Abstract: A two-stage statistical calibration and measurement method and system is disclosed for performing photoplethysmographic measurement of blood analyte concentrations. Concentrations in a tissue sample of MetHb, O.sub.2 Hb, RHb and COHb are estimated by first estimating a concentration of MetHb (in a first stage) and subsequently, if the concentration of MetHb is within a predetermined range, then the estimated concentration of MetHb is assumed to be accurate and this estimated concentration of MetHb is utilized as a "known value" in determining the concentrations of the remaining analytes O.sub.2 Hb, RHb and COHb (in a second stage). That is, by eliminating one "unknown" from the system of equations, these remaining analytes can be calculated with increased accuracy. Each stage is performed using data obtained by transmitting light through the tissue sample (typically a finger or earlobe). The transmitted light is generated by four discrete light emitters, each emitter having a distinct spectral content.

Abstract: A new alarm system for pulse oximeters, based on fuzzy logic, will differentiate false alarms, caused by artifact, from true alarms. Numeric input variables and corresponding fuzzy sets (oxygen saturation HIGH (high O2), NO (normal O2) and YES (desaturation) and rate of change of oxygen saturation (HIGH, MEDIUM and LOW) and their membership functions are defined. An output fuzzy set ARTIFACT is defined. Input voltages from the pulse oximeter are sampled and converted to digital form. The sampled voltages are converted by the membership functions into confidences that each fuzzy set descriptor for oxygen desaturation and reate of change apply. Rules are specified which result in confidences that the fuzzy set descriptors for ARTIFACT apply. Further rules govern the issuance of alarms for oxygen desaturation or for artifacts, momentary or continuous, so that the nurse can take appropriate action. The fuzzy logic alarm system program is written in Quick Basic 4.5, by Microsoft (R).

Abstract: The present invention comprises methods of determining the performance of an absorbance spectrometer, and, in particular, of CO-oximeters. The methods comprise measuring the absorbance spectrum of a quality control sample and comparing it to a standard spectrum of that quality control. Instrumental error will be the primary factor contributing to the observed difference. The present method also provides techniques for converting the instrumental error manifested in the difference between the measured and standard quality control spectra into blood concentration values comparable to that of real blood. Analysis of test samples on a spectrophotometer; and calibration of the spectrophotometer is also provided.

Abstract: An improved pulse oximeter apparatus and method for the measurement of oxygen saturation in the blood, which is faster and more accurate than conventional pulse oximeters. Improved speed and accuracy is attained by elimination of normalization and feedback circuitry and the use of analog to digital converting devices having a wide dynamic range along with a sophisticated computer analysis. The instant invention eliminates inaccuricies resulting from channel matching errors, and detects and eliminates aberrant input data.

Abstract: The present invention provides an adapter which actively connects a two terminal oximeter probe or monitor to a three terminal monitor or probe. This is done actively, with the alternating drive signals from the oximeter monitor providing a control signal for switching the adapter connections. The adapter connections are preferably made with diodes, transistors, or other active devices.

Abstract: A compact pulse oximetry system and method which separates the combined signal into its respective AC and DC components. By separating the signal into AC and DC components, a smaller order bit A/D converter may be used while still maintaining signal accuracy. Instead of using the combined signal to calculate the oxygen saturation content, the system microprocessor computes the Ratio of Ratios using the derivative of the separated AC component of the diffused signal to calculate the oxygen saturation of the measured fluid. To calculate the Ratio of Ratios, a ratio of the derivative value of the separated AC component is used. Instead of taking a single sample between the peak and valley of the signal, the oximeter system samples each value. To decrease the effect of system noise, a linear regression is performed over each sample.

Abstract: Weeds growing around the bases of the stalks of cotton plants growing in a row in a cotton field are sprayed with herbicide without spraying the cotton stalks or wasting herbicide on bare ground. The cotton plants are adequately mature that their stalks exhibit a significantly different spectral reflectance characteristic than the weeds typically growing amid the cotton. The cotton plants are adequately tall that the majority of the leaves of the cotton plants are disposed outside the area which can be sprayed using an electronically-controlled valve and nozzle. Light is transmitted toward an object (a cotton stalk, a weed, or soil) in the row and the reflected light is analyzed. If the object has a spectral characteristic of a growing weed, then the valve is activated and the object is sprayed with herbicide.

