JP3546126B2 - 3D shape measuring device - Google Patents

Description

ここで、Ｉ（ｔ）は受光信号を示しており、ωはレーザ光出力の強度変調周波数、ω′は光検出器２２のゲイン強度変調周波数である。また、この際、それぞれの強度変調信号が有している位相差に関する情報は保存される。
【００２１】
そして、例えばレーザ光出力の強度変調周波数ωを５０ＭＨｚ、光検出器１５，２２のゲイン強度変調周波数ω′を５０．０３ＭＨｚを選択すると、光検出器２２により受光された信号Ｉ（ｔ）は、１００．０３ＭＨｚと、０．０３ＭＨｚの２つの周波数を有する信号となる。この光検出器２２から出力される２つの周波数の信号のうち、０．０３ＭＨｚの信号がローパスフィルタ２３を経由して取り出され、受光信号２４として位相差検出回路１９へ送られる。この位相差検出回路１９は、受光信号２４と参照信号１８との位相差を検出し、位相差信号２５としてユーザインターフェース６へ出力する。このユーザインターフェース６は、上記位相差信号２５と、ｘｙ軸二次元スキャナー１０による計測対象物１３への照射位置を示すスキャナ位置情報１４とから計測対象物１３の３次元形状を求め、表示装置２６に表示する。
【００２２】
上記信号処理における位相の分解能を０．１°とすると、５０ＭＨｚに対応する信号では、最小０．８３ｍｍ（光の速度Ｃは、Ｃ＝３＊１０^８ （ｍ／ｓ）である。また、計測可能距離Ｌは、
Ｌ＝（３＊１０^８ ／（５０＊１０^６ ））＊（１／２）＝３（ｍ）
である。上式における（１／２）は、計測対象物１３により反射された光を処理するので、計測対象物１３までの距離は１／２となる。位相の分解能を０．１°とした場合、最小の計測精度は、
３（ｍ）／３６００＝０．８３（ｍｍ）
の精度での計測が可能になる。
【００２３】
【発明の効果】
以上詳記したように本発明によれば、強度変調を施したレーザ光出力、及び、このレーザ光出力の強度変調周波数と僅かに異なる周波数でゲイン強度変調を施した光検出器を用いることによって、ビートダウン回路等の電気回路や、高速クロックによる位相検波回路等を用いることなく高精度化が可能であり、３次元形状計測装置の低価格化並びにシステムの簡便化を図ることができる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る３次元形状計測装置の構成を示すブロック図。
【図２】同実施形態における動作を説明するためのレーザ光出力、光検出器ゲイン、受光信号の各グラフを示す図。
【符号の説明】
１ レーザ装置
２ レーザ光
３ 変調器
４ レーザ光強度変調用発振器
６ ユーザインターフェース
８ ハーフミラー
９ 集光光学系
１０ ｘｙ軸二次元スキャナー
１１ スキャナー制御回路
１３ 計測対象物
１５ 光検出器
１６ ゲイン変調用発振器
１７ ローパスフィルタ
１９ 位相差検出回路
２１ 受光レンズ系
２２ 光検出器
２３ ローパスフィルタ
２６ 表示装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a three-dimensional shape measuring device used for dimension measurement of hull members, bridges, structural members, and the like.
[0002]
[Prior art]
In a three-dimensional shape measuring apparatus using a general laser beam, there are (1) a pulse method and (2) a phase difference method.
The pulse method of the above (1) irradiates a pulsed laser beam, measures the time difference between the received light and the transmitted light, finds the distance to the measurement target, and determines the direction of the measurement target from the transmission direction. I have.
In the phase difference method (2), the laser light is subjected to intensity modulation and irradiated onto a measurement target, the phase shift between the transmission light and the reception light is measured, the distance to the measurement target is determined, and the transmission direction is determined. The direction of the object to be measured is determined.
[0003]
[Problems to be solved by the invention]
In the conventional three-dimensional shape measuring apparatus, in order to increase the resolution in the distance direction and measure a wide range at a time, the pulse width is narrowed in the pulse method (1), and the pulse width is reduced in the phase difference method (2). , The modulation frequency must be increased.
