AN OPTICAL SYSTEM COMPRISING A LENS WITH AN ADJUSTABLE FOCAL LENGTH

Abstract

The invention relates to an optical system (1) comprising a solid lens barrel (2) for optical elements (3), wherein the lens barrel (2) extends along an optical axis (100) of the optical system (100), the lens barrel (2) holding a plurality of optical elements (3), the plurality comprising a lens system (5), comprising at least one solid lens (53), and a first lens (6) having an adjustable focal length, wherein the first lens (6) comprises a container (62) filled with a transparent fluid, wherein the container (62) comprises an elastically deformable and transparent membrane (61) facing a transparent bottom portion (67) of the container (62), wherein the lens barrel (2) has a first and a second opening (22, 22′) facing along the optical axis (100), wherein the first and/or the second opening (22, 22′) is configured to receive the lens system (5), wherein the lens barrel (2) has a first slot (24) extending perpendicular to the optical axis (100), wherein the first lens (6) is inserted through the first slot (24) perpendicular the optical axis (100) into the lens barrel (2). The invention further relates to method of assembly of such an optical system (1).

Claims

1. An optical system comprising a solid lens barrel for optical elements, wherein the lens barrel extends along an optical axis of the optical system, wherein the lens barrel holds a plurality of optical elements, the plurality comprising: a) a lens system, comprising at least one solid lens, b) a first lens having an adjustable focal length, wherein the first lens comprises a container filled with a transparent fluid, wherein the container comprises an elastically deformable and transparent membrane facing a transparent bottom portion of the container, wherein the lens barrel has a first and a second opening facing along the optical axis, wherein the first and/or the second opening is configured to receive the lens system, wherein the lens barrel has a first slot extending perpendicular to the optical axis, wherein the first lens is inserted through the first slot perpendicular the optical axis into the lens barre.

2. The optical system according to claim 1, wherein the optical system comprises a second lens having an adjustable focal length, wherein the second lens comprises a container filled with a transparent fluid, wherein the container comprises an elastically deformable and transparent membrane facing a transparent bottom portion of the container, wherein the lens barrel has a second slot extending perpendicular to the optical axis, wherein the second lens is inserted through the second slot in the lens barrel.

3. The optical system according to claim 1, wherein for adjusting the focal length of the first and/or the second lens, the membrane of the first and/or the second lens is connected to a circumferential rigid lens shaping element of the first and/or second lens for defining an area of the membrane having an adjustable membrane curvature.

4. The optical system according to claim 1, wherein the container of the first and/or the second lens encloses a lens volume filled with the fluid and a reservoir volume filled with the fluid, wherein the reservoir volume is connected, particularly fluidically connected to the lens volume, wherein the container of the first and/or the second lens comprises an elastically deformable wall member adjacent the reservoir volume of the container of the first and/or the second lens.

5. The optical system according to claim 4, wherein the elastically deformable wall member of the container of the first and/or the second lens is formed by the membrane of the first and/or the second lens.

6. The optical system according to claim 4, wherein the reservoir volume of the container of the first and/or the second lens is arranged laterally next to the lens volume of the container of the first and/or the second lens in a direction perpendicular to the optical axis of the first and/or the second lens.

7. (canceled)

8. The optical system according to claim 4, wherein the first and/or the second lens comprises a rigid pusher plate arranged on the elastically deformable wall member, particularly on a side of the wall member that faces outwards the container, wherein the pusher plate is configured to receive an external force moving the pusher plate inwards or outwards the reservoir volume so as to shrink or increase the reservoir volume and thus to increase or shrink the lens volume accordingly by means of deforming the membrane thereby adjusting the focal length of the first and/or the second lens.

9. The optical system according to claim 4, wherein the membrane of the first and/or the second lens inserted in the first and/or second slot is enclosed by the lens barrel, wherein a container portion comprising the reservoir volume and the deformable wall member protrudes from the lens barrel 2 such that the deformable wall member, particularly the pusher plate is accessible from an outside of the lens barrel, allowing to control the focal length of the first and/or the second lens with an external lens actuator.

