WO2004042690A1

WO2004042690A1 - Display unit with light emitting diode (led) for display billboards and method thereof

Info

Publication number: WO2004042690A1
Application number: PCT/GB2003/004790
Authority: WO
Inventors: Mincham Nathan
Original assignee: Techspan Systems Ltd
Priority date: 2002-11-05
Filing date: 2003-11-05
Publication date: 2004-05-21
Also published as: GB0225699D0; AU2003276473A1

Abstract

A method and apparatus are disclosed for displaying a desired image. The image is a combination of many sub-images each of which is generated by a display module having at least one pixel array.

Description

DISPLAY UNIT WITH LIGHT EMITTING DIODE (LED) FOR DISPLAY BILLBOARDS AND METHOD THEREOF

The present invention relates to a method and apparatus for displaying an image. In particular, but 5 not exclusively, the invention relates to the provision of a road traffic sign.

Various displays for indicating an image to a viewer are known. For example a billboard to which a paper 10 image may be posted or a road sign including a base and indicating panel which bares a desired traffic sign. These have the disadvantage that a good deal of effort is required in order for the displayed image to be altered.

l-> Recently displays have been developed which can display different images. These are called variable message signs. Such displays typically consist of an image panel including rows and columns of lamp units which may be selectively illuminated to form letters or

20 characters according to a programmed input signal. The programmed input signal may come from a remote observation point such as a traffic control station whereby a speed limit or an imminent lane closure may be signalled to a motorist.

25

These types of display unit, whilst being more versatile than previous panel signs, are limited in the variety of images which can be displayed. In particular only a limited range of fixed characters on a fixed

30 number of rows may be selected by a controller. Also the size of the display unit remains limited so that visibility is limited. Another problem is that maintenance of more complex signs is often cumbersome and/or expensive as whole display screens and control apparatus must be replaced when a fault occurs.

It is an aim of the present invention to at least partly mitigate the above-referenced problems.

According to a first aspect of the present invention there is provided a display apparatus for displaying a predetermined- image comprising:

a plurality of display modules each comprising at least one pixel array for providing a respective sub- image associated with that display module; whereby

when said display modules are arranged side by side, sub-images provided by the display modules may be formed simultaneously to thereby provide, in combination, said predetermined image.

According to a second aspect of the present invention there is provided a method for displaying a predetermined image comprising the steps of:

arranging a plurality of display modules, each comprising at least one pixel array, side-by-side; and

simultaneously forming a respective sub-image via each of said plurality of display modules, said sub- images, in combination, forming said predetermined image.

Embodiments of the present invention provide the advantage that a very versatile display is provided which is able to be pre-programmed to display a wide range of characters and shapes. A remote user, for example located at a traffic monitoring station, can select a sign thus pre-selecting an image to be formed by the display. Data signals are communicated to the display and this data is used to selectively turn on or off light emitting diodes in selected display modules. Each display module can provide its own letter, character or number or may form a partial image so that a larger character may be formed in combination with the pixel arrays of one or more adjacent display modules.

By combining images from separate display modules larger characters than have hithertofor been available may be formed. In addition the modular arrangement of the display means that maintenance of the display can be simplified by either removal and replacement of a pixel array in a display module or by replacement of a display module .

For a better understanding of the present invention embodiments of the present invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings in which:

Figure 1 illustrates a front view of a display unit and support;

Figure 2 illustrates a display module;

Figure 3 illustrates a front grille;

Figure 4 illustrates two parts of a front grille may be offset with respect to the location of the EDs; Figure 5 illustrates a side view of a display module;

Figure 6 illustrates a top view of a display module;

Figure 7 illustrates control circuitry for the display unit;

Figure 8 illustrates a sign driver; and

Figure 9 illustrates a back view of a display unit.

In the drawings like reference numerals refer to like parts.

Figure 1 illustrates the front of a display according to a preferred embodiment of the present invention. The display can be used as a road traffic sign, particularly for use along the side of a motorway. It will be understood that further embodiments of the present invention can be used for displaying an image for other purposes. For example in shopping malls, at railway stations or at sports arenas or in other environments where information needs to be transferred to a viewer with high visibility. The information conveyed by the display may change so that different images may be displayed.

