FR2522804A1 - OCULOMETER APPARATUS AND ITS USE IN A HEADSET SYSTEM - Google Patents

Abstract

APPARATUS ALLOWING TO MEASURE WITH PRECISION THE DIRECTION OF ACTUAL SIGHTING OF THE OBSERVER AND TO OPEN IN THE FIELD OF SIGHTINGS CALLED HEAD OR HELMET, THE USE OF A COLLIMATOR DEVICE. IT INCLUDES AN OPTICAL OBJECTIVE 1 TO FORM THE IMAGE OF THE EYE IN A PHOTODETECTION PLAN 3. PROCESSING AND MEASURING CIRCUITS 5 ALLOW TO MEASURE THE CENTER OF THE CIRCULAR IMAGE OF THE PIGMENTED ZONE OF THE EYE. A SEMI-TRANSPARENT OR DICHROIC ICE 2 ALLOWS THE OPERATION OF THE OCCULOMETER AND THE SIMULTANEOUS VISION OF THE LANDSCAPE BY THE OBSERVER. THE IMAGE FORMATION CAN BE CARRIED OUT WITH A BEAM OF ORDERED OPTICAL FIBERS WHICH MAKES THE DETECTION AND MEASUREMENT ASSEMBLY REMOTE. THE EYE CAN BE ILLUMINATED INFRARED BY A LUMINESCENT DIODE 4.

Description

OCULOMETER APPARATUS AND USE THEREOF

IN A VIEW SYSTEM OF HEAD.

  The present invention relates to an oculometer apparatus and its

  use in a viewfinder system.

  In many cases, it is useful to know the direction of the

  look at a human operator without bringing him any gene.

  The problem arises in ergonomics (measurement of eye movements, measurement of reflexes, visual workload, etc.)

  and also in the military field (visual shooting conduct,

visual goal statement, etc.).

  In equipment intended for ergonomics laboratories, it is known to use for this purpose the formation of Purkinje images of an auxiliary point light source on the various diopters constituting the eye (see in particular "Physiological optics" Tome I d Yves Le Grand, editor Masson) Measurements of the position of the

  magnitude and geometric defects in the image allow theoretically

  to know the direction of the main axis of the eye in experimentation The material is generally sophisticated and its

  application is reserved for the field of the laboratory.

  In the military field, it is known to bring to the operator a helmet equipped with an optical device having the collimated image, that is to say projected to infinity, a symbol (a cross by example) that the operator must bring into optical coincidence with the target object Thus, the direction given by the collimated image is related to the helmet, and the problem is to measure the position in the space of a direction related to the helmet himself, or to a fixed object

on the helmet.

  In reality, this last method is only a subterfuge; by requiring the operator to maintain a direction related to his head in the

  direction, the locating of the direction

  same, the identification of an object related to the reference direction This method has two types of serious disadvantages: the operator is obliged to bring to coincide a direction physically related to his head with the direction in which he wants to watch Gold Naturally, the movement of the head relative to the rest of the body constitutes a setting in the "gross" direction of the gaze, the setting in precise direction being ensured by the proper movement of the eye in its orbit relative to the head, movement far more accurate than the first The coincidence is therefore only assured to the accuracy of the coarse positioning; moreover, when the operator has to follow a moving point, the accuracy of the pursuit is limited by the precision of the movement of the head, whereas the pursuit by the combined movement of the head and eyes with respect to the head is otherwise more specific; the eye-pointing operation is unnatural, and the adjustment of the reference direction with respect to the head is fixed once and for all to correspond to the normal direction of aim of the operator, that is, that is, the eye in the rest position; however, experience shows that, depending on the vertical height of the target object, an operator who has no constraint due to an optical collimation system does not always aim according to this

  normal aiming direction and may deviate more or less.

  The object of the invention is to remedy such drawbacks by providing an oculometer, that is to say an apparatus capable of determining the instantaneous aiming direction of the eye by its misalignment.

  angular with respect to a reference direction.

  An object of the invention is to allow, when used in the aforementioned military field, to release the operator whose mission is to aim, the constraint of bringing into coincidence a materially defined line with the direction of the object to be

  to measure the angular movements of limited amplitude

  resulting from the rotational movements of the eyes in relation to

the head.

