KR102148876B1 - Holographic head mounted display apparatus with eyebox and depth of field control and display method thereof - Google Patents

Abstract

A holographic head-mounted display device capable of adjusting an image depth and an eye position, and a display method using the same are provided. A holographic head mounted display device according to an embodiment includes: a spatial light modulator (SLM) in which a plane wave from a laser source is modulated by a computer generated hologram (CGH); A 4f optical unit for forming an intermediate holographic image after being modulated by the spatial light modulator (SLM); And a reflective holographic optical element (HOE) for diffracting light from the intermediate holographic image to provide an enlarged virtual holographic image at a distance greater than a user's eyes.

Description

A holographic head-mounted display device capable of adjusting the depth of image and eye position, and a display method using the same {HOLOGRAPHIC HEAD MOUNTED DISPLAY APPARATUS WITH EYEBOX AND DEPTH OF FIELD CONTROL AND DISPLAY METHOD THEREOF}

The following embodiments relate to a holographic head mounted display technology, and more particularly, to a holographic head mounted display device capable of adjusting an image depth and an eye position, and a display method using the same.

Optical see-through Near-Eye-Display (NED) is a key device for Augmented Reality (AR) applications, and has recently attracted attention. One of the problems of the existing proximity-eye-display (NED) is the Vergence-Accommodation Conflict (VAC). The perceived distance or convergence distance varies depending on the binocular disparity of the content, the focal length or the accommodation distance of individual eyes, but is fixed to the physical image plane of the display panel. Due to this inconsistency, it becomes difficult to achieve realistic optical matching of the real environment and the virtual image in AR applications, and is known to be the cause of many side effects such as eye strain and reduced perceived resolution.

The Maxwellian Proximity-Eye-Display (NED) is one possible approach that can mitigate the convergence-regulation mismatch (VAC) problem. In a Maxwellian configuration, light from the display panel is concentrated at a point in the pupil plane and is projected onto the eye retina. Since the effective pupil of the image is reduced to a point, the depth of field is enlarged so that the image is always in focus, regardless of the actual focal length of the eye lens. The elimination of the depth of focus cue partially solves the convergence-control mismatch (VAC) problem, making the Maxwellian display attractive. The downside of the Maxwellian display is that the eyebox is limited by the size of the pupil.

Techniques have been reported to magnify the eyebox by adjusting the focal point using a dynamic mirror or generating multiple focal points using a holographic optical element (HOE), but these methods require mechanical movement or Since the position of the focal point is still fixed, its usefulness is limited.

Holographic Near-Eye-Display (NED) is another approach. This method completely solves the convergence-control mismatch (VAC) problem by reconstructing the wavefront of a 3D object at an arbitrary distance. Due to this advantage, various studies on holographic near-eye-display (NED) have been actively conducted. However, since the spatial bandwidth product (SBP) of the currently available spatial light modulator (SLM) is not sufficient, the close-eye-display (NED) configuration of the eyebox is limited.

J.-H. Park, "Recent progresses in computer generated holography for three-dimensional scene," J. Inf. Disp. 18(1), 1-12 (2017).

The embodiments describe a holographic head-mounted display device capable of adjusting the depth of an image and the position of the eye, and a display method using the same. More specifically, the depth of field of each virtual 3D image is controlled and the eyebox is adjusted using dynamic adjustment. It provides a technique for a replicable optical see-through holographic proximity eye display device.

The embodiments enable viewing of an image in a wider range by using a holographic optical element (HOE) that functions as a multiplexed concave mirror that duplicates the eyebox, and allows the depth of field of the displayed 3D object to be individually measured. It is to provide a holographic head-mounted display device capable of controlling an image depth and an eye position, and a display method using the same, in which a computer-generated hologram (CGH) can be generated in different ranges of an angular spectrum.

A holographic head mounted display device according to an embodiment includes: a spatial light modulator (SLM) in which a plane wave from a laser source is modulated by a computer generated hologram (CGH); A 4f optical unit for forming an intermediate holographic image after being modulated by the spatial light modulator (SLM); And a reflective holographic optical element (HOE) for diffracting light from the intermediate holographic image to provide an enlarged virtual holographic image at a distance greater than a user's eyes.

The holographic optical element HOE is recorded so that the oblique plane wave from the spatial light modulator SLM is diffracted to form multiple focal points, and may function as a multiplexed oblique concave mirror.

