EP1557811A1 - Transmission apparatus for wireless coupling of an image display device to a computer - Google Patents

Abstract

A transmission device with a transmitter (10) and a receiver (20) picks up image signals directly from an interface available on a related computer (1). This facilitates exceptionally easy control and adaptation to any resolution. A user does not need to undertake software adjustments, and consequently any sort of specials rights, such as administrator's rights.

Description

The present invention relates to a transmission device for coupling a picture device to a computer according to the preamble of claim 1.

In today's business world belongs a portable personal computer or a notebook to normal equipment. For conferences become projectors instead of overhead projectors used that over a cable with a notebook can be connected and therefore very much for presentations are suitable because no more slides must be created.

The use of cables to connect a notebook with a projector is unwieldy. To remedy this problem too can, the image signals are sent wirelessly to a projector transmitted, special units are provided, the connected to the notebook or to the projector.

Products from eg HP, Hewlett Packard, see wwww.hp.com or from OTC Wireless (WiJet), see www.otcwireless.com, are known on the market. These products have in common that you use the technology of a WLAN based on the IEEE 802.11 standard. Further examples can be found at:
www.wireless-forum.ch,
www.win-report.com,
www.eio.com,
www.linksys.com.

The technology of Wi-Fi requires that the notebook on the one hand a Wi-Fi card needs to be plugged in and that driver software installed for access to the respective projector and must be configured. This is how a major hurdle for users, not least this requires that the person has administrator rights must have to actually install this to carry out.

The present invention is therefore based on the object a transmission device for coupling a picture device to indicate to a computer, so that no additional software is to be installed and which for the transmission device very easy to use.

This object is specified by the in claim 1 Measures solved. Advantageous embodiments of the invention are given in further claims.

As a result of that
the transmitter is directly connected to an interface of the computer containing image signals, no driver software is to be installed for commissioning and there are no performance losses with other WLAN applications. A possibly necessary adjustment of the characteristics of the image device such as resolution can be made directly on the computer with the screen settings, this no administrator rights are required.

Preference is given to a proprietary radio link between the transmitting unit and receiving unit, since thereby also an essential Improvement of privacy can be achieved. additionally encryption could be a proprietary solution provided to be transmitted image signals become. When using such devices are often business-confidential Data presented so that can be prevented must be that in the environment of a meeting room this data can be viewed by unauthorized persons.

Figur 1

Übersichtsschema der erfindungsgemässen Übertragungseinrichtung

The invention will be explained in more detail with reference to the drawing, for example. In the only figure 1 is shown:

FIG. 1

Schematic of the inventive transmission device

Below a picture device 2 below a projector, screen, Beamer or a TFT monitor understood. With the flat rate Designation Calculator 1 is in non-conclusive Enumerating a personal computer or a notebook, laptop etc. to understand the usual units of keyboard 4 and Screen 5 has.

Before the detailed description of embodiments First, information about the energy supply is made. Based on the SVGA interface will then be Quantity structure specified.

The power supply can on the side of the image device 2 be realized with a plug-in power supply 30.

On the computer side 1, the power supply from the computer from a USB interface via a cable 8 or from PS2 keyboard / mouse connection. Is possible also to provide a separate power module, e.g. a power supply unit 30, see the figure 1.

The SVGA interface usually uses a 9-pin D-Sub connector. The analog RGB signals are transmitted, one horizontal and one vertical synchronizing signal. The SVGA image resolutions are usually:

It is assumed that the frame rate is at least 60Hz, lower rates are little more with modern graphics cards available. A flicker is, as with the LCD monitor, due the image display technology of the projector 2 is not expected.

Based on the above, the pixel rate at the SVGA output is given below. For this purpose, the following value for the latency is assumed: The latency of the video transmission should not be greater than 0.3s. Pixel rate depending on the resolution resolution pixel rate 800x600 28.8 MP / s 1024x768 47.2 MP / s 1152x864 59.7 MP / s 1280x768 59.0 MP / s 1280x960 73.7 MP / s 1280x1024 78.6 MP / s

Using a proprietary radio transmission according to the invention, be it in analog or digital technology, the radio bands shown in Table 3 are suitable, for example. These bands are also referred to as ISM frequency bands and assigned to the non-specific short range device (SRD) radio service classes. Available ISM frequency bands frequency band permissible transmission power (EIRP) maximum channel width 433 ... 434.8 MHz 10 mW whole volume 868 ... 870 MHz 25 mW whole volume 2400 ... 2483 MHz 10 mW whole volume 5725 ... 5875 MHz 25 mW whole volume 24.0 ... 24.25 GHz 100 mW whole volume 61.0 ... 61.5 GHz 100 mW whole volume 122 ... 123 GHz 100 mW whole volume 244 ... 246 GHz 100 mW whole volume

a) Analoge Übertragungstechnik,

b) Digitale Übertragungstechnik.

