Patent Publication Number: US-2019195455-A1

Title: Headlight device

Description:
TECHNICAL FIELD 
     The disclosure relates to a headlight device. 
     BACKGROUND 
     Vehicle all have headlight device to illuminate the front for drives. The conventional headlight device uses a bulb as light source, and the bulb is surrounded and covered by a semi-ellipsoid reflecting mirror and cooperates with a symmetrical lens, such that light emitted by the bulb is able to be projected to the front of the vehicle. In order to prevent a sight from being disturbed by the light from another vehicle coming in the opposite direction, there is a regulation about a light pattern of the headlight device to ensure the illuminating range of the headlight device is sufficient, and also about a clear cut-off line of the light pattern for preventing mutual disturbing from vehicles coming from opposite directions. 
     The conventional headlight device only can project light to the front of the vehicle, if the vehicle is moving on a winding mountain road, the drive is not able to recognize the road behind corner. Therefore, an adaptive front lighting system is developed for adjusting the light projecting direction of the headlight device as the steering wheel turns. However, the semi-ellipsoid reflecting mirror and the symmetric lens are larger and heavy, it will cause the headlight device insensitive in turning, making the conventional headlight device unable to immediately turn to the desired direction, such that the driver is unable to recognize the road behind the corner, and such headlight device is also hard to meet the regulation. 
     SUMMARY 
     The disclosure provides a headlight device, which is thin and lightweight and is capable of solving the aforementioned problems that the headlight cooperated with the adaptive front lighting system is not sensitive in turning the projecting direction. 
     One embodiment of the disclosure provides a headlight device which includes a light source, a reflector, a Fresnel lens and a blocking plate. The light source is disposed on a circuit board, and has a light emitting surface. The reflector is disposed on a side of the circuit board and covers the light source. The reflector has a reflecting surface facing the light emitting surface, and an opening is formed by a side of the reflecting surface. An angle formed by a direction of the opening and the normal line of the light emitting surface is equal to or greater than 90 degrees. The Fresnel lens is located on a side of the opening opposite to the light source. A light beam emitted from the light emitting surface is reflected by the reflecting surface and then passes through the Fresnel lens. The light beam converges towards an energy convergence area on a vertical plane, and the blocking plate is located between the vertical plane and the light source in order to block part of the light beam so as to create a light pattern having a cut-off. A reference plane is defined to perpendicular to the opening, and an optical axis of the light source is on the reference plane. The reflecting surface and the reference plane intersect at a curved line on the reflecting surface, and the curved line has an opening end and a connecting end opposite to each other. The connecting end is located on a side of the reflector close to the circuit board. The curved line is defined by a quadratic Bezier curved function, and the quadratic Bezier curved function comprises: 
         B   x ( t )=(1− t ) 2   P   0x +2 t (1− t ) P   1x   +t   2   P   2x   , t ∈[0,1]; and
 
         B   y ( t )=(1− t ) 2   P   0y +2 t (1− t ) P   1y   +t   2   P   2y   , t ∈[0,1];
 
     wherein the connecting end is an origin of a coordinate, the X-coordinate and the Y-coordinate of the connecting end are respectively P 0x  and P 0y , the X-coordinate and the Y-coordinate of the opening end are respectively P 2x  and P 2y , the X-coordinate and the Y-coordinate of a reference point in adjusting the curvature of the curved line are respectively P 1x  and P 1y , the coefficient in determining any point on the curved line is t, and the X-coordinate and the Y-coordinate of any point on the curved line are respectively B x (t) and B y (t). 
     According to the headlight device as discussed above, with the cooperation of the reflecting surface of the reflector, which is defined by the quadratic Bezier curved function, and the blocking plate, the light pattern produced by the light beam, emitted by the light source and then passing through the Fresnel lens, not only can meet the requirement of the regulation, but also can decrease the volume and the weight of the headlight device, thereby increasing the turning sensitivity of the headlight device cooperated with the adaptive front lighting system. 
     In addition, the Fresnel lens is smaller and lighter than the lens in the conventional headlight device, which also helps to increase the turning sensitivity of the headlight device cooperated with the adaptive front lighting system. 
     The aforementioned summary and the following detailed description are set forth in order to provide a thorough understanding of the disclosed embodiment and provide a further explanations of claims of the disclosure 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a headlight device according to a first embodiment of the disclosure. 
         FIG. 2  is a cross-sectional view of  FIG. 1 . 
         FIG. 3  is a contour diagram of illuminance produced by the headlight device in  FIG. 1 . 
         FIG. 4  is a cross-sectional view of a headlight device according to a second embodiment of the disclosure. 
         FIG. 5  is a contour diagram of illuminance produced by the headlight device in  FIG. 4 . 
         FIG. 6  is a cross-sectional view of a headlight device according to a third embodiment of the disclosure. 
         FIG. 7  is a contour diagram of illuminance produced by the headlight device in  FIG. 6 . 
         FIG. 8  is a cross-sectional view of a headlight device according to a fourth embodiment of the disclosure. 
