Ultrasonic two-axis rotation detector

transcript

IF,EE TRANSACTIONS ON BTOMEDICAL ENGINEERING. VOL. .37. NO. 5. MAY I99O

Ultrasonic Two-Axis Rotation Detector

REMY ROLLERO, MAURICE OUAKNINE, JEAN_LOUIS VERCHER,JOHN L. SEMMLOW, NaEHasER, IEEE, nNn GABRIEL M. GAUTHIER

Abstract-A two-axis rotation monitor is described which deter-mines the relative displacement between a pair of ultrasonic detectors

using the phase difference of a continurlus ultrasound wave generated

by a single, distant source. The monitor has been used to measure head

rotations around the vertical and horizontal axes, but can easily be

adopted to other body segment rotations or translations. The deviceproduces high sensitivity recordings of wide spatial and dynamic range'

Although the device is quite linear with good isolation between chan-nels, a computer-based linearization/calibration routine is describedwhich further increases linearity and reduces crosstalk' The device is

unobtrusive, inexpensive, and has proven reliable and easy to use'

IrurnooucrloN

/^\VER the past few years researchers in such diverse(-lur"u* u, ,pon, physiology, neurophysiology, bio-physics, and ilinical medicine have worked to developinstruments for monitoring eye, head, or other bodymovements. The fact that for any given body movementno one technique has proved definitive indicates that theproblem is not easily solved by a single, universal ap-proach, and that for each application a specific monitoringtechnique may be optimal.

In the study of gaze control, the neural control of theeyes in space, separate monitoring of the eye position inthe orbit and the head position in space is required. Eyeposition may be monitored by several common techniqueswhich include electrooculography [l-[3], infrared orvideo corneal reflection [3], infrared scleral reflection [3]-[6], and magnetic search coil mounted on a scleral contactlens [3], t7l-tl0l. Head motion has been measured withinfrared light emitted from an array of cells on the head

[11], [2], video recording [13], [4], and, more gener-ally, through uni- or multiaxis potentiometers [5]-[8].

Potentiometric devices are obviously inexpensive, butrequire a cumbersome head mount connecting to the po-

tentiometer. The head mount is usually a helmet which,to prevent slippage, must be tightly secured to the sub-ject's head. The weight, inertia, and tight fit of the helmetmay cause changes in the motor strategies employed when

Manuscript received December 28, 1988; revised August 8, 1989. Thiswork was supported by a grant from ESSILOR of France.

R. Rollero, M. Ouaknine, J.-L. Vercher, and G. M. Gauther are withSensory-Motor Control Laboratory, University of Provence, 13397 Marseilles Cedex 13, France.

J. L. Semmlow is with the Department of Biomedical Engineering, Rut-gers University, Piscataway, and the Department of Surgery, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ 08855.

IEEE Log Number 9034245.

performing sush tasks as reading, target tracking, or tar-get fixation [9]. The magnetic search coil technique, al-though developed to monitor eye movement, may be used

ro advantage in head movements [10], [20]. While the

application of one or two coils to the head is unobtrusive,the large coils used to generate the magnetic fields con-

siderably limit both the field of view and maneuveringspace of the subject.

We have developed an inexpensive, precise, and reli-able technique for measuring head rotation, The devicehas been designed to simultaneously monitor head rota-

tions around horizontal and vertical axes, but may be ap-

plied to other body segment rotations or translations. The

basic physical principle utilizes airbome ultrasound tomeasure the relative displacement between a pair of de-

tectors l2ll, 1221. The detectors are mounted so that themovement of interest produces a change in their relativeposition with respect to a distant reference. This relativedisplacement is measured using the phase difference of a

continuous ultrasonic wave generated by a distant source.

A unique circuit design significantly increases the oper-

ating range for a given ultrasonic frequency without re-

ducing the measurement bandwidth.

Mr,rnon RNn INapLsN,{ENTATIoN

As stated, the relative displacement between a pair ofultrasonic detectors is measured using the phase differ-ence in an ultrasonic wave emitted by a distant source.

