Abstract:
A Fresnel lens includes a plate made of a glass material and Fresnel portions made of plastic material and integrally formed onto the plate. A method of manufacturing the Fresnel lens includes the steps of adding the plastic material in a forming apparatus, curing the plastic material, and then separating the forming apparatus and the plate from each other to form the Fresnel lens. An apparatus for manufacturing the Fresnel lens includes a forming apparatus coupling with the plate of the Fresnel lens, and a forming concave with inversion corresponding to the shape of the forming Fresnel portions. The forming concave shapes the plastic material into the Fresnel portion. Therefore, the Fresnel lens takes lower manufacture cost than the glass Fresnel lens and has better reliability than the plastic Fresnel lens while exposing in high temperature and high light density.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a lens and, more particularly, to a Fresnel lens, the apparatus and the method of manufacturing thereof. 
         [0003]    2. The Related Art 
         [0004]    Please refer to  FIG. 15 . A common Fresnel lens  8  functions as condensing light as a spherical lens  9 . However, the weight and size of the common Fresnel lens  8  are smaller than the spherical lens  9 . Therefore, the common Fresnel lens  8  has replaced the spherical lens  9  in many fields. 
         [0005]    Generally, the common Fresnel lens  8  is applied to an apparatus which needs a thinner and lighter lens, such as a light projector used in lighthouse, an overhead projector, a portable magnifier, etc. The common Fresnel lens  8  is generally made of glass material or plastic material for adapting to different environments. 
         [0006]    The thermal reliability of glass Fresnel lens is better than the plastic Fresnel lens, which is necessary for lens applied in critical environments with high temperature and high light density, such as an outdoor place. The glass Fresnel lens is generally manufactured by assembling pieces of grinding glass lenses or directly molding glass material. Because both the rigidity and the melting point of glass are high, the manufacturing procedure is complex. 
         [0007]    Therefore, the manufacturing cost of a glass Fresnel lens is high and limits the size of a glass Fresnel lens. Nowadays a small glass Fresnel lens is manufactured by molding the glass material and a large glass Fresnel lens is made up of small glasses lenses. 
         [0008]    The plastic Fresnel lens is generally manufactured by molding, impressing, or injection process. Although the cost and the weight of the plastic Fresnel lens are less than those of the glass Fresnel lens, because of its worse thermal reliability, most of the plastic Fresnel lenses are adapting to low temperature environments and low light density environments, such as an indoor space. 
         [0009]    The Fresnel lens is also applied to a solar energy system as a condenser to focus sunlight on small solar cells. In such a light enhancement apparatus, a large glass Fresnel lens becomes one of the necessary components which can provide enough high thermal and high light density reliability. However, the complicated manufacturing procedure results in high cost of a large glass Fresnel lens. 
       SUMMARY OF THE INVENTION 
       [0010]    A first object of the present invention is to provide a Fresnel lens having advantages of the lower manufacture cost and high reliability while exposing in high temperature and high light density. 
         [0011]    According to the invention, the Fresnel lens has a base plate and a Fresnel portion. The base plate is made of a glass material. The Fresnel portion is made of a plastic material and integrated onto a surface of the base plate. Since, the Fresnel lens has advantages of the lower manufacture cost than the glass Fresnel lens and better reliability than the plastic Fresnel lens. 
         [0012]    A second object of the present invention is to provide a method of manufacturing the Fresnel lens. According to the invention, the method includes the following steps. In step  1 , the plastic material is added into a forming apparatus, and then the plastic material is adhered onto the surface of the base plate. In step  2 , the plastic material is cured to solidification to form the Fresnel portion integrated onto the surface of the base plate. In step  3 , the base plate and the forming apparatus are separated from each other. 
         [0013]    A third object of the present invention is to provide an apparatus for manufacturing the Fresnel lens. According to the present invention, the apparatus has a forming apparatus and a forming concave. The forming apparatus is coupled onto the base plate for receiving the plastic material. The forming concave shapes the plastic material in the Fresnel portion integrated onto the base plate. The shape of the forming concave mates the shape of the Fresnel portion. 
