Optical system and image display device

Abstract

A projection optical system (11) comprises: a scanning optical system (2) for scanning light incident from a light source (12); and a condensing optical system (3) for condensing the light scanned by the scanning optical system. The scanning optical system includes: a first scanning unit (21) that scans the light incident from the light source in a first direction; a second scanning unit (22) that scans the light scanned by the first scanning unit in a second direction intersecting the first direction; and an aberration correction unit (20) that adds, to light passing through the scanning optical system, a correction aberration corresponding to an aberration generated in the condensing optical system.

Description

Optical system and image display device

[0001] The present disclosure relates to an optical system and an image display device.

[0002] Patent Document 1 discloses an image display device that directs image light to a viewer's pupil. This image display device includes an image light forming unit that emits image light, a diffractive optical system including a first diffractive unit and a second diffractive unit, and a relay optical system that is arranged closer to the image light forming unit than the second diffractive unit and relays the image light to the second diffractive unit so as to correct chromatic aberration generated in the second diffractive unit. The image light forming unit includes a scanning mirror that two-dimensionally scans laser light from a light source, and a correction lens that corrects astigmatism generated in the second diffractive unit. The correction lens is arranged between the light source and the scanning mirror.

[0003] Patent Literature 2 discloses an image projection device that projects an image onto a user's retina. This image projection device includes a light source that emits laser light, a control unit that generates image light based on input image data and controls the emission of the image light from the light source, a scanning unit that scans the image light emitted from the light source to generate scanned light, and first and second optical converging units. The first optical converging unit is disposed in front of the user's eye and converges the scanned light at a first convergence point near the pupil of the user's eye, and then irradiates the scanned light onto the retina to project an image onto the retina. The second optical converging unit converges the scanned light scanned by the scanning unit to a second convergence point in front of the first optical converging unit, and then irradiates the scanned light onto the first optical converging unit.

[0004] International Publication No. 2019 / 235320 Patent No. 6659917

[0005] The present disclosure provides an optical system and an image display device that can easily suppress aberrations in an image obtained by scanning light.

[0006] An optical system in one aspect of the present disclosure includes a first scanning unit that scans light incident from a light source in a first direction, a second scanning unit that scans the light scanned by the first scanning unit in a second direction that intersects the first direction, a focusing optical system that focuses the light scanned by the second scanning unit, and an aberration correction unit that is arranged between the focusing optical system and the first scanning unit and emits light incident from the light source via the first scanning unit toward the focusing optical system so as to correct field curvature that occurs in the focusing optical system.

[0007] According to another aspect of the present disclosure, there is provided an optical system including a scanning optical system that scans light incident from a light source and a focusing optical system that focuses the light scanned by the scanning optical system, the scanning optical system including a first scanning unit that scans the light incident from the light source in a first direction, a second scanning unit that scans the light scanned by the first scanning unit in a second direction intersecting the first direction, and an aberration correction unit that adds a correction aberration corresponding to an aberration generated in the focusing optical system to the light passing through the scanning optical system.

[0008] In the present disclosure, an image display device includes the above optical system and a light source that supplies light showing an image to the optical system.

[0009] An optical system according to another aspect of the present disclosure scans light incident from a light source and outputs the light to a subsequent optical system, the optical system including: a first scanning unit that scans the light incident from the light source in a first direction; a second scanning unit that scans the light scanned by the first scanning unit in a second direction intersecting the first direction; and an aberration correction unit that adds a correction aberration corresponding to an aberration generated in the subsequent optical system to the light passing through the optical system.

[0010] According to the optical system and image display device of the present disclosure, it is possible to easily suppress aberration in an image obtained by scanning light.

[0011] FIG. 1 shows the configuration of a head-mounted display according to a first embodiment of the present disclosure. FIG. 2 shows a perspective view illustrating the configuration of a projection optical system in the first embodiment. FIG. 3 shows a perspective view illustrating a scanning optical system in the projection optical system of the first embodiment. FIG. 4 shows a side view illustrating a relay optical system in the scanning optical system of the first embodiment. FIG. 5 shows a diagram for explaining correction of aberrations in the projection optical system of the first embodiment. FIG. 6 shows a perspective view illustrating the configuration of a projection optical system in the second embodiment. FIG. 7 shows a side view illustrating a relay optical system in the scanning optical system of the second embodiment. FIG. 8 shows a perspective view illustrating a condensing point in the scanning optical system of the second embodiment. FIG. 9 shows a side view illustrating a condensing point in the scanning optical system of the second embodiment. FIG. 10 shows a diagram for explaining correction of aberrations in the projection optical system of the second embodiment.

[0012] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0013] The inventor(s) provide the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and do not intend for them to limit the subject matter described in the claims.

[0014] First Embodiment Hereinafter, a first embodiment of a projection optical system and a scanning optical system, which are examples of optical systems according to the present disclosure, and a head-mounted display using these will be described.

[0015] 1. Head Mounted Display A head mounted display (HMD) according to the first embodiment will be described with reference to FIG.

[0016] FIG. 1 is a diagram illustrating the configuration of an HMD 1 according to a first embodiment of the present disclosure. The HMD 1 is an example of an image display device that is worn on the head of a user 5 and allows the user 5 to view a projected image 15. The HMD 1 of this embodiment is applicable to various applications such as augmented reality (AR) and virtual reality (VR). Hereinafter, the horizontal direction of the projected image 15 viewed by the user 5 of the HMD 1 is referred to as the H direction, the vertical direction is referred to as the V direction, and the ray direction of the scanning light L10 corresponding to the center position of the projected image 15 is referred to as the Z direction. Furthermore, the exit side of the scanning light L10 may be referred to as the +Z side, and the incident side may be referred to as the -Z side.

[0017] 1, the HMD 1 of this embodiment includes a projection optical system 11, a light source 12, a control circuit 13, and a wearing member 10 that can be attached and detached to the head of a user 5. The HMD 1 of this embodiment, based on Maxwell's principle of vision, converges scanning light L10 that forms a projection image 15 at a position Po (hereinafter referred to as "pupil position Po") that is assumed to be near the center of the pupil of a user 5 wearing the HMD 1, and then renders the projection image 15 on the retina of the user 5. Such an HMD 1 is focus-free for the eyes of the user 5 and can be used for low vision applications, for example.

[0018] The HMD 1 of this embodiment is configured as glasses, for example, as shown in Fig. 1. For example, the wearing member 10 of the HMD 1 has a shape similar to that of a glasses frame and constitutes a housing that houses the above-mentioned components 11 to 13. In this type of HMD 1, it is useful to configure the projection optical system 11 in a compact manner by bending the optical path of the projection optical system 11 from the viewpoint of incorporating it into the limited space in the wearing member 10. However, an optical configuration with such a bent optical path may generate aberrations, such as astigmatism or curvature of field, in the direction of bending.

[0019] Therefore, the HMD 1 of this embodiment employs a projection optical system 11 that facilitates correction of aberrations in such a device configuration (details will be described later). The projection optical system 11 projects image light L1 from a light source 12 as scanning light L10 onto the retina of a user 5 of the HMD 1.

[0020] The light source 12 is, for example, a laser light source. The light source 12 includes, for example, laser light sources for each of the three colors RGB. The light source 12 may also be a monochromatic light source. The light source 12 generates image light L1 that represents the projection image 15 for each pixel in a time-division manner under the control of, for example, the control circuit 13, and supplies the image light L1 to the projection optical system 11. The light source 12 is disposed, for example, at a position for making the image light L1 incident on the projection optical system 11. Alternatively, an optical fiber or the like for supplying the image light L1 may be provided between the light source 12 and the projection optical system 11.

