WO2003060556A1 - Two laser beams rangefinder based on time of flight - Google Patents

Two laser beams rangefinder based on time of flight Download PDF

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Publication number
WO2003060556A1
WO2003060556A1 PCT/RU2002/000451 RU0200451W WO03060556A1 WO 2003060556 A1 WO2003060556 A1 WO 2003060556A1 RU 0200451 W RU0200451 W RU 0200451W WO 03060556 A1 WO03060556 A1 WO 03060556A1
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Prior art keywords
output
linked
input
pulse
sqmo
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PCT/RU2002/000451
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French (fr)
Inventor
Nikolai Nikolaevich Slipchenko
Michail Ilich Krimski
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Nikolai Nikolaevich Slipchenko
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Priority to EP02806414A priority Critical patent/EP1459098A1/en
Publication of WO2003060556A1 publication Critical patent/WO2003060556A1/en

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Classifications

    • 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
    • G01S7/497—Means for monitoring or calibrating
    • 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
    • G01S17/18—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves wherein range gates are used
    • 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
    • G01S17/14—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves wherein a voltage or current pulse is initiated and terminated in accordance with the pulse transmission and echo reception respectively, e.g. using counters
    • 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
    • G01S17/87—Combinations of systems using electromagnetic waves other than radio waves

Definitions

  • the present invention relates to the distance measuring instruments - to rangers.
  • pulse laser rangers are used, for instance, one of them is described in the book by V.V.Molebniy “Systems for optical detection and ranging", edited in Moscow by Mashinostroenie in 1981 , page 52. It comprises the pulse laser with an optical collimating system, emitting short optical pulses at the object; from its output the start reference pulse is branched off to the reference photo receiver with pulse amplification, which is connected with the start pulse of the time-interval counter (TIC).
  • TIC time-interval counter
  • the optical signal reflected from the object through the optical receiving objective, gets into the photo receiver and it is amplified by the pulse amplifier and it is forwarded to the stop input of TIC.
  • Distance to the object is defined by the measured time interval.
  • This ranger comprises the pulse laser (for instance, semiconductor quantum-mechanical oscillator [SQMO] with the scheme of pumping), the optical system making the emission diagram, the reference photo receiver, the receiving photo receiver with the receiving optical system, TIC; all the above-mentioned are set in a clock pulse-oscillator, key schemes, the counter, the memory unit 1 , the memory unit 2, the reader and the indicator, the scheme "or", the reversible counter.
  • the pulse laser for instance, semiconductor quantum-mechanical oscillator [SQMO] with the scheme of pumping
  • the information about distance up to each object is stored in the memory unit of this ranger; the memory unit is a source of information about an object required, being brought out by the reader.
  • FIGURE 1 shows the optical scheme of the submitted laser ranger with the higher level of selectivity of the objects being measured
  • FIGURE 2 shows the epures of signals and the principle of the ranger's operation
  • FIGURE 3 shows the application of two emitting channels with the noncoincided emission diagrams
  • the laser ranger comprises:
  • the laser ranger-detector operates as follows.
  • the controlled oscillator (2) makes a sequence of short pulses T im ⁇ 100 nsec with a repetition frequency F r ⁇ 100 Hz ⁇ 1 kHz (it is suitable for space observation); pulses start in turn SQMO 1 laser (20) and SQMO 2 laser (21) through the linked power amplifier (1).
  • the SQMO emission gets at the objects through the collimating lens (6) and the collimating lens (7).
  • a signal reflected from the object gets at the receiving lens (8), then at the AP photo receiver (22); the photodetected signal is amplified by the amplifier (9) and finally it is brought to the comparators (10) and (11).
  • the first comparator (11) develops an information signal upon overcome of detection threshold, which is formed by three branches.
  • the second comparator (10) develops the control signals, proportional to the noise level of receiving channel.
  • Pbackground is the level of the background noise.
  • a P po er is the level of noise of the AP power regulator.
  • noise ampii f is the level of noise of the amplifier.
  • n oise ⁇ °c is the temperature noise.
  • a number of noise pulses after the second comparator (10) is transformed in integrators (12), (13) into control signals with a different constant of time.
  • the first signal V COntr i (when ⁇ ⁇ « ⁇ 2 ) is speed-response and it is brought through the adder (16) simultaneously with V contr2 at the reference input of the first comparator (11).
  • V CO nt r 3 i the adaptive signal, considering correction of the detection threshold, depending on the signal's changes within the distance. It is required for suppression of signals from the diffusive objects and for signals development from optical systems.
  • con tr2 it settles the task of adaptation of the detection threshold for the factors slowly changing - temperature and slow changes of the background (day, night, clouds etc.)
  • Vcontri it settles the task of adaptation of the detection threshold for the factors quickly changing [difference of background: light/dark, building, shadow, parasitical sources of light in the field of view upon quick space scanning by the ranger].
  • CO ntr3 it settles the task of adaptation of the detection threshold, depending on the distance up to the object in order to decrease amplitude-time error in distance measuring and space-time amplitude selection of the useful objects (optical systems) from the parasitical objects (diffusive-reflective).
  • Optical systems give the reflected signal (glare), according to the signal's level [P op t.re f i is the level of the reflected signal from the optical systems; P i f is the level of the reflected signal from the diffusive objects],
  • the noise immunity, selectivity of detection and measurement of objects' parameters increase.
  • Application of the voice synthesizer (17) enables to receive the information about distance without the interruption of operator from search & observation process, it increases reliability and efficiency of the information's search & record.
  • Application of the separate indicator (18) for the object detection gives possibility to fix quickly position of the field of view of the ranger at the object.
  • the double mode of pumping of the semiconductor quantum-mechanical oscillator [SQMO] is applied.
  • the first mode is the increased repetition frequency F ⁇ kHz upon objects search
  • the second mode is the rarely repeating mode upon getting at an object F r ⁇ 1 Hz.
  • the application of two emitting channels with the noncoincided emission diagrams enables to provide the selection of the useful point objects (optical systems), relatively the extended objects (walls reflecting diffusively etc., glasses in buildings, road signs and so on), using the criteria of the angle and linear dimensions.
  • the optical devices have the reflective aperture of ⁇ 20 ⁇ 50 mm, but the walls, the glasses, the light-reflecting road signs are of much more bigger dimensions. That is why the extended objects, we have two signals from the extended objects from the first SQMO and from the second SQMO. Upon that, the signal of prohibition to supply information is generated into the pulse sharper (19), according to the counter's (14) signal. If there is a signal from the first SQMO, the prohibition is absent.

