JP2020150458A - Image reading device, image reading method, and program - Google Patents

Abstract

To provide an image reading device that can detect a mark position or an edge position of a print medium more accurately than before even if relative transfer speed between the print medium and a line sensor is high.SOLUTION: An image reading device includes: a color image sensor in which a plurality of color filters are arranged in a sheet transfer direction; a driving mechanism that relatively moves a sheet and the color image sensor in the sheet transfer direction; and a control unit that detects the position of the sheet by using luminance data of two or more colors of image data acquired by the color image sensor.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image reader, an image reading method and a program.

An image reading device is known that acquires image data by reading a region whose longitudinal direction is a direction (main scanning direction) perpendicular to the moving direction (secondary scanning direction).

In the image reader of Patent Document 1, two line sensors of each color of R (red), G (green), and B (blue) are arranged at intervals, and the image reading device is switched between the low resolution mode and the high resolution mode for reading. I do. In the low resolution mode, reading is performed while sequentially changing the reading position at intervals between the two line sensors, and image data at the same position is combined. In the high resolution mode, reading is performed while sequentially changing the reading position at intervals obtained by dividing the distance between the two line sensors by a predetermined number, and image data at the same position is combined.

By the way, in the image reading device, the mark position or the edge position is detected by using the pixel information of one color having the highest brightness. Therefore, the conventional image reading device may not be able to cope with the increase in the transport speed of the print medium at the time of image reading.

The present invention has been made in view of the above, and even if the relative transport speed between the print medium and the line sensor is high, the mark position or edge position of the print medium is more accurate than before. It is an object of the present invention to provide an image reading device, an image reading method and a program that can be detected well.

In order to solve the above-mentioned problems and achieve the object, the present invention relates a color image sensor in which color filters of a plurality of colors are arranged in the paper transport direction, and the paper and the color image sensor relative to the paper transport direction. It is characterized by including a drive mechanism for moving the paper, and a control unit for detecting the position of the paper using brightness data of two or more colors among the image data acquired by the color image sensor.

According to the present invention, even if the transport speed of the print medium is increased, the mark position or edge position of the print medium can be detected more accurately than in the conventional case.

FIG. 1 is a diagram showing an example of the overall configuration of an image forming apparatus including the image reading apparatus according to the first embodiment. FIG. 2 is a block diagram showing an example of electrical connection of hardware of an image forming apparatus. FIG. 3 is a block diagram showing an example of the functional configuration of the image reading device according to the first embodiment. FIG. 4 is a diagram showing an example of a color image sensor. FIG. 5 is a diagram schematically showing a time-series positional relationship between the color image sensor and the paper in the reading region. FIG. 6 is a diagram showing an example of luminance data of each color of R, G, and B in the detection region. FIG. 7 is a diagram showing an example of pixel position conversion processing. FIG. 8 is a diagram showing an example of a combination process of relative luminance data. FIG. 9 is a flowchart showing an example of the procedure of the image reading method according to the first embodiment. FIG. 10 is a flowchart showing an example of the procedure of the color selection process. FIG. 11 is a flowchart showing an example of the procedure of the level correction process. FIG. 12 is a flowchart showing an example of the procedure of the pixel position conversion process. FIG. 13 is a flowchart showing an example of the procedure of the color selection process according to the second embodiment. FIG. 14 is a diagram showing an example of color selection information.

Hereinafter, embodiments of an image reading device, an image reading method, and a program according to the present invention will be described in detail with reference to the drawings. Further, the present invention is not limited by the following embodiments, and the components in the following embodiments include those easily conceived by those skilled in the art, substantially the same, and so-called equivalent ranges. Is included. Furthermore, various omissions, substitutions, changes and combinations of components can be made without departing from the gist of the following embodiments.

(First Embodiment)
[Configuration of image forming apparatus]
FIG. 1 is a diagram showing an example of the overall configuration of an image forming apparatus including the image reading apparatus according to the first embodiment. The overall configuration of the image forming apparatus 1 will be described with reference to FIG.

As shown in FIG. 1, the image forming apparatus 1 includes a paper feeding unit 11, a precoating unit 12, an image forming unit 13, a drying / cooling unit 14, an inversion unit 15, and a paper ejection unit 16. I have.

The paper feed unit 11 is a unit that feeds paper, which is a print medium, one by one and conveys it to the precoat unit 12.

