Abstract: Inspection of micromask patterns occurs by both moving an inspecting laser beam relative to a micromask and varying the intensity of said beam in the same manner that occurs during pattern generation. The pattern modulates the inspecting laser beam by one of reflecting or transmitting a modulated laser beam therefrom. The modulated beam then is sensed and used to produce a modulation signal. The modulated signal is compared to a control signal, which controls both the relative movement between a writing laser beam and the micromask and varies the beam intensity during pattern generation. Agreement between the modulation and control signals indicates correct pattern generation and a difference therebetween indicates a pattern inaccuracy.

Abstract: A compensating device in combination with a laser interferometer, which laser interferometer comprises a laser (1), a prism (6) rigidly connected to a movable object, a beam splitter prism (2) and a stationary prism (3). The wavelength of the laser light is subject to changes by external factors, for example meteorologic ones. The compensating device includes mechanism (4,5) capable to change the position of the stationary prism (3) in response to and by means of an electric signal, which represents the desired compensation for magnitudes affecting the accuracy of the laser interferometer.

Abstract: Two magnetically sensitive field plates are provided in a caliper to determine the distance between a movable leg and a stationary leg. The field plates are located on the movable leg adjacent grooves in a portion of the caliper which is magnetic and along which the movable leg is moved. Each plate magnetically senses each groove and produces an electrical signal in response thereto. The field plates are arranged relative to each other so that the signals produced therefrom are out of phase with each other, the phase difference between the two signals indicating the direction of travel of the movable leg and the number of signals indicating the magnitude of the movement of the movable leg. Depending on the direction of travel, the number of signals are added or subtracted to determine the distance between the legs.

Abstract: A scanning device for providing rapid accurate mechanical line scanning of a preferably flat surface includes a radiation source, a radiation sensitive medium and apparatus for providing relative movement between the radiation source and the medium. The apparatus includes a driving device and a slide structure which is designed to oscillate at substantially its self resonant frequency in order to increase accuracy of operation.