JP5220481B2 - Method for measuring wood density by laser-induced plasma emission analysis - Google Patents

Description

  The present invention relates to a method for measuring non-destructive density of wood, and more particularly, uses laser-induced plasma emission analysis for wood density measurement, and the air-dry density (water content) of wood regardless of the water content of wood. This refers to a density at 15% (hereinafter simply referred to as “wood density”).

  The annual rings appearing on the cut surface of the tree are the ones in which the difference in the density of the timber appears visually as shades. By examining this density distribution, the growth amount of the tree, the past growth environment, and the like become clear. On the other hand, the density value of wood is closely related to all the physical properties such as strength, sound propagation, frequency, heat conduction, etc., so the density value is extremely important in understanding the characteristics of these various places. is important.

Since the density is a mass (g) per unit volume (cm ³ ), generally, the measurement of the density of wood is to obtain the volume by dimension measurement when the shape of the sample can be regarded as a correct rectangular parallelepiped. Moreover, what was deform | transformed by shrinkage | contraction, such as a completely dry (water content 0%) measurement object, calculates | requires a volume by the mercury immersion method which applied buoyancy, and should just divide the mass of the sample by the calculated | required volume.

In addition, a technique for nondestructively measuring the density using the transmittance of radiation such as γ-rays and X-rays is also used. Patent Document 1 listed below discloses the density of wood using a microfocus X-ray CT apparatus. An example of a measurement is shown.
JP 2006-78251 A

  However, according to JIS Z2101, which is a test method for measuring the density of wood, it is stipulated that the moisture content of the sample should be 15%. There is a problem that it takes a long time to measure the density of wood because it is necessary to input for three months.

  In addition, in order to measure the density non-destructively using the transmittance of radiation such as γ rays and X rays, these radiations are always affected by water, so the density of wood containing a large amount of water is measured. There is a problem that it is impossible and needs to be dried so as to have a predetermined moisture content, and the density cannot be measured in a short time. Furthermore, in these conventional density measuring methods, since it is necessary to collect a sample from the measurement object, there is a problem that measurement cannot be performed unless the measurement object is destroyed.

  The present invention has a problem that it takes a long time to adjust the moisture content and destroys the object to be measured, even though the density of the wood is a very important value in obtaining the physical properties of the wood. In view of the above, the present invention has been made as a result of earnest research and examination, and an object thereof is to provide a simple and non-destructive method for measuring the density of wood with high accuracy.

  The first invention for achieving the above object is to create a calibration curve between the fluorescence intensity of carbon obtained from the surface of wood by laser-induced plasma emission analysis and the air-dry density of wood obtained as a ratio of mass to volume. In this method, the calibration curve is used to measure the wood density regardless of the moisture content of the wood and nondestructively.

  The moisture content of the measurement object when creating a calibration curve is 15% defined in JISZ2101, but the moisture content of the measurement object when using the created calibration curve is limited to 15%. The density of wood obtained is always a value at a moisture content of 15%.

  According to a second aspect of the present invention, in the first aspect, the object to be measured at the time of creating the calibration curve is a thin object that includes the center of the annual ring and one outer side or both outer sides of the tree in a central and straight line on a smooth cut surface of the tree. A small square plate (hereinafter, also simply referred to as “square plate”), and the fluorescence intensity of carbon obtained from the surface of the wood when the calibration curve is created is centered on the annual ring from the outside in the center and in a straight line. Or a wood density measuring method characterized in that it is an average value of a plurality of measured values from the center of the annual ring to the other outside.

  The object to be measured is not only the above-mentioned square plate, but also sliced felled trees at right angles to the axis, and cut in parallel to the direction of the tree axis around the annual ring as a thin and narrow square plate equivalent. Also good.

  According to a third invention, in the first or second invention, the measurement direction of the fluorescence intensity of carbon obtained from the surface of the wood when the calibration curve is used is perpendicular to the annual ring on a smooth cut surface of the tree. The wood density measuring method is characterized in that weighting is performed so that the number of measurement points per unit area of the wood is equal or equal.

