JP7059026B2 - Eyepiece optical system and observation device and imaging device having it - Google Patents

Description

The present invention relates to an eyepiece optical system, an observation device having the same, and an image pickup device.

Conventionally, in order to observe an image displayed on an image display element such as a liquid crystal panel, an observation device using an eyepiece optical system including a plurality of lenses is known. In order to improve visibility, the eyepiece optical system used for this purpose is required to have a sufficiently large observation field (high magnification), a long eye relief, and high optical performance in which various aberrations are well corrected. There is. Further, image pickup devices such as cameras have been miniaturized, and the observation device used for these image pickup devices is required to use a relatively small image display element having a diagonal length of 20 mm or less on the image display surface of the image display element. ing.

Conventionally, various eyepiece optical systems suitable for an observation device satisfying these requirements have been proposed (Patent Documents 1 to 3). In Patent Documents 1 to 3, a first lens having a positive refractive power, a second lens having a negative refractive power, and a positive lens arranged in order from the object side (image display element side) toward the emission side (observer side). Disclosed is an eyepiece optical system composed of a third lens having a refractive power of.

Japanese Unexamined Patent Publication No. 2016-1666969 Japanese Unexamined Patent Publication No. 2014-228583 Japanese Patent Application Laid-Open No. 2015-135471

In the eyepiece optical system used for the observation device, in order to obtain good optical performance while maintaining a high observation magnification (large observation viewing angle) and long eye relief, the lens configuration of the eyepiece optical system and the refraction of each lens are required. It is important to set the force appropriately. In addition, when using an image display element having a small image display surface, it is important to appropriately set the ratio of the refractive power of the eyepiece optical system to the size of the image display surface.

For example, in the above-mentioned eyepiece optical system including three lenses, if the focal length of the third lens is longer than the focal length of the entire system, it becomes difficult to increase the observation viewing angle. Further, if the focal length of the second lens is longer than the focal length of the first lens, it becomes difficult to obtain a high viewing angle above a certain level. Further, in order to reduce the size of the entire system, if the lens is constructed from a high refraction material, it tends to be difficult to manufacture each lens.

An object of the present invention is to provide an eyepiece optical system having a long eye relief, a wide viewing angle, a small overall system, and high optical performance, and an observation device and an imaging device having the same.

The eyepiece optical system of the present invention is an eyepiece optical system for observing an image displayed on an image display surface.
It is composed of a first lens having a positive refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power, which are arranged in order from the image display surface to the observation side.
The average value of the refractive index of each material of the first lens, the second lens, and the third lens is nd-ave, the focal length of the second lens is f2, the focal length of the third lens is f3, and the eyepiece. When the focal length of the optical system is f,
1.624 ≤ nd-ave <1.699
-0.93 <f2 / f3 <-0.50
0.73 <f3 / f <1.10
It is characterized by satisfying the conditional expression.

According to the present invention, it is possible to obtain an eyepiece optical system having a long eye relief, a wide viewing angle, a small overall system, and high optical performance, and an observation device and an imaging device having the same.

Cross-sectional view of the lens of the observation device having the eyepiece optical system according to the first embodiment of the present invention. Each aberration diagram of the eyepiece optical system according to the first embodiment of the present invention. A cross-sectional view of a lens of an observation device having an eyepiece optical system according to a second embodiment of the present invention. Each aberration diagram of the eyepiece optical system according to the second embodiment of the present invention. Cross-sectional view of the lens of the observation device having the eyepiece optical system according to the third embodiment of the present invention. Each aberration diagram of the eyepiece optical system according to the third embodiment of the present invention. Cross-sectional view of the lens of the observation device having the eyepiece optical system according to the fourth embodiment of the present invention. Each aberration diagram of the eyepiece optical system of Example 4 of the present invention Cross-sectional view of the lens of the observation device having the eyepiece optical system according to the fifth embodiment of the present invention. Each aberration diagram of the eyepiece optical system of Example 5 of the present invention Schematic diagram of the main part of the image pickup apparatus of the present invention

Hereinafter, the eyepiece optical system of the present invention, an observation device having the same, an imaging device, and the like will be described with reference to the attached drawings. The eyepiece optical system of the present invention is for observing an image displayed on an image display surface, and is the first positive refractive power arranged in order from the image display surface side to the observation side (eye point side). It is composed of a lens G1, a second lens G2 having a negative refractive power, and a third lens G3 having a positive refractive power.

