GB2411955A

GB2411955A - Apparatus for determining the cleanliness of the lens of a digital camera

Info

Publication number: GB2411955A
Application number: GB0422745A
Authority: GB
Inventors: Nicola Leotta
Original assignee: NEC Technologies UK Ltd
Current assignee: NEC Technologies UK Ltd
Priority date: 2004-10-13
Filing date: 2004-10-13
Publication date: 2005-09-14
Anticipated expiration: 2024-10-13
Also published as: GB0422745D0; GB2411955B

Abstract

An apparatus for determining the cleanliness of the lens of a digital camera comprising means for recording an image through a lens, means for storing a reference image in a memory, means for comparing the recorded image with the reference image, means for determining the degree of variation of the recorded image from the reference image from the comparison; and means for providing an audio or visual indication that the lens requires cleaning in dependence on the result of the determination. In a separate embodiment, first and second images are recorded and the degree of matching between the images is used for determination. The figure shows the invention when set up to take a comparison photograph.

Description

241 1 955 Apparatus for determining the cleanliness of a lens of a digital

camera The present invention relates to an apparatus for determining the cleanliness of a lens of a digital camera.

In all photographic equipment, the quality of a photograph is compromised when dirt and smears are present on the camera objective (the lens). Modern digital equipment in which a camera is included, for example a digital camera or a communication device incorporating a digital camera, enable the view through the lens to be displayed on the liquid crystal display (LCD) monitor located on the device. However, due to the resolution of the particular LCD monitor, a user may not be able to determine that he is going to achieve a low quality picture due to dirt being present on the lens when viewing the potential picture on the LCD..

Although a user may regularly clean the lens of his camera in order to remove any dirt or smears, there may be times at which he is unable to detect the presence of dirt, which would reduce the quality of the picture, by inspecting the lens visually or by viewing the picture on the LCD on the electronic device. In such cases, and also in case of a user not regularly checking or cleaning the lens, the user will be unaware that he has taken a low quality picture until the photograph is developed (or viewed on a larger display).

We have appreciated that it would be beneficial for the electronic device to be able to determine whether the lens of the camera is sufficiently dirty such that the quality of the photograph would be reduced. The user can then be confident of obtaining photographs that are not affected by dirt on the lens.

Embodiments of the present invention overcome the problem associated with not realising that the lens of a camera is dirty and that the quality of photographs will be affected by allowing the camera to self-test its camera lens's cleanliness. This is performed by including a pre-recorded "ideal" image which is stored within the memory of the device. The camera can be set up to take a comparison photograph relating to the ideal image. The camera compares the ideal image with the comparison image in order to assess the cleanliness of the lens. On comparing the images, the device is able to assess how well the images compare and, therefore, whether there is any dirt on the lens of the camera which will affect the picture quality. Embodiments of the invention are programmed with a predetermined acceptable threshold for the comparison. If the quality of the comparison is below the pre-defined acceptable level, embodiments of the invention indicate to the user that the lens is required to be cleaned in order that the quality of any future photographs be not compromised.

Further embodiments do not use an ideal image but, instead, effect a Pattern image recognition on two images of different subjects taken by the camera. In these embodiments, any similarities in the images are due to the dirt being positioned on the lens which will appear in the same position in both images. If the pattern image recognition identifies the same patterns on the 2 images and they cover an image area above a predetermined threshold then this indicates that the same dirt is present in both images and that the lens should be cleaned.

The invention is now defined in its various aspects in the appended claims to which reference should be made.

An embodiment of the invention is now described in detail with reference to the accompanying figures in which: Figure 1 is a flow diagram showing the steps of operation of an embodiment of the present invention.

Figure 2 shows an embodiment of the invention whilst set up to photograph the template.

Figure 3 is an example of the comparison between the comparison photograph and the standard reference image.

Figure 4 is a flow diagram showing the steps of operation of a second embodiment of the present invention.

Figure 5 is a block diagram showing the hardware included in an embodiment of the invention.

Referring to Figure 1, at 110 the device is prompted to execute a test to determine whether there is dirt on the lens of the camera which will reduce the quality of the photograph. Preferred embodiments of the invention prompt the test automatically at periodic intervals or at a defined time, for example on power up. Further embodiments of the invention enable the user to prompt manually the execution of the test. Other embodiments may include both an automatic test facility as well as a manual prompt for executing the test.