  The measurement of the carbon fluorescence intensity of the measurement object when using the calibration curve may be performed so long as the measurement direction is orthogonal to the annual ring, even if it does not include the center of the annual ring.

  4th invention is 1st thru | or 3rd invention, WHEREIN: The measurement object of the said wood density is timber with an unknown moisture content, Comprising: The said measured wood density from the density of the timber with an unknown moisture content is used. Subtracting, calculating a moisture content of 15% or more or less than 15% per unit volume of wood with unknown moisture content, and using it for drying control of wood with unknown moisture content, It is.

  5th invention is 1st thru | or 3rd invention, WHEREIN: The measurement object of the density of the said wood is wood with an unknown moisture content, Comprising: The said wood density measured from the density of the wood with this unknown moisture content is used. Subtracting, calculating a moisture content of 15% or more or less than 15% per unit volume of wood with unknown moisture content, and using it for selecting the use of wood with unknown moisture content, It is.

  The first invention creates a calibration curve between the fluorescence intensity of carbon obtained from the surface of wood by laser-induced plasma emission analysis and the air-dry density of wood obtained as a ratio of mass to volume, and uses the calibration curve In addition, since it is a method for measuring wood density that is characterized by non-destructive measurement regardless of the moisture content of wood, when creating a calibration curve, a measurement object with a moisture content of 15% is selected. Although it is necessary, the measurement object when using the calibration curve measures the fluorescence intensity of carbon regardless of the moisture content, and reads the wood density corresponding to the fluorescence intensity of the carbon from the calibration curve regardless of the tree species. As a result, the wood density can be measured non-destructively in a short time.

  According to a second invention, in the first invention, the measurement object at the time of preparation of the calibration curve is obtained by slicing a prismatic body made of felled wood in a direction perpendicular to the axis, leaving the center of the annual ring and the corners, and excluding others. A thin, narrow square plate or a felled tree can be sliced perpendicular to the axis, and parallel cut in the direction of the tree axis around the annual ring to make it equivalent to a thin, small square plate including the center of the annual ring. Therefore, it is easy to manufacture the measurement object and calculate the volume when creating a calibration curve, and the fluorescence intensity of carbon used when creating a calibration curve should be a simple average of measured values (spots) measured by laser-induced plasma emission analysis. Therefore, there is an effect that a calibration curve with high accuracy can be created efficiently.

  According to a third invention, in the first or second invention, the measurement direction of the fluorescence intensity of carbon obtained from the surface of the wood when the calibration curve is used is perpendicular to the annual ring on a smooth cut surface of the tree. This is a method for measuring the density of wood, characterized in that it is weighted so that the number of measurement points per unit area of the wood is equal or even, so the carbon of the measurement object when using a calibration curve The measurement of the fluorescence intensity is effective as long as the measurement direction is orthogonal to the annual ring, and the density can be measured even with a pillar material that does not include the center of the annual ring. In addition, since the number of measurement points can be reduced, the wood density can be calculated efficiently using a calibration curve in a short time.

  4th or 5th invention is either 1st thru | or 3rd invention, The measurement object of the density of the said wood is wood with an unknown moisture content, Comprising: The said measurement from the density of this wood with an unknown moisture content Subtracting the density of the wood, calculating a water content of 15% or more or less than 15% per unit volume of the wood with unknown moisture content, and using it for drying control of wood with unknown moisture content or for selecting the use of wood There is an effect that can be.

In the present invention, (1) the main constituent elements of wood are carbon “C”, hydrogen “H”, oxygen “O”, and in addition, trace amounts of Ca, K, Na, Mg, Fe, Mn, Cu, Co , Si, etc., but the weight ratio (%) is substantially constant at C: H: O = 50: 6: 43, and (2) the density of wood is the amount of cell walls per unit volume (3) Since the “C” element of wood shows a constant value in the same volume regardless of the amount of moisture (H ₂ O) composed of “H” and “O”, We focus on the ability to determine the air dry density (water content is 15% as defined in JISZ2101) regardless of the water content by quantifying the “C” element by a simple method using laser-induced plasma emission analysis. .

