JP2007104201A - Image evaluation device, image evaluation method, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image evaluation device capable of evaluating a toner void amount of a line image without losing change information of the toner void, even in the case of terrible toner voids and in the case of minute toner voids in a toner image evaluation device, an image evaluation method, and an image forming device. <P>SOLUTION: The image evaluation device is a toner void amount evaluation device that reads image density linearly in the direction orthogonal to a line drawing of the line image constituted of a background part and a toner image part. The toner void amount evaluation device has a means for calculating profiling data obtained from a read image density signal, a means for replacing a region other than the line image from the profiling data with a feature amount of the background part, a means for calculating a feature amount of a toner line image from the feature amount of the background part and the profiling data, a means for calculating a normalization feature amount from the feature amount of the background part and a feature amount in an ideal line image having no toner void, and a means for calculating a toner void amount from the normalization feature amount and the feature amount of the toner line image. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image evaluation apparatus, an image evaluation method, and an image forming apparatus for evaluating an image of a linear object such as a line, a crack, and a groove, and more particularly to a toner of a line image output from a printer or a copying machine. The present invention relates to an image evaluation apparatus, an image evaluation method, and an image forming apparatus for measuring a missing amount.

Conventionally, when measuring the “missing amount” of a line image composed of a background area portion and a toner area portion, which is generally supposed to be included in the image, a threshold value is used as a method for determining the image quality in the transfer printing method. There has been proposed a method of performing binarization processing and representing the binarized area ratio (see, for example, Patent Document 1).
JP-A-4-145770

  However, if the binarization process is performed after the classification by the threshold value, a part of the information is lost. For example, when missing occurs in an area lower than the threshold, the result is equivalent to a state where there is no toner. For example, taking FIG. 1 as an example, even when the amount of toner missing is large, when toner missing occurs in an area lower than the threshold, the result is equivalent to the background state where there is no toner at all.

  On the other hand, when a toner image with minute toner removal is measured, the result is equivalent to a line where no toner is removed (see the amount of toner removal (middle) in FIG. 1). Therefore, there is a problem in that the evaluation result of the toner missing amount may vary greatly depending on the set threshold value.

  Also, if dust or dust exists in the background area in the periphery of the line image for evaluating the amount of toner missing, an error may occur in the process of calculating the feature amount of the background area, or the toner Even in the process of calculating the feature amount of the region, there is a problem that an error occurs because the feature amount is calculated using the feature amount of the background region portion.

  Further, even when there is a large dust or dust at the measurement target line position, there is a risk of giving an error to the histogram peak value in the background area portion. Also, when a line image is read by an optical device, the absolute values of the three primary colors of light, red (R), green (G), and blue (B), depending on the combination of the color of the background area and the color of the toner area. Will be different. Further, in a line image formed by superposing at least two or more colors of toner, there is a problem in that misalignment between colors causes the line image to become thick.

  The present invention has been made in consideration of the above-described circumstances, and an image evaluation apparatus and an image evaluation method for evaluating the amount of toner missing in a line image without losing information on the change even when toner missing is severe or minute. It is another object of the present invention to provide an image forming apparatus.

  In order to achieve the above object, the invention according to claim 1 is an image having a toner missing amount that linearly reads the image density in a direction orthogonal to the line image of the line image formed of the background portion and the toner image portion. A profiling data calculating means for calculating profiling data obtained from the image density signal of the read image density; a replacement means for replacing an area other than the line image from the profiling data with a feature amount of the background part; Normalization feature from the feature amount calculation means for calculating the toner line image from the feature amount of the area and the profiling data; A normalized feature amount calculating means for calculating the amount, and a toner missing amount calculating means for calculating a toner missing amount from the normalized feature amount and the feature amount of the toner line image Characterized in that it has.

  According to a second aspect of the present invention, in the image evaluation apparatus according to the first aspect, the replacement unit separates the histogram from the profiling data into a background portion and a toner line image portion, and calculates a peak value of the background portion as a feature amount. And means for replacing an area other than the toner area with the feature amount of the background portion.

  According to a third aspect of the present invention, in the image evaluation apparatus according to the first or second aspect, the toner line image feature amount calculating means includes a plurality of line positions in the vertical direction with respect to the line image to be measured. The feature amount calculated from the line position is used as a feature amount of the background portion of one line to be measured.

