A method for correcting the laser drawing position, and a laser drawing apparatus to which this correction method is applied.

Abstract

To provide a method for correcting the drawing position for high-precision laser drawing on high-resolution lines that have become distorted. [Solution] The laser drawing position correction method includes the steps of: having a processor capture an image of a substrate on which a designed pattern has been printed and which will be laser drawn, in an imaging unit before laser drawing, thereby acquiring image data of the substrate; and calculating a correction value for correcting the laser drawing position from a comparison between the designed pattern and the pattern captured in the image data.

Description

Technical Field

[0001] The present invention relates to a method for correcting a drawing position for performing high-precision laser drawing on, for example, a high-definition halftone screen with distortion, and a laser drawing apparatus to which this correction method is applied.

Background Art

[0002] In personal authentication media such as passports, driver's licenses, and ID cards, it is important to prevent forgery and alteration. In particular, for altered products in which the face photo of a stolen item is replaced with that of another person, since parts other than the face are genuine, it is easy to manufacture and difficult to discriminate, so suppressing such alterations has become an issue.

[0003] In contrast, in recent years, personal authentication media that record personal information by laser drawing on a polycarbonate substrate (hereinafter referred to as a polycarbonate substrate) have become widespread. Since laser drawing carbonizes the inside of the substrate itself black, unlike printing, it is difficult to remove it later, which is effective for preventing alteration.

[0004] However, in the case of laser drawing, since the face photo becomes a monochrome image, the information regarding appearance is inferior compared to the color digital face photo printing that has been mainstream until now.

[0005] For this reason, the following methods for achieving both the anti-alteration effect by laser drawing and the colorization of the face image have been studied.

[0006] The first method is to print a halftone pattern of CMY or RGB inside the polycarbonate substrate in advance, draw it black with a laser, and express color by hiding a part of the pattern (such as LASINK of IDEMIA).

[0007] The second method is to print a halftone pattern of CMY or RGB inside the polycarbonate substrate in advance, change the substrate to a scattering structure with a short-wavelength laser, hide a part of the pattern, and express color.

[0008] The third method involves pre-printing CMY or RGB line patterns inside a polycarbonate substrate, then applying a metal vapor deposition layer on top of it, and finally demetallizing a portion of this metal vapor deposition layer with a laser to create color.

[0009] The fourth method involves pre-printing CMY or RGB line patterns inside a polycarbonate substrate and then decolorizing a portion of the pattern using laser drawing at a special wavelength.

[0010] The fifth method involves pre-installing RGB-emitting optical elements inside a polycarbonate substrate, and then using laser drawing to remove or conceal parts of the element.

[0011] The sixth method involves pre-installing particles (such as leuco dyes) inside the polycarbonate substrate that react with laser light to produce color.

[0012] Of these methods, the first method is the easiest and has already been put into practical use.

[0013] Figure 27 is a cross-sectional view of a substrate for a typical personal authentication medium.

[0014] For example, as illustrated in the cross-sectional view of Figure 27, the base material 10 for personal authentication media has a layered structure.

[0015] The substrate 10 is constructed by printing a pattern onto a core substrate 11 to form a pattern printing layer 12, then laminating a color development layer 13 and a transparent layer 14 on top of that, and finally heat laminating it. Alternatively, another layer may be provided on the opposite side (lower side in the figure) of the core substrate 11. The pattern printing layer 12 can be a CMYW line pattern.

[0016] Figure 28 is a cross-sectional view of the substrate shown in Figure 27, showing the state in which laser light is irradiated onto the substrate.

[0017] As shown in Figure 28, when the substrate 10 is irradiated with laser light L by the laser writing device 20, a portion of the color-developing layer 13 becomes colored, forming a black spot K. When the substrate 10 is viewed from above in the figure, a portion of the pattern printing layer 12 is obscured and observed. This creates a personal authentication medium that displays in color. Generally, a near-infrared laser is used as the laser writing device 20 to make the polycarbonate color-developing layer 13 black.

[0018] Figure 29 shows a plan view of an example of a personal authentication medium created in this way, and a partially enlarged plan view of the pattern printing layer.

[0019] The personal authentication medium 130 is used, for example, as an ID card. As shown in Figure 29, a pattern printing layer 12 consisting of a CMYW line pattern with white gaps added to the lines of CMY (cyan, red, yellow), can be pre-installed on a part of the ID card. As described above, it is laser-drawn, and by partially obscuring it, a color image can be displayed. The target color image can be a photograph, a logo, a national flag, an emblem, text information, etc.

[0020] Figure 30 illustrates the principle of displaying color images using laser drawing.

[0021] By using black spot K to obscure the CMYW colors other than the desired color in the pattern printing layer 12 in an appropriate proportion, any color can be represented.

[0022] Figure 30(a) is a partial plan view of the pattern printing layer 12 before laser drawing.

[0023] Figure 30(b) is a partial plan view observed when the color-developing layer 13, on which black spots K are formed by laser drawing, and the pattern-printed layer 12, on which cyan and yellow are obscured by the black spots K, are superimposed.

[0024] FIG. 30(c) is a partial plan view observed when the color developing layer 13 in which the black spots K are formed by laser drawing and the pattern printing layer 12 in which magenta and yellow are concealed by the black spots K are overlapped.

[0025] FIG. 30(d) is a partial plan view observed when the color developing layer 13 in which the black spots K are formed by laser drawing and the pattern printing layer 12 in which magenta and yellow are concealed by the black spots K are overlapped. Note that, unlike the case of FIG. 30(c), yellow is partially concealed by the black spot k1 having a smaller diameter than the black spot K and the black spot k2 having a smaller diameter than the black spot k1.

[0026] Note that the pattern printing layer 12 is not limited to the CMYW dot pattern, and color expression can be performed on the RGBW dot pattern in which white gaps are added to the RGB dots by the same principle.

[0027] By the way, the applicant has established a high-definition printing technology using special equipment applying the gravure offset method.

[0028] FIG. 31 is a diagram showing the results of comparing the line width and pitch of the dot pattern between the high-definition printing technology established by the applicant and the prior art.

[0029] According to the high-definition printing technology, as shown in FIG. 31, a dot pattern having a thinner line width and a smaller pitch than the prior art can be created. Thereby, the resolution of the displayed image is improved and the image quality of the obtained face photo is improved.

[0030] FIG. 32 is a plan view and a partial enlarged view showing an example of a displayed image according to the prior art.

[0031] FIG. 33 is a plan view and a partial enlarged view of a displayed image according to the high-definition printing technology by the applicant.

[0032] As shown in Figure 33, the applicant's high-definition printing technology improves the resolution of the displayed image and clearly improves the image quality of the resulting facial photographs compared to the conventional technology shown in Figure 32. [Prior art documents] [Patent Documents]

[0033] [Patent Document 1] International Publication No. 202069536 [Patent Document 2] International Publication No. 202069547 [Overview of the Initiative] [Problems that the invention aims to solve]

[0034] As mentioned above, the applicant has succeeded in differentiating its technology from conventional methods by increasing the resolution of CMY line printing. This is expected to improve image quality and provide protection against counterfeiting and alteration.

