KR102761435B1 - Holographic display apparatus and method for providing expanded viewing window - Google Patents

Abstract

A holographic display device and display method capable of providing an expanded viewing window are disclosed. The disclosed holographic display device may include a light guide plate having an input coupler and an output coupler; a holographic image generator configured to generate a holographic image and provide the generated holographic image to the input coupler of the light guide plate; and an image processor configured to convert a source image based on a point spread function calculated for each pixel of the holographic image in an image plane to compensate for blur of the holographic image output through the output coupler.

Description

Holographic display apparatus and method for providing expanded viewing window {Holographic display apparatus and method for providing expanded viewing window}

The disclosed embodiments relate to a holographic display device and a display method, and more particularly, to a holographic display device and a display method capable of providing an expanded viewing window.

As a method of implementing 3D images, the glasses method and the glasses-free method are widely commercialized and used. The glasses method includes the polarized glasses method and the shutter glasses method, and the glasses-free method includes the lenticular method and the parallax barrier method. These methods use the binocular parallax of the two eyes, so not only is there a limit to the increase in the number of viewpoints, but the depth perceived by the brain and the focus of the eyes do not match, causing viewers to feel tired.

Holographic display methods are gradually becoming practical as a three-dimensional image display method that can provide full parallax while matching the depth perceived by the brain and the focus of the eyes. The holographic display method uses the principle that when a reference light is irradiated onto a hologram pattern that records an interference pattern obtained by interfering the object light reflected from the original object with the reference light, an image of the original object is reproduced by diffracting the reference light. The holographic display method that is currently being practical does not obtain a hologram pattern by directly exposing the original object, but provides a computer-generated hologram (CGH) as an electrical signal to a spatial light modulator. According to the input CGH signal, the spatial light modulator forms a hologram pattern and diffracts the reference light, thereby generating a three-dimensional image.

A holographic display device and display method capable of providing an expanded viewing window are provided.

A holographic display device according to one embodiment may include: a light guide plate having an input coupler and an output coupler; a holographic image generator configured to generate a holographic image and provide the generated holographic image to the input coupler of the light guide plate; and an image processor configured to convert source image data based on a point spread function calculated for each pixel of the holographic image in an image plane to compensate for blur of the holographic image output through the output coupler.

The light guide plate includes a first surface and a second surface facing the first surface, and both the input coupler and the output coupler can be disposed on the first surface of the light guide plate.

The above holographic image generator may include a light source that emits light; and a spatial light modulator that modulates light emitted from the light source to generate a holographic image.

For example, the spatial light modulator may be a reflective spatial light modulator that modulates reflected light, and the holographic image generator may further include a beam splitter configured to transmit light emitted from the light source to the spatial light modulator and transmit light reflected from the spatial light modulator to the input coupler.

For example, the beam splitter may be a polarizing beam splitter that reflects light having a first linear polarization component and transmits light having a second linear polarization component orthogonal to the first linear polarization component.

Additionally, the holographic image generator may further include a quarter wave plate disposed between the beam splitter and the spatial light modulator.

The light source may include a first light source emitting light having a first linear polarization component and a second light source emitting light having a second linear polarization component, and the spatial light modulator may include a first spatial light modulator arranged to modulate light reflected from the beam splitter and a second spatial light modulator arranged to modulate light transmitted through the beam splitter.

The first spatial light modulator and the second spatial light modulator can be configured to operate in a time-division manner.

Additionally, the spatial light modulator may be a transmissive spatial light modulator that modulates the light it transmits.

The above holographic image generator may further include a lens for focusing the holographic image reproduced from the spatial light modulator onto the input coupler.

In one embodiment, the distance between the lens and the input coupler and the distance between the lens and the spatial light modulator can be equal to the focal length of the lens.

In another embodiment, the distance between the lens and the input coupler may be equal to the focal length of the lens and the distance between the lens and the spatial light modulator may be greater than the focal length of the lens.

Additionally, the holographic image generator may further include a spatial filter positioned facing the input coupler and limiting light incident on the input coupler.

In addition, the holographic image generator may further include a spatial filter for removing unwanted image noise and a high-order holographic image generated by the spatial light modulator; a first lens disposed between the spatial light modulator and the spatial filter, the first lens projecting light from the spatial light modulator onto the spatial filter; a second lens relaying a holographic image transmitted through the spatial filter; and a third lens disposed between the second lens and an input coupler of the light guide plate, the third lens projecting a holographic image transmitted from the second lens onto the input coupler.

The above holographic display device may further include a lens that is positioned facing the output coupler and projects a holographic image output through the output coupler onto an image plane.

The light guide plate may further include an intermediate coupler disposed in an optical path between the input coupler and the output coupler, wherein the input coupler is configured to allow light input to the input coupler to travel in a first direction within the light guide plate, the intermediate coupler is configured to allow light input to the intermediate coupler to travel in a second direction perpendicular to the first direction within the light guide plate, and the output coupler may be configured to output light input to the output coupler to the outside of the light guide plate in a third direction perpendicular to the first direction and the second direction.

The width of the intermediate coupler along the first direction may be greater than the width of the input coupler along the first direction, and the width of the output coupler along the second direction may be greater than the width of the intermediate coupler along the second direction.

The above image processor may be configured to calculate a computer generated hologram (CGH) based on the converted source image data and provide a CGH signal to the spatial light modulator.

Additionally, the image processor may include a first matrix that is pre-calculated and stored and a second matrix that is pre-calculated, and the image processor may be configured to transform first source image data having first depth information based on the first matrix and transform second source image data having second depth information based on the second matrix.

For example, the first matrix and the second matrix can be formed in advance through the steps of: calculating a point spread function for each pixel for the first depth and the second depth based on the first test source image data having the first depth information and the second test source image data having the second depth information to predict a test holographic image to be reproduced on the image plane; comparing the predicted test holographic image for the first depth with the target holographic image for the first depth and calculating corrected first test source image data that minimizes the difference therebetween; comparing the predicted test holographic image for the second depth with the target holographic image for the second depth and calculating corrected second test source image data that minimizes the difference therebetween; calculating a first matrix that converts the first test source image data into the corrected first test source image data; and calculating a second matrix that converts the second test source image data into the corrected first test source image data.

In addition, a holographic display method according to another embodiment may include: a step of providing a CGH (computer generated hologram) signal to a spatial light modulator to generate a holographic image; a step of providing the holographic image to an input coupler of a light guide plate; and a step of reproducing the holographic image, which is output through an output coupler of the light guide plate after traveling along an interior of the light guide plate, on an image plane; wherein the step of providing the CGH signal to the spatial light modulator may include a step of converting source image data based on a point spread function calculated for each pixel of the holographic image on an image plane using an image processor to compensate for a blur of the holographic image output through the output coupler, and a step of calculating the CGH based on the converted source image data.

