Optodetectors have high resolution

Supplied in a fixed U-shaped housing, EE-SX1 series transmissive nonamplified optodectectors have aperture widths of 0.15 to 0.5 mm for high-resolution motion and position detection. Units pair an IR LED with a phototransistor, and come in SMD, through-hole, and panel-mount (with connector) styles.

Devices are available in packages as small as 3.0 x 3.0 x 3.4 mm with slots widths ranging from 1 to 5 mm. The SMD version operates in a typical range of -30° to 85°C, the through-hole -25° to 85°C, and the panel-mount -20° to 70°C. (From $0.50 to $1.10 ea/10,000—available from stock to 10 weeks ARO.)

Omron Electronic Components , Schaumburg , IL
Information 847-882-2288
http://www.components.omron.com/PMS.shtm