Patent Publication Number: US-2021176439-A1

Title: Projector, projector control method, and projector control program

Description:
TECHNICAL FIELD 
     The present invention relates to a projector, a method of controlling a projector, and a program for controlling a projector. 
     BACKGROUND ART 
     In the above technical field, PTL 1 discloses a technique to reduce speckle noise by directly moving a screen, which is one of speckle noise sources. 
     CITATION LIST 
     Non-Patent Literature 
     
         
         NPL 1: Muneharu KUWARA and six others, “Reducing Speckle in Laser Displays with Moving Screen System”, The Journal of The Institute of Image Information and Television Engineers Vol. 65 No. 2, pp. 224-228 (2011) 65_224 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, the technique described in NPL 1 causes a screen as a physically large device to be subjected to direct moving and thus causes the apparatus for speckle noise reduction to increase in size, failing to reduce speckle noise with a simple configuration. 
     Solution to Problem 
     It is an object of the present invention to provide a technique to solve the above problems. 
     To achieve the above object, a projector according to the present invention includes: 
     a light source configured to generate light; 
     an optical system configured to reflect the light from the light source and guide the light to a two-dimensional scanning mirror; 
     the two-dimensional scanning mirror configured to project the light guided by the optical system on a screen; and 
     a driving mechanism configured to drive the optical system at a predetermined period and a predetermined amplitude. 
     To achieve the above object, a method of controlling a projector according to the present invention, the projector including 
     a light source configured to generate light, 
     an optical system configured to reflect the light from the light source and guide the light to a two-dimensional scanning mirror, 
     the two-dimensional scanning mirror configured to project the light guided by the optical system on a screen, and 
     a driving mechanism configured to drive the optical system at a predetermined period and a predetermined amplitude, the method comprising the steps of: 
     generating light from the light source; 
     projecting the generated light on the screen; and 
     driving the optical system. 
     To achieve the above object, a program for controlling a projector according to the present invention, the projector including 
     a light source configured to generate light, 
     an optical system configured to reflect the light from the light source and guide the light to a two-dimensional scanning mirror, 
     the two-dimensional scanning mirror configured to project the light guided by the optical system on a screen, and 
     a driving mechanism configured to drive the optical system at a predetermined period and a predetermined amplitude, the program causing a computer to execute a method of controlling the projector, the method including the steps of: 
     generating light from the light source; 
     projecting the generated light on the screen; and 
     driving the optical system. 
     Advantageous Effects of Invention 
     The present invention allows reduction in speckle noise with a simple configuration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating configuration of a projector according to a first embodiment of the present invention. 
         FIG. 2A  is a diagram illustrating speckle noise generation by a projector in a prerequisite technique for a projector according to a second embodiment of the present invention. 
         FIG. 2B  is a diagram illustrating an overview of reduction in speckle noise by the projector according to the second embodiment of the present invention. 
         FIG. 3A  is a diagram illustrating configuration of the projector according to the second embodiment of the present invention. 
         FIG. 3B  is a partial enlarged view illustrating configuration of a drive section of the projector according to the second embodiment of the present invention. 
         FIG. 3C  is a partial enlarged view illustrating configuration of another drive section of the projector according to the second embodiment of the present invention. 
         FIG. 4  is a diagram illustrating a driving pattern by the drive section of the projector according to the second embodiment of the present invention. 
         FIG. 5  is a flow chart illustrating a processing procedure by the projector according to the second embodiment of the present invention. 
         FIG. 6  is a diagram illustrating configuration of a projector according to a third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present disclosure are exemplarily described below with reference to the drawings. It should be noted that the configuration, the numerical values, the process flows, the functional components, and the like described in the embodiments below are merely examples and may be freely modified or altered. The technical scope of the present invention is not intended to be limited to the following description. 
     First Embodiment 
     As the first embodiment of the present invention, a projector  100  is described with reference to  FIG. 1 . The projector  100  is a device configured to project an image on a screen. 
     As illustrated in  FIG. 1 , the projector  100  includes a light source  101 , an optical system  102 , a two-dimensional scanning mirror  103 , and a drive section  104 . 
     The light source  101  generates light. The optical system  102  reflects the light from the light source  101  and guides the light to the two-dimensional scanning mirror  103 . The two-dimensional scanning mirror  103  projects the light guided by the optical system  102  on a screen  110 . The drive section  104  drives the optical system  102  at a predetermined period and a predetermined amplitude. 
