Patent Publication Number: US-2012033189-A1

Title: Projector and color wheel module thereof

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority of Taiwan Patent Application No. 099126180, filed on Aug. 6, 2010, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a color wheel module, and in particular relates to a color wheel assisting to define an initial position of a color wheel of the color wheel module. 
     2. Description of the Related Art 
     In a projector, to present correct color according to a control signal, an initial position of a color wheel is defined, and an index delay is controlled by a calculating method according to the detected initial position. Conventionally, an infrared reflective optical sensor is utilized in detecting an initial position of a color wheel.  FIG. 1  shows a conventional method for detecting an initial position of a color wheel. A timing label  12  is attached to a shaft  11  of a color wheel  10 . When the color wheel  10  is rotated, a sensor  1  emits a light beam toward the shaft  11 . The light beam  2  is reflected by a surface of the shaft  11 , and is received by the sensor  1 . When the light beam  2  contacts the timing label  12 , the light beam  2  is absorbed thereby, and is not received by the sensor  1 . Thus, the sensor  1  sends an electrical signal according to the light receiving condition to define an initial position of the color wheel  10 . However, the conventional method has the following defects:
         (a) Light interference: Inner light of the projector may enter the infrared reflective optical sensor, generate light interference, and influence the initial position detection.   (b) Dust pollution: Dust may cover the light passage of the sensor, and influence the initial position detection.       

