JP5907612B2 - Eyepiece lens and viewfinder optical system having the same - Google Patents

Description

  The present invention relates to an eyepiece suitable for observing an object image formed on a predetermined surface with a photographing lens and a finder optical system having the eyepiece, and particularly suitable for a finder optical system such as a single-lens reflex camera.

  Conventionally, eyepiece lenses are often used for magnifying and observing an object image formed on a predetermined surface by a photographing lens. As a finder optical system having an eyepiece, a single-lens reflex camera observes a subject image (finder image) formed on a focusing screen by a photographic lens through the finder optical system. This viewfinder optical system is configured to view an object image formed on a focusing screen as an erect image through an erect image forming member such as a penta roof mirror or a penta roof prism, and then enlarge and observe the image with an eyepiece. Yes.

  There have been proposed eyepiece lenses having a configuration capable of obtaining a large observation magnification in a finder optical system of a single-lens reflex camera (Patent Documents 1 and 2). The eyepiece of Patent Document 1 is a meniscus negative lens having a convex surface facing a predetermined surface, a positive lens, and a meniscus negative having a convex surface facing a predetermined surface in order from the predetermined surface (focal plate) side to the observation side. It consists of a lens. Further, the eyepiece lens of Patent Document 2 is composed of a meniscus-shaped negative lens having a concave surface directed to the predetermined surface side, a positive lens, a positive lens, and a negative lens having a concave surface directed to the observation side in order from the predetermined surface side to the observation side. ing.

JP 2001-311881 A JP 2000-111810 A

  In general, an eyepiece that magnifies and observes an object image is used in various environments. For example, it is used in various environments such as high temperature and high humidity and low temperature and low humidity. For this reason, if the water absorption rate of the lens material constituting the eyepiece lens is high, the lens may absorb water when the environment in which it is used changes, resulting in a significant change in optical performance. When a resin material is used as the material of the lens constituting the eyepiece, there is an advantage that the processing of the lens becomes easy and the aspherical processing becomes easy.

  However, in general, many resin materials have a high water absorption rate. For this reason, when a resin material is used as the material of the lens constituting the eyepiece, it is important to select a material that reduces the change in optical performance even when there is an environmental change.

  In the finder optical system disclosed in Patent Document 1, the most observing lens material is made of acrylic resin or polycarbonate resin. When an acrylic resin is used, the water absorption rate of the acrylic resin is high, so the lens surface shape and refractive index change due to changes over time, and this change occurs over a long period of time, especially with a lens with a thick center thickness. It becomes. On the other hand, if the center thickness of the lens is reduced, the observation magnification decreases. Further, when polycarbonate resin is used, the water absorption is lower than that of acrylic resin, so that the change in lens surface shape and refractive index is small, but there is a problem that scratches are likely to occur due to insufficient hardness.

  In the eyepiece lens of the single-lens reflex camera disclosed in Patent Document 2, the eyepiece lens is composed of four lenses so that the center thickness of the lens does not increase. As a result, there is little deterioration in optical performance due to water absorption. However, since the number of eyepiece lenses is large, the mechanical structure is complicated, and the transmittance tends to decrease.

  An object of the present invention is to provide an eyepiece lens that can reduce observation of a finder image due to water absorption by the lens when used in various environments, and can provide good finder image observation, and a finder optical system having the eyepiece. And

The eyepiece of the present invention is an eyepiece for observing an object image formed on a predetermined surface, and a cemented lens obtained by joining a plurality of lenses made of a resin material is disposed on the most observation side of the eyepiece. And
The center thickness of the thickest lens center thickness among lenses constituting the cemented lens t1, the water absorption of the material of the thickest lens center thickness among lenses constituting the cemented lens A, the junction When the center thickness of the lens arranged closest to the observation side among the lenses constituting the lens is t2, and the water absorption rate of the material of the lens arranged closest to the observation side among the lenses constituting the cemented lens is B. ,
1 <B / A <35
2 ≦ t1 / t2 <20
It satisfies the following conditional expression.

  According to the present invention, it is possible to obtain an ocular lens that can reduce the deterioration of observation of a finder image due to water absorption of the lens when used in various environments, and can observe an excellent finder image.

