Patent Publication Number: US-8970566-B2

Title: Input source search support method, and image display apparatus and projector using the search support method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 12/709,180, filed Feb. 19, 2010, which is a continuation of U.S. patent application Ser. No. 11/368,399, filed Mar. 7, 2006, which claims the benefit of priority from prior Japanese Patent Applications No. 2005-063485, filed on Mar. 8, 2005, and No. 2005-135636, filed May 9, 2005. The disclosures of the prior applications are hereby incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates to an input source search support method, and an image display apparatus and a projector using the search support method. 
     2. Related art 
     Generally, a plurality of input sources (e.g., image input devices such as PC, DVD and VTR, and the Internet) can be connected to a projector as an image display apparatus.  FIG. 16  illustrates a related-art projector  500  to which a plurality of input sources are connected. 
     As illustrated in  FIG. 16 , the projector  500  produces image light corresponding to the desired input source of the plural input sources PC 1 , PC 2 , VTR, and DVD and projects the light on a screen S. Input/output interfaces used in the projector  500  in recent years are LAN (wireless or wire) interfaces, as well as input/output interfaces (I computer1 , I computer2 , I video , I s-video ) shown in  FIG. 16 . 
     When this type of projector is used, a desired input source for providing projection display needs to be selected from available input sources. It is, therefore, convenient if information such as what input source of the plural input sources is available and what display it is providing can be easily obtained. 
       FIG. 17  shows a related-art input source search support method. 
     When input source switching command is inputted through a mode switch or a remote controller in the related-art input source search support method shown in  FIG. 17 , the next input source of the currently selected input source is stored in a flag of a RAM (step S 940 ) to display the name of the input source stored in the RAM by OSD (step S 941 ). Subsequently, switching signals requiring image signals to be outputted from the switched input source are outputted to an input switching device (step S 942 ). After time-up of the timer (step S 943 ), the OSD display is deleted (step S 944 ). The input source is switched to another input source, in such a manner as from Video 1 to Video 2, Option, and other devices, for example, every time the input source switching command is inputted (for example, see JP-A-2000-081666). 
     In the related-art input source search support method, therefore, the input source is switched sequentially in accordance with the input source switching command inputted from the user. In this case, information such as what input source is available and what display is currently provided can be securely checked. 
     In the related-art input source search support method, however, processes required for this method are complicated and inconvenient since it is necessary to sequentially switch the input sources while checking whether or not available are input sources including input sources currently unavailable (such input sources as not powered or not connected with the projector). The problem will be more serious if a number of input sources can be connected with the projector as in the cases in recent years. Accordingly, another improved type of related-art image search support method capable of solving these problems has been proposed. 
       FIG. 18  shows the other improved type related-art input source search support method. 
     The related-art input source search support method shown in  FIG. 18  automatically searches for the next input source by detecting image signals while skipping input sources currently unavailable if any, during search for the input source. In this input source search support method, therefore, the input sources currently unavailable which may be contained in the search target input sources are skipped and the next input source is automatically searched. In this case, it is unnecessary to sequentially switch the input sources while checking whether the input sources are available or not and the like. As a result, processes required for this method can be facilitated and thus the usability can be enhanced (for example, see General catalog for business projector ((Epson Sales Japan Corporation, Seiko Epson Corporation) catalog code: CLELSG16A (2004.12.15)) (page 3 (description of Automatic Detection of Image Signals)). 
     In the related-art improved type input source search support method, however, nothing is displayed on the screen when all the input sources including the initially selected input source are unavailable and thus all the input sources are skipped. In this case, the user does not understand why nothing is displayed and is thus bewildered. This deteriorates the usability of the projector. 
     Additionally, in the related-art improved type input source search support method, input sources in the so-called stand-by condition (input source from which image signals have not been generated yet even though they are connected with the projector and powered, hereinafter referred to as stand-by input sources) are skipped similarly to the input sources unavailable. Thus, the user cannot select the stand-by input sources even if they are desired input sources. 
     These problems occur not only in the projector at the time of searching for input sources, but also in another image display apparatus to which a plurality of input sources can be connected at the time of searching for input sources. 
     SUMMARY 
     Accordingly, a first advantage of some aspects of the invention is to provide an input source search support method capable of efficiently searching for an input source currently outputting image signals and providing information that no image signal is outputted from any of input sources to the user even when no image signal is outputted therefrom. 
     A second advantage of some aspects of the invention is to provide an input source search support method capable of selecting stand-by input sources. 
     A third advantage of some aspects of the invention is to provide an image display apparatus and a projector using the search support method. 
     An image display apparatus for displaying an image produced by image signals on a display section according to a first aspect of the invention includes: a plurality of input terminals for receiving each of the image signals supplied from a plurality of input sources; an input selector for selecting a predetermined input terminal from the plural input terminals; a judging section for determining whether the image signals have been inputted to the input terminal selected by the input selector; an operating section which receives requirement of search processing for determining whether the image signals have been inputted to each of the plural input terminals; an image signal correcting section which generates image signals for producing a source search screen indicating search status for each of the input source names corresponding to the input terminals; and a control section for displaying an image of the source search screen produced by the image signals at least on the display section in response to search processing required through the operation section. The control section commands the input selector to sequentially select the input terminals when the search processing is required through the operation section, and commands the judging section to check the presence or absence of the image signals for each of the selected input terminals. The control section commands the image signal correcting section to add to the source search screen an indication that the image signals have not been inputted to any of the checked input terminals when the image signals have not been inputted thereto. The control section commands the image signal correcting section to close the source search screen when it is determined that the image signals have been inputted to any of the input terminals, and commands the display section to display an image produced by the image signals from the input terminal from which the image signals have been detected. 
     In this structure, the control section commands the input selector to sequentially select the input terminals when the search processing is required through the operation section, and commands the judging section to check the presence or absence of the image signals for each of the selected input terminals. The control section commands the image signal correcting section to add to the source search screen an indication that no image signal is inputted to any of the checked input terminals when no image signal is inputted thereto. Thus, the indication that no image signal is inputted from the input source corresponding to the searched input terminal is added to the source search screen on the display section of the image display apparatus one after another. 
     Accordingly, the supply status of the image signals can be visually checked in real time by the user for each input source. Moreover, when no image signal is inputted from any of the input sources, this condition can be visually displayed on the source search screen. 
     Additionally, in this structure, the control section commands the image signal correcting section to close the source search screen when it is determined that the image signals have been inputted to any of the input terminals, and commands the display section to display an image produced by the image signals from the input terminal from which the image signals have been detected. Thus, the image display apparatus closes the source search screen when it is determined that the image signals have been inputted, and projects images produced by the image signals from the input source corresponding to this input terminal on the display section. 
     Accordingly, the image display apparatus can offer visual information that the input source search has been completed to the user and can efficiently search for the image source which is outputting the image signals. 
     Therefore, the image display apparatus according to the first aspect of the invention is capable of efficiently searching for the input source which is outputting image signals and providing information that no image signal is inputted from any of the input sources to the user even when no image signal is inputted therefrom. 
