Optical Design for Near Range Lidar

Nowadays, measurement of air flow and certain gas species in near range are needed for safety and environmental monitoring. Lidar is the appropriate tool for these applications. However, conventional lidar optics has a blind area because of the distance necessary to overlap the transmitted beam and the receiver’s field of view. To detect the near range lidar echo with a narrow field of view, the optical design should be compact and simple. The near range from zero to a few hundred meters ( < a few km) is the target distance. In this chapter, the theoretical calculation of the lidar echo for the near range measurement lidar is presented. The inline optics, which has common optics for the transmitting and receiving optics, is introduced. The signal-to-noise ratio is also estimated from the viewpoint of lowering the transmitted beam power for eye-safety. The actual near range lidar setup, which is based on the analysis, is also presented. The calculated results are compared and evaluated with the optical specification of the lidar. Some studies using the near range lidar, and several types of near range lidars are introduced.

Keywords: Compact lidar, near field lidar, inline lidar, Raman lidar, micropulse lidar, polarization lidar, LED lidar, hydrogen gas, lidar optics, lidar design.