Starting from the technical quantity structures set out above, two different embodiments open up for the present invention:

a) Analog transmission technology,

b) Digital transmission technology.

For an exemplary embodiment in analog transmission technology, the bandwidth requirement shown in Table 4 results. Bandwidth requirement as a function of the number of lines at a fixed frame rate of 60 Hz number of lines frame rate RF channel width PAL 625 25 Hz 6.25 MHz SVGA 600 60 Hz 13.8 MHz SVGA 768 60 Hz 22.6 MHz SVGA 864 60 Hz 28.7 MHz SVGA 960 60 Hz 35.4 MHz SVGA 1024 60 Hz 40.3 MHz

In Table 4 above, the starting point is the analogous Video transmission regarding a television standard also listed. The required for the present invention Bandwidth is up from the 625 lines of the PAL standard extrapolated the respective SVGA line number. Because the horizontal Resolution must also be proportionally better, takes the bandwidth with the square of the line number too.

The bandwidths given in Table 2 above can be realized with the tapes listed in Tables 3.
In order for this analog transmission to be reasonably robust against interference bands and thus avoid the occurrence of image disturbances, it is preferable to provide a more disturbing frequency modulation instead of the amplitude modulation. However, about five times larger bandwidth is required.

It is therefore advisable to realize an analog transmission in the 2.44 GHz or in the 5.8 GHz band. The range r is calculated according to the following formula: r: = λ 4 × π · P t ·G t ·G r S N * F * k * T 0 · B Range depending on transmission / reception parameters for two examples Size symbol example 1 Example 2 carrier frequency f 2440MHz 5800 MHz transmission power P _t 10mW 25mW Antenna gain transmitter G _t 0dB 0dB Antenna gain receiver G _r 0dB 0dB bandwidth B 40.3MHz 40.3MHz Receiver noise figure F 10dB 10dB Signal / noise ratio in front of the demodulator S _N 30dB 30dB Resulting range r 25 m 16 m

k

Boltzmannsche Konstante (1.38e-23 Ws/K);

T₀

Betriebstemperatur des Empfängers in °K, vorliegend T₀ = 295°K, entspricht etwa 25° C;

B

Bandbreite, vorliegend B = 40.3 MHz;

λ

Wellenlänge der Trägerfrequenz f.

In the above formula mean:

k

Boltzmann's constant (1.38e-23 Ws / K);

T ₀

Operating temperature of the receiver in ° K, in this case T ₀ = 295 ° K, corresponds to about 25 ° C;

B

Bandwidth, in this case B = 40.3 MHz;

λ

Wavelength of the carrier frequency f.

After this consideration of the quantity frameworks becomes below a second embodiment specified, wherein the transmission done in digital technology, this is on the figure 1 taken.

Basically, the three RGB signals with a resolution of at least 8 bits and a sampling rate of max. 78.6 MP / s are digitized. Furthermore, line synchronization and image synchronization are required.
In FIG. 1, transmitter 10 denotes a unit which is connected directly to the SVGA interface of a notebook 1 via a connecting cable 6. The transmitting unit 10 includes a coding module 12 in which the aforementioned digitizing is performed. Subsequently, a compression is carried out in the transmission unit 10 in a compression module 13. Compression is preferably provided by the MPEG 2 and MPEG 4 compression methods. These standards are designed for the formats of television pictures and are to be adapted accordingly for the compression of SVGA signals. It can - without disturbing the continuous display by a projector 2 - during transmission individual frames are omitted. On the side of the projector 2 then the frame rate is to be reconstructed by appropriate repetitions.

In a presentation of slides are hardly moving pictures shown. If you allow a certain latency, associated with a maximum frame rate, so can alternatively the classic JPEG compression can be applied. A test of JPEG compression Presentations have shown that the JPEG compression quality at factor 50 (or 5 at Zehnerteilung) shows a sufficient quality. The 1280 x 1024 images could thus reach about 7% of their bitmap size compressed, resulting in file sizes of about 90 kB.

