IMAGE-ACQUIRING SYSTEM FOR PERFORMING BIOMETRIC RECOGNITION OF AN IRIS OF AN INDIVIDUAL

An image-acquiring system, including a holder and a subsystem mounted on the holder, the subsystem including an image-acquiring device configured to acquire at least one image along an axis of sight, a reflective element arranged transversely to the axis of sight and configured to reflect the at least one image onto the image-acquiring device, the reflective element being mounted so as to be rotatable, about a first axis of rotation, with respect to the image-acquiring device, the first axis of rotation being orthogonal to the axis of sight of the image-acquiring device and wherein the subsystem is mounted to be rotatable with respect to the holder about a second axis of rotation, the second axis of rotation being parallel to the axis of sight of the image-acquiring device.

The invention relates to an image-acquiring system.

It more particularly relates to an image-acquiring system for performing biometric recognition, in particular biometric recognition of an iris of an individual, potentially a moving individual.

The invention is particularly applicable to technical fields such as security, in which it may be used to track and recognize information of an individual, in particular biometric information such as irises.

An image-acquiring system for tracking and performing biometric recognition of an iris of an individual, whether stationary or moving, typically comprises: a camera mounted parallel to a holder along an axis of sight of the camera; a first motor that is configured to orient the camera about an axis of rotation considered to be “vertical” and that allows the camera to make a horizontal rotational movement, which is referred to as a “panning” movement; and a second motor that is configured to orient the camera about an axis of rotation considered to be “horizontal” and that allows the camera to make a vertical rotational movement, which is also referred to as a “tilting” movement, thus orienting its inclination or tilt.

In this system, the two (panning and tilting) rotational movements of the camera with respect to the holder may be combined to obtain a capture field that is cone-with-a-rectangular-base shape.

However, at least one drawback of such an image-acquiring system is that it has a relatively large footprint in the plane of the holder, as a result of the arrangement of the camera parallel to the holder.

Another image-acquiring system for tracking and performing biometric recognition of an iris of an individual, whether stationary or moving, typically comprises: a fixedly mounted camera arranged perpendicular to a holder along the axis of sight of the camera; and a mirror positioned facing the camera and transverse to the axis of sight of the camera, the mirror being motorized about two axes of rotation with respect to the axis of sight of the camera, thus allowing the mirror to perform a horizontal rotational movement, referred to as “panning”, and a vertical rotational movement, referred to as “tilting”.

In such a system, the two rotational movements of the mirror may be combined to obtain a capture field that is cone-with-a-rectangular-base shape.

In such a system, the camera typically comprises an objective and a sensor, to which the objective transmits an image.

Such an image-acquiring system has the advantage of a relatively small footprint in the plane of the holder, compared with the image-acquiring system presented above.

Nevertheless, at least one drawback of such an image-acquiring system is that it has a limited capture field, in particular in comparison with the image-acquiring system presented above.

Specifically, the “panning” horizontal rotational movement of the mirror with respect to the axis of sight of the camera generates a rotation of the image reflected by the mirror with respect to the centre of the sensor of the camera.

The image reflected by the mirror then does not remain on the same horizontal line of the sensor of the camera.

Thus, the larger the angle of rotation during the panning movement of the mirror, the higher the risk of obtaining an image, in particular of the eyes and/or irises of an individual, that falls partially or completely beyond the sensor of the camera. This is particularly due to the fact that a camera sensor is typically of rectangular format and not circular, has standardized dimensions and is generally of limited footprint.

Consequently, such a rotation of the image reflected by the mirror onto the sensor during a panning movement limits the capture field of the camera.

In addition, the image perceived by the sensor is then distorted. The rotation of the reflected image on the sensor of the camera thus means that an additional step must be added to the image processing carried out by the image-acquiring system.

The present invention aims to mitigate at least some of these drawbacks, and potentially leads to other advantages.