[0021] The control circuit 13 includes various circuits that control the overall operation of the HMD 1 based on, for example, an externally input video signal. For example, the control circuit 13 includes a light source drive circuit that controls the light emission of the light source 12 to generate image light L1 of the projection image 15 indicated by the video signal, and a horizontal scanning circuit and a vertical scanning circuit that synchronously control horizontal scanning and vertical scanning in the projection optical system 11, respectively.

[0022] 2. Projection Optical System The projection optical system 11 in this embodiment will be described in detail below. In this embodiment, an example of the configuration of the projection optical system 11 that corrects astigmatism in the projected image 15 of the HMD 1 will be described.

[0023] 2 illustrates the configuration of the projection optical system 11 in embodiment 1. As shown in FIG. 2, the projection optical system 11 of this embodiment includes a scanning optical system 2 and a condensing optical system 3. The scanning optical system 2 is an optical system that two-dimensionally scans image light L1 from a light source 12 to generate scanning light L10. The condensing optical system 3 is an optical system that condenses the scanning light L10 incident from the scanning optical system 2 at a pupil position Po of a user 5 wearing, for example, the HMD 1 (FIG. 1).

[0024] 2, the scanning optical system 2 of this embodiment includes a horizontal scanning unit 21, a relay optical system 20, and a vertical scanning unit 22, which are arranged in this order from the incident side of the image light L1 to the exit side of the scanning light L10. Each of the scanning units 21, 22 is configured with a MEMS (Micro Electro Mechanical Systems) mirror having a reflective surface and a rotation axis that can rotate around one axis. The projection optical system 11 of this embodiment uses two uniaxial scanning units 21, 22 in the scanning optical system 2, which makes it easy to ensure a wide scanning range for each of the scanning units, and therefore a wide viewing angle for the projected image 15 (FIG. 1).

[0025] The horizontal scanning unit 21 is disposed, for example, at a position where the image light L1 supplied from the light source 12 to the scanning optical system 2 is incident on the projection optical system 11. The horizontal scanning unit 21 is disposed, for example, such that the rotation direction of the rotation axis corresponds to the horizontal direction (H direction) of the projection image 15.

[0026] The horizontal scanning unit 21 rotates about the rotation axis to horizontally scan the incident image light L1 and generate primary scanning light L11 that represents the one-dimensional scanning result. The horizontal scanning unit 21 is an example of a first scanning unit in this embodiment. The scanning range in the rotation direction of the horizontal scanning unit 21 corresponds to the horizontal viewing angle of the projected image 15.

[0027] The relay optical system 20 is an optical system provided between the horizontal scanning unit 21 and the vertical scanning unit 22 so as to guide the primary scanning light L11 having various light ray directions across the scanning range of the horizontal scanning unit 21 from the horizontal scanning unit 21 to the vertical scanning unit 22. The relay optical system 20 may include various optical elements such as a mirror element, a prism element, or a lens element.

[0028] The relay optical system 20 of this embodiment is configured to have a correction aberration (details will be described later) for canceling the aberration caused by the focusing optical system 3. The relay optical system 20 is an example of an aberration correction unit of this embodiment.

[0029] The vertical scanning unit 22 is disposed, for example, near a position where the primary scanning light L11 guided by the relay optical system 20 is focused in various light ray directions across the scanning range of the horizontal scanning unit 21. The vertical scanning unit 22 is disposed, for example, such that the rotation direction of the rotation axis corresponds to the vertical direction (V direction) of the projection image 15.

[0030] The vertical scanning unit 22 further scans the incident primary scanning light L11 in the vertical direction by rotating the rotation axis, thereby generating scanning light L10 that indicates the two-dimensional scanning result. The vertical scanning unit 22 is an example of a second scanning unit in this embodiment. The scanning range in the rotation direction of the vertical scanning unit 22 corresponds to the vertical viewing angle of the projected image 15.

[0031] In the projection optical system 11 of this embodiment, the focusing optical system 3 includes a lens element 31, a prism element 32, and a holographic optical element (HOE) 33, arranged in order from the incident side to the exit side of the scanning light L10 from the scanning optical system 2, as shown in FIG. 2, for example.

[0032] In the focusing optical system 3 of this embodiment, the lens element 31 is, for example, a spherical lens and has, for example, positive power (focusing power). The lens element 31 collimates the scanning light L10 of various light beam directions across each scanning range of the scanning optical system 2 in the focusing optical system 3. The power can be defined by the reciprocal of the focal length of the corresponding optical element or optical system.

[0033] The prism element 32 is, for example, a wedge prism having a predetermined angle and, for example, no power. The prism element 32 adjusts the traveling direction of the scanning light L10 from the lens element 31 so as to bend the optical path of the scanning light L10 according to the predetermined angle, for example, in the horizontal direction of the light-collecting optical system 3, and guides the scanning light L10 to the HOE 33.

[0034] The HOE 33 is an optical element in which, for example, interference fringes are formed on a light-transmitting material by hologram processing. The HOE 33 diffracts light of a predetermined wavelength in the interference fringes and transmits other light. The predetermined wavelength is set to the wavelength of the light emitted by the light source 12 (i.e., the image light L1). For example, in the case of a three-color light source, an HOE 33 having interference fringes for each color can be used. For example, the HOE 33 can be configured in the form of a sheet that can be attached to the eyepiece portion facing the eyes of the user 5 in the eyeglass-type HMD 1 (FIG. 1).

[0035] The focusing optical system 3 of this embodiment diffracts the scanning light L10 from the prism element 32 using the HOE 33, and focuses the scanning light L10 across the horizontal and vertical scanning ranges of the scanning optical system 2 at the pupil position Po. The HOE 33 is disposed so as to bend the optical path of the scanning light L10, for example, in the horizontal direction of the focusing optical system 3. In the focusing optical system 3, various diffractive optical elements may be used instead of or in addition to the HOE 33.

[0036] 2.1 Relay Optical System The relay optical system 20 in the projection optical system 11 of this embodiment will be described with reference to FIGS.

[0037] FIG. 3 illustrates a perspective view of the scanning optical system 2 in the projection optical system 11 of this embodiment. In the scanning optical system 2 of this embodiment, the relay optical system 20 includes, for example, four mirror elements 20a to 20d, as shown in FIG. 3. For example, the first to fourth mirror elements 20a to 20d are arranged in order from the incident side to the output side along the optical path of the primary scanning light L11. Hereinafter, the direction along the scanning by the horizontal scanning unit 21 is referred to as the H1 direction, and two directions perpendicular to the H1 direction are referred to as the V1 direction and the Z1 direction. The V1 direction corresponds to the scanning direction by the vertical scanning unit 22, and the Z1 direction is perpendicular to the V1 direction.

[0038] The relay optical system 20 of this embodiment employs, for example, a cylindrical reflective surface in each of the mirror elements 20a to 20d that has power in the H1 direction but not in the V1 direction. The H1 direction corresponds to the horizontal direction of a reference ray, such as the central ray of the image light L1. Each of the mirror elements 20a to 20d is arranged, for example, with its longitudinal direction facing the H1 direction. The V1 direction is the width direction of each of the mirror elements 20a to 20d. The Z1 direction is the thickness direction of each of the mirror elements 20a to 20d.

[0039] The first mirror element 20a is disposed, for example, on the +Z1 side of the relay optical system 20, at a position where the primary scanning light L11 from the horizontal scanning unit 21 is incident. The first mirror element 20a has, for example, a reflective surface that is concave in the H1 direction, and is disposed with the reflective surface facing the −Z side.

