Projection optical system and image display device

Abstract

This projection optical system is provided with: a dioptric system having positive refractive power as a whole and having, as a reference, a reference axis disposed at a position on which image light from a primary image plane is incident; and a catoptric system having a reflection plane that reflects the image light emitted from the dioptric system toward a projection plane forming a secondary image plane, and configured such that in a light beam effective range in which the image light is incident, the shape of the reflection plane becomes a rotationally symmetric aspherical shape having a sag amount in a direction opposite to the dioptric system with the reference axis as a rotation axis, and the shape within a cross section including the reference axis of the reflection plane has a shape inclined to approach a right angle in a region farthest from the reference axis in comparison with a region closest to the reference axis.

Description

[Technical Field]

[0001] The present disclosure relates to a projection optical system that projects image light, and an image display device. [Background technology]

[0002] There are projection optical systems and image display devices that display an image on a projection surface such as a screen by reflecting (projecting) image light emitted from a refractive optical system such as a lens onto the projection surface such as a screen using a reflective optical system with a convex reflective surface (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-207168 [Patent Document 2] International Publication No. 01 / 006295 Summary of the Invention

[0004] In a projection optical system having a convex reflecting surface as described above, the angle at which light rays emerge varies depending on the height at which the light rays enter the reflecting surface, making it difficult to display a uniform image across the entire screen.

[0005] It is desirable to provide a projection optical system and an image display device that can improve image quality.

[0006] A projection optical system according to one embodiment of the present disclosure comprises a refractive optical system having an overall positive refractive power and arranged with a reference axis as a reference at a position where image light from a primary image surface is incident, and a reflective optical system having a reflective surface that reflects the image light emitted from the refractive optical system toward a projection surface that forms a secondary image surface, wherein, within the effective light range where the image light is incident, the shape of the reflective surface is a rotationally symmetric aspherical shape with a sag amount in the opposite direction to the refractive optical system, with the reference axis as the axis of rotation, and the shape of the reflective surface in a cross section including the reference axis is inclined so that it approaches a right angle in the region farthest from the reference axis compared to the region closest to the reference axis. The reflective optical system is configured so that, within the effective light ray range in which the image light is incident, the reflection angle of the incident light on the reflective surface is relatively large in the area closest to the reference axis and relatively small in the area farthest from the reference axis. At the same time, the angle of the light beam emitted from the reflecting surface is constant regardless of the height of the light beam. .

[0007] An image display device according to one embodiment of the present disclosure includes an image generation unit that forms a primary image surface, and a projection optical system into which image light from the primary image surface is incident, and the projection optical system is configured by the projection optical system according to the embodiment of the present disclosure.

[0008] In a projection optical system or an image display device according to an embodiment of the present disclosure, the shape of the reflective surface of the reflective optical system is optimized, so that the emission angle of the light beam emitted from the reflective surface can be made approximately constant. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a first configuration example of an image display device according to a comparative example. [Figure 2] FIG. 10 is a cross-sectional view schematically showing a second configuration example of an image display device according to a comparative example. [Figure 3] FIG. 10 is a cross-sectional view showing an example of the configuration of a projection optical system according to a comparative example, together with an optical path. [Figure 4] 1 is a cross-sectional view showing a first configuration example (Example 1) of a projection optical system and an image display device according to an embodiment of the present disclosure, together with an optical path. [Figure 5] 10 is a cross-sectional view showing a second configuration example (Example 2) of a projection optical system and an image display device according to an embodiment, together with an optical path. [Figure 6] 10 is a cross-sectional view showing a third configuration example (Example 3) of a projection optical system and an image display device according to an embodiment, together with an optical path. [Figure 7] 10 is a cross-sectional view showing a fourth configuration example (Example 4) of a projection optical system and an image display device according to an embodiment, together with an optical path. [Figure 8] 10 is a cross-sectional view showing a fifth configuration example (Example 5) of a projection optical system and an image display device according to an embodiment, together with an optical path. [Figure 9] 1 is a cross-sectional view showing the configuration of a projection optical system and an image display device according to Comparative Example 1, together with an optical path. [Figure 10] 10 is a cross-sectional view showing the configuration of a projection optical system and an image display device according to Comparative Example 2, together with an optical path. [Figure 11] FIG. 10 is a characteristic graph showing the relationship between the normalized ray height h and the derivative Z'(h) obtained by first differentiating the function Z(h) indicating the sag amount Z of the aspherical shape of the reflecting surface for each example and each comparative example. [Figure 12] FIG. 10 is a characteristic diagram showing, in graph form, the relationship between the normalized ray height h and the amount of change ΔZ'(h) in the derivative Z'(h) obtained by first differentiating the function Z(h) indicating the sag amount Z of the aspherical shape of the reflecting surface for each example and each comparative example. [Figure 13] FIG. 10 is a characteristic diagram showing, in graph form, the relationship between the normalized light ray height h and the actual light ray height R(h) and the sag amount (Z(h) / R(h)) of the aspherical shape of the reflecting surface for each example and each comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be made in the following order. 0. Comparative Example 1. Configuration of a projection optical system and an image display device according to an embodiment 2. Action and Effects 3. Numerical Examples 4. Other embodiments

[0011] <0. Comparative Example> FIG. 1 schematically shows a first configuration example of an image display device according to a comparative example.