Abstract

The present invention relates to the distance measuring instruments- to rangers. The general aspect of the invention is measurement of the distance to the objects providing spacious selection, it is reached by the second emitting channel introduced into the device; that channel is made as the additional pulse laser, the synthesizer, the second comparator, the additional integrators, the controlled counter and the pulse inhibit sharper.

Description

TWO LASER BEAMS RANGEFINDER BASED ON TIME_OF_FLIGHT
BACKGROUND OF THE INVENTION
The present invention relates to the distance measuring instruments - to rangers.
DESCRIPTION OF THE PRIOR ART
Nowadays, a wide scope of laser rangers of different designation and design exists. To measure the distance to the objects and to provide space selection, pulse laser rangers are used, for instance, one of them is described in the book by V.V.Molebniy "Systems for optical detection and ranging", edited in Moscow by Mashinostroenie in 1981 , page 52. It comprises the pulse laser with an optical collimating system, emitting short optical pulses at the object; from its output the start reference pulse is branched off to the reference photo receiver with pulse amplification, which is connected with the start pulse of the time-interval counter (TIC). The optical signal, reflected from the object through the optical receiving objective, gets into the photo receiver and it is amplified by the pulse amplifier and it is forwarded to the stop input of TIC. Distance to the object is defined by the measured time interval. The drawback of this laser ranger is an impossibility to select an object by the distance and by the field of view, e.g., if there are several targets in the field of view or there is a point object or an extended object, it is impossible to carry out object selection by the angle or reflective characteristics.
Partly the pulse ranger settles this problem (just the same literature, page 55, fig.2.6), that is the prior art of the invention.
This ranger comprises the pulse laser (for instance, semiconductor quantum-mechanical oscillator [SQMO] with the scheme of pumping), the optical system making the emission diagram, the reference photo receiver, the receiving photo receiver with the receiving optical system, TIC; all the above-mentioned are set in a clock pulse-oscillator, key schemes, the counter, the memory unit 1 , the memory unit 2, the reader and the indicator, the scheme "or", the reversible counter.
The information about distance up to each object is stored in the memory unit of this ranger; the memory unit is a source of information about an object required, being brought out by the reader.
The most actual task now is development of compact laser rangers - detectors for hidden surveillance of the applied optical observation means (for example, spy-glasses, periscopes, binoculars, cameras etc.). Upon that, it is necessary to provide selection of this class of objects at the background of parasitical objects (walls, houses, buildings, wood, grass etc.) by the characteristics of reflection (quasi-cat's eye objects at the background of the diffusive objects), as well as by the angle characteristics (point objects at the background of extended objects).
BRIEF DESCRIPTION OF THE DRAWINGS
Other advantages and features of the present invention will now be described in greater detail with reference to an exemplary embodiment, which is intended to explain and not to limit the invention, and is illustrated in the drawing, that is FIGURE 1 shows the optical scheme of the submitted laser ranger with the higher level of selectivity of the objects being measured; FIGURE 2 shows the epures of signals and the principle of the ranger's operation; FIGURE 3 shows the application of two emitting channels with the noncoincided emission diagrams
DESCRIPTION OF THE PREFERRED EMBODIMENT
The laser ranger comprises:
- the first SQMO pulse laser with the optical collimating lens (6),
- the second SQMO pulse laser with the optical collimating lens (7),
- the 2-channel linked amplifier (1) of SQMO pumping,
- the controlled oscillator (2) of SQMO pulse pumping,
- the synchronizer (4),
- the first (12), the second (13) and the third (3) integrators,
- the avalanche photodiode [AP] (22) with the optical receiving lens (8),
- the controlled AP feed regulator (5),
- the first comparator (11) and the second comparator (10),
- the adder (16),
- the controlled counter (14), - the time-interval counter (15),
- the voice synthesizer (17),
- the inhibit pulse shaper (19),
- the indicator (18) for objects detection.
The laser ranger-detector operates as follows. The controlled oscillator (2) makes a sequence of short pulses Tim~100 nsec with a repetition frequency Fr ~ 100 Hz ÷ 1 kHz (it is suitable for space observation); pulses start in turn SQMO 1 laser (20) and SQMO 2 laser (21) through the linked power amplifier (1). The SQMO emission gets at the objects through the collimating lens (6) and the collimating lens (7). A signal reflected from the object gets at the receiving lens (8), then at the AP photo receiver (22); the photodetected signal is amplified by the amplifier (9) and finally it is brought to the comparators (10) and (11). The first comparator (11) develops an information signal upon overcome of detection threshold, which is formed by three branches. The second comparator (10) develops the control signals, proportional to the noise level of receiving channel.
