Distance-specific carrier optimization method, method for generating hologram by using optimal carrier, and apparatus therefor

Abstract

The present specification relates to a technique by which a hologram generation device generates a hologram with reduced speckle noise by optimizing a carrier according to a specific distance. A method by which a hologram generation device generates a hologram, according to an embodiment of the present specification, comprises the steps of: setting a carrier by initializing an arbitrary complex field having a random phase and a random amplitude; removing a specific band component from the frequency band of the set carrier so as to transform the set carrier; propagating the transformed carrier for each specific distance, which is a depth plane in which a target object is present; setting a loss function for each specific distance on the basis of a target uniform amplitude at the specific distance and the amplitude of the carrier propagated to the specific distance; and updating the propagated carrier for each specific distance on the basis of the loss functions set for each specific distance.

Description

Carrier optimization method for specific distances and method for generating a hologram using the optimal carrier, and device according to the same

[0001] This specification relates to computer-generated hologram (CGH) technology, and in particular to a technology for reconstructing high-quality three-dimensional images by reducing speckle noise of a CGH encoded in a single sideband (SSB).

[0002] Computer-generated holograms (CGH) are a technology capable of digitally representing three-dimensional objects and reconstructing them to create actual three-dimensional images, and they have recently been attracting attention in various display fields. Generally, CGH is reconstructed by generating a complex field that includes complex phase and amplitude information of an object, and various carrier waves are used in this process.

[0003] The carrier wave plays a crucial role in determining the phase information of an object on the holographic plane. Conventional random phase carriers offer the advantages of a wide field of view and shallow depth of focus, but they have the disadvantage of causing speckle noise in the reconstructed image. This speckle noise degrades the quality of object reconstruction, making practical applications difficult.

[0004] In conventional technology, various methods have been proposed to suppress speckle noise. For example, time multiplexing technology reduces speckle noise by repeatedly synthesizing CGHs with multiple random phases, but this method is limited by the frame rate of the spatial light modulator (SLM). Additionally, stochastic gradient descent (SGD)-based methods, which require object-specific optimization, enable high-quality reconstruction, but they lack versatility as they require optimization specialized for specific objects.

[0005] Conventional technology has the problem that the quality of the reconstructed image is degraded due to speckle noise generated when using random phase carriers, and that real-time implementation is difficult because the time multiplexing method depends on the frame rate of the SLM. In addition, existing SGD-based methods have limitations in that they require object-specific optimization of the carrier, resulting in poor versatility, and require iterative optimization for new objects.

[0006] To solve these problems, the present specification proposes a technique for designing an optimized carrier wave that can be used independently of objects. According to the invention according to the embodiments of the present specification, speckle noise can be effectively suppressed by generating a carrier wave that is optimized in advance for a specific depth rather than for a specific object, and applying the same carrier wave to various objects.

[0007] Furthermore, this specification aims to overcome the limitations of existing technologies by proposing a technology that can maintain a wide field of view and a shallow depth of focus while considering the limited modulation characteristics of the SLM.

[0008] To solve the above technical problem, a method for generating a hologram with reduced speckle noise through at least one processor using a hologram generating device according to the first embodiment of the present specification may include: a step of initializing an arbitrary complex field having a random phase and a random amplitude and setting it as a carrier; a step of converting the set carrier by removing a specific band component from the frequency band of the set carrier; a step of propagating the converted carrier at specific distances, which is a depth plane where a target object exists; a step of setting a loss function at specific distances based on a target uniform amplitude at specific distances and the amplitude of the carrier propagated at specific distances; and a step of updating the propagated carrier at specific distances based on the loss functions set at specific distances.

[0009] The step of converting the carrier wave set above may include the step of encoding the carrier wave set above using a single sideband (SSB) method.

[0010] The step of setting the loss function may be a step of calculating the difference between the target uniform amplitude and the amplitude of the propagated carrier wave for each specific distance and setting the mean square error as the loss function.

[0011] The step of updating the propagated carrier wave can update the propagated carrier wave using an ADAM optimizer (Adaptive Moment Estimation optimizer) that combines momentum and an adaptive learning rate based on the loss function for each specific distance.

