PIEZOELECTRIC POINTING DEVICE

Abstract

PIEZOELECTRIC POINTING DEVICE A piezoelectric device comprises a fixed frame (1) and a mirror holder (4) defining several support points (4a) fixing a mirror (5). The mirror holder (4) is mounted to be movable in rotation. Several piezoelectric actuators (2) are fixed to the support (1) and deform independently in directed translation according to a first orientation (AA). Each piezoelectric actuator (2) moves the support zone of the mirror holder (4). The mirror holder (4) defines several fixing points. Each fixing point (4b) mechanically connects the mirror holder (4) with a piezoelectric actuator (2). The support points (4a) and fixing points (4b) are distinct. The mirror holder (4) defines a plurality of bending zones (4d). The support points (4a) are movable between them.The piezoelectric actuators (2) powered in push-pull drive the support points (4a) which rotates the mirror (5) perpendicular to the first direction (AA). Figure for abstract: Fig. 9.

Description

Title of the invention: PIEZOELECTRIC POINTING DEVICE Technical field

[0001] The invention relates to a piezoelectric pointing device. Prior art

[0002] In the field of optical pointing, it is known to use piezoelectric devices which have a movable mirror. The mirror moves according to rotations with limited travel to orient an optical beam or a laser beam. In order to move the mirror, piezoelectric actuators are used which are mechanically connected to the mirror so that the deformation of the piezoelectric actuator causes the rotation of the mirror, according to one or two directions perpendicular to a reference optical axis.

[0003] The applicant markets a piezoelectric “tip-tilt” mechanism illustrated in [Fig.l] which has a fixed frame 1 on which four piezoelectric actuators 2 are mounted to deform along four axes which are parallel to a first direction AA defined by the reference optical axis. The piezoelectric actuators 2 are each surmounted by a bending rod 3. The four bending rods 3 form a flexible mechanical connection between the piezoelectric actuators 2 and a mirror holder 4. The mirror holder 4 is surmounted by a mirror 5. The deformation axes of the actuators are arranged equidistant from the center of the circular mirror 5 used.

[0004] The mirror holder 4 is made very rigid so as not to deform under the effect of the forces applied by the piezoelectric actuators 2 and retransmitted by the bending rods 3. The bending rods 3 are connected to an anchoring pad 6 which is immobile. The anchoring pad 6 is connected to the four bending rods 3 by means of a flexible bearing 7 which is formed by four rectilinearly shaped flexors arranged in the form of a cross.

[0005] The flexible bearing 7 is flexible along the first direction AA and stiff in the two directions perpendicular to the latter. The flexible bearing 7 increases the resistance to vibrations and shocks that can be encountered in particular in on-board applications. Finally, in combination with the flexure rods 3, the flexible bearing 7 contributes to transforming a translation of the top of the piezoelectric actuator 2 into a rotation with limited travel, of the top of the flexure rod 3.

[0006] The four piezoelectric actuators 2 work independently of each other. The bending rods 3 are fixedly mounted to the piezoelectric actuator 2 and to the mirror holder 4. To effectively achieve limited-range rotation, it is conventional method of powering the actuators in "push-pull" mode in pairs. Two actuators arranged diametrically opposite with respect to the reference optical axis passing through the center of the mirror 5 are powered in such a way that one actuator expands while the other contracts.

[0007] In the configuration illustrated in [Fig.l], the mechanism has a first pair of actuators aligned along a direction BB to produce a rotation about a direction CC both perpendicular to the direction AA and perpendicular to the direction BB. The second pair of actuators formed by the actuators aligned along the direction CC, produces a rotation about the direction BB.

[0008] It has been found that the piezoelectric device illustrated in [Fig.l] can generate wavefront errors in use. It has been found that these wavefront errors are not always present and come from a deformation of the mirror 5 fixed on the mirror holder 4.

[0009] Another configuration of piezoelectric device is illustrated in document FR2850218 or US6927528, and has these same limitations.

[0010] The piezoelectric actuators 2 have a small travel which greatly limits the angular travel accessible to the mirror holder 4. To produce a greater angular travel in a mechanism such as that illustrated in [Fig.l], there is a compromise to be found with regard to the size and cost of a piezoelectric actuator 2. This generally results in the use of larger actuators 2, at the cost of greater size and cost.

[0011] However, for pointing mechanisms, in addition to the previous constraints, it is required to obtain a high angular travel in a reduced size, with a minimum of parts in order to reduce the cost.

[0012] Another tip-tilt actuator is known, which has an infinitely rigid mirror holder and a mirror that can be deformed on command. The mirror is fixed by means of several screws. An O-ring is placed between the mirror and the mirror holder and is constrained between these two elements. The O-ring is elastically deformed in compression when the screws are tightened. Such a technical solution is disclosed in the document "Low order high accuracy deformable mirror based on electromagnetic actuators" by FP Wildi et al. Proceedings Volume 6715, Optomechatronic Actuators and Manipulation III; 67150C (2007). The mirror is deformed by means of several magnets that are actuated by several magnetic fields. Subject of the invention

[0013] An object of the invention is to provide a piezoelectric device which limits undesirable deformations of the mirror in order to obtain good optical quality.

[0014] These drawbacks tend to be resolved by means of a piezoelectric device which comprises:

[0015] - a fixed frame; - piezoelectric actuators fixed to the fixed frame, the piezoelectric actuators being capable of deforming independently of one another according to a linear translation, each linear translation being directed according to a first orientation; - a mirror holder defining fixing points and at least three support points, the at least three support points being intended to fixedly mount a mirror on the mirror holder, the at least three support points being distinct from the fixing points, the at least three support points defining a support area mounted to rotate relative to the fixed frame around at least a first axis of rotation, the first direction being perpendicular to said at least a first axis of rotation, each fixing point being functionally connected to a piezoelectric actuator; - a converter arranged in at least one mechanical connection connecting the piezoelectric actuators and the support points so that the linear translation of one or more of the piezoelectric actuators causes the rotation of the support zone relative to the fixed frame around said at least one first axis of rotation.

[0016] The piezoelectric device is remarkable in that at least one of the at least three support points is a support point mounted to move independently of the other support points in the first direction by elastic deformation of the mirror holder, in the absence of the mirror.

[0017] Preferably, each support point is a support point mounted to move independently of the other support points in the first direction by elastic deformation of a part of the mirror holder, in the absence of the mirror.

[0018] According to a development, the device comprises a plurality of plates, each support point being mounted on a plate. Each plate is fixed to the rest of the mirror holder by a flexural connection so that each plate is mounted to move independently of the other plates, in the first direction, in the absence of the mirror.

[0019] Preferably, the support points are arranged equidistant from a center. The flexural connections are arranged closer to the center than the support points in an observation along the first direction.

