JP2006180296A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus for using a light emitting diode as a lighting light source, and using a lens for forming an image of an original to a sensor, that can prevent a deficient luminous quantity in the case of copying a thick book the shelfback of which is not in close contact with contact glass by means of a simple and inexpensive configuration. <P>SOLUTION: In the image reading apparatus comprising a light source for lighting the original placed on an original platen and an optical system having at least a lens for forming an image of the lighted original to a read element using a line sensor, the light source is configured by arranging a plurality of the light emitting diodes in parallel with a main scanning direction being the read direction of the line sensor and the light emitting diode whose maximum rated current is greater than those of the other light emitting diodes is arranged in the vicinity of the middle of a light emitting diode array. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading apparatus in a copying machine, a facsimile, or the like, and in particular, configured to form a light source for irradiating a document and to form an image of a document irradiated by the light source on a line sensor using a CCD or the like by a lens and read the document. The present invention relates to an image reading apparatus.

  A reading device for reading a document in a copying machine, a facsimile, or the like is provided under a contact glass 50 on which a document to be copied or transmitted is placed, as shown in FIG. 8 as an example of the configuration of a conventional image reading device. A first scanning frame 54 configured to be movable by providing a rod-shaped light source 51 such as a halogen lamp or a xenon lamp for illuminating a document, a reflective shade 52 for increasing illumination efficiency, and a reflective mirror 53; The original image, which is provided with the reflection mirrors 55 and 56 and is sent through the reflection mirror 53, is formed on the line sensor 59 using a CCD or the like by the lens 58, and the optical path length from the original to the lens 58 is increased. In order to make it constant, the second scanning frame 57 moves in the same direction at half the speed of the first scanning frame 54.

  A line sensor 59 using a CCD or the like is configured by arranging a plurality of CCDs in one direction (hereinafter, this arrangement direction is referred to as a main scanning direction), and an original placed on the contact glass 50 is read according to a reading instruction. When the light source 51 is turned on, the reflecting mirror 53 and the second scanning frame mounted on the first scanning frame body 54 travel from the end of the document to the opposite end (hereinafter referred to as the traveling direction). The read image is formed on the line sensor 59 by the lens 58 through the reflection mirrors 55 and 56 on the body 57.

  In such a copying machine or facsimile, there are cases where a thick book 70 is copied or transmitted as shown in FIG. 9A. When placed on the contact glass 50, the spine portion 71 floats and does not adhere to the contact glass 50, and the center floats as shown in FIG. 9B showing the result of copying or transmission. As indicated by reference numeral 72, there arises a problem that the image becomes a dark image (fogging image) due to insufficient light quantity.

  In order to cope with these problems, for example, Patent Document 1 discloses that a light source for illuminating a document is the main reading direction of a line sensor, instead of a rod-shaped light source 51 such as a halogen lamp or a xenon lamp conventionally used. When the center of a thick book is formed with a plurality of point light sources arranged in parallel to the scanning direction and the fogging image becomes insufficient due to insufficient light, the center of the thick book is scanned during the scanning in the sub-scanning direction. An image reading apparatus is disclosed in which the amount of light is increased to deal with the situation.

JP 2002-314760 A

  However, in general, LEDs are often lit at about half to 70% of the rated current in consideration of breakage and life, and correspond to the central part of a thick book as shown in Patent Document 1. The method of increasing the current value than usual to increase the amount of light in the part may cause deterioration due to use near the limit of the light emitting capacity of the LED, or depending on the configuration of the reading system, for example, the maximum rated current In some cases, the amount of light may be insufficient even if the light is supplied.

  Therefore, in preparation for the case where a large amount of light is required, the LED is driven at a current of 20 to 30% of the maximum rating using an LED with a large rated current, and when scanning a thick book as described above, a portion corresponding to the center portion There is a method of increasing the amount of light during scanning, but it goes without saying that using an LED with a large rated current increases the cost and efficiency.

  Therefore, in the present invention, in an image reading apparatus using a light emitting diode as an illumination light source and using a lens to form an original image on a sensor, a thick book in which the spine portion does not adhere to the contact glass is copied. It is a problem to prevent a shortage of light quantity with a simple and inexpensive configuration.

In order to solve the above problems, an image reading apparatus according to the present invention provides:
In an image reading apparatus comprising: a light source that illuminates a document placed on a document table; and an optical system having at least a lens that forms an image of the illuminated document image on a reading element using a line sensor.
The light source is configured by arranging a plurality of light emitting diodes in parallel to the main scanning direction which is the reading direction of the line sensor, and the maximum rated current is larger than the other light emitting diodes in the vicinity of the central portion of the light emitting diode row. A light emitting diode is provided.

