A laser radar capable of realizing highly sensitive echo detection

Abstract

The present invention discloses a laser radar capable of realizing high-sensitivity echo detection, and relates to the technical field of laser radar ranging. The specific structure is: using a signal source to f 0 The sinusoidal modulation signal is loaded onto the laser current through the bias-T or the laser's own high-speed modulation port, so that the laser contains the modulation signal information in the normal light-emitting state. The output light passes through the spectrometer, and a part of the light is split to the detector, and the remaining light is output as the detection light. The target return light enters the laser, causing the external cavity resonant frequency to resonate with the modulation frequency. The detector output enters the signal acquisition and processing device, detects the amplitude information of the output light signal, and then increases the frequency of the sinusoidal modulation signal by Δ f Repeat the test until the frequency is increased to f m , and finally measured f 0 ~ f m The frequency response characteristic curve of the laser within the range is obtained; the distance between the radar and the target is obtained through calculation. The invention has a simple structure, avoids dependence on the sensitivity of the detector, and also greatly improves the sensitivity range of the detection.

Description

Technical Field

[0001] The present invention relates to the technical field of laser radar ranging, and in particular to a laser radar capable of realizing high-sensitivity echo detection. Background Art

[0002] Laser radar has many advantages such as small error, fast ranging speed, wide measurement range, strong robustness, and no influence from ambient illumination, and has been widely used. Common detection methods are mostly pulse systems, using pulsed lasers as radar emission sources, and measuring the time difference between pulse emission and return after encountering the target, and combining the speed of light to obtain the position information of the target. However, since the propagation of laser in space will be affected by atmospheric loss, particle scattering, etc., the laser power will be greatly attenuated. Therefore, the improvement of detection distance is usually achieved through two aspects: increasing the output power and increasing the detection sensitivity of the detector.

[0003] Limited by existing devices and transmission radiation safety, the output power of pulsed lasers cannot be increased infinitely. Therefore, improving the detection sensitivity of the detector has become the key to increasing the detection distance. The use of single-photon detectors can increase the detection sensitivity to the highest level, but its high cost undoubtedly limits its application in various fields. The coherent detection method can effectively improve the detection sensitivity, but its detection distance is limited by the coherence length of the laser, and it cannot achieve long-distance target detection.

[0004] The above detection methods will all limit the detection sensitivity due to the performance of the detector. Therefore, researchers have explored and discovered a method to use the laser itself to detect the echo. Currently, there are mainly autocorrelation time delay characteristic method and self-mixing interference method.

[0005] The autocorrelation time delay characteristic method uses the light feedback caused by the echo to make the laser generate chaotic laser, and uses the unique time delay characteristics of the chaotic laser to analyze the feedback position. However, the premise of this method is that the laser must generate chaotic laser, and the feedback light intensity required for chaotic laser generation is generally above -45dB, so the sensitivity is subject to certain limitations [J.Lightwave Technol. 1986, 4, 1655]. In the field of absolute distance measurement, the self-mixing interference method also uses the change of the laser center frequency to generate and measure the beat frequency with the echo in the laser. Similar to the coherence method, it achieves high-resolution and high-sensitivity measurement, but the coherence length of the laser limits this method to only short-distance target detection, and cannot detect the target position exceeding the coherence length [Appl. Opt. 1998, 37, 6684].

[0006] In the early days of optical communication research, researchers found that feedback light would distort the modulation characteristic curve of the laser, and analyzed that the distortion of the modulation characteristic curve was 1dB at a feedback intensity of -60dB, which would not affect the modulation and demodulation of optical communication [Electron. Lett. 1989, 25, 1369]. However, this distortion phenomenon was not applied in other fields. When there is periodic modulation distortion on the modulation response curve of an optical feedback semiconductor laser, the frequency interval corresponding to the periodic signal in the modulation curve is equal to the inverse of the time it takes for the laser to be transmitted to the feedback position and then return.

[0007] Therefore, in order to avoid dependence on detector sensitivity and based on the above inspiration, a radar device that uses echo detection with higher sensitivity can be designed. Summary of the invention

[0008] In order to solve the problem that laser radar detection is highly dependent on detector sensitivity and is limited by the coherence length of laser, the present invention provides a laser radar that can achieve high-sensitivity echo detection.