10. The optical system according to claim ,1 wherein the lens system comprises at least one optical element stack with a plurality of stacked optical elements, arranged along and on the optical axis in the lens barrel.

11.-20. (canceled)

21. The optical system according to claim 10, wherein the optical system comprises an image sensor arranged at the lens barrel, wherein the lens barrel comprises two optical element stacks, a first optical element stack and a second optical element stack, with stacked optical elements, wherein the first lens with an adjustable focal length is arranged at a first predefined distance from the image sensor, wherein the second lens with an adjustable focal length is arranged at a second predefined distance from the image sensor, wherein the first optical element stack is arranged on the optical axis between the first lens and the image sensor, wherein the second optical element stack is arranged between the first and the second lens on the optical axis of the lens barrel, particularly such that the optical system forms an optical zoom system, particularly wherein the zoom is adjustable by means of the adjustable focal lengths of the first and the second lens.

22. The optical system according to claim 21, wherein the second predefined distance is twice as large as the first predefined distance.

23. The optical system according to claim 1, wherein a fold mirror or fold prism is arranged at the lens barrel.

24. The optical system according to claim 23, wherein the fold mirror is a tiltable mirror configured to provide particularly closed-loop optical stabilization to the optical system.

25. (canceled)

26. The optical system according to claim 1, wherein the lens barrel comprises transverse openings for the insertion of an alignment tool or an adhesive for fixing the optical elements in the lens barrel.

27. The optical system according to claim 1, wherein the first and/or the second slot has a hard stop portion for the first and/or the second lens for adjoining the first and/or the second lens to said hard stop portion in a predefined position.

28. (canceled)

29. The optical system according to claim 1, wherein the first lens comprises a lens actuator that is configured to act on the elastically deformable first wall member of the container of the first lens to pump fluid from the reservoir volume of the first lens into the lens volume of the first lens or from the lens volume of the first lens into the reservoir volume of the first lens so as to change the curvature of the membrane of the first lens and therewith the focal length of the first lens, and/or wherein the second lens comprises a lens actuator that is configured to act on the elastically deformable second wall member of the container of the second lens to pump fluid from the reservoir volume of the second lens into the lens volume of the second lens or from the lens volume of the second lens into the reservoir volume of the second lens so as to change the curvature of the membrane of the second lens and therewith the focal length of the second lens.

30.-32. (canceled)

33. The optical system according to claim 1, wherein the lens barrel has openings in its barrel wall that are covered with a fabric for protecting the optical system from dust and environmental influences.

34. The optical system according to claim 1, wherein the lens barrel comprises guiding notches for receiving the actuator of the first and/or the second lens, wherein the actuator has corresponding guiding protrusions, wherein the guiding notches allow an axial movement of the actuator adjoining the lens barrel along the lens barrel so as to adjoin the actuator with the deformable wall member of the first and/or second lens.

35. (canceled)

36. A method for assembling the optical system according to claim 1, comprising the steps of: f) Inserting the lens system in the lens barrel through the first and/or second opening of the lens barrel, g) Inserting the first lens in the first slot, h) Adjoining the actuator for the first lens to the first lens and the lens barrel, i) Attaching the folding mirror to the lens barrel, j) Attaching the image sensor to the lens barrel.

37. The method for assembling the optical system according to claim 36, wherein the lens system comprises the first and the second optical element stack, wherein in a first step of inserting the lens system, the first optical element stack is inserted in the lens barrel through the first opening of the lens barrel, and in a second step of inserting the lens system, the second optical element stack is inserted in the lens barrel through the second opening of the lens barrel.