[0012] As shown in FIG. 1, the image display device according to the first configuration example of the comparative example includes a screen 100, an image display element 200, a projection optical system 210, and a light source section 220.

[0013] The image display element 200 is, for example, a DMD (Digital Micromirror Device) having a plurality of micromirrors, and modulates light from a light source section 220 to form a primary image plane IP1.

[0014] Image light from a primary image surface IP1 formed by the image display element 200 is incident on the projection optical system 210. The projection optical system 210 includes, in order from the image light incident side, a refractive optical system 211 and a reflective optical system 212. The refractive optical system 211 is made up of a plurality of lenses, etc. The reflective optical system 212 has a convex reflective surface.

[0015] The reflective optical system 212 reflects (projects) the image light emitted from the refractive optical system 211 by a reflective surface toward the screen 100 as a projection surface. As a result, a secondary image surface IP2 is formed (displayed) on the screen 100.

[0016] FIG. 2 schematically shows a second configuration example of an image display device according to a comparative example.

[0017] 2 further comprises a plane mirror 213 arranged on the optical path between the screen 100 and the reflective surface of the reflective optical system 212, in addition to the configuration of the image display device according to the first configuration example of the comparative example shown in Fig. 1. In the image display device according to the second configuration example of the comparative example, the image light reflected by the reflective surface of the reflective optical system 212 is further reflected by the plane mirror 213, so that the image light is projected towards the screen 100.

[0018] FIG. 3 shows an example of the configuration of a projection optical system 210 according to a comparative example, along with the optical path.

[0019] In the projection optical system 210 according to the comparative example, the reflecting surface of the reflecting optical system 212 becomes a refractive optical system as it moves away from the optical axis Z1. 211 Convex shape on the side, refractive optical system 211 The reflecting surface has an aspherical shape in which the sag deepens in the opposite direction to the optical axis Z1. With this type of reflecting surface shape, the angle of the light beam emitted from the reflecting surface becomes relatively larger as the distance from the optical axis Z1 increases. As shown in Figure 3, the angle of light beam Lb emitted from an area of the reflecting surface far from the optical axis Z1 is relatively larger than the angle of light beam La emitted from an area of the reflecting surface close to the optical axis Z1.

[0020] Therefore, in the projection optical system 210 according to the comparative example, the exit angle of the light beam varies depending on the height of the light beam incident on the reflective surface, and it is difficult to make the exit angle constant regardless of the height of the light beam, which makes it difficult to display a uniform image across the entire screen.

[0021] 1. Configuration of a projection optical system and an image display device according to an embodiment FIGS. 4 to 8 show first to fifth configuration examples of a projection optical system and an image display device according to an embodiment of the present disclosure. FIG. 4 shows a first configuration example of a projection optical system 1 and an image display device according to an embodiment, together with an optical path, and corresponds to the configuration of Example 1, which will be described later. FIG. 5 shows a second configuration example of a projection optical system 2 and an image display device according to an embodiment, and corresponds to the configuration of Example 2, which will be described later. FIG. 6 shows a third configuration example of a projection optical system 3 and an image display device according to an embodiment, together with an optical path, and corresponds to the configuration of Example 3, which will be described later. FIG. 7 shows a fourth configuration example of a projection optical system 4 and an image display device according to an embodiment, together with an optical path, and corresponds to the configuration of Example 4, which will be described later. FIG. 8 shows a fifth configuration example of a projection optical system 5 and an image display device according to an embodiment, together with an optical path, and corresponds to the configuration of Example 5, which will be described later.

[0022] Hereinafter, the configuration of a projection optical system and an image display device according to an embodiment of the present disclosure will be described in association with each of the configuration examples shown in Fig. 4 etc. Note that the technology according to the present disclosure is not limited to each of the configuration examples shown in Figs.

[0023] The image display device according to one embodiment includes a screen 10, an image generating section 20, and a projection optical system (one of projection optical systems 1 to 5).

[0024] The image generating unit 20 has, for example, a reflective liquid crystal display element or a DMD having a plurality of micromirrors. The image generating unit 20 modulates light from the light source unit 220 to form a primary image plane IP1, similar to, for example, the image display element 200 in the image display device according to the comparative example (FIG. 1). The image generating unit 20 may be a transmissive display element. Alternatively, the image generating unit 20 may be a self-luminous display element.

[0025] Image light from a primary image plane IP1 formed by an image generation unit 20 is incident on a projection optical system according to one embodiment. The projection optical system includes, in order from the image light incident side, a refractive optical system 11 and a reflective optical system 12. A prism optical system 30 or the like may be disposed between the image generation unit 20 and the refractive optical system 11, depending on the configuration of the image generation unit 20.

