Optical system and display device

Abstract

An optical system, which is an optical system that images light from a display panel on a retina when combined with an eyeball, includes: a first refractive lens that collects light from the display panel; and a first diffractive lens disposed between the first refractive lens and an image forming position, in which the first diffractive lens is configured to retard a phase of light passing through an outer peripheral portion of the first diffractive lens from a phase of light passing through a central portion of the first diffractive lens.

Description

Technical Field

[0001] This disclosure relates to optical systems and display devices. Background Technology

[0002] In display devices such as head-mounted displays (HMDs), a three-way optical system in which the light path is reflected twice by two reflective surfaces is known (see, for example, Patent Document 1).

[0003] Reference List

[0004] Patent documents

[0005] Patent Document 1: WO2021 / 106048A Summary of the Invention

[0006] Technical issues

[0007] In the display device and its optical system described above, there is still room for consideration in achieving a wide viewing angle. The optical system already contains several lenses, and it is not easy to achieve a wide viewing angle by adding further refractive lenses while maintaining sufficient edge thickness.

[0008] One aspect of this disclosure enables the realization of a wide field of view.

[0009] Solutions to technical problems

[0010] An optical system according to one aspect of this disclosure is an optical system for imaging light from a display panel onto the retina when combined with an eyeball, the optical system comprising: a first refractive lens for converging light from the display panel; and a first diffractive lens disposed between the first refractive lens and the eyeball, wherein the first diffractive lens is configured such that the phase of light passing through the peripheral portion of the first diffractive lens lags behind the phase of light passing through the central portion of the first diffractive lens.

[0011] A display device according to one aspect of the present disclosure includes: a display panel; and an optical system that, when combined with an eyeball, images light from the display panel onto the retina, wherein the optical system includes: a first refractive lens that focuses light from the display panel; and a first diffractive lens disposed between the first refractive lens and the eyeball, and the first diffractive lens is configured such that the phase of light passing through the peripheral portion of the first diffractive lens lags behind the phase of light passing through the central portion of the first diffractive lens. Attached Figure Description

[0012] Figure 1 This is a diagram illustrating a schematic configuration example of the display device 1 according to the first embodiment.

[0013] Figure 2 This is a diagram showing a schematic configuration example of optical system 3.

[0014] Figure 3 This is a diagram showing a schematic configuration example of the diffraction lens 8-1.

[0015] Figure 4 This is a diagram illustrating an example of optical phase delay.

[0016] Figure 5 This is a diagram showing a design example.

[0017] Figure 6 This is a diagram showing a design example.

[0018] Figure 7 This is a diagram showing a design example.

[0019] Figure 8 This is a diagram showing a design example.

[0020] Figure 9 This is a diagram showing a design example.

[0021] Figure 10 This is a diagram showing a design example.

[0022] Figure 11 This is a diagram showing a design example.

[0023] Figure 12 This is a diagram illustrating a schematic configuration example of the display device 1 according to the second embodiment.

[0024] Figure 13 This is a diagram showing a schematic configuration example of optical system 3.

[0025] Figure 14 This is a diagram showing a schematic configuration example of the diffraction lens 8-2.

[0026] Figure 15 This is a diagram illustrating an example of the phase delay amount.

[0027] Figure 16 This is a diagram showing a design example.

[0028] Figure 17 This is a diagram showing a design example.

[0029] Figure 18 This is a diagram showing a design example.

[0030] Figure 19 This is a diagram showing a design example.

[0031] Figure 20 This is a diagram showing a design example.

[0032] Figure 21 This is a diagram showing a design example.

[0033] Figure 22 This is a diagram showing another design example.

[0034] Figure 23 This is a diagram showing another design example.

[0035] Figure 24 This is a diagram showing another design example.

[0036] Figure 25 This is a diagram showing another design example.

[0037] Figure 26 This is a diagram showing another design example.

[0038] Figure 27 This is a diagram showing another design example.

[0039] Figure 28 This is a diagram showing another design example.

[0040] Figure 29 This is a diagram showing a variation.

[0041] Figure 30 This is a diagram showing a variation.

[0042] Figure 31 This is a diagram showing a variation.

[0043] Figure 32 This is a diagram showing a variation.

[0044] Figure Labels

[0045] 1 Display device; 2 Display panel; 2a Display surface; 3 Optical system; 4 Refractive lens; 4-1 Refractive lens; 4-2 Refractive lens; 4a Surface; 5 Semi-transparent mirror; 6 Polarizer; 6-1 Polarizer; 6-2 Polarizer; 6-3 Polarizer; 7 QWP; 7-1 QWP; 7-1a QWP; 7-1b QWP; 7-2 QWP; 7-3 QWP; 7-3a QWP; 7-3b QWP; 8 Diffractive lens; 8-1 Diffractive lens; 811 Central portion; 812 Outer peripheral portion; 8-2 Diffractive lens; 821 Central portion; 822 Outer peripheral portion; 9 Cutoff filter; OA Optical axis; P Pupil position; U User. Detailed Implementation

[0046] In the following, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that in the following embodiments, the same elements are indicated by the same reference numerals, and redundant descriptions may be omitted. The same reference numerals may have different meanings between different embodiments, and in such cases, they may be interpreted according to the description in the embodiments.

[0047] This disclosure will be presented in the following order.

[0048] 0. Introduction

[0049] 1. First Embodiment

[0050] 2. Second Embodiment

[0051] 3. Variations

[0052] 4. Example of the effect

[0053] 0. Introduction

[0054] Display devices such as HMDs include optical systems that, when combined with the eye, image light from the display panel onto the retina. It is not uncommon for optical systems to already include a large number of lenses, and adding further refractive lenses to achieve a wide viewing angle while maintaining sufficient edge thickness is not easy. Furthermore, addressing lateral chromatic aberration can also be problematic.

[0055] For example, one could consider suppressing lateral chromatic aberration by incorporating a meniscus lens into the optical system. However, in this case, the distance from the pupil position to the reflecting surface in the optical system increases, the effective diameter increases, and this further leads to a reduction in edge thickness, making it difficult to achieve a wide viewing angle.

