CA1282251C - Optical fiber transducer driving and measuring circuit and method for using same - Google Patents
Optical fiber transducer driving and measuring circuit and method for using sameInfo
- Publication number
- CA1282251C CA1282251C CA000522732A CA522732A CA1282251C CA 1282251 C CA1282251 C CA 1282251C CA 000522732 A CA000522732 A CA 000522732A CA 522732 A CA522732 A CA 522732A CA 1282251 C CA1282251 C CA 1282251C
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- CA
- Canada
- Prior art keywords
- energy
- reflected
- bursts
- same
- transmitted
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000013307 optical fiber Substances 0.000 title claims abstract description 20
- 238000000034 method Methods 0.000 title claims abstract description 6
- 239000000835 fiber Substances 0.000 claims abstract description 44
- 230000003287 optical effect Effects 0.000 claims abstract description 21
- 230000005540 biological transmission Effects 0.000 claims abstract description 15
- 238000000926 separation method Methods 0.000 claims abstract 7
- 238000012360 testing method Methods 0.000 claims description 25
- 239000008280 blood Substances 0.000 claims description 24
- 210000004369 blood Anatomy 0.000 claims description 22
- 238000005259 measurement Methods 0.000 claims description 20
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical group [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 17
- 229910052760 oxygen Inorganic materials 0.000 claims description 17
- 239000001301 oxygen Substances 0.000 claims description 17
- 230000003111 delayed effect Effects 0.000 claims description 2
- 230000005284 excitation Effects 0.000 claims 5
- 238000002834 transmittance Methods 0.000 claims 1
- 230000002457 bidirectional effect Effects 0.000 abstract description 4
- 238000001514 detection method Methods 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 7
- 102000001554 Hemoglobins Human genes 0.000 description 5
- 108010054147 Hemoglobins Proteins 0.000 description 5
- 238000004364 calculation method Methods 0.000 description 3
- 239000003365 glass fiber Substances 0.000 description 3
- 230000017531 blood circulation Effects 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 210000003743 erythrocyte Anatomy 0.000 description 2
- 238000005534 hematocrit Methods 0.000 description 2
- 238000006213 oxygenation reaction Methods 0.000 description 2
- 101100243025 Arabidopsis thaliana PCO2 gene Proteins 0.000 description 1
- 238000012935 Averaging Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000000747 cardiac effect Effects 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 150000002926 oxygen Chemical class 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 230000000541 pulsatile effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000002792 vascular Effects 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
- A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
- A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/314—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths
- G01N2021/3181—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths using LEDs
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/06—Illumination; Optics
- G01N2201/062—LED's
- G01N2201/0621—Supply
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/08—Optical fibres; light guides
Abstract
ABSTRACT
Disclosed is an optical fiber transducer system with energy generating means for transmitting pulsing energy at various frequencies to bidirectional couplers for each frequency. The couplers record the intensity and further transmit the pulsing energy to a wavelength multiplexer/demultiplexer. The wavelength multiplexer/demultiplexer combines the plurality of energy supply means into a single output for an optic fiber which includes an optical delay sufficient to time separate the pulsing waves of energy. Reflected energy is transmitted back through the same wavelength multiplexer/demultiplexer, bidirectional coupler so that the recorded intensity of transmission and reflectance are comparable without system influence.
A method is also shown for use of an optical fiber system including the components set forth and the system requires the generation and combination of the various frequencies of energy in a multiplexer/demultiplexer, the delay for time separation and the detection in a bidirectional coupler of transmitted and reflected energy.
Disclosed is an optical fiber transducer system with energy generating means for transmitting pulsing energy at various frequencies to bidirectional couplers for each frequency. The couplers record the intensity and further transmit the pulsing energy to a wavelength multiplexer/demultiplexer. The wavelength multiplexer/demultiplexer combines the plurality of energy supply means into a single output for an optic fiber which includes an optical delay sufficient to time separate the pulsing waves of energy. Reflected energy is transmitted back through the same wavelength multiplexer/demultiplexer, bidirectional coupler so that the recorded intensity of transmission and reflectance are comparable without system influence.
A method is also shown for use of an optical fiber system including the components set forth and the system requires the generation and combination of the various frequencies of energy in a multiplexer/demultiplexer, the delay for time separation and the detection in a bidirectional coupler of transmitted and reflected energy.
Description
~8'~251 , ~
, - ;
1' sAcKGRouND OF THE INVENTION
; '.
Field: -This invention relates to a catheter instrument which measures physiological parameters of blood while same is ' located inside the human blood stream. The technique is made ~-feasible by means of an elongated optical fiber transducer which in a well-known manner transmits light into the blood and ~
` carries the reflectance of that light back to the instrument 'F, from which it was transmitted.
State of the Art:
Devices for performing such measurements are known as . ~5 oximeters and same are disclosed in the Shaw United States ,`
; Patents 3,638,640; 3,847,483; 4,114,604; 4,295,470; 4,416,285;
- 15 4,322,164 and Vurek United States Patent 3,799,672 and `~
Heinenmann United States Patent 4,447,150 among others. These patents deal primarily with measurement of oxygen saturation in ; the blood. Oxygen saturation is the relative amount of , oxygenated hemoglobin in all of the hemoglobin of the blood i 20 stream. Hemoglobin is packed in bloconcave disks of shaped red r-blood cells having a diameter of approximately 10 micrometers. --~
Whole blood has a density of about 5 million red blood cells per cubic millimeter. Since the red blood cells both scatter !'~
and transmit the incident radiant energy, the differential 25 absorptio~ by oxygenated and non-oxygenated hemoglobin of the `-radiant energy transmitted through the blood gives a basis for oxygen saturation measurement. It can be seen that an optical fiber catheter transmits light to the position of interest within the flowing blood stream and a return fiber optic light ~-30 guide conducts the reflected light from the blood stream back ~;
to a photo detector.
When blood in a human body is the test medium, there are a number of problems with measuring oxygen saturation which !`','' ,r ~-'' , arise. These problems are fully detailed in the aforesaid patents. Briefly, however, the transducer itself introduces errors due to the two fiber optics connected to the detector ;~-; system used to measure the light transmitted and reflected. In ~ -addition to this, the blood flow is pulsatile and ,as such the conditions to be measured are constantly fluctuating. Previous 5'', ; mathematical compensations or changes in hematocrit blood flow ~-velocity, pH, PCO2, and the like introduce errors into the oxygen saturation measurement. Similarly, variations in osmolarity and in transmissivity of the two optical fibers is also present and can result in influencin~ the ultimate measurement.