According to the disclosed embodiment, light diffracted by the spatial light modulator is transmitted to the inside of the light guide plate using the input coupler of the light guide plate and output to the outside of the light guide plate through the output coupler of the light guide plate. At this time, since the directional component of light incident on the inside of the light guide plate is preserved and output as it is, a holographic image can be reproduced. In particular, a 3D holographic image can be provided to the user with a wide field of view through the output coupler having a large area.

In addition, according to the disclosed embodiment, since an optimized CGH (computer generated hologram) is calculated by considering the blur of the holographic image output through the output coupler and the CGH signal is provided to the spatial light modulator, both an expansion of the viewing window and an improvement in the image quality of the holographic image can be achieved.

FIG. 1 is a schematic diagram showing the configuration of a holographic display device according to one embodiment.
FIG. 2 is a perspective view schematically showing the configuration of a light guide plate of a holographic display device according to one embodiment.
Figure 3 exemplarily shows the depth of a holographic image generated by a holographic image generator.
Figures 4a and 4b exemplarily show the degree of pixel-by-pixel blur according to depth on the image plane of a holographic image output through an output coupler.
Figure 5 conceptually shows the principle of compensating for blur in a holographic image output through an output coupler.
Figure 6 is a block diagram schematically showing a mathematical algorithm for compensating for blur of a holographic image output through an output coupler.
Figure 7 shows an example of a plurality of pre-calculated two-dimensional matrices for changing source image data based on the blur of a holographic image output through an output coupler.
FIG. 8 is a schematic diagram showing the configuration of a holographic display device according to another embodiment.
FIG. 9 is a schematic diagram showing the configuration of a holographic display device according to another embodiment.
FIG. 10 is a schematic diagram showing the configuration of a holographic display device according to another embodiment.
FIG. 11 is a schematic diagram showing the configuration of a holographic display device according to another embodiment.
FIG. 12 is a schematic diagram showing the configuration of a holographic display device according to another embodiment.
Fig. 13 is a schematic diagram showing the configuration of a holographic display device according to another embodiment.
Figures 14 to 18 illustrate various electronic devices employing holographic display devices according to embodiments.
FIG. 19 is a schematic diagram showing the configuration of a holographic display device according to another embodiment.
Fig. 20 is a schematic diagram showing the configuration of a holographic display device according to another embodiment.

Hereinafter, with reference to the attached drawings, a holographic display device and a display method providing an expanded viewing window will be described in detail. In the drawings below, the same reference numerals denote the same components, and the sizes of each component in the drawings may be exaggerated for clarity and convenience of explanation. In addition, the embodiments described below are merely exemplary, and various modifications are possible from these embodiments. In addition, in the layer structure described below, the expression "upper" or "top" may include not only those directly above/below/left/right in contact, but also those above/below/left/right in non-contact.

FIG. 1 is a schematic diagram showing the configuration of a holographic display device according to one embodiment. A holographic display device (100) according to one embodiment may include a holographic image generator (130) configured to generate a three-dimensional holographic image, and a light guide plate (120) that transmits the holographic image generated by the holographic image generator (130) to the eye (E) of an observer.

The light guide plate (120) may be made of a material that is transparent to visible light so that it can act as an optical waveguide that transmits light. For example, the light guide plate (120) may be made of a material such as glass, PMMA (Poly methyl methacrylate), or PDMS (Polydimethylsiloxane). In addition, the light guide plate (120) may have a flat plate shape. The light guide plate (120) may include a first surface (120a) and a second surface (120b) facing the first surface (120a). An input coupler (121) for guiding incident light obliquely into the interior of the light guide plate (120) and an output coupler (122) for outputting light that travels obliquely in the interior of the light guide plate (120) to the exterior of the light guide plate (120) may be arranged on the first surface (120a). For example, the input coupler (121) may be placed at one edge of the first surface (120a) of the light guide plate (120), and the output coupler (122) may be placed at the other edge of the first surface (120a) of the light guide plate (120).

The input coupler (121) is configured to guide light incident in a direction approximately perpendicular to the input coupler (121) obliquely into the interior of the light guide plate (120). For example, the input coupler (121) may be configured to guide light incident on the input coupler (121) within a predetermined incident angle range centered on a direction perpendicular to its surface into the interior of the light guide plate (120). The light guided into the interior of the light guide plate (120) is repeatedly totally reflected at the first surface (120a) and the second surface (120b) of the light guide plate (120) and travels along the interior of the light guide plate (120). The output coupler (122) is configured to output light incident in a direction approximately perpendicular to the output coupler (122) to the exterior of the light guide plate (120). The output coupler (122) can be configured to act only on light incident obliquely on its surface within a predetermined incident angle range, and not on light incident perpendicularly on its surface. In other words, the output coupler (122) can simply act as a transparent plate for light incident perpendicularly on its surface.

The input coupler (121) and the output coupler (122) may be formed of a diffractive optical element (DOE) or a holographic optical element (HOE). The diffractive optical element (DOE) includes a plurality of periodic fine grating patterns. The plurality of grating patterns of the diffractive optical element (DOE) act as a diffraction grating to diffract incident light. In particular, depending on the size, height, period, etc. of the grating patterns, the light incident at a specific angle range is diffracted to generate destructive interference and constructive interference, thereby changing the direction of propagation of the light. In addition, the holographic optical element (HOE) includes periodic fine patterns of materials with different refractive indices instead of the grating pattern. The holographic optical element (HOE) has only a difference in configuration from the diffractive optical element (DOE), and the operating principle may be the same as that of the diffractive optical element (DOE).

In the configuration of this light guide plate (120), light incident on the input coupler (121) is emitted to the outside of the light guide plate (120) through the output coupler (122). In addition, the directionality of light incident on the input coupler (121) and output through the output coupler (122) can be maintained within the angle range coupled by the input coupler (121). Accordingly, the light guide plate (120) can transmit a holographic image generated by the holographic image generator (130) to the viewer's eye (E).

A holographic image generator (130) may include a light source (110) that emits light, a spatial light modulator (113) that modulates the light emitted from the light source (110) to generate a holographic image, a beam splitter (112) that reflects the light emitted from the light source (110) to the spatial light modulator (113) and transmits the light reflected from the spatial light modulator (113), and a lens (114) that focuses the holographic image reproduced from the spatial light modulator (113) onto an input coupler (121) of a light guide plate (120). In addition, the holographic image generator (130) may further include a collimating lens (111) arranged between the light source (110) and the beam splitter (112). The collimating lens (111) serves to convert light emitted and diverged from the light source (110) into parallel light. However, if the light source (110) already emits collimated light, the collimating lens (111) may be omitted. In addition, the holographic image generator (130) may further include an image processor (140) that controls the operation of the spatial light modulator (113) and provides a zero signal to the spatial light modulator (113).

