Apparatus and method for copying book pages

Abstract: A photocopying machine for sequentially copying opposite pages (20,22) of a book or similar bound document, has a V-shaped platen having two platen portions (10,12) jointed along one edge (15) thereof and forming an angle therebetween, so as to form a platen wedge for receiving the pages of a book in a partially open status. A movable mirror (14) is provided in the angle between the two platen portions and is pivotable about the platen joining edge (15), between an active position, in the middle of the platen wedge and an inactive position, parallel to one platen portion (12). In the active position the mirror reflects an image from a book page (22) placed on the one platen portion (12) towards a fixed imaging optic, objective lens (30) which focuses the original onto a fixed photoreceptor (32); when the mirror is in the inactive position, the fixed lens (30) directly images a book page (20) placed on the other platen portion (10) onto the photoreceptor. A book carrier, holder (110) for automatically locating a partially open book onto the platen may be provided. The original is illuminated by a light source (23) emitting either the three primary colors red, green, blue or white light. The photoreceptor may be a two dimensional array of CCD or TFT (thin film transistors) or a linear array of CCD scanning the image plane or a photographic film or an electrophotographic device.

Description: The present invention relates generally to scanning a document. In order to minimize the stress on the spine of bound documents when capturing or copying image content, wedge or angled platens of scanners and copying machines have been developed. While some arrangements provide support for a bound document with a wedge platen having an angle of approximately ninety degrees, other arrangements provide support with wedge platens having angles less than or greater than ninety degrees. For example, a wedge platen having an angle greater than ninety degrees is disclosed in "Library Copier," Guenther, Xerox Disclosure Journal Vol. 12, No. 5, September/October, 1987, pp. 231-232. Alternatively, GB-A- 2 158 599, discloses an electrophotocopier with a wedge platen that is less than ninety degrees. A principal function of wedge or angled scanning surfaces is to prevent damage to a bound document by minimizing stress applied to its binding as it is held open for scanning in a position as close to the platen of a scanner as possible. Typically when using a flat-bed scanner, a force has to be applied to the spine region of a bound document to insure that the document is within the scanner's depth of focus. A wedge or angled platen, however, positions the spine region of a bound document within the scanner's depth of focus without requiring the application of additional force to the document's binding. DE-A-35 46 404 discloses a roof-shaped book support apparatus for use in a copier application. The optics of the roof-shaped copier arrangement provide that opposing pages of a bound book are simultaneously imaged in the same image plane. Consequently, the roof-shaped book support apparatus must have an sensing area large enough to capture two pages of a bound document at a time. In addition, the roof-shaped copier arrangement adjusts the spacing of the images of both pages in the image plane without having to change the position of the book. In scanning a bound document, a problem arises in avoiding damage to the binding while capturing images of two facing pages in sequence. Although the aforementioned wedge scanning systems reduce stress applied to bound edges of documents, most wedge scanning systems scan a single page of a bound document at a time and require that the bound document is repositioned before the opposing page is scanned since only one face of the wedge scanning system is used to record image data. In contrast, other scanning systems such as that disclosed in DE-A-35 46 404 do not require repositioning a bound document in order to image both sides. However, such a scanning system requires an image sensing area sufficiently large to simultaneously capture both pages of the bound document Similarly, another wedge contact scanning system disclosed in US-A-5 359 207 requires two two-dimensional flat panel detectors to image opposing pages of a bound document without having to repositioning it in order to scan both sides. In addition, such contact imaging arrangements have a reduced depth of focus since it is difficult to provide contact sensors with thin yet durable surface protection. This problem can be alleviated by techniques that use structures with light transmissive areas for contacting the facing pages while the bound document is partially opened. The techniques provide two optical paths, one for scanning one facing page, the other for scanning the other facing page. As a result, the facing pages can be captured in sequence. In addition, it would be desirable to provide a wedge scanning system with an increased depth of focus. The techniques can also alleviate this problem because an optical system can be used that has a depth of focus sufficient that pressure on a bound document is not required. In addition, it would be desirable to provide a wedge scanning system that does not require repositioning a bound document