Color imaging lens, preparation method and imaging system

Abstract

This invention discloses a color imaging lens, its fabrication method, and an imaging system. The color imaging lens includes a transparent rigid / flexible substrate and a complete liquid crystal lens or multiple interconnected liquid crystal lens units disposed on the transparent rigid / flexible substrate. Each liquid crystal lens unit is fabricated separately. The imaging system includes the color imaging lens and an imaging device. This invention is simple to fabricate and can produce small-format or large-format liquid crystal lenses, with a wide range of applications.

Description

Technical Field

[0001] The present invention belongs to the field of optical elements, and in particular relates to a color imaging lens, a preparation method and an imaging system. Background Art

[0002] Large-aperture refractive lenses are expensive, have complex manufacturing processes, and are bulky and heavy.

[0003] However, due to the limitations of the imaging principle, the efficiency of a single lens for wide-band imaging is low. Multiple lenses need to be used in combination to obtain a color image, which makes the system redundant, complex, and increases costs. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a color imaging lens, a preparation method and an imaging system.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] On the one hand, the present invention discloses a color imaging lens, comprising: a transparent rigid / flexible substrate and a complete liquid crystal lens or a plurality of liquid crystal lens units spliced ​​to each other arranged on the transparent rigid / flexible substrate, each liquid crystal lens unit being prepared separately.

[0007] Based on the above technical solution, the following improvements can be made:

[0008] As a preferred solution, the liquid crystal molecules in the color imaging lens are oriented to present a Fresnel ring-shaped distribution; or, the liquid crystal molecules in the color imaging lens can be arranged in an orientation so that the incident light forms a phase wavefront of a spherical wave or an aspherical wave with focusing characteristics.

[0009] As a preferred solution, in the color imaging lens, the average director of the liquid crystal molecules in each ring band gradually changes between 0 and π, and can be a discrete value, corresponding to a double optical phase change.

[0010] As a preferred solution, the size of the color imaging lens is between 0.5 cm and 10 m.

[0011] As a preferred solution, the imaging band of the color imaging lens is the visible light band, the color imaging lens is a wide-band imaging liquid crystal lens, and the complete liquid crystal lens or liquid crystal lens unit includes from top to bottom: a liquid crystal polymer layer, a lower orientation layer and a lower substrate.

[0012] As a preferred solution, the liquid crystal molecules of the wide-band imaging liquid crystal lens are arranged along the optical axis using a double-layer antisymmetric liquid crystal polymer molecular structure to achieve wide-band imaging function. The upper layer is a left-handed cholesteric liquid crystal polymer, and the lower layer is a right-handed cholesteric liquid crystal polymer. The phase modulation amount of the incident light by each layer of liquid crystal polymer molecules is λ / 2, and λ is the central operating wavelength.

[0013] On the other hand, the present invention also discloses a method for preparing a wide-band imaging liquid crystal lens, which is used to prepare a large-format color imaging lens, comprising the following steps:

[0014] Dividing the liquid crystal molecule orientation of the pre-prepared liquid crystal lens into blocks according to different regions;

[0015] place the substrate;

[0016] Spin-coat a photo-alignment agent on the substrate to arrange and orient the blocks according to the design;

[0017] Spin coating a cholesteric liquid crystal polymer doped with right-handed molecules, the thickness of which satisfies Δnd=λ / 2, where Δn is the birefringence difference of the liquid crystal material, d is the thickness of the liquid crystal material, λ is the central working wavelength, and the photo-alignment agent is photocured outside the sensitive wavelength band;

[0018] A cholesteric liquid crystal polymer doped with left-handed molecules is coated on the first layer of liquid crystal polymer, with the same thickness as the first layer, and the liquid crystal is automatically anti-symmetrically oriented, and is photocured outside the sensitive band of the photo-orientation agent, and the twist angle of the single-layer liquid crystal molecules is between 60 degrees and 80 degrees;

[0019] The multiple lens liquid crystal units are spliced ​​on a transparent rigid / flexible substrate according to the design to produce a large-format color imaging lens with an aperture of 0.5cm to 10m.

[0020] On the other hand, the present invention also discloses an imaging system, comprising: any one of the above-mentioned small-format or large-format color imaging lenses or a wide-band imaging liquid crystal lens prepared by the wide-band imaging liquid crystal lens preparation method and an imaging device with a filtering function, wherein the distance between the imaging device and the color imaging lens or the wide-band imaging liquid crystal lens is adjustable.

