JP2006297691A - Printing apparatus for printing image on skin and printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of printing an image with a good quality of image as desired on the surface of the skin of a human body. <P>SOLUTION: An apparatus for delivering ink droplets and printing the image on the skin of the human body is equipped with a measuring means for measuring data related to the color shade of the skin, and an image data converting means for converting image data of the image to be printed to the data of the amount of ink. In this printing apparatus, the image data converting means converts the image data to the data of the amount of the ink in taking the data related to the color shade measured into consideration. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for printing an image on the surface of a human skin.

  2. Description of the Related Art Printing apparatuses that eject ink droplets onto a printing medium and print an image have been widely used as an output apparatus for an image created by a computer or an image taken by a digital camera. In addition, as for the printing medium used in such a printing apparatus, various media such as a transparent resin film such as a so-called OHP sheet and a cloth such as a T-shirt have come to be used today. ing. Furthermore, a technique for printing an image on the skin of a human body or the surface of a claw has been proposed (Patent Document 1).

JP 2000-194838 A

  However, in the case of printing an image on the human skin, there is a problem that a good image quality as expected may not be obtained even if the image is simply printed.

  The present invention has been made to solve the above-described problems of the prior art, and an object thereof is to provide a technique capable of printing an image with a good image quality as expected on the surface of the human skin. And

In order to solve at least a part of the problems described above, the printing apparatus of the present invention employs the following configuration. That is,
A printing device that prints an image by ejecting ink droplets onto the skin of a human body,
A color-related data measuring means for measuring data related to the skin color of the skin where the image is to be printed;
Image data conversion means for converting the image data of the image to be printed into ink amount data corresponding to the ink amount for printing the image;
Image forming means for forming the image by ejecting ink droplets on the skin based on the ink amount data; and
The gist of the image data converting means is means for converting the image data into the ink amount data in consideration of the measured color-related data.

Also, the printing method of the present invention corresponding to the above printing apparatus is
A printing method for printing an image by ejecting ink droplets on a human skin,
A first step of measuring color-related data related to the skin color of the area where the image is to be printed;
A second step of converting the image data of the image to be printed into ink amount data corresponding to the ink amount for printing the image;
A third step of forming the image by ejecting ink droplets on the skin based on the ink amount data; and
The gist of the second step is a step of converting the image data into the ink amount data in consideration of the measured color-related data.

  In such a printing apparatus and printing method of the present invention, prior to printing an image on the surface of the human skin, data related to the color of the skin where the image is to be printed (color-related data) is measured. Here, the skin tone is a concept including the color and brightness of the skin. Next, the image data of the image to be printed is converted into ink amount data corresponding to the ink amount for printing the image. Further, when converting the image data, it is converted into the ink amount data in consideration of the color of the skin by considering the measured color-related data. Based on the ink amount data thus obtained, an image is printed by ejecting ink droplets onto the skin.

  In this way, the image can be printed while adjusting the amount of ink according to the color of the skin on which the image is to be printed, so the image can be printed with the desired image quality regardless of the color of the skin. It becomes possible to do.

  In such a printing apparatus, the image data may be converted into ink amount data as follows. First, a plurality of sets of correspondence relationships between image data and ink amount data are stored in advance. Next, after measuring the data related to the skin tone (color-related data), the corresponding relationship was selected from a plurality of stored correspondence relationships according to the obtained color-related data, and then selected. The image data may be converted according to the correspondence relationship.

  In this way, it is possible to convert image data into appropriate ink amount data by setting an appropriate correspondence relationship in advance according to the skin tone, and in turn, printing an image with good image quality. can do. In addition, if the number of types of correspondences to be set is increased, the image data can be converted into more appropriate ink amount data, so that the print image quality can be improved.

  For simplicity, the image data may be converted into ink amount data as follows. First, at least data relating to the brightness of the skin is measured as the color-related data. Next, the image data may be converted so that the amount of ink increases as the brightness decreases (the skin becomes darker).

  When the skin color to be printed becomes black, the color of the image tends to be difficult to understand as compared with the case of printing on white skin. Therefore, if the image data is converted so that the amount of ink increases as the skin color becomes black, the color of the printed image can be easily recognized. As a result, the image quality can be easily improved, which is preferable.

  In the printing apparatus and printing method described above, an image may be printed as follows. That is, as the image is printed by ejecting ink droplets while reciprocating the ejection head on the skin, the spacing member is brought into contact with the surface of the skin prior to ejection of the ink droplets. It is good also as keeping the space | interval with the surface of skin within the predetermined range.

  In the case of printing an image by ejecting ink droplets while reciprocating the ejection head, it is known that the image quality deteriorates if the distance between the ejection head and the surface of the skin changes. Therefore, if the distance between the ejection head and the surface of the skin is kept within a predetermined range prior to ejection of the ink droplets, it is possible to print an image with better image quality.

  Further, when maintaining the distance between the ejection head and the surface of the skin, a first holding member that contacts the skin surface at a plurality of locations outside the region where the image is to be printed, and the region within which the image is to be printed The distance between the ejection head and the surface of the skin may be maintained using a second holding member that moves with the ejection head while contacting the skin surface.

  If the first holding member is used, the gap between the ejection head and the surface of the skin can be generally maintained over a wide range within the region by contacting the skin at a plurality of locations outside the region where the image is to be printed. However, the distance between the ejection head and the skin surface tends to be narrow at a portion far from the contact point with the skin, for example, at the center of the region. On the other hand, the second holding member is in contact with the surface of the skin in the region where the image is to be printed, and moves together with the discharge head. Can be maintained. However, when only the second holding member is used, the interval is held only in the vicinity of the contact portion, and the interval is suddenly narrowed toward the periphery. Therefore, by using the first holding member and the second holding member, the distance between the ejection head and the skin surface can be held within a predetermined range over the entire range of the area where the image is to be printed. It becomes.

