JP7427430B2 - Observation optics and optical equipment - Google Patents

Description

The present invention relates to an observation optical system that enables observation of an optical image of an original image, and relates to an observation optical system suitable for a head-mounted display (HMD), an electronic viewfinder (EVF), and the like.

The above-mentioned observation optical system is provided with a diopter adjustment function to adjust the diopter to an observer who is nearsighted or farsighted. Furthermore, in order to miniaturize the optical equipment equipped with the observation optical system, it is necessary to miniaturize the observation optical system. Patent Document 1 discloses an observation optical system using two semi-transparent surfaces.

Patent No. 3441188

Although there is no explanation about diopter adjustment in Patent Document 1, it is possible to adjust the diopter by moving the entire observation optical system. However, moving the entire observation optical system causes field curvature (curvature of the observation virtual image plane), which is difficult to correct.

The present invention provides an observation optical system that uses two semi-transmissive surfaces and is small in size yet less prone to field curvature during diopter adjustment.

An observation optical system as one aspect of the present invention enables observation of an optical image of an original image displayed on a display surface from a pupil plane. The observation optical system includes a first lens group having a first semi-transparent surface and a second semi-transmissive surface arranged in order from the pupil surface side to the display surface side, and a first lens group having at least one positive lens. It has two lens groups. The diopter can be adjusted by fixing the second lens group to the display surface and moving the first lens group in the optical axis direction , and the lens closest to the display surface in the observation optical system The distance from the surface to the display surface is skd, the focal length of the entire observation optical system is f, and the optical axis of the first lens group and the second lens group when the diopter of the observation optical system is 0D. When the upper interval is DFR and the focal length of the first lens group is fF,
0.01≦skd/f≦0.23
0.08≦DFR/fF≦0.50
It is characterized by satisfying the following conditions . Note that an optical instrument having this observation optical system also constitutes another aspect of the present invention.

According to the present invention, by using two semi-transparent surfaces, it is possible to realize a compact observation optical system in which field curvature is less likely to occur during diopter adjustment.

FIG. 3 is a cross-sectional view of the observation optical system of Example 1. FIG. 2 is a longitudinal aberration diagram of the observation optical system of Example 1 (pupil diameter Φ3.5 mm, eye relief 18 mm, diopter 0D). FIG. 2 is a longitudinal aberration diagram of the observation optical system of Example 1 (pupil diameter Φ3.5 mm, eye relief 18 mm, diopter -4D). FIG. 3 is a cross-sectional view of the observation optical system of Example 2. A longitudinal aberration diagram of the observation optical system of Example 2 (pupil diameter Φ3.5 mm, eye relief 18 mm, diopter 0D). A longitudinal aberration diagram of the observation optical system of Example 2 (pupil diameter Φ3.5 mm, eye relief 18 mm, diopter -4D). FIG. 3 is a cross-sectional view of the observation optical system of Example 3. A longitudinal aberration diagram of the observation optical system of Example 3 (pupil diameter Φ3.5 mm, eye relief 18 mm, diopter 0D). FIG. 3 is a longitudinal aberration diagram of the observation optical system of Example 3 (pupil diameter Φ3.5 mm, eye relief 18 mm, diopter -4D). FIG. 4 is a cross-sectional view of the observation optical system of Example 4. A longitudinal aberration diagram of the observation optical system of Example 4 (pupil diameter Φ3.5 mm, eye relief 18 mm, diopter 0D). A longitudinal aberration diagram of the observation optical system of Example 4 (pupil diameter Φ3.5 mm, eye relief 18 mm, diopter -4D). A diagram illustrating an observation optical system using polarized light. FIG. 7 is a diagram showing an optical device of Example 5.

Embodiments of the present invention will be described below with reference to the drawings. 1, 4, 7, and 10 are cross-sectional views of observation optical systems of Examples 1 to 4 of the present invention.

As shown in FIGS. 1, 4, 7, and 10, the observation optical system of each embodiment is capable of observing an optical image of the display surface ID on which the original image is displayed from the pupil plane SP where the exit pupil is located. do. The original image is an image displayed on an image display element (light modulation element) such as a liquid crystal display element or an organic EL element.

The observation optical system of each embodiment includes a first lens group (hereinafter referred to as diopter LF (referred to as an adjustment lens group) and a second lens group (hereinafter referred to as a subsequent lens group LR) having at least one positive lens. An observer whose eyes are placed on the pupil plane SP can observe an optical image (virtual image) of the original image enlarged by the observation optical system. A light amount diaphragm may be arranged on the pupil plane SP.

Furthermore, the observation optical system of each embodiment is configured such that the diopter can be adjusted by fixing the subsequent lens group LR to the display surface ID (immovable) and moving the diopter adjustment lens group LR in the optical axis direction. has been done.

