Abstract:
The present invention is a projector having a photosensing means for detecting light entering the optical system from outside the optical system, wherein the photosensing means is capable of detecting only the light reflected from within a predetermined area on the screen. According to one aspect, the projector of the present invention includes a linear CCD as a photosensing means resulting in a long, thin area on a screen being detectable by the photosensing means.

Description:
This application is based on Japanese Patent Application No. HEI 10-81963, the content of which is hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a projector for projecting an image on a screen. In one aspect, the present invention relates to a projector capable of detecting light, emitted from outside the projector, at a predetermined position on a screen. 
     BACKGROUND OF THE INVENTION 
     A projector provided with charge-coupled devices (CCD) within an optical system has been proposed. When a position is indicated on a screen using a laser pointer during the projection of an image on the screen, the laser light is reflected by the screen, travels in a direction opposite to that of the projected light, and enters the optical system of the projector. In such projectors, the CCD detects the laser light so that the indicated position on the screen can be determined. 
     For example, a window area, having items such as screen frame forward, frame back, etc., can be displayed along with an internet page or an image photographed with a digital camera. When a desired item is specified by the laser pointer, the specified position on the screen is detected by the projector, and a corresponding frame forward or frame back operation is performed. Further, not only can detecting a specified position trigger an operation, it is also possible to fetch an image corresponding to an area specified by the laser pointer. 
     When using an area CCD as a photosensing means in a conventional projector, the detection area of the reflected light extends over the entire screen, and extensive data processing is required for detection when an area CCD is used. Furthermore, an area CCD is expensive an adds an unnecessary cost to the device. 
     The laser pointers conventionally used for indicating a position on a screen illuminate the screen with the laser light. Since laser light is harmful when it enters the human eye, extreme care must be taken by anyone using a laser pointer so that the laser light does not stray off the screen inadvertently. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a projector capable of detecting only the light reflected from within a predetermined area on a screen. 
     Another object of the present invention is to provide a projector capable of specifying a position without using laser light and detecting the specified position. 
     According to one aspect, the present invention attains these objects by providing a projector having a photosensing means for detecting light entering the optical system from outside the optical system, wherein the photosensing means is capable of detecting only the light reflected from within a predetermined area on the screen. 
     According to another aspect, the projector of the present invention includes a linear CCD as a photosensing means resulting in a long, thin area on a screen being detectable by the photosensing means. 
     According to a further aspect, the projector of the present invention projects an image on a screen, and has a pointing image display means for displaying a pointing image on a screen which specifies a position within the image, photosensing means for detecting the specified position, and spectral means for separating the image light received from the pointing image display means into spectral components so as to direct the spectral components to the photosensing means. 
     These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings, which illustrate specific embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following description, like parts are designated by like reference numbers throughout the several drawings. 
     FIG. 1 is a schematic view of a projector of a first embodiment of the present invention; 
     FIG. 2 is a view of an image projected by the projector of the first embodiment of the present invention; 
     FIG. 3 is a view of another example of a window area according to the present invention; 
     FIG. 4A is a pictorial view of a laser pointer, which has been extended, and FIG. 4B is a pictorial view of a laser pointer, which has been retracted; 
     FIG. 5 is a schematic view of a projector of a second embodiment of the present invention; and 
     FIG. 6A is a schematic view of another embodiment of the projector of the present invention, and FIG. 6B is a view of an image projected by the projector of FIG.  6 A. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments of the present invention are described hereinafter with reference to the accompanying drawings. FIG. 1 shows the construction of a first embodiment of the projector of the present invention. In the drawings, like parts and constructions are designated by like reference numbers, and duplicate descriptions are omitted. In the projector  1 , a light L 1  emitted from a light source  2  is modulated by a liquid crystal panel  3 , transmitted through a projection lens  4 , and projected onto a screen  10 . 
     The laser light L 2  emitted from a laser pointer  20  illuminates a position A on the screen  10  to specify an area. The laser light L 2  is reflected by the screen  10 , and enters the optical system of the projector  1 . The entered laser light L 2  is polarized by a polarization beam splitter  5 , and passes through a condenser lens  6  to enter a linear CCD  7 . Then, the laser light L 2 , which illuminated the position A on the screen  10 , is detected by a sensor  8 . 
