WO2013076769A1 - Optical range finder - Google Patents

Optical range finder Download PDF

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Publication number
WO2013076769A1
WO2013076769A1 PCT/JP2011/006537 JP2011006537W WO2013076769A1 WO 2013076769 A1 WO2013076769 A1 WO 2013076769A1 JP 2011006537 W JP2011006537 W JP 2011006537W WO 2013076769 A1 WO2013076769 A1 WO 2013076769A1
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Prior art keywords
signal
reference signal
modulation
sensitivity
frequency
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PCT/JP2011/006537
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French (fr)
Japanese (ja)
Inventor
勝治 今城
俊平 亀山
幹夫 高林
平野　嘉仁
石村　栄太郎
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三菱電機株式会社
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Priority to PCT/JP2011/006537 priority Critical patent/WO2013076769A1/en
Publication of WO2013076769A1 publication Critical patent/WO2013076769A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S17/36—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated with phase comparison between the received signal and the contemporaneously transmitted signal

Definitions

  • the present invention relates to an optical distance measuring device including a photodetector that receives intensity-modulated light with a single-element photodetector and down-converts the modulation frequency to a low frequency side.
  • devices described in, for example, Patent Document 1 and Patent Document 2 are known as devices for down-converting the modulation frequency of intensity-modulated light to the low frequency side with a photodetector and measuring the distance from the phase difference. ing.
  • intensity-modulated light is down-converted using a pair of adjacent semiconductor elements.
  • the gain of the photodetector is directly modulated, and the output signal is directly down-converted.
  • the photodetector is a photodetector that performs photoelectric conversion by a photovoltaic effect such as an avalanche photodiode (hereinafter referred to as APD (Avalanche Photo Diode))
  • APD avalanche photodiode
  • the light receiving sensitivity characteristic with respect to the bias applied voltage is generally non-linear. For this reason, when the bias application voltage is sinusoidal modulation, the light receiving sensitivity cannot be modulated with the sinusoidal wave, and the efficiency when downconverting to the difference frequency from the frequency of the modulated light becomes very poor. As a result, there has been a problem that the reception signal-to-noise ratio is lowered and the ranging accuracy is low.
  • the present invention has been made to solve such a problem.
  • An optical distance measuring device capable of improving the efficiency when down-converting to a difference frequency from the frequency of modulated light and performing distance measurement with high accuracy is provided.
  • the purpose is to provide.
  • An optical distance measuring device shapes and irradiates a first oscillator that generates a modulation reference signal, a light source that outputs intensity-modulated light based on the modulation reference signal, and light output from the light source.
  • a waveform shaping circuit that shapes the modulation waveform to linearly modulate the sensitivity of the photodetector based on the sensitivity modulation reference signal, and a photodetector that outputs the difference frequency of the received modulated signal as a received signal;
  • a reference signal output unit that outputs a difference signal between the modulation reference signal and the sensitivity modulation reference signal as a reference signal, a phase detector that obtains a phase difference from the received signal and the reference signal, and a phase difference signal output from
  • the optical distance measuring device is provided with a waveform shaping circuit for shaping a modulation waveform signal for linearly modulating the sensitivity of the photodetector based on the sensitivity modulation reference signal output from the second oscillator,
  • the photodetector modulates sensitivity based on the waveform-shaped modulated waveform signal.
  • FIG. 1 is a configuration diagram of the optical distance measuring device according to the first embodiment.
  • the optical distance measuring device according to the present embodiment includes a first oscillator 1, a second oscillator 2, a light source 3, a transmission optical system 4, a waveform shaping circuit 5, a reception optical system 6, and a photodetector 7.
  • An amplifier 8 a mixer 9, a band pass filter (hereinafter referred to as BPF (Band Pass Filter)) 10, a phase detector 11, and a signal processing unit 12.
  • BPF Band Pass Filter
  • the first oscillator 1 and the second oscillator 2 are oscillators that output two different frequencies, respectively, and the first oscillator 1 has a function of generating a modulation reference signal of the light source 3, and the second oscillator 2 Has a function of generating a bias modulation reference signal for modulating the sensitivity of the photodetector 7.
  • the light source 3 is a light source that oscillates laser light that has been intensity-modulated at a frequency based on the modulation reference signal of the first oscillator 1.
  • the transmission optical system 4 is a transmission optical system for shaping the light generated from the light source 3.
  • the waveform shaping circuit 5 is a circuit that generates a bias modulation signal for linearly modulating the bias of the photodetector 7 based on the bias modulation reference signal of the second oscillator 2.
  • the receiving optical system 6 is a receiving optical system for condensing the light received from the transmitting optical system 4 reflected by an object (not shown) on the photodetector 7.
  • the photodetector 7 is a light receiver that modulates sensitivity based on the bias modulation signal shaped by the waveform shaping circuit 5 and outputs an electric signal having a difference frequency from the modulation frequency of the received reflected light.
  • the amplifier 8 is an amplifier such as a transimpedance amplifier that amplifies the difference frequency electrical signal output from the photodetector 7.
  • the mixer 9 is a mixer that mixes the modulation reference signal output from the first oscillator 1 and the bias modulation reference signal output from the second oscillator 2.
  • the BPF 10 is a filter that transmits only the difference frequency among the signals generated by the mixer 9.
  • the mixer 9 and the BPF 10 form a reference signal output unit 13 that outputs a reference signal.
  • the phase detector 11 has a function of detecting a phase difference between the reference signal obtained by the reference signal output unit 13 and the reception signal obtained by the photodetector 7, and generating a phase signal indicating the phase difference.
  • the signal processing unit 12 has a function of calculating a distance value based on the phase signal from the phase detector 11.
  • FIG. 2 shows modulation waveforms output from the first first oscillator 1 and the second oscillator 2.
  • the first oscillator 1 generates a modulation reference signal A having a frequency f m1 as shown in FIG. 2A
  • the second oscillator 2 receives a bias modulation reference signal B having a frequency f m2 as shown in FIG. 2B.
  • the frequency f m1 of the modulation reference signal and the frequency f m2 of the bias modulation reference signal are different frequencies.
  • the modulation reference signal having the frequency f m1 output from the first oscillator 1 is input to the light source 3, and the light source 3 generates intensity-modulated light based on the modulation reference signal having the frequency f m1 .
  • the transmission optical system 4 shapes the intensity-modulated light generated by the light source 3 and irradiates the object.
  • the bias modulation reference signal having the frequency fm2 output from the second oscillator 2 is input to the waveform shaping circuit 5, and the waveform shaping circuit 5 outputs a bias modulation waveform C as shown in FIG.
  • the photodetector 7 is an APD
  • the bias voltage-sensitivity characteristic is generally a non-linear characteristic D as shown in FIG. Therefore, the sensitivity modulation characteristic E shown in FIG. 2D is obtained by giving a certain offset to the bias voltage as shown in FIG. 2C and adding a non-linear modulation waveform.
  • the reflected light from the object is collected by the receiving optical system 6 and received by the photodetector 7.
  • the difference frequency f m1 ⁇ f m2 from the received modulation frequency f m1 is obtained as shown in the output waveform F of FIG.
  • An electric signal is output, and the electric signal is amplified by the amplifier 8 to obtain a received signal.
  • FIG. 3 shows the characteristics of the input conversion noise level with respect to the frequency when a transimpedance amplifier is used as the amplifier 8.
  • the frequency characteristics of the amplifier and the transimpedance gain are inversely proportional, so that the transimpedance gain can be increased if the amplifier has a low frequency characteristic. Accordingly, the noise level is limited by the 1 / f noise determined by the transimpedance amplifier used and the thermal noise determined by the transimpedance gain (see the input conversion noise level characteristic G in the figure), and there is a minimum value of the input conversion noise level.
  • the frequencies f m1 and f m2 are set so that the difference frequency f m1 ⁇ f m2 becomes the minimum value.
  • the mixer 9 mixes the modulated reference signal and a bias modulation reference signal, for generating a difference frequency f m1 -f m @ 2 of frequency f m1 and frequency f m @ 2.
  • the reference signal is generated through the BPF 10 that transmits only the frequency band near the difference frequency f m1 -f m2 .
  • the obtained reference signal and received signal are input to the phase detector 11 and a signal corresponding to the phase difference between the two signals is output. Further, the signal processing unit 12 calculates the distance to the object from the phase difference signal.
  • the waveform shaping circuit 5 can linearly modulate the sensitivity of the photodetector 7.
  • the light is converted into a difference frequency f m1 ⁇ f m2 between the intensity modulation frequency f m1 of the transmission light and the sensitivity modulation frequency f m2 of the photodetector.
