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`US 20050049468Al
`
`(19) United States
`(12) Patent Application Publication
`Carlson et al.
`
`(10) Pub. No.: US 2005/0049468 Al
`Mar. 3, 2005
`(43) Pub. Date:
`
`(54)
`
`INCREASING THE PERFORMANCE OF AN
`OPTICAL PULSOXIMETER
`
`(76)
`
`Inventors: Sven-Erik Carlson, Herrliberg (CH);
`Urban Schnell, Ins (CH); Deborah
`Schegg, Koniz ( CH); Martin Liechti,
`Bern (CH)
`
`Correspondence Address:
`NOTARO AND MICHALOS
`100 DUTCH HILL ROAD
`SUITE 110
`ORANGEBURG, NY 10962-2100 (US)
`
`(21) Appl. No.:
`
`10/654,184
`
`(22) Filed:
`
`Sep. 3, 2003
`
`Publication Classification
`
`(51)
`
`Int. CI.7 ....................................................... A61B 5/00
`
`(52) U.S. Cl. ............................................ 600/323; 600/336
`
`(57)
`
`ABSTRACT
`
`Proposed is a configuration for the acquisition and/or moni(cid:173)
`toring of medical data, in particular the state of the cardio(cid:173)
`vascular and pulmonary system, blood values or blood
`composition, characterised by at least one measuring sensor
`for the acquisition of the medical data such as the state of the
`cardiovascular system, etc. of a person comprising at least
`one light source which can emit light at least at two
`wavelengths, as well as at least one light receiver for
`determining the light transmitted and/or reflected through a
`tissue portion of a person or an animal further comprising
`means in order to increase the optical Signal-to-Noise and/or
`Signal-to-Background ratio.
`
`a
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`Petitioner Apple Inc. – Ex. 1009, p. 1
`
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`

`

`US 2005/0049468 Al
`
`Mar. 3, 2005
`
`1
`
`INCREASING THE PERFORMANCE OF AN
`OPTICAL PULSOXIMETER
`
`[0001] The present invention refers to a configuration for
`the acquisition and/or monitoring of medical data according
`to the introduction of claim 1 and a method for the acqui(cid:173)
`sition and/or monitoring of the state of health or of medical
`data of a person or an animal.
`
`[0002] The invention relates in particular to optical pul(cid:173)
`soximetry used for non-invasive measurement of pulsation
`and oxygen saturation in arterial human or animal blood, and
`is particularly concerned with increasing the technical per(cid:173)
`formance of pulsoximetry in terms of quality and robustness
`of the measurement signal versus environmental distur(cid:173)
`bances and energy consumption.
`
`[0003] Pulsoximetry is a widely used standard optical
`technology for non-invasive monitoring of pulsation and
`oxygen saturation in arterial human or animal blood [1]. The
`method consists of measuring the absorption of reduced
`(Hb )-and oxidized (HbO 2 ) haemoglobin at two optical
`wavelengths, where the relative absorption coefficients dif(cid:173)
`fer significantly, e.g. 660 nm and a second wavelength in the
`range of 800 to 1000 nm, preferably 890 nm or 950 nm. A
`concise description of the measurement method and the
`sensor signals is given in [ 2].
`
`[0004] Commercially available pulsoximeter sensors are
`typically used in hospitals and doctor's offices where the
`( optical) environment and mounting of the sensor onto the
`patient's skin are well defined. In the recent past pulsoxim(cid:173)
`etry measuring devices and methods are also offered and
`used for mobile monitoring and surveying of human indi(cid:173)
`viduals, e.g. suffering of diseases, such as heart problems,
`diabetes, respiratory diseases, insufficient oxygen blood
`saturation, etc. Pulsoximetry measuring devices are also
`used in sports for control and survey of athletes. Respective
`monitoring devices are described within the international
`patent application WO02/089 663 which proposes in this
`respect to monitor in particular persons with cardio vascular
`disorders by means of pulsoximetry with measurements
`being taken by means of pulsoximetry preferably on an ear
`or on a finger. When using pulsoximetry in telemedicine or
`near patient testing applications, which means e.g. at self(cid:173)
`controlling and self-testing of patients in non-ideal environ(cid:173)
`ment, standard pulsoximeter sensors suffer from signal
`instability and insufficient robustness versus environmental
`disturbances.
