Abstract:
A method for calibrating light is adapted to a 3D object generating apparatus including a housing, an optical-transparent component, and a laser light generator. The housing has an accommodating space and an opening communicating with the accommodating space. The optical transparent component is arranged on the opening, and the laser light generator is arranged within the accommodating space. The method includes following steps: providing a first photodetector and a controller, the controller is electrically connected to the first photodetector and the laser light generator; using the controller to drive the laser light generator to generate the light and perform a scanning procedure; and stopping scanning procedure when the first photodetector detecting the light generated by the laser light generator, and then performing a 3D object generating procedure in the working region by moving the laser light generator with a preset distance.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Field of the Invention 
         [0002]    The present disclosure relates to a method for calibrating an optical component. More particularly, the present disclosure relates to a method for calibrating a light of a three-dimensional (3D) object generating apparatus. 
         [0003]    Description of Related Art 
         [0004]    Stereolithography is a method and apparatus for making solid objects by successively printing thin layers of a curable material one on top of the other. A programmed movable spot beam of UV light shining on a surface or layer of UV curable liquid is used to form a solid cross-section of the object at the surface of the liquid. The object is then moved, in a programmed manner, away from the liquid surface by the thickness of one layer, and the next cross-section is then formed and adhered to the immediately preceding layer defining the object. This process is continued until the entire object is formed. 
         [0005]    In general, the light source configured to generate light for curing the fluid medium is positioned to make sure the light generated therefrom can precisely transmit to the locations where the 3D model information defined. 
         [0006]    However, the positioned light source of the 3D object generating apparatus may further shift when delivery, which causes the 3D object generating apparatus cannot generate the 3D object in accordance with the 3D model information. 
       SUMMARY OF THE INVENTION 
       [0007]    According to one aspect of the present disclosure, a method for calibrating a light is adapted to a 3D object generating apparatus including a housing, an optical-transparent component, and a laser light generator. The housing has an accommodating space and an opening communicating to the accommodating space. The optical transparent component is arranged at the opening. The laser light generator is arranged at one side of the optical-transparent component and located within the accommodating space, and is employed to cure a fluid medium arranged at the other side of the optical-transparent component. The method includes following steps: providing a first photodetector and a controller, the controller is electrically connected to the first photodetector and the laser light generator; using the controller to drive the laser light generator to generate the light and perform a scanning procedure; and stopping scanning procedure when the first photodetector detecting the light generated by the laser light generator, and then performing a 3D object generating procedure in the working region by moving the laser light generator with a preset distance. 
         [0008]    According to another aspect of the present disclosure, a method for calibrating a light of a 3D object generating apparatus adapted to a 3D object generating apparatus includes a housing, an optical-transparent component, and a laser light generator. The housing includes an accommodating space and an opening communicating with the accommodating space. The optical-transparent component is arranged on the opening, the laser light generator is arranged on one side of the optical-transparent component and within the accommodating space. The laser light generator is used for curing a fluid medium arranged on the other side of the optical-transparent component and in a working region. The method includes following steps: providing a first photodetector, a second photodetector, and a controller, wherein the controller is electrically connected to the first photodetector, the second photodetector, and the laser light generator, and a line for connecting the first photodetector and the second photodetector is parallel to a first axis; using the controller to drive the laser light generator to generate a linear light, wherein a length of the linear light in the first axis is larger than a length of the line for connecting the first photodetector and the second photodetector in the first axis; using the controller to make the linear light generated by the laser light generator transmit to one of the first photodetector and the second photodetector; using the controlling to move the laser light generator along a second axis and make the linear light transmit to the other one of the first photodetector and the second photodetector, wherein the second axis is perpendicular to the first axis; using the controller to obtain the moved distance of the laser light generator along the second axis and calculate an inclination of the laser light generator; and using the controller to calibrate the position of the laser light generator according to the inclination. 