         FIG. 9  is a contour diagram of illuminance produced by the headlight device in  FIG. 8 . 
         FIG. 10  is a cross-sectional view of a headlight device according to a fifth embodiment of the disclosure. 
         FIG. 11  is a contour diagram of illuminance produced by the headlight device in  FIG. 10 . 
         FIG. 12  is a cross-sectional view of a headlight device according to a sixth embodiment of the disclosure. 
         FIG. 13  is a contour diagram of illuminance produced by the headlight device in  FIG. 12 . 
         FIG. 14  is a cross-sectional view of a headlight device according to a seventh embodiment of the disclosure. 
         FIG. 15  a contour diagram of illuminance produced by the headlight device in  FIG. 14 . 
         FIG. 16  is a front view of a Fresnel lens according to an eighth embodiment of the disclosure. 
         FIG. 17  is a front view of a Fresnel lens according to a ninth embodiment of the disclosure. 
         FIG. 18  is a front view of a Fresnel lens according to a tenth embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIG. 1  and  FIG. 2 .  FIG. 1  is a perspective view of a headlight device according to a first embodiment of the disclosure.  FIG. 2  is a cross-sectional view of  FIG. 1 . 
     The headlight device  10   a  of this embodiment is able to be cooperated with an adaptive front lighting system. The headlight device includes a light source  100   a , a circuit board  200   a , a reflector  300   a , a Fresnel lens  400   a  and a blocking plate  500   a . The light source  100   a  and the reflector  300   a  are disposed on the circuit board  200   a . After a light beam  111   a  emitted by the light source  100   a  is reflected and converged by the reflector  300   a , it will enter into the Fresnel lens  400   a  to be refracted and exist to form a collimating light beam adapting for vehicle lighting. The blocking plate  500   a  blocks part of the light beam  111   a  to create a light pattern having a cut-off line. 
     The light source  100   a  of this embodiment is, for example, a Lambertian source. In this embodiment, the light source  100   a  has, for example, a plurality of LEDs in an array arrangement and a guiding cover, and the guiding cover is located on an illuminating side of the LEDs in order to soften the light emitted by the LEDs and prevent the light from producing a moire fringe pattern. The light source  100   a  has a light emitting surface  110   a , and the light beam  111   a  emitted from the light emitting surface  110   a  of the light source  100   a  has an optical axial light ray  1111   a  and edge light rays  1112   a . The optical axial light ray  1111   a  overlaps an optical axis I of the light source  100   a , and the light energy of the optical axial light ray  1111   a  is greater than the light energy of the edge light rays  1112   a . The light beam  111   a  emitting from the emitting surface  110   a  has a divergence angle α equal to 90 degrees for instance. The divergence angle α is defined by the two edge light rays  1112   a  which are respectively located on two opposite sides of the optical axial light ray  1111   a . In this embodiment, the divergence angle α of the light beam  111   a  emitted from the light emitting surface  110   a  is equal to 90 degrees, but the present disclosure is not limited thereto. In some other embodiments, the divergence angle α of the light beam  111   a  emitted from the light emitting surface  110   a  may range between 90 degrees and 120 degrees. 
     In the headlight device  10   a  of this embodiment, the reflector  300   a  is a half covering-type mirror. The reflector  300   a  is disposed on a side of the circuit board  200   a , and covers the light source  100   a . The reflector  300   a  has a reflecting surface  310   a  facing the light emitting surface  110   a  of the light source  100   a . A side of the reflecting surface  310   a  surrounds and forms an opening  311   a , a direction of the opening  311   a  and a normal line N 2  of the light emitting surface  110   a  have an angle β; the angle β is an angle between a normal line N 1  of a plane P 1 , where the opening  311   a  is located, and the normal line N 2  of the light emitting surface  110   a , and the angle β is equal to or greater than 90 degrees. In this embodiment, the angle β is 90 degrees. In addition, the plane P 1 , where the opening  311   a  is located, is aligned with an edge of the circuit board  200   a , but the present disclosure is not limited thereto. In some other embodiments, a circuit board may indent from a plane, where the opening is located, or may stick out from the plane where the opening is located. 
     Then, a reference plane P 2  is defined. The reference plane P 2  is perpendicular to the plane P 1 , where the opening  311   a  is located, and the optical axis I of the light source  100   a  is located on the reference plane P 2 . In detail,  FIG. 2  is a cross-section view of the headlight device  10   a  taken on the reference plane P 2 . The reflecting surface  310   a  and the reference plane P 2  intersect at a curved line  312   a  on the reflecting surface  310   a , and the curved line  312   a  has an opening end  3121   a  and a connecting end  3122   a . The opening end  3121   a  is located on the plane P 1 , where the opening  311   a  is located, and the connecting end  3122   a  is located on a side of the reflector  300   a  close to the circuit board  200   a . The curved line  312   a  is defined by a quadratic Bezier curved function, and the function includes: 
         B   x ( t )=(1− t ) 2   P   0x +2 t (1− t ) P   1x   +t   2   P   2x   , t ∈[0,1]; and
 
         B   y ( t )=(1− t ) 2   P   0y +2 t (1− t ) P   1y   +t   2   P   2y   , t ∈[0,1].
