Multifocal zone plates for recording and reconstructing multidimensional multispectral wavefields

Abstract

Planar, multifocal zone plate, characterized in that it combines at least two, preferably three, zone plate designs, each calculated for different wavelength ranges of the electromagnetic spectrum, geometrically superimposed as transmission overlays on a common planar support surface, wherein • each zone plate design is configured to focus on a predetermined plane for its respective main wavelength, • the bandwidth of the respective wavelength selectivity of individual zone plate designs are added in such a way that zones with one, several or all wavelength ranges are created on the carrier surface as transmissive for this range, • in optional embodiments, a selectively assigned wavelength filter (e.g. red, green or blue filter) is provided in the zones where only one of the designs is open, • and no filtering occurs in the overlap regions where several or all zone plate designs are open, so that these regions remain transmissive for several or all target wavelengths, thereby enabling multi-color focusing in a planar design without segmentation and without curvature or air space.

Description

Summary

[0001] The invention relates to planar, multifocal zone plates for the optical focusing of multidimensional and / or multispectral image data, in particular for integration on flat screens and other imaging systems. The zone plate according to the invention is characterized in that at least two or more, but preferably three, zone plate designs optimized for different wavelength ranges of the electromagnetic spectrum (e.g., wavelength range for human color perception: red, green, blue) are geometrically superimposed on a common substrate surface. This superposition is carried out in such a way that regions are created in which one, several, or all target wavelengths can be transmitted and focused simultaneously. Optionally, the exclusive zones, which are only transmissive for one wavelength, can be combined with corresponding color filters to further increase color selectivity.The structure is completely planar and allows efficient, color-correct focusing optics without complex segmentation or curvature of surfaces, making it particularly suitable for use in modern display technologies. Technical area

[0002] The invention relates to optical devices for visualizing and displaying multidimensional and multispectral data sets, in particular multifocal zone plates as planar diffractive optics. They are suitable for image processing, measurement systems, and modern display technologies for reproducing three-dimensional, four-dimensional, and / or spectrally enhanced image data on two-dimensional, stereoscopic, or autostereoscopic display devices (such as LCD, OLED, light-field, or head-mounted displays). In order to spatially capture the geometry of a scene, various measurement and / or recording methods are used today, such as triangulation, shadow or fringe projection, laser scanning, time-of-flight measurement, stereoscopy, tomography, holography, integral, or light-field photography. These methods enable the acquisition of three-dimensional or four-dimensional data sets of objects or scenes.

[0003] To enhance information, not only the visible part of the electromagnetic spectrum is used, but also other wavelength ranges, such as X-rays, ultraviolet, infrared, terahertz, radar, microwave, or radio waves. This allows for the generation of a spatial-spectral or multidimensional-multispectral data set. Such data is increasingly being evaluated using electronic data processing (EDP) for a wide variety of applications, such as exploration, surveying, positioning, object recognition, motion capture, reverse engineering, gesture recognition, simulation, VR / AR / MR, CAD, orthotics / prosthetics, or 3D printing.

[0004] A current focus of development is the efficient and clear visualization of such multidimensional data sets. This is usually done on two-dimensional displays, which are enhanced with modern display types such as stereoscopic, autostereoscopic, integral, or light-field displays. This allows spatial image content to be presented realistically; this can be of considerable benefit, for example, in telecommunications, telepresence, and time-critical, spatial applications (such as observation, surveillance, security, or hazard detection). State of the art

[0005] The spatial representation of multidimensional and / or multispectral image data is typically achieved on flat panel displays using additional optical structures applied to the display. The most common are conventional lens arrays, particularly cylindrical lens arrays according to Hess (e.g., CH61475) or microlens arrays according to Lippmann (Épreuves réversibles donnant la sensation du relief, J. Phys. Theor. Appl., vol. 7, no. 1, pp. 821-825, 1908) made of spherical or aspherical lenses. These lens arrays can be manufactured using lithography, etching, injection molding, or embossing techniques (e.g., US4200794, US11818839B2, WO2017102443A1) and laminated or bonded flat onto the display.

[0006] The advantages of these lenticular structures are their ease of manufacture, cost-effective integration, and the ability to specifically control image perception toward 3D or light-field reproduction. However, when applied to flat-panel displays with multiple functional layers (e.g., glass, polarizers, color filters), the problem often arises that the focal point of the lenses is not located on the active display surface, but offset within the layer system. This results in defocusing, image blur, and efficiency losses. The function of segmented or spherical lenticular structures can be further impaired by bonding them to the planar display surface, for example, by shortening the focal length or reducing light throughput.

[0007] Alternatively, parallax barriers are used. These are easier to manufacture and can be mounted as planar filter arrays at a defined distance from the display. The size of the transparent or wavelength-selective filters is usually a projection of the pixel width into the barrier plane. However, parallax barriers have the disadvantage that only a fraction of the display illumination can penetrate the barrier—especially with a large number of perspective views, as is the case with multiview displays.