  Thus, a system of viewfinder head or full helmet will include, in correspondence with the natural movements of the operator, two measuring devices: a known device of direction tracking which measures the instantaneous position of the head of the operator relative at a fixed landmark, representing the land, or the vehicle, according to the intended use; an eye-tracking apparatus according to the invention for measuring the positional deviation, that is the angular misalignment, of the visual axis of the operator with respect to the first marked direction. The viewfinder system head, or helmet, and equipped no longer requires the kind of having an optical collimator device

for aiming.

  According to the present invention, an oculomotor is

  meter for measuring the rotational movements of the eye in its orbit relative to the observer's head, this apparatus

  to measure the angular misalignment presented by the

  the eye of the eye with a reference direction corresponding to

  laying in the normal direction of view of the observer, characterized in that it comprises an optical objective to form the image of the eye in an image plane, a semi-transparent ice placed between the eye and the optics to allow both the reception by the observer of the radiation from the external landscape and the transmission towards the optical objective of the radiation forming said image, the ice being inclined to the reference direction to reflect one of these radiations and transmitting the other, two-dimensional photodetection means being arranged in the image plane, and processing circuitry being provided for reading the photodetection means and processing the signals to measure the

  position of the geometric center of the circular image of the iris.

  The features of the invention will appear in the

  following description given by way of non-limiting example, using

  annexed figures which represent: FIG. 1, a diagram of an oculometer apparatus according to the invention; Fig 2, a preferred embodiment of the oculometer apparatus; FIGS. 3 to 6, diagrams and curves relating to an exemplary embodiment according to FIG. 1 relating respectively to the photodetection means, to the waveforms of the detected signals, to a diagram of the processing and measuring circuits, and to the misalignment angular measured by the circuits;

  Fig 7, a simplified diagram of a use of the oculo-

meter in a helmet viewfinder.

  With reference to FIG. 1, the oculometer apparatus comprises an optical objective 1 which is symbolized, for example, by two lenses and which serves to form the image of the eye in an image plane P. 13 A semitransparent ice 2 is arranged between the eye OE and the optic 1 to allow both the reception by the observer of the radiation RP coming from the external landscape and the transmission towards the optics of the radiation RO which comes from the eye and which serves to form the image of the eye through the lens The mirror 2 is inclined to the reference direction constituted by the normal direction of view DNV, to reflect one of its radiation and transmit the other The normal direction of aim is, as has been said, the direction in which the eye aims when it is at rest in its orbit, that is to say that it is solicited neither to the right, nor to the left, nor towards up, nor down In the depicted version, the

  radiation from the observed scene reaches the eye by trans-

  mission and radiation for imaging is reflected by ice 2; the reverse can be achieved, in that the landscape can be observed by reflection on the ice and the image of the eye formed by transmission Given the distance as presented between the eye and the lens 1 l image of the eye is formed in the image plane P in which are disposed two-dimensional photodetection means 3 which may consist, as shown, in two strips 3 and 3 Y detectors arranged in two directions

orthogonal x and y.

  To remedy a possibly insuf-

  Moreover, it can be provided further illumination means 4 of the eye.

  An advantageous solution is to use an electronic diode

  luminescent solid-gallium arsenide circuit operating in the 0.8 to 1 micron infrared band, on the one hand, given that this element can be of small size (2 to 3 mm in diameter) and can therefore easily be incorporated on the structure, for example mounted integral with the objective, and that, on the other hand, the emitted radiation RI is not visible and therefore not inconvenient for the observer. It is understood that the sensor strips 3 are sensitive to this radiation The diode 4 which emits the infrared radiation Ri is fed continuously by a power supply not shown The apparatus further comprises circuits for reading the photodetector device and the processing of the detected signals for measuring the misalignment AD presented between the instant DIV direction of sight

  of the eye and DNV reference direction.

  In the presence of an illuminating source 4 the semi-trans-

  parent 2 is treated to form a dichroic mirror so

  reflect a radiation and transmit the other; one of the

  is the visible from the external scene, and the other,

  the infrared radiation produced by the emitting diode 4.

  The semitransparent or dichroic mirror 2 may be produced in known manner by the combination of two prisms, as indicated in FIG. 2 by the elements 7 and 8 joined by a treated face.

to form ice 2.

