WO2015170080A1 - Réseau de lentilles et dispositif d'imagerie - Google Patents

Réseau de lentilles et dispositif d'imagerie Download PDF

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Publication number
WO2015170080A1
WO2015170080A1 PCT/GB2015/051310 GB2015051310W WO2015170080A1 WO 2015170080 A1 WO2015170080 A1 WO 2015170080A1 GB 2015051310 W GB2015051310 W GB 2015051310W WO 2015170080 A1 WO2015170080 A1 WO 2015170080A1
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Prior art keywords
lens array
superlenses
lens
image
imaging
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PCT/GB2015/051310
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English (en)
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Shyqyri Haxha
Amar Aggoun
Fathi ABDELMALEK
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University Of Bedfordshire
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Publication of WO2015170080A1 publication Critical patent/WO2015170080A1/fr

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/002—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of materials engineered to provide properties not available in nature, e.g. metamaterials
    • G02B1/007—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of materials engineered to provide properties not available in nature, e.g. metamaterials made of negative effective refractive index materials
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/0006—Arrays
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • H01Q15/0086—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices having materials with a synthesized negative refractive index, e.g. metamaterials or left-handed materials

Definitions

  • the present technique relates to the field of lenses and imaging devices using lenses.
  • the resolution of current optical devices is limited by the wavelength of light used.
  • a conventional lens is unable to resolve objects smaller than the wavelength.
  • the present technique seeks to address this problem.
  • the present technique provides a lens array comprising a plurality of superlenses made from at least one negative refractive index metamaterial, wherein the superlenses are arranged in an array.
  • Negative refractive index metamaterials are new types of materials which refract light in the opposite direction to conventional materials. Hence, a negative refractive index metamaterial refracts the light on the same side of the normal as the incident beam, rather than on the opposite side as in conventional materials.
  • a lens made from at least one negative refractive index metamaterial may be referred to as a superlens, and can provide a higher resolution image because the negative refractive index material of the superlens amplifies the near field so that it contributes to the image, allowing the lens array to resolve objects smaller than the wavelength of light being used.
  • Arranging a number of superlenses in an array enables a single macroscopic lens to be provided in which different portions of the lens have different properties, or allows a microlens array to be provided for high resolution three dimensional imaging for example.
  • Each superlens of the array may be arranged to generate a non-inverted image of an object.
  • Conventional lenses generate an inverted image which means that it is often necessary to provide a further lens system to flip the image back the right way round.
  • each superlens may generate a real non-inverted (upright) image of an object so that it is not necessary to provide further lens arrays to fit the image. This allows the cost of devices using the array to be brought down since fewer components are required.
  • the superlenses may operate at various wavelength bands. However, it is particularly useful for at least some of the superlenses of the array to operate at visible wavelengths. This enables the micro lens array to be used for many practical applications such as three dimensional image capture and playback.
  • the lens array may include superlenses of different types, which allows for new imaging effects which would not be possible with conventional lenses. For example, metamaterials such as photonic crystals can be tuned to have different properties by changing their structure or introducing defects, which is not possible with conventional materials such as glass.
  • the array may include a first set of superlenses which operate at a first range of wavelengths and a second set of superlenses for operating at a second range of wavelengths.
  • this allows an imaging device to capture images at different wavelength bands using a single shot, to avoid needing to provide two separate imaging devices.
  • the first range of wavelengths may comprise infrared wavelengths and the second range of wavelengths may comprise visible wavelengths, so that an imaging device may capture in a single shot both a visible light image and a thermal image.
  • Other superlenses may operate in other parts of the spectrum such as ultraviolet, x-ray, or microwave radiation.
  • the different wavelengths of operation may be achieved by tuning the negative refractive index metamaterial used for the respective set of lenses.
  • photonic crystals can be designed to have different band gaps by providing different numbers, positions and types of defects in the periodic lattice of the photonic crystal, to tune the crystal to operate at different wavelength bands.
  • the array may comprise an alternating arrangement of the first and second sets of superlenses corresponding to the different wavelengths, for example in a checkerboard arrangement.
  • the superlenses within the array may have different focal positions.
  • each superlens can be designed to project the image to a different desired location or point, or capture an image from a different point, and then an array can be built up of superlenses with different focal points.
