EP1894041A1 - Lentille variable contenant des liquides et possedant des menisques - Google Patents

Lentille variable contenant des liquides et possedant des menisques

Info

Publication number
EP1894041A1
EP1894041A1 EP06756067A EP06756067A EP1894041A1 EP 1894041 A1 EP1894041 A1 EP 1894041A1 EP 06756067 A EP06756067 A EP 06756067A EP 06756067 A EP06756067 A EP 06756067A EP 1894041 A1 EP1894041 A1 EP 1894041A1
Authority
EP
European Patent Office
Prior art keywords
meniscus
lens
fluids
spherical aberration
menisci
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP06756067A
Other languages
German (de)
English (en)
Inventor
Bernardus H. W. Hendriks
Stein Kuiper
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
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 Koninklijke Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Priority to EP06756067A priority Critical patent/EP1894041A1/fr
Publication of EP1894041A1 publication Critical patent/EP1894041A1/fr
Withdrawn legal-status Critical Current

Links

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
    • G02B21/00—Microscopes
    • G02B21/02—Objectives
    • G02B21/025—Objectives with variable magnification
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
    • 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
    • G02B26/005—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 based on electrowetting
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/0025—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1372—Lenses
    • G11B7/1378—Separate aberration correction lenses; Cylindrical lenses to generate astigmatism; Beam expanders
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1392—Means for controlling the beam wavefront, e.g. for correction of aberration
    • G11B7/13925—Means for controlling the beam wavefront, e.g. for correction of aberration active, e.g. controlled by electrical or mechanical means

