JP4766688B2 - Image reading device - Google Patents

Description

  The present invention relates to a reading apparatus that reads image information on an image surface of a document with a light source configured by arranging a plurality of LED elements in a line.

  In an image reading apparatus used in an image forming apparatus such as a copying machine or a printer, an illumination apparatus that irradiates an image surface of a document is proposed by using a plurality of LED elements as point light sources arranged in a line. ing.

  Further, an illuminating device using such a plurality of point light sources has been proposed in which the illuminating device is used for detecting the document width size (dimension in the sheet passing width direction) (see, for example, Patent Document 1).

  In this apparatus, after the document pressing member is opened and the document is placed at the reading position of the document placing table, the document pressing member is closed and the document is pressed onto the document placing table. Thereafter, when the image reading start button is pressed, first, a pre-scan for reading the width size of the document is performed. In this prescan, the width size of a document is detected based on the amount of reflected light when the document is illuminated by a light source. After completion of the pre-scan, the image surface of the original is subsequently scanned to read the image information.

In addition, there is a type in which the width size is read by performing pre-scanning in conjunction with the closing operation of the document pressing member after the document is placed at the reading position of the document placing table. This is because, when the document pressing member is closed from the open position toward the closed position, when it is at a predetermined angle (for example, about 20 to 30 degrees) with respect to the document, this is detected by a sensor and pre-scanned. Is something that starts.
Japanese Patent Laid-Open No. 2002-271583

  However, in the above-mentioned Patent Document 1, since the pre-scan for detecting the width size is performed after the reading start button is pressed, the time from the pressing of the reading start button to the end of reading (image reading time) ) Includes a pre-scanning time, and there is a problem that the image reading time is increased accordingly.

  On the other hand, when the document pressing member during the closing operation reaches a predetermined position, the above-described problem, that is, the problem that the image reading time becomes long can be solved. Pre-scanning is performed in an inclined state before closing, so there is a problem that false detection of the document width size, especially false detection of high-concentration document width sizes, and a point light source on the front side There is a problem that light emitted from the light leaks from between the document table and the inclined document pressing member and enters the user's eyes.

  Therefore, the present invention shortens the image reading time, prevents erroneous detection of the document width size, can be detected with high accuracy, and light from a point light source arranged on the near side is applied to the user's eyes. An object of the present invention is to provide an image reading apparatus with less influence on the image reading apparatus.

  The invention according to claim 1 relates to an image reading apparatus that irradiates an image surface of a document and reads image information based on the amount of reflected light from the image surface. The image reading apparatus according to the present invention includes a light-transmitting document placement table on which the document is placed at a reading reference position on the back side, and a front side opened and closed in a substantially vertical direction with respect to the back side. A document pressing member that allows a document to be placed on the placement table and that presses the placed document against the document placement table from above when closed, and is disposed below the document placement table and is located in the frontward direction. And a plurality of point light sources that are arranged in a line to form the light source, and the light source and the document are relatively moved so that the document moves in a direction perpendicular to the alignment direction of the plurality of point light sources. A moving device; and a CCD that reads image information on the image surface based on the amount of reflected light generated from the point light source and reflected on the image surface of the document. Of the document table The width of the document placed in the back position in the depth direction is irradiated with light from the plurality of point light sources before the document pressing member reaches the closed position, and the reflected light is received by the CCD. The control means is configured to detect the amount of irradiation light of the plurality of point light sources at the time of width size detection, and the point arranged on the front side of the point light source arranged on the back side. It is characterized by controlling so that the number of light sources is reduced.

  According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the control unit individually controls the amount of light emitted from the plurality of point light sources at the time of width size detection.

  According to a third aspect of the present invention, in the image reading apparatus according to the first aspect, the control unit divides the plurality of point light sources into two or more groups along the frontward direction, and the amount of irradiation light for each of these groups. It is characterized by setting.

  According to a fourth aspect of the present invention, in the image reading device according to any one of the first to third aspects, when the width size is detected, the light source is moved by the moving means, and the width size is detected in at least two places. It is characterized by that.

  According to a fifth aspect of the present invention, in the image reading device according to any one of the first to fourth aspects, the CCD performs width size detection for each of a plurality of colors of incident light. .

  The invention according to claim 6 is the image reading apparatus according to any one of claims 1 to 5, wherein the point light source is an LED element.

  According to the invention of claim 1, the control means detects the width size of the document by irradiating light from a plurality of point light sources before the document pressing member reaches the closed position and receiving the reflected light by the CCD. To do. Therefore, the document reading time can be shortened compared to Patent Document 1. In addition, since the control means controls the irradiation light quantity of the plurality of point light sources at the time of width size detection so that the point light source arranged on the front side is smaller than the point light source arranged on the back side, Even when the irradiation light from the point light source on the near side enters the user's eyes, it is less dazzling than before. Further, since it is not necessary to reduce the amount of irradiation on the back side where the width size of the document is likely to be erroneously detected, it is possible to prevent a decrease in detection accuracy.

