JP2006038973A - Method for forming area gradation image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming an image by which an area gradation image, for example, to be used for producing a printed material can be commonly used for forming an image on an image medium having layers of a transparent medium and a reflective layer, such as for making a proof. <P>SOLUTION: The image forming method includes: a first step of outputting one image from one output means by using an ensemble of one-bit data of every dots constituting an area gradation image; and a second step of outputting another image from another output means by using the ensemble on an image medium having layers of a transparent medium and a reflective layer and at a position at ≥0.5 μm distance from the reflective layer. The second step includes a dot percent adjusting step to adjust the dot percent of dots included in the area gradation image so as to approximate another image to the one image. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention uses an area gradation image that is used for the production of printed matter, etc., and uses an image medium such as a silver salt photosensitive material in which a transparent medium and a reflective layer are laminated. The present invention relates to an image forming method for forming a toned image.

  It has become common to produce printed originals as digital data on a computer and form an area gradation image for printing through RIP. In normal color printing, at least four areas of cyan (C), magenta (M), yellow (Y), and black (K) are printed for printing, and are used for printing. Is done.

  This area gradation image is configured as an aggregate of dots (pixels), and the gradation of the image is expressed by the size of the halftone dot area. To each dot, 1-bit (binary) data is pasted, which means either a dot in a halftone dot where ink is placed in a corresponding printed matter or a dot in a missing portion without ink. ing.

  By the way, it is wasteful to make corrections after creating and trial printing a printing plate. For this reason, before the printing plate is created, it is usual to produce a proof that outputs the same area gradation image as the printed material and checks the finish of the characters and color tone of the printed material in advance. In other words, the purpose of the proof is to simulate the image quality of the printed material, and it is required to accurately reproduce the image quality of the printed material.

  In an image forming apparatus as a proofer for creating a proof, an output method different from that of this printing machine is used due to a difference in necessary number of sheets to be created. In this case, the area gradation image to be used is usually an image obtained through RIP adjusted for proof different from that for printing. This is because ink is used as a color material in this printing machine, and dot gain with thick halftone dots occurs during printing, whereas in an image forming apparatus, a color material different from ink is used due to the difference in output method. This is because the same dot gain does not always occur. For this reason, conventionally, a printing document created by a computer is usually sent to both the printing RIP and the proofing RIP, and an area gradation image is generated respectively.

  By the way, recently, as an image forming apparatus, a silver salt photosensitive material in which a photosensitive agent layer and a reflective layer, which are transparent media, are laminated is used as an image medium, and the light amount is adjusted in multiple stages using an LED or the like. An exposure method is being widely used because of its high performance. When the overall image quality of the proof obtained from such an image forming apparatus is substantially matched to the printed material, the halftone dot shape and size of the details differ from the printed material due to the difference in the RIP processing described above. was there. Therefore, when the color tone (solid color) of the 100% solid portion of the proof is adjusted, the color tone of the portion where the mesh percent is about 50% is shifted, and the color tone of the solid portion may be shifted and balanced. It was done. Furthermore, due to the difference in RIP, human error such as an error in setting a designated font and an error in setting a halftone dot shape may occur.

  Furthermore, it is generally said that the finished product is more susceptible to various conditions and is more unstable than the finished proof. For example, in color printing, a plurality of printing plates are accurately aligned with each other and sequentially printed, but there may be slight deviations in the positions of these printing plates. Using the image forming apparatus described above and a normal silver salt light-sensitive material having a certain interlayer distance between the photosensitive agent layer and the reflective layer, the image is slightly proofed by a slight deviation of the printing plate. Due to the difference in the halftone dot structure, the printed product and the proof have completely different finishes, and the image quality of the printed product when a slight plate misalignment occurs during printing is as described above. It has also been found that the image forming apparatus cannot reproduce the image.

  As described above, such a proof is a simple check means that changes to a test print. However, recently, by having a function such as adjusting the solid density, it has become possible to simulate the finish when the printing conditions change. In view of these circumstances, it can be said that there is a strong demand for exhibiting behavior similar to printing with respect to various fluctuation factors.

  Here, although there is no description regarding an image medium in which a transparent medium and a reflective layer are laminated, Patent Document 1 expresses dot gain in printing with another output device using the same area gradation image as the printing machine. A possible image calibration method is disclosed. Specifically, providing a halftone bitmap image, estimating a dot half%, calculating a target dot half% using a predetermined color calibration function, and forming a modified image. Therefore, a halftone bitmap image calibration method including a step of calculating the number N of dots to be converted to the on state and the off state and a step of converting the N dots to the on and off states is disclosed. According to this method, it is possible to obtain a proof image that matches the halftone of the printed matter by appropriately setting the color calibration function.

