You have probably heard of polaroid sunglasses which reduce glare. You may also know that if you rotate the glasses (or your head while you're wearing the glasses) the glare becomes stronger. This is because the sunglasses reduce glare in only one dimension. Light waves can have any orientation. Like waves in a pond, light waves can move upward and downward as the light travels forward. But unlike waves in a pond, light waves can also move from left to right and back, as the light travels forward. These two orientations are referred to as vertically and horizontally polarized light, respectively. But light is not restricted to one or the other--in general a light wave consists of both a vertical and a horizontal component. Purely vertical and horizontal light waves are special cases. And if you combine the vertical and horizontal components you obtain a wave that rotates as it travels forward. For example, the wave can rotate in a circle. But again, this is special case. In general, a light wave maps out an ellipse as it travels forward.
If all of this is confusing, don't worry. All you need to understand is the general idea that light waves can be polarized in different, complicated ways. These concepts are important to engineers and physicists who, for example, work in communications. Television and radio station transmitters and antennae, cell phones and transmitters, and the many other conveniences we enjoy are all carefully designed incorporating these concepts. For instance, CD and DVD players need to convert the vertically or horizontally polarized light to circular polarization.
But once again, after we understand and develop a new technology we find it was present all along in nature. In this case, mantis shrimps not only control the polarization of light waves, but they do it better than our best devices. The CD and DVD players, for instance, use a quarter-wave retarder that converts the polarization but only at a single color of light. The mantis shrimp makes the conversion across a broad spectrum of colors. Here is the abstract of a recent paper on the exploits of the mantis shrimp:
Animals make use of a wealth of optical physics to control and manipulate light, for example, in creating reflective animal colouration and polarized light signals. Their precise optics often surpass equivalent man-made optical devices in both sophistication and efficiency. Here, we report a biophysical mechanism that creates a natural full-visible-range achromatic quarter-wave retarder in the eye of a stomatopod crustacean. Analogous, man-made retardation devices are important optical components, used in both scientific research and commercial applications for controlling polarized light. Typical synthetic retarders are not achromatic, and more elaborate designs, such as, multilayer subwavelength gratings or bicrystalline constructions, only achieve partial wavelength independence. In this work, we use both experimental measurements and theoretical modelling of the photoreceptor structure to illustrate how a novel interplay of intrinsic and form birefringence results in a natural achromatic optic that significantly outperforms current man-made optical devices.
You can go here for a good description of the amazing mantis shrimp (optics is not its only speciality) and its most advanced vision system.
And what does evolution have to say about this? Only that it all evolved, somehow. Some mutations happened to occur, fantastic new designs emerged, and they stuck.
As silly as that sounds, it gets worse. As we have discussed before, the amazing optics hardware is only one of the essential components of the design. Without the processing logic and hardware, and behavior algorithms that use the processed signals, the upfront optics hardware, as fantastic as it is, is as useless as a jet engine is without the jet.
