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WO2018167738A1 - Lentille adaptative rapide pour correction d'aberrations optiques - Google Patents

Lentille adaptative rapide pour correction d'aberrations optiques Download PDF

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Publication number
WO2018167738A1
WO2018167738A1 PCT/IB2018/051817 IB2018051817W WO2018167738A1 WO 2018167738 A1 WO2018167738 A1 WO 2018167738A1 IB 2018051817 W IB2018051817 W IB 2018051817W WO 2018167738 A1 WO2018167738 A1 WO 2018167738A1
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WO
WIPO (PCT)
Prior art keywords
flexible glass
lens structure
adaptive lens
membrane
structure according
Prior art date
Application number
PCT/IB2018/051817
Other languages
English (en)
Inventor
Stefano Bonora
Martino QUINTAVALLA
Original Assignee
Dynamic Optics S.R.L.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dynamic Optics S.R.L. filed Critical Dynamic Optics S.R.L.
Publication of WO2018167738A1 publication Critical patent/WO2018167738A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/12—Fluid-filled or evacuated lenses
    • G02B3/14—Fluid-filled or evacuated lenses of variable focal length
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/004—Optical devices or arrangements for the control of light using movable or deformable optical elements based on a displacement or a deformation of a fluid

Definitions

  • the present invention relates to the field of adaptive optics.
  • a first class of tunable lens devices is determined by adaptive lenses with a liquid chamber of constant volume.
  • the constant volume of the liquid chamber is exploited to transfer a force from a few actuators to the optical surfaces in the clear aperture .
  • the fluidic lens is based on a pressure induced liquid redistribution within a lens cell.
  • the lens has an upper aperture that is sealed with a thin elastic outer membrane and a bottom aperture sealed with an inner membrane. Applying an inward pressure to the outer membrane causes the liquid to redistribute and swell the inner membrane outwards which, in turn, forms a plano ⁇ convex lens.
  • ADAPTIVE FLUIDIC PDMS-LENS WITH INTEGRATED PIEZOELECTRIC ACTUATOR F. Schneider, et al . MEMS 2008, Arlington, AZ, USA, January 13-17, 2008.
  • the actuation is allowed by the use of soft elastic membranes (e.g., PDMS or other polymers), whose drawback is the low initial surface quality of the adaptive lens in terms of optical aberrations due to the manufacturing process or problems related to the bonding of soft membranes.
  • the orientation of the lens (vertical or horizontal) has an effect on the shape of the membrane since the force exerted by the gravity on the filling material generates an asymmetrical shape of the lens surface that creates aberrations and degrades the optical quality of the fluidic lens. Because of this effect, the lens size cannot be larger than about 10mm.
  • US patent application 2010/0208357 Al proposes the use [0008] of thin glasses instead of polymeric membranes to solve this problem.
  • the lens shape, and hence the optical power is tuned by varying the pressure in the chamber and transferring a force from the liquid to the glasses.
  • actuation principles are many and include, for example: piezoelectric, electromagnetic or bimetallic-based actuation.
  • all these publications demonstrate how to generate only spherical or parabolic wavefronts. This means that these adaptive lenses can only be used to change the focal length of an optical system, such as in optical zoom or autofocusing systems.
  • WO 2015/114515 describes another type of fluidic adaptive lens realized with rigid windows and piezoelectric actuators.
  • this publication shows how to generate arbitrary wavefronts and not only defocus.
  • An embodiment of this invention uses bimorph actuators, such as the ones used for deformable mirrors and extensively described in many publications [R. Tyson, Adaptive Optics Engineering Handbook, Tyson, R. (ed) , CRC Press, 1999] .
  • WO 2015/114515 relies on the use of a spacer that includes a mix of a rigid ring and a soft elastomer.
  • This solution has the advantage of being able to generate arbitrary optical aberrations but with the disadvantage of having a slow response time.
  • the reason for a slow response time is the use of thick spacers that limit the volume change of the liquid chamber, due to the expansion/contraction of the actuators when they are activated.
  • This publication also includes an embodiment with a reservoir in order to be compliant with volume changes. In this solution, the connection between the liquid chamber and the reservoir generates a fluidic impedance that limits the response time of the device.
  • WO 2015/114515 also discloses the use of a glass disc to stiffen the central part of the optical aperture to create a higher degree of spatial modulation of the wavefront shapes.