The separation distance between the focal points of the holographic optical element (HOE) is set slightly larger than the size of the pupil of the eye, and around each of the focal points, the eyebox is an angular spectrum used for the synthesis of the computer-generated hologram (CGH). It can be formed in a size determined by the range.

The light corresponding to the virtual holographic image is duplicated toward the multi-focal point by the holographic optical element (HOE), so that an eye located in an arbitrary eyebox can see the displayed image.

A display method using a holographic head mounted display device according to another embodiment includes the steps of modulating a plane wave from a laser source by a computer generated hologram (CGH) of a spatial light modulator (SLM); After the modulation, forming an intermediate holographic image after the 4f optical unit; And providing an enlarged virtual holographic image by diffracting the light from the intermediate holographic image by a reflective holographic optical element (HOE) at a distance greater than the user's eyes.

According to embodiments, a holographic head mounted display device capable of adjusting focus without mechanical movement by controlling the depth of field of each virtual 3D image and duplicating the eyebox using dynamic adjustment, and a display method using the same can be provided. have.

According to embodiments, using a holographic optical element (HOE) that functions as a multiplexed concave mirror that duplicates the eyebox, it is possible to observe an image in a wider range, and to reduce the depth of field of the displayed 3D object. It is possible to provide a holographic head-mounted display device capable of controlling an image depth and an eye position, and a display method using the same, in which a computer-generated hologram (CGH) can be individually controlled and generated in different ranges of an angular spectrum.

1 is a diagram illustrating a holographic head mounted display device according to an exemplary embodiment.
2 is a flowchart illustrating a display method using a holographic head mounted display device according to an exemplary embodiment.
3 is a diagram for explaining synthesis of a computer-generated hologram (CGH) according to an exemplary embodiment.
4 is a diagram showing a coordinate system of a holographic optical element (HOE) and a spatial light modulator (SLM) according to an exemplary embodiment.

Hereinafter, embodiments will be described with reference to the accompanying drawings. However, the described embodiments may be modified in various forms, and the scope of the present invention is not limited by the embodiments described below. In addition, various embodiments are provided to more completely explain the present invention to those of ordinary skill in the art. In the drawings, the shapes and sizes of elements may be exaggerated for clearer explanation.

The following embodiments relate to a new holographic near-eye-display (NED) device, and more specifically, an optical type having an eyebox adjustment and depth of field control control function. A technique for a see-through holographic near-eye display is proposed.

The holographic head-mounted display device according to the embodiment uses a holographic optical element (HOE) that functions as a multiplexed concave mirror that duplicates an eyebox, so that an image can be observed in a wider range. Can be. By individually controlling the depth of field of the displayed 3D object, a computer generated hologram (CGH) can be generated in different ranges of the angular spectrum.

Therefore, it is possible to display a 3D scene composed of a holographic 3D image at an arbitrary distance of a shallow depth of field like a general holographic display device, and at the same time without time-multiplexing, a general Maxwellian display device and It is possible to display an image that is always in focus with the same large depth of field. Angular spectrum control adjusts the focal point in the Maxwellian view, making it robust to eye changes and eye rotation. The combination of analog holograms, that is, holographic optical elements (HOEs) with multiplexed oblique concave mirrors and digital holographic display technology, is an eye larger than the limitations of the conventional spatial bandwidth product (SBP) of a spatial light modulator (SLM). Contributes to the expansion of the box.

Next, a configuration of a holographic head mounted display device according to an exemplary embodiment will be described using the results of an optical experiment verifying feasibility.

1 is a diagram illustrating a holographic head mounted display device according to an exemplary embodiment.

Referring to FIG. 1, a holographic head mounted display apparatus 100 according to an exemplary embodiment includes a spatial light modulator (SLM, 120), a 4f optical unit 130, and a holographic optical element (HOE, 140). The depth of the image and the position of the eye can be adjusted.

The spatial light modulator SLM 120 may modulate a plane wave from the laser source 110 by a computer generated hologram CGH.

The 4f optical unit 130 may form an intermediate holographic image A after modulation by the spatial light modulator (SLM) 120.

The holographic optical element HOE 140 may diffract light from the intermediate holographic image A to provide an enlarged virtual holographic image B at a distance greater than the user's eyes.

