Abstract: An improved mounting for a rotating diffraction grating assembly as used in a spectrophotometer directly connects the grating to the galvanometer that rotates the grating. The galvanometer is gimbally mounted on a plate so that its position, and that of the grating, can be adjusted so that the plane of dispersion of the grating passes through a desired point when the grating is rotated.

Abstract: The correlational gas analyzer comprises a light source passed through the gas under study, which features a quasiperiodic pattern of the specified spectral band, and an optical system with sequentially positioned along the optical path condensor, input slit iris, dispersing means to decomposed the specified spectral band of the gas under study, and rotatably mounted output slit iris configures as a disc with a plurality of slits, uniformly distributed along its circumference and equidistant from the disc center. The spacing between the centers of adjacent slits is approximately equal to the scan length of the specified spectral band of the gas under study. The output slit iris scans the specified spectral band of the gas under study across a photoreceiver, the output signal whereof drives two electric signal amplifiers.

Abstract: A correlational gas analyzer, comprising a light source with the light beam passed through the gas under study with a quasiperiodic pattern of the spectral band, and an optical system with sequentially positioned along the light beam condensor, input slit iris, beam dispering element and rotatably mounted output slit iris configured as a disc with a slit shaped as an Archimedes spiral. The Archimedes spiral center is coincident with the disc center and its pitch is approximately equal to the scan length of the specified spectral band of the gas under study. The output slit iris scans the specified spectral band of the gas under study across a photoreceiver, the outputs whereof drive the inputs of a first and second electric signal amplifier, with the outputs thereof connected to connected in series corrector unit and recorder.

Abstract: The optical reflectance or transmittance concentration analyzer includes an acousto-optical tunable filter (AOTF). The AOTF is tuned by a computer controlled digital-to-analog converter through a tunable sweep oscillator. Tuned beams can be selected according to their direction of propagation or according to their polarization behavior. Therefore, if desired, a pair of crossed polarizers can be used to select one of the tuned monochomatic light beams that pass from a light source through the AOTF. To obtain rapid wavelength change along with electronic chopping or wavelength modulation, the digital-to-analog converter output is combined with the output of a high speed signal generator. The modulated light is conducted directly or through a fiber optic cable to the location of the optical measurement and impinges upon the sample where it is reflected or transmitted. The emerging light is collected onto detector(s).

Abstract: In the atomic absorption or atomic fluorescence spectroscopy the problem exists to compensate the background absorption. For this purpose a measuring light beam, which is passed through a sample space, is frequency modulated by using the Doppler effect. This is achieved in that devices for generating a rate of change of the optical path length passing between two points of this path of rays of the measuring light beam (12) are provided in the path of rays of the measuring light beam (12). Different constructional solutions herefor are described. The optical path length can be varied cyclically by movable mirrors. But it is also possible to arrange a crystal (132) in the path of rays, the refractive index of which can be varied cyclically by applying an electric voltage to the field plates. (134 and 146).

Abstract: A system for rapid-scan spectral analysis comprising a concave holographic diffraction grating continuously rotated at a substantially constant angular velocity to provide a rapid scanning monochromator (a monochromator is used to transfer nominal regions of wavelengths out of the continuous light source). The unique sampling circuitry uses an optical shaft encoder. The angular velocity and angular acceleration of the grating are calculated from time measurements, just before the first wavelength of interest falls on the detector. This information is used to control the Analog to Digital converter sampling rate across the region of interest. The samples as a function of time are stored in a memory buffer so that each data point corresponds to a wavelength.

Abstract: A method for determining parameters, especially pressure, temperature, concentration, number of particles and particle size distribution, of gaseous substances present in combustion processes and other high temperature processes, comprises transmitting spectrally broad-band light through an object (2) of measurement, spectrally dividing the light transmitted through said object, and recording the spectral distribution of the light in the studied wavelength range a large number of times. Each recording occurs sequentially in that the spectrally divided light is swept relative to a one-channel detector and for such a short time that the total light intensity of the entire wavelength range is constant during each recording.

