JP2021150858A - Reading device and image formation apparatus - Google Patents

Abstract

To provide a reading device and image formation apparatus which can expand a dynamic range of a reading result of a reading unit and obtain the reading result keeping a gradation on a high density side of a gradation adjustment image in both of a case where the background of a recording medium is dark and a case where the background of the recording medium is bright.SOLUTION: A reading device comprises: a first reading unit which reads a gradation adjustment image formed on a printing medium by an image formation unit; a second reading unit which reads a background region of the printing medium; and a control unit which adjusts a reading condition of a first read value of the gradation adjustment image by the first reading unit on the basis of a second read value of the background region by the second reading unit.SELECTED DRAWING: Figure 3

Description

The present invention relates to a reading device and an image forming device.

In the image forming apparatus, a gradation chart (an example of an image for gradation adjustment) formed on a printing medium such as paper is read by a reading unit such as a scanner, and formed on the printing medium based on the reading result of the gradation chart. A technique has been developed in which data for correcting the gradation of an image to be printed is generated, and the data of the image formed on the print medium is corrected (for example, γ correction) based on the generated correction data. In this technology, when a bright paper (an example of a recording medium with a bright background) is read by a reading unit, the reading conditions such as the gain and the amount of light of the reading unit are adjusted in order to prevent the reading result from being saturated with white. ing. As a result, the gradation chart formed on the bright paper can be read without being saturated with white.

However, when the reading conditions of the reading unit are adjusted so that the reading result of bright paper does not saturate to white, the amount of light and gain of the reading unit become low, resulting in a dynamic range of dark paper (an example of a recording medium with a dark background). It may be difficult to maintain the gradation because it is not possible to read a slight density difference on the high density side of the gradation chart.

The present invention has been made in view of the above, and the dynamic range of the reading result of the reading unit can be increased in both the case where the background of the recording medium is dark and the case where the background of the recording medium is bright. It is an object of the present invention to provide a reading device capable of obtaining a reading result in which gradation is maintained on the high density side of a gradation adjusting image, and an image forming device.

In order to solve the above-mentioned problems and achieve the object, the present invention has a first reading unit that reads an image for gradation adjustment formed on a print medium by an image forming unit, and a first reading unit that reads a background region of the print medium. 2 reading units, a control unit that adjusts the reading conditions of the first reading value of the gradation adjusting image by the first reading unit based on the second reading value of the background region by the second reading unit. To be equipped.

According to the present invention, the dynamic range of the reading result of the reading unit can be increased regardless of whether the background of the recording medium is dark or the background of the recording medium is bright, and the high density side of the gradation adjustment image can be increased. It has the effect of being able to obtain a reading result that maintains the gradation in.

FIG. 1 is a diagram showing an example of the configuration of the image forming apparatus according to the present embodiment. FIG. 2 is a diagram showing an example of the configuration of a resist / image forming unit included in the image forming apparatus according to the present embodiment. FIG. 3 is a block diagram showing an example of the functional configuration of the resist / image forming unit included in the image forming apparatus according to the present embodiment. FIG. 4 is a diagram for explaining an example of a paper resist amount and skew amount detection process by the resist / image forming unit included in the image forming apparatus according to the present embodiment. FIG. 5 is a diagram for explaining an example of the flow of the process of adjusting the reading conditions of the scanner reading value by the resist / image forming unit according to the present embodiment. FIG. 6 is a diagram for explaining an example of the calculation process of the CIS reading value of the background region of the paper by the CIS of the resist / image forming unit according to the present embodiment. FIG. 7 is a diagram for explaining an example of the adjustment processing of the reading conditions of the scanner reading value of the resist / image forming unit according to the present embodiment. FIG. 8 is a diagram for explaining an example of the scanner reading value of the gradation chart by the scanner according to the present embodiment. FIG. 9 is a diagram for explaining an example of the scanner reading value of the gradation chart by the scanner according to the present embodiment. FIG. 10 is a diagram for explaining an example of the scanner reading value of the gradation chart by the scanner according to the present embodiment.