The sign 10 in figure 1 includes a display unit 11 and support 12. The display unit 11 includes a central image forming area 13 surrounded by a frame 14 which includes rigid members (not shown) to help provide a rigid structure. Lanterns 15 are located in each corner these may be red and/or amber lamps. When flashing these form an attention grabbing mechanism so that that the attention of passing motorist is drawn to the sign. It will be understood that embodiments of the present invention are not restricted to requiring use of lanterns. Rather the lanterns may be omitted entirely or their functionality replaced by an area of the display.

The central image forming area displays an overall image. However this overall image is produced by the combinations of multiple sub-images which are produced simultaneously. These sub-images are produced individually by respective display modules each of which has its own respective sub-image forming area 16. The image forming areas of adjacent display modules substantially abut and are arranged, when the display modules are located side by side, proximate to each other so that the sub-images formed by respective display modules combine substantially without any gaps therebetween. It will be understood that embodiments of the present invention provide a display which will often be viewed from many metres away and possibly whilst a viewer is travelling at high speed. Under these conditions the visibility of any small gaps between the sub-images will be much reduced and may be substantially invisible .

A portion ot the image torming area 13 is shown cut away in figure 1 to show a display module mounting framework 17. The framework 17 defines a matrix of locations at each of which a display module may be located and secured. Once a display module is^' secured at each location defined by the framework the sub-images of the thus located modules combine to form a patchwork of partial images making up the overall image. It will be understood that embodiments of the present invention can be provided using any form of means by which the individual display modules can be located and secured. In this sense the framework may include a back panel with locating holes, a mesh or any other suitable means.

The display unit 11 is supported by support 12 which includes a substantially vertical post portion, an overhanging portion 19 and curved connecting portion. The display unit is connected to the overhanging portion of the support by suitable connectors . The support forms a cantilever pole which may be formed from hollow steel . The pole may be a two part welded construction with a flanged joint in the rising member. It will be understood that other shapes and types of support for the matrix of display modules may be used. The supports hold the display unit in a fixed location relative to the ground. It will be likewise understood that the display unit 11 may be supported from above such as from a bridge or from a side.

The display is thus configured as eight rows of twelve modules. In this way the entire face of the display area is built up in a modular fashion. Each display module contains a square array of pixels set out in rows and columns with each pixel comprising red and an amber light emitting diode (LED) elements. It will be understood that the present invention is not limited to use with any particular colour or number of LED elements. Preferably one amber LED and one red LED are provided per pixel. This is provided by each display module 16 comprising four eight times eight pixel PCB assemblies. A display module 16 is illustrated in figure 2. Each LED display module includes four printed circuit boards 20 (PCB) fitted with control electronics and sixty four image forming pixels 21 arranged in an eight times eight matrix.

Each pixel cluster contains one high intensity amber LED and one high intensity red LED. The pixels are arranged on a 20 mm pitch. Luminance control of the pixels is effected through pulse width modulation- of the DC power supply and controlled by an LED display controller as described hereinbelow. Mechanical honeycomb louvers 22 are fitted around the pixels to minimise the effects of direct sunlight on the LED display. Each display module is powered by a 6.5 volt DC power supply and is connected back to an LED control module as described hereinbelow which provides the control and monitoring of the characters via a daisy chained bus link. The display PCBs 20 are individually fixed to the module within the sign by being located into a framework structure on the rear of the honeycomb body 22 and by then being secured by screws. The PCBs are readily removable for maintenance purposes by removing four screws and unplugging power and data leads provided via sub PCBs 23 and 24. Each LED may be individually monitored and single LED failures can be detected. A low test current is used to ensure that testing is unobtrusive. The LEDs used may be un-tinted, non- diffused solid state devices designed to give a high luminous intensity within a well defined viewing angle. Display brightness is controlled by pulse width modulated signals generated by the LED display controller described hereinbelow. Fifteen levels of brightness may be provided though more or less levels may be provided. The LEDs are directly driven without multiplexing to avoid possible strobing affects. Each display PCB of sixty four dual colour pixels is fitted with two multi- way connectors for power, data, control and monitoring signals. It will be understood that embodiments of the present invention may be supplied with power and data connection of other types. The display module controller PCB 24 is fitted with separate connectors for serial data and power. Two of the data conductors are used to provide a data pipe for messages to control and interrogate the display module. The remaining two data conductors are used to provide a synchronisation pulse to the display module that is used to provide synchronised flashing of the display. The same two data conductors may also be used to re-program the software within the controller PCB 24.