Although there is no description regarding RIP, there is an area gradation image forming method in which when a silver halide photosensitive material is used as a color material, the density and dot gain are controlled independently to form an area gradation image. It has been proposed (see, for example, Patent Document 2).
JP 2004-40781 A JP 2002-341470 A

  In the present invention, an area gradation image used for creating one image (for example, printed matter) is also created when another image (for example, proof) is created on an image medium in which a transparent medium and a reflective layer are laminated. An object of the present invention is to provide an image forming method that can be used in common, for example, in which a change in image quality when there is a deviation in the overlay of a plurality of images (printing plates) can be confirmed with the other images. And

  The present invention uses a set of 1-bit data for each dot constituting an area gradation image, and outputs a single image from a single output means. A second step of outputting another image to the image medium in which the transparent medium and the reflective layer are laminated from the means at a position separated by 0.5 μm or more from the reflective layer, and the second step includes: The image forming method is characterized in that the other image is approximated to the first image by including a halftone adjustment step in which halftone dots of halftone dots included in the area gradation image are adjusted.

  Here, it is preferable that the image medium is a silver salt photosensitive material, the transparent medium is an image forming layer, and at least one of the image forming layers is separated from the reflective layer by 0.5 μm or more. Further, it is preferable that the image medium is a silver salt color photosensitive material, the photosensitive agent layer includes at least a magenta coloring layer, and the other image includes a magenta image. In addition, it is preferable that the second step further includes a step of adjusting a dot color.

  Using the same set of 1-bit data as one image, a halftone dot structure almost the same as one image is reproduced on an image medium in which a transparent medium and a reflective layer are laminated. Further, even when the overlapping positions of the printing plates are deviated, it is possible to simulate the behavior of the color tone fluctuation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the entire processing flow when the image forming method of the present invention is embodied. FIG. 1 shows an example in which the printing machine 30 is used as an example of one output unit, and an image forming apparatus called a proofer is used as an example of another output unit. Further, a printed matter 31 is used as an example of one image, and a proof 41 is used as an example of another image. In addition, as an example of an aggregate of 1-bit data for each dot constituting an area gradation image, a 1-bit data obtained by dividing a print original created by the DTP system 10 by the RIP 20 and binarizing the original The aggregate 21 is used. An example of the first step is a step of obtaining the printed matter 31 from the print original 11, and an example of the second step corresponds to a step of obtaining the proof 41 from the print original 11.

  In the processing flow of FIG. 1, first, a print document 11 is created by a computer. As a computer, a DTP (Desk Top Publishing) system 10 using a description language called Postscript is often used. The printed document 11 is created as a file such as PDF (Portable Document Format), for example, and the text portion is composed of a combination of text data and font data. This is combined with graphic part data for graphic display and format data to form the whole.

  The RIP 20 separates a print document including vector data constituting a figure into element colors and develops it into bitmap data which is a set of 1-bit data that can be printed and displayed. The bitmap data obtained by RIP constitutes an area gradation image because gradation representation is performed by the size of a halftone dot (or cell) which is a set of dots. Since it is necessary to process an enormous amount of data in the RIP processing, the RIP is often configured with dedicated hardware, but may be configured with software on a computer. Even if the same printed document is used, the same result is not always obtained when different RIPs are used. Unexpected errors may occur due to different fonts installed in each RIP or different software versions.

  FIG. 2 is a conceptual diagram showing a data structure of a collection of 1-bit data obtained by RIP processing. For each dot, 1-bit data is pasted to indicate whether ink is placed (printed) on each plate, “1 (put ink)” or “0 (do not put ink)” ing. In order to simplify the description, any one of the plates (for example, the Y plate) will be described below, and a plurality of plates will be referred to if necessary.

  FIG. 3 is a diagram schematically showing a part of the area gradation image of any one plate. In FIG. 3, an image substantially corresponding to the standard number of lines is shown as an example. The image is configured as an aggregate of dots, and the halftone dot 5 that is a portion where ink is placed is composed of a set of dots 2 that are shaded to indicate that the ink is placed. Here, the bold, substantially square frame 6 means a region having a size corresponding to one period in which halftone dots appear. A process for obtaining the halftone% with reference to the area in the frame is performed. It will be described later.