In order for the light incident on the spatial light modulator (113) to be diffracted and interfered, the light source (110) may be a coherent light source that emits coherent light. In order to provide light having high coherence, for example, a laser diode (LD) may be used as the light source (110). In addition, the light source (110) may be a light emitting diode (LED). Although the light emitting diode has lower spatial coherence than a laser, if the light has a certain degree of spatial coherence, it can be sufficiently diffracted and modulated by the spatial light modulator (113). In addition to the light emitting diode, any other light source (110) may be used as long as it emits light having spatial coherence.

The spatial light modulator (113) can display a hologram pattern according to a hologram data signal provided from an image processor (140), for example, a computer generated hologram (CGH) signal. Light emitted from a light source (110) and incident on the spatial light modulator (113) is diffracted by a hologram pattern displayed on the screen of the spatial light modulator (113), and then a holographic image having a three-dimensional effect can be reproduced by destructive interference and constructive interference. The spatial light modulator (113) may use any of a phase modulator that can perform only phase modulation, an amplitude modulator that can perform only amplitude modulation, and a composite modulator that can perform both phase modulation and amplitude modulation. In the embodiment illustrated in FIG. 1, the spatial light modulator (113) may be a reflective spatial light modulator that diffracts and modulates incident light while reflecting it. For example, the spatial light modulator (113) may use a liquid crystal on silicon (LCoS), a digital micromirror device (DMD), or a semiconductor modulator.

The image processor (140) generates a CGH signal based on source image data containing information of a holographic image to be reproduced and provides the CGH signal to the spatial light modulator (1130). For example, the image processor (140) may perform a Fourier transform, a fast Fourier transform (FFT), an inverse Fourier transform (IFT), an inverse fast Fourier transform (IFFT), etc. on the source image data to generate the CGH signal. In addition, the image processor (140) may be configured to convert the source image data and generate the CGH signal based on the converted source image data in order to improve the image quality of the holographic image incident on the viewer's eye (E) through the output coupler (122) of the light guide plate (120). This will be described in detail later.

The beam splitter (112) is configured to reflect light incident from a light source (110) and transmit it to a spatial light modulator (113), and transmit light incident from the spatial light modulator (113) to a lens (114). To this end, the beam splitter (112) is arranged in an optical path between the spatial light modulator (113) and the lens (114), and the light source (110) is arranged on one side of the beam splitter (112). For example, the light source (110) may be positioned facing the first surface (112a) of the beam splitter (112), the spatial light modulator (113) may be positioned facing the second surface (112b) of the beam splitter (112) adjacent to the first surface (112a), and the lens (114) may be positioned facing the third surface (112c) of the beam splitter (112) opposite the second surface (112b).

The beam splitter (112) may be, for example, a semi-transmissive mirror that simply reflects half of the incident light and transmits the other half. Alternatively, the beam splitter (112) may be a polarizing beam splitter having polarization selectivity. For example, the beam splitter (112) may be configured to reflect light having a first linear polarization component and transmit light having a second linear polarization component orthogonal to the first linear polarization component. In this case, light having the first linear polarization component among the light emitted from the light source (110) is reflected by the beam splitter (112) and is incident on the spatial light modulator (113), and light having the second linear polarization component is transmitted through the beam splitter (112) and discarded. In addition, the light source (110) may be a polarizing laser that emits only light having the first linear polarization component. Then, all light emitted from the light source (110) can be reflected and incident on the spatial light modulator (113).

A quarter-wave plate (115) may be additionally placed between the beam splitter (112) and the spatial light modulator (113). The quarter-wave plate (115) serves to delay the incident light by 1/4 wavelength of the incident light. Therefore, the light of the first linearly polarized component reflected by the beam splitter (112) becomes light having a first circularly polarized component as it passes through the quarter-wave plate (115). Then, the light is reflected in the opposite direction of the incident direction by the spatial light modulator (113) and has a second circularly polarized component. The light having the second circularly polarized component passes through the quarter-wave plate (115) and has a second linearly polarized component and transmits through the beam splitter (112). This quarter-wave plate (115) may be integrally coupled to the surface of the spatial light modulator (113). In this case, the holographic image generator (130) may not include a separate quarter wave plate (115).

The lens (114) focuses the holographic image and provides it to the input coupler (121) of the light guide plate (120). The distance between the lens (114) and the input coupler (121) may be equal to the focal length of the lens (114), but is not necessarily limited thereto. When the distance between the lens (114) and the input coupler (121) is equal to the focal length of the lens (114), light having various angles that is diffracted by the spatial light modulator (113) and contains the holographic image can be coupled by the input coupler (121) to the greatest extent possible. The distance between the lens (114) and the spatial light modulator (113) may also be equal to the focal length of the lens (114), but is not necessarily limited thereto. When the distance between the lens (114) and the spatial light modulator (113) is equal to the focal length of the lens (114), a holographic image reproduced on the same plane as the spatial light modulator (113) can be transmitted to the observer's eye (E) without any degradation in image quality.

A holographic image modulated and reproduced by a spatial light modulator (113) can be provided to an observer's eye (E) through a lens (114), an input coupler (121) of a light guide plate (120), the inside of the light guide plate (120), and an output coupler (122) of the light guide plate (120). Since the light output through the output coupler (122) preserves the directional component of the light incident on the input coupler (121) as it is, a holographic image can be seen by the observer's eye (E). In particular, according to the present embodiment, since the width (W2) of the output coupler (122) is larger than the width (W1) of the input coupler (121), a viewing window through which an observer can view a holographic image can be expanded. For example, as illustrated in Fig. 1, the observer's eye (E) does not need to be fixed at a specific point, and the holographic image can be sufficiently viewed as long as the observer's eye (E) is positioned within the range of the width (W2) of the output coupler (122).

In addition, since the output coupler (122) acts as a diffraction grating only for light incident obliquely on its surface and directly transmits light incident vertically, the holographic display device (100) according to the present embodiment can be applied to implement augmented reality (AR) or mixed reality (MR). In this case, the holographic display device (100) according to the present embodiment can be a near-eye AR display device. For example, the holographic image (IMG1) reproduced by the spatial light modulator (113) and the external image (IMG2) containing the external scene that vertically transmits the output coupler (122) can be viewed together in the viewer's eye (E).