  • This solution has the disadvantage of creating wavefront distortions by the difference of the refractive index of the stiffening glass disc with respect to the one of the liquid. Although this difference might be reduced by the use of a refractive index matching liquid with the same refractive index and dispersion (change of the refractive index with wavelength) of the glass, the residual errors always have an influence on the transmitted beam.
  • liquid lens When the liquid lens is used in optical systems (such as for example a microscope) this effect can reduce the resolution of the acquired images.
  • the layer of transparent glue used to bond the stiffening disc to the liquid lens aperture creates an additional optical layer that again, can induce a refractive index mismatch or light interference effects, especially if used with coherent light sources such as lasers.
  • This layer also introduces the problem of a reduced damage threshold when the lens is used with laser beams.
  • This invention aims to overcome the limitations of the prior art solutions in the realization of adaptive lenses .
  • an object of the present invention is to provide an adaptive lens which allows to generate arbitrary wavefronts with a high spatial frequency, and having at the same time a fast response time.
  • Another object of the invention is to provide an adaptive lens having an excellent optical quality and an easy manufacturing process, that is suitable for being used in different optical spectral ranges and/or large optical bandwidths .
  • Still another object of the invention is to provide an adaptive lens having a larger damage threshold when used with high energy or high power laser sources.
  • Figure 1 is a schematic view of an adaptive lens structure according to the invention, in one embodiment
  • Figure 2 is a schematic view of an adaptive lens structure according to the invention, in another embodiment ;
  • Figure 3 is a cross section of the lens structure of figure 2, along section plane A-A of figure 2;
  • Figure 4 is diagram showing the response time of the lens structure according to the invention (solid line), compared to the one achievable with prior art lens designs (dashed line) ;
  • Figure 5 is a schematic view of an adaptive lens structure according to the invention, in another embodiment
  • Figure 6 is a plan top view of the lens structure of Figure 5;
  • Figure 7 is a schematic view of an adaptive lens structure according to the invention, in another embodiment.
  • Figure 7a is a modification of the embodiment of figure 7;
  • Figure 8 shows one of the flexible glass membranes of the lens structure, according to another embodiment
  • Figure 9 shows the flexible membrane of Figure 8 when deformed
  • Figure 10 shows one of the flexible glass membranes of the lens structure, according to another embodiment, in the deformed state
  • Figure 11 is a schematic representation of the effect on the light beam of ad adaptive lens structure employing the flexible glass membranes of figures 8 and 9;
  • Figure 12 is a schematic representation of the effect on the light beam of ad adaptive lens structure employing the flexible glass membranes of figure 10; and [0037] Figures 13 and 14 are schematic views of an adaptive lens structure according to the invention, in a still different embodiment, in the inactive and deformed state, respectively.
  • “Flexural rigidity” is defined as the bending moment necessary to bend a structure and depends both on the mechanical properties (modulus of elasticity, Poisson ratio) and the geometry of the considered structure;
  • Glass membrane is defined as a glass or polymeric window with a low flexural rigidity obtained using a material with a high elastic modulus and a large aspect ratio (lateral size to thickness ratio) .
  • a glass membrane shows a high flexibility while still being self- standing.
  • This definition extends to materials transparent to a specific spectral range: glass is a favorite material for UV, visible and near infrared light beams, semiconductors for infrared (for example Germanium) or other crystals and polymers. Typical aspect ratio for this application is between 10 and 1000;
  • Elastomeric layer is a polymeric or rubber-made structure whose flexural rigidity is high enough to avoid gravitational force effects, and therefore is self- standing. Characteristic of this material is the medium/high aspect ratio and low young modulus. For thin layers, typical aspect ratio for this structure is between 1 and 100;
  • Soft membrane is a structure with a low flexural rigidity that is not self-standing. Characteristic of this material is the high aspect ratio and low young modulus and high strain at the yield point (stress at which a material begins to deform plastically) . Typical aspect ratio for this application is between 1 and 1000;
  • Deformable Solid is an elastomeric or gel material with a low modulus, high strain at the yield point .
