JPS62251142A - Device for measuring misregister in multi-color printing - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a misregistration measuring device of the type indicated in the preamble of claim 1.

[Conventional technology]

In multicolor printing, partial patterns printed with each color of printing ink must match with a high degree of precision.

In order to inspect and manage the relative positional deviation of individual color patterns, that is, so-called misregistration, it is common to use a register mark printed with the pattern. Alternatively, as has been done recently, evaluation is performed using photoelectric technology and, in some cases, electric field plates. An example of such a more or less automated register system using photoelectric technology is DE-C-32
48795 (U.S. Pat. No. 3357, Dec. 30, 1981)
All these systems work online in a running printing press using specially constructed register marks and conventional scanning devices adapted accordingly. There are no comparable portable measuring instruments that can be used offline.Although online/offline systems are known in which register marks are scanned and displayed with a television camera, such systems are relatively complex and often too expensive to apply.

[Problem that the invention seeks to solve]

Therefore, the present invention is expected to be particularly suitable for off-line use, to have less structural complexity, to be easy and reliable to operate, and to satisfy the accuracy required for the purpose.
It is an object of the present invention to provide a portable measuring device for misregistration that does not require excessive positioning accuracy during use.

[Means for solving problems]

Although the device according to the invention is based on a device of the type indicated in the preamble of claim 1, the invention is characterized by the points indicated in the characterizing section of claim 1. shall be. Individual characteristic embodiments are indicated in the dependent claims.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

The device shown in FIG. 1 is constructed as a portable measuring instrument, with all its components housed in a housing G, which is shown here only schematically.

In this case, the configuration of the device is largely similar to a portable densitometer, but other embodiments are of course possible.

Inside the housing G are a rotatably mounted scanning spatula)
There is an output unit) D, and the input/output unit) D is
Contains displays and/or interfaces to other equipment. The scanning head A is rotatable about a vertical axis Z and includes a light source 1, an illumination optical system 2, a measuring optical system 3, a filter disk 5 driven by a motor 4, and an aperture plate 6.
, and a photoelectric converter 7, and the photoelectric converter 7 is connected to a measurement value converter M. Other than the fact that the scanning head A is rotatable and the way in which the scanned data is evaluated is different, this device corresponds generally to the commercially available portable densitometers as described above, so no further explanation of its construction is required. is not necessary.

During the measurement work, the printed paper sheet P to be examined
Place this device by hand so that the register mark printed with the pattern is inside the scale plate V provided on the housing G, and then start scanning automatically or by pressing the button. . At this time, the lamp 1 generates an extremely small dot-like light spot LF (FIG. 2) on the printed paper sheet P, and this light spot is projected onto the aperture plate 6 via the measuring optical system 3. The photoelectric converter 7 measures the light that has passed through the aperture plate 6. This light spot is approximately 2
Due to their offset position, when the scanning head A rotates, it moves along a circular path K and the printed sheet P is scanned in a circular manner. The filter disk 5 serves to separate the measured light into colors, making it possible to match the values obtained in the scanning to the individual printing colors.

FIG. 2 explains the method for measuring misregistration.

Here, the deviation between the print direction (direction of sheet movement in the printing press) and the direction perpendicular to the print direction of each color pattern is relative to one freely chosen reference pattern (usually black). be.

The rotating scanning head A moves the register mark PM in a circular trajectory K
scan along. The diameter of this circular orbit is, for example, about 4 mm. The center of the circle given by the projection of the axis of rotation Z of the scanning head A is designated by Z. The light spot LF moves on the circumference in angular increments smaller than, for example, 0.36° (1000 increments per rotation). , of course, for example about 2 per revolution
It is also possible to use increments such as 000 increments or 3000 increments that provide even higher resolution.

Since the radius of the scanning trajectory is fixed, the position of the light spot LF is uniquely determined by its angular position.

The zero point (angle reference line) (arbitrarily defined and unique to the measuring instrument) is α in FIG. It is shown by .

