CN112965074B - Laser ranging method and device based on self-mixing semiconductor laser - Google Patents
Laser ranging method and device based on self-mixing semiconductor laser Download PDFInfo
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- CN112965074B CN112965074B CN202110382963.2A CN202110382963A CN112965074B CN 112965074 B CN112965074 B CN 112965074B CN 202110382963 A CN202110382963 A CN 202110382963A CN 112965074 B CN112965074 B CN 112965074B
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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
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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
- 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
Abstract
The invention provides a laser ranging method and a device based on a self-mixing semiconductor laser, wherein the device comprisesThe laser distance measuring device comprises a shell, a display screen for displaying laser measuring distance parameters and a plurality of operation keys positioned at the lower part of the display screen, wherein a self-mixing semiconductor laser is arranged in the shell, and a control module, a laser emitting module, a laser diode, a laser emitting lens, a laser receiving lens, a photoelectric detector, an amplifying circuit module, a shaping circuit module, a laser receiving module and a timing unit are arranged in the laser; phase modulation amplitude sigma and laser emission return time tau calculated by using ranging signal phase difference module of laser0And finally calculating the distance L from the laser to the measured object through the distance calculation module. The laser distance measuring method and the laser distance measuring device can accurately measure the laser distance without adjusting the radiation wavelength inspection or the distance from the laser to the reflector, and do not need to provide a large number of interference maximum values suitable for the laser wavelength change linear section.
Description
Technical Field
The invention belongs to the technical field of laser ranging, and particularly relates to a laser ranging method and device based on a self-mixing semiconductor laser.
Background
The laser has the advantages of good directivity, high brightness, good monochromaticity and the like, and is applied to the fields of topographic survey, house decoration, engineering survey, artificial satellite distance measurement, robot obstacle avoidance and the like. With the development of technologies such as robots, intelligent driving, intelligent parking of the internet of things and the like, people put higher requirements on the ranging precision, the measuring time and the stability of laser ranging. Due to the influence of various environmental factors, the laser ranging is difficult to achieve an ideal ranging state. Therefore, how to quickly, accurately and stably measure the target distance becomes a problem which needs to be solved urgently in the intelligent industry at present.
Disclosure of Invention
The present invention is directed to the above-mentioned drawbacks, and provides a laser ranging method and apparatus that can accurately measure a laser distance by using self-mixing interference of a self-mixing semiconductor laser and performing harmonic modulation without adjusting a radiation wavelength inspection or a distance to a reflecting mirror, and without providing a large number of interference maxima suitable for a laser wavelength variation linear section.
The invention provides the following technical scheme: a laser ranging method based on a self-mixing semiconductor laser comprises the following steps:
s1: the control module sends a measurement command to the laser emission module, and the laser diode receives a laser emission command sent by the laser emission module and then transmits the emitted radiation natural frequency omega0Feeding back to a ranging signal phase difference calculation module in the control module, and emitting laser, wherein the laser emitting module emits the laser at an initial time point tstartSending the data to a timing module;
s2: the laser returns from the original path after being reflected by the target object and is received by the photoelectric detector in the laser emission cavity, the photoelectric detector converts the received optical signal into an electric signal, the electric signal is amplified and shaped by the amplifying circuit module and the shaping circuit module and is transmitted to the laser receiving module, and the laser receiving module transmits the received optical return signal at the time point tstopThe laser diode radiation frequency deviation increment delta omega is transmitted to a timing module, and the laser diode radiation frequency deviation increment delta omega obtained after reflection is transmitted to a ranging signal phase difference calculation module in a control module;
s3: the distance measurement signal phase difference calculation module calculates radiation frequency omega (j (t)) and radiation power P (j (t)), and applies the radiation frequency omega (j (t)) and the radiation power P (j (t)) to construct a Fourier spectrum S of spectrum component amplitude of the Bessel function series expansion of the corresponding obtained P (j (t))nCalculating the amplitude sigma of the phase modulation by using the spectral harmonic amplitude;
s4: the timing module utilizes the laser emission initial time point t obtained in the step S1startAnd optical return signal time point tstopCalculating the time tau through laser radiation to the object and back to the laser0And transmitting to a distance calculation module;
s5: the distance calculation module adopts the radiation frequency deviation increment delta omega obtained in the step S1, the phase modulation amplitude sigma obtained in the step S3 and the laser obtained in the step S4Time τ of radiation to object and back to the laser0Calculating the distance L between the laser and the measured object;
s6: the display module displays the distance L of the measured object and finishes the measurement;
s7: the reset module resets all the modules to wait for the next measurement command.