[0056] Alternatively, a method could be considered to achieve a wide viewing angle by providing strong optical power, such as using a holographic optical element (HOE). However, in this case, if the HOE system becomes thin, coma aberration will occur, and it will be difficult to obtain sufficient resolution. Although coma aberration can be suppressed by thickening the HOE, the high wavelength selectivity of the HOE system necessitates the use of highly coherent light, such as lasers. This is expensive and increases weight.

[0057] At least some of the aforementioned problems are addressed by publicly available technologies. Diffractive lenses are incorporated into a three-way optical system that includes a refractive lens, thereby achieving a wide field of view, as will be explained in detail later. For example, by bending light passing through the outer periphery of the diffractive lens toward the optical axis, excessive light diffusion that would enlarge the lens can be prevented.

[0058] Two diffractive lenses can be used, and the light beams passing through the outer periphery of each lens can be given phase delays of opposite signs. In other words, the diffractive lens with a positive phase delay has a diverging phase in its outer periphery, while the one with a negative phase delay has a converging phase. The latter diffractive lens directs the light passing through its outer periphery closer to the optical axis, thereby suppressing lens enlargement due to excessive light diffusion. Furthermore, lateral chromatic aberration generated in one diffractive lens can be canceled out by the other. Moreover, by balancing these two aspects, field curvature and astigmatism can be reduced. This achieves good aberration correction and a wide viewing angle.

[0059] Because edge thickness is easier to ensure compared to using a meniscus lens, the field of view (FOV) can be widened. Furthermore, since the optical system can include more refractive lenses compared to using a single HOE system, coma can be reduced accordingly, and higher resolution can be achieved. Note that while it's possible to replace the original refractive lens with a diffractive lens, adding a diffractive lens has the advantage of adding correction terms for field curvature and astigmatism. This allows for even higher resolution, among other benefits.

[0060] 1. First Embodiment

[0061] Figure 1 This is a diagram illustrating a schematic configuration example of the display device 1 according to the first embodiment. The display device 1 is, for example, an HMD device for displaying images for virtual reality (VR). Figure 1 (A) schematically illustrates the eye (pupil) of a user U wearing and using display device 1. The user U's eye (e.g., pupil) is located at or near a position where the light from a point on display device 1 is approximately parallel, thereby allowing the image to be observed by the user U. The position (plane) where the light is approximately parallel is referred to as the pupil position P (pupil plane). Note that, without contradiction, the image may be interpreted as an image and interpreted accordingly.

[0062] The XYZ coordinate system is also shown. Display device 1 and user U are located sequentially in the positive Z-axis direction. Unless otherwise stated, it is assumed that each element of display device 1 extends in the XY plane direction and has thickness in the Z-axis direction. Figure 1 (A) schematically shows the side (which may be a cross-section) of the display device 1 as viewed along the X-axis. Figure 1 The path of several beams (also called light rays or light flux, etc.) is schematically shown in (B).

[0063] The display device 1 includes a display panel 2 and an optical system 3. The display panel 2 and the optical system 3 are arranged sequentially along the positive Z-axis. Note that in Figure 1In (A), the optical axis OA of optical system 3 is represented by a single-dotted line.

[0064] The display panel 2 includes, for example, organic light-emitting diodes (OLEDs), liquid crystals (LCs), and light-emitting diodes (LEDs). The display surface of the display panel 2 is referred to as display surface 2a.

[0065] When combined with the eye, the optical system 3 images light from the display panel 2 onto the retina. The optical system 3 includes a refractive lens 4, a semi-transparent mirror 5, a polarizer 6, a quarter-wave plate 7, and a diffractive lens 8. At least some of these elements may be multiple, and in this example, there are multiple refractive lenses 4, multiple polarizers 6, and multiple quarter-wave plates 7.

[0066] The first refracting lens among the multiple refracting lenses 4 is shown as refracting lens 4-1. The second refracting lens is shown as refracting lens 4-2. Without making a specific distinction between them, they are simply referred to as refracting lens 4.

[0067] The first polarizer of the plurality of polarizers 6 is shown as polarizer 6-1. The second polarizer is shown as polarizer 6-2. Without making a special distinction between them, they are simply referred to as polarizer 6.

[0068] The first of the multiple QWPs 7 is referred to as QWP 7-1. The second QWP is referred to as QWP 7-2. Without distinguishing them from each other, they are simply referred to as QWP 7. Additionally, QWP 7-1 is a pair of QWPs, and is referred to as QWP 7-1a and QWP 7-1b respectively. Without distinguishing them from each other, they are simply referred to as QWP 7-1.

[0069] In this example, the diffraction lens 8 is a single diffraction lens 8, but for ease of description, the diffraction lens 8 is referred to as diffraction lens 8-1 (first diffraction lens) for illustration.

[0070] exist Figure 1 In the example shown in (A), the refractive lens 4-2, polarizer 6-2, QWP 7-2, semi-transparent mirror 5, refractive lens 4-1, QWP 7-1a, polarizer 6-1, QWP 7-1b, and diffractive lens 8-1 are arranged sequentially along the positive Z-axis. Light from display panel 2 passes through these elements and becomes approximately parallel at the pupil position P. Note that in the following description, light traveling along the positive Z-axis in optical system 3 can be simply referred to as light from display panel 2.

[0071] A refractive lens 4-2 is positioned between the display panel 2 and the polarizer 6-2. Light from the display panel 2 passes through the refractive lens 4-2 and is incident on the polarizer 6-2.

[0072] Polarizer 6-2, QWP 7-2, semi-transparent mirror 5, refractive lens 4-1, QWP 7-1a, polarizer 6-1, and QWP 7-1b constitute a so-called three-way optical system. This, for example, can help make optical system 3 thinner and smaller. Optical system 3 is configured to cause light from display panel 2 to pass through refractive lens 4-1 three times by reversing the light path, details of which will be described later. Finally, circularly polarized light exits from QWP 7-1b towards diffractive lens 8-1.

[0073] Here, we will first describe the refractive lens 4-1 and the semi-transparent mirror 5, which are the constituent elements of the three-way optical system described above. The refractive lens 4-1 converges the light from the display panel 2. The refractive lens 4-1 is positioned between the display panel 2 and the pupil position P, and more specifically, in this example, it is positioned between the semi-transparent mirror 5 and the QWP 7-1a, so that the light from the display panel 2 is approximately parallel at the pupil position P.