  According to a fourth aspect of the present invention, in the image evaluation apparatus according to the first aspect, the normalized feature amount calculation means calculates the difference between the feature amount of the ideal line in which the toner does not fall on the background portion and the feature amount of the background portion. A normalized feature value is calculated from an area surrounded by the line width.

  According to a fifth aspect of the present invention, in the image evaluation apparatus according to the first aspect, the toner line image feature amount calculating means generates a color shift line image generated when forming a line image in which at least two toners are superimposed. The measurement range is limited based on the position information of the image density signal.

  The invention according to claim 6 is an image evaluation method for evaluating a toner omission amount by reading a line image composed of a background portion and a toner line image portion for each line in the vertical direction. A profiling data calculation step of obtaining an image density signal by reading and processing the image density signal to calculate profiling data, and replacing a region other than the toner line image from the calculated profiling data with a feature amount of the background portion A toner line image feature amount calculating step for calculating a feature amount of the toner line image from the process, the feature amount of the background portion and the profiling data, and an ideal line where the toner is not missing on the background portion of the feature amount and the background portion. A normalized feature amount calculating step for calculating a normalized feature amount from the feature amount, and a toner calculating amount from the normalized feature amount and the feature amount of the toner line image. And having a chromatography loss amount calculation step.

  According to a seventh aspect of the present invention, in the image evaluation method according to the sixth aspect, in the replacement step, the peak value of the background portion is separated from the histogram of the profiling data into the background portion and the toner line image portion and the feature value is obtained. And a step of replacing a region other than the toner region with the feature amount of the background portion.

  According to an eighth aspect of the present invention, in the image evaluation method according to the sixth or seventh aspect, the profiling data for separating the background portion and the toner region portion has a line position in a direction perpendicular to the line image to be measured. It is characterized in that a feature amount of a background portion of one line to be measured is obtained by calculation from a plurality of line positions.

  According to a ninth aspect of the present invention, in the image evaluation method according to the sixth aspect, in the normalized feature amount calculation step, the feature amount of the ideal line in which the toner does not fall on the background portion and the feature amount of the background portion are calculated. A normalized feature value is calculated from an area surrounded by the line width.

  According to a tenth aspect of the present invention, in the image evaluation method according to the sixth aspect, in the toner line image feature amount calculating step, a color misregistration line image generated when forming a line image in which at least two toners are superimposed, The measurement range is limited based on the position information of the image density signal.

  According to an eleventh aspect of the present invention, there is provided an image forming apparatus having the image evaluation apparatus according to any one of the first to fifth aspects.

  As described above, according to the image evaluation apparatus, the image evaluation method, and the image forming apparatus of the present invention, the image density is linearly read in the direction orthogonal to the line image of the line image composed of the background portion and the toner image portion. In the toner missing amount evaluation device, means for calculating profiling data obtained by processing the read image density signal, means for replacing a region other than the line image from the profiling data with a feature amount of the background portion, A means for calculating the feature amount of the toner line image from the feature amount and the profiling data, a means for calculating the normalized feature amount from the feature amount of the background line, and an ideal line image without toner loss, and normalization It has a means to calculate the toner omission amount from the feature amount and the feature amount of the toner line image, and is calculated from the RGB values read using an optical device. Since performing processing multilevel feature amounts, it is possible to evaluate the loss amount of no line image losing information in the toner leakage is often a line image and fine toner coming off the line image.

  Hereinafter, an image evaluation apparatus, an image evaluation method, and an image forming apparatus of the present embodiment will be described in detail with reference to the drawings. In addition, this embodiment is not limited to what is described below, A various change is possible in the range which does not deviate from the meaning.

  If dirt or dust is present in the background area around the line image, an error occurs in the process of calculating the feature amount of the background area. Even in the process of calculating the toner area feature amount, since the feature amount of the background area portion is used for calculation, an error also occurs here.

  In the present embodiment, the background region portion and the toner region portion are separated using the histogram of the profiling data, the feature amount of the true background region portion is calculated therefrom, and the region other than the toner region portion is determined as the feature amount of the background region portion. By replacing with, dust and dust existing in the background area are removed, and the amount of toner missing is evaluated.