FIG. 1 is a cross-sectional view of a lens of an observation device having an eyepiece optical system according to the first embodiment in a diopter of −1.0 diopter (reference state). FIG. 2 is an aberration diagram in a reference state of the eyepiece optical system of Example 1. FIG. 3 is a lens cross-sectional view of an observation device having an eyepiece optical system according to the second embodiment in a diopter of -1.0 diopter. FIG. 4 is an aberration diagram in a reference state of the eyepiece optical system of the second embodiment. FIG. 5 is a cross-sectional view of a lens of an observation device having an eyepiece optical system of Example 3 in a diopter of −1.0 diopter. FIG. 6 is an aberration diagram in a reference state of the eyepiece optical system of Example 3.

FIG. 7 is a lens cross-sectional view of an observation device having an eyepiece optical system of Example 4 at a diopter of −1.0 diopter. FIG. 8 is an aberration diagram in the reference state of the eyepiece optical system of Example 4. FIG. 9 is a lens cross-sectional view of an observation device having an eyepiece optical system of Example 5 at a diopter of −1.0 diopter. FIG. 10 is an aberration diagram in a reference state of the eyepiece optical system of Example 5. FIG. 11 is a schematic view of a main part of an image pickup apparatus having the observation apparatus of the present invention.

In the cross-sectional view of the lens, LA is an observation device and L0 is an eyepiece optical system. IP is the image display surface of the image display element, GA is the protective member of the image display surface IP, G1 is the first lens of the eyepiece optical system L0, G2 is the second lens of the eyepiece optical system L0, and G3 is the second lens of the eyepiece optical system L0. There are 3 lenses. GB indicates the cover glass of the eyepiece optical system L0, and EP indicates the eye point position (observation position) of the observer. The distance from the lens surface on the observation side of the third lens G3 to the eye point EP is the eye relief.

Further, in the spherical aberration diagram, the solid line d indicates the spherical aberration with respect to the d line (wavelength 587.6 nm), and the two-dot chain line g indicates the spherical aberration with respect to the g line (wavelength 435.8 nm). In the astigmatism diagram, the solid line ΔS is the d-line sagittal image plane, and the dotted line ΔM is the d-line meridional image plane. Distortion is shown for the d-line. The chromatic aberration of magnification diagram shows the chromatic aberration of magnification in the g-line. H is half the diagonal length of the image display surface IP.

In order to observe a small display panel (image display element) having an image display surface IP with a diagonal length of about 20 mm or less at a wide viewing angle (viewing angle of 30 degrees or more), strong positive refractive power is applied to the entire eyepiece optical system L0. You need to have power. Generally, when each lens has a strong positive refractive power or a negative refractive power, it becomes difficult to correct various aberrations such as curvature of field and chromatic aberration of magnification.

Therefore, in the eyepiece optical system L0 of each embodiment of the present invention, the first lens G1 having a positive refractive power, the second lens G2 having a negative refractive power, and the third lens having a positive refractive power are arranged in order from the image display surface IP side. It is composed of a lens G3. By setting the optimum refractive power arrangement, an eyepiece optical system having a long eye relief, a wide viewing angle, a small size, and high optical performance is obtained.

Then, the average value of the refractive indexes of the materials of the first lens G1, the second lens G2, and the third lens G3 is defined as nd-ave. Let f2 be the focal length of the second lens G2, f3 be the focal length of the third lens G3, and f be the focal length of the eyepiece optical system L0. At this time,
1.624 ≤ nd-ave <1.699 ... (1)
-0.93 <f2 / f3 <-0.50 ... (2)
0.73 <f3 / f <1.10 ... (3)
Satisfy the conditional expression.

Next, the technical meaning of each of the above conditional expressions will be described. The conditional expression (1) defines the average value of the refractive index of the material of the lens possessed by the eyepiece optical system L0. If it is less than the lower limit of the conditional expression (1), it becomes difficult to widen the viewing angle, which is not preferable. If the upper limit is exceeded, it becomes difficult to process each lens with high precision.

The conditional expression (2) defines the ratio of the focal lengths of the second lens G2 and the third lens G3. If it is less than the lower limit of the conditional expression (2), it becomes difficult to widen the viewing angle, which is not preferable. Further, if the upper limit is exceeded, chromatic aberration increases and the optical performance deteriorates, which is not preferable.

The conditional expression (3) defines the ratio of the focal length of the entire eyepiece optical system L0 to the focal length of the third lens G3. If it is less than the lower limit of the conditional expression (3), it becomes difficult to widen the viewing angle, which is not preferable. If it exceeds the upper limit, the optical performance will deteriorate, which is not preferable.

