INSPECTION APPARATUS FOR HOMOGENEITY OF OPTICAL MATERIAL

• Main Author: SAWADA HIDEJI
• Format: Patent
• Language: English
• Published: 11.09.1998
• Edition: 6
• Subjects: COLORIMETRY; INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES; MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT,POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRA-RED,VISIBLE OR ULTRA-VIOLET LIGHT; MEASURING; PHYSICS; RADIATION PYROMETRY; TESTING; TESTING STATIC OR DYNAMIC BALANCE OF MACHINES ORSTRUCTURES; TESTING STRUCTURES OR APPARATUS NOT OTHERWISE PROVIDED FOR

PROBLEM TO BE SOLVED: To provide an inspection apparatus by which an object to be inspected is inspected with good accuracy even when the homogeneity of an optical system on the side of the apparatus is not always good and even when the thickness of the object to be inspected is different by a method wherein a base, to be inspected, on which the object to be inspected is placed and which can be moved back and forth in a direction perpendicular to an optical axis is provided and a quantity-of-light regulating system which regulates the quantity of light of a luminous flux is provided. SOLUTION: A luminous flux which is emitted from an infrared laser 31 is changed into a parallel luminous flux by a collimating lens 32, it is transmitted through an object 33 to be inspected, and it is transmitted further through an image formation lens 34 so as to be converged in a focal position. A knife edge 6 is placed near the focal position, the luminous flux is narrowed down to a visual field whose brightness is proper, and the distribution of the refractive index of the object 33 to be inspected is changed into a light and shade contrast so as to be observed by an infrared camera 11. At this time, a quantity of light is regulated so as to be a brightness which is easily observed by a variable ND filter 12. In addition, when the object 33 to be inspected is moved to a direction perpendicular to an optical axis by the base 13 to be inspected, the irregularity in the quantity of light of an optical system on the side of an apparatus can be discriminated from the stria of the object 33 to be inspected. Consequently, even when germanium whose homogeneity is not always good is used for the optical material, the object 33 to be inspected can be inspected precisely.