Since it is desired to monitor orthogonal angular rota-

tions, two detector pairs, derived from three individualdetectors, are mounted on a bracket tFig. l(a)1. The three

detectors are arranged in a right triangle so that in the

initial position one detector pair [D', and D, in Fig. l(a)]is aligned with the vertical axis while the other pair ID"and D,, Fig. l(a)l is aligned horizontally. Taking as areference the point midway between the horizontal pair

[P in Fig. 1(a)], the initial position P1 is assumed to liealong the Z axis tFig. l(b)]. If the plane of the detectortriangle is rotated an angle 0 around the vertical axis and

an angle f away from the horizontal plane, the referencepoint will assume a new position Pz (Fig. l(b)1.

The relative position of the three detectors with respect

to the emitter can be defined in terms of 0 and f . Specif-ically, if we assume that the emitter is sufficiently distantfrom the detectors so that the ultrasonic wavefront can be

o0t8-9294t90/0500-0450$01.00 0 1990 IEEE

ROLLERO ?r d/-: ULTRASONIC ROTATTON DETECTOR

C2 Qcm)

C1 (a cm)

Fig. l. (a) Relative positioning of the three ultrasonic detectors on amounting bracket. (b) Arrangement ofthe source and dctectors. The de_tectors are shown for two possible positions, p, and p,, correspondingto an initial position and to rotations, d and d, about the vertical anàhorizontal axes. The distance L between the sourcrr and the rotationalaxes should be between 30 and 160 cm Ibr reasonably linear output overthe range of +30".

considered everywhere as perpendicular to the Z axis, thenthe relative distance of detector D, from the emitter withrespect to detector D, can be shown to be

.r: C; sinO (r)

shown in Fig. 2. Thesame ultrasonic transducer (MASSAProducts Corp., Model TR-89/B, Type 40) was used forthe emitter and the three detectors. They were frequencymatched (40 + 2 kHz) to maximize signal amplitude.

Using an operating frequency of 40 kHz, with a corre_sponding wavelength of 0.8 mm, implies a maximummeasurement range of 0.4 mm (maximum measurable dis_tance change between the emitter and any detector) as_suming a half-wavelength detection method. Using syn-chronized frequency dividers, the range may be incieaiedby a factor of 2" where n is the number of divider stages.In our application, the emitters were separated by 4 cmand placed l0 cm from the axis of rotation. Thus, a *40.rotation produced a change in distance of 0.28 cm. Usinga full wavelength detection technique, a four-stage fre-quency divider provides more than adequate range.

Only two receiver channels, serving one detector pair,are shown in Fig. 2. The first element in each of the twochannels is an amplifier with a gain of l0 000, imple-mented with two ac-coupled operational amplifier stages,each with a gain of 100. The amplifier outputs are con-verted to square waves using Schmitt triggers. Before thephase difference is determined these square wave outputsare divided by four using binary counters. As describedabove, this divider circuit expands the operating range byextending the measurable phase difference over manycycles. However, it is essential that the divider remainsynchronized.

The phase difference between the output of each detec-tor pair is obtained by first multiplying the two squarewaves, then low-pass filtering the resultant waveforms.This approach, which is similar to that used in balancedmodulator/demodulators and phase-lock loops, providesan analog voltage which is proportional to the phase anglebetween the two signals. The multiplier is implementedusing two interacting flip-flops. The low-pass filter is atwo-pole Butterworth with a cutoff frequency of 1000 Hzand is implemented with standard op-amp circuitry. Thisfilter sets the limiting measurement bandwidth of the de-vice: at 1000 Hz it is more than adequate for trackingphysiological movements.

To minimize the influence of errors caused by inade-quate signal output from any ofthe three detectors, a spe-cial signal monitoring circuit is provided. (Rather laigeerrors occur if the binary counters lose synchronization.)Three similar monitoring circuits evaluate the sign;rls fromeach of the three Schmitt triggers. These monitoring cir-cuits employ a pair of monostable multivibrators ind agate to produce an error signal if the frequency of thesquare wave signal falls above or below preset limits. As_sertion of an error signal from any of the three monitoringcircuits triggers an "error" flip-flop whose output driveian error display LED. Signal loss errors are generally dueto an obstruction between emitter and detectors, or amovement exceeding the range limit of the device, andeither problem can be easily corrected by the operator.

where C1 is the fixed distance between D, and D. [Fig.1(a)1. Similarly, the relative distance of D,. from the sourCewith respect to D. is

! : Cz cos 0 sin @

where C2 is the fixed distance between D, and D,..

