Image reading device, image forming device, and image reading method

Abstract

To detect a change in image characteristics due to a change in optical characteristics of reading means to correct image characteristics used for correction of an image without reducing the number of images to be read.SOLUTION: An image reading device has: reading means including a light source that irradiates, with light, a passage area through which a subject passes, and imaging means that can create visible images and invisible images by picking up an image of reflected light of light irradiated from the light source; a background member that is arranged on the opposite side of the light source across the passage area and has invisible marks that can be identified by the imaging means as the invisible images; detection means that, in the invisible images obtained through the imaging of the invisible marks, detects a change in image characteristics due to a change in optical characteristics of the reading means; and correction means that, based on the change in image characteristics detected by the detection means, determines the amount of correction of the image characteristics used for correction of the image of the subject created by the imaging means, and corrects the image characteristics based on the determined correction amount.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image reading apparatus, an image forming apparatus, and an image reading method. [Background technology]

[0002] In an image reading device that reads an image of a document, etc., a method is known in which a pattern image is formed on a backing roller, and the document image is cut out based on a shadow image and the pattern image extracted from a captured image (see, for example, Patent Document 1). For example, by making the pattern image of the backing roller an invisible image, it is possible to prevent unwanted image patterns from being captured in the document image.

[0003] Also, a method is known in which, when a temperature change of a predetermined level or more is detected, the background surface facing the reading unit is switched to a correction surface on which a chart image is formed, the chart image is read, and a correction magnification for each partial area of ​​the image is calculated (see, for example, Patent Document 2). Summary of the Invention [Problem to be solved by the invention]

[0004] In the method of switching between the background surface and the correction surface on which a chart image is formed, image reading processing cannot be performed while the background surface is being switched to the correction surface. Therefore, the number of images read per unit time decreases as the frequency of switching between the background surface and the correction surface increases. In order to minimize the decrease in the number of images read, the calculation of the magnification correction value is performed only when a temperature change of a predetermined value or more occurs. As a result, when the temperature change is less than the predetermined value, the correction value cannot be calculated, and the correction frequency decreases, resulting in a problem that correction cannot be performed with high accuracy.

[0005] The disclosed technology has been developed in consideration of the above-mentioned problems, and aims to detect changes in image characteristics due to changes in the optical characteristics of the reading means, and to correct the image characteristics used to correct the image, without reducing the number of images read. [Means for solving the problem]

[0006] In order to solve the above technical problems, an image reading device of one embodiment of the present invention includes reading means including a light source that irradiates light onto a passing area through which a subject passes, and imaging means capable of generating a visible image and an invisible image by imaging reflected light of the light irradiated from the light source, a background member that is arranged on the opposite side of the passing area to the light source and has an invisible mark that can be identified as an invisible image by the imaging means, detection means that detects a change in image characteristics due to a change in optical characteristics of the reading means in an invisible image obtained by imaging the invisible mark, and correction means that determines a correction amount of image characteristics to be used to correct an image of the subject generated by the imaging means based on the change in image characteristics detected by the detection means, and corrects the image characteristics based on the determined correction amount. the imaging means has a plurality of pixels arranged in one direction, the invisible marks are figures arranged at predetermined intervals along the one direction on the background member, the detection means detects a rate of change in the interval of the invisible image relative to the interval of the invisible marks arranged in the one direction as the change in the image characteristic, and the interval of the invisible marks provided at a position on the background member where the temperature change is relatively large is set smaller than the interval of the invisible marks provided at a position on the background member where the temperature change is relatively small. It is characterized by: Effect of the Invention

[0007] It is possible to detect a change in image characteristics due to a change in the optical characteristics of the reading means and correct the image characteristics used for correcting the image without reducing the number of images read. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a first embodiment of an image reading device of the present invention; [Diagram 2] 2 is a diagram showing an example of an invisible mark formed on the background member of FIG. 1; FIG. [Diagram 3] 3 is a diagram showing an example of association between the invisible image and the visible image in FIG. 2; FIG. [Figure 4] 2 is a diagram showing an example of correcting a visible image by the image reading device of FIG. 1. [Diagram 5] 1. FIG. 4 is a diagram showing an example of a visible image reading operation by the image reading device of FIG. [Figure 6] 1. FIG. 4 is a diagram showing an example of timing for reading an invisible mark and updating a magnification by the image reading device of FIG. [Figure 7] 13A to 13C are diagrams illustrating an example of correcting a visible image in the image reading device according to the second embodiment of the present invention. [Figure 8] 13A to 13C are diagrams illustrating an example of correcting a visible image in the image reading device according to the third embodiment of the present invention. [Figure 9] 13A to 13C are diagrams showing an example of correcting a visible image in an image reading apparatus according to a fourth embodiment of the present invention. [Figure 10] 13A to 13C are diagrams showing an example of correcting a visible image in an image reading apparatus according to a fifth embodiment of the present invention. [Figure 11] FIG. 13 is a side view showing a sixth embodiment of an image reading device of the present invention. [Figure 12] 1 is a side view showing a first embodiment of an image forming apparatus of the present invention. [Figure 13] 13 is a partial side view showing an example of a main part of the inspection device of FIG. 12. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and duplicated descriptions may be omitted.

[0010] (First embodiment of image reading device) Fig. 1 is a block diagram showing a first embodiment of an image reading device of the present invention. The image reading device 10 shown in Fig. 1 has a reading unit 20, a background member 30, a detection unit 40, and a correction unit 50. For example, the reading unit 20 has a light source 21 and a line sensor 22.

[0011] The light source 21 irradiates light including visible light and invisible light to a passing area PA through which a paper P on which a subject such as an image is formed passes. For example, the invisible light is light in the near infrared region. Note that the subject is not limited to an image on the paper P, but may be an image printed on a resin such as a film or a metal, or may be an uneven pattern formed on the paper P. In the following description, the subject is assumed to be an image on the paper P.