  According to the invention of claim 2, since the control unit individually controls the irradiation light amount of the plurality of point light sources at the time of detecting the width size, the irradiation light amount of the front side point light source is larger than the irradiation light amount of the back side point light source. The irradiation light quantity of each point light source can be arbitrarily set on condition that it decreases. In this case, the back side and the near side refer to a relative positional relationship. Further, in this case, for example, the case where the irradiation light amounts of two adjacent point light sources are the same is not excluded. In other words, the irradiation light amount of the point light source located on the near side should not exceed the irradiation light amount of the point light source located on the far side. However, when the irradiation light amount of the point light source located on the farthest side is A and the irradiation light amount of the point light source located on the front side is B, A> B is satisfied.

  According to the invention of claim 3, the irradiation light amount of the point light source is set for each group on the condition that the irradiation light amount of the point light source of the front side group is smaller than the irradiation light amount of the point light source of the rear group. It can be set arbitrarily. In this case, the back side and the near side refer to a relative positional relationship. Further, in this case, for example, the case where the irradiation light amounts of two adjacent groups of point light sources are the same is not excluded. In other words, the irradiation light amount of the point light source of the group located on the near side is not allowed to exceed the irradiation light amount of the point light source of the group located on the far side. However, it is assumed that C> D is satisfied, where C is the irradiation light amount of the point light source of the group located on the farthest side, and D is the irradiation light amount of the point light source of the group located on the most front side.

  According to the invention of claim 4, the width size of the document can be detected with high accuracy.

  According to the invention of claim 5, for example, it is possible to set a threshold value for each color of R, G, and B. Therefore, due to variations in sensitivity of the CCD and variations in the amount of irradiation light of the point light source, R, G with respect to the CCD. , B can detect the presence or absence of a document at the reading position with high accuracy even when the amount of incident light is poorly balanced.

  In the invention of claim 6, since the LED element is used as the point light source, the amount of irradiation light can be easily changed by changing the value of the current passed through each LED element.

  Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings. In addition, in each drawing, the member etc. which attached | subjected the same code | symbol are the same structures, The duplication description about these shall be abbreviate | omitted suitably. Moreover, in each drawing, members and the like that are not necessary for the description are omitted as appropriate.

<Embodiment 1>
The image reading apparatus 11 according to the present invention will be described with reference to FIGS. 1 and FIG. 2 are views of the longitudinal section of the image reading device 11 as seen from the front side (front side). Further, FIG. 1 shows an optical system, and FIG. 2 shows a drive system. FIG. 3 and 4 are top views for explaining the relationship among the light source 12, the size of the document, and the position of the document at the time of image reading. Further, FIG. FIG. 4 shows a case where the size of the document is an inch size. 1 to 4 show a state where the document pressing plate 60 is removed. In the following description, the left and right in FIGS. 1 to 4 are the left and right of the image reading device 11, the top and the bottom in FIGS. 1 and 2 are the top and bottom of the image reading device 11, and FIGS. The lower and upper parts in the middle will be described as before and after the image reading apparatus 11, respectively. Further, in FIG. 3 and FIG. 4, the vertical dimension of the document is a width size (paper passing width), and the horizontal dimension is a length size (conveyance direction length).

  As shown in FIG. 2, the image reading device 11 includes an illumination device 10, an imaging lens 13, and a CCD (solid-state imaging device) 14. Furthermore, the illumination device 10 includes a light source 12 and a driving device (moving device) 15. The light source 12, the driving device 15, the illumination device 10, the imaging lens 13, and the CCD 14 are all disposed inside a rectangular parallelepiped housing (frame) 16. The housing 16 has an opening 17 on its upper surface, and a transparent (light transmissive) contact glass 18 is disposed in the opening 17.

  As shown in FIGS. 3 and 4, the contact glass 18 is formed in a rectangular shape larger than the document of the maximum size among the sheet-like documents placed on the upper surface thereof. In the contact glass 18, a left indicator plate 20 that is long in the front-rear direction is provided at the left end, and a rear indicator plate 21 and a front indicator plate 22 that are long in the left-right direction are provided at the rear end and the front end, respectively. A position where the rear end of the left indicating plate 20 and the left end of the rear indicating plate 21 intersect is a reading reference position P01. The document placed on the contact glass 18 has a reading position (predetermined position) in which one corner, that is, a corner located at the left end and the rear end (reference corner) is aligned with the reading reference position P01. Placed on. 3 and 4, originals of various sizes in a state where the reference corner is set to the reading reference position P0 are illustrated. Here, the size and orientation of each original are displayed at positions corresponding to the diagonals of the reference corners in the originals of each size. For example, B5 and A4 in FIG. 3 indicate the position of the original when the “long side” of each original is aligned with the left indicating plate 20. Hereinafter, this is referred to as “horizontal placement” of the manuscript. B5R and A4R indicate the position of the original when the “short side” of each original is aligned with the left indicating plate 20. Hereinafter, the “R” attached is referred to as “vertical placement” of the document and is distinguished from “horizontal placement”. According to this, “B4” and “A3” in FIG. 3 should be originally described as “B4R” and “A3R”, but originals of these sizes can be placed horizontally. In other words, only one way of placement is possible and there is no need to distinguish between them.

