DISPLAY DEVICE, MULTI-DISPLAY SYSTEM AND MULTI-DISPLAY METHOD

A display device (and method) includes a receiving unit that receives a video signal output from a superordinate device. A display unit displays at least part of the image according to the video signal. A storage unit-stores the resolution of the image to be displayed on the display unit. A connector can be connected to a subordinate display device. A communication unit, when a subordinate display is connected to the connector, receives a second resolution as the resolution notified by the subordinate display device and outputs the video signal to the subordinate display device. A control unit provides notification to the superordinate device of a third resolution according to the first and second resolutions, the first resolution being a resolution of the display unit and being a resolution of an image to be displayed on the display unit, the resolution of the image being previously stored in the storage unit.

TECHNICAL FIELD

The present invention relates to a display device, a multi-display system and a multi-display method.

BACKGROUND ART

Recently, there has been a large increase in the number of multi-display systems that display a single image by using a plurality of display devices. A multi-display system includes a signal source that supplies a video signal and a plurality of display devices that display images in accordance with the video signal output from the signal source, and performs a multi-display in which a single combined image is formed by joining together images that are displayed by each of the individual display devices. Accordingly, in the multi-display system, it is possible to form a large-scale image with a higher resolution than the image displayed by each single display device.

There is a multi-display system in which a plurality of display devices are cascade connected to a signal source (see Patent Document 1). In this case, the signal source outputs a single video signal, and the display device, which receives the video signal output from the signal source, displays part of the image in accordance with the video signal and transmits the video signal to the display device at the second stage. The display device at the second stage displays part of the image in accordance with the video signal and transmits the video signal to the display device further downstream. In this multi-display system, as the number of display devices cascade connected to the signal source increases, it is possible to create a higher resolution image.

In the above multi-display system, it is necessary to output a video signal with a resolution that corresponds to a synthesized image made up of the images that are to be displayed on individual display devices. This resolution of the synthesized image is determined according to the system configuration of the multi-display system, for example, the number and the resolution of display devices included in the multi-display system, so that the signal source needs to output a video signal that has a resolution that conforms to the system configuration.

When a dedicated signal source for multi display is used as the signal source, the dedicated signal source for multi display usually has a function that allows the user to set the resolution of the video signal that is to be output. Accordingly, it is possible to easily output a video signal that has a resolution that conforms to the system configuration.

RELATED ART DOCUMENTS

Patent Documents

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

However, general signal sources such as PCs (Personal Computer) and the like cannot always output video signals of a desired resolution.

Specifically, the general signal source acquires, from the display device that is connected to the general signal source, EDID (Extended Display Identification Data) that indicates the characteristics of the display device, and outputs the video signal that corresponds to the resolution described in this EDID.

Because the system configuration of a multi-display system differs case by case, the resolution described in EDID does not always conform to the current system configuration. Therefore, the general signal source cannot always output video signals with a resolution that conforms to the system configuration.

Accordingly, use of a general signal source entails the problem in which images having a resolution that conforms to the system configuration cannot be displayed.

It is an object of the present invention to provide a display device, a multi-display system and a multi-display method that can display images with a resolution that conforms to a system configuration even when a general signal source is used.

Means for Solving the Problems

A display device according to the present invention includes:

a receiving unit that receives a video signal output from a superordinate device;

a display unit that displays at least a part of an image according to the video signal;

a storage unit that stores a resolution of the image to be displayed on the display unit;

a connector to which a subordinate display device can be connected;

a communication unit that, when a subordinate display is connected to the connector, receives a second resolution, which is a resolution notified by the subordinate display device, and outputs the video signal to the subordinate display device; and,

a control unit that provides notification to the superordinate device of a third resolution according to a first resolution and the second resolution, wherein the first resolution is a resolution of the display unit and is a resolution of an image that is displayed on the display unit, the resolution of the image being previously stored in the storage unit.

A multi-display system according to the present invention includes:

a signal source that outputs a video signal; and

a plurality of display devices that each displays part of an image according to the video image output from the signal source, wherein

the plural display devices are cascade connected, and

each display device includes:

a receiving unit that receives a video signal output from a superordinate device;

a display unit that displays at least part of the image according to the video signal;

a storage unit that stores a resolution of an image to be displayed on the display unit;

a connector to which a subordinate display device can be connected;

a communication unit that, when a subordinate display is connected to the connector, receives a second resolution, that is a resolution notified by the subordinate display device, and outputs the video signal to the subordinate display device; and,

a control unit that provides notification to the superordinate device of a third resolution according to a first resolution and the second resolution, wherein the first resolution is a resolution of the display unit and is a resolution of an image that is displayed on the display unit, the resolution of the image being previously stored in the storage unit.

A multi-display method according to the present invention, is used in a multi-display system that includes a signal source that outputs a video signal; and a plurality of display devices that each displays part of an image according to the video image output from the signal source, the plural display devices being cascade connected, the multi-display method comprising,

each display device:

detecting that a subordinate display device is connected to the display device;

acquiring, from a storage unit, a first resolution which is a resolution of the display unit and which is a resolution of an image that is displayed on the display unit;

receiving a second resolution which is a resolution notified by the subordinate display device;

providing notification to the superordinate device of a third resolution according to the first and second resolutions;

receiving a video signal according to the third resolution from the superordinate device;

displaying part of the received video signal; and,

outputting the video signal to the subordinate device.

