Nokia RM-42 Service Manual

Also see for RM-42: Service manual

Contents

Introduction to camera module troubleshootingBackground, tools and terminologyFaults or complaints in camera operation can be roughly categorised into three subgroups:1 Camera is not functional at all; no image can be taken.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 seriouslydegraded, or customer complains about image quality..Image quality is very hard to measure quantitatively, and even comparative measurements are difficult(comparing two images) to do, if the difference is small. Especially if the user is not satisfied with his/her device'simage quality, and tells, for example, that the images are not sharp, it is fairly difficult to accurately test thedevice and get an exact figure which would tell whether the device is functioning properly.Often subjective evaluation has to be used for finding out if a certain property of the camera is acceptable ornot. Some training or experience of a correctly operating reference device may be needed in order to detectwhat actually is wrong, or is there anything wrong at all.It is easy for the user to take bad images in bad conditions. Therefore the camera operation has to be checkedalways in constant conditions (lighting, temperature) or by using a second, known-to-be good device asreference. Experience helps significantly in analysing image quality.TermsAutofocus Camera module contains lens movement mechanics for focus adjustment.Autofocus enables camera to take sharp images of objects positionedbetween 10cm to infinity. During AF the viewfinder image will bemomentarily blurred as the camera searches for the right focus setting.Dynamic range Camera's ability to capture details in dark and bright areas of the scenesimultaneously. See "Image taken against light (Page )" for an example.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 tolight coming through optics. Increasing the time will allow for more lighthitting the film and thus results in brighter image. The operation principleis exactly the same with silicon sensor, but the shutter functionality ishandled electronically i.e. there is no mechanical moving parts like in filmcameras.Flicker Phenomenon, which is caused by pulsating in scene lighting, typicallyappearing as wide horizontal stripes in an image.Noise Variation of response between pixels with same level of input illumination.See "Noisy image (Page )" for an example.Resolution Usually the amount of pixels in the camera sensor; for example, RM-42 hasa 1600 x 1200 pixel sensor resolution. In some occasions the term resolutionis used for describing the sharpness of the images.Sensitivity Camera module's sensitivity to light. In equivalent illumination conditions,a less sensitive camera needs a longer exposure time to gather enough lightin forming a good image. Analogous to ISO speed in photographic film.RM-42Camera Module Troubleshooting Nokia Customer Care9241872 (Issue 1) Company Confidential Page 8–5Copyright ©2005 Nokia. All Rights Reserved.