JP4063902B2 - Shading correction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a shading correction method in which shading correction is performed by adjusting gray colors at a plurality of portions on an output medium.
[0002]
[Prior art]
In recent years, in the fields of printing and printers, a technique has been developed that can obtain a color image composed of C, M, Y, and K by processing image data using a signal processing technique. In this case, it is desired that a color image having a desired color and tone can be obtained with high accuracy from the image data.
[0003]
By the way, in the output device for outputting a color image, when an image is recorded on the entire surface of a medium such as printing paper or printing paper based on the same image data, the entire surface does not become a uniform color, so-called shading. May occur. As a cause, for example, in the case of recording an image by scanning a laser beam on a drum on which a medium is mounted, a difference in density occurs because the spot shape of the laser beam varies depending on the position on the drum, When performing thermal transfer recording, it is conceivable that a density difference occurs due to uneven temperature distribution in the axial direction of the drum.
[0004]
On the other hand, such shading can be corrected using, for example, a conventional technique disclosed in Japanese Patent Laid-Open No. 56-141673. This prior art creates a single-color (primary color such as C, M, Y, etc.) halftone color chart, measures the density of each chart, and feeds back the color conversion table that can output a desired color. Is to create. Using this technique, an image based on the same image data is formed on the entire surface of the medium, and a color conversion table is created so that the density of the image is constant regardless of the position on the medium. It is possible to correct shading.
[0005]
However, when the above-described conventional technology is used, shading correction for each single color such as C, M, and Y can be performed, but shading correction for a gray color that is a tertiary color composed of single colors of C, M, and Y can be performed. Is not something that can be done. That is, for the gray color formed by superimposing a plurality of single colors, even if each single color is set correctly and a theoretically accurate gray color can be obtained, for example, trapping or dot gain at the time of printing can be obtained. As a result, the ratio of a single color may fluctuate due to influences and the like, and an accurate gray color may not be obtained.
[0006]
As a conventional technique for correcting a gray color, as shown in Japanese Patent Laid-Open No. 6-237373, a gray color shift between two output devices is set so that an equivalent neutral density (END) value matches. Some corrections using a set correction matrix make it possible to adjust the gray balance of the other output device on the basis of one output device in which the gray color is accurately set.
[0007]
However, in this method, although the relationship of the color conversion for converting the image data into the output data is actually nonlinear, the correction is approximately performed by the linear processing using the correction matrix, so that the high accuracy is achieved. It is difficult to adjust the gray balance. In addition, this conventional technique performs gray color calibration and does not perform shading correction.
[0008]
In addition, in any of the above-described conventional techniques, since the number of measurement points required for highly accurate shading correction is extremely large, a considerable amount of time is required for processing.
[0009]
[Problems to be solved by the invention]
The present invention provides a shading correction method capable of solving the above-described problems and performing high-precision shading correction centering on gray color simultaneously with setting of gray balance with a small number of measurement points. Objective.
[0010]
[Means for Solving the Problems]
  The present invention uses the reference output device (10) in which the reference output adjustment data (α (m)) in which the gray balance and shading are adjusted is used to convert the reference input data (R, G, B (m)). The reference output data (Pr, Pg, Pb (m)) is converted into the reference output data (Pr, Pg, Pb (m)) by the reference output adjustment data (α (m)), and the data is output on the output medium. A reference chart is output, and the reference measurement value (L^*, A^*, B^*(M))And beforeThe reference output device (10) representing the relationship with the reference input data (R, G, B (m))FirstReference output characteristic data(Β(M))Or the reference measurement value (L ^* , A ^* , B ^* (M)) and the second reference output characteristic data (γ (m)) of the reference output device (10) representing the relationship between the reference output data (Pr, Pg, Pb (m)).A first step for determining
  Correct gray balance and shadingThe same configuration as the reference output device (10)Using the target output device (12), gray input data (R = G = B) for forming a gray color is converted into gray output data (Pr, Pg, Pb (ob) by output adjustment data (δ (ob)) before adjustment. )), And outputs a gray chart (T) to a plurality of regions (B0 to Bm) having different positions on the output medium based on the gray output data (Pr, Pg, Pb (ob)), Gray measurement value (L) of the gray chart (T) in the region (B0 to Bm)^*, A^*, B^*(Ob)) a second step for obtaining;
  The gray measurement value (L) of each of the regions (B0 to Bm)^*, A^*, B^*(Ob)) can be obtained from the reference output data (Pr, Pg, Pb (m)) in the reference output device (10).,SaidFirstReference output characteristic data(Β(M))And the reference output adjustment data (α (m)) or the second reference output characteristic data (γ (m))A third step to find using
  The reference output data (Pr, Pg, Pb (m)) of the reference output device (10) corresponding to the gray input data (R = G = B) is used by using the reference output adjustment data (α (m)). A fourth step to find,
  The reference output data (Pr, Pg, Pb (m)) of the respective regions (B0 to Bm) obtained in the third step is used as the reference output data (Pr, Pg, Pb ( m)), correction data (ed) to be corrected is obtained for each of the regions (B0 to Bm), and each correction data (ed)ThanThe gray output data (Pr, Pg, Pb (ob)) is corrected, and the gray input data (R = G = B) is corrected.eachA fifth step of obtaining output adjustment data (θi (ob) (i = 0 to m)) to be converted into gray output data (Pr, Pg, Pb (ob)) for each of the regions (B0 to Bm);
  It is characterized by comprising.
