Abstract:
Device and method are provided for scanning an original copy using a camera containing a line sensor. During the scanning process, an optical path length between the camera and each line being currently scanned is maintained substantially constant.

Description:
BACKGROUND  
       [0001]     A device to scan an original, with a bearing surface on which the original to be scanned rests is known. The device has a camera, provided with an optoelectronic line sensor, that scans the original resting on the bearing surface line-by-line and generates electronic signals.  
         [0002]     Such a device is used to digitize the image content of an original such as, for example, magazines and books. Such originals are frequently bound, such that it is necessary to lay the original open on a work table and scan from above using the incident light principle.  
         [0003]     In the prior art, scanning devices (scanners) are known that use a camera with a CCD area sensor. Such a camera can in fact implement a fast scan, however the resolution of the image structures are significantly limited. At very high resolutions, the CCD sensors necessary for this are very cost-intensive. In particular, cameras that comprise a CCD line sensor are therefore used. Such a camera has a high resolution with high quality and operates economically.  
         [0004]     Given the use of a camera with a CCD line sensor, two tasks are too be solved. On the one hand, to generate a two-dimensional image, a relative motion between the scanning camera and the original must occur, for example by shifting the camera, and the original, the objective of the camera or the line sensor. On the other hand, it is necessary to sufficiently illuminate the original, in particular the line to be scanned.  
         [0005]     In a conventional scan with a camera with line sensor, the camera is located above the original and is moved across the entire document. What is disadvantageous is that the camera must be moved over a relatively long extent, and this motion occurs in the head room of a user. A further disadvantage is that it is difficult to place an illumination such that no glare that impairs the scan quality is present in the image to be scanned.  
         [0006]     A further possibility of scanning is to arrange the camera with the line sensor perpendicular and fixed above the original, and to shift the objective of the camera such that a larger area of the original is scanned line-by-line. This is difficult since the optics must be designed for a large image area, and the image region should correspond at least to the diagonals of the maximum original size. Moreover, the problem exists of the occurrence of glare on the image structure to be scanned.  
         [0007]     In the prior art, halogen or fluorescent lamps are frequently used to illuminate the original. However, such lamps are disadvantageous insofar as they exhibit a slow warm-up behavior, and wherein the color and the brightness change, whereby the scan result also changes. Moreover, the original is exposed to a relatively high radiant heat and, in the case of fluorescent lamps, additionally a UV exposure. A further disadvantage is visible in that such lamps interfere in the work area of an operator and can cause a diaphragm effect at the operator. Moreover, a whole-surface illumination with the aid of such lamps generates glare on the original to be scanned, with the result of reduced scan quality.  
         [0008]     From EP-A-0 164 713, a document reader is known in which a line camera executes a lifting motion and a rotation movement upon line-by-line scanning. The optical distance between the camera and the document to be read remains essentially constant.  
         [0009]     A scanner head to scan originals is known from the German patent DE 19 829 776 C1. The distance between the sensor and the original remains essentially equal, for which a parallelogram mechanism is used. A radiation source that comprises a plurality of LEDs serves to illuminate the original.  
       SUMMARY  
       [0010]     It is an object to specify a device and a method to scan an original that is simply designed and enables a precise scan with high quality.  
         [0011]     A method and device are provided to scan an original. The original to be scanned rests on a support surface. The camera is provided with an opto-electronic lens sensor which scans the original line-by-line. An optical path length between the camera and each current line being scanned is kept essentially constant. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a principle representation of the device with two camera positions;  
         [0013]      FIG. 2  is a design with a single drive motor;  
         [0014]      FIG. 3  is a design with two drive motors;  
         [0015]      FIG. 4  is a design with a rotating mirror;  
         [0016]      FIG. 5  is an illumination arrangement with integrated camera;  
         [0017]      FIG. 6  is a design of an illumination by means of LED rows;  
         [0018]      FIG. 7  is a similar design in a compact arrangement;  
         [0019]      FIG. 8  is a further exemplary embodiment with a pivotable arm, on which is arranged the camera such that it can be linearly moved;  
         [0020]      FIG. 9  is the arrangement according to  FIG. 8  with a spindle-nut combination;  
         [0021]      FIG. 10  is an arrangement with a curve disc that effects the linear motion of the camera on the arm; and  
         [0022]      FIG. 11  is a further arrangement in which a movable diaphragm is used. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the preferred embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and/or method, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur now or in the future to one skilled in the art to which the invention relates.  
         [0024]     A system is provided that keep the optical path length between the camera and the current line to be scanned essentially constant during the scan event. The optics for the camera must only be designed for the length of a line on the original to be scanned, typically for the width of the original. A design of the optics for the entire image diagonal and the entire area of the original is not necessary. The design for the camera is accordingly simplified. Moreover, the optics can be optimally designed to the constant optical path length, such that no optical distortions can be created. A refocusing or a change of the scale, as in known scanning systems, is not necessary.  
