JPS60225158A - Moire inspecting device for photoengraving - Google Patents

Abstract

PURPOSE:To inspect simultaneously four kinds of moires by using a moire simulator in which four kinds of patterns for inspecting moires are recorded in the superposed state with different colors to project the moire simulator or the real image of a reflected original on the other and superposing optically the same. CONSTITUTION:Four kinds of the patterns for inspecting moires having the same patterns as the patterns of respective contact screens for black, magenta, cyan and yellow to be used in the stage of photoengraving are recorded in the superposed state with respective colors. The moire simulator 63 is illuminated by the illuminating light from a lamp 58. The pattern for inspecting moires and angle scale are projected by a projecting lens 47 onto the reflecting original 45 imposed on a stage 42. A base 64 is rotated to rotate the pattern for inspecting moires recorded thereto. A holder 70 is then slided and the point where the moires disappear is found by shifting each slightly the moire simulator 63. The rotating angle and the shifting rate of the focus in this stage are read from the scale.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a method for predicting the presence or absence of a moire phenomenon that occurs between a mesh pattern used in a process and a reflective original, and preventing the moire phenomenon from occurring. The figure relates to a moiré inspection device for plate making to determine the conditions.

[Prior art]

The technology of converting the shading of the original image into the size of the halftone dot area and reproducing it as a print image is widely practiced in the fields of platemaking and printing as a camera method using a contact screen or halftone processing using a direct color scanner. .

Since the contact screen has regularly arranged shading, if there is a part of the image of the document in which the shading is regularly arranged, such as a pattern on clothing, these parts will optically interfere, causing Shade patterns that are not present in the original often occur.

This shading pattern is called moiré, and it significantly impairs image quality. Particularly in the case of color printing, overprinting is performed using four halftone plates for yellow ink, magenta ink, cyan ink, and black ink, which increases the chances of moire occurring. In addition, in the case of color printing, moiré occurs between each color plate, so the screen angle (the angle between the straight line extending in the direction of the halftone dots and the base perpendicular line) differs for each color. A contact screen is used. Various combinations of screen angles are used in practice, but the contact screens used in prepress cameras are 0 degrees for yellow plates, 15 degrees for magenta plates, 75 degrees for cyan plates, and 45 degrees for blank plates. There are many degrees. In addition, for color scanners, for example, MagnaScan 520 (manufactured by Crossfield), the yellow version is 90 degrees and the magenta version is 40 degrees.
5 degrees, the cyan version is 75 degrees, and the blank version is 15 degrees.

If moiré occurs in the prepress photo, it is necessary to shift the arrangement angle of the contact screen or shift the arrangement angle of the document, and then create the prepress photo again. Therefore, countermeasures against moiré require a lot of time and HA loss of materials. In particular, in color printing, if the angle of placement of the contact screen is shifted, moiré may occur between the two different contact screens, and if the angle of placement of the document is shifted, other colors may Since new moiré occurs between the contact screen and the manuscript, it is not possible to eliminate the moiré with a single correction, and multiple mesh resolutions are required, which is extremely troublesome. .

In order to deal with this troublesome moire problem, a moire pre-search gauge has been proposed that can predict whether or not moire will occur before creating a plate-printed photograph. (Sho 59-9338). The moire pre-search gauge uses one sheet on which the same moiré inspection patterns as the four types of mesh patterns output from the direct color scanner, which electrically processes the shading, are recorded separately, and this sheet. It is composed of a scale plate which is rotatably held and has an angle scale attached to its outer periphery. In use, a moire pre-search gauge is set on a projection device, a real image of a transparent document is projected, and the image is optically superimposed on the moire pre-search gauge to predict whether moire will occur between each pattern. However, with this device, four types of moire inspection patterns are recorded separately in four rectangular areas, so it is difficult to check whether four types of moire occur at the same time. could not. Therefore, in order to check whether moire occurs on the entire surface of a transparent original, it is necessary to move the transparent original or the moire pre-search gauge and check whether moire occurs for each color plate and the screen angle at which this disappears. , the inspection work requires a lot of time. In addition, when simultaneously separating four versions using a direct color scanner, it is impossible to change the mounting angle of the document for each color version, so we comprehensively evaluated the four types of moiré and evaluated their effects. It is necessary to check the angle when attaching the document that will cause the least amount of damage, but since the moire pre-search gauge described above checks moire for each color plate, it is possible to attach a common document without the influence of the four types of moire. had the disadvantage that it was extremely difficult to check the angle.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a moire inspection device for plate making that can distinguish and simultaneously inspect four types of moire that occur between four types of mesh patterns used during plate making and a reflective original. That is.