  • the focal point of each lens may vary according to the position of the lens within the array. This can be useful for providing the lens array with a wider field of view (by shifting the focal positions of the superlenses at the edges of the array to wider positions).
  • the different focal point of different lenses may be achieved by tuning the properties of a photonic crystal or the arrangement or layering of other materials.
  • the at least one negative refractive index metamaterial may include at least one of a photonic crystal, silver or another metal, a polymer, and graphene or other low loss transparent materials.
  • the choice of material may depend on the particular application for the lens array.
  • the superlenses may be made from a combination of several different negative refractive index metamaterials. For example, this can be useful to help reduce losses which cause less efficient image propagation.
  • silver may be combined with a polymer or glass or graphene in combination to design a lower loss superlens.
  • the lens array may be mounted on a substrate. Hence, a single platform may be provided with a number of micro lenses arranged in an array on the substrate.
  • the substrate may be at least partially curved.
  • graphene is a flexible material, which can be used as the substrate to allow the substrate to be bent to form a curved lens array.
  • a curved substrate may be useful for example to help increase the field of view of the lens array. By arranging the lens array on a convex surface of the curved substrate, the angle view of the array can be increased.
  • An integrated imaging sensor may be provided on the substrate for capturing images generated by the superlenses of the lens array. This provides a single compact platform for capturing images using the lens array, for example three dimensional (3D) images.
  • the lens array may be a microlens array comprising a plurality of microlenses arranged in an array, each microlens comprising at least one of the superlenses.
  • a micro lens array comprises a number of relatively small lenses arranged in a one dimensional or two dimensional array, typically mounted on a supporting substrate. The lenses may have different shapes or arrangements within the array.
  • Microlens arrays can be used for a range of application and imaging devices. For example, in 3D imaging and display the different lenses may capture or playback different views to enable an observer to see a stereoscopic image. By forming the microlens array using superlenses, a higher resolution image can be obtained.
  • the array of superlenses may form a single macroscopic lens, which can replace an existing single lens in an optical device, but which provides higher resolution and can include superlenses with different properties, such as focal position or focal length, wavelength of operation, refractive index etc., to provide lenses with new optical behaviour.
  • the present technique provides an imaging device comprising the lens array discussed above, where the imaging device is configured to capture images generated by the lens array or playback images to be focused using the lens array.
  • the lens array can be included in a range of imaging devices.
  • the term imaging device should be interpreted as including both image capture devices and image playback devices. If the lens array includes superlenses for operating at different bands of wavelengths then the imaging device may capture in a single shot at least one first image at the first range of wavelengths and at least one image at the second range of wavelengths.
  • the lens array may be the only lens or lens array between an object to be imaged by the imaging device and an imaging sensor of the imaging device. Hence, there is no need for image transfer screens or relay lenses for ensuring that the image of the object is the right way up.
  • the use of negative refractive index metamaterial(s) means an upright image of the object is generated, so no further lenses are required.
  • the further lens may focus an image of an object on to the lens array which then further focuses the image.
  • the further lens may perform further focusing of an image generated using the lens array.
  • the further lens may be another lens array with superlenses made from a negative refractive index metamaterial.
  • the further lens may be another lens array with superlenses made from a negative refractive index metamaterial.
  • the further lens may be a conventional lens made from a material having a positive refractive index.
  • the combination of a super lens array with one or more conventional lenses is very useful for enabling a device to capture images both in the far field and the near field.
  • the further lens (or lens array) with positive refraction may bring far field objects to a position in a near field region of the negatively refracting lens array, which then forms an image of the object in the near field. This allows the far field object to be imaged at higher resolution using the near field capability of the superlens array.
  • the imaging device may be used for capturing or playing back three dimensional images, such as in holoscopic imaging, 3D cinema, or 3D medical imaging. However, it is also possible to use the imaging device for capturing or playing back two dimensional images where the superlens array is able to obtain images with high resolution.
  • imaging device may include at least one of holoscopic imaging or playback, cinematic film capture or display, feature extraction or recognition, medical imaging, surveillance or security imaging, particle sensing, a microscope or device for imaging nanoscale objects, a telescope, optical lithography, imaging in industrial processes, and contact lenses or other optometric devices.
