A close focus projection screen

Abstract

The utility model discloses a kind of near-focus projection screens, comprising: flexible UV glue base;Micro-mirror array, formed on the surface of the flexible UV glue base, including the periodic arrangement of multiple micro-mirrors in X-axis direction and Y-axis direction;Reflective film, formed on the surface of the micro-mirror array;And optical glue protective layer, formed on the surface of the reflective film, wherein the micro-mirror array is configured as: along X-axis direction observation, the micro-mirror optical axis position of array central column is invariable, with the central column as origin, the micro-mirror optical axis of each column on the positive direction side of the X-axis of the central column is translated a certain offset δ n Along X-axis positive direction, the micro-mirror optical axis of each column on the negative direction side of the X-axis of the central column is translated a certain offset δ n Along X-axis negative direction, form continuous variable-axis micro-mirror array.The near-focus projection screen of the utility model has the advantages of wide angle of view, brightness concentration, flexible bending, anti-glare interference and the like.

Description

Technical Field

[0001] This utility model relates to the field of near-focus projection design and manufacturing technology, and in particular to a near-focus projection screen. Background Technology

[0002] The demand for near-focus projection in the current commercial sector is increasing daily. However, near-focus projection systems, where the projector is located extremely close to the screen, suffer from problems such as large projection angles, image distortion, obstruction, and uneven brightness. Traditional projection screens struggle to simultaneously meet the demands for a large field of view, low distortion, and compact size. Furthermore, their high manufacturing precision requirements and small angle tolerances further lead to reduced production yields and increased costs.

[0003] Micrometer-scale mirror arrays are important optical components, widely used in various low-light systems due to their small size, high integration, and excellent optical performance. While near-focus projection systems based on micromirror arrays exist, in traditional periodically arranged arrays, the optical axes of each sub-mirror are parallel and coincide with the principal axis of the entire system. This means that each mirror unit projects light symmetrically and overlappingly onto the entire projection screen. To achieve a wide viewing angle, each mirror must have a large numerical aperture (NA), which leads to severe aberrations and uniform light dispersion across the entire viewing angle, resulting in a decrease in center brightness (gain). Utility Model Content

[0004] In order to overcome the shortcomings of the prior art, this utility model proposes a near-focus projection screen.

[0005] This utility model provides a near-focus projection screen, comprising:

[0006] Flexible UV adhesive substrate;

[0007] A micromirror array, formed on the surface of the flexible UV adhesive substrate, includes multiple micromirrors periodically arranged in the X-axis and Y-axis directions;

[0008] A reflective film is formed on the surface of the micromirror array; and

[0009] An optical adhesive protective layer is formed on the surface of the reflective film.

[0010] The micromirror array is constructed such that, when viewed along the X-axis, the optical axis position of the micromirrors in the central column of the array remains unchanged. Taking the central column as the origin, the optical axis of each column of micromirrors on the positive X-axis side of the central column is shifted by a certain offset δ along the positive X-axis direction. n The optical axis of each micromirror on the negative X-axis side of the central column is shifted by a certain offset δ along the negative X-axis direction. n This forms a continuous variable-axis micromirror array.

[0011] Preferably, when 2K+1 columns of micromirrors are arranged parallel and equally spaced along the X-axis, the offset δ of each column of micromirrors on both sides of the central column is... n The offset of the nth column micromirror is calculated as follows: the column number n ranges from [-K, K]. A negative offset indicates that the optical axis is shifted in the negative direction of the X-axis, while a positive offset indicates that the optical axis is shifted in the positive direction of the X-axis. D is the aperture size of a single micromirror.

[0012] Preferably, the distance between the micromirror and its adjacent micromirrors is 8μm-10μm.

[0013] Preferably, the aperture of the micromirror is 40μm-50μm.

[0014] Preferably, the depth of the micromirror is 5μm-7μm.

[0015] Preferably, the unit structure dimensions of the micromirror satisfy the following: total width not greater than 60 μm, and total height not greater than 10 μm.

[0016] Preferably, the reflective film is a metal reflective film with a thickness of less than 100 nm.

[0017] Preferably, the metal reflective film is an ultrathin silver film deposited by magnetron sputtering.

