Method and apparatus for detecting bark and for determining the degree of barking on wood and chips

A method according to claim 4, further comprising the steps of directing a plurality of the light beams onto the surface of the material, and detecting the two-dimensional extensions of the light images obtained on the surface of said material.

Apparatus for continuously establishing the presence of bark on a material such as logs or wood chips, and/or determining the barking degree of the material, said apparatus comprising:

• means for producing a concentrated light beam on the surface of the material;
• a detecting device which functions to detect the size and/or the shape of a light image obtained on said surface with the aid of the light beam, said shape and size constituting criteria related to the constituents of the material, whereby an elongated light image is obtained when the light beam impinges on a wood surface that is substantially free from bark depending on the spreading of the light in the wood fibers and a light image with the form of a light spot is obtained when the light beam impinges on a bark surface since the light is spread to a smaller extent in bark than on a wood surface that is substantially free from bark, and
• processing means which coact with the detecting device for evaluating the detected values.