Abstract:
An optical engine for an image projector comprises a light source, a taper rod, at least one light condenser, a prism module, a Digital Micromirror Device (DMD) and a projection lens set. One end of the taper rod is adjacent to the light source. Light generated by the light source is guided by the taper rod following a light path. The taper rod has increasing sizes of cross-sections along the light path, so as to decrease the dispersion angle of light, make the light more uniform, and increase the brightness of light. The prism module includes a first prism having a right triangle cross-section and a second prism having a wedge cross-section. The prism module receives the light from the condenser, passes the light toward the DMD, receives the light reflected by the DMD, and then passes the reflected light toward the projection lens set. The projection lens set projects the light on an external projection plane.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention is related to an optical engine. In particular, this invention is related to an optical engine located in an image projector comprising a light source, at least one light condenser, a prism module, and a projection lens set.  
         [0003]     2. Description of the Prior Art  
         [0004]     The quality of the image is highly related to an internal optical engine for an image projector. To get a better quality of image, the lightness, homogeneity and effectiveness of the light source should be considered into the design of the optical engine. Besides, it is of paramount importance that the light travels through the lenses and prisms should not be deflected so the image gained would not be in disagreement with the real one. No less important is the dimness of the light that will let image ends in vagueness and in low contrast. To emphasize the homogeneity of the light, massive optical lenses, polarized lenses and spectroscopes are used in a conventional optical engine. However, the lightness and effectiveness would be given in. So, in the conventional optical engine, higher power and lightness of a light source are used to get an ideal outcome. This is one of the main reasons that results in a higher energy consumption and massiveness of the optical engine.  
       SUMMARY OF INVENTION  
       [0005]     It is therefore one of the objectives of the claimed invention to provide an optical engine whose light source is homogeneous, has a higher effectiveness, lesser lenses and prisms, higher image quality, less energy consumption and comparatively small in size.  
         [0006]     It is therefore one of the objectives of the claimed invention to provide an optical engine that comprises a light source model in which there is a taper rod. The cross-section (which is perpendicular to the light axis) of the taper rod increases gradually along the same direction as light travels. In this way, light rays will scatter less and a homogeneous and lighter light is achieved.  
         [0007]     It is therefore one of the objectives of the claimed invention to provide an optical engine that comprises a set of prisms. This set is comprised of a first prism that is nearer to the converging lens and a second one that is farther away from the converging lens. The first prism is wedged shaped. It is manifested in cone shape along the cross-sectional surface of the traveled light source. The second prism is manifested in right triangle along the cross-sectional surface of the traveled light source. The first prism leans against the surface drawn from an edge of the right triangle along the cross-sectional surface formed by the second prism. Controlling and fine-tuning of the light&#39;s refraction angle and direction is through turning the first prism and the second prism&#39;s relative position.  
         [0008]     It is therefore one of the objectives of the claimed invention to provide the above-mentioned image projector.  
         [0009]     In accordance with one aspect of the present invention, an optical engine is provided, which comprises: a light source, a taper rod, at least one light condenser, a prism module, a Digital Micromirror Device (DMD) And a projection lens set. One end of the taper rod is adjacent to the light source. Light generated by the light source is guided by the taper rod following a light path. The taper rod has increasing sizes of cross-sections along the light path, so as to decrease the dispersion angle of light, make the light more uniform, and increase the brightness of light. The prism module includes a first prism having a wedge cross-section and a second prism having a right triangle cross-section. The prism module receives the light from the condenser, passes the light toward the DMD, receives the light reflected by the DMD, and then passes the reflected light toward the projection lens set. The projection lens set projects the light on an external projection plane. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The details of the present invention will be more readily understood from a detailed description of the preferred embodiments taken in conjunction with the following figures.  
