Abstract:
Distinct designs are provided to reduce dimensions of an image sensing module without affecting the sizes of the original individual components in the image sensing module. According to one embodiment, a mirror is mounted before an optical focus system and used to collect and redirect reflected light from a scanning object being illuminated by an illumination source in the image sensing module, wherein the scanning object is parallel to the optical focus system.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present invention is related to commonly assigned U.S. Pat. No. 6,054,707, entitled “Portable scanners capable of scanning both opaque and transparent materials”, which is hereby incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention generally relates to image sensing modules for optical imaging devices and more particularly relates to image sensing modules practically suitable for being integrated into portable computing devices, wherein the portable computing devices may include, but not be limited to, a palm pilot, a mobile phone and a personal data assistant (PDA).  
           [0004]    2. Description of the Related Art  
           [0005]    There are many applications that need optical imaging devices to convert paper-based objects, such as texts and graphics, to an electronic format that can be subsequently analyzed, distributed and archived. One of the most popular optical imaging devices are flatbed scanners that typically convert scanning objects, including pictures and papers, to images that can be used for example, for building world wide web pages and optical character recognition. Another emerging optical imaging device is what is called sheet-fed scanners that are small and unobtrusive enough to sit between a keyboard and a computer monitor or integrated into a keyboard to provide a handy scanning means. Most optical scanners are referred to as image scanners as the output thereof is generally in digital format.  
           [0006]    [0006]FIG. 1 illustrates a cross section of an exemplary image sensing module  100  that is typically used in those image scanners. Image sensing module  100  includes a light source  102 , an optical system  108 , and an image sensor  110 , all are cast in an elongated rectangular tube. When scanning object  120  passes through image sensing module  100 , it is illuminated by light source  102  through a window  116 . The light reflected by scanning object  120  is then focused through optical path  114  by optical lens system  108  onto image sensor  110 . An image of scanning object  120  is therefor generated.  
           [0007]    Portable imaging devices containing image sensing module  100  have been used as PC scanners, facsimiles and other multi-function peripherals. However, with the recent explosion of the mobile personal computing market, the demand for effective, mobile internet-connective digital imaging and scanning is increasing at a tremendous rate. Optical imaging devices smaller than the existing sheet-fed type scanners are required in many applications, for example, as an integral part of a palm pilot. An image sensing module is a key component in portable imaging devices. Its dimension is vital to the overall size of the entire imaging device. As shown in FIG. 1, in image sensing module  100 , scanning object  120  is perpendicular to optical system  108 . With required length of optical path  114 , it would be impractical to use an image sensing module as shown in FIG. 1 in a portable imaging device. There is therefore a need for smaller designs of an image sensing module practically suitable for being integrated in portable imaging devices.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention has been made in consideration of the above described challenge and needs and has particular applications to portable computing devices that may include, but not be limited to, a palm pilot, a mobile phone and a personal data assistant (PDA).  
           [0009]    According to one aspect of the present invention, distinct designs are provided to reduce dimensions of an image sensing module without affecting the sizes of the original individual components in the image sensing module. According to one embodiment, a mirror is mounted before an optical focus system and used to collect and redirect reflected light from a scanning object being illuminated by an illumination source in the image sensing module. In this configuration, the scanning object can be placed parallel to the optical lens system. The resultant image sensing module is much slimmer compared to the existing image sensing module.  
           [0010]    According to another embodiment of the present invention, the image sensing module comprises an elongated rectangular case or tube. The components, such as an image sensor, an illumination source and an optical lens system, are placed at an angle in the elongated rectangular case such that the size of the elongated rectangular case is minimized without affecting the size of the components. The new configuration results in an image sensing module of reduced size and particularly suitable for the portable computing devices equipped with image scanning capability.  
           [0011]    Accordingly, an important object of the present invention is to provide generic solutions for an image sensing module of reduced size.  
