Micro projector optical system and spectacle type terminal

Abstract

To emit image light with a sufficient visual field (FOV) view angle by a simple configuration in an optical system for composing a micro projector.SOLUTION: A micro projector optical system has a first lens group, a second lens group, a third lens group, and a fourth lens group having a positive refractive index. The configuration of the first lens group and the second lens group is symmetrical to the configuration of the third lens group and the fourth lens group relative to a surface between the second lens group and the third lens group. A first lens surface on a side of the furthest display surface of the first lens group is a convex face projecting toward the display surface. A radius of curvature R1 of the first lens surface and a radius of curvature R2 of the second lens surface on the furthest input side of the first lens group satisfy a predetermined formula. A focal length f2 of the second lens group and a radius of curvature R3 of the third lens surface on the furthest display side of the second lens group satisfy a predetermined formula.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a microprojector optical system and an eyeglass-type terminal. [Background technology]

[0002] BACKGROUND ART Conventionally, there are known eyeglass-type devices, head-mounted displays, and the like that incorporate an optical system having a plurality of lenses and display two-dimensional images or the like for a user to observe (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-182078 [Patent Document 2] Patent No. 6257171 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-145834 [Patent Document 4] Japanese Patent Application Publication No. 2018-10217 Summary of the Invention [Problem to be solved by the invention]

[0004] Such devices often have a complex optical system because they are built into a limited space, and a simple optical system can result in an inability to project an image onto the display area sufficiently, or can cause distortion in the displayed image.

[0005] The present invention has been made in consideration of these points, and aims to provide an optical system for constituting a microprojector that can emit image light with a sufficient field of view (FOV) angle with a simple configuration. [Means for solving the problem]

[0006] In a first aspect of the present invention, there is provided a microprojector optical system for displaying input image light on a display surface, the microprojector optical system comprising, from the display surface side, a first lens group, a second lens group, a third lens group, and a fourth lens group, the first lens group, the second lens group, the third lens group, and the fourth lens group each having a positive refractive index, a configuration of the first lens group and the second lens group and a configuration of the third lens group and the fourth lens group are symmetrical with respect to a plane perpendicular to a line connecting a position of a center of gravity of the second lens group and a position of a center of gravity of the third lens group between the second lens group and the third lens group, a first lens surface of the first lens group closest to the display surface is a convex surface that protrudes toward the display surface, and when a radius of curvature of the first lens surface is R1 and a radius of curvature of a second lens surface of the first lens group closest to an input side is R2, the first lens group satisfies the following formula: JPEG2025161930000002.jpg1277 When the focal length of the second lens group is f2 and the radius of curvature of the third lens surface of the second lens group that is closest to the display surface is R3, the second lens group and the third lens group satisfy the following formula: JPEG2025161930000003.jpg1788 Micro projector optical system.

[0007] When the total focal length of the first lens group, the second lens group, the third lens group, and the fourth lens group is represented by f, the first lens group and the focal length f may satisfy the following formula. JPEG2025161930000004.jpg1678

[0008] The total focal length f of the first lens group, the second lens group, the third lens group, and the fourth lens group may further satisfy the following formula: JPEG2025161930000005.jpg673

[0009] The first lens group and the focal length f may further satisfy the following formula: JPEG2025161930000006.jpg1975

[0010] When the focal length of the first lens group is f1, the first lens group and the second lens group may satisfy the following formula: JPEG2025161930000007.jpg1678

[0011] When the Abbe number of the medium of the lens in the first lens group closest to the display surface side is ν1, the Abbe number ν1 may satisfy the following formula. JPEG2025161930000008.jpg773

[0012] If the average refractive index of the material of the lenses in the second lens group is Nd2, the refractive index Nd2 may satisfy the following formula: JPEG2025161930000009.jpg775

[0013] If the average refractive index of the material of the lenses in the first lens group is Nd1, the refractive index Nd1 may satisfy the following formula: JPEG2025161930000010.jpg776

[0014] At least one of the first lens group and the second lens group may include a cemented lens. The lens of the first lens group closest to the display surface may have a meniscus shape that protrudes toward the display surface.