The pre-coating unit 12 is a unit for pre-applying a pre-coating liquid for fixing ink on paper. Since some papers are difficult to fix the ink, it is possible to easily fix the ink by applying the precoat liquid in advance by the precoat unit 12. Further, the precoating unit 12 applies the precoating liquid to the paper, dries it with a heater, and conveys the paper to the image forming unit 13.

The image forming unit 13 is a unit that winds paper around a drum, conveys it, and performs printing processing (image formation) by a line head type recording head. Details of the configuration of the image forming unit 13 will be described later. The image forming unit 13 conveys the printed paper to the drying / cooling unit 14.

The drying / cooling unit 14 is a unit that dries the moisture of the ink on the paper on which the image is printed and fixes the ink on the paper. Further, the drying / cooling unit 14 dries the paper, cools the high-temperature paper to lower the temperature, and conveys the paper to the reversing unit 15.

When the reversing unit 15 is set for double-sided printing, the reversing unit 15 performs switchback reversal on the paper whose surface is printed, which is transferred from the drying / cooling unit 14, and transfers the paper to the image forming unit 13. It is a unit. Here, the switchback reversal means that the paper tip passes through the reversing roller in order to replace the two opposing sides (the side at the front end of the paper and the side at the rear end of the paper) that are perpendicular to the paper transport direction. This is a reversing method in which the rotation direction of the reversing roller is reversed before the rear end passes, and the end of the paper, which was the rear end, is used as the front end. When the reversing unit 15 is set to normal printing (single-sided printing) instead of double-sided printing, the reversing unit 15 does not perform switchback reversal on the paper and conveys the paper to the paper ejection unit 16.

The paper ejection unit 16 is a unit that ejects the printed paper conveyed from the reversing unit 15 to the stack portion.

The unit configuration of the image forming apparatus 1 shown in FIG. 1 is an example, and other unit configurations may be used. For example, when the paper feed volume of the paper feed unit 11 is large, the paper feed unit may be configured by connecting a plurality of units. Further, for example, a resist unit for adjusting the paper transport timing, adjusting the position, and the like may be arranged between the precoating unit 12 and the image forming unit 13.

The image reading device 20 according to the present embodiment is used for the purpose of reading the paper image position after front surface printing and feeding back to the printing position of the back surface image in the double-sided printing process. Therefore, for example, it is provided on the double-sided transport path in the image forming unit 13.

FIG. 2 is a block diagram showing an example of electrical connection of hardware of an image forming apparatus.

As shown in FIG. 2, the image forming apparatus 1 has a configuration in which the controller 100, the engine unit (Engine) 160, and the engine unit (Engine) 170 are connected by a PCI bus. The controller 100 is a controller that controls overall control, drawing, communication, and input from the operation panel 120, which is an operation display unit, of the image forming apparatus 1. The engine unit 160 is an engine that can be connected to the PCI bus, and is, for example, a scanner engine or the like. In addition to the engine portion, the engine portion 160 also includes an image processing portion such as error diffusion or gamma conversion. The engine unit 170 is an engine that can be connected to the PCI bus, and is, for example, a print engine unit such as an image forming unit 13.

The controller 100 includes a CPU (Central Processing Unit) 111, a north bridge (NB) 113, a system memory (MEM-P) 112, a south bridge (SB) 114, a local memory (MEM-C) 117, and an ASIC. (Application Specific Integrated Circuit) 116 and a hard disk drive (HDD) 118 are provided, and the NB 113 and the ASIC 116 are connected by an AGP (Accelerated Graphics Port) bus 115. Further, the MEM-P112 further includes a ROM 112a and a RAM 112b.

The CPU 111 controls the entire image forming apparatus 1, has a chipset including NB113, MEM-P112, and SB114, and is connected to other devices via this chipset.

The NB 113 is a bridge for connecting the CPU 111 to the MEM-P112, SB114, and the AGP bus 115, and has a memory controller that controls reading and writing to the MEM-P112, a PCI master, and an AGP target.

The MEM-P112 is a system memory used as a memory for storing a program or data, a memory for expanding a program or data, a memory for drawing a printer, or the like, and includes a ROM 112a and a RAM 112b. The ROM 112a is a read-only memory used as a memory for storing a program or data, and the RAM 112b is a writeable and readable memory used as a memory for expanding a program or data, a memory for drawing a printer, and the like.