Several wavelengths are necessary in order to make measurement. That is to say that, light must be transmitted to 15 the oxygenated hemoglobin at a minimum of two different `r;~
wavelengths and the reflectance of those wavelengths when ~`
compared with the light transmitted gives the oxygen saturation .
in accordance with the following equation:
C5 A A,l~ A t As explained in the Shaw United States Patent 4,114,6~4, oxygen ~ -saturation is a function of the ratios of light intensity measurement of the several wavelengths.
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128X2~;1 SUMMARY OF THE INVENTION
The present invention is an advancement in the art of -blood oxygen saturation measuring instruments. Inlparticular, ~-~
it is involved with the arrangement of a single transducer fiber optic element and the related circuitry. The system herein recognizes that transmitting and receiving an optical 2',':
signal must be accurate enough to give repeatable readings of blood oxygenation. Problems with non-uniform attenuation `~~
affects for the various wavelengths, variations in the output from the light sources and weak optical return signals have in the past caused considerable difficulty.
The preferred system has disposable and non-disposable sections. The disposable section is a llrge core approximately 200 micrometers, single glass fiber with ~ suitable connector. :r~
The distal end of the fiber need not be polished to any stringent specification. The multiple wavelengths of light are transmitted and received through that fiber optic element. .
This is enabled by the heart of the system which is a fiber ~
optic bi-directional coupler for each wavelength and an optical ~:
20 fiber wavelength multiplexer/demultiplexer for combining all of the wavelengths. To obtain instantaneous measurements, the 2'~
system operates by using a series of pulsed signals. This `~
eliminates problems with changes as an instantaneous ~`
measurement is obtained from each pulse.
For a given pulse, the source of the timing is a computer or similar electronic device which sends a signal to trigger the transmitted light source through the bi-directional coupler. This is done simultaneously for the several ~-wavelengths or color frequencies. A 100 nanosecond light 30 signal is generated and by means of the cross-talk in the 2-',' bidirectional coupler a detector measures the relative intensity of the energy to be transmitted, and that measurement is stored in sample and hold circuitry. Since there are a .
.
lX8-~251 several color frequencies, the generated pulses to be transmitted from each light source are combined into a single glass fiber by the wavelength multiplexer/demultiplexer from which they travel through a fiber optic delay coil of about 25 meters to thereby separate the timing between the transmitted and reflected pulses.
These signals are then connected and transmitted through the disposable section of the system. That is, the fiber optic, in a catheter in a living human being. The pulsed light reflected from the blood travels the same path but in reverse to the same detector which measures the intensity of the original burst of energy. The reflected signal intensity ~rom the detector is normalized by dividing same by the originally pulsed signal intensity. Since the same detector is used for measuring intensity of transmission and reflectance, and the same fiber optic is used Eor the various wavelengths, no error or differences are introduced by these components. Moreover, ~
since the electronics perform the calculation of oxygen sensor ~-saturation on the ratio of transmitted reflected intensities, variations in the original intensity of the transmitted signal are automatically taken into account.
There are numerous advantages to this arrangement.
Because there is only a single fiber optic, a larger fiber can be used but its overall size will be smaller than that used in i~`
25 a two or three fiber optic system, and the use of a single ,`
fiber enhances a strong return signal. Moreover, the electronics necessary for driving and measuring the trans-mission and reflectance can be compact. It can be seen that since only one fiber optic is used, bending losses, coupling !''`'`
30 losses, fiber defects, and the like are the same for each of , -the wavelengths transmitted and reflected through that single ~ ~
fiber. The only material that treats the various wavelengths ~ -differently is the test medium or blood. In the algorithm used '~'.
, ;, ~' '' .
~28225~ :
for calculating oxygen saturation, the percent reflected signals of each wavelength are divided into each other. In that calculation, the common errors are cancelled. However r wavelength sensitivity affects of the blood or test medium are not cancelled. For all the foregoing reasons, the assembly of the disposable or fiber optic portion becomes much less critical, and once the main electronic circuitry is calibrated, ~- it should not be necessary to recalibrate for each disposable ~:-,~ used. That is to say that, it is merely the differences in the10 reflection of energy from the test medium which is of interest and not the myriad of other factors which normally affect these l~ ~
~'? `.:
types of instruments.
The pulse technique used for making the measurement assures precision by averaging a large number of readings and ' 15 normalizing the signal to cancel the affects of non-consistent source intensities. 8y use of a glass fiber attenuation losses ~, in the 25 meter delay coil are minimized.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a blocked diagram showing the relative 20 relationship of the electronic components of an oxygen , , .
saturation sensor system, and i~ Figure 2 is a time line diagram showing the relative ~;
spacing within a period of time of the events necessary to take ~r.
J one reading. Because of the high speed of this system, 1,000 ' 25 readings can be taken per second and averaged thereby updating -. the output every second. ~-DETAILED DESCRIPTION OF THE DRAWINGS
While a specific preferred embodiment for measurement of ~;
oxygen saturation in blood is shown and disclosed herein, those ~`
30 skilled in the art will no doubt appreciate that dep,ending upon what is sought to be measured in a partlcular test medium the wavelength selected, the number of wavelengths used, the ': . .
.. ~.. , ~ .
~.
, . .
' :
.
~82251 particular construction of the fiber optic, the kind of analysis circuitry applied and the like can be varied.
Therefore, the description here is by way of example in connec-tion with one test medium and one factor to be measured therein; and by no means should the details of the preferred construction be considered as necessary for practicing the :
invention.
igure 1 is a blocked diagram showing the electronic -`
circuitry ~or the system with all of the connections between the various components. In addition to which the reusable and disposable portions of the system are separated by vertical ! dotted line "A" provided between the portions of the system.
! In explaining the electronic circuitry of the reusable portion ,;
of the system various components thereof will first be outlined and their selative functions explained. Thereafter, the connections between those functioning components will be explained in detail. ~.
The timing for the system is established by the computer , 11 which sets the frequency for the pulsed signals and all of the calculation for the received data. The computer 11 ...
includes a readout lla which could be in the form of a visible ~- -screen or a printer or both but is not shown or described herein as skilled artisans will know how same can be applied. s It will be noted that the computer 11 is connected to peak ~.
i 25 sample and hold circuits 12, 13, 14 and 15 for several wavelength frequencies (only two are shown in Figur,e 1). One 1~
is designated as low and the other is designated~as high, it ~:
should be appreciated that as many peak sample and hold circuits could, as are necessary, be used for the number of ~,s. . .
