JP2004304327A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct with good accuracy and in a short time the dispersion recording elements of an array-like print head, and to efficiently reduce density unevenness. <P>SOLUTION: A chart 3 is set on a flat bed scanner 70 in such a way that the array direction of the recording elements for recording a correction image and the array direction of a CCD coincide, and image information is acquired (Step S2). In this stage, the CCD is calibrated to reflect the calibration result on density data (Step S3). The inclination of the image scanned by using a marker for determining the inclination is determined (Step S4). Rotation processing is applied to the image information on the basis of the determination result (Step S5). The density data corresponding to each of the plurality of recording elements of the print head 30 is specified (Step S6), and the amount of correction is calculated with respect to each of the plurality of recording elements (Step S9). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming method and an image forming apparatus for recording an image by correcting a variation in recording characteristics of each recording element of an array print head in which a plurality of recording elements are arranged in an array.
[0002]
[Prior art]
2. Description of the Related Art Recently, with the spread of digital cameras, there has been a great demand for improving the printing performance and image quality of digital minilab machines as digital output devices. In particular, there is a high demand for large-format printing, and development of an exposure engine using a print head in which a plurality of recording elements suitable for the printing are arranged in an array is progressing.
[0003]
Generally, the light emitting recording elements constituting the array print head have individual light emission characteristics that vary from about 20% to 40%. If the variation is insufficiently corrected, the variation will be recorded as it is at the time of print creation as uneven density of the image. When a photograph or the like is reproduced by continuous gradation, it is necessary to correct the variation to at least 2% or less, and to obtain higher quality, to 1% or less.
[0004]
As a technique related to this correction, there has been proposed a method of obtaining light amount data for each recording element while driving a plurality of recording elements, and calculating a correction amount of an exposure amount of each recording element based on the light amount data ( For example, see Patent Document 1.) Further, in order to specify the position of each printing element, the density of an image printed with at least one printing element spaced in the arrangement direction of the printing elements is measured, and the correction amount of the printing characteristics of each printing element is obtained. A method has also been proposed (for example, see Patent Document 2).
[0005]
[Patent Document 1]
JP-A-8-230235
[Patent Document 2]
JP-A-10-811
[0006]
[Problems to be solved by the invention]
However, in the above-described conventional correction method, in order to perform high-precision correction, it is necessary to accurately set the image at the position of the light receiving element of the image reading device when measuring the density of the correction image. there were. For this reason, it has been very difficult to correct variations in the recording elements with high accuracy. In addition, a long array print head suitable for large-format printing has a large number of recording elements and requires a long time for correction calculation.
[0007]
In addition, since the correction of the recording element of the array print head is usually performed before the start of the printing operation, the output of the image for correction is performed at an early stage in a daily operation, often in many cases. The first print in one day. Since the machine that has been stopped all night is operated, the correction image is susceptible to dust and dirt in the photosensitive material transport section. Further, oxides (tar, silver sulfide) and the like of the processing liquid remaining from the end of the previous day on the guide device between the processing tanks in the developing section may adhere to the image, thereby causing stains on the image. In the conventional correction method, there is a problem that the correction accuracy is reduced due to the above-described dust, dust, dirt on the photosensitive material, and the like.
[0008]
In general, when reading an image for correction, scanning is performed using an image reading device such as a flatbed scanner. When the combination of the form of the light source of the image reading device and the set position of the image, the direction is not preferable, at the edge portion of the paper, the light irradiation state is different from other portions, stray light occurs, flare and shade occur, In some cases, it was not possible to read the image of the edge portion stably. Due to the erroneous determination of the edge portion, the position of the pixel in the correction image and the position of the recording element of the print head are displaced, and the correction result of a different pixel is reflected, so that a correct correction result cannot be fed back. Was. In this case, no matter how many times the correction is repeated, the unevenness of shading on the output image is not reduced.
[0009]
The present invention has been made in view of the above-described problems in the related art, and has been made in consideration of the above-described problems, and has been made in consideration of the above-described problems. It is an object to provide a method and an image forming apparatus.
[0010]
[Means for Solving the Problems]
The invention according to claim 1 for solving the above-mentioned problem records a correction image on a photosensitive material using a print head in which a plurality of recording elements are arranged in an array, and a plurality of light receiving elements are arranged in an array. An image forming method for obtaining a correction amount of a recording characteristic of each recording element by acquiring read information from the correction image using an image reading apparatus having an arrayed image receiving heads, and recording an image using the correction amount The image forming method according to claim 1, wherein an arrangement direction of the recording elements of the print head with respect to the correction image and an arrangement direction of the light receiving elements of the image receiving head are the same.
[0011]
Here, the read information in the present invention means information indicating an optical density read by an arbitrary density measuring unit, an image reading device, or numerical information calculated based on the optical density. The optical density itself may be used, but it may be a reflectance, a transmittance, a light absorptance, or the like, or a function value corresponding to these one-to-one, such as a logarithmic value. It may be an amount. When an image is read and measured by an image reading device such as a flatbed scanner, the signal value may be a signal value measured by the image reading device. It may be a numerical value or the like, or a relative value thereof.
[0012]
Further, the correction amount refers to a coefficient for adjusting the exposure amount of each recording element so that each recording element of the array print head can record on the photosensitive material with a uniform exposure amount.
[0013]
Also, the same direction means that the angle between the arrangement direction of the recording elements of the print head and the arrangement direction of the light receiving elements of the image receiving head is within ± 10 degrees. From the viewpoint of improving the tolerance of the inclination of the correction image, the angle is more preferably ± 5 degrees, and most preferably ± 1 degrees.
[0014]
According to the first aspect of the invention, since the arrangement direction of the recording elements of the print head and the arrangement direction of the light receiving elements of the image receiving head are the same in the correction image, By using a long correction image, the scan range of the image reading device can be reduced. Further, the tolerance for the inclination of the correction image is improved, and the correction time can be reduced. Therefore, it is possible to accurately correct variations in the printing elements in a short time and efficiently reduce density unevenness.
[0015]
When acquiring read information from the correction image using the image reading device, it is preferable to read the correction image at a higher resolution than the resolution for recording on the photosensitive material using the array print head. . As a preferable example of an image reading apparatus having an image receiving head in which light receiving elements are arranged in an array, various scanners such as a flatbed scanner and a drum scanner can be cited.
[0016]
According to a second aspect of the present invention, there is provided an image reading apparatus for recording a correction image on a photosensitive material using a print head having a plurality of recording elements arranged in an array, and having an image receiving head having a plurality of light receiving elements arranged in an array. Obtaining an amount of read information from the image for correction using a device, obtaining an amount of correction of the recording characteristics of each recording element, and recording an image using the amount of correction. Wherein the read information of the correction image corresponding to each recording element is specified.
[0017]
According to the second aspect of the present invention, since the read information is subjected to the rotation processing, the read information corresponding to each recording element can be accurately specified, and the correction accuracy of the density unevenness is improved.
[0018]
The invention according to claim 3, wherein the correction image has a tilt determination marker for determining a tilt of the image, and determines the tilt of the correction image using the tilt determination marker; 3. The image forming method according to claim 2, wherein a rotation process is performed on the read information.
[0019]
According to the third aspect of the present invention, since the inclination of the correction image is determined using the inclination determination marker recorded on the correction image, it is easy to determine the angle at which the rotation process is performed, and the density unevenness is reduced. The correction accuracy is improved.
[0020]
The invention according to a fourth aspect is the image forming method according to any one of the first to third aspects, wherein calibration of each light receiving element of the array image receiving head is performed.
[0021]
Here, calibrating the light receiving element means reducing the variation in the light receiving sensitivity of the light receiving element.
[0022]
Just as the light emission amount of each recording element of the array print head varies, the light receiving sensitivity of the light receiving element of the array image receiving head of the image reader slightly varies. If the read information of the correction image includes both the variation of the recording element of the print head and the variation of the light receiving element of the array image receiving head, the accuracy of the feedback to the recording element of the print head is reduced.
[0023]
However, according to the fourth aspect of the present invention, since variations in the individual light receiving sensitivities of the respective light receiving elements are reduced, the accuracy of feedback to the print element of the print head is increased, and density unevenness of high frequency components is reduced. be able to. Therefore, the accuracy of the correction is improved.
[0024]
In the image, the high-frequency component is a component that expresses a fine structure such as hair or eyelashes, and the low-frequency component is a component that exhibits a gradual change in signal intensity, such as a cheek, for example. The density unevenness of the high frequency component refers to the density unevenness that changes in a relatively narrow range, and the density unevenness of the low frequency component refers to the density unevenness that changes smoothly in a relatively wide range.
[0025]
The invention according to claim 5 is the image forming method according to claim 4, wherein calibration of each of the light receiving elements is performed using a part of the correction image.