[0011]
  Further, the present invention uses the reference output device (10) in which the reference output adjustment data (α (m)) in which the gray balance and shading are adjusted is used, and the reference input data (R, G, B (m) ) Is converted into reference output data (Pr, Pg, Pb (m)) by the reference output adjustment data (α (m)), and an output medium is based on the reference output data (Pr, Pg, Pb (m)). The reference chart is output above, and the reference measurement value (L^*, A^*, B^*(M))And beforeThe reference output device (10) representing the relationship with the reference input data (R, G, B (m))FirstReference output characteristic data(Β(M))Or the reference measurement value (L ^* , A ^* , B ^* (M)) and the second reference output characteristic data (γ (m)) of the reference output device (10) representing the relationship between the reference output data (Pr, Pg, Pb (m)).A first step for determining
  Correct gray balance and shadingThe same configuration as the reference output device (10)Using the target output device (12), gray input data (R = G = B) for forming a gray color is converted into gray output data (Pr, Pg, Pb (ob) by output adjustment data (δ (ob)) before adjustment. )), And outputs a gray chart (T) to a plurality of regions (B0 to Bm) having different positions on the output medium based on the gray output data (Pr, Pg, Pb (ob)), Gray measurement value (L) of the gray chart (T) in the region (B0 to Bm)^*, A^*, B^*(Ob)) a second step for obtaining;
  The gray measurement value (L) of each of the regions (B0 to Bm)^*, A^*, B^*(Ob)) can be obtained from the reference output data (Pr, Pg, Pb (m)) in the reference output device (10).,SaidFirstReference output characteristic data(Β(M))And the reference output adjustment data (α (m)) or the second reference output characteristic data (γ (m))A third step to find using
  The reference output data (Pr, Pg, Pb (m)) of the reference output device (10) corresponding to the gray input data (R = G = B) is used by using the reference output adjustment data (α (m)). A fourth step to find,
  in frontEachFrom the areaOne area (Bs) that is less affected by shadingSelectedThe concernedOf region (Bs)Obtained in the third stepFirst correction data (ΔPs) for correcting the reference output data (Pr, Pg, Pb (m)) to the reference output data (Pr, Pg, Pb (m)) obtained in the fourth step is obtained. In the first correction data (ΔPs)ThanThe gray output data (Pr, Pg, Pb (ob)) is corrected, and the gray input data (R = G = B) is converted into the corrected gray output data (Pr, Pg, Pb (ob)). A fifth step for obtaining gray balance adjustment data (MLUT);
  Of other regions (B0 to Bm) excluding the selected region (Bs)Obtained in the third stepBeforeRecordeachSecond correction data (ΔP0 to ΔPm) for correcting the reference output data (Pr, Pg, Pb (m)) to the reference output data (Pr, Pg, Pb (m)) obtained in the fourth step.For each of the other areas (B0 to Bm)The difference between the first correction data (ΔPs) and each of the second correction data (ΔP0 to ΔPm) is selected.TerritoryObtained as third correction data (ΔΔPsi) of the other regions (B0 to Bm) with respect to the region (Bs),eachIn the third correction data (ΔΔPsi)ThanSaidotherShading correction data (BLUT0 to BLUTm) for correcting the gray output data (Pr, Pg, Pb (ob)) of each region (B0 to Bm).For each of the other areas (B0 to Bm)A sixth step to be obtained;
  The gray balance adjustment data (MLUT))Using the gray input data (R = G = B) to form the gray color in all regions (B0 to Bm) of the target output device (12), gray output data that can obtain a desired gray color Convert to (Pr, Pg, Pb (ob))At the same time, the gray output data (Pr, Pg, Pb (ob)) in the other regions (B0 to Bm) of the target output device (12) using the shading correction data (BLUT0 to BLUTm). Perform shading correctionIt is characterized by that.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  FIG. 1 shows a system configuration to which the shading correction method of this embodiment is applied. This system is supplied from the reference output device 10 in which the gray balance is already set with high accuracy and the shading correction is performed.Reference output adjustment data and referenceThe target output device 12 is configured to perform gray balance setting and shading correction according to output characteristic data. In this case, the target output device 12 has the same configuration as the reference output device 10 as a configuration for forming an image, and only the output characteristics as individual differences are different. The recording medium F used in the target output device 12 has substantially the same characteristics as the recording medium used in the reference output device 10.