[0012] A method for generating a hologram may further include: a step of generating an optimal carrier for each specific distance by repeating the steps of updating the propagated carrier, the step of propagating the transformed carrier for each specific distance, the step of setting the loss function, and the step of updating the propagated carrier for each specific distance after the step of updating the propagated carrier; a step of dividing a 3D object, which is the target object for hologram generation, into a plurality of individual layers according to depth; a step of applying the optimal carrier corresponding to the depth of each divided individual layer to each individual layer; and a step of generating a hologram by propagating each individual layer to which the optimal carrier is applied to a hologram plane through a Band-Limited Angular Spectrum (BLAS) method.

[0013] A method for generating a hologram may include: a step of generating an optimal carrier for each specific distance by repeating the steps of updating the propagated carrier, the step of propagating the transformed carrier for each specific distance, the step of setting the loss function, and the step of updating the propagated carrier for each specific distance after the step of updating the propagated carrier; a step of acquiring light field data composed of orthographic views at various observation angles of a 3D object that is the target object for hologram generation; a step of generating an initial hologram by applying a Wigner inverse transform based on the light field data; and a step of generating a final hologram by applying the optimal carrier to the initial hologram.

[0014] A computer-readable recording medium according to the second embodiment of the present specification can record a program for executing a hologram generation method according to the first embodiment of the present invention on a computer.

[0015] A hologram generating device according to the third embodiment of the present specification may include at least one processor that drives a hologram generating program that generates a hologram with reduced speckle noise by optimizing a carrier wave for each specific distance; and a memory that stores the hologram generating program.

[0016] The above hologram generation program initializes an arbitrary complex field having random phase and random amplitude to set it as a carrier wave, transforms the set carrier wave by removing specific band components from the frequency band of the set carrier wave, propagates the transformed carrier wave at specific distances in a depth plane where a target object exists, sets a loss function at specific distances based on a target uniform amplitude at specific distances and the amplitude of the carrier wave propagated at specific distances, and updates the propagated carrier wave at specific distances based on the loss functions set at specific distances.

[0017] In addition, the hologram generation program can generate an optimal carrier wave for each specific distance by repeating the process of propagating the converted carrier wave for each specific distance, the process of setting the loss function, and the process of updating the propagated carrier wave for each specific distance.

[0018] The above hologram generation program can be converted by encoding the set carrier wave using a single sideband (SSB) method.

[0019] The above hologram generation program can calculate the difference between the target uniform amplitude and the amplitude of the propagated carrier wave for each specific distance and set the mean square error as the loss function.

[0020] The above hologram generation program can update the propagated carrier wave by using an ADAM optimizer (Adaptive Moment Estimation optimizer) that combines momentum and adaptive learning rate based on the loss function for each specific distance.

[0021] The above hologram generation program can generate a hologram by generating the optimal carrier wave for each specific distance, dividing a 3D object that is the target object for hologram generation into multiple individual layers according to depth, applying the optimal carrier wave corresponding to the depth of each divided individual layer to each individual layer, and propagating each individual layer to which the optimal carrier wave is applied to the hologram plane through a Band-Limited Angular Spectrum (BLAS) method.

[0022] The above hologram generation program can generate the optimal carrier wave for each specific distance, then acquire light field data consisting of orthographic views at various observation angles of a 3D object that is the target object for hologram generation, generate an initial hologram by applying a Wigner inverse transform based on the light field data, and generate a final hologram by applying the optimal carrier wave to the initial hologram.

[0023] The invention according to one embodiment of the present specification improves the quality of a reconstructed image by reducing speckle noise and ensures universality by pre-designing a carrier optimized according to depth, thereby allowing the same carrier to be applied to various objects located at a specific depth. As a result, high-quality 3D images can be reconstructed by suppressing speckle noise and maintaining a wide field of view and a shallow depth of focus. Furthermore, since additional optimization processes for each object are unnecessary, the speed of CGH synthesis can be significantly improved when changing objects. These effects are expected to make a significant contribution to display and optical applications where high-quality 3D image realization is required.

[0024] The accompanying drawings, included as part of the detailed description to aid in understanding the present specification, provide embodiments of the present specification and explain the technical features of the present specification together with the detailed description.