The SB 114 is a bridge for connecting the NB 113 to the PCI device and peripheral devices. The SB 114 is connected to the NB 113 via a PCI bus, and a network interface (I / F) unit or the like is also connected to the PCI bus.

The ASIC 116 is an IC (Integrated Circuit) for image processing applications having hardware elements for image processing, and has a role of a bridge connecting the AGP bus 115, the PCI bus, HDD 118, and MEM-C117, respectively. This ASIC116 includes a PCI target and an AGP master, an arbiter (ARB) which is the core of the ASIC116, a memory controller which controls MEM-C117, and a plurality of DMACs (Direct Memory) which rotate image data by hardware logic and the like. It consists of an Access Controller) and a PCI unit that transfers data between the engine unit 160 or the engine unit 170 via the PCI bus. A USB 40 and an IEEE 1394 (the Institute of Electrical and Electronics Engineers 1394) interface (I / F) 150 are connected to the ASIC 116 via a PCI bus. The operation panel 120 is directly connected to the ASIC 116.

The MEM-C117 is a local memory used as an image buffer and a code buffer, and the HDD 118 is a storage for accumulating image data, a program, font data, and a form.

The AGP bus 115 is a bus interface for a graphics accelerator card proposed to speed up graphic processing, and speeds up the graphics accelerator card by directly accessing the MEM-P112 with high throughput. ..

The program executed by the image forming apparatus 1 of the present embodiment is a file in an installable format or an executable format, such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disk). It may be configured to be recorded and provided on a computer-readable recording medium.

Further, the program executed by the image forming apparatus 1 of the present embodiment may be stored on a computer connected to a network such as the Internet and provided by downloading via the network. Further, the program executed by the image forming apparatus 1 of the present embodiment may be configured to be provided or distributed via a network such as the Internet.

[Configuration of image reader]
FIG. 3 is a block diagram showing an example of the functional configuration of the image reading device according to the first embodiment. The image reading device 20 includes a color image sensor 21, a driving mechanism 22, and a control unit 23.

The color image sensor 21 is an image reading unit that reads a color image printed on paper, which is a printing medium. The color image sensor 21 is, for example, a three-line image sensor that combines red (R), green (G), and blue (B) filters. FIG. 4 is a diagram showing an example of a color image sensor, FIG. 4A is a diagram showing an arrangement relationship between the color image sensor and a print medium, and FIG. 4B is a diagram showing a color filter inside the color image sensor. It is a figure which shows an example of the arrangement of.

As shown in FIG. 4A, the color image sensor 21 reads an image of the paper 310 to be edge-detected. The color image sensor 21 is arranged so that the transport direction of the paper 310 or the color image sensor 21 is the sub-scanning direction of the color image sensor 21. In the present embodiment, the color image sensor 21 is not a light source line switching type that sequentially switches and reads RGB light sources, but a color filter type in which RGB color filters are arranged in the sub-scanning direction.

The color pixels 211R, 211G, 211B of the color filters arranged in the sub-scanning direction at a predetermined position in the direction perpendicular to the sub-scanning direction (main scanning direction) constitute one pixel. The color pixels 211R, 211G, and 211B within one pixel are arranged, for example, in the scanning direction with a color pixel pitch Δp. The color image sensor 21 reads color data within one pixel for three colors in each scan cycle Δt, but strictly speaking, the color data actually read is color data in a region different by the color pixel pitch Δp in the sub-scanning direction. It means that you have acquired it.

The edge detection target includes the interface between the background 320 and the paper 310 or the interface between the paper 310 and the register mark 311 in the paper, and these edges are detected in the detection area 331 in the scanned image. The number of pixels and the arrangement direction of the color image sensor 21 used here do not necessarily have to match the example shown in FIG.

The drive mechanism 22 moves at least one of the color image sensor 21 and the print medium relatively in the sub-scanning direction of the color image sensor 21.

The control unit 23 acquires image data from the color image sensor 21, detects the position of the paper such as the edge position of the paper or the position of the register mark, and performs processing such as reading the shape of the paper. The control unit 23 includes an image data acquisition unit 231, a color selection unit 232, a level correction unit 233, a pixel position conversion unit 234, and a coupling processing unit 235.

The image data acquisition unit 231 acquires a color image from the color image sensor 21.