Cross-sectional view of essential parts when a finder optical system having an eyepiece of the present invention is applied to a single-lens reflex camera Lens sectional view of Numerical Example 1 of the present invention (A), (B), (C) Aberration diagrams of Numerical Example 1 of the present invention Lens sectional view of Numerical Example 2 of the present invention (A), (B), (C) Aberration diagrams of Numerical Example 2 of the present invention Lens sectional view of Numerical Example 3 of the present invention (A), (B), (C) Aberration diagrams of Numerical Example 3 of the present invention Lens sectional view of Numerical Example 4 of the present invention (A), (B), (C) Aberration diagrams of Numerical Example 4 of the present invention Lens sectional view of Numerical Example 5 of the present invention (A), (B), (C) Aberration diagrams of Numerical Example 5 of the present invention

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The eyepiece of the present invention is an eyepiece for observing an object image formed on a predetermined surface. The most viewing side of the eyepiece lens cemented lens is arranged that by joining a plurality of lens made of a resin material. The eyepiece lens is a joint obtained by joining a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a plurality of lenses made of a resin material in order from a predetermined surface side on which an object image is formed to the observation side. The third lens group includes a lens and a negative refractive power.

  Alternatively, the eyepiece has a negative refractive power including a first lens group having a positive refractive power and a cemented lens in which a plurality of lenses made of a resin material are joined in order from a predetermined surface side on which an object image is formed to the observation side. It consists of two lens groups.

  FIG. 1 is a cross-sectional view of a main part when a finder optical system having an eyepiece of the present invention is applied to a digital single lens reflex camera as an imaging device. FIG. 2 is a lens cross-sectional view of Example 1 of the eyepiece optical system of the present invention. 3A, 3B, and 3C are aberration diagrams when the viewfinder diopter in the first embodiment of the eyepiece optical system according to the present invention is -1 diopter (standard diopter), -3 diopter, and +1 diopter. is there.

  FIG. 4 is a lens sectional view of Example 2 of the eyepiece optical system of the present invention. FIGS. 5A, 5B, and 5C are aberration diagrams when the viewfinder diopter is −1 diopter (standard diopter), −3 diopter, and +1 diopter in Example 2 of the eyepiece optical system of the present invention. is there. FIG. 6 is a lens sectional view of Example 3 of the eyepiece optical system according to the present invention. FIGS. 7A, 7B, and 7C are aberration diagrams when the viewfinder diopter in the third embodiment of the eyepiece optical system of the present invention is −1 diopter (standard diopter), −3 diopter, and +1 diopter. is there.

FIG. 8 is a lens cross-sectional view of Example 4 of the eyepiece optical system according to the present invention. FIGS. 9A, 9B, and 9C are aberration diagrams when the viewfinder diopter is −1 diopter (standard diopter), −3 diopter, and +1 diopter in Example 4 of the eyepiece optical system of the present invention. is there. FIG. 10 is a lens sectional view of Example 5 of the eyepiece optical system according to the present invention. FIGS. 11A, 11B, and 11C illustrate the case where the viewfinder diopter is −1 diopter (standard diopter), −1.7 diopter, and +0.5 diopter in Example 5 of the eyepiece optical system of the present invention. FIG.

  In FIG. 1 and the lens cross-sectional view, reference numeral 1 denotes a photographing lens that can be fixed to or detached from a camera body (not shown). Reference numeral 2 denotes a quick return mirror (QR mirror), which is rotatable as indicated by an arrow 2b around a rotation shaft 2a, and reflects a light beam from the photographing lens 1 upward. Reference numeral 3 denotes a focusing screen (Fresnel lens). Reference numeral 3a denotes a mat surface of the focusing screen 3, on which a subject image (finder image) is formed by the photographing lens 1.

  Reference numeral 4 denotes a penta roof mirror as an erect image forming member. The subject image on the mat surface 3a is an erect image. Reference numeral 4a denotes an incident portion of the penta roof mirror 4, and a light flux related to the subject image from the mat surface 3a enters. 4b is a roof-shaped first reflecting mirror that constitutes the penta roof mirror 4, and reflects the light beam incident from the incident portion 4a to the subject image side (object side) in the subject image formed on the mat surface 3a. ing. Reference numeral 4c denotes a second reflecting mirror that reflects the light beam reflected to the object side by the first reflecting mirror 4b in the observation side direction (eye point IP side).

