Microlens array for image projector

Abstract

A microlens array (100-A, 100-B) for an image projector (200) comprising a support (105-A, 105-B) and a matrix-like unit (101-A, 105-B) having a plurality of lenses (103-A, 103-B) arranged on the support (105-A, 105-B).

Description

[Technical Field]

[0001] The present invention relates to a microlens array for an image projector, an image projector having a microlens array, a microlens array unit and a method for manufacturing a microlens array. [Background technology]

[0002] As for small projectors formed along the optical axis as a stack, image projectors with micro lens arrays (MLA) have recently been used, especially in the automotive field. This projector typically has a collimation optical system that generates collimated light with a predetermined small residual divergence, an optical system stack with an illumination lens array, a slide plane (made of a chrome layer) on which image information is provided through an aperture, a substrate (made of glass) with a focal length thickness, and a projection lens array, which is often identical to the illumination lens array.

[0003] Additionally, the image projector includes electronics, a housing, and a cover disk, which form a multi-channel optical system with a small spread, in which each channel can project the entire image with a large depth of field.

[0004] The document DE 102009024894 A1 relates to a projection display having a light source and regularly arranged optical channels. The optical channels have field lenses, to which an object structure to be imaged and a projection lens are respectively assigned. The distance of the projection lens to the assigned object structure corresponds to the focal length of the projection lens, while the distance of the object structure to be imaged to the assigned field lens is selected to enable Köhler illumination of the assigned projection lens. In this case, the individual projections are superimposed on the overall image. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] German Patent Application Publication No. 102009024894 Summary of the Invention [Means for solving the problem]

[0006] The microlens array for an image projector according to the present invention comprises a support and a matrix of lenses arranged on the support, which offers the technical advantage of being able to produce the microlens array with a lower cost manufacturing method compared to the expensive polymer-on-glass technology. Furthermore, a greater choice of materials is possible, especially for the support. Instead of a polished glass wafer, essentially all optical injection molding materials can be used.

[0007] In another advantageous embodiment of the microlens array, the support and the lenses are made from the same material, which makes it possible to further simplify the production of the microlens array.

[0008] In an advantageous embodiment of the microlens array, the support has a thickness of between 400 μm and 1200 μm, preferably between 500 μm and 700 μm, which allows the microlens array to be manufactured by injection molding or pressing methods.

[0009] In another advantageous embodiment of the microlens array, the matrix of lenses and the carrier are formed in one piece, which allows the microlens array to be produced by injection molding.

[0010] In another advantageous embodiment of the microlens array, the microlens array is a thermoplastic polymer, which allows it to be manufactured by injection molding as well.

[0011] In another advantageous embodiment of the microlens array, the thermoplastic polymer contains polymethylmethacrylate (PMMA), cycloolefin polymer (COP), polycarbonate (PC) or optical silicone, making the material particularly suitable for producing the microlens array.

[0012] The microlens array unit according to the present invention has a first microlens array on the illumination side and a second microlens array on the projection side and can be used as a component in an image projector. A sliding plane with a specially designed aperture for passing light can be arranged between the first and second microlens arrays, which further simplifies the construction.

[0013] In an advantageous embodiment of the microlens array unit, the first support has a thickness in the range of 400 μm to 1200 μm and the second support has a thickness in the range of 2 mm to 5 mm.

[0014] In an advantageous embodiment of the microlens array unit, the lenses of the first microlens array on the illumination side have a larger focal length than the lenses of the second microlens array on the projection side, thereby achieving a sharper projection and a greater depth of field.

[0015] In one advantageous embodiment of the microlens array unit, the lenses on the illumination side have a focal length equal to the sum of the thickness of the support of the first microlens array and the thickness of the support of the second microlens array, thereby improving the performance of the microlens array unit.

[0016] In an advantageous embodiment of the microlens array unit, a slide plane is arranged between the first microlens array and the second microlens array.

[0017] The image projector with the microlens array unit according to the present invention can achieve the same technical advantages as the microlens array.

[0018] The method according to the present invention can be used to manufacture a microlens array by injection molding or hot stamping the microlens array, which achieves the same technical advantages as those achieved by the microlens array.

[0019] The embodiments of the present invention will be described in detail with reference to the following drawings. [Brief explanation of the drawings]

[0020] [Figure 1] 1 shows a schematic diagram of an image projector with a microlens array. [Figure 2] 1 shows a schematic cross-sectional view of a microlens array. [Figure 3] FIG. 2 shows a schematic cross-sectional view of a microlens array unit. [Figure 4] FIG. 1 shows a block diagram of a method for manufacturing a microlens array unit.

[0021] 1 shows a schematic diagram of an image projector 200 (MLA projector) having a microlens array unit 300. The microlens array unit 300 has a first microlens array 100-A on an illumination side 107-A and a second microlens array 100-B on a projection side 107-B.

[0022] The image projector 200 projects a stationary, unchanging image 109 onto a screen, for example a road or a wall, in which case the largest possible luminous flux (lumens) should be produced by the smallest possible image projector 200.