  • the frequencies f m1 and f m2 are set so that the difference frequency f m1 -f m2 becomes the minimum value of the input conversion noise level of the transimpedance amplifier.
  • the received signal level since the received signal level is maintained, the signal can be received under the condition that the signal-to-noise ratio of the received signal is optimal, and the ranging accuracy can be improved.
  • a laser is used as an example of the light source 3.
  • a direct modulation method in which a modulation signal is directly input to the light source 3 may be used, or an external modulation method configuration in which an intensity modulator is provided outside to obtain modulated light may be used.
  • the other light source 3 a light emitting diode (LED: Light Emitting Diode) or a super luminescent diode (SLD: Super Luminescent Diode) may be used.
  • LED Light Emitting Diode
  • SLD Super Luminescent Diode
  • an example in which an APD is used for the photodetector 7 has been shown.
  • a photodiode (PD) or a photomultiplier tube (PMT) is used.
  • the BPF 10 may be a low pass filter (LPF) because the difference frequency f m1 ⁇ f m2 may be selected.
  • LPF low pass filter
  • the difference frequency f m1 -f m2 is configured to be the minimum value of the input equivalent noise level of the transimpedance gain, but from the input equivalent noise level of the modulation frequency f m1 of the light source 3. Any frequency region that can be lowered may be used.
  • phase difference signal is output as a function of the phase detector 11, but it may have a function of outputting a signal corresponding to the amplitude.
  • the reflected light is received by irradiating the light.
  • the scanning optical system is used in the subsequent stage of the transmission optical system 4 to scan both the transmission beam and the reception visual field. It may be configured to. Further, for example, as shown in Japanese Patent Application Laid-Open No. 2010-271275, the reception field of view may be fixed and only the transmission beam may be scanned by the scanning optical system.
  • the modulation frequency of the intensity-modulated light is down-converted by the bias-modulated photodetector 7 to the low frequency side where the input equivalent noise level of the amplifier 8 is lowered. Therefore, it is possible to reduce the degradation of distance measurement accuracy due to the target distance difference and reflectance difference in each field of view of the adjacent light receiving element, which has been a problem in the prior art.
  • the sensitivity of the photodetector 7 can be linearly modulated even when an APD is used for the photodetector 7, and the received modulation signal is shifted to the low frequency side. Can be down-converted. Furthermore, by down-converting to the low frequency side, the received signal can be amplified in a frequency band where the amplifier noise (input converted noise current density) is low, and the signal band noise ratio can be improved. This makes it possible to convert the modulated light into an electrical signal and improve the accuracy of the distance measurement, increase the distance that can be measured, compared to a phase difference optical distance measuring device that detects the phase in the same frequency band, Cost reduction can be achieved by suppressing the output of the light source.
  • the first oscillator that generates the modulation reference signal, the light source that outputs the intensity-modulated light based on the modulation reference signal, and the light source A transmitting optical system for shaping and irradiating the output light, a receiving optical system for collecting reflected light from an object based on the irradiated light, and a second oscillator for generating a sensitivity modulation reference signal, and To modulate the sensitivity based on the modulated waveform signal and output the difference frequency with the received modulated signal as the received signal, and to linearly modulate the sensitivity of the photodetector based on the sensitivity modulation reference signal
  • the amplifier includes an amplifier that amplifies the difference frequency signal from the photodetector, and the difference frequency signal is lower than the input conversion noise level of the frequency of the modulation reference signal in the amplifier.
  • the modulation reference signal and sensitivity modulation reference signal are determined so that the frequency range is equivalent to the input-converted noise level, so the accuracy of distance measurement is increased, the measurable distance is increased, and the light source output is suppressed. The cost can be reduced.
  • FIG. The second embodiment is an example in which the light down-converting photodetector described in the first embodiment is formed in an array.
  • FIG. 4 is a block diagram showing the optical distance measuring device according to the second embodiment, and shows a case where two photodetectors 7a and 7b are used as an example.
  • the optical distance measuring device according to the second embodiment includes a first oscillator 1, a second oscillator 2, a light source 3, a transmission optical system 4, a waveform shaping circuit 5, a reception optical system 6, photodetectors 7a and 7b, and an amplifier 8a. 8b, mixer 9, BPF 10, phase detectors 11a and 11b, signal processing unit 12, multiplexer (hereinafter referred to as MUX circuit) 14, photodetectors 7a and 7b, amplifiers 8a and 8b, phase detector 11a. 11b is a photodetector array 15 having an array configuration. Further, the reference signal output unit 13 is configured by the mixer 9 and the BPF 10 as in the first embodiment.
  • each of the two photodetectors 7a and 7b is the same as that of the photodetector 7 of the first embodiment, and modulates the sensitivity of the photodetector based on the modulation waveform shaped by the waveform shaping circuit 5, and receives the signal.
  • An electric signal having a difference frequency from the modulation frequency of the reflected light is output.
  • the amplifiers 8a and 8b are connected to amplify the outputs of the photodetectors 7a and 7b, respectively.
  • the phase detectors 11a and 11b are configured to obtain phase information from the reference signal from the reference signal output unit 13 and the received signals a and b from the amplifiers 8a and 8b and output the phase information as phase signals a and b, respectively. Yes.
  • the MUX circuit 14 is a multiplexer that switches the phase signals a and b from the phase detectors 11 a and 11 b and outputs them to the signal processing unit 12. Since the configuration other than this is the same as that of the first embodiment, the same reference numerals are given to corresponding portions, and the description thereof is omitted.
  • the operation of the optical distance measuring device will be described. Since the basic operation as the optical distance measuring apparatus is the same as that of the first embodiment, only the characteristic operation of the second embodiment will be described. Reflected light from an object (not shown) is collected by the receiving optical system 6 and received by the photodetector 7a and the photodetector 7b. At this time, since the sensitivities of the photodetectors 7a and 7b are modulated at the frequency f m2 , the electric signal of the difference frequency f m1 ⁇ f m2 from the received modulation frequency f m1 as shown in FIG. Then, the electric signals are amplified by the amplifiers 8a and 8b to obtain a reception signal.
  • the frequencies f m1 and f m2 are set so that the difference frequency f m1 -f m2 becomes the minimum value of the input conversion noise level as in the first embodiment. It is the same.
  • the reference signal obtained by the reference signal output unit 13 and the received signals a and b which are the outputs of the amplifiers 8a and 8b are input to the phase detectors 11a and 11b, respectively, and the phase signal a corresponding to the phase difference between the two signals. And the phase signal b are output. Thereafter, the phase signal is switched by the MUX circuit 14, and the signal processing unit 12 calculates the distance to the object from the phase difference signal of the received signal measured by each of the photodetectors 7a and 7b.
  • the photodetector array 15 by using the photodetector array 15 using the plurality of photodetectors 7a and 7b, distance measurement in the light irradiation region can be performed without the need for a scanning optical system. At this time, a three-dimensional image of the object can be obtained by imaging the distance measurement value of each light receiving element.
  • a laser is used as an example of the light source 3.
  • a direct modulation method in which a modulation signal is directly input to the light source may be used, or an external modulation method configuration in which an intensity modulator is provided outside to obtain modulated light may be used.
  • a light emitting diode (LED) or a super luminescent diode (SLD) may be used as another light source.
  • the APD is used for the photodetectors 7a and 7b .
  • a photodiode (PD) or a photomultiplier tube (PMT) may be used.
  • the BPF 10 may be a low-pass filter (LPF) because the difference frequency f m1 -f m2 may be selected.
  • LPF low-pass filter
  • the amplifier 8a, 8b showed the example using the transimpedance amplifier, you may use a voltage amplifier.
  • the difference frequency f m1 ⁇ f m2 is configured to be the minimum value of the input equivalent noise level of the transimpedance gain, but is lower than the input equivalent noise level at the modulation frequency f m1 of the light source 3. Any frequency range may be used.
  • the phase difference signal is output as the function of the phase detectors 11a and 11b, but it may have a function of outputting a signal corresponding to the amplitude.
  • the waveform shaping circuit 5 is common to the photodetectors 7a and 7b of the photodetector array 15, the waveform shaping circuit 5 is also included in the photodetector array 15 and is associated with each of the photodetectors 7a and 7b. The structure to install may be sufficient. As a result, even if the sensitivity characteristics of the photodetectors 7a and 7b are different from each other, the waveform shaping circuit 5 can calibrate the nonlinear characteristics, and the difference between the minimum values of the input conversion noise levels of the amplifiers 8a and 8b.
  • the frequency f m1 -f m2 can be set.