Definitions

  • the present invention relates to a variable lens, to a method of operating such a variable lens, to apparatus including such a variable lens, including cameras, optical scanning devices, microscopes and telescopes, and to methods of manufacture of such a variable lens and such apparatus.
  • Variable lenses are lenses that have a variable focal point. Variable lenses are used in a variety of applications, such as to allow the focusing of an image in cameras, microscopy or astronomy, or alternatively to change the conjugate distance of an objective lens in apparatus such as optical scanning devices.
  • variable lenses exist in a wide variety of configurations.
  • a variable lens can be formed by mechanically displacing at least one lens or lens group. Such mechanical lenses are relatively expensive, prone to fatigue, and susceptible to vibration.
  • switchable lenses are known, in which a change in the focal length is achieved by switching the configuration of the lens.
  • Some switchable lenses are formed of liquid crystal, with the principal axis of the liquid crystal being switchable between at least two directions. Switching the orientation of the liquid crystal molecules thus changes the refractive index of the lens experienced by incident polarized light, and hence the focal length.
  • switchable lenses are known that are formed of immiscible fluids in contact over a meniscus.
  • the fluids have different refractive indices. Changing the shape of the meniscus provides a change in the focal length provided by the lens.
  • International patent application no. PCT/IB03/00222 published as WO 03/069380 Al describes such a variable focal lens, in which the shape of the meniscus is altered via the electro wetting effect.
  • variable lens Whilst such switchable lenses are generally cheaper and less vulnerable to mechanical effects, changing the focus of the liquid crystal or electro wetting lenses typically results in the generation of unwanted spherical aberration. It is an aim of the embodiment of the present invention to provide a variable lens that addresses one or more problems of the prior art, whether described herein or otherwise. It is an aim of particular embodiments of the present invention to provide a relatively cheap variable lens, which remains free of substantial spherical aberration.
  • a variable lens having an optical axis, the lens comprising: a first lens element comprising two fluids in contact over a first meniscus extending transverse the optical axis, the fluids being non-miscible and having different indices of refraction; a second lens element comprising two fluids in contact over a second meniscus extending transverse the optical axis, the fluids being non-miscible and having different indices of refraction; and a meniscus controller arranged to control the shape of each meniscus, wherein the meniscus controller is arranged to control the shapes of the menisci such that the amount of spherical aberration produced by the first meniscus is substantially compensated by the amount of spherical aberration produced by the second meniscus for radiation of at least a predetermined wavelength.
  • variable lens utilizes the setting of the shapes of the menisci such that the amount of spherical aberration produced by the first meniscus is substantially compensated by that of the second meniscus.
  • Such a configuration allows a variable lens to be formed that provides a continuous range of focal distances, without substantial spherical aberration.
  • the meniscus controller may be arranged to control the shapes of each meniscus to ensure that the net amount of spherical aberration provided by the menisci is less than 200 m ⁇ OPDrms.
  • the meniscus controller may be arranged to control the shapes of each meniscus to ensure that the net amount of spherical aberration provided by the menisci is less than 100 m ⁇ OPDrms.
  • the meniscus controller may be arranged to control the shape of each meniscus such that the net amount of spherical aberration provided by the menisci is less than the diffraction limit.
  • the first lens element and the second lens element may be defined by a single, common fluid chamber containing a first, second and third body of fluid, the first and second bodies of fluid being the two fluids of said first lens element, and the second and third bodies of fluid being the two fluids of said second lens element.
  • the meniscus controller may be arranged to alter the radius of curvature of each meniscus.
  • the lens may further comprise a meniscus detector may be arranged to detect the position of at least one of said menisci, and to provide a signal indicative of the measured position to the meniscus controller.
  • a meniscus detector may be arranged to detect the position of at least one of said menisci, and to provide a signal indicative of the measured position to the meniscus controller.
  • the apparatus may further comprise a spherical aberration detector for determining spherical aberration of a radiation beam transmitted through the variable lens, and arranged to provide a signal to the meniscus controller indicative of the detected spherical aberration.
  • a spherical aberration detector for determining spherical aberration of a radiation beam transmitted through the variable lens, and arranged to provide a signal to the meniscus controller indicative of the detected spherical aberration.
  • the apparatus may comprise at least one of: an optical scanning device, a camera, a mobile phone, a microscope, and a telescope.
  • a method of manufacturing a variable lens having an optical axis comprising: providing a first lens element comprising two fluids in contact over a first meniscus extending transverse the optical axis, the fluids being non-miscible and having different indices of refraction; providing a second lens element comprising two fluids in contact over a second meniscus extending transverse the optical axis, the fluids being non-miscible and having different indices of refraction; and providing a meniscus controller arranged to control the shape of each meniscus, wherein the meniscus controller is arranged to control the shapes of the menisci such that the amount of spherical aberration produced by the first meniscus is substantially compensated by the amount of spherical aberration produced by the second meniscus for radiation of at least a predetermined wavelength.