Hereinafter, embodiments of the reading device and the image forming device will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing an example of the configuration of the image forming apparatus according to the present embodiment. The image forming apparatus 10 according to the present embodiment is a line head type sheet-fed double-sided printing machine or the like. In the present embodiment, as shown in FIG. 1, the image forming apparatus 10 includes a resist / image forming unit 1, a precoating unit 2, a paper feeding unit 3, a drying / cooling unit 4, an inversion unit 5, and a paper ejection unit. 6 is provided.

The paper feed unit 3 feeds paper, which is an example of a recording medium, into the image forming apparatus 10 one by one. The precoat unit 2 applies the undercoat liquid to the paper fed into the image forming apparatus 10 by the paper feed unit 3 to facilitate the ink from fixing to the paper.

The resist / image forming unit 1 prints an image on the paper by the line head while adsorbing the paper on the drum (photoreceptor drum). Further, the resist / image forming unit 1 detects and corrects the resist and skew of the paper. The resist / image forming unit 1 transfers paper from the cylinder to the drum using a gripper (paper transport claw).

The drying / cooling unit 4 dries the ink adhering to the paper. Further, the drying / cooling unit 4 cools the paper which has become hot due to the drying of the ink. When printing an image on the back surface of the paper, the reversing unit 5 executes switchback reversing of the paper and conveys the image to the resist / image forming unit 1. The paper ejection unit 6 ejects and stacks the paper on which the image is printed from the image forming apparatus 10.

FIG. 2 is a diagram showing an example of the configuration of a resist / image forming unit included in the image forming apparatus according to the present embodiment. Next, an example of the configuration of the resist / image forming unit 1 will be described with reference to FIG.

The resist / image sensor 1 includes an image forming unit 101, a drum 102, cylinders 103 and 104, a transfer roller 105, a resist skew correction roller 106, CIS (Contact Image Sensor) 107-1 to 107-3, and a paper tip detection sensor. It has 108-1, 108-2, and a scanner 109.

The resist / image forming unit 1 generates a reference trigger at the timing when the tip of the paper (an example of a print medium) is detected by the paper tip detection sensor 108-1, and CIS107-1 to 107-3 and the resist skew. The correction roller 106 is used to detect and correct the resist amount and skew amount of the paper. In the present embodiment, the CIS 107-1 to 107-3 are arranged on the lower side of the paper transport path, but the present invention is not limited to this, and the CIS 107-1 to 107-3 may be arranged on the upper side of the paper transport path. ..

The drum 102 and the cylinders 103 and 104 are connected by gears and driven. Further, the drum 102 and the cylinders 103 and 104 are respectively equipped with grippers that open and close mechanically, and the grippers carry the paper while holding the tip of the paper. The resist / image forming unit 1 controls the transport roller 105 based on the relationship between the timing at which the tip of the paper is detected by the paper tip detection sensor 108-2 and the signal output from the encoder of the drum 102. , The timing of transporting the paper to the gripper of the cylinder 103 installed on the upstream side in the paper transport direction is adjusted.

Further, the resist / image forming unit 1 detects the rotation speed, the rotation angle, the rotation position, and the like of the drum 102 based on the signal output from the encoder of the drum 102. For example, the resist / image forming unit 1 uses a disk for an encoder provided on the rotation axis of the drum 102, a linear scale for an encoder provided on the surface of the drum 102, or the like to determine the rotation speed, rotation angle, and rotation speed of the drum 102. And the rotation position etc. are detected. Then, the resist / image forming unit 1 is provided on the surface of the drum 102 by controlling the suction timing and the suction amount of the pump based on the detection results such as the rotation speed, the rotation angle, and the rotation position of the drum 102. The paper is conveyed while being attracted to the surface of the drum 102 through the holes.

The image forming unit 101 is an example of an image forming unit that forms an image on paper, and has a plurality of print heads (recording heads). In the present embodiment, the image forming unit 101 has each CMYK print head, and forms an image on the paper by ejecting ink from the print head onto the paper. Further, in the present embodiment, the image forming unit 101 ejects ink from each print head of CMYK to the empty ejection receiving member 102a (for example, sponge) provided on the drum 102.

