GB2415851A

GB2415851A - Multiple display system

Info

Publication number: GB2415851A
Application number: GB0414585A
Authority: GB
Inventors: Humayun Sheikh
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-06-30
Filing date: 2004-06-30
Publication date: 2006-01-04
Also published as: GB0414585D0

Abstract

It is known to connect multiple video display units (VDU) to a common computer to give an increased display area. However, this is only practicable in specialist environments which have sufficient space for free standing units, and where the computer has free slots to accommodate additional video cards. The invention allows a primary VDU (1) to operate on its own in a conventional manner whilst allowing secondary VDU's (2) to be added as retrofits, when the need arises, without modification of the computer hardware and without the provision of duplicate video cables 16 between the computer and the VDUs. The secondary VDU's receive a video signal form the primary VDU where the image signal is split as appropriate for the connected VDU's.

Description

DISPLAY SYSTEM

This invention relates to a display system comprising a number of separate visual display units (VDUs) assembled to increase the area of the total display surface. The invention is likely to be of primary use in connection with computers, and is described herein in relation to computers. However it should be understood that there is no reason why it should not also find value for use in displaying images from any video source, or even a combination of sources.

There are many existing systems and proposals for linking VDUs to a common computer. Electronic "cards" are available which can be slotted into a computer's motherboard to provide an additional video output for this purpose.

This system is highly effective in environments where there is sufficient space to accommodate a number of separate free-standing VDUs on a work surface, where the technical effort of fitting new computer cards is not a problem, and where the computer is known to have sufficient free slots for these cards.

However, most environments where computers are used do not meet all these requirements and therefore the use of this system is generally confined to specialist environments.

Other systems are available, eg as described in patent specifications US 6222507 and US 6690337, which combine together a number of VDUs.

However these are all expensive and they, require, a specially designed or - 2 modified computer to supply appropriately different video signals to the respective VDUs.

This invention arose from the realisation that there would be a potential demand for a VDU which operates on its own but which has a facility to allow extra VDUs to be attached as retrofits, without any need for modification of the computer hardware or for the provision of duplicate video cables between the computer and the displays.

The invention provides a display system comprising: a primary VDU having a port for reception of video signals from a source device; at least one secondary VDU adapted to be connected to the primary VDU to receive video signals from it; and a control system designed to process the video signal so as to display different parts of a video output from the source device on respective different VDUs when a secondary VDU is connected.

By using the invention it becomes possible for a user to purchase initially just that one VDU, at a cost which is comparable with conventional VDUs, knowing that, at a later date, further secondary VDUs can be purchased and fitted. A preferred feature is the inclusion, preferably within one or more of the VDUs, of means for detecting the fitting of a secondary VDU. The system can then automatically configure itself to become a multiple screen system. This is all - 3 possible without modification to the computer hardware or the use of multiple video leads from the computer to the individual VDUs.

The primary VDU will normally comprise a screen contained within a housing/support structure, along with associated drive circuitry and the control system previously referred to. Each secondary VDU will normally also include a screen and associated housing with drive circuitry. Preferably each secondary VDU will comprise means for identifying its presence and properties to the primary VDU and/or the host computer.

Although the secondary VDUs could be self-supporting, and connected only electrically to the primary VDU; a significant preferred feature of the invention is for the secondary VDUs to be supported physically on the primary VDU, making the whole system less intrusive on available workspace. If desired, the connection between the VDUs can be such as to allow them to pivot relative to each other either about an up-down axis so that the screens are inclined towards the user; or about a lateral axis so that say a rectangular screen could be swivelled from a position for displaying a picture in "portrait" format to a position suitable for landscape format. In this latter variation it would be desirable for the detecting means to sense the orientation of the secondary screens and to cause appropriate adjustment of the manner in which the image is displayed. In other arrangements the secondary VDUs could be supported, eg on flexible tubular stems, to allow an infinite variation of adjustments. I: or all - 4 configurations, it is preferred that the secondary VDU should be smaller than the primary VDU since it is believed that in most situations there is one set of information which is more important for the user's attention than others.

The control system is preferably to be within one or more of the VDUs since it is this feature which makes it possible to install and use the system without the use of video cards in the central computer and without individual video leads connected to the computer.

It is to be understood that, when reference is made in this specification to the term "VDU" this refers generically either to a display screen on its own or to the screen and an associated housing, drive circuitry and possibly a physical supporting structure.

The "detecting means," which senses the presence or otherwise of a secondary VDU, is preferably located in a housing or supporting structure of the main VDU. It would be possible for its function to be performed by software within the computer, but this is not preferred because it introduces an extra complication for the user to install such software and such an arrangement would slow the operation of the system.