[0012] The line sensor 22 can generate visible and invisible images by capturing an image of reflected light of light irradiated from the light source 21. For example, when the paper P is moved along the transport direction and is located in the passing area PA, the line sensor 22 captures an image of reflected light from the paper P. When the paper P is not located in the passing area PA, the line sensor 22 captures an image of reflected light from the background member 30. The line sensor 22 is an example of an imaging means.

[0013] The background member 30 is disposed on the opposite side of the light source 21 and the line sensor 22 across the passing area PA. The background member 30 has an invisible mark IVMRK that can be identified as an invisible image by the line sensor 22. The invisible mark IVMRK is detected as reflected light of light from the light source 21 by pixels that detect invisible light of the line sensor 22. Specific examples of the invisible mark IVMRK will be described in FIG. 2 and subsequent figures.

[0014] For example, the background member 30 is formed using a glass or ceramic material having a smaller thermal expansion coefficient than resin and metal. This makes it possible to reduce the amount of expansion and contraction of the intervals of the invisible marks IVMRK due to temperature changes in the background member 30 compared to background members formed from resin or metal. As a result, it is possible to suppress a decrease in the accuracy of correction of the visible image and the invisible image due to temperature changes.

[0015] In contrast, the background member made of resin or metal has a larger thermal expansion rate than the background member 30, and therefore the amount of expansion or contraction of the spacing between the invisible marks IVMRK due to temperature changes becomes larger than that of the background member 30. This reduces the accuracy of correction of the visible image.

[0016] The detection means 40 detects a change in image characteristics due to a change in the optical characteristics of the reading means 20 in the invisible image obtained by capturing an image of the invisible mark on the background member 30. For example, the optical characteristics of the reading means 20 include a change in the luminance or color of the light source 21 due to a temperature change in the image reading device 10, deformation of a lens and a mirror (not shown), or expansion and contraction of the line sensor 22.

[0017] The correction means 50 determines the correction amount of the image characteristics to be used for correcting the image on the paper P captured by the line sensor 22 based on the change in the image characteristics detected by the detection means 40, and corrects the image characteristics based on the determined correction amount. For example, the correction means 50 determines the correction amount of the image characteristics to be used for correcting the visible image data generated by the line sensor 22 corresponding to the visible image on the paper P. Alternatively, the correction means 50 determines the correction amount of the image characteristics to be used for correcting the invisible image data generated by the line sensor 22 corresponding to the invisible image on the paper P. Furthermore, the correction means 50 may determine the correction amount of the image characteristics to be used for correcting each of the visible image data and the invisible image data. Hereinafter, image data may be simply referred to as an image.

[0018] Then, the correction means 50 outputs the corrected image characteristics as a correction result. A subsequent mechanism (not shown) that receives the correction result corrects at least one of the visible image and the invisible image on the paper P based on the corrected image characteristics.

[0019] The detection means 40 and the correction means 50 may be realized by a controller such as a CPU mounted on the image reading device 10 executing an image reading program or an image correction program, etc. Alternatively, the detection means 40 and the correction means 50 may be realized by a field-programmable gate array (FPGA) mounted on the image reading device 10, etc.

[0020] Fig. 2 is a diagram showing an example of invisible marks IVMRK formed on the background member 30 of Fig. 1. The invisible marks IVMRK are formed at intervals S along the longitudinal direction of the elongated background member 30 extending in the horizontal direction of Fig. 2. Although 14 invisible marks IVMRK are shown in Fig. 2, the number of invisible marks IVMRK may be any number as long as it is more than one. The invisible marks IVMRK are an example of figures arranged at predetermined intervals along one direction (main scanning direction) on the background member 30.

[0021] For example, the invisible mark IVMRK is provided at a position corresponding to the pixel PX of the line sensor 22. For example, the line sensor 22 has four photoelectric conversion elements that detect red R, green G, blue B, and near-infrared light N, respectively, arranged in a direction perpendicular to the main scanning direction of the line sensor 22 (the vertical direction in FIG. 2). The four photoelectric conversion elements form one pixel PX. The line sensor 22 detects visible light and invisible light by each of the multiple pixels PX arranged in the main scanning direction. Hereinafter, the photoelectric conversion elements that detect red R, green G, and blue B are also referred to as R pixels, G pixels, and B pixels, respectively. The photoelectric conversion element that detects near-infrared light N is also referred to as N pixels. Hereinafter, the pixels PX are also referred to as pixels a to n when the positions are distinguished from one another.

[0022] The reflected light (invisible light) from the invisible mark IVMRK is detected by pixels a to n arranged at equal intervals in the main scanning direction of the line sensor 22. However, due to changes in the optical characteristics of the reading means 20, the physical positions of the pixels a to n that detect the invisible mark IVMRK (the positions of the pixels PX) change.

[0023] In the following, the distance between the two invisible marks IVMRK corresponding to pixels a and b is referred to as an interval AB or an area AB, and the distance between the two invisible marks IVMRK corresponding to pixels b and c is referred to as an interval BC or an area BC. The same applies to the intervals CD, DE, EF, FG, GH, HI, IJ, JK, KL, LM, and MN.

[0024] Fig. 3 is a diagram showing an example of association between the invisible image and the visible image in Fig. 2. Hereinafter, the invisible image of the invisible mark IVMRK obtained by imaging with the line sensor 22 is also referred to as an invisible mark image.

