Reading device, reading method, and program

Abstract

To provide a reading device, a reading method, and a program capable of performing color correction without imaging a color chart.SOLUTION: A reading device 200 comprises a light source 201 that irradiates a reading target with light having a blue light emission wavelength as a center and light having a yellow light emission wavelength as a center, and a light receiving unit 212 serving as imaging means including a plurality of photoelectric conversion elements each sensitive to any one of a plurality of predetermined light receiving wavelengths. When the color of the reading target is magenta and the predetermined light receiving wavelength is a green light receiving wavelength, a first output of the imaging means is corrected using a second output of the imaging means when the color of the reading target is white and the predetermined light receiving wavelength is a red light receiving wavelength.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reading device, a reading method, and a program. [Background technology]

[0002] 2. Description of the Related Art Conventionally, in an image reading device using a contact image sensor, a technique for correcting color variations caused by wavelength fluctuations of a light source is known.

[0003] Patent Document 1 discloses the use of a level correction means for adjusting the level of image signals output from a plurality of photoelectric conversion elements, and a color chart characteristic correction means for correcting the image signals output from the level correction means when a color chart is imaged by an imaging means, to account for variations in the characteristics of the color chart. Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the conventional technology, there is a problem in that color variations cannot be corrected unless an image of the color chart is captured.

[0005] The present invention has been made in view of the above, and an object of the present invention is to enable color correction without capturing an image of a color chart. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the present invention provides an imaging device comprising a light source that irradiates an object to be read with light centered on a blue emission wavelength and light centered on a yellow emission wavelength, and an imaging means having a plurality of photoelectric conversion elements each having sensitivity to one of a plurality of predetermined light receiving wavelengths, and correcting a first output of the imaging means when the color of the object to be read is magenta and the predetermined light receiving wavelength is a green light receiving wavelength using a second output of the imaging means when the color of the object to be read is white and the predetermined light receiving wavelength is a red light receiving wavelength. [Effects of the Invention]

[0007] According to the present invention, it is possible to perform color correction without capturing an image of a color chart. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of a hardware configuration of a reading device according to the first embodiment. [Figure 2] FIG. 2 is a perspective view showing how the reading device reads an image on a recording sheet. [Figure 3] FIG. 3 is a schematic diagram of an LED array used in the reading device. [Figure 4] FIG. 4 is a schematic diagram of a light receiving unit used in the reading device. [Figure 5] FIG. 5 is a diagram showing an example of the spectral distribution of a white LED. [Figure 6] FIG. 6 is a diagram showing an example of the spectral distribution of a white LED before and after deterioration. [Figure 7] FIG. 7 is a diagram showing an example of an output distribution of green readings when the first color is magenta. [Figure 8] FIG. 8 is a diagram showing the filter characteristics of the red filter for each wavelength. [Figure 9] FIG. 9 is a table summarizing the readings of each color in each state of the white LED. [Figure 10] FIG. 10 is a diagram illustrating an example of a functional block diagram of the correction process according to the first embodiment. [Figure 11] FIG. 11 is a flowchart showing the procedure of the correction process according to the first embodiment. [Figure 12] FIG. 12 is a diagram showing differences in wavelength distribution due to differences in density of the first color. [Figure 13] FIG. 13 is a diagram illustrating an example of a functional block diagram of the correction process according to the second embodiment. [Figure 14] FIG. 14 is a flowchart showing the procedure of the correction process according to the second embodiment. [Figure 15] FIG. 15 is a diagram showing the relationship between the weight of the weighted average used in the correction process and the density. [Figure 16] FIG. 16 is a diagram illustrating an example of a functional block diagram of the correction process according to the third embodiment. [Figure 17] FIG. 17 is a flowchart showing the procedure of the correction process according to the third embodiment. [Figure 18] FIG. 18 is a schematic diagram of a printer equipped with a tone correction device according to the fourth embodiment. [Figure 19] FIG. 19 is an enlarged view of the opposing member and its surroundings. [Figure 20] FIG. 20 is a perspective view for specifically explaining an example of the reference surface member. [Figure 21] FIG. 21 is a diagram showing an example of a band-shaped pattern for tone correction. [Figure 22] FIG. 22 is a diagram illustrating an example of a functional block diagram of the tone correction process according to the fourth embodiment. [Figure 23] FIG. 23 is a flowchart showing the procedure for correcting the magenta read value. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of a reading device, a reading method, and a program will be described in detail with reference to the accompanying drawings.

[0010] (First embodiment) 1 is a diagram showing an example of the hardware configuration of a reading device according to the first embodiment. The reading device 200 of this embodiment includes a light source 201, a light source drive circuit 202, a light receiving unit 212, a CPU (Central Processing Unit) 240, a ROM (Read Only Memory) 241, a RAM (Random Access Memory) 242, and an SSD (Solid State Drive) 243. The light source drive circuit 202, the light receiving unit 212, the CPU 240, the ROM 241, the RAM 242, and the SSD 243 are electrically connected to one another via a system bus 250.

[0011] The light source 201 may be a light emitting element provided at the end of a light guide, an LED (Light Emitting Diode) array, or the like. The light source drive circuit 202 controls the light emission of the light source 201 based on a control signal supplied from the CPU 240. The drive signal supplied to the light source 201 may be a square wave, a sine wave, or a voltage waveform of a predetermined waveform.

[0012] The light receiving unit 212 is an imaging means that receives reflected light of light irradiated by the light source 201 onto the object to be read, and outputs electrical signals corresponding to the red wavelength band, the green wavelength band, and the blue wavelength band, respectively, using the configuration described below.

[0013] The CPU 240 reads programs or data from a storage device such as the ROM 241 or the SSD 243 onto the RAM 242 and executes processing to control the entire reading device 200. Note that some or all of the functions of the CPU 240 may be realized by an electronic circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0014] The ROM 241 is a non-volatile semiconductor memory (storage device) that can retain programs or data even when the power is turned off. The ROM 241 stores programs or data such as BIOS (Basic Input / Output System) and OS (Operating System) settings that are executed when the CPU 240 starts up. The RAM 242 is a volatile semiconductor memory (storage device) that temporarily retains programs or data.

[0015] The SSD 243 is a non-volatile memory (storage device) that stores various data and programs for executing processes by the reading device 100. The SSD 243 stores, for example, a reading program for reading data and a correction program for correcting the read data. As will be described in detail later, the CPU 240 corrects the read data by executing this correction program. Note that instead of the SSD 243, other storage devices such as an HDD (Hard Disk Drive) may be used.

[0016] 2 is a perspective view showing how the reading device 200 reads an image on recording paper P (for example, paper on which images or characters are printed) that is the reading target. The reading device 200 is long in the main scanning direction and is also called a line sensor. Because the detection width of the reading device 200 is longer than the width of the recording paper P in the main scanning direction, it is possible to detect the image density over the entire area of ​​the recording paper P by transporting the recording paper P in the paper transport direction so that it passes through the width indicated by the dotted line in the main scanning direction.