         [0025]     In preferred exemplary embodiments, the camera is arranged on an arm such that it can be moved. The arm is connected with one end in a stationary rotation axle with a lifting column, such that it can be pivoted. Given a pivot movement of the arm, the camera is also simultaneously shifted on this arm, whereby the consistent distance from the line to be scanned is maintained.  
         [0026]      FIG. 1  shows a principle representation of the preferred embodiment. An original  10 , for example a bound book or a bound magazine, lies open on the bearing surface  12  of a work table  14 . One edge of the original  10  is generally aligned parallel to a reference axis, for example the trailing edge  16  of the work table. A camera  20  can be moved along a lifting column  18  that is attached to the work table  16 . The camera  20  comprises an objective and an optoelectronic line sensor, generally a CCD line sensor. The line sensor is preferably arranged in a rotation center  22  around which the camera  20  can rotate.  
         [0027]     The camera  20  is aligned with its objective such that a center beam detects a boundary line  26  to be scanned that has the maximum distance from the reference axis  16 . The direction of the line and the arrangement of the linear line sensor in the camera  20  runs perpendicular to the paper plane of  FIG. 1 . The optical path length w between the camera  20  and the boundary line  26  is a constant quantity to which the objective of the camera  20  is optimally adjusted. In the line-by-line scan of the original  10 , the camera  20  is moved upwards (indicated dashed) along the lifting column  18 , whereby the camera  20  rotates around the rotation center  22  such that its optical axis coincides with the center ray. The optical path length w remains constant and acquires in the upper position of the camera  20  a wider boundary line  28  that has minimal distance from the reference axis  16 . The line-by-line scan occurs during the movement of the camera  20  from the first position (line drawn solid) to the second position (line drawn dashed), whereby electronic signals are generated for the digitization of the image content of the original. The movement is adapted to the area between the boundary lines  26 ,  27  and can be selected correspondingly larger or smaller on the bearing surface  12 .  
         [0028]     As is visible using the principle drawing according to  FIG. 1 , the camera  20  must only be moved over short distances. The movement of the camera  20  is generally outside of the area that is accessible to an operating personnel to the right of the boundary line. The optics of the camera  20  must only be designed for the scanning in the line direction, for example corresponding to the width of the original  10 , or for the width of the support surface  12 , and not for the total dimensions of the original  10 , for example the image diagonals. Since the optical path length  2  remains constant, a refocusing of the camera is not necessary. Also, no scale changes thereby result. The optics can optimally be adapted to the path length w and can be minimized with regard to distortions. Via the alignment of one edge of the original with regard to a reference axis  16 , for example the trailing edge of the work table  14 , the entire area behind the original  10  is available for the placement of illumination elements. Barely any glare reflections are created given the arrangement of corresponding illumination elements, also given significantly curved originals (such as, for example, bound books).  
         [0029]      FIG. 2  shows an example that uses a single drive motor. Identical parts are designated identically. A lifting device  30  can be linearly shifted along the lifting column  18 , along the indicated arrows P 6 . A spindle  32  that is driven by a drive motor  34  is arranged along the support surface  12 . A slide  36  that can execute linear motions corresponding to the drawn arrow P 7  is driven along the spindle  32 . The spindle  32  is arranged in a bearing block. The lifting device  30  and the shifting slider  36  are connected with one another by a strut  40 , whereby the strut  40  is linked such that it can rotate in an axis belonging to the rotation center  22 . The strut  40  is likewise attached to the shift slider  36  such that it can rotate in an axis  42 . The distance of the strut  40  between the points  22  and  42  corresponds to the optical path length w.  
         [0030]     The camera (not shown in  FIG. 2 ) is arranged on the lifting device  30 , whereby the optical axis of the camera is aligned in the direction of the strut  40 . The line sensor of the camera is arranged at the height of the rotation center  22 . The motor  34  drives the spindle  32  such that the shift slider  36  has a speed in the direction transverse to the line direction of the scanned line, the speed corresponding to the line feed speed given line-by-line scanning. During the shift motion of the shift slider  36 , the lifting device  30  is also shifted via the strut  40 , and the camera is rotated at the rotation center  22 . The lower rotation center  42  is preferably arranged in the object plane, meaning in the scan plane for the original  10 . During the line-by-line scan of the original  10 , a lifting motion occurs for the camera with regard to the support surface  12 , and a rotation motion occurs transverse to the line direction.  
         [0031]     In an alternative embodiment of the example according to  FIG. 2 , a drive is connected with the lifting device  30 . The shift slider  36  then follows the driven motion of the lifting device  30 .  
