Optical device for generating holographic images

Abstract

The purpose of the present invention is to provide a structure for adjusting the diopter of an optical device by changing the position of a virtual image reflected by a spatial light modulator by using a computer-generated hologram through an optical device for generating holographic images, and to provide an optical device having minimized aberration by using multiple lenses that satisfy predetermined optical design.

Description

Optical device for generating holographic images

[0001] The present invention relates to an optical device for generating a holographic image using a computer-generated hologram.

[0002] Recent advancements in optical technology have led to the development of head-mounted display devices that allow users to view holographic images while wearing them on their head. These head-mounted display devices operate by generating holographic images in front of the wearer's eyes using a light source (e.g., a laser), a light modulator, and a holographic optical element (HOE).

[0003] However, the problem arises of having to change the position of the holographic image depending on factors such as the wearer's eyesight and wearing condition. The simplest way to solve this problem is to physically move the optical modulator along the optical axis to change the position of the holographic image. While this method has the advantage of optical simplicity, it suffers from the drawback of a complex mechanical structure and poor durability because the optical modulator must be mechanically moved.

[0004] Therefore, research is being conducted to develop a method that can change the position of an accurate holographic image in a more durable and simpler manner.

[0005] (Patent Document 1) Republic of Korea Patent Publication No. 10-2021-0100414 (published on August 17, 2021)

[0006] The present invention aims to provide a structure for adjusting the diopter of an optical device by changing the position of a virtual image reflected by a spatial light modulator using a computer-generated hologram.

[0007] The purpose of the present invention is to provide an optical device that minimizes aberrations by using lenses that satisfy a plurality of predetermined optical designs.

[0008] An optical device for generating a holographic image of the present invention comprises: a first optical system including a laser light source irradiating parallel light; a reflective spatial light modulator (SLM) for reflecting light generated by the laser light source and modulating it with a computer-generated hologram (CGH); a second optical system including a non-diffracted reflection removal filter for removing non-diffracted reflected light and passing diffracted reflected light, onto which light reflected from the spatial light modulator is incident; a third optical system including a positive power for which light passing through the non-diffracted reflection removal filter is incident; a mirror for reflecting light passing through the third optical system; and a fourth optical system including a reflective holographic optical element (HOE) having positive power for which light reflected from the mirror is reflected, wherein the second optical system includes a first lens having positive power and a second lens bonded to the first lens and having negative power, wherein a virtual image whose position can be changed by the spatial light modulator is formed, and an intermediate holographic image can be formed between the mirror and the reflective optical element.

[0009] In an embodiment, the first optical system may further include a polarizer positioned between the spatial light modulator and the second optical system.

[0010] In an embodiment, the second optical system may have a defined refractive power.

[0011] In an embodiment, the light source side surface and the object side surface of the first lens may be convex, the light source side surface of the second lens may be concave, and the object side surface of the second lens may be formed as a plane.

[0012] In an embodiment, the third optical system may further include at least one cylindrical lens.

[0013] In an embodiment, when the power for the first axis of the cylindrical lens is A and the power for the second axis orthogonal to the first axis is B, the following conditional expressions 1 and 2 can be satisfied.

[0014] <Condition 1>

[0015] A < 0

[0016] <Condition 2>

[0017] |B| < 0.2|A|

[0018] In an embodiment, the third optical system may further include four lenses positioned on the object side of the cylindrical lens.

[0019] In an embodiment, the four lenses are sequentially arranged in the object-side direction in the cylindrical lens, and the four lenses may include a fourth lens having positive power; a fifth lens having negative power; a sixth lens having positive power; and a seventh lens having negative power.

[0020] In an embodiment, the following condition 3 can be satisfied.

[0021] <Condition 3>

[0022] 1.0〈 efx / efy〈 1.05

[0023] Here, efx is the effective focal length along the x-axis (short axis), and efy is the effective focal length along the y-axis (long axis).

[0024] In an embodiment, the angle between the first axis connecting the reflective holographic optical element and the object for the optical device and the second axis connecting the reflective holographic optical element and the intermediate holographic image may be 50° to 70°.

[0025] In an embodiment, the reflective holographic optical element may be positioned to form an angle of 0° to 5° with the first axis.