In the observation optical system of each embodiment, the distance between the pupil plane SP as an eye point on the optical axis and the lens surface closest to the pupil plane is called eye relief. In evaluating aberrations, there is a one-to-one correspondence between the aberration of a light ray that has a light emitting point on the display surface side and reaches the pupil plane SP, and the aberration of a light ray that has a light emitting point on the pupil surface side and reaches the display surface ID. Therefore, in each example, the aberration of the light beam reaching the display surface ID is evaluated. 2, 3, 5, 6, 8, 9, 11, and 12 show the observation optical systems of Examples 1 to 4 in which the pupil diameter of the observer (human being) is Φ3.5 mm, and the eye-leaf This figure shows a longitudinal aberration diagram when the distance is 18 mm.

The observation optical system of each embodiment adopts a triple-pass configuration in which light from the display surface ID travels back and forth between the first semi-transparent surface HM1 and the second semi-transparent surface HM2 and heads toward the pupil plane SP. The total length of the observation optical system is shortened. The first semi-transmissive surface HM1 and the second semi-transmissive surface HM2 are provided in the diopter adjustment lens group LF because the triple-pass configuration has high aberration sensitivity to changes in their spacing.

Furthermore, the subsequent lens group LR has at least one positive lens, and thus shares a part of the refractive power of the entire observation optical system.

Furthermore, by adopting a configuration in which the diopter adjustment lens group LF is moved in the optical axis direction while fixing the subsequent lens group LR to the display surface ID when adjusting the diopter, the peripheral part of the observed image when adjusting the diopter can be adjusted. To satisfactorily correct variations in field curvature (diopter deviation).

When dust adheres to the vicinity of the display screen ID, there is a possibility that the dust can be clearly observed by the focus adjustment function of the observer's eyes. In order to avoid observing dust as described above when adjusting the diopter by moving the entire observation optical system in the optical axis direction, it is necessary to move the observation optical system from the lens surface closest to the display surface to the display surface. It is necessary to ensure a long back focus, which is the distance to the ID. However, by providing the trailing lens group LR fixed to the display surface ID when adjusting the diopter as in each embodiment, the space near the display surface ID can be made into a sealed structure using the trailing lens group LR. Can be done. This makes it possible to avoid dust from adhering to the vicinity of the display screen ID, and as a result, it is possible to shorten the back focus of the observation optical system and further reduce the thickness of the observation optical system in the optical axis direction. be able to.

With the above-described basic configuration, the observation optical system of each embodiment can achieve both miniaturization and wide viewing angle, and has high optical performance that suppresses the occurrence of field curvature during diopter adjustment.

It is desirable that the observation optical system of each example satisfies at least one of the conditions shown in equations (1) to (9) below. In equations (1) to (9), as described above, the back focus as the distance from the lens surface closest to the display surface in the observation optical system (subsequent lens group LR) to the display surface ID is defined as skd. The diopter of the observation optical system at this time is 0D (diopter), and if a glass block is placed between the lens surface closest to the display surface and the display surface ID, its air equivalent length is set to the back focus skd. include. Let RHM2 be the radius of curvature of the second semi-transparent surface HM2. Let the total length of the observation optical system be OAL. The total length OAL is the distance from the surface apex on the optical axis of the first surface closest to the pupil plane of the observation optical system excluding the pupil plane SP to the display surface ID when the diopter of the observation optical system is 0D. . If a glass block is arranged between the lens surface closest to the display surface and the display surface ID, the air equivalent length of the glass block for the d-line is included in the total length OAL.

Furthermore, the maximum effective diameter of the diopter adjustment lens group LF is DF, and the maximum effective diameter of the subsequent lens group LR is DR. The maximum effective diameter of the diopter adjustment lens group LF and the subsequent lens group LR is the maximum diameter of the area through which light from the display surface ID passes among those lens groups. Further, the focal length of the diopter adjustment lens group LF is fF, the focal length of the subsequent lens group LR is fR, and the focal length of the entire observation optical system is f. Further, the distance on the optical axis between the diopter adjustment lens group LF and the subsequent lens group LR when the diopter is 0D (reference state) is defined as DFR.

-0.08≦skd/RHM2<0.0 (1)
5.0≦OAL/skd≦20.0 (2)
1.0≦DF/DR≦2.0 (3)
0.1≦fF/fR≦2.0 (4)
-1.0≦f/RHM2<0.0 (5)
0.01≦skd/f≦0.30 (6)
0.8≦fF/f≦2.0 (7)
0.5≦fR/f≦10.0 (8)
0.05≦DFR/fF≦0.50 (9)
The condition of equation (1) is a condition regarding the ratio between the back focus of the observation optical system and the radius of curvature of the second semi-transparent surface HM2. When skd/RHM2 satisfies the condition of formula (1), it is possible to reduce the thickness of the observation optical system while maintaining a wide viewing angle and high optical performance. When skd/RHM2 is less than the lower limit of equation (1), the radius of curvature of the second semi-transparent surface RHM2 becomes too small compared to the back focus. As a result, the action of the second semi-transmissive surface RHM2 as a positive power reflecting surface becomes too strong, making it difficult to correct the Petzval term generated at the reflecting surface. Furthermore, if the back focus becomes too large, the total length of the observation optical system increases. On the other hand, when skd/RHM2 exceeds the upper limit of equation (1), the second semi-transmissive surface RHM2 functions as a reflecting surface equivalent to a plane mirror or a convex mirror, and the reflecting surface cannot share positive power. As a result, if it is attempted to increase the refractive power of the entire observation optical system in order to ensure a wide viewing angle, it becomes difficult to correct the curvature of field, which is not preferable.

