Patent ID: 12259599

DETAILED DESCRIPTION OF THE INVENTION

FIG.1shows an embodiment of an optical device1according to the present invention that is suitable for use in an ophthalmic (testing) device. Particularly, the optical device1comprises a container2enclosing an internal space3of the container2that is filled with a transparent liquid L. The container2further comprises a transparent bottom21and a transparent and elastically deformable membrane22opposing said bottom21such that the liquid L is arranged between the membrane22and the bottom21.

Furthermore, the optical device1comprises a deformable annular lens shaping element4connected to the membrane22so that the lens shaping element4, particularly a circumferential edge41thereof, defines a central area23of the membrane22so that light can pass through the container2via the central area23and the bottom21, wherein in a non-deformed state the lens shaping element4defines a (virtual) plane, and wherein the optical device1comprises an adjustable spherical power, an adjustable prismatic power and an adjustable cylindrical power, wherein for adapting the cylindrical power of the optical device1, the lens shaping element4is configured to be bent out of said plane P (cf.FIG.2) so that the lens shaping element4defines a (virtual) cylindrical surface.

Particularly, when the lens shaping element4is axially moved (i.e. along the optical axis A), tilted with respect to said optical axis A (or with respect to the bottom21), or bent out of the plane, the curvature of the central area23gets deformed accordingly, which allows to adjust the spherical power (movement of the lens shaping element4along the optical axis A), the prismatic power (tilt of the lens shaping element4) and the cylindrical power (bending of lens shaping element4out of its initial plane P), which gives the area23a cylindrical curvature/component.

Particularly, with no pressure differential across the membrane22of the optical device1, its shape closely resembles the Z1−1Zernike function. In order to achieve a purely cylindrical shape (zero power in the reference axis), the spherical component can be generated by increasing/decreasing the pressure of the liquid L in the container2of the optical device1with respect to the ambient pressure, whereinFIG.3(A) shows Δp=0 andFIG.3(B) shows Δp>0;

Alternatively, as shown inFIG.4, the astigmatic (cylindrical) power can also be controlled by deforming the lens shaping element4in the (initial) membrane plane, e.g. by means of in-plane deformation of the lens shaping element's4aperture into a non-circular shape (like an ellipse/rounded rectangle) as shown inFIGS.4(A) and (B). Here, the ideal shape can be determined by minimizing the deviation from the desired wavefront.

In this case, the astigmatic (Z2−2) and spherical (Z20) power of the lens/optical device1are linked by a fixed relation. (e.g. 0 cylindrical power at 0 spherical power) An additional spherically tunable element would be required to achieve all the necessary degrees of freedom.

Furthermore, as indicated inFIG.1, the bottom21of the container2is connected (e.g. integrally) to a circumferential lateral wall24of the container2, which lateral wall24comprises a face side24ato which a flexible sealing element25can be connected (e.g. glued) that connects the lateral wall24to the lens shaping element4.

In the embodiment shown inFIG.1, the spherical power of the optical device1can be adjusted by moving the lens shaping element4along the optical axis A to increase the pressure in the internal space3of the container2and therewith a spherical curvature of the area23of the membrane22or to decrease the pressure in the internal space3and therewith the spherical curvature of the area23.

Alternatively, or in addition, the pressure in the container2may be adjusted according toFIG.5by pumping liquid L with a pump27from a reservoir28through an inlet26into the internal space3of the container2, or by pumping liquid L from the internal space3into the reservoir28.

FIG.6shows a modification of the embodiment shown inFIG.1, wherein here the lateral wall24forms a separate element with respect to the transparent bottom21that is connected, particularly glued, to the lateral wall24.

Further,FIG.7shows a configuration in which the separate sealing element25shown inFIGS.1,5and6is omitted. Instead, the membrane22connects to the face side24aof the lateral wall24and thus comprises the sealing element as an integral portion.

FIG.8shows yet another embodiment of an optical device1according to the present invention, wherein here the rigid bottom21of the container2shown in the embodiments described above is replaced by a bottom in form of a transparent and elastically deformable further membrane21, that connects to the lateral wall24which in this case forms a rigid further lens shaping element24, which defines a central area29of the further membrane21.

Particularly, in this dual surface embodiment, the further fixed and rigid lens shaping element24preferably comprises the same clear aperture as the deformable lens shaping element4.