while sequentially imaging opposing sides of the bound document using a sensing area that captures a single opposing page of a bound document at a time. The techniques can also alleviate this problem. In one aspect of the invention, there is provided apparatus for scanning bound documents in accordance with claim 1. Further embodiments are given by claims 2-9. The apparatus can also include a switch that provides a start scan signal to the controller to start scanning. The apparatus can also include an optical system for projecting an image of the first opposing page and an image of the second opposing page of the bound document onto the image capture means. The image capture means can include a photoreceptor or a two-dimensional array of amorphous silicon sensors. The image capture means can be capable of capturing only one page's image at a time. The apparatus can also include a page turning system. In another aspect of the invention, there is provided a method for scanning a bound document in a partially open position using the apparatus as described above, the method being in accordance with claim 10. The method can, in response to a start scan signal, repeat steps (a) through (f). The method can also turn a page of the bound document after completing steps (a) through (f), and can then repeat steps (a) through (f). The method can repeat each of steps (b), (c), (e), and (f) for each primary color, such as red, green, and blue; the method can then form a composite image using each representation recorded by step (c). The techniques described above are advantageous because they permit sequential capture of two facing pages of a bound document with greatly reduced risk of damage to the binding and without repositioning pages. Furthermore, in comparison with conventional contact imaging scanners, depth of focus can be increased. The invention will now be described by way of examples with reference to the accompanying drawings in which: Figure 1 illustrates a scanning system in one position; Figure 2 illustrates the scanning system shown in Figure 1 in another position; Figure 3 illustrates physical constraints of one embodiment of the scanning system shown in Figures 1 and 2; Figure 4 is a flow chart showing general steps involving the operation of the scanning system; and Figure 5 is an alternate embodiment in which a bound document is scanned in an open and upright position. Figures 1 and 2 show a scanning system 4. Scanning system 4 includes a wedge shaped platen 8 adapted for scanning a bound document 6. Bound document 6 is defined herein as any document having a bound edge such as a book or a periodical. The wedge shaped platen 8 includes a first face 10 and a second face 12 for holding bound input documents in an open position for scanning. Faces 10 and 12 of platen 8 are transparent and can be formed, for example, with any clear glass or plastic. The angled shape of the wedge shaped platen 8 advantageously minimizes stress to the spine region of bound documents when scanning. Unlike flat bed scanners, an angled platen does not require additional pressure to the spine region of a bound document in order for scanned pages to be within the depth of focus of scanning system 4. With reference now to Figure 3, constraints of the angle of wedge shaped platen 8 of the scanning system 4 are shown in detail. Generally, angle  between face 10 and face 12 of wedge platen 8 is defined to be less than ninety degrees in order that a bound document being imaged on wedge shaped platen 8 is open as little as possible. It will, however, be understood by those skilled in the art that wedge platen 8 can operate with an angle  that is greater than or equal to ninety degrees. By minimizing the extent to which a bound document is opened while scanning, the pressure to the spine region of a bound document is minimized. The angle  is minimized to the extent that the wedge shaped platen 8 does not interfere with the projection path of scanning system 4, which is described in detail later. In a preferred embodiment, angle  is selected such that the outermost ray of light reflecting off of mirror 14 or transmitted through side 10 of platen 8 is not eclipsed by side 12 of platen 8 from transmitting through lens or optical system 30. Assuming a one-to-one projection, the angle  is constrained to be greater than or equal to the arctan[2f/(L/2-r)], where "2f" is indicated generally by reference number 48, "r" is indicated generally by reference numeral 49, and where "L" is indicated generally by reference number 46. Specifically, "f" is defined herein as the focal length of lens 30, "r" is defined herein as the radius of lens 30, and "L" is defined herein as the width of the sensing area on each face 10 and 12 of wedge platen 8. Thus, the size of angle  between faces 10 and 12 of wedge shaped platen 8 is optimal when it minimizes the stress on the spine of a bound document while not interfering with the projection path of the imaging system. Dividing the wedge platen 8 is a mirror 14 that is attached to pivot 15 (Figures 1, 2 and 5). Pivot 15, which is motorized, rotates mirror 14 between two operational positions. In an alternate embodiment, pivot 15 is operated manually by an operator. The mirror 14 faces side 12 of wedge 8. In the first operational position, illustrated in