EP0131109A2 - Device for determining and evaluating by a densitometer the colour swatches on a sheet placed on a measuring table - Google Patents

Abstract

A printed sheet (3) which is in any position on a digitizing table (1) is shown. The printed sheet (3) is scanned with a stylus (2) at measuring points (2.1, 2.2, if applicable 2.3) for position detection. Then the color measuring fields (14 - 14.3), which can be arranged between printed sheets in any area depending on the print job, are also scanned once with the stylus (2). Using the position coordinate values stored by the stylus (2), a densitometer (8) can be approached automatically as often as required.

Description

The invention relates to a device according to the preamble of the first claim.

In order to simplify the recurring evaluation of color measurement fields on a printed sheet by means of a densitometer, the densitometer is held movably on rails in the X, Y direction. In the case of constant repetition of individual measurement processes with the same printed sheets, positioning the densitometer by hand is ruled out because of the inaccuracy that occurs.

It is e.g. To move to certain areas of a printing sheet, it is necessary that the printing sheet lies on its base in a defined position. So that the specific areas always have the same coordinates. This means that the printed sheets would always have to be positioned and fixed exactly on their base, but this is not easily possible.

One way of positioning the printed sheets would be e.g. the use of stops on which the printed sheets could be placed. Since these stops protrude from the base, the area around these stops would not be available for certain measuring devices to carry out measurements there.

From DE-OS 2 913 410, for example, a photoelectric measuring device has become known which is intended to detect the position of an edge of a sheet on a surface. The position of the sheet edge should be determined very precisely. Here a number of a plurality of optical fibers lying close together are arranged. Each optical fiber is connected to an evaluation unit, which converts a light signal into an electrical signal, which is processed accordingly. The free flat ends of the optical fibers face a light source and are located in a window of the arch support. The disadvantage of this device, however, is that a special light source must be provided above the light guide, which makes this area inaccessible for measurement purposes. In addition, the sheet must lie exactly flat in this area so that an exact position determination is possible.

Furthermore, a device for determining and evaluating color measurement fields on a printed sheet has become known in DE-OS 3 232 490. A printed sheet lying arbitrarily on a sheet base is photoelectrically detected by means of image sensors. For this purpose, a matrix-like image sensor is used for position detection at a fixed reference point C, or two row-like image sensors.

Starting from this prior art, the invention is based on the object of being able to carry out the densitometric measurement and evaluation of printed sheets inexpensively and quickly.

The object is achieved in a device of the type mentioned by the characterizing part of the first claim.

The position of the printed sheets and the position of the color measuring fields of the printed sheet are known and traded The usual digitizing table with a stylus connected to it can be recorded and stored in a memory. The use of a commercially available digitizing panel considerably reduces the cost of the entire measuring device. Handling with the stylus is particularly easy during operation. First, two or three points for the position detection of the printing sheet are scanned on the digitizing table. The measuring points are converted to a zero point of the digitizing table for relative position detection and saved. Then the individual color measuring fields on the printed sheet are scanned with the stylus, so that these stored values control the densitometer to the correct positions for measurements that can be repeated as often as desired.

The accuracy depends on the selected grid size of the digitizing table and is approx. 1/10 mm, depending on the frequency numbers used for standard magnetostriction cycles.

The measurement process is triggered by placing the stylus on the measuring points of the printed sheet. The scanning of the first three position coordinates can thus be achieved very quickly. Depending on which measurement values are to be measured for repeat measurements using the densitometer, the coordinate values of the color measurement fields are stored in the memory by contact with the stylus.

In this particularly simple manner, a wide variety of measuring points can be recorded quickly and quickly, even with frequent changes to the measuring points, by moving the color measuring fields on the printed sheet.

In order to be able to carry out even more complicated linking functions using the digitizing table, it is possible to use a menu field on the digitizing table. If two measuring points are scanned with the stylus on the printed sheet, it is possible to measure the elongation in one direction, especially the direction in the paper fiber run.

If three measuring points are scanned on the printed sheet to identify the position of the printed sheet, the elongation of the printed sheet can be detected in two directions.

Further advantages and essential features of the invention emerge from the subclaims and the following description of the figures in conjunction with the exemplary embodiments.

• 1 shows a printed sheet lying randomly on a digitizing table on which irregular color measuring fields are arranged,
• 2 shows a coordinate measuring table with a two-axis densitometer and an additional operating device,
• 3 shows a diagram of the measurement field acquisition,
• 4 shows a diagram for the adjustment of the measuring device after scanning the reference points,
• Fig. 5 is a diagram of the menu field and the resulting functions.