Here, particularly, the spherical power (combined effect of both membrane areas23,29), can be dominated by one of the membranes22,21(if stiffnesses differ significantly) and can be controlled by changing the liquid pressure, e.g. by axial movement of one or both lens shaping elements4,24(or by means of a pump27as shown inFIG.5).

Furthermore, prismatic power can be controlled by tilting the lens shaping elements4,24with respect to each other, while the cylindrical power can be controlled by out of plane bending of the deformable lens shaping element4which will be described in more detail below.

Furthermore, according to the embodiment shown inFIG.9, the membrane22can be a shell (e.g. thin member formed e.g. out of a glass, plastic material or polymer and comprising e.g. a thickness in the range from 10 μm to 200 μm) which is characterized in that it can also have significant out of plane forces. This means that a pure cylindrical lens (no power in its reference axis) can be achieved without a pressure differential across the shell22. Further, the spherical power can (almost) exclusively be determined by the shape of further membrane21(given E1>>E2, wherein E1 and E2 corresponds to Young's modulus, respectively).

Now, as demonstrated inFIG.10it has been surprisingly found out, that the cylindrical power can be adjusted by acting on a finite number of selected points S1, . . . of the lens shaping element4. Thus, precise control of the cylindrical power can be achieved with a relatively small number of e.g. linear actuators.

Particularly, as depicted inFIG.10for two different cylinder angles, the desired deformation of the (ring shaped) lens shaping element4(for any cylinder angle) can be achieved by e.g. displacing at least five points, wherein here, as an example six points S1, . . . , S6 are used that are preferably equally spaced on the lens shaping element4along the periphery40of the element4.

Particularly, the displacements for liquid pressure (spherical power) and element tilt (sphere and prism) can be advantageously superimposed. Thus, merely six point displacements along the optical axis A are sufficient for full control of sphere, cylinder and prism.

Particularly, in the different embodiments depicted inFIGS.11to14, the optical device1comprises an actuator system30that is configured to bend the deformable lens shaping element4out of the plane P in order to adjust the cylindrical power using only this rather small number of point displacements.

Particularly, as shown inFIG.11the actuator system30can comprise individual actuators31, wherein each actuator31is configured to displace one of the points S1, . . . , S6 to bend the deformable lens shaping element4out of the plane P in order to adjust the cylindrical power, and particularly also the other powers (sphere and prism).

Particularly, the respective actuator31may comprise a stator32and a mover33that is movable along the optical axis A by means of the actuator31and is coupled via a compliant coupling34to the respective point S1, . . . , S6 of the lens shaping element4. As shown inFIG.11, the respective actuator31can be a linear push-pull actuator31that can displace the respective point S1, . . . , S6 in opposite directions along the optical axis A/vertical axis A.

Alternatively, the respective actuator31can be configured to push against the respective point S1, . . . , S6, wherein a restoring force is provided by an associated spring element5as depicted in the embodiments ofFIGS.12,13and14. Also here, the respective actuator31can be used to also adjust the spherical and/or prismatic power.

Particularly, according toFIG.12, the respective spring element5can be a coil spring5. Further, the respective spring element5can be arranged in the internal space3(i.e. is immersed in the liquid L) and is supported on the bottom21of the container2. Particularly, the lens shaping element4is coupled via a point contact35to the respective mover33and via an opposing point contact35to the respective spring element5.

In contrast toFIG.12, the respective spring element5can also be formed by a leaf spring5which can be supported on the lateral wall24of the container2instead. As shown inFIG.13(A), the respective leaf spring5can extend radially inwards from the lateral wall24and may be mounted to the lateral wall24via a seal36to avoid leakage of the container2(cf.FIG.13(B)).

Furthermore, according toFIG.14, the respective leaf spring5can also be supported on the lateral wall24of the container2outside the internal space3as shown inFIGS.14(A) and14(B) and may extend radially inwards to connect with the lens shaping element4. Particularly, in the embodiment shown inFIG.14, the lens shaping element4and the springs5can be integrally connected to one another and may form a single unit.

FIG.15shows in conjunction withFIGS.16and17yet another embodiment of an actuator300that may be used in conjunction with other actuators of an actuator system or alone to adjust the cylindrical power of the optical device1.

