Display panel using metamaterial for under display image sensor, manufacturing method thereof, and display device including same

Abstract

The present invention relates to a display panel, a manufacturing method thereof, and a display device including same. The display panel maximizes light and reduces high-order light in order to obtain a high-quality image and / or video by reducing the influence of rotated light by using a metamaterial for an under display camera (UDC). A metamaterial designed by adjoint optimization is formed under a display substrate having a periodic arrangement structure.

Description

Display panel using metamaterial for under-display image sensor, manufacturing method thereof, and display device including same

[0001] The present invention relates to a display panel using a metamaterial for an under-display image sensor, a method for manufacturing the same, and a display device including the same, and more particularly, to a technology for maximizing light and reducing high-order light to obtain high-quality images and / or videos by reducing the influence of rotated light using a metamaterial for an under-display camera (UDC).

[0002] Under Display Camera (UDC) technology hides a camera or Time of Flight (ToF) sensor beneath the display panel, eliminating visual distractions like display holes and notches. UDC technology maximizes user immersion by eliminating visual obstructions and maximizes panel area relative to the device's front surface, making it a promising next-generation display technology.

[0003] However, because display panels transmit radio waves through periodically arranged apertures, they transmit images to the UDC that are damaged by diffraction. Consequently, the image quality of the UDC is significantly inferior to that of cameras positioned in conventional hole or notch structures.

[0004] To reduce this diffraction phenomenon and solve the problem of low-quality images, a technology to lower the pixel density (PPI) of the existing display has been proposed, but there was a limitation that a mosaic pattern (or screen door effect) appeared on the display due to the lowered display pixel density PPI (Pixels Per Inch).

[0005] In addition, in order to solve the problem of low-quality images by reducing the diffraction phenomenon, a technology to restore degraded images by additionally utilizing existing computer algorithms such as Deep Learning and GAN was proposed, but there was a drawback that real-time image restoration and real-time video restoration were difficult due to the additional computer operations. In addition, a technology was proposed to improve the quality of images captured with UDC by adjusting the arrangement of existing display pixels, but there was a limit to the actual free arrangement because the pixel arrangement was affected by the pixel arrangement of the entire display and the circuit board.

[0006] Therefore, conventional technologies have failed to address the mosaic pattern problem that appears on displays due to low display pixel density (PPI). Despite the numerous technologies developed to date and the advantages of large screens, many companies have not adopted UDC in mobile phones due to the aforementioned issues.

[0007] The purpose of the present invention is to propose a meta-optical structure for reducing the influence of diffraction phenomena on images and / or videos and a backpropagation design technique (Adjoint optimization) for designing the same.

[0008] The purpose of the present invention is to design a metasurface using a backpropagation design technique (Adjoint optimization) so that diffraction does not occur in a UDC structure.

[0009] The purpose of the present invention is to propose a display panel that restores the phenomenon of light diffracted due to a periodic grating structure back to a plane wave by arranging a metasurface designed using the backpropagation design technique (adjoint optimization).

[0010] However, the technical problems to be solved by the present invention are not limited to the above problems, and can be expanded in various ways without departing from the technical spirit and scope of the present invention.

[0011] In a display panel using a metamaterial for an under display image sensor according to an embodiment of the present invention, a metamaterial designed using an adjoint optimization technique is formed on the lower part of a display substrate having a periodic array structure.

[0012] A display device including the display panel according to an embodiment of the present invention is provided.

[0013] A method for manufacturing a display panel using a metamaterial for an under display image sensor according to an embodiment of the present invention includes a step of forming a metamaterial designed using an adjoint optimization technique under a display substrate having a periodic array structure.

[0014] According to an embodiment of the present invention, by designing a metasurface using a backpropagation design technique (Adjoint optimization) to maximize the intensity of 0th-order diffracted light and reduce the intensity of higher-order light, the image and / or video quality degraded due to the diffraction phenomenon, which is a fundamental problem of UDC technology, can be significantly improved.

[0015] According to an embodiment of the present invention, a display structure including a meta-optical structure capable of maintaining a high pixel density while improving the quality of an image and / or video in real time can be proposed.

