Image reading apparatus

Abstract

To surely detect an end side of an original without being affected by a noise shadow caused by ruggedness or the like of a surface of the original.SOLUTION: The first lighting device 31 can selectively irradiate the target area with the light of the first primary color and the light of the second primary color from the first irradiating section 310. The second illumination device 32 is configured to irradiate the target area with light of a third primary color from the second irradiating section 320. The control portion 5b causes the first illumination device 31 and the second illumination device 32 to execute a sequential radiation process of sequentially radiating light of the three primary colors to the target area when the optical scanning process is executed. When the optical scanning process and the sequential irradiation process are executed, the image data output portion 4 sequentially outputs line image data of three colors corresponding to the detected light amounts of the light of the three primary colors detected by the line sensor. A linear shadow image along the front end side or the rear end side of the document is detected from the plurality of sets of three color line image data.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image reading device capable of detecting the leading edge of a document. [Background technology]

[0002] The image reading device includes a light irradiation unit, a scanning device, a line sensor, and an AFE (Analog Front End). The light irradiation unit sequentially irradiates light of three primary colors. The scanning device scans the light irradiated from the light irradiation unit onto an original.

[0003] The scanning device is a document transport device or a unit moving device. The document transport device transports the document along a transport path that passes through an area where the light of the three primary colors is irradiated. The unit moving device transports a scanning unit including the irradiation unit along a platen glass on which the document is placed.

[0004] The image sensor detects the amount of light reflected from the document, and the AFE sequentially outputs three-color line image data corresponding to the amount of light of the three primary colors detected by the line sensor when the three primary colors of light are scanned onto the document.

[0005] In the image reading device, an image processing unit may detect the leading edge of the document. Specifically, the image processing unit detects the leading edge by detecting a shadow image formed by the leading edge from multiple sets of line image data of the three colors.

[0006] In the image reading device, noise shadows caused by surface conditions such as unevenness or dirt on the surface of the document may adversely affect detection of the leading edge of the document.

[0007] In order to prevent the occurrence of the noise shadow, it is known that two illumination devices irradiate the original with two types of light having different light intensities from two directions (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-284357 Summary of the Invention [Problem to be solved by the invention]

[0009] However, when two types of light with different intensities are irradiated onto the document from two directions, the difference between the pixel value corresponding to the shadow of the leading edge of the document and the other pixel values ​​becomes small, which may make it impossible to distinguish the shadow of the leading edge from the noise shadow.

[0010] SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus that can reliably detect the edge of a document without being affected by noise shadows caused by unevenness on the surface of the document. [Means for solving the problem]

[0011] According to one aspect of the present invention, an image reading device includes a first illumination device, a second illumination device, a line sensor, a scanning device, a control unit, an image data output unit, and an image processing unit. The first illumination device has a first illumination unit arranged on one side of a target area, the longitudinal direction of which is a first direction, in a second direction intersecting the first direction, and is capable of selectively irradiating the target area with light of a first primary color and light of a second primary color, which are two of the three primary colors, from the first illumination unit. The second illumination device has a second illumination unit arranged on the other side of the target area in the second direction, and is capable of irradiating the target area with light of a third primary color, which is the other of the three primary colors, from the second illumination unit. The line sensor detects the amount of light reflected from the target area toward a position between the first illumination unit and the second illumination unit. The scanning device performs an optical scanning process in which the light irradiated by the first illumination unit and the second illumination unit is scanned over an original along the second direction. The control unit, when the optical scanning process is performed, causes the first lighting device and the second lighting device to perform a sequential irradiation process in which the three primary color lights are sequentially irradiated onto the target area. The image data output unit, when the optical scanning process and the sequential irradiation process are performed, sequentially outputs three-color line image data corresponding to the light intensities of the three primary color lights detected by the line sensor. The image processing unit detects a linear shadow image along the leading edge or trailing edge of the document from multiple sets of the three-color line image data obtained when the optical scanning process and the sequential irradiation process are performed. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an image reading device that can reliably detect the edge of a document without being affected by noise shadows caused by unevenness on the surface of the document. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing the configuration of an image reading apparatus according to the first embodiment. [Figure 2]FIG. 2 is a block diagram showing the configuration of a user interface and a control device in the image reading device according to the first embodiment. [Figure 3] FIG. 3 is a block diagram showing the configuration of processing modules in the CPU of the image reading device according to the first embodiment. [Figure 4] FIG. 4 is a configuration diagram of a sensor unit in the image reading device according to the first embodiment, seen from the side. [Figure 5] FIG. 5 is a configuration diagram of the sensor unit in the image reading device according to the first embodiment, viewed from above. [Figure 6] FIG. 6 is a flowchart showing an example of a procedure for image reading control in the image reading device according to the first embodiment. [Figure 7] FIG. 7 is a time chart showing an example of changes in the lighting signal in the image reading device according to the first embodiment. [Figure 8] FIG. 8 is a diagram showing how a linear shadow image on the leading edge of a document is detected in the image reading device according to the first embodiment. [Figure 9] FIG. 9 is a diagram showing how a linear shadow image on the trailing edge of a document is detected in the image reading device according to the first embodiment. [Figure 10] FIG. 10 is a diagram schematically showing a plurality of line image data obtained in the image reading device according to the first embodiment. [Figure 11] FIG. 11 is a configuration diagram of a sensor unit in an image reading device according to the second embodiment. [Figure 12] FIG. 12 is a configuration diagram of a sensor unit in an image reading device according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is an example of the present invention, and does not limit the technical scope of the present invention.

