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Seems like adapting the machine would be easier than trying to design a custom scanner from scratch. Depending on the volume I would at least look into contracting a company that makes scanners to make a custom model meant to fit in place of the old one. I would guess that trying to design something like that from scratch would require a lot of custom mechanical components which would get very expensive in small quantities. I don't see how you'd beat a company that already makes this sort of thing. Surely there are OEM scanner engine type modules meant for integration into customer equipment. Similar to the way early laser printers almost all had Canon engines inside.
Hey guys, give me some numbers. I will average them and from statistical point of view, we should get the correct number. You have all information I had when I started the project.
We didn't try usb cameras. There is a limited space available over and under the card in the machine, now there is 6 cm (but could be a little more). What distance would two (top and bottom) standard usb cameras need to output sharp image without distortion? And I also think it would not be easy to perfectly glue at least two video frames (it is not possible to take just one frame as part of the card is always hidden behind mechanism of the scanner) to obtain complete image of the card and not to distort any characters on the card (OCR is then used). And realtime. Another delay of one or two seconds is not very good. But I'm not expert in this area.
Distortion is not a big deal if you have a decent quality lens that doesn't have other problems (heavy chromatic aberration, for ex) - just calibrate the lens using e.g. a checkerboard pattern (do once and then store the calibration in a file) and then undistort images in software. The same could be done to deal with keystone correction if the camera isn't exactly perpendicular. If there is PC involved you have plenty of computational power to do this type of processing - it moves the complexity from hardware to software which may be easier to deal with. Libraries like OpenCV are a popular solution for this type of stuff. The distance problem can be handled e.g. using a wide-angle (fisheye) lens and/or a mirror. Both are fairly common tricks in these situations.
Good points, thanks. How much you think would be a suitable USB camera?
Illumination could also be challenging. The cards are shiny.
We are talking about a device with manufacturing cost of 80 - 90 USD of electronic part (image sensors, illlumination, motor, electronics). These machine vision cameras are out of the budget. If the client would consider going this way then the price of both cameras must be well under 50 USD. I guess webcam or some chinese camera module is the only solution but then resulting image quality would be questionable.
Approx 3 months of pure time.
That is damn fast, considering you had to do HW as well. That is generally the timeline for a POC with multiple engineers on a medium sized project.
Remember one of the reasons for in-house dev was avoiding cases where the manufacturer EOLs the whole scanner. You don't want to get yourself into the same issue by designing around a no name Chinese cam that may or may not exist anymore in 6 months, would be even worse.