  • Figure 1 illustrates an array of superlenses made from a negative refractive index meta material
  • Figures 2A to 2C illustrate positive refraction using conventional materials
  • Figures 3A to 3C illustrate negative refraction using metamaterials
  • Figure 4 shows a comparison between lenses made from a positive and negative refractive index materials respectively
  • Figure 5 illustrates an example of a near-field super lens
  • Figure 6 illustrates how negative index metamaterials can increase dispersion of different wavelengths
  • Figure 7 illustrates an example of a holoscopic imaging camera using a microlens array of superlenses
  • Figure 8 illustrates an example of an array of superlenses acting as a single lens platform
  • Figure 9 illustrates two examples of performing imaging using several superlens arrays in parallel
  • Figure 10 schematically illustrates an example of a lens array having different types of superlenses with different wavelengths of operation
  • Figure 11 illustrates an example of a lens array with an integrated imaging sensor
  • Figure 12 shows an example of a curved lens array.
  • a metamaterial superlens (M-Lens) operating at visible light region is proposed for applications in 3D holoscopic imaging and other applications.
  • M-Lens metamaterial superlens
  • Such a perfect lens can produce a perfect image.
  • the superlens can be based on metal slab, photonic crystal structure, or any other design which performs the negative refraction or metamaterial or left-hand behaviour. It has been demonstrated that by careful selection of photonic crystal slab parameters such as refractive index or structure configurations, such as air cylinders or air holes in a slab, optical evanescent waves passing through the slab (superlens or perfect lens) are reproduced so that significant high resolution or almost perfect image reconstruction of the object can be obtained.
  • the concept/idea for building an array of integrated superlenses based on metamaterials/negative refraction/LH model that would capture, record, obtain, project, or transfer ultra-high resolution images, in unidirectional and/or omnidirectional.
  • the superlens can be designed to operate in the visible light region, based on photonic crystals (which could be 1 D, 2D, 3D... ), for example including defects to control the negative refraction/left hand/metamaterial.
  • the defects may be of any geometrical shape (e.g.
  • Negative refraction is used to focus the light.
  • a flat slab of material may produce two foci: one inside the medium, the other outside.
  • the proposed structure comprises an array of superlenses that may be placed in a single platform/substrate that may consist of many different superlenses each designed carefully in order to obtain a desired image of the object.
  • Various combinations or arrangements can be made such as one single superlens with many others in a single platform or several superlens platforms in certain/desired configuration(s) in order to achieve desired image resolutions.
  • the careful arrangement of each superlens, and superlenses in a single platform applying geometrical optics may be performed in order to capture the object details from all angles to obtain ultra-high resolution of the image.
  • the array of superlenses may effectively act as a single lens, but by providing superlenses with different properties, new imaging effects may be obtained.
  • the array may act as a single lens with a wider field of view than conventional lenses.
  • a single lens can capture images at different wavelength bands (e.g. visible and infrared).
  • the array of superlenses may form a microlens array which can be used for example for 3D image capture or playback, where each microlens corresponds to one of the superlenses or multiple superlenses.
  • each microlens may comprise the superlens array described in the previous paragraph.
  • the proposed superlens can be designed or built from various transparent materials with low losses enabling imaging at visible wavelength or different wavelengths.
  • the proposed ideas may be used for many applications, such as 3D holoscopic imaging.
  • the superlenses may be made from various materials depending on the applications and the practical suitability.
  • the proposed idea would be applicable for: Live capture of 3D content (optics and Electronics), real-time computer generation of 3D holoscopic content, 3D games, 3D video coding, 3D virtual for mixed 3D content generation, 3D digital cinema (large scale 3D video projection), 3D feature extraction and recognitions, Medical Imaging (3D medical visualisation), surveillance and security (3D face recognition), Sensing applications (such as environmental, food, and air pollutions-size particle detections in 3D and the density of particles...
  • a tiny camera may be passed through the body to carry out close quarter observations of internal organs, in much the same way as a traditional colonoscopy. Images may be sent to a doctor who can examine them without the need for any patient intrusion and at a fraction of the cost of a regular exploratory operation.
  • our proposed array of superlenses it is possible to transmit ultra-high resolution 3D images from the inside human body.
  • Figure 1 shows an example of a lens array 2 comprising a number of superlenses 4 arranged in a two-dimensional array.
  • Each superlens 4 is made of at least one metamaterial having a negative refractive index.