`
`[ 0005] Critical points are:
`[0006] Human tissue scatters and transmits light in
`the visible and near infrared (NIR) wavelength
`range. Therefore, suppression of environmental opti(cid:173)
`cal radiation, e.g. sunlight, is difficult by geometric
`means of the architecture of the pulsoximeter sensor.
`[0007] The power spectrum of environmental optical
`radiation strongly varies as a function or time and
`place where the pulsoximeter is used, e.g. day versus
`night, indoor versus outdoor. Therefore, the back(cid:173)
`ground ( offset) in the detected optical power varies
`in a large range, making difficult the analog and
`digital signal processing of the primary sensor sig(cid:173)
`nal.
`[0008] The temporal spectrum of pulsoximeter sig(cid:173)
`nals varies in the range of 0.5 Hz to 5 Hz where
`
`environmental optical radiation may have significant
`components leading to parasitic contributions which
`cannot be separated from the pulsoximeter signals of
`interest.
`
`[0009] Realization of a performing electronic band
`pass filter in the range of 0.5 Hz to 5 Hz, in order to
`suppress DC offset and high frequency contribution
`in the pulsoximeter signal, is technically challeng(cid:173)
`ing. Further, optical contributions, e.g. temporally
`structured day-light, and electronic noise, e.g. 1/f
`(1/frequency-Noise), are stronger in the low fre(cid:173)
`quency range 0.5 Hz to 10 Hz than in higher fre(cid:173)
`quency ranges.
`
`[0010]
`It is therefore an object of the present invention to
`define optical and/or electronic means for increasing the
`Signal-to-Noise ratio (SIN) and Signal-to-Background ratio
`(SIB) of a pulsoximeter sensor for robust application of
`pulsoximetry in telemedicine- and near patient testing appli(cid:173)
`cations in rough ( optical) environmental conditions, e.g. at
`changing light influences, such as sunlight, shadow, artificial
`light, etc.
`
`[0011] The posed problem is solved by means of a con(cid:173)
`figuration/method according to the invention. Proposed is a
`configuration for monitoring which comprises at least one of
`the following components:
`
`[0012] at least one measuring sensor for the acquisi(cid:173)
`tion of the medical data, such as the state of the
`cardiovascular and pulmonary system, as e.g. pulsa(cid:173)
`tion frequency, oxygen saturation of blood, breathing
`frequency, etc. of a human being or an animal,
`comprising at least one light source which can emit
`light at least at two wavelengths, as well as at least
`one light receiver for determining the light transmit(cid:173)
`ted through a tissue portion of the person or the
`animal;
`
`[0013] at least one beam shaping optical element to
`direct the emitted light to a human or animal tissue
`and the light receiver in order to increase the optical
`signal power.
`
`[0014] The basic idea therefore is to use a beam-shaping
`element, such as e.g. diffractive or refractive lenses, to direct
`the emitted optical radiation of, e.g., the LED light source
`into the human or animal tissue and the photon detecting
`element in order to increase the optical signal power,
`detected by the pulsoximeter sensor, and thus increasing the
`Signal/Noise-and signal/Background ratio. The increase of
`the SIB ratio is estimated e.g. to a factor 5.
