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WO2007033608A1 - Recepteur optique muni d'un photodetecteur module - Google Patents

Recepteur optique muni d'un photodetecteur module Download PDF

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Publication number
WO2007033608A1
WO2007033608A1 PCT/CN2006/002507 CN2006002507W WO2007033608A1 WO 2007033608 A1 WO2007033608 A1 WO 2007033608A1 CN 2006002507 W CN2006002507 W CN 2006002507W WO 2007033608 A1 WO2007033608 A1 WO 2007033608A1
Authority
WO
WIPO (PCT)
Prior art keywords
photo
optical
detector
modulated
modulation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CN2006/002507
Other languages
English (en)
Inventor
Torsten Wipiejewski
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hong Kong Applied Science and Technology Research Institute ASTRI
Original Assignee
Hong Kong Applied Science and Technology Research Institute ASTRI
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hong Kong Applied Science and Technology Research Institute ASTRI filed Critical Hong Kong Applied Science and Technology Research Institute ASTRI
Priority to CN2006800257194A priority Critical patent/CN101263402B/zh
Publication of WO2007033608A1 publication Critical patent/WO2007033608A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C3/00—Measuring distances in line of sight; Optical rangefinders
    • G01C3/02—Details
    • G01C3/06—Use of electric means to obtain final indication
    • G01C3/08—Use of electric radiation detectors
    • 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
    • G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
    • 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
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/4861—Circuits for detection, sampling, integration or read-out

