Sept. 26, 1944.
`
`G. A. MILLIKAN
`
`OXYGEN METER
`
`2,358,992
`
`Filed June 28, 1941
`
`2 Sheets-Sheet 1
`
`
`
`5
`
`: MHALDT
`
`ZO
`
`3 VA
`SZ
`
`ir
`
`6 g/
`
`78
`
`nN
`
`¢
`g
`6
`ONE
`On
`_@
`on
`0
`Sar: ee =fI BS
`22
`
`iNf
`
`BO
`
`IZ
`
`TP
`
`INVENTOR
`14. ANMillikan
`
`Glent
`BY
`
`ATTORNEY
`
`IPR2018-00294
`Apple Inc. EX1015 Page 1
`
`IPR2018-00294
`Apple Inc. EX1015 Page 1
`
`

`

`Sept. 26, 1944.
`
`G. A. MILLIKAN
`OXYGEN METER
`
`2,358,992
`
`Filed June 28, 1941
`
`2 Sheets-Sheet 2
`
`
`>»
`
`
`
`cdSS
`
`AES
`
`
`
` LigA,
`
`Oxyhemoglobti
`
`ft
`
`
`LoLg3.
`
`
`
`aLightabsorption
`
`
`
`O7 Ligaytlhoftransinttledtight
` aeOE “INVENTOR 7.
`adie sue
`Glenn AMMlkan
`
`Wave length & GIVIPreCAIV Piro.
`
`
`ATTORNEY
`
`IPR2018-00294
`Apple Inc. EX1015 Page 2
`
`IPR2018-00294
`Apple Inc. EX1015 Page 2
`
`

`

`Patented Sept. 26, 1944
`
`2,358,992
`
`UNITED STATES PATENT OFFICE
`
`10
`
`18
`
`20
`
`25
`
`30
`
`2,858,992
`_
`OXYGEN METER
`Glenn A, Millikan, New York, N. Y.
`Application June 28,.1941, Serial No. 400,285
`(Cl. 88—14)
`11 Claims.
`scale which will suit that subject within a prac-
`This invention relates to colorimetry, and is
`tical degree of accuracy; and then by direct read-
`particularly useful in determining the amount of
`ings indicates on that scale the percentage of
`oxygen in the blood.
`It provides a means by
`oxygen content
`in the blood. The particular
`which the depletion of oxygen—as in the case of.
`scientific principles by which this is accomplished
`aviators flying at high altitudes or patients under
`will be described more in detail later in the speci-
`anesthesia—can be continuously observed,
`s0
`fication.
`that appropriate measures may be taken before
`In the drawings forming part of this specifica-
`the danger point is reached. Various other appli-
`tion, Fig. 1 is a.schematic view illustrating the
`cations in colorimetry will become apparent to
`general principles of a typical device.
`those skilled in the art. The objects of the inven-
`Fig. 2 is a side elevation view mostly in section
`tion are to provide a simple and practical device
`of a light sensitive cell and lamp unit which may
`for purposes such as those stated;
`to make it
`be clamped to the ear or other desired specimen.
`_ applicable to persons having different physical
`Fig. 3 is a front view of one form of the red
`characteristics:
`to permit frequent checking of
`and green filters used with the light sensitive
`the accuracy of the instrument; to protect the
`cell.
`person being tested from pain or discomfort; to
`Pig. 4 is a chart showing the comparative light
`give greater ease and accuracy of operation; and
`absorption of hemoglobin when high in oxygen
`in general to improve the performance, conven-
`and when reduced in oxygen, from which char-
`ience and utility of stich devices.
`acteristics the function of the green ‘Alter
`is
`The general principles upon which the sappa-
`deduced.
`ratus is based are as follows.
`It has long been
`Fig. 5 shows the logarithmic curves of trans-
`recognized that
`the hemoglobin of
`the blood
`mitted light and oxygen saturation for various
`changes color from red toward blue as the oxygen
`types of ears, labelled “thick ear,” “medium. ear”
`content diminishes.