  • a method of operating a variable lens having an optical axis comprising: a first lens element comprising two fluids in contact over a first meniscus extending transverse the optical axis, the fluids being non-miscible and having different indices of refraction; a second lens element comprising two fluids in contact over a second meniscus extending transverse the optical axis, the fluids being non-miscible and having different indices of refraction; the method comprising: controlling the shape of each meniscus such that spherical aberration of the first meniscus substantially compensates for spherical aberration of the second meniscus for radiation of at least a predetermined wavelength.
  • the method may further comprise: receiving a signal indicative of the desired focal length of the lens; and reading data indicative of the desired shape of each meniscus to provide the desired focal length.
  • the method may further comprise: determining the shape of at least one of said menisci for determining the desired shape of the other meniscus.
  • the method may further comprise: determining a signal indicative of measuring the spherical aberration of a radiation beam transmitted through the variable lens; and controlling the shape of each meniscus to decrease the net spherical aberration provided to the radiation beam.
  • the meniscus controller may be arranged to control the shape of at least one of said menisci by the electro wetting effect.
  • At least one of said lens elements may comprise a fluid chamber containing the two respective fluids: the method then further comprising: controlling the shape of the meniscus of said lens element comprising a chamber by adjusting the volume of each fluid contained within said chamber.
  • Figure 1 is a schematic diagram illustrating the layout of a variable lens in a device in accordance with an embodiment of the present invention
  • Figure 2 is schematic diagram of an optical scanning device incorporating a variable lens in accordance with an embodiment of the present invention
  • Figure 3 is a schematic diagram of a variable lens controlled using the electro wetting effect, in accordance with an embodiment of the present invention.
  • Figure 4 is a schematic diagram of a lens element controlled using pumping, for use in a variable lens in accordance with a further embodiment of the present invention.
  • variable fluid-based lens can be formed which provides minimal spherical aberration, by providing a fluid-based lens comprising two menisci.
  • the overall focal length of the lens is determined by the shape of both menisci.
  • Each meniscus is the interface between two respective immiscible (non- miscible) fluids, with each of the two fluids having a different index of refraction.
  • Each meniscus will define a respective focal distance, dependent upon the shape of that meniscus.
  • the net focal distance or focal length of the variable lens is due to the combined focal distances of the menisci.
  • the radius of curvature defines the focal distance.
  • Each setting of each meniscus will give rise to a predetermined amount of spherical aberration.
  • the setting of the menisci is chosen such the amount of spherical aberration produced by the first meniscus is substantially compensated by that of the second meniscus. This can be performed for a continuous range of lens focal lengths.
  • Determination of the shape of each menisci can be performed by utilizing a look-up table.
  • a database is formed, incorporating data indicative of the desired shape (e.g. radius of curvature) for each meniscus to provide the variable lens with each desired focal length, with the variable lens being substantially aberration free at all focal lengths.
  • the shape of each meniscus can be dynamically controlled. For example, a quality signal indicative of the spherical aberration of a radiation beam transmitted through the variable lens can be determined. The shape of each meniscus is then controlled, to optimize the quality signal, but maintain the desired focal length. For example, the shape of each meniscus might be altered, and then the quality signal re-measured, over a number of iterations, to determine the optimum shapes/settings of the meniscus. This optimization could be performed using an optimization algorithm e.g. based on the steepest descent method.
  • Figure 1 is a schematic diagram of a variable lens 130 incorporated within an apparatus 100.
  • the variable lens 130 can be regarded as being formed of two lens elements.
  • the first lens element comprises two fluids in contact over a first meniscus 132 i.e. the first meniscus 132 is the interface between the two fluids.
  • the two fluids are non-miscible, and have different indices of refraction.
  • the first fluid has an index of refraction n ls with the other fluid having a different index of refraction n 2 .
  • the second lens element also comprises two fluids in contact over a second meniscus 134.
  • the fluids are non-miscible, and have different indices of refraction.
  • the fluids of the second lens element have an index of refraction of respectively n 2 and n 3 .
  • both lens elements are defined by three bodies of fluid.
  • n 2 a single, common body of fluid of refractive index n 2 separates the menisci 132, 134.
  • the variable lens 130 has an optical axis 19, with both menisci extending transverse (across) the optical axis.
  • Figure 1 also indicates a meniscus controller 110 that is utilised to controllably vary the shape of each meniscus 132, 134.
  • the entrance radiation beam 120 is a parallel beam, with an entrance pupil radius h (i.e. the beam waist of the incident radiation beam 120 is of radius h).
  • K 1 and K 2 as the optical power of the first and second meniscus respectively, and defining K as the total power of the variable lens 130, gives:
  • T 1 is the radius of curvature of first meniscus 132
