Image reading device and image reading method

Abstract

To provide an image reading device and an image reading method which enable a user to easily find a document defect and accurately cut out an image, with a simple structure as it is.SOLUTION: An image reading device comprises a control unit 15 for controlling reading of an image. The control unit 15 reads, in the absence of a document, a white background part and a black background part of background plates 13c of image sensors 13e serving as a reading unit, generates white shading data being correction data for correcting read data of a document based on the read data of the read white background part and the black background part, and after reading the image of the document, cuts out the image data of the document based on the read data of the document in the black background part opposing the black background part.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image reading apparatus and an image reading method.

Background Art

[0002] In an image reading apparatus, it is necessary to reduce the influence of density unevenness between pixels caused by uneven illumination of a reading light source. For this reason, the dark reference data when the image signal output from the image sensor is converted into digital data when the reading light source of the image sensor is turned off and read, and the white reference data when the image signal output from the image sensor is converted into digital data when a pure white white reference image is read are stored. By the shading correction function based on the dark reference data and the white reference data, the influence of density unevenness between pixels of the digital data obtained by converting the output analog signal of the image sensor by an analog / digital (A / D) converter is reduced. In the case of a scanner which is an image reading apparatus, a background plate is provided facing the image sensor. This background plate should be as white as possible for obtaining white reference data as described above.

[0003] On the other hand, in the case of a document with a white background color, it is convenient for the purpose of finding document defects or for an image cropping function to eliminate the margins of the read image that the background plate is black. For this reason, there is a device having a function of switching the background plate from white to black. There may be a case where there is a dark area such as a photograph or a drawing in a part of the document, and the darker the black background plate is, the more accurately it can be detected. For this reason, as an image reading apparatus capable of changing the background plate from white to black or from black to white so as to read white and black backgrounds, the one disclosed in Patent Document 1 is known.

[0004] In the image reading apparatus disclosed in Patent Document 1, white and black background plates are prepared, and by moving the background plate, the background plate facing the image sensor can be made white or black.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-98716 [Overview of the project] [Problems that the invention aims to solve]

[0006] The conventional image reading devices described above have a mechanism for moving the background plate, which presents the challenge of a complex structure. This invention makes it easier to detect missing parts in the original document and enables accurate image extraction while maintaining a simple structure. [Means for solving the problem]

[0007] This invention relates to the transport of a document. In the transport route An image reading device comprising a reading unit arranged in a width direction intersecting the transport direction for reading an image of the transported document, and a background plate arranged opposite the reading unit, wherein the reading unit and the background plate are fixed so as not to move in the transport direction, and the background plate is arranged opposite the reading area of ​​the reading unit in the transport path and includes a high-brightness white background area for shading correction and a black background area with lower brightness than the white background area for shading correction and document cutting, the area of ​​the black background area is larger than the area of ​​the white background area, and the white background area and the black background area are arranged side by side in the main scanning direction of reading by the reading unit.

[0008] In the above configuration, the reading unit and the background plate are the original document In the transport routeThe background plate is fixed so as not to move in the transport direction. The background plate is positioned opposite the reading area of ​​the reading unit in the transport path and includes a high-brightness white background area for shading correction and a black background area with lower brightness than the white background area for shading correction and for cutting out the original document. Furthermore, since the white background area and the black background area are arranged side by side in the main scanning direction of reading by the reading unit, when the fixed reading unit reads the fixed background plate, it outputs so-called white image data based on the high-brightness white background area and so-called black image data based on the low-brightness black background area. In addition, the area of ​​the black background area is larger than the area of ​​the white background area, and for example, the length of the edge corresponding to the black background area is longer than the length of the edge corresponding to the white background area at the boundary between the edge of the original document and the background plate. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view showing the configuration of an image reading device. [Figure 2] This is a schematic plan view showing the configuration of the transport path for the image reading device. [Figure 3] This is a schematic block diagram showing the overall configuration of the image reading device. [Figure 4] This is a schematic diagram showing the background plate and image sensor. [Figure 5] This is a flowchart of the conventional pre-processing steps. [Figure 6] This figure shows the output characteristics of the image sensor. [Figure 7] This is a flowchart for calculating conventional white shading data. [Figure 8] This is a flowchart of the pretreatment process for the present invention. [Figure 9] This figure shows the output of the reading unit corresponding to the background plate of the present invention. [Figure 10] This is a flowchart for calculating the white shading data of the present invention. [Figure 11] This figure shows the first pattern of the manuscript cutting process. [Figure 12] It is a diagram showing a second pattern of the original document cutting process. [Figure 13] It is a diagram showing a third pattern of the original document cutting process. [Figure 14] It is a schematic diagram showing a background plate and a reading unit according to a modified example. [Figure 15] It is a diagram showing a fourth pattern of the original document cutting process. [Figure 16] It is a diagram showing a fifth pattern of the original document cutting process. [Figure 17] It is a schematic diagram showing a background plate and a reading unit according to a modified example. [Figure 18] It is a diagram showing a sixth pattern of the original document cutting process. [Figure 19] It is a schematic diagram showing a background plate and a reading unit according to a modified example. [Figure 20] It is a schematic diagram showing a background plate and a reading unit according to a modified example. [Figure 21] It is a diagram showing a sixth pattern of the original document cutting process. [Figure 22] It is a schematic diagram showing a background plate and a reading unit according to a modified example.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described based on the drawings. FIG. 1 is a schematic cross-sectional view showing the configuration of an image reading apparatus, FIG. 2 is a schematic plan view showing the configuration of the conveyance path of the image reading apparatus, and FIG. 3 is a schematic block diagram showing the overall configuration of the image reading apparatus. The image reading apparatus 10 includes a placement unit 11 for placing the original document G, a conveyance unit 12 for conveying the original document G placed on the placement unit 11 along a predetermined conveyance path, a reading unit 13 for reading the conveyed original document G, a detection unit 14 for detecting the presence or absence of the original document G in the conveyance path, a control unit 15 for controlling the present image reading apparatus 10, and a touch panel 16 capable of display and input. In a system in which a control device such as an external personal computer is connected to the image reading apparatus 10, the control device may perform control and determination together with the control unit 15.

