HI Steve O
Yes the flying spot environment room does have to be dark depending on what your doing it depends but on the amount of flying spot light you have and how light in colour the flying spot light is reflecting back to the sensor doing the scanning it was even pushing it for me with my PMT ,i had to do the reflective off objects work at night lights off ,my scope is very weak after its projected at a distance .
So Gebseng you will have to experiment a lot what works i would go test cards first work your way up to televising people .
Here's one of my sons via scope flying spot and PMTpick up .......when you get yours working the quality will be many times better think these were on 64 line
gebseng wrote:Thanks Keith and Harry for the very useful explanations and examples!!!
The setup with a photographic lens seems easy to do and straight forward, I will keep you updated on my results. I don't think I can use a laser duo to safety issues, since it would be shining into people's eyes directly when scanning a face.
About the solar cells: My understanding is that a solar cell is more or less the same as a photo diode. But opposed to a photo diode, which is engineered to have high sensitivity/low dark current and is used in reverse bias for quick response time, the solar cell is optimized to generate as much energy as possible. So, the question is if a solar cell still has a response time at least in the 500kHz range, which I would need for my resolution. Do you have any experiences or suggestions with that, before I start experimenting? E.g. should I start with amorphous, monocrystalline or polycrystalline cells?
best,
geb
Hi Gebseng
That's ok i think you sort of get the idea of a set up on the flying spot scanner one of those things once you see it going its easier
I like you are pushing the Nipkow to this line rate and size of the thing !.
Its not that one is more sensitive than the other and you want a sensitive device for you head amp ...but the surface area pick up is very important i tried lens in in front of photo diodes and such but for that idea at the time it ended up being solar solar cells my limits of know how at the time ...
A Fresnel lens would be another idea in front of a photo diode or bank of photo diodes ...just need to get that surface area pickup evenly or it will go from once extreme to the other picking up your light signals .
As far as the bandwidth go's Steve 0 has done light transmitting on higher bandwidths had to ask him on he's pick up device.
Solar cells have a bandwidth where they are sensitive more or less to different light wave lengths so 500khz would be nothing to it but i understand the response time is something to take into account and i have only ever worked them in audio frequencies ..if you could modulate a led at this frequency ? and connect a scope to the cell ,suppose they have oscilloscopes in this range and have a look ...again i have only done this at audio frequencies .
As far as which cells are better than another i your guess is as good as mine due the sensitivity on the dome sensor which seems to be a tiny solar cell i tried it but again surface area still to small using just one donated via Gary as i did.
http://www.excelitas.com/Lists/Photodio ... aspx?ID=46As far as lasers i took the lens off mine so no beam the light dot seen via the last photos posted were pointing adjusting the distance of the defocused laser to the line scan size via the back of the nipkow disk and then a lens.....here photo below is it with the nipkow removed really just a very bright torch light circle grows larger with distance like this ..I can understand the worry with a laser but it is defused light more than likely safe enough now behind a nipkow scanning .