  The notations such as “B5”, “B5R”, “A4”, “A4R”, “B4”, “A3”, etc. are not actually shown on the contact glass 18 but on the left indicator plate 20 and the rear indicator plate 21. Has been. For example, the positions indicated by reference signs P1, P2, P3, and P4 on the left indicating plate 20 are represented as “B5R”, “A4R”, “B5, B4”, and “A4, A3” in this order. On the other hand, the positions indicated by reference signs P5, P6, P7, and P8 on the rear indicating plate 21 are labeled “B6R, B5”, “A5R, A4”, “B5R”, and “A4R” in this order. Thus, the user can know the size and orientation of the document when the document is placed at a predetermined position on the contact glass 18. Therefore, for example, when an image is formed on a sheet of paper or the like by a copying machine or a printer based on the image reading result of the document, it is a reference when selecting the size and orientation of the sheet used for image formation. It can be. In FIG. 4, the size of the document is displayed in inches. In the contact glass 18 in FIG. 3, the width that is slightly larger than the sheet passing width of “A4, A3” is the maximum image reading width (maximum irradiation width), and “11 × 17” in the contact glass 18 in FIG. 4. The range slightly longer than the length size of “” is the maximum image reading length (maximum irradiation length). The light source 12, which will be described later, can irradiate the entire maximum reading area surrounded by the maximum reading width and the maximum reading length.

  As shown in FIGS. 1 to 4, an illumination optical movement frame unit (first optical system unit) 23 is disposed below the left end side of the contact glass 18. The illumination optical movement frame unit 23 has a movement frame 24 having a length in the front-rear direction longer than the above-described maximum reading width. On the moving frame 24, a light source main substrate (substrate) 25 to which the light source 12 is attached, a concave mirror 26, and a first mirror 27 are mounted. 3 and 4, the light source main board 25 is formed such that the length in the front-rear direction is longer than the maximum reading width, and the light source 12 is attached to the upper surface thereof. ing. In the present embodiment, the light source 12 is configured by arranging a plurality (22 in FIG. 3 and FIG. 4) of LED elements L1 to L22, which are point light sources, in a line shape in the front-rear direction. Here, the line shape is not limited to a case where the lines are aligned on a single straight line, but includes, for example, a case where the lines are aligned in a staggered pattern and are substantially linear. These LED elements L1 to L22 are aligned at a predetermined pitch P (15 mm in the present embodiment) that can irradiate the image surface of the original document evenly along the line direction (front-rear direction). 3 and 4, the distance from the center of the rearmost LED element L1 to the center of the frontmost LED element L22 is set to 315 mm (= 15 mm × 21). These LED element L1 and LED element In the example shown in FIG. 3, the long side (= 297 mm) of the A4 size original having the maximum sheet passing width or the short side (= 297 mm) of the A3 size original is inserted between L22 and FIG. In the example shown in FIG. 5, the long side or the short side is set so that the long side or the short side of the document having an 11-inch (≈279 mm) length is included. As shown in FIG. 1, the light source 12 composed of a plurality of LED elements L <b> 1 to L <b> 22 irradiates the reading line L set on the upper surface of the contact glass 18 from the lower right side. The LED elements L1 to L22 will be described later again.

  As shown in FIG. 1, the concave mirror 26 is disposed at a position that is substantially line-symmetric with the light source 12 with respect to a perpendicular h that is lowered from the reading line L. As described above, since the light source 12 irradiates the document on the contact glass 18 from the lower right side, a shadow is formed at the left end of the document, and this shadow tends to be read as a linear image in the front-rear direction. It is. The concave mirror 26 reflects light from the light source 12 and guides it to the reading line L to remove the shadow. A first mirror 27 is disposed in a portion of the illumination optical movement frame unit 23 located immediately below the reading line L. The first mirror 27 is attached in a state in which 45 degrees on the upper left is turned. As described above, the illumination optical moving frame unit 23 has a guide member (not shown) laid in the left-right direction with the light source 12, the light source main board 25, the concave mirror 26, and the first mirror 27 mounted on the moving frame 24. ) Along the horizontal direction. That is, it is possible to move in a direction orthogonal to the linear (linear) light source 12. The illumination optical moving frame unit 23 emits light from the light source 12 toward the reading line L while moving rightward, and guides reflected light from the image surface of the document to a second mirror 28 described below. It is.

