Device for generating an optical delay

Abstract

Device for generating an optical delay, the device (D) comprising at least one mobile element (101) and at least one spring (200), the at least one spring (200) being attached to the at least one mobile element (101), the at least one spring and the at least one mobile element forming a mechanical oscillator configured to oscillate at a resonance frequency, Fr, when the spring undergoes an excitation, and the mobile element (101) being configured to translate at least one mirror along an optical axis during oscillation.

Description

[0001] DESCRIPTION

[0002] TITLE: DEVICE FOR GENERATING AN OPTICAL DELAY

[0003] Technical field.

[0004] The present invention relates to a device for generating an optical delay. The field of the invention is more particularly that of devices for generating an optical delay in interferometric devices.

[0005] State of the prior art

[0006] The state of the art of interferometric devices for measuring optical elements has undergone constant development. From the earliest experiments in interferometry to recent technological advances, these systems have been widely used to accurately characterize a wide range of optical elements. Classical techniques such as Michelson, Mach-Zehnder, and Fizeau interferometry have paved the way for more sophisticated methods such as white-light interferometry and optical coherence techniques. These approaches have made it possible to measure properties such as shape, flatness, refractive index, thickness, and surface defects of lenses, mirrors, prisms, and other optical components. Despite these advances, some limitations persist.Indeed, there are still gaps in the generation of good quality variable delay in interferometry devices, especially optical ones.

[0007] The aim of the present invention is to resolve at least one of the aforementioned drawbacks.

[0008] Statement of the invention

[0009] At least one of these aims is achieved with a device for generating an optical delay, the device comprising at least one movable element and at least one spring, the at least one spring being fixed to the at least one movable element, the at least one spring and the at least one movable element forming a mechanical oscillator configured to oscillate at a resonance frequency, Fr, when the spring undergoes excitation, the movable element being configured to translate at least one mirror along an optical axis during the oscillation. The device makes it possible to generate an optical delay, that is to say a controlled delay in the time of the passage of light. The device according to the invention makes it possible to generate a variable delay of good quality in an interferometry device for example.Good quality means that the intensity of the delayed signal is not significantly affected by the delay, i.e. the direction of the optical intensity reflected by a delay line remains fairly constant.

[0010] Resonance reduces the excitation energy required for each cycle of the delay line. The device also allows for precise control of the optical delay by adjusting the resonance amplitude of the mechanical oscillator. This provides great flexibility for adjusting the optical delay to the specific needs of the application. The device according to the invention also allows the moving element to have a large amplitude of movement. The movement is also fast. The device according to the invention is also compact and low cost.

[0011] According to one embodiment, the at least one mirror can be attached to the movable element. This mirror can be placed in front of an optical system focusing a beam thereon. Provided that the mirror is substantially perpendicular to an optical beam illuminating it, it is capable of returning this initial optical beam in the direction from which it came. The optical beam then returns to the optical system with a delay modulated by the delay line. The mirror can be placed at a specific distance from the beam emission, allowing the length of the optical path to be adjusted. By controlling this distance, the optical delay generated by the device can be adjusted. Preferably, the mirror is attached to one end of the movable element.

[0012] According to an advantageous embodiment, the at least one spring may comprise at least one guide blade.

[0013] The moving element may be connected to at least one guide blade, or preferably two guide blades which connect it more or less directly to a fixed part. The spacing between the two guide blades ensures the absence of angular deviation of the moving element, i.e. translational guidance, in a more or less constant direction, preferably close to that of the moving element. A guide blade is understood to mean an element generally much wider than it is thick, giving it sufficient elasticity or deformation. The guide blade has a certain length, smaller or larger than its width. The greater the length compared to the width, the more significant deformations the guide blade can withstand, the greater the area swept by the delay line, the lower the resonant frequency of the assembly.

[0014] A spring may include one or more guide blades.

[0015] The at least one guide blade may include at least one inner type guide blade and at least one outer type guide blade.

[0016] The at least one inner blade and the at least one outer blade may be connected by at least one intermediate point.

[0017] In order to clarify the description of the exemplary embodiments, we will call Z the direction of the axis materialized by the mobile element, X and Y two perpendicular axes, and saying that X is the axis linked to the length of one or more guide blades, Y linked to the width of said guide blades.

[0018] Variations are of course possible around this definition.

[0019] According to a first embodiment, one or two guide blades can be connected by one of their side to a fixed part which we will call the chassis, and by the other of their side - in the so-called lengthwise direction - to the mobile element.

