JPH08242347A - Picture reader - Google Patents

Abstract

PURPOSE: To more accurately measure the height of an original and to correct a photographed picture based upon a measured result by detecting both the height of the original and the height of an original platen. CONSTITUTION: A book type original is set up on an original platen 1 to be vertically moved so that the original faces of right and left pages are almost horizontally held and the side face shape of the original reflected in a mirror 5 is read out by a line sensor built in an image pickup camera part 2 through an optical system to detect the height of the original. On the other hand, a black-and-white density pattern formed on the side face of the original platen 1 which is reflected in the mirror 5 is photographed by the line sensor to detect the height of the original platen 1. The height of the original is more accurately found out based upon both the detected height of the original and the detected height of the original platen 1 and focusing or picture distortion is corrected based upon the more accurate original height.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for reading an original such as a book, and more specifically, an image in which a thick original such as a book is placed upward and an original is read by a reading means from above. More specifically, the present invention relates to an image reading apparatus that accurately detects the height of a thick original such as a book and corrects the distortion of the image that occurs when the original is read from above.

[0002]

2. Description of the Related Art Conventionally, there has been known a technique for detecting the height of a spatially curved document such as a book document and correcting the image distortion based on the image reading device for photographing a document placed facing upward. Has been.

For example, a distance measuring plate serving as a document positioning stopper is provided on the back side of the document, and the upper edge (back side) of the document is pressed against this to photograph the upper edge of the surface of the upward document. There is known an image reading apparatus that detects a difference in brightness between the surface and a distance measuring plate on the background and corrects an image based on the difference (for example, Japanese Patent Laid-Open No. 60-25486).
No. 9). Here, the upper surface of the distance measuring plate is a focus detection surface having a reflectance different from that of the document table surface and the document surface, which is a thick document such as a book and the thickness of which changes in the horizontal direction. In this case, a part of the focus detection surface is shielded by the thickness of the document, and the length of the focus detection surface in the main scanning direction (depth direction) detected by an image sensor such as a CCD line sensor changes. Therefore, by detecting this length, it is possible to detect the change in the thickness of the document and focus the image.

Further, the present applicant has proposed an image reading apparatus which photographs the side edge of a document, detects the brightness difference between the side and the background, recognizes the shape, and detects the height of the document. (See Japanese Patent Application No. 5-1697200).
According to this technique, the sensor, which is the image pickup device, simultaneously scans the document surface placed on the document table and the document side surface reflected on the mirror inclined behind the document table. The height of the document can be obtained by reading and detecting the number of pixels of the image sensor corresponding to the read edge portion of the side surface of the document. As a result, it is possible to focus on all sides of the document and obtain an image that is not in harmony.

Further, the applicant of the present invention, with respect to these image reading apparatuses, can move the left and right of the document table independently up and down in response to the difference in the thickness of the opened right page / left page of the book document. It is also proposed to provide a manuscript table (see Japanese Patent Application No. 6-046993). According to this, the difference between the left and right opened thickness of a document such as a book is absorbed, and the left and right pages of the spread of the document surface to be photographed are located on the same plane, so that the distortion of the read data is corrected, etc. Data processing work becomes easier and accuracy improves. Further, since it is not necessary to press the facing page of the book manuscript with a transparent plate or the like, it is possible to avoid the possibility of damaging the manuscript.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention By the way, as described in the above-mentioned JP-A-60-254869,
In an image reading apparatus that captures the top edge of the document surface and detects the document height by this, the top edge of the document surface may be tilted and slanted due to the distortion of the document page installed on the document table, If the original is placed away from the distance measuring plate that serves as a positioning stopper as described above due to improper installation, the top edge of the original surface will be misaligned from its original position when the image is taken. Recognized as low height. Therefore, in actuality, when the document height is "0 mm", the data of the document height of a negative value lower than that appears, and therefore, accurate height data cannot be obtained and reproduced. There was a problem with the image quality.

On the other hand, in order to solve this problem, the applicant of the present invention cannot actually cause a phenomenon such as a document height of a negative value. Therefore, when negative height data is generated, , It can be determined that the document is separated, and the minimum value of the document height data that is negative with respect to the reference position is detected, and all the document heights are set so that this value becomes “0 mm”. An image reading device for shifting data has been proposed (see Japanese Patent Application No. 6-262067).

However, the above-mentioned Japanese Patent Application No. 6-04369.
A document table that can move up and down like the one described in No. 3
When combined with an image reading device that captures the top edge of the document surface and detects the document height, the document table height is not set to a fixed position of "0 mm", Since it moves, the minimum value of the height data does not always become “0 mm”, which causes a problem that an accurate shift amount of the height data cannot be obtained.

Further, as described in the above-mentioned Japanese Patent Application No. 169720/1993, an image reading device for photographing the side surface of a document to detect the height of the document is combined with a vertically movable document table. In this case, when trying to recognize a place with a small number of pages such as near the front cover of the document from the horizontal direction, the document may be too thin to detect the brightness difference, and it may not be possible to recognize that there is a document. There is a risk that the document table may be erroneously recognized as a document. For this reason, there has been a problem that it is not possible to obtain accurate data of the document height. Further, in this case, when the platen rises, the shape of the side surface of the document is recognized from slightly downward to upward in the horizontal direction. At this time, near the cover of the document, the side surface of the document is located at a position away from the side surface of the document table. When placed so that the position of the document is positioned, the side surface of the document is hidden behind the document table, and there is a possibility that the document height cannot be detected.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide an image reading apparatus in which a document is placed facing upward and the image is optically scanned and photographed. An object of the present invention is to provide an image reading apparatus that detects the height of a document more accurately by detecting both the height of the document and the height of the document table, and corrects a photographed image using the height of the document.

[0011]

The present invention for achieving the above object is capable of moving up and down in an image reading apparatus in which a thick original such as a book is placed upward and the original is read by the reading means from above. Document table, means for detecting the height of the document table, means for detecting the height of the document placed on the document table, and image correction based on the detected document table height and document height An image reading apparatus comprising: a correction unit.