[0026] The refractive optical system 11 is made up of, for example, a plurality of lenses. The refractive optical system 11 has a positive refractive power as a whole and is disposed at a position where image light from a primary image surface IP is incident, with a reference axis Za as a reference. The reference axis Za may be coaxial with an optical axis Z1 of the refractive optical system 11 and the reflective optical system 12.

[0027] The reflective optical system 12 has a reflecting surface that reflects (projects) the image light emitted from the refractive optical system 11 toward a screen 10 that serves as a projection surface that forms a secondary image plane IP2.

[0028] The shape of the reflecting surface of the reflecting optical system 12 is a rotationally symmetric aspheric shape within the effective light ray range where image light is incident, with the reference axis Za as the axis of rotation and an amount of sag in the opposite direction to that of the refractive optical system 11. The reflecting optical system 12 is also configured so that the shape of the reflecting surface in a cross section including the reference axis Za is inclined so as to approach a right angle near the region farthest from the reference axis Za compared to near the region closest to the reference axis Za.

[0029] It is desirable that the reflective optical system 12 is configured so that, within the effective light range into which the image light is incident, the reflection angle of the incident light on the reflective surface is relatively large near the area closest to the reference axis Za and relatively small near the area farthest from the reference axis Za.

[0030] The screen 10 as a projection surface has, for example, a shape of a body of revolution with the reference axis Za as its axis of rotation. For example, the screen 10 may have a cylindrical shape with the reference axis Za as its axis of rotation. The screen 10 may also have a planar shape. The screen 10 may also have a spherical shape.

[0031] In the first to third configuration examples shown in Fig. 4 to Fig. 6, the screen 10 has a cylindrical surface shape with the reference axis Za as the axis of rotation. In the fourth configuration example shown in Fig. 7, the screen 10 has a flat shape. In the fifth configuration example shown in Fig. 8, the screen 10 has a spherical shape.

[0032] The screen 10 may be, for example, a transmissive or reflective screen having anisotropic diffusion characteristics in which the light diffusion characteristics differ between the horizontal and vertical directions.

[0033] It is desirable that a projection optical system and an image display device according to one embodiment satisfy the following conditional expression (1): In conditional expression (1), the height of a light ray from a reference axis Za normalized to a maximum value of 1.0 is defined as h (see FIG. 4). In conditional expression (1), the function representing the sag amount of the aspherical shape of the reflecting surface is defined as Z(h), and the derivative obtained by first differentiating the function Z(h) with respect to the normalized light ray height h is defined as Z'(h).

[0034] -0.20 <Z’(1.0)-Z’(0.2)<0.50 ……(1) however, Z'(1.0): The first derivative of the function Z(h) when the normalized ray height h is 1.0 Z'(0.2): The first derivative of the function Z(h) when the normalized ray height h is 0.2 Let's say.

[0035] The function Z(h) representing the amount of sag of the aspherical shape is expressed, for example, by the following formula (A): The derivative Z'(h) is expressed, for example, by the following formula (B): The function Z(h) representing the amount of sag of the aspherical shape expressed by the following formula (A) is also applied to the aspherical shape of the refractive optical system 11 in the numerical examples described later.

[0036]

number

[0037]

number

[0038] However, in formula (A) and formula (B), Z: Depth of aspheric surface (amount of sag) c: Paraxial curvature = 1 / r, r is the radius of curvature h: Distance (height) from the optical axis Z1 (reference axis Za) to the lens surface or reflecting surface K: Eccentricity (second-order aspheric coefficient) Ai: ith aspherical coefficient Let's say.

[0039] Furthermore, it is desirable that the projection optical system and image display device according to one embodiment satisfy the following conditional expression (2): In conditional expression (2), the height of a light ray from a reference axis Za normalized to a maximum value of 1.0 is defined as h (see FIG. 4). In conditional expression (2), the function representing the sag amount of the aspherical shape of the reflecting surface is defined as Z(h), and the derivative obtained by first differentiating the function Z(h) with respect to the normalized height of the light ray h is defined as Z'(h).

[0040] 0.00<ΔZ'(h)max-ΔZ'(h)min<0.50 ……(2) however, ΔZ'(h)max: Maximum change in the first derivative of the function Z(h) ΔZ'(h)min: The minimum change in the first derivative of the function Z(h) Let's say.

[0041] Furthermore, it is desirable that the projection optical system and image display device according to one embodiment satisfy the following conditional expression (3): In conditional expression (3), the height of a light ray from a reference axis Za normalized to a maximum value of 1.0 is defined as h (see FIG. 4). Also, the function representing the sag amount of the aspherical shape of the reflecting surface is defined as Z(h), and the actual height of a light ray on the reflecting surface at the normalized height h is defined as R(h) (see FIG. 4).

[0042] -0.20<|Z(1.0) / R(1.0)-Z(0.2) / R(0.2)|<0.20 ……(3) however, Z(1.0): The sag of the reflecting surface when the normalized ray height h is 1.0 Z(0.2): The sag of the reflecting surface when the normalized ray height h is 1.0 R(1.0): Actual ray height at the reflecting surface when the normalized ray height h is 1.0 R(0.2): Actual ray height at the reflecting surface when the normalized ray height h is 0.2 Let's say.

