Patent Publication Number: US-2020301245-A1

Title: Optical system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of application Ser. No. 15/977,176, filed on May 11, 2018, which claims the benefit of U.S. Provisional Application No. 62/505,420, filed May 12, 2017, and China Patent Application No. 201810428101.7, filed May 7, 2018, the entirety of which are incorporated by reference herein. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     Field of the Disclosure 
     The present disclosure relates to an optical system, and more particularly to an optical system that has a function of optical image stabilization. 
     Description of the Related Art 
     As technology has progressed, many kinds of electronic devices such as tablet computers and smartphones have begun to include the functionality of digital photography or video recording. A user can take photos having different effects through the configuration of a lens system with a long focal length. Electronic devices with the lens system with a long focal length have gradually become popular. 
     However, when a lens with a long focal length is disposed in the aforementioned electronic device, the thickness of the electronic device may increase, which is disadvantageous in the effort to miniaturize the electronic device. Therefore, a reflecting member is generally disposed inside the lens system, and incident light is directed to a light-sensing element in the lens system through reflection. Based on the configuration, the thickness of the electronic device can be reduced. However, when the electronic device is shaken, the position of the light-sensing element where the incident light reaches may shift to a position that is different from the predetermined position, resulting in unclear imaging by the lens system. 
     Therefore, how to design the structure of a lens system to prevent the problem of an unclear image resulting from the shaking of the lens system is a topic nowadays that needs to be discussed and solved. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     Accordingly, one objective of the present disclosure is to provide an optical system having a plurality of driving assemblies, so as to solve the above problems. 
     According to some embodiments of the disclosure, an optical system includes a light-sensing element, at least one optical lens, a reflecting unit and a first driving assembly. The reflecting unit includes a reflecting surface, configured to receive an incident light and to reflect a reflecting light. The reflecting light is projected into the light-sensing element through the optical lens. The first driving assembly is configured to control the reflecting unit to move along a first axis direction, so as to adjust a focus position of the reflecting light on the light-sensing element. 
     In some embodiments, the reflecting unit and the optical lens are arranged along a first direction, the incident light is emitted to the reflecting unit along a second direction, and a third direction is perpendicular to the first direction and the second direction, wherein the first axis direction is not parallel to the third direction. In some embodiments, the first direction is substantially perpendicular to a light-sensing surface of the light-sensing element. 
     In some embodiments, the reflecting surface includes an arc structure. In some embodiments, a center of the arc structure corresponds to a center of the incident light. In some embodiments, the reflecting surface includes a radius, and the radius substantially ranges from 100 to 1000 mm. In some embodiments, the reflecting surface further includes a flat surface, and the arc structure surrounds the flat surface. In some embodiments, the arc structure is a convex structure or a concave structure. 
     In some embodiments, the optical system further includes a second driving assembly, configured to drive the reflecting unit to rotate around a second axis. In some embodiments, the optical system further includes a third driving assembly, configured to drive the reflecting unit to rotate around a third axis. 
     The present disclosure provides an optical system with a long focal length that is installed in an electronic device for capturing images. The optical system can have a lens module, a reflecting module, a light-sensing element, and a plurality of driving assemblies. The reflecting module includes a reflecting unit. The reflecting unit can reflect an external light to the lens module and then to the light-sensing element, so as to generate a digital image. It should be noted that when the optical system is shaken, the plurality of driving assemblies can control the reflecting unit to move along a first axis direction, rotate around a second axis and/or rotate around a third axis, to adjust the focus position of the reflecting light on the light-sensing element, so as to achieve the purpose of optical image stabilization. Therefore, the image quality of the light-sensing element can also be improved. 
     In some embodiments, the reflecting surface of the reflecting unit is a flat surface, and the driving assemblies can only control the reflecting unit to move along the first axis direction, so as to achieve the purpose of compensating for the focus position. In addition, in some embodiments, the reflecting surface of the reflecting unit can further include an arc structure. Based on the design of the arc structure, the focus position of the light which is reflected by the periphery of the reflecting surface onto the light-sensing element can be more accurate. 