Furthermore, the present invention can be realized using a computer by causing a computer to read a program for realizing the above-described printing method and executing a predetermined function. Therefore, the present invention includes the following program or a mode as a recording medium on which the program is recorded. That is, the program of the present invention corresponding to the printing method described above is
A program for realizing, using a computer, a method for printing an image by ejecting ink droplets on the skin of a human body,
A first function for measuring color-related data related to the skin color of the area where the image is to be printed;
A second function for converting the image data of the image to be printed into ink amount data corresponding to the ink amount for printing the image;
A third function for forming the image is realized using a computer by ejecting ink droplets onto the skin based on the ink amount data, and
The gist of the second function is that it converts the image data into the ink amount data while taking into account the measured color-related data.

The recording medium of the present invention corresponding to the above program is
A recording medium in which a program for printing an image by ejecting ink droplets on the skin of a human body is recorded in a computer-readable manner,
A first function for measuring color-related data related to the skin color of the area where the image is to be printed;
A second function for converting the image data of the image to be printed into ink amount data corresponding to the ink amount for printing the image;
Storing a program that uses a computer to realize the third function of forming the image by ejecting ink droplets onto the skin based on the ink amount data;
The gist of the second function is that it converts the image data into the ink amount data while taking into account the measured color-related data.

  By loading these programs into a computer and realizing the various functions described above, it is possible to print images with good image quality as expected on the surface of the skin, regardless of the color of the skin. Become.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Device configuration:
B. Image printing process of the first embodiment:
C. Image printing process of the second embodiment:

A. Device configuration :
FIG. 1 is an explanatory diagram showing the overall configuration of a printing apparatus 10 that prints an image on the skin surface of a human body. As shown in the figure, the printing apparatus 10 according to the present embodiment includes a display screen 110 that mainly controls an interface with a controller 100 as a center, and a main body 130 that performs image printing. The upper and lower stages 140 are configured to move up and down with a portion on which an image of a human body is to be printed. A printing unit 200 that actually prints an image is provided inside the main body unit 130, and the printing unit 200 slides inside the main body unit 130 while being guided by the drive shaft 202 and the sliding shaft 204. The sliding stage 201 includes various mechanisms mounted on the sliding stage 201. The control unit 100 is also connected with a data reading unit 150 for reading data from various recording media such as a flexible disk and a compact disk, and a scanner 120 for reading an image output on printing paper. Yes.

  FIG. 2 is an explanatory diagram showing the structure of the printing unit 200 by taking a cross section along a plane perpendicular to the drive shaft 202 and the slide shaft 204. As shown in the figure, the printing unit 200 is roughly composed of a slide stage 201 that slides while being guided by a drive shaft 202 and a slide shaft 204, a carriage 240 that is assembled to the slide stage 201, and the like. Has been. The driving mechanism of the sliding stage 201 will be described later with reference to another drawing. The carriage 240 includes an ink cartridge 241 containing black (K) ink, an ink cartridge 242 containing cyan (C) ink, an ink cartridge 243 containing magenta (M) ink, and a yellow (Y ) An ink cartridge 244 containing ink is mounted. Also, on the bottom surface of the carriage 240, an ejection head 245 that ejects ink droplets of K ink, an ejection head 246 that ejects ink droplets of C ink, an ejection head 247 that ejects ink droplets of M ink, and Y ink The ejection heads 248 that eject the ink droplets are provided, and one holding member 236 is provided on each end of each of the ejection heads 245 to 248 so as to be parallel to the direction in which the heads are arranged. The configuration of the bottom surface of the carriage 240 will be described later with reference to another drawing.

  A guide race 233 is provided inside the slide stage 201, and the carriage 240 is slidable in the direction perpendicular to the drive shaft 202 and the slide shaft 204 while being guided by the guide race 233. A carriage motor 230 and a pulley 232 are provided on the upper surface of the sliding stage 201, and a drive belt 231 is stretched between the carriage motor 230 and the pulley 232. The carriage 240 is attached to the drive belt 231. When the drive belt 231 is driven by the carriage motor 230, the carriage 240 can be reciprocated. An origin switch 234 for detecting the origin position of the carriage 240 is also provided on the upper surface of the sliding stage 201. Hereinafter, the direction in which the carriage 240 reciprocates is referred to as “main scanning direction”, and the direction in which the sliding stage 201 slides (that is, the direction perpendicular to the main scanning direction) is referred to as “sub-scanning direction”. I will call it.

  An optical sensor 250 is provided on the side surface of the carriage 240. In the optical sensor 250, there are an irradiation unit that irradiates white light toward the skin surface on which an image is to be printed, a light detection unit that collects the reflected light from the skin surface, and detects the light intensity. It has been incorporated.

  FIG. 3 is an explanatory view showing the internal structure of the main body 130 and the driving mechanism of the sliding stage 201 by taking a longitudinal section of the main body 130 in a plane parallel to the drive shaft 202 and the slide shaft 204. As shown in the figure, a printing unit 200 is provided in the approximate center of the main body 130, an upper and lower stage 140 is provided below the printing unit 200, and a digital camera 160 is provided above the printing unit 200. ing. An actuator is incorporated in the upper and lower stages 140, and a portion on which an image is to be printed can be placed on the upper surface of the stage and moved up and down. In addition, the digital camera 160 is mounted at a position where an image of a body part placed on the upper surface of the upper and lower stage 140 can be taken.

  As shown in FIGS. 1 and 2, the slide stage 201 of the printing unit 200 is attached to the drive shaft 202 and the slide shaft 204. A spiral male screw is cut on the outer peripheral surface of the drive shaft 202, and a female screw is cut on the inner peripheral surface of the corresponding portion of the sliding stage 201 and fitted to each other. In addition, a drive motor 206 is connected to one end of the drive shaft 202, and when the drive motor 202 is rotated by the drive motor 206, the slide stage 201 is moved in the sub-scanning direction (the drive shaft 202 and the slide) according to the rotation angle. It moves in the direction of the axis 204). In addition, a rotary encoder for detecting the rotation angle of the drive shaft 202 is incorporated in the drive motor 206. The control unit 100 can accurately control the amount of movement of the slide stage 201 by controlling the rotation angle of the drive shaft 202 by controlling the drive motor 206 while feeding back the output of the rotary encoder. It has become.

