IR Interferometry


The INTERFIRE II family of infra-red interferometers is available with a choice of lasers operating at 10.6 microns wavelength, in the 3-5 micron wavelength range, at 1.55 microns or 850 nanometres and allows fringes to be obtained quickly and easily with excellent signal-to-noise.

The INTERFIRE II series of infrared interferometers can be used in development, test or production laboratories and is used for the accurate measurement of wavefront aberration of thermal imaging lenses, optical homogeneity of infra red materials and flatness of optical surfaces.

The construction of the INTERFIRE II, combined with a fast warm-up time means that fringe images can be quickly and easily produced with no focus drift. All instruments feature a focal plane array camera which is much more sensitive than previous cameras and has significantly reduced noise, allowing high quality images of fringes to be acquired quickly, easily and with no focus drift. When used with phase shifting fringe analysis software, the acquisition of fringes is much more reliable. The phase shifting technique used allows the highest degree of precision and enables full use of standard accessories.

The INTERFIRE II 850 nm utilises two laser diode sources, one as a marker beam and one for the measurements at 850 nm. These are coupled into a fibre optic to give very precise alignment. The laser diodes supply plenty of power, but the sensitivity of the camera is sufficient that they can be operated at relatively low power.

The INTERFIRE II 1.55 has been designed to meet the needs for testing the increasing numbers of optical systems operating at 1.55 micron wavelength. The instrument features a CCD camera with NIR conversion optics and glass lenses and mirrors. The high resolution near infrared converter between a large format lens and the camera converts the 1.495 – 1.595 micron wavelength band to wavelengths detectable using standard CCD cameras without fading or lag during use. A large format anti-reflection coated input window ensures maximum image resolution is transferred to the attached CCD camera. Optical systems designed for use in the near infrared at 1.55 microns are highly popular because the radiation at this wavelength is partially eye-safe. Applications include ranging systems, designation systems and scene illumination systems for surveillance. This wavelength is also used extensively in the communications industry.

The INTERFIRE-II 3-5 operates in the mid IR waveband (3-5 microns) using a 3.39 micron HeNe laser source. Alternative lasers are available for different wavelengths.

The INTERFIRE-II 10.6 operates in the far IR waveband (8-12 microns) using a stabilised CO2 waveguide laser source operating at 10.6 microns. Alternative lasers are available for different wavelengths.