Abstract:
An image scanning apparatus scans an image formed on a surface of a document. The image scanning apparatus includes a contact glass, a plurality of moving members including a light source and a plurality of reflection mirrors, an imaging lens, and an image pickup device. The contact glass holds the document thereon. The plurality of moving members are provided below the contact glass and move in a sub-scanning direction. The light source outputs light for illuminating the surface of the document. The plurality of reflection mirrors sequentially reflect the light reflected obliquely from the surface of the document. The imaging lens collects the reflected light. The image pickup device forms thereon an image from the light output from the imaging lens.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to Japanese patent application no. 2005-042613 filed on Feb. 18, 2005, the entire contents of which are hereby incorporated by reference herein.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an image scanning method and apparatus for scanning an image on a document by applying light output from a light source to the document and guiding a reflected light from the document through an imaging lens to an image pickup device to form an image thereon.  
         [0004]     2. Description of the Background Art  
         [0005]      FIGS. 1 and 2  illustrate a background image scanning apparatus  1 . The image scanning apparatus  1  includes a contact glass  2 , a first moving member  3 , a second moving member  4 , an imaging lens  5 , a one-dimensional CCD (charge-coupled device)  6 , a reflector  7 , a lamp  8 , and reflection mirrors  9 ,  10 , and  11 .  
         [0006]     In the image scanning apparatus  1 , a document S carrying thereon an image to be scanned is placed on the contact glass  2 . The first moving member  3  and the second moving member  4  are provided below the contact glass  2 , and are driven by a motor (not illustrated) to move in a sub-scanning direction (i.e., a direction indicated by an arrow Y in  FIGS. 1 and 2 ). The one-dimensional CCD  6  is an image pickup device extending in a main-scanning direction, (i.e., a direction indicated by an arrow X in  FIGS. 1 and 2  or a direction perpendicular to the drawing surface). The lamp  8  is a light source for applying light to the contact glass  2  directly or by the reflector  7  to illuminate a scanning region (i.e., an imaging region) ds of the document S. The lamp  8  and the reflection mirror  9  are provided as part of the first moving member  3 . Meanwhile, the reflection mirrors  10  and  11  are provided as part of the second moving member  4 . The lamp  8  and the reflection mirrors  9 ,  10 , and  11  extend in the main-scanning direction.  
         [0007]     The light output from the lamp  8  is reflected by the document S, and transmits to the contact glass  2 . Then, the light is reflected by the reflection mirrors  9 ,  10 , and  11 , and is formed into an image on the CCD  6  by the imaging lens  5 . This process is repeated while the first and second moving members  3  and  4  are moving in the sub-scanning direction. Thereby, images of minute scanning regions are sequentially accumulated, and the entire image on the document S is two-dimensionally acquired by the CCD  6 .  
         [0008]     In the image scanning apparatus  1 , the reflection mirrors  9 ,  10 , and  11  are placed at an angle of approximately forty-five degrees with respect to a surface of the document S (i.e., a surface  12  of the contact glass  2 ). Thus, optical axes of a scanning optical system through which the reflected light from the document S passes (i.e., scanning optical axes) are either parallel or perpendicular to the surface of the document S. To increase illumination intensity of the scanning region ds, the lamp  8  is preferably provided such that the distance between the lamp  8  and the scanning region ds is reduced as much as possible. That is, the lamp  8  is preferably provided such that an illuminating optical axis L 1  extending directly from the lamp  8  to the contact glass  2 , which is one of illuminating optical axes, i.e., optical axes of an illuminating optical system through which the illuminating light to the document S passes, is as perpendicular to the surface of the document S as possible, i.e., that an incident angle θ (theta) of the illuminating optical axis L 1  (illustrated in  FIG. 2 ) with respect to the surface of the document S is reduced as much as possible.  
         [0009]     If the lamp  8  is placed close to the scanning region ds, however, the lamp  8  is also close to a scanning optical axis R 1  (i.e., an optical axis extending from the surface of the document S to the reflection mirror  9  provided as part of the first moving member  3 ). Therefore, the lamp  8  may touch the contact glass  2  or block an optical path of the scanning optical system due to such factors as slight size errors in components and vibration caused by movement of the first moving member  3  and the second moving member  4 . As a result, a jitter may occur in a scanned image. Further, the illumination intensity of the scanning region ds may become insufficient to cause a defective scanning operation and degradation in quality of a background image.  