The printing direction and the direction perpendicular thereto are indicated by the coordinate axes X and y.

In FIG. 2, only a portion of the entire register mark is shown for ease of viewing.

That is, only the black central cross mark 15 and the hook-shaped (L-shaped) mark 12 of one color are shown. Each time the light spot traverses one of the linear legs of the individual colored marks on its scanning path, a distinct change in the diffuse reflection occurs, which is used to detect the position of the traversal point. It is evaluated in the control/calculation circuit E, as is customary. The angular position of the cross-cutting point obtained in this way is shown in the figure from α1 to α
Shown up to 6. From these angles, the distances ΔX and Δy between the central cross mark 15, which served as a reference in this example, and the hook-shaped mark 12 are determined by the following equations.

In the same way, distances to marks of other colors are also found. It is known from simple calculations that the positioning of the device on the printed paper sheet in △ The angular position is also irrelevant. It is self-evident that the positioning of the device can be rough, but at least the register mark is on the device.
[Here] it must be done without going outside the circular scanning area.

The numerical ratio of the diffuse reflection signals supplied from the photoelectric converter 7 is performed in an amplification/A/D converter M.

The calculation of the distances △X and △y and the calculation of the misregistration therefrom (by subtracting the distances in a fixed ideal case) is carried out by an evaluation device which is included in or constituted by the control/calculation circuit E. carried out by. Control/calculation circuit E
In addition to controlling the drive motors S and 4 and the light source 1, it also controls all the individual steps necessary during the measurement process, as is done in modern computer-controlled portable densitometers. Copenate. The operation of the device and the display of measurement results are the same as with a portable concentration meter, but
This is done by the input/output unit D.

The width of the line of the register mark is preferably about 0.1 mm, and the spread size of the mark itself is, for example, 7 x 7.
It is mm2. The distance between two mutually parallel and adjacent legs of individual marks belonging to each color is approximately 0.8 mm.

Therefore, a practical device with high accuracy (001) is achieved.

The scanning of the individual color marks can be done in single channel or multichannel, successively or in parallel. In the case shown here, the color separation is performed by color filters mounted on a filter disk.

Of course, other methods can also be applied. It is important that the position of each color mark line is accurately measured and
This means that it can be made to correspond to each printing color.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the device according to the invention with a circular movement of the scanning head, and FIG. 2 is a sketch diagram for explaining the detection/calculation of misregistration by circular scanning. A...Scanning head E...Evaluation device (control/
calculation circuit),

Claims (1)

[Claims] 1. A photoelectric scanning device (A) that scans register marks (PM) printed on a sheet of paper together with a pattern in different colors and measures the relative position of each register mark (PM). A device for measuring the registration between individual colors in multicolor printing, comprising an evaluation device (E) working in combination with a scanning device (A) for the purpose of (E) together with the housing (G) to be placed at the desired measurement location on the stationary printed sheet (P);
the scanning device (A) has a scanning head (A) arranged movably within the housing (G) for performing a scanning movement; A sheet of paper (
Apparatus for measuring registration in multicolor printing, characterized in that drive means (S) are provided in the scanning head (A) for moving the scanning head (A) relative to P). 2. The device according to claim 1, wherein the scanning head (A) is arranged to be linearly movable within the housing (G). 3. Device according to claim 1, in which the scanning head (A) is arranged for rotation within the housing (G). 4. The scanning device (A) and the evaluation device (E) are configured to detect a linear or line-containing registration mark and measure their relative positions. Apparatus according to any one of clauses 3. 5. At least one aperture plate (51, 52) in the form of a linear slit in such a way that they are parallel to the linear register mark (PM) to be scanned during installation of the device. 5. The device according to claim 4, wherein the device is mounted on the scanning head (A) so that it can be easily moved relative to the housing (G). 6. The scanning head (A) is preferably 45° or 9
6. Device according to claim 5, comprising two slit-shaped aperture plates (51, 52) arranged at an angle of 0[deg.].