» noise ~ "background ' » APpower ' noise/amplif —■ v noiseT°C
Where:
Pbackground is the level of the background noise. APpo er is the level of noise of the AP power regulator. noise ampiif is the level of noise of the amplifier. noiseτ°c is the temperature noise.
A number of noise pulses after the second comparator (10) is transformed in integrators (12), (13) into control signals with a different constant of time. A slowly changing signal Vcontr2 (with τ2) is brought to the controllable feed regulator (5), that regulates an AP amplification coefficient, due to this the noise level's constancy (of the detection threshold) is provided within the wide range of exploitation conditions (Pbackground = 0÷10"5 W, T°C = -40°÷50°C).
The first signal VCOntri (when τ\ « τ2) is speed-response and it is brought through the adder (16) simultaneously with Vcontr2 at the reference input of the first comparator (11). At the same moment, the third signal Vcontr3 from the third integrator (3) with τ3 ≤ Tnearestzone is brought to the adder (16) (where Tnearestzone = 1÷2 m sec is the zone of short range detection ~ 50 ÷ 300 m).
VCOntr3 i the adaptive signal, considering correction of the detection threshold, depending on the signal's changes within the distance. It is required for suppression of signals from the diffusive objects and for signals development from optical systems.
Three control branches applied settle the following tasks: contr2: it settles the task of adaptation of the detection threshold for the factors slowly changing - temperature and slow changes of the background (day, night, clouds etc.)
Vcontri : it settles the task of adaptation of the detection threshold for the factors quickly changing [difference of background: light/dark, building, shadow, parasitical sources of light in the field of view upon quick space scanning by the ranger]. COntr3 : it settles the task of adaptation of the detection threshold, depending on the distance up to the object in order to decrease amplitude-time error in distance measuring and space-time amplitude selection of the useful objects (optical systems) from the parasitical objects (diffusive-reflective).
Optical systems give the reflected signal (glare), according to the signal's level [Popt.refi is the level of the reflected signal from the optical systems; P if is the level of the reflected signal from the diffusive objects],
θdif.
Popt.refi = Pdif. = Pdif. - (102 ÷ 103)
Figure imgf000007_0002
Figure imgf000007_0001
that is much more bigger, than diffusive objects do, where: θdif. s 120° ÷ 180° ~ (2 ÷ 3) rad θ0pt. Ξ 1 ° ÷ 5° ~ (0,017 ÷ 0, 1) rad
In practice it is allowed to use the regulation law: t
Vcontr(t) ≡ 0 • e "
Owing to these technical solutions, the noise immunity, selectivity of detection and measurement of objects' parameters increase. Application of the voice synthesizer (17) enables to receive the information about distance without the interruption of operator from search & observation process, it increases reliability and efficiency of the information's search & record. Application of the separate indicator (18) for the object detection gives possibility to fix quickly position of the field of view of the ranger at the object.
Also to increase the secretiveness and to decrease the average capacity of the laser ranger emission in order to decrease the threshold of detection, using the night viewing devices, the double mode of pumping of the semiconductor quantum-mechanical oscillator [SQMO] is applied. The first mode is the increased repetition frequency F ~ kHz upon objects search, the second mode is the rarely repeating mode upon getting at an object Fr ~ 1 Hz.
These modes create the conditions of the failure in detection of the laser ranger, it enables to hidden detect the observers with day and night optical devices for observation.
The application of two emitting channels with the noncoincided emission diagrams (see FIG.3) enables to provide the selection of the useful point objects (optical systems), relatively the extended objects (walls reflecting diffusively etc., glasses in buildings, road signs and so on), using the criteria of the angle and linear dimensions.
For example, the optical devices have the reflective aperture of ~20÷50 mm, but the walls, the glasses, the light-reflecting road signs are of much more bigger dimensions. That is why the extended objects, we have two signals from the extended objects from the first SQMO and from the second SQMO. Upon that, the signal of prohibition to supply information is generated into the pulse sharper (19), according to the counter's (14) signal. If there is a signal from the first SQMO, the prohibition is absent.