  In addition, when there is a large dust or dust at the measurement target line position, there is a risk of giving an error to the histogram peak value in the background area portion. For this reason, in the present embodiment, in the process of calculating the feature amount of the background area portion, the feature amount is calculated from a plurality of line positions including line positions in the vertical direction with respect to the line image to be measured. As a result, it is possible to calculate the feature amount of the background area that is not affected by dust or dust.

  When a line image is read using an optical device, the RGB absolute values differ depending on the combination of the color of the background area and the color of the toner area. In the present embodiment, the toner missing amount is calculated from the difference between the feature amount on the ideal line where no toner is missing on the background region portion and the normalized feature amount calculated from the background region portion feature amount, and the background region portion The toner omission amount can be evaluated using all combinations in which the toner area portion is other than the same color. In this embodiment, the difference between the toner feature value and the normalized feature value is calculated for each line, thereby performing the evaluation by removing the skew (skew: inclination, distortion) that occurs when reading with the optical device. Is also possible.

  Further, in an image evaluation method using a line image formed by overlapping toners of at least two colors or more, the misregistration between colors causes the line image to become thick. In the present embodiment, the measurement range can be limited based on the RGB position information read by the optical device. Therefore, it is possible to remove the thickening of the line image due to color misregistration and evaluate the target line image.

  The present embodiment also includes an image forming apparatus having the above-described image evaluation apparatus for toner missing amount. Such an image forming apparatus has a toner removal amount evaluation device, a drum-shaped photosensitive member, an image transfer member, and a charger, which are at least equipped with the above-described optical device. Can be formed.

[First Embodiment]
(I) Feature amount calculation of background portion In this embodiment, a CCD camera is used as an optical device. In this embodiment, a CCD camera is used for explanation, but any optical device may be used, and there is no particular limitation.

  In the present embodiment, as shown in FIG. 3A, data as an image is read in a direction perpendicular to the line image 11 formed of the toner line image portion including the background portion by the CCD camera.

  In the present embodiment, the background portion is assumed to be paper, and the toner color is described using magenta. However, the color of the toner is not limited as in the case of a CCD camera which is an example of an optical device. The toner image also includes an image of two or more superimposed colors. The RGB value profiling data read by the CCD camera is converted into luminance signal profiling data. This is shown in FIG.

  From the converted luminance profiling data, it is divided into a range and converted into a histogram (the number of luminance signals for each location (measurement line) in the reading direction. In other words, “integrated amount within the range divided into a range”) The feature value of the background portion is determined by the peak value (the integrated amount of the portion divided into a certain range).

  In other words, this histogram is executed (calculated) by scanning the luminance value on the vertical axis from the luminance value on the vertical axis to the profiling data 1 by changing the threshold value (measurement line) shown in FIG. be able to.

  Actually, as shown in FIG. 3 (a), there are two peaks, a toner line image color peak and a background color peak (see Sa in FIG. 3 (a)), but here the background portion is paper. Therefore, as shown in FIG. 4B, the higher value of the two peaks obtained from the histogram is used as the feature amount of the background portion. Here, when large dust or dust exists on the measurement target line Sa, the histogram peak of the background portion may not appear clearly as shown in FIG.

  In such a case, when calculating the feature value of the background portion, in order to calculate the histogram peak value of the stable background portion, as shown in FIGS. It is calculated from a plurality of line positions including the position.

(Ii) Removal of dirt and dust from the background portion When dust and dust are present in the background portion, the value increases in the process of calculating the feature amount of the toner line image portion. In such a case, as shown in FIG. 5, by replacing the profiling data of the region (measurement line) other than the toner line image with the feature amount 3 of the background portion, data obtained by removing dust and dust from the background portion is obtained. Obtainable.

(Iii) Calculation of Feature Value of Toner Area Portion The difference between the feature amount 3 of the background portion and the luminance profiling data is taken, and the product sum value is the feature amount 4 of the toner line image portion which is the shaded area portion shown in FIG. And

(Iv) Normalized feature amount calculation When a line image is read by an optical device, the absolute values of RGB differ depending on the combination of the color of the background area portion and the color of the toner line image portion. In the present embodiment, a “solid image” of the same color as the line image is read on the paper with a CCD camera, and the value of the luminance signal calculated from the obtained RGB values is set as the lower base value of the ideal line image. Further, the upper base value is a feature amount of the background area, and the right side value and the left side value are line image positions. Assuming that the four sides are normalized boundary lines 5 as shown in FIG. 7, an area surrounded by the boundary lines is a normalized feature amount.