     In the image display apparatus according to the first aspect of the invention, it is preferable that the control section commands the image signal correcting section to close the source search screen and commands the input selector to select the input terminal corresponding to the selected input source when no image signal is inputted to any of the input terminals and processing for selecting any of the input sources is executed on the source search screen through the operation section. 
     In this structure, the control section commands the image signal correcting section to close the source search screen and commands the input selector to select the input terminal corresponding to the selected input source when processing for selecting any of the input sources is executed on the source search screen. Thus, the image display apparatus can select the input terminal corresponding to the input source selected on the source search screen even when no image signal is inputted to any of the input terminals. 
     Accordingly, the image display apparatus according to the first aspect of the invention can select input sources in the standby condition. 
     In the image display apparatus according to the first aspect of the invention, it is preferable that the image display apparatus further includes a storage section for storing an initial input terminal selected by the input selector before the search processing is required, and that the control section commands the image signal correcting section to close the source search screen and commands the input selector to select the initial input terminal stored in the storage section when it is determined that no image signal has been inputted to any of the input terminals and processing for selecting any of the input sources is not executed through the operation section within a predetermined time. 
     In this structure, the control section commands the image signal correcting section to close the source search screen and commands the input selector to select the initial input terminal stored in the storage section when it is determined that no image signal has been inputted to any of the input terminals and processing for selecting any of the input sources is not executed through the operation section within the predetermined time. Thus, the image display apparatus automatically returns to the initial setting after elapse of the predetermined time when the search processing is completed and no image signal is detected. 
     Accordingly, the image display apparatus can provide definite and visual information that the search processing has been completed to the user by closing the source search screen and returning to the condition of initial setting. Additionally, if the search processing is again required in this condition, the image display apparatus similarly returns to the initial setting. This notifies the user that any operation such as operation requiring any of the input sources to output image signals needs to be executed so as to display images. 
     In the image display apparatus according to the first aspect of the invention, it is preferable that, in the case where image signals have been inputted to the initial terminal selected by the input selector before the search processing is required, the control section commands the image signal correcting section to generate image signals for producing the source search screen including the input source name corresponding to the initial input terminal and the indication that image signals have been inputted to the initial input terminal in response to the search processing required through the control section before the respective sections perform operation corresponding to the search processing. 
     In this structure, the control section commands the image signal correcting section to generate image signals for producing the source search screen including the input source name corresponding to the initial input terminal and the indication that the image signals have been inputted to the initial input terminal in response to the search processing executed through the control section before the respective sections perform operation corresponding to the search processing in the case that image signals have been inputted to the initial input terminal. Thus, the image display apparatus displays the indication that image signals have been inputted to the initial input terminal and searches for other input sources supplying image signals even when image signals have been inputted to the initial input terminal. 
     Accordingly, the image display apparatus according to the first aspect of the invention can display the information that image signals have been inputted to the initial input terminal on the search screen and search for other input sources supplying image signals even when image signals have been inputted to the initial input terminal. 
     In the image display apparatus according to first aspect of the invention, it is preferable that the control section commands the input selector to select the initial input terminal and commands the image signal correcting section to superpose the source search screen, which is smaller than the image produced by the image signals inputted from the initial input terminal, on the image signals inputted from the initial input terminal for a predetermined time when no image signal is inputted to input terminals other than the initial input terminal. 
     In this structure, the control section commands the input selector to select the initial input terminal and commands the image signal correcting section to superpose the source search screen, which is smaller than the image produced by the image signals inputted from the initial input terminal, on the image signals inputted from the initial input terminal for the predetermined time when no image signal is inputted to input terminals other than the initial input terminal. Thus, the image display apparatus displays the source search screen for the predetermined time on the background of the image produced by the image signals inputted from the initial input terminal after the completion of the search processing. 
     Accordingly, the image display apparatus can display the source search screen while providing visual information showing that image signals have been inputted from the input source corresponding to the initial input terminal to the user using the background image produced by the image signals from the initial input terminal. Since the superposition of the source search screen finishes after elapse of the predetermined time, only the image produced by the image signals inputted from the initial input terminal is displayed. 
     An image display apparatus for displaying an image produced by image signals on a display section according to a second aspect of the invention includes: a plurality of input terminals for receiving each of the image signals supplied from a plurality of input sources; an input selector for selecting a predetermined input terminal from the plural input terminals; a judging section for determining whether the image signals have been inputted to the input terminal selected by the input selector; an operating section which receives requirement of search processing for determining whether the image signals have been inputted to each of the plural input terminals; an image signal correcting section which generates image signals for producing a source search screen indicating search status for each of the input source names corresponding to the input terminals; and a control section for displaying an image of the source search screen produced by the image signals at least on the display section in response to search processing required through the operation section. The control section commands the input selector to sequentially select the input terminals when the search processing is required through the operation section, and commands the judging section to check the presence or absence of the image signals inputted for each of the selected input terminals. The control section commands the image signal correcting section to sequentially add an indication of the presence or absence of the image signals for each of the input terminals having been checked by the judging section on the source search screen so as to check the presence or absence of the image signals for all the input terminals. 
     In this structure, the control section commands the input selector to sequentially select the input terminals when the search processing is required through the operation section, and commands the judging section to check the presence or absence of the image signals inputted for each of the selected input terminals. The control section commands the image signal correcting section to sequentially add the indication of the presence or absence of the image signals for each of the input terminals having been checked by the judging section on the source search screen so as to check the presence or absence of the image signals for all the input terminals. Thus, the image display apparatus checks the presence or absence of the image signals for all the input terminals while adding the information on the presence or absence of the image signals for each of the input terminals, and displays a list showing the results. 
     Accordingly, the image display apparatus can provide visual information on the checking status of the image signals to the user for each input source one after another, and efficiently notify the search results using the source search screen including the list which shows the presence or absence of the image signals for all the input terminals. Since the list on the source search screen showing the presence or absence of the image signals for all the input sources allows the user to select the desired input source when the image signals from the plural input sources are detected, the usability of the image display apparatus is enhanced. 
     Accordingly, the image display apparatus can efficiently search for the input source which is outputting the image signals. When no image signal is inputted from any of the input sources, the image display apparatus provides to the user visual information on this fact. 
     In the image display apparatus according to the second aspect of the invention, it is preferable that the control section commands the image signal correcting section to close the source search screen and commands the input selector to select the input terminal from which image signals have been detected first when the processing for selecting any of the input sources is not executed through the operation section within a predetermined time after checking the presence or absence of image signals for all the input terminals. 
     In this structure, the control section commands the image signal correcting section to close the source search screen and commands the input selector to select the input terminal from which image signals have been detected first when the processing for selecting any of the input sources is not executed through the operation section within the predetermined time after checking the presence or absence of image signals for all the input terminals. Thus, the image display apparatus closes the source search screen and displays the image produced by the image signals from the input source corresponding to the input terminal from which the image signals have been detected first. 
     Accordingly, the image display apparatus can efficiently search for the input source which is outputting the image signals, and automatically display the image produced by the image signals from this input source. 