Claims

The laser ranger, comprising the pulse laser (the semiconductor quantum- mechanical oscillator [SQMO]) with the optical system and the pumping channel, the SQMO oscillator of pulse pumping, the photo receiver at the base of the avalanche photodiode (AP) with the optical system integrated into the field of the SQMO optical system, the pulse amplifier, the comparator, the time-interval counter, the distance indicator up to the object, differing by that, in order to provide the increased selection of point optical objects, the second SQMO is introduced, which is linked to the second channel of the SQMO pumping amplifier, the synthesizer with its output, linked to the control input of the two- channel pumping amplifier, the controlled feed regulator of the avalanche photodiode (AP), the second comparator, linked through its first input to the output of the amplifier and through its gating input to the second output of the synthesizer, the first and the second integrators, linked through their inputs to the output of the second comparator, the third integrator, linked through its input to the second output of the synthesizer, the counter with its three inputs linked to the outputs of the first, the second and the third integrators respectively, and its output is linked to the second input of the first comparator, the controlled counter, linked to the output of the first comparator, the gate oscillator, linked through its input to the output of the controlled counter and through its output to the input of the oscillator of pulse pumping, the inhibit pulse shaper, linked through its input to the output of the controlled counter, the voice synthesizer, linked through its first input to the TIC output (time-interval counter) and through its second input to the output of the pulse sharper and by its output to the second input of the power amplifier, and the indicator for object detection, linked through its input to the output of the controlled counter.
PCT/RU2002/000451 2001-12-27 2002-10-14 Two laser beams rangefinder based on time of flight WO2003060556A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP02806414A EP1459098A1 (en) 2001-12-27 2002-10-14 Two laser beams rangefinder based on time of flight

Applications Claiming Priority (2)

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RU2001135382 2001-12-27
RU2001135382/28A RU2001135382A (en) 2001-12-27 2001-12-27 LASER RANGEFINDER

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4020834C1 (en) * 1990-06-29 1991-10-24 Messerschmitt-Boelkow-Blohm Gmbh, 8012 Ottobrunn, De Driverless transport system control - uses laser sensor with laser diodes working in push=pull to detect position from retroreflective strips
US5336899A (en) * 1992-11-24 1994-08-09 The United States Of America As Represented By The Secretary Of The Army Adjustable near infrared rangefinder illuminator
US5359404A (en) * 1989-03-27 1994-10-25 Laser Technology, Inc. Laser-based speed measuring device
EP0747725A2 (en) * 1995-06-07 1996-12-11 HE HOLDINGS, INC. dba HUGHES ELECTRONICS Low cost laser range finder system architecture

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5359404A (en) * 1989-03-27 1994-10-25 Laser Technology, Inc. Laser-based speed measuring device
DE4020834C1 (en) * 1990-06-29 1991-10-24 Messerschmitt-Boelkow-Blohm Gmbh, 8012 Ottobrunn, De Driverless transport system control - uses laser sensor with laser diodes working in push=pull to detect position from retroreflective strips
US5336899A (en) * 1992-11-24 1994-08-09 The United States Of America As Represented By The Secretary Of The Army Adjustable near infrared rangefinder illuminator
EP0747725A2 (en) * 1995-06-07 1996-12-11 HE HOLDINGS, INC. dba HUGHES ELECTRONICS Low cost laser range finder system architecture

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