Optical Encoders

Optical encoders measure motion, such as position, velocity, and acceleration in a variety of equipment and machinery. Disk encoders measure rotation and line encoders measure linear motion.

GM Nameplate creates film encoders by direct laser imaging, photographically by contact exposure of photographic film directly from chrome-on-glass or emulsion-on-film masters. Metal encoders are chemically or laser etched.


Metal and film are the most common encoder materials.

Glass is highly durable and capable of the highest resolution encoder, but also the most expensive.

Metal encoders are also highly durable but usually low resolution.

Film encoders, the most common and least expensive, feature high resolution and modest durability.

Encoder resolutions range from 20 (0.7874 L/mm) to 550 (21.654 L/mm) lines per inch (LPI) with line and space widths from .025" to .00091" (.635 to .023mm).

Glass masters can produce a maximum image size of 22.8 x 31.5 inches (579.12 x 800.10mm).

Standard film masters and Glass masters can produce a maximum image size of 22 x 26 inches (558.8 x 660.4mm).

Glass is the preferred material for masters, being both dimensionally stable and clear. Because glass masters represent a significant cost, film masters are often used during prototyping. Proofs created from film verify the master before production.

With our special imaging equipment, GM Nameplate can produce film masters up to 48 x 110 inches (1219.2 x 2794.0mm).


Encoders are fabricated with Class-A tooling and optically controlled punch presses to achieve the best tolerances and image registration.

Optically punched holes serve as the center mounting holes for encoder disks and as Class-A tooling registration holes.

With an upper limit of 1" (25.4mm) diameter, registration holes can be punched at the same diameter as the center hole to eliminate setting up two or more punches.

Most affected by the fabrication process is the Total Indicated Runout (TIR) of an encoder disk. With optical targets, TIR can be held to .0004" (0.010mm).

Final shape and interior holes fabricated by Class-A tools will hold tolerances of plus/minus .005" (0.127mm) and optically punched mounting holes plus/minus .001" (0.0254mm).