CA2077191A1 - Apparatus for mounting electrodes - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Apparatus for mounting electrodes (10) on a human body in order to obtain human biosignals is disclosed. The apparatus includes close fitting clothing apparatus (70), a plurality of electrodes (10) mounted to the close fitting clothing apparatus (70), removable cover sheet (12) apparatus for providing a sterile interface between the skin and at least one of the electrodes and joining apparatus for joining the removable cover sheet apparatus to at least one of the plurality of electrodes. A variety of applications of the apparatus are also disclosed, including apparatus for detecting drowsiness in a subject and for alerting the subject as a result and a fetal biosignal probe.

Description

7 ~ ~ 1 FIELD OF T~E lNVENT~ON
The pre~ent invention relates generally to appar~tus for the rapid plac~ment of electrodes on and acquisition of ~ignals fro~ ~he human body BAC~GROUlND . OF T~ INVENTION
Many ~edical t~t- requirs th~ ~cquisition of bioelectric signal- fro~ th~ brain, eyes, mu~cles or nerv~s or ~ro~ a co~bin~tion of th abovem~ntioned body parts Other biosignal-, such a- elQctroder~al signals, heart pulse, voice signal~, tc , are often ~180 required U S Patent 3,882,8~6 de~cribe~ a capacitive electrode for acquiring el-ctroc~rdiographic (ECG) signal~ which do~ not n~c~--itato the U8~ of conductive gel~ or thQ pr~paration of thQ ~kin of ~ subject before ~cquirlng th EC~ ~lgnal~ While a ma~or lmprove~ent in the practicality of EoG ~1gnal acquisition, the ~ap~citi~ electrode still r-quir~ u~e of a co m ntional conducti~e electrodo as a reference ground In ~ddit~on, ther~ i~ no convonient way to sterilize the capacitlv~ lec*ro~o bstw ~n pati~nt~
urthQr~or~, wh~n pair~ of the capacitive electrod~ are utilized to obtain differen~ial voltage 2S ~e~ure~onts o~ bio~lectr~c sisnal~, the robustness o~
the sign~l acquisition in th~ face of v~rious move~ent-rel~ted arti~act~ i8 low Noi~e p~ckup fro~ extraneous electromagnetic ~ource~ due to cabling is sub~tantial It i~ known in th~ art that pr~paring the skin '': ' . ~ : ~

W091~13~W PCT/USgliO1260 . .

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and the electrodes, placing the electrodes in their correct location on the body, and fastenin~ them to the body is a time-consuming process requiring much skill Many devices have been cr-ated to ensure correct S placement of the electrod-s on the body on- such d-vice i~ describ d ln U S Patent 4,800,888 It compri--- a h l- t onto which is mounted an electrode a~--mbly Each el-ctrod- of the as~embly flo~t~ in ~ cylinder which i- mountQd on a pressure lo responsive drive When the pre~sure responsive drive is under pressure, it carrie- the lectrode to the scalp of a subject SUMMARy QF THE INVENTIQ~
It i~ therefore an ob~-ct of th- present inv-ntion to provid an apparatu- for mounting electrodQs on th- hu~an body and for acquiring bioelQctric ignal- ther ~rom without skin preparation and with mini al Qxp~rti~e It i- al~o an ob~ect of the present invention to provide practical mean- for ~terile use of capacitive electrodes Th r- i~ th-r-fore provided, in accordance with a pref-rr d abodim nt of the pr~s-nt invention, apparatus for mounting l-ctrode~ on a hu~an body which ~ 25 apparatus is op rative to obtain hu~an biosignals and ; compri~-s clo-e fitting clothing apparatus, a plurality of electrode- mounted to the close fitting clothing apparatu~, re o~able cov-r sheet ~pparatus for providing a ~teril- intarface b4tw en the ~kin and at least one of the electrode- and joining apparatu~ for joining the cover sheet apparatu~ to at least one of t~e plurality of lectrode~
Additionally, in accordance with a preferred embodi~ent of the present invention, the apparatus for mounting electrodes on a hu~an body also comprises signal processing appar~tus uounted on the close fitting clothing apparatus for preamplifying, transient . : : . , -- . , .................. . - . . .. . .

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protecting and filtering at least one differential signal obtained betw en two of the el~ctrodes Moreover, in accordance with a preferred embodiment of the prQsent invention, the cover sheet apparatus includes r-f-r ne- apparatus for providing a refer-nc- signal for at l-a-t on- of the plurality of eleetrodes Alternatively, the eover sheet apparatus inelude~ eonduetiv apparatu- for providing a conductive path between at least on of the plurality of electrodes and the hu~an body Still furth-r, in aeeordanee with a preferred embod$~cnt of th- pr-sent inv-ntion, at l-ast one of the plurality of leetrode~ i~ a e~paeitive electrode Addltionally, in accordance with a preferred embodiment of the present invention, the elose fitting clothing apparatus ean be a glove, a faee mas~, goggles, a h-adband, gla~--J, a eap or a pilot flight hælmet If the elo~- fitting apparatus i~ a glove, a photopl~thys~ographie en or ~ay b- ineluded Ther i- al~o provide~, in aeeordanee with an embodi~ nt of th pr-s-nt invention, a referenced eapaeitive leetrode assQobly for ~ounting on human skin eo~pri-ing a eapaeitiv~ etrode ~ounted in a sub~trat-, ~t-rilizabl- re~ovabl- eov-r apparatus separat- tro~ th eapaeitive eleetrode for providing an ~l-etrieal r fer-ne- ~ignal and for providing a s parabl- int-rfaee betw -n the hu an skin and at least on of th l-etrodes and ~oining apparatus for joining the covQr apparatu~ to the eapaeitive eleetrode Th-re i~ additionally provided, in accordance with an embodi~ent of the present invention, a ref~reneed eap~eitive sensor ehannel assembly for mounting on hu~an skin for the purpose of measuring bioelectrie signals The sensor ehannel comprises a set of at least two capacitive eleetrodes mounted in a subfitrate, removable cover apparatus separate from the set of capaeitive electrode~ for providing a separable _ . _ _ _ _ _ - ~ . .;, ,, , ~ ., . . .

W091~13584 PCT/US9~/Ot260 2~7~ ~

interface between the human skin and at least one of the capaeitive electrode~ and including refer-nce apparatus for providing an electrical referenco signal for the sensor cbannel, joining apparatus for joining the cover apparatus to the capacitive electrode~ and signal proce~sinq apparatus for proee-sing th- bioelectric ~ignals Further ore, there i~ provided, in accordance with an embodiment of the pre~-nt in~ention, a capacitive electrode for mounting on hu~an skin and compri~ing a housing having a ~kin-faeing side in which ther is an op ning, a eonduetive l-ment placed in the op-ning and lying along the ~kin-faeing side, and a dielectrie eov r eovering th op ning and touching the eonduetive l~cent Th-r i~ further provid d, in aecordanee with a preferr d e bodi ent of th- pr-~ent invention, apparatus for al-rting a drow~ing sub~eet eomprising a elos- fitting fr~o mount-d on th sub~eet~s head, a plurality of l-etrode~ ~ounted to the elose fitting fra~e for mQa~uring bio~ignal aetivity oecurring generally in th- ar a of the face and h-ad of the sub~-et, data proe-s~ing apparatu~ for proee~sing the biosignal aetivity into ba~eline eurves and for d t-roining when th- bio~ignal activity crosses a thre-hold related to the baseline eurves for longer than a pr d-tQr~ined ~m~unt of tim- indicating an increased ri~k of drow~ine~, and al-rting apparatus for alerting the drow~ing ub~-ct upon deteroination by the data proees~ing apparatu~ that an inereased risk of drowsiness has oeeurred Additionally, in accordanc- with a preferred embodiment of the inv-ntion, the biosignals ean be of high and/or low frequency and the apparatus includes respon~e detection means for detecting the subject's response to an alert is~ued by the alerting apparatus Moreover, in accordanee with a preferred , , ., .. -; . : :
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-- s -- -embodiment of the pres-nt invention, th- alerting apparatus includes apparatu- for produclng a variety of audible sound~ The al-rting appar~tus al~o includes apparatus for varying th- int-nsity of the audi~le sounds Further, in accordance with a proferred embodiment of the pres-nt invention, a head motion sensor for detecting head motion i- also optionally included in the apparatu~ for alerting a drowsing subject Still further, in accordance with an embodiment of th- pre~ent invention, the close fitting frame is a frame of a pair of eyegl~sses, a set of goggles, a headband or a fra e of a face mask lS There i8 further provided, in accordance with an embodi~ent of the pr~sent invention, a ~ethod of al-rting a drow ing sub~-ct including th- steps of r-ceiving bio-ignal- from l-ctrod-s placed on and near the fac- of the sub~ect, processing the biosignals into b~s-lin- curv-s, and d-t-roining whon amplltudes of the biosignalfi cross the baseline cur~es for longer than a predetQrmined ~ount of tim indicating an increased risk of drowsiness, alerting th- subject via an alerting action every ti~e the increasQd risk of drowsiness is indicat d, and dotecting a response to the alerting action Further, in accordance with an embodiment of th pres-nt inv-ntion, the al-rting action differs each ti~e th- increa~ed ri~k of drowsinQss is indicated The alerting action is an audible sound who~e intensity is initially low and intensifie~ until the subject gives a confirmatory response indicating that the subject is alert There is further provided, in accordance with an embodim~nt of the present invention, apparatus for rapidly preparing to obtain biosignals from a human body and comprising close fitting clothing apparatus, a ,. . ..