  • r 2 is the radius of curvature of second meniscus 134. Both T 1 and r 2 are defined as positive when the menisci they represent are convex as seen from . the second body of fluid of refractive index n 2 .
  • the parameter ⁇ is defined as the magnification of the second meniscus, and is given by:
  • variable lens is substantially spherical aberration free
  • a lens can be formed for which there exists settings of the radii T 1 and r 2 that makes the variable lens substantially aberration free, over a continuous range of focal distances.
  • Table I illustrates various solutions of this equation 5, showing how various spherical aberration free lenses can be formed.
  • the net spherical aberration of the variable lens is aberration free to at least third order aberration analysis.
  • this is only one measure of the degree to which the system can be formed to be spherical aberration free.
  • the precise degree to which spherical aberration affects an apparatus will determine the degree to which it is desirable to remove the spherical aberration from a variable lens within that apparatus. For instance, in some applications it may be desirable that the degree of spherical aberration is such that the effect of the spherical aberration is less than the diffraction limit.
  • the apparatus is regarded as substantially spherical aberration free if OPDrms ⁇ 200m ⁇ , where OPDrms is the root mean square optical path length difference across the wave front of the radiation beam. More preferably, OPDrms ⁇ 100m ⁇ , and even more preferably OPDrms ⁇ 70m ⁇ . If OPDrms is less than or equal to 70m ⁇ , then the degree of spherical aberration of the radiation beam is regarded as less than the diffraction limit.
  • An example of a variable lens will now be described, having a generally similar structure to that shown in Figure 1.
  • the lens has an entrance pupil diameter of 1.5mm.
  • the lens is substantially aberration free for an incident radiation of wavelength 405mm.
  • the two menisci are separated by a distance of, with D being the distance from the last meniscus to the focal point (e.g. in Figure 1, D would correspond to the distance from meniscus 134 to F 12).
  • D is the distance from the last meniscus to the focal point (e.g. in Figure 1, D would correspond to the distance from meniscus 134 to F 12).
  • Table II provides a list of appropriate settings of such a variable lens, that give rise to substantially zero spherical aberration.
  • the increase in aberration for smaller values of D is due to the increase in numerical aperture.
  • the spherical aberration is expressed as the root mean square optical path length difference, in units of m ⁇ (where ⁇ is the wavelength of incident radiation). If the root mean square of the optical path length difference is less than 70 m ⁇ , then the variable lens will be considered as being free of the spherical aberration.
  • the apparatus 100 shown in Figure 1 can be any apparatus in which it is desirable to incorporate a variable lens e.g. the apparatus could be a camera, a microscope, a telescope or an optical scanning device.
  • the apparatus could be any device incorporating any of the aforesaid apparatus e.g. the apparatus could be a mobile telephone, a personal digital assistant (PDA), a computer or an electronic toy incorporating a camera.
  • PDA personal digital assistant
  • the term camera is taken to encompass both a still-picture (photo) camera or a video camera.
  • the camera may be a film or a digital camera.
  • Figure 2 shows a device 1 for scanning a first information layer 2 of a first optical record carrier 3 by means of a first radiation beam 4, the device including an objective lens system 8.
  • the optical record carrier 3 comprises a transparent layer 5, on one side of which information layer 2 is arranged.
  • the side of the information layer 2 facing away from the transparent layer 5 is protected from environmental influences by a protective layer 6.
  • the side of the transparent layer facing the device is called the entrance face.
  • the transparent layer 5 acts as a substrate for the optical record carrier 3 by providing mechanical support for the information layer 2.
  • the transparent layer 5 may have the sole iunction of protecting the information layer, while the mechanical support is provided by a layer on the other side of the information layer 2, for instance by the protective layer 6 or by an additional information layer and transparent layer connected to the uppermost information layer.
  • the information layer has first information layer depth 27 that corresponds, in this embodiment as shown in Figure 1, to the thickness of the transparent layer 5.
  • the information layer 2 is a surface of the carrier 3.
  • the optical scanning device 1 includes a radiation source 7, a collimator lens 18, a beam splitter 9, and an objective lens system 8 having an optical axis 19a, a variable lens 30, and a detection system 10.
  • the optical scanning device 1 includes a servo circuit 11, a focus actuator 12, a radial actuator 13, and an information-processing unit 14 for error correction.
  • the radiation source 7 is arranged for consecutively or separately supplying a first radiation beam 4, a second radiation beam 4' and a third radiation beam 4".
  • the radiation source 7 may comprise a tunable semiconductor laser for consecutively supplying two of the radiation beams 4, 4'and 4" with a separate laser supplying the third beam, or three semiconductor lasers for separately supplying these radiation beams.
  • the radiation beam 4 has a wavelength ⁇ i and a polarization P 1
  • the radiation beam 4' has a wavelength ⁇ 2 and a polarization p 2
  • the radiation beam 4" has a wavelength ⁇ 3 and a polarization p 3 .
  • the wavelengths ⁇ lt ⁇ 2) and ⁇ 3 are all different.
  • the difference between any two wavelengths is equal to, or higher than, 20nm, and more preferably 50nm.
  • Two or more of the polarizations pi, p 2 , and p 3 may differ from each other.
  • the collimator lens 18 is arranged on the optical axis 19a for transforming the divergent radiation beam 4 into a substantially collimated beam 20. Similarly, it transforms the radiation beams 4' and 4" into two respective substantially collimated beams 20' and
