Abstract:
An outer suspension type lens shielding mask for a projection apparatus including a sheet body and holding element, in which a rectangular hole is opened in the sheet body, and the sheet body is combined with the holding element to be fixed on a projection apparatus. Another outer suspension type lens shielding mask includes a base plate, in which a rectangular hole is opened in the middle part thereof, and upper and lower adjustable plates are installed behind the base plate. An open rectangular notch is respectively disposed at the middle parts of the upper and the lower adjustable plates. An adjustment mechanism includes a plurality of connecting elements connected to the base plate and the upper and the lower adjustable plates for adjusting the relative positions thereof, to avoid bad shadows yielded outside of a picture due to light diffraction and improve the quality of visual amusement.

Description:
This application is a Divisional of co-pending application Ser. No. 11/453,137, filed on Jun. 15, 2006, which is a divisional of application Ser. No, 10/952,836, filed on Sep. 30, 2004, and for which priority is claimed under 35 U.S.C § 120; and this application claims priority of Application No. 093114660 filed in Taiwan, R.O.C. on May 24, 2004 under 35 U.S.C. § 119; the entire contents of all are hereby incorporated by reference 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an outer suspension type lens shielding mask for a projection apparatus, and more particularly to a lens shielding mask mounted outside of a projection lens and designed for matching all kinds of aspect ratios of projection pictures to reduce the leaking of the diffusion light outside of the picture. 
   2. Description of Related Art 
   Diffusion light is yielded in a general projector when light is experienced a several reflection and projection after it is emitted from an optical engine. And, a contrast is lowered after the diffusion light is leaked out through the projection lens so that the quality of a dark scene is influenced when the projector is used on such as a home video picture playing. 
   Therefore, for lowering the darkness of the dark scenes of a motion picture in a projector to enhance the performance of contrast, an optical grating is always added in an optical engine system. But, not only needs it to add elements in entire optical engine or change a design but also helps it nothing for a currently existed projector model if the optical grating is added in the optical engine. Therefore, substantially, it is necessary to add an optical grating device without changing the internal structure of a current projector and increasing production cost 
   SUMMARY OF THE INVENTION 
   The main object of the present invention is to provide an outer suspension type lens shielding mask for a projection apparatus, capable of being mounted outside of a projection lens and being designed to a static optical grating or adjustable optical grating matching with every kind of different aspect ratio of projection picture. 
   Another object of the present invention is to provide an outer suspension type lens shielding mask for a projection apparatus, capable of reducing production cost by elevating the picture quality from the outside of the projection apparatus without changing the design of an optical engine. 
   Still another object of the present invention is to provide an outer suspension type lens shielding mask for a projection apparatus, capable of avoiding bad shadow outside of a picture caused from diffraction light so as to improve the quality of sight amusement. 
   For attaining to the objects mentioned above, an outer suspension type lens shielding mask for a projection apparatus according to the present invention comprises a sheet body and a holding element, in which a rectangular hole is opened in the sheet body and the sheet body is combined with the holding element together for being fixed on a projection apparatus. Another outer suspension type lens shielding mask according to the present invention comprises a base plate, in which a rectangular hole is opened in the middle part thereof, upper and lower adjustable plates, installed behind the base plate and an open rectangular notch is respectively disposed at the middle parts of the upper and the lower adjustable plates, and an adjustment mechanism, consisting a plurality of connecting elements connected to the base plate and the upper and the lower adjustable plates for adjusting the relative positions of the upper and the lower adjustable plates on the base plate. 
   Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the present invention, and in which: 
       FIG. 1  is a prospective view, showing a lens shielding mask with a fixed type optical grating of a preferred embodiment according to the present invention; 
       FIGS. 2A and 2B  are schematic views, showing a motion for mounting a lens shielding mask with a fixed type optical grating onto a projection apparatus; 
       FIG. 3  is an explosive view, showing a lens shielding mask with an adjustable optical grating of another preferred embodiment according to the present invention; 
       FIG. 4  is a cross sectional view, showing an assembled lens shielding mask with an adjustable optical grating of another embodiment according to the present invention; 
       FIG. 5  is a schematic view, showing a motion for mounting a lens shielding mask with a fixed type optical grating onto a projection apparatus; 
       FIG. 6  is an explosive view, showing a lens shielding mask with an adjustable optical grating of still another preferred embodiment according to the present invention; and 
       FIG. 7  is a cross sectional view, showing an assembled lens shielding mask with an adjustable optical grating of still another embodiment according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Please refer to  FIG. 1 .  FIG. 1  is a prospective view showing a lens shielding mask with a fixed type optical grating of a preferred embodiment according to the present invention. A lens shielding mask  10  with a static optical grating mainly comprises a circular disc type sheet body  101  made from an opaque material or a flat plate coated with an opaque material on the surface thereof and used for shielding diffraction light projected from a lens of a projector; the diameter thereof is approximately equal to the inner diameter of a outer frame in front of the lens of the projector as  FIGS. 2A and 2B  show. A rectangular hole  102  whose shape and location depend on the type of the lens is opened in the sheet body  101 . Because the aspect of a general picture is 16:9, although the ratio of the length and the width of the rectangular hole is always fabricated to be 16:9, but it can also be fabricated to be 4:3 or even 2.35:1 for accommodating it to a different aspect ratio. The hole  102  is deviated from the center of the sheet body  101  according to the present invention. A plurality of clamping ears  103  are disposed around the circumference of the sheet body  101 . These clamping ears can be formed with the sheet body  101  into one body or combined with the sheet body  101  by means of adhesion or welding. The numbers and the locations of the clamping ears  103  are not particularly defined, only that a user can mount the lens filtering mask  10  conveniently on the outer frame of the lens of the projector is enough. In addition, a material such as fiber can be stuck on the circumference of the circular sheet body  101  for being taken as a clamping element to allow the sheet body to be engaged tightly in the outer frame of the lens. 
