Abstract: The advantage of sustained wavelength accuracy and mechanical simplicity of a spectrophotometer using a photodiode array as photometric detector and a fixed diffraction grating as dispersion means may be limited to a relatively short wavelength range by problems of stray light, second order errors and overloading of the detector at portions of the wavelength range. By utilizing repeat scanning of the array, each scan being modified by using a different source lamp and correction filters, freedom from the cited problems over part of each scanned wavelength range can be effected. A computer controls the scan sequence and combines the usable portion of each scan to produce error free operation over an extended range.

Abstract: An apparatus and method for monitoring the light intensity of individual light emitting diodes in an array of light emitting diodes. Means are provided to measure current flow through an unenergized diode adjacent to an energized diode. Current flow through the unenergized diode is porportional to light intensity of the light emitted by its energized adjacent diode.

Abstract: A predetermined volume of a gaseous mixture of combustion products component is collected in a gas mixer up to a preselected pressure. A portion of the mixture is discharged successively through the tubular column and a sample chamber for a predetermined time period with the mixture being initially at the preselected pressure in the volume. Detection of delayed output of gas constituents from the column provides an analysis of constituents. The apparatus further comprises a furnace, a magazine for holding the plurality of test samples, a transfer device connected to the furnace for sequentially transferring a successive sample from the magazine to the furnace, and a furnace seal integral with the transfer device for temporal sealing of the furnace from ambient atmosphere after the sample is transferred to the furnace until subsequent transferral.

Abstract: A mechanical stop permitting rotation of more than one revolution, but less than two revolutions. A wheel having a pin attached is rotated about an axis. A pair of pivoting flip-flops each having two perpendicular legs is placed in the path of the pin. The pin, after passing each flip-flop, flips the flip-flop into a stop position from an initial pass position. This permits the pin to pass each flip-flop only once during rotation in one continuous direction. The flip-flop spacing determines the distance beyond one revolution the wheel is permitted to travel. The flip-flops reset each time the wheel reverses direction.

Abstract: A Rowland circle-type polychromator with the Rowland circle arc pivotally connected to the concave grating. Separate adjustments are provides for shifting the spectral lines and focussing. A tie rod is used to adjust the focus of the spectral lines. Dectectors are predeterminedly spaced along the arc to simultaneously detect unique spectral lines for analysis of multiple elements contained in a single sample.

Abstract: An apparatus for loading workpieces without exposure of a work chamber to the atmosphere comprises a transfer chamber formed in part by an inner plate section which serves as a cover plate with an inner port therethrough to the work chamber. An entry plate section has an entry port therethrough to the atmosphere, is spaced laterally from the inner port and has a door. A plurality of tubular loading members are equally spaced arcuately in a wheel member mounted in the transfer chamber. Each loading member is displaceable at a loading site between a normal position in the wheel in which each loading member is relocatable laterally by the wheel, and a sealed position proximate the entry port. A seal between the entry plate section and the loading member in its sealed position allows access of a workpiece to the loading cylinder through the entry port without exposing the remainder of the transfer chamber to the atmosphere.

Abstract: A differentially pumped seal apparatus (14) comprising a rough port nozzle (R), a medium port nozzle (M) and a high port nozzle (H), each with a centrally located sleeve (34,36,40) defining concentric apertures (44,48,52). Each nozzle is configured as a sector of a circular cylinder which provides for large channels (62, 72, 76) to be formed for connecting the sleeve apertures (44,48,52) of each nozzle directly to vacuum pumps (46,50,54) to thereby provide a graded seal with high conductance and increased pumping efficiencies, higher vacuum and a smaller gap between the sleeve (34,36,40) and a workpiece (12).

Abstract: An arc plasma generating system includes components for adjusting spacing between the cathode and the anode. A piston affixed to the cathode is slidingly positioned in a cylinder partitioning therein a first chamber and a second chamber. The first chamber is receptive of discharged cooling fluid at reduced pressure. A first valve selectively infuses pressurized control fluid into the second chamber such as to move the piston against the reduced pressure and thereby move the cathode axially in a first direction. A second valve selectively discharges the control fluid from the second chamber such that the reduced pressure in the first chamber moves the piston opposite the first direction. Telescoping tubing affixed between the piston and the end wall of the cylinder is located within the cylinder and conveys cooling fluid to the cathode. A flexible electrical cable connected between the cathode and a source of arc current is located within the cylinder member such as to be cooled by fluid therein.

