interferometers - INTERFIRE II 3-5



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 instrument 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.

It features 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. This is of particular importance in the 3-5 micron wavelength range where the lasers are generally of low power.



Twyman-Green Unequal Path Interferometer


3 - 5 microns


675mm (l) x 260mm (w) x 280 mm (h)


30 kg approx

Laser source type

head dimensions

head weight

Externally coupled HeNe (operating at 3.39 microns

110mm (l) x 160 mm (w) x 130 mm (h)

20kg approx

Clear aperture

Nominally 35mm (greater than 31.5 mm guaranteed). Expandable with accessories

Fringe detection

Focal plane array with fringe contrast adjustments


CCIR compatible or as specific user requirements


Integral co-linear visible HeNe laser

Optical zoom

Continuously variable x1 - x3

Remote control

Full control of reference mirror tilt/tip

Main/alignment, aperture focusing, optical zoom,

Accuracy (PV)

STATIC: l/20     PHASE: l/50

Repeatability (PV)

STATIC: l/50     PHASE: l/1000

Data acquisition time

STATIC: 0.04 sec     PHASE: 0.167 - 1.33 sec

Minimum hardware

Pentium© computer with maths processor,

vacant expansion slot for framegrabber board







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