  • the distance measurement is performed in the irradiation area without using the scanning optical system.
  • the reception field of view is fixed, and only the transmission beam is detected by the scanning optical system. It may be configured to scan.
  • the scanning optical system 16 and the synchronization circuit 17 are installed, and the MUX circuit 14 is synchronized. . That is, the synchronization circuit 17 synchronously controls the MUX circuit 14 so as to select the scanning direction of the scanning optical system 16 and the received signals from the photodetectors 7a and 7b that receive the reflected light from the object in the scanning direction.
  • the other configuration is the same as the configuration shown in FIG.
  • the photodetector array 15 includes the plurality of photodetectors 7a and 7b, the intensity and phase can be measured with one light receiving element. As a result, the number of effective pixels in the acquired image is not reduced.
  • the first oscillator that generates the modulation reference signal, the light source that outputs the intensity-modulated light based on the modulation reference signal, and the light source A transmitting optical system for shaping and irradiating the output light, a receiving optical system for collecting reflected light from an object based on the irradiated light, and a second oscillator for generating a sensitivity modulation reference signal, A plurality of photodetectors that modulate the sensitivity based on a signal of a given modulation waveform and output a difference frequency from the received modulation signal as a respective reception signal, and a plurality of light detections based on the sensitivity modulation reference signal A waveform shaping circuit that shapes the modulation waveform to linearly modulate the sensitivity of the detector, a reference signal output unit that outputs a difference signal between the modulation reference signal and the sensitivity modulation reference signal as a reference signal, and a plurality of received signals and reference signals Each phase difference A plurality
  • the invention of the present application can be freely combined with each embodiment, modified with any component in each embodiment, or omitted with any component in each embodiment. .
  • the optical distance measuring device includes the light receiver that down-converts the modulation frequency to the low frequency side, and is suitable for use in a laser radar device or the like.

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  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
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Abstract

In the present invention, a first oscillator (1) generates a modulation reference signal, and a second oscillator (2) generates a sensitivity modulation reference signal. A waveform shaping circuit (5) shapes a modulation waveform signal for linearly modulating the sensitivity of a photodetector (7) on the basis of the sensitivity modulation reference signal. The photodetector (7) modulates the sensitivity on the basis of the waveform-shaped modulation waveform signal. The signal obtained by the photodetector (7) is amplified by an amplifier (8) and inputted as a reception signal into a phase detector (11). The phase detector (11) determines the phase difference from the reception signal and a referred signal, and a signal processor (12) measures the distance to the subject from the phase difference signal.

Description

光測距装置Optical distance measuring device
　本発明は、強度変調光を単素子の光検出器で受信し、変調周波数を低周波側にダウンコンバートする光検出器を備えた光測距装置に関するものである。 The present invention relates to an optical distance measuring device including a photodetector that receives intensity-modulated light with a single-element photodetector and down-converts the modulation frequency to a low frequency side.
　従来技術として、強度変調光の変調周波数を光検出器で低周波側にダウンコンバートし、その位相差から測距する装置としては、例えば特許文献１や特許文献２に記載されたものが知られている。特許文献１に記載の装置では、隣接する一対の半導体素子を用いて強度変調光をダウンコンバートしている。また、特許文献２に記載の装置では、光検出器のゲインに直接変調をかけ、出力信号を直接ダウンコンバートしている。 As a conventional technique, devices described in, for example, Patent Document 1 and Patent Document 2 are known as devices for down-converting the modulation frequency of intensity-modulated light to the low frequency side with a photodetector and measuring the distance from the phase difference. ing. In the apparatus described in Patent Document 1, intensity-modulated light is down-converted using a pair of adjacent semiconductor elements. In the apparatus described in Patent Document 2, the gain of the photodetector is directly modulated, and the output signal is directly down-converted.
特表２００４－５２５３５１号公報Special table 2004-525351 gazette 特開平１１－１０８６２３号公報Japanese Patent Laid-Open No. 11-108623
　上記の特許文献１の記載されたシステムでは、強度変調光の変調周波数を、低周波側にダウンコンバートするために、少なくとも２つ以上の受光素子を用いる必要がある。それぞれの受光素子にて受信視野が異なっていた場合、異なる反射率や距離からの反射光を受信するため、強度変調光の変調周波数を低周波側にダウンコンバートした測定値に誤差が生じるという問題があった。また、アレイ状の受光素子をもつ光検出器であった場合、取得画像の有効画素数は実際の受光素子数より減少してしまう課題もあった。 In the system described in Patent Document 1, it is necessary to use at least two light receiving elements in order to down-convert the modulation frequency of the intensity-modulated light to the low frequency side. If each light receiving element has a different reception field of view, it receives reflected light from different reflectivities and distances, resulting in an error in the measurement value obtained by down-converting the modulation frequency of the intensity-modulated light to the low frequency side. was there. Further, in the case of a photodetector having an array of light receiving elements, there is a problem that the number of effective pixels of the acquired image is smaller than the actual number of light receiving elements.
　また、特許文献２に記載された装置では、光検出器がアバランシェフォトダイオード（以下、ＡＰＤ（Ａｖａｌａｎｃｈｅ　Ｐｈｏｔｏ　Ｄｉｏｄｅ）という）のような光起電力効果による光電変換を行う光検出器であった場合、そのバイアス印加電圧に対する受光感度特性は一般的に非線形である。そのため、バイアス印加電圧が正弦波変調であった場合、受光感度を正弦波で変調することはできず、変調光の周波数との差周波にダウンコンバートするときの効率が非常に悪くなる。これにより、結果的に受信信号対雑音比が低下し、測距精度が低いという課題があった。 In the device described in Patent Document 2, when the photodetector is a photodetector that performs photoelectric conversion by a photovoltaic effect such as an avalanche photodiode (hereinafter referred to as APD (Avalanche Photo Diode)), The light receiving sensitivity characteristic with respect to the bias applied voltage is generally non-linear. For this reason, when the bias application voltage is sinusoidal modulation, the light receiving sensitivity cannot be modulated with the sinusoidal wave, and the efficiency when downconverting to the difference frequency from the frequency of the modulated light becomes very poor. As a result, there has been a problem that the reception signal-to-noise ratio is lowered and the ranging accuracy is low.
　この発明は、かかる問題を解決するためになされたもので、変調光の周波数との差周波にダウンコンバートするときの効率を向上させ、高精度に測距を行うことができる光測距装置を提供することを目的とする。 The present invention has been made to solve such a problem. An optical distance measuring device capable of improving the efficiency when down-converting to a difference frequency from the frequency of modulated light and performing distance measurement with high accuracy is provided. The purpose is to provide.
　この発明に係る光測距装置は、変調基準信号を発生する第１の発振器と、変調基準信号に基づき、強度変調された光を出力する光源と、光源より出力した光を整形し、照射する送信光学系と、照射された光に基づく対象物からの反射光を集光する受信光学系と、感度変調基準信号を発生する第２の発振器と、与えられた変調波形の信号に基づいて感度を変調し、受光した変調信号との差周波を受信信号として出力する光検出器と、感度変調基準信号に基づき、光検出器の感度を線形に変調するため変調波形を整形する波形整形回路と、変調基準信号と感度変調基準信号の差信号を参照信号として出力する参照信号出力部と、受信信号と参照信号から位相差を求める位相検波器と、位相検波器から出力される位相差信号から、距離を計測する信号処理部とを備えたものである。 An optical distance measuring device according to the present invention shapes and irradiates a first oscillator that generates a modulation reference signal, a light source that outputs intensity-modulated light based on the modulation reference signal, and light output from the light source. A transmission optical system, a reception optical system that collects reflected light from an object based on the irradiated light, a second oscillator that generates a sensitivity modulation reference signal, and a sensitivity based on a signal of a given modulation waveform And a waveform shaping circuit that shapes the modulation waveform to linearly modulate the sensitivity of the photodetector based on the sensitivity modulation reference signal, and a photodetector that outputs the difference frequency of the received modulated signal as a received signal; A reference signal output unit that outputs a difference signal between the modulation reference signal and the sensitivity modulation reference signal as a reference signal, a phase detector that obtains a phase difference from the received signal and the reference signal, and a phase difference signal output from the phase detector , Measure distance It is obtained by a No. processor.