[0015] In a second aspect of the present invention, there is provided a glasses-type terminal worn by a user, comprising: a display surface provided on at least one of a lens for the user's right eye and a lens for the user's left eye, which displays the image light so that the user can see it; a frame for fixing the lens for the user's right eye and the lens for the left eye; an image light emitting unit provided on the frame, which emits the image light; and the microprojector optical system of the first aspect, which is provided on the frame, into which the image light emitted from the image light emitting unit is input and which displays the input image light on the display surface. [Effects of the Invention]

[0016] According to the present invention, an optical system for configuring a microprojector has an effect of being able to emit image light with a sufficient viewing angle with a simple configuration. [Brief explanation of the drawings]

[0017] [Figure 1] 1 shows an example of the configuration of an eyeglass-type terminal 10 according to this embodiment. [Figure 2] 1 shows an example of the configuration of a microprojector optical system 100 according to this embodiment. [Figure 3] An example of design values ​​for the microprojector optical system 100 according to this embodiment is shown below. [Figure 4] An example of parameters of the four lens groups corresponding to the design values ​​shown in FIG. 3 is shown below. [Figure 5] 1 shows an example of astigmatism in the microprojector optical system 100 according to this embodiment. [Figure 6] 1 shows an example of distortion of the microprojector optical system 100 according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] <Configuration example of eyeglass-type terminal 10> FIG. 1 shows an example of the configuration of an eyeglass-type terminal 10 according to this embodiment. The eyeglass-type terminal 10 is, for example, a wearable device worn by a user. The eyeglass-type terminal 10 projects image light onto a display surface provided on the lenses of the eyeglasses while allowing the user to observe a scene through the eyeglasses. The eyeglass-type terminal 10 includes a display surface 20, a frame 30, an image light emitting unit 40, and a microprojector optical system 100.

[0019] The display surface 20 is provided on at least one of the lens for the right eye and the lens for the left eye of the user. The display surface 20 displays image light irradiated from the microprojector optical system 100 so that it can be viewed by the user. The display surface 20 is provided, for example, on the second surface of the lens, and projects the image light onto the second surface while transmitting at least a portion of the light incident from the first surface of the lens to the user's eye. Here, the first surface of the lens is the surface of the lens that faces away from the user when the eyeglass-type terminal 10 is worn by the user. The display surface 20 may be a partial area of ​​the second surface of the lens, or alternatively, it may be substantially the entire area of ​​the second surface of the lens.

[0020] The frame 30 fixes lenses. For example, the frame 30 fixes a lens for the user's right eye and a lens for the user's left eye. Alternatively, the frame 30 may be provided with one lens for both eyes of the user. In this case, the frame 30 may have a goggle shape. The frame 30 has parts such as temples and a strap so that the user can wear the eyeglass-type terminal 10.

[0021] The image light emitting unit 40 is provided on the frame 30 and emits image light for projecting the image light onto the display surface 20. One or more such image light emitting units 40 are provided on the frame 30. Fig. 1 shows an example in which the frame 30 is provided with an image light emitting unit 40a for displaying image light L1 on the display surface 20a and an image light emitting unit 40b for displaying image light L2 on the display surface 20b.

[0022] The image light output unit 40 may be provided in a portion of the frame 30 where the lenses are fixed, or may be provided in a temple or the like of the frame 30. It is desirable that the image light output unit 40 is provided so as to be integrated with the frame 30. The image light output unit 40 may have, for example, a liquid crystal or the like, and the image to be displayed on the display surface 20 may be displayed on the liquid crystal.

[0023] The micro-projector optical system 100 is provided on the frame 30, receives the image light emitted from the image light emitting unit 40, and displays the input image light on the display surface 20. The micro-projector optical system 100 has a plurality of lenses, expands the field of view angle of the input image light, and outputs it toward the display surface 20. Note that the image light output from the micro-projector optical system 100 may be irradiated onto the display surface 20 via a mirror or the like. FIG. 1 shows an example in which a micro-projector optical system 100a corresponding to the image light emitting unit 40a and a micro-projector optical system 100b corresponding to the image light emitting unit 40b are provided on the frame 30.

