Abstract: A charge-coupled imaging device (FIG. 3) is thinned to allow for backside illumination. The device is further enhanced using ion implantation techniques to establish an electrical field (44) at the back surface, which functions to drive free electrons to potential wells generated beneath a gate structure (40) on the front surface. The device structure allows for both front side and backside illumination and is useful as a imaging device in applications where it is necessary to combine images from two different optical sources. The imaging device is particularly useful in terrestrial guidance systems (FIG. 5) where the imaging device is used to detect guide stars from a large guide star field. In such systems, the imaging device must be translated within an X-Y plane in order to cover the entire guide star field. In order to accurately know the position of the imaging device, optical fiducial marks are imaged onto a side of the imaging device opposite the side receiving the guide star photons.

Abstract: A wavefront sensor (10) includes a radiation sensor (2) and an array (12) of lenslets (12A) that are optically coupled to the radiation sensor. The array of lenslets has a radiation receiving surface for receiving an incident wavefront and for focussing the wavefront at a plurality of focal positions upon the radiation sensor. Each of the lenslets comprises a diffractive optical element having an optical center that is located at a predetermined point for inducing an equal and opposite tilt to a portion of the wavefront incident on the lenslet. As a result, an aberration within that portion of the wavefront is cancelled. The predetermined point is determined to be equal to and opposite a focal spot shift of the lenslet.

Abstract: Optical metrology apparatus includes one or more first sample point interferometers (SPIs) (16) having a wide dynamic range for measuring a rigid body position of a surface of a structure, such as a segmented mirror (11). At least one second SPI (18), having a lower dynamic range, is employed for measuring a figure of the segmented mirror. Either the first or the second SPIs may also be employed to measure a lateral displacement between the mirror segments (11a, 11b). The use of multiple SPIs, having differing dynamic ranges, within a closed-loop mirror control system is also described.

Abstract: A method is provided for calibrating a beamline (24) used for X-ray lithography. The beamline includes an elongated evacuated tube (28) extending from an X-ray source (22) for containing the X-ray beam to a closure (32) at an opposite end including a beryllium window. A target wafer (34) aligned with, but external of, the tube is positioned in a plane transverse of the X-ray beamline and is coated with a uniform layer of light sensitive material. A carbon filter (31) intermediate the X-ray source and the target wafer is provided within the tube to block electromagnetic radiation having wavelengths generally in the region of ultraviolet, visible, and infrared ranges of the spectrum. The beam from the X-ray source is scanned through the beamline, through the filter, and onto the target wafer. Thereafter, the wafer is subjected to an etch process thereby forming a contoured surface (34A) emulating the non-uniformities caused by the components of which the beamline is comprised.

Abstract: This invention forces a multi-spectral line laser to operate on a single spectral line by modifying the gain of the medium instead of the standard approach of modifying the loss of the cavity. The spectral line selected by the system of the present invention is always the same identical spectral line. There are no ambiguities in knowing which line has been selected as there are with other methods. The invention involves a system for using more than one type of gain media within the laser cavity. Each medium gives rise to a distinct set of spectral line frequencies at which it has gain. Only occassional coincidences will occur at which spectral lines from two or more media fall within a linewidth of each other. Where these coincidences do not occur, the gain for a spectral line is only proportional to the amount of the individual medium present and will be below threshold.

Abstract: A monochromator 18 has a thin faceplate which reduces temperature-induced distortion in a strain-free region by placing it close to a two-level heat exchanger 46, 64. The heat exchanger has a first level 46 in juxtaposition with the faceplate 22 for efficient heat extraction, and a second level 64 which establishes a constant temperature plane along a neutral bending axis of the monochromator 18. The first level heat exchanger is operated at a temperature below the zero CTE point of the silicon faceplate so that the integrated CTE of the faceplate is approximately zero. Pumps 30 and 32 are disposed respectively at the coolant inlets 26 and outlets 28 for fine-tuning the coolant pressure so that a minimal pressure across the faceplate 22 may be established to minimize bending moments on the thin faceplate.

Abstract: A standard thick silicon charge-coupled device (FIG. 1A) has its pixel face mounted to a transparent, optically flat glass substrate using a thin layer of thermoset epoxy. The backside silicon of the charge-coupled device is thinned to 10 .+-.0.5 um using a two-step chemi-mechanical process. The bulk silicon is thinned to 75 um with a 700 micro-grit aluminium oxide abrasive and is then thinned and polished to 10 um using 80 nm grit colloidal silica. Access from the backside to the aluminum bonding pads (36 of FIG. 5) of the device is achieved by photolithographic patterning and reactive ion etching of the silicon above the bonding pads. The charge-coupled device is then packaged and wire-bonded in a structure which offers support for the silicon membrane and allows for unobstructed backside illumination.

Abstract: Optical metrology method and apparatus wherein three optical wavelengths of a fixed polarization are generated and separated into a reference beam (RB) and a measurement or object beam (OB) having, ideally, equal optical path lengths. After reflecting from surfaces being measured OB is combined with RB and provided to sensors which measure the intensity associated with each of the wavelengths. Any difference between the intensities is indicative of a difference in the optical path lengths of OB and RB and is a function of the polarization state of each of the three returned wavelengths. Differences in optical path length may be indicative of a difference between a reference surface and a test surface, or a difference in thickness or index of refraction across an object. Two multi-mode laser diodes (12, 14) are provided for generating the three optical wavelengths.

Abstract: Hermetically sealed optical fiber arrays comprising a bundle of metal-coated optical fibers which are sealed to each other and to a metal-coated supporting structure. The hermetic seals are formed by a process which uses fluxless solder and preferably a vacuum to enhance application of the solder.

