Abstract:
An image capturing apparatus is provided for scanning documents, each of which has first and second pages of data. The image capturing apparatus includes first and second image sensors for reading the first and second pages of data of the documents. The method of capturing images includes scanning the m-th document and registering the first and the second image data in the first and second memories of one memory set and outputting the image data, wherein the value m has an initial value of 1; and increasing m by an increment of 1 when in the first and the second memories of at least one memory set are stored no image data or the first and the second image data are being completely output, and repeating the step of scanning the m-th document until the image capturing of all the documents is completed.

Description:
This application claims the benefit of Taiwan application Serial No. 092123073, filed Aug. 21, 2003, the subject matter of which is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates in general to an image capturing apparatus, which can do one pass duplex image scanning, and its method, and more particularly to an image capturing apparatus and method, which can reduce the period of time in waiting for image data in buffer memories to be transmitted before the next document can be scanned and improve the scan efficiency. 
   2. Description of the Related Art 
   Today&#39;s technology places emphasis on speed and efficiency. Hence, scanners are constantly innovated in order to increase the scan speed in addition to providing high-quality images by resolution improvement. For example, flatbed scanners in early years took a lot of time reading images, for documents can only be manually placed on the flatbed and be scanned sheet by sheet. After the automatic document feeding technique has been developed, the scanner equipped with the automatic document feeder (ADF) can continuously scan tens of sheets of documents and transmit the image data thereof to computers for further processing, thereby saving the time of placing and retrieving each of the documents manually. Some scanners with automatic document feeding function can even read documents by one pass duplex scanning. 
   Referring to  FIG. 1A , a lateral view of a flatbed image capturing apparatus, which is equipped with an ADF to perform one pass duplex scanning, is shown. The image capturing apparatus  100  includes a base  110 , and an ADF  120  disposed on the base  110 . The ADF  120  is provided for feeding to-be-scanned documents  122 , and each document  122  has a first page of data  122   a  (the page facing upward) and a second page of data  122   b  (the page facing downward). The base  110  includes a flatbed  112 , a first image sensor  114 , and a circuit board  116 , while the ADF  120  includes a second image sensor  124 . As the documents  122  are to be scanned, they are fed onto the flatbed  112  via the ADF  120 , in which the first page of data  122   a  and the second page of data  122   b  of each document are respectively read by the first image sensor  114  installed in the base  110  and the second image sensor  124  installed in the ADF  120 . The image data thereof are converted to electrical signals and stored in memories on the circuit board  116 , or further transmitted to an exterior host  130 .  FIG. 1B  shows a lateral view of a one-pass-duplex-scanning sheet-fed scanner. Its process of one pass duplex scanning is similar to that of the flatbed scanner having the ADF as shown in  FIG. 1A . 
   Referring to  FIG. 1C , a block diagram illustrating the image reading of the image sensors, and the storage and transmission of the corresponding image data in  FIG. 1A  and  FIG. 1B  is shown. The circuit board  116  includes a memory module  117  and an image processor  118 . The memory module  117  includes a first memory (buffer memory)  117   a  and a second memory (buffer memory)  117   b  for respectively registering the image data I 112   a , corresponding to the first page of data  122   a  and read by the first image sensor  114 , and the image data I 122   b , corresponding to the second page of data  122   b  and read by the second sensor  124 . The image processor  118  is provided for processing the image data transmitted from the memory module  117  and transmitting them to the host  130 . 