  As shown in FIGS. 1 and 2, below the left end side of the contact glass 18, a reflection optical moving frame unit (second optical system unit) 30 is located to the left of the illumination optical moving frame unit 23. It is arranged. The reflective optical moving frame unit 30 has a moving frame 31 that is longer in the front-rear direction than the above-described maximum reading width. A second mirror 28 is mounted on the moving frame 31 in a state where the lower right angle is 45 degrees, and a third mirror 32 is mounted in an attitude where the upper right angle is 45 degrees. Further, the moving frame 31 rotatably supports the movable pulley 33 at its front end and rear end. As described above, the reflection optical moving frame unit 30 is mounted in the left-right direction along the guide member (not shown) laid in the left-right direction with the second mirror 28, the third mirror 32, and the movable pulley 33 mounted thereon. Can be moved to. The optical movement frame unit 30 for reflection reflects light from the first mirror 27 of the optical movement frame unit 23 for illumination described above by the second mirror 28 and the third mirror 32 while moving to the right. It leads to the imaging lens 13.

  As shown in FIG. 2, fixed left pulleys 34 and 34 are provided at the front and rear ends in the vicinity of the left end of the housing 16, and fixed right pulleys 35 and 35 are provided at the front and rear ends in the vicinity of the right end of the housing 16. Are rotatably arranged. Further, a motor 36 capable of forward and reverse rotation is disposed below the fixed right pulleys 35 and 35 in FIG. Further, a drive pulley 38 that is integral with the drive shaft 37 is disposed on the left side of the motor 36, and a drive belt 41 is stretched between the output shaft 40 of the motor 36 and the drive pulley 38. Yes. Wire drums 42 and 42 are fixed to the front end and the rear end of the drive shaft 37, and optical wires 43 and 43 are wound around the wire drums 42 and 42, respectively. One end portions 44 of the optical wires 43 are fixed to the inner surface of the left side wall 45 of the housing 16. The optical wires 43, 43 extend rightward from here, hang around the right half of the movable pulleys 33, 33 of the reflecting optical moving frame unit 30, are folded back leftward, and left of the fixed left pulleys 34, 34. After being stretched over the half, it is folded rightward and extends toward the fixed right pulleys 35 and 35. Further, it is stretched to the left half of the fixed right pulleys 35 and 35 and extends to the left. After being fixed to the illumination optical movement frame unit 23 in the middle, it further extends to the left and the movable pulleys 33 and 33 It is stretched over the left half, folded back to the right, and locked to a hook 47 protruding on the lens mount 46. When the motor 36 rotates counterclockwise in FIG. 2 based on the routing of the optical wires 43, 43, the wire drums 42, 42 are also anti-clockwise via the drive belt 41, the drive pulley 38, and the drive shaft 37. Rotate clockwise. Along with this, the illumination optical movement frame unit 23 and the reflection optical movement frame unit 30 move to the right by being pulled by the optical wires 43 and 43. At this time, since the movable pulleys 33 and 33 of the reflecting optical moving frame unit 30 act as a so-called moving pulley, the moving distance becomes half of the moving distance of the illumination optical moving frame unit 23. Accordingly, the optical path length from the contact glass 18 to the imaging lens 13 is kept constant regardless of the movement of the illumination optical moving frame unit 23 and the reflecting optical moving frame unit 30, and the imaging lens described below The light passing through 13 forms an image on the CCD 14. In the present embodiment, the entire configuration for moving the light source 12 as described above corresponds to a driving device (moving device).

  As shown in FIG. 2, the imaging lens 13 is fixed on a lens mounting plate 48 fixed to the lens mounting base 46 described above. The light emitted from the light source 12 is reflected by the image surface of the document and follows an optical path K shown in FIG. That is, the reflected light from the image surface is reflected by the first mirror 27, the second mirror 28, and the third mirror 32 and is incident on the imaging lens 13. The incident light is imaged on the CCD 14 described next.

  The CCD 14 is attached to a “U” -shaped CCD adjustment plate 52 that is fixed to the above-described lens mounting base 46 via a CCD mounting plate 51 that is fixed to the left end surface and the upper end portion 50 is bent to the left. ing. Bosses 53 and 53 having internal threads threaded on the inner diameter are fixed to the front end portion and the rear end portion of the CCD adjustment plate 52, and the upper end portion 50 of the CCD mounting plate 51 is attached to these bosses 53 and 53. The penetrated pins 54 and 54 are screwed together. Further, compression springs 55 and 55 are interposed between the CCD mounting plate 51 and the CCD adjustment plate 52 to urge the CCD mounting plate 51 upward. In this state, the height position of the CCD 14 can be finely adjusted via the CCD mounting plate 51 by turning the pins 54 and 54 clockwise or counterclockwise. By performing this fine adjustment at the front end and the rear end of the CCD 14, the vertical position adjustment of the CCD 14 can be performed.