     Additional features and advantages of the disclosure will be set forth in the description which follows, and, in part, will be obvious from the description, or can be learned by practice of the principles disclosed herein. The features and advantages of the disclosure can be realized and obtained by means of the instruments and combinations pointed out in the appended claims. These and other features of the disclosure will become more fully apparent from the following description and appended claims, or can be learned by the practice of the principles set forth herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic diagram of an optical system installed on a portable electronic device according to an embodiment of the present disclosure. 
         FIG. 2  shows a schematic diagram of the optical system according to the embodiment of the present disclosure. 
         FIG. 3  shows an exploded diagram of a reflecting module according to the embodiment of the present disclosure. 
         FIG. 4  shows a partial structural diagram of the reflecting module according to the embodiment of the present disclosure. 
         FIG. 5  shows a schematic diagram of the reflecting module in another view according to the embodiment of the present disclosure. 
         FIG. 6  shows a partial structural diagram of the reflecting module in another view according to the embodiment of the present disclosure. 
         FIG. 7A  to  FIG. 7C  show diagrams illustrating that the optical system is in different states according to the embodiment of the present disclosure. 
         FIG. 8  shows a schematic side view of a reflecting unit according to another embodiment of the present disclosure. 
         FIG. 9A  to  FIG. 9C  show diagrams of an optical system in different states according to another embodiment of the present disclosure. 
         FIG. 10  shows a schematic side view of a reflecting unit according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS 
     In the following detailed description, for the purposes of explanation, numerous specific details and embodiments are set forth in order to provide a thorough understanding of the present disclosure. The specific elements and configurations described in the following detailed description are set forth in order to clearly describe the present disclosure. It will be apparent, however, that the exemplary embodiments set forth herein are used merely for the purpose of illustration, and the inventive concept may be embodied in various forms without being limited to those exemplary embodiments. In addition, the drawings of different embodiments may use like and/or corresponding numerals to denote like and/or corresponding elements in order to clearly describe the present disclosure. However, the use of like and/or corresponding numerals in the drawings of different embodiments does not suggest any correlation between different embodiments. The directional terms, such as “up”, “down”, “left”, “right”, “front” or “rear”, are reference directions for accompanying drawings. Therefore, using the directional terms is for description instead of limiting the disclosure. 
     In this specification, relative expressions are used. For example, “lower”, “bottom”, “higher” or “top” are used to describe the position of one element relative to another. It should be appreciated that if a device is flipped upside down, an element at a “lower” side will become an element at a “higher” side. 
     The terms “about” and “substantially” typically mean+/−20% of the stated value, more typically +/−10% of the stated value and even more typically +/−5% of the stated value. The stated value of the present disclosure is an approximate value. When there is no specific description, the stated value includes the meaning of “about” or “substantially”. 
     Please refer to  FIG. 1 , which shows a schematic diagram of an optical system  100  installed on a portable electronic device  50  according to an embodiment of the present disclosure. The portable electronic device  50  can be any kind of portable electronic devices or handheld device, such as a personal digital assistant (PDA), a smartphone, a tablet, a mobile phone, a mobile Internet device (MID), a notebook computer, a car computer, a digital camera, a digital media player, a gaming device or any other type of mobile computing device. However, it will be understood by a person skilled in the art that the present disclosure is not limited to those devices. In this embodiment, the optical system  100  can be a camera system with a long focal length and can provide a better image effect of a photo for a user. Light is emitted into the optical system  100  through an opening  52 , so as to generate one or several digital images. 
     Please refer to  FIG. 2 , which shows a schematic diagram of the optical system  100  according to the embodiment of the present disclosure. As shown in  FIG. 2 , the optical system  100  can include a lens module  200 , a reflecting module  300  and a light-sensing element  400 . In addition, the optical system  100  can further include a casing (not shown in the figures), disposed in the portable electronic device  50  shown in  FIG. 1 , and the lens module  200 , the reflecting module  300  and the light-sensing element  400  are disposed in the casing. Specifically, the lens module  200 , the reflecting module  300 , and the light-sensing element  400  are arranged along a first direction. For example, they are arranged along the Y-axis direction in  FIG. 2 . Furthermore, as shown in  FIG. 2 , the lens module  200  includes at least one optical lens (such as an optical lens  202 ), and the reflecting module  300  include a reflecting unit  302  (such as a reflecting mirror). Therefore, the reflecting unit  302  and the optical lens  202  are arranged along the first direction (for example, along the Y-axis direction) as well. 
