How Is a Dark Frame Taken in CCD Cameras?

[Pingona]

Hello,

I have two question regarding CCD camera technology.

How is a dark frame(image) taken ? ( Is this simply the state of the pixel array when the shutter is in close position?

How can one determine the camera efficiency as a function of energy from energy dependent measurements? What data or parameters should I look into for this analysis.

Thank you

 

[berkeman]

Hello,

I have two question regarding CCD camera technology.

How is a dark frame(image) taken ? ( Is this simply the state of the pixel array when the shutter is in close position?

How can one determine the camera efficiency as a function of energy from energy dependent measurements? What data or parameters should I look into for this analysis.

Thank you

What is the context of your question? Is this for research, or industrial application, or a school report? What reading have you done up to now, and can you point us to some of those information resources?

 

[Pingona]

Research work. I am reading the book by James Jainseck on CCD technology. what we have is images from a CCD camera

 

[mgb_phys]

How is a dark frame(image) taken ? ( Is this simply the state of the pixel array when the shutter is in close position?

Yes, you generally want to take a dark with the same exposure as the real image.

How can one determine the camera efficiency as a function of energy from energy dependent measurements?

if you mean the Quantum Efficiency then you need a standard brightness source (or another calibrated camera to compare it against).
Charge transfer efficency you can do with an iron 55 source, the radiation creates a fixed number of electrons per event - you can then measure the measured signal in adjacent pixels.

You can also use the fe55 to measure the gain (numbers in your image compared to real electrons in the CCD) - there is also a signal variance technique you can do with real data

I don't know how easy it is to get online but there is an excellent review of CCDs in "MacKay, C.D. 1986, Annual Review Astronomy&Astrophysics 24, 255, “Charge-coupled devices in astronomy” it's a lot more readable than Janesick's book