Sensors, as the term is used here, refer to systems that react to a change in the environment. Pressure sensors react to an applied force or pressure using a variety of physical principles. Optical sensors change their optical properties under applied force. Similarly, electrically resistive, or simply resistive, sensors have an electrical resistance that changes under applied force. Piezoresistive sensors measure the change in electrical resistance of a piezoresistive material as pressure is applied.
Capacitive sensors change capacitance. This can be in response to an applied force; it can also be in response to the proximity of an object with relatively large capacitance, such as a person. Capacitive sensors can be combined with measurements of electrical resistance, as described in related U.S. application Ser. No. 11/352,107 now U.S. Pat. No. 7,208,960; U.S. application Ser. No. 11/732,150 now U.S. Pat. No. 7,276,917; U.S. application Ser. Nos. 11/732,680, 11/351,693 now U.S. Pat. No. 7,301,351, and U.S. application Ser. No. 11/351,735, incorporated herein by reference.
Lighting for a sensor (in a car dash board or piece of clothing, for example) can be advantageously aligned with a sensor; it is sometimes desirable to locate a sensor in close proximity to and/or under a light emitting device. Because the sensors and lighting devices are often separate components, the electrical addressing required to drive them both is often complicated and costly. In all cases, aligning a light emitting device with a separately constructed sensor involves extra material and other manufacturing costs owing to the required connections and alignment of the two.