Image reading device

Abstract

This makes it possible to appropriately set the reading resolution used in the process of acquiring correction data for shading correction. [Solution] The control unit of the image reading device performs a pre-acquisition process to acquire correction data for shading correction using the reading means before receiving a user instruction to start reading a document when a document is placed in the document tray. The control unit has two operating modes for the pre-acquisition process: a first mode in which, when a second resolution is specified as the reading resolution, the pre-acquisition process is performed using the second resolution to acquire the correction data; and a second mode in which, when a second resolution is specified as the reading resolution, the pre-acquisition process is performed using the first resolution to acquire the correction data.

Description

Technical Field

[0001] The present invention relates to an image reading device.

Background Art

[0002] In an image reading device (document reading device) equipped with an automatic document feeder (ADF), in order to improve the productivity of image reading processing, for example, it is required to shorten the FCOT (First Copy Output Time), which is the time from the read start instruction to the output of the first sheet. In an image reading device, as a preparation operation for starting the reading process of reading a plurality of documents in a flowing manner, a reference white plate inside the device is read, and acquisition processing of correction data for shading correction is performed. Patent Document 1 describes a technique for shortening the FCOT by performing the acquisition processing of correction data for shading correction prior to the start of job execution.

[0003] When acquiring correction data for shading correction, the reading resolution usually needs to be the same as the reading resolution when reading a document. If a different reading resolution is specified at the start of job execution after the acquisition of correction data, it is necessary to re-perform the acquisition processing of correction data, which leads to an increase in the FCOT. Patent Document 2 describes a technique for notifying a change without waiting for the start of job execution and performing the acquisition processing of correction data for shading correction in advance when a change in resolution setting is instructed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Image scanning devices sometimes set (change) the scanning resolution to a higher resolution than the specified scanning resolution when scanning a document. In such cases, the scanning resolution of the correction data for shading correction, which is acquired at the specified scanning resolution, may differ from the scanning resolution of the data scanned from the document.

[0006] Therefore, the present invention aims to provide a technology that enables the appropriate setting of the reading resolution used in the acquisition process of correction data for shading correction. [Means for solving the problem]

[0007] An image reading device according to one aspect of the present invention is capable of setting at least a first resolution and a second resolution lower than the first resolution as a reading resolution for reading a document transported from a document tray, and comprises a reading means for reading a document at the set reading resolution, and a control means for performing a pre-acquisition process to acquire correction data for shading correction using the reading means before receiving an instruction to start reading a document when a document is placed in the document tray, wherein the control means has an operating mode for the pre-acquisition process, which is a first mode in which, when the second resolution is specified as the reading resolution, the pre-acquisition process is performed using the second resolution to acquire the correction data, and a second mode in which, when the second resolution is specified as the reading resolution, the pre-acquisition process is performed using the first resolution to acquire the correction data. [Effects of the Invention]

[0008] According to the present invention, it becomes possible to appropriately set the reading resolution used in the acquisition process of correction data for shading correction. [Brief explanation of the drawing]

[0009] [Figure 1] A perspective view showing an example configuration of an image reading device. [Figure 2] A cross-sectional view showing an example of the configuration of an image reading device. [Figure 3] A block diagram showing an example of the control configuration of an image reading device. [Figure 4] A diagram showing an example of the configuration of the control unit. [Figure 5] A diagram showing an example of shading correction. [Figure 6] A diagram showing an example of the operation screen displayed on the control panel. [Figure 7] A diagram showing examples of data for reading setting notifications and reading start instructions. [Figure 8] A flowchart illustrating an example of the image reading process. [Figure 9] A flowchart illustrating an example of the procedures for pre-acquisition processing and resolution setting processing. [Figure 10] Diagram illustrating the detection of oblique movement. [Figure 11] Diagram explaining skew correction. [Figure 12] A diagram illustrating the relationship between skew correction and resolution. [Figure 13] A flowchart showing an example of the procedure for processing S102 (second embodiment). [Modes for carrying out the invention]

[0010] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0011] [First Embodiment] Figure 1 is a perspective view showing an example of the configuration of an image reading device according to the first embodiment. The image reading device (document reading device) 10 of this embodiment includes an image reading unit (reader) 100 that reads a document and an automatic document feeder (ADF) 200 that transports the document toward the reader 100.

[0012] The image reading device 10 further includes an operation unit 90 (FIG. 4). The operation unit 90 includes a display unit 91 and an operation key group 92 including a start key (start button) 93. Further, the image reading device 10 further includes a controller 310 (FIG. 3) as a control unit that controls the entire device.

[0013] <Configuration example of the reader 100> FIG. 2 is a cross-sectional view showing a configuration example of the image reading device 10. The reader 100 includes a document table glass 101, a surface reading unit 104 including a flow reading glass 102, a surface LED 105 (FIG. 3), and a surface reading sensor 108 (FIG. 3), a white reference plate 110 used for acquiring correction data for shading correction, and an optical motor 225 (FIG. 3). When performing document reading control, the reader 100 reads the surface of the document placed on the document table glass 101 line by line while moving the surface reading unit 104 along the reading movement guide 109 using the optical motor 225, thereby reading the image of the document. Also, during flow reading control, the image of the document conveyed onto the flow reading glass 102 by the ADF 200 is read by the surface reading unit 104.

[0014] <Configuration example of the ADF 200> As shown in FIG. 2, the ADF 200 includes a document tray 201 on which a document bundle S composed of one or more document sheets is placed, and a separation roller pair 206 and a pickup roller 205 as a separation mechanism that restricts the document bundle S from protruding from the document tray 201 and entering downstream before the start of document conveyance.