[0074] The surface of the refractive lens 4-1 on the pupil position P side (eyeball side, positive Z-axis side) is referred to as surface 4a. In one embodiment, surface 4a of the refractive lens 4-1 may have an inflection point. This results in maintaining aberration balance. For example, when plotting the second derivative of the amount of sag on surface 4a of the refractive lens 4-1 with respect to the distance from the optical axis OA, the sign of the second derivative is reversed at a certain distance serving as a boundary. Specific examples will be described later.

[0075] A semi-transparent mirror 5 is disposed between the display panel 2 and the refractive lens 4-1, and more specifically, in this example, between the QWP 7-2 and the refractive lens 4-1. The semi-transparent mirror 5 allows a portion (e.g., about 50%) of the incident light to pass through and reflect the remainder. The semi-transparent mirror 5 can be a semi-transparent mirror film disposed on the surface of the refractive lens 4-1 on the display panel 2 side (negative Z-axis side).

[0076] A diffractive lens 8-1 is positioned between the refractive lens 4-1 and the pupil position P; more specifically, in this example, it is positioned between the QWP 7-1b and the pupil position P. Circularly polarized light from the QWP 7-1b becomes approximately parallel light at the pupil position P after passing through the diffractive lens 8-1. In one embodiment, the diffractive lens 8-1 can be a polarizing diffractive lens. Therefore, it is easy to handle oblique incidence and wavelength variations. The following explanation assumes that the diffractive lens 8-1 is a polarizing diffractive lens.

[0077] Reference Figure 2 Further explanation of optical system 3.

[0078] Figure 2This is a diagram illustrating a schematic configuration example of optical system 3. Note that although in Figure 2 The elements are drawn as arranged with intervals, but in practice, the elements can be arranged at intervals shorter than those shown, or they can be arranged adjacent to or overlapping each other.

[0079] exist Figure 2 In the optical system 3, the direction of light is schematically indicated by white arrows at several locations. The light beam can include various types of polarized light (polarization components). Examples of polarized light include linearly polarized light and circularly polarized light. The polarization direction is schematically indicated by black arrows. In linearly polarized light, light polarized along the X-axis is called X-polarized light. Light polarized along the Y-axis is called Y-polarized light. Circularly polarized light is either right-handed or left-handed circularly polarized light, and is indicated by the terms RCP or LCP.

[0080] Polarizer 6-2 allows only light of a specific polarization to pass through and reflects other polarized light. Polarizer 6-2 is, for example, a polarizer, a wire grid polarizer, etc. In this example, polarizer 6-2 allows Y-polarized light to pass through.

[0081] By setting the polarizer 6-2, the polarized light incident on the QWP 7-2 after the polarizer 6-2 can be limited. For example, this is effective when the display panel 2, such as an OLED, emits light containing various types of polarized light. When the display panel 2, such as an LCD, emits light containing only specific polarized light, the polarizer 6-2 can be omitted.

[0082] QWP 7-2 converts linearly polarized light from polarizer 6-2 into circularly polarized light. In this example, QWP 7-2 converts Y-polarized light from polarizer 6-2 into right-hand circularly polarized light. A portion of the right-hand circularly polarized light passes through the semi-transparent mirror 5, then through the refracting lens 4-1, and is incident on QWP 7-1a.

[0083] QWP 7-1a converts right-handed circularly polarized light, which has passed through refractive lens 4-1, into Y-polarized light. In this example, polarizer 6-1 allows X-polarized light to pass through and reflects Y-polarized light. Therefore, the Y-polarized light from QWP 7-1a is reflected by polarizer 6-1 and re-enters QWP 7-1a. QWP 7-1a converts the Y-polarized light from polarizer 6-1 into right-handed circularly polarized light. The right-handed circularly polarized light passes through refractive lens 4-1, and a portion of it is reflected by semi-transparent mirror 5. The reflected light becomes left-handed circularly polarized light, passes through refractive lens 4-1, and enters QWP 7-1a. QWP 7-1a converts the left-handed circularly polarized light, which has passed through refractive lens 4-1, into X-polarized light. The X-polarized light passes through polarizer 6-1 and enters QWP 7-1b. In this way, by reversing the light path, the light passes through refractive lens 4-1 three times.

[0084] QWP 7-1b converts X-polarized light from polarizer 6-1 into right-hand circularly polarized light. The right-hand circularly polarized light is then incident on diffraction lens 8-1.

[0085] As described above, the diffraction lens 8-1 here is a polarizing diffraction lens, configured to reverse the diffraction order corresponding to the polarization direction of the incident circularly polarized light, and also functions as a lens. Furthermore, the polarization direction (rotation direction) of the circularly polarized light emitted from the diffraction lens 8-1 is opposite to the polarization direction of the circularly polarized light incident on the diffraction lens 8-1. In this example, since right-handed circularly polarized light from QWP 7-1b is incident on the diffraction lens 8-1, the circularly polarized light emitted from the diffraction lens 8-1 becomes left-handed circularly polarized light.

[0086] The diffraction lens 8-1 is also called a polarization-orientation plane lens, a Pancharatnam-Berry phase lens, a geometric phase lens, etc. Various known configurations can be employed. Briefly, some examples are given; for instance, the diffraction lens 8-1 can have a configuration in which a photoalignment film and a liquid crystal layer are sequentially disposed on a substrate (single-layer planar configuration). The photoalignment film is exposed by polarization interference, and the liquid crystal layer is aligned along the photoalignment film. A photoalignment film and a liquid crystal layer can then be disposed on the liquid crystal layer (double-layer planar configuration). Additionally, various known configurations such as a double-layer twisted configuration can be employed.

[0087] The thickness of the diffractive lens 8-1 can be less than that of the refractive lens 4. For example, it is easier to incorporate the lens into the optical system 3 compared to using a refractive lens similar to the refractive lens 4. This can help to make the optical system 3 thinner and smaller.

[0088] In this embodiment, the diffraction lens 8-1 is configured to have a diverging phase at its outermost periphery. See also... Figure 3 and Figure 4 Please provide an explanation.

