Patent Document

BACKGROUND 
     1. Field of the Invention 
     The present invention generally relates to a method for detecting tilt of an optical pickup head. 
     2. Description of Related Art 
     In recent years, optical disk recording and/or reproducing devices have been widely used as portable storing and reproducing electronic consuming devices in our daily life. Each optical disk recording and/or reproducing device mainly includes an optical pickup head for emitting a light beam, a guiding apparatus for movably supporting the optical pickup head, and a driving mechanic for driving the optical pickup head to move. 
     Referring to  FIG. 8 , an optical disk recording and/or reproducing device  10  is used for recording data to and/or reproducing data from an optical disk  150 . In the optical disk recording and/or reproducing device  10 , an optical pickup head  120  is movably supported in two guiding poles  106 , and a stepping motor  108  is used for moving the optical pickup head  120  along the guiding poles  106 . When the guiding poles  106  are not parallel to each other, a tilt occurs. If the guiding poles  106  are parallel to each other, but the virtual plane defined by the guiding poles  106  is not parallel to the turntable  104 , the tilt is also generated. When the optical pickup head  120  is tilted, light from the optical pickup head  120  cannot be vertically projected to the optical disk  150 . The tilt of the optical pickup head  120  is a main factor influencing recording and reproducing capability of the optical disk recording and/or reproducing device  10 . 
     Therefore, it is important to detect the tilt of the optical pickup head  120 . Referring to  FIGS. 9 ,  10 , a conventional method is used to detect the tilt using a collimator  200  and three reflecting planes  132 ,  134 ,  136 . The reflecting planes  132 ,  134 ,  136  are set on the turntable  104 , and two ends of the guiding poles  106  respectively. In operation, the collimator  200  emits light beams, and the light beams are projected to the reflecting planes  132 ,  134 ,  136  and reflected therefrom. The reflected light beam are received and analyzed by the collimator  200 , and information carried in the reflected light beams is displayed on a display screen (not shown). Referring also to  FIG. 11 , three light spots  42 ,  44 ,  46  are displayed in an image  40 . Herein, the light spots  42 ,  44  are formed by the light beams reflected from the reflecting planes  134 ,  136 , which are defined as static spots. The light spot  46  is formed by the light beam reflected from the reflecting plane  132 , which is defined as dynamic spot. 
     If the static spots  42 ,  44  are both laid on center of the dynamic spot  46 , it is determined that no tilt is generated. If one of the static spots departs from the center of the dynamic spot  46 , a first distance between the center of the departure static spot and the center of the dynamic spot represents a first unparallel degree of the guiding poles  106  to the turntable  104 , and a second distance between the center of the static spot  42  and the center of the static spot  44  represents a second unparallel degree of the guiding poles  106 . If the static spots both depart from the center of the dynamic spot  46 , a bigger distance between the center of the dynamic spot  46  and the centers of the static spots  42 ,  44  represents the first unparallel degree. Herein, the center means a geometric center of a minimum virtual rectangle that can enclose a spot. 
     In practice, the first and the second distances are measured manually to determine the tilt. Therefore, the conventional method includes some deficiencies, such as man-made determination error and low work efficiency. 
     Therefore, improvements for a tilt detecting method are needed in the industry to address the aforementioned deficiency. 
     SUMMARY 
     A tilt detecting method is used for detecting a tilt of an optical pickup head. The tilt detecting method includes the steps of: capturing a plurality of images; converting the images to bitmap images; superposing the bitmap images together to form an superimposed bitmap image; setting a two-dimensional coordinating system of the superimposed bitmap image; determining coordinates of a first static spot, a second static spot, and dynamic spot; calculating a first distance between the first static spot and the dynamic spot, and a second distance between the second static spot and the dynamic spot based on the coordinates to determine a maximum distance; and comparing the maximum distance with a first predetermined standard distance to attain a conclusion whether the tilt is in an acceptable range. 
     Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is schematic diagram showing a collimator and the three reflecting planes used for detecting tilt of an optical disk recording and/or reproducing device in accordance with an exemplary embodiment; 
         FIG. 2  is schematic diagram showing three light spots displayed in a image formed by three reflected light beams from the reflecting planes; 
         FIG. 3  is a process flow diagram showing a tilt detecting method in accordance with an exemplary embodiment; 
         FIG. 4  is a schematic diagram showing a concrete structure of a bitmap image of static spots and a dynamic spot; 
         FIG. 5  is schematic diagram showing an superimposed bitmap image generated by superposing three bitmap images, and a two-dimensional coordinate system of the superimposed bitmap image; 
         FIG. 6  is schematic diagram showing an superimposed bitmap image generated by superposing four bitmap images; 
         FIG. 7  is a process flow diagram showing a analyzing procedure for analyzing the superimposed bitmap image of  FIG. 4 ; 
         FIG. 8  is schematic diagram showing an optical disk recording and/or reproducing device; 
         FIG. 9  is schematic diagram showing a conventional collimator and three reflecting planes used for detecting tilt of the optical disk recording and/or reproducing device of  FIG. 8 , viewed from an up aspect; 
         FIG. 10  is schematic diagram showing the collimator and the three reflecting planes used for detecting tilt of the optical disk recording and/or reproducing device of  FIG. 8 , viewed from a side aspect; and 
         FIG. 11  is schematic diagram showing three light spots displayed in a image formed by three reflected light beams from the reflecting planes of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made to the drawings to describe a preferred embodiment of the present tilt detecting method. 
     Referring to  FIG. 1 , a collimator  300  and three reflecting planes  332 ,  334 ,  336  are used to detect the tilt of an optical pickup head  320  using a tilt detecting method in accordance with an exemplary embodiment. The reflecting planes  332 ,  334 ,  336  are set on a turntable  304 , and two ends of a guiding pole  306  correspondingly. When operating, the collimator  300  emits light beams; the light beams are projected to the reflecting planes  332 ,  334 ,  336  and reflected back. Reflected light beams are received and analyzed by the collimator  300 , and information corresponding to the reflected light beams is displayed on a display screen (not shown). 
     Referring also to  FIG. 2 , three light spots  32 ,  34 ,  36  are displayed in an image  30 . Herein, the light spots  32 ,  34  formed by the reflected light beams from the reflecting planes  334 ,  336 , are defined as static spots. The light spot  36  is formed by the light beam reflected from the reflecting plane  332 , which is defined as dynamic spot. 
     Referring to  FIG. 3 , a flow chart showing a detecting procedure of the tilt detecting method for detecting tilt of the optical pickup head  120  is illustrated. The detecting procedure includes the following steps. 
     Step S 501 , the collimator  300  captures several images including the static spots and the dynamic spots under the same conditions. That is, the images are taken from the collimator  300  with a same focus and at a same capture angle. Moreover, other photoelectricity apparatus can also be used to capture the images. For exemplary purposes, in the preferred embodiment, the amount of the images is 3. However, the number of the images can be any other value that is not less than 3. 
     Step S 503 , the images are converted to bitmap images composed of pixels. Each of the pixels is represented by a pixel value. Referring to  FIG. 4 , for exemplary purposes, each of the pixels corresponding to the static spots and the dynamic spots has a pixel value of “1”, representing a dark color such as black, and the pixels outside the spots each has a pixel value of “0”, representing bright color such as white. 
     Step S 505 , the bitmap images are superimposed together correspondingly to form a superimposed bitmap image. When the bitmap images are superimposed together, the pixel values are correspondingly added up to derive pixel values of bitmap data of the superimposed image. Referring to  FIG. 5 , a superimposed bitmap image  78  is generated by superimposing three bitmap images  72 ,  74 ,  76  together. There are three spots  782 ,  784 ,  786  in the superimposed bitmap image  78 . The pixel values of the bitmap image  78  vary from a minimum value of “0” to a maximum value of “3”. Since a distribution of the max value of the spots  782 ,  784  is relatively high, the spots are defined as concentrated spots. For example, the static spot  782  has two pixel values of “2” and five pixel values of “3”, and the static spot  784  has one pixel value of “2” and six pixel values of “3”. Thus, the static spots  782 ,  784  are concentrated. The spot  786  is a dynamic spot, which has comparative more small pixel values, such as seventeen pixel values of “1”, and large overlaid area. This means that the dynamic spot  786  is dispersed. 
