Reducing the influence of direct reflection on return signal detection in a 3D imaging lidar system by rotating the polarizing beam splitter

Abstract

The direction rule of the laser beam traveling through a deflected polarizing beam splitter (PBS) cube is derived. It reveals that, due to the influence of end-face reflection of the PBS at the detector side, the emergent beam coming from the incident beam parallels the direction of the original case without rotation, with only a very small translation interval between them. The formula of the translation interval is also given. Meanwhile, the emergent beam from the return signal at the detector side deflects at an angle twice that of the PBS rotation angle. The correctness has been verified by an experiment. The intensity transmittance of the emergent beam when propagating in the PBS is changes very little if the rotation angle is less than 35 deg. In a 3D imaging lidar system, by rotating the PBS cube by an angle, the direction of the return signal optical axis is separated from that of the origin, which can decrease or eliminate the influence of direct reflection caused by the prism end face on target return signal detection. This has been checked by experiment.

Recent Advances in Light Detection and Ranging: Optical Modulation Solutions and Novel Nanotechnologies

“…This strategy effectively curbs the interference from direct reflection on the detection of return signals, thereby improving the system's overall functionality. [52] M. Bawart et al presented a compact, on-axis apparatus specifically engineered for the 2D guidance of a transmitted beam's trajectory. As can be seen in Figure 4c, This device consists of two neighboring diffractive optical elements (DOEs), which effectively act as a pair of offset Fresnel lenses with inverse optical strengths.…”

“…Types Solution References mutual interference pulsed ToF random pulse trains [35] generate random sequence of double pulses by binary chaos generator [42] constitute CPPM by algorithm to generate random sequence [33] generate random signal sequence by LED+CMOS SPAD [36,[54][55][56] develop a multi-pulse detection algorithm [57] FMCW the interference signal can be extracted from the low-pass filter with wavelet denoising [58] few-mode frequency-modulated LiDAR receivers [40] frequency-Hopping modulator [39] RMCW use ASE laser to generate chaos signals [41] random signals generated by external optical perturbation [43][44][45][46][47][48][49] ghost image optic rotate the angle of the polarizing beam splitter to reduce the reflections of mirrors [52] adjust optical polarization to defocus unwanted stray light reflections [59][60][61] add anti-reflection mode and filter to suppress ghost reflection [62] enhance self-heterodyne synthetic aperture Imaging radar (Coherent Radar Architecture) [63] a higher gain length and a more powerful output from a single diode. However, the active region's vertical thickness is small compared to the horizontal width due to the designed geometry, producing an asymmetric elliptical beam profile rather than an ideal circular Gaussian beam.…”

“…This strategy effectively curbs the interference from direct reflection on the detection of return signals, thereby improving the system's overall functionality. [ 52 ] M. Bawart et al. presented a compact, on‐axis apparatus specifically engineered for the 2D guidance of a transmitted beam's trajectory.…”

“…Reproduced with permission. [ 52 ] Copyright 2016, Optica Publishing Group c) The diagrammatic illustration of two off‐center diffractive lenses possessing inverse optical strengths. (left).…”

“…Copyright 2018, Elsevier b) The scheme is a conceptual depiction of the directionality associated with the incident beam's reflection and refraction, as well as the returning signal from the target when a polarizing beam splitter (PBS) is rotated by a certain angle. Reproduced with permission [52]. Copyright 2016, Optica Publishing Group c) The diagrammatic illustration of two off-center diffractive lenses possessing inverse optical strengths.…”