  According to the variant shown in FIG. 2, the image formation uses an optical fiber transmission enabling the processing and measurement means to be placed at a distance. This transmission comprises a first optical element 9 which forms the image of the eye OE on a end face of an ordered optical fiber bundle 10, the actual image produced at the other end face of this bundle of fibers is taken up by a second optic 11 to be

  formed, for example, on the screen of a tube vidicon shooting.

  Block 12 represents the vidicon tube and associated circuits by which measurement of the misalignment measurement is carried out. In a version of this kind, the processing and measurement circuits may be more elaborate, based on correlation-form identification techniques. by video tracking etc. We can refer in particular to the French patent 2 302 004 which describes a video tracking system The principle of such a signal processing is based

  on the exploitation of luminance transitions in the video signal.

  Once the transitions useful for tracking are determined, a calculation

  It delimits a rectangular portion of the so-called window image where the object to be pursued can be located. Then, by dividing this image portion into four equal areas by axes parallel to the edge of the window, the computer will weigh to measure the proportion of the object area included in each zone,

  and deduce the new position of the centroid of the image.

  1 S For understanding the operation was explained using the following Figs 3 to 6 by means of a simplified embodiment of the detector consisting of two barrettes according to Fig I and elementary circuits according to Fig 5 The photodetection means are determined to enable the position to be measured

  of the geometric center of the image of the pigmented zone of the eye,

  to say the iris, and that is represented by the circle Cl One surrenders

  account that the detector elements of the barrettes which are in the

  the interior of the circle Cl receive less light than the elements which are outside this circle since these external cells correspond either to the white of the eye, or to the skin of the observer considered clearer than the iris The circle Cl intersects the bar 3 X at points A and B and the barette 3 Y at points C and D. Given what has just been said, the signals Si and 52

  respectively detected by these bars are shown schematically

  4 can be considered that these signals have an average amplitude V 2 outside the pigmented zone of the circle and a lower level, of the order of VI, within the zone.

  The detectors may consist of

  Such solid circuit strips of this type can provide a fine resolution, comprising up to about 2,000 points, i.e., elements, per strip For carrying out the mounting of the detector device 3 we will be able to

  refer, for example, to French Patent 2,450,463.

  A time base circuit or clock 13 produces a clock signal S which makes it possible to clock the DTC circuits forming the 3 X and 3 Y strips. The clock circuit is also used to synchronize the processing circuits shown in FIG. 5 for one of the channels, the X channel, it being understood that a similar arrangement is provided for the Y channel. The signal SI is applied to the input of a comparator circuit 14 where it is compared to a threshold VS which is predetermined to be between the values V 2 and VI (Fig 4), so when the detection signal crosses the points A and B corresponding to the limits of the circle CI, there occurs each time a tilting of the

  output of the comparator 14 This output commands a communication

  controller 15 which makes it possible to switch the local clock frequency from the value H to the value H / 2 by means of a dividing circuit by two 16 incorporated on the corresponding link. The clock signal of frequency H, or H / 2, is applied to a counting circuit 17 followed by a buffer memory 18 which supplies the measurement value XM of the point M A downstream edge detection circuit 19 serves to reset the counter and to control the memory

buffer 18.

  After each reset of the system the clock controls the reading of the detector cell after cell This reset is performed at the beginning of each reading As long as it is the area that corresponds to the white part of the eye is detected , the signal remains of high value and exceeds the threshold VS, the switch 15 remains in the position such that the signal H is transmitted to the counter 17 This counter totals the number of clock strokes that was necessary to reach the point A, located on the border of the white and pigmented areas of the eye As soon as the signal becomes weak in A, and therefore below the threshold, the counter has recorded the number NA of clock pulses proportional to the distance FA the switch 15 switches and transmits then the signal H / 2 to the counter which totals half the number of clock strokes necessary to go from A to B, that is to say (NB-NA) / 2 Finally, when the signal goes back to B the counter has totaled (NA + NB) / 2 which represents the abscissa of the midpoint of AB, ie the abscissa XM of the center M of the pigmented zone CI This value is transferred into the memory 18 at the end of this counting cycle and the previously stored value in the course of the preceding cycle is transmitted to the utilization A new counting cycle can start again The detection of the edge corresponding to the point B of the signal SI is carried out by the circuit 19 connected at the output of the comparator 14 and which controls the reading of the counter whose information is stored in memory 18 and resets the system. A similar processing circuit is associated with the output 52 of the other detector 3 Y to provide the ordinate YM of the same point M The coordinates of M give the position of the center of the

pupil of the eye.