     The present embodiment allows reduction in speckle noise with a simple configuration. 
     Second Embodiment 
     With reference to  FIGS. 2A through 4 , a projector according to the second embodiment of the present invention is then described.  FIG. 2A  is a diagram illustrating speckle noise generation by a projector in a prerequisite technique for the projector according to the present embodiment. When laser light  211  from a laser light source  201  is projected on a screen  202 , as illustrated in an enlarged view ( 221 ) of the area where the laser light  211  is projected, a surface  227  of the screen  202  is uneven and the laser light  211  is thus scattered on the surface  227  of the screen  202 . When a person looks at an image or the like projected on the screen  202 , the scattered laser light  211  is coherent with each other. Accordingly, when the coherent light passes through the crystalline lens  241  of the human eyeball  204  and forms an image on the retina  242 , the image appears to flicker. This is speckle noise  203  as a tiny speckle pattern. 
       FIG. 2B  is a diagram illustrating an overview of reduction in speckle noise by the projector according to the present embodiment. 
     In the projector according to the prerequisite technique illustrated in  FIG. 2A , an image or the like is constantly drawn in the same position and thus the scattered light becomes coherent. To prevent this, the position where the laser light  211  from the laser light source  201  is projected on the screen  202  is slightly shifted (moved). This allows variation in interference patterns of the scattered light. Generation of the plurality of interference patterns then causes averaging of the interference patterns, and as a result, allows reduction in the speckle noise  203 . In this context, a movement (amount of shifting) of the projected position is a displacement as small as approximately one pixel. 
     With reference to  FIG. 2B , a first frame  221  represents a reference position  250  (X=0, Y=0) for drawing. In a second frame  222 , the reference position  250  for drawing is shifted by one pixel in a −Y direction for drawing (X=0, Y=−1). In a third frame  223 , the reference position  250  for drawing is shifted by one pixel in a +X direction for drawing (X=1, Y=−1). In a fourth frame  224 , the reference position  250  for drawing is shifted by one pixel in a +Y direction for drawing (X=1, Y=0). In a fifth frame  225 , the reference position  250  for drawing is shifted by one pixel in a −X direction for drawing (X=0, Y=0). In a sixth frame  226 , the four frames from the second frame  222  to the fifth frame  225  are averaged to allow reduction (decrease) in speckle noise. Note that one frame is assumed to represent 1/60 of a second. 
       FIG. 3A  is a diagram illustrating configuration of a projector  300  according to the present embodiment. The projector  300  has a light source  301 , a light beam adjustment section  302 , a mirror  303 , a mirror  304 , a two-dimensional scanning mirror  305 , a drive section  306 , and a drive section  307 . The projector  300  is configured to project an image on a screen  310 . 
     The light source  301  is, for example, an RGB LD (RGB laser diode). The light source  301  further has a B-LD  311  (blue), a G-LD  312  (green), and R-LD  313  (red). Light beams generated by the light source  301  are then incident on the light beam adjustment section  302 . The light beam adjustment section  302  includes collimators  321 ,  322 , and  323  and mirrors  324 ,  325 , and  326 . The mirrors  324 ,  325 , and  326  are, for example, dichroic mirrors. The light beam adjustment section  302  is an optical device that converts the laser light generated from the light source  301  to parallel light and synthesize RGB laser light. 
     The light beams incident on the light beam adjustment section  302  become parallel light in the collimators  321 ,  322 , and  323  and then incident on the mirrors  324 ,  325 , and  326 . The light beams reflected on the mirrors  324 ,  325 , and  326  are synthesized and exit the light beam adjustment section  302  to be incident on the mirror  303  as a light beam  311 . The light beam  311  incident on the mirror  303  is reflected on the mirror  303  and then incident on the mirror  304 . The light incident on the mirror  304  is reflected on the mirror  304  and then incident on the two-dimensional scanning mirror  305 . The light incident on the two-dimensional scanning mirror  305  is projected on the screen  310  from the two-dimensional scanning mirror  305 . 
     The mirror  303  is a mirror to reflect the light beam  311  from the light source  301 . The mirror  303  reflects the light beam  311  to the mirror  304 . The mirror  303  is, but not limited to, a dichroic mirror, for example. 