Here, the holographic optical element (HOE) 140 is recorded so that the oblique plane wave from the spatial light modulator (SLM) 120 is diffracted to form multiple focal points, and may function as a multiplexed oblique concave mirror.

The spacing distance between the focal points of the holographic optical element (HOE, 140) is set slightly larger than the size of the pupil of the eye, and around each focal point, the eyebox 150 is used for computer-generated hologram (CGH) synthesis. It can be formed to a size determined by the angular spectral range.

The light corresponding to the virtual holographic image (B) is duplicated toward the multi-focal point by the holographic optical element (HOE) 140, so that an eye located in an arbitrary eyebox 150 can see the displayed image. .

It should be noted that the generation of multiple focal points by the holographic optical element (HOE, 140) is not achieved by higher order diffraction. The holographic optical element (HOE) 140 can be recorded as a single signal waveform converging at multiple focal points. Accordingly, the holographic head mounted display apparatus 100 according to an exemplary embodiment may use first-order diffraction of the holographic optical element (HOE) 140 that generates a plurality of points.

Hereinafter, the holographic head mounted display device 100 will be described in more detail.

2 is a flowchart illustrating a display method using a holographic head mounted display device according to an exemplary embodiment.

Referring to FIG. 2, in the display method using the holographic head-mounted display device according to an embodiment, a step in which a plane wave from a laser source is modulated by a computer-generated hologram (CGH) of a spatial light modulator (SLM) (S110). , After modulation, the step of forming an intermediate holographic image after the 4f optical unit (S120), and the light from the intermediate holographic image is diffracted by a reflective holographic optical element (HOE) to enlarge a virtual holographic image It may be accomplished including the step (S130) of providing the user at a distance farther than the eyes of the user.

According to embodiments, the depth of field of each virtual 3D image is controlled and the eyebox is duplicated using dynamic adjustment to adjust the focus without mechanical movement.

In particular, by using a holographic optical element (HOE) that functions as a multiplexed concave mirror that duplicates the eyebox, an image can be observed in a wider range. Further, by individually controlling the depth of field of the displayed 3D object, a computer-generated hologram (CGH) may be generated in different ranges of the angular spectrum.

A display method using a holographic head mounted display device according to an exemplary embodiment will be described below by way of example.

A display method using the holographic head mounted display device according to an exemplary embodiment may be described in more detail using the holographic head mounted display device according to the exemplary embodiment described above. The holographic head mounted display device according to an exemplary embodiment may include a spatial light modulator (SLM), a 4f optical unit, and a holographic optical element (HOE).

In step S110, the plane wave from the laser source may be modulated by a computer generated hologram (CGH) of a spatial light modulator (SLM).

In step S120, an intermediate holographic image may be formed after the 4f optical unit after modulation by the computer-generated hologram CGH of the spatial light modulator SLM.

In step S130, light from the intermediate holographic image is diffracted by the reflective holographic optical element (HOE) to provide an enlarged virtual holographic image at a distance greater than the user's eyes.

Here, the holographic optical element HOE is recorded so that the oblique plane wave from the spatial light modulator SLM is diffracted to form multiple focal points, and may function as a multiplexed oblique concave mirror. The spacing distance between the focal points of the holographic optical element (HOE) may be set slightly larger than the size of the pupil of the eye. Around each focal point, the eyebox can be formed to a size determined by the angular spectral range used for computer-generated holographic (CGH) synthesis. The light corresponding to the virtual holographic image is duplicated toward the multi-focal point by the holographic optical element (HOE), so that an eye placed in any eyebox can see the displayed image.

According to embodiments, using a holographic optical element (HOE) that functions as a multiplexed concave mirror that duplicates the eyebox, it is possible to observe an image in a wider range, and to reduce the depth of field of the displayed 3D object. Individually controlled computer-generated holograms (CGHs) can be generated over different ranges of the angular spectrum.

Hereinafter, a holographic head mounted display device according to an exemplary embodiment and a display method using the same will be described in more detail.

Depth of field control for individual holographic images

In the holographic head mounted display device according to an embodiment, a depth of field of an individual holographic image may be controlled by an angular spectrum range used for synthesis of a corresponding computer-generated hologram (CGH). In the maximum angular spectral range limited by the pixel pitch of the spatial light modulator (SLM), the effective eyebox for that image has a maximum size, so that the depth of field can be minimized around a specified distance of the holographic image. In the minimum angular spectral range, the depth of field can be maximized to provide an image that is always in focus.

