Abstract:
A method for improving a symmetrical projection is provided. The projection system includes a light source, a light valve, and an integration rod. The method utilizes the light source to emit light beams that travel through the integration rod and obliquely project onto the light valve, and adjusting a cross section of the integration rod to offset image distortion existing in the projection system.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a projection method and, more particularly, to a projection method and systems for improving asymmetrical projection.  
           [0003]    2. Description of the Prior Art  
           [0004]    In recent years, data visualization has become an important issue in the information industry. The demand and importance for a projection display device capable of displaying data have rapidly increased. Therefore, manufacturers make an effort to provide a projection display device that produces high image quality.  
           [0005]    Please refer to FIG. 1, which is a schematic diagram of an optic projection system  20  according to the prior art. The optic projection system  20  is a single panel digital micro-mirror device (DMD) projection system. A light source  21  comprises a parabolic reflector  211 . Light beams  22 , generated by the light source  21  and reflected by the parabolic reflector  211 , pass through a converging lens  23  and then converge into a color wheel  24  that is formed by a series of red, green and blue filters for transforming the white light beams  22  into colored light beams  221 . After the light beams  22  pass through the color wheel  24  and are transformed into the colored light beams  221 , the colored light beams  221  enter an integration rod  25  to uniform the brightness of the colored light beams  221 , and then sequentially pass through a condenser lens  26 , a stop  27 , and a relay lens  28 , and finally converge into a prism illumination system  30  which is capable of reflecting the colored light beams  221  with a reflection surface  31  onto a light valve  10 , like a digital micro-mirror device (DMD).  
           [0006]    The light valve  10  is formed with a plurality of pixel lens (not shown) which are disposed in a matrix and capable of pivotably rotating within a range of +12 to −12 degrees. When the light valve  10  is in an ON state, the pixel lenses reflect an incident light beam onto a screen. When the light valve  10  is in an OFF state, the pixel lenses reflect an incident light beam onto a region outside of the screen. When the light valve  10  is in a FLAT state, the pixel lenses are disposed parallel to the substrate of the light valve  10 . The light valve  10  selectively reflects the colored light beams  221  through the prism illumination system  30  and further through a projection lens  32  and finally onto a screen  33 .  
           [0007]    Please refer to FIG. 2 and FIG. 3. If the converging lens  23 , the color wheel  24 , the integration rod  25 , the condenser lens  26 , the stop  27 , and the relay lens  28  are all perfectly symmetrical and assembled, a cross section of rectangular-shaped light beams  41  projected from the relay lens  28  is similar to the cross section of the integration rod  25 . As shown in FIG. 3, the length of a first diagonal line L 1  equals the length of a second diagonal line L 2 . That is, no image-distortion occurs. When the normal rectangular-shaped light beams  41  continue to travel into the prism illumination system  30 , the reflection surface  31  of the prism illumination system  30  reflects the rectangular-shaped light beams  41  onto the light valve  10  and forms a light spot  42  shown as dashed lines in FIG. 4. Referring to FIG. 4, which shows the light spot  42  obliquely projected from the reflection surface  31  onto the light valve  10  of the optic projection system  20  according to the prior art, because the light beams  41  are obliquely projected onto the light valve  10 , the rectangular-shaped light beams  41  are inevitably distorted and transformed into the light spot  42 , the first diagonal line L 1  and the second diagonal line L 2  of which being not equal (L 1 &gt;L 2 ). The distorted rectangular-shaped light beam  42  is indicated by dashed lines. Therefore, the light spot  42 , failing to completely cover the light valve  10 , disables the light valve  10  from completely reflecting the whole image onto the screen  33 . To overcome this drawback, the method adopted by the optic projection system  20  in the prior art is to enlarge the light spot  42  into an enlarged light spot  43  to cover the whole light valve  10 .  
