Optical device

Abstract

The invention relates to an optical device and to a method for producing an optical device. The optical device (1) according to the invention comprises - a transparent substrate (2) and - a connected transparent layer (3) enclosing the substrate (2) on at least three sides, which transparent layer • forms a plurality of first optical lenses (5) on a first surface (4) and • forms a plurality of second optical lenses (7) on a second surface (6), which is arranged on a substrate side opposite the first surface (4), the transparent layer (3) having a predetermined thickness.

Description

[0001] OPTICAL DEVICE AND INJECTION MOLDING METHOD FOR ITS MANUFACTURE

[0002] The invention relates to an optical device and a method for producing an optical device.

[0003] DE102015121691 A1 discloses a method for producing a microlens array comprising at least one light-transmitting base body with a planar extension, wherein the base body has a microlens structure on at least one base surface. The at least one base body is produced using an injection molding tool in an injection molding process, so that the microlens structure is molded from a negative structure in the injection molding tool.

[0004] The optical device according to the invention comprises - a transparent substrate and

[0005] - a continuous transparent layer enclosing the substrate on at least three sides, which o forms a plurality of first optical lenses on a first surface and o forms a plurality of second optical lenses on a second surface arranged opposite the first surface, wherein the transparent layer has a predetermined thickness.

[0006] "Transparent" is defined as a substrate and / or layer that transmits a specific portion of incident light of a specific wavelength. Preferably, the specific portion of transmitted light in a wavelength range between 400 nm and 750 nm is greater than 90%.

[0007] The invention is particularly intended for use as a microprojector. Its object is to create a cost-effective optical element with a small installation space, which is capable of projecting a sharp, undistorted image. Because the continuous transparent layer encloses the substrate on at least three sides and has a predetermined thickness, the optical device according to the invention can be produced by overmolding the substrate with a layer-forming material. During overmolding, flowable layer-forming material can distribute itself around the substrate via a layer-forming injection molding space and enclose it. Upon solidification, a substrate-enveloping layer is thus formed, which imparts high mechanical robustness to the optical device according to the invention and prevents detachment of individual lenses.

[0008] The optical device according to the invention preferably comprises an image carrier layer arranged between the substrate and at least one lens-forming portion of the transparent layer. This enables the use of the optical device according to the invention as a projector.

[0009] The transparent layer preferably comprises an injection point on a substrate side facing away from the lens. During a manufacturing process, a flowable layer-forming material is distributed from the injection point into the layer-forming injection molding chamber. By locating the injection point on a substrate side facing away from the lens, it can be ensured that an optically functional region of the optical device according to the invention is not impaired by injection defects and / or manufacturing-related artifacts, such as injection lands.

[0010] The transparent layer of the optical device according to the invention preferably has a thickness in a range of 0.5 mm to 5 mm. The thickness is particularly preferably between 0.5 mm and 1 mm. This ensures sufficient material flow during a manufacturing process using an injection molding process.

[0011] Preferably, the transparent layer of the optical device according to the invention is thick enough that at least one second optical lens lies at a focal point of a first optical lens, and at least a portion of the image carrier layer lies at the focal point of the at least one second optical lens. This enables a sharp projection of image information stored in the image carrier layer.

[0012] Particularly preferably, the substrate of the optical device according to the invention consists of a substrate material, such as glass, and the transparent 3

[0013] A layer made of a layer material that has a lower melting and / or glass transition temperature than the substrate material, such as polycarbonate (PC), polymethyl methacrylate (PMMA), cycloolefin polymer (COP), cycloolefin copolymer (COC), or other optically transparent plastics, in particular polymers with thermoplastic behavior. This enables the optical device according to the invention to be manufactured in a process temperature range in which the substrate material is temperature-stable and the layer material is injection-moldable. This prevents temperature-induced damage to the substrate, such as deformation or melting, during a manufacturing process.

[0014] Preferably, the first optical lenses and the second optical lenses of the optical device according to the invention are of the same dimensions. This allows them to be manufactured using the same injection mold. For example, in a manufacturing process, the first optical lenses can first be injection-molded onto a first substrate side, and then, by rotating the substrate and / or the injection mold, the second optical lenses can be injection-molded onto a second substrate side using the same injection mold.

[0015] Preferably, the first optical lenses consist of a first layer material with a first refractive index, and the second optical lenses consist of a second layer material with a second refractive index, wherein the first refractive index is large enough that at least one second optical lens lies at a focal point of a first optical lens, and wherein the second refractive index is large enough that at least a portion of the image carrier layer lies at the focal point of the at least one second optical lens. This enables a sharp projection of image information stored in the image carrier layer, despite the first and second optical lenses being of identical dimensions.

[0016] The method according to the invention for producing an optical device comprises the steps:

[0017] S1 : Applying an image carrier layer to a transparent substrate;

[0018] S2: Positioning the substrate in an injection mold;

[0019] S3: Injection molding of a layer-forming material into the injection mold, such that the layer-forming material, upon solidification, forms a coherent transparent layer enclosing the substrate on at least three sides, which layer forms a plurality of first optical lenses on a first surface and which forms a plurality of second optical lenses on a second surface arranged on a substrate side opposite the first surface. By injection molding the first and second optical lenses on opposite substrate sides, thickness deviations between different substrates can be compensated. Determined by the injection mold, the first and second lenses always have the same distance from one another, the same shape, and thus also the same optical functionality, regardless of possible substrate thickness fluctuations.