  The aggregate 21 of 1-bit data obtained through the RIP process 20 is sent to the printing machine 30 and the image forming apparatus 40 as they are, and a printed matter 31 and a proof 41 are obtained from them. Here, since the processing in the RIP 20 is common to the printing press 30 and the image forming apparatus 40, the basic halftone dot structure such as the halftone dot shape and the number of lines is the same in both. However, on the other hand, the image forming apparatus 40 performs processing described below with reference to FIG. 4 to FIG. 17 or FIG. 18 in order to cope with a change in color tone caused by a difference in dot gain or color material generated during printing. It will be described later.

  This printing machine 30 uses Y (yellow), M (magenta), C (cyan), and K (black) plates, which are process colors, and a special color plate that is used as necessary, on a printing sheet in a predetermined order. Each ink is printed on top of each other. Various colors are expressed by overprinting ink. For example, in the combination of YMCK, four colors of each one, 11 colors by a combination of a plurality of plates, and a total of 16 colors including a white background are expressed.

  FIG. 4 shows a printing plate in which, when a YMCK plate, which is a process color, is used in a printed material, a solid color of 100% halftone on the printed material indicated in the color name column is indicated by white circles in the same row It means that it is expressed by overprinting. Here, “+” means that colors are overprinted. The display of the color of the plate used in the following description is as shown in FIG. It is optional to add a feature plate to this.

  As an example of the image forming apparatus 40, a photosensitive material in which a transparent medium that is a silver halide color photosensitive agent layer of Y, M, and C colors and a reflective layer are laminated as an image medium is used. An example in which the color of each row is colored by a combination of Y, M, and C coloring layers, which are the element colors of the photosensitive material, will be described. Such an image forming apparatus includes, for example, a conversion apparatus that generates an area gradation image suitable for proof formation from an aggregate 21 of 1-bit data, and a silver halide photosensitive material using an image output from the conversion apparatus. An output device for exposing with an LED or the like, and a developing device for developing the silver halide photosensitive material exposed with the output device are provided. The conversion device is provided on a general-purpose computer, an output device is connected to the control output, and a developing device is connected to the output device.

  In such an image forming apparatus, for each of 15 colors excluding white (W) in FIG. 4, each of R (red), G (green), and B (blue) for each element color of the silver halide photosensitive material. By changing the exposure amount of the LED in multiple stages, it is possible to change the density almost continuously. As a result, it is possible to cope with various color differences associated with differences in ink and printing paper grades.

  FIG. 5 is a schematic cross-sectional view showing a layer structure of a silver halide color photosensitive material 50 used as an image medium in the image forming apparatus 40 (slanting lines indicating the cross section are omitted for easy understanding of the drawing). The phenomenon that occurs peculiar to the photosensitive material will be described using this. The photosensitive material 50 includes a photosensitive agent layer from a surface layer 51 to a yellow coloring layer 56, a reflective layer composed of a titanium oxide layer 57 and a titanium oxide-containing polyethylene layer 58, a photosensitive layer composed of a paper layer 59 and a back layer 60. It consists of an agent layer and a support layer of a reflective layer, which are sequentially laminated. Such a photosensitive material can be manufactured using conventionally known materials and manufacturing methods. For example, the silver halide photosensitive material No. 1 described in Example 1 of JP-A-2002-341470 is disclosed. 101 and the manufacturing method thereof can be exemplified, but the present invention is not limited thereto.

  Here, attention is paid to the magenta coloring layer 54 in the photosensitive agent layer. FIG. 5 particularly shows a portion where the magenta image 61 is generated. The reason for paying attention to magenta is that although the same phenomenon occurs in any of the coloring layers, the phenomenon is particularly remarkable in magenta where human vision is most sensitive.

  When light rays A to C from the outside are incident on the photosensitive material 50 as shown in FIG. 5, the light rays are reflected on the surface of the reflective layer 57 as shown. It is assumed that there is an observation device (not shown) in the direction of the arrow of the reflected light shown in FIG. The light ray A reaches the reflection layer 57 without passing through the magenta image 61 at the time of incidence, but passes through the magenta image 61 at the time of emission. The light beam B reaches the observation device after passing through the magenta image 61 both when entering and exiting the photosensitive material 50. Further, the light ray C passes through the magenta image 61 at the time of incidence, but reaches the observation device without passing through the magenta image 61 at the time of emission.