[Features of the invention]

In order to achieve the above object, the present invention uses a moire simulator in which four types of moire inspection patterns are recorded in different colors in an overlapping state, and uses a variable magnification optical system to detect the moire simulator or reflective original. One real image is projected onto the other and optically superimposed.

When inspecting moire that occurs in a plate-making camera, the moire inspection pattern includes a contact screen for black, a contact screen for magenta,
The same number of turns as the cyan contact screen and yellow contact screen are used. Further, when inspecting moire generated in a direct color scanner, the same pattern as the four types of electrically generated mesh no-turns is used as a moire inspection pattern.

[Summary of the invention]

FIG. 1 shows an example in which a real image of a moire simulator is projected onto a reflective original.

Light emitted from a light source 1 reaches a transmissive moiré simulator 2 and illuminates it from behind. This Moiré Simulator 2 has four types of moiré inspection patterns that have the same patterns as the black contact screen, magenta contact screen, cyan contact screen, and yellow contact screen used during plate making, with appropriate transmittance. Each color is recorded on a transparent sheet, overlapping each other, while maintaining the same color. The moire simulator 2 is rotatable in a plane perpendicular to the optical axis 3 and movable along the optical axis 3. The four types of moire inspection patterns recorded in the moire simulator 2 are imaged by an optical system 4 with variable magnification on a reflective original 5 such as a color print photograph at enlarged, reduced or same magnification. Note that since the moire simulator 2 is, for example, enlarged and projected onto the reflective original 5 by the optical system 4, the number of screen lines can be substantially changed. For example, if the moire simulator 2, which has a screen line count of 200, is doubled, the screen line count will be 00, so it can be used instead of a moire simulator 2 that has a screen line count of 100.

As shown in FIG. 2, the moiré simulator 2 includes a yellow sheet 20. Magenta sheet 21, cyan sheet 22. It is composed of a blank sheet 23 and a scale plate 24 with an angle scale. Each of the sheets 20 to 2
3 is a transparent film with a moiré inspection pattern recorded on it in the same color as the color plate, for example yellow in yellow sheet 20, and with an appropriate light transmittance, and a transparent film with an angle scale on the outer periphery. It is attached to a scale plate 24 in the same direction as the contact screen used during plate making. Since the moire inspection pattern is preferably the same as the contact screen used for printing, a moire simulator suitable for the contact screen actually used is selected and used.

Generally, the contact sleeve has a pattern shape, 1
It is specified by the number of halftone dots per inch and the screen angle. The shapes of this pattern include cross lines, squares, chains, dots, and ovals.

There are triangles, etc. The screen angle represents the angle between a straight line extending in the direction in which the halftone dots are lined up and a perpendicular line that serves as the base, and is determined by the specifications of the plate-making camera or scanner used.

When inspecting moire, the light source 1 is turned on to project real images of four types of moire inspection patterns recorded in the moire simulator 2 onto the reflective original 5. The reflective original 5
If there is a part in which the light and shade changes periodically, optical interference will occur between the real image of the moire inspection pattern and, therefore, if you look at the reflective original 5 with the eye 6, you will be able to observe the moire that occurs during plate making. I can do it. In this Moire Simulator 2, each moire inspection pattern is recorded in a color corresponding to the color plate, so by examining the color of moire, it is possible to predict with which contact screen moire will occur during plate making. be able to. If this moire is occurring, the moire simulator 2 is rotated in a plane perpendicular to the optical axis 3. When you rotate this moiré simulator 2,
The moiré inspection pattern recorded on this rotates. Then, find a place where the four types of moiré disappear or can be ignored, and check the rotation angle at that time.