평면에 위치하고 단일 삼각형 조리개가 3개의 정점 중 하나를 갖는

평면에 위치하도록, 즉

가 로컬 좌표 원점에 위치하도록, 글로벌

및 로컬

좌표 시스템이 정의된다고 가정한다. 단일 삼각형 조리개

의 각도 스펙트럼은 다음 식과 같이 주어질 수 있다.Computer-generated hologram (CGH) synthesis using angular spectral range control can be achieved using several types of computer-generated holograms (CGH) (Non-Patent Document 1). In an implementation according to an embodiment, an analytical triangular mesh based computer generated hologram (CGH) technique is used for direct control of the angular spectrum in computer generated hologram (CGH) synthesis. In an analytical triangular mesh-based computer-generated hologram (CGH), a 3D object is modeled as a set of triangular-shaped clear apertures that are illuminated by a carrier wave. Hologram

A single triangular aperture located in a plane and having one of three vertices

To be in a plane, i.e.

Is located at the local coordinate origin,

And local

Assume that a coordinate system is defined. Single triangular aperture

The angular spectrum of can be given by the following equation.

[Equation 1]

및

는 글로벌 좌표계 시스템의 공간 주파수의

및

벡터이다.

은 로컬 좌표계 시스템의 공간 주파수 벡터이며, 로컬 좌표계 시스템은

회전 행렬 R을 사용하는

에 의한 글로벌 공간 주파수 벡터

과 관련된다. 두 개의 공간 주파수 벡터

및

은

을 만족하며,

는 파장이다.

는

에 의해 주어지는

벡터이다.

은 이진 함수

의 푸리에 변환이다. 이진 함수

은 기준 삼각형 내부에서 1이며 외부에서 0이다. A는

에 의해 로컬 평면에서 삼각형 조리개를 기준 삼각형에 관련시키는

행렬이다. 그리고

는

에 대한 컨볼루션을 나타낸다.here,

And

Is the spatial frequency of the global coordinate system

And

It is a vector.

Is the spatial frequency vector of the local coordinate system, and the local coordinate system is

Using rotation matrix R

Global spatial frequency vector by

Is related to. Two spatial frequency vectors

And

silver

Satisfying

Is the wavelength.

Is

Given by

It is a vector.

Is a binary function

Is the Fourier transform of. Binary function

Is 1 inside the reference triangle and 0 outside. A is

By relating the triangular aperture to the reference triangle in the local plane

It is a procession. And

Is

Represents the convolution of

는 아래와 같이 정의되는 수학식 1의

항을 조절하여 연산될 수 있으며, 다음 식과 같이 나타낼 수 있다.Angular spectrum of holographic images

Is of Equation 1 defined as below

It can be calculated by adjusting the terms, and can be expressed as the following equation.

[Equation 2]

는 반송파의 각도 스펙트럼이다. here,

Is the angular spectrum of the carrier wave.

3 is a diagram for explaining synthesis of a computer-generated hologram (CGH) according to an exemplary embodiment.

인 단일 평면 반송파의 경우, 홀로그래픽 이미지의 각도 스펙트럼

는, 도 3 (a)의 좌측에 도시된 바와 같이, 3D 피사체의 공간 대역폭과 평면파

의 공간 주파수 주위에 집중되어 있다. 눈동자 평면에서, 홀로그래픽 이미지의 좁은 각도 스펙트럼은, 도 3 (a)의 우측에 도시된 바와 같이, 홀로그래픽 광학 소자(HOE)에 의해 복제된 초점 지점으로 변환된다. 초점 지점의 폭은 눈동자보다 훨씬 작으므로, 가상의 홀로그래픽 이미지는 사용자 눈의 실제 초점 거리에 관계없이 항상 초점이 맞춰진 큰 피사계 심도로 보여진다.

For single-plane carriers, the angular spectrum of the holographic image

Is, as shown on the left of FIG. 3 (a), the spatial bandwidth and plane wave of the 3D object

Is concentrated around the spatial frequency of In the pupil plane, the narrow angular spectrum of the holographic image is transformed into a replicated focal point by the holographic optical element (HOE), as shown on the right side of Fig. 3(a). Since the width of the focal point is much smaller than that of the pupil, the virtual holographic image is always viewed with a large depth of field in focus, regardless of the actual focal length of the user's eye.