Abstract: A pulse oximetry sensor has a light emitting and light detecting part containing light emitting diodes and a photo detector electrically connected to a pulse oximetry instrument, and a two-halved clamp. An optical fiber cable is connected between the part and the clamp, and a power distributor transfers part of the available electric power from the pulse oximetry instrument to a power receiver supplying electric power to a signal amplifier.

Abstract: A pulse oximeter sensor with a light source optimized for low oxygen saturation ranges and for maximizing the immunity to perturbation induced artifact. Preferably, a red and an infrared light source are used, with the red light source having a mean wavelength between 700-790 nm. The infrared light source can have a mean wavelength as in prior art devices used on patients with high saturation. The sensor of the present invention is further optimized by arranging the spacing between the light emitter and light detectors to minimize the sensitivity to perturbation induced artifact. The present invention optimizes the chosen wavelengths to achieve a closer matching of the absorption and scattering coefficient products for the red and IR light sources. This optimization gives robust readings in the presence of perturbation artifacts including force variations, tissue variations and variations in the oxygen saturation itself.

Abstract: The invention relates to apparatus for testing a pulsed light oximeter, such as a non-invasive oximeter which emits pulses of red and infrared light. A light sensor produces an electrical pulse signal representative of light flashes emitted by the oximeter, and a signal generator produces a plurality of absorbance signals representative of the optical absorbance of an anatomical part at the wavelength of each light flash. A signal selector responds to time interval, duration and amplitude features of the electrical pulse signal, or to electrical signals produced by the oximeter itself, and thereby selects one of the plurality of absorbance signals to produce a selected absorbance signal. The selected absorbance signal is converted to light and conveyed to the oximeter to simulate the effect of the anatomical part on the light flashes emitted by the oximeter.

Abstract: An optical probe, which is particularly suited to reduce noise in measurements taken on an easily compressible material, such as a finger, a toe, a forehead, an earlobe, or a lip, measures characteristics of the material. A neonatal and adult disposable embodiment of the probe include adhesive coated surfaces to securely affix the probe onto the patient. In addition, the surface of the probe is specially constructed to minimize light piping effects. Furthermore, a flex circuit acts as a spring to absorb shock which may misalign the emitter and detector. One embodiment of the adult probe includes a cushioning pocket formed for a fingertip to align the probe and to absorb motion of the probe due to contact. The neonatal probe is formed with a unique V-configuration which provides multiple advantages.

Abstract: A technique for making precise spectrophotometric measurements illuminates a sample with two or more modulated light sources at two or more, typically closely spaced, wavelengths. Light from the sources is combined, homogenized, and directed to the sample, and the light from the sample is collected and detected by a photodetector. The optical output powers of two sources are modulated with the same periodicity and with a reversed amplitude. Variations in the concentrations of species in the sample affect the modulation amplitude representing the sum of the optical powers from two sources in such a way as to produce an output signal. That output signal, based on an electrical component varying with a periodicity at the fundamental frequency, provides a measure of the difference in the transmissions (or other optical properties) of the sample at the two wavelengths. Feedback methods, such as null-point detection, provide stable, sensitive measurements.

Abstract: In a method of optically determining the total hemoglobin concentration (tHb) in non-hemolyzed whole blood, using at least two wavelengths for measuring, a first wavelength of .lambda.<805 nm and a second wavelength of .lambda.>805 nm is employed, such the following is valid for the absorption coefficients of hemoglobin derivatives O.sub.2 Hb and RHb at the two measurement wavelengths .lambda..sub.1 and .lambda..sub.2 : .sigma.O(.lambda..sub.1).about..sigma.R(.lambda..sub.2) and .sigma.R(.lambda..sub.1).about..sigma.O(.lambda..sub.2). The sum of absorption values A.sub.1 and A.sub.2 measured at wavelengths .lambda..sub.1 and .lambda..sub.2 will be a quantity which is proportional to the total hemoglobin concentration tHb and independent of the oxygen saturation O.sub.2sat.