Effect of the Invention

According to the present invention, it is possible to output a video signal having a resolution that conforms to a system configuration even when a general signal source is used.

MODE FOR CARRYING OUT THE INVENTION

Next, the exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the present description and the drawings, the same components having the same functions are allotted the same reference numerals, so that repeated description may be omitted.

The First Exemplary Embodiment

FIG. 1is a diagram showing a configuration of a multi-display system according to the first exemplary embodiment of the present invention.

Multi-display system100shown inFIG. 1includes two projectors10and PC (Personal Computer)20as a signal source of video signals. Of the two projectors10, the projector10connected directly to PC20and arranged on the left side when viewed toward the images projected by the projectors is called master projector10M. The projector10arranged on the right side when viewed toward the images projected by projectors10is called slave projector10S.

Input terminal1of master projector10M is connected to PC20while output terminal8of master projector10M is connected to input terminal1of slave projector105.

Master projector10M displays the left half of the image based on the video image output by PC20and outputs the video signal to slave projector105. Slave projector10S displays the right half of the image based on the video image output by PC20(Master projector10M).

It is assumed in this case that master projector10M and slave projector10S each display an image having a resolution of 1024×768. Thereby, the multi-display system as a whole displays an image having a resolution of 2048×768.

FIG. 2is a block diagram showing a configuration of projector10of multi-display system100.

Input terminal1is connected to a superordinate device via cable and receives video signals and control signals output from the superordinate device. In the present exemplary embodiment, when projector10is master projector10M, the superordinate device connected to input terminal1is PC20, whereas when projector10is slave projector10S, the superordinate device is master projector10M. Here, when the superordinate device performs an EDID acquisition process via this input terminal1, EDID is notified to the superordinate device via input terminal1.

Input terminal1supports the standards such as, for example, HDMI (High-Definition Multimedia Interface), DVI (Digital Visual Interface), and DP (Display Port). In conformity with these standards, video signals, audio signals and control signals are transmitted by way of a single cable. It is assumed in the present exemplary embodiment that input terminal1is a terminal that supports the HDMI standard. Input terminal1outputs the received video signal and control signal to receiving unit3.

EDID memory2is a storage unit that stores EDID that represents the performance, functions and the like of display unit5. Since the characteristics of the video signal that display unit5supports are different depending on the performance and functions of display unit5, this means that EDID represents the characteristics of the video signal that display unit5supports. EDID includes the resolution of the video signal that display unit5supports. The signal source can acquire an EDID to automatically set up the formats of the video and audio that the signal source outputs. The resolution contained in the EDID is the resolution of the video signal when single display unit5displays the image based on the video signal. The resolution when each projector10alone displays the image based on the video signal in the above way will be called individual resolution in order to distinguish it from the resolution of the combined image of the images that are displayed by a plurality of projectors10. In the present exemplary embodiment, the resolution in EDID that is stored in EDID memory2is renewed to a predetermined resolution so as to change the resolution of the video that a signal source outputs.

Receiving unit3is a receiver that supports the standard of input terminal1, and is an HDMI receiving unit in the present exemplary embodiment. Receiving unit3receives video signals and control signals output from input terminal1and performs various signal processes for the received signals. The signal processes performed by receiving unit3herein may include serial-to-parallel conversion of video signals, signal level conversion, decoding of various timing signals included in control signals. Here, the timing signals may include, for example, a horizontal synchronization signal that represents separations of the video signal in the horizontal direction, a vertical synchronization signal that represents separations of the video signal in the vertical direction, a DE (Data Enable) signal which is a display area information that represents the valid periods in which display is given and the invalid periods in which no display is given in the video signal, a dot clock that indicates the reciprocal of the time required for displaying a single dot, and the like. Receiving unit3outputs the video signal after conversion and the control signal that includes various timing signals after decoding to video signal processing unit4and output unit7.

Video signal processing unit4receives the video signal and control signal output by receiving unit3, and performs a video signal process based on the received video signal. The video signal process performed by video signal processing unit4may include, for example, a7-correcting process, a distortion correcting process and the like. Video signal processing unit4outputs a video signal with which the video signal process is performed and the control signal to drive unit6.

Display unit5displays the image in accordance with the supplied input video signal. Display unit5includes, for example, a light source that emits light, a display element that outputs light of the image by modulating the light from the light source in accordance with the input video signal, and a projection optical system that projects the light of the image output by the display element. Display unit5is driven by drive unit6and the image based on the video signal is displayed by projecting light emitted from the light source.

Drive unit6drives display unit5. For example, drive unit6drives the display element, the light source and the like of display unit5to thereby cause display unit5to emit the image light. At this time, drive unit6, in accordance with the DE signal included in the received control signal, supplies the video signal to the display element to cause display unit5to display at least part of the image according to the video signal during the valid period. For example, when the horizontal resolution of the image according to the input video signal is higher than the resolution of display unit5, drive unit6causes display unit5to display the partial image from the lead of the image according to the video signal to the position that corresponds to the horizontal resolution of the display unit5.

Output unit7performs various kinds of signal processes on the video signal and control signal output from receiving unit2and outputs the signal-processed video signal and control signal.

