WO2003090168A1

WO2003090168A1 - Prevention of photoepileptic seizures

Info

Publication number: WO2003090168A1
Application number: PCT/IB2003/002110
Authority: WO
Inventors: Henry James William Dienn
Original assignee: Henry James William Dienn
Priority date: 2002-04-19
Filing date: 2003-04-17
Publication date: 2003-10-30
Also published as: EP1497792A1; CA2482796A1; AUPS185102A0

Abstract

A system for preventing photosensitive epileptic seizures for viewers of images from computers, televisions, gaming consoles, video players, mobile telephone or personal digital assistants is provided. The system detects and interferes with potentially harmful images rendering them photosensitive epilepsy safe.

Description

_PREVENTI_ON OF PHOTOEPILEPTIC SEIZURES

FIELD OF THE INVENTION

The invention relates to a system for preventing photoepileptic seizures and in particular to a system for use in conjunction with visual displays to prevent photoepileptic seizures.

The invention has been developed primarily for use with visual display units in computers, televisions, personal digital assistants, telephones, digital or analogue video recorders and players and gaming consoles and will be described hereinafter with reference to these applications. However, it will be appreciated that the invention is not limited to these applications and is applicable to other applications and fields.

BACKGROUND OF THE INVENTION

It is well know that approximately 5% of epileptics are photosensitive in which seizures can be triggered by flickering lights or small patterns, particularly contrasting vertical stripe patterns. Children in the range of 6 to 20 years of age are most susceptible to seizures, and girls in particular.

Sources that can potentially trigger seizures in photosensitive epileptics include visual display units associated with computers, gaming consoles, personal digital assistants, televisions, telephones, video cassette digital video or laser disc recorders or players, video cameras or other display devices.

Extensive studies evaluating a variety of aspects of photosensitive epilepsy have been conducted including sources of photoepileptic seizures and for example, some of their results have shown that particular patterns, intense flashes of colours divided by sharp angles or images flashing in the range of 6 to 20 Hz can increase the risk of seizures.

Reference is made to studies in the area including those by Harding GF and Jeavons PM, Photosensitive Epilepsy, London: MacKeith; 1994; Harding GF, Edson A and Jeavons PM, Persistence Of Photosensitivity, Epilepsia 1997; 38:663-9; Harding GF, TV can be bad for your health, Nat Med 1998; 4: 265-7; and Jeavons PM and Harding GF, Photosensitive Epilepsy, clinics in developmental medicine, Vol. 56, London: Heinemann, 1975; the disclosure of these publications being incorporated into the disclosure of this specification by reference thereto.

Producers of film and television broadcasts and video sales and rentals are often aware of the effects of many of the sources of photoepileptic seizures and intentionally avoid producing material that will enhance the risk of a viewer suffering a seizure. However, this does not always prevent image flash rates or specific images which may enhance the risk of a seizure from being broadcast. For example, in Tokyo in December 1997, the Television Tokyo Channel 12 broadcast a cartoon television program based on a popular children's game. Seizures in viewers were reported during the program and approximately 600 people suffered a photoepileptic seizure of some degree as a result of watching the program. The Reuters news agency journalist Janet Snyder published one of many reports on the incident on 17 December, 1997.

In the United Kingdom, the Independent Telecommunication (TTC) produced a set of revised and re-issued guidelines in July, 2001 entitled 'TTC Guidance Note for Licensees on Flashing Images and Regular Patterns in Television", the Guidance Note being incorporated into the disclosure of this specification by reference thereto.

In the Guidance Note, definitions are provided for what constitutes allowable flashing images and irregular patterns in television to avoid the risk of inducing seizures. Three primary image characteristics and their allowable content are described as a potentially harmful flash (PHF), rapidly changing image sequences and potentially harmful regular patterns (PHP). A PHF is defined to occur when there is a pair of opposing changes in luminance and, a rapidly changing image sequence is considered provocative if this results in areas of the display that flash. A PHP is defined as a pattern which contains clearly discernable stripes having more than five light-dark pairs of stripes regardless of their orientation. More detail on potentially harmful images or sequences is provided in the Guidance Note.

