Abstract: A diffusion-type gas sample chamber for use in a gas analyzer consists of an elongated hollow tube having an inwardly-facing specularly-reflective surface that permits the tube to function also as a light pipe for transmitting radiation from a source to a detector through the sample gas. A number of filtering apertures in the wall of the otherwise non-porous hollow tube permit the sample gas to enter and exit freely under ambient pressure. Particles of smoke and dust of a size greater than 0.1 micron are kept out of the chamber by use of a semi-permeable membrane that spans the apertures in the hollow tube. Condensation of the sample gas components is prevented by heating the sample chamber electrically to a temperature above the dew point of the component of concern.

Abstract: A compact low-cost fire detector responds quickly by detecting an increase in the concentration of carbon dioxide gas in the ambient air. The detector also calculates the rate of build-up of carbon dioxide. The detector avoids the use of moving parts by employing a differential temperature black body source of infrared radiation in conjunction with a dual pass band filter. One of the pass bands is located at the 4.26 micron absorption band of carbon dioxide gas and the other pass band is located at 2.20 microns at which none of the atmospheric gases has an absorption band. The latter channel serves as a reference and renders the detector immune to false alarms caused by dust or smoke particles in the air or due to deterioration of certain components. The fire detector makes use of a sample chamber that consists of a serpentine passage in a block of material, the walls of the serpentine passsage being highly reflective so as to act as a light pipe.

Abstract: A system for detecting fires uses at least two carbon dioxide sensors positioned at spaced locations in a room. Each sensor produces an electrical output signal representative of the carbon dioxide concentration in its vicinity. A computer calculates the ratio of the concentration sensed by each sensor to the concentration sensed by each of the other sensors, and any imbalance in the distribution of carbon dioxide will be reflected in these ratios. Random variations prevent the ratios from being equal, and the magnitude of the random variations is quantized by calculating the standard deviation of the ratios. The ratios are then normalized and compared to a threshold level that corresponds to a chosen false alarm rate.

Abstract: A sample chamber for use in measuring the absorption of radiation as it passes through a gas within the chamber includes a block having an extended serpentine passage through it. The walls of the extended passage are coated with a highly reflective material so that the extended passage acts as a light pipe for transmitting the radiation. A number of smaller passages permit gases in the space surrounding the sample chamber to diffuse into the extended passage through which the radiation is conducted. The sampling chamber is made by joining two halves, each of which has a planar face in which an elongated groove is produced. The halves are molded of plastic and in quantity the chamber is quite inexpensive.

Abstract: A fire detector that responds more rapidly than the widely used smoke detectors senses increases in the concentration of carbon dioxide associated with a fire. The build-up of carbon dioxide is sensed by measuring the concomittant increase in the absorption of a beam of radiation whose wavelength is located at a strong absorption band of carbon dioxide. The device is considerably simplified by the use of a window to the sample chamber that is highly permeable to carbon dioxide but which keeps out particles of dust, smoke, oil, and water. This permits the fire detector to be built of very inexpensive materials.

Abstract: A concentration detector having a light source that is responsive to a chemical absorption peak to produce substantially monochromatic light at a wavelength of this absorption peak. The wavelength can be stabilized against an absorption peak in a reference chemical or by an absorption peak in a sample being measured in the concentration detector.

Abstract: An instrument for determining the concentration of a particular gas that might be present in a sample has no moving parts and is extremely compact. The instrument uses as a source of radiation a device that has a radiating element whose temperature is alternated between T.sub.1 and T.sub.2 and whose spectrum approximates that of a blackbody. Radiation from this source is passed through a dual pass band filter that has two non-overlapping pass bands, one of which is centered at a wavelength at which the gas absorbs and the other of which is centered at a wavelength at which the sample does not absorb radiation. After passing through this filter, the radiation passes through the sample chamber and then is intercepted by a detector which produces an electrical signal determined by the radiation intercepted. The electrical signal is processed to provide an indication of the concentration of the gas.