[0017] 3 is a schematic diagram illustrating a configuration in which an LED array is used as the light source 201 of the reading device 200. The light source 201 has a shape extending in the main scanning direction, similar to the reading device 200, and m (m is a natural number) LED chips (LEDs 201-1 to 201-m) are arranged side by side on a light source substrate 201-0. This allows light to be irradiated onto a reading target having a width in the main scanning direction, and the reflected light can be read by the light receiving unit 212.

[0018] Another configuration of the light source 201 is to use a light guide member whose longitudinal direction is the main scanning direction, and to emit a line of light by lighting two LED chips arranged on both ends of the light guide member and passing the light through the light guide member. The light guide member makes it possible to emit light with uniform brightness in the main scanning direction.

[0019] In addition to these, the light source 201 may have a configuration different from the above examples as long as it is capable of emitting a line of light in the main scanning direction. For example, a configuration may be provided in which a light guide lens is provided to efficiently guide light from the LED array to an area through which the edge of the conveyed recording paper P in the main scanning direction passes.

[0020] 4 is a schematic diagram of the light receiving unit 212 used in the reading device 200. The light receiving unit 212 has a substrate 212a, a pixel array 212r that receives red light, a pixel array 212g that receives green light, and a pixel array 212b that receives blue light.

[0021] A pixel array is an element in which photoelectric conversion elements, such as PDs (Photo Diodes), that convert optical signals into electrical signals are arranged in an array in the width direction. One photoelectric conversion element corresponds to one pixel, and outputs an electrical signal according to the amount of light received. An "electrical signal according to the amount of light received" is a typical example of a detection signal. A pixel array outputs electrical signals for one line of pixels.

[0022] As shown in the figure, the pixel array 212r, the pixel array 212g, and the pixel array 212b are arranged side by side in the paper transport direction with the main scanning direction and the pixel arrangement direction being approximately parallel to each other.

[0023] The pixel array 212r, which receives red light, has a red color filter in front of its light-receiving surface. By receiving red light that passes through the color filter, the pixel array 212r is sensitive to red wavelengths. The red color filter passes light in the red wavelength band and absorbs or reflects light in other wavelength bands. Similarly, the pixel array 212g and the pixel array 212b have green and blue color filters, respectively, and by receiving light in the green and blue wavelength bands, the pixel array 212r is sensitive to green and blue wavelengths, respectively. Here, the red wavelength band (light-receiving wavelength centered on red), the blue wavelength band (light-receiving wavelength centered on blue), and the green wavelength band (light-receiving wavelength centered on green) are examples of the first light-receiving wavelength and the second light-receiving wavelength.

[0024] In this way, the light receiving unit 212 is an imaging means having a plurality of photoelectric conversion elements that are sensitive to any of a plurality of predetermined light receiving wavelengths (red light receiving wavelength, green light receiving wavelength, blue light receiving wavelength, etc.) With this configuration, the light receiving unit 212 outputs electrical signals corresponding to the red reading value, the green reading value, and the blue reading value from the reading object.

[0025] The pixel array may be a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide-Semiconductor). The light receiving unit 212 may also be configured using a CCD or CMOS area sensor having a two-dimensional pixel array. Furthermore, to increase the light collection efficiency of the light receiving unit 212, a lens array such as a rod lens array may be provided to guide light reflected by the recording paper P to the pixel array.

[0026] The reading device 200 may also be configured with a CIS (Contact Image Sensor). A CIS is an image sensor that integrates a light receiving section, a light source section, and a rod lens array (equal magnification imaging lens). By using a CIS, it is possible to obtain the effect of being able to get close to the surface of the recording paper P and read the edge position compactly, for example.

[0027] When using a white LED with a wide wavelength distribution as the LED chip, a common method is to reproduce a pseudo-white color by combining a blue LED with a yellow phosphor. Figure 5 shows an example of the spectral distribution of a white LED. In this way, the white LED is a light source that emits blue LED light centered on a first emission wavelength (450 nm in Figure 5) and yellow phosphor light centered on a second emission wavelength (560 nm in Figure 5).

[0028] The degree of temperature change of each LED chip is not uniform and varies. Furthermore, LED chips deteriorate rapidly when the temperature rises significantly. As a result, LED chips with large temperature changes deteriorate more from their initial state. Furthermore, when multiple LED chips are arranged on a substrate as shown in Figure 3, areas other than the ends are affected by heat from the adjacent LED chips on both sides, while the ends are only affected by heat from one adjacent LED chip, so the areas other than the ends are likely to be affected by heat more. Note that when two LED chips arranged on both ends of a light-guiding member are used as light source 201, only the two LED chips are affected by variations in temperature change.

[0029] Figure 6 shows an example of the spectral distribution of a white LED before and after the yellow phosphor deteriorates over a long period of use. In this figure, the emission intensity of the yellow phosphor, which has a peak around 560 nm, deteriorates (decreases) from the distribution shown by the solid line to the distribution shown by the dashed line.

[0030] When the emission intensity of the yellow phosphor of the white LED deteriorates in this way, the output in the green wavelength band (green reading value) fluctuates for a reading target having a specific color (first color). FIG. 7 shows an example of the output distribution of green reading values ​​when the first color is magenta. In this figure, the dashed-dotted line represents the green reading value for the light reflected from the white reading target illuminated by the white LED before deterioration, and shows the filter characteristics for each wavelength of the green filter. The solid and dashed lines represent the green reading value for the light reflected from the magenta reading target. The solid line in FIG. 7 represents the green reading value for the emission intensity before deterioration of the yellow phosphor (the solid line in FIG. 6), and the dashed line in FIG. 7 represents the green reading value for the emission intensity after deterioration of the yellow phosphor (the dashed line in FIG. 6).

[0031] Because the filter characteristics of the green filter have a peak around 560 nm, when a green filter is applied to the reflected light of a magenta object to be read, the read intensity decreases due to the degradation of the yellow phosphor. In this embodiment, to correct this, the output of the red wavelength band (red read value) when the object to be read is a second color (white) is used. The white object to be read is a reference member (described below) or a blank space on the paper (non-image printed area).

[0032] Figure 8 shows the red reading value for the reflected light from a white reading target illuminated by a white LED before deterioration. For output in the red wavelength band, a red filter is applied to the reflected light, so Figure 8 shows the filter characteristics for each wavelength of the red filter. As the red filter has the characteristic of passing light in the wavelength range of the yellow phosphor (around 560 nm), the red reading value decreases due to the deterioration of the yellow phosphor.

[0033] When the object to be read is the first color (magenta), the green reading value is Mg, when the object to be read is the second color (white), the red reading value is Wr, and when the corrected value of Mg (corrected value) is Mg', Mg' is calculated using the following formula.

[0034] Mg′=α×(Mg / Wr) (1)

[0035] Here, α is a predetermined coefficient for adjusting the degree to which Wr is reflected in the correction value Mg'. α may be determined through evaluation experiments when designing the reading device, or through tests for each reading device during the manufacturing process. α may also be dynamically changed depending on the usage status of the reading device 200.