[0025] Figure 1 is a diagram illustrating computer-generated hologram technology and speckle noise generated during the hologram generation process.

[0026] FIG. 2 is a diagram illustrating the overall process of a carrier optimization method according to an embodiment of the present specification.

[0027] FIG. 3 is a flowchart showing, in chronological order, a method for optimizing a carrier wave in a method for generating a hologram using a hologram generating device according to an embodiment of the present specification.

[0028] FIG. 4 is a diagram illustrating the overall process of synthesizing a hologram according to an embodiment of the present specification.

[0029] FIG. 5 is a diagram showing, in chronological order, a method of generating a hologram using an optimal carrier wave and a multilayer-based method, in a method of generating a hologram using a hologram generating device according to an embodiment of the present specification.

[0030] FIGS. 6 and 7 are diagrams comparing a method using an optimal carrier wave according to an embodiment of the present specification and a conventional method using a random phase in a multilayer-based CGH.

[0031] FIG. 8 is a diagram showing, in chronological order, a method of generating a hologram using an optimal carrier wave in a method of generating a hologram by a hologram generating device according to an embodiment of the present specification.

[0032] FIGS. 9 and 10 are diagrams comparing a method using an optimal carrier wave according to an embodiment of the present specification and a conventional method using a random phase in a WLFH CGH.

[0033] FIG. 11 is a block diagram showing a hologram generating device according to an embodiment of the present specification.

[0034] Embodiments of the present specification will be described in detail below with reference to the drawings. However, detailed descriptions of known functions or configurations that may obscure the essence of the embodiments in the following description and the attached drawings are omitted. Additionally, throughout the specification, the term 'comprising' a component means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0035] The terms used herein are merely for describing specific embodiments and are not intended to limit the specification. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as “comprising” or “comprising” are intended to specify the existence of the described features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0036] Unless specifically defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this specification pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this specification.

[0037] Figure 1 is a diagram illustrating computer-generated hologram technology and speckle noise generated during the hologram generation process.

[0038] Computer-generated holograms (CGH) are a technology capable of displaying three-dimensional objects, and are used to synthesize holograms based on amplitude data of three-dimensional objects using various carrier waves that determine the phase distribution of the object's surface. In particular, in CGH synthesis, complex fields with random phases are generally used as carrier waves to achieve a wide field of view and a shallow depth of focus (DOF).

[0039] CGH is represented as complex data that indicates the complex field of an object in the holographic plane as amplitude and phase distributions. In a simulation environment, it is possible to obtain noise-free object reconstruction by numerically propagating the CGH, expressed as complex values, to the object plane. However, to perform actual optical reconstruction, the complex data must be converted into amplitude or phase data and encoded due to the limited modulation characteristics of currently available Spatial Light Modulators (SLMs). This process results in some loss of the original complex data, and this data loss causes various types of noise during holographic reconstruction. In particular, one of the major types of noise is speckle noise.

[0040] Referring to Fig. 1, the reason for speckle noise is illustrated. Speckle noise is caused by the integration of light with random phases within the resolvable points of the observation system. This is because the random phase distribution used as a carrier wave during CGH synthesis causes speckle noise during the reconstruction of the encoded CGH. Thus, the main reason for speckle noise in CGH lies in the characteristics of the carrier wave having a random phase distribution, and such a carrier wave degrades the quality of the reconstructed image.

[0041] This specification proposes a novel approach to optimizing a carrier wave to reduce speckle noise occurring in CGH. Instead of using a conventional carrier wave with a random phase distribution, the invention according to the embodiments of this specification optimizes the carrier wave so that the intensity of the reconstructed object is uniform at a specific distance. This reduces amplitude fluctuations of the carrier wave and effectively reduces speckle noise in the reconstructed image.

[0042] First Embodiment: Carrier Optimization

[0043] FIG. 2 is a diagram illustrating the overall process of a carrier optimization method according to an embodiment of the present specification.

[0044] The carrier wave is an auxiliary complex field used in the CGH synthesis of a given object. An object is defined by the amplitude distribution of object points in a two-dimensional plane or three-dimensional space. Therefore, the phase distribution of object points provides degrees of freedom that can be assigned in the CGH synthesis. The phases of object points can be assigned individually or determined by assuming a wave illuminating the object. The carrier wave is a virtual wave illuminating the object and determines the phase distribution of the object points.

