Abstract: Method and an apparatus for determining line centers in a microminiature element such as on a semiconductor wafer or a mask having linewidths and other spacings below the one micron range. The invention uses, two focussed laser beams which are directed across a line on the element, both beams being illuminated successively with a distance therebetween below the classic resolving power. A portion of the incident beam and a portion of the beam reflected from the line is conducted to respective detectors which respectively generate measurement and reference signals. These signals are treated to eliminate high frequency noise components therein. Subsequently, the filtered measurement and reference signals are digitized and synchronously processed to provide two sine shaped curves whose intersection point corresponds to the center of the scanned line.

Abstract: In this circuit, video signals with a continuously increasing or decreasing amplitude are applied to the signal input of a threshold difference comparator at whose reference inputs selectively determined high and low threshold signals are applied. The output of the threshold difference comparator is applied at the first input of a threshold AND gate having a second input connected to a clock. The output of the threshold AND gate supplies a clock pulse sequence which has a duration corresponding with the time during which the input video signal has an amplitude which continuously increases or decreases from one of the threshold reference amplitudes to the other. The clock pulse sequences contained in successive measuring intervals have their respective pulses counted by a counter, and are stored in a buffer. A measurement series is performed corresponding to different focus settings, optimum focus adjustment being achieved when a minimum count of clock pulses in a clock pulse sequence is obtained.

Abstract: A probe head arrangement for contacting a plurality of closely adjacent conductor lines 2 comprises a minimum of one probe head 3, where a plurality of fingers 4 together with a back 5 are made in one piece of monocrystalline silicon in semiconductor technique. A plurality of such probe heads 3 are composed to form a tester. At the beginning of each test it is determined which fingers 4 are to be, and are not to be placed onto the individual conductor lines 2 of a card 1 to be tested. Subsequently, the short and interruption tests can be implemented after the correlation of finger and probe head addresses with the conductor line addresses.

Abstract: A deflection arrangement is described which comprises several piezocrystal elements which are separately driven by a positive or a negative voltage. In this configuration, there is no elastic hysteresis. The arrangement is particularly suitable for automatic focusing systems.