[0025] As described in Fig. 2, the visible image is detected by R pixels, G pixels, and B pixels, and the invisible image is detected by N pixels. The light of the visible image and the light of the invisible image received by the line sensor 22 have different wavelengths. Furthermore, since the positions of the R pixels, G pixels, B pixels, and N pixels are different from one another, for example, the light receiving characteristics of a lens (not shown) arranged on the light receiving surface of the line sensor 22 in Fig. 1 are slightly different. Furthermore, the light receiving characteristics of the lens also change due to deformation of the lens caused by temperature.

[0026] For this reason, the magnification, which is the amount of image correction, differs between the visible image and the invisible image. For example, the magnification is used to correct the length in the main scanning direction. The magnifications of the visible image and the invisible image differ between the visible image and the invisible image due to differences not only in the pixel positions but also in the wavelength and the light receiving characteristics of the lens. However, the tendency of the change in magnification in the main scanning direction is the same for the visible image and the invisible image.

[0027] Therefore, in this embodiment, the ratio of the magnification of the visible image to the magnification of the invisible image is calculated based on the interval between the invisible mark images detected by the detection means 40, and is used as the correction amount of the image characteristics to be used for correcting the visible image. An example of the calculation of the correction amount of the image characteristics is described in FIG.

[0028] Fig. 4 is a diagram showing an example of correcting a visible image by the image reading device 10 of Fig. 1. For example, the detection means 40 of Fig. 1 detects the interval AB between two invisible marks IVMRK corresponding to an area AB as a change in image characteristics, based on an invisible mark image captured by the line sensor 22.

[0029] The detection means 40 calculates the ratio S / AB of the interval S between the two invisible marks IVMRK to the interval AB. The interval S is an inherent value determined when the background member 30 is manufactured, and is, for example, the interval (design value, etc.) between the invisible marks IVMRK at a standard temperature (for example, 25°C, etc.). The ratio AB / S indicated by a white diamond indicates the rate of change of the interval AB to the interval S due to temperature change. The ratios BC / S, CD / S, ..., MN of the other intervals BC, CD, ..., MN also indicate the rate of change of each interval to the interval S due to temperature change.

[0030] The correction means 50 determines the ratio S / AB of the invisible mark images calculated by the detection means 40 as the correction amount of the image characteristics to be used for correcting the visible image present in the area AB. The correction means 50 also determines the ratio S / AB of the invisible mark images calculated by the detection means 40 as the correction amount of the image characteristics to be used for correcting the invisible image present in the area AB. For example, an image correction section connected downstream of the correction means 50 corrects the image by multiplying at least one of the visible image and the invisible image in the area AB by S / AB in the main scanning direction.

[0031] The detection means 40 also calculates the ratios S / BC, S / CD, ..., S / MN for the other regions BC, CD, ..., MN. The correction means 50 determines the ratios S / BC, S / CD, ..., S / MN as the correction amounts of the image characteristics to be used for correcting the invisible image and the visible image in each region BC, CD, ..., MN. By correcting the visible image using the correction amounts based on the above ratios, it is possible to generate a visible image in which the change in magnification of each part of the image due to temperature change is reduced, and the accuracy of the image can be improved. In addition, by correcting the invisible image using the correction amounts based on the above ratios, it is possible to eliminate the change in magnification of each part of the image due to temperature change, and generate an invisible image in a state equivalent to that in the absence of temperature change.

[0032] Fig. 5 is a diagram showing an example of a visible image reading operation by the image reading device 10 of Fig. 1. That is, Fig. 5 shows an example of an image reading method by the image reading device 10. The background surface of the background member 30 shown in Fig. 5 shows a surface on which an invisible image is formed. The invisible mark IVMRK of the background member 30 shown in Fig. 1 always faces the light source 21 and the line sensor 22. Therefore, when the paper P does not exist in the passing area PA of Fig. 1, the line sensor 22 can always read the invisible mark IVMRK.

[0033] 1 can thereby determine the amount of correction of image characteristics used to correct the visible image and the invisible image at each reading interval of the paper P. That is, the reading time of the invisible mark IVMRK can be included in the period of the reading operation of successive sheets of paper P. Note that the determination of the amount of correction may be performed each time multiple sheets of paper P are read, or may be performed before the first sheet is read. Also, the interval for determining the amount of correction may be set shorter as the temperature increases.

[0034] An example of the operation of the image reading device that requires switching between the background surface and the correction surface is shown in brackets at the bottom of Fig. 5. The background surface shown on the correction member in brackets indicates the surface used as the background when reading an image on paper P. The correction surface shown on the correction member in brackets indicates the surface on which a correction pattern (invisible image or visible image) is formed.

[0035] In an image reading device that performs the operation in the quotation marks, for example, switching between the background surface and the correction surface is performed between reading the (N-1)th sheet of paper P and reading the Nth sheet of paper P. Then, the amount of correction of the image characteristics is determined using the visible image or invisible image on the correction surface.

[0036] In this case, the number of sheets of paper P read per unit time decreases as the frequency of switching between the background side and the correction side increases, and the efficiency of reading the paper P decreases. In order to suppress the decrease in the reading efficiency, it is necessary to reduce the frequency of reading the correction side and to reduce the frequency of determining the correction amount. In this case, the accuracy of image correction decreases.

[0037] Fig. 6 is a diagram showing an example of invisible mark reading and magnification update timing by the image reading device 10 of Fig. 1. That is, Fig. 6 shows an example of an image reading method by the image reading device 10. Fig. 6 shows an operation of continuously reading a plurality of sheets of paper P (image acquisition operation). In this case, the reading means 20 of Fig. 1 reads the invisible mark IVMRK of the background member 30 before reading the first sheet of paper P and at each reading interval of the sheet of paper P, and determines the correction amount of the image characteristics of the visible image and the invisible image. Note that the reading of the invisible mark IVMRK may be performed every time a predetermined number of sheets of paper P are read.

