Abstract: A light pipe, including a transparent housing member characterized by a first refractive index, a light source positioned to shine a light beam through the transparent housing member, and at least one enclosed pocket positioned within the transparent member. The enclosed pocket is characterized by a second refractive index, wherein the first refractive index is substantially greater than the second refractive index. Light shining through the transparent member is totally internally reflected by the enclosed pocket.

Abstract: A system for measuring torque comprises a pair of drive shafts connected by a torsion bar, a wheel affixed to each of the drive shafts and having at least one slot cut through it, a light source positioned on the side of one of the wheels opposite the other, and a light detection device on the opposite side of the other wheel positioned to detect light from the light source which passes through the slots in both wheels. The slots are positioned in the wheels such that the light that can pass from the light source, through both wheels, and to the detector changes as the angular position of the wheels changes relative. The light detection device observes the changes in this pattern of light to produce a signal indicative of the torque on the drive shaft that is producing the observed angular displacement of the wheels.

Abstract: A sensor (20, 100, 200, 300) for detecting the approach and exit of a vehicle (42) to a tunnel (46). In one embodiment there is a sensor (20, 100, 200, 300) with a photodiode (22a) that receives light through an inclined channel (30, 30′) or aperture (32, 332, 432). The channel provides a field of view (44, 344, 31) ahead and above the vehicle. The photosensor (22a) is thus sensitive to the change in light from this field of view (44, 344, 31) as a vehicle enters (46a) and exits (46b) a tunnel (46). Some embodiments of the present invention include a second photosensor (22b) with a wider field of view (112, 112″, 111) for detecting ambient light.