 
     The connecting end  3122   a  is an origin of a coordinate, and the X-coordinate and the Y-coordinate of the connecting end  3122   a  are respectively P 0x  and P 0y . The X-coordinate and the Y-coordinate of the opening end  3121   a  are respectively P 2x  and P 2y . The X-coordinate and the Y-coordinate of a reference point in adjusting the curvature of the curved line  312   a  are respectively P 1x  and P 1y . The coefficient in determining any point on the curved line  312   a  is t. The X-coordinate and the Y-coordinate of any point on the curved line  312   a  are respectively B x (t) and B y (t). 
     The Fresnel lens  400   a  is located on another side of the opening  311   a  which is opposite to the light source  100   a . The Fresnel lens  400   a  includes a central part  410   a , an upper part  420   a  and a lower part  430   a . The central part  410   a  is located between the upper part  420   a  and the lower part  430   a , and the upper part  420   a  is closer to the opening end  3121   a  of the curved line  312   a  than the lower part  430   a . In this embodiment, the light beam  111   a  is reflected by the reflecting surface  310   a  and then converges towards an energy convergence area. The so-called energy convergence area is where the smallest cross section of the light beam  111   a  being reflected by the reflector  300   a . In addition, in this embodiment, a vertical plane P 3 , where the energy convergence area is located, is located on a side of the Fresnel lens  400   a  away from the light source  100   a ; that is, behind the Fresnel lens  400   a . Therefore, the optical axial light ray  1111   a  being reflected by the reflecting surface  310   a  of the reflector  300   a  will enter into the upper part of the Fresnel lens  400   a.    
     Then, a relationship between a position on the Fresnel lens  400   a , where the optical axial light ray  1111   a  passes through, and a position of the vertical plane P 3 , where the energy convergence area is located, is illustrated from a position of the light source  100   a  and the shape of the curved line  312   a . By adjusting the position of the light source  100   a  (i.e. adjusting a distance between the light source  100   a  and the connecting end  3122   a  of the reflector  300   a ), the optical axial light ray  1111   a , after being reflected by the reflecting surface  310   a  of the reflector  300   a , is ensured to be converged downwards and then to enter into the Fresnel lens  400   a . Basically, the following condition is required: |B y (t x )/tan(Φ)|≥L−X, wherein t x  is a coefficient in determining a point on the curved line  312   a  which is corresponding to the light source  100   a , angle Φ is an angle between the optical axial light ray  1111   a  of the light source  100   a  after being reflected by the reflecting surface  310   a  and the direction (i.e. the normal line N 1 ) of the opening  311   a , L is a horizontal distance between the opening end  3121   a  and the connecting end  3122   a , and X is a distance between the light source  100   a  and the connecting end  3122   a  of the reflector  300   a.    
     More specifically, when the condition that the optical axial light ray  1111   a , after being reflected by the reflecting surface  310   a  and leaving from the reflector  300   a , converges downwards is satisfied, the vertical plane P 3 , where the energy convergence area is located, is converged and located on the side of the Fresnel lens  400   a  away from the light source  100   a . The following condition is required: |B y (t x )/tan(Φ)|≥D, wherein D is a distance between the light source  100   a  and the Fresnel lens  400   a . At this moment, the optical axial light ray  1111   a , after being reflected by the reflecting surface  310   a , will enter into the upper part  420   a  of the Fresnel lens  400   a.    
     The aforementioned paragraphs describe the condition that the optical axial light ray  1111   a  enters into the upper part of the Fresnel lens  400   a  after being reflected by the reflector  300   a , but the present disclosure is not limited thereto. In some other embodiments, a position of the light source or a shape of the curved line may be adjusted to change the vertical plane P 3  to a side of the Fresnel lens  400   a  close to the light source  100   a ; that is between the Fresnel lens  400   a  and the light source  100   a . By doing so, after the optical axial light ray  1111   a  being reflected, it will be changed to enter into the lower part  430   a . In detail, if it is attempted to make the optical axial light ray  1111   a  to enter into the lower part  430   a  of the Fresnel lens  400   a  after being reflected by the reflecting surface  310   a , the vertical plane P 3 , where the energy convergence area is located, would be located between the Fresnel lens  400   a  and the light source  100   a , and then the position of the light source  100   a  is able to be adjusted in order to satisfy the following condition: |B y (t x )/tan(Φ)|≤D. 
     Therefore, no matter the optical axial light ray  1111   a  enters into the upper part  420   a  or the lower part  430   a , the part of the Fresnel lens  400   a , where the optical axial light ray  1111   a  does not pass through, is able to be cut off. For example, when the optical axial light ray  1111   a  enters into the upper part  420   a , the part of the lower part  430   a  is able to be cut off. On the contrary, the part of the upper part  420   a  would be cut off. By doing so, the volume and weight of the Fresnel lens  400   a  are further decreased. 
