focal plane

American  

noun

Optics.

1. a plane through a focal point and normal to the axis of a lens, mirror, or other optical system.

2. the transverse plane in a telescope where the real image of a distant view is in focus.

---

focal plane British  

noun

1. the plane that is perpendicular to the axis of a lens or mirror and passes through the focal point

2. the plane in a telescope, camera, or other optical instrument in which a real image is in focus

---

Etymology

Origin of focal plane

First recorded in 1890–95

Example Sentences

The process was time consuming in instances when a worm left the focal plane of the camera, blurring the image, in which case Ran needed to click by hand to record its position.

From Science Daily

Zhang and his colleagues use an electronically tunable lens, or ETL, that changes the focal plane of the imaging system without moving parts.

From Science Daily

The researchers believe that their approach is especially effective when trying to understand what is happening in living systems with spatial structure, which can often exhibit background light outside the desired focal plane.

From Science Daily

Tiny robot arms position the ends of 5000 optical fibers to match the locations of galaxies on the telescope’s focal plane, and quickly reposition them when the telescope moves to different part of the sky.

From Science Magazine

They also designed a handheld device to store the images and created a miniaturized watch-type imaging interface with an adjustable focal plane and a screen display for displaying the images in real time.

From Science Daily