JP2013214018A5 - - Google Patents

Description

Finder optical system of the present invention, an erect forming member for an object image formed to a predetermined Teimen and erected, in a finder optical system having an eyepiece for observing the object image through the positive statue forming member ,
The eyepiece has, in order from the object 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,
The second lens group moves in the optical axis direction so that the interval between adjacent lens groups changes during diopter adjustment,
When the focal length of the entire system when the finder diopter is -1 diopter is f, the focal length of the first lens group is f1, and the focal length of the third lens group is f3,
-2.40 <f1 / f <-1.15
-1.6 <f3 / f <-0.8
It satisfies the following conditional expression.

Reference numeral 6 denotes an eyepiece, which constitutes a part of the finder optical system. The eyepiece 6 includes a first lens unit L1 having a negative refractive power, a second lens L2 having a positive refractive power, and a third lens unit L3 having a negative refractive power from the penta roof mirror 5 side to the observation side. Then, diopter adjustment is performed by moving the second lens unit L2 along the optical axis La of the eyepiece 6 (finder optical system). That is, the distance between adjacent lens groups changes during diopter adjustment. Here, each lens group consists of a single lens or a plurality of lenses. Reference numeral 7 denotes an eye point where an observer's eye is located. The distance from the final lens surface Rb of the eyepiece 6 to the eye point 7 on the observation side corresponds to the eye relief.

In each embodiment, when the finder diopter is −1 diopter, the focal length of the entire system is f, the focal length of the first lens unit L1 is f1, and the focal length of the third lens unit L3 is f3. The first lens unit L1 includes one negative lens, and the Abbe number of the negative lens material is νd. At this time, one or more of the following conditions are satisfied.

In each embodiment, the first lens unit L1 includes a negative lens having a concave surface on the observation side. The second lens unit L2 is composed of a biconvex positive lens. The third lens unit L3 is composed of a positive convex positive lens and a biconcave negative lens in Examples 1 to 7 in order from the object side to the observation side . In Example 8, the third lens unit L3 is composed of a negative lens having a concave surface on the observation side. The first lens group L1 and the second lens group L2 may be composed of two or more lenses, and the third lens group L3 may be composed of three or more lenses.

r1 corresponds to the matte surface (the surface on which the object image is formed) of the focusing screen 4. r2 is a design dummy surface provided on the object side of the eyepiece 6. In Numerical Examples 1 to 7, r3 to r10 and in Numerical Example 8 r3 to r8 are the radii of curvature of the lens surfaces constituting the eyepiece 6. The final side shows the Ipon yarn. 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 is a conic coefficient , and A4, A6, A8, and A10 are aspheric coefficients ,

Claims (5)

An erect forming member for an object image formed to a predetermined Teimen and erected, in a finder optical system having an eyepiece for observing the object image through the positive figurine forming member,
The eyepiece has, in order from the object 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,
The second lens group moves in the optical axis direction so that the interval between adjacent lens groups changes during diopter adjustment,
When the focal length of the entire system when the finder diopter is -1 diopter is f, the focal length of the first lens group is f1, and the focal length of the third lens group is f3,
-2.40 <f1 / f <-1.15
-1.6 <f3 / f <-0.8
A finder optical system characterized by satisfying the following conditional expression: The first lens group consists of one negative lens, when the Abbe number of the material of the negative lens with [nu] d,
νd <25
The finder optical system according to claim 1 , wherein the following conditional expression is satisfied. The first lens group is composed of a negative lens having a concave surface on the observation side, the second lens group is composed of a biconvex positive lens, and the third lens group is in order from the object side to the observation side. finder optical system according to claim 1 or 2, characterized in that it is composed of a positive lens and a double concave negative lens of biconvex shape. The first lens group is composed of a negative lens having a concave surface on the observation side, the second lens group is composed of a biconvex positive lens, and the third lens group has a concave surface on the observation side. The finder optical system according to claim 1 , wherein the finder optical system is constituted by a negative lens.   An imaging apparatus comprising: the finder optical system according to claim 1; and an imaging unit that receives an image corresponding to an object image displayed by the finder optical system.