     The blocking plate  500   a  is disposed between the vertical plane P 3 , where the energy convergence area is located at, and the light source  100   a . More specifically, the blocking plate  500   a  is located between the Fresnel lens  400   a  and the light source  100   a , and the blocking plate  500   a  leans on the edge of the circuit board  200   a . To ensure that the optical axial light ray  1111   a  would not be blocked by the blocking plate  500   a  after being reflected by the reflector  300   a  and to make the blocking plate  500   a  effectively block the others to form a light patter having a cut-off line, it requires to meet the following condition: M≤B y (t x ), wherein M is a vertical distance between the highest point of the blocking plate  500   a  and the connecting end  3122   a.    
     In this embodiment, the blocking plate  500   a  leans on the circuit board  200   a , but the present disclosure is not limited thereto. In some other embodiments, the blocking plate  500   a  may not lean on the edge of the circuit board  200   a , and the blocking plate  500   a  and the circuit board  200   a  may be spaced apart by a distance, and the distance between the blocking plate  500   a  and the Fresnel lens  400   a  requires to be smaller than or equal to the focal length of the Fresnel lens  400   a ; that is, the blocking plate  500   a  is located between the focus of the Fresnel lens  400   a  and the Fresnel lens  400   a  or is located on the focus of the Fresnel lens  400   a . In addition, if the blocking plate  500   a  and the circuit board  200   a  are spaced apart by a distance, the overall length of the blocking plate  500   a  is required to be large enough to block the opening  311   a  of the reflector  300   a  to prevent the scattered light from entering into the Fresnel lens  400   a.    
     Among them, the optical axial light ray  1111   a  when being reflected by the reflecting surface  310  of the reflector  300   a  has an incident angle θ 1  and a reflected angle θ 2 . To ensure that the optical axial light ray  1111   a  would converge and form the energy convergence area with other edge light rays  1112   a  after being reflected by the reflecting surface  310   a , the incident angle θ 1  and the reflected angle θ 2  both are required to be smaller than 45 degrees while designing the curved line  312   a.    
     To achieve that the incident angle θ 1  and the reflected angle θ 2  of the optical axial light ray  1111   a  are smaller than 45 degrees, the coefficient t x  in determining a point on the curved line  312   a  which is corresponding to the light source  100   a  is required to be greater than 0.35, so that the X-coordinate of the light source  100   a  is required to meet the following condition: B x (t x )=(1−t x ) 2 P 0x +2t x (1−t x )P 1x +t x   2 P 2x , t x ∈(0.35,1], wherein the B x (t x ) is the X-coordinate of the light source  100   a . Thus, the minimum value of the X-coordinate of the light source  100   a  is obtained. 
     In order to ensure that the light beam  111   a  emitted by the light source  100   a  can be reflected by the reflector  300   a , the maximum value of the X-coordinate of the light source  100   a  is required to meet the following condition: L−H≥X, wherein H is a vertical distance between the opening end  3121   a  and the connecting end  3122   a.    
     Therefore, the minimum value and the maximum value of the X-coordinate of the light source  100   a  are obtained by deriving the aforementioned conditions, i.e. (0.65 2 P 0x +0.7 (1−0.35)P 1x +0.35 2 P 2x )&lt;B x (t x )&lt;L−H. 
     In order to ensure that the light beam  111   a  after being reflected and then passing through the Fresnel lens  400   a  would not overly diverge and still meet the regulation of the light pattern, the minimum angle is defined by the optical axial light ray  1111   a , after being reflected by the reflecting surface  310   a , and the direction of the opening  311   a  and is required to be −28.78 degrees, and a luminous intensity direction passing through the Fresnel lens  400   a  and the direction of the opening  311   a  are required to have an angle ranging between 0 degree and −2 degrees, wherein negative value of the angles represents the angles below the direction of the opening  311   a . The so-called luminous intensity direction is a path of a light ray in the light beam  111   a  which has the greatest luminous intensity and passes through the Fresnel lens  400   a.    
     In other words, no matter how much the coefficient of the curved line  312   a  of the reflector  300   a  is, the angle between the optical axial light ray  1111   a , after being reflected by the reflecting surface  310   a , and the direction of the opening  311   a  must be greater than −28.78 degrees. In addition, except the limitation of the angle between the optical axial light ray  1111   a , after being reflected by the reflecting surface  310   a , and the direction of the opening  311   a , the angle between the luminous intensity direction and the direction of the opening  311   a  can be ranging between 0 degree and −2 degrees by, for example, adjusting the curvature of the Fresnel lens  400   a , or vertically moving upward the Fresnel lens  400   a  to utilize the stronger refractive power of the downside of the Fresnel lens  400   a.    
     The following is a practical example, wherein the X-coordinate and the Y-coordinate of the connecting end  3122   a  of the curved line  312   a  on the reflector  300   a  at the reference plane P 2  are respectively 0 and 0, the X-coordinate and the Y-coordinate of the connecting end  3122   a  of the curved line  312   a  are respectively 45 and 29.5, and the X-coordinate and the Y-coordinate of the reference point are respectively 0 and 17.728. 