[0020] This embodiment has the disadvantage that the translation of the mobile element in the Z direction is accompanied by a translation also in the X direction, of much lesser amplitude. The appearance of a translation in X is however compatible with the return of the beam which is then reflected on a point which moves on the mirror. However, the mirror maintains a fixed angle relative to the frame, which does not degrade the quality of the optical return.

[0021] According to a second embodiment, the device comprises more guide blades, typically four, in order, for example, to increase the possible movement, without widening the device. In this embodiment, the blades are separable into two types: those connecting the fixed part or the frame to an intermediate point and those connecting this intermediate point to the mobile element. The first type is called an “external” blade, the second type is called an “internal” blade in the remainder of the description. “Intermediate point” means a particular area of ​​the guide blade. The term “point” is not limiting. The intermediate point may, for example, correspond to an opening or a hole in the blade or a defined part of the blade.

[0022] An inner blade can be connected to an outer blade by an intermediate point. An intermediate point can be the connection between several blades, for example two outer blades and one inner blade.

[0023] Preferably, the intermediate points of the at least one internal blade and the at least one external blade may be connected by at least one connecting element. It is advantageous to add a connecting element between intermediate points of several blades, or sets of different blades, or parts of different springs.

[0024] Advantageously, at least one guide blade may have a variable width profile. These variable profile blade shapes make it possible to produce a more compact blade, for a given stiffness, as well as for a given amplitude of movement of the moving element.

[0025] At least two guide blades may belong to the same plane. The at least one spring may comprise at least two guide blades secured to each other.

[0026] A third embodiment may also be preferred with at least eight guide blades forming four springs, fixed symmetrically on either side of the movable element, in order to eliminate the X translation coupled with the Z translation, by symmetry of deformation of the blades located on either side of the movable element. This then provides an essentially Z translation for the movable element.

[0027] In a further advantageous embodiment, several blades can be grouped in the same plane, by assembly, or by making the spring with several blades from a larger plate encompassing the blades that compose it. In this latter embodiment, a spring can bring together, for example, two groups of three blades, in the shape of an "E" and a symmetrical "E". The upper and lower "-" bars of the "E" can then be "external" blades, the central bar an "internal" blade. For the shape of the blades, it can be a rectangular shape, that is to say for which the width of the blade is constant as a function of a displacement in the lengthwise direction.

[0028] But advantageously, the shape of the blade can be modulated according to the length. For example, by identifying by x = 0 the position equal to or close to the attachment of the mobile element, by x = L the position equal to or close to the intermediate point (or the attachment to the chassis), we can make the width decrease linearly from an initial value W up to x = L / 2, with a quasi-zero value of width at L / 2, then make the width increase linearly when x increases from L / 2 to L, to reach W again. This resembles two triangles which would touch by their points, a place of quasi-zero width. As this zone of quasi-zero width is fragile, we can also leave a linear decrease near X = L / 2 to obtain more width in this central zone of the blade. This profile can be repeated for each type of "internal" or "external" blade.

[0029] The at least one guide blade may comprise at least one substantially oval opening. Advantageously, the at least one spring comprises at least one opening having a substantially “8” shape. Indeed, the juxtaposition of these external / internal / external blades in each E previously mentioned leads to, for example, two substantially oval openings between the guide blades, which may be reminiscent of two “8”s lying down for the complete spring with the E and E symmetrical.

[0030] Advantageously, the device may comprise at least one electronic assembly and at least one magnet coupled to the mobile element, the at least one electronic assembly comprising at least one electrical generator (preferably sinusoidal) as a source of alternating current, at least one amplifier and at least one solenoid, the alternating current inducing the oscillation by the interaction between the at least one magnet and the at least one solenoid.

[0031] According to one embodiment, the at least one movable element may be coupled to at least one magnet. The at least one magnet provides a stable restoring force for the movable element, which helps to improve the stability and reproducibility of the optical delay generated by the device. The device may include at least one second magnet. This second magnet may be attached to the movable element, or to an intermediate point, and / or a connecting element (if used). The at least one electronic assembly may further include at least one second solenoid, preferably coupled to the at least second magnet, at least one second amplifier, at least one signal amplitude analysis circuit and at least one comparator.

[0032] According to another aspect of the invention, an interferometry system is provided comprising at least one device according to the invention. The system according to the invention makes it possible to maintain the amplitude of the oscillation of the device to generate an optical delay in accordance with that expected.