The color selection unit 232 selects a color to be used for determining the edge position by using the luminance data collected from the luminance information of each of the R, G, and B colors in the acquired color image. As will be described later, the color selection unit 232 selects a plurality of colors when there are two or more colors whose maximum absolute brightness exceeds the threshold value.

FIG. 5 is a diagram schematically showing a time-series positional relationship between the color image sensor and the paper in the reading region. In this figure, the horizontal axis represents time and the vertical axis represents position. When the scan cycle of the color image sensor 21 is Δt, the transfer distance interval, which is the distance (secondary scanning resolution) that the paper 310 or the color image sensor 21 is conveyed in the time of Δt, is ΔL. Each time _{t i (i = n, n} + 1, n + 2, n + 3, ···) will be referred to as a position read by the color image sensor 21 in the line.

In a general image reading device, edge detection data is calculated using only the luminance information of one color among the luminance information acquired by the color pixels arranged in the transport direction. In this case, the luminance information could be acquired only at the transport distance interval ΔL.

On the other hand, in the present embodiment, attention is paid to the fact that a plurality of color filters (color pixels 211R, 211G, 211B) are arranged in the sub-scanning direction, and the luminance information acquired by at least two color pixels is used. That is, the detection result of the reference color pixel is complemented by using the detection result of another color pixel. As a result, the luminance information can be acquired at intervals less than the transport distance interval ΔL.

When brightness information is acquired by extracting only one color, for example, G data, as in a general image reader at times t _{n to} t _{n + 3} in FIG. 5, the obtained luminance information is the transport distance. There are only four points with an interval of ΔL. However, if at least one of the color data of the R data and the B data can be used in addition to the G data, the color data of at least one position of ΔL + Δp and ΔL−Δp is sampled in addition to the G data of the transport distance interval ΔL. The points can be complemented. Therefore, the apparent resolution in the sub-scanning direction is increased, and the ability to follow the change in brightness in the vicinity of the edge is improved.

Therefore, in the present embodiment, the color selection unit 232 calculates the maximum luminance value for the luminance data (hereinafter, also referred to as color data) of each color of R, G, and B in the detection region 331, and the maximum luminance value is a predetermined threshold value. Select the above color. When there are two or more selected colors, the color selection unit 232 sets a correction processing execution flag indicating the execution of the correction processing described below. If there is only one selected color, the correction processing execution flag is not set.

FIG. 6 is a diagram showing an example of luminance data of each color of R, G, and B in the detection region. In this figure, the horizontal axis represents time (position) and the vertical axis represents the brightness of each pixel. For example, when the threshold value used as a reference for determination is TH1, the maximum luminance value of the luminance data of R and G exceeds the threshold value TH1, but the maximum value of the luminance data of B does not exceed the threshold value TH1. Therefore, here, R and G are selected as color pixels, and a correction processing execution flag is set.

The level correction unit 233 converts the absolute luminance data for the color selected by the color selection section 232 into relative luminance data, and performs correction to match the level of the luminance data of each color. For example, by aligning the white level of the acquired image data with all colors, the luminance data of the image is converted from the absolute luminance to the relative luminance. Relative brightness is expressed as a percentage with the minimum brightness value as 0% and the maximum brightness value as 100%. The minimum luminance value and the maximum luminance value of the m-th pixel are searched within the range indicated by the detection area 331 in the read image data. For example, the relative brightness of the m-th pixel of the n-th line is obtained by the following equation (1).
Relative brightness (n-line, m-pixel)%
= Absolute brightness (n-line, m-pixel) ÷ [Maximum brightness (m-pixel) -Minimum brightness (m-pixel)] x 100 ... (1)

This correction is nothing other than performing shading correction on the paper background and background (LED ON) instead of the normal shading correction performed on absolute white (white reference plate) and absolute black (LED OFF).

The pixel position conversion unit 234 performs a conversion process for shifting the relative luminance data of the color selected by the color selection unit 232 from the data line position to the pixel position in consideration of the position of the color pixel in the actual color image sensor 21. Do. For example, from FIG. 4 and FIG. 5, among the pixel data acquired at the same time, the color pixel 211G is used as the reference pixel. The color pixels 211R and 211B are displaced by ± Δp with respect to the position of the reference pixel. The pixel position conversion unit 234 performs a process of aligning the position of the relative luminance data acquired by the color pixels other than the reference pixel with the position coordinates of the relative luminance data of the reference pixel.

