A linear sensor arrangement is presented as a means of measuring the three-dimensional grain angle of wood. The measurement principle is based on an optical characteristic of a wood surface where the microscopic cell structure causes preferential reflection of light perpendicular to the wood grain. This response is notable among the several other techniques for measuring wood grain angle in that it enables identification of diving (out-of-plane) angle in addition to the surface (within-plane) angle. The basic measurement principle has been previously investigated using a circular array of light sensors to measure the spatial distribution of the light reflected from a wood surface. That procedure works reasonably well for surface points near the center of the circle and for modest dive angles. The linear sensor arrangement investigated here is designed to extend measurement functionality so as to be able to measure grain angle at any point along a central line and over a greater range of dive angle. A prototype scanner system is presented together with example experimental results for clear wood samples and for a face knot sample.

References

References
1.
Forest Products Laboratory
,
2010
, “
Wood Handbook: Wood as an Engineering Material
,” USDA Forest Products Laboratory, Madison, WI, Technical Report No. 190.
2.
Bechtel
,
F. K.
,
Byers
,
R. K.
,
Logan
,
J. D.
,
Allen
,
J. R.
,
Strevy
,
M. G.
, and
Uskoski
,
D. A.
,
1996
, “
Apparatus for Testing Lumber Stiffness
,” U.S. Patent No. 5503024.
3.
Schajer
,
G. S.
,
2001
, “
Lumber Strength Grading Using X-Ray Scanning
,”
For. Prod. J.
,
51
(
1
), pp.
43
50
.
4.
McDonald
,
K. A.
,
1978
, “
Lumber Defect Detection by Ultrasonics
,” USDA Forest Products Laboratory, Madison, WI, Research Paper No. FPL 311.
5.
McLauchlan
,
T. A.
,
Norton
,
J. A.
, and
Kusec
,
D. J.
,
1973
, “
Slope of Grain Indicator
,”
For. Prod. J.
,
23
(
5
), pp.
50
55
.
6.
Steele
,
P. H.
,
Neal
,
S. C.
, and
McDonald
,
S. M.
,
1991
, “
The Slope-of-Grain Indicator for Defect Detection in Unplanned Hardwood Lumber
,”
For. Prod. J.
,
41
(
1
), pp.
15
20
.
7.
Daval
,
V.
,
Pot
,
G.
,
Belkacemi
,
M.
,
Meriaudeau
,
F.
, and
Collet
,
R.
,
2015
, “
Automatic Measurement of Wood Fiber Orientation and Knot Detection Using an Optical System Based on Heating Conduction
,”
Opt. Soc. Am.
,
23
(
26
), pp.
33529
33539
.
8.
Schajer
,
G. S.
, and
Orhan
,
F. B.
,
2006
, “
Measurement of Wood Grain Angle, Moisture Content and Density Using Microwaves
,”
Holz Roh-Werkst.
,
64
(
6
), pp.
483
490
.
9.
Zhou
,
J.
, and
Shen
,
J.
,
2003
, “
Ellipse Detection and Phase Demodulation for Wood Grain Orientation Measurement Based on the Tracheid Effect
,”
Opt. Lasers Eng.
,
39
(
1
), pp.
73
89
.
10.
Hu
,
C.
,
Tanaka
,
C.
, and
Ohtani
,
T.
,
2004
, “
On-Line Determination of the Grain Angle Using Ellipse Analysis of the Laser Light Scattering Pattern Image
,”
J. Wood Sci.
,
50
(
4
), pp.
321
326
.
11.
Matthews
,
P. C.
, and
Soest
,
J. F.
,
1986
, “
Method for Determining Localized Fiber Angle in a Three Dimensional Fibrous Material
,” U.S. Patent No. 4606645.
12.
Soest
,
J.
,
Matthews
,
P.
, and
Wilson
,
B.
,
1993
, “
A Simple Optical Scanner for Grain Defects
,”
Fifth International Conference on Scanning Technology and Process Control for the Wood Products Industry
, Atlanta, GA, Oct. 25–27, pp. 192–200.
13.
McGunnigle
,
G.
,
2009
, “
Estimating Fibre Orientation in Spruce Using Lighting Direction
,”
IET Comput. Vision
,
3
(
3
), pp.
143
158
.
14.
Schajer
,
G. S.
, and
Sutton
,
D. B.
,
2016
, “
Identification of 3D Wood Grain Angle by Directional Reflection Measurement
,”
Wood Mater. Sci. Eng.
,
11
(
3
), pp.
170
175
.
15.
Nicodemus
,
F.
,
1965
, “
Directional Reflectance and Emissivity of an Opaque Surface
,”
Appl. Opt.
,
4
(
7
), pp.
767
775
.
16.
Glaeser
,
G.
,
1999
, “
Reflections on Spheres and Cylinders of Revolution
,”
J. Geometry Graph.
,
3
(
2
), pp.
121
139
.
17.
Pan
,
Q.
, and
Schajer
,
G. S.
,
2018
, “
Two-Line Spatial Reflection Method for Measuring Wood Grain Direction
,”
For. Prod. J.
(in press).http://www.forestprodjournals.org/doi/abs/10.13073/FPJ-D-18-00004?code=frps-site
You do not currently have access to this content.