  A holding plate 238 is provided immediately below the sliding stage 201, and the holding plate 238 has a distance from the discharge heads 245 to 248 provided on the bottom surface of the carriage 240 to the bottom surface of the holding plate 238. It is fixed to the main body 130 at a position at a predetermined interval. Further, the front end of the holding member 236 that protrudes from the bottom surface of the carriage 240 is in the same position as the bottom surface of the holding plate 238.

  FIG. 4 is an explanatory view showing the shape of the holding plate 238 when viewed from above. For reference, in FIG. 4, the drive shaft 202, the slide shaft 204, and the slide stage 201 are also indicated by thin one-dot chain lines. A hatched area 239a in the drawing represents a range in which an image can be printed. A region 239b protruding to the side of the printable range is a portion provided for retracting the ejection heads 245 to 248 when the image is not printed. The holding plate 238 is provided with an opening 239 so as to surround the movable range of the discharge heads 245 to 248.

  As described above, the holding plate 238 having the opening 239 is provided immediately below the sliding stage 201. For this reason, when an object to be printed (part of the body) is placed on the upper and lower stages 140 and the upper surface of the stage is raised, the surface of the body is pressed against the holding plate 238 and held. The opening 239 of the plate 238 comes to the surface of the skin whose periphery is pressed by the holding plate 238 and made flat. As described above, the distance from the tip of the discharge heads 245 to 248 provided on the bottom surface of the carriage 240 to the lower surface of the holding plate 238 is set to a predetermined value. The distance between the tip of 248 and the skin surface is maintained at a predetermined distance.

  However, since the surface of the body is elastic, the surface of the skin slightly rises at the opening 239 of the holding plate 238. Therefore, in the vicinity of the center of the opening 239, the tips of the discharge heads 245 to 248 and the skin surface The distance becomes slightly narrower. In view of these points, a holding member 236 protrudes from the bottom surface of the carriage 240, and the front end of the holding member 236 is located on the lower surface of the holding plate 238. For this reason, the portion where the skin surface is slightly raised is pressed by the holding member 236, and the distance between the tip of the ejection heads 245 to 248 and the skin surface is maintained at a predetermined value. The holding member 236 protrudes from the bottom surface of the carriage 240 and moves together with the carriage 240. As a result, the distance between the tips of the ejection heads 245 to 248 and the skin surface is always kept at a predetermined value.

  FIG. 5 is an explanatory diagram showing the configuration of the bottom surface of the carriage 240. As shown in the drawing, on the bottom surface of the carriage 240, a K ink ejection head 245, a C ink ejection head 246, an M ink ejection head 247, and a Y ink ejection head 248 are arranged side by side in the main scanning direction. ing. In each of these ejection heads, a plurality of nozzles Nz for ejecting ink droplets are formed in a staggered manner with an interval of the nozzle pitch k. Further, holding members 236 are provided on both sides of the ejection heads 245 to 248 in the sub-scanning direction.

  The operations of the upper and lower stages 140, the display screen 110, the digital camera 160, the data reading unit 150, etc., including the printing unit 200 described above, are all controlled by the control unit 100. FIG. 6 is an explanatory diagram illustrating the configuration of the control unit 100 that controls the overall operation of the printing apparatus 10. The control unit 100 is mainly composed of a CPU, a ROM storing various data and programs, a RAM storing temporary data, a VIF (video interface) for driving the display screen 110, various types A PIF (peripheral device interface) and the like for exchanging data with peripheral devices are connected to each other via a bus. The display screen 110 is connected to the control unit 100 via the VIF. Also, external devices such as the scanner 120, the upper and lower stages 140, the data reading unit 150, and the digital camera 160 are connected to the control unit 100 via the PIF. Furthermore, the carriage 240, carriage motor 230, drive motor 206, origin switch 234, and the like provided in the printing unit 200 described above are also connected to the control unit 100 via the PIF. As described above, the display unit 110 is connected to the control unit 100 via the VIF, and the printing unit 200, the upper and lower stage 140, the data reading unit 150, the digital camera 160, and the like are connected to the control unit 100 via the PIF. The entire operation of the apparatus 10 is configured to be controllable.

  Since the printing apparatus 10 having the above-described configuration prints an image on the surface of the skin as follows, the image is printed with a good image quality as expected on any color skin. It is possible. Hereinafter, the process of printing an image on the skin surface of the human body (image printing process) will be described in detail.

B. Image printing process of the first embodiment:
FIG. 7 is a flowchart showing the flow of the image printing process of the first embodiment. This process is a process executed by a CPU built in the control unit 100 that controls the operation of the printing apparatus 10 shown in FIG. Hereinafter, it demonstrates according to a flowchart.

  When the image printing process of the first embodiment is started, the CPU of the control unit 100 first starts a process (print image selection process) for selecting an image to be printed (step S100). Such processing is performed while the operator of the printing apparatus 10 confirms the display screen 110 incorporated in the apparatus.

  FIG. 8 is a flowchart showing the flow of print image selection processing performed to select an image to be printed. When the print image selection process is started, first, the CPU of the control unit 100 displays a plurality of print images stored in advance on the display screen 110 of the printing apparatus 10 (step S102). FIG. 9 is an explanatory diagram illustrating a state in which a plurality of print images are displayed on the display screen 110. In FIG. 9, only three types of images are displayed, but more images may be displayed.

  Next, it is determined whether or not a print image has been selected (step S104). The display screen 110 is a so-called touch panel, and an image can be selected by touching a portion where “OK” is displayed after touching a portion where the image is displayed on the screen. If the user wants to change the image, he / she touches the portion where “Cancel” is displayed. FIG. 9 shows a state where a butterfly image is touched. Furthermore, instead of selecting from the displayed images, when printing an image prepared in advance by the operator of the printing apparatus 10, “original image” is selected. In step S104, the above processing is performed until any image displayed on the display screen 110 is selected and it is confirmed that “OK” is pressed.

  If any image on the display screen 110 is selected and it is confirmed that “OK” is pressed (step S104: yes), it is determined whether or not the selected image is an original image. (Step S106). When it is determined that the selected image is not the original image (step S106: no), the print image stored in advance in the control unit 100 is selected, and the selected image is selected from the ROM of the control unit 100. A process of reading the image data of the print image is performed (step S112).