[0020] Preferably, the support points are arranged equidistant from a center. The support points are further from the center than the fixing points.

[0021] According to a development, the support points are arranged equidistant from a center. A top portion of at least one of the piezoelectric actuators comprises a bar extending in a direction perpendicular to the first direction radially relative to the center so that the mechanical connection between the piezoelectric actuator and the associated attachment point is closer to the center than to the piezoelectric bar of the piezoelectric actuator, in an observation according to the first direction.

[0022] Preferably, the plates are configured to move in at least one direction perpendicular to the first direction.

[0023] Advantageously, the support points are arranged equidistant from a center. The flexural connection is also configured to allow radial displacement of the support points perpendicular to the first direction and relative to the center.

[0024] According to another development, the device comprises additional plates. The center is fixedly mounted relative to the fixed frame by means of an anchoring stud. Arms extend from the center, each arm being fixed to one of the plates by the flexural connection, each arm being fixed to one of the additional plates by a torsional connection, the torsional connection pivoting the arm relative to the additional plate about an axis perpendicular to the first direction, each additional plate receiving a fixing point.

[0025] According to a further development, the torsional connection is arranged closer to the center than the flexural connection, along the direction of extension of the arm from the center to the opposite end.

[0026] Advantageously, the torsional connection is arranged closer to the center than the support point, when viewed in the first direction.

[0027] In one development, the arms extend in the form of spirals.

[0028] Advantageously, the flexure joint also defines a torsional joint about an axis parallel to the first direction and passing through the flexure joint.

[0029] Advantageously, the mirror holder is directly fixed to at least one of the piezoelectric actuators such that the at least one fixing point moves in a linear translation in the first direction.

[0030] In one development, each piezoelectric actuator is directly fixed to one of the fixing points, each fixing point belonging to an additional plate which is more rigid than the arm on which the additional plate is fixed by the torsional joint.

[0031] Preferably, each flexure joint has an arcuate-shaped portion around the center.

[0032] According to another development, the support points are arranged equidistant from a center. The center is fixedly mounted relative to the fixed frame by means of an anchoring pad. The fixing points are connected to the piezoelectric actuators by a bending rod extending mainly in the first direction, one end of the bending rod being fixed to one of the actuators, another end of the bending rod being fixed to one of the fixing points.

[0033] Advantageously, the plates and the flexural connections are defined by first slits which are through in the first direction. In an observation in the first direction, each straight line connecting one of the support points to a fixing point spans at least one of the first slits.

[0034] Preferably, the mirror holder has second slots which are transverse in the first direction and which extend in the form of spirals from the center, the second slots separating the center and the fixing points.

[0035] It is advantageous to provide that each support point is arranged equidistant from two of the fixing points which are closest.

[0036] Preferably, the support points are arranged equidistant from a center. The center is movable relative to an anchoring pad in the first direction. The converter has a flexible bearing having a fixed portion fixedly mounted relative to the fixed frame by means of the anchoring pad and flexors extending from the fixed portion in directions perpendicular to the first direction, the flexors being fixedly mounted at the fixing points. The piezoelectric actuators are connected to the fixing points by flexing rods. The fixing points are mounted immobile relative to each other in the mirror holder.

[0037] Advantageously, the device comprises a mirror fixed to the mirror holder by means of the support points, the mirror defining a mechanical connection with the support points which fixes the position of the at least one movable support point relative to the other support points. Summary description of the drawings

[0038] Other advantages and characteristics will emerge more clearly from the following description of particular embodiments and implementations of the invention given as non-limiting examples and represented in the appended drawings, in which:

[0039] [Fig-1]: [Fig.l] illustrates, in a schematic manner, a perspective view of a prior art piezoelectric device surmounted by a mirror;

[0040] [Fig.2]: [Fig.2] schematically represents, in perspective, a mode of production of a piezoelectric device including four piezoelectric actuators surmounted by a bending rod and a mirror holder with deformable zones;

[0041] [Fig.3]: [Fig.3] schematically represents an exploded view of the device piezoelectric shown in [Fig.2];

[0042] [Fig.4]: [Fig.4] schematically represents a top view of the carrier- mirror shown in [Fig.3];

[0043] [Fig.5]: [Fig.5] schematically represents, in perspective, another mode of producing a piezoelectric device including four piezoelectric actuators surmounted by a lever arm, a bending rod and a mirror holder with deformable zones;

[0044] [Fig.6]: [Fig.6] schematically represents an exploded view of the device piezoelectric shown in [Fig.5];

[0045] [Fig.7]: [Fig.7] schematically represents a perspective view of a piezoelectric actuator whose top part has an actuating arm offsetting a bending rod;

[0046] [Fig.8]: [Fig.8] schematically represents a view of a mirror holder illustrated in [Fig.6] intended to support a mirror;

[0047] [Fig.9]: [Fig.9] schematically represents a perspective view of a third embodiment of a piezoelectric device surmounted by a mirror with a mirror holder with deformable zones;

[0048] [Fig. 10]: [Fig. 10] schematically represents an exploded view of the piezoelectric device illustrated in [Fig.9];

[0049] [Fig.11]: [Fig.11] schematically represents a top view of a mirror holder providing the mechanical connection between the mirror, the piezoelectric actuators, and the anchoring pad;

[0050] [Fig. 12]: [Fig. 12] schematically represents another embodiment of a mirror holder which can be used as a replacement for the mirror holder illustrated in [Fig.8];

[0051] [Fig. 13]: [Fig. 13] schematically represents another embodiment of a mirror holder which can be used as a replacement for the mirror holder illustrated in [Fig.8];

[0052] [Fig. 14]: [Fig. 14] schematically represents yet another embodiment of a mirror holder which can be used as a replacement for the mirror holder illustrated in 8;

[0053] [Fig. 15]: [Fig. 15] schematically represents yet another embodiment of a mirror holder which can be used as a replacement for the mirror holder illustrated in 8 in order to use a mirror assembled by gluing;

[0054] [Fig. 16]: [Fig. 16] schematically represents the mirror holder of [Fig. 15] assembled with a glued mirror. Description of the embodiments

[0055] Different configurations of piezoelectric devices are illustrated in Figures 2 to 16. A piezoelectric device has a fixed frame 1 which serves as a support and a first face of which is surmounted by several piezoelectric actuators 2, preferably at least two piezoelectric actuators 2, even more preferably at least three non-aligned piezoelectric actuators 2 or even four or at least four non-aligned piezoelectric actuators 2. The piezoelectric actuators 2 are fixed to the fixed frame 1. In the different embodiments illustrated, four piezoelectric actuators 2 are used.