Definitions

  • This invention relates to optical receivers and, more particularly, to optical receivers with modulated photo-detectors. More specifically, although not exclusively, this invention relates to optical receivers for optical remote sensing and/or optical distance measurement.
  • a typical optical system comprises an optical transmitter and an optical receiver.
  • An optical receiver usually comprises a photo-detector which converts incoming optical signals into electrical output signals for processing by downstream signal processing circuitry.
  • a photo-detector usually comprises a semi-conductor absorbing layer. When optical signals of an appropriate wavelength impinge on the absorbing layer of a photo-detector, electron-hole pairs will be created. Bias-voltage at the terminals of the photo- detector will accelerate the carriers in the electric field between the terminals, whereby in-coming light is converted into electric current.
  • a photo-detector may comprise a photo-diode, for example, a PIN diode for an avalanche diode, photo- resistors or, more recently, MSM photo-detectors.
  • Photo-detectors are typically at a pre-determined biasing condition adapted for specific applications.
  • the present invention has described an optical receiver comprising a photo-detector, wherein said photo-detector is modulated whereby it has a time-variant photo-responsivity following the modulation on the photo- detector.
  • a distance measuring means comprising an optical system of as described herein, wherein modulation of said optical receiver and the modulated optical signals transmitted by said optical transmitter have the same modulation frequency.
  • an optical system comprising an optical transmitter and an optical receiver as described herein, wherein said optical transmitter comprises an optical source which transmits modulated optical signals, modulation of said optical receiver and said optical transmitter is of the same format.
  • said the photo-detector is pulse modulated and the photo- response of said photo-detector follows the pulse modulation applied to said photo-detector.
  • photo-responsivity of said photo-detector is bias-voltage dependent, modulation is applied to said photo-detector to vary the photo- responsivity of said photo-detector for signal detection.
  • polarity of bias-voltage polarity of said photo-detector is reversible
  • polarity of photocurrent output of said photo-detector is reversible and is dependent on the polarity of said bias-voltage.
  • said photo-detector is pulse modulated.
  • said photo-detector is pulse modulated with alternate on and off pulses.
  • said photo-detector is turned on and off respectively by said on and off pulses.
  • said photo-detector comprises a MSM photo-detector.
  • pulse modulation is applied to terminals of said photo-detector.
  • modulation of said optical receiver and the modulated optical signals transmitted by said optical transmitter have the same modulation frequency.
  • modulation of said optical receiver and the modulated optical signals transmitted by said optical transmitter are rectangular pulses of the same period and pulse width (T).
  • modulation of said optical receiver and the modulated optical signals transmitted by said optical transmitter have a constant phase relationship.
  • modulation of said optical receiver and the modulated optical signals transmitted by said optical transmitter are anti-phased.
  • modulation of said optical receiver and the modulated optical signals transmitted by said optical transmitter have a constant phase difference.
  • modulation of said optical receiver and the modulated optical signals transmitted by said optical transmitter have a constant phase difference.
  • distance information of an object is obtained upon reception of modulated optical signals transmitted by said optical transmitter by said optical receiver after the optical signals are reflected from said object.
  • distance information is obtained by comparing photocurrent output of said photo-detector when said photo-detector is modulated and when said photo-detector is un-modulated.
  • the distance of an object is determined by varying the pulse width of the light source and by detecting the maxima or minima of photocurrent output of said photo-detector.
  • the distance of multiple reflection points is determined by evaluating several relative minima in the optical response function.
  • the distance of an object is determined by varying the delay time of the gating function and detecting the maximum of the modulated photocurrent as function of the delay time.
  • the distance of multiple reflection points is determined by evaluating relative maxima in the optical response function.
  • Fig. 1 is a cross-sectional view of a typical MSM photo-detector
  • Fig. 2 shows photo-current output vs. voltage characteristics of a typical MSM photo-detector
  • Fig. 3 illustrates timing diagrams of transmitted signal, reflected signal and photo-detector gating time of a first preferred application of its invention
  • Fig. 4 illustrates a schematic system configuration of a first preferred embodiment of this invention
  • Fig. 5 is a graph showing the variation of detected photo-current vs. delay time with reference to the arrangement of Figs. 3 and 4,
  • Fig. 6 is a graph showing the variation of detected photo-current vs. variation in modulation frequency of a second preferred embodiment
  • Fig. 7 shows timing diagram relationship between transmitter signals, reflected signals and photo-detector gating time in which the delay of the photo- detecting gating time is varied of a third preferred embodiment
  • Fig. 8 shows a graph of variation of detected photo-current vs. delay time d of the photo-detector gating time of Fig. 7 showing a second preferred embodiment of this invention
  • Fig. 9 illustrates an exemplary application of this invention on a three- dimensional object.
  • Photo-detectors in conventional optical receivers are typically biased at a constant DC bias-voltage to prepare for reception of incoming optical signals.
  • a bias-voltage is applied to a photo-detector to accelerate electron and hole pairs according to the polarity of the applied electric field to produce photo-current output.
  • bias-voltage of a specific and constant polarity must be applied to the terminals of the photo-detector in order to generate a correct electric field for meaningful photo-detection.
  • a photo-detector is usually reverse biased.
  • Metal-semiconductor-metal (MSM) photo-detectors have been used for light detection in fibre optic systems for many years.
  • a typical MSM photo- detector is shown in Fig 1 and comprises inter-digitated electrodes which are deposited on an absorbing layer.
  • the absorbing layer can be, for example, undoped GaAs.
  • An exemplary MSM photo-detector is described in US 5,461 ,246 which is incorporated herein by reference.
  • the I-V characteristics of an ideal MSM photo-detector have positive/negative symmetry with respect to bias-voltage, as shown in Fig. 2.
  • the direction of the resulting photo-current will depend on the polarity of the voltage bias.
  • the direction of photo-current will be reversed if the polarity of the bias-voltage is reversed.
  • MSM photo-detectors In conventional non-MSM photo-detectors, carriers are generated proximal to the metal electrodes where a built-in electrical field due to metal Schottky contact on the semi-conductor surface exists. On the other hand, due to the highly symmetrical structure of a MSM photo-detector, random carriers generated under un-biased conditions will be cancelled out by similar carrier motions occurring at the other electrode. As a result, there is no net induced current output from a MSM photo-detector at zero biased voltage. This unique characteristic of MSM photo-detectors is advantageous for use in an optical receiver, especially an optical receiver for distance measurements.