[0004]
The pulse method of (1) means that the clock of the means for measuring the reflected light is increased in the clock speed and the signal is broadened, resulting in a drawback that the device becomes complicated and the price increases.
Further, in the phase difference method (2), when the phase shift exceeds one wavelength, it becomes difficult to measure the absolute distance, and only the relative distance can be measured, and the area to be measured at one time is limited.
[0005]
This means that high-precision measurement in a wide area means moving the measuring device to the vicinity of the object to be measured, making the measuring system larger and more expensive, and a clock for measuring the reflected light. It means higher speed, wider signal bandwidth, and more complicated device.
[0006]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a three-dimensional shape measuring apparatus which has a simple configuration, can increase the resolution in the distance direction, and can measure a wide area at a time. The purpose is to do.
[0007]
[Means for Solving the Problems]
Three-dimensional shape measurement apparatus according to the present invention includes a laser device for generating a laser beam, modulating means for the laser light intensity modulation output from the laser device, any elevation the modulated laser beam by the modulating means A scanner that scans in the azimuth direction and irradiates the object to be measured, scanner control means that controls the scanner according to a scanning setting signal and outputs scanner position information, and part of the laser light modulated by the modulation means a half mirror for reflecting a first photodetector for receiving the laser beam reflected by the half mirror, and a second photodetector for receiving the laser light reflected from the measurement object, the first and gain modulating means for gain intensity modulate the light detector and the second optical detector at a frequency slightly different from the intensity modulation frequency of the laser light, the first Intensity of the first selection means and said second detection signal by the photodetector which outputs a low frequency signal of the difference between the intensity modulation frequency and gain intensity modulation frequency of the detection signal from the light detector as selected and reference light A second selector for selecting a low-frequency signal having a difference between a modulation frequency and a gain intensity modulation frequency and outputting the selected signal as a light receiving signal; and a reference light selected by the first selector and the second selector. Phase difference detection means for detecting a phase difference with the selected light receiving signal and outputting the same as a phase difference signal; and a phase difference signal output from the phase difference detection means and scanner position information output from the scanner control means. Processing means for measuring a three-dimensional shape of the measurement object .
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a three-dimensional shape measuring apparatus according to one embodiment of the present invention.
As shown in FIG. 1, a laser beam 2 generated by a laser device 1 is subjected to laser intensity modulation by a modulator 3 in an analog manner. The modulator 3 is supplied with a modulation electric signal 5 from a laser light intensity modulation oscillator 4. The laser beam intensity modulation oscillator 4 can oscillate at a frequency of, for example, several to several hundred MHz, and operates via a user interface 6 in accordance with a frequency switching signal 7 specified by a user (measurer).
[0009]
The laser light modulated by the modulator 3 is scanned in arbitrary elevation and azimuth directions by an xy-axis two-dimensional scanner 10 via a half mirror 8 and a condensing optical system 9. The xy-axis two-dimensional scanner 10 is configured by a combination of, for example, a two-axis rotating device such as a stepping motor and a member having a light reflecting function such as a mirror, and is controlled by a scanner control circuit 11. The scanner control circuit 11 controls the xy-axis two-dimensional scanner 10 via the user interface 6 according to the scanning setting signal 12 specified by the user (measurer), and irradiates the measurement target 13 with the laser beam 2a. . Further, the scanner control circuit 11 outputs the position information 14 of the xy-axis two-dimensional scanner 10 to the user interface 6.
[0010]
A part of the laser light modulated by the modulator 3 is reflected by the half mirror 8 and enters the photodetector 15. This photodetector 15 is subjected to gain intensity modulation by a gain modulation oscillator 16 at a frequency slightly different from the intensity modulation frequency of the laser light output. For example, when the modulation frequency of the laser light is 50 MHz, the modulation frequency of the gain modulation is set to 50.03 MHz. As described above, a low frequency signal of 0.03 MHz is generated by beatdown by superposition of two types of waves in the photodetector 15. This low-frequency signal is taken out by the low-pass filter 17 and sent to the phase difference detection circuit 19 as the reference signal 18.