         [0009]    According to further another aspect of the present disclosure, a method for calibrating a light of a 3D object generating apparatus adapted to a 3D object generating apparatus comprising a housing, an optical-transparent component, and a laser light generator. The housing includes an accommodating space and an opening communicating with the accommodating space. The optical-transparent component is arranged on the opening, and the laser light generator is arranged on one side of the optical-transparent component and within the accommodating space. The laser light generator used for curing a fluid medium arranged on the other side of the optical-transparent component and in a working region. The method includes following steps: providing a first photodetector, a second photodetector, and a controller, wherein the controller is electrically connected to the first photodetector, the second photodetector, and the laser light generator, and a line for connecting the first photodetector and the second photodetector is parallel to a diagonal of the optical-transparent component; using the controller to drive the laser light generator to generate a surface beam and generate a scanning procedure, wherein the scanning procedure is performed by making the surface beam be projected to the first photodetector and the second photodetector; and using the controlling to calibrate the position of surface beam projected to the optical-transparent component according to the first signal sent from the first photodetector and the second signal sent form the second photodetector. 
     
    
     
       BRIEF DESCRIPTION OF DRAWING 
         [0010]    The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, may be best understood by reference to the following detailed description of the invention, which describes an exemplary embodiment of the invention, taken in conjunction with the accompanying drawings, in which: 
           [0011]      FIG. 1  is a schematic view of a part of components of a three-dimensional (3D) object generating apparatus according to a first embodiment of the present invention; 
           [0012]      FIG. 2  is a top view of the optical-transparent component shown in the  FIG. 1 ; 
           [0013]      FIG. 3  is a circuit block diagram of the 3D object generating apparatus shown in  FIG. 1 ; 
           [0014]      FIG. 4  is a schematic view of a part of components of a 3D object generating apparatus according to a second embodiment of the present invention; 
           [0015]      FIG. 5  is schematic view of a part of components of a 3D object generating apparatus according to a third embodiment of the present invention; 
           [0016]      FIG. 6  is a top view of the optical transparent component shown in the  FIG. 5 ; 
           [0017]      FIG. 7  is a circuit block diagram of the 3D object generating apparatus shown in  FIG. 5 ; 
           [0018]      FIG. 8  is a top view of a part of components of the 3D object generating apparatus according to the third embodiment of the present invention; 
           [0019]      FIG. 9  is another top view of a part of components of the 3D object generating apparatus according to the third embodiment of the present invention; 
           [0020]      FIG. 10  is an operation diagram of the 3D object generating apparatus according to the third embodiment of the present invention; 
           [0021]      FIG. 11  is an operational diagram of the 3D object generating apparatus according to the third embodiment of the present invention; 
           [0022]      FIG. 12  is a schematic view illustrating what an inclination is like; 
           [0023]      FIG. 13  is a schematic view of a part of components of a 3D object generating apparatus according to a fourth embodiment of the present invention; 
           [0024]      FIG. 14  is a schematic view of a part of components of a 3D object generating apparatus according to a fifth embodiment of the present invention; 
           [0025]      FIG. 15  is a top view of the optical transparent component shown in the  FIG. 14 ; 
           [0026]      FIG. 16  is a circuit block diagram of the 3D object generating apparatus shown in  FIG. 14 ; 
           [0027]      FIG. 17  is a schematic view of a projected image and a laser light projected image according to the fifth embodiment of the present invention; 
           [0028]      FIG. 18  is a graph of relative radiant intensity distribution of the surface beam reaches the first photodetector; and 
           [0029]      FIG. 19  is a schematic view of a part of components of a 3D object generating apparatus according to a sixth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    A preferred embodiment of the present invention will be described with reference to the drawings. 
         [0031]    Reference is made to  FIG. 1 , which is a schematic view of a part of components of a three-dimensional (3D) object generating apparatus according to a first embodiment of the present invention. In  FIG. 1 , the 3D object generating apparatus includes an optical-transparent component  100  and a laser light generator  120 . The laser light generator  120  and a container (its reference numeral is omitted) filled with a fluid medium  20  (such as photocurable resin) for producing the 3D object are arranged at opposite sides of the optical-transparent component  100 . In this embodiment, the optical-transparent component  100  made of glass allows light generated by the laser light generator  120  passing therethrough and has a characteristic of dustproof. The 3D object generating apparatus  10  may further includes an input unit (not shown) for receiving the 3D model information defining the 3D object, and the 3D object is generated within the fluid medium  20  which is selectively cured by spot beam of laser light emitted from the laser light generator  120  brought to selective focus prescribed by the 3D model information. 
