JP2014022793A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader which deals with reduction in amount of light by a simple constitution with respect to variation in the state of light distribution by illumination means.SOLUTION: The image reader comprises: illumination means 21 for guiding light radiated from at least one light-emitting diode 22, to a document surface via a light guide 23; imaging means 29 for reading reflected light from the document surface by forming an image of the reflected light with reflectors 25, 26, 27 and image forming means 28; document transportation means 40 for transporting documents one by one to the standstill position of the illumination means 21; angle change means for adjusting a reading eye line by changing the installation angle of the reflector 25; and a reference pattern 36 for reflecting the light having been emitted from the illumination means 21 and measuring the intensity of the light with the imaging means 29. While the illumination means 21 and the reflector 25 are standstill, the light reflected by the reference pattern 36 at a predetermined position for reading a transported document image is measured by the imaging means 29 and the installation angle of the reflector 25 is changed on the basis of the intensity of the light.

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus that optically reads a document image.

  In general, in an image reading apparatus that optically reads a document image, a platen method that reads an image of a document placed on a platen glass by an optical system that moves in one direction (sub-scanning direction), and a stationary The reading position of the optical system is roughly classified into a sheet-through method in which a document is read while being conveyed in one direction (sub-scanning direction).

  Further, when an LED (light emitting diode) is used as the light source of the reading optical system, the light distribution vertex in the sub-scanning direction of the illumination light has a sharp light distribution characteristic as compared with a case where a lamp such as a fluorescent lamp is used as the light source. It will be. Therefore, when the LED is used as a light source, the amount of light decreases greatly only a little in the sub-scanning direction from the light distribution vertex position.

  Further, in an illumination system using a high-brightness LED using a light guide, not only the light amount of the LED itself is reduced due to heat generation of the LED itself, but also the light guide is deformed, and the light distribution state changes, thereby reading position. The light intensity at is reduced. In such a case, on which side of the reading line in the sub-scanning direction the maximum amount of light is located varies depending on the deformation of the light guide and the variation in the relative position of the LED with respect to the light guide. Due to the change in the amount of light at the reading position, when reading a large number of images in succession, there is a problem that a uniform image density cannot be obtained in the read images of the few, tens and hundreds. Yes.

  By the way, when the current supplied to the LED is increased with respect to the decrease in the amount of light at the reading position, the LED generates more heat, which causes further deformation of the light guide and the like. Therefore, it is necessary to make the light quantity at the reading position constant by a method that does not contribute to the heat generation of the LED. Patent Document 1 describes an image forming apparatus in which a reference density patch is read and a lamp voltage is controlled to adjust to an appropriate light amount. However, when this technique is used in an image reading apparatus using LEDs as light sources, problems due to the heat generation occur.

Japanese Patent Laid-Open No. 07-281514

  An object of the present invention is to provide an image reading apparatus that can cope with a decrease in light amount with a simple configuration against fluctuations in the light distribution state of an illumination means.

An image reading apparatus according to a first aspect of the present invention is:
Illuminating means comprising at least one light emitting diode and a light guide that guides light emitted from the light emitting diode to the document surface;
Imaging means for reading reflected light from the document surface;
An imaging means for imaging the reflected light from the document surface on the imaging means;
A reflecting mirror for guiding reflected light from the document surface to the imaging means;
Document conveying means for conveying documents one by one to a stationary position of the illumination means;
Angle changing means for adjusting the reading line of view by changing the installation angle of the reflecting mirror;
A reference pattern for reflecting the light emitted from the illuminating means and measuring the intensity by the imaging means;
With
When the illumination unit and the reflecting mirror are in a stationary state, an image of a document conveyed by the document conveying unit is read at a predetermined reading position,
Changing the installation angle of the reflecting mirror by the angle changing means based on the light intensity measured by the imaging means for the light reflected by the reference pattern;
It is characterized by.

The image reading apparatus according to the second aspect of the present invention is:
Illuminating means comprising at least one light emitting diode and a light guide that guides light emitted from the light emitting diode to the document surface;
Imaging means for reading reflected light from the document surface;
An imaging means for imaging the reflected light from the document surface on the imaging means;
A reflecting mirror for guiding reflected light from the document surface to the imaging means;
A slider capable of moving in one direction while holding the illumination means and the reflecting mirror;
A document placement glass disposed immediately above the movement locus of the slider;
Angle changing means for adjusting the reading line of view by changing the installation angle of the reflecting mirror;
A reference pattern for reflecting the light emitted from the illuminating means and measuring the intensity by the imaging means;
With
Reading the image of the document placed on the document placement glass by moving the slider in one direction,
Changing the installation angle of the first reflecting mirror by the angle changing means based on the light intensity measured by the imaging means for the light reflected by the reference pattern;
It is characterized by.