[0023] The image projector 200 comprises a light source 113 and a collimating lens 115 for generating parallel light beams. Nevertheless, the spatial dimensions and number of components of the image projector 200, particularly along the axis of the light propagation direction, should be kept as small as possible. This is advantageous when the construction space for lighting is limited, particularly in the automotive field. For this purpose, the image projector 200 is configured as a multi-aperture approach. In the multi-aperture approach, miniaturized projectors (channels), each with separate lenses 103-A and 103-B, are arranged in parallel, thereby achieving a miniaturized construction thickness.

[0024] Furthermore, the small spatial extent of lenses 103-A and 103-B can produce a large depth of field, which allows sharp imaging of image 109 on tilted screens with different projection distances without tilting the object plane and the lens plane (Scheimpflug principle).

[0025] In this embodiment, the same microlens arrays 100-A and 100-B with the same focal length are used for the lens 103-A on the illumination side 107-A and the lens 103-B on the projection side 107-B. In this case, the focal lengths are selected so that the respective foci are located on the opposite lenses 103-A and 103-B (BL<->PL). Therefore, to ensure good illumination with proper collimation, it is desirable to have as small a distance as possible between the lens 103-A on the illumination side 107-A and the slide plane 111.

[0026] The lenses 103-A and 103-B are manufactured by injection molding. The slide plane 111 is made of a chrome layer, and the chrome layer is provided with image information through an aperture.

[0027] Support 105-A is fabricated together with lens 103-A and is positioned on illumination side 101-A. Support 105-A typically has a thickness between 400 μm and 800 μm, and in this embodiment, it is 550 μm. Support 105-A or 105-B may be formed from polymethylmethacrylate (PMMA) or cycloolefin polymer (COP). This has the technical advantage that these materials have low dispersion, which prevents color defects and color fringes during polychromatic white projection. Supports 105-A and 105-B may be made from polycarbonate or optical silicone. Supports 105-A and 105-B have a length of 5 mm to 50 mm and a width of 5 mm to 50 mm, and are preferably 10 mm x 10 mm. The support 105-A has a thickness of, for example, between 400 μm and 1200 μm, and the support 105-B has a thickness of 2 mm to 5 mm.

[0028] The lenses 103-A and 103-B on the supports 105-A and 105-B have a center-to-center spacing of, for example, 500 μm to 1000 μm, 800 μm in this embodiment. The lenses 103-A and 103-B are arranged in a hexagonal pattern on the supports 105-A and 105-B and have focal lengths of between 1.5 mm and 4 mm, 2 mm in this embodiment. The lenses 103-A and 103-B may be formed, for example, from the same or different material as the supports 105-A or 105-B. The supports 105-A and / or 105-B have dimensions of 10 mm x 10 mm, and the lenses 103-A and 103-B are, for example, 12 x 12 mm in size. The focal lengths of the lenses 103-A and 103-B are, for example, greater than the thickness of the support 105.

[0029] The sufficient thickness of the supports 105-A and 105-B allows the microlens arrays 100-A and 100-B to be manufactured by injection molding or pressing. The focal length of the lenses 103-A on the illumination side 107-1 can be slightly increased, thereby achieving the best possible illumination of the slide structure (image information) in the slide plane 111 and the associated lenses 103-B on the projection side 107-B. The supports 105-A and 105-B and each lens 103-A and 105-B of each microlens array 100-A and 100-B may be integrally formed from the same material.

[0030] In this embodiment, different focal lengths are used for the lens 103-A on the illumination side 107-A and the lens 103-B on the projection side 107-B, so that the focal plane of the lens 103-A on the illumination side 107-A is located exactly within the lens 103-B on the projection side 107-B. This results in the maximum allowable angle of residual divergence of the collimation. The focal length of the lens 103-B on the projection side 107-B is selected so that the focal plane is located within the slide plane 111. This allows for a sharp projection with the same advantages as a high depth of field for projection onto an oblique plane, for example.

[0031] 2 shows a schematic cross-sectional view of the microlens array 100-A. The layer of the support 105-A has a thickness of 520 μm. Due to the thickness of the support 105-A, the microlens array 100-A can be manufactured by an injection molding method.

[0032] On the opposite side is an adhesive layer 119 (bonding design) with a thickness of 40 μm. The adhesive layer 119 fixes the slide plane 111. This results in an overall spacing of 670 μm from the apex of the lens 103-A to the slide plane 111. The microlens array 100-B on the projection side 107-B is configured to correspond to the microlens array 100-A on the illumination side 107-A, except that it may have a support 107-B with a greater thickness.

[0033] The alternative integrated structure of the microlens array 100-A allows the microlens array 100-A to be manufactured by a low-cost, low-labor manufacturing method, such as injection molding. When the microlens array 100-A is injection molded, the matrix-like units 101-A of the plurality of lenses 103-A and the supports 105-A are formed by casting a thermoplastic polymer.