[0021] As a preferred solution, the imaging device is a switchable red, green and blue narrow-band filter with a monochrome CCD and COMS imaging device. The red narrow-band filter has a band of 600nm to 700nm, the green narrow-band filter has a band of 500nm to 560nm, and the blue narrow-band filter has a band of 400nm to 460nm.

[0022] As a preferred solution, the imaging system adopts time division multiplexing technology. When the imaging device moves to the set monochromatic light imaging focal plane, it only accepts the image formed by this monochromatic light. The imaging device is moved to the color imaging lens or the wide-band imaging liquid crystal lens at different times for the incident light of three wavelengths, and then the images are received at different focal planes. The size and / or intensity of the collected RGB monochrome image are optimized and adjusted to make the three images coordinated and unified. Then, they are combined into one image through image reconstruction, and color imaging is achieved through a single color imaging lens or a wide-band imaging liquid crystal lens.

[0023] The present invention provides a color imaging lens, a preparation method and an imaging system. The color imaging lens can include a complete liquid crystal lens or a plurality of liquid crystal lens units spliced ​​to each other. Each liquid crystal lens unit is prepared separately. The color imaging lens is easy to prepare and can be used to prepare small-format or large-format liquid crystal lenses, which have a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 A regional preparation diagram of a color imaging lens provided in an embodiment of the present invention.

[0026] Figure 2 Phase distribution diagram of liquid crystal polymer in the color imaging lens provided by an embodiment of the present invention.

[0027] Figure 3 This is a diagram of the optical axis distribution of liquid crystal molecules provided by an embodiment of the present invention.

[0028] Figure 4 This is a diagram of the arrangement of liquid crystal molecules in a wide-band color imaging lens provided by an embodiment of the present invention.

[0029] Figure 5 The imaging system provided in the embodiment of the present invention adopts the time division multiplexing technology to achieve achromatic imaging principle.

[0030] Among them: 1-liquid crystal lens unit, 2-color imaging lens, 3-imaging device, 4-first focal plane, 5-first focal plane, 6-first focal plane. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] like Figure 1 and 2As shown, an embodiment of the present invention discloses a color imaging lens including: a transparent rigid / flexible substrate and a complete liquid crystal lens disposed on the transparent rigid / flexible substrate.

[0034] In order to further optimize the implementation effect of the present invention, in some other embodiments, a color imaging lens 2 includes: a transparent rigid / flexible substrate and a plurality of liquid crystal lens units 1 spliced ​​to each other and arranged on the transparent rigid / flexible substrate, and each liquid crystal lens unit 1 is prepared separately.

[0035] By adopting the above preferred implementation scheme, the size of each liquid crystal lens unit 1 is between 100μm and 1m, the stitching error between adjacent liquid crystal lens units 1 is less than 1 micron, and the RMS value of the surface root mean square error of the entire wave surface is less than 1 / 8 wavelength. The color imaging lens 2 is a diffractive liquid crystal lens. Through the splicing technology, the lens liquid crystal units are prepared in blocks and finally spliced ​​to prepare a large-format diffractive liquid crystal lens. Liquid crystal polymers are used to change the phase of the incident polarized light to achieve the effect of positive focal length or negative focal length. Specific liquid crystal molecular orientation is generated by technical means such as optical orientation. The device is simple to prepare and can be transferred to a transparent rigid / flexible substrate, which expands the use occasions. Large-format spliced ​​lenses (diameter of 5cm to 10m) are suitable for space imaging.

[0036] The color imaging lens 2 is a diffractive liquid crystal lens, which works in conjunction with the wave plate and the polarizer. The large-format lens can be prepared separately in multiple parts and then spliced ​​on the substrate without affecting its imaging performance.

[0037] The color imaging lens 2 can be made of liquid crystal polymer (LCP) and can use a transparent flexible substrate, which has the advantages of being flexible, ultra-thin, and colorless. When the liquid crystal diffraction lens using a transparent flexible substrate is used, it can be folded or rolled up to reduce the floor space, and then unfolded when used.

[0038] The large-format lens is divided into different areas and prepared separately. Since the color imaging lens is a planar imaging device, the liquid crystal polymer can be easily aligned and spliced ​​on a transparent flexible substrate. The imaging performance will not be affected and the preparation difficulty and cost are greatly reduced.

[0039] In order to further optimize the implementation effect of the present invention, in some other embodiments, the other characteristic technologies are the same, except that, for any of the above-mentioned color imaging lenses, the orientation of liquid crystal molecules in the color imaging lens presents a Fresnel ring-shaped distribution, and the relationship between the focal length and the wavelength of the incident light is:

[0040]

[0041] r nis the radius from the nth annulus to the center of the circle, n = 1, 2, 3…, f is the focal length, and λ is the incident wavelength.