     As shown in  FIG. 1  and  FIG. 2 , an external incident light IL is emitted along a second direction (such as along the Z-axis direction) into the casing through the opening  52  of the portable electronic device  50  and then into reflecting unit  302 . A third direction (such as the X-axis direction) is perpendicular to the first direction (the Y-axis direction) and the second direction (the Z-axis direction). In this embodiment, the reflecting unit  302  can have a reflecting surface  3021 , which is configured to receive the incident light IL emitted along the second direction (the Z-axis direction) and to reflect a reflecting light RL. Then the reflecting light RL is projected along the first direction (the Y-axis direction) into the lens module  200 . In this embodiment, the lens module  200  in  FIG. 2  only shows one optical lens  202 , but it is not limited to this embodiment. For example, the lens module  200  can include a plurality of optical lenses therein. When the reflecting light RL is projected into the lens module  200 , the optical lens  202  of the lens module  200  is configured to guide the reflecting light RL to the light-sensing element  400 , and the light-sensing element  400  generates an electronic signal after receiving the reflecting light RL. The electronic signal is transmitted to the a processor (not shown in the figures) of the portable electronic device  50 , so as to generate a digital image. 
     In addition, it should be noted that, as shown in  FIG. 2 , the light-sensing element  400  has a light-sensing surface  402 , and the first direction is substantially perpendicular to the light-sensing surface  402 . That is, the reflecting light RL is also substantially perpendicular to the light-sensing surface  402 . 
     Please refer to  FIG. 3 , which shows an exploded diagram of a reflecting module  300  according to the embodiment of the present disclosure. As shown in the figure, the reflecting module  300  includes a reflecting unit  302 , an outer frame  304 , a first elastic member  306 , an optical element holder  308 , a supporting base  310 , a base  312 , a plurality of second elastic members  314 , a first driving assembly DA 1 , a second driving assembly DA 2 , and a third driving assembly DA 3 . In this embodiment, when the portable electronic device  50  is shaken, the first driving assembly DA 1 , the second driving assembly DA 2 , and the third driving assembly DA 3  can be configured to drive the reflecting unit  302  to move or rotate, so that the reflecting light RL in  FIG. 2  can be stably reflected to the lens module  200  and the light-sensing element  400 , so as to achieve the purpose of optical image stabilization. In addition, in this embodiment, the first elastic member  306  may be a spring sheet which includes a central portion  3061 , a side portion  3062  and a side portion  3063 . The central portion  3061  is connected to the side portion  3062  and the side portion  3063 , and the central portion  3061  can be rotated relative to the side portion  3062  and the side portion  3063 . 
     In this embodiment, the supporting base  310  includes a first housing  3101  and a second housing  3103 . The first housing  3101  is fixedly connected to the second housing  3103 , such as being fixed to each other with a glue material. In addition, the third driving assembly DA 3  can include two third driving coils CL 31  and CL 32  which are disposed between the first housing  3101  and the second housing  3103 . In addition, as shown in  FIG. 3 , the first housing  3101  includes a central groove  3105  and two side walls  3107 . The central groove  3105  is formed between the two side walls  3107 , and the central groove  3105  is configured to accommodate the optical element holder  308  and the second driving assembly DA 2 . 