; 30 wavelengths required. There are peak sample and hold circuits ' 12, 13, 14, 15, etc. for transmission and reflectance for each p'-~
color frequency or wavelength of energy. A trigger signal of .
1282ZSl the required frequency is sent from the computer 11 to a driver power supply 16 which generates timed bursts of power of the given frequency to an LED source. Detector amplifiers 17 or 18 receive a fixed percentage of the energy emitted by the LED ~`~
source. The relative level of energy in the original burst from the LED is, therefore, measured and sent to its peak sample and hold 12, 13, lg, or 15 for storage. The detector 17 or 18 also includes an amplifier which increases the signal.
For each of the color frequencies used, there is a detector amplifier 17 or 18. `
A preferred fiber-optic chassis is made by the ~aptron Corporation of Palo Alto, California and is described as FOMD-04. This chassis contains bL-directional couplers 19, 20, etc.
and wavelength multiplexer/demultiplexer 21. While the detector amplifier 17 or 18 and the bi-directional coupler 19 or 20 are shown as independent components in the block diagram ;
of Figure 1, it should be appreciated by skilled artisans that devices are available and combine the functions of detector and i;:
bi-directional coupler. However, for clarity in the description and simplification of the understanding of the ~n`
various functions of the system, the block diagram shows these functions separately. In addition to that, the LED light- ~' emitting diode is mentioned as a separate part conn,ected to the '~i-driver power supply 16. In the particular Model FOMD-04, a bi-directional coupler of the Kaptron Corporation, there is an LED
; emitter and a beam divider such that the driver power supply `;
will, in accordance with the computer input, set the color ;~
frequency for powering the light emitting diode located in the `;`~
bi-directional coupler 19 or 20.By means of a beam divider, the burst of energy will be supplied not only outwardly toward the fiber optic in the catheter, but also inwardly toward the '~
detector whereby the intensity of a given emission of the light '~
emitting diode will be measured concurrently with its i;
transmission. `~
~';' lX8;~25~ ~
In accordance with the frequency established by the computer, the bi-directional coupler 19 or 20 will put out a burst of energy at 660 nm or 840 nm when same are in an oxygen -saturation measuring circuit. The bi-directional couplers 19 - 5 and 20 are connected to a wavelength division multiplexer ~
/demultiplexer 21 as shown in Figure 1. This coupler is used to combine light signals at two distinct color frequencies or wavelengths into an output to be transmitted by a singie fiber or in the reverse to split two signals on the same fiber into two separate signals or outputs depending on which direction the signal is transmitted through the wavelength division multiplexer/demultiplexer 21. It is an all-passive arrangement, and therefore, is highly reliable. Normally these devices are used for dual channel video transmission or telecom circuit conversation, i.e., four wire circuits to a single fiber. Here, however, the wavelength multiplexer/demultiplexer 21 is used to combine the color frequencies 660 nm and 840 nm so that same may be sent through a single fiber to the test medium. In the particular circumstance described herein, the r-20 fiber passes through a catheter and the test medium i5 human s blood inside a living human. Reflectance of the energy is `i received by the wavelength division multiolexer/demultiplexer 21 and split into the two color frequencies whereby same are .` -sent back to the detectors via the bi-directional couplers 19 25 and 20 so that the intenslty of the reflected signal can be 'j measured. Wavelength division multiplexers/demultiplexers are available for more than two inputs.
The output of the wavelength division multiplexer/
demultiplexer 21 is connected to a fiber optic optical delay 30 22. Optical delay 22 is, therefore, located bet~een the ; catheter 23 and the wavelength division multiplexer/demultiplexer 21. The optical delay 22 is nothing '' ~' ' , ~ '.
'-~28~251 , g more than an increased distance approximately 25 meters through which the optical signal must travel. That is to say that, the signal that has been combined by the wavelength division multiplexer/demultiplexer 21 is carried along a lengthened path whereby the time necessary for it to travel through the optical delay 22 is increased. The purpose of this time delay being to ' give enough ~ime (as will be described in connection with ~-Figure 2) to allow the electronics controlling the sample and ,;
f hold circuits sufficient time spacing between signals to ; 10 consider each burst of energy for each of the color ;
- frequencies. Beyond the optical delay 22 is the disposable portion of the optical fiber transducer system eor measuring a ; :
parameter Oe a test medium such as blood. .
In the particular circumstances of the preferred :~
. '. :
; 15 embodiment, there is a single fiber optic element about 200 um -diameter in a catheter 23. This fiber optic is obtained from ~ -Ens~gn-3ickford Optics Company and is about four feet long. It is radiation resistant and clad in hard polymer in order to ?' .
help the transmission of energy therethrough. The length of , 20 the optical delay 22 is approximately 25 meters, and when ~.
' combined with the length of the fiber optic catheter 23 the signal is delayed sufficiently to allow the measuring of both ~:.
:' ~ T, color frequencies, i.e., the reflectance and transmission ~, i without mixing either with the other. The fiber optic and '~
cathetec 23 in the preferred system are disposable. The combination of the two have an outer diameter of approximately ,.!, 0.1 inches and are designed for insertion into the vascular i~
., j. .~
' system of the human being.
In operation, light transmitted through the fiber optic 23 r:
to the test medium 24 is influenced by the test medium such ~' .,: : ~, , that reflected light returning up the fiber optic catheter 23 through the delay 22 and into the wavelength division ~ -, ... .
.. .
~: .
~;' . ~ . .
~'~8Z25~
multiplexer/demultiplexer 21 is influenced as a function of the parameter of the test medium to be measured. In the particular circumstance of oxygen saturation in blood and in accordance with description in the background and summary herein that -reflectance is a measure of the oxygen saturation of the hematocrit. In the wavelength division multiplexer/
demultiplexer 21 the color frequencies of 660nm and 840nm are split or divided and sent back to their respective bi- ~`
directional couplers 19 or 20 wherein the light passing therethrough remains distinct from the light being transmitted .-therethrough and is thereby transmitted to the detector 17 or l3 respectively where the intensity of the reflected light from the test medium is measured. Thereafter the signal is ii`~
transmitted to the peak sample in hold circuits for reflected i lS light 13 or 14 to be held until such time as the computer 11 is ~,r `
ready to receive that information and use same to calculate the ~ -difference between specific bursts of transmitted light and J~ `
reflected light. A level of saturated oxygen in the blood or any other parameter in any other test medium can be obtained in ,~iri 20 that way and that information will then be displayed on the ~`' readout lla of the computer 11. ~,,,!~
Turning now to Figure 2 which is a time diagram showing the relative relationship between the events of the system described in connection with block diagram of Figure 1, time is s' shown on the absysa and the total time shown for one cycle of the sytem is .5 microseconds. In particular, the first .1 microsecond is al~ocated for the generation of pulses at 660nm and 840 nm. The next .lS microseconds is used to measure the ;' relative intensity of the generated pulses whereby same can be ~
30 detected in the detector ampllfier 17 or 18 and stored in the ~``
peak sample and hold 12 or 15. During the next .1 microseconds ,;~
the reflected pulse is detected and the subsequent .15 '~.
