Laser ranging system and method

Abstract

The invention discloses a laser ranging system and method, and the system comprises a signal generation module which is used for generating an orthogonal signal and a local oscillator signal, an orthogonal frequency mixing modulation module which is used for generating a modulation signal, a laser module which is used for generating a laser signal modulated by the modulation signal, a light path module, and a processing module. The processing module comprises an APD unit, and the diameter of the photosensitive surface of the APD unit is smaller than or equal to 100 microns. According to the laser ranging system and method, the orthogonal frequency mixing modulation technology is adopted to generate the modulated laser signal for laser ranging, the distance information in the laser signal is obtained through coherent demodulation, the precision is high, the anti-interference capacity is high, the problems that high-frequency waveforms are prone to distortion due to interference and the high-frequency sampling rate is insufficient during waveform sampling are solved, and the system and method are suitable for large-scale popularization and application. And the accuracy of phase calculation is improved. By adopting the APD unit with the narrow photosensitive surface, the spatial resolution and the signal strength of the system are effectively improved, lower cross interference is realized, and dark current and noise are suppressed.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser ranging, and particularly relates to a laser ranging system and method. Background Art

[0002] At present, laser ranging technology has been widely used in many fields, but traditional laser ranging technology has certain limitations in terms of accuracy, anti-interference ability, and measurement range. For example, phase-based laser ranging is susceptible to environmental factors during long-distance measurement, resulting in inaccurate phase measurement and thus affecting ranging accuracy; pulse-based laser ranging has a relatively large measurement range but relatively low accuracy. Therefore, a new laser ranging solution is needed to improve ranging accuracy and stability and expand the measurement range.

[0003] The information disclosed in this background art section is only intended to enhance the overall understanding of the present invention and should not be regarded as an admission or any form of suggestion that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0004] The purpose of the present invention is to provide a laser ranging system and method that can improve measurement accuracy and anti-interference ability.

[0005] To achieve the above object, the technical solution provided by a specific embodiment of the present invention is as follows:

[0006] A laser ranging system, comprising: a signal generation module for generating quadrature signals and local oscillator signals;

[0007] An orthogonal mixing modulation module, connected to the signal generation module, for performing orthogonal mixing modulation on the local oscillator signal based on the orthogonal signal to generate a modulation signal; a laser module, connected to the orthogonal mixing modulation module to generate a laser signal modulated by the modulation signal; an optical path module, arranged on the optical path of the laser signal, for generating a reference optical signal based on the laser signal, and for adjusting the transmission direction of the laser signal to reflect the laser signal through a target to be measured to generate a reflected optical signal; a processing module, including an APD unit, the APD unit is arranged on the optical path of the reference optical signal and the optical path of the reflected optical signal, the APD unit is used for performing photoelectric conversion on the reference optical signal to generate a reference signal, and for performing photoelectric conversion on the reflected optical signal to generate an echo signal, the diameter of the photosensitive surface of the APD unit ≤ 100um, the processing module is connected to the signal generation module to receive the local oscillator signal, the processing module is used for performing coherent demodulation on the reference signal based on the local oscillator signal to generate a first demodulation signal, performing coherent demodulation on the echo signal based on the local oscillator signal to generate a second demodulation signal, and calculating the distance of the target to be measured based on the first demodulation signal and the second demodulation signal.

[0008] In one or more embodiments of the present invention, the optical path module includes a beam splitter arranged on the optical path of the laser signal, the beam splitter is used for separating the laser signal into a reference optical signal and a detection optical signal, and adjusting the transmission direction of the detection optical signal to reflect the detection optical signal through the target to be measured to generate the reflected optical signal.

[0009] In one or more embodiments of the present invention, the optical path module further includes an objective lens arranged on the optical path of the reflected optical signal, the objective lens is used for focusing the reflected optical signal.

[0010] In one or more embodiments of the present invention, the objective lens includes a cemented lens.

[0011] In one or more embodiments of the present invention, the optical path module further includes a first filter arranged on the optical path of the reference optical signal; and / or the optical path module further includes a second filter arranged on the optical path of the reflected optical signal.