[0040] The second mirror element 20b is disposed at an incident position of the primary scanning light L11 reflected by the first mirror element 20a, for example, on the −Z1 side of the relay optical system 20. The second mirror element 20b has a reflecting surface that is convex in the H1 direction, for example, and is disposed with the reflecting surface facing the +Z side.

[0041] The third mirror element 20c is disposed adjacent to the first mirror element 20a in the V direction, for example, at the incident position of the primary scanning light L11 reflected by the second mirror element 20b. The third mirror element 20c has, for example, a convex reflective surface similar to that of the second mirror element 20b, and is disposed facing the −Z side, which is the opposite direction to that of the second mirror element 20b.

[0042] The fourth mirror element 20d is disposed adjacent to the second mirror element 20b in the V direction, for example, at the incident position of the primary scanning light L11 reflected by the third mirror element 20c. The fourth mirror element 20d has a concave reflective surface similar to that of the first mirror element 20a, for example, and is disposed facing the +Z side, which is opposite to the first mirror element 20a.

[0043] The relay optical system 20 of this embodiment has a positive power in the H1 direction as a result of combining the powers of the reflecting surfaces of the first to fourth mirror elements 20 a to 20 d, for example. Figure 4 shows a side view of the relay optical system 20 as seen from the H1 direction.

[0044] 4, the relay optical system 20 has a positional relationship in which the first and fourth mirror elements 20a and 20d are point-symmetrical to each other and the second and third mirror elements 20b and 20c are point-symmetrical to each other with respect to a center point Pi between the horizontal scanning unit 21 and the vertical scanning unit 22. The relay optical system 20 can, for example, collect the primary scanning light L11 that passes through each of these mirror elements 20a to 20d and covers the scanning range of the horizontal scanning unit 21 from the horizontal scanning unit 21 to the vertical scanning unit 22.

[0045] 4, the relay optical system 20 includes a support base 23a on which the first and third mirror elements 20a and 20c are arranged, and a support base 23b on which the second and fourth mirror elements 20b and 20d are arranged. In the relay optical system 20 of this embodiment, the distance Di between these two support bases 23a and 23b is set from the viewpoint of providing the primary scanning light L11 passing therethrough with corrective aberration.

[0046] For example, during manufacturing of the projection optical system 11, the distance Di between the two support bases 23 a, 23 b can be changed while maintaining the position of the center point Pi of the relay optical system 20. This simultaneously changes the distance between the first and second mirror elements 20 a, 20 b, the distance between the second and third mirror elements 20 b, 20 c, and the distance between the third and fourth mirror elements 20 c, 20 d. This allows the power or composite focal length of the relay optical system 20 of this embodiment to be easily adjusted in the H1 direction.

[0047] In this way, the relay optical system 20 of this embodiment can have, as a corrective aberration, astigmatism that shifts the focal point in the horizontal direction at which the rays of the scanning light L10 after reflection by the vertical scanning unit 22 are focused from the focal point in the vertical direction. In the relay optical system 20 of this embodiment, the distance Di for such a corrective aberration can be set, for example, by measuring the astigmatism of the focusing optical system 3 in advance and setting it so as to cancel out the astigmatism of the focusing optical system 3.

[0048] In the projection optical system 11 of this embodiment, the relay optical system 20 is not limited to the above-described configuration example. For example, the relay optical system 20 of this embodiment is not limited to four mirror elements 20a to 20d, but may include three or fewer, or five or more, mirror elements 20a to 20d. The relay optical system 20 may also include lens elements or prism elements. The relay optical system 20 may also have power in the V1 direction.

[0049] 2.2. Aberration Correction The correction of aberrations in the projection optical system 11 of this embodiment will be described with reference to FIG.

[0050] 5A is a graph showing the MTF (Modulation Transfer Function) through focus of the focusing optical system 3 having astigmatism. FIG. 5B is a graph showing the MTF through focus of the projection optical system 11 in this embodiment. In the graphs of FIGS. 5A and 5B, the vertical axis represents the MTF as a value between 0 and 1, and the horizontal axis represents the diopter in diopters. The diopter corresponds to the defocus position.

[0051] 5A and 5B, various MTF throughputs were measured by numerical simulation to compare aberrations before and after correction in the projection optical system 11 of this embodiment. In this case, a stripe pattern with a predetermined period in the H direction (referred to as an "H pattern") and a stripe pattern with a predetermined period in the V direction (referred to as a "V pattern") were used for the projection image 15 used for MTF measurement. The predetermined period of each pattern was 3 cycles / deg., i.e., three periods per degree of the angle of view of the projection image 15.

[0052] In this simulation, the MTFs of the H pattern and V pattern were measured at various diopters near the center of the projected image 15, at both ends in the H direction (i.e., near the +H end of the ±H ends), near the −H end, and at both ends in the V direction (i.e., near the +V end of the ±V ends). As a result, the MTF curves shown in Figures 5A and 5B were obtained. The optical design software CODE V was used for this numerical simulation. The wavelength at which the light source 12 emitted the projected image 15 for each pattern was 587.6 nm.

[0053] 5A shows the MTF through-focus results when, instead of the scanning optical system 2 of this embodiment, scanning light obtained by two-dimensionally scanning aberration-free image light L1 is incident on the focusing optical system 3, in order to confirm the aberration of the focusing optical system 3. In the example of FIG. 5A, the peak positions of the MTF curves of the H pattern and the V pattern are different from each other. This shows that astigmatism occurs in the focusing optical system 3 between the H direction and the V direction.

[0054] Therefore, the projection optical system 11 of this embodiment uses the scanning optical system 2 in which a correction aberration is set in the relay optical system 20 to offset the astigmatism of the focusing optical system 3. Specifically, the relay optical system 20 is set so that the distances d1 and d2 from the vertical scanning unit 22 to the focusing point of the scanning light L10 that has passed through the vertical scanning unit 22 in the H and V directions, respectively, satisfy the following equation: 1 / d1=-0.0024 mm －１ 1 / d2=0.0000mm －１

[0055] In the above equation, the positive and negative values ​​of the distances d1 and d2 are determined such that the traveling direction of the scanning light L10 is positive. That is, a negative value of the distance d1 indicates the state in which the primary scanning light L11 is condensed before reaching the vertical scanning unit 22. The setting as in the above equation can be realized, for example, by adjusting the interval Di in the relay optical system 20 configured as described above to provide an appropriate amount of positive power in the H1 direction and maintaining zero power in the V1 direction.

[0056] FIG. 5B shows the results of MTF through-focus measurements, which indicate the astigmatism of the projection optical system 11 of this embodiment. As shown in FIG. 5B, the peak positions of the MTF curves for the H pattern and the V pattern do not deviate from each other as in the example of FIG. 5A, but overlap at approximately 0 diopters. In other words, the astigmatism of the example of FIG. 5A is eliminated. Thus, it was confirmed that the projection optical system 11 of this embodiment can correct the astigmatism of the focusing optical system 3 by using the relay optical system 20, which has a corrective aberration in the scanning optical system 2.

[0057] 3. Summary As described above, the projection optical system 11, which is an example of an optical system in this embodiment, includes the scanning optical system 2 that scans light incident from the light source 12 and the focusing optical system 3 that focuses the light scanned by the scanning optical system 2. The scanning optical system 2 includes the horizontal scanning unit 21, which is an example of a first scanning unit, the vertical scanning unit 22, which is an example of a second scanning unit, and the relay optical system 20, which is an example of an aberration correction unit. The horizontal scanning unit 21 scans the light incident from the light source 12 in the horizontal direction, which is an example of a first direction. The vertical scanning unit 22 scans the light scanned by the horizontal scanning unit 21 in the vertical direction, which is an example of a second direction intersecting the first direction. The relay optical system 20, which serves as an aberration correction unit, adds a correction aberration corresponding to the aberration generated in the focusing optical system 3 to the light passing through the scanning optical system 2.

