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[Reply #15 on:]

..where he prefaces the article with the following

Just like a dog walking on its hind legs one marvels, not that it is done well, but that it is done at all.

[Reply #16 on:]

No-one has yet said "it can't be done" for all values of "it", but LEDs are not designed to convert photons to current, so there is no particular attempt in the manufacturing process to make them so.
You're going to need a fair amount of amplification to do this, and that is going to be tricky and expensive in a large rectangular array, so the idea of making a linear array and scanning it either my moving the array, or by moving the image over it has a lot going for it.

See now that's an answer that helps me, I thought thats what an LED in a reading state did, it gave out a output voltage dependant on the input? (I am trying to read and understand this paper you gave me)

I understand a little bit more about what you mean by scanning, obviously that's not going to give me the 1/60th of a second I need, so it would have to be more like a cameras pixel area, 2D.

This is the sort of input sensor I was looking at:

http://uk.rs-online.com/web/p/photodiode/6548643/

Which has a very good spectral sensitivity to the visible light spectrum (and above) which I can filter out,

I can't find what sort of output that will give, but I assume it's just a voltage which I can measure and convert to a digital signal?

[Reply #17 on:]

Grumpy_Mike has some information on using LEDs as sensors - http://www.thebox.myzen.co.uk/Workshop/LED_Sensing.html

Yeah I seen that a littler earlier on, thanks.

[Reply #18 on:]

I dunno why you need to create your own sensor using large LEDs.  I would think adapting an existing vision system (web cam, pin hole camera, security camera, DSLR, etc.) would work better.  Or if you are still wanting to recreate a vision chip, you probably need to shrink it down, rather than using discrete components.  In any case, it is likely to get expensive.

A quick google shows the following project: http://www.ardueye.com/pmwiki.php?n=Main.HomePage, which uses Arduinos and sensors.  However, I can't figure from the site where to actually order the chips.

A big problem with using Arduinos is the lack of memory and the speed (or lack thereof) of the processor is not enough to process more than a really small size image.  If you want to process larger images you need to go to a chip with a larger memory system (and possibly floating point hardware depending on your processing), such as many ARM based chips.  Or by using single board computers.  Or use Android systems, using their camera.

If you still want to using the Arduino, the video experimenter shield (http://nootropicdesign.com/ve/) can take images from a camera producing an analog composite signal, and give your very low res. images.

Another thing is the HackHD camera PCB: http://www.hackhd.com/.

[Reply #19 on:]

Instead of trying to read 900 sensors at once why not read one sensor 900 times. Just mechanically move it from spot to spot. Sounds like something an arduino could pull off. Now it's a mechanically more challenging project but robotics is right up arduino's alley.

Your subject won't move so you can just leave the lens's shutter open. Move the sensor to a spot take a reading, trigger the flash if needed. Go to the next spot and do it again. Voila, a rudimentary scanning back.

Just a thought.

[Reply #20 on:]

Instead of trying to read 900 sensors at once why not read one sensor 900 times

As far as I know, the arduino only has one ADC, so you can only read one sensor at a time.

Think about this:
The ADC can do a reading in 0.1 ms. (10,000 reads/second). So 900 reads should take around 0.1 seconds, but you also have to work the sensor multiplexing (remember, only one ADC), store the data, do something with the data, and send the data to your output device.

Oh, and the Arduino only has 2K SRAM... That might be enough for one exposure.

No one is saying it can't be done. As a learning project it has merit. But it would be like watering your garden with a leaky thimble... it would take a while and not produce good results.

[Reply #21 on:]

The reason I am designing from scatch is over the past two years of my degree we've done probably 30 different experiments on all different types of sensors, we study the science behind imgaging. This would be for my final project and I feel that they have tough us everything we need to know to be able to make it logically work - but they haven't taught us is how to actually put a sensor together and practically go through the proccess, only theory - so i thought it would be a good idea.

However like I said I have no knowledge of the electronics, thinking about it now, I don't actualy have to use flash lighting, I can shoot under constant light for a longer duration.

 John when you say 2k, would that be during the total time of the exicutable program or would I be able to, and if this is in the right terms, read a sensor, run it through the ADC, save the data and move onto the next sensor, but empty the sdram between?