[0043] Furthermore, it is desirable that the projection optical system and image display device according to one embodiment satisfy the following conditional expression (4): The emission angle of a ray emitted from a reflecting surface in conditional expression (4) is, for example, the angle of the emitted ray La or the emitted ray Lb shown in FIG. 4 relative to the reference axis Za. In FIG. 4, the emitted ray La indicates the chief ray that is closest to the reference axis Za within the effective light range of the reflecting surface. In FIG. 4, the emitted ray Lb indicates the chief ray that is farthest from the reference axis Za within the effective light range of the reflecting surface.

[0044] 1.00<θmax / θmin<1.10 ……(4) however, θmax: The maximum angle of the light ray emitted from the reflecting surface relative to the reference axis Za θmin: The minimum angle of the light ray emitted from the reflecting surface relative to the reference axis Za Let's say.

[0045] <2. Actions and Effects> Next, the operation and effects of the projection optical system and image display device according to the embodiment will be described. The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0046] In the projection optical system and image display device according to one embodiment, the shape of the reflective surface of the reflective optical system 12 is optimized, so that the angle of emergence of the light beam from the reflective surface can be made substantially constant, thereby improving image quality.

[0047] In a projection optical system and an image display device according to one embodiment, the shape of the reflective surface in a cross section including the reference axis Za of the reflective optical system 12 is gradually inclined so as to approach a right angle near the region farthest from the reference axis Za compared to the region closest to the reference axis Za. In this case, the reflective surface has a shape that approaches an acute angle from a right angle as it approaches the reference axis Za, and is optimized, for example, to have a shape similar to a cone with a pointed center that is convex toward the refractive optical system 11 at the center. Note that in the projection optical system according to one embodiment, the region of the reflective surface near the reference axis Za is outside the effective range of light. Therefore, the shape of the center of the reflective surface (the region near the reference axis Za, outside the effective range of light) is not limited to a convex shape and may be any shape.

[0048] As a result, within the effective light beam range into which image light is incident, the reflection angle of the reflective optical system 12 with respect to the incident light beam on the reflective surface is relatively large near the region closest to the reference axis Za and relatively small near the region farthest from the reference axis Za. On the other hand, the angle of the light beam emitted from the refractive optical system 11 is generally relatively small near the optical axis Z1 and relatively large as it moves away from the optical axis Z1. As a result, it is possible to make the emission angle of the light beam emitted from the reflective surface substantially constant regardless of the height of the light beam. As a result, for example, as shown in FIG. 4, it is possible to make the emission angle of the emitted light beam Lb from the region far from the optical axis Z1 on the reflective surface substantially the same as the emission angle of the emitted light beam La from the region close to the optical axis Z1 on the reflective surface.

[0049] In the projection optical system and image display device according to one embodiment, by satisfying the above conditional expressions (1) to (4), it is possible to make the emission angle of the light beam emitted from the reflecting surface substantially constant regardless of the height of the light beam.

[0050] For example, if the upper limit of conditional expressions (1) and (2) is exceeded, the reflection angle of the incident light on the reflecting surface becomes relatively too large in the region close to the reference axis Za. Also, if the lower limit of conditional expressions (1) and (2) is exceeded, the reflection angle of the incident light on the reflecting surface becomes relatively too small in the region close to the reference axis Za.

[0051] Furthermore, if the upper limit of conditional expression (3) is exceeded, the reflection angle of the incident light on the reflecting surface becomes too large relative to the area closer to the reference axis Za as the distance from the reference axis Za increases, while if the lower limit of conditional expression (3) is exceeded, the reflection angle of the incident light on the reflecting surface becomes too small relative to the area closer to the reference axis Za as the distance from the reference axis Za increases.

[0052] Furthermore, if the upper or lower limit of conditional expression (4) is exceeded, it becomes difficult to keep the angle of emergence of the light beam from the reflecting surface relative to the reference axis Za substantially constant within the effective light beam range, regardless of the height of the light beam. [Example]

[0053] <3. Numerical Examples> Next, specific numerical examples of the projection optical system and the image display device according to the embodiment of the present disclosure will be described.

[0054] [Configuration common to each embodiment] Each of the image display devices according to Examples 1 to 5 below has a configuration that satisfies the configuration of the image display device according to the above-described embodiment, and includes a screen 10, an image generation unit 20, and a projection optical system (any of projection optical systems 1 to 5). Each of the projection optical systems 1 to 5 according to Examples 1 to 5 below also has a configuration that satisfies the configuration of the projection optical system according to the above-described embodiment, and includes, in order from the image light incident side, a refractive optical system 11 and a reflective optical system 12.