FIG. 2 is a perspective view schematically showing the configuration of a light guide plate (120) of a holographic display device (100) according to one embodiment. Referring to FIG. 2, the light guide plate (120) may further include an intermediate coupler (123) arranged in an optical path between an input coupler (121) and an output coupler (122). The intermediate coupler (123) is arranged in the +y direction with respect to the input coupler (121), and the output coupler (122) is arranged in the -z direction with respect to the intermediate coupler (123). In this case, the input coupler (121) may be configured so that light incident on the input coupler (121) travels in the +y direction inside the light guide plate (120). In addition, the intermediate coupler (123) may be configured so that light incident on the intermediate coupler (123) travels in the -z direction perpendicular to the +y direction inside the light guide plate (120). Accordingly, the direction of light propagation inside the light guide plate (120) is bent by about 90 degrees by the intermediate coupler (123). The output coupler (122) can be configured to output light incident on the output coupler (122) to the outside of the light guide plate (120) in the +x direction perpendicular to the +y direction and the -z direction.

The intermediate coupler (123) serves to expand the field of view in the +y direction. For this purpose, the width (W2) of the intermediate coupler (123) along the +y direction may be larger than the width (W1) of the input coupler (121) along the +y direction. The width (W3) of the intermediate coupler (123) along the -z direction is the same as the width (W3) of the input coupler (121) along the -z direction. The output coupler (122) serves to expand the field of view in the -z direction. For this purpose, the width (W4) of the output coupler (122) along the -z direction is larger than the width (W3) of the intermediate coupler (123) along the -z direction. In addition, the width (W2) of the output coupler (122) along the +y direction is the same as the width (W2) of the intermediate coupler (123) along the +y direction. Therefore, the field of view can be expanded in two directions perpendicular to each other to become wider.

Meanwhile, since the three-dimensional holographic image generated by the holographic image generator (130) has various depths, the viewer can feel a three-dimensional effect. For example, FIG. 3 exemplarily shows the depths of the holographic image generated by the holographic image generator (130). Referring to FIG. 3, the holographic image can have various depths (-dn, ..., -d1, d0, d1, d2, d3, ..., dn) based on the plane of the spatial light modulator (113). The depth of the holographic image can be determined by the diffraction pattern displayed by the spatial light modulator (113) based on the CGH signal provided from the image processor (140).

However, if a light guide plate (120) is interposed between the spatial light modulator (113) and the observer's eye (E), and the distance between the spatial light modulator (113) and the observer's eye (E) increases, the degree to which the point of light constituting the holographic image is diffused varies depending on the depth, which may cause a deterioration in image quality. In addition, additional deterioration in image quality may occur due to repeated reflection within the light guide plate (120) and diffraction at the input coupler (121) and the output coupler (122). For example, if the spatial light modulator (113) is positioned at the focal length of the lens (114), an image at the same depth (d0) as the plane of the spatial light modulator (113) can be transmitted to the observer's eye (E) with almost no deterioration in image quality. However, as the distance from the spatial light modulator (113) increases, the degree to which light is diffused increases, which may cause a greater deterioration in image quality.

For example, FIGS. 4A and 4B exemplarily show the degree of blur per pixel according to depth on an image plane of a holographic image output through an output coupler (122). Here, the image plane may be, for example, the retina of an observer's eye (E). First, FIG. 4A shows a state in which a two-dimensional image of the same depth (d0) as the plane of a spatial light modulator (113) is transmitted to the retina of the observer's eye (E). In FIG. 4A, P ₁₁ , P ₁₂ , P ₁₃ , P ₁₄ , P ₂₁ , P ₃₁ , and P ₄₁ represent two-dimensional pixel arrays of the targeted holographic image at the depth d0 . And, S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂₁ , S ₃₁ , S ₄₁ represent spots of light actually transmitted to the retina of the observer's eye (E) through the lens (114) and the light guide plate (120). Referring to FIG. 4a, in the case of an image at the same depth (d0) as the plane of the spatial light modulator (113), the spots of light (S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂₁ , S ₃₁ , S ₄₁ ) transmitted to the retina of the observer's eye (E) coincide with the pixels (P ₁₁ , P ₁₂ , P ₁₃ , P ₁₄ , P ₂₁ , P ₃₁ , P ₄₁ ) of the target holographic image. Therefore, when the spatial light modulator (113) is positioned at the focal length of the lens (114), an image at the same depth (d0) as the plane of the spatial light modulator (113) can be transmitted to the retina of the observer's eye (E) without any degradation in image quality.

In addition, Fig. 4b shows a state in which a two-dimensional image of a depth (d1) different from the plane of the spatial light modulator (113) is transmitted to the retina of the observer's eye (E). Referring to FIG. 4b, in the case of an image at a different depth (-dn, ..., -d1, d1, d2, d3, ..., dn) from the plane of the spatial light modulator (113), the spots of light (S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂₁ , S ₃₁ , S ₄₁ ) transmitted to the retina of the observer's eye (E) are diffused, and the sizes of the spots (S ₁₁ , S ₁₂ , S _{13 , S 14 , S 21 , S 31 , S 41 ) become larger than the pixels (P 11 , P 12 , P 13 , P 14 , P 21 , P 31 , P 41 ) of the target holographic image .} Due to this, adjacent spots (S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂₁ , S ₃₁ , S ₄₁ ) overlap in one pixel (P ₁₁ , P ₁₂ , P ₁₃ , P ₁₄ , P ₂₁ , P ₃₁ , P ₄₁ ). Therefore, when the spatial light modulator (113) is positioned at the focal length of the lens (114), images at different depths (-dn, ..., -d1, d1, d2, d3, ..., dn) from the plane of the spatial light modulator (113) may have their image quality deteriorated while being transmitted to the retina of the observer's eye (E). And, as the depth of the holographic image gets farther from the focal length of the lens (114), the spots of light (S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂₁ , S ₃₁ , S ₄₁ ) transmitted to the retina of the observer's eye (E) spread more. Furthermore, the extent to which these spots (S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂₁ , S ₃₁ , S 41 ) spread may vary depending on the two-dimensional positions of the spots (S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂₁ , S ₃₁ , S ₄₁ ) even within _the same depth.

Accordingly, the blur of the holographic image output through the output coupler (122) _can be _compensated by considering the degree of diffusion of the spots (S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂₁ , S ₃₁ , S ₄₁ ) according to the depth of the holographic image and the two-dimensional positions of the spots (S ₁₁ , S ₁₂ , S ₁₃ , S 14 , S 21 , S ₃₁ , S ₄₁ ). In other words, by calculating the point spread function for each depth and pixel of the holographic image transmitted to the retina of the observer's eye (E) and converting the source image data based on the calculated point spread function, the blur of the holographic image transmitted to the retina of the observer's eye (E) can be compensated for, thereby providing a clear holographic image to the observer.