The use of computers, gaming consoles, personal digital assistants and telephones are becoming increasingly more common, especially among children, and there are no conditions placed on image content provision which restrict the broadcast and transmission of images which can to trigger or potentially trigger a seizure in photosensitive epileptic viewers. In respect of display units which can receive images remotely, for example televisions computers, personal digital assistants and telephones, an unwanted image or sequence of images may be transmitted to a user which, once viewed, will increase the risk of or cause an epileptic seizure. Such images may be transmitted by people with the intent to trigger a photoepileptic seizure, for example, by transmitting an image or sequence of images by email to a computer or personal digital assistant or by SMS message to a telephone.

Many methods are known to identify and characterize the effects of photosensitive epilepsy. These include US Patent No. 6,239,904 and US Patent No. 5,243 ,517 which disclose specific apparatus for detecting photosensitive epileptic seizures in a person.

Japanese Patent Application No. 10270187 is directed towards limiting the intensity of one or more image colour channels. There is disclosed a television receiver which analyses the red- green-blue (RGB) components of a television signal and reduces the contrast of one or more of the components whose intensity exceeds a predetermined level. The system aims to provide images purely for the aesthetic benefit of a viewer.

Methods and apparatus for detecting the presence of subliminal images and to protect observers from them are also known, for example those disclosed in US Patent Nos. 6,122,322 and 6,341,168. However, these systems do not detect or prevent images which can trigger or potentially trigger a photoepileptic seizure, rather subliminal advertising or nefarious messages.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a system to minimise the risk of an image or sequence of images from triggering a photoepileptic seizure.

SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided a system for interfering with an image or sequence of images being displayed on a visual display unit of a device generating the image or images, the system including a programmable image control device disposed in electrical communication with the image generating device and configured to process images generated by the image generating device wherein the image control device interferes with an image or sequence of images with predetermined characteristics that can trigger or potentially trigger photoepileptic seizures.

Preferably, the image control device is integrated into the image generating device and is programmable to interfere with patterns in images, image colour intensities and rate that images flash in a sequence of images having the predetermined characteristics that can trigger or potentially trigger photoepileptic seizures.

Preferably, the image control device is programmable by a viewer to prevent images or sequences of images which the person can be sensitive to from being displayed. Also preferable, the image control device is remotely programmable to update images or sequences of images that can trigger or potentially trigger photoepileptic seizures.

The image control device preferably interferes with an image or sequence of images by blocking or dimming the display of patterns or colours with predetermined characteristics that can trigger or potentially trigger photoepileptic seizures and the image control device modifies the rate of flashing of a sequence of images that can trigger or potentially trigger photoepileptic seizures to within a predetermined rage.

In preferred embodiments of the invention, the image generating device includes a computer, gaming console, video or mobile telephone, personal digital assistant, video cassette digital video or laser disc recorder or player, video camera or television.

According to a second aspect of the invention there is provided a method of using the system according to the first aspect for interfering with an image or sequence of images having predetermined characteristics that can trigger or potentially trigger epileptic seizures, the method including the steps of: communicating an image or sequence of images from the image generating device to an input of the image control device; processing the image or sequence of images in the image control device; removing images or portions of images that have the predetermined characteristics; modifying the rate of flashing of a sequence of images that have the predetermined characteristics to within a predetermined range; outputting the removed image or modified sequence of images from the image control device to the visual display unit.

According to another aspect of the invention there is provided a programmable image control device for use in conjunction with an image generating device, the image control device being disposed in electrical communication with the image generating device and configured to process images received or generated by the image generating device wherein the image control device interferes with an image or sequence of images with predetermined characteristics that can trigger or potentially trigger photoepileptic seizures.

BRIEF DESCRIPTION OF THE FIGURES

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawing in which:

Fig 1 is a block diagram of a system for modifying potentially harmful images according to a first preferred embodiment;

Fig 2 is a block diagram of a system for modifying potentially harmful images according to a second preferred embodiment; Fig 3 is a block diagram of a system for modifying potentially harmful images according to a third preferred embodiment; and

Fig 4 is a typical delivery claim for digital images in the embodiment of Fig 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, there is illustrated a system 1 provided for interfering with an image or sequence of images being displayed on a visual display unit 2 associated with a device 3 which generates the image or sequence of images.

The image generating device 3 illustrated is in the form of a computer and visual display unit 2 is a computer monitor, however, the image generating device can also include a gaming console, video or mobile telephone, personal digital assistant, video cassette digital video or laser disc player, video camera or television wherein the image generating device 3 and visual display 2 are integrated into a unit. A programmable image control device 4 is disposed in electrical communication with the image generating device 3, shown integrated into the image generating device 3 in Fig 1 and illustrated in Fig 2 as intermediate the image generating device 3 and visual display unit 2.