     The linear CCD  7  is provided as a photosensing means in the projector  1  of the present embodiment. The linear CCD  7  detects the light reflected from within the area B on the screen  10 . 
     FIG. 2 shows an image projected by the projector  1 . This drawing shows the projection of an image photographed by a digital camera and shows the image of a window area  11  displayed in the upper left corner of the screen in combination with the photographic image. Items numbered  12  through  17  are displayed within the window area  11 , and include various operations listed from the top, including “next”  12 , “back”  13 , “last”  14 , “first”  15 , “auto play”  16 , and “stop”  17 . The area B of the window area  11  is the detectable area of the linear CCD  7 . 
     When the laser pointer  20  illuminates the item “next”  12  in the window  11 , the light reflected from item  12  enters the optical system of the projector  1 , and is detected by the linear CCD  7 . Then, the position illuminated by the laser light L 2  is determined as a position corresponding to the item “next”  12  by the sensor  8  and a command is outputted to change the projection image on the screen  10  to the next frame. This output command is received by an LCD drive controller  9  which controls the liquid crystal panel  3  to display the next frame image on the screen  10 . 
     Since the area specified for illumination by the laser light L 2  (i.e., items  12  through  17  of window  11 ) is determined beforehand, the image layout can be set such that this area forms a line-like area on the screen, and the light reflected by this area can be detected by linear CCD  7 . 
     Unlike conventional projectors, the use of an expensive area CCD is unnecessary, thereby allowing an inexpensive projector to the produced. Furthermore, because the area to be illuminated by the laser light L 2  is a long, thin line-like area corresponding to the linear CCD  7 , this line-like area can be arranged along the lateral edge of the image so as to not obstruct other areas of the image. 
     The form of the window area  11  is not limited to the form described in FIG.  2 . Another example of the window area  11  is shown in FIG. 3, wherein items  12  through  17  in window  11  are text items describing the operations including “next”  12 , “back”  13 , “last”  14 , “first”  15 , “auto play”  16 , and “stop”  17 . In this instance, area B alone corresponds to the photosensing area of the linear CCD  7 . 
     Window  11  may be projected at a position adjacent to the projected image, and need not be combined with the projected image as in the previously described embodiment. 
     Furthermore, in general, the illumination shape of the laser pointer  20  may be adjusted from a point to a line. When the position illuminated by laser light is detected by linear CCD  7  as in the present embodiment, a line-like illumination shape of the light of laser pointer  20  can be more readily detected by linear CCD  7  than a spot-like illumination since the photosensing area is a long, thin line-like area. 
     An example of the laser pointer  20  having a laser illumination shape, which is adjustable from a point to a line, is described below. As shown in FIGS. 4A and 4B, the laser pointer  20  comprises a plurality of rods  21  of different thicknesses. 
     When the grip  22  is held and the light emitting tip  23  is pulled from the retracted state, each rod  21  slides out in extension. A light source and a collimator lens for collimating the light emitted form the light source are built into the light emitting unit  23 , and laser light is emitted from an emission window (not illustrated) in the tip of the light emitting unit  23 . A rotary switch  24  is provided on the end of the grip section  22 . 
     When the rotary switch  24  is rotated, the light source can be switchably turned ON and OFF. The light emitting unit  23  and the rotary switch  24  of the grip section  22  are electrically connected through the interior of each rod  21 , and this electrical connection is maintained even when the rods  21  slide in extension. The light source is switched ON/OFF by operating the rotary switch  24 . The power source may be, for example, built into the grip section  22 , or power may be supplied externally. 
     The distance between the light source and the collimator lens changes and the illumination shape of the emitted laser light can be switched between point-like and line-like by switching the rotary switch  24 . Changing the distance between the light source and the collimator lens may be accomplished by moving the light source in the optical axis direction, or moving the collimator lens in the optical axis direction. These movements may be accomplished electrically or mechanically. 
     An operation unit for switching the light source ON/OFF and switching the illumination shape of the light may be provided at the tip of the laser pointer  20 . In this instance, the internal construction may be simplified so that the relative positions of the operation unit and the light source do not change even when the laser pointer  20  is extended. 