[0036] Figure 9 is a table summarizing the read values ​​(Mg, Wr) of each color in each state (before and after deterioration) of the white LED. As shown, the Mg value is large when the white LED is in the state before deterioration and decreases moderately after deterioration, but Wr is also large before deterioration and decreases moderately after deterioration, so by performing the division in equation (1) above, the effect of deterioration is canceled out in the correction value Mg'.

[0037] In the above equation (1), division by Wr is used for correction, but subtraction by Wr as follows can also be used instead of division.

[0038] Mg′=Mg−β×Wr (2) Here, β is a predetermined coefficient for adjusting the degree to which Wr is reflected in the correction value Mg'. β may be determined through evaluation experiments when designing the reading device, or through tests for each reading device during the manufacturing process. β may also be dynamically changed depending on the usage status of the reading device 200.

[0039] 10 is a diagram showing an example of a functional block diagram of the correction process according to this embodiment. The correction process in the CPU 240 has an Mg input unit 810, a Wr input unit 811, a coefficient read unit 812, and an Mg correction unit 813.

[0040] The Mg input unit 810 inputs a green read value Mg when the read object is a first color (magenta). The Wr input unit 811 inputs a red read value Wr when the read object is a second color (white). The coefficient reading unit 812 reads out the coefficient α of equation (1) or the coefficient β of equation (2) stored in a storage device such as the ROM 241, RAM 242, or SSD 243.

[0041] The Mg correction unit 813 corrects Mg using Wr and a coefficient according to equation (1) or (2), and outputs a corrected value Mg'.

[0042] 11 is a flowchart showing the procedure of the correction process according to this embodiment. First, the CPU 240 inputs the green read value Mg (step S10), inputs the red read value Wr (step S11), and reads out the coefficient α of equation (1) or the coefficient β of equation (2) stored in the storage device (step S12). Here, the order in which each piece of data is input and read out is not limited to the order shown in the flowchart. For example, Wr may be input, the coefficients may be read out, and then Mg may be input.

[0043] Next, the CPU 240 corrects Mg using Wr and a coefficient according to equation (1) or (2) to calculate a corrected value Mg' (step S13).

[0044] As described above, according to this embodiment, the reading value of the first color, magenta, can be corrected using white as the second color, making it possible to correct the effects of LED degradation without the need to read a special color chart. Note that a white board, which is typically used for scanner calibration, may also be used as the white reading target. Alternatively, the margins of the printed recording paper P may also be used.

[0045] (Second embodiment) FIG. 12 illustrates differences in wavelength distribution due to differences in the density of the first color. In FIG. 12, the solid line represents the green reading (Mg) when the first color is dark magenta, and the dashed line represents the green reading when the first color is light magenta. When the first color is magenta, the output level of the reflected light from the blue LED is low, so the influence of the reflected light from the yellow phosphor is relatively large on the green reading. For this reason, as described in the first embodiment, correction was performed using the red reading Wr, which can reflect the influence of deterioration on the yellow phosphor. On the other hand, when the density of the first color, magenta, is light, the reading approaches the reading of white, so it is better to increase the proportion of the green reading and decrease the proportion of the red reading in correction. Therefore, for the reading of light magenta, the green reading (Wg) for white is used for correction, as in normal reading correction.

[0046] In this embodiment, Mg is corrected using only Wr for dark magenta reading targets, Mg is corrected using the average value of Wr and Wg for medium-density magenta reading targets, and Mg is corrected using only Wg for light magenta reading targets. It is also possible to correct using both Wr and Wg for dark magenta and both Wr and Wg for light magenta. It is also possible to correct using both Wr and Wg for dark magenta and only Wg for light magenta. Furthermore, for medium-density magenta, the reflection ratio of either Wr or Wg may be increased rather than the average value of Wr or Wg. However, the ratio of Wr is increased for dark magenta and the ratio of Wg is increased for light magenta.

[0047] 13 is a diagram showing an example of a functional block diagram of the correction processing according to the second embodiment. The correction processing in the CPU 240 has an Mg input unit 810, a Wr input unit 811, a Wg input unit 821, a coefficient reading unit 822, and an Mg correction unit 823. The operations of the Mg input unit 810 and the Wr input unit 811 are the same as those in the first embodiment.

[0048] The Wg input unit 821 inputs a green read value Wg when the read object is a second color (white). The coefficient read unit 822 reads out a coefficient used in a correction calculation described later. The Mg correction unit 823 corrects Mg by a correction calculation described later using Wr, Wg, and the coefficient, and outputs a corrected value Mg'.

[0049] The correction value Mg′ is calculated by the following formulas (3A) to (3C) or (4A) to (4C).

[0050] Mg′=γ×(Mg / Wr) (3A) Mg′=γ×(Mg / (Wr+Wg) / 2) ···(3B) Mg′=γ×(Mg / Wg) (3C) Mg′=Mg−δ×Wr (4A) Mg′=Mg-δ×(Wr+Wg) / 2 ···(4B) Mg′=Mg−δ×Wg (4C)

[0051] Here, equation (3A) or (4A) is used for correction when the first color magenta is high density, equation (3B) or (4B) is used for correction when the first color magenta is medium density, and equation (3C) or (4C) is used for correction when the first color magenta is low density. Furthermore, γ and δ are predetermined coefficients that adjust the degree to which Wr, (Wr + Wg) / 2, or Wg is reflected in the correction value Mg'. These coefficients may be determined through evaluation experiments when designing the reading device, or through tests for each reading device during the manufacturing process. These coefficients may also be dynamically changed depending on the usage status of the reading device 200.

[0052] 14 is a flowchart showing the procedure of the correction process according to this embodiment. First, the CPU 240 inputs the green read value Mg (step S20), inputs the red read value Wr (step S21), inputs the green read value Wg (step S22), and reads out the coefficient γ of equations (3A) to (3C) or the coefficient δ of equations (4A) to (4C) stored in the storage device (step S23). Here, the order in which each piece of data is input and read out is not limited to the order shown in the flowchart. For example, Wr and Wg may be input, and the coefficients may be read out, followed by input of Mg.

[0053] Next, the CPU 240 corrects Mg using Wr, Wg and the coefficients according to equations (3A) to (3C) or equations (4A) to (4C) to calculate a corrected value Mg' (step S24).

[0054] Thus, according to this embodiment, by correcting the first color, magenta, according to the density of the magenta to be read, it is possible to appropriately adjust the influence of the reflected light from the yellow phosphor of the white LED and the influence of the reflected light from the blue LED.

[0055] (Third embodiment) In the second embodiment, when the density of the magenta to be read has three levels, correction is performed using a correction formula for each density. However, the CPU 240 may determine the density d of the read object and perform correction using the following formula (3D) or (4D).