Figure 1, mirror 14 is located at the central divide of the wedge shaped platen 8. Correspondingly, in the second operational position illustrated in Figure 2, mirror 14 is located immediately adjacent face 12 of platen 8. Depending on the angle , shown in Figure 3; between faces 10 and 12, mirror 14 is rotated a predetermined distance between each operational position shown in Figures 1 and 2. As depicted generally by arrow 17 in Figure 1, mirror 14 is returned to the first operational position after side 20 of bound document 6 is imaged. Correspondingly, as depicted generally by arrow 18 shown in Figure 2, mirror 14 is rotated to the second operational position after side 22 of bound document 6 is imaged. Opposing sides 20 and 22 of bound document 6 resting face down on platen 8 are illuminated by flash lamp or light source 23. Lamp 23 includes a reflector and three individual light sources that selectively emit the primary colors red, green, and blue (RGB). Figures 1 and 2 illustrate flash lamp 23 illuminating both sides 22 and 20 of bound document 6, respectively. It will be appreciated, however, by those skilled in the art that light source 23 can comprise any lighting arrangement suitable for recording color or black and white images. Thus, light source 23 can be any arrangement that emits white light, a single primary color, or a combination of primary colors. The specific light source used in any embodiment depends on the type of input document (e.g. color or black and white) and the form of a recorded image (e.g. colors or gray scale). With reference initially to Figure 1 where mirror 14 is in the first operational position, flash lamp 23 illuminates side 22 of bound document 6 with a short-lived flash of light. Reflected illumination from the page of side 22 travels along a path depicted generally by ray 28, reflecting off of mirror 14 before passing through focal optics 30 and projecting onto two-dimensional sensor array or imager 32. With reference now to Figure 2 where mirror 14 is in the second operational position, flash lamp 23 illuminates side 20 of bound document 6 with a flash of light. Reflected illumination from the page of side 20 travels along a path depicted generally by ray 34 and, unlike ray 28, is transmitted directly onto imager 32 as focused by optics 30. In the illustrated embodiment, the optical path depicted by ray 28 is almost exactly the same length as the optical path depicted by ray 34, so that no other adjustment should be necessary when mirror 14 changes position. It will be appreciated by those skilled in the art that optics 30 are generally depicted in Figures 1 and 2. The optics 30 may be a traditional combination of lenses, apertures, mirrors and other optical elements designed to focus, reduce, enlarge, or fold images from sides 10 and 12 of wedge shaped platen 6 onto imager 32. It will be understood by those skilled in the art that magnification or reduction can be performed either by digital image processing techniques or by moving the combination of lenses forming optics 30. No adjustment of optics 30 should be required when mirror 14 changes position, however, because rays 28 and 34 have substantially the same length. Image data that is detected by the single page imager 32 has either been reflected by or transmitted unobstructed by mirror 14. It will be appreciated by those skilled in the art that any sensor array or imager 32 that is adapted to record documents in contact with either side 10 or side 12 of wedge shaped platen 8 will suffice for the purposes of the present invention. The present invention operates using an active or a passive imaging system that detects a single page of a bound document sensed thereon. In the preferred embodiment, imager 32 is an array of active photosensors that converts optical image data represented by beams 28 or 34 into electrical image signals. Active photosensor arrays include imagers such as a flat panel detector, and a charge coupled device (CCD). As a flat panel detector, imager 32 comprises an array of thin film transistors and sensors that function as pixel element detectors. These thin film elements are generally constructed over a translucent substrate such as glass, forming a two dimensional detecting surface. An example of the thin film arrays are disclosed in US-A-5 017 989. Alternatively, imager 32 can comprise a two-dimensional CCD photosensitive array, or a one-dimensional CCD photosensitive array that sequentially scans each side of the image plane using a movable optical carriage system. An example of a scanning carriage system using a CCD is disclosed in US-A-5 276 530. Once an image is projected from either side 20 or 22 of bound document 6 onto imager 32, electrical representations are read out of array 32 by suitable electronics in the form of digital image data and transmitted to an electronic subsystem (ESS) 38. At the ESS 38, the digital image data may either undergo further image processing or it may be stored on a storage device 40 which may include RAM, flash memory, floppy disk, or another form of optical or magnetic storage. Generally, ESS 38 includes a microprocessor and control software responsive to user or system demand for the processing and routing of image data. Image data stored on storage device 40 can be transmitted by ESS 38 through port 