Abstract:
A registration detection system for determining a registration problem in an apparatus having an optical reader adapted to scan a document. The system comprising a test pattern generator and a mixer for combining an output of the test pattern generator with an output of the optical reader.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to document processing machines and, more particularly, to document scanning requiring document registration. 
     2. Prior Art 
     Referring to FIG. 1, there is shown a perspective view of a document processing apparatus  10 . The apparatus  10  could be any suitable type of document processing apparatus, such as a copier, a facsimile machine, a scanner, a computer printer, or a multifunction device having two or more functions. Referring also to FIG. 2, in this embodiment the apparatus  10  is a copier which includes an original document feed system  11  and a copy document feed system  13 . A scanner or image obtainer  12  is provided under a transparent glass platen  15 . The scanned information from an original document fed through the original document feed system  13  is imaged onto paper selected from paper trays  14  or  16 . Paper selected from either of the paper trays  14 , 16  is moved by the copy document feed system  13  through the apparatus  10  by means of various belts  18  and rollers  19  schematically depicted in FIG.  2 . The original document feed system  11  also comprises suitable belts and rollers for automatically moving original documents through the document system. 
     Various document systems require that an automatic document handling apparatus within the system operate so as to align a particular edge of a document with a given coordinate. For example, in an x-y coordinate system this could be the coordinates 0,0, on a copier platen where the scanner or copier optics have also been aligned to begin imaging at the 0,0 coordinates on the copier platen. This process of aligning the document relative to a given coordinate is known as document registration. In a manual copying operation, an original document is registered by the user with ruler markings along the sides of the platen. In systems having automatic document handling systems document registration is automatic and is generally accomplished by the use of various belts, rollers and sensors situated along the document path. If the original document is not properly registered then undesirable dark borders and shadow images may appear on the copy. Thus, while proper document registration is critical to the operation of a document processing system it is yet one of the most difficult to achieve features of an automatic document handling system. An automatic document handling system must rapidly and accurately register each original document. In general, the document registration accuracy desired is on the order of one millimeter. In addition, improper registration due to document skewing by the paper rollers can damage original documents and affect the further automatic operation of the document handler. 
     Various methods exist for measuring and aligning the registration of documents within a document handling system. For example, U.S. Pat No. 4,831,420 to Walsh et al. discloses a system for setting registration using pre-printed and specially constructed test. The test documents are comprised of identifying registration marks identifying registration position and a registration cutout window. Setting the registration involves registering and copying a preprinted test sheet using the document feeder in its initial and unadjusted, registration setting. The copy produced is then compared with the original test document by placing the copy of the test document under the original test document so that the test patterns on the copy are visible through the cutout window. Thus, the test patterns on the copy may be compared with the test patterns on the original revealing the amount of registration adjustment required. 
     Other methods that exist for setting document registration also involve the use of expensive, specially constructed, preprinted master test documents for a variety of paper sizes and test patterns. Other disadvantages to the preprinted master test document approach are lead times for printing the various test documents required and storage by the user, whether on site or by the field service engineer. 
     SUMMARY OF THE INVENTION 
     A registration detection system for measuring document registration in an apparatus having an optical reader adapted to scan a document. The system comprising a test pattern generator and a mixer for combining an output of the test pattern generator with an output of the optical reader. 
     A method for determining if a scanner registration problem exists in an apparatus adapted to scan a document, the method comprising the steps of: scanning a first image; combining a first test pattern with the scanned first image; and providing informative feedback resulting from the step of combining the first test pattern with the scanned first image. 
     A scanner device registration measuring system for determining a scanner registration problem in a scanner device. The system comprising a test pattern generator, an input document scanning device, and an image transfer system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a conventional document processing apparatus; 
     FIG. 2 is a schematic view of paper paths within the paper processing apparatus shown in FIG. 1; 
     FIG. 3 is a block diagram of a document registration system incorporating features of the present invention; 
     FIG. 4 is a flowchart of one method for measuring document registration using the system shown in FIG. 3; 
     FIG. 4 a  is an exploded flowchart of the one method for measuring document registration shown in FIG. 4; and 
     FIG. 5 is a schematic representation of combining a printed test pattern with the same test pattern residing in memory. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although the present invention will be described with reference to the single embodiment shown in the drawings, it should be understood that the present invention can be embodied in many alternate forms of embodiments. Referring now to FIG. 3 there is shown a block diagram of one embodiment of a document registration measuring system  21  incorporating features of the present invention. The system  21  is generally intended to be used for registering documents in a document processing apparatus such as described above with reference to FIGS. 1 and 2 (e.g.: a copier, a facsimile machine, a computer printer, a scanner, or a multifunction device). The system  21  generally comprises an optical scanner  22 , a test pattern generator  24 , test pattern memory  25 , a combiner  26 , and a selector  29  for selecting the output of the test pattern generator  24  or combining the output with information provided by the optical scanner  22 . 