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plurality of electrode~ ~ounted to the close fitting clothing apparatus, wherein at lea-t one of the electrodes i~ a capacitive lectrod- and r-ference apparatus mounted to the clo~e fitting clothing apparatus for providing a r ference signal for use together with the at l-ast one capacitive electrode Moreover, th re i- provided, in accordance with an embodi~ent of the present invention, eye tracking apparatus for tracking the direction of a sub~ect's gaze comprising, close fitting clothing apparatus ~ounted close to th face of the sub~ect, at least fir~t and second pairs of capacit$ve electrodes for obtaining biosignals relating to the gaze mounted onto the close fitting clothing apparatus, wherein the first pair i~ mounted 80 as to be above and below one of the subject'~ eye~ and wherein th- second pair is ~ounted 80 as to b- on oppo~lte ~idQs of one of the ~ub~-ct's y s, and apparatus for converting the biosignals into position infor ation Additionally, there is provided, in accordance with an embodiment of the present invention, a fetal biosignal probe for rapidly obtaining bio~ignals of a fetus, typically during labor, compri~ing at least one capacitive electrode apparatus ~ounted on a flexible body for obtaining fetal biosignal~ and referencing apparatu~ for providing a reference signal for the capacitive electrode apparatu~
Furthermore, in accordancc with an embodiment of the pr-s-nt im ntion, ther i~ provid-d a system for rapidly obtaining f-tal bio~ignals comprising at least two fetal biosignal probes to be temporarily attached to a fetus scalp and signal processing apparatus for processing fetal electroencephalographic signals Finally, there is provided in accordance with an embodiment of the present invention, apparatus and a method for measuring a critical flicker fusion frequency of a subject and comprisinq a plurality of light sources . . - . , , , ,~
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arranged in a predetermined pattern, typically familiar to a sub~ect, comprising a first multiplicity of background light source- ~nd a second multiplicity of flicker group light source~, driving circuitry apparatus for illuminating the background light ~ources so as to appear non-flickering, for o~cillating the flicker group light sources at a gradually decreas~ng oscillation frequency and for maintaining the background and flicker group light ~ources vi-u~lly indistinguishabl~, and input apparatu~ oper~ted by the sub~Qct for indicating to the driving circuitry apparatu~ at which frequency fllcker is first ob~erved in the ~licker group and which of the plurality of light sources belongs to the flicker group.
~gI~E~E~CRIP~QN OF THE D~AwIN~s The pre~ent invention will be understood and appreciatod more fully fro~ th following detailed de~cription taken in con~unction with the drawings in which:
Fig. lA is an i~ometric illu~tr~tion of an electrode a~seibly and a cover sheet assembly covering the lectrode as~embly constructed and operative in accordance with an e~bodi~ent of the present invention;
Fig. 1~ is a side view sectional illustration of the electrode and cover sheet assemblies of Fig. lA;
Fig~. lC and lD are side view sectional illu~trations of alternative e~bodiments of the el~ctrode of Fig. lA;
Fig. 2 is a side view sectional illustration of ~n electrode ~ssembly and an alternative embodiment of the cover ~heet assembly of Fig. lB useful for incorporating conductive lubrication means;
Fig. 3A is a schematic illustration of a face mask having any one of the electrode assemblies of Fig.
1 and two sterile integrated electrode covers constructed and operative in accordance with an embodiment of the present invention:

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Fig. 3B is a detalled schematic illustration of one of the sterile integrated electrode covers of Fig. 3A;
Fig. 4 i8 a sche~atic illu~tration of an alternat~ embodiment of the face n~k of Fig. 3 in conjunction with a flexible printed circuit;
Fig. 5 iB a d-tall-d sch-n~tic illustration of the flexible printed circuit o~ Fig. 4:
Fig. 6 i~ an l-ctronic ~ch ~atic diagram of a circuit for prea~plification, transiQnt protection and filtering of bioelectric ~ignals:
Fig. 7A i~ a pictorial illu~tration of a c~p in which ar- incorporated the electrode assemblies of Fig. 2;
Figs. 7B and 7C ~re pictorial illustrations of a pilot flight h-ln t into which are incorporated capacitiv- electrode-;
Fig. 8 is a pictorial illustration of a glove in which are incorporated any one of the electrode assemblies o~ F~g. l;
Fig~. 9A, 9B and 9C are pictori~l illu~trations of an apparatu~ for detecting drowsiness of a ~ub~ect and for ~ub~-gu-ntly ~lerting ~aid sub~ect;
Flgs. lOA and lOB are graphic illustrations of RMS ~plitude curv~ of low and high frequency ~ignals produced by the apparatus of Figs. 9A - 9C;
Fig. ll ~8 a block diagra~ illustration of proc~-~ing apparatus useful in th~ appar~tus of Fig~. 9A - 9C;
Fi~. 12 i~ a ~chem~tic circuit diagram of a signal conditionin~ ~odule useful in the processing mQans of Fig. 11;
Fig. 13 ic a ~ch~matic illustr~tion of fl~xible circuit board appara~ug us~ful in the apparatus of Figs. 9A - 9C;
Fig~. 14A, 14~ and 14C are front, back and side view illustr~tions of ~ fetal biosignal probe ,- . . `: . . ,.. , : . , , ., ,-, .... . ~ . .. . ... . ~ ,~
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utilizing the electrode~ of Fig Figs 15A, 15B and 15C are front, back and sid~ view illustrations of an alternative embodiment of a fetal biosignal probe utilizing the electrodes of Fig 1 ~
Fig 16 i~ a part pictorial, part block diagr~o illu~tration of a y teo for obtaining fetal bioQignal~ during d-liv-ry u-ing one or both of the fetal biosignal prob- of ~lg- 14 and 15 Fig 17 is a part pictorial, part block diagra~ illu~tration of apparatus for ~easuring Critical Flicker Fu~ion and Fig 18 is an lectronic sche~atic of circuitry for~ing part of th apparatu~ of Fig 17 DETAIL~ DESCRIPTION OF PRESENT INVENTION
Refer nc- i~ now uade to Fig~ lA and lB which illustrat- an el-ctrod- aa-- bly 10 and a cover sheet as~ mbly 12 El-ctrod- a--- bly 10 typically co~prises a capacitive electrod- 14, such a~ thOSQ available from Heart Rate Inc of Costa ~esa, Ca Electrod a~e bly 10 additionally comprises a flexible non-conducting substrate 16, such as silicone rubber or o~t pla-tlc, in which i~ ~ounted capacitive electrode 14 Al~o ~ounted in substrate 16, near l-ctrod 14, i~ at l-a~t one electrical contact site, shown in Fig lB as two contact sites 18 and 20 Attach d to electrical contact sites 18 and 20 and to electrode 14, and pa~ing through or residing within sub~trat- 16, are electrical conductors 22 El-ctrical conductor~ 22 ter~inate at an electrical connector 24 Cover ~heet a~s mbly 12 is typically a thin sheet which i~ typically dispo~ablQ but may alternatively be permanent It typically comprises at least one electrical contact ~ediu~, shown in Fig lB as contact media 26 and 28, ~or touching human skin and for providing an electrical reference signal to electrode 8UE~STITIJTE 8~EET
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,~ . , - . . , wos1/13~ PCT/USgi/01260 14 Media 26 and 28 are typically eonduetive silver impregnated eloth el~ctrod 8, ~ueh ac th E301 or E331 electrodes anufaetured by In-Vivo ~etrie of Healdsburq, Ca , and are typically ~ounted on a non-eonduetive substrate 30, ~ueh as a thin plastie sh~et Through openings in substrate 30, m dia 26 and 28 are electrieally eonn-ct-d to m tallie contaet~ 32 and 34 ~he ~etallic contacts 3Z and 34 ar designed to easily and re~ovably attach but rlruly to cont~ct sites 18 and 20, thereby providing a reference signal for ~lectrode 14 In the pr f-rred obodimQnt hown hereinabove, a p~ir of one contact site 18 or 20 and one metallic contact 32 or 34 creat-- both a m chanical and an eleetrieal eonneetion betw -n the eov~r sheet assembly 12 and the ~leetrode assembly 10 An appropriate pair is a male-f4rale press eontaet pair such as the Dot eontaet ~anufaetur-d by TRW Corpor~tion of the USA
Alternativ-ly, th pair ean b- ~orned of silver impregnated eloth fa~t-ner~ for ed of Velero (registered trademar~) In an alt-rnate embodiment, th- mechanical ~oining and tho lectrical ~oining c~n be produced separat~ly by two separat- eonneetion assemblies An exa~plo of sueh a dual joining ass~hly is an adhesive band around th~ border of cover 12 on th- side of substr~te 30 whleh i~ not in contact with the skin for m ehanieal ~oining and a separate Dot contact pair insid the border for electrical ~oining An alt-rnate Qmbodinent of olectrode assembly, labeled 40, is shown in Fig 2 and i~ intended for use, in conjunction with a cover sheet assembly 42, on areas covered by body~hair Cover sheet assembly 42 comprises a substrat- 44, preierably made of a thin plastic film, and a multiplicity of ~ponges 46 f~lled with a moist conductive gQl or similar conductive m~dium and attached to the sub~trate 44 A prot-ctive, sealing cover film 48, such ~s is used in commercial disposable ECG

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W091/l3~ PCT/US91/01260 2 ~

electrode~ ~uch as the Red Dot electrode manufactured by 3M Corporation of Minnesota, USA, maintains the gel in sponge 46 in a wetted statQ and i5 typically peeled from the cover 42 after the cover 42 iB attached to electrode As in cover sheet assembly 12, cover sheet assembly 42 additionally compriseJ contact media 26 and 28 and ~etallic contacts 32 and 34 for providing a reference signal for el-ctrode 14 Si~ilar to electrode assembly 10, electrode assembly 40 comprises a sub~trate 50, sîmilar to flexible ~ubstrate 16, in which are mounted electrode 14, contacts 18 and 20 and any neces~ary wires Cover sheet ~88~bly 42 is attached to sub~trate so via adhesive pads 52 suc~ that sponges 46 lie on top of electrode 14 and ~edia 26 and 28 Alternatively, adhesiv- pad~ 52 can be nad- of Velcro (registered trademark) It will be appreciated that sponge 46 provides a moi~t lectrical connection between the sk~n and sub~tr~te 4~ Substrate 44 may optionally have pores under spongQ 46 to establi~h electrical contact with electrode 14 and media 26 and 28 ~he sealing cover film 48 i8 made to hermetically se~l off all sides of cover 42 80 ~8 to preserve the ~oistness of sponges 46 Sealing cov-r film 4~ is s~milar to those used for dispo~able ECG electrodes It will further be appreciated that the electrode apparatu~ 10 or 40 is fir~t covered by its respective cov-r ~heet assembly 12 or 42 and then the combination i~ placed onto the ekin of a subject, with tha cover assembly ~ide located against the s~in Via the electrode and cover sheet asse~bly combination, reference ~nd bioelectric signal~ are gathered, without the nece~sity of skin preparation Due to the replaceability of cover a~se~blies 12 and 42, electrode as~emblie~ 10 and 40 are hygienic and suitable for SU~STITUTE SHEET
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wosl/13s84 PCT/US9i/0126 sterile u~ with a multiplicity of subjects Reference i~ now madQ to Fig6 lC and lD which illustrate alternative e~bodiments of electrode assembly 40 in which a single diQlectric layer sepArates the skin from the conductive ele~ent of the capacitive electrode 14 In accordance with thi~ Q bodi~ nt of the pre~-nt inv-ntion, the capaclti~e electrode, here denoted 60, co~pri~-- a conducti~ le~ent 62, such as a lo piece of metal, a di-l-ctric ~aterial 64, such as a thin plastic sh~t, ~orming a cov~r to a thre--sided housing 66, and a buff-r amplifi-r 68 Capacitive QlectrodQ 60 performs as a capacitor after being mounted, dielectric material 64 side down, onto th~ hu an skin Buffer amplifier 68 operatQs in a manner sinilar to thQ buffer amplifier in U S Pat-nt 3,882,8~6 It is op~rative on the signal d~tected by th~ co bination of th- conductive element 62 and th- di~lectric nat-rial 64 Th~ conductiv~ ent 62 and the buffer amplifi-r 68 ar~ encloaed within hou~ing 66 which is covered by dielectric material 64 Conductive element 62 i~ placed inaid- hou-ing 66 in a location close to the ~id~ of hou-ing 66 which is covered by dielectric mat-rial 64 In thi- anner, conductive element 62 touchs~ di~l-ctric natQrial 64 The diel-ctric material 64 c~n b- for- d as an int gral part of housing 66, as ~hown in Fig lC, or a~ a detachable element, as shown in Fig lD In the embodiment of Fig. lD,. the dielectric mat-rial 64 operate~ both as a dielectric and as the cubstrate of cover sheet asse~bly 12 of Fig lB
It will be approciated that the capacitive electrodes 60 of Figs lC and lD can be utilized in place of capacitive electrode 14 in the assembly of Fig lB Capacitiv- electrode 60 is advantageous over capacitive electrode 1~ in that capacitive electrode 14 typically has two dielectric l~yers, one inside the 8UBSTITUl~ SHEET