[0058] According to the above-described projection optical system 11, aberrations occurring in the focusing optical system 3 can be corrected by the aberration correction unit in the scanning optical system 2, making it easier to suppress aberrations in an image obtained by scanning and then focusing light. From the viewpoint of suppressing aberrations of light focused by the focusing optical system 3, the corrected aberrations can be set so as to cancel out at least a portion of the aberrations of light focused by the focusing optical system 3.

[0059] In the projection optical system 11 of this embodiment, the aberration correction unit is configured with a relay optical system 20 that is disposed between the horizontal scanning unit 21 and the vertical scanning unit 22 and guides the light scanned by the horizontal scanning unit 21 to the vertical scanning unit 22. As a result, the projection optical system 11 of this embodiment can correct aberrations in the focusing optical system 3 by utilizing the relay optical system 20 used between the two scanning units 21, 22, and can suppress an increase in the number of parts required for aberration correction. From this perspective, the projection optical system 11 of this embodiment can facilitate aberration correction.

[0060] In the projection optical system 11 of this embodiment, the correction aberration includes astigmatism in the direction opposite to the astigmatism generated in the focusing optical system 3, for example, in terms of positive and negative astigmatism. As a result, the projection optical system 11 of this embodiment can correct the astigmatism generated in the focusing optical system 3 by including astigmatism in the direction that corrects the astigmatism generated in the focusing optical system 3 in the correction aberration.

[0061] In the projection optical system 11 of this embodiment, the relay optical system 20 serving as an aberration correction unit includes mirror elements 20a to 20d, which are an example of optical elements that have different powers in the horizontal and vertical directions in accordance with the opposite astigmatism in the corrected aberration. With this aberration correction unit, the distance between the vertical scanning unit 22 and the focal point of the light beam emitted from the scanning optical system 2 can be made different in the horizontal and vertical directions. In this way, the projection optical system 11 of this embodiment can correct the astigmatism of the focusing optical system 3. The focal point in the horizontal or vertical direction may be a position where the light beam substantially converges in the corresponding direction, or may be a position where the spot diameter of the light beam is smallest, i.e., a focal point. The aberration correction unit of this embodiment may make the powers in the two directions different by eliminating a focal point in one of the two directions.

[0062] In the projection optical system 11 of this embodiment, the focusing optical system 3 includes a prism element 32 and an HOE 33 as examples of optical elements that bend the optical path of light incident from the scanning optical system 2. The optical path of the focusing optical system 3 is bent, for example, in the horizontal direction. The projection optical system 11 of this embodiment can correct aberrations that occur in the focusing optical system 3 due to such bending in the scanning optical system 2, making it easier to correct aberrations and thereby improving the design freedom of the HMD 1.

[0063] In this embodiment, an HMD 1, which is an example of an image display device, includes a projection optical system 11 and a light source 12. The light source 12 supplies image light L1, which represents a projection image 15 as an example of light representing an image, to the projection optical system 11. The configuration of the projection optical system 11 in the HMD 1 of this embodiment makes it easier to suppress aberrations in an image such as the projection image 15 obtained by scanning light.

[0064] In this embodiment, the scanning optical system 2, which is an example of an optical system, includes a horizontal scanning unit 21 that scans light incident from the light source 12 in a first direction, a vertical scanning unit 22 that scans the light scanned by the horizontal scanning unit 21 in a second direction intersecting the first direction, and an aberration correction unit that adds a predetermined correction aberration to light passing through the scanning optical system 2. Such a scanning optical system 2 can also easily suppress aberrations in an image such as the projected image 15 obtained by scanning light. In the scanning optical system 2, the correction aberration may be set to cancel out aberrations caused by a subsequent optical system, such as the condensing optical system 3, onto which the light scanned by the scanning optical system 2 is incident. The subsequent optical system of the scanning optical system 2 is not limited to the condensing optical system 3, and may be any optical system that generates aberrations.

[0065] Second Embodiment Hereinafter, a second embodiment of the present disclosure will be described with reference to Figures 6 to 9. In the first embodiment, an HMD 1 that corrects astigmatism of the focusing optical system 3 in the projection optical system 11 has been described. In the second embodiment, an HMD 1 that corrects field curvature will be described.

[0066] Hereinafter, the projection optical system 11A and the HMD 1 according to this embodiment will be described, with the description of the same configuration and operation as the projection optical system 11 and the HMD 1 according to the first embodiment being omitted as appropriate.

[0067] 6 illustrates an example of the configuration of a projection optical system 11A in embodiment 2. The HMD 1 of this embodiment has a configuration similar to that of embodiment 1 (FIG. 1), for example, but includes a projection optical system 11A as illustrated in FIG. 6 instead of the projection optical system 11 in FIG. 2.

[0068] The projection optical system 11 (FIG. 2) of the first embodiment uses an HOE 33 in the focusing optical system 3. The projection optical system 11A of the present embodiment has a configuration similar to that of the projection optical system 11 of the first embodiment, but includes a focusing optical system 3A using a mirror element instead of the focusing optical system 3, as shown in FIG.

[0069] 6, the focusing optical system 3A of this embodiment includes two concave mirrors 34 and 36 and a doublet lens 35 disposed therebetween. Each of the concave mirrors 34 and 36 has positive power in both the horizontal and vertical directions, for example.

[0070] In the focusing optical system 3A of this embodiment, the first concave mirror 34 reflects the scanning light L10 incident from the vertical scanning unit 22 of the scanning optical system 2A and outputs the scanning light L10 to the second concave mirror 36 via the doublet lens 35. The second concave mirror 36 reflects the incident scanning light L10 and focuses it at the pupil position Po. In this way, the projection optical system 11A of this embodiment can project the projection image 15 by the scanning light L10 via the pupil position Po of the user 5 of the HMD 1 ( FIG. 1 ), similar to the first embodiment.

[0071] The doublet lens 35 is configured by cementing, for example, one positive lens element and one negative lens element. The doublet lens 35 makes it easy to suppress chromatic aberration. The focusing optical system 3A of this embodiment is not limited to the doublet lens 35, and may instead or in addition include two uncemented lens elements, or one or three or more lens elements. Furthermore, the focusing optical system 3A is not limited to the concave mirrors 34 and 36, and may include various mirror elements. In this embodiment, an example configuration of the projection optical system 11A will be described when such a focusing optical system 3A has field curvature that needs to be corrected.

[0072] 7 illustrates an example of a relay optical system 25 in a scanning optical system 2A of the present embodiment 2. The scanning optical system 2A of the present embodiment has a configuration similar to that of the scanning optical system 2 (FIG. 2) of the first embodiment, but includes a relay optical system 25 having a correction aberration for field curvature instead of the relay optical system 20 having a correction aberration for astigmatism.

[0073] 7, the scanning optical system 2A of this embodiment further includes a doublet lens 24 disposed between the light source 12 and the horizontal scanning unit 21. The doublet lens 24 makes it easy to suppress chromatic aberration in the scanning optical system 2A. In the scanning optical system 2A, the doublet lens 24 may be omitted as appropriate, or one or more other lens elements may be used.

[0074] 6 illustrates the first transmitting surface 25a, the first reflecting surface 25b, the second reflecting surface 25c, and the second transmitting surface 25d, which have optical power, in the relay optical system 25 of this embodiment. As shown in FIG. 7, for example, the relay optical system 25 of this embodiment is configured as an integrated prism element in which the above-mentioned optical surfaces 25a to 25d are arranged in order from the incident side to the output side of the primary scanning light L11. Using such a prism relay optical system 25 can reduce the number of steps required to assemble the scanning optical system 2A.