     In the image display apparatus according to first or second aspect of the invention, it is preferable that the control section commands the image signal correcting section to superpose an indication that the image signals are being detected on the source search screen while the judging section is checking the presence or absence of image signals for each of the selected input terminals. 
     In this structure, the control section commands the image signal correcting section to superpose the indication that image signals are being detected on the source search screen while the judging section is checking the presence or absence of image signals for each of the selected input terminals. Thus, the image display apparatus superposes on the source search screen the indication that image signals are being detected while the judging section is checking the presence or absence of image signals for each of the selected input terminals. 
     Accordingly, the image display apparatus can provide visual information that image signals are being detected to the user. This eliminates such anxiety that the operation might have frozen from the user. 
     In the image display apparatus according to the first or second aspect of the invention, it is preferable that, in the case where the source search screen is closed and that image signals have not been inputted to the input terminal selected by the input selector in response to the operations by the respective sections based on the search processing or to the selecting processing through the operation section, the control section commands the image signal correcting section to generate image signals for producing a screen showing the selected input source name and an indication that image signals have not been inputted on the display section. 
     In this structure, the control section commands the image signal correcting section to generate and display image signals for producing the screen showing the selected input source name and the indication that image signals have not been inputted on the display section in the case that image signals have not been inputted to the input terminal selected by the input selector after completion of the search processing. Thus, the image display apparatus displays the screen including the indication that no image signal has been inputted to the selected input source after the search processing is completed and the search screen is closed. 
     Accordingly, the image display apparatus can provide to the user visual information that image signals have not been inputted to the selected input terminal after the search processing is completed and the input terminal is selected. This notifies the user that any operation such as operation requiring output of image signals to input sources needs to be executed so as to display images. 
     It is preferable that the image display apparatus according to the first or second aspect of the invention is a projector which modulates light emitted from a light source section into modulated light in accordance with the image signals using light modulating elements, and enlarges and projects the modulated light using a projection lens. 
     A projector which can provide enlarged images using a projection lens have been widely used for various purposes such as presentation using a PC (personal computer) and movie watching using a DVD. In these applications, the number of input sources connected to the projector is generally small as in the case where only a PC and a DVD are used. Thus, there is a demand from the user of the projector for quick selection of the input source supplying image signals or for checking if image signals have been outputted from the input source. 
     Thus, the image display apparatus according to the first or second aspect of the invention can be appropriately used as a projector. 
     Accordingly, the projector according to the first or second aspect of the invention can efficiently search for the input source which is outputting image signals and notify the user that no image signal is inputted from any of the input sources when no image signal is inputted therefrom. 
     An input source search support method according to a third aspect of the invention includes: a first step for receiving input source search start requiring processing from the user and showing a source search screen including a list of input sources which can be displayed on an image display apparatus (also referred to as “input source list screen”) while an image corresponding to an input source is being displayed; and a second step for executing processing for detecting the presence or absence of image signals for input sources which can be displayed on the image display apparatus other than the input source whose image is being displayed in the first step until image signals are detected sequentially in a predetermined order. An image corresponding to any of the input sources starts to be displayed when image signals therefrom are detected, and information showing that no image signal has been detected is displayed on the source search screen when no image signal is detected in the second step. 
     When all the input sources are unavailable and no image signal is detected in the image source search support method according to the third aspect of the invention, the information that no image signal has been detected is visually shown on the source search screen. Thus, when all the input sources are unavailable, this information can be visually shown to the user and the first advantage according to some aspects of the invention can be offered. 
     In the input source search support method according to the third aspect of the invention, the condition where an image corresponding to an input source is being displayed in the first step includes the case where a message screen saying “no image signal inputted” and the like is displayed since image signals are not inputted from this input source, as well as the case where an image produced by image signals from this input source is being displayed. 
     In the input source search support method according to the third aspect of the invention, it is preferable that the information on the presence or absence of image signals is stored, and that this information is displayed for each of the input sources when the source search screen is displayed. 
     In this method, the information on the presence or absence of image signals can be displayed on the source search screen for each input source during and after the source search. It is therefore possible to check from which input source the image signals are coming, and thus the usability is enhanced. 
     In the input source search support method according to the third aspect of the invention, it is preferable that, in the case where no image signal is detected in the second step and the user selects a particular input source through the source search screen, an image corresponding to the particular input source starts to be displayed. 
     In this method, the input source in the standby condition can be selected by selecting the particular input source through the source search screen. Thus, the second advantage according to some aspects of the invention can be offered. 
     In the input source search support method according to the third aspect of the invention, it is preferable that the image corresponding to the input source which is being displayed in the first step starts to be displayed when no image signal is detected in the second step and the user executes canceling operation or no operation within the predetermined time. 
     Search for input sources is generally conducted when the power switch of the image display apparatus is turned on or while the image of the input source which is being displayed in the first step is under display in the image display apparatus. Thus, when the user executes canceling operation or no operation within the predetermined time in the latter case, the screen can be returned to the initial screen. Accordingly, the usability of the image display apparatus can be enhanced. 
     In the input source search support method according to the third aspect of the invention, it is preferable that the image corresponding to the input source which is being displayed in the first step is displayed as the background of the source search screen when no image signal is detected in the second step. 
     As mentioned above, search for input sources is generally conducted when the power switch of the image display apparatus is turned on or while the image of the input source which is being displayed in the first step is under display in the image display apparatus. Thus, when no image signal is detected in the second step in the latter case, the initial screen is displayed as the background of the source search screen. Accordingly, the usability of the image display apparatus can be enhanced. 
     In the input source search support method according to the third aspect of the invention, it is preferable that information on the input source which is being searched and information showing that image signals are being detected are displayed on the source search screen while the image signals are being detected in the second step. 
     Since information on the input source which is being searched and information showing that image signals are being detected are displayed on the source search screen while the image signals are being detected in this method, the information on the search condition can be securely provided to the user. Thus, the usability of the image display apparatus can be enhanced. 
     An input source search support program according to a fourth aspect of the invention executed by an image display apparatus for displaying images produced by image signals, under which program the image display apparatus executes: a first step for receiving input source search start requiring processing from the user and showing a source search screen including a list of input sources which can be displayed on an image display apparatus while an image corresponding to an input source is being displayed; and a second step for executing processing for detecting the presence or absence of image signals for input sources which can be displayed on the image display apparatus other than the input source whose image is being displayed in the first step until image signals are detected sequentially in a predetermined order. An image corresponding to any of the input sources starts to be displayed when image signals therefrom are detected, and information showing that no image signal has been detected is displayed on the source search screen when no image signal is detected in the second step. 
     When all the input sources are unavailable in the input source search support method according to the third aspect of the invention used in the image display apparatus, no image signal is detected and thus the information that no image signal is detected is shown on the source search screen. Accordingly, when all the input sources are unavailable, this information is shown to the user. 