Output terminal8is a connector that can be connected via HDMI cable to another projector10as a subordinate display device. Output terminal8is a terminal that conforms to the HDMI standard in this exemplary embodiment.

Control unit9is a control device such as, for example, CPU (Central Processing Unit) or the like, and controls receiving unit3, video signal processing unit4, drive unit6, output unit7and the like.

When there is a second projector10connected to output terminal8, control unit9regards the second projector10as slave projector105, acquires the EDID of slave projector10S via output unit7and output terminal8, and sets the resolution described in the acquired EDID to be the second resolution.

Control unit9provides notification to the superordinate device of the third resolution according to the first and second resolutions, the first resolution being the resolution described in the EDID stored in EDID memory2, the second resolution being the resolution notified by the subordinate device. At this time, control9notifies the third resolution to the superordinate device when the first resolution and the second resolution are same.

Concretely, control unit9calculates, based on the first resolution and the second resolution, the resolution of the synthesized image of the image displayed by display unit5and the image displayed by slave projector10S, and sets the calculated result as the third resolution that is to be notified to the superordinate device. Control unit9notifies the third resolution to the superordinate device, which is PC20, by replacing the resolution in the EDID stored in EDID memory2with the third resolution.

Here, when, for example, control unit9has detected a signal that indicates that the power of projector10has been turned off, or has detected a signal that indicates cancellation of multi-display system100, control unit9may rewrite the EDID stored in the updated EDID memory2to the initial EDID. For example, when control unit9has detected the signal that indicates that the power of projector10has been turned off, control unit9may rewrite the third resolution stored in the updated EDID memory2with the first resolution.

FIG. 3shows a block diagram showing a detailed configuration of output unit7of projector10.

Output unit7is a communication unit which, when a subordinate display device is connected to output terminal8, receives the second resolution that is the resolution notified from the subordinate display device and outputs the video signal to the subordinate display device. Output unit7includes an aftermentioned format converter11, DE processing unit12and transmitting unit13

Format converter11receives the video signal output from receiving unit3and converts the format of the video signal into a format that conforms to the selected standard. Format converter11outputs the format-converted video signal to transmitting unit13.

DE processing unit12receives the control signal output from receiving unit3and processes the ED signal included in the received control signal into information that corresponds to the section that is displayed by projector10S which is the subordinate display device connected to output terminal8of projector10. DE processing unit12outputs the control signal that includes the processed DE signal to transmitting unit13.

Herein, DE signal processing process by DE processing unit12will be described more specifically. There are two kinds of DE signals, namely, the horizontal DE signal and the vertical DE signal. The horizontal DE signal indicates the valid period of the video signal in the horizontal direction. The vertical DE signal shows the valid period of the video signal on the vertical direction.

FIG. 4is a diagram for illustrating processing of the horizontal DE signal. In the exemplary embodiment, the video signal having a resolution of 2048×768 is input while the input horizontal DE signal input to DE processing unit12of master projector10M indicates that the entire period provided by 2048 dots of the video signal in the horizontal direction is the valid period. DE processing unit12processes the input horizontal DE signal so that the section, that corresponds to the left side 1024 dots in the image based on the video signal and which is the part to be displayed by master projector10M, is set to an invalid period (so that the section, that corresponds to the right side 1024 dots in the image based on the video signal and which is the part to be displayed by slave projector10S, is set to a valid period). The horizontal DE signal after processing is shown in the bottom inFIG. 4.

FIG. 5is a diagram for illustrating processing of the vertical DE signal. In the present exemplary embodiment, slave projector10S is connected to master projector10M only in the horizontal direction while these projectors are not connected in the vertical direction. Accordingly, DE processing unit12will not perform any processing of the vertical DE signal because each projector10displays all sections of the video signal in the vertical direction. The input vertical DE signal supplied to DE processing unit12and the output vertical DE signal output from DE processing unit12each indicate that the entire period of the video signal of 768 lines is a valid period.

Returning to explanation withFIG. 3, transmitting unit13outputs the video signal, that is output from format converter11, and the control signal to the downstream slave projector10S connected to output terminal8. At this time, the control signal includes the DE signal that is output from DE processing unit12, the horizontal synchronization signal, the vertical synchronization signal, dot clocks and the like.

FIG. 6is a sequence diagram for illustrating an operation example of multi-display system100.

Control unit9of master projector10M checks whether there is a device connected to output terminal8(Step S100). Specifically, control unit9of master projector10M checks whether there is any device connected to input terminal1and output terminal8by using the hot-plug function of input terminal1and output terminal8. When the user connects output terminal8of master projector10M to input terminal1of slave projector10S by HDMI cable, control unit9of master projector10M detects slave projector10S as a connected device.

Then, control unit9of master projector10M detects that master projector10M is the topmost display device of multi-display system100from the fact that a device that is connected to output terminal8is present whereas there is no device that is connected to input terminal1. Control unit9of master projector10M acquires the EDID from EDID memory2of slave projector10S connected to output terminal8and registers the individual resolution described in the acquired EDID as the second resolution (Step105).