Once the test is initiated the camera automatically takes a comparison photograph at 120. In a first embodiment of the invention, the camera is arranged in order to take a predetermined picture, i.e. the camera should be pointed at a predetermined subject and be positioned at a known angle and distance from the subject.

Once the comparison photograph has been taken, this is compared with a standard reference image at 130 which is stored in the memory of the device.

The reference image represents a photograph of the predetermined subject taken in ideal conditions, i.e. with a clean lens. The reference image may be programmed during manufacture or entered by the user. Typically, the picture comparison will be executed via a comparison algorithm. The algorithm assesses the similarity between the comparison photograph and the reference image and determines an error level. The acceptable level of error may be programmed into the device during manufacturing or may be able to be controlled by the user depending on the user's particular needs.

At 140, the device determines whether the error level was within the acceptable limit. If not, and the pictures are less similar than is expected, the device automatically prompts an alarm to indicate to the user that the lens of the camera is unacceptably dirty and that the quality of photographs taken with the lens in its current state will be below the acceptable level. Different embodiments of the invention include different indicating means. Preferred embodiments of the invention include an audio means to alert the user that the lens must be cleaned.

However, further embodiments may incorporate visual indicators including LEDs which are lit or made to flash when the lens is required to be cleaned. Other embodiments provide a visual indication on the LCD screen of the device to indicate that the lens should be cleaned. Alternatively, if at 140 the comparison is within the acceptable limit, the device does not indicate that the lens is required to be cleaned. Further embodiments may indicate that a test has been executed and that the results are satisfactory.

In order to enable the camera to take a predetermined comparison photograph, embodiments of the invention include the facility for the subject to be positioned at a known location and angle with respect to the lens. Such an example is shown in Figure 2.

Figure 2 shows an embodiment of the invention when set up to take a comparison photograph. The portable device 200 incorporating the camera 210 is positioned on a stand 220 this may be, for example, a charger stand. The stand includes a stand for displaying the predetermined subject. The subject stand 220 is positioned at a set location from the camera lens. The embodiment of Figure 2 ensures that the subject to be photographed is an expected distance and angle from the lens of the camera in order to introduce a reliable reproducibility of the viewing conditions. The reproducibility of the position of the subject for the comparison photograph is essential in order that a reliable comparison can be made.

Preferred embodiments of the present invention may also include software capable of rotating or re-centering the comparison image or stretching the image in the X or Y directions in order to overlap with the reference image. Such embodiments would be able to take account of the situation when the subject of the comparison photograph is in a slightly unexpected position or distance from the camera lens. In such a case, the comparison photograph and reference picture would not be able to be superimposed directly but, instead, a specific algorithm will be used to re-centre, rotate, or stretch the picture so as to align at least the borders of the pictures. Standard subjects may include crosses in the corners to aid with the alignment process. Only after the comparison photograph has been re-aligned with the stored reference image is the actual comparison algorithm used to generate an error level in the result. Further embodiment of the invention will execute the algorithm on all comparisons in order to ensure that the patterns are correctly aligned before comparison.

Figure 3 shows an example of a comparison between the comparison photograph and the reference image. In this example a pattern template is used as the subject. However, further embodiments may use any suitable subject.

There are a number of parameters to consider when selecting the pattern template for use in individual embodiments and the pattern should be optimised for the type of camera sensor incorporated in the particular device. For example, the type of colours used in the pattern and the intricacy of the pattern should be chosen depending on the resolution of the camera and the purpose of the camera. There will be no benefit in having a pattern which is either too gross or too minute for the sensor to detect in terms of its resolution or colour.

Furthermore, the pattern selected for the template may be chosen depending on the most common cause for the missed picture. For example, if the most common cause is the gathering of dust near the edge of the lens, causing a hazy picture or general loss of resolution mostly near the edge of the picture, then an appropriate pattern to identify this type of dirt might be several parallel lines in black and white of increasing width and interval, extending to near the edges of the reference image. It may also be appropriate to include lines of different directions. In general, different patterns or colours are suitable for different types or quality of cameras and, therefore, the particular type of pattern should be selected by the user or manufacturer depending on the requirements of the user

of specification of the device.

