Light spectroscopy in the frequency-domain has been used to study the optical properties of biological tissues. We have analyzed the possibility of using LEDs as intensity modulated light sources for frequency-domain spectroscopy. The use of LEDs presents several advantages: one LED's output covers a spectral region of about 80 nm, and commercially available LEDs allow for the coverage of the spectral range from 550 to 900 nm, which is a region of interest in near-IR medical applications; the light output of an LED is stable with respect to that of lasers and lamps; the wide angular distribution make LEDs safe for in vivo studies. Furthermore, LED frequency-domain spectroscopy is a relatively inexpensive technique. We describe some circuits we used to modulate the intensity of LEDs at radio frequency, and point out the possibility of building a multisource spectrometer. Some applications of LED frequency-domain spectroscopy, both in vitro and in vivo, are shown.

Date Published: 19 May 1994
PDF: 7 pages
Proc. SPIE 2135, Advances in Laser and Light Spectroscopy to Diagnose Cancer and Other Diseases, (19 May 1994); doi: 10.1117/12.176004

Published in SPIE Proceedings Vol. 2135:
Advances in Laser and Light Spectroscopy to Diagnose Cancer and Other Diseases
Robert R. Alfano, Editor(s)