  • the beam splitter 9 is arranged for transmitting the radiation beams along an optical path towards the objective lens system 8.
  • the radiation beams are transmitted towards the objective lens system 8 by transmission through the beam splitter
  • the optical axis 19a of the objective lens system 8 is common with an optical axis of the radiation source 7.
  • the objective lens system 8 is arranged for transforming the collimated radiation beam 20 to a first focused radiation beam 15 so as to form a first scanning spot 16 in the position of the information layer 2.
  • the record carrier 3 rotates on a spindle (not shown in
  • the focused radiation beam 15 reflects on the information layer 2, thereby forming a reflected beam 21, which returns on the optical path of the forward converging beam 15.
  • the objective lens system 8 transforms the reflected radiation beam 21 to a reflected collimated radiation beam 22.
  • the beam splitter 9 separates the forward radiation beam 20 from the reflected radiation beam 22 by transmitting at least part of the reflected radiation 22 along an optical path towards the detection system 10.
  • the reflected radiation beam In the illustrated example, the reflected radiation beam
  • the beam splitter 9 is a polarizing beam splitter.
  • a quarter wave plate 9' is positioned along the optical axis 19a between the beam splitter 9 and the objective lens system 8.
  • the combination of the quarter wave plate 9' and the polarizing beam splitter 9 ensures that the majority of the reflected radiation beam 22 is transmitted towards the detection system 10 along detection system optical axis 19b.
  • the detection system optical axis 19b is a continuation of the optical axis 19a, due to the beam splitter 9 transmitting at least part of the reflected radiation 22 towards the detection system 10.
  • the objective lens system optical axis comprises the axes indicated by reference numerals 19a and 19b.
  • the detection system 10 includes a convergent lens 25 and a detector 23, which are arranged for capturing said part of the reflected radiation beam 22.
  • a variable lens 30 in accordance with an embodiment of the present invention is located on the optical path between the beam splitter 9 and the detector 23. Preferably, the variable lens 30 is located between the beam splitter 9 and the convergent lens 25. The variable lens 30 is utilized to control the focusing of said part of the reflected radiation beam 22.
  • the images formed by different radiation beams will be at different axial positions. This can be due to use of different conjugate settings for the different radiation beams and/or the radiation sources being at different axial positions. In order to compensate for the different axial positions of the images, in many instances prior art optical scanning devices will contain different detectors for different radiation beams. This increases both the cost and the size of such optical scanning devices.
  • variable lens 30 In the embodiment described here, to solve this problem of different axial positions of the images, the focal length of the variable lens 30 is adjusted, so as to ensure that spots from different radiation beams are focused on the same image plane (i.e. that of the information detector). Thus, a single information detector can be utilized. In prior art variable lens, adjusting the focal length would produce different amounts of unwanted spherical aberration. This problem is circumvented by the variable lens 30.
  • the menisci of the variable lens 30 are controlled, so as to provide a desired focal distance, but to ensure that the net amount of spherical aberration produced by the combination of the two menisci is negligible i.e. such that the spherical aberration produced by the variable lens is sufficiently low that it does not impact the performance of the optical scanning device.
  • the detector 23 is arranged to convert said part of the reflected beam to one or more electrical signals.
  • One of the signals is an information signal, the value of which represents the information scanned on the information layer 2.
  • the information signal is processed by the information-processing unit 14 for error correction.
  • the focus error signal represents the axial difference in height along the Z-axis between the scanning spot 16 and the position of the information layer 2.
  • this signal is formed by the "astigmatic method" which is known from, inter alia, the book by G. Bouwhuis, J. Braat, A. Huijiser et al, "Principles of Optical Disc Systems", pp. 75-80 (Adam Hilger 1985, ISBN 0-85274-785-3).
  • the radial tracking error signal represents the distance in the XY-plane of the information layer 2 between the scanning spot 16 and the center of track in the information layer 2 to be followed by the scanning spot 16.
  • This signal can be formed from the "radial push-pull method” which is also known from the aforesaid book by G. Bouwhuis, pp. 70-73.
  • the servo circuit 11 is arranged for, in response to the focus and radial tracking error signals, providing servo control signals for controlling the focus actuator 12 and the radial actuator 13 respectively.
  • the focus actuator 12 controls the position of the objective lens 8 along the Z-axis, thereby controlling the position of the scanning spot 16 such that it coincides substantially with the plane of the information layer 2.
  • the radial actuator 13 controls the radial position of the scanning spot 16 so that it coincides substantially with the centerline of the track to be followed in the information layer 2 by altering the position of the objective lens 8.
  • the objective lens 8 is arranged for transforming the collimated radiation beam 20 to the focused radiation beam 15, having a first numerical aperture NA 1 , so as to form the scanning spot 16.
  • the optical scanning device 1 is capable of scanning the first information layer 2 by means of the radiation beam 15 having the wavelength ⁇ ls the polarization P 1 and the numerical aperture NA 1 .
  • the optical scanning device in this embodiment is also capable of scanning a second information layer 2' of a second optical record carrier 3' by means of the radiation beam 4', and a third information layer 2" of a third optical record carrier 3" by means of the radiation beam 4".
