What are differences between CCDs used in scanners and CCDs used in cameras?

[sara.s]

What are differences between CCDs used in scanners and CCDs used in cameras? Do they have different sensitivity to light?

I have two electrical circuit for a CCD sensor used in scanner and a CCD sensor used in camera. the latest works even for lights far from the sensor, but the formest works only when a light source is sufficiently near to sensor. why?
:bang::bang::bang::bang:

 

[KlausST]

Hi,

best is to look at datasheets.

My assumptions:
* CCDs in scanners are linear (mechanical), all sensors in a row. Maybe 1024 seonsors in one row.
* CCDs in cameras are two dimensional: X * Y, maybe 1024 * 768
* CCDs in scanners are often only for gray scale. And they have three colored light sources (LEDs) only one ON at a time. maybe they change color within milliseconds.
* CCDs in cameras have sensors for red, sensors for green, sensors for blue. They can´t work with LEDs

I assume there are a lot of informations in the internet how scanners work and how cameras work.

Klaus

 

[sara.s]

Thaks for your answer.
But i have the most problem with the distance between light source and CCD sensor. One of my CCD (a linear colored CCD used in scanner)
, despite the other one (used in camera),
responds when the light sorce is so near to it
but it doesn't respond by moving the light sorce far from it!
what can this problem be related to?????

 

[KlausST]

Hi,

for sure it will respond. Somehow.

But what do you expect? And what is not like you expected.
Best if you give a draft, a table with values...(both: expected and reading)

Klaus

 

[sara.s]

Hi,

I have an experiment with this CCD in which
When the light sorce is so near to CCD, It indicates some output voltage on oscilloscope screen according to intensity of light on it's pixels. However, by moving the sorce light far from CCD, the output will equal to zero (i.e. dark ).
I want to know that this may be related to some restriction in the distance between light sorce and CCD (which used in scanners)
or some restriction in kind of light sorce?
I have used both a typical lamp (100 watt) and laser.
Do this CCDs works for specific distance between them and sorce or
Should i use some sorce such as xenon lamp (similar to scanners) to see the non-zero output voltage for any distance between sorce and CCD?

 

[KlausST]

Hi,

It´s just a question of brightness.
And brightness decreases with the square of distance...

So if you have 100% brightness at a dsitacnce of 10cm, then you have a brightness of 1% with a distance of 1m. (for a punctual light source. If you have a bigger light source then you have to correct for distance)


Klaus

 

[sara.s]

Thanks. According to the CCD's data sheet, response or sensitivity of this sensor isn't high.
Perhaps it needs some special optical system and a source with high intensity
such as xenon lamp (which used in scanners) to get better results.

I have another related problem:

My work is based on FPGA and VHDL. analog output of CCD sensor ,observed on oscilloscope screen, has below typical shape. but it acts reversely. that is, the differences between the reference level and data level will be max while dark source and it will be min (near to zero) while max of intensity of light source!!! I don't know why it act reversely...
Moreover, after the converting of analog to digital, the observed output of AFE is noisy in both states of dark source and light source.
can you help me?



https://obrazki.elektroda.pl/6714992000_1476961011.png

 

[Warpspeed]

If its just a bare camera CCD it will probably just see an overall washed out brightness level, essentially the same dc level for all pixels.
Probably not much to see on an oscilloscope.
Especially if the signal is ac coupled which charge coupled devices tend to be.

It may need a lens or pin hole to actually form an image onto the CCD so different pixels see different things. Don't really know, never played with one.

 

[sara.s]

because of low sensitivity of this CCD, I have some restriction about using optical system (mirrors and lens to focus light on CCD) with typical light source (such as typical lamp) which haven't sufficient intensity.

Do you say that I can't see some non-noisy digital output of a bare CCD ,without optical system?