   The motion for mounting the lens filtering mask with a fixed type optical grating mentioned above can be seen in  FIGS. 2A and 2B . A user only uses his fingers to clip the clamping ears  103  on the sheet body  101  and aims the mask at and then mounts it on the outer flame  3  outside of the lens  2  of the projector  1 . Thereafter, the fingers are again used to clip the lens filtering mask  10  to rotate the sheet body  101  until the rectangular hole is aligned with a formation zone of image after the lens shielding mask  10  is mounted on the outer frame  3 . 
   Next, please refer to  FIGS. 3 and 4 .  FIGS. 3 and 4  are explosive and cross sectional views respectively showing parts and after-assembly structure of a lens shielding mask with an adjustable optical grating of another preferred embodiment according to the present invention. A lens filtering mask  20  with an adjustable optical grating comprises a base plate  201  and upper and lower adjusting plates  202  and  203 . A sleeve  2011  is disposed at each corner of the base plate  201  and a rectangular hole  204  whose shape and location is disposed depending oil the aspect of a lens is opened in the base plate  201 ; according to the present invention, the hole is symmetrical to a center line in the direction of the width of the base plate (i.e. line A–A′ in  FIG. 3 ), and the center point of the hole  204  is also disposed at a location beyond the center line in the direction of the length of the base plate (i.e. line B–B′ in  FIG. 3 ) according to the design of the location of a picture projected from a general projector. Furthermore, open type rectangular notches  2022  and  2032  are respectively disposed at the centers of the lower edge of the upper adjusting plate  202  and the upper edge of the lower adjustable plate  203 , the sizes of these two open type rectangular notches  2022  and  2032  are same and corresponding to each other. And, sleeves  2021  and  2031  are respectively disposed at both of the left and the right sides of the rectangular notches  2022  and  2032  of the upper and the lower adjustable plates  202  and  203 . The sizes of the center holes of the sleeves  2011 ,  2021  and  2031  respectively disposed at the left and the right sides of the base plate  201  and the upper and the lower adjustable plates are same; the center lines of the center holes at the left and the light sides are respectively aligned into one line and the two lines are parallel after assembly as  FIG. 4  shows. In addition, screws exist in the center holes of only one pair of the sleeve  2021  at the right side of the upper adjustable plate  202  and the sleeve  2031  at the left side of the lower adjustable plate  203 , and the sleeve  2021  at the left side of the upper adjustable plate  202  and the sleeve  2031  at the fight side of the lower adjustable plate  203  and can be extended out of them to screw thread portions  2023  and  2033  to strengthen the moving stability when the upper and the lower adjustable plates driven by a bolt  205 . For convenience in explanation, the former structure is adopted in  FIGS. 3 and 4 , i.e. the screw threads are only disposed in the center holes of the sleeve  2021  at the right side of the upper adjustable plate  202  and the sleeve  2031  at the left side of the lower adjustable plate  203 . And, no screw thread exists in the center holes of all the sleeves on the base plate  201 . 
   Please refer to  FIG. 4 . When the base  201  and the upper and the lower adjustable plate  202  and  203  want to be assembled to a lens filtering mask, the upper and the lower adjustable plates  202  and  203  are first placed between the upper and the lower sleeves  2011  on the base plate  201 . Next, two bolts  205  are respectively inserted into the sleeves  2011 ,  2021 ,  2031  and  2011  disposed into one straight line at the two sides of the base plate and the upper and the lower adjustable plates  202  and  203 . Fixing washers  207  are then engaged with end parts  2052  of the bolts  205  to prevent the assembling elements from falling down after the bolts  205  are passed through the lowermost end of the sleeve  2011 , for conforming to a different aspect of projection picture, only rotate a rotating button on the bolt  205 , and the left sleeve  2021  on the upper adjustable plate  202  engaged with the bolt  205  or/and right sleeve  2031  on the lower adjustable  203  can then be driven to move the upper or/and lower adjustable plate/plates upwards or downward to change the size of a close rectangular hole formed by the open type rectangular notches  2022  and  2032 . Generally speaking, the ratio of the length and the width of the adjusted close rectangular hole can be an aspect ratio of a general projection picture such as 4:3, 16:9, 2.35:1 or anything else. 