Hence, 0 and @ are directly related to x and y which inturn can be determined from a measurement of the phasedifference between the ultrasound signals detected aipairsD, - D, and D,,, - D,. Note that this relationship is in_dependent of the distance between the emitter and the de-tectors IZ in Fig. l(b)] and is insensitive ro translationmovements. Moreover, if 0 and @ are small, the smallangle approximation applies and the distance measure_ments, x and y are linearly related to 0 and @. As will beshown in the next section the relationship between deviceoutput and input rotations is, in fact, very nearly linearand the cross coupling implied by (2) is minimal.-

A block diagram of the instrumentation developed tomeasure the phase difference between the detector pairs is

30<L<160cm

Ampliliers Schmitttriggers

frequency limitdetectors

Emitter: NASSA pR9DUCTS CoRpHeceptors: modet TR-A9/8. TUpe 40

Fig. 2. Block diagram showing the principalsenslng monrtor.

IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING. VOL. 37. NO. 5. MAY I99O

divider phase comparator

Fc= 1 kHz

initialization

subsections of the rotation

ligure2:

After correction, the error condition must be reset by theoperator via a "reset" push button. In addition to clearingthe error flip-flop and error detector circuitry, the resetoperation initializes the binary counters, synchronizing thedivide operation.

The outputs of the two phase comparators are analogvoltages proportional to the two angles of interest 0 and@. These voltages are fed through two final amplifierswhich provide variable gain and bias.

Proper operation of the device requires only that theoverall working area be relatively free of metallic objectswhich can produce artifact-inducing reflections, and thatthe space between emitter and detectors be free of objectswhich would block the ultrasonic source.

EvnLuarroN

The device has been evaluated with respect to accuracy,linearity, cross-coupling between channels, and static anddynamic range. Accuracy and linearity were evaluated bymounting the detector bracket 6 cm in front of a shaftrotating around the vertical axis. Precise measurement ofthe rotation was obtained from a potentiom:ter coupled tothe shaft. We measured instrument outputs over an 80"range then carried out a similar operation after turning thedetector bracket by 90'. Thus, we calibrated both x andy channels and evaluated the cross coupling betweenchannels in both directions. Fig. 3 shows the calibrationcurves obtained with the emitter placed 100 cm from thedetector bracket. Both;r [Fig. 3(a)] and y [Fig. 3(b)] chan-

Fig. 3. Static response curves obtained from caliLrrated rotations about asingle axis. (a) -v (and -{) outputs versus {. (b) -r (and -r') outputs versus0.

nel outputs are quite linear over a !20" range about thecenter of rotation. Beyond that range saturation slowlydeveloped. At the extreme amplitudes of f40' the non-linearity was less than l0% of the maximum response.

-l-l30 40

ROLLERO ?r d/.: ULTRASONTC ROTATION DETECTOR

The cross-coupling increased proportionally with rota-tion around the main axis. At its maximum, it was foundto be around 8% of the output of the tested channel. Thenature ofthe cross-coupling curves suggested that most ofthe interaction between vertical and horizontal channelsresults from either misalignment or improper positioningof the detectors.

The accuracy of both x and y channels was assessed forthree values of separation between emitter and receptors.Fig. 4(a) and (b) shows the calibration curves of rhe xchannel and y channels for distances of 160, 100, and 25cm. For this evaluation, the detector bracket was l0 cmin front of the axis. The graph shows that the linear rangedecreased from *40o, at an emitter/receptor distance of160 cm, to *30" at a distance of 25 cm. If the distancebetween the emitter and detectors is kept between 30-160cm, the linearity will be better than 5% over the *30"operating range.

The linearity of the monitor was also assessed along thediagonal axes. This was obtained by offsetting the emitterf 45' with respect to the axis of the rotation and measur-ing x and y outputs. The curves thus obtained were fairlylinear throughout the tested range of +40. [Fig. 5(a) and(b)1.