  FIG. 9 is a table showing the analysis results of the weight ratio of the constituent elements of the wood. The analysis result shows that the weight ratio (%) of C: H: O is C: H: O = 50: 6: 43. Consistent with the above, the analysis results show that this ratio is the same for different tree species.

  First, an analysis apparatus used in an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram for explaining a LIBS (laser-induced plasma emission analyzer) 100 according to an embodiment of the present invention.

  In FIG. 1, reference numeral 30 denotes a laser transmitter (for example, a YAG laser transmitter), which is a pulse laser beam L having a predetermined pulse width based on a drive pulse generated at a predetermined timing by a main control device (not shown) as control means. Is output.

  40 is an optical fiber incident system for condensing the pulsed laser light output from the laser transmitter, 20 is an optical system unit whose details will be described later, 50 is an optical fiber for laser light transmission, one end of which is an optical fiber incident system The other end is connected to the optical system unit 20. Reference numeral 10 denotes a measurement object obtained by processing wood into a predetermined shape, and is arranged so that the focal point of the pulsed laser light L is the measurement surface of the wood.

  Reference numeral 70 denotes a fluorescence measuring instrument 70 for measuring all wavelengths and intensities by spectroscopically analyzing fluorescence emitted from wood as a measuring object, and 80 is included in the measuring object 10 from the measurement values obtained by the fluorescence measuring instrument 70. A computer 90 for calculating the elements and their amounts, and a display 90 for displaying analysis results. Reference numeral 60 denotes an optical fiber for fluorescence transmission, one end of which is connected to the optical system unit 20 and the other end is connected to a fluorescence measuring instrument. The operation timing of the fluorescence measuring instrument 70 and the computer 80 is controlled by a timing adjustment mechanism (not shown).

  FIG. 2 is a cross-sectional view of the optical system unit 20 according to the embodiment of the present invention. In FIG. 2, reference numeral 21 denotes a cylindrical main body cylinder portion whose axis is the optical axis of the pulse laser light L, and 22 is a side portion of the main body cylinder portion 21 in a direction orthogonal to the optical axis of the pulse laser light L. It is the fluorescent light guide cylinder part provided.

  An end of a laser light transmission optical fiber 50 is connected to a base end which is one end of the main body cylinder portion 21, and a pulse laser beam is transmitted through a laser light emission surface 50 a which is an end of the laser light transmission optical fiber 50. L is emitted to the inside of the main body cylinder portion 21. Reference numeral 23 denotes a flat plate-like distribution reflecting mirror, which is installed at a substantially central portion in the main body cylindrical portion 21 so as to be inclined by 45 ° with respect to the optical axis of the pulse laser light L. A fluorescent reflection surface 231 is formed on the lower surface of the distribution reflection mirror 23 and reflects the fluorescence F including visible light and ultraviolet light while being transmitted toward the tip which is the other end.

  Reference numeral 25 denotes a fluorescence F emitted from atoms contained in the surface of the measurement object 10 while condensing the pulse laser light L transmitted through the optical fiber 50 for laser light transmission to irradiate the measurement object 10. Is a condensing lens group for condensing the light and guiding it to the optical fiber 60 for fluorescence transmission. This condensing lens group 25 is arranged at the tip of the main body cylinder portion 21, condenses the pulsed laser light L transmitted through the distribution reflection mirror 23, and then irradiates the measuring object 10. A first lens 251 that is flat and has a laser beam exit surface projecting into a convex arc surface, a second lens 252 that has a laser beam incident surface projecting into a convex arc surface, and the laser beam exit surface is recessed into a concave arc surface, laser Each of the light incident surface and the laser light emitting surface is constituted by a third lens 253 projecting in a convex arc shape, and the fourth lens 254 having a laser light emitting surface projecting in a convex arc shape and a flat laser light emitting surface. Has been.