     The mirror  304  is a mirror to reflect the light beam  311  reflected on the mirror  303 . The mirror  304  reflects the light beam  311  to the two-dimensional scanning mirror  305 . The mirror  304  is, but not limited to, a fold mirror, for example. At least one of the mirrors  303  and  304  may be a dichroic mirror or a fold mirror, or both may be dichroic mirrors or fold mirrors. 
     The two-dimensional scanning mirror  305  is a mirror to project the light beam  311  reflected on the mirror  304  on the screen  310 . The two-dimensional scanning mirror  305  is, for example, a two-dimensional MEMS (micro electro mechanical system) mirror. The two-dimensional scanning mirror  305  is a driving mirror driven based on a control signal input from outside and is a device that vibrates to reflect laser light by varying the angle in the horizontal direction (X direction) and the vertical direction (Y direction). Instead of using the two-dimensional scanning mirror  305 , the two-dimensional scanning mirror may be configured using, for example, two one-dimensional scanning mirrors. 
     The mirror  303  is provided with the drive section  306 , and the mirror  304  is provided with the drive section  307 . The drive sections  306  and  307  drive the mirrors  303  and  304  to vibrate them. When the mirrors  303  and  304  are driven (vibrated) by the drive sections  306  and  307 , the position where the light beam  311  generated from the light source  301  is projected varies and no image is depicted in the same position on the screen  310 . The amounts of driving by the drive sections  306  and  307  are, for example, amounts to the extent of not being visible to human eyes and similarly the periods of driving by the drive sections  306  and  307  are also periods to the extent of not being detected by human eyes while the amounts and the periods are not limited to above. 
     The drive section  306  drives (vibrates) the mirror  303  to shift the reference position  250  for drawing (drawing area) of one frame only by one pixel. The driving direction is, for example, the X direction while it may be the Y direction. The drive section  307  similarly drives the mirror  304  to shift the reference position  250  for drawing (drawing area) of one frame only by one pixel. The driving direction is, for example, the Y direction while it may be the X direction. The driving directions by the drive sections  306  and  307  may be in the same direction, directions different from each other, or directions orthogonal to each other while they are not limited to these directions. The drive sections  306  and  307  may be provided in either one of the mirrors  303  and  304 . The number of the mirrors  303  and  304  is not limited to two and may be three or more. If the number of mirrors is three or more, such a drive section may be provided in part or all mirrors. 
       FIG. 3B  is a partial enlarged view illustrating configuration of the drive section  307  of the projector  300  according to the present embodiment. The drive section  307  has a piezoelectric element  371 , a fulcrum member  372 , and a base member  373 . The piezoelectric element  371  and the fulcrum member  372  are mounted on the base member  373 . The drive section  307  drives (vibrates) the mirror  304 , for example, in the X direction. 
     When a voltage is applied to the piezoelectric element  371 , the piezoelectric element  371  expands or contracts in the direction of an arrow  374  to move the mirror  304  about the fulcrum member  372  as a pivot. Since the mirror  304  thus moves, the light beam  311  reflected on the mirror  304  also moves. The amount of driving (moving, vibrating) the mirror  304  is an amount to shift the reference position  250  for drawing of one frame only by one pixel. The drive section  307  drives the mirror  304 , for example, in the X direction. 
       FIG. 3C  is a partial enlarged view illustrating configuration of the other drive section  306  of the projector  300  according to the present embodiment. The drive section  306  has a piezoelectric element  361  and a fulcrum member  362 . The drive section  306  also has a base member, not shown. The piezoelectric element  361  and the fulcrum member  362  are mounted on the base member. The drive section  306  drives the mirror  303 , for example, in the Y direction. 
     When a voltage is applied to the piezoelectric element  361 , the piezoelectric element  361  expands or contracts to move the mirror  303  about the fulcrum member  362  as a pivot. Since the mirror  303  thus moves, the light beam  311  reflected on the mirror  303  also moves. The amount of driving (moving, vibrating) the mirror  303  is an amount to shift the reference position  250  for drawing of one frame only by one pixel. The drive section  306  drives the mirror  303 , for example, in the Y direction. 