In the present invention thus constructed, when a thick document such as a book is read, the document is placed face up on the document table. Here, since the document table can move up and down, it absorbs the difference in the left and right thickness of a document such as a book, improves the sitting of the document, and keeps the surface of the document to be photographed substantially horizontal. Then, the height of the document table and the height of the document placed on the document table are respectively detected. The correct document height is obtained based on both the document height and the document table height obtained in this way, and the correction unit corrects the image photographed by the reading unit using this.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

(1) Overall Configuration An image reading device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of the image reading apparatus, and FIG. 2 shows a state in which a book as a document (hereinafter referred to as a book document B) is placed on a document table 1. A book document B such as a book or a file, which is a subject, is placed facing upward on the document table 1, and a line sensor for reading the spread surface of the book document B by optical scanning is provided above it. The image pickup camera section 2 is provided. The document placing surface of the document table 1 is colored darker than the background color of a general document, and the book document B
When the document is read with the document mounting surface as the background, the document surface and the document mounting surface can be identified. In this apparatus, an illumination unit 3 arranged above the document table 1 and illuminating a book document B on the document table 1, an operation panel 4 for setting image reading conditions and the like, and a document table 1 at the back. Of the book document B, which is arranged obliquely to the side and reflects the side surface of the book document, a reference plate 8 which is also arranged on the back side of the document table 1 and serves as a positioning reference of the book document B, and a preliminary scanning operation of the imaging camera unit 2. Also, a control unit (see FIG. 20) for controlling the photographing operation such as the main scan operation is provided. The image data captured by the imaging camera unit 2 is subjected to various processes by the control unit and output to a desired output device (printer, computer, etc.).

Here, the names of the respective parts of the book document B placed on the document table 1 are defined. Opened Book Manuscript B
Of the entire left and right pages, which is read by the imaging camera unit 2 is referred to as a document surface BS, and the side edges of the document surface BS on the back side of the placed book document are the upper edge BE and the book document B. The back side edge of the cover is referred to as a cover top edge BC.

FIG. 3 and FIG. 4 show schematic configurations of the apparatus as viewed from the front and the sides, respectively. The image pickup camera unit 2 includes a CCD line sensor 7 in which a plurality of image pickup elements are arranged in a line from the front side of the apparatus to the rear side (main scanning direction), and a document surface B.
And an optical system having an imaging lens 6 for projecting the image of S onto the line sensor 7. The line sensor 7 is a document surface BS
The image on the document surface BS is read by moving in the sub-scanning direction (the direction of the arrow in FIG. 3) orthogonal to the main scanning direction on the image forming plane on which the image of (1) is formed. In addition, the imaging lens 6
Is provided so as to be movable in the optical axis direction by a lens driving device, and is moved according to the height of the document obtained by height detection described later, and is always focused on the document surface BS on the line sensor 7. Form an image of. The book document B is positioned by pressing the upper edge BC of the front cover against the reference plate 8 and placing it on the original table 1 so that the upper edge BC of the front cover coincides with the reference position. That is, the reference plate 8 protrudes from the document mounting surface of the document table 1 to the extent corresponding to the thickness of the cover of the book document B, and the upper edge BC of the cover of the book document B is pressed against the protruding reference plate 8. The original is placed so that the central portion of the original matches the center of the original table 1. Mirror 5
Is extended in the sub-scanning direction on the back side of the document table 1 and is installed at an angle of 45 ° with respect to the document placement surface of the document table 1, and the book document B placed on the document table 1 is placed. Side view of.
The side image of the book document B reflected on the mirror 5 is the document surface B.
Along with S, it is projected by the lens 6. The line sensor 7 has a length sufficient to read the projected image of the document surface BS and the side surface, and simultaneously reads the image of the document surface BS and the side surface by scanning movement. Although the line sensor is used in this embodiment, an area sensor may be used instead of the line sensor.

(2) Configuration of Document Plate FIG. 5 shows a platen plate 12 which serves as a document platen surface of the document platen 1.
FIG. 3 is a perspective view showing a state when viewed from the back side of the reading device. The loading plate 12 is configured by rotatably connecting four plates to each other, moves up and down according to the weight distribution of the left and right pages of the book document B to be loaded, and reads both left and right pages. Keep the surface BS at approximately the same height. Four
On the side surfaces of the left and right outer plates 16a, 16b located on the outer side of the one plate, white strip-shaped patterns 40a, 40b having a width W and a black strip-shaped pattern 41 are formed.
a and 41b are given. When an original is placed in a state where the left and right pages are distributed differently, the mounting plate on the side with the smaller distribution (for example, 16b in FIG. 5) rises, the patterns 40b and 41a provided on the side surface are reflected on the mirror 5, and the line sensor 7
Thus, the patterns 40b and 41b are read. As a result, the height of the placing plate 12, which is the document placing surface, is detected.

In the figure, at the position indicated by the alternate long and short dash line A, the distribution of the left and right pages of the book original B to be placed is substantially the same, and the placing plate 12 is placed at the reference position where it forms a plane. The position of the upper surface of the mounting plate is shown, and in various height detections described later, the height is detected with this position as a reference. That is, the alternate long and short dash line A in the figure indicates the position of height "0".

FIG. 6 is a perspective view showing the document table viewed from the front side, FIG. 7 is its front view, and FIG.
FIG. 7 is an enlarged view of the central connecting member shown in FIG. 6. As shown in FIGS. 5 and 6, the document table 1 is roughly shaken via a base plate 10 that is in contact with a base 9 (see FIG. 1) of the image reading apparatus and a coupling member to the base plate 10. The mounting plate 12 is movably connected to the mounting plate 12 described above.

The mounting plate 12 comprises a set of inner plates 14a, 14b installed adjacent to the central portion and outer plates 16a, 16b located outside the respective inner plates 14a, 14b. The left and right mounting plates 12a and 12b are composed of inner and outer plates that are rotatably connected to each other via rotating shafts 18a and 18b. Of these, the inner plates 14a and 14b are the original placement surface 12s (see FIG. 7).
When a document placed on the reference document is a so-called book document B such as a book, the plate corresponds to the spine of the book document B (see FIG. 7C).