  • the adaptive lens structure has an optical axis X along which, in the use of said lens structure, a light beam L is transmitted.
  • the adaptive lens structure comprises a first and a second spaced apart flexible glass membranes 101, 115.
  • the first flexible glass membrane has a first outer surface 101a and a first inner surface 101b, opposite said first outer surface.
  • the first flexible glass membrane has a first central portion 101' transparent to the light beam L, which defines one side of the optical aperture of the lens structure.
  • the second flexible glass membrane 115 has a second inner surface 115a, facing said first inner surface 101b, and a second outer surface 115b, opposite to second inner surface 115a.
  • the second flexible glass membrane 115 has a second central portion 115' transparent to light beam L, which defines the other side of the optical aperture of the lens structure.
  • the first and second central portions 101', 115' have the same size and shape; in other embodiments, these central portions 101', 115' can be different in both size and shape. In these cases, the central portion having the smallest cross section defines the cross section of the optical aperture of the lens.
  • First actuator means 105 are placed on a peripheral portion of the first flexible glass membrane 101; second actuator means 110 are placed on a peripheral portion of the second flexible glass membrane 115.
  • the first actuator means 105 are placed on the first outer surface 101a
  • the second actuator means 110 are placed on the second outer surface 115b.
  • the actuator means 105, 110 are suitable for deforming the optical aperture shape reversibly and accordingly to a command signal or a series of command signals.
  • the command signal is an electric signal; however, the command signal can be of a different nature, such as pneumatic, mechanical, optical, chemical, electromagnetic, electrostatic or a combination thereof.
  • the actuators means can be piezoelectric, piezoelectric multi-layer, piezoelectric benders, piezoelectric bimorph, electromagnetic, piezoelectric stack, magnetostrictive or bimetallic strip or others.
  • These actuator means can be of any shape, such as annular, square, rectangular or linear.
  • the actuators means 105, 110 are divided in independent sectors.
  • the shape of the actuator means 105, 110 matches the shape of the incoming light beam portion to be modulated.
  • the shape of the actuator means
  • each flexible glass membrane has a flexural rigidity such that a sufficient deformation can be induced by the force exerted by the actuator means 105, 110 when the latter are activated but, at the same time, the effect of other forces, such as vibrations or gravity, are negligible as regards the optical quality.
  • This property is achieved by tuning the glass membrane flexural rigidity by means of a proper choice of the material elasticity modulus and geometry.
  • Typical flexural rigidity for this application is between 0.005 and 1 Nm.
  • the lens structure comprises a soft membrane 120; 125 to seal the space between the flexible glass membranes 101, 115 so as to form a sealed chamber 200 suitable for receiving a filling liquid.
  • the space or volume defined by the sealed chamber 200 substantially corresponds to the optical aperture of the lens structure.
  • the soft membrane 120; 125 extends between the facing edges of the transparent central portions 101', 115' of the flexible glass membranes 101, 115.
  • This soft membrane 120; 125 can expand when the actuator means are activated, in order to take account for the volume changes of the sealed chamber 200.
  • Figure 1 shows an example of realization of the soft membrane 120 in the form of a soft membrane bellow.
  • the soft membrane 125 is provided with stiffening ribs 130 made of elastomeric layers to support the flexible glass membranes .
  • a soft membrane 120; 125 allows shortening the response time of the adaptive lens as compared to other solutions including elastomeric rings and/or rigid spacers.
  • An example of a measured reduction of the rise time is illustrated in the diagram of figure 4, that compares the displacement of the actuator means as a function of time in case of a fluidic lens with sealed chamber according to the prior art (dashed line) and in case of the adaptive lens according to the invention (solid line) .
  • the adaptive lens structure comprises a rigid frame 140 connecting the flexible glass membranes 101, 115.
  • a plurality of passing-trough apertures 140' are formed in the rigid frame 140.
  • Each of these apertures 140' is sealed by a soft membrane 125.
  • the soft membranes 125 allow the expansion and contraction of the sealed chamber 200.
  • sealed chamber 200 is delimited by the two flexible glass membranes 101, 115, the rigid frame 140 and the soft membranes 125.