Control unit9of master projector10M acquires the individual resolution described in the EDID stored in EDID memory2of master projector10M and registers the individual resolution as the first resolution, and compares the first resolution with the second resolution acquired at Step S105to determine whether the individual resolution of master projector10M and that of slave projector10S are the same (Step S110). When the individual resolution of master projector10M and that of slave projector10S are not the same, master projector10M ends the operation of the multi-display system.

On the other hand, when the individual resolution of master projector10M and that of slave projector10S are the same, control unit9of master projector10M calculates the system resolution that is the resolution of the synthesized image in which the image displayed by display unit5of master projector10M and the image displayed by display unit5of slave projector10S are joined together. Specifically, control unit9of master projector10M calculates the system resolution based on the resolutions of individual images displayed by different projectors included in multi-display system100and based on the allocation of each image in the synthesized image. In the present exemplary embodiment, since it is assumed that two images displayed by projectors10are joined horizontally, control unit9calculates the system resolution so that the horizontal resolution of the system resolution is twice the horizontal resolution of master projector10M and the vertical resolution of the system resolution is equal to the vertical resolution of master projector10M (Step S115).

Then, display unit5of master projector10M displays that the system resolution is selectable. Specifically, display unit5of master projector10M displays resolution options that include, for example, the individual resolution of master projector10M and the system resolution. At this stage, display unit5can display resolution options by using OSD (On Screen Display) or the like (Step S120).

Herein, when the user enters, as a selected resolution, the system resolution on master projector10M (Step S125), control unit9of master projector10M rewrites the resolution of the EDID stored in EDID memory2with the system resolution (Step S130).

Then, when the user connects PC20and master projector10M by HDMI cable, PC20acquires the EDID from master projector10M (Step S135). PC20outputs the video signal, that corresponds to the system resolution described in the acquired EDID, and the control signal to master projector10M (Step S140).

Master projector10M, upon receiving the video signal and control signal, processes the ED signal included in the control signal. At this time, DE processing unit12processes the DE signal so that the part of the video signal, that is displayed by master projector10M, forms an invalid period (so that the part of the video signal, that is displayed by slave projector105, forms a valid period) (Step S145).

Then, display unit5of master projector10M, in accordance with the DE signal that is received by receiving unit3, displays the left half of the image according to the video signal (Step S150).

Output terminal8of master projector10M outputs the video signal and the control signal that includes the processed DE signal to slave projector10S (Step S155).

Display unit5of slave projector105, which has received the video signal and control signal, displays the right half of the image according to the video signal in accordance with the DE signal included in the received control signal (Step S170).

As described above, according to the present exemplary embodiment, the display device provides notification to the superordinate device of the third resolution according to the first and second resolutions, the first resolution being the resolution of display unit5, the second resolution being the resolution notified by the subordinate device. As a result, since the superordinate device can recognize the resolution of the subordinate display devices connected to the superordinate device, the signal source, which is the superordinate device, is able to output the video signal whose resolution accords with the notified third resolution. Accordingly, even when a general-purpose signal source such as a PC is used, the signal source can output the video signal with a resolution corresponding to the system configuration, hence the display device can display an image whose resolution corresponds to the system configuration.

Further, according to the present exemplary embodiment, when the first resolution and the second resolution are the same, the third resolution is notified to the superordinate device. When parts of a rectangular image are displayed by a plurality of display devices to form a large image by joining together the individual images that are displayed, there are cases where the images displayed by individual display devices cannot be joined to form an integrated image of a rectangular shape if a plurality of display devices that have different vertical resolutions are put together in the horizontal direction or if a plurality of display devices that have different horizontal resolutions are put together in the vertical direction. In this way, even if the images that are displayed by individual display devices are joined together, this does not mean that the display devices will operate correctly. Accordingly, when modification of the resolution to be notified is limited to the case where the first and second resolutions are the same, it is possible to secure a normal operation of display unit5.

Moreover, according to the present exemplary embodiment, the third resolution is notified to the superordinate device by replacing the first resolution stored in EDID memory2with the third resolution. As a result, it is possible for the superordinate device to output the video signal conforming to the third resolution without making any additional modification to the reading operation of the resolution on the superordinate device side.

According to the present exemplary embodiment, the display device acquires the resolution of the subordinate display device, which is the second resolution, from the EDID of the subordinate display device. The display device processes the ED signal that represents the area to be displayed in the video signal into the information that corresponds to the area that is displayed by the subordinate display device. As a result, the subordinate display device can display the image that corresponds to the third resolution without making any additional modification to the operation on the superordinate device side.

According to the present exemplary embodiment, in master projector10M to which PC20which is the superordinate device and slave projector10S which is the subordinate display device are connected, the resolution of the synthesized image, in which the images that are displayed by display unit5and slave projector10S are joined together, is calculated based on the first resolution and the second resolution, and the calculated resolution is notified to PC20, which is the superordinate device, as the third resolution. As a result, master projector10M can notify the resolution of the synthesized image to PC20which is the signal source.

The Second Exemplary Embodiment

FIG. 7is a diagram showing a configuration of a multi-display system according to the second exemplary embodiment of the present invention.