(V) Toner missing amount calculation The difference between the normalized feature amount calculated in (iv) and the normalized range of the toner region portion feature amount calculated in (i) to (iii) (right hatched portion in FIG. 7) Is a toner missing amount 6 (left hatched portion in FIG. 7).

  From the above (i): calculation of the feature amount of the background portion (v): the line image in the calculation of the toner omission amount and the toner omission amount evaluation for each line in the vertical direction of A4 size (FIG. 8A). FIG. 8B shows the result of evaluation of the entire vertical line drawn on the paper. The larger the toner missing amount value, the larger the amount of toner missing from the image. Since the measurement of this evaluation is performed for each line in the direction perpendicular to the line image, as can be seen from the result of FIG. 8B, the evaluation including the periodicity of the toner missing amount can be performed. it can.

[Second Embodiment]
Evaluation of the amount of toner missing on the transfer belt In this embodiment, the amount of toner missing on the transfer belt was evaluated. Since the transfer belt used in this embodiment is a belt using a carbon-based material, the color is close to black. A magenta toner was used as the toner. In the background area portion in the present embodiment, a low value of two peaks is used as the feature amount of the background area portion. Other processes are the same as (i) to (v) in the first embodiment.

  FIG. 11 shows the result of evaluating the amount of toner missing on one line on the transfer belt in the present embodiment obtained in this way.

[Third Embodiment]
In this embodiment, in the case of a color misregistration line, evaluation is performed by limiting the range from the entire line including the color misregistration to a target line area from which the misregistration portion is removed. . Here, in a line image forming a blue line image using magenta toner and cyan toner, a line image in which cyan toner is shifted to the left and magenta toner is shifted to the right is used.

  FIG. 9 shows RGB profiling data of color misregistration lines. An evaluation range is calculated in advance from RGB profiling data. The left side of the evaluation range calculates the position from the profiling data of the B signal, and the right side calculates the position from the profiling data of the R signal.

  In the present embodiment, (iv): In the process of calculating the left and right boundary lines in the normalized feature value calculation, the position of the line image including the color shift is replaced with the position of the blue line obtained in advance, and A region surrounded by the boundary line is used as a normalized feature value, and the other processes are the same as those in the first embodiment. FIG. 10 shows the result of evaluating the amount of toner missing from the blue line portion from which the color misregistration line portion has been removed.

  In this way, the color misregistration portion was removed by limiting the measurement range of the line causing the color misregistration from the information based on the RGB signal position. As a result, it became possible to evaluate without being affected by line thickening due to color misregistration.

  As described above, according to the image evaluation apparatus, the image evaluation method, and the image forming apparatus of the present embodiment, since processing is performed with a plurality of feature amounts calculated from RGB values read using an optical device, toner loss is eliminated. It is possible to evaluate the missing amount of a line image without losing information even with a large number of line images or a minute toner missing line image.

  In addition, since the calculation is based on the difference between the feature amount of the toner region portion and the normalized feature amount on the ideal line where no toner is missing on the background region portion, the background region portion and the toner region portion are not all the same color. Evaluations can be made in combination. Furthermore, since the calculation is performed for each line, it is possible to obtain the effect of eliminating the skew when reading with the optical device.

It is a figure which shows the relationship between the luminance signal of a toner line image of this embodiment, and a toner omission amount measurement threshold value. It is a figure which shows an example of the profiling data of the toner line image which concerns on this embodiment. (A) is a figure which shows typically an example of the brightness | luminance which appears in the measurement line which crosses the toner line image 11 of this embodiment, (b) is a histogram of the brightness | luminance which appears in this measurement line. (A) is a figure which shows typically another example of the brightness | luminance which appears on the measurement line which crosses the toner line image 11 of this embodiment, (b) is a histogram of the brightness | luminance which appears on this measurement line. is there. It is a figure which shows the profiling data which excluded the influence of dust etc. other than the toner line image measurement line of this embodiment. It is a figure which shows the feature-value of the toner line image part which concerns on this embodiment. It is a figure which shows the toner omission amount of this embodiment. (A) is a diagram schematically showing a sheet and vertical lines on which the toner missing amount evaluation method of the present embodiment is executed, and (b) is a diagram showing an evaluation result of the toner missing amount evaluation method. FIG. 6 is a diagram illustrating an example of color misregistration when a toner missing amount evaluation method of the present embodiment is executed. It is a figure which shows another example of the color shift at the time of performing the toner omission amount evaluation method of this embodiment. It is a figure which shows another example of the color shift at the time of performing the toner omission amount evaluation method of this embodiment.