`
`[0015]
`In addition to the above mentioned configuration or
`as an alternative, it is proposed to use a configuration for
`monitoring e.g. pulsation frequency, oxygen saturation
`within blood and breathing frequency which comprises at
`least the following components:
`
`[0016] at least one measuring sensor to the person or
`the animal for the acquisition or monitoring of
`medically relevant data which sensor comprises at
`least one light source that can emit light at least at
`two wavelengths, as well as at least one light receiver
`for determining the light transmission through a
`tissue portion of the person or the animal, and
`
`Petitioner Apple Inc. – Ex. 1009, p. 18
`
`

`

`US 2005/0049468 Al
`
`Mar. 3, 2005
`
`2
`
`[0017] at least one light baffle or light trap, respec(cid:173)
`tively, and/or an optical wavelength filter which is
`adapted to the power spectrum of the light source
`and the absorption spectrum of human or animal
`arterial blood. The basic idea of using geometric
`baffles or light traps, respectively, and/or optical
`wavelength filters is to suppress by geometric and/or
`optical means the parasitic contribution of environ(cid:173)
`mental radiation in order to increase or stabilize the
`S/B (Signal/Background) ratio vs. environmental
`conditions. The increase of the S/B ratio is e.g.
`estimated to a factor 10-100.
`
`[0018] Again, in addition to the above mentioned two
`configurations, or as an alternative, a further configuration is
`proposed which comprises at least the following compo(cid:173)
`nents:
`
`[0019] at least one measuring sensor on the person or
`the animal for the acquisition or the monitoring of
`medically relevant data, such as in particular data,
`which describe the cardio vascular and pulmonary
`function and/or contained data regarding blood val(cid:173)
`ues or blood composition, which sensor comprises at
`least one light source which can emit light at least at
`two wavelengths, as well as at least one light receiver
`for determining the light transmitted through a tissue
`portion of the person, and
`
`[0020] at least one light source frequency modulating
`means to frequency modulate the optical radiation of
`the light source at a carrier frequency in order to shift
`the power spectrum of the pulsoximeter signals. The
`basic idea of using AC-Coupling or Lock-In Ampli(cid:173)
`fication (synchronous detection), is to temporarily
`modulate the amplitude of the optical radiation of,
`e.g., the LED at a carrier frequency fc in order to shift
`the power spectrum of the pulsoximeter signals into
`a higher frequency range where environmental opti(cid:173)
`cal radiation is unlikely and electronic band pass
`filtering is technologically less stringent. Thus, the
`pulsoximeter signals are readily discriminated from
`electronic and parasitic contributions of environmen(cid:173)
`tal optical radiation outside the frequency range of,
`e.g. fc +/-5 Hz, increasing significantly the SIN
`(Signal/Noise)- and SIB ratio.
`
`[0021] Further specific designs of the configurations are
`described within the dependent claims.
`
`[0022] Furthermore, the above mentioned problem is
`solved according to the invention by means of methods
`according to the invention. Proposed is a method for moni(cid:173)
`toring e.g. pulsation frequency, oxygen saturation in blood
`or breathing frequency, which comprises at least one of the
`following steps:
`
`[0023] measuring or monitoring medically relevant
`data of a person or an animal, such as in particular
`data, which describe the cardiovascular and pulmo(cid:173)
`nary function and/or contain data regarding blood
`values or blood composition with the use of at least
`one measuring sensor, which sensor comprises at
`least one light source which can emit light at least at
`two wavelengths:
`
`[0024] direct the emitted light or optical radiation,
`respectively, by using a beam shaping element, such
`as e.g. a diffractive or refractive lens to the human or
`animal tissue;
`
`[0025]
`the emitted and
`receiving and detecting
`shaped light with at least one light receiving element
`for determining the light transmitted through the
`tissue portion of the person or the animal.
`
`[0026]
`In addition to the mentioned method or as alterna(cid:173)
`tive, it is further proposed to filter the emitted light by using
`geometrical baffles or light traps, respectively, and/or optical
`wavelength filters to suppress by geometric and/or optical
`means the parasitic contribution of environmental radiation.
`[0027] Again, in addition to the above mentioned two
`methods or as an alternative, it is further proposed to
`temporarily modulate the amplitude of the optical radiation
`of the light source by using e.g. AC-Coupling or Lock-In
`Amplification detection means. The basic idea of using
`AC-Coupling or Lock-In Amplification detection means is
`to temporarily modulate the optical radiation of, e.g., the
`LED at the carrier frequency fc in order to shift the power
`spectrum of the pulsoximeter signals into a higher frequency
`range where an environmental optical radiation is unlikely
`and electronic band pass filtering is technologically less
`stringent.