  • the objective lens system 8 transforms the collimated radiation beam 20' to a second focused radiation beam 15', having a second numerical aperture NA 2 so as to form a second scanning spot 16' in the position of the information layer 2'.
  • the objective lens 8 also transforms the collimated radiation beam 20" to a third focused radiation beam 15", having a third numerical aperture NA 3 so as to form a third scanning spot 16" in the position of the information layer 2".
  • any one or more of the scanning spots 16, 16', 16" may be formed with two additional spots for use in providing an error signal. These associated additional spots can be formed by providing an appropriate diffractive element in the path of the optical beam 20.
  • the optical record carrier 3' includes a second transparent layer 5' on one side of which the information layer 2' is arranged with the second information layer depth 27', and the optical record carrier 3" includes a third transparent layer 5" on one side of which the information layer 2" is arranged with the third information layer depth 27 ".
  • the menisci within variable lens 30 may be controlled using a meniscus controller that receives a signal indicative of the type of optical record carrier being scanned (e.g. the signal is indicative of the desired focal length of the variable lens), with the controller then reading data (e.g. from a memory store or look-up table) indicative of the desired shape of each meniscus needed to provide the desired focal length of the variable lens, with substantially spherical aberration free operation.
  • a meniscus controller that receives a signal indicative of the type of optical record carrier being scanned (e.g. the signal is indicative of the desired focal length of the variable lens), with the controller then reading data (e.g. from a memory store or look-up table) indicative of the desired shape of each meniscus needed to provide the desired focal length of the variable lens, with substantially spherical aberration free operation.
  • the detection system 10 may also detect the spherical aberration and/or spot focal point, and provide a lens control signal to servo circuit 11, for controlling the operation of the variable lens 30.
  • the spherical aberration signal is thus used as a quality signal, as an input to determine the optimal setting of the shape (the radius of curvature) of each of the menisci, so as to achieve optimum operation i.e. with substantially net spherical aberration being provided by the variable lens, for a given desired focal length.
  • the given desired focal length is when the focus error signal determined by the detection system 10 is minimal.
  • the optical record carrier 3, 3' and 3" are, by way of example only, a "Blue-ray Disc”- format disc, a DVD - format disc and a CD-format disc, respectively.
  • the wavelength ⁇ i is comprised in the range between 365 and 445 nm, and preferably, is 405 nm.
  • the numerical aperture NA 1 equals about 0.85 in both the reading mode and the writing mode.
  • the wavelength ⁇ 2 is comprised in the range between 620 and 700 nm, and preferably, is 650 nm.
  • the numerical aperture NA 2 equals about 0.6 in the reading mode and is above 0.6, preferably 0.65, in the writing mode.
  • the wavelength ⁇ 3 is comprised in the range between 740 and 820 nm and, preferably is about 785 nm.
  • the numerical aperture NA 3 is below 0.5, and is preferably 0.45 for the reading of information from CD-format discs, and preferably between 0.5 and 0.55 for writing information to CD- format discs.
  • variable lens 30 as described herein forms part of a microscope.
  • a microscope objective lens transforms the light emitted by the specimen into a parallel beam. In prior art devices, this is typically accomplished by letting the focal point of the objective coincide with the specimen, by mechanically displacing the objective. If a normal prior art liquid lens was utilized for performing this focusing operation (by changing the focal length of the liquid lens), this would generally introduce different amounts of aberration to the beam, thus deteriorating the optical quality of the beam.
  • the focal length of the variable lens can be altered without spherical aberration being introduced into the beam.
  • the operation of altering the shape of the menisci between the two fluids can be performed using a variety of techniques.
  • the electro wetting effect cam be utilised to alter the shape (e.g. radius of curvature) of the meniscus.
  • International Patent Applications WO 99/18456 & WO 00/58763 describe variable focus lenses.
  • First and second lens elements in accordance with an embodiment of the present invention may each be formed from a respective one of such known variable focus lenses, with the addition of an appropriate voltage control so as to ensure that the voltage applied to the fluids in each lens element ensures that the shapes of the meniscus within each lens element is appropriate.
  • each meniscus is formed within a separate fluid chamber or cell.
  • the variable lens in accordance with an embodiment of the present invention is thus formed by placing two (or more) of such lens elements in series, with a common optical axis extending through each lens element.
  • Each lens element thus comprises two fluids in contact over a meniscus extending transverse the optical axis, with the two fluids of each lens element being non-miscible and having different indices of refraction.
  • the second lens element may utilize the same fluids as the first lens element, or may utilize one or more different fluids.
  • the two menisci are formed within a single, common chamber, with a single body of fluid separating both menisci (e.g. as shown in Figure 1).
  • Figure 3 shows one example of an electro wetting lens 330 in accordance with an embodiment of the present invention.
  • the variable lens 330 is generally similar to the zoom lens described in International Patent Application No. PCT/IB2003/004595 (published as WO 2004/038480).
  • the variable lens 330 comprises a chamber 300.
  • Three fluids A, B, B' are located within the chamber 300.