The VDU housings will normally include a frame or border around the edge of the screen. Conventional thinking would suggest that it is best to minimise the width of this frame and to minimise the space between adjacent screens.

However, it is now believed that there can be an advantage in maintaining a visual separateness of the different screens, because they can then be used for displaying different images of a type which benefit from being visually separate. For example an illustration might be displayed on one screen whilst an accompanying text is displayed on another screen. The fact that the screens are separate avoids the risk that the appearance of text immediately adjacent the picture would detract from the visual appreciation of the picture. Thus, there can be benefit from accentuating the "separateness" of the screens by giving the pictures different visual characteristics, for example different background colour schemes, different contrast values, or different intensities. This is easily done if, as is preferred, the primary VDU has a port for the reception of digital control signals from the computer.

One embodiment of the invention will now be described with reference to the accompanying drawings of a multiple screen display unit constructed in accordance with the invention. In the drawings: Fig I is a perspective view of a display system constructed in accordance with the invention, as seen from the front, Fig 2 is a rear perspective view of the display system, one of the secondary VDU's being shown separated to illustrate the way in which it is connected; - 6 Fig 3 is a schematic block diagram showing principles of operation of electronics contained within housings of the system illustrated in Figs 1 and 2; and Fig 4 shows schematically how subsidiary screens of the invention can be designed so as to face selectively towards or away from the principal user so as to allow someone on the opposite side of the display to view information.

Referring firstly to Figs 1 and 2, the illustrated system comprises a primary VDU 1 having a screen 11, a housing 12 containing the screen and electronic circuitry, and a stand 13. At the rear of the housing 12 (FIG 2) is a removable cover 14. This conceals a number of plug and socket arrangements 15 shown only schematically in Fig 3. One of these connects a video cable 16 to the VDU 1; another is for a data cable 17 connected to a computer; and a third for a power cable 18. Other connections 15 are for linking to the secondary VDUs, if fitted, as described below. The fact that only one video cable 16 is needed is an important and contrasts with known systems which rely on the fitting of extra video cards into the host computer.

In the illustrations, two secondary VDUs 2 are hinged at opposite sides of the main VDU 1 so that they can be angled as shown in Fig 1 to face towards a common viewing point. Each secondary VDU 2 has a screen 21, smaller than the screen 11, a housing 22, and a cable 23 (Fig 2) for carrying video signals, power and data signals. The cable 23 fits into a groove 23A and has a plug 24 which connects releasably to a connector, on the primary VDU l, hidden beneath the removable cover 14 Fig 2 illustrates how a secondary VDU 2 is hinged by brackets 3 each having two lugs 31 which form a push fit into corresponding holes 32 in the housings.

Referring now to Fig 3, an analogue video signal in Video Graphics Array (VGA) format enters the VDU 1 along cable 16. An input video buffer 19 interfaces to the incoming VGA signal and provides amplification to allow the signal to be split between three identical screen processing units 1 10.

A clock generator 111 uses synchronization signals from the VGA feed to extract a master clock for the system. This master clock is further used to generate timing signals to control the sampling of incoming colour signals, and to generate control and timing for all parts of the screen processing units l l 0.

Each unit l 10 has a high speed analogue to digital converter 1 12 which converts the incoming analogue colour signals (red, green and blue), to a digital form. An input interface 113 performs a "windowing" or "filtering" function under the control of a microcomputer 20 to be described later. It selects which data to pass and which to block. In this way, the desired portion of the incoming data, window or picture is selected for further processing. - 8

Since the incoming data is almost always at a different rate from the outgoing data, a local temporary memory in the form of pixel buffer 114 is included to buffer the incoming data before it is required at the output.

There may be situations where it is a requirement for the windowed input screen format to be different from the output screen format. In such cases, the number of pixels in a line, and/or the number of lines in a screen may need to be changed. An image processing block 115 achieves this by controlling the relationship between the pixel data entering and leaving the pixel buffer 1 14. In addition, there may be times when a more sophisticated level of pixel manipulation is necessary, and this may take the form of adjacent pixel mixing or interpolation. Finally, similar data manipulation may take place on a line-by- line basis, for achieving the modification of screen size in the vertical axis.

An output interface block 116 controls the timely presentation of the processed data for feeding to the LCD panel 11.

In addition to the screen content data, an LCD display requires one or more timing signals to ensure the correct alignment of the picture on the physical screen. These timing (or synchronization) signals are generated by a TTI, to LVDS format converter 1 18 which receives synchronizing signals from a signal generator 1 19 controlled by the clock generator 1 1 1. The format converter I 19 will be discussed later.

The screen processing unit 1 10 thus serves to manipulate incoming video data to extract selected data and reformat it as necessary for the individual LCD display. One screen processing unit l l0 is required for each display panel in the system and in this particular embodiment of the invention all three processing units 110 are housed in the principal VDU housing 12. However it would be possible, in alternative designs, to locate each processing unit 110 in the housing of its respective VDU.