     With regard to the aforesaid laser pointer  20 , not only can laser light be emitted to specify an area on the screen, the tip (light emitting unit  23 ) may make direct contact with the screen to indicate an area by extending the pointer  20 . For example, when using the projector for a presentation at a conference and the like, an area may be specified using the laser light, or the laser pointer  20  may be used to directly indicate an area, thereby improving the effectiveness of the presentation. 
     A second embodiment of the present invention is described below with reference to FIG.  5 . The light L 1 , emitted by the light source  2 , is modulated by the liquid crystal panel  3  and transmitted through a polarization beam splitter  5 , formed of a film having 90% transmittance, and the projection lens  4 , so as to be projected onto the screen  10 . Illumination light L 3 , emitted from an LED  32 , enters the polarization beam splitter  5  from a different direction than the light L 1 , which is emitted by the light source  2 . 
     Part of the split light L 3   a  is polarized by the polarization beam splitter  5  so as to advance in the same direction as the light L 1  and be projected onto the screen  10 . This projected image forms a pointing image for specifying position A on the screen  10 . Another part of the split light L 3   b  is transmitted through the polarization beam splitter  5  and condenser lens  6 , and enters the linear CCD  7 . In this way, the sensor unit  8  can detect the illumination position A of the light L 3   a  on the screen  10 . 
     The illumination position A of the light L 3   a  is movable across the entire surface of the screen  10  by the operation unit  33 . That is, when a user operates the operation unit  33 , the LED drive controller  34  moves the LED  32  along a plane perpendicular to the optical axis in accordance with the operation of the operation unit  33 . The operation unit  33  may not only be simply operated by a user, it may also be operated, for example, by a joystick or the like which performs the operation via a lever. 
     The projector of the second embodiment is capable of detecting the illumination position A of the LED  32  on the screen  10  similar to the first embodiment. Since an area on the screen  10  can be specified by the light L 3 , there is no chance of exposure to a human eye to the illumination light. Furthermore, there is no chance of injury to a human eye since laser light is not used. 
     The photosensing means  7  comprises an area CCD in the second embodiment since the LED  32  moves along a plane perpendicular to the optical axis. However, the movement of the LED  32  is not limited to a straight line perpendicular to the optical axis and, therefore, the photosensing means  7  may comprise a linear CCD insofar as there is a determined area for projecting the pointing image for executing frame advancement and the like on the screen  10 , as in the first embodiment. 
     Next, another embodiment relating to a rear projection type projector is described with reference to FIG.  6 . The rear projector  40  projects an image from behind the screen  10 . A projector  41  is provided within a body  40   a , and the screen  10  is disposed in front of the body  40   a . This projector  41  differs from the projectors of the first and second embodiments in that it is only provided with an optical system for projecting an image. 
     A window  11  is formed within the predetermined edge area around the periphery of an image projected on the screen  10 , and the normal image is displayed in the center of the screen  10 . The items  12  through  17  are displayed in this window  11 , and these items  12  through  17  are identical to the items in the first embodiment shown in FIG.  2 . 
     When the laser light L 2  emitted by the laser pointer  20  (not shown) illuminates the items  12  through  17  in the window  11  from the front of the screen  10 , the brightness of the illumination position on the screen  10  changes. The image on the back side of the window  11  is reflected by a reflecting mirror  5 , provided behind the screen  10 , and this reflected light is projected through the condenser lens  6  onto the linear CCD  7 . The sensing unit  8  detects the illumination position A of the laser light L 2  on the screen  10 . In this instance, a linear CCD can be used as the CCD  7  because the items  12  through  17  of window  11  are provided on the peripheral edge of the screen  10 . 
     A linear CCD  7  may be used as the photosensing means because the area of illumination by the laser light L 2  is limited beforehand as in the first embodiment. 
     The present invention has been described by way of examples of detecting a specified position on a screen as a trigger for operations such as next frame and previous frame of the screen image in the aforesaid embodiments and the embodiment of the rear projector. It is to be understood, however, that the application of data of the detected specification position is not limited, and it is possible, for example, to retrieve the image of the specified position for output to an external device. 
     Although the present invention has been described with reference to a presently preferred embodiment, it will be appreciated by those skilled in the art that various modifications, alternatives, variations, etc., may be made without departing from the spirit and scope of the invention as defined in the appended claims.