[0011] The transport unit 12 includes a feed roller 12a positioned on the lower side of the transport path, a separation roller 12b positioned on the upper side of the transport path opposite to the feed roller 12a, transport rollers 12c positioned on the upper and lower sides of the transport path, and discharge rollers 12d positioned on the upper and lower sides of the transport path. Transport rollers 12c and 12d, located on the lower side of the transport path, are connected to a drive mechanism and are rotationally driven. Transport roller 12c transports the document G to the reading unit 13, and discharge roller 12d transports and discharges the document G that has been read by the reading unit 13.

[0012] The feed roller 12a and the separation roller 12b are positioned in the central part of the width direction of the conveying path. The conveying roller 12c and the discharge roller 12d are positioned downstream of the feed roller 12a and the separation roller 12b in the conveying direction. The width of each roller of the conveying roller 12c and the discharge roller 12d is wider than the width of the roller of the feed roller 12a. Also, the width of each roller of the conveying roller 12c and the discharge roller 12d is wider than the width of the roller of the separation roller 12b. The detection unit 14 detects the presence or absence of the original document G at each part of the transport path and includes a placement unit detection sensor 14a that detects the original document at the placement unit 11, an original document detection sensor 14b that detects the original document at a downstream position near the transport roller 12c, and a double feed detection sensor 14c that detects double feeding.

[0013] The reading unit 13 comprises a pair of reading units 13a and 13b facing each other across the transport path. Each reading unit 13a and 13b is equipped with a background plate 13c, an LED 13d as a light source, and an image sensor 13e as the reading unit. The LED 13d emits light toward the opposing document, and the image sensor 13e outputs a detection signal corresponding to the intensity of the reflected light. The background plate 13c is located on the opposite side of the document. The image sensor 13e has numerous reading elements arranged in a line in the width direction of the transport path, with each reading element corresponding to one pixel. The reading units 13a and 13b read images from both sides of the document G as it is transported along the transport direction. The image sensor is also called a line sensor.

[0014] The image sensor 13e of the reading unit 13 is positioned to intersect with the document transport path and corresponds to the reading unit that reads the image of the document G as it passes through the transport path. The background plate 13c is positioned opposite the image sensor 13e, which is the reading unit, across the transport path. In this embodiment, the background plate 13c and the image sensor 13e are fixed in predetermined positions so as not to move in the direction of document transport. Furthermore, because they are fixed, the background plate 13c and the image sensor 13e do not rotate.

[0015] The touch panel 16 displays a predetermined image based on instructions from the control unit 15, and outputs the touch position to the control unit 15 when the user touches it. The control unit 15 can instruct the user to display a menu or acquire the user's operation based on the user's touch position.

[0016] Figure 4 is a schematic diagram showing the background plate and image sensor. The image sensor 13e has numerous reading elements arranged in a row in the width direction of the transport path. In this embodiment, however, the remaining reading elements are used, excluding those at both ends and their vicinity, and the width of the reading elements used becomes the maximum effective pixel width. The background plate 13c is positioned opposite the reading area of ​​the image sensor 13e. The ends of the transport path in the width direction are high-brightness white background sections 13c1, 13c1 for shading correction, and the section in between is a black background section 13c2 with lower brightness than the white background section 13c1, for shading correction and document cutting. That is, the white background section 13c1, the black background section 13c2, and the white background section 13c1 are arranged in a row in the main scanning direction of reading by the image sensor 13e, which is the reading unit.