         [0011]      FIG. 1  illustrates an embodiment of the optical engine which is located in an image projector according to the present invention;  
         [0012]      FIG. 2  illustrates an exploded 3-D diagram of an embodiment of the optical engine according to the invention;  
         [0013]      FIG. 3  illustrates the exploded 3-D diagram of an embodiment of the optical engine according to the invention viewed in the other angle;  
         [0014]      FIG. 4  illustrates the optical track of this optical engine of the invention shown in  FIG. 2 ;  
         [0015]      FIG. 5  illustrates a 3-D diagram of a preferred embodiment of the first prism of prism module according to the invention;  
         [0016]      FIG. 6  illustrates a 3-D diagram of the preferred embodiment of the second prism of prism module according to the invention;  
         [0017]      FIG. 7  illustrates a 3-D diagram of the preferred embodiment of the prism supporting piece of prism module according to the invention;  
         [0018]      FIG. 8  illustrates an exploded 3-D diagram of a first embodiment of the illuminator module of the optical engine according to the invention;  
         [0019]      FIG. 9  shows a diagram of an embodiment of the light is reflected along the way through the taper rod according to the invention;  
         [0020]      FIG. 10  illustrates an exploded 3-D diagram of a second embodiment of the illuminator module of the optical engine according to the invention;  
         [0021]      FIG. 11  illustrates an exploded 3-D diagram of a third embodiment of the illuminator module of the optical engine according to the invention;  
         [0022]      FIG. 12  shows the combination diagram of the heat dissipating element to the illuminator module shown in  FIG. 11 ; and  
         [0023]      FIG. 13  shows the combination diagram of the base, concave mirror, converging lens and the prism set to the illuminator module shown in  FIG. 12 . 
     
    
     DETAILED DESCRIPTION  
       [0024]      FIG. 1  illustrates an embodiment of the optical engine which is located in an image projector according to the present invention. Please refer to  FIG. 1 ; an optical engine  10  of the present invention is furnished inside an image projector  1 . The image projector  1  generally comprises the Optical Engine  10  of the invention, a PCB Module  20 , a Heat Sink Module  30 , Operation Interface Module  40  and a Casing  50 .  
         [0025]     The Optical Engine  10  is used to produce and project image. It is the main technical characteristic of the invention. The PCB Module  20  is connected to Optical Engine  10  to control its function. PCB Module  20  also contains several connecting interfaces  21  for connecting external devices (ex. PC, DVD or image broadcasting device, or memory card, not shown in FIG.). A Heat Sink Module  30  is used for dissipating heat from Optical Engine  10  and PCB Module  20 . The Heat Sink Module  30  includes at least one fan  31 , a properly devised air-flow channel (not numbered) for heat dissipation and at least one heat dissipating airway  32 . A Operation Interface Module  40  is connected to PCB Module  20  for controlling the operation of Image Projector  1 . In general, there are several control keys  41  or switches on Operation Interface Module  40 . Optical Engine  10 , PCB Module  20 , Heat Sink Module  30 , Interface Module  40  are all assembled inside a Casing  50 .  
         [0026]      FIGS. 2, 3  and  4  illustrate embodiments of the optical engine  10  according to the invention.  FIG. 2  is an exploded diagram of an embodiment of the optical engine  10  according to the invention.  FIG. 3  is the exploded diagram of an embodiment of the optical engine  10  according to the invention viewed in the other angle.  FIG. 4  illustrates the optical track (light path) of the optical engine  10  according to the present invention shown in  FIG. 2 .  
         [0027]     As shown in  FIG. 2 ˜ 4 , optical engine  10  comprises an illuminator module  11 , a concave mirror  12 , a converging lens  13 , a prism module  14 , a Digital Micromirror Device (DMD)  15  and a projection lens set  16  comprising a plurality of lenses  161  and a diaphragm  162 . As light projects from the illuminator module  11 , the light ray is gathered first by the taper rod in the illuminator module  11 . Then, the concave mirror  12  refracts and converges the light ray toward an expected direction. The light ray is then converged by the converging lens  13  and the prism module  14  refracts the light ray toward the Digital Micromirror Device (DMD)  15 . As the light ray is refracted by Digital Micromirror Device (DMD)  15  and image is formed, the prism module  14  again refracts it toward the projection lens set  16  then an image is focused and formed on an external projection surface  91 .  