           [0008]    Please refer to FIG. 5, which shows the enlarged light spot  43  projected on the light valve  10  of the optic projection system  20  according to the prior art. In contrast to the light spot  42 , although the light spot  43  indeed covers the whole light valve  10 , part of the light spot  43 , a light spot  431  shown as a hashed area in FIG. 5, still cannot be reflected onto the screen  33  by the light valve  10 , resulting in luminance loss of the optic projection system  20 .  
           [0009]    In summary, the optic projection system in the prior art has at least two drawbacks:  
           [0010]    1. Poor light uniformity due to the distortion of the light beams  42 ; and  
           [0011]    2. Low illumination efficiency due to the luminance loss resulting from the prolonged first diagonal line L 1 .  
         SUMMARY OF THE INVENTION  
         [0012]    One objective of the invention is to provide an integration rod to offset the distortion and to transform the asymmetrical light spot to a symmetrical light spot to increase the illumination efficiency and uniformity of the projection system.  
           [0013]    Other objective of the invention is to provide an integration rod to extend colored light beams to directions along a certain axis to form an oval-shaped light spot to overcome the drawback of the overlapping between the ON-state light beams and the FLAT-state light beams and to increase the contrast and the illumination efficiency.  
           [0014]    According to the invention, the projection system includes a light source, a light valve, and an integration rod. The method includes utilizing the light source to emit light beams that travel through the integration rod and obliquely project onto the light valve, and adjusting a cross section of the integration rod to offset image distortion existing in the projection system.  
           [0015]    It is an advantage of the invention that a projection system having a distorted cross-sectioned integration rod can transform an asymmetrical light spot to a symmetrical light spot.  
           [0016]    These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    37 CFR 1.84 (b) (2)  
         [0018]    The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s)will be provided by the Office upon request and payment of the necessary fee.  
         [0019]    [0019]FIG. 1 is a schematic diagram of an optic projection system according to the prior art.  
         [0020]    [0020]FIG. 2 shows a diagram of a cross section of the integration rod of the optic projection system shown in FIG. 1.  
         [0021]    [0021]FIG. 3 shows a diagram of a cross section of rectangular-shaped light beams projected from the relay lens.  
         [0022]    [0022]FIG. 4 shows a light spot obliquely projected from the reflection surface and onto the light valve of the optic projection system shown in FIG. 1.  
         [0023]    [0023]FIG. 5 shows an enlarged light spot projected on the light valve of the optic projection system shown in FIG. 1.  
         [0024]    [0024]FIG. 6 is a projection system according to the present invention.  
         [0025]    [0025]FIG. 7 shows a cross section of the integration rod of the projection display system shown in FIG. 6.  
         [0026]    [0026]FIG. 8A is a diagram of light distribution of the colored light beams projected onto the light valve of the optic projection system shown in FIG. 1.  
         [0027]    [0027]FIG. 8B is a diagram of light distribution of the colored light beams projected onto the light valve of the projection system shown in FIG. 6.  
         [0028]    [0028]FIG. 9A is a screen diagram of the optic projection system shown in FIG. 1.  
         [0029]    [0029]FIG. 9B is a screen diagram of the projection system shown in FIG. 6.  
         [0030]    [0030]FIG. 10A shows a light spot of colored light beams on the diaphragm according to the prior art.  
         [0031]    [0031]FIG. 10B shows a light spot of colored light beams on the diaphragm according to the present invention.  
         [0032]    [0032]FIG. 11 shows the light spot of ON-state light beams, OFF-state light beams, and FLAT-state light beams on the diaphragm according to the prior art and the present invention.  