The scanner 109 is provided on the drum 102 and reads a paper, an image formed on the paper, a reading target such as the surface of the drum 102, and the like. Since the scanner 109 is arranged away from the reading target, it is preferably a reduction optical system. When the width of the scanner 109 in the main scanning direction (pixels in the main scanning direction) is insufficient with respect to the width of the drum 102 in the main scanning direction, the resist / image forming unit 1 has a width with respect to the main scanning direction of the drum 102. By arranging the plurality of scanners 109 in a staggered pattern, all the scanning targets existing in the main scanning direction of the drum 102 are read.

FIG. 3 is a block diagram showing an example of the functional configuration of the resist / image forming unit included in the image forming apparatus according to the present embodiment. Next, an example of the functional configuration of the resist / image forming unit 1 included in the image forming apparatus according to the present embodiment will be described with reference to FIG.

In the present embodiment, as shown in FIG. 3, the resist / image forming unit 1 (an example of a reading device) includes a main control unit 301, a drum rotation encoder 302, paper tip detection sensors 108-1, 108-2, and printing. It has a timing sensor 304, a reading timing sensor 305, a drum drive motor 306, a print head 307, CIS107-1 to 107-3, a scanner 109, and a drive circuit 310-313.

The main control unit 301 controls the entire image forming apparatus 10. In the present embodiment, the main control unit 301 has a CIS control unit 301a and a scanner control unit 301b.

The CIS control unit 301a uses the CIS 107-1, 107-2 arranged on the paper transport path to move the paper outside the paper range, which is the range where the paper does not exist on the surface of the drum 102, and the paper existing on the surface of the drum 102. The edge position of the paper is detected based on the difference between the reading, the outside of the paper range, and the reading value of the paper (hereinafter referred to as CIS reading value. An example of the second reading value. For example, density and reflectance). Then, the CIS control unit 301a detects the resist amount and the skew amount of the paper based on the edge position of the paper, and calculates the resist amount and the skew amount correction amount of the paper. Next, the CIS control unit 301a corrects the resist and skew of the paper by the resist skew correction roller 106 based on the calculated correction amount.

Further, the CIS control unit 301a reads the out-of-paper range and the paper by the CIS 107-2 and 107-3 arranged on the paper transport path, and the reading values of the out-of-paper range and the paper (hereinafter, CIS reading values). An example of the second reading value. For example, the edge position of the paper is detected based on the difference in density and reflectance. Then, the CIS control unit 301a again detects the resist amount and the skew amount (hereinafter, referred to as correction error) of the paper based on the edge position of the paper. Next, the CIS control unit 301a controls the drive circuit 311 of the print head 307 based on the correction error to move the position where the image is formed on the paper.

Further, the CIS control unit 301a controls CIS107-1 to 107-3 to read the paper, and passes the CIS reading value of the background region of the paper to the scanner control unit 301b. Therefore, in the present embodiment, CIS 107-1 to 107-3 function as an example of a second reading unit that reads the background region of the paper.

The scanner control unit 301b is the difference between the reading value read by the scanner 109 (hereinafter referred to as the scanner reading value; an example of the first reading value) and the density or reflectance of the image instructed by the writing control unit. The correction amount for writing the image by the image forming unit 101 is calculated based on the above. Here, the scanner reading is the reading by the scanner 109 of the gradation chart (an example of the gradation adjustment image) formed on the paper by the print head 307 (for example, at least one of the density and the reflectance of the gradation chart). Is.

Further, the scanner control unit 301b is based on the CIS reading value (for example, at least one of the density and the reflectance of the background area of the paper) of the background area of the paper read by CIS107-1 to 107-3, and the floor by the scanner 109. It functions as an example of a control unit that adjusts the reading conditions (for example, gain) of the scanner reading value of an image such as a tuning chart. Here, the reading conditions are, for example, the gain of the scanner 109 and the amount of light emitted from the scanner 109 onto the paper. As a result, even when the scanner 109 reads the gradation chart formed on the paper having a dark background area, the scanner 109 reads the gradation chart formed on the paper having a bright background area by the scanner 109. The dynamic range of scanner readings can be increased. As a result, among the scanner readings of the scanner 109, the gradation can be maintained even at the scanner reading on the high gradation side of the gradation chart.