As shown in FIG. 8, both inner plates 1
4a and 14b are attached to the outer plates 16 by the torsion coil springs 20 attached to the rotary shafts 18a and 18b.
It is biased so as to rotate in the direction of arrow C about the rotating shafts 18a and 18b with respect to a and 16b, and the rotation is stopped at the position shown in FIG. It has become so. Therefore, when the book original B is not placed and the original table 1 is at the reference position shown in FIG. 8A, the left and right placing plates 12a, 1 are placed.
2b is located on the same plane (same height) (height shown at the reference position A in FIG. 5).

Further, as shown in the drawing, a substantially V-shaped central connecting member 22 is rotatably supported at the bent portion of the central portion of the base plate 10 (only the front side is shown). 22a, 2 of arms of the connecting member 22
Each of the tip ends of 2b has a rotating shaft 18a,
18b is provided. As shown in FIGS. 6 and 7, the outer connecting members 24a and 24b rotatably connected to the outer end portions of the outer plates 16a and 16b are rotatable near the left and right end portions of the base plate 10. Supported (only the front side is shown).

As shown in FIG. 7B, each member of the original table 1 is composed of a base plate 10 and connecting members 22, 24.
The rotary shaft 22 that is connected to (collective term of 24a and 24b)
c, 25a (22c, 25b) and each outer plate 16
a and 16b are connected to the rotary shafts 18a and 18c (18b and 18d) to which the respective connecting members 22 and 24 are connected to each other so that a parallelogram is formed. , 18c (18b, 18d), the inter-axis distance L1 is
Rotating shafts 22c, 25a (22c, of the base plate 10)
25b) is the same as the inter-axis distance L2. In addition, two rotary shafts 1
The inter-axis distance L3 of 8c, 25a (18d, 25b) is 2
It is equal to the inter-axis distance L4 between the two rotating shafts 22c and 25a (22c and 25b). Therefore, the document placing surface 12s is always kept parallel to the base plate 10 even if it is moved by the rotation of the connecting members 22 and 24.

Further, as shown in FIGS. 8 (A) and 8 (B), at the center of the base plate 10, rollers 2 attached to the center sides of both inner plates 14a, 14b.
A grooved cam 28 that engages 6 is attached. In addition,
Although the groove cam 28 is a member actually attached to the document table 1, the groove cam 28 is shown by a chain double-dashed line and the supporting structure is omitted to facilitate understanding of the drawings.

This groove cam 28 is provided on both inner plates 14a and 14b when the mounting plate 12 is at the reference position.
Are positioned in parallel with the outer plates 16a and 16b (see FIG. 8A). On the other hand, when the connecting members 22 and 24 are rotated and the left and right mounting plates 12a and 12b are moved, as shown in FIG.
8 is moved along the groove, and one inner plate 14a is inclined. As described above, when the connecting members 22 and 24 are rotated and the outer plates 16a and 16b are moved to predetermined positions, the outer plates 16a located on the upper side are connected regardless of the weight of the book document B and the like. The inner plate 14a is securely tilted. The inner plate 1
As a means for inclining the 4a and 14b, a cam other than the grooved cam, or other than the cam, for example, a mechanism including a link mechanism or a rack and pinion can be used.

Further, as shown in FIG. 8, the central connecting member 22 is urged by the elastic force of the torsion coil spring 30 attached to the base plate 10, and the book document B is removed and placed. When the load applied to the mounting plate 12 disappears, the mounting plate 12 is moved to the position shown in FIG.
The state shown in FIG. 8 returns to the reference position shown in FIG. It should be noted that the mounting plate 12 is located at the reference position even when a load is evenly applied to the left and right mounting plates 12a and 12b.

In the present embodiment, as shown in FIG. 8, the detection plate 42 is fixed to the rotating shaft 22c of the central connecting member 22, and the position sensor 43 detects this detection plate 42, whereby It is configured so that it can be determined whether the document table 1 is at the reference position.

As shown in FIG. 7C, when a book original B such as a book is placed on the placing plate 12 and the ratio of the left and right pages of the book original B is not equal,
Since the loads applied to the left and right mounting plates 12a and 12b are different, the central connecting member 22 is rotated about the rotating shaft 22c, and one outer plate 16b moves upward,
The other outer plate 16a moves downward. At this time, it is the outer plate 16a on the side supporting a larger weight that moves downward, so that the left and right heights of the double-page spread reading surface S of the book document B automatically become substantially equal. Therefore, the document surface BS can be made almost horizontal without pressing it with a transparent glass plate,
Document reading accuracy is improved. Further, it is possible to prevent a situation in which the book document B is damaged when the book document B is pressed by a glass plate or the like. As shown in FIG. 7C, as a result of the roller 26 of the inner plate 14b connected to the outer plate 16b located on the relatively upper side moving along the groove cam 28, the inner plate 14b tilts.

By the way, in the case where the original is a so-called book original B, when the reading work progresses and the pages are sequentially turned, the so-called throat Ba of the opened book original B (see FIG. 7).
(See (C)) gradually moves. That is, the center position Ba of the spread original surface BS is in the width direction (left-right direction) of the original.
To move to. The amount of movement increases as the thickness of book document B increases. Therefore, the double-sided document surface BS
In order to always arrange the book document B at a predetermined position with respect to the reading means such as the CCD line sensor, it is necessary to horizontally move the position of the book document B in the opposite direction according to the above-mentioned movement amount.

In the document table 1 according to the embodiment, attention is paid to the fact that the left and right weights of the book document B are changed by turning the pages, and the platen plate on which the book document B is placed is utilized by utilizing this weight change. 12 is moved in the width direction. That is, when the supporting weights of the left and right mounting plates 12a and 12b are different, the left and right outer plates 16a and 16b move up and down relatively to cause a height difference. The amount of movement of the plate 12 in the width direction is determined.