[0075] The first transmitting surface 25a is disposed, for example, on the −Z1 side of the relay optical system 25, at a position where the primary scanning light L11 from the horizontal scanning unit 21 is incident. In the relay optical system 25 of this embodiment, the first transmitting surface 25a is formed of a free-form surface that is concave toward the outside of the prism so as to have negative power in the H1 direction, and also has power in the V1 direction, as shown in FIG.

[0076] The first reflecting surface 25b is disposed at an incident position of the primary scanning light L11 transmitted through the first transmitting surface 25a, for example, on the +Z1 side of the relay optical system 25. The first reflecting surface 25b is configured as a free-form surface that is convex toward the outside of the prism so as to have positive power in the H1 direction, as shown in FIG.

[0077] The second reflecting surface 25c is disposed at an incident position of the primary scanning light L11 reflected by the first reflecting surface 25b, for example, on the −Z1 side of the relay optical system 25. The second reflecting surface 25c is formed of a free-form surface that is convex toward the outside of the prism, similar to the first reflecting surface 25b.

[0078] The second transmitting surface 25d is disposed at an incident position of the primary scanning light L11 reflected by the second reflecting surface 25c, for example, on the +Z1 side of the relay optical system 25. The second transmitting surface 25d is formed of a free-form surface that is concave toward the outside of the prism, similar to the first transmitting surface 25a.

[0079] 2. Aberration Correction In the projection optical system 11A of this embodiment, the free-form surface of the relay optical system 25 can change the power that rays of the scanning light L10 from various positions in the scanning range of the horizontal scanning unit 21 receive at positions where they pass through the various optical surfaces 25a to 25d of the relay optical system 25. By setting the shape of the free-form surface so that such a change in power generates a curvature of field of the same magnitude as but in the opposite direction to the curvature of field of the focusing optical system 3A, the relay optical system 25 can be provided with a correction aberration for the curvature of field of the focusing optical system 3A.

[0080] 8A to 8C are diagrams illustrating the light-converging points in the scanning optical system 2A of this embodiment. Hereinafter, the horizontal direction of the scanning light L10 after reflection by the vertical scanning unit 22 is referred to as the H2 direction, and the vertical direction of the scanning light L10 is referred to as the V2 direction. The ray direction of the central ray of the scanning light L10 after reflection is referred to as the Z2 direction.

[0081] 8A to 8C illustrate various converging points P10, P11, and P12, a first curve L20, a second curve L30, and a curved surface C10 for the scanning light L10 emitted from the vertical scanning unit 22. At the converging point P10, a light beam at the center of the angle of view is converged. At the converging point P11, a light beam tilted at a predetermined angle θ in the H2 direction with respect to the light beam at the center of the angle of view is converged. At the converging point P12, a light beam tilted at a predetermined angle θ in the V2 direction is converged. The predetermined angle θ can be set appropriately to, for example, the angle of view of the projected image 15 or less.

[0082] The first curve L20 indicates a locus connecting various light-converging points P10 and P11 resulting from horizontal scanning by the scanning optical system 2A. The second curve L30 indicates a locus connecting various light-converging points P10 and P12 resulting from vertical scanning by the scanning optical system 2A. The curved surface C10 is defined to include the first curve L20 corresponding to the horizontal direction and the second curve L30 corresponding to the vertical direction as described above, and indicates an intermediate image position where an intermediate image including each of the light-converging points P10 to P12 is formed in the scanning optical system 2A.

[0083] In the scanning optical system 2A of this embodiment, by scanning the scanning units 21 and 22, for example, the scanning light L10 is projected onto the curved surface C10 so as to sequentially focus the scanning light L10 at each of the focusing points P10 to P12 along the first and second curves L20 and L30, thereby forming an intermediate image on the curved surface C10. Aberrations such as field curvature on the curved surface C10 of the intermediate image can be controlled by an aberration correction unit such as the relay optical system 25 in the scanning optical system 2A. For example, the first curve L20 and the second curve L30 can have different curvatures. The curved surface C10 of the intermediate image may also be measured in a state where the focusing optical system 3A is omitted from the projection optical system 11A, or may be measured by optical analysis simulation.

[0084] In the scanning optical system 2A of this embodiment, the relay optical system 25 disposed between the horizontal scanning unit 21 and the vertical scanning unit 22 facilitates control of field curvature, for example, in the horizontal direction. This allows, for example, correction aberrations to be set in the relay optical system 25 to eliminate asymmetry even when the field curvature of the focusing optical system 3A is asymmetric between the horizontal and vertical directions, making it easy to reduce the field curvature. Furthermore, components of the field curvature of the focusing optical system 3A that are symmetric between the horizontal and vertical directions can be easily eliminated with a configuration separate from the relay optical system 25. For example, a corrective optical element may be provided downstream of the vertical scanning unit 22 (see FIG. 13 ).

[0085] According to the scanning optical system 2A of this embodiment, it is possible to make different the distance d11 from the convergence point P11 of the light beam tilted in the H2 direction to the vertical scanning unit 22 and the distance d12 from the convergence point P11 of the light beam tilted in the V2 direction to the vertical scanning unit 22. In addition, the distance d11 from the convergence point P11 of the light beam tilted in the H2 direction to the vertical scanning unit 22 can be made larger or smaller than the distance d10 from the convergence point P10 of the central light beam to the vertical scanning unit 22.

[0086] In the scanning optical system 2A of this embodiment, the distances d10, d11, and d12 from the various light-converging points P10 to P12 can be adjusted by varying the curved surface shape at the positions through which the corresponding light rays pass in the relay optical system 25. For example, by increasing the local curvature at the positions through which each light ray passes on the free-form surface of the relay optical system 25, the power acting on the light ray can be strengthened.

[0087] 9A and 9B are diagrams for explaining aberration correction in the projection optical system 11A of this embodiment. Fig. 9A shows the MTF through focus of the focusing optical system 3A having field curvature, similar to Fig. 5A. Fig. 9B shows the MTF through focus of the projection optical system 11A of this embodiment, similar to Fig. 5B.

[0088] In the numerical simulation for the MTF measurements in Figures 9(A) and 9(B), three colors, 640 nm, 520 nm, and 460 nm, were used as light source wavelengths under the same settings as in Figures 5(A) and 5(B). Each MTF curve was calculated by averaging the measurement results for the three colors.

[0089] 9A, the peak positions of the MTF curves at the ±H side ends are different from the peak positions of the MTF curves at the center and +V side ends. This indicates that the focusing optical system 3A has different curvatures of field between the horizontal and vertical directions. Therefore, the projection optical system 11A of this embodiment uses a scanning optical system 2A in which correction aberrations are set in the relay optical system 25 to offset the curvature of field of the focusing optical system 3A.

[0090] Specifically, the relay optical system 25 was set so that the distances d10, d11, and d12 from the vertical scanning unit 22 to the light-converging points P10, P11, and P12 at the center position, the H-side end, and the V-side end respectively satisfied the following equation: 1 / d10=0.21 mm －１ 1 / d11=0.19mm －１ 1 / d12=0.22mm －１

[0091] The setting as in the above formula can be realized, for example, by adjusting the free-form surface shape in the relay optical system 25 configured as described above so that the power changes for each passing position of each ray.