   Generally, the image data I 122   b  can be transmitted to the memory module  117  only after the image data I 122   a , previously stored in the memory module  117 , has been transmitted to the image processor  118 . For scanners having a high resolution of, for instance, 600 dpi, the speed of the image sensors  114  and  124  reading documents  122  is usually higher than that of transmitting image data I 122   a  and I 122   b  from the memory module  117  to the image processor  118 . That is, the scan time (ts) is usually smaller than the data transmission time (td) as shown in  FIG. 1D . Supposed that T 1  is the time of performing one pass duplex scanning of one sheet of document  122 , and T 1   a  and T 1   b  are respectively the time of transmitting the corresponding image data I 122   a  and I 122   b  from the memory module  117  to the image processor  118 , both T 1   a  and T 1   b  are larger than T 1 . Therefore, the image data I 122   a  and I 122   b  corresponding to a certain sheet of document  122  can only be registered in the memory module  117  after those corresponding to the prior sheet of document  122  are being completely transmitted. This period of delay time Tw is (T 1   a +T 1   b −T 1 ). The delay time Tw recurs and adds up as each sheet of document  122  is being scanned, so the more documents are being scanned, longer the period of the delay time will be in the scanning process. As a result, the scan speed and scan efficiency will be greatly reduced. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to provide an image capturing apparatus and a method for reducing the period of time that image sensors wait for the image data in the memory set to be transmitted before beginning to read the data of the next document and in result improving the scan speed by increasing the number of memory sets in the image capturing apparatus. 
   The invention achieves the above-identified objects by providing an image capturing apparatus for scanning a number of documents. Each document has a first page of data and a second page of data. The image capturing apparatus includes a first image sensor and a second image sensor. The first image sensor is provided for reading the first page of data and outputting the first image data corresponding to the first page of data. The second image sensor is provided for reading the second page of data and outputting the second image data corresponding to the second page of data. The image capturing apparatus further includes a number of first memories and a number of second memories for correspondingly registering the first image data and the second image data of each document. 
   The invention achieves the above-identified objects by providing a method for an image capturing apparatus to scan n documents. Each document has a first page of data and a second page of data, and the image capturing apparatus has q memory sets, wherein the values q and n are positive integers. The method includes the steps of: scanning the m-th document; respectively registering the corresponding first image data and second image data in the first memory and the second memory of one of the memory sets in the memory module; outputting the first image data and the second image data, wherein m≦n, and the value m is a positive integer and has an initial value of 1; increasing the value m by an increment of 1 when in the first memory and the second memory of at least one of the q memory sets are stored no image data or the first image data and the second image data are being completely output; and repeating the step of scanning the m-th document until the image capturing apparatus has completed capturing the image of all the n documents. 
   The invention achieves the above-identified objects by further providing a method for an image capturing apparatus to scan n documents. Each document has a first page of data and a second page of data, and the image capturing apparatus has q memory sets. The method includes the steps of: setting a value m to 1; determining if the value m is smaller than q, wherein k=m if the value m is smaller than q, and k=(m mod q)+1 if the value m is not smaller than q; reading the first page of data and the second page of data of the m-th document with the first image sensor and the second image sensor; registering the first image data Ima and the second image data Imb, respectively corresponding to the first page of data and the second page of data of the m-th document, into the k-th memory set and outputting the first image data Ima and the second image data Imb; and determining if the value m is smaller than n, wherein if m is smaller than n, increasing m by 1 and returning to the step of determining if m is smaller than q. 
   Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a lateral view of a flatbed image capturing apparatus, which is equipped with an ADF to perform one pass duplex scanning; 
       FIG. 1B  is a lateral view of a one-pass-duplex-scanning sheet-fed scanner; 
       FIG. 1C  is a block diagram illustrating the image reading of the image sensors and the storage and transmission of the corresponding image data in  FIG. 1A  and  FIG. 1B ; 
       FIG. 1D  is a schematic diagram of the comparison between the scan time (ts) and the data transmission time (td) in  FIG. 1C ; 
       FIG. 2A  is a schematic view of the flatbed scanner equipped with an ADF according to a preferred embodiment of the invention; 
       FIG. 2B  is a schematic view of a one-pass-duplex-scanning sheet-fed scanner; 
       FIG. 2C  is a block diagram illustrating the image reading of the image sensors, and the storage and transmission of the corresponding image data in  FIG. 2A  and  FIG. 2B ; 
       FIG. 3A  is a flow chart of the image capturing method according to a preferred embodiment of the invention; and 
       FIG. 3B  is a schematic diagram of the comparison among the scan time (ts) in the image capturing process of  FIG. 3A , the conventional scan time (tso), and the transmission time (td) of image data in the memory set. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In order to reduce the period of time in waiting for image data in the memory to be completely transmitted to an image processor before the scanning process of a next document begins and to improve the scan speed, especially in one pass duplex scanning process, at least two memory modules, into which both pages of data of each document are registered, are provided, so that as the first memory module is transmitting the image data of one document, the next document can be scanned and the corresponding image data can be registered into the second memory module. The image data in the second memory module will be transmitted after that in the first memory module has been transmitted. Therefore, the overall scan time can be effectively reduced. 