Z25~L
microseconds is used for measurement of the intensity of the reflected pulses in the detector amplifier 17 and 18 and storage of same in the peak sample and hold circuits 13 and 14.
It can be seen then that the entire time for a given cycle is .5 microseconds and same is sufficiently long because of the optical delay 22 which allows time for the switching of the sample and hold circuits.
Because the wavelength division multiplexer/demultiplexer can be expanded to handle multiple (up to 20) color frequencies, the technique described here can be likewise expanded to measure multiple parameters in the test medium. In the example of measuring blood oxygenation, a third wavelength at 940nm can be added, and measurement of cardiac output can be performed using indocyanide green injection as described in the ~- -15 literature. . :
~ .
While a particular system for a parameter, oxygen saturation in blood, has been described in detail, it should be ~ `~
appreciated that the basic concept is the combination of the various frequencies into a single output for one fiber optic. i~
20 This concept permits a more compact system and eli~inates the ~
disparities introduced by several fiber optics. In additlon to ~r ,,, this, the importance of using the same detector for measuring ~`
transmitted and reflected intensity eliminates any error ~:
introduced by having more than one detector. The optical delay ;~;
25 makes this possible. Finally, the high pulse rate of the -system insures high precision. Skilled artisans will no doubt .
appreciate that other components could be used with the aforesaid concepts to achieve the results desired. With this :
in mind, the claims which follow are designed to cover the '~
30 broader concept suggested as well as the particularly preferred .`
embodiment. i-~
,. ~
~ `.
, - ;
1' sAcKGRouND OF THE INVENTION
; '.
Field: -This invention relates to a catheter instrument which measures physiological parameters of blood while same is ' located inside the human blood stream. The technique is made ~-feasible by means of an elongated optical fiber transducer which in a well-known manner transmits light into the blood and ~
` carries the reflectance of that light back to the instrument 'F, from which it was transmitted.
State of the Art:
Devices for performing such measurements are known as . ~5 oximeters and same are disclosed in the Shaw United States ,`
; Patents 3,638,640; 3,847,483; 4,114,604; 4,295,470; 4,416,285;
- 15 4,322,164 and Vurek United States Patent 3,799,672 and `~
Heinenmann United States Patent 4,447,150 among others. These patents deal primarily with measurement of oxygen saturation in ; the blood. Oxygen saturation is the relative amount of , oxygenated hemoglobin in all of the hemoglobin of the blood i 20 stream. Hemoglobin is packed in bloconcave disks of shaped red r-blood cells having a diameter of approximately 10 micrometers. --~
Whole blood has a density of about 5 million red blood cells per cubic millimeter. Since the red blood cells both scatter !'~
and transmit the incident radiant energy, the differential 25 absorptio~ by oxygenated and non-oxygenated hemoglobin of the `-radiant energy transmitted through the blood gives a basis for oxygen saturation measurement. It can be seen that an optical fiber catheter transmits light to the position of interest within the flowing blood stream and a return fiber optic light ~-30 guide conducts the reflected light from the blood stream back ~;
to a photo detector.
When blood in a human body is the test medium, there are a number of problems with measuring oxygen saturation which !`','' ,r ~-'' , arise. These problems are fully detailed in the aforesaid patents. Briefly, however, the transducer itself introduces errors due to the two fiber optics connected to the detector ;~-; system used to measure the light transmitted and reflected. In ~ -addition to this, the blood flow is pulsatile and ,as such the conditions to be measured are constantly fluctuating. Previous 5'', ; mathematical compensations or changes in hematocrit blood flow ~-velocity, pH, PCO2, and the like introduce errors into the oxygen saturation measurement. Similarly, variations in osmolarity and in transmissivity of the two optical fibers is also present and can result in influencin~ the ultimate measurement.
Several wavelengths are necessary in order to make measurement. That is to say that, light must be transmitted to 15 the oxygenated hemoglobin at a minimum of two different `r;~
wavelengths and the reflectance of those wavelengths when ~`
compared with the light transmitted gives the oxygen saturation .
in accordance with the following equation:
C5 A A,l~ A t As explained in the Shaw United States Patent 4,114,6~4, oxygen ~ -saturation is a function of the ratios of light intensity measurement of the several wavelengths.
~"'''.
~''.
: ~,,.'' ,,, :., .
~, . '.
128X2~;1 SUMMARY OF THE INVENTION
The present invention is an advancement in the art of -blood oxygen saturation measuring instruments. Inlparticular, ~-~
it is involved with the arrangement of a single transducer fiber optic element and the related circuitry. The system herein recognizes that transmitting and receiving an optical 2',':
signal must be accurate enough to give repeatable readings of blood oxygenation. Problems with non-uniform attenuation `~~
affects for the various wavelengths, variations in the output from the light sources and weak optical return signals have in the past caused considerable difficulty.
The preferred system has disposable and non-disposable sections. The disposable section is a llrge core approximately 200 micrometers, single glass fiber with ~ suitable connector. :r~
The distal end of the fiber need not be polished to any stringent specification. The multiple wavelengths of light are transmitted and received through that fiber optic element. .
This is enabled by the heart of the system which is a fiber ~
optic bi-directional coupler for each wavelength and an optical ~:
20 fiber wavelength multiplexer/demultiplexer for combining all of the wavelengths. To obtain instantaneous measurements, the 2'~
system operates by using a series of pulsed signals. This `~
eliminates problems with changes as an instantaneous ~`
measurement is obtained from each pulse.
For a given pulse, the source of the timing is a computer or similar electronic device which sends a signal to trigger the transmitted light source through the bi-directional coupler. This is done simultaneously for the several ~-wavelengths or color frequencies. A 100 nanosecond light 30 signal is generated and by means of the cross-talk in the 2-',' bidirectional coupler a detector measures the relative intensity of the energy to be transmitted, and that measurement is stored in sample and hold circuitry. Since there are a .