     Please refer to  FIG. 3  and  FIG. 4 .  FIG. 4  shows a partial structural diagram of the reflecting module  300  according to the embodiment of the present disclosure. In this embodiment, the reflecting unit  302  is an optical reflecting mirror which is fixedly connected to the optical element holder  308  through the central portion  3061  of the first elastic member  306 , and the side portion  3062  and the side portion  3063  of the first elastic member  306  are respectively fixedly connected to the two side walls  3107  of the first housing  3101 . Therefore, the reflecting unit  302  and the optical element holder  308  are suspended in the central groove  3105  of the first housing  3101  by the first elastic member  306 . As shown in  FIG. 3 , the third driving assembly DA 3  further includes a pair of third magnetic elements MG 31  and a pair of third magnetic elements MG 32 . The two pairs of third magnetic elements MG 31  and MG 32  are respectively fixedly disposed on opposite sides of the optical element holder  308 . In addition, the second driving assembly DA 2  can include a second driving coil CL 2  and a second magnetic element MG 2 . The second driving coil CL 2  is disposed on an inner surface of the central groove  3105 , and the second magnetic element MG 2  is disposed on a position of the optical element holder  308  corresponding to the second driving coil CL 2 . 
     Next, in this embodiment, the outer frame  304  sheaths on the first housing  3101  of the supporting base  310 , and the outer frame  304  can have four protruding portions  3041  which are protruded along the X-axis direction. Thus, the base  312  can be connected to the four protruding portions  3041  of the outer frame  304  through the four second elastic members  314 , as shown in  FIG. 2 . In addition, as shown in  FIG. 3 , the first driving assembly DA 1  can include a first magnetic element MG 11 , a first magnetic element MG 12 , a first magnetic element MG 13 , a first driving coil CL 11 , a first driving coil CL 12  and a first driving coil CL 13 . In this embodiment, as shown in  FIG. 3 , the first magnetic element MG 11  is fixedly disposed on the first housing  3101  of the supporting base  310  and faces the base  312 , and the first driving coil CL 11  corresponding to the first magnetic element MG 11  is disposed on the base  312 . In addition, the first magnetic element MG 12  and the first magnetic element MG 13  are fixedly disposed on two sides of the second housing  3103 , and the first driving coil CL 12  and the first driving coil CL 13  are respectively disposed on two extending portions  3121  of the base  312 , facing the corresponding first magnetic element MG 12  and the first magnetic element MG 13 . 
     As shown in  FIG. 2  and  FIG. 3 , based on the above structural configuration, the first driving assembly DA 1  can control the supporting base  310  to drive the reflecting unit  302  to move along a first axis direction, so as to adjust a focus position of the reflecting light RL on the light-sensing element  400 . For example, the first driving assembly DA 1  can control the supporting base  310  to move along the first axis direction, such as along the Y-axis direction or along the Z-axis direction. However, it should be noted that the first axis direction is not parallel to the third direction (the X-axis direction). In addition, it should be noted that positions of the magnetic elements and the driving coils of the first driving assembly DA 1 , the second driving assembly DA 2  and the third driving assembly DA 3  are not limited to this embodiment. For example, the positions of the magnetic elements and the driving coils can be interchanged. Furthermore, ways of driving the supporting base  310  to move by the first driving assembly DA 1  are not limited to this embodiment. For example, the first driving assembly DA 1  can also be implemented by a stepping motor or piezoelectric driving elements. 
     Please refer to  FIG. 5 , which shows a schematic diagram of the reflecting module  300  in another view according to the embodiment of the present disclosure. For clearly illustrating the first driving assembly DA 1 , the base  312  is illustrated by dotted lines. In this embodiment, the magnetic pole direction of the first magnetic element MG 11  is along the Y-axis direction. For example, the direction of the N-pole of the first magnetic element MG 11  goes toward the Y-axis direction, and the direction of the S-pole goes toward the −Y-axis direction. When the first driving coil CL 11  is provided with electricity, an electromagnetic driving force Fy is generated by the first driving coil CL 11  and the first magnetic element MG 11  according to Lenz&#39;s law, so as to drive the reflecting unit  302  with the outer frame  304  to move along the Y-axis direction relative to the base  312 . Moreover, in this embodiment, the second elastic members  314  include a spiral structure, and when the outer frame  304  is moved along the Y-axis direction relative to the base  312 , the second elastic members  314  may be stretched or compressed. 