  Then, the fluorescence F emitted by the irradiation of the pulsed laser light L onto the measurement object 10 is incident on the condenser lens group 25, and the fluorescence F is collected and then reflected by the distribution reflection mirror 23. The light is guided to the surface 231 and reflected by the fluorescent light guide tube portion 22. Therefore, this condensing lens group 25 is a fluorescence condensing optics as a fluorescence condensing means for condensing the fluorescence F emitted from the atoms contained in the surface of the measurement object 10 irradiated with the pulse laser beam L. It is also a system.

  A fluorescent condensing lens 24 condenses the fluorescent light F reflected by the fluorescent reflecting surface 231 of the distribution reflecting mirror 23, and is connected to and held at the tip of the fluorescent light guide tube portion 22 via the fluorescent incident surface 60a. The light is guided to the optical fiber 60.

  FIG. 3 is a graph for explaining the relationship between the wavelength of the distribution reflection mirror 23 according to the embodiment of the present invention, the transmittance, and the reflectance. The distribution reflection mirror 23 is a pulse having a shorter wavelength. The laser beam L is transmitted, and the fluorescence F having a longer wavelength is reflected.

  Next, an element analysis method for an object to be measured by the analyzer according to the embodiment of the present invention will be described.

  After setting the measurement object 10, which is wood that has been processed into a predetermined shape, at the focal position of the pulsed laser light L emitted from the analyzer, the laser oscillator 30 outputs the pulsed laser light L. The output pulsed laser light L is condensed by the optical fiber incident system 40 and then transmitted to the optical system unit 20 by the laser light transmission optical fiber 50, passes through the distribution reflection mirror 23, and is collected by the condensing lens group 25. The light is condensed and irradiated on the surface of the measurement object 10.

  By irradiation with the pulse laser beam L, the surface of the measurement object 10 is instantaneously heated to a high temperature and turned into plasma, and plasma is generated from the surface of the measurement object 10.

  After the plasma is generated from the surface of the measurement object 10, the irradiation of the pulse laser beam L from the laser oscillator 30 is stopped, and the plasma generated on the surface of the measurement object 10 is recombined with the stop of the irradiation of the pulse laser beam L. During the period of several μs to several tens of μs, the element in the measurement object 10 becomes an atom in an excited state, and when the atom in this excited state transitions to a lower level, the atom is proportional to the number of atoms. Fluorescence F is emitted.

  The emitted fluorescent light F enters the condenser lens group 25, is collected by the condenser lens group 25, is reflected by the fluorescent reflecting surface 231 of the distribution reflecting mirror 23, and is guided into the fluorescent light guide tube portion 22. Is done. The fluorescence F guided into the fluorescence light guide tube portion 22 is collected by the fluorescence condenser lens 24 and guided to the fluorescence incident surface 60 a of the fluorescence transmission optical fiber 60.

  Then, the fluorescence F guided by the fluorescence transmission optical fiber 60 is transmitted into the fluorescence measuring instrument 70, and the fluorescence F is spectrally separated by the fluorescence measuring instrument 70, and all wavelengths and intensities are measured. The elements contained in 10 and their amounts are determined, and the analysis results are displayed on the display 90.

  Thus, the condensing lens group 25 condenses the pulse laser light L transmitted through the laser light transmitting optical fiber 50 and irradiates the measurement object 10, and the measurement object 10 is irradiated by the pulse laser light L. Since the fluorescence F emitted from the atoms contained in the surface of the sample is condensed and transmitted to the optical fiber 60 for fluorescence transmission, there is little sensitivity degradation due to the influence of the shape of the measurement object 10, and high analysis accuracy is obtained. .

  The above-described analysis apparatus and analysis method are examples for carrying out the present invention, and the present invention is not limited to this. Needless to say, an analysis apparatus and an analysis method modified from these can be applied.