Much of the functionality of the screen processing unit 110 is provided by a single integrated circuit, an example of a suitable device being the Philips SAA67 1 3AH.

As the amount of data required by an LCD is relatively large (in excess of 200MB/s), the interconnection on flexible connection 23 between the processing unit ll0 and the LCDs 2 presents a serious problem. Ideally, one would use a small number of electrical connections operating at a high data rate (a "serial" link). However a serial link would entail a bit rate in excess of 2 Gb/s which is not viable. The alternative is a "parallel" link, where a large number of electrical connections are used, each operating at a relatively low speed. This, however, would require in excess of sixty connections, which is - 10 also not practical for a flexible coupling. The illustrated embodiment uses LVDS to allow the connection to be made using a relatively small number of interconnects (about 10 per channel), and the data rate on each is quite high.

The power required is minimised and the noise immunity enhanced, (whilst minimising radiated noise), by using a low voltage data signal in a differential configuration.

The smaller LCD screens 21 of the secondary LCDs do not have an LVDS interface and therefore an LVDS to TTL converter 22 is included.

LCD panels require background lighting to operate properly. Such lighting is normally created by a "backlight" integrated into the LCD panel, and these are generally of a cold cathode fluorescent type. These backlights require a high AC voltage to operate and an inverter circuit 119, operating from a low voltage DC source generates these voltages.

The primary VDU 1 is linked to a computer (not shown) by a conventional data link, in this case a USB connection 17. An interface 120 provides a general- purpose communication interface to the PC, for the transmission of non- video data. It is used to transfer system configuration parameters to and from the display system. Such information may consist of: number of display panels connected and their format; size of required display windows; auxiliary display data, for example, display border size and colour, and possibly overlay text; brightness and contrast controls.

A small self-contained microcomputer 121 provides the processing capability to S communicate with the PC and the display modules. It identifies the system capabilities and windowing requirements and sets up the screen processing configurations to suit. In particular it sets the filtering function of the interfaces 113 to ensure that the desired image or the desired part of an image is displayed on each VDU. The microcomputer 121 also controls power control circuits 122 which supply a low voltage supply to the LCD backlight inverters.

The microcomputer 121 also acts as a detector to determine which secondary VDUs are fitted. It controls the interface units 113 depending on the result of this determination. In order to ascertain the presence and parameters of each of the secondary VDUs, a communication channel exists between the microcomputer 121 of the primary VDU and each of the secondary VDUs.

In the illustrated embodiment, this communication channel is a two or three wire serial data link, for example RS232 or 12C (Inter-Integrated Circuit) shown at 121A on Fig 3. The primary VDU microcomputer 121 determines the presence of secondary VDUs each time the system is powered up and intermittently thereafter. It does this by sending a message on each 12 communication channel 121 A and awaiting a response. A correct response on a given channel indicates the presence of a secondary VDU 2.

Each secondary screen contains means to communicate with the microcomputer 121 in the primary VDU and, in the illustrated implementation, this is a small microcomputer 2A in each secondary VDU.

Finally, a power supply circuit 123 takes the incoming AC supply on cable 1.8 and generates all the low voltage DC rails required by the electronics.

On start-up of the computer, The microcomputer 121 in the primary VDU determines, from the microcomputers 2A of any secondary VDU, (a) the fact that that VDU is present and if so (b) its screen parameters, for example screen size ("x" by "y" pixels).

Using information from the host computer, via the data interface block 12O, defining the portion of the incoming screen data, requested to be sent to the secondary screen, together with the secondary screen parameters, the microcomputer 121 sets up functional parameters of each screen processing unit 1 10 to perform the appropriate image processing.

For example, let us suppose that two secondary VDUs are present, that each has a pixel size of 512 x 768, and that incoming screen data from the host computer - 13 has a pixel size of 2048 x 768. The microcomputer 121 sets up the appropriate screen processing units 110 to filter this image data from the incoming screen information, then to scale the image to fit the secondary screen pixel size if required. s

Microsoft Corporation provides a device driver layering facility which enables drivers to be written which sit between one interface and another. These drivers are known as "filter drivers." It is envisaged that VDUs employing the invention will be supplied with driver software for installation on the host computer which includes a filter driver positioned between the user and the standard video driver. The filter driver will present a view to the user of several different displays but the underlying video driver will actually be instructed to use a single display of a size which can be split, by the hardware, into the required number of displays. As an example, suppose there are three VDUs. The principal screen is 1024 x 768 pixels and the two secondary displays are 512 x 768 pixels. The user can use them as if they were three separate displays using the standard Windows interface (Windows is a registered Trade Mark of Microsoft Corporation). However the filter driver has actually instructed the video driver to use a display of 2048 x 768 pixels and the custom hardware is splitting the output video signal between the three physical displays.