[0026]
According to the fifth aspect of the invention, it is possible to calibrate the light receiving element in the same state as reading the part used for the correction calculation. Therefore, it is possible to correct the variation of the recording element of the print head after grasping the variation of the light receiving element, thereby improving the accuracy of the correction. In addition, since an image reading device can be used in common instead of using a separate photometric unit to calibrate the light receiving element, the calibration can be easily performed.
[0027]
The invention according to claim 6, wherein the density of the image for calibrating each of the light receiving elements is set at a portion of the characteristic curve of the photosensitive material that is not a straight line. Image forming method.
[0028]
FIG. 5 shows a characteristic curve of the photosensitive material. The horizontal axis indicates the logarithm of the exposure amount, and the vertical axis indicates the image density for that exposure amount. The linear portion of the characteristic curve refers to a portion where the change in density (gradient of the graph) with respect to the change in the logarithm of the exposure amount is constant as shown in part c of FIG. As shown in portions a, b, and d of FIG. 5, a portion where the change in image density with respect to a change in exposure amount is smaller than that in the linear portion of the characteristic curve.
[0029]
According to the sixth aspect of the present invention, each light receiving element is calibrated by using a portion of the characteristic curve of the photosensitive material that is not a straight line, that is, a portion that changes softly. Density fluctuation can be suppressed. Therefore, the calibration accuracy of the variation of the light receiving element is improved.
[0030]
The invention according to claim 7 is the image forming method according to claim 5 or 6, wherein calibration of each of the light receiving elements is performed using a non-exposed portion of the correction image.
[0031]
Here, the non-exposed portion is a portion where the slope of the characteristic curve of the photosensitive material is almost 0 and the effect does not appear due to an increase in density even when light acts, as shown in a portion a of FIG. That is, a portion where the print head does not substantially expose the photosensitive material.
[0032]
According to the seventh aspect of the invention, since each light receiving element is calibrated using the non-exposed portion of the image for correction, simple and highly accurate correction can be performed.
[0033]
The invention according to claim 8 uses a print head in which a plurality of recording elements are arranged in an array, and a correction image is formed on a photosensitive material moving relative to the plurality of recording elements in a plurality of lines. Recording, obtaining read information from the correction image using an image reading device, obtaining a correction amount of a recording characteristic of each recording element based on a plurality of read information obtained for each recording element, and obtaining the correction amount. In the image forming method for recording an image by using a plurality of read information obtained by selecting each of the print elements, a correction amount of a print characteristic of each print element is obtained based on the read information after the selection. Is an image forming method.
[0034]
According to the invention described in claim 8, the correction amount of the recording characteristic of each recording element is obtained based on data selected from a plurality of pieces of read information obtained from the correction image, so that dust, dust, Unique data due to contamination of the photosensitive material can be excluded. Therefore, the tolerance for peculiar data which causes the correction accuracy to be reduced is improved, a highly accurate correction result can be obtained, and density unevenness can be reduced.
[0035]
In selecting the read information, the selection may be performed in the range of data corresponding to each recording element, or the selection may be performed in the range of the entire data of all recording elements.
[0036]
The invention according to claim 9 is the image forming method according to claim 8, wherein the selection is based on the magnitude of the plurality of pieces of read information.
[0037]
According to the ninth aspect of the present invention, since the criteria for selecting read information becomes clear, an accurate correction result can be obtained by an easy method, and density unevenness can be reduced.
[0038]
The invention according to claim 10 is the image forming method according to claim 9, wherein the selection uses 95% or less of the plurality of pieces of read information.
[0039]
According to the tenth aspect of the present invention, since 95% or less of the plurality of read information is used, the number of data to be excluded increases, and the tolerance for peculiar data which lowers the correction accuracy is improved. Therefore, an accurate correction result can be obtained, and density unevenness can be reduced.
[0040]
The data used is preferably 95% or less of the total data, more preferably 90% or less, and further preferably 80% or less. The data used is preferably 10% or more of all data, more preferably 20% or more, and further preferably 30% or more.
[0041]
The invention according to claim 11, wherein the selection is such that the standard deviation of the read information after the selection is σ and the average value is μ, and the 3σ value of the plurality of read information is 0.1 μ or less. 9. The image forming method according to claim 8, wherein a maximum value and / or a minimum value are excluded.
[0042]
According to the eleventh aspect of the present invention, it is possible to perform the correction calculation using the read information with less variation, so that an accurate correction result can be obtained. The 3σ value is preferably 0.1 μ or less, more preferably 0.05 μ or less, and even more preferably 0.01 μ or less.
[0043]
The invention according to claim 12 is the image forming method according to any one of claims 1 to 11, wherein the correction image is fixed to the image reading device using a pressing member. .
[0044]
Here, the pressing member refers to a member for pressing the correction image. It is preferable that this pressing member has a substantially uniform density such as black. The pressing member is preferably made of a soft material such as rubber or sponge that can be easily bent. Further, it is preferable that the material is low in chargeability and hardly adheres to dust.
[0045]
According to the twelfth aspect, it is possible to accurately determine the edge of an image, and the accuracy of correction is improved. Further, by suppressing the floating of the correction image, it is possible to reduce the density unevenness of the low frequency component.
[0046]
The image forming method according to any one of claims 1 to 12, wherein the correction image has a number of lines to be recorded in a range of 50 or more and 1000 or less. It is.
[0047]
According to the thirteenth aspect, by setting the number of lines to 50 or more, it is possible to secure the number of data and stabilize the average of the read information data, thereby reducing the density unevenness of the high frequency component. Can be. Even if the number of data is too large, the average of the data of the read information converges. Therefore, by setting the number of lines to 1000 or less, unused portions can be reduced and the calculation time can be shortened.
[0048]
The invention according to claim 14 is the image forming method according to claim 13, wherein 10% or more of the number of lines recorded in the correction image is used for acquiring the read information.
[0049]
According to the fourteenth aspect, by using 10% or more of the number of recorded lines for acquiring read information, a correction image can be reduced, and the image reading apparatus can be downsized. .
[0050]
The invention according to claim 15 is the image forming method according to any one of claims 1 to 14, wherein the photosensitive material is a silver halide photosensitive material.
[0051]
According to the fifteenth aspect, a silver halide photosensitive material is used as the photosensitive material, which is effective in reducing density unevenness.
[0052]
The invention according to claim 16 is the image forming method according to any one of claims 1 to 15, wherein the photosensitive material has a reflective support.
[0053]
According to the sixteenth aspect, since the photosensitive material has the reflective support, it is effective in reducing density unevenness.
[0054]
According to a seventeenth aspect of the present invention, there is provided a print head in which a plurality of recording elements capable of recording a correction image on a photosensitive material are arranged in an array, and a plurality of light receiving elements for acquiring read information from the correction image. An image reading apparatus having an image receiving head arrayed in the image forming apparatus, and a correction processing unit for obtaining a correction amount of a recording characteristic of each recording element based on the acquired read information, An image forming apparatus, wherein the arrangement direction of the recording elements of the print head and the arrangement direction of the light receiving elements of the image receiving head are the same.
[0055]
According to the seventeenth aspect of the present invention, the arrangement direction of the recording elements of the print head and the arrangement direction of the light receiving elements of the image receiving head are the same in the correction image. By using a long correction image, the scan range of the image reading device can be reduced. Further, the tolerance for the inclination of the correction image is improved, and the correction time can be reduced. Therefore, it is possible to accurately correct variations in the printing elements in a short time and efficiently reduce density unevenness.
[0056]
The invention according to claim 18 is a print head in which a plurality of recording elements capable of recording a correction image on a photosensitive material are arranged in an array, and a plurality of light receiving elements for acquiring read information from the correction image are arranged in an array. An image forming apparatus comprising: an image reading apparatus having an image receiving head arrayed in the image forming apparatus; and a correction processing unit that calculates a correction amount of a recording characteristic of each recording element based on the acquired read information. An image forming apparatus comprising: performing a rotation process on the read information; and specifying read information of the correction image corresponding to each recording element.
[0057]
According to the eighteenth aspect of the present invention, since the read information is subjected to the rotation processing, the read information corresponding to each recording element can be accurately specified, and the correction accuracy of the density unevenness is improved.
[0058]
The invention according to claim 19, wherein the correction image has a tilt determination marker for determining the tilt of the image, and the correction processing unit uses the tilt determination marker to generate the correction image. 19. The image forming apparatus according to claim 18, wherein a tilt is determined, and a rotation process is performed on the read information.
[0059]
According to the nineteenth aspect, the inclination of the correction image is determined using the inclination determination marker recorded on the correction image, so that the angle for performing the rotation process can be easily determined, and the density unevenness can be reduced. The correction accuracy is improved.
[0060]
20. The image forming apparatus according to claim 17, wherein the correction processing unit performs calibration of each light receiving element of the array image receiving head. is there.
[0061]
According to the twentieth aspect of the present invention, since the variation in the individual light receiving sensitivity of each light receiving element is reduced, the accuracy of feedback to the recording element of the print head is increased, and the density unevenness of the high frequency component can be reduced. it can. Therefore, the accuracy of the correction is improved.