To this end, according to a first aspect, an image-acquiring system is provided that comprises a holder and a subsystem mounted on the holder, said subsystem comprising an image-acquiring device configured to acquire at least one image along an axis of sight, a reflective element arranged transversely to said axis of sight and configured to reflect the at least one image onto said image-acquiring device, said reflective element being mounted so as to be rotatable, about a first axis of rotation, with respect to said image-acquiring device, the first axis of rotation being orthogonal to said axis of sight of said image-acquiring device and wherein said subsystem is mounted so as to be rotatable with respect to said holder about a second axis of rotation, the second axis of rotation being parallel to said axis of sight of said image-acquiring device.

The image-acquiring system according to the invention makes it possible to acquire at least one image of an individual, for example an optionally high-resolution image of an entire face, or even in particular of the eyes, of the irises for example, if necessary while the individual is moving.

The reflective element is arranged to have a single axis of rotational freedom with respect to the image-acquiring device.

The arrangement of the reflective element with respect to the image-acquiring device allows the image-acquiring system to acquire at least one image during a vertical rotational movement about the first axis of rotation, referred to as “tilting”, of the reflective element with respect to the image-acquiring device.

The arrangement of the subsystem with respect to the holder allows the image-acquiring system to acquire at least one image during a horizontal rotational movement about the second axis of rotation, referred to as “panning”, of the subsystem with respect to the holder.

The two, vertical and horizontal, rotational movements may be combined to obtain a capture field that is cone-with-a-rectangular-base shape.

In other words, the overall arrangement of the image-acquiring system makes it possible to guarantee, in particular during a panning movement of the subsystem about the second axis of rotation, that the images reflected by the reflective element onto the image-acquiring device preserve the same angular orientation with respect to said axis of sight of the image-acquiring device.

Thus, compared with a prior-art image-acquiring system, the image-acquiring system according to an example of implementation of the invention has a relatively small footprint in the plane of the holder, and in particular in the system's depth direction, while achieving a field of image capture that is relatively larger panning-wise.

For example, the reflective element is configured to have a range of travel about the first axis of rotation of 70°.

In other words, the reflective element is configured to have, in particular, a travel of plus or minus 35° with respect to a nominal centre position at 45° to a nominal plane including the first axis and being orthogonal to the axis of sight of the image-acquiring device.

For example, the subsystem is configured to have a range of travel about the second axis of rotation of 40°.

In one embodiment, the second axis of rotation coincides with the axis of sight of the image-acquiring device, this being advantageous in respect of control.

In one embodiment, said image-acquiring device comprises at least one first image-acquiring unit, said at least one first image-acquiring unit comprising a sensor and an objective, the objective focusing the at least one image onto the sensor, the objective defining an optical axis of the first image-acquiring unit.

For example, said optical axis of said at least one first image-acquiring unit is parallel to said axis of sight of said image-acquiring device.

For example, said optical axis of said at least one first image-acquiring unit diverges from said axis of sight of said image-acquiring device by an angle of deviation of predetermined value.

In one embodiment, said image-acquiring device comprises at least one second image-acquiring unit, said second image-acquiring unit comprising a sensor and an objective, the objective of the second image-acquiring unit focusing the at least one image onto the sensor of the second image-acquiring unit, the objective of the second image-acquiring unit defining an optical axis of the second image-acquiring unit.

These two image-acquiring units make it possible to cover a wider field and in particular to acquire both eyes of a person at the same time, making it easier to distinguish between the left eye and right eye.

In one embodiment, the optical axis of at least the first image-acquiring unit or the second image-acquiring unit diverges with respect to said axis of sight of said image-acquiring device by an angle of deviation of a predetermined value.

In other words, at least the first or second image-acquiring unit is arranged so as to be inclined, and in particular to diverge, with respect to the axis of sight of the image-acquiring device.

This arrangement forms an angle of deviation between the optical axis of the first or second image-acquiring unit and the axis of sight of the image-acquiring device.

In one embodiment, the first image-acquiring unit and the second image-acquiring unit are arranged to diverge, with respect to the axis of sight of the image-acquiring device.

The angle of deviation between the optical axis of the first image-acquiring unit and the axis of sight of the image-acquiring device may be equal to the angle of deviation between the optical axis of the second image-acquiring unit and the axis of sight of the image-acquiring device.