`In recent years colorimeter
`and “thin ear’; from which the necessity for
`tests involving light passing thru a specimen to
`different scales for different types of ears will be
`fall on a light sensitive cell operating a galva-
`seen.
`nometer have been developed, so as to give some
`Similar reference numerals refer to similar
`means of determination independent of the mere
`parts thruout the various views.
`,
`judgment of the human eye. To calibrate the
`Referring first to Fig. 1, a light sensitive cell
`results laboratory analyses of blood samples in
`{ embodying separate units capabie of respond-
`each instance were required. In order to produce
`ing to different selected colors is placed in prox-
`a more direct reading method, and one adaptable
`imity to the specimen to be analyzed, such as the
`to persons of various physical characteristics, the
`human ear 2, thru which light from the electric
`present device uses a system of readings and
`light bulb 3 passes to energize the light sensitive
`scales by which coordinated results of sufficient
`cell f. To control the color of the light which is
`accuracy for most practical purposes can be
`to energize the celi {, color filters 4 and 4’, la-
`quickly obtained.
`belled R for red and G for green respectively, are
`A beam of light canbe passed thru a thin part
`interposed between the light 3 and the cell .
`of the body, suchas the ear or the web of a
`The light sensitive cell {
`is of the compound or
`finger, to fail upon 4 light sensitive cell operating
`multiple type, so that part of it responds only to
`a galvanometer.
`If all ears were alike, the prob-
`the light falling on it thru the green filter, and
`jem would present few difficulties. But the varia-
`another part responds only to the light falling on
`tions in thickness and texture of the tissues in
`it thru the red filter.
`‘These parts are labelled
`different individuals introduce variations in the
`R for red and G for green, and these letters are
`light transmitted quite independent of the color
`also applied to switch terminals, indicator lights,
`of the blood; so that different individuals with
`rheostats, and similar parts to be later described,
`equal proportions of oxygen in their blood may
`so that the red and green circuits can be readily
`produce quite different photo-electric readings.
`traced.
`:
`:
`The problem then is to provide a sound basis
`The cell { is therefore really two light sensitive
`for. calibration independent of such individual
`ces having a common ground wire § but other-
`peculiarities.
`:
`wise operating independently, one portion being
`In general the problem is solved in the present
`sensitive to green light and the other portion
`apparatus by providing a system which first de-
`being sensitive to red light.
`It is the well known
`termines a classification within which the indi-
`property of any light sensitive cell that when
`vidual subject falls, and selects a calibration
`
`ooen
`
`40
`
`45
`
`50
`
`55
`
`IPR2018-00294
`Apple Inc. EX1015 Page 3
`
`IPR2018-00294
`Apple Inc. EX1015 Page 3
`
`

`

`20
`
`25
`
`30
`
`45
`
`50
`
`55
`
`2 l
`
`2,858,992
`ight falls upon it an electro-motive force is gen-~
`circuit must be provided for the electric light
`erated, which is usually capable of operating a
`21 that shines on the galvanometer mirror. This
`measuring instrument such as a galvanometer,
`circuit is controlled by the switch 22, which really
`When the light thru the green filter 4’ falis on
`has only two positions, on and off; but for con-
`the corresponding portion of the cell {, the cir-
`venience of manufacture it may be provided with
`cuit is thru the conductor 6 to the terminal of
`contact points similar to the switches 1, 14 and
`the switch 1 marked G, then thru the conductor
`15, so that it may be operateg by the sameshaft:
`8 to the galvanometer 9, and back thru the
`but in the case of the switch 22 all the points
`ground wire 5 to the cell #.
`G, Z, and R are connected together so that the
`‘When the red portion of the cell | is in action,
`light 2! remains on regardless of the position of
`the light after passing thru the redfilter 4 falls
`the switch 22, unless it is in the “off” position.