For example, in the manuscript table 1 of the above-described embodiment, the central connecting member 22 is used to form the outer plates 16a, 1a.
By converting the vertical displacement of 6b into the widthwise displacement, the mounting plate 12 is moved in the widthwise direction, and the document surface BS
The center position Ba of is moved. As shown in FIG. 7C, in this structure, the central position D of the mounting plate 12 is moved in the direction of the arrow toward the outer plate 16a that has been moved downward. In this way, the document surface BS
By suppressing the movement of the center position Ba in the width direction, the document surface BS can always be kept at a predetermined position within the angle of view of the line sensor.

By appropriately changing the angle and length of the arm of the central connecting member 22 and the connecting positions (positions of the rotating shafts 18a, 18b, 22c) with the left and right mounting plates 12a, 12b, One outer plate 16a (1
6b) when the other outer plate 16b (1
6a) and the amount of movement in the width direction of the central position D of the mounting plate 12 can be changed. Therefore,
By changing the shapes of the central connecting member 22 and the outer connecting member 24, the mounting plate can be set in accordance with the installation space for the document table 1 secured in the image reading device and the specifications such as the size or type of the book document to be read. The vertical movement distance of 12 and the movement amount in the width direction can be arbitrarily set.

Further, in the original table 1 of the above-described embodiment, the placing plate is moved to move the original in the width direction by using the substantially V-shaped connecting member 22, but the original is moved in the width direction. The means for moving the mounting plates 12a, 1 to the left and right is not limited to this.
The vertical movement of 2b may be detected by a detection unit such as a displacement sensor, and the mounting plates 12a and 12b may be moved in the width direction by a driving unit such as a motor by an amount corresponding to the detected vertical movement.

Further, instead of the torsion coil springs 20 and 30, an elastic body made of an elastic material such as a compression coil spring, sponge or rubber is used to attach each plate and each connecting member in a predetermined direction. You may be encouraged. Here, since the performance of the elastic body (for example, a spring constant in the case of a spring) is one of the factors that determine the vertical movement distance of the outer plates 16a and 16b and the movement distance in the width direction, the paper quality of the original document (for example, continuous amount). Etc.) is preferable. Further, in the case of so-called book document B, an intermediate elastic body is selected in order to support many kinds of book document B, and when the book document B is actually placed, the heights of the left and right reading surfaces S are increased. If the values do not match, the operator may match the heights of the reading surface S. That is, since the stop position of the mounting plate 12 has a predetermined width due to the influence of friction of the engaging portions of the respective members, the left and right heights of the document surface BS at the initial stop position of the mounting plate 12 are high. Even if the heights do not match, if the desired stop position where the left and right heights match is within the width range described above, the operator can manually move the mounting plate 12 to the desired position. The heights of the left and right document surfaces BS can be easily matched.

Further, in the above-described embodiment, the inner plates 14a and 14b are inclined by using the cam mechanism composed of the roller 26 and the groove cam 28, and the torsion coil spring 30 is used. Only one of the spring 30 and the cam mechanism may be used as long as 14a and 14b can be positioned at predetermined positions. Of these, spring 30
When only one is used, the inner plates 14a and 14b are tilted by the load received from the book original B according to the tilting direction of the spine of the book. Further, when the groove cam 28 is provided, the inner plates 14a and 14b are positioned by the groove cam 28, so that it is not necessary to separately provide the above-mentioned stop member (not shown).

(3) Height Detection When the book document B placed on the document table 1 is placed face up in an open state, its document surface BS is spatially curved in the height direction. It becomes the shape. Therefore, the height of the book document B at each position in the sub-scanning direction is detected, and the distortion of the read image and the focus adjustment of the image formed on the line sensor 7 are adjusted according to this height. There is a need to do. FIG. 9 is a diagram showing the principles of the two height detection processes used in this embodiment. In the first height detection processing, by placing the book document B at a predetermined position, the mirror 5 is
The image 11 of the side surface of the book document B is imaged, and the image 11 of the side surface of the book document B imaged on the mirror 5 is read by the line sensor 7 to obtain the document height distribution.

Further, in the second height detection processing, the shape (image forming position) of the image of the document surface BS formed by the lens 6 changes according to the height of the document. The distribution of the document height can be calculated and obtained from the image. In FIG. 9, the reading range of the line sensor 7 is indicated by a chain line E, and the addresses of the image pickup elements of the CCD line sensor 7 are indicated by 1 to n in order from the left side of the drawing.

First, the left and right pages of the book document B placed on the document table 1 are evenly distributed, and the placement plates 12a,
The height detection of the book document B when 12b is located at the standard position will be described, and then the mounting plate 12 will be described.
The height detection when a and 12b are not on the same plane, that is, when the left and right pages are not evenly distributed and the placement plate moves up and down due to the weight difference between the left and right pages will be described.

FIG. 10 shows mounting plates 12a and 12b.
6 is a diagram showing a state of image data when a book document B is read in a state of being located at a standard position. FIG. In the figure, a is the image of the document surface BS, b is the image of the document table 1, c is the image of the background portion reflected on the mirror 5, d is the image of the side surface of the book document B reflected on the mirror 5, and e is the reference. The image of the plate 8 and f indicate the alignment reference of the document. Image a on the document side and image d on the side of the document
Is read as curved in the main scanning direction due to the height change of the document. The document surface and the document side surface are generally white and are read as white. On the other hand, the document table 1 and the reference plate 8 which are colored darker than the background of the document, and the image c of the background portion reflected on the mirror 5 have a small amount of reflected light and are read in black. Further, since the image e of the reference plate 8 is interposed between the image a of the document surface and the image d of the document side surface reflected on the mirror 5, the image a of the document surface and the image d of the side surface in the main scanning direction.
Can be distinguished.