38. (canceled)

Description

[0154] In the following, further features as well as embodiments of the present invention are described with reference to the Figures that are appended to the claims, wherein:

[0155] FIG. 1 shows an exploded schematic view of an optical zoom system according to the invention;

[0156] FIG. 2 shows the insertion process of the first and second lens into the first and second slot;

[0157] FIG. 3 shows a schematic exploded cross-section through an optical element stack with contact portions having inclined contact surfaces;

[0158] FIG. 4A+B shows a schematic cross-section through an optical element stack with contact portions having inclined contact surfaces and glue pockets formed by the adjoining contact portions;

[0159] FIG. 5 shows a schematic cross-section through an optical element stack with contact portions having inclined contact surfaces and one contact surface being perpendicular to the optical axis;

[0160] FIG. 6 shows three azimuthally flat portions of the lens barrel;

[0161] FIG. 7 shows a schematic cross-section through an assembled optical element stack with an aperture element attached to a solid lens;

[0162] FIG. 8 shows a schematic cross-section through an optical zoom system having equidistantly arranged first and second lenses;

[0163] FIG. 9 shows a schematic cut through the lens barrel having gluing holes for assembly;

[0164] FIG. 10 shows the assembly process of the actuators to the optical system;

[0165] FIG. 11 shows mating pins for the fold mirror and the assembly process to the lens barrel; and

[0166] FIG. 12 shows a schematic cross-section of the optical system comprising a clamping device.

[0167] FIG. 1 shows a schematic exploded cross-section of an exemplary embodiment of the optical system 1 according to the invention. The optical system 1 comprises the lens barrel 2 extending along the optical axis 100 of the optical system 1. The lens system 5 to be inserted into the lens barrel 2 is composed of two distinct optical element stacks 51, 52, a first optical element stack 51 and second optical element stack 52, wherein each of the two stacks 51, 52 comprises a plurality of solid lenses 53 and spacers 54. The first optical element stack 51 is to be inserted into the barrel 2 through the first opening 22 of the barrel 2, wherein the second optical element stack 52 is to be inserted through a second opening 22′ of the lens barrel 2. The first opening 22 of the lens barrel 2 is located on the side facing the incident light coming from a folded mirror 4, wherein the second opening 22′ of the lens barrel 2 is located opposite the first opening 22, namely on the side facing an image sensor 9 of the optical system 1.

[0168] In the assembled state of the optical system 1 the fold mirror 4 is attached to the lens barrel 2 and also the image sensor 9 is attached to the lens barrel 2 for example by means of an adhesive.

[0169] The lens barrel 2 comprises a first slot 24 (see e.g. FIG. 2) and a second slot 25 (see e.g. FIG. 2) for receiving a first tunable lens 6 and a second tunable lens 7.

[0170] The first tunable lens 6, also referred to as the first lens 6 in the context of the current specification, has an adjustable focal length. Also the second tunable lens 7 has an adjustable focal length.

[0171] The first and the second lens 6, 7 each have a container 62, 72 enclosing a reservoir with a transparent fluid.

[0172] The reservoir is covered at a lens volume of the container 62, 72 with an elastically deformable membrane 61, 71 that acts as the adjustable lens surface.

[0173] Opposite the membrane 61, 71 the container 62, 72 comprise a transparent bottom portion 67, 77. In this example the bottom portion 67, 77 is a rigid bottom portion.

[0174] The first and the second lens 6, 7 each comprise an optical axis that extends perpendicularly through the membrane 61, 71.

[0175] The container 62, 72 of the first 6 and the second lens 7 extends laterally from the optical axis 100 of the first and second lens 6, 7 to one side. The container 62, 72 comprises a reservoir volume (not shown) that is arranged laterally shifted with respect to the lens volume (not shown) under the membrane 61, 71. The reservoir volume and the lens volume of the first and/or second lens 6, 7 are either directly fluidically connected or connected in a communicating manner, e.g. by means of a third membrane separating the reservoir volume from the lens volume.

[0176] The reservoir volume is covered with a deformable wall portion 63, 73, wherein in this example the wall member 63, 73 is formed by the elastically deformable membrane 61, 71.

[0177] The membrane 61, 71 is connected with a lens shaping device surrounding the membrane 61, 71 in a circular fashion, enabling the membrane 61, 71 to bulge or bend symmetrically around the optical axis 100.

