Abstract: Multichannel infrared detector assemblies for use in the detection and monitoring of gas concentrations are provided.

Abstract: A fire detector which combines an NDIR CO.sub.2 gas detector with a photoelectric smoke detector to minimize false alarms by logic means that can be integrated into a single chip that can have an ASIC section and a microprocessor section. The NDIR CO.sub.2 detector can be single or dual channel. The NDIR CO.sub.2 gas detector and the photoelectric smoke detector can be separate or combined in a single device in which they are optically isolated by a light-tight barrier but still use a common light source. Also, the CO.sub.2 and smoke detectors can be combined on a single substrate within a common housing.

Abstract: A passive source infrared gas detector which uses an ambient temperature source and the space between the detector assembly and the source as the sample chamber is provided, the gas detector includes an infrared detector assembly for producing a first output, a second output, and a third output, the first output being indicative of the radiation received by the detector assembly at a first non-neutral spectral band which is absorbable by a preselected gas to be detected, the second output being indicative of the radiation received by the detector assembly at a first neutral spectral band from the passive infrared source, and the third output being indicative of the radiation received by the detector assembly at a second neutral spectral band from the passive infrared source. Signal processing means are included for manipulating the three outputs to determine the concentration of the gas being monitored.

Abstract: An apparatus for measuring the concentration of selected solute in a solution. This apparatus is particulary suitable for measuring the concentration of blood components, such as blood late Maillard products. A beam of exposing light is imaged through a wall of a containment vessel onto a region of the sample adjacent to this wall to induce from said selected solute emission of light that includes at least one emission peak that can be used to calculate the concentration of this solute. At least one detector is positioned to maximize the strength of detected signal, if other components of this solution strongly absorb the emitted light. The exposing light is directed such that the detected signal is maximized as a function of the path of this exposing light. A particular embodiment is a low-cost, non-invasive blood Maillard products concentration detector. In this embodiment, the containment vessel is preferably one of the patient's fingers.

Abstract: A fire detector having a greatly reduced frequency of generating false alarms. An AND gate is responsive to outputs from first and second fire detector modules that are responsive to the detection of first and second characteristics of a fire, respectively, to signal the detection of a fire if both of these characteristics have been detected. At least one override path is included to enable the occurrence of a particular type of fire to be signalled that would not otherwise be signalled by the output of said AND gate.

Abstract: Apparatus for measuring the concentration of a gas present in a sample chamber by ambient pressure diffusion employs a nondispersive infrared gas analysis technique. The sample chamber has the form of a tube that is closed at one end, with a source of radiation and a detector mounted side by side at the other end. The inwardly-facing surfaces of the tube are specularly reflective, whereby the optical length of the sample chamber is twice its physical length. A gas filter cell located in the optical path permits the concentration of an analyte gas to be measured accurately despite the presence in the sample chamber of an interfering gas. A small ultrasonic vibrator affixed to the wall of the sample chamber prevents unwanted particles from accumulating on the semipermeable membranes through which ambient gases diffuse into and out of the sample chamber.

Abstract: The sensitivity of a nondispersive infrared gas analyzer increases with increasing pathlength, which increases the absorption of the infrared radiation by the gas whose concentration is to be determined. The present invention includes the addition of an obstructing element that further increases the average pathlength. In one embodiment the obstructing element consists of a highly reflective elongated cylinder located with its axis collinear with the axis of the tubular chamber. In another embodiment, the sample chamber includes a converging section, the smaller end of which is joined to an elongated tubular section of uniform cross section. The improvements are applicable to both pumped and diffusion-type sample chambers.

Abstract: A miniaturized NDIR gas sensor is manufactured using semiconductor micromachining techniques from a semiconductor material such as Si or GaAs. The NDIR gas sensor comprises an optical waveguide, a light source at one end of the waveguide, at least one light detector at the end of the waveguide opposite the light source, a diffusion type gas sample chamber formed within the waveguide and interposed in the optical path between the light source and light detector so that the light source and light detector are thermally isolated from the gas sample, and a separate bandpass filter interposed between the light source and each light detector. Because the NDIR sensor is fabricated out of a semiconductor material, the source driver and signal processing electronics may be added directly to the sensor using integrated circuit fabrication techniques. Particles and smoke and dust may be kept out of the sample chamber by application of a gas permeable membrane over apertures in the sample chamber walls.

Abstract: The sensitivity of a nondispersive infrared gas analyzer increases with increasing pathlength, which increases the absorption of the infrared radiation by the gas whose concentration is to be determined. The present invention includes the addition of an obstructing element that further increases the average pathlength. In one embodiment the obstructing element consists of a highly reflective elongated cylinder located with its axis collinear with the axis of the tubular chamber. In another embodiment, the sample chamber includes a converging section, the smaller end of which is joined to an elongated tubular section of uniform cross section. The improvements are applicable to both pumped and diffusion-type sample chambers.

Abstract: A radiation source is presented that exhibits an improved efficiency of converting input energy into a quasi-blackbody output beam. A wavelength selective element can be included to transit one or more narrow bands of this radiation for use in spectroscopy. The intensity of the output beam can be varied quickly, thereby decreasing measurement times and enabling synchronous detection techniques to be implemented at reasonable frequencies. A feedback mechanism can be integrated into this device to enable accurate control of the blackbody temperature. This radiation source can be manufactured by conventional integrated circuit manufacturing techniques, thereby producing an inexpensive quasi-blackbody source of accurately and repeatably controlled performance.