[0033] The interferometry system can correspond to a full-field low-coherence interferometer.

[0034] The interferometry system can correspond to a low coherence interferometer by point mode beam.

[0035] Description of figures and embodiments

[0036] Other advantages and particularities of the invention will appear on reading the detailed description of implementations and embodiments which are in no way limiting, and the following appended drawings:

[0037] [Fig. 1] illustrates a schematic representation of a device for generating an optical delay according to the invention.

[0038] [Fig. 2] illustrates a spring according to one embodiment of the invention.

[0039] [Fig. 3a to 3e] illustrates several embodiments and a schematic representation of the deformation of a spring according to the invention.

[0040] [Fig. 4] illustrates a stress versus position curve on a blade forming part of a spring, the blade having a uniform profile.

[0041] [Fig. 5] illustrates a stress versus position curve on a blade according to the invention, the blade having a modulated profile.

[0042] [Fig. 6] illustrates a schematic representation of an exemplary device according to the invention according to another embodiment. [Fig. 7] illustrates a schematic representation of an exemplary interferometric system comprising the device according to the invention.

[0043] These embodiments being in no way limiting, it will be possible in particular to consider variants of the invention comprising only a selection of characteristics described or illustrated subsequently isolated from the other characteristics described or illustrated (even if this selection is isolated within a sentence comprising these other characteristics), if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection comprises at least one preferably functional characteristic without structural details, and / or with only a part of the structural details if this part only is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0044] We will first describe, with reference to Figure 1, a device D for generating an optical delay according to an embodiment of the invention. The device D comprises a movable element 101 and two springs 200, the two springs 200 being fixed on the movable element 101. In the embodiment of Figure 1, the movable element 101 corresponds to a rod. The movable element 101 may be in one part or several parts depending on the embodiment. The springs 200 correspond to two guide blades L1 and L2 secured to each other by one of their sides, the guide blade L1 being secured by its right lateral side to the guide blade L2 being secured by its left lateral side. The guide blades are generally made of metal for example but can be made of any material sufficiently elastic to withstand the deformation of said guide blades."Elastic" means that the guide blade returns to its nominal position without breaking.

[0045] Figure 2 shows a spring 200 according to one embodiment. The spring 200 has a substantially rectangular shape. The shape and dimensions of the spring 200 described in this embodiment are not limiting. The springs 200 may also have a square, oval or other shape for example. This spring 200 comprises six guide blades, L1.1 to L1.3 on the left, L2.1 to L2.3 on the right in the same plane. Preferably, the blades Lx.y have a non-parallel shape.

[0046] According to the embodiment shown in Figure 2, the guide blades of the spring 200 are positioned so as to form two openings 204 having a general shape of an “8” lying in the spring 200, each blade Lx.y to Lx.y+1 defining two substantially oval openings. Each blade has in its central part a part having a shape close to a double triangle.

[0047] The shape and dimensions of the openings described in the embodiment of Figure 2 are not limiting. The openings 204 defined in the spring 200 make it possible to make the central part where the hole 201 of the spring 200 is located movable, relative to the external parts which receive in their center 203 the fixings to the chassis.

[0048] The spring 200, as shown in Figure 2, therefore comprises fixing holes 201 and 203, the three holes 201, 203 being positioned on the central part of the spring 200 so as to form a line. A fixing hole 202 or intermediate point 202 is positioned on each side of the spring. The hole 201 is configured to receive the movable element 101. The holes 203 make it possible to fix the spring in an interferometry device and more particularly on a chassis. The intermediate points 202 are configured to receive, according to the embodiment, connecting elements.

[0049] The spring 200 then comprises a fixed part and a movable part. During a translation of the movable element 101, the parts comprising the holes 201, 202 are movable. The springs 200 are fixed to the movable element 101 via fixing elements such as the holes previously described.

[0050] In some embodiments, the movable element may comprise connecting elements, making it possible to securely fix the springs 200 on the movable element 101 over a fairly wide portion.

[0051] Figures 3a to 3d illustrate different embodiments of the device D according to the invention. For each of Figures 3a to 3d, only the upper half is shown, the other half is similar, in the lower part of the drawing. The movable element 101 is secured to a magnet 102 in the upper part, to a magnet 103 and mirror 104 in the lower part not shown. An embodiment from two guide blades constituting two springs is presented in Figure 3a, in top view, according to the thickness of the blades and springs, without intermediate point. Two guide blades are connected by one of their side to a fixed part that we will call chassis via the holes 203, and by the other of their side - in the so-called lengthwise direction - to the movable element 101.

