Darren New nous apporta ses lumieres en ce 2007/11/17 19:45:
> Rune wrote:
>> A lot of preprocessing is done in the eyes themselves before the 
>> visual data is sent to the brain.
> 
> You'd be amazed. :-)
> 
>> For example, the eyes have an edge detecting layer I think, or 
>> something along those lines.
> 
> First a change detector layer, then from that a bunch of edge detectors, 
> then object detectors, then motion detection, then ...
> 
> Before it leaves you're eyes, they already know there's something large 
> coming towards you from the left. That info is hooked directly from eyes 
> to neck muscles.
> 
>> This layer could find all the edges of the bars in your image and send 
>> information about these edges on to the brain, so that the brain can 
>> tell how many bars there are. 
> 
> True.
> 
>> The eyes also send the actual "raw" brightness info on to the brain, 
>> but this may be in a "low resolution" where no more than 16 different 
>> shades can be told apart. 
> 
> Well, it's an analog pulse train. Actually, I'm not sure how far up the 
> pile before *you* decide it's no longer eyes and has become brain. I'm 
> also not sure if the cells that actually sense light are integrated into 
> anything at a higher level at all, or whether all their info is 
> processed before getting to the "brain" part.
> 
>> However, the brain can still count all the bars, becuase of the edges 
>> detected in the eyes.
> 
>> I'm not saying it's like that; just that your image doesn't prove 
>> anything about the amount of gray scales the brain can tell apart. So 
>> it really comes down to what you mean by "human visual system" - the 
>> eyes or the brain.
> 
> I think if you're picking out a monitor, you're worried about your 
> brain's perception of it. :-)
> 
Processing steps for human vision:
- retina catch light
- Raw image processing by the retina itself
- More image processing between the retina and the optical nerve
- Still more processing by the optical nerve (maybe the only nerve that have 
actual processing capability)
- Final gross processing by the brain
- Pattern recognition and image reconstruction
- Visual memory cross references image completion
I may have missed/myss ordered some steps...

-- 
Alain
-------------------------------------------------
There will always be beer cans rolling on the floor of your car when the boss 
asks for a ride home from the office.

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