  Reference numeral 4 d denotes an emission part of the penta roof mirror 4. The erect image forming member may be composed of a penta roof prism or a plurality of prisms in addition to the penta roof mirror. Reference numeral 5 denotes an eyepiece, which constitutes a part of the finder optical system. In Examples 1 to 4 of FIGS. 2, 4, 6, and 8, the eyepiece 5 includes, in order from the penta roof mirror 4 side to the observation side, a first lens unit L1 having a negative refractive power and a positive refractive power. The second lens L2 includes a third lens unit L3 having a negative refractive power.

Then, by moving the second lens group L2 along the optical axis La of the eyepiece lens 5 (finder optical system), the distance between adjacent lens groups is changed to adjust the diopter. Here, each lens group consists of a single lens or a plurality of lenses.

In Example 5 of FIG. 10, the eyepiece 5 is composed of a first lens unit L1 having a positive refractive power and a second lens unit L2 having a negative refractive power including a cemented lens in order from the penta roof mirror 4 side to the observation side. Yes. Then, by moving the first lens unit L1 along the direction of the optical axis La, the distance between adjacent lens units is changed to adjust the diopter. Reference numeral 6 denotes an eye point where an observer's eye is located. The distance from the last lens surface of the eyepiece 5 to the eye point 6 on the observation side corresponds to the eye relief. IP is an image plane of the photographic lens 1 and corresponds to an imaging surface of a solid-state imaging device (imaging means) such as a CCD sensor or a CMOS sensor or a photosensitive surface such as a film (imaging means).

  The finder optical system in the present embodiment is formed on the mat surface 3 a of the focusing screen 3 by reflecting the subject image by the photographing lens 1 with the quick return mirror 2. The finder image formed on the mat surface 3a is observed from the eye point 6 through the eyepiece 5 as an erect image by the penta roof mirror 4.

  When an image is formed on the image pickup means, the quick return mirror 2 is rotated as indicated by an arrow 2b so that the light flux from the photographing lens 1 is incident on the image plane IP. Then, an image corresponding to the subject image formed on the mat surface 3a (a part or all of the subject image or an image of a portion larger than the subject image) is photoelectrically converted (received) by the imaging means arranged on the image plane IP. .

  In the spherical aberration diagram, the solid line d is d line and the two-dot chain line g is g line. In the astigmatism diagram, M is a meridional image plane, and S is a sagittal image plane. Distortion is shown for the d-line. In the lateral chromatic aberration diagram, the g-line with respect to the d-line is shown. φ is the pupil diameter. h is the image height on the mat surface 3a side.

Eyepiece 5 in each example are arranged cemented lens in which a plurality of lenses made of a resin material and most observation side (eye point side 6). The center thickness of the lens having the thickest center thickness among the lenses constituting the cemented lens and the water absorption rate of the material are t1 and A, respectively. The center thickness of the lens arranged closest to the observation side and the water absorption rate of the material among the lenses constituting the cemented lens are t2 and B, respectively. At this time,
1 <B / A <35 (1)
2 ≦ t1 / t2 <20 (2)
The following conditional expression is satisfied.

  Here, the water absorption rate is a numerical value representing the amount of water absorption when a certain material is immersed in water and sufficiently absorbs water as a ratio to a certain amount of dry matter. The water absorption rate is measured by the JIS measurement method. Here, the conditional expression (1) defines the water absorption rate of the material of each lens of the cemented lens while considering the optical performance of the eyepiece lens, and the conditional expression (2) is the optical axis of each lens of the cemented lens. Specifies the thickness ratio above.

  These conditional expressions (1) and (2) are conditional expressions for realizing a high finder magnification while reducing deterioration of the optical performance of the finder optical system due to a change with time. More than half of the volume of each lens constituting the cemented lens is made of a material with a low water absorption rate, and the center thickness is increased to reduce the deterioration of the optical performance of the finder optical system due to changes over time, while providing high magnification. Has been realized. More preferably, the numerical ranges of conditional expressions (1) and (2) are set as follows.

1.2 <B / A <32.0 (1a)
3 ≦ t1 / t2 <15 (2a)
As described above, according to each embodiment, a finder optical system having a high-magnification eyepiece can be obtained while maintaining a strength as an appearance part with a simple configuration and little change with time. Further, among the cemented surfaces of the cemented lens, when the radius of curvature of the cemented surface closest to the observation side is Ra, and the radius of curvature of the lens surface closest to the observation side of the cemented lens is Rb,
0.9 <Ra / Rb <1.1 (3)
It is trying to become.