For example, FIG. 5 conceptually shows a principle of compensating for blur of a holographic image output through an output coupler (122). Referring to FIG. 5, all spots of light (p ₁ , p ₂ , ..., p ₃ ) transmitted along the x direction on the retina of an observer's eye (E) are added. Then, the source image data can be transformed so that the result becomes the minimum with respect to the target holographic image I(x) on the retina of the observer's eye (E). Although FIG. 5 simply illustrates one-dimensionally, the calculation is actually performed two-dimensionally. For example, all spots of light transmitted along the x and y directions on the retina of an observer's eye (E) are added, and the source image data can be transformed so that the result becomes the minimum with respect to the target holographic image I(x, y) on the retina of the observer's eye (E). Then, the above-described process can be individually performed for each of all depths. Then, the image quality of the holographic image formed on the retina of the observer's eye (E) can be improved regardless of the depth. All of these processes can be performed by the image processor (140).

In addition, FIG. 6 is a block diagram schematically showing a mathematical algorithm for compensating for blur of a holographic image output through an output coupler (122). Referring to FIG. 6, light constituting a holographic image of a certain depth generated by a spatial light modulator (113) can be mathematically expressed as a plurality of complex wave fields having a complex number form having both phase information and intensity information. Then, a point spread function can be applied to a plurality of complex wave fields to calculate a complex wave field transmitted to the retina of an observer's eye (E). Then, by combining the calculated complex wave field data, the complex pixel value of the holographic image formed on the retina of the observer's eye (E) can be obtained for each pixel.

Thereafter, the real part information and the imaginary part information of the target holographic image to be reproduced, the real part and the imaginary part information of the complex pixel value of the holographic image formed on the retina of the observer's eye (E), can be compared pixel by pixel. And based on the comparison result, the complex wave fields of the optimized holographic image generated by the spatial light modulator (113) so as to minimize the difference between the holographic image actually formed on the retina of the observer's eye (E) and the target holographic image can be obtained. The image processor (140) can convert the source image data based on the complex wave fields of the optimized holographic image, calculate the CGH signal using the converted source image data, and provide the CGH signal generated in this way to the spatial light modulator (113).

Meanwhile, if the optical characteristics of the lens (114), the light guide plate (120), the input coupler (121), and the output coupler (122) are fixed, the depth-wise and pixel-wise diffusion degree of the light transmitted onto the retina of the observer's eye (E) is always maintained constant. Therefore, there is a constant depth-wise and pixel-wise relationship between the source image data converted to provide improved image quality and the original source image data. If this relationship is calculated in advance and stored, the image processor (140) can convert the original source image data using the pre-calculated and stored relationship without having to perform complex operations each time.

This relationship between the transformed source image data and the original source image data to provide improved image quality can be stored in the form of a two-dimensional matrix pre-calculated for each depth. For example, FIG. 7 illustrates a plurality of pre-calculated two-dimensional matrices for each depth to change the source image data based on the blur of the holographic image output through the output coupler (122). Referring to FIG. 7, a plurality of two-dimensional matrices (M1, M2, ...., Mn) can be pre-calculated and then stored to transform the original source image data of the corresponding depth, respectively. Each of the two-dimensional matrices (M1, M2, ...., Mn) has pre-calculated transformation information for each pixel. A plurality of two-dimensional matrices (M1, M2, ...., Mn) may be stored in an unillustrated memory of an image processor (140), and the image processor (140) may convert original source image data by referring to the plurality of two-dimensional matrices (M1, M2, ...., Mn), and then generate a CGH using the converted source image data. For example, the image processor (140) may convert first source image data having first depth information based on a first matrix (M1), and may convert second source image data having second depth information based on a second matrix (M2).

A plurality of two-dimensional matrices (M1, M2, ...., Mn) can be obtained in the manner described with reference to FIGS. 5 and 6. For example, based on a plurality of original test source image data having a plurality of depth information, a point spread function can be calculated for each depth and each pixel for each depth, so as to predict a test holographic image to be reproduced on an image plane, for example, on the retina of an observer's eye (E). Then, the predicted test holographic image for each depth can be compared with a target holographic image for each depth, and corrected depth-specific test source image data that minimizes the difference therebetween can be calculated. For example, the predicted test holographic image for a first depth can be compared with the target holographic image for the first depth, and the corrected first test source image data for the first depth that minimizes the difference therebetween can be calculated. In addition, the predicted test holographic image for a second depth can be compared with the target holographic image for the second depth, and the corrected second test source image data for the second depth that minimizes the difference therebetween can be calculated.

Thereafter, by comparing the original test source image data for each depth with the corrected test source image data for each depth, a plurality of two-dimensional matrices (M1, M2, ..., Mn) for converting the original test source image data for each depth into the corrected test source image data for each depth can be calculated for each depth. For example, a first matrix (M1) for converting the original test source image data for a first depth into the corrected test source image data for the first depth can be calculated, and a second matrix (M2) for converting the original test source image data for a second depth into the corrected test source image data for the second depth can be calculated.

According to the embodiments described above, since a CGH optimized to compensate for blur of a holographic image output through an output coupler (122) is calculated and a CGH signal is provided to a spatial light modulator (113), it is possible to achieve both expansion of the viewing window and improvement in the image quality of the holographic image.

FIG. 8 is a schematic diagram showing the configuration of a holographic display device according to another embodiment. In the holographic display device (200) illustrated in FIG. 8, the beam splitter (112) may be configured to transmit light emitted from a light source (110) and reflect light reflected from a spatial light modulator (113). To this end, the light source (110) may be arranged to face a first surface (112a) of the beam splitter (112), and the spatial light modulator (113) may be arranged to face a fourth surface (112d) of the beam splitter (112) that faces the first surface (112a). The beam splitter (112) may be configured to transmit light having a first linearly polarized component and reflect light having a second linearly polarized component orthogonal to the first linearly polarized component. The light source (110) may be a polarizing laser that emits only light having a first linear polarization component. The remaining configuration of the holographic display device (200) except for the arrangement position of the spatial light modulator (113) may be the same as the configuration of the holographic display device (100) illustrated in FIG. 1.

FIG. 9 is a schematic diagram showing the configuration of a holographic display device according to another embodiment. Referring to FIG. 9, the holographic display device (300) may further include a spatial filter (116) that is positioned facing the input coupler (121) of the light guide plate (120) and restricts light incident on the input coupler (121). The remaining configuration of the holographic display device (300) excluding the spatial filter (116) may be the same as the configuration of the holographic display device (100) illustrated in FIG. 1.