Each display module 16 is constructed as an easily removable module. Removal is achieved by loosening easily accessible retaining fixings and disconnection of power and control leads only. The weight of the display module is such that handling in all conditions of operation and maintenance is a simple procedure. The display module also includes a front cover 25 which provides a front face which is transparent and has specially shaped cut-outs (formed by a grille 26) to control the ingress of ambient light and angles over which the pixels are required to be seen. The front cover 25 forms a polycarbonate shield which may be sealed when the module 16 is mounted in the display. This helps provide complete protection against ingress of alien material . It will be understood that the present invention is not limited to use of such material.

A grille 26 is included on the front of the front cover. Due to the low fraction of cut out material of the grille, and the fact that the remaining material is coated with a matt black finish, there is comparatively little of the polycarbonate shield visible from the front. This provides a display with a dark background and high contrast ratio. The front of the polycarbonate shield may be coated with hard anti-reflective film to resist abrasion and minimise reflected light. On the inside face a coating is used which will provide protection against misting or fogging due to the presence of small quantities of water in combination with certain critical temperature conditions. This film operates by preventing the water from forming into beads due to local surface tension and spoiling the otherwise clear optical properties of the shield. It will be understood that both or either of the antireflective film or coating may be omitted. The use of the inside face coating is however helpful particularly when a cold start option for a display is envisaged.

Figure 3 illustrates a front view of a portion of the front grille 26 with cutaway areas 30 and 31. The cutaway areas 30 are larger than cutaway areas 31. The cutaway portions 30 are located generally in front of the two LED elements in each pixel whilst the cutaway areas 31 are generally located in front of an area of a PCB 20 to which the LED elements are secured. Grille posts 32 are located at selected positions between LED elements in adjacent pixels so as to provide rigidity to the grille structure and to help provide a desired dark background and high contrast ratio to the display module 16. Figure 4 illustrates the location of the grille posts 32 with respect to the location of two LEDs 40 and 41 forming a single pixel pair. As will be seen the posts 32 have a predetermined offset from a location directly in front of a respective LED. This is to ensure that the image making characteristics of the display module satisfy stringent standards . Most notably predetermined standards demand that light intensity viewed laterally at an angle of 10 degrees from normal (i.e. directly in front of) an LED is within a certain percentage of the light intensity when that LED is viewed straight on. The dotted line 42 shown in figure 4 illustrates the intensity profile of LED 40 with no grille element 32 present. With the grille element present the intensity directly in front of the LED 40 is diminished due to the grille. However the intensity of the LED 40 when considered directly in front of LED 40 is still sufficiently intense to satisfy well known standards. By having the grille offset the viewed intensity of the LEDs 40 and 41 when viewed at an angle of 10 degrees from the normal is also within a predetermined fraction threshold of the intensity when the LED is viewed straight on.

As shown in Figure 5 the honeycomb 22 serves to divide the pixels into individual cells. The horizontal sections prevent the incidence of ambient light, from sunlight etc, above an angle of 10° from the normal from reaching the LEDs and reflecting back to the view thus destroying the contrast ratio. Vertical sections may be included to prevent stray light from one pixel leaching into the next position which would also reduce image sharpness .

At the end of the honeycomb 22 the front face of the printed circuit boards may be finished in a matt black coat to reduce reflections and provide a good contrast level between on and off states of the LEDs . The printed circuit boards themselves may be coated with a protective lacquer finish to prevent damage by moisture. In more detail the honeycomb 22 includes a louvre portion having a substantially horizontal surface 50 which sits and projects outwardly above each horizontal row of LEDs. A downwardly angled surface 51 of each louvre extends downwardly and away from a lower surface of each row of LED elements. In this way light emitted from each LED is prevented from being observed by a viewer located substantially above the respective row of the LEDs .