[0178] The deformable wall portion 63, 73 is connected to the container walls 66, 76. The deformable wall portion 63, 73 is located on the same side as the membrane 61, 71. On the deformable wall member 63, 73 a pusher plate (not shown) is arranged, configured to be moved by an actuator piston (not shown). The pusher plate can be glued to the deformable wall member.

[0179] When the actuator piston pushes the pusher plate towards the reservoir volume, said volume shrinks as the deformable wall member 63, 73 bulges towards the reservoir volume. Accordingly, the membrane 61, 71 experiences a force driving the membrane 61, 71 outwards the lens volume, thereby adjusting the focal length of the first and/or second lens 6, 7.

[0180] In the assembled state or during assembly, the first lens 6 and the second lens 7 are inserted to the lens barrel 2 through the laterally arranged slots 24, 25 of the lens barrel 2 (e.g. cf. FIG. 2). This allows an independent and rapid assembly of first and second lens 6, 7, the optical element stacks 51, 52, the image sensor 9 and the fold mirror 4.

[0181] The lens barrel 2 provides protection against dust, humidity and light as well as other environmental influences. The lens barrel 2 is formed as a housing and configured to hold and fix the optical elements 3 in the optical system 1. The lens barrel 2 is a stiff and rigid component of the optical system 1 in order to provide stability to the assembled optical elements 3.

[0182] Due to the laterally shifted reservoir volume of the containers 62, 72 of the first and the second lens 6, 7, the actuators 68, 78 are arranged outside the lens barrel 2. This layout provides improved heat decoupling between the optically active region of the first and the second lens 6, 7, i.e. the membrane 61, 71, the lens volume and the transparent bottom portion 67, 77. Heat generated by the respective actuator 68, 78 can be dissipated more efficiently outside the lens barrel 2 and does not couple directly to the optical active region of the first and/or second lens 6, 7.

[0183] The improved thermal isolation of the optical active region of the first and second lens 6, 7 due to the specific layout of the container 62, 72 allows for more compact and robust optical systems.

[0184] The fold mirror 4 of the optical system 1 is an actuated fold mirror for optical image stabilization.

[0185] As can be seen in FIG. 2, the first and the second lens 6, 7 are inserted in the first and second slot 24, 25 without the actuators 68, 78, which allows a simplified assembly.

[0186] During assembly the optical axis 100 of the system 1 is particularly oriented along the gravity vector, minimizing gravity sag, leaving the optical system 1 closer to its nominal performances.

[0187] The final alignment of the first and second lens 6, 7 as well as the lens system 5 can be done by means of a laser or an optocentric device and a multi-axis stage system.

[0188] The first and the second lens 6, 7 are glued with an adhesive to the lens barrel 2. The slots 24 25 for the first and the second lens 6, 7 have dedicated glue pockets and interfaces 26 to which the first and the second lens 6, 7 are brought to stop and glued together.

[0189] The lens barrel 2 can be made from plastics or a metal, for example by means of injection molding, machining e.g. EDM, additive manufacturing or the like.

[0190] FIG. 3 shows an exploded view of an optical element stack 51, 52 comprising a plurality of solid lenses 53. Each lens 53 comprises an integrally formed rim portion 55 with at least one contact portion 56 for adjoining the lenses 53. The two solid lenses 53 on the left and right side of the stack each comprise one contact portion 56 having a contact surface 57 inclined towards the optical axis 100 and towards the lens 53 arranged in the middle. The middle lens comprises two contact portions 56 and two contact surfaces 57. The contact surfaces 57 are inclined towards the optical axis 100 such that they form complementary surfaces 57 to the contact surfaces 57 of the left and right lens 53. Thus, in the assembled state of the three lenses 53 the lenses 53 adjoin at the contact surfaces 57 and are glued together with the contact surfaces 57. Due to the conically inclined contact surfaces 57 the three lenses 53 self-center, when they are brought in contact at the contact portions 56. The assembly can for example be facilitated by stacking the lenses 53 vertically on a vibrating shaker device such that the lenses 53 automatically align.