Abstract: A specimen distance measuring system uses a plate (36) to obstruct the flux of backscattered electrons produced by an electron beam (18), and to cast a shadow across a measurement detector (32) which is sensitive to the position of the shadow. The shadow plate (36) and measurement detector (32) are aligned at an angle of approximately 45 degrees with a substrate (14) in order to allow calibration of the distance measuring system by scanning the electron beam (18). The measuring system is particularly useful as a height sensor (10) in an electron beam lithography apparatus (12) for sensing the height of a substrate (14). The distance measuring system may also include a reference detector (34) which is positioned in order to receive backscattered electron flux without obstruction from the shadow plate (36).

Abstract: A conjugate interferometer includes a first interferometer and a second interferometer arranged so that the common optical element thereof is the respective translating mirrors of the first and second interferometers.

Abstract: A well corrected ring field catadioptric optical system utilizing refractive elements of the same glass type. A virtual relay corrected for axial and lateral primary color incorporates an air-surface doublet and two field lenses to correct for field aberrations to provide a well corrected ring field virtual image. A spherical mirror is used to make the virtual image accessible.

Abstract: A plasma generating system comprises a plasma gun including a hollow cylindrical anode member, a hollow cylindrical intermediate member electrically isolated from and juxtaposed coaxially with the anode member to form a plasma-forming gas passage through the intermediate member and the anode member, and an axially movable cathode member. The intermediate member comprises tubular segments separated by resilient insulating spacing rings held in compression. Arc radiation is blocked from the spacer rings by meanders in the inter-segment slots and further by ceramic barrier rings. An electric motor or pneumatic piston responsive to a measurement of arc voltage continually adjusts the axial position of the cathode tip relative to the anode nozzle so as to maintain a predetermined arc voltage.

Abstract: Apparatus is disclosed for automatically transferring a semiconductor wafer between a horizontal and a vertical plane, beginning and ending in precisely located positions. A wafer support arm is carried by a transfer member which also includes a motor for rotating the support arm between a "start" position and an intermediate position in a horizontal plane. Another motor is provided for rotating the transfer member to position the support arm in a vertical plane. The wafer support arm is then returned to its original position relative to the transfer member, thus establishing a "finish" position in the vertical plane.

Abstract: A method for calibrating a monochromator to compensate for mechanical imperfections in its diffraction grating and grating drive assembly employs a two stage interactive procedure which permits the use of small (0.2 nm) spectral regions for the identification of emission lines. An iterative, self-consistent, discrete Fourier transform is used for the determination of multiple positioning correction terms. When the Fourier calculations are completed, the results of the calibration procedure are presented by the system to the analyst for acceptance. If accepted, the positioning error of the primary calibration line is measured, stored and used by the system to maintain a zero centered distribution of positioning errors each time the monochromator is reinitialized.

Abstract: A cooled mirror with a compensating backplate which has an integral heat exchanger on the substrate. The substrate has a faceplate with an integral heat exchanger which is in the optical path of the incoming radiation and which is in same size and made of the same material as the backplate. The frontplate and backplate are symmetrically located on opposite sides of the substrate. Cooling fluid at the same pressure flows at the same rate through both the frontplate and the backplate. The optical surface, such as a mirror, can be located on the frontplate or both the frontplate and the backplate.

Abstract: There is disclosed an improvement in wide angle lenses wherein very flat field characteristics are achieved. This is accomplished by a novel two element field flattener just before the image plane. One of the elements is positive and the other negative. It is possible to thereby correct both third and fifth order Petzval curvature, as well as third and fifth order distortion.

Abstract: There is disclosed a high performance lens usable in the ultraviolet region of the spectrum. It is a lens of triplet form modified by the addition of double-Gaussshells with a strong field flattening lens near the fast end.

Abstract: An induction plasma system comprises a torch and an induction coil. A sample substance is injected into the plasma at an axial position that is adjustable while the plasma is being energized. The plasma-forming gas flows through the induction coil prior to passing through the plasma torch. A piezoelectric crystal is used for initiating the plasma. An oscillator network generates radio frequency power at a first frequency, and an output LC network that includes the induction coil is tuned to a second frequency higher than the first frequency. Means for maintaining constant power to the plasma includes an AC circuit for duty cycling AC power input to a DC power supply in response to a feedback signal relative to the rectified voltage. Thus a change in the rectified voltage effects an inverse change in the duty cycling such as to nullify the change in the rectified voltage.

Abstract: Method and apparatus are disclosed for speeding up reticle changes during the production of semiconductor wafers under those circumstances wherein three reticles are employed, one (C) having a substantially longer exposure period than the others (A, B). The wafer is exposed to the reticles in the sequence ACB-BCA-ACB, etc.

Abstract: The invention resides in the temperature control of the oven of a gas chromatograph. A variable speed fan circulates air within the oven. Vents in the oven wall open automatically in response to pressure imbalances between the ambient atmosphere and the oven interior. Temperature is controlled by regulated exchanges of ambient and oven air produced by variations in fan speed.