Component manufacturing and placement accuracy/precision

Question

I am involved in a community project where I need to employ computer vision on common smartphone models (Samsung Galaxy S 5/6/7, iPhones etc.). Doing that involves calibrating the phone's camera for computer vision. People will be using their phones within the project and I wonder whether I may be able to calibrate the camera on given phone models myself and only supply calibration data to the users so they wont have to bother with a camera calibration themselves. The camera's focus will be fixed (probably to infinity).

I think the problem goes back to the smartphone's camera manufacturing precision - if it is good enough, a "pre-calibration" may be possible. The sensor placement within PCB and (autofocus) lens properties are probably in question here. Unfortunately I nave no experience with surface mount large-scale manufacturing process to judge on the precision. I guess the camera modules are probably supplied as a whole which I think could help to keep the precision (sensor and lens are enclosed in a single device which is then places on phone's motherboard?).

EDIT: Simply said - should all the cameras of the exact given model be physically same (both dimensions and placement of lens vs sensor, also same lens distortion) than a single calibration (or say an average from 10 calibrations on 10 various phone pieces of that same model) should be enough for the rest of the crowd (1000s of users) using that model.

Answer 1

Simply said - should all the cameras of the exact given model be physically same (both dimensions and placement of lens vs sensor) than a single calibration (or say an average from 10 calibrations on 10 various phone pieces of that same model) should be enough for the rest of the crowd (1000s of users) using that model.

So, first of all, I doubt you'll be able to figure out the exact given model – just because two phones look identical on the outside doesn't mean all the components inside are the same. Such phones are manufactured in large numbers, and supply for some of the components needed will be, by a skillful supply management, eventually be switched over, if economic or availability reasons require it.

Then: while I'd indeed expect the manufacturing tolerances of the opto-mechanic aspects of the cameras to be very close, these are not devices sold as calibrated camera systems (as you'd buy them if you were e.g. someone strapping a CV system onto a car). So, the manufacturer won't be spending calibration time on the cameras, and they will somewhat differ.

Then, the camera is somehow fixed inside your phone's enclosure. There's a range of ways of doing that: Gluing the camera to the case, soldering it onto the main PCB, connecting it with a flex cable, fixing it with elastic bands... So, that placement is absolutely not going to be as reliable for different models.

Then: Even if this works, you'll need to implement a calibration routine for one phone. The nice thing about software is: it inherently runs on all compatible computers, so you can run the same calibration on any phone. "Community Project" means that you can probably set up some calibration rig where you just strap your phone onto a well-defined holder, and then calibrate against your calibration target, get e.g. an OpenCV camera distortion matrix, and be done with it within seconds. And then, you'd be able to support any phone with sufficiently good camera!