the CCD camera 6 and the rotation speed of the polygon mirror 3 will be described. First, the imaging time of the CCD camera 6 is based on the VD signal, and is 1/60 second per screen in this embodiment. Therefore, 60 screens are captured in one second. The rotation speed of the polygon mirror 3 is such a high rotation speed that the laser beam is scanned a plurality of times within the imaging time of one screen of the CCD camera 6.

The rotation speed is calculated as follows by taking as an example the case where a polygon mirror 3 having 12 surfaces is used and scanning is performed six times within the imaging time of one screen.
First, the rotation angle of the polygon mirror 3 required for one scan is 360 ° / 12, which is 30 °. Therefore, the rotation angle required for six scans is 180 °. Therefore, since it has to rotate 180 °, that is, a half rotation in 1/60 seconds, the rotation speed becomes 30 rotations per second, that is, 1800 rpm. This rotation speed is high enough to be regarded as constant speed rotation by ignoring fluctuations in rotation speed of the motor 9 such as wow and flutter and jittering.
It is possible to perform constant-speed coupling with. Note that the rotation speed may be further increased by further increasing the number of scans within one image capturing time.

As described above, the scanning of the laser beam is performed many times within the imaging time of one screen of the CCD camera 6, but the blinking pattern is reset by the PD signal, and the same pattern is repeated each time from the beginning. The same stripe pattern is generated on the object Q, and the integration is imaged. Therefore, different stripe patterns are not superimposed on one screen.

Next, an operation flow of the shape measuring apparatus will be described with reference to FIG. In this shape measuring apparatus, blinking control of the laser light is performed according to the contents of the pattern memory 17 during measurement. That is, as described above, if the data is "0", it is dark, and if it is "1", it is light. Then, in S1, it is determined whether or not the pulse of the main clock 16 has risen.
When the main clock rises (S1: Yes), S2
Increments the memory address (0-255). That is, the address number is incremented by 1. Main clock 16
Is on the order of several MHz, and the address increment also follows this.

At S3, it is determined whether the PD signal has risen. When the PD signal rises (S3: Ye
s) In S4, the address of the memory is cleared to 0.
That is, no matter how many address numbers are set, they are returned to 0, and the blinking pattern is reset. Therefore, the same blinking pattern is repeated again thereafter. Since the PD signal rises each time the laser light is scanned, the same blinking pattern is repeated for each scan.

Then, in S5, it is determined whether or not the VD signal has risen. When the VD signal rises (S5: Y
es), the bits (0 to 7) of the memory are changed in S6.
Therefore, thereafter, laser emission is performed in another blinking pattern. Since the VD signal rises every time one screen of the CCD camera 6 is imaged, the next screen will be imaged with a new blinking pattern when the image of one screen is completed.

At S7, the laser light source 1 is controlled according to the data of the memory contents at the present time. That is, S
When there is a change due to any of S2, S4, and S6, the emission control of the laser light source 1 is performed according to the changed data. After that, the process returns to S1 and the same operation is repeated.

The relationship between the surface angle of the polygon mirror 3, the PD signal, the VD signal, and the blinking pattern in the shape measurement by the above flow will be described with reference to the timing chart of FIG. This timing chart shows polygon mirror 3
As an example, a case where scanning is performed six times within one screen imaging time is shown, and time is taken on the horizontal axis.

First, the angle and surface number of the uppermost mirror surface will be described. The angle of the mirror surface shown here means the angle of the surface of the reflection surface of the polygon mirror 3 which actually reflects the laser light. Since the polygon mirror 3 is rotating at a constant speed, it changes linearly, and when one scanning is completed and the next reflecting surface is reached, it changes from the reference angle again.
It becomes a sawtooth waveform as shown. The surface number here (0
6) are numbered within the imaging time of one screen of the CCD camera 6, and do not indicate the number of surfaces of the polygon mirror 3 itself.

The PD signal at the second stage will be described. As described above, this signal is transmitted when each reflecting surface of the polygon mirror 3 makes a specific angle with respect to the photodetector 18, and rises once for each laser beam scanning. That is, a sawtooth wave having an angle of the mirror surface rises every time when each sawtooth has a predetermined height.

