Image Bit Errors - Nokia RM-51 Service Manual

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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.
3 User has tried to take pictures in too dark conditions, and images are blurred due to handshake or movement.
This is no cause to replace camera module.
4 There is dirt between the protection window and 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.
6 The camera lens is misfocused because of a manufacturing error.
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.
• 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.
Steps
1. Take several images of small objects in the distance of 1-2 metres.
2. Analyse the images on a PC screen at 100% scaling with the reference images.
Pay attention to the computer display settings: at least 65000 colors (16-bit) have to be used. True colour
(24-bit, 16 million colours) or 32-bit (full colour) setting is recommended.
Next action
If there appears to be a clearly noticeable difference between the reference image and the test images, the
module might have a misfocused lens -> change the module.
Re-check the resolution after changing the camera module.
If the changed module produces the same result, the fault is probably in the camera window. Check the window
by looking carefully through it when replacing the module.

Image bit errors

Bit errors are image defects caused by data transmission errors between the camera module and the phone
baseband and/or errors inside the module.
Usually bit errors can be easily detected in images, and they are best visible in full resolution images. A good
practice is to use a uniform white test target when analysing these errors. The errors are clearly visible, colourful
sharp dots or lines in camera images. See the following figure.
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Camera module troubleshooting
9238460 (Issue 1)
RM-51