[0012] In one or more embodiments of the present invention, the APD unit includes a first APD detector and a second APD detector connected to the signal generation module. The first APD detector is disposed on the optical path of the reference optical signal. The first APD detector is configured to perform optoelectronic conversion on the reference optical signal to generate the reference signal and mix the reference signal and the local oscillator signal to generate a first mixed signal. The second APD detector is disposed on the optical path of the reflected optical signal. The second APD detector is configured to perform optoelectronic conversion on the reflected optical signal to generate the echo signal and mix the echo signal and the local oscillator signal to generate a second mixed signal. The processing module further includes a first filtering unit and a first control unit. The first filtering unit is connected to the first APD detector to filter the first mixed signal to generate the first demodulated signal, and the first filtering unit is connected to the second APD detector to filter the second mixed signal to generate the second demodulated signal. The first control unit is connected to the first filtering unit to calculate the distance of the target to be measured based on the first demodulated signal and the second demodulated signal.

[0013] In one or more embodiments of the present invention, the processing module further includes a mixing unit, a second filtering unit, and a second control unit. The mixing unit is connected to the signal generation module to receive the local oscillator signal. The mixing unit is connected to the APD unit to receive the reference signal and the echo signal. The mixing unit is configured to mix the reference signal and the local oscillator signal to generate a first mixed signal, and mix the echo signal and the local oscillator signal to generate a second mixed signal. The second filtering unit is connected to the mixing unit to filter the first mixed signal to generate the first demodulated signal and filter the second mixed signal to generate the second demodulated signal. The second control unit is connected to the second filtering unit to calculate the distance of the target to be measured based on the first demodulated signal and the second demodulated signal.

[0014] In one or more embodiments of the present invention, the quadrature signal is a low-frequency signal and the local oscillator signal is a high-frequency signal.

[0015] A specific embodiment of the present invention further provides a laser ranging method. Based on the above laser ranging system, the laser ranging method includes: generating the quadrature signal and the local oscillator signal through the signal generation module; performing quadrature mixing modulation on the local oscillator signal based on the quadrature signal through the quadrature mixing modulation module to generate the modulation signal; generating the laser signal modulated by the modulation signal through the laser module; generating the reference optical signal based on the laser signal through the optical path module, and adjusting the transmission direction of the laser signal to reflect the laser signal through the target to be measured to generate the reflected optical signal; performing photoelectric conversion on the reference optical signal through the APD unit to generate the reference signal, and performing photoelectric conversion on the reflected optical signal to generate the echo signal, performing coherent demodulation on the reference signal based on the local oscillator signal through the processing module to generate the first demodulation signal, performing coherent demodulation on the echo signal based on the local oscillator signal to generate the second demodulation signal, and calculating the distance of the target to be measured based on the first demodulation signal and the second demodulation signal.

[0016] In one or more embodiments of the present invention, the laser ranging method further includes changing the frequency of the local oscillator signal for repeated measurement, and calculating the accurate distance of the target to be measured based on the results of multiple measurements.

[0017] Compared with the prior art, the laser ranging system and method of the present invention use quadrature mixing modulation technology to generate a modulated laser signal for laser ranging, and obtain the distance information in the laser signal through coherent demodulation, with high accuracy and strong anti-interference ability. It overcomes the problems that the high-frequency waveform is easily distorted by interference and the high-frequency sampling rate is insufficient during waveform sampling, and improves the accuracy of phase calculation. By using an APD unit with a narrow photosensitive surface, the spatial resolution and signal intensity of the system are effectively improved, lower cross-interference is achieved, and dark current and noise are suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is the system structure diagram of the laser ranging system in an embodiment of the present invention.

[0020] Figure 2 It is the flowchart of the laser ranging method in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] To enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] "Coupled", "connected", or "linked" in the specification includes both direct connection and indirect connection. Indirect connection is a connection through an intermediate medium, such as a connection through an electrical conduction medium, which may have parasitic inductance or parasitic capacitance; indirect connection may also include a connection through other active or passive devices on the basis of achieving the same or similar functional purposes, such as a connection through circuits or components such as switches and follower circuits. Additionally, in the invention, words such as "first", "second", etc. are mainly used to distinguish one technical feature from another technical feature, and do not necessarily require or imply that there is a certain actual relationship, quantity, or order between these technical features.