[0045] The phase distribution of an object defines the angular spectrum of the object's complex field, which determines angular characteristics such as diffusivity, field of view, and depth of focus (DOF) of the reconstructed object surface.

[0046] When a uniform phase plane carrier is used, the reconstructed object surface appears like a reflective surface. The angular spectrum is concentrated at the center, providing a very limited field of view and deep depth of field.

[0047] In contrast, random phase carriers form a diffuse object surface. Such holograms have a wide-angle spectrum covering the entire spatial frequency domain and, while limited by the spatial sampling interval of the hologram, provide a shallow DOF and a wide field of view.

[0048] During the CGH synthesis process, the object phase distribution imparted by the carrier affects the reconstruction's field of view, depth of field (DOF), and speckle noise. A uniform phase distribution provides a clean, speckle-free reconstruction but is limited by a small field of view and deep DOF. Conversely, a random phase distribution maximizes the wide field of view and shallow DOF, but the reconstruction becomes contaminated by speckle noise. Therefore, a trade-off exists between these two approaches.

[0049] Since it is important to suppress speckle noise while maintaining a shallow depth of field for vivid 3D object reconstruction, it is necessary to find an optimal carrier that balances the depth of field and speckle noise. Conventional approaches optimize the carrier for a given object, so a new optimization process must be performed for a new object. On the other hand, the hologram generation method according to the embodiments of this specification finds a carrier optimized at a specific object distance, and since it is not specialized for the object, it can be universally applied to any object at the same distance.

[0050] Referring to Fig. 2, an initial carrier wave with random amplitude and random phase distribution is generated in the hologram plane (z = 0). The initial carrier wave is converted into an angular spectrum through a Fourier transform, which represents the spatial frequency information of the carrier wave.

[0051] Subsequently, Single Sideband (SSB) filtering is applied to the angular spectrum. SSB filtering serves to adjust the carrier wave by removing specific components from the frequency band.

[0052] The angular spectrum with SSB filtering applied is converted back into the spatial domain through the Inverse Fourier Transform, and the carrier wave propagates to the target plane (z = ξ).

[0053] The uniform amplitude set as the target in the target plane is compared with the actual amplitude (random amplitude) of the propagated carrier wave. The result of this comparison is calculated as a loss function and is used as an indicator for optimizing the carrier wave in the target plane.

[0054] Subsequently, the carrier is updated based on a loss function representing the difference between the target amplitude and the actual amplitude, and the updated carrier returns to the initial stage to repeat the optimization process to generate the optimal carrier. A detailed explanation of the method for optimizing the carrier will be provided in Figure 3.

[0055] FIG. 3 is a flowchart showing, in chronological order, a method for optimizing a carrier wave in a method for generating a hologram using a hologram generating device according to an embodiment of the present specification.

[0056] Referring to FIG. 3, in step S110, the hologram generating device can initialize an arbitrary complex field having a random phase and a random amplitude and set it as a carrier wave.

[0057] In step S120, the hologram generating device can convert the set carrier by removing specific band components from the frequency band of the set carrier. At this time, the hologram generating device can encode the set carrier using a single sideband (SSB) method. In this process, half-band blocking in the frequency band of the set carrier may be considered.

[0058] Spatial Light Modulators (SLMs) have a limitation in that currently available devices cannot directly process complex values ​​and can only modulate using amplitude or phase data. Consequently, there is a high probability of direct current (DC) and conjugate noise occurring during the process of encoding complex data into amplitude or phase data.

[0059] The DC component is a zero-frequency component in the frequency domain, a low-frequency component with very high light intensity. The DC component causes excessive brightness at the center of the reconstructed image and can distort useful reconstruction data.

[0060] Conjugate noise is a symmetric component of a complex signal that occurs when complex data is encoded into real data, and during hologram reconstruction, the conjugate component creates unnecessary mirror image reconstruction, interfering with the original signal.

[0061] Accordingly, the hologram generating device according to the embodiment of the present specification can encode the set carrier wave in a single-sideband manner to remove DC and conjugate noise and leave only the desired signal.