     The optical scanner  22  generally comprises any suitable system for detecting light and translating it into electric signals in order to reproduce or sense and subsequently transmit an image. This is usually accomplished by the use of various photoelectric devices, such as a photoelectric cell. Optical sensing typically involves moving a finely focused beam of light across a document and recording variations in intensity or another property of light as the light is transmitted or reflected from an original document. Alternatively, any suitable photocopying, processes that use chemical, electrical, or photographic techniques to copy printed or pictorial matter may be used. 
     The test pattern generator  24  generally comprises an integrated circuit board  24   a  generally capable of image processing functionality such as magnification, screening, contrast control, and test pattern generation. Generally, the test pattern generator is controlled by user input from the user interface  8  (see FIG.  1 ), but could also be controlled by onboard switches or an external interface such as a portable service workstation. 
     The test pattern memory  25  generally comprises a data storage medium capable of storing various test patterns. The medium may be any suitable data medium such as Read-Only-Memory chips located on board the test pattern generator  24 , or within a software program. 
     The selector  29  for selecting the test pattern generator is represented symbolically as a switch. However, any suitable means for selecting between the output of the test pattern generator  24  or combing the output with the output of the optical scanner  22  in the combiner  26  may be used. 
     In general, the combiner  26  comprises a combiner capable of mixing the input from the optical scanner  22  with the input from the test pattern generator  24  so as to overlay the test pattern on the copy. This is represented graphically in FIG.  5 . Test pattern TP 1   a  is printed on hardcopy  70 . Hardcopy  70  is scanned and combined with test pattern TP 1   b  from test pattern generator  24  in combiner  26 . The output from the combiner  26  is hardcopy  80  which shows TP 1   b  overlying TP 1   a . The difference between the patterns represents the registration error. In addition, the combiner  26  may digitally mix the input signals to provide registration information and instruction to correct registration error such as shown in  80   b . The combiner may be any suitable combiner that is compatible with the document processing apparatus and the test pattern generator and could include a digital mixing circuit. The combiner  26  may use any suitable method for combing the output of the test pattern generator  24  with the output of the optical scanner  22 . 
     Referring also to FIG. 4 there is shown a flowchart of one method for measuring document registration using the system shown in FIG.  3 . In short, the user merely prints  52   a , scans  52   b , an combines  52   c , to determine document registration. These steps are further illustrated in FIG. 4 a . The user can start by selecting various parameters unique to the system under test via the user interface  8  (see FIG. 1) or an external interface such as portable work station. These parameters may include fast or slow scan size scales and copy document size  53 . Next the operator can select the desired test pattern  54 . The test pattern may be crosshair, edged, edged crosshair, grid, edged grid, or any suitable type of test pattern appropriate to the system under test. The operator can then direct the system to print  56  a copy of the test pattern directly to the output (i.e., switch  29  in FIG. 3 is in the  29   a  position). A test pattern so produced is now designated as the master test pattern document. The master test pattern document is loaded into the document handling system  11  of copier  10  or manually placed on the platen  12  (see FIG.  1 ). The master test pattern document is then cycled through the copier by normal operation. The optical scanner  22  scans the master test pattern document and provides the scanned test pattern as one input to the combiner  26 . Meanwhile switch  29  has been automatically or manually moved to the  29   b  or electronic overlay position  59  so that the test pattern that was previously printed is now provided as a second input to combiner  26 . Combiner  26  electronically overlays  59  the test pattern from the test pattern generator  26  over the scanned test pattern from the optical scanner  22 . The combination is printed onto a single output document  60  for visual analysis  62  by the user. Ideally, the overlayed test pattern should be identical with the scanned test pattern resulting in what would appear to the operator as a single test pattern print out. However, in practice some tolerance is allowed, thus if the registration is within the allowable tolerance the registration of the automatic handling device is acceptable. If otherwise, the user can adjust the components affecting registration  66  as necessary and repeats the steps described above. Optionally, it may be desirable to mix the digital signals in the combiner  26  so as to produce a difference signal indicating numerically the magnitude and direction of a registration problem of the document handling system  11 . Another test pattern option for determining document registration may be the selection of complimentary or cooperating test patterns. Cooperating test patterns would be designed to measure the registration of the entire document. For example the test pattern overlaid on the copied test pattern need not be identical as described above but could be the second half of a stored image such that when overlaid with the image of the first half the output is the complete image. If the two images do not form the whole image or if the image seam(s) are distorted the user may immediately detect a registration problem and proceed to correct as described above. 
     Thus, as described above, an advantage of this invention over other methods is that the user has immediately available a variety of master test designed to measure document registration. Other methods for measuring document registration require expensive and specially constructed preprinted master test documents. With one embodiment of this invention the user may print specific test patterns on specific paper sizes as needed to visually or electronically measure document registration as described above. 
     Another advantage of this invention over other methods concerns the logistics of providing master test documents for measuring document registration. The present invention allows the user to print a specific test pattern on a specific size document as needed. Prior art methods using preprinted master test documents require ordering and storing the test documents well in advance of actual required use due to long lead times generally associated with specially constructed test documents. Thus, the present invention allows the user to measure and determine the extent of a registration problem without external special supplies such as preprinted test documents. 
     It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.