[0016] According to embodiments of the present invention, the quality of images and / or videos can be improved without additional computational processes, such as artificial intelligence algorithms used for image enhancement in UDC technology, thereby enabling real-time, high-quality image and / or video capture. Furthermore, superior image and / or video quality can be achieved even at higher PPI (Pixels Per Inch) compared to current UDC technology.

[0017] However, the effects of the present invention are not limited to the above effects, and can be expanded in various ways without departing from the technical spirit and scope of the present invention.

[0018] FIG. 1a and FIG. 1b are schematic diagrams illustrating the process of a backpropagation design technique for controlling diffraction phenomena according to an embodiment of the present invention.

[0019] FIG. 2 is a structural diagram of a display panel on a UDC according to an embodiment of the present invention.

[0020] FIG. 3 illustrates a cross-sectional view of a display panel including a metamaterial according to an embodiment of the present invention.

[0021] FIGS. 4A to 4I illustrate graphs of results of a function (MTF) for measuring the resolution of a camera according to an embodiment of the present invention.

[0022] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined solely by the scope of the claims.

[0023] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, operations, and / or elements.

[0024] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0025] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. Identical components in the drawings are designated by the same reference numerals, and redundant descriptions of identical components are omitted.

[0026]

[0027] The present invention aims to maximize light and reduce high-order light to obtain high-quality images and / or videos by reducing the influence of rotated light using metamaterials for UDC (Under Display Camera).

[0028] The present invention proposes an inverse metasurface that improves image quality by restoring diffraction caused by the periodic aperture of a display. The inverse metasurface is a metasurface that converts higher-order diffracted waves, whose propagation direction has changed due to diffraction, into 0th-order diffracted waves whose propagation direction is the same as before diffraction. The present invention designs the inverse metasurface using the backpropagation design technique, which is a high-performance free-form metasurface design method. In addition, it was confirmed through simulation that the inverse metasurface improves the power ratio of the 0th-order diffracted wave in the UDC structure from the existing 59.59% to 88.98%.

[0029] Meta-optical structures function to minimize diffraction effects caused by the display panel by maximizing the intensity of the 0th-order diffracted light and reducing the intensity of higher-order light. This can address the problem of image quality degradation caused by diffraction in UDCs.

[0030] The present invention optimizes a meta-optical structure using the adjoint method. While specific values ​​may be utilized during this optimization process, these values ​​are determined during the actual implementation and design process and can be adjusted to achieve optimal image quality.

[0031] The various descriptions, functions, procedures, suggestions, and methods described in the present invention can be applied to various devices for photographing and measuring using under-display image sensors (cameras and / or sensors).

[0032] Hereinafter, the present invention will be described in detail with reference to FIGS. 1 to 4.

[0033]

[0034] FIG. 1a and FIG. 1b are schematic diagrams illustrating the process of a backpropagation design technique for controlling diffraction phenomena according to an embodiment of the present invention.

[0035] Figures 1a and 1b illustrate the process of designing a metamaterial that maximizes 0th-order diffraction and reduces higher-order light according to an embodiment of the present invention using the backpropagation design technique. More specifically, Figure 1a illustrates a forward-propagation simulation, and Figure 1b illustrates a backpropagation simulation.

[0036] When light passes through periodically arranged apertures, as the number of apertures increases, the peak of the diffraction order (0) increases due to destructive interference as shown in Fig. 1a. th ), the remaining light is either eliminated or its intensity is reduced due to destructive interference.

[0037] In the case of light diffraction, even a periodic arrangement of 20 or more apertures of the same shape produces results nearly identical to an infinite array of apertures. Therefore, for a UDC display with 30 or more repeating pixel structures of the same shape, an infinitely periodic arrangement of apertures can be assumed.

[0038] Accordingly, the present invention utilizes the Bloch boundary condition to assume periodically arranged apertures. Since the Bloch boundary condition assumes an infinitely periodic repeating arrangement, only one unit section is simulated, and the results are the same as those obtained in a structure in which the unit section is infinitely repeated.

[0039] In this simulation result, only the light of the peak of the diffraction order remains, and a metamaterial that controls the intensity of the peak light of this diffraction order is designed.

[0040] Metamaterials are optical structures that can alter the phase, amplitude, and polarization properties of light by varying their effective refractive index. The present invention proposes a backpropagation design technique (adjoint optimization) for designing metamaterials that can reduce the impact of diffraction on images and / or video.

