Saturday, November 2, 2013

Vision & Perception ~ How Cones Work

How Cones Work

In regards to color vision, The Young-Helmholtz trichromatic model advocates the existence of, within the eye, three cone types with differing photosensitive pigments that determine what part of the visible spectrum of light; long, medium, or short waves, are being perceived.  Night vision utilizes rods, and color is irrelevant to rods.  However, this theory leaves many unanswered questions and paradoxical phenomenon.5
The most obvious unanswered question is why are the cones shaped like cones?  The Cone Spectrometer Model suggests that the tapered shape is fundamental to the workings of cones.  Light, focused on the retina by the eye’s optics, enters the photosensitive receptors, which are small, only marginally bigger than the wavelength of light.6
White light enters the wide opening, and then travels down the tapered shaft.  As the path narrows, only shorter waves can continue down the path, getting shorter and shorter as the path tapers.  The longest waves are shunted out first, i.e. for human perception, the Reds in positive light, then the Greens, finally the Blues.  This allows the cone to determine what length/color the wavelength is, based upon penetration depth.7

The following picture illustrates Spectral Dispersion in the Order Hemisphere.

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