Method for improving detection capability of laser range finder

Abstract

The invention provides a method for improving the detection capability of a laser range finder, which can effectively improve the laser range finding capability, is low in cost and can ensure the effectiveness of the method. Comprising the following steps: S1, emitting a plurality of laser beams to a measured target, and obtaining return light migration time # imgabs0 # caused by the measured target according to a signal emission time interval t0 and a return light signal time interval t1 of two adjacent frames, v0 being the speed of the measured target, and c being the light speed; and S2, adding a fixed offset between two adjacent frames of transmitting signals according to the return light offset time delta t, and adding the translated two adjacent frames of signals in a staggered manner to obtain a final shifted and superposed return signal.

Description

Technical Field

[0001] The invention relates to the technical field of laser ranging detection, and in particular to a method for improving the detection capability of a laser rangefinder. Background Art

[0002] Laser ranging technology is widely used in the field of space ranging as the basic technology of high-end technologies such as laser tracking, laser three-dimensional imaging and laser radar (LiDAR). Existing military laser rangefinders mostly use the time-of-flight method, that is, a laser is used to shoot a laser beam at the target. The light beam is reflected by the surface of the target to be measured and then received by the photoelectric element. The time from the emission to the reception of the laser beam is measured, so as to calculate the distance between the laser source and the target to be measured. However, there are still shortcomings. Once the object to be measured is too far away, the return light signal will be relatively weak, or even submerged in the noise, thereby reducing the ranging capability.

[0003] There are currently several methods to improve ranging capabilities:

[0004] (1) Improve the intensity of the return light signal: increase the receiving aperture and increase the laser output power, but this will lead to a larger volume, heavier volume, increased power consumption, and higher heat dissipation requirements;

[0005] (2) Reduce the noise level: Add narrowband attenuation sheets, reduce the receiving divergence angle, and select low-noise chips to reduce line noise. However, adding narrowband attenuation sheets will significantly increase costs and are easily affected by temperature, requiring the addition of a temperature control system. Reducing the divergence angle will increase the difficulty of installation and adjustment, and the ability to resist vibration and impact will be limited. The methods for controlling the noise level of the circuit are relatively limited.

[0006] (3) Improve the return light detection capability: Choose a highly sensitive detector, such as a single photon detector or electron multiplier tube, but the cost of such a device is relatively high;

[0007] Based on this, it is particularly important to develop a method that can improve the ranging capability. Summary of the invention

[0008] In view of the above problems, the present invention provides a method for improving the detection capability of a laser rangefinder, which can effectively improve the laser ranging capability, has low cost, and can ensure the effectiveness of the method.

[0009] The present invention adopts the following technical solution, a method for improving the detection capability of a laser rangefinder, comprising the following steps:

[0010] S1, send multiple laser beams to the target to be measured, and obtain the return light offset time caused by the target to be measured based on the time interval t0 of the emission signal between two adjacent frames and the time interval t1 of the return light signal Among them, v0 is the speed of the target being measured, and c is the speed of light;

[0011] S2. According to the return light offset time Δt, a fixed offset is added between the transmission signals of two adjacent frames, and then the signals of the two adjacent frames after translation are misaligned and added to obtain the final return signal after shifting and superposition:

[0012]

[0013] Among them, x i (t) is the amplitude of the echo signal of the i-th frame at time t;

[0014] n is the number of superimposed frames.

[0015] Furthermore, in step S1, the speed of the target being measured

[0016] Among them, L i , L i-1 Represent the ranging values ​​of the i-th and i-1-th frames respectively.

