Optical system, finder optical system, relay type finder optical system, eyepiece optical system, and single-lens reflex camera

A finder optical system, comprising:

• a relay optical system operable to re-form a subject image at a secondary image-formation position wherein the subject image is a primary image formed at a primary image-formation position through an objective optical system, and
• an eyepiece optical system operable to view an image re-formed through the relay optical system, wherein:
• the finder optical system comprises at least four reflecting surfaces including an F3 reflecting surface, an F2 reflecting surface, an F1 reflecting surface and an R1 reflecting surface located between the primary image-formation position and the secondary image-formation position side and in an optical path order from a primary image-formation position side to a secondary image-formation position side, and at least one positive lens located between the F1 reflecting surface and the R1 reflecting surface,
• the finder optical system has an optical axis reflected at each of the reflecting surfaces, and
• when a direction of a light ray traveling on an optical axis is taken as an optical axis direction and a component parallel with an optical axis direction exiting the eyepiece optical system is taken as a transverse component,
• a transverse component in an optical axis direction exiting from the F2 reflecting surface is opposite to an optical axis direction exiting the eyepiece optical system, and
• a transverse component in an optical axis direction exiting from the R1 reflecting surface is opposite to the optical axis direction exiting the eyepiece optical system.

A finder optical system, comprising:

• a relay optical system operable to re-form a subject image at a secondary image-formation position wherein the subject image is a primary image formed at a primary image-formation position through an objective optical system, and
• an eyepiece optical system operable to view an image re-formed through the relay optical system, wherein:
• the finder optical system comprises at least four reflecting surfaces including an F3 reflecting surface, an F2 reflecting surface, an F1 reflecting surface and an R1 reflecting surface located between the primary image-formation position and the secondary image-formation position side and in an optical path order from a primary image-formation position side to a secondary image-formation position side, and at least one positive lens located between the F1 reflecting surface and the R1 reflecting surface,
• the finder optical system has an optical axis reflected at each of the reflecting surfaces, and
• when a direction of a light ray traveling on an optical axis is taken as an optical axis direction and a component parallel with an optical axis direction exiting the eyepiece optical system is taken as a transverse component,
• a transverse component in an optical axis direction incident on the F1 reflecting surface is opposite to an optical axis direction exiting the eyepiece optical system, and
• a transverse component in an optical axis direction exiting from the R1 reflecting surface is opposite to the optical axis direction exiting the eyepiece optical system.

A finder optical system, comprising:

• a relay optical system operable to re-form a subject image at a secondary image-formation position wherein the subject image is a primary image formed at a primary image-formation position through an objective optical system, and
• an eyepiece optical system operable to view an image re-formed through the relay optical system, wherein:
• the finder optical system comprises at least four reflecting surfaces including an F3 reflecting surface, an F2 reflecting surface, an F1 reflecting surface and an R1 reflecting surface located between the primary image-formation position and the secondary image-formation position side and in an optical path order from a primary image-formation position side to a secondary image-formation position side, and at least one positive lens located between the F1 reflecting surface and the R1 reflecting surface,
• an optical axis is acutely reflected at the F1 reflecting surface and acutely reflected at the R1 reflecting surface, and
• an angle that the F1 reflecting surface subtends the R1 reflecting surface is an acute angle, provided that when at least one of the F1 reflecting surface and the R1 reflecting surface is a curved reflecting mirror, the subtending angle is given by an angle that tangent planes subtend each other at a position of incidence of an optical axis.

A single-lens reflex camera, comprising:

• a light beam splitter means operable to split light beams incident through an objective optical system into a light beam incident on an image pickup device and a light beam incident on a finder optical system operable to bend a light beam to view a subject image, and
• a finder optical system operable to bend a light beam from the objective optical system to view a subject image, wherein:
• the finder optical system comprises a focal plane plate located at a primary image-formation position set at a surface optically equivalent to the image pickup device,
• a relay optical system operable to re-form a subject image at a secondary image-formation position wherein the subject image is a primary image formed at the primary image-formation position, and
• an eyepiece optical system operable to view an image re-formed through the relay optical system, and wherein:
• the finder optical system further comprises:
• an F1 reflecting surface, an R1 reflecting surface and an R2 reflecting surface located in an optical path order from a primary image-formation position side to a secondary image-formation position side, and
• at least one positive lens located between the F1 reflecting surface and the R1 reflecting surface, wherein:
• an optical axis of the finder optical system is reflected at each of the reflecting surfaces, wherein an optical axis is acutely reflected at the light beam splitter means, an optical axis is acutely reflected at the F1 reflecting surface, an optical axis is acutely reflected at the R1 reflecting surface,
• an angle that the F1 reflecting surface subtends the R1 reflecting surface is an acute angle, provided that when at least one of the F1 reflecting surface and the R1 reflecting surface is a curved reflecting mirror, the angle that the F1 reflecting surface subtends the R1 reflecting surface is given by an angle that tangent planes subtend each other at a position of incidence of an optical axis, and
• an optical axis of the eyepiece optical system is substantially parallel with an optical axis of the objective optical system.

