A geometric collection of light rays that share a common focal point, forming a narrow cone. In optical design, engineers trace these pencils through lenses and mirrors to calculate aberrations, focal lengths, and image sharpness. Unlike a broad beam, a pencil represents the specific light paths connecting one object point to one image point.
Heard on the job
The collimator is misaligned, causing the pencil of rays to hit the sensor at an oblique angle.
Also heard as
- pencil of rays
Related terms
Beam angle
The angle across a light's beam at which intensity has fallen to 50 percent of its center value.
Focal point
The specific point in space where collimated light rays converge after passing through a lens.
Optical axis
The imaginary straight line passing through the center of curvature of a lens or optical system.