[0042] By adopting the above-mentioned preferred embodiment, when polarized light is incident, a continuously gradual parabolic phase distribution is added to the outgoing wavefront, thereby making the light beam converge or diverge.

[0043] like Figure 3 As shown, Figure 3 The short and medium lines represent the changes in the optical axis in the color imaging lens. After the photo-orientation agent is oriented by specific polarized light and injected into the liquid crystal, it will orient the liquid crystal molecules to form a Fresnel ring structure. When polarized light is incident, a continuous and gradual parabolic phase distribution is added to the outgoing wavefront, thereby achieving a positive or negative focal length.

[0044] Of course, in other embodiments, the liquid crystal molecules in the color imaging lens can be arranged in an orientation such that the incident light forms a phase wavefront of a spherical wave or an aspherical wave with focusing characteristics.

[0045] In order to further optimize the implementation effect of the present invention, based on the above implementation, in the color imaging lens, the average director of the liquid crystal molecules in each ring band gradually changes between 0 and π, and can be a discrete value, corresponding to a double optical phase change.

[0046] There is a continuous change from 0 to π, and the optical axis of the liquid crystal molecules in the plane changes as follows:

[0047]

[0048] Among them, α is the azimuth angle of the liquid crystal molecule, r represents the distance between the liquid crystal molecule and the center of the liquid crystal lens, f is the focal length set by the color imaging lens, and λ represents the free space wavelength.

[0049] The beneficial effect of adopting the above preferred implementation scheme is that the liquid crystal in the color imaging lens is oriented continuously and gradually, and the directors of the liquid crystal molecules are continuously arranged, which greatly improves the diffraction efficiency of the lens to 95%.

[0050] In order to further optimize the implementation effect of the present invention, in some other implementations, the remaining characteristic technologies are the same, except that the size of the color imaging lens 2 is between 0.5 cm and 10 m.

[0051] It can be prepared into ultra-large format lenses ranging from 0.5 cm to 10 meters.

[0052] In order to further optimize the implementation effect of the present invention, in some other embodiments, the other characteristic technologies are the same, the difference is that the imaging band of the color imaging lens is the visible light band, the color imaging lens is a wide-band imaging liquid crystal lens, and the complete liquid crystal lens or liquid crystal lens unit includes from top to bottom: a liquid crystal polymer layer, a lower orientation layer and a lower substrate.

[0053] In order to further optimize the implementation effect of the present invention, on the basis of the above-mentioned implementation mode, the liquid crystal molecules of the wide-band imaging liquid crystal lens are arranged along the optical axis using a double-layer antisymmetric liquid crystal polymer molecular structure to realize the wide-band imaging function, the upper layer is a left-handed cholesteric liquid crystal polymer, and the lower layer is a right-handed cholesteric liquid crystal polymer. The phase modulation amount of the incident light by each layer of liquid crystal polymer molecules is λ / 2, λ is the central operating wavelength, and the central wavelength is 550nm.

[0054] Adopt the above-mentioned preferred embodiment, such as Figure 4 As shown, the color imaging lens 2 adopts a double-twisted structure and can be applied to wide-band imaging, that is, it is divided into two layers of antisymmetric liquid crystal polymer molecular structure, the upper layer is a left-handed cholesteric liquid crystal polymer, and the lower layer is a right-handed cholesteric liquid crystal polymer. The phase modulation amount of each layer of liquid crystal polymer molecules to the incident light is λ / 2, λ is the central working wavelength, and d is the thickness of a single layer of liquid crystal polymer.

[0055] On the other hand, the present invention also discloses a method for preparing a wide-band imaging liquid crystal lens, which is used to prepare a large-format color imaging lens, comprising the following steps:

[0056] Dividing the liquid crystal molecule orientation of the pre-prepared liquid crystal lens into blocks according to different regions;

[0057] place the substrate;

[0058] Spin-coat a photo-alignment agent on the substrate to arrange and orient the blocks according to the design;

[0059] Spin coating of cholesteric liquid crystal polymer doped with right-handed molecules, the thickness of which satisfies Δnd=λ / 2, where Δn is the birefringence difference of the liquid crystal material, d is the thickness of the liquid crystal material, λ is the central working wavelength, which can be a typical green light wavelength, and the photo-alignment agent is photocured outside the sensitive wavelength band;

[0060] A cholesteric liquid crystal polymer doped with left-handed molecules is coated on the first layer of liquid crystal polymer, with the same thickness as the first layer, and the liquid crystal is automatically anti-symmetrically oriented, and is photocured outside the sensitive band of the photo-orientation agent, and the twist angle of the single-layer liquid crystal molecules is between 60 degrees and 80 degrees;

[0061] The multiple lens liquid crystal units are spliced ​​on a transparent rigid / flexible substrate according to the design to produce a large-format color imaging lens with an aperture of 0.5cm to 10m.