  As described above, the image surface of the original is irradiated along the reading line L by the light source 12 of the optical system (main scanning), and further, the reading line L is moved to the right by the driving system to perform scanning (sub scanning). As a result, the image surface of the document can be sequentially read by the CCD 14 over the entire area.

  As shown in FIGS. 5 and 6, the image reading apparatus 11 includes a plate-shaped document pressing plate (document pressing member) 60 that can be freely opened and closed. 5 and 6 are views of the image reading device 11 as viewed from the right side. FIG. 5 shows a state in which the document pressing plate 60 is disposed at the open position A (fully opened state), and FIG. A half-open state in which the document pressing plate 60 is inclined at a predetermined width size detection angle α with respect to the width size detection position B, that is, the contact glass 18 while the document pressing plate 60 is moved from the open position A to the closed position is shown. The size detection angle is preferably in the range of approximately 20 to 30 degrees, but will be described as being 20 degrees in the following description.

  As shown in these drawings, a support member 61 is fixed to the rear side of the casing 16 of the image reading apparatus 11, and the document pressing plate 60 has a rear end portion 62 formed by an upper end portion of the support member 61. It is supported rotatably. As a result, the entire document pressing plate 60 can swing substantially vertically with the rear end 62 as the swing center. By this swinging, the document pressing plate 60 takes an open position A (fully opened position) shown in FIG. 5 and a closed position (fully closed position: not shown) that presses the document D on the contact glass from above. A white mat 63 having the same shape and the same size as the contact glass 18 is attached to the lower surface of the document pressing plate 60. The white mat 63 presses the document D from above when the document pressing plate 60 is closed, so that the image surface (lower surface) of the document D is brought into close contact with the contact glass 18.

  On the rear side of the housing 16, a detection unit 64 that is turned on / off when the document pressing plate 60 passes the width size detection position B is disposed. The detection means 64 is supported by the support member 61 so as to be movable up and down and is urged upward by an urging member (not shown), and light shielded by the light shielding portion 66 of the detection rod 65. A transmissive sensor 67. On the other hand, a pressing member 68 is attached to the document pressing plate 60 side so as to abut against the upper end of the detection rod 65 by the closing operation of the document pressing plate 60 and press the detection rod 65 against the urging force of the urging member. . When the angle of the document pressing plate 60 with respect to the contact glass 18 is between 0 and 20 degrees, the detection means 64 is turned off by the light shielding portion 66 of the detection rod 65 shielding the sensor 67, and on the other hand, 20 degrees or more. At the angle of, it is in the on state. As will be described later, when the document pressing plate 60 at the open position A is closed and the angle reaches the width size detection angle α (= 20 degrees), the detection unit 64 is switched from on to off. It is done. The control means 71 (see FIG. 6) turns on the light source 12 for a short time in order to detect the width size of the document D based on the signal at this time. The operation flow for width size detection will be described later with reference to FIG.

  The length size of the document D is detected by a light reflection type length detection sensor 70 shown in FIGS. As shown in FIG. 1, the length detection sensor 70 is attached to a stay (not shown) fixed to the casing 16, below the contact glass 18, and on the movement path of the illumination optical movement frame unit 23. It is arranged downward and upward. As shown in FIG. 3, the horizontal position of the length detection sensor 70 is slightly to the right of the right edge of the A5R document placed at the reading position of the contact glass 18 in the left-right direction, and the front-rear direction. Regarding the direction, it is arranged in front of the front edge of the A6R size document arranged at the reading position and in the rear side of the front edge of the B6R size document. The length detection sensor 70 detects whether or not there is a document above the length detection sensor 70. That is, for example, for an A-size or B-size document, if the length detection sensor 70 detects that there is no document while the document is placed at the reading position on the contact glass 18, the document Is one of A6R, B6R, B5, A5R, and A4. On the other hand, when the presence of a document is detected, it is one of B5R, A4R, B4, and A3. In the present embodiment, the size and orientation of the document are determined based on information on the length size of the document detected by the length detection sensor 70 and information on the width size described later.

  In the present invention, as described above, the image reading time can be shortened, the width size can be detected with high accuracy without erroneous detection of the width of the document, and the light emitted from the light source is given to the user. Reduced the impact. Hereinafter, these points will be described in detail. In the following description, it is assumed that the plurality of LED elements L1 to L22 can change the irradiation light amount individually or for each group.