`on, the corresponding portion of the cell i, gener-
`The switches 7, 14, 15 and 22, being of similar
`ating an electro-motive force in accord With the
`mechanical construction, are readily moved in
`intensity of the red light. When the switch 1 is
`unison by a single shaft 24 indicated by the broken
`turned to the terminal R,for the red circuit, the
`line, which is operated by the handle 25. When
`current flows thru the conductor 10, switch 1, and
`this handle 25 moves the switches 1, (4, (8 and 22
`conductor 8 to the galvanometer 9, and back thru
`from the “off” position to G (green), the gal-
`the ground wire § to the cell {. There are thus
`vanometer 9 is put in circuit with that portion of
`two simple alternative circuits, one energized by
`the ight sensitive cell 1 which is under the green
`red light and the other by green light, either of
`color filter 4’;
`the green indicator light
`12.
`is
`which may be read on the galvanometer §, by
`turned on; the light source 3 is turned up toa
`throwing the switch 7 to the appropriate position.
`higher intensity; and the galvanometer reading
`The point marked Z on the switch 7 is used for
`light 21 is turned on. When the handle 25 moves
`setting the zero reading of the galvanometer 9;
`the switches 7, 14, 15 and 22 to the “zero” posi-
`and the point marked O (for “oif”) is used when
`tion, the light sensitive cell circuits are discon-
`the apparatus is entirely shutoff. Since the cur-
`nected, as is the light source 3, but the gal-
`rent is generated by the direct action of the light
`vanometer light 21 remains on, so that the gal-
`falling on the light sensitive cell, no battery or
`vanometer can be set for zero reading, to give it
`other external power source is required for this
`the proper preliminary adjustment. When the
`part of the apparatus, these reading circuits being
`handle 25 moves the switches 1, 14, 15 and 22 to
`self-contained and independent of the supple-
`the R (red) position, the galvanometer is con-
`mentarycircuits now tobe described.
`:
`nected to that portion of the light sensitive cell
`To assist the operator in using the apparatus,
`energized by the light thru the red color filter 4;
`indicator lights 12 and {3 are Provided, the light
`the light source 3 is dimmed to a degree previ-
`{2 being on when the green Circuit is in use and
`ously set by the resistance 18; and the galvanom-
`the light [3 being on when the red circuit is in
`eter light 21 remains on to provide the reading
`use. These lights are operated by the switch 14,
`spot or indicator. Thus the zero setting, and the
`which has four switch points, O (off), R (red),
`readings produced by either the red or the green
`% (zero set), and G (green), similar to the switch
`1
`light are conveniently obtained, and their pres-
`ence indicated, by simultaneous switch movements
`The light source 3 which supplies the light to
`all operated by a single handle.
`the specimen 2 and light cell {, is preferably an
`The electricity for the indicator lights 12, 13,
`ordinary. light bulb of the miniature type, and
`the light source 3, and the galvanometer light 21,
`is controlled by the switch 15, which has four
`may be obtained from any suitable source indi-
`contact points similar to those of switches 7 and
`cated conventionally by the reference numeral 30,
`14, that is, marked O (off), G (green), Z (zero
`ordinary electric light lines being generally used
`set), and R (red). Light sensitive Cells are gener-
`when available.
`ally much more responsive to red rays: than to
`The light sensitive cell ( and color filters @ and
`green, and this would normally necessitate chang-
`4’ have been described as simply red and green
`ing thescale or resistance of the galvanometeror
`units set close together so as to utilize the same
`other measuring instrument.
`In order to take
`light source 3. The green filter andcell are made
`readings from both the red and green circuits
`larger in area than the red filter and cell, be-
`without changing the galvanometer, means are
`cause of the fact that-red light activates the light
`provided to reduce the intensity of the light source
`sensitive cell much more strongly than green, as
`3 when the red screen is in use; or conversely, to
`previously stated; and this difference in the green
`increase therelative intensity of the light source
`and red areas helps to bring the galvanometer
`3 when the green screenis in tse.