[0013]
  When the target output device 12 is supplied with image data C, M, Y, K consisting of C (cyan), M (magenta), Y (yellow), K (black), the image data C, An image data conversion unit 14 that performs predetermined image processing on M, Y, and K and converts the data into R (red), G (green), and B (blue) device data R, G, and B, and the device data An output unit 16 that forms an image on a recording medium F based on R, G, and B; a measuring instrument 18 that obtains a colorimetric value by measuring an image (chart) formed on the recording medium F; Supplied from the colorimetric value and reference output device 10Reference output adjustment data and referenceBased on the output characteristic data, it basically comprises a gray balance / shading adjustment unit 20 for setting the gray balance of the target output device 12 and performing shading correction.
[0014]
  Further, the output unit 16 performs laser recording from device data R, G, and B supplied from the image data conversion unit 14 in accordance with output adjustment data that has been subjected to gray balance setting and shading correction as will be described later. ForNoThe output control data generation unit 24 that generates the user power data Pr, Pg, and Pb, and the exposure head 26 that controls the laser using the laser power data Pr, Pg, and Pb and forms an image on the recording medium F The
[0015]
The image data converter 14 may convert the image data C, M, and Y into device data R, G, and B, and the colorimetric value L^*, A^*, B^*May be converted into device data R, G, and B. Furthermore, the colorimetric value L is temporarily obtained from the image data C, M, Y, and K.^*, A^*, B^*Then, desired image processing may be performed, and then converted into device data R, G, and B.
[0016]
The system configuration to which the shading correction method of this embodiment is applied is basically as described above. Next, a gray balance setting method and a shading correction method in the target output device 12 in this configuration will be described with reference to FIG. This will be described based on the flowchart shown in FIG. Steps SA1 to SA3 represent processing in the reference output device 10, and steps Sa1 to Sa7 represent processing in the target output device 12. Further, in the following description, (m) is appended to the end of the data as necessary for the data related to the reference output device 10, and (ob) is necessary for the data related to the target output device 12 at the end of the data. ).
[0017]
  Therefore, data for converting device data R, G, B (m) into laser power data Pr, Pg, Pb (m) in the reference output device 10 in which gray balance is set and shading correction is performed with high accuracy. TheStandardoutputAdjustmentLet it be data α (m). In the reference output device 10, theStandardUsing the output adjustment data α (m), a chart of all color regions in which the gray color neighborhood is finely set is created on the recording medium (step SA1), and the colorimetric value L of each patch constituting the chart is created.^*, A^*, B^*(M) is measured (step SA2), device data R, G, B (m) and the colorimetric value L^*, A^*, B^*The number representing the relationship with (m)1Output characteristic data β (m) is obtained. In addition,StandardoutputAdjustmentData α (m) and the above1From the output characteristic data β (m), the laser power data Pr, Pg, Pb (m) and the colorimetric value L^*, A^*, B^*No. showing the relationship with (m)2Output characteristic data γ (m) is obtained (step SA3). theseStandardoutputAdjustmentData α (m),First output characteristic dataβ (m) andSecond output characteristic dataγ (m) is supplied from the reference output device 10 to the gray balance / shading adjustment unit 20 of the target output device 12.
