Lighting for defect inspection of sheet-shaped objects, defect inspection apparatus for sheet-shaped objects, and method of defect inspection of sheet-shaped objects

A method of defect inspection of sheet-shaped objects, the method for inspecting presence or absence of a defect of a sheet-shaped object by using a lighting unit and an imaging unit and by imaging light that is emitted by the lighting unit and transmitted through the sheet-shaped object with the imaging unit, the method comprising:

• emitting, with the lighting unit, light with which an angle formed by a transmission direction of light transmitted through the sheet-shaped object with an optical axis of the imaging unit is larger than an aperture angle of the imaging unit at each position at which the light emitted by the lighting unit is transmitted through the sheet-shaped object, along a second direction orthogonal to a first direction on a surface of the sheet-shaped object, the first direction being a direction in which the sheet-shaped object moves relative to the lighting unit;
• imaging with the imaging unit whose imaging direction is parallel to the second direction of the sheet-shaped object and whose optical axes at positions along the imaging direction are parallel to each other;
• and
• determining presence or absence of a defect of the sheet-shaped object by using image data imaged by the imaging unit.

A method of defect inspection of sheet-shaped objects, the method for inspecting presence or absence of a defect of a sheet-shaped object by using a lighting unit and an imaging unit and by imaging light that is emitted by the lighting unit and reflected on the sheet-shaped object with the imaging unit, the method comprising:

• emitting, with the lighting unit, light with which an angle formed by a reflection direction of specular reflection light reflected on the sheet-shaped object with an optical axis of the imaging unit is larger than an aperture angle of the imaging unit at each position at which the light emitted by the lighting unit is reflected on the sheet-shaped object, along a second direction orthogonal to a first direction on a surface of the sheet-shaped object, the first direction being a direction in which the sheet-shaped object moves relative to the lighting unit;
• imaging with the imaging unit whose an imaging direction is parallel to the second direction of the sheet-shaped object and whose optical axes at positions along the imaging direction are parallel to each other;
• and
• determining presence or absence of a defect of the sheet-shaped object by using image data imaged by the imaging unit.