         [0032]      FIG. 3  shows a further exemplary embodiment of the invention. The camera  20  is arranged on a positioning unit  44  that is driven via a spindle  46  and a motor  48  such that it can move along the lifting column  18 . The positioning unit  44  bears a rotation device  50  that is rotationally adjusted by a further motor (not shown). Given the line-by-line scanning of the original, the position of the camera  20  is adjusted by both motors such that the distance between the camera  20  and the current line to be scanned is kept essentially constant. The drive curves of both motors must be tuned to one another such that the required combined rotation and lifting motion is executed. The advantage of this example according to  FIG. 3  lies in the compact design.  
         [0033]      FIG. 4  shows a further example in which a mirror  52  that can be rotated around the arrow P 1  is arranged on the lifting column. The camera  20  is also arranged on the lifting column  18 . The mirror  52  is provided in the beam path between camera  20  and scanned line. The line feed upon scanning is effected by adjustment of the rotation angle P 1  of the rotating mirror  52 . The lifting motion can occur either via adjustment of the camera  20  in the direction of the double arrow P 2  or via adjustment of the rotating mirror  52  in the direction of the double arrow P 3  (drawn dashed). The camera  20  can be installed fixed given a movement of the rotating mirror  52  in the direction of the double arrow P 3 .  
         [0034]     As already mentioned previously, sufficient space exists in the selected arrangement to provide an illumination device that illuminates the original. An illumination unit that generates a ray band along the currently scanned line is preferably used to illuminate the original  10  during the scan event.  
         [0035]      FIG. 5  shows a preferred exemplary embodiment in which the camera  20  is incorporated in an illumination unit  54 . As mentioned, the camera  20  executes a linear motion corresponding to the arrow P 4  and a rotation movement around the rotation center  22 , corresponding to the arrow P 5 . The illumination unit  54  simultaneously rotates with the camera  20  around the common rotation center  22  and generates a ray band  56  that illuminates the current line to be scanned. Via the common shifting and rotation of camera and illumination unit  54 , the radiation band also remains the same in terms of its properties on the original during the shifting motion, whereby, for example, the brightness curve always remains constant in the scanning.  
         [0036]      FIG. 6  shows an example for an illumination unit  54  for line-by-line illumination of the original  10 . LEDs  60  are arranged in lines on both sides of a circuit board  58 . These LEDs are arranged along a first focal line of two elliptical cylinder mirror elements  62 ,  64 . These mirror elements  62 ,  64  focus the radiation in their respective second mutual focal line  66 , that spatially coincides and illuminates the line on the original  10 . The shown illumination unit  54  has a compact design since the emission characteristic of the LEDs, which emit radiation only in a half-space, is linked with the advantageous figure projection properties of the elliptical mirror elements  62 ,  64 . The camera  20  can be arranged in a center region of the circuit board, along the longitudinal axis of the circuit board  58 .  
         [0037]      FIG. 7  shows a design with only one line of LEDs  60  on the circuit board  58 . The elliptical mirror  62  is directly connected with the circuit board  58 , whereby an assembly simpler in terms of design results. The line to be illuminated is slightly tilted relative to the vertical in which the circuit board  58  lies. The line-shaped illuminated object can be scanned in the axial direction  68  with the aid of the camera  20  (not shown).  
         [0038]     Further examples for an illumination unit that can illuminate the original  10  line-by-line are specified in DE 10108075 by the same applicant. The content of this document is hereby included by reference in the disclosure content of the present application.  
         [0039]     The specified illumination unit  54  has a plurality of advantages. Only a narrow light stripe is generated, such that a gating of the user in the operating region is prevented. The original itself is charged with a relatively low radiation energy, and thus with a low heat. The use of LEDs allows a fast activation and deactivation without brightness changes. A permanent effect of radiation on the original is prevented. Given use of polychromatic LEDs that, for example, emit white light, a UV charge is foregone. Furthermore, the energy consumption is comparably low.  
         [0040]      FIGS. 8, 9  and  10  show exemplary embodiments in which the rotation axle for the rotation motion of the camera with constant height is arranged on the lifting column. The identical parts are also designated identically in these examples.  
         [0041]     In  FIG. 8 , an arm  70  that can be pivoted according to the rotation arrow P 8  is positioned on the lifting column  18  in a stationary rotation axle  72 . The arm  70  bears the camera  20  that is positioned (for example, in a rail) such that it can be shifted relative to the arm  70  in the direction of the arrow P 9 . The arm  70  is pivoted in the direction of the rotation arrow P 8  upon scanning of a line on the original  10 . The camera  20  is simultaneously shifted in the direction of the arrow P 9 , such that the optical path length w between the camera  20  and the current line to be scanned remains essentially constant during the scan event. In this manner, a compact design is given, such that an operating personnel  74  has a large access space to the original  10 . The rotation axle  72  is stationary for a predetermined work surface. To change the scan angle or the size of the scan area, this rotation axle  72  can also adopt different positions in terms of height along the lifting column  18 .  