         [0028]     To locate the above-mentioned elements precisely, the optical engine  10  of the invention is specifically devised as shown in  FIGS. 2 and 3 . The optical engine  10  further includes a base  17  and an upper lid  18 . The base  17  and the upper lid  18  is made of plastic materials, manufacture with injection molding technique. Upon the base  17 , there are a right cover  171  and a lower lid  172 . Inside the right cover  171 , a first space  173  is formed to the contain Digital Micromirror Device (DMD)  15  and in the lower lid  172 , a v-shaped lower concave base  174  and a below-prism shading piece  175  connected in adjacent to right cover  171  are formed. Also, there is a lower concave groove  176  located between v-shaped lower concave base  174  and below-prism shading piece  175 . Upper lid  18  provides connection for lower lid  172  of base  17 . Upon upper lid  18 , there are a v-shaped upper concave base  181 , an above-prism shading piece  182  and an upper groove (not shown in the figures) whose locations correspond to v-shaped lower concave base  174 , below-prism shading piece  175  and a lower concave groove  176  respectively. As upper lid  18  covers up with lower lid  172 , a space is formed between them. The optical engine  10  of the present invention is assembled as follows: prism module  14  is located in between above-prism shading piece  182  and below-prism shading piece  175 . Converging lens  13  is located in between upper concave groove and lower concave groove  176 . Concave mirror  12  is located in the corner formed by v-shaped upper concave base  181  and v-shaped lower concave base  174 . At the end of v-shaped upper concave base  181  and v-shaped lower concave base  174 , a taper rod  112 , a fixing stand  115  and a spring clip  116  are furnished. In addition, below the prism module  14 , there are a prism supporting piece  143  and a spring  144  to orientate and fine-tune the location of prism module  14 . So, by means of the special invention of base  17  and upper lid  18 , the other elements mentioned can be oriented in combination toward an expected angle, relative position and distance in a faster, easier and precise way.  
         [0029]     As shown in  FIG. 3 , Digital Micromirror Device DMD  15  includes a DMD chip  151 , a DMD outlet socket  152  to plug in DMD chip  151 , a DMD PCB  153  to connect to DMD outlet socket  152 , and a DMD electric connecting-socket  154  to connect to DMD PCB  153 . As Digital Micromirror Device DMD  15  is installed in the space formed by base  17  and right cover  171 , DMD chip  151  is exposed exactly on the central window of the first space  173  to accept light that comes from prism module  14 . The projector lens set  16  is located in one side of the space formed in between above-prism shading piece  182  and below-prism shading piece  175 . In addition to that, the projector lens set  16  includes a rubber case  163  and a fastening ring  164 . The rubber case  163  is connected to projector lens set  16  externally and its edges fit exactly into the space formed by above-prism shading piece  182  and below-prism shading piece  175  to prevent light interference. The fastening ring  164  locks projector lens set  16  into an extension frame  177  of right cover  171 .  
         [0030]     Please refer to  FIG. 5, 6 , and  7  as well as  FIG. 2  and  4 .  FIG. 5  illustrates a 3-D diagram of the preferred embodiment of the first prism  141  of prism module  14  according to the invention.  FIG. 6  illustrates a 3-D diagram of the preferred embodiment of the second prism  142  of prism module  14  according to the invention.  FIG. 7  illustrates a 3-D diagram of the preferred embodiment of the prism supporting piece  143  of prism module  14  according to the invention. In this embodiment, the prism module  14  acts as a reversed total internal reflection (RTIR). The prism module  14  includes a first prism  141  and a second prism  142 . The first prism  141  is located near the converging lens  13  and the second prism  142  is located near Digital Micromirror Device (DMD)  15 . Both of these prisms are made of a transparent material with a predetermined refraction coefficient.  
         [0031]     As shown in  FIG. 5 , the first prism  141  is a wedge prism which presents itself in pyramidal shape ( FIG. 4 ) on the cross-sectional surface of the light ray as it travels along the track. The six surfaces  1411 ˜ 1416  of the wedge prism are flat surfaces which are not parallel to any other among themselves and each surface is connected to the other in a tilted way. Surface  1413  is the incident surface of light and surface  1416  is the light exit surface. The joining lines of the four surfaces  1411 ,  1412 ,  1413  and  1416  of the first prism  141  are very thin in thickness (i.e. surfaces  1413  and  1416  have the shortest distance in this location), but for surfaces  1413 ,  1414 ,  1415  and  1416 , their joining lines are comparatively thick (i.e. surfaces  1413  and  1416  have the longest distance in this location).  