　この発明に係る光測距装置は、第２の発振器から出力される感度変調基準信号に基づいて、光検出器の感度を線形に変調するための変調波形信号を整形する波形整形回路を設け、光検出器は、波形整形された変調波形信号に基づいて感度を変調するようにしたものである。これにより、変調光の周波数との差周波にダウンコンバートするときの効率を向上させることができる。 The optical distance measuring device according to the present invention is provided with a waveform shaping circuit for shaping a modulation waveform signal for linearly modulating the sensitivity of the photodetector based on the sensitivity modulation reference signal output from the second oscillator, The photodetector modulates sensitivity based on the waveform-shaped modulated waveform signal. Thereby, the efficiency at the time of down-conversion to the difference frequency with the frequency of modulated light can be improved.
この発明の実施の形態１の光測距装置を示す構成図である。It is a block diagram which shows the optical ranging apparatus of Embodiment 1 of this invention. この発明の光測距装置における各部の出力波形を示す説明図である。It is explanatory drawing which shows the output waveform of each part in the optical distance measuring device of this invention. この発明の光測距装置におけるトランスインピーダンスアンプの雑音特性と差周波との関係を示す説明図である。It is explanatory drawing which shows the relationship between the noise characteristic of a transimpedance amplifier in the optical ranging apparatus of this invention, and a difference frequency. この発明の実施の形態２の光測距装置を示す構成図である。It is a block diagram which shows the optical ranging apparatus of Embodiment 2 of this invention. この発明の実施の形態２の光測距装置の他の例を示す構成図である。It is a block diagram which shows the other example of the optical distance measuring device of Embodiment 2 of this invention.
　以下、この発明をより詳細に説明するために、この発明を実施するための形態について、添付の図面に従って説明する。
実施の形態１．
　図１は、実施の形態１による光測距装置の構成図である。
　本実施の形態による光測距装置は、図示のように、第１の発振器１、第２の発振器２、光源３、送信光学系４、波形整形回路５、受信光学系６、光検出器７、アンプ８、ミキサ９、バンドパスフィルタ（以下、ＢＰＦ（Ｂａｎｄ　Ｐａｓｓ　Ｆｉｌｔｅｒ）という）１０、位相検波器１１、信号処理部１２を備えている。 Hereinafter, in order to explain the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 is a configuration diagram of the optical distance measuring device according to the first embodiment.
As shown in the figure, the optical distance measuring device according to the present embodiment includes a first oscillator 1, a second oscillator 2, a light source 3, a transmission optical system 4, a waveform shaping circuit 5, a reception optical system 6, and a photodetector 7. , An amplifier 8, a mixer 9, a band pass filter (hereinafter referred to as BPF (Band Pass Filter)) 10, a phase detector 11, and a signal processing unit 12.
　第１の発振器１及び第２の発振器２は、それぞれ二つの異なる周波数を出力する発振器であり、第１の発振器１は光源３の変調基準信号を発生する機能を有し、第２の発振器２は光検出器７の感度を変調するためのバイアス変調基準信号を発生する機能を有している。光源３は、第１の発振器１の変調基準信号に基づいた周波数で強度変調をかけたレーザ光を発振する光源である。送信光学系４は、光源３から発生した光を整形するための送信光学系である。波形整形回路５は、第２の発振器２のバイアス変調基準信号に基づき、光検出器７のバイアスを線形に変調するためのバイアス変調信号を生成する回路である。 The first oscillator 1 and the second oscillator 2 are oscillators that output two different frequencies, respectively, and the first oscillator 1 has a function of generating a modulation reference signal of the light source 3, and the second oscillator 2 Has a function of generating a bias modulation reference signal for modulating the sensitivity of the photodetector 7. The light source 3 is a light source that oscillates laser light that has been intensity-modulated at a frequency based on the modulation reference signal of the first oscillator 1. The transmission optical system 4 is a transmission optical system for shaping the light generated from the light source 3. The waveform shaping circuit 5 is a circuit that generates a bias modulation signal for linearly modulating the bias of the photodetector 7 based on the bias modulation reference signal of the second oscillator 2.
　受信光学系６は、送信光学系４から照射された光が図示しない対象物で反射した受信光を光検出器７に集光するための受信光学系である。光検出器７は、波形整形回路５で整形されたバイアス変調信号に基づいて感度を変調し、受信する反射光の変調周波数との差周波の電気信号を出力する受光器である。アンプ８は、光検出器７から出力された差周波の電気信号を増幅するトランスインピーダンスアンプといった増幅器である。ミキサ９は、第１の発振器１から出力された変調基準信号と、第２の発振器２から出力されたバイアス変調基準信号とをミキシングするミキサである。ＢＰＦ１０は、ミキサ９で生成された信号のうち、差周波のみを透過するフィルタである。また、これらミキサ９とＢＰＦ１０とにより、参照信号を出力する参照信号出力部１３が形成されている。位相検波器１１は、参照信号出力部１３で得られる参照信号と、光検出器７で得られる受信信号との位相差を検出し、その位相差を示す位相信号を発生する機能を有し、信号処理部１２は、位相検波器１１からの位相信号に基づき、距離値を算出する機能を有する。 The receiving optical system 6 is a receiving optical system for condensing the light received from the transmitting optical system 4 reflected by an object (not shown) on the photodetector 7. The photodetector 7 is a light receiver that modulates sensitivity based on the bias modulation signal shaped by the waveform shaping circuit 5 and outputs an electric signal having a difference frequency from the modulation frequency of the received reflected light. The amplifier 8 is an amplifier such as a transimpedance amplifier that amplifies the difference frequency electrical signal output from the photodetector 7. The mixer 9 is a mixer that mixes the modulation reference signal output from the first oscillator 1 and the bias modulation reference signal output from the second oscillator 2. The BPF 10 is a filter that transmits only the difference frequency among the signals generated by the mixer 9. The mixer 9 and the BPF 10 form a reference signal output unit 13 that outputs a reference signal. The phase detector 11 has a function of detecting a phase difference between the reference signal obtained by the reference signal output unit 13 and the reception signal obtained by the photodetector 7, and generating a phase signal indicating the phase difference. The signal processing unit 12 has a function of calculating a distance value based on the phase signal from the phase detector 11.
　次に、実施の形態１の光測距装置の動作について説明する。
　図２は、第１の第１の発振器１と第２の発振器２で出力される変調波形を示したものである。第１の発振器１では図２（ａ）のような周波数ｆｍ１の変調基準信号Ａを発生し、第２の発振器２では図２（ｂ）のような周波数ｆｍ２のバイアス変調基準信号Ｂを発生する。このとき、変調基準信号の周波数ｆｍ１とバイアス変調基準信号の周波数ｆｍ２は異なった周波数である。 Next, the operation of the optical distance measuring device according to the first embodiment will be described.
FIG. 2 shows modulation waveforms output from the first first oscillator 1 and the second oscillator 2. The first oscillator 1 generates a modulation reference signal A having a frequency f m1 as shown in FIG. 2A, and the second oscillator 2 receives a bias modulation reference signal B having a frequency f m2 as shown in FIG. 2B. appear. At this time, the frequency f m1 of the modulation reference signal and the frequency f m2 of the bias modulation reference signal are different frequencies.
　第１の発振器１から出力された周波数ｆｍ１の変調基準信号は光源３に入力され、光源３では、周波数ｆｍ１の変調基準信号に基づいた強度変調光を発生する。送信光学系４では、光源３で発生した強度変調光を整形して対象物に照射する。 The modulation reference signal having the frequency f m1 output from the first oscillator 1 is input to the light source 3, and the light source 3 generates intensity-modulated light based on the modulation reference signal having the frequency f m1 . The transmission optical system 4 shapes the intensity-modulated light generated by the light source 3 and irradiates the object.
　また、第２の発振器２から出力された周波数ｆｍ２のバイアス変調基準信号は波形整形回路５に入力され、波形整形回路５では、図２（ｃ）のようなバイアス変調波形Ｃを出力する。ここで、光検出器７がＡＰＤの場合、一般的にバイアス電圧－感度特性は図２（ｄ）のような非線形特性Ｄである。従って、図２（ｃ）のようなバイアス電圧に一定のオフセットを持たせ、さらに非線形の変調波形を加えることで、図２（ｄ）に記載の感度変調特性Ｅを得る。 The bias modulation reference signal having the frequency fm2 output from the second oscillator 2 is input to the waveform shaping circuit 5, and the waveform shaping circuit 5 outputs a bias modulation waveform C as shown in FIG. Here, when the photodetector 7 is an APD, the bias voltage-sensitivity characteristic is generally a non-linear characteristic D as shown in FIG. Therefore, the sensitivity modulation characteristic E shown in FIG. 2D is obtained by giving a certain offset to the bias voltage as shown in FIG. 2C and adding a non-linear modulation waveform.