  • the chamber 300 is, in this embodiment, a cylindrical chamber defined by side walls 306 and end walls 302, 304.
  • Optical axis 19 extends through the chamber.
  • Two menisci 332, 334 are defined by the three fluids A, B, B' within the chamber. Each meniscus 332, 334 extends transverse the optical axis 19. At least one of the fluids A, B, B' within the chamber 300 is electrically susceptible (i.e. the fluid is affected by the application of an electric field), whilst at least one of the fluids is not electrically susceptible.
  • fluid A is not electrically susceptible e.g. it is an insulator, such as an oil or alkane.
  • Fluids B, B' are electrically susceptible fluids e.g. the fluids B, B' are electrically conductive fluids, such as an aqueous salt solution.
  • First meniscus 332 is defined by the interface between fluids A, B. Fluids A and B have different indices of refraction.
  • Second meniscus 334 is defined by the interface between fluids A and B'. Fluids A and B' have different indices of refraction. Fluids B and B 'may have identical indices of refraction (and may be the same fluid), but in this particular embodiment they are different fluids with different indices of refraction.
  • the ends 302, 304 of the chamber are defined by an optically transparent material e.g. glass.
  • the ends 302, 304 also act as electrodes for applying a voltage to the respective adjacent fluid B, B'.
  • This can be obtained by coating the ends with a transparent electrical conductor, e.g. an indium tin oxide layer.
  • the side 316 of the cylindrical chamber 300 is coated with an insulating layer 306, for example parylene.
  • a thin hydrophobic coating e.g. AF- 1600
  • Cylindrical electrode 316 thus extends around the outer surface of the insulating cylindrical chamber side wall 306.
  • the electrode 316 can be constructed of a metal tube.
  • a first voltage source 312 is arranged to apply a voltage cross first end electrode 302 and cylindrical side electrode 316, so as to change the shape of meniscus 332.
  • a second voltage source 314 is arranged to apply a voltage across second end electrode 304 and cylindrical side electrode 316, so as to change the shape of meniscus 334.
  • Electro wetting is the phenomenon by which the wettability of a surface by a fluid varies under application of a voltage. This results in the change of the contact angle of the meniscus at the three-phase line, and hence changes the shape of the meniscus.
  • the three- phase line is the line of contact between the surface and the two adjacent fluids.
  • the three-phase line for meniscus 332 is the point at which the perimeter of the meniscus contacts the cylindrical side wall 306.
  • the wettability of the surface 306 can be altered, leading to a change in the three-phase contact line and hence a consequent change in the radius of curvature of the meniscus.
  • the shape of meniscus 334 can be controlled by application of a voltage between electrodes 304 and 316.
  • a meniscus controller 310 is provided by voltage sources 312, 314 and electrodes 302, 304 and 316, which allows the control of the shapes of both menisci.
  • the meniscus controller 310 is arranged to control the shapes of the menisci so that the amount of spherical aberration produced by the first meniscus 332 is substantially compensated by the amount of spherical aberration produced by the second meniscus 334.
  • the meniscus controller is further arranged to control the shapes of the menisci to allow a range of variable focal lengths to be provided by the variable lens 330.
  • Figure 4 shows a lens element 430 suitable for use in a variable lens in accordance with an embodiment of the present invention.
  • the lens element 430 utilizes a pumping system, to change the volume of fluids A, B located within the chamber 400.
  • Optical axis 19 extends through the chamber 400.
  • the chamber 400 has side walls 410 that are of uniform wettability.
  • the chamber 400 is shaped as a truncated cone, with the side wall 410 being curved (as opposed to linear).
  • the shape of the meniscus 432 changes.
  • the meniscus 432 attempts to maintain a constant three-phase contact angle, as the wettability of the surface is uniform.
  • the shape of the meniscus changes as it moves along the optical axis 19.
  • Inlets 402, 404 are connected at respective ends of the chamber 400 to a pump 406.
  • Pump 406 is utilised to alter the respective volumes of the immiscible fluids A, B within the chamber, so as to alter the position of the meniscus along the optical axis.
  • pump 406 acts as the meniscus controller, to change the shape of the meniscus 432 by translation of the meniscus 432 along the optical axis.
  • a similar lens element would be provided in series with that shown in Figure 430, with an appropriate controller, so as to ensure that the variable lens formed by the two lens elements provides negligible spherical aberration to incident radiation of a predetermined wavelength, or range of wavelengths.
  • the configuration of figure 4 is used in combination with pinning of the meniscus to the wall. The menisci perimeter can be pinned to a particular position on the wall by a sudden change in geometry or wettability of the wall. Changing the volume by pumping then provides to a change in meniscus shape and not in position.
  • a variable lens comprises two menisci.
  • a meniscus controller is arranged to control the shapes of the menisci, such the amount of spherical aberration produced by the first meniscus is substantially compensated by the amount of spherical aberration produced by the second meniscus.
  • This allows the variable lens to be tuned over a range of focal distances (and/or a range of wavelengths of incident radiation) to provide a suitable variable lens that provides negligible spherical aberration.
  • a relatively cheap variable lens can be provided, that is spherical aberration free, and not prone to being affected by vibrations.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Astronomy & Astrophysics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Lenses (AREA)
  • Mechanical Light Control Or Optical Switches (AREA)
  • Optical Head (AREA)