[0018]
  The aboveStandardoutputAdjustmentData α (m) and the above2Output characteristic data γ (m), device data R, G, B (m), laser power data Pr, Pg, Pb (m) and colorimetric value L^*, A^*, B^*The relationship with (m) is shown in FIG.
[0019]
Next, in the target output device 12, output adjustment data δ before adjustment that is set in the output control data generation unit 24 of the output unit 16 and converts the device data R, G, B into laser power data Pr, Pg, Pb. Using (ob), device data R, G, B (R = G = B) (ob) (see data a in FIG. 3) to form a gray color is converted into laser power data Pr, Pg, Pb (ob). Based on the laser power data Pr, Pg, Pb (ob), a chart T that should be gray is created on the recording medium F (step Sa1).
[0020]
Here, in the output unit 16, as shown in FIG. 4, the laser beam from the exposure head 26 is applied to the recording medium F wound around the outer periphery of the exposure drum 28 rotating in the arrow X direction. The image is formed by scanning. In this case, it is assumed that the exposure drum 28 has a non-uniform temperature distribution along the arrow Y direction. Further, it is assumed that the beam spot shape of the laser beam guided from the exposure head 26 onto the recording medium F is not the same depending on the scanning position in the arrow Y direction. For this reason, shading occurs in the recording medium F along the arrow Y direction. For example, even when images are recorded using the same device data R, G, and B, the shading occurs in the arrow Y direction. On the other hand, it is assumed that a uniform image is not obtained.
[0021]
Therefore, as shown in FIG. 4, the chart T is gray for each of the regions A0 to A4 along the arrow X direction, for example, set as R = G = B = 50, 100, 150, 200, 250. Created according to device data R, G, B (R = G = B) (ob) to be color, and divides each of the areas A0 to A4 into a plurality of areas B0 to Bm along the arrow Y direction where shading appears Will be processed. Instead of the chart T, as shown in FIG. 5, subcharts T0 to Tm in which the regions A0 to A4 are formed in a lattice shape may be created along the arrow Y direction. In this case, the subcharts T0 to Tm correspond to the positions of the regions B0 to Bm.
[0022]
  The chart T or sub-chart T0 to Tm created as described above is measured by the measuring device 18, and the colorimetric value L for each region B0 to Bm.^*, A^*, B^*(Ob) is obtained (see step Sa2, data c in FIG. 3). The laser power data Pr, Pg, Pb (ob) (see data b in FIG. 3) and the colorimetric value L of the target output device 12^*, A^*, B^*(Ob) (refer to data c in FIG. 3) as output characteristic data ε (ob),StandardoutputAdjustmentData α (m),Second output characteristic dataγ (m),Output characteristic dataThe relationship between ε (ob) and output adjustment data δ (ob) is shown in FIG.
[0023]
  Next, in each of the regions B0 to Bm, the colorimetric value L obtained in step Sa2.^*, A^*, B^*(Ob) The laser power data Pr, Pg, Pb (m) of the reference output device 10 corresponding to (data c in FIG. 3)2It is obtained using the output characteristic data γ (m) (see step Sa3, data d in FIG. 3).
[0024]
  The colorimetric value L^*, A^*, B^*The relationship of the laser power data Pr, Pg, Pb (m) to (m) is the colorimetric value L for the laser power data Pr, Pg, Pb (m).^*, A^*, B^*As the inverse transformation of the relationship of (m), for example, the Newton-Raphson method or any other calculation method can be used. The first2Instead of using output characteristic data γ (m),1Using the output characteristic data β (m), the colorimetric value L^*, A^*, B^*After determining the relationship of the device data R, G, B (m) with respect to (m) by the Newton-Raphson method or the like,StandardoutputAdjustmentBy obtaining the laser power data Pr, Pg, Pb (m) using the data α (m), as a result, the colorimetric value L^*, A^*, B^*The relationship of the laser power data Pr, Pg, Pb (m) to (m) may be obtained.
[0025]
  Next, the laser power data Pr, Pg, Pb (m) when the device data R, G, B (R = G = B) (ob) (data a in FIG. 3) is given to the reference output device 10 ( Data e) in Fig. 3StandardoutputAdjustmentAfter obtaining using the data α (m), difference data (ed) between the data d and e is obtained for each of the regions B0 to Bm (step Sa4).