7A and 7B are diagrams showing an example of pixel position conversion processing, FIG. 7A is a diagram showing relative luminance data before the conversion processing is performed, and FIG. 7B is a diagram showing an example of R data conversion processing. , (C) are diagrams showing an example of B data conversion processing, and (d) is relative luminance data after the conversion processing is performed. In these figures, the horizontal axis represents the detection position and the vertical axis represents the relative brightness. The scale on the horizontal axis indicates the color pixel pitch Δp. Here, it is assumed that the transport distance interval ΔL in the scan cycle Δt is half of the color pixel pitch Δp. Further, it is assumed that all the colors are selected by the color selection unit 232.

As shown in FIG. 7A, relative luminance data of each color of R, G, and B can be obtained. Here, the pixel position conversion processing of the relative luminance data of R and B is performed with reference to the relative luminance data of G acquired by the color pixels 211G arranged in the center of the color image sensor 21 in the sub-scanning direction.

First, as shown in FIG. 7B, the pixel position conversion process of the relative luminance data of R is performed. As shown in FIG. 4B, within one pixel of the color image sensor 21, the color pixels 211R of R are arranged so as to be offset by the color pixel pitch Δp in the sub-scanning direction with respect to the color pixels 211G of G. There is. Therefore, the position of each relative luminance information constituting the relative luminance data of R is shifted in the direction of the color pixel 211G of G by the color pixel pitch Δp.

Then, as shown in FIG. 7C, the pixel position conversion process of the relative luminance data of B is performed. As shown in FIG. 4B, within one pixel of the color image sensor 21, the color pixels 211B of B are arranged so as to be offset by the color pixel pitch Δp in the sub-scanning direction with respect to the color pixels 211G of G. There is. Therefore, the position of each relative luminance information constituting the relative luminance data of B is shifted in the direction of the color pixel 211G of G by the color pixel pitch Δp. As a result of performing the above processing, as shown in FIG. 7D, the relative luminance data of R and B is shifted to the detection position of the relative luminance data of G as a reference.

Here, the color pixel 211G of G arranged in the center of the color image sensor 21 in the sub-scanning direction is used as a reference pixel, but it is also possible to use the color pixel 211G of R at both ends or the color pixel 211B of B at both ends as a reference. .. Further, when the distance between edges is calculated based on the results of detecting a plurality of edge positions for the purpose of calculating the center position of the register mark, the reference pixels used for detecting all the edge positions are unified.

The combination processing unit 235 sorts and combines the relative luminance data of all the colors obtained by the pixel position conversion unit 234 in the order of the data positions, so that the edge detection has an increased resolution as compared with the case of a single color. Generate brightness change data for. At this time, when a plurality of relative luminance information exists at the same position due to the relationship between the transport speed, the scan cycle, and the color pixel pitch, the coupling processing unit 235 sets the average value of them as the data at that position. Perform the averaging process.

FIG. 8 is a diagram showing an example of a combination process of relative luminance data, FIG. 8A is a diagram showing an example of an averaging process for the relative luminance data of FIG. 7D, and FIG. It is a figure which shows the example of the combination processing using the data of a). At the positions P1 and P2 in FIG. 8A, the relative luminance information of R, G, and B exists at the same detection position. Therefore, the coupling processing unit 235 calculates an average value of a plurality of relative luminance information at the same detection position, and uses this average value as the relative luminance information at the calculated detection position. After performing the averaging process at all the detection positions where a plurality of relative brightness information exists, the relative brightness information, or the average values of the relative brightness information and the relative brightness information are sorted and combined in the order of the detection positions. The luminance change data shown in 8 (b) can be obtained.

By executing the correction processing in the level correction unit 233, the pixel position conversion unit 234, and the coupling processing unit 235 over the entire data range (n _max × m _max ) of the scanned image, at each pixel position in the main scanning direction. Luminance change data for edge detection is generated.

[Image reading method]
Next, an image reading method in such an image reading device 20 will be described. FIG. 9 is a flowchart showing an example of the procedure of the image reading method according to the first embodiment. First, adjustment processing of the reading system such as shading correction and black-and-white level adjustment is performed (step S11), and image reading is performed by the color image sensor 21 (step S12). As a result, the image data acquisition unit 231 acquires the image data read by the color image sensor 21.

