US 6,549,286 B2 · Method and measuring arrangement for measuring paper surface

Abstract

The invention relates to a method and a measuring arrangement for determining roughness of paper or paperboard. The paper or paperboard surface is illuminated with collimated light substantially parallel with the normal of the paper or paperboard surface. An image is produced from the paper or paperboard surface by means of reflected optical radiation. The reflected optical radiation is used for producing an image of the paper or paperboard surface onto the pixels of the camera's detector surface, each of the pixels imaging an area in the order of micrometers of the paper or paperboard surface. An aperture provided in front of the camera is used for adjusting the depth of focus of the image, which affects the measurement of roughness. Roughness of paper or paperboard is measured on the basis of the intensity of the pixels on the camera's detector surface.

Claims28

Dependent claims

A method of determining a surface property of paper or paper board, the method comprising:

illuminating the paper or paperboard surface with collimated light substantially parallel with the normal of the paper or paperboard surface;
controlling the reflected optical radiation with an aperture of the desired size before the camera;
producing an image of the illuminated paper or paperboard surface onto the pixels of the camera's detector surface by means of the reflected optical radiation, each of the pixels imaging a surface area in the order of micrometers of the paper or paperboard, and
measuring at least the roughness of the paper or paperboard surface as a micro surface property on the basis of the intensity of the pixels on the camera's detector surface.

1 more element

A measuring arrangement for determining a surface property of paper or paperboard, the measuring arrangement comprising an optical power source for illuminating the paper or paperboard surface and a camera for producing an image of the illuminated paper or paperboard surface onto the pixels of the camera's detector surface, wherein the measuring arrangement according to the invention comprises:

a collimating optical block for collimating the optical radiation emitted by the optical power source;
a partially permeable mirror for projecting the optical radiation onto the paper or paperboard surface substantially parallel with the normal of the paper or paperboard surface;
an imaging optical block for producing an image of the illuminated paper or paperboard surface onto the pixels of the camera's detector surface by means of the reflected optical radiation;
and
an aperture of the desired size for controlling the reflected optical radiation;
and the measuring arrangement being arranged to measure at least roughness of the paper or paperboard surface on the basis of the intensity of the pixels on the camera's detector surface.

3 more elements

Dependencies are inferred from the claim text.

Method and measuring arrangement for measuring paper surface

Life of this patent

Method and measuring arrangement for measuring paper surface

Life of this patent

Abstract

Claims28