[0024] The eyeglass-type terminal 10 described above has an optical system that is built into a limited space, which can result in a complex optical system. Furthermore, a simple optical system can result in insufficient projection of image light onto the display surface 20, or distortion of the displayed image. Therefore, the microprojector optical system 100 according to this embodiment provides a large field of view of, for example, about 60 degrees with a simple optical system, while reducing distortion. Such a microprojector optical system 100 will now be described.

[0025] <Configuration example of microprojector optical system 100> FIG. 2 shows an example of the configuration of the micro-projector optical system 100 according to this embodiment. In this embodiment, the axis approximately parallel to the optical axis is the X-axis. The direction in which image light enters the micro-projector optical system 100 and the direction in which the micro-projector optical system 100 outputs image light are the +X direction. Three mutually orthogonal axes are the X-axis, Y-axis, and Z-axis. An image light output unit 40 is shown on the input side of the micro-projector optical system 100.

[0026] The microprojector optical system 100 includes, from the display surface 20 side, a first lens group 110, a second lens group 120, a third lens group 130, and a fourth lens group 140. Here, a "lens group" refers to one or more lenses. FIG. 2 shows an example in which the first lens group 110, the second lens group 120, the third lens group 130, and the fourth lens group 140 each consist of a single lens, and the microprojector optical system 100 is configured with a total of four lenses. In this embodiment, the "display surface 20 side" refers to the eyepoint side of the eyepiece, and the "input side" refers to the object side of the eyepiece.

[0027] The first lens group 110, the second lens group 120, the third lens group 130, and the fourth lens group 140 have positive refractive indexes. The first lens group 110, the second lens group 120, the third lens group 130, and the fourth lens group 140 are fixed to a main body (not shown) of the microprojector optical system 100. It is desirable that the first lens group 110, the second lens group 120, the third lens group 130, and the fourth lens group 140 be provided so as to be movable in the optical axis direction.

[0028] For example, the main body of microprojector optical system 100 is configured so that a user can manually adjust the positions of first lens group 110, second lens group 120, third lens group 130, and fourth lens group 140. Alternatively, microprojector optical system 100 may further include an actuator or the like that moves each lens group individually.

[0029] When moving multiple lens groups, for example, if only one of the lens groups has a positive refractive index, the magnitude of the refractive index fluctuates significantly, which increases the aberration occurring in the image light output from the microprojector optical system 100, making it difficult to correct the aberration.

[0030] In contrast, when two lens groups with positive refractive indexes are moved, the fluctuation in the magnitude of the refractive index is smaller than when only one lens group has a positive refractive index, and the aberration generated in the image light can be reduced. Therefore, when changing the magnification, the microprojector optical system 100 of this embodiment moves, for example, the second lens group 120 and the third lens group 130 in the optical axis direction. This allows the microprojector optical system 100 to change the magnification while reducing the deterioration of aberration.

[0031] In particular, it is preferable that the microprojector optical system 100 is configured so that the second lens group 120 and the third lens group 130 move in the same direction. This reduces the space required for changing the magnification. Furthermore, the microprojector optical system 100 can reduce fluctuations in coma aberration when changing the magnification.

[0032] The microprojector optical system 100 may be configured to move the first lens group 110 and the second lens group 120 in the same direction, which allows the magnification and other parameters of the microprojector optical system 100 to be changed while keeping the diopter of the microprojector optical system 100 approximately constant.

[0033] 2, the surface of first lens group 110 facing in the +X direction is referred to as first lens surface 111, and the surface facing in the -X direction is referred to as second lens surface 112. Similarly, the surface of second lens group 120 facing in the +X direction is referred to as third lens surface 121, and the surface facing in the -X direction is referred to as fourth lens surface 122. Furthermore, the surface of third lens group 130 facing in the +X direction is referred to as fifth lens surface 131, and the surface facing in the -X direction is referred to as sixth lens surface 132. Furthermore, the surface of fourth lens group 140 facing in the +X direction is referred to as seventh lens surface 141, and the surface facing in the -X direction is referred to as eighth lens surface 142.

