Abstract:
An image sensor comprises signal generation unit for generating an image signal on the basis of reflected light using a plurality of photoelectric converters arranged on a substrate, and image forming unit for projecting the reflected light, from an original image, within a predetermined area on the substrate on which the signal generation unit is provided, wherein the signal generation unit includes signal output unit for outputting the image signal from the plurality of photoelectric converters to the outside of the signal generation unit, and a part or all of the signal output unit is arranged outside of the predetermined area on the substrate. Accordingly, reflection of light by the electrodes is prevented, and no light noise incidents on the photoelectric converters. Therefore, it is possible to increase the S/N ratio of the image sensor.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an image sensor and, more particularly, to an image sensor which detects reflected light from an original image using photoelectric converters and generates image signals, and an image processing apparatus using the image sensor. 
     FIG. 10 is a cross-sectional view showing a configuration of a conventional image sensor of the aforesaid type. Referring to FIG. 10, the image sensor is basically configured with a sensor array  1  composed of a sensor substrate  101  and sensor ICs  102  mounted on the sensor substrate  101 , an lens array  2 , an illumination device  3  for illuminating an original image, a cover glass  4 , and a frame  5  for holding the foregoing elements and devices at fixed positions. 
     The lens array  2  is formed by arranging a plurality of rod lens elements, each of which functions as a lens by graduating index of refraction from the peripheral portion toward the central portion of the lens element, in a line. The lens array  2  propagates reflected light from the original image and forms an image on the sensor ICs  102 . An imaging area on the sensor substrate  101  is shown in detail in FIG.  11 . In FIG. 11, X 0  denotes the radius of the imaging area. Since imaging areas of the lens elements having radius X 0  overlap to each other, although it is not shown in FIG. 11, the overall imaging area of the lens array  2  on the sensor substrate  101  has a band shape whose width is X (=2×X 0 ). 
     As shown in FIGS. 10 and 11, the sensor IC  102  is electrically connected with the sensor substrate  101  via an electric connection portion  104  and a conductive thin wire  103 . Further, the surface of the electrical connection portion  104  of the sensor substrate  101  is formed with metals, such as gold and silver, and the portion  104  is formed within the imaging area of the lens array  2 . 
     However, the reflectivity of metals, such as gold and silver, forming the electrical connection portion  104  on the sensor substrate  101  of the aforesaid conventional image sensor is high. Accordingly, when light propagated through the lens arrays  2  incidents on the electrical connection portion  104 , the light is mostly reflected by the metal and becomes stray light. As a result, there is a problem in which the stray light incidents on photo-sensing portions of the sensor ICs  102  as light noise, which causes deterioration of the S/N ratio of sensor output. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in consideration of the above situation, and has as its object to provide an image sensor whose S/N ratio is improved. 
     According to the present invention, the foregoing object is attained by providing an image sensor comprising: signal generation means for generating an image signal on the basis of reflected light using a plurality of photoelectric converters arranged on a substrate; and image forming means for projecting the reflected light, from an original image, within a predetermined area on the substrate on which the signal generation means is provided, wherein the signal generation means includes signal output portions for outputting the image signal from the plurality of photoelectric converters to the outside of the signal generation means, and a part or all of the signal output portions is arranged outside of the predetermined area on the substrate. 
     With the present invention as described above, since incoming light does not incident on electrodes on the sensor substrate, no light is reflected by the electrodes, thereby no noise light incidents on a photoelectric converter. 
     It is another object of the present invention to provide a down-sized and down-weighed image sensor. 
     According to the present invention, the foregoing object is attained by providing the image sensor comprising aperture stop for reducing the diameter of the imaging area of the lens. 
     With the present invention as described above, mounting density of the photoelectric converters and electrodes on the sensor substrate can be increased. 
     It is another object of the present invention to provide an image processing apparatus capable of performing high quality scanning of an image. 
     According to the present invention, the foregoing object is attained by providing an image processing apparatus comprising: original feeding means for feeding an original image; reading means for reading the original image using an image sensor and generating image signals; print medium feeding means for feeding a print medium; and print means for printing an image on the print medium on the basis of the image signals read by the reading means, wherein the image sensor used in the reading means comprises: signal generation means for generating an image signal on the basis of light information using a plurality of photoelectric converters arranged on a substrate; and image forming means for projecting the light information, from the original image, within a predetermined area on the substrate on which the signal generation means is provided, wherein the signal generation means includes signal output portions for outputting the image signal from the plurality of photoelectric converters to the outside of the signal generation means, and a part or all of the signal output portions is arranged outside of the predetermined area on the substrate. 
     With the present invention as described above, it is possible to install an image sensor having a good S/N ratio of sensor output to an image processing apparatus. 
     The invention is particularly advantageous since the S/N ratio of the output from the image sensor is improved and it is possible to provide an image sensor and an image processing apparatus capable of performing high-quality scanning of an image. 
     Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
     FIG. 1 is a cross-sectional view of an image sensor according to a first embodiment of the present invention; 
     FIG.  2 .is a top view of the image sensor according to the first embodiment; 
     FIG. 3 is a side view of an illumination device according to the first embodiment; 
     FIG. 4 is a view showing an operation of the illumination device according to the first embodiment; 
     FIG. 5 is a perspective view of the image sensor for showing an imaging area of a lens array according to the first embodiment; 
     FIG. 6 is a cross-sectional schematic representation showing an arrangement of an electrical connection portion of a sensor substrate according to the first embodiment; 
     FIG. 7 is a cross-sectional schematic representation showing another arrangement of the electrical connection portion of the sensor substrate according to the first embodiment; 
     FIG. 8 is a cross-sectional view showing an image sensor according to a modification of the first embodiment; 
     FIG. 9 is a cross-sectional view of an,image processing apparatus according to a second embodiment; 
     FIG. 10 is a cross-sectional view of a conventional image sensor; and 
     FIG. 11 is a view showing a focusing area of a lens array of the conventional image sensor. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be described in detail in accordance with the accompanying drawings. 
     First Embodiment 
     FIG. 1 is a cross-sectional view of an image sensor according to the first embodiment of the present invention, and FIG. 2 is a top view of the image sensor. Referring to FIGS. 1 and 2, the image sensor comprises a sensor array  1  of a predetermined number of sensor ICs  102 , having line-shaped photoelectric converters, precisely arranged in a line on a sensor substrate  101  made of, e.g., epoxy glass; a lens array  2  for transmitting reflected light from an original image thereby forming an image on the sensor array  1 ; an illumination device  3  for illuminating the original image; a cover glass made of transparent material for holding the original image; a frame  5  made of metal, such as aluminum, or resin, such as a polycarbonate, for supporting the foregoing elements and units at fixed positions. 
     Further, reference numeral  104  denotes a electrical connection portion, and reference numeral  103  denotes a gold wire connecting between the sensor IC  2  and the connection portion  104 . 
     Next, a basic function of the image sensor is explained. An original image, held by being pressed against the cover glass, is illuminated obliquely by the illumination device  3  while sequentially changing colors of light, red (R), green (G), and blue (B). An optical images of the original image illuminated by the R, G and B light are formed on the sensor ICs  102  by the lens array  2 . The sensor ICs  102  convert the respective optical images into electric signals and transmits them to a system where these electric signals are processed and a color image is reproduced. 
     In the above description, a case of reading the original image by receiving reflected light from it is explained, however, the present invention is applicable to a system, having an image sensor and an illumination device which is provided independently of the image sensor, for reading a transparent original image by receiving light transmitted through it. 
     FIG. 3 is a side view of the illumination device  3 , and FIG. 4 is a detail view of the illumination device  3  showing an operation of the illumination device  3 . Referring to FIGS. 3 and 4, the illumination device  3  is basically configured with an LED light source  31  packaged with a red (R) LED  311 , a green (G) LED  312 , and a blue (B) LED  313 , and a light guide  32  made of a material, such as acrylic resin, having excellent light transmission characteristics. Further, reference numeral  321  is a notch portion of the light guide  32 ; and  322 , a position fixer. These elements will be described later in detail. Furthermore, reference numeral  314  denotes a lead for electrically connecting between the LED light source  31  and the sensor substrate  101 . In the LED light source  31 , the wavelength of the R LED  311  at the peak intensity is selected between 600 and 660 nm, that of the G LED  312  is selected between the 510 and 550 nm, and that of the B LED  313  is selected between the 430 to 480, for realizing good color reproduction. 
     The LED light source  31  is arranged so that emitted light enters the light guide  32  from one or both ends of the light guide  32 . The entered light propagates inside of the light guide  32  by being fully reflected at the boundary between the air and the light guide  32 , repeatedly. Further, fine notches (notch portion  321 ) are formed along the length of the light guide  32 , as shown in the detail view of the illumination device  3  in FIG.  4 . When the light incidents on the notch portion  321 , it is reflected at a different angle from when it reflected by other boundaries of the light guide  32 . More specifically, the traveling path of the light is greatly changed toward the original image (to upward in FIG. 4) when the light is reflected by the notch portion  321 , thereby the incidence angle of this reflected light on the boundary between the air and the light guide  32  is less than the critical angle. In this manner, the light can be controlled to exit from the light guide  32  in the desired direction. 
     The notch portion  321  may be made reflective by depositing aluminum or printing silver or white ink, or may be designed to change the light path by only utilizing characteristics of the critical angle. Alternatively, without the notch portion  321 , by simply printing white ink or roughening the surface, corresponding to the notch portion  321 , of the light guide  32 , for instance, similar effect of the notch portion  321  is also achieved. 