[0026] In an embodiment, the spatial light modulator may be formed to form an angle of 30° to 60° with the axis of the second optical system.

[0027] In an embodiment, the focal length of the fourth optical system may be 18 mm to 24 mm.

[0028] When the focal length for the first axis of the second optical system is f21, the focal length for the second axis orthogonal to the first axis is f22, the focal length for the first axis of the third optical system is f31, and the focal length for the second axis is f32, the following conditional expression 4 can be satisfied.

[0029] <Condition 4>

[0030] f31 / f21+f32 / f21 < 3.5

[0031] The present invention has the advantage of being able to adjust the diopter of an optical device by changing the position of the virtual image reflected by the spatial light modulator using a computer-generated hologram.

[0032] The present invention has the advantage of minimizing aberrations and increasing the angle of view by using a lens that satisfies a plurality of predetermined optical designs.

[0033] FIG. 1 is a drawing illustrating an optical structure of an optical device for generating a holographic image according to one embodiment of the present invention.

[0034] FIG. 2 is a drawing illustrating a location on an optical device that generates a holographic image according to one embodiment of the present invention.

[0035] FIG. 3 is a drawing showing the position and arrangement of a holographic optical element according to one embodiment of the present invention.

[0036] FIG. 4 illustrates optical data for individual lenses included in an optical device according to one embodiment of the present invention.

[0037] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Regardless of the drawing reference numerals, identical or similar components will be assigned the same reference numerals, and redundant descriptions thereof will be omitted. Furthermore, when describing embodiments disclosed in this specification, if a detailed description of a related known technology is judged to obscure the gist of the embodiments disclosed in this specification, the detailed description thereof will be omitted.

[0038] Terms that include ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another.

[0039] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0040] In this application, each step described may be performed regardless of the listed order, except in cases where a special causal relationship requires that the steps be performed in the listed order.

[0041] In this application, terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0042]

[0043] Hereinafter, the present invention will be described with reference to the attached drawings.

[0044] FIG. 1 is a drawing illustrating an optical structure of an optical device for generating a holographic image according to one embodiment of the present invention.

[0045] Referring to FIG. 1, the optical device of the present invention generates a holographic image. The optical device of the present invention is configured so that the wearer's pupil corresponds to an object (700), and the object's focus is formed at the true focal point of the holographic image of the present invention.

[0046] The optical device of the present invention includes a laser light source (100), a first optical system (200), a second optical system (300), a third optical system (400), a mirror (500), and a fourth optical system (600). Here, the laser light source (100), the first optical system (200), the second optical system (300), the third optical system (400), the mirror (500), and the fourth optical system (600) are sequentially arranged in a direction from the laser light source (100) toward an object (700).

[0047] A laser light source (100) generates light and irradiates the generated light to a first optical system (200). In particular, the laser light source (100) generates parallel light and irradiates the parallel light to a spatial light modulator (210) of the first optical system (200).

[0048] In the present invention, it is preferable that the light source is a laser light source. The reflective holographic optical element (610) in the present invention has a narrow wavelength range, so chromatic aberration may occur when an LED with a wide wavelength range is used.

[0049] The first optical system (200) includes a spatial light modulator (SLM) (210). In the present invention, the spatial light modulator (210) is preferably a reflective type. The reflective type spatial light modulator (210) may be, for example, an LCoS spatial light modulator. The spatial light modulator modulates light generated by a laser light source using a computer-generated hologram (CGH) to generate a virtual image. The position of the virtual image can be adjusted based on the spatial light modulator (210).

[0050] The first optical system (200) may further include a polarizer (220). In particular, when a reflective type spatial light modulator (210) is used, the polarizer (220) may be necessarily included. The polarizer (220) is positioned between the spatial light modulator (210) and the second optical system (300).

[0051] The second optical system (300) receives light reflected from the spatial light modulator (210). When the first optical system (200) includes a polarizing plate (220), only light with aligned polarization can be received by the second optical system (300).

[0052] The second optical system (300) may have overall positive refractive power. The second optical system (300) may include at least one lens. Specifically, the second optical system (300) may include a first lens (310) and a second lens (320). The first lens (310) and the second lens (320) may be sequentially arranged in the direction from the light source side to the object side.