42 to other devices such as an electronic printer or facsimile for hard copy reproduction. In an alternate embodiment, imager 32 comprises a passive photosensor such as a photoreceptor, or photographic film, or any other material that is sensitive to light. As a photoreceptor, imager 32 is regulated by ESS 38 which uses operating software stored in a memory (not shown) to control various stations (not shown) of imager 32. Generally, the photoreceptor is in the form of a movable belt or drum which is charged at a charging station to a relatively high, substantially uniform potential. Next, the charged photoconductive belt is advanced through imaging station 32 at which light rays reflected from one of the pages of the bound document 6 being copied on wedge shaped platen 8, as described above, create an electrostatic latent image on the photoconductive surface. In the event imager 32 is a photoreceptor, ESS 38 must insure that the intensity of flash lamp 23 is sufficient to expose the surface of the photoreceptor, and that the speed at which the photoreceptor belt or drum is travelling is matched to the duration of the flash exposure If the speed of the belt or drum is too great then excessive blurring of the latent image will occur. Subsequently, the electrostatic latent image is developed at a development station by a developer unit, such as a magnetic brush development unit, (not shown) and the developed image is transferred at a transfer station to a copy sheet supplied from a paper tray (not shown). Following transfer, the copy sheet bearing the transferred image is fed to a fusing station where a fuser (not shown) permanently affixes the toner powder image to the copy sheet. Such electrophotographic systems are well known in the art, an example of which is disclosed in US-A-5 322 970. In operation, ESS 38 is coupled to pivot 15, flash lamp 23, storage device 40, output port 42, scan switch mechanism 44, and imager 32. After detecting a start scan signal from switch 44, ESS 38 acts as a driver to each coupled component for synchronous flash exposure of side 20 and 22 of bound document 6 using lamp 23 once mirror 14 is positioned into operational position two and operational position one, respectively. Specifically, before flash exposure of side 20 of bound document 6, ESS 38 directs pivot 15 through control line 16 to rotate counter-clockwise until mirror 14 is substantially adjacent to side 12 of platen 8 (as shown in Figure 2). Correspondingly, before flash exposure of side 22 of bound document 6, ESS 38 directs pivot 14 through control line 16 to rotate clockwise until mirror 14 is properly positioned between the two sides 10 and 12 of wedge 8. In addition, ESS 38 insures proper timing between exposures by lamp 23 so that previously sensed image data is fully recorded on storage device 40 before subsequent exposure of imager 32 to a new image. Figure 4 is a flow diagram illustrating control steps of scanning system 4 in operation. At step 70, ESS 38 senses that scan switch mechanism 43 has been invoked by an operator. Subsequently at step 72, ESS 38 directs pivot 15 through control line 16 to rotate mirror 14 to the first operational position. The first operational position which is between sides 10 and 12 of wedge scanner 8 is shown generally in Figure 1. After positioning mirror 14, ESS 38 turns ON and directs the red light source of lamp 23 to side 10 of platen 8, at step 74. After exposure by the first primary color, red, ESS 38 reads a digital representation of side 22 of bound document 6 from imager 32. The digital representation contains information defining parts of side 22 of bound document 6 that are sensitive to red light. ESS 38 either stores the digital representation on storage device 40 or outputs the digital representation through port 42 as described above. Once the digital representation is detected and recorded by imager 32, the red light source of lamp 23 is turned OFF. Steps 76 and 78 repeat step 74 except that the red light source of lamp 23 is replaced by the green light source and the blue light source of lamp 23. After completing steps 74, 76, and 78 for each of the red, green, and blue primary colors, the three digital representations of each primary color are then combined to derive an image having both intensity and color hue of side 22 of document 6. After imaging side 12 of platen 8, ESS 38 directs pivot through control line 16 to rotate mirror 14 to the second operational position. In the second operational position, mirror 14 is rotated out of the optical path between side 10 of platen 8 and imager 32, as shown generally in Figure 2. Similar to steps 74, 76, and 78, corresponding steps 82, 84, and 86 are performed on side 10 of platen 8 subsequent to completing step 80. After completing steps 82, 84, and 86, an image having both intensity and color hue of side 20 of document 6 is recorded on storage device 40 or output through port 42 as coordinated by ESS 38. At step 88, ESS 38 determines whether more pages are to be scanned by detecting a signal from switch mechanism 44. After step 86 and before repeating step 72, it is assumed that an operator will turn the page of bound document 6 before invoking the scan switch 44. If no start-scan signal is detected from switch mechanism 44, ESS 38 remains in a ready scan state at