Range-Gated LIDAR Utilizing a LiNbO3 (LN) Crystal as an Optical Switch

Abstract

In this paper, a range-gated LIDAR system utilizing an LN crystal as the electro-optical switch and a SCMOS (scientific complementary metal oxide semiconductor) imaging device is designed. To achieve range-gated operations, we utilize two polarizers and an LN (LiNbO3) crystal to form an electro-optical switch. The optical switch is realized by applying a pulse voltage at both ends of the crystal due to the crystal’s conoscopic interference effect and electro-optical effect. The advantage of this system is that low-bandwidth detectors, such as a CMOS and a CCD (charge-coupled device), can be used to replace conventional high-bandwidth detectors, such as an ICCD (intensified charge-coupled device), and it displays better imaging performance under specific conditions at the same time. However, after using an electro-optical crystal as an optical switch, a new inhomogeneity error will be introduced due to the conoscopic interference effect of the electro-optical crystal, resulting in a range error for the LIDAR system. To reduce the influence of inhomogeneity error on the system, this paper analyzes the sources of inhomogeneity error caused by the electro-optical crystal and calculates the crystal’s inhomogeneity mathematical expression. A compensation method is proposed based on the above inhomogeneity mathematical expression. An experimental LIDAR system is constructed in this paper to verify the validity of the compensation method. The experimental results of the range-gated LIDAR system show that in a specific field of view (2.6 mrad), the LIDAR system has good imaging performance; its ranging standard deviation is 3.86 cm and further decreases to 2.86 cm after compensation, which verifies the accuracy of the compensation method.

Keywords

• range-gated
• LIDAR
• conoscopic interference
• electro-optic crystal