[0015] Furthermore, a document detection sensor 204 for detecting the document loaded on the document tray 201, a separation sensor 209 for detecting the front and rear ends of the document on the paper conveyance path, a lead sensor 212, and a paper discharge sensor 218 are connected. In addition, a tray width guide sensor 224 for detecting the document width restricted by the tray width guide plate 203 on the document tray 201 and a tray length sensor 202 capable of detecting the approximate length in the sub-scanning direction of the document bundle placed on the document tray 201 are connected.

[0016] In the ADF200, the separation motor 227 (Figure 3) and the transport motor 228 (Figure 3) are rotated, causing the pickup roller 205 to drop and rotate onto the top of the stack of documents S loaded on the document tray 201. This sends the document on top of the stack to the separation roller pair 206. The document sent by the pickup roller 205 is then separated and transported one sheet at a time by the action of the separation roller pair 206, which is driven by the separation motor 227, similar to the action of the pickup roller 205. The document separated by the separation roller pair 206 is then sent to the transport roller pair 207, which is driven by the transport motor 228. After the transport of documents by the transport roller pair 207 begins, the separation motor 227 is stopped, and the document feeding process ends.

[0017] Downstream of the transport roller pair 207, a transport path is arranged to transport the document that has passed through the transport roller pair 207 toward the front-side reading glass 102 and the back-side reading glass 217. The document sent to the transport path is transported to the front-side reading glass 102 by the transport roller pair 207 and the lead upstream roller pair 211. In the case of front-side reading, the document passing through the front-side reading glass 102 is illuminated from below by the surface LED 105. The surface image of the document is input by reading the reflected light with the surface reading sensor 108 at the surface reading position 213.

[0018] The ADF200 also includes a back-side reading glass 217, a back-side reading unit 216 including a back-side LED 222 (Figure 3) and a back-side reading sensor 223 (Figure 3), and a back-side white reference plate 215 used for acquiring correction data for shading correction. In the case of double-sided reading, the front side is read by the front-side reading unit 104 as described above. The document whose front side has been read by the front-side reading unit 104 is transported to the back-side reading glass 217 by the lead downstream roller pair 214. Subsequently, the document passing under the back-side reading glass 217 is illuminated from above by the back-side LED 222 (Figure 3). The reflected light is read by the back-side reading sensor 223 through a back-side mirror and lens (not shown) to input the back-side image of the document. The read document is then discharged onto the output tray 220 by the output roller pair 219.

[0019] The front reading unit 104 and the back reading unit 216 may be composed of a direct optical system using a lens array, in addition to the reduction optical system described above.

[0020] <Control Configuration> Figure 3 is a block diagram showing an example of the control configuration of the image reading device 10. The CPU 301 comprehensively controls the reader 100 and the ADF 200 units. The ROM 302 is a storage device that stores the control content to be executed by the CPU 301 as a program. The RAM 303 is a storage device used as a work area necessary for the CPU 301 to perform control.

[0021] The CPU 301 is connected to a separation motor 227 and a transport motor 228, which drive each of the transport rollers, in order to implement the document transport function. The separation motor 227 is connected to the pickup roller 205 and the separation roller 206.

[0022] In this embodiment, the separation motor 227 and the transport motor 228 are pulse motors. The CPU 301 manages the rotation amount of each motor by controlling the number of drive pulses. Based on this number of pulses, the CPU 301 measures the transport distance of the document being transported and controls the loads and other factors to transport the document.

[0023] Furthermore, the CPU 301 is connected to a separation sensor 209, a lead sensor 212, and a paper output sensor 218, which detect the edges of documents on the paper transport path. In addition, the CPU 301 is connected to a document detection sensor 204, which detects documents loaded in the document tray 201, a tray width guide sensor 224, which detects the document width restricted by the tray width guide plate 203 on the document tray 201, and a tray length sensor 202.

[0024] The CPU 301 is connected to an optical motor 225 and an optical system HP sensor 226, an image memory 305, an image processing unit 306, and an image transfer unit 304, respectively, to realize the image reading function. The surface reading unit 104 consists of a surface LED 105, which is a light source, and a surface reading sensor 108, which is a line sensor. The reading surface of the transported document is illuminated by the light source LED 105, and the illuminated light is photoelectrically converted line by line by the light receiving element of the surface reading sensor 108 and read as image data. The back surface reading unit 216 consists of a back surface LED 222, which is a light source, and a back surface reading sensor 223, which is a line sensor. The reading surface of the transported document is illuminated by the light source back surface LED 222, similar to the surface, and the illuminated light is photoelectrically converted line by line by the light receiving element of the back surface reading sensor 223 and read as image data. The image memory 305 is a storage device that temporarily stores image data read by the front reading unit 104 and the back reading unit 216.

[0025] The image processing unit 306 performs image processing corrections on the read image stored in the image memory 305. The shading memory 307 is connected to the image processing unit 306 and holds the shading correction data, which will be described later. The CPU 301 can also read from and write to the shading memory 307 via the image processing unit 306. The image transfer unit 304 transfers the image data processed by the image processing unit 306 to the image transfer unit 314 of the controller 310, which will be described later, via the image transfer line 402.

[0026] <Controller> The controller 310 controls the entire image reading system, including the reader 100 and ADF 200. The CPU 311 comprehensively controls each unit of the controller 310. The ROM 312 is a memory device that stores the control content to be executed by the CPU 311 as a program. The RAM 313 is a memory device used as a workspace necessary for the CPU 311 to perform control.

[0027] The image transfer unit 314 receives images from the image transfer unit 304 and stores them in the image memory 315. The operation unit 90 is used to give user instructions for the entire image reading system, display messages to the user, and display the read images, and communicates with the CPU 311 to perform desired displays and inputs.