   Referring to  FIG. 2A , a schematic view of the flatbed scanner equipped with an ADF according to a preferred embodiment of the invention is shown. The image capturing apparatus  200  is provided for scanning n to-be-scanned documents  222 , and each document  222  has a first page of data (the page facing upward)  222   a  and a second page of data (the page facing downward)  222   b . The image capturing apparatus  200  includes a base  210  and an ADF  220  (such as a U-type ADF) disposed on the base  210 . The base  210  includes a flatbed  212 , a first image sensor  214 , and a circuit board  216 . The first image sensor  214  is provided for reading the first page of data  222   a  of the documents  222 . In addition, the ADF  220 , used for feeding the documents  222 , has a second image sensor  224  for reading the second page of data  222   b  of the documents  222 . 
   As the image capturing apparatus is performing the one pass duplex scanning, one of the documents  222  is fed through the ADF  220  and then onto the flatbed  212 , where the first page of data  222   a  and the second page of data  222   b  are read simultaneously with the first image sensor  214  and the second image sensor  224 , and the corresponding image data are registered into the memory on the circuit board  216  or further transmitted to the host  230 . 
     FIG. 2B  shows a schematic view of a one-pass-duplex-scanning sheet-fed scanner according to the invention. The process of one pass duplex scanning is similar to that of the flatbed scanner having the ADF as described above. 
   The first and the second image sensors  214  and  224  can be charge-coupled devices (CCDs) or contact image sensors (CISs). 
   Referring to  FIG. 2C , a block diagram illustrating the image reading of the image sensors, and the storage and transmission of the corresponding image data in  FIG. 2A  and  FIG. 2B  is shown. The circuit board  216  includes a memory module  240  and an image processor  218 . The invention features at least one more memory set in the memory module  240  than that in the prior art. The memory module  240  includes q (q is a positive integer) memory sets  241 , and each memory set  241  includes a first memory  241   a  and a second memory  241   b  for respectively registering the first image data Ima (m is a positive integer not larger than n) corresponding to the first page of data  222   a  and the second image data Imb correspond to the second page of data  222   b . The image processor  218 , controlled by the computer host  230 , processes the first and the second image data transmitted from the memory module  240  and transmits them to the computer host  230 . The first memory  241   a  and the second memory  241   b  each have sufficient memory spaces for respectively registering the first and the second image data Ima and Imb corresponding to the first and the second pages of data  222   a  and  222   b  of one document  222 . 
   In the following description, the scanner, which has q memory sets and is capable of scanning n documents  222 , will be taken as an example to illustrate the image capturing method according to the invention. Referring to  FIG. 3A , a flow chart of the image capturing method according to a preferred embodiment of the invention is shown. In the step  302 , a value m is given and set to 1, wherein m≦n and m is a positive integer. In the step  304 , whether m is smaller than q is determined. If m&lt;q, k=m. If m≧q, k=(m mod q)+1. Subsequently, in the step  306 , the first page of data  222   a  and the second page of data  222   b  of the m-th document  222  are respectively read with the first image sensor  214  and the second image sensor  224 , where one pass duplex scanning is being performed. In the step  308 , the first image data Ima and the second image data Imb respectively corresponding to the first page of data  222   a  and the second page of data  222   b  of the m-th document are registered in the k-th memory set  241  and subsequently being output. 