[0017] Thus, the white background section 13c1 is provided in the areas at both ends of the background plate 13c in the direction intersecting the transport path, and the black background section 13c2 is provided in the area between the white background sections 13c1, 13c1.

[0018] The high-brightness white background area 13c1 generally refers to a color as white as possible, and the black background area 13c2, which is lower in brightness than the white background area 13c1, generally refers to a color as black as possible. There is no specific brightness threshold. Also, the white background area 13c1 can be substituted with an intermediate gray.

[0019] The black background area 13c2 positioned in the center is wider than the expected width of the main document G, and in comparison, the white background areas 13c1 positioned at both ends only occupy the remaining portion at the ends. In other words, the area of ​​the black background area 13c2 is larger than the area of ​​the white background area 13c1. For example, if the expected main document G is precisely positioned in the center in the width direction of the transport path and transported straight without distortion, then parts of the black background area 13c2 will appear on both sides in the width direction of the document G, and the image sensor 13e will be able to read the black background area 13c2 as an image.

[0020] The white background portion 13c1 and the black background portion 13c2 of the background plate 13c are arranged on the same plane at the same distance from the image sensor 13e, which is the reading portion. The image sensor 13e, which is the reading portion, has multiple reading elements arranged in the main scanning direction, and a portion of the white background portion 13c1 is positioned opposite the effective reading elements near the ends of the reading elements. In this embodiment, the reading elements face the white background portion 13c1 at both ends within the range of the maximum effective pixel width, but within the range of the maximum effective pixel width, they may be positioned to face only the white background portion 13c1 at one end. By making the distance from the image sensor 13e, which is the reading unit, to the background plate 13c the same, the accuracy of shading correction and cropping processing is improved.

[0021] In the image reading device 10 of this embodiment, a document supply unit 11 and a feed roller 12a are located at the starting end of the transport path to supply the original document G. Furthermore, a separation roller 12b is located approximately in the center of the transport path in the width direction to prevent multiple original documents from being supplied. In relation to this separation means, the black background section 13c2 of this embodiment is located in the width direction, which is the direction intersecting the transport direction, and includes the separation roller 12b, while the white background sections 13c1, 13c1 are located in a position that does not include the separation roller 12b.

[0022] Furthermore, the document detection sensor 14b is located approximately in the center of the transport path, the black background section 13c2 is located in the width direction, which is the direction intersecting the transport direction, and includes the document detection sensor 14b, while the white background sections 13c1, 13c1 are located in the direction that does not include the document detection sensor 14b. Similarly, the double feed detection sensor 14c is located near the middle of the transport path, although not in the exact center. The black background section 13c2 is located in the width direction relative to the transport direction, including the double feed detection sensor 14c, while the white background sections 13c1, 13c1 are located in the width direction, excluding the double feed detection sensor 14c. In addition, the separation roller 12b, transport roller 12c, discharge roller 12d, document detection sensor 14b, and double feed detection sensor 14c are located between the white background sections 13c1, 13c1. Furthermore, both the white background section 13c1, 13c1 and the black background section 13c2 are located opposite LED 13d.

[0023] Figure 5 is a flowchart of the conventional pre-processing, Figure 6 shows the output characteristics of the image sensor, and Figure 7 is a flowchart for calculating conventional white shading data. Figure 6 shows the input-output relationship of each reading element that makes up the image sensor 13e. In this figure, the horizontal axis represents the input and the vertical axis represents the output. When a black background (black target) is imaged without illuminating the reading element, and when an as white reference chart (white target) is imaged with illumination, the output values ​​range from the darkest input to the brightest input, as shown on the horizontal axis. This indicates that the output of the reading element changes in the range of 0 to 255 within that range.

[0024] As shown in Figure 6, the input changes within the range of real-world black (minimum) to white (maximum), and does not necessarily change from zero to the maximum value in absolute terms. Therefore, the output does not change from zero (0) to the maximum value (255). For this reason, processing is required to correlate the change range of the output element of each reading element with the maximum actual change range of brightness. This mapping requires processing at the time of factory shipment and processing at the start of scanning. Figure 5 shows the factory shipment processing. Note that the conventional background plate can be switched between white or gray and black, as described above, and at the time of factory shipment below, the white or gray side will be set as the background plate side.