  Next, a method for creating a calibration curve will be described. (1) First, measurement objects having different densities are produced. FIG. 4 is an illustration for explaining the measurement object according to the embodiment of the present invention, and FIG. 4 (A) shows a smooth square plate obtained by slicing a columnar body made of felled wood into a direction perpendicular to the axis. The slice plane is shown. FIG. (B) is a measurement object for creating a calibration curve according to the present embodiment, and shows a square plate in which the center of the annual ring and corner portions of the square plate in FIG. The square plate may be obtained by slicing a felled tree at right angles to the axis, and further cutting it in parallel with the tree ring in the direction of the tree axis so that it is equivalent to a thin and narrow square plate including the center of the annual ring. A half from the center of the annual ring to one end of the square plate equivalent may be used.

  There are several types of measurement objects. The tree species may be of the same type or different types as long as they have different densities. However, in preparing the calibration curve, the moisture content needs to be 15% as defined in JISZ2101 in order to utilize soft X-ray densitometry that has been used conventionally as a method for measuring the density of trees.

  That is, the density of the tree varies depending on the water content, but the created calibration curve displays the density when the water content is 15%.

  (2) FIG. 5 is a graph for explaining a method of drawing a calibration curve according to the embodiment of the present invention. The left side (second quadrant) of FIG. 5 is a graph displaying the density of trees by soft X-ray densitometry, which is conventionally used as a method for measuring the density of trees. The horizontal axis is the X-ray transmittance, the vertical axis is the density of the tree, and the straight line is the calibration curve R.

  The right side (first quadrant) is a graph displaying the density of trees by laser-induced plasma emission analysis according to the present embodiment. The horizontal axis represents the fluorescence intensity of carbon, the vertical axis represents the density of the tree, and the straight line represents the calibration curve S. The calibration curve R is obtained from the values actually measured by the conventional soft X-ray densitometry (X on the graph), and the details are omitted.

  (3) For the same object as the measurement object (refer to FIG. 4B) corresponding to the point (T) on the calibration curve R, the carbon of the carbon is measured at a predetermined interval on the straight line including the center of the annual ring and the corners of both ends. The fluorescence intensity is measured, the average value is taken on the horizontal axis of the first quadrant (point 1, unit is au), and the density of the tree on the calibration curve R (T) (on the vertical axis, point 2) ).

  (4) A point (V) is obtained in the first quadrant from the point 1 on the horizontal axis and the point 2 on the vertical axis.

  (5) Similarly to (2), for the same object as the measurement object corresponding to the point (U) on the calibration curve R, the fluorescence of carbon at a predetermined interval on the straight line including the center of the annual ring and the corners of both ends. The intensity is measured, and the average value is taken on the horizontal axis of the first quadrant (point 3, unit is au), and the density of the tree on the calibration curve R (T) (vertical axis, point 4) Take.

  (6) A point (W) is obtained in the first quadrant from the point 3 on the horizontal axis and the point 4 on the vertical axis.

  (7) When a straight line passing through the points (V) and (W) plotted in the first quadrant is drawn, this straight line is the calibration curve S.

  The horizontal axis may be arbitrarily set so that the calibration curve S has a predetermined inclination.

  In the present embodiment, the object to be measured is a square plate or a square plate equivalent, but is not limited to this. The measurement object is a square plate or a square plate equivalent because the average value obtained by simply averaging the fluorescence intensities of carbon measured as spots when taking a calibration curve should be taken on the horizontal axis. This is because the volume calculation is easy.

  In addition, the measurement points of the fluorescence intensity of carbon are preferably set at equal intervals of 200 μm or less in the direction perpendicular to the annual rings in the cross section of the mouth so as to represent a general structure of wood.

  Next, a method for calculating the wood density using the created calibration curve will be described.

  (1) For a smooth cut surface of a tree, the fluorescence intensity (spot) of carbon is measured at predetermined intervals on a straight line including the center of the annual ring to both outer sides, and the average value is obtained.

  However, the measurement values of the measurement points are weighted so that the measurement points of the fluorescence intensity of carbon are equally distributed or even with respect to the cross-sectional area of the wood.