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electrode housing and one defining substrate 30, while cap~citive el-ctrode 60 has only one dielectric layer 64 which serves both a6 a di-l-ctric and as a cover sheet assQmbly.
Reference is now ~ade to Figs 3A, 3~, 4 and 5 which illustrate apparatua 70, constructed and operative in accordanc- with a pr-f-rr d e~bodi~ent of the present invention, for rapidly applying ~l~ctrode~, such as any of the l-ctrode~ of Fig 1, to tho fac- of a subject Appar~tus 70 require~ no ~kin or lectrod preparation, nor do-~ it r~quire ~uch knowl dg- on the part of the operator as to the corr ct plac-~nt of the electrodes It i~ design-d to be ea~y for an un~killed operator to use and to b- comfortabl- and hygi-nic for a subject to wear Accordingly, apparatus 68 i~ typically eibodied in a face nask 70, including a p~ir of frames 71, ~i ilar to th fra~ ~ of wi~ r's goggle~ and typically nanufactured of _ oft ~aterial such as silicone rubber or a soft pla~tic, an adjustable bridge ~2 for on_bling the Sac- ~a~k 70 to adapt to the particular int-rocular di-tance of a ~ubject and an adju-tabl- band 74, typically ~n lastic band, for fir ly ~aintaining the fac- ~a~k 70 again~t the face of a ~ubj-ct - Th adju~tability of th adju table band 74 acco-oodate- subject~ with differ-nt head sizes Mounted onto fac- ~ask 70 are a multiplicity of l-ctrod- asse~blie~, ~uch a~ apparatu~ 10 (Figs lA
and lB), label-d lOa - 10~, ~or r cei~ing facial bio~ignal~ The electrod- a~emblie~ lOa - lOj are - located in predetermined locations around the eyes so as to measure ~io~ignals relating to eye ~ovement and eye position Sp cifically, electrodes lOa and lOb are located in fra~e 71 so as to be above a subject's pupils and electrodes lOg and lOh ar~ arranged so as to be located below the subject's pupils Electrodes lOe and lOf are loc~ted ~o a~ to be placed in the inner canthus ", . : ` .. .. . . ~ , ;

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of the eyes and electrode~ 10~ and lOi are located so as to be placed in th- outer canthi of the eyes El-ctrodes lOc and lOd ar arrang d to b- located at the temples and are therefor- plac d on ad~ustable band 72 Typical bio~ignal- to b m-asured are as follows l-ctrod- pair- lOa and lOg and lOb and lOh measur l-ctrooculogran (EOGs) relatlng to the vertic~l ~otion and po-ltion of th- l-ft and right eyes, respectively, and el-ctrod- pairs 10~ and lOe and lof and lOi ~ asur- EOGs r lating to the horizontal motion and position of the l-ft and right y-~, respectively alternatlv~ly, el-ctrode~ 10- and lOf ~ay b- replaced by a single l-ctrode at 10-, at lOf, on the nose bridge, or betwQen the eyebrow~ The horizontal and vertical motion neasurenents are us-ful for detecting nystagmus and for ~ a~uring a sub~ect's blink response and the converg-nc- capablllty of a ubj-ct's y-s El-ctrod - lOa and lOb, located above the pupils, are al~o u~-~ul ~or m a~urlng the electromyogram (EMG) of facial nuscle~ and l-ctrodes lOc and lOd are use~ul for ~ea~uring EMG- o~ ~uscles associated with eye lids and ey- nove~ nt~ or with facial relaxation In accordance with a preferred embodiment of the pre~Qnt inv ntion, th cover ~h et asse~blies 12 corre~ponding to th- nultlpllclty of electrodes lOa -10~ ar for~ed in two integrated cover sheet assemblies 76 and 78 Cov r~ 76 and 78 ar- de~igned so as to cover all of th- portions o~ fac- na~k 70 which come into contact with the skin of a sub~ect, including the templo- and the area- n-ar the inner oanthi of the eyes They are r-placeable ~o 3s to ensure that apparatus 70 i~ hygienic and can be u~od with a multiplicity of sub~ect~ without concern o~ spreading disQase from one subject to the next 3~ Cover sheet ass-~bly 78 is shown in detail in Fig 3B and co~er shQet as-e~blie~ 76 and 78 are both shown in Fig 4 Cover sheQt a~se~bly 78 includes .~ .. ;..... , . :- . :.. . .

W091~13 ~ PCT/US91/01260 ; ..
~7~1 substrate 30 onto which ar placed one or more media 26 and 28, where, for clarity'- sake, only one pair of media 26 and 28 are shown Media 26 and 28 are arranged on substrate 30 such that they will mate with the S corregponding electrode a--eibly 10 located on face mask 70 Th~ entirety o~ ctrod a---mblies 10 are connected to ~ignal proc---ing equipm nt via electrical connection- 80 ~Fig S), typically co~pris-d of wires In accordance with a pref~rred bodi~ent of the present invention, l~ctrode as~bli-~ 10 and th~r respective el~ctrical connections 80 are eib-dded in flexible printed circuit~ 82 (Figs 4 and 5) which are fixedly or removably attach-d to face mask 70 and extend along ad~ustable band 74 The electrical connections 80 typically ter inate at a ~ingle connector 84 located on the face ~ask 70 or within a cable 86 which extends from the face ask 70 Flexibl- print-d circuits 82 can be molded directly onto fac- mask 70 Alternatively, they can be formed into a soft plastic ribbon or otherwi~e surrounded with electrical and mechanical insulation The soft pla~tic ribbon can then b- removably mounted to face ~-k 70 u-ing renewable adhesive pads or other renewable bind$ng mean-Additionally, in accordance with a preferred~bodiment of th- pre~ent invention, preamplification, trans$-nt prot-ction and bandpass ~iltering circuits, d~scribed in ~or detail her-inbelow with reference to Fig 6, ar~ a~sociated with face ma~k 70 for each pair - of electrod- assemblies 10 attached to face mask 70 The circuit~ for the entirety o~ the pairs of electrode asseiblie~ 10 corresponding to each eye are preferably incorporated a~ a hybrid circuit in signal processors 88 and 90 attach-d to frame 71 ~y attaching signal processors 88 and 90 to the frame 71, noise pickup caused by cabling is reduced 8UBSTITI.JTE SHEET
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WO9l/13S84 PCT/US91iO1260 - 16 - 2~ 7 71 9~
Moreover, sine- the majority of the biosignals to be mea~ur-d will b~ m a-ured a~ diff-r-ntial signals, a ref-rene- ~ignal i8 provid-d for co~ on ~ode rejection This is provided by a reference electrode 92 preferably eonprised of a silver impregnated cloth eleetrode, sueh as the E301 or E331 eleetrode manufaetured by In-Vivo ~ trie A~ m ntioned her-in~bove, ~ignal proeessing equipment l- typieally provided with f~ee mask 70 It typieally compri~es a power ~upply 94 for supplying the required voltage~ to the leetrode a-~emblies 10 of the faee mask 70 and ~plifier- 96 for further conditioning and proee~sing of the pr aoplified biosignals received from ~ignal proee~sors 88 and 90 Specifically, the electrod- a~enbly 10 and th- ignal proce~sors 88 and 90 normally reguire power in th- 10 - 500 milliwatt rang-Further digital signal proee~sing, such asfrequency analy~i~, ~ay oeeur in digital eireuitry 98 It will b- appreeiated that power ~upply 94, amplifiers 96 and digital eircuitry 98 are typically located separately rrom fae- ~a~k 70 It will al~o be appr-eiat d that ~ingl- eonn etor 84 enables face mask 70 to b- readily and ea~ily s-paratable from the signal proe-~ing equipment Speeifie referenee is now made to Fig 5 which d-tail- eleuent~ of one of the flexible printed circuit bo~rd~ 82 Shown are the leetrieal connections 80 whieh bring th voltage from power ~upply 94 to the eleetrod as--~bly 10 and bring to the amplifiers 96 the deoired differ-ntial biooignal~ fro~ signal processor 88 Speeifieally, eonneetions 80a and 80b provide r voltage to the eleetrodo asse~bly 10 and to the signal proee~sor 88, conneetion 80e eonneets to reference eleetrode 92, and eonneetions 80d and 80e provide preamplified, filtered signals from the two pairs of eleetrode assemblies 10 81JBSTITUTE SH~ET
. . . . . ., ................ .... ... ... . ~ . ..

. ~, . .. ,. .... . . .... .. .. ...... .~ ~ .. .. . .
,',' . . . . . . ' : , . ' WO91/t3 ~ PCT/US91/01260 In order to obtaln a diff~rential signal between the pair of electrodes lOc and lOd on the temples, the two connections 80f are both connected to connector 84 Connections 80f are connected to electrodes lOc and lOd and are located on the respective flexible printed circuit boards 82 The differential signal i8 then typically cr ated in one of signal processors 88 and 90 The -ction of flexible circu~t board 82 on which lies electrode lOe is preferably bent in order to match the curvature of the area between the eye and the nose bridge Reference i5 now ~ade to Fig 6 which illustràtes a typical circuit for preamplification, transient protection and bandpass filtering Or a single differential signal acguired from a pair of electrodes and a reference electrode Th- circuit is beiieved to be self-explanatory and therefore, in the interest of concisQness, a full description will not be given It will be noted that the couponents are selected to provide low and high frequency cutoffs at predetermined frequQnciQs, such a8 0 5 and 200 Hz The circuit of Fig 6 is replic~ted for each differential voltage signal to be measured and is implemented a8 ~ single hybrid circuit Signal processors 88 and 90 typically contain at least one circuit such as i8 shown in Fig 6 Referring back to Figs l - 5, ~ace mask 70 is utilized a8 follows Preparatory to placing the face ma~k 70 on a sub~ect's face, an operator attaches cover sheet assemblies 76 and 78 to face mask 70 by snapping together the contact pairs 18 and 32 and 20 and 34 ~ypically, the mask 70 is then placed onto the subject's face, and the ad~ustable bridge 71 is ad~usted, if neces~ary Finally, connector 84 is attached to cables connected to the signal processing equipment The electrode assemblies lO are in their proper location and . ~. , , ~ ....... , . , ` .. :
, , ., ~ ~, - , . .