Abstract: The quantitative determination of various materials in highly scattering media such as living tissue may be determined in an external, photometric manner by the use of a plurality of light sources positioned at differing distances from a sensor. The light from said sources is amplitude modulated, and, in accordance with conventional frequency domain fluorometry or phosphorimetry techniques, the gain of the sensor is modulated at a frequency different from the frequency of the light modulation. Data may be acquired from each of the light sources at differing distances at a frequency which is the difference between the two frequencies described above. From these sets of data from each individual light source, curves may be constructed, and the slopes used to quantitatively determine the amount of certain materials present, for example glucose, oxyhemoglobin and deoxyhemoglobin in living tissue.

Abstract: The method and apparatus of the present invention provides a system wherein light-emitting diodes (LEDs) can be tuned within a given range by selecting their operating drive current in order to obtain a precise wavelength. The present invention further provides a manner in which to calibrate and utilize an LED probe, such that the shift in wavelength for a known change in drive current is a known quantity. In general, the principle of wavelength shift for current drive changes for LEDs is utilized in order to allow better calibration and added flexibility in the use of LED sensors, particularly in applications when the precise wavelength is needed in order to obtain accurate measurements. The present invention also provides a system in which it is not necessary to know precise wavelengths of LEDs where precise wavelengths were needed in the past. Finally, the present invention provides a method and apparatus for determining the operating wavelength of a light emitting element such as a light emitting diode.

Abstract: A position detecting apparatus utilizing optical interferometry changes the wavelength of a light beam from the light source. The variation in the wavelength causes an increment and decrement Cx, Co in the number of waves in the measurement and reference lengths Lx, Lo. The position data calculating section calculates the measurement length Lx on the basis of the detected increment and decrement Cx, Co and the reference length Lo according to an equation, Lx=Lo(Cx/Co). The position detecting apparatus can easily detect an absolute position of an object to be detected.

Abstract: The present invention provides a method and apparatus for adapting to noise sources affecting a pulse oximeter. Various available frequencies are evaluated to determine their respective noise levels and one is selected to act as the operating demultiplexer frequency. During normal operation of the pulse oximeter, the various available demultiplexer frequencies are periodically scanned to determine which has the lowest associated noise. The noise level associated with the operating frequency is used to determine the signal-to-noise ratio of the pulse oximeter signals and thereby qualify certain signals from the pulse oximeter. Those pulses associated with a signal-to-noise ratio below a predetermined threshold are rejected and excluded from use in calculating blood oxygen saturation.

Abstract: An improved circuit for processing the received signals of a pulse oximeter includes at least first and second light-emitting diodes for transmitting light of first and second frequencies toward the finger of a user. The first diode is responsive to a first control signal for transmitting light of the first frequency. The second diode is responsive to a second control signal for transmitting light of the second frequency. Also, the first diode is responsive to a modulated control signal for transmitting a modulated light signal also of the first frequency. A photodetector is constructed to receive a first composite signal, representing the amount of light transmitted by the first diode in response to the first control signal, and a second composite signal, representing the amount of light transmitted by the second diode in response to the second control signal, wherein the first and second composite signals each include a desired signal portion and an undesired signal portion.

Abstract: Non-invasive in-vivo and in-vitro methods for determining a person's total hemoglobin concentration as well as the concentration of the hemoglobin species which contribute to this total concentration, i.e., oxy-, deoxy-, carboxy-, and methemoglobin are described. The measurement comprises a ratio formed by dividing absorbance data at analyte wavelengths by absorbance data at reference wavelengths. In a first embodiment the analyte wavelengths occur at a local maximum of each of the hemoglobin species in the visible region. The reference wavelengths include those in the short wavelength near-infrared region from 800 to 1300 nm. In order to determine the concentration of each hemoglobin species a dA/A treatment is utilized comprising a difference term of absorbance data in the region from 800 to 1300 nm divided by the absorbance at a local maximum for each species.

Abstract: An object of the present invention is to estimate subject illuminating light using the minimum number of on-photography information. When no flashes of light exist, color differences R-G and G-B are calculated based on image information detected by an image sensor and the calculated color differences are plotted on color coordinates. It is further determined whether R-G and G-B distributions fall within a fluorescent-lamp light region or a tungsten light region (106). If it is determined that the distributions fall within the fluorescent-lamp light region, then the subject illuminating light is estimated as light such as a night view or fireworks, which is emitted from a light source other than the fluorescent lamp, when an average intensity (BV).ltoreq.-1.5 ?EV!. Further, the subject illuminating light is estimated as the fluorescent-lamp light when -1.5 ?EV!<BV.ltoreq.3 ?EV! and is estimated as daylight producing a green failure when 3 ?EV!<BV.

