FI-20265194-A1 - Defect inspection system and defect inspection method

FI20265194A1FI 20265194 A1FI20265194 A1FI 20265194A1FI-20265194-A1

Abstract

Images of a face surface and a back surface of a plywood (10) that is conveyed on belt conveyors (5U) and (5D) are captured by imaging devices of first illumination and imaging units (1F) and (1B) to generate depth information, a shape of the plywood (10) is measured by shape measurement units (3F) and (3B), which are provided at locations different from a location of a gap (51) where the image capturing is performed, to generate shape information, and the depth information is corrected based on the shape information, and then a defect in the plywood (10) is detected based on the depth information. By detecting a defect in the plywood (10) based on the depth information corrected using the shape information that is measured without being affected by vibrations that occur when the plywood (10) is conveyed over the gap (51), a defect such as warpage or bending can be accurately detected without deformation occurring in the plywood (10) being flattened by the correction of the depth information.

Inventors

IWAMOTO MASAMICHI
TOKUYAMA Takehiko
YAMAGUCHI KEIJIRO
MIURA MASATO

Assignees

MEINAN MACHINERY WORKS

Dates

Publication Date: 20260302
Application Date: 20240903
Priority Date: 20231012

Claims (1)

CLAIMS [Claim 1] A defect inspection system, characterized by comprising: imaging devices that generate depth information in a board thickness direction by capturing images of a face surface and a back surface of a plywood, which is sequentially conveyed by conveyors disposed spaced apart from each other in a conveying direction, in a gap between the conveyors; a shape measurement device that generates shape information by measuring a shape in the board thickness direction at a location different from a location of the gap between the conveyors; and an analysis device that detects a defect in the plywood by analyzing the depth information acquired by the imaging devices and the shape information acquired by the shape measurement device, wherein the analysis device includes a correction processing unit that corrects the depth information based on the shape information, and a defect detection unit that detects a defect in the plywood due to deformation based on the depth information. 36 [Claim 2] The defect inspection system according to claim 1, characterized in that the depth information and the shape information are information indicating a distance from a reference position to the face surface or the back surface of the plywood in the board thickness direction, and the correction processing unit calculates a difference value between the depth information and the shape information, and corrects the depth information by using the difference value as a correction value for the depth information. [Claim 3] The defect inspection system according to claim 1, characterized in that when a shape in the board thickness direction indicated by the depth information acguired by the imaging devices is different from the shape in the board thickness direction indicated by the shape information acguired by the shape measurement device at the same position as a position where the depth information is acquired, the correction processing unit corrects the depth information based on the shape information. 37 [Claim 4] The defect inspection system according to claim 1, characterized in that the imaging devices are installed vertically above and vertically below the gap between the conveyors at positions that are vertically aligned in a straight line, and simultaneously capture the images of the face surface and the back surface of the plywood. [Claim 5] The defect inspection system according to any one of claims 1 to 4, characterized by further comprising: a first illumination that irradiates the face surface and the back surface of the plywood with a first illumination light for capturing a color image; and a second illumination that irradiates the face surface and the back surface of the plywood with a second illumination light for acquiring depth information, wherein the imaging devices generate planar color images and the depth information by capturing the images of the face surface and the back surface of the plywood in the gap between the conveyors in a state where the face surface and the back surface are irradiated with the first illumination light and the second illumination light, and the analysis device detects a plurality of types of 38 defects in the plywood based on the planar color image, and detects a defect in the plywood due to deformation based on the depth information. [Claim ©] The defect inspection system according to claim 5, characterized in that the second illumination light is illumination light for light sectioning measurement. [Claim 7] The defect inspection system according to any one of claims 1 to 4, characterized in that the shape measurement device includes a side surface imaging device that generates a side surface color image by capturing an image of a side surface of the plywood, and a side surface shape recognition unit included in the analysis device, and the side surface shape recognition unit generates shape information of the plywood in the board thickness direction by analyzing the side surface color image acquired by the side surface imaging device. [Claim 8] The defect inspection system according to claim 7, 39 characterized in that the analysis device further detects a defect existing on the side surface of the plywood based on the side surface color image. [Claim 9] A defect inspection method, characterized by comprising: a step of generating, by imaging devices, depth information in a board thickness direction by capturing images of a face surface and a back surface of a plywood, which is sequentially conveyed by conveyors disposed spaced apart from each other in a conveying direction, in a gap between the conveyors; a step of generating, by a shape measurement device, shape information by measuring a shape in the board thickness direction at a location different from a location of the gap between the conveyors; and a step of detecting, by an analysis device, a defect in the plywood by analyzing the depth information acguired by the imaging devices and the shape information acguired by the shape measurement device, wherein the step of detecting, by the analysis device, a defect in the plywood includes a first step of correcting, a correction processing unit of the analysis device, the 40 depth information based on the shape information, and a second step of detecting, by a defect detection unit of the analysis device, a defect in the plywood due to deformation based on the depth information corrected by the correction processing unit. 41