         [0014]    The base plate is made of glass material. The Fresnel portion is made of the plastic material received in the forming apparatus and shaped by the forming concave, which is integrated onto the surface of the base plate. Because a glass material constructs the main body of the Fresnel lens and a thin plastic material forms the optical Fresnel portion, such a Fresnel lens has advantages of the lower manufacture cost than the glass Fresnel lens and better reliability than the plastic Fresnel lens. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the attached drawings, in which: 
           [0016]      FIG. 1  is a section view showing a Fresnel lens; 
           [0017]      FIG. 2  is a flow chart showing a first method of manufacturing the Fresnel lens according to the present invention; 
           [0018]      FIG. 3  is a flow chart showing steps of the first method of manufacturing the Fresnel lens according to the present invention; 
           [0019]      FIG. 4  is a flow chart showing a second method of manufacturing the Fresnel lens according to the present invention; 
           [0020]      FIG. 5  is a flow chart showing steps of the second method of manufacturing the Fresnel lens according to the present invention; 
           [0021]      FIG. 6  is a flow chart showing a third method of manufacturing the Fresnel lens according to the present invention; 
           [0022]      FIG. 7  is a flow chart showing steps of the third method of manufacturing the Fresnel lens according to the present invention; 
           [0023]      FIG. 8  shows a second mold according to the present invention; 
           [0024]      FIG. 9  is a flow chart showing a fourth method of manufacturing the Fresnel lens according to the present invention; 
           [0025]      FIG. 10  is a flow chart showing steps of the fourth method of manufacturing the Fresnel lens according to the present invention; 
           [0026]      FIG. 11  shows a first forming plate according to the present invention; 
           [0027]      FIG. 12  is a partial enlarged view showing a tip of a concave portion of the first forming plate according to the present invention; 
           [0028]      FIG. 13  shows a second forming plate according to the present invention; 
           [0029]      FIG. 14  is a partial enlarged view showing a tip of a concave portion of the second forming plate according to the present invention; and 
           [0030]      FIG. 15  shows a section view of a common Fresnel lens and a section view of a spherical lens. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    Please refer to  FIG. 1 , showing a preferred embodiment of a Fresnel lens  1 . The Fresnel lens  1  has a base plate  10  and a Fresnel portion  11 . The base plate  10  is made of a glass material. The Fresnel portion  11  is made of a plastic material and integrated onto a surface of the base plate  10 . Specially, the thickness of the Fresnel portion  11  is less than 2.5 millimeters. 
         [0032]    For the purpose of easily manufacturing the Fresnel lens  1  in this invention, the main portion of the Fresnel lens  1  being the glass base plate  10 , and the remainder portion of Fresnel lens  1  being the plastic Fresnel portion  11  are required. A small size Fresnel lens and a middle size Fresnel lens can be directly manufactured by integrating a plastic Fresnel portion  11  onto a surface of the glass base plate  10 . A large size Fresnel lens can be made up of many small size Fresnel lens. Therefore, the Fresnel lens  1  has the advantages of both high thermal reliability and low cost. 
         [0033]    Specially, the base plate  10  of the Fresnel lens  1  may be any type of a plane plate, a wedge-shaped plate, a convex plate and a concave plate. The plastic material may be a thermosetting plastic such as a silicone, or an ultraviolet curing plastic such as an epoxy resin or an acrylic resin. The plastic material is formed to Fresnel portion  11  by a forming concave of a forming apparatus and then cured to solidification by heating up or radiating ultraviolet. 
         [0034]    Please refer to  FIG. 2  and  FIG. 3 .  FIG. 2  is a flow chart of a first method of manufacturing the Fresnel lens  1 .  FIG. 3  is a flow chart showing steps of the first method of manufacturing the Fresnel lens  1 . In this embodiment, the forming apparatus is a first mold  2  and the forming concave is a cavity  20  of the first mold  2 . The method of manufacturing the Fresnel lens  1  includes the following steps. The shape of the cavity  20  of the first mold  2  is mating with the shape of the Fresnel portion  11 . 
