| 摘要 |
PURPOSE:To enable highly sensitive detection of a defect such as oblong bubble and knot existing in a light transmitting sheet, by providing a plurality of light receivers each having a linear light receiving surface. CONSTITUTION:This apparatus is provided with a light receiver D1 for detecting transmitted light, light receivers D2A and D2B for detecting proximity paraxial transmission scattered light receivers D3A and D3B for detecting paraxial transmission scattered light and light receivers D4A and D4B for detecting teleaxial transmission scattered light. These light receivers are arranged with linear light receiving surfaces parallel one another thereof while being made at an angle of theta with respect to the X axis as scanning direction of a light spot. The angle theta is set within a range of 5 deg.-45 deg.. When any defect 41 as oblong knot exists in glass sheet 30, a light spot may be projected to the defect to scatter the proximity paraxial transmission scattered light in the X axis as indicated by the arrows 42A and 42B, yet the proximity paraxial transmission scattered light reaches the light receivers D2A and D2B, thereby allowing detection of the existence of the knot. When the defect 41 is an oblong bubble, the light spot may be projected onto the bubble to scatter the teleaxial transmission scattered light in the X axis, yet the light reaches the light receivers D44 and D4B, thereby enabling detection of the existence of the bubble. |
