Camera Module Troubleshooting - Nokia RM-12 Troubleshooting Instructions

Nokia Customer Care

Camera Module Troubleshooting

Background, tools and terminology
A fault or complaint associated to camera operation can be roughly categorized to three sub-
groups:
1 Camera is not functional at all, no image can be obtained
2 Images can be taken but there is nothing recognizable in them
3 Images can be taken and they are recognizable but for some reason the quality of
images is seriously degraded, or customer complains about image quality
Image quality is very hard to measure quantitatively, and even comparative measurements are
difficult (comparing two images) if the difference is small. Especially if the user is not satisfied
with his/her devices' image quality, and tells e.g. that the images are not sharp, it is fairly diffi-
cult to accurately test the device and get an exact figure which then would tell if the device is
OK or not.
Most often, subjective evaluation has to be used for finding out if a certain property of the cam-
era is acceptable or not. Some training or experience of a correctly operating reference device
may be needed in order to detect what actually is wrong, or is there anything wrong at all. It is
easy for the user to take bad looking images in bad conditions; thus the camera operation has
to be checked always in constant conditions (lighting, temperature) or by using a second,
known to be good device as a reference. Experience significantly helps in analyzing image
quality.
Terms
Dynamic range: camera's ability to capture details in dark and bright areas of the scene si-
multaneously. See Image which has been taken against light. The actual object is dark for ex-
ample.
Exposure time: camera modules use silicon sensor to collect light and for forming an image.
The imaging process roughly corresponds to traditional film photography, in which exposure
time means the time during which the film is exposed to light coming through optics. Increasing
the time will allow for more light hitting the film and thus results in brighter image. The operation
principle is exactly the same with silicon sensor, but the shutter functionality is handled elec-
tronically i.e. there is no mechanical moving parts like in film cameras.
Flicker: Phenomenon, which is caused by pulsating in scene lighting, typically appearing as
wide horizontal stripes in image.
Noise: Variation of response between pixels with same level of input illumination. See e.g.
Noisy image taken in +70 degrees Celsius for example of noisy image.
Resolution: Usually the amount of pixels in the camera sensor, e.g. this product has 1152 x
864 pixel sensor resolution. In some occasions the term resolution is used for describing the
sharpness of the images.
Sensitivity: camera module's sensitivity to light. In equivalent illumination conditions, a less
sensitive camera needs longer exposure time to gather enough light for forming a good image.
Analogous to ISO speed in photographic film.
Issue 1 11/2004 Copyright©Nokia. All rights reserved
RM-12
Page 72