`[0028] Further preferred methods are described in the
`dependent claims.
`[0029] Further preferred embodiment variants, in particu(cid:173)
`lar of an ear sensor employed for measurements by means of
`pulsoximeter, are found in the international patent applica(cid:173)
`tion WO 02/089 663 which herewith is included as an
`integral component of the present patent application.
`[0030] The invention will be explained in further detail by
`examples and with reference to the enclosed figures.
`[0031] Therein depicted:
`[0032] FIG.1 schematically the arrangement of an ear clip
`for oximetric measurement;
`[0033] FIG. 2 schematically the ear clip of FIG. 1 in cross
`section view;
`[0034] FIG. 3 schematically a light source to be used in an
`oximetric sensor without beam shaping optics;
`[0035] FIG. 4 schematically two light emitting sources for
`an oximetric sensor including beam shaping optics;
`[0036] FIG. Sa a diagram showing the light absorption
`curves of with oxygen saturated (HbO 2) and unsaturated
`(Hb) haemoglobin;
`[0037] FIG. Sb a diagram showing the spectrum sensitiv(cid:173)
`ity of a photo detecting element;
`[0038] FIG. Sc in a diagram the transmission spectrum of
`a double band pass filter;
`[0039] FIG. 6a in perspective view a part of an oximetric
`sensor with arranged baffles to avoid stray light;
`[0040] FIG. 6b the part of the sensor of FIG. 6a in
`longitudinal section;
`[0041] FIG. 6c an oximetric sensor in perspective view,
`containing optical lenses, filters and geometrical baffles;
`
`Petitioner Apple Inc. – Ex. 1009, p. 19
`
`

`

`US 2005/0049468 Al
`
`Mar. 3, 2005
`
`3
`
`[0042] FIG. 7a a diagram showing power spectrum of
`physiological signals;
`[0043] FIG. 7b a diagram showing power spectrum of
`ambient light;
`[0044] FIG. 7c a diagram showing power spectrum of
`physiological signals and ambient light without phase shift(cid:173)
`ing or modulation of the light source of a sensor,
`[0045] FIG. 8 a diagram showing power spectrum of
`physiological signals and ambient light with phase shifting
`or modulation of the light source of a sensor;
`[0046] FIG. 9 a principal of using band pass filtering
`means at a sensor with applied phase shifting or modulation
`of the light source at a sensor, and
`[0047] FIGS. lOa+b a further fixing system for arranging
`a pulsoximetric sensor system as an alternative to a clip
`according to FIGS. 1 and 2.
`[0048] FIG. 1 shows schematically the arrangement of an
`ear sensor 1 which can be arranged in form of an ear clip.
`This sensor 1 can be arranged e.g. at an earlobe of ear 2.
`Furthermore, the sensor or ear clip is connected via a wire
`3 and the connection 5 with the main unit 7 including e.g. a
`power source, like a battery, and measuring and/or moni(cid:173)
`toring electronics.
`[0049]
`In FIG. 2, the ear clip 1 is shown in cross section
`where it can specifically be seen that the sensor is designed
`in form on a clip 13. The sensor or ear clip 13 furthermore
`includes a light source 15 which emits a light beam 8 to a
`light receiver 11. The light is guided or emitted through the
`ear skin or earlobe 2.
`[0050] As already mentioned in the introduction, the sen(cid:173)
`sor is working according to the oximetric principal which is
`known best out of the state of the art. Optical pulsoximetry
`is used for non-invasive measurement, e.g. for pulsation and
`oxygen saturation in the human body. The light source is
`emitting light at two wavelengths, at 660 nm and a second
`wavelength within the range of 800 to 1000 nm, which
`means in the present case at 890 nm. Therefore, it is of
`course also possible to have two light emitting sources
`arranged, which means two LEDs. The light receiver is
`determining the light transmitted through the earlobe, which
`means through the tissue portion of a person to be surveyed.