The drum rotation encoder 302 is an encoder used for detecting the rotation speed, rotation angle, rotation position, etc. of the drum 102. The drum rotation encoder 302 is preferably installed at a plurality of locations in order to eliminate eccentricity unevenness of the drum 102. For example, the main control unit 301 uses a disk for an encoder attached to the rotation axis of the drum 102 and a drum rotation encoder 302 for detecting a linear scale for the encoder attached to the surface of the drum 102, and uses the rotation speed of the drum 102. , Rotation angle, rotation position, etc. are detected. Further, the drum rotation encoder 302 is preferably an encoder capable of outputting a Z-phase signal in addition to the A-phase or B-phase signal in order to detect the home position HP which is a reference position in the rotation of the drum 102. Alternatively, the home position HP may be detected by using a sensor (home position sensor) different from the drum rotation encoder 302.

The paper tip detection sensor 12 is a reflective sensor or the like, and detects the tip of the paper in the paper transport direction.

The print timing sensor 304 is used to control the timing of ejecting ink from the print head 307. The main control unit 301 is based on the pulse signal output from the drum rotation encoder 302 with reference to the timing when the paper is detected by the print timing sensor 304 (for example, the timing when the paper passes directly under the print timing sensor 304). , Ink is ejected from the print head 307. Alternatively, the main control unit 301 may eject ink from the print head 307 based on the timing at which the tip of the paper is detected by the paper tip detection sensor 12 without using the print timing sensor 304. However, it is preferable that the sensor used for controlling the timing of ink ejection from the print head 307 is installed in the vicinity of the print head 307.

The reading timing sensor 305 is used to control the timing of reading an image by the scanner 109. The scanner control unit 301b is based on the pulse signal output from the drum rotation encoder 302 with reference to the timing when the paper is detected by the reading timing sensor 305 (for example, the timing when the paper passes directly under the reading timing sensor 305). The scanning of the image by the scanner 109 is started. Alternatively, the scanner control unit 301b may read the image by the scanner 109 with reference to the timing at which the tip of the paper is detected by the paper tip detection sensor 12 without using the reading timing sensor 305. However, it is preferable that the sensor used for controlling the timing of reading the image by the scanner 109 is set in the vicinity of the scanner 109.

The drum drive motor 306 is an AC servomotor or the like, and is a drive source for the drum 102. The main control unit 301 outputs a drive signal to the drive circuit 310 based on the pulse signal output from the drum rotation encoder 302. The drum drive motor 306 rotates the drum 102 based on the drive signal input from the drive circuit 310.

The print head 307 is an inkjet print head or the like, and forms an image on the paper by ejecting droplets of ink or the like onto the paper. The print head 307 is a line head of each color of CMYK. The main control unit 301 determines the timing of ejecting ink from the print head 307 based on the signals input from the print timing sensor 304 and the drum rotation encoder 302, and prints based on the image data to be image-formed. A drive signal corresponding to the drive waveform of the head 307 is output to the drive circuit 311. The print head 307 ejects ink to the paper based on the drive signal input from the drive circuit 311.

CIS107-1 to 107-3 are sensors used for detecting the edge position (conveyance position) of paper. The main control unit 301 determines the timing for reading the paper by CIS107-1 to 107-3 based on the timing when the paper tip is detected by the paper tip detection sensor 12. Next, the main control unit 301 determines the paper reading conditions according to CIS 107-1 to 107-3 based on the determined timing, and outputs a drive signal corresponding to the reading conditions to the drive circuit 312. CIS107-1 to 107-3 read the paper based on the drive signal output from the drive circuit 312.

