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Correlation among gravimetric, spectrophotometric and radiographic data from dried wood samples of Scots pine (Pinus sylvestris L) was observed. A diffractive optical element (DOE) based sensor was applied to investigate density variations as well as optical anisotropy inside year rings of the wood samples. The correlation between bulk density of wood and spectrophotometric data (reflectance and transmittance) was investigated for the wavelength range 200-850 nm and the highest correlation was found at wavelengths from 800 to 850 nm. The correlation at this wavelength was smaller than the correlation between bulk density and radiography data. The DOE sensor was found to be capable of sensing anisotropy of the wood samples inside the year ring.

Wood quality is of great importance for all of forest industry, because it affects on suitability of wood as raw material for the wood processing industry. In the future, the aim will be to use the right materials for the right end products. For this purpose we need to understand how the material properties of wood are distributed in the stem, and how the properties of wood vary from a tree to tree and from a stand in relation to the genetics, site properties and silvicultural history. Currently, detailed information is lacking how genetic, environmental and forest management influence wood properties (i.e. between and within ring variation). This is although, for example, wood density and equally percentage of latewood, which is known to reduced by faster diameter growth, i.e. larger proportion of earlywood. Wood density reflects also the amount of cell wall material, and it is considered as a key property. It also correlates to other properties of the wood like strength (important for mechanical industry) and pulp yield in terms of the quantity of chemical and mechanical pulp obtained from the volume unit. For the pulp and paper industry, the earlywood/latewood ratio is respectively of great importance, because latewood tracheids of softwoods have thick walls, which increase the density and mechanical strength of wood. On the other hand, considerably more energy is needed in defibration of latewood than earlywood.In the future, it is needed sophisticated tools for intraring wood property analysis, which could give accurate information of intraring properties but still could be reasonable in regard to simplicity of use (time saving) but also in regard to cost. In this context, the general aim of the study was to develop a novel laser based method to produce an unbiased application (mathematical procedure) based on x-ray technique, which will output the shape of an intraring density profile.In this work we investigated HeNe laser light components scattered through small wood samples of Scots pine (Pinus sylvestris L.) by using a diffractive optical element (DOE) based sensor, which was already observed to be effective elsewhere [l4]. The geometric arrangement of the present DOE sensor is shown in Fig.l. The optical signals from DOE sensor were compared with the optical density data of x-ray negatives taken from the respective samples. Good agreement between the x-ray and optical signals was observed when gravimetric density values of Pine samples were considered as shown in Fig.2.