A spatial filter (116) may be arranged closer to the input coupler (121) between the lens (114) and the input coupler (121). The spatial filter (116) may have a small opening (116a) through which light passes. The spatial filter (116) may be arranged such that the center of the opening (116a) is on the optical axis of the lens (114). Since the light passes only through the small opening (116a) of the spatial filter (116) and enters the input coupler (121), light having a large diffraction angle among the light diffracted by the spatial light modulator (113) may be blocked by the spatial filter (116). Accordingly, since the diffusion of light passing through the light guide plate (120) and reaching the pupil of the observer's eye (E) is suppressed, the image quality of the holographic image may be improved.

When using a spatial filter (116), depth information of a holographic image is lost, so the three-dimensional effect may be reduced. Therefore, the spatial filter (116) may be used when displaying subtitles, etc., for which three-dimensional effect is not important. To this end, the spatial filter (116) may be configured to be interposed in the optical path between the lens (114) and the input coupler (121) or removed from the optical path between the lens (114) and the input coupler (121) as needed. Alternatively, the spatial filter (116) may be configured in the form of a variable aperture in which the diameter of the opening (116a) changes as needed.

FIG. 10 is a schematic diagram showing the configuration of a holographic display device according to another embodiment. In the holographic display device (400) illustrated in FIG. 10, the distance between the spatial light modulator (113) and the lens (114) is greater than the focal length of the lens (114). The remaining configuration of the holographic display device (400) excluding the distance between the spatial light modulator (113) and the lens (114) may be the same as the configuration of the holographic display device (100) illustrated in FIG. 1. When the distance between the spatial light modulator (113) and the lens (114) is greater than the focal length of the lens (114), a clear image without image quality degradation is provided to the viewer when the depth of the holographic image reproduced by the spatial light modulator (113) is located at the focal length of the lens (114). In this case, the viewer sees the image as if it were located at an infinite distance.

In addition, the image quality improvement method described in FIGS. 5 to 7 can be applied as is to the holographic display device (400) illustrated in FIG. 10. However, in the embodiment illustrated in FIG. 10, since the plane of the spatial light modulator (113) does not match the focal length of the lens (114), the reference depth without image quality deterioration is not the same plane as the spatial light modulator (113). Therefore, only the relative depth between the plane of the spatial light modulator (113) and the holographic image reproduced by the spatial light modulator (113) becomes different from the embodiment illustrated in FIG. 1.

FIG. 11 is a schematic diagram showing the configuration of a holographic display device (500) according to another embodiment. Referring to FIG. 11, the holographic display device (500) according to the present embodiment may include two spatial light modulators (113a, 113b). For example, the first spatial light modulator (113a) may be arranged to face the second surface (112b) of the beam splitter (112), and the second spatial light modulator (113b) may be arranged to face the fourth surface (112d) of the beam splitter (112). The first and second spatial light modulators (113a, 113b) may operate simultaneously or alternately in a time-division manner, as necessary. When two spatial light modulators (113a, 113b) are used, it is possible to provide a holographic image with rich depth that is difficult to provide with only one spatial light modulator, or to provide independent and separate images simultaneously or alternately in a time-division manner.

In addition, the holographic display device (500) may further include a first 1/4 wave plate (115a) disposed between the first spatial light modulator (113a) and the beam splitter (112) and a second 1/4 wave plate (115b) disposed between the second spatial light modulator (113b) and the beam splitter (112). The first 1/4 wave plate (115a) and the second 1/4 wave plate (115b) may be integrally bonded to the surfaces of the first spatial light modulator (113a) and the second spatial light modulator (113b), respectively. In this case, the first 1/4 wave plate (115a) and the second 1/4 wave plate (115b) may be omitted.

The beam splitter (112) may be configured to reflect light having a first linear polarization component and transmit light having a second linear polarization component orthogonal to the first linear polarization component. In this case, the light source (110) may be configured to emit light having all polarization components. Alternatively, the light source (110) may include a first light source (110a) that emits only light having the first linear polarization component and a second light source (110b) that emits only light having the second linear polarization component.

Among the light emitted from the light source (110), the light having the first linear polarization component is reflected from the beam splitter (112) and is reflected and modulated by the first spatial light modulator (113a). Then, the first linear polarization component is changed into the second linear polarization component while passing through the first 1/4 wave plate (115a) twice. Accordingly, the light reflected and modulated by the first spatial light modulator (113a) passes through the beam splitter (112) and enters the lens (114). In addition, among the light emitted from the light source (110), the light having the second linear polarization component passes through the beam splitter (112) and is reflected and modulated by the second spatial light modulator (113b). After that, the second linear polarization component changes into the first linear polarization component as it passes through the second 1/4 wave plate (115b) twice. Accordingly, the light reflected and modulated by the second spatial light modulator (113b) is reflected from the beam splitter (112) and enters the lens (114).

So far, the spatial light modulators (113, 113a, 113b) have been described as being reflective, but a transmissive spatial light modulator that modulates the transmitted light may also be used. For example, FIG. 12 is a schematic diagram showing the configuration of a holographic display device (600) according to another embodiment. Referring to FIG. 6, the holographic display device (600) may include a light guide plate (120) having an input coupler (121) and an output coupler (122), a light source (110), a collimating lens (111), a spatial light modulator (113'), and a lens (114). The light source (110), the collimating lens (111), the spatial light modulator (113'), and the lens (114) may be sequentially arranged along the direction of light propagation, facing the input coupler (121) of the light guide plate (120). Here, the spatial light modulator (113') is a transmissive spatial light modulator that modulates the transmitted light. For example, the spatial light modulator (113') may use a semiconductor modulator based on a compound semiconductor such as GaAs, or an LCD (liquid crystal device). When a transmissive spatial light modulator (113') is used, the beam splitter (112) can be omitted, so the configuration of the optical system can be simplified.

In addition, FIG. 13 is a schematic diagram showing the configuration of a holographic display device (700) according to another embodiment. Referring to FIG. 13, the holographic display device (700) may further include two lenses (118, 119) and a spatial filter (116) arranged in an optical path between a beam splitter (112) and a lens (114) compared to the holographic display device (100) illustrated in FIG. 1. The two lenses (118, 119) may have the same focal length, and the focal lengths of the lenses (118, 119) and the focal lengths of the lens (114) may be the same or different from each other. The distance between the lens (119) and the spatial light modulator (113) is equal to the focal length of the lens (119), and the distance between the lens (119) and the lens (118) is equal to the focal length of the lenses (118, 119). And, the distance between the lens (118) and the lens (114) is equal to the sum of the focal length of the lens (118) and the focal length of the lens (114). The distance between the lens (114) and the input coupler (121) is equal to the focal length of the lens (114).

