Abstract: A sample to be measured, a black reference and at least one reference having a color similar to that of the sample are exposed successively and cyclicly to the same incident light beam, the light beams which are reflected successively by the sample and the references are detected photoelectrically, the ratio of the intensities of the light beams reflected by a sample and one reference color on the one hand and by the black reference and a reference color on the other hand is established electronically, the second ratio is subtracted electronically from the first and a difference which is directly proportional to the brilliance of the color of the sample is automatically obtained during each exposure or measurement cycle at a determined measurement frequency (FIG. 1).

Abstract: The invention relates to an arrangement for color detection when evaluating printed materials, maps or the like in that a color pattern under investigation is arranged substantially in the plane of a reference color pattern and both being cyclicly detected by an opto-electronic detection unit. The detector, itself consists of only one opto-electronic transducer comprising a plurality of detecting faces which receive the color informations from an illumination source reflected at both color patterns. The opto-electronic transducer is followed by an evaluation electronic means which compares the reference color pattern and the investigated color pattern and associates the respective patterns.

Abstract: An apparatus including a white light and first, second, and third filters through which the white light is transmitted is utilized to sequentially irradiate a solar cell. The light impinging upon the solar cell from the first, second, and third filters has first, second, and third "tristimulus" distributions. The resulting first, second, and third electrical output quantities produced by the solar cell are measured and utilized to compute normalized spectral response coefficients by normalizing each of the electrical output quantities with respect to the sum of the three. First, second, and third response differences are obtained by subtracting the first, second, and third response coefficients from first, second and third response coefficients previously obtained from a reference solar cell.

Abstract: The color of gemstones or the like is assessed by projecting light onto the stone, using an interrupting member to regularly interrupt the path of the light shortly before it reaches the stone, the member having a normally white, diffusing interrupting surface, and using a detector for detecting the color of the light coming from the gemstone and from the interrupting surface of the interrupting member. Preferably, the stone is mounted in a chamber having normally white, diffusing internal walls and the diffusing interrupting surface is within the chamber.

Abstract: Apparatus for measuring and controlling the color of a moving web in which a circular variable bandpass filter having a passband varying substantially continuously with angular displacement through the optical spectrum is interposed in the optical path between the web and a detector and is rotated to produce a detector output which periodically scans the optical spectrum. In one disclosed embodiment, the detector outputs at the various wavelengths are weighted to produce X, Y and Z tristimulus values while, in another disclosed embodiment, dye flows are so controlled as to minimize the total square error between the measured reflectance spectrum and the desired reflectance spectrum.

Abstract: A method and apparatus are disclosed for an analyzer which measures concentration of a liquid specimen by monitoring the coloration of test paper which is either dipped into the specimen or is otherwise painted with it. In the method, inner stray rays produced by a light source which do not reach the test paper are experimentally monitored, so that the effect of such inner stray rays upon the accuracy of the test paper analysis is eliminated. Additionally, a method of relating relative reflectivity of the test paper to the concentration of the specimen is disclosed, in which method the calibration curve is modeled as a section of a hyperbola. In the apparatus, a microcomputer performs the evaluation and the detection of the coloration of the test paper and the compensation for various sources of instrumental error takes place electronically.

Abstract: A photometric system for determining the absorbance ratio, in a sample, of two different wavelength lights. First and second lights, each having a different wavelength, are passed through the sample in alternation with each other. The radiation intensity from each light that has passed through the sample is detected. A comparator, up/down counter and digital to analog converter are coupled so that a scaling factor is derived which, when multiplied with an analog signal proportional to the intensity of the first light after it has passed through the sample, is equal to an analog signal proportional to the intensity of the second light after it has passed through the sample. The output of the counter comprises a digital word corresponding to the ratio of the absorbance ratio of the first light and the second light.

Abstract: Spectrum analyzer for the light absorption of a solution comprising a small transparent measuring cell containing the solution; a light source; means for dividing the beam of light of the source into two beams, one being the reference beam and the other the measuring beam transmitted respectively to a reference absorber element and to the measuring cell; means for selecting the measuring wavelength; means for modulating the reference and measuring beams which have respectively traversed the absorber element and the measuring cell; means for detecting the energies of each of the modulating beams after they have traversed the reference absorber element and the sample; the modulation means comprising alternate transparent and bireflecting sectors in front of each of the beams which have passed through the reference absorber and the measuring cell, said sectors being associated with means for selecting the wavelength of the beams in such a way that, as a function of the successive positions of the sectors relativ

Abstract: A method for compensating for error in amount of indicator added to a sample under test in bleaching chemistry analysis involves adding a reagent system comprising an indicator and a dye in relative amounts such that the indicator at one wavelength (the "measuring" wavelength) and the dye at a different wavelength (the "reference" wavelength) exhibit the same absorbance at zero concentration of the parameter of interest. Error in the amount of indicator added to the sample is compensated for by measuring the decrease in absorbance at the measuring wavelength after reaction of the indicator with the parameter of interest, against the absorbance at the reference wavelength.