[0038] This allows the reading means 20 to periodically read the invisible mark IVMRK and update the magnification. In other words, the magnification can be periodically updated without decreasing the frequency of reading the paper P. As a result, it becomes possible to always perform optimal correction on the image read from the paper P.

[0039] As described above, in the first embodiment, the image reading device 10 performs an operation of reading an image on the paper P in a state where the invisible marks IVMRK formed on the background member 30 are always opposed to the passing area PA. This allows the image reading device 10 to detect a change in the optical characteristics of the reading means 20 based on the rate of change in the interval of the invisible marks IVMRK at any timing when the paper P is not present in the passing area PA. Then, the image reading device 10 can determine the amount of correction of the image characteristics to be used for correcting the image according to the detected change in the optical characteristics.

[0040] That is, the image reading device 10 can detect the change in image characteristics due to the change in the optical characteristics of the reading means and determine the amount of correction for the image characteristics without reducing the number of images read. The image reading device 10 can periodically read the invisible mark IVMRK and update the magnification, so that it is possible to always perform optimal correction for the image read from the paper P.

[0041] By forming figures such as invisible marks IVMRK at a predetermined interval on the background member 30, the image reading device 10 can detect a change in the optical characteristics of the reading means 20 based on the captured figures. In addition, by arranging figures such as invisible marks IVMRK at equal intervals S on the background member 30, the rate of change (magnification) of the intervals for each position in the main scanning direction can be calculated by a simple calculation.

[0042] The correction means 50 determines the correction amount of the image characteristics to be used for correcting the visible image, using the rate of change of the interval between the invisible marks IVMRK detected by the detection means 40 as the rate of change of the visible image. This makes it unnecessary to calculate the rate of change of the interval between the visible images, and simplifies the calculation process of the correction means 50. Therefore, the time required to determine the correction amount of the image characteristics can be shortened.

[0043] By forming the background member 30 using a glass or ceramic material that is less susceptible to temperature changes, it is possible to suppress deterioration in the accuracy of correction of the visible image due to temperature changes.

[0044] (Second embodiment of image reading device) Fig. 7 is a diagram showing an example of correcting a visible image in the second embodiment of the semiconductor integrated circuit of the present invention. The same elements as those described in Figs. 1 to 6 are given the same reference numerals, and detailed description will be omitted. In the image reading device 10 including the background member 30 shown in Fig. 7, the function of the correction means 50 differs from the function of the correction means 50 described in Figs. 1 to 6. The other functions of the image reading device 10 are the same as the functions described in Figs. 1 to 6.

[0045] The correction means 50 of this embodiment has a conversion table 51 that holds the magnification (rate of change) of a visible image relative to the magnification (rate of change) of an invisible image for each of areas AB, ..., MN provided along the main scanning direction. The conversion table 51 includes correspondence relationships between a plurality of sets of magnifications (rates of change) of invisible images and magnifications (rates of change) of visible images for each of areas AB, etc.

[0046] For example, the magnification of area AB is a change rate indicated by the ratio AB / S. Conversion table 51 is an example of a storage unit that stores the relationship between the change rate and the correction amount of the subject image for each of a plurality of locations along the main scanning direction.

[0047] Normally, the amount of change in magnification (distortion) for each region in the main scanning direction is determined by the lens characteristics and wavelength of light used. However, when the same lens is used to read visible and invisible images in one image reading device 10, it is possible to uniquely associate the amount of change in magnification with each other as long as the wavelengths of the visible and invisible lights do not change.

[0048] The correction means 50 refers to the conversion table 51 for each region such as AB, and uses the rate of change of the visible image corresponding to the rate of change of the invisible image corresponding to the invisible mark IVMRK to determine the amount of correction for each pixel of the visible image obtained by reading the paper P. For example, when the rate of change of the invisible image detected by the detection means 40 is 1.005 times, the correction means 50 uses the corresponding rate of change of the visible image = 1.015 times and determines the magnification used for correcting the visible image to be in the ratio 1 / 1.015. This makes it possible to improve the accuracy of correction compared to the case where the rate of change of the invisible image is used directly to determine the magnification used for correcting the visible image.

[0049] As described above, in this embodiment as well, similarly to the above-mentioned embodiment, the image reading device 10 can detect a change in the optical characteristics of the reading means 20 based on the rate of change in the interval of the invisible marks IVMRK at any timing when the paper P is not present in the passing area PA. Then, the image reading device 10 can determine the correction amount of the image characteristics to be used for correcting the image according to the detected change in the optical characteristics.

[0050] Furthermore, in this embodiment, the image reading device 10 has a conversion table 51 in which the magnification of an invisible image corresponds to the magnification of a visible image for each region provided along the main scanning direction. This allows the image reading device 10 to improve the accuracy of correction of the image on the paper P compared to a case in which the rate of change of the invisible image is used directly to determine the magnification used for correcting the visible image.

[0051] (Third embodiment of image reading device) 8 is a diagram showing an example of correcting a visible image in the third embodiment of the semiconductor integrated circuit of the present invention. The same elements as those described in FIGS. 1 to 7 are given the same reference numerals, and detailed description thereof will be omitted.

[0052] In this embodiment, changes in the optical characteristics of the reading means 20 are evaluated in advance for each image reading device 10 (for example, for each machine A and machine B), and a conversion table 51 set according to the evaluation results is stored in the correction means 50. The configuration and functions of each image reading device 10 are similar to the configuration and functions of the image reading device 10 described in FIG. 7. That is, the image reading device 10 of this embodiment has the same functions as the image reading device 10 described in FIG. 1 to FIG. 6, except that it has the functions of the correction means 50 described in FIG. 7.

[0053] As described above, this embodiment can also provide the same effects as the above-mentioned embodiment. Furthermore, in this embodiment, the amount of image correction can be determined according to the optical characteristics of the reading means 20 of each image reading device 10.