[0015] [First embodiment] The image reading device 10 according to the first embodiment executes image reading processing to read an image of a document 9. For example, the image reading device 10 may be configured as a part of an image processing device such as a copying machine, a facsimile machine, or a multifunction peripheral.

[0016] [Configuration of image reading device 10] The image reading device 10 includes a main body 101, a document cover 102, a scanning unit 2, an AFE (Analog Front End) 4, a document transport device 15, a platen glass 16a, a contact glass 16b, and a unit moving device 17 (see FIG. 1).

[0017] Furthermore, the image reading device 10 also includes a user interface device 6 and a control device 5 .

[0018] The scanning unit 2 includes an image sensor unit 3. A first direction D1 shown in each drawing is the longitudinal direction of the scanning unit 2 and the image sensor unit 3. That is, the scanning unit 2 and the image sensor unit 3 are arranged along the first direction D1.

[0019] 1 and 4, the depth direction into the drawing is the first direction D1. The second direction D2 is a direction intersecting the first direction D1. In this embodiment, the second direction D2 is a direction perpendicular to the first direction D1.

[0020] The first direction D1 is the so-called main scanning direction, and the second direction D2 is the so-called sub-scanning direction.

[0021] The main body 101 is a housing that houses the scanning unit 2 and the unit moving device 17. The platen glass 16a and the contact glass 16b form part of the top surface of the main body 101.

[0022] The platen glass 16a and the contact glass 16b are transparent plates. The platen glass 16a is a portion on which the document 9 is placed. The platen glass 16a and the contact glass 16b are arranged with an interval between them in the second direction D2.

[0023] In this embodiment, one transparent glass plate 16 includes a platen glass 16a and a contact glass 16b (see FIGS. 1, 5, and 6).

[0024] The scanning unit 2 is supported by the main body 101. The scanning unit 2 is supported so as to be movable along the second direction D2 in a movable region extending from below the platen glass 16a to below the contact glass 16b.

[0025] The unit moving device 17 moves the scanning unit 2 in the second direction D2 within the movable range. The unit moving device 17 includes a unit support 17a, a motor 17b, a power transmission mechanism 17c, and a motor drive circuit 17d.

[0026] The unit support part 17a supports the scanning unit 2 so that it can move along the second direction D2. The motor 17b is a drive source for a mechanism that moves the scanning unit 2. The power transmission mechanism 17c converts the rotational force of the motor 17b into a force along the second direction D2 and transmits the force to the scanning unit 2.

[0027] When the motor 17b rotates in the first rotation direction or the second rotation direction, the scanning unit 2 moves to one side or the other along the second direction D2.

[0028] The motor drive circuit 17d rotates the motor 17b in accordance with a control command from the control device 5. The control device 5 operates the unit moving device 17 by outputting the control command.

[0029] The document cover 102 is supported so as to be rotatable between a closed position and an open position. In the closed position, the document cover 102 covers the upper surfaces of the platen glass 16a and the contact glass 16b. In the open position, the document cover 102 exposes the upper surfaces of the platen glass 16a and the contact glass 16b.

[0030] The image reading device 10 is capable of performing a stationary document reading process. In the stationary document reading process, the unit moving device 17 moves the scanning unit 2 along the lower surface of the platen glass 16a, and the image sensor unit 3 reads an image on the lower surface of the document 9 placed on the platen glass 16a.

[0031] The inner surface of the document cover 102 forms a first background surface 100a that serves as the background surface of the document 9 on the platen glass 16a.

[0032] The document transport device 15 is provided on the document cover 102. The document transport device 15 sends out the document 9 on the supply tray 151 to the transport path 150. The document transport device 15 then transports the document 9 along the transport path 150 that passes over the upper surface of the contact glass 16b. The document transport device 15 then discharges the document 9 from the transport path 150 onto the discharge tray 152.

[0033] Above the contact glass 16b, a second background surface 100b is formed, which serves as a background surface for the document 9 transported along the upper surface of the contact glass 16b.

[0034] The light reflection characteristics of the first background surface 100a and the second background surface 100b each correspond to the light reflection characteristics of a blank piece of paper.

[0035] The image reading device 10 can perform a transported document reading process with the document cover 102 closed. In the transported document reading process, the unit moving device 17 holds the scanning unit 2 below the contact glass 16b, and the document transport device 15 transports the document 9 along the transport path 150. Furthermore, the image sensor unit 3 reads an image on the underside of the document 9 passing over the contact glass 16b.

[0036] The image sensor unit 3 outputs a line image signal Ia0 representing the read image. The AFE 4 converts the analog line image signal Ia0 into a plurality of digital line image data Id0 and outputs the plurality of line image data Id0 to the control device 5. Each line image data Id0 includes a plurality of pixel data for one line in the first direction D1.

[0037] The plurality of line image data Id0 corresponding to one page of the document 9 is the data of the read image corresponding to one page of the document 9.