  On the other hand, if “original image” is selected as the print image (step S106: yes), a screen for acquiring the original image is displayed (step S108). FIG. 10 is an explanatory diagram illustrating a state in which a screen for acquiring an original image is displayed on the display screen 110. When the original image is recorded as electronic data on a recording medium such as a flexible disk or a memory, the user touches the portion where “Read data from recording medium” is displayed on the left side of the display screen 110. Then, after displaying that the recording medium is to be inserted, the image data of the original image is read from the recording medium (step S114). On the other hand, when using an image output on a print sheet or a handwritten image as an original image, the user touches the portion displayed on the right side of the display screen 110 where “read an image with a scanner” is displayed. Then, after displaying that the original image is set on the scanner 120 incorporated in the printing apparatus 10, the set image is captured by the scanner 120 as image data (step S116).

  In the printing apparatus 10 of the present embodiment, the image data is so-called RGB image data expressed by a combination of gradation values of RGB colors. Of course, the format of the image data is not limited to RGB image data, and can be image data expressed by a luminance signal and two types of color difference signals, which are widely used in so-called television broadcasting. Alternatively, the image data may be expressed by the coordinate values of an XYZ color space or Lab color space that is widely used as a so-called color space.

  When a print image is selected, finally, a process for setting a size (image size) for printing the image is performed (step S118). Here, for convenience, it is assumed that one of three sizes of “large”, “medium”, and “small” is selected on the display screen 110, but the image size can be changed continuously. Also good. Alternatively, the image size may be set by changing the aspect ratio. Furthermore, a digital camera is incorporated in the printing apparatus 10 in advance, a part of the body including the part to be printed is photographed, and the photographed image and the print image are superimposed on the display screen 110, The image size may be settable.

  When the print image is selected and the image size of the print image is set as described above, the print image selection process shown in FIG. 8 is terminated and the process returns to the image print process shown in FIG.

  In the image printing process, after returning from the print image selection process, a process of converting the image data of the selected print image into a print resolution is performed (step S110 in FIG. 7). That is, since the image size has already been set in the above-described print image selection process, it is possible to determine how many pixels each of the actually printed images will be in both the vertical and horizontal directions. Therefore, processing for determining image data for each pixel of the actually printed image is performed from the image data of the printed image.

  When the number of pixels constituting the image data is larger than the number of pixels of the image to be actually printed, the number of pixels is reduced by thinning out the pixels of the image data at a certain rate. Conversely, if the number of pixels that make up the image data is less than the number of pixels in the image that is actually printed, new pixels are added at a certain rate, and interpolation is performed between adjacent pixels. The RGB gradation value for the selected pixel is calculated. In step S110 of FIG. 7, in this way, processing for determining RGB gradation values for each pixel of the image to be actually printed is performed.

  Next, the brightness of the skin on which an image is to be printed is measured (step S120). In other words, since the brightness of human skin varies from white skin to sunburn and black skin, even if the image is printed in the same way, the impression of the image obtained depends on the brightness of the skin. End up. Therefore, in order to correct the influence of the brightness of the skin and print the image appropriately, the brightness of the skin is measured in advance before printing the image.

  In the process of measuring the brightness of the skin, first, a screen as shown in FIG. 11 is displayed on the display screen 110. According to the display on the screen, the operator of the printing apparatus 10 places a body part on which an image is to be printed on the upper and lower stages 140 and lightly presses a portion where “OK” is displayed on the display screen 110. Then, the upper surface of the stage is raised by the actuator built in the upper and lower stages 140, and a portion where an image on the skin is to be printed is pressed against the opening 239 of the holding plate 238. In this state, by moving the slide stage 201 in the sub-scanning direction while reciprocating the carriage 240 in the main scanning direction, the lightness of the skin is measured over the entire range where the image is to be printed. The brightness of the skin can be measured by an optical sensor 250 attached to the carriage 240. That is, as described above, an irradiation unit that emits white light is provided inside the optical sensor 250, and light is emitted from the irradiation unit toward the skin. Next, the intensity of light reflected from the skin is detected by a light detection unit built in the optical sensor 250. Since the reflected light becomes weaker as the lightness of the skin becomes smaller (the skin becomes darker), the lightness of the skin can be measured by detecting the intensity of the reflected light.

  Here, the description has been made on the assumption that the brightness of the skin is measured over the entire area where the image is printed. However, since the brightness of the skin does not vary greatly depending on the location in normal cases, only the carriage 240 is main scanned without sub-scanning the sliding stage 201 to measure the brightness of a part of the skin. Also good. As described above, in step S120 in FIG. 7, the lightness of the skin of the portion where the image is to be printed is measured in this way.

  Next, color conversion of the image data is performed (step S130). In the color conversion process, RGB image data expressed by a combination of R, G, and B gradation values is converted into data corresponding to the ink amounts of the C, M, Y, and K color inks mounted on the carriage 240 ( Ink amount data).

  Color conversion is performed by referring to a three-dimensional numerical table called a color conversion table (LUT). FIG. 12 is an explanatory diagram conceptually showing a color conversion table (LUT) referred to in color conversion. Assuming that the gradation value of each color of RGB can take a value from 0 to 255, considering a color space in which the gradation values of each of R, G, and B are taken on three orthogonal axes as shown in FIG. The image data can be associated with a point inside a cube (color solid) whose origin is the apex and whose side is 255 in length. Therefore, if the color solid is subdivided into a grid shape perpendicular to the RGB axes, each grid point can be associated with each RGB image data. Therefore, a combination of gradation values corresponding to the use amounts of the respective color inks such as C, M, Y, and K is stored in advance at each grid point associated with the RGB image data in this way. In this way, when RGB image data is given, the gradation values stored in the grid points are read out as follows, so that the RGB image data is converted into data corresponding to the usage amount of each color ink ( Ink amount data) can be quickly converted.