[0056] The piezoelectric actuators 2 are fixed to the fixed frame 1 and extend from one face of the fixed frame 1. The piezoelectric actuators 2 are capable of deforming independently of each other according to a linear translation. Each linear translation is directed along an axis which is parallel to a first direction AA. The piezoelectric actuators 2 are connected to a control circuit configured to actuate the piezoelectric actuators, and preferably capable of actuating them independently of each other.

[0057] The piezoelectric device has a mirror holder 4 intended to receive and support a mirror 5. The mirror 5 is mounted removably relative to the mirror holder 4. The mirror holder 4 provides the mechanical connection between the piezoelectric actuators 2 and the mirror 5. The mirror holder 4 defines several support points 4a intended to fixedly mount the mirror 5. The support points 4a define a support zone of the mirror holder 4. The support zone of the mirror holder 4 is mounted to rotate about at least one first axis of rotation BB relative to the fixed frame 1 so that the mirror 5 is mounted to rotate about said at least one first axis of rotation BB which is perpendicular or substantially perpendicular to the first direction AA.Preferably, the support area of ​​the mirror holder 4 is configured so that the mirror 5 is also mounted to be rotatably mounted about a second axis of rotation CC which is perpendicular to the first direction AA and perpendicular to the first axis of rotation BB. The support points 4a of the mirror holder 4 cooperate with the support points 5a of the mirror 5. The mirror holder 4 has at least three support points 4a for effectively fixing the mirror 5 on the mirror holder 4, preferably at least four support points 4a. Once the mirror 5 is fixed to the mirror holder 4, the mirror 5 follows the same movements as the support area.

[0058] The mirror holder 4 defines several fixing points 4b, preferably at least three fixing points, for example four fixing points 4b. The support points 4a are distinct from the fixing points 4b. Each piezoelectric actuator 2 is mechanically associated with a fixing point 4b, by a direct or indirect mechanical connection, so that the actuation of the piezoelectric actuator 2 moves the associated fixing point 4b. The mechanical connection between the piezoelectric actuator 2 and the mirror holder 4 is a connection which makes it possible to push or pull the mirror holder 4 to rotate the mirror 5 in one direction or the other depending on the direction of deformation of the piezoelectric actuator 2.

[0059] Each piezoelectric actuator 2 is mechanically connected to the mirror holder 4 so that the deformation of the piezoelectric actuator 2 moves a fixing point 4b which moves the support zone of the mirror holder 4 relative to the fixed frame 1 to obtain a rotation component around the first rotation axis BB and even actually of the second axis of rotation CC. The actuation of the piezoelectric actuators 2 acts on the mirror holder 4 and causes the rotation of the support area and therefore the rotation of the mirror 5.

[0060] The piezoelectric device comprises a converter which is configured to convert the linear translations resulting from the deformations of the piezoelectric actuators 2 into at least one rotation of the support zone relative to the fixed frame 1. The converter may be formed by elements which are distinct from the mirror holder 4 and / or from the zones of the mirror holder 4. The converter may be formed by one or more parts. The converter may be distinct from the mirror holder 4 or monolithic with the mirror holder 4. Different converter configurations are illustrated in FIGS. 2 to 16.

[0061] The piezoelectric device comprises an anchoring pad 6 which is fixedly mounted on the fixed frame 1. The anchoring pad 6 extends in the first direction AA. The anchoring pad 6 can be used to fixedly mount a part of the mirror holder 4 and / or elements of the converter relative to the fixed frame 1. The anchoring pad 6 can be removable or irremovable from the fixed frame 1.

[0062] The inventors have observed that in the devices of the prior art, part of the deformations present in the mirror 5 after its mounting on the mirror holder 4 are due to the hyperstaticism introduced by the fixing of the mirror 5 on the mirror holder 4. Indeed, taking into account the manufacturing tolerances, the support points 5a of the mirror 5 are never strictly at the same dimension as the support points 4a, in particular along the direction AA. The difference in the dimensions causes a set of constraints in the mirror 5 during the rigid fixing on the mirror holder 4.

[0063] When the mirror 5 is fixed to the mirror holder 4 by four support points 4a, the configuration is, by definition, hyperstatic and a lack of flatness in the support points 4a of the mirror holder 4 and / or in the support points 5a of the mirror 5 leads, during fixing, to the generation of a set of constraints. The mirror holder 4 being much more rigid than the mirror 5, the constraints are mainly introduced into the mirror 5 which ends up deforming.

[0064] In a configuration with three support points 4a and three support points 5a, a hyperstatic situation also appears because the support points 4a / 5a are not punctual. The support points are more or less extensive surfaces. When the surfaces of the support points 4a and 5a do not define the same plane, sets of constraints are introduced during fixing which end up deforming the mirror 5.

[0065] Unlike the rigid mirror holder of the prior art, different configurations of a deformable mirror holder 4 are proposed. The mirror holder 4 has at least one of the support points 4a which is mounted to move in the first direction AA by de forming a part of the mirror holder 4, preferably by elastic deformation of the mirror holder 4. One of the support points 4a is mounted to be movable independently of the other support points 4a in order to better adapt the position of the support points 4a of the mirror holder 4 to the position of the support points 5a of the mirror 5 and thus reduce the stress play introduced into the mirror 5.

[0066] It is particularly advantageous that at least two support points 4a are mounted independently of each other and relative to the others so as to better adapt to the positions of the support points 5a. The two support points 4a can be mounted movably along the first direction AA. Even more preferably, each support point 4a is mounted movably independently of the others at least along the first direction AA. It is then easier to commonly adapt the positions of the support points 4a and 5a relative to each other.

[0067] The support point or points 4a are mounted movably independently of the others in the absence of fixing the mirror 5. When the mirror 5 is fixed, the support points 4a become fixed relative to each other.

[0068] The movement of the support points 4a relative to each other is carried out by elastic deformation of the mirror holder 4, for example by means of a spring connection or by means of an elastically deformable washer arranged between a support point 4a and a support point 5a. The deformation of the spring or the washer allows a better adaptation. However, it appears that this configuration is not the most interesting because it requires the introduction of an additional part which can be a source of error during assembly.

[0069] Particularly advantageously, the support point 4a, the support points 4a or each support point 4a are mounted to be movable relative to the rest of the mirror holder 4 by means of a plate 4c fixed by a flexural connection 4d. Such a configuration allows easy adjustment between the support points 4a and the support points 5a with automatic and adjusted adaptation.

[0070] When fixing the mirror 5 with the mirror holder 4, the support points 4a move until they come into contact with the support points 5a and thus adapt to the configuration of the mirror 5. The mirror 5 is then fixedly mounted on the mirror holder 4. The mirror 5 moves according to the movements of the support points 4a.

[0071] In the illustrated embodiments, the direction AA passing through the center O of the mirror holder 4 coincides with the direction of the optical axis of the mirror 5 when the latter is in its rest position, that is to say when the piezoelectric actuators 2 are not stressed, as shown in [Fig.2] or in [Fig.5].