[0056] Mg′=γ×(Mg / (d×Wr+(Dd)×Wg) / D) ···(3D) Mg′=Mg-δ×((d×Wr+(Dd)×Wg) / D) ···(4D)

[0057] Here, Equation (3D) performs the correction of Mg by division, and Equation (4D) performs the correction of Mg by subtraction. Also, it is assumed that the concentration d can theoretically range from 0 to D (D > 0). When d = D (the thickest case), Equation (3D) becomes equal to Equation (3A), and Equation (4D) becomes equal to Equation (4A). When d = D / 2, Equation (3D) becomes equal to Equation (3B), and Equation (4D) becomes equal to Equation (4B). When d = 0 (the thinnest case), Equation (3D) becomes equal to Equation (3C), and Equation (4D) becomes equal to Equation (4C).

[0058] Note that the actual concentration d is determined within the range of d1 (d1 > 0) to d2 (d2 < D). FIG. 15 is a diagram showing the relationship between the weighted average weights (d / D, (D - d) / D) of Wr and Wg used for division or subtraction in Equations (3D) and (4D), and the concentration d. Also, FIG. 15 shows that when the concentration of the reading target is d, the application rate of Wr in the correction calculation is d / D, and the application rate of Wg is (D - d) / D.

[0059] FIG. 16 is a diagram showing an example of a functional block diagram of the correction process according to the third embodiment. The correction process in the CPU 240 includes a Mg input unit 810, a concentration determination unit 831, a Wr input unit 811, a Wg input unit 821, a coefficient reading unit 822, and a Mg correction unit 833. The operations of the Mg input unit 810 and the Wr input unit 811 are the same as those in the first embodiment, and the operations of the Wg input unit 821 and the coefficient reading unit 822 are the same as those in the second embodiment.

[0060] The concentration determination unit 831 determines the concentration d of the first color (magenta) that is the reading target. When the object is a printed matter such as a strip pattern used in the fourth embodiment described later, the concentration can be determined using the information described in the layout of the printed matter. Also, when reading a printed matter of a strip pattern during the adjustment of the manufacturing process of the reading device, the concentration of each strip can be set in advance. In this case, the concentration determination unit 831 can determine the concentration depending on which strip is being read.

[0061] The density determination may be performed by estimating the density d using the green read value. For example, if the correlation between the density of the object to be read and the green read value is determined in an evaluation experiment or the like at the design stage, the density d can be estimated from the green read value.

[0062] Furthermore, the method of determining density may be changed by checking the degree of variation due to deterioration of the reading device, etc., and the degree of variation in the printing of band-shaped patterns, etc. For example, when there is a large variation in reading, density may be determined using layout information on the printed matter or information on which band is being read, and when there is a large variation in printing, density may be determined from the green reading value.

[0063] 17 is a flowchart showing the procedure of the correction process according to this embodiment. First, the CPU 240 inputs the green read value Mg (step S30), determines the density d of the object to be read (step S31), inputs the red read value Wr (step S32), inputs the green read value Wg (step S33), and reads out the coefficient γ of equation (3D) or the coefficient δ of equation (4D) stored in the storage device (step S34). Here, the order in which each piece of data is input and read out is not limited to the order shown in the flowchart. For example, Wr and Wg may be input, and the coefficients may be read out, before inputting Mg and determining the density.

[0064] Next, the CPU 240 corrects Mg using d, Wr, Wg and the coefficients according to equation (3D) or equation (4D) to calculate a corrected value Mg' (step S35).

[0065] As described above, according to this embodiment, the density of the object to be read is determined, and the read value of the first color, magenta, can be appropriately corrected using the density. Furthermore, since the correction can be performed using an equation that uses the density as a variable, correction can be easily performed even when the number of density levels is greater than three.

[0066] (Fourth embodiment) 18 is a schematic diagram of a printer (the present printer) equipped with a tone correction device according to the fourth embodiment. In the fourth embodiment, the reading device 200 according to the first to third embodiments is applied to the tone correction device equipped in the present printer.

[0067] This printer has four process units 2Y, 2M, 2C, and 2K for forming toner images of yellow (Y), magenta (M), cyan (C), and black (K). The printer also has a paper feed path 30, a pre-transfer transport path 31, a manual paper feed path 32, a manual feed tray 33, a pair of registration rollers 34, and a transport belt unit 35. The printer also has a fixing device 40, a transport switching device 50, a pair of paper discharge rollers 52, a paper discharge tray 53, a first paper feed cassette 101, a second paper feed cassette 102, a re-feed device, and the like. The printer also has two optical writing units 1YM and 1CK. The process units 2Y, 2M, 2C, and 2K each have a drum-shaped photosensitive element 3Y, 3M, 3C, and 3K that serves as a latent image carrier.

[0068] The first paper feed cassette 101 and the second paper feed cassette 102 each contain a stack of recording paper P therein. Then, by the rotational drive of paper feed rollers 101a and 102a, the topmost recording paper P in the paper stack is sent out toward paper feed path 30. This paper feed path 30 is connected to a pre-transfer conveyance path 31 for conveying the recording paper just before the secondary transfer nip, which will be described later. The recording paper P as a recording member sent out from the paper feed cassettes (101, 102) passes through paper feed path 30 and enters pre-transfer conveyance path 31.

[0069] A manual feed tray 33 is disposed on the side of the printer housing so as to be able to open and close relative to the housing, and a stack of papers is manually fed onto the top surface of the tray when it is open relative to the housing. The topmost recording paper P of the manually fed stack is sent out toward the pre-transfer conveyance path 31 by a feed roller of the manual feed tray 33.

[0070] The two optical writing units 1YM and 1CK, which act as exposure devices for exposing the photoconductor surfaces to light and forming electrostatic latent images on the photoconductor surfaces, each include a laser diode, a polygon mirror, and various lenses. Each optical writing unit 1YM and 1CK drives a laser diode as a light source based on image data read by an external scanner or image data sent from a personal computer. The laser diode then optically scans the photoconductors 3Y, 3M, 3C, and 3K of the process units 2Y, 2M, 2C, and 2K. Specifically, the photoconductors 3Y, 3M, 3C, and 3K of the process units 2Y, 2M, 2C, and 2K are rotated counterclockwise in the figure by driving devices. The optical writing unit 1YM performs optical scanning by irradiating the driven photoconductors 3Y and 3M with a laser beam deflected along their respective rotation axes. As a result, electrostatic latent images based on the Y and M image data are formed on the photoconductors 3Y and 3M. The optical writing unit 1CK performs optical scanning by irradiating the photoconductors 3C and 3K with laser light while deflecting it in the direction of their rotation axes, thereby forming electrostatic latent images based on the C and K image data on the photoconductors 3C and 3K.

[0071] Each of the process units 2Y, 2M, 2C, and 2K is a single unit that supports a photosensitive element (latent image carrier) and various peripheral devices on a common support, and these units are detachably attached to the printer body. They have similar configurations except for the toner colors they use. Taking the Y process unit 2Y as an example, it includes a photosensitive element 3Y and a developing device 4Y for developing the electrostatic latent image formed on the photosensitive element's surface into a Y toner image. It also includes a charging device 5Y that uniformly charges the surface of the rotationally driven photosensitive element 3Y, and a drum cleaning device 6Y that cleans residual toner remaining on the surface of the photosensitive element 3Y after it passes through the Y primary transfer nip (described later).