[0025] The process involves, in step S102, having the image sensor perform a reading operation with the LED turned off to acquire black reference data BK; in step S104, having the image sensor read the background plate with the LED turned on to acquire background plate data GR; and in step S106, calculating the background plate RAW data based on the following formula (1), and then storing the background plate RAW data in non-volatile memory. Background panel RAW data = GR - BK …(1)

[0026] Next, in step S108, with the LEDs lit, the white reference chart is placed along the transport path, and the image sensor is made to perform a reading operation to acquire the white reference data WH. In step S110, the white reference RAW data is calculated based on the following formula, and then the white reference RAW data is stored in the non-volatile memory. White-based RAW data = WH - BK …(2) In this way, at the time of factory shipment, the background plate RAW data and the white reference RAW data are stored in non-volatile memory.

[0027] Due to various factors such as aging, the input / output characteristics of the image sensor change. Therefore, a process to calculate white shading data to correct this is performed immediately before scanning. In this process, a white or gray surface is used as the background plate surface.

[0028] In step S122, with the LED turned off, the image sensor is made to perform a reading operation to obtain black reference data BK_S. In step S124, with the LED turned on, the image sensor is made to perform a background plate reading operation to obtain background plate data GR_S. In step S126, the previous background plate RAW data is calculated based on the following equation (3). Immediate background plate RAW data = GR_S - BK_S …(3)

[0029] Next, in step S128, the white shading data is calculated based on the following equation (4) using the white reference RAW data and background plate RAW data stored in the non-volatile memory, as well as the calculated previous background plate RAW data. White shading data = (White base RAW data) / (Background board RAW data) × Previous background board RAW data …(4)

[0030] The value Dout, obtained by applying shading correction to each input pixel data Din, is expressed by the following equation (5). Dout=(Din-Bk) / (Wh-Bk)×255 …(5) Once the white shading data is calculated, the surface of the background plate is mechanically changed to a black surface. This is because a black background plate increases the difference in brightness between it and the original document, thereby improving the accuracy of the original document cutting.

[0031] In order to calculate white shading data using this process while simultaneously improving the accuracy of document cutting, conventional methods required a background plate with two sides, white and black, and a mechanism to switch between the two sides. In contrast, the background plate 13c of this embodiment, as shown in Figure 4, is not configured to switch between surfaces, but rather has a white background section 13c1 at both ends and a black background section 13c2 in the center.

[0032] Therefore, the reading element of the image sensor 13e facing the white background portion 13c1 cannot measure the input / output relationship when facing the black background portion, and the reading element of the image sensor 13e facing the black background portion 13c2 cannot measure the input / output relationship when facing the white background portion. In this embodiment, in light of situations where measurement is not possible, the measurement results are supplemented by calculation. All calculations are performed by the control unit 50 or an externally connected PC.

[0033] Figure 8 is a flowchart of the pre-processing steps of the present invention, and Figure 9 shows the output of the reading unit corresponding to the background plate of the present invention. First, in step S202, with the LED 13d turned off, the image sensor 13e is made to perform a reading operation to acquire black reference data BK. Then, in step S204, with the light LED 13d turned on, the image sensor 13e is made to perform a reading operation of the background plate 13c to acquire background plate data GR. The background plate data GR includes data for the white background area 13c1 and data for the black background area 13c2. After that, in step S206, the image sensor 13e is made to perform a reading operation of the white reference chart to acquire white reference data WH. The white reference data WH is stored in the non-volatile memory.

[0034] Next, in step S208, the calculation for the missing measurement results mentioned above is performed. First, since the center of the background plate 13c is black, the following calculation is performed to create data for the center. The difference between the white reference data WH and the white background portion 13c1 of the background plate 13c is calculated. This is done by calculating the L difference using equation (6) and the R difference using equation (7) for the leftmost data (white) GR_L of the leftmost white background portion 13c1 and the rightmost data (white) GR_R of the rightmost white background portion 13c1, and then calculating them individually. Here, it is sufficient to calculate the average value for all pixels in the region. L difference = (white reference data WH_L) - (left edge data of background plate (white) GR_L) ... (6) R difference = (white reference data WH_R) - (background panel right edge data (white) GR_R) ... (7)

[0035] Next, based on equations (8) and (9), the measurement results for the pixels in the central part of the missing background plate 13c against a white background (background plate center left data GR_S_L and background plate center right data GR_S_R) are calculated. Background panel center left data GR_S_L = White reference data WH (center) - L difference …(8) Data for the right center of the background panel GR_S_R = White reference data WH (center) - R difference …(9) In this way, the background plate data "GR" consists of values ​​arranged from left to right as GR_L, GR_S_L, GR_S_R, and GR_R.

[0036] In other words, in order to obtain white shading data, a white background area 13c1, which is a white or gray area with high brightness, is required as the background plate 13c, but this is insufficient in the black background area 13c2. Therefore, for the black background area 13c2, the difference between the measurement results of the white background area 13c1 measured at both ends and the white reference chart is calculated, and the measurement result corresponding to the white background area is estimated by subtracting this difference from the measurement result of the white reference chart measured in the black background area 13c2.