The VD signal at the third stage will be described. As described above, this signal controls the imaging operation of the CCD camera 6, and rises when the screen is changed. Since it is assumed that scanning is performed 6 times within the image pickup time of one screen here, the image pickup time of one screen is from the rising of the VD signal to the next rising. Also, the sawtooth wave of the angle of the mirror surface has six sawtooth teeth during the imaging time of one screen. The PD signal and the VD signal do not necessarily have to have the same phase.

The irradiation pattern (bit) of the fourth stage will be described. This indicates the memory bits (0 to 7 in Table 1) of the data stored in the pattern memory 17 that the laser light blinking operation actually follows, and is changed in synchronization with the rise of the VD signal (see FIG. 2). S6). Therefore, when the CCD camera 6 continuously captures a plurality of screens, stripe patterns with different blinking patterns by different memory bits are captured each time.

The irradiation pattern (address) at the fifth stage will be described. This memory address (0 to 255 in Table 1)
Is incremented by the rise of the main clock (see S2 in FIG. 2), and the frequency of the main clock is constant at several MHz, so that the address number increases linearly. Then, the signal is cleared in synchronization with the rising edge of the PD signal and newly starts from 0 (see S4 in FIG. 2). Therefore, the sawtooth waveform has the same cycle as the angle of the mirror surface, and each scan within the imaging time of one screen is performed with the same blinking pattern. Therefore, a stripe pattern of a different blinking pattern is not superimposed on one screen captured by the CCD camera 6.

Next, the calculation of the shape of the object Q to be measured by the triangulation method in the calculation circuit 15 will be briefly described with reference to FIG. As shown in FIG. 4, the height from the measurement reference plane of the laser light source 1 (the plane perpendicular to the optical axis of the CCD camera 6) is hl, the deflection angle is θ, and the height of the laser irradiation position of the measurement object Q is z, the height of the objective lens 7 of the CCD camera 6 from the measurement reference plane is hc, the focal length of the objective lens 7 is f, the CCD
The distance on the reference plane from the reference point O of the optical axis of the camera 6 is 1,
The position of the received pixel on the photosensitive surface 8 of the CCD camera 6 is x,
And

At this time, the height z can be expressed by z = {xhc-f (l-hltan θ)} / (x + ftan θ). From FIG. 4, it can be seen that hc, f, l, and hl are all fixed values that are unrelated to the measurement object Q. That is, if x and θ are known, z can be calculated from this equation. Therefore, if the value of θ corresponding to each x is known, the shape of the measurement object Q can be obtained. x is CCD
This is the position where the image was captured by the camera 6,
Read from digitized data in. On the other hand, θ is the irradiation angle from the polygon mirror 3 at that time. Although the coordinates in the y direction do not appear in FIG. 4, the coordinates are directly derived from the pixel position in the y direction of the CCD camera 6, and three-dimensional measurement is performed.

Next, since the light quantity can be adjusted in the shape measuring apparatus of this embodiment, this will be described. As described above, in this shape measuring device, one of the CCD cameras 6 is used.
Laser light scanning is performed a plurality of times (six times in the case shown in FIG. 3) during the image pickup time of the screen, and the same stripe pattern with the same blinking pattern is integrated. Therefore, instead of performing laser irradiation in all the scans,
If the irradiation is performed only partly, the light amount will be narrowed down. Then, the light quantity is adjusted by selecting the number of times of irradiation. 1 shown in FIG.
Table 2 shows an example of adjusting the light amount when scanning is performed six times during the image capturing time of the screen. By changing the number of reflecting surfaces to be illuminated, six-stage adjustment from 1/6 to 6/6 is possible.

[0043]

[Table 2]

Thus, the shape measurement can be performed by controlling the light amount according to the brightness without controlling the output of the laser light source 1 itself. That is, the light amount 5/6 or 6/6 may be used in the dark case, and the light amount 1/6 or 2/6 may be used in the bright case. In addition, when there is a bright part and a dark part in one visual field, it is also possible to create a pattern having appropriate brightness in the entire visual field by selectively using the light amount.