[0089] Figure 3 This diagram illustrates a schematic configuration example of the diffraction lens 8-1. It schematically shows the diffraction lens 8-1 as viewed from the front (along the Z-axis). In this example, the diffraction lens 8-1 has a circular shape with its center located on the optical axis OA. The radius of the diffraction lens 8-1 is called the radius D1. The distance from the center of the diffraction lens 8-1 is called the distance r1. Unless otherwise stated, it is assumed that the diffraction lens 8-1 has a shape that is centrally symmetrical. In this case, the distance r1 can be the distance x from the center in the X-axis direction or the distance y from the center in the Y-axis direction.

[0090] The diffractive lens 8-1 includes a central portion 811 and an outer peripheral portion 812. The central portion 811 is the portion containing the center of the diffractive lens 8-1. The outer peripheral portion 812 is the portion containing the outermost periphery of the diffractive lens 8-1 (also called the edge portion containing the edge). When described using distance r, the central portion 811 corresponds to the range of relatively small distances r1 (including r1 = 0). The outer peripheral portion 812 corresponds to the range of relatively large distances r1 (including r1 = D1).

[0091] The diffractive lens 8-1 has a diverging phase at the outer peripheral portion 812. Specifically, the diffractive lens 8-1 is configured such that the phase of the light passing through the outer peripheral portion 812 lags behind the phase of the light passing through the central portion 811. For example, the diffractive lens 8-1 imparts a positive phase delay to the light passing through the outer peripheral portion 812, and imparts a smaller positive or negative phase delay to the light passing through the central portion 811 than the light passing through the outer peripheral portion 812.

[0092] The phase retardation of light passing through the central portion 811 of the diffraction lens 8-1 is called the phase retardation 811p. The phase retardation of light passing through the outer peripheral portion 812 of the diffraction lens 8-1 is called the phase retardation 812p.

[0093] Figure 4 This is a graph illustrating an example of phase retardation. The horizontal axis of the graph represents distance r1. The vertical axis of the graph represents phase retardation. Phase retardation is represented by a value normalized to the wavelength λ of the light. As a general trend, phase retardation increases positively with increasing distance r1. The phase retardation 812p of light passing through the outer peripheral portion 812 is positive. The phase retardation 811p of light passing through the central portion 811 is either positive or negative, less than the phase retardation 812p. When the phase retardation is positive, the incident light is diverged. On the other hand, when the phase retardation is negative, the incident light is converged.

[0094] As explained above Figure 1 and Figure 2 As shown, a diffractive lens 8-1 with a diverging phase at the outermost periphery is positioned between the refracting lens 4-1 and the pupil position P, and the right-handed polarized light from the diffractive lens 8-1 becomes approximately parallel light at the pupil position P.

[0095] Based on the above configuration, since the optical system 3 includes not only the refracting lens 4-1 but also the diffractive lens 8-1, the lens function can be correspondingly improved. With the improved lens function, the possibility of achieving a wide-angle field of view increases.

[0096] <Design Example>

[0097] Figures 5 to 11This is a diagram illustrating a design example. Assume that the size of one pixel in display device 1 is 6.3 μm.

[0098] Figure 5 An example of a modulation transfer function (MTF) of 80 lines / mm (MTF corresponding to one pixel) is shown. Based on the dimensions taken into account when the eye rotates, the resolution for each incident light event is shown, more specifically, the resolution in the tangential (T) and radial (R) directions for each angle. Here, the wavelength of light is assumed to be 554 nm. Specifically, as... Figure 6 As shown, let the eye rotation angle be θ and the interocular distance be ER. This illustrates the value of the position where the eye leaves (deviates from) the optical axis OA by the formula w = ER × tanθ. For example... Figure 5 As shown in the graph, a high resolution was achieved. For example, a center resolution of approximately 48 pixels per degree (PPD) was obtained.

[0099] Figure 7 An example of lateral chromatic aberration during eye rotation is shown. The vertical axis of the graph represents the angle (field angle) when viewing optical system 3. The horizontal axis represents the distance (difference) between the positions of two light beams of different wavelengths on display panel 2 (e.g., display surface 2a). The Short-Long curve represents the difference between the positions of light with a wavelength of 456nm and light with a wavelength of 658nm on display panel 2. The Short-Ref curve represents the difference between the positions of light with a wavelength of 456nm and light with a wavelength of 554nm on display panel 2. When the angle is small, the lateral chromatic aberration is very small and has a good value of less than one pixel. When the angle is large, the lateral chromatic aberration increases, but if the angle is a specific value, the lateral chromatic aberration can be addressed through signal processing, etc. A practical lateral chromatic aberration is thus achieved.

[0100] Figure 8 Examples of longitudinal aberration, astigmatism, and distortion are shown. Longitudinal aberration is only slightly higher than 0.2 at most and varies very little. Astigmatism is within ±0.1. Distortion tilts towards the negative side and changes monotonically (without an inflection point).

[0101] Figure 9 An example of the inflection point of surface 4a of the refractive lens 4-1 is shown. The horizontal axis of the graph represents the distance of surface 4a of the refractive lens 4-1 from the optical axis. The vertical axis of the graph represents the second derivative of surface 4a of the refractive lens 4-1, and more specifically, the second derivative of the sag on the side of surface 4a relative to the distance from the optical axis OA. The sign of the second derivative is reversed at a certain value of the distance from the optical axis OA (in this example, a value slightly less than 15 mm). For example, the shape of surface 4a of the refractive lens 4-1 with the inflection point is defined based on such a second derivative value. As mentioned above, surface 4a of the refractive lens 4-1 has an inflection point, thereby maintaining aberration balance.

[0102] Figure 10 and Figure 11 Examples of data for several optical surfaces are shown. Figure 10 Examples of data for optical surfaces s1 to s21 are shown. The specific locations of each optical surface are as follows: Figure 11 As shown. Note that optical surface s1 is the optical surface at the pupil position P (e.g., the pupil of user U).

[0103] like Figure 10 As shown in (A), in this example, the diagonal length of display panel 2 (panel diagonal) is 2.28 inches. The horizontal length of display panel 2 (e.g., in the X-axis direction) (panel size horizontal) is 24.2 mm. The horizontal viewing angle (horizontal FoV) is 100°. The rotation angle is 70°. The eye distance is 12 mm.