         [0032]    Reference is made to  FIG. 2 , the optical-transparent component  100  includes a working region  102  and a first calibrating region  104 . The area of the working region  102  is, for example, larger than that of the first calibrating region  104 . In  FIG. 2 , the optical-transparent component  100  is substantially a rectangular and has a first axis X and a second axis Y perpendicular to the first axis X, and the first calibrating region  104  is arranged on the left side of the working region  102  in the first axis X. 
         [0033]    With referring again to  FIG. 1 , the fluid medium  20  is arranged at one side of the optical-transparent component  100  and in the work region  102  and the laser light generator  120  is arranged at the other side of the optical-transparent component  100 . The laser light generator  120  includes a light-emitting surface  122  facing the optical-transparent component  100 . The spot beam of the laser light generated by the laser light generator  120  is not only transmitted to the work region  102  but also transmitted to the first calibrating region  104 , and a 3D object generating procedure for generating the 3D object and a calibrating procedure for calibrating positions of the spot beam of the laser light generated by the laser light generator  120  are performed at different times. More particularly, the 3D object generating procedure is performed while the spot beam is transmitted to the work region  102 , and the calibration procedure is performed while the spot beam is transmitted to the first calibrating region  104 . 
         [0034]    A first photodetector  30  is arranged on the optical-transparent component  100  and configured to detect the laser light emitted from the laser light generator  120 . More particularly, the first photodetector  30  has a light detecting surface  300  facing the light emitting surface of the laser light generator  120 . In  FIG. 1 , the first photodetector  30  and the laser light generator  120  are arranged at the same side of the optical-transparent component  100 . The first photodetector  30  is arranged at the first calibrating region  104 , wherein the length of the first calibrating region  104  in the first axis X is equal to or larger than that of the first photodetector  30  in the first axis X, and there is a preset distance d between a central axis of the first photodetector  30  and the work region  102 . The first photodetector  30  is, for example, charge coupled device (CCD) or complementary metal-oxide-semiconductor (COMS) sensor. 
         [0035]    The first photodetector  30  is electrically connected to the controller  40 , as shown in  FIG. 3 , and the controller  40  is also electrically connected to the laser light generator  120 . The controller  40  receives a first signal sent from the first photodetector  30  and controls the acts of the laser light generator  120  (such as the positions of the spot beam of the laser light emitted therefrom) according to the first signal. 
         [0036]    The calibrating procedure starts with driving the laser light generator  120  to generate the spot beam by a controller  40 . The controller  40  further drives the laser light generator  120  to perform the scanning procedure by positioning the spot beam generated by the laser light generator  120  across the optical-transparent component  100 . The scanning procedure is continuously performed until the light reaches the first photodetector  30 . More particularly, the laser light generator  120  can continuously or discontinuously emit light during the scanning procedure is performed, and the scanning procedure can only be performed across the first calibration region  104 . 
         [0037]    The controller  40  makes the laser light generator  120  stop preforming scanning procedure when the spot beam generated by the laser light generator  120  reaches the first photodetector  30 . After that, the spot beam of the laser light generator  120  is controlled to move the preset distance d by the controller  40 , and then the 3D object generating procedure can be precisely performed in the working region  102 . 
         [0038]    In the present invention, the scanning procedure positioning the spot beam generated by the laser light generator  120  is performed before performing the 3D object generating procedure, therefore the spot beam generated by the laser light generator  120  can precisely project to the working region  102  and generate 3D object according to the 3D model information. 
         [0039]    Reference is made to  FIG. 4 , which is a part of components of a 3D object generating apparatus according to a second embodiment of the present invention. In  FIG. 2 , the 3D object generating apparatus  10  includes an optical-transparent component  100 , a laser light generator  120 , and a housing  130 . The housing  130  includes an accommodating space  132  and an opening  134  communicating with the accommodating space  132 . The optical-transparent component  100  is arranged on the opening  134 , a container (its reference numeral is omitted) filled with a fluid medium  20  for producing the 3D object is arranged at one side of the optical-transparent component  100 , and the laser light generator  120  is arranged at the other sider thereof. More particularly, the laser light generator  120  is located within the accommodating space  132 . 