If the moire does not disappear even after rotating the moire simulator 2, set the moire simulator 2 at an angle that reduces the four types of moire the most, and in this state, move either the moire simulator 2 or the reflective original 5 along the optical axis. Shift it little by little along 3. While shifting this focus, find a place where the moiré disappears or can be ignored, and check the amount of focus shift at that time.

Depending on the angle obtained as described above, the inclination of the reflective original 5 mounted on the original tram of the direct color scanner is changed. For example, the angle checked with a moiré inspection device for plate making is 15
In the case of a degree, the reflective original 5 is set in the original tram with the reflective original 5 rotated 15 degrees from the normal position. Furthermore, if the moiré disappears by adjusting the focus, the focus is shifted to the reading head or exposure by the amount of shift. Note that if moiré occurs only in a certain color plate, it is possible to know in which color plate the moire occurs from the color of the moire, and the focus of that color plate can be shifted.

In the case of a scanner that uses a plate-making camera and a contact screen, the screen angle can be changed for each color plate, so the occurrence of moiré can be eliminated by the following method, which is different from the method described above. In other words, since it is possible to know in which color plate moire occurs from the moire color, the rotation angle of the moire simulator 2 at which moire disappears for each color plate is checked, and the angle with the moire inspection pattern is considered. Then, the screen angle is calculated, and the original is rotated according to this screen angle to produce a photo plate. If the moire does not disappear, check the amount of focus shift for each color plate and shift the focus for that color plate.

FIG. 3 shows an example in which a real image of a reflective original is projected onto a moiré simulator, and the same members as in FIG. 1 are given the same reference numerals. A reflective original 5 is illuminated by a lamp 1, and the light is reflected from its surface and passes through an optical system 4 to reach a transmissive screen 8. This transparent screen 8
is placed in close contact with the moiré simulator 2 or slightly separated therefrom. The transmission screen 8 includes:
The image recorded on the reflective original 5 is projected by the optical system 4 at the same magnification as during plate making, and is optically combined with the moire inspection pattern recorded on the moire simulator 2. In the case of this embodiment, the image of the reflective original is magnified or enlarged so that it has the same size as that at the time of plate making.

Since the image is reduced and projected onto the transmission screen 8, it is possible to observe the same moiré that occurs during plate making.

[Configuration of First Embodiment] FIGS. 4 and 5 show a moire inspection device for plate making that embodies the embodiment shown in FIG. 1.

An opening 41 is formed below the casing 40,
A stage 42 made of a white acrylic plate is fitted into this. On this stage 42, a transparent document mounting plate 44 on which a grid-like reference line 43 is recorded is placed.

In this document attachment, a reflective document 45 is fixed flatly on a plate 44 with a transparent tape 46.

A projection lens 47 is arranged above the stage 42, and a bellows 49 is attached between the opening 48 and the projection lens 47. A lens barrel 50 holding the projection lens 47 is fixed to a slide lever 51 having a rank gear 51a. This rank gear 51a has
Pinion gear 53 rotated by magnification adjustment knob 52
are engaged with each other, and by turning the magnification adjustment knob 52, the slide lever 51 is moved along the optical axis 54,
The magnification factor can be adjusted to a desired value. Note that as this magnification conversion mechanism, one used in a known projector can be used as is.

A lamp house 57 is attached above the casing 40 via an arm 56. This lamp house 57 houses a lamp 58 and a mirror 59 placed behind it.