     In this embodiment, the magnetic pole directions of the first magnetic element MG 12  and the first magnetic element MG 13  are along the Z-axis direction. When the first driving coil CL 12  and the first driving coil CL 13  are provided with electricity, the first driving coil CL 12  and the first driving coil CL 13  respectively act with the first magnetic element MG 12  and the first magnetic element MG 13  to generate two electromagnetic driving forces Fz, so as to drive the supporting base  310  with the reflecting unit  302  to move along the Z-axis direction relative to the base  312 . Therefore, based on the configuration of the first driving assembly DA 1 , the reflecting unit  302  can be driven to move relative to the base  312  along the Y-axis direction or the Z-axis direction. 
     Please refer to  FIG. 4  and  FIG. 6 .  FIG. 6  shows a partial structural diagram of the reflecting module  300  in another view according to the embodiment of the present disclosure. As shown in  FIG. 6 , when the second driving coil CL 2  of the second driving assembly DA 2  is provided with electricity, the second driving coil CL 2  acts with the second magnetic element MG 2  to generate an electromagnetic driving force Fz along the Z-axis direction, so as to drive the optical element holder  308 , the reflecting unit  302 , and the central portion  3061  of the first elastic member  306  to rotate around a second axis Ax relative to the side portion  3062  and the side portion  3063 . That is, the electromagnetic driving force Fz can drive the reflecting unit  302  to rotate around the second axis Ax relative to the supporting base  310  ( FIG. 4 ). 
     Similarly, as shown in  FIG. 6 , when the third driving coils CL 31  and CL 32  of the third driving assembly DA 3  are provided with electricity (the currents received by the third driving coils CL 31  and CL 32  have the same magnitude but opposite phases), the third driving coils CL 31  and CL 32  respectively act with the third magnetic elements MG 31  and MG 32  to generate two electromagnetic driving forces Fv in opposite directions, so as to drive the optical element holder  308 , the reflecting unit  302  and the central portion  3061  of the first elastic member  306  to rotate around a third axis Ay relative to the side portion  3062  and the side portion  3063 . That is, the electromagnetic driving forces Fv can drive the reflecting unit  302  to rotate around the third axis Ay relative to the holding base  310  ( FIG. 4 ). It should be noted that the direction of the electromagnetic driving force Fv is substantially perpendicular to the reflecting surface  3021  of the reflecting unit  302 , that is, the direction of the electromagnetic driving force Fv is parallel to the normal vector of the reflecting surface  3021 . In addition, directions of the second axis Ax and the third axis Ay are not parallel to the direction of the electromagnetic driving force Fv. For example, directions of the second axis Ax and the third axis Ay are substantially perpendicular to the direction of the electromagnetic driving force Fv. 
     Please refer to  FIG. 7A  to  FIG. 7C .  FIG. 7A  to  FIG. 7C  show diagrams illustrating that the optical system  100  is in different states according to the embodiment of the present disclosure. In  FIG. 7A , the optical system  100  is parallel to a reference plane (such as being parallel to the horizontal plane), and the reflecting light RL is reflected to a central position C (a focus position) of the light-sensing element  400 .  FIG. 7B  is a diagram of the optical system  100  rotated clockwise at an angle relative to the horizontal plane. As shown in  FIG. 7B , because the optical system  100  is rotated at an angle (such as being rotated 5 degrees) relative to the horizontal plane, the position of the reflecting light RL on the light-sensing element  400  may deviate. As shown in  FIG. 7B , the reflecting light RL is reflected to a first position P 1  on the light-sensing element  400 . 
     In order to compensate for the deviated distance of the reflecting light RL on the light-sensing element  400  (that is, the distance between the central position C and the first position P 1 ), the first driving assembly DA 1  ( FIG. 5 ) can drive the reflecting unit  302  to move along the direction (the −Y-axis direction) indicated by the arrow shown in  FIG. 7B . Thus, the reflecting unit  302  can be moved from the position in  FIG. 7B  to the position in  FIG. 7C . Therefore, as shown in  FIG. 7C , the position of the reflecting light RL on the light-sensing element  400  returns from the first position P 1  to the central position C, so as to achieve the purpose of optical image stabilization. 