step 90. It will be readily understood by those skilled in the art that steps 74, 76, and 78, and corresponding steps 82, 84, and 86 can occur in any order so long as ESS 38 correctly combines images representing the primary colors of each respective side once all the steps have completed. It will also be understood by those skilled in the art that scanning system 4 can be readily modified to have imager 32 record gray scale representations of black and white images. To record a black and white image, a single illumination and recording step is performed in place of steps 74, 76, and 78, and corresponding steps 82, 84, and 86. Specifically the single step consists of recording a gray scale representation of sides 10 and 12 after exposing each side with white light or one of the three primary colors red, green, or blue. Figure 5 is an alternate embodiment in which scanning system 4 is inverted relative to scan bound document 6 in an open and upright position. In this embodiment, scanning system 4 includes a carriage 110 that is supported in a seating cavity 112. Rollers 114 move the carriage 110 laterally relative to the seating cavity 112 as indicated by arrow 116. The lateral movement of carriage 110 insures that the center of bound document 6 between sides 20 and 22, which varies depending on which pages to which bound document 6 are open, is centered in the middle of wedge platen 8. A pair of pivotally mounted support plates 118 and 120 are each secured to the carriage 110 by pistons 124 and 126, respectively, for angular movement about edge 125 as indicated by arrows 122. A drive assembly 128 moves the seating cavity 112 in a direction indicated by arrows 130. A position sensor 132 located at the apex of wedge platen 8 is retractable therein upon contact with bound document 6. ESS 38 communicates with drive assembly 128 to move seating cavity 112 vertically relative to wedge platen 8, and with rollers 114 to move the carriage laterally relative to the seating cavity 112. In response to a start scan signal from start scan switch mechanism 44, ESS 38 controls movement of the drive assembly 128 and rollers 114 to position bound document 6 in contact with wedge platen 8 for scanning. In addition, ESS 38 actuates pistons 124 and 126 to ensure that pages of bound document 6 are firmly in contact with each side of wedge platen 8. Once each side of bound document 6 has been recorded by imager 32, ESS 38 actuates drive assembly 128 to lower seating cavity 112 away from wedge platen 8. It should be understood by those skilled in the art that position sensor 132 can alternatively be a magnetic or capacitive proximity sensor, or an optical detector. It will further be appreciated that scanning system 4 can be modified to automatically turn pages of a bound document. Examples of systems that turn pages of bound documents are disclosed in European Patent Application No. 96 309 002.2 and US-A-5 612 791. It will no doubt be appreciated that there are a number of possible manners in which to implement scanning system 4. One implementation uses a wedge shaped platen having positioned therebetween a mirror, and the mirror pivots between a first and a second operational position. These features enable sequential imaging of opposing pages of a bound document with a single page imager. The imager can be formed using active or passive devices that include: a two-dimensional array of amorphous silicon, a CCD array, a photoreceptor, or photographic film. Furthermore, the single active or passive imaging system, which can be sensitive to color or gray scale, detects pages of a bound document reflected thereon by each of the three primary colors red, green, and blue. It will further be appreciated by those skilled in the art that reductions and enlargements of a side of bound document 6 can be achieved by altering the position and makeup of optics or optical system 30. It will also be appreciated that scanning system 4 can be readily modified to include job level programming as described in US-A-5 119 206. Job level programming can include programming that manages input scanning as well as output rendering. Programming options for scanning bound documents include input commands for specifying whether to scan one or both sides of a bound document. Programming options for rendering scanned images of a bound document include specifying whether opposing sides of a bound document are to be printed on a common print media sheet or on separate print media sheets. Sequential control of scanning system 4 in ESS 38 may be readily implemented in software using software development environments that provide portable source code that can be used on a vanety of hardware platforms. Alternatively, the disclosed system may be implemented partially or fully in hardware using standard logic circuits. Whether software or hardware is used to implement the system varies depending on the speed and efficiency requirements of the system and also the particular function and the particular software or hardware systems and the particular microprocessor or microcomputer systems being utilized. The system, however, can be readily developed by those skilled in the applicable arts without undue experimentation from the functional description provided herein together with a general knowledge of the computer arts.