Fig. 1 shows a digitizing table 1, to which a stylus 2 is connected with a contact cable 2.4. A printed sheet 3 with measuring points 2.1-2.3 and color measuring fields 14-14.2 can lie arbitrarily on the digitizing table 1. Depending on the remaining space between the individual print images of the printing ink application, the color measuring fields 14 - 14.3 are arranged on the printing sheet.

The color measuring fields 14 - 14.3 have markings for the stylus 2 at their beginning and end.

If the printed sheet 3 lies indiscriminately on the digitizing table 1, then the measuring points 2.1-2.3 are first scanned with the stylus 2 in order to fix the position of the printed sheet 3 on the digitizing table 1. The stylus 2 is then keyed onto a menu field 9 in order to save the position of the color measuring fields 14-14.3 without great expenditure of time for later repeat measurements by keys. In the lower left corner of the digitizing table 1 there is a measuring element 17 for calibrating the calculation coordinates between the stylus 2 and the digitizing table 1 and a densitometer 8.

2 shows the digitizing table 1 on a coordinate table 1.1. The densitometer 8 can be moved on a crossbar 15, the crossbar 15 with bearings 12, 13 being movable on a guide rail 11. The densitometer 8 can thus move to all areas of the digitizing table 1. The cross member 15 is secured with end stops 16 on both sides of the guide rail 11. On a An operating console 18 is provided with a keyboard 10 for entering a wide variety of data. Data is entered particularly quickly by pressing the stylus 2 at the desired point. Between the coordinate measuring table 1.1 and the digitizing table 1 there is a transition area 19. In the lower left corner there is a measuring element 17 for the zero adjustment.

3 shows the data input of the measuring points 2.1-2.3 from the stylus 2 to the memory 4. The coordinate values of the color measuring fields 14-14.3 go directly to a computer 6. The storage values of the printed sheet 3 go from the memory 4 to the computer 6. Both data values are stored in a memory 5 and can be called up from the memory 5 for a wide variety of uses.

In FIG. 4 it can be seen that the measurement points 2.1-2.3 are entered into the memory 4 only for sheet detection. The position data of the color measuring fields 14 - 14.3 are forwarded from the memory 5 directly to the computer 6 in order to be able to control the densitometer 8 from the computer 6 with both position data. The position data of the color measuring fields 14 - 14.3 are always in the same positions within a print job. With the stylus 2, only two measuring points 2.1-2.3 are thus scanned on the digitizing table 1 for position detection of the printed sheet 3.

If the elongation of the printed sheet is also to be recorded, three measuring points 2.1-2.3 are scanned with the stylus 2.

FIG. 5 shows the diagram when a functional field of the menu field 9 is scanned on the digitizing table 1 with the stylus 2. The specified data from the menu field 9 is sent to a computer 7, which processes these values together with values from the memory 4. The processed data arrive at the respective required functions from the computer 7.

Identifier list

• 1 digitization table
• 2 styles
• 2.1 measuring points
• 2.2 "
• 2.3 "
• 3 printed sheets
• 4 memory
• 5 "
• 6 computers
• 7
• 8 densitometers
• 9 Menu field
• 10 keyboard
• 11 guide rail
• 12 bearings
• 13
• 14 -
• 14.3 Color measuring field
• 15 traverse
• 16 end stop
• 17 measuring element
• 18 Control console
• 19 transition surface
• 1.1 coordinate measuring table
• 2.4 Contact cable

Claims (4)

1.) Device for determining and evaluating color measurement fields on a printing sheet lying on a measuring table with a densitometer, in which the position of the color measurement fields and the printing sheet can be detected with a device and stored in memories, the densitometer, which can be moved in two directions, being stored Values can be moved repeatedly onto the color measuring fields of the printing sheet,
characterized,
that the position of the printed sheets (3) and the position of the color measuring fields (14 - 14.3) of the printed sheet (3) with a known and commercially available digitizing table (1) and with a stylus (2) connected to it can be recorded and stored (4 , 6) can be filed. 2.) Device according to claim 1,
characterized,
that on the digitizing table (1) a menu field (9) is arranged, which can be scanned by means of the stylus (2) for performing different functions. 3.) Device according to claim 1,
characterized,
that the color measuring fields (14 - 14.3) can be scanned at two end points with the stylus (2). 4.) Device according to claim 1,
characterized,
that the printed sheet (3) can be scanned at three measuring points (2.1 - 2.3) in such a way that the elongation of the printed sheet (3) can be checked in two directions.

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