Would the wireless data transmission based on an IEEE 802.11g system can be set, with a payload of at least 10 Mbps can be expected. This results in a Transmission time of approx. 72 ms. With a sufficiently powerful Image compression can therefore have a minimum frame rate of 10 frames per second can be achieved.

On the side of the image device 2, a receiver 20 is provided, which may also be called receiver unit 20. In mirror image of the transmission unit 10 includes this Receive module 21. The received signals are a decompression module 23 fed and then in a decoding module transformed into corresponding analog video signals. The above-mentioned correspondence includes the of Calculator 1 provided at its plug signals accordingly the respective screen type setting. The connection Receiver unit 20 with the project 2 via a common cable 7. Another control connection is thanks to the present invention not required, except a possible energy supply by an external Power supply unit 30.

In a further embodiment can be provided, in addition in the transmitting unit 10 and the receiving unit 20 each to provide an encryption module (not in the figure 1) ) Shown. This is preferably implemented with crypto chips, such cryptochips are for example on bank cards available.

Alternatively, for the radio link, the available IEEE 802.11g technology is used for this Addressing either set to fixed or with so-called DIP switches to set adjustable address parameters. It would also be possible, this via a V.24 cable 8 or an additional 8 USB link. Is preferred however, a proprietary digital radio link 9, so that possible no further adjustment required during use are.

The aforementioned dip switches can also serve at Requires electrical adjustment of the receiver unit 20 set image signals can be adjusted.

In a further development of the present invention can Also an additional control channel can be implemented to For example, control data for adjusting the focus of the lens 3 to transmit.

The invention is not limited to that in this embodiment called SVGA interface limited, but can also for other interfaces are used, e.g. on a DVI interface, to demonstrate video or DVD presentation to be able to.

List used reference numerals

1

Calculator, personal computer, notebook

2

Image device, projector, screen, beamer, TFT monitor

3

lens

4

keyboard

5

screen

6

Connecting cable Notebook → Transmitter

7

Connection cable receiver → image device

8th

optional additional cable, USB range, V.24 range

9

radio link

10

Transmitter, transmitter unit

11

transmitter module

12

encoding module

13

bulk modulus

20

Receiver, receiving unit

21

receiver module

22

Decoding module

23

decompression

30

External power supply unit, plug-in power supply

List of abbreviations used

DVD

Digital Video Disc

DVI

Digital video input

EIRP

Effective Isotropic Radiated Power

IEEE

Institute of Electric and Electronic Engineers

ISM

Industrial, Scientific, Medical

JPEG

joint photografic expert group; Method for compressing and storing image and video data

MPEG

motion pictures expert group

PAL

Phase Alternation Line, standard for coding a Television picture signal (NTSC National Television Standards Committee)

RGB

Red, green, blue - color model

SRD

Short range device

SVGA

Super Video Grafics Array

TFT

Thin film transistor, screen technology

USB

Universal Serial Bus

V.24

Serial interface

VGA

Video Graphics Array

Claims (7)

Transmission device (10, 20) for coupling a picture device (2) to a computer (1) comprising a transmitting unit (10) and a receiver unit (20), wherein the picture device (2) can be connected wirelessly to the transmitter () which can be connected to the computer (1). 10) is coupled,
characterized in that
the transmitter (10) can be electrically connected directly to an interface of the computer (1) containing image signals. Transmission device (10, 20) according to claim 1,
characterized in that
the wireless coupling (9) is implemented by a transmission (9) using analog technology, wherein the transmitting unit (10) has a transmitting module (11) with which the image signals are transmitted in a frequency-modulated manner. Transmission device (10, 20) according to claim 1,
characterized in that
the wireless coupling (9) is implemented by a transmission (9) using analog technology, wherein the transmitting unit (10) has a transmitting module (11) with which the image signals are transmitted in an amplitude-modulated manner. Transmission device (10, 20) according to claim 1,
characterized in that
the wireless coupling (9) is implemented by a transmission (9) in digital technology, wherein the transmitting unit (10) has a coding module (12) for digitizing the image signals and a transmitting module (11). Transmission device (10, 20) according to Claim 4,
characterized in that
the transmitting unit (10) has a compression module (13) for compressing the digitized image signals, which is connected to the coding module (12). Transmission device (10, 20) according to claim 5,
characterized in that
the compression module (13) is alternatively designed as MPEG-2 or MPEG-4 or as a JPEG compression module. Transmission device (10, 20) according to one of claims 4 to 6,
characterized in that
the transmitting unit (10) and the receiving unit (20) each have an encryption module in order to transmit the image signals in encrypted form.

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