Claims: Apparatus (4) for scanning bound documents (6) comprising: a wedge shaped platen (8) having a first transparent surface (12) including a first light transmissive area and a second transparent surface (10) including a second light transmissive area, the platen (8) contacting first and second opposing pages (20, 22) of a bound document (6) that is in a partially open position; the first and second opposing pages (20, 22) facing respective ones of the first and second light transmissive areas (10, 12) when contacted by the platen (8); illumination means (23) for illuminating the first and second transmissive areas of the platen (8); image capture means (32); and reflection means (14) for reflecting images from the platen (8) to the image capture means (32), the reflection means (14) being moveable between a first position in which it reflects an image of the first opposing page (22) from the first light transmissive area on a first optical path (28) to the image capture means (32) and a second position; characterized in that in the second position, the reflection means (14) is outside a second optical path (34) for an image of the second opposing page (20) from the second light transmissive area (10) to the image capture means (32) such that the image of the second opposing page can be imaged directly onto the image capture means (32). Apparatus according to claim 1, wherein said illumination means (23) is arranged to selectively emit red light, green light and blue light. Apparatus according to claim 1, wherein said illumination means (23) is arranged to emit white light. Apparatus according to any preceding claim, further comprising a controller (38) for coordinating sequential illumination of the first opposing page (22) and the second opposing page (20) of the bound document (6) with said illumination means (23), said controller (38) positioning said reflection means (14) in the first position before illuminating the first opposing page (22) of the bound document (6), and positioning said reflection means (14) in the second position before illuminating the second opposing page (20) of the bound document (6). Apparatus according to claim 4, further comprising a storage medium (40) communicating with said controller (38) for storing an image from the image capture means (32) representing the first opposing page (22) and an image representing the second opposing page (20) of the bound document (6). Apparatus according to any preceding claim, further comprising a pivot (15); the reflection means (14) comprising a mirror attached to the pivot (15) for movement between the first and second positions. Apparatus according to any preceding claim, wherein the first transparent surface and the second transparent surface of said wedge shaped platen are offset by an angle () of less than ninety degrees. Apparatus according to any preceding claim, further comprising an optical system (30) for projecting an image of the first opposing page (22) and an image of the second opposing page (20) of the bound document (6) onto the image capture means (32). Apparatus according to any preceding claim, wherein the image capture means (32) comprises a photoreceptor or a two-dimensional array of amorphous silicon sensors. A method for scanning a bound document (6) in a partially open position using the apparatus according to any preceding claim, the method comprising the steps of: (a) positioning the reflection means (14) in the first position; (b) illuminating the first opposing page (22); (c) capturing an image of the first opposing page (22); (d) positioning the reflection means (14) in the second position; (e) illuminating the second opposing page (20); and (f) capturing an image of the second opposing page (20).

Inventors: WU XIAODONG, WU, XIAODONG
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1997
Main classification: G03B27
IPC codes: G03B27, G03G15, H04N1