  For example, if the R component of the image data is RA, the G component is RG, and the B component is RB, this image data is associated with point A in the color space (see FIG. 12). Therefore, a cube dV containing point A is detected from the fine cubes that subdivide the color solid, and the gradation values of the color inks stored in the lattice points of the cube dV are read out. Then, if the interpolation calculation is performed from the gradation values of these grid points, the gradation value at the point A can be obtained. As described above, the color conversion table LUT is a gradation value corresponding to the use amount of each color ink such as C, M, Y, and K at each grid point indicated by a combination of gradation values of RGB colors. It can be thought of as a three-dimensional number table that stores combinations of With reference to the color conversion table, it is possible to quickly convert the RGB image data into ink amount data corresponding to the usage amount of each color ink.

  When the ink amount data for each pixel is obtained by performing the color conversion as described above, the ink amount data is corrected according to the previously measured skin brightness (step S140).

  FIG. 13 is a flowchart showing a flow of processing for correcting ink amount data obtained by color conversion. FIG. 14 is an explanatory diagram conceptually showing how ink amount data is corrected. Hereinafter, the ink amount data correction process will be described with reference to FIGS. 13 and 14.

  When the ink amount data correction process is started, first, a process of multiplying the ink amount data of each color ink of C, M, Y, and K obtained by the color conversion by a correction coefficient corresponding to the brightness of the skin is performed (FIG. 13 step S142). The brightness of the skin is measured in advance prior to image printing (see step S120 in FIG. 7). The correction coefficient is set to an appropriate value according to the brightness of the skin, and is stored in advance in the ROM of the control unit 100 as a table.

  FIG. 15 is an explanatory diagram conceptually showing a table in which an appropriate correction coefficient is set according to the brightness of the skin. As shown in the figure, a correction coefficient close to “1.0” is set for a numerical value with a large (bright) skin brightness, but it is larger as the brightness value is smaller (darker). Value correction coefficient is set. In other words, when the lightness of the skin on which the image is to be printed is high (when the skin is whitish), the ink amount data obtained by color conversion is used as it is, but when the lightness of the skin is low (when the skin is dark) In such a case, correction is performed to increase the ink amount according to the lightness.

  After the ink amount data for each pixel is thus multiplied by the correction coefficient (step S142 in FIG. 13), the total value of the ink amount data for each color multiplied by the correction coefficient is calculated for each pixel (step S144). Then, it is determined whether or not the total value is within a predetermined allowable range (step S146). Such processing will be described with reference to FIG.

  FIG. 14A is an explanatory diagram illustrating ink amount data obtained by color conversion for a certain pixel. In the present embodiment, ink amount data for each color can be obtained by color conversion in correspondence with printing an image using four colors of C, M, Y, and K. In FIG. 14A, for convenience of explanation, the ink amount data is displayed as having a value other than “0” for any of C, M, Y, and K, but the value “0” is displayed. Ink amount data may be included.

  In addition, the right end of FIG. 14A shows a total value of the ink amount data of each color. An allowable upper limit value is set for the total value of the ink amount data, and the ink amount data for each color is set to a value such that the total value does not exceed the allowable upper limit value. This is due to the following reason. As described above, the printing apparatus 10 according to the present embodiment prints an image by ejecting ink droplets onto the skin surface. The ink droplets ejected onto the skin dries quickly while remaining on the surface without penetrating into the skin. However, when too many ink droplets are ejected, drying cannot catch up. As a result, a situation such as mixing with ink droplets ejected next to each other and the color becoming cloudy occurs, and the image quality deteriorates. In order to prevent this from happening, an allowable upper limit value is provided for the total value of the ink amount data. In FIG. 14, the allowable upper limit value of the total value is represented by a two-dot chain line.

  This allowable upper limit value is set to the following value with respect to the maximum value of the ink amount data that each color ink can take. That is, it is set to a value that is larger than the total value of the ink amount data for two colors but smaller than the total value of the ink amount data for three colors. Here, the allowable upper limit of the amount of ink that can be ejected onto the skin is a value that is naturally determined within a certain range depending on the state of the skin. In view of this, the fact that the total value of the ink amount data for the three colors cannot exceed the allowable upper limit value, conversely, the dye concentration of each color ink so that the total value does not exceed the allowable upper limit value. (Or pigment concentration) must be set appropriately. If the density of each color ink is set appropriately, a process called “under color removal” described later is performed, so that the total value of the ink amount data of each color ink falls within the allowable upper limit value. Is possible. Such ink amount data of each color is set at each grid point of the color conversion table shown in FIG. In step S142 of the ink amount data correction process shown in FIG. 13, the ink amount data of each color is multiplied by a correction coefficient corresponding to the brightness of the skin.

  FIG. 14B shows a result obtained by multiplying the ink amount data of each color by a correction coefficient. As described above, the ink amount data of each color obtained by color conversion is set so that the total value is equal to or less than the allowable upper limit value. However, after the ink amount data for each color is multiplied by the correction coefficient, the total value of the ink amount data is not always less than the allowable upper limit value. Therefore, the ink amount data after multiplication by the correction coefficient is summed (step S144 in FIG. 13), and it is determined whether or not the obtained total value is equal to or less than the allowable upper limit value (step S144). If the total value of the ink amount data is within the allowable upper limit after multiplication by the correction coefficient (step S144: yes), the ink amount data correction process is terminated as it is, and the image printing shown in FIG. Return to processing.

  On the other hand, when it is determined that the total value of the ink amount data of each color has exceeded the allowable upper limit value by multiplying by the correction coefficient (step S146: no), the ink droplet is ejected according to the ink amount data as it is. If so, the image quality will deteriorate. Therefore, as described below, a process of correcting the ink amount data after the correction coefficient multiplication is performed so that the total value of the ink amount data of each color falls within the allowable upper limit value.

  In correcting the ink amount data, first, consider replacing each ink of C, M, and Y with K ink. According to the so-called subtractive color mixing principle, it is known that black can be obtained by mixing C, M and Y colors. From this, it should be possible to replace the C, M, and Y ink amount data with the same amount of K ink amount data in the same amount. The operation of replacing the three inks C, M, and Y with K ink in this way is called “under color removal”. If the undercolor removal is performed, the three inks C, M, and Y can be replaced with one K ink, so that the total amount of ink can be reduced to one third.