[0023] In the detailed description of the specification, reference is made to the accompanying drawings that form a part thereof, in which the same reference numerals always represent the same components, and which are shown by way of exemplary embodiments that can be implemented. It should be understood that other embodiments can be utilized and structural or logical changes can be made without departing from the scope of the present application. Therefore, the following detailed description should not be construed as having a limiting meaning.

[0024] The various operations in the specification can be described as a number of discrete actions or operations in the order that is most helpful for understanding the claimed subject matter. However, the order of description should not be construed as implying that these operations must be order-related. Specifically, these operations may not be performed in the order presented. The described operations can be performed in an order different from the described embodiments. Various additional operations can be performed in additional embodiments and / or the described operations can be omitted.

[0025] For the purposes of the present application, the phrase "A and / or B" means (A), (B), or (A and B). For the purposes of the present application, the phrase "A, B, and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

[0026] Various components and devices may be referred to or shown herein in the singular form, but this is merely for the convenience of discussion, and any element referred to in the singular form may include multiple such elements in accordance with the teachings herein.

[0027] The specification describes the use of the phrases "in one embodiment", "in other embodiments", or "in some embodiments", which may each refer to one or more of the same or different embodiments. Additionally, the terms "comprising", "including", "having", etc. used with respect to the embodiments of the present application are synonymous.

[0028] As Figure 1 shown, the laser ranging system in one embodiment of the present invention includes a signal generation module 10, a quadrature mixing modulation module 20, a first amplifier circuit 30, a second amplifier circuit 40, a laser module 50, an optical path module 60, and a processing module 70.

[0029] Among them, the signal generation module 10 is used to generate a quadrature signal I(t), a quadrature signal Q(t), and a local oscillator signal L(t).

[0030] In one embodiment, the quadrature signal I(t) and the quadrature signal Q(t) are low-frequency signals, and the local oscillator signal L(t) is a high-frequency signal. Specifically, the quadrature signal I(t) is a sine wave signal and can be expressed as: I(t) = sin(ω M t), the quadrature signal Q(t) can be expressed as: Q(t) = cos(ω M t), where ω M is the angular frequency of the quadrature signal. The local oscillator signal L(t) is a sine wave signal and can be expressed as: L(t) = cos(ω C t), where ω C is the angular frequency of the local oscillator signal.

[0031] The quadrature mixing modulation module 20 is connected to the signal generation module 10 and is used to perform quadrature mixing modulation on the local oscillator signal L(t) based on the quadrature signal I(t) and the quadrature signal Q(t) to generate a modulation signal STX(t).

[0032] In one embodiment, the quadrature mixing modulation module 20 can adopt an electro-optic modulator, an acousto-optic modulator, or other modulation devices.

[0033] The first amplifier circuit 30 is connected to the quadrature mixing modulation module 20 and the laser module 50. The first amplifier circuit 30 is used to amplify the modulation signal STX(t) and output the amplified modulation signal STX(t) to the laser module 50.

[0034] The laser module 50 is used to generate a laser signal modulated by the modulation signal STX(t).

[0035] The optical path module 60 is arranged on the optical path of the laser signal and is used to generate a reference optical signal based on the laser signal, and is used to adjust the transmission direction of the laser signal to reflect the laser signal through the target to be measured to generate a reflected optical signal.

[0036] The second amplifier circuit 40 is connected to the signal generation module 10 and the processing module 70. The second amplifier circuit 40 is configured to amplify the local oscillator signal L(t) and output the amplified local oscillator signal L(t) to the processing module 70.

[0037] The processing module 70 includes an APD unit 71 (APD: avalanche photodiode). The APD unit 71 is disposed on the optical path of the reference optical signal and the optical path of the reflected optical signal. The APD unit 71 is configured to perform photoelectric conversion on the reference optical signal to generate a reference signal, and perform photoelectric conversion on the reflected optical signal to generate an echo signal. The diameter of the photosensitive surface of the APD unit 71 is ≤100um.

[0038] The processing module 70 is connected to the second amplifier circuit 40 to receive the local oscillator signal L(t). The processing module 70 is configured to perform coherent demodulation on the reference signal based on the local oscillator signal L(t) to generate a first demodulation signal SDE1(t), perform coherent demodulation on the echo signal based on the local oscillator signal L(t) to generate a second demodulation signal SDE2(t), and calculate the distance of the target to be measured based on the first demodulation signal SDE1(t) and the second demodulation signal SDE2(t).