[0034] The first lens group 110, the second lens group 120, the third lens group 130, and the fourth lens group 140 have positive refractive indices. The configurations of the first lens group 110 and the second lens group 120 and the configurations of the third lens group 130 and the fourth lens group 140 are symmetrical with respect to a reference plane that is orthogonal to a line connecting the center of gravity of the second lens group 120 and the center of gravity of the third lens group 130 between the second lens group 120 and the third lens group 130. In Figure 2, the reference plane is a plane perpendicular to the optical axis and approximately parallel to the YZ plane.

[0035] First lens surface 111 of first lens group 110, which is closest to display surface 20, is a convex surface that protrudes toward display surface 20. Similarly, eighth lens surface 142 of fourth lens group 140, which is closest to image light output section 40, is a convex surface that protrudes toward image light output section 40. By making first lens surface 111, which is closest to display surface 20, convex toward display surface 20, when the angle of view of the user's field of view is increased, the deviation angle of light rays with a large angle of view can be reduced, and spherical aberration, astigmatism, field curvature, coma aberration, etc. can be reduced.

[0036] Then, when the radius of curvature of first lens surface 111 is R1 and the radius of curvature of second lens surface 112 on the most input side of first lens group 110 is R2, first lens group 110 satisfies the following equation.

number

[0037] Furthermore, if the focal length of second lens group 120 is f2 and the radius of curvature of third lens surface 121 of second lens group 120 closest to display surface 20 is R3, second lens group 120 and third lens group 130 satisfy the following equation.

number

[0038] Microprojector optical system 100 can have a large field of view angle of about 60 degrees by having first lens group 110, second lens group 120, third lens group 130, and fourth lens group 140 satisfy equations (1) and (2). When second lens group 120 and third lens group 130 satisfy equation (2) and third lens surface 121 of second lens group 120 closest to display surface 20 and fourth lens surface 122 of second lens group 120 closest to input side are biconvex, field curvature, astigmatism, coma, etc. can be effectively corrected and reduced. Furthermore, by having the lens of third lens group 130 closest to display surface 20 satisfy equation (2), the deflection angle of light irradiating display surface 20 can be minimized.

[0039] Furthermore, if the overall focal length of the first lens group 110, the second lens group 120, the third lens group 130, and the fourth lens group 140 is f, it is desirable that the first lens group 110 and the focal length f satisfy the following equation.

number

[0040] The overall focal length f of the microprojector optical system 100 is significantly affected by the radius of curvature R1 of the first lens surface 111 of the first lens group 110, and also by optical characteristics such as astigmatism and coma. Therefore, equation (3) is a conditional equation for correcting astigmatism, coma, and the like when the diopter of the microprojector optical system 100 is set to a wide angle such as 60 degrees. For example, if the right-hand side of equation (3) falls below the lower limit of the left-hand side, the deviation angle of light rays with a large angle of view increases, which undesirably worsens astigmatism and coma, resulting in a decrease in perceived resolution.

[0041] In the microprojector optical system 100, when the focal length of the first lens group is f1, it is desirable that the first lens group 110 and the second lens group 120 satisfy the following formula.

number

[0042] The spherical aberration, field curvature, etc. of the microprojector optical system 100 are greatly affected by the focal length f1 of the first lens group 110 and the focal length f2 of the second lens group 120. Therefore, equation (4) is a conditional equation for suppressing the occurrence of spherical aberration, field curvature, etc. of the microprojector optical system 100.

[0043] For example, if f1 / f2 falls below the lower limit of the left side of equation 4, the refractive index of the first lens group 110 at the focal length f1 becomes relatively strong, resulting in significant distortion and curvature of field. Also, if f1 / f2 exceeds the upper limit of the right side of equation 4, the refractive index of the second lens group 120 at the focal length f2 becomes relatively strong, which is undesirable because moving the lens groups to change magnification causes significant spherical aberration.

