BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
FIG. 1 is a diagrammatic, perspective view of a tabletop color measuring device with a plurality of measuring heads having differently operating measuring devices; and
FIG. 2 is a perspective view of the measuring head having differently operating measuring devices.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a measuring table 2 which has a movable measuring beam 1. The measuring beam 1 has an electric drive, so that the measuring beam 1 can be moved from left to right or vice versa in the x direction over the printing material 3 lying on the measuring table 2. As the measuring beam 1 moves over the printing material 3, the printing material 3 is measured calorimetrically by use of measuring heads 8 in the measuring beam 1. It can be seen that on the printing material 3, in addition to the actual printed image, color measuring areas 13 in the form of a color measuring strip are applied to the lower end. The color measuring areas 13 are used for color monitoring and have specific standardized characteristics, such as specific hues. The color measured values registered by the measuring beam 1 are passed on to a computer 4, which displays the measured values to the operator on a monitor 5. In order to control the measuring operations, the operating personnel can make entries via a keyboard 6. In addition, the computer 4 is connected to the machine computer of a printing press 7, so that the measured color results from the computer 4 can be used directly to control the inking units in the printing press 7. If deviations are determined between a printing original and the printing material 3 to be measured, these deviations can be controlled out appropriately in the inking units in the printing press 7. The measuring apparatus in FIG. 1 is capable of registering both the lateral color measuring areas 13 and the entire printed image on the printing material 3; for this purpose, measuring heads 8 in the measuring beam 1 can be moved sideways in the y direction by a further electric drive.
In FIG. 2, the measuring head 8 from the measuring beam 1 in FIG. 1 is illustrated in more detail as an example. It can be seen that the measuring head 8 contains a plurality of measuring devices 9, 10, 11. If the direction of travel of the measuring beam 1 in FIG. 1 runs from left to right during the measuring operation, then a preview sensor 9 is located disposed in front of and on the right of the further measuring devices 10, 11. The preview sensor 9 is constructed as a line sensor, which has a high geometric resolution for the registration of light/dark differences. By use of the preview sensor 9, it is possible to register the start and end and also the position of color measuring areas 13 on the printing material 3 exactly. Therefore, rapid subsequent positioning of the spectral measuring device 10 over the color measuring area 13 to be measured is possible. The spectral measuring device 10 does not have to have a particularly high geometric resolution; instead it measures with a high colorimetric spectral resolution in order to be able to register color measured values exactly. As a result of the detection of the exact position of the color measuring area 13, the spectral measuring device 10 does not have to carry out short measurements continuously but can measure the color measuring areas 13 to be registered precisely with a correspondingly longer exposure time. Between the measurements, the entire measuring head 8 can be moved quickly, since the preview sensor 9 registers the position of the next color measuring area 13 quickly and exactly in advance. As a result of skipping the regions on the printing material 3 that are not to be measured, the measuring beam 1 can thus be moved more quickly from left to right, which shortens the time of the entire measuring operation. The preview sensor 9 in FIG. 2 can additionally control the illuminating devices 12 which are used for defined illumination of the color measuring areas 13 to be measured on the printing material. By use of the light/dark measurements of the preview sensor 9, the illumination intensity of the illuminating devices 12 can thus be regulated as a function of the lightness of the detected color measuring area 13.
The measuring head 8 in FIG. 2 additionally has a scanning measuring device 11, which likewise operates with a relatively high geometric resolution of 200 dpi. The scanning measuring device 11 primarily has measuring heads 8 which, in the measuring beam 1 in FIG. 2, do not measure in the lateral regions in which the color measuring areas 13 are located but which are intended to register the entire printed image on the printing material 3 like a scanner. The scanning measuring device 11 is capable of registering a large number of pixels on the printing material 3 simultaneously, in order in this way likewise to permit a more rapid measuring operation. However, the color measuring accuracy of the scanning measuring device 11, exactly like that of the preview sensor 9, is lower than that of the spectral measuring device 10. In order nevertheless to achieve a high colorimetric measuring accuracy, the measured results from the scanning measuring device 11 or the preview sensor 9 are compared in the computer 4 with the measured values from the spectral measuring device 10. In this way, the scanner 11 and the preview sensor 9 are calibrated calorimetrically, as described further below, by the spectral color measuring device 10. Because of their high geometric resolution, the sensors 9 and 11 can also be used to detect register marks or register crosses on the printing material 3, in order in this way to detect register deviations between the individual color separations or register deviations between the front and rear side. For this purpose, however, the sensors must have a resolution of at least 1000 dpi, which can be achieved by changing the sensors to a fine measuring mode. Although this slows down the measuring speed, it is not necessary for the entire sheet 3 to be measured in this mode; it is sufficient to register the regions having the register marks and register crosses, which are physically very limited. Via the computer 4, the deviations can be corrected for the following printing materials 3 by control interventions in the printing press 7. Furthermore, the sensors 9, 11 can be used for the purpose of registering bar codes on the printing material 3. If a deviation is established, the computer 4 registers this as a reject, and the sheet 3 is separated out. A resolution of 200 dpi is sufficient for this purpose. With this resolution, the sensors 9, 11, together with the computer 4, can also check texts on the sheet 3 for correctness and thus, for example, can detect false inscriptions on medicament packs, which are then likewise separated out.
As already explained, the spectral measuring device 10 primarily registers calorimetrically standardized color measuring areas 13. The spectral measuring device 10 operates calorimetrically very exactly. If reference areas like these standardized color measuring areas 13 that are present on the printing material 3 are registered both by the spectral measuring device 10 and by the scanning measuring device 11, then the measured values from the two devices 10, 11 can be compared with one another. Calibration of the spectral measuring device 10 by the scanning measuring device 11 is also possible. In this way, the speed of the scanning measuring device 11 can be combined with the high color accuracy of the spectral measuring device 10 and, in this way, create an accurate and fast color measuring apparatus. The measuring heads 8 in the measuring beam 1 in FIG. 1 can either all be constructed like the measuring head 8 in FIG. 2 but it is also possible for the measuring heads 8 in each case to have only one preview sensor 9 and one spectral measuring device 10, or for the measuring heads 8 to have one spectral measuring device 10 and one scanning measuring device 11. Of course, it is also possible for some measuring heads 8 in each case to have two of the sensors 9, 10 or 10, 11, and other measuring heads 8 to have all three measuring devices 9, 10, 11.
Patent Application
20080030717