[0039] In other embodiments, the first amplifier circuit 30 may not be provided, and the laser module 50 is directly connected to the quadrature mixing modulation module 20 to receive the modulation signal STX(t). The second amplifier circuit 40 may not be provided, and the processing module 70 is directly connected to the signal generation module 10 to receive the local oscillator signal L(t).

[0040] As Figure 1 shown, the signal generation module 10 may include a digital-to-analog converter and a frequency synthesizer.

[0041] The digital-to-analog converter is configured to generate an in-phase signal I(t) and a quadrature signal Q(t). In one embodiment, the digital-to-analog converter generates a differential form of the in-phase signal I(t) and a differential form of the quadrature signal Q(t) to improve signal accuracy and anti-interference ability.

[0042] The frequency synthesizer is configured to generate the local oscillator signal L(t). In one embodiment, the frequency synthesizer may employ a voltage-controlled oscillator, a phase-locked loop, a direct digital frequency synthesizer (DDS), or other forms of frequency synthesis circuits. The frequency synthesizer may generate a differential form of the local oscillator signal L(t) to improve signal accuracy and anti-interference ability.

[0043] As Figure 1As shown, the laser module 50 may include a connected laser power supply and a laser emitter. The laser power supply receives an external PWM signal LD_PWM. The laser power supply is used to generate the power voltage required by the laser emitter based on the PWM signal LD_PWM. The laser emitter is connected to the first amplifier circuit 30 to receive the modulation signal STX(t). The laser emitter is used to generate a laser signal modulated by the modulation signal STX(t).

[0044] As Figure 1 shown, the optical path module 60 includes a beam splitter 61, a mirror 62, an objective lens 63, a first filter 64, and a second filter 65.

[0045] Among them, the beam splitter 61 is disposed on the optical path of the laser signal. The beam splitter 61 is used to separate the laser signal into a reference optical signal and a detection optical signal, and adjust the transmission direction of the detection optical signal so that the detection optical signal is reflected by the target to be measured to generate a reflected optical signal.

[0046] In one embodiment, the beam splitter 61 may employ a beam splitting prism, an optical fiber coupler, or other beam splitting devices.

[0047] Both the mirror 62 and the first filter 64 are disposed on the optical path of the reference optical signal. The mirror 62 is used to reflect the reference optical signal to adjust the propagation direction of the reference optical signal so that the reference optical signal can pass through the first filter 64 and irradiate on the photosensitive surface of the APD unit 71. The first filter 64 is used to filter the reference optical signal, remove interference components, and improve the signal-to-noise ratio.

[0048] The objective lens 63 and the second filter 65 are disposed on the optical path of the reflected optical signal. The objective lens 63 is used to focus the reflected optical signal so that the reflected optical signal can pass through the second filter 65 and be focused within the photosensitive surface of the APD unit 71, improving the collection efficiency of the reflected optical signal.

[0049] In one embodiment, the objective lens 63 includes a cemented lens. Specifically, the cemented lens may employ a doublet lens composed of a plano-convex lens and a meniscus lens cemented together.

[0050] Preferably, the objective lens 63 is a large-aperture lens. Further, its aperture is 20 cm.

[0051] The second filter 65 is used to filter the reflected optical signal, remove interference components, and improve the signal-to-noise ratio.

[0052] In one embodiment, the reference optical signal passes through the mirror 62 and the first filter 64 in sequence and then enters the APD unit 71. The reflected optical signal passes through the objective lens 63 and the second filter 65 in sequence and then enters the APD unit 71. In other embodiments, the order of the mirror 62 and the first filter 64 and / or the order of the objective lens 63 and the second filter 65 may also be swapped.

[0053] In other embodiments, one or more of the mirror 62, the first filter 64, and the second filter 65 may not be provided, and an objective lens for focusing the reference optical signal on the photosensitive surface of the APD unit 71 may also be provided on the optical path of the reference optical signal.

[0054] In one embodiment, as Figure 1 shown, the APD unit 71 may include a first APD detector and a second APD detector connected to the second amplifier circuit 40, and a high-voltage power supply connected to the first APD detector and the second APD detector. The high-voltage power supply receives an external PWM signal HV_PWM, and the high-voltage power supply is used to generate the power supply voltage required for the first APD detector and the second APD detector based on the PWM signal HV_PWM.