According toFIGS.15to17, this actuator300is a bending (e.g. bimorph) actuator, that comprises an annular passive layer4carranged between a first and second annular active layer4a,4b, wherein said layers4a,4b,4care comprised by the lens shaping element4or may even form the lens shaping element4, and wherein the first active layer4ais configured to anisotropically expand or contract in a first direction D1, and wherein the second active layer4bis configured to anisotropically expand or contract in a second direction D2 being orthogonal to the first direction D1 to bend the lens shaping element4out of said plane P so that the lens shaping element4defines a cylindrical surface parallel to a cylinder reference axis C1 (cf.FIG.15).

Expansion or contraction of the active layers4a,4bmay be achieved as described above (e.g. by means of an electrical field in case the active layers comprise a piezo-electric material)

However, the bimorph actuator300depicted inFIGS.15to17might only allow to tune the cylindrical power of one given reference axis. In that case two such deformable lens shaping elements4,24/actuators300,301are required, whose cylinder reference axes C1, C2 form an angle of 45° as shown inFIG.15.

Such a configuration comprising two actuators300,301is schematically illustrated inFIG.18. Here, the optical device1is configured as described in conjunction withFIG.8, but the further lens shaping element24is now also deformable (like the lens shaping element4), wherein in a non-deformed state the further lens shaping element24defines a further plane P′, wherein for adapting the cylindrical power of the optical device1, the further lens shaping element24, like the lens shaping element4, is configured to be bent out of said further plane P′ so that the further lens shaping element24also defines a cylindrical surface or generates a cylindrical power. In order to achieve a variable reference axis, the two actuators300,301can be rotated with respect to one another by said 45° as shown inFIG.15.

FIG.19shows in conjunction withFIGS.20and21a further embodiment of an actuator302of an optical device1according to the present invention, wherein here the actuator302is a bending (e.g. bimorph) actuator300that comprises an annular passive layer4band an annular active layer4a, wherein said layers4a,4bare comprised by the lens shaping element4or even form the lens shaping element4, and wherein the active layer4acomprises adjacent segments S1, . . . , S12 arranged side by side in a circumferential direction of the active layer4athat are configured to be selectively activated to contract or expand isotropically or anistropically. This allows a variable out-of-plane bending of the lens shaping element4as shown inFIGS.20and21.

Particularly, the active layer4amay comprise twelve segments S1, . . . , S12, wherein each segment comprises a length in the circumferential direction that corresponds to a center angle B of the annular active layer4aof 30°.

Also here, expansion or contraction of the respective segment S1, . . . , S12 may be achieved as described above (e.g. by means of an electrical field in case the segments comprise a piezo-electric material).

Particularly, such an actuator302can be used in any embodiment according to the present invention. Particularly,FIG.22shows an application of such an actuator302, wherein the lens shaping element4that is formed by the actuator300is elastically mounted to a holding structure7(e.g. a fixed base) of the optical device1via an elastic mounting6.

Using this coupling, the container2can be tilted with respect to the optical axis A (e.g. by a suitable further actuator of the actuator system) to adjust the prismatic power of the optical device1. Furthermore, the container2or bottom21can be moved along the optical axis A of the optical device1with respect to the lens shaping element4to adjust the spherical power of the optical device1.

Furthermore,FIG.23shows a further embodiment of the present invention, wherein here, the cylindrical power, and particularly the spherical power, is adjustable by means of individual actuators31, wherein each actuator31comprises e.g. an electromagnet32that moves a magnet33(mover) coupled to the lens shaping element4, so that the latter can be bent out of its initial plane P as described above (e.g. by displacing at least five points, particularly six points, of the lens shaping element4as describe above). In order to tune the prismatic power, the optical device1further comprises a transparent optical element210arranged between the membrane22and the bottom21such that the internal space3of the container2of the optical device1is divided into two separate regions3a,3b, wherein each region3a,3bis filled with the liquid L and wherein the optical device1comprises a flexible first lateral wall240that can be formed by a bellows, and a flexible second lateral wall241, that can also be formed by a bellows, wherein the first lateral wall240connects the lens shaping element4to the optical element1, and wherein the second lateral wall241connects the optical element to the bottom21. Thus, the bottom21can now be tilted by an actuator of the actuator system with respect to the optical element210(e.g. a transparent flat glass or polymer member) in order to adjust the prismatic power of the optical device1, whereas the actuators31can be used to displace the magnets33to adjust the cylindrical power and/or the spherical power of the optical device1.