The condition of equation (2) is a condition regarding the ratio of the total length of the observation optical system to the back focus. When OAL/skd satisfies the condition of formula (2), it is possible to make the entire observation optical system smaller and to ensure an appropriate back focus. When OAL/skd falls below the lower limit of equation (2), the ratio of back focus to the total length becomes too large. As a result, the focal length of the entire observation optical system increases (refractive power decreases), the virtual image magnification of the observation optical system decreases, and it becomes difficult to widen the viewing angle. On the other hand, if OAL/skd exceeds the upper limit of equation (2), the ratio of the back focus to the total length becomes too small. As a result, the overall length is increased by ensuring an interval for arranging glass blocks such as glass plates that protect the display surface of the image display element that displays the original image.

The condition of equation (3) is a condition regarding the ratio of the maximum effective diameter of the diopter adjustment lens group LF and the subsequent lens group LR. When DF/DR satisfies the condition of formula (3), it is possible to realize an observation optical system that can accommodate a small-sized image display element while ensuring a wide viewing angle and long eye relief. When DF/DR falls below the lower limit of equation (3), the lens outer diameter of the diopter adjustment lens group LF becomes too small relative to the lens outer diameter of the subsequent lens group LR. As a result, the eye relief for ensuring a desired viewing angle becomes too short, or the observation optical system becomes large because it can only accommodate large-sized image display elements. On the other hand, if DF/DR exceeds the upper limit of equation (3), the lens outer diameter of the diopter adjustment lens group LF becomes too large relative to the lens outer diameter of the subsequent lens group LR, causing the diopter to move during diopter adjustment. This is not preferable because the power adjustment lens group LF becomes larger in diameter and the mechanism for driving it also becomes larger.

The condition of equation (4) is a condition regarding the ratio of the focal length of the diopter adjustment lens group LF and the focal length of the subsequent lens group LR. When fF/fR satisfies the condition of equation (4), high optical performance can be achieved even during diopter adjustment. When fF/fR falls below the lower limit of equation (4), the focal length of the diopter adjustment lens group LF becomes too small compared to the focal length of the subsequent lens group LR. As a result, the refractive power of the diopter adjustment lens group LF becomes too strong, making it difficult to correct variations in field curvature, which is a problem when adjusting the diopter by moving the entire observation optical system. On the other hand, if fF/fR exceeds the upper limit of equation (4), the focal length of the diopter adjustment lens group LF becomes too large compared to the focal length of the subsequent lens group LR, and the focal length of the lens group LF during diopter adjustment becomes This is not preferable because the amount of movement increases and the observation optical system becomes larger.

The condition of equation (5) is a condition regarding the ratio between the radius of curvature of the second semi-transparent surface HM2 and the focal length of the entire observation optical system. When f/RHM2 satisfies the condition of equation (5), it is possible to reduce the thickness of the observation optical system while relaxing the curvature of the second semi-transmissive surface RHM2 and achieving high optical performance. When f/RHM2 falls below the lower limit of equation (5), the radius of curvature of the second semi-transparent surface RHM2 becomes too small. As a result, it becomes difficult to correct the Petzval term generated on the second semi-transmissive surface RHM2 as a reflective surface, and the thickness of the observation optical system increases, which is not preferable. On the other hand, when f/RHM2 exceeds the upper limit of equation (5), the action of the second semi-transmissive surface RHM2 as a reflecting surface is equivalent to that of a plane mirror or a convex mirror, and the positive power cannot be shared by the reflecting surface, resulting in a wide field of view. This is not preferable because it becomes difficult to secure the corners.

The condition of equation (6) is a condition regarding the ratio between the back focus of the observation optical system and the focal length of the entire system. When skd/f satisfies the condition of equation (6), the thickness of the observation optical system can be reduced. When skd/f falls below the lower limit of equation (6), the back focus becomes too small compared to the focal length of the entire system. As a result, it becomes difficult to widen the viewing angle of the observation optical system, and it becomes difficult to arrange the glass blocks described above. On the other hand, if skd/f exceeds the upper limit of equation (6), the back focus will become too large compared to the focal length of the entire system, and the total length of the observation optical system will increase, which is not preferable.