Abstract: This probe makes use of a simplified housing construction that significantly reduces the cost of the manufacture of the probe housing. The housing is implemented using two molded housing halves, which are pivotally connected together and which include an integral spring member. In addition, the housing includes a connector mounted thereon for enabling the probe to be disengaged from the cable and its associated connector that interconnects the probe with the medical monitoring equipment. As a further improvement, a notch is provided on the housing so that the conductors can be positioned to exit the probe in any direction to minimize the possibility of the conductors inadvertently pulling the probe loose from the patient's finger.

Abstract: An apparatus for measuring the concentration of blood constituents in which the architecture of the electronic processor reduces the amount of controller processing time required for tasks such as data acquisition and generation of system control signals. A demodulator is coupled to a probe for converting a first electrical signal to digital data. An interface is coupled to the demodulator for receiving the digital data and generating interrupts when a first amount of the digital data has been received. A buffer memory is coupled to the interface for storing the digital data. A controller having a controller memory (in specific embodiments, a CPU having a CPU memory) is also coupled to the buffer memory. The controller transfers the digital data from the buffer memory to the controller memory in response to the interrupts. The controller then processes the digital data to calculate the blood oxygen concentration.

Abstract: An apparatus for monitoring multiple physiological variables of a patient at a single site on the patient can be used to facilitate assessment of the patient's well being during medical surgery as well as during ambulatory monitoring, home monitoring, procedure monitoring and similar situations. The apparatus has an infrared (IR) temperature sensor, a pulse oximeter sensor and a communication circuit for outputting information produced from the pulse oximeter and information produced from the infrared temperature measuring device. These elements are integrally placed within a mold or plug made to fit the ear of the patient.

Abstract: An apparatus (10) and method for measurement of oxygen saturation of venous blood for use with a central venous catheter (60) are described. The apparatus (10) includes a fiber optic bundle (12) having a distal end (14) and a proximal end (16). The fiber optic bundle (12) further includes afferent and efferent light-conducting fibers (18) for sending signals and receiving signals for generating oxygen saturation measurements. A sheath (28) is disposed about the fiber optic bundle (12) for encapsulating and protecting the fiber optic bundle (12) and exposing the distal end (14) of the fiber optic bundle (12). The apparatus (10) includes a locking device (30) for locking the fiber optic bundle (12) relative to a catheter (11) into which the fiber optic bundle (12) is inserted to fix the relative relationship between the fiber optic bundle (12) and the catheter (11) when disposed in situ during an oxygen saturation measurement procedure.

Abstract: A pulse oximeter which modifies the alarm condition when motion is detected. Basically, if the lack of a pulse is determined to be as a result of motion artifact, the generation of an alarm is postponed. In addition, the display indicates that motion is present and that the last reading is questionable due to the presence of motion. The invention also determines if motion artifact is present from the pulse oximeter detector signal itself. The ratio of the positive and negative peaks of the derivative of the pulse signal are compared to a motion/blood pulse threshold.

Abstract: Motion compensation is based on analysis of intensity signals received by detectors, without separately measuring a motion signal, without providing feedback to cancel the motion signal and without attempting to mathematically eliminate the motion signal. Instead, the present invention mathematically recognizes the presence of the motion signal and recognizes a few key characteristics of the motion signal and makes corresponding assumptions. First, it is recognized that the motion/noise in each wavelength signal is proportional. Second, it is assumed that the blood pulse signal is not affected by motion.

Abstract: The present invention provides an encoding mechanism for a medical sensor which uses a modulated signal to provide the coded data to a remote analyzer. The modulated signal could be, for instance, a pulse width modulated signal or a frequency modulated signal. This signal is amplitude independent and thus provides a significant amount of noise immunity.