[0035] However, the increased resolution of the line printing created a problem in that it became difficult to align the laser drawing. The pattern printing layer 12 is provided inside the polycarbonate substrate. Since the polycarbonate substrate is formed by thermal lamination, uneven expansion and contraction due to heat and pressure can cause localized distortion in the line pattern of the pattern printing layer 12. When attempting to conceal the lines with laser drawing, the laser drawing position may shift from the color to be concealed, resulting in incorrect color development. To prevent this, a position correction technique is required to perform laser drawing in accordance with the distorted line pattern.

[0036] Figure 34 shows the results of comparing the line width and pitch of a line pattern, the amount of distortion, the effects of distortion, and the need for drawing correction between high-resolution printing technology and conventional technology.

[0037] As shown in Figure 34, in conventional technology, the pitch of the line pattern was large and the line width was thick. Therefore, even if distortion occurred due to lamination, it remained within the range of the line width, and the impact on image quality was minimal. However, when the line is highly detailed, as in high-resolution printing technology, the same amount of distortion has a greater impact on image quality. Therefore, it is necessary to correct the laser drawing position according to the distortion.

[0038] This invention has been made in view of these circumstances, and aims to provide a method for correcting the drawing position for performing high-precision laser drawing on high-resolution lines that have been distorted, and a laser drawing apparatus to which this correction method is applied. [Means for solving the problem]

[0039] To achieve the above objectives, the present invention employs the following measures.

[0040] A first aspect of the present invention is a method for correcting the laser drawing position, comprising the steps of: having a processor capture an image of a substrate on which a designed pattern is printed and to be laser drawn by an imaging unit before laser drawing, thereby acquiring image data of the substrate; and calculating a correction value for correcting the laser drawing position from a comparison between the designed pattern and the pattern captured in the image data.

[0041] A second aspect of the present invention is a correction method according to the first aspect, wherein the calculation step includes a substep of calculating the amount of distortion of the pattern captured in the image data relative to the designed pattern as a correction value.

[0042] A third aspect of the present invention is a correction method according to the first aspect, wherein the correction value includes a first correction value which includes the stretch ratio and rotation angle of the pattern captured in the image data with respect to the designed pattern, and a second correction value which is the amount of local distortion of the pattern captured in the image data with respect to the designed pattern.

[0043] A fourth aspect of the present invention is a correction method according to the third aspect, wherein at least two registered marks are arranged for a designed pattern, and the calculation steps are to calculate a scaling factor from the ratio of the length between the corresponding two registered marks arranged for the pattern captured in the image data to the length between the two registered marks arranged for the designed pattern, and to calculate a rotation angle from the slope of the straight line connecting the corresponding two registered marks arranged for the pattern captured in the image data to the straight line connecting the two registered marks arranged for the designed pattern.

[0044] A fifth aspect of the present invention is a laser drawing apparatus comprising: a laser irradiation unit for laser drawing by irradiating a laser onto a designated location on a substrate printed with a designed pattern; an imaging unit for imaging the substrate and acquiring image data of the substrate before the laser irradiation unit irradiates the substrate; a correction value calculation unit for calculating a correction value to correct the location for laser irradiation by comparing the designed pattern with the pattern captured in the image data; and a laser drawing control unit for controlling the relative position between the substrate and the laser irradiation unit based on the correction value.

[0045] A sixth aspect of the present invention is a laser writing apparatus according to the fifth aspect, wherein the laser writing control unit controls the relative position of the laser irradiation unit by moving it with respect to the substrate.

[0046] A seventh aspect of the present invention is a laser writing apparatus according to a fifth or sixth aspect, further comprising a linear stage for positioning a substrate and a drive unit for moving the linear stage according to control by a laser writing control unit, wherein the laser writing control unit controls the relative position by moving the linear stage with respect to the substrate using the drive unit. [Effects of the Invention]

[0047] According to the correction method of the present invention, a correction value for performing high-precision laser drawing on high-resolution lines that have been distorted can be obtained.

[0048] Furthermore, with the laser drawing apparatus of the present invention, by performing laser drawing on high-definition lines that have been distorted using the correction value obtained by this correction method, it becomes possible to perform laser drawing with high precision even on high-definition lines that have been distorted. [Brief explanation of the drawing]

[0049] [Figure 1] Figure 1 is a plan view illustrating the adjustment of the laser drawing position, which is performed by reading a registered mark placed on a portion of the pattern printing layer. [Figure 2] Figure 2 is a plan view showing an example of a patterned printed layer that has been uniformly deformed overall by thermal lamination. [Figure 3] Figure 3 is a plan view showing an example of a patterned printed layer that has been locally distorted in part due to thermal lamination. [Figure 4] Figure 4 is a planar photograph of the laser-printed pattern layer. [Figure 5] Figure 5 is a plan view showing the relationship between a pattern printing layer consisting of a line pattern with a line width of 50 μm and a color-developing layer in which black spots K are formed by laser drawing. [Figure 6] Figure 6 is a plan view showing the relationship between the pattern printing layer illustrated in Figure 5(a), which is distorted by 20 μm, and the coloring layer on which the black spot group K is formed by laser drawing. [Figure 7] Figure 7 is a plan view showing the relationship between a pattern printing layer consisting of a line pattern with a line width of 20 μm and a color-developing layer in which black spots K are formed by laser drawing. [Figure 8] Figure 8 is a plan view showing the relationship between the pattern printing layer illustrated in Figure 7(a), which is distorted by 20 μm, and the coloring layer on which the black spot group K is formed by laser drawing. [Figure 9] Figure 9 is a plan view showing the relationship between the pattern printing layer illustrated in Figure 7(a), which is distorted by 20 μm, and the coloring layer in which the black spot group K is formed by corrected laser drawing. [Figure 10]Figure 10 is a diagram illustrating the principle of the laser drawing position correction method according to an embodiment of the present invention. [Figure 11] Figure 11 is a plan view showing the distortion of the lines in the pattern printing layer and the drawing direction corrected accordingly. [Figure 12] Figure 12 shows various patterns of registered trademarks. [Figure 13] Figure 13 is an image showing an example of a patterned printing layer with two registered trademarks. [Figure 14] Figure 14 is a plan view showing the reference points set from the image shown in Figure 13. [Figure 15] Figure 15 is an enlarged plan view showing the actual printed line (magenta M) near reference point 1. [Figure 16] Figure 16 shows the amount of strain at each reference point. [Figure 17] Figure 17 shows the distortion of the printed line M reproduced from Figure 16. [Figure 18] Figure 18 is a diagram illustrating the first correction value. [Figure 19] Figure 19 is a diagram illustrating the second correction value (the correction value for local distortion). [Figure 20] Figure 20 is a diagram illustrating the second correction value (the correction value for local distortion). [Figure 21] Figure 21 illustrates the transformation of drawing data performed by a two-stage drawing correction process. [Figure 22] Figure 22 is a block diagram showing an example configuration of a laser writing apparatus according to an embodiment of the present invention. [Figure 23] Figure 23 shows the laminated structure of the display sheet along with the product name. [Figure 24] Figure 24 is a photograph of an evaluation card obtained from a sheet used for the display unit. [Figure 25] Figure 25 shows an example of distortion correction. [Figure 26]Figure 26 shows photographs of (a) the color display created in this embodiment and (b) a color display for comparison. [Figure 27] Figure 27 is a cross-sectional view of a substrate for a typical personal authentication medium. [Figure 28] Figure 28 is a cross-sectional view of the substrate shown in Figure 27, showing the state in which laser light is irradiated onto the substrate. [Figure 29] Figure 29 shows a plan view of an example of a personal authentication medium, and a partially enlarged plan view of the pattern printing layer. [Figure 30] Figure 30 illustrates the principle of displaying color images using laser drawing. [Figure 31] Figure 31 shows a comparison of the line width and pitch of a line pattern using high-resolution printing technology and conventional technology. [Figure 32] Figure 32 shows a plan view and a partially enlarged view illustrating an example of a display image using the conventional technology. [Figure 33] Figure 33 shows a plan view and a partially enlarged view of the display image obtained using the applicant's high-definition printing technology. [Figure 34] Figure 34 shows the results of comparing the line width and pitch of a line pattern, the amount of distortion, the effects of distortion, and the need for drawing correction between high-resolution printing technology and conventional technology. [Modes for carrying out the invention]

