A plane that runs perpendicular to the optical axis of a lens or mirror, passing through the focal point. In practical optical systems, this is the exact physical location where the film, camera sensor, or projection screen must sit to capture or display a perfectly sharp image.
Heard on the job
Make sure the sensor is seated exactly on the focal plane, or the entire image will be soft.
Related terms
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.
Focus
The point where light rays converge to form a sharp image, or the state of being sharply defined.