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I recently wrote an automated firmware test for a handheld oscilloscope, where I obtain screenshots using its own screenshot feature, then process the images using OCR software.

Now I am requested to port this test to handheld Digital Multimeter. Something that looks like this.

Problem is HHDMM doesn't have a built-in screenshot feature. So I plan to attach a camera on top of the screen to obtain screenshot images. The images must then be automatically retrieved by PC for further processing.

I have no previous experience or knowledge regarding camera selection for this type of purpose. Can anyone educate me about that?

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Some from experience, I am not a camera expert in any way-

Cameras have a few features you care about plus some eco system concerns.

Interface- "webcam" USB cameras, standalone cameras with card or USB interface to pull images from but doesn't allow control over shooting (capture, start, stop, zoom) and then there all kinds of hybrids or more professional cameras.

Image- resolution (even 640x480 could be enough to identify screen reading from an HHDMM), frame rate of video (you'll need high FPS for video, low numbers will probably do fine for your case), compression or lack of (I suppose you have no need for RAW images, but smaller png's could be a plus), color depth

Physical properties- lens quality and characteristics (aka zoom or auto focus), physical size and attachments (can you add a tripod ?)

Software- on and off the camera, API or software suite on a connected PC, image processing online or offline, software drivers and support

Price...

In your case I really think that a cheap webcam is more than enough, then use some code to capture images.

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  • Thank you for the analysis. I guess my biggest concern right now is to how to programmatically control it using C#. I have found Versatile, do you know something similar to that?
    – Liren Yeo
    Commented Nov 3, 2015 at 2:14
  • unfortunately no
    – Rsf
    Commented Nov 3, 2015 at 11:48
  • @Liren, I tried a decent webcam, not low end, but still very cheap, 640x480 30 fps webcam. To do image capture and image recognition with SikuliX, it was not good enough. Even with (admittedly naive, hand coded) filtering and 30x supersampling of the image, there is so much noise, that SikuliX can not recognize any icons or anything at all of the captured screen. (One must also get rid of reflections and glare, but that is another story...) I believe it can be done, but maybe it is too hard for me. The image must be cleaned of noise somehow... that kind of signal processing is above my league
    – Prof. Falken
    Commented Jun 28, 2017 at 7:05

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