The image control device 4 is configured to process images generated by the image generating device 3 such that the image control device 4 interferes with an image or sequence of images having predetermined characteristics that can trigger or potentially trigger photoepileptic seizures. The interference to the image or sequence of images provided by image control device 4 occurs when an image or sequence of images is detected that have a predetermined pattern, colour or flash rate characteristic which can trigger or potentially trigger photoepileptic seizures in viewers.

In the case of images having a pattern or colours with predetermined characteristics that can trigger or potentially trigger the photoepileptic seizures, the image control device 4 blocks the display of those patterns or colours on the visual display unit 2. Alternatively, the image will be displayed on the visual display unit 2 but be dimmed substantially by the imaging control device 4.

In the case of the sequence of images, the image control device 4 modifies the rate of flashing of the sequence of images from the range which can trigger or potentially trigger photoepileptic seizures to within a predetermined range which is preferably less than 5Hz. Alternatively, the sequence of images will be displayed on the visual display unit 2 however the intensity will be dimmed substantially by the imaging control device 4.

The embodiment of Fig 1 illustrates the image control device 4 being integrated within the image generating device 3. In this embodiment, the image control device 4 can receive the images generated by the image generating device 3 either before processing the image or sequence of images and generating a video signal for display on the visual display unit 2 or after converting the image or sequence of images to a form for display on the visual display unit 2. In the embodiment of Fig 2, the image control device 4 can only interfere with images or sequences of images from the image generating device 3 once the device 3 has outputted the images in a form suitable for display on a visual display unit 2.

The system 1 further includes a programming receiver device 5 which is in communication with the image control device 4 for programming predetermined images or sequences of images that can trigger or potentially trigger photoepileptic seizures into the image control device 4. The programming device 5 can be actuated by a viewer to program the image control device 4 to prevent images or sequences of images to which that viewer can be sensitive to from being displayed.

The programming receiver device 5 can also be actuated remotely so as to update images or sequences of images that can trigger or potentially trigger photoepileptic seizures from in future being displayed. In embodiments where the image generating device 3 is a computer or telephone, the programming receiver 5 can be remotely contacted via a telephone or other communication means to update imaging control device 4 with the images or sequences of images. Alternatively, the programming receiver device 5 can be actuated from a key panel or other input device (not illustrated) on the image generating device 3.

The integration of the image control device 4 into the image generating device 3 and disposing it such that it receives the image or sequence of images prior to the image generating device 3 processing them can be used in preventing, for example, computer email or telephone SMS messages having images or sequences of images that can trigger or potentially trigger photoepileptic seizures from being received, processed and/or displayed by the image generating device 3. The remote programming of the image generating device 3 allows the relatively quick updating of the device 3 with hitherto unknown images or sequences of images that can trigger or potentially trigger photoepileptic seizures.

Also, the system 1 can provide reports or notifications of the detection of potentially harmful images when encountering potentially harmful images or on a periodic basis.

The system 1 can also be employed by producers of films, television programs or video games, for example, to review a program or game before releasing it for public consumption. In this way, the system 1 will provide an indication to the producer of the presence of images or sequences of images that can trigger photoepileptic seizures and the interference provided by the imaging control device 4 in response.

Figure 3 illustrates the embodiment in which the system 1 is applied to an image generating device in the form of a video cassette, video disc or laser disc recorder 3. In this embodiment, the imaging control device 4 interferes with images or sequences of images that can trigger photoepileptic seizures before being recorded on the cassette or disc 6 or being displayed on a camera visual display unit 2.

In another preferred embodiment, the process of interfering with an image or sequence if images being displayed is decomposable into two principal parts. In the first part, or interception, the system is required to monitor graphical content destined for display on a visual display unit (VDU). If the programmable image control device (PICD) opts to modify images, the system must be able to substitute the modified image in place of the original image in the display. In this embodiment, the process of communicating an image to the PICD is referred to as acquisition and the subsequent output of modified images for display is referred to as delivery. This process of acquisition and delivery of images forms an interception subsystem.

In the second part or filtering, the system detects potentially harmful images in the content being monitored, according to a predetermined set of rules and specified parameters. The system is required to modify the content to remove the potentially harmful images. In this embodiment the process of identifying potentially harmful patterns, colours or flashes is referred to as detection and the subsequent modification of images to remove offending material is referred to as correction. This process of detection and correction forms a filtering sub-system.

