Acoustic pressure is directly converted to a parallel 3-bit binary code using optical interference. Since the diaphragm deforms sinusoidally when pressure is applied, the interference is different from point to point on the diaphragm. We simultaneously detected the interference intensity at an adequate sampling of three points. A quantized bit plane is produced in parallel without scanning. The dynamic range is ±240 Pa, and good linearity is obtained. This method can be used to measure other quantities such as temperature and voltage.
© 1983 Optical Society of America
Hitoshi Mada and Katsuo Koide, "Optical direct analog-to-digital conversion for microphones," Appl. Opt. 22, 3411-3413 (1983)