Abstract: Optical metrology method and apparatus wherein three optical wavelengths are generated and separated into a reference beam (RB) and an object beam (OB) having substantially equal optical path lengths. After reflecting from a surface being measured OB is combined with RB and provided to sensors which measure the intensity associated with each of the wavelengths. Any difference between the intensities is indicative of a difference in the optical path lengths of OB and RB and is a function of the polarization state of each of the three returned wavelengths. Differences in optical path length are shown to be indicative of a displacement of the object being measured. Preferably, two multimode laser diodes (12,14) are provided for generating the three optical wavelengths. Two synthetic wavelengths are derived from the three optical wavelengths and are employed to improve the precision of measurement while retaining a large dynamic range made possible by the use of a large synthetic wavelength.

Abstract: A CW and/or pulse coherent radiation detection system (10) includes at least one radiation detector (14) having a plurality of discrete radiation detector elements (A-D) disposed upon a surface thereof. A coherence length discriminator (CLD), for example an etalon (12), is constructed so as to vary an optical path length therethrough at a plurality of locations. The CLD is disposed relative to the radiation detector such that radiation passing through the CLD is received by the discrete radiation detector elements. The apparatus further includes a drive (16) for translating the CLD relative to the radiation detector so as to modulate only coherent radiation passing through the CLD. The drive is preferably a reactionless drive having an energy consumption made small by the use of small CLD motions that correspond to the dimensions of individual detector elements. The coherent radiation detector is also shown to be usable for detecting an angle of arrival of coherent radiation.

Abstract: In a Raman cell (10) which is subject to optical distortion of the path of a laser beam (40) by heating of the gas from the Raman conversion process, vibrating blades (50) cause the gas to mix and thus provide thermal homogeneity within the beam path.

Abstract: A hermetically sealed integrated wafer wherein the integrated wafer is sandwiched between a support layer and expansion buffering layer. The expansion buffering layer includes a centrally-located opening through which integrated circuits located on the wafer may extend. A sealing ring and cover plate are bonded to the expansion buffering layer to provide hermetic sealing of integrated circuits or other electronic elements located on the wafer.

Abstract: A semiconductor-to-metal optical switch or device for power limitation in the infrared spectral region includes two thin semiconductor layers sandwiched between two transparent electrodes. An electrical voltage is applied across the two semiconductor layers to produce an active device for blocking incident light in the 8 to 12 .mu.m spectral region. The material composition and thickness of the two semiconductor layers are such that enough photo-excited electrons are generated in the first semiconductor layer so that the second semiconductor layer undergoes a rapid semiconductor-to-metal transition at a predetermined light intensity. The semiconductor layers remain transparent below the predetermined light intensity and the second layer will become metal-like at a light intensity above a threshold level. Upon becoming metal-like, the second semiconductor layer will block the incident light.

Abstract: A waveform tracking clipper circuit for limiting the instantaneous amplitude of a processed vibration test signal at the input to a shaker amplifier to the instantaneous amplitude of an unprocessed vibration test signal, the unprocessed vibration test signal having been processed to develop the processed vibration test signal. Included is clamper circuitry connected to the input of the amplifier. Numerous variations are disclosed, including the use of precision rectifiers and a variety of redundancy configurations to guard against the potentially-devastating consequences of a component failure or control misadjustment.

Abstract: A system for fabricating optical elements includes a source of optical radiation that provides an optical beam, the system includes an intensity controller in the path of the beam. The intensity controlled beam is directed toward a substrate disposed on a stage. The stage is adopted to be controllably translated in accordance with an optical intensity map.

Abstract: A method and composition for protecting and enhancing the solderability of a metallic surface. A mixture which includes a chosen protective material and a dicarboxylic acid fluxing agent is applied to the metallic surface to form a protective film or coating which also enhances the solderability of the metallic surface. The mixture is applied to the metallic surface as a solution having a solvent carrier which evaporates to leave the film. the film is heat activated at soldering temperatures to release the fluxing agent.

Abstract: A semiconductor laser pulse compression radar system utilizes a semiconductor laser source 16 for generating light for transmission towards a target 27. A modulator 15 pulses and modulates the light according to a preselected code, and a transmitter telescope 18 launches the light. Portions of the pulsed light reflected by the target 27 are gathered by a receiver telescope 28 and are converted to electrical current pulses by an avalanche photodiode 30. The pulses of electrical current are demodulated by demodulator 31, which includes a pulse compression filter 35 which has the conjugate time-frequency characteristic of the modulator. A display/counter 36 displays the range of the target from the system.

Abstract: A fluxless solder for application to metal surfaces which include contaminants such as metal oxides. The fluxless solder includes a reducing agent which reacts with interfering metal oxides to form essentially inert compounds which require no further cleaning. Reducing agents, such as lithium, calcium, strontium and cesium are disclosed for use in lead-tin solders, in amounts ranging from about 0.5 to 10 atom percent. Various methods for forming the fluxless solder are also disclosed.

Abstract: Apparatus and method for continuously forming sputter-coated glass fibers. The apparatus includes a sputter vessel into which freshly drawn fiber is passed before surface contamination can occur. The sputter vessel includes modular sputtering units which are arranged to provide sputter deposition of one or more coatings onto the fiber or capillary tube as it passes through the sputter vessel. Roughing chambers may be provided on either end of the sputter vessel and include orifices sized to allow passage of the fiber through the orifice without contact. An improved sputter coating apparatus is also disclosed.