[0026]
  Then, using the difference data (ed), the device data R, G, B (R = G = B) (ob) of the target output device 12 (data a in FIG. 3).FromLaser power data Pr, Pg, Pb (ob) (data in FIG. 3b)Lead output adjustment data δ (ob),
    f−b = ed
To satisfy the relationshipShiThe corrected output adjustment data θi (ob) (i = 0 to m) is obtained for each region B0 to Bm (step Sa5). The output adjustment data θi (ob) is obtained not by using the difference data (ed), but by obtaining the ratio data e / d between the data d and the data e, and the ratio data e / d is converted into the data b. MultiplicationThe relationship between the data f obtained by the above and device data R, G, B (R = G = B) (ob)You can ask for it.
[0027]
The output adjustment data θi (ob) obtained for each of the regions B0 to Bm as described above is set in the output control data generation unit 24 that constitutes the output unit 16 of the target output device 12 (step Sa6). In this case, the output adjustment data θi (ob) is set roughly along the arrow Y direction of the exposure drum 28. Therefore, the output adjustment data θi (ob) is further interpolated using the output adjustment data θi (ob) set for the adjacent regions B0 to Bm, as shown in FIG. Subdivided output adjustment data LUTj (j = 0 to n, n> m) is set in the output control data generation unit 24 (step Sa7). The output adjustment data LUTj may be obtained for each scanning line by the exposure head 26, or may be obtained for each predetermined number of scanning lines according to the degree of shading.
[0028]
The output adjustment data LUTj obtained as described above sets the gray balance in the (n + 1) area obtained by subdividing each of the areas B0 to Bm, and sets the gray balance for each (n + 1) area. Thus, shading between the (n + 1) regions is also corrected. In this way, the target output device 12 outputs the minimum necessary chart using the device data R, G, B (R = G = B) that should be gray, and then easily and quickly the gray balance. And shading correction can be performed simultaneously.
[0029]
The processing of steps Sa1 to Sa7 is repeatedly performed as necessary, so that output adjustment data LUTj that can perform more accurate gray balance setting and shading correction for the target output device 12 is obtained. .
[0030]
In the target output device 12 of the present embodiment, image conversion processing is performed using the output adjustment data LUTj (j = 0 to n) set as described above.
[0031]
That is, the image data C, M, Y, and K supplied to the image data converter 14 are converted into device data R, G, and B, and then transferred to the output unit 16. In the output control data generation unit 24 of the output unit 16, as shown in FIG. 7, the output adjustment data LUTj in which the device data R, G, B is selected according to the scanning position data of the laser beam by the exposure head 26. The laser power data Pr, Pg, and Pb are converted by (j = 0 to n). Next, the laser beam is controlled based on the laser power data Pr, Pg, Pb, and a desired image is formed on the recording medium F. In this case, the gray balance of the image is adjusted with high accuracy, and the shading is corrected according to the scanning position, so that a desired color is reproduced on the recording medium F.
[0032]
In addition, by performing the processing of the steps Sa1 to Sa7 every time immediately before outputting each image, it is possible to obtain a highly accurate image in which the gray balance and shading are always adjusted. Further, when the target output device 12 is turned on, the processes of steps Sa1 to Sa7 may be performed. In this case, the chart T shows device data R, G, B subdivided from the device data R, G, B (R = G = B = 50, 100, 150, 200, 250) described in the above embodiment. By using this, it is possible to adjust gray balance and shading with higher accuracy.
[0033]
Next, another embodiment of the method for setting the gray balance and correcting the shading for the target output device 12 will be described based on the flowchart shown in FIG.
[0034]
First, a region Bs (0 ≦ s ≦ m) in which the influence of shading due to the temperature of the exposure drum 28 is small and the characteristics are most stable is selected, and device data R, G, B ( Laser power data Pr, Pg, Pb (m) and colorimetric value L of the reference output device 10 for R = G = B)^*, A^*, B^*The correction amount ΔPs, which is the first correction data consisting of the difference from the laser power data Pr, Pg, Pb (m) of the reference output device 10 with respect to is obtained in the same manner as in step Sa4 (step Sb1).
[0035]
  Next, using the correction amount ΔPs, output adjustment data θs (ob) capable of setting the gray balance for the region Bs is obtained in the same manner as in step Sa7, and the output adjustment data θs (ob) is obtained. Gray balance in the target output device 12AdjustmentThe data is MLUT (step Sb2).