[0050] Embodiments of the present invention will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of the sizes of the parts, etc., are not necessarily the same as those of reality. Furthermore, even when representing the same part, the dimensions and ratios may be represented differently in the drawings. In this specification and each drawing, elements similar to those described in previously shown drawings are denoted by the same reference numerals, and detailed explanations and redundant explanations are omitted as appropriate.

[0051] [Correction Method] First, a correction method according to an embodiment of the present invention will be described.

[0052] The correction method according to an embodiment of the present invention calculates a correction value for performing high-precision laser drawing on a high-resolution line that has been distorted.

[0053] First, let's explain the distortion that occurs with high-resolution lines.

[0054] As mentioned above using Figure 27, a technique has been put into practical use in which a pattern printing layer 12 consisting of a CMYW line pattern is printed in advance inside a polycarbonate substrate 10, and then the color is expressed by laser drawing, as shown in Figure 28. This technique involves embedding the pattern printing layer 12 consisting of a CMYW line pattern inside the polycarbonate substrate 10, and then laminating printed polycarbonate sheets by applying heat and pressure. In this heat lamination process, the polycarbonate sheets melt and bond together, making it unavoidable that the sheets will become distorted.

[0055] Figure 1 is a plan view illustrating the adjustment of the laser drawing position, which is performed by reading a registered mark placed on a portion of the pattern printing layer.

[0056] In conventional technology, as shown in Figure 1, the laser drawing position is adjusted by reading the register marks R (for example, R1 to R4) provided at the four corners of the pattern printing layer 12.

[0057] Figure 2 is a plan view showing an example of a patterned printed layer that has been uniformly deformed overall by thermal lamination.

[0058] Figure 3 is a plan view showing an example of a patterned printed layer that has been locally distorted in part due to thermal lamination.

[0059] Figure 4 is a planar photograph of the laser-printed pattern layer.

[0060] If the deformation of the pattern printing layer 12 due to thermal lamination is uniform throughout, then, as shown in Figures 2(a), 2(b), and 2(c), it is possible to read the register marks R1 to R4 at the four corners and deform the image to be drawn, thereby correcting and printing according to the line pattern.

[0061] However, as shown in Figure 3, if only a portion of the pattern printing layer 12 is locally distorted, the correction cannot be made using only the register marks R1 to R4 at the four corners. As a result, even if laser drawing is intended to produce the same color throughout, color shifts occur in the areas where the lines are distorted, as shown in Figure 4(a). Figure 4(b) shows an example where laser drawing was performed so that the color lines of each color are produced, but color shifts occur mainly near the center.

[0062] Figure 5 is a plan view showing the relationship between a pattern printing layer consisting of a line pattern with a line width of 50 μm and a color-developing layer in which black spots K are formed by laser drawing.

[0063] Figure 5(a) shows a plan view of the pattern printing layer 12 consisting of a line pattern with a line width of 50 μm, Figure 5(b) shows a plan view of the color development layer 13 in which black spot K group is formed by laser drawing, and Figure 5(c) shows a plan view of the color development layer 13 shown in Figure 5(b) superimposed on the pattern printing layer 12 shown in Figure 5(a). The pattern printing layer 12 consists of a CMYW line pattern with white gaps added to the lines of blue, red, and yellow CMY, similar to Figure 29.

[0064] Figure 6 is a plan view showing the relationship between the pattern printing layer illustrated in Figure 5(a), which is distorted by 20 μm, and the coloring layer on which the black spot group K is formed by laser drawing.

[0065] Figure 6(a) shows a plan view of the pattern printing layer 12 shown in Figure 5(a) which is distorted by 20 μm, Figure 6(b) shows a plan view of the coloring layer 13 in which black spots K group are formed by laser drawing, similar to Figure 5(b), and Figure 6(c) shows a plan view of the state in which the coloring layer 13 shown in Figure 6(b) is superimposed on the pattern printing layer 12 shown in Figure 6(a).

[0066] As illustrated in Figure 5(a), in conventional technology, the line width of the line pattern was about 50 μm, which was relatively thick relative to the amount of distortion.

[0067] Therefore, as illustrated in Figure 6(a), even if localized distortion of up to approximately 20 μm occurs in the substrate, the colored lines can be concealed with black spot K almost exactly as designed, as shown in Figure 6(c), and no unexpected colors were produced.

[0068] However, the applicant's increased line width to approximately 20-30 μm has made the required precision for laser lithography more stringent.

[0069] Figure 7 is a plan view showing the relationship between a pattern printing layer consisting of a line pattern with a line width of 20 μm and a color-developing layer in which black spots K are formed by laser drawing.

[0070] Figure 7(a) shows a plan view of the pattern printing layer 12 consisting of a line pattern with a line width of 20 μm, Figure 7(b) shows a plan view of the color development layer 13 in which black spots K group are formed by laser drawing, and Figure 7(c) shows a plan view of the state in which the color development layer 13 shown in Figure 7(b) is superimposed on the pattern printing layer 12 shown in Figure 7(a).

[0071] Figure 8 is a plan view showing the relationship between the pattern printing layer illustrated in Figure 7(a), which is distorted by 20 μm, and the coloring layer on which the black spot group K is formed by laser drawing.

[0072] Figure 8(a) shows a plan view of the pattern printing layer 12 shown in Figure 7(a) which is distorted by 20 μm, Figure 8(b) shows a plan view of the coloring layer 13 in which black spots K group are formed by laser drawing, similar to Figure 7(b), and Figure 8(c) shows a plan view of the state in which the coloring layer 13 shown in Figure 8(b) is superimposed on the pattern printing layer 12 shown in Figure 8(a).

