Overhead sidelight

A one overhead sidelight illuminating method for illumination a paper or cardboard web for deviation detection, comprising:

• turning on LEDs of the overhead sidelight arranged above the web, which width of the overhead sidelight is shorter than a width of the web or as wide as the web, and which LEDs are side-directed towards a first edge of the web when looking at the sidelight from the direction whereto the paper or cardboard web runs for illuminating a first half of width of the web from center to the first edge of the web for capturing an image of the first half of width of the web by at least one imaging device;
• turning off the LEDs that are side-directed towards the first edge of the web:
• turning on LEDs of the same overhead sidelight, which LEDs are side-directed towards a second edge of the web when looking at the sidelight from the direction whereto the paper or cardboard web runs for illuminating a second half of width of the web from center to the second edge of the web for capturing an image of the second half of width of the web by at least one imaging device;
• and
• turning off the LEDs that are side-directed towards the second edge of the web;
• wherein the method further comprises:
• transmitting image data of the captured wherein the method further comprises:
• analysing the image data that is captured when the web is illuminated by the sidelight by using a sidelight type of monitoring profile;
• and,
• wherein the method further comprises:
• analysing the image data that is captured when the web is illuminated by the transmission light by using a transmission type of monitoring profile, wherein the sidelight type of monitoring profile and the transmission type of monitoring profile profiles have different parameters for monitoring.

An overhead sidelight arranged to be positioned over a paper or cardboard web for illuminating the web for imaging, comprising:

• a plurality of LEDs;
• and
• an elongated body arranged to support the LEDs,
• wherein the length of the elongated body is shorter or equal length than the width of the web, and wherein a first part of the LEDs is side-directed towards a first edge of the web when looking at the sidelight from the direction whereto the paper or cardboard web runs for illuminating a first half of width of the web from center to the first edge of the web as a first part of the rectangular area, and
• wherein a second part of the LEDs is side-directed towards a second edge of the web when looking at the sidelight from the direction whereto the paper or cardboard web runs for illuminating a second half of width of the web from center to the second edge of the web as a second part of the rectangular area, and wherein the first and second part of the LEDs are on and off alternately, and
• wherein the width of the overhead sidelight is shorter than a width of the web or as wide as the web.

A computer program product embodied on a non-transitory computer readable medium, comprising computer program code configured to, when executed on at least one processor, cause a system to perform the method comprising:

• turning on LEDs of an overhead sidelight arranged above a paper web, which width of the overhead sidelight is shorter than a width of the web or as wide as the web, and which LEDs are side-directed towards the first edge of the web for illuminating a first half of width of the web from center to the first edge of the web for capturing an image of the first half of width of the web by an imaging device;
• turning off the LEDs that are side-directed towards the first edge of the web;
• turning on LEDs of the overhead sidelight, which LEDs are side-directed towards the second edge of the web for illuminating a second half of width of the web from center to the second edge of the web for capturing an image of the second half of width of the web by an imaging device;
• and
• turning off the LEDs that are side-directed towards the second edge of the web.