[0038] The line sensor 34 reads the image of the document 9 as a color image. Therefore, the data of the read image is color image data that represents the amount of reflected light of the three colors of red, green, and blue.

[0039] 2, the user interface device 6 includes an operation device 6a and a display device 6b. The operation device 6a is a device that accepts operations by a person, and includes, for example, operation buttons and a touch panel.

[0040] The display device 6b includes a display panel such as a liquid crystal panel that can display images and other information. Note that the human operation includes not only operation by a human hand, but also operation by a human voice or operation by a human line of sight.

[0041] The control device 5 includes a CPU (Central Processing Unit) 51, a RAM 52, a secondary storage device 53, a communication device 54, and the like.

[0042] The secondary storage device 53 is a computer-readable non-volatile storage device. The secondary storage device 53 can store computer programs and various data. For example, one or both of an SSD (Solid State Drive) and a hard disk drive may be used as the secondary storage device 53.

[0043] The CPU 51 is a processor that performs various data processing and control by executing computer programs stored in the secondary storage device 53. It is also possible that another processor, such as a DSP, performs the data processing and control instead of the CPU 51.

[0044] The RAM 52 is a computer-readable volatile storage device that is accessed by the CPU 51. The RAM 52 temporarily stores data to be processed by the CPU 51 and data generated by the CPU 51.

[0045] The communication device 54 is a communication interface device capable of communicating with a host device (not shown), which is an external device, via a network such as a LAN (Local Area Network). The host device is a computer capable of communicating with the image reading device 10.

[0046] The CPU 51 performs all transmission and reception of data to and from the host device through the communication device 54. For example, the CPU 51 transmits data of the read image obtained by the image reading process to the host device through the communication device 54.

[0047] The CPU 51 includes a plurality of processing modules that are realized by executing the computer programs, including a main control unit 5a, a reading control unit 5b, and an image processing unit 5c (see FIG. 3).

[0048] The main control unit 5a mainly monitors operations on the operation device 6a and data reception by the communication device 54, and when an operation or data reception is detected, controls the start of processing according to the detected content.

[0049] The reading control unit 5b controls the motor drive circuit 17d and the image sensor unit 3 to cause the image reading device 10 to execute the stationary document reading process. Furthermore, the reading control unit 5b controls the document transport device 15 and the image sensor unit 3 to cause the image reading device 10 to execute the transported document reading process.

[0050] The image processing unit 5c executes various processes on the plurality of line image data Id0 obtained by the stationary document reading process or the conveyed document reading process.

[0051] For example, the image processing unit 5c executes a process of detecting the leading edge 9a of the document 9 based on the plurality of line image data Id0 (see FIG. 8). As will be described later, the image processing unit 5c detects the leading edge 9a by detecting images of linear shadows SH1 formed along the leading edge 9a and the trailing edge 9b of the document 9.

[0052] However, noise shadows caused by the surface condition of the document 9, such as unevenness or dirt on the surface, may adversely affect the detection of the edge of the document 9.

[0053] In order to prevent the occurrence of the noise shadow, it is known that two types of light with different light intensities are irradiated onto the original 9 from two directions.

[0054] However, when two types of light with different intensities are irradiated onto the document 9 from two directions, the difference between the pixel value corresponding to the shadow of the leading edge 9a of the document 9 and the other pixel values ​​becomes small, which may make it impossible to distinguish the shadow of the leading edge 9a from the noise shadow.

[0055] The image reading device 10 has a configuration for reliably detecting the edge of the document 9 without being affected by the noise shadows caused by the unevenness of the surface of the document 9. The configuration will be described below.

[0056] [Image sensor unit 3 configuration] The image sensor unit 3 includes a first illumination device 31, a second illumination device 32, a lens 33, and a line sensor 34 (see FIG. 4).

[0057] The first lighting device 31 has a first irradiating section 310. The first irradiating section 310 is arranged on a first side in a second direction D2 with respect to a target area AR1, whose longitudinal direction is the first direction D1. On the other hand, the second lighting device 32 has a second irradiating section 320. The second irradiating section 320 is arranged on a second side in the second direction D2 with respect to the target area AR1.

[0058] 4, 5, 8 and 9, the right side of the drawing is the first side, and the left side of the drawing is the second side.

[0059] In the following description, the scanning direction of light onto the original 9 when the stationary original reading process is performed is referred to as a first scanning direction D21, while the scanning direction of light onto the original 9 when the transported original reading process is performed is referred to as a second scanning direction D22.

[0060] 4, 5, 8, and 9, a first scanning direction D21 is a direction from the second side to the first side along the second direction D2, and is a movement direction of the scanning unit 2 when the stationary document reading process is performed.

[0061] In the examples shown in FIGS. 4, 5, 8 and 9, the second scanning direction D22 is a direction from the first side to the second side along the second direction D2.

[0062] When the transported document reading process is performed, the document 9 is transported on the contact glass 16b in a first scanning direction D21. The second scanning direction D22 is a direction opposite to the transport direction of the document 9 on the contact glass 16b.

[0063] The first irradiating section 310 and the second irradiating section 320 may be disposed in the opposite positional relationship to that shown in FIGS.