     An image display apparatus according to a fifth aspect of the invention has: a first function for receiving search processing from the user and showing a source search screen including a list of input sources which can be displayed on an image display apparatus while an image corresponding to an input source is being displayed; and a second function for executing processing for detecting the presence or absence of image signals for input sources which can be displayed on the image display apparatus other than the input source whose image is being displayed in the first function until image signals are detected sequentially in a predetermined order. An image corresponding to any of the input sources starts to be displayed when image signals therefrom are detected, and information showing that no image signal has been detected is displayed on the source search screen when no image signal is detected in the second function. 
     When all the input sources are unavailable in the image display apparatus according to the fifth aspect of the invention, no image signal is detected and thus the information that no image signal is detected is shown on the source search screen. Accordingly, when all the input sources are unavailable, this information is shown to the user. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers refer to like elements. 
         FIG. 1  schematically shows a projector in a first embodiment. 
         FIG. 2  is a flowchart showing an input source search support method in the first embodiment. 
         FIG. 3  shows an example of a display screen. 
         FIG. 4  shows an example of a display screen. 
         FIG. 5  shows an example of a display screen. 
         FIG. 6  shows an example of a display screen. 
         FIG. 7  shows an example of a display screen. 
         FIG. 8  shows an example of a display screen. 
         FIG. 9  shows an example of a display screen. 
         FIG. 10  shows an example of a display screen. 
         FIG. 11  shows an example of a display screen in a second embodiment, 
         FIG. 12  shows an example of a display screen. 
         FIG. 13  shows an example of a display screen. 
         FIG. 14  is a flowchart showing an input source search support method in a third embodiment. 
         FIG. 15  shows an example of a display screen. 
         FIG. 16  illustrates a related-art projector to which a plurality of input sources are connected. 
         FIG. 17  shows a related-art input source search support method. 
         FIG. 18  illustrates another related-art input source support method. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Several embodiments according to the invention are hereinafter described in detail with reference to the accompanying drawings. 
     First Embodiment 
     Structure of Projector 
       FIG. 1  is a block diagram schematically showing a structure of a projector as an image display apparatus according to the invention. The general structure of a projector  100  is now discussed with reference to  FIG. 1 . 
     The projector  100  divides white light emitted from a lamp  51  as a light source into three primary colors of red light, blue light and green light. The respective color lights are modulated by liquid crystal light valves  52 R,  52 G and  52 B as display sections based on image signals supplied from input sources. The modulated lights are synthesized into full-color light, which is then enlarged and projected on a screen SC using a projection lens  65 . Thus, the projector  100  is a so-called liquid crystal three-plate type projector. 
     The liquid crystal valves  52 R,  52 G and  52 B are light modulating elements, each of which is used for red light, green light and blue light, respectively, and is contained in an optical section  64 . 
     The projector  100  includes the lamp  51 , an operation section  53 , a remote controller  54 , an operation receiving section  55 , input terminals T 1  through T 4 , an input selector  56 , a judging section  57 , an image converter  58 , an image signal processing section  59 , a frame memory  60 , an image signal correcting section  61 , an OSD memory  62 , a liquid crystal panel driving section  63 , the optical section  64 , the projection lens  65 , a control section  66 , a storage section  67 , a power source section  68 , a lamp driving section  69  and others. 
     The lamp  51  is formed by a discharge-type lamp capable of providing high luminance such as a high-pressure mercury lamp, a metal halide lamp and a halogen lamp. 
     The operation section  53  is provided on the upper surface of the main body of the projector  100 , and has a plurality of operation buttons used for manipulation of the projector  100 . The plural operation buttons include a “power source button” for startup and shutdown of the projector  100 , an “source search button” for searching for an input source currently providing image signals, a “source selection button” provided for each input source for selecting a desired input source, and other buttons (all these buttons are not shown). 
     The remote controller  54  as the operation section is a remote controller for controlling the projector  100  from a remote site, and has a plurality of operation buttons similar to those of the operation section  53  for operating the projector  100 . 
     When the operation section  53  or the remote controller  54  is operated, the operation receiving section  55  receives this processing and transmits operation signals to the control section  66  as triggers for various operations. 
     The input terminals T 1  through T 4  are input terminals through which each of the image signals supplied from a plurality of external electronic devices PC 1 , PC 2 , DV and VI as input sources is inputted to the projector  100 . 
     The input terminals T 1  and T 2  are formed by mini D-sub 15 pin terminals, for example, through which analog RGB signals supplied from personal computers PC 1  and PC 2  are inputted. It is also possible to input component signals by changing use allocations of signal conductors of 15 pins provided on the mini D-sub 15 pin terminals. 
     The input terminal T 3  is formed by an S terminal, for example, through which S signals are supplied from a DVD player DV, S video player and the like. 
     The input terminal T 4  is formed by a 1RCA terminal, for example, through which composite signals are supplied from a video player VI, TV tuner and the like. 
     Other input terminals such as a stereo mini jack or other audio input terminals through which audio signals are inputted, an USB terminal for allowing various information exchanges between an external PC and the projector  100 , and an RS232C terminal are equipped as input terminals of the projector  100 , but these input terminals are not shown for simplification of the description. 
     The external electronic devices PC 1 , PC 2 , DV and VI are now discussed showing how they are expressed in the input source names. 
     More specifically, the personal computers PC 1  and PC 2  are expressed as “computer 1” and “computer 2” in the input source names. Similarly, the DVD player DV and the vide player VI are expressed as “S-Video” and “Video”. 
     The input selector  56  is a selection switch for selecting a desired input terminal from the input terminals T 1  through T 4 . The input selector  56  selects any one of the four input terminals based on the selection signals from the control section  66 . Thus, when the input source associated with the selected input terminal supplies image signals Vin, the projector  100  projects an image produced by the image signals Vin. 
     The default input source of the projector  100  at the time of shipment is set to “Computer 1”. By operating the “source search button” of the remote controller  54  after startup of the projector  100 , for example, the input selector  56  sequentially selects the input terminals T 1  through T 4 , thereby switching the input source from “Computer 1” to “Computer 2”, “S-Video”, and “Video” in this order. 
     At the time of shutdown of the projector  100 , the input source information selected at that time is stored in the storage section  67 , and the same input source reappears at the next startup. 
     The judging section  57  is formed by a comparator, for example, and determines whether the image signals Vin are supplied from the input source selected by the input selector  56  or not by checking the presence or absence of synchronous signals contained in the image signals Vin. The judging section  57  then transmits judging signals showing the presence or absence of the inputted image signals Vin to the control section  66 . 
     The image converter  58  converts the analog image signals Vin into digital image signals Din, and outputs the digital image signals Din. The conversion into digital signals is performed so that various image signal processing can be applied to the image signals Yin. The image converter  58  contains a decoder. 
     More specifically, the image converter  58  applies the image signal processing including the AID conversion processing to the image signals Vin when they are analog RGB signals from the input sources “Computer 1” and “Computer 2”. However, the image converter  58  applies the image signal processing including the A/D conversion processing to the image signals Vin after they are converted into component signals by the decoder accommodated in the image converter  58  when the image signals Vin are S signals from the input source “S-Video” or composite signals from the input source “Video”. 
