Calibration device and method for an optical defect scanner

Claim 1

A calibration device for a system of the type for visually detecting microscopic defects in a certain specularly reflecting surface of a given object, said system comprising first means for scanning said reflecting surface with an incident beam of light that illuminates a relatively small spot area of said entire reflecting surface area, which spot area is large relative to the area of any microscopic defect, the incident beam of light being directed to said surface illuminated by the incident beam of light is detected substantially independently of light specularly reflected from the same surface, and a second means for varying the threshold of detection of the scattered light, wherein said calibration device service as a reference object with artificially created microscopic defects comprises: a substrate having a characteristic pattern of a plurality of different arrays of artificial defects, all of the artificial defects of a particular array being of the same size and being evenly spaced from each other, each artificial defect being provided with a surface, which, in response to an incident beam of light of said system at a preselected intensity, scatters the incident light to provide together with a predetermined plurality of adjacent artificial defects a visually observable pattern corresponding to actual microscopic defects of a known dimension.

Claim 8

A method for calibrating a system of the type that optically detects microscopic defects in a certain specularly reflecting surface of a given object, wherein said method comprises the steps of: forming on a substrate a calibration device having a characteristic pattern of a plurality of different arrays of artificial microscopic defects, all the defects of each array being of the same size and being evenly spaced from each other, a predetermined adjacent plurality of said artificial defects representing a visually observable pattern corresponding to actual microscopic defects of a known dimension; scanning said pattern with a beam of light of said system having a given spot size, and detecting scattered light reflected from the illuminated pattern and generating an electrical signal representing the scattered light from said pattern, the magnitude of the electrical signal being indicative of the sensitivity of said system.

Claim 9

A method for calibrating a system of the type that optically detects microscopic defects in a certain specularly reflecting surface of a given object, wherein said method comprises the steps of: forming on a substrate a calibration device having a characteristic pattern of a plurality of different arrays of artificial microscopic defects, all the defects of each array being of the same size and being evenly spaced from each other, a predetermined adjacent plurality of said artificial defects representing a visually observable pattern corresponding to actual microscopic defects of a known dimension; scanning said pattern with a beam of light of said system having a given spot size, and detecting scattered light reflected from the illuminated pattern and generating an electrical signal representing the scattered light from said pattern, the magnitude of the electrical signal being indicative of the sensitivity of said system.