[0037] In the case of equations (6) to (9), in order to improve the accuracy of the estimation, the difference value at the left edge and the difference value at the right edge are separated, and for the black background area 13c2, the difference value at the left edge is applied to the area close to the left edge, and the difference value at the right edge is applied to the area close to the right edge. LED 13d does not illuminate the entire surface, but some have the light source placed at the right edge or left edge and use a light guide plate to spread the light to the entire surface. In such cases, even when a light guide plate is used, the illuminance on the side opposite to the position of the light source tends to be low. For this reason, the accuracy may be further improved by applying the difference value at the left edge and the difference value at the right edge to the central pixel, weighted according to the distance from the light source.

[0038] In this manner, for the area of ​​the background plate 13c designated as the low-luminance black background area 13c2, the background plate data GR was calculated from the measurement results in the black background area 13c2 relative to the white reference chart, using the difference value between the high-luminance white background area 13c1 and the white reference chart. In this embodiment, white background sections 13c1, 13c1 are placed at both ends, and a black background section 13c2 is placed in the center. However, background plate data can be obtained even with the black background section 13c2 by using the measurement results of the white background section 13c1. Therefore, various variations in the arrangement of the white background section 13c1 and the black background section 13c2 are possible, and these will be described later. However, by providing a white background section 13c1, which serves as a white reference, at both ends, it is possible to increase the amount of white reference data acquired compared to providing it at only one end, which leads to improved shading correction.

[0039] Subsequently, in step S210, the background board RAW data is calculated based on the following equation (10), and in step S212, the white reference RAW data is calculated based on the equation (11). Background panel RAW data = GR” - BK …(10) White-based RAW data = WH - BK …(11) The data is stored in non-volatile memory and shipped from the factory.

[0040] Figure 10 is a flowchart for calculating the white shading data of the present invention. Immediately before scanning, the white shading data is calculated as follows: In step S222, with the LED 13d turned off, the image sensor 13e is made to perform a reading operation to obtain the black reference data BK_S. In step S224, with the LED 13d turned on, the background plate 13c is made to be read by the image sensor to obtain the background plate data GR_S. The background plate data GR_S is calculated in the same manner as equations (6) to (9). At this time, the white reference data WH stored in the non-volatile memory is used. Subsequently, in step S226, the RAW data of the background plate immediately preceding the image is calculated based on equation (12).

[0041] Previous background RAW data = GR_S - BK_S …(12) Furthermore, in step S228, the calculation is performed based on equation (13). White shading data = (White base RAW data) / (Background board RAW data) × Previous background board RAW data … (13) As described above, according to the present invention, shading correction and document cutting can be performed appropriately without providing a mechanism for switching between white and black on the background plate, and the number of parts can be reduced.

[0042] As described above, the image reading device of the present invention includes a control unit 15 that controls the reading of the image. This control unit 15 reads the white background area 13c1 and the black background area 13c2 with the image sensor 13e, which is the reading unit, when there is no original document G present, and generates correction data to correct the reading data of the original document G based on the reading data of the white background area 13c1 and the black background area 13c2 that it has read.

[0043] As described above, the black background area 13c2 positioned in the center is wider than the expected width of the main document G. If the expected main document G is accurately positioned in the center in the width direction of the transport path and transported straight, then parts of the black background area 13c2 will appear on both sides of the document G in the width direction, allowing for accurate image cropping. However, the original document G does not always pass straight and without tilt as expected, through the center of the transport path. The following describes the original document cutting process when the black background section 13c2 is placed on the background plate 13c.

[0044] • When the edges of the background panel are white and the center is black. The background plate 13c has white background sections 13c1, 13c1 positioned on the outer edges in the width direction, with a black background section 13c2 positioned between them. The width of the black background section 13c2 is wider than the width of the expected main document G. When the size is such that pixels included in the white areas at both ends of the width direction of the background plate 13c are excluded from processing, and the document is cut out from the black area.

[0045] Figure 11 shows the first pattern of the document cutting process. 1) If the original document G is within the size of the black background area 13c2, then the scanned image data should ideally contain four vertices within the black area. 1: Extract the parts that form vertices within the black region. 2. If four vertices are extracted, identify the straight line formed by connecting the four vertices as the black boundary and determine its slope. 3: Use the black border of the black background to crop the image and correct the tilt. As shown on the left side of Figure 11, the entire original document G is contained within the black area, and as shown on the right side of the same figure, the image formed by connecting the four vertices is cropped after tilt correction.

[0046] 2) When the original document G falls within the white area of ​​the background plate 13c Figure 12 shows a second pattern of the document cutting process. (Part 1) 1: Extract the parts that form vertices within the black region. 2: If there are three vertices within the black region, identify the black boundary forming the top edge and determine its slope.