;... . . . .~ . :...... - . . . . `

,i ' ~ ' ' ' . ' i "' ' ....

WOgl/13~W PCT/US91/01260 - 18 - 2~7~
are now ready to obtain m a-urem nts No further ad~ust~ent- ar- required In thi~ manner, the eleetrode~ are plae-d on a ub~eet with ease It i- a f-atur- of the pr---nt invention that an operator do-~ not n- d to be skill-d in s~in or electrod~ preparation or in l-ctrode plae-~ent to utiliz- th- fae- nask 70 of th- pr ~ent invention With littl- work on the part of th op rator and little discomfort to th ub~-et, the apparatus 70 is ready to obtain the de~ired biosignals It will b- appr ciated that th- apparatus 70 can be utiliz-d for det-rmining a vertical and/or horizontal gaz- po-ition r-latlv- to the position of the head A- i- known in th- art, th horizontal and vertical components of th- thre--dimensional gaze angle, deflned here as the horizontal and ~ertical gaze po~ition~, incr a~e monotonieally with th amplitude of th EOG signal obtain d from v-rtieal and horizontal pair- of el-etrod -, r ~p etiv ly The r-lationship b-tw ~n th- gaz- po~ition and th- a~plitud- of the EOG
signal i~ obtain d by having th- sub~ect observe targets at known angular position~ r-lative to ~straight ahead"
a~ is eom on praetiee in n urological test~ of EOG and eye ~ov-~ nt~
A~ m ntion d her inabove, the vertical EOG is obtain~d from a pair of l-etrod-~, illustrat~d in Fig S a~ lOa and lOg or lOb and lOh, whieh are typically loeat d abov- and below one eye, r -peetively The horizontal EQG i~ obtained from th- pair of electrodes lOg and lOi whieh are typieally plaeed near the outer eanthus of eaeh eye The gaze position can be utilized in an eye mouse, an apparatus for providing one or two-dimensional po~itional input to a eomputer, providing much the same information as that provided by a m ehanical mouse The eye mouse is utilized a~ follows while keeping his head fixed, a subj-ct calibrates the eye 8UBSTmlTE SHEET
. , . . ., . . ............ ' ., - .

~ ~ , `, .. .. . .. . . .

- wo 91/13584 PCI/US91/01260 19 - 2~7~9 ~
mouse by looking at a predetermined calibration position on the computer scre-n or within his field of view and by confirming through ~om tandard input route, such as via a keyboard or a m chanlcal mouse button, that he is S looking at the calibration position known to the computer Co~puter softwar , i~ple -ntlng equations 1 -6 hereinb-low, rec-iv - th horizontal and vertical EOG
a~plitud-s, after low pa-- f~ltering by digital circuitry 98 to re~ov- transients and sudden jerks or other high fr-guency noises or artifacts, and associates them with th- pr det-rain d calibration position While maintaining hi- h-ad in a fixed pocition, th- ~ùb~-ct then loo~ at a s-cond pred-termin-d calibration point at a location significantly horizontally and v-rtically far from the fir~t pr d-t-r ined calibration polnt and confirms his gaze as de~crib4d hereinabove Th- computer software r-ceiv-- th- EOG a~plitud - for th- ~econd point and co~put-~ fro~ th~ , fro~ th first EOG amplitudes, and fro~ the coordinatcs of th two calibration points, a r lationship b tween th- s~b~ect's horizontal and vertical EOG aaplitude~, EX and EY rospectively, and the po~ition X, Y of a point at which th- sub~ect is gazing for a giv n distanc- and ori-ntation of th head rel~tiv- to th- computer scr -n Th- X, Y po~ition of the point is typically a lin-~r function of th EOC a~plitudes EX and EY as follow~
X - AX~EX + BX (1) Y - AY~EY I BY (2) where AX, AY, BX and 8Y are defined a~ follows AX - (X2 - Xl)/(EX2 - EXl) (3) BX - Xl - AX~EXl (4) ~ AY ~ (Y2 - Yl)/(EY2 - EYl) (5) BY - Yl - AY~EYl (6) and wh~re (Xl, Yl) and (X2, Y2) are the computer - . : ` . , `

~0gl/13~ PCT/US91iO1260 - 20 ~
coordinates of the respective calibration points X2 is different from Xl and Y2 i~ d$fferent from Yl EXl and EX2 are the horizontal EOG amplitud-~ received when the subject looked at point- (Xl, Yl) and (X2, Y2) and EYl and EY2 are the vertical EOG amplitudes received when the sub~ect looked at point- (Xl, Yl) and (X2, Y2) Alternatlvely, in a second calibration method, the sub~-ct can look sequ ntially at the points of a grid or oth r -t (Xl, Yl), (X2, Y2), , (Xn, Yn), known to th- computer, with each point having an a~sociated m a~ured (EXn, EYn~ a two-dimensional mathematical function relating true (Xi, Yi) to measured (EXi, EYi) i- thu~ ~ampled By fitting the sampl-d lattice Or points (xi~ Yi) for given value~ (EXi, EYi) with linear, polynominal or other math~catical ~odels known in the art, any po~ition (X, Y) can be e~ti~ted fro~ the mea-ured (EX, EY) of an arbitrary point a~ long as the ~ub~-ct's head maintain~ a fix~d orientation and di~tance r lativ to th calibration points In ither of th- abovementioned calibration methods, upon moving hi~ h-ad, the ub~ect indicates to th computer by k ypad or similar input means that his head is b-ing rQpositioned When a new position is taken, th ~ub~-ct indicate~ via the above mean~ that he i8 r ady for the computer to redefine the new position The co~puter sequentially di~play~ one or more points, g n rally f w r than in the original calibration set, and the ~ub~-ct ~-quentially ~ov-~ only his eyes to focu~ on the mo~t recent point thereby to indicate to the computer when each point i8 in view If the subject has not rotated his head or mov-d it sub~tantially (i e the mapping of the eye position to the computer position i8 baQically the ~ame but the offset BX, BY has changed), then typically a ~ingle calibration point can be u~ed to identify the new position of his eye In this manner, the eye mouse can be utilized ... . . ... ` . .. : ...... .. . . :

..
. .; . . ....... .. .

WO91/13 ~ PCTJUS91/012 , - 21 - 2 07 71 ~
for indieating position lnformation to the computer It will be appr-eiat-d that the eye mouse remains ealibr~ted only as long a8 th sub~ect's head remains in a eonstant po-itlon relative to the sereen -~ 5 Refer-nee i8 now ~ade to Figs 7A - 7C which illustrate alternativ- e bodi~ents of the present in~ ntion for us- in a-ily aequiring brain, eye, scalp musele and faeial aetivity ignal~ In Fig 7A, ~leetrod- apparatu~, sueh a~ leetrod- assemblies 40, are ~ount-d onto a eap or hat shap d element lOO, siJilar to a hat eo~ionly ~old to sport~ fans, in appropriat- loeations for aequiring electro-ene-phalograph (EEG) ~ignal~
In one preferr d bodiment, the eleetrode ass- blio- ~0 ar- loeat-d along the ~idline of the skull wherein el-etrode as~eobli-~ 40d and ~Oe are at the eentral and oeeipital r gion~, r-sp etiv 1y, and el-etrode a~-- bli-~ 40a, ~Ob and ~Oe are on the ~or h ad El-etrod- as-~ bli-~ 40i and 40~ are held against th- ~kin in th ar a- b-hind the ears via xtension- of th- eap el-ment lOO
A ref-r nee el-etrode 41, such as described hereinabov-, ia pr-ferably loeated on th- forehead Alt~rnativ-ly, el-etrod- a--- bly ~0 are plaeed at a multiplieity of points on the skull eorr-sponding to the int-rnational lO - 20 sy~t-a of EEC eleetrode placement In thi- alternativ- eobodlu nt, the output of the l-etrod- as-- bly 40, after appropriate amplification, ean b utiliz-d, for exampl-, in standard commercial polygraphie ~tripehart or brain mapping analysis sy~t-~s Either electrod- plaee~ent eonfiguration, ineorporated alternativ-ly into a elo~e-fitting pilot flight h-l~et a~ shown in Fig 7B and de~eribed in more detail hereinbelow, ean be used to deteet the pilot~s EEG, EOG and EMG signals Sueh an apparatus can be utilized for d~t-cting change~ in pilot status such as . . . , , ,. ............................. : ~

..;:
. .

WO9l/13584 PCT/US9l/01260 - 22 ~ t'~ J i 1088 of consciousness As in the previous embodiment of the present invention, the electrode as-enbly 40 are typically mounted to the cap el~- nt 100 via an appropriately S shaped flexible printed eireuit (not ~hown) As in the previous enbodiment, an int grated eover sheet asse~bly, of the typ- shown in F~g 2, ean be utilized; the integrat-d eov r she-t ~-senbly in this embodi~ent would be a singl- kull eap eo~po-ed of a ~ultiplicity of cover sheet a~se~blies 42 Cap 100 is adjustable to ensure that it firnly fits to any size head Fig 7B illustrates th- apparatus of the prQs nt invention ~bedded in a pilot flight hel~et 102 Th- apparatu- co~pri--- a plurality of eapacitive elQetrodQs 14 ranged about the face of a sub~ect, with or without th- U8- of a co~-r sheet ass-~bly A
refer nc- l-etrod- 10~, sueh as a silv-r i~pregnated eloth eleetrod-, provid-- a r-f-r-ne- signal for the apparatus and is typieally loeated n-ar th sub~ect's forehead Flexible wire~ 106 extend fron the electrodes to an int-rnal wiring conneetor 108, typieally placed inside the h l~ t 102 A pre-anplirier can be included in wiring eonn-etor 108 and the output of the eonnector 108 is typically eonn ct-d to circuitry (not shown) such a~ that hown in Fig 4 A ~icrophone outlet 110 is typieally ineluded in sueh flight hel~ets and is operativo, in thi~ e~bodin-nt, to provide a convenient acees- fro~ th- eonnector 108 to the circuitry Typically, a standard pilot flight helmet is retrofitt-d to produce the apparatus shown in Fig 7 Fig 7C illu~trates this operation A pilot flight hel~et typieally eonprises a hel~et and padding (not shown) eovored by a typically leather liner 112 A
plurality of acee~s holes 114 are cut into the liner 112 of the helmet 102 and capacitive electrodes 14 are placed into the~ Reference electrode 104 is attached ~ ` ,.... . . . .

