Patent Abstract:
An image projector apparatus includes a cooler having a variable capability to cool a light source, a commanding section which gives a command to terminate a lighting operation of the light source, a selecting section responsive to the command given by the projection light processor for selecting a cooling capability of the cooler, and a control section for causing the cooler to cool the light source with the cooling capability selected by the selecting section.

Full Description:
This application is a Divisional Application of U.S. application Ser. No. 12/141,142, filed Jun. 18, 2008, now U.S. Pat. No. 7,866,826, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to image projectors and more particularly to such projector using especially a light source such as a high-pressure mercury lamp, and a method and program for controlling the operation of the projector. 
     2. Description of the Related Art 
     An image projector is proposed which cools its light source to a predetermined temperature after terminating an image projection event, as disclosed, for example, in Japanese Published Unexamined Patent Application 2005-156750. This projector is constituted so as to increase the rotational speed of a cooling fan thereof automatically after terminating its image projection event, thereby cooling the lamp quickly in as short time as possible. 
     In an actual environment where the projector is set up, participants in the image projection event can hold a discussion or briefing about the projected image after the image projection event is terminated. If in such a case the projector is cooled quickly to move the projector away out of the environment, great noise would be produced, thereby hampering the discussion or briefing. 
     It is therefore an object of the present invention to provide an image projector in which after terminating its image projection event the light source is cooled in a manner appropriate for the environment of the projector such that noise produced by the projector is reduced low enough not to hamper the discussion or briefing. It is another object of the present invention to provide a method and program for controlling the cooling operation of the light source of the projector so as not to produce great noise after terminating its image projection event. 
     SUMMARY OF THE INVENTION 
     In order to achieve the above object, the present invention provides an image projector apparatus comprising: a light source; a projector subunit that produces an optical image based on an image signal and light from the light source and projects the optical image; a cooler having a variable capability to cool the light source after the light source is turned off; commanding means for giving a command to terminate the lightening operation of the light source; selecting means responsive to the command given by the commanding means for selecting a cooling capability of the cooler; and control means for causing the cooler to cool the light source with the cooling capability selected by the selecting means. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the present invention and, together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the present invention in which: 
         FIG. 1  is a block diagram of a circuit configuration of an image projector according to a first embodiment of the present invention; 
         FIG. 2  is an illustration of the composition of a key switch unit of the projector; 
         FIG. 3  is a flowchart of operation of the projector to be performed when its power supply is turned off; 
         FIG. 4  is a flowchart of operation of the projector to be performed when its power supply is turned off in a second embodiment; and 
         FIG. 5  is a flowchart of operation of the projector to be performed when its power supply is turned off in a third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     An image projector  10  of a DLP™ (Digital Light Processing) type according to the first embodiment of the present invention will be described with respect to the accompanying drawings. 
     Referring to  FIG. 1 , there is shown the functional configuration of an electronic circuit of the projector  10  according to the first embodiment. In  FIG. 1 , an input/output connector  11  comprises, for example, video input terminals of a pin/jack (RCA) type, RGB input terminals and USB terminals. 
     Various standardized image signals inputted from the input/output connector  11  to the projector  1  are converted by an image converter  13  to image signals of a predetermined format through an input/output interface (I/F)  12  and a system bus SB. These image signals are then forwarded to a projection driver  14 . In this case, a mode image for an OSD (On-Screen Display) and symbols such as a pointer are forwarded carried on the image signal to the projection driver  14 , as required. 
     The projection driver  14  loads and stores the received image on and in a video RAM  15 , and then produces a video signal from the image stored in the RAM  15 . For displaying purposes, the projection driver  14  drives a spatial optical modulator (SOM) such as a micro-mirror device  16  in a high-speed time-divisional manner based on a product of a frame rate of the video signal, for example, of 60 frames/sec, the number of color components and a display grey scale number. 
     A light source comprising, for example, a very high-pressure mercury lamp  18 , disposed within a reflector  17  emits high-brightness white light, which is then colored sequentially in three (for example, red, green and blue) primary colors in a time-divisional manner through a color wheel  19 , changed to a light flux of uniform brightness distribution by an integrator  20 , wholly reflected by a mirror  21  and then applied to the micro-mirror device  16 . 
     The reflected light from the micro-mirror  16  forms an optical image, which is then projected onto a screen (not shown) through an optical lens unit  22  which has an image enlarging function. The optical lens unit  22  has a variable focal position and a variable zoom position (or projection angle of view). More particularly, a focus lens and a zoom lens (both not shown) of the optical lens unit  22  are controlled so as to be movable along an optical axis by a stepping motor (M)  23 . 
     A cooling fan  24  which cools the light source  18  is driven by a motor (M)  25  which is driven at a selected one of “high”, “medium” and “low” rotational speeds. The color wheel  19  is driven by a motor (M)  26 . 