Additional tests were carried out to directly evaluatelinearity, stability, and measurement bandwidth. Fig. 6shows recordings obtained when the detector bracket wasmounted 8 cm off the axis of rotation of a servo-controlledvertical shaft. For each group of curves, the upper traceis the stimulus as measured by the potentiometer, the mid-dle trace is the output of the vertical channel, and thelower trace is the output of the horizontal channel. Withthe detector bracket mounted horizontally, a sinusoidalwaveform was applied to stimulate the x channel [Fig.6(a)1. To stimulate the y channel, the detector bracket wàsturned 90' [Fig. 6(b)] while rhe srimulus for oblique ro-tations was produced by mounting the bracket diagonallywith respect to the shaft [Fig. 6(c)]. Step stimuli were alsoapplied to the shaft with the bracket in both horizonraltFig. 6(d)l and verrical [Fig. 6(e)] positions. Finally, a 3Hz sinusoidal waveform was applied with the bracketmounted obliquely on the shaft [Fig. 6(f)]. All recordingsshow exceptional linearity as table rotation and monitôroutputs are nearly identical. The cross coupling is quitelow, less than lO%, as predicted by the static calibrationcuryes. The high frequency oscillations noted in the stepresponses tFig. 6(d) and (e)l are due to servo-motor in-stabilities and demonstrate the high frequency response ofthe two-axis rotation detector.

HuveN Sus:Ecr EveluerroNAn alternative evaluation of device performance may

be_ conveniently carried out in a protocol which closelyfollows the intended use of the device, that is, monitoringtwo-axis human head rotations. Fig. 7(a) shows the ei_perimental configuration. The subject was seated in frontof a video screen on which visual targets were presented.The task of the subject was to shift his gaze from a start_ing target to another target presented l0-20" from the ini_

Fig. 4. Static response curves obtained f'rom calibrated about a single axisfor various spacings between source and detectors. (a) _v ( and r )

-outputs

versus {. (b) x (and _y) outputs versus 0.

Fig. 5. Static response curves obtained from calibrated rotations about twoaxes simultaneously. (a) x and _l,outputs for *g and +d rotations. (b).rand y outputs for f 0 and _@ rotations.

tial point. The head was free to move, so that both thehead and eyes were involved in the gaze shift.

In these experiments the detector unit was attached toa small bite-bar consisting of dental wax and secured be_tween the subject's teeth. This arrangement was ideal forsecurely positioning the detectors with respect to the headwhile avoiding an alteration of the subject's movementstrategy. The subject was 60 cm from the screen so thata distance ofabout 50 cm separated the detectors from theemitter.

IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING' VOL' 37' NO' 5' MAY I99O

æ cteg

---nlV>-^-VVtz.--

down for convenience so, that they will appear to be less

than the calibration stimulus' The calibration curve cal-

culated by the computer from these data is shown in Fig'

zi.j. eig. 7(d) shows a series of movements similar to

ifr"i" "tîtg.'Z(U)

atter compensation by the linearization/

calibrationllgorithm described below''-fgno.ing thi intentional reduction in scale' the data of

Figl ZO) à.*onrtrut" good linearity over the range tested'

Nonetheless, an on-line linearization/calibration algo-

tifttn itptoved both linearity and crosstalk' resulting in

a highly accurate two-dimensional output [Fig' 7(d)] ' This

;lg;?"il is based on the assumption that the decoupled'

iin'*rit"A outputs V.and tr/, could be described' to a first

approximation, by the following set of equations:

Vv: av *ias

az'xlat'l*aq'x'Y'x2+aa'!2

Vv: bt -f bz' x ) fu ' ! * bq' x' Y

* bs' xz + b6' y2.

Coefficients ai and b, were computed using a second-

order polynomial least-square regression from the 25 data

pairs obtained during calibration. Thes-e values were

stored and used to determine V, and Z'' from the output

channels.r and y. This linearization program was carried

out on-line at a rate of 100 samples/s.Fig. 8 shows a typical eye/head tracking sequence re-

cordéd after calibration while the subject shifted gaze from

a center fixation target to a second target l5o in the pe-

riphery. The gaze movement ("G" in Fig. 8) is calcu-

laied as the algebraic addition of the head ("Ë1" in Fig'

AEwrMWI

Fis. 6. Dynamic responses obtained by mounting the detectors on a servo-- -ariu.n turntable. Ëor each data group the upper trace is from a poten-

,iorn",., connected to the tumtabie, tÀt ttnt"t ttuct is the -v channel out-

;; ;;â ,h" lo*", trace is the x channel output The left-hand groups

show sinusoids and step responses for changes in d' while the center and

ri;îi-Ë;;d ;;p. trtoi" the same data fbrthanges in d and combined

rotations, resPectivelY.