[0104] Figure 10 (B) shows the surface type, radius of curvature, thickness, refractive index, Abbe number, and reflecting surface of each of the optical surfaces s1 to s21. Additionally, some key elements of the optical elements described so far are also shown in relation to them. The surface type is any of spherical, diffractive, or aspherical. In the case of an aspherical surface, the radius of curvature is the paraxial radius of curvature. Thickness here represents the distance from one optical surface to the next. Positive thickness values ​​correspond to the length in the negative Z-axis direction, while negative thickness values ​​correspond to the length in the positive Z-axis direction. The refractive index is the refractive index at the d-line. The Abbe number is the Abbe number of the difference between the C-line and F-line with reference to the d-line. In the case of a reflecting surface, it is denoted as reflection.

[0105] Figure 10 Further data for the optical surface s3 is shown in (C). The optical surface s3 corresponds to the surface of the aforementioned diffractive lens 8-1 and imparts a phase delay to the light passing through it. When the phase delay is expressed in terms of φ, φ is expressed by the following formula (1). N is the diffraction order, λ0 is the normalized wavelength, and h is the height (distance) from the axis OA. Figure 10 (C) shows c in formula (1) n Numerical examples (n = 1 to 8).

[0106]

[0107] Figure 10 Further data for optical surfaces of aspherical type are shown in (D). Specifically, coefficients defining the aspherical sag of optical surfaces s7, s8, s9, and s20 are shown. The aspherical sag is expressed by the following formula (2). R is the radius of curvature, and h is the height from the optical axis OA. C' in formula (2) n Numerical examples of (n = 2 to 7) are in Figure 10It is shown in (D).

[0108]

[0109] Among the other optical surfaces of aspherical type, the aspherical sag of optical surfaces s10 and s14 is similar to that of optical surface s7. The aspherical sag of optical surfaces s9 and s15 is similar to that of optical surface s8.

[0110] Note that the total system focal length of the optical system 3 obtained through this design example is approximately 17.1 mm.

[0111] 2. Second Embodiment

[0112] Figure 12 This is a diagram illustrating a schematic configuration example of the display device 1 according to the second embodiment. Figure 12 As shown in (A), the display device 1 also includes a diffraction lens 8-2. The diffraction lens 8-2 is a second diffraction lens disposed separately from the diffraction lens 8-1. Similar to the diffraction lens 8-1, the diffraction lens 8-2 may have a thickness smaller than that of the refractive lens 4, and may be a polarizing diffraction lens. In the following text, it is assumed that both the diffraction lens 8-1 and the diffraction lens 8-2 are polarizing diffraction lenses. Note that... Figure 12 Several optical paths are schematically shown in (B).

[0113] Figure 13 This is a diagram illustrating a schematic configuration example of optical system 3. In this example, QWP 7-2 converts Y-polarized light from polarizer 6-2 into left-handed polarized light. The left-handed polarized light is incident on diffractive lens 8-2.

[0114] A diffraction lens 8-2 is positioned between the display panel 2 and the refractive lens 4-1; more specifically, in this example, it is positioned between the QWP 7-2 and the semi-transparent mirror 5. Since left-handed circularly polarized light from the QWP 7-2 is incident on the diffraction lens 8-2, the circularly polarized light exiting from the diffraction lens 8-2 becomes right-handed circularly polarized light. A portion of the right-handed circularly polarized light passes through the semi-transparent mirror 5. Subsequent operations are the same as described above. Figure 2 The operation is similar, so it will not be explained again here.

[0115] As described above, diffraction lens 8-1 is configured to have a diverging phase at its outermost periphery. On the other hand, diffraction lens 8-2 is configured to have a converging phase at its outermost periphery. See also... Figure 14 and Figure 15 Please provide an explanation.

[0116] Figure 14This diagram illustrates a schematic configuration example of the diffraction lens 8-2. It schematically shows the diffraction lens 8-2 as viewed from the front (along the Z-axis). In this example, the diffraction lens 8-2 has a circular shape with its center located on the optical axis OA. The radius of the diffraction lens 8-2 is called radius D2. The distance from the center of the diffraction lens 8-2 is called distance r2. Unless otherwise stated, it is assumed that the diffraction lens 8-2 has a shape that is centrally symmetric. In this case, distance r2 can be either distance x from the center in the X-axis direction or distance y from the center in the Y-axis direction.

[0117] The diffractive lens 8-2 includes a central portion 821 and an outer peripheral portion 822. The central portion 821 is the portion containing the center of the diffractive lens 8-2. The outer peripheral portion 822 is the portion containing the outermost periphery of the diffractive lens 8-2 (also called the edge portion containing the edge). When described using a distance r2, the central portion 821 corresponds to the range of relatively small distances r2 (including r2 = 0). The outer peripheral portion 822 corresponds to the range of relatively large distances r2 (including r2 = D2).

[0118] The diffractive lens 8-2 has a converging phase in its outer peripheral portion 822. Specifically, the diffractive lens 8-2 is configured such that the phase of the light passing through the outer peripheral portion 822 is ahead of the phase of the light passing through the central portion 821. For example, the diffractive lens 8-2 imparts a negative phase delay (positive phase lead) to the light passing through the outer peripheral portion 822 and imparts a negative or positive phase delay to the light passing through the central portion 821 with an absolute value smaller than that of the light passing through the outer peripheral portion 822.

[0119] The phase retardation of light passing through the central portion 821 of the diffraction lens 8-2 is called the phase retardation 821p. The phase retardation of light passing through the outer peripheral portion 822 of the diffraction lens 8-2 is called the phase retardation 822p.

[0120] Figure 15 A diagram illustrating an example of the phase delay amount. Figure 15 (A) shows the phase retardation given by the diffraction lens 8-1. The phase retardation increases positively with increasing distance r1. The phase retardation 812p of light passing through the outer peripheral portion 812 is positive. The phase retardation 811p of light passing through the central portion 811 is a positive value less than the phase retardation 812p or zero. Figure 15 (B) shows the phase retardation given by the diffraction lens 8-2. The phase retardation increases negatively with increasing distance r2. The phase retardation 822p of light passing through the outer peripheral portion 822 is negative. The phase retardation 821p of light passing through the central portion 8211 is a negative value or zero with an absolute value less than the phase retardation 822p.

