Image Quality Analysis - Nokia RM-57 Service Manual

RM-57/58
Nokia Customer Care Camera Module Troubleshooting
Figure 80 Camera module bottom view including serial numbering
The camera module as a component is not a repairable part, meaning that the components inside the module
may not be changed. Cleaning dust from the front face is allowed only. Use clean compressed air.
The camera module uses socket type connecting. For versioning, laser marked serial numbering is used on the
PWB.
The main parts of the module are:
• Lens unit including lens aperture.
• Infrared filter; used to prevent infrared light from contaminating the image colors. The IR filter is glued to
the EMI shielded camera body.
• Camera body; made of conductive metallized plastic and attached to the PWB with glue.
• Sensor array including DSP functions is glued and wire-bonded to the PWB.
• PWB, FR-4 type
• Passive components
• Camera protection window; part of the phone cover mechanics
• Dust gasket between the lens unit and camera protection window

Image quality analysis

Testing for dust in camera module
Context
For detecting these kinds of problems, take an image of a uniform white surface and analyse it in full resolution.
A good quality PC monitor is preferred for analysis. Search carefully, since finding these defects is not always
easy. Figure "Effects of dust on optical path" is an example image containing easily detectable dust problems.
When taking a white image, use uniformly lightened white paper or white wall. One possibility is to use uniform
light but in this case make sure that the camera image is not flickering when taking the test image. In case
flickering happens, try to reduce illumination level. Use JPEG image format for analysing, and set the image
quality parameter to 'High Quality'.
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.
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