  First, consider a case where a plurality of LED elements L1 to L22 constituting the line-shaped light source 12 are lit with the same light amount. Here, the home position HP of the light source 12 is set to the position shown in FIG. If the home position HP is too close to the left indicator plate 20, the light reflected from the left indicator plate 20 may have a greater effect on the CCD 14 when light is emitted from the light source 12, so the home position HP is The distance from the left indicating plate 20 is set so that this effect does not occur. Further, the home position HP needs to be on a document having a minimum sheet passing width (A6R in FIG. 3). Further, at the start of image reading, the light source 12 once moves to the left side and then moves to the right side to read the image. From this point, it is preferable that the light source 12 is closer to the left indicating plate 20. As described above, the home position HP is preferably set as close to the left indicator plate 20 as possible so that the light source 12 is applied to a document having a minimum sheet passing width and is not affected by the left indicator plate 20 during light irradiation.

  A procedure for document size detection (width size and length size detection) will be described with reference to the flowchart of FIG.

  First, the document pressing plate 60 is opened from the closed position to the open position A shown in FIG. 5 (step S1). Along with this, the detecting means 64 that is in the off state at the closed position of the document pressing plate 60 is turned on (step S2). Accordingly, the illumination optical movement frame unit (first optical system unit) 23 and the reflection optical movement frame unit (second optical system unit) 30 are set to the home position HP (see FIG. 3, provided that the reflection optical movement frame unit is used). The home position of 30 is not shown) (step S3) The document is set at the reading position on the contact glass 18 (step S4). Thereafter, the document pressing plate 60 at the open position A is moved toward the closed position (step S6). At this time, when the document pressing plate 60 reaches the width size detection position B of 20 degrees with respect to the contact glass 18, the detection means 64 is switched from on to off (switch off: step S6). When the detection means 64 is turned off, the LED elements L1 to L22 of the light source 12 are turned on for a short time with the same amount of irradiation light (step S7). The reflected light reflected by the original by this lighting is incident on the CCD 14 through the first mirror 27, the second mirror 28, the third mirror 32, the imaging lens 13, and the like. When the CCD 14 detects a pixel boundary based on the incident light (YES in step S8), the CCD 14 detects (determines) the width size of the document based on the pixel boundary (step S9). On the other hand, if no pixel boundary is detected in step S8 described above (NO in step S8), it is determined that there is no document (step S10).

  In step S6, when the detection means 64 is turned off, the length detection sensor 70 detects and confirms the length size of the document in parallel with the detection of the width size by the CCD 14 (step S11). Then, the size of the document is determined from the detection result of step S9 for the width size of the document and the detection result of step S11 for the length size (step S12). This completes the document size detection.

  Here, as described above, the white mat 63 is attached to the back surface of the document pressing plate 60. For this reason, it is difficult to discriminate between the original and the white mat 63 even if an attempt is made to detect the width size of the original in a state where the original pressing plate 60 is disposed at the closed position, that is, when the opening of the original pressing plate 60 is zero. Therefore, the document width size cannot be detected with high accuracy.

  On the other hand, when detecting the width size with the document pressing plate 60 opened as in the present embodiment, if the opening of the document pressing plate 60 is too large, indoor illumination light or the like enters the CCD 14 as disturbance light. Therefore, the width size cannot be detected with high accuracy.

  Therefore, in the present embodiment, the width size detection angle α is set to 20 degrees (20 to 20 degrees) as described above in order to wipe out the closed state of the document pressing plate 60 (opening is 0) and the problem when the opening is too large. 30 degrees). Then, when the document platen plate 60 moves from the open state to the closed state, the width size is detected when passing through the width size detection position B where the width size detection angle α is 20 degrees. did.

  As a result, the time required for the entire image reading can be reduced as compared with the conventional example in which the width size of the document is detected after the image reading button is pressed.

  However, by setting the width size detection angle α as described above, it becomes possible to detect the document width size to some extent accurately, but it is insufficient to prevent erroneous detection with high accuracy. . The reason will be explained. As shown in FIG. 6, when the document pressing plate 60 is at the width size detection position B, the distance between the contact glass 18 and the white mat 63 is closer to the rear side (back side) and further to the front side (front side). For this reason, when a document is not placed on the contact glass 18, the amount of light reflected from the white mat 63 is large on the rear side, and there is a possibility of erroneous detection that there is a document. More specifically, in the pixel area (first pixel area) of the CCD 14 used for detecting the width size of the small document placed on the rear side of the contact glass 18, the document pressing plate 60 is positioned at the width size detection position. When the amount of reflected light received from the white mat 63 at B is, for example, 90/256 (0 indicates black, 256 indicates white), the threshold value for document boundary detection in the first pixel region is also set with a margin. Including 100. In this case, if the amount of reflected light is 100 or more, it is detected that there is a document. However, when this threshold value is applied to the front (front side) pixel area (second pixel area) of the CCD 14, if the document has a high density of 100 or less, erroneous detection occurs in all pixel areas. Conversely, in the pixel area (second pixel area) of the CCD 14 used to detect the width size of a large document placed on the front side of the contact glass 18, the document pressing plate 60 is at the width size detection position B. At this time, the amount of reflected light received from the white mat 63 is 60/256, and the entire document boundary detection threshold value including the margin is set to 70. In this case, the CCD 14 erroneously detects the reflected light of the white mat 63 in the first pixel area on the rear side, and erroneous detection that there is a document occurs.