FIG. 11 shows the output of one line read in the main scanning direction by the line sensor 7. In this example, the case where the image at the position indicated by the dotted line in FIG. 10 is read by the line sensor 7 is shown. Line sensor 7 on the horizontal axis
The image sensor address and the vertical axis show the output (image density) of each image sensor. In the figure, an image c of the background portion reflected on the mirror 5 is an image d of the side surface of the document reflected on the mirror 5,
Indicates an image of the surface of the reference plate 8, an image a of the document surface BS, and an image of the document table b on the image sensor. Dt
h is a predetermined threshold value for discriminating whether the image is a document image or another image. n1 is a minimum address value of the image sensor having an output exceeding the threshold value Dth, that is, a value indicating a position where the upper edge BE of the document surface in the image 11 on the document side surface is imaged.
n2 is a minimum address value in the image sensor that reads the image of the reference plate 8 and is a fixed value. n3 is a minimum value of the address of the image pickup device having an output exceeding the threshold value Dth at n2 or more, that is, a value indicating a position where the upper edge BE of the document surface BS is imaged. n4 is a maximum value of the address of the image pickup device having an output exceeding the threshold value Dth at n2 or more, that is, a value indicating a position where the lower edge 10c of the document surface BS is imaged. In addition, n5 is an address value of the image pickup device corresponding to the document alignment reference, and is a fixed value. (N2-n1) is the number of pixels corresponding to the height of the document used in the first height detection process, and (n5-n3) and (n4-n5) are the number of pixels of the document used in the second height detection process. It is the number of pixels indicating the amount of change in the image forming position of the document surface image in the main scanning direction, which changes in association with the height. Hereinafter, the number of pixels obtained by (n2-n1) used in the first height detection process will be referred to as height data N1, and the number of pixels obtained by (n5-n3) used in the second height detection process will be referred to as height. Data N2
Called.

As described above, when the mounting plates 12a and 12b are in the standard position, the left and right pages of the book document B are not evenly distributed, and the left and right pages of the book document B are not evenly distributed. Due to the weight difference, the mounting plate 12
The case where a and 12b deviate from the standard position will be described.

FIG. 12 shows how the line sensor 7 outputs one line in the main scanning direction when the book document B placed on the raised outer plate is read. Note that FIG.
The same reference numerals are given to those common to and the description thereof will be omitted. Here, is the outer plate 1 reflected on the mirror 5.
The image of the white pattern 40b (40a) on the side surface of 6b (16a) is an area on the image sensor of the image of the black pattern 41b (41a) on the side surface of the outer plate 16b (16a) (see FIG. 5). In the figure, n6 is the maximum address value of the image sensor having an output of n2 or less and exceeding the threshold value Dth, that is, the image forming position of the boundary between the white pattern 40b (40a) and the black pattern 41b (41a). Therefore, n6-n2 corresponds to the height of this boundary portion, and the height of the height of the upper surface of the outer plate 16b (16a) is obtained by adding the width W of the white pattern 40b (40a) to this height.

FIG. 13 shows the mounting plate 12b (12a).
Of the book document B and the plate 12b (12
It is a figure which shows the mode of the output of the line sensor 7 when a clearance gap (shown by code | symbol F in FIG. 14) arises with a). The gap F appears on the output of the line sensor 7 as a low output portion between and. Also in this case, the white pattern 4
0b (40a) and the black pattern 41b (41a), the image forming position of the boundary portion, n6 is obtained by detecting the maximum upper address of the image sensor having an output exceeding the threshold value Dth in the range of n2 or less.

(3-1) First Height Detection Processing When the CCD line sensor 7 scans and moves in the sub-scanning direction,
The value of n1 described above changes according to the height of the document surface at each position in the sub-scanning direction, so that the height that is the number of pixels corresponding to the height of the document surface at each position in the sub-scanning direction. Data N1 can be obtained. By dividing the height data N1 by the reading resolution, the document surface height (the distance from the document mounting surface of the document table 1 to the document surface BS) can be obtained. (3-2) Second Height Detection Processing Similarly to the above, when the CCD line sensor 7 scans and moves in the sub-scanning direction, the value of n3 changes according to the height of the document surface at each position in the sub-scanning direction. As a result, the height data N2, which is the number of pixels corresponding to the height of the document surface at each position in the sub-scanning direction, can be obtained. This height data N
By calculating 2 using a coefficient determined by the photographing optical system, the height of the document surface can be obtained. FIG. 15 is a diagram showing this state, and the arithmetic expression is as follows. However,
H: height of document, D: distance from lens center to document table, L3: distance from optical axis center to alignment reference,
K: Read resolution.

H = {D × (n5-n3) / K} / {L3
+ (N5-n3) / K} That is, H = (D × N2 / K) / (L3 + N2 / K) (3-3) Height detection of the mounting plate When the line sensor 7 scans and moves in the sub-scanning direction, In the area where the mounting plate is elevated from the standard position, the above-mentioned address value n6 is detected according to the height of the mounting plate. Therefore, n6−n2 is calculated, and this value is read and read. The white pattern 40b (40
The height of the boundary between a) and the black pattern 41b (40a) is obtained. The width W of the white pattern 40b (40a) is added to this, and the raised outer plate 16b (16a)
Ask for the height of. Raised outer plate 16b (16
If the height of a) is obtained, the other outer plate 16a
Since (16b) descends together, the height obtained earlier is given a minus sign, and the outer plate 16 descends.
Find the height of a (16b).

(3-4) Correction of Height Data First height detection processing described in the above section (3-1), (3
In the second height detection processing described in the section -2), an error may occur in the detected height of the book document depending on the placement state of the book document B. This error
The height data of the mounting plate obtained by the height detection of the mounting plate described in (3-3) is used for correction.

First, the correction of the height of the book original obtained by the first height detection processing will be described. As shown in FIG. 14, when the book document B is placed with either the right or left page having only the cover BD, for example, if the cover BD has a high density such as black, the book document is reflected on the mirror 5. It is difficult to identify the side view of B. That is, there is no difference in the contrast between the background portion c and the side image d reflected on the mirror 5 shown in FIG. 10, and the side image d cannot be discriminated. FIG.
6 shows the distribution of the height data of the first height detection processing in this case, and the solid line Hb in the figure is the height data, and originally corresponds to the cover BD as shown by the one-dot chain line in the figure. The height data should be obtained, but the height data is missing in this part. Therefore, the missing height data (the portion indicated by the alternate long and short dash line in the figure) is replaced with the detected height data of the mounting plate (indicated by the dotted line Ha1 in the figure) for correction.