     The image signal processing section  59  performs image signal processing such as writing the image data of the image signals Din to the frame memory  60  and reading the image data therefrom under predetermined conditions so that the image signals Din can be appropriately displayed using the liquid crystal light valves  52 R,  52 G and  52 B. This image signal processing includes scaling processing for enlarging and reducing the images produced by the image signals Din so that the resolution of the images coincides with the resolution of the liquid crystal light valves  52 R,  52 G and  52 B, frame rate alteration processing for altering frame rates indicating the number of times of image-drawing updates per second, and other processing. The image signals Din to which this image signal processing have been applied are outputted as digital image signals Dsc. 
     The image signal correcting section  61  applies γ correcting processing for changing the gradation value of the image signals Dsc to a gradation value appropriate for the display using the liquid crystal light valves  52 R,  52 G and  52 B, color non-uniformity correction processing for correcting color non-uniformity caused due to luminance non-uniformity peculiar to each of the liquid crystal light valves  52 R,  52 G and  52 B. The image signal correcting section  61  then converts the image signals Dsc into analog image signals Vout and outputs the analong image signals Vout. 
     Additionally, the image signal correcting section  61  has OSD (On-Screen Display) function for superposing the input source name on the image produced by the image signals Vin. The image signal correcting section  61  reads out the “input source name” and the “source search” screen of the input source, for example, from the OSD memory  62  based on the OSD signals coming from the control section  66 , and superposes theses information on the image signals Dsc. 
     When the image signals Vin are not inputted, the image signal correcting section  61  reads out the “standby” screen showing the “input source name” and the message in characters saying “no image signal inputted” on the blue background screen, for example, from the OSD memory  62 . The image signal correcting section  61  generates and outputs the image signals Vout for producing the “standby” screen. 
     The OSD memory  62  is formed by nonvolatile memory, and stores screens, various character patterns and the like showing the operating conditions of the projector for the On-Screen Display such as “input source names”, various examples of “source search” screens of the input sources, and the “standby” screen. 
     The liquid crystal panel driving section  63  is a liquid crystal driver, which supplies the image signals Vout, driving voltage and the like to the liquid crystal light valves  52 R,  52 G and  52 B and projects images on the liquid crystal light valves  52 R,  52 G and  52 B. 
     The optical section  64  includes: an integrator optical system (not shown) for converting white light emitted from the lamp  51  into substantially collimated light having stable luminance distribution; a separation optical system (not shown) for separating the white light having stable luminance distribution into three primary light colors constituted by red, green and blue light components and for supplying these lights to the respective liquid crystal light valves  52 R,  52 G and  52 B; and a synthesis optical system for synthesizing the respective color lights each of which has been modulated by the liquid crystal light valves  52 R,  52 G and  52 B based on the image signals Vout. 
     The respective modulated color lights released from the liquid crystal light valves  52 R,  52 G and  52 B are synthesized by a cross dichroic prism  73  as the synthesis optical system having a dichroic film  71  for reflecting blue light and transmitting green light and a dichroic film  72  for reflecting red light and transmitting green light. The synthesized full-color light which has been modulated based on the image signals Vout is then released as the substantially collimated and modulated light. 
     The projection lens  65  is constituted by a convex lens and the like. The projection lens  65  enlarges the modulated light coming from the cross dichroic prism  73  so that the light can be projection light, and projects images on the screen SC. The projection lens  65  has a zoom function for controlling the rates of enlargement of the projection light, and a focus function for controlling the focus of the projection light. 
     The control section  66  is formed by a CPU (Central Processing Unit). The control section  66  transmits and receives signals to and from the respective sections through bus lines Bus, and controls the operations of the respective sections in accordance with operation signals coming from the control receiving section  55  and the like. 
     The storage section  67  is formed by a nonvolatile memory such as flash memory in which data is rewritable, for example. The storage section  67  stores various control programs, firmware, and accompanying data used for commanding and controlling the operation of the projector  100 . 
     The control programs include a “source search program” as a search support program used for searching the input source which is supplying the image signals. The accompanying data includes the input terminal name having been selected by the input selector before performing the “source search program, and other data. 
     The power source section  68  introduces alternating current power from an external power source  80  through a plug (not shown), and applies processing such as transformation, rectification and smoothing to the alternating current by an AC/DC converting section (not shown) contained in the power source section  68  so as to supply stabilized direct current to the respective sections of the projector  100 . 
     The lamp driving section  69  includes an igniter circuit (not shown) for receiving power supply from the power source section  68  and forming a discharge path by generating high voltage so as to turn on the lamp  51  as a discharge type lamp, and a ballast circuit (not shown) for maintaining the stable turned-on condition of the lamp  51  after it is turned on. 
     First Example of Input Source Search 
       FIG. 2  is a flowchart showing an input source search support method in the first embodiment.  FIGS. 3 through 10  illustrate examples of display screens in the first embodiment. 
     In this embodiment, an example of the input source search executed by the projector  100  is described with reference to  FIG. 2  chiefly, and also  FIGS. 1 and 3  through  10  as supplementary figures. 
     The input source search support method in the first embodiment is an input source search support method performed on the assumption that search for the input source is executed after startup of the projector  100 . 
     In the input source search support method according to the first embodiment, it is assumed that the image of the input source “Computer 1” associated with the input terminal T 1  is displayed when the power source switch of the projector  100  is turned on. It is also assumed that image signals are not outputted from the input source “Computer 1” at that time. 
     As shown in  FIG. 2 , the input source search support method in the first embodiment has a first step S 10  and a second step S 20 . 
     When the “power source button” of the remote controller  54  is operated, operation signals are transmitted from the operation receiving section  55  to the control section  66 . The control section  66  having received the operation signals brings the respective sections into startup conditions, and initializes these sections. The control section  66  commands the input selector  56  to selects the input terminal T 1  as the default input terminal. 
     In step S 11 , the control section  66  commands the image signal correcting section  61  to generate image signals for producing the “standby” screen shown in  FIG. 3  and project the corresponding image based on the judging signals coming from the judging section  57  showing that no image signal is inputted from the input source “Computer 1” associated with the input terminal T. The message “no image signal inputted” is displayed on the “standby” screen. 
     In step S 12 , the control section  66  receives the operation signals from the operation receiving section  55  which are transmitted when the “source search button” of the remote controller  54  is operated, and executes the “source search program” stored in the storage section  67 . The operations carried out by the respective sections in the following respective steps are performed under the “source search program”. The control section  66  commands the storage section  67  to store the input terminal selected by the input selector  56  at the start of the source search processing as the initial input terminal. 
     In step S 13 , the control section  66  commands the image signal correcting section  61  to generate the image signals for producing the “source search” screen shown in  FIG. 4 , and project the corresponding image. The “source search” screen in  FIG. 4  includes a message “none”, which shows no image signal is inputted, for the input source “Computer 1”. 
     The steps S 11  through S 13  discussed above correspond to the first step S 10 . 
     In step S 21 , the control section  66  commands the input selector  56  to select the next input terminal of the input terminal currently selected by the input selector  56  in the selection order. The selection order circulates as: “input terminal T 1 ”, “input terminal T 2 ”, “input terminal T 3 ”, “input terminal T 4 ” and back to “input terminal T 1 ”. 