에 대해

가 되도록 하는 반송파로서 사용되면, 도 3 (b)의 좌측에 도시된 바와 같이, 홀로그래픽 이미지의 각도 스펙트럼이 확장되고, 도 3 (b)의 우측에 도시된 바와 같이, 눈동자 평면 내의 홀로그래픽 광학 소자(HOE)에 의해 확장된 폭이 형성된다. 충분히 넓은 범위의 평면 반송파를 사용하면, 아이박스 폭이 눈동자보다 크므로, 재구성을 위해 관찰 가능한 최소 피사계 심도가 제공된다.Conversely, the range of plane waves

About

When used as a carrier wave so as to be, the angular spectrum of the holographic image is expanded, as shown on the left side of Fig. 3 (b), and the holographic optics in the pupil plane, as shown on the right side of Fig. 3 (b). An extended width is formed by the element HOE. With a sufficiently wide range of planar carriers, the eyebox width is larger than the pupil, thus providing the minimum observable depth of field for reconstruction.

This angular spectrum control can be performed for each triangular aperture of the subject or for each 3D subject in the entire scene. Therefore, it is possible to reconstruct a 3D image having a different depth of field for each subject.

Focus point adjustment for images that are always in focus

에 의존하기 때문에, 다중 초점 지점은 컴퓨터 생성 홀로그램(CGH) 합성에서

의 변화를 통해 그들의 분리를 유지하면서 조정될 수 있다. 초점 지점 분리는 눈동자 크기보다 약간 크게 설정되기 때문에, 눈 추적 시스템에 의해 그 위치가 검출되면, 눈동자에 단일 초점 지점을 투사하는 것이 가능하다. 이 특징은 일 실시예에 따른 홀로그래픽 헤드 마운티드 디스플레이 장치가 종래의 맥스웰(Maxwellian) 디스플레이 장치 보다 눈동자의 크기 변화 및 안구 회전에 대해 더욱 강건해지게 한다.In the case of a single plane carrier, the displayed image is always in focus, like a typical Maxwellian display device. However, it is noteworthy that the holographic head mounted display device according to an embodiment can adjust the focus without any mechanical movement. Focus adjustment in the holographic head mounted display device according to an embodiment is simply performed by synthesizing a computer-generated hologram (CGH) with different single plane carriers. A single plane wave is diffracted by a holographic optical element (HOE) to form multiple focal points, and the lateral position offset within the pupil plane is the spatial frequency of the plane carrier.

Depends on, the multi-focal point is used in computer-generated holographic (CGH) synthesis.

Can be adjusted while maintaining their separation through changes in Since the focal point separation is set slightly larger than the pupil size, it is possible to project a single focal point on the pupil once its position is detected by the eye tracking system. This feature makes the holographic head-mounted display device according to the embodiment more robust against changes in the size of the pupil and rotation of the eyeball than the conventional Maxwellian display device.

Holographic optical element (HOE) aberration correction

In the holographic head mounted display device according to an embodiment, a holographic optical element (HOE) functions as a concave mirror, which can enlarge an intermediate holographic image forming a virtual image of itself at a distance. . Due to the inclined configuration and large magnification as shown in Fig. 1, the formed virtual image experiences large aberrations. The holographic head-mounted display apparatus according to an exemplary embodiment may form a virtual image in a clear shape by precompensating for this aberration.

4 is a diagram showing a coordinate system of a holographic optical element (HOE) and a spatial light modulator (SLM) according to an exemplary embodiment.

만큼 기울어진 공간 광 변조기(SLM)으로부터의 평면파가 회절되어 거리

에서 지점을 형성하도록 기록된다. 홀로그래픽 광학 소자(HOE) 평면

내의 각각의 점에 대하여, 자유 공간 격자 벡터

는 다음 식과 같이 나타낼 수 있다. 4, a holographic optical element (HOE) is at an angle with respect to a holographic optical element (HOE) plane.

The plane wave from the spatial light modulator (SLM) tilted by

Is recorded to form a point in. Holographic optical element (HOE) plane

For each point in the free space grid vector

Can be expressed as the following equation.