The filtering method is independent of the method of interception so that the two sub-systems can be decoupled. Decoupling the system in this way offers a number of advantages in allowing for the concurrent development of filtering and interception components, allowing for reuse of the same filtering method with a range of different interception methods, and simplifying the design of components required by the system. This division also conveniently separates platform independent and platform specific implementations. The interception methods preferably contain platform specific features, for example, access to the operating system image representation, while the filtering methods can be written in terms of generic, platform independent concepts.

In this embodiment, the following predetermined rules are used to govern the behaviour of the PICD in detecting harmful flashes, colours and patterns. The rules of this embodiment are derived from the ITC Guidance Note referred to above. In each instance the rule is named and the conditions on which it depends are listed. In use, a rule is violated when all dependent conditions are met.

Rule 1 Potentially Harmful Flash (PHF)

• Pair of opposing changes in luminance • > Δ cd.m^"2 difference in luminance

• < Δ _/cd.m^" dark image in luminance

• >A_P display area

Rule 2 Potentially Harmful Red Flash (PHR) • change to saturated red and back, subject to tolerance e.

Rule 3 Potentially Harmful Pattern (PHP)

• a pattern or more than five light-dark pairs of stripes

Rule 4 Prohibited Flash Sequence (PFS)

• >N PHF flash violations

• >A_V display area

• >f Hz frequency

Rule 6 Prolonged sequence (PS)

• tι s period of continual PHF or PHR flash violations Rule 7 Prohibited Static Pattern (PSP)

• PHP pattern violation

• >A_P display area

• > L cd.m^"2 difference in luminance

-2

< pCd.m^" dark image

Rule 8 Prohibited Dynamic Patter (PDP)

• oscillating, flashing, or reverse contrast PHP

• >A_d display area • > L_p cd.m^"2 difference in luminance

<L_pCd.m^"2 dark image

In the above rules, the symbols used are:

Λ

The display peak white luminance ( L ) Display gamma value ( γ_d )

Maximum sage period before ong flash sequence' in seconds (t_t )

Maximum safe display area before flash is classed as potentially harmful, as a ratio in the interval [0,1] (A_p)

Maximum safe display area before flash is classed as a violation, as a ratio in the interval [0,1] (A_v)

Maximum safe frequency for flashes, in Hz (/)

Maximum safe difference in luminance for flashes, in cd.m^"2 (Δ _/ )

Minimum safe luminance for flash dark image, in cd.m^"2 (Lf)

Maximum safe number of consecutive flashes (N)

Tolerance in matching saturated red in YUV domain, as a ratio in the interval [0,1] (e)

Maximum safe display area for pattern, as a ratio in the interval [0,1] (A_p)

Maximum safe difference in luminance for pattern, in cd.m^"2 (Δ _p )

Minimum safe luminance for pattern dark bar, in cd.m^"2 (L_p);

Maximum safe display area for flashing pattern, as a ratio in the interval [0,1] (A_d).

Typical operating values of these parameters are:

In this embodiment, as with the embodiment of Fig 1 above having a computer and VDU 2, Fig 4 shows the delivery chain for digital images being the path from content creator to the viewer.

There is an opportunity to intercept and modify the visual data after each delivery stage. At one extreme, the content creators themselves may take responsibility for filtering the visual data (as noted above) and, at the opposite extreme, the viewer may take steps to avoid the effects of photosensitive epilepsy PSE (also as noted above). At each stage in between, there is an opportunity intercept the data, but with varying degrees of difficultly in implementation in each case.

One pragmatic solution includes using a stand-alone hardware image processor inserted between the computer and VDU as in Fig 2 described above (see point E of Fig 4). This method allows the entire display to be monitored for harmful content, regardless of the software that created it. The implementation can also be constrained to software solutions, the images can be intercepted at points B to D shown in the typical delivery chain of digital images of Fig 4. At point B, the visual data is being transferred from the storage medium to the application that requires it, for example, Microsoft^® MediaPlayer reading an AVI file from a CD-ROM.

At point C, the application sends its output to the operating system for display, using one of the standard graphics interfaces, for example, GDI under Mirosoft Windows^®. Therefore, the image control device 4 processes the images before being processed by the image generating device 3.