[0064] In this embodiment, each of the first irradiating unit 310 and the second irradiating unit 320 is a light-guiding member whose longitudinal direction is the first direction D1. The light-guiding member guides light incident on one end of the light-guiding member along the first direction D1 and irradiates the light to the target area AR1.

[0065] When the stationary document reading process is performed, the target area AR1 is an area along the upper surface of the platen glass 16a. That is, when the unit moving device 17 operates, the target area AR1 is an area along the upper surface of the platen glass 16a.

[0066] The unit moving device 17 moves the scanning unit 2 along the platen glass 16a on which the original 9 is placed, thereby scanning the original 9 with the light emitted from the first irradiation section 310 and the second irradiation section 320.

[0067] On the other hand, when the transported document reading process is executed, the target area AR1 is an area along the upper surface of the contact glass 16b. That is, when the document transport device 15 operates, the target area AR1 is an area along the upper surface of the contact glass 16b.

[0068] The document transport device 15 transports the document 9 along a transport path 150 that passes through the target area AR1, thereby scanning the document 9 with the light emitted from the first irradiation section 310 and the second irradiation section 320.

[0069] Each of the unit moving device 17 and the document transport device 15 is an example of a scanning device.

[0070] The first illumination device 31 can selectively irradiate the target area AR1 with light of a first primary color, which are two of the three primary colors of red, green, and blue, and light of a second primary color, from the first illumination unit 310. Therefore, the first illumination device 31 has a first light-emitting unit 311 that can selectively emit at least light of the first primary color and light of the second primary color to the first illumination unit 310.

[0071] On the other hand, the second illumination device 32 can irradiate the target area AR1 with light of a third primary color, which is another one of the three primary colors, from the second illumination unit 320. Therefore, the second illumination device 32 has a second light-emitting unit 321 that can emit at least light of the third primary color to the second illumination unit 320.

[0072] 4, 5, 8, and 9, the first and second primary colors are red and green, and the third primary color is blue. However, other combinations of the first, second, and third primary colors may also be used.

[0073] 4, 5, 8, and 9, first light-emitting unit 311 includes red light source 31R and green light source 31G, and second light-emitting unit 321 includes blue light source 32B. Note that first light-emitting unit 311 may be a single light source that can selectively emit light of the first primary color and light of the second primary color depending on the type of input drive signal.

[0074] The lens 33 collects the reflected light that is reflected in the target area AR1 toward the gap between the first irradiating section 310 and the second irradiating section 320. The line sensor 34 detects the amount of the reflected light that has passed through the lens 33.

[0075] The line sensor 34 sequentially outputs a line image signal Ia0 that indicates the detected amount of the reflected light.

[0076] Each of the unit moving device 17 and the document transport device 15 performs an optical scanning process of scanning the document 9 with the light emitted from the first irradiating section 310 and the second irradiating section 320 along the second direction D2.

[0077] [Image reading control] Next, an example of the procedure of image reading control executed by the reading control unit 5b and the image processing unit 5c will be described with reference to the flowchart shown in FIG.

[0078] The image reading control is executed when the start of reading is detected by the operation device 6a.

[0079] In the following description, S1, S2, ... represent identification codes of a plurality of steps in the image reading control. In the image reading control, the processing of step S1 is executed first.

[0080] <Process S1> In step S1, the reading control section 5b causes the unit moving device 17 or the document transport device 15 to perform the optical scanning process, and also causes the first lighting device 31 and the second lighting device 32 to perform the irradiation process in sequence.

[0081] For example, the reading control unit 5b causes the document transport device 15 to perform the optical scanning process when a document sensor (not shown) detects the document 9 on the supply tray 151. On the other hand, the reading control unit 5b causes the unit moving device 17 to perform the optical scanning process when the document sensor does not detect the document 9 on the supply tray 151.

[0082] The sequential irradiation process is a process of sequentially irradiating the target area AR1 with the light of the three primary colors, and is performed in parallel with the optical scanning process.

[0083] The time chart of FIG. 7 shows an example of changes in the lighting signals of red light source 31R, green light source 31G, and blue light source 32B when the sequential irradiation process is performed.

[0084] In the sequential irradiation process, it is sufficient that the red light source 31R, the green light source 31G, and the blue light source 32B are turned on one by one in order, and the order of lighting shown in FIG. 7 is merely an example.

[0085] When the process of step S1 is executed, the line sensor 34 and the AFE 4 operate. By executing the process of step S1, the AFE 4 sequentially outputs a plurality of line image data Id0.

[0086] The AFE 4 sequentially outputs three-color line image data Id0 corresponding to the light amounts of the three primary colors detected by the line sensor 34. The AFE 4 is an example of an image data output unit.

[0087] That is, the AFE4 sequentially outputs red line image data Id0 corresponding to the light of the red light source 31R, green line image data Id0 corresponding to the light of the green light source 31G, and blue line image data Id0 corresponding to the light of the blue light source 32B.

[0088] After the processing of step S1 is started, the processing of step S2 is executed in parallel with the processing of step S1.

[0089] <Process S2> In step S2, the image processing unit 5c acquires a plurality of line image data Id0 obtained when the optical scanning process and the sequential irradiation process are being performed.