[0092] FIG. 9B shows the results of MTF through-focus measurements, which indicate the field curvature of the projection optical system 11A of this embodiment. As shown in FIG. 9B, the peak positions of the MTF curves at the ±H side edges and the peak positions of the MTF curves at the center and side edges do not deviate from each other as in the example of FIG. 9A, but overlap at approximately 0 diopter. In other words, the field curvature of the example of FIG. 9A is eliminated. Thus, it was confirmed that the projection optical system 11A of this embodiment can correct the field curvature of the focusing optical system 3 by using the relay optical system 25, which has corrective aberrations in the scanning optical system 2A.

[0093] 3. Summary As described above, the projection optical system 11A, which is an example of an optical system in this embodiment, includes the horizontal scanning unit 21, which is an example of a first scanning unit, the vertical scanning unit 22, which is an example of a second scanning unit, the focusing optical system 3A, and the relay optical system 20, which is an example of an aberration correction unit. The first scanning unit scans light incident from the light source 12 in a first direction. The second scanning unit scans the light scanned by the first scanning unit in a second direction intersecting the first direction. The focusing optical system 3A focuses the light scanned by the second scanning unit. The aberration correction unit is disposed between the focusing optical system 3A and the first scanning unit, and outputs light incident from the light source 12 via the first scanning unit toward the focusing optical system 3A so as to correct field curvature generated in the focusing optical system 3A.

[0094] According to the above-described projection optical system 11A, it is possible to easily suppress aberrations such as field curvature in an image obtained by scanning light by correcting the field curvature occurring in the light-converging optical system 3A using an aberration correction unit such as the relay optical system 20. The correction of field curvature by an aberration correction unit such as the relay optical system 20 may be such that it cancels out part of the field curvature of the light-converging optical system 3A and suppresses the field curvature of the entire projection optical system 11A.

[0095] In the projection optical system 11A of this embodiment, the field curvature generated in the focusing optical system 3A is asymmetric between, for example, the first direction and the second direction. The aberration correction unit includes a relay optical system 20 as an example of one or more optical elements arranged between the first scanning unit and the second scanning unit. As a result, the projection optical system 11A of this embodiment can reduce asymmetric aberration in the field curvature of the focusing optical system 3A by using the relay optical system 20, making it easier to suppress aberration in the projection optical system 11A.

[0096] In the projection optical system 11A of this embodiment, for example, the relay optical system 20 of the aberration correction unit causes the light scanned by the first scanning unit to form an image on a curved surface C10 including a first curve L20 corresponding to the first direction and a second curve L30 corresponding to the second direction via the second scanning unit. The aberration correction unit corrects the field curvature generated in the focusing optical system 3A based on the difference between the curvature of the first curve L20 and the curvature of the second curve L30. As a result, the projection optical system 11A of this embodiment can easily suppress aberrations in the projection optical system 11A by controlling the curvature of the curved surface C10 of the intermediate image using the aberration correction unit.

[0097] In the projection optical system 11A of this embodiment, the corrected aberration includes, for example, in terms of positive and negative field curvature, a field curvature in the opposite direction to the field curvature generated in the focusing optical system 3. As a result, the projection optical system 11A of this embodiment can correct the field curvature generated in the focusing optical system 3A by including, in the corrected aberration, a field curvature in the direction that corrects the field curvature generated in the focusing optical system 3A, making it easier to suppress aberrations in an image obtained by scanning and then focusing light.

[0098] In the projection optical system 11A of this embodiment, the relay optical system 25 serving as an aberration correction unit includes a prism element as an example of an optical element that has different powers acting on light rays that are angled at a predetermined angle θ from the central ray during horizontal scanning and light rays that are angled at a predetermined angle θ from the central ray during scanning in the second direction. This aberration correction unit can cause the distances d11 and d12 to the vertical scanning unit 22 to differ between a convergence point P11 of a light ray inclined at the predetermined angle θ in the H2 direction and a convergence point P12 of a light ray inclined at the predetermined angle θ in the V2 direction. In this way, the projection optical system 11A of this embodiment can correct field curvature that differs between the horizontal and vertical directions.

[0099] In the projection optical system 11A of this embodiment, the relay optical system 25 serving as an aberration correction unit includes a prism element (see FIG. 7 ) as an example of an optical element that differentiates the power acting on the edge beam during horizontal scanning from the power acting on the central beam. This aberration correction unit can differentiate the distances d10 and d11 to the vertical scanning unit 22 between the focal point P10 of the central beam and the focal point P11 at the end in the H2 direction. In this way, the projection optical system 11A of this embodiment can correct field curvature that occurs in the horizontal direction. The configuration of the optical elements of the aberration correction unit in the relay optical system 25 of this embodiment is not limited to the above. For example, in addition to the horizontal power described above, the relay optical system 25 may be configured to differentiate the power acting on the edge beam during vertical scanning from the power acting on the central beam.

[0100] In the projection optical system 11A of this embodiment, the relay optical system 25 serving as the aberration correction unit includes a prism element having a plurality of reflective surfaces 25b, 25c that reflect light in the scanning optical system 2 and a plurality of transmissive surfaces 25a, 25d that refract and transmit light, as shown in Fig. 7, for example. This configuration simplifies the configuration of the aberration correction unit and makes it easier to correct aberrations in the projection optical system 11A. In the relay optical system 25 of this embodiment, the configuration of the optical element of the aberration correction unit is not limited to the above, and it may be, for example, a prism element having one reflective surface and two transmissive surfaces.

[0101] (Other Embodiments) As described above, embodiments 1 and 2 have been described as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, it is also possible to combine the components described in each of the above embodiments to create a new embodiment. Therefore, other embodiments will be described below as examples.

[0102] In the above-described first and second embodiments, the projection optical system 11, 11A is described in which the relay optical system 20, 25 in the scanning optical system 2, 2A is configured to have aberration correction. The present disclosure is not limited to this, and for example, the scanning optical system 2, 2A may be configured so that the aberration correction can be adjusted after the fact. Such a modification will be described with reference to FIG. 10 .

[0103] 10 shows a side view of the scanning optical system 2B of Modification 1. The scanning optical system 2B of this embodiment has a configuration similar to that of the scanning optical system 2 of Embodiment 1, and further includes an adjustment mechanism 23c for adjusting the intervals Di between the mirror elements 20a to 20d as an aberration correction unit in the relay optical system 20. The adjustment mechanism 23c is configured to be able to move the two support bases 23a, 23b in opposite directions in the Z1 direction while maintaining the positions of the center points Pi of the mirror elements 20a to 20d, for example.

[0104] In the scanning optical system 2B of this embodiment, the distance Di can be changed by the adjustment mechanism 23c, and therefore it is possible to change the degree of correction aberration, such as astigmatism, imparted to the relay optical system 20. For example, if there is a tolerance in the predetermined angle of the prism element 32 in the focusing optical system 3 (FIG. 2), the distance Di can be changed by the adjustment mechanism 23c, and the scanning optical system 2B can be made to have a correction aberration according to the variation in astigmatism due to the tolerance of the focusing optical system 3.

[0105] As described above, in this embodiment, the scanning optical system 2B or its projection optical system 11 further includes the adjustment mechanism 23c, which is an example of an adjustment unit that adjusts the corrected aberration. This allows the corrected aberration in the scanning optical system 2B to be adjusted afterward, making it easier to correct the aberration in the projection optical system 11. For example, even if variations occur in the focusing optical system 3 during mass production of the projection optical systems 11, the aberration can be corrected with high precision in each projection optical system 11.

[0106] In this embodiment, the aberration correction unit includes multiple mirror elements 25a-25d, each having multiple reflective surfaces arranged so that light passing through the scanning optical system 2B is sequentially reflected. The adjustment mechanism 23c adjusts the spacing Di between the multiple reflective surfaces. This simple configuration makes it easy to adjust the aberration correction.