[0034] 3 shows a schematic cross-sectional view of a microlens array unit 300. On the slide plane 111, each partial pattern in an area DiA2 is defined. The area DiA2 is smaller than the area DiA1. The area DiA2 of the pattern is defined by the focal length of the lens 103-A and a distance d1. The area outside the circle containing the area DiA2 may be covered with an absorbing or reflective material 121 to block light from passing through. The distance d1 may be smaller than the focal length of the matrix unit 101-A.

[0035] The supports 105-A and 105-B may have multiple layers of different materials, and specific material combinations may be technically advantageous for manufacturing based on specific material properties and requirements, such as a support for a chromium layer.

[0036] 4 shows a block diagram of a method for manufacturing a microlens array unit 300. In step S101, a first microlens array 100-A having a matrix-like unit 101-A with a plurality of lenses 103-A arranged on a support 105-A is formed by injection molding of a thermoplastic polymer. The microlens array 100-A may be manufactured from the support 105-A by hot embossing, in which the lenses 103-A are generated on the surface of the support 105-A by an embossing stamp.

[0037] In step S102, a second microlens array 100-B having a matrix of units 101-B each including a plurality of lenses 103-B arranged on a support 105-B is formed by injection molding of a thermoplastic polymer. The second microlens array 100-B may also be manufactured by hot stamping.

[0038] In step S103, a slide plane 111 is placed between the first microlens array 100-A and the second microlens array 100-B. Image information is present on the slide plane 111 through a specially configured aperture. In step S104, the first microlens array 100-A and the second microlens array 100-B are bonded to each other while the slide plane 111 is placed therebetween. This allows for a simple fabrication of a microlens array unit 300 that can be used in the image projector 200. Furthermore, this manufacturing method allows for a greater selection of materials for the lenses 103-A and 103-B and the supports 105-A and 105-B, which is advantageous both optically and in terms of manufacturing costs.

[0039] The technical advantage of the present invention is the low-cost manufacturing method compared to the expensive polymer-on-glass technology, which also allows a greater material choice, especially for the supports 105-A and 105-B: essentially all optical injection molding materials may be used instead of expensive polished glass wafers.

[0040] Based on its dimensions, the described microlens array unit 300 is particularly suitable as a lighting fixture in the automotive field, for example for light carpets, as symbol projection in hotels, as security projection in aircraft, as effect lighting, as guidance projection or as danger zone projection in buildings.

[0041] All the features described and illustrated in connection with the individual embodiments of the invention may be provided in the subject matter according to the invention in various combinations, so that its advantageous effects are realized at the same time.

[0042] All method steps may be performed by apparatus suitable for performing the respective method step. All functions performed by the embodied features may be method steps of the method.

Claims

1. Supports (105-A, 105-B); a matrix-shaped unit (101-A, 101-B) having a plurality of lenses (103-A, 103-B) arranged on a support (105-A, 105-B); A microlens array (100-A, 100-B) for an image projector (200), comprising:

2. 2. The microlens array (100-A, 100-B) according to claim 1, wherein the supports (105-A, 105-B) and the lenses (103-A, 103-B) are made of the same material.

3. The microlens array (100-A, 100-B) according to claim 2, wherein the support (105-A) has a thickness between 400 μm and 1200 μm, preferably between 500 μm and 700 μm.

4. A microlens array (100-A, 100-B) according to any one of claims 1 to 3, wherein a matrix-shaped unit (101-A, 101-B) of a plurality of lenses (103-A, 103-B) and a support (105-A, 105-B) are integrally formed.

5. The microlens array (100-A, 100-B) according to any one of claims 1 to 4, wherein the microlens array (100-A, 100-B) is a thermoplastic polymer.

6. The microlens array (100-A, 100-B) according to claim 5, wherein the thermoplastic polymer comprises polymethylmethacrylate (PMMA), cycloolefin polymer (COP), polycarbonate (PC) or optical silicone.

7. A microlens array unit (300) having a first microlens array (100-A) according to any one of claims 1 to 6 on an illumination side (107-A) and a second microlens array (100-B) according to any one of claims 1 to 6 on a projection side (107-B).

8. The microlens array unit (300) of claim 7, wherein the lenses (103-A) of the first microlens array (100-A) on the illumination side (107-A) have a larger focal length than the lenses (103-B) of the second microlens array (100-B) on the projection side (107-B).

9. 9. The microlens array unit (300) according to claim 7 or 8, wherein the first support (105-A) has a thickness in the range of 400 μm to 1200 μm, and the second support (105-B) has a thickness in the range of 2 mm to 5 mm.

10. 10. The microlens array unit (300) according to claim 7, wherein the lens (103-A) on the illumination side has a material focal length equal to the sum of the thickness of the support (105-A) of the first microlens array (100-A) and the thickness of the support (105-B) of the second microlens array (100-B).

11. The microlens array unit according to any one of claims 8 to 10, wherein a slide plane (111) is disposed between the first microlens array (100-A) and the second microlens array (100-B).

12. An image projector (200) comprising a microlens array unit (300) according to any one of claims 7 to 11.

13. A method for manufacturing a microlens array (100-A, 100-B) according to any one of claims 1 to 6, comprising the step of injection molding or hot stamping the microlens array (100-A, 100-B) according to any one of claims 1 to 6.

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