[0011]
Then, the laser beam 2 b reflected by the measurement target 13 is condensed via the light receiving lens system 21 and enters the photodetector 22. The photodetector 22 is intensity-modulated at a frequency of, for example, 50.03 MHz by the gain modulation oscillator 16 in the same manner as the photodetector 15 and outputs a low frequency signal of 0.03 MHz as a result of beat down. The low frequency signal output from the photodetector 22 is input to the phase difference detection circuit 19 as a light receiving signal 24 via the low pass filter 23.
[0012]
The phase difference detection circuit 19 detects a phase difference between the reference signal 18 and the light receiving signal 24, and outputs a phase difference signal 25 to the user interface 6. The user interface 6 outputs and displays three-dimensional information of the measurement target 13 to the display device 26 based on the scanner position information 14 and the phase difference signal 25.
[0013]
Next, the operation of the above embodiment will be described.
The laser light 2 generated by the laser device 1 is input to a modulator 3 and is intensity-modulated in an analog manner at a frequency of, for example, 50 MHz based on a modulation electric signal 5 output from a laser light intensity modulation oscillator 4. . The laser light modulated by the modulator 3 is scanned in arbitrary elevation and azimuth directions by an xy-axis two-dimensional scanner 10 via a half mirror 8 and a focusing optical system 9. The scanner control circuit 11 controls the xy-axis two-dimensional scanner 10 via the user interface 6 according to the scanning setting signal 12 specified by the user (measurer), and scans the laser beam 2a in the azimuth and elevation directions. Then, the measurement object 13 is irradiated, and the position information 14 of the xy-axis two-dimensional scanner 10 is output to the user interface 6.
[0014]
A part of the laser light modulated by the modulator 3 is reflected by the half mirror 8 and enters the photodetector 15. In the photodetector 15, since the gain modulation is performed by the gain modulation oscillator 16 at a frequency slightly different from the intensity modulation frequency of the laser light output, a low-frequency signal of the difference is extracted by the low-pass filter 17. , As a reference signal 18 to the phase difference detection circuit 19.
[0015]
Then, the laser beam 2 b reflected by the measurement target 13 is condensed via the light receiving lens system 21 and enters the photodetector 22. The photodetector 22 is intensity-modulated by the gain modulation oscillator 16 at the same frequency as that of the photodetector 15. The signal is input to the detection circuit 19.
[0016]
2 (a) to 2 (c) show the laser beam output applied to the object 13 to be measured, the gain of the photodetectors 15 and 22, the light receiving signal 24 extracted through the photodetector low-pass filter 23, FIG.
[0017]
In the graph of “laser light output” shown in FIG. 2A, the vertical axis indicates the output intensity of the laser light, and the horizontal axis indicates time. As shown in this graph, the output of the laser light in the present invention is temporally modulated in intensity. For example, in a shape measuring device with an accuracy of several millimeters, intensity modulation corresponding to a frequency of several to several hundred MHz is usually used.
[0018]
In the graph of "detector gain" shown in FIG. 2B, the vertical axis indicates the gain intensity of the photodetectors 15 and 22, and the horizontal axis indicates time. That is, this shows a state in which the gain of the photodetectors 15 and 22 is temporally modulated.
[0019]
In the graph of “light reception signal” shown in FIG. 2C, the vertical axis indicates the light reception signal intensity, and the horizontal axis indicates time.
The laser light output subjected to the intensity modulation as described above and the light receiving signal using the photodetector 22 subjected to the gain intensity modulation at a frequency slightly different from the intensity modulation frequency of the laser light output are as follows. It is observed as a signal having the frequency shown by the equation.
[0020]

Here, I (t) indicates a light receiving signal, ω is an intensity modulation frequency of the laser light output, and ω ′ is a gain intensity modulation frequency of the photodetector 22. At this time, information on the phase difference of each intensity-modulated signal is stored.
