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.
Testing camera image sharpness
Symptoms and diagnosis
If pictures taken with a device are claimed to be blurry, there are five possible sources for the problem:
1 The protection window is fingerprinted, soiled, dirty, visibly scratched or broken.
2 The camera module has failed to focus correctly, producing a blurred image.
3 User has tried to take pictures in too dark conditions and images are blurred due to handshake or
movement. This is not a cause to replace camera module.
4 There is dirt between the protection window and the camera lens.
5 The protection window is defective. This can be either a manufacturing failure or caused by the user. The
window should be changed.
A quantitative analysis of sharpness is very difficult to conduct in any other environment than optics
laboratory. Therefore, subjective analysis should be used.
If no visible defects (items 1-4) are found, a couple of test images should be taken. Generally, a well-
illuminated typical indoor scene, such as the one in Figure "Good image taken indoors", can be used as a
target. The main considerations are:
•
The camera module has to be given time to focus correctly. Correct focusing is normally indicated with a
flashing icon or green bracket in the viewfinder. During focusing, the image in the viewfinder moves
slightly back and fourth, this is normal and shows that the lens unit is moving. During the movement a
faint sound can be heard from the camera head.
•
The protection window has to be clean.
•
The amount of light (300 – 600 lux (bright office lighting)) is sufficient.
•
The scene should contain, for example, small objects for checking sharpness. Their distance should be 1
– 2 meters.
•
If possible, compare the image to another image of the same scene, taken with a different device. Note
that the reference device has to be a similar Nokia phone.
There are several conditions in which AF operation is challenging for the camera module, i.e. failing from
time to time. These include:
•
Low light scenes and night mode
•
Scenes with low contrast
•
Fast-moving objects
AF operation is disabled on purpose in “night”, “landscape”, “sports”, and “video” modes. When using these
modes the lens is set to a predetermined focal position and isn’t moved during use.
Under low light and night mode the AF function is slower than under good light, it may even fail to find
correct focus position. Low contrast scenes or fast moving objects may also slow down or cause AF to fail.
This is normal operation, and is not a cause to replace camera.
RM-484; RM-485; RM-486
Camera Module Troubleshooting
Issue 1 COMPANY CONFIDENTIAL Page 5 –11
Copyright © 2009 Nokia. All rights reserved.
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