         [0033]    [0033]FIG. 12 shows a table of experimental performance results of the projection systems respectively according to the prior art and the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0034]    Please refer to FIG. 6, which is a preferred embodiment of a projection system  50  according to the present invention. A light source  51  comprises an elliptical reflector  511  to reflect light beams  512  generated by the light source  51  and to converge the light beams  512  into a color-generating device  52 , such as a color wheel or a filter, that is formed by a series of red, green, and blue filters for sequentially filtering the light beams  512  and transforming the light beams  512  into colored light beams  513 . The colored light beams  513  enter an integration rod  53  to uniform the brightness of the colored light beams  513  and then sequentially pass through a condenser lens  54 , a stop  55 , a relay lens  56 , and finally converge onto a prism illumination system  58  capable of reflecting the colored light beams  513  with a reflection surface  581  onto a light valve  57 , for example a digital micro-mirror device (DMD). The light valve  57  is formed with a plurality of pixel lens, which is disposed in a matrix and capable of pivotably rotating within a range of +12 to −12 degrees, and selectively reflects the colored light beams  513  by means of ON-state or OFF-state. After being reflected by the light valve  57  and passing through the prism illumination system  58 , the colored light beams  513  enter a diaphragm  591  of a projection lens  59  and finally project onto a screen  592 .  
         [0035]    Please refer to FIG. 7, which shows a cross section of the integration rod  53  of the projection system  50  according to the present invention. The projection system  50  offsets the image distortion existing in the prior art optic projection system  20  with the integration rod  53 , which has a distorted cross section, to improve the asymmetrical light spot  42  of the prior art into a symmetrical light spot. The shape of the cross section of the integration rod  53  is determined by the image distortion formed by the oblique projection of the colored light beams  513 . That is, the integration rod  53 , whose parallelogram-shaped cross section has two diagonal lines L 3  and L 4  respectively extending in two directions respectively opposite to the prolonged directions of the first diagonal line L 1  and of the second diagonal line L 2 , deforms the colored light beams  513  before the colored light beams  513  reach the light valve  57  to generate the symmetrical light spot. In such away, the asymmetrical light spot  42  originated from the colored light beams  513  reflected by the reflection surface  581  and obliquely projecting onto the light valve  57  will be offset by the asymmetrical cross section of the integration rod  53  in advance and therefore form the symmetrical light spot.  
         [0036]    Of course, a different cross section of the integration rod  53  can be applied to offset the distortion to any extent. The integration rod  53  can be hollow or solid. Additionally, certain sizes of colored light beams  513  can be integrated by the integration rod  53  having specific characteristics.  
         [0037]    Please refer to FIG. 8A and FIG. 8B. FIG. 8A is a diagram of light distribution of the colored light beams  221  projected onto the light valve  10  of the optic projection system  20  according to the prior art. FIG. 8B is a diagram of light distribution of the colored light beams  513  projected onto the light valve  57  of the projection system  50  according to the present invention. As shown in FIG. 8A, a bottom-left corner and a top-right corner of the light distribution diagram are both prolonged (the first diagonal line L 1  is longer than the second diagonal line L 2 , referring to FIG. 5) due to the obliquely projecting colored light beams  211  of the optic projection system  20 . On the other hand, because the colored light beams  513  have been offset by the integration rod  53  having the distorted cross section before the colored light beams  513  projects onto the light valve  57 , the light distribution diagram shown in FIG. 8B has been improved from the asymmetrical light spot  42  to a symmetrical rectangular-shaped light spot. It can be readily seen that the prolonged corners of the light distribution diagram shown in FIG. 8A have been improved.  
         [0038]    Therefore, parts of the light spot out of the light valve  57  are smaller than that of the prior art, so the loss of the symmetrical light spot generated by the projection system  50  is less than that of the asymmetrical light spot  42  generated by the optic projection system  20  and the brightness of projected images of the projection system  50  is greater than that of the projected images of the prior art optic projection system  20 .  