  (2) Taking the fluorescence intensity of carbon obtained in (1) as the horizontal axis of the graph showing the calibration curve created earlier, the density of the wood on the vertical axis is obtained from the intersection with the calibration curve S. This density of wood is the density of wood when the moisture content is 15%.

  In the above description, the calibration curve R has been described for the case where the soft X-ray densitometry method is used. However, without using this, a plurality of measurement target woods having different densities are prepared and obtained from the conventional volume and mass. A calibration curve may be determined using density and laser-induced plasma emission analysis.

  As described above, by using the calibration curve created by the method according to the present embodiment, it is possible to know the density when the moisture content of the measurement object is 15%. By subtracting the density at a moisture content of 15% obtained by the measurement method according to the present embodiment, a moisture content of 15% or more or less than 15% per unit volume can be obtained. Moisture management, strict control of the drying process, selection of wood usage due to dryness, etc. can be done nondestructively in the field in a short time, so its utility is great.

  Moreover, since the measurement of the fluorescence intensity of carbon according to the present embodiment can be performed in the atmosphere, online measurement at the manufacturing site is possible.

  In addition, it is possible to measure the surface distribution of the smooth cut surface of the tree, and because spot analysis is performed by laser irradiation, the surface of the smooth cut surface of the tree can be analyzed by local destruction. -By repeating the irradiation, it is possible to measure the fluorescence intensity of carbon from which the influence of foreign matter adhering to the cut surface has been removed. Furthermore, remote analysis can be performed by separating the analyzer main body and the measurement head by optical fiber transmission, so analysis incorporated in the production line is possible.

(1) Analyzer (LIBS)
TOSHIBA ELECTRON TUBE DEVICES CORPORATION LIS-201 Series (2) Object to be measured Tree species Cedar Shape Square plate
Length x width x thickness: about 160mm x 25mm x 5mm
Water content 15%
Number of measurement objects 6 (3) Measurement Measurement surface Smooth surface of measurement object Measurement range / direction Longitudinal direction of measurement object on the center line of the measurement object including the center of the annual ring from one end to the other end perpendicular to the annual ring
Measurement interval 500μm
Laser spot diameter 360μm
(4) Measurement Results FIG. 6 is a graph showing the wavelength and fluorescence intensity of the constituent elements of wood by laser induced plasma emission analysis according to the embodiment of the present invention. Strong fluorescence due to carbon appears at a wavelength of 247.9 nm.

  FIG. 7 is a calibration curve created by the laser-induced plasma emission analysis method according to the embodiment of the present invention, and shows data on the left side of one measurement object among the six measurement objects. Displays the fluorescence intensity of carbon for each measurement point on the left side up to the left end including the center of the annual ring of the measurement object in arbitrary units (a.u. is omitted), and the oil attached to the cutting blade is the measurement object. In order to remove the variation in the initial measurement data, which is considered to be the influence attached to the surface of the mouth, the data after the fourth time are shown (the graph showing the variation for each number of measurements is omitted). The late wood part (annual ring part) has high carbon fluorescence intensity, and the early part (annual ring part) has low carbon fluorescence intensity, and the difference in the wood structure is displayed as the difference in carbon fluorescent intensity. ing.

  FIG. 8 is a calibration curve created by utilizing laser-induced plasma emission analysis according to an embodiment of the present invention. The □ points are obtained by sliding the actual measurement points of soft X-ray densitometry onto the calibration curve. ● The points are the density obtained from the volume and mass of the measurement object by the conventional method, and the carbon of the present invention. Although it is an actual measurement point obtained from the relationship with the fluorescence intensity, the deviation from the calibration curve using the soft X-ray densitometry of the point ● by the conventional method is small, and the calibration curve according to the present invention is highly accurate. It is possible to measure the wood density with high accuracy using the wire.

  At the time of preparing the calibration curve, the point ● in FIG. 8 is displayed using a simple average value of the fluorescence intensity (horizontal axis) of carbon with respect to the distance from the center of the annual ring of the measurement object shown in FIG. If the value obtained by integrating the fluorescence intensity (horizontal axis) with respect to the distance and dividing the integrated value by the measurement range (distance) is used, the accuracy can be further improved.