  When an image is formed using the photosensitive material 50, as shown in FIG. 5, the light beam A passes through the magenta image and reaches the observation device, although there is no original image. As described above, the peripheral portion of the image has information different from the actual image density. In the case of printed matter, since a thin ink film is formed on the printing paper, light rays are reflected on the surface of the ink and the surface of the paper, and this phenomenon is unlikely to occur. For this reason, in the case of the photosensitive material 50, characteristic dot gain and color bleeding that are not present in the printed matter occur.

  A similar phenomenon also occurs in the yellow coloring layer 56 that appears to be in direct contact with the reflective layer 56. This is because the coloring layer of the light-sensitive material has a structure in which the coloring point is floating inside the transparent layer, and the reflective layer 57 is a layer coated with titanium oxide particles. It depends on what cannot be said. In particular, when the distance d between the reflective layer 57 and the color forming layer is 0.5 μm or more, this phenomenon tends to become remarkable, and countermeasures are required. Note that the distance d is the distance from the surface of the reflective layer 57 to the surface of each colored layer on the reflective layer side (the lower end of the colored layer in FIG. 5). FIG. 5 illustrates the distance d related to the magenta coloring layer 54.

  A schematic flow of processing performed in the image forming apparatus 40 of FIG. 1 is shown in FIG. When the 1-bit data aggregate 21 that has passed through the RIP 20 is input to the image forming apparatus 40, dot gain data at the time of printing measured using a standard printed material is also input (S10). Here, the dot gain of the printed material is determined by optically measuring the density of the white background of the standard printed material of 0% white and 100% solid, and the density of 50% of the intermediate halftone between them. This is obtained in advance by calculating the amount of weight in the printed matter having a halftone dot of 50% in the area gradation image of the printed matter.

  Also, the color tone level of the adjustment color for adjusting the change in image quality due to the difference in color material is input (S10). Here, the tone level means a code for specifying a multiplication rate for the YMC density of the solid portion of the proof via a multiplication rate table described later. As a result, the adjustment color can be specified. The specified adjustment color is used to adjust the difference in image quality caused by the difference in color material between the printed material and the proof. The multiplication rate varies depending on the printing conditions (ink type, paper quality, etc.), so that the image quality of the proof output from the image forming apparatus 40 using the same area gradation image as the standard printed material matches the image quality of the standard printed material. Preset in advance. Therefore, if the printing conditions are specified, the multiplication rate is also specified.

  The solid color of 100% of the proof mesh is preferably matched to the solid color of the printed material as much as possible. Hereinafter, this solid color may be referred to as a standard color in contrast to the adjustment color. When the halftone dot structure such as the size and shape of the halftone dot of the proof is matched to the printed matter, the color of one of the dots constituting the halftone dot is shifted by this adjustment color, reflecting the phenomenon specific to the photosensitive material described above. The image quality is adjusted accordingly. At that time, the multiplication factor mentioned above is used. Details will be described later.

  Next, with respect to each of the regions 6 in FIG. 3, halftone% of the image in the region is obtained using the aggregate 21 of 1-bit data (S20). Specifically, in the area gradation image composed of the aggregate 21 of 1-bit data, it is divided into regions 6 of the same size of 14 × 14 = 196 dots in FIG. The ratio of dots (hatched) in which 1-bit data is “1 (place ink)” is obtained. The obtained net% is set as the net% of the area, and is stored for each area in the net% table shown in FIG. Thereby, adjustment corresponding to halftone% of the image can be performed.

  In this way, the halftone percentage for each area of the area gradation image is obtained because the dot gain in the printed matter changes depending on the halftone percentage as shown in FIG. Because it is different. Note that tone jumps near 50% of the mesh were ignored for the sake of simplicity. In order to prevent unintentional unevenness due to the division of the region 6, a moving average between the regions may be obtained. In addition, the size of the area 6 can be appropriately enlarged or reduced. However, if this area is too large, the accuracy for obtaining the halftone ratio increases, but the calculation load increases, and further, the processing for reducing the above-described unevenness. This impairs the sharpness of the image. On the other hand, if it is too small, the calculation load is small, but the adjustment accuracy deteriorates. For this reason, it is preferable that the area be approximately 60% of the period in which halftone dots appear (14 × 14 dots in this example). Further, instead of defining the halftone for each region, the region 6 may be defined around each dot to obtain the halftone in the region, and this halftone may be defined as the half percent of the central dot. In this case, halftone% is defined for each dot.