[0191] The flat region 28 of the rim portion 55 facing outwards the optical axis 100 and towards the lens barrel 2 can be used to fix the stacked lenses 53 to the lens barrel 2, e.g. by means of an adhesive.

[0192] FIG. 4A shows an optical element stack 51, 52 in the assembled state, wherein the stack 51, 52 comprises not only lenses 53 but also spacer elements 54. FIG. 4B shows the stack in an exploded drawing. All optical elements 53, 54 of the stack have adjoining and complementary contact surfaces 57 at their rim portion 55 for self-aligning the optical element 53, 54 with respect to the other optical elements 53, 54 of the stack.

[0193] As can be seen, the contact portions 56 of two adjoining optical elements 53, 54 form a recess 57b for an adhesive. These recesses 57b are also referred to as glue pockets, as the adhesive can be provided to these recesses 57b in order to transpire between the contact surfaces 57 and glue the surfaces 57 to each other.

[0194] These recesses 57b are accessible for an outside even in the assembled state of the stack 51, 52, which allows for a rapid and simple assembly of the stack. The stack can thus be assembled and glued together outside the lens barrel 2 or inside. For this reason the lens barrel 2 might comprise predefined openings 29 for provision of the adhesive.

[0195] It is explicitly noted that the specific combination of spacers 54 and lenses 53 shown in this example is not limiting the general principle of recesses 57b that are formed from adjoining optical elements 3, 53, 54.

[0196] FIG. 5 shows an assembled optical element stack inside the lens barrel 2. It can be seen that the flat areas 28 facing towards the lens barrel 2 can be used to glue the optical element 53 to an inner lens barrel wall 27.

[0197] Moreover, on the side of the second opening 22′ of the lens barrel 2 the lens barrel 2 has a contact surface on its inside that is oriented perpendicular to the optical axis 100. The rightmost optical element 53r also has a contact portion 56 with a contact surface 57a extending perpendicular to the optical axis 100, such that the rightmost optical element 53r can be brought to stop at the contact surface of the lens barrel 2. This geometry allows a self-alignment, particularly along the optical axis 100 of the optical element stack with the lens barrel 2. As for example the images sensor 9 is arranged at the second opening 22′ at a predefined distance, the position of the lenses along the optical axis 100 inside the lens barrel 2 of also of great importance. The rightmost optical element 53r has also an inclined contact surface 57 on the side facing the adjoining optical element 53, such as to self-align the adjoining optical element 53 as described above.

[0198] FIG. 6 shows three azimuthally flat portions 27a of the lens barrel 2 that are configured to fix a circular optical element 3 at a specific orientation inside the lens barrel 2. This geometry has the advantage that the contact areas between the optical element 3 and the lens barrel 2 are clearly defined as in contrast to a completely circular lens barrel wall 27 geometry.

[0199] The flat portions 27a are secants to a circle that aligns with the remaining contour of the lens barrel 2 cross-section.

[0200] It can also be seen that the lens barrel 2 can have an inner cross-section (here almost circular) that differs from the outer contour (which is rectangular in this example), providing an increased stiffness to the lens barrel 2.

[0201] FIG. 7 shows a schematic cross-section through an assembled optical element stack with an aperture element 59a attached to a solid lens 53. The lens 53 has a ring-shaped area 58 extending perpendicular to the optical axis 100. This area 58 is used to arrange and glue a thin aperture 59a between two lenses 53 that have to be spaced so close to each other along the optical axis 100 that the aperture element 59a cannot be formed as a separate optical element 3 with contact portions 56.

[0202] Such an aperture 59a is attached to the lens 53 prior to the assembly of the optical element stack.

[0203] FIG. 8 shows a schematic exploded cross-section through an optical zoom system 1 having an equidistantly arranged first and second lens 6 7. Such a zoom system 1 is a special case of the optical system 1 shown in FIG. 1. Therefore, elements and features explained already in FIG. 1 are not repeated here.