  Therefore, first, a value (ink excess amount) obtained by subtracting the allowable upper limit value from the total value of the ink amount data after the correction coefficient multiplication is calculated (step S148). Next, half of the obtained ink excess amount is subtracted from the ink amount data of each color of C, M, and Y, and half of the ink excess amount is added to the K ink amount data (steps S150 and S152). That is, the under color is removed by half of the excess ink amount. In this way, the total value of the ink amount data can be suppressed to just the allowable upper limit value. FIG. 14C conceptually shows a state in which the total value of the ink amount data is suppressed to the allowable upper limit value by performing the undercolor removal as described above. That is, the ink amount data for C, M, and Y is decreased by half of the ink excess amount, and the ink amount data for K is increased by half of the ink excess amount. The white arrows shown in the figure schematically show how the ink amount data for each color is increased or decreased as the undercolor is removed.

  As described above, in the ink amount data correction process of FIG. 13, the ink amount data obtained by color conversion is multiplied by the correction coefficient corresponding to the lightness of the skin to correct the ink amount data. . If the total value of the ink amount data after multiplication does not exceed the allowable upper limit value, the process is terminated as it is. If the total value exceeds the allowable upper limit value, the ink of each color is set so that the total value falls within the allowable upper limit value. Processing to correct the quantity data is performed. When the ink amount data is obtained in this way, the process returns to the image printing process shown in FIG.

  As shown in FIG. 7, in the image printing process, after returning from the process of correcting the ink amount data, a process called “halftone” is started (step S160). Halftone processing is the following processing. The ink amount data can take values from gradation value 0 to gradation value 255. On the other hand, since the printing unit 200 prints an image by ejecting ink droplets to form dots, it can only take the state of whether or not to form dots for each pixel. Therefore, it is necessary to convert ink amount data having 256 gradations into data (dot data) expressed by the presence or absence of dot formation for each pixel. Halftone processing is processing for converting ink amount data into dot data in this way.

  As a method for performing the halftone process, various methods such as an error diffusion method and a dither method can be applied. The error diffusion method is to determine whether or not dots are formed for a certain pixel so as to diffuse an error in gradation expression generated in that pixel to surrounding pixels and to eliminate the error diffused from the surroundings. This is a method of determining the presence or absence of dot formation for each pixel. In the dither method, the threshold value randomly set in the dither matrix and the ink amount data are compared for each pixel, and it is determined that a dot is formed in a pixel having a larger ink amount data. This is a method of obtaining dot data for each pixel by determining that a dot is not formed for a larger pixel. In the image printing process of the present embodiment, halftone processing can be performed using either the error diffusion method or the dither method, but here it is assumed that the halftone processing is performed using the dither method. To do.

  FIG. 16 is an explanatory diagram illustrating a part of the dither matrix in an enlarged manner. In the illustrated matrix, threshold values that are uniformly selected from the range of gradation values 0 to 255 are randomly stored in a total of 4096 pixels, 64 pixels in the vertical and horizontal directions. Here, the threshold gradation value is selected from the range of 0 to 255. In this embodiment, the ink amount data is 1-byte data, and the gradation value assigned to the pixel is a value of 0 to 255. It corresponds to what can be taken. Note that the size of the dither matrix is not limited to 64 pixels in the vertical and horizontal directions as illustrated in FIG. 16, and can be set to various sizes including those having different numbers of vertical and horizontal pixels. It is.

  FIG. 17 is an explanatory diagram conceptually showing a state in which the presence / absence of dot formation is determined for each pixel with reference to the dither matrix. When determining the presence / absence of dot formation, first, the ink amount data of the pixel of interest (the pixel of interest) as the object of determination is compared with the threshold value stored at the corresponding position in the dither matrix. The thin broken arrow shown in the figure schematically represents that the ink amount data of the pixel of interest is compared with the threshold value stored at the corresponding position in the dither matrix. If the ink amount data of the pixel of interest is larger than the threshold value of the dither matrix, it is determined that a dot is formed on that pixel. On the other hand, when the threshold value of the dither matrix is larger, it is determined that no dot is formed in the pixel.

  In the example shown in FIG. 17, the ink amount data of the pixel in the upper left corner is the gradation value 97, and the threshold value stored at the position corresponding to this pixel on the dither matrix is 1. Accordingly, for the pixel in the upper left corner, the tone value 97 of the ink amount data is larger than the threshold value 1 of the dither matrix, and therefore it is determined that a dot is formed in this pixel. An arrow indicated by a solid line in FIG. 17 schematically shows a state in which it is determined that a dot is to be formed in this pixel and the determination result is written in the memory. On the other hand, for the pixel on the right side of this pixel, the gradation value of the ink amount data is 97, and the threshold value of the dither matrix is 177. Since the threshold value is larger, it is determined that no dot is formed for this pixel. . In this way, by comparing the ink amount data and the threshold value set in the dither matrix, it is possible to determine whether or not dots are formed for each pixel.

  As described above, in step S160 of the image printing process shown in FIG. 7, the above-described process is performed on the ink amount data of each color corrected according to the brightness of the skin, so that a dot is obtained for each pixel. A process for generating dot data by determining whether or not to form dot data is performed.

  When the halftone process is thus completed, the interlace process is started (step S170). Interlace processing is the following processing. First, in the halftone process, dot data indicating whether or not to form dots for each pixel constituting the image is obtained. This data is data arranged in the order of pixels. However, as described above with reference to FIG. 5, the ejection heads 245 to 248 provided on the bottom surface of the carriage 240 of the printing unit 200 are provided with nozzles Nz for ejecting ink droplets at intervals of the nozzle pitch k. . Accordingly, since ink droplets are ejected at intervals of the nozzle pitch k, simply ejecting ink droplets while performing main scanning on the carriage 240 results in rasters being formed at intervals of the nozzle pitch k. A raster at the position of the gap must be formed separately. That is, when an image is actually printed, it is not formed sequentially from the raster above the image. In addition, since one raster is printed in a plurality of times, dots are not formed in order from the end pixels even within the raster. Therefore, it is necessary to perform a process of supplying the ejection heads 245 to 248 in accordance with the order in which dots are formed after rearranging the dot data in consideration of the order in which the ejection heads 245 to 248 of each color actually form dots. . In the interlacing process, the dot data is rearranged in this way, and the process of outputting to the ejection heads 245 to 248 is performed.