`readings into the same general order of magni-
`For this purpose, adjustable resistances iT and
`tude and avoids the necessity for changing the
`{8 are provided in the circuit of the light bulb
`galvanometer scale or
`resistance, particularly
`3, and are arranged so that the resistance {1,
`when this is combined with the alteration of the
`connected to the green circuit terminal G of the
`light source intensity above described.
`,
`switch 15 is less than the resistance '8, which is
`The difference between the red and green
`connected to the red circuit terminal R of the
`areas will best be seen in Fig. 2 and Fig. 3 which
`switch 15. This gives @ brighter light at 3 when
`show in greater detail a light cell unit more
`the switch 5 is at the point G of the green side,
`simply shown in Fig. 1. Referring now to Fig. 2,
`and a dimmerlight when the switch (8 is on the
`the housing 31 contains the color filters 4 and 4’
`point R of the red side. Conductors (9 lead to
`and the light sensitive cell. 1, which is conven-
`the light bulb 3. A voltmeter 20 is connected
`tionally shown in Fig. 2 and in somewhat greater.
`across the circuit of the light bulb 2 as an addi-
`detail in the front view of Fig, 3. The h
`tional means of checking the setting of that light
`31 is preferably made of hard rubber, plastic or
`if desired.
`similar smooth material so that it may be placed
`If the galvanometer: or other Treading instru-
`against the ear without discomfort; and is pro-
`ment § is of the type using a spot of light as its
`vided with an opening 32 to. admit light from
`indicator point, ag is generally the case, then a 76 the electric light bulb 3. This bulb 3 is sup
`
`-
`60
`
`65
`
`70
`
`IPR2018-00294
`Apple Inc. EX1015 Page 4
`
`IPR2018-00294
`Apple Inc. EX1015 Page 4
`
`

`

`10
`
`30
`
`ported on 8 hollow arm 33 extending from the
`housing 31, thru which the wires 19 pess to
`supply electricity to the bulb.3. The enc of the
`arm 33 extends back toward the housing 3{ and
`is provided with a threaded neck 38 on which
`is screwed a knurled ring 36 having smoothly
`rounded surfaces:on the side adjacent the hous-
`ing 31, so that it may be clamped on the human
`ear or other thin part of the body without dis-
`comfort.
`In use, the thin upper portion or shell
`of theearis slipped between the housing 3! and
`the ring 36, and the latter is then screwed up
`until it is gently clamped on the ear. The pres-
`sure should not be enough to impede the circu-
`lation, but only enough to hold the device lightly
`in place and exclude light other than that from
`the bulb 3. A gentle pressure is sufficient and
`is not uncomfortable.
`While the apparatus may be constucted with
`only one green light area and one red light area,
`it is generally desirable to construct the green
`light area in two parts connected together, with
`the relatively small red light area located in
`between, as shown in Fig. 3, where the green
`filter and cell areas are labelled G and the red
`filter and cell area is labelled R. This provides
`& more uniform distribution and guards against
`errors which might be ind.t¢-u by local varia-
`tions in brightness on one side. While such an
`arrangement is mechanically made up of three
`or more parts, in principle they are the equiva-
`lent of but two regions, since all the green areas
`are connected to the same conductor 6 and so
`act as one; and similarly, the red areas, if they
`were divided, would all act as one by being con-
`nected to the same conductor 10.
`The apparatus and the principles which have
`been described would suffice to determine blood
`color and thereby oxygen. content under most
`conditions were it not for the fact that varia-
`tions in the thickness and tissue of the ear in
`different individuals cause wide variations in the
`light transmitted thru the ear,
`irrespective of
`whether the blood in the ear is the same color.
`If all ears had the same thickness and texture, 4:
`relatively simple readings would suffice. But
`that not being the case, it is necessary to pro-
`vide means to overcome errors induced by such
`individual peculiarities.
`The present solution to this portion of the
`problem involves the following general, steps.