As described above in detail, in the shape measuring apparatus according to the present embodiment, the photodetector 18 is provided on the polygon mirror 3, and the blinking pattern of the laser light is generated by the PD signal generated when the rotation angle reaches a specific phase. Since we decided to reset and repeat the same pattern again,
Scanning of the laser beam is performed a plurality of times within the imaging time of one screen of the D camera 6, and the same stripe pattern can be integrated and imaged. As a result, the polygon mirror 3 rotates at a high speed.
Can be rotated at high speed.

Accordingly, the motor 9 can be used at a rotational speed that can be regarded as a constant speed ignoring the speed fluctuation component.
High-precision rotation accurately synchronized with the video rate of the D camera 6 can be obtained without using a high-resolution encoder or the like. Thus, a high-resolution shape measuring device using the polygon mirror 3 is realized. In addition, by selecting the number of times of actually blinking and irradiating the laser light among the scanning performed a plurality of times within the imaging time of one screen of the CCD camera 6, the light amount adjustment without the output control of the laser light source 1 itself is required. Therefore, the shape can be measured with an appropriate amount of light according to the brightness of the visual field.

It should be noted that this embodiment does not limit the present invention at all, and it is needless to say that various modifications and improvements can be made without departing from the spirit of the present invention. For example, the numerical values and the like shown in the embodiments are merely examples.

[0048]

As is apparent from the above description, in the shape measuring apparatus according to the present invention, the polygon mirror is rotated at a high speed so that the laser beam is scanned a plurality of times within the imaging time of one screen, and the polygon mirror is rotated. The rotation speed of the laser light source is controlled by the blinking pattern stored in the pattern memory when the rotation becomes a specific phase, and the image is integrated and captured, so stable rotation can be obtained. There is provided a small-sized and low-cost shape measuring apparatus that can perform a deflection scan using a and can measure without using an encoder. In addition, because the number of times that the flashing of the laser light is actually emitted can be selected from the multiple scans during image storage, the light amount can be adjusted without controlling the output of the laser light source itself to adjust the light amount to a bright or dark place. A shape measuring device that can measure both is provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a shape measuring apparatus according to the present invention.

FIG. 2 is a flowchart illustrating an operation of the shape measuring device.

FIG. 3 is a timing chart of a surface angle, various signals, and the like in the shape measuring device.

FIG. 4 is a conceptual diagram illustrating calculation of coordinates by a triangulation method.

FIG. 5 is a configuration diagram of a conventional shape measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light source 3 Polygon mirror 5 Control part 6 CCD camera 9 Motor 15 Arithmetic circuit 17 Pattern memory 18 Photodetector

Claims (2)

(57) [Claims] 1. A laser light source for flashing a laser beam,
A pattern memory storing a plurality of types of blinking patterns of the laser light, a polygon mirror for deflecting and scanning the laser light toward the object to be measured, and an imaging for imaging an image generated on the surface of the object to be measured by the irradiation of the laser light A shape measuring device having means and a shape calculating means for calculating the shape of an object to be measured based on the image data obtained by the image pickup means; drive means for rotationally driving the polygon mirror to deflect and scan; and rotation of the polygon mirror. Phase reference signal generation means for detecting a phase of the laser and generating a phase reference signal at a specific phase, and blinking control of the laser light source according to one of blinking patterns stored in the pattern memory with the phase reference signal as a reference. Blinking control means, and a blinking pattern which the blinking control means follows when the imaging of one screen is completed. A pattern changing means for changing the shape of the polygon mirror, wherein the driving means rotationally drives the polygon mirror so that scanning is performed a plurality of times within an image pickup time of one screen of the image pickup means. . 2. The shape measuring device according to claim 1, wherein the number of scans in which blinking light emission of laser light is actually performed is set among a plurality of scans performed within an image capturing time of one screen by the image capturing unit. A shape measuring device provided with a light amount adjusting means for performing the measurement.