Dynamic polarization stereo imaging system

Abstract

The invention provides a dynamic polarization three-dimensional imaging system, which relates to the technical field of anti-counterfeiting encryption and comprises a light source, a polarization film and a color three-dimensional imaging module which are sequentially arranged along a light path, the light source is used for providing visible band incident light; the polarizing film is configured to transmit TM polarized light when rotating 0 degree and transmit TE polarized light when rotating 90 degrees; the color three-dimensional imaging module comprises a micro lens array, a transparent spacing layer and a micro image-text array which are sequentially arranged along a light path; the micro image-text array comprises a metal coating layer, a grating layer and a glass substrate which are stacked from top to bottom, wherein the grating layer forms a Fabry-Perot-like microcavity resonance structure; the polarization state of the incident light is switched by rotating the polarization film, so that the stereo image of the micro image-text array is dynamically switched among an appearing state, a hiding state or a color changing state. According to the invention, wide-color-gamut and dynamically-adjustable color stereo imaging is realized, and the complexity and the identifiability of anti-counterfeiting encryption are improved.

Description

Technical Field

[0001] The present invention relates to the field of anti-counterfeiting and encryption technology, and in particular to a dynamic polarization stereoscopic imaging system. Background Art

[0002] Traditional printing technology usually presents fixed colors and images on a flat surface. The same image is observed from all angles and cannot provide depth information. Although combining microlens arrays with micro-images can control the phase of light to achieve three-dimensional imaging, and the microlens preparation process is mature and can be used in the field of anti-counterfeiting and encryption, the existing technology still has many shortcomings.

[0003] Among the current public anti-counterfeiting technologies, anti-counterfeiting technologies based on diffraction photovariable images, such as holographic image technology, security thread technology, and nuclear micropore anti-counterfeiting technology, are widely used. Among them, holographic image three-dimensional anti-counterfeiting technology is the most commonly used. However, with its widespread application in banknotes, trademarks, packaging and other fields, technical details are easy to reproduce and imitate, and it is gradually losing its advantages.

[0004] Existing technologies combining microlens arrays with micrographic arrays for security applications, such as those proposed in U.S. Patents US5712731, US2005 / 0180020A1, and US2008 / 0037131A1, utilize gravure printing to create a micrographic array with a minimum resolution of 5 microns. Photoresist is applied to a flexible film such as PET, and recesses are embossed with a relief plate bearing the micrographic. These recesses are then filled with ink to create the corresponding color. This method achieves image color by filling the micrographic with colored ink, resulting in a monochromatic micrographic and preventing color imaging. Chinese invention patent CN101850680A discloses a film with a dynamic 3D effect. While this achieves dynamic 3D imaging by aligning microlenses within the microlens array layer with micrographics within the micrographic layer, it requires strong light sources for supplemental illumination and cannot meet anti-counterfeiting requirements under natural light. The reflective optical imaging film proposed in Chinese invention patent CN113820872A avoids crosstalk through reflective imaging and expanded field of view, and the grating micro-pattern can make the moiré image colorful, solving the problems of ink color uniformity and pollution. However, it only extends to the realization of color three-dimensional imaging and does not propose polarization-based anti-counterfeiting encryption methods.

[0005] Therefore, in order to realize a new generation of anti-counterfeiting and encryption technology that is colorful, environmentally friendly, easy to identify, and has dynamic polarization response, a new technical solution is needed. The dynamic polarization stereoscopic imaging system proposed in this application involves the moiré magnification phenomenon. When the microlens array is combined with the micro-image array, the micro-image can be imaged in color stereoscopic form, and combined with dynamic polarization adjustment technology, it can be well used in the fields of anti-counterfeiting and encryption. Summary of the Invention

[0006] To this end, the embodiment of the present application provides a dynamic polarization stereoscopic imaging system for solving the problems of single color, dependence on strong light source, lack of dynamic polarization control means and insufficient stereoscopic imaging effect in the prior art.

[0007] To solve the above problems, the embodiment of the present application provides a dynamic polarization stereoscopic imaging system, comprising a light source, a polarization film and a color stereoscopic imaging module arranged in sequence along an optical path.

[0008] The light source is configured to provide visible band incident light.