     BRIEF SUMMARY OF THE INVENTION 
     A color wheel module is provided. The color wheel module includes a stator, a rotor, a color wheel and a sensor. The rotor surrounds the stator, wherein the rotor includes a rotor body, a turn table and a balance yoke, and the balance yoke is disposed on the turn table, and the balance yoke includes an N pole portion and an S pole portion, and the rotor body is tube shaped, and the turn table is disposed on an end of the rotor body. The color wheel is disposed on the rotor. The sensor corresponds to the balance yoke, wherein when the balance yoke is rotated, the N pole portion and the S pole portion are rotated to generate a magnetic field variation, and the sensor outputs an electric signal according to the magnetic field variation to define an initial position of the color wheel. 
     In the embodiment of the invention, the sensor outputs an electric signal (Hi/Lo electric signal) according to the magnetic field variation to define an initial position of the color wheel, and an index delay is controlled by a calculating method according to the detected initial position to show a correct color. Compared to the conventional method, the color wheel module of the embodiment of the invention has no light interference or dust pollution problems; thus, the initial position of the color wheel can be defined accurately. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  shows a conventional method for detecting an initial position of a color wheel; 
         FIG. 2  is an assembly view of a color wheel module of an embodiment of the invention; 
         FIG. 3  is an exploded view of the color wheel module of the embodiment of the invention; 
         FIG. 4  is a front view of a color wheel; 
         FIG. 5  is a sectional view of the color wheel; 
         FIG. 6A  shows a sensor of the embodiment of the invention detecting a magnetic field variation; 
         FIG. 6B  shows an electric signal (Hi/Lo electric signal) according to the magnetic field variation; 
         FIG. 7  shows a projector of another embodiment of the invention; and 
         FIGS. 8A and 8B  show modified examples of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
       FIG. 2  is an assembly view of a color wheel module  100  of an embodiment of the invention, and  FIG. 3  is an exploded view of the color wheel module  100  of the embodiment of the invention. With reference to  FIGS. 2 and 3 , the color wheel module  100  comprises a stator  110 , a rotor  120 , a color wheel  130  and a sensor  140 . The rotor  120  surrounds the stator  110 . The rotor  120  comprises a rotor body  121 , a turn table  127  and a balance yoke  122 . The balance yoke  122  is disposed on the turn table  127 . The balance yoke  122  comprises an N pole portion  123 , an S pole portion  124  and a pole border line  125 . The pole border line  125  is located between the N pole portion  123  and the S pole portion  124 . The rotor body  121  is tube shaped, and the turn table  127  is disposed on an end of the rotor body  121 . The color wheel  130  is disposed on the rotor  120 , and is sandwiched between the rotor body  121  and the balance yoke  122 . The pole border line  125  corresponds to a particular portion of the color wheel  130 . 
       FIG. 4  is a front view of the color wheel  130 . The color wheel  130  comprises a first color area  131 , a second color area  132  and a color border line  139 , and the color border line  139  and the pole border line  125  are collinear. The first color area  131  comprises a first red portion R 1 , a first green portion G 1  and a first blue portion B 1 , and the second color area  132  comprises a second red portion R 2 , a second green portion G 2  and a second blue portion B 2 , and the first green portion G 1  is located between the first red portion R 1  and the first blue portion B 1 , and the second green portion G 2  is located between the second red portion R 2  and the second blue portion B 2 , and the first red portion R 1  is adjacent to the second blue portion B 2 , and the second red portion R 2  is adjacent to the first blue portion B 1 . 
       FIG. 5  is a sectional view of the color wheel  130 . The rotor  120  further comprises a shaft  126 , and the shaft  126  is disposed on the balance yoke  122 . The stator  110  comprises a hole  111 , and the shaft  126  is inserted into the hole  111 . The rotor body  121  comprises a permanent magnet, and the stator  110  comprises a plurality of electromagnetic elements  112 , and the electromagnetic elements  112  surround the hole  111 , and the electromagnetic elements  112  are located between the hole  111  and the rotor body  121 . The electromagnetic elements  112  are arranged equidistantly. 
     With reference to  FIGS. 2 ,  6 A and  6 B, the sensor  140  corresponds to the balance yoke  122 . When the color wheel  130  and the balance yoke  122  are rotated, the N pole portion  123  and the S pole portion  124  are rotated to generate a magnetic field variation. The sensor  140  outputs an electric signal (Hi/Lo electric signal) according to the magnetic field variation to define an initial position of the color wheel  130 , and an index delay is controlled by a calculating method according to the detected initial position to show a correct color. Compared to the conventional method, the color wheel module of the embodiment of the invention has no light interference or dust pollution problems; thus, the initial position of the color wheel can be defined accurately. 
     Additionally, magnetic force generated by the N pole portion  123  and the S pole portion  124  also pass the turn table  127 . Therefore, in one embodiment, the sensor  140  can be disposed on a side of the turn table  127  (not shown) to detect the magnetic field variation of the balance yoke  122 . 
     In the embodiment above, the color wheel  130  comprises a first red portion R 1 , a first green portion G 1 , a first blue portion B 1 , a second red portion R 2 , a second green portion G 2  and a second blue portion B 2 . However, the invention is not limited. The color wheel  130  can be modified. For example, the color wheel can have only one red portion, one green portion and one blue portion, or the color wheel can have one red portion, one green portion, one blue portion and one transparent portion. 
     In the embodiment above, the color border line and the pole border line are collinear. However, the invention is not limited. The pole border line can correspond to any position of the color wheel, and the calculating method can be modified to control index delay and to show a correct color. 
     In the embodiment above, the external rotor DC brushless motor is utilized. However, the invention is not limited. Motors of other types can also be utilized in the invention. 
       FIG. 7  shows a projector  200  of another embodiment of the invention, which comprises a light source  210 , an optical engine  220  and the color wheel  100  mentioned above. The light source  210  provides a light beam  211 . The light beam  211  passes through the color wheel module  100  to the optical engine  220 . The sensor  140  is located between the color wheel  130  and the light source  210 . 
       FIGS. 8A and 8B  show modified examples of the invention, wherein a non-magnetic area is formed between the N pole portion  123 ′ and the S pole portion  124 ′. The N pole portion  123 ′ does not close neighbor on the S pole portion  124 ′. As shown in  FIGS. 8A and 8B , the N pole portion  123 ′ and the S pole portion  124 ′ can be modified. 
     Use of ordinal terms such as “first”, “second”, “third”, etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements. 
     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.