Nokia RM-484 Service Manual

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Contents

Nokia RM-484 Service Manual Manual pdf 144 page image

Image quality analysisPossible faults in image qualityWhen checking for possible errors in camera functionality, knowing what error is suspected significantlyhelps the testing by narrowing down the amount of test cases. The following types of image quality problemsmay be expected to appear:• Dust (black spots)• Lack of sharpness• Bit errorsIn addition, there are many other kinds of possibilities for bad image quality, but those are ruled out fromthe scope of this document since the probability of their appearance is small.Testing for dust in camera moduleSymptoms and diagnosisFor detecting these kinds of problems, take an image of a uniform white surface and analyse it in fullresolution. A good quality PC monitor is preferred for analysis. Search carefully, since finding these defectsis not always easy. Figure "Effects of dust on optical path" is an example image containing easily detectabledust problems.When taking a white image, use uniformly lightened white paper or white wall. One possibility is to useuniform 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 theimage quality parameter to ‘High Quality’.Black spots in an image are caused by dirt particles trapped inside the optical system. Clearly visible andsharp edged black dots in an image are typically dust particles on the image sensor. These spots are searchedfor in the manufacturing phase, but it is possible that the camera body cavity contains a particle, which maymove onto the image sensor active surface, for example, when the phone is dropped. Thus it is also possiblethat the problem will disappear before the phone is brought to service. The camera should be replaced if theproblem 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 areout of focus, and appear in the image as large, grayish and fading-edge 'blobs'. Sometimes they are invisibleto the eye, and thus the user probably does not notice them at all. However, it is possible that a larger particledisturbs the user, causing need for service.Figure 44 Effects of dust on optical pathRM-484; RM-485; RM-486Camera Module TroubleshootingPage 5 –10 COMPANY CONFIDENTIAL Issue 1Copyright © 2009 Nokia. All rights reserved.