[0072] The flexural connection 4d deforms elastically, which makes it possible to adapt the position of the support points 4a of the mirror holder 4 to the position of the support points 5a of the mirror 5. The shape of the plate 4c and / or the bending connection 4d will be chosen judiciously to best adapt to the constraints of the mirror 5. In the case of a plane mirror, this ensures that the flatness of its reflecting surface 5b is maintained and therefore a reduction in wavefront errors.

[0073] After fixing, the mirror 5 defines a more rigid mechanical connection between the different support points 4a. The mirror 5 limits the mobility of the support points 4a. In this way, the behavior of the mirror holder 4 is different depending on whether the mirror 5 is fixed or not fixed to the mirror holder 4. The support point(s) 4a which are initially movable relative to the others become fixed to each other. The position of the support points 4a is defined by the mirror 5 to adapt the dimensional differences. Once fixed to the mirror holder 4, the mirror 5 is able to pivot about the first axis of rotation BB and / or the second axis of rotation CC depending on the deformations applied to the piezoelectric actuators 2 in a manner identical or substantially identical to a mirror holder of the prior art such as that illustrated in [Fig. 1].

[0074] The use of a support point 4a mounted movable in flexion also makes it possible to have a support point which is movable relative to the fixing points 4b. The flexion connection 4d which intervenes in the mechanical connection connecting the support point 4a to the fixing point 4b makes it possible to filter part of the vibrations and to better preserve the mechanical integrity of the mirror 5 with respect to the shocks and vibrations induced by the fixed frame 1.

[0075] Different configurations of support points 4a movable between them and movable relative to the fixing points 4b are illustrated in FIGS. 2 to 14.

[0076] The use of a mirror holder 4 which is deformable goes against the teachings of the prior art which propose an infinitely rigid mirror holder 4 to ensure good efficiency of the piezoelectric actuators 2. The use of a mirror holder 4 which is deformable makes it possible to form a mirror holder 4 which is thinner and therefore less heavy than those of the prior art. The saving in mass to be moved makes it possible to reduce the size of the piezoelectric actuators 2 and the electrical consumption.

[0077] The inventors have also observed that in the devices of the prior art, part of the deformations appear in the mirror 5 during temperature variations. This deformation is due to the difference in expansion between the mirror holder 4 and the mirror 5 which are made of different materials, having different expansion coefficients. During temperature variations, the rigid mirror holder 4 of the prior art expands more than the mirror, and imposes its deformation on the mirror 5 which is more flexible, and deforms.

[0078] To form plates 4c mounted movable in flexion in a mirror holder 4 in the form of a plate, it is advantageous to use first slots 4f. In a particular embodiment illustrated in FIGS. 2 to 8, the mirror holder 4 has plates 4c each having a support point 4a. The plates 4c are terminated by the flexural connection 4d which fixes the plate 4c to the rest of the mirror holder 4. The shapes of the plates 4c and the flexural connections 4d are defined by first slots 4f which pass through the mirror holder 4 in the direction AA. The shape and position of the first slots 4f make it possible to define the deformation permitted for each flexural connection 4d and therefore the possible displacement for each support point 4a in the first direction AA.

[0079] In the illustrated embodiment, the first slots 4f which define the plates 4c and the flexural connections 4d for the support points 4a are in the form of a cutout which goes around each support point 4a with the exception of the flexural connection(s) 4d to maintain a mechanical connection.

[0080] As illustrated in Figures 4, 8, 13, 14 and 15, it is particularly advantageous to define first slots 4f which separate each support point 4a from the other support points 4a, the observation being carried out by drawing a straight line between each pair of two support points 4a movable independently of each other. It is also advantageous to define first slots 4f such that they separate each support point 4a and the center O of the mirror holder 4 as illustrated in [Fig.4], the observation being carried out by drawing a straight line between each support point 4a and the center O. It is also advantageous to define first slots 4f which separate each support point 4a and its two closest fixing points 4b when drawing an imaginary straight line between the support point 4a and the fixing point 4b considered.

[0081] Unlike the rigid mirror holder of the prior art, different configurations of deformable mirror holders are also proposed, which make it possible to obtain movable mirror support points both in the AA direction and also in the BB and CC directions, so that the mirror support can expand in the BB and CC directions without deforming the mirror during temperature variations.

[0082] To form a deformable mirror holder 4, it is advantageous to use a mirror holder 4 which is in the form of a plate. The dimension of the plate is much greater along the axes of rotation BB and CC than along the direction AA, for example at least five times greater, or even at least ten times greater. Preferably, the mirror holder 4 is made of a thin metal plate, preferably less than 3 mm, preferably less than 2 mm and even more preferably less than 1 mm. The thin thickness of the plate makes it possible to reduce the mass of the mirror holder 4. By reducing the mass of the mirror holder 4, a reduced force applied by the piezoelectric actuator 2 makes it possible to rotate the mirror holder 4.

[0083] In order to more effectively reduce the deformations induced in the mirror 5, it is advantageous to reduce as much as possible the introduction of a set of constraints due to the differential expansion between the mirror 5 and the mirror holder 4. It is advantageous that at least one support point 4a is movable relative to the other support points 4a in a direction perpendicular to the first direction AA. Preferably at least two or even all of the support points 4a are movable independently of each other in at least one direction perpendicular to the first direction AA.

[0084] In a particular embodiment illustrated in [Fig. 15], the plates 4c receiving the support points 4a are mounted to move in the first direction AA by means of the first slots 4f. It is advantageous that the first slots 4f allow the support points 4a to move in the directions BB and CC. In the embodiment illustrated in [Fig. 15], the support points 4a are provided to provide bonding surfaces for bonding a mirror 5, illustrated in [Fig. 16].

[0085] It is also advantageous that the mobility of the support point 4a along the at least one direction perpendicular to the first direction AA is obtained by elastic deformation of the mirror holder 4 so that the mirror holder 4 adapts continuously and automatically to the position of the support point 5a as a function of the change in temperature. Such a configuration of the mirror holder 4 makes it possible to better adapt to the problems of hyperstaticism and / or differential expansion.

[0086] It is advantageous for the support points 4a to be arranged equidistant from a center O of the mirror holder 4. More preferably, the support points 4a are regularly distributed along an imaginary circle which passes through all the support points 4a and center O to better compensate for differential expansions. There is an offset equal to 90° when four support points 4a are used or equal to 120° for three support points 4a. This configuration is illustrated in Figures 2 to 16.