[Equation 3]

는 자유 공간

에서의 파수(wave number)이다. 홀로그래픽 광학 소자(HOE) 매체 내부의 실제 격자 벡터는 이 매체의 굴절률로 인하여 수학식 3의 자유 공간 격자 벡터 K와는 다르다. 그럼에도 불구하고, 자유 공간 격자 벡터 K를 사용한 다음과 같은 분석은 자유 공간에서의 모든 파동 벡터 및 위상 분포에 대해 여전히 유효하다.here,

Is free space

It is the wave number at. The actual lattice vector inside the holographic optical element (HOE) medium is different from the free space lattice vector K of Equation 3 due to the refractive index of the medium. Nevertheless, the following analysis using the free space lattice vector K is still valid for all wave vectors and phase distributions in free space.

에 가상 이미지 포인트를 형성하기 위해, 자유 공간에서 회절된 광의 파동 벡터

이 다음 식과 같이 나타낼 수 있다. In reconstruction, as shown in Figure 4,

To form a virtual image point on the wave vector of diffracted light in free space

This can be expressed as the following equation.

[Equation 4]

를 유도할 수 있으며, 다음 식과 같이 나타낼 수 있다.Equation 4 above is a corresponding wave vector of incident light from a spatial light modulator (SLM)

Can be derived, and can be expressed as the following equation.

[Equation 5]

[Equation 6]

의 해당 위상 분포를 찾을 수 있으며, 다음 식과 같이 나타낼 수 있다.From Equation 5 and Equation 6, we can obtain the incident light in the plane of the holographic optical element (HOE) as follows.

The corresponding phase distribution of can be found and can be expressed as the following equation.

[Equation 7]

및

는 유도(미분)에 사용된다. In the above equation,

And

Is used for derivation (differentiation).

의 축간 오목 거울에서의 단일 포인트 이미지 형성의 위상 함수에 불과하다. 따라서 틸트에 의해 야기되는 수차를 보상하기 위해 고려해야 할 것은 각도 스펙트럼 영역에서 공간 주파수

축을 따라

에 의한 시프트에 해당하는 세 번째 항

이다. The first two terms on the right side of Equation 7 are the focal length

It is only a phase function of the formation of a single point image in an inter-axis concave mirror. Therefore, to compensate for the aberration caused by tilt, the spatial frequency in the angular spectrum domain

Along the axis

The third term corresponding to the shift by

to be.

를 가지는 홀로그래픽 광학 소자(HOE) 평면의 각도 스펙트럼은

에 의한 일반적인 축 상(on-axis) 각도 스펙트럼

와 관련된다.For general intermediate holographic 3D images, tilt aberration correction

The angular spectrum of the plane of a holographic optical element (HOE) having

Typical on-axis angular spectrum by

Is related to.

가 결정되면, 공간 광 변조기(SLM) 평면에서의 대응하는 각도 스펙트럼

이 두 평면 사이의 기하학적 관계로부터 얻어진다. 보다 구체적으로, 공간 광 변조기(SLM) 평면

의 각도 스펙트럼은 (비특허문헌 1)에 의해 다음 식과 같이 나타낼 수 있다. Angular spectrum from the desired intermediate holographic image

Is determined, the corresponding angular spectrum in the spatial light modulator (SLM) plane

It is obtained from the geometric relationship between these two planes. More specifically, the spatial light modulator (SLM) plane

The angular spectrum of can be represented by the following equation by (Non-Patent Document 1).

[Equation 8]

In Equation 8 above,

[Equation 9]

이며,

Is,

이다.

to be.

내에서의 각도 스펙트럼이 공간 광 변조기(SLM)의 공간 주파수 그리드

에서 획득할 수 있다. 수학식 8의

은 홀로그래픽 광학 소자(HOE)에 의해 확대될 원하는 중간 홀로그래픽 이미지에 대해, 앞에서 설명된 각도 스펙트럼 범위를 고려하여 일반적인 분석 삼각형 메쉬 기반 컴퓨터 생성 홀로그램(CGH) 기법을 사용하여 평가될 수 있다. 공간 광 변조기(SLM) 평면