　対象物からの反射光を受信光学系６で集光し、光検出器７で受光する。このとき、光検出器７の感度は周波数ｆｍ２で変調されているため、図２（ｅ）の出力波形Ｆに示すように、受信する変調周波数ｆｍ１との差周波ｆｍ１－ｆｍ２の電気信号を出力し、アンプ８でその電気信号を増幅して受信信号を得る。 The reflected light from the object is collected by the receiving optical system 6 and received by the photodetector 7. At this time, since the sensitivity of the photodetector 7 is modulated at the frequency f m2 , the difference frequency f m1 −f m2 from the received modulation frequency f m1 is obtained as shown in the output waveform F of FIG. An electric signal is output, and the electric signal is amplified by the amplifier 8 to obtain a received signal.
　図３にアンプ８にトランスインピーダンスアンプを用いた場合の周波数に対する入力換算雑音レベルの特性を示す。一般的に、アンプの周波数特性とトランスインピーダンスゲインは逆比例しているため、低周波特性のアンプであればトランスインピーダンスゲインを高くすることができる。従って、雑音レベルは使用するトランスインピーダンスアンプで決まる１／ｆ雑音とトランスインピーダンスゲインで決まる熱雑音によって制限され（図中、入力換算雑音レベル特性Ｇ参照）、入力換算雑音レベルの最小値が存在する。本装置では、差周波ｆｍ１－ｆｍ２をその最小値となるように周波数ｆｍ１とｆｍ２を設定する。 FIG. 3 shows the characteristics of the input conversion noise level with respect to the frequency when a transimpedance amplifier is used as the amplifier 8. In general, the frequency characteristics of the amplifier and the transimpedance gain are inversely proportional, so that the transimpedance gain can be increased if the amplifier has a low frequency characteristic. Accordingly, the noise level is limited by the 1 / f noise determined by the transimpedance amplifier used and the thermal noise determined by the transimpedance gain (see the input conversion noise level characteristic G in the figure), and there is a minimum value of the input conversion noise level. . In this apparatus, the frequencies f m1 and f m2 are set so that the difference frequency f m1 −f m2 becomes the minimum value.
　一方、ミキサ９によって、変調基準信号とバイアス変調基準信号をミキシングし、周波数ｆｍ１と周波数ｆｍ２の差周波ｆｍ１－ｆｍ２を発生する。このとき、周波数ｆｍ１と周波数ｆｍ２の和周波ｆｍ１＋ｆｍ２も同時に発生するため、差周波ｆｍ１－ｆｍ２付近の周波数帯のみを透過するＢＰＦ１０を通し、参照信号を生成する。 On the other hand, the mixer 9 mixes the modulated reference signal and a bias modulation reference signal, for generating a difference frequency f m1 -f m @ 2 of frequency f m1 and frequency f m @ 2. At this time, since the sum frequency f m1 + f m2 of the frequency f m1 and the frequency f m2 is also generated at the same time, the reference signal is generated through the BPF 10 that transmits only the frequency band near the difference frequency f m1 -f m2 .
　得られた参照信号と受信信号を位相検波器１１に入力し、二つの信号の位相差に相当する信号を出力する。さらに信号処理部１２で、位相差信号より対象物までの距離を算出する。 The obtained reference signal and received signal are input to the phase detector 11 and a signal corresponding to the phase difference between the two signals is output. Further, the signal processing unit 12 calculates the distance to the object from the phase difference signal.
　本発明の実施の形態１に係わる光測距装置では、波形整形回路５によって光検出器７の感度に対して線形に変調をかけることができる。これにより、光検出器７の光電変換領域において、送信光の強度変調周波数ｆｍ１と光検出器の感度変調周波数ｆｍ２の差周波ｆｍ１－ｆｍ２に変換する。このとき、差周波ｆｍ１－ｆｍ２をトランスインピーダンスアンプの入力換算雑音レベルの最小値となるように周波数ｆｍ１とｆｍ２を設定する。一方、受信信号レベルは保持されるため、受信信号の信号対雑音比が最良となる条件で信号を受信することができ、測距精度を改善することができる。 In the optical distance measuring device according to Embodiment 1 of the present invention, the waveform shaping circuit 5 can linearly modulate the sensitivity of the photodetector 7. Thus, in the photoelectric conversion region of the photodetector 7, the light is converted into a difference frequency f m1 −f m2 between the intensity modulation frequency f m1 of the transmission light and the sensitivity modulation frequency f m2 of the photodetector. At this time, the frequencies f m1 and f m2 are set so that the difference frequency f m1 -f m2 becomes the minimum value of the input conversion noise level of the transimpedance amplifier. On the other hand, since the received signal level is maintained, the signal can be received under the condition that the signal-to-noise ratio of the received signal is optimal, and the ranging accuracy can be improved.
　ここで、光源３の例としてレーザを使用する。このとき、光源３に直接変調信号を入力する直接変調方式でもよいし、外部に強度変調器を設置して変調光を得る外部変調方式の構成でもよい。また、その他の光源３として、発光ダイオード（ＬＥＤ：Ｌｉｇｈｔ　Ｅｍｉｔｔｉｎｇ　Ｄｉｏｄｅ）やスーパールミネッセントダイオード（ＳＬＤ：Ｓｕｐｅｒ　Ｌｕｍｉｎｅｓｃｅｎｔ　Ｄｉｏｄｅ）でもよい。 Here, a laser is used as an example of the light source 3. At this time, a direct modulation method in which a modulation signal is directly input to the light source 3 may be used, or an external modulation method configuration in which an intensity modulator is provided outside to obtain modulated light may be used. Further, as the other light source 3, a light emitting diode (LED: Light Emitting Diode) or a super luminescent diode (SLD: Super Luminescent Diode) may be used.
　本発明の実施の形態１に係わる光測距装置では、光検出器７にＡＰＤを用いた例を示したが、例えば、フォトダイオード（ＰＤ：Ｐｈｏｔｏ　Ｄｉｏｄｅ）や光電子増倍管（ＰＭＴ：Ｐｈｏｔｏｍｕｌｔｉｐｌｉｅｒ　Ｔｕｂｅ）でもよい。また、ＢＰＦ１０は差周波ｆｍ１－ｆｍ２を選定すればよいため、ローパスフィルタ（ＬＰＦ：Ｌｏｗ　Ｐａｓｓ　Ｆｉｌｔｅｒ）でもよい。また、アンプ８にトランスインピーダンスアンプを用いた例を示したが、電圧アンプを用いてもよい。 In the optical distance measuring apparatus according to the first embodiment of the present invention, an example in which an APD is used for the photodetector 7 has been shown. For example, a photodiode (PD) or a photomultiplier tube (PMT) is used. ) The BPF 10 may be a low pass filter (LPF) because the difference frequency f m1 −f m2 may be selected. Moreover, although the example which used the transimpedance amplifier for the amplifier 8 was shown, you may use a voltage amplifier.
　実施の形態１の光測距装置では、差周波ｆｍ１－ｆｍ２をトランスインピーダンスゲインの入力換算雑音レベルの最小値となる構成としたが、光源３の変調周波数ｆｍ１の入力換算雑音レベルより低くなる周波数領域であれば良い。 In the optical distance measuring device of the first embodiment, the difference frequency f m1 -f m2 is configured to be the minimum value of the input equivalent noise level of the transimpedance gain, but from the input equivalent noise level of the modulation frequency f m1 of the light source 3. Any frequency region that can be lowered may be used.
　実施の形態１の光測距装置では、位相検波器１１の機能として位相差信号のみを出力しているが、振幅に相当する信号を出力する機能を有していてもよい。 In the optical distance measuring device of the first embodiment, only the phase difference signal is output as a function of the phase detector 11, but it may have a function of outputting a signal corresponding to the amplitude.
　実施の形態１の光測距装置では、光を照射して反射光を受光する構成であったが、送信光学系４の後段に走査光学系を用いて、送信ビームと受信視野の両方をスキャンする構成であってもよい。また、例えば特開２０１０－２７１２７５号公報に示すように、受信視野を固定し、送信ビームのみを走査光学系でスキャンする構成であってもよい。 In the optical distance measuring device according to the first embodiment, the reflected light is received by irradiating the light. However, the scanning optical system is used in the subsequent stage of the transmission optical system 4 to scan both the transmission beam and the reception visual field. It may be configured to. Further, for example, as shown in Japanese Patent Application Laid-Open No. 2010-271275, the reception field of view may be fixed and only the transmission beam may be scanned by the scanning optical system.