Figure 6 illustrates another view of a display module showing further elements of the honeycomb 22. The honeycomb 22 includes vertical baffles 60 which extend towards the front of the display module away from the PCBs to which the LEDs are mounted. These baffles help determine how light emitted from each particular LED may be observed. This is illustrated in figure 6 by virtue of the red LED element 61 and the amber LED 62 which together form a pixel . Optical specifications for the sign such as MCE 2214 Motorway Signal Mark 4 requirements or the TR 2136 Optical Performance Functional Specification for Discontinuous Variable Message Signs Specification provide rules which the light emitted from the LEDs must satisfy. Notably the intensity of the LEDs 10 degrees from a location normal (or straight on) to the LED is defined. Thus the tips of the baffle part 60 of the honeycomb 22 extend only so far without preventing light emitted from the LEDs 10 degrees from normal to be viewed by a viewer. As shown in figure 6 the front cover 25 may be chamfered at region 63 so that the light emitted by the LEDs satisfies further parameters. Notably if light emitted from an LED must be viewed through only one intervening body then chamfering the front panel helps ensures the peripheral LEDs on the edges of the display module satisfy this condition. This avoids the case where an LED is viewed through two pieces of the front cover at the border between adjacent display modules.

At the rear of the module the main body includes a seating interface 27 which enables the display module 16 to be mounted to a module mounting surface of the main display unit. The module mounting surface may form a framework within which the individual display module 16 may be mounted. A continuous closed cell ethylene propylene diene monomer (epdm) seal 28 or some other suitable sealing arrangement may be fitted to the mounting framework. The seating area of the display module beds into this seal and can provide a total environmental barrier and prevent ingress to the enclosure. Where the module 16 is attached to the mounting surface locating pins ensure that the module is accurately attached within the array. Depth stops may also be included which control the pinch of the seal and retain the parallelism of the module with respect to adjacent display modules. When all of the display modules are located in the display unit the edges of the front faces of the modules abut and the front face of the whole display is completely sealed against ingress.

When maintenance is required, one of at least two methods may be used to attend to a defect. If there is a display board failure then one of the printed circuit boards may be changed from the rear of the display module 16 without removing the actual display module from the mounting surface of the display. The circuit boards are connected by means of industry standard connectors for power and data signal and may thus simply be removed and re-connected. If a display module 16 is physically damaged then it may be changed also using only rear access from the display. It is possible to remove the display module rear fixings, and then withdraw it through an orifice associated with the display module in the rear of the display unit . A restraining strap may be included. The use of the strap may be procedurally enforced so that whilst the module is being manoeuvred the strap must be used. This prevents the possibility of a module being dropped at the front of the display.

Figure 7 illustrates in block diagram format the circuitry and system for controlling the formation of images in the display. As shown in figure 7 the display modules 16 are connected together using a serial data bus. Each display module contains a local controller and forms an intelligent slave node on the data bus Further controllers are used to control and monitor the lighting of the lantern assemblies 15. As noted above an LED amber/red lantern is located in each corner of the front face of the display unit . The lanterns flash in pairs from top to bottom (amber) or right to left (red) whenever required.

A master sign driver 71 is provided and this coordinates the control and monitoring of all the display modules and lanterns and interfaces these to a control source 72 which may be a remote traffic control station or any other node where an image to be displayed by the display can be predetermined. Control signals from the control source 32 to the sign driver 71 may be made over a data bus or other communication link such as a wireless interface. The sign driver forms a master control unit within the display unit 11 and sends and receives data to and from slave display controller units, lantern controllers and aux controllers by means of a serial data bus . The sign driver 71 also interfaces with an auxiliary control module 73. The auxiliary control module supervises the environmental control elements, located in the display unit, including heaters, monitors for the temperature and humidity levels and heater integrity as will be described hereinafter. The sign driver 71 also interfaces with an externally mounted ambient light monitor 74 which is located externally of the display unit. The ambient light monitor incorporates ambient light sensors for determining the light levels in the surrounding region.

The sign driver 71 receives commands from the control source and is responsible for a number of functions. Notably these include interfacing between the control source 72 and display unit network using a predetermined protocol. The driver also creates a bitmap of the image which is to be displayed. The image is determined by a user at the control source 72. The driver unit 71 includes fonts and graphic images stored within an internal memory (not shown) . In response to the receipt of control signals determining a predetermined image to be displayed the sign driver 71 issues commands and monitors the display of the display modules unit 16 and LED lanterns to set and clear text/character images. The sign driver 71 also issues command and monitors the auxiliary control module to control and monitor the environmental control system. Likewise the sign driver 71 can issue commands and monitor the ambient light monitor 74 to monitor ambient light sensors. The sign driver control unit 71 derives its power from an internal power supply mounted in the display unit. The display module 16 derive power from a number of internal power supplies. One power supply is provided for every three display modules. The LED display controller 24 within each display module interfaces with the sign driver via a serial data link and responds to commands from the sign driver to set or clear display data in addition to continuously monitoring the LED modules for correct operation and returning the operational status of each LED to the sign driver 71.

