Abstract:
A thin transparent media adapter is used when scanning transparent media on a contact image sensor or reduction optics scanner. The adapter uses illumination from a light guide assembly to illuminate a diffuser and the media. A lens assembly is used to focus the light from the media to create an intermediate image between the adapter and the scanner platen glass. The adapter is an optical assembly that forms an intermediate image of the transparent media in the object side focal plane of existing scanner optics. The existing scanner optics can then capture and focus the light from the intermediate image onto the scanner&#39;s existing sensor array. The adapter magnetically couples to the scan system to allow the lens array to follow movement of the optical system of the scanner.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an optical scanning system. More specifically, the present invention discloses an optical adapter that magnetically couples with a contact image sensor scanner module for effectively scanning transparent media. 
         [0003]    2. Description of the Prior Art 
         [0004]    A conventional image scanner is capable of producing digital images from printed text or photographic images. In the tradition system, an opaque media is place on the platen glass of the scanner. A light source in the scanner emits light onto the opaque media in order to illuminate the media. Light is reflected off the media and is picked up by a series of lenses or a lens array. The lens array focuses the reflected light onto a sensor array which captures the light in order to produce the digital image of the opaque media. However, while the conventional image scanner is useful when used with opaque media, it is ineffective when used with transparent media. 
         [0005]    Opaque media is capable of reflecting light whereas the light emitted from the scanner light source will simply pass through the transparent media. As a result, the sensor array is unable to detect a useful amount of light and cannot capture an accurate image of the transparent media. Therefore until now, it was necessary to utilize a dedicated scanner for transparent media. 
         [0006]    A dedicated transparent media scanner houses the light source in a cover over the top of the transparent media and emits the light on the back of the media. The lens array mounted in the bottom of the scanner then focuses the light onto the sensor array. The sensor array captures the light in order to capture a digital image of the transparent media. However, this transparent media scanner is relatively expensive since either a large area light emitting panel or a small panel with an additional motor and drive system are also required in the cover. Also, contact image sensor scan modules utilize lens arrays that have very short depth of focus that limits the range of transparent media types that can be scanned. Additionally, alignment and coordination between the bottom system and cover system is complex and prone to misalignment. Furthermore, it is a waste of resources to require the need for a dedicated transparent media scanner when a conventional image scanner can be adapted to scan transparent media. 
         [0007]    Therefore there is need for an optical transparent media adapter that efficiently flattens and backlights transparent media and which can be used with a contact image sensor type of scanner module. 
       SUMMARY OF THE INVENTION 
       [0008]    To achieve these and other advantages and in order to overcome the disadvantages of the conventional method in accordance with the purpose of the invention as embodied and broadly described herein, the present invention provides a media adapter with magnetically coupled optics and light guide for scanning transparent media. 
         [0009]    The transparent media adapter (TMA) can be utilized for scanning transparent media on contact image sensor (CIS) scanners. The present invention provides an optical assembly that forms an intermediate image of the transparent media in the object side focal plane of the existing scanner optics. The existing scanner optics can then capture and focus the light from the intermediate image onto the scanner&#39;s existing linear sensor array. 
         [0010]    The TMA of the present invention comprises a lens assembly, a light guide assembly, a diffuser, and a media holder. The TMA uses illumination from the light guide assembly to illuminate the diffuser and media. The lens assembly is used to focus the light from the media to create an intermediate image between the TMA and scanner platen glass. 
         [0011]    A magnet attached to the lens assembly magnetically couples with the optical system of a scanner. As the optical system moves, the lens assembly follows the movement. This allows the lens assembly to follow the movement of the scanner as it scans and allows the lens assembly and the underlying scan module to properly align and move in a synchronized manner. 
         [0012]    The present invention has the advantage of providing a compact, low cost transparent media adapter that can be magnetically coupled to the scan system. This allows the cost of the transport system to be reduced because the need for a motor and drive belt are eliminated. The TMA captures a large amount of light and all the light can be transmitted to the underlying scanner module. Additionally, the TMA has the advantage that it can create an intermediate image of the transparent media in the correct focal plane for the underlying scan module. This is particularly important for CIS based scanners because they have very shallow depth of field and cannot scan media that is above the platen glass. 