[0052] An embodiment from two internal blades and two external blades (constituting two springs) is shown in Figure 3b, with intermediate points 202. In this embodiment, each guide blade comprises an internal blade 200a and an external blade 200b.

[0053] The inner blade 200a is connected to the outer blade 200b by their intermediate points 202. The two inner blades 200a and outer blades 200b are connected by a connecting element 1010 via their intermediate points 202. The two guide blades are connected by one of their sides to a fixed part that we will call the chassis via the holes 203.

[0054] An embodiment from four internal blades and four external blades (constituting four springs of two blades each) is shown in Figure 3c. The guide blades in Figure 3c are identical to Figure 3b, their number has simply been increased.

[0055] The springs in Figure 3d correspond to those in Figure 2, but viewed according to the thickness of the springs.

[0056] According to Figure 3e, the device D forms a mechanical oscillator configured to oscillate at a resonance frequency Fr when the mechanical oscillator undergoes excitation. The mobile element 101 then performs a translational movement along an optical axis. The translation of the mobile element 101 causes the spring(s) 200 of the device D to be stressed. In the case of a spring as shown in Figure 3e, certain blades of the spring 200 initially undergo compression on one half of their face, an extension on the other half, when the mobile element 101 translates in one direction. When the mobile element 101 translates in the opposite direction, the compression and extension zones are exchanged. The spring 200 then deforms according to the translation of the mobile element 101. According to the embodiment of Figure 3d, the device comprises connecting elements 1010.The connecting elements 1010 are positioned between two springs 200 and are fixed to said springs 200 via the holes 202. The connecting elements correspond to rods. The connecting elements 1010 may be made of plastic, for example.

[0057] The stress applied to the spring 200 is defined in Figure 5. The stress corresponds to the deformation of the surface of the blade. In the diagram of Figure 5, the stress value on one of the faces of a blade is represented, as a function of the position on the blade. The sign changes when moving from compression to extension. In terms of design, it is appropriate that the maximum stress, obtained here on each face, and on the lateral edges of the spring 200, remains lower in absolute value than the stress tolerable by the material, to avoid rupture. It can be seen that a spring 200 with modulated width blades has a stress that remains closer to 1 for a longer time compared to the stress of a uniform profile leaf spring as described in Figure 4.

[0058] We will now describe, with reference to figure 6, an example of device D according to another embodiment.

[0059] The device D comprises, in addition to what has been described in figures 1 to 3 for example, a sinusoidal source 301, an amplifier 302, a first solenoid 303 and a second solenoid 304. The mobile device is positioned between the two solenoids 303, 304 to generate a controlled movement. The second solenoid 304 is connected on an output, to a second amplifier 305 followed by a circuit for analyzing the amplitude of the signal 306 developed by the second solenoid 304. The device D also comprises a comparator 308. The comparator 308 is connected to an electronic element 307 distributing at least one setpoint. The comparator 308 is also connected to the amplifier 302.

[0060] Advantageously, two magnets 102, 103 are fixed to the mobile element 101. In addition, in the embodiment described, a mirror 104 is fixed to one of the ends of the mobile element 101.

[0061] In use, the sinusoidal electrical generator 301 supplies energy to the device D and sends an electrical signal. The signal is then amplified by the amplifier 302 which then passes into the first solenoid 303 which counter produces an alternating signal. The alternating signal is excited at a frequency equal to or close to the mechanical resonance frequency Fr of D. The signal is then called the excitation signal Vex. The alternating signal makes it possible to set the mobile element 101 in translational movement via the magnets 102, 103. The mobile element 101 is moved in back and forth movements depending on the alternating signal which deforms the springs 200 as described previously. The movement then creates an alternating signal in the second solenoid 304. This alternating signal received by the second solenoid 304 is amplified via the second amplifier 305.The amplified signal is detected by the amplitude analysis circuit 306 which deduces amplitude information from it. This is called the observation signal Vobs.

[0062] A comparison is made via the comparator 308 with a setpoint equal to a voltage value. The difference between the setpoint value and the value of the signal measured by the amplitude analysis circuit 306 makes it possible to modify the gain of the amplifier 302, in order to maintain the amplitude of the oscillation in accordance with that expected. It is therefore possible to modify the amplitude of the excitation signal Vex as a function of the signal Vobs in order to control the mechanical amplitude of the oscillation of the mobile element 101, by the feedback 310. The setpoint value can be defined beforehand by the user.