The condition of equation (7) is a condition regarding the ratio of the focal length of the diopter adjustment lens group LF to the focal length of the entire observation optical system. When fF/f satisfies the condition of equation (7), the sensitivity of the diopter adjustment of the diopter adjustment lens group LF can be made appropriate. When fF/f falls below the lower limit of equation (7), the focal length of the diopter adjustment lens group LF becomes too small compared to the focal length of the entire system. As a result, the power of the diopter adjustment lens group LF becomes too strong, making it difficult to correct aberration fluctuations during diopter adjustment. On the other hand, if fF/f exceeds the upper limit of equation (7), the focal length of the diopter adjustment lens group LF becomes too large compared to the focal length of the entire system, and the sensitivity of diopter adjustment decreases, causing the diopter This is not preferable because the amount of movement of the adjustment lens group LF increases and the size of the observation optical system increases.

The condition of equation (8) is a condition regarding the ratio of the focal length of the subsequent lens group LR to the focal length of the entire observation optical system. When fR/f satisfies the condition of equation (8), the aberration correction during diopter adjustment can be appropriately assigned to the diopter adjustment lens group LF. When fR/f falls below the lower limit of equation (8), the focal length of the subsequent lens group LR becomes too small compared to the focal length of the entire system. As a result, the power of the subsequent lens group LR becomes too strong, making it difficult to correct field curvature in the reference state (diopter 0D) of the observation optical system. On the other hand, if fR/f exceeds the upper limit of equation (8), the focal length of the subsequent lens group LR will become too large compared to the focal length of the entire system, and its contribution to aberration correction will decrease, resulting in a reduction in diopter adjustment. This is undesirable because it becomes difficult to correct variations in field curvature in .

The condition of equation (9) is the distance on the optical axis between the surface vertex of the lens surface closest to the display surface in the diopter adjustment lens group LF and the surface vertex of the lens surface closest to the pupil surface in the subsequent lens group LR. , is a condition regarding the ratio of the focal length of the diopter adjustment lens group LF. When DFR/fF satisfies the condition of equation (9), a space is secured for the movement of the diopter adjustment lens group LF during diopter adjustment. When DFR/fF falls below the lower limit of equation (9), the distance between the diopter adjustment lens group LF and the subsequent lens group LR on the optical axis becomes too small. As a result, when adjusting the diopter to the minus side, the diopter adjustment lens group LF and the subsequent lens group LR interfere. On the other hand, if DFR/fF exceeds the upper limit of equation (9), the distance between the diopter adjustment lens group LF and the subsequent lens group LR on the optical axis becomes too large, and the total length of the observation optical system increases, which is preferable. do not have.

In Examples 1 to 3, it is more preferable that the numerical ranges of formulas (1) to (9) are as follows. However, equation (4a) only needs to be satisfied in Examples 1 to 3.

-0.06≦skd/RHM2≦-0.01 (1a)
7.5≦OAL/skd≦18.0 (2a)
1.05≦DF/DR≦1.75 (3a)
0.15≦fF/fR≦1.50 (4a)
-0.70≦f/RHM2≦-0.15 (5a)
0.03≦skd/f≦0.23 (6a)
0.9≦fF/f≦1.7 (7a)
0.65≦fR/f≦7.0 (8a)
0.08≦DFR/fF≦0.40 (9a)
Further, it is more preferable that the numerical ranges of formulas (1a) to (9a) are as follows. However, equations (4b) and (7) only need to be satisfied in Examples 1 to 3.

-0.05≦skd/RHM2≦-0.02 (1b)
9.0≦OAL/skd≦15.0 (2b)
1.1≦DF/DR≦1.5 (3b)
0.2≦fF/fR≦1.0 (4b)
-0.4≦f/RHM2≦-0.31 (5b)
0.06≦skd/f≦0.13 (6b)
1.0≦fF/f≦1.2 (7b)
0.8≦fR/f≦4.0 (8b)
0.1≦DFR/fF≦0.3 (9b)
In the observation optical system of each example, the first semi-transparent surface HM1 is a flat surface. Furthermore, it is preferable to use a polarization selective semi-transmissive reflective element as the first semi-transmissive surface HM1. An example of the polarization selective transflective element is "WGF" manufactured by Asahi Kasei Corporation. Such film-shaped polarizing elements can be applied to curved surfaces, but by arranging them as flat surfaces, disadvantages such as misalignment of the axis, changes in surface shape, and poor appearance caused by stress when the film is bent are reduced. be able to.

Further, as in the observation optical system of the fourth embodiment, a lens group L1 fixed with respect to the display surface ID may be disposed between the pupil plane SP and the diopter adjustment lens group LF during diopter adjustment. By arranging the lens group L1 in this manner, the movable diopter adjustment lens group LF does not need to be touched directly from the pupil surface side with a hand, etc., making it possible to provide an observation optical system that is more robust against external disturbances. .

The observation optical systems of Examples 1 to 4 have the following configurations to prevent ghost light (leakage of unnecessary light) from the optical path that passes through the semi-transparent surface without being reflected even once while suppressing a decrease in light intensity. ) can be reduced. FIG. 13 shows the configuration of an observation optical system using polarized light. In FIG. 13, the first semi-transmissive surface HM1 includes a polarization-selective transflective element A and a first quarter-wave plate B, which are arranged in order from the pupil surface side to the display surface side. Further, the second semi-transparent surface HM2 is constituted by a half mirror C. A second quarter-wave plate D and a polarizing plate E are arranged between the second semi-transparent surface HM2 and the display surface ID. Straight arrows, circular arrows, and symbols with a dot inside a circle in the figure indicate the polarization direction of light traveling through the position to which they are attached.