Further embodiments of the invention may enable a user to update the reference image. This may be particularly useful if, for example, a user loses the standard pattern and so would have no way of taking further pictures to compare them with the reference image, or improves the quality of his camera and so a more intricate pattern would be appropriate. Of course, when taking a reference photograph, the user should ensure that the lens is clean of all dirt and taken under ideal conditions. Since the conditions and the cleanliness of the lens may be too difficult to ensure and that, in addition, the best pattern may be difficult for the user to decide, it may be for the best that the manufacturer does not allow the user to update this reference image, but keep this feature as a way to update or repair the customer's camera's clean-Lens-check mechanism. Alternatively, the manufacturers may issue new patterns eg on their website or by selling new templates.

One factor that may affect the comparison is the quality of external light. This could be dealt with through the comparison algorithm or by minimising the effect using back lighting on the pattern or post lighting by a light source when taking the comparison photograph. Embodiments of the invention enable the brightness of the comparison image to be adjusted in order to match the brightness of the reference image before comparison. In further embodiments, the portable device may incorporate a light source (flash light) in order to illuminate the image.

In further embodiments, the charger stand may also include a light source to illuminate the pattern. This allows improved reproducibility of the colours of the pattern which minimizes the influence of the environment lighting conditions.

Alternative embodiments of the invention use image recognition rather than using a standard template. An example of the steps taken in such an embodiment is shown in figure 4. At 400, the device records a currently sensed image through the lens of the camera. At 410, the currently sensed image is compared with a recently sensed and stored image. The image is compared at 420 using an image recognition algorithm in order to determine whether dirt or dust has accumulated on the lens since the last stored image.

Typical image recognition algorithms do not check pixel per pixel whether the two images are matching. Instead, such algorithms look for specific patterns in a first image, for example a square, triangle or snowflake. Preferably, the algorithm looks for a complex pattern made of a specific shape of colour shading (like a triangle or colour turned into a darker version of itself, eg red to dark red, blue to dark blue, etc). The algorithm then searches for the same pattern in a second image. For instance, with triangle shaped dust on the lens, image 1 (a blue sky) would include a darker blue triangle pattern and image 2 (a white wall) would include the same triangle pattern but of grey colour. In this example, technically speaking, the two images would be 100% different (ie one being largely blue and the other largely white), but the same triangle shading pattern could be recognized in both of them. Generally, image recognition algorithms are preferable compared with image comparison algorithms in such embodiments since, if the only check that is made is image comparison, as a dark blue triangle and a dark grey one do not match, it is quite likely that the dust will not be identified. Although the above example is with a triangle, it should be appreciated that other shapes should also be checked that are appropriate to represent a typical dust particle on a lens.

in practice, such image recognition embodiments will be most effective when the two images are as different from each other as possible. In this case, any parts of the image which match are not due to the subject matter being the same but, instead, are due to dirt being present on the lens which appears in the same position in both images. The image recognition algorithm will try to match parts or patterns of the first captured picture with the second. If they match patterns for an overall area of the patterns that would be above a specific threshold level, then the lens is dirty. The matching parts are dirt on the lens which will be present in the same position in both images regardless of the subject of the image. If dust is detected, the device indicates that the lens requires cleaning at 440.

Therefore, the area of the image artefacts caused by the dust being above the predefined area threshold indicates that there is dirt on the lens. This embodiment would decrease the production costs of the device as no stand would be required to set the unit up for a comparison photograph. Furthermore, since such embodiments are attempting to identify dirt which is present on the lens (and has not moved) between recordings, such embodiments will not require the software to align the images. Again, this will reduce the cost of manufacture.

Figure 5 is a block diagram showing the components of an embodiment of the present invention. A device 500 incorporates a lens 510 to view the subject. The device also includes a means for digitising the image at 520. The device includes a memory 530 for storing a reference image. The memory may be programmed during manufacture or may be programmed with a more recently taken image.

The memory 530 and digitiser 520 are linked to a comparator 540 which is used to compare the reference image with the comparison image in order to determine the error level. If the degree of comparison is below a predefined limit, the comparator instructs the indicator 550 to indicate to the user that the lens of the camera should be cleaned. The indicator may be an audio device or a visual device, for example an LED or LCD screen on the unit. Further embodiments of the invention also include a flashlight 560 in order to illuminate the subject of the photograph.