.
lX8-~251 several color frequencies, the generated pulses to be transmitted from each light source are combined into a single glass fiber by the wavelength multiplexer/demultiplexer from which they travel through a fiber optic delay coil of about 25 meters to thereby separate the timing between the transmitted and reflected pulses.
These signals are then connected and transmitted through the disposable section of the system. That is, the fiber optic, in a catheter in a living human being. The pulsed light reflected from the blood travels the same path but in reverse to the same detector which measures the intensity of the original burst of energy. The reflected signal intensity ~rom the detector is normalized by dividing same by the originally pulsed signal intensity. Since the same detector is used for measuring intensity of transmission and reflectance, and the same fiber optic is used Eor the various wavelengths, no error or differences are introduced by these components. Moreover, ~
since the electronics perform the calculation of oxygen sensor ~-saturation on the ratio of transmitted reflected intensities, variations in the original intensity of the transmitted signal are automatically taken into account.
There are numerous advantages to this arrangement.
Because there is only a single fiber optic, a larger fiber can be used but its overall size will be smaller than that used in i~`
25 a two or three fiber optic system, and the use of a single ,`
fiber enhances a strong return signal. Moreover, the electronics necessary for driving and measuring the trans-mission and reflectance can be compact. It can be seen that since only one fiber optic is used, bending losses, coupling !''`'`
30 losses, fiber defects, and the like are the same for each of , -the wavelengths transmitted and reflected through that single ~ ~
fiber. The only material that treats the various wavelengths ~ -differently is the test medium or blood. In the algorithm used '~'.
, ;, ~' '' .
~28225~ :
for calculating oxygen saturation, the percent reflected signals of each wavelength are divided into each other. In that calculation, the common errors are cancelled. However r wavelength sensitivity affects of the blood or test medium are not cancelled. For all the foregoing reasons, the assembly of the disposable or fiber optic portion becomes much less critical, and once the main electronic circuitry is calibrated, ~- it should not be necessary to recalibrate for each disposable ~:-,~ used. That is to say that, it is merely the differences in the10 reflection of energy from the test medium which is of interest and not the myriad of other factors which normally affect these l~ ~
~'? `.:
types of instruments.
The pulse technique used for making the measurement assures precision by averaging a large number of readings and ' 15 normalizing the signal to cancel the affects of non-consistent source intensities. 8y use of a glass fiber attenuation losses ~, in the 25 meter delay coil are minimized.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a blocked diagram showing the relative 20 relationship of the electronic components of an oxygen , , .
saturation sensor system, and i~ Figure 2 is a time line diagram showing the relative ~;
spacing within a period of time of the events necessary to take ~r.
J one reading. Because of the high speed of this system, 1,000 ' 25 readings can be taken per second and averaged thereby updating -. the output every second. ~-DETAILED DESCRIPTION OF THE DRAWINGS
While a specific preferred embodiment for measurement of ~;
oxygen saturation in blood is shown and disclosed herein, those ~`
30 skilled in the art will no doubt appreciate that dep,ending upon what is sought to be measured in a partlcular test medium the wavelength selected, the number of wavelengths used, the ': . .
.. ~.. , ~ .
~.
, . .
' :
.
~82251 particular construction of the fiber optic, the kind of analysis circuitry applied and the like can be varied.
Therefore, the description here is by way of example in connec-tion with one test medium and one factor to be measured therein; and by no means should the details of the preferred construction be considered as necessary for practicing the :
invention.
igure 1 is a blocked diagram showing the electronic -`
circuitry ~or the system with all of the connections between the various components. In addition to which the reusable and disposable portions of the system are separated by vertical ! dotted line "A" provided between the portions of the system.
! In explaining the electronic circuitry of the reusable portion ,;
of the system various components thereof will first be outlined and their selative functions explained. Thereafter, the connections between those functioning components will be explained in detail. ~.
The timing for the system is established by the computer , 11 which sets the frequency for the pulsed signals and all of the calculation for the received data. The computer 11 ...
includes a readout lla which could be in the form of a visible ~- -screen or a printer or both but is not shown or described herein as skilled artisans will know how same can be applied. s It will be noted that the computer 11 is connected to peak ~.
i 25 sample and hold circuits 12, 13, 14 and 15 for several wavelength frequencies (only two are shown in Figur,e 1). One 1~
is designated as low and the other is designated~as high, it ~:
should be appreciated that as many peak sample and hold circuits could, as are necessary, be used for the number of ~,s. . .
; 30 wavelengths required. There are peak sample and hold circuits ' 12, 13, 14, 15, etc. for transmission and reflectance for each p'-~
color frequency or wavelength of energy. A trigger signal of .
1282ZSl the required frequency is sent from the computer 11 to a driver power supply 16 which generates timed bursts of power of the given frequency to an LED source. Detector amplifiers 17 or 18 receive a fixed percentage of the energy emitted by the LED ~`~
source. The relative level of energy in the original burst from the LED is, therefore, measured and sent to its peak sample and hold 12, 13, lg, or 15 for storage. The detector 17 or 18 also includes an amplifier which increases the signal.
For each of the color frequencies used, there is a detector amplifier 17 or 18. `
A preferred fiber-optic chassis is made by the ~aptron Corporation of Palo Alto, California and is described as FOMD-04. This chassis contains bL-directional couplers 19, 20, etc.