  That is, the shape of the cemented lens surface of the cemented lens and the shape of the lens surface closest to the observation side (eye point side) of the cemented lens are made substantially the same. If the shape of the cemented lens surface of the cemented lens and the shape of the lens surface closest to the observation side of the cemented lens are greatly different, there is a problem that the mold structure becomes complicated at the time of manufacturing by injection molding or the like. By satisfying the conditional expression (3) that the shape of the cemented lens surface of the cemented lens and the shape of the lens surface closest to the observation side of the cemented lens are substantially the same, the lens can be easily manufactured.

[Example 1]
Hereinafter, with reference to FIG. 2, an eyepiece lens 5 constituting a finder optical system according to Example 1 of the present invention will be described. The eyepiece 5 includes, in order from the focal plane 3 side to the observation side (eye point IP side), a first lens unit L1 including a first lens G1 having a negative refractive power and a second lens G2 including a second lens G2 having a positive refractive power. The lens unit L2 includes a third lens unit L3 including a third lens G3 having a negative refractive power. Diopter adjustment is performed by moving the second lens G2 in the optical axis direction. The third lens G3 is a cemented lens obtained by cementing a lens G3a made of styrene resin and a lens G3b made of acrylic resin.

  By making the center thickness of the lens Ga3 made of styrene resin having a low water absorption rate thicker than that of the lens G3b made of an acrylic resin having a high water absorption rate, the deterioration of the optical performance of the finder optical system due to change over time can be reduced. High magnification is realized. In addition, the eye point IP side is formed by a lens G3b made of an acrylic resin, so that the strength as an external component is sufficiently maintained.

[Example 2]
Hereinafter, with reference to FIG. 4, an eyepiece lens 5 constituting a finder optical system according to a second embodiment of the present invention will be described. The eyepiece 5 includes, in order from the focal plane 3 side to the observation side, a first lens unit L1 including a first lens G1 having a negative refractive power, a second lens unit L2 including a second lens G2 having a positive refractive power, and a negative lens unit L2. The third lens unit L3 includes the third lens unit L3. Diopter adjustment is performed by moving the second lens G2 in the optical axis direction. The third lens G3 is a cemented lens in which a lens G3a made of polycarbonate resin and a lens G3b made of acrylic resin are joined.

  The lens G3a made of a polycarbonate resin having a low water absorption rate is made thicker than the lens G3b made of an acrylic resin having a high water absorption rate, thereby reducing the deterioration of the optical performance of the finder optical system due to changes over time. High magnification is realized. In addition, the eye point IP side is formed by a lens G3b made of an acrylic resin, so that the strength as an external component is sufficiently maintained.

[Example 3]
Hereinafter, with reference to FIG. 6, an eyepiece lens 5 constituting a finder optical system according to Example 3 of the present invention will be described. The eyepiece 5 includes, in order from the focal plane 3 side to the observation side, a first lens unit L1 including a first lens G1 having a negative refractive power, a second lens unit L2 including a second lens G2 having a positive refractive power, and a negative lens unit L2. The third lens unit L3 includes a third lens G3 having refractive power. Diopter adjustment is performed by moving the positive second lens G2 in the optical axis direction.

  The third lens G3 is a cemented lens in which a lens G3a made of an olefin resin and a lens G3b made of an acrylic resin are joined. By making the center thickness of the lens G3a made of an olefin resin having a low water absorption rate thicker than that of the lens G3b made of an acrylic resin having a high water absorption rate, the deterioration of the optical performance of the finder optical system due to changes over time can be reduced. High magnification is realized. In addition, the eye point IP side is formed by a lens G3b made of an acrylic resin, so that the strength as an external component is sufficiently maintained.

[Example 4]
Hereinafter, with reference to FIG. 8, an eyepiece lens 5 constituting a finder optical system according to Example 4 of the present invention will be described. The eyepiece 5 includes, in order from the focal plane 3 side to the observation side, a first lens unit L1 including a first lens G1 having a negative refractive power, a second lens unit L2 including a second lens G2 having a positive refractive power, and a negative lens unit L2. The third lens unit L3 includes a third lens G3 having a refractive power. Diopter adjustment is performed by moving the second lens G2 in the optical axis direction. The third lens G3 is a cemented lens in which a lens G3a made of acrylic resin, a lens G3b made of olefin resin, and a lens G3c made of acrylic resin are joined.