[0090] The image processing unit 5c executes the process of step S3 based on the plurality of line image data Id0 obtained in step S2.

[0091] 8 shows how a linear shadow SH1 is formed along the leading edge 9a of the document 9 when the leading edge 9a passes through the target area AR1 during the transported document reading process. The optical scanning direction in FIG. 8 is the second scanning direction D22.

[0092] 8, the linear shadow SH1 appears along the leading edge 9a of the document 9 when the target area AR1 is irradiated with light from one of the two irradiation units 310, 320 that is located downstream in the optical scanning direction. On the other hand, the linear shadow SH1 hardly appears when the target area AR1 is irradiated with light from one of the two irradiation units 310, 320 that is located upstream in the optical scanning direction.

[0093] Therefore, the linear shadow SH1 along the leading edge 9a of the document 9 is mainly reflected in the data corresponding to the color of light from one of the two irradiators 310, 320 that is located downstream in the optical scanning direction. In the example shown in Fig. 8, the linear shadow SH1 is mainly reflected in the data corresponding to the color of light from the second irradiator 320, and is hardly reflected in the data corresponding to the color of light from the first irradiator 310.

[0094] <Process S3> In step S3, the image processing unit 5c executes a process of identifying a plurality of shadow pixels G1 in the plurality of sets of line image data Id0 of the three colors (see FIG. 10).

[0095] Hereinafter, the plurality of pixel data corresponding to one or both of the first primary color and the second primary color in the plurality of sets of three-color line image data Id0 will be referred to as a plurality of first pixel data, while the plurality of pixel data corresponding to the third primary color in the plurality of sets of three-color line image data Id0 will be referred to as a plurality of second pixel data.

[0096] 4, 5, 8, and 9, the plurality of first pixel data are data corresponding to one or both of red and green. In this case, an example of the plurality of first pixel data is a plurality of red pixel data included in the red line image data Id0, or a plurality of green pixel data included in the green line image data Id0.

[0097] 4, 5, 8, and 9, the plurality of first pixel data may be integrated data for each pixel of the plurality of red pixel data and the plurality of green pixel data. For example, the integrated data may be average data or weighted average data for each pixel of the plurality of red pixel data and the plurality of green pixel data.

[0098] In the examples shown in FIGS. 4, 5, 8, and 9, the plurality of second pixel data are a plurality of blue pixel data in a plurality of sets of three-color line image data Id0.

[0099] For example, the image processing unit 5c identifies a plurality of shadow pixels G1 by executing a primary color data comparison process based on a plurality of sets of the three-color line image data Id0.

[0100] The primary color data comparison process is a process of comparing each of the plurality of first pixel data with each of the plurality of second pixel data.

[0101] For example, the primary color data comparison process is a process for determining whether a comparison value, which is a difference or ratio between each of the plurality of first pixel data and each of the plurality of second pixel data, falls within a predetermined reference range or falls outside the reference range. The image processing unit 5c identifies, as a plurality of shadow pixels G1, a plurality of pixels whose comparison value falls outside the reference range.

[0102] Furthermore, the image processing unit 5c may identify a plurality of shadow pixels G1 by executing color comparison processing based on a plurality of sets of line image data Id0 of the three colors.

[0103] The color comparison process is a process of comparing the saturation or hue angle of each of a plurality of pixels derived based on a plurality of sets of line image data Id0 of the three colors with a preset reference value.

[0104] As described above, the linear shadow SH1 is mainly reflected in the data corresponding to the color of light from one of the two irradiation units 310, 320 located downstream in the optical scanning direction.

[0105] 8, the linear shadow SH1 is mainly reflected in the blue line image data Id0 among the multiple sets of three-color line image data Id0. In this case, the reference value is a value that distinguishes between blue or colors similar to blue and other colors.

[0106] 8, the linear shadow SH1 is mainly reflected in the red and green line image data Id0 among the sets of three-color line image data Id0. In this case, the reference value is a value that distinguishes between yellow or a color similar to yellow and other colors.

[0107] After executing the process of step S3, the image processing unit 5c executes the process of step S4.

[0108] <Process S4> In step S4, the image processing unit 5c detects a straight line image formed by the plurality of shadow pixels G1 identified in step S3 as a linear shadow image. The linear shadow image is an image of a linear shadow SH1 (see FIG. 10).

[0109] The linear shadow image detected in step S4 is an image of a linear shadow SH1 formed along the leading edge 9a of the document 9. Hereinafter, the image of the linear shadow SH1 formed along the leading edge 9a of the document 9 will be referred to as a first linear shadow image.

[0110] After executing the process of step S4, the image processing unit 5c executes the process of step S5.

[0111] <Process S5> In step S5, the image processing unit 5c derives the tilt angle θ of the first linear shadow image with respect to the first direction D1 (see FIG. 10).

[0112] After executing the process of step S5, the image processing unit 5c executes the process of step S6.

[0113] <Process S6> In step S6, the image processing unit 5c executes a process of identifying a plurality of shadow pixels G1, similar to step S3. In step S6, the image processing unit 5c identifies a plurality of shadow pixels G1 for data obtained after the data of the first linear shadow image in the plurality of sets of three-color line image data Id0.