         [0039]    Please refer to FIG. 9A and FIG. 9B. FIG. 9A is a screen diagram of the optic projection system  20  according to the prior art. FIG. 9B is a screen diagram of the projection system  50  according to the present invention. In FIG. 9A and FIG. 9B, red dots represent high light intensity and green dots represent low light intensity. It can be seen that the high light intensity region occupied by the red dots in FIG. 9B is larger and more even than that in FIG. 9A. So, the projection system  50  according to the present invention is superior to the prior art optic projection system  20 . An x-axis screen curve shown on the bottom side of FIG. 9B is flatter than an x-axis screen curve shown on the bottom side of FIG. 9A and a y-axis screen curve shown on the right side of FIG. 9B is flatter than a y-axis screen curve shown on the right side of FIG. 9A, further supporting the above conclusion.  
         [0040]    Please refer to FIG. 10A and FIG. 10B. FIG. 10A shows a light spot of colored light beams projected onto the diaphragm of the projection lens  32  when the integration rod  25  has a rectangular-shaped cross section (the lengths of two diagonal lines of a rectangular are equal) according to the prior art. FIG. 10B shows a light spot of colored light beams projected onto the diaphragm  591  of the projection lens  59  when the integration rod  53  has a parallelogram-shaped cross section (the lengths of two diagonal lines of a parallelogram are not equal) according to the present invention. The shape of the light spot shown in FIG. 10A due to the rectangular-shaped integration rod  25  is circular. However, the integration rod  53  having parallelogram-shaped cross section extends the light spot shown in FIG. 10A to directions along a certain axis, say a y-axis, transforming the circular light contrast diagram to an elliptical one.  
         [0041]    Please refer to FIG. 11, which shows the light spot of ON-state light beams, OFF-state light beams, and FLAT-state light beams on the diaphragm according to the prior art and to the present invention respectively. ON-state light beams  61 , FLAT-state light beams  62 , and OFF-state light beams  63  according to the prior art are respectively represented by solid lines, and ON-state light beams  64 , FLAT-state light beams  65 , and OFF-state light beams  66  according to the present invention are respectively represented by dashed lines. Theoretically, only the ON-state light beams will enter the diaphragm of the projection lens, so the larger the radius of the diaphragm of the projection lens and the larger the ON-state light beams  64 , the higher brightness of projected images. However, when the ON-state light beams  61  continue getting larger and form another ON-state light beam  67 , the OFF-state light beams  63  and the FLAT-state light beams  62  will accordingly get larger and then respectively form another FLAT-state light beams  68  and another OFF-state light beams  69 . The FLAT-state light beams  68  overlap the ON-state light beams  67  and thus reduce the contrast of the projected images. Consequently, that the light beams  61 ,  62 , and  63  are adjacent but not overlapping one another is a tradeoff between the brightness and the contrast of the projected images.  
         [0042]    In contrast to the prior art optic projection system  20 , the present invention can provide a projection system  50  for offsetting distortion in projected images with the integration rod  53  having the parallelogram-shaped cross section to transform the asymmetrical light spot  42  into a symmetrical light spot. Additionally, the ON, FLAT, and OFF-state light beams  61 ,  62  and  63  can be extended in directions along the y-axis and respectively form the ON, FLAT, and OFF-state light beams  64 ,  65 , and  66 , whose size are larger than that of the ON, FLAT, and OFF-state light beams  61 ,  62  and  63 , to increase the intensity of light beams and to prevent the ON, FLAT, and OFF-state light beams  64 ,  65 , and  66  from overlapping one another.  
         [0043]    Please refer to FIG. 12, which is a table of experimental results from the projection systems of the prior art and the present invention respectively. The data of a DMD efficiency, an overfill, and an ON-state projection output respectively corresponding to the prior art, the present invention, and the improvement ratio are listed in FIG. 12. For example, the improvement ratio for the DMD efficiency, the overfill, and the ON-state projection output are respectively 5.8%, 37.0% and 6.3%.  
         [0044]    The light valve  57  of the embodiment of the projection system  50  is a reflective DMD valve. The light valve  57  can be also a penetrative liquid crystal display or a reflective liquid crystal on silicon (LCOS) display panel.  
         [0045]    Following the detailed description of the present invention above, those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.