Note that reference numeral 60 is a thumbscrew, and by loosening this, the arm 56 can be removed from the casing 40. The light emitted from the lamp house 57 passes through the upper opening 62 of the casing 40 and enters the moire simulator 63.
to illuminate. The light transmitted through this moiré simulator 63 is reflected downward by a mirror 77 and then enters the projection lens 47.
The real image of the moiré simulator 63 is projected onto the "-" of the moire simulator 63.

As shown in FIG. 6, the moire simulator 63 records four moire inspection patterns (not shown) in the same color as the color plate overlappingly on one transparent haze 64. . In addition, this heath 64 has a finger hole 64a,
A stepped portion 64b and an index 64C are formed. Scale plate 6
5 is provided with a flange 65a having an angle scale, and this flange 65a abuts against the stepped portion 64b of the heath 64, and holds the hese 64 so that it can rotate without coming out. Further, the moire simulator 63 includes a transparent plate 67
It is rotatably held at three points relative to the transparent plate 67 by one fastener 68 attached to the transparent plate 67 and two rollers 69 placed below.

The transparent plate 67 is held by a holder 70, and a rank gear 70a is formed on this holder 70. This rank gear 70a is meshed with a pinion gear 72 that is rotated by a focus adjustment knob 7I. When the bottle knob 71 is rotated, the holder 70 moves in the arrow direction while holding the moiré simulator 63. During this focus adjustment, since the focus m-node knob 71 has a scale that indicates the amount of deviation from the focus plane, it is possible to know the amount of deviation from the focus plane by reading the scale that matches the index 73. can.

An opening/closing lid 76 is attached to the upper part of the casing 40 via a hinge 75, so that the moiré simulator 63 can be replaced depending on the contact screen used in the plate-making camera or scanner.

[Operations of the first embodiment] First, to attach the original, a reflective metal 11% 45 is placed on top of the handle 44 and fixed with transparent tape 46 so that it does not move.

To mount the original with the reflective original 45 fixed, the plate 44 is placed on the stage 42. Next, turn the magnification adjustment knob 52 to set the desired magnification. This magnification adjustment knob 5
2, the pinion gear 53 rotates, the slide lever 51 moves up and down, and the projection lens 47 is aligned with the optical axis 5.
4, the cent can be placed at the desired magnification position.

Also, operate the focus adjustment knob 7I to adjust the projection lens 4.
The moiré simulator 63 is positioned at the focal plane of 7.

The mower simulator 63 is illuminated with illumination light from the lamp 58, and the light transmitted therethrough is incident on the projection lens 47 via the mirror 77. This projection lens 47 allows the moire inspection pattern and the angle scale to be projected onto the stage 4.
The image is projected onto a reflective original 45 placed on the screen 2. The scale plate 65 is rotated and set so that the "zero" of the angle scale projected on the reflective original 45 coincides with a desired one of the reference lines 43 recorded on the slope 44 for mounting the original. next,
For the finger rest, insert your finger into the hole 64a and rotate the head 64.
Adjust the index 64c of the head 64 to "zero" on the angle scale.

If there is a part in the reflection group 1i%45 where the density changes periodically, optical interference will occur with the moiré simulator 63, and the same moiré as that which occurs during mesh resolution will occur. When this moire occurs, when the header 64 is rotated, the moire inspection pattern recorded thereon is rotated. Then, find a place where moiré disappears or can be ignored for all four colors or for each color plate, and then find the index 64b at that time.
Check the angle scale that matches a.

If the moire does not disappear even after rotating the moire simulator 63, set the moire simulator 63 to the angle that will reduce the moire the most, and then turn the focus adjustment knob 7.
1 to rotate the holder 7 from the focal plane of the projection lens 47.
0 to shift the moiré simulator 63 little by little. Then, find a place where the moiré disappears or can be ignored, and read the amount of focus shift at that time from the scale on the focus adjustment knob 7J.

[Second Embodiment] FIG. 7 shows a moiré inspection device for plate making that embodies the embodiment shown in FIG. 3, and the same parts as in FIGS. 4 and 5 are given the same reference numerals. It is.

