A hypercentric or pericentric lens is a

lens A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...

system where the

entrance pupil In an optical system, the entrance pupil is the optical image of the physical aperture stop, as 'seen' through the optical elements in front of the stop. The corresponding image of the aperture stop as seen through the optical elements behin ...

is located in front of the lens, in the space where an object could be located. In a certain region, objects that are further away from the lens produce larger

images An image or picture is a visual representation. An image can be two-dimensional, such as a drawing, painting, or photograph, or three-dimensional, such as a carving or sculpture. Images may be displayed through other media, including a project ...

than objects that are closer to the lens. This is in stark contrast to the behavior of the

human eye The human eye is a sensory organ in the visual system that reacts to light, visible light allowing eyesight. Other functions include maintaining the circadian rhythm, and Balance (ability), keeping balance. The eye can be considered as a living ...

or any ordinary

camera A camera is an instrument used to capture and store images and videos, either digitally via an electronic image sensor, or chemically via a light-sensitive material such as photographic film. As a pivotal technology in the fields of photograp ...

(both

entocentric lens An entocentric lens is a compound lens which has its entrance or exit pupil inside the lens.shadow A shadow is a dark area on a surface where light from a light source is blocked by an object. In contrast, shade occupies the three-dimensional volume behind an object with light in front of it. The cross-section of a shadow is a two-dimensio ...

cast by the object from the imaginary point of light. The closer an object gets to that point (the center of the entrance pupil), the larger its image will be. Reverse_perspective_portrait

This inversion of normal

perspectivity In geometry and in its applications to drawing, a perspectivity is the formation of an image in a picture plane of a scene viewed from a fixed point. Graphics The science of graphical perspective uses perspectivities to make realistic images in p ...

can be useful for

machine vision Machine vision is the technology and methods used to provide image, imaging-based automation, automatic inspection and analysis for such applications as automatic inspection, process control, and robot guidance, usually in industry. Machine vision ...

. Imagine a six-sided die sitting on a

conveyor belt A conveyor belt is the carrying medium of a belt conveyor system (often shortened to a belt conveyor). A belt conveyor system consists of two or more pulleys (sometimes referred to as drums), with a closed loop of carrying medium—the conveyor b ...

being imaged by a hypercentric lens system directly above, whose entrance pupil is below the conveyor belt. The image of the die would contain the top and all four sides at once, because the bottom of the die appears larger than the top.

References

* {{cite journal , title = A camera model for cameras with hypercentric lenses and some example applications , author = Markus Ulrich, Carsten Steger , journal = Machine Vision and Applications , volume = 30 , pages = 1013–1028 , date = 2019 , issue = 6 , doi = 10.1007/s00138-019-01032-w , doi-access = free Photographic lenses Machine vision

See also

References