Appliance Design - February 2008 - (Page 35) mixing requires a coherent optical source, such as a laser, and VCSELs can be optimized to enhance the self-mixing effects. Another useful application of a VCSEL based sensor is in detecting the proximity of an object. The most ubiquitous example of a proximity sensor is the automated flush systems incorporated in many public restrooms. Today’s devices utilize LEDs as the transmitter. This seemingly benign sensor consumes several megawatts of electricity each year and is the cause for several tons of CO2 emission each year. (That calculation assumes 100 M sensors, with each LED consuming 200 mW of power, operated with a duty cycle of 10 percent, and an average CO2 production of 1.35 lbs. per kW/hr). Simply replacing the LED with a VCSEL would reduce the amount by more than a factor of 10, and would result in a better sensor. Some of the advantages of the VCSEL-based proximity sensor include the ability to sense objects further away, sense smaller objects, increased ambient light rejection, and more. The very same sensor can be used to measure either the displacement or the amount of movement of an object by simply measuring the relative amounts of signal before and after the displacement. Displacement sensors are useful to determine if a mechanical motion has occurred, such as a piston movement. Optoelectronic sensors represent one of several technical solutions available to the appliance design engineer today. The advent of VCSELs as a new source within optoelectronics has opened up a new set of useful sensors that can be utilized to make more efficient and smarter appliances. < For more information, enter . . . . . . . . . . . . . . . . . . 304 Or email: Jim .tatum@finisar .com References 1. J. A. Tatum, “Vertical Cavity Surface Emitting Lasers: Packaging Propels VCSELs beyond Communications,” Laser Focus World, 2000. 2. J. A. Tatum and A. Lalonde, “VCSELs in Various Sensor Applications,” Sensors Expo Conference, 2007. 3. Light Scattering by Small Particles, H. C. Van de Hulst, Dover Press, 1981. 4. A. Boscolo and S. Stibelli, “A New Sensing Device for Washing Machines,” IEEE Transactions on Industry Applications, vol. 24, no. 3, pp 499-502 (1988). 5. L. Scalise, Y. Yu, G. Guiliani, G. Plantier, and T. Bosch, “Self-Mixing Laser Diode Velocimetry: Application to Vibration and Velocity Measurement,” IEEE Transactions on Instrumentation and Measurement, vol. 53, No. 1, pp. 223-232, 2004. For more Information Enter 115 www.applianceDESIGN.com AD02084CF.indd 1 applianceDESIGN February 2008 35 1/15/08 10:59:16 AM http://www.caereports.com http://www.caereports.com http://www.appliancedesign.com
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