By incorporating a laser source and detector array on the same chip, engineers at MicroE Systems have produced an optical digital encoder they claim is the world's smallest (6 mm square by 4 mm high) at a cost that will allow their use in mass production products, such as printers and copiers, as well as stepper motors.
The ChipEncoderô uses a vertical cavity surface emitting laser (VCSEL) to generate a precise beam to reflect off a moving microetched scale onto a detector array beside the laser on the same hybrid circuitódetermining position or velocity. The reflected beam is diffracted, creating a wide region of interference, within which the detector operates. This large interference zone enables wide tolerances so that no alignment is necessary after final assembly, says William Manning, marcom manager. Four factory pre-set resolutions (interpolation levels) range from 3,300 to 160,000 counts/revolution and 100 to 1,000 counts/millimeter. Engineers choose a VCSEL for its longer life and better performance compared to more common edge-emitting lasers.
The same chip-scale encoder package can be used with a linear or rotary reflective scale, with a built-in index mark, which increases production volume and helps drive down costs (in OEM quantities, the encoder's price is $49). The encoder produces a three-channel differential output with reference pulse for home-position determination. Cost is also held down by specifying one of four interpolation methods as opposed to making them integer selectable as on MicroE Systems more precise but larger, industrial-shielded programmable encoders.
As a non-contact, optical device, the ChipEncoder has zero wear, backlash, and hysteresis. The surface-mount package is compatible with automated manufacturing equipment, including pick-and-place and solder-reflow systems.
CONTACT:William Manning, MicroE Systems Tel (800) 355-4047; Fax (508) 655-7084; e-mail: firstname.lastname@example.org://rbi.ims.ca/3845-501
System on a chip: The 6 mm2x4mm high
ChipEncoder allows motion control to fit in tight volumes. It is low
costs, due in part to the same device being suitable for linear and
rotaryconfigurations, which facilitates use in such products as office
equipment printers and copiers.