Quantal Image Formation on the Retina Isn’t Quite Instantaneous!
December 8th, 2006 | 1 Comment »I have written in the last few comments about the introduction of time in considering the vision process. I termed the quantum limited image that forms on the retinal surface as being ‘instantaneous’ at least as viewed from the perspective of the brain that ‘looks back’ at the retina following the ‘time delay’ that the image signal encounters in traveling through the optic nerve. In reality even the quantal image formed on the retina can be (must be) even further sub-divided in time as I will express.
I have written about this before. There is a time difference in the formation of the three (RGB) Fourier transforms that constitute light interaction on the retinal surface. The first ‘red’ transform (detected by cone-cone appositions) travels the shortest most direct path to the central, millimeter diameter, all-cone fovea. The second exact mid-band or ‘green’ (detected by cone-rod appositions) is refracted to a longer path (the hypotenuse of the triangle) with peak intensity at ~ 7 degrees of retinal angle. The third ‘blue’ transform (rod-rod appositions) is refracted to an even longer path with intensity increasing at 15-20 degrees. The latter two wavelength transforms thus lag behind the initial long wavelength interaction. The image is formed ‘red first’ followed by the green and blue interactions on the retinal surface. These time differences will be very short indeed – in the femtosecond (or 10-15 sec) time domain – but there can be no argument that they must be present!
And then…do these three time delineated ‘signal packages’ that form the visual image travel separately along the optic nerve arriving at separate time at the visual cortex of the brain? Might such time delineation offer some insight into the way that the brain processes the visual image synthesizing the three transforms? Might there be some experiments to demonstrate this?
It occurs to me that I will define here for the reader who hasn’t gathered in this explanation of the vision process the three separate transforms that it becomes obvious that the retina detects:
1.) The central, all-cone fovea detects by means of cone-cone ‘optical antenna’ appositions the precise long wavelength end of the visual band. We term this ‘red’ as one of the ‘primary’ colors of vision. The retina is at the focal or Fourier plane (not the ‘image’ plane!) of the eye so that the Fourier transform effected at the fovea encodes the ‘outline sketch’ of the perceived image.
2.)The retinal angle of ~ 7 degrees, where cone-rod appositions reach their maximum density, defines the geometrically precise midpoint of the visual band. We term this ‘green’ as the second of the primary colors. A function comparing intensities on either side of this midpoint determines ‘color’ exactly as Edwin Land deduced!
3.) At retina angles of 15-20 degrees rod-rod appositions become predominant defining the ‘blue’ precise end of the visual band and the third of the primary colors. Beyond this retinal angle and to the peripheral retina I have proposed (and there is evidence of this) that rod receptors are connected in parallel (‘ganged together’) to form a ‘wide angle light meter’ that controls papillary constriction and light entrance into the eye.
It is important to note that these three bands encode light intensity at each of the three wavelengths! Wavelength differentiation traditionally thought to be a function of the retina is effected by light refraction within the eye – what has been (I believe erroneously) termed ‘chromatic aberration’. THREE BANDS OF RGB INTENSITY!
All of these factors fit together simply, logically (and beautifully) for anyone who takes the time to understand.
GCH
12/08/06
It is a pleasure to read such a clear and interesting explanation.
December 21st, 2006 at 12:15 pmI would like to ask what about the phase information in image forming process; the problem is crucial as it can solve a huge human discrepancy.