On-Site Measurement of the Spectral Transmittance of a Stripe Filter

Abstract:

A simple on-site transmittance measurement setup that is easy to move and install is proposed in this study. It is especially suitable for those cases when laboratory instruments are not applicable. Ordinarily, witness samples are measured since the uniformity is good enough inside the thin film coator and the size of the sample is proper for the facilities to measure. When the spot size of the measuring instrument is too large for the filter or the size of the test sample is too large to fit into the instrument. The proposed setup is shown to work well for this measurement. An application for this setup is also presented. The test target was a stripe filter, which has five band-pass thin films and nominal dimensions of 120 x 3.6 mm each film. Distance between neighboring films is 3.85 mm. The width of each film is so narrow and the size the stripe filter is large such that the traditional method for spectral transmittance is not applicable. The proposed measurement setup consists of a light source, integration sphere and spectrophotometer. The setup was installed inside a dark room. It shows that the setup can provide as accurate results as those data measured by an accreditated instrument. The difference between the present setup and accreditated instrument was found within 7% for high radiance. When the radiance of the incident light is low the accuracy decreases, which can be compensated by stronger light source. In addition, since the measurement spot size is estimated as 1.5 x 2.1 mm it can provide local transmittance data along the stripe thin film rather than a single data represented by the witness sample.

• Periodical: Applied Mechanics and Materials (Volume 870)
• Pages: 3-8
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.870.3
• Online since: September 2017
• Authors: Ho Lin Tsay, Po Han Huang, Kun Huan Wu, Ting Ming Huang*
• Keywords: Integration Sphere, Stripe Filter, Transmittance

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