Nokia 6630 Service Manual rm 1 08_camera_trouble

Nokia Customer Care

8 — Camera Module

Troubleshooting

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Nokia Customer Care Camera Module Troubleshooting

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Table of Contents

Introduction to camera module troubleshooting...............................................................................................................8–5

The effect of image taking conditions on image quality..................................................................................................8–6

Image quality analysis ..............................................................................................................................................................8–10

Testing for dust in camera module..................................................................................................................................8–10

Testing camera image sharpness.....................................................................................................................................8–11

Dirty camera lens protection window............................................................................................................................8–12

Image bit errors.....................................................................................................................................................................8–13

Camera troubleshooting flowcharts......................................................................................................................................8–13

Camera hardware failure message troubleshooting.................................................................................................8–13

Camera baseband HW troubleshooting.........................................................................................................................8–15

Camera viewfinder troubleshooting...............................................................................................................................8–17

Bad camera image quality troubleshooting.................................................................................................................8–18

List of Figures

Figure 76 Blurred image. Target too close..............................................................................................................................8–6

Figure 77 Blurring caused by shaking hands.........................................................................................................................8–7

Figure 78 Noisy image taken in +70 degrees Celsius..........................................................................................................8–8

Figure 79 Image taken against light.........................................................................................................................................8–8

Figure 80 Flicker in an image; object illuminated by strong fluorescent light...........................................................8–9

Figure 81 A lens reflection effect caused by sunshine........................................................................................................8–9

Figure 82 Good image taken indoors.....................................................................................................................................8–10

Figure 83 Good image taken outdoors..................................................................................................................................8–10

Figure 84 Effects of dust on optical path..............................................................................................................................8–11

Figure 85 Image taken with clean protection window....................................................................................................8–13

Figure 86 Image taken with greasy protection window.................................................................................................8–13

Figure 87 Bit errors caused by JPEG compression..............................................................................................................8–13

Figure 88 Example of differential amplitude. The differential amplitude in this figure is (96 mV + 140 mV) / 2 =

118mV..............................................................................................................................................................................................8–16

Figure 89 Example of common mode voltage. The common mode voltage in this figure is (980 mV + 860 mV) /

2 = 920mV.......................................................................................................................................................................................8–16

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Introduction to camera module troubleshooting

Background, tools and terminology

Faults 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 seriously

degraded.

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's image quality, and tells, for example, that the images are not sharp, it is fairly difficult to accurately test the device 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 or not. Some training or experience of a correctly operating reference device may be needed in order to detect what actually is wrong.

It is easy for the user to take bad images in bad conditions. Therefore the camera operation has to be checked always in constant conditions (lighting, temperature) or by using a second, known-to-be good device as reference.

When checking for possible errors in camera functionality, knowing what error is suspected significantly helps the testing by narrowing down the amount of test cases. The following types of image quality problems may be expected to appear:

• Dust (black spots)

• Lack of sharpness

• Bit errors

Terms

Dynamic range Camera's ability to capture details in dark and bright areas of the scene

simultaneously. 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 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 electronically 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 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-1 has a

1280 x 960 pixel sensor resolution. In some occasions the term resolution is used for describing the sharpness of the images.

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Nokia Customer Care Camera Module Troubleshooting

Sensitivity Camera module's sensitivity to light. In equivalent illumination conditions,

a less sensitive camera needs a longer exposure time to gather enough light in forming a good image. Analogous to ISO speed in photographic film.

Sharpness Good quality images are 'sharp' or 'crisp', meaning that image details are

well visible in the picture. However, certain issues, such as non-idealities in optics, cause image blurring, making objects in picture to appear 'soft'. Each camera type typically has its own level of performance.

The effect of image taking conditions on image quality

There are some factors, which may cause poor image quality, if not taken into account by the end user when shooting images, and thus may result in complaints. The items listed are normal to camera operation and are not a reason for changing the camera module.

Distance to target

The lens in the module is specified to operate satisfactorily from 40 cm to infinite distance of scene objects. In practice, the operation is such that close objects may be noticed to get more blurred when distance to them is shorter than 40 cm. The lack of sharpness is first visible in full resolution (1280 x 1024) images. If observing just the viewfinder, even very close objects may seem to appear sharp. This is normal; do not change the camera module.

Figure 76 Blurred image. Target too close.

The amount of light available

In dim conditions camera runs out of sensitivity. The exposure time is long (especially in the night mode) and the risk of getting shaken (= blurred) images increases. In addition, image noise level grows. The maximum exposure time in the night mode is ¼ seconds. Therefore, images need to be taken with extreme care and by supporting the phone when the amount of light reflected from the target is low. Because of the longer exposure time and larger gain value, noise level increases in low light conditions. Sometimes blurring may even occur in daytime, if the image is taken very carelessly. See the figure below for an example. This is normal; do not change the camera module.

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