         [0040]    In  FIG. 4 , a first photodetector  30 , such as phototransistor, CCD, or COMS sensor, is arranged on the housing  130  and near to the optical-transparent component  100 . The first photodetector  30  is configured to detect spot beam generated by the laser light generator  120 . The first photodetector  30  is, for example, mount on a circuit board  31  arranged on an inner surface  136  of the housing  130 , thus the movable angle of the laser light generator  120  in the scanning procedure can be reduced, and advantages of convenience and accuracy is then provided. The first photodetector  30  is electrically connected to the controller  40 , and the controller  40  is further electrically connected to the laser light generator  120  via conducting wire  312 . 
         [0041]    The controller  40  makes the laser light generator  120  generate spot beam and control the position of the spot beam projecting to the fluid medium while the scanning procedure is performed. The controller  40  further makes the laser light generator  120  stop preforming scanning procedure when the spot beam reaches the first photodetector  30 , and the 3D object generating procedure is performed after the controller  40  makes the spot beam move the preset distance d (from the first calibrating region  104  to the working region  102 ) by positioning the laser light generator  120 . 
         [0042]    Reference is made to  FIG. 5 , which is a schematic view of a part of components of a 3D generating apparatus according to a third embodiment of the present invention. In  FIG. 5 , the 3D object generating apparatus  10  includes an optical-transparent component  100 , a laser light generator  120 , and a housing  130 . A container (its reference numeral is omitted) filled with a fluid medium  20  for producing the 3D and the laser light generator  120  is arranged at the opposite sides of the optical-transparent component  100 . The laser light generator  120  for generating the laser light has a light emitting surface  122  facing the fluid medium  20 , and the laser light is projected to the fluid medium  20  for curing the fluid medium  20 . The housing  130  has an accommodating space  132  and an opening  134  communicating with the accommodating space  130 , the optical-transparent component  100  is arranged on the opening  100 . 
         [0043]    Reference is made to  FIG. 6 , the optical-transparent component  100  includes a working region  102 , a first calibrating region  104 , and a second calibrating region  106 . The working region  102  is between the first calibrating region  104  and the second calibrating region  106  and connected thereto, wherein the area of the working region  102  is not only larger than that of the first calibrating region  104  but also larger than that of the second calibrating region  106 . In  FIG. 6 , the optical-transparent component  100  is, for example, a rectangular, and has a first axis X and a second axis Y perpendicular to the first axis X, wherein the first calibrating region  104  is arranged at the left side of the working region  102  in the first axis X, and the second calibrating region  106  is arranged at the right side of the working region  102  in the first axis X. 
         [0044]    The container filled with the fluid medium  20  for producing the 3D object is arranged at the working region  102 . The laser light generated by the laser light generator  120  is a linear light across the working region  102 , the first calibrating region  104 , and the second calibrating region  106 . More particularly, the length of the linear light generated by the laser light generator  120  is at least equal to that of a line connecting the first photodetector  30  and the second photodetector  32  in the first axis X. 
         [0045]    The first photodetector  30  is arranged on the first calibrating region  104 , and the second photodetector  32  is arranged in the second calibrating region  106 . In particular, the line connecting the first photodetector  30  and the second photodetector  32  is parallel to the first axis X. The first photodetector  30  and the second photodetector  32  are electrically connected to the controller  40 , as shown in  FIG. 7 , and the controller  40  is further electrically connected to the laser light generator  120 . 
         [0046]    The controller  40  receives a first detecting signal sent from the first photodetector  30  and a second detecting signal sent from the second photodetector  32 , and controls acts of the laser light generator  120  is accordance with the first detecting signal and the second detecting signal. The first photodetector  30  and the second photodetector  32  are, for example, phototransistors, CCDs, and CMOS sensors. 