[0036]
On the other hand, correction amounts ΔP0 to ΔPm as second correction data are obtained for the other regions B0 to Bm excluding the region Bs in the same manner as in step Sb1 (step Sb3). Then, a difference ΔΔPsi, which is third correction data including a difference between the correction amount ΔPs obtained for the region Bs and each of the correction amounts ΔP0 to ΔPm,
ΔΔPsi = ΔPs−ΔPi (i = 0 to m)
(Step Sb4).
[0037]
Next, using the difference ΔΔPsi, the shading correction data BLUT0 to BLUTm for the areas B0 to Bm are obtained (step Sb5). In this case, for example, the shading correction data BLUTi uses the difference ΔΔPsi to show the relationship of the laser power data Pr, Pg, Pb after the shading correction with respect to the laser power data Pr ′, Pg ′, Pb ′ before the shading correction as shown in FIG. It is set like this. Further, the shading correction data BLUTs are set as shown in FIG. 9B in which the relations between the laser power data Pr ′, Pg ′, Pb ′ before the shading correction and the laser power data Pr, Pg, Pb after the shading correction are equal. .
[0038]
  Gray balanceAdjustmentThe data MLUT and the shading correction data BLUT0 to BLUTm can be obtained using ratio data instead of being obtained based on the difference data. That is, in the region Bs, the ratio data e / d between the data d and the data e shown in FIG. 3 is obtained, and the ratio data e / d, which is the first correction data, is multiplied by the data b to thereby output the output adjustment data θs (ob ), And this is the gray balance for all areas B0 to BmAdjustmentData MLUT is assumed. On the other hand, the output adjustment data θi (ob) is obtained by multiplying the ratio data e / d, which is the second correction data, by the data b for the other areas B0 to Bm excluding the area Bs. These differences δPsi, which are correction data, are
    δPsi = θs (ob) −θi (ob)
Asking. Then, using this difference δPsi, shading correction data BLUT0 to BLUTm for each region B0 to Bm are obtained in the same manner as in step Sb5.
[0039]
Here, since the shading correction data BLUTi obtained as described above is set roughly along the arrow Y direction of the exposure drum 28, the output adjustment data LUTj (j = 0) in the above-described embodiment. In the same manner as in the case of .about.n, n> m), the shading correction data SLUTj (j = 0 to n, n> m) subdivided by the interpolation process is obtained (step Sb6).
[0040]
  Gray balance obtained as described aboveAdjustmentThe data MLUT and the shading correction data SLUTj are set in the output control data generation unit 24, and the process for the device data R, G, B is performed as shown in FIG. That is, the device data R, G, and B supplied to the output unit 16 are gray-balanced in the output control data generation unit 24.AdjustmentGray balance by data MLUTAdjustmentThe converted laser power data Pr ′, Pg ′, and Pb ′. Next, the laser power data Pr ′, Pg ′, and Pb ′ are subjected to shading correction by the shading correction data SLUTj (j = 0 to n) selected according to the scanning position data of the laser beam by the exposure head 26. It is converted into laser power data Pr, Pg, Pb. Then, the laser is controlled based on the laser power data Pr, Pg, Pb, and a desired image is formed on the recording medium F.
[0041]
【The invention's effect】
  As described above, according to the present invention, it is possible to quickly perform highly accurate shading correction centering on a gray color with a small number of measurement points with respect to the target output device. In addition to shading correction, gray balanceAdjustmentCan be performed with high accuracy.
[0042]
Furthermore, the gray balance and shading of a large number of target output devices can be quickly and accurately adjusted using the output characteristic data in the reference output device in which the gray balance and shading have already been adjusted with high accuracy.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a system to which a shading correction method of an embodiment is applied.
FIG. 2 is a flowchart illustrating a gray balance setting method and a shading correction method in the target output device.
FIG. 3 is an explanatory diagram of a gray balance setting method in the target output device.
FIG. 4 is an explanatory diagram of a chart and region division for performing shading correction in a target output device.
FIG. 5 is an explanatory diagram of a chart and region division for performing shading correction in a target output device.
FIG. 6 is an explanatory diagram of interpolation processing of output adjustment data for shading correction.
