CA2590347A1

CA2590347A1 - Internal and external wood rot indentification, for optimum trimming, using soft x-rays

Info

Publication number: CA2590347A1
Application number: CA002590347A
Authority: CA
Inventors: Marcel Lizotte
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-05-29
Filing date: 2007-05-29
Publication date: 2008-11-29

Abstract

A wood-quality system and method, comprising an imaging system to view lumber, image processing hardware and software, and an output to communicate to a trim-saw system where the lumber should be cut to optimize recovery. The ima ge processing system specifically identifies areas of rot using soft x-rays and image processing software. Although trees produce wood in a continuum of sizes, most lumber is sold i n selected standard sizes. It is common practise in the softwood industry for pieces to be trimmed to a standard length before drying, but this trimming is often based solely on surface profile information (wane - areas of bark and the associated volume where there is no wood (usually from the top of the tree)), or surface profile and visua l examination for surface rot (usually from the base of the tree). Therefore, trimming removes not only bonafide scrap, but also removes sound wood, so as to produce lumber of a standard size. If rot is identified at a later stage in processing, an additional trimming may be required - and to maintain the lumber at a standard length it is often a who le two foot length of scrap which will be generated. Failure to identify rot internal to lumber is also to be avoided, as it reduces the quality of the piece. Additional losses, inherent in unidentified rot, exist in the form of energy wasted in drying non-saleable wood, wasted drying-kiln space, etc. Conversely, rot evident at the surface of a piece may be only superficial, a nd quite acceptable in some grades of wood. To trim it would be wasteful. This inspection system is ideally suited to being placed on the 'green-chain ,' before the first trimming and drying operation is performed. It may also be applied to lumber passing longitudinally, as it does in the area of a planer mill.</SDO AB>

Description

SPECIFICATION
The present invention relates to a method and a system for identifying the presence and extent of both surface and internal rot in boards, for calculating the optimum locations for trimming, and for communicating these trim locations to a system of cut-off saws.
It is common practise to use laser profiling to examine for wane, and perhaps a manual or conventional camera system to examine for surface rot. These methods can not evaluate the true nature of rot evident at the surface. Nor can they find internal rot that is not evident from the surface.
The subject of this patent uses soft x-rays (such as from the generator, item 1 in figure 1) to penetrate the wood. It uses an imaging device (such as the line-scan camera, item 2 in figure 1) to evaluate this penetration. An image processing system is used to assemble this information and to generate an image of the lumber. In this image, sound wood may be differentiated from dry rot and water-logged rot. It is to be noted that the image represents a cross-section of the lumber, so that rot anywhere within the wood can be identified.
Using the algorithm presented in figure 2, the image may be digitally processed, and an appropriate location for the trim-line may be determined.
Because of the nature of machine vision, this system can also be easily adapted to the examination of lumber being presented longitudinally, as it would in the area of a planer mill.

BRIEF DESCRIPTION OF THE DRAWINGS
In the appended drawings:
Figure 1 is a schematic view of pieces of wood passing through the portion of a typical sawmill downstream of the scanner where surface profile is examined, and upstream of the saws where the pieces will be trimmed to length before being sorted into bins before drying.

Figure 2 presents the algorithm of the logical engine.

DESCRIPTION OF THE PREFERRED EMBODIMENT
In the preferred embodiment, an x-ray imaging system, using a generator of soft x-rays (1) and and x-ray-line-scan camera (2) are mounted to acquire images of planks of lumber (4) as they are transported on a conveying chain (3). On signal from a sensor (5), an image of the plank is acquired. This image is then processed to eliminate the conveying chain, and to differentiate between sound and punk wood. A
recommendation as to where the piece should be cut is pronounced.
Although this description concentrates on the examination of the but-end of lumber presented transversely, the nature of the image from a line-scan camera can quite easily be adapted to provide for the examination of the totality of lumber in longitudinal presentation.

Drawings:
Figure 1; Attached:
= Showing isometric of system, including pointers to X-ray generator, Line-scan camera, Chain, Wood, Sensor.
Figure 2; Logic Algorithm:
0) Wait until next piece is advantageously positioned for imaging.
1) Capture multi-bit grey-level image of wood (we use 12-bit image on a 0.4mm pitch line-scan array).

2) Determine where the edges of the wood are.

3) Using the density of the wood near the top of the image as an initial threshold, determine appropriate areas of sound wood, dry rot and wet rot.

4) By examining the gradient of intensity between these areas, determine appropriate thresholds between sound wood and rot for this piece.

5) Determine the boundaries of rot in the piece.

6) Based on user entered threshold parameters:
1) If the rot in the first segment (user-set-length) is significant (user-threshold-1): This segment is to be removed; The next segment is to be examined. Else (if no rot in the first segment): No rot to be removed.
2) For subsequent segments: If rot is not trivial (user-threshold-2), then:
This segment is also to be removed; The next segment is to be examined. Else (if rot in this segment is trivial, or absent): The next segment is to be evaluated unless there have been several (user-set-quantity) consecutive segments not to be removed.
3) If at last segment, or no more rot to be removed, then end.

7) With determination of number of segments to be removed, this number is communicated to the system controlling the cut-off saws.

Claims

CLAIMS:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

1. An artificial vision system that differentiates between rot and sound wood in lumber by examining through the thickness of the lumber using soft x-ray imaging technology.

2. A system described in claim 1, which evaluates the severity of rot and makes intelligent decisions on where the wood should be trimmed in the interests of optimizing recovery.

3. A system described in claim 2, which can examine lumber in transverse or longitudinal presentation. Where used on lumber in longitudinal presentation, the imaging system could be placed where the lumber is passed through the air, from one conveyor to another.