[0028] CPU 311 exchanges control commands and control data related to image reading control with CPU 301 via communication line 401. For example, CPU 311 receives an image reading job start instruction from the user via the operation unit 90 and sends an image reading start request to CPU 301. For example, CPU 311 receives information such as instructions for monochrome or color reading, reading resolution, document size, and reading job start instruction from the operation unit 90 via the operation key 92 and sends control information such as document feeding start instruction and document reading instruction to CPU 301. The document feeding start instruction includes reading resolution, and the document reading instruction includes information on the document size. In addition, CPU 311 receives the status of the document reader 10 from CPU 301 and displays a message to the user on the operation unit 90 according to the status of the device.

[0029] <Operation section> Figure 4 shows an example of the configuration of the operation unit 90. The operation unit 90 comprises a display unit 91 and a group of operation keys 92 including a numeric keypad and a start button 93. The start button 93 is used to input an instruction to start the image reading process. The CPU 311 displays a message or operation screen to the user on the display unit 91 and accepts instructions from the user.

[0030] <Process for acquiring correction data for shading correction> The front white reference plate 110 and the back white reference plate 215 are white reference plates used to create white level correction data for shading correction. Before the start of scanning the original document, the front white reference plate 110 is scanned by the front reading unit 104 and the back white reference plate 215 is scanned by the back reading unit 216, and image processing is performed on the scanning results to create correction data for shading correction.

[0031] In the shading correction in the front reading unit 104, the front white reference plate 110 is read. Figure 5 shows an example of the brightness value of the read white reference plate and shading correction. Figure 5(A) is an example when the reading resolution in the main scanning direction is set to 600 dpi. A correction coefficient is calculated for each pixel so that the difference in reading levels for each pixel, as shown in the figure, is corrected to a constant white level Tgtw. The correction coefficient corresponds to the part indicated by the arrow in the figure. This correction coefficient corresponds to the correction data for shading correction, and the obtained correction data is stored in the shading memory 307. Similarly, a correction coefficient is calculated for the back reading unit 216 and stored in the shading memory 307 for the back side. The correction data consists of data that includes a correction coefficient for each of the three primary colors (R, G, B) of the light source, for the number of pixels in the main scanning direction. When reading a document, each time a line is read, the image processing unit 306 corrects the read line image using the correction coefficient (correction data) stored in the shading memory 307 to generate image data of the read image after shading correction. The generated image data is stored in the image memory 305.

[0032] Figure 5(B) shows an example of shading correction when the reading resolution in the main scanning direction is set to 300 dpi. When reading an image of the same width, the number of pixels in the main scanning direction is half the number of pixels at 600 dpi. Therefore, as shown in the figure, the characteristics of the correction coefficient in the main scanning direction also differ from those at 600 dpi, and the shading correction coefficient at 600 dpi cannot be directly used for image reading at 300 dpi. For this reason, it is necessary to match the reading resolution applied to the acquisition process of correction data for shading correction with the reading resolution applied when actually reading the document.

[0033] <Scrawl detection processing from read images> This section describes the skew detection process, which detects the amount of skew in the document during transport from the scanned image. Figure 10 is an explanatory diagram showing how to detect skew in the document from the scanned image. Figure 10(A) is the document to be scanned. Figure 10(B) shows the scanned image obtained by scanning the surface of the document in Figure 12(A) using a skimming method. When scanning the document image with the surface scanning unit 104, considering the possibility of skew occurring in the document, an area larger than the document size is scanned in advance, as shown in Figure 10(C). Specifically, the scanning area is expanded so that the entire document can be scanned even if skew occurs up to the upper limit of the amount allowed by the automatic document scanning device. The main scanning width of the scanning area is fixed to the maximum width that can be scanned by the surface scanning unit 104 and the back scanning unit 216. The sub-scan scanning area is determined by the ON / OFF timing of the read sensor 212.

[0034] The lead sensor 212 is positioned approximately in the center of the main scanning direction. In Figure 2, let L be the distance between the lead sensor 212 and the surface reading position 213. If the document is not skewed, reading can begin from the leading edge of the document by transporting it a distance L from the moment the lead sensor 212 detects that the document is ON (document present). However, if the document is skewed, the lead sensor 212 measures that at position t0, corresponding to the sensor position in Figure 10(B), the timing of the document's leading edge and the reading start position are aligned, but at position t1, where the document is transported fastest due to the skew, the leading edge of the document has already passed. Therefore, if reading is started from this position, the image at t1 will be cut off. Thus, as shown in Figure 10(B), the CPU 301 starts reading the image after the lead sensor 212 has turned ON and the document has been transported to a position before the leading edge skew detection margin Lpre, which is a transport distance (L-Lpre) beyond the distance L. This ensures that the leading edge of the document is read without being cut off.

[0035] The same applies to the trailing edge of the document. When the trailing edge of the document reaches the read sensor 212 and the sensor is detected as OFF (no document), the document is transported a distance L from that point. At position b0, which corresponds to the sensor position, the timing of the main scan coincides with the end of reading the trailing edge of the document. However, at position b2, where transport is most delayed due to skew, the trailing edge of the document has not yet passed the reading position, so when reading is completed, the image at b2 will be missing. Therefore, as shown in the figure, the CPU 301 turns off the read sensor 212 and then transports the document to a position beyond the trailing edge skew detection margin Lpost, which is the transport distance (L+Lpost). This allows the document to be read without the trailing edge being cut off, as the reading is completed only after the document has reached the sensor.

[0036] The image processing unit 306 then performs skew detection processing on the scanned image of the entire document obtained in this way. When scanning a document, a shadow is cast on the outer edge of the document due to the thickness of the document itself. This shadow is detected to determine the leading edge of the document, and the amount of skew is calculated.