[0018] Preferably, the optical adhesive protective layer is an OCA optical adhesive protective layer.

[0019] The beneficial effects of this invention are as follows: Compared with traditional projection screens, the near-focus projection screen of this invention has advantages such as a wide field of view, concentrated brightness, flexible bending, and anti-glare interference, thus improving the gain and brightness of near-focus projection. In particular, this invention overcomes the defect of traditional micromirror arrays where a large viewing angle and high gain cannot be simultaneously achieved. Compared with traditional micromirror arrays, it achieves a wider field of view while also obtaining a higher gain, and better anti-glare interference performance. Furthermore, the OCA optical adhesive protective layer effectively protects the variable-axis micromirror array with micro-nano structures on the surface of the near-focus projection screen, extending the lifespan of the near-focus projection screen. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0021] Figure 1 This is a front view of a near-focus projection screen according to a preferred embodiment of the present invention;

[0022] Figure 2 This is a side view of a near-focus projection screen according to a preferred embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the optical axis variation of the continuously variable axis micromirror array according to a preferred embodiment of the present invention;

[0024] Among them, 10 is a flexible UV adhesive substrate; 20 is a continuous variable-axis micro-mirror array; 30 is a silver reflective film; 21 is a micro-mirror; and 40 is an OCA optical adhesive protective layer. Detailed Implementation

[0025] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0026] As attached Figures 1 to 3 As shown, a near-focus projection screen according to a preferred embodiment of the present invention includes: a flexible UV adhesive substrate 10, a variable-axis micro-reflector array 20, a magnetron sputtered ultrathin silver film 30, and an OCA (Optically Clear Adhesive) optical adhesive protective layer 40.

[0027] In each preferred embodiment, the flexible UV adhesive substrate 10 is a flexible material capable of directly fabricating or transferring micro / nano structures to facilitate the formation of the variable-axis micromirror array 20 thereon. The size or dimensions of the flexible UV adhesive substrate 10 can be flexibly designed according to actual needs or experimental conditions.

[0028] In each preferred embodiment, such as Figure 1 and Figure 2As shown, a variable-axis micromirror array 20 is formed on the surface of a flexible UV substrate 10, including multiple micromirrors 21 periodically arranged in the X-axis and Y-axis directions. Here, the variable-axis mirrors 21 are also micrometer-scale structures. For example... Figure 3 The diagram shown is a top view of a preferred embodiment of the continuous variable-axis micromirror array of this utility model. The black dot in the center of each micromirror represents the position of its optical axis. Specifically, the variable-axis micromirror array 20 is constructed such that, when viewed along the X-axis, the optical axis position of the micromirrors in the central column (X=0) remains unchanged. Taking the central column as the origin, the optical axis of each column of micromirrors on the positive X-axis side of the central column is translated by a certain offset δ along the positive X-axis direction. n The optical axis of each micromirror on the negative X-axis side of the central column is shifted by a certain offset δ along the negative X-axis direction. n This forms a continuous variable-axis micromirror array.

[0029] More preferably, when a total of 2K+1 columns of micromirrors are arranged parallel and equally spaced along the X-axis, the offset δ of each column of micromirrors on both sides of the central column is... n The offset of the nth column micromirror is calculated as follows: the column number n ranges from [-K, K]. A negative offset indicates that the optical axis is offset in the negative direction of the X-axis, and a positive offset indicates that the optical axis is offset in the positive direction of the X-axis. D is the aperture size of a single micromirror. Through the above design, the optical axis of each column of micromirrors 21 in the micromirror array 20 continuously increases in offset (that is, the optical axis tilt continuously increases) from the center column outward.

[0030] In a preferred embodiment, an ultrathin silver film 30 deposited by magnetron sputtering is used as a reflective film covering the upper layer of the variable-axis micromirror array 20. The thickness of the ultrathin silver film 30 deposited by magnetron sputtering is preferably less than 100 nm. In other preferred embodiments, the reflective film may also be other metal films.