  • the superlenses may be based on photonic crystal slabs 6, polymer or metal layered structures 8 such as the PMMA/silver/PMMA structure described below, or other negative index metamaterials, or a combination of different materials.
  • Each lens may be designed by simulating the properties of the lens using finite-difference time-domain (FDTD) methods for example, and tuning the properties of the lens to achieve a desired focal point, wavelength of operation, or optical efficiency for example.
  • FDTD finite-difference time-domain
  • a number of superlenses 4 may form a lens array 10 which may effectively act as a single lens (an imaging device using the lens array 10 may still capture a single image using the overall lens array 10).
  • a single lens platform 10 may include an array of multiple superlenses which may have different properties.
  • a number of superlens array platforms 10 can then be combined to form a microlens array 14, where each microlens of the microlens array 14 corresponds to one or more superlenses.
  • the microlens array may be used to obtain a number of images corresponding to different microlenses, such as different views of an object, e.g. for three-dimensional image displays.
  • each microlens may act as a pinhole to obtain an image of an object within a front field of view and project it to a back field of view.
  • the image produced by each superlens may be a real, non-inverted image.
  • An ultra high resolution imaging sensor 12 may be arranged behind the microlens array 14 to capture images focused by the array.
  • each microlens of the microlens array 14 comprises a lens array 10 comprising multiple superlenses
  • Figure 1 shows an example where each microlens has a convex surface facing the front field of view, it is also possible to provide microlenses with concave or flat surfaces.
  • a microlens array for a given application which previously used convex lenses could be modified to have concave lenses instead to give the desired effect.
  • the precise shape of the lenses depends on the application and the desired focal position of the lens.
  • a negative index metamaterial may be a two-dimensional (2D) structured metamaterial called a split ring resonator which operates at microwave frequencies [3, 4], and has been proved using measurements of scattering data to exhibit negative permittivity and permeability and a negative refractive index, n.
  • 2D two-dimensional
  • n a negative refractive index
  • a multilayer structure may be used which functions as a superlens for improving the resolution of optical lithography [5, 6].
  • a planar structure comprising layers of PMMA/silver/PMMA may be used as the superlens planar structure (see Figure 5).
  • Poly(methyl methacrylate) (PMMA) is a transparent thermoplastic, often used as a lightweight or shatter-resistant alternative to glass which allows the transport of light and image formation. It has been demonstrated that spatial resolution can be achieved by properly selecting the thickness of each layer. Under the 365 nm illumination (i.e. ultraviolet wavelengths), 200 nm spatial resolution can be realized even for 70 nm propagation distance [7].
  • a negative refractive index material has the power to focus all Fourier components of a 2D image, even those that do not propagate in a radiative manner.
  • Such "superlenses" can be realized in different wavelength bands.
  • a version of the lens operating at the frequency of visible light can be realized in the form of a thin slab of silver. This optical lens of 'superlens' can resolve objects in a few nanometres across [2].
  • the operating wavelength for a superlens can be tuned from ultraviolet to visible wavelengths by tuning either the permittivity of the surrounding medium or the permittivity of the metal [8]. Therefore the proposed tunable far-field superlens enables possible applications of the far-field superlens in sub-diffraction-limited imaging and sensing over a wide range of wavelength.
  • photonic crystals may be used to form the superlenses.
  • Two-dimensional photonic crystal slabs for operating at visible wavelengths have been demonstrated by several research groups.
  • the 2D photonic crystal able to operate in this spectral range is of critical importance to applications in spectroscopy, microscopy, imaging and displays etc [10, 11 , 12].
  • the transmission spectra of air-bridged photonic crystal slabs with the incident illumination angle can vary.
  • Figures 2A to 2C and 3A to 3C show a comparison of imaging with a traditional lens and a superlens.
  • a negative refractive index medium (LH) bends light to a negative angle relative to the surface normal.
  • Light formerly diverging from a point source is set in reverse and converges back to a point (see Figure 3A in comparison to Figure 2A). Released from the medium the light reaches a focus for a second time.
  • a superlens prevents image degradation and beats the diffraction limit established by Abbe.
  • the resonant nature of the amplification places severe demands on materials: they are preferably of low loss.
  • the image of the object is a real upright (non-inverted) image.