[0008] In order to increase the luminance, combinations of parallax barriers and lenticular zone plates have already been proposed in the literature (e.g. EP1895782A2), in which the transparent barrier segments are manufactured in the size of the central (open) zone.

[0009] Zone plates can also be used directly as diffraction-based, ultra-flat optical elements to enable targeted intermediate imaging onto the planar display surface. Such zone plates, in Fresnel or Gabor configurations or as photon sieves, can be advantageously implemented as planar, diffractive structures, thus combining a low profile with precisely adjustable focal length—ideal for integration onto or into the display surface.

[0010] A disadvantage of the classic zone plate, however, is that it is always optimized for a single wavelength (monochromatic light). With color screens (RGB) or broadband light, chromatic aberrations such as color fringing or focus errors occur, making sharp reproduction of all colors simultaneously impossible. To overcome these limitations, segmented approaches (compound zone plates, multicolor diffractive lenses, etc.) have been introduced. In these, the display surface is divided into sub-areas, each of which has a zone plate structure designed for a specific wavelength (see, for example, ...). In these cases, however, the color transmittance in the respective area is spatially separated, and the structure is not suitable for simultaneous transmission or focusing of all colors in the same optical section. Segmented approaches also require more complex manufacturing processes (e.g.sequential lithography or masking) and lead to pixelation of the color or reduced light output. Disadvantages of previous solutions are therefore: • Defocusing and light losses in conventional lenticular screens due to the optical layers of the display, • chromatic aberration and limited color representation in classic, monofocal Fresnel zone plates, • and limited color transmission ranges as well as increased manufacturing complexity for segmented or composite multicolor zone plates. Object of the invention

[0011] The invention is based on the object of providing an optical structure with which multidimensional and / or multispectral image data can be displayed efficiently, sharply and color-corrected on a planar image surface (in particular on flat screens with several functional layers).

[0012] In particular, a device is to be created that • can be easily and smoothly integrated onto the surface of a screen, • no complex curvature or air space required for function, • can produce a common, focused intermediate image for several wavelength ranges (especially for the three primary colors red, green, blue), • largely avoids defocusing, image blur and chromatic aberrations, • offers high light output and efficiency and • can be manufactured using known manufacturing technologies (e.g. lithography, embossing processes).

[0013] Furthermore, the structure should be suitable for providing a targeted color-sensitive function (e.g., multi-color focus up to full white-light compatible focusing) with or without explicit color filtering and be used for integration into modern multidimensional display systems. Description of the invention

[0014] The present invention achieves the aforementioned object by means of a planar, multifocal zone plate that superimposes several zone plate designs on the common surface, with each individual zone plate being optimized for a specific wavelength (in particular for the red, green, and blue color channels of the visible spectrum). These designs are added arithmetically—i.e., mask-based—directly geometrically, creating regions in the resulting mask pattern that are specifically transmissive for one, several, or all of these wavelengths.

[0015] For this purpose, the zone plate structure is first calculated on a flat substrate. This allows focusing on the selected image plane (e.g., the surface of a flat screen) for the target wavelength, e.g., red (approx. 630 nm), green (approx. 532 nm), or blue (approx. 450 nm). The open (transparent) zones obtained from the respective radially symmetric (or strip-shaped) masks are superimposed in a mask-based manner. This results in a jointly usable, planar optical area that is transparent to multiple colors simultaneously in the overlapping zones and selectively open to individual colors elsewhere.

[0016] Optionally, the areas exclusively open to a single wavelength can be covered with suitable color filters, limiting the optical transmission to that color channel. The overlapping areas can be designed without filters, allowing multiple color channels to be focused together.

[0017] This additive superposition creates a planar, multifocal zone plate that can be easily and seamlessly integrated onto or into the surface of a screen or image sensor. The structure requires no curvature or air space, but can be designed in a single mask and manufacturing step. The zone arrangement can be rotationally symmetrical (circular zone plates), strip-shaped (10), or as a photon sieve.

[0018] Depending on the desired function, any wavelength range can be considered; the invention is not limited to RGB, but also includes multispectral or hyperspectral arrangements.

[0019] The invention allows the planar integration of a multifocal, color-selective diffractive optic that minimizes chromatic aberrations and enables more efficient use of the incident light. Fabrication is preferably carried out using a single- or multi-step lithography process, nanoimprinting, direct laser exposure, or comparable techniques.