[0062]
21. The image forming apparatus according to claim 20, wherein the correction processing unit performs calibration of each of the light receiving elements using a part of the correction image. .
[0063]
According to the twenty-first aspect, it is possible to calibrate the light receiving element in the same state as reading the part used for the correction calculation. Therefore, it is possible to correct the variation of the recording element of the print head after grasping the variation of the light receiving element, thereby improving the accuracy of the correction. In addition, since an image reading device can be used in common instead of using a separate photometric unit to calibrate the light receiving element, the calibration can be easily performed.
[0064]
The invention according to claim 22, wherein the density of the image for calibrating each of the light receiving elements is set at a portion of the characteristic curve of the photosensitive material that is not a straight line. Image forming apparatus.
[0065]
According to the invention described in claim 22, since each light receiving element is calibrated by using a portion of the characteristic curve of the photosensitive material that is not a straight line, that is, a portion that changes softly, it is caused by the variation in the exposure amount of the recording element. Density fluctuation can be suppressed. Therefore, the calibration accuracy of the variation of the light receiving element is improved.
[0066]
23. The image forming apparatus according to claim 21, wherein the correction processing unit performs calibration of each of the light receiving elements using a non-exposure part of the correction image. Device.
[0067]
According to the twenty-third aspect, since each light receiving element is calibrated using the non-exposed portion of the correction image, simple and highly accurate correction can be performed.
[0068]
According to a twenty-fourth aspect of the present invention, there is provided a print head in which a plurality of recording elements capable of recording a correction image having a plurality of lines on a photosensitive material are arranged in an array, and read information is obtained from the correction image An image reading apparatus, and a correction processing unit that obtains a correction amount of a recording characteristic of each recording element based on a plurality of pieces of read information obtained for each recording element, wherein the correction processing unit includes: An image forming apparatus characterized in that sorting is performed on a plurality of pieces of read information obtained for each of the printing elements, and a correction amount of a printing characteristic of each printing element is obtained based on the read information after the sorting.
[0069]
According to the invention described in claim 24, the correction amount of the recording characteristic of each recording element is obtained based on the data selected from the plurality of read information obtained from the correction image, so that dust, dust, Unique data due to contamination of the photosensitive material can be excluded. Therefore, the tolerance for peculiar data which causes the correction accuracy to be reduced is improved, a highly accurate correction result can be obtained, and density unevenness can be reduced.
[0070]
The invention according to claim 25 is the image forming apparatus according to claim 24, wherein the selection is based on the magnitude of the plurality of pieces of read information.
[0071]
According to the twenty-fifth aspect of the present invention, since the criteria for selecting the read information is clear, an accurate correction result can be obtained by an easy method, and density unevenness can be reduced.
[0072]
The invention according to claim 26 is the image forming apparatus according to claim 25, wherein the selection uses 95% or less of the plurality of pieces of read information.
[0073]
According to the twenty-sixth aspect, since 95% or less of the plurality of read information is used, the number of data to be excluded increases, and the tolerance for peculiar data that causes the correction accuracy to decrease is improved. Therefore, an accurate correction result can be obtained, and density unevenness can be reduced.
[0074]
The invention according to claim 27, wherein, in the selection, the standard deviation of the read information after the selection is σ, and the average value is μ, and until the 3σ value becomes 0.1 μ or less, the plurality of read information The image forming apparatus according to claim 24, wherein a maximum value and / or a minimum value are excluded.
[0075]
According to the invention described in claim 27, it is possible to perform the correction calculation using the read information with less variation, so that a highly accurate correction result can be obtained.
[0076]
The invention according to claim 28 is the image forming apparatus according to any one of claims 17 to 27, wherein the correction image is fixed to the image reading device using a pressing member. .
[0077]
According to the twenty-eighth aspect, it is possible to accurately determine the edge of an image, and the accuracy of correction is improved. Further, by suppressing the floating of the correction image, it is possible to reduce the density unevenness of the low frequency component.
[0078]
29. The image forming apparatus according to claim 17, wherein the correction image has a number of lines to be recorded in a range of 50 or more and 1000 or less. It is.
[0079]
According to the invention described in claim 29, by setting the number of lines to 50 or more, it is possible to secure the number of data and stabilize the average of the data of the read information, thereby reducing the density unevenness of the high frequency component. Can be. Further, by setting the number of lines to 1000 or less, the unused portion can be reduced, and the calculation time can be shortened.
[0080]
The invention according to claim 30 is the image forming apparatus according to claim 29, wherein 10% or more of the number of lines recorded in the correction image is used for acquiring the read information.
[0081]
According to the thirty-first aspect, by using 10% or more of the number of recorded lines for acquiring read information, the size of the correction image can be reduced, and the image reading apparatus can be downsized. .
[0082]
The invention according to claim 31 is the image forming apparatus according to any one of claims 17 to 30, wherein the photosensitive material is a silver halide photosensitive material.
[0083]
According to the thirty-first aspect, a silver halide photosensitive material is used as the photosensitive material, which is effective in reducing density unevenness.
[0084]
The invention according to claim 32 is the image forming apparatus according to any one of claims 17 to 31, wherein the photosensitive material has a reflective support.
[0085]
According to the invention described in Item 32, since the photosensitive material has the reflective support, it is effective in reducing density unevenness.
[0086]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated example.
[0087]
FIG. 1 shows a schematic configuration of an image forming apparatus 10 according to the embodiment. As shown in FIG. 1, the image forming apparatus 10 includes a support drum 1, a red print head 30a, a green print head 30b, a blue print head 30c, a print head control unit 40, a correction processing unit 60, a flatbed scanner 70, and the like. It is configured.
[0088]
The support drum 1 is a transport unit that is rotated by a drive source (not shown). A photographic paper (hereinafter, referred to as photographic paper) 2 for a color photograph, which is a silver halide photosensitive material unwound from a roll (not shown), is transported in the direction of the arrow.
[0089]
Each of the red print head 30a, the green print head 30b, and the blue print head 30c is a print head in which a plurality of recording elements are arranged in an array.
Here, the array shape includes not only a linear shape as shown in FIG. 2A but also a staggered array as shown in FIG. 2B and an array as shown in FIG. 2C. In each case, the numbers shown in the drawing are assigned to the respective printing elements, and the adjacent elements in the printing element arrangement direction indicate the elements next to the numbers. Further, the arrangement direction of the recording elements of the print head refers to the direction in which more recording elements are arranged as shown in FIGS. 2 (a), 2 (b) and 2 (c).
[0090]
An LED (Light Emitting Diode) light source is used for the red print head 30a. The green print head 30b and the blue print head 30c employ a vacuum fluorescent print head (VFPH) which has a relatively high luminance and a high speed response and can easily separate colors by a color filter.
[0091]
The print head control unit 40 sequentially shifts the timing for each color with respect to the red print head 30a, the green print head 30b, and the blue print head 30c so that the RGB image data is recorded at a predetermined position on the photographic paper 2. While performing recording control.
[0092]
The correction processing unit 60 calculates a correction amount for correcting the light emission characteristics of each recording element of the red print head 30a, the green print head 30b, and the blue print head 30c from the density data and outputs the correction amount to the print head control unit 40. (See FIGS. 6S3 to S9).
[0093]
The flatbed scanner 70 is an image reading device including a light source, a CCD (Charge Coupled Device), an A / D converter, and the like. The image receiving head of the flatbed scanner 70 is configured such that CCDs as light receiving elements are arranged in an array. The arrangement direction of the CCDs, like the arrangement direction of the recording elements, refers to the direction in which more CCDs are arranged as shown in FIGS.
[0094]
The flatbed scanner 70 irradiates the image placed on the document table with light from a light source, and converts the reflected light into an electric signal (analog signal) by a CCD to acquire read information. The acquired read information is converted into digital data by the A / D converter. This digital data is sent to the correction processing unit 60 as image information. The image information is information in which the position of the read image is associated with measurement data (hereinafter, referred to as density data) indicating the density of each of the three RGB color components.
[0095]
As shown in FIG. 1, when the photographic paper 2 fed from the roll is transported in the direction of the arrow by the support drum 1, the red print head 30a, the green print head 30b, and the blue print head 30c are imaged by the print head control unit 40. Exposure is controlled in accordance with the data, and a predetermined position of the printing paper 2 is sequentially exposed for each color, so that a latent image of a color image is formed on the printing paper 2. When the exposure process is completed, the photographic paper 2 is transported by the support drum 1 to a developing process in the next processing step. The photographic paper 2 is not limited to a roll, but may be cut paper. The transporting means of the photographic paper 2 may be another means such as transporting it on a belt.