Point D shows the image data being delivered to the graphics card by the operating system. Recent developments, such as DirectDraw^®, allow applications to have closer access to a graphics card. This gives the impression that the application is bypassing the operating system and writing directly to the display (represented by the dotted arrow in Fig 4). In this case, the image control device 4 is integrated into the image generating device 3.

It is noted that only the hardware solution can guarantee to intercept the entire display and that support for third-party filters in the standard media player applications will be required to intercept the images at points B and C.

In general, it appears that the most effective software method is to intercept data being sent between the operating system and the graphics card (point D in Fig 4). Intercepting image data before it reaches the application may be the most expedient method to implement, however, as noted above it will not guarantee the capture of all display content. It is considered that there is some scope for intercepting data after it has been rendered to the display memory, for example, using GDI screen capture.

There are potentially many methods for detecting potentially harmful images which is broken down into the detection of flashes and the detection of patterns. In the detection of flashes, analysis of the variation of image luminance over time is employed. . Since the distributed area of the flash must also be measured, a localised (blockwise) analysis is conducted. In this analysis, each image block is classified according to rules 1 to 8 above and flash luminance is determined by measuring the mean luminance of image blocks. The flash area is determined by the cumulative area of blocks who violate the PHF rule and the flash frequency is determined by analysing the distribution of PHF violations of time.

In the detection of patterns, either a histogram or frequency method is used. In the former, a histogram of the image intensity values can be used to quickly determine whether an image is PSE-safe, or requires further investigation. In the latter method, the potentially harmful patterns occur in three main forms: parallel stripes, concentric circles (including spirals), and radial (spoke like). It is noted that variations and combinations of these, such as checkerboards, concentric rectangles, etc are possible.

Frequency transforms, such as the Fourier transform decompose signals into a measure of the frequencies present. The photosensitive epilepsy (PSE) inducing patterns will result in large magnitude values at the frequencies of the patterns present (and multiples of). These can be further highlighted by contrasting with a 1// frequency distribution mode in which known (ie PSE-safe) images normally follow.

For Fourier domain analysis, it is necessary to scan the frequency both radially and concentrically to detect radial and angular frequencies. Local (blockwise) transforms can be used to identify which locations contain potentially harmful patterns, and lead to a value for the total area affected.

As with the detection methods above, many methods for correcting PSE inducing images can be used fortunately, the process of correcting images to remove potentially harmful content is relatively simple compared to the detection process. Correction is simply the application of well-known image manipulation operations. It is important that the application of correction methods does not itself introduce harmful flashes.

Potentially harmful flashes are preferably corrected by one of the following methods: replacing contrasting luminance with contrasting chromaticity (isoluminance) for example replacing black-white flash with red-green; reducing the luminance contrast by adjusting the brightness of neighbouring images towards the mean; or flashes of saturated red may be substituted for an alternative colour, for example green.

All of these methods can be implemented using pixel- wise, linear arithmetic operations.

Potentially harmful patterns are preferably corrected by one of the following methods: replacing contrasting luminance with contrasting chromaticity (isoluminance) for example, replace black- white with red-green; reducing the luminance contrast of the image; or applying a two-dimensional low-pass filter to the image to reduce the sharpness of edges in the image.

Again, all these operations can be implemented using pixel- wise, linear arithmetic operations.

The foregoing describes only a preferred embodiment of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

Claims

1. A system for interfering with an image or sequence of images being displayed on a visual display unit of a device generating the image or images, the system including a programmable image control device disposed in electrical communication with the image generating device and configured to process images generated by the image generating device wherein the image control device interferes with an image or sequence of images with predetermined characteristics that can trigger or potentially trigger photoepileptic seizures.

2. A system according to claim 1 wherein the image control device is integrated into the image generating device and is programmable to interfere with patterns in images, image colour intensities and rates that images flash in a sequence of images having the predetermined characteristics that can trigger or potentially trigger photoepileptic seizures.

3. A system according to claim 2 wherein the image control device is programmable by a viewer to prevent images or sequence of images to which the person can be sensitive from being displayed.

4. A system according to claim 2 or 3 wherein the image control device is remotely programmable to update images or sequences of images that can trigger or potentially trigger photoepileptic seizures.

5. A system according to any one of claims 1 to 4 wherein the image control device detects images having the predetermined characteristics that can trigger or potentially trigger photoepileptic seizures by a time dependent analysis including frequency transforms or histogram analysis.