Abstract: A system for ascertaining the thickness of thin films, especially on semiconductor substrates, comprising a light source, a randomized bifurcated fiber optic bundle, a pentamirror, a rapid scanning monochromator with a rotating grating, a photodetector, and A/D converter, an interface and a data reduction computer. The randomized bifurcated fiber optic bundle via the pentamirror directs light to and receives reflected light from a surface of the thin film, the reflected light passes through the bifurcated bundle to the monochromator and to the photodetector whose output is read by the A/D converter. A timing control circuit is provided which has an input from an encoder coupled to the motor rotating the grating and clock and trigger outputs coupled to the A/D converter so that the A/D converter consistently samples the analog signal representative of the same portions of the reflected visible spectra returned from the thin film under test.

Abstract: An optical scanning device, such as a chromatoscanner, includes a spectroscope having a rectangular outlet slit for producing a light beam in the shape thereof. A rotatable disk having a spiral slit is disposed in the path of the light beam to produce light pulses along radial lines of the disk which are directed to the surface of a specimen. The absorbancy of the light pulses at discrete positions of the specimen is measured and stored in a memory in accordance with the corresponding location on the specimen as derived from measuring the rotation angle of the disk.

Abstract: A photodiode assembly including a photodiode array having a linear arrangement of photodiodes, and a mask associated with the photodiode array to shade one or more selected photodiodes from incoming light of a particular frequency. The mask includes a frame provided with an elongated slot, and at least one bridge formed across the slot for shading the selected photodiode. The bridge portion is sufficiently wide to fully cover the selected photodiode and to partially cover the two adjacent photodiodes. An aperture is provided through the bridge in alignment with the selected photodiode to allow a portion of the incident light to impinge upon the selected photodiode.

Abstract: An improved rapid-scan spectrophotometer with an optical grating continuously rotating at a constant angular velocity. An optical trigger actuated by the rotating turntable supporting the grating, actuates an analog to digital converter to sample at discrete times an output signal from the sample detector over the desired wavelength range and to store the digitized information in a direct memory access (DMA) buffer. The information may be retrieved as desired from the buffer for further processing or permanent data storage. With each revolution of the optical grating, the range (typically 15.degree.) of wavelengths from the grating that provides useful information is sampled by the analog to digital converter and stored in the buffer. Because the grating is continuously rotating at a constant angular velocity and is not limited by the inertia of optical components, the spectrophotometer can be operated at a much higher scanning speed than an oscillating or vibrating grating spectrophotometer.

Abstract: To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.

Abstract: A method and apparatus for controlling the spectral components of a light beam are described. The apparatus comprises means (3-7) for generating a collimated light beam; means (9) for dispersing the collimated beam; a mask (1) including an aperture (2) the size of which is such that a portion of the dispersed beam passes through the aperture in use; and movement means (not shown) for causing relative transverse movement between the light beam and the aperture. A memory (not shown) is provided for storing in use a profile of the relative transverse movement between the light beam and the aperture (2) required to obtain a desired spectral response in the transmitted light beam, the movement means being responsive to the stored profile to cause relative transverse movement in accordance with the predetermined profile.

Abstract: A method for microphotometering individual volume elements of a microscope specimen 10, comprising generating a luminous dot or cursor and progressively illuminating a plurality of part elements in the focal plane 11 of the microscope through the specimen. The mutual position between the specimen and the focal plane is then changed and a plurality of part elements in the focal plane are illuminated. Reflected and/or fluorescent light and transmitted light respectively created by the illumination is collected, detected and stored for generating a three-dimensional image of that part of the specimen composed of the volume elements. Illumination of multiples of part elements is implemented by deflecting the cursor and/or by moving the specimen. The change in the relative mutual position between the specimen and the focal plane of the microscope is effected either by displacing the specimen or the objective.