  By making the center thickness of the lens G3b made of an olefin resin having a low water absorption rate thicker than that of the lenses G3a and G3c made of an acrylic resin having a high water absorption rate, the deterioration of the optical performance of the finder optical system due to changes over time is reduced. Realizes higher viewfinder magnification. In addition, since the focal plane 3 side and the most eyepoint IP side are formed by lenses G3a and G3c made of acrylic resin, the strength as an external part is sufficiently maintained and scratches do not easily occur during assembly. It has become a structure.

[Example 5]
Hereinafter, with reference to FIG. 10, an eyepiece lens 5 constituting a finder optical system according to Example 5 of the present invention will be described. The eyepiece 5 includes, in order from the focal plane 3 side to the observation side, a first lens group L1 including a first lens G1 having a positive refractive power and a second lens group L2 including a second lens G2 having a positive refractive power. ing. Diopter adjustment is performed by moving the first lens G1 in the optical axis direction. The second lens G2 is a cemented lens in which a lens G2a made of styrene resin and a lens G2b made of acrylic resin are joined.

  By making the center thickness of the lens G2a made of a styrene resin having a low water absorption rate thicker than that of the lens G2b made of an acrylic resin having a high water absorption rate, the deterioration of the optical performance of the finder optical system due to changes over time can be reduced. High magnification is realized. In addition, since the eye point IP side is formed by the lens G2b made of an acrylic resin, the strength as an external component is sufficiently maintained. In addition, you may comprise the 2nd lens G2a from the lens which consists of a 3 or more resin material.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  Next, numerical examples corresponding to the respective examples will be shown. In each numerical example, the surface number indicates the order from the focusing screen 3. ri is the radius of curvature of the i-th optical element surface in order from the focusing screen 3 side, and di is the i-th optical element thickness and air spacing in order from the focusing screen 4 side. ndi and νdi are respectively the refractive index and Abbe number of the material of the i-th optical element in order from the focusing screen 3 side.

  r1 corresponds to the mat surface (surface on which the object image is formed) 3a of the focusing screen 3. r2 is a design dummy surface provided on the object side of the eyepiece 5. In Numerical Examples 1 to 3, r3 to r9, r3 to r10 in Numerical Example 4, and r3 to r7 in Numerical Example 5 are the radii of curvature of the lens surfaces constituting the eyepiece 5. The final surface shows the eye point. In each numerical example, an asterisk represents an aspherical surface. The aspherical shape has an X axis in the optical axis direction, a Y axis in the direction perpendicular to the optical axis, and the light traveling direction is positive, and R is a paraxial radius of curvature. , K, A4, A6, A8, A10,

Is defined by Further, the display of “e-0X” means “10 ^−X ”. In the numerical examples, the eye point indicates the distance (eye relief) from the final lens surface of the eyepiece to the eye point. Table 1 shows the relationship between the conditional expressions described above and the numerical values in the numerical examples.

[Numerical Example 1]
Unit mm
Surface data surface number rd nd νd
1 ∞ 69.30
2 ∞ 0.56
3 -1001.758 1.73 1.58306 30.2
4 * 28.991 (variable)
5 * 17.588 5.50 1.52470 56.2
6 * -26.872 (variable)
7 * 32.352 9.00 1.57090 33.8
8 * 12.500 1.00 1.49171 57.4
9 * 12.500 18.70
10 (eye point)

Aspheric data 4th surface
K = 4.48789e + 000 A 4 = -4.44800e-005 A 6 = 2.46811e-007 A 8 = -3.81009e-009 A10 = 6.51901e-012

5th page
K = 1.62127e-001 A 4 = -4.23052e-005 A 6 = 3.57575e-007 A 8 = -3.25228e-009 A10 = 3.45322e-012

6th page
K = -1.32438e + 000 A 4 = 1.09304e-005 A 6 = 1.15404e-007 A 8 = -2.20037e-010 A10 = -4.73186e-012

7th page
K = -2.41809e + 001 A 4 = 5.51729e-005 A 6 = -9.36119e-007 A 8 = 9.32374e-009 A10 = -3.33107e-011

8th page
K = 4.06428e-001 A 4 = -1.24602e-004 A 6 = -9.23245e-007 A 8 = 2.78945e-008 A10 = -2.89467e-010

9th page
K = 4.06428e-001 A 4 = -1.24602e-004 A 6 = -9.23245e-007 A 8 = 2.78945e-008 A10 = -2.89467e-010

Various data diopters -1 -3 +1
Focal length 59.90 60.85 58.69
Eyepoint 18.70 18.70 18.70

