User Guide

Nokia Customer Care 6(a) - Baseband Troubleshooting

Company Confidential RH-51/52, RH-67/68

Image quality analysis

Possible faults in image quality

When checking for possible errors in camera functionality, knowing what error is sus-

pected will significantly help the testing by narrowing down the amount of test cases.

The following types of image quality problems may be expected to appear (in order of

appearance probability):

• Dust (black spots)

• Lack of sharpness

• Bit errors

In addition, there are many other kinds of possibilities for getting bad image quality, but

those are ruled out from the scope of this document since probability of their appear-

ance is going to be minimized by production testing.

Testing for dust

For detecting this kind of problems, take an image of uniform white surface and analyse

it in full resolution; search carefully – finding these defects is not always easy. See the

following figure.

Effects of dust in the optical path are an example of image containing easily detectable

dust problems.

Black spots in image are caused by dirt particles trapped into the optical system: clearly

visible and sharp edged black dots in image are typically dust particles on the image sen-

sor.

These spots are searched for in the manufacturing phase, but it is possible that the lens

holder cavity contains a particle, which may move onto the image sensor active surface,

e.g. when the phone is dropped. Thus, it is also possible that the problem will disappear

before the phone is brought to service. The camera should be replaced if it has been in

some phase verified that the problem has been present.

If dust particles are located on infrared filter surface on either side, they are much harder

to locate because they will be out of focus, and appear in image as large, greyish and

fading-edge ‘blobs’. Sometimes they will be very hard to find, and thus the user probably

will not notice them at all since they do no harm. But it is possible that a larger particle

disturbs the user, causing need for service.