Explanation of symbols

1 Profiling Data 2 background portion of the peak 3 background feature quantity 4 toner line image portion characteristic quantity 5 normalized boundaries 6 toner leakage amount 11 line image Sa, S ₁ to S ₅ measuring line

Claims (11)

An image evaluation apparatus for toner missing amount that linearly reads an image density in a direction orthogonal to a line image of a line image composed of a background portion and a toner image portion,
Profiling data calculating means for calculating profiling data from the read image density signal of the image density;
Replacement means for replacing a region other than a line image from the profiling data with the feature amount of the background portion;
A toner line image feature amount calculating means for calculating a feature amount of a toner line image from the feature amount of the background portion and the profiling data;
Normalized feature amount calculating means for calculating a normalized feature amount from the feature amount of the background portion and the feature amount in an ideal line image without toner loss;
An image evaluation apparatus comprising: a toner missing amount calculating unit that calculates a toner missing amount from the normalized feature amount and the feature amount of the toner line image.   The replacement means separates the histogram from the profiling data into the background portion and the toner line image portion and uses the peak value of the background portion as a feature amount, and the feature amount of the background portion other than the toner region The image evaluation apparatus according to claim 1, further comprising: means for replacing the region.   The toner line image feature quantity calculating means calculates a feature quantity calculated from a plurality of line positions including a line position in a vertical direction with respect to the line image to be measured. The image evaluation apparatus according to claim 1, wherein the image evaluation apparatus is a feature amount.   The normalized feature value calculating means calculates the normalized feature value from a region surrounded by a line width between a feature value of an ideal line and a feature value of a background part where no toner is missing on the background part. The image evaluation apparatus according to claim 1, wherein the apparatus is an image evaluation apparatus.   The toner line image feature amount calculation unit limits a measurement range of a color misalignment line image generated when forming a line image in which at least two toners are overlapped from position information of the image density signal. Item 2. The image evaluation apparatus according to Item 1. An image evaluation method for evaluating a toner missing amount by reading a line image composed of a background portion and a toner line image portion for each line in a vertical direction,
A profiling data calculation step of reading the line image to obtain an image density signal, image-processing the image density signal, and calculating profiling data;
A replacement step of replacing a region other than the toner line image from the calculated profiling data with the feature amount of the background portion;
A toner line image feature amount calculating step of calculating a feature amount of the toner line image from the feature amount of the background portion and the profiling data;
A normalization feature amount calculating step of calculating a normalization feature amount from the feature amount of the background portion and the feature amount of an ideal line in which toner is not missing on the background portion;
An image evaluation method comprising: a toner missing amount calculating step of calculating a toner missing amount from the normalized feature amount and the feature amount of the toner line image.   The replacement step includes a step of separating the background portion and the toner line image portion from the histogram of the profiling data and using the peak value of the background portion as a feature amount, and a feature amount of the background portion other than the toner region. The image evaluation method according to claim 6, further comprising a step of replacing the region.   The profiling data for separating the background portion and the toner region portion is calculated from a plurality of line positions including line positions in the vertical direction with respect to the line image to be measured, and features of one line of the background portion to be measured The image evaluation method according to claim 6, wherein an amount is obtained.   The normalized feature value calculating step calculates the normalized feature value from a region surrounded by a line width between a feature value of an ideal line and a feature value of the background part where no toner is missing on the background part. The image evaluation method according to claim 6, wherein:   The toner line image feature amount calculating step limits a measurement range of a color misalignment line image generated when forming a line image in which at least two toners are overlapped from position information of the image density signal. Item 7. The image evaluation method according to Item 6.   An image forming apparatus comprising the image evaluation apparatus according to claim 1.

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