[0073] Figure 9 is a plan view showing the relationship between the pattern printing layer illustrated in Figure 7(a), which is distorted by 20 μm, and the coloring layer in which the black spot group K is formed by corrected laser drawing.

[0074] Figure 9(a) shows a plan view of the pattern printing layer 12, similar to that in Figure 8(a); Figure 9(b) shows a plan view of the coloring layer 13, in which black spots K are formed by laser drawing corrected for a 20 μm distortion; and Figure 9(c) shows a plan view of the coloring layer 13 shown in Figure 9(b) superimposed on the pattern printing layer 12 shown in Figure 9(a).

[0075] As illustrated in Figure 7(a), when the line width of the line pattern becomes thinner than conventional methods, such as 20 μm, even a localized strain of 20 μm in the substrate will have a relatively larger effect, as illustrated in Figure 8(a).

[0076] Therefore, as illustrated in Figure 8(c), it becomes impossible to conceal the colored lines with black spot K as designed, resulting in a color shift from the intended color.

[0077] Therefore, for high-resolution printing with a line width of 20 μm to improve security, it is necessary to correct the laser drawing position to match the distortion of the line pattern, as illustrated in Figure 9(b). As a result, as illustrated in Figure 9(c), the color lines can be concealed with black spot K almost exactly as designed, making it possible to obtain the intended color.

[0078] {Principle of the laser drawing position correction method} The principle of this laser drawing position correction method will be explained.

[0079] Figure 10 is a diagram illustrating the principle of the laser drawing position correction method according to an embodiment of the present invention.

[0080] Figure 10(a) is a plan view showing an example of a locally distorted patterned printing layer 12.

[0081] Figure 10(b) is an enlarged plan view of the pattern printing layer 12 in the undistorted area, Figure 10(e) is an enlarged plan view of the pattern printing layer 12 in the area distorted diagonally upward to the right, and Figure 10(h) is an enlarged plan view of the pattern printing layer 12 in the area distorted diagonally downward to the right. The pattern printing layer 12 consists of a CMYW line pattern, similar to Figure 29, with CMY (blue, red, yellow) and white gaps added to the lines.

[0082] Figure 10(c) shows a plan view of the color-developing layer 13 on which a group of black spots K is formed by laser drawing for the pattern-printed layer 12 shown in Figure 10(b). Figure 10(f) shows a plan view of the color-developing layer 13 on which a group of black spots K is formed by laser drawing for the pattern-printed layer 12 shown in Figure 10(e). Figure 10(i) shows a plan view of the color-developing layer 13 on which a group of black spots K is formed by laser drawing for the pattern-printed layer 12 shown in Figure 10(h).

[0083] Figure 10(d) shows a plan view of the pattern printing layer 12 shown in Figure 10(b) with the color development layer 13 shown in Figure 10(c) superimposed on it; Figure 10(g) shows a plan view of the pattern printing layer 12 shown in Figure 10(e) with the color development layer 13 shown in Figure 10(f) superimposed on it; and Figure 10(j) shows a plan view of the pattern printing layer 12 shown in Figure 10(h) with the color development layer 13 shown in Figure 10(i) superimposed on it.

[0084] As shown in Figure 10(b), the pattern printing layer 12 is an undistorted area, and by laser drawing in the horizontal direction as shown in Figure 10(c), the cyan C and yellow Y can be concealed by the black spot K as designed, as shown in Figure 10(d).

[0085] As shown in Figure 10(e), the pattern printing layer 12 is distorted diagonally upward to the right. Therefore, as shown in Figure 10(f), by correcting it diagonally upward to the right by the same angle as the lines and performing laser drawing, the black spot K can be used to conceal the cyan C and yellow Y as designed, as shown in Figure 10(g).

[0086] As shown in Figure 10(h), the pattern printing layer 12 is distorted diagonally downward to the right. Therefore, as shown in Figure 10(i), by correcting it diagonally downward to the right by the same angle as the lines and performing laser drawing, the black spot K can hide the cyan C and yellow Y as designed, as shown in Figure 10(j).

[0087] In this way, by basically using the three correction patterns described above, it is possible to draw a laser line that matches the distorted lines.

[0088] Figure 11 is a plan view showing the distortion of the lines in the pattern printing layer and the drawing direction corrected accordingly.

[0089] The standard laser drawing direction is horizontal, from left to right. However, as shown in Figure 11(a), for areas where the lines are distorted, the laser drawing device is corrected by tilting its drawing direction upwards or downwards, as shown in Figure 11(b).

[0090] {Basic correction procedure} As mentioned above, the following procedure is followed to perform laser drawing in accordance with the distortion of the lines.

[0091] Step 1 involves capturing an image of the entire line pattern on the pattern printing layer 12; Step 2 involves extracting line distortion data and calculating correction values; and Step 3 involves drawing the laser according to the input correction values. The details of these three steps are explained below.

[0092] (Step 1: Photograph the entire line pattern) To capture an image of the entire line pattern of the pattern printing layer 12 and detect distortion, various cameras, scanners, CNC (Computer Numerical Control) image measuring machines, etc., can be used, although these are not limited to those mentioned above.

[0093] Alternatively, for example, using a microscope equipped with a high-magnification lens can capture the entire line pattern and detect distortion. However, the higher the magnification and the more accurately the measurement, the narrower the field of view becomes, resulting in a trade-off between the resolution obtained and the area of ​​focus.

[0094] The image of the entire grid pattern is captured by selecting an appropriate camera and lens according to the size of the image displayed by the pattern printing layer 12, i.e., the required shooting area, and, if necessary, by setting up multiple cameras and combining the images.

[0095] When taking images using a camera in this way, it is necessary to consider factors such as image distortion caused by the lens and errors that occur when combining images from multiple cameras.

[0096] Line scanners can also be used to photograph multi-line patterns. In this case, there are two methods: one in which the substrate 10 is fixed and the image sensor is moved, as with a flatbed scanner; and another in which the image sensor is fixed and the substrate 10 is moved, as with a sheet-feed scanner. In either case, unlike with a camera, lens distortion does not need to be considered, but precision in the drive mechanism for movement is required.

[0097] For example, images can be captured using a commercially available high-resolution flatbed scanner, processed by computer, and then the distortion correction data can be input into the laser lithography device. Alternatively, a linear stage and line scanner can be installed in the lithography device, and images can be captured as the display unit is moved from the supply unit to the laser lithography position.

[0098] While CNC image measuring machines allow for more accurate distortion measurement, their large size and high cost are problematic. Furthermore, the long acquisition time makes them unsuitable for practical use; therefore, they are best used to guarantee the accuracy of measurements taken with cameras or scanners. Measurement accuracy can also be verified and guaranteed using calibration plates with precisely engraved grids, such as quartz plates.

[0099] (Step 2: Extraction of distortion data and calculation of correction values) "Detecting drawing position using registered trademarks" To perform image correction, it is necessary to extract distortion from the image captured in step 1.

[0100] To extract distortion from image data, a reference point is necessary. The pattern printing layer 12 generally has a specific mark, such as the aforementioned register mark R, for alignment of the drawing, and this can be used to extract distortion. Alternatively, distortion can be extracted by detecting the end of the lines themselves.