Even when the front cover BD of the book original B is light in color and the side image can be identified, as shown in FIG. 17, when the book original B is placed tilted in the G direction, it rises. In some cases, the side surface of the book document B is not reflected on the mirror 5 because it is hidden behind the outer plate 16b, and the side image of the book document B is not partially projected on the line sensor 7. FIG. 18 shows the distribution of the height data of the first height detection method in this case, where the solid line Hb is the height data, and the side image is hidden behind the outer plate 16b and is not projected. Height data is missing in part J.
Therefore, as in the previous case, the missing height data is replaced with the detected height data of the mounting plate (indicated by the dotted line Ha1 in the figure) for correction.

Next, the correction of the height of the book original obtained by the second height detection processing will be described. FIG. 19 shows a distribution of height data in the second height detection process when the book document B is placed apart from the reference plate 8. Here, because the book document B is placed apart from the reference plate 8, the detected height data Hb is generally lower than the actual height Hb ′ of the book document B. ing. Therefore, the height data Hb is set so that the minimum values h1 and h2 of the height data of the left and right pages of the book document B detected match the height data Ha1 and Ha2 of the detected outer plates 16a and 16b. Correct by shifting to the whole. With such a correction, the book document B becomes the reference plate 8
It is possible to obtain accurate height data of an original even when the original is placed apart from the above.

(4) Control Circuit FIG. 20 shows a block configuration of the control circuit. In the present embodiment, the line sensor 7 precedes the scanning operation (main scanning operation) for actual image reading, and the document surface BS
A preliminary scan is performed to detect the height at each position in the sub-scanning direction. The output (image data) of the line sensor obtained by the preliminary scan is A / D converted by the A / D converter 31 in order from the image pickup device at address 1 for each line, and then input to the comparator 32. . The threshold value Dth described above is preset in the comparator 32 by the CPU 33. When pixel data having a level exceeding the threshold value Dth is input to the comparator 32, the counter 34
The count value of is taken into the memory 38. Counter 3
The counter 4 counts in synchronization with the dot clock applied to the line sensor 7, and the count value of the counter 34 indicates the address of the image data compared by the comparator 32. The CPU 33 sets, for each line, the minimum value of the count values fetched in the memory 38 to n1,
Of the count values greater than n2, the smallest value is n3,
The maximum value among the count values smaller than n2 is recognized as n6, and n1, n3 and n6 for each line are stored in the memory 38.
To memorize. The image data of the line sensor 7 obtained by the main scanning operation is A / D converted by the A / D converter 31 in order from the image pickup device at address 1 for each line, and then the image data for several lines is stored. Sequentially written to the possible buffer memory 39. Since the written image data includes the image data of the side surface of the book document B described above, the image data of the side surface is deleted and only the image data of the document surface BS is sequentially read by the image processing circuit 30. The image data is appropriately corrected and output to the printer PR for printing. Here, the image processing circuit 30
In (1), the distortion of the image in the main scanning direction and the sub scanning direction is corrected based on the count values n1, n3, n6 of each line obtained by the preliminary scanning. Also, CPU3
3 indicates count values n1, n3, during the main scan operation.
Based on n6, a control signal is output to the lens driving device 36, the lens is moved according to the reading position of the line sensor 7, and the image of the document surface BS is always focused on the line sensor 7 in the focused state. To do so. Also, the CPU 33
Outputs a control signal to the sensor moving unit 35 and the lamp control unit 37 to control the scan movement of the line sensor and the lighting of the lamp of the illumination unit.

(5) Basic Flowchart FIG. 21 is a flowchart showing the procedure of the reading operation controlled by the CPU 33 of the image reading apparatus configured as described above. When a reading operation start command is input from the operation panel 4, the CPU 33 turns on the lamp of the illumination unit 3 via the lamp control unit 37 to illuminate the book document B (# 1). Next, the sensor moving unit 35 is instructed to start the preliminary scan (# 2), and sampling of the count values n1, n3, n6 for each reading line is executed. In this operation, while the CCD line sensor 7 is moved from one end in the sub-scanning direction, the side surface of the document and the document surface BS reflected on the mirror 5 are photographed, and the count value n
1, n3 and n6 are stored in the memory 38 (# 3). This operation is repeated at a constant cycle until the preliminary scan is completed for all lines, and when the preliminary scan is completed (YES in # 4), the sampled count value n
Height data N1 and N2 are obtained from 1, n3 and n6, and the correction processing of the height data N1 and N2 is executed (# 5).
The processing here is as described above. First, (3-
The height of the book original is detected by the first height detection processing described in the section 1) and the second height detection processing described in the section (3-2), and in the section (3-3). The height of the mounting plate is detected as described. Next, as described in the section (3-4), the height data obtained by the first height detection processing and the second height detection processing is corrected by the height data of the mounting plate. After that, the first height detection process, the second
Final height data is created based on both height data corrected by the height detection processing.

When the above operation is completed, the sensor moving unit 35 is instructed to start the main scan, and the line sensor 7 is scanned and moved in the direction opposite to the preliminary scan.
A main scan for photographing the book document B is performed (# 6). During the main scan operation, the CPU 33 outputs a control signal to the lens driving device 36 based on the final height data obtained in the process of # 5 to execute the focus adjustment of the lens 6 (# 7 ), In order to correct the distortion of the pixel data obtained by the main scan operation,
A correction amount is set based on the height data (# 8). When the main scan operation is completed for all lines (Y in # 9
ES), the lamp is turned off (# 10), and the image reading operation ends.

(6) Operation of the Embodiment According to the reading device of the present embodiment, the mirror 5 is installed on the back side of the book original B and reflects the book original B and the side surface of the placing plate. The line sensor 7 as a reading unit reads the side surface image reflected on the document surface BS and the mirror 5 via the lens 6. Then, the document height is calculated based on the read image data. Here, the document table 1 on which the book document B is placed has a platen plate 12 corresponding to a portion on which the left and right open pages of the book document B are placed.
By moving a and 12b up and down independently, the difference in the left and right thickness of the book document B is absorbed, the sitting of the document is improved, and the surface of the document to be read is kept substantially horizontal.

