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why you need such sensor , you can the send charector in read mode.
is i right ? or else you want the other think .
actually i am not get the que .
basically what is your need be more specific.
yup..i could send it over the bus..thing is i wana read the characters on existing LCDs..and of course the LCD is inside a casing..so i was thinking of a photo/light based sensor..is it possible?
Yes, I'm pretty sure it is possible, as almsot anything is these days. But....it would almost certainly involve the use of a CMOS camera and HEAVY processing (google OCR...optical character recognition). Although, your job would be easier, considering its reading an LCD, and not handwriting...so you've only got a few pixels to read, with (almost) standard character patterns...and they are simply ON, or OFF. That is off course assuming you want to 'read' just one type of LCD, so your LCD reader need only be designed for that one display.
In fact, if that really is the case...I would still say you'll need a CMOS camera..as opposed to what I usually suggest, which would be true DIY....... like...
[useless idea]
Imagine a phototransistor for each pixel, use a lens (or a 'cone', big end on the detector) to make the tiny area of each pixel 'shine' on each detector, then 'scan' across your sensor. You could move this across the LCD, in sections of one character length, so you only need one 'array', or just build many. Can be done with a simple PIC micro...and a LOT of time.
[/useless idea]
But...with a CMOS camera, the processing wouldn't be that bad really. Probably need an ARM micro at least. And then you would probably need to scan a few times in quick succession...because LCD's multiplex, so a single quick snap shot might not show all the on pixels 'on'. Failing that, CMOS camera + PC would do it.
However, all that is compeltely over the top if you can somehow get into your 'case' where the LCD is. As someone already suggested... once you have access to the bus, its easy. You wouldn't need to 'read' the display itself, just what commands its getting. But, bear in mind you'll have to keep up with it, as most character LCD's auto increment the DRAM address (next character placeholder), so after every character written, you'll have to increment your own counter to keep up.
I must say, its a pretty bizare question really, but challenge nonetheless
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