Description

DESCRIPTION Title of Invention: DEFECT INSPECTION SYSTEM AND DEFECT INSPECTION METHOD Technical Field [0001] The present invention relates to a defect inspection system and a defect inspection method, and is particularly suitable for use in a system that detects defects existing in a plywood formed by laminating a plurality of veneers cut from a log. Background Art [0002] Generally, a plywood is manufactured by superimposing a plurality of veneers, which are produced by cutting a log, which is a natural material, using a veneer lathe, and bonding the veneers together with an adhesive. A plywood produced from a log contains a variety of defects. Each plywood is sorted into one of a plurality of quality ranks depending on the type, size, number, or the like of the defects. Conventionally, a defect inspection apparatus that detects defects existing in a plywood is used to perform the sorting. Defects in the plywood that are detected by 1 the defect inspection apparatus include discoloration (mold, dirt, bark inclusion, and the like), holes, contaminant, unevenness, warpage, bending, and the like of a face surface and a back surface. [0003] Conventionally, an inspection apparatus that irradiates a face surface of a wood laminate with vertical irradiation light and oblique irradiation light and irradiates a back surface of the wood laminate with vertical irradiation light and oblique irradiation light and that determines the properties of each of the face surface and the back surface by analyzing image data obtained by capturing images of the face surface and the back surface of the wood laminate using line sensor cameras has been known (for example, refer to PTL 1). [0004] In addition, among apparatuses that inspect the thickness of an object to be inspected such as a decorative board manufactured by affixing a plywood and a sheet-shaped decorative material together, an apparatus that inspects the thickness of the object to be inspected based on a difference between a plurality of first displacement data representing a distance from a position on one surface of the object to be inspected to a reference point set in advance, which is measured by one of a pair of displacement 2 sensors disposed with the object to be inspected interposed therebetween, and a plurality of second displacement data representing a distance from a position on the other surface of the object to be inspected to the reference point, which is measured by the other displacement sensor, has also been known (for example, refer to PTL 2). [0005] By the way, when capturing images of or measuring the face surface and the back surface of the plywood is simultaneously performed as in PTLs 1 and 2, it is necessary to separate conveying devices (conveyors) for conveying the plywood into an upstream side and a downstream side and to dispose the two conveyors with a spatial gap therebetween. Therefore, when the plywood is transferred from the upstream conveyor to the downstream conveyor, namely, when capturing images of or measuring the plywood is performed, the plywood may bounce and the influence of the bouncing may appear as an error in the captured or measured data. Particularly, when the plywood is warped or bent, the plywood is likely to bounce due to the warpage or bending. [0006] Note that, in this regard, PTL 2 describes that a stripe pattern appears in a captured image due to vibrations of the object to be inspected that occur when the object to be inspected passes over an inspection surface of the 3 displacement sensor, but an image in which a change in surface height caused by the vibrations of the object to be inspected is cancelled out can be acquired by taking the difference between the first displacement data and the second displacement data. [0007] However, the technology described in PTL 2 is not for detecting defects in the plywood, but for measuring the thickness of the plywood. Therefore, when the technology described in PTL 2 is applied to a defect inspection apparatus for a plywood, in a case where a plywood has a defect such as warpage or bending, the defect is simultaneously removed by taking the difference between the first displacement data and the second displacement data, and a defect such as warpage or bending cannot be detected, which is a problem. Citation List Patent Literature [0008] PTL 1: JP2023-29260A PTL 2: JP2014-222156A Summary of Invention Technical Problem 4 [0009] The invention has been made to solve such problems, and an object of the invention is to be able to accurately detect defects such as warpage or bending existing in a plywood. Solution to Problem [0010] In order to solve the above-described problems, in the invention, images of a face surface and a back surface of a plywood that is conveyed on conveyors are captured by imaging devices to generate depth information of both the surfaces of the plywood, a shape of the plywood in a board thickness direction is measured by a shape measurement device, whic