Abstract:
An automatic paper feeder including an upper light source comprises of a paper tray for holding a plurality of scanning documents, a base frame for mounting on the scanning platform of a scanner, a channel for guiding the scanning document to move along a desired direction and path, an upper light source, a transmission unit for picking up and moving the scanning document, a control unit for controlling the transmission unit and the upper light source, and a cable for wiring the automatic paper feeder to the scanner. The paper feeder enables the scanner to perform paper-feeding type scanning at high scanning efficiency. Beside providing automatic single page feeding, the automatic paper feeder also able to perform transparency scanning through its upper light source. The scanner equips with this automatic paper feeder thus able to perform dual function of reflective type and transparency scanning.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an automatic paper feeder which includes an upper light source and particularly an automatic paper feeder for use with a scanner that is able to automatically feed paper and facilitate both reflective and transparent documents scanning functions. 
     2. Description of the Prior Art 
     Conventional flatbed type scanning and copying equipment such as optical scanners and copiers usually have a document placed on a transparent platform stationary, then having a scanning means moving across the transparent platform to perform scanning process. This type of scanning equipment can process only one piece of document at a time. Its operation is labor intensive and not efficient for high volume scanning work. To remedy this problem, an automatic paper feeder has been introduced. FIG. 1 shows an example of such device for scanning or copying machine use. The automatic paper feeder  1  includes a paper tray  11  which can hold a plurality of scanning documents  13  and a transmission unit  12  which has a plurality of rollers for automatically picking a sheet of document  13  at a time to feed into a channel  14 . There is a cable  15  to wire the paper feeder  1  to a control circuit board  21  in a scanner  2 . Then a software is employed to coordinate and control the operations of the paper feeder  1  and the scanner  2 . 
     When in use, the transmission unit  12  picks up a document  13  and feeds it into the channel  14  until it laid upon a scanning platform  22 . Then a scanning means  23  is activated to move across the scanning platform  22  to perform scanning process. After scanning completed, the transmission unit  12  discharges the document  13  from the scanning platform  22 , and picks up another document in the paper tray  11  for another cycle of scanning operation. 
     In this type of scanner, the scanning document is laid stationary on the scanning platform during scanning process. Document movement is intermittent and becomes a drag on operation which is still not very efficient if a lot of documents are to be scanned. In addition, it suits only reflection type scanning work. As it has only a lower light source  231  located in the scanning means  23  to project light through the transparent scanning platform  22  upon the document  13  held in the channel  14 . It generally is no good for transparency scanning (such as projection transparency, slide, negative film, and etc.) as the channel  14  has an allowance which makes the document cannot be held upon the platform closely or evenly. Therefore it often results in poor scanning quality such as double image, overlapping image or blurring image when performing transparency scanning. 
     SUMMARY OF THE INVENTION 
     In view of aforesaid disadvantages, it is therefore an object of this invention to provide an automatic paper feeder including an upper light source that moves the document against a stationary scanning means so that scanning process is continuous rather than intermittent. It thus greatly enhances scanning efficiency. Furthermore, the upper light source can provide light emitting through a transparent document when there is a need to perform transparency scanning. Reflection type scanning can also be performed by switching off the upper light source and use the lower light source in the scanning device for providing reflecting light. Its dual functionality is more flexible an versatile than conventional scanners. 
     In order to achieve aforesaid object, the automatic paper feeder according to this invention includes a paper tray which can hold a plurality of scanning documents, a base frame for mounting on a transparent platform of a scanner, a channel, an upper light source, a transmission unit for picking up document from the paper tray, a control unit for controlling the transmission unit and the upper light source, and a cable to connect the automatic paper feeder with the scanner. The base frame has a transparent zone at the bottom mating against the transparent platform of the scanner. The channel has one end engaging with the paper tray for receiving document and has another end extending over the transparent zone. The channel further has a transparent window and a reflection plate located above the transparent zone. The upper light source is located above the transparent window opposite to the transparent zone. 
     When in use, the base frame of the paper feeder of this invention is mounted on the scanner with the transparent zone located above the transparent platform. The scanning means of the scanner is moved to a desired position under the transparent zone. Then transmission unit picks up scanning document from the paper tray one by one continuously. The scanning document is carried by the transmission unit and passes the transparent zone and over the scanning means for scanning. The scanning documents are moving continuously while the scanning means is stationary. Therefore scanning process may be performed continuously like a feed-sheet type scanner at high speed rather than intermittently like a conventional flatbed type scanner. It thus has a much greater scanning efficiency. 