     A projection light processor  27  controls the driving of the stepping motor  23 , the lighting-up operation of the light source  18 , and the driving of the motor  26  for the color wheel  19  and of the motor  25  for the cooling fun  24 . The projection light processor  27  also receives temperature data from a temperature sensor  28  which senses the temperature of the light source  18  attached to the reflector  17 . 
     A CPU  29  controls all those circuits of the projector  10 , using a non-volatile program memory  30  which has stored an operation program and various definite data and a main memory including a RAM  31 . The CPU  29  is connected through the system bus SB to a key switch unit  32 , an indicator  33  and a voice processor  34 . 
       FIG. 2  illustrates the composition of the key switch unit  32  disposed, for example, on an upper surface of a housing of the projector  10 . The key switch unit  32  comprises a power supply key  32   a , a quick power off key  32   b , a mode key  32   c , a cancel (C) key  32   d , focus keys  32   e ,  32   f , zoom keys  32   g ,  32   h , cursor keys “↑”, “↓”, “←” and “→”  32   i - 32   l , and an enter key  32   m.    
     When operated, the power supply key  32   a  gives a command to turn on/off the power supply. When operated, the quick power off key  32   b  gives a command to turn off the power supply, thereby causing quick cooling of the light source  18  after terminating the image projection. When operated sequentially a predetermined number of times, the mode key  32   c  sequentially gives a like number of different commands to set corresponding operation modes in a cycle. When operated, the cancel (C) key  32   d  gives a restore command to cancel a current operational state and restore the previous operational state. When operated, the focus keys  32   e  and  32   f  give commands to move the focus lens in one and the other direction, respectively, along the optical axis. When operated, the zoom keys  32   g  and  32   h  give commands to increase and decrease, respectively, the angle of view of the zoom lens. When operated, one of the cursor keys  32   i - 32   l  gives a command to move an item selected at that time in a corresponding direction. When operated, the enter key  32   m  gives a command to fix an item selected at that time. 
     When any one of these keys of the key switch unit  32  is depressed by the user, a corresponding operation signal is forwarded to the CPU  29 , which in turn performs a corresponding control operation. 
     The indicator  33  is composed, for example, of a plurality of LEDs to display various operation states of the projector and an abnormal temperature of the light source  18  in corresponding lightening colors and corresponding flashing patterns. 
     The voice processor  34  comprises a sound circuit such as a PCM sound source which converts voice data given at a time of image projection to analog data, which is then amplified and emanated as a voice or peep sound by a speaker  35  attached, for example, to a back of the projector  10  casing. 
     Operation of the embodiment will be described.  FIG. 3  is a flowchart of operation of the projector to be performed when a command to turn off the power supply of the projector is given by the power supply key  32   a  or by the quick power off key  32  of the key switch unit  32 . This operation is performed by the CPU  29  mainly via the projection light processor  27  based on the operation program stored in the program memory  30 . 
     At the beginning, the lightening operation of the light source  18  is stopped and the light source  18  is turned off (step A 01 ). Then whether the quick cooling for the light source  18  is required is determined depending on whether the turn-off command for the lamp  18  is given by operation of the quick power off key  32   b  (step A 02 ). 
     If it is determined that the quick cooling for the light source  18  is required (step A 02 ), the motor  25  is set to the highest “high” one of the “high”, “medium” and “low” rotational speeds, thereby cooling the lamp  18  quickly (step A 03 ). 
     Then it is determined based on a sensed temperature of the light source  18  from the temperature sensor  28  whether the light source  18  has been cooled below a predetermined threshold temperature Tth or to such an extent that the quick cooling can be terminated, which is awaited (step A 04 ). That determination is repeatedly performed. 
     If it is determined that the turn-off command for the power supply is given by the usual power key  32   a  and not by the quick power off key  32   b  in step A 02 , the motor  25  is set to the “medium” rotational speed, thereby performing the usual (non-quick or silent) cooling for the light source  18  (step A 05 ). 
     Then it is determined based on a sensed temperature of the light source  18  from the temperature sensor  28  in the usual cooled state whether the light source  18  has been cooled below the predetermined threshold temperature Tth or to such an extent that the usual (non-quick or silent) cooling can be terminated, which is awaited (step A 06 ). That determination is repeatedly performed. 
     When it is determined that the light source  18  has been cooled below the predetermined threshold Tth in step A 03  or A 05 , then it is determined that the quick or usual cooling has been terminated and the cooling operation of the motor  25  or the cooling fan  24  is stopped (step A 07 ). This stops all the operations of the elements of the projector  10  including a display of the indicator  33  and operation of the voice processor  34  involving sound emanation from the speaker  35  (step A 08 ). Thus, the operation of the CPU  29  shown in  FIG. 3  is terminated. 