W091/13584 PCT/~S91/01260 - 23 - '~?A~
to the skin-~ide of liner 112 and lts connecting wiring is passed through a small hole (not shown) in liner 112 towards internal wiring connectox 108 An individual co~-r sheet assembly 116 can be placed over each capacitiv- lectrod 14, or a single cover sh-et a~sQ~bly 118 can be plac-d over a plurality of capacitive electrodes l~ The cover~ 116 and 118 are operative to keep sweat ~nd dirt ~way from the capacitive electrodQ~ 14 and are typically non-conductive If cover 118 i8 utilized, then referenceelectrode 104 is located on th~ pilot's skin side of cover 118 Alternatively, th- padding which is covered by liner 112 can be augment-d by, or replaced by, padding of appropriate shape and thic~ness which already contains the aforementioned electrodes and wiring circuitry Reference i~ now made to Fig 8 which illu~trate~ another alternate embodiment of the present inv-ntion for us- in ea~ily acquirlng spontaneous or evoked mU8Cle activity signal~, a~ w ll as photopletheysmographic mea~urements of blood flow and h-art rate In thi~ embodiment, the apparatus for rapidly applying lQctrodes compri~e~ a modified glove 120 onto which are ~ounted, via the elements described h-reinabove, two standard conductive electrodes 122, ~uch a~ th- ~ilver impregnated cloth electrode manufactured by In-Vi~o Metric, ~or providing electrical stimuli to th- hand, two capacitivo electrode as~emblies lO for acquiring EMG signals in response to the signals providQd by the electrode3 122, and a photo-plethey~ographic sensor ~24, such a~ a light source and photodiode combination found in the Model 6390 Omni-Sat ear ~ensor by Critikon of Tampa, Fl of the USA, for providing blood flow data This apparatus is useful for m~asuring neuromu~cular tr2n~mission across the wrist, .
.

24 ;~rl~
in order to determine deliberate muscle relaxation during surgery or inten~iv- eare, while si~ultaneously monitoring relative blood flow in the finger As in the pr-viou- two ~ bodiments of the present invention, glov- 120 is ela~tic and has an adjustable band on the baek to en~ur~ that it fits firmly to any ~ze hand It i~ a feature of the pr~--nt invention that common artiel~- of clothing arQ u--d to ~ount the various leetrode a~semblies to the ~ubject's body This helps to nake th sub~ect eomfortable with the testing to be perfor ed by the apparatu- of the present invention and it ensur - th~t th both the sub~ect and the op~rator know how to plaee the artiele of clothing on the body A further e~bodim~nt of the present invention, shown in Fig- 9a, 9B and 9C, is us-ful for detecting and r~sponding to drow~in --, or pre-alQQp b~havior, of a sub~eet In thia ~obodi~ nt of th~ inv-ntion, labeled 130, el~etrod- aa~Qoblies 10 are typieally mounted on a frame 131 who~e funetion i~ ~imilar to that of frame 71 Tho eleetrod- a~Q bliQ- lOq - lOt are loeated near the outer eanthi of the ey~s, templQs and/or below the eyes for ~easuring th- EOC and other ye-related signals The el-etrod a~-e~blies lOg - lOt are typieally located a- cloae to the yea as co~fortably pos~ible, preferably without re~tricting the subj~ct' 8 visual field A
r-ferenee l-etrod- 132, such as ~ silver impregnated eloth ~lectrode ~anufactured by In-Vivo M~tric, is also mounted onto fr~e 131 By placing the electrode assembli-s 10 close to the eyes, the efficiency of the signal aequisition i~ maximized and spurious pickup of brainwavec (the electroencephalogram or EEG) is minimized 3S Alternatively, electrode lOq can be located behind the ear of the side of the head opposite to electrode lOt, which may be located anywhere around the ., ........ , ., ~ .............. , . ~ . - :
. . .

U~D9l/l3584 PCT/US91/01260 - 2s - 2~ 7 7 ~ ~
eye or forehead Frano 131 can be any clos- fitting frame or clothing which can place a plurality of electrode assemblies near the eyes A minimal set of electrode assenblies includes one above one eye, one at a reference location and another near an eye or behind the ear, contralateral to the lectrod- assemblie~ above the eye Examples of such fr~oe- ar an yeglass frame, a face mask, a cap, goggl--, a headband or ~eadphones Apparatus 130 optionally comprises head ~otion sensors 134a and 134b Thes- can b~ electrodes such as the E220 silver/silvQr-chloriao electrodes manufactured by In-Vivo Metric or any standard metallic electrode type, and ar u~ed in con~unction with signal conditioning equipment for detecting low frequency signal~ Alternatively, head motion ~ensors 134a and i34b can be accelorometric motion detectors, used in conjunction with appropriato signal conditioning equipment ~ead sensors 134a and 134b are mounted on frane 131 in a location which ensures that they are not in contact with the ~ubject'~ skin, thereby ensuring that they do not pick up any bioelectric signals but instead, ~ a~ure only head motion Th- biosignals and optional head motion signal~ are collect~d via flexible circuit boards 136, one of which i~ shown in Fig 13, which are similar to the ones de~cribed hereinabove with reference to Fig 5 Flexibl- circuit boards 136 can be fixedly or removably attached to the frame 131, as described hereinabove Typically, i~ frame 131 is the ~ubject's eyeglasses, the flexible circuit boards 136 are removably attached The signals are sent, via a cable 138, to processing ~eans 140, described in more detail hereinbelow An integrated cover sheet assembly (not shown) is also optionally included Apparatus 130 is typically utilized for passively and non-obtrusively monitoring a subject for SUBSllTUTE SHEET

W091/13584 PCT/US91iO1260 - 26 - 2~r~ f~
signs of drowsiness. Such an appar~tu~ can be used for monitoring truck drivers or other pQrsonnel in jobs in which they must not fall asleep. To ensure that the subjects do not fall asleep, the processing means 140 S comprise a detQctor modul- 142 for detecting behavior associated with an incrQ~-d risk of falling asleep, known hereinafter as th- drowsines- condition, and an alerting ~odul- 144 for ~lerting th- 8ub~ect upon the detection of drow~iness. Processing ~Qans 140 are typically powcred by a power supply 146.
In accordance with a preferred embodiment of the present invention, the alerting module 144 typically activates a loudspeaker 148, such as an earphone, a hearinq-aid type spQaker, or a small speakQr incorporated into alerting module 144, located near the sub~ect, to produce an audibl~ alerting sound. Upon detection of th~ drow~in~ condition, the alerting module 144 produce~ the alerting ~ound at a low intensity and increa-e~ the intensity until the subject responds, typically by blinking or by moving the head.
In one e~bodiment, to prevent accommodation by the subject, the ~lerting sound is alternatively selected by the alerting ~odule 144 fron among a multiplicity of different r-cordQd or progr~ed sounds such that the g~n sound i~ never used to alert the subject twice in a row. Alternativ~ly, the same sound m~y be used two or mor~ t~e~ in a row.
Pr~-~leep behavior, typically occurring for many sQconds before the onset of sleep, tends to be characterizQd by quiescent behavior and the relaxation of facial musclQs. Conv~rsely, awake behavior is characterized at least in part by eye, facial and head movements, bl$nking, ~nd or talking. The bioelectric signals to be obtained from the vicinity of the eyes while a sub~ct is awake have substantial signal amplitudes in a high frequency range of typically 30 - 1500 Hz. and in a low frequency range of typically SUE~STITUTE SHEET
~, . . .
.. .. ... , ~

,.' ' ' ' , ' ' ~; ' '~' ' wosl/l3ss4 PCT/US91/01260 2 ~

1 - 10 Hz Conversely, the average amplitudes of the biosignals obtained at the on6et of drowsine~s are ~uch smaller than those obtain-d from an awake subject The high frequency range typically characterizes muscle activity and the low fr qu ncy rang- typically characterizes eye moveu nt~, blinks and motion artifacts In a preferred ~ bodi~ent of the present invention, the alerting odule 144 i- to be activated lo whenever the amplitud-s of the biosignals in the low and/or high frequency r~nge~ drop substantially below baselin value~, ~ea6ured when the subject is awake, for more than a selectable nu~ber of seconds The baseline values nay b- record-d during a s-t-up period occurring at the beginning of th- use of the apparatus 130 or they may be updated periodically during use of the apparatu~ 130 Typical RMS a~plitude curves of biosignals representing a ~everal ~inut- period in which a typical sub~Qct fall- a-leep ar- ~hown in Fig~ lOA and lOB
The biosignal~ are fro~ electrode a~semblies 10 located near the ey 8 Th- aboci~sa- of the graphs in Figs lOA
and lOB are in ~inute~ and the ordinates are in arbitrary a~plitude units proportional to an integrated average RNS a~plitude of the signal in its pass band The pa~- band for the low frequency signal is 0 5 - lo ~z and the paa~ band for the high freguency signal is 30 - 1500 Hz In Fig lOA, curve 150 is the actual RMS
amplitude of the high frequency portion of the biosig~al, averaged using a moving window of a duration of typically a few ~econds Curve 152 is a typical baseline curve calculated by averaging the RMS values of the biosignal using a moving 1 - 2 ~inute window ending 30 - 60 seconds before the current time It will be appreciated that at a point 154 in ti~e, the high frequency activity drops below a :