Abstract: A photometer comprising a light source, a rotating plate provided with a plurality of filter means having different wave lengths, a reference plate and a sample means, said rotating plate disposed between said light source and said reference plate and sample means, and a half-mirror and a reflection plate located between said light source and said rotating plate, said half-mirror and reflection plate being disposed so as to form a first light passage adapted to extend to the reference plate, and a second light passage adapted to extend to the sample means, whereby alternate radiation through one of said filter means against the reference plate and the sample means is made by the rotation of said rotary plate.

Abstract: A two beam alternating light colorimeter is disclosed wherein a light beam passing through a lens system having a shutter is periodically deflected by a pivoting mirror. In a first non-deflecting position of the pivotable mirror a first measuring beam is created which passes through a first measuring cell and is guided to a common photo cell. In a second deflecting position of the mirror a second measuring beam is created which is guided through a second measuring cell to the same photo cell. Signals from the photo cell are connected through a controlled switching element to an analog memory. A computing circuit is provided which connects to an output of the analog memory and also to the photo cell. The switching element connects the first measuring signal to the analog memory when the mirror is in a non-deflecting position and opens when the mirror is in a deflecting position. The computing circuit compares the signals corresponding to the first and second measuring beams.

Abstract: A spectrometer for measuring the spectra and concentration of airborne chemicals at long ranges wherein the optical signals may be occluded by dust. A single lasing medium is utilized both for producing a transmitted optical signal and for amplifying a received optical signal, the frequencies of radiation of the transmitted and received optical signals being offset as the radiation propagates to a distant reflector and back to the lasing medium. The frequency offset is obtained by sweeping the transmitted frequency at a rate commensurate with the round trip propagation time whereby the offset is sufficient to place the received frequency at a peak at the amplifying spectrum of the lasing medium. A laser containing the laser medium further incorporates an interferometric structure within the optical path for sequentially shifting the frequency of oscillation to produce a comb spectrum for sampling the spectra of the chemicals to provide identifying signatures thereof.

Abstract: Apparatus for determining the nitrogen oxide concentration in a gaseous mixture while minimizing measuring errors. The radiation from a hollow cathode lamp emitting the nitrogen oxide resonance radiation is modulated by a device for generating alternatively an unfiltered or test beam and a reference beam. The reference beam is filtered by a nitrogen oxide filled filter. An absorption cell is disposed in the path of the reference beam. Further, a monochromator or filter is provided and a detector for receiving the radiation from the monochromator filter. A signal processing unit is coupled to the detector for forming electric signals corresponding to the signal from the unfiltered and the reference beam and for forming the quotient thereof. A ray splitter is disposed in the path of the two beams to provide a different beam path and an additional radiation detector is disposed in the additional path.

Abstract: Apparatus for determining the content of moisture or other substance in a material by measuring its relative reflectance at two infrared wavelengths. A chopped radiation beam is produced by arranging a tuning fork such that an oscillating element alternatively moves first and second spaced optical bandpass filters having first and second passband wavelengths into position to intercept a beam of source radiation. The chopped beam is directed on the material being analyzed, and radiation reflected therefrom is applied to a radiation detector. The relative transmittances of the filters at their passband wavelengths are such that the radiation detector generates alternating pulses of equal amplitude for a material having a specified content of the substance. The tuning fork also includes a third filter of zero transmittance which periodically interrupts the beam of source radiation so that the detector provides a background signal which is used to correct the amplitudes of the alternating pulses.

Abstract: A sorting apparatus for sorting articles randomly disposed across a wide path is characterized by a plurality of side-by-side viewer elements each assigned a corresponding side-by-side sector of an illuminated viewed area through which the articles to be sorted pass. Electrical signals indicative of the instantaneous average value of light reflected from articles at two predetermined wavelengths as those articles pass through a sector of the viewed area are multiplexed and a classification signal functionally related to the ratio of the two signals is determined. The classification signal is compared to a reference signal indicative of an article having a predetermined physical characteristic, and a reject signal is generated if the compared signals differ by a predetermined amount. The reject signal is stored in an assigned memory location corresponding to the sector of the viewed area through which the article passed.

Abstract: A tristimulus colorimeter employs a multiplexed dual slope integrator digital voltmeter wherein unknown and reference light beams are compared by sequentially applying unknown and reference electrical signals representative of the two respective light beams to the non-inverting and inverting inputs, respectively, of the integrator amplifier. Moreover, a compensating circuit provides for compensation of the colorimeter output signals with respect to reflectance error encountered in the optics portion of the colorimeter.