Abstract: An apparatus for detecting defects in patterns, particularly defects in chip patterns of photomasks used for manufacturing semi-conductor integrated circuits comprises means such as a flying spot scanner for producing a scanning light spot, an optical system for projecting said scanning light spot simultaneously on to identical portions of two patterns to be compared with each other, said patterns being placed on a carrier stage, first and second photoelectric converters, each converter receiving the light spot passing through or reflected from a respective pattern to produce an output electrical signal; and an electric circuit for receiving the output signals from said first and second photoelectric converters and subtracting one of them from the other to produce a difference signal which represents detected defects in the patterns.

Abstract: An apparatus for automatically adjusting a microscope in focus, said microscope comprising a stage on which a specimen is to be placed, an objective, an objective tube and a driving member for relatively moving said stage and objective tube. Said apparatus comprises a nozzle member mechanically coupled to said objective tube and being opposed to the specimen, said nozzle being connected to an air pump so as to blow or suck an air stream from said nozzle member, a pressure detector for detecting pressure variations of said air stream to produce an electric signal which varies as a function of a distance between said objective and specimen and an electric motor energized with a signal related to said electric signal and mechanically coupled to said driving member of the microscope.