[0062] The process of encoding using a single sideband method can improve the Signal-to-Noise Ratio (SNR) by blocking half of the angular spectrum of the carrier wave set above.

[0063] In step S130, the hologram generating device can propagate the transformed carrier wave at specific distances, which is the depth plane where the target object exists. Since an arbitrary complex field having random phase and random amplitude is used as the initial carrier wave, the transformed carrier wave still has a random amplitude.

[0064] In step S140, the hologram generating device can set a loss function for each specific distance based on the target uniform amplitude at a specific distance and the amplitude of the carrier wave propagated to the specific distance.

[0065] At this time, the hologram generating device can calculate the difference between the target uniform amplitude and the amplitude of the propagated carrier wave for each specific distance and set the mean square error as the loss function.

[0066] In step S150, the hologram generating device can update the propagated carrier wave for specific distances based on loss functions set for specific distances.

[0067] At this time, the hologram generation device can update the propagated carrier wave using an ADAM optimizer (Adaptive Moment Estimation optimizer) that combines momentum and an adaptive learning rate based on the loss function for each specific distance.

[0068] effect

[0069] According to the embodiments of the present specification, the optimal carrier wave optimized is designed to minimize amplitude fluctuations at a specific distance, which is the depth plane where the target object exists, so that the optimal carrier wave can achieve a clean reconstructed image with significantly reduced speckle noise at the object distance while maintaining the carrier wave's inherent randomness.

[0070] Furthermore, when generating a hologram using the optimal carrier wave described above, there is an advantage in that the carrier wave optimized at a specific distance can be applied to other objects at the same distance. Since the optimal carrier wave is content-independent, a carrier wave optimized once at a specific distance can be repeatedly used for various objects, which significantly improves computational efficiency compared to existing object-specific optimization methods and contributes to reducing reconstruction time while maintaining the quality of CGH reconstruction.

[0071] Second Embodiment: Hologram generation using an optimal carrier wave

[0072] FIG. 4 is a diagram illustrating the overall process of synthesizing a hologram according to an embodiment of the present specification.

[0073] Referring to Fig. 4, it can be seen that the optimal carrier wave is applied to any optical field or multilayer structure.

[0074] A hologram generating device according to an embodiment of the present specification can generate a hologram using a multi-layer-based method or a WLFH (Wigner Light Field Holography) method.

[0075] The multilayer-based method divides a 3D object into multiple individual layers based on depth and synthesizes a hologram using the information from each layer. Each individual layer is located at a specific depth and propagates to the holographic plane via the Band-limited Angular Spectrum (BLAS) method. The multilayer-based method has the advantage of clearly defining information in each layer and being able to finely reflect the depth information of the target object.

[0076] The WLFH method is a technique that generates holograms by applying the Wigner Inverse Transform (WIT) based on light field data. The light field data consists of orthographic views of an object from various viewing angles, which enables more precise hologram synthesis that includes the object's angular information, unlike multilayer-based methods. The WLFH method enables more realistic 3D reconstruction by utilizing data from various viewing angles.

[0077] A detailed explanation of the method for generating a hologram by applying the optimal carrier wave to each method is provided in Figures 5 and 8, respectively.

[0078] Referring to FIG. 5, in step S160, the hologram generating device can generate an optimal carrier wave for each specific distance by repeating the steps of propagating the converted carrier wave for each specific distance (step S130), setting the loss function (step S140), and updating the propagated carrier wave for each specific distance (step S150).

[0079] Step S170 represents the step of generating a hologram by applying the optimal carrier wave to the multilayer-based method.

[0080] In step S171, the hologram generating device can divide a 3D object, which is the target object for hologram generation, into multiple individual layers according to depth.

[0081] The hologram generating device is the three-dimensional object Multiple discrete layers depending on depth The process of dividing into can be expressed by the following mathematical formula.

[0082]

[0083] In the above mathematical formula, represents the index of the individual layer mentioned above.

[0084] In step S173, the hologram generating device can apply the optimal carrier corresponding to the depth of each of the divided individual layers to each of the individual layers.

[0085] In step S175, the hologram generating device can generate a hologram by propagating each of the individual layers to which the optimal carrier is applied into the hologram plane through a band-limited angle spectrum method.