`(1) Providing a meansfor classifying the speci-
`mens or ears according to their physical char~
`acteristics of thickness and texture and other
`individual peculiarities affecting the transmis-
`sion of light, independent of the color. of the
`plood, so that, the classifications would not be
`affected by the oxygen content of the moment.
`(2) Having then segregated the ears into groups
`which act alike, the present invention provides
`separately calibrated scales for each group, on
`which can be correctly read the oxygen content
`of any individual in that group, at any particu-
`lar moment.
`The scientific principles on which this solution
`is based will be better understood after referring
`to Fig. 4, which is a typical chart. showing the
`light absorption of oxyhemoglobin, or blood high
`in oxygen—indicated in solid lines— as compared
`with reduced hemoglobin, or blood iow in oxygen,
`shown in broken lines, both curves being plotted.
`with light absorption as the ordinates and light
`wave length, A., that is color, as the abscissae.
`In the chart the spectrum runs from red on ‘the
`right to the blue violet on the left.
`It will be
`
`2,358,902
`seen that on the right the red ght is absorbed
`much more by the reduced hemoglobin than by
`the oxyhemoglobin, as would be expected from
`. the fact that the blood with more oxygen is
`redder in color and so transmits red light more
`freely. On the other hand, the left portions of
`the curves indicate that with the bluer light
`the oxyhemoglobin absorbs more, that is, is more
`resistant to the passage of blue light than blood
`reduced in oxygen, which is bluer.. While these
`characteristics are naturally to be expected, the
`interesting fact appears. in the-middle of. the
`curves that the two curves repeatedly crose sach
`other, with the oxyhemoglobin sometimes. above
`and sometimes below. Where they cross, the two
`curves have of course the same value; which:
`means that there are certain colors or wave
`lengths which are absorbed equally by. either
`oxyhemoblogin or reduced. hemoglobin; that is,
`that light of a certain color will be absorbed to
`the same degree regardless of whether the blood
`is high or low in oxygen. Since ‘with light of
`that color the oxygen content does not enter
`into the problem, that particular color can be
`used to measure the various other physical char-
`acteristics or peculiarities that retard the pass-
`age of light, such as thickness, texture of the
`tissues, color of the skin, etc.
`In general it may
`be said that the amount of the selected green
`light transmitted is determined almost entirely
`by the amount of blood in the ear, independent
`of how much oxygen it contains. The green
`light thus measures what may be termed the
`“blood thickness” of the ear.
`:
`While any one of
`the cross-over points of
`the two curves might be used, it is preferable
`with human subjects to use the cross-over. point
`at about 5900 A., which we have called the
`. “green”light. Using this color, which is absorbed
`40
`in the same degree with any oxygen content of
`the blood, we test out various individual ears
`and find some transmit the light rather freely,
`and others not so freely, according generally as
`they are thin or thick or vary in texture. The
`transmission of the green light, as indicated by
`the action of the light sensitive cell | on the
`galvanometer $, shows the general. resistance to
`light attributable to the personal characteristics
`of the individual, aside from the. oxygen content
`of his blood; and we use such a determination
`of the “blood thickness” of the ear to select the
`proper scale suitable for that type of person.
`Referring now to Fig. 5, which shows the oxy-
`gen saturation plotted against the logarithm of
`the transmitted light, for various types of ears
`labelled “Thick ear,” “Medium ear,” and “Thin
`ear”—it will be seen that the curves are not only
`spaced from each other, but are not parallel, that
`is, have different slopes. This means that the
`calibration curves for such different types of ears
`will be quite different; and any single scale on the
`galvanometer reading directly in terms of percent
`oxygen in the blood would not be accurate forall
`types of people.
`In practice it has been found
`that by using a reasonable numberof scales, pref-
`erably four, the oxygen content can be directly
`read with a sufficient degree of accuracy for most
`practical purposes.
`is provided
`Accordingly the galvanometer 9.