         [0010]     In light of the above, a lamp having relatively high brightness intensity may be used to maintain a certain distance between the lamp and the scanning region ds. However, such a lamp is relatively expensive and consumes a relatively large amount of power. Further, there is a technical limit in increasing the brightness intensity of the lamp.  
         [0011]     In view of this, there is another background image scanning apparatus in which a lamp is placed above a contact glass. This background image scanning apparatus can scan a transparent document but not a reflective document. Further, an upper part of the background image scanning apparatus is increased in size, and the number of components forming the background image scanning apparatus is increased. As a result, cost of the background image scanning apparatus increases.  
       SUMMARY OF THE INVENTION  
       [0012]     This patent specification describes an image scanning apparatus for scanning an image formed on a surface of a document. In one example, an image scanning apparatus for scanning an image formed on a surface of a document includes a contact glass, a plurality of moving members, an imaging lens, and an image pickup device. The contact glass is configured to hold the document thereon. The plurality of moving members are provided below the contact glass and are configured to move in a sub-scanning direction. The plurality of moving members includes a light source and a plurality of reflection mirrors. The light source is configured to output light for illuminating the surface of the document. The plurality of reflection mirrors are configured to sequentially reflect the light reflected obliquely from the surface of the document. The imaging lens is configured to collect the reflected light. The image pickup device is configured to form thereon an image from the light output from the imaging lens.  
         [0013]     This patent specification further describes another image scanning apparatus for scanning an image formed on a surface of a document. In one example, the another image scanning apparatus for scanning an image formed on a surface of a document includes document holding means, moving means, imaging means, and image pickup means. The document holding means holds the document thereon. The moving means moves below the document holding means in a sub-scanning direction. The moving means includes light source means for outputting light for illuminating the surface of the document, and reflecting means for sequentially reflecting the light reflected obliquely from the surface of the document. The imaging means collects the reflected light. The image pickup means forms thereon an image from the light output from the imaging means.  
         [0014]     This patent specification further describes an image scanning method for scanning an image formed on a surface of a document. In one example, an image scanning method for scanning an image formed on a surface of a document includes: placing a document on a contact glass; moving a plurality of moving members below the contact glass in a sub-scanning direction; outputting light from a light source for illuminating the surface of the document; sequentially reflecting the light reflected obliquely from the surface of the document by a plurality of reflection mirrors; and focusing the reflected light through an imaging lens to an image pickup device to form an image thereon. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:  
         [0016]      FIG. 1  is a schematic sectional view of an optical system in a background image scanning apparatus;  
         [0017]      FIG. 2  is an enlarged view of a part near the first moving member in the image scanning apparatus illustrated in  FIG. 1 ;  
         [0018]      FIG. 3  is a perspective view of an image scanning apparatus according to an embodiment of the present invention;  
         [0019]      FIG. 4  is a schematic sectional view of an optical system in the image scanning apparatus illustrated in  FIG. 3 ;  
         [0020]      FIG. 5  is an enlarged view of a part near the first moving member in the image scanning apparatus illustrated in  FIG. 4 ;  
         [0021]      FIG. 6  is a graph indicating illumination intensity distribution curves with respect to a document surface, measured for the background image scanning apparatus illustrated in  FIG. 1  and the image scanning apparatus illustrated in  FIG. 3 ; and  
         [0022]      FIG. 7  is an enlarged view of a part near the first moving member in an image scanning apparatus according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     In describing the embodiments illustrated in the drawings, specific terminology is employed for the purpose of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so used, and it is to be understood that substitutions for each specific element can include any technical equivalents that operate in a similar manner.  
         [0024]     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, particularly to FIGS.  3  to  5 , a configuration and functions of an image scanning apparatus  20  according to an exemplary embodiment of the present invention are described.  
         [0025]     As illustrated in  FIGS. 3 and 4 , the image scanning apparatus  20  includes a box-shaped housing  21 , a contact glass  22 , a first moving member  23 , a second moving member  24 , a motor  25 , an imaging lens  26 , a one-dimensional CCD  27  functioning as an image pickup device, a lamp  28 , scan belts  29 , pulleys  30  and  31 , and reflection mirrors  33 ,  34 , and  35 .  