     It should be noted that, in this embodiment, the reflecting surface  3021  of the reflecting unit  302  is a flat surface, and it only needs to move the reflecting unit  302  along the −Y-axis direction without rotating the reflecting unit  302  to achieve the purpose of compensation. In addition, based on the structural configuration of this embodiment, the reflecting light RL which is reflected onto the light-sensing element  400  can still have good quality, so that the light-sensing element  400  can generate a clear image. 
     In this embodiment, when the optical system  100  is rotated clockwise relative to the horizontal plane, the first driving assembly DA 1  can drive the reflecting unit  302  to move along the −Y-axis direction, and therefore the deviated distance of the reflecting light RL on the light-sensing element  400  can be compensated for. Similarly, when the optical system  100  is rotated counterclockwise relative to the horizontal plane, the first driving assembly DA 1  can drive the reflecting unit  302  to move along the Y-axis direction, and therefore the deviated distance of the reflecting light RL on the light-sensing element  400  can be compensated for. In this embodiment, the distance of the reflecting unit  302  compensated by the first driving assembly DA 1  may correspond to an angle between the optical system  100  and the horizontal plane. For example, when the optical system  100  is rotated clockwise 1 degree relative to the horizontal plane, the first driving assembly DA 1  drives the reflecting unit  302  to move with 125 μm along the −Y-axis direction, so as to achieve the purpose of compensating for the deviated distance. 
     Please refer to  FIG. 8 , which shows a schematic side view of a reflecting unit  302 ′ according to another embodiment of the present disclosure. In this embodiment, the reflecting unit  302 ′ includes a reflecting surface  3022 , and the reflecting surface  3022  includes an arc structure. As shown in  FIG. 8 , in contrast to the reflecting unit  302  of the previous embodiment, the structure of the reflecting surface  3022  in this embodiment can increase the angle between the reflecting light RL and the incident light IL. For example, when two parallel light beams are emitted onto the reflecting surface  3022 , two reflected light beams with different reflecting angles are generated. As a result, the effect of compensation can be further improved. 
     Please refer to  FIG. 9A  to  FIG. 9C , which show diagrams of an optical system  100 A in different states according to another embodiment of the present disclosure. In this embodiment, the optical system  100 A includes a reflecting unit  302 A. A reflecting surface  3023  of the reflecting unit  302 A includes an arc structure, and the center of the arc structure corresponds to the center of an incident light ILL In addition, in this embodiment, the arc structure of the reflecting surface  3023  is a convex structure and is curved away from the lens module  200 , but it is not limited thereto. For example, in other embodiments, the arc structure of the reflecting surface  3023  can also be a concave structure and is curved toward the lens module  200 . Furthermore, in this embodiment, the arc structure can have a radius, and the radius ranges from about 100 to 1000 mm. 
     In  FIG. 9A , the optical system  100 A is not shaken and is parallel to the horizontal plane, and an incident light IL 1  and an incident light IL 2  are emitted to the reflecting unit  302 A along the Z-axis direction. Next, a reflecting light RL 1  and a reflecting light RL 2  are respectively reflected to a central position C 1  and a side position C 2  on the light-sensing element  400 .  FIG. 9B  is a diagram of the optical system  100 A after rotating counterclockwise at an angle relative to the horizontal plane according to the embodiment of the present disclosure. As shown in  FIG. 9B , because the optical system  100 A is rotated at an angle (such as being rotated 5 degrees) relative to the horizontal plane, the positions of the reflecting light RL 1  and the reflecting light RL 2  reflected on the light-sensing element  400  may deviate. As shown in  FIG. 9B , the reflecting light RL 1  and the reflecting light RL 2  are respectively reflected to a second position P 2  and a third position P 3  on the light-sensing element  400 . 