[0009] The present invention is achieved through the following technical scheme: a laser radar capable of realizing high-sensitivity echo detection, comprising a signal source, a laser, a spectrometer, a detector and a signal acquisition and processing device, wherein the signal source is loaded onto the laser through bias-T or the laser's own high-speed modulation port, the output light of the laser is split by a spectrometer, a part of the light is sent to the detector, and the remaining light is output as detection light to the target to be measured, and the detector is connected to the signal acquisition and processing device.

[0010] The present invention changes the ranging principle of laser radar, utilizes the reflection generated by the target to be measured as the echo, returns to the laser, and implements external microwave frequency sweep modulation on the laser at the same time. The frequency response curve of the laser output will show the characteristics of periodic oscillation under the action of the reflected echo, and then the relationship between the periodic oscillation and the feedback position can be used to realize the detection of fault or target position.

[0011] Preferably, the laser is a semiconductor laser capable of spatial output.

[0012] Preferably, the splitting ratio of the spectrometer is any ratio of 1:99 to 50:50, and further, the ratio is 1:99.

[0013] The above-mentioned high-sensitivity echo detection method of the laser radar capable of realizing high-sensitivity echo detection is specifically as follows: using a signal source to transmit a frequency of fThe sinusoidal modulation signal of 0 is loaded onto the laser current through bias-T or the high-speed modulation port of the laser, so that the laser contains the information of the modulation signal in the normal light-emitting state. The laser output light passes through a 99:1 optical splitter, 1% of the light is divided into the detector, and the remaining 99% of the light is output as the detection light; the target return light enters the laser, so that the external cavity resonant frequency resonates with the modulation frequency, and the detector output enters the signal acquisition and processing device, which detects the amplitude information of the output light signal, and then increases the frequency of the sinusoidal modulation signal by Δ f Repeat the test until the frequency is increased to f m , and finally measured f 0~ f m Frequency response characteristic curve of laser within the range; f m - f The value of 0 is not less than 2 / τ, where τ is the round trip time from the laser to the target position, Δ f Less than 1 / 2τ; the measured curve will show periodic fluctuations, because in the frequency response curve, the interval between the peaks of the periodic fluctuations is 1 / τ , so the unit of the fluctuation period is Hz, and the period information can be quickly extracted using the inverse Fourier transform calculation. τ Multiply by the speed of light in space v g This is the round trip distance from the laser to the target position, divided by 2, which is the distance from the radar to the target. L , the calculation formula is as follows:

[0014]

[0015] .

[0016] Preferably, the signal acquisition and processing device is a spectrum analyzer, a vector network analyzer or an oscilloscope.

[0017] Compared with the prior art, the present invention has the following beneficial effects: the laser radar provided by the present invention can realize high-sensitivity echo detection, has a simple structure, uses a laser to receive reflected echoes, and the detection distance is not limited by the laser coherence length, and also avoids dependence on the sensitivity of the detector, while also greatly improving the sensitivity range of detection. The fluctuation on the modulation curve is still 1dB at a feedback intensity of -60dB, and a more sensitive echo response can be achieved through a certain periodic signal extraction method, and the resolution is far superior to the pulse flight time method. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the present invention.

[0019] Figure 2 The response curve diagram (left) and result diagram (right) of the echo detection of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific embodiments.

[0021] A laser radar that can achieve high-sensitivity echo detection, such as Figure 1 As shown: it includes a signal source, a laser, a spectrometer, a detector and a signal acquisition and processing device. The signal source is loaded on the laser through bias-T or the laser's own high-speed modulation port. The output light of the laser is split by the spectrometer, a part of the light is sent to the detector, and the remaining light is output as detection light to the target to be measured. The detector is connected to the signal acquisition and processing device.

[0022] In this embodiment, the laser is a semiconductor laser capable of spatial output; the signal acquisition and processing device is a spectrum analyzer, a vector network analyzer or an oscilloscope, any of which can display a response characteristic curve; and the splitting ratio of the splitter is 1:99.