[0107] 11 shows a side view of a scanning optical system 2C of Modification 2. The scanning optical system 2C of this embodiment has a configuration similar to that of the scanning optical system 2 of Embodiment 1, for example, but includes a relay optical system 27 including a plurality of prism elements 27a and 27b instead of the relay optical system 20 including mirror elements 20a to 20d. The scanning optical system 2C of this embodiment also includes a toroidal lens 26 disposed between the light source 12 and the horizontal scanning unit 21, for example.

[0108] In the scanning optical system 2C of this embodiment, the first prism element 27a has a reflecting surface that reflects the primary scanning light L11, similar to, for example, the first and second mirror elements 20a and 20b of Embodiment 1. The first prism element 27a also has a transmitting surface that receives the primary scanning light L11 and a transmitting surface that emits the primary scanning light L11 to the second prism element 27b.

[0109] The first and second prism elements 27a and 27b are disposed adjacent to each other in the V1 direction, for example. The second prism element 27b has a reflective surface that reflects the primary scanning light L11, similar to the third and fourth mirror elements 20c and 20d of embodiment 1. The second prism element 27b also has a transmission surface through which the primary scanning light L11 is incident and a transmission surface through which the primary scanning light L11 is emitted to the vertical scanning unit 22.

[0110] As described above, in the scanning optical system 2C of this embodiment, the relay optical system 27 serving as an aberration correction unit includes a plurality of prism elements 27a, 27b, each of which has a plurality of reflective surfaces. In the scanning optical system 2C of this embodiment, the adjustment unit may be any of various mechanisms for adjusting the spacing between the plurality of prism elements 27a, 27b. According to the scanning optical system 2C of this embodiment, the power of the relay optical system 27 can be changed and the corrected aberration can be adjusted by moving the first and second prism elements 27a, 27b in opposite directions in the Z1 direction, for example. The scanning optical system 2C of this embodiment also facilitates correction of aberrations in the projection optical system 11, as in the above embodiments.

[0111] In the above embodiments, the relay optical system 20 between the horizontal scanning unit 21 and the vertical scanning unit 22 has been described as an example of an aberration correction unit. In this embodiment, the aberration correction unit of the projection optical system 11 is not limited to the relay optical system 20, and may include various optical elements arranged in the scanning optical system 2. Such modified examples will be described with reference to FIGS. 12 and 13 .

[0112] 12 shows a perspective view of a projection optical system 11B of Modification 1. The projection optical system 11B of this embodiment has a configuration similar to that of the projection optical system 11 of Embodiment 1, but further includes a toroidal lens 28 as an aberration correction unit disposed between the light source 12 and the horizontal scanning unit 21 in the scanning optical system 2. The toroidal lens 28 is set with a correction aberration for suppressing aberration in the focusing optical system 3, for example. Furthermore, in the projection optical system 11B of this embodiment, the relay optical system 20 does not need to be set with a particular correction aberration. Alternatively, in the projection optical system 11B of this embodiment, the correction aberration may be shared between the toroidal lens 28 and the relay optical system 20.

[0113] FIG. 13 is a perspective view of a projection optical system 11C of Modification 2. The projection optical system 11C of this embodiment has a configuration similar to that of the projection optical system 11 of Embodiment 1, but further includes a toroidal lens 29 as an aberration correction unit disposed between the vertical scanning unit 22 and the focusing optical system 3 in the scanning optical system 2. The toroidal lens 29 is configured to correct aberrations, for example, to suppress aberrations in the focusing optical system 3. In addition, in the projection optical system 11C of this embodiment, the relay optical system 20 does not need to be configured with a particular aberration correction. Alternatively, in the projection optical system 11C of this embodiment, the aberration correction may be shared between the toroidal lens 29 and the relay optical system 20. In addition, in the projection optical system 11C of this embodiment, a toroidal lens 28 may be further disposed between the light source 12 and the horizontal scanning unit 21. In addition, various lens elements or optical elements may be used as appropriate in the aberration correction unit instead of or in addition to the toroidal lenses 28 and 29.

[0114] Furthermore, in the above-described embodiments, the case where the focusing optical system 3 using the HOE 33 has astigmatism and the case where the focusing optical system 3A using a mirror element has curvature of field have been described. The projection optical system 11 of the present embodiment is not particularly limited to this, and the aberration correction unit in the scanning optical system 2 can be set appropriately depending on the aberration of the focusing optical system 3. For example, if the focusing optical system 3 using the HOE 33 has curvature of field, the scanning optical system 2 may employ the relay optical system 25 as in embodiment 2. Furthermore, if the focusing optical system 3A using a mirror element has astigmatism, the scanning optical system 2A may employ the relay optical system 20 as in embodiment 1. Furthermore, even for a focusing optical system 3 having both astigmatism and curvature of field, the above-described embodiments can be appropriately combined to configure a projection optical system in which correction aberrations for such aberrations are set in the aberration correction unit of the scanning optical system 2.

[0115] In the above embodiments, the horizontal scanning unit 21 and the vertical scanning unit 22 have been described as examples of the first and second scanning units. In the present embodiment, the first and second scanning units are not limited to the above examples, and various configurations can be adopted. For example, the order of the horizontal scanning unit 21 and the vertical scanning unit 22 may be reversed, or scanning may be performed in a direction other than the horizontal and vertical directions. Furthermore, each of the scanning units 21 and 22 is not limited to a MEMS mirror, and may be another reflective scanner, or a transmissive scanner such as a prism.

[0116] In the above embodiments, an eyeglass-type HMD 1 has been described as an example of an image display device, but the present disclosure is not particularly limited thereto. For example, in the present embodiments, the HMD 1 is not limited to eyeglass-type devices, and may be, for example, goggle-type, hat-type, or helmet-type devices. Furthermore, the attachment member 10 of the HMD 1 is not limited to eyeglass frames, and may be, for example, nose pads, forehead pads, or fixing bands. Furthermore, the image display device of the present embodiments is not limited to the HMD 1, and may be various image display devices, such as an electronic viewfinder or a head-up display.

[0117] (Examples of Aspects) Various aspects of the present disclosure will be described below.

[0118] A first aspect of the present disclosure is an optical system including a first scanning unit that scans light incident from a light source in a first direction, a second scanning unit that scans the light scanned by the first scanning unit in a second direction intersecting the first direction, a focusing optical system that focuses the light scanned by the second scanning unit, and an aberration correction unit that is disposed between the focusing optical system and the first scanning unit and emits light incident from the light source via the first scanning unit toward the focusing optical system so as to correct field curvature generated in the focusing optical system.

[0119] In a second aspect, in the optical system described in the first aspect, the field curvature generated in the focusing optical system is asymmetric between the first direction and the second direction, and the aberration correction unit includes one or more optical elements arranged between the first scanning unit and the second scanning unit.

[0120] In a third aspect, in the optical system described in the first or second aspect, the aberration correction unit images the light scanned by the first scanning unit onto a curved surface including a first curve corresponding to the first direction and a second curve corresponding to the second direction via the second scanning unit, and corrects the field curvature occurring in the focusing optical system due to the difference between the curvature of the first curve and the curvature of the second curve.

[0121] A fourth aspect is an optical system including a scanning optical system that scans light incident from a light source and a focusing optical system that focuses the light scanned by the scanning optical system. The scanning optical system includes a first scanning unit that scans the light incident from the light source in a first direction, a second scanning unit that scans the light scanned by the first scanning unit in a second direction intersecting the first direction, and an aberration correction unit that adds a correction aberration corresponding to an aberration generated in the focusing optical system to the light passing through the scanning optical system.