[0031] In a preferred embodiment, such as Figure 2 As shown, an OCA optical adhesive protective layer 40 is formed on the surface of the reflective film 30. The OCA optical adhesive protective layer 40 has a light transmittance >93% and features no adhesive residue and low bubble count. Preferably, the OCA optical adhesive protective layer 40 is conveniently applied to the surface of the reflective film 30 by brushing. Since near-focus projection screens are easily worn in actual use, the OCA optical adhesive protective layer 40 effectively protects the micro-nano structured variable-axis micromirror array 20 on the surface of the near-focus projection screen, extending the service life of the near-focus projection screen.

[0032] In each preferred embodiment, the spacing between each micromirror 21 constituting the continuous variable-axis micromirror array 20 and its adjacent micromirrors 21 can be set to 8μm-10μm. That is, the spacing between each micromirror 21 and the micromirrors 21 in its four directions (up, down, left, and right) can be set to 8μm-10μm. Furthermore, the dimensional parameters of a single micromirror 21 can be set to satisfy the following range: the aperture of the micromirror 21 is 40μm-50μm, and its depth is 5μm-7μm. In addition, the unit structure dimensional parameters of the micromirror 21 satisfy the following: the total width is not greater than 60μm, and the total height is not greater than 10μm.

[0033] Based on the aforementioned range of micromirror 21 size parameters, optimally, the spacing between two adjacent micromirrors 21 can be set to 8 μm, and the aperture of a single micromirror 21 can be 50 μm, with a depth of 7 μm. This size setting allows the continuous variable-axis micromirror array 20 with this structure to achieve optimal design in terms of field of view, bending resistance, and gain performance. Specifically, the gain of the mirror array can reach 2.16, the flexible bending rate can reach 73.8°, and the field of view can reach 149.6°.

[0034] In summary, the continuously variable-axis micromirror array structure of the preferred embodiment of this utility model successfully fabricates the required micro-nano structures on a flexible material substrate. Specifically, a continuously variable-axis micromirror array is constructed on a flexible UV adhesive substrate. Utilizing the excellent optical performance and variable-axis design of the micron-scale mirror array, the projection array possesses advantages such as a wide field of view, concentrated brightness, flexible bending, and anti-glare interference. This overcomes the shortcomings of existing near-focus projection screens, such as a small field of view, low gain, inability to bend flexibly, susceptibility to glare, and cross-interference, thus improving the gain and brightness of near-focus projection. In particular, this utility model overcomes the limitation of traditional micromirror arrays where a large viewing angle and high gain cannot be simultaneously achieved. It can obtain a large field of view while achieving a high gain, and also achieve better anti-glare interference performance.

[0035] The beneficial technical effects achieved by the structure of this utility model will be described in detail below from the perspective of optical principles. In the micromirror array (MLA) with its unique continuously variable axis design, the optical axis of each micromirror has a specific translation relative to the main axis of the system. Each mirror is no longer responsible for the entire field of view, but only for a specific direction within the field of view. The outputs of all mirrors are combined to cover the entire target field of view, thus decoupling the contradiction between viewing angle and gain.

[0036] 1. Compared with the traditional periodically arranged micromirror array, the continuous variable axis micromirror array structure of this utility model has a wider field of view.

[0037] The effective viewing angle of a traditional periodically arranged micromirror array is essentially equivalent to the viewing angle θ of a single mirror. max For a single micromirror, its theoretical viewing angle at the diffraction limit is primarily determined by its numerical aperture (NA). For a mirror with a focal length of f and a diameter of D, its numerical aperture is:

[0038]

[0039] Right now

[0040] The viewing angle of a variable-axis micromirror array is no longer determined by the NA (naïve angle) of a single mirror, but rather by the range of deflection angles of the optical axis of each mirror and the divergence angle of the mirror itself. The variable-axis effect is achieved by translating the optical axis of the mirrors, and the optical axis deflection angle produced by the variable-axis mirrors can be calculated using geometric optics. Where δ is the optical axis translation and f is the focal length of the mirror. Each mirror also has its own inherent divergence angle, determined by the NA, and calculated using the same method as for periodic MLA.

[0041] Divergence angle of traditional micromirror arrays:

[0042] Divergence angle of variable-axis micromirror array:

[0043]

[0044] As can be seen from the above formula, the continuous variable axis micromirror array structure of this invention has a wider field of view compared with the traditional periodically arranged micromirror array.