In each embodiment, it is preferable to set the conditional expressions (1), (2), and (3) in the numerical range as follows.

1.620 <nd-ave <1.685 ... (1a)
-0.91 <f2 / f3 <-0.52 ... (2a)
0.732 <f3 / f <1.090 ... (3a)

It is more preferable to satisfy one or more of the following conditional expressions in each embodiment. The radius of curvature of the lens surface on the image display surface side of the first lens G1 is R11, and the radius of curvature of the lens surface on the observation side is R12. Let the refractive index and Abbe number of the material of the second lens G2 be nd2 and νd2, respectively.

When the eyepiece optical system L0 of each embodiment is used for observing an image displayed on the image display surface IP of the image display element, half of the diagonal length of the image display surface IP of the image display element is H. At this time, it is preferable to satisfy one or more of the following conditional expressions.

-0.20 <(R11 + R12) / (R11-R12) <1.20 ... (4)
-1.10 <f2 / f <-0.50 ... (5)
1.55 <nd2 <1.75 ... (6)
19.0 <νd2 <32.0 ... (7)
0.25 <H / f <0.40 ... (8)

Next, the technical meaning of each of the above conditional expressions will be described. The conditional expression (4) defines the curvatures of the lens surfaces of the first lens G1 on the IP side of the image display surface and the EP side of the observation surface. If it is less than the lower limit of the conditional expression (4), the positive refractive power of the first lens G1 is weakened and it becomes difficult to widen the viewing angle, which is not preferable. Further, if it exceeds the upper limit value, the optical performance of the off-axis luminous flux deteriorates, which is not preferable.

The conditional expression (5) defines the ratio of the focal length of the entire eyepiece optical system L0 to the focal length of the second lens G2. If it is less than the lower limit of the conditional expression (5), the curvature of each lens surface of the second lens G2 becomes strong and the molding difficulty increases, which is not preferable. If it exceeds the upper limit, it becomes difficult to correct chromatic aberration, which is not preferable.

The conditional expression (6) defines the refractive index of the second lens G2. If it is less than the lower limit of the conditional expression (6), the curvature of each lens surface of the second lens G2 becomes too strong, and the molding difficulty increases, which is not preferable. If the upper limit is exceeded, the Petzval sum of the eyepiece optical system L0 increases, and curvature of field and astigmatism increase, which is not preferable.

The conditional expression (7) defines the Abbe number of the material of the second lens G2. If the Abbe number νd of the material of the second lens G2 becomes smaller than the lower limit of the conditional expression (7), the chromatic aberration is excessively corrected, which is not preferable. Further, if it exceeds the upper limit value, the correction of chromatic aberration becomes insufficient, which is not preferable.

Conditional expression (8) defines the ratio of half the diagonal length of the effective surface of the image display surface IP of the image display element to the focal length of the entire system. The conditional expression (8) is for ensuring a high magnification while ensuring an eye relief of a predetermined length. If the upper limit of this conditional expression (8) is exceeded, the focal length of the entire system becomes short, which is advantageous for increasing the magnification, but it becomes difficult to secure high optical performance. If it falls below the lower limit, the refractive power of the entire system becomes weak and it becomes difficult to secure a high magnification. Further, it is preferable to set the numerical range of the conditional expressions (4) to (8) as follows.

0.50 <(R11 + R12) / (R11-R12) <1.10 ... (4a)
-0.90 <f2 / f <-0.52 ... (5a)
1.60 <nd <1.70 ... (6a)
19.0 <νd <25.0 ... (7a)
0.28 <H / f <0.38 ... (8a)

In each embodiment, as the eyepiece optical system L0, it is preferable that the first lens G1 is made of a glass material, the second lens G2 is made of a resin material, and the third lens G3 is made of a resin material. This makes it possible to reduce the weight by reducing the number of glass materials and to reduce the diameter of the lens using the glass material. In the eyepiece optical system L0 having a three-lens configuration, since the first lens G1 usually has the smallest diameter, it is preferable to use the first lens G1 as a glass material. As the eyepiece optical system L0, it is preferable that at least one side of the second lens G2 has an aspherical shape.

Next, an embodiment of the image pickup apparatus using the eyepiece optical system shown in each embodiment will be described with reference to FIG. 11. The object image formed by the image pickup optical system 101 is converted into an electric signal by the image pickup element 102 which is a photoelectric conversion element. As the image pickup element 102, a CCD sensor, a CMOS sensor, or the like is used.