Further embodiments of the invention include a means for aligning automatically the reference image with the comparison image. Further still embodiments include a means for adjusting the brightness of the comparison image before comparing the image with the reference image.

It should be appreciated that Figure 5 represents a preferred embodiment of the invention. Further embodiments of the present invention incorporate the main features of Figure 5 but in different arrangements. For example, the comparator could be incorporated inside the memory or image recorder. Furthermore, other embodiments include an automatic prompter for comparison which could be an on/off switch, a 'take picture' switch or a separate manual selectable prompt.

It will be obvious to those skilled in the art that the present invention could be incorporated into any digital device including a camera. For example, the invention may be incorporated into a digital still camera, a digital camcorder or a mobile telephone incorporating a digital camera.

Claims

1. A method for determining the degree of cleanliness of a lens of a digital camera comprising the steps of; recording an image through a lens, comparing the image with a reference image stored in a memory, determining the degree of variation between the recorded image and the reference image from the comparison, and providing an indication that the lens requires cleaning in dependence on the result of the determination.

2. A method for determining the cleanliness of the lens of a digital camera according to claim 1 further comprising a pre-programmed threshold to the degree of variation.

3. A method for determining the cleanliness of the lens of a digital camera according to claim 2 wherein step of providing an indication is performed if the degree of variation is above the threshold.

4. A method for determining the cleanliness of the lens of a digital camera according to claims 1, 2 or 3 wherein the reference image is an image of a predefined subject.

5. A method for determining the cleanliness of the lens of a digital camera according to claim 4 wherein the subject of the recorded image is the same as the subject of the reference image.

6. A method for determining the cleanliness of the lens of a digital camera according to any of claims 1 to 5 wherein the reference image is recorded through the lens.

7. A method for determining the cleanliness of the lens of a digital camera according to any of claims 1 to 5 wherein the reference image is a template stored in the digital camera.

8. A method for determining the degree of cleanliness of the lens of a digital camera according to any preceding claim including the further step of aligning the recorded image with the reference image before comparison.

9. A method for determining the cleanliness of the lens of a digital camera according to any of claims 1 to 8 comprising the further step of updating the reference image.

10. A method for determining the cleanliness of the lens of a digital camera according to claims 1 to 9 wherein the step of comparing is prompted by a user.

11. A method for determining the cleanliness of the lens of a digital camera according to claims 1 to 10 wherein the step of comparing is prompted automatically.

12. A method for determining the cleanliness of the lens of a digital camera according to claim 11 wherein the step of comparing is prompted periodically.

13. A method for determining the cleanliness of the lens of a digital camera according to any of claims 1 to 12 wherein the step of providing an indication is made by a visual indicator.

14. A method for determining the cleanliness of the lens of a digital camera according to any of claims 1 to 13 wherein the step of providing an indication is made by an audio indicator.

15. A method for determining the cleanliness of the lens of a digital camera substantially as herein described with reference to the accompanying figures.

16. An apparatus for determining the degree of cleanliness of a lens of a digital camera comprising; means for recording an image through a lens, means for comparing the image with a reference image stored in a memory, means for determining the degree of variation of the recorded image from the reference image from the comparison, and means for providing an indication that the lens requires cleaning in dependence on the result of the determination.

17. An apparatus for determining the cleanliness of the lens of a digital camera according to claim 16 further comprising a pre-programmed threshold to the degree of variation.

18. An apparatus for determining the cleanliness of the lens of a digital camera according to claim 17 wherein the indication is provided if the degree of variation is above the threshold.

19. An apparatus for determining the cleanliness of the lens of a digital camera according to claims 16, 17 or 18 wherein reference image is an image of a predefined subject.

20. An apparatus for determining the cleanliness of the lens of a digital camera according to claim 16, 17, 18 or 19 wherein the subject of the recorded image is the same as the subject of the reference image.

21. An apparatus for determining the cleanliness of the lens of a digital camera according to any of claims 16 to 20 wherein the reference image is recorded through the lens.

22. An apparatus for determining the cleanliness of the lens of a digital camera according to any of claims 16 to 20 wherein the reference image is a template stored in the digital camera.

23. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to any of claims 16 to 22 further comprising a means for aligning the recorded image with the reference image before comparison.

24. An apparatus for determining the cleanliness of the lens of a digital camera according to any of claims 16 to 23 further comprising a means for updating the reference image. 1 1

25. An apparatus for determining the cleanliness of the lens of a digital camera according to claims 16 to 24 further comprising a means to enable the user to prompt the means for comparing.