[0063] Figure 7 is a schematic representation of an example of an interferometric system that may comprise the device according to the invention.

[0064] The system 6000, shown in Figure 7, is a full-field low-coherence interferometer. The system 6000 is based on a Michelson or Linnik interferometer formed by a splitter element 604, in the form of a cube or a splitter plate, with a measuring arm which directs a measuring beam 606 towards the optical element to be measured 1000, and a device D for generating an optical delay, further comprising a mirror 605 fixed to one end of the movable element to form a reference beam 616.

[0065] The system 6000 is illuminated by a low coherence source 612 via an illumination splitter element 603 in the form of a cube or a splitter plate. The source 612 may comprise, for example, a superluminescent diode (SLD), a diode, a thermal light source (halogen lamp, etc.) or a supercontinuum source. The source 612 may also comprise a filtering device, for example with a grating and a slit, or interference filters, to adjust the coherence length to a few tens or a few hundreds of microns. The source 612 may be arranged to emit in visible or near infrared wavelengths, around one or more wavelengths.

[0066] Of course, the separating elements 603, 604 can be non-polarizing, or polarizing and associated with quarter-wave plates to make lossless couplers.

[0067] The measurement beams 606 and reference beams 616, reflected respectively in the two arms of the device, are directed via the lighting splitter blade 603 towards a camera 601 with a sensor 602 comprising a detection matrix, for example of the CMOS or CCD type.

[0068] When the difference in optical paths between the measurement beams 606 and reference beams 616 is less than the coherence length of the source 612, interference is obtained on the detector 602.

[0069] The system 6000, as shown in Figure 7, also includes a focusing lens or objective 607, and a tube lens 609, arranged to define a conjugate object plane of an image plane formed on the sensor 602. The system 6000 further includes an objective 610 which also defines, with the tube lens 609, a conjugate reference object plane of the image plane of the sensor 602.

[0070] The system 6000 is a full-field imaging device, which makes it possible to image interfaces 703 of the optical element 1000 according to a field of view 708 which is determined by the field of view of the imaging system and by its numerical aperture at the level of the focusing objective 607. Indeed, to obtain a measurement, the specular reflection of the measuring beam 606 on the interfaces 703 must be recoupled into the imaging system.

[0071] Typically, the system 6000 includes optical elements for focusing the illumination beam into the back focal plane of the focusing lens 607 and the lens 610 of the movable element. The illumination beams are not shown in the figure for clarity.

[0072] The system 6000 also includes a device D for generating an optical delay, translating the movable element 101, and thus moving the reference mirror 605.

[0073] The objective 610 of the reference arm may also be adjustable to maintain the reference mirror 605 in an object plane conjugate with the image plane formed by the sensor 602. The system 6000 also comprises a second displacement means 608 whose function is to move the object plane conjugate with the image plane formed by the sensor 602, so as, for example, to sequentially image the successive interfaces 703 on the sensor 602. This displacement means 608 may comprise a system for moving the focusing objective 607 or lenses of this objective, for example with a linear translation device. Alternatively or in addition, this displacement means 608 may comprise a translation device or plate for moving the system 6000 relative to the optical element 1000, or vice versa.

[0074] Figure 8 is a schematic representation of a non-limiting exemplary embodiment of an interferometric device that can be implemented within the framework of the present invention.

[0075] The 4000 interferometer, shown in Figure 8, is a narrow-field, low-coherence, time-domain interferometer.

[0076] The 4000 interferometer can operate, for example, in the infrared.

[0077] The interferometer 4000 operates in point mode, that is to say that it only allows one point 408 to be acquired at a time from a field of view 808 of the surfaces or interfaces of the optical element 1000 to be measured.

[0078] In the embodiment illustrated in Figure 8, the interferometer 4000 comprises a dual Michelson interferometer based on single-mode optical fibers. The dual interferometer is illuminated by a fiber light source 402. The light source 402 may be a superluminescent diode (SLD).

[0079] The light from the source 402 is directed through a fiber coupler 409 and a fiber 406 to a collimator 407, to constitute the point measurement beam 806. A portion of the beam is reflected in the fiber 406 at the collimator 407, for example at the silica-air or glass-air interface constituting the end of the fiber, to constitute a reference wave.