Multi-display system200according to the second exemplary embodiment of the present invention includes a plurality of projectors10and PC20that is a signal source of video signals. Of the plural projectors10, the projector10that is directly connected to PC20is called master projector10M. The projector10that is not directly connected to PC20is called slave projectors105. In the present exemplary embodiment, multi-display system200includes two slave projectors10S, and master projector10M is arranged on the leftmost side of the three projectors10. Of the two slave projectors105, the projector10S that is directly connected to master projector10M and arranged on the left side (at the middle of the three), when viewed toward the image projected by the projectors, is called first slave projector105-1. The projector10S that is connected to slave projector105-1and arranged on the rightmost side, when viewed toward the image projected by the projectors, is called second slave projector10S-2.

Input terminal1of master projector10M is connected to PC20while output terminal8of master projector10M is connected to input terminal1of first slave projector10S-1. Output terminal8of first slave projector10S-1is connected to input terminal1of second slave projector10S-2.

Each projector10displays an image having a resolution of 1024×768. In this case, multi-display system200as a whole displays an image having a resolution of 3072×768.

FIGS. 8A and 8Bare sequence diagrams for illustrating an operation example of multi-display system200.

Referring first toFIG. 8A, control unit9of master projector10M checks whether there is any device connected to input terminal1and output terminal8by using the hot-plug function of input terminal1and output terminal8(Step S200). When the user connects master projector10M to first slave projector105-1by HDMI cable and connects first slave projector105-1to second slave projector10S-2by HDMI cable, control unit9of master projector10M detects first slave projector105-1that is connected to output terminal8as a connected device.

When control unit9of master projector10M detects its connection to first slave projector105-1, control unit9recognizes that master projector10M is the topmost display device of multi-display system200from the fact that a device that is connected to output terminal8is present whereas there is no device that is connected to input terminal1. Then, control unit9creates a resolution inquiry message, and outputs the created resolution inquiry message from output terminal8to first slave projector105-1(Step S205).

Receiving unit3of first slave projector10S-1, which has received the resolution inquiry message, acquires the individual resolution from EDID memory2. Receiving unit3also notifies control unit9that a resolution inquiry message has been received. Control unit9of first slave projector105-1which has received this message checks whether there is any device that is connected to output terminal8of first slave projector105-1by using the hot-plug function of output terminal8(Step S210).

In the present exemplary embodiment, since output terminal8of first slave projector105-1is connected to second slave projector10S-2which is a subordinate display device, control unit9of first slave projector105-1further outputs a resolution inquiry message to second slave projector10S-2(Step S215).

Receiving unit3of second slave projector10S-2, which has received the resolution inquiry message, acquires the individual resolution from EDID memory2. Receiving unit3also notifies control unit9that a resolution inquiry message has been received. Control unit9of second slave projector10S-2, which has received this message, checks whether there is any device connected to output terminal8of second slave projector10S-2by using the hot-plug function of output terminal8(Step S220).

Then, control unit9of second slave projector10S-2detects the number of subordinate display devices connected downstream thereof, i.e., subordinate display device number N, and outputs the information, that indicates the subordinate display device number N, together with the individual resolution of second slave projector10S-2to first slave projector10S-1, which is the superordinate display device, via input terminal1(Step S225). In the present exemplary embodiment, since there is no devices that are connected to output terminal8of second slave projector10S-2, control unit9of second slave projector10S-2outputs information that indicates that the number of devices connected to output terminal8of second slave projector10S-2is zero. The value of subordinate display device number N may differ depending on the definition regarding whether its own device is included in that number. In the present exemplary embodiment, the subordinate display device number N is set to the number of display devices that are present downstream of the device that generates subordinate display device number N. Accordingly, the display device at the terminal, to which no subordinate device is connected, generates and outputs a subordinate display device number N that indicates zero.

Control unit9of first slave projector10S-1, which has received the subordinate display device number N=0 and the individual resolution from second slave projector10S-2, detects that first slave projector10S-1has only one subordinate display device, from the fact that the received subordinate display device number N is zero. Then, control unit9of first slave projector10S-1determines whether the individual resolution that is notified from second slave projector10S-2is the same as the individual resolution of first slave projector10S-1(Step S230).

When the individual resolution of first slave projector10S-1is not the same as the individual resolution of second slave projector10S-2, control unit9of first slave projector10S-1sets subordinate display device number N to be zero (N=0) (Step S235).

On the other hand, when the individual resolution of first slave projector105-1is the same as the individual resolution of second slave projector10S-2, control unit9of first slave projector105-1adds 1 to the received subordinate display device number N so that N=1 (Step S240). Then, control unit9of first slave projector105-1notifies this subordinate display device number N and the individual resolution of first slave projector105-1to master projector10M which is the superordinate device (Step S245).

Then, control unit9of master projector10M determines whether the individual resolution of master projector10M and the individual resolution of first slave projector105-1are the same (Step S250). When the individual resolution of master projector10M is not the same as the individual resolution of first slave projector105-1, control unit9of master projector10M ends the operation of the multi-display system.

On the other hand, when the individual resolution of master projector10M is the same as the individual resolution of first slave projector10S-1, control unit9of master projector10M calculates the system resolution that is the resolution of the synthesized image in which the images displayed by display unit5of each of master projector10M, first slave projector105-1and second slave projector10S-2are joined together.