[0009] The polarization film is a rotatable single-layer metal polarization film or a double-layer metal polarization film, configured to transmit TM polarized light when rotated by 0° and transmit TE polarized light when rotated by 90°.

[0010] The color stereoscopic imaging module comprises a microlens array, a transparent spacer layer and a micro-pattern array arranged in sequence along an optical path.

[0011] The micro-pattern array comprises a metal coating layer, a grating layer and a glass substrate stacked from top to bottom, wherein the grating layer constitutes a Fabry-Perot microcavity resonance structure.

[0012] The polarization state of the incident light is switched by rotating the polarization film, so that the stereoscopic image of the micro-pattern array is dynamically switched between the appearance, hiding or color changing states.

[0013] Preferably, the single-layer metal polarization film is composed of a substrate and a single-layer metal grating.

[0014] Preferably, the double-layer metal polarization film is composed of two layers of metal films covering the periodic grating structure.

[0015] Preferably, the resonance wavelength λ of the microcavity resonance structure satisfies:

[0016]

[0017] In the formula, n eff is the effective refractive index of the grating layer, closely related to the period Λ of the grating, d is the thickness of the grating layer, and m is a positive integer.

[0018] Preferably, the microlens array is arranged on one side surface of the transparent spacer layer and is composed of periodically arranged microlens units, and the micro-pattern array is arranged on the other side surface of the transparent spacer layer and is composed of micro-pattern units, the micro-pattern units comprising a plurality of grating structures.

[0019] Preferably, the microlens units of the microlens array and the micro-pattern units of the micro-pattern array correspond one-to-one or one-to-many, and the micro-pattern array is located on the focal plane of the microlens array.

[0020] Each pixel of the micro-pattern array is distributed in free space through the microlens array to restore the light field, which is equivalent to the observer observing the three-dimensional imaging reconstructed by the micro-pattern array, and the observer observes the field of view angle Omega of the reconstructed three-dimensional imaging without crosstalk, which satisfies:

[0021]

[0022] Wherein, P0 is the center distance of the microlens array, and g is the thickness of the transparent spacer layer.

[0023] Preferably, the magnification M of the three-dimensional imaging satisfies:

[0024]

[0025] In the formula, T r is the period of the microlens array, T b is the period of the micro-pattern array, and theta is the relative angle between the microlens array and the micro-pattern array.

[0026] Preferably, the grating structure of the micro-pattern unit is at least one of one-dimensional grating, two-dimensional asymmetric grating or two-dimensional symmetric grating.

[0027] Preferably, the two-dimensional asymmetric grating is a rectangular, elliptical, cross-shaped or elliptical ring structure.

[0028] Preferably, the two-dimensional symmetric grating is a square, circular, cross-shaped or circular ring structure.

[0029] From the above technical solutions, the present application has the following beneficial effects:

[0030] The present application provides a dynamic polarization three-dimensional imaging system, which combines a rotatable single-layer or double-layer metal polarization film with a micro-pattern array of a Fabry-Perot micro-cavity resonance structure, switches TM / TE polarized light incidence by rotating the polarization film, simultaneously utilizes the different response characteristics of one-dimensional grating, two-dimensional symmetric and asymmetric grating in the micro-pattern array to realize dynamic switching and color modulation of the three-dimensional image; and through the focal plane setting of the microlens array and the transparent spacer layer, the field of view angle and the magnification are regulated by a specific formula, the light field is restored to realize three-dimensional imaging. The present application breaks through the limitations of single color of anti-counterfeiting image and dependence on strong light source in the prior art, utilizes broadband filtering and dynamic polarization adjustment of the polarization film, combines wavelength selectivity of the micro-cavity resonance structure to realize wide color gamut color three-dimensional imaging, and through multi-dimensional combination of polarization state and grating structure, forms dynamic encryption dimension to improve the anti-counterfeiting ability of the anti-counterfeiting technology, and meets the new generation anti-counterfeiting encryption demand of easy identification under natural light and environment-friendly. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly described below. The features and advantages of the present application can be more clearly understood by referring to the drawings, which are schematic and should not be construed as any limitation to the present application. Those skilled in the art can obtain other drawings according to these drawings without any creative effort. Among them:

[0032] Figure 1 A schematic diagram of a dynamic polarization stereoscopic imaging system according to the present application;

[0033] Figure 2 A sectional view of a color stereoscopic imaging module according to the present application;

[0034] Figure 3 A schematic diagram of a grating structure according to the present application, wherein Figure 3 (a) is a schematic diagram of a one-dimensional grating constituting a micro-pattern, Figure 3 (b) is a schematic diagram of a two-dimensional symmetric square grating constituting a micro-pattern; Figure 3 (c) is a schematic diagram of a two-dimensional asymmetric elliptical grating constituting a micro-pattern;

[0035] Figure 4 A schematic diagram of the principle of a dynamic polarization stereoscopic imaging system according to the present application;

[0036] Figure 5 A schematic diagram of Embodiment One of the present application, wherein Figure 5 (a) is a schematic diagram of the arrangement of a one-dimensional grating and a two-dimensional symmetric square grating in a micro-pattern unit, Figure 5 (b) is a schematic diagram of the principle of polarization imaging;

[0037] Figure 6 A schematic diagram of Embodiment Two of the present application, wherein Figure 6 (a) is a schematic diagram of the arrangement of a one-dimensional grating and a two-dimensional symmetric square grating in a micro-pattern unit, Figure 6 (b) is a schematic diagram of the principle of polarization imaging;

[0038] Figure 7 A schematic diagram of Embodiment Three of the present application, wherein Figure 7 (a) is a schematic diagram of the arrangement of a one-dimensional grating in a micro-pattern unit, Figure 7 (b) is a schematic diagram of the principle of polarization imaging;

[0039] Figure 8 A schematic diagram of Embodiment Four of the present application, wherein Figure 8 (a) is a schematic diagram of the arrangement of a one-dimensional grating in a micro-pattern unit, Figure 8 (b) is a schematic diagram of the principle of polarization imaging;

[0040] Figure 9 Figure 5 is a schematic diagram of an embodiment of the present application. Figure 9 (a) is a schematic diagram of the arrangement of two-dimensional asymmetric elliptical gratings and two-dimensional symmetric square gratings in a micrograph unit, Figure 9 (b) is a schematic diagram of the principle of polarization imaging.

[0041] Figure 1 is a schematic diagram of an embodiment of the present application. DETAILED DESCRIPTION

[0042] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0043] In order to solve the problems of single color, dependence on strong light source, lack of dynamic polarization control means and insufficient stereoscopic imaging effect of the anti-counterfeiting technology in the prior art, as shown in Figure 1 the present application proposes a dynamic polarization stereoscopic imaging system, which comprises a light source 1, a polarization film 2 and a color stereoscopic imaging module 3 arranged in sequence along an optical path.

[0044] The light source 1 is used to provide incident light in a visible band.

[0045] The polarization film 2 is a rotatable single-layer metal polarization film or a double-layer metal polarization film, which is configured to transmit TM polarized light when rotated by 0° and transmit TE polarized light when rotated by 90°.

[0046] The color stereoscopic imaging module 3 comprises a microlens array 6, a transparent spacer layer 7 and a micrograph array arranged in sequence along an optical path.

[0047] The micrograph array comprises a metal coating layer 8, a grating layer 9 and a glass substrate 10 stacked from top to bottom, wherein the grating layer 9 constitutes a Fabry-Perot microcavity resonance structure.

[0048] By rotating the polarization film 2, the polarization state of the incident light is switched, so that the stereoscopic image of the micrograph array is dynamically switched between the appearing, hiding or color changing states.

[0049] From the above technical scheme can be known, the application proposes a kind of dynamic polarization stereoscopic imaging system, its core structure includes in turn along optical path direction: light source, polarization film, microlens array, transparent spacer layer and microtext array.It is realized that dynamic switching (appearance, hide or discoloration) of stereoscopic image by rotating polarization film to adjust incident light polarization state, in combination with the optical modulation of microlens array and microtext array.The application not only can achieve the purpose of security and anti-fake, but also can be used in encryption field.

[0050] Further, the light source 1 of the application is used to provide visible band incident light, which can be natural light or artificial light source.