[0204] The optical zoom system 1 has the image sensor 9, the first and the second lens 6, 7 arranged in predefined distances to each other. The first lens 6 is arranged at a first predefined distance 101a along the optical axis, wherein the second lens 7 is arranged in a second distance along the optical axis to the image sensor 9, wherein the second distance 101b is twice as large as the first predefined distance 101a. Therefore, the slots of the lens barrel (not shown) are arranged accordingly on the lens barrel 2.

[0205] Arranging the lenses 6, 7 at these specific distances 101a, 101b to the image sensor 9 allows using the same actuator type.

[0206] The zoom system 1 has an aperture stop 59a close to a first solid lens. This allows for a compact zoom system.

[0207] FIG. 9 shows a schematic cut through the lens barrel 2 having holes 29 for the provision of an adhesive. The holes 29 are arranged over the flat areas 28 of the rim portions 55 of the optical elements 3, 53, 54. Such that an adhesive provided to the holes 29 seeps through the holes 29 and transpires between the inner lens barrel wall 27 and the flat areas 28 of the optical elements 3, 53, 54 so as to fix the optical elements 3, 53, 54 to the lens barrel 2.

[0208] The holes 29 can be covered after provision of the adhesive with an appropriate cloth or compound so as to provide protection against dust and humidity.

[0209] FIG. 10 shows the assembly process of the actuators 68, 78 to the optical system 1. After the lens system 5 is provided and fixed to the lens barrel 2, the first and the second lens 6, 7 are inserted through the first and the second slot 24, 25.

[0210] The portion of the container of the first and the second lens 6, 7 comprising the deformable wall members 63, 73 are outside the lens barrel 2.

[0211] The lens barrel 2 comprises guiding notches 21 that are configured to receive the actuator 68, 78 in a second position by a lateral movement indicated by a hollow arrow, the actuator 68, 78, has a portion that is designed to adjoin to the guiding notches 21.

[0212] From the second position, also referred to a mating zone, the actuators can be moved parallel (indicated by a hollow arrow) to the optical axis 100 by means of the guiding notches 21 of the system such as to adjoin and potentially engage (i.e. mate) with the deformable wall member 63, 73 of the first and second lens 6, 7 in a third position. Only on the third positon a contact is made between the actuator piston and the deformable wall member 63, 73 or the pusher plate arranged on the wall member 63, 73.

[0213] In the third positon the actuator 68, 78 can be locked to the optical system 1 or glued to the lens barrel 2 and/or the first and second lens 6, 7 respectively.

[0214] This allows assembling a plurality of different optical system having different actuators, and/or adjustable lenses and/or lens system. A modular optical system is created that can be assembled rapidly and easily. This is a novel and advantageous aspect of the invention.

[0215] The first and/or second lens 6, 7, the lens barrel 2 and the actuator 68, 78 therefore form a particularly rigid system that is resistant to mechanical shocks.

[0216] The actuator 68, 78 is configured to provide an actuation force parallel to the optical axis 100 of the system 1.

[0217] The deformable wall member 63, 73 is configured to receive an actuation force parallel to the optical axis 100.

[0218] In order to arrange the fold mirror 4 at the correct position to the lens barrel 2, the lens barrel 2 comprises mating pins 23 and/or mating holes 23 at a side facing along the optical axis 100, see e.g. FIG. 11.

[0219] The fold mirror 4 comprises corresponding mating holes 23 and/or pins 23 that are configured to position the fold mirror 4 in a predefined orientation and position to the barrel 2. An adhesive can be provided to the mating pins 23 and holes 23. This allows for simple assembly of the fold mirror 4 to the optical system 1.

[0220] FIG. 12 shows a schematic cross-section of the optical system 1 comprising a clamping device 8 (broken line). The clamping device 8 exerts a clamping force to the lens barrel 2, particularly along the optical axis 100, therefore providing additional stability.

[0221] The clamping device 8 can be formed as a housing such as to provide protection against dust and other external influences.