`[0051] Within the main unit 7 the measured values can be
`compared with reference values being representative for a
`certain health status of the person to be surveyed.
`
`[0052] Of course, the sensor can also be arranged at other
`parts of the human body, such as e.g. at a finger or a toe. In
`addition, the monitoring can also be executed at animals,
`which means that pulsoximetric sensors can also be arranged
`e.g. at the ear of animals, such as e.g. cows. According to an
`alternative design of the sensor, it could also be possible to
`arrange the light receiver in such a way so that the light
`reflected through the earlobe is determined. Again, accord(cid:173)
`ing to a further alternative, it could even be possible by
`arranging at least two light receivers to determine the light
`transmitted through the earlobe and the light reflected by the
`earlobe.
`
`[0053] FIG. 3 shows a light beam emitted by a LED where
`it is clear that most of a light beam with such a large
`spreading angle does not hit the receiver. Walking around
`
`through various rooms, one time halogen light is influencing
`the light beam 8, the other time conventional light is
`influencing the measurement, and again at another time, for
`the person using a car, the sunlight is influencing the
`measurement, e.g. if sunlight and shadow alternate within a
`short period of time.
`[0054] Therefore, it is proposed, as shown in FIG. 4, to
`use beam shaping optics 20 to direct the emitted optical
`radiation 8 emitted from the two LEDs 15 to the middle of
`the earlobe. As it is shown clearly in FIG. 4, using the beam
`shaping optics 21, the two initial light beams 8 are guided in
`form of bundled beams 12 to a relatively small area within
`the middle ear 2. By using the beam shaping optics 21, of
`course the influence of environmental light or noise, respec(cid:173)
`tively, can be reduced substantially by increasing the SIB
`ratio. First or all, the light beam is bundled and, in addition,
`the optical signal power can be increased.
`[0055] As an alternative or in addition to using beam
`shaping optics, it is also possible to influence the sensor
`architecture of the pulsoximetric sensor. First of all, it is
`possible to use a light receiving or light sensitive element 11
`with reduced light sensitivity outside the spectral range of
`the band limited light source as LEDs. FIG. Sa shows the
`light absorption curves of with oxygen saturated 22 and
`unsaturated 23 blood. As visible from the shown diagram,
`the sensor architecture, which means the spectrum sensitiv(cid:173)
`ity, should be in the range within approximately 500 nm to
`approximately 1000 nm. In addition, in FIG. Sa the two
`wavelengths A1 and A2 are indicated at which the pulsoxi(cid:173)
`metric sensor is operated.
`[0056] As a consequence, FIG. Sb shows the spectrum
`sensitivity of a silicon photo detecting element which is
`suitable for the use in a pulsoximetric sensor according to
`the present invention. As shown, the detection sensitivity is
`within a range of approximately 500 to 1000 nm. In other
`words, any light below or above this range would not be
`detected by the light receiving element with a sensitivity as
`shown in FIG. Sb. In addition, it is possible to arrange an
`optical wavelength filter or double pass filter which is e.g.
`light permeable at the wavelength of approximately 660 nm
`and in the range of approximately 850 nm to 910 nm. A
`corresponding transmission spectrum of such a double band
`pass filter will be suitably used in a pulsoximetric sensor as
`shown in FIG. Sc.
`[0057] Preferably, the two means, as described with ref(cid:173)
`erence to FIGS. Sb and c, are combined as wavelength filters
`might be also light permeable in lower wavelengths areas
`and higher wavelengths areas which, by using a selective
`light detecting element, can be eliminated.
`[0058] Of course, it is furthermore possible to combine
`wavelength filters, wavelength sensitive receivers like pho(cid:173)
`todiodes, with beam shaping optics as described with ref(cid:173)
`erence to FIG. 4.