  Note that the dot gain for the halftone is calculated according to the dot gain curve of FIG. 8 based on the dot gain at the halftone of 50% of the standard printed material input in step S10, and the dot gain of FIG. The dot gain value is stored in the table. In FIG. 9, “× 1.0” is described in the dot gain column of the line where the halftone is 50% because the dot gain data input in step S10 is multiplied by 1.0. It means to store in the column. In the other columns, values obtained according to the curve of FIG. 8 are stored.

  Next, the boundary dot of the halftone dot is specified (S30). The halftone dot boundary dot is a dot located at the outermost periphery of the halftone dot among the dots included in each halftone dot of the area gradation image. Specifically, using the filter shown in FIG. 10, the 1-bit data of the center dot 70 of the filter is “1 (put ink)”, and the inspection dot 71 located in the vicinity of 4 with respect to the center dot 70. When any one bit data is “0 (no ink is placed)”, the central dot 70 is referred to as a boundary dot. The boundary dot identification result is stored in the boundary dot table shown in FIG. Here, for each of all dots, “1” is stored if it is a boundary dot, and “0” is stored if it is not a boundary dot. Boundary dots are specified in this way because they are used to express halftone dots with a proof corresponding to the dot gain of the printed matter, to increase the halftone dots outside the boundary dots, and for the colors of the printed matter and the proof. This is because the difference in image quality due to the difference in materials is adjusted by changing the color of the boundary dots.

  Next, the dot gain for each area is obtained from the dot% table storing the dot% for each area in FIG. 7 with reference to the dot gain table in FIG. Further, the number of dot rows for thickening halftone dots is specified for each region with reference to the increased dot number table of FIG. 12 from this dot gain (S40).

  Here, the increased dot number table in FIG. 12 should be increased outside the halftone dot boundary of the proof in order to reproduce halftone dots of approximately the same size as the thick dots due to the dot gain of the printed material. It is a table storing the number of dots for which bit data should be “1”. The data of the number of dots is determined in advance corresponding to the number of lines of the area gradation image. Naturally, as the dot gain of the printed material increases, the number of dots with 1-bit data “1” to be increased outside the proof halftone dot also increases. Thereby, the size of the halftone dot of the proof can be made substantially the same size as the printed matter.

  Next, by specifying the position of the increased dot 3 using the increased number of dots for each area specified in step S40 and the boundary dot table in FIG. 11, the halftone dot of the area gradation image is determined for each area. Fatten (S50). At this time, the positions of the increasing dots are first randomly filled from the position in contact with the halftone dot 5, and are arranged randomly in the second line when the contacting position is filled and increased by one line. FIG. 13 shows a schematic diagram of a portion corresponding to FIG. 3 of the area gradation image 22 obtained in this way. The increased dot 3 is indicated by a bold line. When FIG. 13 is compared with FIG. 3, it can be seen that the increasing dots 3 that are less than one line are randomly arranged outside the halftone dot 5. As a result, in FIG. 13, the halftone dot 7 is approximately one size larger than the halftone dot 5, and the thickening of the halftone dot in printing is reproduced by proofing. Note that steps S10 to S50 in FIG. 6 are examples of constituting a half% adjustment step in which the half% of the second image is adjusted.

  By doing so, even when the printing plate is misaligned, the halftone dot structure in the proof is approximated, and an approximated image can be obtained even in such a case. Further, it is preferable to adjust the color tone of any or all of the halftone dots in order to make the image quality more approximate in response to the phenomenon peculiar to the photosensitive material described above. Accordingly, the dot color in the halftone dot 7 is based on the solid color and the adjustment color is used for the boundary dot specified earlier. This will be described subsequently.

  In the next step S60, the solid YMC density is specified from the look-up table. The look-up table is a table that stores a so-called device profile of the image forming apparatus 40, and is the color density of YMC, which is the element color of the silver halide photosensitive material, required to reproduce the 15 colors of the printed matter by proofing. It is a table which specifies the combination of. This table is obtained by combining the color of each layer of Y, M, and C in advance in the output device in a multi-stage condition, and for the color patch created by exposure / development under those conditions in the CIELAB color space. By measuring the Y, M, and C densities measured under the *, a *, b * coordinates and status T, the data of the appropriate YMC density corresponding to the color of the printed matter is stored and stored. is there. An example of this table is shown in FIG. In order to simplify the description, it is assumed that the color of the printed matter determined by the printing conditions has already been specified using values in the L * a * b * coordinate system. Further, it is assumed that an area gradation image is required for all the color plates used in the printed material.