[0037] Figure 10(C) shows the edge extraction results in the skew detection region indicated by the diagonal lines in the scanned image of Figure 10(B). Figure 10(D) shows the leading edge of the document and the amount of skew determined from the edges extracted in Figure 10(C). As shown in Figures 10(C) and (D), among the edges extracted from within the skew detection region, the continuous edges closest to the leading edge of the document are detected as the leading edge and lateral edge, and the leading edge skew amount θ is determined from the angle formed by the main scanning direction and the leading edge of the document. TOP The following is calculated. In addition, the coordinates of the reference point indicating the document position are calculated from the intersection of the leading edge and the lateral edge. The coordinates of the reference point are used as the reference for rotation processing during skew correction. The document width is detected from the length of the leading edge of the document.

[0038] After performing the oblique detection process, the image processing unit 306 stores the aforementioned tip oblique amount and the coordinates of the reference point in the RAM 302.

[0039] Figure 11 illustrates a method for correcting the skew of a scanned image. Figure 11(A) shows the scanned image obtained by skimming the surface of the document, and Figure 11(B) shows the image after skew correction. The skew correction process corrects the skew by rotating the image around a reference point.

[0040] The image processing unit 306 rotates the image by the skew correction amount around the aforementioned reference point according to the following formula, and calculates the pixel positions (main scan (X), sub-scan (Y)) for correcting the skew correction amount θ corresponding to the amount of tilt. x0 and y0 are the amounts of translation required to move the tilt-corrected data so that the reference point becomes the center of rotation, and are calculated from the reference point coordinates and the skew correction amount. This makes it possible to align the output positions of the leading edge and lateral edge of the image. X = xcosθ - ysinθ - x0 Y = xsinθ + ycosθ - y0

[0041] X: Corrected pixel position in the main scanning direction, Y: Corrected pixel position in the sub-scanning direction x: Pixel position before correction in the main scanning direction, y: Pixel position before correction in the sub-scanning direction x0: Amount of translation in the main scanning direction (main scanning tilt correction reference position) y0: Amount of translation in the sub-scan direction (reference position for sub-scan tilt correction) θ: Skew correction amount based on the tilt calculated from the leading edge of the document.

[0042] In this embodiment, tilt detection and correction were performed by detecting the shadow of the leading edge of the document and by rotating the image. However, the present invention is not limited to this method, and other methods may be used as long as the position of the rotation center and the oblique angle can be obtained.

[0043] <Mode settings when scanning narrow documents> Let's explain an example of scanning a narrow document. When a document narrower than a specified width, such as a receipt or business card, is placed in the document tray 201, even if the tray width guide plate 203 of the document tray 201 holds the document in place, it is difficult to control its position during transport. Also, because the document is small and the area in contact with each roller inside the device during transport is small, skew is likely to occur.

[0044] Figure 12 is an explanatory diagram illustrating the relationship between resolution and the effective angle for skew correction. It shows an example of skew detection results when scanning a document with the same skew angle at sub-scan resolutions of 600 dpi, and main scan resolutions of 300 dpi and 600 dpi.

[0045] In the case of a main scan of 300 dpi (dotted line in the figure), only the main scan direction is compressed by half, resulting in a tip oblique amount θ. TOP In the case where both the main scan and sub-scan are at 600 dpi (solid line in the figure), the detected angle is twice the actual angle θ, which is 2θ. Since there is an upper limit to the correctable angle, if the angle is detected as twice the actual angle, the range of angles in which skew can be corrected is narrowed to half. For example, if the correction limit is 5°, and the main scan is input at 300 dpi, even if the actual tilt is 3°, the detected angle will be 6°, which exceeds 5°, making complete correction impossible. Therefore, in functions and modes where significant skew is expected, it is desirable to input images at a high resolution in order to maximize the range of angles in which correction is possible.

[0046] Furthermore, in order to perform reading operations with high resolution during transport, the transport speed generally needs to be set slower than in the case of low resolution. By lowering the transport speed, improvements in skewed reading can also be expected.

[0047] Therefore, if the width of the document is restricted by the tray width guide plate 203 and detected by the tray width guide sensor 224 and determined to be narrower than a predetermined threshold, even if the controller specifies a resolution of 300 dpi, the scanning operation will be performed at a scanning resolution of 600 dpi, and the image will be converted to 300 dpi when transferred to the controller 310. If the resolution instruction from the controller is 600 dpi, the scanning operation will be performed at 600 dpi as usual, regardless of the width of the document, and the image will be transferred at that resolution.

[0048] <Example of operation screen> Figure 6 shows an example of the screen flow from the CPU 311 to the CPU 301, which notifies the CPU 301 of a resolution instruction to start the correction data acquisition process based on the input from the operation unit 90.

[0049] Figure 6(A) shows an example of the top screen for setting various scan transmission modes. Buttons for basic settings such as scan color mode selection 613, transmission resolution 614, and duplex function 615 are provided. Settings beyond the basic ones can be further selected by pressing the "Other Functions" button 616. The destination can be selected from an address book (not shown) displayed by pressing the address book button 611, or a new destination can be set using the "New Input" button 612.

[0050] Figure 6(B) shows an example of the screen displayed when the reading color mode selection button 613 is pressed. The options available on this screen are the automatic detection button 621, the color button 622, and the black and white button 623, with automatic detection being the default setting. After selecting the desired mode, the reading color mode is confirmed by pressing the OK button 625. The setting change can also be canceled by pressing the cancel button 624.