Further, the step of S3 includes the steps of:
s31: constructing a self-mixing laser radiation power model:
P(j(t))＝P1(j(t))+P2cos(ω(j(t))τ0(t))；
wherein, the P1(j (t)) is the laser radiation power independent of the distance of the object to be measured, P2For the phase power reflected from the object to the laser that broadcasts interference with the laser wave emitted by the laser, τ0(t) is the time for the laser radiation to reach the object and return to the laser, ω (j (t)) is the radiation frequency of the semiconductor laser, which depends on the pump current density j (t) and the feedback laser level;
s32: the radiation frequency ω (j (t)) and the power P1(j (t)) the calculation formula is as follows:
ω(j(t))＝ω0+Δω·sin(2πv1t)；
P1(j(t))＝I1sin(2πv1t)；
wherein, the ω is0For the natural frequency of the semiconductor laser, Δ ω is the laser diode radiation frequency deviation increment, v1For the current modulation frequency of the semiconductor laser, I1Is the power P1(j (t)) current modulation amplitude;
s33: the radiation frequency omega (j (t)) obtained in the step S32 and the P are combined1(j (t)) substituting into the self-mixing laser radiation power model constructed in the step S31, calculating the semiconductor laser radiation power:
P(j(t))＝I1sin(2πv1t)+P2cos(ω0τ0+Δωτ0sin(2πv1t))；
s34: using class I JnA series decomposition of a Bessel function to represent the power P (j (t)) of the self-mixing signal:
wherein θ is the self-mixing signal phase of the semiconductor laser, and θ ═ ω0τ0(ii) a The omega is the angular frequency of the current modulation of the semiconductor laser, and 2 pi v is equal to omega1；
S35: listing the power P (j (t)) decomposition coefficient of the self-mixing signal as anAnd bnFourier series of (a):
s36: constructing a Fourier spectrum S of spectrum component amplitude of the Bessel function series expansion corresponding to the P (j (t)) obtained in the step S34 according to the power P (j (t)) of the self-mixing signal obtained in the step S34 and the Fourier sequence of the P (j (t)) obtained in the step S35nSpectral harmonic amplitude model of (1):
introducing said Fourier spectrum SnOdd spectral component model S of Fourier series decomposition2n+1And even spectral component S2nModel:
s37: constructing Fourier spectrum harmonic even spectrum component S except for n-12nModel and Fourier spectral harmonic odd spectral component S2n+1Model:
S2n＝2cos(θ)·P2·J2n(σ)；
S2n+1＝-2sin(θ)·P2·J2n+1(σ)；
s38: fourier spectrum harmonic even spectrum component S constructed by adopting the step S372nModeling, determining Fourier spectrum harmonic even spectral component S2nSum component S2n+2First ratio of (2):
S2n/S2n+2＝(J2n(σ))/(J2n+2(σ))；
the odd spectral components S of the sum Fourier spectrum harmonic wave constructed by the step S372n+1Model, determining odd spectral component S of Fourier spectral harmonic2n+1Sum component S2n+3Second ratio of (c):
S2n+1/S2n+3＝(J2n+1(σ))/(J2n+3(σ))；
and determining the amplitude sigma of the phase modulation by using the first ratio and the sent second ratio.
Further, the τ in the step S40The calculation formula of (a) is as follows:
τ0＝tstop-tstart。
further, the step S5 is defined by tau02L/c, and σ Δ ω τ0Therefore, the distance L from the laser to the object to be measured can be obtained:
wherein c is the speed of light.
