| 摘要 |
<p>Method for controlling printing quality in a web printing press by measuring at least the darkness of the colour surface in the printed product by employing a web sensor, wherein on a moving paper web there is arranged a test spot (9) and/or test patterns in the middle and/or aside the saleable printing, and wherein the operation of the web sensor is synchronized with the said test spots while they move along the paper web past the sensor, and wherein a light beam is focused onto the paper web from the light source of the web sensor, and the reflections of the said light beam from the test spot are measured by employing a light detector. The invention is characterized by the fact that the spot of light (10) formed on the paper web by the light beam is limited in comparison with a normally used spot of light (8) at least in the motional direction of the paper web so that it remains roughly between 1-2 mm. By aid of the limited spot of light of the same web sensor, there is measured the reciprocal registering of the different colours. Moreover, the same test spots and/or patterns are used while measuring the darkness of the colour surface and the registration of different colours.</p> |