[0087] In such a configuration, in order to better control the position of the mirror 5 relative to the mirror holder 4 and the stresses induced during temperature changes, it is preferable for the plate 4c to also move along a radial component. The flexural connection 4d and / or the plate 4c allow the support point 4a to move along a radial component. For example, according to [Fig.4], the flexural connection 4d extends in the form of an arc of a circle around the center O. Alternatively or in addition, the plate 4c has cutouts in an arc of a circle around the center O. When the temperature changes, the differential expansion applies stresses to the cutouts which deform. With such cutouts the support points 4a and the support points 5a move slightly in a radial direction, perpendicular to the direction AA and which passes through the center O.This helps to better maintain the flatness of the mirror 5 and reduce wavefront errors, over a wider temperature range.

[0088] Different configurations are possible to define a displacement of a support point 4a according to the radial component. [Fig.4] illustrates a plate 4c whose bending zone 4d which fixes the plate 4c to the rest of the mirror holder 4 is in the form of an arc of a circle with center O. Preferably, the multiple plates 4c have equivalent arcs of a circle, that is to say of the same radius, the same center and the same angular arc. Figures 13, 14 and 15 show other configurations of mirror holder 4 where the conformation of the plate 4c associated with the conformation of the flexure zone 4d facilitates obtaining a radial displacement of the support point 4a when it is fixed to the mirror 5. For example, the flexure connection 4d illustrated in [Fig.8] can be modified to form a flexure connection 4d in an arc of a circle as illustrated in [Fig. 14].

[0089] Figures 9 to 11 show another embodiment with a plate 4c mounted on an arm 4g extending in a spiral from the center O and whose flexural connection 4d also allows torsion in a plane perpendicular to the first direction AA to allow the support point 4a to move radially in relation to the deformation of the spiral arm 4e which supports the plate 4c. The arm 4g extends mainly in a plane perpendicular to the first direction AA, preferably in at least one direction.

[0090] Preferably, at least one first 4d bending connection is formed by a plurality of first 4f slots which define circular arcs around the center O of the mirror holder 4. Such first 4f slots make it possible to form a 4d bending connection with a radial component as defined above.

[0091] It is also advantageous that two first slots 4f, used to define a bending connection 4d for a support point 4a, come from the same cutting line, that is to say correspond to the extension of the same cut in the material. It is also advantageous that a circular arc is in continuity of cutting line with at least one circular arc preferably with two circular arcs of the adjacent bending connection 4d. Such a configuration allows better control of the bending as well as the introduction of a torsional deformation for the plate 4c.

[0092] It is preferable that the bending connection(s) 4d associated with each support point 4a are arranged closer to the center O of the mirror holder 4 than the corresponding support point 4a, when observed along the first direction AA as illustrated in FIGS. 4, 8, 11, 12, 13 and 14. The distance is measured in a straight line between the center O and the support point 4a. Such a configuration makes it possible to have a displacement of the support points 4a better suited to compensating for differential expansion. However, an inverse configuration is possible or even preferable when the mirror 5 is large, for example when it extends beyond the mirror holder 4 as illustrated in [Fig. 13] or 15.

[0093] In a preferred embodiment illustrated in FIGS. 8, 12, 13 and 14, the support points 4a are arranged further from the center O of the mirror holder 4 than the fixing points 4b in an observation according to the first direction AA, radially. By this means, a displacement of the fixing points 4b produced by the piezoelectric actuators 2, preferably in push-pull mode, generates a higher angular tilt of the mirror 5 than if the same displacement was applied to the support points 4a. Thus it is possible to use smaller actuators 2 than those which would be necessary for an actuation of the support points 4a. There is therefore an advantage in having the fixing points 4b as close as possible to the center O of the mirror holder 4 to have the largest possible rotation amplitude for the mirror 5. The embodiment illustrated in the [Fig.4] represents 4b fixing points which are further from the center O than the 4a support points, but it is possible to use an inverted configuration.

[0094] However, the closer the fixing points 4b are to the center O, the more compact the piezoelectric actuators 2 must be in order to be able to be installed in a reduced volume, for a fixed deformation in the direction AA in order to obtain a significant rotation of the mirror holder 4.

[0095] In order to increase the amplitude of the rotation of the support zone for a predefined translation of one or more of the piezoelectric actuators 2, it is advantageous to bring the fixing points 4b as close as possible to the center O of the mirror holder 4 or to the central axis parallel to the direction AA and passing through the center O. However, if a configuration is retained in which the piezoelectric actuators 2 are in the extension of the fixing points 4b in the direction AA, this amounts to bringing the piezoelectric actuators closer to each other and therefore to generating a space requirement problem for installing the piezoelectric actuators 2.

[0096] It is particularly advantageous to provide that at least one of the piezoelectric actuators 2 and preferably all the piezoelectric actuators 2 are surmounted by a bar 8 fixed to the top part of the piezoelectric actuator 2 as illustrated in [Fig. 7] and in the piezoelectric device presented in Figures 5 and 6. The bar 8 extends perpendicular to the first direction AA and radially relative to the central axis. The bar 8 moves in the first direction AA in a manner identical to the movement produced by the deformation of the piezoelectric actuator 2 in the first direction AA. The bar 8 is rigid in order to limit its bending and thus maintain significant efficiency on the rotation of the mirror 5. The end of the bar 8 closest to the center O can be fixed directly or indirectly to the mirror holder 4 depending on the configurations. In the particular embodiment illustrated in [Fig.7], the offset end of bar 8 is . surmounted by a bending rod 3. The first end of the bending rod 3 is fixed to the bar 8 by a fixing device, for example a screw 9 and the second end of the bending rod 3 is fixed to the fixing point 4b, for example by a screw.

[0097] Figures 5 and 6 illustrate an embodiment using the piezoelectric actuators 2 provided with the bars 8 directed towards the center of the structure. An equivalent technical solution can be applied in the embodiment illustrated in [Fig.2] or in that illustrated in [Fig.9]. This makes it possible to use larger piezoelectric actuators 2 without having a space requirement problem near the anchoring pad 6.

[0098] The fixing points 4b receive the mechanical stresses coming from the piezoelectric actuators 2. In order to have good control of the angle of rotation of the mirror 5 for a predefined translation of a piezoelectric actuator 2, it is advantageous to have a rigid mechanical connection with the flexion zones 4d of the support points 4a and preferably as rigid as possible between the fixing points 4b. The rigid mechanical connection is configured so that the fixing points 4b are mounted immobile relative to each other or substantially immobile relative to each other.

[0099] In a particular embodiment illustrated in Figures 2 to 8, the mirror holder 4 is in the form of a plate whose external design defines a disc or a connected polygon. The external peripheral zone of the plate is continuous and continuously connects all the fixing points 4b in order to form a mechanical connection as rigid as possible without making the mirror holder 4 too heavy. This configuration makes it possible to easily form, with a small excess weight, fixing points 4b that are immobile or almost immobile between them.