의 각도 스펙트럼은 최종 복소 진폭, 즉 공간 광 변조기(SLM) 평면 내의 홀로그램을 제공하기 위해 최종적으로 푸리에 변환될 수 있다.In other words, using Equation 8, a spatial light modulator (SLM) plane

The angular spectrum within the spatial frequency grid of a spatial light modulator (SLM)

Can be obtained from. Of Equation 8

Can be evaluated using a conventional analytical triangular mesh-based computer generated hologram (CGH) technique, taking into account the angular spectral range described above for the desired intermediate holographic image to be magnified by a holographic optical element (HOE). Spatial light modulator (SLM) plane

The angular spectrum of can be finally Fourier transformed to give the final complex amplitude, i.e., a hologram in the spatial light modulator (SLM) plane.

Eyebox size and focus point adjustment range

In the holographic head mounted display device according to an embodiment, the size of the eyebox and the range of adjustment of the focus point may be determined by the spatial frequency range of the planar carrier.

로 나타내면, 공간 광 변조기(SLM)에 의해 지원되는 공간 주파수 범위는

와 같이 주어지며, 여기서

또는

이다. The pixel pitch of the spatial light modulator (SLM)

Expressed as, the spatial frequency range supported by the spatial light modulator (SLM) is

Is given as, where

or

to be.

에서

및

는

방향의

및

방향의

에 의해 공간 광 변조기(SLM)의 공간 주파수

및

와 관련된다. From Equations 8 and 9, the on-axis angular spectrum

in

And

Is

Direction of

And

Direction of

Spatial frequency of the spatial light modulator (SLM) by

And

Is related to.

에 대해 사용 가능한 공간 주파수 범위는

방향에 대해

이며,

방향에 대해

이다. 공간 주파수

를 가지는 평면 파동은 홀로그래픽 광학 소자(HOE) 초점 길이

를 가지는

에서 눈동자로 초점이 맞춰진다. 따라서, 단일 아이박스의 크기 또는 눈동자 평면의 초점 지점 조정 범위는 최종적으로 다음 식과 같이 나타낼 수 있다. therefore,

The available spatial frequency range for is

About the direction

Is,

About the direction

to be. Spatial frequency

The plane wave with is the focal length of a holographic optical element (HOE)

Having

The focus is on the pupils. Accordingly, the size of a single eyebox or the range of adjustment of the focal point of the pupil plane can be finally expressed as the following equation.

[Equation 10]

Equation 10 represents the size of a single eyebox or an adjustment range of a single focus point. The holographic head-mounted display apparatus according to an exemplary embodiment duplicates an eyebox or a focal point using a holographic optical element (HOE), so that an entire range in which an eye can be positioned is multiplexed.

As described above, for the optical see-through function and the eyebox replication, a holographic optical element is used as an optical combiner, which is a multiplexed tilt concave mirror that forms multiple copies of the eyebox. It functions as (multiplexed tilted concave mirrors). For depth of field control and eyebox adjustment, a hologram of a computer-generated three-dimensional object is synthesized into different ranges of the angular spectrum.

In an optical experiment, it was confirmed that the holographic head mounted display device according to an embodiment can always display a focused image, and this image is large at different distances with a low depth of field without time-multiplexing. It has a depth of field and a three-dimensional image.

The apparatus described above may be implemented as a hardware component, a software component, and/or a combination of a hardware component and a software component. For example, the devices and components described in the embodiments include, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA), It can be implemented using one or more general purpose computers or special purpose computers, such as a programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications executed on the operating system. In addition, the processing device may access, store, manipulate, process, and generate data in response to the execution of software. For the convenience of understanding, although it is sometimes described that one processing device is used, one of ordinary skill in the art, the processing device is a plurality of processing elements and/or a plurality of types of processing elements. It can be seen that it may include. For example, the processing device may include a plurality of processors or one processor and one controller. In addition, other processing configurations are possible, such as a parallel processor.

The software may include a computer program, code, instructions, or a combination of one or more of these, configuring the processing unit to behave as desired or processed independently or collectively. You can command the device. Software and/or data may be interpreted by a processing device or to provide instructions or data to a processing device, of any type of machine, component, physical device, virtual equipment, computer storage medium or device. Can be embodyed in The software may be distributed over networked computer systems and stored or executed in a distributed manner. Software and data may be stored on one or more computer-readable recording media.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the medium may be specially designed and configured for the embodiment, or may be known and usable to those skilled in computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floptical disks. -A hardware device specially configured to store and execute program instructions such as magneto-optical media, and ROM, RAM, flash memory, and the like. Examples of the program instructions include not only machine language codes such as those produced by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like.