[0101] Figure 12 shows various patterns of registered trademarks.

[0102] For example, when using the registered trademark mark R, it can be placed at the four corners of the pattern printing layer 12 as shown in Figure 12(a), or at only two locations as shown in Figure 12(b). If it does not obstruct facial images or other elements, the registered trademark mark R can also be placed across the entire line pattern.

[0103] The shape of the registered trademark mark R is not limited to a cross line; it can be any shape, such as a circle, a dot, or a rectangle.

[0104] For printing the registered trademark mark R, invisible inks such as UV fluorescent inks or infrared absorbing inks, which emit light at specific wavelengths or can be photographed with special cameras, can be used instead of ordinary black or CMY inks. Furthermore, the registered trademark mark R is not necessarily limited to printing; it can also be realized by leaving a portion of the line pattern unprinted (omitting it), as shown in the registered trademark marks R1 to R9 in Figure 12(c).

[0105] "Setting reference points for distortion measurement" To measure the amount of distortion, it is necessary to determine a reference point. Therefore, at least two register marks R are read, and based on the readings, a reference point for measuring the amount of distortion is determined.

[0106] Figure 13 is an image showing an example of a patterned printing layer with two registered trademarks.

[0107] The image shown in Figure 13 was obtained by scanning the pattern printing layer 12, and the cross lines at the top and bottom are the registered trademarks R1 and R2.

[0108] Figure 14 is a plan view showing the reference points set from the image shown in Figure 13.

[0109] Figure 14 shows nine reference points 1 to 9, which were set based on the reading results of the two register marks R1 and R2, as shown in the image in Figure 13.

[0110] To establish these reference points 1 to 9, as shown in Figure 14, a virtual line S0 was drawn connecting the two register marks R1 and R2. Virtual lines S1 and S2 were added parallel to this line at equal intervals to the left and right, and three virtual lines S3, S4, and S5 were added perpendicular to these virtual lines at equal intervals. The nine virtual intersection points obtained in this way were designated as reference points 1 to 9. In Figure 14 and subsequent drawings, the virtual lines S(S0 to S5) are shown as dashed lines.

[0111] Figure 15 is an enlarged plan view showing the actual printed line (magenta M) near reference point 1.

[0112] If the substrate 10 is not expanding or contracting, or if it is expanding or contracting uniformly across the entire surface, the printed line M (hereinafter, the printed line for magenta M will be referred to as "printed line M") is set to lie on the reference point 1. However, if the substrate 10 is partially expanding or contracting and distortion occurs, the reference point 1 and the printed line M will be misaligned, as shown in Figure 15. This misalignment is defined as the amount of distortion.

[0113] Figure 16 shows the amount of strain at each reference point.

[0114] Figure 17 shows the distortion of the printed line M reproduced from Figure 16.

[0115] In Figure 16, the amount of strain at reference point 1 is shown as strain amount 1, the amount of strain at reference point 2 as strain amount 2, and so on. A positive sign (+) in the strain amount indicates that it is shifted below the reference point in Figure 15. Therefore, if it is shifted above the reference point in the figure, a negative sign (-) is given to the strain amount.

[0116] Figure 16 shows that at reference points 1, 2, and 3, the printed line M is shifted horizontally downward by 2 μm; at reference point 4, the printed line M is shifted horizontally downward by 4 μm; at reference point 5, the printed line M is shifted horizontally downward by 7 μm; and at reference point 6, the printed line M is shifted horizontally downward by 2 μm.

[0117] These results show that the substrate 10 expands and contracts, causing distortion, and the printed line M is tilted and shifted diagonally downward to the right from reference point 4 to reference point 5, and diagonally upward to the right from reference point 5 to reference point 6, as shown in Figure 17.

[0118] According to the laser drawing position correction method of the embodiment of the present invention, the amount of distortion can be calculated in this manner. In the above explanation, an example in which nine reference points 1 to 9 are set was used, but the number of reference points is not limited to nine and may be more than nine. Also, if the amount of distortion is small, the number of reference points can be less than nine.

[0119] Ideally, setting a reference point for every line would allow for a more accurate calculation of distortion. However, increasing the number of reference points increases the computational load. Therefore, an appropriate number of reference points should be set based on the computer's processing speed, the required accuracy, and the drawing accuracy of the laser drawing device.

[0120] Furthermore, the above example uses a CMYW grid with horizontal lines arranged repeatedly in the vertical direction as an illustration. In this example, even if the laser drawing is slightly misaligned horizontally, it will not affect the color. However, if the laser drawing is even slightly misaligned vertically (for example, if the line width is 20 μm and it is misaligned by half, or 10 μm), the resulting color will be significantly different from the designed color. Therefore, although the above example only explains the amount of distortion in the vertical direction, if a CMYW matrix is ​​used for pattern printing instead of a grid, the vertical misalignment will also be important. In that case, the amount of distortion needs to be measured not only in the vertical direction but also in the horizontal direction.

[0121] (Method for calculating correction values ​​when performing rendering correction in two stages) The calculation of the line distortion is as described above. The line distortion is important information for determining the correction value of the laser writing device 20. However, the information for determining the correction value of the laser writing device 20 includes not only the line distortion, but also misregistration and distortion of the print, large expansion and contraction of the outer shape of the substrate 10 caused by lamination, local distortion caused by uneven lamination pressure and substrate inconsistencies, tilt and misalignment when the substrate is processed into an ID card, etc., and installation errors when the substrate is placed in the laser writing device 20.

[0122] If you try to correct all of these at once, it becomes difficult to distinguish between the reference point and the corresponding line because the lines being measured for distortion have the same repeating pattern. However, if the external shape has been corrected once, the discrepancy between the reference point and the target line can be reduced, making identification easier.

[0123] Therefore, in this embodiment, an example of performing drawing correction in two stages using the following two types of correction values ​​will be described.

[0124] The first of the two types of correction values ​​is a correction value for the amount of deformation of the outer shape of the substrate 10 (distance and angle between register marks R), and includes the stretching ratio and rotation angle of the pattern captured in the image data relative to the designed pattern.

[0125] The second of the two correction values ​​is a correction value for the local amount of distortion of the substrate 10 (deviation from a virtual reference point deformed to match the outer shape), and is the amount of local distortion of the pattern captured in the image data relative to the designed pattern.

[0126] The first correction value (correction value for the amount of deformation of the external shape) is obtained as follows.

[0127] Figure 18 is a diagram illustrating the first correction value.

[0128] Figure 18(a) shows the line design data for a pattern printing layer 12 with cross-line registered marks R1 and R2 at the top and bottom. When this line design data is printed onto the polycarbonate substrate 10, printing misalignment occurs, and expansion and contraction occur during heat lamination. In subsequent processes such as card die-cutting, the cards may be tilted or the die-cutting position may be off. Furthermore, when the polycarbonate substrate 10 is set in the laser drawing device 20, installation errors such as misalignment and tilting occur.