[0051] Further, the polarization film 2 of the application is arranged behind the light source 1, the polarization film 2 is rotatable single-layer metal polarization film or double-layer metal polarization film, which is configured to transmit TM polarized light when rotating 0° and transmit TE polarized light when rotating 90°, wherein the single-layer metal polarization film is composed of a substrate and a single-layer metal grating, and the double-layer metal polarization film is composed of two layers of metal film covering on the periodic grating structure. The polarization film 2 can make the specific polarization state of wide-band visible light pass through, and has a wide-band polarization filtering effect: only allowing TM polarized light to pass through; if the polarization film 2 is rotated by 90°, only TE polarized light is allowed to pass through. Rotating the polarization film 2 can switch the microtext 11 between "appearance-hidden".

[0052] The partial sectional view of the color stereoscopic imaging module 3 is shown in Figure 2 , which includes a microlens array 6, a transparent spacer layer 7 and a microtext array arranged in turn along the optical path, wherein the microtext array includes a metal coating layer 8, a grating layer 9 and a glass substrate 10 stacked from top to bottom.

[0053] It should be noted here that the "grating layer 9" in the application needs to meet the following characteristics:

[0054] (1) has optical anisotropy, which can produce differential response to the polarization state (TE / TM) of incident light;

[0055] (2) together with the metal coating layer 8 to form a Fabry-Perot resonant cavity, and the resonant wavelength is controlled by the structural parameters to realize the color display function.

[0056] In a typical embodiment, the grating layer 9 adopts grating structure (such as one-dimensional / two-dimensional grating), but the protection scope is not limited thereto, and any microstructure that can simultaneously realize polarization selectivity and wavelength selectivity color display belongs to the patent claim.

[0057] Specifically, the material of the metal coating layer 8 is a high refractive index metal (such as aluminum, silver), and the thickness is 40-80 nm; the grating layer 9 is prepared by photoresist exposure and development, and the period is 280-600 nm, and the duty cycle is 0.4-0.6; and the glass substrate 10 is silicon dioxide.

[0058] Further, the microlens array 6 is arranged on one side surface of the transparent spacer layer 7 and is composed of periodically arranged microlens units, and the microtext array is arranged on the other side surface of the transparent spacer layer 7 and is composed of microtext units, and the microtext unit includes a plurality of grating structures (such as the first grating structure 4 and the second grating structure 5 in FIG. 1). Figure 1 By setting the period size of the grating structure in the microtext unit, different color texts can be obtained under irradiation of light in different polarization states, and after magnification by the microlens array 6, a stereoscopic effect is obtained. The grating structure of the microtext unit is at least one of a one-dimensional grating, a two-dimensional asymmetric grating or a two-dimensional symmetric grating, and the schematic diagrams are shown in FIGS. 3(a), 3(b) and 3(c), respectively. Figure 3

[0059] It should be noted here that the two-dimensional asymmetric grating can be a rectangular, elliptical, cross-shaped or elliptical ring structure. The two-dimensional symmetric grating can be a square, circular, cross-shaped or circular ring structure. The two-dimensional symmetric grating has isotropic characteristics in geometry and has similar modulation capabilities for orthogonal polarization components (TE polarization and TM polarization) of incident light, so it exhibits polarization insensitivity. For a one-dimensional grating or a two-dimensional asymmetric grating, the periodicity of the one-dimensional grating only exists in a single direction, resulting in a significant difference in response to TE polarization and TM polarization; the two-dimensional asymmetric grating causes different polarization components of incident light to experience different propagation paths or phase modulations in the structure. This results in the microtext unit of the one-dimensional grating structure and the two-dimensional asymmetric grating also showing microtext 11 under TM polarization incidence, and almost showing black under TE polarization incidence. Therefore, by rotating the polarizing film 2, the corresponding microtext unit shows different color stereoscopic images.

[0060] The principle schematic diagram of the dynamic polarization stereoscopic imaging system of the application is shown in FIG. 4. Figure 4 The first grating structure 4 and the second grating structure 5 are located on the left and right sides of the focal plane of the microlens array 6, and after passing through the microlens array 6, the images are located at V2 and V1 in free space, respectively; which is equivalent to reconstructing the light field information of the microtext pixel, and the observer will observe a stereoscopic image.