[0020] An advantageous embodiment of the invention is set out in the first claim. An embodiment of the invention is described with reference to Fig. 1 to 8. They show: Fig. 1 the striped 1D zone plate structure for red (e.g. 630 nm), Fig. 2: the striped 1D zone plate structure for green (e.g. 532 nm), Fig. 3: the striped 1D zone plate structure for blue (e.g. 450 nm), Fig. 4: the striped 1D superimposed multifocal zone plate (color-coded), Fig. 5: the rotationally symmetric zone plate structure for red (e.g. 630 nm), Fig. 6: the rotationally symmetric zone plate structure for green (e.g. 532 nm), Fig. 7: the rotationally symmetric zone plate structure for blue (e.g. 450 nm), Fig. 8: Multifocal zone plate superimposed on the rotationally symmetric zone plate structure (color-coded).

[0021] Fig. Figure 1 shows the zone plate structure calculated for the wavelength red (1), e.g., 630 nm. Fig. 2 shows the corresponding design of the zone plate for the wavelength green (2), e.g., 532 nm. Fig. Figure 3 shows the zone plate structure optimized for blue (3), e.g., 450 nm. Fig. Figure 4 shows the arithmetic superposition of these three individual masks according to the inventive teaching. Areas 1 are visible in which all three zone plates are open simultaneously (7), areas with only one open zone appear red (2), green (3), or blue (4), as well as zones that are permeable to combinations of two colors. These are, for example, zones for red and green (4), red and blue (5), or green and blue (6).

[0022] The resulting multifocal zone plate structure thus provides a focusing effect for each selected wavelength, both for each individual color and in the overlapping area. If the exclusively color-specific zones are covered with corresponding color filters, targeted selective transmission for each color can be achieved. In the overlapping area, the mask is transparent to the entire visible spectrum (or the selected target wavelengths).

[0023] In Fig. 5 is a rotationally symmetric zone plate structure shown for the wavelength red, where the white areas are transparent for this wavelength. Fig. 6 shows a rotationally symmetric zone plate structure calculated for the wavelength green and Fig. 7 a rotationally symmetric zone plate structure calculated for the wavelength blue. In Fig. In Figure 8, these three rotationally symmetric zone plate structures are shown as a multifocal zone plate in gray values, with certain gray values ​​corresponding to defined wavelengths or wavelength ranges.

[0024] The entire structure is planar, so it can be easily applied to the surface of an LCD or OLED display.

[0025] In a further embodiment, the zone plates can be defined to focus on different planes. This is particularly advantageous when the color pixels of a specific wavelength are located on defined planes. This is the case, for example, with vertically stacked full-color micro-LEDs (see, for example, J. Shin et al., Vertical full-color micro-LEDs via 2D materials-based layer transfer, Nature, vol. 614, no. 7946, pp. 81-87, Feb. 2023). QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 4200794

[0005] US 11818839B2

[0005] WO 2017102443A1

[0005] Zitierte Nicht-Patentliteratur

[0000] Reversible tests giving the sensation of relief, J. Phys. Theor. Appl., vol. 7, no. 1, pp. 821-825, 1908

[0005] J. Shin et al., Vertical full-color micro-LEDs via 2D materials-based layer transfer, Nature, vol. 614, no. 7946, p. 81-87, Feb. 2023

[0025]

Claims

[1] Planar, multifocal zone plate, characterized by that it combines at least two, preferably three, zone plate designs, each calculated for different wavelength ranges of the electromagnetic spectrum, geometrically superimposed on a common planar support surface as transmission overlays, whereby • each zone plate design is configured to focus on a predetermined plane for its respective main wavelength, • the bandwidth of the respective wavelength selectivity of individual zone plate designs are added in such a way that zones with one, several or all wavelength ranges are created on the carrier surface as transmissive for this range, • in optional embodiments, a selectively assigned wavelength filter (e.g. red, green or blue filter) is provided in the zones where only one of the designs is open, • and no filtering occurs in the overlap regions where several or all zone plate designs are open, so that these regions remain transmissive for several or all target wavelengths, thereby enabling multi-color focusing in a planar design without segmentation and without curvature or air space. [2] Zone plate according to claim 1, wherein the zone plate designs are rotationally symmetrical (circular), strip-shaped or otherwise. [3] Zone plate according to one of the preceding claims, wherein the binary mask patterns are produced photolithographically or by another microstructure-forming process. [4] Zone plate according to one of the preceding claims, wherein the zone plate designs are manufactured according to a Gabor zone plate as non-binary wavelength-selective zone plates. [5] Zone plate according to one of the preceding claims, wherein photon sieves are used instead of the zone plates. [6] Zone plate according to one of the preceding claims, wherein phase-modulating optics, in particular multi-stage diffraction structures or phase-only elements, are used instead of the zone plates. [7] Zone plate according to one of the preceding claims, for integration into or onto a flat screen display, in particular for displaying multidimensional and / or multispectral image data. [8] Zone plate according to one of the preceding claims, for integration into a display which is viewed with magnifying optics or eyepieces, in particular into a head-mounted display. [9] Zone plate according to one of the preceding claims, for integration into a display constructed with color (sub)pixels in several levels, in particular from vertically stacked LEDs or micro-LEDs.

Images