On the other hand, the line sensor 7 includes white and black patterns 40a, 40 provided on the side surface of the document table 1.
Also, b, 41a and 41b are read to calculate the height of the document table. An accurate document height is calculated based on both the document height and the document table height obtained in this way, and using this, focus adjustment and image distortion correction are performed.

(7) Other Embodiments In the above-mentioned embodiment, the height of the document table is detected by reading the side image reflected on the mirror 5 by using the line sensor 7. It is also possible to directly read the side image with a line sensor dedicated to the side without using a mirror to detect the height. In this case, a two-dimensional area sensor is provided instead of the mirror, or a one-dimensional line sensor is used for side scanning.

Various other means are also conceivable. For example, in the method using the line sensor as in the above-described embodiment, a method of detecting the upper edge (back side) / lower edge (front side) edge of the document table surface (the same principle as the above-described second height detection processing) is also applicable. Conceivable. However, in this case, since the edge may be hidden by the document, it is necessary to devise a method of limiting the edge detection position to, for example, the left and right edges where the document is not placed.

Further, as shown in FIG. 22, when the placing plate 12a of the document table 1 is lowered, a step is formed between the platen 12a and the main body, and the light K from the illuminating section 3 causes a shadow K of the step on the surface of the document table 1. There is also a method that utilizes what occurs at the top. That is,
Since the size of the shadow K in the depth direction is proportional to the amount of lowering of the document table 1, the width of the shadow K can be detected by using the line sensor and the amount of lowering of the document table can be obtained. As described above, if the amount of lowering of the mounting plate on one side can be detected, the amount of rising of the mounting plate on the other side can be calculated.

Further, in the above-mentioned embodiment, the white and black density patterns in the horizontal direction are formed on the side surfaces of the outer plates 16a, 16b of the document table, but as shown in FIG. 23, the density patterns are formed in the vertical direction. It is also possible to use white and black density patterns 42a, 42b, 43a, 43b. In this case, since the height of the document table is discontinuously detected, it is possible to recognize the document table by identifying this discontinuous pattern M as shown in FIG.

Further, in the above embodiment, the position sensor 43 for detecting the movement of the document table is provided to surely distinguish the document and the document table, but only the height data obtained by the line sensor 7 is provided. It is also possible to identify with. in this case,
The height of the document changes in the sub-scanning direction, but the height of the document table is flat and does not change in the sub-scanning direction. That is, the distribution of the height data is obtained in the sub-scanning direction, and when the variation is small, it can be discriminated from each other by determining that it is the document table.

On the other hand, unlike the above embodiment, the original table 1
There is also a method of detecting the amount of movement of the object using a dedicated sensor. In the present embodiment, the document table itself makes a vertical motion in the vertical direction, and the central connecting member 22 rotates around the rotation shaft 22c. Therefore, there are generally many methods for directly / indirectly detecting these. Are known.

Specifically, for example, an optical or magnetic encoder may be used. As a method for detecting the rotational movement, a plurality of slits 51a formed at equal intervals in the circumferential direction of the detection disk 51 connected to the rotating shaft 22c may be detected by an optical sensor 52 (see FIG. 25), or A plurality of protrusions 53a made of a magnetic material are provided at equal intervals in the circumferential direction of the disk 53 connected to the rotating shaft 22c.
The amount of movement of the document table 1 can be measured by detecting with the magnetic sensor 54 (see FIG. 26).
Further, as a method of detecting the linear movement, the slit 55a formed in the strip plate 55 attached to the end portion of the placing plate 16b of the document table 1 is detected by the optical sensor 52 (see FIG. 27), or the document table is detected. The amount of movement of the document table 1 is detected by the magnetic sensor 54 detecting the protrusion 56a made of a magnetic material provided on the strip plate 56 attached to the end of the first mounting plate 16b (see FIG. 28). Can also be measured directly.

It is also possible to use an electric sensor that uses changes in resistance value and capacitance value. For example, in FIG.
As shown in FIG. 6, a contact terminal 59 is provided on a disk 57 composed of a resistor connected to the rotary shaft 22c, while a contact plate 58 fixed to the main body is brought into contact with the surface of the disk 57. Then, the change in the resistance value between the contact plate 58 and the contact terminal 59 can be detected by rotating the rotating shaft 22c. In addition, it is also possible to detect the change in the electric capacitance value by the same method.

Further, a distance sensor using laser light or ultrasonic waves can be used. For example, as shown in FIG. 30, above the end portion of the placing plate 16b of the document table 1,
An irradiation unit 61 that emits a laser beam and a light receiving unit 62 that receives the light that is emitted and reflected by the mounting plate 16b are provided to measure the height of the mounting plate 12b, that is, the movement amount of the document table 1. You can The irradiation unit 61 and the light receiving unit 62 may be replaced with ultrasonic wave transmitters and receivers, and the movement amount of the document table 1 can be measured with the same configuration.

Further, as shown in FIG. 31, a light receiving sensor 63 for receiving light from the irradiation section 3 is provided on the front side of the document table 1 to detect the descending amount of the mounting plate 16b of the document table 1, It is also possible to measure the movement amount of the document table 1.

[0064]

As described above, according to the present invention, in an image reading apparatus in which an original is placed upward and the original is read by the reading means from above, the original table that can be moved up and down and the original table Since it has a means for detecting the height, a means for detecting the height of the original placed on the original table, and a correcting means for correcting the image based on the detected original table height and the original height, By detecting both the height of the document and the height of the document table, the height of the document can be measured more accurately, and the captured image can be properly corrected.

[Brief description of drawings]

FIG. 1 is a perspective view showing an overall configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a state in which a book, which is a document, is placed on a document table.

FIG. 3 is a schematic configuration diagram of the present apparatus when viewed from the front.

FIG. 4 is a schematic configuration diagram of the apparatus as viewed from the side.

