Optical device for generating rainbow-like light effects,

Abstract

Optical device for generating rainbow-like light effects, comprising a body in the form of a thin plate: - made of one or more dispersive materials, - containing Fresnel prism structures having optical entry and / or exit surfaces arranged wedge-shaped to each other, - whose Fresnel prism structure is bent, wherein the bending of the Fresnel prism structure is perpendicular to the spectral splitting of the light and perpendicular to the direction of propagation of the light in the Fresnel prism structure, and the body is integrated into the surface of a window or roller shutter.

Description

The object of the invention is to make the production of a curved rainbow possible using simple means, in a very user-friendly and effective manner, and to offer it to the consumer market at attractive prices. Therefore, currently only the optical device according to claim 1 is suitable for this purpose. vivid description Elongated prisms (Fig. 1) are well-known and can be placed on a windowsill to, for example, spectrally decompose sunlight (also called solar prisms). These prisms have a relatively large volume. To keep the volume and mass of lenses and prisms low, so-called Fresnel lenses and Fresnel prisms (Fig. 2) are used. Conventional Fresnel prisms have linear, elongated structures and are mostly used to deflect light in one direction (Fig. 3). The invention describes a Fresnel prism optimized for color dispersion, wherein the Fresnel structures are not linear or straight but curved. This causes the passing, approximately parallel (sun)light to be refracted in an arc shape and simultaneously spectrally, resulting in a rainbow-like appearance. This phenomenon can be used for decorative, aesthetic, and perhaps even esoteric and / or architectural purposes. Use of Fresnel optics Fresnel lenses are well-known and can be used, for example, in overhead projectors or as wide-angle lenses in car rear windows. Fresnel prisms work on the same principle, except that here the light beam is not focused or defocused, but rather deflected in a different direction (prism effect). Applications of such Fresnel prisms are primarily found in ophthalmology (optometry), for example, in prism lenses to correct strabismus (crossed eyes). They are also used in stereo 3D imaging (stereoscopy). A significant drawback of these applications is the large amount of chromatic aberration, which causes rainbow-like light effects in the images. These effects are not suitable for creating an artificial rainbow. The invention presented here refracts a beam of light into an artificial curved rainbow using a flat optical device. Various devices for generating artificial rainbows are already known. State of the art Utility model DE 202020002440 U1 describes a "curved solar prism for producing an artificial, curved rainbow effect." In its practical implementation, this device is quite bulky. To achieve significant color separation (dispersion), the prism area must not be too narrow. A curved glass solar prism would then become very heavy. Manufacturing a curved solar prism from a suitable plastic is complex. Mechanical production (machining, polishing) is very time-consuming. Production using a liquid plastic or injection molding process is also time-consuming, as the curing process takes a long time due to the large volume. Furthermore, the prism's shape can warp during the curing process. Document US 000005146364 A shows a conventional prism and a convex mirror, whereby the radiation passing through the prism is reflected by the mirror, thus producing a round rainbow. Document US 00004953956 A discloses an optical device in the form of a V-shaped tub made of flexible material, filled with liquid. Light effects can be produced in this device by bending the tub's walls. The publication JP 002001141914 A shows a prismatic optical device in which the light is reflected internally in the prism at a curved surface. The publication WO 002004095369 A2 shows an optical device in which the light is split into a round rainbow using mirrors and many prisms. In the printed document DE 102006020052 A1, an artificial rainbow is created using an illuminated spray. While the aforementioned printed materials do allow for the creation of a rainbow, they lack a geometric shape suitable for decorative purposes. Furthermore, the construction of the known devices is complicated and impractical. In a number of publications concerning Fresnel lenses or optical devices or systems with Fresnel lenses (US 020190025474 A1, DE 000069603115 T2, DE 102016204605 A1, US 020150124315 A1, DE 202017105910 U1, DE 000003624188 A1, DE 000068921967 T2, DE 4443996 A1 and DE 8705103 U1), rainbow-like color effects or unwanted ghost images or sidelights are mentioned, which have a disturbing effect on the intended image, but which cannot be used to generate an artificial and curved rainbow. Internet research revealed that there are no optical products for producing curved rainbows available in the consumer goods, decorative items, giftware, or architectural sectors. Rainbow prisms are often polished objects that produce more or less point-like spectral light effects. So-called solar prisms are elongated prisms that produce only a spectral band, not a curved rainbow (Fig. 1). The object and condition of the invention is that the production of a curved rainbow can be manufactured using simple means, is very user-friendly, effective, and can be offered to the consumer market at attractive prices. Therefore, currently only the rainbow Fresnel prism is suitable for this purpose. Technical description The prismatic Fresnel structure of a rainbow Fresnel prism can be one-sided (Fig. 3) or two-sided (Fig. 4). However, to achieve better color separation (dispersion, chromatic aberration), it is recommended to implement the Fresnel structure on both sides. The bending of the prismatic Fresnel structure is perpendicular to the spectral splitting of the light and perpendicular to the direction of propagation of the light in the rainbow Fresnel prism. The exact design of the prism, such as the bending radius of the Fresnel structure, is not important. This can also vary along the prism, resulting in irregular rainbow shapes that can be very decorative. In order to manufacture a rainbow Fresnel prism in a stable plate, sufficient material must be present at the thinnest points. This can be visualized as several thin, individual curved solar prisms (single prisms) stacked inside one another (Fig. 5). In a variation of this, a rainbow Fresnel prism can also consist of individual curved solar prisms that are connected or glued together (Fig. 5b). The individual prisms can then be made of curved semi-finished material. In an advanced form, the double-sided rainbow Fresnel prism is not symmetrical; rather, each side has a different angle of refraction (Fig. 5c). The advantage is that, depending on the height of the incident (sun)light, the rainbow Fresnel prism can be rotated (by 180° from the vertical) and thus the side with the better angle of incidence can be selected (the optimal angle of incidence equals the angle of reflection). The material of a rainbow Fresnel prism must be dispersive. This means that light of different colors (wavelength λ) is refracted to different degrees (the refractive index n is wavelength-dependent: n(λ)). Examples include glass, plastics (e.g., Plexiglas, PMMA), and crystalline materials. Ideally, the material should be easily machinable (injection molding, pressing, mechanical processing). A rainbow Fresnel prism should be positioned relative to the (sun)light so that the entrance surface is illuminated as evenly as possible. Ideally, it should be hung from a window, for which a hanging device (e.g., a hook) may be provided. A mounting cord is attached through a hole in the rainbow Fresnel prism. Flat surfaces can also be provided (dashed areas in Fig. 4) to which double-sided adhesive pads or films can be attached, so that the rainbow Fresnel prism can be glued to a pane. A rainbow Fresnel prism can also be integrated into a more or less opaque surface, such as a window or roller shutter (Fig. 6). Fresnel prisms are very well suited for this purpose due to their flat design. When the morning or evening sun shines on the roller shutter with a rainbow Fresnel prism, the artificial rainbow is impressively visible in the dark room. A two-sided rainbow Fresnel prism can also consist of two one-sided rainbow Fresnel prisms, with each one-sided rainbow Fresnel prism being mounted (glued) onto one side of a (window) pane (Fig. 7a). In another embodiment, a rainbow Fresnel prism can be combined with a mirror. Ideally, a one-sided rainbow Fresnel prism is then mounted with its flat side facing the mirror (Fig. 7b). The refracting angles γ1 and γ2 are then identical. Since the dispersive prism effect occurs in each individual prism, the colored components overlap perpendicular to the spectral splitting shortly behind the rainbow Fresnel prism, and the rainbow effect is diffuse. Only at a distance several times the height of the Fresnel prism does the light of the same wavelength overlap in such a way that a brilliant rainbow effect becomes visible. Description of the characters Fig. 1: Refraction at a triangular prism with symmetrical beam path. Fig. 2: Comparison between a conventional and a Fresnel prism. Fig. 3: Beam path and function of a Fresnel prism (without chromatic aberration). Fig. 4: Schematic diagram of a rainbow Fresnel prism: on the left, the view of the rainbow Fresnel prism plate; on the right, section A-A. The three small dashed areas are flat and represent adhesive surfaces that can be used for mounting on a disk. Fig. 5: Detail views B of section A-A from Fig. 4 (schematic diagrams): a. Equilateral Fresnel prism design. b. Fresnel prism that has been glued together at the contact points from curved prisms (e.g., semi-finished products). c. Asymmetrical Fresnel prism design Fig. 6: Rainbow Fresnel prism integrated into a roller shutter slat. Fig. 7: a.a. Two one-sided rainbow Fresnel prisms with different refractive partial angles γ1 and γ2, mounted on opposite sides of a disk. b. One one-sided rainbow Fresnel prism mounted on a mirror. Reference symbol list The nomenclature commonly used in the literature, with Greek letters, was essentially adopted. α Angle of incidence α' Angle of reflection β Angle of deflection γ Refractive angle (vertical angle), divisible into the refracting partial angles γ1 and γ2L Longitudinal axis s Base