The polarization-selective transflective element A is an element configured to reflect linearly polarized light having the same polarization direction as when it passes through the polarizing plate E, and to transmit linearly polarized light having a polarization direction perpendicular to this. , for example a wire grid polarizer. The wire grid forming surface of the wire grid polarizer functions as a semi-transparent surface. Further, the first quarter-wave plate B and the second quarter-wave plate D are arranged with their respective slow axes tilted by 90 degrees with respect to the polarization transmission axis of the polarizing plate E. The slow axis of the first quarter-wave plate B is arranged at an angle of 45°. The half mirror C is formed by, for example, a dielectric multilayer film or metal vapor deposition, and functions as a semi-transparent surface.

In the observation optical system configured in this way, the light emitted from the display surface ID is converted into linearly polarized light by the polarizing plate E, converted into circularly polarized light by the second 1/4 wavelength plate D, and then sent to the half mirror C. incident on . A portion of the light incident on the half mirror C is reflected, becomes circularly polarized light in the opposite direction, and returns to the second quarter-wave plate D. The reversely circularly polarized light returned to the second quarter-wave plate D has a polarization direction perpendicular to the polarization direction when it first passes through the polarizing plate E by the second quarter-wave plate D. It is converted into linearly polarized light, returns to the polarizing plate E, and is absorbed by the polarizing plate E.

On the other hand, the remainder of the light incident on the half mirror C is transmitted through it and converted into linearly polarized light in the same polarization direction as when it passed through the polarizing plate E by the first 1/4 wavelength plate B. The light enters the transmissive/reflective element A. This linearly polarized light is reflected by the polarization selectivity of the polarization selective transflective element A. The light reflected by the polarization-selective transflective element A is circularly polarized in the opposite direction to that when it is first converted into circularly polarized light by the first quarter-wave plate B and the second quarter-wave plate D. The light is converted into polarized light, enters the half mirror C, and is reflected there.

The light reflected by the half mirror C becomes circularly polarized light in the opposite direction to the light before reflection and enters the first 1/4 wavelength plate B, and the polarization direction is different from that when it first passed through the polarizing plate E. The light is converted into linearly polarized light having orthogonal polarization directions, and is incident on the polarization-selective transflective element A. This linearly polarized light passes through the polarization selective transflective element A due to its polarization selectivity and is guided to the pupil plane SP.

In this way, only the light that transmitted through the second semi-transparent surface HM2, was reflected on the first semi-transparent surface HM1, was reflected on the second semi-transmissive surface HM2, and transmitted through the first semi-transparent surface HM1. is guided to the pupil plane SP.

The observation optical system of Example 1 shown in FIG. 1 has a first semi-transparent surface HM1 and a second semi-transparent surface HM2 arranged in order from the pupil plane (SP) side to the display surface (ID) side. It is composed of a power adjustment lens group LF and a subsequent lens group LR consisting of one positive lens. When adjusting the diopter, the subsequent lens group LR is fixed to the display surface ID, and the diopter adjusting lens group LF is moved in the optical axis direction. More specifically, the diopter adjustment lens group LF includes a plano-convex lens having a first semi-transparent surface HM1 and a biconcave non-concave lens having a second semi-transparent surface HM2, which are arranged in order from the pupil surface side. It is composed of a spherical lens. The subsequent lens group LR is composed of one plano-convex lens.

A specific numerical example of this example is shown in Table 1 as Numerical Example 1. Further, FIG. 2 shows a longitudinal aberration diagram of the observation optical system of Numerical Example 1 with a pupil diameter of Φ3.5 mm, an eye relief of 18 mm, and a diopter of 0D, and FIG. A longitudinal aberration diagram at a diopter of -4D is shown.

The basic configuration of the observation optical system of the second embodiment shown in FIG. 4 is the same as that of the first embodiment. However, the diopter adjustment lens group LF is composed of a cemented lens of a plano-convex lens having a first semi-transparent surface HM1 and a plano-concave lens having a second semi-transparent surface HM2, which are arranged in order from the pupil surface side. . By arranging the second semi-transparent surface HM2 on the cemented surface of the cemented lens and eliminating the contact surface with air, the environmental resistance of the semi-transparent metal film against oxidation and the like can be improved. Furthermore, the subsequent lens group LR is composed of one biconvex lens.

A specific numerical example of this example is shown in Table 2 as Numerical Example 2. Further, FIG. 5 shows a longitudinal aberration diagram of the observation optical system of Numerical Example 2 with a pupil diameter of Φ3.5 mm, an eye relief of 18 mm, and a diopter of 0D, and FIG. A longitudinal aberration diagram at a diopter of -4D is shown.

