For the infrared laser ranging system, the measurement accuracy of the commonly used single-threshold judgment method is not high enough, and the time discrimination error is large. The pulse width correction circuit can improve the measurement accuracy, but the circuit is complicated and will introduce additional noise. Therefore, aiming at the problem of insufficient measurement accuracy of the laser ranging system, this paper establishes a pulse width correction method for the infrared laser ranging system based on the BP neural network algorithm, and verifies the ideal correction of the method to different intensity waveforms through experiments. The experimental result shows that the time difference of flight time under different laser light intensity at the same distance is reduced from 20ns to 6ns, and there’s no need to add time discrimination circuit and correction circuit. The correction value can be obtained by directly using neural network optimization, omitting the complicated middle process. It is proved that this method can be used to improve the accuracy of the laser positioning system.
The detection error of the laser ranging system determines its application and has always been one of the research hotspots in the field of laser ranging. In order to improve the resolution of the laser ranging system, this paper designs a laser receiving circuit with low noise and a double threshold time discrimination circuit from the perspective of reducing the ranging error. Firstly, based on the input noise of the laser receiving system, we select the appropriate transimpedance amplifier and secondary amplifier according to the noise characteristics of the optical receiving system. Then, based on the energy of the received echo signal, we derive the design formula of the double threshold circuit. Finally, we verify the designed double-threshold laser receiving circuit by experiments, and find that it can significantly reduce the detection error of the system.
The traditional pulse laser ranging system based on the measurement of time of flight often ignores the nonlinear influence of the intensity of the echo light power on the range error of the receiver system. Based on the transistor model (Gummel-Poon model), this paper makes a systematic modeling of the pulsed laser range finding receiver system. By means of computer aided analysis, the relationship between the input current waveform and the leading edge of the response pulse of the receiving system is analyzed. And thus, the relationship model of the echo light power and front of response echo pulse is derived in the paper. Based on the above model and by involving the method of differential threshold time discrimination, the walking error in the laser ranging system is corrected. Finally, the experimental results show that this method can effectively correct the nonlinear error caused by the fluctuation of the echo power and improve the accuracy of the ranging system.
Aiming at the influence of the energy distribution of incident light on the traditional location algorithm of four-quadrant detector (4-QD), the generation rule of measurement error is analyzed. A model to express the energy distribution of the light spot of 4-QD is established by using characteristic parameters, and the measurement error model related to the characteristic parameters is derived. In the actual system, for different spot locations, we can use this model to fit the energy distribution, and get the spot characteristic parameters of the system, and then use it to calculate the measurement error caused by the traditional algorithm in 4-QD system. In the experiment, the energy distribution image of the incident beam is obtained by the beam quality analyzer, and the actual moving distance of the spot is compared with the calculation result of the traditional measurement algorithm. From the experimental results, it can be proved that the measurement error model of the four-quadrant detector, which is described in this paper, is consistent with the experimental results. It can further modify the calculation results of the 4-QD system in practical applications, to improve the measurement accuracy.
Laser and visual imagery have been broadly utilized in computer vision and mobile robotics applications because these sensors provide complementary information. So we focus attention on the fusion of 1-D laser rangefinder and camera. However, finding the transformation between the camera and the 1-D laser rangefinder is the first necessary step for the fusion of information. Many algorithms have been proposed to calibrate camera and 2-D or 3-D laser rangefinder, but few methods for 1-D laser rangefinder. In this paper, we propose a robust extrinsic calibration algorithm that is implemented easily and has small calibration error. Due to the 1-D laser rangefinder only returns a data in one dimension direction, it is difficult to build geometric constraint equations like 2-D laser rangefinder. So we are no longer constrained to build constraint equations to finish calibration. Due to the spot of the single-point laser rangefinder we commonly use is mostly invisible, we can determine the full calibration even without observing the laser rangefinder observation point in the camera image. We evaluate the proposed method demonstrating the efficiency and good behavior under noise. Finally we calibrate the installation error of camera utilizing the calibration result.
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