  • the image is the object.
  • the evanescent waves are re-grown in a negative refractive index slab and fully recovered at the image plane as illustrated in Figure 4.
  • the evanescent wave is a near-field wave with an intensity that exhibits exponential decay as a function of the distance from the boundary at which the wave was formed.
  • conventional lenses cannot capture the evanescent wave.
  • the evanescent wave can be recovered at the image plane so that higher resolution is possible.
  • the prism effect refers to separation of colors by refraction through a prism.
  • the dispersion or variation of refractive index with wavelength, i.e., the derivative (dn/dA) of the refractive index with wavelength is low.
  • dispersion is small, but dn/dA can be made unusually large in photonic crystals, as shown in Figure 6.
  • a graded photonic crystal slab can be used as the superlenses for the array shown in Figure 1.
  • Numerical simulations using finite-difference time-domain (FDTD) methods were performed to quantitatively analyze the relation between the object and image distances. We also analyzed negative refraction of a single Gaussian beam incidence.
  • Graded photonic crystal has the better resolution compared with the ordinary triangular lattice photonic crystal. It is found that by varying the superlensing frequency, we were able to improve the image resolution.
  • the photonic crystal has potential for optical components that can be applied to integrated optics devices [13].
  • a triangular 2D photonic crystal comprising a two- dimensional (in x-y directions) periodic array of cylindrical (in z-direction) air holes embedded in a thick slab of dielectric matrix, with the air holes arranged in a triangular pattern (or hexagonal packed pattern) rather than a square grid pattern, can provide a highly circular constant frequency contour in a relevant band, and as a result an isotropic propagation of the refracted waves occurs.
  • a superlens based on Photonic Crystal (PC) structure may be designed to perform the imaging with ultra-high resolution.
  • a photonic crystal is a periodic array of lossless dielectric materials.
  • Many possible photonic crystal designs and structures can be used to perform the superlens imaging, including 1 D, 2D or 3D photonic crystals. Defects (where some parts of the crystal have different properties to other parts - e.g. refractive index tuning) may be introduced in the photonic crystal structures to design the superlens with low losses that perform the image projection from all desired angles at any desired location.
  • the photonic crystal may comprise air holes arranged in a triangular pattern in a dielectric matrix, or metal cylinders arranged in a periodic array within an air matrix.
  • the arrangement of the objects forming the periodic array in the photonic crystal may be asymmetric or symmetric.
  • the properties may be graded or varying across the crystal so that factors such as the size of the objects or separation of the objects may vary at different points of the crystal. Defects may be introduced to make some points of the crystal have different properties to other points, to ensure a certain behaviour of light propagation (e.g. some air holes may be filled or formed of a different shape, or some particles may be made of a different material).
  • the superlenses based on photonic crystal structure may be arranged in a single platform together to perform image activities for many applications, such as filming, video, mobile, sensing, medical, telescope, microscope... etc, including applications at different scales and distances.
  • the photonic crystal superlenses may be adjusted, aligned and arranged in such a form that when they are put together in a single platform they act as a 'single' lens consisting of many tiny PC superlenses (including superlenses based on silver, other metal, polymer, organic, inorganic, hybrid, graphene, and other possible materials and designs).
  • Each superlens may project or perform a certain part from the object from desired angles and project the image at certain desired position, location, angle, or rotation.
  • Each superlens may capture or project images at a desired wavelength, such as visible, infrared, microwave ultraviolet, x-ray or other wavelengths. It is possible to provide a superlens array with different lenses capturing or projecting images at different wavelength
  • the arrangement of the superlenses in a single platform can be used for image projections, image transfer and any other image manipulations at any desired position/location.
  • the proposed idea of using the superlenses in a single platform will transfer the image to any desired position, which reduces the complexity of current imaging cameras that use several microlens array platforms, one as input relay optics, then image transfer and then output relay optics (Macrolens Array).
  • the two arrays of microlenses forming the image transfer screen are not required because the proposed array can do the same job with much higher performance.
  • the proposed idea will be significantly less complex, resulting in a simple superlenses and platforms of superlenses then currently existing imaging cameras using lenses.
  • current 3D holoscopic Image Cameras have a first array of lenses acting as input relay optics for capturing an image of an object, an image transfer screen for transferring the image to output relay optics, and output relay optics for inverting the image so that an upright image of the object is formed at a film plane.