         [0035]    In S 01 , the first mold  2  is fixed and the cavity  20  is facing the base plate  10 . In S 02 , the plastic material  3  is added into the cavity  20  by a nozzle, until the cavity  20  is filled up with the plastic material  3 . In S 03 , the base plate  10  is covered on the cavity  20  for being adhered to cure the plastic material  3 . In S 04 , the plastic material  3  is cured to solidification to form the Fresnel portion  11 . In S 05 , the first mold  2  and the base plate  10  are separated from each other. Therefore, the base plate  10  is integrated with the Fresnel portion  11  to form the Fresnel lens  1 . 
         [0036]    Please refer to  FIG. 4  and  FIG. 5 .  FIG. 4  is a flow chart of a second method of manufacturing the Fresnel lens  1 .  FIG. 5  is a flow chart showing the steps of the second method of manufacturing the Fresnel lens  1 . In this embodiment, the forming apparatus is the first mold  2  and a sleeve  4 . The forming concave is the cavity  20  of the first mold  2 . The method of manufacturing the Fresnel lens  1  includes the following steps. 
         [0037]    In S 11 , the base plate  10  is fixed. In S 12 , the sleeve  4  is located onto the base plate  10 . In S 13 , the plastic material  3  is added onto the space enclosed by base plate  10  and the sleeve  4  until filled up. In S 14 , the first mold  2  having the cavity  20  faces to the sleeve  4 , and then covers on the sleeve  4  gradually. Since, the cavity  20  of the first mold  2  is fully filled with the plastic material  3 . 
         [0038]    In S 15 , the plastic material  3  is cured to solidification for forming the Fresnel portion  11 . In S 16 , the first mold  2 , the sleeve  4  and the base plate  10  are separated respectively. Therefore, the base plate  10  can be integrated with the Fresnel portion  11  to form the Fresnel lens  1 . In this embodiment, the dimension of the sleeve  4  and the dimension of the cavity  20  of the first mold  2  are mating with the dimension of the Fresnel portion  11  of the Fresnel lens  1 . 
         [0039]    In the first method and the second method, if the plastic material  3  is the thermosetting plastic, then heating up the plastic material  3  will be preferable in the curing step. If the plastic material  3  is ultraviolet curing plastic, then radiating ultraviolet to the plastic material  3  will be preferable in the curing step. Besides, the manufacturing method can be implemented in a vacuum room to prevent from forming air bubbles between the base plate  10  and the plastic material  3  while the plastic material adheres to the base plate  10 . 
         [0040]    Please refer to  FIG. 6  to  FIG. 8 .  FIG. 6  is a flow chart of a third method of manufacturing the Fresnel lens  1 .  FIG. 7  is a flow chart showing the steps of the third method of manufacturing the Fresnel lens  1 .  FIG. 8  shows a second mold  5  having a cavity  50  and a passage  51  connected to the cavity  50  from the outside. In this embodiment, the forming apparatus is the second mold  5  with the forming cavity  50 . The method of manufacturing the Fresnel lens  1  includes the following steps. 
         [0041]    In S 21 , the second mold  5  having the cavity  50  is faced to the base plate  10 , and then the second mold  5  and the base plate  10  are coupled to each other. Therefore, the second mold  5  becomes a closed space. In S 22 , the plastic material  3  is added into the second mold  5  through the passage  51  until the second mold  5  is fully filled with the plastic material  3 . 
         [0042]    In S 23 , the plastic material  3  is cured to solidification to form the Fresnel portion  11 . In S 24 , the second mold  5  and the base plate  10  are separated from each other. Therefore, the base plate  10  is integrated with the Fresnel portion  11  to form the Fresnel lens  1 . In this embodiment, the plastic material  3  can be injected into the cavity  50  by injecting pressure, or sucked into the cavity  50  by vacuum attraction 
         [0043]    Please refer to  FIG. 9  to  FIG. 12 .  FIG. 9  is a flow chart of a fourth method of manufacturing the Fresnel lens  1 .  FIG. 10  is a flow chart showing the steps of the fourth method of manufacturing the Fresnel lens  1 .  FIG. 11  shows a first forming plate  6 .  FIG. 12  is a partial enlarged view showing a tip  61  of a concave portion  60  of the first forming plate  6 . In this embodiment, the forming apparatus is the sleeve  4  and the first forming plate  6 . The forming concave is the concave portion  60 . 