[0055] The meanings of the symbols used in the following tables are as follows: "Si" indicates the number of the ith surface, with the symbols increasing sequentially from the primary image plane IP1 side. "ri" indicates the value (mm) of the paraxial radius of curvature of the ith surface. "Di" indicates the value (mm) of the distance on the optical axis between the ith surface and the (i+1)th surface. "ndi" indicates the value of the refractive index at the d-line (wavelength 587.6 nm) of the material of the optical element that makes up the ith surface. "νdi" indicates the value of the Abbe number at the d-line of the material of the optical element that makes up the ith surface. The portion where the value of "ri" is "∞" indicates a flat surface or an aperture surface.

[0056] "Type" indicates the attributes of the surface, such as an aspherical surface. "STO" indicates that it is an aperture stop St. "REF" indicates that it is a reflective surface. "ASP" indicates that the surface shape is aspherical. The aspherical shape is expressed by the above formula (A). "Sc" indicates that it is a screen 10 (projection surface). "Cy" indicates that the shape of the screen 10 is a cylindrical surface. "SP" indicates that the shape of the screen 10 is a spherical surface. "Pl" indicates that the shape of the screen 10 is flat.

[0057] In each table showing aspherical coefficients, "Ei" is an exponential notation with a base of 10, i.e., "10 -i " For example, "0.12345E-05" represents "0.12345 x 10 -5 " represents.

[0058] [Example 1] FIG. 4 shows a cross-sectional configuration of the projection optical system 1 and the image display device according to the first embodiment, together with the optical path.

[0059] Table 1 shows numerical data showing the basic configuration of the projection optical system 1 and the image display device according to Example 1. In the image display device according to Example 1, the screen 10 has a cylindrical surface shape with the reference axis Za as the axis of rotation. In the image display device according to Example 1, a prism optical system 30 is disposed between the image generation unit 20 and the refractive optical system 11.

[0060] In the projection optical system 1 according to Example 1, surfaces S13 and S14 in the refractive optical system 11 and the reflecting surface (S15) of the catoptric system 12 are aspherical. Table 2 shows the values of aspherical coefficients that indicate these aspherical shapes.

[0061] In the image display device according to Example 1, the screen 10 is disposed at a decentered and tilted position relative to the refractive optical system 11 and the reflective optical system 12. Table 3 shows detailed shape data of the screen 10 in the image display device according to Example 1, as well as data related to the decentered and tilted positions. Here, the optical axis of the screen 10 (the axis perpendicular to the screen surface (projection surface)) is defined as the Z axis. The X axis is defined as the horizontal axis of the screen surface, and the Y axis is defined as the vertical axis of the screen surface. The X axis is defined as the axis perpendicular to the paper surface of FIG. 4. The Y axis is defined as the axis parallel to the paper surface of FIG. 4 and perpendicular to the X axis. In Table 3, RDY indicates the radius of curvature in the Y axis direction, and RDX indicates the radius of curvature in the X axis direction. Furthermore, in Table 3, (XDE, YDE, ZDE) indicate data on the decentered positions (amount of decentered positions). (ADE, BDE, CDE) indicate data on the Euler angles (tilt angles). ADE refers to the amount of rotation of the screen surface from the Z axis direction to the Y axis direction around the X axis. BDE means the amount of rotation from the X-axis direction to the Z-axis direction around the Y-axis. CDE means the amount of rotation from the X-axis direction to the Y-axis direction around the Z-axis. The same applies to tables showing detailed shape data of the screen 10 and data related to eccentricity and tilt in other examples described later.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Table 3]

[0065] [Example 2] FIG. 5 shows a cross-sectional configuration of a projection optical system 2 and an image display device according to the second embodiment, together with an optical path.

[0066] Table 4 shows numerical data showing the basic configuration of the projection optical system 2 and the image display device according to Example 2. In the image display device according to Example 2, the screen 10 has a cylindrical surface shape with the reference axis Za as the axis of rotation. In the image display device according to Example 2, a prism optical system 30 is disposed between the image generation unit 20 and the refractive optical system 11.

[0067] In the projection optical system 2 according to Example 2, surfaces S14 and S15 in the refractive optical system 11 and the reflecting surface (S16) of the catoptric system 12 are aspherical. Table 5 shows the values of aspherical coefficients that indicate these aspherical shapes.

[0068] In the image display device according to Example 2, the screen 10 is disposed at a decentered and tilted position with respect to the refractive optical system 11 and the reflective optical system 12. Table 6 shows detailed shape data of the screen 10 in the image display device according to Example 2, and data related to the decentered and tilted positions.

[0069] [Table 4]

[0070] [Table 5]

[0071] [Table 6]

[0072] [Example 3] FIG. 6 shows a cross-sectional configuration of a projection optical system 3 and an image display device according to a third embodiment, together with an optical path.

[0073] Table 7 shows numerical data showing the basic configuration of the projection optical system 3 and the image display device according to Example 3. In the image display device according to Example 3, the screen 10 has a cylindrical surface shape with the reference axis Za as the axis of rotation.

[0074] In the projection optical system 3 according to Example 3, the surfaces S1, S2, S3, S4, S8, and S9 in the refractive optical system 11 and the reflecting surface (S11) in the catoptric system 12 are aspherical. Table 8 shows the values of the aspherical coefficients that indicate these aspherical shapes.

