Abstract:
A dual lens optical system includes a first optical system and a second optical system selectively redirecting at least one of two lights of representing images of object from two incident lenses into a first optical axis of light toward an image sensor by at least one reflection member, wherein, at least one optical element is disposed between an image sensor and the reflection member.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/974,874, filed on Oct. 16, 2007, which claims the benefit of Korean Patent Application No. 10-2006-0101030, filed on Oct. 17, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND 
     The present invention relates to a dual lens optical system and a dual lens camera having the same. 
     Recently, digital cameras have gradually become smaller and thinner. To this end, many cameras are adopting a refraction optical system. Also, many digital cameras are adopting a zoom optical system to improve convenience. However, as digital cameras become smaller and thinner, the inner space of the digital camera decreases so that there is a limit in adjusting the focal length using the zoom optical system. Accordingly, there is a limit in increasing the optical zoom ratio. A digital zoom is employed to compensate for the limit using software. However, since digital zoom uses a part of an image for magnification, image quality is deteriorates. Thus, the optical zoom ratio can be increased by simultaneously adopting the zoom optical system having a focal length in a standard range and a single focus optical system having a shorter focal length. 
     There are two conventional methods to adopt both of the different optical systems. The first method is to include a single image sensor and a plurality of optical systems and selectively use the appropriate optical system. The second method is to include a plurality of image sensors and a plurality of optical systems. 
     Japanese Patent Publication No. 10-254055 discloses an optical system using the first method. Referring to  FIG. 1A , light passing through a first optical system  1  is reflected by a first reflection mirror  4  and incident on an image sensor  7 . Referring to  FIG. 1B , as the first reflection mirror  4  is moved to a vertical orientation, light passing through a second optical system  2  is reflected by a second reflection mirror  5  and incident on the image sensor  7 . Referring to  FIG. 1C , as the first and second reflection mirrors  4  and  5  are moved to the vertical orientation, light passing through a third optical system  3  is reflected by a third reflection mirror  6  and incident on the image sensor  7 . Since all the optical systems  1 ,  2 , and  3  to be adopted need to be included inside a compact camera, it is difficult to reduce the number of parts and make the camera compact. 
     Likewise, in an optical system using the second method, since the number of parts is further increased compared to the first method, it is difficult to reduce the costs for materials and make a camera compact. 
     SUMMARY 
     To solve the above and/or other problems, the present invention provides a dual lens optical system and a dual lens camera having the same. 
     According to an aspect of the present invention, there is provided a dual lens optical system comprising a first optical system reflecting an optical axis of light indicating an image of an object by 90° to form an image on an image sensor, and a second optical system having a movable reflection member configured to be selectively located on the part of a redirected axis of the optical axis of light passing through the first optical system, and refracting the light indicating the image of the object by 90° using the movable reflection member to be formed on the image sensor, wherein the first optical system and the second optical system share lenses and the image sensor located along an optical path after the movable reflection member. 
     The first and second optical systems share parts existing on the same optical path located after the movable reflection member. For example, the first and second optical systems share the second zoom lens group, the focusing lens group, and the image sensor. Thus, the number of parts is reduced compared to the conventional methods and there is less restriction in design space. 
     The first optical system comprises a first incident lens where light indicating the image of the object is incident, a first prism refracting the optical axis of the light by 90°, a first zoom lens group and a second zoom lens group adjusting a focal length to change a zoom ratio while moving along the optical axis, an image sensor where the light indicating the image of the object is formed, and a focusing lens group arranged to move along the optical axis between the second zoom lens group and the image sensor and adjusting focus so that the light indicating the image of the object is well formed on the image sensor. 
     The second optical system comprises a movable reflection member selectively positioned on the optical axis of light between the first zoom lens group and the second zoom lens group to allow light incident from an optical axis perpendicular to the part of the redirected optical axis of the first optical system to be formed on the image sensor, a second incident lens where the light indicating the image of the object is incident toward the movable reflection member in a direction perpendicular to the redirected optical axis of the first optical system, the second zoom lens group, and the image sensor. 