  Therefore, in the present embodiment, in order to eliminate the above-described erroneous detection, a plurality of LED elements arranged in a line are divided into a plurality of groups along the line, and the irradiation amount of each LED element is larger in the rear group. Moreover, it set so that the irradiation light quantity of each LED element might decrease, so that the front side group. On the rear side, the difference in the amount of reflected light is small between when there is a document and when there is no document. Therefore, the erroneous detection of the CCD 14 can be prevented by increasing the amount of reflected light and increasing the difference in the amount of reflected light. it can. On the other hand, since there is a large difference in the amount of reflected light between when the document is present and when there is no document, the difference in the reflected light amount can be increased even if the irradiation light amount is reduced, thus preventing false detection sufficiently. can do.

  Further, by reducing the amount of light emitted from the front LED element, even when the light source 12 is turned on to detect the document width size in the state where the document pressing plate is at the width size detection position B, the front side close to the user Since the amount of light emitted from the LED element is small, the influence on the user can be reduced.

  Hereinafter, as an example, a case will be described in which a plurality of LED elements are divided into two groups G1 and G2, and the LED elements belonging to the front group G2 are set to have a light amount smaller than that of the LED elements belonging to the rear group G1. For convenience of explanation, the 22 LED elements L1 to L22 are divided into 11 groups, the LED elements L1 to L11 belong to the rear group G1, and the LED elements L12 to L12 belong to the front group G2. Grouped so that L22 belongs.

  The document pressing plate 60 is placed at the width size detection position (width size detection angle α is 20 degrees) B with no document placed on the contact glass 18. The LED elements L1 to L22 are turned on. Conventionally, the amount of light emitted from each of the LED elements L1 to L22 is the amount of light emitted when all the LED elements L1 to L22 are lit with the same light amount when detecting the width size of the document. Here, among the pixel regions corresponding to the group G1 in the CCD 14, the reflected light amount of the pixel region R11 corresponding to the region having the smallest reflected light amount, that is, the LED element L11 is detected. For example, assume that the amount of reflected light received is 70/256. Similarly, the reflected light reception amount of the pixel region corresponding to the group G2 in the CCD 14 having the smallest reflected light reception amount, that is, the pixel region R22 corresponding to the LED element L22 is detected. For example, assume that the amount of reflected light received is 50/256.

  Next, a reference original, for example, an A4 size landscape original is set at the reading position on the contact glass 18, and the original pressing plate 60 is closed and placed at the closed position. In this state, the LED elements L <b> 1 to L <b> 22 are turned on with an irradiation light amount when image reading is performed. This irradiation light quantity is the same for all the LED elements L1 to L22, and is at least larger than the irradiation light quantity when detecting the width size. Gradually reduce the amount of irradiation light. Then, the amount of irradiation light when the amount of reflected light received in the pixel region R11 of the CCD 14 is 70/256 is detected, and the voltage value V11 that is the amount of irradiation light is detected. Similarly, the irradiation light quantity is gradually decreased, and the irradiation light quantity when the reflected light reception quantity in the pixel region R22 of the CCD 14 is 50/256 is detected, and the voltage value V22 (V11>) serving as this irradiation light quantity is detected. V22) is detected. Then, the voltage values V11 ′ and V22 ′ higher than the voltage values V11 and V22 (however, V11 ′> V22 ′) including the margin are determined as the driving voltages when the document width size is detected. That is, when detecting the width size, when the document pressing plate 60 at the open position A is closed and reaches the width size detection position B, the LED elements L1 to L22 are turned on to detect the width size of the document. However, at this time, the same voltage value V11 ′ is applied to the LED elements L1 to L11 of the group G1, while the same voltage value V22 ′ is applied to the LED elements L12 to L22 of the group G2. Thereby, the effect mentioned above, ie, false detection, can be prevented, and the burden on a user's eyes can be reduced. The document size detection procedure when the LED elements L1 to L22 are grouped is the same as the procedure of the flowchart shown in FIG.