         [0026]     As illustrated in  FIGS. 4 and 5 , the contact glass  22  is placed on an upper surface of the housing  21 , and a document S carrying thereon an image to be scanned is placed on the contact glass  22 . The first and second moving members  23  and  24  are movably provided below the contact glass  22  in the sub-scanning direction (i.e., the direction indicated by the arrow Y). Further, the first and second moving members  23  and  24  are fastened onto the scan belts  29  that extend in the sub-scanning direction. The scan belts  29  are extended between the pulleys  30  and  31 . As a driving force for the motor  25  is transmitted to the pulleys  30 , the pulleys  30  are rotated. Thereby, the scan belts  29  move, and the first and second moving members  23  and  24  move in the sub-scanning direction.  
         [0027]     As illustrated in  FIG. 4 , the first moving member  23  is provided with the reflection mirror  33  and the lamp  28  functioning as a light source. Meanwhile, the second moving member  24  is provided with the reflection mirror  34  for receiving a light reflected by the reflection mirror  33 , and the reflection mirror  35  for receiving a light reflected by the reflection mirror  34 . The lamp  28  provided as part of the first moving member  23  is formed by a small-sized elongated fluorescent light (e.g., a backlight fluorescent tube) or an LED (light-emitting diode), for example, and extends in the main-scanning direction. The lamp  28  has an output aperture  36  (illustrated in  FIG. 5 ) from which illuminating light is output to the document S and that extends in the main-scanning direction.  
         [0028]     The lamp  28  is preferably set such that, on a surface of the document S (i.e., a surface  41  of the contact glass  22 ), a scanning region (i.e., an imaging region) ds on the document S substantially overlaps, in the sub-scanning direction, a peak position in an illumination intensity distribution of the illuminating light output from the lamp  28  (i.e., a position in an illumination area or an illuminating range illuminated by the lamp  28  having the highest illumination intensity). Specifically, within the scanning region ds, the surface of the document S intersects with an illuminating optical axis L 1  extending from the lamp  28  to the contact glass  22  (i.e., a line connecting the radial center of the lamp  28  with the circumferential center of the output aperture  36 , and the extended line of the line). Accordingly, the position of the highest illumination intensity in the illumination area of the lamp  28  substantially overlaps the scanning region ds. Accordingly, an illumination intensity necessary for scanning the image on the document S is effectively obtained.  
         [0029]     The imaging lens  26  is placed to receive a light reflected by the reflection mirror  35  provided as part of the second moving member  24 . The CCD  27  is placed at an image forming position of the imaging lens  26 . The CCD  27  includes a plurality of CCD pixels arranged in a line. Each of the reflection mirrors  33 ,  34 , and  35 , and the CCD  27  is formed into an elongated shape and extends in the main-scanning direction (i.e., the direction indicated by the arrow X in FIGS.  3  to  5 ).  
         [0030]     In the image scanning apparatus  20 , an illuminating light flux output from the lamp  28  penetrates the contact glass  22  and directly illuminates the scanning region ds on the document S. The illuminating light on the document S is reflected according to the density of the image on the document S. The light thus reflected penetrates the contact glass  22  again, and is reflected and guided by the reflection mirrors  33 ,  34 , and  35  to the imaging lens  26 . Then, the light is formed into an image on the CCD  27 , and the image is scanned. A sequence of these operations is performed while the first and second moving members  23  and  24  move in the sub-scanning direction with the image forming position with respect to the surface of the document S being kept on the CCD  27 . Accordingly, the two-dimensional image carried on the document S is picked up.  
         [0031]     The reflection mirrors  34  and  35  provided as part of the second moving member  24  are placed at an angle of approximately forty-five degrees with respect to the surface of the document S. Meanwhile, the reflection mirror  33  provided as part of the first moving member  23  is placed at an angle changeable with respect to the surface of the document S. Specifically, the angle of the reflection mirror  33  is adjusted such that a scanning optical axis R 1  extending from the surface of the document S to the reflection mirror  33  provided as part of the first moving member  23  is not perpendicular to the surface of the document S but is tilted away from the lamp  28  so as not to touch the lamp  28 . Further, the angle of the reflection mirror  33  is adjusted such that a scanning optical axis R 2  extending from the reflection mirror  33  to the reflection mirror  34  provided to the second moving member  24  is substantially parallel to the surface of the document S. That is, the angle of the reflection mirror  33  is adjusted such that an incident angle φ (phi) of the scanning optical axis R 1  with respect to the reflection mirror  33  provided to the first moving member  23  becomes larger than forty-five degrees.  
