Design of infrared wide waveband double-layer harmonic diffractive optical system

Diffractive optical element(DOE) and harmonic diffractive optical element(HDOE) have overwhelming superiority on achromatisation and athermalisation over traditional refraction and reflection optical elements due to their unique dispersion and temperature effect, which may improve the performance of the optical system and simplify the system structure. But, the diffraction efficiency of both are dependent upon wavelength, that will reduce the imaging contrast in wide waveband. However, Double-layer HDOE could weak the dependence. So,they were used in this infrared wide waveband system, the materials were Ge and ZnSe respectively, the microstructure thickness of corresponding diffractive surface were 73.3 m and 149.3 m. The diffraction efficiency of the system over whole waveband was larger than 97.5%. The emulational result in Code V indicates that various aberrations in system is satisfactory. Especially, the chromatic aberration of wide waveband(8-14 m) is well corrected, secondary spectrum is controlled preferably, and MTF closes to the limit of diffraction. Finally,the measured result indicate that all performances meet optical system expectation.