Abstract: When light from a laser diode having a wavelength in the interval from 670 to 880 nm is directed through a sample containing nitrogen molecules, the nitrogen molecules do not absorb the laser light; but if the sample is energized under suitable conditions so that the nitrogen molecules are raised to the normally unpopulated ##EQU1## energy level, which differs in energy from a higher energy level .beta..sup.3 .pi.g by an energy difference corresponding to the wavelength of the laser light, then some of the laser light will be absorbed by driving the energized nitrogen molecules from the ##EQU2## energy level to the .beta..sup.3 .pi.g energy level. The amount of absorpiton is proportional to the concentration of nitrogen molecules in the sample. Thus, if the absorption by a sample having a known concentration of nitrogen molecules is determined, the unknown concentration of nitrogen molecules in a second sample can be determined by measuring the absorption in the second sample.

Abstract: An apnea detector uses an active pulsed source of radiation to monitor the respiration of a patient. Radiation from the source is formed into a collimated beam that is directed through the space into which the patient is breathing. The exhaled gases contain a smaller concentration of oxygen and a larger concentration of carbon dioxide compared with the atmosphere. Each exhalation of the patient produces a small cloud of the exhaled gases, which rapidly diffuse and disperse. Corresponding to the appearance and disappearance of these clouds of gas, the transmission of the collimated beam will vary in step with the patient's breathing. The fluctuations in the transmitted radiation are analyzed by a signal processor which generates an alarm signal when either the magnitude or the frequency of these fluctuations falls outside of preset limits. Either carbon dioxide or oxygen may be monitored as the absorbing gas.

Abstract: Apparatus for inserting and removing several filters from an optical path and for determining at all times the instantaneous positional relationship of each filter with respect to the optical path includes a set of filters mounted on a carrier which is attached to a resonant piezoelectric system, and further includes reference tracks also located on the carrier and extending in the direction of the oscillatory motion and including a sequence of binary indicia progressing in the direction of the oscillatory motion. The reference tracks are read optically to produce a series of binary electrical signals which are processed to yield the instantaneous position of the carrier and filters with respect to a fixed optical path.

Abstract: A catheter for delivering radiant energy, such as a laser beam, is used in a technique to controllably apply the radiant energy in a patient's body, such as in a blood vessel. The radiant energy is applied in a manner which erodes biological material and may be used to drill through vascular obstructions. The catheter emits the radiant energy from its distal end in a pattern which defines a relatively small working region in which the energy density level is sufficiently high to remove the biological material. The energy distribution is substantially uniform across the beam. Distally beyond the working region, the energy density of the beam decays sharply so that biological material beyond the working region is not removed.

Abstract: A shutter having no moving parts and intended for use at infrared wavelengths includes a thin film of vanadium dioxide deposited on an insulative layer of silicon oxide that has been grown on a thin substrate of semiconductive silicon. The layers are in good thermal contact, but the vanadium dioxide film is electrically insulated from the silicon substrate. The vanadium dioxide film is heated by passing a heating current through the semiconductive substrate, and is cooled by radiation. The resistance of the vanadium dioxide film is sensed continuously, and is used for turning on and turning off the heating current.

Abstract: An apparatus and method for measurement of viscoelastic properties of mammalian cervical mucous by generating a bulk acoustic wave which is reflected off of a face in contact with the mucous whereby an output which is a function of the viscoelastic properties is generated based upon at least one characteristic of the reflected bulk wave.

Abstract: The measurement of weak absorption lines is facilitated by the use of a long transmission path length, which is difficult to obtain in compact or portable instruments. In the present invention, light is made to travel through a limited volume of gas thousands of times. The light is placed on a closed optical path on which it circulates through the gas sample. After a desired number of passes through the gas sample, the light is removed from the closed optical path. Introduction of the light to the closed optical path and removal therefrom is accomplished through the use of a polarizing beamsplitter and a pockels cell located on the closed path. Light is put onto the closed path by the polarizing beamsplitter which imparts a specific polarization. During the first circuit the pockels cell alters the polarization by 90 degrees thereby preventing the light from escaping back out through the polarizing beamsplitter.

