LED matrix lighting device

1. An LED matrix lighting device for illuminating a lighting pattern with even intensity, the LED matrix lighting device comprising a plurality of LEDs, a collimating lens in front of each LED for collimating light of the LED, and a light refracting element in front of collimating lenses arranged to refract light of at least a first part of the LEDs with a different refraction angle than at least a second part of the LEDs, and wherein current provided for at least one LED is adjustable based on detected intensity deviations in a captured image, and which a FWHM viewing angle of the collimated light of LEDs is substantially as large as the difference between the refraction angles.

2. The LED matrix lighting device according to claim 1 , wherein the LED matrix lighting device further comprises at least one powering circuit of LEDs and an amount of current provided for the first part of LEDs is different than an amount of current provided for at least the second part of LEDs.

3. The LED matrix lighting device according to claim 1 , wherein the first part of LEDs comprises one LED, one line of LEDs of the LED matrix or one column of LEDs of the LED matrix.

4. The LED matrix lighting device according to claim 1 , wherein the refraction angle is determined based on the place of an LED in the LED matrix lighting device.

5. The LED matrix lighting device according to claim 1 , wherein

a refraction angle is an angle between an optical central axis of collimated light of an LED and an optical central axis of the refracted light of the same LED.

6. The LED matrix lighting device according to claim 1 , wherein current provided for at least one LED is adjustable.

7. A machine vision system for detecting deviations from a wood fibre web, wherein the machine vision system comprises:

an LED matrix lighting device for illuminating a lighting pattern with even intensity, the LED matrix lighting device comprises a plurality of LEDs, a collimating lens in front of each LED for collimating light of the LED, and a light refracting element in front of collimating lenses arranged to refract light of at least a first part of the LEDs with a different refraction angle than at least a second part of the LEDs, and wherein current provided for at least one LED is adjustable based on detected intensity deviations in a captured image, and which a FWHM viewing angle of the collimated light of LEDs is substantially as large as the difference between the refraction angles,

at least one imaging device for capturing images of the illuminated area, and

a data processing device.

8. The machine vision system according to claim 7 , wherein the data processing device is arranged to analyse image data for detecting intensity deviations in the captured images.

9. A method comprising:

obtaining image data,

analyzing image data,

detecting intensity deviations in an illumination pattern provided by an LED matrix lighting device in the captured images, which LED matrix lighting device comprising a plurality of LEDs, a collimating lens in front of each LED for collimating light of the LED, and a light refracting element in front of collimating lenses arranged to refract light of at least a first part of the LEDs with a different refraction angle than at least a second part of the LEDs, and wherein current provided for at least one LED is adjustable based on detected intensity deviations in a captured image, and which a FWHM viewing angle of the collimated light of LEDs is substantially as large as the difference between the refraction angles, and

adjusting current provided for at least one LED of the LED matrix lighting device based on detected intensity deviations in a captured image.

10. 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:

obtaining image data,

analyzing image data,

detecting intensity deviations in an illumination pattern provided by an LED matrix lighting device in the captured images, which LED matrix lighting device comprises a plurality of LEDs, a collimating lens in front of each LED for collimating light of the LED, and a light refracting element in front of collimating lenses arranged to refract light of at least a first part of the LEDs with a different refraction angle than at least a second part of the LEDs, and wherein current provided for at least one LED is adjustable based on detected intensity deviations in a captured image, and which a FWHM viewing angle of the collimated light of LEDs is substantially as large as the difference between the refraction angles, and

adjusting current provided for at least one LED of the LED matrix lighting device based on detected intensity deviations in a captured image.