The invention also provides a laser ranging device based on the self-mixing semiconductor laser, which comprises a shell, a display screen for displaying laser measured distance parameters and a plurality of operation keys positioned at the lower part of the display screen, wherein the self-mixing semiconductor laser is arranged in the shell, and a control module, a laser emitting module, a laser diode, a laser emitting lens, a laser receiving lens, a photoelectric detector, an amplifying circuit module, a shaping circuit module, a laser receiving module and a timing unit are arranged in the laser;
the control module is used for controlling laser emission, target distance calculation and result display and comprises a ranging signal phase difference calculation module, a distance calculation module, a display module and a reset module;
the laser emitting module is used for transmitting a laser command signal for emitting distance measurement and transmitting the signal to the laser diode and the timing module;
the laser diode is used for transmitting laser used for ranging to the laser transmitting lens and the ranging signal phase difference calculating module in the control module;
the laser emitting lens is used for diverging the laser to a target object;
the receiving laser lens is used for reflecting the target object to the laser distance measuring device and converging the target object to the laser receiving module;
the photoelectric detector is used for receiving the converged laser and converting the converged laser into an electric signal;
the amplifying circuit module is used for amplifying the electric signal and transmitting the electric signal to the shaping circuit module;
the shaping circuit module is used for shaping and converting the amplified electric signals into square wave electric signals and transmitting the square wave electric signals to the laser receiving module;
the laser receiving module is used for receiving an electric signal of laser reflected by the outside and transmitting the electric signal to the ranging signal phase difference calculating module and the timing module of the control module;
the timing module is used for receiving a laser command transmitted by the laser transmitting module and generating the laser transmitting initial time point tstartAnd is used for receiving the reflected light arrival command of the laser receiving module and generating the light return signal time point tstopCalculating the time tau through which the laser radiation reaches the object and returns to the laser0And transmitting to a distance calculation module;
the laser emitting module, the laser emitting lens, the laser receiving lens and the photoelectric detector are all positioned in a laser emitting cavity of the laser.
Further, the timing unit comprises an inner optical path receiving module and an outer optical path receiving module,
the inner light path receiving module is used for receiving the electric signal of the laser diode and generating a laser starting time point tstart；
The external light path receiving module is used for receiving the electric signal of the laser receiving module and generating a laser receiving time point tstop。
Further, the laser emission unit is a frequency-modulated semiconductor self-mixing laser diode RLD-650 having a quantum size structure of a diffraction-limited single spatial mode.
Further, the photodetector is an integrated avalanche photodiode.
Furthermore, the timing module is externally connected with a clock oscillator.
Furthermore, an optical filter and a diaphragm are arranged in front of the receiving laser lens.
The beneficial effects of the invention are as follows:
1. the natural frequency omega of laser emitted by the laser diode is obtained by a laser frequency modulation calculation module according to the phase difference of the ranging signal through laser waves which are emitted by interference mixing and are based on the inside of the self-mixing semiconductor laser and laser waves reflected by a measured object, and the laser waves are subjected to frequency modulation calculation0And calculating the interference radiation frequency omega (j (t)) of the semiconductor laser according to the laser diode radiation frequency deviation increment delta omega received by the laser receiving module.
2. Fourier spectrum S of spectrum component amplitude by establishing Bessel function series expansion corresponding to the obtained P (j (t))nThe amplitude sigma of phase modulation is calculated by the spectrum harmonic wave amplitude, and the modulation amplitude sigma of the phase can be accurately positioned by different harmonic even spectral components and different harmonic odd spectral components in the spread Fourier spectrum, so that the accuracy of subsequent distance calculation is further ensured.
3. The method is based on the self-mixing semiconductor laser to carry out harmonic modulation and utilizes the method for measuring the distance between the reflecting surface and the emitted laser to measure the distance from a measured object, the radiation wavelength deviation or the distance from a reflector do not need to be adjusted, the defect that the small-distance measurement precision is improved under the condition that the laser wavelength deviation is insufficient and a large amount of interference maximum values suitable for the laser wavelength change linear section are not allowed to be provided is made up.
4. The design of the optical device is improved, and the precision of the optical device is improved, so that the stability of the whole device is improved, and the measurement error is reduced.
5. Light weight, small volume, convenient carrying, simple operation, high speed and accuracy, non-contact measurement and safety to human eyes.