[0061] ​Further, the microlens units of the microlens array 6 correspond to the microtext units of the microtext array one by one or one to many, and the microtext array is located at the focal plane of the microlens array 6. Each pixel of the microtext array is distributed in free space through the microlens array 6 to restore the light field, and the observer observes the reconstructed stereoscopic image of the microtext array, and the observer observes the reconstructed stereoscopic image without crosstalk. The field of view angle Ω satisfies: where P0 is the center distance of the microlens array 6, and g is the thickness of the transparent spacing layer 7. It should be noted that the pixel modulated into parallel light of a certain direction by the microlens array 6 is observed as a pixel by the human eye, which is equivalent to the microtext array being imaged at infinity by the microlens array 6. Therefore, the depth of the stereoscopic image through the structure can be considered as infinity.

[0062] Further, the magnification M(r, θ) of the stereoscopic image is derived from the period difference and the relative angle of the microlens array 6 and the microtext array. Wherein the period of the microlens array 6 is T r , the period of the microtext array is T b , θ is the relative angle between the two, so the magnification of the image is:

[0063]

[0064] Further, the grating layer 9 of the microtext array constitutes a Fabry-Perot microcavity resonance structure, and the resonance wavelength of the microcavity resonance structure is determined by the thickness, grating period, duty cycle, height and thickness of the metal coating layer 8 of the grating layer 9. In turn, the color of the microtext array is determined.

[0065] Specifically, the resonance wavelength λ of the microcavity resonance structure satisfies:

[0066]

[0067] Wherein

[0068]

[0069] In the formula, n eff is the effective refractive index of the grating layer 9, d is the thickness of the grating layer 9, m is the diffraction order, Λ is the grating period, λ1 is the incident wavelength, and θ is the diffraction angle.

[0070] As can be seen from the above, by adjusting Λ and d, a specific resonance wavelength can be selected.

[0071] It should be noted that the grating periods constituting the Fabry-Perot microcavity resonance structure produce microtext 11 of different colors to achieve color stereoscopic imaging.

[0072] Further, the present application makes the stereoscopic image of the micro-pattern array appear by controlling the resonance wavelength of the micro-pattern array and matching the wavelength of the TM polarized light passing through the polarizing film 2, and makes the stereoscopic image of the micro-pattern array disappear after rotating the polarizing film 2, so as to realize the switching of the micro-pattern 11 between “appearance” and “disappearance”.

[0073] Further, the present application makes the stereoscopic image of the micro-pattern array appear by controlling the resonance wavelength of the micro-pattern array and matching the wavelength of the TM polarized light passing through the polarizing film 2, and makes the stereoscopic image of the micro-pattern array disappear after rotating the polarizing film 2, so as to realize the switching of the micro-pattern 11 between “appearance” and “disappearance”.

[0074] The working process of the dynamic polarization stereoscopic imaging system of the present application is as follows:

[0075] (1) The light source 1 emits natural light, and the natural light forms TM polarized light (rotated by 0°) or TE polarized light (rotated by 90°) after being filtered by the polarizing film 2.

[0076] (2) The polarized light is focused by the microlens array 6 and projected to the micro-pattern array through the transparent spacer layer 7.

[0077] (3) The grating layer 9 of the micro-pattern array constitutes a Fabry-Perot microcavity resonance structure, and selectively reflects / transmits light through resonance wavelength.

[0078] (4) The reflected light is reconstructed into a light field by the microlens array 6, and a dynamic color stereoscopic image is formed, and the observer sees the “appearance-disappearance” or “color change” effect.

[0079] The technical solutions and effects of the present application will be described below in combination with specific examples.

[0080] Example 1

[0081] The present embodiment provides a dynamic polarization stereoscopic imaging system, which comprises a light source 1, a polarizing film 2, a microlens array 6, a transparent spacer layer 7 and a micro-pattern array, wherein the micro-pattern array comprises a metal coating layer 8, a grating layer 9 and a glass substrate 10. The metal coating layer 8 is aluminum, and the thickness is 60 nm. The grating layer 9 has a period of 360 nm and 480 nm, and a duty cycle of 0.5.