A pair of lamps 80.81 are arranged above the stage 42, and these lamps 80.81 reflect the original 4.
5 is illuminated. The light reflected on the surface of the reflective original 45 passes through the projection lens 41 = Mi 1-77 and reaches the transmission screen 83, and a real image of the reflection original 45 is focused on the transmission screen 83 at the same magnification as during plate making. imaged. The image formed on the transmission screen 83 and the moire inspection pattern recorded on the moire simulator 64 are optically aligned, so when viewed from the front of the moire simulator 64, it is the same as the moire that occurs during plate making. can be observed.

In addition, when using a transparent original, place it on the stage 42, turn on the illumination unit 85 placed below the stage 42, and illuminate the transparent original from behind. The real image of the original is displayed on a transmission screen 83
All you have to do is image it.

〔Effect of the invention〕

The present invention having the above-mentioned configuration uses a moire simulator in which 4 ft moire inspection patterns are recorded in different colors, and uses an optical system that can adjust the magnification to a desired magnification to perform the four types of moire inspection. By projecting one side of the image pattern or reflective original onto the other, it is possible to simultaneously inspect four types of moiré, and to comprehensively evaluate these moiré patterns and select the common moiré pattern that minimizes their effects. You can easily check the mesh conditions. Therefore, the present invention has a great practical effect on direct color scanners that electrically process shading.

Also, it is possible to know in which color plate moire occurs depending on the color of the moire.1. If a contact screen is used, it is possible to know the screen angle that minimizes moiré for each color plate. Therefore, unlike conventional devices, there is no need to move the moire simulator (moire pre-search gauge), which simplifies the inspection work and allows the moire simulator to be made more compact.

[Brief explanation of the drawing]

FIG. 1 is an optical path diagram schematically showing an embodiment in which an image of a moiré simulator is projected onto a reflective original. FIG. 2 is an exploded perspective view showing an example of a moiré simulator. FIG. 3 is an optical path diagram showing an embodiment in which the image of a reflective original is projected onto a transmission screen placed close to a moiré simulator. FIG. 4 is an external view showing an example of a moire inspection device for plate making that embodies the embodiment shown in FIG. 1. FIG. 5 is a sectional view of FIG. 4. FIG. 6 is an exploded perspective view showing another embodiment of the moiré simulator. FIG. 7 is a sectional view of a moiré inspection device for plate making embodying the embodiment shown in FIG. 1... Light source 2... Moiré simulator 4... Optical system 5... Reflective original 8... Transmissive screen 42... Stage 44... Original mounting plate 45... Original 47... Projection lens 52... Magnification adjustment knob 57... Lamp house 58... Lamp 63... Moiré simulator 64... Heath 65... Scale plate 71... Focus adjustment knob 80. 81... Lamp 83... Transmissive screen. -111, -1110

Claims (1)

[Claims] fll A moire inspection device for plate making for pre-inspecting moire occurring during plate making, comprising a stage on which a reflective original is placed, a mesh pattern for yellow, a mesh pattern for magenta, and a mesh pattern for cyan used during plate making. 4 according to the mesh pattern for black and the mesh pattern for black
a moire simulator in which different types of moire inspection patterns are recorded in an overlapping state using different colors; a variable magnification optical system that projects a real image of either the moire simulator or a reflective original onto the other; and the moire simulator A plate-making mower V characterized by comprising means for rotatably holding the mower V and moving the mower V in the optical axis direction.
Inspection equipment. (2) The moire simulator is composed of four sheets on which four types of moire inspection patterns are recorded, and a scale plate having angle scales attached to the outer periphery and to which the four sheets are fixed. A moire inspection device for plate making according to claim 1, characterized in that: (3) The moire simulator is composed of one sheet on which four types of moire inspection patterns are recorded and a scale plate having an angle scale on the outer periphery. The moire inspection device for plate making according to item 1. (4) The moire inspection device for plate making according to claim 3, wherein the sheet is rotatably housed inside the scale plate.