Computer graphics processing and selective visual display system – Plural display systems
Reexamination Certificate
1998-07-10
2004-03-30
Shankar, Vijay (Department: 2673)
Computer graphics processing and selective visual display system
Plural display systems
C345S001200, C345S204000
Reexamination Certificate
active
06714172
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a display control system, which connects a display controller having an image memory for storing image information, and a plurality of display devices, and controls the plurality of display devices to display an image on the basis of the image information, and its control method.
The present invention also relates to a switching device and connection device, which connect a plurality of peripheral devices to a single host equipment, and a peripheral device system using these devices. More specifically, the present invention relates to a switching device which connects a plurality of printers to a host computer having one printer interface, and a peripheral device system. Furthermore, the present invention relates to a branch device suitable for building a display system that connects a plurality of display devices to a single host equipment to display, a peripheral device system using that device, and their control method.
As a display device for a computer equipment or the like, a CRT display device is generally known. However, since the CRT display device requires a considerable depth in the thickness direction of its display screen, it has a large volume as a whole, and the entire system can hardly be made compact. Display control of such CRT display device must use a CRTC (CRT controller) or the like to refresh display data, and is complex.
As a display device that can compensate for the shortcomings of such conventional CRT display device, a liquid crystal display device, which can realize a size reduction, especially, a low-profile structure, of the display device, is known. Of such liquid crystal device, a display device (to be referred to as an FLCD: FLC display hereinafter) using a ferroelectric liquid crystal (to be abbreviated as FLC hereinafter) is known. As one of the features of the FLCD, its liquid crystal cells retain their display states upon application of an electric field. That is, the FLCD has very low-profile liquid crystal cells, in each of which an elongated FLC element orients itself in a first or second stable state according to the applied direction of the electric field, and maintains its orientation state after the electric field is removed. With the bistability of the FLC elements, the FLCD using such feature has memory characteristics of the display state. Such FLC and FLCD are described in detail in, e.g., U.S. Pat. No. 4,964,699.
A display controller for such FLCD need not refresh the screen all the time unlike a CRT display controller. By preferentially updating the display contents of a display area corresponding to a portion where the contents of a display memory have been updated, data can be displayed even on a large screen without dropping the refresh rate.
As an application of such display device, in events such as exhibitions, demonstrations, and the like held in broad sites, a plurality of display devices are set, and identical image information is displayed on these display devices, thus providing identical image information to many people.
On the other hand, as a display control system that displays different contents of image information on a plurality of display devices, the following three systems are known.
(1) LAN-connected System
A plurality of host computers are connected via a LAN, and display devices are connected to these host computers via display controllers.
(2) System Using a Plurality of Graphic Sub-systems
A plurality of display controllers are connected to a single host computer. Display devices are connected to these display controllers.
(3) Display Memory Dividing System
A display memory on a single host computer and single display controller is logically divided into a plurality of memory areas, which are assigned to a plurality of display devices connected.
However, in order to output identical or different image information contents to a plurality of conventional display devices, display controllers for controlling the display devices are required in correspondence with the number of display devices.
Especially, in order to display different image information contents to a plurality of display devices, the above-mentioned systems respectively have the following shortcomings.
(1) LAN-connected System
This system requires high cost since one display device requires one each host computer and display controller. Since a plurality of host computers must be controlled, a large-scale, complex control program is required.
(2) System Using a Plurality of Graphic Sub-systems
This system requires high cost since one display device requires a single display controller. Also, since the number of display controllers that can be connected to a single host computer is limited, the number of display devices that can be connected is inevitably limited.
(3) Display Memory Dividing System
Data must be sequentially read out from a plurality of divided memory areas. For this reason, the number of display devices that can be connected is limited by the read speed from the display memory.
On the other hand, a switching device shown in
FIG. 19
is generally known. By switching a switch
3
provided to a switching device
332
, one of two printers
334
a
and
334
b
is selected to print. When such switching devices are connected in series with each other, as shown in
FIG. 20
, one of a plurality of printers
334
a
to
334
c
can be selected.
FIG. 21
shows an arrangement for selecting one of printers
334
a
to
334
e
using more switching devices
332
a
to
332
d.
When the number of printers connected increases, and the number of switching devices increases, the total length of connection cables between adjacent switching devices becomes large, and the load viewed from a host computer
331
increases. For this reason, each switching device requires a circuit for shaping the signal waveform, and the like. Operating such waveshaping circuit and the like requires electric power. Hence, the individual switching devices have power supplies and power switches
335
a
to
335
d
for turning on/off these power supplies (FIG.
21
).
In a display system that connects a plurality of displays to a single host equipment, as shown in
FIG. 27
, displays
4100
,
4120
, and
4130
are connected via branch switches
4202
,
4203
, and
4204
.
However, in the arrangement shown in
FIG. 21
, in order to print using the printer
334
d
, all the power switches
335
a
to
335
d
of the switching devices
332
a
to
332
d
must be manually turned on by the user.
When the printers
334
a
and
334
b
are used but the printers
334
c
to
334
e
are not used, the power switches
335
a
and
335
b
of the switching devices
332
a
and
332
b
must be turned on, but the power switches
335
c
and
335
d
of the switching devices
332
c
and
332
d
need not be turned on. In terms of power savings, these switching devices
332
c
and
332
d
are preferably kept OFF. Such combination of the ON states of the power switches
335
a
to
335
d
must also be determined by the user.
Furthermore, since some switching devices have ON power switches and some other have OFF power switches, the user sometimes forgets to turn off such power switches.
In the above-mentioned display system which includes the branch connectors which distribute and supply image data from the host equipment to a plurality of displays, as the numbers of displays and branch connectors become larger, the user must turn on/off a larger number of switches every time the system is activated/deactivated, resulting in a heavy load on the user.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above-mentioned problems, and has as its object to provide a flexible display control system, which can control a plurality of display devices by a single display controller and is not restrained by the number of display devices connected, its control method, and a computer readable memory.
It is another object of the present invention to provide a switching device which automatically turns on/off required power
Ichihashi Nobuharu
Inoue Kenji
Matsumoto Yuichi
Matsuzaki Eiichi
Morimoto Hajime
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