[0082] Figure 5 (a) is a schematic diagram of the arrangement mode of the one-dimensional grating and the two-dimensional symmetrical square grating in the micro-pattern unit, and the micro-pattern 11 is arranged according to “A” and “B” in (a). Figure 5 (a) is a schematic diagram of the arrangement mode of the one-dimensional grating and the two-dimensional symmetrical square grating in the micro-pattern unit, and the micro-pattern 11 is arranged according to “A” and “B” in (a). Figure 5As shown in (b). Because the two gratings have different periods, the image of micro-image "A" appears red under natural light, and the image of micro-image "B" appears green. When TM polarized light is incident, after being reflected by the micro-image array and passing through the microlens array 6, the image of micro-image "A" appears red, and the image of micro-image "B" appears green. When TE polarized light is incident, micro-image "A" is not imaged due to the polarization sensitivity of the one-dimensional grating, while the two-dimensional symmetrical square grating is polarization-insensitive, so the image of micro-image "B" appears green. The polarization film 2 provides broadband filtering, capable of achieving multiple colors and possessing a wide color gamut.

[0083] Example 2

[0084] The difference between this embodiment and the first embodiment is that the period of the one-dimensional grating and the two-dimensional symmetrical square grating is the same, both of which are 360 ​​nm. Other aspects are the same as the first embodiment.

[0085] Figure 6 (a) is a schematic diagram of the arrangement of one-dimensional grating and two-dimensional symmetrical square grating in the micro-graphic unit. Micro-graphic 11 is based on Figure 6 In the arrangement of (a), the two gratings "A" and "B" have the same period, so the images of the micro-images "A" and "B" appear green under natural light. Figure 6 (b) When TM polarized light is incident, the images of micro-images "A" and "B" appear green after the micro-images are reflected by the microlens array 6. When TE polarized light is incident, the one-dimensional grating is polarization-sensitive and therefore does not form an image, while the two-dimensional symmetrical square grating forms an image normally, resulting in a green image of micro-image "B." By rotating the polarizing film 2 to change the polarization state of the incident light, different image effects can be achieved, demonstrating the ability to dynamically control polarization.

[0086] Example 3

[0087] The difference between this embodiment and the first embodiment is that the micro-image 11 is composed of orthogonally arranged one-dimensional gratings with a period of 300 nm. Other aspects are the same as the first embodiment.

[0088] Figure 7 (a) is a schematic diagram of the arrangement of one-dimensional gratings in the micro-graphic unit. Figure 7 The arrangement of "A" and "B" in (a) is as follows: Figure 7 (b) Because the one-dimensional gratings have the same period, the images of micro-textures "A" and "B" appear blue under natural light. When incident with TM polarized light, the image of micro-texture "A" appears blue after reflection from the micro-textures through the microlens array 6. When incident with TE polarized light, only the image of micro-texture "B" appears blue. By rotating the polarizing film 2 for broadband filtering, color 3D imaging with dynamic polarization control can be achieved.

[0089] Example 4

[0090] The difference between this embodiment and the third embodiment is that the one-dimensional grating periods are 360 ​​nm and 480 nm respectively. Other aspects are the same as those of the third embodiment.

[0091] Figure 8 (a) is a schematic diagram of the arrangement of one-dimensional gratings in the micro-graphic unit. Figure 8 The arrangement of "A" and "B" in (a) is as follows: Figure 8 (b) Because the gratings have different periods, the image of micro-image "A" appears green, while the image of micro-image "B" appears red. When TM polarized light is incident, micro-image "A" appears only green after the micro-image is reflected by the microlens array 6; when TE polarized light is incident, micro-image "B" appears only red. By rotating the polarizing film 2 to change the polarization state of the incident light, different graphic effects can be achieved, demonstrating dynamic polarization control. Furthermore, the polarizing film 2 provides broadband filtering, enabling a wide range of colors and a wide color gamut.

[0092] Example 5

[0093] The difference between this embodiment and the first embodiment is that the micro-image 11 is composed of a two-dimensional symmetrical square grating and a two-dimensional asymmetrical elliptical grating, with periods of 360nm and 480nm respectively.

