Abstract: A linear amplifier provides an output signal that is proportional to an input signal. A differential voltage control unit tracks the output signal voltage and controls the outputs of two pulse width modulators which drive a linear amplifier. The differential voltage control unit controls the output of the positive pulse width modulator to a fixed predetermined value in accordance with at least one of the input or output signals. The positive and negative pulse width modulators are driven by a positive and negative high voltage direct current power supplies respectively.

Abstract: Lens systems for wide band infrared camera having a bandwidth of 1-5 .mu.m with a low f-number and 100% cold stop efficiency.

Abstract: Thermal expansion caused by the absorption of thermal energy from exposure dosages can cause misalignment and other problems in the exposure process. The present invention compensates for this problem by developing scaling and backlash coefficients based on the amount of amount of energy absorbed by the substrate undergoing the exposure process. Scaling and backlash are then compensated for in the alignment map which controls the exposure process. In this fashion, scaling and backlash are accounted for prior to exposure, thus ensuring the proper exposure during the lithography process.

Abstract: A method and apparatus for determining performance characteristics in lithographic tools includes projecting a predetermined image with a projection system having a known predetermined performance characteristic to obtain data indicative of the relationship between the size of the projected image and the predetermined performance characteristic. The same image is then projected in a system having an unknown value for the predetermined performance characteristic. The predetermined performance characteristic for the system under consideration is then determined based on the data obtained when the image was projected in the system having the known predetermined performance characteristic.

Abstract: A large aperture wide angle zoom lens system including four groups of lenses. The four lens groups, viewed from the object side, include a first group with negative refractive power, a second group with positive refractive power, a third group with negative refractive power, and a fourth group with positive refractive power. The zoom lens system is capable of maintaining the position of the image constant during zooming, has fine imaging performance despite a large zoom ratio of 2.times. and a speed which is as fast as F/2.8 with an angle of view of 84.degree. on the wide side.