reference will now be made to the drawings to describe a preferred embodiment of the present tilt detecting method . referring to fig1 , 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 fig2 , 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 fig3 , 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 fig4 , 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 fig5 , 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 fig5 , 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 . referring also to fig6 , 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 .