[0021]
When the intensity modulation frequency ω of the laser beam output is selected to be 50 MHz and the gain intensity modulation frequency ω ′ of the photodetectors 15 and 22 is selected to be 50.03 MHz, the signal I (t) received by the photodetector 22 becomes The signal has two frequencies of 100.03 MHz and 0.03 MHz. Of the two frequency signals output from the photodetector 22, a 0.03 MHz signal is extracted through the low-pass filter 23 and sent to the phase difference detection circuit 19 as a light receiving signal 24. The phase difference detection circuit 19 detects a phase difference between the light receiving signal 24 and the reference signal 18 and outputs the same to the user interface 6 as a phase difference signal 25. The user interface 6 obtains a three-dimensional shape of the measurement target 13 from the phase difference signal 25 and scanner position information 14 indicating an irradiation position of the xy-axis two-dimensional scanner 10 on the measurement target 13, and displays the display device 26. To be displayed.
[0022]
Assuming that the phase resolution in the signal processing is 0.1 °, a signal corresponding to 50 MHz has a minimum of 0.83 mm (light speed C is C = 3 * 10 ⁸ (m / s). The possible distance L is
L = (3 * 10 ⁸ / (50 * 10 ⁶ )) * (1/2) = 3 (m)
It is. Since (1/2) in the above equation processes light reflected by the measurement target 13, the distance to the measurement target 13 is 1/2. When the phase resolution is 0.1 °, the minimum measurement accuracy is
3 (m) / 3600 = 0.83 (mm)
Measurement with an accuracy of.
[0023]
【The invention's effect】
As described in detail above, according to the present invention, by using a laser light output subjected to intensity modulation, and a photodetector subjected to gain intensity modulation at a frequency slightly different from the intensity modulation frequency of the laser light output, The accuracy can be improved without using an electric circuit such as a beat-down circuit, a phase detection circuit using a high-speed clock, and the like, and the cost of the three-dimensional shape measuring apparatus can be reduced and the system can be simplified.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a three-dimensional shape measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a view showing respective graphs of a laser light output, a photodetector gain, and a light receiving signal for explaining the operation in the embodiment.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 laser device 2 laser light 3 modulator 4 laser light intensity modulation oscillator 6 user interface 8 half mirror 9 focusing optical system 10 xy-axis two-dimensional scanner 11 scanner control circuit 13 measurement object 15 photodetector 16 gain modulation oscillator 17 Low Pass Filter 19 Phase Difference Detection Circuit 21 Light Receiving Lens System 22 Photo Detector 23 Low Pass Filter 26 Display Device

Claims (1)

A laser device for generating a laser beam, modulating means for the laser light intensity modulation output from the laser device, the measurement object with the laser light modulated by said modulating means by scanning any elevation-azimuth A scanner for irradiating the scanner, scanner control means for controlling the scanner according to a scanning setting signal and outputting scanner position information, a half mirror for reflecting a part of the laser light modulated by the modulation means, and the half mirror A first photodetector that receives the reflected laser light, a second photodetector that receives the laser reflected light from the object to be measured, the first photodetector, and the second photodetector and gain modulating means for gain intensity modulated by the laser light intensity modulation frequency and slightly different frequencies, the intensity modulation of the signal detected by the first photodetector First selection means for outputting a reference light by selecting the low-frequency signal of the difference between the wave number and the gain intensity modulation frequency, the intensity modulation frequency and gain intensity modulation frequency of the signal detected by the second photodetector Second selecting means for selecting a low frequency signal having a difference and outputting the selected signal as a light receiving signal; and a phase difference between the reference light selected by the first selecting means and the light receiving signal selected by the second selecting means. Phase difference detecting means for detecting the three-dimensional shape of the object to be measured from the phase difference signal output from the phase difference detecting means and the scanner position information output from the scanner control means. A three-dimensional shape measuring apparatus comprising: a processing means for measuring.

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