[0023] The above-mentioned laser radar echo detection method capable of realizing high-sensitivity echo detection is specifically as follows: using a signal source to generate a signal with a frequency of f The sinusoidal modulation signal of 0 is loaded onto the laser current through bias-T or the high-speed modulation port of the laser, so that the laser contains the information of the modulation signal in the normal light-emitting state. The laser output light passes through a 99:1 optical splitter, 1% of the light is divided into the detector, and the remaining 99% of the light is output as the detection light; the target return light enters the laser, so that the external cavity resonant frequency resonates with the modulation frequency, and the detector output enters the signal acquisition and processing device, which detects the amplitude information of the output light signal, and then increases the frequency of the sinusoidal modulation signal by Δ f Repeat the test until the frequency is increased to f m , and finally measured f 0~ f m Frequency response characteristic curve of laser within the range; f m - f The value of 0 is not less than 2 / τ, where τ is the round trip time from the laser to the target position, Δ f Less than 1 / 2τ; the measured curve will show periodic fluctuations, because in the frequency response curve, the interval between the peaks of the periodic fluctuations is 1 / τ , so the unit of the fluctuation period is Hz, and the period information can be quickly extracted using the inverse Fourier transform calculation. τ Multiply by the speed of light in space v gThis is the round trip distance from the laser to the target position, divided by 2, which is the distance from the radar to the target. L , the calculation formula is as follows:

[0024]

[0025] .

[0026] The above method is used to Figure 1 To detect the distance in, when the frequency is f When a sinusoidal modulation signal of 0 is loaded onto the laser, Figure 2 The left figure shows the frequency f 0 response curve, when the frequency of the sinusoidal modulation signal is increased by Δ f Repeat the test until the frequency is increased to f m hour, Figure 2 The right side of the figure is the fluctuation period response curve, and the above two formulas are used to calculate the distance L , the result is the distance between the radar and the target.

[0027] The scope of protection claimed by the present invention is not limited to the above specific embodiments. For those skilled in the art, the present invention may have various deformations and changes. Any modifications, improvements and equivalent substitutions made within the concept and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser radar echo detection method capable of realizing high-sensitivity echo detection, characterized in that: The laser radar for realizing the echo detection method comprises a signal source, a laser, a spectrometer, a detector and a signal acquisition and processing device. The output light of the laser is split by the spectrometer, a part of the light is split to the detector, and the remaining light is output as detection light to the target to be measured. The detector is connected to the signal acquisition and processing device. Echo detection is as follows: Use a signal source with a frequency of f The sinusoidal modulation signal of 0 is loaded onto the laser current through bias-T or the high-speed modulation port of the laser, so that the laser contains the information of the modulation signal in the normal light-emitting state. The laser output light passes through a 99:1 optical splitter, 1% of the light is divided into the detector, and the remaining 99% of the light is output as the detection light; the target return light enters the laser, so that the external cavity resonant frequency resonates with the modulation frequency, and the detector output signal enters the signal acquisition and processing device, which detects the amplitude information of the output light signal, and then increases the frequency of the sinusoidal modulation signal by Δ f Repeat the test until the frequency is increased to f m , and finally measured f 0~ f m Frequency response characteristic curve of laser within the range; f m - f The value of 0 is not less than 2 / τ, where τ is the round trip time from the laser to the target position, Δ f Less than 1 / (2τ); the measured curve will show periodic fluctuations, because in the frequency response curve, the interval between the peaks of periodic fluctuations is 1 / τ , so the unit of the fluctuation period is Hz, and the period information is extracted using the inverse Fourier transform calculation. τ Multiply by the speed of light in space v g This is the round trip distance from the laser to the target position, divided by 2, which is the distance from the radar to the target. L , the calculation formula is as follows: ， 。 2. The laser radar echo detection method capable of realizing high-sensitivity echo detection according to claim 1, characterized in that: The laser is a semiconductor laser capable of spatial output.

3. The laser radar echo detection method capable of realizing high-sensitivity echo detection according to claim 1, characterized in that: The signal acquisition and processing device is a spectrum analyzer, a vector network analyzer or an oscilloscope.

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