  By knowing the position of the oculometer with respect to the head (FIG. 6), which amounts to knowing the position of the detector plane with respect to the center of rotation CR of the eye, it is possible to determine the

  direction of the focus by the relationships giving the angular misalignment

  in the AG field and at the AS site: tg AG = XM / L and tg AS = YM / L where the parameter L represents the distance between the center of rotation CR and the image plane P. In an eye-tracking device conforming to the The image of the eye and the difference in reflectivity of the whiteness of the eye and of the pigmented part are used. This pigmented part being circular, its center which is very substantially in the center of the pupil can

  to be easily identified by a two-dimensional

  or with a more elaborate pattern recognition circuit. Fig. 7 shows use on a helmet sight The helmet sight system comprises a direction-finding apparatus which may be, for example, of the optical type shown with a light-emitting diode array mounted on the helmet 21, a sensor 22 and a computer 23 for processing the signals detected at 22 and measuring the reference direction DR connected to the helmet The successive and sequential supply of the diodes is produced from the block 23 The sensor is fixed on the aircraft, mounted inside The solutions of this type are numerous we can refer in particular to the French patent 2,399,033 The direction tracking device can also be made according to a magnetic solution; in this version a sensor is secured to the helmet and the radiator element is integral with the aircraft, or the vehicle considered A measuring device of this kind is described

  in French Patent 2,458,838, the sensor and the radiator comprise

  each is a three-coil assembly defining the axes of a Cartesian triede. The helmet viewfinder system furthermore comprises the oculometer apparatus represented by its mirror 2, the optics 9 and the

  fiber 10 which makes it possible to position the detection means remotely.

  The value AD represents the additional value to be added in value-and in sign to that measured by the locating assembly 20, 22, and the value of the misalignment AD to the calculator 23. 23

  to obtain the actual and instantaneous direction of sighting of the

  Ice 2 is rotatably mounted around an R-shaped hinge so that it can be placed in the dotted rest position when the operator does not need to aim. In the version shown, the reference direction DR Helmet related was chosen corresponding to the normal DNV sighting direction of the observer.

Claims (6)

  1 Oculometer apparatus for measuring movement of   rotation of the eye in its orbit relative to the observer's head.   the apparatus for measuring the instantaneous angular misalignment presented by the aiming direction of the eye with a reference direction corresponding to the normal aiming direction (DNV) of the observer, characterized in that it comprises a optical objective (1) for forming the image of the eye in an image plane (P), a semitransparent ice (2) placed between the eye and the optics   to allow both the reception by the observer of the   (RP) from the external landscape and the transmission to the optical radiation (RO) forming said image, the ice being inclined to the reference direction to reflect one of these rays and transmit the other, means of photodetection   two-dimensional representation (3) in the image plane, and processing circuits   (5) signals detected to read the detection means and process the signals to measure the position   of the geometric center of the image of the iris of the eye.   Oculometer according to claim 1, characterized in that   it further comprises means for illuminating the eye (4).   Oculometer according to claim 2, characterized in that   the lighting means consist of an electronic diode   luminescent solid circuit, radiating in the near infrared,   and that the ice (2) is treated dichro Tque.   Eye-tracking apparatus according to any of the claims   cations, characterized in that the image forming means are constituted by means of a bundle of ordered optical fibers (10), one end of which is coupled by an optic (9) to the ice (2) and whose the other end is coupled by another   optics (11) to the photodetection and processing means (12).   He apparatus according to any one of the claims   cations, characterized in that the means for   detection (3) comprise two bars arranged in two directions   orthogonal arrangements, the bars being in DTC circuit.   6. Oculometer according to any one of claims 1 to 4, characterized in that the photodetection means use a vidicon tube and that the processing and measuring circuits carry out pattern recognition by correlation or video chase.   7 Using on a Head Viewfinder or Headset on a Device   Oculometer according to any one of the preceding claims,   the sight assembly being constituted by the oculometer apparatus and by a direction locating apparatus (20, 22, 23) of the optical or magnetic type. 8 Use according to claim 7 and wherein the oculometer apparatus is preferably made according to claim 4, characterized in that the ice of the oculometer apparatus is pivotally mounted to be disposed out of the field of vision when it is not not used, and that the means of photodetection and treatment are located away from the helmet.