The arrangement of the second image-acquiring unit is thus symmetrical to the arrangement of the first image-acquiring unit with respect to the axis of sight.

This angle of deviation thus makes it possible to make the optical axis of the at least one first and second image-acquiring units diverge with respect to the axis of sight of the image-acquiring device.

This angle of deviation in particular makes it possible to make the optical axis of the at least one first and second image-acquiring units diverge from one another.

Such a divergence of the optical axes thus makes it possible to increase the capture field of said image-acquiring device, while preserving an overlap of the capture fields of said at least one first and second image-acquiring units.

For example, the value of the angle of deviation is chosen so that a capture field of said image-acquiring device allows both eyes of an individual to be captured at the same time, including at a minimum operating distance of the image-acquiring system, which for example is 50 cm, or even less.

Specifically, the closer an individual is to the image-acquiring system, the more difficult it may be to acquire an image of both eyes simultaneously. The closer an individual is to the image-acquiring system, the wider a field of view of the image-acquiring system must be.

The divergent arrangement of at least two image-acquiring units thus makes it possible to widen this field.

For example, the value of the angle of deviation is chosen to obtain an overlap of the capture fields of the image-acquiring units, avoiding the presence of a blind spot in the image reconstructed from the at least one image delivered by the at least one first and second image-acquiring units.

For example, the value of the angle of deviation between the optical axis of the first or second image-acquiring unit and the axis of sight is comprised between 1.4° and 1.5°, and for example between 1.45° and 1.5°.

For example, the sensors of the at least one first and second image-acquiring units are positioned as close as possible to the axis of sight of the image-acquiring device, but not so close that the objectives of the at least one first and second image-acquiring units must touch.

For example, a distance between a centre of the sensor of the at least one first image-acquiring unit and the centre of the second image-acquiring unit depends on the optical formula of the objectives of the at least one first and at least one second image-acquiring units.

For example, this distance is comprised between 20 mm and 25 mm, and for example is in the region of 23 mm.

In one embodiment, said image-acquiring device comprises at least one second image-acquiring unit, said second image-acquiring unit comprising a sensor and an objective, the objective of the second image-acquiring unit focusing the at least one image onto the sensor of the second image-acquiring unit, the objective of the second image-acquiring unit defining an optical axis of the second image-acquiring unit, and wherein the optical axis of said first image-acquiring unit and the optical axis of said second image-acquiring unit diverge with respect to said axis of sight of said image-acquiring device by an angle of deviation of a predetermined value.

In one embodiment, said image-acquiring device comprises a bent holder comprising at least two flaps, a first of the two flaps bearing the sensor of the first image-acquiring unit and a second of the two flaps bearing the sensor of the second image-acquiring unit, said at least two flaps being connected to each other by at least one hinge zone, said hinge zone being configured so that said two flaps make a bending angle to each other.

The at least one hinge zone of the bent holder allows the bent holder to adopt a bending angle of predetermined value so as to incline the at least two flaps of the bent holder to each other.

Thus, the at least one hinge zone makes it possible to achieve the divergence of the optical axes of the at least one first and second image-acquiring units by applying a bending angle between the flaps which bear the sensors of said at least one first and second image-acquiring units.

For example, the bent holder is a printed circuit board (PCB).

For example, the at least one hinge zone of the bent holder is flexible, or bendable.

For example, the at least two flaps of the bent holder are rigid.

For example, the at least one hinge zone of the bent holder has a thickness that is smaller than the thickness of the at least two flaps.

In one embodiment, said image-acquiring device comprises a translating device configured to translate at least said objective of said at least one first image-acquiring unit with respect to said sensor of said at least one first image-acquiring unit along said axis of sight of said image-acquiring device.

The translating device allows the optical distance of the at least one first image-acquiring unit to be adjusted.

In other words, the translating device allows the distance between the sensor and the objective of the at least one first image-acquiring unit to be adjusted via a simple translational movement parallel to the axis of sight of the image-acquiring device.

In one embodiment, the translating device comprises a slide configured to bear said objective of the at least one first image-acquiring unit.