　このように、実施の形態１の光測距装置では、バイアス変調された光検出器７で、強度変調光の変調周波数を、アンプ８の入力換算雑音レベルが低くなる低周波側にダウンコンバートするため、従来技術で課題となっていた隣接受光素子の各視野におけるターゲットの距離差や反射率差による測距精度の劣化を低減することができる。 As described above, in the optical distance measuring device according to the first embodiment, the modulation frequency of the intensity-modulated light is down-converted by the bias-modulated photodetector 7 to the low frequency side where the input equivalent noise level of the amplifier 8 is lowered. Therefore, it is possible to reduce the degradation of distance measurement accuracy due to the target distance difference and reflectance difference in each field of view of the adjacent light receiving element, which has been a problem in the prior art.
　また、波形整形回路５によって変調波形を整形することにより、光検出器７にＡＰＤを用いた場合でも光検出器７の感度を線形に変調することができ、受信した変調信号を低周波側にダウンコンバートすることができる。さらに、低周波側にダウンコンバートすることにより、アンプ雑音（入力換算雑音電流密度）が低い周波数帯で受信信号を増幅することができ、信号帯雑音比を改善することができる。これにより、変調光を電気信号に変換し、同様の周波数帯で位相検波している位相差方式の光測距装置と比べて、測距精度の高精度化、測定可能距離の長距離化、光源の出力を抑えることによる低コスト化を図ることができる。 Further, by shaping the modulation waveform by the waveform shaping circuit 5, the sensitivity of the photodetector 7 can be linearly modulated even when an APD is used for the photodetector 7, and the received modulation signal is shifted to the low frequency side. Can be down-converted. Furthermore, by down-converting to the low frequency side, the received signal can be amplified in a frequency band where the amplifier noise (input converted noise current density) is low, and the signal band noise ratio can be improved. This makes it possible to convert the modulated light into an electrical signal and improve the accuracy of the distance measurement, increase the distance that can be measured, compared to a phase difference optical distance measuring device that detects the phase in the same frequency band, Cost reduction can be achieved by suppressing the output of the light source.
　以上説明したように、実施の形態１の光測距装置によれば、変調基準信号を発生する第１の発振器と、変調基準信号に基づき、強度変調された光を出力する光源と、光源より出力した光を整形し、照射する送信光学系と、照射された光に基づく対象物からの反射光を集光する受信光学系と、感度変調基準信号を発生する第２の発振器と、与えられた変調波形の信号に基づいて感度を変調し、受光した変調信号との差周波を受信信号として出力する光検出器と、感度変調基準信号に基づき、光検出器の感度を線形に変調するため変調波形を整形する波形整形回路と、変調基準信号と感度変調基準信号の差信号を参照信号として出力する参照信号出力部と、受信信号と参照信号から位相差を求める位相検波器と、位相検波器から出力される位相差信号から、距離を計測する信号処理部とを備えたので、変調光の周波数との差周波にダウンコンバートするときの効率が向上し、測距精度の向上に寄与することができる。 As described above, according to the optical distance measuring device of the first embodiment, the first oscillator that generates the modulation reference signal, the light source that outputs the intensity-modulated light based on the modulation reference signal, and the light source A transmitting optical system for shaping and irradiating the output light, a receiving optical system for collecting reflected light from an object based on the irradiated light, and a second oscillator for generating a sensitivity modulation reference signal, and To modulate the sensitivity based on the modulated waveform signal and output the difference frequency with the received modulated signal as the received signal, and to linearly modulate the sensitivity of the photodetector based on the sensitivity modulation reference signal A waveform shaping circuit for shaping the modulation waveform, a reference signal output unit for outputting a difference signal between the modulation reference signal and the sensitivity modulation reference signal as a reference signal, a phase detector for obtaining a phase difference from the received signal and the reference signal, and phase detection Phase output from the detector From the signal, since a signal processing unit for measuring the distance, it improves efficiency when down-converted to a difference frequency between the frequency of the modulated light, it is possible to contribute to improvement of accuracy of distance measurement.
　また、実施の形態１の光測距装置によれば、光検出器からの差周波信号を増幅するアンプを備えると共に、差周波信号が、アンプにおける変調基準信号の周波数の入力換算雑音レベルより低い入力換算雑音レベルとなる周波数領域となるよう変調基準信号と感度変調基準信号とを決定するようにしたので、測距精度の高精度化、測定可能距離の長距離化、光源の出力を抑えることによる低コスト化を図ることができる。 Further, according to the optical distance measuring device of the first embodiment, the amplifier includes an amplifier that amplifies the difference frequency signal from the photodetector, and the difference frequency signal is lower than the input conversion noise level of the frequency of the modulation reference signal in the amplifier. The modulation reference signal and sensitivity modulation reference signal are determined so that the frequency range is equivalent to the input-converted noise level, so the accuracy of distance measurement is increased, the measurable distance is increased, and the light source output is suppressed. The cost can be reduced.
実施の形態２．
　実施の形態２は、実施の形態１で説明した光ダウンコンバートする光検出器をアレイ状とした場合の例である。 Embodiment 2. FIG.
The second embodiment is an example in which the light down-converting photodetector described in the first embodiment is formed in an array.
　図４は、実施の形態２における光測距装置を示す構成図であり、例として２つの光検出器７ａ，７ｂを用いた場合を示している。
　実施の形態２の光測距装置は、第１の発振器１、第２の発振器２、光源３、送信光学系４、波形整形回路５、受信光学系６、光検出器７ａ，７ｂ、アンプ８ａ，８ｂ、ミキサ９、ＢＰＦ１０、位相検波器１１ａ，１１ｂ、信号処理部１２、マルチプレクサ（以下、ＭＵＸ回路という）１４を備えており、光検出器７ａ，７ｂ、アンプ８ａ，８ｂ、位相検波器１１ａ，１１ｂはアレイ構成の光検出器アレイ１５となっている。また、ミキサ９とＢＰＦ１０で参照信号出力部１３が構成されているのは実施の形態１と同様である。 FIG. 4 is a block diagram showing the optical distance measuring device according to the second embodiment, and shows a case where two photodetectors 7a and 7b are used as an example.
The optical distance measuring device according to the second embodiment includes a first oscillator 1, a second oscillator 2, a light source 3, a transmission optical system 4, a waveform shaping circuit 5, a reception optical system 6, photodetectors 7a and 7b, and an amplifier 8a. 8b, mixer 9, BPF 10, phase detectors 11a and 11b, signal processing unit 12, multiplexer (hereinafter referred to as MUX circuit) 14, photodetectors 7a and 7b, amplifiers 8a and 8b, phase detector 11a. 11b is a photodetector array 15 having an array configuration. Further, the reference signal output unit 13 is configured by the mixer 9 and the BPF 10 as in the first embodiment.
　二つの光検出器７ａ，７ｂのそれぞれの構成は実施の形態１の光検出器７と同様であり、波形整形回路５で整形された変調波形に基づいて光検出器の感度を変調し、受信する反射光の変調周波数との差周波の電気信号を出力するよう構成されている。また、アンプ８ａ，８ｂは、それぞれ光検出器７ａ，７ｂの出力を増幅するよう接続されている。位相検波器１１ａ，１１ｂは、それぞれ、参照信号出力部１３からの参照信号とアンプ８ａ，８ｂからの受信信号ａ，ｂから位相情報を得て、位相信号ａ，ｂとして出力するよう構成されている。ＭＵＸ回路１４は、位相検波器１１ａ，１１ｂからの位相信号ａ，ｂを切り替えて信号処理部１２に出力するマルチプレクサである。これ以外の構成は、実施の形態１と同様であるため、対応する部分に同一符号を付してその説明を省略する。 The configuration of each of the two photodetectors 7a and 7b is the same as that of the photodetector 7 of the first embodiment, and modulates the sensitivity of the photodetector based on the modulation waveform shaped by the waveform shaping circuit 5, and receives the signal. An electric signal having a difference frequency from the modulation frequency of the reflected light is output. The amplifiers 8a and 8b are connected to amplify the outputs of the photodetectors 7a and 7b, respectively. The phase detectors 11a and 11b are configured to obtain phase information from the reference signal from the reference signal output unit 13 and the received signals a and b from the amplifiers 8a and 8b and output the phase information as phase signals a and b, respectively. Yes. The MUX circuit 14 is a multiplexer that switches the phase signals a and b from the phase detectors 11 a and 11 b and outputs them to the signal processing unit 12. Since the configuration other than this is the same as that of the first embodiment, the same reference numerals are given to corresponding portions, and the description thereof is omitted.
