JP2011131383A - Image processing system and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To overcome the problems that also a time for measuring the whole patch chart becomes long because it is necessary to take a long time for measurement in order to stably converge random noise to nearly zero when measuring a patch by a sensor, and that a total measurement time for measuring the whole patch chart becomes long as a result of that a measurement time per patch is matched with a time that enables the darkest patch to be stably measured in the case of measuring scanning the patch chart by a sensor. <P>SOLUTION: A measurement speed is controlled for every patch so that the measurement speed for a patch low in optical density and the measurement speed for a patch high in optical density become fast and slow, respectively. Control information for a sensor is formed, and control of the sensor is performed using the control information at measuring with the sensor which measures while keeping the measurement speed constant. The patch chart can be measured in a short time while the SN of a dark patch high in optical density is improved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image processing system and an image processing method capable of obtaining a measurement value by measuring a printed patch with a sensor.

  In recent years, many image output devices such as large-format ink jet printers equipped with a colorimeter are on the market. These are introduced for the purpose of correcting the print density of the printer and stabilizing the color, creating a ICC profile, and the like. There are various types of mounting of the colorimeter, and there are a form in which the colorimeter is mounted on the carriage part of the print head and a form in which the colorimeter unit is attached and fixed to the paper discharge port. The measuring method of the colorimeter can be roughly divided into a contact type and a non-contact type. In the contact type, the measurement is performed in contact with the paper surface in order to eliminate the influence of external light, so the colorimeter must be stationary on the paper surface during measurement. It is possible to measure while scanning. Patent Document 1 proposes a technique for measuring without stopping the scanning head while scanning with a non-contact sensor. An object of the present invention is to efficiently perform color measurement of a plurality of color patches. When performing color measurement of a patch while moving the head in the width direction of the medium, a certain amount of time is required for color measurement of the patch. Therefore, the long side of each patch is set to be longer than the length obtained by multiplying the moving speed of the head by the time required for color measurement of the head, and the color measurement start coordinates are shifted with respect to the coordinates of the boundaries of each patch. Thus, color measurement can be performed without stopping the head.

  On the other hand, as a colorimeter incorporated in a commercially available printer, a colorimeter constituted by a sensor manufactured at a relatively low cost is often used as compared with a normal expensive colorimeter. The signal received by the sensor always contains noise. However, when the signal received by the sensor is sufficiently large with respect to the noise, that is, when the S / N ratio is large, there is not much problem. However, in a patch having a high optical density, that is, a dark patch, the received signal is small, and the ratio of noise components is relatively large, so that the SN ratio is deteriorated. In particular, an inexpensive sensor has a small S / N ratio, which is the ratio of signal value to noise, and the ratio of noise to signal value is relatively high. Therefore, the influence of noise on the signal value is high, and the measurement accuracy is low. Become.

JP 2000-283852 A

  As a countermeasure against this problem, for example, a method of increasing the amount of light or a method of increasing the amplification factor can be considered. When the amount of light is increased, problems such as thermal problems and changes in the spectral characteristics of the light source may occur, and the signal may be saturated with a bright patch. Even with the method of increasing the amplification factor, there is a possibility that the signal is saturated with a bright patch, and there is a problem that the noise itself is amplified. In general, a colorimetric sensor performs color measurement after calibrating against a white reference, but it is necessary to perform color measurement under the same conditions as when performing calibration to prevent the above errors during colorimetry. For this reason, changing the light amount and the amplification factor for each patch during color measurement leads to an increase in color measurement error.

  Therefore, in general, an averaging process is used as a representative method. Random noise generated when measuring with a sensor has the property of converging to zero by averaging over time. That is, by increasing the measurement time and increasing the number of samplings for averaging, it is possible to reduce the relative noise ratio and increase the accuracy.

  FIG. 1 is a diagram for explaining the SN ratio when a patch is measured by a sensor. FIG. 1A shows a signal value when a patch having a low optical density, that is, a patch having a high reflected signal value is measured. On the other hand, FIG. 1B shows a signal value when a patch having a high optical density, that is, a patch having a low reflection signal value is measured. Although random noise is included in the signal value, when the reflected signal value is large as shown in FIG. 1A, the influence of noise is small, so that measurement can be performed in a relatively short measurement time t1. Sampling is performed a plurality of times during the measurement time t1, and an averaging process is performed. On the other hand, when the reflected signal value is small as in the case of FIG. 1B, the influence of noise is large, so that accuracy cannot be ensured at the measurement time t1. Therefore, a measurement time t2 longer than t1 is necessary. In this case, the averaging process is performed during the measurement time t2 with a larger number of samplings than in FIG.