[0054] (Fourth embodiment of image reading device) Fig. 9 is a diagram showing an example of correcting a visible image in the fourth embodiment of the image reading device of the present invention. The same elements as those described in Fig. 1 to Fig. 6 are given the same reference numerals, and detailed description is omitted. In the image reading device 10 of this embodiment, the interval between the invisible marks IVMRK formed on the background member 30 is different from the interval between the invisible marks IVMRK formed on the background member 30 in Fig. 2.

[0055] Since there are multiple intervals between the two invisible marks IVMRK, the pixel position at which the change rate is calculated by the detection means 40 differs from that in FIG. 4. Here, the change rate is the ratio between the inherent interval S1 (or S2) between the two invisible marks IVMRK and the interval between the two invisible marks IVMRK. In this embodiment, the pixel position to which the magnification used for image correction by the correction means 50 is applied is set according to the position of the interval between the two invisible marks IVMRK. Other configurations and functions of the image reading device 10 are similar to those of the image reading device 10 shown in FIGS. 1 to 6.

[0056] In the example shown in FIG. 9, the temperature change is greater on the left side of the figure, and is smaller on the right side of the figure. As shown in FIG. 9, in positions in the main scanning direction where the temperature change is large, the change in magnification is greater than in positions where the temperature change is small. Therefore, in order to accurately detect the rate of change and accurately determine the magnification for correcting the visible image, in this embodiment, the positions in the main scanning direction where the temperature change is large are determined to be smaller than the rate of the temperature change. Small main scanning direction The interval between the invisible marks IVMRK is set smaller than that between the invisible marks IVMRK and the position of the invisible marks IVMRK.

[0057] For example, in FIG. 9, in the areas AB, BC, CD, DE, EF, FG, GH, and HI where the temperature change is relatively large, the interval between two invisible marks IVMRK is set to S1. Small Area In IJ, JK, KL, LM, and MN, the interval between two invisible marks IVMRK is set to S2, which is larger than S1. Note that, although there are two types of intervals, S1 and S2, in FIG. 9, three or more types may be set.

[0058] This makes it possible to detect the rate of change for each small region and change the correction amount (magnification) at a position where the temperature change is large and the change in magnification is large. This makes it possible to improve the accuracy of image correction for each position in the main scanning direction. Note that the correction means 50 mounted on the image reading device 10 shown in FIG. 9 may have a conversion table 51, as in FIG. 7. The correction means 50 may determine the correction amount for each pixel of the visible image obtained by reading the paper P, using the rate of change of the visible image stored in correspondence with the rate of change of the invisible image corresponding to the invisible mark IVMRK for each region.

[0059] As described above, this embodiment can also provide the same effects as the above-mentioned embodiment. Furthermore, in this embodiment, the accuracy of image correction for each position in the main scanning direction can be improved by reducing the interval between the invisible marks IVMRK in the area where the temperature change is large.

[0060] (Fifth embodiment of image reading device) Fig. 10 is a diagram showing an example of correcting a visible image in the fifth embodiment of the image reading device of the present invention. In the image reading device 10 including the background member 30 shown in Fig. 10, the function of the correction means 50 differs from the function of the correction means 50 described in Fig. 1 to Fig. 6. The other functions of the image reading device 10 are similar to the functions described in Fig. 1 to Fig. 6.

[0061] The correction means 50 of this embodiment derives an approximation line (an approximation curve in the example of FIG. 10) by interpolating the magnification (correction amount) of the pixel position where the invisible mark IVMRK is not placed based on the change rate (e.g., AB / S) calculated by the detection means 40. For example, if the same change rate is used for each predetermined area (e.g., AB or BC) to determine the magnification, there is a risk of the image being left uncorrected or overcorrected. By deriving the approximation line, the possibility of left uncorrected or overcorrected can be reduced, and the accuracy of the correction of the image on the paper P can be improved.

[0062] 7, the correction means 50 mounted on the image reading device 10 shown in Fig. 10 may have a conversion table 51. In this case, the correction means 50 derives an approximation line of the change rate based on the change rate calculated for each region by the detection means 40, and determines the magnification of the visible image for each pixel position by referring to the conversion table 51. The approximation line of the change rate may be derived by the detection means 40.

[0063] As described above, this embodiment can also provide the same effects as the above-mentioned embodiment. Furthermore, in this embodiment, the magnification (correction amount) of the pixel position is interpolated to derive an approximation line, so that the possibility of undercorrection or overcorrection can be reduced, and the accuracy of correction of the image on the paper P can be further improved.

[0064] (Sixth embodiment of image reading device) Fig. 11 is a side view showing a sixth embodiment of the image reading device of the present invention. Detailed description of elements and functions similar to those of the above-mentioned embodiments will be omitted. The image reading device 60 shown in Fig. 11 has a reading unit 70 and an ADF (Auto Document Feeder) unit 80, and is a so-called sheet-through type document reading device.

[0065] The reading unit 70 has a contact glass 71, a reference white plate 72, a light source 73, a first carriage 74, a second carriage 75, a lens 76, a sensor board 77 equipped with a line sensor 77a, a scanner motor 78, and a reading window 79. The reading unit 70 also has the detection means 40 and the correction means 50 shown in Fig. 1. The ADF unit 80 has a document tray 81 on which a document 82 is placed, a transport drum 83, a paper discharge roller 84, a paper discharge tray 85, and a background member 86.

[0066] 1, the background member 86 has a plurality of invisible marks IVMRK (not shown) formed at intervals along the scanning direction of the line sensor 77a (depth direction in FIG. 11). The invisible marks IVMRK are formed on the surface of the background member 86 on the light source 73 side. The background member 86 also serves as a pressing member that presses the original 82 against the reading window 79 when the ADF unit 80 transports the original 82 to the reading window 79.