         [0047]    In normal condition, the linear light L generated by the laser light generator  120  is parallel to the first axis X, as shown in  FIG. 8 , and the linear light L can be simultaneously detected by the first photodetector  30  and the second photodetector  32 . In the other words, when the first photodetector  30  and the second photodetector  32  cannot simultaneously detect the linear light L generated by the laser light generator  120  (as shown in  FIG. 9 ), the linear light L is not parallel to the first axis X because the position of the laser light generator  120  is tilted, and therefore the 3D object generating apparatus  10  cannot generate the 3D object in accordance with the 3D model information precisely. 
         [0048]    The following calibrating procedure is employed for calibrating the position of the laser light generator  120  to overcome the problem that the linear light L generated by the laser light generator  120  is not parallel to the first axis X (or called is tilted) and the 3D object generating apparatus  10  cannot generate the 3D object in accordance with the 3D model information precisely. 
         [0049]    At first, the controller  40  makes the laser light generator  120  to generate the linear light L. The length of the linear light L is not smaller than the line connecting to the first photodetector  30  and the second photodetector  32 . After that, the controller  40  makes the laser light generator  120  move along the second axis Y until the linear light L reaches at least one of the first photodetector  30  and the second photodetector  32  (as shown in  FIG. 10 ). At this time, the position of the laser light generator  120  is not tilt while the first photodetector  30  and the second photodetector  32  simultaneously detect the linear light L, and the scanning procedure is completed, and the 3D object generating procedure can be performed. 
         [0050]    However, the position of the laser light generator  120  is tilt in the second axis when the first photodetector  30  and the second photodetector  40  cannot simultaneously detect linear light L. As can be seen in  FIG. 10 , the linear light L only reaches the first photodetector  30 . After that, the controller  40  must makes the laser light generator  120  continuously move along the Y axis until the linear light L reaches the second photodetector  32  (as shown in  FIG. 11 ). 
         [0051]    By calculating the moved distance between the linear light reached the first photodetector  30  and the second photodetector  32  in the Y axis, an inclination (or called the tilted angle) can be obtained by the controller  40 . Reference is made to  FIG. 12 , when the inclination of the laser light generator  120  is A, a distance between the first photodetector  30  and the second photodetector  32  in the first axis is x, and a moved distance of the laser light generator  120  in the second axis is y, the following condition is satisfied: 
         [0000]        A =tan−1( x/y ).
 
         [0052]    In order to calibrate the position of the laser light generator  120  shown in  FIG. 11  with the left side tilted upwards, the controller  40  makes the left side of the laser light generator  120  move downwards with the inclination. After that, the linear light L generated by the laser light generator  120  can be parallel to the first axis A. 
         [0053]    Thereafter, the 3D object generating apparatus  10  can perform the 3D object generating procedure. However, the 3D object generating apparatus  10  can perform the scanning procedure for the second time to make sure the first photodetector  30  and the second photodetector  32  can simultaneously detect the linear light L before performing the 3D object generating procedure 
         [0054]    In should be noted that the first photodetector  30  and the second photodetector  32  cannot be limited to be arranged on the optical-transparent component  100 . As can be shown in  FIG. 13 , the first photodetector  30  and the second photodetector  32  are mount on the housing  130  of the 3D object generating apparatus  10 , wherein  FIG. 13  is a schematic view of a part of components of a 3D object generating apparatus according to a fourth embodiment of the present invention. 
         [0055]    In the  FIG. 13 , the first photodetector  30  and the second photodetector  32  are mount on a circuit board  31  arranged on an inner surface of the housing  130 . The circuit board is close to the optical-transparent component  100 , and the first photodetector  30  and the second photodetector  32  face each other. More particularly, a line connecting to first photodetector  30  and the second photodetector  32  is parallel to the first axis X and has the same horizontal level in the third axis Z. Besides, an emitting angle of the linear light L simultaneously covers the first photodetector  30  and the second photodetector  32 , thus the scanning procedure which is the same as mentioned in the third embodiment can be performed to calibrating whether the laser light generator  120  has the inclination or not, and the controller  40  can calibrate the laser light generator  120  while the inclination is existed. 