[0096]
FIG. 3 is a block diagram of a drive control circuit for explaining an image data writing operation of the print head 30 for one color. As shown in FIG. 3, when image data representing a gradation by an 8-bit digital value for each color is input, the print head control unit 40 determines a correction amount based on a correction amount generated by the correction processing unit 60. The image data is corrected and converted into serial digital image data for one line for each recording element, and a set pulse signal for transferring image bit data to the latch circuit 32 and a light emission time are calculated. An enable signal for control is generated and output to the print head 30 for one color. Here, the image bit data refers to specific bit data of the image data.
[0097]
In the print head 30, first, MSB (Most Significant Bit: most significant bit) data is transferred to the shift register 31 as image bit data for one line from the print head control unit 40. When the set pulse signal is input to the latch circuit 32, the data of the MSB is collectively latched by the latch circuit 32 for one line in synchronization with the set pulse signal. Then, when the enable signal corresponding to the gradation is input to the driver circuit 33, the drive control is performed for each recording element of the print head 30 in the section of the time width of the enable signal, and the drive signal is controlled according to the latched image data. Light emission is performed. That is, the driver circuit 33 selectively transmits a drive signal to the recording element array 34 to the element whose latched data is "1", and emits light for the time width of the enable signal. The irradiation light forms an image on the photographic printing paper 2 via the SELFOC lens array 35 to form a latent image. Such processing is sequentially performed on all bits from the MSB to the LSB (Least Significant Bit: least significant bit). The order of the bits may start from the LSB or other order, and is not limited. Although one color has been described above, the same control is performed for all three colors.
[0098]
In the green print head 30b and the blue print head 30c, green and blue color separation filters (not shown) are disposed below the SELFOC lens array 35, respectively.
[0099]
Next, the correction image will be described. The photographic paper on which the correction image is recorded is hereinafter referred to as a chart.
[0100]
As shown in FIG. 4A, the chart 3 used in the present embodiment includes density measurement areas 4a, 4b, 4c, and 4d, markers 5a and 5b for determining inclination, and marker steps 6a and 6b for specifying recording elements. included. Arrows in FIG. 4A indicate the arrangement direction of the recording elements.
[0101]
The density measurement areas 4a, 4b, 4c and 4d are portions where the density is measured in order to make the exposure amount of the recording element uniform. For example, an image in which a red print head 30a, a green print head 30b, and a blue print head 30c perform recording at the same location and each of the basic color dyes cyan, magenta, and yellow dyes, that is, a gray image Is used. As shown in FIG. 4A, it is desirable that the correction image is recorded at a plurality of locations on the chart with a plurality of image data, that is, at a plurality of densities. FIG. 4A shows an example in which four types of density measurement areas are provided.
[0102]
The density measurement areas 4a, 4b, 4c, and 4d may be images recorded discretely in the arrangement direction of the recording elements, such as those having at least one recording element arranged in the arrangement direction of the recording elements. It is preferable that the image is not solid and has a solid shape. Further, it is preferable that the density be as uniform as possible in the arrangement direction of the recording elements.
[0103]
It is preferable that the concentration measurement areas 4a, 4b, 4c, and 4d are as large as possible and are located at many places. However, as the size of the correction image increases, it takes time to form and read the image, and the amount of loss paper also increases. become. Further, when the number of data exceeds a certain value, the result converges, so that even if a large amount of data is taken, it becomes useless.
[0104]
Therefore, the number of lines recorded in the density measurement areas 4a, 4b, 4c, and 4d is preferably in the range of 50 to 1,000, more preferably 50 to 200, and more preferably 60 to 100. Is more preferable. Here, the number of lines refers to the number of pixels in a direction perpendicular to the arrangement direction of the recording elements. In addition, it is preferable that the density measurement is performed for obtaining the correction amount for 10% to 90% of the number of recorded lines, and the density measurement is performed for obtaining the correction amount for 20% to 80% of the recorded line number. More preferably, a measurement is made.
[0105]
The inclination determination markers 5a and 5b are used to determine the inclination of the correction image. As shown in FIG. 4A, the inclination determination markers 5a and 5b are recorded as a pair near both ends of the chart 3 in the arrangement direction of the recording elements. Also, since the inclination determination markers 5a and 5b are used for the purpose of grasping the position, it is preferably recorded with a small number of lines by a small number of recording elements and recorded in a small area as much as possible.
[0106]
The recording element specifying marker stages 6a and 6b are used to specify the position of each recording element of each print head 30. The interval between the recording element specifying marker stages 6a and 6b in the recording element arrangement direction is preferably small. The interval between the recording element specifying marker stages 6a and 6b is preferably within 10 pixels, more preferably within 5 pixels, and most preferably 1 pixel. One pixel interval means that ON, OFF, ON, and OFF are repeated in the arrangement direction of the recording elements.
[0107]
In addition, since there is a concern that the mounting position of the print head 30 may include some errors, it is preferable that each print head 30 has a single color recording element identifying marker. FIG. 4B is an enlarged view of the recording element specifying marker step 6a. As shown in FIG. 4B, a marker stage (cyan) for specifying the position of each recording element of the red print head 30a and a marker stage (magenta) for specifying the position of each recording element of the green print head 30b ), A marker stage (yellow) for specifying the position of each recording element of the blue print head 30c is recorded.
[0108]
Further, when the chart includes a density measurement area recorded at a plurality of locations, it is preferable to record a marker step for specifying a recording element near the density measurement area.
[0109]
The chart 3 is also used for calibrating the CCD of the flatbed scanner 70. Calibration of a CCD refers to reducing the variation in the light receiving sensitivity of the CCD. The image used for the calibration of the CCD is desirably an image having a density of a part (a part, b part and d part in FIG. 5) of the characteristic curve of the photosensitive material which is not a straight line.
[0110]
As shown in the characteristic curve of the photosensitive material in FIG. 5, until the exposure amount exceeds a certain value (point A), even if light acts, the effect does not appear as an increase in density (part a; non-exposure). Part). At a certain exposure, the density starts to increase as the exposure increases. From point A to point B, the characteristic curve becomes a downwardly convex curve (part b). From the point B to the point C, the characteristic curve becomes linear, and the change in density with respect to the change in the logarithm of the exposure amount becomes constant (part c). When the exposure amount exceeds the point C, the density increase with the increase in the logarithm of the exposure amount decreases, and the characteristic curve becomes an upwardly convex curve (d part). In other words, in the portions a, b (low density) and d (high density) in which the characteristic curves are not straight lines, the characteristic curves are different from those in the straight portion c (intermediate density) in the image density with respect to the change in the exposure amount. Change is small. Therefore, it is less susceptible to density fluctuations due to variations in the exposure amount of the recording element.
[0111]
In the case where the color is generated due to a cause other than the exposure of the print head, for example, even if there is coloring due to residual color, stain, fog of the photosensitive material due to slight leakage light, it is regarded as a non-exposed portion, but it is clearly colored visually. Is confirmed, it is preferable not to use it for correction calculation by performing reprinting or the like.
[0112]
The image for calibrating the CCD may be located at one place or may be present at a plurality of places. Further, when images for calibrating the CCD exist at a plurality of locations, they may have the same density or different densities.
[0113]
When the photosensitive material is not in the form of a roll but is in the form of a sheet such as cut and conveyed, the correction image is preferably recorded at the center of the chart in the conveying direction in order to prevent contamination by the developing solution. It is preferable to have a portion where no image is recorded on the direction side. Further, when reading an image with the flatbed scanner 70, since there is variation in the leading portion, it is preferable that no image is recorded on the leading direction side of the chart.
[0114]
Regarding the size of the chart, for example, when photographic paper is recorded after cutting, the length (LV) of the print head 30 in the direction perpendicular to the recording element arrangement direction is the length of the print head 30 in the recording element arrangement direction. (L / H) is preferably not too long, and from the viewpoints of transportability of photosensitive material, reduction of loss paper, and effects on development processing, LV / LH is preferably within 2.0 times, and 1.2 times or less. Is more preferably within 0.9 times, and further preferably within 0.9 times.
[0115]
Next, the density unevenness correction processing of the image forming apparatus 10 will be described. The density unevenness correction processing is performed in order to reduce the variation in the recording characteristics of each recording element of the print head 30 and obtain a uniform exposure amount.
[0116]
As shown in FIG. 6, first, a chart 3 (see FIG. 4A) on which a correction image is recorded is output (step S1). The chart 3 is set on the flatbed scanner 70, the image for correction is scanned, and the density is measured (step S2). That is, image information is obtained from the correction image. Specifically, density data corresponding to each basic color RGB at each position of the correction image is output to the correction processing unit 60.
[0117]
Here, the arrangement direction of the recording elements of the print head 30 on which the image for correction is recorded and the arrangement direction of the CCDs of the flatbed scanner 70 are the same direction, that is, the arrangement direction of the recording elements and the arrangement direction of the CCDs. The chart 3 is set so that the angle is within ± 10 degrees. In order to accurately obtain the density of the correction image corresponding to each recording element, it is preferable that the flatbed scanner 70 reads the correction image at a higher resolution than the resolution at which the print head 30 performs printing.