Specifically, control unit9detects, based on the number of the subordinate display devices that is notified by first slave projector105-1, the number of slave projectors10S that are connected via output terminal8of master projector10M. Based on the detected number of slave projectors105, the individual resolution of master projector10M, the individual resolution of first slave projector105-1and the individual resolution of second slave projector10S-2, control unit9calculates the system resolution that is the resolution of the synthesized image in which the images displayed by display unit5of each of master projector10M, first slave projector105-1and second slave projector10S-2are joined together.

In the present exemplary embodiment, since it is assumed that plural projectors10are cascade connected in the horizontal direction and that the number of slave projectors10S are two, control unit9calculates the system resolution to have three times the horizontal resolution of master projector10M and the same vertical resolution as that of master projector10M (Step S255).

Here, the system resolution is not limited to the resolution that corresponds to all of the number of the detected slave projectors10S, but may use the resolution calculated based on a number equal to or lower than the number of the detected slave projectors10S. In the present exemplary embodiment, both the system resolution to have two times the horizontal resolution of master projector10M and the system resolution to have three times the horizontal resolution of master projector10M may be calculated.

Then, display unit5of master projector10M displays that the system resolution is selectable. Specifically, display unit5displays resolution options including, for example, the individual resolution of master projector10M and the calculated system resolutions. At this time, master projector10M can display resolution options by using OSD or the like (Step S260).

Herein, when the user selects and enters, as a selected resolution, a system resolution from the displayed resolution options on master projector10M (Step S265), control unit9of master projector10M replaces the resolution of the EDID stored in EDID memory2with the system resolution (Step S270).

When the system resolution is selected as the selected resolution, control unit9of master projector10M transmits, to first slave projector10S-1, information that indicates that multi-display is selected. This information that indicates that multi-display is selected is notified downstream to at least the slave projector10S that corresponds to the selected system resolution. Here, the information that indicates that multi-display is selected includes information that instructs processing of DE signals (Step S275).

Then, when the user connects PC20to master projector10M by HDMI cable, PC20acquires the EDID of master projector10M (Step S280). PC20outputs the video signal, that corresponds to the system resolution described in the acquired EDID, and the control signal to master projector10M (Step S285).

Referring next toFIG. 8B, master projector10M, upon receiving the video signal and control signal, processes the ED signal included in the control signal. Herein, video signal processing unit4of master projector10M processes the DE signal so that the area in the video signal, that is to be displayed by master projector10M, forms a valid period. On the other hand, DE processing unit12processes the DE signal so that the area in the video signal, that is to be displayed by master projector10M, forms an invalid period (Step S290). Here, the area that is to be displayed by master projector10M is a section, with respect to the horizontal direction, from the start of the valid period of the DE signal supplied to master projector10M to the end of the width of the resolution of the display unit.

FIG. 9is a diagram for illustrating the processing of the horizontal DE signal. In the present exemplary embodiment, a video signal having a resolution of 3072×768 is supplied. The input horizontal DE signal, which is the horizontal DE signal input to DE processing unit12of master projector10M, indicates that the entire period provided by 3072 dots of the video signal in the horizontal direction is the valid period. DE processing unit12of master projector10M processes the input horizontal DE signal so that the period of the first 1042 dots of the video signal indicates an invalid period.

Returning to the explanation ofFIG. 8B, display unit5of master projector10M, in accordance with the DE signal processed by video signal processing unit4, displays the image according to the video signal (part from the first dot to 1024thdots or the 1024 dots on the left side) (Step S295). Master projector10M outputs the video signal and the control signal that includes the DE signal processed by DE processing unit12to first slave projector105-1(Step S300).

First slave projector105-1, upon receiving the video signal and the control signal, processes the DE signal included in the control signal. Video signal processing unit4of first slave projector105-1processes the DE signal so that the area in the video signal, that is to be displayed by first slave projector105-1, is set to a valid period. On the other hand, DE processing unit12of first slave projector105-1processes the DE signal so that the area in the video signal, that is to be displayed by slave projector105-1, is set to an invalid period. Here, the area that is to be displayed by first slave projector105-1is a section, with respect to the horizontal direction, from the start of the valid period of the DE signal supplied to slave projector105-1to the end of the width of the resolution of the display unit.

Returning again toFIG. 9, DE processing unit12of first slave projector10S-1processes the horizontal DE signal output from master projector10M so that the period of the middle 1042 dots of the video signal is set to an invalid period (Step S305).

Returning again to the explanation ofFIG. 8B, display unit5of first slave projector10S-1, in accordance with the DE signal processed by video signal processing unit4, displays the image according to the video signal. Thereby, display unit5of first slave projector10S-1displays the image according to the video signal from the start of the valid period indicated by the DE signal to the end of the width of the horizontal resolution of display unit5(Step S310).

First slave projector10S-1outputs the video signal and the control signal that includes the DE signal processed by DE processing unit12of first slave projector10S-1to second slave projector10S-2(Step S315).

Upon receiving the video signal and the control signal, second slave projector10S-2does not need to process the DE signal included in the control signal because second slave projector10S-2is the device at the distal end. Here, the area that is to be displayed by second slave projector10S-2is a section, with respect to the horizontal direction, from the start of the valid period of the DE signal input to second slave projector10S-2to the end of the width of the resolution of the display unit.