Drawings
The invention will be described in more detail hereinafter on the basis of embodiments and with reference to the accompanying drawings. Wherein:
FIG. 1 is a flow chart of a laser ranging method based on a self-mixing semiconductor laser according to the present invention;
FIG. 2 is a structural diagram of a laser distance measuring device based on a self-mixing semiconductor laser provided by the invention;
fig. 3 is a schematic structural diagram of an internal module in a laser ranging device based on a self-mixing semiconductor laser according to embodiment 1 of the present invention;
fig. 4 is a schematic structural diagram of an internal module in a laser distance measuring device based on a self-mixing semiconductor laser according to embodiment 2 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
As shown in fig. 1, a laser ranging method based on a self-mixing semiconductor laser provided by this embodiment includes the following steps:
s1: the control module sends a measurement command to the laser emitting module, and the laser diode receives a laser emitting command sent by the laser emitting module and then emits the natural frequency of the emitted radiationω0Feeding back to a ranging signal phase difference calculation module in the control module, and emitting laser, wherein the laser emitting module emits the laser at an initial time point tstartSending the data to a timing module;
s2: laser is reflected by a target object and returns along the original path, and is received by a photoelectric detector in a laser emission cavity, the photoelectric detector converts a received optical signal into an electric signal, the electric signal is amplified and shaped by an amplifying circuit module and a shaping circuit module and is transmitted to a laser receiving module, and the laser receiving module transmits the received optical return signal at a time point tstopThe laser diode radiation frequency deviation increment delta omega is transmitted to a timing module, and the laser diode radiation frequency deviation increment delta omega obtained after reflection is transmitted to a ranging signal phase difference calculation module in a control module;
s3: the distance measurement signal phase difference calculation module calculates radiation frequency omega (j (t)) and radiation power P (j (t)), and applies the radiation frequency omega (j (t)) and the radiation power P (j (t)) to construct a Fourier spectrum s of spectrum component amplitude corresponding to the obtained Bessel function series expansion of P (j (t))nCalculating the amplitude sigma of the phase modulation by using the spectral harmonic amplitude;
specifically, the method comprises the following steps:
s31: constructing a self-mixing laser radiation power model:
P(j(t))＝P1(j(t))+P2cos(ω(j(t))τ0(t))；
wherein, P1(j (t)) is the laser radiation power independent of the distance of the object to be measured, P2For phase power of the broadcast reflected from the object to the laser interfering with the laser wave emitted by the laser, τ0(t) is the time for the laser to radiate to the object and return to the laser, ω (j (t)) is the radiation frequency of the semiconductor laser, which depends on the pump current density j (t) and the feedback laser level;
s32: radiation frequency ω (j (t)) and power P1(j (t)) the calculation formula is as follows:
ω(j(t))＝ω0+Δω·sin(2πv1t)；
P1(j(t))＝I1sin(2πv1t)；
wherein the content of the first and second substances,ω0Δ ω is the laser diode radiation frequency deviation increment, v, for the natural frequency of the semiconductor laser1For modulating the frequency of the current of semiconductor lasers, I1Is a power P1(j (t)) a current modulation amplitude;
s33: the radiation frequency omega (j (t)) and P obtained in the step S32 are compared1(j (t)) is substituted into the self-mixing laser radiation power model constructed in the step S31 to calculate the semiconductor laser radiation power:
P(j(t))＝I1sin(2πv1t)+P2cos(ω0τ0+Δωτ0sin(2πv1t))；
s34: using class I JnThe series decomposition of the Bessel function represents the power P (j (t)) from the mixed signal:
where θ is the self-mixing signal phase of the semiconductor laser, and θ is ω0τ0(ii) a Omega is the angular frequency of current modulation of the semiconductor laser, and is 2 pi v1；
S35: the power P (j (t)) decomposition coefficient of the self-mixing signal is listed as anAnd bnFourier series of (a):
s36: constructing Fourier spectrum S of spectrum component amplitude of Bessel function series expansion corresponding to P (j (t)) obtained in step S34 according to power P (j (t)) of self-mixing signals obtained in step S34 and Fourier series of P (j (t)) obtained in step S35nSpectral harmonic amplitude model of (a):
introduction of Fourier spectrum SnOdd spectral component model S of Fourier series decomposition2n+1And even spectral component S2nModel:
s37: constructing Fourier spectrum harmonic even spectrum component S except for n-12nModel and odd spectral component S of Fourier spectral harmonic2n+1Model:
S2n＝2cos(θ)·P2·J2n(σ)；
S2n+1＝-2sin(θ)·P2·J2n+1(σ)；
s38: fourier spectrum harmonic even spectral component S constructed by adopting S37 step2nModeling, determining Fourier spectrum harmonic even spectral component S2nSum component S2n+2The first ratio of (a):
S2n/S2n+2＝(J2n(σ))/(J2n+2(σ))；
odd spectral components S of harmonic wave of sum Fourier spectrum constructed by adopting step S372n+1Model, determining odd spectral components S of harmonic of Fourier spectrum2n+1Sum component S2n+3Second ratio of (c):
S2n+1/S2n+3＝(J2n+1(σ))/(J2n+3(σ))；
determining the amplitude sigma of the phase modulation by using the first ratio and the sent second ratio;
s4: the timing module utilizes the laser emission initial time point t obtained in the step S1startAnd the optical return signal time point tstopCalculating the time tau of the laser radiation to the object and back to the laser0，τ0＝tstop-tstartThe timing module calculates the obtained time tau0Transmitting to a distance calculation module;
s5: the distance calculation module adopts the radiation frequency deviation increment delta omega obtained in the step S1, the phase modulation amplitude sigma obtained in the step S3 and the time tau obtained in the step S4 that the laser is radiated to the object and then returns to the laser0Calculating the distance L from the laser to the measured object from tau02L/c, and σ ═ Δ ω τ0Therefore, the distance L from the laser to the measured object can be obtained:
where c is the speed of light.
