Linearly variable bandpass and edge filters

REO, a manufacturer of high volume precision optical solutions, has launched a range of linearly variable bandpass and edge filters useful for applications in spectrometry and temperature sensing. In these variable response coatings, the centre wavelength of operation changes with position in a linear manner over the surface of the part. In the past, the company says, high manufacturing costs for this class of filters has limited their use to a few specialised applications. But now, REO has developed a unique, proprietary, volume scalable technology which enables cost effective production of linearly variable filters over a wide range of sizes.

REO currently offers bandpass filters for operation in the visible (380nm – 760nm), near infrared (600nm – 1100nm) and mid-infrared (1.3µm – 2.6µm) spectral ranges. Nominal bandwidth is 1 per cent (FWHM) of the centre wavelength, with a peak transmission of 60 per cent and a linearity of ±0.5 per cent. These can be delivered on a wide array of optical glass, fused silica, as well as other substrate materials in the 3mm x 1.5mm (L x W) to 150mm x 65mm size range. Short wave pass and long wave pass edge filters are also available over the same spectral range and substrate sizes. All these filters are fabricated using ion beam sputtering (IBS) technology in order to minimise scatter and absorption, and to make coating response totally insensitive to changes in temperature and humidity.