Abstract:
A flatbed scanner includes a housing, a transparent platen atop the housing for receiving an object to be scanned, and a carriage operable to travel along a horizontal direction and a vertical direction. The carriage includes a light source for illuminating the object and a rectangular photodetector array for simultaneously detecting light intensity of multiple scan lines.

Description:
RELATED APPLICATION 
     This application is a divisional application of commonly-assigned U.S. patent application Ser. No. 10/821,821, filed Apr. 8, 2004, entitled “TWO-DIMENSIONAL CMOS SENSOR ARRAY TO IMAGE DOCUMENTS AND OTHER FLAT OBJECTS,” hereby incorporated by reference in its entirety. 
    
    
     DESCRIPTION OF RELATED ART 
     When using a conventional flatbed scanner, the document is placed on the glass platen and the cover is closed. A light source (e.g., cold cathode fluorescent lamp, a xenon lamp, or light emitting diodes) is used to illuminate the document. A scan head (e.g., consisting of mirrors, lens, filter, and image sensor array) is moved slowly down the document (e.g., by a belt that is attached to a stepper motor or a gear set linked to a DC motor). The scan head is attached to a stabilizer bar to ensure that there is no wobble or deviation in the pass (i.e., a single complete scan of the document). 
     The image of the document is reflected by angled mirrors to form a folded light path. The last mirror reflects the image onto a lens. The lens focuses the image on an image sensor. A typical charged coupled device (CCD) image sensor has 3 linear CCD sensor arrays. Each linear array has a different color filter (e.g., red, green, and blue) placed directly on top of the CCD sensors. The scanner then combines the data from the linear CCD sensor arrays into a single full-color image. In comparison, a typical contact image sensor (CIS) has one linear complementary metal oxide semiconductor (CMOS) sensor array that captures an image sequentially illuminated by red, green, and blue light sources (e.g., light emitting diodes). The scanner then combines the data from the linear CMOS sensor array into a single full-color image. 
     Scanners vary in resolution and sharpness. Most flatbed scanners have a true hardware resolution of at least 600×600 dots per inch (dpi). The scanner&#39;s dpi is determined by the number of sensors in a single row (x-direction sampling rate) of the sensor array and by the precision of the stepper motor (y-direction sampling rate). For example, if the resolution is 600×600 dpi and the scanner is capable of scanning a letter-sized document, then the CCD image sensor would have three linear arrays each having 5,100 sensors while a CIS would have one linear array of 5,100 sensors. The stepper motor in this example is able to move in increments equal to 1/600ths of an inch. 
     SUMMARY 
     In one embodiment of the invention, a scanner includes a housing, a transparent platen atop the housing for receiving an object to be scanned, and a carriage operable to travel along a horizontal direction and a vertical direction. The carriage includes a light source for illuminating the object and a rectangular photodetector array for simultaneously detecting light intensity of multiple scan lines. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a top view of a flatbed scanner in one embodiment of the invention. 
         FIGS. 2 and 3  illustrate cross-sectional side views of the flatbed scanner of  FIG. 1  in one embodiment of the invention. 
         FIGS. 4 and 5  illustrate movement of a rectangular photodetector array in embodiments of the invention. 
         FIG. 6  illustrates a cross-sectional side view of a sheet feeder scanner in one embodiment of the invention. 
         FIG. 7  illustrates a cross-sectional side view of a flatbed scanner in one embodiment of the invention. 
     
    
    