[0067] The line sensor 77a is, for example, a CCD image sensor or a CMOS image sensor. The line sensor 77a reads at least one of a visible image and an invisible image on the document 82, and outputs the read image to the correction means 50. The line sensor 77a also reads an invisible mark IVMRK on the background member 86, and outputs the read image as an invisible image to the detection means 40 and the correction means 50. The detection means 40 and the correction means 50 have the detection function and the correction function of any of the above-mentioned embodiments.

[0068] The ADF unit 80 has a function of automatically feeding the document 82, whose image is to be read, one sheet at a time onto a transport drum 83, and transporting the document 82 toward the reading window 79. The document 82 transported to the reading window 79 is irradiated with light by the light source 73 when it passes through the reading window 79. Then, the light reflected from the document is reflected by the mirrors of the first carriage 74 and the second carriage 75, passes through the lens 76, and is imaged in a reduced form on the light receiving surface of the line sensor 77a on the sensor board 77.

[0069] In flatbed reading in which the image reading device 60 reads an image of an original 82 placed on the contact glass 71, the scanner motor 78 moves the light source 73, the first carriage 74, and the second carriage 75 in the left-right direction in Fig. 11. Then, the light source 73 moving under the contact glass 71 irradiates light onto the original 82 placed on the contact glass 71, and the reflected light from the original 82 is reflected by the mirrors of the first carriage 74 and the second carriage 75 which move in conjunction with the movement of the light source 73.

[0070] The reflected light passes through lens 76 and is reduced and imaged on the light receiving surface of line sensor 77a on sensor board 77. At this time, first carriage 74 moves at speed V. Second carriage 75 moves at 1 / 2V, half the speed of first carriage 74, in conjunction with the movement of first carriage 74. In this way, image reading device 60 reads the entire image of document 82. Note that while reading unit 70 shown in FIG. 11 is configured with first carriage 74 and second carriage 75, each including a mirror, lens 76, and sensor board 77, which are separate, it may also be configured using an integrated sensor module in which these are integrated.

[0071] As described above, this embodiment can also provide the same effects as the above-mentioned embodiment. For example, the image reading device 10 can detect a change in the optical characteristics of the reading means 20 based on the rate of change in the interval of the invisible marks IVMRK at any timing when the paper P is not present in the passing area PA. Then, the image reading device 10 can determine the amount of correction of the image according to the detected change in the optical characteristics.

[0072] (First embodiment of image forming apparatus) FIG. 12 is a side view showing a first embodiment of an image forming apparatus of the present invention. In FIG. 12, the inside of the apparatus is shown in a transparent manner to facilitate understanding. Detailed description of elements and functions similar to those of the above-mentioned embodiment will be omitted. The image forming apparatus 1 shown in FIG. 12 functions as a printing system including a printing apparatus such as a commercial printing machine (production printing machine) that continuously prints a large number of sheets in a short period of time. Note that the image forming apparatus 1 of this embodiment may be a printing apparatus other than a commercial printing machine.

[0073] The image forming apparatus 1, which is a printing system, includes a printing device 100, an inspection device 200, and a stacker 300. The printing device 100 includes an operation panel 101, tandem electrophotographic imaging units 103Y, 103M, 103C, and 103K, a transfer belt 105, a secondary transfer roller 107, a paper feed unit 109, a pair of conveying rollers 102, a fixing roller 104, and a reverse path 106.

[0074] The operation panel 101 accepts various operations for the printing device 100 and the inspection device 200 based on operations by an operator of the image forming device 1. The operation panel 101 also displays various screens showing the operating status of the image forming device 1 and the like.

[0075] Each of the image forming units 103Y, 103M, 103C, and 103K performs an image forming process to form a toner image, and the formed toner image is transferred to the transfer belt 105. For example, the image forming process includes a charging step, an exposure step, a developing step, a transfer step, and a cleaning step. For example, a yellow toner image is formed on the image forming unit 103Y, and a magenta toner image is formed on the image forming unit 103M. A cyan toner image is formed on the image forming unit 103C, and a black toner image is formed on the image forming unit 103K. However, the types of image forming units are not limited to four colors.

[0076] Transfer belt 105 conveys the toner images (full-color toner images) transferred and superimposed from image forming units 103Y, 103M, 103C, and 103K to a secondary transfer position of secondary transfer roller 107. For example, a yellow toner image is first transferred onto transfer belt 105, and then a magenta toner image, a cyan toner image, and a black toner image are transferred in this order and superimposed. However, the transfer order of the toner images is not limited to the above.

[0077] The paper feed unit 109 accommodates a plurality of recording media, which are to be processed (transported objects), stacked together, and feeds the recording media toward the pair of transport rollers 102. For example, the recording media is recording paper (transfer paper). However, the recording media may be media capable of recording images, such as coated paper, cardboard, an overhead projector (OHP) sheet, plastic film, prepreg, or copper foil.

[0078] The conveying roller pair 102 conveys the recording medium fed by the paper feed unit 109 on the conveying path a in the direction of the arrow s. The secondary transfer roller 107 collectively transfers the full-color toner image conveyed by the transfer belt 105 onto the recording medium conveyed by the conveying roller pair 102 at a secondary transfer position.

[0079] The fixing roller 104 fixes the full-color toner image onto the recording medium by applying heat and pressure to the recording medium onto which the full-color toner image has been transferred. In the case of single-sided printing, the printing device 100 sends the printed matter, which is the recording medium onto which the full-color toner image has been fixed, to the inspection device 200. On the other hand, in the case of double-sided printing, the printing device 100 sends the recording medium onto which the full-color toner image has been fixed to the reversal path 106.

