The return signal of coaxial and noncoaxial lidar systems with central obstruction has been calculated by integration of the irradiance in the focal plane. As in the coaxial unobstructed case, a small detector in the focal plane allows a geometrical compression of the detector signal dynamics. In coaxial systems, the shadow cast by the obstruction results in a reduction of the near signal. In noncoaxial arrangements a signal reduction occurs for distances that depend on the transmitter-receiver separation and the inclination angle, whereas the influence of an obstruction is almost negligible. Adequate signals can be obtained from short to long distances with both types of geometry.
© 1979 Optical Society of America
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