`with four separately calibrated scales labelled
`“Wafer,” ‘“Thin,”. “Medium,” and “Heavy,” as
`shown in Fig. 1, with curves running from 50% to
`100% oxygen content crossing them in a generally
`diagonal direction.
`In operating the apparatus
`these are used in the following manner.
`
`3
`
`IPR2018-00294
`Apple Inc. EX1015 Page 5
`
`35
`
`60
`
`65
`
`70
`
`75
`
`IPR2018-00294
`Apple Inc. EX1015 Page 5
`
`

`

`4
`
`'
`
`20
`
`_ 2,358,992
`First to warm up and properly dilate the blood
`changes in the lamp, voltage, lamp luminosity,
`vessels in the ear, the switches are turned to the
`and sensitivity of the light sensitive cell:
`It is
`green position, which it will be recalled makes
`advisable to check this incident “green” light
`the lamp 3 hotter than in the red position, This
`reading at the beginning and end ofa run to see
`green position is usually too hot for comfort if
`that it has not changed by more than a few per-
`Jeft.on continuously, and therefore during the
`cent,
`initial warming up period of from five to fifteen
`Beer's law, as applied to a mixture of two sub-
`minutes, the light is turned-on intermittently and
`stances, such as hemoglobin and oxyhemoglobin,
`left on each time until the ear begins to feel un-
`states that for a monochromatic light which is
`comfortable. Once the ear is properly vasodi-
`differently absorbed by them, the logarithm of the
`lated,as indicated by a steady reading on the gal-
`transmitted lightis linearly related to the frac-
`vanometer, the dimmerred light should be warm -
`tion of one substance in the mixture. Beer's law
`enough to keep it so, and the green need only be
`has been found to hold adequatelyeven for the
`flashed on occasionally—say at one minuteto five
`optically complex system of blood in the human
`minute intervals—to see that the blood thickness
`ear, so long as the amount of blood in the ear
`of the ear has not changed. This reading with
`remains fairly constant; as determined by the
`the switch on “green” shows how much blood
`“green” reading.
`It should be emphasized that
`there is between the lamp 3 and the photo-cell {,
`there are many reasons why Beer's law should not
`that ts, the “blood thickness” of the ear.
`hold in a system so far removed from that of a
`Whenthis green reading has arrived ata steady
`clear solution of pigment in’a parallel sided
`Value, we find it within one or another of the
`trough, and the happy validity ofthe law for the
`heavy black. blocks shown staggered along the
`human ear within the desired degree of accuracy
`four scales of the galvanometer. For example, if
`does not justify its extension to other tissues
`it were in the region of the figures 60-90 on the
`without independent check.
`:
`upper scale, it would fall within the block of the
`It follows
`from Beer’s law that.
`there ig a
`scale labelled “Wafer”; if the green reading were
`.Straight line relationship between the logarithm
`in the region of 50-60 on the upper scale, it would
`of the transmitted light and the percent satura-
`fall within the block on the scale labelled “Thin”;
`tion. This, however, is only true if. both the in-
`if in the region of 60-70 on the lower scale it would
`tensity of the incident light and the total pigment:
`lie in the block of the scale labelled “Medium”;
`concentration Chemoglobin plug oxyhemoglobin)
`and if in the region of 50-60 on the lower scale, it
`remain unchanged.
`If the light intensity is in-
`would lie in the block of
`the Scale labelled
`creased, this straight line is shifted to the right
`“Heavy.” With fewer or more scales the blocks
`in Fig. 5 without changeofslope, while if the Pig-
`would be different but the principle would be the
`same,
`.
`ment becomes more concentrated its slope is de-
`creased. The position of the line can be uniquely
`Since the blocks do not overlap, the galvanom-
`determined if its slope is known and if one point
`eter indication on the “green” setting is always
`on it is determined experimentally. The first
`within one block or another, and a glance at the
`quantity can be predicted from the “green” read-
`scales suffices to select
`the scale to ‘be used.