[0020] The dependent claims describe further advantageous embodiments of the invention.

[0021] Preferred embodiments are explained in more detail with reference to the following figures. Figure 1 shows a first embodiment of an optical device according to the invention in a side view,

[0022] Figure 2 shows the optical device shown in Figure 1 in a plan view and

[0023] Figure 3 shows a first embodiment of a method according to the invention for manufacturing an optical device. The first embodiment of an optical device 1 according to the invention shown in Figures 1 and 2 is a multi-lens array (MLA), which can be used as a projector in combination with a light source.

[0024] The optical device 1 comprises a transparent substrate 2. In the exemplary embodiment, this is a rectangular planar glass plate. An image carrier layer 8 encompassed by the device 1 is applied to a front side of the substrate 2. This layer is formed as a thin metal layer structured by lithography or laser.

[0025] Furthermore, the substrate 2 with the image carrier layer 8 is enclosed on all sides by an injection-molded, continuous transparent layer 3 made of polycarbonate (PC). On the front side of the substrate 2, the transparent layer 3 forms a plurality of first optical lenses 5 on a first surface 4. The image carrier layer 8 is located, as shown in Figure 1, between the substrate 2 and the lens-forming layer region. The back side of the substrate 2 is also covered by the transparent layer 3. On this substrate side, opposite the first surface 4, the transparent layer 3 forms a plurality of second optical lenses 7 on a second surface 6.

[0026] In the exemplary embodiment, the first optical lenses 5 serve as light coupling bodies. Light generated by a light source strikes the image carrier layer 8 through the first optical lenses 5. A portion of the light can pass through structured regions of the image carrier layer 8 and record image information. The transmitted light then exits the optical device 1 through the second optical lenses 7. The transparent layer 3 on the front and back of the substrate 2 is so thick that the second optical lenses 7 lie at a focal point of the first optical lenses 5 and the image carrier layer 8 lies at the focal point of the second optical lenses 7. The emerging light image can therefore produce a sharp light image in a projection plane.

[0027] Furthermore, the four remaining sides of the rectangular planar glass plate are also enclosed by the transparent layer 3. Only small partial areas on the sides of the glass plate (not shown), where it was clamped in an injection mold during a manufacturing process, are not covered by polymer due to the manufacturing process.

[0028] In the exemplary embodiment, the transparent layer 3 has a predetermined thickness of 1 mm on all sides of the substrate 2. In regions in which the transparent layer 3 forms optical lenses 5, 7, the predetermined thickness is illustrated in Figure 1 by a double arrow. The predetermined thickness makes it possible to produce the optical device 1 shown in Figures 1 and 2 by overmolding the substrate 2. Heated, flowable PC can flow around the substrate 3 via a layer-forming injection molding chamber, which defines the thickness of the transparent layer 3.

[0029] Since the glass from which the substrate 2 is made has a significantly higher melting temperature than the layer-forming PC, temperature-induced substrate damage can be avoided during the manufacturing process. In further embodiments not shown, a substrate 2 can also consist of a high-melting transparent polymer. Furthermore, the substrate 2 and the transparent layer 3 can also consist of different types of glass with different melting points.

[0030] In the exemplary embodiment, the transparent layer 3 comprises two injection points 9 (see Figure 1) on opposite substrate sides facing away from the lens. From the injection points 9, flowable PC can be distributed in the layer-forming injection molding chamber during a manufacturing process. This ensures that the optical functionality of the lens-forming layer regions is not impaired by injection artifacts and / or defects.

[0031] A first embodiment of a method according to the invention suitable for producing the optical device 1 shown in Figures 1 and 2 is shown in Figure 3. In a first step S1 of the method, a vapor deposition device applies a thin metallic image carrier layer 8 to a transparent substrate 2. This layer is then patterned in a subsequent lithography process. In a second step S2 of the method, a dedicated machine or a worker positions the substrate 2 with the image carrier layer 8 in an injection mold. In a third step S3 of the method, an injection molding system injection molds molten PC into the injection mold.The PC flows around the substrate 2 on all sides and, upon solidification, forms a coherent transparent layer 3 which forms a plurality of first optical lenses 5 on a first surface 4 and which forms a plurality of second optical lenses 7 on a second surface 6 arranged on the substrate side opposite the first surface 4.

[0032] A second embodiment of an optical device according to the invention also has the structure schematically illustrated in Figure 1, comprising a substrate 2, a transparent layer 3, an image carrier layer 8, first optical lenses 5, and second optical lenses 7. The first and second optical lenses 5, 7 are manufactured using the same injection mold and have the same dimensions. "Equally dimensioned" in this context means that for each first optical lens 5, there is an associated second optical lens 7 on an opposite side of the substrate, which second optical lens has the same geometric dimensions and radii of curvature.