[0053] The first lens (310) may have a defined power. It is preferable that the first lens (310) be a lens with convex surfaces on both sides, but in some cases, a lens with a convex surface at least on the light source side may be used.

[0054] The second lens (320) may be a meniscus-shaped lens and may be bonded to the first lens (310). The second lens (320) may have at least one of positive power and negative power, but specifically may have negative power. However, it is preferable that the power of the second lens (320) be less than that of the first lens (310).

[0055] Additionally, the light source side and object side of the first lens (310) may be formed convexly. The light source side of the second lens (320) may be formed concavely, and the object side may be formed flat.

[0056] The second optical system (300) may include a non-diffracted reflection removal filter (DC filter) (330). The non-diffracted reflection removal filter (330) may be positioned on the object side of the second lens (320). Therefore, the non-diffracted reflection light passes through a portion of the reflected light of the light source (100) that has passed through the second lens (320) and blocks the other portion. Specifically, the non-diffracted reflection removal filter (330) blocks the 0th-order diffracted light that has not been diffracted and selectively passes only the 1st-order or higher diffracted light.

[0057] The third optical system (400) receives light that has passed through the non-diffracted reflection removal filter (330). Therefore, only the diffracted light among the reflected light of the light source (100) that has passed through the second optical system (300) is received by the third optical system (400).

[0058] The third optical system (400) may have a defined power as a whole. The third optical system (400) may include at least one lens. Specifically, the third optical system (400) may include a third lens (410), a fourth lens (420), a fifth lens (430), and a sixth lens (440). The third lens (410), the fourth lens (420), the fifth lens (430), and the sixth lens (440) may be sequentially arranged in a direction from the light source (100) side to the object (700) side.

[0059] In the attached drawing, the third optical system (400) is depicted as having four lenses arranged sequentially, but the number of individual lenses may be changed depending on the case.

[0060] The third optical system (400) includes at least one cylindrical lens. In the attached drawing, the third lens (410), which is located closest to the light source (100) among the lenses of the third optical system (400), is depicted as being a cylindrical lens.

[0061] The cylindrical lens corresponding to the third lens (410) may be formed to have a negative power for the first axis and no separate power for the second axis. Here, the first axis may be the y-axis (major axis) in the vertical direction, and the second axis may be the x-axis (minor axis) in the horizontal direction. Specifically, the light source-side surface of the third lens (410) may be formed as a concave surface, and the object-side surface may be formed as a plane.

[0062] Specifically, when the power for the first axis of the cylindrical lens (410) is A and the power for the second axis is B, the following conditional expressions 1 and 2 are satisfied.

[0063] <Condition 1>

[0064] A < 0

[0065] <Condition 2>

[0066] |B| < 0.2|A|

[0067] <Conditional expression 1> means that the cylindrical lens (410) has negative power with respect to the first axis. <Conditional expression 2> means that the cylindrical lens (410) has smaller power with respect to the second axis in terms of the absolute value than with respect to the first axis. Specifically, since the absolute value of the power of the cylindrical lens (410) with respect to the second axis is within 0.2 times the absolute value of the power with respect to the first axis, this can mean that there is virtually no separate power.

[0068] By means of this cylindrical lens (410), the optical device of the present invention satisfies the following conditional expression 3.

[0069] <Condition 3>

[0070] 1.0〈 efx / efy〈 1.05

[0071] Here, efx is the effective focal length along the x-axis (short axis), and efy is the effective focal length along the y-axis (long axis).

[0072] The third optical system (400) may include four lenses positioned on the object side from the cylindrical lens (410). That is, the four lenses may be arranged sequentially in the order of the third lens, which is the cylindrical lens (410), the fourth lens (420), the fifth lens (430), the sixth lens (440), and the seventh lens (450) in the object side direction.

[0073] At this time, the fourth lens (420) may have positive power, be formed concavely toward the light source side, and be formed convexly toward the object side. The fifth lens (430) may have negative power, be formed concavely toward the light source side, and be formed convexly toward the object side. The sixth lens (440) may have positive power, be formed convexly toward the light source side, and be formed convexly toward the object side. The seventh lens (450) may have negative power, be formed convexly toward the light source side, and be formed concavely toward the object side.