     The first optical system may be a zoom optical system and the second optical system may be a single-focus optical system having a focal length shorter than the focal length of the first optical system. Thus, the dual lens optical system according to an embodiment of the present invention integrally adopts the zoom optical system and the single-focus optical system. Thus, a wider range of an optical zoom ratio can be obtained compared to when the zoom optical system is only used. 
     The movable reflection member may be a prism or a reflection mirror. Also, the dual lens optical system may further comprise a lens cover selectively blocking the light on the second incident lens. 
     The lens cover blocks the second incident lens when the movable reflection member is not located on the optical axis between the first zoom lens group and the second zoom lens group and opens the second incident lens when the movable reflection member is located on the optical axis between the first zoom lens group and the second zoom lens group. 
     According to another aspect of the present invention, there is provided a dual lens camera comprising the dual lens optical system, a control unit receiving an electric signal from the image sensor and performing operation, and a memory unit electrically connected to the control unit and storing data indicating the image of the object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which: 
         FIGS. 1A through 1C  illustrate the operations of an optical system of a conventional multi-focus camera; 
         FIG. 2A  illustrates a dual lens optical system in a W mode according to an embodiment of the present invention; 
         FIG. 2B  illustrates a dual lens optical system in an M mode according to an embodiment of the present invention; 
         FIG. 2C  illustrates a dual lens optical system in a T mode according to an embodiment of the present invention; 
         FIG. 2D  illustrates a dual lens optical system in a SINGLE-FOCUS mode according to an embodiment of the present invention; 
         FIG. 3A  illustrates a dual lens optical system in a W mode according to another embodiment of the present invention; 
         FIG. 3B  illustrates a dual lens optical system in an M mode according to another embodiment of the present invention; 
         FIG. 3C  illustrates a dual lens optical system in a T mode according to another embodiment of the present invention; 
         FIG. 3D  illustrates a dual lens optical system in a wide angle mode according to another embodiment of the present invention; 
         FIG. 4A  illustrates a dual lens optical system in a W mode according to yet another embodiment of the present invention; 
         FIG. 4B  illustrates a dual lens optical system in an M mode according to yet another embodiment of the present invention; 
         FIG. 4C  illustrates a dual lens optical system in a T mode according to yet another embodiment of the present invention; 
         FIG. 4D  illustrates a dual lens optical system in a wide angle mode according to yet another embodiment of the present invention; and 
         FIG. 5  schematically illustrates a dual lens camera according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the invention with reference to the attached drawings. Like reference numerals in the drawings denote like elements. 
       FIGS. 2A ,  2 B, and  2 C respectively illustrate a dual lens optical system in a wide angle mode (“W mode”), a medium angle mode (“M mode”), and a telephoto mode (“T mode”) according to an embodiment of the present invention. Referring to  FIGS. 2A ,  2 B, and  2 C, the dual lens optical system according to the present embodiment includes a first optical system  10  and a second optical system  20 . In the current embodiment, the first optical system  10  is related to a zoom optical system while the second optical system  20  is related to a wide angle single-focus optical system. 
     The first optical system  10  includes a first incident lens  11 , a first prism  12 , a first zoom lens group  13 , a second zoom lens group  15 , a focusing lens group  16 , and an image sensor  17 . The first prism  12  redirects the optical axis of a path along which light proceeds, by 90°, the light representing an image of an object. The first zoom lens group  13  and the second zoom lens group  15  move along the optical axis to adjust a focus length and determine a zoom ratio. The focusing lens group  16  moves along the optical axis to adjust the focus so that the light representing the image of the object can be well formed on the image sensor  17 . Although in the drawings the focusing lens group  16  is a single lens, it may also include two or more lenses. The image sensor  17  receives the light representing the image of the object and converts the light to an electric signal for each pixel thereof. The image sensor  17  can be a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), or any other suitable image sensing device. 