In one embodiment, said translating device comprises a stepper motor and a worm gear, said motor being configured to rotate said worm gear, and said worm gear being configured to make said slide translate along the axis of sight of said image-acquiring device.

In one embodiment, said translating device is further configured to translate said objective of said at least one second image-acquiring unit with respect to said sensor of said at least one second image-acquiring unit along said axis of sight of said image-acquiring device.

The image-acquiring device thus allows the optical distance of the at least one first and second image-acquiring units, i.e. the distance between the sensor and the objective of each image-acquiring unit, to be adjusted via a single translational movement of the objectives of the at least one first and second image-acquiring units.

In one embodiment, said slide is further configured to bear the objectives of the at least one first and second image-acquiring units, this particularly allowing them to be translated together.

In one embodiment, said image-acquiring system comprises a reflective-element motor configured to pivot said reflective element with respect to said image-acquiring device about said first axis of rotation.

For example, the reflective-element motor is a direct drive motor.

Direct drive motors are configured so that the load driven by a motor is directly secured to the rotor of the motor.

Such a motor makes it possible to avoid introducing play between the shaft rotated by the motor and the load driven by the motor.

Such a motor allows a more precise rotational movement.

Such a motor allows noise to be decreased.

Such a motor allows wear of the motor to be decreased, leading to an improvement in its lifespan.

For example, the reflective-element motor is a brushless direct drive motor.

Such a motor allows wear to be decreased, and very fluid control able to meet the need to track the eyes of a moving person to be obtained.

In one embodiment, said image-acquiring system comprises a subsystem motor configured to pivot said subsystem with respect to said holder about said second axis of rotation.

For example, the subsystem motor is a direct drive motor.

For example, the subsystem motor is a brushless direct drive motor.

For example, as a variant, the horizontal rotational movement about the axis of rotation D3, referred to as “panning”, of the subsystem with respect to the holder is achieved manually by an operator of the image-acquiring system.

In one embodiment, said image-acquiring system comprises a reflective-element motor configured to pivot said reflective element about said first axis of rotation and a subsystem motor configured to pivot said subsystem about said second axis of rotation.

In one embodiment, the holder comprises an electrical interface and the subsystem comprises an electrical interface, and the image-acquiring system comprises a flexible connecting element configured to electrically connect the electrical interface of said holder to the electrical interface of said subsystem, said flexible connecting element being arranged around said second axis of rotation.

The flexible connecting element allows the electrical interfaces of the holder and of the subsystem to be connected while accompanying the horizontal rotational movement of the subsystem, with respect to the holder, with a flexion of the connecting element around the second axis of rotation.

In other words, the flexible connecting element winds and unwinds around the second axis of rotation, or in particular around the subsystem motor.

The flexion of the flexible connecting element around a single axis thus allows its lifespan to be increased, limiting, or even avoiding, flexions about two different axes, and/or torsion.

One advantage of such an image-acquiring system comprising such a connecting element is that only one cable need move.

For example, the flexible connecting element is arranged around the subsystem motor.

For example, said flexible connecting element allows transmission of various signals, such as electrical power, video signals, or even motor-control signals.

For example, the flexible connecting element is a cable or wire.

For example, the electrical interface of the holder allows communication with a control unit.

For example, the electrical interface of the subsystem allows communication with the image-acquiring device, the reflective-element motor, the subsystem motor and in particular the stepper motor.

In one embodiment, said image-acquiring system comprises an elastic guiding element arranged around said flexible connecting element, said elastic guiding element having a first end joined to said holder and a second end joined to said subsystem, the elastic guiding element being configured to be elastically deformed during a rotation of the subsystem about the second axis of rotation with respect to the holder.

Said elastic guiding element makes it possible to ensure that the flexible connecting element will remain in place independently of the gravitational force acting on said flexible connecting element.

Support of the flexible connecting element by the elastic guiding element makes it possible to prevent the flexible connecting element from sagging.

Support of the flexible connecting element by the elastic guiding element makes it possible to avoid contact of the flexible connecting element with other parts of the image-acquiring system, such contact particularly generating friction with the flexible connecting element.

