Testing Camera Image Sharpness - Nokia RM-57 Service Manual

RM-57/58
Camera Module Troubleshooting
If a dust particle is lying on the infrared filter surface on either side, they are hard to locate because they are
out of focus, and appear in the image as large, grayish and fading-edge 'blobs'. Sometimes they are invisible
to the eye, and thus the user probably does not notice them at all. However, it is possible that a larger particle
disturbs the user, causing need for service.
If large dust particles get trapped on top of the lens surface in the cavity between camera window and lens,
they will cause image blurring and poor contrast. The dust gasket between the window and lens should prevent
any particles from getting into the cavity after the manufacturing phase.
If dust particles are found on the sensor, this is classified as a manufacturing error of the module and the camera
should be replaced. Any particles inside the cavity between the protection window and lens have most probably
been trapped there in the assembly phase at a Nokia factory. Unauthorized disassembling of the product can
also be the root of the problem. However, in most cases it should be possible to remove the particle(s) by using
clean compressed air. Never wipe the lens surface before trying compressed air; the possibility of damaging
the lens is substantial. Always check the image sharpness after removing dust.
See Also
• Testing camera image sharpness (Page 8–13)

Testing camera image sharpness

Context
If pictures taken with a device are claimed to be blurry, there are six possible sources for the problem:
1 The protection window is fingerprinted, soiled, dirty, visibly scratched or broken.
2 The photographed object is too close – the camera lens operates with distances from 40 cm to infinity. This
is no cause to replace camera module.
Issue 1
Figure 81 Effects of dust on optical path
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