       FIG. 4  is a diagram illustrating a driving pattern by the drive sections  306  and  307  of the projector  300  according to the present embodiment. As indicated by  401 , after drawing for one frame, the position of the light beam  311  is shifted to offset the entire screen in the X direction and the Y direction by one pixel. The amount (magnitude) of driving is not limited to the magnitude of one pixel and may be a predetermined amplitude (magnitude). 
     In addition,  402  indicates timing, that is, the timing (predetermined period) to drive the mirrors  303  and  304  by the drive sections  306  and  307 , and the drive sections  306  and  307  drive (shift) them, for example, for each frame. It should be noted that the timing for driving is not limited to this. The reference numeral  403  indicates driving in the X direction and driving in the Y direction. A neutral position indicates a state where the mirrors  303  and  304  are not driven. 
       FIG. 5  is a flow chart illustrating a processing procedure by the projector  300  according to the present embodiment. At step S 501 , the projector  300  causes the light beam  311  to be generated from the light source  301 . At step S 503 , the projector  300  causes the generated light beam  311  to be projected on the screen  310 . At step S 505 , the projector  300  causes the mirrors  303  and  304  to be driven. At step S 507 , the projector  300  adjusts the driving of the mirrors  303  and  304 . The adjustment is made by varying the period and/or the amplitude based on, for example, a feedback image of the image projected on the screen  310  or the like while the adjustment is not limited to this method. At step S 509 , the projector  300  determines whether the adjustment of driving is finished. When determined that the adjustment is not finished (NO at step S 509 ), the projector  300  returns to step S 507  and continues the adjustment. When determined that the adjustment is finished (YES at step S 509 ), the projector  300  is finished with the process. 
     Since the optical devices on an optical path are driven, the present embodiment allows reduction in speckle noise without increasing optical devices. In addition, since the mechanism to drive the optical devices on an optical path is provided, the present embodiment allows reduction in speckle noise with a simple configuration. 
     Third Embodiment 
     With reference to  FIG. 6 , an information processing unit according to the third embodiment of the present invention is then described.  FIG. 6  is a diagram illustrating configuration of a projector  600  according to the present embodiment. The projector  600  according to the present embodiment differ from the second embodiment in having two one-dimensional scanning mirrors. Other configuration and operation are same as those in the second embodiment, and the same reference signs are given to the same configuration and operation to omit the detailed description. Note that, in  FIG. 6 , the light source is omitted from the illustration. 
     The projector  600  has a one-dimensional scanning mirror  601  and a one-dimensional scanning mirror  602 . The one-dimensional scanning mirror  601  scans the light beam  311  reflected on the mirror  304  in the X direction. The light beam  311  scanned in the X direction by the one-dimensional scanning mirror  601  is then scanned in the Y direction by the one-dimensional scanning mirror  602 . The light beam  311  scanned in the Y direction by the one-dimensional scanning mirror  602  is projected on the screen  310 . The scanning directions by the one-dimensional scanning mirrors  601  and  602  may be vice versa. 
     Since the optical devices on an optical path are driven, the present embodiment allows reduction in speckle noise without increasing optical devices. In addition, since a mechanism to drive the optical devices on an optical path is provided, the present embodiment allows reduction in speckle noise with a simple configuration. Moreover, since the two one-dimensional scanning mirrors are used, the present embodiment improves the degree of freedom in disposing optical systems. 
     Other Embodiments 
     While the present invention has been described with reference to the above embodiments, the present invention is not limited to these embodiments. Various modifications understood by those skilled in the art may be made to the present invention in the configuration and details withing the scope of the present invention. In addition, the scope of the present invention also includes all systems and devices that are made by any combination of separate characteristics included in the respective embodiments. 
     Still in addition, the present invention may be applied to a system configured from a plurality of devices or may be applied to a single device. Moreover, the present invention is also applicable to the case of supplying an information processing program to achieve the functions in embodiments directly or remotely to the system or the device. Accordingly, the scope of the present invention includes a program installed in a computer to achieve the functions of the present invention by the computer, a medium having the program stored therein, and a WWW (world wide web) server to download the program. In particular, the scope of the present invention includes at least a non-transitory computer readable medium having a program causing a computer to execute the processing steps included in the above embodiments. 
     This application claims priority based upon the prior Japanese Patent Application No. 2017-161700, filed in Japan Patent Office on Aug. 25, 2017, the entire disclosure of which is incorporated herein by reference.