The elastic guiding element allows the flexion of the flexible connecting element to be controlled.

The elastic guiding element allows the stresses generated during the flexing movement of said flexible connecting element to be exerted foremost on said elastic guiding element, rather than on the flexible connecting element.

Under the effect of the stresses generated by the rotational movement of the subsystem around the second axis of rotation, the elastic guiding element deforms elastically.

Thus, such an elastic guiding element allows the lifespan of said connecting element to be increased.

For example, the guiding element is fastened by its ends to the holder and subsystem by straps, or brackets.

In one embodiment, the elastic guiding element is a spring.

Use of a spring with a determined number of turns as an elastic guiding element allows a number of contact points with the flexible connecting element to be set through the number of turns of the spring.

A high number of contact points between the elastic guiding element and the flexible connecting element allows stresses to be better distributed over the entirety of the flexible connecting element.

For example, to define the number of turns of the spring, a nominal distance between two consecutive turns of the spring is set approximately equal to a diameter of the flexible connecting element.

In one embodiment, the sensor of the at least one first image-acquiring unit and/or of the at least one second image-acquiring unit is a sensor employing a global shutter.

A sensor employing a global shutter need be illuminated only during an exposure time.

A sensor employing a global shutter may be more brightly illuminated and for a shorter overall time than a sensor employing a rolling shutter.

A sensor employing a global shutter allows the motion blur of the image-acquiring device to be decreased compared with a sensor employing a rolling shutter.

A sensor employing a global shutter makes it possible to guarantee a sufficient signal level and limited noise compared with a sensor employing a rolling shutter.

A sensor employing a global shutter allows the at least one image-acquiring unit to be made less sensitive to infrared wavelengths potentially present in the luminous environment of said image-acquiring system, compared with a sensor employing a rolling shutter.

In one embodiment, said image-acquiring system comprises at least one context-image-acquiring device configured to acquire at least one context image, said at least one context-image-acquiring device being fastened to said holder.

The expression “context image” here designates an image providing an overview of a capture field, and allowing a detail, in the present case for example a face or even the eyes of an individual, to be chosen and located more precisely. The at least one image-acquiring device of the system according to the invention is then configured to point at this detail.

In one particular example, providing two context-image-acquiring devices allows the eyes to be located in three dimensions.

Acquisition of a context image, in particular of an individual, by the at least one context-image-acquiring device allows the three-dimensional aiming accuracy of the image-acquiring device of the subsystem to be increased.

In other words, the at least one context-image-acquiring device makes it possible to improve tracking of the individual by said subsystem if the individual is moving.

For example, the at least one context-image-acquiring device is attached to the holder of the image-acquiring system by way of a vertical frame that frames the image-acquiring system.

In one embodiment, said image-acquiring system comprises two context-image-acquiring devices.

For example, a first of the two context-image-acquiring devices is positioned above the subsystem.

For example, a second of the two context-image-acquiring devices is positioned below the subsystem.

For example, said two context-image-acquiring devices are centred on said axis of sight of said image-acquiring device, i.e. placed along said axis of sight.

Such an arrangement of the two context-image-acquiring devices makes it possible to improve the accuracy of the subsystem and to improve the centrality of the image reflected by the reflective element onto the image-acquiring device.

Identical elements shown in the aforementioned figures have been identified by identical reference numbers.

FIG.1shows an image-acquiring system20according to one example of embodiment of the invention.

In the described example, the image-acquiring system20comprises a holder21.

The holder21comprises a first wall22defining a planar mounting surface.

The holder21comprises a second wall23orthogonal to the first wall22.

The second wall23here facilitates installation of the system into a control unit.

The second wall23here comprises a frame105(not shown inFIG.1).

In the described example, the image-acquiring system20comprises a subsystem30.

The subsystem30is rotatable about an axis of rotation D3with respect to the holder21.

In the described example, the subsystem30comprises an image-acquiring device40.

The image-acquiring device40is configured to acquire at least one image along an axis of sight D1.

In the described example, the axis of rotation D3is parallel to the axis of sight D1of said image-acquiring device40.

The image-acquiring device40here comprises a first image-acquiring unit41.