26. An apparatus for determining the cleanliness of the lens of a digital camera according to claims 16 to 25 further comprising a means to prompt the comparison automatically.

27. An apparatus for determining the cleanliness of the lens of a digital camera according to claim 26 further comprising a means to prompt the comparison periodically.

28. An apparatus for determining the cleanliness of the lens of a digital camera according to any of claims 16 to 27 wherein the means for indicating is a visual indicator.

29. An apparatus for determining the cleanliness of the lens of a digital camera according to any of claims 16 to 28 wherein the means for indicating is an audio indicator.

30. An apparatus for determining the cleanliness of the lens of a digital camera substantially as herein described with reference to the accompanying figures.

31. A method for determining the degree of cleanliness of the lens of a digital camera comprising the steps of: recording a first image of a first subject through a lens of a digital camera; recording a second image of a second subject through the lens of the digital camera; effecting image recognition of patterns between the first and second recorded images; determining the degree of matching between the first and second images; and, providing an indication that the lens requires cleaning in dependence on the result of the determination.

32. A method for determining the degree of cleanliness of the lens of a digital camera according to claim 31 wherein the step of effecting uses an image recognition algorithm.

33. A method for determining the degree of cleanliness of the lens of a digital camera according to claim 31 or 32 further comprising a preprogrammed image Area threshold for the total area of matching patterns.

34. A method for determining the degree of cleanliness of the lens of a digital camera according to claim 33 wherein the step of indicating that the lens requires cleaning is performed if the total image area of matching patterns in between the 2 images is above the pre-programmed threshold.

35. A method for determining the degree of cleanliness of the lens of a digital camera according to claims 31 to 35 wherein the step of effecting is prompted by a user.

36. A method for determining the degree of cleanliness of the lens of a digital camera according to claims 36 wherein the step of effecting is prompted automatically.

37. A method for determining the degree of cleanliness of the lens of a digital camera according to claim 31 to 34 wherein the step of effecting is prompted periodically.

38. A method for determining the degree of cleanliness of the lens of a digital camera according to any of claims 31 to 38 wherein the step of providing an indication is made by a visual indicator.

39. A method for determining the degree of cleanliness of the lens of a digital camera according to any of claims 31 to 38 wherein the step of providing an indication is made by an audio indicator.

40. A method for determining the degree cleanliness of the lens of a digital camera substantially as herein described with reference to the accompanying figures.

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_ is, -Up;' - -- Am d! _ _ _ ! 47. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claim 46 wherein the means for effecting is prompted periodically.

48. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to any of claims 41 to 47 wherein the means for providing an indication includes a visual indicator.

49. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to any of claims 41 to 48 wherein the means for providing an indication includes an audio indicator.

50. An apparatus for determining the degree cleanliness of the lens of a digital camera substantially as herein described with reference to the accompanying figures.

Amendments to the claims have been filed as follows 1. A method for determining the degree of cleanliness of a lens of a digital camera comprising the steps of; recording an image through a lens, comparing the image with a reference image stored in a memory, determining the degree of variation between the recorded image and the reference image from the comparison, and providing an indication that the lens requires cleaning in dependence on the result of the determination.

2. A method for determining the degree of cleanliness of the lens of a digital camera according to claim 1 further comprising a pre-programmed threshold to the degree of variation.

3. A method for determining the degree of cleanliness of the lens of a digital camera according to claim 2 wherein step of providing an indication is performed if the degree of variation is above the threshold.

4. A method for determining the degree of cleanliness of the lens of a digital camera according to claims 1, 2 or 3 wherein the reference image is an image of a predefined subject.

5. A method for determining the degree of cleanliness of the lens of a digital camera according to claim 4 wherein the subject of the recorded image is the same as the subject of the reference image.

6. A method for determining the degree of cleanliness of the lens of a digital camera according to any of claims 1 to 5 wherein the reference image is recorded through the lens.

7. A method for determining the degree of cleanliness of the lens of a digital camera according to any of claims 1 to 5 wherein the reference image is a template stored in the digital camera.

9. A method for determining the degree of cleanliness of the lens of a digital camera according to any of claims 1 to 8 comprising the further step of updating the reference image.