         [0032]     Please refer to  FIG. 6 , in the embodiment, the second prism  142  presents itself on the cross-sectional surface of the traveling light ray as a right triangle which comprises five surfaces  1421 ˜ 1425 . Surfaces  1424  and  1425  are right triangular surfaces which are parallel to each other. Surface  1421  is located in between these two surfaces and perpendicular to their longest sides. This surface serves as the incidence surface for light. Surfaces  1422  and  1423  are located perpendicularly to the other two sides of surfaces  1424  and  1425 , respectively. These two surfaces are perpendicular to each other as well. The surface  1416  of the first prism  141  is equipped against surface  1421  (the surface extended from the longest edge of the right triangle) of the second prism  142 . Digital Micromirror Device (DMD)  15  and projection lens set  16  are adjacent to surfaces  1423  and  1422  (the two surfaces extended from the two perpendicular sides of the right triangle) of the second prism  142 .  
         [0033]     As shown in  FIG. 7 , the prism supporting piece  143  has a right triangular supporting surface  1431  for surface  1425  of the second prism  142  to sit on. The second prism  142  can be glued on the prism supporting piece  143 . In the edges of supporting surface  1431  of the prism supporting piece  143 , several resisting pieces  1432  can be used to prevent the second prism  142  from sliding. Underneath the prism supporting piece  143 , there is a screwing column  1433  (not shown in the figures) for screwing base  17  to the below-prism shading piece  175 . Through fine screwing movement of the screw, the relative position and angle of the first prism  141  and the second prism  142  can be adjusted, so as to fine-tune the direction and angle of the light ray.  
         [0034]      FIG. 8  is a similar exploding diagram to  FIG. 2  which shows the first embodiment of an illuminator module  11  of the optical engine  10  according to the invention. This illuminator module  11  includes a light source  111 , a taper rod  112 , light reflection piece, a PCB  114 , a fixing column  115  and a spring clip  116 . This illuminator module  11  also combines a heat-dissipating component  117  to dissipate heat.  
         [0035]     Light source  111  is set to emit light ray toward in the direction of a predetermined light axis. In an embodiment, light source  111  is a light emitting diode (LED). The taper rod  112  is adjacent to light source  111 . The taper rod  112  includes a plurality of narrow and long surfaces  1121  along the extended direction of the light source. The perpendicular cross-sectional surface of the taper rod  112  and the light axis forms a polygon in this way. Each of narrow and long surfaces  1121  has two corresponding long edges  1122  and  1123  that generally extend along the direction of the light source and two corresponding short edges  1124  and  1125  that are generally perpendicular to the light axis. The length of the narrow and long surface  1121  nearer to the short edge  1125  of the light source is shorter compared with the short edge  1124  of the light source. So, the taper rod  112  becomes bigger gradually in the direction departing away from the light source  111 . The concave mirror  12  is located at the end where the cross-sectional area of the taper rod  112  is the largest.  
         [0036]     The reflecting means is implemented to the narrow and long surface  1121  to reflect light ray emitted from the light source and guides it toward the direction of the light axis. A preferred embodiment is shown in  FIG. 8 . The taper rod  112  is a hollow cone made of transparent material, for example, glass, plastics, crystal or quartz, but not limited to these. The interior surfaces of the narrow and long surface  1121  are formed with light reflective materials  113  (e.g. Silver, etc.) so that total reflection occurs as the light travels from the end with the smaller cross-sectional area to the end of the larger cross-sectional area of the taper rod  112 . In this way, the taper rod  112  invented guides the traveling light toward the axis of the light.  
         [0037]     PCB  114  is used for supporting the light source  111  (Light Emitting Diode, LED). There are several electrical elements (not numbered) of a light source drive  111  (Light Emitting Diode, LED) and a connector  1142 . The fixing stand  115  is connected to PCB  114 . On the fixing stand  115 , a square-shaped hollow sink  1151  is used for installing the end with the smaller cross-sectional area of the taper rod  112  and the location of the light source  111  corresponds exactly to the end with the smaller cross-sectional area of the taper rod  112 . The fixing stand  115  includes two stands  1152  and  1153  and a sliding route  1154  in between them. The size of the sliding route  1154  matches exactly with the size of PCB  114  so that PCB  114  can slide into the sliding route  1154  to attach with the fixing stand  115 .  