[0047] From this point on, two methods of cutting are possible. 3-1: Determine the coordinates of the remaining vertex in the white region based on the coordinates of the three vertices. Crop the image containing the four vertices after tilt correction. The process of cropping the image containing the four vertices after tilt correction is the same as the method shown in Figure 11. 3-2: Cut out the part of the image that extends into the white area, correct the tilt, and then crop it. Cutting the image results in an irregular pentagon shape, but it doesn't look out of place because the background is white. As shown on the left side of Figure 12, there are three vertices within the black region. As shown in the center of the same figure, assuming there are four vertices, the image of the white region is ignored, and as shown on the right side of the same figure, only the part included in the black region is tilt-corrected and cropped out.

[0048] In this way, the control unit 15 does not use the reading data of the part of the document G that extends beyond the black area if three of the four vertices of the document G are within the black area. By doing so, the accuracy of document cutting can be improved and the amount of data can be reduced.

[0049] (Part 2) If there are no vertices within the black region, or if there are one or two vertices within the black region, it is difficult to accurately determine the edge of the image because there are no three vertices within the black region. Figure 13 shows the third pattern of the document cutting process. As shown in the upper part of the figure, both the left and right sides overlap with the white area. Although the exact position of the image is unknown because all four corners are in the white area, it is always within the paper transport path.

[0050] 1: Assume the case where the document is shifted to the leftmost end of the transport path. This is shown on the left side of the lower section of Figure 13. 2: The slope of the black boundary forming the upper edge that appears near the top edge of the black region. Assuming that the original document G is shifted to the left of the transport path, the intersection of the line extending the upper edge black boundary to the left and the left end of the transport path can be considered as one vertex. 3. By considering the slope of the black boundary at the top edge and using the assumed intersection point as one vertex, and finding the black boundary that forms the bottom edge appearing near the bottom edge within the black region, the length of the image can be determined. 4. Once the image length is determined, consider the side edges that intersect the top edge at a 90-degree angle from the previously assumed intersection point, and identify the leftmost vertex of the bottom edge based on the calculated image length. Then, determine the distance L1 between this vertex and the left edge of the white region. 5. Regarding the right edge, if we assume that the original document G is shifted to the right of the transport path, based on the slope of the black boundary forming the bottom edge that appears near the bottom edge of the black region, then we can assume that the intersection of the line extending the black boundary of the bottom edge to the right and the right edge of the transport path is one vertex. 6. Using the intersection point on the right side of the bottom edge as a vertex, we assume a side edge that intersects the bottom edge at a 90-degree angle from the intersection point, and identify the rightmost vertex of the top edge from the length of the image obtained. Then, we determine the distance L2 between this vertex and the right edge of the white region. 7: The lower left side of Figure 13 shows the image enclosed by the four identified vertices. As shown in the center of the same figure, the left side is cut out from the left edge by a width of length L1, and the right side is cut out from the right edge by a width of length L2. 8. Finally, crop the image with both sides cut off by correcting the previously determined tilt. At this point, the left and right edges of the cropped image may contain a white background, but since it is white, it will not look unnatural.

[0051] As described above, the image reading device of the present invention includes a control unit 15 that controls the reading of the image. This control unit 15 generates correction data for correcting the reading data of the original document G as described above, and further extracts the image data of the original document based on the reading data of the original document G in the black areas after reading the image of the original document G. Therefore, with a simple background plate structure in which only a portion of a fixed surface is designated as a white background area 13c1 and the remainder as a black background area 13c2, the accuracy of cutting out the original document can be improved.

[0052] Furthermore, if two or fewer of the four vertices of the document G are located within the black region, the control unit 15 identifies the leading or trailing vertex of the document G based on the intersection of the extension of the leading or trailing edge (black boundary) of the document passing through the black region and the edge (left or right edge) of the reading area in the image sensor 13e of the reading unit, which is a white region. Based on the distances L1 and L2 obtained using this vertex as a reference, the control unit 15 avoids using the reading data for areas outside the reading area.

[0053] As mentioned above, in the background plate 13c, it is not necessarily required that the white background sections 13c1, 13c1 be located at both ends and the black background section 13c2 be located in the center. Figure 14 is a schematic diagram showing a background plate and reading unit according to a modified example. As shown in the figure, compared to the background plate 13c described above, the white background section 13c1 located on the right has been removed, and the black background section 13c2 has been extended to this area. Based on the maximum effective pixel width of the image sensor 13e, the reading element at the left end of the image sensor 13e faces the white background section 13c1, and the reading element at the right end faces the black background section 13c2. One end of the background plate 13c is white (either the left side or the right side only), and the remaining part of the background plate 13c, excluding the end, is black.