[0121] As previously explained Figure 12 and Figure 13 As shown, a diffractive lens 8-1 with a diverging phase at its outermost periphery is positioned between the refracting lens 4-1 and the pupil position P, while a diffractive lens 8-2 with a converging phase at its outermost periphery is positioned between the display panel 2 and the refracting lens 4-1. The diffractive lens 8-2 directs the direction of light passing through the outer peripheral portion 822 closer to the direction of the optical axis OA (optical axis direction). As a result, excessive light diffusion and lens enlargement are prevented, increasing the possibility of achieving a wider viewing angle. Furthermore, the lateral chromatic aberration generated by one of the diffractive lenses 8-1 and 8-2 can be canceled out by the other, suppressing lateral chromatic aberration. Moreover, the balance between the two reduces field curvature and astigmatism, achieving good aberration correction and a wide viewing angle.

[0122] The refractive lens 4-2 will be further explained. The refractive lens 4-2 is disposed between the display panel 2 and the diffractive lens 8-2, and more specifically, in this example, between the refractive lens 4-2 and the polarizer 6-2, and imparts positive optical power to light passing through its outermost peripheral portion (also referred to as the outer peripheral portion). In other words, the refractive lens 4-2 is configured to bring the light from the display panel 2 closer to the direction of the optical axis OA (optical axis direction). As a result, aberration balance is maintained. Balance between field curvature and distortion is also maintained.

[0123] <Design Example>

[0124] Figures 16 to 21 This is a diagram illustrating a design example. Conditions not specifically described may be the same as those in the first embodiment described above. Figure 16 An example of an MTF is shown. It is evident that a high resolution has been achieved. For example, a center resolution of approximately 50 PPD has been obtained. Figure 17 An example of lateral chromatic aberration is shown when the eye rotates. Figure 18 Examples of longitudinal aberrations, astigmatism, and distortion are shown. It is evident that practical lateral chromatic aberration has been achieved. Figure 19 An example of the inflection point of surface 4a of the refractive lens 4-1 is shown. The inflection point is used to maintain aberration balance.

[0125] Figure 20 and Figure 21 Examples of data for several optical surfaces are shown. Figure 20 Examples of data for optical surfaces s1 to s22 are shown. The specific locations of each optical surface are as follows: Figure 21 As shown. Figure 20 As shown in (A), in this example, the diagonal length of display panel 2 (panel diagonal) is 1.3 inches. The horizontal length of display panel 2 (panel size horizontal) is 24.2 mm. The horizontal viewing angle (horizontal FoV) is 100°. The rotation angle is 70°. The eye distance is 12 mm. Figure 20Data for optical surfaces s1 to s22 are shown in (B). Figure 20 (C) shows further data for optical surfaces s3 and s18. Optical surfaces s3 and s18 correspond to the surfaces of the aforementioned diffractive lens 8-1 and diffractive lens 8-2, respectively, and each imparts a phase delay to the light passing through them. Optical surface s18 also corresponds to QWP 7-2 and polarizer 6-2. The amount of phase delay is expressed by the above formula (1), and c in formula (1) n Numerical examples of (n = 1 to 8) are in Figure 20 As shown in (C). Figure 20 Further data for optical surfaces whose surface type is aspherical is shown in (D). Specifically, coefficients defining the aspherical sag of optical surfaces s7, s8, s20, and s21 are shown. The aspherical sag is expressed by the above formula (2), where C' n Numerical examples of (n = 2 to 7) are in Figure 20 As shown in (D). Note that the total system focal length of the optical system 3 obtained through this design example is approximately 17.5 mm.

[0126] <Another Design Example>

[0127] Figures 22 to 28 This diagram illustrates another design example. A wider viewing angle than the design described above can be achieved while minimizing the increase in the size of display panel 2. Figure 22 An example of the amount of optical phase delay given by the diffraction lens 8 is shown. Figure 22 (A) shows the amount of phase delay given by the diffraction lens 8-1. Figure 22 (B) shows the phase retardation given by diffraction lens 8-2. The overall trend is the same as above. Figure 15 Similar to that in [the text], therefore its explanation is omitted.

[0128] Figure 23 An example of MTF is shown. It is evident that a high resolution is achieved. For example, if the size of a pixel in display device 1 is 6.3 μm, a center resolution of approximately 77 PPD can be obtained. Even if the size of a pixel is 11 μm, a center resolution of approximately 44 PPD can be obtained. Figure 24 An example of lateral chromatic aberration is shown when the eye rotates. Figure 25 Examples of longitudinal aberrations, astigmatism, and distortion are shown. It is evident that practical lateral chromatic aberration has been achieved. Figure 26 An example of the inflection point of surface 4a of the refractive lens 4-1 is shown. The inflection point is used to maintain aberration balance.

[0129] Figure 27 and Figure 28 Examples of data for several optical surfaces are shown. Figure 27Examples of data for optical surfaces s1 to s22 are shown. The specific locations of each optical surface are as follows: Figure 27 As shown. Figure 27 As shown in (A), in this example, the diagonal length (panel diagonal) of display panel 2 is 2.28 inches. The horizontal length (panel size horizontal) of display panel 2 is 42.4 mm. The horizontal viewing angle (horizontal FoV) is 120°. The rotation angle is 80°. The eye distance is 12 mm. Figure 27 (B) shows the data for optical surfaces s1 to s22. Figure 27 (C) shows more data for optical surfaces s3 and s18. Figure 27 (D) shows more data for the aspherical optical surfaces, specifically optical surfaces s7, s8, s20, and s21. Note that the total system focal length of the optical system 3 obtained through this design example is approximately 28.0 mm.

[0130] 3. Variations

[0131] In one variation, optical system 3 may include a cutoff filter to block unnecessary circularly polarized light. (See reference...) Figures 29 to 32 The following explanation is provided. Note that in the following explanation, without specifically distinguishing between diffraction lens 8-1 and diffraction lens 8-2, they are simply referred to as diffraction lens 8.

[0132] Figures 29 to 32 This is a diagram showing a variation. For example... Figure 29 and Figure 31 As shown, the optical system 3 also includes a cutoff filter 9. The cutoff filter 9 cuts off (e.g., removes or attenuates) one of the two types of circularly polarized light that may be contained in the light from the diffraction lens 8. The cutoff filter 9 includes a QWP 7-3 and a polarizer 6-3.