A finder optical system, comprising:

• a relay optical system operable to re-form a subject image at a secondary image-formation position wherein the subject image is a primary image formed at a primary image-formation position through an objective optical system, and
• an eyepiece optical system operable to view an image re-formed through the relay optical system, wherein:
• the relay optical system comprises an FP lens group of positive refracting power, an N lens group of negative refracting power and an RP lens group of positive refracting power, wherein:
• the FP lens group of positive refracting power consists of a first lens having positive refracting power, and a second lens located on a side of the first lens facing the eyepiece optical system and having positive refracting power,
• the N lens group of negative refracting power consists of a third lens group located on a side of the FP lens group facing the eyepiece optical system and having negative refracting power, and
• the RP lens group of positive refracting power consists of a fourth lens located on a side of the N lens group facing the eyepiece optical system and having negative refracting power and a fifth lens located on an eyepiece optical system side with respect to the fourth lens and having positive refracting power, and
• the relay optical system satisfies the following condition with respect to a composite focal length, flr, of the EP lens group, the N lens group and the RP lens group, and an axial distance, dl, between the primary image-formation position and a surface of the first lens on a primary image-formation position side:
• 0.3<dl/flr<3 (3-1)

A finder optical system, comprising:

• a relay optical system operable to re-form a subject image at a secondary image-formation position wherein the subject image is a primary image formed at a primary image-formation position through an objective optical system, and
• an eyepiece optical system operable to view an image re-formed through the relay optical system, wherein:
• the relay optical system comprises an FP lens group of positive refracting power, an N lens group located on a side of the FP lens group facing the eyepiece optical system and having negative refracting power, and an RP lens group located on a side of the FP lens group facing the eyepiece optical system and having positive refracting power, wherein:
• the RP lens group consists of, in order from a primary image-formation position side to a secondary image-formation position side, a negative lens and a positive lens, and
• the relay optical system satisfies the following condition (3-2) with respect to an axial distance, drf, from a surface located in, and nearest to a secondary image-formation position side of, the FP lens group to a surface located in the N lens group and on a secondary image-formation position side and an axial distance, drr, from a surface located in the N lens group and on a secondary image-formation position side to a surface located in, and nearest to a primary image-formation position side of, the RP lens group:
• 0.2<drf/drr<0.8 (3-2)

A finder optical system, comprising:

• a relay optical system operable to re-form a subject image at a secondary image-formation position wherein the subject image is a primary image formed at a primary image-formation position through an objective optical system, and
• an eyepiece optical system operable to view an image re-formed through the relay optical system, wherein:
• the relay optical system comprises an FP lens group of positive refracting power, an N lens group of negative refracting power and an RP lens group of positive refracting power, wherein:
• the FP lens group of positive refracting power consists of a first lens having positive refracting power, and a second lens located on a side of the first lens facing the eyepiece optical system and having positive refracting power,
• the N lens group of negative refracting power consists of a third lens group located on an eyepiece optical system side with respect to the FP lens group and having negative refracting power, and
• the RP lens group of positive refracting power is located on an eyepiece optical system side with respect to the N lens group, and
• the relay optical system satisfies the following conditions (3-1) and (3-3) with respect to a composite focal length, fir, of the EP lens group, the N lens group and the RP lens group, an axial distance, dl, between the primary image-formation position and a surface of the first lens on a primary image-formation position side, and an axial distance, ds, from a surface located in the RP lens group and on a secondary image-formation position side to the secondary image-formation position:
• 0.3<dl/flr<3 (3-1)
• 0.5<ds/flr<2 (3-3)

A finder optical system, comprising:

• a relay optical system operable to re-form a subject image at a secondary image-formation position wherein the subject image is a primary image formed at a primary image-formation position through an objective optical system, and
• an eyepiece optical system operable to view an image re-formed through the relay optical system, wherein:
• the relay optical system comprises an FP lens group of positive refracting power, an N lens group of negative refracting power and an RP lens group of positive refracting power, wherein:
• the FP lens group of positive refracting power consists of a first lens having positive refracting power, and a second lens located on a side of the first lens facing the eyepiece optical system and having positive refracting power,
• the N lens group of negative refracting power consists of a third lens group located on an eyepiece optical system side with respect to the FP lens group and having negative refracting power, and
• the RP lens group of positive refracting power consists of a fourth lens located on an eyepiece optical system side with respect to the N lens group and having negative refracting power, and a fifth lens located on a side of the fourth lens facing the eyepiece optical system having positive refracting power, and
• the relay optical system satisfies the following conditions (3-1), (3-2) and (3-3) with respect to a composite focal length, flr, of the EP lens group, the N lens group and the RP lens group, an axial distance, dl, between the primary image-formation position and a surface of the first lens on a primary image-formation position side, an axial distance, drf, from a surface located in, and nearest to a secondary image-formation position side of, the FP lens group to a surface located in the N lens group and on a secondary image-formation position side, an axial distance, drr, from a surface located in the N-lens group and on a secondary image-formation position side to a surface located in, and nearest to a primary image-formation position side of, the RP lens, and an axial distance, ds, from a surface located in the RP lens group and on a secondary image-formation position side to the secondary image-formation position:
• 0.3<dl/flr<3 (3-1)
• 0.2<drf/drr<0.8 (3-2)
• 0.5<ds/flr<2 (3-3)

An eyepiece optical system, comprising, in order from a side of an image being viewed,

• a first lens having negative refracting power,
• a second lens having positive refracting power,
• a third lens having positive refracting power, and
• a fourth lens having positive refracting power,
• wherein the eyepiece optical system satisfies the following condition:
• 2.5≦f123/fA≦8 (4-1)
• where f123 is a composite focal length of the first lens, the second lens and the third lens, and
• fA is a focal length of the eyepiece optical system.

An eyepiece optical system, comprising, in order from a side of an image being viewed,

• a first lens having negative refracting power,
• a second lens having positive refracting power,
• a third lens having positive refracting power, and
• a fourth lens having positive refracting power,
• wherein the eyepiece optical system satisfies the following condition:
• 1≦f4/fA≦2 (4-2)
• where f4 is a focal length of the fourth lens, and
• fA is a focal length of the eyepiece optical system.

An eyepiece optical system, comprising, in order from a side of an image being viewed,

• a first lens having negative refracting power,
• a second lens having positive refracting power,
• a third lens having positive refracting power, and
• a fourth lens having positive refracting power,
• wherein the eyepiece optical system satisfies the following condition:
• 0.02≦d4/fA≦0.2 (4-3)
• where d4 is an axial thickness of the fourth lens, and
• fA is a focal length of the eyepiece optical system.

A relay type finder optical system, comprising:

• a relay optical system operable to re-form a primary image formed through a taking optical system, and
• an eyepiece optical system operable to view an image re-formed through the relay optical system, wherein:
• the eyepiece optical system comprises, in order from a relay optical system side,
• a first lens having negative refracting power,
• a second lens having positive refracting power,
• a third lens having positive refracting power, and
• a fourth lens having positive refracting power.

A relay type finder optical system, comprising:

• a relay optical system operable to re-form a subject image at a secondary image-formation position wherein the subject image is a primary image formed at a primary image-formation position through an objective optical system, and
• an eyepiece optical system operable to view an image re-formed through the relay optical system, wherein:
• the relay type finder optical comprises at least three reflecting surfaces located between the primary image-formation position and the secondary image-formation position, and
• the relay type finder optical system comprises a one-piece prism P1, wherein:
• of the at least three reflecting surfaces, two reflecting surfaces lying side by side on an optical axis in an optical path through the relay optical system are internal reflecting surfaces of the prism P1, and two such reflecting surfaces are total-reflection surfaces.

A relay type finder optical system, comprising:

• a relay optical system operable to re-form a subject image at a secondary image-formation position wherein the subject image is a primary image formed at a primary image-formation position through an objective optical system, and
• an eyepiece optical system operable to view an image re-formed through the relay optical system, wherein:
• the relay type finder optical comprises at least three reflecting surfaces located between the primary image-formation position and the secondary image-formation position, and
• the relay type finder optical system comprises a one-piece prism P1, wherein:
• of the at least three reflecting surfaces, two reflecting surfaces lying side by side on an optical axis in an optical path through the relay optical system are internal reflecting surfaces of the prism P1, and an angle of incidence of an optical axis on two such internal reflecting surfaces is greater than 45°.