[0114] 9 shows how a linear shadow SH1 is formed along the trailing edge 9b of the document 9 when the document 9 passes through the target area AR1 during the document reading process. The optical scanning direction in FIG. 9 is the second scanning direction D22.

[0115] As shown in FIG. 9, the linear shadow SH1 is generated along the rear edge 9b of the document 9 when the light from one of the two irradiation units 310, 320, which is located upstream in the optical scanning direction, is irradiated onto the target area AR1.

[0116] Therefore, the linear shadow SH1 along the trailing edge 9b of the document 9 is mainly reflected in the data corresponding to the color of light from one of the two irradiators 310, 320 that is located downstream in the optical scanning direction. In the example shown in Fig. 9, the linear shadow SH1 is mainly reflected in the data corresponding to the color of light from the first irradiator 310, and is hardly reflected in the data corresponding to the color of light from the second irradiator 320.

[0117] In step S6, the image processing unit 5c identifies a plurality of shadow pixels G1 by executing the primary color data comparison process or the color comparison process based on a plurality of sets of line image data Id0 of the three colors, similar to step S3.

[0118] However, the color in which the linear shadow SH1 is reflected in step S6 is different from the color in which the linear shadow SH1 is reflected in step S3. Therefore, when the primary color data comparison process is employed, the reference value for the difference or ratio between the plurality of first pixel data and the plurality of second pixel data differs between step S3 and step S6. Similarly, when the color comparison process is employed, the reference value differs between step S3 and step S6.

[0119] After executing the process of step S6, the image processing unit 5c executes the process of step S7.

[0120] <Process S7> In step S7, the image processing unit 5c detects a straight line image formed by the plurality of shadow pixels G1 identified in step S6 as the linear shadow image.

[0121] The linear shadow image detected in step S7 is an image of a linear shadow SH1 formed along the rear edge 9b of the document 9 (see FIG. 9). Hereinafter, the image of the linear shadow SH1 formed along the rear edge 9b of the document 9 will be referred to as a second linear shadow image.

[0122] After executing the process of step S7, the image processing unit 5c executes the process of step S8.

[0123] <Process S8> In step S8, the image processing unit 5c identifies data of the document area corresponding to the size of the document 9 in the plurality of sets of three-color line image data Id0.

[0124] For example, the image processing unit 5c identifies the data of the area between the first linear shadow image and the second linear shadow image as the data of the document area.

[0125] Furthermore, the image processing unit 5c may specify data of an area of ​​a preset document size with the first linear shadow image as a starting point as the data of the document area, in which case the processes of steps S6 to S7 may be omitted.

[0126] Hereinafter, the data of the document area contained in the plurality of sets of three-color line image data Id0 will be referred to as “document image data.” After executing the process of step S8, the image processing unit 5c executes the process of step S9.

[0127] <Process S9> In step S9, the image processing unit 5c performs skew correction processing on the document image data based on the skew angle θ obtained in step S5.

[0128] The tilt correction process is a process of rotating the document image data by the tilt angle θ obtained in step S5 in a direction opposite to the tilt direction represented by the tilt angle θ.

[0129] After executing the process of step S9, the image processing unit 5c executes the process of step S10.

[0130] <Process S10> In step S10, the image processing unit 5c outputs the document image data that has been subjected to the skew correction to a preset output destination, such as the host device or secondary storage device 53, which is a transmission destination via the communication device 54.

[0131] After executing the process of step S10, the image processing unit 5c ends the image reading control. Note that, when the transported document reading process is executed for a plurality of documents 9, the processes of steps S1 to S10 are repeated until the document sensor no longer detects the documents 9 on the supply tray 151, and then the image reading control ends.

[0132] By employing the image reading device 10, it is possible to reliably detect the leading edge 9a and trailing edge 9b of the document 9 without being affected by the noise shadows caused by unevenness or dirt on the surface of the document 9.

[0133] [Second embodiment] Next, an image reading device 10A according to a second embodiment will be described with reference to Fig. 11. In Fig. 11, the same components as those shown in Fig. 4 are denoted by the same reference numerals.

[0134] The following describes the differences between the image reading device 10A and the image reading device 10.

[0135] The image reading device 10A has a configuration in which the image sensor unit 3 in the image reading device 10 is replaced with an image sensor unit 3A.

[0136] The image sensor unit 3A has a configuration in which the first illumination device 31 and the second illumination device 32 in the image sensor unit 3 are replaced with a pair of multi-illumination devices 31x and 32x. The pair of multi-illumination devices 31x and 32x can selectively irradiate the target area AR1 with light of the three primary colors, respectively.

[0137] The first multi-illumination device 31x has a configuration in which the first light-emitting section 311 of the first illumination device 31 is replaced with a first light-emitting section 311x. The first light-emitting section 311x includes a red light source 31R, a green light source 31G, and a blue light source 31B.

[0138] Similarly, the second multi-illumination device 32x has a configuration in which the second light-emitting section 321 of the second illumination device 32 is replaced with a second light-emitting section 321x. The second light-emitting section 321x has a red light source 32R, a green light source 32G, and a blue light source 32B.

[0139] In this embodiment, the reading control unit 5b selects one of the pair of multi-lighting devices 31x, 32x to be controlled as the first lighting device 31 and the other to be controlled as the second lighting device 32, depending on which of the unit moving device 17 and the document transport device 15 is operating in step S1 of the image reading control.