  Next, the YMC density is designated for each dot constituting the halftone dot 7 in FIG. 13 using the lookup table in FIG. An example of the exposure table generated in this way is shown in FIG. In the table of FIG. 15, each density of Y, M, and C used in the output device is stored for each dot. Thus, the color of the dots constituting the halftone dot 7 becomes a color that matches the solid color of the printed matter.

  Next, among the dots constituting the halftone dot 7 in FIG. 13, the multiplying rate corresponding to the tone level input in step S10 is determined for the boundary dot specified in step S30 and the result stored in the table in FIG. , Read from the multiplication rate table of FIG. From this multiplication rate and the YMC density of the lookup table, the YMC density of the adjustment color is specified (step S70).

  The multiplication rate table stores predetermined multiplication rates from 0.1 times to 2.0 times depending on the color tone level. This multiplication rate is multiplied by each of the YMC densities specified in the lookup table, so that the YMC density of the adjustment color for the solid color can be generated. When the multiplication rate is less than 1.0, the color of the boundary dot is lighter than the solid color, and when the multiplication rate is greater than 1.0, the color of the boundary dot is darker than the solid color.

  Next, the YMC density data of the adjustment color is stored in the YMC density table for each dot in FIG. 15 while referring to the table in FIG. As a result, the YMC density of the boundary dot is replaced with the YMC density of the adjustment color from the solid YMC density (step S80). FIG. 17 shows a schematic diagram of the area gradation image 23 formed in this way. FIG. 17 is a schematic diagram of a portion corresponding to FIGS. 3 and 13. 13 and FIG. 17 are compared, among the dots of the halftone dots 7 in FIG. 13, the color of the increased dots 3 is a solid color, and the color of the dots 4 located at the halftone dot boundary in FIG. It can be seen that the color has been changed from (displayed with a thick diagonal line) to an adjustment color (displayed with a thin vertical line). Thereby, it is possible to eliminate the influence of a phenomenon peculiar to the photosensitive material due to the difference in the color material. Steps S30, S70, and S80 constitute an example of a color tone adjustment step.

  In the image of FIG. 17, since the halftone dot shape and size are similar to the printed matter, the same halftone dot structure deviation can be reproduced with the proof against the deviation of the printing plate. In addition, the solid color existing in the central part and the peripheral part of the halftone dot is as close as possible to the solid color of the printed matter. Furthermore, since the color tone adjustment for the phenomenon peculiar to the photosensitive material is also performed, the image quality of the entire image is also adjusted to approximate to the printed matter.

  Next, for each density of YMC, an exposure code corresponding to an output device (not shown) is specified by the exposure code table shown in FIG. 19 (step S90), and this exposure code is output to the output device (S100). Step). In the output device, each of the RGB LEDs scans the silver halide photosensitive material two-dimensionally, and exposes the silver halide photosensitive material according to the exposure amount code for each sent dot. Subsequently, the exposed photosensitive material is developed and fixed by a developing device (not shown) to create a proof. This completes the processing in the image forming apparatus.

  A proof obtained by such an image forming method uses a halftone dot shape on a target printed matter, even though an area gradation image having undergone the same RIP as that of this printing press is used as it is in the image forming apparatus 40. The halftone dot structure is very similar, and the solid color of 100% halftone can be almost the same color. In addition, despite the difference in color materials, the image quality of the entire image is excellent and it is an excellent proof. Furthermore, an approximate image can be obtained corresponding to the positional deviation of the printing plate.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the specific aspect of the invention shown above. For example, in the above description, the function of the control device of the image forming apparatus 40 is realized by a computer program executed on a general-purpose computer, but it goes without saying that it may be realized by dedicated hardware. Further, this program may be stored in a computer-readable recording medium. When storing a program in a recording medium, it is also possible to divide the program into a plurality of parts and store the divided parts in a storage medium. Here, the recording medium means a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, a hard disk built in a computer system, and the like.

  Further, the dot used as the adjustment color is not limited to the boundary dot of the original halftone dot, and may be the halftone dot after conversion, for example, the increased dot 3 shown in FIG. You may concentrate and arrange | position in the center part. In any case, it is only necessary to arrange the adjustment color dots so that the solid color can be confirmed by separating the adjustment color from the solid color, and moire or the like does not occur. It should be noted that, instead of setting only specific dots as adjustment colors, all the colors of dots constituting halftone dots may be adjusted colors separately. An example of such an image in the above example is shown in FIG. In FIG. 18, all of the dots constituting the halftone dot 9 are the adjustment color (displayed with a thin diagonal line). In this case, the adjustment color deviates from the solid color. However, this adjustment may be performed as long as the deviation is within an allowable range. In this case, the calculation load of the image forming apparatus is reduced.