[0017] The beneficial effect of the present invention is that after adding a fixed time offset between adjacent frame rates and then performing multi-frame addition, the return signal after shift superposition can be obtained, which not only ensures the effectiveness of the ranging method, but also after the signal is superimposed, the signal is enhanced and the noise is suppressed, and the entire echo signal can be effectively extracted, further improving the laser ranging capability and having good use value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of the present invention;

[0019] Figure 2 is a signal diagram without offset in the present invention;

[0020] Figure 3 It is a return signal diagram after shifting and superposition in the present invention. DETAILED DESCRIPTION

[0021] like Figure 1 , Figure 2 , Figure 3 As shown, the present invention provides a method for improving the detection capability of a laser rangefinder, comprising the following steps:

[0022] S1, send multiple laser beams to the target through a high repetition rate laser, and obtain the return light offset time caused by the target according to the time interval t0 of the emission signal between two adjacent frames and the time interval t1 of the return light signal

[0023] The speed of the target is

[0024] L i , Li-1 They represent the distance measurement values ​​of the i-th and i-1-th frames respectively; c is the speed of light;

[0025] Specifically, for example, two laser pulses are sent to the target, and the pulse interval is t0. If the target and the detector are stationary, the interval between the two pulse echoes received by the detector is also t0. However, due to the relative motion between the target and the detector, when the target receives the two beams of light, the time difference between the return beams will no longer be t0, but will change (increase or decrease) to t1.

[0026] S2. According to the return light offset time Δt, a fixed offset is added between the transmission signals of two adjacent frames, and then the signals of the two adjacent frames after translation are misaligned and added to obtain the final return signal after shifting and superposition, that is:

[0027]

[0028] Among them, x i (t) is the amplitude of the echo signal of the i-th frame at time t;

[0029] n is the superposition frame frequency, which depends on the transient speed of the target and the pulse width τ of the transmitted signal;

[0030] Each frame of signal starts with a pulse transmission signal. If there is no relative motion between the target and the detector, the nth data in the frame will be an echo signal.

[0031] When the distance measurement is just started, there is no series of experience values. It is necessary to use certain experience to infer the speed range of the measured target. The existing traversal method is used for estimation. Assuming that the speed range of the measured target is expected to be within the range of [v1, v2], the speed interval Δv is used to predict the range one by one, and the final maximum effective signal is used as the basis for judgment.

[0032]

[0033] v1, v2 are assumed values.

[0034] Figure 1 This is the effect of not adding offset, the effective echo signals are not superimposed and the intensity is not increased; Figure 2 This is the effect after adding offset, and the intensity is enhanced.

[0035] The present invention uses a high repetition rate laser with low energy, high frequency and relatively low cost to improve the signal-to-noise ratio by superimposing multiple echoes, thereby extracting weak signals. Among them, after the existing simultaneous multi-frame superposition, due to the randomness of the noise and the high correlation of the signal, the signal amplitude after superimposing n frames is approximately The signal amplitude is increased by n times, and the signal-to-noise ratio is improved. At the same time, after multiple accumulations, the noise amplitude over the entire ranging time also approaches a constant value. When the existing method measures high-speed targets, there is a relative displacement between adjacent frame rates, which will cause the superposition effect to deteriorate or even fail. Therefore, the present invention finds the deviation between adjacent frame rates and then performs staggered superposition on each frame number, thereby ensuring the effectiveness of the high repetition rate algorithm when measuring high-speed targets.

[0036] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0037] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for improving the detection capability of a laser rangefinder, characterized in that: The following steps are involved: S1, send multiple laser beams to the target to be measured, and obtain the return light offset time caused by the target to be measured based on the time interval t0 of the emission signal between two adjacent frames and the time interval t1 of the return light signal Among them, v0 is the speed of the target being measured, and c is the speed of light; S2. According to the return light offset time Δt, a fixed offset is added between the transmission signals of two adjacent frames, and then the signals of the two adjacent frames after translation are misaligned and added to obtain the final return signal after shifting and superposition: Among them, x i (t) is the amplitude of the echo signal of the i-th frame at time t; n is the number of superimposed frames.

2. The method for improving the detection capability of a laser rangefinder according to claim 1, characterized in that: In step S1, the speed of the target is Among them, L i , L i-1 Represent the ranging values ​​of the i-th and i-1-th frames respectively.

Images