`[0059] A further possibility for the better performance of
`a pulsoximetric sensor, is to arrange geometric means as e.g.
`so-called geometrical baffles (light trap). In FIG. 6a, a part
`of a pulsoximetric sensor is shown, which means the part of
`the sensor after the transmitted light has passed, e.g. the
`earlobe of a human or animal individual. Within the men(cid:173)
`tioned sensor part 31, after e.g. a double pass filter 33,
`circumferential extending baffles 37 are arranged to avoid
`stray light to reach the photo detecting element.
`
`Petitioner Apple Inc. – Ex. 1009, p. 20
`
`

`

`US 2005/0049468 Al
`
`Mar. 3, 2005
`
`4
`
`[0060] For any stray light which has entered the sensor
`e.g. before or at the area of the earlobe, will be trapped
`within the depressions of the baffles 37, and therefore will
`not substantially influence the emitted light of the LEDs.
`[0061] FIG. 6b shows the part of the sensor of FIG. 6a in
`a longitudinal section. The stray light will be trapped sub(cid:173)
`stantially within the depressions of the baffles 31, while the
`emitted light by the LEDs will reach the optical sensor 35.
`[0062] According to the preferred embodiment of the
`invention, the various described optical and geometric
`means, such as the beam shaping element as shown in FIG.
`4, the wavelength filters, the sensor architecture, and the
`mentioned baffles, can be combined as shown in principle
`and perspective view in FIG. 6c. Again, light is emitted
`from the two LEDs 15 and is shaped by the two beam
`shaping elements or lenses 21 to be guided as beams 12
`through the earlobe 2. After the earlobe, the double pass
`filter 33 is arranged to guarantee that only light in the range
`of approximately 660 nm and in the range of approximately
`890 nm is transmitted through the filter. After the filter, any
`stray light, entered the sensor e.g. trough the earlobe from
`the side, will be trapped within the baffles 37 which are
`arranged in circumferential direction. Finally, a photo
`detecting element 35 is arranged with specific spectrum
`sensitivity.
`[0063] By using sensor architecture as shown in FIG. 6c,
`the Signal-to-Background ratio may be increased in a range
`of a factor 50 to 1000.
`[0064] According to a further aspect of the present inven(cid:173)
`tion, it is furthermore possible to use a light source modu(cid:173)
`lation to temporarily modulate the optical radiation of the
`LED.
`[0065] The basic idea of using AC-Coupling or Lock-In
`Amplification (synchronous detection), is to temporarily
`modulate the optical radiation of the LED at the carrier
`frequency fc in order to shift the power spectrum of the
`pulsoximeter signals into a higher frequency range where
`environmental optical radiation is unlikely and electronic
`band pass filtering is technologically less stringent. AC(cid:173)
`Coupling or Lock-In Amplification is well known out of the
`state of the art and is described in literature 3.
`[0066] FIG. 7a shows a spectrum of physiological signals,
`such as pulsation frequency, breathing frequency, etc. The
`frequency of physiological events is within the range of
`approximately 0.5 Hz (30 heartbeats in one minute) up to
`approximately 3 Hz (180 heartbeats in one minute) that can
`be even higher and therefore is supposed to go up to 5 Hz.
`[0067] The frequency spectrum of ambient light is sche(cid:173)
`matically shown in diagram 7b. Sunlight is at 0 Hz, while
`artificial light, such as e.g. electrical in-house light, is going
`up to approximately 120 Hz (USA). In other words, within
`the range of frequencies of physiological signals, we have
`high influence of frequencies of sunlight and ambient light.
`A corresponding combined frequency spectrum is shown in
`Fig. c, which would be detected by a photo diode without the
`use of any means as described above in relation to FIGS. 1
`to 6. FIG. 7c shows a basic signal contribution due to
`physiological signal and additional signal contribution due
`to ambient light. In other words, the influence of ambient
`light is quite substantial, and therefore the deviations of the
`measured values compared to the real values can be dra(cid:173)
`matic.
