User Guide

Black spots in an image are caused by dirt particles trapped inside the optical system. Clearly visible and

sharp edged black dots in an image are typically dust particles on the image sensor. These spots are searched

for in the manufacturing phase, but it is possible that the camera body cavity contains a particle, which may

move onto the image sensor active surface, for example, 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 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.

Figure 26 Effects of dust on optical path

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.

RA-6

Camera Module Troubleshooting

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