[0129] Figure 18(b) shows the state in which the lines have shrunk and tilted just before the drawing process, when the polycarbonate substrate 10 is set in the laser drawing device 20. The stretch ratio relative to the original design data is obtained from the ratio of the length of the imaginary line connecting the register marks R1 and R2 in Figure 18(b) to the length of the imaginary line connecting the register marks R1 and R2 in Figure 18(a). The rotation angle is obtained from the tilt of the imaginary line in Figure 18(b).

[0130] Furthermore, the second correction value is obtained as follows.

[0131] Figures 19 and 20 are diagrams illustrating the second correction value (the correction value for local distortion).

[0132] Figure 19(a) is similar to Figure 18(a) and shows the line design data for a pattern printing layer 12 with cross-line register marks R1 and R2 at the top and bottom. Using this line design data, virtual reference points (for example, reference points 1 to 9) are defined in accordance with the line design data before stretching, as shown in Figure 19(b).

[0133] Next, using the aforementioned scaling ratio and rotation angle, the position of the virtual reference point is corrected to obtain the deformed reference points (reference points 1 to 9), as shown in Figure 19(c).

[0134] Next, the deformed reference points (reference points 1-9) shown in Figure 20(b) are superimposed on the actual line pattern shown in Figure 20(a), and the amount of distortion at each reference point is calculated. Note that Figure 20(b) is the same figure as Figure 19(c).

[0135] When the deformed reference points shown in Figure 20(b) are superimposed on the actual line pattern shown in Figure 20(a), the positions of the register marks R1 and R2 coincide in both Figure 20(a) and Figure 20(b). Therefore, the discrepancy between the reference points and their corresponding lines is minimized, and as shown in Figure 20(c), only the local amount of distortion can be extracted. Since the amount of local distortion is information unique to each ID card, it can also be used as an artifact metric for authenticity determination.

[0136] (Laser drawing method when performing drawing correction in two stages) Next, we will explain the laser drawing method that is performed using the two-stage drawing correction method described above.

[0137] Figure 21 illustrates the transformation of drawing data performed by a two-stage drawing correction process.

[0138] The basic, uncorrected drawing data Da shown in Figure 21(a) is modified by applying the scaling factor and rotation angle used to determine the first correction amount to obtain the outline-corrected drawing data Db shown in Figure 21(b).

[0139] Furthermore, the local distortion amount at each reference point, which was used to determine the second correction amount, is applied to the plotting data Db to obtain plotting data Dc with local distortion correction applied, as shown in Figure 21(c).

[0140] The laser drawing device 20 uses the drawing data Dc shown in Figure 21(c) and uses the register mark R as a reference point, enabling it to accurately align with the distortion of the lines and perform laser drawing.

[0141] If the number of reference points is sufficiently large, one can connect each reference point horizontally with a straight line and draw the laser line along it. Alternatively, one can perform polynomial regression to fit multiple reference points and draw the laser line along a curve approximated by a quadratic or cubic equation.

[0142] This laser drawing method, which applies drawing correction in two stages, allows for laser drawing while correcting distortion even in repeating patterns such as grid lines. Furthermore, it can also correct distortion in grid lines with special shapes, such as waveforms rather than straight lines. In other words, even if the grid line pattern is distorted by, for example, thermal lamination, accurate laser drawing can be performed on the distorted grid lines, providing a color display without color shift. The accuracy of this correction can be, for example, less than half the line width of the grid line.

[0143] Furthermore, this laser drawing method can be applied not only to distortions, but also to pattern printing layers 12 where the periodicity of the pattern is partially incomplete, such as a line pattern, a line pattern that is not straight, or a line pattern where the pitch and angle of the lines differ. Therefore, even pattern printing layers 12 with incomplete periodicity can be laser drawn with correction, providing high-quality color display without color shifts.

[0144] As described above, according to the correction method of the embodiment of the present invention, in order to conceal a part of the pattern printing layer 12 in which a repeating color pattern is provided inside the polycarbonate substrate 10 and display an arbitrary color image, it is possible to correct the position of the laser drawing by measuring the local distortion of the pattern printing.

[0145] Furthermore, in the above description, as illustrated in Figure 27, the color development layer 13 is provided on the substrate 10 adjacent to the pattern printing layer 12 and on the surface side (upper side in Figure 27) of the pattern printing layer 12. However, the location of the color development layer 13 may also be adjacent to the pattern printing layer 12 and on the back side (lower side in Figure 1) of the pattern printing layer 12. Alternatively, it may be provided on both sides of the pattern printing layer 12, sandwiching the pattern printing layer 12.

[0146] [Laser drawing device] Next, a laser writing apparatus according to an embodiment of the present invention will be described.

[0147] Figure 22 is a block diagram showing an example configuration of a laser writing apparatus according to an embodiment of the present invention.

[0148] The laser drawing device 20 applies the correction method described above and comprises a CPU 22, a recording medium reading unit 24, an imaging unit 25, a laser irradiation unit 26, a drive unit 27, a memory 30, and a storage unit 40, all connected to each other by a bus 21.

[0149] The CPU 22 is a computer that controls the operation of each part of the laser drawing device 20 according to various programs stored in the memory 30.

[0150] The memory unit 40 is a storage device consisting of, for example, an SSD (Solid State Drive) or an HDD (Hard Disk Drive).

[0151] The substrate 10, which is laser-printed by the laser writing apparatus 20, is placed on a linear stage 50 driven by a drive unit 27. The substrate 10 contains a pattern printing layer 12 on which a line pattern is arranged, as illustrated in Figure 1. In Figure 1, the linear stage 50 is not included in the laser writing apparatus 20, but it may be considered as part of the laser writing apparatus 20.

[0152] The imaging unit 25 images the substrate 10, which is placed on the linear stage 50, from the surface (top) side. As shown in Figure 27, the surface of the substrate 10 is a transparent layer 14, and the color-developing layer 13 beneath the transparent layer 14 is also transparent. Therefore, by imaging the substrate 10 from the surface side, the imaging unit 25 can acquire high-precision image data of the line pattern placed on the pattern printing layer 12.

[0153] As mentioned above, the imaging unit 25 can be equipped with various cameras, scanners, CNC (Computer Numerical Control) image measuring machines, etc.

[0154] The imaging unit 25 outputs the acquired image data a to the memory 30.

[0155] The memory 30 stores various programs for realizing the laser drawing device 20, and these programs enable the correction value calculation unit 32 and the laser drawing control unit 34.

[0156] The correction value calculation unit 32 reads the register mark R from the image data a to determine multiple reference points and calculates the amount of distortion for each reference point. The amount of distortion is used to determine the correction value of the laser writing device 20.

[0157] However, the information used to determine the correction value of the laser drawing device 20 includes not only the amount of distortion of the lines, but also misregistration and distortion of the printed material, large expansion and contraction of the outer shape of the substrate 10 caused by lamination, local distortion caused by uneven lamination pressure and substrate inconsistencies, tilt and misalignment when the substrate 10 is processed into an ID card, etc., and installation errors when the substrate 10 is placed on the linear stage 50.