Next, the color selection unit 232 executes a color selection process for selecting a color pixel used for edge position determination (step S13).

FIG. 10 is a flowchart showing an example of the procedure of the color selection process. First, the color selection unit 232 initializes the color data correction processing execution flag (step S31). The correction processing execution flag indicates whether or not to carry out the correction processing for generating the luminance change data in which the relative luminance information of two or more colors is combined.

Next, the color selection unit 232 calculates the maximum luminance value for the absolute luminance data of each color (step S32), and determines whether there are two or more absolute luminance data whose maximum luminance value is equal to or more than the threshold value (step S33). When there are two or more absolute luminance data in which the maximum luminance value is equal to or greater than the threshold value (Yes in step S33), the color selection unit 232 selects a color having the maximum luminance value equal to or greater than the threshold value and corrects it. The process execution flag is set (step S34). The reason for excluding the color data whose maximum luminance value is less than the threshold value here is that if the dynamic range of the absolute luminance is low, the accuracy of the intermediate luminance near the edge deteriorates when converted to the relative luminance. That is, the threshold value can be set to such a degree that the accuracy of the intermediate brightness near the edge does not deteriorate when converted to the relative brightness. Then, the process returns to FIG.

Further, when there are less than two absolute luminance data whose maximum luminance value is equal to or greater than the threshold value (No in step S33), the correction process according to the present embodiment cannot be executed, so that the color selection unit 232 , The absolute luminance data having the highest maximum luminance value is selected (step S35). At this time, the color selection unit 232 does not set the correction processing execution flag. Then, the process returns to FIG. If the color data correction processing execution flag is not set, the subsequent level correction processing in step S14 to the pixel position conversion processing in step S15 are not executed, and the brightness data of one color is used in step S16. Edge position determination processing will be performed.

After that, returning to FIG. 9, the level correction unit 233 performs a level correction process for converting the absolute luminance data of the selected color into the relative luminance data (step S14).

FIG. 11 is a flowchart showing an example of the procedure of the level correction process. The level correction unit 233 determines whether the correction processing execution flag is set for the color pixel R (step S51). When the correction processing execution flag is set (Yes in step S51), the level correction unit 233 uses the equation (1) to relative the absolute luminance data acquired by the color pixel R in the image data. It is converted into luminance data (step S52).

After that, or when the correction processing execution flag is not set in step S51 (No in step S51), the level correction unit 233 determines whether the correction processing execution flag is set for the color pixel G (step S53). ). When the correction processing execution flag is set (Yes in step S53), the level correction unit 233 uses the equation (1) to relative the absolute luminance data acquired by the color pixels G in the image data. It is converted into luminance data (step S54).

After that, or when the correction processing execution flag is not set in step S53 (No in step S53), the level correction unit 233 determines whether the correction processing execution flag is set for the color pixel B (step S55). ). When the correction processing execution flag is set (Yes in step S55), the level correction unit 233 uses the equation (1) to relative the absolute luminance data acquired by the color pixel B in the image data. It is converted into luminance data (step S56). After that, or when the correction processing execution flag is not set in step S55 (when No in step S55), the level correction processing ends and the processing returns to FIG.

In the example of edge detection of the paper 310 in FIG. 4, the minimum level is set to the background of the transport path, and the maximum level is changed to match the background of the paper 310. By this operation, the absolute luminance change amount of each color data near the paper edge is converted into the relative luminance change between the transport path background and the paper background, and the relative luminance level of each color pixel different depending on the paper color is unified. It can be expressed by quantity.

Returning to FIG. 9, after the level correction process, the pixel position conversion process using the converted relative luminance data of each color is performed (step S16).

FIG. 12 is a flowchart showing an example of the procedure of the pixel position conversion process. Here, it is assumed that the line exists from the 0th to the nth (n is a natural number of 2 or more) and the pixel exists from the 0th to the m (m is a natural number of 2 or more). Further, an example will be given in which the color pixel G is used as the reference pixel.

First, the pixel position conversion unit 234 selects the 0th line and the 0th pixel (step S71). Next, the pixel position conversion unit 234 determines whether the correction processing execution flag is set for the color pixel R (step S72). When the correction processing execution flag is set (Yes in step S72), the relative brightness information of the color pixel R of the mth pixel at the nth line is shifted by the color pixel pitch Δp from the color pixel G (step). S73). For example, the line positions in the sub-scanning direction (conveying direction) of the relative luminance information acquired by the color pixels R of interest and x _nm, when the relative luminance and V _Rnm, color data R _nm after shift (x _nm + Δp, V _Rnm ).