     In order to make the intensity of light illuminating the original image uniform, the width of notch is widened or width of the printed area, when printing white ink, is gradually widened in proportion to the distance from the light source  31 . Further, by covering a portion other than a portion where light should exit from the light guide  32 , with a white member having good reflectance of light, for instance, loss of light upon propagating along the light guide  32  is reduced, thereby increasing the illuminance of the original image. 
     The lens array  2  is configured with a plurality of rod lens elements  201  (FIG.  5 ), precisely arranged in line, each of which functions as a lens by graduating index of refraction from the peripheral portion toward the central portion of the lens element manufactured by ion exchange. 
     The imaging area of the lens array  2  is shown in FIG.  5 . The imaging area of one of the lens elements  201 , forming the lens array  2 , when light reflected by the original image incidents on the sensor ICs  102  is shown by a circle of radius X 0 . Since imaging areas of the lens elements  201  overlay from each other, an overall imaging area  202  of the lens array  2  has a band shape having a width X (=2×X 0 ) on a plane. 
     Further, on the sensor array  1 , the plurality of line-shaped sensor ICs  102  having a plurality of photoelectric converters are adhered in line, so as to stretch for a predetermined length, on the sensor substrate  101  made of, e.g., epoxy glass, by an adhesive. The sensor ICs  102  and the sensor substrate  101  are connected via the gold wires  103  so as to provide power and electric signals for operating the sensor ICs  102  from the sensor substrate  101  to the sensor ICs  102 , and to transfer output signals from the sensor ICs  102  to the sensor substrate  101  for providing the output to a system which processes the output signals. On the surfaces of the electrical connection portions  104  where the sensor substrate  101  is connected to the gold wires  103 , metal film of gold or silver, for instance, which have good connectivity with gold is formed by electroplating. 
     Note, in the conventional image sensor, the electrical connection portions  104  are arranged within the imaging area  202  of the lens array  2 . Since reflectance of the surface of the electrical connection portions  104  is much higher than other portions of the sensor substrate  101 , due to lustrous characteristics of metal forming the electrical connection portions  104 , when light propagated via the lens array  2  incidents on the electrical connection portions  104 , most of the incident light is reflected. A part of this reflected light is further reflected by the internal surface of the frame  5  or the surface of the lens array  2 , and this reflected light becomes stray light, which would incident on photo-sensing portions of the sensor ICs  102  as noise light. This deteriorates the S/N ratio of the sensor ICs  102 . 
     In the first embodiment, the electrical connection portions  104  of high reflectance are provided outside of the imaging area  202  of the lens array  2  on the sensor substrate  101 , thereby preventing light propagated through the lens array  2  from incidenting on the electrical connection portions  104 . Accordingly, no stray light, i.e., light reflected by the electrical connection portions  104 , incidents on the photo-sensing portions of the sensor ICs  102 , thereby improving the S/N ratio of the sensor ICs  102 . 
     Note, the electrical connection portions  104  are where the gold wires  103  are connected on the sensor substrate  101 , and how the gold wires  103  are connected to the sensor substrate  101  is not limited to above. Further, medium for electrically connecting between the sensor ICs  102  and the electrical connection portions  104  is not limited to the gold wires  103 , and aluminum wires or wires made of other conductive material may be used. 
     FIGS. 6 and 7 are cross-sectional schematic representations showing examples of arrangements of the sensor ICs  102  according to the first embodiment of the present invention. In FIGS. 6 and 7, TC is a length between the conjugate planes. In this case, the lens array  2  of the image sensor is set at a position where the photo-sensing surfaces of the ICs  102  and the original image are on the conjugate planes of the lens array  2 . In other words, the length TC is the distance between the photo-sensing surfaces of the ICs  102  and the original image. In FIG. 6, each photo-sensing surface is provided at approximately the center of each of the sensor ICs  102 , and the width of the sensor IC  102  is narrower than the width X of the imaging area of the lens array  2 . Further, in FIG. 7, the sensor IC  102  is arranged so that an edge portion of the sensor IC  102  is placed near the central axis of the lens array  2 , and the width of the sensor ICs  102  is narrower than the radius X 0  of the imaging areas of the lens elements  201  forming the lens array  2 . In either case, the electrical connection portions  104  are provided outside of the imaging area (width X) of the lens array  2 . 
     Note, all the electrical connection portions  104  are not necessarily provided outside of the imaging area of the lens array  2 , and by providing a part of the electrical connection portions  104 , at least, outside of the imaging area, less stray light is produced, compared to the conventional arrangement, thus effective. 
     A method for manufacturing the image sensor according to the first embodiment is briefly explained with reference to FIGS. 1 and 3. 