     As described above, according to the present embodiment, after the image projection of the image projector is terminated the light source is cooled in a cooling capability appropriate for an environment of the projector. 
     In addition, in the above embodiment one of the quick and usual cooling operations of the light source  18  is selected depending on whether a corresponding one of the quick power off and usual power supply keys  32   b  and  32   a  of the key switch unit  32  is depressed by the user. Thus, it is ensured that the user&#39;s intention is reflected on his or her operation, thereby avoiding erroneous setting up of the quick cooling, which would produce great noise to hamper questions and answers or discussion about the images projected and presented on the screen. 
     In the above embodiment, it is illustrated that one of the quick and usual cooling operations is selected depending on a corresponding one of the quick power off and usual power supply keys  32   b  and  32   a  being depressed. Alternatively, arrangement may be such that the quick cooling operation is selected depending on a manner in which a particular key is operated, for example, when the power supply key  32   a  is depressed continuously over 2 seconds, even when no dedicated key such as the quick power off key  32   b  is especially provided in the key switch unit  32 . 
     In the above embodiment, it is illustrated that one of the quick and usual cooling operations is selected depending on a corresponding one of the power off and usual power supply keys  32   b  and  32   a  being depressed by the user after the image projection is terminated. Alternatively, only cases in which the light source  18  should be cooled in the usual (non-quick or silent) manner may be set before the start of the image projection without providing the quick power off key  32   b  in the key switch unit  32  so that when one of the cases is met after the image projection and the power supply is turned off by the power supply key  32   a , the light source  18  is cooled in the usual manner. By such arrangement, the usual cooling operation appropriate for the environment of the projector is performed automatically by the same power supply key  32   a  that is used to turn on the power supply after the image projection event is terminated. 
     Second Embodiment 
     A second embodiment of the image projector  10  of a DLP™ type will be described with respect to the drawings. The electronic circuits of this image projector are the same in configuration and function as those of the  FIG. 1  first embodiment excluding that no key such as the quick power off key  32   b  is provided in the key switch unit  32  of  FIG. 2 . Thus, like parts are denoted by like reference numerals in Figures of the drawings and further description thereof will be omitted. 
     Operation of the embodiment will be described.  FIG. 4  is a flowchart of operation of the projector to be performed when a command to turn off the power supply of the projector is given by the power supply key  32   a  of the key switch unit  32 . The CPU  29  causes the projection light processor  27  to perform all this operation based on the operation program stored in the program memory  30 . 
     At the beginning, the light source  18  is turned off (step B 01 ). Then at this time it is determined whether an image signal is still being received via the input/output connector  11  (step B 02 ). 
     When it is determined that no image signal is being inputted, it is regarded that the power supply for the external device which is expected to be connected to the input/output connector  11  is already turned off at this time and that there is a high probability that the image projector  10  will be immediately withdrawn. Thus, the motor  25  is set to the highest “high” one of the “high”, “medium” and “low” rotational speeds, thereby cooling the light source  18  quickly (step B 03 ). 
     Then it is determined based on a sensed temperature of the light source  18  from the temperature sensor  28  whether the light source  18  has been cooled below a predetermined threshold temperature Tth or to such an extent that the quick cooling can be terminated, which is awaited (step B 04 ). That determination is repeatedly performed. 
     If the image signal is still being received by the image projector  10  via the input/output connector  11  in step B 02  and the power supply for the external device connected to the input/output connector  11  is on at this time, it is regarded that there is no possibility that the image projector  10  will be immediately withdrawn. Thus, the motor  25  is set to the “medium” rotational speed, thereby cooling the light source  18  in a usual (non-quick or silent) manner. (step B 05 ). 
     Then it is determined based on a sensed temperature of the light source  18  from the temperature sensor  28  in the usual cooled state whether the light source  18  has been cooled below the predetermined threshold temperature Tth or to such an extent that the usual cooling can be terminated, which is awaited (step B 06 ). That determination is repeatedly performed. 
     When it is determined that the light source  18  has been cooled below the predetermined threshold Tth in step B 03  or B 05 , it is regarded that the quick or usual cooling has been terminated and then the cooling operation of the motor  25  or the cooling fan  24  is stopped (step B 07 ). This stops all the operations of the elements of the projector  10  including a display of the indicator  33  and operation of the voice processor  34  involving sound emanation from the speaker  35  (step B 08 ). Thus, the operation of the CPU  29  shown in  FIG. 4  is terminated. 
     As described above, according to this embodiment only when no image signal is being received, this situation is sensed automatically and then the quick cooling of the light source  18  is performed. As long as the image signal continues to be received by the image projector  18 , no quick cooling operation is performed. Thus, it is ensured that a situation is avoided in which questions and answers and discussions which may be had about the presented images would be hampered by noises due to the quick cooling after the power supply is turned off. 