   The first and the second image data Ima and Imb registered in the k-th memory set  241  can be output at the same time as another memory set  241  is registering another image data. That is, at the same time as the (m+1)-th sheet of document  222  is scanned and the corresponding first and second image data I(m+1)a and I(m+1)b are registered into the (k+1)-th memory set, the first and the second image data Ima and Imb can be transmitted from the k-th memory set to the image processor  218 . 
   Proceeding to the step  310 , whether m is smaller than n is determined. If m is smaller than n, m is set to (m+1), and the process is returned to the step  304 . If m is not smaller than n, the process is ended after the first and the second image data Ima and Imb registered in the q memory sets  241  has all been transmitted, which indicates that the process of scanning n documents  222  is completed. 
   Referring to  FIG. 3B , a schematic diagram of the comparison among the scan time (ts) in the image capturing process of  FIG. 3A , the conventional scan time (tso), and the transmission time (td) of image data in the memory set  241  is shown. As described above, let Tm be the time of scanning two pages of data  222   a  and  222   b  of the m-th (m=1, . . . ,n) document  222  and registering the corresponding image data Ima and Imb into the k-th (k=1, . . . ,q) memory set  241 . Let Tma and Tmb be respectively the time that the image data Ima and Imb are transmitted from the k-th memory set  241  to the image processor  218 . Since at least two memory set  241  are disposed in the scanner of the invention, the 2-th, . . . , and the q-th documents  222  can be continuously scanned after the first sheet of document  222 , and the waiting time Tw (=T 1   a +T 1   b −T 1 ) before the scanner begins to scan the second document  222  in the prior art is unnecessary. Moreover, the waiting time Tw 2  of the (q+1)-th document  222  after the q-th document  222  is scanned is only (T 1   a +T 1   b −(T 1 +T 2 + . . . +Tq)), which is much shorter than the conventional delay time Tw (=T 1   a +T 1   b −T 1 ). Even the image sensor can continuously read all the documents at a time without wasting any waiting time. Since the waiting time is shortened (Tw 2 &lt;Tw), a period of time Tr is saved from implementing the invention during the process of the scanning of the n-th document  222  and the complete transmission of the image data Ina and Inb to the image processor  218 : Tr=T(n−q+1)a+T(n−q+1)b+ . . . +Tna+Tnb−Tn, which is more than the conventional waiting time Tw (=T 1   a +T 1   b −T 1 ). As the value n or q is increased, the time Tr becomes lengthened, which could be useful for doing printing jobs or other trivial jobs, such as changing papers for printers. Therefore, the scan speed and the efficiency of the scanner can be effectively improved. 
   In the embodiment of the invention, the memory module  240 , including q memory sets, is disposed on the circuit board  216  in the base  210 . However, the first memories  241   a  and the second memories  241   b  of the q memory sets can be respectively disposed in the base  210  and in the ADF  220 , which can also achieve the goal of reducing the waiting time. Moreover, the image capturing apparatus  200  can be a flatbed scanner equipped with a ADF. Or it can be a sheet-fed scanner, which has the automatic document feeding function and has the first and the second image sensors  214  and  224  as mentioned above respectively disposed in the base and in the upper cover for one pass duplex scan. Even the image capturing apparatus in the invention can also be a manual flatbed scanner. As long as at least one memory set is added in the memory module according to the invention, the aim to reduce the waiting time can be achieved. Therefore, all these alternatives will not depart from the skill scope of the invention. 
   As the preferred embodiment illustrates above, the image capturing apparatus in the invention has the following advantages: using at least two memory sets to subsequently register image data corresponding to at least two to-be-scanned documents can reduce the conventional waiting time for the image data corresponding to the first document to be transmitted from the first memory set before the second sheet of document is scanned. For this reason, the time saved during the process of the scanning of all the documents and the complete transmission of their corresponding image data from the memory module to the image processor will be much more than the conventional waiting time, and the time saved can be used for doing printing jobs or changing papers for printers. Therefore, the scan speed and the efficiency of the scanner can be largely improved. 
   While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.