The spatial filter (116) may be placed in the optical path between the lens (118) and the lens (119). For example, the spatial filter (116) may be placed at the center between the lens (118) and the lens (119). The lens (119) placed between the spatial light modulator (113) and the spatial filter (116) projects light from a point of the spatial light modulator (113) onto the spatial filter (116). The spatial filter (116) removes unwanted image noise and high-order holographic images generated by the spatial light modulator (113) and transmits only the desired holographic images. The lens (118) relays a holographic image transmitted through the spatial filter (116) to the lens (114), and the lens (114) positioned between the lens (118) and the input coupler (121) projects the holographic image transmitted from the lens (118) onto the input coupler (121).

In general, the spatial light modulator (113) includes an array of a plurality of pixels arranged two-dimensionally, and the physical pixel array of the spatial light modulator (113) acts as a diffraction grating that diffracts light incident from a light source (110). Therefore, the light incident from the light source (110) is diffracted not only by the holographic pattern displayed by the spatial light modulator (113) but also by the regular diffraction grating formed by the pixel array of the spatial light modulator (113). The light diffracted by the holographic pattern displayed by the spatial light modulator (113) forms a holographic image, while the light diffracted by the pixel array of the spatial light modulator (113) forms regular lattice points. These regular lattice points become image noise that makes it uncomfortable to view the holographic image. In addition, the holographic image includes a first-order holographic image formed by the first-order diffracted light by the holographic pattern displayed by the spatial light modulator (113) and a higher-order holographic image formed by the second-order or higher-order diffracted light. In addition, there is also noise generated by light that is not diffracted by the spatial light modulator (113). In order to prevent these numerous noises from being visible to the viewer, the holographic image can be reproduced by avoiding numerous noises through an off-axis method.

According to the axial bias method, the spatial filter (116) can be arranged to pass only the first-order holographic image. For example, the spatial filter (116) can be arranged so that the opening (116a) of the spatial filter (116) in the optical path between the lens (118) and the lens (119) matches the path of the first-order holographic image. Depending on the path of the first-order holographic image, the center of the opening (116a) can be located on the optical axis of the lens (118, 119) or can be located off the optical axis of the lens (118, 119). Then, the higher-order holographic image and other noise components that proceed along a different path from the first-order holographic image can be removed.

As described above, the holographic display device (100, 200, 300, 400, 500, 600, 700) can be applied to implement augmented reality or mixed reality. For example, FIGS. 14 to 18 illustrate various electronic devices employing the holographic display device (100, 200, 300, 400, 500, 600, 700) according to the embodiments described above. As illustrated in FIGS. 14 to 16, the holographic display device (100, 200, 300, 400, 500, 600, 700) can configure a wearable device. In other words, the holographic display device (100, 200, 300, 400, 500, 600, 700) can be applied to a wearable device. For example, the holographic display device (100, 200, 300, 400, 500, 600, 700) can be applied to a head mounted display (HMD). In addition, the holographic display device (100, 200, 300, 400, 500, 600, 700) can be applied to a glasses-type display, a goggle-type display, etc. The wearable electronic devices illustrated in FIGS. 14 to 16 can also be operated in conjunction with a smart phone. These holographic display devices (100, 200, 300, 400, 500, 600, 700) may be head-mounted, glasses-type or goggle-type virtual reality (VR) display devices, augmented reality (AR) display devices, or mixed reality (MR) display devices that can provide virtual reality or provide virtual images and external real images together.

In addition, as illustrated in FIGS. 17 and 18, the holographic display device (100, 200, 300, 400, 500, 600, 700) may also be applied to a mobile device such as a tablet or a smartphone. In this case, the output coupler (122) may be arranged on part or the entire screen on the front of the tablet or smartphone. Then, the user can view the holographic image through the screen of the tablet or smartphone.

In addition, the holographic display device can be applied not only to a glasses-type display structure but also to a projection-type display structure. For example, FIG. 19 is a schematic diagram showing the configuration of a holographic display device according to another embodiment. Referring to FIG. 19, the holographic display device (800) can include a light guide plate (120) having an input coupler (121) and an output coupler (122), a light source (110) that emits light, a spatial light modulator (113) that modulates light emitted from the light source (110) to generate a holographic image, a beam splitter (112) arranged to face the input coupler (121), and a lens (117) arranged to face the output coupler (122).

The beam splitter (112) is configured to reflect light emitted from a light source (110) to a spatial light modulator (113) and transmit the light reflected from the spatial light modulator (113). The light reflected from the spatial light modulator (113) transmits the beam splitter (112) and enters the input coupler (121). Then, the light is guided obliquely into the interior of the light guide plate (120) by the input coupler (121) and travels through the interior of the light guide plate (120). Then, the light is output to the outside of the light guide plate (120) by the output coupler (122). The light output by the output coupler (122) is focused into the space outside the light guide plate (120) through the lens (117). Therefore, the lens (117) is a projection lens for projecting a holographic image. According to this embodiment, since the image output over a wide area by the output coupler (122) having a wide area is focused by the lens (117), the viewing angle of the holographic image can be increased.

In addition, FIG. 20 is a schematic diagram showing the configuration of a holographic display device according to another embodiment. Referring to FIG. 20, a holographic display device (900) according to another embodiment may include a light guide plate (120) having an input coupler (121) and an output coupler (122), a light source (110), a collimating lens (111), a spatial light modulator (113'), and a lens (117). The light source (110), the collimating lens (111), and the spatial light modulator (113') may be sequentially arranged along the direction of light propagation while facing the input coupler (121) of the light guide plate (120). Here, the spatial light modulator (113') is a transmissive spatial light modulator that modulates transmitted light. In addition, the lens (117) is arranged facing the output coupler (122) and focuses the light output by the output coupler (122) into the space outside the light guide plate (120). Compared to the holographic display device (800) illustrated in FIG. 19, the holographic display device (900) illustrated in FIG. 20 differs in that it uses a transmissive spatial light modulator (113') instead of a reflective spatial light modulator (113).

The holographic display device (800, 900) illustrated in FIGS. 19 and 20 described above can be applied to mobile devices such as tablets or smartphones illustrated in FIGS. 17 and 18.

The holographic display device and display method providing the expanded viewing window described above have been described with reference to the embodiments illustrated in the drawings, but these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the disclosed embodiments should be considered from an illustrative rather than a restrictive perspective. The scope of the rights is indicated by the claims, not the above description, and all differences within the scope equivalent thereto should be construed as being included in the scope of the rights.

