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camera to detect small objects

asked 2013-10-20 15:06:50 -0500

Ulrikop gravatar image

Hi, I'm looking for an adequate camera for a project of mine. As I am not very experienced in this field I ask you for your help.

I want to recognize and analyze lego bricks which are transported on a flat conveyor individually (using OpenCV of course). Therefore the lego brick is supposed to be as recognizable and sharp as possible in a close up with a distance of 10-20 cm. Additionally the color should not get falsified, so it remains distinguishable (for support I will take care of ideal lighting conditions - if somebody has any hints on this I would be very grateful too).

My program is running on Linux. There the camera should work without great effort, ideally with Plug and Play. Using OpenCV and Linux makes the control of the focus problematic in most cases. Which is why a manual focus would be of advantage,

In short: Which camera with manual focus is advisable for close ups of small objects?

Thanks for your help!

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answered 2013-10-20 15:58:07 -0500

antonio gravatar image

I think your question has more to do with selecting the right lenses for your camera. In the following link you can find a nice white paper that explains what lenses a camera should have, and what the right resolution of the camera should be, for a given application. It contains some examples too. It's all about working distance and maximum size (width/height) of the objects that you'd like to image: Choosing the right lenses

For a basic (and easy to follow) optics tutorial you can have a look here

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Thanks for the links to the information on the different lenses. That's a very interesting topic. But I am afraid that the prices for such camera-systems might easily rise very high. Or did you think if mounting such a lens onto any old webcam? Because of it being just a small project I would prefer a cheaper solution (about 120 Dollar at most). Ideally I would like to use a camera available in a normal electronics store. Does anyone have an advice on ready-made standard cameras?

Ulrikop gravatar imageUlrikop ( 2013-10-23 07:54:01 -0500 )edit

I'm afraid you cannot attach lenses to a standard webcam as the later comes with its onw lenses (which are usually wide angle lenses). What you can do though is to follow the instructions given in the first link I gave, and estimate what's the right focal length for your application. Then go and find a webcam with lenses of similar focal length. The tricky think is that very few webacams provide specifications for their lenses. You might have to ask the manufacturer then.

antonio gravatar imageantonio ( 2013-10-23 08:43:41 -0500 )edit
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Asked: 2013-10-20 15:06:50 -0500

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Last updated: Oct 20 '13