[0118]
Subsequently, the CCD is calibrated based on the image information acquired from the correction image (step S3). For calibration of the CCD, image information having a density of a non-exposed part of the correction image or a part of the characteristic curve of the photosensitive material which is not a straight line is used. In the subsequent processing, it is assumed that the density data corresponding to each basic color RGB of the image information reflects the result of the CCD calibration.
[0119]
Next, the inclination of the scanned image is determined (step S4).
The procedure for determining the image inclination will be described with reference to the schematic diagram of the image information acquired by the flatbed scanner 70 shown in FIG. As shown in FIGS. 7A and 7B, the image information includes markers 7a and 7b for inclination determination and a portion 8 used for correction calculation.
[0120]
In the acquired image information, image processing such as binarization processing using an arbitrary threshold value and position determination using a center of gravity, a Feret's diameter, and the like are performed in order to determine the positions of the inclination determination markers 7a and 7b. Will be In addition, in order to remove the influence of dust and dirt, the area, moment, and expected position range of the inclination determination markers 7a and 7b are set in advance, and the inclination is determined by comparison with the acquired image information. The positions of the markers 7a and 7b may be determined.
[0121]
Then, as shown in FIG. 7A, the distance X between the inclination determining markers 7a and 7b in the CCD arrangement direction and the direction perpendicular to the CCD arrangement direction from the positions of the inclination determination markers 7a and 7b. The distance Y is obtained, and the inclination θ of the image is determined (tan θ = Y / X).
[0122]
Next, a rotation process is performed on the image information based on the determined image inclination θ (step S5). It is preferable to use an affine transformation as the rotation processing. The image information is converted into image information without inclination by performing a rotation process of the angle θ.
[0123]
Then, from the density measurement results of the recording element specifying marker stages 6a and 6b, density data corresponding to each recording element of the red print head 30a, the green print head 30b, and the blue print head 30c is specified (step S6).
[0124]
The calculation of the correction amount is performed for each print head 30. The density data corresponding to the recording element i of the print head 30 is D _i far. When there is a plurality of density data of the same image data for the printing element i, an average may be taken or a representative value such as a median may be used.
[0125]
Next, the density data D _i Average value D in the arrangement direction of the recording elements ₀ Is calculated (step S7). And the average value D ₀ And the density data D of the recording element i _i Are compared (step S8), and the correction amount C of the printing element i is _i = D ₀ / D _i Is calculated (step S9).
[0126]
When an image is formed by the image forming apparatus 10, the print head controller 40 controls the image data and the correction amount C calculated by the correction processor 60. _i , And are output to the print head 30.
[0127]
It is desirable that the color balance setup has been completed before the printing element correction processing is performed. Setting up the color balance means adjusting the recording amount of each print head 30 or the average value of the exposure amount so that the image data of each basic color has a desired density. Adjusting the color balance. It is preferable that the adjustment can be performed for each of RGB.
[0128]
Hereinafter, various experimental results of image output using the image forming apparatus 10 will be described.
[0129]
(Experimental example 1)
In Experimental Example 1, when the output correction image was set on the flatbed scanner 70, the correction time was evaluated by changing the angle of the array image receiving head with respect to the CCD arrangement direction.
[0130]
(1) When the recording element array direction of the correction image shown in FIG. 4A is set perpendicular to the CCD array direction (vertical direction), (2) the recording element array direction of the correction image and the CCD (3) when the angle between the array direction of the correction image and the array direction of the CCD is 1 degree (horizontal direction); (4) When the angle between the recording element array direction of the correction image and the CCD array direction is 5 degrees (horizontal direction), (5) When the angle between the recording element array direction of the correction image and the CCD array direction is 10 degrees (Horizontal direction), (6) The evaluation was performed when the angle between the recording element array direction of the correction image and the CCD array direction was 11 degrees (horizontal direction).
[0131]
After correcting the recording element of the print head 30 for each of the RGB basic colors, a visual evaluation of density unevenness was performed. A human image including a gray gradation was used as an evaluation image, and the images were compared based on the following criteria. In the following experimental examples, this evaluation image is used for evaluation of density unevenness. The evaluation result is
A: Very good image quality with no density unevenness.
：: Very good image quality although density unevenness of high-frequency components is partially confirmed slightly.
Δ: Good image quality, although density unevenness of high-frequency components is slightly confirmed.
D: Density unevenness was observed, and the image quality was unfavorable.
XX: Density unevenness was clearly confirmed, and the image quality was poor.
Are shown in five stages. The same applies to the following experimental results.
[0132]
Further, in a substantially uniform density portion of the evaluation image, density data of about 500 pixels was measured for the R density, and the standard deviation σ of the R density data was measured. _R Is the average value of R concentration data μ _R 3σ divided by _R / Μ _R (%) Was calculated. This value indicates a variation in the density data, and thus serves as an index of density unevenness.
[0133]
FIG. 8 shows the evaluation results of Experimental Example 1. The correction time is shown by (1) a ratio based on the case where it is set in the vertical direction. (2) When the horizontal direction is set so that the angle between the recording element array direction of the correction image and the CCD array direction is 0 degrees, (1) the scan area is compared with the case where the vertical direction is set. , The correction time was reduced to about 55%. As the angle between the recording element arrangement direction and the CCD arrangement direction increases, the correction time also increases ((3) to (6)). (5) When the angle between the recording element array direction of the correction image and the CCD array direction is 10 degrees, and (6) When the angle between the recording element array direction of the correction image and the CCD array direction is 11 degrees. Since the correction time differs by 23% based on the case where the correction time is set in the vertical direction, it is preferable that the angle between the recording element array direction of the correction image and the CCD array direction be within 10 degrees.
[0134]
In the visual evaluation of density unevenness, (1) when set in the vertical direction, density unevenness was clearly confirmed, and the image quality was poor (xx). When set in the horizontal direction from (2) to (4) (angles of 0 degree, 1 degree, and 5 degrees), although the density unevenness of the high frequency component is partially confirmed slightly, the image quality is very good. (○). (5) When the angle between the arrangement direction of the recording element of the correction image and the arrangement direction of the CCD is 10 degrees, the density unevenness of the high frequency component is slightly confirmed (△), and (6) the arrangement direction of the recording element of the correction image. When the angle between the array direction of the CCD and the CCD was 11 degrees, density unevenness was confirmed, and the image quality was unfavorable (x).
[0135]
FIG. 8 shows a numerical evaluation (3σ) of density unevenness. _R / Μ _R (%)). This numerical value is 3σ _R Μ _R Is expressed as a percentage based on When set in the vertical direction, the variation in data is the largest, and when set in the horizontal direction, the variation increases as the angle between the recording element array direction of the correction image and the CCD array direction increases. .
[0136]
As shown in the results of Experimental Example 1, the scanning range of the flatbed scanner 70 is reduced by setting the arrangement direction of the recording elements of the print head and the arrangement direction of the CCD of the image receiving head in the same direction with respect to the image for correction. In addition, it was possible to suppress the variation in transport of the CCD relatively low. In addition, the tolerance for the inclination of the correction image is improved, and the correction time can be reduced. Therefore, it was possible to accurately correct the variation of the recording elements in a short time and efficiently reduce the density unevenness.
[0137]
(Experimental example 2)
In the experimental example 2, (1) a case where the CCD of the flatbed scanner 70 is calibrated, and (2) a case where the calibration is not performed, paying attention to the density unevenness, particularly the density unevenness of the high frequency component, and the same evaluation as the experimental example 1 Visual evaluation (person image including gray gradation) was performed based on the standard. The angle between the recording element array direction of the correction image and the CCD array direction was set to 0 degree.
[0138]
FIG. 9 shows the evaluation results of Experimental Example 2. In the visual evaluation of density unevenness, (1) when the CCD of the flatbed scanner 70 was calibrated, there was no density unevenness and the image quality was extremely good (（). {Circle around (2)} When the CCD was not calibrated, the density unevenness of the high-frequency component was partially slightly confirmed (○).
Further, by correcting the CCD in the non-exposed portion of the correction image, an effect was obtained by improving the density unevenness.
[0139]
As shown in the results of Experimental Example 2, by calibrating the CCD and reducing variations in individual light receiving sensitivities, the accuracy of feedback to the print element of the print head is increased, and density unevenness of high frequency components is reduced. I was able to.
[0140]
Also, by calibrating the CCD with the non-exposed part of the correction image, it is possible to calibrate the CCD in the same state as reading the part used for the correction calculation. Thus, variations in the recording elements of the print head could be corrected, and the accuracy of the correction was improved.
[0141]
(Experimental example 3)
In Experimental Example 3, when the density of the image used for calibration of the CCD of the flatbed scanner 70 is (1) low density (non-linear portion; b portion in FIG. 5), (2) intermediate density (linear portion; FIG. (C part 5), (3) high density (non-linear part; d part in FIG. 5) ((1) to (3) were set in the horizontal direction), (4) medium density When set in the vertical direction, the four types were compared, and a visual evaluation of the corrected density unevenness (person image including gray gradation) was performed. The angle between the recording element array direction of the correction image and the CCD array direction was set to 0 degree.