8) and eye ("E" ) movements' A large saccade was pro-

duced mâving the eye almost to the target' As the head

started to move toward the peripheral target, the eye re-

turned in a well coordinated motion to a centered position

in the orbit. During the eye re-centering sequence' gaze

remained stable in space.

These movements were obtained using a simple' linear

calibration procedure requiring only a few seconds' This

simplifieO piocedure was reproducible from run to run and

*us ,uffi"ient to produce linear recordings without need

of further "orr""tion

over a *30o range' For larger

ïanges, the on-line linearization/calibration was neces-

,uri to compensate for crosstalk and saturation nonline-

arity.

CoNcl-ustoN

The two-axis rotation detector developed for head

movement recording (but easily adapted to other move-

ments) is well suited to high-sensitivity recordings with

wide dynamic range. Linearization is not necessary over

a 60" iange if the movement is restricted to one axis at a

time. Foitwo-axis monitoring, calibration/linearizationis necessary for movements which extend beyond 20-30'from center. The linearization algorithm described here is

quite efficient with respect to processor time, so that a

rypical microcomputer can perform this linearization on-

tine, at a data sampling rate of around 100 samples per

second.Intensive use of the device over the past twelve months

in eye/head tracking experiments has proved that the ul-

ROLLERO e, a/.: ULTRASONIC ROTATION DETECTOR

Time (ms)

Fig. 8. Time recording of a gaze movement response showing the headmovement and eye movement components.,Il: head movement; E: eyemovement; and G: gaze movement computed as the sum ofhead and eyemovements.

'îl,. - .

-t'fr.-.,. .v.r

-t ---'-''. -a

-t' **"-(, - -{'l/iitv/i\

{;- -- -?' .--1'

I",f ' --" '*' -ia " --'- --tI I (d)'

ttiitr --" .:1r

..,ti.

r:E*4ial * ."-::;

(.' l'1

r'tltI

Fig. 7. Experimental arrangement for evaluating the performance of thetwo axis monitor on a human subject during gaze movements. (a) Thesubject is shown during the calibration of head-only movements. An eyepointer attached to the mouth piece l) is used to align the head with a

succession of targets presented on a video screen 3). Also representedare the eye movement detectors 2) and associated electronics 4), and thehead movement monitor 5) including the ultrasonic detectors l). (b) Twoaxis monitor outputs obtained from head-only movements. Scale is in-tentionally decreased to be less than the calibration grid. (c) Computergenerated calibration curve derived from the head-only movement re-corded in (b). (d) Head movements recorded and shown on the screen,superimposed on the 25 point stimulus grid. The head movement monitoroutputs were processed on-line using the linearization/calibration algo-rithm.

trasonic approach is highly reliable. Potential artifactsfrom reflections off metallic objects can be easily avoided.Objects placed laterally or beyond the emitter usually donot induce problems; however, large metallic massesplaced behind the detectors may produce reflections whichwill disrupt phase comparison. When such problems arise,the alarm light (LED) provides clear indication of the dis-turbance.

Although highly reliable and precise, the monitor canbe constructed with inexpensive components. We antici-pate that this device will provide a cost effective mea-surement technique for researchers involved in the studyof head and arm movement in both man and animals.

Note: A schematic diagram of the monitor and relatedinformation can obtained by writing: Dr. Gabriel Gau-thier, Laboratoire de Controles Sensorimoteurs, U.A.C.N.R.S., Université de Provence, Avenue EscadrilleNormandie-Niemen, 13397 Marseilles Cedex 13, France.

o)oE!-

.9.=ooo-

RepenpNces

tll J.C. Armington and R. M. Chapman, "Temporal potentials and eyemovements," EEC clin. Neurophvsiol., vol. I I, pp. 346-348, 1959.