and wavelength multiplexer/demultiplexer 21. While the detector amplifier 17 or 18 and the bi-directional coupler 19 or 20 are shown as independent components in the block diagram ;
of Figure 1, it should be appreciated by skilled artisans that devices are available and combine the functions of detector and i;:
bi-directional coupler. However, for clarity in the description and simplification of the understanding of the ~n`
various functions of the system, the block diagram shows these functions separately. In addition to that, the LED light- ~' emitting diode is mentioned as a separate part conn,ected to the '~i-driver power supply 16. In the particular Model FOMD-04, a bi-directional coupler of the Kaptron Corporation, there is an LED
; emitter and a beam divider such that the driver power supply `;
will, in accordance with the computer input, set the color ;~
frequency for powering the light emitting diode located in the `;`~
bi-directional coupler 19 or 20.By means of a beam divider, the burst of energy will be supplied not only outwardly toward the fiber optic in the catheter, but also inwardly toward the '~
detector whereby the intensity of a given emission of the light '~
emitting diode will be measured concurrently with its i;
transmission. `~
~';' lX8;~25~ ~
In accordance with the frequency established by the computer, the bi-directional coupler 19 or 20 will put out a burst of energy at 660 nm or 840 nm when same are in an oxygen -saturation measuring circuit. The bi-directional couplers 19 - 5 and 20 are connected to a wavelength division multiplexer ~
/demultiplexer 21 as shown in Figure 1. This coupler is used to combine light signals at two distinct color frequencies or wavelengths into an output to be transmitted by a singie fiber or in the reverse to split two signals on the same fiber into two separate signals or outputs depending on which direction the signal is transmitted through the wavelength division multiplexer/demultiplexer 21. It is an all-passive arrangement, and therefore, is highly reliable. Normally these devices are used for dual channel video transmission or telecom circuit conversation, i.e., four wire circuits to a single fiber. Here, however, the wavelength multiplexer/demultiplexer 21 is used to combine the color frequencies 660 nm and 840 nm so that same may be sent through a single fiber to the test medium. In the particular circumstance described herein, the r-20 fiber passes through a catheter and the test medium i5 human s blood inside a living human. Reflectance of the energy is `i received by the wavelength division multiolexer/demultiplexer 21 and split into the two color frequencies whereby same are .` -sent back to the detectors via the bi-directional couplers 19 25 and 20 so that the intenslty of the reflected signal can be 'j measured. Wavelength division multiplexers/demultiplexers are available for more than two inputs.
The output of the wavelength division multiplexer/
demultiplexer 21 is connected to a fiber optic optical delay 30 22. Optical delay 22 is, therefore, located bet~een the ; catheter 23 and the wavelength division multiplexer/demultiplexer 21. The optical delay 22 is nothing '' ~' ' , ~ '.
'-~28~251 , g more than an increased distance approximately 25 meters through which the optical signal must travel. That is to say that, the signal that has been combined by the wavelength division multiplexer/demultiplexer 21 is carried along a lengthened path whereby the time necessary for it to travel through the optical delay 22 is increased. The purpose of this time delay being to ' give enough ~ime (as will be described in connection with ~-Figure 2) to allow the electronics controlling the sample and ,;
f hold circuits sufficient time spacing between signals to ; 10 consider each burst of energy for each of the color ;
- frequencies. Beyond the optical delay 22 is the disposable portion of the optical fiber transducer system eor measuring a ; :
parameter Oe a test medium such as blood. .
In the particular circumstances of the preferred :~
. '. :
; 15 embodiment, there is a single fiber optic element about 200 um -diameter in a catheter 23. This fiber optic is obtained from ~ -Ens~gn-3ickford Optics Company and is about four feet long. It is radiation resistant and clad in hard polymer in order to ?' .
help the transmission of energy therethrough. The length of , 20 the optical delay 22 is approximately 25 meters, and when ~.
' combined with the length of the fiber optic catheter 23 the signal is delayed sufficiently to allow the measuring of both ~:.
:' ~ T, color frequencies, i.e., the reflectance and transmission ~, i without mixing either with the other. The fiber optic and '~
cathetec 23 in the preferred system are disposable. The combination of the two have an outer diameter of approximately ,.!, 0.1 inches and are designed for insertion into the vascular i~
., j. .~
' system of the human being.
In operation, light transmitted through the fiber optic 23 r:
to the test medium 24 is influenced by the test medium such ~' .,: : ~, , that reflected light returning up the fiber optic catheter 23 through the delay 22 and into the wavelength division ~ -, ... .
.. .
~: .
~;' . ~ . .
~'~8Z25~
multiplexer/demultiplexer 21 is influenced as a function of the parameter of the test medium to be measured. In the particular circumstance of oxygen saturation in blood and in accordance with description in the background and summary herein that -reflectance is a measure of the oxygen saturation of the hematocrit. In the wavelength division multiplexer/
demultiplexer 21 the color frequencies of 660nm and 840nm are split or divided and sent back to their respective bi- ~`
directional couplers 19 or 20 wherein the light passing therethrough remains distinct from the light being transmitted .-therethrough and is thereby transmitted to the detector 17 or l3 respectively where the intensity of the reflected light from the test medium is measured. Thereafter the signal is ii`~
transmitted to the peak sample in hold circuits for reflected i lS light 13 or 14 to be held until such time as the computer 11 is ~,r `
ready to receive that information and use same to calculate the ~ -difference between specific bursts of transmitted light and J~ `
reflected light. A level of saturated oxygen in the blood or any other parameter in any other test medium can be obtained in ,~iri 20 that way and that information will then be displayed on the ~`' readout lla of the computer 11. ~,,,!~
Turning now to Figure 2 which is a time diagram showing the relative relationship between the events of the system described in connection with block diagram of Figure 1, time is s' shown on the absysa and the total time shown for one cycle of the sytem is .5 microseconds. In particular, the first .1 microsecond is al~ocated for the generation of pulses at 660nm and 840 nm. The next .lS microseconds is used to measure the ;' relative intensity of the generated pulses whereby same can be ~
30 detected in the detector ampllfier 17 or 18 and stored in the ~``
peak sample and hold 12 or 15. During the next .1 microseconds ,;~
the reflected pulse is detected and the subsequent .15 '~.
Z25~L
microseconds is used for measurement of the intensity of the reflected pulses in the detector amplifier 17 and 18 and storage of same in the peak sample and hold circuits 13 and 14.
It can be seen then that the entire time for a given cycle is .5 microseconds and same is sufficiently long because of the optical delay 22 which allows time for the switching of the sample and hold circuits.
Because the wavelength division multiplexer/demultiplexer can be expanded to handle multiple (up to 20) color frequencies, the technique described here can be likewise expanded to measure multiple parameters in the test medium. In the example of measuring blood oxygenation, a third wavelength at 940nm can be added, and measurement of cardiac output can be performed using indocyanide green injection as described in the ~- -15 literature. . :
~ .
While a particular system for a parameter, oxygen saturation in blood, has been described in detail, it should be ~ `~
appreciated that the basic concept is the combination of the various frequencies into a single output for one fiber optic. i~
20 This concept permits a more compact system and eli~inates the ~
disparities introduced by several fiber optics. In additlon to ~r ,,, this, the importance of using the same detector for measuring ~`
transmitted and reflected intensity eliminates any error ~:
introduced by having more than one detector. The optical delay ;~;
25 makes this possible. Finally, the high pulse rate of the -system insures high precision. Skilled artisans will no doubt .
appreciate that other components could be used with the aforesaid concepts to achieve the results desired. With this :
in mind, the claims which follow are designed to cover the '~
30 broader concept suggested as well as the particularly preferred .`
embodiment. i-~
,. ~
~ `.