`
`[0068] Besides the high influence of ambient light, also
`sunlight can have a dramatic influence, e.g. if a person is
`walking through streets with relatively quick changing con(cid:173)
`ditions between sunlight and shadow. Another serious pos(cid:173)
`sibility is caused by a tree avenue when driving along the
`trees. Sunlight then is received e.g. by the pulsoximetric
`sensor at a certain frequency, which means that every time
`when passing a tree, sunlight is attenuated and between the
`trees sunlight is influencing the measurement of the pul(cid:173)
`soximetric sensor.
`
`[0069] As a consequence, it is therefore proposed to emit
`light by the LEDs not as current or continuous light but as
`pulsed light. The frequency is chosen in such a way that it
`is outside the frequency spectrum of sunlight and of ambient
`light which, according to FIG. 7b, is in the range of above
`approximately 1000 Hz. Thus, the pulsoximeter signals are
`readily discriminated from electronic and parasitic contri(cid:173)
`butions of environmental optical radiation outside the fre(cid:173)
`quency fc+/-5 Hz increasing significantly the Signal-to(cid:173)
`Noise and Signal-to-Background ratio. FIG. 8 shows the
`shift spectrum of signal to a region where there is little
`influence, e.g. of ambient light. Fa is the chosen frequency
`of the emitted light to operate the pulsoximeter sensor and
`the range between fa-5 Hz and fa+s Hz is the consequence
`of the influence of the frequency due to physiological signal.
`Therefore, as shown in FIG. 8, the frequency spectrum of
`signal at the photo diode does have a basic signal contribu(cid:173)
`tion due to physiological signal. The signal contribution
`which is shown at the top of the signal contribution due to
`physiological signal and which is due to ambient light, is
`very small and as a consequence is approximately neglect(cid:173)
`able. Any noise or sunlight within the range of 0 to 120 Hz,
`while the light beam for the pulsoximetric measurement is
`within the range of approximately fa-5 Hz to fa+S Hz, will
`not influence the measurement of the pulsoximetric sensor.
`Fa could be e.g., as mentioned, 1000 Hz which of course is
`a frequency far outside of any indoor light source, as e.g.
`halogen light, conventional light, etc. fa of course can be
`chosen at any other frequency, as e.g. 2000 Hz or even
`higher. By using light source modulation, it is even possible
`to use an additional filter removing a certain frequency
`spectrum. Looking e.g. at FIG. 9, it is possible to arrange a
`filter band pass 51 which is e.g. removing any frequencies in
`the range of 0 to 120 Hz. The respective filter is shown in
`form of the dashed line 51. As a result, we end up by a
`diagram according to FIG. 9b only showing any measure(cid:173)
`ments in the range of fa-5 Hz to fa+S Hz.
`
`[0070] Finally, after the measurements with pulse light
`have been executed, of course a reversed phase shifting or
`modulation has to be executed to calculate the real values of
`the Pulsoximetric measurement. Again, this reverse face
`shifting on modulation according to Lock-In technique is
`known out of the state of the art.
`
`[0071] Again, it is of course possible to combine the light
`source modulation as described with reference to FIGS. 8
`and 9 with any of the prior means such as the sensor
`architecture, as shown with respect to FIGS. 5 and 6 and
`with beam shaping optics, as described in FIG. 4.
`
`[0072] By using one of the proposed devices or methods,
`respectively, according to the present invention or a com(cid:173)
`bination thereof, it is possible to use pulsoximetric measure(cid:173)
`ment or monitoring to survey the health condition of a
`
`Petitioner Apple Inc. – Ex. 1009, p. 21
`
`

`

`US 2005/0049468 Al
`
`Mar. 3, 2005
`
`5
`
`person or an animal which is mobile. In other words,
`pulsoximetric measurement is not restricted for use in, e.g.,
`a hospital but can also be used, if a person is travelling, is
`staying at home, etc. Furthermore, it is also possible to study
`health conditions of animals li