  • the existing optics can be replaced with a single superlens platform that can provide image projection with much better resolution.
  • the output relay optics and image transfer screen are no longer required because the image generated by the superlens platform is non-inverted.
  • the superlens platform may be the only lens array between the object and an imaging sensor.
  • the system complexity will reduce significantly, and by reducing the number of optical components the cost of manufacturing a 3D imaging device can be greatly reduced. Similar cost reductions can be achieved in other imaging devices which use a microlens array.
  • the metamaterial lens or the superlens will be designed to project an almost perfect image of the object. It can be designed to enhance the near field in order to project perfect image.
  • the superlens can be based on transparent dielectric material that operates at visible light region and it will be used to construct an array of superlenses substituting existing microlens array that form the image transfer screen.
  • the superlens can have various designs depending on the angle of the object and image projections.
  • an array of superlenses can be constructed to obtain fine details (fine details-Pixels) of the object and project them (or construct) a perfect image resulting in a ultra-high resolution that has not been seen before.
  • This can revolutionise applications in Cameras, Microscopes, Mobile Phones, TV, optical lithography and medical and related industry and applications where human beings will be able to see even human blood cells with necked eyes using the cameras that have embedded the above proposed superlenses.
  • the array of superlenses may be combined with existing (non-metamaterial) lenses or microlens arrays to project a high resolution image of the object to various distances. Combination of these superlenses with the current microlens arrays will make significant contribution to the imaging industry.
  • the superlens array obtains the image of the object due to strong enhancement of near field.
  • the commercial lens or microlens array can be used.
  • the conventional lenses made from positive refractive index materials
  • the conventional lenses may be used for the far field, to bring the image close to the region/zone (within the near field) which will cover the superlens array, and then the superlens array may be used for the near field to obtain a high resolution image from any desired distance or location/position.
  • long distance object images can be brought close to a certain distance (x) by using the non-metamaterial array and then from this particular (x) distance the array of superlenses can be used to obtain the image which has been brought close within the superlens's operation region.
  • the objects' image will be transferred using two sets of lenses.
  • the lens array 10 (which can be used as a single lens or as a microlens within a microlens array 14) may include superlenses of different types.
  • different microlenses within a microlens array may be of different types.
  • the superlenses include a first type of superlens (V) operating at visible wavelengths and a second type of superlens (T) operating at thermal (infrared) wavelengths.
  • the two types of superlenses are arranged in an alternating checkerboard pattern (other arrangements are possible). This allows an imaging device to capture both a visible light image and a thermal image using the light focused by the lens array, in a single shot with essentially the same field of view for both images.
  • Other examples may have lenses targeting other regions of the spectrum such as x-rays or ultraviolet light, or may have more than two differnet types of lenses.
  • the array could include different types of lenses which differ in other ways than by wavelength of operation.
  • different lenses may project or capture an image at a different focal point relative to the central position of the lens.
  • the focal position of each superlens may depend on its position within the lens array 10 (e.g. so that superlenses on opposite edges of the lens array 10 have focal positions directed in opposite directions away from the lens so that a wider field of view is possible).
  • different lenses may have different shapes. Also, it will be appreciated that there could be more than two different types of lenses.
  • lens arrays with a square or rectangular lenses arranged in a grid
  • other shapes and arrangements are possible.
  • round or hexagonal superlenses may be used, which may be arranged in a hexagonal close packed arrangement similar to a fly's eye.
  • arrays are shown as two-dimensional in the above examples, it will be appreciated that the lenses may also extend in the depth direction, either due to thickness of the lens or due to the lenses' curvature.
  • Figure 1 1 shows an example in which imaging sensor is integrated with the lens array 10 or microlens array 14 on the same substrate. This provides a single platform for focusing and capturing images.
  • the lens array 10 or microlens array 14 may be mounted on a curved substrate. If an integrated imaging sensor 12 is included, the imaging sensor may also be curved. For example, graphene may be used as the negative index metamaterial, and graphene is flexible so that the lens array can be bent or shaped. A curved lens array is useful for widening the field of view of the device. By forming the lens array 10 or microlens array 14 on a concave surface of the substrate, the angle of view can be increased compared to a flat array. In a similar way to Figure 12, the designs shown in Figures 8 and 10 may also be arranged in a curved or half spherical shape.