[0051] Figure 6(C) shows an example of the screen displayed when the transmission resolution button 614 is pressed. The available transmission resolutions are 100×100dpi button 631, 300×300dpi button 632, and 600×600dpi button 633, with 300×300dpi selected as the default setting. After changing the transmission resolution, you can confirm the transmission resolution with the OK button 635 or cancel the setting change by pressing the Cancel button 634.

[0052] Figure 6(D) shows an example of the screen displayed when the double-sided button 615 is pressed. The up / down opening button 641 and the left / right opening button 642 are provided as selectable double-sided modes. In the default setting, neither is selected. In this state, it is in single-sided mode. After changing the double-sided mode, you can confirm the transmission resolution with the OK button 644, or cancel the setting change by pressing the Cancel button 643.

[0053] In this embodiment, the CPU 311 of the controller 310 sends a read setting notification, including the read settings, to the CPU 301 of the reader 100 each time the user operates one of the operation screens (setting screens) described above. Figure 7(A) shows an example of the read settings included in the read setting notification. For setting items that have not been set using the buttons on each screen, the default setting (initial setting) is included in the read setting notification.

[0054] Furthermore, when the start button 93 on the operation unit 90 is pressed, the CPU 311 sends a start-reading instruction to the CPU 301 to initiate the reader 100's document scanning operation. Figure 7(B) shows an example of the scanning settings included in the start-reading instruction.

[0055] <Processing Procedure> Figure 8 is a flowchart showing an example of the image reading process performed by the CPU 301 of the reader 100.

[0056] While the image reading device 10 is in standby mode, the CPU 301 determines whether or not it has received a reading setting notification from the CPU 311 while the document detection sensor 204 is detecting a document loaded in the document tray 201 (S101). Upon receiving the reading setting notification, the CPU 301 proceeds to S102 and executes a preliminary acquisition process to acquire correction data for shading correction using the reading settings included in the reading setting notification, following the procedure described later using Figure 9(A) (S103). After the preliminary acquisition process is completed, the image reading device 10 transitions to a state waiting for a reading start instruction.

[0057] While waiting for a read start instruction, if a predetermined time elapses without receiving a read start instruction from CPU 311, causing a timeout (YES in S103), CPU 301 executes a cancellation process (S104) which includes discarding the acquired correction data, and returns processing to S101. As a result, the image reading device 10 returns to the standby state.

[0058] While waiting for a read start instruction, if CPU 301 receives another read setting notification from CPU 311 (YES in S105), CPU 301 executes a resolution setting process based on the latest read settings included in the received notification (S106). If CPU 301 determines, as a result of executing the resolution setting process, that it is necessary to change the read resolution setting (YES in S107), it executes a cancellation process (S108) that includes discarding the acquired correction data, and returns to S102. As a result, CPU 301 acquires new correction data by performing a pre-acquisition process again based on the newly received read setting notification.

[0059] As mentioned above, for documents prone to skew, it is desirable to perform image scanning with a higher resolution setting. Here, we will explain the case where scanning is performed with a changed resolution for documents where the width in the main scanning direction of the document is narrower than a predetermined threshold.

[0060] In Figure 2, when a user places a narrow document on the document tray 201, the CPU 301 can obtain the document width based on the output of the tray width guide sensor 224 by setting the tray width guide plate 203 to match the width of the document.

[0061] Based on the determination in S101, the following cases are assumed as conditions for executing the advance acquisition process (S102).

[0062] Case 1 is when the user places the document on the document tray 201, aligns the tray width guide plate 203, and then performs the settings from the control unit 90. The CPU 301 receives the scanning setting notification with the document detection sensor 204 already turned ON. In this case, the value of the tray width guide sensor 224 is already determined when the pre-acquisition process starts, so the document width can be determined.

[0063] Case 2 is when the user inputs various settings from the control unit 90, places the document on the document tray 201, and aligns the tray width guide plate 203. The CPU 301 receives the scanning setting notification while the document detection sensor 204 is OFF, and then detects that the document detection sensor 204 has changed to ON. In this case, depending on how the document is placed, - The tray width guide plate 203 is set before the document detection sensor 204 changes to ON. - The tray width guide plate 203 is set after the document detection sensor 204 turns ON. Two patterns are possible. In the former case, similar to Case 1, the document width can already be determined at the start of the pre-acquisition process. On the other hand, in the latter case, the value of the tray width guide sensor 224 may not yet be determined when the document detection sensor 204 turns ON and the pre-acquisition process starts. For example, suppose the value of the tray width guide sensor 224 at the start of the pre-acquisition process is greater than a predetermined threshold, and then the value of the tray width guide sensor 224 is determined to be smaller than the predetermined threshold. In this case, since the document is narrow, it may be necessary to change the scanning resolution, and the scanning settings required for the actual scanning operation may differ from the scanning settings in the pre-acquisition process.

[0064] Therefore, in the state of waiting for a read start instruction after the completion of the pre-acquisition process (correction data acquisition process), it is determined whether the document width expected from the value of the tray width guide sensor 224 has changed since the start of the pre-acquisition process (S109). If the document width has changed (YE in S109), it is determined whether it is necessary to change the current reading resolution setting due to the change in document width, even if a new reading setting notification has not been received (S107). If it is necessary to change the reading resolution (YES in S107), after canceling the pre-acquisition process (S108), the system does not return to the standby state, but instead executes the pre-acquisition process again with the reading resolution setting determined based on the latest document width (S102).

[0065] When the image reader 10 is in a state of waiting for a read start instruction, if it receives a read start instruction from the CPU 311 (YES in S110), the image reader 10 transitions to a read state, and the CPU 301 starts executing the image reading process. When the image reading process is completed, the CPU 301 returns to S101, and the image reader 10 returns to a standby state.