  When the ejection heads 245 to 248 receive data supplied from the control unit 100 in a state where the interlacing process is performed in this manner, the ejection heads 245 to 248 eject ink droplets according to the data. In accordance with this, the carriage motor 230 and the drive motor 206 are driven to perform main scanning and sub scanning of the carriage 240. As a result, an image is printed on the surface of the skin (step S180).

  In the image printing process of the first embodiment described above, when printing an image on the surface of the skin, the brightness of the skin is measured in advance, and the correction is made to increase the ink amount when the skin is dark. I do. Since the image is printed based on the ink amount data corrected in this way, it is possible to appropriately print the image on skin of any brightness.

  In addition, the lightness of the skin can be measured relatively easily. In addition, if the correction is performed according to the brightness of the skin, the correction of the ink amount data can be performed relatively easily. For this reason, it is possible to easily print an appropriate image.

  Further, at the time of printing an image, the surface of the skin to be printed is pressed against the holding plate 238 so as to have a substantially flat shape. In addition, the discharge members 245 to 248 are held by the holding member 236 provided on the carriage 240. The distance between the lower surface of the skin and the skin surface is maintained at an appropriate distance. For this reason, an appropriate image can be printed.

  In the image printing process of the first embodiment described above, the ink amount data obtained by the color conversion is uniformly corrected regardless of the location, on the assumption that the brightness of the skin does not vary greatly depending on the location. It demonstrated as what correct | amends using a coefficient. However, strictly speaking, since the brightness of the skin is slightly different depending on the location, the ink amount data may be individually corrected according to the brightness of the skin at each location where the image is to be printed. .

C. Image printing process of the second embodiment:
In the image printing process of the first embodiment described above, the brightness of the skin is measured in advance, and correction is performed so that the ink amount increases as the brightness decreases. Of course, the skin condition differs not only in lightness, whether it is light or dark, but also in color, such as reddish or yellowish skin. Therefore, if the ink amount data is corrected in consideration of such a color difference, an image can be printed more appropriately. Hereinafter, the image printing process of the second embodiment will be described.

  FIG. 18 is a flowchart showing the flow of the image printing process of the second embodiment. This process is different from the image printing process of the first embodiment shown in FIG. 7 in that the color is measured instead of the lightness of the skin and the color measurement result is used instead of correcting the ink amount data. The difference is that color conversion is performed using the color conversion table selected in the above. Below, it demonstrates according to the flowchart of FIG. 18 focusing on these differences.

  In the image printing process of the second embodiment, as in the image printing process of the first embodiment, when the process is started, first, a process for selecting an image to be printed is performed (step S200). That is, as described above with reference to FIGS. 8 to 10, the operator of the printing apparatus 10 selects a print image and sets an image size while checking the display screen 110 incorporated in the apparatus.

  Next, similarly to the image printing process of the first embodiment described above, a process of converting the image data of the selected print image into a print resolution is performed (step S210). That is, the number of pixels in the main scanning direction and sub-scanning direction of the image to be actually printed is determined from the image size, and then the image data for each pixel is determined based on the image data of the selected print image. Do. Since this processing is the same as the processing in the first embodiment described above, detailed description thereof is omitted here.

  In the image printing process of the second embodiment, the color of the skin on which an image is to be printed is subsequently measured (step S220). That is, taking into account not only the brightness of the skin but also the color of the skin, the color of the skin is measured in order to print the image more appropriately.

  In the image printing process of the second embodiment, the optical sensor 250 mounted on the side surface of the carriage 240 corresponds to the color measurement of the skin, so-called color measurement in which the following mechanism is incorporated. It is a sensor. In other words, an irradiation unit that emits white light toward the skin surface on which an image is to be printed, an optical system that collects the reflected light from the skin surface and separates it into RGB colors, and detects the light intensity after spectroscopy A photodetection unit is incorporated. And it is possible to obtain a colorimetric value of the skin by detecting the light intensity after the spectrum.

  The process for measuring the color of the skin itself is performed in substantially the same manner as in the first embodiment. That is, first, a screen as shown in FIG. 19 is displayed on the display screen 110. When the operator of the printing apparatus 10 places a body part on which an image is to be printed on the upper and lower stage 140 and touches a place where “OK” is displayed on the display screen 110, the upper and lower stage 140 is raised. The skin is pressed against the opening 239 of the holding plate 238. Then, the color of the skin is measured over the entire range where the image is to be printed by moving the slide stage 201 in the sub-scanning direction while reciprocating the carriage 240 in the main scanning direction.

  Next, in the image printing process of the second embodiment, an appropriate color conversion table is selected according to the obtained colorimetric values (step S230). That is, in the second embodiment, a plurality of color conversion tables in which the ink amount data is adjusted so that an appropriate image can be obtained for skin having various colorimetric values are obtained in advance by an experimental method. . The plurality of color conversion tables are stored in the ROM of the control unit 100 in a state associated with the skin colorimetric values.

  FIG. 20 is an explanatory diagram conceptually showing a state in which a plurality of color conversion tables are set in accordance with skin colorimetric values. FIG. 20 shows a state where four types of color conversion tables “A” to “D” are set in an area corresponding to skin color in a so-called Lab color space. In step S230 of the second embodiment, a color conversion table corresponding to the colorimetric value of the skin is selected based on such correspondence.

  Next, by performing color conversion while referring to the color conversion table thus selected, the image data is converted into ink amount data of each color of C, M, Y, and K (step S240). In the image printing process of the second embodiment, since an appropriate color conversion table is selected according to the colorimetric value of the skin, the ink amount data obtained in this way is an appropriate ink in consideration of the skin color. It is quantity data.

  Therefore, in the second embodiment, when the ink amount data is obtained by the color conversion process, the halftone process is started immediately (step S250). As a result, the ink amount data is converted into data (dot data) indicating whether or not to form dots for each pixel.

  Thereafter, as in the image printing process of the first embodiment described above, after interlace processing is performed on the dot data (step S260), ink droplets are ejected while performing main scanning and sub scanning of the carriage 240. Thus, an image is printed (step S270). As a result, the selected image is printed on the skin.