[0158] Therefore, when determining the correction value while also considering these factors, the correction value calculation unit 32 calculates a first correction amount, which is a correction value for the deformation amount of the outer shape, and a second correction amount, which is a correction value for the local strain amount.

[0159] In this case, as shown in Figure 18(b), the correction value calculation unit 32 uses a diagram representing the state in which the lines are contracted and tilted at the stage immediately before drawing, when the polycarbonate substrate 10 is set on the linear stage 50, to calculate a virtual line S connecting the register marks R1 and R2. b The length of the virtual line S connecting register marks R1 and R2 in the original design data, as shown in Figure 18(a). a The scaling factor relative to the original design data is obtained from the ratio with respect to the length. The correction value calculation unit 32 further calculates the virtual line Sa Virtual line S for b The rotation angle is obtained from the slope. The first correction amount is calculated from the scaling factor and the rotation angle.

[0160] The correction value calculation unit 32 further calculates the second correction amount by using the line design data of the pattern printing layer 12 exemplified in Figure 19(a) to define virtual reference points (for example, reference points 1 to 9) in accordance with the line design data before stretching, as shown in Figure 19(b). Using the aforementioned stretching ratio and rotation angle, it corrects the position of the virtual reference points to obtain deformed reference points (reference points 1 to 9), as shown in Figure 19(c). Next, the deformed reference points (reference points 1 to 9), as shown in Figure 20(b), are superimposed on the actual line pattern, as shown in Figure 20(a), to obtain the amount of distortion at each reference point. The second correction amount is calculated from the amount of distortion at each reference point (reference points 1 to 9).

[0161] Furthermore, since the local amount of strain is information unique to each substrate 10, it can be used as an artifact metric for authenticity determination. For this reason, the laser writing device 20 can store the local amount of strain of each substrate 10 in the memory unit 40. Alternatively, only the characteristic points of the strain amount may be extracted, compressed, and stored as a two-dimensional code or the like. Or it may be stored on an IC chip. Such artifact metric technology can be used to prevent counterfeiting and alteration.

[0162] The laser drawing control unit 34 controls the relative position between the laser irradiation unit 26 and the substrate 10 based on the output from the correction value calculation unit 32. This can be achieved, for example, by moving the position of the laser irradiation unit 26 relative to the substrate 10, or by moving the position of the linear stage 50 on which the substrate 10 is placed relative to the laser irradiation unit 26 using the drive unit 27. As mentioned above, the second correction value is prepared as data with the same array as the input image. The laser drawing control unit 34 determines the final laser drawing position corresponding to each pixel of the input image data on the substrate 10 placed on the linear stage 50 by combining this data with the scaling factor and rotation angle. Then, it controls the laser irradiation unit 26 and the drive unit 27 to perform laser drawing at the determined laser drawing position.

[0163] The programs that implement the correction value calculation unit 32 and the laser drawing control unit 34 may be pre-stored in the memory 30, or they may be read into the memory 30 from an external recording medium 23 such as a memory card via the recording medium reading unit 24. These programs are designed to be unrewritable.

[0164] In addition to this user-unrewritable area, the memory 30 also includes a writable data area 36 for storing rewritable data.

[0165] The drive unit 27 moves the linear stage 50 on which the substrate 10 is placed, under the control of the laser writing control unit 34. This allows the substrate 10 to be moved, for example, along a direction perpendicular to the lines on the substrate 10 (Y-axis direction, sub-scanning direction).

[0166] The laser irradiation unit 26, under the control of the laser writing control unit 34, irradiates the substrate 10 placed on the linear stage 50 with laser light L while moving along the direction of the X axis (main scanning direction) using a galvanometer mirror such as a 1-axis galvanometer or a 2-axis galvanometer.

[0167] In the laser irradiation section 26, it is preferable to use a near-infrared laser as the laser light L. Laser writing using a near-infrared laser causes the color-developing layer 13 inside the substrate 10 to develop color (carbonize), forming the black spot K as described above, and making it possible to conceal a part of the lines.

[0168] However, laser drawing for color display is not limited to black opacity; it can also be achieved by white opacity, which involves creating a scattering structure (foaming) of the substrate 10 itself. This can be achieved by using PC, PVC, or PET for the substrate 10 and irradiating it with a short-wavelength laser instead of a near-infrared laser from the laser irradiation unit 26.

[0169] As described above, the laser drawing device 20, with the above configuration, can correct for distortion even if the substrate 10 on which the lines are printed is distorted, for example during lamination, and accurately align the laser drawing to the lines, thereby achieving color display without color shift. This effect is particularly suitable for color displays on high-definition printed ID cards, where the impact of color changes due to distortion is significant.

[0170] Furthermore, by utilizing this effect, it becomes possible to digitize information unique to the ID card (artifact metrics) and record it in the storage unit 40, a server (not shown), or the ID card itself created from the base material 10, thereby enabling more sophisticated authenticity determination. In addition, it becomes possible to print not only conventional linear patterns but also repeating patterns of special shapes such as waveforms as the line pattern printed on the base material 10. By complicating the pattern, it becomes possible to improve the performance of preventing counterfeiting and tampering, and to contribute to the realization of easy authenticity determination through magnified observation. [Examples]

[0171] Next, an example of drawing performed using the laser drawing apparatus 20 according to an embodiment of the present invention will be described. The drawing was performed according to the following procedure. (1) Printing a line pattern onto a polycarbonate sheet, (2) Creation of a display unit by laminating polycarbonate sheets, (3) Capture an image of the entire line pattern. (4) Creation of correction data based on the amount of distortion of the lines, (5) Laser drawing using the input correction data.

[0172] The following explains each of the above steps.

[0173] (1) Printing of a grid pattern onto a polycarbonate sheet Using a gravure offset printing press, a CMY three-color line pattern was printed on a 50μm laser-colorable polycarbonate sheet (Mitsubishi Gas Chemical Co., Ltd.: SL2000) (hereinafter referred to as "polycarbonate sheet"). The line widths were 20μm for cyan (C), 20μm for magenta (M), and 20μm for yellow (Y), with a spacing of 10μm between C and M, and between M and Y, and a spacing of 40μm between Y and C. This resulted in a CMYW pattern with a repeating pitch of 20μm. The line length was 30mm horizontally, and the CMYW lines were repeated 400 times vertically in that order, without any gaps. This created a CMYW pattern printing area of ​​30mm horizontally and 48mm vertically. Furthermore, a cross line was added as a register mark R in the center of the C line at the top and the C line at the bottom. To facilitate reading, a 1mm gap was left around the cross line without any lines.

[0174] (2) Creation of a display unit by laminating polycarbonate sheets As described above, a color-developing layer sheet with a printed CMY pattern area, a core layer sheet, and a transparent layer sheet were laminated as shown in Figure 23 and fused together by heat pressing to create a sheet for display.

[0175] Figure 23 shows the laminated structure of the display sheet along with the product name.

[0176] Figure 24 is a photograph of an evaluation card obtained from a sheet used for the display unit.