When the correction processing execution flag is not set (No in step S72), the relative luminance information is set as empty data because the R data is not used (step S74). In the above example, the color data R _nm after shifting is (x _nm + Δp, null).

After step S73 or after step S74, the pixel position conversion unit 234 determines whether the correction processing execution flag is set for the color pixel G (step S75). When the correction processing execution flag is set (Yes in step S75), the relative brightness information of the color pixel G of the m-th pixel at the n-th line is shifted by the color pixel pitch from the color pixel G (step S76). ). Here, since the color pixel G is used as the reference pixel, the color pixel pitch is 0. For example, the line positions in the sub-scanning direction (conveying direction) of the relative luminance information acquired in the color pixel G of interest and x _nm, when the relative luminance and V _GNM, color data G _nm after shift (x _nm , V _Gnm ).

When the correction processing execution flag is not set (No in step S75), the relative luminance information is set as empty data because G data is not used (step S77). In the above example, the color data G _nm after shifting is (x _nm , null).

After step S75 or after step S77, the pixel position conversion unit 234 determines whether the correction processing execution flag is set for the color pixel B (step S78). When the correction processing execution flag is set (Yes in step S78), the relative brightness information of the color pixel B of the m-th pixel on the n-th line is shifted by the color pixel pitch Δp from the color pixel G (step). S79). For example, the line positions in the sub-scanning direction (conveying direction) of the relative luminance information acquired in the color pixel B of interest and x _nm, when the relative luminance and V _Bnm, color data B _nm after shift (x _nm −Δp, V _Bnm ).

When the correction processing execution flag is not set (No in step S79), the relative luminance information is set as empty data because the B data is not used (step S80). In the above example, the color data B _nm after shifting is (x _nm −Δp, null).

After step S79 or after step S80, the combination processing unit 235 sorts and combines the color data of the m-th pixel in the order of the converted positions (step S81). After that, the combination processing unit 235 determines whether or not a plurality of color data exists at the same position (step S82). When a plurality of color data exist at the same position (Yes in step S82), the combination processing unit 235 calculates the average value of the relative luminance information of the color data at the same position, and the calculated average value is used as the corresponding position. Performs averaging processing using the relative luminance information of (step S83).

After that, or when a plurality of color data do not exist at the same position in step S82 (No in step S82), the pixel position conversion unit 234 determines whether the line currently being processed is the last line (when it is No). Step S84). That is, it is determined whether or not another line exists. If it is not the last line (No in step S84), the next line is selected (step S85), and the process returns to step S72. Then, by performing the processes of steps S72 to S83 at the positions of all the lines for the m-th pixel, the luminance change data for edge detection can be obtained.

If it is the last line (Yes in step S84), the pixel position conversion unit 234 selects the 0th line (step S86), and is the pixel currently being processed the last pixel? Is determined (step S87). That is, it is determined whether or not another pixel exists. If it is not the last pixel (No in step S87), the next pixel is selected (step S88), and the process returns to step S72. Then, by performing the processes of steps S72 to S88 for all the pixels, the luminance change data for edge detection can be obtained at the position of each pixel in the main scanning direction. After that, the process returns to FIG.

Returning to FIG. 9 again, the edge position determination process is performed using the obtained luminance change data for edge detection (step S16). This completes the process.

As described above, in the first embodiment, among the luminance data of R, G, and B read by the color image sensor 21, the reference luminance data is complemented by using other luminance data, and the edge is formed. Create luminance change data for detection. In this way, by using the luminance data of two or more colors, the number of data points can be increased and the apparent resolution can be improved. Therefore, even if the transport speed of the print medium is increased, the mark on the print medium can be improved. It has the effect that the position or edge position can be detected more accurately than in the past. For example, when the transport speed increases and the transport distance interval ΔL increases, the number of data in the vicinity of the edge decreases in a general image reading device, and the edge detection accuracy deteriorates. However, in the image reading device according to the first embodiment, by performing data complementation by a plurality of color pixels, it is possible to suppress the influence of a decrease in accuracy due to an increase in the transport speed.

