Holographic Circle-to-Point Converter

The figure schematically depicts the use of a special-purpose holographic plate to focus light from (1) circular interference fringes generated by a Fabry-Perot etalon to (2) a series of points, each illuminated in a different wavelength interval. This holographic circle-to-point converter was invented to enable efficient utilization of the output light of a Fabry-Perot etalon in an incoherent Doppler lidar system. (The role of the etalon in such a system is to resolve, within a fairly narrow frequency band, the spectrum of light back-scattered by atmospheric particles that have been illuminated by a laser in the system.) If photodetectors are placed at the illuminated points to measure the intensities of light in the various wavelength intervals, then the photodetector outputs can be used to characterize the spectrum of light coming through the Fabry-Perot etalon.