     According to the aforementioned arrangement, the distance between the connecting end  3122   a  of the curved line  312   a  and the plane P 1 , where the opening  311   a  is located, is 45 mm (i.e. the horizontal distance L between the opening end  3121   a  and the connecting end  3122   a ), and the vertical distance H between the opening end  3121   a  and the connecting end  3122   a  is 29.5 mm. As such, the maximum value of the X-coordinate of the light source  100   a  is L-H=15.5 mm. In addition, under the condition that the incident angle θ 1  and reflected angle θ 2  of the optical axial light ray  1111   a  both are required to be smaller than 45 degrees, the minimum value of the X-coordinate of the light source  100   a  is 5.5. Therefore, the light source  100   a  is able to be disposed at a position that distances between 5.5 mm and 15.5 mm from the connecting end  3122   a , i.e. the distance between the light source  100   a  and the connecting end  3122   a  of the reflector  300   a  ranges from 5.5 mm to 15.5 mm. 
     Then, in an example, the distance X between the light source  100   a  and the connecting end  3122   a  of the curved line  312   a  is 7 mm, the distance D between the light source  100   a  and the Fresnel lens  400   a  is 76 mm, and the front focal length, the diameter and the thickness of the Fresnel lens  400   a  are respectively 44.598 mm, 55 mm and 7 mm. 
     According to the aforementioned arrangement, when the angle between the normal line N 1  of the plane P 1 , where the opening  311   a  is located, and the normal line N 2  of the light emitting surface  110   a  is 90 degrees, and the divergence angle α of the light source  100   a  is equal to 90 degrees, then obtain: t x =0.395, B y (t x )=13.23, and tan(Φ)=0.095. 
     As such, B y (t x )/tan(Φ)=139.3 and D=76, and that satisfy the condition of |B y (t x )/tan(Φ)|≥D. That is, the optical axial light ray  1111   a  enters into the upper part  420   a  of the Fresnel lens  400   a  after being reflected by the reflector  300   a , and the vertical plane P 3 , where the energy convergence area is located, is located on the side of the Fresnel lens  400   a  away from the light source  100   a.    
     In addition, B y (t x )/tan(Φ)=139.3 and L−X=38 satisfy the condition of B y (t x )/tan(Φ)&gt;L−X. That is, the optical axial light ray  1111   a , after being reflected by the reflector  300   a , would converge downward to enter into the Fresnel lens  400   a.    
     Please refer to  FIG. 3 .  FIG. 3  is a contour diagram of illuminance produced by the headlight device in  FIG. 1 . In the aforementioned examples, it can be seen that the light beam  111   a , passing through the Fresnel lens  400   a  and then projecting on a wall at 25 m away, creates a clear cut-off line, and the greater illuminance area is concentrated on the central area of the wall. That is, the reflecting surface  310   a  of the reflector  300   a , which is defined by the quadratic Bezier curved function, with the help of the blocking plate  500   a  can make the light pattern, produced by the light beam emitted by the light source  100   a  and then passing through the Fresnel lens  400   a , meets the requirement of the regulation. 
     In addition, in this embodiment, the position of the light source  100   a  can be adjusted by adjusting the distance X between the light source  100   a  and the connecting end  3122   a  of the reflector  300   a , such that the optical axial light ray  1111   a , after being reflected by the reflector  300   a , is able to be adjusted to enter into the upper part  420   a  or the lower part  430   a  of the Fresnel lens  400   a , and the part of the Fresnel lens  400   a  which is not passed by the optical axial light ray  1111   a  is able to be cut off, thereby further decreasing the volume and weight of the Fresnel lens  400   a . As such, the Fresnel lens  400   a  is lightweight, and it helps to decrease the volume and weight of the overall headlight device  10   a , such that the turning sensitivity of the headlight device  10   a  cooperated with the adaptive front lighting system is able to be increased. 
     The aforementioned embodiment adopts the Fresnel lens, but the present disclosure is not limited thereto. Please refer to  FIG. 4  and  FIG. 5 .  FIG. 4  is a cross-sectional view of a headlight device according to a second embodiment of the disclosure.  FIG. 5  is a contour diagram of illuminance produced by the headlight device in  FIG. 4 . 
     In a headlight device  10   b  of this embodiment, it adopts a hemisphere-type lens  400   b , and the front focal length, the back focal length, the diameter and the thickness of the lens  400   b  are respectively 44.598 mm, 60.533 mm, 55 mm and 23.8 mm. The X-coordinate and the Y-coordinate of a connecting end  3122   b  of a curved line  312   b  of a reflector  300   b  on a reference plane P 2  are respectively 0 and 0, the X-coordinate and the Y-coordinate of an opening end  3121   b  of the curved line  312   b  are respectively 45 and 29.5, the X-coordinate and the Y-coordinate of a reference point of the curved line  312   b  are respectively 0 and 17.728. A distance X between the connecting end  3122   b  of the curved line  312   b  and a light source  100   b  is 7 mm, a horizontal distance L between the connecting end  3122   b  of the curved line  312   b  and the opening end  3121   b  is 45 mm. The distance D between the light source  100   b  and the lens  400   b  is 76 mm. 