[0055] The first APD detector is disposed on the optical path of the reference optical signal. The reference optical signal irradiates on the photosensitive surface of the first APD detector after passing through the first filter 64. The first APD detector is used to perform photoelectric conversion on the reference optical signal to generate a reference signal and mix the reference signal with the local oscillator signal L(t) to generate a first mixed signal MIX1(t). The diameter of the photosensitive surface of the first APD detector is ≤100um.

[0056] The second APD detector is disposed on the optical path of the reflected optical signal. The reflected optical signal is focused on the photosensitive surface of the second APD detector after passing through the objective lens 63 and the second filter 65. The second APD detector is used to perform photoelectric conversion on the reflected optical signal to generate an echo signal and mix the echo signal with the local oscillator signal L(t) to generate a second mixed signal MIX2(t). The diameter of the photosensitive surface of the second APD detector is ≤100um.

[0057] By using an APD detector with a narrow photosensitive surface for optical signal acquisition, the spatial resolution of the system is improved, and it is possible to better focus on and receive optical signals in a specific area, thereby more accurately positioning and detecting optical signals, reducing edge effects or interference from external light sources, reducing cross-interference in the optical system, and suppressing dark current. Especially in the case of multiple light sources or complex light field conditions, a narrow photosensitive surface can effectively improve the signal-to-noise ratio (SNR), thereby improving the accuracy of signal detection. In a low-light environment, a narrow photosensitive surface can help the APD detector to be more focused and improve the reception efficiency of the target signal, avoiding unnecessary energy waste and enhancing the power efficiency of the APD detector.

[0058] As Figure 1As shown, the processing module 70 further includes a first filtering unit 72 and a first control unit. The first filtering unit 72 is connected to the first APD detector to filter the first mixing signal MIX1(t) to generate a first demodulation signal SDE1(t), and the first filtering unit 72 is connected to the second APD detector to filter the second mixing signal MIX2(t) to generate a second demodulation signal SDE2(t). The first control unit is connected to the first filter and the second filter to calculate the distance of the target to be measured based on the first demodulation signal SDE1(t) and the second demodulation signal SDE2(t).

[0059] Among them, the first filtering unit 72 may include a first filter and a second filter. The first filter is connected to the first APD detector to filter the first mixing signal MIX1(t) to generate a first demodulation signal SDE1(t), and the second filter is connected to the second APD detector to filter the second mixing signal MIX2(t) to generate a second demodulation signal SDE2(t).

[0060] In other embodiments, signal mixing may not be performed through the first APD detector and the second APD detector. At the same time, the processing module 70 may also include a mixing unit, a second filtering unit, and a second control unit. The mixing unit is connected to the second amplification circuit 40 to receive the local oscillator signal L(t), and the mixing unit is connected to the first APD detector and the second APD detector in the APD unit 71 to receive the reference signal and the echo signal. The mixing unit is used to mix the reference signal and the local oscillator signal L(t) to generate a first mixing signal MIX1(t), and mix the echo signal and the local oscillator signal L(t) to generate a second mixing signal MIX2(t). The second filtering unit is connected to the mixing unit to filter the first mixing signal MIX1(t) to generate a first demodulation signal SDE1(t), and filter the second mixing signal MIX2(t) to generate a second demodulation signal SDE2(t). The second control unit is connected to the second filtering unit to calculate the distance of the target to be measured based on the first demodulation signal SDE1(t) and the second demodulation signal SDE2(t).

[0061] Among them, the mixing unit may include a first mixer and a second mixer. The first mixer and the second mixer are connected to the second amplifier circuit 40 to receive the local oscillator signal L(t). The first mixer is connected to the first APD detector to receive the reference signal. The first mixer is used to mix the reference signal and the local oscillator signal L(t) to generate a first mixed signal MIX1(t). The second mixer is connected to the second APD detector to receive the echo signal. The second mixer is used to mix the echo signal and the local oscillator signal L(t) to generate a second mixed signal MIX2(t). The second filtering unit may include a third filter and a fourth filter. The third filter is connected to the first mixer to filter the first mixed signal MIX1(t) to generate a first demodulated signal SDE1(t). The fourth filter is connected to the second mixer to filter the second mixed signal MIX2(t) to generate a second demodulated signal SDE2(t).