  • the radial extension of the second flexible glass membrane 115 is larger than the radial extension of the first flexible glass membrane 101. Furthermore, in this embodiment, the central portion 115' of the second flexible glass membrane 115 is larger than the central portion 101' of the first flexible glass membrane 101.
  • the rigid frame 140 comprises a peripheral portion 140" having a radial component extending parallel to the flexible glass membrane 101, 115.
  • the passing-trough apertures 140' are formed in this peripheral portion 140".
  • the different cross section of the central portions 101', 115' allow the two sides of the adaptive lens to generate deformations with a different spatial distribution.
  • actuator means 105 coupled to the first flexible glass membrane 101 may generate a different light wavefront shape than the actuator means 110 coupled to the second flexible glass membrane 115.
  • dashed line 155 shows an example of deformation of the first flexible glass membrane when the first actuator means 105 is activated.
  • the resulting wavefront in the optical aperture is indicated with dashed line 165.
  • dashed line 160 shows an example of deformation of the second glass membrane 115 when the second actuator means 110 are activated.
  • the resulting wavefront in the optical aperture is indicated with dashed line 170.
  • the difference in the generated wavefront shapes can be exploited to create arbitrary wavefronts by combined activation of the actuator means, such as defocus, astigmatism, coma, trefoil, spherical aberration etc.
  • the space between the flexible glass membranes 101, 115 is completely or partially filled with a transparent deformable solid 300, for example an elastomer or a gel.
  • the deformable solid 300 absorbs the flexible glass membranes deformations and acts as the element that connects the flexible glass membranes 101, 115.
  • the filling material has a linear response and therefore the response time is faster than in previous cases where the filling liquids have a viscous response to the flexible glass membrane deformation that causes an energy loss that is proportional to the actuation response time.
  • a further advantage of this embodiment is that the deformable solid 300 is strong enough to support both the flexible glass membranes 101, 115 and therefore there is no need of further spacing or supporting elements, allowing an easier manufacturing process.
  • Figure 7 shows an embodiment where the deformable solid 300 extends only to fill the space of the optical aperture between the two glass membranes 101, 115 and their respective actuator means 105, 110.
  • Figure 7a shows another embodiment where the deformable solid 300 extends over the entire size of the adaptive lens.
  • Other embodiments - not illustrated in the drawings - can include different thickness of the deformable solid, for example having a transparent portion in the optical aperture and opaque or colored outside.
  • Other possible embodiments can include mix of different elastomers.
  • lens structure according to the embodiments of Figure 1, 2 and 5 can also be realized by using such a deformable solid material in the place of the liquid.
  • the actuator means 105, 110 are placed on both sides of each of the flexible glass membrane 101, 115.
  • the difference in the expansion of the actuator means and of the flexible glass membranes is symmetric and is cancelled out.
  • the adaptive lenses shown in previous embodiments can undergo strong unwanted bending because of different CTE of the glass membrane and the piezo actuator. This might be a limitation in industrial and outdoor applications where the environmental conditions are not under control.
  • Figure 8 shows a portion of a further embodiment of the adaptive lens comprising a flexible glass membrane 101 with actuator means 105.
  • the flexible glass membrane 101 is provided with an annular portion 180 of reduced thickness within the transparent central portion 101'.
  • This annular portion 180 offers a lower flexural rigidity and can therefore generate a localized curvature, as shown in Figure 9.
  • the reduced thickness portion width can be very thin with respect to the transparent central portion 101', having therefore a negligible effect on the transmitted beam wavefront and intensity distribution.
  • preferred values for reduced thickness portion are lOOum wide and 50um thick.
  • Figure 10 shows another possible embodiment where a different curvature of the transparent central portion 101' is induced by reducing the glass membrane thickness in a sub-portion 101" of the transparent central portion 101' .
  • Figures 11 and 12 illustrate the effect of the annular portions 180 of reduced thickness and of sub- portions 101", 115" of reduced thickness, respectively, on the wavefront of the light beam L. In these examples, the annular portions 180 and the sub-portions 101", 115" have different diameters.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Light Control Or Optical Switches (AREA)