Abstract: A monochromator comprises a first and a second concave grating. An entrance slit is imaged by the concave grating in the plane as a spectrum. A disc comprises a spiral slot. A section of the slot forms an intermediate slit periodically sweeping transversely across the spectrum. A concave mirror images the fanning point of the concave grating. Thereby the fanned beams are recombined to a single beam. An exit slit is located in an image plane in which an image of the entrance slit is generated. The spectrum can be scanned quickly and cyclically without the gratings having to be rotated. There is also the effect of a double monochromator. Another embodiment comprises two concave mirrors to generate the image.

Abstract: A spectrophotometer is provided for measuring and displaying an absorbance change as a function of time, a wavelength spectra, or an absorbance difference as a function of time between two specific wavelengths, which comprises a wavelength scanner for scanning through a plurality of wavelengths in a scan range, a wavelength reader for generating wavelength signals corresponding to the scanned wavelengths, photodetectors for detecting the light intensity of a scanned wavelength, an A-D converter for converting analog signals of a scanned wavelength to digital signals, a storage device for storing data generated from the A-D converter corresponding to each wavelength, an operational circuit for processing stored data, and display devices for displaying the processed data.

Abstract: There is disclosed herein a novel spectral background corrector system which, by employing light refracting techniques, causes wavelength scanning or modulation which allows substantial elimination of spectral background.

Abstract: This specification discloses a dark current correcting device in a spectrophotometer utilizing, as the photoelectric converting element, an image sensor capable of electrical scanning such as a photo-diode array to improve the scanning speed and the reliability, thus eliminating the error component by the dark current from the photoelectric conversion signal obtained from each photoelectric converting element of the image sensor and enabling obtainment of a true photoelectric conversion signal.

Abstract: This specification discloses a spectrophotometer utilizing, as the photoelectrical converting element, an image sensor capable of electrical scanning such as a photo-diode array, thus adjusting the integration time thereof, namely, the scanning time of the image sensor and enhancing the S/N (signal-to-noise ratio).

Abstract: A spectrometer for use with optical elements which pass both undispersed and dispersed irradiation onto detectors coupled to a transversal filter and a comparitor means which open gates said filter to receive dispersed signals when an initial undispersed threshold is exceeded, thereafter said comparitor inhibits signals exceeding the undispersed threshold during spectral analysis of the dispersed signals.

Abstract: An improved optical system is disclosed for rapid, accurate spectral analysis of the reflectivity or transmissivity of samples. A concave holographic diffraction grating oscillated at high speed is utilized to provide a rapid scanning of monochromatic light through a spectrum of wavelengths. The grating is positively driven at very high speed by a unique cam drive structure comprising identically shaped conjugate cams. The rapid scan by the grating enables the reduction of noise error by averaging over a large number of cycles. It also reduces the measurement time and thus prevents sample heating by excessive exposure to light energy. A filter wheel having dark segments for drift correction is rotated in the optical path and is synchronous with the grating. Source optics is employed to optimally shape the light source for particular applications.

Abstract: A spectral photometer emits light towards an object of interest, receives e light reflected back from the object of interest, and includes a timer or synchronizer operative for causing the spectral photometer to produce an output signal whose successive values correspond to the intensity of the spectrum derived from the object of interest at successive wavelengths. The spectral photometer output signal is applied to an oscilloscope for display of the thusly generated spectrum. The oscilloscope screen is provided with interpretation marks at characteristic points of the displayed spectrum, either by providing such marks on a transparent plate mounted in front of the screen, or by applying to the oscilloscope signals causing the scope itself to generate these marks. These marks may be curves shaped and located to be intersected by both maxima of an oxygenated-hemoglobin spectrum irrespective of the degree of oxygenation.

Abstract: In a multi-wavelength spectrophotometer using a self-scanning detector, the range of wavelengths to be scanned by the detector is divided into plural subranges. These wavelength subranges are subjected to the wavelength scanning with different integration times respectively. The detector output at the scanning of each wavelength subrange is stored in a memory. Thereafter, the stored data is read out in a form of a continuous wavelength range.