The output signal from the image pickup device 102 is processed by the image processing circuit 103 to form an image. The formed image is recorded on a recording medium 104 such as a semiconductor memory, a magnetic tape, or an optical disk. Further, the image formed in the image processing circuit 103 is displayed on the observation device 105. The observation device 105 includes an image display element 1051 and an eyepiece optical system 1052 of each embodiment. The image display element 1051 is composed of a liquid crystal display element LCD, a CRT, or the like. The image information displayed by the image display element 1051 is observed from the eye point 106 via the eyepiece optical system 1052.

As described above, by applying the eyepiece optical system 1052 of the present invention to an image pickup device such as a digital camera or a video camera, it is possible to obtain an image pickup device having a wide viewing angle, a small size, and high optical performance.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the gist thereof.

Numerical data corresponding to each embodiment of the present invention are shown below. In the numerical data, "ri" indicates the paraxial radius of curvature of the i-th surface in order from the image display surface IP to the observation side EP. r1 and r2 are surfaces of the image display element, and r1 is an image display surface. r3 and r4 are surfaces of the protective member. r11 and r12 are the surfaces of the cover glass. di indicates the axis upper surface distance between the i-th surface and the i + 1th surface in order from the image display surface IP. Further, ndi indicates the refractive index of the i-th material with respect to the d-line (wavelength = 578.6 nm), and ν di indicates the Abbe number of the i-th material with respect to the d-line.

In the numerical data, [mm] is used as the unit of the described length unless otherwise specified. However, since the eyepiece optical system can obtain the same optical performance even if it is proportionally expanded or contracted, the unit is not limited to [mm], and other appropriate units can be used. In the numerical data, the surface in which the subscript "*" is written in the column of the radius of curvature of the paraxial axis is an aspherical shape defined by the following equation (1).

In Equation 1, x is the distance in the optical axis direction from the apex of the lens surface, h is the height in the direction perpendicular to the optical axis, R is the paraxial radius of curvature at the apex of the lens surface, and k is a conical constant. A4, A6, and A8 are paraxial coefficients. In the aspherical coefficient, "Ei" represents an exponential notation with a base of 10, that is, "10- ⁱ ". Table 1 shows the calculation results of the above-mentioned conditional expressions in each numerical data.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the gist thereof.

LA observation device L0 Eyepiece optical system G1 1st lens G2 2nd lens G3 3rd lens

Claims (8)

An eyepiece optical system for observing an image displayed on an image display surface.
It is composed of a first lens having a positive refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power, which are arranged in order from the image display surface to the observation side.
The average value of the refractive index of each material of the first lens, the second lens, and the third lens is nd-ave, the focal length of the second lens is f2, the focal length of the third lens is f3, and the eyepiece. When the focal length of the optical system is f,
1.624 ≤ nd-ave <1.699
-0.93 <f2 / f3 <-0.50
0.73 <f3 / f <1.10
An eyepiece optical system characterized by satisfying the conditional expression. When the radius of curvature of the lens surface on the image display surface side of the first lens is R11 and the radius of curvature of the lens surface on the observation side is R12,
-0.20 <(R11 + R12) / (R11-R12) <1.20
The eyepiece optical system according to claim 1, wherein the eyepiece optical system satisfies the conditional expression. The eyepiece optical system is
-1.10 <f2 / f <-0.50
The eyepiece optical system according to claim 1 or 2, wherein the conditional expression is satisfied. The eyepiece optical system according to any one of claims 1 to 3, wherein the first lens is made of a glass material, and the second lens and the third lens are made of a resin material. When the refractive index and Abbe number of the material of the second lens are nd2 and νd2, respectively,
1.55 <nd2 <1.75
19.0 <νd2 <32.0
The eyepiece optical system according to any one of claims 1 to 4, wherein the eyepiece optical system satisfies the conditional expression. It is characterized by having an image display element for displaying an image and an eyepiece optical system according to any one of claims 1 to 5 used for observing an image displayed on an image display surface of the image display element. Observation device. When half of the diagonal length of the image display surface of the image display element is H,
0.25 <H / f <0.40
The observation device according to claim 6, wherein the observation device satisfies the conditional expression. The sixth or seven claim 6 or 7 for observing an image pickup optical system that captures an object image, an image display element that displays an object image captured by the image pickup optical system, and an image displayed by the image display element. An image pickup device characterized by having an observation device.

Images