  However, in this averaging process, in order to converge the noise component to near zero, it is necessary to take a longer measurement time for darker patches, and the time for measuring the entire patch chart also becomes longer. When measuring a patch chart while moving by a sensor, it is necessary to adjust the measurement time per patch to the time when the darkest patch can be stably measured. However, if the speed at which each patch is measured matches the speed at which the darkest patch can be measured stably, there arises a problem that the total measurement time for measuring all the patches becomes longer.

  In view of the above problems, an object of the present invention is to provide an image processing system capable of performing highly accurate measurement in a short time even when a patch is measured during relative movement between a sensor and a recording medium.

  In order to solve the above problems, the present invention provides a patch image data generation unit that generates patch image data including a plurality of patches each having a different optical density, and prints the plurality of patches on a recording medium based on the patch image data. Printing means, a sensor for optically measuring the plurality of patches during relative movement with respect to the recording medium, and control means for controlling the speed of the relative movement between the recording medium and the sensor, The speed of the relative movement is such that the speed of measuring the patch of the first optical density is slower than the speed of measuring the patch of the second optical density lower than the first optical density. It is characterized by controlling.

  According to the present invention, the patch measurement speed, that is, the relative movement speed between the sensor and the recording medium is controlled according to the optical density of the patch, thereby improving the SN of the patch having a high optical density and in a short time. The effect is that the patch chart can be measured.

It is a figure for demonstrating SN ratio. It is a figure which shows the structural example which can apply this invention. It is a figure for demonstrating operation | movement of the printing part of a printer, and a measuring machine. It is a figure which shows the flow of a process of the system which can apply this invention. It is a figure which shows UI of a patch chart setting. It is a figure which shows the flow of patch chart preparation. It is a figure which shows the example of the color value data to input. It is a figure showing a correspondence of RGB value and measurement speed V. It is a figure which shows the example of a patch chart. It is a figure explaining the method of calculating a measurement speed by spectral reflectance.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best embodiment according to the present invention will be described in detail with reference to the drawings.

<Schematic configuration of the device>
FIG. 2A shows a first configuration of the image processing system in the embodiment according to the present invention. As a typical example of the image processing system of this embodiment, an example using an ink jet printer is given. A personal computer (hereinafter simply referred to as “PC”) 21 is connected to the printer device 20 as an information processing device. The printer device 20 includes a print unit 220 for output and a measuring device 230 for measurement. Is done. In this measuring machine, reflected light of the irradiated light is received by a sensor built in the measuring machine, and the reflectance is measured from the intensity of the reflected light of the target document. As the measuring instrument, a colorimeter using spectral reflectance may be used. In this embodiment, as shown in FIG. 3, the measuring device 230 is mounted on a movable carriage portion of the printing unit 220. However, the measuring device 230 is attached to a paper discharge port or connected to the outside of the printer. It may be in any form. However, the measurement method of the measuring machine is a non-contact type and performs measurement while scanning on the patch without being stationary.

  The PC 21 performs various processes regarding the control of the printer device 20. The PC 21 includes an operation unit 211, a CPU 212, a work memory 213, a storage device 214, and a data input / output device 215. The operation unit 211 serving as a user interface (hereinafter referred to as a UI) performs input by the user and display to the user, and includes an input device such as a keyboard and a mouse and a display device such as a display. The storage device 214 is a storage device such as a hard disk that stores the system program of this embodiment and the print data created on the PC 21. The CPU 212 executes a process for controlling the printing unit 220 and the measuring machine 230 according to a program stored in the storage device 214, and the work memory 213 is used as a work area for the process.

  A user can usually cause the printer device 20 to output documents, images, and the like processed by various applications on the PC 21. That is, predetermined image processing is performed on the image processed by the print application in the PC 21, and the print data is sent to the printer driver. The printer driver converts the print data into CMYK, which is the ink color of the printer, performs halftone processing, and outputs it to the printer device 20. The printer device 20 develops the data after halftone processing received from the PC 21 on the output paper, and generates a hard copy in the printing unit 220. In this embodiment, the color conversion processing and the halftone processing are executed by the printer driver. However, the above processing may be executed in the printer device 20.