S6: the display module displays the distance L of the measured object and finishes the measurement;
s7: the reset module resets all modules to wait for the next measurement command.
The distance between the laser and the measured object and the time tau of the laser reflected back can be calculated by utilizing the timing modules respectively0And the natural radiation frequency omega of the semiconductor laser fed back to the ranging signal phase difference calculation module by the laser diode0And laser diode radiation frequency deviation increment delta omega received by the photoelectric detector and finally fed back to the ranging signal phase difference calculation module by the laser receiving module so as to calculate interference radiation frequency omega (J (t)) of the laser transmitter capable of generating laser interference, and further carrying out the first type JnThe series of Bessel functions decomposes a Fourier series from the power P (j (t)) and the spread P (j (t)) of the self-mixing signal, constructs a Fourier spectrum S corresponding to the amplitude of the spectrum component of the series expansion of the Bessel functions of P (j (t))nThe spectral harmonic amplitude model of (1) can pass through the harmonic even spectral component S of the Fourier spectrum2nSum component S2n+2Ratio of (1) and odd spectral component S2n+1Sum component S2n+3Determining the amplitude sigma of the phase modulation, and then using the determined amplitude sigma of the phase modulation, the radiation frequency deviation increment delta omega and the time tau of returning the laser to the object through the laser radiation0The method is characterized in that the distance L from the laser to the measured object is calculated, phase difference, namely phase modulation amplitude sigma, is calculated before distance calculation is carried out, the laser distance can be accurately measured without adjusting radiation wavelength inspection or the distance from the laser to a reflector, and a large amount of laser distance measuring methods and devices suitable for the interference maximum value of a laser wavelength change linear section are not required to be provided.
The timing jitter generated by noise and the timing walking error of a system are reduced, and the accuracy of the final object distance measurement is improved.
And is shown byThe power P (j (t)) of the self-mixing signal includes the laser radiation power P independent of the distance of the measured object1(j (t)) is, and the phase power P reflected from an object to the laser which broadcast interferes with the laser wave emitted by the laser2The accuracy of final distance measurement can be ensured, and factors which need to be considered and cause different radiation frequencies of final waves of laser interference cannot be reduced.
Example 2
As shown in fig. 2-3, the laser distance measuring device based on the self-mixing semiconductor laser provided for this embodiment includes a housing 1, a display screen 2 for displaying laser measured distance parameters, and a plurality of operation keys 3 located at a lower portion of the display screen, wherein the self-mixing semiconductor laser is disposed inside the housing 1, and a control module, a laser emitting module, a laser diode, a laser emitting lens, a laser receiving lens, a photodetector, an amplifying circuit module, a shaping circuit module, a laser receiving module, and a timing unit are disposed in the laser;
the control module is used for controlling laser emission, target distance calculation and result display and comprises a ranging signal phase difference calculation module, a distance calculation module, a display module and a reset module;
the laser emission module is used for transmitting a laser command signal for emitting distance measurement and transmitting the signal to the laser diode and the timing module;
the laser diode is used for transmitting laser used for ranging to the laser transmitting lens and the ranging signal phase difference calculating module in the control module;
a laser emitting lens for emitting laser light to a target object;
the receiving laser lens is used for reflecting the target object to the converging laser receiving module of the laser ranging device;
the photoelectric detector is used for receiving the converged laser and converting the converged laser into an electric signal;
the amplifying circuit module is used for amplifying the electric signal and transmitting the electric signal to the shaping circuit module;
the shaping circuit module is used for shaping and converting the amplified electric signals into square wave electric signals and transmitting the square wave electric signals to the laser receiving module;
the laser receiving module is used for receiving an electric signal of laser reflected by the outside and transmitting the electric signal to the ranging signal phase difference calculating module and the timing module of the control module;
a timing module for receiving the laser command from the laser emission module and generating an initial time point t of laser emissionstartAnd is used for receiving the reflected light arrival command of the laser receiving module and generating a light return signal time point tstopCalculating the time tau of the laser radiation to the object and returning to the laser0And transmitting to a distance calculation module;
the laser emitting module, the laser emitting lens, the laser receiving lens and the photoelectric detector are all positioned in a laser emitting cavity of the laser.