     The first optical system  10  is a zoom optical system that changes between W, M and T modes according to the movements of the first and second zoom lens groups  13  and  15 . In detail, the focal length is the distance between the lens and the film (or image sensor) when the focus is on an image located at an infinite distance. In terms of a 35 mm camera, a standard focal length is between 40-100 mm. In the W mode, the focal length is relatively short, for example, 39 mm, so that a viewing angle is wide and a range of vision is large. Since the focal length is shorter than the standard, the W mode is a wide angle mode. Conversely, in the T mode, the focal length is relatively long, for example, 144.3 mm, so that the viewing angle is narrow and the range of vision is small. Since the focal length is longer than the standard, the T mode is telephoto mode. In the T mode, the optical zoom ratio is 3× because the focal length is three times longer than the focal length in the W mode. 
     In the above zoom optical system, the optical zoom ratio is determined by the movements of the first and second zoom lens groups  13  and  15  in a Z-axis direction. As digital cameras become smaller and thinner, there is a limit in increasing the optical zoom ratio. Thus, the dual lens optical system according to the present embodiment additionally adopts the second optical system  20 . 
       FIG. 2D  illustrates a dual lens optical system in a SINGLE-FOCUS mode according to an embodiment of the present invention. Referring to  FIG. 2D , the second optical system  20  is a wide angle single-focus optical system. The second optical system  20  includes a lens cover  23 , a second incident lens  21 , a second prism  22 , a first zoom lens group  13 , a second zoom lens group  15 , a focusing lens group  16 , and a image sensor  17 . The lens cover  23  may manually or automatically block light incident on the second incident lens  21 . Although in the drawing the lens cover  23  is a single plate and moves to another position, a method of closing or opening the second incident lens  21  by the lens cover  23  can be easily modified by those skilled in the art. That is, the lens cover  23  is made of a plurality of pieces like a camera shutter and, as the pieces rotate around a predetermined axis, the second incident lens  21  can be closed or open. 
     When a user tries to use the second optical system  20 , the lens cover  23  is opened to allow light to pass through the second incident lens  21  and the second prism  22  which is positioned on an axis between the first zoom lens group  13  and the second zoom lens group  15 . The driving direction of the second prism  22  can be a Y-axis direction as shown in  FIG. 2D  or an X-axis direction as shown in  FIG. 5 . The driving of a prism can be performed by a motorized mechanism such as a piezoelectric motor or a voice coil motor. The present invention is not limited thereto and many other motorized mechanisms capable of performing a linear motion can be used therefor. 
     When the second prism  22  is arranged along the optical axis which is between the first and second zoom lenses  13  and  15 , the second prism  22  redirects the light passing through the second incident lens  21  by 90° to proceed toward the image sensor  17  and simultaneously block the light passing through the first incident lens  11 . 
     In the present invention, as an embodiment of a single-focus optical system, a wide angle single-focus optical system having a focal length shorter than that of the zoom optical system in the W mode is illustrated. The focal length of the single-focus optical system can be 24 mm. Thus, since the viewing angle is wider, a larger number of objects can be photographed in the same photo. That is, the dual lens optical system according to the present embodiment integrally adopts the first optical system  10  (the zoom optical system) and the second optical system  20  (the single-focus optical system). Thus, an optical zoom ratio in a range wider than that when only the zoom optical system is used. 
     In particular, the first and second optical systems  10  and  20  may share at least some elements on the same optical path disposed after the second prism  22  that is a movable reflection member. For example, the first and second optical systems  10  and  20  share the second zoom lens group  15 , the focusing lens group  16 , and the image sensor  17 . Thus, the number of elements is reduced compared to conventional methods and therefore there is more efficient use of design space. That is, compared to conventional methods, the present invention provides a high optical zoom ratio in a smaller and thinner digital camera. Also, the cost for materials can be reduced. 