1 is a block diagram for explaining a LIBS (laser induced plasma emission analyzer) according to an embodiment of the present invention. FIG. It is sectional drawing of the optical system unit which concerns on embodiment of this invention. It is a graph for demonstrating the relationship of the wavelength of the distribution reflective mirror which concerns on embodiment of this invention, and the transmittance | permeability and reflectance. It is illustrated in order to explain a measuring object concerning an embodiment of the present invention. It is a graph for demonstrating the drawing method of the calibration curve which concerns on embodiment of this invention. It is the graph which showed the wavelength and fluorescence intensity of the structural element of wood by the laser induction plasma emission analysis which concerns on embodiment of this invention. It is the graph which showed the fluorescence intensity of carbon of the measuring object which concerns on the Example of this invention. 3 is a calibration curve created by utilizing laser induced plasma emission analysis according to an embodiment of the present invention. It is the table | surface which showed the ratio (weight ratio) of the structural element of wood.

Explanation of symbols

100 ... LIBS (Laser Induced Plasma Emission Spectrometer)
10 ... Measurement object (square plate)
DESCRIPTION OF SYMBOLS 20 ... Optical system unit 21 ... Main body cylinder part 22 ... Fluorescence light guide cylinder part 23 ... Distributive reflection mirror 231 ... Fluorescence reflection surface 24 ... Fluorescence condensing lens 25 ... Collection Optical lens group 251 ... 1st lens 252 ... 2nd lens 253 ... 3rd lens 254 ... 4th lens 30 ... Laser transmitter 40 ... Optical fiber incident system 50 ... Optical fiber (for laser light transmission)
50a ... Laser light emitting surface 60 ... Optical fiber (for fluorescence transmission)
60a ... Fluorescence incident surface 70 ... Fluorescence measuring instrument 80 ... Calculator 90 ... Indicator L ... Pulse laser beam F ... Fluorescence

Claims (5)

  The fluorescence intensity of carbon obtained from the surface of wood by laser-induced plasma emission analysis and the air-dry density of wood obtained as a ratio of mass to volume (the density at a moisture content of 15%; hereinafter simply referred to as “wood density”). ) And a non-destructive measurement method using the calibration curve regardless of the moisture content of the wood.   The measurement object at the time of preparing the calibration curve is a thin, small square plate (hereinafter referred to as “square plate”) that includes the center of the annual ring and one outer side or both outer sides of the tree in a central and straight line on a smooth cut surface of the tree. And the fluorescence intensity of carbon obtained from the surface of the wood at the time of preparation of the calibration curve is a plurality from the center and straight line from one outer side to the center of the annual ring or from the center of the annual ring to the other outer side. The wood density measuring method according to claim 1, wherein the measuring value is an average value of the measured values of the points. Measuring direction of the fluorescence intensity of carbon derived from the surface of the wood definitive when using the calibration curve, the smooth cut surface of the tree, is a direction orthogonal to the annulus, and the number of measurement points per unit area of the timber 3. The method for measuring a wood density according to claim 1, wherein weighting is performed so as to be evenly distributed or evenly distributed . A said tree Zaimitsu of the measured moisture content unknown timber, the obtained by the measuring method of the wood density according to any one of claims 1 to 3 from the density of the wood is the measurement object Subtracting the wood density, calculating a moisture content of 15% or more or less than 15% per unit volume of the wood to be measured, and performing drying control of the wood to be measured based on the obtained moisture content A drying control method characterized by the above . A said tree Zaimitsu of the measured moisture content unknown timber, the obtained by the measuring method of the wood density according to any one of claims 1 to 3 from the density of the wood is the measurement object Subtract the wood density, calculate a moisture content of 15% or more per unit volume of the wood to be measured, or less than 15%, and perform application selection of the wood to be measured based on the obtained moisture content A method of selecting applications .

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