The scanner 109 reads the gradation chart formed on the paper. The main control unit 301 determines the timing for reading the gradation chart by the scanner 109 based on the signals input from the reading timing sensor 305 and the drum rotation encoder 302. Further, the main control unit 301 determines the reading conditions of the scanner 109 based on the reading target such as the gradation chart, and outputs the drive signal corresponding to the reading conditions to the drive circuit 313. The scanner 109 reads a reading target such as a gradation chart based on the drive signal output from the drive circuit 313.

FIG. 4 is a diagram for explaining an example of a paper resist amount and skew amount detection process by the resist / image forming unit included in the image forming apparatus according to the present embodiment. Next, an example of a paper resist amount and skew amount detection process by the resist / image forming unit 1 will be described with reference to FIG.

The CIS control unit 301a reads out of the paper range and the paper by CIS 107-1 to 107-3, and detects the edge position of the paper X based on the difference between the CIS reading values of the out-of-paper range and the paper. At that time, the CIS control unit 301a may detect the edge positions E1 and E2 based on the CIS readings of all the RGB channels of CIS107-1 to 107-3, or the CIS of any one channel. The edge position may be detected based on the reading.

For example, as shown in FIG. 4, the CIS control unit 301a reads the out-of-paper range and the paper X by the CIS 107-1 and 107-2, and based on the difference between the CIS reading values of the out-of-paper range and the paper X, respectively. The edge positions E1 and E2 of the paper X are detected. Then, the CIS control unit 301a detects the resist amount and the skew amount of the paper X based on the edge positions E1 and E2 of the paper X, and calculates the resist amount and the skew amount correction amount of the paper X. Next, the CIS control unit 301a corrects the resist and skew of the paper X by the resist skew correction roller 106 based on the calculated correction amount.

Further, as shown in FIG. 4, the CIS control unit 301a reads the out-of-paper range and the paper X by the CIS 107-2 and 107-3, and based on the difference between the CIS reading values of the out-of-paper range and the paper X, respectively. , Detects edge positions E3 and E2'of paper X. Then, the CIS control unit 301a again detects the correction error, which is the resist amount and the skew amount of the paper X, based on the edge positions E3 and E2'of the paper X. Next, the CIS control unit 301a controls the drive circuit 311 of the print head 307 based on the correction error to move the position where the image is formed on the paper X.

FIG. 5 is a diagram for explaining an example of the flow of the process of adjusting the reading conditions of the scanner reading value by the resist / image forming unit according to the present embodiment. Next, an example of the flow of the adjustment processing of the reading conditions of the scanner reading value by the resist / image forming unit 1 according to the present embodiment will be described with reference to FIG.

The CIS control unit 301a reads out of the paper range and the paper according to CIS 107-1 to 107-3 (step S501). Next, the CIS control unit 301a calculates the CIS reading value of the background region of the paper according to CIS107-1 to 107-3 based on the outside of the paper range according to CIS107-1 to 107-3 and the reading result of the paper (step S502). ).

Next, the scanner control unit 301b calculates the predicted value of the scanner reading value of the paper background area by the scanner 109 based on the CIS reading value of the paper background area by CIS 107-1 to 107-3 (step S503). .. Then, the scanner control unit 301b calculates a correction value of the reading condition (for example, gain) of the scanner reading value of the gradation chart by the scanner 109 based on the calculated predicted value (step S504), and is based on the correction value. Adjust (correct) the reading conditions of the scanner reading.

After that, the scanner control unit 301b reads the gradation chart formed on the paper conveyed by the drum 102 by the scanner 109 (step S505).

FIG. 6 is a diagram for explaining an example of the paper reading process outside the paper range and the paper reading process by the CIS of the resist / image forming unit according to the present embodiment.

In FIG. 6, the vertical axis represents the out-of-paper range according to CIS107 and the reading value (CIS reading value) of the paper, and is, for example, an RGB value (8 bits). Further, the CIS reading value may be an XYZ value or a density converted from an RGB value. Further, the CIS reading value may be the value of all of the RGB values (3 channels), or may be the value of any one channel among the RGB values. Further, the CIS reading value may be a moving average (main scanning moving average) with the reading value of pixels adjacent to the main scanning direction of the CIS 107. Further, the reading may be the reading of one line in the sub-scanning direction of CIS107, or the average of the readings of a plurality of lines (β lines) in the sub-scanning direction of CIS107 (sub-scanning average). Is also good.