[0080] The reversing path 106 switches back the fed recording medium, inverting it so that it is transported in the direction of the arrow t. The recording medium transported by the reversing path 106 is transported again in the direction of the arrow s by the transport roller pair 102. Then, a full-color toner image is transferred onto the opposite side of the recording medium by the secondary transfer roller 107. The toner image transferred onto the recording medium is fixed by the fixing roller 104, and the printed matter is sent to the inspection device 200 and the stacker 300.

[0081] The inspection device 200, located downstream of the printing device 100, has a reading device 201 and a density reference member 202. The density reference member 202 is, for example, a white board, and is used as a reference for the reading level of the reading device 201. The inspection device 200 also has a pair of transport rollers 210 and 211 that form a transport path a that transports the recording medium sent from the printing device 100 to the stacker 300. The density reference member 202 is disposed between the pair of transport rollers 210 and the pair of transport rollers 211.

[0082] The reading device 201 receives reflected light from a reading target and outputs it as an image signal. For example, the reading target of the reading device 201 is a color pattern provided on a recording medium sent from the printing device 100 or a color patch arranged in the inspection device 200. The reading device 201 also reads a density reference member 202.

[0083] Then, the inspection device 200 ejects the recording medium after reading to the stacker 300. The stacker 300 has a tray 301. The stacker 300 stacks the recording media discharged by the inspection device 200 on the tray 301.

[0084] 13 is a side view showing an example of a main part of the inspection device 200 of FIG. 12. In FIG. 13, the inside of the device is shown in a transparent manner for ease of explanation. The inspection device 200 has a light source 220, a contact glass 230, a background member 240, conveying rollers 251 and 252, reflecting mirrors 261, 262, and 263, a lens unit 270, a sensor board 280 equipped with a line sensor 280a, a detection unit 40, and a correction unit 50. Some of the elements shown in FIG. 13 may be included in the reading device 201 of FIG. 2.

[0085] For example, the light source 220, the contact glass 230, the background member 240, and the line sensor 280a correspond to the light source 21, the passing area PA, the background member 30, and the line sensor 22 in Fig. 1. Also, the light source 220, the contact glass 230, the background member 240, the transport rollers 251, 252, and the reflecting mirrors 261, 262, and 263 correspond to the light source 73, the reading window 79, the background member 86, the transport drum 83, and the reflecting mirrors of the first and second carriages 74 and 75 in Fig. 11. The sensor board 280 including the lens unit 270 and the line sensor 280a corresponds to the sensor board 77 including the lens 76 and the line sensor 77a in Fig. 11.

[0086] The light source 220 irradiates light onto the recording medium 290 or background member 240 sent from the printing device 100 through the contact glass 230. The background member 240 has a plurality of invisible marks IVMRK (not shown) similar to those in FIG. 2. The reflecting mirrors 261, 262, and 263 guide the reflected light from the recording medium 290 or the background member 240 to the lens unit 270. The lens unit 270 forms an image of the reflected light on the line sensor 280a.

[0087] The line sensor 280a is, for example, a CCD image sensor or a CMOS image sensor. The line sensor 280a reads at least one of a visible image and an invisible image on the recording medium 290, and outputs the read image to the correction means 50. The line sensor 280a also reads an invisible mark IVMRK on the background member 240, and outputs the read image as an invisible image to the detection means 40 and the correction means 50. The detection means 40 and the correction means 50 have the detection function and the correction function of any of the above-mentioned embodiments.

[0088] Then, the inspection device 200 detects the presence or absence of an abnormality in the image formed on the recording medium 290 sent from the printing device 100, and feeds back the result to an image forming unit such as an imaging unit of the printing device 100. In this embodiment, the inspection device 200 calculates the rate of change of the invisible mark IVMRK of the background member 240, and feeds back a magnification (amount of correction of image characteristics) which is the reciprocal of the calculated rate of change to the printing device 100. The printing device 100 corrects the image formation position and the image formation magnification based on the fed back information.

[0089] As described above, this embodiment can also provide the same effects as the embodiment of the image reading device described above. Furthermore, in this embodiment, the image printed on the recording medium 290 by the printing device 100 can be corrected based on the magnification (correction amount) determined based on the invisible mark IVMRK read by the inspection device 200. That is, the accuracy of the image printed by the printing device 100 can be improved.

[0090] Although the present invention has been described above based on the embodiments, the present invention is not limited to the requirements shown in the above embodiments. These points can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form.

[0091] For example, in the above-described embodiment, an example has been described in which a linear invisible mark IVMRK extending in a direction perpendicular to the main scanning direction is formed on the background member 30. However, the shape of the invisible mark IVMRK may be other shapes as long as it is possible to detect a change in the distance between two invisible marks IVMRK. Furthermore, the detection means 40 may detect the size (area) of the invisible mark IVMRK instead of detecting a change in the distance between two invisible marks IVMRK. [Explanation of symbols]

[0092] 1. Image forming device 10 Image reading device 20 Reading means 21 Light source 22 Line sensor 30 Background material 40 Detection Methods 50 Correction means 51 Conversion Table 60 Image reader 70 Reading unit 73 Light source 77 Sensor Board 77a Line sensor 79 Reading window 80 ADF section 82 Manuscripts 86 Background material 100 Printing equipment 103C, 103K, 103M, 103Y Image creation section 200 Inspection Equipment 201 Reading Device 220 light source 240 Background material 280 Sensor Board 280a Line Sensor 290 Recording media IVMRK invisible mark P paper PA passing area PX pixels [Prior art documents] [Patent documents]