The basic configuration of the observation optical system of the third embodiment shown in FIG. 7 is the same as that of the first embodiment. However, by increasing the size of the image display element compared to the first embodiment, the viewing angle is made wider, and the shape of each lens is different from the first embodiment.

A specific numerical example of this example is shown in Table 3 as Numerical Example 3. Further, FIG. 8 shows a longitudinal aberration diagram of the observation optical system of Numerical Example 3 with a pupil diameter of Φ3.5 mm, an eye relief of 18 mm, and a diopter of 0D, and FIG. A longitudinal aberration diagram at a diopter of -4D is shown.

The basic configuration of the observation optical system of the fourth embodiment shown in FIG. 10 is the same as that of the first embodiment. However, in addition to reducing the size of the image display element compared to Embodiment 1, as described above, a lens fixed to the display surface ID is provided between the pupil plane SP and the diopter adjustment lens group LF during diopter adjustment. A group L1 is provided, and the shape of each lens is different from that of the first embodiment.

The lens group L1 is composed of one positive aspherical lens having a meniscus shape and convex toward the pupil surface. The diopter adjustment lens group LF includes a parallel flat plate having a first semi-transparent surface HM1 and a meniscus having a second semi-transmissive surface HM2 and convex toward the display surface ID, which are arranged in order from the pupil surface side. It is composed of a negative shaped lens.

The subsequent lens group LR includes a biconvex aspheric lens and a plano-convex lens, which are arranged in order from the pupil surface side.

A specific numerical example of this example is shown in Table 4 as Numerical Example 4. In addition, FIG. 11 shows a longitudinal aberration diagram of the observation optical system of Numerical Example 4 with a pupil diameter of Φ3.5 mm, an eye relief of 18 mm, and a diopter of 0D, and FIG. A longitudinal aberration diagram at a diopter of -4D is shown.

The observation optical system of each of the above embodiments is both compact and wide viewing angle, and has high optical performance even when adjusting the diopter.

Note that it is also possible to electronically correct distortion aberration and chromatic aberration of magnification generated in the observation optical system by correcting the original image displayed on the image display element.

Numerical values of Numerical Examples 1 to 4 are shown below. In the surface data of each numerical example, the surface number i indicates the i-th surface when counted from the pupil surface side. r is the radius of curvature of the i-th surface (mm), d is the lens thickness or air gap (mm) between the i-th and (i+1)-th surfaces, and nd is the refractive index at the d-line of the material of the i-th optical member It is. νd is the Abbe number of the material of the i-th optical member based on the d-line. The Abbe number νd is expressed as νd=(Nd-1 )/(NF-NC). The effective diameter indicates the maximum diameter of the area through which light from the original image passes on each surface.

The "*" attached to the surface number means that the surface has an aspherical shape. For the aspherical shape, x is the displacement in the optical axis direction at a height h from the optical axis with respect to the surface vertex, R is the paraxial radius of curvature, k is the conic constant, A4, A6, A8, and A10. When is the aspheric coefficient, it is expressed by the following formula.

x=(h ² /R)/[1+{1-(1+k)(h/R) ² } ^1/2 ]
+A4・h ⁴ +A6・h ⁶ +A8・h ⁸ +A10・h ¹⁰
"e±XXX" in each aspheric coefficient means "×10 ^±XXX ".

In addition, various data include focal length (mm), F number, half angle of view (°), image height (mm), total length OAL of the observation optical system (mm), and back focus skd (mm). In the lens group data and single lens data, G indicates a glass block.

Further, the values of formulas (1) to (9) in Numerical Examples 1 to 4 are summarized in Table 5.
(Table 1)
Numerical example 1
Unit: mm
Surface data Surface number rd nd νd Effective diameter
1(SP) ∞ (variable) 3.50
2 ∞ 3.87 1.48749 70.2 25.50
3 -42.003 0.80 25.50
4* -40.519 -0.80 Reflective surface 25.50
5 -42.003 -3.87 1.48749 70.2 25.50
6 ∞ 3.87 Reflective surface 25.50
7 -42.003 0.80 25.50
8* -40.519 2.10 1.63550 23.9 25.50
9* 223.601 (variable) 21.00
10 ∞ 3.38 1.69680 55.5 19.00
11 -26.816 0.56 19.00
12 ∞ 0.80 1.51633 64.1 25.00
13 ∞ 0.30 25.00
ID ∞

Aspheric data 4th surface
K = 0.00000e+000 A 4= 2.02196e-006 A 6= 3.03993e-008 A 8=-1.05562e-010 A10= 5.55446e-013

Side 8
K = 0.00000e+000 A 4= 2.02196e-006 A 6= 3.03993e-008 A 8=-1.05562e-010 A10= 5.55446e-013

9th page
K = 0.00000e+000 A 4=-3.85813e-005 A 6= 2.95674e-008 A 8= 5.59443e-010 A10=-5.30609e-014

Various data focal length 13.99
F number 4.00
Half angle of view 24.41
Image height 6.35
OAL 14.45
skd(in air) 1.38