     In order to compensate for the deviated distances of the reflecting light RL 1  and the reflecting light RL 2  on the light-sensing element  400 , the first driving assembly DA 1  ( FIG. 5 ) can drive the reflecting unit  302 A to move along the direction (the −Y-axis direction) indicated by the arrow shown in  FIG. 9B . Thus, the reflecting unit  302 A can be moved from the position in the  FIG. 9B  to the position in  FIG. 9C . Therefore, as shown in  FIG. 9C , the position of the reflecting light RL 1  on the light-sensing element  400  returns from the second position P 2  to the central position C 1 , and the position of the reflecting light RL 2  on the light-sensing element  400  returns from the third position P 3  to the side position C 2 , so as to achieve the purpose of optical image stabilization. 
     Similarly, in this embodiment, when the optical system  100 A is rotated clockwise relative to the horizontal plane, the first driving assembly DA 1  can drive the reflecting unit  302 A to move along the Y-axis direction, and the deviated distances of the reflecting light RL 1  and the reflecting light RL 2  on the light-sensing element  400  can be compensated for. 
     Please refer to  FIG. 10 , which shows a schematic side view of a reflecting unit  302 B according to another embodiment of the present disclosure. As shown in  FIG. 10 , a reflecting surface  3025  of the reflecting unit  302 B includes a flat surface PS and an arc structure CS, and the arc structure CS surrounds the flat surface PS. In this embodiment, the arc structure CS has a radius, and the radius ranges from about 100 to 1000 mm. The reflecting unit  302 B in this embodiment is similar to the reflecting unit  302 A 
     In the embodiments of  FIG. 9A  and  FIG. 10 , based on the design of the reflecting surface having an arc structure, the focus position of the light which is reflected by the periphery of the reflecting surface onto the light-sensing element  400  can be more accurate. For example, the compensation effect of the reflecting light RL 2  in  FIG. 9C  can be more accurate. 
     In addition, in the other embodiments of the present disclosure, in order to further improve the compensation result, the plurality of driving assemblies may further control the reflecting unit to move and rotate together. For example, in some embodiments, the first driving assembly DA 1  and the second driving assembly DA 2  can control the reflecting unit to move along the Y-axis direction and rotate around the second axis Ax together, so as to achieve the purpose of two-axis compensation. In some embodiments, the first driving assembly DA 1  can control the reflecting unit to move along the Y-axis direction and the Z-axis direction together, so as to achieve the purpose of two-axis compensation. 
     In addition, in some embodiments, the first driving assembly DA 1  and the second driving assembly DA 2  can control the reflecting unit to move along the Y-axis direction, move along the Z-axis direction, and rotate around the second axis Ax together, so as to achieve the purpose of three-axis compensation. In addition, in some embodiments, the first driving assembly DA 1 , the second driving assembly DA 2 , and the third driving assembly DA 3  can control the reflecting unit to move along the Y-axis direction, move along the Z-axis direction, rotate around the second axis Ax and rotate around the third axis Ay, so as to achieve the purpose of four-axis compensation. 
     In conclusion, the present disclosure provides an optical system with a long focal length that is installed in an electronic device for capturing images. The optical system can have a lens module  200 , a reflecting module  300 , a light-sensing element  400 , and a plurality of driving assemblies. The reflecting module  300  includes a reflecting unit. The reflecting unit can reflect an external light to the lens module  200  and then to the light-sensing element  400 , so as to generate a digital image. It should be noted that when the optical system is shaken, the plurality of driving assemblies can control the reflecting unit to move along a first axis direction, rotate around a second axis and/or rotate around a third axis, to adjust the focus position of the reflecting light on the light-sensing element  400 , so as to achieve the purpose of optical image stabilization. Therefore, the image quality of the light-sensing element  400  can also be improved. 
     In some embodiments, the reflecting surface of the reflecting unit is a flat surface, and the driving assemblies can only control the reflecting unit to move along the first axis direction, so as to achieve the purpose of compensating for the focus position. In addition, in some embodiments, the reflecting surface of the reflecting unit can further include an arc structure. Based on the design of the arc structure, the focus position of the light which is reflected by the periphery of the reflecting surface onto the light-sensing element  400  can be more accurate. 
     Although the embodiments and their advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods, and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. In addition, each claim constitutes a separate embodiment, and the combination of various claims and embodiments are within the scope of the disclosure.