[0062] Taking the photo-alignment preparation method as an example, during the preparation, the photo-alignment agent is first spin-coated on the substrate, and then the orientation is performed, and then the reactive cholesteric liquid crystal polymer doped with right-handed molecules is spin-coated to make it meet the thickness of Wherein Δn is the birefringence difference of the liquid crystal material, d is the thickness of the liquid crystal material, λ is the central operating wavelength, and after the first layer of liquid crystal polymer is UV-cured, a reactive cholesteric liquid crystal polymer doped with left-handed molecules is directly spin-coated on the first layer of liquid crystal polymer, and the thickness is the same as the first layer. The liquid crystal will automatically undergo a twisted orientation and form an antisymmetric structure with the first layer of liquid crystal polymer molecules.

[0063] The color imaging lens can convert incident right-handed circular polarization into focused left-handed circular polarized light, and for left-handed circularly polarized incident light, divergent right-handed circular polarization can be obtained.

[0064] On the other hand, an embodiment of the present invention further discloses an imaging system, which includes: a small-format or large-format color imaging lens 2 as disclosed in any of the above embodiments, or a wide-band imaging liquid crystal lens prepared by a wide-band imaging liquid crystal lens preparation method, and an imaging device 3 with a filtering function, wherein the distance between the imaging device 3 and the color imaging lens or the wide-band imaging liquid crystal lens is adjustable.

[0065] The imaging device 3 is a switchable red, green and blue narrow-band filter with a monochrome CCD and COMS imaging device. The red narrow-band filter has a wavelength of 600nm to 700nm, the green narrow-band filter has a wavelength of 500nm to 560nm, and the blue narrow-band filter has a wavelength of 400nm to 460nm.

[0066] The filter may be, but is not limited to, a switchable structure such as a rotating wheel, and may be placed on the surface of the photosensitive device or at a certain position between the photosensitive device and the lens.

[0067] The imaging system adopts time division multiplexing technology. When the imaging device moves to the set monochromatic light imaging focal plane, it only accepts the image formed by this monochromatic light. The imaging device is moved to the color imaging lens or the wide-band imaging liquid crystal lens at different times for the incident light of three wavelengths, and then the images are received at different focal planes. The size and / or intensity of the collected RGB monochrome images are optimized and adjusted to make the three images coordinated and unified. Then, they are combined into one image through image reconstruction, and color imaging is achieved through a single color imaging lens or a wide-band imaging liquid crystal lens.

[0068] The above preferred implementation scheme has the beneficial effect that the imaging device used has a filtering function, and the imaging device includes red, green and blue filters. When it moves to the focal plane, it only accepts the image formed by monochromatic light. The imaging system adopts time division multiplexing technology, and moves the imaging device to different focal planes behind the lens at different times for the incident light of three wavelengths of red, green and blue, and then receives the image formed by them, and then reconstructs the image to combine them into one image, so that color imaging can be achieved through a single lens.

[0069] like Figure 5 As shown, the imaging device 3 can move on the optical axis, sequentially receive the monochromatic images at the first focal plane 4, the second focal plane 5 and the third focal plane 6, and finally combine them into one image to achieve the purpose of achromatization. The first focal plane 4 is the focal plane position of the red light imaging with a wavelength of 660nm at infinity; the second focal plane 5 is the focal plane position of the green light imaging with a wavelength of 550nm at infinity; the third focal plane 6 is the focal plane position of the blue light imaging with a wavelength of 450nm at infinity.

[0070] It is worth noting that the liquid crystal orientation of the color imaging lens disclosed in any of the above embodiments can be achieved by orienting the liquid crystal polymer through rubbing orientation, photo orientation, oblique evaporation, atomic force probe relief orientation, etc.

[0071] The present invention provides a color imaging lens, a preparation method and an imaging system. The color imaging lens can include a complete liquid crystal lens or a plurality of liquid crystal lens units spliced ​​to each other. Each liquid crystal lens unit is prepared separately. The color imaging lens is easy to prepare and can be used to prepare small-format or large-format liquid crystal lenses, which have a wide range of applications.