         [0013]    As a result, the present invention solves the problem of how to flatten and backlight transparent media in a scanner and how to locate the media in the focal plane of the module, which is typically located very close to the top surface of the platen glass. Additionally, the present invention reduces the cost and complexity of the TMA solution. 
         [0014]    These and other objectives of the present invention will become obvious to those of ordinary skill in the art after reading the following detailed description of preferred embodiments. 
         [0015]    It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
           [0017]      FIG. 1  is a drawing illustrating a side view of an optical system of an image scanner and transparent media adapter with magnetically coupled optics and light guide according to an embodiment of the present invention; 
           [0018]      FIG. 2  is a drawing illustrating a side view of an optical system of an image scanner and transparent media adapter module using long total conjugate lens according to an embodiment of the present invention; and 
           [0019]      FIG. 3  is a drawing illustrating the relationship between lens diameter and light angles according to an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
         [0021]    Refer to  FIG. 1 , which is a drawing illustrating a side view of an optical system of an image scanner and transparent media adapter with magnetically coupled optics and light guide according to an embodiment of the present invention. 
         [0022]    As shown in  FIG. 1 , the CIS scanner module  105  of the image scanner comprises a sensor board  120  with a sensor array  115 , a light source  125 , and a lens array  1110 . The CIS module  125  is the existing scan module in the scanner. On the top of the image scanner is platen glass  130  on which the transparent media adapter of the present invention rests. 
         [0023]    The transparent media adapter module  100  comprises a media holder  170 , a diffuser  180 , a light guide assembly  185 , and a lens assembly  150 . The media holder  170  positions and holds the transparent media  175 . On top of the media holder  170  and transparent media  175  is a diffuser  180  for diffusing light. The light guide assembly  185  comprises a light source  190  for illuminating the transparent media  175 . On the bottom of the light guide assembly  195  are wheels that facilitate movement of the light guide assembly  185 . 
         [0024]    The lens assembly  150  comprises a lens array  155 . Similar to the light guide assembly  185 , the lens assembly  150  has wheels  165  on the bottom of the assembly  150  which roll across glass  145 . A magnet  160  or a plurality of magnets is disposed on the lens assembly  150  for magnetically coupling with a magnet  112  connected to the optical system of the scanner module  105 . 
         [0025]    In the embodiment illustrated in  FIG. 1 , the light guide assembly  185  is connected to the lens assembly  150 . This allows the light guide assembly  185  and lens assembly  150  to move together. However, in other embodiments a magnet or a plurality of magnets is disposed on the light guide assembly to magnetically couple with the lens assembly. 
         [0026]    In operation, the TMA  100  uses illumination from the light source  190  of the light guide assembly  185  to illuminate the diffuser  180  and transparent media  175 . The light source  125  in the scanner module  105  is disabled when the TMA  100  is operating. The lens assembly  150  is used to focus the light from the media to create an intermediate image  140  between the TMA  100  and the scanner platen glass  130 . In  FIG. 1 , the scanner module  105  uses a lens array  110 , such as the  12 E lens array from Nippon Sheet Glass, to focus the intermediate image  140  onto the sensor array  110  to enable the scanner module  105  to capture an image of the media  175 . 
         [0027]    As the optical system of the scanner module  105  moves the magnetically coupled light guide assembly  185  and lens assembly  150  follow the optical system. In this way, as the light guide assembly  185  illuminates a portion of the media  175 , an intermediate image  140  of the media  175  is formed by the lens assembly  150  and captured by the sensor array  115 . As the optical system continues to move across the media  175 , this process continues until a complete image of the media  175  is captured. 
         [0028]    Refer to  FIG. 2 , which is a drawing illustrating a side view of an optical system of an image scanner and transparent media adapter module using long total conjugate lens according to an embodiment of the present invention. The TMA illustrated in  FIG. 2  is similar to the one in  FIG. 1  but with an alternative lens assembly. In  FIG. 1 , a lens array with a short total conjugate length, such as the  12 E lens array, is utilized to form the intermediate image of the media. However, in  FIG. 2 , the lens assembly utilizes long total conjugate lens array such as the  12 B lens array from Nippon Sheet Glass. 