Variable interval -1 -3 +1
d 4 1.81 0.44 3.47
d 6 2.16 3.45 0.47

[Numerical Example 2]
Unit mm
Surface data surface number rd nd νd
1 ∞ 69.30
2 ∞ 0.56
3 -1001.568 1.73 1.58306 30.2
4 * 29.127 (variable)
5 * 17.639 5.50 1.52470 56.2
6 * -26.806 (variable)
7 * 31.898 9.00 1.58306 30.2
8 * 12.500 1.00 1.49171 57.4
9 * 12.500 18.70
10 (eye point)

Aspheric data 4th surface
K = 4.55671e + 000 A 4 = -4.39571e-005 A 6 = 2.45415e-007 A 8 = -3.81667e-009 A10 = 6.47179e-012

5th page
K = 1.85509e-001 A 4 = -4.16754e-005 A 6 = 3.54706e-007 A 8 = -3.25787e-009 A10 = 3.36024e-012

6th page
K = -1.47199e + 000 A 4 = 9.98196e-006 A 6 = 1.18620e-007 A 8 = -2.30085e-010 A10 = -4.78101e-012

7th page
K = -2.33584e + 001 A 4 = 5.53951e-005 A 6 = -9.39138e-007 A 8 = 9.36912e-009 A10 = -3.36195e-011

8th page
K = 3.82770e-001 A 4 = -1.23813e-004 A 6 = -9.30213e-007 A 8 = 2.89711e-008 A10 = -2.98842e-010

9th page
K = 3.82770e-001 A 4 = -1.23813e-004 A 6 = -9.30213e-007 A 8 = 2.89711e-008 A10 = -2.98842e-010

Various data diopters -1 -3 +1
Focal length 59.71 60.59 58.53
Eyepoint 18.70 18.70 18.70

Variable interval -1 -3 +1
d 4 1.81 0.44 3.47
d 6 2.16 3.45 0.47

[Numerical Example 3]
Unit mm
Surface data surface number rd nd νd
1 ∞ 69.30
2 ∞ 0.56
3 -989.318 1.73 1.58306 30.2
4 * 28.587 (variable)
5 * 17.422 5.50 1.52470 56.2
6 * -26.938 (variable)
7 * 34.611 9.00 1.52470 56.2
8 * 12.500 1.00 1.49171 57.4
9 * 12.500 18.70
10 (eye point)

Aspheric data 4th surface
K = 4.36424e + 000 A 4 = -4.40489e-005 A 6 = 2.07436e-007 A 8 = -3.61883e-009 A10 = 6.55971e-012

5th page
K = 1.13930e-001 A 4 = -4.14679e-005 A 6 = 3.21259e-007 A 8 = -3.24935e-009 A10 = 4.63036e-012

6th page
K = -1.75427e + 000 A 4 = 7.64947e-006 A 6 = 1.10899e-007 A 8 = -2.82219e-010 A10 = -4.29459e-012

7th page
K = -2.81253e + 001 A 4 = 4.84317e-005 A 6 = -8.90632e-007 A 8 = 9.44677e-009 A10 = -3.56521e-011

8th page
K = 9.84666e-002 A 4 = -1.06692e-004 A 6 = -6.61384e-007 A 8 = 2.64803e-008 A10 = -2.51819e-010

9th page
K = 9.84666e-002 A 4 = -1.06692e-004 A 6 = -6.61384e-007 A 8 = 2.64803e-008 A10 = -2.51819e-010

Various data diopters -1 -3 +1
Focal length 60.33 61.50 59.02
Eyepoint 18.70 18.70 18.70

Variable interval -1 -3 +1
d 4 1.72 0.39 3.46
d 6 2.28 3.48 0.47

[Numerical Example 4]
Unit mm
Surface data surface number rd nd νd
1 ∞ 69.30
2 ∞ 0.56
3 -993.303 1.73 1.58306 30.2
4 * 32.764 (variable)
5 * 18.960 5.50 1.52470 56.2
6 * -30.115 (variable)
7 * 28.341 1.00 1.49171 57.4
8 * 28.341 8.00 1.57090 33.8
9 * 12.500 1.00 1.49171 57.4
10 * 12.500 18.70
11 (eye point)

Aspheric data 4th surface
K = -2.34785e + 001 A 4 = 5.89174e-005 A 6 = -4.87523e-007 A 8 = 3.42804e-009 A10 = -1.32130e-011