A common brightness control line ensures that the display modules 16 are maintained at a similar brightness level. Various brightness levels may be available. The lanterns 15 also have various brightness levels which may be selected.

The display unit 10 includes light emitting diode lanterns 15 which include neutral filters and which are mounted in the corners of the display enclosure. The lanterns flash in pairs from top to bottom or right to left when requested by the sign driver 71. Their flashing is controlled by a respective lantern controller. According to a preferred embodiment there may be one hundred and sixty red LEDs and one hundred and sixty amber LEDs arranged in chains of ten operating from 32 volts DC. The 32 volts DC power feed is pulse width modulated by the lantern controllers to provide control over the brightness of the lantern LEDs . Mechanical louvers create the different viewing cones for red and amber as is known in the art . Each lantern module is constructed as an easily removable module. Removal may be achieved by loosening easily accessible retaining fixings and disconnection of power and control leads only. The weight of each lantern module 15 is such that it is safe to handle in all conditions of operation and maintenance .

An externally mounted ambient light monitor (ALM) is fitted with two sensors external to the display unit 10. One sensor faces in a forward direction in the same plane as the face of the sign whilst the other sensor faces upwards. Via these light monitors the ALM will compute a luminance level of light in the surrounding region.

The temperature and relative humidity within the enclosure of the display unit are maintained by means of a combination of heater, thermal switches, humidity controllers and natural convection ventilation as controlled by the auxiliary controller 73. Heaters in the base of the enclosure can prevent condensation in cold weather.

The display unit enclosure may be manufactured from aluminium section and sheet which is folded and welded to form an enclosure within which a box and channel section frame 14 provides vertical and horizontal sheer strength. The front face of the enclosure to which each display module mount is formed as part of a square honeycomb construction 17 fixed within the enclosure. This structure is supported by attachment to the frame 14.

According to the preferred embodiment the control signals are transmitted from the control source 72 and received at the sign driver 71 in five byte packets. The packets are generated at the control source according to pre-programmed rules which determine, responsive to a desired image indicated by a user at the control source, a coded sequence of bits which will, when transmitted and acted upon, result in the display unit displaying a desired image. As illustrated in figure 8 which shows a sign driver 71 in more detail, the five byte packets are received on input 81 by data packet receiver 82. This incoming data is transferred to a bitmap construction unit 83. This reassembles multi-message data strings produced at the control source and constructs a bitmap of the image requested by the commands using stored fonts and graphic images stored in an internal database. The bitmap includes an entry for a respective one pixel in the pixel arrays of each display module. In this way by setting each entry in the bitmap to a 1 or 0 the illumination of a respective LED in each pixel array of each display module can be determined. In this way individual pixels can be selectively turned on or off which permits pixels in pixel arrays of adjacent display modules to be illuminated so that the combination of images from adjacent display modules combine to form an overall image. The bitmap generated by the bitmap generation apparatus 83 is transmitted to the LED display modules.

Each sign driver also includes a status collection and collation processor 84 which collects environmental data so that the temperature and humidity and lighting of the display can be monitored and controlled. A lantern control unit 85 is also provided which controls illumination of the lantern units as herein described.

It will be understood that according to embodiments of the present invention each LED display controller will be arranged to process commands received from the sign driver such as direct bitmaps and status requests . The character fonts and image definitions will be held by the sign driver however a fixed sixteen times sixteen font may be held in a memory array of each LED display control for use in test bitmaps.

As illustrated in figure 9, which illustrates a reverse view of the display 11, pairs of side hinged rear doors 90 with stays and individual locking provide service access to the back of the display modules. The display 11 of figure 9 is shown cut away to show the module mounting surface 17.

Embodiments of the present invention provide a single LED display having a large overall size. Manufacturing and maintenance of such a display is achieved, in part, by the fact that the display is constructed in a modular fashion. Each module of the display is square or some other shape which can tessellate. In this way adjacent display modules will fit closely together so as to give the appearance of one large overall display. The pixel arrays each of which comprise a multitude of light emitting diodes are arranged within the module so that the light emitting diodes extend substantially across the whole extent of the area of the display module. In this way the light emitting diodes at a peripheral region of a display module will be proximate to light emitting diodes at an opposing peripheral region of an adjacent display module. Gaps between the light emitting diodes of adjacent modules are kept to a minimum so that the image formed by the combination of images of the two adjacent display modules shows no interface. This may preferably be achieved by matching the pitch, that is the distance between LEDs, of the LEDs arranged in each individual display module with the pitch between LEDs at the edge regions of two adjacent display module when the two display modules are located side by side and/or one above another.