     In step S 22 , the control section  66  commands the judging section  57  to check the presence or absence of the image signals transmitted from the input source corresponding to the input terminal selected in step S 21 . When it is determined that the image signals have been inputted, the flow advances to step S 27 . When it is determined that the image signals have not been inputted, the flow goes to step S 23 . 
     In the respective steps, the control section  66  commands the image signal correcting section  61  to update the “source search” screen in accordance with the search conditions one after another. 
     The “source search” screen shown in  FIG. 5  is a screen indicating that image signals transmitted from the input source “Computer 2” corresponding to the input terminal T 2  are being detected. This screen includes the message saying “now detecting signal status”. The “source search” screen shown in  FIG. 6  is a screen where the image signals transmitted from the input source “Video” corresponding to the input terminal T 4  are being detected. This screen includes a message saying “now detecting signal status” similarly to the screen shown in  FIG. 5 . 
     In step S 23 , the control section  66  checks whether image signals have been detected for all the input terminals T 1  through T 4 . When detection of the image signals is completed for all the input terminals, the flow advances to step S 24 . When detection is not completed for any of the input terminals, the flow returns to step S 21 . 
     In step S 24 , the control section  66  commands the image signal correcting section  61  to generate image signals for producing the “source search” screen shown in  FIG. 7 , and project the corresponding image. The “source search” screen in  FIG. 7  indicates that image signals have not been inputted from any of the input sources. The “source search” screen displays the message saying “No signal detected. Please select input source manually”. 
     In step S 25 , the control section  66  checks whether the “source selection button” of the operation section  53  or the remote controller  54  has been operated within a predetermined time based on the presence or absence of the operation signals transmitted from the operation receiving section  55 . When operation signals for selecting any of the input sources are detected, the flow proceeds to step S 26 . When the operation signals for selecting any of the input sources are not detected, the flow goes to step S 28 . The predetermined time herein is approximately 10 seconds. 
     In step S 26 , the control section  66  commands the image signal correcting section  61  to close the “source search” screen, and commands the input selector  56  to select the input terminal corresponding to the input source selected in step S 25 . 
     The processes to be performed when it is determined that the image signals have been inputted in step S 22  are now discussed. 
     In step S 27 , the control section  66  commands the image signal correcting section  61  to close the “source search” screen, and project images produced by the image signals inputted to the input terminal from which the image signals have been detected in step S 22 .  FIG. 8  shows a screen in the case that the image signals have been detected from the input terminal T 2 . The screen produced by the input source “Computer 2” is shown by dots for simplification. 
     Next, the processes to be performed when it is determined that the processing for selecting any of the input sources has not been conducted in step S 25  are explained. 
     In step S 28 , since it is determined that the processing for selecting any of the input sources has not been conducted, the control section  66  commands the image signal correcting section  61  to close the “source search” screen. The control section  66  then reads out the information on the initial input terminal from the storage section  67 , and commands the input selector  56  to select this input terminal. 
       FIG. 9  shows a screen in this condition. This screen is similar to the “standby” screen shown in  FIG. 3 . When the initial input terminal is the input terminal T 4 , for example, a screen shown in  FIG. 10  is displayed. 
     The steps S 22  through S 28  described above correspond to the second step S 20 . 
     According to this embodiment, the following advantages are offered. 
     (1) When search processing is required through the remote controller  54 , the control section  66  commands the input selector  56  to select the input terminals T 1  through T 4  sequentially, and commands the judging section  57  to check the presence or absence of the inputted image signals for each of the selected input terminal. When it is determined that image signals have not been inputted to the input terminal checked by the judging section  57 , a message showing this fact is added to the source search screen by the image signal correcting section  61 . Thus, an indication showing the presence or absence of the image signals for each input terminal searched is sequentially added to the source search screen projected by the projector  100 . 
     Accordingly, the supply status of image signals for each input source can be visually checked in real time by the user of the projector  100 . Moreover, when no image signal is inputted from any of the input sources, this condition can be visually displayed on the source search screen. 
     Furthermore, the control section  66  commands the image signal correcting section  61  to close the source search screen when it is determined that image signals have been inputted to any of the input terminals, and project images produced by the image signals coming from the input terminals from which the image signals have been detected. Thus, the projector  100  closes the source search screen when it is determined that the image signals have been inputted, and projects images produced by the image signals from the input source corresponding to this input terminal. 
     Accordingly, the projector  100  can offer visual information that the input source search has been completed to the user and can efficiently search for the image source which is outputting image signals. 
     Therefore, the projector  100  can not only efficiently search for the input source which is outputting image signals, but also can notify the user that no image signal is inputted from any of the input sources even when no image signal is inputted therefrom. Moreover, the projector  100  can display the status of image signals for each image source by one action of easy search processing, and automatically connects the associated input sources when image signals from the input source are detected. Thus, usability of the projector  100  is enhanced. 
     (2) When processing for selecting any of the input sources is executed through the source search screen, the control section  66  commands the image signal correcting section  61  to close the source search screen and commands the input selector  56  to select the input terminal corresponding to the selected image source. Thus, the projector  100  selects the input terminal associated with the image source selected through the source search screen even when it is determined that no image signal is inputted to any of the input terminals. 
     Accordingly, the projector  100  can select input sources in the standby condition. 
     (3) When no image signal is inputted to any of the input terminals and processing for selecting any of the input sources is not executed within the predetermined time through the operation section, the control section  66  commands the image signal correcting section  61  to close the source search screen and commands the input selector  56  to select the initial input terminal stored in the storage section  67 . Thus, the projector  100  automatically returns to the initial setting after elapse of the predetermined time if no image signal is detected after completion of the search processing. 
     Accordingly, the projector  100  can provide definite and visual information that the search processing has been completed to the user by closing the source search screen and returning to the condition of initial setting. Additionally, if the search processing is again executed in this condition, the projector  100  similarly returns to the initial setting. This notifies the user that any operation such as operation requiring any of the input sources to output image signals needs to be executed so as to display images. 
     (4) The control section  66  commands the image signal correcting section  61  to superpose the message saying that image signals are being detected on the source search screen while the judging section  57  is checking the presence or absence of image signals for each of the selected input terminals. Thus, the projector  100  projects the screen including the message that image signals are being detected while the judging section  57  is checking the presence or absence of image signals for each of the selected input terminals. 
     Accordingly, the projector  100  can provide visual information that image signals are being detected to the user. This eliminates such anxiety that the operation might have frozen from the user. 
     (5) When it is determined that image signals have not been inputted to the input terminal selected by the input selector  56  after completion of the search processing, the control section  66  commands the image signal correcting section  61  to generate image signals for producing the screen which displays the selected input source name and the message saying that image signals have not been inputted. Thus, the projector  100  displays the screen including the message that no image signal has been inputted to the selected input source after the search processing is completed and the search screen is closed. 
