Pinhole

Part of speech: noun

Pronunciation: /ˈpɪnˌhoʊl/

Definitions

1. A minute hole created by a pointed object, which serves as an entrance for light in optical instruments while restricting other forms of illumination
2. A small aperture formed by piercing, utilized particularly in lenses to manage light entry while obstructing unwanted rays
3. A very small opening made by piercing that allows light to pass through in a controlled manner

Etymology: "Pinhole" is a plain compound: "pin" joined to "hole," with the first word naming the size and shape of the opening. A pin is a slender pointed piece of metal, so a pinhole is the tiny perforation a pin leaves behind when it pierces something. The word therefore describes a hole defined by the object that made it rather than by any measured dimension. That literal sense is the one that carried the word into optics. A pierced card or sheet with a very small opening can admit light while blocking most of the rays that would otherwise scatter across a wider aperture. This is why the term came to describe the simple lens-free device known as a pinhole camera, and why the same principle appears in any setting where a small opening is used to sharpen an image or limit light.

Synonyms: small hole, aperture