[0075] In the image display device according to Example 3, the screen 10 is disposed at a decentered and tilted position with respect to the refractive optical system 11 and the reflective optical system 12. Table 9 shows detailed shape data of the screen 10 in the image display device according to Example 3, and data related to the decentered and tilted positions.

[0076] [Table 7]

[0077] [Table 8]

[0078] [Table 9]

[0079] [Example 4] FIG. 7 shows a cross-sectional configuration of a projection optical system 4 and an image display device according to a fourth embodiment, together with an optical path.

[0080] Table 10 shows numerical data showing the basic configuration of the projection optical system 4 and the image display device according to Example 4. In the image display device according to Example 4, the screen 10 has a planar shape. In the image display device according to Example 4, a prism optical system 30 is disposed between the image generation unit 20 and the refractive optical system 11.

[0081] In the projection optical system 4 according to Example 4, surfaces S13 and S14 in the refractive optical system 11 and the reflecting surface (S15) of the catoptric system 12 are aspherical. Table 11 shows the values of the aspherical coefficients that indicate these aspherical shapes.

[0082] Table 12 shows detailed shape data and data related to decentering and tilting of the screen 10 in the image display device according to Example 4. In the image display device according to Example 4, the screen 10 is not disposed so as to be decentered or tilted relative to the refractive optical system 11 and the reflective optical system 12.

[0083] [Table 10]

[0084] [Table 11]

[0085] [Table 12]

[0086] [Example 5] FIG. 8 shows a cross-sectional configuration of a projection optical system 5 and an image display device according to a fifth embodiment, together with an optical path.

[0087] Table 13 shows numerical data showing the basic configuration of the projection optical system 5 and the image display device according to Example 5. In the image display device according to Example 5, the screen 10 has a spherical shape. In the image display device according to Example 5, a prism optical system 30 is disposed between the image generation unit 20 and the refractive optical system 11.

[0088] In the projection optical system 5 according to Example 5, surfaces S13 and S14 in the refractive optical system 11 and the reflecting surface (S15) of the catoptric system 12 are aspherical. Table 14 shows the values of the aspherical coefficients that indicate these aspherical shapes.

[0089] Table 15 shows detailed shape data and data related to decentering and tilting of the screen 10 in the image display device according to Example 5. In the image display device according to Example 5, the screen 10 is not disposed so as to be decentered or tilted relative to the refractive optical system 11 and the reflective optical system 12.

[0090] [Table 13]

[0091] [Table 14]

[0092] [Table 15]

[0093] [Other numerical data for each example and comparison with comparative examples] [Table 16] shows a summary of the values of the above-mentioned conditional expressions for each example. As can be seen from [Table 16], the projection optical system according to each example satisfies each conditional expression. [Table 17] also shows a summary of the values of the above-mentioned conditional expressions for Comparative Examples 1 and 2.

[0094] [Table 16]

[0095] [Table 17]

[0096] 9 shows the configuration of a projection optical system and an image display device, together with an optical path, according to Comparative Example 1. The projection optical system and the image display device according to Comparative Example 1 correspond to the example shown in FIGS. 21 and 22 of Patent Document 1 (JP 2002-207168 A).

[0097] 10 shows the configuration of a projection optical system and an image display device, together with an optical path, according to Comparative Example 2. The projection optical system and image display device according to Comparative Example 2 correspond to the example shown in FIGS. 28 and 29 of Patent Document 1 (JP 2002-207168 A).

[0098] The configurations of the image display devices according to the first and second comparative examples correspond to the configuration of the image display device according to the comparative example shown in FIG.

[0099] Fig. 11 shows a graph of the relationship between the normalized light ray height h and the derivative Z'(h) obtained by first differentiating the function Z(h) indicating the sag amount Z of the aspherical shape of the reflecting surface for each example and comparative example. The characteristics shown in Fig. 11 are characteristics related to the above conditional expression (1).

[0100] Fig. 12 shows a graph of the relationship between the normalized ray height h and the amount of change ΔZ'(h) in the derivative Z'(h) obtained by first differentiating the function Z(h) indicating the sag amount Z of the aspherical shape of the reflecting surface for each example and comparative example. The characteristics shown in Fig. 11 are characteristics related to conditional expression (2).

[0101] Fig. 13 shows a graph of the relationship between the normalized light ray height h and the actual light ray height R(h) and the sag amount (Z(h) / R(h)) of the aspherical shape of the reflecting surface for each example and comparative example. The characteristics shown in Fig. 13 are related to conditional expression (3).

[0102] As shown in Table 16, Table 17, and Figures 11 to 13, there are significant differences in configuration and characteristics between each Example and each Comparative Example. In the configurations of the projection optical system and image display device according to Comparative Examples 1 and 2, the exit angle of the light beam varies depending on the height of the light beam incident on the reflective surface, making it difficult to maintain a constant exit angle regardless of the height of the light beam. This makes it difficult to display a uniform image across the entire screen.