  FIG. 2B shows a second configuration of the image processing system in the embodiment according to the present invention. In the second configuration, the calculation unit 210 is configured in the printer device 20 instead of the PC 21 described above. The calculation unit 210 performs various processes regarding control of the print unit 220 and the measurement unit 230 as an information processing apparatus. The calculation unit 210 includes an operation unit 211, a CPU 212, a work memory 213, a storage device 214, and a data input / output device 215. The role of each component is the same as in the first configuration. A user normally issues an execution command such as printing in response to an instruction from the PC 21 or the operation unit 211. However, when an execution command such as printing is issued from the operation unit 211, the processing is completed only by the printer device 20, and thus the PC 21 is indispensable. is not.

  FIG. 4 is a flowchart schematically showing a flow of processing from patch chart creation to measurement in the first configuration in the image processing system of the present embodiment. Hereinafter, the flow of execution will be described in detail along the flowchart.

  First, in step S401, the user activates a program stored in the storage device 214 of the PC 21 and displays a patch chart setting menu screen. FIG. 5 is a menu screen showing a patch chart setting UI.

  In step S402, settings relating to patch chart creation and measurement are performed. First, the paper type, paper feed port, paper size, print quality, and color conversion that can be used by the printer are selected. In 501 of FIG. 5, information on the media can be selected from a pull-down menu. As the paper feed port, roll paper, manual feed on the back surface, or the like can be selected, and the paper type can be selected from plain paper, coated paper, art paper, glossy paper, and the like. The print quality is selected from standard, beautiful, highest, etc. corresponding to the paper type. The color conversion is selected from “photograph”, “bright color”, “minimum color difference”, etc., which can be selected by the printer driver. When no color conversion is performed, “no color conversion” can be selected. In 502, input data is designated. The format of input data is selected from RGB or CMYK. Then, when a reference button is pressed, a dialog (not shown) is displayed, and a file in which color value data as a patch creation source is described is designated. Reference numeral 503 denotes settings relating to patch measurement. Select the measurement direction from one-way or two-way. Also, ON / OFF of the patch rearrangement process is selected. The patch rearrangement process will be described later. When the start button 504 is pressed, the process proceeds to the next step. When the cancel button 505 is pressed, the process is stopped and the execution menu display state is restored.

  In step S403, the patch chart setting selected in step S402 is checked whether the paper type and paper size are compatible with patch printing and the input data is checked. If the selected paper is a printable paper and there is no problem with the color value data of the input file, an execution confirmation dialog (not shown) is displayed on the screen of the PC 21. When OK is selected, the process proceeds to the next step. When cancel is selected, the execution menu display state is restored.

  Next, in step S404, a patch chart is created. The creation of the patch chart is performed according to a method described later by a program stored in the storage device 214 of the PC 21. At this time, parameters stored in the storage device 214 of the PC 21 are referred to for parameters such as resolution conversion and error diffusion for generating patch image data of the patch chart, and an image processing table. At the time of creating the patch chart, sensor control information for controlling the sensor when measuring a plurality of patches is also created at the same time.

  In step S405, the patch chart is printed. The patch chart is printed according to the content of the paper feed port, paper type, paper size, print quality, and color conversion selected in S402.

In step S406, the patch chart is measured. In this embodiment, measurement is performed while scanning the patch chart by the measuring device 230 mounted on the carriage portion of the print head. This patch chart measurement process is performed with reference to the sensor control information created in step S404.
Finally, the measured value is stored in step S407. The measurement value is converted into a predetermined format and stored in a predetermined area of the storage device 214. When the storage of the measured value is finished, the execution process is finished.

<Create patch chart>
Next, the creation of the patch chart in S404, which is a feature of the present invention, will be described in detail with reference to FIG. Creation of a patch chart, which is patch image data, is performed by a program stored in the storage device 214 of the PC 21.