[0066] In standby mode, if a read start instruction is received (YES in S112) but no read setting notification is received (NO in S101), the CPU 301, because the corresponding prior acquisition process has not been performed, executes the acquisition process for shading correction data (S113) according to the read settings included in the read start instruction, and then executes the image reading process (S111).

[0067] <Prior acquisition process> Figure 9(A) is a flowchart showing an example of the procedure for the pre-acquisition process (S102). When the pre-acquisition process is executed, the operating mode of the pre-acquisition process, including the resolution, is determined based on the mode data received in the read setting notification (S121), and the acquisition process of correction data for shading correction is performed according to the determined setting (S122). The operation performed in the resolution setting process (S121) is the same as the process in S106 in Figure 8.

[0068] Figure 9(B) is a flowchart showing an example of the resolution setting process (S106, S121). In this embodiment, the CPU 301 has at least a first mode and a second mode as operating modes for the pre-acquisition process. The first mode is an operating mode in which, when the user specifies a second resolution as the reading resolution, the pre-acquisition process is performed using the second resolution to acquire correction data. The second mode is an operating mode in which, when the user specifies a second resolution as the reading resolution, the pre-acquisition process is performed using the first resolution to acquire correction data. In the following example, the setting of the reading resolution in S134 corresponds to the setting using the first mode, and the setting of the reading resolution in S133 corresponds to the setting using the second mode.

[0069] The CPU 301 confirms the reading resolution (specified resolution) for the main scanning direction notified in the reading setting notification (S131). If the specified resolution is 600 dpi (first resolution), the CPU 301 sets the reading resolution used for the pre-acquisition process to 600 dpi, the same as the notified resolution, regardless of the document width.

[0070] On the other hand, if the specified resolution is 300 dpi (second resolution), the CPU 301 assumes that the tray width guide plate 203 is aligned with the document and uses the tray width guide sensor 224 to detect the width of the document placed in the document tray 201. If the document width is below a predetermined threshold (e.g., 100 mm) (YES in S132), the CPU 301 sets the reading resolution used in the pre-acquisition process to be changed from 300 dpi (second resolution) to 600 dpi (first resolution). If the document width is above a predetermined threshold (e.g., 100 mm) (NO in S132), the CPU 301 sets the notified specified resolution as the reading resolution used in the pre-acquisition process. The CPU 301 will then execute the pre-acquisition process using the reading resolution in the main scanning direction that was set in the resolution setting process.

[0071] Correction data obtained through the pre-acquisition process and stored in the shading memory 307 is used for shading correction of the read image. For example, the image processing unit 306 is configured to perform shading correction using the correction data on the image data of the read image obtained by reading the document by the front reading unit 104 (or back reading unit 216). Specifically, when the second resolution is specified as the reading resolution and correction data is acquired in the first mode, the image processing unit 306 performs shading correction using the correction data on the image data of the read image generated at the second resolution by the front reading unit 104 (or back reading unit 216), and outputs the corrected image data. Also, when the second resolution is specified as the reading resolution and the correction data is acquired in the second mode, the image processing unit 306 performs shading correction using the correction data on the image data of the read image generated at the first resolution by the front reading unit 104 (or back reading unit 216), performs a downsampling process on the corrected image data to convert the image resolution from the first resolution to the second resolution, and outputs the image data after the downsampling process.

[0072] As described above, the image reading device 10 of this embodiment allows setting at least a first resolution (e.g., 600 dpi) and a second resolution lower than the first resolution (e.g., 300 dpi) as the reading resolution for reading a document transported from the document tray 201, and includes a surface reading unit 104 that reads the document at the set reading resolution. The CPU 301 detects the width of the document placed on the document tray 201, for example, using a tray width guide sensor 224. With a document placed on the document tray 201, the CPU 301 performs a pre-acquisition process to acquire correction data for shading correction using the surface reading unit 104 before receiving an instruction to start reading the document. The CPU 301 has two operating modes for the pre-acquisition process: a first mode in which, when the second resolution is specified as the reading resolution, the pre-acquisition process is performed using the second resolution to acquire correction data, and a second mode in which, when the second resolution is specified as the reading resolution, the pre-acquisition process is performed using the first resolution to acquire correction data.

[0073] This makes it possible to select an appropriate operating mode (i.e., set an appropriate reading resolution) to match the reading resolution actually applied during document scanning, even if the reading resolution specified by the user (e.g., second resolution) differs from the reading resolution used when scanning the document (e.g., first resolution), and then perform the pre-acquisition process. As a result, the reading resolution used when acquiring correction data for shading correction can be matched with the reading resolution used when scanning the document, preventing the FCOT from becoming longer due to having to redo the correction data acquisition process at the start of document scanning. Thus, according to this embodiment, it becomes possible to appropriately set the reading resolution used in the correction data acquisition process for shading correction.

[0074] [Second Embodiment] In the second embodiment, an example is described in which the FCOT is prevented from becoming prolonged by stopping the process under predetermined conditions during the execution of the prior acquisition process (S102) and restarting the prior acquisition process. In the following, the explanation of parts common to the first embodiment will be omitted.

[0075] As explained in the first embodiment, the process of acquiring correction data for shading correction is performed by the CPU 301 in the following procedure. (1) Turn on the surface reading sensor 108. (2) Move the surface reading unit 104 to a predetermined position (HP position) below the surface white reference plate 110. (3) With the surface LED 105 turned off, run the black sample and adjust the black level. (4) Turn on the surface LED 105 and perform the first white sample. (5) Based on the results of the first sample, a threshold is determined for extracting singularities indicating contamination within 110 on the white reference plate. (6) The second sample is taken while moving the surface reading unit 104 within the range below the surface white reference plate 110. This is to actually extract singularities and determine the correction coefficient. (7) Move the surface reading unit 104 back to the HP position. (8) The surface reading unit 104 is moved under the surface white reference plate 110 to perform a third sample. The value of the third sample is used as the actual sample for shading correction. (9) This sample data is corrected for singularities using the correction coefficient determined in the second sample to generate correction data for shading correction, which is then stored in the shading memory 307.