  • the distance measuring system comprises an optical transmitter 110 and an optical receiver 120.
  • the optical transmitter transmits optical signals towards a remote object 130, the distance of which is to be measured.
  • Optical signals reflected by the remote object 130 are received by an optical receiver 120.
  • Distance information of the remote object 130 is obtained by reference to the temporal relationship, or more specifically, temporal differences, between the originally transmitted signals and the signals received by the optical transmitter after reflection by the remote object 130.
  • modulated optical signals 1120 are generated and then transmitted by an optical source of the optical transmitter 110.
  • the optical source may comprise laser or a LED.
  • the modulated optical signals are transmitted towards the remote object 130 and are reflected towards the optical receiver 120 for reception.
  • the optical signals 1120 will have travelled a total distance x before the signals are received by the optical receiver 120, assuming that the remote object 130 is distant from both the optical transmitter 110 and the optical receiver 120 so that the separation between the optical transmitter 110 and the optical receiver 120 is negligible.
  • the difference travelled by the transmitted and reflected can be un-equal and the difference can be accounted for using ordinary arithmetic principles without loss of generality.
  • the time shift or delay (t) between the reflected signal stream 1320 and the originating signal stream 1120 will represent the time required to cover the total distance x, which is twice the separation between the optical receiver and the remote object in this example.
  • the total distance travelled, namely, x, and the distance of the remote object, that is, x/2 can be found.
  • the reflected optical pulses 1320 arrive at the optical receiver 120 with a time delay t with respect to the originally transmitted signal 1120. This time delay represents the time required for light to travel from the optical transmitter to the optical receiver.
  • time-average photo-current output of the photo-detector can be varied by gating the photo-detector with a modulated signal which defines a time-variant or time- dependent photo-responsivity.
  • time-variant, or time-dependent in this specification means a photo-responsivity which is not constant but is variable within a specific period of time, that is, within a cycle.
  • the term "gating" here means applying a biasing voltage to the control terminal(s) of a photo-detector to vary the photo-responsivity of the photo-detector.
  • the photo-detector is gated by modulation signals which are identical to the timing characteristics of the transmitted optical signal. Similar to the transmitted signals, a binary gating modulation function is used and the photo-detector is turned off during the off time of the modulation, which corresponds to a low modulation voltage.
  • the time-average photo-current output of the photo-detector will be equal to the time-average photo-current output (l_n) of the photo-detector with a constant DC bias-voltage which turns the photo-detector on to operate at a pre-determined photo-responsivity.
  • the photo-current output (l_g) by the gated photo-detector decreases. As shown in Fig.
  • the time delay t exceeds the pulse width T of the transmitted optical signal, photo-current output from the optical receiver will increase and will reach a maxima when the time delay t equals the period of the transmitted signals.
  • a MSM photo-detector is employed in this example because it gives no photo-current output when the bias-voltage is zero.
  • the dotted graph 152 of Fig. 5 shows an exemplary photo-detector output when there is stray light (l_s).
  • the distance information can be obtained by the ratio (1 - l_g/l_n) as shown in the above equation.
  • the distance of a remote object can be measured by the arrangement of Fig. 4 by variation of the modulation gating frequency of the MSM photo-detector.
  • the gating modulation function is initially set to be anti-phased to the laser output modulation so that there is a 180° phase shift between the gating modulation function and the laser output source.
  • the distance x between the optical transmitter and the optical receiver is zero, only photo-current due to incident stray light (l_s) is generated by the photo-detector.
  • the photo-current output intensity l_g will increase until it reaches a maxima at frequency f_1 when the photo-current output of the photo-detector is equal to the photo-current output (l_n) of an ungated photo-detector.
  • the intensity of the photo-current output l_g again corresponds approximately to the ambient stray light detected.
  • This periodic relationship between the gated photo-current signal (l_g) and frequency will repeat at odd and even harmonics of the fundamental frequency f_0.
  • Exemplary relationship between the total distance x and the first (M) and second (f_3) maxima are set out in table below in which f 3 is 3 x f 1.
  • the first frequency maxima M can be obtained by linear extrapolation of a plurality of data points between f_0 and M . Additional data points between M and f_2 can be collected and processed for extrapolating the maxima and/or minima to further enhance accuracy. By tracking the relative maxima and minima, adverse influence due to stray light can be mitigated.
  • the distance of a remote object is measured by varying the delay time of the gating modulation function of the photo-detector.
  • the pulse-timing diagrams 1221 and 1320 corresponding respectively to the gating modulation pulses and the received reflected pulses of Fig. 7, because the pulse width of the reflected pulse of 1320 and the gating pulse 1221 have the same pulse width and pulse period, the photo-detector output will be maximum when the on-pulses overlap.
  • the time of occurrence of the maximum photo-detector output can be evaluated from the second derivative of the function photo-current output vs. delay time.
  • the delay time and therefore the distance x/2 can be obtained by measuring the time-average values of the optical signals l_n, l_s and l_g.
  • a three-dimensional imaging of a remote object can be measured by one and two dimensional photo- detector arrays. The difference in the distance travelled by light between the various surfaces of a remote object to the photo-detector arrays will provide three- dimensional information of the remote object.
  • the optical transmitter 110 and optical receiver 120 of Fig. 4 can be set up for distance measurement without requiring reflection from an object.
  • the length of an optical fibre cable can be measured by connecting optical fibre of length x between the optical transmitter and the optical receiver.
  • the total length of the optical fibre x can be measured by comparing the photo-current output of the gated photo-detector and by applying the above relationships mutatis-mutandis without loss of generality.
  • pulse shape for example, half-sinusoid, Gaussian or other pulse shapes can be used and the distance-delay time relationship can be calculated using known algorithms.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Electromagnetism (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Optical Radar Systems And Details Thereof (AREA)