10. A method for determining the degree of cleanliness of the lens of a digital camera according to claims 1 to 9 wherein the step of comparing is prompted by a user.

11. A method for determining the degree of cleanliness of the lens of a digital camera according to claims 1 to 10 wherein the step of comparing is prompted automatically.

12. A method for determining the degree of cleanliness of the lens of a digital camera according to claim 11 wherein the step of comparing is prompted 1 5 periodically.

13. A method for determining the degree of cleanliness of the lens of a digital camera according to any of claims 1 to 12 wherein the step of providing an indication is made by a visual indicator.

14. A method for determining the degree of cleanliness of the lens of a digital camera according to any of claims 1 to 13 wherein the step of providing an indication is made by an audio indicator.

15. A method for determining the degree of cleanliness of the lens of a digital camera substantially as herein described with reference to the accompanying figures numbered 1 to 3.

17. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claim 16 further comprising a preprogrammed threshold to the degree of variation.

18. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claim 17 wherein the indication is provided if the degree of variation is above the threshold.

19. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claims 16, 17 or 18 wherein reference image is an image of a predefined subject.

20. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claim 16, 17, 18 or 19 wherein the subject of the recorded image is the same as the subject of the reference image.

21. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to any of claims 16 to 20 wherein the reference image is recorded through the lens.

22. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to any of claims 16 to 20 wherein the reference image is a template stored in the digital camera.

24. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to any of claims 16 to 23 further comprising a means for updating the reference image. iS

25. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claims 16 to 24 further comprising a means to enable the user to prompt the means for comparing.

26. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claims 16 to 25 further comprising a means to prompt the comparison automatically.

27. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claim 26 further comprising a means to prompt the comparison periodically.

28. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to any of claims 16 to 27 wherein the means for indicating is a visual indicator.

29. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to any of claims 16 to 28 wherein the means for indicating is an audio indicator.

30. An apparatus for determining the degree of cleanliness of the lens of a digital camera substantially as herein described with reference to the accompanying figures numbered 1 to 3.

31. A method for determining the degree of cleanliness of the lens of a digital camera comprising the steps of: recording a first image of a first subject through a lens of a digital camera; recording a second image of a second subject through the lens of the digital camera; effecting image recognition of patterns between the first and second recorded images; determining the degree of matching between the first and second images; and, providing an indication that the lens requires cleaning in dependence on the result of the determination. I q

34. A method for determining the degree of cleanliness of the lens of a digital camera according to claim 33 wherein the step of indicating that the lens requires cleaning is performed if the total image area of matching patterns in between the 2 images is above the pre-programmed threshold. I 35. A method for determining the degree of cleanliness of the lens of a digital camera according to claims 31 to 35 wherein the step of effecting is prompted by a user.

40. A method for determining the degree cleanliness of the lens of a digital camera substantially as herein described with reference to the accompanying figures numbered 4 to 5.

41. An apparatus for determining the degree of cleanliness of the lens of a digital camera comprising: means for recording a first image of a first subject through a lens of a digital camera; means for recording a second image of a second subject through the lens of the digital camera; means for effecting image recognition of patterns between the first and second; l O means for determining the degree of matching between the first and second images; and, I means for providing an indication that the lens requires cleaning in dependence on the result of the determination.

42. An apparatus for determining the degree of cleanliness of the lens of a I digital camera according to claim 41 wherein the means for effecting includes an image recognition algorithm.

43. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claim 41 or 42 further comprising a means for pre- I programming an image Area threshold for the total area of matching patterns.

44. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claim 43 wherein the means for indicating provides an indication if the total image area of matching patterns in between the 2 images is above the pre-programmed threshold.

45. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claims 41 to 44 wherein the means for effecting is prompted by a user.

46. A method for determining the degree of cleanliness of the lens of a digital camera according to claims 41 to 45 wherein the means for effecting is prompted automatically. 1

47. An apparatus for determining the degree of cleanliness of the lens of a digital camera according to claim 46 wherein the means for effecting is prompted periodically.

49 An apparatus for determining the degree of cleanliness of the lens of a digital camera according to any of claims 41 to 48 wherein the means for providing an indication includes an audio indicator.

50. An apparatus for determining the degree cleanliness of the lens of a digital camera substantially as herein described with reference to the accompanying figures numbered 4 to 5. Zen