Nokia N70 Service Manual 8 camera module troubleshooting

RM-84/99

Nokia Customer Care Camera Module Troubleshooting

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Table of Contents

Introduction to camera module troubleshooting................................................................................................................1–5

The effect of image taking conditions on image quality...................................................................................................1–6

Image quality analysis ...............................................................................................................................................................1–10

Testing for dust in camera module...................................................................................................................................1–10

Testing camera image sharpness......................................................................................................................................1–11

Dirty camera lens protection window.............................................................................................................................1–12

Image bit errors......................................................................................................................................................................1–13

Camera troubleshooting flowcharts.......................................................................................................................................1–13

Back camera troubleshooting.............................................................................................................................................1–13

Camera hardware failure message troubleshooting............................................................................................1–13

Camera baseband HW troubleshooting.....................................................................................................................1–15

Camera viewfinder troubleshooting...........................................................................................................................1–16

Bad camera image quality troubleshooting............................................................................................................1–17

RM-84 front camera troubleshooting...............................................................................................................................1–18

Front camera hardware failure message troubleshooting.................................................................................1–18

Front camera HW baseband troubleshooting.........................................................................................................1–19

Front camera viewfinder troubleshooting...............................................................................................................1–21

Front camera bad image quality troubleshooting.................................................................................................1–22

Flash LED troubleshooting.........................................................................................................................................................1–23

Introduction to flash LED troubleshooting.....................................................................................................................1–23

Flash LED and image taking conditions...........................................................................................................................1–23

Flash LED construction...........................................................................................................................................................1–27

Analysing image quality.......................................................................................................................................................1–28

Possible faults in image quality...................................................................................................................................1–28

Testing flash module functionality.............................................................................................................................1–28

Testing image colours with flash................................................................................................................................1–29

Testing flash power..........................................................................................................................................................1–29

Flash LED troubleshooting flowcharts..............................................................................................................................1–30

Bad image quality when using flash LED..................................................................................................................1–30

Flash LED indicator mode troubleshooting..............................................................................................................1–30

Flash LED HW baseband troubleshooting.................................................................................................................1–31

List of Figures

Figure 1 Blurred image. Target too close................................................................................................................................1–6

Figure 2 Blurring caused by shaking hands............................................................................................................................1–7

Figure 3 Near objects get skewed when taking images from a moving vehicle........................................................1–7

Figure 4 Noisy image taken in +70 degrees Celsius.............................................................................................................1–8

Figure 5 Image taken against light...........................................................................................................................................1–8

Figure 6 Flicker in an image; object illuminated by strong fluorescent light..............................................................1–9

Figure 7 A lens reflection effect caused by sunshine...........................................................................................................1–9

Figure 8 Good image taken indoors.......................................................................................................................................1–10

Figure 9 Good image taken outdoors....................................................................................................................................1–10

Figure 10 Effects of dust on optical path..............................................................................................................................1–11

Figure 11 Image taken with clean protection window....................................................................................................1–13

Figure 12 Image taken with greasy protection window.................................................................................................1–13

Figure 13 Bit errors caused by JPEG compression..............................................................................................................1–13

Figure 14 Example of a good quality image taken with the flash LED........................................................................1–23

Figure 15 overexposed image..................................................................................................................................................1–24

Figure 16 Dark and noisy image..............................................................................................................................................1–25

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Nokia Customer Care Camera Module Troubleshooting

Figure 17 Shaken image.............................................................................................................................................................1–26

Figure 18 Camera white balance failure and overexposure...........................................................................................1–27

Figure 19 Color difference between flash colour limit samples....................................................................................1–27

Figure 20 Mechanical construction of the flash LED module..........................................................................................1–28

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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.

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.

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.

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.

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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 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 1 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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Figure 2 Blurring caused by shaking hands

Movement in bright light

If an image is taken of moving objects or if the device is used in a moving vehicle, object 'skewing' or 'tilting' may occur. This phenomenon is fundamental to most CMOS camera types, and usually cannot be avoided. The movement of camera or object sometimes cause blurring indoors or in dim lighting conditions because of long exposure time. This is normal; do not change the camera module.

Figure 3 Near objects get skewed when taking images from a moving vehicle

Temperature

High temperatures inside the mobile phone cause more noise to appear in images. For example, in +70 degrees (Celsius), the noise level may be very high, and it further grows if the conditions are dim. If the phone processor has been heavily loaded for a long time before taking an image, the phone might have considerably higher temperature inside than in the surrounding environment. This is also normal to camera operation; do not change the camera module.

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Figure 4 Noisy image taken in +70 degrees Celsius

Phone display

If the display contrast is set too dark, the image quality degrades: the images may be very dark depending on the setting. If the display contrast is set too bright, image contrast appears bad and "faint". This problem is solved by setting the display contrast correctly. This is normal behaviour; do not change the camera module.

Basic rules of photography (especially shooting against light)

Because of dynamic range limitations, taking images against bright light might cause either saturated image or the actual target appear too dark. In practice, this means that when taking an image indoors and having, for example, a window behind the object, the result is usually poor. This is normal behaviour; do not change the camera module.

Figure 5 Image taken against light

Flicker

In some occasions a bright fluorescent light may cause flicker in the viewfinder and captured image. This phenomenon may also be a result, if images are taken indoors under the mismatch of 50/60 Hz electricity network frequency. The electricity frequency used is automatically detected by the camera module. In some very few countries, both 50 and 60 Hz networks are present and thus probability for the phenomenon increases. Flickering occurs also under high artificial illumination level. This is normal behaviour; do not change the camera module.

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Figure 6 Flicker in an image; object illuminated by strong fluorescent light

Bright light outside of image view

Especially the sun can cause clearly visible lens glare phenomenon and poor contrast in images. This happens because of undesired reflections inside the camera optics. Generally this kind of reflections are common in all optical systems. This is normal behaviour; do not change the camera module.

Figure 7 A lens reflection effect caused by sunshine

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Examples of good quality images

Figure 8 Good image taken indoors

Figure 9 Good image taken outdoors

Image quality analysis

Testing for dust in camera module

Context

For detecting these kinds of problems, take an image of a uniform white surface and analyse it in full resolution. A good quality PC monitor is preferred for analysis. Search carefully, since finding these defects is not always easy. Figure "Effects of dust on optical path" is an example image containing easily detectable dust problems.

When taking a white image, use uniformly lightened white paper or white wall. One possibility is to use uniform 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 the image quality parameter to ‘High Quality’.

Black spots in an image are caused by dirt particles trapped inside the optical system. Clearly visible and sharp edged black dots in an image are typically dust particles on the image sensor. These spots are searched for in the manufacturing phase, but it is possible that the camera body cavity contains a particle, which may move onto the image sensor active surface, for example, when the phone is dropped. Thus it is also possible that the problem will disappear before the phone is brought to service. The camera should be replaced if the problem is present when the service technician analyses the phone.

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+ 22 hidden pages

Nokia N70 Service Manual 8 camera module troubleshooting

Specifications and Main Features

Frequently Asked Questions

User Manual

Introduction to camera module troubleshooting

The effect of image taking conditions on image quality

Image quality analysis

Testing for dust in camera module