[0080] The retroreflections coming from, for example, the interfaces 803 of the optical element 1000, are coupled into the fiber 406 and directed with the reference wave towards a decoding interferometer built around a fiber coupler 401. This decoding interferometer has an optical correlator function whose two arms are, respectively, a fixed reference 404 and a time delay line 405. The signals reflected at the level of the reference 404 and the delay line 405 are combined, through the coupler 401, on a detector 403 which is a photodiode. The function of the delay line 405 is to introduce an optical delay between the incident and reflected waves, variable over time in a known manner, obtained for example by the movement of a mirror.

[0081] The length of the arms of the decoding interferometer is adjusted so as to allow the differences in optical paths between the reference wave reflected at the collimator 407 and the retroreflections from the interfaces of the optical element 1000 to be reproduced with the delay line 405, in which case an interferogram is obtained at the detector 403 whose shape and width depend on the spectral characteristics of the source 402, and in particular on its optical coherence length.

[0082] Thus, the measurement zone of the interferometer 4000, relative to the collimator 407 or to the interface of the collimator which generates the reference wave, is determined by the difference in optical length between the arms of the decoding interferometer, and by the maximum travel of the delay line 405. This measurement zone corresponds to a coherence zone in which the interface to be measured 803 must be located.

[0083] To obtain geometric information, such as optical shapes, of the interfaces 803, the field of view 808 can be scanned according to a plurality of measurement points 408 at different positions (X, Y).

[0084] Device D can be used in particular in the production of optical elements to make camera modules, for example, for smartphones, digital tablets, computers, web cams.

[0085] The D device can also be used to mass-produce camera modules that can be used in the automotive industry, as driver assistance or to power more autonomous piloting systems, or for taking images or piloting flying systems such as airplanes, drones, and helicopters, for example.

[0086] The device D can also be used to control optical elements used in medicine such as endoscopes, or even camera modules for video surveillance for example. Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention.

Claims

CLAIMS 1. Device for generating an optical delay, the device (D) comprising at least one movable element (101) and at least one spring (200), the at least one spring (200) being fixed to the at least one movable element (101), the at least one spring and the at least one movable element forming a mechanical oscillator configured to oscillate at a resonant frequency, Fr, when the spring undergoes excitation, the movable element (101) being configured to translate at least one mirror along an optical axis during the oscillation.

2. Device according to claim 1, wherein the at least one mirror (104) is fixed to the movable element (101).

3. Device according to any one of claims 1 to 2, in which the at least one spring (200) comprises at least one guide blade.

4. Device according to claim 3, wherein the at least one guide blade comprises at least one internal type guide blade and at least one external type guide blade.

5. Device according to claim 4, in which the at least one internal blade and the at least one external blade are connected by at least one intermediate point.

6. Device according to claim 5, wherein the intermediate points of the at least one inner blade and the at least one outer blade are connected by at least one connecting element (1010).

7. Device according to any one of claims 3 to 6, in which at least one guide blade has a variable width profile.

8. Device according to any one of claims 3 to 7, in which at least two guide blades belong to the same plane.

9. Device according to any one of claims 1 to 8, in which the at least one spring (200) comprises at least two guide blades secured to each other.

10. Device according to any one of claims 3 to 8, in which the at least one guide blade comprises at least one substantially oval opening.

11. Device according to any one of claims 1 to 10, wherein the at least one spring (200) comprises at least one opening having a substantially “8” shape.

12. Device according to any one of claims 1 to 11, wherein the device (D) comprises at least one electronic assembly and at least one magnet coupled to the movable element (101), the at least one electronic assembly comprising at least one electric generator (301) as a source of alternating current, at least one amplifier (302) and at least one solenoid (303), the alternating current inducing the oscillation by the interaction between the at least one magnet and the at least one solenoid.

13. Device according to claim 12, wherein the device comprises at least one second magnet.

14. Device according to any one of claims 12 to 13, wherein the at least one electronic assembly further comprises at least one second solenoid (304), at least one second amplifier (305), at least one signal amplitude analysis circuit (306) and at least one comparator (308).

15. Interferometry system comprising at least one device (D) according to any one of claims 1 to 14.

16. The interferometry system of claim 15, wherein the interferometry system corresponds to a full-field low coherence interferometer (6000).

17. The interferometry system of claim 15, wherein the interferometry system corresponds to a narrow-field low-coherence interferometer (4000).

Images