[0041] The backpropagation design technique (Adjoint optimization) is an optimization algorithm that calculates the change in the figure of merit for the entire design domain with only two simulations (forward propagation and backward propagation) through the concepts of Lorenz isotropy and equivalent dipole for the target design domain, and designs a structure that achieves maximization or minimization of the target figure of merit.

[0042] To be more specific, the backpropagation design technique sets the Figure of Merit (FoM) function to be maximized through the designed structure, and then calculates the derivative of the Figure of Merit function through two simulations, including a forward simulation and a backward propagation simulation (adjoint simulation). Then, through the process of repeating these two simulations and the gradient descent method, the amount of change in the Figure of Merit function according to changes in the permittivity or permeability of the design region can be predicted, and based on this, a structure that maximizes or minimizes the Figure of Merit function can be designed. At this time, the source of the backpropagation, the adjoint source, is determined based on the amount of change in the Figure of Merit function when a pre-specified change in permittivity occurs in each pixel within the design region. Through this iterative process, the amount of change in the Figure of Merit function when a material is placed in the design region can be calculated.

[0043] Referring to Fig. 1, a unit section of one d is simulated using block boundary conditions to assume a periodically arranged display structure, and the result is the same as that in a structure in which the unit section is infinitely repeated.

[0044] At this time, the performance index function to be maximized is as shown in [Mathematical Formula 1] below.

[0045] [Mathematical Formula 1]

[0046]

[0047]

[0048] Here, P 00 represents the power of the 0th order diffracted wave, and P ij represents the power of the diffraction order wave corresponding to the ith and jth along the x-axis and y-axis, respectively. Here, i and j are determined during the actual implementation and design process and can be adjusted to obtain optimal image quality.

[0049] By optimizing the structure that maximizes the performance index function of [Mathematical Formula 1], a meta-optical structure that maximizes the intensity of 0th-order diffraction light and reduces the intensity of higher-order light can be obtained.

[0050]

[0051] FIG. 2 is a structural diagram of a display panel on a UDC according to an embodiment of the present invention.

[0052] Figure 2 is a drawing of a display panel on a UDC according to an embodiment, which may be changed during actual implementation and design processes.

[0053] The display presented in the embodiment of the present invention includes a display structure as shown in FIG. 2.

[0054] Referring to FIG. 2, the display structure includes a unit pixel (200), and is composed of an absorptive pixel define layer (210), a transparent electrode (220), and an R subpixel (230), a G subpixel (240), and a B subpixel (250). The present invention aims to reduce the influence of the diffraction phenomenon on images and / or moving images by using a metamaterial designed by the adjoint optimization technique in a periodically arranged display structure. In addition, the present invention can obtain a meta-optical structure that maximizes the intensity of 0th-order diffracted light and reduces the intensity of higher-order light by the adjoint optimization technique described in the embodiments for all display structures in which pixels are periodically arranged.

[0055]

[0056] FIG. 3 illustrates a cross-sectional view of a display panel including a metamaterial according to an embodiment of the present invention.

[0057] Referring to FIG. 3, a metasurface optimized using a backpropagation design technique according to an embodiment of the present invention is positioned between the display panel and the camera lens and / or sensor.

[0058] A metamaterial structure optimized according to the method presented in the embodiments of the present invention is placed between a display panel and a camera lens and / or sensor. The structure functions to maximize the intensity of 0th-order diffracted light and reduce the intensity of higher-order light, thereby reducing diffraction effects caused by the display panel.

[0059] Looking at the unit pixel (300) in the display panel in FIG. 3, there is an encapsulation layer (310) that protects the LED of the display, and within it, red, green, and blue subpixels are positioned on the pixel driving circuit (320), and the subpixels are distinguished by an absorptive pixel division layer (330). In addition, a transparent region (340) is positioned between the pixel driving circuits (320). In addition, a metasurface (370) designed using a reverse propagation design technique according to an embodiment of the present invention is positioned below the display substrate (350) and the optical adhesive layer (360), and a metasurface substrate (380) is positioned below the metasurface (370).