[0072] This printer has a so-called tandem configuration in which four process units 2Y, 2M, 2C, and 2K are arranged along the endless movement direction of an intermediate transfer belt 61, which will be described later.

[0073] The photoreceptor 3Y is a drum-shaped member made of a tube such as aluminum, on which a photosensitive layer is formed by applying an organic photosensitive material having photosensitivity, although an endless belt-shaped member may also be used.

[0074] The developing device 4Y develops a latent image using a two-component developer (hereinafter simply referred to as developer) containing magnetic carrier and non-magnetic Y toner. The developing device 4Y is appropriately replenished with Y toner from a Y toner bottle 103Y by a Y toner replenishing device. A toner concentration detecting means is provided within the developing device 4Y. The toner concentration detecting means detects the magnetic permeability caused by the carrier, which is a magnetic material, and calculates the toner concentration from the amount of carrier contained in a certain volume. This toner concentration detecting means detects the toner concentration within the developing device and controls the toner concentration within the developing device within a certain range (for example, 5 wt% to 9 wt%).

[0075] The drum cleaning device 6Y uses a polyurethane rubber cleaning blade that presses against the photoreceptor 3Y, but other types may also be used. To improve cleaning performance, this printer uses a rotatable fur brush that abuts against the photoreceptor 3Y. This fur brush also serves to scrape the lubricant from the solid lubricant, turning it into a fine powder and applying it to the surface of the photoreceptor 3Y.

[0076] A discharge lamp is disposed above the photoconductor 3Y, and this discharge lamp is also part of the process unit 2Y. The discharge lamp discharges the surface of the photoconductor 3Y by irradiating it with light after it has passed through the drum cleaning device 6Y. The discharged surface of the photoconductor 3Y is then uniformly charged by the charging device 5Y and optically scanned by the optical writing unit 1YM. The charging device 5Y is rotated while receiving a charging bias from a power source. Alternatively, a scorotron charger may be used, which charges the photoconductor 3Y without contact.

[0077] Although the process unit 2Y for Y has been described, the process units 2M, 2C, and 2K for M, C, and K have the same configuration as that for 2Y, and therefore a detailed description thereof will be omitted.

[0078] A transfer unit 60 is disposed below the four process units 2Y, 2M, 2C, and 2K. This transfer unit 60 moves an intermediate transfer belt 61, an image carrier stretched by multiple rollers, endlessly in the clockwise direction in the drawing by rotating one of the rollers while bringing the intermediate transfer belt 61 into contact with the photosensitive elements 3Y, 3M, 3C, and 3K. This forms primary transfer nips for Y, M, C, and K where the photosensitive elements 3Y, 3M, 3C, and 3K come into contact with the intermediate transfer belt 61.

[0079] Near the primary transfer nips for Y, M, C, and K, primary transfer rollers 62Y, 62M, 62C, and 62K disposed inside the belt loop press the intermediate transfer belt 61 toward the photoconductors 3Y, 3M, 3C, and 3K. A primary transfer bias is applied to each of these primary transfer rollers 62Y, 62M, 62C, and 62K by a power source. As a result, a primary transfer electric field is formed in the primary transfer nips for Y, M, C, and K that electrostatically moves the toner images on the photoconductors 3Y, 3M, 3C, and 3K toward the intermediate transfer belt 61.

[0080] As the intermediate transfer belt 61 moves endlessly clockwise in the figure, it passes through the primary transfer nips for Y, M, C, and K in sequence, and toner images are sequentially superimposed and primarily transferred onto the front surface of the intermediate transfer belt 61 at each primary transfer nip. As a result of this superimposed primary transfer, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the front surface of the intermediate transfer belt 61.

[0081] A secondary transfer roller 72 is disposed below the intermediate transfer belt 61 in the drawing, and this forms a secondary transfer nip by contacting the front surface of the intermediate transfer belt 61 with the secondary transfer backup roller 68 at a position where the intermediate transfer belt 61 is wound around the secondary transfer backup roller 68. This forms a secondary transfer nip where the front surface of the intermediate transfer belt 61 and the secondary transfer roller 72 come into contact with each other.

[0082] A secondary transfer bias is applied from a power source to the secondary transfer roller 72. Meanwhile, the secondary transfer backup roller 68 in the belt loop is grounded, thereby forming a secondary transfer electric field in the secondary transfer nip.

[0083] The above-mentioned registration roller pair 34 is disposed on the right side of the secondary transfer nip in the drawing, and the recording paper P sandwiched between the rollers is sent to the secondary transfer nip at a timing that allows it to be synchronized with the four-color toner image on the intermediate transfer belt 61. Within the secondary transfer nip, the four-color toner image on the intermediate transfer belt 61 is secondarily transferred all at once onto the recording paper due to the influence of the secondary transfer electric field and nip pressure, and combined with the white color of the recording paper, it becomes a full-color image.

[0084] Between the primary transfer nip and the secondary transfer nip, there is disposed a toner adhesion amount detection sensor 64, which is a reflective optical sensor. The reflective optical sensor has a light-emitting element and a light-receiving element, and light emitted from the light-emitting element is reflected by the toner patch formed on the intermediate transfer belt 61, received by the light-receiving element, and converted into a signal. By reading the change in this signal, information on the test pattern is inferred and the amount of adhesion of the toner patch is detected.

[0085] Residual toner that was not transferred to the recording paper P at the secondary transfer nip adheres to the front surface of the intermediate transfer belt 61 that has passed through the secondary transfer nip. This residual toner is cleaned by a belt cleaning device 75 that comes into contact with the intermediate transfer belt 61.

[0086] After passing through the secondary transfer nip, the recording paper P separates from the intermediate transfer belt 61 and is delivered to the conveyor belt unit 35. In this conveyor belt unit 35, an endless conveyor belt 36 is stretched by a drive roller 37 and a driven roller 38, and is moved endlessly counterclockwise in the drawing by the rotational drive of the drive roller 37. The recording paper delivered from the secondary transfer nip is then held on the upper stretching surface of the belt and conveyed as the belt moves endlessly, and is delivered to the fixing device 40.

[0087] The recording paper P that has passed through the secondary transfer nip is sent into the fixing device 40 and sandwiched in the fixing nip. Then, the toner image is fixed by the action of pressure, heat, etc. The recording paper P, which has had the toner image transferred to its first surface in the secondary transfer nip and has had the toner image fixed to its first surface by the fixing device 40, is sent out toward the conveyance switching device 50.