  In this way, a light emitting diode is used as a light source, and a light emitting diode having a maximum rated current larger than that of other light emitting diodes is disposed near the center of the light emitting diode row, thereby supporting a back cover when copying a thick book. Insufficient light intensity in the part can be prevented by increasing the light emission intensity of the light emitting diode with a large maximum rated current, and even if the insufficient light intensity is compensated, the maximum rated current of the light emitting diode is large, so that it deteriorates like a conventional device. It is possible to provide an image reading apparatus that compensates for the shortage of light with a simple and inexpensive configuration.

  The light emitting diodes arranged in the vicinity of the central portion of the light emitting diode row usually emit light with the same light amount as other light emitting diodes by increasing the light emission intensity in the book manuscript reading mode, and the light amount only when necessary. Can be used efficiently.

  In addition, by providing a mark for matching the central portion of the book document at a position corresponding to the center of the light emitting diode arrangement direction on the document table of the image reading apparatus, it is possible to ensure that the back cover portion of a thick book has insufficient light quantity. Can be supplemented.

  Furthermore, the current value for increasing the light emission intensity in the light emitting diode having the maximum rated current larger than that of the other light emitting diodes is set to a value intermediate between the rated current values in the light emitting diodes having a large light emission intensity and other light emitting diodes. Therefore, it is possible to avoid the use of the light emitting diode to the maximum rating, and to extend the life.

  As described above, according to the present invention, in an image reading apparatus using a light emitting diode as an illumination light source and using a lens to form an original image on a sensor, the spine portion is thick enough not to be in close contact with the contact glass. It is possible to provide an image reading apparatus that prevents a shortage of light when copying a book with a simple and inexpensive configuration.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is a perspective view of a light source in an image reading apparatus according to the present invention for reading a thick book, FIG. 2 is a partially omitted perspective view schematically showing a configuration example of the image reading apparatus according to the present invention, and FIG. FIG. 4 is a flowchart showing the arrangement of light emitting diodes that increase the amount of light emitted when reading a book, FIG. 4 is a flow diagram when reading a thick book, and FIG. 5 is an equivalent diagram of light emitting diodes of the light source in the image reading apparatus according to the present invention. FIG. 6 is a graph showing the relationship between the distance from the light emitting diode and the illuminance, and FIG. 7 is a contact glass that constitutes the document table and the light emission intensity when reading a book document. It is a graph showing the illumination intensity in a surface.

  The image reading apparatus according to the present invention is shown in the perspective view of the light source 30 in FIG. 1, and the configuration example of the image reading apparatus having the light source 30 is partially omitted in FIG. As in the conventional image reading apparatus shown in FIG. 1, a light emitting diode is mounted on a moving first scanning frame 11 under a contact glass (not shown) on a document table on which a document for reading an image is placed. And a reflection mirror unit 20 fixed to a second scanning frame (not shown) that moves in the same direction at half the speed of the first scanning frame 11.

  Among these, the light source unit 12 fixed to the first scanning frame 11 includes first and second light emitting diodes arranged on wiring terminals on both sides of a window 17 extending in the central main scanning direction. The light emitting diode mounting plate 31 (first light emitting diode mounting plate) and 32 (second light emitting diode mounting plate) are provided so that the position can be adjusted as a whole. A first reflecting mirror (not shown) (corresponding to the reflecting mirror 54 in FIG. 8) is provided below the window 17 of the light source unit 12.

  Further, in the reflection mirror unit 20 fixed to the second scanning frame body in FIG. 2, an image of a document sent from a reflection mirror (not shown) provided in the first scanning frame body 11 is shown in FIG. Are provided with a second reflecting mirror 21 and a third reflecting mirror 22, and the first scanning frame 11 is provided with a constant optical path length from the document to the lens 24 as described above. Sub-scanning is performed by moving in the same direction at half the moving speed.

In the image reading apparatus of the present invention configured as described above, the maximum rated currents of some of the light emitting diodes indicated by 34 in FIG. 1 are larger than the maximum rated currents of the other most of the light emitting diodes 33 ₁ and 33 ₂ . In this case, a larger current is passed through the light emitting diode indicated by 34 than the light emitting diodes 33 ₁ and 33 ₂ to increase the light emission intensity.

  The portion where the light emitting diode 34 having a maximum rated current larger than that of the other light emitting diodes is arranged in the vicinity of the center portion of the arranged light emitting diodes, that is, the scanning direction of the line sensor (not shown). The position of the book original 40 placed on the contact glass 41 is in the vicinity of the central portion in the main scanning direction, and the center mark 23 attached to the end on the contact glass 41 corresponding to the optical axis in the lens 24 shown in FIG. The spine cover 42 is placed so that the back cover 42 comes to be an area of the light emitting diode 34 having a large maximum rated current.