[0062] In one embodiment, the first filter, the second filter, the third filter, and the fourth filter are low-pass filters.

[0063] In one embodiment, the first control unit or the second control unit may include an MCU controller. The first control unit or the second control unit may also be connected to a digital-to-analog converter to control the digital-to-analog converter to generate the quadrature signals I(t) and Q(t). The first control unit or the second control unit may also be connected to a frequency synthesizer to control the frequency synthesizer to generate the local oscillator signal L(t). The first control unit or the second control unit may also be connected to a laser power supply to generate the PWM signal LD_PWM required by the laser power supply. The first control unit or the second control unit may also be connected to a high-voltage power supply to generate the PWM signal HV_PWM required by the high-voltage power supply.

[0064] As Figure 2 shown, this embodiment also provides a laser ranging method. Based on the above laser ranging system, the laser ranging method includes:

[0065] Generate the quadrature signals I(t), Q(t), and the local oscillator signal L(t) through the signal generation module 10. Perform quadrature mixing modulation on the local oscillator signal L(t) based on the quadrature signals I(t) and Q(t) through the quadrature mixing modulation module 20 to generate a modulation signal STX(t). Generate a laser signal modulated by the modulation signal STX(t) through the laser module 50. Generate a reference optical signal based on the laser signal through the optical path module 60, and adjust the transmission direction of the laser signal to reflect the laser signal through the target to be measured to generate a reflected optical signal.

[0066] The reference optical signal is photoelectrically converted by the APD unit 71 to generate a reference signal, and the reflected optical signal is photoelectrically converted to generate an echo signal. The processing module 70 coherently demodulates the reference signal based on the local oscillator signal L(t) to generate a first demodulated signal SDE1(t), coherently demodulates the echo signal based on the local oscillator signal L(t) to generate a second demodulated signal SDE2(t), and calculates the distance of the target to be measured based on the first demodulated signal SDE1(t) and the second demodulated signal SDE2(t).

[0067] Specifically, in one embodiment, the laser ranging method includes:

[0068] The reference optical signal is photoelectrically converted by the first APD detector to generate a reference signal, and the reference signal and the local oscillator signal L(t) are mixed to generate a first mixed signal MIX1(t). The reflected optical signal is photoelectrically converted by the second APD detector to generate an echo signal, and the echo signal and the local oscillator signal L(t) are mixed to generate a second mixed signal MIX2(t).

[0069] The first filter unit 72 filters the first mixed signal MIX1(t) to generate a first demodulated signal SDE1(t), and filters the second mixed signal MIX2(t) to generate a second demodulated signal SDE2(t). The first control unit calculates the distance of the target to be measured based on the first demodulated signal SDE1(t) and the second demodulated signal SDE2(t).

[0070] In other embodiments, the laser ranging method may also include:

[0071] The reference signal and the local oscillator signal L(t) are mixed by the mixing unit to generate a first mixed signal MIX1(t), and the echo signal and the local oscillator signal L(t) are mixed to generate a second mixed signal MIX2(t). The second filter unit filters the first mixed signal MIX1(t) to generate a first demodulated signal SDE1(t), and filters the second mixed signal MIX2(t) to generate a second demodulated signal SDE2(t). The second control unit calculates the distance of the target to be measured based on the first demodulated signal SDE1(t) and the second demodulated signal SDE2(t).

[0072] Specifically, the modulation signal STX(t) can be expressed as:

[0073] STX(t) = sin(ω M t)cos(ω C t) + cos(ω M t)sin(ω C t)

[0074] That is:

[0075] STX(t) = sin[(ω C + ω M )t]

[0076] The laser signal generated after the laser module 50 is modulated by the modulation signal STX(t) has the same frequency, waveform, and phase as the modulation signal STX(t).

[0077] The reference signal can be expressed as:

[0078] REF(t) = sin[(ω C + ω M )t - ψ REF )

[0079] where ψ REF is the phase shift of the reference optical signal.

[0080] The echo signal can be expressed as:

[0081] SRF(t) = sin[(ω C + ω M )t - ψ SRF )

[0082] where ψ SRF is the phase shift of the reflected optical signal.