FIG. 7 is an explanatory diagram of device data conversion processing using output adjustment data for adjusting gray balance and shading.
FIG. 8 is a flowchart showing another embodiment of a gray balance setting and shading correction method in the target output device.
9A and 9B are explanatory diagrams of shading correction data.
FIG. 10 is an explanatory diagram of a device data conversion process using gray balance setting data and shading correction data.
[Explanation of symbols]
10 ... Standard output device 12 ... Target output device
14 ... image data conversion unit 16 ... output unit
18 ... Measuring instrument
20. Gray balance / shading adjustment section
24: Output control data generation unit

Claims (4)

Using the reference output device in which the reference output adjustment data in which the gray balance and shading are adjusted is set, the reference input data is converted into the reference output data by the reference output adjustment data, and on the output medium based on the reference output data to output the reference chart, the first reference output characteristic data of the reference output device showing the relationship between the baseline measurement and the previous SL reference input data of the reference chart, or the baseline measurement and of the reference output data A first step of obtaining second reference output characteristic data of the reference output device representing a relationship ;
Using a target output device having the same configuration as the reference output device for correcting gray balance and shading, gray input data forming a gray color is converted into gray output data by output adjustment data before adjustment, and the gray output data is converted into the gray output data. A second step of outputting a gray chart to a plurality of regions having different positions on the output medium based on the gray chart and obtaining a gray measurement value of the gray chart in each region;
The reference output data in the reference output device capable of obtaining the gray measured value of the respective regions, the first reference output characteristic data and the reference output adjustment data, or determined using said second reference output characteristic data The third step;
A fourth step of obtaining reference output data of the reference output device corresponding to the gray input data using the reference output adjustment data;
Said reference output data of the respective areas obtained in said third step, said fourth obtain correction data for correcting said reference output data obtained in step for each of the respective regions, and more the gray output to the each corrected data data corrected, and fifth step of obtaining an output adjustment data for converting the gray input data to corrected each gray output data to each of said regions,
A shading correction method comprising: The method according to claim 1, wherein the output adjustment data for each of the areas set in the fifth step is subjected to interpolation processing to be further output adjustment data for each of the areas. Shading correction method. Using the reference output device in which the reference output adjustment data in which the gray balance and shading are adjusted is set, the reference input data is converted into the reference output data by the reference output adjustment data, and on the output medium based on the reference output data to output the reference chart, the first reference output characteristic data of the reference output device showing the relationship between the baseline measurement and the previous SL reference input data of the reference chart, or the baseline measurement and of the reference output data A first step of obtaining second reference output characteristic data of the reference output device representing a relationship ;
Using a target output device having the same configuration as the reference output device for correcting gray balance and shading, gray input data forming a gray color is converted into gray output data by output adjustment data before adjustment, and the gray output data is converted into the gray output data. A second step of outputting a gray chart to a plurality of regions having different positions on the output medium based on the gray chart and obtaining a gray measurement value of the gray chart in each region;
The reference output data in the reference output device capable of obtaining the gray measured value of the respective regions, the first reference output characteristic data and the reference output adjustment data, or determined using said second reference output characteristic data The third step;
A fourth step of obtaining reference output data of the reference output device corresponding to the gray input data using the reference output adjustment data;
Before SL selects one region is less affected shading from each region, the first correction that corrects the reference output data obtained in the third step of the region, the reference output data obtained in said fourth step for data, and a fifth step of obtaining a gray balance adjustment data for converting the first corrected more the gray output data to the correction data, the gray input data to corrected the gray output data,
Said selected pre Symbol respective reference output data obtained in the third step of the other region excluding the region, the second correction data the other for each area is corrected to the reference output data obtained in said fourth step to seek, the difference between the first correction data and said respective second correction data, determined as the third correction data of the other of the regions for the selected realm, more the other to the each third correction data A sixth step of obtaining shading correction data for correcting the gray output data of each area for each of the other areas ;
Made, using said gray balance adjustment data, in the entire region of the target output device, and converts the gray output data that can be gray input data to form the gray obtain the desired gray, A shading correction method comprising performing shading correction of the gray output data in each of the other regions of the target output device using the respective shading correction data . The method of claim 3, wherein
The shading correction method according to claim 6, wherein the shading correction data for each of the regions set in the sixth step is subjected to interpolation processing to be further divided into shading correction data for each of the regions.

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