6. A system according to any one of claims 1 to 4 wherein the image control device interferes with images having potentially harmful flashes by replacing contrasting luminance with contrasting chromaticity, reducing the luminance contrast by adjusting the brightness of neighbouring image portions towards a mean luminance or substituting potential harmful flashes of red with another predetermined color; and the image control device interferes with potentially harmful patterns by replacing contrasting luminance with contrasting chromaticity, reducing the luminance contrast by adjusting the brightness of neighbouring image portions towards a mean luminance or applying a two-dimensional low-pass filter to the pattern to reduce the sharpness of the pattern edges.

7. A system according to any one of the preceding claims wherein the image control device interferes with an image or sequence of images by blocking or substantially dimming the display of patterns or colours with the predetermined characteristics that can trigger or potentially trigger photoepileptic seizures, and modifies the rate of flashing of a sequence of images that can trigger or potentially trigger photoepileptic seizures to within a predetermined range, substantially dimming portions of the images, by changing colors of portions of the image or by reducing sharpness of image edges in the sequence.

8. A system according to any one of the preceding claims wherein the image generating device includes a computer, gaming console, video or mobile telephone, personal digital assistant, video cassette digital video or laser disc recorder or player, video camera and television.

9. A system according to any one of claims 1 to 8 wherein the image control device is disposed to process the image or sequences of images before being processed by the image generating device.

10. A method of using the system according to any one of the claims 1 to 9 for interfering with an image or sequence of images having predetermined characteristics that can trigger or potentially trigger epileptic seizures, the method including the steps of: communicating an image or sequence of images from the image generating device to an input of the image control device; processing the image or sequence of images in the image control device; removing images or portions of images that have the predetermined characteristics; modifying the images that have the predetermined characteristics to within a predetermined range; outputting the removed image or modified sequence of images from the image control device to the visual display unit.

11. A method according to claim 10 wherein the step of processing the image includes the step of detecting the images having the predetermined characteristics that can trigger or potentially trigger a photoepileptic seizure by time dependent analysis selected from the group consisting of frequency transforms or histogram analysis.

12. A method according to claim 10 or 11 wherein the steps of: modifying the images having potentially harmful flashes by replacing contrasting luminance with contrasting chromaticity, reducing the luminance contrast by adjusting the brightness of neighbouring image portions towards a mean luminance or substituting potentially harmful flashes of red with another predetermined colour; and modifying the images having potentially harmful patterns by replacing contrasting luminance with contrasting chromaticity, reducing the luminance contrast by adjusting the brightness of neighbouring image portions towards a mean luminance or applying a two- dimensional low-pass filter to the pattern to reduce the sharpness of the pattern edges.

13. A method of programming the imaging control device according to any one of claims 1 to 9, the method including the steps of: communicating an image or sequence of images that have the predetermined characteristics to a programming receiver device which is in communication with the imaging control device; and storing the images or sequence of images in the imaging control device.

14. A method according to claim 13 further including the step of communicating an image or sequence of images to be removed from the imaging control device and removing the image or sequence.

15. A programmable image control device for use in conjunction with an image generating device, the image control device being disposed in electrical communication with the image generating device and configured to process images received or generated by the image generating device wherein the image control device interferes with an image or sequence of images with predetermined characteristics that can trigger or potentially trigger photoepileptic seizures.

16. A programmable image control device according to claim 15 wherein the image control device is integrated into the image generating device and is programmable to interfere with potentially harmful patterns and potentially harmful flashes in images having the predetermined characteristics that can trigger or potentially trigger photoepileptic seizures.

17. A programmable image control device according to claim 16 wherein the image control device is programmable by a viewer to prevent images or sequence of images to which the person can be sensitive from being displayed.

18. A programmable image control device according to claim 16 or 17 wherein the image control device is remotely programmable to update images or sequences of images that can trigger or potentially trigger photoepileptic seizures.

19. A programmable image control device as defined in any one of claims 15 to 18 wherein the image control device interferes with an image or sequence of images by blocking substantially dimming portions of the images, by changing colors of portions of the image or by reducing sharpness of image edges in the sequence.

20. A programmable image control device according to any one of claims 15 to 19 wherein the image generating device includes a computer, gaming console, video or mobile telephone, personal digital assistant, video cassette digital video or laser disc recorder or player, video camera and television.

Dated this 17t^mhDay of April, 2003