5th page
K = 3.79092e-001 A 4 = -4.26165e-005 A 6 = 1.75238e-007 A 8 = -4.05800e-009 A10 = 2.33043e-011

6th page
K = 1.78039e + 000 A 4 = 3.51228e-005 A 6 = -2.56307e-008 A 8 = -2.10183e-009 A10 = 2.05158e-011

7th page
K = -3.24761e + 000 A 4 = -5.21113e-006 A 6 = 2.51342e-007 A 8 = -3.20582e-009 A10 = 1.71320e-011

8th page
K = -3.24761e + 000 A 4 = -5.21113e-006 A 6 = 2.51342e-007 A 8 = -3.20582e-009 A10 = 1.71320e-011

9th page
K = -3.28686e + 000 A 4 = 1.01430e-004 A 6 = 1.01729e-006 A 8 = -3.43287e-008 A10 = 2.95975e-010

10th page
K = -3.28686e + 000 A 4 = 1.01430e-004 A 6 = 1.01729e-006 A 8 = -3.43287e-008 A10 = 2.95975e-010

Various data diopters -1 -3 +1
Focal length 59.66 60.73 58.54
Eyepoint 19.70 19.70 19.70

Variable interval -1 -3 +1
d 4 1.73 0.32 3.51
d 6 2.23 3.56 0.46

[Numerical Example 5]
Unit mm
Surface data surface number rd nd νd
1 ∞ 69.90
2 ∞ (variable)
3 * 105.777 3.74 1.49171 57.4
4 -65.790 (variable)
5 * 15.734 9.00 1.57090 33.8
6 12.500 1.00 1.49171 57.4
7 12.500 18.00
8 (Eyepoint)

Aspheric data 3rd surface
K = 1.56581e + 001 A 4 = 1.79204e-006 A 6 = -6.30549e-008 A 8 = 4.42203e-010 A10 = -9.28471e-013

5th page
K = -2.33470e + 000 A 4 = 6.58237e-005 A 6 = 2.50247e-008 A 8 = -6.18204e-010 A10 = 3.08283e-012

Various data diopters -1 -1.7 +0.5
Focal length 60.95 61.23 60.88
Eyepoint 18.00 18.00 18.00

Variable interval -1 -1.7 +0.5
d 2 3.27 0.50 8.84
d 4 6.39 9.16 0.82

The numerical values of the conditional expressions in each example are shown below .

1: Shooting lens 2: Quick return mirror 3: Focus plate 4: Pentadaha mirror 5: Eyepiece

Claims (6)

An eyepiece lens for observing an object image formed on a predetermined surface, and a cemented lens in which a plurality of lenses made of a resin material are cemented is arranged on the most observation side of the eyepiece lens to constitute the cemented lens. T1 is the center thickness of the lens having the thickest center thickness among the lenses to be processed, A is the water absorption rate of the material of the lens having the thickest center thickness among the lenses constituting the cemented lens, and the lens constituting the cemented lens. When the center thickness of the lens arranged closest to the observation side is t2, and the water absorption of the material of the lens arranged closest to the observation side among the lenses constituting the cemented lens is B,
1 <B / A <35
2 ≦ t1 / t2 <20
An eyepiece that satisfies the following conditional expression: Of the cemented surfaces of the cemented lens, when the radius of curvature of the cemented surface closest to the observation side is Ra, and the radius of curvature of the lens surface closest to the observation side of the cemented lens is Rb,
0.9 <Ra / Rb <1.1
The eyepiece according to claim 1, wherein the following conditional expression is satisfied. The eyepiece lens includes, in order from the predetermined surface side to the observation side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power including the cemented lens. The distance between adjacent lens groups changes when adjusting diopter,
The eyepiece lens according to claim 1, wherein diopter adjustment is performed by moving the second lens group in an optical axis direction. The eyepiece includes a first lens group having a positive refractive power and a second lens group having a positive refractive power including the cemented lens in order from the predetermined surface side to the observation side, and adjacent lens groups for diopter adjustment. The interval of
The eyepiece lens according to claim 1 or 2, wherein diopter adjustment is performed by moving the first lens group in an optical axis direction.   5. A finder optical system comprising: an erect image forming member having an object image formed on the predetermined surface as an erect image; and the eyepiece according to claim 1.   6. An imaging apparatus comprising: the finder optical system according to claim 5; and imaging means for receiving an image corresponding to a subject image displayed by the finder optical system.