Although the above preferred embodiments have been described in detail with respect to the accompanying drawings it will be understood that the present invention is not limited to the details described herein. Rather variations and modifications may be made without departing from the scope of the present invention.

Claims

CLAIMS :

1. Display apparatus for displaying a predetermined image comprising:

when said display modules are arranged side by side, sub-images provided by the display modules may be formed simultaneously to thereby provide, in combination, said predetermined image .

2. The display apparatus as claimed in claim 1 whereby:

each pixel in the at least one pixel array comprises at least one light emitting diode which may be selectively illuminated to thereby provide a sub-image; and

light emitting diodes of pixels in a selected plurality of display modules may simultaneously be illuminated whereby sub-images from the selected plurality of display modules are simultaneously formed.

3. The display apparatus as claimed in claim 1 further comprising:

a module mounting framework defining a plurality of locations at each of which a one of said display modules is locatable; whereby, when so located, said display modules are disposed side-by-side.

4. The display apparatus as claimed in claim 3 wherein said plurality of display modules are arranged in a plurality of rows and columns when located by said framework; whereby,

when so located, the image area, on which a sub- image is formed, of the at least one pixel array of adjacent display modules, substantially abut.

5. The method as claimed in any one of claims 1 to 4 wherein:

said at least one pixel array comprises four pixel arrays each comprising a plurality of N rows and M columns of pixels, each said pixel being provided by at least one light emitting diode arranged to be illuminated by application of a predetermined voltage on a respective control line.

6. The display apparatus as claimed in claim 5 wherein each pixel comprises one amber light emitting diode and one red light emitting diode.

7. The display apparatus as claimed in claim 5 wherein at least one pixel array in each respective display module is mountable so that the sub-image formed by said array is formed at a front side of the module and each of the at least one pixel arrays is removable from a reverse side of said display module.

8. The apparatus as claimed in claim 3 or any claim dependent therefrom further comprising a rigid support frame surrounding, and secured to, said module mounting framework, said frame including a central window region through which the predetermined image, formed by the combination of sub-images provided by the display modules located by the framework, may be viewed.

9. Apparatus as claimed in claim 8 further comprising:

at least one lighting unit disposed at a peripheral region of said frame for drawing viewers attention to the predetermined image .

10. Apparatus as claimed in claim 8 further comprising a support post securable to said frame for supporting and positioning said display apparatus.

11. The apparatus as claimed in any preceding claim further comprising:

a master display controller arranged to receive data, determining an image to be displayed, from a remote server and for generating at least one control signal for selectively illuminating light emitting diodes of pixels in respective pixel arrays of a plurality of said display modules .

12. Apparatus as claimed in claim 11 further comprising:

at least one pixel display controller for receiving said control signal and generating illumination control signals which selectively turn light emitting diodes, comprising pixels, on or off in said pixel array.

13. Apparatus as claimed in any preceding claim wherein each display module has a square shape front face.

14. Apparatus as claimed in any one of claims 1 to 12 wherein the shape of the front face of the display module can tessellate.

15. Apparatus as claimed in any preceding claim wherein the pitch between light emitting diodes in each pixel array substantially matches the pitch between light emitting diodes at the opposing edge regions of display modules when located adjacent each other.

16. A method for displaying a predetermined image comprising the steps of:

17. The method as claimed in claim 16 further comprising the steps of :

for each of said plurality of display modules, illuminating at least one light emitting diode of a respective pixel array to thereby form a respective sub- image .

18. The method as claimed in any preceding claim further comprising the steps of:

mounting said plurality of display modules via a mounting framework of display apparatus, thereby locating each of said plurality of display modules at respective locations defined by said framework.

19. The method as claimed in claim 18 whereby said display modules are located side-by-side so that the image area of each adjacent display module substantially abuts.

20. Display apparatus constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings .

21. A method for displaying a predetermined image substantially as hereinbefore described with reference to the accompanying drawings .