0.0D -4.0D
d 1 18.00 18.87
d9 2.63 1.76

Entrance pupil position 0.00
Exit pupil position 17.59
Front principal point position 25.31
Back principal point position -13.69

Lens group data group Starting surface Focal length Lens length Front principal point position Rear principal point position
SP 1 ∞ 0.00 0.00 -0.00
LF 2 14.51 6.78 2.55 -8.45
LR 10 38.48 3.38 1.99 0.00
G 12 ∞ 0.80 0.26 -0.26

Single lens data lens starting surface focal length
1 1 86.16
2 8 -53.81
3 10 38.48
G12 0.00

(Table 2)
Numerical example 2
Unit: mm

Surface data Surface number rd nd νd Effective diameter
1(SP) ∞ (variable) 3.50
2 ∞ 3.63 1.48749 70.2 26.00
3 -40.438 -3.63 Reflective surface 26.00
4 ∞ 3.63 Reflective surface 26.00
5 -40.438 1.86 1.87070 40.7 26.00
6 ∞ (variable) 26.00
7 27.178 3.87 1.69680 55.5 18.00
8 -78.998 0.55 18.00
9 ∞ 0.80 1.51633 64.1 25.00
10 ∞ 0.30 25.00
ID ∞

Various data focal length 13.26
F number 3.79
Half angle of view 25.60
Image height 6.35
OAL 15.46
skd(in air) 1.38

0.0D -4.0D
d 1 18.00 18.90
d 6 4.44 3.54

Entrance pupil position 0.00
Exit pupil position 15.44
Front principal point position 24.86
Back principal point position -12.96

Lens group data group Starting surface Focal length Lens length Front principal point position Rear principal point position
SP 1 ∞ 0.00 0.00 -0.00
LF 2 14.82 5.49 1.75 -6.31
LR 7 29.46 3.87 0.59 -1.72
G 9 ∞ 0.80 0.26 -0.26

Single lens data lens Starting surface Focal length
1 1 82.95
2 5 -46.44
3 7 29.46
G9 0.00

(Table 3)
Numerical example 3
Unit: mm

Surface data Surface number rd nd νd Effective diameter
1(SP) ∞ (variable) 4.99
2 ∞ 5.23 1.48749 70.2 31.50
3 -47.003 0.83 31.50
4* -45.303 -0.83 Reflective surface 32.00
5 -47.003 -5.23 1.48749 70.2 31.50
6 ∞ 5.23 Reflective surface 31.50
7 -47.003 0.83 31.50
8* -45.303 1.73 1.63550 23.9 32.00
9* 287.628 (variable) 27.00
10 ∞ 5.03 1.59522 67.7 25.50
11 -33.994 0.22 25.50
12 ∞ 0.80 1.51633 64.1 30.00
13 ∞ 0.10 30.00
ID ∞

Aspheric data 4th surface
K = 0.00000e+000 A 4= 2.46248e-007 A 6= 1.38723e-008 A 8=-4.08353e-011 A10= 1.26569e-013

Side 8
K = 0.00000e+000 A 4= 2.46248e-007 A 6= 1.38723e-008 A 8=-4.08353e-011 A10= 1.26569e-013

9th page
K = 0.00000e+000 A 4=-3.20201e-005 A 6= 1.27623e-007 A 8=-4.33897e-010 A10= 7.63002e-013

Various data focal length 15.86
F number 4.53
Half angle of view 29.27
Image height 8.89
OAL 46.05
skd(in air) 0.85

0.0D -4.0D
d 1 18.00 19.06
d9 1.99 0.93

Entrance pupil position 0.00
Exit pupil position 25.91
Front principal point position 25.60
Back principal point position -15.76

Lens group data group Starting surface Focal length Lens length Front principal point position Rear principal point position
SP 1 ∞ 0.00 0.00 -0.00
LF 2 16.10 7.79 3.37 -10.10
LR 10 57.11 5.03 3.15 0.00
G 12 ∞ 0.80 0.26 -0.26

Single lens data lens Starting surface Focal length
1 1 96.42
2 8 -61.46
3 10 57.11
G12 0.00

(Table 4)
Numerical example 4
Unit: mm

Surface data Surface number rd nd νd Effective diameter
1(SP) ∞ 18.00 3.50
2 43.600 1.38 1.53110 55.9 18.00
3* 122.693 (variable) 18.00
4 ∞ 1.00 1.51633 64.1 19.00
5 ∞ 2.43 19.00
6 -38.943 -2.43 Reflective surface 19.50
7 ∞ -1.00 1.51633 64.1 19.00
8 ∞ 1.00 Reflective surface 19.00
9 ∞ 2.43 19.00
10 -38.943 0.80 2.00272 19.3 19.50
11 -70.526 (variable) 17.60
12* 20.881 3.00 1.54390 56.0 16.50
13* -18.670 0.50 16.50
14 ∞ 3.32 1.48749 70.2 15.50
15 -15.787 0.80 15.00
16 ∞ 0.60 1.51633 64.1 20.00
17 ∞ 0.30 20.00
ID ∞