       FIGS. 3A through 3D  illustrate a dual lens optical system according to another embodiment of the present invention.  FIGS. 4A through 4D  illustrate a dual lens optical system according to yet another embodiment of the present invention. The difference in the embodiments of  FIGS. 3 and 4  from  FIGS. 2A through 2D  is that the movable reflection member is a reflection mirror  122  not the second prism  22 . In addition, in  FIGS. 4A through 4D , the reflection mirror  222  is in a different position, obviating the need for a separate lens cover  23 . 
     The dual lens optical systems shown in  FIGS. 3A through 3D  and  FIGS. 4A through 4D  adopt reflection mirrors  122  and  222 , respectively, instead of the second prism  22  illustrated in  FIGS. 2A through 2D . When the dual lens optical systems shown in  FIGS. 3A through 3C  and  FIGS. 4A through 4C  are used as zoom optical systems, the reflection mirrors  122  and  222  are not located on the optical axis between the first and second zoom lens groups  13  and  15 . 
     In  FIGS. 3A through 3D , the lens cover  23  blocks the second incident lens  21  to prevent the light indicating the image of the object from being incident on the second incident lens  21 . Thus, the light representing the image of the object passes through the first incident lens  11  and is redirected by the first prism  12  by 90° and passes through the first zoom lens group  13 , the second zoom lens group  15 , and the focusing lens group  16  for the image to be formed on the image sensor  17 . 
     When the second optical system  20  (the single-focus optical system) is used, the lens cover  23  opens the second incident lens  21  and the reflection mirror  122  pivots to be located on an axis between the first and second zoom lens groups  13  and  15 . It is important that the reflection mirrors  122  is accurately positioned at  450  with respect to the axis between the first and second zoom lens groups  13  and  15  to allow the incident light to accurately proceed toward the image sensor  17 . 
     In the dual lens optical systems shown in  FIGS. 4A through 4D , the reflection mirror  222  is arranged close to the second incident lens  21  and the lens cover  23  is not provided, unlike the dual lens optical system shown in  FIGS. 3A through 3D . When the first optical system  10  (the zoom optical system) is used, the reflection mirror  222  is arranged parallel to the optical axis between the first zoom lens group  13  and the second zoom lens group  15 . Accordingly, since the reflection mirror  222  blocks the light representing the image of the object passing through the second incident lens  21 , the lens cover  23  is not needed. 
     When the second optical system  20  (the single-focus optical system) is used, the reflection mirror  222  pivots by 45° to be located on an axis between the first zoom lens group  13  and the second zoom lens group  15 . Thus, the light representing the image of the object incident on the first incident lens  11  is blocked by the reflection mirror  222 . Only the light representing the image of the object incident on the second incident lens  21  is redirected by 90° by the reflection mirror  222  and proceeds toward the image sensor  17 . It is important that the reflection mirror  222  is accurately positioned at  450  with respect to the axis between the first zoom lens group  13  and the second zoom lens group  15  to allow the incident light to accurately proceed toward the image sensor  17 . 
       FIG. 5  schematically illustrates a dual lens camera according to an embodiment of the present invention. The dual lens camera  100  includes the dual lens optical systems ( 10  and  20 ), a control unit (not shown), and a memory unit (not shown). Also, the dual lens camera  100  further includes a view finder (not shown). 
     The image sensor  17  of the optical system receives light representing the image of the object and converts the light to an electric signal for each pixel thereof. An electric signal output from the image sensor  17  is input to the control portion through a signal transfer unit, for example, a flexible printed circuit board (FPCB). The control portion operates and processes the signal to generate image data and may transfer the image data to the memory portion and/or the view finder as necessary. 
     As described above, in the dual lens camera having the dual lens optical systems  10  and  20  according to the present invention, since the optical systems  10  and  20  share at least some elements, the dual lens camera can be made smaller and thinner. Also, the cost for materials can be reduced. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.