An image reading apparatus according to a third aspect of the present invention is:
Illuminating means comprising at least one light emitting diode and a light guide that guides light emitted from the light emitting diode to the document surface;
Imaging means for reading reflected light from the document surface;
An imaging means for imaging the reflected light from the document surface on the imaging means;
A first reflecting mirror, a second reflecting mirror and a third reflecting mirror for guiding reflected light from the document surface to the imaging means;
A first slider capable of moving in one direction while holding the illumination means and the first reflecting mirror;
A second slider holding the second reflecting mirror and the third reflecting mirror and movable in the same direction as the first slider;
A document placing glass disposed immediately above the movement locus of the first slider and the second slider;
Document conveying means for conveying documents one by one to the stationary positions of the first slider and the second slider;
Angle changing means for adjusting the reading line of view by changing the installation angle of the first reflecting mirror;
A first reference pattern and a second reference pattern for reflecting the light emitted from the illuminating means and measuring the intensity by the imaging means;
With
The first reference pattern is disposed at a reading position of a document conveyed by the document conveying means,
When the first slider and the second slider are in a stationary state, when the image of the document conveyed by the document conveying unit is read at the reading position, the light reflected by the first reference pattern is measured by the imaging unit. Changing the installation angle of the first reflecting mirror by the angle changing means based on the light intensity,
The second reference pattern is arranged on the upstream side in the moving direction of the first slider and the second slider from the reading start position of the document placed on the document placement glass,
When the image of the original placed on the original placement glass is read by moving the first slider and the second slider in one direction, the light reflected by the second reference pattern is measured by the imaging means. Changing the installation angle of the first reflecting mirror by the angle changing means based on the light intensity
It is characterized by.

  In the image reading device, by changing the installation angle of the reflecting mirror by the angle changing means based on the light intensity measured by the imaging means for the light emitted from the illumination means and reflected by the reference pattern, The reading line is adjusted to the position where the light intensity is the highest. That is, a simple mechanism of changing the angle of the reflecting mirror can cope with a decrease in the amount of light caused by a change in the light distribution state of the illumination means.

  ADVANTAGE OF THE INVENTION According to this invention, it can respond to a light quantity fall with a simple structure with respect to the fluctuation | variation of the light distribution state of an illumination means.

It is a schematic block diagram which shows the image reading apparatus which is one Example. It is explanatory drawing which shows the illumination light distribution state of the said image reading apparatus, and the angle change of a mirror. It is explanatory drawing which shows the holding state in the both ends of the said mirror. It is explanatory drawing which shows the 1st example of an angle change means. It is a perspective view which shows the principal part of the said 1st example. It is explanatory drawing which shows the 2nd example of an angle change means. It is explanatory drawing which shows the 3rd example of an angle change means. It is a perspective view which shows the principal part of the said 3rd example. It is a flowchart figure which shows the main routine of the control procedure of the said image reading apparatus. It is a flowchart figure which shows the subroutine of adjustment operation | movement.

  Embodiments of an image reading apparatus according to the present invention will be described below with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the same member and part in each figure, and the overlapping description is abbreviate | omitted.

  First, a schematic configuration of an image reading apparatus 10 according to an embodiment will be described with reference to FIG. The reading optical system 20 is well known per se, and includes an illuminating means 21 comprising a light guide 23 and an auxiliary mirror 24 provided with high-intensity LEDs 22 (light emitting diodes) at one or both ends, and mirrors 25, 26, 27, an imaging lens 28, and an image sensor 29 (CCD). The illumination means 21 and the mirror 25 are mounted on the first slider 31, and the mirrors 26 and 27 are mounted on the second slider 32. The first and second sliders 31 and 32 can reciprocate in the sub-scanning direction Y. With respect to the document placed on the platen glass 11, the first slider 31 moves at the speed V and the second slider 32 moves at the speed V / 2 in the sub-scanning direction Y, thereby reading the image of the document. A reading start position is indicated by a symbol B. Note that reading of an image by the platen method by the optical system 20 is conventionally known.