Abstract: Apparatus for measuring the absorption of a gaseous sample and particularly suitable for measuring the concentration of gaseous oxygen makes use of a diode laser whose emission wavelength is adjacent to but spaced from the wavelength of a distinct absorption line. The diode drive current is altered to cause the junction temperature of the laser to change, thereby changing the wavelength of the emitted radiation and in effect scanning it through a range of wavelengths that includes the absorption line. The absorption is determined by a ratio technique and therefore is independent of changes in the laser output power level and drifts and changes in other parts of the optical system.

Abstract: A multi-component non-dispersive gas analyzer of a type typically used to measure the concentrations of gases present in automotive emissions and in breath analyzers has no moving parts and employs electrically operated means for effectively inserting and removing a reference cell from the optical path and for selecting a particular filter to determine momentarily the wavelengths of radiation being examined. The means for accomplishing these ends include a substrate on which a layer of vanadium dioxide is deposited. The layer is a good reflector at temperatures greater than 67.degree. C. and reflects only slightly at lower temperatures. The layer is alternately heated by an electrical current and is then allowed to cool to provide the desired optical switching action. This electrically-controlled selectively reflective layer is then used in conjunction with the reference cell and with an array of filters to implement the necessary switching and selection of the components.

Abstract: The device electronically measures fluid viscosity and temperature simultaneously principally for determining the changes in the properties of cervical mucus at the onset of ovulation. Interdigital transducers are used to generate and detect surface and bulk acoustic waves on one side of a slab of fused quartz. The change of phase of surface acoustic waves and the change in amplitude of doubly-reflected bulk acoustic waves are used to detect respectively the temperature and viscosity of fluid sample deposited on the opposite face of the slab.

Abstract: A method and apparatus are described for detecting the presence and amount of elemental oxygen in a sample cell. The intensity of extreme ultraviolet light passing through the sample cell at a wavelength band overlapping at least one of the Schumann-Runge absorption lines of oxygen is detected and compared with a predetermined non-absorbed condition of the ultraviolet light. The non-absorbed condition may be achieved by narrowing the wavelength band such that the band does not overlap the Schumann-Runge absorption line, or may be achieved by detecting the ultraviolet light passing through a reference cell. Also described is a novel ultraviolet source in which a cold zone captures neutral atoms of the emission gas to reduce the affect of resonance absorption of emitted ultraviolet light by such neutral atoms.

Abstract: A carbon dioxide analyzer for medical purposes is rendered self-calibrating by continuously measuring pairs of two or three each of several components as follows:1st pair: vacuum cell, open hole and sample cell reference cell, open hole and sample cell2nd pair: vacuum cell, standard cell reference cell, standard cell3rd pair: vacuum cell, open hole reference cell, open hole4th pair: vacuum cell, standard cell, sample cell reference cell, standard cell, sample cellThe ratios of these measurement pairs are treated mathematically in a computer or microprocessor to obtain a reading for CO.sub.2 and to correct other readings and to monitor the integrity of the standard cell. A novel two-wheel chopper and mirror arrangement facilitates the measurements.

Abstract: This invention provides a screw-on device for valve stems of automobile tires which will indicate to an automobile operator when a particular tire is under the selected standard psi. The indicator is a visible device that projects towards the outer end of the tubular member of the invention where it can be observed. The automobile operator thereupon adds air to the tire by the usual service station compressed air device and no tire guage is necessary to determine the right pressure. If insufficient pressure has been inserted in the tire the indicator will show up again, when the operator ceases adding air; if too much air has been added the device acts to relieve the excess pressure and the device will automatically close off relief flow when the standard pressure has been achieved. The pressure responsive mechanism is pre-calibrated to a particular pressure, for example 24 psi, 28 psi, 32 psi, etc.