         [0056]    Reference is made to  FIG. 14 , which is a schematic view of a 3D object generating apparatus according to the first embodiment of the present invention. In  FIG. 14 , the 3D object generating apparatus  10  includes an optical-transparent component  100  and a laser light generator  120 . The optical-transparent component  100  includes a first surface  101  and a second surface  103  opposite to the first surface  101 . A container (not shown) filled with a fluid medium (not shown) for producing the 3D object are arranged on the first surface  103  of the optical-transparent component  100 , and the spot beam of the laser light generated by the laser light enters the fluid medium via the second surface  103  of the optical-transparent component  100 . The 3D object generating apparatus  10  may further includes an input unit (not shown) for receiving the 3D model information defining the 3D object, and the 3D object is generated within the fluid medium which is selectively cured by spot beam of laser light emitted from the laser light generator  120  brought to selective focus prescribed by the 3D model information. 
         [0057]    In  FIG. 15 , the optical-transparent component  100  includes a working region  102 , a first calibrating region  104 , and a second calibrating region  106 , and the fluid maternal  20  is arranged on the working region  102 . The first calibrating region  102  and the second calibrating region  106  are arranged along a diagonal of the working region  102 , the first calibrating region  104  and the working region  102  overlaps to define a first overlapping region  108 , and the second calibrating region  106  and the working region  102  overlaps to define a second overlap region  110 . 
         [0058]    Reference is made to  FIG. 14 , the laser light generator  120  includes a light emitter  124 , a first scanning mirror  126 , and a second scanning mirror  128 . The light emitter  124  is, for example, laser diode, and is configured to generate light for curing the fluid medium. In the optical path view, the first scanning mirror  126  and the second scanning mirror  128  are arranged between the laser light generator  120  and the optical-transparent component  100 , and the scanning direction of the first scanning mirror  126  is parallel to the second scanning mirror  128 . More particularly, the first scanning mirror  126  is close to the light emitter  122  for expanding the spot beam generated by the light emitter  122  to the linear beam, the second scanning mirror  128  is close to the optical-transparent component  100  for expanding the linear beam generated by the light emitted  122  and expanded by the first scanning mirror  126  to the surface beam and then projected to the optical-transparent component  100 . 
         [0059]    A first photodetector  30  and a second photodetector  32  are arranged on the optical-transparent component  100 , and the first photodetector  30 , the second photodetector  32 , and the laser light generator  120  are arranged at the same side of the optical-transparent component  100 . The first photodetector  30  is in the first overlapping region  108 , the second photodetector  32  is in the second overlapping region  110 , and detecting surface  300 ,  320  of the first photodetector  30  and a second photodetector  32  face the laser light generator  120 . 
         [0060]    The first photodetector  30  and the second photodetector  32  are electrically connected to the controller  40 , as shown in  FIG. 16 . The controller  40  is further electrically connected to the light emitter  124 , the first scanning mirror  126 , and the second scanning mirror  128 . The controller  40  receives the first signal sent from the first photodetector  20  and the second signal sent from the second photodetector  30  and controls the acts of the first scanning mirror  126  and the second scanning mirror  128  according to the first signal and the second signal, thus the position of the surface beam projected to the optical-transparent component  100  can be controlled. 
         [0061]    In normal condition, the surface beam generated by the laser light generator  120  is projected into the working region  102  for curing the fluid medium. However, in abnormal condition, the 3D object generate by the 3D object generating apparatus  10  in accordance with the 3D model information is inaccuracy since the surface beam generated by the laser light generator  120  is tilted and not completely projected to the working region, as shown in  FIG. 17 . 
         [0062]    The following calibrating procedure is employed for calibrating the position of the first scanning mirror  126  and the second scanning mirror  128  to overcome the problem that the position of surface beam cannot reach the working region  102  and the 3D object generating apparatus  10  cannot generate the 3D object in accordance with the 3D model information precisely. 