         [0038]     Spring clip  116  is used to clip the taper rod  112  to the fixing stand  115 . In a preferred embodiment, the spring clip  116  includes a plurality of clips  1161 , at least one buttoning clip  1162  on each Clip  1161  and a hole  1163  on each clip  1161 . The size of the hole  1163  is greater than the larger cross-sectional area end of the taper rod  112 . The taper rod  112  is fixed to the fixing stand  115  with the hole  1163  of the spring clip  116  encases upon the taper rod  112  and with the help of at least a clip  1161  to clip onto the edge of fixing stand  115 . In a preferred embodiment, a convex piece  1126  is devised on at least on one of the narrow and long surface  1121  of the taper rod  112  so when the hole  1163  of the spring clip  116  encases upon the taper rod  112 , the convex piece  126  serves to go against the spring clip  116  and the fixing stand  115  to prevent occurrence of displacement.  
         [0039]     The heat sink module  117  includes a heat dissipating surface  1171  and a plurality of heat dissipating fins  1172  extended from the heat dissipating surface  1171 . On the heat dissipating surface  1171 , there is a convex surface  1173  with predetermined shape. The fixing stand  115  and the PCB  114  are connected to the heat dissipating surface  1171 . The location of the convex surface  1173  forms exactly a space with the two stands  1152  and  1153  so that the light source  111  on PCB  114  may be contacted to the convex surface  1173  on the heat dissipating surface  1171 .  
         [0040]      FIG. 9  shows a diagram of an embodiment of the light is reflected along the way through the taper rod  112  according to the invention. The special structure of the taper rod  112  is designed in the purpose of minimizing light scattering angle. As shown in  FIG. 9 , light travels into the end with the smaller cross-sectional surface of the taper rod  112  in θ 1  angle and the taper rod  112  itself gets larger gradually (i.e. the cross-sectional area gets larger) in θ 3  angle with the traveling light source, so when the light gets out of the end with the larger cross-sectional surface in the angle of θ 2 , where θ 2 &lt;θ 1 . In this way, the scattering angle of the light is minimized and the light ray is gathered, distribution of the light is more even and the utilizing effectiveness is maximized.  
         [0041]     Most of the elements that come in the following introduction, other preferred embodiment of the present invention are similar or the same to the above introduced examples. So, we only add an alphabet to the listed number to differentiate.  
         [0042]      FIG. 10  illustrates a block diagram of a second embodiment of the illuminator module  11   a  of the optical engine according to the invention. The illuminator module  11   a  shown here in  FIG. 10  is similar to the illuminator module  11  shown in  FIG. 8  in that, it also includes: light source  111  (light emitting diode, LED), taper rod  112   a,  light reflection piece, PCB module  114 , a fixing stand  115   a  and a spring clip  116 . It also has a heat dissipating element  117  to dissipate heat. The difference in illuminator module  11   a  is that it has a hollow oriented casing  118  and at the end of the larger cross-sectional area of the taper rod  112   a,  there is a bulging edge  1127 . The taper rod  112   a  is transfixed into the hollow oriented casing  118  so that the bulging edge  1127  is fixed on the upper and inner fold  1181  of the hollow oriented casing  118 . The other end of the casing  118  is fixed to the PCB module  114  and the fixing stand  115   a  through connecting element  1182 . The taper rod  112   a  is a solid pyramid. There are light reflecting means on the outer narrow and long surfaces  1121   a  made of light reflecting material  113   a.  Besides, the bulging edge  1127  of the taper rod  112   a  and the taper rod  112   a  are made of one piece.  
         [0043]      FIG. 11  illustrates a block diagram of a third embodiment of the illuminator module  11   b.  According to  FIG. 11 , illuminator module  11   b  is similar to illuminator module  11   a  in general. It also includes: a light source  111  (light emitting diode), taper rod  112   b,  a light reflection piece, PCB  114 , a fixing stand  115   b,  a spring clip  116  and an oriented casing  118   b.  The difference between the two illuminator modules is that the bulging edge  1127   b  of the taper rod  112   b  is an independent part from the taper rod and it is made of a transparent piece-like material (e.g. Glass or acrylic resin) whose size is a bit larger than the larger cross-sectional surface of the taper rod  112   b.  Besides, the bulging edge is glued to the pole  112   b.    
         [0044]      FIG. 12  shows the combination diagram of the heat dissipating element  117  to the illuminator module  11   b  shown in  FIG. 11 .  
         [0045]      FIG. 13  shows the combination diagram of the base  17 , the concave mirror  12 , the converging lens  13  and the prism set  14  to the illuminator module  11   b  shown in  FIG. 12 .  
         [0046]     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, that above disclosure should be construed as limited only by the metes and bounds of the appended claims.