Complex structures focus reflected light: lobster
The eye of a lobster focuses reflected light onto the retina using a perfect geometric configuration of square tubes.
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"These well-arranged squares are in fact the ends of tiny square tubes forming a structure resembling a honeycomb. At first glance, the honeycomb appears to be made up of hexagons, although these are actually the front faces of hexagonal prisms. In the lobster's eye, there are the squares in place of hexagons.
"Even more intriguing is that the sides of each one of these square tubes are like mirrors that reflect the incoming light. This reflected light is focused onto the retina flawlessly. The sides of the tubes inside the eye are lodged at such perfect angles that they all focus onto a single point.
"The extraordinary nature of the design of this system is quite indisputable. All of these perfect square tubes have a layer that works just like a mirror. Furthermore, each one of these cells is sited by means of precise geometrical alignments so that they all focus the light at a single point." (Yahya 2002:11)
Lobster eye illustration. Artist: Emily Harrington. Copyright: All rights reserved. See gallery for details.
"It turns out that the square arrangement of the facet array (almost unique to the decapod crustaceans) is crucial here. The principle is that of the 'corner reflector' [like those mirrors found in corners of stores]…A ray reflected from the two mirrors must be rotated through a total of two right angles, which means that it will return parallel to its original direction, no matter what angle the ray initially makes with the mirror pair. In other words, apart from a slight lateral displacement of the reflected ray, a corner mirror behaves as though it were a single mirror, but one that is always at right angles to the incoming ray. This property turns out to be very useful, for example in radar reflectors for ships and buoys, and it is also the property that makes reflecting superposition possible…
"Various other features of these eyes are important for their function. The mirror boxes must be the right depth, two to three times the width, so that most rays are reflected from two of the faces, but not more. Rays that pass straight through are intercepted by the unsilvered 'tail' of the mirror boxes, and Vogt (1980) showed that its refractive index decreases in such a way that appropriate critical angle reflexion continues to occur through the clear zone. Finally, there is the weak lens in the cornea of the crayfish. This lens 'pre-focuses' the light that enters the mirror box, thus given a narrower beam at the retina. All these features provide an image generally comparable in quality to that produced by refracting superposition optics (Bryceson and McIntyre), although it does seem that rays which make too many or too few reflections contribute to measurable stray light (glare) in the image of on the retina." (Land and Nilsson 2002:172-174)
Organism/taxonomy data provided by:
Species 2000 & ITIS Catalogue of Life: 2008 Annual Checklist
Application Ideas: Cargo inspection devices, portable x-ray imaging applications for medical diagnostics, daylighting for buildings.
Industrial Sector(s) interested in this strategy: Security, medical, optics, constructionHotZone™ radiant heater, using IRLens™ - Radiant heaters inspired by lobster eyes