[0133] exist Figure 29 In the example shown, the cutoff filter 9 is positioned after the diffraction lens 8-1, and more specifically, in this example, between the diffraction lens 8-1 and the pupil position P (see [reference]). Figure 12 (etc.). QWP 7-3 and polarizer 6-3 are arranged sequentially along the positive Z-axis. QWP 7-3 converts left-handed circularly polarized light into X-polarized light and right-handed circularly polarized light into Y-polarized light. Polarizer 6-3 allows X-polarized light to pass through while blocking (e.g., reflecting) Y-polarized light.

[0134] Left-handed circularly polarized light from diffraction lens 8-1 is converted to X-polarized light by QWP 7-3, and becomes approximately parallel light after passing through polarizer 6-3. Here, as virtually shown by a dashed line, right-handed circularly polarized light, generated as stray light, may be slightly mixed in with the light from diffraction lens 8-1. The right-handed circularly polarized light is converted to Y-polarized light by QWP 7-3 and is removed by polarizer 6-3.

[0135] Figure 30 The above is shown Figure 29 Here are some data examples for several optical surfaces in the configuration. The approximate positions of each optical surface can be similar to those described above. Figure 21 That is how it is represented, so it will not be shown here again.

[0136] exist Figure 31 In the example shown, the cutoff filter 9 is positioned after the diffraction lens 8-2, and more specifically, in this example, between the diffraction lens 8-2 and the semi-transparent mirror 5. QWP 7-3 is a pair of QWPs, and is shown as QWP 7-3a and QWP 7-3b respectively. QWP 7-3a, polarizer 6-3, and QWP 7-3b are arranged sequentially along the positive Z-axis.

[0137] In this example, QWP 7-3a converts right-handed circularly polarized light into Y-polarized light and left-handed circularly polarized light into X-polarized light. Polarizer 6-3 allows Y-polarized light to pass through while blocking X-polarized light. QWP 7-3b converts Y-polarized light into right-handed circularly polarized light.

[0138] The right-hand circularly polarized light from diffraction lens 8-2 is converted to Y-polarized light by QWP 7-3a, passes through polarizer 6-3, is converted to right-hand circularly polarized light by QWP 7-3b, and then incident on the semi-transparent mirror 5. Here, as shown by the dashed line, the light from diffraction lens 8-2 may contain a slight amount of left-hand circularly polarized light generated as stray light. The left-hand circularly polarized light is converted to X-polarized light by QWP 7-3a and then removed by polarizer 6-3.

[0139] Figure 32 The above is shown Figure 31 Here are some data examples for several optical surfaces in the configuration. The approximate positions of each optical surface can be similar to those described above. Figure 21 That is how it is represented, so it will not be shown here again.

[0140] For example, as described above, it is possible to cut off unnecessary circularly polarized light from the right-handed and left-handed polarized light that may be contained in the light from the diffraction lens 8. By removing unnecessary circularly polarized light, for example, flare can be suppressed.

[0141] 4. Example of the effect

[0142] For example, the aforementioned technology is specified as follows. One of the disclosed technologies is optical system 3. (See reference...) Figures 1 to 4 , Figures 12 to 15 , Figure 29 , Figure 31 As described above, the optical system 3 is an optical system that images light from the display panel 2 onto the retina when combined with the eyeball, and includes a refractive lens 4-1 (first refractive lens) that focuses light from the display panel 2 and a diffractive lens 8-1 (first diffractive lens) disposed between the refractive lens 4-1 and the pupil position P (eyeball). The diffractive lens 8-1 is configured such that the phase of light passing through the peripheral portion 812 lags behind the phase of light passing through the central portion 811.

[0143] According to optical system 3, since optical system 3 includes not only refracting lens 4-1 but also diffractive lens 8-1, the lens function can be improved accordingly. As a result, a wide viewing angle can be achieved.

[0144] For reference Figure 1 , Figure 2 , Figure 12 , Figure 13 , Figure 29 , Figure 31 As described above, the optical system 3 can be configured to allow light from the display panel 2 to pass through the refractive lens 4-1 three times by reversing the light path. For example, a wide viewing angle can be achieved in such a three-way optical system 3.

[0145] For reference Figures 12 to 15 , Figure 29 , Figure 31 As described above, the optical system 3 may include a diffraction lens 8-2 (a second diffraction lens) disposed between the display panel 2 and the refractive lens 4-1. The diffraction lens 8-2 can be configured such that the phase of light passing through the outer peripheral portion 822 is ahead of the phase of light passing through the central portion 821. By providing such a diffraction lens 8-2, excessive light diffusion and lens enlargement can be prevented, increasing the possibility of achieving a wider viewing angle.

[0146] For reference Figure 3 , Figure 14 , Figure 15 As described above, diffraction lens 8-1 can provide a positive phase delay (phase delay amount 821p) for light passing through the outer peripheral portion 812, and diffraction lens 8-2 can provide a negative phase delay (phase delay amount 822p) for light passing through the outer peripheral portion 822. As a result, the lateral chromatic aberration produced by one of the diffraction lenses 8-1 and 8-2 can be canceled out by the other diffraction lens, thus suppressing lateral chromatic aberration. Furthermore, through the balance between the two, field curvature and astigmatism can be reduced. Good aberration correction results can be obtained, and a wider viewing angle can be achieved.

[0147] For reference Figure 1 , Figure 2 , Figure 12 , Figure 13 , Figure 29 , Figure 31 As described above, the optical system 3 may include a refractive lens 4-2 (a second refractive lens) disposed between the display panel 2 and the diffractive lens 8-2. The refractive lens 4-2 may be configured to bring the light from the display panel 2 close to the optical axis direction (direction of the optical axis OA) of the optical system 3. As a result, aberration balance can be maintained, and field curvature and distortion balance can also be maintained.

[0148] For reference Figure 1 , Figure 9 , Figure 19 , Figure 26 As described above, the refractive lens 4-1 can have an inflection point on surface 4a on the pupil position P side (eyeball side). As a result, aberration balance can be maintained.

[0149] For reference Figure 1 , Figure 2 , Figure 12 , Figure 13 , Figure 29 , Figure 31 As described above, the diffraction lens 8 (diffraction lens 8-1, diffraction lens 8-2) can be a polarizing diffraction lens. As a result, it is easy to handle oblique incidence and wavelength variation.