Further, when the luminance information of a plurality of colors exists at the same position when the luminance change data is generated, the average value of the luminance information of the plurality of colors is used as the luminance information of the same position. This has the effect of reducing the variation in luminance data.

Further, for the luminance data of the reference color and other colors, the absolute luminance information was converted into the relative luminance information. This has the effect of eliminating the influence of the absolute difference in luminance depending on the color and treating the luminance data of all colors equally.

Further, the luminance data of the color in which the maximum value of the luminance data obtained by the color filters of a plurality of colors is larger than a predetermined value is used for the position detection. This has the effect that the user can select the optimum color data for position detection without being aware of the color or type of the paper.

(Second Embodiment)
In the first embodiment, the color data of two or more colors having the maximum luminance of the threshold value or more is selected in the color selection process to be used, but the color data may be selected by another method.

FIG. 13 is a flowchart showing an example of the procedure of the color selection process according to the second embodiment. First, the color selection unit 232 initializes the color data correction processing execution flag (step S101). Then, the color selection unit 232 reads the paper information (step S102). The paper information is manually input by the user at the start of printing, and is information indicating the color of the paper.

After that, the color selection unit 232 selects the color data corresponding to the paper information from the color selection information (step S103). FIG. 14 is a diagram showing an example of color selection information. The color selection information is information in which two or more colors of R, G, and B used for position detection are associated with the color of the paper.

Then, the correction processing execution flag is set for the selected color data (step S104), and the processing is completed.

When the relationship between the paper color and the pixels used is clear by the user, or when the user wants to realize an arbitrary combination depending on the paper, the flow of FIG. 13 can be applied instead of the flow of FIG.

It should be noted that all the acquired color data may be used without performing the color selection process of FIGS. 10 and 13.

In the second embodiment, a color is selected from the paper information manually input by the user by referring to the color selection information in which the color of the paper is associated with two or more colors used for position detection. Thereby, the effect that the color information or arbitrary color data can be selected by the user can be obtained in addition to the effect of the first embodiment.

1 Image forming device 20 Image reading device 21 Color image sensor 22 Drive mechanism 23 Control unit 211R, 211G, 211B Color pixel 231 Image data acquisition unit 232 Color selection unit 233 Level correction unit 234 Pixel position conversion unit 235 Coupling processing unit

JP-A-2009-60463

Claims (8)

A color image sensor in which multiple color filters are arranged in the paper transport direction, and
A drive mechanism that moves the paper and the color image sensor relative to the paper transport direction, and
A control unit that detects the position of the paper using luminance data of two or more colors among the image data acquired by the color image sensor, and a control unit.
An image reader comprising. The control unit
Using the pitch of the color filter of the other color in the paper transport direction with respect to the color filter of the reference color, the position of the brightness data of the other color was used as the reference for the position used in the brightness data of the reference color. Convert to position and
The image reading device according to claim 1, wherein the luminance data of the reference color and the luminance data of the other colors are combined to generate the luminance change data. A claim that the control unit uses the average value of the luminance information of the plurality of colors as the luminance information of the same position when the luminance information of a plurality of colors exists at the same position at the time of generating the luminance change data. 2. The image reading device according to 2. The image reading device according to claim 2 or 3, wherein the control unit converts absolute luminance information into relative luminance information for the luminance data of the reference color and the other color. The control unit uses any one of claims 1 to 4 to use the luminance data of a color in which the maximum value of the luminance data obtained by the color filters of the plurality of colors is larger than a predetermined value for the position detection of the paper. The image reading device according to 1. The control unit refers to the color selection information in which the color of the paper and the two or more colors used for position detection of the paper are associated with each other, and corresponds to the input paper information including the color information of the paper. The image reading device according to any one of claims 1 to 4, wherein the color used for position detection of the paper is selected. The first step of moving the color image sensor in which multiple color filters are arranged and the paper relative to the paper transport direction, and
The second step of capturing image data with the color image sensor and
A third step of detecting the position of the paper using the luminance data of two or more colors in the image data, and
Image reading method including. A computer that controls an image reading device including a color image sensor in which color filters of a plurality of colors are arranged in the paper transport direction and a drive mechanism for moving the paper and the color image sensor relative to the paper transport direction.
The first step of capturing image data with the color image sensor and
The second step of detecting the position of the paper using the luminance data of two or more colors in the image data, and
A program to execute.