As described above, although the embodiments have been described by the limited embodiments and drawings, various modifications and variations are possible from the above description by those of ordinary skill in the art. For example, the described techniques are performed in a different order from the described method, and/or components such as a system, structure, device, circuit, etc. described are combined or combined in a form different from the described method, or other components Alternatively, even if substituted or substituted by an equivalent, an appropriate result can be achieved.

Therefore, other implementations, other embodiments, and claims and equivalents fall within the scope of the claims to be described later.

Claims (5)

A spatial light modulator (SLM) in which plane waves from a laser source are modulated by a computer generated hologram (CGH);
A 4f optical unit for forming an intermediate holographic image after being modulated by the spatial light modulator (SLM); And
Reflective holographic optical element (HOE) that diffracts light from the intermediate holographic image to provide an enlarged virtual holographic image at a distance greater than the user's eyes
Including,
The holographic optical element (HOE),
The oblique plane wave from the spatial light modulator (SLM) is diffracted and recorded to form multiple focal points, and functions as a multiplexed oblique concave mirror that duplicates the eyebox to observe an image in a wider range,
The separation distance between the focal points of the holographic optical element (HOE) is set larger than the eye pupil size, and around each of the focal points, the eyebox is the angular spectrum range used for synthesis of the computer-generated hologram (CGH). The computer-generated hologram (CGH) is generated in different ranges of the angular spectrum by individually controlling the depth of field of the holographic image, and the holographic optical element ( HOE) to display an image with the depth of field by adjusting the focal point,
The computer-generated hologram (CGH) is synthesized with different single plane carriers to adjust the focus without mechanical movement, but multiple focal points are generated through first-order diffraction, and the single plane carrier is transferred to the holographic optical element (HOE). Is diffracted to form a multi-focal point, and because the lateral position offset in the pupil plane depends on the spatial frequency of the single plane carrier, the multi-focal point is the spatial frequency of the single plane carrier in the synthesis of The focus is adjusted while maintaining the focus point separation through the change,
By duplicating the eyebox or focal point using the holographic optical element (HOE), the entire range in which the eye can be positioned is multiplexed.
A holographic head mounted display device, characterized in that. delete delete The method of claim 1,
The light corresponding to the virtual holographic image is duplicated toward the multi-focal point by the holographic optical element (HOE), so that an eye located in an arbitrary eyebox can see the displayed image.
A holographic head mounted display device, characterized in that. The plane wave from the laser source is modulated by a computer generated hologram (CGH) of a spatial light modulator (SLM);
After the modulation, forming an intermediate holographic image after the 4f optical unit; And
The light from the intermediate holographic image is diffracted by a reflective holographic optical element (HOE) to provide an enlarged virtual holographic image at a distance greater than the user's eyes.
Including,
The holographic optical element (HOE),
The oblique plane wave from the spatial light modulator (SLM) is diffracted and recorded to form multiple focal points, and functions as a multiplexed oblique concave mirror that duplicates the eyebox to observe an image in a wider range,
The separation distance between the focal points of the holographic optical element (HOE) is set larger than the eye pupil size, and around each of the focal points, the eyebox is the angular spectrum range used for synthesis of the computer-generated hologram (CGH). The computer-generated hologram (CGH) is generated in different ranges of the angular spectrum by individually controlling the depth of field of the holographic image, and the holographic optical element ( HOE) to display an image with the depth of field by adjusting the focal point,
The computer-generated hologram (CGH) is synthesized with different single plane carriers to adjust the focus without mechanical movement, but multiple focal points are generated through first-order diffraction, and the single plane carrier is transferred to the holographic optical element (HOE). Is diffracted to form a multi-focal point, and because the lateral position offset in the pupil plane depends on the spatial frequency of the single plane carrier, the multi-focal point is the spatial frequency of the single plane carrier in the synthesis of The focus is adjusted while maintaining the focus point separation through the change,
By duplicating the eyebox or focal point using the holographic optical element (HOE), the entire range in which the eye can be positioned is multiplexed.
A display method using a holographic head-mounted display device, characterized in that.

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