[0140] For example, the reading control unit 5b controls the first multi-illumination device 31x as the first illumination device 31 and the second multi-illumination device 32x as the second illumination device 32 when the unit moving device 17 is operating.

[0141] On the other hand, the reading control unit 5b controls the second multi-illumination device 32x as the first illumination device 31 and the first multi-illumination device 31x as the second illumination device 32 when the document transport device 15 is operating.

[0142] According to this embodiment, the image processing unit 5c can detect the first linear shadow image corresponding to the leading edge 9a of the document 9 by the same processing regardless of whether the unit moving device 17 or the document transport device 15 is operating (see step S4 in Figure 6).

[0143] Similarly, the image processing unit 5c can detect the third linear shadow image corresponding to the rear edge 9b of the document 9 by the same processing regardless of whether the unit moving device 17 or the document transport device 15 is operating (see step S7 in Figure 6).

[0144] When the image reading device 10A is employed, the same effects as when the image reading device 10 is employed can be obtained.

[0145] [Third embodiment] Next, an image reading device 10B according to a third embodiment will be described with reference to Fig. 12. In Fig. 12, the same components as those shown in Figs. 4 and 11 are denoted by the same reference numerals.

[0146] Image reading device 10B is a modified version of image reading device 10A. Below, differences between image reading device 10B and image reading device 10A will be described.

[0147] The image reading device 10B has a configuration in which the image sensor unit 3A of the image reading device 10A is replaced with an optical unit 3B, and a plurality of mirrors 33a and a line sensor 34a are added.

[0148] In the image reading device 10B, the scanning unit 2, which is the object of movement by the unit movement device 17, includes an optical unit 3B and some of the mirrors 33a. The optical unit 3B has a configuration in which the line sensor 34 is removed from the image sensor unit 3A.

[0149] The line sensor 34a is fixed inside the main body 101. A plurality of mirrors 33a guide the reflected light that has passed through the lens 33 to the line sensor 34a.

[0150] For example, the line sensor 34 of the image reading devices 10 and 10A is a CMOS type image sensor, whereas the line sensor 34a of the image reading device 10B is a CCD type image sensor.

[0151] In this embodiment, the reading control unit 5b and the image processing unit 5c perform the same processes as the reading control unit 5b and the image processing unit 5c of the image reading device 10A.

[0152] When the image reading device 10B is used, the same effects as when the image reading devices 10 and 10A are used can be obtained.

[0153] The pair of multi-illumination devices 31x and 32x of the optical unit 3B in the image reading device 10B may be replaced with the first illumination device 31 and the second illumination device 32 of the image reading device 10. In this case, the reading control unit 5b and the image processing unit 5c perform the same processes as the reading control unit 5b and the image processing unit 5c of the image reading device 10.

[0154] [Variations] In the image reading control, the reading control unit 5b may execute an inclination notification process of notifying information about the inclination angle θ of the first linear shadow image through the display device 6b or the communication device .

[0155] For example, the reading control unit 5b may determine the degree of inclination of the first linear shadow image by comparing the inclination angle θ derived in step S5 with one or more preset angles, and may notify the information on the degree of inclination. Alternatively, if the inclination angle θ exceeds an upper limit angle, the reading control unit 5b may issue an error notification.

[0156] [Notes on the Invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0157] <Appendix 1> a first lighting device having a first irradiation unit arranged on one side of a target area having a first direction as a longitudinal direction thereof in a second direction intersecting the first direction, and capable of selectively irradiating the target area with light of a first primary color and light of a second primary color, which are two of three primary colors, from the first irradiation unit; a second illumination device having a second illumination unit arranged on the other side of the target area in the second direction, and capable of irradiating the target area with light of a third primary color that is another one of the three primary colors from the second illumination unit; a line sensor that detects the amount of light reflected in the target area toward a position between the first irradiation unit and the second irradiation unit; a scanning device that performs an optical scanning process of scanning the document with the irradiation light from the first irradiation unit and the second irradiation unit along the second direction; a control unit that causes the first lighting device and the second lighting device to perform a sequential irradiation process of sequentially irradiating the target area with the light of the three primary colors when the optical scanning process is performed; an image data output unit that sequentially outputs three-color line image data corresponding to the detected light amounts of the three primary color lights by the line sensor when the optical scanning process and the sequential irradiation process are performed; an image processing unit that detects a linear shadow image along the leading edge or trailing edge of the document from multiple sets of line image data of the three colors obtained when the optical scanning process and the sequential irradiation process are performed.

[0158] <Appendix 2> the image processing unit identifies a plurality of shadow pixels by performing a primary color data comparison process based on a plurality of sets of line image data of the three colors, and detects a straight line image formed by the plurality of shadow pixels as the linear shadow image; The image reading device described in Appendix 1, wherein the primary color data comparison process is a process of comparing each of a plurality of first pixel data corresponding to one or both of the first primary color and the second primary color in multiple sets of three-color line image data with each of a plurality of second pixel data corresponding to the third primary color in multiple sets of three-color line image data.