[0100] As an alternative illustrated in [Fig. 12], the mirror holder 4 may be devoid of the peripheral rigid zone. The fixing points 4b are held fixedly to each other by other means, for example a localized thickening of the mirror holder 4. [Fig. 12] substantially reproduces the shape of the mirror holder 4 of [Fig.4] whose peripheral zone has been removed.

[0101] In another embodiment, the mirror holder 4 is in the form of a plate which is devoid of a continuous annular peripheral portion and the fixing points 4b are arranged to be movable relative to each other. In this embodiment, to effectively take advantage of the forces applied by the piezoelectric actuators 2, it is preferable to have as many support points 4a as fixing points 4b. The mirror holder 4 comprises several arms 4e mounted movable in flexion and each arm 4e has a plate 4c with its support point 4a and a fixing point 4b as illustrated in FIGS. 9 to 11.

[0102] In the embodiment illustrated in Figures 9 to 11, the mirror holder 4 has an anchoring point 4i mounted immobile relative to the fixed frame 1. The anchoring point 4i can be fixedly mounted by means of the anchoring stud 6. It is particularly advantageous for the anchoring point 4i to be the center O to facilitate the production of the mirror holder 4 and the use of the piezoelectric device. Arms 4e extend from the anchoring point 4i and are movable in flexion from the anchoring point 4i at least in the first direction AA. Each fixing point 4b is fixed to a piezoelectric actuator 2. Preferably, the fixing point 4b is fixed directly to a piezoelectric actuator 2 to be stressed in translation in the direction AA. The arm 4e is mounted in flexion by means of a flexing connection 4g.

[0103] In order to have greater efficiency, the fixing point 4b is formed on an additional plate 4m which is very rigid. The additional plate 4m can be locally reinforced to increase its stiffness in comparison with the arm 4e. It is possible to provide a greater thickness of the material forming the mirror holder 4 or to add a rigid element by welding, gluing, screwing, riveting or any other suitable technique to limit the deformation of the additional plate 4m in comparison with the arm 4e in the first direction AA. The additional plate is connected to the arm 4e by a deformable mechanical connection 4h, preferably a torsion connection to facilitate the flexion movement of the arm 4e and a linear translation in the direction AA of the fixing point 4b.

[0104] The support point 4a is connected to the arm 4e by the flexural connection 4d. The fixing point 4b is connected to the arm 4e by the deformable mechanical connection 4h. The two connections 4d and 4h work in their elastic deformation domain. The two connections 4d and 4h ensure that the support points 4a are movable between them (in the absence of the mirror) and that the fixing points 4b are movable between them. The two connections 4d and 4h ensure that, for an arm 4e, the fixing point 4b is movable relative to the support point 4a. The mobility between the fixing points 4b makes it possible to better accommodate hyperstaticity originating from the piezoelectric actuators 2. Slight differences in height (along the first direction AA) are compensated by the mirror holder 4 without this preventing or limiting the angular range of the mirror holder 4 in its rotations.Better accommodation of hyperstaticity allows for the relaxation of dimensional manufacturing constraints on piezoelectric actuators 2 and thus reduces manufacturing costs.

[0105] The support points 4a and the fixing points 4b are movable relative to the anchoring point 4L. The arms 4e are flexible and deform according to the stress imposed by each piezoelectric actuator 2. The stress on a fixing point 4b by a piezoelectric actuator 2 causes the movement of the fixing point 4b and therefore the movement of the flexibly mounted arm 4e. This causes the movement of the support point 4a and rotates mirror 5.

[0106] It is particularly advantageous to form the 4d bending connection as well as the 4h mechanical connection by localized thinning.

[0107] In a particular embodiment, the flexing zone 4d is arranged after the mechanical connection 4h, along the direction of extension of the arm 4e from the anchoring point 4i towards the opposite end. This configuration is advantageous because it allows for a greater angular offset of the support point 4a compared to the reverse configuration or direct actuation on the support point 4a. Even more advantageously, the torsional connection 4h is arranged closer to the center O than the flexural connection 4d, along the direction of extension of the arm 4e from the center O to the opposite end. It is preferable for the torsional connection 4h to be arranged closer to the center O than the support point 4a of the same arm, in an observation along the first direction AA. The distance is measured in a straight line.

[0108] In an advantageous embodiment, the arms 4e extend in the form of spirals from the anchoring point 4L. The portion-spiral shape of the arms 4e makes it possible to increase their effective length connecting the anchoring point 4i to the fixing points 4b, to increase the angular range accessible for the rotation of the mirror 5.

[0109] This embodiment is particularly advantageous because it allows the direct attachment of the mirror holder 4 to the piezoelectric actuators 2 and to an anchoring pad 6 as well as the direct attachment of the mirror 5 to the mirror holder 4. Since the mirror holder 4 can be in the form of a plate, this allows a more compact configuration to be produced than the configurations of the prior art along the first direction AA as well as a less heavy configuration with fewer parts.

[0110] The embodiment illustrated in Figures 9 to 11 makes it easy to move the piezoelectric actuators 2 further away from the center O, which reduces the space constraints linked to the integration of the multiple piezoelectric actuators 2. The fixing points 4b extend from the arms 4e in a spiral in radial directions away from the center O. To maintain significant rotation efficiency, it is preferable for the additional plate 4m which includes the fixing point 4b up to the mechanical connection 4h to be very rigid so that the linear translation applied by the piezoelectric actuator 2 is substantially identical between the mechanical connection 4a and the piezoelectric actuator 2.

[0111] It is advantageous for the mirror holder 4 to have axial symmetry, the axis of symmetry of which is parallel to the first direction AA. It is also advantageous for the mirror holder 4 to have rotational symmetry, for example rotation through 90° or 120°.

[0112] It is advantageous to use four piezoelectric actuators 2 instead of three piezoelectric actuators 2 because this facilitates the management of the rotation of the mirror holder 4 around two axes of rotation BB and CC.

[0113] The piezoelectric actuators 2 deform to define a linear translation between a first end 2a and a second end 2b. The linear translation is observed along the first direction AA. The first end 2a is fixedly mounted on the fixed frame 1, the deformation of the second end 2b is a linear translation which is mainly oriented along the first direction AA. The deformation of the piezoelectric actuator 2 results in a moving closer or further apart between the first end 2a and the second end 2b along the first direction AA. Different configurations of piezoelectric actuators 2 are possible, but it is advantageous to use the configurations described in documents US6927528 and FR2740276. The piezoelectric actuator has a bar made of piezoelectric material.The use of the bar allows the actuation point to be moved closer to the center O than to the piezoelectric bar in an observation along the first direction AA.