[0054] If the read image data contains four vertices within a black region, the straight line formed by connecting the four vertices is identified as the black boundary, and its slope is corrected before extraction.

[0055] When the original document G overlaps the white area of ​​the background plate. If there are three vertices within the black region Figure 15 shows the fourth pattern of the document cutting process. In this case, the method for cutting out the original document is to apply the case where the original document G overlaps the white area of ​​the background plate, and where three vertices are included within the black area, as shown in (Part 1). Figure 16 shows the fifth pattern of the document cutting process. In this case, when cutting out the original document, if the original document G overlaps the white background plate, the previously mentioned "case where there are no vertices in the black area or there are 1-2 vertices in the black area (part 2)" should be applied.

[0056] Figure 17 is a schematic diagram showing a modified version of the background plate and reading unit. As shown in the figure, compared to the background plate 13c described above, the boundary between the white background areas 13c1 on the left and right and the black background area 13c2 in the center is a gradient that is just barely not detectable by edge detection in image processing. Since the gradient itself is not extracted by edge detection, the edges of the original document can be extracted by edge detection. Thus, a gradient background area with gradually changing brightness is provided between the white background area 13c1 and the black background area 13c2.

[0057] Figure 18 shows the sixth pattern of the document cutting process. If there are four vertices in the black region, simply extract the image as is. If there are three vertices, apply the method described in (Part 1) above.

[0058] When the original document overlaps the background plate in the gradient area If there are two vertices within a black area and a gradient area 1: Determine the slope from the upper edge black boundary that appears at the upper end of the black region. 2. Find the vertices that exist within the gradient region. 3. Extract an image from two vertices in the black region and two vertices found by edge detection, then perform tilt correction to extract the image. As shown in Figure 18, the two vertices on the left side of the original G are in the gradient region, and the two vertices on the right side are in the black region. Therefore, four vertices can be identified. If all four vertices of manuscript G are entirely within the white area of ​​the background plate, then the previously mentioned "case where there are no vertices in the black area or where there are 1-2 vertices in the black area (part 2)" should be applied.

[0059] Figure 19 is a schematic diagram showing a modified version of the background plate and reading unit. The background plate 13c shown in the figure is a background plate 13c in which one end is white (only the left side or only the right side) and the remaining end is black, as shown in Figure 14. The boundary between the white background portion 13c1 and the black background portion 13c2 is a gradient that is just barely not detectable by image processing.

[0060] If there are vertices within the black region and the gradient region 1: Find two vertices within the black region. 2. Find vertices within the gradient region using edge detection. 3: Determine the slope from the upper edge black boundary that appears at the top of the black region. 4. Crop the image enclosed by the four vertices you found, correcting for tilt.

[0061] If the vertex is within the white region The previously mentioned case, "when there are no vertices within the black region or when there are 1-2 vertices within the black region (part 2)," should be applied.

[0062] Figure 20 is a schematic diagram showing a modified version of the background plate and reading unit. As shown in the figure, it is also possible to make the background plate 13c a black and white stripe. In this manner, multiple white background sections 13c1 and black background sections 13c2 are arranged alternately.

[0063] Figure 21 shows the sixth pattern of the document cutting process. If there are no vertices within the black region, or if there are one or two vertices within the black region, you should perform the same processing as in "When there are no vertices within the black region or if there are one or two vertices within the black region (part 2)". If there are three vertices within the black area, the original document G can be tilt-corrected and cropped using two methods, as shown in (Method 1) above.

[0064] Figure 22 is a schematic diagram showing a modified version of the background plate and reading unit. As shown in the figure, the background plate 13c is made of black and white stripes, and the boundary between the white background area 13c1 and the black background area 13c2 is a gradient that is just barely not detectable by image processing.

[0065] If a vertex is located within a black area or gradient area 1: Determine the slope from the upper edge black boundary that appears at the upper end of the black region. 2. Find vertices within the gradient region using edge detection. 3. Find the vertices within the black area. 4. Crop the image enclosed by the four vertices you found, correcting for tilt. If there are vertices within the white region, the same processing as in "When there are no vertices in the black region or when there are 1-2 vertices in the black region (part 2)" should be performed. In this way, by preparing a background plate with a black background in the center and white backgrounds at both ends, aligned in the main scanning direction, it is not necessary to switch between the white and black parts of the background plate, enabling shading correction and image cropping with an inexpensive configuration. In particular, the black center of the background plate is useful for detecting defects in the original document.