[0142]
Further, in the substantially uniform density portion of the evaluation image, density data of about 1000 pixels was measured for the R density, and the standard deviation σ of the R density data was measured. _R Is the average value of R concentration data μ _R 3σ divided by _R / Μ _R (%) Was calculated.
[0143]
FIG. 10 shows the evaluation results of Experimental Example 3. In the visual evaluation of density unevenness, (1) when a low-density (non-linear portion) image is set in the horizontal direction and (3) when a high-density (non-linear portion) image is set in the horizontal direction, There was no density unevenness, and the image quality was extremely good (◎). {Circle around (2)} When the image of the intermediate density (linear portion) was set in the horizontal direction, the density unevenness of the high-frequency component was partially slightly confirmed (確認). {Circle around (4)} When set in the vertical direction at an intermediate density, density unevenness was clearly confirmed, and the image quality was poor (XX).
[0144]
In addition, numerical evaluation of density unevenness (3σ) _R / Μ _R (%)), In the case of using (3) a high-density or (1) low-density non-linear portion density image, (2) a variation in density data as compared with the case of using an intermediate-density image. Was small. {Circle around (4)} When set in the vertical direction, the dispersion of the density data was the largest.
[0145]
As shown in the results of Experimental Example 3, by calibrating the CCD using a portion of the characteristic curve of the photosensitive material that is not a straight line, that is, a portion that changes softly, the exposure amount of the recording element is varied. Density variation can be suppressed, and the accuracy of calibration of CCD variations is improved, so that density unevenness can be reduced with high accuracy.
[0146]
(Experimental example 4)
In Experimental Example 4, dust and dirt were attached to the output correction image using the image forming apparatus 10 that had not performed the processing for one week, and the recording element was corrected. The density data used for the correction is selected, and the ratios of the density data used for the correction processing are: (1) 100% (no selection), (2) 96%, (3) 95%, (4) 90%, The correction was performed by changing the values of 5% to 80%, 6% to 30%, 7% to 20%, 8% to 10%, and 9% to 9%. Person image including gradation).
[0147]
The method of selecting the density data to be used is to exclude the maximum value and / or the minimum value of the density data from the plurality of density data for each printing element until the ratio of each condition is satisfied. The angle between the recording element array direction of the correction image and the CCD array direction was set to 0 degree.
[0148]
Further, in an approximately uniform density portion of the evaluation image, density data of about 1000 pixels was measured for the G density, and the standard deviation σ of the G density data was measured. _G Is the average value of G concentration data μ _G 3σ divided by _G / Μ _G (%) Was calculated.
[0149]
FIG. 11 shows the evaluation results of Experimental Example 4. In the visual evaluation of density unevenness, (1) when the usage rate of the density data was 100%, the density unevenness was clearly confirmed, and the image quality was poor (xx). (2) When the usage rate of the density data is 96%, density unevenness of the high frequency component is slightly confirmed (△), and when (3) 95%, the density unevenness of the high frequency component is partially small. (○). When the usage rates of the density data were (4) 90%, (5) 80%, (6) 30%, and (7) 20%, there was no density unevenness, and the image quality was extremely good (）). . (8) When the usage rate of the density data is 10%, the density unevenness of the high frequency component is partially confirmed slightly (○), and when (9) 9%, the density unevenness of the high frequency component is slightly (△).
[0150]
In addition, numerical evaluation of density unevenness (3σ) _G / Μ _G (%)), (1) when the usage rate of the density data was 100%, the variation of the G density data of the evaluation image was the largest. As the usage rate of the density data was lowered to (2) 96%, (3) 95%, (4) 90%, and (5) 80%, the dispersion of the G density data became smaller. Among the experimental examples 5 of this time, (6) the variation was the smallest when the usage rate of the density data was 30%. Even if the data to be used becomes too small, the accuracy of the correction deteriorates. Therefore, as the usage rate of the density data is further reduced to (7) 20%, (8) 10%, (9) 9%, The variation in the data of the G concentration became larger.
[0151]
As shown in the results of Experimental Example 4, the amount of correction of the recording characteristics of each recording element is determined based on data selected from a plurality of density data obtained from the correction image, so that dust and dust can be obtained. In addition, since peculiar data due to contamination of the photosensitive material or the like can be excluded, the tolerance for peculiar data which causes a decrease in correction accuracy is improved, and a highly accurate correction result can be obtained. Therefore, density unevenness could be reduced.
[0152]
In addition, by excluding the maximum value and / or the minimum value from the plurality of density data for each recording element and using 95% or less of the density data, the number of data to be excluded increases, so that accurate correction results can be obtained. As a result, density unevenness could be reduced.
[0153]
(Experimental example 5)
In Experimental Example 5, similarly to Experimental Example 4, using the image forming apparatus 10 that did not perform any processing for one week, dust and dirt were attached to the output correction image, and the recording element was corrected. . Regarding the density data used for the correction, the standard deviation of the density data after selection is σ and the average value is μ, and the 3σ values are (1) 0.11 μ, (2) 0.1 μ, (3) 0.05 μ, {Circle around (4)} Screening was performed so as to be 0.01 μm, correction was performed based on the selected data, and visual evaluation of the density unevenness after correction (person image including gray gradation) was performed. For comparison, (5) the case where no sorting was performed was also evaluated.
[0154]
The method of selecting the density data to be used is to exclude the maximum value and / or the minimum value of the density data from the plurality of density data for each printing element until the ratio of each condition is satisfied. The angle between the recording element array direction of the correction image and the CCD array direction was set to 0 degree.
[0155]
Further, in a substantially uniform density portion of the evaluation image, density data of about 500 pixels was measured for the B density, and the standard deviation σ of the B density data was measured. _B Is the average μ of the B concentration data _B 3σ divided by _B / Μ _B (%) Was calculated.
[0156]
FIG. 12 shows the evaluation results of Experimental Example 5. In the visual evaluation of density unevenness, (5) when density data was not selected, density unevenness was clearly confirmed, and the image quality was poor (xx). (1) When the 3σ value is 0.11 μ, density unevenness of the high-frequency component is slightly confirmed (△), and when (2) 3σ value is 0.1 μ, the density unevenness of the high-frequency component is partially. Slightly observed (に). When the 3σ values were (3) 0.05 μ and (4) 0.01 μ, there was no density unevenness and the image quality was extremely good (（).
[0157]
In addition, numerical evaluation of density unevenness (3σ) _B / Μ _B (%)), When the data of (5) density was not selected, the variation of the data of B density of the image for evaluation was large. As 3σ / μ of the density data after sorting became smaller, the variation of the B density data of the evaluation image also became smaller. In particular, when the (1) 3σ value is 0.11μ, 3σ _B / Μ _B (%) Is 13.89, whereas (2) 3σ when the 3σ value is 0.1 μm _B / Μ _B (%) Was 5.76, and the variation in B concentration data was significantly reduced.
[0158]
As shown in the results of Experimental Example 5, accurate correction results could be obtained by performing correction calculation using density data having a 3σ value of 0.1 μ or less and less variation.
[0159]
(Experimental example 6)
In Experimental Example 6, the conditions were set based on the angle of the array-type image receiving head with respect to the CCD array direction when the output correction image was set on the flatbed scanner 70 and whether or not to perform the rotation process using the affine transformation at the time of correction. Alternatively, visual evaluation of the corrected density unevenness (person image including gray gradation) was performed. Note that the rotation angle in the rotation processing was obtained by calculating the inclination angle using the inclination determination markers 5a and 5b of the correction image.
[0160]
(1) The recording element arrangement direction of the correction image is set perpendicular to the arrangement direction of the CCD (vertical direction), and if no rotation processing is performed, (2) the recording element arrangement direction of the correction image and the CCD Is set to 4.8 degrees (horizontal direction) and the rotation process is performed. (3) The angle between the recording element array direction of the correction image and the CCD array direction is 4.8 degrees. When the rotation processing is not performed (4), the angle between the recording element array direction of the correction image and the CCD array direction is set to 9.5 degrees (horizontal direction), and the rotation processing is performed. (3), the angle between the recording element array direction of the correction image and the CCD array direction was set to 9.5 degrees (horizontal direction), and the case where no rotation processing was performed was evaluated. .
[0161]
Further, in a substantially uniform density portion of the evaluation image, density data of about 1000 pixels was measured for the B density, and the standard deviation σ of the B density data was measured. _B Is the average μ of the B concentration data _B 3σ divided by _B / Μ _B (%) Was calculated.