  In the above description, the multiplication rate is the same for all of the YMC densities. However, for each of Y, M, and C, a different multiplication rate may be used for each adjustment color. Further, instead of using a multiplication rate table, a lookup table may be separately prepared for each adjustment color. Further, the adjustment color may not be specified by inputting the color tone level, but the color tone level may be determined in advance according to the printing conditions. The screening method is not limited to AM screening, and may be FM screening. The processing flow in FIG. 5 is not limited to this, and the order of the steps can be changed as necessary. Further, the image medium is not limited to a photosensitive material, and a transparent coating layer may be provided on the reflective layer, and a proof image may be formed thereon by an image forming apparatus such as an ink jet system. Hereinafter, it demonstrates further more concretely by an Example and a comparative example.

  First, a 100 × 100 mm standard patch print screened with a flat mesh with a mesh percentage ranging from 0% to 100% in increments of 5% and the original data (printed manuscript) of the standard patch are separated by RIP. A set of binary data of area gradation images for printing was prepared. The halftone dot shape of the area gradation image is square and the number of lines is 175 lines. In addition, the standard patch prints were also prepared with prints in which the magenta printing plate was slightly shifted. The color tone of these printed materials was measured, and the color difference between when the plate was misaligned and when it was not found was 2.3. The results are shown in Table 1. Here, the color tone is measured using a spectrocolorimeter CM-2022 manufactured by Minolta Co., Ltd., and each printed matter is side-lit using a geometric condition dn of illumination and light reception, and a xenon pulse light source, and a 2 ° visual field auxiliary standard. This was done by determining the value of L * a * b * at light D50. In addition, the dot gain at 50% of the standard patch print was measured.

  Next, the silver halide photosensitive material No. 1 described in Example 1 of JP-A-2002-341470 is disclosed. In 101, the amount of gelatin in the second layer between the first layer (reflective layer) and the third layer (magenta coloring layer) is variously changed, and the distance between the reflective layer and the image forming layer shown in Table 1 below is changed. , 0.00 μm (A), 0.39 μm (I), 0.53 μm (U), 0.65 μm (D), and 0.95 μm (E) were prepared. The magenta color forming layer is a photosensitive agent layer closest to the reflective layer, and the color tone is adjusted by mixing a small amount of yellow coupler into the magenta coupler according to a conventional method.

  Next, an image forming apparatus including the following conversion device, output device, and developing device was prepared. First, in the lookup table of the converter, the YMC density was adjusted in advance so that the solid color of the proof matched the solid color of the standard patch. Next, the area gradation image prepared above was modified. The area gradation image was divided into 15 × 15 dot regions, and halftone% was estimated from the number of dots occupied by halftone dots in each region. Further, the dot gain at each half% was obtained from the dot gain of the standard patch at the halftone 50% measured above and the curve of FIG. Further, the number of dots to be increased in each area corresponding to this dot gain was obtained for each area using the table shown in FIG. Based on the number of dots to be increased, dots for the number of dots to be increased were randomly added outside the halftone dots for each region to obtain a modified area gradation image. Furthermore, when the dot gain is measured for a proof whose halftone dot is large and corresponds to the case where there is no plate deviation, the dot gain becomes the same value as that of the printed matter without the plate deviation. As described above, the solid density of the dots constituting the halftone dots was uniformly adjusted (the density was lowered).

  The output device was adjusted so that 10 LEDs of B as a light source were arranged in the main scanning direction and the same place could be exposed by 10 LEDs by delaying the exposure timing little by little. In addition, an exposure head was prepared in which 10 LEDs were arranged in the sub-scanning direction and exposure for adjacent 10 dots could be performed at once. Similarly, for G and R, exposure heads were prepared by combining LEDs. The diameter of each beam was about 10 μm, the beams were arranged at this interval, and the sub-scanning pitch was about 100 μm. The exposure time per dot was about 100 nanoseconds. Further, the developing device was prepared so that the silver halide photosensitive material after the exposure could be subjected to the same development processing as that described in Example 1 of the publication.

  Using the modified area gradation image and the image forming apparatus prepared as described above and the photosensitive materials (a) to (e) above, the Y, M, and C area gradation images are respectively output to the output device. A proof corresponding to a standard patch print without magenta plate displacement and a proof in which the M image was shifted corresponding to a print with magenta plate displacement were obtained. The color tone of these proofs was measured in the same manner as described above, and proofs having the same thickness of the second layer but different in the presence or absence of plate misalignment were compared to determine their color difference. Note that the deviation of the M image in the proof was 3 dots corresponding to the size of the deviation of the printing plate. The results are shown in Table 1. In addition, the difference between the color differences between the proofs and the color difference between the printing plates was determined, and the difference in color difference between the proof and the printing is shown in Table 1.