[0083] The first mixing signal MIX1(t) can be expressed as:

[0084] MIX1(t) = sin[(ω C + ω M )t - ψ REF × cos(ω C t)

[0085] That is:

[0086]

[0087] After filtering out the high-frequency signal through the first filter, the first demodulation signal SDE1(t) is:

[0088]

[0089] Similarly, the second mixing signal MIX2(t) can be expressed as:

[0090]

[0091] The second demodulation signal SDE2(t) is:

[0092]

[0093] Next, the first control unit can simultaneously sample the first demodulation signal SDE1(t) and the second demodulation signal SDE2(t) through an internal timer and an internal multi-channel analog-to-digital converter, then perform a fast Fourier transform on the first demodulation signal SDE1(t) and the second demodulation signal SDE2(t), calculate the phases of the two signals, and after subtracting the two phases, convert them into a phase difference within a periodic range through periodicity, so as to obtain the phase shift ψ of this reference optical signal. REF and the phase shift ψ of the reflected optical signal SRF The phase difference Δψs within one period.

[0094] Since the first demodulation signal SDE1(t) and the second demodulation signal SDE2(t) are low-frequency signals, their waveform quality is better and the anti-interference ability is strong. After the high-frequency signal is converted to a low-frequency signal, the waveform is broadened in the time domain. With the ADC sampling rate unchanged, more points are sampled within one period, so that the identified phase shift is more accurate.

[0095] As Figure 1 shown, based on the principle of phase ranging, the distance of the target to be measured can be approximately expressed as:

[0096]

[0097] where c is the speed of light, t is the time experienced by the reflected optical signal from transmission to reception, ω D is the angular frequency of the modulation signal STX(t), ω D = ω C + ω M , Δψ is the phase difference between the phase shift ψ REF of the reference optical signal and the phase shift ψ SRF of the reflected optical signal, N is the integer period number of the phase difference Δψ, and ΔN is the non-integer period coefficient of the phase difference Δψ. For the convenience of calculation, the additional phase shift of the reference optical signal between the optical splitter 61 and the mirror 62 is ignored in the above formula, and correction parameters can be introduced according to the actual setting of the optical path for correction during the actual calculation process.

[0098] Based on the above formula, can be regarded as the measurement range corresponding to the modulation signal STX(t) with an angular frequency of ω D . Through the above method, the rough distance value of the target to be measured under the measurement range corresponding to the frequency of this modulation signal can be obtained. For distance measurements exceeding this measurement range, there will be a problem of phase shift ambiguity.

[0099] Furthermore, the laser ranging method may further include: changing the frequency of the local oscillator signal L(t) for repeated measurement, and calculating the accurate distance of the target to be measured based on the results of multiple measurements.

[0100] By changing the frequency of the local oscillator signal L(t), the frequency of the modulation signal STX(t) can be further changed. Since modulation signals of different frequencies correspond to different ranging distances, by adopting the multi-frequency phase ranging method, measuring the phase differences Δψs at multiple frequencies and synthesizing this information, the problem of phase shift ambiguity at long distances can be solved, thereby accurately calculating the exact distance of the target to be measured.

[0101] In the above process, by adopting the quadrature mixing modulation technology to generate the modulated laser signal for laser ranging and obtaining the distance information in the laser signal through coherent demodulation, it has high precision and strong anti-interference ability, overcomes the problems that the high-frequency waveform is easily distorted by interference and the high-frequency sampling rate is insufficient during waveform sampling, and improves the accuracy of phase calculation.

[0102] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed claim.

[0103] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A laser ranging system, characterized in that, Comprising: A signal generation module, configured to generate an orthogonal signal and a local oscillator signal; An orthogonal mixing modulation module, connected to the signal generation module, configured to perform orthogonal mixing modulation on the local oscillator signal based on the orthogonal signal to generate a modulation signal; A laser module, connected to the orthogonal mixing modulation module to generate a laser signal modulated by the modulation signal; An optical path module, disposed on the optical path of the laser signal, configured to generate a reference optical signal based on the laser signal, and configured to adjust the transmission direction of the laser signal to reflect the laser signal through a target to be measured to generate a reflected optical signal; A processing module, including an APD unit, the APD unit is disposed on the optical paths of the reference optical signal and the reflected optical signal, the APD unit is configured to perform photoelectric conversion on the reference optical signal to generate a reference signal, and configured to perform photoelectric conversion on the reflected optical signal to generate an echo signal, the diameter of the photosensitive surface of the APD unit ≤ 100um, the processing module is connected to the signal generation module to receive the local oscillator signal, the processing module is configured to perform coherent demodulation on the reference signal based on the local oscillator signal to generate a first demodulation signal, perform coherent demodulation on the echo signal based on the local oscillator signal to generate a second demodulation signal, and calculate the distance of the target to be measured based on the first demodulation signal and the second demodulation signal.