Abstract

L'invention concerne une lentille variable et son procédé de fonctionnement. Cette lentille variable possède un axe optique (19). Elle comporte un premier et un deuxième élément de lentille. Le premier élément de lentille contient deux liquides en contact par l'intermédiaire d'un premier ménisque (132) s'étendant dans un sens transversal par rapport à l'axe optique, ces liquides étant non miscibles et présentant différents indices de réfraction. Le deuxième élément de lentille contient deux liquides en contact par l'intermédiaire d'un deuxième ménisque (134) s'étendant dans un sens transversal par rapport à l'axe optique, ces liquides étant non miscibles et présentant différents indices de réfraction. Un contrôleur de ménisque est conçu pour contrôler la forme de chaque ménisque. Ce contrôleur (110) est conçu pour contrôler les formes des ménisques, de sorte que le niveau d'aberration sphérique produit par le premier ménisque est sensiblement encouragé par le niveau d'aberration sphérique produit par le deuxième ménisque pour un rayonnement d'au moins une longueur d'onde prédéterminée. Cette lentille variable peut être incorporée dans une variété de dispositifs, tels qu'un dispositif de balayage optique, une caméra, un microscope ou un télescope.
EP06756067A 2005-06-10 2006-06-06 Lentille variable contenant des liquides et possedant des menisques Withdrawn EP1894041A1 (fr)

Priority Applications (1)

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EP06756067A EP1894041A1 (fr) 2005-06-10 2006-06-06 Lentille variable contenant des liquides et possedant des menisques

Applications Claiming Priority (3)

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EP05105116 2005-06-10
PCT/IB2006/051800 WO2006131882A1 (fr) 2005-06-10 2006-06-06 Lentille variable contenant des liquides et possedant des menisques
EP06756067A EP1894041A1 (fr) 2005-06-10 2006-06-06 Lentille variable contenant des liquides et possedant des menisques

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EP1894041A1 true EP1894041A1 (fr) 2008-03-05

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JP (1) JP2008546031A (fr)
KR (1) KR20080022186A (fr)
CN (1) CN101194188A (fr)
MY (1) MY146797A (fr)
TW (1) TW200706916A (fr)
WO (1) WO2006131882A1 (fr)

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CN102096126A (zh) * 2011-01-07 2011-06-15 南京邮电大学 基于离子液体的微流控液体变焦透镜
CN102103220A (zh) * 2011-02-28 2011-06-22 南京邮电大学 基于离子液体的微流控液体变焦透镜
CN103472507B (zh) * 2013-09-11 2015-06-24 云南大学 基于非对称液芯柱透镜精确测量液体折射率及液相扩散系数的方法
KR101822895B1 (ko) 2016-04-07 2018-01-29 엘지전자 주식회사 차량 운전 보조 장치 및 차량
CN106094070B (zh) * 2016-06-19 2018-01-02 云南大学 测量液体折射率和液相扩散系数的消球差可变焦双液芯柱透镜
CN109643015A (zh) * 2016-06-22 2019-04-16 康宁股份有限公司 像差减小的可调节流体透镜
DE102017207013A1 (de) * 2017-04-26 2018-10-31 Carl Zeiss Microscopy Gmbh Verfahren und Vorrichtung zur Regelung von in eine Lochblende eingestrahlten Intensitäten und/oder spektralen Anteilen einer Strahlung
CN109709668A (zh) * 2019-02-02 2019-05-03 北京空间机电研究所 一种自动相位调节单元及调节方法
CN113238307B (zh) * 2021-04-29 2022-03-01 四川大学 一种基于电湿润液面间距可变的自适应变焦液体透镜

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MY146797A (en) 2012-09-28
JP2008546031A (ja) 2008-12-18
KR20080022186A (ko) 2008-03-10
TW200706916A (en) 2007-02-16
WO2006131882A1 (fr) 2006-12-14
CN101194188A (zh) 2008-06-04

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