  First, in step S601, the input RGB values of the patch are input to the program as color value data. This is an RGB value for each patch described in the color value file designated by 502 in FIG. In the present embodiment, the case where the RGB values R, G, and B are each 8 bits input (0 to 255) will be described as an example. An example of input color value data is shown in FIG. The number of data, the type of data (RGB, CMYK, etc.), and the number of input bits are specified in the header part, and the color value of the patch is arranged below it. If no color conversion is selected in the patch chart setting of S402, the RGB values are used as they are. However, if color conversion is selected, after color conversion corresponding to the paper type is applied. RGB values are used as input values.

  In step S602, the measurement speed is obtained from the input RGB value of each patch using an arithmetic expression. In this embodiment, RGB values are used as color data that is most commonly used as input values for patches. Then, by using an arithmetic expression described later, it is determined so as to minimize the speed of measuring the darkest patch, that is, the patch having the highest optical density. The speed at which the patch is measured in this embodiment is the moving speed of the sensor. In this embodiment, the speed is obtained from the RGB values, but any value may be used as long as it affects the amount of light received by the sensor. For example, spectral reflectance, RGB value, CMYK value and the like can be mentioned.

  The measurement speed is obtained by the following formula.

  Here, max (r, g, b) represents the maximum value of the input values r, g, b, and min (r, g, b) represents the minimum value of the input values r, g, b. X1 obtained by Expression (1) is a variable obtained by dividing the difference between the maximum value and the minimum value by the digital count value 255. r, g, b are primary colors R (255, 0, 0), G (0, 255, 0), B (0, 0, 255) or C (0, 255, 255), M (255, 0). , 255), Y (255, 255, 0), the maximum is 1. When r = g = b, which is an achromatic color, it is a variable that is 0 at the minimum. X2 obtained by the equation (2) is a variable that becomes 1 at the maximum when r = g = b = 0, that is, black, and becomes 0 at the minimum when r = g = b = 255, that is, white. Moreover, the measurement speed V is calculated | required by Formula (3). α1 and α2 are weighting coefficients. The value β is an offset value, which is a minimum measurement speed necessary for measuring a patch having a predetermined patch length. When x1 ≧ x2, x1 and α1 are used to obtain the measurement speed V, and when x1 <x2, x2 and α2 are used. In this embodiment, as an example, α1 = −4, a2 = −6, and b = 7.

  FIG. 8 shows the relationship between the measurement speed V obtained by the above equation and the input color values r, g, and b. The value of the measurement speed V is expressed as a stepwise integer from 1 to 7, and is temporarily stored in the storage device 214 in a form associated with each patch. Note that when the measurement speed is determined by a common arithmetic expression that does not depend on the paper to be printed in this way, a difference occurs in color development on the paper surface due to the difference in the paper to be printed. Therefore, the relationship between the actual density and the measurement speed V is Not clear. On the other hand, for example, plain paper with low color developability tends to have a low optical density. Therefore, the measurement speed can be changed depending on the printing paper by reducing the offset value β. Similarly, art paper with high color developability tends to have a high density, so β is increased. Here, although the case where RGB input is designated in S402 has been described, an arithmetic expression is created in the same way for CMYK input, and the measurement speed V is obtained.

  When the calculation of the measurement speed is finished, a patch layout is performed in step S603. The patch layout is performed according to the settings relating to the patch chart measurement in step S402. FIG. 9 is a diagram illustrating an example of a patch chart, in which 90 represents a sensor, 900 represents a patch chart, and 901 represents a patch. In this figure, a patch with a darker color has a higher optical density, and a patch with a whiter color has a lower optical density. When the patch rearrangement in the patch measurement setting 503 in FIG. 5 is set to OFF, the patches are arranged in the order of input data in the sensor moving direction (scanning direction) as shown in FIG. Laid out. Then, a patch with a high optical density (first optical density patch) is measured at a lower scanning speed than a patch with a low optical density (second optical patch lower than the first optical density). Note that (a) is a patch chart when the direction to be measured is specified as bidirectional. On the other hand, when the patch rearrangement is set to ON, as shown in FIG. 9B, patches having the same measurement speed are continuously arranged in parallel. In particular, it is desirable to print a patch with a high optical density first, print a patch with a low optical density later, and then start measurement from the patch with a low density. This is to ensure a sufficient drying time of the patch having a high optical density during the measurement, thereby shortening the time from printing to measurement. In addition, by arranging patches with the same measurement speed in succession, changes in the measurement speed can be controlled collectively for each block, and the measurement sequence can be simplified.