Further, in FIG. 6, the horizontal axis represents the position of the pixel (CIS main scanning pixel) in the main scanning direction of CIS 107. The CIS main scanning pixels are associated with positions in the main scanning direction (direction orthogonal to the paper transport direction) of the paper transport path. CIS107 is a line sensor mounted parallel to the main scanning direction of the paper transport path. Further, it is preferable that the CIS 107 has a function of detecting an angle (inclination) of the paper transport path with respect to the main scanning direction and correcting the position of the CIS main scanning pixel according to the detected angle.

Further, in FIG. 6, “0” on the horizontal axis represents the leftmost CIS main scanning pixel in the main scanning direction of CIS 107. Further, in FIG. 6, “x1” on the horizontal axis represents the CIS main scanning pixel of the edge (paper edge) between the outside of the paper range and the paper in the main scanning direction of CIS107. Further, in FIG. 6, “x2” on the horizontal axis is the CIS of the boundary (print area boundary) between the background area of the paper and the print area (the area where the image such as the gradation pattern is formed) in the main scanning direction of CIS107. Represents a main scanning direction pixel. Further, "X" on the horizontal axis represents the CIS main scanning pixel at the right end in the main scanning direction of CIS 107.

The print area boundary in the main scanning direction of the CIS 107 is preset as a specification of the image forming apparatus, and is the position of the CIS main scanning pixel determined relative to the paper edge. When the paper is skewed, the relative position from the paper edge to the print area boundary changes according to the amount of paper skew, so it is necessary to reset the print area boundary according to the amount of paper skew. be. The CIS reading of CIS107 shown in FIG. 6 is a reading when the skew amount of the paper is "0" (that is, when the paper is conveyed orthogonally to the main scanning direction of CIS107). ..

Next, with reference to FIG. 6, an example of the paper reading process outside the paper range and the paper reading process by CIS107-1 to 107-3 of the resist / image forming unit 1 will be described.

As shown in FIG. 6, in the main scanning direction of CIS107, the CIS main scanning pixels in the background region of the paper are “x1” to “x2”. Therefore, the CIS control unit 301a calculates the CIS reading values of the CIS main scanning pixels of "x1" to "x2" among the CIS main scanning pixels of the CIS 107 as the CIS reading values of the background region of the paper.

However, the CIS control unit 301a is preset with reference to the boundary between the outside of the paper range and the paper edge and the boundary of the print area in consideration of the influence of flare on the boundary between the outside of the paper range and the paper edge and the boundary of the print area. It is preferable that the CIS readings of the CIS main scanning pixels existing in the range of the number of pixels α are not used for the CIS readings of the background region of the paper.

For example, the CIS control unit 301a is used for a plurality of lines (β lines) in the sub-scanning direction of the CIS reading value of each CIS main scanning pixel in the section from the CIS main scanning pixel (x1 + α) to the CIS main scanning pixel (x2-α). Is calculated as the CIS reading value of the background area of the paper. Further, for example, the CIS control unit 301a may calculate the average of the CIS reading values of the background area of the paper by each of CIS 107-1 to 107-3 as the CIS reading value of the background area of the paper.

FIG. 7 is a diagram for explaining an example of the adjustment processing of the reading conditions of the scanner reading value of the resist / image forming unit according to the present embodiment. In FIG. 7, the horizontal axis represents the CIS reading value of the background area of the paper by CIS107, for example, RGB value (8 bits), and the vertical axis represents the predicted value of the scanner reading value of the background area of the paper by the scanner 109, for example. Represents an RGB value (8 bits). In the present embodiment, as shown in FIG. 7, the predicted values are classified by four threshold values A to D.

Next, with reference to FIG. 7, an example of a process in which the scanner control unit 301b adjusts the gain, which is the image reading condition of the scanner 109, based on the predicted value of the scanner reading value of the background area of the paper by the scanner 109. explain.