Display unit5of second slave projector10S-2, in accordance with the DE signal that is included in the received control signal, displays the image according to the video signal. Thereby, display unit5of second slave projector10S-2displays the image (the part from 2049thto 3072nddots, 1024 dots on the right side) that conforms to the video signal from the start of the valid period indicated by the DE signal to the end of the width of the horizontal resolution of display unit5(Step S320).

Here, in multi-display system200, for master projector10M, PC20is the superordinate device while first slave projector10S-1and second slave projector10S-2are the subordinate display devices. The individual resolution of master projector10M corresponds to the first resolution, the individual resolution of slave projector10S corresponds to the second resolution and the system resolution corresponds to the third resolution.

For first slave projector10S-1, master projector10M is the superordinate device while second slave projector10S-2is the subordinate display device. The individual resolution of first slave projector10S-1corresponds to the first resolution, the individual resolution of second slave projector10S-2corresponds to the second resolution and the individual resolution of first slave projector10S-1and second slave projector10S-2correspond to the third resolution.

In the description herein, first slave projector10S-1checks whether the individual resolution of first slave projector10S-1is the same as the individual resolution of second slave projector10S-2, and notifies the number of the subordinate display devices and the individual resolution of first slave projector10S-1to master projector10M when the resolutions are the same. However, first slave projector10S-1may report the individual resolution of both first slave projector10S-1and second slave projector10S-2to master projector10M. In this case, master projector10M can check whether the individual resolution of master projector10M, first slave projector10S-1and second slave projector10S-2are all the same to perform the operation of master projector10M.

As has been described above, according to the present exemplary embodiment, the display device provides notification to the superordinate device of the third resolution according to the first and second resolutions, the first resolution being the resolution of display unit5, the second resolution being the resolution notified by the subordinate device. As a result, since the superordinate device can recognize the resolution of the subordinate display devices connected to the superordinate device, the signal source, which is the superordinate device, is able to output the video signal whose resolution accords with the notified third resolution. Accordingly, even when a general-purpose signal source such as a PC is used, the signal source can output the video signal with a resolution corresponding to the system configuration, hence the display device can display an image whose resolution corresponds to the system configuration.

Also in this present exemplary embodiment, when the first resolution and the second resolution are the same, the third resolution is notified to the superordinate device. When parts of a rectangular image are displayed by a plurality of display devices to form a large image by joining together the individual images that are displayed, there are cases where the images displayed by individual display devices cannot be joined to form an integrated image of a rectangular shape if a plurality of display devices that have different vertical resolutions are put together in the horizontal direction or if a plurality of display devices that have different horizontal resolutions are put together in the vertical direction. In this way, even if the images that are displayed by individual display devices are joined together, this does not mean that the display devices will operate correctly. Accordingly, when modification of the resolution to be notified is limited to the case where the first and second resolutions are the same, it is possible to secure a normal operation of display unit5.

Moreover, according to the present exemplary embodiment, the third resolution is notified to the superordinate device by replacing the first resolution stored in EDID memory2with the third resolution. As a result, it is possible for the superordinate device to output the video signal conforming to the third resolution without making any additional modification to the reading operation of the resolution on the superordinate device side.

According to the present exemplary embodiment, the display device acquires the resolution of the subordinate display device, which is the second resolution, from the EDID of the subordinate display device. The display device processes the ED signal that represents the area to be displayed in the video signal into the information that corresponds to the area that is displayed by the subordinate display device.

According to the present exemplary embodiment, in master projector10M to which PC20which is the superordinate device and slave projector10S which is the subordinate display device are connected, the resolution of the synthesized image, in which the images that are displayed by display unit5and slave projector10S are joined together, is calculated based on the first resolution and the second resolution, and the calculated resolution is notified to PC20, which is the superordinate device, as the third resolution. As a result, master projector10M can notify the resolution of the synthesized image to PC20which is the signal source.

As has been described, in the second exemplary embodiment, slave projector10S which is a subordinate display device notifies the individual resolution to the superordinate device. However, the present invention should not be limited to this example. For example, slave projector10S may notify the resolution of the image combined of the images displayed by slave projectors10S including itself and subordinate projectors, to the superordinate device. At this time, slave projector10S replaces the resolution described in the EDID with the resolution to be notified.

Further, in the above exemplary embodiment, slave projector10S which is a subordinate display device transmits the number of subordinate devices to the superordinate device. However, the present invention should not be limited to this example. For example, the number of subordinate devices may be written into the EDID so as to be notified to the superordinate device. For example, the number of subordinate devices may be described and rewritten in the area of the EDID that indicates the device name (Monitor Name), together with the device name in a manner such that the number of subordinate devices can be differentiated from the device name. Alternatively, the number of subordinate devices may be described in the other area that does not affect the operation in which the EDID is used.

Although the present invention has been explained with reference to the exemplary embodiments, the present invention should not be limited to the above exemplary embodiments. Various modifications that can be understood by those skilled in the art may be made to the structures and details of the present invention within the scope of the present invention.

For example, the above exemplary embodiment has been described by taking projector10as an example of the display device. But the present invention should not be limited to this example. The display device may be a display device that includes a display panel such as a liquid crystal display device, organic EL (Electro Luminescence) display device and the like. Further, the display device may be an information processing apparatus that includes a projector or a display panel.

Further, the above exemplary embodiment has been described by taking PC20as one example of the signal source for supplying the video signal to projector10, but the present invention should not be limited to this example. The signal source may be an information processing apparatus other than PC20. The display device and the signal source may be an integrated apparatus.