         [0042]     The line-by-line scanning of the original  10  occurs via rotation of the arm  70  around the rotation axle  72 . To compensate the distance change, the camera  20  is linearly shifted on the arm. To pivot the arm  70  and the shift the camera  20 , motor units driven independently from one another can be used whose respective motion is coordinated by a control program. The rotation motion and linear shifting motion preferably occurs with the aid of a single motor drive.  
         [0043]      FIG. 9  shows an example for the realization of the pivot motion. A motor  76  is mounted stationary on the lifting column  18 . A linear motion in the direction of the arrow P 10  can be generated with the aid of a spindle-nut combination. The end of the spindle is connected at the point  80  such that it can be rotated with the arm  70 .  
         [0044]      FIG. 10  shows the realization of the relative motion of the camera  20  on the arm  70 . This example can preferably be combined with the example according to  FIG. 9 . A curve disc  82  is connected firmly with the lifting column  18 . A pin  84  connected with the camera  20  slides on this curve disc  82 . Given a pivoting motion of the arm  70  with constant speed, the camera  20  is shifted relatively on the arm  72  dependent on the curve course and angle of the arm  70 , whereby the optical path length w between the camera  20  and the current line to be scanned is held constant. The exemplary embodiment according to  FIG. 10  has a particularly simple design and requires only a single motor unit with which the pivot motion of the arm  70  is generated with largely constant angular velocity.  
         [0045]     The exemplary embodiments according to  FIGS. 8 through 10  can also be advantageously combined with the illumination arrangements according to  FIGS. 5 through 7 .  
         [0046]     A fundamental problem in the image scanning with the aid of a camera exists in the homogenous and efficient illumination of the original to be scanned. The illumination geometry must be selected such that no direct reflections of the radiation emitted by the light source arrives at the camera. Such reflections lead to significant artifacts in the acquired scan images. Primarily when the originals are placed on a glass plate or similar unit for definite alignment of the acquisition geometry, the illumination must be selected such that a direct reflection is prevented. For example, the light source is conventionally positioned far away at a flat angle so that no direct reflected light can arrive at the camera. However, this procedure leads to an inefficient use of the emitted light quantity. Nevertheless, in order to achieve a high image quality, whereby a small diaphragm opening of the imaging optics is necessary, the amount of light is typically increased. However, this is in direct contradiction to a gentle treatment of the object, above all given valuable and sensitive originals. The charge of the original with heat and light energy, in particular of UV light, and the ergonomic problems for the operating personnel created thereby, is critical. In particular for incident light scanners with which books, antique scripts and other large-format originals are scanned, the charge via diaphragm and heat radiation is significant for the operating personnel.  
         [0047]     In  FIG. 11 , an example is shown as to how interfering effects due to glare and direct reflection can be prevented given high utilization of the incident light quantity. In  FIG. 11 , a camera scans an original  94  arranged beneath a glass plate  92  line-by-line, as this has already been specified further above. An illumination device  96  with a large-surface radiating area  98  emits radiation onto the original  94 . The illumination device  96  can comprise a plurality of light sources  100 . The illumination device  96  is arranged directly above the original  94 , and thus emits radiation directly onto the original  94  and the glass plate  92 , such that the radiation radiated by the light sources  100  is optimally used.  
         [0048]     A movable diaphragm  102  that can be moved in the arrow directions P 11 , P 12  transverse to the line direction is arranged in front of the radiant surface  98 . The line direction here runs perpendicular to the paper plane. In tune with the line-by-line scanning of the camera, the diaphragm  102  is moved to a position in which it screens radiation (originating from the illumination device  96 ) that would otherwise arrive at the camera  90  via reflection in the scanning of a current line. When, for example, the camera  90  scans a current line  104  on the original  94 , a reflection optical path results with the legs  106 ,  108 , whereby radiation from the illumination device  96  that impinges along the leg  108  effects a glare effect, or a direct reflection would be caused on the glass plate  92  or the original  94  in the direction of the camera  90 . Based on the position of the diaphragm  102  indicated in  FIG. 11 , the radiation is gated along the leg  108 , and this negative effect is suppressed. Via the diaphragm  102 , only a small reduction of the radiation quantity radiated by the illumination device  96  occurs, because the diaphragm  102  can be implemented relatively small in comparison with the large-surface radiant area  98 .  
         [0049]     The example according to  FIG. 11  can be combined with the additional examples specified before. The camera  90  can be movable, or can be arranged at a fixed location in order to effect the line-by-line scanning via rotation motion or via optical means. The glass plate  92  can be coated or omitted entirely. The light sources  100  can have different embodiments, as also already mentioned previously.  
         [0050]     While a preferred embodiment has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention both now or in the future are desired to be protected.