In the present embodiment, the gain of the scanner 109 is divided into four gains η1 to η5 corresponding to each of the four threshold values A to D of the predicted value. It is assumed that the gain of the scanner 109 increases in the order of η1, η2, η3, η4, η5. The scanner control unit 301b reads a preset reading target (for example, a calibrated white reference plate or a density-compensated chart) by the CIS 107 and the scanner 109, and based on the reading result, the paper according to the CIS 107. It functions as an example of a calculation unit that calculates a relational expression (for example, a linear function expression) between the CIS reading value of the background area and the predicted value of the scanner reading value of the background area of the paper by the scanner 109. Further, the scanner control unit 301b sets the gain of the scanner 109 when reading a preset reading target to the gain η0.

Then, the scanner control unit 301b calculates the predicted value of the scanner reading value of the scanner 109 corresponding to the CIS reading value of the background area of the paper by CIS107 using the calculated relational expression, and obtains the calculated predicted value. When it is η0, it is a predicted value of the scanner reading value of the background area of the paper by the scanner 109. When the scanner reading value of the scanner 109 is an RGB value, it is preferable that the scanner control unit 301b calculates the relational expression and the predicted value of the scanner reading value of the scanner 109 for each channel of the RGB value.

Next, the scanner control unit 301b adjusts (corrects, sets) the gain of the scanner 109 based on the predicted value of the scanner reading value of the background area of the paper by the scanner 109 in the case of the gain η0. Specifically, the scanner control unit 301b increases the gain of the scanner 109 as the predicted value of the scanner reading value of the background area of the paper by the scanner 109 at the gain η0 decreases, that is, as the background area of the paper becomes darker. Adjust to value. On the other hand, the scanner control unit 301b adjusts the gain of the scanner 109 to a smaller value as the predicted value of the scanner reading value of the background area of the paper by the scanner 109 at the gain η0 increases, that is, as the background area of the paper becomes brighter. do.

For example, when the gain η0 = η1 of the scanner 109, the scanner control unit 301b determines that the predicted value of the scanner reading value of the background area of the paper by the scanner 109 is equal to or more than the threshold value A and less than the threshold value B of the scanner 109. Adjust the gain η0 to the gain η4. As a result, even when the background area of the paper is dark, the dynamic range of the scanner reading value of the scanner 109 can be increased as in the case where the background area of the paper is bright. As a result, among the scanner readings of the scanner 109, the gradation can be maintained even at the scanner reading on the high gradation side of the gradation chart.

8 to 10 are diagrams for explaining an example of the scanner reading value of the gradation chart by the scanner according to the present embodiment. In FIGS. 8 to 10, the vertical axis represents the scanner reading value by the scanner 109, and the horizontal axis represents the gradation of the gradation chart.

Next, an example of the scanner reading value of the gradation chart by the scanner 109 according to the present embodiment will be described with reference to FIGS. 8 to 10.

For example, in a conventional reading device, reading conditions such as the gain and the amount of light of the scanner 109 are adjusted so that the reading result of paper having a bright background area is not saturated with white. Therefore, in the conventional reading device, when the gradation chart formed on the paper having a bright background area is read by the scanner 109, the dynamic range of the scanner reading value of the scanner 109 can be increased as shown in FIG. .. However, in the conventional reading device, when the gradation chart formed on the paper having a dark background area is read by the scanner 109, the dynamic range of the scanner reading value of the scanner 109 becomes small as shown in FIG. 9, and the gradation It becomes difficult to detect the density difference on the high gradation side of the chart.

Therefore, in the present embodiment, the scanner control unit 301b is based on the CIS reading value (that is, the type of paper) of the background region of the paper by the CIS 107 located on the upstream side of the scanner 109 in the paper transport direction. Adjust the gain of the scanner 109. As a result, even when the gradation chart formed on the paper having a dark background area is read by the scanner 109, as shown in FIG. 10, the gradation chart formed on the paper having a bright background area is read by the scanner 109. Similarly, the dynamic range of the scanner reading of the scanner 109 can be increased. As a result, among the scanner readings of the scanner 109, the gradation can be maintained even at the scanner reading on the high gradation side of the gradation chart.