     Accordingly, the projector  100  can provide visual information that image signals have not been inputted to the selected input terminal after the search processing is completed and the input terminal is selected. This notifies the user that any operation such as operation requiring output of image signals to input sources needs to be executed so as to display images. 
     (6) In the first step S 10 , the projector  100  receives operation requiring start of input source search from the user and displays the source search screen including a list of input sources available for display by the projector  100  under the condition where an image provided by one of the input sources is being displayed. In the second step S 20 , detection of presence or absence of image signals continues in the predetermined order until image signals are detected from any of the input sources other than the input source which is providing the image. 
     When image signals are detected from any of the input sources in the second step S 20 , display of the corresponding input source starts. When no image signal is detected in this step, the information that no image signal has been detected is displayed on the source search screen. Thus, according to the image source search support method employed in the projector  100 , no image signal is detected when all the input sources are unavailable, and the information that no image signal has been detected is displayed on the source search screen. 
     Accordingly, when all the input sources are unavailable in the image source search support method used in the projector  100 , visual information showing that no input source is available is shown to the user. For practicing this search support method, the projector  100  executes the “source search program”. 
     Therefore, when all the input sources are unavailable, the “source search program” can provide visual information that no input source is available to the user. 
     Second Embodiment 
     Second Example of Input Source Search 
       FIGS. 11 through 13  show examples of display screens in a second embodiment.  FIG. 11  corresponds to  FIG. 3  in the first embodiment,  FIG. 12  corresponds to  FIG. 7  in the first embodiment, and  FIG. 13  corresponds to  FIG. 9  in the first embodiment. The input source search support method in the second embodiment is a method for searching an input source different from the input source currently used by the projector  100  while the projector  100  is being operating. 
     The structure of the projector and the control programs stored in the storage section  67  and the like are similar to those of the projector  100  in the first embodiment. 
     The second embodiment is now explained referring to chiefly  FIG. 2 , and  FIG. 1  and  FIGS. 11 through 13  and other figures as supplementary figures, focusing on the differences from the first embodiment only. 
     In step S 11 , an image shown in  FIG. 11  is displayed as the initial screen produced by image signals from the input source “Computer 1”. The image provided by the input source “Computer 1” is shown by dots for simplification. 
     In step S 13 , the control section  66  commands the image signal correcting section  61  to generate image signals for producing the source search screen including the name of the input source corresponding to the initial input terminal and the indication that image signals have been inputted thereto, and project the corresponding image. 
     In step S 24 , the image of the input source “Computer 1” is displayed on the background of the “source search” screen as illustrated in  FIG. 12 . The size of the “source search” screen is smaller than the size of the image produced by the image signals from the input source “Computer 1”. 
     When the processing for selecting any of the input sources is not executed within the predetermined time in step S 25 , the image of the input source “Computer 1” shown in  FIG. 13  is displayed in step S 28 . 
     In other points, the input source search support method according to the second embodiment is similar to the input source search support method according to the first embodiment. 
     Accordingly, the following advantages are offered in the second embodiment in addition to the advantages provided in the first embodiment. 
     (1) When it is determined that image signals have been inputted to the initial input terminal and the input search processing is required through the remote controller  54 , the control section  66  commands the image signal correcting section  61  to generate image signals for producing the source search screen including the input source name corresponding to the initial input terminal and the message that the image signals have been inputted before the input source search processing is conducted by the respective sections. Thus, even when image signals are detected in the initial input terminal, the projector  100  can display this information on the source search screen and then search for other input sources supplying image signals. 
     Accordingly, in the case where image signals have been inputted to the initial input terminal, the projector  100  can display the indication that image signals have been inputted thereto on the source search screen, and search for other input sources supplying image signals. 
     (2) When no image signal is inputted to the input terminals other than the initial input terminal, the control section  66  commands the input selector  56  to select the initial input terminal, and commands the image signal correcting section  61  to superpose the source search screen, which is smaller in size than the image produced by the image signals inputted from the initial input terminal, on the image signals inputted from the initial input terminal for a predetermined time. Thus, the projector  100  displays the source search screen for the predetermined time on the background of the image produced by the image signals inputted from the initial input terminal after completion of the search processing. 
     Accordingly, the projector  100  can display the source search screen while providing visual information showing that image signals have been inputted from the input source corresponding to the initial input terminal to the user using the background image produced by the image signals from the initial input terminal. Since the superposition of the source search screen finishes after elapse of the predetermined time, only the image produced by the image signals inputted from the initial input terminal can be displayed. 
     Third Embodiment 
     Third Example of Input Source Search 
       FIG. 14  is a flowchart showing an input source search support method in a third embodiment. 
       FIG. 15  is an example of a display screen in the third embodiment. 
     The structure of the projector is similar to that of the projector  100  in the first embodiment. 
     Only the “source search program” stored in the storage section  67  of the projector  100  in the third embodiment is different from that of the projector  100  in the first embodiment. 
     In this embodiment, an example of the input source search executed by the projector  100  is described with reference to  FIG. 14  chiefly, and also  FIGS. 1 and 15  and other figures as supplementary figures. 
     When the “power source button” of the remote controller  54  is operated, operation signals are transmitted from the operation receiving section  55  to the control section  66 . The control section  66  having received the operation signals starts and initializes the respective sections. The control section  66  commands the input selector  56  to select the input terminal T 1  as the default input terminal. It is assumed that no image signal is outputted from the input source “Computer 1” at this stage. 
     In step S 31 , the control section  66  commands the image signal correcting section  61  to generate image signals for producing the “standby” screen shown in  FIG. 3  based on the judging signals from the judging section  57  indicating that no image signal is inputted from the input source “Computer 1” corresponding to the input terminal T 1 , and commands the image signal correcting section  61  to project the corresponding image. The message saying “no image signal inputted” is displayed on the “standby” screen. 
     In step S 32 , the control section  66  receives operation signals from the operation receiving section  55  after the “source search button” of the operation section  53  is operated, and executes the “source search program” stored in the storage section  67 . The operations performed by the respective sections in the following respective steps are carried out under the “source search program”. The control section  66  stores the input terminal selected by the input selector  56  when search processing is required in the storage section  67  as the initial input terminal. 
     In step S 33 , the control section  66  commands the image signal correcting section  61  to generate image signals for producing the “source search” screen shown in  FIG. 4  and project the corresponding image. The message “none” indicating that no image signal is inputted from the input source “Computer 1” is displayed on the “search source” screen in  FIG. 4 . 
     In step S 34 , the control section  66  commands the input selector  56  to select the next input terminal of the input terminal currently selected by the input selector  56  in the selection order. The selection order circulates as: “input terminal T 1 ”, “input terminal T 2 ”, “input terminal T 3 ”, “input terminal T 4 ” and back to “input terminal T 1 ”. 
     In step S 35 , the control section  66  commands the judging section  57  to check the presence or absence of the image signals transmitted from the input source corresponding to the input terminal selected in step  834 . The control section  66  also commands the storage section  67  to store the information on the presence or absence of the image signals for each of the checked input sources. 