  On the other hand, in the case of the sheet-through method, the optical system 20 is performed in a state where it is stationary at the reading position A shown in FIG. Here, the conveyance unit 40 that conveys a document to the reading position A when reading an image by the sheet-through method will be described.

  The document transport unit 40 includes a paper feed tray 41, a pickup roller 42, a paper feed roller 43a and a separating roller 43b, a registration roller pair 44, a transport roller pair 45, a pre-reading roller pair 46, and a discharge roller pair 47. And a discharge tray 48. The original is conveyed by the various rollers from the paper feed tray 41 to the discharge tray 48 via the reading glass 35 (reading position A), and an image is read by the optical system 20 at the reading position A. Conventionally, document conveyance by the document conveyance unit 40 and image reading by the sheet-through method by the optical system 20 are well known.

  Here, FIG. 2A shows a light distribution state of light irradiated to the reading position A from the light guide 23 using the LED 22 as a light source. The light guide 23 extends in a direction orthogonal to the sub-scanning direction Y, and the illumination light from the light guide 23 has a light distribution characteristic that is sharp in the sub-scanning direction Y. In such a light distribution characteristic, due to heat generation of the LED 22 itself or variations in the mounting position of the LED 22 with respect to the light guide 23, the peak portion of the illumination light moves from the original reading position A in the sub-scanning direction Y. There may be a shift to the upstream side or the downstream side, resulting in a decrease in the amount of light on the reading line.

  Therefore, in this embodiment, the first reference pattern 36 and the second reference pattern 37 for reflecting the light emitted from the illuminating means 21 and measuring the intensity thereof with the image sensor 29 and the first slider 31 are mounted. In addition, angle changing means (which will be described in detail below) for changing the installation angle θ of the mirror 25 is provided. The first reference pattern 36 is used at the time of image reading in the sheet-through method, and is arranged immediately above the reading glass 35. The second reference pattern 37 is used at the time of image reading by the platen method, and is arranged on both upper sides in the sub-scanning direction Y with respect to the reading start position B. Further, a white reference plate 38 for performing shading correction or the like is disposed between the reading start position B and the second reference pattern 37.

  As shown in FIG. 2A, the mirror 25 is set to the initial angle θ, and its reading line is directed to the reading position A. At this time, when the vertex of the illumination light is shifted downstream in the sub-scanning direction Y as indicated by the dotted line, the light amount on the reading line (measured light amount at the image sensor 29) is lower than the light amount reduction allowable range. become. In such a case, by changing the mirror 25 to the angle θ1 as shown by the dotted line, the reading line can be directed in the maximum light amount direction, and the light amount can be prevented from being reduced during image reading. Decline can be prevented. Further, when the vertex of the illumination light is shifted in the reverse direction (upstream in the sub-scanning direction Y), the mirror 25 may be changed to the angle θ2, as indicated by a dotted line in FIG.

  Specifically, while the reflected light from the first reference pattern 36 is measured by the imaging device 29, the mirror 25 is rotated in the direction in which the measured light intensity increases, and the rotation is performed in the vicinity where the light intensity reaches the maximum value. Control to stop. In the case of the sheet-through method, this light amount correction control is performed immediately before reading the image of the first document, and thereafter the light amount is passed while the trailing edge of the previous document and the leading edge of the next document pass through the reading position A. Perform correction control. However, the timing at which the light amount correction control is performed is arbitrary. For example, the light quantity correction control may be performed every time the number of read images is counted and the count value reaches a predetermined value.

  Although the case where the light amount correction is performed using the first reference pattern 36 in the sheet-through method has been described above, the same applies to the case where the light amount correction is performed using the second reference pattern 37 in the platen method. In the platen method, when the reading line is shifted from the original reading position A due to the rotation of the mirror 25, it is preferable to shift the reading start position B of the document based on the shift amount. Thus, the original image can be read from the leading edge to the trailing edge without any leakage.

  By the way, the present inventor considered moving the illumination system as a whole or moving the imaging lens and the imaging device in order to adjust the reading line position in accordance with the change in illumination light distribution. However, the movement of the entire illumination system requires a large number of components such as LEDs, light guides, and heat dissipation members to be moved together, which is a large-scale device. In order to move the imaging lens and the imaging element, it is necessary to make the reflecting mirror larger than it is now, and it is difficult to avoid an increase in the size of the apparatus. On the other hand, if the configuration is such that only the angle of the mirror 25 is adjusted as in the present embodiment, it is possible to cope with a decrease in the amount of light with a very simple configuration.