     Step S 507 , a two-dimensional coordinate system  788  is set on the superimposed bitmap image  78 . Referring to  FIG. 5 , an X-axis of the two-dimensional coordinate system  788  is under the lower side of the superimposed bitmap image  78 , and a Y-axis of the two-dimensional coordinate system  788  is near the left side of the superimposed bitmap image  78 . 
     Step S 509 , the superimposed bitmap image  78  is analyzed. Coordinates of the static spots  782 ,  784  and the dynamic spot  786  are derived from the two-dimensional coordinate system  788 . 
     Step S 511 , a first distance between the static spot  782  and the dynamic spot  786 , and a second distance between the static spot  784  and the dynamic spot  786  are calculated. A maximum distance of the first distance and the second distance is determined. 
     Step S 513 , a third distance between the static spot  782  and the static spot  784  is calculated. 
     Step S 515 , the maximum distance is compared with a first predetermined standard distance, and the third distance is compared with a second predetermined standard distance, in order to obtain a result that shows whether the tilt is in an acceptable range. If the maximum distance is greater than the first predetermined standard distance or the third distance is greater than the second predetermined standard distance, the tilt is beyond the acceptable range. If the maximum distance is not greater than the first predetermined standard distance and the third distance is not greater than the second predetermined standard distance, the tilt is in the acceptable range. 
     Step S 517 , a result summary is displayed. The detecting result includes the conclusion, the maximum distance and the third distance. 
     Step S 519 , the detecting result is stored. 
     Referring also to  FIGS. 6 ,  7 , an superimposed bitmap image  80  generated by superposing four bitmap images is taken for example to depict how to analyze the superimposed bitmap image  80  in the step S 509  mentioned above. The analyzing procedure includes the following steps. 
     Step S 901 , pixels having pixel value of “4” are detected in the superimposed bitmap image  80 . Herein, a pixel having pixel value of “4” means static spots or dynamic spots of the four bitmap images are overlaid on the same pixel. 
     Step S 903 , a first static range  802  is determined by collecting all pixels with pixel values of “4” together in a first static spot (not labeled). The first static range  802  must be a square. 
     Step S 905 , a center pixel of the first static range  802  is determined, and a first static coordinate of the center pixel is calculated. 
     Step S 907 , the other pixels out of the first static range  802  within the first static spot are cleared. 
     Step S 909 , the superimposed bitmap image  80  is detected to determine whether other pixels out of the first static range  80  have pixel value of “4”. 
     Step S 911 , if the other pixels have pixel value of “4”, a second static range  804  is determined by collecting all pixels with pixel value of “4” together in a second static spot (not labeled), and a second static coordinate of a center pixel of the second static range  804  is calculated, and the analyzing procedure goes to step S 915 . 
     Step S 913 , if no pixels out of the first static range  80  have pixel value of “4”, it is concluded that a first static spot and the second static spot are superposed together, and a second static coordinate is equal to the first static coordinate, and the analyzing procedure goes to step S 917 . 
     Step S 915 , the other pixels out of the second static range  804  within the second static spot are cleared. 
     Step S 917 , the superimposed bitmap image  80  is detected to determine a dynamic range  810  which is a rectangle containing pixels having values “1”, “2”, “3” out of the first static range  802  and the second static range  804 . A dynamic coordinate of a center pixel of the dynamic range  810  is calculated. 
     As mentioned above, the first static coordinate, the second static coordinate, and the dynamic coordinate are determined automatically using the tilt detecting method. Moreover, the conclusion whether the tilt is in an acceptable range is obtained automatically. Therefore, man-made determination error can be averted and work efficiency can be elevated. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Technology Category: 3