Browse Prior Art Database

Calibration of Spectrophotometers

IP.com Disclosure Number: IPCOM000090745D
Original Publication Date: 1969-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Pliskin, WA: AUTHOR

Abstract

In this method, strong interference fringes formed by transmission or reflection can be obtained and utilized for calibration of infrared spectrophotometers. In such calibration, there are various difficulties. To cover the entire range of wavelengths, a number of products must be used. Over a limited range, the absorption bands due to atmospheric water and carbon dioxide are used. For the long ranges, various solvents giving sharp lines are used. The bands or lines are not usually symmetrical about the peak band position. Thus, calibration of a particular line depends on the spectral slit width of the spectrophotometer.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 55% of the total text.

Page 1 of 1

Calibration of Spectrophotometers

In this method, strong interference fringes formed by transmission or reflection can be obtained and utilized for calibration of infrared spectrophotometers. In such calibration, there are various difficulties. To cover the entire range of wavelengths, a number of products must be used. Over a limited range, the absorption bands due to atmospheric water and carbon dioxide are used. For the long ranges, various solvents giving sharp lines are used. The bands or lines are not usually symmetrical about the peak band position. Thus, calibration of a particular line depends on the spectral slit width of the spectrophotometer.

In this method, infrared light is transmitted through a uniform film or wafer which has a high-refractive index and is thin enough to result in infrared fringes. The fringes so formed are fairly uniform. Their positions can be determined very precisely provided the refractive index of the material and the film thickness are known. Thin uniform silicon or germanium wafers, a uniform silicon ribbon, or a silicon wafer having a silicon nitride coating are used.

The material need only be a few mils thick. Since the refractive index of silicon is known precisely through the infrared region, the exact wavelength corresponding to each minima or maxima is known. Thus precise calibration is obtained throughout the infrared region. Two precise calibration points are needed to establish the wafer or ribbon thickness if it i...