WO91/13584 PCT/US9liOl260 .
- 28 ~ 7 ~
predetermined threshold l-v-l, mark d 156 In Fig lOA, threshold l-v l 156 i8 50~ of the current baseline value A~ ~hown in Fig lOA, point 154 stays below threshold level 156 for longer than a predetermined period Tl, typically 10 - 20 aecond~ The end of period Tl marks the achievQ~Qnt of the drow~iness condition and is the activation point of the alertlng ~odule 144 The actual ons-t of ~1QeP~ characteriz-d by very low amplitud- l-v-l- and lndlcated by r f-r-nce numeral 158, typically occurs after the activation point of the alertinq module 144, assu~ing that the alertinq module 144 h~ not been activat d Fig- lOA and lOB
illustrate the typical b havior of th~ biosignals in which the alerting module 144 i~ not activated Fig lOB illustr~tes the low frequency behavior o~ a typical biosignal fro~ electrodes placed near th- eye~ where curv- 160 i~ th- low freguency RMS
amplitud~ curv- similar to curv~ 150 Curve 162 is a typical ba~-line curv- c~lculated a~ described herein~bov- In Fig lOB, the predetermined threshold level, marked 166, is typically 50~ and the pr-deter~ined period is marked ~2 At point 168, the onset of ~leep occurs It will be appreciatQd that the alerting modul- 1~ can be activat-d when one of the two curves 150 or 160 achi-ve~ the drow6in ~8 condition or when both i~ultan~ou~ly indicate the drowsines~ condition, or when ono achieve~ the drow~iness condit$on and the other achieve~ it within a predetermined period of time Additionally, alerting module 144 can be periodically activated to check that th~ subject is still alert In such an embodi~ent, the ti~e from the alert until the subject respond6, herein denoted the re~ponse time, is m~asured Alerting module 144 can also be activated in relation to the length of the response time or the length of time a subject remains active or guiescent after previously being alerted W09t~13~ PCT/US9t/01260 ~ t Head ~otion- ar optionally d-t-cted by head ~otion sensors 134a and 13~b for tho-- applieations whieh involv sub~tantlal h ad otlon Their signals ar- proee-- d in a ~ann r i~ilar to that of the low frequeney r~nge signal- d -eribed h r inabove The head motion aetivity i- th n r nov d fron the low and high fregu~ney blosignal~ by ~anJ of r~ ti adaptive filt~ring ~oftwar ~ueh a~ that d- er~b d in chapter 9, "Adaptiv Fllt-ring,~ of ~ L~o~C:~L~CC:2~
Vol 1, written by Arnon Cohen, publi-hed by CRC Press, ~oea Raton, Fl in 1986 and incorporat d herein by r-f~rene-Sub~-et r ~pon~e to the al-rt i~ detected by ~ an~ of th aegui-ition l-ctronic a- d-~eribed her~inabov R ~pon~- d teetion i~ achieved by eo~paring the pre~ent a~plltud- to that whieh iY diately pr c d d tb- al-rt A ~ub~tantial inerease i- eon~tru d a~ a ~ub~-ct r ~pon~-Alt-rnatlv ly, tb pr --nt a~plitud- is co~pared to tbat r eord~d wb n tb ~ub~-ct is known to be aware and alert Alt-rnatively, the present a~plitud i- co~pared to a p ak a~plitude obtained when tb- ~ub~-et i~ blinking but i~ otberwi~- quie~eent, or tb- ~ignal i- eo~par d to a wavefor~ of r presentative blink~ r eord d wh-n tb- ~ub~ et i~ otherwi~e guieseent, u~ing ~ateh~d filter or cro-~ eorr lation ~ethods ~ueh a- tho~- pre~-nt~d in the abov refarenee by Arnon Coh-n Eaeh ti~ th alerting ~odule 144 i~
activated, th r~spon~- detection ~eans are aetivated and th- r ~pons- ti~e i~ ~ a~ured The re~pon~e time is additionally co~par-d to the pr-~iou~ response time If th- r--pon~e ti~ has iner-ased, typieally indieating an incr-a~e in drow~ine~, the time between periodic alerting i~ d-er-a~ed Further~ore, the alerting module 144 is operative to gradually inerea~e the intensity of the 8UBSTITUTE 8HEE r , wosl/13S84 PCT/US91iOI260 ,:

- 30 - ~7 audible sound until the r -pon~e dotection means indicate that a respon-- ha- been u asured The proc-~sing ans 140 are d~tailed in Fig 11 to which reference i8 now ad Detector module 144 comprises two prea~plifi-r- 172, of t~ type described with refer nce to Fig 6, for a plifying by a gain of typically 500 to 1000, dlff-r ntial bio~ignals r~ceiv-d fro~ two pair- of l-ctrod- a~ blies lo Pr uuplifi-ra 172 ar~ not lncorporat d into the proce-sing ~ ans 140 if th- inco~ing signal6 are r-ceived fro~ ignal proc-a-or~ 88 on fr~oQ 131 Each prea~plifier 172 receivos ~ignal- fro~ one pair of electrode aaae~blies 10 Th two a~plifi-d aignal- are ~nt to a pair of identical low frequency band pa~a filters 174 for filt-ring frequoncie~ in a pa~ band of typically 1 - 10 Hz and to a pair of id-ntical high fr-qu-ncy band pass filt~r- 176 for filtering fr qu nci-a in a pas~ band of typlcally 100 - lSOO Hz Fllt-r- 174 and 176 attenuate fregu-nci-- out~ld th ir r ap ctiv- pa~a band~ by at lea~t 12 dB p r octav Signal proce~aora 178 typically receive the filt-r-d high fr qu ncy ignal- fro filters 176 and r ctify, p ak n~- and int grate the~, producing 2s r lativoly auooth ~ignala Th re~ultant ~ignals are proportional to the poak-to-p ak a~plitude o~ the filt-r d high fr quency aignal- and have a limited bandwidth of typically o - 100 Hz A typical ~ignal proc-a-or 178 i8 shown in Fig 12 where integrated circuit~ Vl aro the TL06~ chipo ~anufacturQd by Motorola and integratod circuit~ V2 are the LM393 chip~, ~anufactured by National S-~iconductor Amplifi-r pair~ 180 and 182 amplify the ro~p ctive~filtered low and high freguency signals receivod, ro~p ctively, fro~ filters 174 And processors 178, to an amplitude in the range of a few, typically 1 - 5, volt~

~W091/13S84 PCT/US91/012~
: .
- 31 - ~7~
An A/D converter 184, typically a multichannel A/D convert-r having on- channel for each electrode assembly pa~r input, converts the amplified signals from amplifiers 180 and 182 to four digltal signals of at least 2Ni ~a~ple~ per second, where Ni is the bandwidth of th ith channel The resolution of th- samples is typically ight bit- A/D converter 184 can optionally be a coubination of an A/D convert-r and a multiplexer A ~icroproc---or 186, typically a low power consu~ing microprocessor such as the Motorola 68HCll, proco~s~ th- four digital ignals in accordance with the ~ethod de~cribed hereinabove with refcrence to Figs lOA and lOB At the appropriate ~o~ents, the microproce~or 186 activat-~ alerting ~odule 144, describ d in ~ore detail her inb-low Software pseudocode outlining th~ op ration of the microprocessor 186 is incorporat-d her-in in Annex A
Al-rting module 1~ co~prises an audio genQrator 188, such as a ton or voice synthesizer, which i~ controlled by ~icroprocessor 186, for producing on- of a ~ultitud~ of preprogrammed tone ~ignals or sounds stor d in ~icroproc-ssor 186, and an audio a~plifier 190, such as a Walkuan audio amplifier ~anufactur d by Sony of Japan, for amplifying the tone ~ignals produc d by the audio generator 188 Audio a~pliti-r 190 is al~o controlled by microprocessor 186 to n~ble the alerting module 144 to vary the amplitude of th al-rting sound according to the subject's res-pons- or lack thereof Th~ tone signals emanating from audio ~ plifier 190 are made audible by loudspeaker 148 Refer-nce is now made to Figs 14A - 14C which re~pectively illustrate front, back and side views of an s~bodi~ent of a ~etal biosignal probe 200 using any of the electrode assemblies of Fig The probe 200 typically comprises a capacitive electrode a~embly 202, such as described hereinabove particularly with respect to Fig 1, and a wiring cable 8UBSTITI.JTE SHEET
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204 for connecting the electrode 202 to a data processing syste~, described in ~ore detail hereinbelow with respect to Fig 16 The electrode 202 and wiring cable 204 are typically e~bedded in a r~latively flat probe body 206 which i~ typically couprl-~d of a stiff but flexible ~aterial, such a- nylon or oth-r co~ on plastic, and is Or suf~icient l~ngth to r-ach fro~ a tetal scalp to completely outside the ~oth~r'~ cervlx A typical lenqth i8 between 40 - 50 cm The probe 200 additionally comprises a referenc- el-ctrode 208 for providing an lectrical reference signal, sinilar to those described hereinabove in Fig 1 The refer nc electrod 208 i~ ~ounted on an outer surfac- 210 of body 206 facing the fet~l scalp and its wiring 212 is onbeddQd in body 206 Th wirinq cablea 20~ and 212 ~ay comprise a flexible print-d circuit- whos- wir~s s-rve to provide thQ wiring to l-ctrod - 202 and 208, in a manner si~ilar to that illustrat d in Fig 5 On th outer scalp-sid- surface 210 of probe 200 is a frictionous or adh r nt ar-a 214 for enabling the prob- 200 to adher to th ~calp of the fetus, ther by pr~venting th- probe 200 fro~ slipping relative to the surrac- of th- ~calp Frictionous area 214 is typic~lly co~prisQd of a layer of ribbed, soft rubber such ~8 that u~ed for dishwashing gloves, ~uch as ranu~actured by Playt-x, Inc of the USA A surface 216, on th- oppo~ite side of the probe fro~ surface 210, includQs a ~ooth ~urface 218, on the opposite side of the probe 200 from area 214, for enabling generally easy slippag- of the probe 200 against the uterine wall The probe 200 i5 typically operated a~
follows During labor, the probe 200 is inserted into the uterus of the mother and i8 positioned in a desired po~ition on the scalp of a fetus Area 214 and surface 218 enable the probe 200 to travel with the fetal head ' ' ~ ' ', ' . , '. ' ' ' ~ ' . ' ' . ' .,. ' , , . .' !. , '' '' ' ,. ,, `', .,. : :. , ~O91/13~ PCT~US91/01260 2 ~ 7 ~ ~ 9 ~