It will be appreciated that the embodiment illustrated in Figs 1, 2 and 3 is just one of many variants which are possible within the scope of the invention. For - 14 example, in an alternative construction the secondary VDUs could be designed to plug in to the primary VDU using connections which provide the necessary physical support and electrical and communication contacts. In another variation the video and data communication between the primary and secondary VDUs could be by radio, infra-red, optical or other non-wired methods. Another variation would be to design the connection between VDUs so that a secondary VDU can be adjusted to face away from the main user so as to be viewed by another person. For example a secondary VDU could be mounted above the main VDU on a hinge allowing it to be swivelled so as to face in the reverse lO direction. Such swivelling could be about an up-down axis so that the image itself would not need to be inverted. Another possible physical configuration is shown very schematically, from the back, in Fig 4 and comprises a primary VDU 41 supported on a stand 42. Universal swivel joints 43 attach, to the primary VDU, two secondary VDUs 44 allowing them to be swivelled as shown by the arrows, about vertical axes, allowing their screens (not shown in the drawing) to lie against each other, folded away, when not in use. The secondary VDUs 43 can also be swivelled about a horizontal axis Y so that they become visible to someone facing in the opposite direction, away from the user. In this arrangement, a suitable connection for data and video signals, eg an optical link, is incorporated into the swivel connection shown only schematically at 43. An arrangement such as this could be useful in an environment such a bank where the main user wishes to show selected information, displayed on one or more secondary VDU, to a customer sitting or standing opposite. In a variation, one - 15 of the secondary VDUs could be a touch-screen allowing the customer to enter information such as a personal identification number. This facility is considered to be inventive in its own right and accordingly, a second aspect of this invention provides a multiple screen display system in which the screens are pivoted so that they can be adjusted so as to face in opposite directions or away from each other.

It is pointed out that, although the particular embodiments described use an analogue video input signal, alternative variations could be designed for use with digital video input or S-video inputs.

In many of its various forms, it is believed that the invention will provide a significant benefit to users who do not initially wish to commit to the expense of a multiple-display unit but who wish to keep open the possibility of expanding the dimensions of their display at a later date when the need arises and when funds permit. - 16

Claims

1. A display system comprising: a primary VDU having a port for reception of video signals from a source device; at least one secondary VDU adapted to be connected to the primary VDU to receive video signals from it; and a control system designed to process the video signal so as to display different parts of a video output from the source device on respective different VDUs when a secondary VDU is connected.

2. A display system according to Claim 1 including detecting means for detecting whether a secondary VDU is connected and in which the control system is arranged to receive the output of the detecting means and to process the video signal in a way which depends on that output.

3. A display system according to Claim 1 in which the control system is incorporated as part of one or more of the VDUs

4. A display system according to any preceding Claim in which each VDU comprises a screen and a screen supporting structure, the supporting structure including connector means by which the or each secondary VDU can be mounted on and supported by the main VDU as a retrofit. - 17

5. A display system according to Claim 4 in which the main VDU includes a port for receiving the incoming video signal, the control system serving to use an appropriate part or parts of this signal for display on the or each secondary VDU. s

6. A display system according to any preceding Claim in which the detector is included in the main VDU.

7. A display system according to any preceding Claim in which the main VDU has a data port for the reception of control signals for defining required visual characteristics of the images displayed each VDU.

8. A display system according to Claim 7 in which the visual characteristics of the VDUs are independently controllable by the control signals so that they can be set differently on different VDUs.

9. A display system according to any preceding Claim in which the secondary VDU comprises means for identifying its presence and its properties to the primary VDU and/or the source device.

lO. A display system according to any preceding claim including a pivot connection between the main VDU and at least one secondary VDU. - 18

11. A display system according to Claim 10 including means for measuring the angle of one screen relative to another and for adjusting the appropriate video signal according to that measurement

12. A display system according to any preceding claim in which the screen of the main VDU is larger than the screen of a secondary VDU.

13. A display system according to any preceding Claim in which each screen support structure includes a frame surrounding the screen.

14 A display device according to any preceding claim in which the secondary VDU is pivoted to the primary VDU so that it can be adjusted so that the VDUs face away from each other.

15. A VDU for use as the primary VDU of a system in accordance with any preceding Claim and including a port for receiving the video signals and means for connection to at least one secondary VDU for feeding video signals thereto.

16. A multiple screen display system in which the screens are pivoted so that they can be adjusted so as to face in opposite directions or away from each other. - 19

17. A display system according to Claim I and substantially as described with reference to Fig 2 of the accompanying drawings.