Micro Variable Infrared Filter

Abstract

A micro infrared filter capably of transforming a transmitted wavelength is the most important component of a micro infrared spectroscope. This report describes the spectrum characteristics resulting from a Micro Variable Infrared Filter being experimentally produced. The design theory of the filter is based on the phenomenon that as the spacer layers thickness varies along the length of the filter, so dose the transmitted wavelength. The correlation between coating thickness and spatial position is very repeatable. We adopted a structure that transforms the center wavelength by changing the thickness of the only type spacer layer in the five layers SHW filter. The thickness of the spacer ranges of 400nm to 550nm. By using a sputtering system that includes a slit shutter with a film thickness error within 1% of the 1inch diameter, we can make the Micro Variable Infrared Filter with a continuous wavelength of 1.8 to 2.1μm. The results of the experiment are in good agreement with the thinfilm optical simulation for the spectrum transmission characteristics, with the linearity of the transmitted band being within 1% for different wavelengths.