[0074] The mirror (500) reflects light passing through the third optical system (400). Due to the reflection shape of the mirror (500), the optical device of the present invention can be designed in the shape of glasses as a whole.

[0075] The fourth optical system (600) includes a reflective holographic optical element (HOE) (610) that reflects light reflected from the mirror (500) and has a defined power. The reflective holographic optical element (HOE) (610) is an element that has the characteristic of off-axis reflection. Therefore, even if the reflective holographic optical element (HOE) (610) is positioned in a form close to perpendicular to the wearer's face, it can generate emitted light that is incident perpendicularly on the wearer's eye. An intermediate holographic image (550) is formed between the mirror (500) and the reflective optical element by the reflective holographic optical element (610).

[0076] For this purpose, the focal length of the fourth optical system (600) may be 18 mm to 24 mm, and the focal length of the fourth optical system (600) may be changed depending on conditions.

[0077] Meanwhile, the focal length for the first axis of the second optical system (300) may be f21, and the focal length for the second axis orthogonal to the first axis may be f22. In addition, when the focal length for the first axis of the third optical system (400) may be f31, and the focal length for the second axis may be f32, the following conditional expression 4 may be satisfied.

[0078] <Condition 4>

[0079] f31 / f21+f32 / f21 < 3.5

[0080] For example, the focal length of the second optical system (300) with respect to the X-axis may be 35 mm, and the focal length of the second optical system (300) with respect to the Y-axis may be 35 mm. In addition, the focal length of the third optical system (400) with respect to the X-axis may be 55 mm, and the focal length of the third optical system (400) with respect to the Y-axis may be 64 mm. In this case, f31 / f21+f32 / f21 becomes 3.4, which is less than 3.5.

[0081]

[0082] Hereinafter, with reference to FIG. 2, a virtual image (250) generated by a computer-generated hologram in the present invention will be described. The virtual image generated by the computer-generated hologram may correspond to an illusion.

[0083] The virtual image (250) can be positioned differently by a computer-generated hologram. Specifically, the virtual image (250) can be positioned differently within a range in the forward and backward directions relative to the spatial light modulator (210). In the attached FIG. 2, the virtual image (250) is depicted as being positioned between the spatial light modulator (210) and the second optical system (300). However, in some cases, the virtual image (250) can also be generated as a virtual image behind the spatial light modulator (210).

[0084] As the position of the virtual image (250) changes, the position of the intermediate holographic image (550) generated by the optical device of the present invention can move. Accordingly, the optical device of the present invention can adjust the diopter without moving a separate spatial light modulator (210).

[0085] The spatial light modulator (210) may be formed to form an angle of 30° to 60° with the axis (310) of the second optical system. Depending on the tilt arrangement of the spatial light modulator (210), aberrations caused by off-axis reflection in the holographic optical element (610) can be reduced.

[0086]

[0087] Hereinafter, with reference to FIG. 3, the position and arrangement of the reflective holographic optical element (HOE) (610) in the present invention will be described in detail.

[0088] There may be a virtual first axis (611) connecting the reflective holographic optical element (610) and the object (700). Additionally, there may be a virtual second axis (612) connecting the reflective holographic optical element (610) and the intermediate holographic image (550).

[0089] Here, the angle between the first axis (611) and the second axis (612) may be 50° to 70°.

[0090] Additionally, the reflective holographic optical element (610) may be tilted to form an angle of 0° to 5° with respect to the first axis (611). Depending on the tilt arrangement of the reflective holographic optical element (610), aberrations caused by off-axis reflection in the holographic optical element (610) may be reduced.

[0091] By the operation of the optical device described above, the user's pupil (700) corresponding to the object can view a holographic image (561, 562). Here, the position of the holographic image (561, 562) can be adjusted by adjusting the position of the virtual image (250) described above. Specifically, when the optical device is set to 2.0 diopter as illustrated in FIG. 3, a holographic image (561) corresponding to a position spaced apart from the object by a distance (D1) of 0.5 m is generated. In addition, when the optical device is set to 0.0 diopter, a holographic image (562) corresponding to a position spaced apart from the object by an infinite distance (D2) is generated.