     First, the illumination device  3  and the lens array  2  are inserted into predetermined grooves formed on the frame  5 , thereby the positions of these elements are determined both in the lengthwise direction and in the widthwise direction. Next, the position fixer  322  of the illumination device  3  is pressed against the top surface of the lens array  2  by the cover glass  4 . Under this state, the cover glass  4  is adhered to two flat portions of the frame  5 , which are approximately on the same plane of the upper surface of the lens array  2 , and the illumination device  3  and the lens array  2  are arranged between the two flat portions. Accordingly, it is possible to precisely place and fix the illumination device  3  and the lens array  2  in position. Therefore, it is possible for the illumination device  3  to correctly emit light toward a desired direction, thus, reflected light is properly focused by the lens array  2  throughout its length. 
     Then, the sensor array  1  on which the electrical connection portions  104  for connecting between the sensor substrate  101  and the sensor ICs  102  are provided, on the sensor substrate  101 , outside of the imaging area of the lens array  2  is fit into the frame  5 , and the sensor array  1  is adhered to the frame  5  by an adhesive or fixed to the frame  5  by caulking a part of the frame  5 . Then, the lead  314  of the illumination device  3  is electrically connected to the sensor substrate  101  with, e.g., solder, and the image sensor according to the first embodiment is completed. 
     Modification of the First Embodiment 
     Next, a modification of the first embodiment is explained. 
     FIG. 8 is a cross-sectional view of an image sensor according to the modification of the first embodiment. The image sensor is characterized in that an imaging area of the lens array  2  is narrowed by aperture stop  6  of, e.g., slits, provided between the lens array  2  and the sensor ICs  102 . 
     By narrowing the imaging area of the lens array  2 , it is possible to form the electrical connection portions  104 , outside of the imaging area, at positions closer to the sensor ICs  102  compared to the configuration of the first embodiment. As a result, it is possible to increase the packaging density on the sensor substrate  101 , therefore, it is possible to reduce the size of the sensor substrate  101 . Accordingly, it is possible to downsize the image sensor as well as an image processing apparatus using this type of image sensor. 
     Further, by reducing the diameter of each lens element configuring the lens array  2 , it is also possible to reduce the imaging area of the lens array  2 , which can achieve the same effect as described above. 
     Second Embodiment 
     Next, an example when the image sensor of the present invention is applied to an image processing apparatus is explained with reference to figures. 
     For example, a facsimile apparatus may be configured using an image sensor of the present invention. FIG. 9 is a cross-sectional view of a facsimile apparatus according to the second embodiment of the present invention. In FIG. 9, reference numeral  701  denotes a feeding roller for feeding an original image  10  to a reading position;  702 , a separation claw for separating pages of the original image  10  to be fed one by one; and  703 , a conveyance roller, provided at the reading position of a photoelectric conversion unit  700 , for conveying the original image  10  pass the reading position. 
     Here, the photoelectric conversion unit  700  comprises the image sensor of the present invention and configures an image reading unit which generates image data by illuminating the original image  10  and receiving the reflected light. 
     Further, reference character W denotes a print medium in a form of a rolled paper on which images are printed on the basis of image information read by the photoelectric conversion unit  700  or image information received from outside, in a case of a facsimile apparatus, for instance. Further, reference numeral  704  denotes a printhead for printing an image, and a thermal head and a bubble-jet printhead, for instance, may be used as the printhead  704 . The printhead  704  may be of a serial type or a line type. 
     Reference numeral  705  denotes a platen roller for conveying the print medium W to the print position of the printhead  704  thereby controlling the print position of the print medium W;  706 , an operation panel, including a display unit, where an operation instruction, for example, is inputted;  707 , a system control board on which a control unit for controlling respective units and elements of the facsimile apparatus, an operation circuit for operating the photoelectric conversion unit  700 , a processing unit for processing image information, a transmission/reception unit, and so on, are provided; and  708 , a power supply for the apparatus. 
     Note, in addition to the facsimile apparatus, it is also possible to apply the image sensor of the present invention to an information processing apparatuses, such as an image scanner, which do not have a printhead for forming an image and transmit read image information to a computer or on a network. 
     Further, in the second embodiment, a case where reading operation is performed while moving the original image  10 , however, the present invention is not limited to this, and reading operation may be performed by moving the photoelectric conversion unit  700  while fixing the position of the original image  10 , for example. In other words, relative position between the original image  10  and the photoelectric conversion unit  700 , including the image sensor is to be moved while performing reading operation. 
     According to the second embodiment as described above, by using an image sensor, whose S/N ratio is improved, to input an image to an image processing apparatus, it is possible to provide an image processing apparatus capable of performing high quality reading of an image. 
     The present invention is not limited to the above embodiments and various changes and modifications can be made within the spirit and scope of the present invention. Therefore to apprise the public of the scope of the present invention, the following claims are made.