[0094] Figure 9 (a) is a schematic diagram of a two-dimensional asymmetric elliptical grating and a two-dimensional symmetric square grating in a micro-graphic unit. Figure 9 The arrangement of "A" and "B" in (a) is as follows: Figure 9 As shown in (b). Because the gratings have different periods, the image of micro-image "A" appears red, and the image of micro-image "B" appears blue. When TM polarized light is incident, after the micro-image is reflected by the micro-image and passes through the microlens array 6, the image of micro-image "A" appears red, and the image of micro-image "B" appears blue. When TE polarized light is incident, the two-dimensional asymmetric elliptical grating is polarization-sensitive, so micro-image "A" is not imaged, while the two-dimensional symmetric square grating is polarization-insensitive, so the image of micro-image "B" appears blue. Two-dimensional gratings with different morphologies achieve different graphic effects because rotating the polarization film 2 changes the polarization state of the incident light, demonstrating the ability to dynamically control polarization. Furthermore, when combined with the microlens array 6 and the polarization film 2, they can achieve color stereoscopic imaging.

[0095] Obviously, the above embodiments are merely example for clearly illustrating, and are not limitation to the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and can not be exhausted. The obvious changes or variations derived therefrom are still within the scope of the present invention.

Claims

1. A dynamic polarization stereoscopic imaging system, characterized in that: It includes a light source, a polarizing film, and a color stereoscopic imaging module arranged in sequence along the light path; The light source is used to provide incident light in the visible band; The polarizing film is a rotatable single-layer metal polarizing film or a double-layer metal polarizing film, configured to transmit TM polarized light when rotated 0° and transmit TE polarized light when rotated 90°; The color stereoscopic imaging module includes a micro lens array, a transparent spacer layer and a micro image array arranged in sequence along the optical path; The micro-image array comprises a metal coating layer, a grating layer and a glass substrate stacked from top to bottom, wherein the grating layer forms a Fabry-Perot microcavity-like resonant structure; The polarization state of the incident light is switched by rotating the polarizing film, so that the three-dimensional image of the micro-image array is dynamically switched between the visible, hidden or color-changing states.

2. The dynamic polarization stereoscopic imaging system according to claim 1, wherein: The single-layer metal polarizing film consists of a substrate and a single-layer metal grating.

3. The dynamic polarization stereoscopic imaging system according to claim 1, wherein: The double-layer metal polarizing film is composed of two layers of metal films covering a periodic grating structure.

4. The dynamic polarization stereoscopic imaging system according to claim 1, wherein: The resonant wavelength λ of the microcavity resonant structure satisfies: Where n eff is the effective refractive index of the grating layer, which is closely related to the period Λ of the grating, d is the thickness of the grating layer, and m is a positive integer.

5. The dynamic polarization stereoscopic imaging system according to claim 1, wherein: The microlens array is arranged on one side surface of the transparent spacer layer and is composed of periodically arranged microlens units. The micro-graphic array is arranged on the other side surface of the transparent spacer layer and is composed of micro-graphic units. The micro-graphic units include multiple grating structures.

6. The dynamic polarization stereoscopic imaging system according to claim 5, characterized in that: The microlens units of the microlens array correspond one-to-one or one-to-many to the micro-image and text units of the micro-image and text array, and the micro-image and text array is located in the focal plane of the microlens array; Each pixel of the micro-image array is distributed in free space by the micro-lens array to restore the light field. For the observer, it is equivalent to observing the stereoscopic image reconstructed by the micro-image array. The field angle Ω of the observer observing the reconstructed stereoscopic image without crosstalk satisfies: Wherein, P0 is the center distance of the microlens array, and g is the thickness of the transparent spacer layer.

7. The dynamic polarization stereoscopic imaging system according to claim 6, wherein: The magnification M of the stereoscopic imaging satisfies: Where, T r is the period of the microlens array, T b is the period of the micro-image array, and θ is the relative angle between the microlens array and the micro-image array.

8. The dynamic polarization stereoscopic imaging system according to claim 5, wherein: The grating structure of the micro-image unit is at least one of a one-dimensional grating, a two-dimensional asymmetric grating or a two-dimensional symmetric grating.

9. The dynamic polarization stereoscopic imaging system according to claim 8, wherein: The two-dimensional asymmetric grating is a rectangular, elliptical, cross-shaped or elliptical ring structure.

10. The dynamic polarization stereoscopic imaging system according to claim 8, wherein: The two-dimensional symmetrical grating is a square, circular, cross or annular structure.

Images