Aspheric data 3rd surface
K = 0.00000e+000 A 4= 2.14652e-007 A 6=-2.01734e-008 A 8= 2.91421e-010

Side 12
K = 0.00000e+000 A 4=-1.55694e-004 A 6=-1.25143e-006

Page 13
K = 0.00000e+000 A 4= 1.49295e-004 A 6=-1.35522e-006 A 8= 6.11466e-009 A10=-3.33498e-011

Various data focal length 13.78
F number 3.94
Half angle of view 19.95
Image height 5.00
OAL 18.80
skd(in air) 1.50

0.0D -4.0D
d3 1.24 2.96
d11 3.43 1.71

Entrance pupil position 0.00
Exit pupil position 8.62
Front principal point position 36.60
Back principal point position -13.48

Lens group data group Starting surface Focal length Lens length Front principal point position Rear principal point position
SP 1 ∞ 0.00 0.00 -0.00
L1 2 126.58 1.38 -0.49 -1.39
LF 4 23.10 4.23 1.60 -7.65
LR 12 12.74 6.82 2.50 -2.51
G 16 ∞ 0.60 0.20 -0.20

Single lens data lens Starting surface Focal length
1 1 126.58
2 4 0.00
3 10 -87.84
4 12 18.62
5 14 32.39
G16 0.00

FIG. 14 shows an optical device as a fifth embodiment of the present invention, and is a schematic diagram of an imaging device 100 equipped with an eyepiece optical system of each embodiment. In FIG. 14, a subject image formed by a photographic lens (imaging optical system) 101 is converted into an electrical signal by an image sensor 102, which is a photoelectric conversion element. As the image sensor 102, a CCD sensor, a CMOS sensor, or the like is used.

Image data is formed by processing the output from the image sensor 102 in the image processing circuit 103. This image data is recorded on a recording medium 104 such as a semiconductor memory, magnetic tape, or optical disk. Further, image data formed by the image processing circuit 103 is displayed on an electronic viewfinder (EVF) 105. The electronic viewfinder 105 includes a display element (liquid crystal display element, organic EL element, etc.) 1051 and an eyepiece optical system 1052 of each embodiment. The user 106 can capture an image while observing the electronic viewfinder.

The eyepiece optical system of each embodiment is applicable to various imaging devices such as digital cameras and video cameras.

The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention.

LF Diopter adjustment lens group LR Subsequent lens group HM1 First semi-transparent surface HM2 Second semi-transparent surface SP Pupil plane ID Display surface

Claims (11)

An observation optical system that enables observation of an optical image of an original image displayed on a display surface from a pupil plane,
arranged in order from the pupil surface side to the display surface side,
a first lens group having a first semi-transparent surface and a second semi-transparent surface;
a second lens group having at least one positive lens;
The diopter can be adjusted by fixing the second lens group to the display surface and moving the first lens group in the optical axis direction ,
The distance from the lens surface closest to the display surface of the observation optical system to the display surface is skd, the focal length of the entire system of the observation optical system is f, and the diopter of the observation optical system is 0D. When the distance on the optical axis between the first lens group and the second lens group is DFR, and the focal length of the first lens group is fF,
0.01≦skd/f≦0.23
0.08≦DFR/fF≦0.50
An observation optical system characterized by satisfying the following conditions . When the radius of curvature of the second semi-transparent surface is RHM2,
-0.08≦skd/RHM2<0.0
The observation optical system according to claim 1, wherein the observation optical system satisfies the following conditions. When the total length of the optical system is OA L ,
5.0≦OAL/skd≦20.0
The observation optical system according to claim 1 or 2, wherein the observation optical system satisfies the following conditions. When the maximum diameters of the areas through which light from the original image passes among the first lens group and the second lens group are respectively DF and DR,
1.0≦DF/DR≦2.0
4. The observation optical system according to claim 1, wherein the observation optical system satisfies the following conditions. When the focal length of the second lens group is fR,
0.1≦fF/fR≦2.0
5. The observation optical system according to claim 1, wherein the observation optical system satisfies the following conditions. When the radius of curvature of the second semi-transparent surface is RHM 2 ,
-1.0≦f/RHM2<0.0
The observation optical system according to any one of claims 1 to 5, wherein the observation optical system satisfies the following conditions. 0 . 8≦fF/f≦2.0
7. The observation optical system according to claim 1, wherein the observation optical system satisfies the following conditions. When the focal length of the second lens group is fR ,
0.5≦fR/f≦10.0
8. The observation optical system according to claim 1, wherein the observation optical system satisfies the following conditions. 9. The observation optical system according to claim 1, wherein the first semi-transparent surface is a flat surface. 10. The lens according to claim 1, further comprising a lens group that is fixed between the pupil plane and the first lens group when the first lens group moves. Observation optical system. An optical instrument comprising the observation optical system according to any one of claims 1 to 10 .