         [0032]     As described above, in the image scanning apparatus  20 , the scanning optical axis R 1  (i.e., the light reflected from the surface of the document S) is tilted away from the lamp  28 . In the image scanning apparatus  20 , therefore, the scanning region ds is closer to the lamp  28  than in the background image scanning apparatus  1  in which the scanning optical axis R 1  is perpendicular to the surface of he document S. Thus, the incident angle θ of the illuminating optical axis L 1  with respect to the surface of the document S can be reduced in the image scanning apparatus  20 . According to the image scanning apparatus  20 , therefore, the illumination intensity of the scanning region ds can be easily increased to a higher level than the background image scanning apparatus  1 .  
         [0033]     Since a tilt angle of the reflection mirror  33  is changed, the width of the scanning region ds in the sub-scanning direction is larger in the image scanning apparatus  20  than in the background image scanning apparatus  1 . With the amount of light applied to illuminate the scanning region ds being unchanged, the illumination intensity decreases as the width of the scanning region ds in the sub-scanning direction increases. In this regard, the illumination intensity decreases in the image scanning apparatus  20 . However, a decrease in the illumination intensity due to the change in the width of the scanning region ds in the sub-scanning direction is relatively small compared with an increase in the illumination intensity due to the change in the incident angle of the light with respect to the surface of the document S.  FIG. 6  is a graph representing distribution curves of the illumination intensity on the surface of the document S measured for the image scanning apparatus  20  (indicated as ISA  20  in  FIG. 6 ) and the background image scanning apparatus  1  (indicated as ISA  1  in  FIG. 6 ). As observed from the graph, the peak of the illumination intensity (i.e., the illumination intensity of the scanning region ds) is higher in the image scanning apparatus  20  than in the background image scanning apparatus  1 .  
         [0034]     In the image scanning apparatus  20  according to the present embodiment, the light output from the lamp  28  illuminates the surface of the document S, and the light reflected obliquely from the surface of the document S is reflected by the reflection mirror  33 . Therefore, the incident angle θ of the illuminating optical axis L 1  with respect to the surface of the document S can be reduced, and thus the lamp  28  can be placed closer to the scanning region ds. Thereby, the illumination intensity of the scanning region ds can be increased. According to the image scanning apparatus  20 , therefore, illumination efficiency is increased to decrease power consumption. Further, the illumination intensity necessary for the scanning region ds is obtained, and thus a high-quality image scanning operation can be performed.  
         [0035]     The image scanning apparatus  20  has a relatively simple structure in which the tilt of the reflection mirror  33  is adjusted. Thus, unlike background image scanning apparatuses, a lamp having a relatively high brightness intensity is unnecessary, and the size of the upper portion of the image scanning apparatus  20  and the number of components forming the image scanning apparatus  20  are not increased. Accordingly, the image scanning apparatus  20  can be manufactured at relatively low cost, and can decrease power consumption.  
         [0036]     Further, the image scanning apparatus  20  is versatile, being capable of scanning reflective documents as well as transparent documents.  
         [0037]     The image scanning apparatus  20  is not limited to the example described above. For example, as illustrated in  FIG. 7 , a reflector  38  may be added to the first moving member  23  for reflecting the illuminating light output from the lamp  28  in the direction of the contact glass  22 . The reflector  38  is placed opposite to the lamp  28  such that a part of the illuminating light output from the lamp  28  but not directly advancing to the surface of the document S is reflected by the reflector  38  onto the surface of the document S. Accordingly, the light output from the lamp  28  can be effectively used.  
         [0038]     The reflector  38  may be preferably placed such that the surface of the document S intersects, in the scanning region ds, with an illuminating optical axis L 2  extending from the lamp  28  to the contact glass  22  guided by the reflector  38 , i.e., that the peak position in the illumination intensity distribution of the illuminating light reflected by the reflector  38  substantially overlaps the scanning region ds in the sub-scanning direction on the surface of the document S. Accordingly, the illumination intensity of the scanning region ds can be further effectively obtained.  
         [0039]     The above-described embodiments are illustrative, and numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative and exemplary embodiments herein may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.