Nokia RM-12 Troubleshooting Instructions page 83

RM-12
Nokia Customer Care
For taking a white image uniformly lightened white paper or white wall can be used. One pos-
sibility is to use uniform light but make sure that camera image is not flickering when taking test
image. In case flickering happens try to reduce illumination level. JPEG image format can be
used for analyzing but image quality parameter should be set to 'High Quality'.
Black spots in image are caused by dirt particles trapped inside the optical system. Clearly vis-
ible and sharp edged black dots in image are typically dust particles on image sensor. These
spots are searched for in manufacturing phase, but it is possible that the camera body 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 the problem is present when the service
technician analyses the phone.
If dust particle is lying 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, grayish 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.
Figure 12: Effects of dust on optical path
If large dust particles get trapped on top of the lens surface in the cavity between camera win-
dow and lens, they will cause image blurring and poor contrast (see also item 'sharpness'). The
dust gasket between the window and lens should prevent any particles from getting into the
cavity after manufacturing phase.
If dust particles are found on sensor, this is classified as a manufacturing error of the module
and thus the camera should be replaced. Any particles inside the cavity between protection
window and lens have most probably been trapped there in assembly phase at Nokia factory.
Unauthorized disassembling of product can also be root cause for the problem. However, in
most cases it should be possible to remove the particle(s) by using clean compressed air. Nev-
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Page 81 Issue 1 11/2004