as it emerges during delivery R f-renc- is now ~ade to Fig~ lSA - lSC which resp-ctively illustrate front, back and side views of an alternative e~bodinent of fetal biosignal probe 200 using the electrode of Fig l Si~ilar reference numerals refQr to si~ilar leuents In thi- e~bodin nt, the prob 200 is optionally u--d in conjunct~on with a cover shQath 220 which cov~r- th ntlr~ l-ngth or prob- 200 and is prof-rably ~ad- of a thin pla~tic, such a~ polyethylene or ~ther co on plastic Sh ~th 220 is preferably ~t~rile and is prefer~bly di~po~abl-Th r-Sorence lectrod- 208 i~ ~ounted on an outer surfac- 222 oS sh~ath 220 facing tho fetal scalp The electrode wiring, h-r- al~o l~beled 212, passes through th wall of shQath 220 and runs down its length to wh-r it xit~ th h-ath 220 In thi~ e~bodiment, th frictionou- or adher nt ar a, h r- label-d 224, is si~ilar to that d--crib d abov , and i~ on the outer sur~ac- 222 of sh ath 220 Th uooth surface, here labeled 226, is on an outer surfac- 228 of Rheath 220 ReferencQ is now ~ad- to Fig 16 which illustrate~ a ~yst-n for obtaining fotal biosiqnals during dolivory usinq at l-ast two probes 200 of either of th abov aentionod embodi~ nts Th ~y-t-4 typ~cally couprises at least two prob-- 200 for obtaining dirf-rential fetal signals typically plac-d on oppo~ito ido~ of the fetus~s head Th- ~y~t-u al~o co~prise~ ~ignal processing equipment si~ilar to tho~- doscribed herein~bove with reference to Fig 4 Spocifically, the signal processing equipment compriaes a~plifiors 230, connected to probe 200 via electrode wiring 212 and wiring cable 204, digital 3s circuitry 240 and a power supply 245 In this configuration, however, the probes 200 will acquire fetal ECG signal~ in addition to fetal EEG ~ignals This complicates tha EEG analysis. Therefore, to remove the fetal ECG signal from the total acquired signal, an ECG amplifier 250, such as a Hewlett Packard fetal monitor model 8030 or 840, is included in the signal processing equipment. The output of amplifiers 230 and the ECG signal from amplifier 250 are typically input to digital circuitry 240 containing real-time adaptive filter software 260, such as described in Chapter 9 of the book Biomedical Signal Processing: Vol. 1 of Aronon Cohen. Software 260 removes the fetal ECG signal from the differential biosignal free of ECG signal from providing the EEG and EMG signals free of ECG artifact.
The ECG amplifier 250 preferably obtains the unamplified biosignal from one of probes 200 via the input connections to amplifiers 230. A maternal electrical reference electrode 270, such as the standard silver/silver-chloride gel disposed type disclosed hereinabove, typically placed on the mother's thigh.
Alternatively, ECG amplifier 250 can be incorpated into amplifiers 230.
If only the fetal ECG signal is desired, a single fetal probe 200 and the maternal reference electrode 270, can be used in conjunction with ECG
amplifier 250.
Reference is now made to Figs. 17 and 18 which respectively illustrate apparatus for accurately measuring a true Critical Flicker Fusion Test (CFFT) frequency score of a subject constructed and operative in accordance with a preferred embodiment of the present application and electronics to drive the apparatus.
One psychological test of particular importance for the detection of impaired cognitive function is the CFFT. Numerous clinical studies have documented the effects of various drugs, fatigue and other factors on the CFFT. Many clinical studies have the article "Critical Flicker Frequency and Psychotropic W091/13S84 PCT/US91/Ot260 ~ ~ ~ 7 ~
- 3s -Drugs in Nor~al Human Sub~-cts - A Revi-wn, by Smith and Misiak, published in ~ C~ Y~ Y~ Vol 47, pp 175 - 182, l976 These ~tudies have shown that a reduced CFFT frequency scor can be indicative of impairment of cognitive functions, uch as reaction time, visual p rception and decision ~aking In th CFFT, a ub~-ct ob~erv ~ a light source who~- int-n-ity ~ari-~ ~ccording to an o-cillation frequency Th ub~ect i- requir-d to peci~y the highest oscillation frequency, known as the critical flicker fu~ion frequency, at which the liqht source appears to flicker For frQquenci~6 greater than the critical fr quency, the light ~ourc- i~ p rcei~ed by the sub~ect to b- con~tantly lit, d-noted her in a~
lS supercritical non-flick r; for frequenc~e~ less than the critical froqu ncy, th- light source appears to flicker The purpose of the pr-sont invention i$ to provid- a r liabl- CFFT ~cor ~en for sub~ects who may have an inter-~t in trying to avoid providing an accurat- ~ti~at- of th- CFPT Such action by a subject i8 lik-ly if a low or reduced CFFT frequency score indicate- that th sub~ect has an l~pair~ent The apparatus of the pre-Qnt invention, an embodi~ent of which is ~hown in Fig 17, makes it highly i~probable for a sub~ect to clai~ a higher CFFT
fr-quency than hi~ true CPP~ frequency This is achi-v d by r-quiring the sub~ect to ~dentify a pattern of flick ring light aource6 e~beddQd or a~sociated with surrounding non-flickering light source~ which are either constant (DC) in the~r intensity or supercritically non-flickering The non-flickering sources are otherwise identical in appearance to the flickering sources In the following discussion, the light sources are LEDs it being under~tood that any light source capable of rapid intensity modulation is suitable A preferred e~bodiment of the apparatus 8UB8TITU~ SHEET
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wogl/l3s84 PCT/USgl/01260 36 ;~ 7 o ~ ~ i _ comprises a ~et of 12 id-ntical LED~ 300 capable of rapid inten~ity oscillation, arranged in a circular pattern similar to a clock face O~her patterns of multiple light source~, uch as l~near arrays, matrices S or dot array~ can alternativ~ly be e~ployed Driving electronic circuitry 302, hown in d tail in Fig 18, under th- control of a co puter 304 uppli-8 oscillating electric ~ignal- to th LED~ 300, thereby causing their inten~iti-~ to vary accordingly Th ~ubj-ct communicat-~ with the computer 304 via an input keyboard 306 or similar input means The LED~ 300 are dlvided into two groups, a background group 308 and a flick r group 310 The flicker group 310 comprise~ at l-a~t one LED The LEDs of the background group 308 ~re osc~llated at a fr-quency far great-r than any known CFFT frequency, typically 250 ~z, or ar- h-ld at a constant (DC) int-nsity Any fr quency can b- us-d to dr$ve the LEDs of th- flicker group 310 ~he o~cillation~ ~re generally ~inu~oidal although other alternating patterns can be used Th- op-ration of the apparatus is as follows LED~ of th- flicker group 310 ar- initially oscillated at a fregu ncy of approximat-ly 60 Hz, a frequency known 2s to b~ above th~ critical flicker fr quency The oscillation fr-qu-ncy of the flicker group 310 is r duc-d, typically at a rat- of 1 Hz per second, until the ub~-ct id-ntifi-~ to th computer 304 via the k-ybo~rd 306 that he d~t~ct~ ~t lea~t one of the LEDs 300 flickering Th co~puter 304 th~n ~tops reducing the o~cillation fr-quency of the flicker group 310 The recording of the ~ub~ect~s CFFT frequency score i~ d-pendent on hi~ identifying the correct flicker group Incorrect identification of the flicker 35 group can be indicative of a deliberate attempt to gain a fraudulent ~core For example, assu~ing that just the LED in the 8UBSTlllJTE SHEET

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6 o'clock position belongs to the flicker group 310, the ubject has only a 1 in 12 chance of gues~ing correctly the flickering LED b-for- hi- tru- CFFT i~ reached If two LEDs aro used, the sub~ect has le~8 than a 1~ chance of correctly pinpointing which LEDs are flickering before hi~ true CFFT is reached Not only doe- the proposQd appar~tu~ prevent a sub~ect fro~ deliber~tely raising hi- tru- CFFT, but the subj-ct i~ al~o unlik ly to r-port a CFFT below his true lo readout This is bec~use th- ~ub~ect, after detecting flick ring of on Or th LED , i- not lik ly to wa~te ti~ in trying to r cogniz- th- entir flicker group whil- th- o~c$11ation fr qu-ncy continue~ to drop, th-reby giving a CFFT scorQ bolow his tr~- score Instead, the sub~ect i8 ~ore likely to first notify the computer 304 that he has detected flickering in at least on- of th- LED~ H c~n then identify the other flickoring LED~ without low ring hi- ~coro It will b appr-clat-d by porsons skilled in the art that th- pre~-nt invention 18 not limited to what has been particularly shown and described her~inabovo Rather the 8cope of the present invention is defined only by th clai~ which follow 8U8STlTlJTE SHEET
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Claims (75)

AMENDED CLAIMS
[received by the International Bureau on 29 August 1991 (29.08.91);
original claims 1-75 replaced by amended claims 1-75 (11 pages)]

1. Apparatus for mounting electrodes on a human body in order to obtain human biosignals comprising:
close-fitting clothing means;
a plurality of electrodes, at least one of which is capacitive, mounted to said close-fitting clothing means:
removable cover sheet means for providing a sterile interface between the skin and at least one of said at least one capacitive electrode and for providing an electrical reference signal for at least one of said at least one capacitive electrode: and joining means for joining said removable cover sheet means to at least one of said at least one capacitive electrode.

2. Apparatus according to claim 1 and also including flexible circuit means for mounting said plurality of electrodes onto said close-fitting clothing means.

3. Apparatus according to claim 2 and wherein said flexible circuit means are fixedly attached to said close-fitting frame.

4. Apparatus according to claim 2 and wherein said flexible circuit means are removably attached to said close-fitting frame.

5. Apparatus according to claim 2 and also comprising signal processing means mounted on said flexible circuit means for preamplifying, transient protecting and filtering at least one differential biosignal obtained between signals received from two of said electrodes.

6. Apparatus according to claim 1 and also comprising signal processing means for preamplifying, transient protecting and filtering at least one differential biosignal obtained between signals received from two of said electrodes.

7. Apparatus according. to claim 1 and wherein said joining means include electrical contact means between said reference means and at least one of said plurality of electrodes.

8. Apparatus according to claim 1 and wherein said removable cover sheet means include conductive means for providing a conductive path between at least one of said plurality of electrodes and the human body.

9. Apparatus according to claim 1 and wherein said joining means are of the following group: press contact pairs, adhesive pads or Velcro (registered trademark).

10. Apparatus according to claim 1 and wherein said close-fitting clothing means is one of the following group: a glove, a face mask, goggles, a cap, a sweat band, a head band or a helmet.

11. Apparatus according to claim 10 and also including a photoplethysmographic sensor.

12. Apparatus for mounting electrodes on a human body in order to obtain human biosignals comprising:
close-fitting clothing means:
a plurality of electrodes, at least one of which is capacitive, mounted to said close-fitting clothing means;
removable cover sheet means for providing a sterile interface between the skin and at least one of said at least one capacitive electrode: and joining means for joining said removable cover sheet means to at least one of said at least one capacitive electrodes.

13. Apparatus according to claim 12 and wherein said removable cover sheet means include reference means for providing a reference signal for at least one of said plurality of electrodes.

14. A referenced capacitive electrode assembly for mounting on human skin comprising;
a capacitive electrode mounted in a substrate;
removable cover sheet means separate from said capacitive electrode for providing a reference signal to said capacitive electrode and for providing a separable interface between said human skin and at least one of said electrodes;
and joining means for joining said cover sheet means to said capacitive electrode.

15. Assembly according to claim 14 and wherein said joining means include electrical contact means between said cover sheet means and at least one of said plurality of electrodes.

16. Assembly according to claim 14 and wherein said removable cover sheet means include moist conductive means for providing a moist conductive path between at least one of said plurality of electrodes and said human skin.

17. Assembly according to claim 14 and wherein said joining means are one of the following group: press contact pairs, adhesive pads, or Velcro (registered trademark).