[0122] In a fifth aspect, in the optical system according to any one of the first to fourth aspects, the scanning optical system includes a relay optical system disposed between the first scanning unit and the second scanning unit, which guides the light scanned by the first scanning unit to the second scanning unit. The aberration correction unit is configured by the relay optical system.

[0123] In a sixth aspect, in the optical system according to any one of the first to fifth aspects, the corrected aberration includes astigmatism in the opposite direction to the astigmatism generated in the focusing optical system.

[0124] In a seventh aspect, in the optical system described in the sixth aspect, the aberration correction unit includes one or more optical elements having different powers in the first direction and the second direction depending on the opposite astigmatism in the corrected aberration.

[0125] In an eighth aspect, in the optical system according to any one of the first to seventh aspects, the corrected aberrations include a curvature of field in the opposite direction to the curvature of field generated in the focusing optical system.

[0126] In a ninth aspect, in the optical system described in the eighth aspect, the aberration correction unit includes an optical element that has different powers acting on light rays that have a predetermined angle from the central ray when scanning in the first direction and on light rays that have a predetermined angle from the central ray when scanning in the second direction.

[0127] In a tenth aspect, in the optical system described in the eighth or ninth aspect, the aberration correction unit includes an optical element that has a different power acting on the end rays during scanning in the first or second direction from the power acting on the central ray.

[0128] In an eleventh aspect, in the optical system according to any one of the first to tenth aspects, the light-converging optical system includes an optical element that bends the optical path of the light incident from the scanning optical system.

[0129] In a twelfth aspect, the optical system according to any one of the first to eleventh aspects further comprises an adjustment section that adjusts the correction aberration.

[0130] In a thirteenth aspect, in the optical system according to the twelfth aspect, the aberration correction unit has a plurality of reflecting surfaces arranged so that light passing through the scanning optical system is reflected sequentially, and the adjustment unit adjusts the spacing between the plurality of reflecting surfaces.

[0131] In a fourteenth aspect, in the optical system according to the thirteenth aspect, the aberration correction unit includes a plurality of prism elements each having a plurality of reflecting surfaces, and the adjustment unit adjusts the spacing between the plurality of prism elements.

[0132] In a fifteenth aspect, in the optical system according to any one of the first to thirteenth aspects, the aberration correction unit includes a prism element having a reflective surface that reflects light and a transmissive surface that transmits light in the scanning optical system. The prism element may have one or more reflective surfaces. The prism element may have, for example, multiple transmissive surfaces.

[0133] A sixteenth aspect is an image display device comprising the optical system according to any one of the first to fifteenth aspects, and a light source that supplies light that shows an image to the optical system.

[0134] A seventeenth aspect is an optical system that scans light incident from a light source and outputs the light to a subsequent optical system, the optical system including: a first scanning unit that scans the light incident from the light source in a first direction; a second scanning unit that scans the light scanned by the first scanning unit in a second direction intersecting the first direction; and an aberration correction unit that adds a correction aberration corresponding to an aberration generated in the subsequent optical system to the light passing through the optical system.

[0135] In the optical system, the correction aberration may be set to cancel out aberration caused by a subsequent optical system onto which the light scanned by the optical system is incident. The optical system may further include an adjustment unit that adjusts the correction aberration.

[0136] As described above, the embodiments have been described as examples of the technology in the present disclosure, and for that purpose, the accompanying drawings and detailed description have been provided.

[0137] Therefore, the components shown in the accompanying drawings and detailed description may include not only essential components for solving the problem, but also components that are not essential for solving the problem in order to illustrate the above technology. Therefore, the fact that these non-essential components are shown in the accompanying drawings or detailed description should not be interpreted as immediately indicating that these non-essential components are essential.

[0138] Furthermore, since the above-described embodiments are intended to illustrate the technology of the present disclosure, various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

[0139] The present disclosure is applicable to an image display device that projects an image and its optical system, and is applicable to, for example, an HMD.

Claims

1. An optical system comprising: a first scanning unit that scans light incident from a light source in a first direction; a second scanning unit that scans the light scanned by the first scanning unit in a second direction that intersects with the first direction; a focusing optical system that focuses the light scanned by the second scanning unit; and an aberration correction unit that is disposed between the focusing optical system and the first scanning unit and outputs light incident from the light source via the first scanning unit toward the focusing optical system so as to correct field curvature generated in the focusing optical system.

2. The optical system according to claim 1, wherein the field curvature generated in the focusing optical system is asymmetric between the first direction and the second direction, and the aberration correction unit includes one or more optical elements disposed between the first scanning unit and the second scanning unit.

3. The optical system according to claim 1, wherein the aberration correction unit images the light scanned by the first scanning unit, via the second scanning unit, onto a curved surface including a first curve corresponding to the first direction and a second curve corresponding to the second direction, and corrects the curvature of field occurring in the focusing optical system due to the difference between the curvature of the first curve and the curvature of the second curve.

4. An optical system comprising: a scanning optical system that scans light incident from a light source; and a focusing optical system that focuses the light scanned by the scanning optical system, wherein the scanning optical system includes: a first scanning unit that scans the light incident from the light source in a first direction; a second scanning unit that scans the light scanned by the first scanning unit in a second direction intersecting the first direction; and an aberration correction unit that adds correction aberration corresponding to aberration generated in the focusing optical system to light passing through the scanning optical system.

5. The optical system according to claim 4, wherein the scanning optical system includes a relay optical system disposed between the first scanning unit and the second scanning unit, which guides the light scanned by the first scanning unit to the second scanning unit, and the aberration correction unit is configured by the relay optical system.

6. The optical system according to claim 4, wherein the corrected aberration includes astigmatism in the opposite direction to the astigmatism generated in the focusing optical system.

7. The optical system according to claim 6, wherein the aberration correction section includes one or more optical elements having different powers in the first direction and the second direction depending on the astigmatism in the opposite direction in the corrected aberration.

8. The optical system according to claim 4, wherein the corrected aberration includes a curvature of field in the opposite direction to the curvature of field generated in the focusing optical system.

9. The optical system according to claim 8, wherein the aberration correction unit includes an optical element that has different powers acting on rays that have a predetermined angle from the central ray during scanning in the first direction and on rays that have the predetermined angle from the central ray during scanning in the second direction.

10. The optical system according to claim 8, wherein the aberration correction unit includes an optical element that has different powers acting on the light beams at the ends of the scanning in the first direction or the second direction and on the central light beam.

11. The optical system according to claim 4, wherein the focusing optical system includes an optical element that bends the optical path of the light incident from the scanning optical system.

12. The optical system according to claim 4, further comprising an adjustment unit that adjusts the correction aberration.

13. The optical system according to claim 12, wherein the aberration correction unit has a plurality of reflecting surfaces arranged so that light passing through the scanning optical system is reflected sequentially, and the adjustment unit adjusts the spacing between the plurality of reflecting surfaces.

14. The optical system according to claim 13, wherein the aberration correction unit includes a plurality of prism elements each having a plurality of reflecting surfaces, and the adjustment unit adjusts the spacing between the plurality of prism elements.

15. The optical system according to claim 4, wherein the aberration correction section includes a prism element in the scanning optical system having a reflecting surface that reflects light and a transmitting surface that transmits light.

16. An image display device comprising: the optical system according to claim 4; and a light source that supplies light showing an image to said optical system.

17. An optical system that scans light incident from a light source and outputs it to a subsequent optical system, comprising: a first scanning unit that scans the light incident from the light source in a first direction; a second scanning unit that scans the light scanned by the first scanning unit in a second direction intersecting the first direction; and an aberration correction unit that adds corrective aberration corresponding to aberration generated in the subsequent optical system to the light passing through the optical system.

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