  In any sample, it can be seen that a color difference approximate to the printed material can be obtained, and the deviation of the printing plate can be reproduced even by proofing. In particular, it can be seen that even a sample having a thickness of the second layer of 0.5 μm or more has a similar color difference and is a preferable mode.

  [Comparative Example 1] Using the photosensitive materials (a) to (e) in the same manner as in Example 1 except that the adjustment color was not used and the area gradation image was not modified. A proof reflecting the presence or absence of plate misregistration was created to obtain the color difference. The results are shown in Table 1. Although it can be seen that the color difference tends to be small as a whole as compared with the printed material, the thicker the second layer, the smaller the color difference and the greater the deviation from the behavior of the printed material.

  The experiment was performed in the same manner as in Example 1 except that the dot shape was a chain dot. The results are shown in Table 1. Although it can be seen that the color difference varies depending on the condition of area gradation, it is preferable because a stable improvement effect is obtained as a whole.

  The same experiment as in Example 1 was performed with the halftone dot shape being square, chain dot, and round, and the number of lines being 150, 175, and 200 lines. Table 1 shows the result of obtaining the standard deviation of the difference from the color difference variation of printing. Although good results are obtained as a whole, it can be seen that a stable effect can be obtained particularly in a sample having a thickness of the second layer of 0.5 μm or more.

  The dot gain measured by the proof is not adjusted by adjusting the solid density, but is changed so that only the boundary dot density described above is adjusted to adjust the dot gain. Then, the evaluation of Examples 1 to 3 was repeated. It was confirmed that the same effects as in Examples 1 to 3 were obtained again. Furthermore, when a full-color image was created by this method, it was confirmed that a high-quality proof image similar to that created by the conventional method could be obtained.

1 is a schematic block diagram illustrating an overall flow of an image forming method. It is the conceptual diagram which showed the example of the data structure of an area gradation image. It is the schematic diagram which showed the example of the area gradation image regarding any one plate. FIG. 4 is a diagram illustrating printing of a color plate for each color that can be expressed by the printing press. It is sectional drawing which showed the outline of the layer structure of the photosensitive material typically. 3 is a flowchart showing an outline of a processing flow in the image forming apparatus. It is the conceptual diagram which showed the example of the net | network% table. It is the figure which showed the example of the dot gain curve with respect to halftone. It is the conceptual diagram which showed the example of the dot gain table. It is the conceptual diagram which showed the example of the filter. It is the conceptual diagram which showed the example of the table which specifies a boundary dot. It is the conceptual diagram which showed the example of the increase dot number table. It is the schematic diagram which showed the example of the area gradation image which reflected the dot gain. It is the conceptual diagram which showed the example of the lookup table. It is the conceptual diagram which showed the example of the exposure table. It is the conceptual diagram which showed the example of the multiplication table. It is the schematic diagram which showed the example of the modified area gradation image. It is the schematic diagram which showed the other example of the modified area gradation image. It is the conceptual diagram which showed the example of the exposure amount code table.

Explanation of symbols

1 dot (non-halftone dot)
2 dots (halftone dot)
3 dots (halftone dot)
4 dots (original halftone dot boundary)
5 dot 6 area 7 dot 8 and 9 dot 70 center dot 71 inspection dot

Claims (4)

  A first step of outputting one image from one output means using an aggregate of 1-bit data for each dot constituting an area gradation image, and a transparent medium from the other output means using the aggregate And a second step of outputting another image at a position separated by 0.5 μm or more from the reflective layer on the image medium in which the reflection layer and the reflective layer are laminated, and the second step includes the area gradation An image forming method, comprising: a half% adjusting step for adjusting halftone dots of halftone dots included in an image, wherein the other image is approximated to the first image.   The image medium is a silver salt photosensitive material, the transparent medium is an image forming layer, and at least one of the image forming layers is separated from the reflective layer by 0.5 μm or more. The image forming method described.   3. The image formation according to claim 1, wherein the image medium is a silver salt color photosensitive material, the photosensitive layer includes at least a magenta coloring layer, and the other image includes a magenta image. Method. The image forming method according to claim 1, wherein the second step further includes a step of adjusting a dot color.

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