  In the above description, when dividing the plurality of LED elements L1 to L22 into the two groups G1 and G2, as an example, an example in which the boundary is set between the LED elements L11 and L12 has been described. This boundary can be set at an arbitrary position.

  Moreover, in the above description, the case where the LED elements L1 to L22 are divided into two groups has been described as an example. The present invention is not limited to this, and the plurality of groupings may be divided into three or more groups. In this case, the irradiation light amount is increased as the LED elements of the rear group are increased, and the irradiation light amount is decreased as the LED elements of the front group. The amount of irradiation light for each group can be determined in the same manner as in the case of the two groups described above. The greater the number of groups, the lower the risk of false detection. Furthermore, it is also possible to individually change the irradiation light amount of the plurality of LED elements.

  In the above description, the case where there are 22 LED elements L1 to L22 has been described as an example. However, the present invention is not limited as long as it has two or more LED elements. It is possible to apply to the LED element.

  In the above description, the light source 12 is fixed and the detection is performed at one place when detecting the width size. Instead, the light source 12 and the like are moved in the sub-scanning direction, and at least two or more places. The width size may be detected. In this case, the document width size can be detected with high accuracy by averaging data detected at a plurality of locations.

  Further, the CCD 14 may set a threshold value for each color of R, G, B, for example. In this case, even when the balance of the incident light amounts of R, G, and B with respect to the CCD 14 is poor due to variations in the sensitivity of the CCD 14 and the irradiation light amounts of the LED elements L1 to L22, the presence / absence of the document at the reading position is accurately determined. Can be detected.

  In the above description, the case where the present invention is applied to the image reading apparatus has been described as an example. However, the present invention is widely applied to, for example, a case where the size of a document or sheet is detected with the document pressing plate half open. Generally applicable.

It is the figure which looked at the longitudinal section of the image reading device from the front side (front side), and is a figure explaining an optical system. It is the figure which looked at the longitudinal section of the image reading device from the front side (front side), and is a figure explaining a drive system. FIG. 4 is a top view for explaining the relationship between a light source, the size of a document, and the position of a document at the time of image reading, and a diagram for explaining a case where the size of the document is A row and B row. It is a top view explaining the relationship between a light source, the size of an original, and the position of the original at the time of image reading, and is a figure explaining the case where the size of an original is an inch size. FIG. 4 is a diagram of the image reading device viewed from the right side, and is a diagram for explaining a state where the document pressing plate is disposed at an open position (a fully opened state). FIG. 4 is a diagram of the image reading device viewed from the right side, and is a diagram illustrating a state in which the document pressing plate is disposed at a width size detection position in the middle of moving from the open position to the closed position. 6 is a flowchart for explaining a procedure of document size detection (width size and length size detection).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Illuminating device, 11 ... Image reading device, 12 ... Light source, 13 ... Imaging lens, 14 ... CCD (solid-state image sensor), 18 ... Contact glass (original platen), 60 ... Original Press plate (original pressing member), 71... Control means, D... Original, G 1 .. rear group, G 2 .. front group, L... Reading line, L 1 to L 22. )

Claims (6)

In an image reading apparatus that irradiates an image surface of a document and reads image information based on the amount of reflected light from the image surface,
A light transmissive document placing table on which the document is placed at a reading position on the back side;
The front side is opened and closed in the vertical direction with respect to the back side. When opened, the document can be placed on the document placing table, and when closed, the placed document is pressed against the document placing table from above. A document pressing member;
A plurality of point light sources that are arranged below the document table and arranged in a line in the front direction to form the light source;
A moving device that relatively moves the light source and the document so that the document moves in a direction perpendicular to the alignment direction of the plurality of point light sources;
A CCD that reads image information on the image surface based on the amount of reflected light generated from the point light source and reflected on the image surface of the document,
The document pressing member is opened and the width of the document placed on the reading position of the document placing table in the frontward direction is determined from the plurality of point light sources before the document pressing member reaches the closed position. The control means for irradiating the light and detecting the reflected light by receiving the reflected light by the CCD is provided, and the control means is arranged on the back side with the irradiation light amounts of the plurality of point light sources at the time of width size detection. Control so that the number of point light sources arranged on the near side of the point light source is less,
An image reading apparatus. The control means individually controls the amount of light emitted from the plurality of point light sources at the time of width size detection.
The image reading apparatus according to claim 1. The control means divides the plurality of point light sources into two or more groups along the frontward direction, and sets the irradiation light amount for each of these groups.
The image reading apparatus according to claim 1. At the time of width size detection, the width of light is detected by at least two locations by moving the light source by the moving means.
The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus. The CCD performs width size detection for each of a plurality of colors of incident light.
The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus. The point light source is an LED element;
The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus.

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