Infrared diffractive optical element fabricated on aspheric substrate

A hybrid diffractive-refractive infrared lens of germanium was fabricated by means of diamond turning, in which the diffractive surface was produced on an aspheric substrate. The test results for the hybrid lens and a comparative lens without the diffractive structure show that the diffractive surface is fabricated with good accuracy. It reduces the chromatic aberration of the single lens system, and significantly improves the image quality of the system, which corresponds well to the design result.