[0103] <4. Other embodiments> The technology according to the present disclosure is not limited to the above-described embodiments and examples, and various modifications are possible.

[0104] For example, the shapes and numerical values of each part shown in the above examples are merely examples of specific embodiments for implementing this technology, and the technical scope of this technology should not be interpreted in a limited manner based on these.

[0105] For example, the present technology can be configured as follows. According to the present technology having the following configuration, the shape of the reflecting surface of the reflective optical system is optimized so that the angle of emission of light rays from the reflecting surface is approximately constant, thereby making it possible to improve image quality.

[0106] [1] a refractive optical system having a positive refractive power as a whole and disposed at a position where image light from a primary image surface is incident, with a reference axis as a reference; a reflective optical system having a reflecting surface that reflects the image light emitted from the refractive optical system toward a projection surface that forms a secondary image surface, wherein the shape of the reflecting surface is a rotationally symmetric aspherical shape having a sag amount in the opposite direction to the refractive optical system with the reference axis as the rotation axis within an effective light ray range into which the image light is incident, and wherein the shape of the reflecting surface in a cross section including the reference axis is inclined so as to approach a right angle in a region farthest from the reference axis compared to a region closest to the reference axis; Equipped with Projection optical system. [2] The reflection optical system is configured so that, within the effective light beam range into which the image light is incident, the reflection angle of the incident light beam on the reflection surface is relatively large in an area closest to the reference axis and relatively small in an area farthest from the reference axis. The projection optical system according to [1] above. [3] When the ray height from the reference axis normalized to a maximum value of 1.0 is h, a function representing the sag amount of the aspherical shape of the reflecting surface is Z(h), and a derivative obtained by first differentiating the function Z(h) with respect to the normalized ray height h is Z'(h), the following conditional expression is satisfied: The projection optical system according to the above [1] or [2]. -0.20 <Z’(1.0)-Z’(0.2)<0.50 ……(1) however, Z'(1.0): The first derivative of the function Z(h) when the normalized ray height h is 1.0 Z'(0.2): The first derivative of the function Z(h) when the normalized ray height h is 0.2 Let's say. [4] When the ray height from the reference axis normalized to a maximum value of 1.0 is h, a function representing the sag amount of the aspherical shape of the reflecting surface is Z(h), and a derivative obtained by first differentiating the function Z(h) with respect to the normalized ray height h is Z'(h), the following conditional expression is satisfied: The projection optical system according to any one of [1] to [3] above. 0.00<ΔZ'(h)max-ΔZ'(h)min<0.50 ……(2) however, ΔZ'(h)max: the maximum value of the change in the first derivative of the function Z(h) ΔZ'(h)min: The minimum value of the change in the first derivative of the function Z(h) Let's say. [5] When the ray height from the reference axis normalized to a maximum value of 1.0 is h, a function representing the sag amount of the aspherical shape of the reflecting surface is Z(h), and the actual ray height on the reflecting surface at the normalized ray height h is R(h), the following conditional expression is satisfied: The projection optical system according to any one of [1] to [4] above. -0.20<|Z(1.0) / R(1.0)-Z(0.2) / R(0.2)|<0.20 ……(3) however, Z(1.0): The sag amount of the reflecting surface when the normalized ray height h is 1.0 Z(0.2): The sag amount of the reflecting surface when the normalized ray height h is 1.0 R(1.0): The actual ray height at the reflecting surface when the normalized ray height h is 1.0 R(0.2): The actual ray height on the reflecting surface when the normalized ray height h is 0.2 Let's say. [6] The following condition is satisfied: The projection optical system according to any one of [1] to [5] above. 1.00<θmax / θmin<1.10 ……(4) however, θmax: the maximum value of the angle of the light ray emitted from the reflecting surface relative to the reference axis θmin: The minimum angle of the light ray emitted from the reflecting surface relative to the reference axis Let's say. [7] The projection surface has a shape of a body of revolution with the reference axis as a rotation axis. The projection optical system according to any one of [1] to [6] above. [8] The projection surface has a cylindrical shape. The projection optical system according to [7] above. [9] The projection surface is flat. The projection optical system according to any one of [1] to [6] above.

[10] The projection surface is spherical. The projection optical system according to any one of [1] to [6] above.

[11] an image generating unit that forms a primary image plane; a projection optical system onto which image light from the primary image plane is incident; Including, The projection optical system includes: a refractive optical system having a positive refractive power as a whole and disposed at a position where the image light from the primary image surface is incident, with a reference axis as a reference; a reflective optical system having a reflecting surface that reflects the image light emitted from the refractive optical system toward a projection surface that forms a secondary image surface, wherein the shape of the reflecting surface is a rotationally symmetric aspherical shape having a sag amount in the opposite direction to the refractive optical system with the reference axis as the rotation axis within an effective light ray range into which the image light is incident, and wherein the shape of the reflecting surface in a cross section including the reference axis is inclined so as to approach a right angle in a region farthest from the reference axis compared to a region closest to the reference axis; Equipped with Image display device.