　次に、実施の形態２の光測距装置の動作について説明する。なお、光測距装置としての基本的な動作は実施の形態１と同様であるため、実施の形態２の特徴的な動作についてのみ説明する。
　図示しない対象物からの反射光を受信光学系６で集光し、光検出器７ａと光検出器７ｂとで受光する。このとき、光検出器７ａ，７ｂそれぞれの感度は周波数ｆｍ２で変調されているため、図２（ｅ）のような受信する変調周波数ｆｍ１との差周波ｆｍ１－ｆｍ２の電気信号を出力し、アンプ８ａ，８ｂでその電気信号を増幅して受信信号を得る。また、アンプ８ａ，８ｂにトランスインピーダンスアンプを用いた場合の、差周波ｆｍ１－ｆｍ２が入力換算雑音レベルの最小値となるよう周波数ｆｍ１とｆｍ２を設定するのは実施の形態１と同様である。 Next, the operation of the optical distance measuring device according to the second embodiment will be described. Since the basic operation as the optical distance measuring apparatus is the same as that of the first embodiment, only the characteristic operation of the second embodiment will be described.
Reflected light from an object (not shown) is collected by the receiving optical system 6 and received by the photodetector 7a and the photodetector 7b. At this time, since the sensitivities of the photodetectors 7a and 7b are modulated at the frequency f m2 , the electric signal of the difference frequency f m1 −f m2 from the received modulation frequency f m1 as shown in FIG. Then, the electric signals are amplified by the amplifiers 8a and 8b to obtain a reception signal. Further, when the transimpedance amplifier is used as the amplifiers 8a and 8b, the frequencies f m1 and f m2 are set so that the difference frequency f m1 -f m2 becomes the minimum value of the input conversion noise level as in the first embodiment. It is the same.
　参照信号出力部１３で得られた参照信号と、アンプ８ａ，８ｂの出力である受信信号ａ，ｂをそれぞれ位相検波器１１ａ，１１ｂに入力し、二つの信号の位相差に相当する位相信号ａと位相信号ｂを出力する。その後、ＭＵＸ回路１４で位相信号を切り替え、信号処理部１２で、各光検出器７ａ，７ｂで測定された受信信号の位相差信号より対象物までの距離を算出する。 The reference signal obtained by the reference signal output unit 13 and the received signals a and b which are the outputs of the amplifiers 8a and 8b are input to the phase detectors 11a and 11b, respectively, and the phase signal a corresponding to the phase difference between the two signals. And the phase signal b are output. Thereafter, the phase signal is switched by the MUX circuit 14, and the signal processing unit 12 calculates the distance to the object from the phase difference signal of the received signal measured by each of the photodetectors 7a and 7b.
　実施の形態２では、複数の光検出器７ａ，７ｂを用いた光検出器アレイ１５とすることにより、走査光学系を必要とすることなく、光照射領域中の測距を行うことができる。このとき各受光素子の測距値を画像化することにより、対象物の３次元画像を取得することができる。 In the second embodiment, by using the photodetector array 15 using the plurality of photodetectors 7a and 7b, distance measurement in the light irradiation region can be performed without the need for a scanning optical system. At this time, a three-dimensional image of the object can be obtained by imaging the distance measurement value of each light receiving element.
　ここで、光源３の例としてレーザを使用する。このとき、光源に直接変調信号を入力する直接変調方式でもよいし、外部に強度変調器を設置して変調光を得る外部変調方式の構成でもよい。また、その他の光源として、発光ダイオード（ＬＥＤ）やスーパールミネッセントダイオード（ＳＬＤ）でもよい。 Here, a laser is used as an example of the light source 3. At this time, a direct modulation method in which a modulation signal is directly input to the light source may be used, or an external modulation method configuration in which an intensity modulator is provided outside to obtain modulated light may be used. Further, as another light source, a light emitting diode (LED) or a super luminescent diode (SLD) may be used.
　さらに、実施の形態２では、光検出器７ａ，７ｂにＡＰＤを用いた例を示したが、例えばフォトダイオード（ＰＤ）や光電子増倍管（ＰＭＴ）でもよい。また、ＢＰＦ１０は差周波ｆｍ１－ｆｍ２を選定すればよいため、ローパスフィルタ（ＬＰＦ）でもよい。また、アンプ８ａ，８ｂはトランスインピーダンスアンプを用いた例を示したが、電圧アンプを用いてもよい。 Furthermore, in the second embodiment, an example in which the APD is used for the photodetectors 7a and 7b has been described. However, for example, a photodiode (PD) or a photomultiplier tube (PMT) may be used. The BPF 10 may be a low-pass filter (LPF) because the difference frequency f m1 -f m2 may be selected. Moreover, although the amplifier 8a, 8b showed the example using the transimpedance amplifier, you may use a voltage amplifier.
　また、実施の形態２では、差周波ｆｍ１－ｆｍ２をトランスインピーダンスゲインの入力換算雑音レベルの最小値となる構成としたが、光源３の変調周波数ｆｍ１のときの入力換算雑音レベルより低くなる周波数領域であれば良い。 In the second embodiment, the difference frequency f m1 −f m2 is configured to be the minimum value of the input equivalent noise level of the transimpedance gain, but is lower than the input equivalent noise level at the modulation frequency f m1 of the light source 3. Any frequency range may be used.
　また、実施の形態２では、位相検波器１１ａ，１１ｂの機能として位相差信号のみを出力しているが、振幅に相当する信号を出力する機能を有していてもよい。さらに、波形整形回路５は光検出器アレイ１５の光検出器７ａ，７ｂに対して共通としたが、波形整形回路５も光検出器アレイ１５に含め、各光検出器７ａ，７ｂに対して設置する構成でもよい。これにより、各光検出器７ａ，７ｂの感度特性が異なっていた場合でも、波形整形回路５でその非線形特性を校正することができ、各アンプ８ａ，８ｂの入力換算雑音レベルの最小値に差周波ｆｍ１－ｆｍ２を設定することができる。 In the second embodiment, only the phase difference signal is output as the function of the phase detectors 11a and 11b, but it may have a function of outputting a signal corresponding to the amplitude. Further, although the waveform shaping circuit 5 is common to the photodetectors 7a and 7b of the photodetector array 15, the waveform shaping circuit 5 is also included in the photodetector array 15 and is associated with each of the photodetectors 7a and 7b. The structure to install may be sufficient. As a result, even if the sensitivity characteristics of the photodetectors 7a and 7b are different from each other, the waveform shaping circuit 5 can calibrate the nonlinear characteristics, and the difference between the minimum values of the input conversion noise levels of the amplifiers 8a and 8b. The frequency f m1 -f m2 can be set.
　また、上記の実施の形態２の光測距装置では、走査光学系を用いずに照射領域中の測距を行う構成であったが、受信視野を固定し、送信ビームのみを走査光学系でスキャンする構成でもよい。このとき、光の照射方向と光検出器７ａ，７ｂにおける受光スポットは同期するため、図５に示すように、走査光学系１６と同期回路１７を設置し、ＭＵＸ回路１４を同期する構成とする。すなわち、同期回路１７は、走査光学系１６の走査方向と、その走査方向における対象物からの反射光をうける光検出器７ａ，７ｂからの受信信号を選択するようＭＵＸ回路１４を同期制御する。他の構成は図４に示した構成と同様であるため、ここでの説明は省略する。 In the optical distance measuring apparatus of the second embodiment, the distance measurement is performed in the irradiation area without using the scanning optical system. However, the reception field of view is fixed, and only the transmission beam is detected by the scanning optical system. It may be configured to scan. At this time, since the light irradiation direction and the light receiving spots in the photodetectors 7a and 7b are synchronized, as shown in FIG. 5, the scanning optical system 16 and the synchronization circuit 17 are installed, and the MUX circuit 14 is synchronized. . That is, the synchronization circuit 17 synchronously controls the MUX circuit 14 so as to select the scanning direction of the scanning optical system 16 and the received signals from the photodetectors 7a and 7b that receive the reflected light from the object in the scanning direction. The other configuration is the same as the configuration shown in FIG.
　このように、実施の形態２の光測距装置によれば、複数の光検出器７ａ，７ｂを備えた光検出器アレイ１５としたので、一つ受光素子で強度・位相を測定することができるため、取得画像の有効画素数の減少がなくなる。 As described above, according to the optical distance measuring device of the second embodiment, since the photodetector array 15 includes the plurality of photodetectors 7a and 7b, the intensity and phase can be measured with one light receiving element. As a result, the number of effective pixels in the acquired image is not reduced.