[0088] In this printer, the re-transport means is made up of the transport switching device 50, the re-feed path 54, the switchback path 55, the post-switchback transport path 56, etc. Specifically, the transport switching device 50 switches the subsequent transport destination of the recording sheet P received from the fixing device 40 between the discharge path 57 and the re-feed path 54. Specifically, when a print job in a single-sided mode in which an image is formed only on the first side of the recording sheet P is executed, the transport destination is set to the discharge path 57. As a result, the recording sheet P with an image formed only on the first side is sent to the pair of discharge rollers 52 via the discharge path 57 and discharged onto a discharge tray 53 outside the printer. Also, when a print job in a double-sided mode in which images are formed on both sides of the recording sheet P is executed, the transport destination is also set to the discharge path 57 when the recording sheet P with images fixed on both sides is received from the fixing device 40. As a result, the recording sheet P with images formed on both sides is discharged onto a discharge tray 53 outside the printer. On the other hand, when a print job in double-sided mode is executed, if the recording sheet P with an image fixed only on the first side is received from the fixing device 40, the transport destination is set to the re-feed path .

[0089] A switchback path 55 is connected to the re-feed path 54, and the recording sheet P sent to the re-feed path 54 enters this switchback path 55. Then, when the entire area of ​​the recording sheet P in the conveying direction enters the switchback path 55, the conveying direction of the recording sheet P is reversed, and the recording sheet P switches back. In addition to the re-feed path 54, a post-switchback conveying path 56 is connected to the switchback path 55, and the switched-back recording sheet P enters this post-switchback conveying path 56. At this time, the recording sheet P is turned upside down. Then, the upside-down turned recording sheet P is re-fed to the secondary transfer nip via the post-switchback conveying path 56 and the above-mentioned paper feed path 30. The recording sheet P, on whose second side a toner image has also been transferred at the secondary transfer nip, passes through the fixing device 40, where the toner image is fixed to the second side, and is then discharged onto the paper discharge tray 53 via the conveying switching device 50 and the paper discharge roller pair 52. A reading device 200 and an opposing member 93 are provided in front of the discharge roller pair 52 as a detection means for detecting the image density on the recording paper P, and read a white reference surface and the image on the recording paper P during the gradation correction operation described below.

[0090] Next, the opposing member 93 disposed opposite the reading device 200 will be described with reference to FIG. 19. FIG. 19 is an enlarged view of the opposing member 93 and its surroundings. As shown in FIG. 19, the opposing member 93 includes four rollers 931, 932, 933, and 934 as rotatable rotating bodies, three reference surface members 991, 992, and 993 as curved opposing portions having reference surfaces, and a guide member 994. The four rollers 931, 932, 933, and 934 are driven to rotate so as not to interfere with the transport of the recording paper P when the recording paper P is transported so that it can be read at a position with the appropriate focal length of the reading device 200. The four rollers 931, 932, 933, and 934 are rotatably held by a roller bracket 935, and the three reference surface members 991, 992, and 993 and the guide member 994 are fixedly held by the roller bracket 935. By rotating the roller bracket 935 of the opposing member 93, the four rollers 931, 932, 933, and 934, the three reference surface members 991, 992, and 993, and the guide member 994 rotate integrally. This allows the opposing member 93 to selectively switch and position each of the four rollers 931, 932, 933, and 934, the reference surface members 991, 992, and 993, and the guide member 994 at a predetermined reading position where the reading device 200 reads an image. The reading device 200 also performs reading in the direction of an arrow 940 through the contact glass 94.

[0091] FIG. 20 is a perspective view for specifically explaining an example of the reference surface member 991. As shown in FIG. 20, the reference surface member 991 is a member having a white reference surface 991a, which is a uniform white surface serving as a reference surface. By disposing the reference surface member 991 at the reading position, the reference surface member 991 can be used as a white reading target used for the correction of the reading device 200 described above. Note that detailed explanations of the other reference surface members 992 and 993 will be omitted, but they can be used for correction as members having a uniform black surface or a reference color patch. Furthermore, the guide member 994 is a member that functions as a guide when the reading device 200 is not performing reading and is only performing the operation of transporting the recording paper P.

[0092] FIG. 21 shows an example of a band-shaped pattern for gradation correction. In this example, a single color band-shaped pattern is printed on one sheet of recording paper P. In this case, 11 band-shaped patterns, each with a different number of gradations, are formed on one sheet of recording paper P. Multiple band-shaped patterns are formed so that the number of gradations increases by 20 from the downstream side in the recording paper advance direction. In this embodiment, band-shaped patterns of 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, and 220 gradations are printed for one color. The number of band-shaped patterns formed on one sheet of recording paper and the number of gradations of each band-shaped pattern may be set as appropriate. For example, the number of printed sheets may be reduced by reducing the number of band-shaped patterns or the number of gradations of each band-shaped pattern.

[0093] In the example of Figure 21, the image density at each position in the main scanning direction of multiple band-shaped patterns of Y, M, C, and K colors formed on four sheets of recording paper P is detected by the reading device 200, and multiple density unevenness in the main scanning direction for each color is obtained. Here, density unevenness refers to density fluctuations in the main scanning direction that occur in images printed by a printer due to deviations in the main scanning direction caused by variations in mechanical precision, etc. In this embodiment, a total of 11 density unevenness in the main scanning direction are obtained: 20 gradations, 40 gradations, 60 gradations, 80 gradations, 100 gradations, 120 gradations, 140 gradations, 160 gradations, 180 gradations, 200 gradations, and 220 gradations.

[0094] 22 is a diagram showing an example of a functional block diagram of the gradation correction process according to this embodiment. The gradation correction process in the gradation correction device of this embodiment is realized by the CPU 240 of the reading device 200. The gradation correction process in the CPU 240 has a density unevenness acquisition unit 840 and an image processing unit 850. The density unevenness acquisition unit 840 is made up of a reading unit 841, a correction unit 842, a temperature change detection unit 843, and a memory unit 844.

[0095] The density unevenness acquisition unit 840 acquires the density unevenness of the image density on the recording paper P read by the reading device 200, corrects the green reading value data for the magenta belt pattern using the processing described in the first to third embodiments, and inputs the corrected density unevenness data to the image processing unit 850.

[0096] The image processing unit 850 performs various image processing, such as black shading correction and white shading correction, on the data read by the reading device 200. For example, the image processing unit 850 determines the amount of gradation correction for each area in the main scanning direction for each gradation between band-shaped patterns based on the density unevenness data. The image processing unit 850 also determines a gradation correction table from the amount of gradation correction and performs gradation correction for each area in the main scanning direction based on the gradation correction table. The amount of gradation correction may be determined by a known method as long as it corrects density unevenness to prevent unevenness from occurring. The gradation correction table is a table that associates each of the gradation values ​​1 to 230 of the image data with the corrected gradation number, and is determined by a known method using the amount of gradation correction.

[0097] Next, each functional unit of the density unevenness acquisition unit 840 will be described. The reading unit 841 acquires read values ​​(red read values ​​and green read values) of the white read target, which is the output of the imaging means of the reading device 200, when the gradation correction process is started and when a temperature change, which will be described later, is equal to or greater than a predetermined threshold. The reading unit 841 also acquires read values ​​of the belt-shaped pattern used for gradation correction. The correction unit 842 corrects the data of the magenta green read value among the read values ​​of the belt-shaped pattern used for gradation correction, using the data of the white red read value and the green read value.

