Reference Optical Engineering Bulletin, March 1994 Number 2. Supported by the U.S. National Science Foundation and the U.S. Department of State. FFV sensors Flexible-fuel vehicles are being developed by the automotive industry. The engine then makes the necessary adjustments for efficient combustion. This information is supplied to the engine electronic unit which adjusts the fuel flow rate, exhaust gas recirculation, and the spark timing.
Optical sensors designed for FFVs measure the differences in the fuel mixture index of refraction.
The collimated light passes through an optical-glass rod prism. The light is refracted at an angle proportional to the fuel mixture index of refraction. The light beam is reflected by a mirror and is again refracted a second time as it passes through the same boundary surface. The light beam then travels back through the rod prism at a different angle from the first passage. A condensing lens converges the light beam and it is then directed to a position-sensitive detector.