When the gain of the scanner 109 is increased, the noise included in the scanner reading value of the scanner 109 may increase. In this case, the scanner control unit 301b reads the gradation chart at a plurality of reading positions (reading lines) by the scanner 109, and calculates the average of the scanner reading values at each reading line as the scanner reading value of the gradation chart. Therefore, the influence of noise included in the scanner reading value of the scanner 109 can be suppressed.

As described above, according to the image forming apparatus 10 according to the present embodiment, even when the gradation chart formed on the paper having a dark background area is read by the scanner 109, the gradation formed on the paper having a bright background area. The dynamic range of the scanner readings of the scanner 109 can be increased in the same manner as when the chart is read by the scanner 109. As a result, among the scanner readings of the scanner 109, the gradation can be maintained even at the scanner reading on the high gradation side of the gradation chart.

The program executed by the image forming apparatus 10 of the present embodiment is provided by being incorporated in a ROM (Read Only Memory) or the like in advance. The program executed by the image forming apparatus 10 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, a DVD (Digital Versatile Disk), or the like. It may be configured to be recorded and provided on a computer-readable recording medium.

Further, the program executed by the image forming apparatus 10 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 10 of the present embodiment may be configured to be provided or distributed via a network such as the Internet.

The program executed by the image forming apparatus 10 of the present embodiment has a module configuration including each of the above-mentioned parts (main control unit 301), and the actual hardware is a CPU (Central Processing) that functions as an example of a processor. When the Unit) reads the program from the ROM and executes it, each of the above units is loaded on the main storage device, and the main control unit 301 is generated on the main storage device.

In the above embodiment, the image forming apparatus of the present invention will be described with reference to an example in which the image forming apparatus of the present invention is applied to a multifunction device having at least two functions of a copy function, a printer function, a scanner function and a facsimile function. It can be applied to any image forming apparatus such as a printer, a scanner apparatus, and a facsimile apparatus.

1 Resist / image formation unit 2 Precoating unit 3 Feeding unit 4 Drying / cooling unit 5 Inversion unit 6 Paper ejection unit 10 Image forming device 101 Image forming unit 102 Drum 102a Empty discharge receiving member 103, 104 Cylinder 105 Conveying roller 106 Resist・ Skew correction roller 107-1 to 107-3 CIS
108-1, 108-2 Paper tip detection sensor 109 Scanner 301 Main control unit 301a CIS control unit 301b Scanner control unit 302 Drum rotation encoder 304 Print timing sensor 305 Read timing sensor 306 Drum drive motor 307 Print head 310-313 Drive circuit

Japanese Unexamined Patent Publication No. 2011-003950

Claims (5)

The first reading unit that reads the gradation adjustment image formed on the print medium by the image forming unit, and
A second reading unit that reads the background area of the print medium,
A control unit that adjusts the reading conditions of the first reading value of the gradation adjusting image by the first reading unit based on the second reading value of the background region by the second reading unit.
A reader comprising. The reading device according to claim 1, wherein the reading condition includes a gain of the first reading unit. The reading device according to claim 1 or 2, wherein the reading condition includes the amount of light emitted from the first reading unit onto the printing medium. A calculation unit for calculating the relational expression between the predicted value of the first reading value of the background area by the first reading unit and the second reading value of the background area by the second reading unit is further provided.
The control unit calculates the predicted value corresponding to the second reading value of the background region read by the second reading unit using the relational expression, and sets the reading condition based on the predicted value. The reading device according to any one of claims 1 to 3 to be adjusted. The first reading unit that reads the gradation adjustment image formed on the print medium by the image forming unit, and
A second reading unit that reads the background area of the print medium,
A control unit that adjusts the reading conditions of the first reading value of the gradation adjusting image by the first reading unit based on the second reading value of the background region by the second reading unit.
An image forming apparatus comprising.

Images