Claims (14)
1. An optical fiber transducer system for measurement of a parameter of a test medium by transmitting energy and comparing same to energy reflected by the medium comprising:
a first energy source connected to a power supply for emitting bursts of energy at a predetermined color frequency;
a second energy source connected to said power supply for emitting bursts of energy at another predetermined color frequency;
a wavelength division multiplexer/demultiplexer associated with said first and second energy sources for receipt of said bursts of energy, for combination of same and further transmission thereof while maintaining their discrete color frequencies and for separation of the reflective energy of same into individual channels of each color frequency upon return of said bursts of energy;
a fiber optic means attached to said wavelength division multiplexer/demultiplexer for first receipt of said combined bursts of energy and transmission of same to and for the carrying of the reflectance of same from a test medium;
an optical delay means associated with said fiber optic means for extending the distance of said transmission and said reflectance in order to permit time separation of adjacent bursts of transmitted and reflected energy for purposes of discrete measurement of same;
detector means independently associated respectively with each of said first and second energy sources for initially measuring and storing the level of said bursts of energy during transmission and the subsequent measuring and storing of said reflected energy of said same burst of energy for comparison of each, and computer means for establishing the timing of said bursts of energy and receipt of said detected level of energy transmitted and reflected to establish the actual percent reflected for a specific burst of energy for each of said first and second predetermined color frequencies.
a first energy source connected to a power supply for emitting bursts of energy at a predetermined color frequency;
a second energy source connected to said power supply for emitting bursts of energy at another predetermined color frequency;
a wavelength division multiplexer/demultiplexer associated with said first and second energy sources for receipt of said bursts of energy, for combination of same and further transmission thereof while maintaining their discrete color frequencies and for separation of the reflective energy of same into individual channels of each color frequency upon return of said bursts of energy;
a fiber optic means attached to said wavelength division multiplexer/demultiplexer for first receipt of said combined bursts of energy and transmission of same to and for the carrying of the reflectance of same from a test medium;
an optical delay means associated with said fiber optic means for extending the distance of said transmission and said reflectance in order to permit time separation of adjacent bursts of transmitted and reflected energy for purposes of discrete measurement of same;
detector means independently associated respectively with each of said first and second energy sources for initially measuring and storing the level of said bursts of energy during transmission and the subsequent measuring and storing of said reflected energy of said same burst of energy for comparison of each, and computer means for establishing the timing of said bursts of energy and receipt of said detected level of energy transmitted and reflected to establish the actual percent reflected for a specific burst of energy for each of said first and second predetermined color frequencies.
2. The optical fiber transducer system of Claim 1 wherein said color frequencies are about 660 nm and 840 nm respectively and the test medium is blood and the measured parameter is oxygen saturation.
3. The optical fiber transducer system of Claim 1 wherein said fiber optic means is in series with said optical delay means and the combination of same is long enough to allow the time necessary for said computer means to determine the transmitted and reflected energy by time delay separation between the two resulting from the increased distance of travel necessary for the transmitted and reflected energy pulses.
4. The optical fiber transducer system of Claim 1 wherein said computer means triggers said power supply to establish said bursts of energy for the transmitted wave and compares that energy with the energy received from the reflectance of that wave.
5. A method for measurement of a parameter of a test medium by transmitting energy and comparing same to energy reflected by the medium comprising the following steps:
triggering a signal for a power supply in accordance with at least two color frequencies of timed pulses, generating a pulsing power supply of energy at predetermined color frequencies in response to said triggering of energy, emitting bursts of light energy at said predetermined color frequencies in response to said pulsing power supply, detecting said bursts of light at said predetermined color frequencies as same are transmitted and storing information relative to same, multiplexing said predetermined transmitted light bursts of predetermined color frequencies into a common output, imposing a delay upon said common transmitted distinct color frequencies, sending said delayed common output along a fiber optic to a test medium, receiving said color frequencies reflected from a test medium through said fiber optic, detecting and storing said reflected color frequencies with the same detector, and providing the detected information JJ:
regarding the transmitted and reflected color frequencies to a computer so that the percentage of reflected energy can be calculated.
triggering a signal for a power supply in accordance with at least two color frequencies of timed pulses, generating a pulsing power supply of energy at predetermined color frequencies in response to said triggering of energy, emitting bursts of light energy at said predetermined color frequencies in response to said pulsing power supply, detecting said bursts of light at said predetermined color frequencies as same are transmitted and storing information relative to same, multiplexing said predetermined transmitted light bursts of predetermined color frequencies into a common output, imposing a delay upon said common transmitted distinct color frequencies, sending said delayed common output along a fiber optic to a test medium, receiving said color frequencies reflected from a test medium through said fiber optic, detecting and storing said reflected color frequencies with the same detector, and providing the detected information JJ:
regarding the transmitted and reflected color frequencies to a computer so that the percentage of reflected energy can be calculated.
6. An optical fiber transducer system for measurement of a parameter of a test medium by transmitting energy and comparing same to energy reflected by the medium comprising:
one energy source connected to a power supply for emitting bursts of energy at a predetermined color frequency;
at least another energy source connected to said power supply for emitting bursts of energy at another predetermined color frequency;
a wavelength division multiplexer/demultiplexer associated with said one and another energy sources for receipt of said bursts of energy, for combination of same and further transmission thereof while maintaining their discrete color frequencies and for separation of the reflective energy of same into individual channels of each of said color frequencies upon return of said bursts of energy;
an optical delay means attached to said wavelength division multiplexer/demultiplexer for extending the distance of travel for said bursts of energy in order to permit time separation of adjacent bursts of transmitted and reflected energy for purposes of discrete measurement of same;
a fiber optic associated with said optical delay means for first receipt of said combined bursts of energy from said multiplexer/demultiplexer and transmission of same to and for return of the reflectance of same from a test medium;
detector means independently associated respectively with each of said one and another energy sources for initially measuring and storing the level of said bursts of energy sent during transmission and the subsequent measuring and storing of said reflected energy of said same burst of energy for comparison of each, and computer means for establishing the timing of said bursts of energy and receipt of said detected level of energy transmitted and reflected to establish the actual percent reflected for a specific burst of energy for each of said one and another predetermined color frequencies.