The above exemplary embodiment has been described on the assumption that projectors10as well as PC20and master projector10M are connected by terminals and cables that support the HDMI standard. However, the present invention should not be limited to this example. Devices may be connected by using wired or wireless connection means and any standard that supports terminals, cables and wireless interface may be used.

For description simplicity, the above exemplary embodiments have been described by giving cases where two projectors10are used and where three are used. However, the present invention should not be limited to these examples. It is possible to configure a multi-display system with four or more projectors.

The above exemplary embodiments have been described by giving an example of a multi-display system in which the images that are displayed by the projectors are joined together in the horizontal direction. However, the present invention should not be limited to this example. For example, the images that are displayed by the projectors may be joined together in the vertical direction. In this case, instead of the horizontal DE signal, the vertical DE signal is processed.

The above exemplary embodiments have been described by giving an example where the image according to the video signal is divided into multiple areas that do not overlap and the display devices each displays each area. However, the present invention should not be limited to this example. When the display devices are projectors, there is a case where part of the projected image of each projector is laid over the others so that the multiple projected images produce smooth seams. In this case, each projector may and should take into account the overlapping portions to calculate the system resolution and process the DE signal.

Further, in the above exemplary embodiments, a process of setting up a multi-display system is performed when the individual resolutions are the same. However, in the case in which the images are arranged in the horizontal direction, the multi-display system may be set up when the vertical resolutions are the same, and furthermore, in the case in which the images are arranged in the vertical direction, the multi-display system may be set up when the horizontal resolutions are the same for arranging the images in the vertical direction. In this case, the second resolution to be notified by the subordinate display device to the superordinate device should be the resolution of the combined image of the images displayed by the display devices connected downstream of the notifying device. In this case, the combined synthesized image of the images displayed by individual display devices forms a rectangular shape so that the synthesized image can be displayed normally.

In the above exemplary embodiment, control unit9uses hot-plug function to recognize that projector10is the topmost display device (master projector10M) of multi-display system200. However, control unit9may set a projector10as the topmost display device (master projector10M) of multi-display system200, based on a signal that indicates a predetermined operation performed by the user, for example, an operation for setting up the projector10to be master projector10M. Further, in this case, if master projector10M is set as the topmost display device of multi-display system200, control unit9of master projector10M may check whether there is a device connected to output terminal8, and then if control unit9detects slave projector10S that is connected to output terminal8, control unit9may issue a resolution inquiry message to perform a predetermined process. Alternatively, control unit9of master projector10M may check whether there is a device connected to output terminal8based on a signal that represents a predetermined operation performed by the user, for example, a signal that represents an operation of setting up a system resolution, and then if control unit9detects slave projector10S that is connected to output terminal8, control unit9may issue a resolution inquiry message to perform a predetermined process.

Also, it goes without saying that the configurations and processing content in each of the above exemplary embodiments can be used in combination.

For example, the first exemplary embodiment gave an example of two projectors10while the second exemplary embodiment gave an example of three projectors10. However, the present invention should not be limited to these examples. The process of the second exemplary embodiment may be applied to a multi-display system using two projectors.

In the first exemplary embodiment, video signal processing unit4does not process the DE signal while display unit5displays the image from the start of the DE signal according to the resolution of display unit5. In the second exemplary embodiment, video signal processing unit4processes the DE signal in accordance with the resolution of display unit5while display unit5displays the image according to the processed DE signal. The above process of the second exemplary embodiment may be applied to the first embodiment, and also the above process of the first exemplary embodiment may be applied to the second embodiment.

In the first exemplary embodiment, the superordinate device directly acquires EDID. In the second exemplary embodiment, EDID is acquired by way of receiving unit3of the subordinate display device. The direct EDID acquisition process by the superordinate device may be performed in the configuration of the second exemplary embodiment. Also, the process of acquiring EDID via receiving unit3of the subordinate display device may be performed in the configuration of the first exemplary embodiment.

In the first exemplary embodiment, the superordinate device acquires the EDID itself of the subordinate display device. In the second exemplary embodiment, the superordinate device acquires the individual resolution described in the EDID of the subordinate display device. The process of acquiring the EDID itself may be performed in the configuration of the second exemplary embodiment. Also, the process of acquiring the individual resolution may be performed in the configuration of the first exemplary embodiment.

In the above exemplary embodiments, although the resolution in the EDID is acquired and used, the present invention should not be limited to this example. A resolution that is included in the information other than EDID, that indicates the performance and functions of display unit5or the like that are stored in the storage unit, may be acquired and used.

The first exemplary embodiment was explained by showing an operation on the assumption that multi-display system100includes two projectors10. The second exemplary embodiment was explained by showing an operation in which multi-display system100detects the current system configuration. In the configuration of the first exemplary embodiment, an operation of detecting the current system configuration may be carried out. Also, in the configuration of the second exemplary embodiment, a predetermined system configuration may be assumed. When a predetermined system configuration may be assumed, it is possible to consider a case where a predetermined system configuration has been fixed as the specifications of projectors10, or a case where the user enters the number of projectors10to be connected at the time of configuring a system.

DESCRIPTION OF REFERENCE NUMERALS