  FIG. 6 is a graph showing the relationship between the distance from the contact glass surface and the illuminance. For example, the light emitting diode is driven at a current of 5 A (mA) at a distance of 5 mm from the contact glass surface as compared with the case of a distance of 0 mm. In this case, the illuminance is changed from 68000 to 27000 (lx), when driven at a current of 2 A (mA), from 40000 to 16000 (lx), and when the current is 0.67 A (mA), from 17000 to 6000 (lx). , Each is about 60% lower. Therefore, for example, when the light emitting diode is driven with a current of 0.67 A and the distance from the contact glass surface is 5 mm, it is necessary to drive the light emitting diode with a current of 2 A.

Accordingly, when the spine portion 71 of the thick book 70 as shown in FIG. 9A is lifted from the contact glass 50 by about 5 mm, the amount of light is reduced by 60%. In the present invention, this reduced amount of light is reduced. As described above, the maximum rated current of the central portion of the light emitting diode indicated by 34 arranged in the light source unit 12 of the light source 30 shown in FIG. It is set to be larger than the maximum rated current in 33 ₁ and 33 ₂ .

In this image reading apparatus, for example, if the light emitting diodes indicated by 33 ₁ and 33 ₂ are LED-A, and the light emitting diode having a large maximum rated current indicated by 34 is LED-B, a character original (character mode) other than a book original is used. In the case of a normal document whose entire surface can be in close contact with the contact glass surface, both LED-A and LED-B emit light with a current of 0.67 A as an example.

  The illuminance on the contact glass surface in this case is shown in the graph of FIG. 5, where the horizontal axis represents the distance from the center of the lens 24 (corresponding to “image height” in the table of FIG. 2), and the vertical axis Represents the illuminance, and since the light emitting diodes 33 and 34 are driven with the same current value, the light emission intensity is almost the same, and the illuminance on the contact glass surface is constant at about 28000 (lx).

  On the other hand, in the mode of reading a book document, LED-A is 0.67 A, and the same current value as normal is supplied, and LED-B is supplied with a current larger than 1.0 to 1.3 A. . FIG. 7 shows the illuminance on the contact glass surface in that case, and the illuminance at the center portion is increased by increasing the emission intensity by passing a large current through LED-B as shown in FIG. As described above, even if the spine portion 42 of the thick book 40 floats off the contact glass 41, the insufficient illuminance is compensated.

  For instructions on the mode for reading a book document, an instruction button such as “book mode” is provided on a control console such as a copying machine or a facsimile provided with an image reading device, and the illuminance at the portion of the back cover 42 is measured at the time of reading. However, an optimum light amount may be obtained in correspondence with the insufficient light amount. FIG. 4 shows this control flow. Next, an image reading operation in the “book mode” will be described with reference to FIG.

  In step S1 in FIG. 4, when a power source of a copying machine or a facsimile provided with an image reading device is turned on, for example, a button indicating “book mode” on the control console is turned on, first, in step S2 itself. Known shading correction (processing for determining a reference white level before reading a document) is performed, and image reading is prepared in the next step S3. When an image reading, that is, a copy or fax transmission start button is pressed in step S4, it is determined whether or not a book mode is selected in step S5. Note that operations from S1 to S4 are common to the character mode using a normal document and the book mode.

  If the book mode is not selected at this time, the process goes to step S6, and all LEDs including LED-B are driven at a normal current value of, for example, a current value of 0.67A. As shown in FIG. The illuminance on the surface becomes uniform and normal reading is started.

  On the other hand, when the book mode is selected, the first scanning frame 11 provided with the light source 30 shown in FIG. 1 moves to the reading tip of the book document, and the LED is illuminated with a normal light amount before reading. Turns on and confirms the output of the line sensor using a CCD or the like (not shown).

  The confirmation is first performed in step S8. If the line sensor output of a CCD or the like (not shown) at the position corresponding to the light emitting diode indicated by 34 in FIG. 1 is smaller than, for example, 200/255, the process proceeds to the next step S10. If it is larger, the process proceeds to step S9. When the process proceeds to step S9, the current value of LED-B is set to 1.0 A, and reading is started in a state where the amount of light is increased as compared with the normal case.

  If it is selected in step S8 to proceed to step S10, it is further determined in step S10 whether the output of a line sensor such as a CCD is 150/255 or less. If smaller, the process proceeds to next step S12. Advances to step S11. When the process proceeds to step S11, the current value of LED-B is set to 2.0A, the light amount is further increased than in the case of step S9, and reading is started.