[0060] Accordingly, the gist of the present invention is to restore the light generated in the transmission area (340) by the metasurface (370) so that light can pass through without being distorted by diffraction.

[0061] The present invention simulated a metasurface designed using the backpropagation technique by placing it under a display with a periodic arrangement as shown in Fig. 3, and confirmed that the diffraction effect of radio waves on the sensor or camera under the display was reduced.

[0062] Embodiments of the present invention may include applications utilizing cameras that capture images and / or video under a display panel, as well as sensors that measure under a display. The sensors include any optical-based sensor, including a Time of Flight (ToF) sensor and an optical fingerprint recognition device.

[0063]

[0064] FIGS. 4A to 4I illustrate graphs of results of a function (MTF) for measuring the resolution of a camera according to an embodiment of the present invention.

[0065] More specifically, FIG. 4a is a graph showing the experimental results of the MTF (Modulation Transfer Function) obtained by simulation in the absence of a diffractive structure for a RED pixel, FIG. 4b is a graph showing the experimental results of the MTF (Modulation Transfer Function) obtained by simulation in the presence of a diffractive structure without a metasurface for a RED pixel, and FIG. 4c is a graph showing the experimental results of the MTF (Modulation Transfer Function) obtained by simulation in the presence of a diffractive structure including a metasurface for a RED pixel.

[0066] In addition, FIG. 4d is a graph showing the experimental results of the MTF (Modulation Transfer Function) obtained through simulation in the absence of a diffractive structure for a GREEN pixel, FIG. 4e is a graph showing the experimental results of the MTF (Modulation Transfer Function) obtained through simulation in the presence of a diffractive structure without a metasurface for a GREEN pixel, and FIG. 4f is a graph showing the experimental results of the MTF (Modulation Transfer Function) obtained through simulation in the presence of a diffractive structure including a metasurface for a GREEN pixel.

[0067] In addition, FIG. 4g is a graph showing the experimental results of the MTF (Modulation Transfer Function) obtained through simulation in the absence of a diffractive structure for a BLUE pixel, FIG. 4h is a graph showing the experimental results of the MTF (Modulation Transfer Function) obtained through simulation in the presence of a diffractive structure without a metasurface for a BLUE pixel, and FIG. 4i is a graph showing the experimental results of the MTF (Modulation Transfer Function) obtained through simulation in the presence of a diffractive structure including a metasurface for a BLUE pixel.

[0068] Referring to FIGS. 4c, 4f, and 4i, it can be confirmed that even in a state with a diffraction structure, if a metasurface is included, the resolution is almost similar to that in a state without a diffraction structure, as shown in FIGS. 4a, 4d, and 4g.

[0069] Accordingly, it can be seen that the camera resolution of the UDC is significantly increased by including a metasurface designed using the backpropagation design technique (Adjoint optimization) according to an embodiment of the present invention, and by suppressing diffraction when such a metasurface is present, a clear, undistorted image and / or video can be obtained.

[0070] Through this invention, we propose a metasurface designed using the backpropagation technique to address the diffraction problem inherent in UDCs. The simulations described above demonstrate that the metasurface designed using the backpropagation technique effectively limits radio wave diffraction. Therefore, the proposed metasurface is expected to enable high-resolution under-display image sensors in various devices.

[0071]

[0072] The systems or devices described above may be implemented as hardware components, software components, and / or a combination of hardware components and software components. For example, the devices and components described in the embodiments may be implemented using one or more general-purpose computers or special-purpose computers, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a programmable logic unit (PLU), a microprocessor, or any other device capable of executing instructions and responding to them. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to the execution of the software. For ease of understanding, the processing device is sometimes described as being used alone; however, one of ordinary skill in the art will recognize that the processing device may include multiple processing elements and / or multiple types of processing elements. For example, a processing unit may include multiple processors, or a processor and a controller. Other processing configurations, such as parallel processors, are also possible.

[0073]

[0074] Software may include a computer program, code, instructions, or a combination of one or more of these, which may configure a processing device to perform a desired operation or may, independently or collectively, command the processing device. The software and / or data may be permanently or temporarily embodied in any type of machine, component, physical device, virtual equipment, computer storage medium or device, or transmitted signal wave, for interpretation by the processing device or for providing instructions or data to the processing device. The software may also be distributed over networked computer systems and stored or executed in a distributed manner. The software and data may be stored on one or more computer-readable recording media.