[0093] [Patent Document 1] JP 2012-239114 A [Patent Document 2] JP 2020-106862 A

Claims

1. A reading means including a light source that irradiates light onto a passing area through which a subject passes, and an imaging means that can generate a visible image and an invisible image by capturing an image of reflected light of the light irradiated from the light source; a background member disposed on the opposite side of the light source across the passing area, the background member having an invisible mark that can be identified as an invisible image by the imaging means; a detection means for detecting a change in image characteristics due to a change in optical characteristics of the reading means in an invisible image obtained by imaging the invisible mark; a correction means for determining an amount of correction of the image characteristics to be used for correcting the image of the subject generated by the imaging means, based on the change in the image characteristics detected by the detection means, and correcting the image characteristics based on the determined amount of correction; having The imaging means has a plurality of pixels arranged in one direction, the invisible marks are figures arranged at predetermined intervals along the one direction on the background member, the detection means detects a rate of change in an interval between the invisible images relative to an interval between the invisible marks arranged in one direction as the change in the image characteristic; The interval between the invisible marks provided at a position on the background member where the temperature change is relatively large is set to be smaller than the interval between the invisible marks provided at a position on the background member where the temperature change is relatively small. An image reading device comprising:

2. A reading means including a light source that irradiates light onto a passing area through which a subject passes, and an imaging means that can generate a visible image and an invisible image by capturing an image of reflected light of the light irradiated from the light source; a background member disposed on the opposite side of the light source across the passing area, the background member having an invisible mark that can be identified as an invisible image by the imaging means; a detection means for detecting a change in image characteristics due to a change in optical characteristics of the reading means in an invisible image obtained by imaging the invisible mark; a correction means for determining an amount of correction of the image characteristics to be used for correcting the image of the subject generated by the imaging means, based on the change in the image characteristics detected by the detection means, and correcting the image characteristics based on the determined amount of correction; having The imaging means has a plurality of pixels arranged in one direction, the invisible marks are figures arranged at predetermined intervals along the one direction on the background member, the detection means detects a rate of change in an interval between the invisible images relative to an interval between the invisible marks arranged in one direction as the change in the image characteristic; The correction means interpolates correction amounts of the image characteristics at positions on the background member where no invisible mark is present, based on the change rates corresponding to the respective invisible marks. An image reading device comprising:

3. The correction means uses the rate of change to determine a correction amount of the image characteristic to be used for correcting the image of the subject generated by the imaging means.

3. The image reading device according to claim 1, wherein:

4. a storage unit that stores a relationship between the rate of change and a correction amount of the image of the subject in correspondence with each of a plurality of positions along the one direction; The correction means determines, for each of the plurality of locations, a correction amount of the image characteristic to be used for correction of each pixel of the image of the subject, by using the correction amount stored in the storage unit in correspondence with the rate of change.

4. The image reading device according to claim 1, wherein:

5. The interval between the invisible marks provided at a position on the background member where the temperature change is relatively large is set to be smaller than the interval between the invisible marks provided at a position on the background member where the temperature change is relatively small.

3. The image reading device according to claim 2, wherein:

6. The correction means interpolates correction amounts of the image characteristics at positions on the background member where no invisible mark is present, based on the change rates corresponding to the respective invisible marks.

2. The image reading device according to claim 1,

7. The detection of the change in the image characteristics by the detection means and the determination of the correction amount and the correction of the image characteristics by the correction means are performed before the image of the subject is acquired by the reading means, and further, when a plurality of images of the subject are continuously acquired by the reading means, the detection of the change in the image characteristics by the detection means and the determination of the correction amount and the correction of the image characteristics by the correction means are performed every time a predetermined number of images of the subject are acquired by the reading means.

7. The image reading device according to claim 1, wherein:

8. The background member is made of a glass or ceramic material.

8. The image reading device according to claim 1, wherein:

9. The rate of change is set for each image reading device.

5. The image reading device according to claim 1, wherein:

10. 10. An image forming apparatus comprising the image reading device according to claim 1.

11. A reading means including a light source that irradiates light onto a passing area through which a subject passes, and an imaging means that can generate a visible image and an invisible image by capturing an image of reflected light of the light irradiated from the light source; a background member disposed on an opposite side of the light source across the passing area, the background member having an invisible mark identifiable as an invisible image by the imaging means, the imaging means having a plurality of pixels aligned in one direction, the invisible mark being a figure arranged at a predetermined interval along the one direction on the background member, detecting a change in image characteristics due to a change in optical characteristics of the reading means in an invisible image obtained by imaging the invisible mark; determining an amount of correction of the image characteristics to be used for correcting the image of the subject generated by the imaging means based on the detected change in the image characteristics, and correcting the image characteristics based on the determined amount of correction; detecting a rate of change in the spacing between the invisible images relative to the spacing between the invisible marks arranged in one direction as the change in the image characteristic; The interval between the invisible marks provided at a position on the background member where the temperature change is relatively large is set to be smaller than the interval between the invisible marks provided at a position on the background member where the temperature change is relatively small. An image reading method comprising:

12. A reading means including a light source that irradiates light onto a passing area through which a subject passes, and an imaging means that can generate a visible image and an invisible image by capturing an image of reflected light of the light irradiated from the light source; a background member disposed on an opposite side of the light source across the passing area, the background member having an invisible mark identifiable as an invisible image by the imaging means, the imaging means having a plurality of pixels aligned in one direction, the invisible mark being a figure arranged at a predetermined interval along the one direction on the background member, detecting a change in image characteristics due to a change in optical characteristics of the reading means in an invisible image obtained by imaging the invisible mark; determining an amount of correction of the image characteristics to be used for correcting the image of the subject generated by the imaging means based on the detected change in the image characteristics, and correcting the image characteristics based on the determined amount of correction; detecting a rate of change in the spacing between the invisible images relative to the spacing between the invisible marks arranged in one direction as the change in the image characteristic; and interpolating correction amounts of the image characteristics at positions on the background member where no invisible mark is present, based on the rate of change corresponding to each of the invisible marks. An image reading method comprising:

Images