`ing, while the second datum can be obtained either
`Whichever scale has the block in which.
`the
`by forcing the saturation up.to 100% by breathing
`“green” reading falls is the scale on which the
`oxygen or by assuming the saturation is 96%
`Percent oxygen is read when the “red” setting is
`when air is breathed normally,
`used.
`The effective wave lengths depend both upon
`The proper scale having been so determined, the.
`the transmission characteristics of
`the filters
`switch is then moved to the “red” position. The
`used and upon the spectral Sensitivities of the
`four scales are so arranged that in each case 100%
`light sensitive cell. The choice of the color fil.
`saturation corresponds to the full scale deflection
`ters therefore depends to some extent on the par.
`of the measuring instrument.. The adjustment
`ticular photocell used. For the red light an ef-
`of the chosen scale is obtained by varying the in-
`fective wave length is desired which is very dif-
`‘ cident. “red”light intensity by meansof the rheo-
`ferently absorbed by reduced hemoglobin than by
`- stat [8 until the correct reading for a known oxy-
`oxyhemoglobin. A number of regions might be
`gen content (100% with oxygen or 96% with air)
`used, but for measurements on man the most
`is obtained for one point on the scale, Any other
`suitable region is from 6200 A. to 6600 A. For
`degree of oxygen can then be read directly on
`example, a “Wratten No, 29” filter having a con-
`that scale. The reading is quick, almost instan-
`trol wave length of 6400 A. was found to be sat-
`taneous; and by holding one’s breath, can be seen
`isfactory. For the green light an effective wave
`to drift down froma normal content of about
`length is desired which is equally absorbed by
`96% to say 80%, 70% or lower, depending on the
`oxyhemoglobin or reduced hemoglobin. Such a
`depletion of oxygen occurring. This rapid and
`region lies between 5200 A. and 6000 A., and vari-
`continuous reading of the oxygen content of the
`ous other points as indicated in Fig. 4. A band
`blood, without taking blood samples, is the chief
`in the neighborhood of 5900 A., obtained with
`advantage of the instrument.
`“Wratten No, 61” filter has been found satisfac-
`Care should be taken that carbon monoxide is
`tory. By keeping in mind the principles above
`not: present, as its effect on the color of the blood
`outlined various suitable selections can be made.
`is similar to oxygen.
`The apparatus has been described in the form
`In order to compare one ear with another, the
`of a single unit capable of handling one person
`incident light, in the “green” position of the
`at a time. Where it is desired to test a number
`switch, must always be the same,
`‘This is secured
`of persons simultaneously, multiple types can
`by initially placing a neutral filter of constant
`be made by the mere duplication or multiplica-
`transmission in the position of the ear and then
`tion of the corresponding parts.
`:
`adjusting the brightness of the lamp until the in-
`While I have in the foregoing described certain
`strument comes to a predesignated mark on the
`particular embodiments of the invention, it will
`calibration scale, determined by the original cali-
`be understood that they are merely for purposeg
`bration from known data. This method of ad-
`of illustration to make clear the Principles there-
`Justment automatically compensates for slow
`of, and that the invention is not limited to the
`
`5
`
`10
`
`2h
`
`ao
`
`AC
`
`45
`
`50
`
`55
`
`60
`
`65
`
`70
`
`if)
`
`IPR2018-00294
`Apple Inc. EX1015 Page 6
`
`IPR2018-00294
`Apple Inc. EX1015 Page 6
`
`

`

`5
`
`15
`
`20
`
`25
`
`35
`
`40
`
`30
`
`2,858,002
`‘strument operable by either of said cells, said in-
`particular form described, but is subject to vari-
`strument having different scales with marks at
`0US modifications and adaptations in different
`different locations thereon to indicate which type
`installations as will be apparent to those skilled
`scale is to be used, said indication being made by
`in the art without departing from the scope of
`operation of the first mentioned filter and cell,
`the invention as stated in the following claims.