[0072] In order to better understand the present invention, a specific embodiment is introduced below:

[0073] A color imaging lens with an aperture of 50 cm and a focal length of 50 cm for a wavelength of 550 nm can be prepared by dividing it into 50*50 regions with a single area of ​​1 cm*1 cm. The liquid crystal polymer in each region is oriented by a photo-orientation method, and then spliced ​​on a transparent optical tape to achieve a planar imaging lens with a thickness of about 50 μm. The focal length of this lens for a wavelength of 660 nm is 41.67 cm, and the focal length for a wavelength of 450 nm is 61.11 cm. The imaging device can move along the optical axis to collect images at the imaging focal planes of 660 nm, 550 nm, and 450 nm, respectively, and then reconstruct the images and combine them into one image to achieve color imaging through a single lens.

[0074] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable ordinary technicians in the field to understand the content of the present invention and implement it. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a wide-band imaging liquid crystal lens, which is used to prepare a color imaging lens, wherein the color imaging lens comprises: A transparent rigid / flexible substrate and a plurality of mutually spliced ​​liquid crystal lens units disposed on the transparent rigid / flexible substrate, wherein each of the liquid crystal lens units is prepared separately; The imaging band of the color imaging lens is the visible light band. The liquid crystal lens unit includes, from top to bottom, a liquid crystal polymer layer, a lower alignment layer, and a lower substrate. The liquid crystal molecules of the wide-band imaging liquid crystal lens are arranged along the optical axis using a double-layer antisymmetric liquid crystal polymer molecular structure to achieve a wide-band imaging function. The upper layer is a left-handed cholesteric liquid crystal polymer, and the lower layer is a right-handed cholesteric liquid crystal polymer. The phase modulation amount of each layer of liquid crystal polymer molecules to the incident light is λ / 2, and λ is the central working wavelength. The method for preparing the wide-band imaging liquid crystal lens comprises the following steps: The liquid crystal molecules of the pre-prepared liquid crystal lens are oriented in different areas according to the Fresnel ring distribution or the orientation arrangement that can form a phase wave front of a spherical wave or an aspherical wave with focusing characteristics for the incident light; place the substrate; Spin-coat a photo-alignment agent on the substrate to arrange and orient the blocks according to the design; Spin coating a cholesteric liquid crystal polymer doped with right-handed molecules, the thickness of which satisfies Δnd=λ / 2, where Δn is the birefringence difference of the liquid crystal material, d is the thickness of the liquid crystal material, λ is the central working wavelength, and the photo-alignment agent is photocured outside the sensitive wavelength band; A cholesteric liquid crystal polymer doped with left-handed molecules is coated on the first layer of liquid crystal polymer, with the same thickness as the first layer, and the liquid crystal is automatically anti-symmetrically oriented, and is photocured outside the sensitive band of the photo-orientation agent, and the twist angle of the single-layer liquid crystal molecules is between 60 degrees and 80 degrees; The multiple lens liquid crystal units are spliced ​​on a transparent rigid / flexible substrate according to the design to produce a large-format color imaging lens with an aperture of 0.5cm to 10m.

2. The method for preparing a wide-band imaging liquid crystal lens according to claim 1, characterized in that: In the color imaging lens, the average director of the liquid crystal molecules in each ring band gradually changes between 0 and π, which is a discrete value, corresponding to a double optical phase change.

3. An imaging system, characterized in that include: A color imaging lens and an imaging device with a filtering function prepared by the method for preparing a wide-band imaging liquid crystal lens according to claim 1 or 2, wherein the distance between the imaging device and the color imaging lens is adjustable.

4. The imaging system according to claim 3, characterized in that The imaging device is a switchable red, green and blue narrow-band filter with a monochrome CCD and COMS imaging device. The red narrow-band filter has a wavelength of 600nm to 700nm, the green narrow-band filter has a wavelength of 500nm to 560nm, and the blue narrow-band filter has a wavelength of 400nm to 460nm.

5. The imaging system according to claim 4, characterized in that: The imaging system adopts time division multiplexing technology. When the imaging device moves to the set monochromatic light imaging focal plane, it only accepts the image formed by this monochromatic light. After the imaging device is moved to the color imaging lens or the wide-band imaging liquid crystal lens at different times for incident light of three wavelengths, the images are received at different focal planes. The size and / or intensity of the collected RGB monochromatic image are optimized and adjusted to make the three images coordinated and unified. Then, the three images are combined into one image through image reconstruction, and color imaging is realized through the single color imaging lens or the wide-band imaging liquid crystal lens.

Images