  • the curved shape of the lens array 10, 14 may be in two possible designs, one with an integrated sensor 12 and one with the sensor 12 detached and at a certain distance from the lens array 10, 14. Hence, as well as the design shown in Figure 12 it is also possible to provide a curved lens array 10, 14 without the sensor 12.
  • the lens array 10 may be based on a solid silver superlens, or any other dielectric slab with low losses that exhibits left hand or negative refraction.
  • the superlenses may be based on a photonic crystal structure operating at visible wavelength.
  • a nanohole array may act as a single lens which is then used to construct an array of superlens.
  • Defects may be included in the crystal structure to guide the light to different angles, positions and rotations.
  • the photonic crystal can be constructed to refract light at a given angle and operate at a given wavelength.
  • silver, a polymer (e.g. PMMA), an organic or inorganic material, hybrid material, graphene or other type of material can be used.
  • the material may be elastic (flexible) or inelastic.
  • Arrays of superlenses may be placed in a single platform.
  • platforms can be built and each of them can be placed to manipulate the image in any desired configuration, form, location, position, or resolution.
  • These superlens platforms can be arranged one after each other or at any desired angle, location or position (e.g. see Figure 9) in order to bring the image of the object at any desired location/position, depending on the applications. In this way the captured image of the object (which could be very far from the superlens) can be transferred into a desired location, or the image can be brought closer.
  • image 1 could be the first captured with the first superlens platform, but in case if this image is not fulfilling a desired criterion, then the image 1 can be brought to another position/location by using another superlens platform. This process can be repeated as many times as required.
  • Different superlenses and different superlens platforms can be designed, depending on the applications.
  • the arrangements of superlenses in a single platform can be in such a way that superlens platforms can be different depending on the requested applications.
  • Several similar/identical or different superlens platforms can be designed depending on the applications.
  • the single superlenses and superlens platforms can be arranged in parallel or at any other space angle arrangements in order to capture or project the image at any desired position, depending on the applications.
  • the superlenses and their arrangements can be designed at any light region operations, depending on the applications.
  • the superlens can be based in photonic crystal structures exhibiting metamaterial performance, or in any photonic crystals structure, or any slab, or based on any materials and combination of some or all of them in order to design a superlens or superlenses with desired size dimensions and applications requirements at visible light region or any other light regions.
  • These superlenses than can be designed placed in an array of superlenses in different single platforms depending on the applications and region of the light operations/applications.
  • 3D Display Mobile Phones, Laptops, tablet computers, personal computers, television, LCD displays (including examples with overlaid touchscreen for example).
  • the above and other similar devices may have the proposed superlens array embedded on the display surface which may be covered for protection by a transparent solid plate such as glass where 3D images can be displayed.
  • the complete 3D display system can be designed using the proposed superlens arrays.
  • the array may also be used for nanoparticle imaging.
  • the superlens array can depict a clear, high-resolution 3D image of nano-sized objects because each superlens (constructed in an array of superlenses) uses both normal propagating EM radiation, and evanescent waves to construct the 3D image.
  • the technique that we are proposing produces a ultra-high compact optical package that would perform, ultra-high-resolution at any desired wavelength in 1 D, 2D or 3D display.
  • Other applications include telescopes, microscopes, contact lenses, security or surveillance imaging, other medical imaging, etc.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Transforming Light Signals Into Electric Signals (AREA)
  • Stereoscopic And Panoramic Photography (AREA)

Abstract

Un réseau de lentilles (2) comprend un réseau de superlentilles (4) réalisées à partir d'au moins un métamatériau à indice de réfraction négatif, qui permet l'imagerie avec une résolution supérieure et de nouveaux effets optiques. Le réseau (2) peut être utilisé pour une gamme d'applications, telles que l'imagerie en 3D et la rediffusion.
PCT/GB2015/051310 2014-05-06 2015-05-05 Réseau de lentilles et dispositif d'imagerie WO2015170080A1 (fr)

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GB1407922.2A GB2525862A (en) 2014-05-06 2014-05-06 Lens array and imaging device

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CN111837068A (zh) * 2018-03-01 2020-10-27 海思智财控股有限公司 具有多重景深显像的近眼显示方法
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