[2] W. G. Iacono and D. T. Lykken, "Two-year retest stability eyetracking performance and a comparison of EOG and infrared record-ing techniques: evidence of EEG in the EOG," psycltoph,tsiol., vol.18, pp.49-55, 1981.

[3] G. Hung, K. Ciuffreda, and J. Semmlow, "The near response: Mod-eling, instrumentation, and clinical applications," IEEE Truns.Biomed. Eng., vol. BME-31, pp. 910-9t8, 1984.

t4l G. M. Gauthier and M. Volle, "Two-dimensional eye moven)entmonitor for clinical and laboratory recordings," EEG clin. Neuro-physiol., vol. 39. pp. 285-291, t915.

[5] K. Kielgast, "The reliability of the NAC-V: A preliminary test," inEye Movements: From Physiology to Cognition, J. K. O'Regan andA. Levy-Schoen, Eds. North-Holland: ElsevierScience, 19g7, pp.656-657.

t6l J. P. H. Reulen, J. T. Marcus, D. Koops, F. R. De Vries, and G.Tiesinga, "Precise recording ofeye movement: The IRIS techniquePart 1," Med. Biol. Eng. Comput., vol. 26, pp. 20-26. l9gg.

t7l D. A. Robinson, "A method of measuring eye movement using ascleral search coil in a magnetic field,," IEEE Trans. Biomatl. Eng..vol. BME-10, pp. 137-145, 1963.

[8] H. Collewijn, F. Van Der Mark, and T. C. Jansen, .,precise record-ing of human eye movements," Vision Res., vol. 15, pp. 441'.45O,t975.

tgl R. S. Remmel, "An inexpensive eye movement monitor using thescleral search coil technique," IEEE Trans. Biomed Cng., vol.BME-31, pp. 388-390. 1984.

[0] H. J. Kasper, B. J. M. Hess, and N. Dieringer, ..A precise and in-expensive magnetic field search coil system tbr measuring eye andhead movements in small laboratory animals." J. Neurosci. Meth.,vol. 19, pp. ll5-124, 1987.

tlll H. J. Woltring, "Calibration and measurement in 3-climensionalmonitoring of human motion by optoelectronic means," Bioteleme-try, vol. 2, pp. 169-196, 1975.

I l2] D. K. Shirachi, D. L. Monk, and J. H. Black,,.Head rotational spec-tral characteristics during two-dimensional smooth pursuit tasks,"IEEE Trans. Biomed. Eng., vol.8, pp.7t5-124. 1978.

[3] J. R. Charlier, J. L. Bariseau, V. Chuffart, S. Marsy, andJ. C. Hache,"Real-time pattern recognition on feature analysis from video signalapplied to eye movement and pupillary reflex monitoring,,' in proc.VIth Int. Visual Field Symp., L. A. HEIJ and E. L, Greve, Eds.Dodrecht: Dr. W. Junk, 1985, pp. l8l-189.

ll4l J. P. Papin, "Use of the NAC Eye Mark Recorder to study visualstrategies of military airfract pilots," in Theoretit'al ontt Applietl As-pects of Eye Movement Research, A. G. Gale and F. Johnson. Eds.North-Holland: Elseview Science Publishers. 1984, pp. 361 -37 l.

[5] C. J. Funk and M. E. Anderson, "saccadic eye movements and eye-head coordination in children,' perceptual and Motor Ski11s, vol. 44,pp. 599-610, 1977.

[6] G. M. Gauthier, B. J. Martin, and L. Stark, ,.Adapted head-and-eyemovement responses to added-head inertia," Aviat. Space Environ.Med.. vol. 57, pp. 336-342. 1986.

[7] C. Pedrono, G. Obrecht, and L. W. Stark, ..Eye-head coordinarionwith laterally modulated gaze field," Amer. J. Optometrl, ph,-siot.Optics, vol.64, pp. 853-860, 1987.

[8] J. Rodenburg, A. Kasteel-Van Linge, and A. J. J. Mass, ,.Coordi-

nation of head and eye position during fixation," in Els Mot,enrents:From Physiology to Cognition, J. K. O'Regan and A. Levy-Schoen.Eds. North-Holland: ElsevierScience, 1987, pp. 2ll-218.