     The headlight device  10   b  in this embodiment is similar to the aforementioned headlight device  10   a , and they are only different in appearance (the Fresnel lens  400   a  and the lens  400   b ). Therefore, a path of an optical axial light ray  1111   b  emitted by the light source  100   b  before entering into the lens  400   b  would be the same as that of the aforementioned embodiment because the reflectors  300   b  are the same in shape, so it is not repeated hereinafter. 
     However, the lens  400   b  of this embodiment is the optically equivalent lens of the aforementioned Fresnel lens  400   a . Therefore, the Fresnel lens  400   a  and the lens  400   b  have similar characteristics, for example, they have similar capability of refracting and converging light. The Fresnel lens  400   a  and the lens  400   b  have one difference is that the thickness of the lens  400   b  would make a light ray enter into different position of the curved surface of the lens  400   b  resulting in different refractive power. Therefore, the strength of the refractive power is able to be adjusted by vertically moving the lens  400   b.    
     In detail, by moving the lens  400   b  upward, a central axis C, passing through the lens  400   b , and the connecting end  3122   b  have a vertical distance K therebetween, and the distance K is, for example, 5.5 mm. In other words, the central axis C of the lens  400   b  is moved 5.5 mm upward from the connecting end  3122   b , and an illuminance contour diagram produced by the lens  400   b  is shown in  FIG. 5 . 
     According to the aforementioned arrangement, it can be seen that a clear cut-off line on a wall at 25m away is produced by the headlight device  10   b , and the greater illuminance area is concentrated on the central area of the wall. As such, a light pattern produced by the headlight device  10   b  meets the requirement of the regulation. 
     To further compare with  FIG. 2  and  FIG. 4 , although the lens  400   b  in the embodiment of  FIG. 4  is the equivalent lens of Fresnel lens  400   a  in the embodiment of  FIG. 2  and is able to produce similar effect, the volume of the headlight device  10   a  having symmetrically disposed and flat Fresnel lens  400   a  is 33.05% of the volume of the headlight device  10   b  having the lens  400   b.    
     The light source, the Fresnel lens and the curved line of the reflector in the aforementioned embodiments are not restricted. Please refer to  FIG. 6  and  FIG. 7 .  FIG. 6  is a cross-sectional view of a headlight device according to a third embodiment of the disclosure.  FIG. 7  is a contour diagram of illuminance produced by the headlight device in  FIG. 6 . 
     In a headlight device  10   c  of this embodiment, the X-coordinate and the Y-coordinate of a connecting end  3122   c  of a curved line  312   c  of a reflector  300   c  on a reference plane P 2  are respectively 0 and 0, the X-coordinate and the Y-coordinate of an opening end  3121   c  of the curved line  312   c  are respectively 33.395 and 25.008, and the X-coordinate and the Y-coordinate of a reference point of the curved line  312   c  are respectively 1.820 and 18.691. A distance X between the connecting end  3122   c  of the curved line  312   c  and a light source  100   c  is 8.395 mm, a horizontal distance L between the connecting  3122   c  of the curved line  312   c  and the opening end  3121   c  is 33.395 mm. A distance D between the light source  100   c  and a Fresnel lens  400   c  is 68.5 mm. In addition, a vertical distance K between a central axis C of the Fresnel lens  400   c  and the connecting end  3122   c  is 4 mm, and a vertical distance M between the highest point of a blocking plate  500   c  and the connecting end  3122   c  is 4.5 mm, wherein the highest point and the lowest point on an upper edge of the blocking plate  500   c  have a vertical distance of 1 mm therebetween. 
     As shown in  FIG. 6 , according to the aforementioned arrangement, an optical axial light ray  1111   c , after being reflected by the reflector  300   c , would then enter into an upper part  420   c  of the Fresnel lens  400   c , such that a vertical plane P 3 , where an energy convergence area is located, is located on a side of the Fresnel lens  400   c  away from the light source  100   c.    
     According the aforementioned arrangement, it can be seen that a clear cut-off line on a wall at 25m away is produced by the headlight device  10   c , and the greater illuminance area is concentrated on central area of the wall, such that a light pattern produced by the headlight device  10   c  meets the requirement of the regulation. 
     The energy convergence areas produced by the headlight devices of the aforementioned embodiments are located on the side of the Fresnel lens away from the light source, but the present disclosure is not limited thereto. Please refer to  FIG. 8  and  FIG. 9 .  FIG. 8  is a cross-sectional view of a headlight device according to a fourth embodiment of the disclosure.  FIG. 9  is a contour diagram of illuminance produced by the headlight device in  FIG. 8 . 