Claims

Optical device for generating rainbow-like light effects, comprising a body in the form of a thin plate: - made of one or more dispersive materials, - containing Fresnel prism structures having optical entry and / or exit surfaces arranged wedge-shaped to each other, - whose Fresnel prism structure is bent, wherein the bending of the Fresnel prism structure is perpendicular to the spectral splitting of the light and perpendicular to the direction of propagation of the light in the Fresnel prism structure, and the body is integrated into the surface of a window or roller shutter. Device according to claim 1, characterized in that the Fresnel prism structure is applied only on one side. Device according to claim 1, characterized in that the Fresnel prism structures are applied to both sides. Device according to claim 3, characterized in that in the optical device with Fresnel prism structure applied to both sides, the partial angles γ1 and γ2, which together give the refracting angle γ, are unequal. Device according to one of the preceding claims, characterized in that the bending of the Fresnel prism structure of the optical device: - comprises circular, elliptical or variable shapes, - is asymmetrical to the vertex angle of the prismatic structure. Device according to one of the preceding claims, characterized in that the optical device is composed of several curved Fresnel prism structures. Device according to one of the preceding claims, characterized in that the optical device has a mounting device comprising one or more bores or flat surfaces by means of which the optical device can be glued to a surface. Device according to one of the preceding claims, characterized in that one or two optical devices with a one-sided Fresnel prism structure are mounted on a transparent disk or several disks arranged one behind the other, or the optical device with a preferably one-sided Fresnel prism structure is mounted on a mirror. Device according to one of the preceding claims, characterized in that the refractive partial angles γ1 and γ2 of the optical device vary from partial prism to partial prism in such a way that a lens effect is achieved, so that in a certain distance range the light of the same wavelength is optimally superimposed.

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