`and different oxygen calibrations on said scales
`TI claim:
`1, In an oxygen meter, the combination of a —
`whereby the oxygen content may be directly
`read by operating the instrument by the second
`light source, 2 color filter and light sensitive cell
`color filter and cell and reading the oxygen con-
`for the selection of types operable by said light
`tent on the scale previously indicated, means for
`source and responsive to wave lengths which
`increasing thebrightness of the light source when
`are equally absorbed by oxyhemoglobin and re-
`the first color filter and cell is used and means
`duced hemoglobin, a second color filter and light
`for reducing the brightness when the second
`sensitive cell for oxygen determination operable
`filter and cell is used, a switch selectively con-
`by said light source and responsive to wave
`nected to eitherlight sensitivecell and the meas-
`lengths which are absorbed differently by reduced
`uring instrument, a second switch connected to
`hemoglobin than by oxyhemoglobin,: a measur-
`the means. for rendering operative the brightness
`ing instrument, a switch for connecting the
`control means of the light source according. to
`measuring instrument
`to either light sensitive
`which filter and cell is used, and means for op-
`cell.so that it is operable by either of said cells,
`erating said switches simultaneously.
`said instrument having different scales with
`5. In an oxygen meter, means for obtaining
`marks at different locations thereon to indicate
`electrical indications comprising in combination
`which type scale is to be used, said indication be-.
`@ light source, a red light filter and light sensi-
`ing made by operation of the first mentioned
`tive cell, a green light filter and light sensitive
`filter and cell, and different oxygen calibrations
`cell, said green filter and cell being of greater
`on said scales, whereby the oxygen content may
`area than the red filter and cell whereby effects
`be directly read by operating the instrument by
`of the same general order of magnitude are ob-
`the second color filter and cell and reading the
`tained when applied to oxygen determination in
`oxygen content on the scale previously indicated.
`the blood, means for attaching said light source,
`2. In a colorimeter, the combination of a light
`filters and cells to the ear, whereby they may re-
`filter and a light sensitive cell responsive to green
`spond to the color of the blood in the ear, and a
`light which is equally absorbed by: oxyhemo-
`measuring instrument operable by either of said
`globin and reduced hemoglobin, the type of the
`cells.
`specimen being determined by its absorption of
`6. In an oxygen meter, means for obtaining
`green light, a second light filter and light sensi-
`electrical indications comprising in combination
`tive cell responsive to red light, a light source for
`@ light source, a red light filter andlightsensi-
`said filters and cells, an electrical measuring in-
`tive cell, a green light filter and light sensitive
`strument operable by either of said cells, said in-
`cell, said green filter and cell being of greater
`strument having differently calibrated scales for
`area than the red filter and cell, a measuring in-
`different types of specimens, said calibrations in-
`strument operable by either of ‘said cells, and
`dicating the absorption by the specimen of the
`means for increasing the brightness of the light
`red light, said instrument also having type in-
`source when the green filter and cell is used and
`dicators on said scales for use with the green
`for reducing the brightness when the red filter
`light to determine which scale is to be used, said
`and cell is used, whereby the same generalscale
`types being independentof the oxygen content of
`of measurement may be used with either the red
`hemoglobin due to the equal light absorption,
`or the green light indications when applied to
`whereby direct readings of the red light absorp-
`oxygen determination in the blood.
`tion may be madeon the proper scale selected
`7. In an oxygen meter, the combination of a
`according to the green light absorption.
`light source, a color filter and light sensitive cell
`3. In an oxygen meter, the combination of a
`for the selection of types operable by said light
`light source, a green color filter and light sensl-
`source and responsive to wave lengths which are
`tive cell, a red color filter and light sensitive cell,"
`equally absorbed by oxyhemoglobin and reduced
`a measuring instrument for said cells, a rheo-
`hemoglobin, a second color filter and light sensi-
`stat in circuit with the light source to dim it
`tive cell for oxygen determination responsive to
`when the red filter and cel