[0114] A converter transforming the linear translation of the second end 2a into a rotation of one of the support points 4a can be obtained in different ways. In the embodiments illustrated in Figures 2 to 6, a flexure rod 3 connects a piezoelectric actuator 2 and a fixing point 4b. The flexure rod 3 is configured to deform in flexion and thus transform the translational movement of the second end 2a into a rotation of the associated fixing point 4b. In order to facilitate obtaining the rotational movement, the fixing point 4b is also fixed to a flexor which is in the form of an arm, one end of which is fixedly mounted to the fixing point 4b and the other end of which is fixedly mounted to the fixed frame 1, preferably to the anchoring stud 6. Preferably, this assembly is carried out for each piezoelectric actuator 2.The flexors can be mounted together as one piece forming a flexible bearing 7. In the embodiment illustrated in Figures 2 to 4, the mirror holder 4 is not directly attached to the fixed frame 1. In this embodiment, the converter is formed by the flexible bearing 7 and the flexing rods.

[0115] In another embodiment illustrated in Figures 5 to 8, the flexing rods 3 connect the piezoelectric actuators 2 and the fixing points 4b. An anchoring portion 4i also forming the center O of the mirror holder 4 immobilizes the center O relative to the fixed frame 1. In this embodiment where the flexors are not used, it is preferable to structure the mirror holder 4 in order to make it more flexible than in the configuration illustrated in [Fig.2] and thus better adapt the inclination of the fixing point 4b to the deformation of the flexing rod 3. It is particularly advantageous to form second through slots 4k such as cutouts that extend in the form of spirals from the anchoring area 4i to the fixing points 4b. The second through slots 4k in the form of spirals make it possible to reduce the bending stiffness of the mirror holder between the fixing points 4b and the anchoring point 4L

[0116] Finally, in another embodiment illustrated in FIGS. 9 to 11, the converter is integrally formed in the mirror holder 4 so that the piezoelectric actuators 2 can be directly fixed to the mirror holder 4.

[0117] Advantageously, the piezoelectric actuators 2 are amplified piezoelectric actuators, based on a piezoelectric stack and an amplifying shell having a second end 2b fixed by screwing to a fixing point 4b.

[0118] In the embodiment illustrated in [Fig.7], the piezoelectric actuator 2 has a bar 8 removably mounted and fixed by means of a screw 9. In the embodiment illustrated in FIGS. 9 to 11, the screw 9 is intended to be screwed into the end 2b of the piezoelectric actuator 2 to fix the mirror holder 4 on the piezoelectric actuator 2. The screw 9 passes through the hole forming the fixing point 4b. Figures 2, 3, 5 and 6 illustrate the use of bolt 10 to fix mirror 5 to mirror holder 4. Bolts 10 can be used for the embodiment of Figures 9 to 11. In the embodiments illustrated in Figures 2 to 7, the flexure rod 3 is terminated by a threaded section associated with at least one nut to fix mirror holder 4 to the end of the flexure rod 3.

[0119] The support points 4a and the fixing points 4b ensure the formation of a mechanical connection with the mirror holder 4. They may have smooth or threaded through holes, threaded non-through holes, threaded protruding areas, flats intended for glued connections, or any other means which allows the attachment with the mirror holder 4. It is advantageous to use bolts to fix the different elements together, in order to ensure good mechanical strength in response to external vibrations. In the illustrated embodiments, the fixing points 4b and the support points 4a have through holes in the mirror holder 4 for example for the passage of a screw or a bolt 10.

[0120] Preferably, the piezoelectric actuators 2 are associated in pairs and the piezoelectric actuators 2 of a pair are arranged in opposite directions relative to a first direction AA which passes through the center of the support zone and, where appropriate, of the mirror 5. It is advantageous to associate the piezoelectric actuators 2 in pairs opposed by the control circuit, with the aim of producing a “push-pull” mode intended to produce a rotational movement with limited travel of the mirror holder 4 and the mirror 5. This mode is obtained by supplying the two actuators piezoelectric actuators 2 of the pair opposite with respect to the direction AA such that one piezoelectric actuator 2 expands while the other contracts.

[0121] It is advantageous to have two fixing points 4b aligned along an axis of rotation BB and to align two other fixing points 4b along another axis of rotation CC perpendicular to the previous one. To pivot the support area around the axis of rotation BB, the two piezoelectric actuators 2 associated with the two fixing points 4b aligned along the axis CC are actuated in opposite directions along the direction AA. One contracts and the other expands. To pivot the support area around the axis of rotation CC, the two piezoelectric actuators 2 associated with the two fixing points 4b aligned along the axis BB are actuated in opposite directions along the direction AA. One contracts and the other expands.

[0122] In a configuration with three piezoelectric actuators, it is preferable to distribute the actuators regularly, i.e. with an angular offset equal to 120° all around the axis AA which passes through the center of the support zone. It is also advantageous to place the fixing points 4b equidistant from the axis AA which passes through the center of the support zone and to use identical actuators. An advantageous use of the "push-pull" mode is possible by applying to each actuator of a pair of close neighbors a command such that their stroke is opposite and equal to half the amplitude of the stroke of the remaining actuator. The center of the mirror is aligned with the center of the support zone in the direction AA.

[0123] The deformation of one or more piezoelectric actuators 2 following a linear translation in the direction AA, for example in push-pull mode, causes the displacement of one or more fixing points 4b, which induces a rotation of the mirror holder 4 by means of the converter. This rotation moves the support zone and therefore the support points 4a relative to the fixed frame 1. The mirror 5 moves in rotation because it is immobile or almost immobile relative to the mirror holder 4. The introduction of flexibility into the mirror holder 4 via the support points 4a movable between them means that the forces introduced by the piezoelectric actuators 2 are not or almost not applied to the interior of the mirror 5, which limits the deformation of the mirror 5 without this preventing the control of the rotation.

[0124] The piezoelectric device is intended for optical pointing applications, such as free-space optical communication, designation, scanners, laser machining or laser surgery. These are on-board applications or those in harsh environments, encountered in the space, optronics, aeronautics, defense, industrial or medical sectors.

Claims

Claims

1. A piezoelectric pointing device comprising: - a fixed frame (1); - piezoelectric actuators (2) fixed to the fixed frame (1), the piezoelectric actuators (2) being capable of deforming independently of one another according to a linear translation, each linear translation being directed according to a first orientation (AA);- a mirror holder (4) intended to receive and support a mirror (5) and to provide the mechanical connection between the piezoelectric actuators (2) and the mirror (5), the mirror holder (4) defining fixing points (4b) and at least three support points (4a), the at least three support points (4a) being intended to fixedly mount a mirror (5) on the mirror holder (4), the at least three support points (4a) being distinct from the fixing points (4b), the at least three support points (4a) defining a support zone mounted so as to be movable in rotation relative to the fixed frame (1) around at least a first axis of rotation (BB), the first direction (AA) being perpendicular to said at least a first axis of rotation (BB), each fixing point (4b) being functionally connected to a piezoelectric actuator (2); - a converter arranged in at least one mechanical connection connecting the piezoelectric actuators (2) and the support points (4a) so that the linear translation of one or more of the piezoelectric actuators (2) causes the rotation of the support area relative to the fixed frame (1) around said at least one first axis of rotation (BB); piezoelectric device characterized in that the mirror holder (4) is in the form of a plate defining the fixing points (4b) and the at least three support points (4a) and in that the mirror holder (4) is deformable so that at least one of the at least three support points (4a) is a support point (4a) mounted movably independently of the other support points (4a) in the first direction (AA) by elastic deformation of the mirror holder (4), in the absence of the mirror (5).

