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new to optics, need help please!

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/16/2008 at 05:03
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Optics GrassHopper
Optics GrassHopper

Joined: December/16/2008
Status: Offline
Points: 4
Hi there,

I found myself stuck to a simple question really. Trying to find a solution on my own doesn't guarantee a success. Therefore I would appreciate if any of you can offer me helps to solve the following questions.

1. how big a image a lens can see? You see, when you put the image at the focus of the lens, you get a collimated beam behind the lens, which is then focussed onto a ccd by another lens. Normally, I think this is determined by NA. I did  some calculation and found that the spot  size is much less than what the lens see. So, how can I know how big an area a lens can see. (given its focal length)

2. this is a related questio to question 1: how can I completely fill ccd? how to determine the focal length of the lenses necessary to fill completely the ccd area.

many thanks,
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/16/2008 at 09:48
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Optics Master
Optics Master

Joined: November/27/2004
Location: United States
Status: Offline
Points: 1436

Can't help you with the answers to your specific questions but, I do have a couple of thoughts that might help you in your search:

1.  It sounds to me like you are asking questions about cameras.  (Spotting scopes don't have CCD sensors Big Grin)  Therefore, you would likely have more success addressing your questions on a forum specific to cameras (and camera design).
2. When asking a question, you should be careful not to use abbreviations for technical terms that you have not specifically defined.  For example, what is "NA?"
3.  Although I admit to knowing only a very little (almost nothing in fact) about cameras, I am nevertheless unaware of any (digital) camera that allows for the kind of tinkering that it sounds like you are wanting to do - other than trying to find a specific lens for a given DSLR that would maybe offer some specific focal length that would "completely fill the ccd" - the value of which seems rather dubious.  Furthermore, if you already know how to do the necessary calculations to determine that the "spot size is much less than what the lens see[s],"  then you already have the ability to answer your question about "filling the ccd." 
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