  Next, the holding form of the mirror 25 will be described. The mirror 25 has a long shape parallel to the light guide 23 in a direction orthogonal to the sub-scanning direction Y, and one end portion in the long side direction is formed on the frame 51 as shown in FIG. The projection 52 is supported at one point, and as shown in FIG. 3B, the other end portion in the long side direction is supported at two points by projections 53 and 54 formed on the frame 51. In this embodiment, one of the protrusions 53 and 54 that support the mirror 25 at the other end is attached to the frame 51 so as to be able to advance and retract (see FIGS. 4 and 6). The arrangement angle of the mirror 25 can be changed by moving the projection 54 back and forth.

  Hereinafter, a first example, a second example, and a third example of angle changing means for adjusting the angle of the mirror 25 will be described.

  As shown in FIGS. 4 and 5, the first example of the angle changing means includes actuators 61 and 62 each having a boss portion 55 provided coaxially with a protrusion 54 having a screw formed on the outer peripheral portion as a drive source. It is intended to reverse and reverse. The back surface of the mirror 25 is elastically biased toward the protrusion 54 by a spring 56. Actuators 61 and 62 that operate with a small stroke using a piezoelectric element as a driving source are well known, and the projection 54 is rotated forward or reverse by the frictional force between the actuators 61 and 62 and the outer peripheral surface of the boss portion 55, thereby providing a mirror. Adjust the angle of 25.

  In the second example of the angle changing means, as shown in FIG. 6, an actuator 63 using a piezoelectric element as a drive source is attached to the end of the projection 54, and the projection 54 is directly advanced and retracted by the operation of the actuator 63. is there.

  The third example of the angle changing means is not a three-point support by the projections 52, 53, 54, but the mirror 25 is fixed to a rotatable holder 57 as shown in FIGS. The actuators 61 and 62 are used for rotation. The angle of the mirror 25 is adjusted in synchronization with the rotation of the holder 57.

  Next, an example of a control procedure of the image reading apparatus 10 will be described. As shown in FIG. 9, when the image reading is a sheet-through method (YES in step S1), a normal reading operation is executed (step S2), and the original from which the image is read is not the last page ( If the trailing edge of the original passes through the reading position A (YES in step S4), an adjustment operation of the mirror 25 is executed (step S5). If it is the last page (YES in step S3), the control is terminated after the trailing edge of the document has passed the reading position A (YES in step S6). Note that details of the process (step S7) when the image reading is a platen method (NO in step S1) are omitted.

  The adjustment operation executed in step S5 will be described with reference to FIG. First, it is determined whether there is a difference between the reading light intensity of the first reference pattern 36 and the reading light intensity on the previous page. If there is a difference (YES in step S11), the mirror 25 is reciprocated by a predetermined amount. (Step S12), and the mirror 25 is set to an angle at which the light intensity is maximized (Step S13). If there is no difference (NO in step S11), the adjustment operation is stopped (step S14).

(Other examples)
It should be noted that the image reading apparatus according to the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the gist thereof.

  As described above, the present invention is useful for an image reading apparatus, and is particularly excellent in that it can cope with a decrease in the amount of illumination light with a simple configuration.

DESCRIPTION OF SYMBOLS 10 ... Image reader 11 ... Platen glass 20 ... Reading optical system 21 ... Illumination means 22 ... LED
DESCRIPTION OF SYMBOLS 23 ... Light guide 25 ... Mirror 28 ... Imaging lens 29 ... Imaging device 31, 32 ... Slider 36, 37 ... Reference pattern 51 ... Frame 52, 53, 54 ... Supporting protrusion 61, 62, 63 ... Actuator A ... Reading position Y ... Sub-scanning direction

Claims (10)