[0159] <Appendix 3> the image processing unit identifies a plurality of shadow pixels by executing a color comparison process based on a plurality of sets of line image data of the three colors, and detects a straight line image formed by the plurality of shadow pixels as the linear shadow image; The image reading device described in Appendix 1, wherein the color comparison process is a process of comparing the saturation or hue angle of each of multiple pixels derived based on multiple sets of line image data of the three colors with a predetermined reference value.

[0160] <Appendix 4> The image reading device described in any one of Supplementary Note 1 to Supplementary Note 3, wherein the scanning device includes one or both of a document transport device that transports the document along a transport path that passes through the target area, and a unit moving device that moves a scanning unit including the first irradiation unit and the second irradiation unit along a platen glass on which the document is placed.

[0161] <Appendix 5> the scanning device includes the document transport device and the unit moving device; the first lighting device and the second lighting device are a pair of multi-lighting devices each capable of selectively irradiating the target area with light of the three primary colors, The image reading device described in Appendix 4, wherein the control unit selects one of the pair of multi-lighting devices to be controlled as the first lighting device and the other to be controlled as the second lighting device depending on which of the document transport device and the unit moving device is operating.

[0162] <Appendix 6> The image reading device described in any one of Supplementary Note 1 to Supplementary Note 5, wherein the image processing unit performs inclination correction of the document image data contained in the multiple sets of three-color line image data according to the inclination of the linear shadow image. [Explanation of symbols]

[0163] 2: Scanning unit 3: Image sensor unit 3A: Image sensor unit 3B: Optical unit 5: Control device 9: Manuscript 9a: Tip edge 9b: Back edge 10: Image reader 10A: Image reader 10B: Image reader 15: Document transport device 17: Unit moving device 17c: Power transmission mechanism 17d: Motor drive circuit 31: First lighting device 31x: 1st multi-illumination device 32: Second lighting device 32x: Second multi-illumination device 33: Lens 33a: Mirror 34: Line sensor 34a: Line sensor 310: 1st irradiation section 311: First light-emitting unit 311x: First light-emitting part 320:Second irradiation section 321: Second light-emitting part 321x: Second light-emitting unit AR1: Target Area D1: 1st direction D2 :Second direction D21: First scanning direction D22: Second scanning direction G1: Shadow pixels

Claims

1. a first lighting device having a first irradiation unit arranged on one side of a target area having a first direction as a longitudinal direction thereof in a second direction intersecting the first direction, and capable of selectively irradiating the target area with light of a first primary color and light of a second primary color, which are two of three primary colors, from the first irradiation unit; a second illumination device having a second illumination unit arranged on the other side of the target area in the second direction, and capable of irradiating the target area with light of a third primary color that is another one of the three primary colors from the second illumination unit; a line sensor that detects the amount of light reflected in the target area toward a position between the first irradiation unit and the second irradiation unit; a scanning device that performs an optical scanning process of scanning the document with the irradiation light from the first irradiation unit and the second irradiation unit along the second direction; a control unit that causes the first lighting device and the second lighting device to perform a sequential irradiation process of sequentially irradiating the target area with the light of the three primary colors when the optical scanning process is performed; an image data output unit that sequentially outputs three-color line image data corresponding to the detected light amounts of the three primary colors of light by the line sensor when the optical scanning process and the sequential irradiation process are performed; an image processing unit that detects a linear shadow image along the leading edge or trailing edge of the document from multiple sets of three-color line image data obtained when the optical scanning process and the sequential irradiation process are performed.

2. the image processing unit identifies a plurality of shadow pixels by performing a primary color data comparison process based on a plurality of sets of line image data of the three colors, and detects a straight line image formed by the plurality of shadow pixels as the linear shadow image; 2. The image reading device of claim 1, wherein the primary color data comparison process is a process of comparing each of a plurality of first pixel data corresponding to one or both of the first primary color and the second primary color in the plurality of sets of three-color line image data with each of a plurality of second pixel data corresponding to the third primary color in the plurality of sets of three-color line image data.

3. the image processing unit identifies a plurality of shadow pixels by executing a color comparison process based on a plurality of sets of line image data of the three colors, and detects a straight line image formed by the plurality of shadow pixels as the linear shadow image; 2. The image reading device according to claim 1, wherein the color comparison process is a process of comparing the saturation or hue angle of each of a plurality of pixels derived based on a plurality of sets of line image data of the three colors with a preset reference value.

4. 4. The image reading device according to claim 1, wherein the scanning device includes one or both of a document transport device that transports the document along a transport path that passes through the target area, and a unit moving device that moves a scanning unit including the first irradiation unit and the second irradiation unit along a platen glass on which the document is placed.

5. the scanning device includes the document transport device and the unit moving device; the first lighting device and the second lighting device are a pair of multi-lighting devices each capable of selectively irradiating the target area with light of the three primary colors, 5. The image reading device according to claim 4, wherein the control unit selects one of the pair of multi-lighting devices to be controlled as the first lighting device and the other to be controlled as the second lighting device depending on whether the document transport device or the unit moving device is operating.

6. 4. The image reading device according to claim 1, wherein the image processing unit corrects tilt of the document image data included in the plurality of sets of line image data of the three colors in accordance with the tilt of the linear shadow image.

Images