[0098] The temperature change detection unit 843 detects a temperature change in the reading device 200. Here, the temperature change in the reading device 200 is detected using the output of a temperature sensor installed inside or near the reading device 200 and the time that the light source 201 of the reading device 200 has been irradiating light. For example, if the irradiation time of the light source 201 is short, such as immediately after starting up the printer, the temperature is low, and if the irradiation time is long, the temperature rises due to heat generated by the LED. Therefore, the time that the LED is lit from the start of reading can be counted, and the counted time can be used as data on the temperature change.

[0099] The storage unit 844 stores the read value of the white read target acquired by the reading unit 841. Specifically, data on the red read value and the green read value for the reference surface member 991 is stored in a storage device such as the SSD 243 or HDD. The predetermined threshold is a value determined in advance by the time of determining the temperature change, and may be determined by an evaluation experiment when designing the reading device 200, or may be determined by testing for each reading device during the manufacturing process. The predetermined threshold may also be dynamically changed depending on the usage status of the reading device 200, etc.

[0100] In order to perform correction that reflects the deterioration state of the LED, it is desirable that the read value of the white read target used by the correction unit 842 be acquired immediately before correcting the data of the magenta green read value. Furthermore, in a light source using an LED, a decrease in light intensity and a shift in wavelength occur as the temperature rises. A decrease in light intensity causes the read value to become smaller (darker), and a shift in wavelength causes the color of the read value to change. Because the read value fluctuates before and after the temperature rise of the LED, it is also desirable from such a short-term perspective that the read value of the white read target be acquired immediately before the data is corrected by the correction unit 842.

[0101] On the other hand, when belt-shaped patterns used for tone correction are printed and read on multiple sheets in succession, taking into consideration the amount of processing, it is desirable to reuse the data acquired by the reading unit 841 so that it can be used for correction processing by the correction unit 842. For example, when the printing area of ​​each tone in the above-mentioned belt-shaped patterns is enlarged, the belt-shaped patterns for each color are generated on multiple sheets. When dividing each color, Y, M, C, and K, into two sheets, a total of eight sheets must be printed and read.

[0102] In this embodiment, the read values ​​of the white reading target are acquired and stored at the start of the gradation correction process and when the temperature change exceeds a predetermined threshold, and the read values ​​of the band-shaped pattern are corrected using the most recently acquired read value when the temperature change is large, and using the stored read value when the temperature change is small.

[0103] 23 is a flowchart showing the procedure for correcting the magenta read value. First, the reading unit 841 acquires the read value of the white read target (step S40), and the memory unit 844 stores the acquired read value (step S41).

[0104] Next, the reading unit 841 reads the band-shaped pattern used for gradation correction (step S42), and the correction unit 842 corrects the magenta read value using the read value of the white reading target and outputs it to the image processing unit 850 (step S43). Here, the correction unit 842 may either directly use the read value acquired by the reading unit 841 in step S40 for correction, or read the read value stored by the memory unit 844 in step S41 from a storage device and use it for correction.

[0105] Next, if the gradation correction job continues, such as when there are multiple belt-shaped patterns (step S44: No), the density unevenness acquisition unit 840 determines the temperature change detected by the temperature change detection unit 843 (step S45). If the temperature change is equal to or greater than the threshold (step S45: Yes), the process proceeds to step S40, and the above-described procedures of steps S40 to S44 are repeated.

[0106] On the other hand, if the temperature change is not equal to or greater than the threshold value (step S45: No), the process proceeds to step S42, where the correction unit 842 corrects the magenta read value using the read value of the white read target (step S43). Here, the correction unit 842 reads the data of the white read target stored in the memory unit 844 from the storage device and uses it for correction.

[0107] As described above, according to this embodiment, when reading density unevenness data used for gradation correction processing in a printer, correction can be performed to reduce the influence of deterioration of the white LED, making it possible to perform gradation correction processing appropriately. Also, by using the reading device 200 according to the second or third embodiment, density unevenness data can be corrected according to the density of the band-shaped pattern used for gradation correction, making it possible to perform gradation correction processing more appropriately.

[0108] Furthermore, when the temperature change within the reading device 200 is small, the magenta read value is corrected using the data of the white read target stored in the memory unit 844, thereby reducing the amount of processing and enabling efficient correction. On the other hand, when the temperature change within the reading device 200 is large, the magenta read value is corrected using the data of the white read target acquired immediately before acquiring the read value of the band-shaped pattern. This allows for accurate correction even when the LED light intensity or wavelength fluctuates due to temperature changes. As a result, for example, when performing gradation correction processes continuously, more accurate correction can be achieved by performing correction using the white read value acquired when the temperature is high, rather than using the white read value acquired when the machine temperature is low immediately after starting the printer.

[0109] The scope of application of correction in the first to fourth embodiments may be the entire reading screen, a main scanning area unit, an LED chip unit, etc. Correcting the entire reading screen requires a large amount of calculation, so it is practically preferable to perform correction in main scanning area units, as in the fourth embodiment. However, if the deterioration status differs for each LED chip, correction may be performed for each LED chip.

[0110] Furthermore, while the correction of the magenta reading value using a green filter when a blue LED and yellow phosphor are used as the light source has been described, the light source and light receiving unit of this embodiment are not limited to this. For example, if the value O11 read for the first color and the value O22 read for the second color both tend to decrease due to deterioration of a light source with a specific spectral distribution, the correction value O11' for O11 can be calculated using either equation (5) or (6) below.

[0111] O11′=α×(O11 / O22) ···(5) O11′=O11−β×O22 (6)

[0112] Therefore, in this embodiment, the light source is not limited to a white LED, the first color and the second color are not limited to magenta and white, and the filters applied to the light receiving unit are not limited to a red filter and a green filter. Furthermore, if the value O21 read from the second color can be used for correction according to the density d of the first color, the correction value O11' can be calculated using either equation (7) or (8) below.

[0113] O11′=γ×(O11 / (d×O22+(Dd)×O21) / D) ···(7) O11′=O11-δ×((d×O22+(Dd)×O21) / D) ···(8)

[0114] Here, the coefficients α, β, γ, and δ are predetermined coefficients, and may be the same as or different from the coefficients in the first to third embodiments.