Abstract: An interpolation circuit for a measuring device capable of increasing a resolution and providing a velocity proportional output. Both sin .theta. signal and cos .theta. signal outputted from a sensor is fed to a balanced modulation adding circuit, resulting in providing a sin(.omega.t-.theta.) signal, which is then shaped into a pulse wave in a waveform shaping circuit. Then, a higher harmonic component is extracted by a BPF and then mixed with cos n.omega.t and sin n.omega.t signals in mixers, so that cos n.theta. and sin n.theta. signals are taken out of LPFs, respectively. The signals are subject to interpolation in a voltage comparison interpolation circuit of which the number of dividing is m, resulting in providing an interpolation circuit of which the whole number of dividing is m.multidot.n. Interpolation output A-phase and B-phase thereof each are a velocity proportional output.

Abstract: A method for manufacturing a heat-sealed neo-natal medical monitoring probe requires a pair of light sources and a light detector to be placed between two layers or conformable material used to implement the probe. The layers are designed to be self-aligning when placed in the assembly press for heat-sealing the perimeter of the probe. The heat-sealing process both protects the light sources and detector from fluids and also functions to precisely position and secure these devices.

Abstract: An optical probe for measurements, which is particularly suited to reduce noise in measurements taken on an easily compressible material, such as a finger, a toe, a forehead, an earlobe, or a lip. The probe includes a base having an aperture which leads to a chamber. The base is placed adjacent a portion of the material, the chamber being placed directly adjacent any easily compressible portion of the material. A photodetector is located within the chamber and does not contact the material. A light emitting diode (LED) is affixed to the material, opposite the photodetector and above the chamber. The material which is supported by the aperture and therefore rests above or has intruded into the chamber is inhibited from compression since nothing comes in contact with this portion of the material, even when the material moves. Thus, light from the LED is directed through a stabilized portion of the material, i.e.

Abstract: The use of luminescent probe substances is detailed in methods and an apparatus for the determination of the concentration and distribution in space and time of numerous analytes of biologic and physical import in vivo and in vitro by the steady-state determination of luminescence lifetime. In the instance of analytes that quench excited states, a fluorophore whose excited state is quenched by the analyte in question is free to undergo Brownian rotation alone or when conjugated to a carrier molecule within a medium of suitable viscosity. The analysis medium is irradiated with continuous linearly polarized light at a wavelength strongly absorbed by the fluorophore. The emitted luminescence is resolved into its vector components parallel and perpendicular to the plane of polarization of the excitation light, thereby permitting the calculation of the luminescence anisotropy of the irradiated specimen.

Abstract: A protective sheath for a pulse oximetry sensor. The sheath covers the sensor and inhibits contamination thereof during use. The sheath obviates the need to clean the pulse oximetry sensor after each use while reducing the likelihood of cross-patient contamination. The sheath allows the use of reusable pulse oximetry sensors and thus significantly reduces the overall costs of such sensors per use.

Abstract: A backscatter type non-invasive blood oximeter utilizes a coherent, polarized and tuneable monochromatic light source to measure parameters related to blood oxygen content. A microprocessor calculates information related to blood oxygen content from the sensed information and a display system displays the blood oxygen content.

Abstract: A pulse oximeter includes light-emitting devices for irradiating different wavelengths of light into a living tissue through which arterial blood flow, a light-receiving device for detecting at least one of transmitted and reflected light after the different wavelengths of light have been absorbed by the living tissue, first correlation function computing device for determining first correlation function for the waveform of received light at one of the different wavelengths obtained from the output of the light-receiving device, second correlation function computing device for determining second correlation function for the waveforms of received light at another of the different waveforms obtained from the output of the light-receiving device, dividing device for determining the ratio between the first correlation function obtained by the first auto-correlation function computing device and the second correlation function obtained by the cross-correlation function computing device, the ratio determined on the

Abstract: Disclosed is a drive circuit for driving a light emitting diode in a pulse oximeter comprising at least two light emitting elements different in wavelength for irradiating a living tissue containing an arterial blood; a light receiving element for receiving light containing one of a reflected light and a transmitted light irradiated from the light emitting elements; a power supply for applying intermittently an inverse bias voltage toward the light emitting elements; and an inductor for applying an inverse electromotive voltage to the light emitting elements, the inductor being connected to the light emitting elements in parallel, wherein a ratio between light absorption change with respect to two wavelengths obtained from optical outputs of the light receiving element so as to obtain a degree of oxygen saturation of arterial blood.

