Knight Optical can offer Zinc Selenide (ZnSe) Optics for Infra-red systems over the waveband of 0.6 to 21µm. We offer ZnSe optics for the NIR (0.7-1.5), MWIR (3 to 5µm), and LWIR (8 to 20µm) Imaging Systems. ZnSe has a good transmission in the MWIR and LWIR wavelengths, and can be used with Silicon or Germanium, given its refractive index range is lower than the two of them, to form corrected doublets and lens systems.

These systems include, for example, Forward Looking Infra-Red (FLIR) systems, and thermography. ZnSe has a range of refractive indices from 2.6312 at 0.58µm, 2.4892 at 1µm, to 2.3278 at 18µm. This glass will produce a well corrected lens system using other IR glasses, such as Silicon, Germanium, or Calcium Fluoride.

ZnSe can be be combined with other IR glasses to provide a wavelength corrected lens for use in a Fourier Transform Infra-Red (FTIR) spectroscope. When combined with the ZnSe Attenuated Total Reflectance (ATR) prism, the wavelength range is from 0.6 to 20µm.

The figure shows an image of a ZnSe prism as used in an ATR spectroscopy system. The figure shows the prism is in contact with the sample, for example, paper pulp, or printing ink that remains un-diluted whereas it has to be diluted using other spectroscopes. Therefore, the ATR is quicker and continuously works on the production line.. The measurement is taken by using, for example, bright lights, such as collimated LEDs. This beam is directed into the ATR crystal so that evanescent wave is at the boundary surface of the sample and prism. This wave will be modulated by the sample as it flows over the surface. Any difference in the reflected spectrum will show up on the FTIR and presented to the user as an intensity plot versus wavenumber, or wavelength. These machines are used, for example, in forensics for matching soil spectra from the scene of crime and that found on a suspects clothing.

Zinc Selenide (ZnSe) Optics for Infra-Red Systems