Abstract

A very high-sensitivity Fourier transform spectrometer incorporating a 2-D photon counting technique is investigated and constructed for the first time, we believe, for measurement of ultraweak biophoton emission phenomena in the visible region. The phenomenon of ultraweak photon emission, which is closely related to life processes and biological activities, has recently been recognized in various biological tissues, cells, and substances. We have previously developed a highly sensitive computer-controlled spectral analysis system called a filter spectral analyzer system for this use.¹ For further improvement of the sensitivity and reliability, we studied and designed a new type of Fourier transform spectrometer. Fourier transform spectroscopy Is well known for high-speed and high-resolution measurement and analysis due to its advantages of multiplexing (Fellgett) and optical throughput (Jaquinot). However, detection sensitivity is mainly limited by two factors: one is the sensitivity of the detector array used and the other is the brightness of the optical system. Taking into consideration these points, a Sagnac-type common path configuration, which has no mechanical moving parts for the Fourier transform spectrometer, was constructed and tested. Hence the interferogram is generated spatially and is detected by a highly sensitive 2-D photon counting system controlled by a microcomputer. This arrangement makes it possible to achieve easy alignment and operation along with good stability and reproducibility.

© 1988 Optical Society of America