[0044] In the microprojector optical system 100, when the Abbe number for the d-line of the medium of the lens of the first lens group 110 closest to the display surface 20 is v1, it is desirable that the Abbe number v1 satisfies the following formula.

number

[0045] The axial chromatic aberration, lateral chromatic aberration, etc. of microprojector optical system 100 are greatly affected by the medium of the lens closest to display surface 20. Therefore, equation (5) is a conditional expression for suppressing the occurrence of axial chromatic aberration, lateral chromatic aberration, etc. of microprojector optical system 100. For example, if the lens surface closest to display surface 20 (first lens surface 111) is convex, it is undesirable for the left side of equation (5) to exceed the upper limit of the right side, since this will increase the axial chromatic aberration and lateral chromatic aberration.

[0046] Moreover, it is desirable that the overall focal length f of the first lens group 110, the second lens group 120, the third lens group 130, and the fourth lens group 140 satisfy the following formula:

number

[0047] The value of the left side of equation (6) may be 3.00 or more. Such a microprojector optical system 100 can have sufficient aberration correction capability. For example, when image light formed by an LED or the like is irradiated onto the display surface 20, a user wearing the eyeglass-type terminal 10 can observe an image with reduced aberration.

[0048] Furthermore, it is desirable that the focal length f of the first lens group 110 and the entire first lens group 110, second lens group 120, third lens group 130, and fourth lens group 140 satisfy the following formula.

number

[0049] In the microprojector optical system 100 according to this embodiment, it is desirable that each of the lens groups be made of a material whose refractive index at the d-line is higher than 1.50. This makes it easier for the microprojector optical system 100 to achieve a wide field of view. Furthermore, by including a material with a high refractive index in each lens group, the curvature can be made gentler, and the spacing between the lens groups, which is necessary for achieving a high zoom ratio, can be made smaller.

[0050] By using a high refractive index material for the first lens group 110, which is closest to the display surface 20, the spacing between the lens groups required for achieving high zoom ratios can be reduced. Furthermore, by using a high refractive index material for the lenses, the magnitude of various lens aberrations can be reduced. For example, by using high refractive index lenses for the first lens group 110 and the second lens group 120, astigmatism, field curvature, and the like can be reduced.

[0051] For example, if the average refractive index of the material of the lenses of the first lens group 110 is Nd1, it is desirable that the refractive index Nd1 satisfy the following formula.

number

[0052] Furthermore, if the average refractive index of the material of the lenses of the second lens group 120 is Nd2, it is desirable that the refractive index Nd2 satisfy the following formula.

number

[0053] In the microprojector optical system 100 according to this embodiment, it is desirable that at least one of the first lens group 110 and the second lens group 120 includes a cemented lens. A cemented lens combines multiple lenses, and therefore can effectively correct chromatic aberration that occurs in a single lens. Furthermore, by using such a cemented lens in a movable lens group, such as the first lens group 110 or the second lens group 120, it is possible to reduce an increase in aberration that accompanies lens movement.

[0054] In addition, in such a cemented lens, the lens in the first lens group 110 closest to the display surface 20 preferably has a meniscus shape that protrudes toward the display surface 20. By using a meniscus cemented lens as the lens in the first lens group closest to the display surface 20, the deviation angle of off-axial light in the microprojector optical system 100 can be reduced, and coma aberration correction can be reduced.

[0055] Such a cemented lens may be used as the lens closest to the input side of the fourth lens group. In this case, it is desirable that the cemented lens has a meniscus shape that protrudes toward the input side. By using a meniscus cemented lens as the lens closest to the input side of the fourth lens group, it is possible to reduce distortion aberration of the microprojector optical system 100.

[0056] <Design example of microprojector optical system 100> The micro-projector optical system 100 according to this embodiment can emit image light with a sufficient field of view angle with a simple configuration. Fig. 3 shows an example of design values ​​for the micro-projector optical system 100 according to this embodiment. Fig. 4 shows an example of parameters of the four lens groups corresponding to the design values ​​shown in Fig. 3.

[0057] The applicants have confirmed through simulations that a large field of view angle, such as 60 degrees, can be achieved with low distortion by using the design values ​​shown in Figures 3 and 4. The applicants have discovered that such a large field of view angle can be achieved by setting the optical characteristics within the range of equations (1) to (9). For example, the eyepieces shown in Patent Documents 2 to 4 have optical characteristics that are not within the range of equations (1) to (9), and therefore cannot achieve a large field of view angle such as 60 degrees.