[0076] In this way, the process of acquiring correction data for shading correction involves repeatedly moving the surface reading unit 104 and performing a sample operation.

[0077] If the value of the tray width guide sensor 224 is determined during each of these processes, detecting a change in the document width after the completion of the currently running pre-acquisition process, and then performing the shading correction data acquisition process again after the cancellation process, will increase the FCOT (Field Correction Time). Therefore, in this embodiment, if it is detected that the width of the document placed in the document tray 201 has changed by more than a threshold during the execution of the pre-acquisition process, a decision is made to cancel the currently running pre-acquisition process. Subsequently, by executing the pre-acquisition process again with a reading resolution corresponding to the changed document width, it is possible to prevent the FCOT from becoming longer.

[0078] One case in which the pre-acquisition process is canceled is when a user sets a narrow document and pushes the document all the way in first, causing the document detection sensor 204 to react and enter the "document present" state, after which they move the tray width guide 203. In this case, the pre-acquisition process that is currently running becomes invalid and it has been determined that it will have to be restarted later. Therefore, the CPU 301 cancels the pre-acquisition process that is currently running.

[0079] Figure 13 is a flowchart illustrating an example of the procedure for the pre-acquisition process (S102) in the second embodiment. In S102, the CPU 301 starts the pre-acquisition process using the reading settings included in the reading setting notification (S201). As a result, the image reader 10 transitions to a state of waiting for the pre-acquisition process to finish. If the CPU 301 detects that the document width has changed during the execution of the pre-acquisition process (YES in S202), it executes the resolution setting process according to the procedure in Figure 9(B) (S203). If the CPU 301 determines, as a result of executing the resolution setting process, that it is necessary to change the reading resolution setting (YES in S204), it stops the pre-acquisition process that is currently running (S205). After that, without the state of the image reader 10 returning to the standby state, it starts the pre-acquisition process again using the set (changed) reading resolution (S201).

[0080] On the other hand, if the CPU detects that the document width has changed but there is no need to change the reading resolution setting (NO in S204), the ongoing pre-acquisition process continues. After the pre-acquisition process is completed (YES in S206), the CPU 301 transitions the image reader 10 to a state where it is waiting for a reading start instruction, and proceeds to S103.

[0081] As described above, in this embodiment, when the CPU 301 detects that the width of the document has changed during the execution of the pre-acquisition process, it determines whether it is necessary to change the reading resolution setting based on the changed width of the document, and cancels the pre-acquisition process according to the result of that determination. Furthermore, after canceling the pre-acquisition process, it sets the reading resolution to be used in the pre-acquisition process again based on the specified reading resolution and the changed width of the document, and executes the pre-acquisition process using the set reading resolution. This makes it possible to restart the pre-acquisition process due to a change in reading resolution at an earlier timing than if the pre-acquisition process that is currently running were to continue without being canceled, and thus prevents FCOT from becoming slow.

[0082] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0083] The disclosures herein include the following image reading devices. (Item 1) An image reading device, The reading resolution for reading a document transported from the document tray can be set to at least a first resolution and a second resolution lower than the first resolution, and the reading means reads the document at the set reading resolution. The system includes a control means that performs a pre-acquisition process to acquire correction data for shading correction using the reading means before receiving an instruction to start reading the document while the document is placed in the document tray, The control means includes, as an operating mode for the pre-acquisition process, a first mode in which, when the second resolution is specified as the reading resolution, the pre-acquisition process is performed using the second resolution to acquire the correction data, and a second mode in which, when the second resolution is specified as the reading resolution, the pre-acquisition process is performed using the first resolution to acquire the correction data. (Item 2) The system further includes a detection means for detecting the width of a document placed in the document tray, When the second resolution is specified as the reading resolution, the control means selects either the first mode or the second mode based on the width of the document and performs the pre-acquisition process. The image reading device described in item 1. (Item 3) When the second resolution is specified as the reading resolution, the control means performs the pre-acquisition process in the second mode if the width of the document is below a threshold. The image reading device described in item 2. (Item 4) When the second resolution is specified as the reading resolution, the control means performs the pre-acquisition process in the first mode if the width of the document is not below the threshold. The image reading device described in item 3. (Item 5) When the first resolution is specified as the reading resolution, the control means uses the first resolution for the pre-acquisition process, regardless of the width of the original document. An image reading device as described in any one of items 2 through 4. (Item 6) After the completion of the pre-acquisition process, if the detection means detects that the width of the document has been changed before the start instruction is received, the control means determines whether it is necessary to change the reading resolution setting based on the changed width of the document, and executes the pre-acquisition process again according to the result of the determination. An image reading device as described in any one of items 2 through 5. (Item 7) If the user changes the specified reading resolution after the completion of the pre-acquisition process but before receiving the start instruction, the control means determines whether it is necessary to change the setting of the reading resolution based on the specified reading resolution and the width of the document, and executes the pre-acquisition process again according to the result of the determination. An image reading device as described in any one of items 2 through 6. (Item 8) When the control means determines that it is necessary to change the reading resolution setting, it will execute the prior acquisition process again using the changed reading resolution. An image reading device as described in item 6 or 7. (Item 9) If the detection means detects that the width of the document has changed during the execution of the pre-acquisition process, the control means determines whether it is necessary to change the reading resolution setting based on the changed width of the document, and cancels the pre-acquisition process according to the result of the determination. An image reading device as described in any one of items 1 through 8. (Item 10) If the control means determines that it is necessary to change the reading resolution setting during the execution of the pre-acquisition process, it will terminate the pre-acquisition process. The image reading device described in item 9. (Item 11) After the pre-acquisition process is terminated, the control means sets the reading resolution to be used in the pre-acquisition process again based on the specified reading resolution and the modified width of the original document, and then executes the pre-acquisition process using the set reading resolution. The image reading device described in item 10. (Item 12) The control means discards the correction data acquired in the prior acquisition process if a predetermined time has elapsed after the completion of the prior acquisition process but before the start instruction is received. An image reading device as described in any one of items 1 through 11. (Item 13) The control means, before receiving the start instruction, obtains the reading resolution specified by the user via a setting screen displayed on the display unit, and sets the reading resolution to be used in the pre-acquisition process based on the obtained reading resolution and the width of the document. An image reading device as described in any one of items 1 through 12. (Item 14) The system further includes a processing means for performing shading correction on the image data of the read image obtained by reading the document by the reading means, using the correction data. The processing means is When the second resolution is specified as the reading resolution and the correction data is acquired in the first mode, the reading means performs shading correction on the image data of the read image generated at the second resolution using the correction data, and outputs the corrected image data. When the second resolution is specified as the reading resolution and the correction data is acquired in the second mode, the reading means performs shading correction on the image data of the read image generated at the first resolution using the correction data, performs a downsampling process on the corrected image data to convert the image resolution from the first resolution to the second resolution, and outputs the image data after the downsampling process. An image reading device as described in any one of items 1 through 13.