FIG. 5 shows a mounting plate which is a document mounting surface of a document table,
FIG. 3 is a perspective view showing a state as viewed from the back side of the reading device.

6A to 6C are perspective views showing a state in which the document table is viewed from the front side.

FIG. 7A to FIG. 7C are diagrams showing a state in which the document table is viewed from the front.

8A and 8B are enlarged views of the central connecting member shown in FIG.

FIG. 9 is a diagram showing the principle of two height detection processes used in the present embodiment.

FIG. 10 is a diagram showing a state of image data when a book document is read in a state where the mounting plate is located at a standard position.

11 is a diagram showing a state of output for one line in the main scanning direction read by a line sensor at a position indicated by a dotted line in FIG.

FIG. 12 is a diagram showing how a line sensor outputs one line in a main scanning direction when a book document placed on a raised outer plate is read.

FIG. 13 is a diagram showing an output state of the line sensor when the placing plate rises and a gap is created between the book document and the placing plate.

FIG. 14 is a diagram showing a state in which a book document is placed with one of the left and right pages of the present apparatus having only a front cover.

FIG. 15 is a diagram illustrating a method of obtaining a document height by a second height detection process.

FIG. 16 is a diagram showing a distribution of height data in the first height detection process in the case of the state of FIG.

FIG. 17 is a diagram showing a state in which a document is tilted and, as a result, is set apart from the distance measuring mirror.

FIG. 18 is a diagram showing a distribution of height data in the first height detection method in the case of the state of FIG. 17;

FIG. 18 is a diagram showing how the height of the original and the original table in the sub-scanning direction changes when the original is placed away from the distance measuring plate.

FIG. 19 is a diagram showing a distribution of height data in the second height detection process when a book document is placed apart from the reference plate.

FIG. 20 is a diagram showing a block configuration of a control circuit of the present apparatus.

FIG. 21 is a flowchart showing the procedure of a reading operation controlled by the CPU of the image reading apparatus.

FIG. 22 is a diagram showing a state in which when the document table is lowered, a step is formed between the document table and the main body cover, and a shadow of light from the illumination unit is generated on the upper surface of the document table.

FIG. 23 is a perspective view schematically showing a placement plate of a document table according to another embodiment as viewed from the back side.

FIG. 24 is a diagram showing a distribution in which the side surface of the placing plate of the document table shown in FIG. 23 is detected in the sub-scanning direction.

FIG. 25 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 26 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 27 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 28 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 29 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 30 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 31 is a diagram showing means for detecting the height of a document according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Manuscript stand, 2 ... Imaging camera part, 3 ... Illumination part, 5 ... Mirror, 6 ... Imaging lens, 7 ... CCD line sensor, 30 ... Image processing circuit, 33 ... CPU, B ... Manuscript.

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[Procedure amendment]

[Submission date] January 18, 1996

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a perspective view showing an overall configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a state in which a book, which is a document, is placed on a document table.

FIG. 3 is a schematic configuration diagram of the present apparatus when viewed from the front.

FIG. 4 is a schematic configuration diagram of the apparatus as viewed from the side.

FIG. 5 shows a mounting plate which is a document mounting surface of a document table,
FIG. 3 is a perspective view showing a state as viewed from the back side of the reading device.

6A to 6C are perspective views showing a state in which the document table is viewed from the front side.

FIG. 7A to FIG. 7C are diagrams showing a state in which the document table is viewed from the front.

8A and 8B are enlarged views of the central connecting member shown in FIG.

FIG. 9 is a diagram showing the principle of two height detection processes used in the present embodiment.

FIG. 10 is a diagram showing a state of image data when a book document is read in a state where the mounting plate is located at a standard position.

11 is a diagram showing a state of output for one line in the main scanning direction read by a line sensor at a position indicated by a dotted line in FIG.

FIG. 12 is a diagram showing how a line sensor outputs one line in a main scanning direction when a book document placed on a raised outer plate is read.

FIG. 13 is a diagram showing an output state of the line sensor when the placing plate rises and a gap is created between the book document and the placing plate.

FIG. 14 is a diagram showing a state in which a book document is placed with one of the left and right pages of the present apparatus having only a front cover.

FIG. 15 is a diagram illustrating a method of obtaining a document height by a second height detection process.

FIG. 16 is a diagram showing a distribution of height data in the first height detection process in the case of the state of FIG.

FIG. 17 is a diagram showing a state in which a document is tilted and, as a result, is set apart from the distance measuring mirror.

FIG. 18 is a diagram showing a distribution of height data in the first height detection method in the case of the state of FIG. 17;

FIG. 19 is a diagram showing a distribution of height data in the second height detection process when a book document is placed apart from the reference plate.

FIG. 20 is a diagram showing a block configuration of a control circuit of the present apparatus.

FIG. 21 is a flowchart showing the procedure of a reading operation controlled by the CPU of the image reading apparatus.

FIG. 22 is a diagram showing a state in which when the document table is lowered, a step is formed between the document table and the main body cover, and a shadow of light from the illumination unit is generated on an upper portion of the surface of the document table.

FIG. 23 is a perspective view schematically showing a placement plate of a document table according to another embodiment as viewed from the back side.

FIG. 24 is a diagram showing a distribution in which the side surface of the placing plate of the document table shown in FIG. 23 is detected in the sub-scanning direction.

FIG. 25 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 26 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 27 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 28 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 29 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 30 is a diagram showing means for detecting the height of a document according to another embodiment.

FIG. 31 is a diagram showing means for detecting the height of a document according to another embodiment.

[Explanation of Codes] 1 ... Original platen, 2 ... Imaging camera section, 3 ... Illumination section, 5 ... Mirror, 6 ... Imaging lens, 7 ... CCD line sensor, 30 ... Image processing circuit, 33 ... CPU, B ... Original.

Claims (1)

[Claims] 1. An image reading apparatus in which a thick document such as a book is placed upward and the document is read from above by a reading unit, and a document table movable up and down, and means for detecting the height of the document table. An image reading apparatus comprising: means for detecting the height of a document placed on a document table; and correction means for correcting an image based on the detected document table height and document height.