           [0012]    Other objects, together with the foregoing are attained in the exercise of the invention in the following description and resulting in the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:  
         [0014]    [0014]FIG. 1 illustrates a cross section of an image sensing module commonly used in an existing optical scanner;  
         [0015]    [0015]FIG. 2 shows a cross-section view of an image sensing module according to one embodiment of the present invention;  
         [0016]    [0016]FIG. 3 shows a cross-section view of an image sensing module according to another embodiment of the present invention; and  
         [0017]    [0017]FIG. 4 shows a side view of a portion of a portable computing device equipped with image scanning capability using an image sensing module of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    The invention pertains to improved designs of image sensing modules suitable for being integrated in portable computing devices that may include, but not be limited to, personal data assistant (PDA), mobile phones and palm computing devices. With the employment of the current invention, it is now possible to equip the portable computing devices with a scanning capability that may, in many cases, alleviate the inputting dilemma commonly seen on the portable computing devices. For example, a Palm Pilot requires a user to enter data by writing letters on its small writing pad using a set of special stroking rules. It is indeed tedious and laborious to input a long text. With an integrated scanning mechanism employing the image sensing module of the present invention, it is possible to scan in a long text without too much effort.  
         [0019]    Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.  
         [0020]    Referring now to the drawings, in which like numerals refer to like parts throughout the several views. FIG. 2 illustrates a side view of an image sensing module according to one embodiment of the present invention. As shown in the figure, image sensing module  200  comprises an illumination source  202 , a mirror  206 , an optical lens system  208 , and an image sensor  210 . Depending on an exact implementation illumination source  202  may be a monochromatic light or 3 different color lights (e.g. a set of Red, Green or Blue light emitting diodes). Mirror  206  is used to redirect light path. In one embodiment, optical lens system  208  is an array of rod lens. Image sensor  210  may be 1-Dimensional or 2-Dimensional photodetectors based on CCD or CMOS technologies. From the description herein, it will be evident to those skilled in the art to understand how to integrate the parts (i.e.  202 ,  206 ,  208  and  210 ) in an elongated tube.  
         [0021]    In one embodiment, image sensing module  200  includes a transparent window  216 . When there is a relative movement between scanning object  220  and image sensing module  200 , scanning object  220  is illuminated by illumination source  202 . After light hits scanning object  220  and is then reflected through optical path  212  onto mirror  206  and further redirected by mirror  206  onto image sensor  210  through optical lens system  208 . The reflected light passing through optical path  212  is imaged by image sensor  210 . Different from the image sensing module shown in FIG. 1, one of the important features of the present invention is that the reflected lights from the scanning object is redirected by the mirror. As a result, it is possible to design a slim image sensing module and scan the scanning object parallel to optical lens system  208 .  
         [0022]    [0022]FIG. 3 illustrates a cross-section view of another image sensing module according to one embodiment of the present invention. As shown in the figure, image sensing module  300  comprises an illumination source  302 , an optical lens system  308  and an image sensor  310 , all cast in an elongated rectangular tube  330 . Instead of placing illumination source  302 , optical lens system  308  and image sensor  310  squarely in elongated rectangular tube  330 , they are now placed diagonally inside elongated rectangular tube  330 . According to one embodiment, illumination source  302 , optical lens system  308  and image sensor  310  are placed at around 45 degree. As a result, the overall size of the image sensing module could be reduced by about 30% (i.e. 0.707:1) provided to maintain the same illumination source, optical lens system and image sensor. This configuration is very desirable for integration with portable devices such as palm pilots.  
         [0023]    Referring now to FIG. 4, there is shown a side view of a portion of a portable computing device  400  that is equipped with image scanning capability. A user can now scan in, for example, a business card. It is generally convenient and customary to hold such portable computing device tilted when scanning a scanning object  402  across. Although it is possible to still employ a regular image sensing module, such as the one in FIG. 1, to accommodate the tilting scanning position, it would be mechanically difficult or at least inefficient to integrate such image sensing module in the portable computing device. As shown in the figure, a improved image sensing module  404 , such as the example in FIG. 3, can be conveniently integrated at the end of portable computing device  400  and at the same time provide the tilting scanning position when scanning a scanning object  402 . According to one embodiment, a roller  406  is provided. The roller  406  rotates when portable computing device is caused to move across scanning object  402 . Roller  406  may be coupled to an encoder (not shown) to record the motion to synchronize the image scanning by image sensing module  404 .  
         [0024]    The present invention has been described in sufficient detail with a certain degree of particularity. The utilities thereof are appreciated by those skilled in the art. It is understood to those skilled in the art that the present disclosure of embodiments has been made by way of examples only and that numerous changes in the arrangement and combination of parts may be resorted without departing from the spirit and scope of the invention as claimed. Accordingly, the scope of the present invention is defined by the appended claims rather than the forgoing description of embodiments.