[0086] The hologram generated based on each of the individual layers to which the optimal carrier wave is applied can be expressed by the following mathematical formula.

[0087]

[0088] In the above mathematical formula, represents the above-mentioned optimized carrier, and the symbol F represents the Fourier transform, represents the propagation kernel.

[0089] The propagation kernel can be expressed by the following mathematical formula.

[0090]

[0091] Here, and means spatial frequency, and represents the wavelength.

[0092] FIGS. 6 and 7 are diagrams comparing a method using an optimal carrier wave according to an embodiment of the present specification and a conventional method using a random phase in a multilayer-based CGH.

[0093] Figure 6 shows the results of a comparative experiment when the specific distance, which is the depth plane where the target object exists, is 1 cm, and Figure 7 shows the results of a comparative experiment when the specific distance is 3 cm.

[0094] Parts (a) of FIG. 6 and (d) of FIG. 7 show reference data (Ground truth), parts (b) of FIG. 6 and (e) of FIG. 7 show the result of generating a hologram using the optimal carrier wave according to the embodiment of the present specification at the top, and the result of generating a hologram using a conventional random phase at the bottom.

[0095] Parts (c) of Fig. 6 and (f) of Fig. 7 show the amplitude distribution measured according to the vertical solid line ("Yellow line" part) inside the small box in parts (a) and (b) of Fig. 6 and parts (d) and (e) of Fig. 7, respectively, where the solid line represents reference data and the dotted line represents the simulation results according to each method.

[0096] As can be seen in Figures 6 and 7, the result of generating a hologram by applying the optimal carrier wave to the multilayer-based method is of higher quality than the existing method, and also shows superior results when comparing the amplitude distribution with reference data.

[0097] FIG. 8 is a diagram showing, in chronological order, a method of generating a hologram using an optimal carrier wave in a method of generating a hologram by a hologram generating device according to an embodiment of the present specification.

[0098] Referring to FIG. 8, in step S160, the hologram generating device can generate an optimal carrier wave for each specific distance by repeating the steps of propagating the converted carrier wave for each specific distance (step S130), setting the loss function (step S140), and updating the propagated carrier wave for each specific distance (step S150).

[0099] Step S180 represents the step of generating a hologram by applying the optimal carrier wave to the WLFH method.

[0100] In step S181, the hologram generating device can acquire optical field data consisting of orthogonal views from various observation angles of the 3D object that is the target object for hologram generation.

[0101] The above optical field data It can be given as. In this case, represents spatial coordinates in the holographic plane. Spatial frequency is the ray angle Since it is related to optical field data various observation angles Orthogonal view in It can be represented as a set of.

[0102] In step S183, the hologram generating device can generate an initial hologram by applying an inverse Wigner transform based on the optical field data.

[0103] The above initial hologram can be represented by the following mathematical formula.

[0104]

[0105] In the above mathematical formula, represents the carrier wave. Specifically, in the initial hologram generated in step S183 represents an arbitrary carrier wave of the initial hologram above.

[0106] The initial hologram of the above mathematical formula 4 is the given optical field data It can be calculated as follows from.

[0107]

[0108] In the above mathematical formula, is an angle coordinate It represents the Fourier transformed axis of the above mathematical equation 5. , and has the following relationship.

[0109]

[0110] In step S185, the hologram generating device can generate a final hologram by applying the optimal carrier wave to the initial hologram.

[0111] At this time, of the above mathematical formula 4 It is replaced and applied with the above optimal carrier wave.

[0112] FIGS. 9 and 10 are diagrams comparing a method using an optimal carrier wave according to an embodiment of the present specification and a conventional method using a random phase in a WLFH CGH.

[0113] Figure 9 shows the results of a comparative experiment when the specific distance is 10 mm, and Figure 10 shows the results of a comparative experiment when the specific distance is -7 mm.

[0114] Parts (a) of FIG. 9 and (d) of FIG. 10 show reference data (Ground truth), parts (b) of FIG. 9 and (e) of FIG. 10 show the result of generating a hologram using the optimal carrier wave according to the embodiment of the present specification at the top, and the result of generating a hologram using a conventional random phase at the bottom.

