What is the scan rate for a human eye?
How long does it take from the moment the light hits the cells in the back of our eye to when the signal reaches the appropriate region of the brain. ie. How fast does the cells change light into an electrical signal and how fast does the signal travel through the optic nerve? How effient are those cells? Could they be grown on mass via genetic engineering or other means in order to create usable electrical current?
PerfectDark
I don’ t know what the nerve conduction speed is.
As for the “scan rate” of the eye, if something flashes faster than about 60 Hz, we see it as continuous light. If it’s slower, we can generally tell that it’s flashing. So I guess you could say that’s roughly the “scan rate.” Some people are more sensitive than others, and also, the peripheral vision is more sensitive than the center of the field. I hear this is because the peripheral vision was primarily for detecting approaching predators, so it’s more sensitive to movement.
IIRC, from a show (on the discovery channel?):
The eye sees in real time (minus the speed of light but lets not go there) but the brain takes time to process the image. So we actually ‘see’ things that are slightly late - somehow the brain adds a corection factor to make us think we are seeing realtime - some sort of premtive processing.
I think that the actual rate is somewhat dependant on viewing conditions. For the cinema the standard figure is 47 Hz so that the projector runs at 24 frames/sec with a double shutter which shows each frame twice which makes 48 Hz. Certainly for computer monitors anything < 60 Hz can give you a headache.
I’m surprised that no-one has mentioned persistance of vision.
You can ‘see’ things a moment after they have vanished.
I’m afraid I don’t know how long the image is retained for but I guess it could be for quite some time if camera flashguns are anything to go by.
Tell you what though it has made me wonder a little about the gypsy legend that the eye retains the last image just before death and that some individuals can ‘see’ into it.
As for the tv thing, screen phosphers glow when struck by high energy particles but it takes time for it to be dissipated.
If you mange the trick of charging your body up with static electricity and slide your finger across the tv screen you will see an illuminated trail follow your excited digit.
Differnat pesistance phopshors are used in differant applications, radar displays have far longer ones than say computor monitors.
It DOES take each rod or cone time to process and “reset”, but I’m not at any of my references now. I’ll see what I can find later.
The interesting differences between the human eye and a TV camera are that: A.) The “detector elements” of the eye are not arranged in regular rows, like those of a TV camera and B.) I don’t think that the eye’s receptors “scan” sequentially, like a TV camera does. As a result, you don’t get the same “beating” and aliasing problems with the eye that you do with TV. Nevertheless, the process of receiving a signal and re-setting the detector does take time, in either case, so there’s something analogous to a “scan rate” for the eye.