Three-dimensional Correlation Imaging Based on Time-of flight Technology

Different from traditional optical imaging technology, correlated imaging uses a single-pixel detector and a spatial light modulator to reconstruct object image information based on correlation calculations, having the characteristics of super-resolution, non-local, and anti-interference. Time-off-light (TOF) technology is an effective method for optical remote sensing and three-dimensional imaging of target recognition. Compared with traditional laser correlation imaging, 3D correlation imaging can not only obtain the two-dimensional light field intensity information of the target object, but also effectively obtain the longitudinal distance information between the target objects, so that the size and position of the imaging target can be quantitatively analyzed. Three-dimensional correlation imaging technology mainly includes steroscopic vision and TOF imaging technology. To improve the image reconstruction quality of intensity 3D correlation imaging, this paper employs differential correlation imaging reconstruction algorithm and TOF technology, and the theoretical formula of intensity correlation 3D imaging is deduced. The working mode is that the short-pulse laser forms pseudothermal light through the rotating frosted glass. After passing through the beam splitter, one of the beams irradiates the target object to be measured and then is received by the Photomultiplier Tube (PMT); the other beam is detected by the array detector. The high-speed data acquisition system digitizes the peak light intensity signal detected by the PMT into discrete data points, uses the TOF technology to divide the detection signal into slice signals of different time (distance) , and then integrates the signals in the respective slices to obtain the slice signal detection value, and finally the DUI algorithm is used to perform two-dimensional correlation imaging reconstruction calculation for each slice signal separately. This paper mainly investigates the influence of the light source laser power and reconstruction algorithm parameters on the imaging quality in the pseudo-thermo-optic 3D correlation imaging. The imaging results of two flat objects to be measured (the front-end target is a four-pointed star and the back-end target is the letter F) with a distance of 80 cm and a resolution of 200 pixel x 200 pixel in the numerical simulation are given. Among them, the simulation pulse laser uses the function p(t)= exp (-tau(2)/sigma(2)), the detection times is 20 000, and the sampling rate is 50%. In order to further verify its effectiveness, a pseudo-thermo-optical 3D correlation imaging experimental system is built. This paper uses a 532 nm pulsed laser as the light source and frosted glass as the spatial light modulator to build a set of pseudo-thermal light three-dimensional correlation imaging experimental system, which realizes the three-dimensional image reconstruction of a 200 pixel x 200 pixel target object with a longitudinal distance of 60 cm at an absolute distance of 5.5 m in the laboratory environment. The reconstructed 3D slice images that are lower than the set threshold parameters in the simulation and experimental results are reset to zero, thereby reducing the influence of the background noise of other slice images on the quality of the reconstructed images during the 3D correlation imaging stacking process. Within a certain threshold parameter range, appropriately increasing the threshold parameter can effectively improve the reconstruction quality of 3D correlated imaging images. To further investigate the performance of the 3D correlation imaging experimental system, experimental tests are carried out for 3D correlation imaging under different laser powers, respectively. The experimental verification shows that by properly increasing the power of the laser light source, the influence of the time jitter of the echo signal on the reconstructed image quality can be effectively suppressed, and the longitudinal distance reconstruction quality and measurement accuracy of the 3D image can be further improved. The work has a reference significance for promoting the application of intensity 3D correlation imaging technology in the field of lidar imaging.