[0162]
FIG. 13 shows the evaluation results of Experimental Example 6. In the visual evaluation of the density unevenness, (1) when the image for correction was set in the vertical direction and no rotation processing was performed, the density unevenness was clearly confirmed, and the image quality was poor (XX). When the correction image is set in the horizontal direction and the rotation process is not performed, when the set angle is (3) 4.8 degrees, the density unevenness of the high-frequency component is partially slightly confirmed (○). ), (5) 9.5 degrees, slight unevenness in the density of the high frequency component was confirmed (△). When the correction image was set in the horizontal direction and the rotation process was performed, the density was not uneven at all when the angle to be set was (2) 4.8 degrees and (4) 9.5 degrees. Good image quality (良好).
[0163]
In addition, numerical evaluation of density unevenness (3σ) _B / Μ _B (%)), When the correction image is set in the horizontal direction and the rotation process is performed, the angle to be set is (2) 4.8 degrees, and (4) 9.5 degrees. The variation in the B density data of the evaluation image was small.
[0164]
As shown in the results of Experimental Example 6, by performing a rotation process on the image information acquired from the correction image, the density of the image corresponding to each recording element can be specified accurately, and the correction accuracy of the density unevenness can be determined. Has improved. In addition, since the inclination of the correction image is determined using the inclination determination markers 5a and 5b recorded in the correction image, the angle for performing the rotation process can be easily determined, and the correction calculation can be easily performed by a simple device. It is now possible to do it.
[0165]
(Experimental example 7)
In Experimental Example 7, the effect of the pressing member when the correction image was read by the flatbed scanner 70 was evaluated. As a pressing member, black rubber having low chargeability and a substantially uniform concentration was used, and the chart was set by pressing the chart with the black rubber when reading the image for correction.
[0166]
By using the pressing member, the edge of the image can be accurately determined, and the floating and curving of the paper are reduced, so that the unevenness of the low-frequency component is reduced and the correction accuracy is improved.
[0167]
(Experimental example 8)
In Experimental Example 8, the ratio between the number of lines of the image for correction and the number of lines used for density measurement was changed under the conditions shown in FIG. Then, the density unevenness after the correction was evaluated. The angle between the recording element array direction of the correction image and the CCD array direction was set to 0 degree.
[0168]
FIG. 14 shows the evaluation results of Experimental Example 8. In the case where the ratio of the number of lines used for density measurement is 75%, the number of corrections required until density unevenness is eliminated is smaller when the number of lines is 50 than when the number of lines is 40, and the density unevenness is also reduced. There were few. Further, when the number of lines was 60, the number of necessary corrections was smaller, and there was no density unevenness in the evaluation of density unevenness, and the image quality was extremely good.
[0169]
In addition, when the number of lines was 1,000, the number of corrections required before the density unevenness disappeared was smaller when the number of lines was 1000 than when the number of lines was 1050, and the density unevenness was smaller. Further, when the number of lines was 200, the number of necessary corrections was smaller. Further, when the number of lines was 100, the number of necessary corrections was smaller, and in the evaluation of density unevenness, there was no density unevenness, and the image quality was extremely good.
[0170]
When the number of lines was 50, the number of necessary corrections was smaller and the density unevenness was smaller when the ratio of the number of lines used for density measurement was 10% than when the ratio was 5%. Furthermore, when the usage rate was 20%, the number of necessary corrections was smaller, and there was no density unevenness in the evaluation of density unevenness, and the image quality was extremely good.
[0171]
When the number of lines was 1,000, the number of necessary corrections was smaller when the ratio of the number of lines used for density measurement was 90% than when the ratio was 95%, and density unevenness was smaller. Further, when the usage rate was 80%, the number of necessary corrections was smaller, and there was no density unevenness in the evaluation of density unevenness, and the image quality was extremely good.
[0172]
As shown in the results of Experimental Example 8, by increasing the number of lines of the correction image to 50 or more and widening it, it is possible to secure the number of data and stabilize the average of the density data. Can be reduced. Further, by setting the number of lines to 1000 or less, the unused portion was reduced, and the calculation time was shortened.
[0173]
Further, by using 10% or more of the number of recorded lines for density measurement, the correction image could be reduced. Therefore, the calculation time was shortened, and loss paper was able to be reduced.
[0174]
The description in the above embodiment is an example of a suitable image forming apparatus according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of each unit constituting the image forming apparatus can be appropriately changed without departing from the spirit of the present invention.
[0175]
For example, a print head in which recording elements are arranged in an array may be one in which a plurality of recording elements are arranged in one or more rows at predetermined intervals in order to obtain a desired resolution. Preferable examples of the print heads arranged in an array include those in which LED light emitting elements and vacuum fluorescent tubes are arranged, a PLZT print head using an appropriate backlight, an optical shutter array such as a liquid crystal shutter array print head, and a semiconductor laser. Are arranged in an array, a light emitting element utilizing the electroluminescence phenomenon such as a thermal head and an organic EL material.
[0176]
Further, as the image forming apparatus, an apparatus capable of forming an image of a plurality of gradations, such as an apparatus for performing recording on a silver halide photosensitive material with various recording element arrays and an apparatus for performing recording with a thermal head using sublimable ink is preferable. .
[0177]
In the above-described embodiment, the CCD is calibrated using the chart 3 on which the correction image for correcting the recording element is recorded. However, a dedicated image for calibrating the CCD is output. Then, the CCD may be calibrated. However, since the light receiving sensitivity of the CCD of the array-type image receiving head slightly varies depending on the state such as the elapsed time from the start of energization of the flatbed scanner 70 and the frequency of use, the calibration of the CCD is not performed much. It is preferable to read the correction image before the time has elapsed.
[0178]
Further, in the above-described embodiment, the case where the chart 3 is provided with two inclination determination markers 5a and 5b is described. However, more inclination determination markers may be provided.
[0179]
Further, in the above-described embodiment, the density data of each color of RGB is used as the read information acquired from the image. However, the read information is not limited to the density, and may be a reflectance, a transmittance, a light absorption rate, or the like. Or a function value corresponding to these.
[0180]
【The invention's effect】
According to the first and 17th aspects of the present invention, the arrangement direction of the recording elements of the print head and the arrangement direction of the light receiving elements of the image receiving head are the same in the correction image. By using a longer correction image, the scan range of the image reading apparatus can be reduced. Further, the tolerance for the inclination of the correction image is improved, and the correction time can be reduced. Therefore, it is possible to accurately correct variations in the printing elements in a short time and efficiently reduce density unevenness.
[0181]
According to the present invention, since the read information is subjected to the rotation processing, the read information corresponding to each recording element can be accurately specified, and the correction accuracy of the density unevenness is improved.
[0182]
According to the third and 19th aspects of the present invention, the inclination of the correction image is determined by using the inclination determination marker recorded on the correction image. The unevenness correction accuracy is improved.
[0183]
According to the fourth and twentieth aspects of the present invention, variations in the individual light receiving sensitivities of the respective light receiving elements are reduced, so that the accuracy of feedback to the recording element of the print head is increased, and the density unevenness of the high frequency component is reduced. be able to. Therefore, the accuracy of the correction is improved.
[0184]
According to the invention described in claims 5 and 21, it is possible to calibrate the light receiving element in the same state as the state where the part used for the correction calculation is read. Therefore, it is possible to correct the variation of the recording element of the print head after grasping the variation of the light receiving element, thereby improving the accuracy of the correction. In addition, since an image reading device can be used in common instead of using a separate photometric unit to calibrate the light receiving element, the calibration can be easily performed.
[0185]
According to the present invention, each light receiving element is calibrated by using a portion of the characteristic curve of the photosensitive material which is not a straight line, that is, a portion which changes softly, so that the exposure amount of the recording element varies. Can be suppressed. Therefore, the calibration accuracy of the variation of the light receiving element is improved.
[0186]
According to the inventions described in claims 7 and 23, since each light receiving element is calibrated using the non-exposed portion of the correction image, simple and highly accurate correction can be performed.
[0187]
According to the invention described in claims 8 and 24, the correction amount of the recording characteristics of each recording element is obtained based on the data selected from the plurality of read information obtained from the correction image. Unique data due to dust, dirt on the photosensitive material, etc. can be excluded. Therefore, the tolerance for peculiar data which causes the correction accuracy to be reduced is improved, a highly accurate correction result can be obtained, and density unevenness can be reduced.
[0188]
According to the ninth and twenty-fifth aspects of the present invention, since the criteria for selecting read information become clear, accurate correction results can be obtained by an easy method, and density unevenness can be reduced.
[0189]
According to the tenth and twenty-sixth aspects of the present invention, since 95% or less of a plurality of pieces of read information is used, the number of data to be excluded increases, and the tolerance for peculiar data that causes a decrease in correction accuracy is improved. I do. Therefore, an accurate correction result can be obtained, and density unevenness can be reduced.
[0190]
According to the eleventh and twenty-seventh aspects of the present invention, it is possible to perform the correction calculation using the read information with less variation, so that a highly accurate correction result can be obtained.
[0191]
According to the twelfth and twelfth aspects of the present invention, it is possible to accurately determine the edge of an image, and the accuracy of correction is improved. Further, by suppressing the floating of the correction image, it is possible to reduce the density unevenness of the low frequency component.
