focal plane: meaning, definition, pronunciation and examples
Low-frequency / TechnicalTechnical / Scientific
Quick answer
What does “focal plane” mean?
The plane in an optical system where light rays from an object converge to form a sharp image.
Audio
Pronunciation
Definition
Meaning and Definition
The plane in an optical system where light rays from an object converge to form a sharp image.
In optics, photography, and astronomy, the flat surface where the image is in perfect focus. In particle physics, a detector plane in a particle accelerator. More broadly, a conceptual plane of primary focus or attention.
Dialectal Variation
British vs American Usage
Differences
No significant lexical or grammatical differences. Pronunciation of "plane" may show the slight /eɪ/ vs /eɪ/ (longer in RP) variance, but the term itself is identical.
Connotations
None; identical technical connotation in both varieties.
Frequency
Equally low-frequency and confined to technical fields in both UK and US English.
Grammar
How to Use “focal plane” in a Sentence
The [Noun: lens/mirror] forms an image on the focal plane.Adjust the [Noun: sensor/film] to coincide with the focal plane.The focal plane of the [Noun: telescope/camera] is [Adjective: flat/curved].Vocabulary
Collocations
Examples
Examples of “focal plane” in a Sentence
adjective
British English
- focal-plane array
- focal-plane shutter
American English
- focal-plane array
- focal-plane shutter
Usage
Meaning in Context
Business
Virtually never used.
Academic
Common in physics, engineering, and astronomy papers and textbooks. Example: 'The CCD sensor was positioned at the telescope's focal plane.'
Everyday
Extremely rare. Might be used by photography enthusiasts discussing equipment.
Technical
Core term in optics, photography, microscopy, and astronomy. Example: 'The focal plane shutter reduces image distortion at high speeds.'
Vocabulary
Synonyms of “focal plane”
Neutral
Weak
Vocabulary
Antonyms of “focal plane”
Watch out
Common Mistakes When Using “focal plane”
- Misspelling as *"focul plane" or *"focal plain".
- Using it as a verb (e.g., *'to focal plane something').
- Confusing it with 'focal length', which is a distance, not a plane.
FAQ
Frequently Asked Questions
It is a two-word compound noun, usually hyphenated when used as an adjective (e.g., focal-plane shutter).
Its use is almost exclusively technical. Metaphorical use in general language is very rare and would likely be understood only in context by a technical audience.
A focal point is a single point where rays converge. A focal plane is the entire flat surface, perpendicular to the optical axis, that contains all such focal points for objects at different distances (for a thin lens).
No. Simple lenses often have a curved focal plane (field curvature). Complex lens systems are designed to flatten the focal plane for use with flat film or sensors.
The plane in an optical system where light rays from an object converge to form a sharp image.
Focal plane is usually technical / scientific in register.
Focal plane: in British English it is pronounced /ˈfəʊkl̩ pleɪn/, and in American English it is pronounced /ˈfoʊkl̩ pleɪn/. Tap the audio buttons above to hear it.
Learning
Memory Aids
Mnemonic
Imagine a FOCAL PLANE as a flat sheet of glass (PLANE) where a camera lens FOCUSES (FOCAL) all the light to make the picture sharp.
Conceptual Metaphor
A CENTER OF ATTENTION IS A FOCAL PLANE (e.g., 'The debate placed economic inequality in the focal plane of public discourse.' - rare).
Practice
Quiz
What is the primary function of a focal plane shutter?