[0033] The first optical lenses 5 consist of a first layer material, in the exemplary embodiment PMMA, with a first refractive index of 1.49 and the second optical lenses 7 consist of a second layer material, in the exemplary embodiment a transparent polyester (OKP optical plastic), with a second refractive index of 1.64. The first refractive index and the substrate and layer dimensions are selected such that all second lenses 7 lie at the focal points of the respectively associated first lenses 5. Furthermore, the second refractive index is selected such that the focal point of every second optical lens 7 lies in the image carrier layer 8. As a result, the emerging light image can produce a sharp light image in a projection plane.

[0034] The second embodiment of the optical device according to the invention can be produced using a second embodiment of a method according to the invention (not shown). In a first step S1 of the method, a cathode sputtering system applies a thin metallic image carrier layer 8 to a transparent substrate 2. This layer is then structured using a laser. In a second step S2 of the method, a dedicated machine or a worker positions the substrate 2 with the image carrier layer 8 in an injection mold. In a third step S3 of the method, an injection molding system injection molds molten PMMA and molten transparent polyester into the injection mold.

[0035] The third step S3 is carried out in three sub-steps S3a, S3b, S3c. In step S3a, the injection molding system firstly injection-molds a first partial region of the transparent PMMA layer onto a first substrate side. The first partial region protrudes beyond the first substrate side and encloses the substrate edges. Upon solidification, the first partial region forms the first optical lenses 5 on a first surface 4. Subsequently, in the second sub-step S3b, a machine provided for this purpose repositions the substrate in the injection mold. In the exemplary embodiment, this is done by rotating a substrate-holding index plate. In further embodiments, the repositioning can also be carried out by rotating an injection molding tool using a turntable or by displacing the substrate 2 relative to the 8

[0036] Injection molding tool. In the third sub-step S3c, the injection molding system injection-molds a second sub-region of the transparent layer 3 from molten transparent polyester onto a second substrate side. Upon solidification, the second sub-region forms the second optical lenses 7 on a second surface. The second sub-region protrudes beyond the second substrate side and forms a material-to-material bond with the first sub-region at the substrate edges.

Claims

9 Patent claims:

1. Optical device (1) comprising - a transparent substrate (2) and - a continuous transparent layer (3) enclosing the substrate (2) on at least three sides, which o forms a plurality of first optical lenses (5) on a first surface (4) and o forms a plurality of second optical lenses (7) on a second surface (6) arranged opposite the first surface (4) of the substrate, wherein the transparent layer (3) has a predetermined thickness.

2. Optical device (1) according to claim 1, comprising an image carrier layer (8) which is arranged between the substrate (2) and at least one lens-forming sub-region of the transparent layer (3).

3. Optical device (1) according to one of the preceding claims, wherein the transparent layer (3) is produced by overmolding the substrate (2).

4. Optical device (1) according to one of the preceding claims, wherein the transparent layer (2) comprises a injection point (9) on a substrate side facing away from the lens.

5. Optical device (1) according to one of the preceding claims, wherein the transparent layer (3) has a thickness in a range of 0.5 mm to 5 mm.

6. Optical device (1 ) according to one of the preceding claims in combination with claim 2, wherein the transparent layer (3) is so thick that at least one second optical lens is located at a focal point of a first optical lens and at least a partial area of ​​the image carrier layer (8) is located at the focal point of the at least one second optical lens (7).

7. Optical device (1) according to one of the preceding claims, wherein the substrate (2) consists of a substrate material and the transparent layer 10 (3) consists of at least one layer material which has a lower melting and / or glass transition temperature than the substrate material. Optical device (1) according to any one of the preceding claims, wherein the first optical lenses (5) and the second optical lenses (7) are of the same dimensions. Optical device (1) according to claim 8, wherein - the first optical lenses (5) consist of a first layer material with a first refractive index and the second optical lenses (7) consist of a second layer material with a second refractive index and wherein - the first refractive index is so large that at least a second optical lens (7) lies at a focal point of a first optical lens (5) and wherein - the second refractive index is so large that at least a portion of the image carrier layer (8) lies at the focal point of the at least one second optical lens (7). Method for manufacturing an optical device (1) comprising the steps: S1: Application of an image carrier layer (8) onto a transparent substrate (2); S2: Positioning the substrate (2) in an injection mold; S3: Injection molding of a film-forming material into the injection mold, such that the film-forming material solidifies to form a continuous transparent layer (3) surrounding the substrate (2) on at least three sides, which forms a plurality of first optical lenses (5) on a first surface (4) and a plurality of second optical lenses (7) on a second surface (6) of the substrate opposite the first surface (4). The method according to claim 10, wherein, during injection molding in step S3, liquid film-forming material flows around the substrate (2) simultaneously on at least three sides. The method according to claim 10, wherein the injection molding in step S3 comprises the following sub-steps: 11 S3a: Injection molding of a first partial area of ​​the transparent layer (3) encompassing the first optical lenses (5); S3b: Repositioning the substrate (2) and / or the injection mold S3c: Injection molding of a second sub-area of ​​the transparent layer (3), comprising the second optical lenses (7), wherein the second sub-area is bonded to the first sub-area.