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Infrared filter

赤外域用フィルタ

The IR region is defined as that from 0.7 to 1,000μm, and is usually divided into 3 sections, which are near infrared (0.7 to 2.5μm), mid infrared (2.5 to 25μm) and far infrared (25μm to 1,000μm). Objects at normal temperature (around 300K) emit in the IR around 10μm wavelength, which requires the use of mainly multi-layer interference filters for their detection. They are used for the following reasons;
1)There are several substrate materials which have high refractive index and are transparent;
2)Light division by absorption can only be used as supplementary since mid IR is much wider region comparing to visible region.

Feature

This is a filter which controls IR light by interference effects made by multi layered thin film coating on IR optical substrate, such as Quartz, Sapphire, Silicon, Germanium. We select an optical substrate, which is closest to the required optical specification.

Applications

Those filters are used for measurement, controlling machine, equipment and other optics utilizing IR light such as;
1) IR gas analysis; the filter is for detecting mainly CO2, CO, HC, NO x, SO x, O3 gas density, is used for flame sensor, organic sensor, exhaust gas sensor, etc.;
2) IR water analysis; the filter is for detecting H2O absorption to measure moisture;
3) IR radiometric thermometer, which is used for thermograph, thermometer, etc.;
4) IR thickness analysis, which is used for a measurement of film thickness detecting HC absorption region contained in polymer;
5) Order sorting filter for diffraction grating;
6) Human detector; the filter is used for human detection sensor such as automatic door, security alarm sensor, etc.

Typical characteristics