[0058] <Example of Simulation Results of Microprojector Optical System 100> FIG. 5 shows an example of astigmatism of the micro-projector optical system 100 according to this embodiment. FIG. 6 shows an example of distortion of the micro-projector optical system 100 according to this embodiment. FIGS. 5 and 6 show simulation results when the diopter of the micro-projector optical system 100 is −1 [ / m] using the design values ​​of FIGS. 3 and 4. The “first light ray,” “second light ray,” and “third light ray” shown in FIGS. 5 and 6 correspond to the “first light ray,” “second light ray,” and “third light ray” shown in FIG. 2. FIGS. 5 and 6 show that the micro-projector optical system 100 can achieve a large field of view angle of 60 degrees with low distortion.

[0059] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments. [Explanation of symbols]

[0060] 10 Eyeglass-type terminal 20 Display surface 30 frames 40 Image light emitting unit 100 Microprojector optical system 110 First lens group 111 First lens surface 112 Second lens surface 120 Second lens group 121 Third lens surface 122 Fourth lens surface 130 Third lens group 131 5th lens surface 132 6th lens surface 140 4th lens group 141 7th lens surface 142 8th lens surface

Claims

1. A microprojector optical system for displaying input image light on a display surface, comprising: The optical system includes, from the display surface side, a first lens group, a second lens group, a third lens group, and a fourth lens group, the first lens group, the second lens group, the third lens group, and the fourth lens group have positive refractive indices; a configuration of the first lens group and the second lens group and a configuration of the third lens group and the fourth lens group are symmetrical with respect to a plane orthogonal to a line connecting a center of gravity of the second lens group and a center of gravity of the third lens group between the second lens group and the third lens group, a first lens surface of the first lens group closest to the display surface side is a convex surface that protrudes toward the display surface, When the radius of curvature of the first lens surface is R1 and the radius of curvature of the second lens surface closest to the input side of the first lens group is R2, the first lens group satisfies the following formula: When a focal length of the second lens group is f2 and a radius of curvature of a third lens surface of the second lens group that is closest to the display surface side is R3, the second lens group and the third lens group satisfy the following formula: Microprojector optics.

2. When the total focal length of the first lens group, the second lens group, the third lens group, and the fourth lens group is f, the first lens group and the focal length f satisfy the following formula: The microprojector optical system of claim 1 .

3. The total focal length f of the first lens group, the second lens group, the third lens group, and the fourth lens group further satisfies the following formula: The microprojector optical system according to claim 2 .

4. The first lens group and the focal length f further satisfy the following equation:

4. The microprojector optical system according to claim 2 or 3.

5. When the focal length of the first lens group is f1, the first lens group and the second lens group satisfy the following formula:

5. The microprojector optical system according to claim 1.

6. When the Abbe number of the medium of the lens closest to the display surface in the first lens group is ν1, the Abbe number ν1 satisfies the following formula: The microprojector optical system according to any one of claims 1 to 5.

7. If the average refractive index of the material of the lenses in the second lens group is Nd2, the refractive index Nd2 satisfies the following formula:

7. The microprojector optical system according to claim 1.

8. If the average refractive index of the material of the lenses in the first lens group is Nd1, the refractive index Nd1 satisfies the following formula: The microprojector optical system according to any one of claims 1 to 7.

9. The microprojector optical system according to claim 1 , wherein at least one of the first lens group and the second lens group includes a cemented lens.

10. 10. The microprojector optical system according to claim 1, wherein the lens of the first lens group closest to the display surface has a meniscus shape that protrudes toward the display surface.

11. A glasses-type terminal worn by a user, a display surface provided on at least one of a lens for a right eye and a lens for a left eye of the user, the display surface displaying the image light so as to be visible to the user; a frame for fixing a lens for the right eye and a lens for the left eye of the user; an image light emitting section provided on the frame and emitting the image light; the microprojector optical system according to any one of claims 1 to 10, which is provided on the frame, receives the image light emitted from the image light emitting portion, and displays the input image light on the display surface; A glasses-type terminal comprising:

Images