The first image-acquiring unit41comprises an objective42and a sensor43(not shown inFIG.1).

The objective42of the at least one image-acquiring unit41focuses the at least one image onto the sensor43of the at least one image-acquiring unit41, and thus defines an optical axis D4.

In the present case, the image-acquiring device40further comprises a second image-acquiring unit41′.

The second image-acquiring unit41′ is here identical to the first acquiring unit41.

However, it could be different.

Thus, an objective of the second image-acquiring unit41′ here defines an optical axis D5.

In the present case, each optical axis D4, D5, of the first and second image-acquiring units41,41′, respectively, diverges with respect to the axis of sight D1of said image-acquiring device40by an angle of deviation of a predetermined value.

In other words, a distance of separation, between each optical axis D4, D5and the axis of sight D1, here increases with a distance with respect to the respective objective of the at least one first and at least one second image-acquiring units41,41′.

In the present case, the at least one first and at least one second image-acquiring units here have characteristics such that, in the far field, i.e. at at least 1.2 m, the resolution is sufficient for an iris of an individual to be recognized, i.e. for an iris of 10.2 mm diameter to be imaged by 160 pixels.

In the present case, the at least one first and at least one second image-acquiring units here have characteristics such that, in the near field, i.e. at about 0.5 m at most, the lateral field of the two cameras combined is sufficient to capture both eyes of an individual, with a margin allowing for misaiming.

The objectives of the at least one first and at least one second image-acquiring units are here chosen to have a focal length comprised between 40 mm and 60 mm, and for example in the region of 50 mm.

In the described example, the subsystem30comprises a reflective element60.

The reflective element60is arranged transversely to said axis of sight D1.

The reflective element60is configured to reflect an image onto the image-acquiring device40.

In the present case, the reflective element60here reflects an image onto the first and second image-acquiring units41,41′ of the image-acquiring device40.

The reflective element60is mounted so as to be rotatable with respect to said image-acquiring device40, about an axis of rotation D2.

The axis of rotation D2is orthogonal to the axis of sight D1of the image-acquiring device40.

In the present case, the reflective element60is here of hexagonal geometric shape, but it could be of any other geometric shape.

The reflective element60here comprises a reflective surface61that is configured to reflect an image.

The reflective element60further comprises a casing62configured to hold the reflective surface61of the reflective element60, and by means of which the pivoting action of the reflective element60is actuated.

In the described example, the subsystem30comprises a reflective-element motor70, also called the “tilting” motor.

The reflective-element motor70is configured to pivot said reflective element60with respect to the image-acquiring device40about the axis of rotation D2.

The reflective-element motor70for example comprises a portion referred to as the “fixed” portion, attached to a scaffold31that is described below, and a portion referred to as the “mobile” portion, configured to pivot with respect to the fixed portion, and to which the reflective element60is attached.

In the present case, the reflective-element motor70is here a direct drive motor that is preferably brushless, this also decreasing wear and allowing very fluid control able to meet the need to track the eyes of a moving person.

In the described example, the image-acquiring system20comprises a subsystem motor80.

The subsystem motor80is configured to pivot the subsystem30with respect to the holder21about the axis of rotation D3.

The subsystem motor80, also called the “panning motor”, for example comprises a portion referred to as the “fixed” portion, attached to the subsystem30, and a portion referred to as the “mobile” portion, configured to pivot with respect to the fixed portion, and to which the holder21, and in particular here the first wall22, is attached.

However, as a variant, the fixed portion could be attached to the holder21and the mobile portion could be attached to the subsystem30.

In the present case, the subsystem motor80is here a direct drive motor that is preferably brushless, this also decreasing wear and allowing very fluid control able to meet the need to track the eyes of a moving person.

In the described example, the subsystem30comprises the scaffold31.

In the present example, the image-acquiring device40, the reflective-element motor70and the subsystem motor80are arranged on the scaffold31.

The subsystem30is here attached to the mounting surface of the first wall22of the holder21by way of the subsystem motor80, and the reflective element60is attached to the scaffold31of the subsystem30by way of the reflective-element motor70.