Abstract

Un récepteur optique comprend un photodétecteur, ledit photodétecteur étant modulé et possédant une photo-réaction variant dans le temps en fonction de la modulation dans le photodétecteur.
PCT/CN2006/002507 2005-09-26 2006-09-25 Recepteur optique muni d'un photodetecteur module Ceased WO2007033608A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN2006800257194A CN101263402B (zh) 2005-09-26 2006-09-25 具有调制光探测器的光接收机

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
HK05108487.8 2005-09-26
HK05108487 2005-09-26

Publications (1)

Publication Number Publication Date
WO2007033608A1 true WO2007033608A1 (fr) 2007-03-29

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CN (1) CN101263402B (fr)
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2506538C1 (ru) * 2012-07-04 2014-02-10 Общество с ограниченной ответственностью "Си Тех" Лазерное устройство для проведения измерений с повышенной точностью

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107024179A (zh) * 2017-03-30 2017-08-08 江苏昂德光电科技有限公司 一种非接触式远程光纤位移测量装置及其测量方法
CN109425865B (zh) 2017-08-22 2020-09-08 深圳市道通智能航空技术有限公司 一种无人机测距方法、装置及无人机
CN112965079B (zh) * 2021-02-04 2023-11-17 苏州奥瑞图光电科技有限公司 一种基于msm探测的amcw远距离激光成像方法及系统

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5180922A (en) * 1990-01-26 1993-01-19 Erwin Sick Gmbh Optik-Elektronik Distance measuring apparatus with phase detection
JPH0563648A (ja) * 1991-09-02 1993-03-12 Hitachi Ltd 光注入同期装置、光受信装置および光通信装置
US5214526A (en) * 1991-06-04 1993-05-25 Apple Computer, Inc. Pulse modulated infrared data communications link
DE19520663A1 (de) * 1995-06-07 1996-12-12 Thomas Merker Abstandssensor
US6515740B2 (en) * 2000-11-09 2003-02-04 Canesta, Inc. Methods for CMOS-compatible three-dimensional image sensing using quantum efficiency modulation
CN1449501A (zh) * 2000-08-25 2003-10-15 库尔特·吉格 测距方法及装置
CN1466692A (zh) * 2000-09-27 2004-01-07 ���ء����߸� 在测距装置中信号检测的装置和方法
US6753950B2 (en) * 2000-01-26 2004-06-22 Instro Precision Limited Optical distance measurement
CN1643397A (zh) * 2002-01-23 2005-07-20 微光测量技术有限公司 光学测距的方法和装置

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5180922A (en) * 1990-01-26 1993-01-19 Erwin Sick Gmbh Optik-Elektronik Distance measuring apparatus with phase detection
US5214526A (en) * 1991-06-04 1993-05-25 Apple Computer, Inc. Pulse modulated infrared data communications link
JPH0563648A (ja) * 1991-09-02 1993-03-12 Hitachi Ltd 光注入同期装置、光受信装置および光通信装置
DE19520663A1 (de) * 1995-06-07 1996-12-12 Thomas Merker Abstandssensor
US6753950B2 (en) * 2000-01-26 2004-06-22 Instro Precision Limited Optical distance measurement
CN1449501A (zh) * 2000-08-25 2003-10-15 库尔特·吉格 测距方法及装置
CN1466692A (zh) * 2000-09-27 2004-01-07 ���ء����߸� 在测距装置中信号检测的装置和方法
US6515740B2 (en) * 2000-11-09 2003-02-04 Canesta, Inc. Methods for CMOS-compatible three-dimensional image sensing using quantum efficiency modulation
CN1643397A (zh) * 2002-01-23 2005-07-20 微光测量技术有限公司 光学测距的方法和装置

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2506538C1 (ru) * 2012-07-04 2014-02-10 Общество с ограниченной ответственностью "Си Тех" Лазерное устройство для проведения измерений с повышенной точностью

Also Published As

Publication number Publication date
CN101263402A (zh) 2008-09-10
CN101263402B (zh) 2012-05-30

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