A high-speed real-time structured light imaging system is presented in this paper. The improved linear structured light imaging method is transplanted to the FPGA hardware system, and the imaging frequency is greatly increased. The best imaging effect can be obtained when imaging objects with different reflectivity. Experiments show that this method can achieve outstanding imaging effect for complex objects, and the imaging frame rate can reach 60 Fps.
High precision time measurement technology is the basis of many scientific applications. It plays an important role in radar, sonar, laser ranging, particle physics and other advanced scientific fields. Meanwhile, the ability of high-precision time measurement is also an important factor limiting the development of these fields. Time to digital conversion (TDC) is a commonly used time interval measurement method, which is widely used in the above-mentioned advanced areas. This paper presents a new TDC design method based on the delay chain structure, and the measurement accuracy is further improved by the combination of rough and exquisite counting. The theoretical basis of the TDC is described. The calculation formula of the total time to be measured is given. Then, by combining the start and the stop signal reasonably, the time of gate signal is within an acceptable range, which reduces the instability of the signal and the number of input signal sources. The designed TDC achieves excellent delay uniformity and stability through the reasonable layout and routing of Carry4 delay chain module in FPGA. In addition, in the design of latch unit, a two-stage latch unit is designed according to the mean time between failures (MTBF) theorem, which ensures the consistency of delay and the correctness of timing, avoids the generation of metastable state, and improves the timing accuracy. Finally, in order to verify the performance of the proposed TDC design scheme, reasonable post simulation and board level verification are conducted under different clock frequencies. The verification results show that the maximum mean error of TDC is 3.99ps and the minimum is 2.82ps.
Polarization is steadily attracting attention in machine vision due to its ability to capture the information not readily available in standard color or greyscale camera. In this paper, the degree of polarization image and intensity image are used to calculate the position and posture of stamping parts. First, the degree of polarization image and intensity image were acquired from polarization camera. Canny edge operator is used to filter the polarization degree image to get the edge image. Morphological analysis and connected domain statistics are performed on the edge image, and location holes are extracted from the connected domain according to the geometric characteristics. Combined with the extracted location holes region, the obtained polarization intensity image is segmented by local threshold, and the edge contour of the location hole is extracted and the coordinates of the center point are calculated.
Three-dimensional contour imaging is used to reconstruct the surface of complex contour. Line-structured light is characterized by fast measurement, large amount of data and nondestructive to contour surface and is widely used in 3-D imaging. Therefore, a series of calibration methods for line-structured light are also produced, such as cross-ratio invariance, triangulation method, polynomial and so on. However, the traditional calibration methods are complex and take a long time, so a simplified method is proposed. This method omits the complicated process of calculating the cross-ratio and obtains the equation of light plane by accurately calculating the external parameters between the target and the camera and get the 3-D points of the line-structured light by the pinhole camera model. What’s more, RANSAC is applied to get the more precious line-structured light plane by eliminating the wrong points. Moreover, errors are measured and analyzed during the process of structure light calibration.
In this paper, a two-dimensional (2D) laser radar system is designed. The working principle of pulsed two-dimensional laser radar is introduced. The driving circuit of laser emitting system is designed and simulated. The suitable parameters are acquired. Afterwards, the ranging result is calculated by the TDC-GP22, and the azimuth angle is acquired based on the encoder. The experiments are carried out, and the echo signals are measured at different distances. It provides the basis for unmanned aerial vehicle technology.
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