18. A referenced capacitive sensor channel assembly for mounting on human skin for the purpose of measuring bioelectric signals comprising:
a set of at least two capacitive electrodes mounted in a substrate;
removable cover shed means separate from said set of capacitive electrodes for providing a separable interface between said human skin and at least one of said set of capacitive electrodes and including reference means for providing a reference signal for said sensor channel;
joining means for joining said cover sheet means to said set of capacitive electrodes; and signal processing means for processing said bioelectric signals.

19. Apparatus for alerting a drowsing subject comprising:
a close-fitting frame mounted on a head of said subject;
a plurality of electrodes mounted to said close-fitting frame for measuring biosignal activity occurring generally in the area of the face and head of said subject;
data processing means for processing said biosignal activity into baseline curves and for determining when said biosignal activity crosses a threshold related to said baseline curves for longer than a predetermined amount of time indicating an increased risk of drowsiness;
alerting means for alerting said drowsing subject upon determination by said data processing means that a state of drowsiness has occurred; and response detection means for detecting the subjects response to an alert issued by said alerting means.

20. Apparatus according to claim 19 and wherein at least one of said plurality of electrodes is capacitive.

21. Apparatus according to claim 19 and wherein said alerting means include means for producing a variety of audible sounds.

22. Apparatus according to claim 21 and wherein said alerting means also include means for varying the intensity of said audible sounds.

23. Apparatus according to claim 19 and wherein said response detection means include means for measuring time to respond.

24. Apparatus according to claim 23 and wherein said means for measuring time to respond include means for comparing a current time to respond with a previous time to respond.

25. Apparatus according to claim 24 and wherein said alerting means include means for increasing the intensity of said audible sounds until said response detection means detect a response.

26. Apparatus according to claim 19 and also including a head motion sensor for detecting head motion.

27. Apparatus according to claim 19 and wherein said close-fitting frame is one of the following group: a frame of a pair of eyeglasses, a frame of a face mask, a hat, a cap, or a head band.

28. Apparatus according to claim 19 and also including flexible circuit means for mounting said plurality of electrodes to said close-fitting frame.

29. Apparatus according to claim 19 and wherein said mounting means are fixedly attached to said close-fitting frame.

30. Apparatus according to claim 19 and wherein said mounting means are removably attached to said close-fitting frame.

31. A method of alerting a drowsing subject including the steps of:
receiving biosignals from electrodes placed on and near the face of said subject:
processing said biosignals into baseline curves and determining when amplitudes of said biosignals cross said baseline curves for longer than a predetermined amount of time indicating an increased risk of suspected drowsiness:
alerting said subject via an alerting action when said state of drowsiness is indicated; and detecting a response to said alerting action.

32. The method of claim 31 and wherein said alerting action differs each time said increased risk of drowsiness is indicated.

33. The method of claim 31 and wherein said alerting action is an audible sound.

34. The method of claim 31 and wherein an intensity of said audible sound is initially low and intensifies until said subject gives a confirmatory response.

35. The method of claim 31 and also including the steps of measuring reaction time from initiation of an alerting action to detection of subject response, and comparing said reaction tine to those of previous alerting actions thereby to estimate alertness.

36. The method of claim 31 and also including the step of periodically alerting the subject and testing the subject's reaction time even if no drowsiness is detected thereby to verify alertness.

37. Apparatus for rapidly preparing to obtain biosignals from a human body comprising:
close-fitting clothing means;
a plurality of electrodes mounted to said close-fitting clothing means, wherein at least one of said electrodes is a capacitive electrode; and electrical reference means removably mounted to said close-fitting clothing means for providing an electrical reference signal for use together with said at least one capacitive electrode.

38. Apparatus according to claim 37 and wherein said close-fitting clothing means is at least part of a pilot flight helmet.

39. Apparatus according to claim 37 and also including flexible circuit means for mounting said plurality of electrodes onto said close-fitting clothing means.

40. Apparatus according to claim 37 and wherein said flexible circuit means are fixedly attached to said close-fitting clothing means.

41. Apparatus according to claim 38 and wherein said flexible circuit means are removably attached to said flight helmet.

42. Apparatus according to claim 38 and also comprising signal processing means mounted on said flexible circuit means for preamplifying, transient protecting and filtering at least one differential biosignal obtained between signals received from two of said electrodes.

43. Apparatus according to claim 37 and also comprising signal processing means for preamplifying, transient protecting and filtering at least one differential biosignal obtained between signals received from two of said electrodes.

44. Apparatus according to claim 37 and also including a cover covering at least one of said electrodes.

45. Eye tracking apparatus for tracking the direction of a subject's gaze comprising:
close-fitting clothing- means mounted close to the face of said subject;
at least first and second pairs of capacitive electrodes for obtaining biosignals relating to said gaze mounted onto said close-fitting clothing means wherein said first pair is mounted so as to be above and below one of said subject's eyes and wherein said second pair is mounted so as to be on opposite sides of one of said subject's eyes; and means for converting said biosignals into position information.

46. Eye tracking apparatus according to claim 45 and including apparatus at which to be gazed while maintaining the subject's head fixed.

47. Eye tracking apparatus according to claim 46 and wherein said means for converting include means for calibrating between said gaze and positions on said apparatus at which to be gazed.

48. A fetal biosignal probe for rapidly obtaining biosignals of a fetus comprising:
at least one capacitive electrode means mounted on a flexible body for obtaining fetal biosignals; and reference means for providing a reference signal for said capacitive electrode means.

49. A fetal biosignal probe according to claim 48 and wherein said reference means is a conductive electrode.

50. A fetal biosignal probe according to claim 48 and wherein said reference means is mounted on said flexible body.

51. A fetal biosignal probe according to claim 48 and also including a removable cover sheath for maintaining sterility of said probe.

52. A fetal biosignal probe according to claim 51 and wherein said reference means is mounted to said cover sheath.

53. A fetal biosignal probe according to claim 48 and also including a frictionous area for enabling said probe to adhere to a portion of fetal skin.

54. A fetal biosignal probe according to claim 51 and also including an adherent area on said sheath for enabling said probe to adhere to a portion of fetal skin.

55. A system for rapidly obtaining fetal biosignals comprising:
at least two fetal biosignal probes according to claim 48 to be temporarily attached to a fetus scalp; and signal processing means for processing fetal electroencephalographic signals.

56. A system for rapidly obtaining biosignals of a fetus comprising;
at least one fetal biosignal probe according to claim 48 temporarily attached to a fetal scalp;
an electrode attached to skin of a mother of said fetus for receiving a maternal electrical reference signal;
and signal amplifying and filtering electronics attached to said electrode and to said fetal biosignal probe for acquiring fetal electrocardiographic biosignals.

57. A system according to claim 55 and including means for providing fetal non-electroencephalograph signals and filter means for removing said fetal non-electroencephalograph from said fetal electroencephalograph signals.

58. A system according to claim 57 and wherein said means for providing fetal non-electroencephalograph signals include a fetal biosignal probe and an electrode attached to skin of a mother of said fetus for receiving a maternal electrical reference signal.

59. Apparatus for measuring a critical flicker fusion frequency of a subject comprising:
a plurality of light sources arranged in a predetermined pattern comprising a first multiplicity of background light sources and a second multiplicity of flicker group light sources:
driving circuitry means for illuminating the background light sources so as to appear non-flickering, for oscillating the flicker group light sources at a gradually decreasing oscillation frequency and for maintaining the background and flicker group light sources visually indistinguishable;
input means operated by the subject for indicating to the driving circuitry means at which frequency flicker is first observed in the flicker group and which of said plurality of light sources belongs to the flicker group.

60. Apparatus according to claim 59 and wherein said predetermined pattern is a pattern familiar to said subject.

61. Apparatus according to claim 59 and wherein said driving circuitry means maintains a time-averaged intensity of said background group and said flicker group equivalent.

62. Apparatus according to claim 59 and wherein said pattern is a member of the group consisting of: hour positions of a clockface, number positions on a calculator keypad, number positions on a telephone keypad, linear arrays, a matrix representing an alphanumeric character, a matrix containing a pattern representing a familiar object or a matrix containing a pattern representing a familiar scene.

63. Apparatus according to claim 59 and wherein said oscillation frequency is initially set at a frequency above the highest known critical fusion frequency.

64. Apparatus according to claim 59 and wherein the background light sources are maintained at a constant intensity and thereby, do not flicker.

65. Apparatus according to claim 59 and wherein the background light sources are oscillated at a frequency above the highest known critical fusion frequency.

66. Apparatus according to claim 59 and wherein said second multiplicity is 1.

67. A method for measuring a critical flicker fusion frequency of a subject comprising:
providing a plurality of light sources arranged in a pattern familiar to a subject comprising a first multiplicity of background light sources and a second multiplicity of flicker group light sources;
illuminating the background light sources so as to appear non-flickering;
oscillating the flicker group light sources at a gradually decreasing oscillation frequency;
maintaining the background and flicker group light sources visually indistinguishable;
requiring the subject to indicate at which frequency flicker is first observed in the flicker group and which of said plurality of light sources belongs to the flicker group light sources.

68. A method according to claim 67 and wherein the background light sources are maintained at a constant intensity.

69. A method according to claim 67 and wherein the background light sources are oscillated at a frequency above the highest known critical fusion frequency.

70. A method according to claim 67 and wherein the step of requiring comprises the step of indicating at which frequency the flicker is observed before the step of indicating which of said light sources belong to the flicker group light sources.

71. A method according to claim 67 and wherein the difference in the frequency of the background light sources and the frequency of the flicker group light sources is never less than a highest known critical flicker frequency.

72. A method according to claim 67 and including the step of maintaining a time-averaged intensity of said background group and said flicker group equivalent.

73. A method according to claim 67 and wherein said pattern is a member of the group consisting of: hour positions of a clockface, number positions on a calculator keypad, number positions on a telephone keypad, linear arrays, a matrix representing an alphanumeric character, a matrix containing a pattern representing a familiar object or a matrix containing a pattern representing a familiar scene.

74. For mounting on human skin, a capacitive electrode whose capacitive element comprises:
a housing having a skin-facing side in which there is an opening, said skin-facing side to be placed adjacent to said human skin:
a conductive element placed in said opening lying along said skin-facing side; and a removable dielectric cover covering said opening and touching said conductive element and said human skin.

75. A referenced capacitive electrode assembly for mounting on human skin comprising;
a substrate;

a housing, mounted in said substrate, having an opening on a skin-facing face, said skin-facing face to be placed adjacent said human skin;
a conductive element placed in said opening along said skin-facing face;
a removable dielectric cover covering said opening and touching said conductive element for providing a sterile interface between said human skin and at least one of said electrodes; and joining means for joining said cover to said substrate.