Abstract: The invention performs coordinate measurement employing multiple-frequency intensity-modulated laser radar. A laser diode source is intensity modulated by variation of its excitation current. Its output beam is directed to a target using scanning mirrors or other opto-mechanical means, and the light returned from the target is detected. The modulation frequency is alternated between two or more values, creating a dataset of several relative phase measurements that uniquely determine the distance to the target without ambiguity.

Abstract: A technique for the derivation of a pulse oximetry signal using fractal dimension analysis of detected light signals. First and second light sources transmit light through the patient's finger or reflect light off the blood vessels in the patient's finger. A light detector detects light from each of the light sources and generates a measured intensity signal. The measured intensity signal includes the true intensity of light transmitted from each of the light sources as well as noise introduced during the measurement process. A data sample from each of the light sources is digitized and a set of equations developed as a function of a ratio value indicative of oxygen saturation in the patient. The fractal dimension is determined for the set of signal functions over the normal physiological range for the ratio value. Maximum and/or minimum fractal dimension values are calculated to determine the desired ratio values which are possible indicatives of the ratio of true physiological signals or noise signals.

Abstract: An optical sensor for use in clinical patient examination by spectrophotometric apparatus, having a body with softly deformable material which is conformable to a selected area on the body of the patient and internally-mounted electro-optical source and receivers for obtaining patient pathology data by transmission of selected wavelengths through a tissue volume adjacent the selected area, including substantially non-deforming light-transfer members disposed in alignment with the source and detectors and between them and the patient, to provide substantially constant and unchanging light-transfer passages or conduits therebetween. In the most preferred form, the light-transfer members comprise generally tubular elements having light-reflective interior walls, and the sensor body comprises either a layered structure of opaque, soft polymeric foam or the like (e.g. , cellular urethane) or a substantially one-piece, molded or other such structure of generally comparable or analogous material and characteristics.

Abstract: An optical proximity sensor generates information indicative of a distance to an object in a field and in some embodiments also generates information indicative of a spectral reflectance characteristic of the object. The information indicative of the spectral reflectance characteristic can be used to determine whether the object in the field is a living plant or another object such as soil. Light emitted from the optical sensor for reflection off the object is modulated so that reflected light from the optical sensor can be discriminated from reflected ambient sunlight. The optical sensor is scanned over the field to map objects in the field and/or to determine the location of rows of crop plants. A sensor in accordance with the present invention has many uses in agriculture including spraying, cultivation and vehicle guidance.

Abstract: A compact pulse oximetry system which separates the combined signal into its respective AC and DC components. By separating the signal into AC and DC components, a smaller order bit A/D converter may be used while still maintaining signal accuracy. Instead of using the combined signal to calculate the oxygen saturation content, the system microprocessor computes the Ratio of Ratios using the derivative of the separated AC component of the diffused signal to calculate the oxygen saturation of the measured fluid. To calculate the Ratio of Ratios, a ratio of the derivative value of the separated AC component is used. Instead of taking a single sample between the peak and valley of the signal, the oximeter system samples each value. To decrease the effect of system noise, a linear regression is performed over each sample.

Abstract: An apparatus for non-invasively measuring the oxygen saturation in the blood of a subject comprises light sources for irradiating a sample of blood in tissue with at least a first light beam and a second light beam having different wavelengths. A switching device drives the light sources and sequentially switches the irradiation of the sample of blood between the first and second laser beams. A photoelectric detector detects light transmitted through or reflected from the sample of blood and provides an electrical output signal indicative of the intensity of the detected light. A converter converts the electrical output signal of the photoelectric detecting device to a power spectrum, and a processor processes the power spectrum and calculates the oxygen saturation of the sample of blood.

Abstract: A diagnostic instrument for determining a cardiovascular system parameter. In one embodiment, the instrument takes the form of a portable pulse oximeter comprising a light to frequency converter (LFC) as a sensor. Also provided is a light to frequency converter comprising a photoresistor and capacitor in circuit communication with an inverting Schmitt trigger and configured such that the inverter generates a periodic electrical signal corresponding to the amount of electromagnetic radiation illuminating the photoresistor.