2. The laser ranging system according to claim 1, characterized in that The optical path module includes a beam splitter disposed on the optical path of the laser signal, the beam splitter is configured to separate the laser signal into a reference optical signal and a detection optical signal, and adjust the transmission direction of the detection optical signal to reflect the detection optical signal through the target to be measured to generate the reflected optical signal.

3. The laser ranging system according to claim 2, wherein, The optical path module further includes an objective lens disposed on the optical path of the reflected optical signal, the objective lens is configured to focus the reflected optical signal.

4. The laser ranging system according to claim 3, wherein The objective lens includes a cemented lens.

5. The laser ranging system according to claim 2, wherein, The optical path module further includes a first filter disposed on the optical path of the reference optical signal; and / or The optical path module further includes a second filter disposed on the optical path of the reflected optical signal.

6. The laser ranging system according to claim 1, wherein The APD unit includes a first APD detector and a second APD detector connected to the signal generation module, the first APD detector is disposed on the optical path of the reference optical signal, the first APD detector is configured to perform photoelectric conversion on the reference optical signal to generate the reference signal and mix the reference signal and the local oscillator signal to generate a first mixed signal, the second APD detector is disposed on the optical path of the reflected optical signal, the second APD detector is configured to perform photoelectric conversion on the reflected optical signal to generate the echo signal and mix the echo signal and the local oscillator signal to generate a second mixed signal; The processing module further includes a first filtering unit and a first control unit. The first filtering unit is connected to the first APD detector to filter the first mixing signal to generate the first demodulation signal. The first filtering unit is connected to the second APD detector to filter the second mixing signal to generate the second demodulation signal. The first control unit is connected to the first filtering unit to calculate the distance of the target to be measured based on the first demodulation signal and the second demodulation signal.

7. The laser ranging system according to claim 1, wherein The processing module further includes a mixing unit, a second filtering unit and a second control unit. The mixing unit is connected to the signal generation module to receive the local oscillator signal. The mixing unit is connected to the APD unit to receive the reference signal and the echo signal. The mixing unit is configured to mix the reference signal and the local oscillator signal to generate a first mixing signal, and mix the echo signal and the local oscillator signal to generate a second mixing signal. The second filtering unit is connected to the mixing unit to filter the first mixing signal to generate the first demodulation signal and filter the second mixing signal to generate the second demodulation signal. The second control unit is connected to the second filtering unit to calculate the distance of the target to be measured based on the first demodulation signal and the second demodulation signal.

8. The laser ranging system according to claim 1, characterized in that, The quadrature signal is a low-frequency signal, and the local oscillator signal is a high-frequency signal.

9. A laser ranging method, based on the laser ranging system according to any one of claims 1 to 8, characterized in that, The laser ranging method includes: generating the quadrature signal and the local oscillator signal through the signal generation module; performing quadrature mixing modulation on the local oscillator signal based on the quadrature signal through the quadrature mixing modulation module to generate the modulation signal; generating the laser signal modulated by the modulation signal through the laser module; generating the reference optical signal based on the laser signal through the optical path module, and adjusting the transmission direction of the laser signal to reflect the laser signal through the target to be measured to generate the reflected optical signal; performing photoelectric conversion on the reference optical signal through the APD unit to generate the reference signal, and performing photoelectric conversion on the reflected optical signal to generate the echo signal. Through the processing module, performing coherent demodulation on the reference signal based on the local oscillator signal to generate the first demodulation signal, performing coherent demodulation on the echo signal based on the local oscillator signal to generate the second demodulation signal, and calculating the distance of the target to be measured based on the first demodulation signal and the second demodulation signal.

10. The laser ranging method according to claim 9, characterized in that, The laser ranging method further includes changing the frequency of the local oscillator signal to perform repeated measurements, and calculating the accurate distance of the target to be measured based on the results of multiple measurements.

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