     In the respective steps, the control section  66  commands the image signal correcting section  61  to update the “source search” screen in accordance with the search conditions one after another, The “source search” screen shown in  FIG. 5  is a screen showing that the presence or absence of the image signals transmitted from the input source “Computer 2” corresponding to the input terminal T 2  is being checked. This screen displays the message saying “now detecting signal status”. 
     In step S 36 , the control section  66  checks whether image signals have been detected for all the input terminals T 1  through T 4 . When detection is completed for all the input terminals, the flow advances to step S 37 . When detection is not completed for any input terminal, the flow returns to step S 34 . 
     In step S 37 , the control section  66  commands the image signal correcting section  61  to generate image signals for producing the “source search” screen shown in  FIG. 15 , and project the corresponding image. The “source search” screen in  FIG. 15  includes a list indicating the presence or absence of inputted image signals for all the input sources. The “source search” screen displays the message saying “Please select input source manually”. 
     In step S 38 , the control section  66  checks whether the “source selection button” of the operation section  53  or the remote controller  54  has been operated within a predetermined time from the presence or absence of the operation signals transmitted from the operation receiving section  55 . When the operation signals for selecting any of the input sources are detected, the flow proceeds to step S 41 . When the operation signals for selecting the input source are not detected, the flow goes to step S 39 . 
     In step S 39 , the control section  66  having displayed the “source search” screen shown in  FIG. 15  in step S 37  checks whether a predetermined time has elapsed. When it is determined that the predetermined time has elapsed, the flow proceeds to step S 40 . When it is still before elapse of the predetermined time, the flow returns to step S 37  to continue the display of the “source search” screen. The predetermined time herein is approximately 10 seconds. 
     In step S 40 , the control section  66  commands the image signal correcting section  61  to close the “source search” screen. Then, the control section  66  reads out the input terminal corresponding to the input source from which the image signals have been detected first from the storage section  67 , and commands the input selector  56  to select this input terminal. In the “source search” screen shown in  FIG. 15 , the input terminal T 2  corresponding to the input source “Computer 2” from which image signals have been detected first is selected. As a result, the image produced by the image signals from the “Computer 2” shown in  FIG. 8  is projected. 
     When it is determined as a search result in step S 37  that no image signal is detected in any of the input sources as shown in  FIG. 7 , the control section  66  commands the image signal correcting section  61  to close the “source search” screen. Then, the control section  66  reads out the information on the initial input terminal from the storage section  67 , and commands the input selector  56  to select this input terminal. 
     The processes to be performed when it is determined that the processing for selecting any of the input sources has been executed in step S 38  are now discussed. 
     In step S 41 , the control section  66  commands the image signal correcting section  61  to close the “source search” screen, and commands the input selector  56  to select the input terminal corresponding to the input source selected in step S 38 . 
     The projector  100  can perform similar search processing even when it is determined that image signals have been inputted to the initial input terminal. The search processing executed when it is determined that image signals have been inputted to the initial input terminal is now explained focusing on the different points from the operation mentioned above only. 
     In step S 31 , the image shown in  FIG. 11  produced by the image signals from the input source “Computer 1” is displayed as the initial screen. 
     In step S 33 , the control section  66  commands the image signal correcting section  61  to generate image signals for producing the source search screen including the input source name corresponding to the initial input terminal and the message showing that image signals have been inputted, and project this image. 
     In step S 37 , the image of the image source “Computer 1” is displayed as the background of the “source search” screen. 
     Accordingly, the following advantages can be offered in this embodiment. 
     (1) When search processing is required through the operation section  53 , the control section  66  commands the input selector  56  to select the input terminals sequentially and commands the judging section  57  to check the presence or absence of inputted image signals for each of the selected input terminals. The control section  66  commands the image signal correcting section  61  to sequentially add the indication showing the presence or absence of image signals for each of the checked input terminals to the source search screen so as to check the presence or absence of the image signals for all the input terminals. Thus, the projector  100  checks the presence or absence of image signals for all the input terminals while adding the information on the presence or absence of image signals for each of the input terminals one after another, and displays a list showing the results on the source search screen. 
     Accordingly, the projector  100  can provide visual information on the checking status of the image signals to the user for each input source one after another, and efficiently notify the search results using the source search screen including the list which shows the presence or absence of the image signals for all the input terminals. Since the list on the source search screen showing the presence or absence of image signals for all the input sources allows the user to select the desired input source when image signals from the plural input sources are detected, the usability of the projector  100  is enhanced. 
     Therefore, the projector  100  can efficiently search for the input source which is outputting the image signals. When no image signal is inputted from any of the input sources, the projector  100  provides visual information on this fact to the user. 
     (2) When the processing for selecting any of the input sources is not executed through the operation section  53  within the predetermined time after the checking of the presence or absence of image signals is completed for all the input terminals, the control section  66  commands the image signal correcting section  61  to close the source search screen and commands the input selector  56  to select the input terminal from which image signals have been detected first. Thus, the projector  100  closes the source search screen and displays the image produced by the image signals from the input source corresponding to the input terminal from which the image signals have been detected first. 
     Accordingly, the projector  100  can efficiently search for the input source which is outputting the image signals, and automatically display the image produced by the image signals from this input source. 
     (3) Even in the case that image signals have been inputted to the initial input terminal, the projector  100  can execute search processing similar to the search processing in the case that no image signal is inputted to the initial input terminal and offer advantages similar to those provided in the case that no image signal is inputted thereto. 
     The scope of the invention is not limited to the embodiments described and depicted herein, but various modifications and improvements may be given to those. Modified examples within the scope of the invention are shown below. 
     MODIFIED EXAMPLE 1 
     This example is explained with reference to  FIG. 1 . The projector  100  in the above embodiments is a liquid crystal three-plate and projection type projector using the three liquid crystal light valves  52 R,  52 G and  52 B as light modulation elements, but the projector according to the invention is not limited to this type. 
     For example, the projector may include a single-plate-type liquid crystal light valve which has red, green and blue color filters regularly arranged in a grid pattern and each of which is capable of emitting full-color modulated light. The projector also may be a reflection-type liquid crystal display device or contain a tilt mirror device. 
     In these structures, advantages similar to those in the above embodiments and modified example can be offered. 
     MODIFIED EXAMPLE 2 
     This example is explained with reference to  FIG. 1 . The input source search support method according to the invention is employed in the front-type projector  100  in the above embodiments and modified example. However, this method may be used in a rear-type projection TV, a liquid crystal TV, a plasma TV, a CRT TV, a PC monitor, an organic EL display, and other various image display apparatus. 
     MODIFIED EXAMPLE 3 
     This example is explained with reference to  FIG. 1 . The input sources are the four input sources of “Computer 1”, “Computer 2”, “S-Video”, and “Video” in the above embodiments and the modified examples. However, a “component video” and a “digital video” may be added to those input sources, and input terminals, mini D-sub 15 pin terminals, and IEEE 1394 (Institute of Electrical and Electronic Engineers 1394) terminals corresponding to the respective input sources may be additionally equipped. 
     In structures using other input sources and input sources constituted by communication means such as the Internet, advantages similar to those in the above embodiments and modified examples can be offered.