A timing unit including an inner optical path receiving module and an outer optical path receiving module,
the inner light path receiving module is used for receiving the electric signal of the laser diode and generating a laser starting time point tstart；
The external light path receiving module is used for receiving the electric signal of the laser receiving module and generating a laser receiving time point tstop。
The laser emission unit is a frequency-modulated semiconductor self-mixing laser diode RLD-650 with a quantum size structure of diffraction-limited single spatial mode, and can emit laser with the wavelength of 650nm during the working process.
The photoelectric detector is an integrated avalanche photodiode and is a photoelectric detector with internal gain, although avalanche gain is much smaller than a photomultiplier PMT, the sensitivity of APD is still much higher than that of a PIN photodiode, the problem of low sensitivity of the PIN photodiode is solved, and the advantages of the integrated avalanche photodiode are more obvious in high-speed modulation weak signal detection.
The timing module is externally connected with a clock oscillator, so that the timing accuracy of the timing module is ensured.
When the device works, the transmitting unit transmits measuring rays in the direction of a measuring object, the measuring rays are diffusely reflected after reaching a target object to be measured, the measuring rays are received, amplified and shaped by the receiving unit of the photoelectric element (the built-in laser receiving unit), the time from transmitting to receiving of a laser beam is measured by the timer, and the distance of the target object is displayed by the display unit after the distance calculation unit finishes calculation.
The ranging work flow is as follows: firstly, a reset switch K is turned on, the whole ranging system is reset, and ranging preparation is made. Meanwhile, the laser is triggered to command the laser emitting module to control the laser diode to emit a main wave signal, the laser emitting module commands the timing module to start timing, most of energy in the signal is emitted to a target object, the other small part of energy is taken as a reference signal and is transmitted to the ranging signal phase difference calculation module to interfere with laser reflected by the object on the one hand, the laser reflected by the object is sequentially converted into an electric signal radiation frequency deviation increment delta omega by the photoelectric detector after being reflected, the converted electric signal is correspondingly amplified and shaped and then is transmitted to the laser receiving module, the laser receiving module transmits the reflected light wave electric signal to the ranging signal phase difference calculation module, the timing module is commanded to stop timing, and the phase modulation amplitude sigma and the laser emission return time tau calculated by the ranging signal phase difference calculation module are controlled by the laser emitting module to emit a main wave signal, the laser emitting module commands the timing module to stop timing, and the ranging signal phase difference calculation is controlled to perform ranging on the ranging signal0And the radiation frequency deviation increment delta omega finally calculates the distance L from the laser to the measured object through the distance calculation module, and after the display module displays the distance measurement result, the reset module resets to wait for the next distance measurement.
Example 3
The present embodiment is different from embodiment 2 only in that, in order to reduce the interference of stray light and the like to the photodetector, a filter and a diaphragm are provided in front of the receiving laser lens.