     When the scanning document is a transparency, the scanning means is moved under the transparent winder below the upper light source. The upper light source is turned on while a lower light source in the scanning means is turned off When the transparency passes over the transparent zone, the upper light source projects light through the transparency and trigger the scanning means to perform scanning process. 
     For reflective scanning, the scanning means is moved away from the transparent window and is located under the reflection plate. The upper light source is turned off while the lower light source is turned on. When an opaque document passes over the transparent zone, the lower light source projects light upon the opaque document and reflects the light back to the scanning means for scanning process. Therefore this invention can provide dual scanning function for one scanner. 
     In another embodiment of this invention, the automatic paper feeder may includes a pair of photo sensors (one emission member and one receiving member) located at two sides of the channel and in front of the transparent zone (in terms of paper movement direction). The photo sensors can detect if a passing document is transparent or opaque from light density difference at the receiving member, then activate the scanning means to move to a location desired for either transparency scanning or reflective scanning. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The invention, as well as its many advantages, may be further understood by the following detailed description and drawings in which: 
     FIG. 1 is a schematic side view of a conventional automatic paper feeder used with a scanner. 
     FIG. 2 is a sectional view of an embodiment of this invention used with a scanner. 
     FIG. 3 is a sectional view of another embodiment of this invention used with a scanner. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 2 illustrates an automatic paper feeder  4  according to this invention for use with a scanner  3  that is able to scan transparency and opaque documents. The scanner  3  may be a flatbed type optical scanner or a copier. In the scanner  3 , there are provided with a scanning means  33 , a transmission means  34  and a control circuit board  31  for controlling operation of the scanning means  33  and the transmission means  34 . The scanning means  33  includes a lower light source  331  and other required components. Taking a charged couple device (CCD) scanning means for instance, the optic components include at least one reflection mirror, a lens set and a CCD member (all these components are not shown in the figure). When the automatic paper feeder  4  of this invention is not being used with this scanner  3 , the transmission means  34  may drive the scanning means  33  to move along a scanning platform  32  for scanning a document placed upon the transparent scanning platform  32 . 
     The automatic paper feeder  4  includes a paper tray  41  which can hold a plurality of scanning documents  411 , a base frame  42  mountable on the scanning platform  32 , a channel  43 , an upper light source  44 , a transmission unit  45  for picking up documents  411  and moving them along the channel  43 , an upper light source  44 , a control unit  46  for controlling the operation of the transmission unit  45  and the upper light source  44 , and a cable  47  for wiring the paper feeder  4  to the scanner  3 . 
     The base frame  42  has a transparent zone  421  at the bottom which is covered by a transparent sheet made of a plastics, glass or other desirable materials. The transparent zone  421  enables light to pass through and also may prevent dusts from entering into the paper feeder  4  or prevents documents  411  from dropping out of the paper feeder  4 . The bottom of the base frame  42  further has engaging pins  422  engageable with positioning holes formed on the platform  32  so that the paper feeder  4  may be mounted securely and easily on the scanner, and also making the transparent zone  421  aligning with the transparent scanning platform  32 . 
     The channel  43  aims to guide scanning document  411  to move in a predetermined path and direction. It includes a first guide plate (inner plate)  431  spaced from a second guide plate  432  (outer plate) at a selected gap (preferably between 0.7-2 mm) and forms a continuous path consisting of a number of sections. One end of the channel  43  engages with the paper tray  41  for receiving documents  411 . The first guide plate  431  is continuous and passes over the transparent zone  421  with a transparent window  433  above a selected location above the transparent zone  421 . The second guide plate  432  has another end meeting an edge of the transparent zone  421  and with another edge of the transparent zone  421  connects with another section of the second guide plate  432  so that the transparent zone  421  becomes a portion of the second guide plate  432  over the scanning platform  32  of the scanner  3 . The first guide plate  431  further has a reflection plate  434  and a correction plate  435  located thereunder above the transparent zone  421  at desired positions. The transparent window  433  is an elongate slot which enables light emitted by the upper light source  44  to pass through. The reflection plate  434  is a white plate with desirable reflection property or a diffusion plate. The correction plate  435  is for correcting and adjusting brightness and darkness like the one used in a conventional scanner. The size of the transparent window  433 , reflection plate  434  and correction plate  435  are smaller than the transparent zone  421 . 