The scaffold31is here attached to the subsystem motor80, and more particularly to the fixed portion of the subsystem motor80.

The scaffold31of the subsystem30here comprises a main body32and an arm33.

The main body32is here configured to hold the image-acquiring device40.

The main body32here has a rectangular profile.

The arm33here extends from the main body32.

The arm33is here configured to hold the reflective-element motor70, and more particularly the fixed portion of the reflective-element motor70.

In the present case, the arm33here comprises a first portion extending from the main body32at an angle of 45° to the axis of sight D1of the image-acquiring device40and comprises a second portion extending the first portion parallel to the axis of sight D1of the image-acquiring device40.

The arrangement of the arm33thus allows the reflective element60to be centred with respect to the axis of sight D1of the image-acquiring device40.

FIGS.2a,2band2cshow in greater detail the arrangement of the two image-acquiring units41,41′ of the image-acquiring system20ofFIG.1.

In the described example, the image-acquiring device40comprises a bent holder45.

The bent holder45comprises at least two flaps47,47′.

The at least two flaps47,47′ each bear one sensor43of the at least one first and at least one second image-acquiring units41,41′.

The at least two flaps47,47′ are connected by at least one hinge zone46.

The hinge zone46is configured so that the at least two flaps47,47′ make a bending angle to each other.

In the present case, the hinge zone46is here configured to be bowed, or to be curved, or to be bent, so that the at least two flaps make to each other a bending angle of determined value.

This bending angle here makes it possible to achieve a different orientation of the two sensors43, and in particular here makes it possible to make the optical axes D4, D5of the at least one first and at least one second image-acquiring units41,41′ diverge.

In the present case, the bent holder45is here a printed circuit board or PCB, at least one hinge zone46of which here has a thickness smaller than the thickness of the at least two flaps47,47′.

In the described example, the subsystem30comprises a translating device50.

The translating device50is configured to translate at least the objective42of the at least one first image-acquiring unit41with respect to the sensor43of the at least one first image-acquiring unit41along the axis of sight D1of the image-acquiring device40, this allowing focus to be adjusted.

In the present case, the translating device50is here configured to simultaneously translate the objective of each of the first and second image-acquiring units41,41′ via a single translational movement, parallel to the axis of sight D1.

In other words, the objectives of each of the first and second image-acquiring units41,41′ may be translated together, this allowing an identical focal plane to obtained for the two image-acquiring units41,41′ at a given time.

In the present example of embodiment, the translating device50comprises a slide51, a worm gear52and a stepper motor53.

The slide51is configured to bear the objective42of the first and second image-acquiring units41,41′.

The worm gear52is configured to translate said slide51along the axis of sight D1of said image-acquiring device40.

The stepper motor53is configured to make said worm gear52rotate.

The slide51further comprises a nut (not shown).

The nut is engaged with the worm gear52.

The nut is configured to be blocked rotationally by the slide51so that the worm gear52causes the nut, and therefore the slide52, to translate along the axis of sight D1.

The translating device50thus allows a movement resolution consistent with a depth of field of the objectives42.

A back focus (objective/sensor distance) of the image-acquiring device40may thus be adjusted very precisely by virtue of the translating device50.

FIGS.3to6show an image-acquiring system20according to another example of embodiment of the invention, comprising the features of the example of embodiment illustrated inFIGS.1and2, and additional features that are described below.

In this example, the holder21further comprises an electrical interface (not shown).

The electrical interface of the holder21is configured to communicate with a control unit external to the image-acquiring system20.

In this example, the subsystem30comprises an electrical interface92.

The electrical interface92of the subsystem30is configured to ensure communication and to distribute electrical power between the electrical interface of the holder21and the image-acquiring device40, the reflective-element motor70, the subsystem motor80and the stepper motor53.

In the described example, the image-acquiring system20comprises a flexible connecting element90.

The flexible connecting element90is configured to electrically connect the electrical interface of the holder21to the electrical interface92of the subsystem30.

The flexible connecting element90is arranged around the axis of rotation D3.

In the present case, the flexible connecting element90is here arranged around the subsystem motor80.