While the invention has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (9)
1. A laser ranging method based on a self-mixing semiconductor laser is characterized by comprising the following steps:
s1: the control module sends a measurement command to the laser emission module, and the laser diode receives a laser emission command sent by the laser emission module and then transmits the emitted radiation natural frequency omega0Feeding back to a ranging signal phase difference calculation module in the control module, and emitting laser, wherein the laser emitting module emits the laser at an initial time point tstartSending the data to a timing module;
s2: the laser is reflected by the target object and returns along the original path, and is received by the photoelectric detector in the laser emission cavity, the photoelectric detector converts the received optical signal into an electric signal, the electric signal is amplified and shaped by the amplifying circuit module and the shaping circuit module and is transmitted to the laser receiving module, and the laser receiving module transmits the received optical return signal at the time point tstopThe laser diode radiation frequency deviation increment delta omega is transmitted to a timing module, and the laser diode radiation frequency deviation increment delta omega obtained after reflection is transmitted to a ranging signal phase difference calculation module in a control module;
s3: the distance measurement signal phase difference calculation module calculates interference radiation frequency omega (j (t)) and radiation power P (j (t)), and applies the interference radiation frequency omega (j (t)) and the radiation power P (j (t)) to construct a Fourier spectrum S of spectral component amplitude of Bessel function series expansion of the corresponding obtained P (j (t))nCalculating the amplitude sigma of the phase modulation according to the spectrum harmonic amplitude;
s4: the timing module utilizes the laser emission initial time point t obtained in the step S1startAnd the optical return signal time point tstopCalculating the time tau through laser radiation to the object and back to the laser0And transmitting to a distance calculation module;
s5: the distance calculation module adopts the radiation frequency deviation increment delta omega obtained in the step S1, the phase modulation amplitude sigma obtained in the step S3 and the time tau obtained in the step S4 that the laser is radiated to the object and then returns to the laser0Calculating the distance L between the laser and the measured object;
s6: the display module displays the distance L of the measured object and finishes the measurement;
s7: the reset module resets all the modules to wait for the next measurement command;
the step of S3 includes the steps of:
s31: constructing a self-mixing laser radiation power model:
P(j(t))＝P1(j(t))+P2cos(ω(j(t))τ0(t))；
wherein, the P1(j (t)) is the laser radiation power independent of the distance of the object to be measured, P2For the phase power reflected from the object to the laser that broadcasts interference with the laser wave emitted by the laser, τ0(t) is the time for the laser radiation to reach the object and return to the laser, and ω (j (t)) is the frequency of the interfering radiation of the semiconductor laser;
s32: the radiation frequency ω (j (t)) and the power P1(j (t)) the calculation formula is as follows:
ω(j(t))＝ω0+Δω·sin(2πv1t)；
P1(j(t))＝I1sin(2πv1t)；
wherein, v is1For the current modulation frequency of the semiconductor laser, I1Is the power P1(j (t)) current modulation amplitude;
s33: the radiation frequency omega (j (t)) obtained in the step S32 and the P are combined1(j (t)) substituting into the self-mixing laser radiation power model constructed in the step S31, calculating the semiconductor laser radiation power:
P(j(t))＝I1sin(2πv1t)+P2cos(ω0τ0+Δωτ0sin(2πv1t))；
s34: using class I JnThe series decomposition of the Bessel function represents the power P (j (t)) from the mixed signal:
wherein θ is the self-mixing signal phase of the semiconductor laser, and θ ═ ω0τ0(ii) a The omega is the angular frequency of the current modulation of the semiconductor laser, and 2 pi v is equal to omega1；
S35: listing the power P (j (t)) decomposition coefficient of the self-mixing signal as anAnd bnThe Fourier sequence of (2):
s36: constructing a Fourier spectrum S of spectrum component amplitude of the Bessel function series expansion corresponding to the P (j (t)) obtained in the step S34 according to the power P (j (t)) of the self-mixing signal obtained in the step S34 and the Fourier sequence of the P (j (t)) obtained in the step S35nSpectral harmonic amplitude model of (1):
introducing the Fourier spectrum SnOdd spectral component model S of Fourier series decomposition2n+1And even spectral component S2nModel:
s37: constructing Fourier spectrum harmonic even spectrum component S except for n-12nModel and Fourier spectral harmonic odd spectral component S2n+1Model:
S2n＝2cos(θ)·P2·J2n(σ)；
S2n+1＝-2sin(θ)·P2·J2n+1(σ)；
s38: fourier spectrum harmonic even spectral component S constructed by adopting the step S372nModeling, determining Fourier spectrum harmonic even spectral component S2nSum component S2n+2The first ratio of (a):
S2n/S2n+2＝(J2n(σ))/(J2n+2(σ))；
the odd spectral component S of the sum Fourier spectrum harmonic wave constructed by the step of S372n+1Model, determining odd spectral components S of harmonic of Fourier spectrum2n+1Sum component S2n+3Second ratio of (c):
S2n+1/S2n+3＝(J2n+1(σ))/(J2n+3(σ))；
and determining the amplitude sigma of the phase modulation by using the first ratio and the second ratio.