     In a headlight device  10   d  of this embodiment, the X-coordinate and the Y-coordinate of a connecting end  3122   d  of a curved line  312   d  of a reflector  300   d  on a reference plane P 2  are respectively 0 and 0, the X-coordinate and the Y-coordinate of an opening end  3121   d  of the curved line  312   d  are respectively 43.063 and 25.050, and the X-coordinate and the Y-coordinate of a reference point of the curved line  312   d  are respectively 4.553 and 25.185. A distance X between the connecting end  3122   d  of the curved line  312   d  and a light source  100   d  is 10.063 mm, and a horizontal distance L between the connecting end  3122   d  of the curved line  312   d  and the opening end  3121   d  is 43.063 mm. A distance D between the light source  100   d  and a Fresnel lens  400   d  is 76.5 mm. In addition, a vertical distance K between a central axis C of the Fresnel lens  400   d  and the connecting end  3122   d  is 4 mm, and a vertical distance M between the highest point of a blocking plate  500   d  and the connecting end  3122   d  is 4.5 mm, wherein the highest point and the lowest point on an upper edge of the blocking plate  500   d  have a vertical distance of 1 mm therebetween. 
     As shown in  FIG. 8 , according to the aforementioned arrangement, an optical axial light ray  1111   d , after being reflected by the reflector  300   d , then enters into a lower part  430   d  of the Fresnel lens  400   d , such that a vertical plane P 3 , where an energy convergence area is located, is located between the Fresnel lens  400   d  and the light source  100   d.    
     According to the aforementioned arrangement, it can be seen that a clear cut-off line on a wall at 25m away is produced by the headlight device  10   d , and the greater illuminance area is concentrated on central area of the wall in  FIG. 9 , such that a light pattern produced by the aforementioned headlight device  10   d  meets the requirement of the regulation. 
     In the headlight devices of the aforementioned embodiments, the angle β between the normal line N 2  of the light emitting surface of the light source and the normal line N 1  of the plane P 1 , where the opening is located, is 90 degrees, but the angle β is not restricted. Please refer to  FIG. 10  and  FIG. 11 .  FIG. 10  is a cross-sectional view of a headlight device according to a fifth embodiment of the disclosure.  FIG. 11  is a contour diagram of illuminance produced by the headlight device in  FIG. 10 . 
     In this embodiment, a headlight device  10   e  is similar to the headlight device  10   a  in  FIG. 2 . A normal N 1  of a plane P 1 , where an opening  311   e  is located, and a normal line N 2  of a light emitting surface  110   e  of a light source  100   e  have an angle β of 100 degrees, and a distance between a blocking plate  500   e  and a Fresnel lens  400   e  of the headlight device  10   e  is increased to 43.5 mm, such that a distance D between the light source  100   e  and the Fresnel lens  400   e  is 81.5 mm. A vertical distance K between a central axis C of the Fresnel lens  400   d  and a connecting end  3122   e  is 4 mm, and a vertical distance M between the highest point of a blocking plate  500   e  and the connecting end  3122   e  is 4.5 mm, wherein the highest point and the lowest point on an upper edge the blocking plate  500   e  have a vertical distance of 1 mm therebetween. 
     According to the aforementioned arrangement, it can be seen that a clear cut-off line is produced on a wall at 25m away by the headlight device  10   e , and the greater illuminance area is concentrated on central area of the wall, such that a light pattern produced by the aforementioned headlight device  10   e  meets the requirement of the regulation. 
     Then, please refer to  FIG. 12  and  FIG. 13 .  FIG. 12  is a cross-sectional view of a headlight device according to a sixth embodiment of the disclosure.  FIG. 13  is a contour diagram of illuminance produced by the headlight device in  FIG. 12 . 
     In this embodiment, a headlight device  10   f  is similar to the headlight device  10   e  of  FIG. 10 . It is noted that that an angle θ between a normal line N 1  of a plane P 1 , where an opening  311   f  is located, and a normal line N 2  of a light emitting surface  110   f  of a light source  100   f  is 110 degrees. 
     According to the aforementioned arrangement, it can be seen that a clear cut-off line is produced on a wall at 25m away by the headlight device  10   f , and the greater illuminance area is concentrated on central area of the wall, such that a light pattern produced by the aforementioned headlight device  10   f  meets the requirement of the regulation. 
     Then, please refer to  FIG. 14  and  FIG. 15 .  FIG. 14  is a cross-sectional view of a headlight device according to a seventh embodiment of the disclosure.  FIG. 15  is a contour diagram of illuminance produced by the headlight device in  FIG. 14 . 
     In this embodiment, a headlight device  10   g  is similar to the headlight device  10   e  of  FIG. 10 . It is noted that an angle θ between a normal line N 1  of a plane P 1 , where an opening  311   g  is located, and a normal line N 2  of a light emitting surface  110   g  of a light source  100   g  is 120 degrees. 
     According to the aforementioned arrangement, it can be seen that a clear cut-off line is produced on a wall at 25m away by the headlight device  10   g , and the greater illuminance area is concentrated on central area of the wall, such that a light pattern produced by the aforementioned headlight device  10   g  meets the requirement of the regulation. 
