Telecentric f-theta scanning lens design for terahertz imaging systems

Beam scanning system using f-theta lenses which are telecentric in the image space offers a linear beam displacement with the incident beam deflection angle and a focused beam has a normal incidence angle on the target plane. Therefore, the beam from the source reflects and travels back through the system to the source. The reflection coefficient (S11) measurement can lead to the inspection of the target plane reflectivity. In this work, a telecentric f-theta lens is designed using ray tracing optimization and later, to verify ray tracing results, physical-optics simulations are performed on the system at 500 GHz. The designed lens has a thickness of 37 mm and shows acceptable f-theta distortion (0.5% for deflection angle of 10° with 22mm beam displacement) and telecentricity.