         [0029]    Since the  12 B lens array  156  is relatively long it is impractical to place the lens array  156  vertically. Therefore, in  FIG. 2  the lens array  156  is placed horizontally and a plurality of mirrors or prisms is used to reflect the image of the media  175  illuminated by the light guide assembly  185 . In this embodiment a first mirror  151  reflects the light from the media  175  towards a first prism  152  at approximately 90 degrees. The first prism  152  reflects this light and through the lens array  156  towards a second prism  153 . The first prism  152  reflects the light from the first mirror  151  by approximately 180 degrees. The second prism  153  reflects the light from the first prism  152  by approximately another 180 degrees towards a second mirror  157 . The second mirror  157  reflects the light by approximately 90 degrees to form an intermediate image  140  of the media  175  between the TMA  100  and the scanner platen glass  130 . 
         [0030]    Refer to  FIG. 3 , which is a drawing illustrating the relationship between lens diameter and light angles according to an embodiment of the present invention.  FIG. 3  also shows the relationship of the two lens arrays  12 B and  12 E. 
         [0031]    For the  12 E lens array shown on the bottom of  FIG. 3 , the capture angle is approximately 6 degrees in the y direction and 12 degrees in the x direction (along the scan line). For the  12 B lens array, the light angles at the intermediate image allow the image to be completely captured provided the  12 E and  12 B are aligned to approximately +/−0.5 mm. Beyond this range, the percentage of light captured decreases as the misalignment increases. This means it is important to achieve good alignment and good magnetic tracking to capture all the light present in the intermediate image. 
         [0032]    An advantage of the present invention is that since the lens assembly, light guide assembly, and optical system of the scanner module are magnetically coupled, no motor or drive assembly are required in the TMA. This saves expense and reduces complexity of the TMA Additionally, the magnets that are used to couple the existing scan module allow the TMA and the underlying scan module to properly align and move in a synchronized manner. The magnets keep the TMA aligned with the scan module as it moves from left to right or from right to left. 
         [0033]    In another embodiment of the present invention, the light guide assembly, lens assembly, or scan module use a metal plate instead of a magnet, as long as the magnet on the other module is strong enough to provide sufficient coupling to the metal plate. For example, when using a scan module with a metal plate instead of a magnet installed, positioning a magnet or magnets on the lens assembly allows the magnet of the lens assembly to couple with the scan module and follow the scan module movement. Alternatively, a metal plate is attached to light guide assembly. A magnet on the lens assembly couples to the metal plate and allows the light guide assembly to move with the lens assembly. 
         [0034]    In another embodiment of the present invention, the light guide assembly, lens assembly, or scan module use an electromagnet instead of a magnet, as long as the electromagnet is strong enough to provide sufficient coupling to the other module. For example, when using a scan module with an electromagnet instead of a magnet installed, positioning a magnet or magnets on the lens assembly allows the magnet of the lens assembly to couple with the electromagnet on the scan module and follow the scan module movement. 
         [0035]    In the embodiments illustrated in  FIG. 1  and  FIG. 2 , wheels are attached to the lens assembly and light guide assembly. However, in other embodiments of the present invention slides are used in place of the wheels. The slides are made of a low friction material that allows the assemblies to easily slide and follow the movement of the optical system. 
         [0036]    As described above, the present invention provides a compact, low cost transparent media adapter that is magnetically coupled to the scan system. This allows the cost of the transport system to be reduced because the need for a motor and drive system are eliminated. 
         [0037]    The present invention backlights the transparent media so it can be imaged by the underlying scanner module. The lens assembly captures a significant amount of light and focuses the light to create an intermediate image of the media. 
         [0038]    The transparent media adapter with magnetically coupled optics and light guide of the present invention solves the problem of how to flatten and backlight transparent media for a CIS or reduced optics based scanner. The magnetic coupling allows the optics and illumination to be optimized for a narrow region that moves in sync with the scan module. 
         [0039]    Furthermore, the present invention has the advantage that it can transfer the media image to the correct focal plane for the underlying scan module. This is particularly important for CIS based scanners because they have very shallow depth of field and cannot scan media that is above the platen glass. 
         [0040]    It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the invention and its equivalent.