[9] J. G. Melvill, D. Guitton, and A. Berthoz, "Changing panerns ofeye-head coordination during 6 h of optically reversed vision," Exp.Brain. Res., vol.69, pp. 531-544, 1988.

[20] H. Collewijn, "Eye and head movements in freely moving rabbirs,"J. Physiol (London), vol. 266, pp. 47 l-498, t977 .

[21] K. Lindstrom. L. Manvitzson, G. Beroni, P. Seudmon, and S. S.Willner, "Application of air borne ultrasound to biomedical mea-surements," Med. Biol. Eng. Conput.. vol.20, pp.393-400, 1982.

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IEEE TRANSACTIONS ON BIOMËDICAL ENGINEERINC. VOL. 37. NO. 5. MAY I99O

Remy Rollero was born in Nantes, France, in1964. He was graduated as an Engineer l'rom theSuperior School of Physics. Marseille, in 1987.

During 1988, he worked as an electronics en-gineer in the Sensorimotor Laboratory of the Uni-versity of Provence, Marseille, designing an in-frared eye movement monitor and the ultrasonicmovement detector described in the ref'ered paper.Since October 1988, he has been working as aproject engineer with SchlumbergerTechnologiesin Saint-Etienne, France, involved with OTDR fbr

optic fibers.

Maurice Ouaknine was born in Rabat, Morocco,in 1945. He received the engineering degree fromthe University of Provence, Marseille, in 1969.

He has been working as a project engineer inthe Department of Psychophysiology of rhe Uni-versity of Provence since graduation. His mainachievements are in designing and development ofapparatus for neuroscience experimentation in manantl animals. His latest device is a computer con-trolled communication system for motor disabledpatienls based on eye movement monitoring.

Jean-Louis Vercher was born in Alger, Algeria,in 1958. He received the undergraduate degree inneurophysiology in 1980 and the Doctor's degreein 1984. studying the role cerebellum on visuo-oculo-manual coordination, both from the Uni-versity of Marseille.

From 1984 to 1988, he worked as a Researchassociate for the French Department of Defense.He was involved in studies dealing with the effectsof drugs on smooth pursuit system an<J eye-handtracking, in trained baboons. Since he joined the

National Scientific Research Center (CNRS) in 198g, he has been workingwith the Sensorimotor Control Laboratory, University of provence, iiMarseille, studying motor control, particularly oculo-manual and eye-headcoordination. His interests include vestibulo-ocular reflex, smooth pursuittracking and disabled patient instrumentation.

John L. Semmlow (M'79-SM'89), fbr a phorograph and biography, seep. 373 of the April 1990 issue of this TnnNsacrrons.

itli,i

Gabriel M. Gauthier received the engineeringdegree in 1965 from the Electronics Institute inGrenoble where he also studied physiology.Working under Prof. Lawrence Stark in Chicago,IL, and then in Berkeley, he received the Ph.D.degree in 1970, his thesis on the role of the cere-bellum in the control of eye movements.

He is currently Director of Research at theCentre National de Recherche Scientifique and acts

as head of the Sensory Motor Control Laboratoryin the Department of Psychophysiology of the

ROLLERO cr a1.: ULTRASONIC ROTATION DETECTOR 457

University of Provence, Marseille, where he conducts research on move-ment control in man and monkey. His particular interests are in adaptivecontrol of the vestibulo-ocular system. He is also involved in instrumen-tation applied to video control of robots and manual control of aircraft. Heis also a lecturer at the University of Provence, teaching biocybemetics.He was a visiting researcher at The Johns Hopkins Hospital in Baltimorein 1976, with Prof. D. A. Robinson; at the University of California, San

Francisco and Berkeley in 1979 with Prof. W. B. Hoyt and L. Stark, re-spectively: at the University of Tokyo with Prof. M. Ito and at the Japan

Marine Science Technology Center with Dr. K. Seki in 1981.

Dr. Gauthier is member of the European Neuroscience Association andthe French Physiology Association and Neuroscience Society.

Ultrasonic two-axis rotation detector

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