[0115] Parts (c) of Fig. 9 and (f) of Fig. 10 show the amplitude distribution measured according to the vertical solid line ("Yellow line" part) inside the small box in parts (a) and (b) of Fig. 9 and parts (d) and (e) of Fig. 10, respectively, where the solid line represents reference data and the dotted line represents the simulation results according to each method.

[0116] As can be seen in Figures 9 and 10, the result of generating a hologram by applying the optimal carrier wave to the WLFH method is of higher quality than the existing method, and also shows superior results when comparing the amplitude distribution with reference data.

[0117] Meanwhile, a computer-readable recording medium according to an embodiment of the present specification may record a program for executing a hologram generation method according to an embodiment of the present specification on a computer. The computer-readable recording medium includes all types of recording devices in which data that can be read by a computer system is stored.

[0118] Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage devices. Additionally, computer-readable recording media can be distributed across networked computer systems, allowing computer-readable code to be stored and executed in a distributed manner.

[0119] FIG. 11 is a block diagram showing a hologram generating device according to an embodiment of the present specification, which is a reconstruction of the hologram generating method according to an embodiment of FIG. 3 in terms of hardware configuration. To avoid duplication of description, only an overview of the operation and function of each configuration is briefly described.

[0120] Referring to FIG. 11, a hologram generating device (10) may include at least one processor (20) that runs a hologram generating program that generates a hologram with reduced speckle noise by optimizing a carrier wave for specific distances; and a memory (30) that stores the hologram generating program. In this case, the processor (20) and the memory (30) may be electrically connected, but may be directly or indirectly connected.

[0121] In the above processor (20), the hologram generation program initializes an arbitrary complex field having a random phase and a random amplitude to set it as a carrier wave, converts the set carrier wave by removing a specific band component from the frequency band of the set carrier wave, propagates the converted carrier wave at specific distances, which is a depth plane where a target object exists, sets a loss function at specific distances based on a target uniform amplitude at specific distances and the amplitude of the carrier wave propagated at specific distances, and updates the carrier wave propagated at specific distances based on the loss functions set at specific distances. Additionally, the hologram generation program can generate an optimal carrier wave at specific distances by repeating the process of propagating the converted carrier wave at specific distances, the process of setting the loss function, and the process of updating the carrier wave propagated at specific distances.

[0122] In the above processor (20), the hologram generation program can be converted by encoding the set carrier wave using a single sideband (SSB) method.

[0123] In the above processor (20), the hologram generation program can calculate the difference between the target uniform amplitude and the amplitude of the propagated carrier wave for each specific distance and set the mean square error as the loss function.

[0124] In the above processor (20), the hologram generation program can update the propagated carrier wave using an ADAM optimizer (Adaptive Moment Estimation optimizer) that combines momentum and adaptive learning rate based on the loss function for each specific distance.

[0125] In the above processor (20), the hologram generation program can generate a hologram by generating the optimal carrier wave for each specific distance, dividing a 3D object that is the target object for hologram generation into multiple individual layers according to depth, applying the optimal carrier wave corresponding to the depth of each divided individual layer to each individual layer, and propagating each individual layer to which the optimal carrier wave is applied to the hologram plane through a Band-Limited Angular Spectrum (BLAS) method.

[0126] In the above processor (20), the hologram generation program can generate the optimal carrier wave for each specific distance, then acquire light field data consisting of an orthographic view at various observation angles of a 3D object that is the target object for hologram generation, generate an initial hologram by applying a Wigner inverse transform based on the light field data, and generate a final hologram by applying the optimal carrier wave to the initial hologram.

Claims

1. A method in which a hologram generating device generates a speckle noise-reduced hologram through at least one processor, A step of initializing an arbitrary complex field having random phase and random amplitude and setting it as a carrier wave; A step of converting the set carrier wave by removing a specific band component from the frequency band of the set carrier wave; A step of propagating the converted carrier wave at specific distances in the depth plane where the target object exists; A step of setting a loss function for each specific distance based on a target uniform amplitude at a specific distance and the amplitude of a carrier wave propagated over a specific distance; and A method for generating a hologram, comprising the step of updating the propagated carrier wave for each specific distance based on loss functions set for each specific distance.