[0177] The heating conditions for fusion were 190°C for 7 minutes, and the cooling conditions were 20°C for 5 minutes. The pressure during heating and cooling was adjusted as appropriate according to the elapsed time. The resulting sheet was punched out to ID1 card size to obtain evaluation cards. The photograph shown in Figure 24 is an image of the evaluation card obtained in this way.

[0178] (3) Capture an image of the entire line pattern. A flatbed scanner, the GT-X820 (manufactured by Seiko Epson Corporation), was used to photograph the line pattern portion of the evaluation card. The scanning resolution was set to 4800 dpi, and a full-color bitmap image was obtained.

[0179] (4) Creation of correction data based on the amount of distortion of the lines (3) Correction data for local distortion was created from the bitmap image obtained by capturing the image. The distortion correction data is a data file that defines the correction amount for each scan height (sub-scan position). One correction amount was defined for each laser pulse output from the input image for drawing. Therefore, the distortion correction data size is created to be the same as the input image size.

[0180] The distortion correction data has an array with the same number of vertical and horizontal pixels as the input image, and each element has a 1-byte value. The distortion correction value of each element is expressed from -128 (80h) to +127 (7Fh), and the actual amount of distortion is expressed in μm as (distortion correction value) × (resolution (μm)).

[0181] Figure 25 shows an example of distortion correction.

[0182] The left-hand diagram in Figure 25 shows an example of a negative distortion correction value. It indicates that the cyan C printed line is shifted downwards relative to the reference line H (shown by the dotted line), indicating that the laser drawing needs to be corrected downwards. The right-hand diagram in Figure 25 shows the opposite: the printing is shifted upwards, indicating that a positive correction value is used to correct the drawing upwards.

[0183] (5) Laser drawing using the input correction data During laser drawing, the drawing data is corrected using the two correction values ​​mentioned above: the first correction value, which is a correction value for the amount of deformation of the outer shape, and the second correction value, which is a correction value for the amount of local distortion.

[0184] The first correction value is obtained by photographing the registration mark R with the imaging unit 25 of the laser writing device 20 after the evaluation card has been placed on the linear stage 50. This makes it possible to correct for large expansion and contraction of the substrate, as well as misalignment and tilt when the evaluation card is placed. The first correction value is defined by the expansion ratio and rotation angle values ​​obtained from the distance and tilt of the two registration marks R.

[0185] Figure 26 shows photographs of (a) the color display created in this embodiment and (b) a color display for comparison.

[0186] As mentioned above, the second correction value is prepared as data with the same array as the input image. By combining this data with the first correction value, which is the scaling factor and rotation angle, the final laser drawing position corresponding to each pixel of the input image data on the evaluation card is determined. Laser drawing is then performed on the evaluation card at the determined laser drawing position to obtain a color display as illustrated in Figure 26(a).

[0187] The laser drawing position was moved in the direction of the laser lines (X-axis, main scanning direction) by driving the galvanometer mirror, and in the direction perpendicular to the laser lines (Y-axis, sub-scanning direction) by moving the linear stage 50 on which the evaluation card was mounted. Drawing correction was performed by minutely driving the Y-axis galvanometer mirror when drawing in the X-axis direction.

[0188] The galvanometer mirror has a resolution of 12 μrad, a rendering resolution of 2.4 μm (at a processing surface of 10 mm with an f-θ lens), and a linear stage has a resolution of 1 μm.

[0189] (Creation of comparative samples and verification of effects) For comparison with the color display created in this embodiment, as illustrated in Figure 26(a), a comparison color display was created by laser drawing using the same procedure as above, but without using the second correction value. Figure 26(b) is a photograph of this comparison color display.

[0190] Comparing the two color displays, as shown in Figure 26(b), the color display created by laser drawing without using the second correction value exhibited partial color misalignment (failure to produce the expected colors). On the other hand, the color display shown in Figure 26(a) showed no color misalignment and produced the expected colors correctly overall, confirming that the laser drawing position correction method of this embodiment can achieve high-quality color display without color misalignment.

[0191] The best mode for carrying out the present invention has been described above with reference to the accompanying drawings, but the present invention is not limited to this configuration. Within the scope of the invented technical idea of ​​the claims, a person skilled in the art can conceive of various modifications and alterations, and it is understood that such modifications and alterations also fall within the technical scope of the present invention. [Explanation of Symbols]

[0192] 1~9 Reference points 10 Base material 11 Core substrate 12 Pattern Printing Layers 13. Color-developing layer 14 Transparent layer 20 Laser writing device 21 Bus 22 CPU 23 External recording media 24 Recording medium reading unit 25 Imaging Department 26 Laser irradiation area 27 Drive unit 30 Personal Authentication Media 32 Correction Value Calculation Unit 34 Laser lithography control unit 36. Writable data area 40 Storage section 50 Linear Stage 130 Personal Authentication Media a Image data Da - Drawing data before correction Db Drawing data after outline correction Dc local distortion correction data H reference line K Black spot L laser light R Registered trademark S virtual line

Claims

1. A method for correcting the laser drawing position, The processor, The steps include: acquiring image data of a substrate on which a designed pattern has been printed and which will be laser-drawn, by having the substrate imaged by an imaging unit before laser drawing; The steps include: calculating a correction value to correct the laser drawing position by comparing the designed pattern with the pattern captured in the image data; Correction methods, including those mentioned above.

2. The calculation step is a substep in which the amount of distortion of the pattern captured in the image data relative to the designed pattern is calculated as the correction value. The correction method according to claim 1, including the method described in claim 1.

3. The correction value includes a first correction value that includes the stretch ratio and rotation angle of the pattern captured in the image data with respect to the designed pattern, and a second correction value that is the amount of local distortion of the pattern captured in the image data with respect to the designed pattern. The correction method according to claim 1.

4. Due to the aforementioned designed pattern, at least two registered trademark symbols are positioned. The calculation step described above is: The scaling factor is calculated from the ratio of the length between two corresponding registered marks positioned for the pattern captured in the image data to the length between two registered marks positioned for the designed pattern. The rotation angle is calculated from the slope of a straight line connecting two corresponding registered marks, which are positioned for the pattern captured in the image data, with respect to a straight line connecting two registered marks positioned for the designed pattern. The correction method described in claim 3.

5. A laser irradiation unit for laser drawing by irradiating a laser onto a designated location on a substrate printed with a designed pattern, An imaging unit captures an image of the substrate before the laser irradiation unit irradiates it with a laser, and acquires image data of the substrate. A correction value calculation unit calculates a correction value for correcting the location for irradiating the laser, based on a comparison between the designed pattern and the pattern captured in the image data. A laser drawing control unit controls the relative position between the substrate and the laser irradiation unit based on the correction value. A laser drawing device equipped with a laser.

6. The laser drawing apparatus according to claim 5, wherein the laser drawing control unit controls the relative position by moving the laser irradiation unit with respect to the substrate.

7. A linear stage for positioning the substrate, The system further comprises a drive unit that moves the linear stage according to the control of the laser drawing control unit, The laser writing apparatus according to claim 5 or 6, wherein the laser writing control unit controls the relative position by moving the linear stage relative to the substrate using the drive unit.

Images