     The upper light source  44  is located above the transparent window  433  and opposite to the transparent zone  421  and can project light to pass through the transparent window  433 , transparent zone  421 , scanning platform  32  and reaches the scanning means  33 . 
     The transmission unit  45  connects the paper tray  41  with the channel  43  for moving scanning documents  411  one by one along the channel  43  to pass over the transparent zone  421 . In the embodiment shown in FIG. 2, the transmission unit  45  includes a paper picking roller  451 , a paper separation means, a paper transporting roller  452 , a paper discharging roller  453  and a plurality of idlers  454 ,  455 ,  456  and  457 . The paper picking roller  451  and paper separation means are located at one end of the channel  43  and engages with the paper tray  41  for picking up one sheet of document at a time from the paper tray  41  and feeding the document into the channel  43 . The paper separation means includes an idler  454  and a friction strip (not shown in the figure). Its structure is known in the art and forms no part of this invention, and therefore will be omitted here. The paper transporting roller  452  is located in the middle portion of the channel  43  and between the paper picking roller  451  and the transparent window  433 . It moves the scanning document to the transparent zone  421 . The paper discharging roller  453  is located at another end of the channel  43  for discharging document  411  that has been scanned at the transparent zone  421  out of the paper feeder  4 . The idlers  454 ,  455 ,  456  and  457  couple respectively with the rollers  451 ,  452 ,  453  to facilitate document  411  movement. There is a sensor  48 , preferably a microswitch, adjacent the paper transporting roller  452  to detect if the document  411  being moved to a selected location in the channel  43 . 
     The control unit  46  is wired to the transmission unit  45  and the upper light source  44  for controlling their operation. The cable  47  connects the paper feeder  4  with the scanner  3 , and couples the control unit  46  with a control circuit board  31  of the scanner  3 . 
     Through above wiring and coupling, signal transmission between the control unit  46  and the control circuit board  31  may be performed in coordinated manner with the motion of the transmission unit  45 , upper light source  44 , lower light source  331  and the scanning means  33 . 
     When in use, the base frame  42  is mounted on the platform of the scanner  3  with the transparent zone  421  located above the scanning platform  32 . The scanning means  33  is moved to the correction plate  434  for setting required brightness/darkness parameters. Then the scanning means  33  is moved under the reflection plate  434  (for reflection type scanning) or moved under the transparent window  433  (for transparency scanning). Thereafter the transmission unit  45  picks up a document  411  from the paper tray  41  and moves the document  411  to the transparent zone  421  for scanning process. 
     If the document is a transparency, the scanning means  33  will be located under the transparent window  433  (indicated by solid line in FIG.  2 ). The upper light source  44  will be turned on while the lower light source  331  will be turned off. If the document is opaque, the scanning means  33  will be moved under the reflection plate  434  (shown by broken line in FIG.  2 ), the upper light source  44  is turned off while the lower light source  331  is turned on, then a reflective scanning will be performed for the passing document  411 . 
     FIG. 3 shows another embodiment of this invention. Like components as shown in FIG. 2 will be marked by like numerals. It is constructed substantially like the one shown in FIG. 2 except that a pair of photo sensors  49  being disposed at the channel  43  beyond the transporting roller  452  but in front of the transparent zone  421 . The photo sensors  49  includes an emission member  491  and a receiving member  492  located respectively at two sides of the channel  43 . When a transparency document  411  passes through the photo sensors  49 , the receiving member  492  will receive a strong signal which will then trigger the scanning means  33  to move under the transparent window  433  for transparency scanning under the upper light source  44 . When an opaque document passes through the photo sensors  49 , the receiving member  472  will receive weak or no signal, then the scanning means  33  will be moved under the reflection plate  434  for reflective scanning through the lower light source  331 . 
     The selection of transparency scanning or reflective scanning may be determined by one of the following methods: 
     1. Using photo sensors  49  shown in FIG. 3 to detect if a document is transparent or opaque to automatically switch scanning mode. Mixed document types may be placed in the paper tray  41 . 
     2. Using computer softwares and user commands to select which scanning mode desired. This method may be used when the scanner is hooked up with a computer. 
     3. Using a switch (not shown in the figure) installed on the automatic paper feeder  4  or the scanner  3  to make selection manually. 
     It may thus be seen that the objects of the present invention set forth herein, as well as those made apparent from the foregoing description, are efficiency attained. While the preferred embodiments of the invention has been set forth for purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.