Abstract: A spectrometer capable of providing a predetermined wavelength of output light in accordance with a control voltage signal applied to a scanning element is described. The scanning element located at the grating image of the spectrometer is a small mirror attached to the rotor of a galvanometer whose angular position is accurately controlled by a closed-loop electronic control. The spectrum reflected from the mirror is passed through a slit to provide the output light of a predetermined wavelength. Selection of the waveform of the control signal allows the spectrometer to be operated as a dual wavelength spectrometer, to use a linear wavelength scan, or other wavelength scan patterns for absorbance analyses of a sample.

Abstract: The present invention relates to a phase corrected raster scanned light modulator in which information modulated on a carrier is used to form a grating whose spatial frequency along the scanning line varies in accordance with the signal modulation frequency. Thickness variation in the medium on which the grating is formed causes an undesired phase modulation of the light which may be corrected by altering the carrier frequency. A novel oscillator is described which may be stepped discontinuously in frequency while the waveform and its slope remain continuous, which is of sufficient accuracy and agility to provide a real time region by region phase correction of the raster in the light modulator. The variable frequency oscillator is of high stability and can step from one value to another for intervals as short as one microsecond.

Abstract: Method and apparatus for the spectroscopic analysis of a specimen in which the specimen is irradiated with a narrow band of monochromatic light over a range of wavelengths, the light reflected from the specimen is scanned to generate a signal representative thereof, the signal is converted into a digital signal and stored. Digital data representative of selected spectroscopic characteristics is also stored and the digital data and the spectroscopic data are read out to identify the spectroscopic characteristics of the specimen. A TV camera scanner enables selective gating by varying the respective horizontal and vertical portions of the video signal. The video signal may be visually monitored to alter the scanning of the specimen and to determine those portions of the signal to be gated.

Abstract: An apparatus and method for utilizing the opto-galvanic effect to perform ectroscopic or analytic investigations of atomic or molecular species. A sample of the substance to be analyzed is vaporized in an analytical flame, gas discharge tube, high temperature furnace or the like, and the vapor is irradiated with chopped or pulsed variable wavelength monochromatic light. The electrical resistance of the vapor is monitored as the frequency of the radiation is tuned through one or more electronic transition frequencies of the substance. The resistance spectrum resembles the optical absorption spectrum of the species in the vapor. The optogalvanic effect may also be used to frequency lock a laser to a transition frequency of a substance in a gas discharge cell.

Abstract: A wide field of view is scanned to determine spectral and positional infotion of a point source of optical radiation. The wide field of view is optically scanned by a scanner having an instantaneous narrow field of view to sequentially direct radiation from successive scanned portions of the field onto a detector included in an image plane of radiation. An optical dispersion means for the radiation is provided in a first optical path that includes the scanning means and the detector. A second optical path between the source and detector includes the scanning means, but does not include the dispersion means. The dispersion means and the scanning means cause a convolution of spectral energy from the source in the image plane, resulting in a displacement of the relative occurrence times, during a scan, of a wavelength of the radiation as it impinges on the image plane via the two optical paths.

Abstract: A spectrum analyzing system measures or analyzes the colorimetric properties of a test sample at a preselected wavelength or range of wavelengths within the ultraviolet, visible, and near infrared regions. The system includes a spectrophotometer provided with a wideband light source, optical devices providing a sample light path and a reference light path, a chopper wheel allowing light to be directed alternately along the sample and reference paths interspersed with dark periods during which no light travels along either path, a dispersion grating for dispersing the light from both paths, a series of neutral density filters for limiting to various degrees the amount of light traversing each path, and a linear array of photodiodes for detecting the dispersed light at different wavelengths.

Abstract: A spectrometer with the basic optical elements is described which scans the spectrum electronically rather than by mechanical manipulation or use of image tubes. The detecting elements are light sensitive charge coupled device detector arrays.

Abstract: A scanning spectrophotometer employes fixed optics to produce a dispersion f optical energy. The dispersed optical energy is scanned by a fixed position surface acoustic wave photoelectric transducer. The scan rate of the surface acoustic wave photoelectric transducer is determined by associated electronic circuitry to produce scan rates permitting real-time spectral measurements from a moving platform.