     The Fresnel lenses in the aforementioned embodiments are all symmetric lenses, but the present disclosure is not limited thereto. Please refer to  FIG. 16  to  FIG. 18 .  FIG. 16  is a front view of a Fresnel lens of a headlight device according to an eighth embodiment of the disclosure. As shown in  FIG. 16 , in a Fresnel lens  400   h  of this embodiment, part of a lower part  430   h  is cut off so that the Fresnel lens  400   h  is asymmetric, and this decrease the volume of the headlight device having the Fresnel lens  400   h  down to 84.32% of the original volume.  FIG. 17  is a front view of a Fresnel lens of a headlight device according to a ninth embodiment of the disclosure. As shown in  FIG. 17 , in a Fresnel lens  400   i  of this embodiment, part of a lower part  430   i  and part of an upper part  420   i  are cut off, but the parts being cut off are different, such that the Fresnel lens  400   i  is asymmetric, thereby decreasing the volume of the headlight device having the Fresnel lens  400   i  down to 79.97% of the original volume.  FIG. 18  is a front view of a Fresnel lens of a headlight device according to a tenth embodiment of the disclosure. As shown in  FIG. 18 , in a Fresnel lens  400   j  of this embodiment, the Fresnel lens  400   j  is cut from different sides so as to from a lens that is asymmetric at the upside and the downside but symmetric at the left side and the right side, such that the volume of the headlight device having the Fresnel lens  400   j  is decreased to 57.55% of the original volume, but the present disclosure is not limited thereto. In some other embodiments, a Fresnel lens may be a lens that is asymmetric at all sides. 
     According to the headlight device as discussed above, because the reflecting surface of the reflector, which is defined by the quadratic Bezier curved function, with the help of the blocking plate, the light pattern produced by the light beam, emitted by the light source and then passing through the Fresnel lens, not only meets the requirement of the regulation, but also can decrease the volume and the weight of the headlight device, thereby increasing the turning sensitivity of the headlight device cooperated with the adaptive front lighting system. 
     In addition, the position of the light source can be adjusted so as to make the light ray, after being reflected by the reflector, enter into the upper part or lower part of the Fresnel lens, so the part of the Fresnel lens which is not passed by the light ray is able to be cut off, thereby further decreasing the volume and the weight of the Fresnel lens. As such, the much lighter Fresnel lens is able to decrease the volume and weight of the overall headlight device, such that the turning sensitivity of the headlight device cooperated with the adaptive front lighting system is able to be increased. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure. It is intended that the specification and examples be considered as exemplary embodiments only, with a scope of the disclosure being indicated by the following claims and their equivalents. 
     SYMBOL DESCRIPTION 
     
         
           10   a ,  10   b ,  10   c ,  10   d ,  10   e ,  10   f  and  10   g : headlight device 
           100   a ,  100   b ,  100   c ,  100   d ,  100   e ,  100   f  and  100   g : light source 
           110   a ,  110   e ,  110   f  and  110   g : light emitting surface 
           111   a : light beam 
           1111   a ,  1111   b ,  1111   c  and  1111   d : optical axial light ray 
           1112   a : edge light ray 
           200   a : circuit board 
           300   a ,  300   b ,  300   c  and  300   d : reflector 
           310   a : reflecting surface 
           311   a ,  311   e ,  311   f  and  311   g : opening 
           312   a ,  312   b ,  312   c  and  312   d : curved line 
           3121   a ,  3121   b ,  3121   c  and  3121   d : opening end 
           3122   a ,  3122   b ,  3122   c ,  3122   d  and  3122   e : connecting end 
           400   a ,  400   c ,  400   d ,  400   e ,  400   h ,  400   i  and  400   j : Fresnel lens 
           400   b : lens 
           410   a : central part 
           420   a ,  420   c  and  420   i : upper part 
           430   a ,  430   d ,  430   h  and  430   i : lower part 
           500   a ,  500   c ,  500   d  and  500   e : blocking plate 
         α: divergence angle 
         β: angle 
         C: central axis 
         N 1  and N 2 : normal line 
         P 1 : plane 
         P 2 : reference plane 
         P 3 : vertical plane 
         I: optical axis 
         K: distance 
         M: vertical distance between the highest point of blocking plate and connecting end 
         θ 1 : incident angle 
         θ 2 : reflected angle 
         P 0x : X-coordinate of connecting end 
         P 0y : Y-coordinate of connecting end 
         P 2x : X-coordinate of opening end 
         P 2y : Y-coordinate of opening end 
         P 1x : X-coordinate of reference point of curved line 
         P 1y : Y-coordinate of reference point of curved line 
         t: coefficient in determining any point on the curved line 
         B x(t) : X-coordinate of any point on curved line 
         B y(t) : Y-coordinate of any point on curved line 
         t x : a coefficient in determining a point on curved line which is corresponding to light source 
         Φ: angle between optical axial light ray of light beam on optical axis of light source, reflected by reflecting surface, and direction of opening 
         L: horizontal distance between opening end and connecting end 
         X: distance between light source and connecting end 
         D: distance between light source and Fresnel lens 
         H: vertical distance between opening end and connecting end