OPTICAL SENSOR

The APOLLO project [1] developed the technology incorporated in an optical positioning sensor to measure the displacement of a contact patch on a tire surface relative to the rim. A diagram showing the sensor setup is shown in Figure 1. It consists of a position sensitive diode (PSD), a lens and a light source on the inner liner of the tire.

As shown in the figure, a light beam emitted from the IR-diode is focused on the PSD-chip. The light spot on the PSD-lens generates current at the corners of the PSD-chip. Movement of the light beam influences the relative current at the four corners. This data can be used to obtain the distance of the IR-Diode to the inner liner [1].

OMRON Corporation, in Japan, introduced an optical spatial filter sensor for ground speed. It works on the principle of optical spatial filtering and uses pulse-driven light emitting diodes as a source of illumination [2].

Figure 1: 3-axial Optical Sensor on the Inner Liner [1].

References

[1] "Intelligent Tyre for Accident-free Traffic," APOLLO Final Report, IST-2001-34372, July 2005.

[2] Yasunobu Sakai, Tetsuya Uno, Junichi Takagi and Tsukasa Yamashita, "Optical Spatial Filter Sensor for Ground Speed," The Optical Society of Japan, vol. 2, pp. 65-67, Jan. 1995.