　以上説明したように、実施の形態２の光測距装置によれば、変調基準信号を発生する第１の発振器と、変調基準信号に基づき、強度変調された光を出力する光源と、光源より出力した光を整形し、照射する送信光学系と、照射された光に基づく対象物からの反射光を集光する受信光学系と、感度変調基準信号を発生する第２の発振器と、それぞれが、与えられた変調波形の信号に基づいて感度を変調し、受光した変調信号との差周波をそれぞれの受信信号として出力する複数の光検出器と、感度変調基準信号に基づき、複数の光検出器の感度を線形に変調するため変調波形を整形する波形整形回路と、変調基準信号と感度変調基準信号の差信号を参照信号として出力する参照信号出力部と、複数の受信信号と参照信号からそれぞれ位相差を求める複数の位相検波器と、複数の位相検波器からの出力を切り替えるマルチプレクサと、マルチプレクサで切り替えられた位相差信号から、前記各光検出器に対応する距離を計測する信号処理部とを備えたので、複数の光検出器を有する光測距装置であっても、変調光の周波数との差周波にダウンコンバートするときの効率を向上させることができる。 As described above, according to the optical distance measuring device of the second embodiment, the first oscillator that generates the modulation reference signal, the light source that outputs the intensity-modulated light based on the modulation reference signal, and the light source A transmitting optical system for shaping and irradiating the output light, a receiving optical system for collecting reflected light from an object based on the irradiated light, and a second oscillator for generating a sensitivity modulation reference signal, A plurality of photodetectors that modulate the sensitivity based on a signal of a given modulation waveform and output a difference frequency from the received modulation signal as a respective reception signal, and a plurality of light detections based on the sensitivity modulation reference signal A waveform shaping circuit that shapes the modulation waveform to linearly modulate the sensitivity of the detector, a reference signal output unit that outputs a difference signal between the modulation reference signal and the sensitivity modulation reference signal as a reference signal, and a plurality of received signals and reference signals Each phase difference A plurality of phase detectors, a multiplexer that switches outputs from the plurality of phase detectors, and a signal processing unit that measures a distance corresponding to each photodetector from the phase difference signal switched by the multiplexer. Therefore, even an optical distance measuring device having a plurality of photodetectors can improve efficiency when down-converting to a difference frequency from the frequency of the modulated light.
　また、本願発明はその発明の範囲内において、各実施の形態の自由な組み合わせ、あるいは各実施の形態の任意の構成要素の変形、もしくは各実施の形態において任意の構成要素の省略が可能である。 Further, within the scope of the present invention, the invention of the present application can be freely combined with each embodiment, modified with any component in each embodiment, or omitted with any component in each embodiment. .
　以上のように、この発明に係る光測距装置は、変調周波数を低周波側にダウンコンバートする受光器を備えたものであり、レーザレーダ装置等に用いるのに適している。 As described above, the optical distance measuring device according to the present invention includes the light receiver that down-converts the modulation frequency to the low frequency side, and is suitable for use in a laser radar device or the like.
　１　第１の発振器、２　第２の発振器、３　光源、４　送信光学系、５　波形整形回路、６　受信光学系、７，７ａ，７ｂ　光検出器、８，８ａ，８ｂ　アンプ、９　ミキサ、１０　バンドパスフィルタ（ＢＰＦ）、１１，１１ａ，１１ｂ　位相検波器、１２　信号処理部、１３　参照信号出力部、１４　マルチプレクサ（ＭＵＸ回路）、１５　光検出器アレイ、１６　走査光学系、１７　同期回路。 1. 1st oscillator, 2nd oscillator, 3 light source, 4 transmission optical system, 5 waveform shaping circuit, 6 reception optical system, 7, 7a, 7b photodetector, 8, 8a, 8b amplifier, 9 mixer, 10 Bandpass filter (BPF), 11, 11a, 11b phase detector, 12 signal processing unit, 13 reference signal output unit, 14 multiplexer (MUX circuit), 15 photodetector array, 16 scanning optical system, 17 synchronization circuit.

Claims (3)

  1. 　変調基準信号を発生する第１の発振器と、
    　前記変調基準信号に基づき、強度変調された光を出力する光源と、
    　前記光源より出力した光を整形し、照射する送信光学系と、
    　前記照射された光に基づく対象物からの反射光を集光する受信光学系と、
    　感度変調基準信号を発生する第２の発振器と、
    　与えられた変調波形の信号に基づいて感度を変調し、受光した変調信号との差周波を受信信号として出力する光検出器と、
    　前記感度変調基準信号に基づき、前記光検出器の感度を線形に変調するための変調波形を整形する波形整形回路と、
    　前記変調基準信号と前記感度変調基準信号の差信号を参照信号として出力する参照信号出力部と、
    　前記受信信号と前記参照信号から位相差を求める位相検波器と、
    　前記位相検波器から出力される位相差信号から、距離を計測する信号処理部とを備えた光測距装置。     A first oscillator for generating a modulation reference signal;
    A light source that outputs intensity-modulated light based on the modulation reference signal;
    A transmission optical system for shaping and irradiating the light output from the light source;
    A receiving optical system for collecting reflected light from the object based on the irradiated light;
    A second oscillator for generating a sensitivity modulation reference signal;
    A photodetector that modulates sensitivity based on a signal of a given modulation waveform and outputs a difference frequency with the received modulation signal as a received signal;
    A waveform shaping circuit for shaping a modulation waveform for linearly modulating the sensitivity of the photodetector based on the sensitivity modulation reference signal;
    A reference signal output unit that outputs a difference signal between the modulation reference signal and the sensitivity modulation reference signal as a reference signal;
    A phase detector for obtaining a phase difference from the received signal and the reference signal;
    An optical distance measuring device comprising: a signal processing unit for measuring a distance from a phase difference signal output from the phase detector.
  2. 　変調基準信号を発生する第１の発振器と、
    　前記変調基準信号に基づき、強度変調された光を出力する光源と、
    　前記光源より出力した光を整形し、照射する送信光学系と、
    　前記照射された光に基づく対象物からの反射光を集光する受信光学系と、
    　感度変調基準信号を発生する第２の発振器と、
    　それぞれが、与えられた変調波形の信号に基づいて感度を変調し、受光した変調信号との差周波をそれぞれの受信信号として出力する複数の光検出器と、
    　前記感度変調基準信号に基づき、前記複数の光検出器の感度を線形に変調するための変調波形を整形する波形整形回路と、
    　前記変調基準信号と前記感度変調基準信号の差信号を参照信号として出力する参照信号出力部と、
    　前記複数の受信信号と前記参照信号からそれぞれ位相差を求める複数の位相検波器と、
    　前記複数の位相検波器からの出力を切り替えるマルチプレクサと、
    　前記マルチプレクサで切り替えられた位相差信号から、前記各光検出器に対応する距離を計測する信号処理部とを備えた光測距装置。     A first oscillator for generating a modulation reference signal;
    A light source that outputs intensity-modulated light based on the modulation reference signal;
    A transmission optical system for shaping and irradiating the light output from the light source;
    A receiving optical system for collecting reflected light from the object based on the irradiated light;
    A second oscillator for generating a sensitivity modulation reference signal;
    A plurality of photodetectors each for modulating the sensitivity based on a signal of a given modulation waveform and outputting a difference frequency from the received modulation signal as a respective reception signal;
    A waveform shaping circuit for shaping a modulation waveform for linearly modulating the sensitivity of the plurality of photodetectors based on the sensitivity modulation reference signal;
    A reference signal output unit that outputs a difference signal between the modulation reference signal and the sensitivity modulation reference signal as a reference signal;
    A plurality of phase detectors for respectively obtaining a phase difference from the plurality of received signals and the reference signal;
    A multiplexer that switches the output from the plurality of phase detectors;
    An optical distance measuring device comprising: a signal processing unit that measures a distance corresponding to each of the photodetectors from the phase difference signal switched by the multiplexer.
  3. 　光検出器からの差周波信号を増幅するアンプを備えると共に、
    　前記差周波信号が、前記アンプにおける変調基準信号の周波数の入力換算雑音レベルより低い入力換算雑音レベルとなる周波数領域となるよう前記変調基準信号と感度変調基準信号とを決定することを特徴とする請求項１記載の光測距装置。     With an amplifier that amplifies the difference frequency signal from the photodetector,
    The modulation reference signal and the sensitivity modulation reference signal are determined so that the difference frequency signal is in a frequency region where the input conversion noise level is lower than the input conversion noise level of the frequency of the modulation reference signal in the amplifier. The optical distance measuring device according to claim 1.
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* Cited by examiner, † Cited by third party
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CN106646502A (en) * 2016-11-10 2017-05-10 深圳市摩天射频技术有限公司 Novel laser ranging device and method
CN106646502B (en) * 2016-11-10 2023-12-08 深圳市摩天射频技术有限公司 Laser ranging equipment and method

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