  Next, in step S604, sensor control information is generated. When the patch layout is completed, sensor control information converted into a predetermined format for controlling the operation of the sensor is stored in the storage device 214 based on the patch layout information and the measurement speed V for each patch. This sensor control information is input to control the measurement speed of the sensor during patch measurement.

  Finally, in step S605, the laid out patch chart data is stored in a predetermined area of the storage device 214, and the process is terminated.

  The flow from the generation of the patch chart data to the measurement in the image processing system of the present embodiment has been described above. According to this embodiment, when the sensor measures the patch while moving relative to the recording medium, the measurement speed of the patch is changed according to the color value of the patch, so that high-precision measurement can be performed in a short time. Can do. In the present embodiment, an ink jet printer is used as a representative example, but the present invention is not limited to this, and the present invention can also be applied to a copying machine, an electrophotographic printer, or the like. Further, although RGB values are used as input values for patches, CMYK values or the like may be used.

  In step S602 of the above-described embodiment, the measurement speed of each patch is determined from the patch color data by an arithmetic expression. On the other hand, in this embodiment, a description will be given of a mode in which a lookup table (hereinafter referred to as LUT) for converting patch color data into measurement speed is stored in advance and the measurement speed is determined with reference to the LUT. Hereinafter, a method for creating the LUT will be described.

  First, the measurement speed is calculated by the arithmetic expression in step S602 for 9 × 9 × 9 = 729 input RGB values obtained by changing RGB in 9 steps. Then, an LUT is created using tetrahedral interpolation, which is an existing general technique. The LUT created in this way is stored in the storage device 214 in advance. Then, when the measurement speed is determined in step S602, the LUT for converting the RGB value into the measurement speed is referred to.

  Further, a mode in which an LUT for converting the color value of the patch into the measurement speed is held for each corresponding sheet is also conceivable. This is because, as described in step S602, a difference occurs in the color development on the paper surface due to the difference in the paper to be printed. Therefore, the correspondence between the actual density and the measurement speed V is greater when the LUT is held on each paper. Because it can keep. By holding the LUT in advance in this way, the time can be further reduced.

  The LUT described in the second embodiment was created by determining the measurement speed from the color data of the patch using an arithmetic expression, but was created based on the measured spectral reflectance for each patch printed on the paper. May be. Hereinafter, the creation method will be described in detail.

  First, 9 × 9 × 9 = 729 patches in which RGB is changed in 9 stages are printed on paper that can be printed by a printer. Next, the spectral reflectance of the patch is measured by a colorimeter. It is desirable to use the same colorimeter as that incorporated in the printer. After measuring the spectral reflectance, the measurement speed is determined from the measured spectral reflectance. FIG. 10 shows the spectral reflectance of a patch when a patch having different input RGB values is printed on a certain sheet and the spectral reflectance is measured. 1000 is a white patch, (r, g, b) = (255, 255, 255), 1001 is a red patch, (r, g, b) = (255, 0, 0), and 1002 is black (R, g, b) = (0, 0, 0). On the other hand, for example, a method of calculating a measurement speed by obtaining a wavelength region where the spectral reflectance is equal to or less than a predetermined threshold value t and obtaining a ratio to the entire wavelength region is conceivable. That is, a patch having a low spectral reflectance in the entire wavelength region, such as a black patch 1002, has a minimum measurement speed because the spectral reflectance is not more than the threshold value t in the entire wavelength region. In addition, a patch having a high spectral reflectance such as a 1000 white patch has a maximum measurement speed because there is no wavelength that is equal to or less than the threshold value t. In addition, when the spectral reflectance of a specific region is low like the red patch 1001, the measurement speed is moderate. For example, when the threshold value t = 0.1, 380 to 580 nm is below the threshold value with respect to the entire wavelength region 380 to 730 nm, and the measurement speed is determined according to the ratio.

  The LUT created in this way is prepared in advance for each type of recording medium and stored in the storage device 214. Then, when the measurement speed is calculated in S602, the LUT for converting the RGB value into the measurement speed is referred to. The LUT interpolation processing is performed using tetrahedral interpolation, which is an existing general technique. Interpolation is not a feature of the present invention, and is therefore omitted. In this embodiment, the measurement speed is determined with one threshold. However, a method using a plurality of thresholds in stages, a method for obtaining speed based on information obtained by integrating spectral reflectance with wavelength, Other methods may be used as long as the same effect can be obtained, such as a method using a minimum value.