2. In Paragraph 1, The step of converting the carrier wave set above is, A method for generating a hologram, comprising the step of encoding the set carrier wave using a single sideband (SSB) method.

3. In Paragraph 1, The step of setting the above loss function is, A method for generating a hologram, characterized by calculating the difference between the target uniform amplitude and the amplitude of the propagated carrier wave for each specific distance and setting the mean square error as a loss function.

4. In Paragraph 3, The step of updating the propagated carrier wave is, A hologram generation method characterized by updating the propagated carrier wave using an ADAM optimizer (Adaptive Moment Estimation optimizer) that combines momentum and an adaptive learning rate based on the loss function for each specific distance.

5. In Paragraph 1, After the step of updating the propagated carrier wave mentioned above, A step of generating an optimal carrier wave for each specific distance by repeating the steps of propagating the converted carrier wave for each specific distance, setting the loss function, and updating the propagated carrier wave for each specific distance; A step of dividing a 3D object, which is the target object for hologram generation, into multiple individual layers according to depth; A step of applying the optimal carrier wave corresponding to the depth of each of the divided individual layers to each of the individual layers; and A method for generating a hologram, further comprising the step of generating a hologram by propagating each of the individual layers to which the optimal carrier wave is applied into a holographic plane through a Band-Limited Angular Spectrum (BLAS) method.

6. In Paragraph 1, After the step of updating the propagated carrier wave mentioned above, A step of generating an optimal carrier wave for each specific distance by repeating the steps of propagating the converted carrier wave for each specific distance, setting the loss function, and updating the propagated carrier wave for each specific distance; A step of acquiring light field data composed of orthographic views from various observation angles of a 3D object that is the target object for hologram generation; A step of generating an initial hologram by applying a Wigner inverse transform based on the above optical field data; and A method for generating a hologram, comprising the step of generating a final hologram by applying the optimal carrier wave to the initial hologram.

7. A computer-readable recording medium storing a program for executing the method of any one of claims 1 to 6 on a computer.

8. At least one processor that runs a hologram generation program that generates a hologram with reduced speckle noise by optimizing the carrier wave for specific distances; and A memory for storing the above-mentioned hologram generation program; is included, The above hologram generation program is, Initialize an arbitrary complex field having random phase and random amplitude to set it as a carrier wave, transform the set carrier wave by removing specific band components from the frequency band of the set carrier wave, propagate the transformed carrier wave at specific distances in the depth plane where the target object exists, set a loss function at specific distances based on the target uniform amplitude at specific distances and the amplitude of the carrier wave propagated at specific distances, update the carrier wave propagated at specific distances based on the loss functions set at specific distances, A hologram generating device that generates an optimal carrier wave for each specific distance by repeating the process of propagating the converted carrier wave for each specific distance, the process of setting the loss function, and the process of updating the propagated carrier wave for each specific distance.

9. In Paragraph 8, The above hologram generation program is, A hologram generating device characterized by converting by encoding the set carrier wave using a single sideband (SSB) method.

10. In Paragraph 8, The above hologram generation program is, A hologram generating device characterized by calculating the difference between the target uniform amplitude and the amplitude of the propagated carrier wave for each specific distance and setting the mean square error as a loss function.

11. In Paragraph 10, The above hologram generation program is, A hologram generation device characterized by updating the propagated carrier wave using an ADAM optimizer (Adaptive Moment Estimation optimizer) that combines momentum and an adaptive learning rate based on the loss function for each specific distance.

12. In Paragraph 8, The above hologram generation program is, After generating the optimal carrier wave for each specific distance, A hologram generating device that divides a 3D object, which is the target object for hologram generation, into multiple individual layers according to depth, applies an optimal carrier wave corresponding to the depth of each divided individual layer to each individual layer, and generates a hologram by propagating each individual layer to which the optimal carrier wave is applied to a hologram plane through a Band-Limited Angular Spectrum (BLAS) method.

13. In Paragraph 8, The above hologram generation program is, After generating the optimal carrier wave for each specific distance, A hologram generation device that acquires light field data composed of orthographic views from various observation angles of a 3D object that is the target object for hologram generation, generates an initial hologram by applying a Wigner inverse transform based on the light field data, and generates a final hologram by applying the optimal carrier wave to the initial hologram.

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