         [0063]    Referred is made to  FIG. 14  and  FIG. 17 , the calibrating procedure starts with driving the laser light generator  120  to generate the surface beam by a controller  40 . The controller  40  further drives the laser light generator  120  to perform the scanning procedure by positioning the surface beam generated by the laser light generator  120  across the first calibrating region  104  of the optical-transparent component  100 , and receives the first signal in accordance with the radiant intensity of the surface beam sent from the first photodetector. 
         [0064]    Referred is made to  FIG. 18 , which is a graph of relative radiant intensity distribution of the surface beam reaches the first photodetector. As can be seen in  FIG. 18 , when the surface beam projected to the first overlapping region  108  is directly inject into the first photodetector  30  (when an axis of the surface beam is aligned with the axis of the first photodetector  30  or the distance between the optical axes of the surface beam and the first photodetector  30  is zero), the highest radian intensity is obtained by the first photodetector  30 , and when the distance between the axes between the surface beam and the first photodetector  30  is increased, the radian intensity obtained by the first photodetector  30  is decreased. Thus, the position of the first photodetector  30  arranged on the optical-transparent component  100  can be obtained according to the peak value of the first signal. 
         [0065]    Thereafter, the controller  40  make the surface beam of the laser light generated by the laser light generator  120  projected to the second calibrating region  106  and perform scanning procedure within the second calibrating region  106 . Thus, the position of the second photodetector  32  arranged on the optical-transparent component  100  can be obtained according to the peak value of the second signal representing the radial intensities while the surface beam calibrating in the second calibrating region  106 . 
         [0066]    The controller  40  can make the first scanning mirror  126  and/or the second scanning mirror  128  change the scanning angle(s) after obtaining the positions of the first photodetector  30  and the second photodetector  32  according to the first signal and the second signal, thus the surface beam of the laser light generated by the laser light generator  120  can precisely project to the working region  102 . 
         [0067]    Thereafter, the 3D object generating apparatus  10  can perform the 3D object generating procedure. However, the 3D object generating apparatus  10  can perform the scanning procedure for the second time to make sure the surface beam generated by the laser light generator  120  is precisely projected to the working region  102 . 
         [0068]    In should be noted that the first photodetector  30  and the second photodetector  32  cannot be limited to be arranged on the optical-transparent component  100 . As can be shown in  FIG. 19 , the first photodetector  30  and the second photodetector  32  are arranged on the housing  130  of the 3D object generating apparatus  10 , wherein  FIG. 19  is a schematic view of a part of components of a 3D object generating apparatus according to a fourth embodiment of the present invention. 
         [0069]    In the  FIG. 19 , the 3D object generating apparatus includes an optical-transparent component  100 , a laser light generator  120 , and a housing  130 . The housing  130  includes an accommodating space  132  and an opening  134  communicating with the accommodating space  132 . The optical-transparent component  100  is arranged on the opening  134 , the laser light generator  120  is arranged within the accommodating space  132 , and the first photodetector  30  and the second photodetector  32  are arranged on an inner surface  136  of the housing  130 , wherein the inner surface  136  is, for example, connected to the optical-transparent component  100 . 
         [0070]    The line for connecting the first photodetector  30  and the second photodetector  32  is parallel to the diagonal of the optical-transparent component  100 . When the scanning procedure is performed, the controller  40  makes the laser light generator  120  generate the surface beam for obtaining the positions of the first photodetector  30  and the second photodetector  32 , and then makes the first scanning mirror  126  and the second scanning mirror  128  adjust rotating angle when the surface beam is not precisely projected to the working region  102 . After that, the surface beam generated by the laser light generator  120  can be precisely projected to the working region. 
         [0071]    Thereafter, the 3D object generating apparatus  10  can perform the 3D object generating procedure. However, the 3D object generating apparatus  10  can perform the scanning procedure for the second time to make sure the surface beam generated by the laser light generator  120  is precisely projected to the working region  102 . 
         [0072]    Although the present invention has been described with reference to the foregoing preferred embodiment, it will be understood that the invention is not limited to the details thereof. Various equivalent variations and modifications can still occur to those skilled in this art in view of the teachings of the present invention. Thus, all such variations and equivalent modifications are also embraced within the scope of the invention as defined in the appended claims.