Abstract: A method and apparatus are provided for detecting and compensating for a kink in an optical fiber. A distal sensor (11) monitors a level of a parameter in an environment in which the distal sensor is immersed. The distal sensor is disposed at a tip of the optical fiber (17) and the optical fiber conveys green light signals and near infrared (NIR) light signals to and from the distal sensor. A photodetector (59') records the signal and reference values for the green light signals and the NIR light signals conveyed by the optical fiber at consecutive data points. A microcontroller (42) is electronically coupled to the photodetector and receives the signal and reference values for the green light signals and the NIR light signals. A kink in the optical fiber is detected when a change between NIR signal values recorded at a pair of consecutive data points recorded by the photodetector is greater than a predetermined threshold.

Abstract: The present invention provides a medical sensor for detecting a blood characteristic. The sensor includes a transducer for producing an analog signal related to the blood characteristic. The analog signal is converted into a transmission signal which is in amplitude-independent form for transmission to a remote analyzer. In one embodiment, a current-to-frequency converter converts a signal from a pulse oximeter sensor into a frequency signal which can be transmitted over a transmission line to a remote pulse oximeter.

Abstract: The present invention provides a method and apparatus for adapting to noise sources affecting a pulse oximeter. Various available frequencies are evaluated to determine their respective noise levels and one is selected to act as the operating demultiplexer frequency. During normal operation of the pulse oximeter, the various available demultiplexer frequencies are periodically scanned to determine which has the lowest associated noise. The noise level associated with the operating frequency is used to determine the signal-to-noise ratio of the pulse oximeter signals and thereby qualify certain signals from the pulse oximeter. Those pulses associated with a signal-to-noise ratio below a predetermined threshold are rejected and excluded from use in calculating blood oxygen saturation.

Abstract: A pulse oximeter probe includes a measuring member including a light-emitting element and a light receiving element, a pair of holding members for holding the basal part of an earlobe, the measuring member mounted on the holding member, the holding members including compressing portions for holding the basal part of the earlobe, the compressing portions being separated in position from the measuring member.

Abstract: A compact pulse oximetry system which separates the combined signal into its respective AC and DC components. By separating the signal into AC and DC components, a smaller order bit A/D converter may be used while still maintaining signal accuracy. Instead of using the combined signal to calculate the oxygen saturation content, the system microprocessor computes the Ratio of Ratios using the derivative of the separated AC component of the diffused signal to calculate the oxygen saturation of the measured fluid. To calculate the Ratio of Ratios, a ratio of the derivative value of the separated AC component is used. Instead of taking a single sample between the peak and valley of the signal, the oximeter system samples each value. To decrease the effect of system noise, a linear regression is performed over each sample.

Abstract: To intensity-modulate laser light periodically wavelength-modulated by and emitted from a wavelength-variable semiconductor laser 11. To separate the laser light into optical paths 13a, 13b with a beam splitter 14 to irradiate an examined location 17 for assessing blood sugar through path 13a. To detect the intensity of transmitted or reflected light from examined location 17 with a first detector 21 and the intensity of laser light passing through path 13b with a second detector 22 to detect the ratio of the former intensity to the latter intensity with a logarithmic ratio amplifier 25. To detect the rate of change in the ratio with respect to the change in wavelength of the wavelength modulation with a lock-in amplifier 26 to obtain a derivative spectral signal of the absorption spectrum of glucose. An arithmetic processor 27 detects blood sugar in the examined location from the derivative spectrum.

Abstract: Methods of imaging objects with diffused light. The methods preferably can comprise the steps of illuminating the object with a source of light which can be scattered by the object, collecting the scattered light with a detector from multiple positions surrounding the object, measuring a mean free path of photons scattered from the object from the collected scattered light, and determining a diffusion constant for the photons scattered from the object as a function of the measured mean free path, and determining in the transmission of the photons between the source and the detector as a function of the diffusion constant, thereby imaging the object. Methods and apparatus described herein efficiently image objects with diffuse light by taking into account source-detector orientation and boundary effects.

Abstract: A pulse oximeter sensor that is designed to surround an appendage of the patient, such as a finger, toe or foot is disclosed. The sensor has a reusable member which preferably includes a photodetector. A disposable, flexible member preferably contains the photoemitter and can be wrapped around the patient's appendage to secure it to the appendage and the reusable member. When secured, the photoemitter and photodetector end up on opposite sides of the appendage. The disposable member connects to the reusable member to establish electrical contact. The reusable member is connected to a cable which can be plugged into a sensor monitoring system.