[0192]
According to the invention of claims 13 and 29, by setting the number of lines to 50 or more, it is possible to secure the number of data and stabilize the average of the read information data, thereby reducing the density unevenness of the high frequency component. Can be done. Further, by setting the number of lines to 1000 or less, the unused portion can be reduced, and the calculation time can be shortened.
[0193]
According to the fourteenth and thirty aspects of the present invention, by using 10% or more of the number of recorded lines for obtaining read information, the correction image can be reduced, and the image reading apparatus can be downsized. It becomes.
[0194]
According to the inventions described in claims 15 and 31, a silver halide photosensitive material is used as the photosensitive material, which is effective in reducing density unevenness.
[0195]
According to the sixteenth and thirty-second aspects, the photosensitive material has a reflective support, which is effective in reducing density unevenness.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus 10 according to an embodiment of the present invention.
FIG. 2 is a diagram for explaining an arrangement of recording elements of an array print head and an arrangement of light receiving elements of an array image receiving head.
FIG. 3 is a block diagram of a drive control circuit for explaining an image data writing operation of a print head 30 of the image forming apparatus 10.
FIG. 4 is a schematic diagram of a chart on which a correction image is recorded.
FIG. 5 is a diagram showing a characteristic curve of a photosensitive material.
FIG. 6 is a flowchart illustrating a correction process of a recording element performed by the image forming apparatus.
FIG. 7 is a schematic diagram of image information acquired by the flatbed scanner 70.
FIG. 8 is a diagram showing evaluation results of Experimental Example 1.
FIG. 9 is a diagram showing evaluation results of Experimental Example 2.
FIG. 10 is a diagram showing evaluation results of Experimental Example 3.
FIG. 11 is a diagram showing evaluation results of Experimental Example 4.
FIG. 12 is a diagram showing evaluation results of Experimental Example 5.
FIG. 13 is a diagram showing evaluation results of Experimental Example 6.
FIG. 14 is a diagram showing evaluation results of Experimental Example 8.
[Explanation of symbols]
1 Support drum
2 photographic paper
3 Chart
4a, 4b, 4c, 4d Density measurement area
5a, 5b Incline determination marker
6a, 6b Marker stage for specifying recording element
10 Image forming apparatus
30 print head
30a red print head
30b green printhead
30c blue print head
31 shift register
32 Latch circuit
33 Driver Circuit
34 Recording element array
35 Selfoc lens array
40 Printhead control unit
60 Correction processing unit
70 Flatbed scanner

Claims (32)

A correction image is recorded on a photosensitive material using a print head in which a plurality of recording elements are arranged in an array, and the correction image is recorded using an image reading apparatus having an image receiving head in which a plurality of light receiving elements are arranged in an array. In the image forming method of obtaining the read information, obtaining the correction amount of the recording characteristics of each recording element, and recording an image using the correction amount,
An image forming method, wherein the arrangement direction of the recording elements of the print head with respect to the correction image and the arrangement direction of the light receiving elements of the image receiving head are the same. A correction image is recorded on a photosensitive material using a print head in which a plurality of recording elements are arranged in an array, and the correction image is recorded using an image reading apparatus having an image receiving head in which a plurality of light receiving elements are arranged in an array. In the image forming method of obtaining the read information, obtaining the correction amount of the recording characteristics of each recording element, and recording an image using the correction amount,
An image forming method comprising: performing a rotation process on the read information to specify read information of the correction image corresponding to each recording element. The correction image has a tilt determination marker for determining the tilt of the image,
The image forming method according to claim 2, wherein the inclination of the correction image is determined using the inclination determination marker, and the read information is subjected to a rotation process. The image forming method according to any one of claims 1 to 3, wherein calibration of each light receiving element of the array image receiving head is performed. The image forming method according to claim 4, wherein calibration of each of the light receiving elements is performed using a part of the correction image. 6. The image forming method according to claim 5, wherein the density of an image for calibrating each of the light receiving elements is set at a portion of the characteristic curve of the photosensitive material that is not a straight line. 7. The image forming method according to claim 5, wherein calibration of each of the light receiving elements is performed using a non-exposed portion of the correction image. Using a print head in which a plurality of recording elements are arranged in an array, a correction image is recorded with a plurality of lines on a photosensitive material that moves relative to the plurality of recording elements, and an image reading device is used. Image formation in which read information is obtained from the correction image, a correction amount of a recording characteristic of each recording element is obtained based on a plurality of read information obtained for each recording element, and an image is recorded using the correction amount In the method,
An image forming method comprising: selecting a plurality of pieces of read information obtained for each printing element; and obtaining a correction amount of a printing characteristic of each printing element based on the read information after the selection. 9. The image forming method according to claim 8, wherein the selection is based on the magnitude of the plurality of pieces of read information. The image forming method according to claim 9, wherein the selection uses 95% or less of the plurality of pieces of read information. The selection is a standard deviation of the read information after the selection is σ, the average value is μ,
9. The image forming method according to claim 8, wherein a maximum value and / or a minimum value of the plurality of pieces of read information are excluded until the 3σ value becomes 0.1 μ or less. The image forming method according to claim 1, wherein the correction image is fixed to the image reading device using a pressing member. The image forming method according to claim 1, wherein the correction image has a number of lines to be recorded in a range of 50 or more and 1000 or less. 14. The image forming method according to claim 13, wherein 10% or more of the number of lines recorded in the correction image is used for acquiring the read information. The image forming method according to claim 1, wherein the photosensitive material is a silver halide photosensitive material. The image forming method according to claim 1, wherein the photosensitive material has a reflective support. A print head in which a plurality of recording elements capable of recording a correction image on a photosensitive material are arranged in an array,
An image reading device having an image receiving head in which a plurality of light receiving elements for acquiring read information from the correction image are arranged in an array,
A correction processing unit that calculates a correction amount of a recording characteristic of each recording element based on the acquired read information;
An image forming apparatus comprising:
An image forming apparatus, wherein the arrangement direction of the recording elements of the print head with respect to the correction image and the arrangement direction of the light receiving elements of the image receiving head are the same. A print head in which a plurality of recording elements capable of recording a correction image on a photosensitive material are arranged in an array,
An image reading device having an image receiving head in which a plurality of light receiving elements for acquiring read information from the correction image are arranged in an array,
A correction processing unit that calculates a correction amount of a recording characteristic of each recording element based on the acquired read information;
An image forming apparatus comprising:
The image forming apparatus, wherein the correction processing unit performs a rotation process on the read information and specifies read information of the correction image corresponding to each recording element. The correction image has a tilt determination marker for determining the tilt of the image,
19. The image forming apparatus according to claim 18, wherein the correction processing unit determines a tilt of the correction image using the tilt determination marker, and performs a rotation process on the read information. The image forming apparatus according to any one of claims 17 to 19, wherein the correction processing unit performs calibration of each light receiving element of the array image receiving head. 21. The image forming apparatus according to claim 20, wherein the correction processing unit performs calibration of each of the light receiving elements using a part of the correction image. 22. The image forming apparatus according to claim 21, wherein an image density for calibrating each of the light receiving elements is set at a portion of the characteristic curve of the photosensitive material that is not a straight line. The image forming apparatus according to claim 21, wherein the correction processing unit performs calibration of each of the light receiving elements using a non-exposure part of the correction image. A print head in which a plurality of recording elements capable of recording a correction image composed of a plurality of lines on a photosensitive material are arranged in an array,
An image reading device that acquires read information from the correction image,
Based on a plurality of read information obtained for each recording element, a correction processing unit that determines the correction amount of the recording characteristics of each recording element,
An image forming apparatus comprising:
The image forming apparatus according to claim 1, wherein the correction processing unit performs selection on a plurality of pieces of read information obtained for each of the print elements, and obtains a correction amount of a print characteristic of each print element based on the read information after the selection. apparatus. The image forming apparatus according to claim 24, wherein the selection is based on the magnitude of the plurality of pieces of read information. 26. The image forming apparatus according to claim 25, wherein the selection uses 95% or less of the plurality of pieces of read information. The selection is a standard deviation of the read information after the selection is σ, the average value is μ,
The image forming apparatus according to claim 24, wherein a maximum value and / or a minimum value of the plurality of pieces of read information is excluded until the 3σ value becomes 0.1 μ or less. The image forming apparatus according to any one of claims 17 to 27, wherein the correction image is fixed to the image reading device using a pressing member. The image forming apparatus according to any one of claims 17 to 28, wherein the correction image has a number of lines to be recorded in a range of 50 or more and 1000 or less. 30. The image forming apparatus according to claim 29, wherein 10% or more of the number of lines recorded in the correction image is used for acquiring the read information. The image forming apparatus according to any one of claims 17 to 30, wherein the photosensitive material is a silver halide photosensitive material. The image forming apparatus according to any one of claims 17 to 31, wherein the photosensitive material has a reflective support.

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