one energy source connected to a power supply for emitting bursts of energy at a predetermined color frequency;
at least another energy source connected to said power supply for emitting bursts of energy at another predetermined color frequency;
a wavelength division multiplexer/demultiplexer associated with said one and another energy sources for receipt of said bursts of energy, for combination of same and further transmission thereof while maintaining their discrete color frequencies and for separation of the reflective energy of same into individual channels of each of said color frequencies upon return of said bursts of energy;
an optical delay means attached to said wavelength division multiplexer/demultiplexer for extending the distance of travel for said bursts of energy in order to permit time separation of adjacent bursts of transmitted and reflected energy for purposes of discrete measurement of same;
a fiber optic associated with said optical delay means for first receipt of said combined bursts of energy from said multiplexer/demultiplexer and transmission of same to and for return of the reflectance of same from a test medium;
detector means independently associated respectively with each of said one and another energy sources for initially measuring and storing the level of said bursts of energy sent during transmission and the subsequent measuring and storing of said reflected energy of said same burst of energy for comparison of each, and computer means for establishing the timing of said bursts of energy and receipt of said detected level of energy transmitted and reflected to establish the actual percent reflected for a specific burst of energy for each of said one and another predetermined color frequencies.
7. The optical fiber transducer system of Claim 6 wherein there are a plurality of said energy sources.
8. The optical fiber transducer system of Claim 6 wherein said fiber optic is in series with said optical delay means and the combination of same is long enough to allow the time necessary for said computer means to determine the transmitted and reflected energy by time delay separation between the transmitted and reflected energy of a single burst as a result of the increased distance of travel imposed by said optical delay means.
9. The optical fiber transducer system of Claim 6 wherein said computer means triggers said power supply to establish said bursts of energy for the transmitted wave and compares that energy with the energy received from the reflectance of that wave resulting from that same burst.
10. An optical fiber excitation and measuring system comprising: a plurality of energy supplying means for generating and transmitting pulsing energy at various frequencies each said means connected to a bi-directional coupler for detecting the intensity and further transmitting said pulsing energy to a wavelength multiplexer/demultiplexer for combining said plurality of pulsating energy waves into a single output; optic means including an optical delay sufficient to separate and extend the length of time for travel of said combined pulsating wave energy and a disposable fiber optic connected to said optical delay and for placement into a test medium thereby transmitting said pulsating energy waves to and from the test medium.
11. An optical fiber excitation and measuring system as defined in claim 10 wherein said wavelength multiplexer/
demultiplexer receives reflected energy through said disposable fiber optic and separates said plurality of pulsating energy waves into discrete wavelengths and transmitted to said bi-directional coupler.
demultiplexer receives reflected energy through said disposable fiber optic and separates said plurality of pulsating energy waves into discrete wavelengths and transmitted to said bi-directional coupler.
12. An optical fiber excitation and measuring system as defined in claim 10 wherein said bi-directional coupler detects reflected pulsating energy waves.
13. An optical fiber excitation and measuring system as defined in claim 10 wherein said bi-directional coupler is situated between said plurality of power supplies and said multiplexer/demultiplexer so that said pulsing energy is detected upon transmittance and again upon reflectance.
14. An optical fiber excitation and measuring system as defined in claim 13 wherein said detected energy is compared in a computer with capacity to store, associate and read out the measurement of said energy.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US797,299 | 1985-11-12 | ||
| US06/797,299 US4936679A (en) | 1985-11-12 | 1985-11-12 | Optical fiber transducer driving and measuring circuit and method for using same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1282251C true CA1282251C (en) | 1991-04-02 |
Family
ID=25170439
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000522732A Expired - Fee Related CA1282251C (en) | 1985-11-12 | 1986-11-12 | Optical fiber transducer driving and measuring circuit and method for using same |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4936679A (en) |
| EP (1) | EP0222555B1 (en) |
| JP (1) | JPS62156542A (en) |
| AU (1) | AU586296B2 (en) |
| CA (1) | CA1282251C (en) |
| DE (1) | DE3681117D1 (en) |
| ES (1) | ES2026132T3 (en) |
| MX (1) | MX164286B (en) |
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|---|---|---|---|---|
| CA971768A (en) * | 1972-02-01 | 1975-07-29 | Robert F. Shaw | Oximeter and method |
| US3892468A (en) * | 1973-09-28 | 1975-07-01 | Bell Telephone Labor Inc | Optical scanner utilizing organ arrays of optical fibers |
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| US4114604A (en) * | 1976-10-18 | 1978-09-19 | Shaw Robert F | Catheter oximeter apparatus and method |
| JPS5524004A (en) * | 1978-06-22 | 1980-02-20 | Minolta Camera Kk | Oxymeter |
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| US4476870A (en) * | 1982-03-30 | 1984-10-16 | The United States Of America As Represented By The Department Of Health And Human Services | Fiber optic PO.sbsb.2 probe |
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| US4622974A (en) * | 1984-03-07 | 1986-11-18 | University Of Tennessee Research Corporation | Apparatus and method for in-vivo measurements of chemical concentrations |
| AU571369B2 (en) * | 1985-02-28 | 1988-04-14 | Boc Group, Inc., The | Oximeter |
-
1985
- 1985-11-12 US US06/797,299 patent/US4936679A/en not_active Expired - Lifetime
-
1986
- 1986-10-29 ES ES198686308436T patent/ES2026132T3/en not_active Expired - Lifetime
- 1986-10-29 DE DE8686308436T patent/DE3681117D1/en not_active Expired - Lifetime
- 1986-10-29 EP EP86308436A patent/EP0222555B1/en not_active Expired
- 1986-11-10 MX MX4311A patent/MX164286B/en unknown
- 1986-11-12 CA CA000522732A patent/CA1282251C/en not_active Expired - Fee Related
- 1986-11-12 AU AU65077/86A patent/AU586296B2/en not_active Ceased
- 1986-11-12 JP JP61269487A patent/JPS62156542A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0222555A2 (en) | 1987-05-20 |
| ES2026132T3 (en) | 1992-04-16 |
| AU6507786A (en) | 1987-05-14 |
| AU586296B2 (en) | 1989-07-06 |
| DE3681117D1 (en) | 1991-10-02 |
| US4936679A (en) | 1990-06-26 |
| EP0222555B1 (en) | 1991-08-28 |
| EP0222555A3 (en) | 1988-03-30 |
| JPS62156542A (en) | 1987-07-11 |
| MX164286B (en) | 1992-07-30 |
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