[0066] This invention can be understood not only as an invention of a tangible article, but also as an invention of a method, considering the processing steps involved, which are evident from the flowcharts. It goes without saying that the present invention is not limited to the embodiments described above. It goes without saying that those skilled in the art will understand this, - Apply the mutually interchangeable members and configurations disclosed in the above embodiments by appropriately changing their combinations. • Although not disclosed in the above embodiments, it is possible to appropriately substitute and modify the combinations of publicly known components and components that are interchangeable with those disclosed in the above embodiments. • Although not disclosed in the above embodiments, the members and components that a person skilled in the art could conceive of as substitutes for the members and components disclosed in the above embodiments based on prior art, etc., may be appropriately substituted, and their combinations may be modified for application. This is disclosed as one embodiment of the present invention. [Explanation of Symbols]

[0067] 10...Image reading device, 11...Placement unit, 12...Transport unit, 12a...Feeding roller, 12b...Separation roller, 12c...Transport roller, 12d...Discharge roller, 13c1...White background unit, 13c2...Black background unit, 13(13a,13b)...Reading unit, 13c...Background plate, 13c1...White background unit, 13c2...Black background unit, 13d...LED, 13e...Image sensor, 14...Detection unit, 14a...Placement unit detection sensor, 14b...Document detection sensor, 14c...Double feed detection sensor, 15...Control unit, 16...Touch panel.

Claims

1. A reading unit is positioned in the width direction intersecting the transport direction in the transport path through which the document is transported, and reads the image of the transported document. An image reading device comprising a background plate positioned opposite the reading unit, The reading unit and the background plate are fixed so as not to move in the transport direction. The background plate is positioned opposite the reading area of ​​the reading unit and includes a high-brightness white background area for shading correction and a black background area with lower brightness than the white background area for shading correction and for cutting out the original document. The area of ​​the black background is larger than the area of ​​the white background. An image reading device characterized in that the white background portion and the black background portion are arranged side by side in the main scanning direction for reading by the reading unit.

2. A document supply unit for supplying the document is located at the starting end of the transport path. A separation mechanism is positioned approximately in the center of the width direction of the transport path to prevent multiple documents from being supplied at once. The image reading device according to claim 1, characterized in that the black background portion is located in a position including the separation means in the transport direction, and the white background portion is located in a position not including the separation means.

3. The image reading device according to claim 1 or 2, characterized in that the white background portion and the black background portion of the background plate are arranged on the same plane at the same distance from the reading portion.

4. The image reading device according to any one of claims 1 to 3, characterized in that the white background portion is provided in the region at both ends of the background plate in a direction intersecting the transport path, and the black background portion is provided in the region between the white background portions.

5. The image reading device according to any one of claims 1 to 4, characterized in that the reading unit has a plurality of reading elements arranged in the main scanning direction, and a part of the white background is positioned opposite to the effective reading elements near the ends of the reading elements.

6. The image reading device according to any one of claims 1 to 5, characterized in that a gradient background portion with gradually changing brightness is provided between the white background portion and the black background portion.

7. The image reading device according to any one of claims 1 to 6, characterized in that a plurality of the white background portion and the black background portion are arranged alternately.

8. It includes a control unit that controls the reading of the image. The control unit reads the white background area and the black background area with the reading unit when there is no original document, and generates correction data to correct the original document reading data based on the read data of the white background area and the black background area. The image reading device according to any one of claims 1 to 7, characterized in that, after reading the image of the document, it extracts image data of the document based on the reading data of the document in the black background area.

9. The image reading device according to claim 8, characterized in that the control unit does not use the reading data of the original document that extends beyond the black background when three of the four vertices of the original document are located within the black background area.

10. The image reading device according to claim 8, characterized in that, if two or fewer of the four vertices of the original document are located within the black background area, the control unit identifies the vertex of the trailing end of the original document based on the intersection of the extension of the leading edge of the original document passing through the black background area and the edge of the reading area in the reading unit, and does not use the reading data of the area outside the reading area based on that vertex.

11. A reading unit is positioned so as to intersect the transport direction in the transport path through which the document is transported, and reads the image of the transported document. A background plate is positioned opposite the reading unit, Equipped with, The reading unit and the background plate are fixed so as not to move in the document transport direction. The background plate is positioned opposite the reading area of ​​the reading unit and includes a high-brightness white background area for shading correction and a black background area with lower brightness than the white background area for shading correction and for cutting out the original document. The area of ​​the black background is larger than the area of ​​the white background. An image reading method for an image reading device, wherein the white background portion and the black background portion are arranged side by side in the main scanning direction for reading by the reading unit, The process includes: reading the white background area and the black background area with the reading unit when the original document is not present, and generating correction data to correct the original document reading data based on the reading data of the white background area and the black background area that have been read; An image reading method for an image reading device, characterized by comprising the steps of: reading the image of the document, and then cutting out image data of the document based on the reading data of the document in the black background area.

Images