Camera suggestions for monochrome LCD

[muks]

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I have done OCR, and I stand by my recommendation.  I would actually prefer about 3 pixels per pixel, but 2 will work okay.

You have to have enough detail to examine every pixel even if you are just looking for missing vertical lines, etc.  It is still pixel level details.

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Hey bruce didnt mean to prove you wrong but i just suggested webcam since i finished a recent project using that.I agree that u defenetly need to examine pixel level even then for obtaining consistency.Suggested webcam since cost is also a criteria. 

[muks]

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I do need to make minor measurements besides OCR such as detecting when the display intensity has been lowered. I'll be measuring when its at it lowest, darkest and in the middle. I will get the character count and pixel per character later (the specs and unit are not in front of me.

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I didnt see that coming bruce 

[BruceAmmons]

This really sounds like a project that requires a machine vision camera and a good quality lens.  A webcam just doesn't have the capabilities for this.  You want a grayscale camera with good resolution and low noise and control over gain, shutter speed, etc.

You might be able to use a webcam to prototype the system, as long as you aren't expecting too much.

Bruce

[Robert_Eastlund]

I agree with Bruce.  I would recommend a minimum of 2 x 2 pixels to define the smallest character feature that needs to be detected.  For example, the dot over the letter eye, or the gap separating the characters.  3 x 3 or 4 x 4 would be far more comfortable.  Further, the camera should be monochrome.  A color camera will fuzz up the edge information.

Assuming that the field of view is 6 (152.4 mm) and that the smallest feature is 1 mm, then a VGA camera should work well (152.4/4 = 0.2375 pixels per mm), http://www.graftek.com/pages/imb-11ft.htm.  The further the camera can be positioned away from the object, the better.  In this case, I will suggest a H0514-MP lens.  If you would like to discuss further, I can be reached at eastlund@graftek.com or 512-416-1099 x101.

-Robert Eastlund

[AnalogKid2DigitalMan]

Are LCD characters/pixels multiplexed? You may need a range of shutter speeds to experiement with to eliminate aliasing (ie sometimes you see CRT displays with horizontal lines and creeping areal intensities when redisplayed on cameras or video footage).

Not sure if this is a valid concern or not, have never tried it.

[muks]

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Are LCD characters/pixels multiplexed? You may need a range of shutter speeds to experiement with to eliminate aliasing

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Yup that is a valid point that needs to be considered