Double Focus Laser Displacement Sensor Suppressing Laser Jitter and Target Tilt

Measurement precision of laser displacement sensor is subject to various factors, among which laser jitter and target tilt will directly lead to the position movement and shape variation of the laser spot, resulting in displacement measurement errors, so that researchers have to do a lot of research on the spot centering algorithm to weaken the above effects, which can treat the symptoms but not the root cause. Starting from the source of the problem, this paper proposes a double focus double peak solution, which uses a reflector to change the direction of the optical path, so that the imaging spots of the designed two optical paths focus on the same CMOS, forming a double peak structure. When laser jitter or target tilt occurs, the center of the two laser spots is shifted, but they move in the same direction, while their relative position remains unchanged. Therefore, the displacement can be characterized by the relative position of the two laser spots, so that laser jitter and target tilt are suppressed from the source. However, the two spots imaged on CMOS form a non-Gaussian distributed double peak structure, so the conventional laser spot centering algorithms are no longer applicable. To this end, a double peak adaptive threshold waveform extraction method combined with grayscale gravity method is proposed for spot centering algorithm, which combines the suppression of laser jitter and target tilt from the source and the improvement of spot positioning precision which represents the displacement measurement precision, and is experimentally verified.