     Third Embodiment 
     A third embodiment of the image projector of a DLP™ type will be described with respect to the drawings. The electronic circuits of this image projector also are the same in configuration and function as those of the  FIG. 1  first embodiment excluding that no key such as the quick power off key  32   b  is provided in the key switch unit  32  of  FIG. 2 . Thus, like parts are denoted by like reference numerals in Figures of the drawings and further description thereof will be omitted. 
     Operation of the embodiment will be described.  FIG. 5  is a flowchart of operation of the projector to be performed when a command to turn off the power supply of the projector is given by the power supply key  32   a  or the quick power off key  32  of the key switch unit  32 . This operation is performed by the CPU  29  mainly via the projection light processor  27  based on the operation program stored in the program memory  30 . 
     At the beginning, the lightening operation of the light source  18  is stopped and the light source  18  is turned off (step C 01 ). Then at this time it is determined whether there is an external device connected to the input/output connector  11  (step C 02 ). 
     This determination is performed based on whether the input terminals of the input/output connector  11  are open, or the external device side impedance as viewed from the input terminals of the input/output connector  11  is infinite. When it is determined that no external device is connected to the input/output connector  11 , then the motor  25  is set to the highest “high” rotational speed, thereby cooling the light source  18  quickly (step C 03 ). 
     Then it is determined based on a sensed temperature of the light source  18  from the temperature sensor  28  whether the light source  18  has been cooled below a predetermined threshold temperature Tth or to such an extent that the quick cooling can be terminated, which is awaited (step C 04 ). That determination is repeatedly performed. 
     When it is determined in step C 02  that the external device is still connected to the input/output connector  11 , then the motor  25  is set to the “medium” rotational speed, thereby cooling the light source  18  in a usual (non-quick or silent) manner. (step C 05 ). 
     Then it is determined based on a sensed temperature of the light source  18  from the temperature sensor  28  in the usual cooled state whether the light source  18  has been cooled below the predetermined threshold temperature Tth or to such an extent that the usual cooling operation can be terminated, which is awaited (step C 06 ). That determination is repeatedly performed. 
     When it is determined that the light source lamp  18  has been cooled below the predetermined threshold Tth in step C 03  or C 05 , it is regarded that the quick or usual cooling has been terminated and then the cooling operation of the motor  25  or the cooling fan  24  is stopped (step C 07 ). This stops all the operations of the elements of the projector  10  including a display of the indicator  33  and operation of the voice processor  34  involving sound emanation from the speaker  35  (step C 08 ). Thus, the operation of the CPU  29  shown in  FIG. 5  is terminated. 
     As described above, according to this embodiment, when the power supply is turned off, whether the quick cooling operation of the light source  18  should be performed is determined based on whether the external device is not connected to the input/output connector  11 . Thus, when the external device is completely disconnected from the connector  11 , this situation is determined automatically and the quick cooling operation is started. As long as the external device is still connected to the input/output connector  11 , no quick cooling operation is performed. Thus, it is ensured that a situation is avoided in which questions and answers and discussions about the presented images would be hampered by noises due to the quick cooling. 
     In this embodiment, whether the input terminals of the connector are open is illustrated as determined based on whether the external device side impedance as viewed from the input terminals of the input/output connector  11  is infinite. Alternatively, any well-known appropriate electric or mechanical detector may be used to determine whether an external device is connected to the input/output connector  11 . 
     While in any of the first-third embodiments the termination of the quick or usual cooling operation is illustrated as determined depending on whether the light source  18  has been below a predetermined threshold temperature Tth, arrangement may be such that a timer (not shown) provided in the CPU  29  counts a predetermined time set for the quick or usual cooling operation to determine the termination of that cooling operation without using the temperature sensor  28  which senses the temperature of the light source  18 . 
     While in any of the above first-third embodiments the present invention is illustrated as applied to the image projectors  10  of a DLP™, the present invention is not limited to such projectors, but applicable to any image projectors such as ones of a liquid crystal display type in which images are projected onto a transparent color liquid display panel as a display, monochromatic OHPs (Overhead Projectors) and slide projectors, in which the light source is required to be cooled after the image projection is terminated. 
     Various modifications and changes may be made thereunto without departing from the broad spirit and scope of this invention. The above-described embodiments are intended to illustrate the present invention, not to limit the scope of the present invention. The scope of the present invention is shown by the attached claims rather than the embodiments. Various modifications made within the meaning of an equivalent of the claims of the invention and within the claims are to be regarded to be in the scope of the present invention. 
     This application is based on Japanese Patent Application No. 2007-162611 filed on Jun. 20, 2007 and including specification, claims, drawings and summary. The disclosure of the above Japanese patent application is incorporated herein by reference in its entirety.

Technology Classification (CPC): 6