[0092]

[0093] FIG. 4 illustrates optical data for individual lenses included in an optical device according to one embodiment of the present invention.

[0094]

[0095] The technical features disclosed in each embodiment of the present invention are not limited to that embodiment, and, unless they are mutually incompatible, the technical features disclosed in each embodiment may be combined and applied to different embodiments.

[0096] Therefore, although each embodiment focuses on its own technical features, each technical feature can be applied in combination with each other as long as they are not mutually incompatible.

[0097] The present invention is not limited to the above-described embodiments and the attached drawings, and various modifications and variations are possible within the scope of those skilled in the art. Therefore, the scope of the present invention should be defined not only by the claims of this specification but also by equivalents thereof.

Claims

1. A laser light source that illuminates parallel light; A first optical system including a reflective spatial light modulator (SLM) that reflects light generated by the laser light source and modulates it by a computer-generated hologram (CGH); A second optical system including a non-diffracted reflection removal filter that removes non-diffracted reflected light and passes diffracted reflected light, upon which light reflected from the spatial light modulator is incident; A third optical system having a positive power and into which light passing through the above non-diffraction reflection removal filter is incident; A mirror that reflects light passing through the third optical system; and A fourth optical system including a reflective holographic optical element (HOE) having a defined power and in which light reflected from the above mirror is reflected, The above second optical system, A first lens having a defining power and a second lens bonded to the first lens and having a negative power, A virtual image whose position can be changed is formed by the above spatial light modulator, An intermediate holographic image is formed between the above mirror and the above reflective optical element. An optical device that produces a holographic image.

2. In paragraph 1, The first optical system further includes a polarizer positioned between the spatial light modulator and the second optical system. An optical device that produces a holographic image.

3. In paragraph 1, The above second optical system has a defined refractive power. An optical device that produces a holographic image.

4. In paragraph 1, The light source side and object side of the first lens are convex, The light source side surface of the second lens is concave, and the object side surface of the second lens is formed as a plane. An optical device that produces a holographic image.

5. In paragraph 1, The third optical system further comprises at least one cylindrical lens. An optical device that produces a holographic image.

6. In paragraph 5, When the power for the first axis of the above cylindrical lens is A and the power for the second axis orthogonal to the first axis is B, the following conditional expressions 1 and 2 are satisfied. An optical device that produces a holographic image. <Condition 1> A < 0 <Condition 2> |B| < 0.2|A| 7. In paragraph 5, The third optical system further includes four lenses positioned on the object side of the cylindrical lens. An optical device that produces a holographic image.

8. In paragraph 7, The above four lenses are arranged sequentially in the object-side direction in the above cylindrical lens, The above four lenses are, A fourth lens with defining power; The fifth lens with the power of wealth; A sixth lens having the power of definition; and Contains the 7th lens with the power of wealth An optical device that produces a holographic image.

9. In paragraph 1, Satisfying the following condition 3 An optical device that produces a holographic image. <Condition 3> 1.0〈 efx / efy〈 1.05 Here, efx is the effective focal length along the x-axis (short axis), and efy is the effective focal length along the y-axis (long axis).

10. In paragraph 1, The angle between the first axis connecting the reflective holographic optical element and the object to the optical device and the second axis connecting the reflective holographic optical element and the intermediate holographic image is 50° to 70°. An optical device that produces a holographic image.

11. In clause 10, The above reflective holographic optical element is positioned to form an angle of 0° to 5° with the first axis. An optical device that produces a holographic image.

12. In paragraph 1, The above spatial light modulator is formed to form an angle of 30° to 60° with the axis of the second optical system. An optical device that produces a holographic image.

13. In paragraph 1, The focal length of the fourth optical system is 18 mm to 24 mm. An optical device that produces a holographic image.

14. In paragraph 1, The focal length for the first axis of the second optical system is f21, and the focal length for the second axis orthogonal to the first axis is f22. When the focal length for the first axis of the third optical system is f31 and the focal length for the second axis is f32, the following conditional expression 4 is satisfied. An optical device that produces a holographic image. <Condition 4> f31 / f21+f32 / f21 < 3.5

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