[0075]

[0076] The method according to the embodiment may be implemented in the form of program commands that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program commands, data files, data structures, etc., alone or in combination. The program commands recorded on the medium may be those specially designed and configured for the embodiment or may be those known and available to those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program commands, such as ROMs, RAMs, and flash memories. Examples of the program commands include not only machine language codes generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiment, and vice versa.

[0077] Although the embodiments described above have been described by way of limited examples and drawings, those skilled in the art will appreciate that various modifications and variations can be made based on the above teachings. For example, appropriate results can still be achieved even if the described techniques are performed in a different order than described, and / or components of the described systems, structures, devices, circuits, etc. are combined or combined in a different manner than described, or are replaced or substituted with other components or equivalents.

[0078]

[0079] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims described below.

Claims

1. In a display panel using metamaterials for an under display image sensor, A display panel in which a metamaterial designed using the adjoint optimization technique is formed on the lower part of a display substrate having a periodic array structure.

2. In paragraph 1, The above metamaterial is Comprising a three-dimensional (3D) metamaterial or a two-dimensional (2D) metasurface A display panel, characterized by:

3. In paragraph 2, The above metamaterial is It is formed as a metasurface on the lower part of the display substrate, and restores the diffraction of light occurring in the transmission area into a plane wave due to the periodic array structure of the display. A display panel, characterized by:

4. In paragraph 3, The above metasurface is Formed as a metamaterial that maximizes the performance index function using the above backpropagation design technique, it maximizes the intensity of 0th order diffracted light and reduces the intensity of higher order light. A display panel, characterized by:

5. In paragraph 1, The above backpropagation design technique A display panel that sets the performance that the metamaterial aims for as a figure of merit function, calculates the change in the figure of merit function through two simulations including a forward simulation and an adjoint simulation, and designs a structure that achieves maximization or minimization of the figure of merit function through this.

6. In paragraph 5, The above backpropagation design technique The above two simulations are performed multiple times (iterations) to obtain a structure that maximizes the performance index function using the gradient descent method. A display panel, characterized by:

7. Including a display panel according to any one of clauses 1 to 6. A display device characterized by:

8. In paragraph 7, The above display panel A display device, wherein the panel includes a periodic display structure.

9. In paragraph 7, The above display device A display device including the metamaterial designed using the adjoint optimization technique, located between the display panel and the camera lens.

10. In paragraph 7, The above display device A display device including the metamaterial designed using the adjoint optimization technique, located between the display panel and the sensor.

11. In paragraph 10, The above sensor A display device comprising at least one of a ToF (Time of Flight) sensor, an optical fingerprint recognition device, and an optical measuring device.

12. A method for manufacturing a display panel using a metamaterial for an under display image sensor, Step of forming a metamaterial designed using the adjoint optimization technique on the bottom of a display substrate with a periodic array structure A method for manufacturing a display panel, comprising:

13. In paragraph 12, The above metamaterial is Comprising a three-dimensional (3D) metamaterial or a two-dimensional (2D) metasurface A method for manufacturing a display panel, characterized by:

14. In paragraph 12, The above forming steps are A method for manufacturing a display panel, which forms a metamaterial structure that restores diffraction of light occurring in a transmission area into a plane wave due to a periodic array structure under a display substrate.

15. In paragraph 14, The above forming steps are Forming a metamaterial that maximizes the performance index function using the backpropagation design technique between the display panel and the image sensor to maximize the intensity of the 0th order diffracted light and reduce the intensity of the higher order light. A method for manufacturing a display panel, characterized by:

16. In paragraph 12, The above forming steps are A method for manufacturing a display panel, which uses the above-described backpropagation design technique to design a structure that achieves maximization or minimization of the figure of merit by calculating the change in the figure of merit through two simulations including a forward simulation and a backpropagation simulation after setting the target performance of the metamaterial as a figure of merit function.

17. In paragraph 16, The above forming steps are Forming the metamaterial designed by the backpropagation design technique that obtains a structure that maximizes the performance index function using the gradient descent method by performing multiple iterations of the trials consisting of the above two simulations. A method for manufacturing a display panel, characterized by:

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