This paper relates to the implementation of moving object position estimation by Pulsed LiDAR that can detect objects with high precision, speed, and spatial resolution. LiDAR measures the distance by calculating a return travel time when target is reflected. The retro-reflector, regardless of incident angle, can be reflected horizontally in the incident direction. This algorithm proposes a new approach method using LiDAR and retro-reflectors. According to the above algorithm, position can be determined by automatically detecting 90% of the reflected return beam intensity from moving objects to which the retro-reflector is attached. When this algorithm was applied indoors, it was possible to locate the position of the scanner accurately within ±5 mm error in 2,500 × 2,500 (mm) space. Also, it can detect a space of up to 5,000 × 5,000 (mm), making this an effective method for determining the position of a moving object in indoors.

Optical dimensional metrology has playing a long-term key role from high-precision engineering to large-scale industrial manufacturing. Various methods of optical dimensional metrology have been proposed and demonstrated to respond to the ever-growing industrial demands as well as fundamental science demands for the measurement precision and range. However, most of them demonstrated under laboratory conditions have a long way to go outside the laboratory. Here, we present a progress review on optical modulation technique-based dimensional metrology, which has already been used in real applications and has been commercialized. Amplitude modulation (AM) and frequency modulation (FM) based dimensional measurement techniques are described with their operating principles, and recent progresses and applications in 3D imaging are presented in this review.

A spectral-domain interferometer with dual reference paths and orthogonal polarization states to avoid measurement errors when interference signals overlap is proposed and realized. In our previous study, by using dual reference mirrors, two inherent problems of the spectral-domain interferometer, the non-measurable range and the directional ambiguity problem, were successfully solved. However, because of the overlap of interference signals, the absolute distance values were distorted. In this study, the polarization states of beams from two reference paths were made orthogonal to eliminate the interference signal between them, so that the overlap can be essentially avoided. First, we performed a numerical simulation on the measurement error with respect to the degree of superposition of the interference signals. Simulation results show that with the previous method the measurement error can be up to approximately 1 μm within the overlap region, but the proposed method drastically reduced this error to below 100 nm. Then, the proposed method was experimentally realized and verified. In conclusion, the proposed method can measure the absolute distances without the inherent problems as well as the measure errors caused by the overlap of the interference signals.