[0107] This application claims priority based on Japanese Patent Application No. 2019-188725, filed on October 15, 2019, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0108] Those skilled in the art will recognize that various modifications, combinations, subcombinations, and variations may occur depending on design requirements and other factors, and are intended to be within the scope of the appended claims and their equivalents.

Claims

1. a refractive optical system having a positive refractive power as a whole and disposed at a position where image light from a primary image surface is incident, with a reference axis as a reference; a reflective optical system having a reflecting surface that reflects the image light emitted from the refractive optical system toward a projection surface that forms a secondary image surface, wherein the shape of the reflecting surface is a rotationally symmetric aspherical shape having a sag amount in the opposite direction to the refractive optical system with the reference axis as the rotation axis within an effective light ray range into which the image light is incident, and wherein the shape of the reflecting surface in a cross section including the reference axis is inclined so as to approach a right angle in a region farthest from the reference axis compared to a region closest to the reference axis; Equipped with The reflection optical system is configured so that, within the effective light beam range into which the image light is incident, the reflection angle of the incident light beam on the reflection surface is relatively large in an area closest to the reference axis and relatively small in an area farthest from the reference axis, and so that the emission angle of the light beam emitted from the reflection surface is constant regardless of the light beam height. Projection optical system.

2. When the ray height from the reference axis normalized to a maximum value of 1.0 is h, a function representing the sag amount of the aspherical shape of the reflecting surface is Z(h), and a derivative obtained by first differentiating the function Z(h) with respect to the normalized ray height h is Z'(h), the following conditional expression is satisfied: The projection optical system according to claim 1 . -0.20<Z'(1.0)-Z'(0.2)<0.50...(1) however, Z'(1.0): the first derivative of the function Z(h) when the normalized ray height h is 1.0 Z'(0.2): the first derivative of the function Z(h) when the normalized light ray height h is 0.2 Let's say.

3. When the ray height from the reference axis normalized to a maximum value of 1.0 is h, a function representing the sag amount of the aspherical shape of the reflecting surface is Z(h), and a derivative obtained by first differentiating the function Z(h) with respect to the normalized ray height h is Z'(h), the following conditional expression is satisfied: The projection optical system according to claim 1 . 0.00<ΔZ'(h)max-ΔZ'(h)min<0.50...(2) however, ΔZ′(h)max: the maximum value of the change in the first derivative of the function Z(h) ΔZ′(h)min: the minimum value of the change in the first derivative of the function Z(h) Let's say.

4. When the ray height from the reference axis normalized to a maximum value of 1.0 is h, a function representing the sag amount of the aspherical shape of the reflecting surface is Z(h), and the actual ray height on the reflecting surface at the normalized ray height h is R(h), the following conditional expression is satisfied: The projection optical system according to claim 1 . -0.20<|Z(1.0) / R(1.0)-Z(0.2) / R(0.2)|<0.20...(3) however, Z(1.0): The sag amount of the reflecting surface when the normalized light ray height h is 1.0 Z(0.2): The sag amount of the reflecting surface when the normalized light ray height h is 1.0 R(1.0): The actual ray height on the reflecting surface when the normalized ray height h is 1.0 R(0.2): Actual ray height on the reflecting surface when the normalized ray height h is 0.2 Let's say.

5. The following condition is satisfied: The projection optical system according to claim 1 . 1.00<θmax / θmin<1.10...(4) however, θmax: the maximum value of the angle of the light ray emitted from the reflecting surface relative to the reference axis θmin: the minimum angle of the light ray emitted from the reflecting surface relative to the reference axis Let's say.

6. The projection surface has a shape of a body of revolution with the reference axis as a rotation axis. The projection optical system according to claim 1 .

7. The projection surface has a cylindrical shape.

7. The projection optical system according to claim 6.

8. The projection surface is flat. The projection optical system according to claim 1 .

9. The projection surface is spherical. The projection optical system according to claim 1 .

10. an image generating unit that forms a primary image plane; a projection optical system onto which image light from the primary image plane is incident; Including, The projection optical system includes: a refractive optical system having a positive refractive power as a whole and disposed at a position where the image light from the primary image surface is incident, with a reference axis as a reference; a reflective optical system having a reflecting surface that reflects the image light emitted from the refractive optical system toward a projection surface that forms a secondary image surface, wherein the shape of the reflecting surface is a rotationally symmetric aspherical shape having a sag amount in the opposite direction to the refractive optical system with the reference axis as the rotation axis within an effective light ray range into which the image light is incident, and wherein the shape of the reflecting surface in a cross section including the reference axis is inclined so as to approach a right angle in a region farthest from the reference axis compared to a region closest to the reference axis; Equipped with The reflection optical system is configured so that, within the effective light beam range into which the image light is incident, the reflection angle of the incident light beam on the reflection surface is relatively large in an area closest to the reference axis and relatively small in an area farthest from the reference axis, and so that the emission angle of the light beam emitted from the reflection surface is constant regardless of the light beam height. Image display device.

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