Illuminating means comprising at least one light emitting diode and a light guide that guides light emitted from the light emitting diode to the document surface;
Imaging means for reading reflected light from the document surface;
An imaging means for imaging the reflected light from the document surface on the imaging means;
A reflecting mirror for guiding reflected light from the document surface to the imaging means;
Document conveying means for conveying documents one by one to a stationary position of the illumination means;
Angle changing means for adjusting the reading line of view by changing the installation angle of the reflecting mirror;
A reference pattern for reflecting the light emitted from the illuminating means and measuring the intensity by the imaging means;
With
When the illumination unit and the reflecting mirror are in a stationary state, an image of a document conveyed by the document conveying unit is read at a predetermined reading position,
Changing the installation angle of the reflecting mirror by the angle changing means based on the light intensity measured by the imaging means for the light reflected by the reference pattern;
An image reading apparatus.   When the image of the document is read by the document conveying means, the light reflected by the reference pattern is measured by the imaging means while the trailing edge of the previous document and the leading edge of the next document pass through the reading position. The image reading apparatus according to claim 1, wherein the reflecting mirror is rotated in a direction in which the measured light intensity increases, and the rotation is stopped in the vicinity of the light intensity reaching a maximum value. Illuminating means comprising at least one light emitting diode and a light guide that guides light emitted from the light emitting diode to the document surface;
Imaging means for reading reflected light from the document surface;
An imaging means for imaging the reflected light from the document surface on the imaging means;
A reflecting mirror for guiding reflected light from the document surface to the imaging means;
A slider capable of moving in one direction while holding the illumination means and the reflecting mirror;
A document placement glass disposed immediately above the movement locus of the slider;
Angle changing means for adjusting the reading line of view by changing the installation angle of the reflecting mirror;
A reference pattern for reflecting the light emitted from the illuminating means and measuring the intensity by the imaging means;
With
Reading the image of the document placed on the document placement glass by moving the slider in one direction,
Changing the installation angle of the first reflecting mirror by the angle changing means based on the light intensity measured by the imaging means for the light reflected by the reference pattern;
An image reading apparatus.   When reading an image of a document placed on the document placement glass, the light reflected by the reference pattern is measured by the imaging means, and the reflecting mirror is rotated in a direction in which the measured light intensity increases. The image reading apparatus according to claim 3, wherein the rotation is stopped in the vicinity of the light intensity reaching a maximum value.   5. The image according to claim 3, wherein when the reading line is shifted from a predetermined position due to rotation of the reflecting mirror, the reading start position of the document is shifted based on the shift amount. Reader.   The image reading apparatus according to claim 5, wherein the reference pattern is disposed upstream of the reading start position in the moving direction of the slider. The reflecting mirror has a long shape, one end in the long side direction is supported at one point, and the other end is supported at two points.
The angle changing means has a driving means for moving at least one protrusion supporting the other end of the reflecting mirror at two points in the protrusion direction;
The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus. The reflecting mirror has a long shape, one end in the long side direction is supported at one point, and the other end is supported at two points.
At least one protrusion that supports the other end of the first reflecting mirror at two points is screwed to the frame with a screw;
The angle changing means includes a driving means for rotating the protrusion with respect to the frame;
The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus.   9. The image reading apparatus according to claim 7, wherein the driving unit uses a piezoelectric element as a driving source. Illuminating means comprising at least one light emitting diode and a light guide that guides light emitted from the light emitting diode to the document surface;
Imaging means for reading reflected light from the document surface;
An imaging means for imaging the reflected light from the document surface on the imaging means;
A first reflecting mirror, a second reflecting mirror and a third reflecting mirror for guiding reflected light from the document surface to the imaging means;
A first slider capable of moving in one direction while holding the illumination means and the first reflecting mirror;
A second slider holding the second reflecting mirror and the third reflecting mirror and movable in the same direction as the first slider;
A document placing glass disposed immediately above the movement locus of the first slider and the second slider;
Document conveying means for conveying documents one by one to the stationary positions of the first slider and the second slider;
Angle changing means for adjusting the reading line of view by changing the installation angle of the first reflecting mirror;
A first reference pattern and a second reference pattern for reflecting the light emitted from the illuminating means and measuring the intensity by the imaging means;
With
The first reference pattern is disposed at a reading position of a document conveyed by the document conveying means,
When the first slider and the second slider are in a stationary state, when the image of the document conveyed by the document conveying unit is read at the reading position, the light reflected by the first reference pattern is measured by the imaging unit. Changing the installation angle of the first reflecting mirror by the angle changing means based on the light intensity,
The second reference pattern is arranged on the upstream side in the moving direction of the first slider and the second slider from the reading start position of the document placed on the document placement glass,
When the image of the original placed on the original placement glass is read by moving the first slider and the second slider in one direction, the light reflected by the second reference pattern is measured by the imaging means. Changing the installation angle of the first reflecting mirror by the angle changing means based on the light intensity
An image reading apparatus.

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