   Please refer to  FIG. 5 ,  FIG. 5  is a schematic view showing a lens shielding mask is mounted on a projector according to the present invention. When the lens shielding mask  20  wants to be mounted on the projector  1 , holding sheets on the base plate  201  are respectively clamped at the upper and the lower rims of the projector close to the projection lens  2  and the ratio of the length and the width of the close rectangular hole is adjusted according to the steps mentioned above to conform to the aspect ratio of a projection picture. 
   Please refer to  FIGS. 6 and 7 .  FIGS. 6 and 7  are explosive and cross sectional views respectively showing parts and after-assembly structure of a lens shielding mask with an adjustable optical grating of still another preferred embodiment according to the present invention. A lens shielding mask  30  with an adjustable optical grating comprises a base plate  301  and upper and lower adjustable plates  302  and  303 . A sleeve  3011  is disposed on every corner of the base plate  301 ; no screw thread is existed in any one of these four sleeves. A rectangular hole  304  is further opened in the base plate  301 ; the disposition location is identical to the rectangular hole  204  in the last preferred embodiment mentioned above so that the detail thereof is omitted here. Furthermore, in the base plate  301 , two guide notches  307  are disposed at the lateral center line of the rectangular hole  304  and adjacent to the two flank sides of the base plate. Two open type rectangular notches  3022  and  3032 , which are corresponding to each other and have a same size, are respectively disposed in the middles of the lower end of the upper adjustable plate  302  and the upper end of the lower adjustable plate  303 ; the width of the open type rectangular notches are almost equal to the one of the rectangular hole in the base plate. And, a lever plate connecting seat  308  is respectively disposed at each one of the two sides of the open type rectangular notches of the upper and the lower adjustable plates  302  and  303 ; an accepting hole  3081  is opened in each connecting seat  308 . Both of sleeves  3021  and  3031  are respectively disposed at the left and the right sides of the upper and the lower adjustable plates  302  and  303 . The sizes of the center holes of the sleeves at the same sides are equal, and screw threads are disposed in the center holes of the sleeves at the same side; the threads are disposed in the center holes of the sleeves at the left sides of the plates according to the present invention only for explaining the detail easily. 
   The assembling of the lens filtering mask  30  according to the present invention can be seen in  FIG. 7 . First, a buckling pin  3091  disposed on a lever plate shown in  FIG. 6  is buckled into the accepting hole  3092  disposed in a corresponding and the end of the buckling pin  3091  is engaged into the guide notch  307 , and then another buckling pin  3091  on each lever plate is engaged into the accepting hole  3081  in the each connecting seat  308  on the upper and the lower adjustable plate  302  and  303 . Each connecting point after being connected including the one between the lever plates  309  and the one between the lever plate  309  and connecting seat  308  is pivotally connected. Thereafter, the whole set of after-combination upper and lower adjustable plates  302  and  303  and the lever plate  309  are mounted between the upper and the lower sleeves  3011  on the base plate  301 . After the center holes of the sleeves  3011 ,  3021 ,  3031  and  3011  on the left and right sides of the base plate  30  and the upper and the lower adjustable plates  302  and  303  are aligned, a bolt with both of left and right screw threads respectively disposed on the upper and the lower parts thereof and a straight shaft shown in  FIG. 6  are respectively inserted into the left and the right sides of sleeve arrays. Fixing washers are used to engage respectively with both ends of the bolt  305  and the straight shaft  306  to prevent all the assembling elements from dropping after the bolt  305  and the straight shaft  306  are passed through the lowermost end of the sleeve  3011  the upper and the lower adjustable plates  302  and  303  can be closed and opened synchronically to adjust the size of the close opening formed by the open type rectangular notches  3022  and  3032  to conform to the size of the projection picture after the bolt with left and right screw threads respectively disposed on the upper and the lower parts thereof is engaged with the sleeves  3021  and  3031  in which the threads in the center holes of them are reverse to each other respectively disposed on the left sides of the upper and the lower adjustable plates. The coordination of the lever plates  309  and guide notches  307  and the coordination of the straight shaft  306  and the sleeves on the right side are operated to guide the upper and the lower adjustable plates  302  and  303  to move up and down smoothly. 
   Furthermore, the thread of the center holes of the sleeves at the left side can also be extended to the outsides of the sleeves to increase the driven stability of the upper and the lower adjustable plates, it is the same situation as described in the preferred embodiment of the present invention mentioned above. 
   Besides, the holding element used in the preferred embodiment mentioned above can also be used in this preferred embodiment for mounting convenience. The detail for mounting the mask on a projector is also omitted here because it is not different from the situation mentioned in the last preferred embodiment. 
   It is noted that the outer suspension type lens shielding mask for a projection apparatus described above is the preferred embodiments of the present invention for the purpose of illustration only, and are not intended as a definition of the limits and scope of the invention disclosed. Any modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of the present invention