  As yet another embodiment, a description will be given of a method in which LUT creation in the second embodiment is performed on a recording medium added by a user instead of a recording medium prepared in advance by a printer driver. This can be realized by creating a LUT by the user himself / herself performing the same method as in the third embodiment after performing a procedure for adding a user-specified sheet.

  Specifically, when a recording medium is added, 9 × 9 × 9 = 729 patches in which RGB is changed in 9 stages are printed. Then, in the same manner as in Example 3, the spectral reflectance of the patch is measured by a colorimeter, and an LUT for the additional recording medium is created. The created LUT is stored in the storage device 214 in a form associated with the added recording medium, and is referred to when the measurement speed is determined using the recording medium.

  In the first embodiment and the third embodiment described above, the method of obtaining the measurement speed in a plurality of steps from the input RGB value and the spectral reflectance has been described, but a simpler configuration is also conceivable. For example, a certain standard measurement speed is determined, and the measurement speed is decreased only when the value V obtained from the input RGB value of the patch by a calculation formula exceeds a predetermined threshold, and when the value does not exceed the threshold, the standard measurement is performed. Speed. As in the case of FIG. 9B, the patches can be efficiently measured by arranging patches having the same measurement speed in parallel and continuously.

(Other examples)
In the above-described embodiment, an example in which the sensor moves on the recording medium has been described. However, the present invention is not limited to this, and the patch is optically measured during the relative movement between the recording medium and the sensor. Any form is acceptable. For example, the measurement may be performed when the recording medium moves with respect to a fixed sensor.

20 Printer device 21 PC
210 Calculation unit 211 UI
212 CPU
213 Work memory 214 Storage device 215 Data input / output device 220 Print unit 230 Measuring machine 90 Sensor 900 Patch chart 901 Patch

Claims (9)

Patch image data generation means for generating patch image data including a plurality of patches each having a different optical density;
Printing means for printing the plurality of patches on a recording medium based on the patch image data;
A sensor for optically measuring the plurality of patches during relative movement with respect to the recording medium;
Control means for controlling the speed of the relative movement between the recording medium and the sensor;
The control means is configured to control the relative movement so that a speed at which the patch having the first optical density is measured is slower than a speed at which the patch having the second optical density lower than the first optical density is measured. An image processing system characterized by controlling speed. Patch image data generation means for generating patch image data including a plurality of patches each having a different optical density;
Printing means for printing the plurality of patches on a recording medium based on the patch image data;
A sensor for optically measuring the plurality of patches during relative movement with respect to the recording medium;
Control means for controlling the speed of the relative movement between the recording medium and the sensor;
The image processing system, wherein the control unit controls the speed of the relative movement so that the higher the optical density in the plurality of patches, the slower the measurement speed.   3. The image according to claim 1, wherein the control unit controls the speed of the relative movement using an arithmetic expression for controlling the speed of the relative movement from the optical density of the plurality of patches. Processing system.   The image processing system according to claim 3, wherein the arithmetic expression is different for each type of recording medium.   The said control means controls the speed | rate of the said relative movement using the look-up table for controlling the speed | rate of the said relative movement from the optical density of these several patches. Image processing system.   The image processing system according to claim 5, wherein the look-up table is different for each type of the recording medium.   7. The patch image data generation unit generates the patch image data so as to arrange patches having the same measurement speed among the plurality of patches along the relative movement direction. The image processing system according to any one of the above.   The image processing system according to claim 1, wherein the sensor is attached to a movable carriage. A patch image data generation step for generating patch image data including a plurality of patches each having a different optical density;
A printing step of printing the plurality of patches on a recording medium based on the patch image data;
A colorimetric step of optically measuring the plurality of patches by a sensor during relative movement with respect to the recording medium;
A control step of controlling the speed of the relative movement between the recording medium and the sensor,
In the control step, the relative movement is performed so that the speed at which the patch having the first optical density is measured is slower than the speed at which the patch having the second optical density lower than the first optical density is measured. An image processing method characterized by controlling the speed of the image.

Images