[0115] For example, aspects of the present invention are as follows. <1> The reading device comprises a light source that irradiates a reading object with light having a blue emission wavelength as its center and light having a yellow emission wavelength as its center, and an imaging means having a plurality of photoelectric conversion elements, each of which has sensitivity to one of a plurality of predetermined light receiving wavelengths, and corrects a first output of the imaging means when the color of the reading object is magenta and the predetermined light receiving wavelength is a green light receiving wavelength, using a second output of the imaging means when the color of the reading object is white and the predetermined light receiving wavelength is a red light receiving wavelength. <2> The reading device includes a light source that irradiates a reading object with light centered on a blue emission wavelength and light centered on a yellow emission wavelength, an imaging means having a plurality of photoelectric conversion elements each having sensitivity to one of a plurality of predetermined light receiving wavelengths, and corrects a first output of the imaging means when the color of the reading object is magenta and the predetermined light receiving wavelength is a green light receiving wavelength using a second output of the imaging means when the color of the reading object is white and the predetermined light receiving wavelength is a red light receiving wavelength, and a third output of the imaging means when the reading object is white and the predetermined light receiving wavelength is a green light receiving wavelength. <3> a ratio of the second output and the third output used to correct the first output is changed according to the density of the magenta; <2> The reading device is described in <4> The image capturing device further includes a reading unit that acquires an output of the image capturing means, a temperature change detection unit that detects a temperature change of the reading device, and a storage unit that stores the second output, and when the temperature change detection unit detects a temperature change equal to or greater than a predetermined threshold, the reading unit acquires the second output, the storage unit stores the second output, and the first output is corrected using the second output acquired by the reading unit or the second output stored in the storage unit. <1> The reading device is described in <5> The image capturing device further includes a reading unit that acquires an output of the imaging means, a temperature change detection unit that detects a temperature change of the reading device, and a storage unit that stores the second output and the third output, and when the temperature change detection unit detects a temperature change equal to or greater than a predetermined threshold, the reading unit acquires the second output and the third output, the storage unit stores the second output and the third output, and the first output is corrected using the second output and the third output acquired by the reading unit or the second output and the third output stored in the storage unit. <2> The reading device is described in <6> the temperature change detection unit detects the temperature change using an output from a temperature sensor installed inside or near the reading device; <4> or <5> The reading device is described in <7> the temperature change detection unit detects the temperature change using a time period during which the light source irradiates light; <4> or <5> The reading device is described in <8> This is a reading method comprising: an irradiation step of irradiating a reading object with light from a light source that irradiates the reading object with light centered on a blue emission wavelength and light centered on a yellow emission wavelength; a first reading step of reading the reflected light from the reading object with a photoelectric conversion element that is sensitive to wavelengths centered on a green light reception wavelength; and a second reading step of reading the reflected light from the reading object with a photoelectric conversion element that is sensitive to wavelengths centered on a red light reception wavelength, in which a first output from the first reading step when the color of the reading object is magenta is corrected using a second output from the second reading step when the color of the reading object is white. <9> This is a program that causes a computer to function as an irradiation means that irradiates a read object with light from a light source that irradiates the read object with light centered on a blue emission wavelength and light centered on a yellow emission wavelength, a first reading means that reads the reflected light from the read object with a photoelectric conversion element that has sensitivity to wavelengths centered on a green light reception wavelength, and a second reading means that reads the reflected light from the read object with a photoelectric conversion element that has sensitivity to wavelengths centered on a red light reception wavelength, and the program corrects a first output of the first reading means when the color of the read object is magenta using a second output of the second reading means when the color of the read object is white. [Explanation of symbols]

[0116] 201 Light source 202 Light source driving circuit 212 Light receiving part 810 Mg input section 811 Wr input section 812 Coefficient reading unit 813 Mg correction section 840 Density unevenness acquisition unit 841 Reading unit 842 Correction Unit 843 Temperature change detection unit 844 Storage section 850 Image Processing Unit [Prior art documents] [Patent documents]

[0117] [Patent Document 1] Patent No. 5100623

Claims

1. a light source that irradiates a reading object with light having a blue emission wavelength as its center and light having a yellow emission wavelength as its center; an imaging means having a plurality of photoelectric conversion elements each sensitive to one of a plurality of predetermined light receiving wavelengths; Equipped with a first output of the imaging means when the color of the object to be read is magenta and the predetermined light receiving wavelength is a green light receiving wavelength, a reading device that performs correction using a second output of the imaging means when the color of the object to be read is white and the predetermined light receiving wavelength is a red light receiving wavelength;

2. a light source that irradiates a reading object with light having a blue emission wavelength as its center and light having a yellow emission wavelength as its center; an imaging means having a plurality of photoelectric conversion elements each sensitive to one of a plurality of predetermined light receiving wavelengths; a first output of the imaging means when the color of the object to be read is magenta and the predetermined light receiving wavelength is a green light receiving wavelength, a second output of the imaging means when the color of the object to be read is white and the predetermined light receiving wavelength is a red light receiving wavelength; and a third output of the imaging means when the object to be read is white and the predetermined light receiving wavelength is a green light receiving wavelength.

3. 3. The reading device according to claim 2, wherein a ratio of the second output and the third output used to correct the first output is changed according to the density of the magenta.

4. a reading unit that acquires an output of the imaging means; a temperature change detection unit that detects a temperature change of the reading device; a storage unit that stores the second output, When the temperature change detection unit detects a temperature change equal to or greater than a predetermined threshold, the reading unit acquires the second output, and the storage unit stores the second output; correcting the first output using the second output acquired by the reading unit or the second output stored in the storage unit; The reading device according to claim 1 .

5. a reading unit that acquires an output of the imaging means; a temperature change detection unit that detects a temperature change of the reading device; a storage unit that stores the second output and the third output, when the temperature change detection unit detects a temperature change equal to or greater than a predetermined threshold, the reading unit acquires the second output and the third output, and the storage unit stores the second output and the third output; correcting the first output using the second output and the third output acquired by the reading unit or the second output and the third output stored in the storage unit; The reading device according to claim 2 .

6. the temperature change detection unit detects the temperature change using an output from a temperature sensor installed inside or near the reading device; 6. The reading device according to claim 4 or 5.

7. the temperature change detection unit detects the temperature change using a time period during which the light source irradiates light; 6. The reading device according to claim 4 or 5.

8. an irradiation step of irradiating the object to be read with light from a light source that irradiates the object with light having a blue emission wavelength as its center and light having a yellow emission wavelength as its center; a first reading step of reading reflected light from the object to be read using a photoelectric conversion element having sensitivity to wavelengths centered around a green light receiving wavelength; a second reading step of reading the reflected light from the object to be read using a photoelectric conversion element having sensitivity to wavelengths centered around a red light receiving wavelength; and A reading method, comprising: correcting a first output of a first reading step when the color of the read object is magenta using a second output of the second reading step when the color of the read object is white.

9. Computer, an illumination means for irradiating the object to be read with light from a light source that irradiates the object with light having a blue emission wavelength as its center and light having a yellow emission wavelength as its center; a first reading means for reading the reflected light from the object to be read using a photoelectric conversion element having sensitivity to wavelengths centered around a green light receiving wavelength; a second reading means for reading the reflected light from the object to be read using a photoelectric conversion element having sensitivity to wavelengths centered around a red light receiving wavelength; It functions as a program for correcting a first output of a first reading means when the color of the read object is magenta, using a second output of the second reading means when the color of the read object is white;

Images