  If it is selected in step S10 to proceed to step S12, the current value of LED-B is set to 5.0 A, and the amount of light is further increased than in step S11, and reading is started.

  By doing so, the maximum rated current is the same for all LEDs as in the above-mentioned Patent Document 1, and the LED is always lit at a current value of about 50 to 70% of the maximum rating, and only for a book document. A method of increasing the amount of light at a position corresponding to the spine 42 in the scanning direction, or conversely, using a LED with a large maximum rated current, it is usually driven at a current of 20 to 30% of the maximum rated current and reading a book document. In the case of increasing the amount of light by increasing the current value of the LED only in the case of the above, deterioration is accelerated because it is used near the limit of the light emitting capacity of the LED as described above, or it may be maximum depending on the configuration of the reading system. Even if the rated current is supplied and the light is emitted, the amount of light may be insufficient. Further, when an LED having a large maximum rated current is used, the cost is increased. Without these problems occur, it is possible to provide an image reading apparatus which compensates for the insufficient quantity of light in a simple and inexpensive construction.

  Although the current values of the light emitting diodes have been variously increased in the above description, these are all examples, and it is obvious that the present invention is not limited to these numerical values.

  As described above, according to the present invention, a light emitting diode is used as a light source, and a light emitting diode having a maximum rated current larger than that of other light emitting diodes is disposed near the center of the light emitting diode array. Insufficient light intensity in the part corresponding to the back cover when copying a book can be prevented by increasing the light emission intensity of the light emitting diode with a large maximum rated current, and even if the insufficient light intensity is compensated, the maximum rating of the light emitting diode It is possible to provide an image reading apparatus that compensates for a shortage of light with a simple and inexpensive configuration without causing deterioration or shortage of light as in the conventional apparatus because of a large current.

  The light emitting diodes arranged in the vicinity of the central portion of the light emitting diode row usually emit light with the same light amount as other light emitting diodes by increasing the light emission intensity in the book manuscript reading mode, and the light amount only when necessary. Can be used efficiently.

  Further, by providing a mark for matching the central portion of the book document at a position corresponding to the center of the light emitting diode arrangement direction on the document table of the image reading apparatus, it is possible to reliably compensate for the insufficient light amount of the spine portion of the thick book. be able to.

  Advantageous Effects of Invention According to the present invention, it is possible to provide an image reading apparatus that can prevent a shortage of light when copying a thick book whose back cover portion is not in close contact with the contact glass with a simple and inexpensive configuration. Is what it brings.

It is a perspective view of the light source in the image reading apparatus which becomes this invention for reading a thick book. 1 is a partially omitted perspective view schematically showing a configuration example of an image reading apparatus according to the present invention. It is the figure which showed arrangement | positioning of the light emitting diode which increases emitted light quantity when reading a thick book. It is a flowchart when reading a thick book. It is a graph showing the illuminance when the light emitting diode of the light source in the image reading apparatus according to the present invention emits light with an equal amount of light. It is the graph showing the relationship between the distance from a light emitting diode, and illumination intensity. 5 is a graph showing the light emission intensity when reading a book document and the illuminance on the contact glass surface constituting the document table. It is a figure showing an example of composition in a conventional image reading device. (A) is explanatory drawing when a thick book is copied or transmitted, (B) is the figure which showed the copy result or transmission result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 Light source unit 17 Window 30 Light source 31 1st light emitting diode mounting board 32 2nd light emitting diode mounting board 33 ₁ , 33 ₂ Light emitting diode 34 of normal maximum rated current 34 Light emitting diode with large maximum rated current

Claims (4)

In an image reading apparatus comprising: a light source that illuminates a document placed on a document table; and an optical system having at least a lens that forms an image of the illuminated document image on a reading element using a line sensor.
The light source is configured by arranging a plurality of light emitting diodes in parallel to the main scanning direction which is the reading direction of the line sensor, and the maximum rated current is larger than the other light emitting diodes in the vicinity of the central portion of the light emitting diode row. An image reading apparatus comprising a light emitting diode.   The image reading apparatus according to claim 1, wherein the light emitting diodes arranged in the vicinity of the center of the light emitting diode row increase the light emission intensity in the book document reading mode.   3. The image reading apparatus according to claim 1, wherein a mark for matching a central portion of the book original is provided at a position corresponding to the center of the light emitting diode arrangement direction on the original table of the image reading apparatus. .   The current value for increasing the light emission intensity in the light emitting diode having the maximum rated current larger than that of the other light emitting diodes is an intermediate value between the rated current values of the light emitting diodes having a large light emission intensity and other light emitting diodes. The image reading apparatus according to claim 2 or 3.

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