2. A laser ranging method based on self-mixing semiconductor laser as claimed in claim 1 wherein said step S4 is that said τ is in step S40The calculation formula of (a) is as follows:
τ0＝tstop-tstart。
3. the laser ranging method based on the self-mixing semiconductor laser as claimed in claim 1, wherein the step S5 is performed according to the value τ02L/c, and σ ═ Δ ω τ0Therefore, the distance L from the laser to the object to be measured can be obtained:
wherein c is the speed of light.
4. A laser distance measuring device based on a self-mixing semiconductor laser adopting the method of claim 1, comprising a shell (1), a display screen (2) for displaying laser measuring distance parameters and a plurality of operation buttons (3) positioned at the lower part of the display screen, wherein the shell is internally provided with the self-mixing semiconductor laser, and the laser is internally provided with a control module, a laser emitting module, a laser diode, a laser emitting lens, a laser receiving lens, a photoelectric detector, an amplifying circuit module, a shaping circuit module, a laser receiving module and a timing unit;
the control module is used for controlling laser emission, target distance calculation and result display and comprises a ranging signal phase difference calculation module, a distance calculation module, a display module and a reset module;
the distance measurement signal phase difference calculation module is used for calculating interference radiation frequency omega (j (t)) and radiation power P (j (t)), and applying the interference radiation frequency omega (j (t)) and the radiation power P (j (t)) to construct a Fourier spectrum S of spectrum component amplitude of Bessel function series expansion of the P (j (t)) which is correspondingly obtainednCalculating the amplitude sigma of the phase modulation according to the spectrum harmonic amplitude;
the distance calculation module is used for calculating the phase modulation amplitude sigma and the time tau of returning the laser to the object through laser radiation by utilizing the radiation frequency deviation increment delta omega, the distance measurement signal phase difference calculation module0Calculating the distance L between the laser and the measured object;
the laser emitting module is used for transmitting a laser command signal for emitting distance measurement and transmitting the signal to the laser diode and the timing module;
the laser diode is used for transmitting laser used for ranging to the laser transmitting lens and the ranging signal phase difference calculating module in the control module;
the laser emitting lens is used for diverging the laser to a target object;
the receiving laser lens is used for reflecting the target object to the laser distance measuring device and converging the target object to the laser receiving module;
the photoelectric detector is used for receiving the converged laser and converting the converged laser into an electric signal;
the amplifying circuit module is used for amplifying the electric signal and transmitting the electric signal to the shaping circuit module;
the shaping circuit module is used for shaping and converting the amplified electric signals into square wave electric signals and transmitting the square wave electric signals to the laser receiving module;
the laser receiving module is used for receiving an electric signal of laser reflected by the outside and transmitting the electric signal to the ranging signal phase difference calculating module and the timing module of the control module;
the timing module is used for receiving a laser command transmitted by the laser transmitting module and generating the laser transmitting initial time point tstartAnd is used for receiving the reflected light arrival command of the laser receiving module and generating the time point t of the light return signalstopCalculating the time tau of the laser radiation to the object and returning to the laser0And transmitting to a distance calculation module;
the laser emitting module, the laser emitting lens, the laser receiving lens and the photoelectric detector are all positioned in a laser emitting cavity of the laser.
5. The laser ranging device according to claim 4, wherein the timing unit comprises an inner optical path receiving module and an outer optical path receiving module,
the inner light path receiving module is used for receiving the electric signal of the laser diode and generating a laser starting time point tstart；
The outer light path receiving module is used for receiving the electric signal of the laser receiving module and generating a laser receiving time point tstop。
6. The laser ranging device as claimed in claim 4, wherein the laser emitting unit is a frequency-modulated semiconductor self-mixing laser diode RLD-650 with a quantum size structure of diffraction limited single spatial mode.
7. A laser rangefinder apparatus according to claim 4 wherein said photodetector is an integrated avalanche photodiode.
8. The laser ranging device as claimed in claim 4, wherein the timing module is externally connected with a clock oscillator.
9. A laser rangefinder apparatus according to claim 4 wherein an optical filter and an optical stop are provided in front of said receiving laser lens.
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