         [0044]    The first forming plate  6  is of a rectangle shape. A long edge of the first forming plate  6  is cut in the concave portion  60 . A shape of the concave portion  60  is mating with a cross-section-shape of the Fresnel portion  11  of the Fresnel lens. The tip  61  of the concave portion  60  is cut in a slanting edge  62 . The length of the concave portion  60  equals to the diameter of the Fresnel portion  11  of the Fresnel lens  1 . The method of manufacturing the Fresnel lens  1  includes the following steps. 
         [0045]    In S 31 , the base plate  10  is fixed. In S 32 , the sleeve  4  is located onto the base plate  10 . In S 33 , the plastic material  3  is added onto the space enclosed by the base plate  10  and the sleeve  4 . In S 34 , the plastic material  3  is cured in a semi-solid state. In S 35 , the concave portion  60  of the first forming plate  6  is pressed into the semi-solid-state plastic material  3 . In S 36 , the first forming plate  6  is rotated to urge the slanting edge  62  of the tip  61  of the concave portion  60  to press the semi-solid-state plastic material  3 . In the meanwhile, the semi-solid-state plastic material  3  is cured to solidification to form the Fresnel portion  11 . In S 37 , the first forming plate  6 , the sleeve  4  and the base plate  10  are separated. Finally, the base plate  10  is integrated with the Fresnel portion  11  to form the Fresnel lens  1 . 
         [0046]    Please refer to  FIG. 13  and  FIG. 14 .  FIG. 13  shows a second forming plate  7 .  FIG. 14  is a partial enlarged view showing a tip  71  of a concave portion  70  of the second forming plate  7 . Furthermore, the first forming plate  6  can be replaced by the second forming plate  7 . The second forming plate  7  is of a rectangle shape. A long edge of the second forming plate  7  is cut in the concave portion  70 . A shape of the concave portion  70  is mating with a half cross-section-shape of the Fresnel portion  11  of the Fresnel lens  1 . The tip  71  of the concave portion  70  is cut in an arc-shaped edge  72 . The length of the concave portion  70  equals to the radius of the Fresnel portion  11  of the Fresnel lens  1 . 
         [0047]    While the second forming plate  7  is rotated, the arc-shaped edge  72  of the tip  71  of the concave portion  70  is urged to press the semi-solid-state plastic material  3 . 
         [0048]    As described above, the base plate  10  is integrated with the Fresnel portion, formed by the forming apparatus such as the mold, the sleeve and the forming plate, to form the Fresnel lens  1 . For the purpose of easily manufacture the Fresnel lens, a glass base plate  10  being the main portion of the Fresnel lens  1 , and the plastic Fresnel portion  11  being the remainder portion of Fresnel lens  1  directly integrated onto the glass base plate  10  are required. 
         [0049]    The small size Fresnel lens and the middle size Fresnel lens can be directly manufactured by forming the plastic Fresnel portion  11  integrated onto the surface of the glass base plate  10 . The large size Fresnel lens can be made up of many small size Fresnel lens. Therefore, the Fresnel lens takes lower manufacture cost than the glass Fresnel lens and has better reliability than the plastic Fresnel lens while exposing in high temperature and high light intensity 
         [0050]    The Fresnel lens  1  adapts to be applied to the light enhancement apparatus of the solar energy system. The Fresnel lens  1  can condense light on a solar cell to urge the solar cell to absorb as much solar energy as of which with the far larger dimension lens does. Since the Fresnel lens  1  can cooperate with the high efficiency solar cell for providing much power. 
         [0051]    The Fresnel lens  1  can also be applied to a heat absorbing pipe. The Fresnel lens  1  can condense light on the heat absorbing pipe to urge it to absorb as much solar energy as of which with the far larger dimension lens does. Since the heat absorbing pipe can heat up the liquid therein, it can be applied to a water heating system, a radiator, and a thermal electric apparatus, etc. 
         [0052]    Furthermore, the present invention is not limited to the embodiments described above; various additions, alterations and the like may be made within the scope of the present invention by a person skilled in the art. For example, respective embodiments may be appropriately combined.