[0150] For reference Figure 29 , Figure 31 As described above, the optical system 3 may include a cutoff filter 9 that cuts off one of the two types of circularly polarized light (right-handed circularly polarized light and left-handed circularly polarized light) that may be contained in the light from the diffraction lenses 8 (diffraction lenses 8-1 and 8-2). For example, by removing unnecessary circularly polarized light, light spots can be suppressed.

[0151] For reference Figure 1 , Figure 2 , Figure 12 , Figure 13 As mentioned above, the thickness of the diffractive lens 8 (diffractive lens 8-1, diffractive lens 8-2) can be less than the thickness of the refractive lens 4. This helps to make the optical system 3 thinner and smaller.

[0152] Reference Figures 1 to 4 , Figures 12 to 15 , Figure 29 , Figure 31The display device 1 described above is also one of the disclosed technologies. The display device 1 includes: a display panel 2; and an optical system 3, which, when combined with the eyeball, images light from the display panel 2 onto the retina. For example, the display device 1 can be an HMD device. Similarly, in such a display device 1, as described above, a wide viewing angle can be achieved.

[0153] The effects described in this manual are for illustrative purposes only and are not limited to the disclosed content. Other effects are possible.

[0154] Note that this technology can also have the following configurations.

[0155] (1) An optical system in which light from a display panel images the retina when combined with an eye, the optical system comprising:

[0156] A first refractive lens focuses light from the display panel; and

[0157] A first diffractive lens is disposed between the first refractive lens and the eyeball, wherein...

[0158] The first diffractive lens is configured such that the phase of light passing through the outer peripheral portion of the first diffractive lens lags behind the phase of light passing through the central portion of the first diffractive lens.

[0159] (2) According to the optical system described in (1), wherein,

[0160] By reversing the light path, the light from the display panel passes through the first refractive lens three times.

[0161] (3) The optical system according to (1) or (2) includes:

[0162] The second diffractive lens is positioned between the display panel and the first refractive lens.

[0163] (4) The optical system according to (3), wherein,

[0164] The second diffractive lens is configured such that the phase of light passing through the outer peripheral portion of the second diffractive lens is ahead of the phase of light passing through the central portion of the second diffractive lens.

[0165] (5) The optical system according to (4), wherein,

[0166] The first diffractive lens imparts a positive phase delay to the light passing through its outer periphery, and

[0167] The second diffraction lens causes a negative phase delay to the light passing through the outer periphery of the second diffraction lens.

[0168] (6) The optical system according to any one of (3) to (5), comprising:

[0169] The second refractive lens is positioned between the display panel and the second diffractive lens.

[0170] (7) The optical system according to (6), wherein,

[0171] The second refracting lens is configured to bring light from the display panel close to the optical axis of the optical system.

[0172] (8) The optical system according to (6) or (7), wherein,

[0173] The first refractive lens has an inflection point on the surface on the side of the eyeball.

[0174] (9) The optical system according to any one of (1) to (8), wherein,

[0175] A diffractive lens is a polarization diffractive lens.

[0176] (10) The optical system according to (9) includes:

[0177] The cutoff filter removes one of the two types of circularly polarized light that may be present in the light from the diffractive lens.

[0178] (11) The optical system according to any one of (1) to (10), wherein,

[0179] A diffractive lens has a thickness that is less than that of a refracting lens.

[0180] (12) A display device, comprising:

[0181] Display panel; and

[0182] An optical system, when combined with the eye, images light from a display panel onto the retina, in which...

[0183] The optical system includes:

[0184] The first refractive lens focuses the light from the display panel; and

[0185] The first diffractive lens is positioned between the first refracting lens and the eyeball, and

[0186] The first diffractive lens is configured such that the phase of light passing through the outer peripheral portion of the first diffractive lens lags behind the phase of light passing through the central portion of the first diffractive lens.

[0187] (13) The display device according to (12), wherein,

[0188] Display devices include head-mounted display devices.

Claims

1. An optical system, when combined with an eye, images light from a display panel onto the retina, said optical system comprising: The first refractive lens focuses the light from the display panel; as well as A first diffractive lens is disposed between the first refracting lens and the eyeball, wherein The first diffractive lens is configured such that the phase of light passing through the outer peripheral portion of the first diffractive lens lags behind the phase of light passing through the central portion of the first diffractive lens.

2. The optical system according to claim 1, wherein By reversing the light path, the light from the display panel passes through the first refractive lens three times.

3. The optical system according to claim 1, comprising: A second diffractive lens is disposed between the display panel and the first refractive lens.

4. The optical system according to claim 3, wherein The second diffractive lens is configured such that the phase of light passing through the outer peripheral portion of the second diffractive lens is ahead of the phase of light passing through the central portion of the second diffractive lens.

5. The optical system according to claim 4, wherein The first diffractive lens imparts a positive phase delay to the light passing through its outer peripheral portion, and The second diffractive lens imparts a negative phase delay to the light passing through the outer peripheral portion of the second diffractive lens.

6. The optical system according to claim 3, comprising: The second refractive lens is disposed between the display panel and the second diffractive lens.

7. The optical system according to claim 6, wherein The second refractive lens is configured to bring light from the display panel close to the optical axis of the optical system.

8. The optical system according to claim 6, wherein The first refractive lens has an inflection point on the surface on the eyeball side.

9. The optical system according to claim 1, wherein The diffraction lens is a polarization diffraction lens.

10. The optical system of claim 9, comprising: The cutoff filter removes one of the two types of circularly polarized light that may be present in the light from the diffractive lens.

11. The optical system according to claim 1, wherein The diffractive lens has a thickness smaller than that of the refractive lens.

12. A display device, comprising: Display panel; as well as An optical system, when combined with the eye, images light from the display panel onto the retina, wherein The optical system includes: The first refractive lens focuses the light from the display panel; as well as A first diffractive lens is disposed between the first refracting lens and the eyeball, and The first diffractive lens is configured such that the phase of light passing through the outer peripheral portion of the first diffractive lens lags behind the phase of light passing through the central portion of the first diffractive lens.

13. The display device according to claim 12, wherein The display device includes a head-mounted display device.

Images