Abstract

Selon l'invention, une structure de lentille adaptative comprend une première et une deuxième membrane en verre souples espacées (101, 115), formant des côtés opposés de l'ouverture optique de la lentille adaptative, et au moins une membrane souple (120 ; 125) s'étendant entre les membranes en verre souples (101, 115) de manière à sceller un espace entre les membranes en verre souples (101, 115) pour former une chambre étanche (200) adaptée à la réception d'un liquide de remplissage. La membrane souple est conçue pour se dilater élastiquement afin de prendre en compte des changements de volume de la chambre étanche (200).
PCT/IB2018/051817 2017-03-17 2018-03-19 Lentille adaptative rapide pour correction d'aberrations optiques WO2018167738A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT102017000029980A IT201700029980A1 (it) 2017-03-17 2017-03-17 Fast adaptive lens for the correction of optical aberrations
IT102017000029980 2017-03-17

Publications (1)

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WO2018167738A1 true WO2018167738A1 (fr) 2018-09-20

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11693159B2 (en) * 2017-06-30 2023-07-04 Polight Asa Adaptive lens

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070030573A1 (en) 2005-05-14 2007-02-08 Holochip Corporation Fluidic optical devices
US20100208357A1 (en) 2005-05-14 2010-08-19 Holochip Corporation Fluidic lens with reduced optical aberration
US20130176628A1 (en) * 2010-02-16 2013-07-11 Holochip Corporation Adaptive optical devices with controllable focal power and aspheric shape
EP2860555A1 (fr) * 2013-10-08 2015-04-15 Optotune AG Lentille réglable
WO2015114515A1 (fr) 2014-01-28 2015-08-06 Adaptica S.R.L. Structure de lentille déformable pour des dispositifs d'optique adaptative

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070030573A1 (en) 2005-05-14 2007-02-08 Holochip Corporation Fluidic optical devices
US20100208357A1 (en) 2005-05-14 2010-08-19 Holochip Corporation Fluidic lens with reduced optical aberration
US20130176628A1 (en) * 2010-02-16 2013-07-11 Holochip Corporation Adaptive optical devices with controllable focal power and aspheric shape
EP2860555A1 (fr) * 2013-10-08 2015-04-15 Optotune AG Lentille réglable
WO2015114515A1 (fr) 2014-01-28 2015-08-06 Adaptica S.R.L. Structure de lentille déformable pour des dispositifs d'optique adaptative

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
F. SCHNEIDER; TUCSON, AZ ET AL.: "ADAPTIVE FLUIDIC PDMS-LENS WITH INTEGRATED PIEZOELECTRIC ACTUATOR", MEMS 2008, 13 January 2008 (2008-01-13)
H. REN ET AL.: "Variable-focus liquid lens", OPTICS EXPRESS, vol. 15, no. 10, 14 May 2007 (2007-05-14), pages 5931 - 5936, XP002532100, DOI: doi:10.1364/OE.15.005931
R. TYSON: "Adaptive Optics Engineering Handbook", 1999, CRC PRESS

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11693159B2 (en) * 2017-06-30 2023-07-04 Polight Asa Adaptive lens

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