     Use of the same reference numbers in different figures indicates similar or identical elements. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a flatbed scanner  10  in one embodiment of the invention. Scanner  10  includes a housing  12 , a cover  14  hingedly attached to housing  12 , a transparent (e.g., glass) platen  16  atop housing  12 , and a carriage  18  within housing  12 . Carriage  18  travels within housing  12  on a vertical gear channel  20  and a horizontal gear channel  22 . Carriage  18  includes a rectangular photodetector array  24  and an illumination ring  26 . 
     In one embodiment, photodetector array  24  has multiple (e.g., more than three) rows of complementary metal oxide semiconductor (CMOS) sensors. In one embodiment, photodetector array  24  consists of a variety of red, blue, and green photodiodes and the actual color at the site of each photodiode is interpolated from the colors of the neighboring photodiodes. In a lower-end scanner with a slower throughput, photodetector array  24  may have a resolution of 352×288 pixels. In a higher-end scanner with a faster throughput, photodetector array  24  may have 1.3 megapixel of resolution to enable the entire page to be scanned more quickly. In one embodiment, illumination ring  26  are light emitting diodes (LEDs) formed around photodetector array  24  on the same die. 
       FIG. 2  illustrates a cross-section view of carriage  18  along line A ( FIG. 1 ) in one embodiment of the invention. Photodetector array  24  and illumination ring  26  are mounted on a plate  32 . Mounting plate  32  includes a horizontal guide  34 . A motor  36  and associated gear system  38  are mounted to plate  32 . A horizontal carriage bar  40  defines a horizontal guide channel  42  that receives guide  34 . Horizontal carriage bar  40  further defines gear channel  22  that receives a gear from gear system  38 . Gear channel  22  includes teeth that engage gear system  38 . In operation, motor  36  drives gear system  38  to move carriage  18  horizontally across the object to be scanned. A flex cable  50  ( FIG. 3 ) moves the image data from photodetector array  24  to horizontal carriage bar  40 . 
       FIG. 3  illustrates a cross-section view of carriage  18  along line B ( FIG. 1 ) in one embodiment of the invention. Horizontal carriage bar  40  includes vertical guides  44 A and  44 B. A motor  46  and associated gear system  48  are mounted to horizontal carriage bar  40 . Housing  12  defines vertical guide channels  52 A and  52 B that receive corresponding guides  44 A and  44 B. Housing  12  further defines gear channel  20  that receives a gear from gear system  48 . Gear channel  20  includes teeth that engage gear system  48 . In operation, motor  46  drives gear system  48  to move carriage  18  vertically down the object to be scanned. A flex cable  52  moves the image data from horizontal carriage bar  40  to the scanner base for the data to be processed by the scanner electronics. 
     During scanning, the object to be scanned is placed on glass platen  16 . Illumination ring  26  then illuminates a portion of the object. Light is reflected from this portion of the object and simultaneously captured as multiple (e.g., more than three) scan lines by rectangular photodetector array  24 . Photodetector array  24  converts the light intensity of this portion into electrical signals.  FIG. 4  illustrates that, instead of slowly moving scan line by scan line as in conventional flatbed scanners, carriage  18  moves horizontally or vertically in large increments (e.g., exemplified by a movement  62  of sensor  64 ) equal to or greater than the corresponding width and height of photodetector array  24  in one embodiment of the invention. This allows for a faster scanning process. After the entire object is scanned, software is used to interpolate pixel colors and to stitch together the scanned portions into a single color image of the object. Software can also be used to correct any non-uniform lighting. 
       FIG. 5  illustrates that the resolution can be increased by micro-stepping rectangular photodetector array  24  both horizontally and vertically in small increments (e.g., exemplified by a movement  66  of sensor  64 ) in one embodiment of the invention. The horizontal increment is less than the horizontal spacing between adjacent sensors while the vertical increment is less than the vertical spacing between adjacent sensors. For example, if photodetector array  24  produces 300×300 dpi, then the resolution can be doubled to 600×600 dpi by (1) capturing an image of the object, (2) moving photodetector array  24  by half (½) a dpi in the horizontal and the vertical directions, and (3) capturing another image of the object. Software is then used to combine the two images to form a 600×600 dpi image of the object. After a micro-step, carriage  18  can move horizontally or vertically in a large increment to scan the next area on the object, followed by another micro-step. 
       FIG. 6  illustrates a side cross-sectional view of a sheet feeder scanner  100  in one embodiment of the invention. Scanner  100  includes a housing  102 , a sheet feeder  104 , feed rollers  106 , and a carriage  108  within housing  102 . Sheet feeder  104  grabs a single sheet  110  of document from a stack  112  and moves it vertically to feed rollers  106 . Feed rollers  106  move sheet  110  past carriage  108 . Carriage  108  includes rectangular photodetector array  24  and illumination ring  26 . To scan sheet  110 , carriage  108  travels horizontally within housing  102  on horizontal gear channel  22  and horizontal guide channel  42 . Carriage  108  is similar to carriage  18  but without the vertical travel components because feed rollers  106  function to move the paper vertically past carriage  108 . Instead of moving the paper slowly scan line by scan line as in conventional sheet feeder scanners, feed rollers  106  vertically move single sheet  110  in large increments equal to or greater than the height of photodetector array  24 . Again, this allows for a faster scanning process because portions of the documents are simultaneously captured as multiple scan lines by rectangular photodetector array  24 . 
       FIG. 7  illustrates a side cross-sectional view of a flatbed scanner  200  in one embodiment of the invention. Scanner  200  includes a housing  212 , a glass platen  216  atop housing  212 , a stationary rectangular photodetector array  218  with optics  220 , and light sources  222 . 
     During scanning, the object to be scanned (e.g., object  224 ) is placed on glass platen  16 . Light sources  222  then illuminates the entire object by directing light onto object  224  or bouncing light off the sidewalls of housing  212  and then onto object  224 . Light is reflected from object  224  and directed by optics  220  onto rectangular photodetector array  218 . Photodetector array  218  converts the light intensity of the scanned object into electrical signals. Instead of moving a carriage as in conventional scanners, photodetector array  218  remains stationary and scans the entire object at once. Again, this allows for a faster scanning process because multiple scan lines are captured simultaneously by photodetector array  218 . Software can be used to interpolate pixel colors and to correct any non-uniform lighting. 
     Various other adaptations and combinations of features of the embodiments disclosed are within the scope of the invention. Numerous embodiments are encompassed by the following claims.