Edge sensor and flaw detection apparatus

Abstract

The invention provides an edge sensor and defect inspection device capable of reliably detecting breach, crack, or the like defects produced in transparent or semitransparent objects. When inventive edge sensor detects the edge position of transparent body or semitransparent body located in a parallel monochromatic light from the output of line type sensor formed by a plurality of light sensitive units arranged in a specified spacing, the edge sensor start to search the output of the line type sensor from free-space side, detects a first detection position where the luminous quantity drops to the first luminous quantity threshold in a luminous quantity distribution pattern produced by the edges of the object, and then detects a second detection position where the luminous quantity further drops to a second luminous quantity threshold value. So that the breach, crack, or the like defects are detected by variations of the first and second detection positions during scanning checkpoints along the edge.

Description

technical field [0001] The present invention relates to an edge sensor suitable for detecting chipping and cracking of, for example, an edge of a liquid crystal glass, and a defect inspection device using the edge sensor. Background technique [0002] The inventors of the present application have previously proposed a proposal focusing on the Fresnel diffraction of monochromatic parallel light at the edge of an object, and analyzing the light intensity distribution pattern detected by a line sensor using a plurality of photosensitive cells arranged at predetermined intervals. The position of the edge of the above-mentioned object can be detected with high precision at an accuracy equal to or greater than the arrangement pitch of photosensitive cells of the type sensor (refer to Japanese Patent No. 3858994). [0003] Furthermore, a technique has been proposed to detect the edge position with high precision by paying attention to the above-mentioned Fresnel diffraction for tra...

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Problems solved by technology

[0004] However, once there is a gap or crack at the edge of the vitreous body, it will be affected by the reflected light from the defect caused by the above-mentioned gap or crack inside the vitreous body

Therefore, it is difficult to correctly detect the edge from the above-mentioned Fresnel diffraction light quantity distribution pattern

Also, even if a line sensor is moved along the edge to detect the edge position of a glass body that has a chipped or cracked edge, it is difficult to unambiguously detect a change in edge position

Therefore, it is also difficult to identify the defect site in the vitreous body where the gap or crack occurs

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