[0045] 2. The continuous variable axis micromirror array structure of this utility model has a higher brightness gain compared with the traditional periodically arranged micromirror array.

[0046] Traditional periodic MLA redistributes all light rays to a cone angle of θ. max Within the conical region. According to the law of energy conservation, the theoretical upper limit of its axial brightness gain is:

[0047] Where Ω is the solid angle formed by the beam, Ω=2π(1-cos)θ max η is the optical efficiency.

[0048] The core of variable-axis design lies in distributing more light energy to the central or important areas of the field of view. Its axial gain formula becomes... By using a variable axis design, the light energy distribution can be more concentrated near the center of the field of view while maintaining the total luminous flux and field of view. This means that Ωeffective <Ω total This leads to G 0,off-axis >G 0,symmetric Compared with traditional periodically arranged micromirror arrays, the continuous variable axis micromirror array structure of this invention has a higher brightness gain.

[0049] The near-focus projection screen fabrication method of this embodiment first employs laser direct-write 3D lithography technology to fabricate the structural features of a continuous variable-axis micromirror array onto photoresist in a single lithographic exposure. Furthermore, during the lithography process, the exposure parameters obtained by calculating the optical imaging inversion model of the lithography allow for control of the structural feature error within a small range, down to within 0.8 nm. Next, the structure of the photoresist replica is transferred to glass via IBE etching to facilitate subsequent transfer work. Then, PDMS material is coated onto the glass replica, cured at high temperature, and peeled off to obtain a PDMS mold. Further, the PDMS mold undergoes plasma cleaning and silanization surface treatment. Next, a silver film of a predetermined thickness, such as 80 nm thick, is deposited on the surface of a flexible UV substrate using a magnetron sputtering instrument. Finally, an OCA optical adhesive protective layer is formed on the surface of the reflective film by brush coating and appropriately cured, thereby fabricating the near-focus projection screen of this invention.

[0050] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A near-focus projection screen, characterized in that, include: Flexible UV adhesive substrate; A micromirror array, formed on the surface of the flexible UV adhesive substrate, includes multiple micromirrors periodically arranged in the X-axis and Y-axis directions; A reflective film is formed on the surface of the micromirror array; as well as An optical adhesive protective layer is formed on the surface of the reflective film. The micromirror array is constructed such that, when viewed along the X-axis, the optical axis position of the micromirrors in the central column of the array remains unchanged. Taking the central column as the origin, the optical axis of each column of micromirrors on the positive X-axis side of the central column is shifted by a certain offset δ along the positive X-axis. n The optical axis of each micromirror on the negative X-axis side of the central column is shifted by a certain offset δ along the negative X-axis direction. n This forms a continuous variable-axis micromirror array.

2. The near-focus projection screen according to claim 1, characterized in that, With 2K+1 columns of micromirrors arranged parallel and equally spaced along the X-axis, the offset δ of each column of micromirrors on both sides of the central column is... n The offset of the nth column micromirror is calculated as follows: the column number n ranges from [-K, K]. A negative offset indicates that the optical axis is shifted in the negative direction of the X-axis, while a positive offset indicates that the optical axis is shifted in the positive direction of the X-axis. D is the aperture size of a single micromirror.

3. The near-focus projection screen according to claim 2, characterized in that, The distance between the micromirror and its adjacent micromirror is 8μm-10μm.

4. The near-focus projection screen according to claim 2, characterized in that, The aperture of the micromirror is 40μm-50μm.

5. The near-focus projection screen according to claim 2, characterized in that, The depth of the micromirror is 5μm-7μm.

6. The near-focus projection screen according to claim 2, characterized in that, The unit structure dimensions of the micromirror meet the following requirements: total width not greater than 60μm and total height not greater than 10μm.

7. The near-focus projection screen according to claim 2, characterized in that, The reflective film is a metal reflective film with a thickness of less than 100 nm.

8. The near-focus projection screen according to claim 7, characterized in that, The metal reflective film is an ultrathin silver film deposited by magnetron sputtering.

9. The near-focus projection screen according to claim 1, characterized in that, The optical adhesive protective layer is an OCA optical adhesive protective layer.

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