Abstract: A gas sample chamber that is particularly advantageous for use with a semiconductor laser has the form of an elongated hollow tube with a specularly reflective inside surface, a semiconductor laser located at one end of the tube and a detector located at the opposite end of the tube. In one embodiment, apertures in the wall of the tube permit a gas to enter and leave the sample chamber by free diffusion. In another embodiment the gas flows into the hollow tube from a pressurized source through a port or is drawn through the tube by a suction pump. In other embodiments, the tube is partitioned into two successive sections by means of a window located within the tube. The window is transparent to radiation of two different wavelengths that coincide with the absorption bands of two different gases. The semiconductor laser is tuned to these wavelengths successively so that two gas components can be detected and measured simultaneously.

Abstract: An apparatus for measuring the concentration of a selected solute in a solution. This apparatus is particularly suitable for measuring the concentration of blood components, such as blood glucose. A beam of exposing light is imaged through a wall of a containment vessel onto a region of the sample adjacent to this wall to induce from said selected solute emission of light that includes at least one emission peak that can be used to calculate the concentration of this solute. At least one detector is positioned to maximize the strength of detected signal, if other components of this solution strongly absorb the emitted light. The exposing light is directed such that the detected signal is maximized as a function of the path of this exposing light. A particular embodiment is a non-invasive blood glucose tester that can be used painlessly by diabetics to monitor their blood glucose levels. In this embodiment, the containment vessel is preferably one of the patient's fingers.

Abstract: The fire detector includes a carbon dioxide sensor and a microcomputer. When the rate of increase of the concentration of carbon dioxide at the sensor exceeds a threshold, an alarm is produced. The threshold is set at one of three possible levels by the microcomputer in response to the state of the atmosphere at the sensor as determined by the microcomputer based on several variables that are derived from the sensed concentration of carbon dioxide. The derived variables include the average concentration of carbon dioxide, the average rate of change of carbon dioxide concentration, the monotonicity of the increase or decrease of the carbon dioxide concentration and the range of concentrations sensed in each cycle of operation. The threshold setting is determined every ten seconds. In this way, the setting of the rate threshold is responsive to variations in the carbon dioxide level at the sensor that are caused by entities other than a fire, such as the presence or absence of people in a closed room.

Abstract: Some cyclic variables include within each cycle a value that can be determined extrinsically. In such case, the sensed value may differ from the known value by an amount that is a combination of long-term drift of the sensor and random measuring error. The drift component can be evaluated and eliminated by the following method. Once each cycle, for a number of cycles, the sensor measures the variable at a time when its value should equal the extrinsically-known value. The differences are plotted versus time, and a best-fitting straight line is determined, which indicates the drift. Throughout the next cycle as the variable is continuously sensed, the drift determined from the best-fitting straight line is continuously applied to correct the sensed value.

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 and inexpensive. A novel waveguiding structure serves both as an optical element and as the sample chamber. As an optical element, the waveguiding structure collects radiation from a blackbody source located at the entrance end of the waveguiding structure and conducts the radiation through the waveguiding structure, concentrating it on two infrared detectors mounted at the opposite end of the waveguiding structure. As a sample chamber, the waveguiding structure causes the radiation to undergo multiple reflections that result in the average path length being substantially greater than the physical length of the waveguiding structure. Each of the detectors has its own optical filter, and baffling assures that each detector responds only to radiation which has passed through its filter.

Abstract: The improved sample chamber includes an elongated hollow tube closed at one end and having specularly-reflective inwardly facing surfaces. A source of radiation and a detector of radiation are mounted side by side in the open end of the hollow tube, both facing the closed end. A plurality of filtering apertures are formed in the tube, and each aperture is covered by a sheet of a semipermeable membrane that serves to prevent airborne particles larger than a predetermined size from entering the chamber while not interfering with the free diffusion of the gas to be measured into and out of the chamber. The use of an elongated hollow tube that is closed at one end results in no loss in the efficiency with which the radiation is conducted from the source to the detector while decreasing the external length of the chamber by 50 percent.

Abstract: The proper operation of an NDIR toxic gas sensor can be checked by using a non-toxic gas that has an absorption band that overlaps the absorption band used for measuring the toxic gas. The NDIR sensor cannot distinguish which of the two gases is responsible for causing the observed absorption of radiation in the sensor. Since detectors of toxic gases typically operate at low concentration levels, the extent of overlap between the absorption band of the toxic gas and of the non-toxic gas may be relatively small, since a larger concentration of the non-toxic gas can be used with no ill effects. The method may be applied to sensors for detecting carbon monoxide or methane for example.

Abstract: A 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 conducting radiation from a source to a detector through the sample gas. A number of apertures in the wall of the elongated hollow tube permit the sample gas to enter and exit. 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. In one embodiment, at least one detector are spaced around the periphery of the elongated hollow tube adjacent one end of it. In another embodiment, at least one detector are spaced along the length of the elongated hollow tube.

Abstract: An affordable ventilation controller comprises a low cost and very stable carbon dioxide sensor and a remote-controlled louvered suction fan equipped with an air filter. The ventilation controller operates independently of any existing heating or cooling system that might be present in a closed room. The carbon dioxide sensor measures accurately the gas concentration level in parts-per-million (ppm's) as a ventilation index. When a predetermined ventilation index is exceeded indicative of bad ventilation, a remote-controlled suction fan equipped with a louver and an air filter is activated to draw in fresh air from the outside in order to regulate the CO.sub.2 concentration and provide good ventilation. However, if an exceedingly high concentration of CO.sub.2 is sensed, the controller inhibits the control signal to the suction fan, since such a high level might indicate the presence of a fire.

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 emtis 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 disribution 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. Biological material is removed in very limited layer-like regions and in a manner in which a distally propagated segment of the beam will not have sufficient energy density to puncture the blood bessel wall.