The flexible connecting element90here allows transmission of various signals, and for example electrical power to be supplied.

The flexible connecting element90is here an electrical wire, in particular a micro-coaxial cable allowing impedance to be controlled, various signals to be transmitted over sufficiently long distances of the order of 20 cm to 50 cm and the radius of curvature of the electrical wire to decrease during movements, and in particular one using the MIPI CSI protocol.

In the present case, the electrical interface92of the subsystem30is here configured at least to control the reflective-element motor70, the subsystem motor80and the stepper motor53.

The electrical interface92of the subsystem30also here allows the supply of electrical power to the subsystem30, and in particular to the reflective-element motor70, to the subsystem motor80and to the stepper motor53, to be centralized.

In the present case, the electrical interface of the holder21may here be likened to a main processing platform configured at least to process the at least one image delivered by the image-acquiring device40.

In the described example, the image-acquiring system20comprises an elastic guiding element95.

The elastic guiding element95is in particular configured to hold the flexible connecting element90in place.

The elastic guiding element95is here arranged around said flexible connecting element90.

The elastic guiding element95comprises a first end joined to said holder21and a second end joined to said subsystem30.

The elastic guiding element95is configured to be elastically deformed during a rotation of the subsystem30with respect to the holder21about the axis of rotation D3.

In the present case, the elastic guiding element95here comprises a spring.

In the described example, the image-acquiring system20comprises at least one context-image-acquiring device100.

The at least one context-image-acquiring device100is configured to acquire at least one context image, i.e. an image having a larger capture field than the at least one image obtained by the image-acquiring device40, so that the image-acquiring device40may subsequently be aimed accurately.

The at least one context-image-acquiring device100in particular here makes it possible to choose and accurately locate a face, or the eyes of an individual.

The at least one context-image-acquiring device100is fastened to said holder21.

In the present case, the image-acquiring system20here comprises first and second context-image-acquiring devices100.

The first and second context-image-acquiring devices100in particular here allow to the eyes of an individual to be located via stereoscopy.

The first and second context-image-acquiring devices100are in particular arranged to be sufficiently far apart from each other that the eyes of an individual may be located with sufficient accuracy in three dimensions.

The subsystem30is here placed between the first context-image-acquiring device100and the second context-image-acquiring device100.

The first and second context-image-acquiring devices100are here centred on the axis of sight D1of said image-acquiring device40.

In the present case, the first and second context-image-acquiring devices100are attached to the holder21by way of the frame105.

The frame105here completely frames the subsystem30.

In other words, the first context-image-acquiring device100is located above the subsystem30, while the second context-image-acquiring device100is located below the subsystem30.

In the present case, the frame105here further comprises an indicator light configured to guide a gaze of an individual towards the first context-image-acquiring device100.

This indicator light in particular here makes it possible to guarantee that the individual's gaze is centred in a photo of her or his face and that the individual's irises are oriented towards the image-acquiring device40.

In the present case, the electrical interface of the holder21may here be likened to a main processing platform configured at least to process the at least one image delivered by the image-acquiring device40, the at least one image delivered by the at least one context-image-acquiring device100and to manage the indicator light.

As illustrated inFIG.4, the imaging device40has a vertical capture field that depends on the rotational movement of the reflective element60about the axis of rotation D2.

The reflective element60is here configured to have a range of travel of in the region of 70° about the axis of rotation D2, and in particular to have a travel of plus or minus 35° with respect to a nominal centre position at 45° to a nominal plane including the axis D2and orthogonal to the axis of sight D1.

As illustrated inFIG.5, the imaging device40has a horizontal capture field that depends on the rotational movement of the subsystem30about the axis of rotation D3.

The subsystem30is here configured to have a range of travel of in the region of 40° about the axis of rotation D3, and preferably a symmetrical travel with respect to this axis D3of plus or minus 20°, with a view to scanning the scene horizontally.

FIG.6illustrates the overall capture field of the image-acquiring system20obtained by combining the range of travel of the reflective element60about the axis of rotation D2and the range of travel of the subsystem30about the axis of rotation D3.