  In the image printing process of the second embodiment described above, not only the brightness of the skin but also the color of the skin is taken into consideration, so that an image can be printed with an appropriate color for any skin. It becomes possible.

  In addition, although a plurality of color conversion tables must be stored in advance, color conversion is performed using an appropriate color conversion table selected according to the colorimetric value of the skin, so that the image data is converted into an appropriate ink amount. Can be converted to data immediately. For this reason, a process for correcting the ink amount data is not necessary, so that an image can be printed quickly.

  In the image printing process of the second embodiment described above, the skin color has been described as not significantly different depending on the location. Therefore, after selecting one color conversion table based on the colorimetric value of the skin, the image data is converted into ink amount data using this color conversion table. Strictly speaking, however, the color of the skin is slightly different depending on the location, so the image data is transferred to the ink amount while switching the appropriate color conversion table according to the color of the skin at each location where the image is to be printed. It may be converted into data.

  Although various embodiments have been described above, the present invention is not limited to all the embodiments described above, and can be implemented in various modes without departing from the scope of the invention.

It is explanatory drawing which shows the whole structure of the printing apparatus which prints an image on the human skin surface. It is explanatory drawing which showed the structure of the printing part by taking a cross section in a surface perpendicular | vertical to a drive shaft and a sliding shaft. It is explanatory drawing which showed the internal structure of the main-body part, and the drive mechanism of a sliding stage by taking the longitudinal cross-section of a main-body part in a surface parallel to a drive shaft and a sliding shaft. It is explanatory drawing which showed the shape of the holding plate seeing from the upper side. It is explanatory drawing which showed the structure of the bottom face of the carriage integrated in the sliding stage. It is explanatory drawing which shows the structure of the control part which controls the whole operation | movement of a printing apparatus. 3 is a flowchart illustrating a flow of image printing processing according to the first embodiment. 4 is a flowchart illustrating a flow of a print image selection process performed during the image print process of the first embodiment. It is explanatory drawing which illustrated a mode that the some print image is displayed on the display screen. It is explanatory drawing which illustrated a mode that the screen for acquiring an original image is displayed on the display screen. It is explanatory drawing which illustrated the screen displayed on a display screen, when measuring the brightness of skin. It is explanatory drawing which showed notionally the color conversion table referred in the case of color conversion. It is a flowchart which shows the flow of the process which correct | amends the ink amount data obtained by color conversion. It is explanatory drawing which showed notionally the mode that ink amount data was correct | amended. It is explanatory drawing which showed notionally the table in which the appropriate correction coefficient was set according to the brightness of the skin. It is explanatory drawing which expanded and illustrated a part of dither matrix. It is explanatory drawing which showed notionally the mode that the presence or absence of dot formation was judged for every pixel, referring a dither matrix. It is a flowchart which shows the flow of the image printing process of 2nd Example. It is explanatory drawing which illustrated the screen displayed on a display screen, when measuring the color of skin. It is explanatory drawing which showed notionally the mode that the several color conversion table was set according to the colorimetric value of skin.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Printing apparatus, 100 ... Control part, 110 ... Display screen,
120 ... Scanner, 130 ... Main unit, 140 ... Upper and lower stages,
150 ... Data reading unit, 160 ... Digital camera, 200 ... Printing unit,
201 ... sliding stage, 202 ... drive shaft, 204 ... sliding shaft,
236 ... Holding member, 238 ... Holding plate, 240 ... Carriage,
250: Optical sensor

Claims (8)

A printing device that prints an image by ejecting ink droplets onto the skin of a human body,
A color-related data measuring means for measuring data related to the skin color of the skin where the image is to be printed;
Image data conversion means for converting the image data of the image to be printed into ink amount data corresponding to the ink amount for printing the image;
Image forming means for forming the image by ejecting ink droplets on the skin based on the ink amount data; and
The printing apparatus, wherein the image data conversion unit is a unit that converts the image data into the ink amount data in consideration of the measured color-related data. The printing apparatus according to claim 1,
A correspondence storage means for storing a plurality of sets of correspondence between the image data and the ink amount data;
The image data converting means is a printing apparatus which is means for converting the image data based on a correspondence selected in accordance with the color-related data from the plurality of stored correspondences. The printing apparatus according to claim 1,
The hue-related data measuring means is means for measuring data related to the brightness of the skin,
The printing apparatus, wherein the image data conversion means is a means for converting the image data so that the amount of ink increases as the lightness of the skin decreases. The printing apparatus according to claim 1,
The image forming unit includes:
An ejection head for ejecting the ink droplets while reciprocating on the skin;
A printing apparatus comprising: an interval holding member that holds an interval between the discharge head and the surface of the skin within a predetermined range by contacting the surface of the skin. The printing apparatus according to claim 4, wherein
The spacing member is
A first holding member that contacts the surface of the skin at a plurality of locations outside the region to be printed with the image;
And a second holding member that moves with the ejection head while contacting the surface of the skin in a region where the image is to be printed. A printing method for printing an image by ejecting ink droplets on a human skin,
A first step of measuring color-related data related to the skin color of the area where the image is to be printed;
A second step of converting the image data of the image to be printed into ink amount data corresponding to the ink amount for printing the image;
A third step of forming the image by ejecting ink droplets on the skin based on the ink amount data; and
The second method is a printing method in which the image data is converted into the ink amount data in consideration of the measured color-related data. The printing method according to claim 6, comprising:
The third step includes
A sub-process of ejecting the ink droplets while reciprocating on the skin;
A printing method comprising: a sub-step of maintaining a distance between the ejection head and the skin surface within a predetermined range by contacting the skin surface prior to ejection of the ink droplets. A program for realizing, using a computer, a method for printing an image by ejecting ink droplets on the skin of a human body,
A first function for measuring color-related data related to the skin color of the area where the image is to be printed;
A second function for converting the image data of the image to be printed into ink amount data corresponding to the ink amount for printing the image;
A third function for forming the image is realized using a computer by ejecting ink droplets onto the skin based on the ink amount data, and
The second function is a program for converting the image data into the ink amount data in a state where the measured color-related data is taken into consideration.

Images