[0084] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of Symbols]

[0085] 10: Image reading device, 100: Reader (image reading unit), 200: ADF (Automatic Document Feeder), 310: Controller, 301, 311: CPU

Claims

1. An image reading device, The reading resolution for reading a document transported from the document tray can be set to at least a first resolution and a second resolution lower than the first resolution, and the reading means reads the document at the set reading resolution. The system includes a control means that performs a pre-acquisition process to acquire correction data for shading correction using the reading means before receiving an instruction to start reading the document while the document is placed in the document tray, The control means includes, as an operating mode for the pre-acquisition process, a first mode in which, when the second resolution is specified as the reading resolution, the pre-acquisition process is performed using the second resolution to acquire the correction data, and a second mode in which, when the second resolution is specified as the reading resolution, the pre-acquisition process is performed using the first resolution to acquire the correction data.

2. The system further includes a detection means for detecting the width of a document placed in the document tray, When the second resolution is specified as the reading resolution, the control means selects either the first mode or the second mode based on the width of the document and performs the pre-acquisition process. The image reading device according to claim 1.

3. When the second resolution is specified as the reading resolution, the control means performs the pre-acquisition process in the second mode if the width of the document is below a threshold. The image reading device according to claim 2.

4. The control means, when the second resolution is specified as the reading resolution, performs the pre-acquisition process in the first mode if the width of the document is not below the threshold. The image reading device according to claim 3.

5. When the first resolution is specified as the reading resolution, the control means uses the first resolution for the pre-acquisition process, regardless of the width of the original document. The image reading device according to any one of claims 2 to 4.

6. After the completion of the pre-acquisition process, if the detection means detects that the width of the document has been changed before the start instruction is received, the control means determines whether it is necessary to change the reading resolution setting based on the changed width of the document, and executes the pre-acquisition process again according to the result of the determination. The image reading device according to any one of claims 2 to 4.

7. If the user changes the specified reading resolution after the completion of the pre-acquisition process but before receiving the start instruction, the control means determines whether it is necessary to change the setting of the reading resolution based on the specified reading resolution and the width of the document, and executes the pre-acquisition process again according to the result of the determination. The image reading device according to any one of claims 2 to 4.

8. When the control means determines that it is necessary to change the reading resolution setting, it will execute the prior acquisition process again using the changed reading resolution. The image reading device according to claim 6.

9. If the detection means detects that the width of the document has changed during the execution of the pre-acquisition process, the control means determines whether it is necessary to change the reading resolution setting based on the changed width of the document, and cancels the pre-acquisition process according to the result of the determination. The image reading device according to any one of claims 2 to 4.

10. If the control means determines that it is necessary to change the reading resolution setting during the execution of the pre-acquisition process, it will terminate the pre-acquisition process. The image reading device according to claim 9.

11. After the pre-acquisition process is terminated, the control means sets the reading resolution to be used in the pre-acquisition process again based on the specified reading resolution and the modified width of the original document, and then executes the pre-acquisition process using the set reading resolution. The image reading device according to claim 10.

12. The control means discards the correction data acquired in the prior acquisition process if a predetermined time has elapsed after the completion of the prior acquisition process but before the start instruction is received. The image reading device according to any one of claims 1 to 4.

13. The control means, before receiving the start instruction, obtains the reading resolution specified by the user via a setting screen displayed on the display unit, and sets the reading resolution to be used in the pre-acquisition process based on the obtained reading resolution and the width of the document. The image reading device according to any one of claims 2 to 4.

14. The system further includes a processing means for performing shading correction on the image data of the read image obtained by reading the document by the reading means, using the correction data. The processing means is When the second resolution is specified as the reading resolution and the correction data is acquired in the first mode, the reading means performs shading correction on the image data of the read image generated at the second resolution using the correction data, and outputs the corrected image data. When the second resolution is specified as the reading resolution and the correction data is acquired in the second mode, the reading means performs shading correction on the image data of the read image generated at the first resolution using the correction data, performs a downsampling process on the corrected image data to convert the image resolution from the first resolution to the second resolution, and outputs the image data after the downsampling process. The image reading device according to any one of claims 1 to 4.

Images