100, 200, 300, 400, 500, 600, 700, 800, 900.....Holographic display device
110, 110a, 110b.....Light source 111.....Collimating lens
112.....Beam splitter 113, 113a, 113b, 113'.....Space light modulator
114, 117, 118, 119.....lens 115.....1/4 wave plate
116.....Space filter 120.....Light guide plate
121.....Input coupler 122.....Output coupler
123.....Intermediate Coupler 130.....Holographic Image Generator
140.....Image Processor

Claims (24)

A light guide plate having an input coupler and an output coupler;
A holographic image generator configured to generate a holographic image and provide the same to an input coupler of the light guide plate; and
In order to compensate for the blur of the holographic image output through the above output coupler, an image processor configured to convert source image data based on a point spread function calculated for each pixel of the holographic image in an image plane is included;
The image processor comprises a first matrix that is pre-calculated and stored and a second matrix that is pre-calculated,
A holographic display device, wherein the image processor is configured to transform first source image data having first depth information based on the first matrix and to transform second source image data having second depth information based on the second matrix. In paragraph 1,
A holographic display device, wherein the light guide plate includes a first surface and a second surface facing the first surface, and both the input coupler and the output coupler are disposed on the first surface of the light guide plate. In paragraph 1,
The above holographic image generator:
a light source that emits light; and
A holographic display device including a spatial light modulator that modulates light emitted from the light source to generate a holographic image. In the third paragraph,
The above spatial light modulator is a reflective spatial light modulator that modulates reflected light.
A holographic display device, wherein the holographic image generator further includes a beam splitter configured to transmit light emitted from the light source to the spatial light modulator and transmit light reflected from the spatial light modulator to the input coupler. In paragraph 4,
A holographic display device wherein the above beam splitter is a polarizing beam splitter that reflects light having a first linear polarization component and transmits light having a second linear polarization component orthogonal to the first linear polarization component. In paragraph 5,
A holographic display device, wherein the holographic image generator further includes a quarter wave plate disposed between the beam splitter and the spatial light modulator. In paragraph 5,
The light source includes a first light source emitting light having a first linearly polarized component and a second light source emitting light having a second linearly polarized component,
A holographic display device, wherein the spatial light modulator comprises a first spatial light modulator arranged to modulate light reflected from the beam splitter and a second spatial light modulator arranged to modulate light transmitted through the beam splitter. In paragraph 7,
A holographic display device in which the first spatial light modulator and the second spatial light modulator are configured to operate in a time-division manner. In the third paragraph,
The above spatial light modulator is a holographic display device that is a transmissive spatial light modulator that modulates the light that passes through it. In the third paragraph,
A holographic display device, wherein the holographic image generator further includes a lens for focusing the holographic image reproduced from the spatial light modulator onto the input coupler. In Article 10,
A holographic display device wherein the distance between the lens and the input coupler and the distance between the lens and the spatial light modulator are equal to the focal length of the lens. In Article 10,
A holographic display device wherein the distance between the lens and the input coupler is equal to the focal length of the lens and the distance between the lens and the spatial light modulator is greater than the focal length of the lens. In the third paragraph,
A holographic display device, wherein the holographic image generator is positioned facing the input coupler and further includes a spatial filter that limits light incident on the input coupler. In the third paragraph,
The above holographic image generator:
A spatial filter for removing unwanted image noise and high-order holographic images generated by the above spatial light modulator;
A first lens disposed between the spatial light modulator and the spatial filter, the first lens projecting light from the spatial light modulator onto the spatial filter;
A second lens for relaying a holographic image passing through the above spatial filter; and
A holographic display device further comprising a third lens, the third lens being positioned between the second lens and the input coupler of the light guide plate, and projecting a holographic image transmitted from the second lens onto the input coupler. In paragraph 1,
A holographic display device further comprising a lens that is arranged facing the output coupler and projects a holographic image output through the output coupler onto an image plane. In paragraph 1,
The above light guide plate further includes an intermediate coupler arranged in the optical path between the input coupler and the output coupler,
A holographic display device, wherein the input coupler is configured to allow light input to the input coupler to travel in a first direction within the light guide plate, the intermediate coupler is configured to allow light input to the intermediate coupler to travel in a second direction perpendicular to the first direction within the light guide plate, and the output coupler is configured to output light input to the output coupler to the outside of the light guide plate in a third direction perpendicular to the first and second directions. In Article 16,
A holographic display device, wherein the width of the intermediate coupler along the first direction is greater than the width of the input coupler along the first direction, and the width of the output coupler along the second direction is greater than the width of the intermediate coupler along the second direction. In the third paragraph,
A holographic display device, wherein the image processor is configured to calculate a computer generated hologram (CGH) based on the converted source image data and provide a CGH signal to the spatial light modulator. delete In paragraph 1,
The first matrix and the second matrix are:
A step of predicting a test holographic image to be reproduced on an image plane by calculating a point spread function for each pixel for the first depth and the second depth based on first test source image data having first depth information and second test source image data having second depth information;
A step of comparing a predicted test holographic image for a first depth with a target holographic image for the first depth, and calculating a corrected first test source image data that minimizes the difference;
A step of comparing a predicted test holographic image for a second depth with a target holographic image for a second depth, and calculating a corrected second test source image data that minimizes the difference;
A step of calculating a first matrix for converting the first test source image data into the corrected first test source image data; and
A holographic display device formed in advance through a step of calculating a second matrix that converts the second test source image data into the corrected first test source image data. A step of generating a holographic image by providing a CGH (computer generated hologram) signal to a spatial light modulator;
A step of providing the above holographic image to an input coupler of a light guide plate; and
A step of reproducing a holographic image output through an output coupler of the light guide plate after proceeding along the interior of the light guide plate on an image plane;
The step of providing a CGH signal to the above spatial light modulator is:
In order to compensate for the blur of the holographic image output through the above output coupler, a step of converting the source image data based on the point spread function calculated for each pixel of the holographic image on the image plane using an image processor, and
Comprising a step of calculating CGH based on the converted source image data,
The image processor comprises a first matrix that is pre-calculated and stored and a second matrix that is pre-calculated,
The steps for converting the above source image data are:
A step of converting first source image data having first depth information based on the first matrix, and
A holographic display method further comprising the step of converting second source image data having second depth information based on the second matrix. delete delete In Article 21,
The first matrix and the second matrix are:
A step of predicting a test holographic image to be reproduced on an image plane by calculating a point spread function for each pixel for the first depth and the second depth based on first test source image data having first depth information and second test source image data having second depth information;
A step of comparing a predicted test holographic image for a first depth with a target holographic image for the first depth, and calculating a corrected first test source image data that minimizes the difference between them;
A step of comparing a predicted test holographic image for a second depth with a target holographic image for a second depth, and calculating a corrected second test source image data that minimizes the difference;
A step of calculating a first matrix for converting the first test source image data into the corrected first test source image data; and
A holographic display method formed in advance through a step of calculating a second matrix that transforms the second test source image data into the corrected first test source image data.

Images