2. A piezoelectric pointing device according to claim 1, wherein each support point (4a) is a support point (4a) mounted movably independently of the other support points (4a) in the first direction (AA) by elastic deformation of a portion of the mirror holder (4), in the absence of the mirror (5).

3. Piezoelectric pointing device according to claim 2, comprising a plurality of plates (4c), each support point (4a) being mounted on a plate (4c), in which each plate (4c) is fixed to the rest of the mirror holder (4) by a flexural connection (4d) so that each plate (4c) is mounted movably independently of the other plates (4c), in the first direction (AA), in the absence of the mirror / Si

4. IPI- A piezoelectric pointing device according to claim 3, wherein the support points (4a) are arranged equidistant from a center (0) and wherein the flexural links (4d) are arranged closer to the center (0) than the support points (4a) in an observation along the first direction (AA).

5. A piezoelectric pointing device according to any one of claims 1 to 4, wherein the support points (4a) are arranged equidistant from a center (0) and wherein the support points (4a) are further from the center (0) than the fixing points (4b).

6. A piezoelectric pointing device according to any one of claims 1 to 5, wherein the support points (4a) are arranged equidistant from a center (0) and wherein a top portion of at least one of the piezoelectric actuators (2) comprises a bar (8) extending in a direction perpendicular to the first direction (AA) radially relative to the center (0) so that the mechanical connection between the piezoelectric actuator (2) and the associated attachment point (4b) is closer to the center (0) than to the piezoelectric bar of the piezoelectric actuator (2), when viewed in the first direction (AA).

7. Piezoelectric pointing device according to any one of claims 3 to 6, wherein the plates (4c) are configured to move in at least one direction perpendicular to the first direction (AA).

8. A piezoelectric pointing device according to claim 7, wherein the support points (4a) are arranged equidistant from a center (0) and wherein the flexural connection (4d) is also configured to allow radial displacement of the support points (4a) perpendicular to the first direction (AA) and relative to the center (0).

9. Piezoelectric pointing device according to the preceding claim, comprising additional plates (4m), in which the center (0) is fixedly mounted relative to the fixed frame (1) by means of a stud anchoring (6), and in which arms (4e) extend from the center (0), each arm (4e) being fixed to one of the plates (4c) by the bending connection (4d), each arm (4e) being fixed to one of the additional plates (4m) by a torsion connection (4h), the torsion connection pivoting the arm (4e) relative to the additional plate (4m) around an axis perpendicular to the first direction (AA), each additional plate (4m) receiving a fixing point (4b).

10. A piezoelectric pointing device according to the preceding claim, wherein the torsional link (4h) is arranged closer to the center (0) than the bending link (4d), along the extension direction of the arm (4e) from the center (0) to the opposite end.

11. Piezoelectric pointing device according to one of claims 9 and 10, wherein the torsional connection (4h) is arranged closer to the center (0) than the support point (4a), in an observation in the first direction (AA).

12. A piezoelectric pointing device according to any one of claims 9 to 11, wherein the arms (4e) extend in the form of spirals.

13. A piezoelectric pointing device according to claim 12, wherein the flexural link (4d) also defines a torsional link about an axis parallel to the first direction (AA) and passing through the flexural link (4d).

14. Piezoelectric pointing device according to one of claims 9 to 13 in which the mirror holder (4) is directly fixed to at least one of the piezoelectric actuators (2) so that the at least one fixing point (4b) moves in a linear translation in the first direction (AA).

15. Piezoelectric pointing device according to the preceding claim, in which each piezoelectric actuator (2) is fixed directly to one of the fixing points (4b), each fixing point (4b) belonging to an additional plate (4m) which is more rigid than the arm (4e) on which the additional plate is fixed (4m) by the torsional connection (4h).

16. A piezoelectric pointing device according to claim 8, wherein each flexural link (4d) has a portion shaped as an arc of a circle around the center (0).

17. A piezoelectric pointing device according to any one of claims 3 to 8 and 16, wherein the support points (4a) are arranged equidistant from a center (0), wherein the center (0) is movable relative to an anchoring pad (6) in the first direction (AA), wherein the converter has a flexible bearing (7) having a fixed portion fixedly mounted relative to the fixed frame (1) by means of the anchoring pad (6) and flexors extending from the fixed portion in directions perpendicular to the first direction (AA), the flexors being fixedly mounted at the fixing points (4b), wherein the piezoelectric actuators (2) are connected to the fixing points (4b) by flexing rods (3) and wherein the fixing points (4b) are mounted immobile relative to each other in the mirror holder (4).

18. Piezoelectric pointing device according to claim 17, in which the plates (4c) and the flexural connections (4d) are defined by first slots (4f) which are through in the first direction (AA) and in which, in an observation in the first direction (AA), each straight line connecting one of the support points (4a) to a fixing point (4b) spans at least one of the first slots (4f).

19. A piezoelectric pointing device according to any one of claims 3 to 8 and 16, wherein the support points (4a) are arranged equidistant from a center (0) and wherein the center (0) is fixedly mounted relative to the fixed frame (1) by means of an anchoring stud (6), and wherein the fixing points (4b) are connected to the piezoelectric actuators (2) by a bending rod (3) extending mainly in the first direction (AA), one end of the bending rod (3) being fixed to one of the actuators, another end of the bending rod (3) being fixed to one of the fixing points (4b).

20. Piezoelectric pointing device according to claim 5, wherein the mirror holder (4) has second slots (4k) which are transverse in the first direction (AA) and which extend in the form of spirals from the center (0), the second slots (4k) separating the center (0) and the fixing points (4b).

21. A piezoelectric pointing device according to any one of claims 1 to 4, wherein each support point (4a) is disposed equidistant from two of the fixing points (4b) which are closest.

22. A piezoelectric pointing device according to any preceding claim, comprising a mirror (5) fixed to the mirror holder (4). by means of the support points (4a), the mirror (5) defining a mechanical connection with the support points (4) which fixes the position of the at least one movable support point (4a) relative to the other support points (4a).