JP2009014906A - Finder optical system and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make degradation of image performance small while making a reflection surface into a curved surface in a finder optical system. <P>SOLUTION: The finder optical system includes a reflection member 5 which has the curved reflection surface 5a reflecting light from an object so as to make it go toward eyepiece optical systems 6 to 8, and a holding member 12 to which the reflection member is joined. The joining surfaces 5b, 12a and 12b of the reflection member and the holding member and the curved reflection surface 5a are constituted of curved surfaces parallel with one another. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a so-called TTL (Through The Lens) type finder optical system and an imaging apparatus such as a single-lens reflex camera including the finder optical system.

  Light from an object reflected by a quick return mirror through an imaging lens is guided to a TTL finder optical system often used in an imaging apparatus such as a single-lens reflex camera. The finder optical system generally has a roof-type first reflecting surface that reflects incident light, and a second reflecting surface that reflects the light reflected by the first reflecting surface and guides it to the eyepiece optical system.

Patent Documents 1 and 2 disclose a finder optical system in which the second reflecting surface has a curved surface shape and is arranged obliquely with respect to the optical axis of the eyepiece optical system so that a high finder magnification can be obtained. Yes.
JP 2000-356799 A Japanese Utility Model Publication No. 2-41613

  However, when the second reflecting surface is formed in a curved shape and is inclined with respect to the optical axis of the eyepiece optical system as described above, the influence of the arrangement error on the image performance of the finder optical system is large. That is, unless the second reflecting surface is positioned with high accuracy, the image performance is deteriorated. In addition, since the decentration aberration is increased as compared with the case where the second reflecting surface is a flat surface, the image performance is more likely to be deteriorated. Further, in order to correct the decentration aberration, it is necessary to dispose a prism having a curved surface in the eyepiece optical system or to decenter the lenses constituting the eyepiece optical system. For this reason, it becomes difficult to give a good diopter adjustment function to the eyepiece optical system.

  The present invention provides a finder optical system and an image pickup apparatus including the finder optical system that can reduce degradation of image performance while making a reflecting surface a curved surface.

  A finder optical system according to one aspect of the present invention includes a reflective member having a curved reflective surface that reflects light from an object and directs the light toward an eyepiece optical system, and a holding member to which the reflective member is bonded. The joining surface of the reflecting member and the holding member and the curved reflecting surface are constituted by curved surfaces parallel to each other.

  According to another aspect of the present invention, a finder optical system manufacturing method includes a reflecting member having a curved reflecting surface that reflects light from an object and directs it toward an eyepiece optical system, and a holding member to which the reflecting member is bonded. And a step of joining the reflecting member to the holding member. Then, the joining surface of the reflecting member and the holding member and the curved reflecting surface are constituted by curved surfaces parallel to each other, and the reflecting member is positioned with respect to the holding member along the joining surface, and then joined to the holding member. It is characterized by.

  Note that an imaging apparatus including the finder optical system also constitutes another aspect of the present invention.

  According to the present invention, it is possible to realize a finder optical system that can not only obtain a high finder magnification by a curved reflecting surface but also can easily adjust the position of the curved reflecting surface and obtain good image performance, and an imaging apparatus including the finder optical system. Can do.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows the configuration of an image pickup apparatus that is Embodiment 1 of the present invention. 2 to 4 show the configuration of the finder optical system provided in the imaging apparatus. FIG. 2 shows directions of “up”, “down”, “left”, and “right” used in the following description.

  In FIG. 1, reference numeral 1 denotes an imaging lens that forms a subject image as an optical image on light from a subject (object). Reference numeral 2 denotes a reflecting mirror for guiding the light from the imaging lens 1 to the finder optical system, and is generally called a quick return mirror. When the quick return mirror 2 is disposed in the optical path from the imaging lens 1 (imaging optical path) as shown in FIG. 1, it reflects the light from the imaging lens 1 and guides it to the finder optical system. At the time of imaging, the quick return mirror 2 is retracted out of the imaging optical path. Thereby, a subject image is formed on the image sensor 9 by the light from the imaging lens 1.

  The imaging element 9 is a photoelectric conversion element such as a CCD sensor or a CMOS sensor that photoelectrically converts a subject image. An electronic image of a subject generated based on an output signal from the image sensor 9 is displayed on a display (not shown) or recorded on a recording medium such as a semiconductor memory.

  Hereinafter, the configuration of the finder optical system will be described.

  Reference numeral 3 denotes a focusing plate. A subject image is formed on the focusing plate 3 by the light reflected by the quick return mirror 2.

  Reference numeral 12 denotes a resin-made holding member, which has an upper surface part having a roof shape and left and right side parts as shown in FIG. A reflective surface (hereinafter referred to as a roof reflective surface) 4 is formed on the roof-type ceiling surface (lower surface of the upper surface portion) of the holding member 12 by vapor-depositing a high reflectance material such as aluminum. The roof reflecting surface 4 reflects light from the quick return mirror 2 toward the subject.

  Reference numeral 5 denotes a reflecting member that reflects the light reflected by the roof reflecting surface 4 to the opposite side of the subject and directs it to an eyepiece optical system to be described later. The first surface 5b of the reflecting member 5 has a curved shape, and a high reflectivity material such as aluminum is vapor-deposited on the central portion of the first surface 5b as shown in enlarged views in FIGS. Thus, a concave reflection surface (curved reflection surface) 5a is formed. The concave reflecting surface 5a contributes to the improvement of the finder magnification.

  In addition, the left and right peripheral portions (hereinafter referred to as a joining surface 5b) of the first surface 5b of the reflecting member 5 are joined to the holding member 12 described above. The joining with the holding member 12 will be described later.

  Reference numerals 6, 7, and 8 denote three eyepiece lenses constituting the eyepiece optical system. Here, the reflecting member 5 (concave reflecting surface 5a) is a curved surface inclined with respect to the optical axis (hereinafter referred to as a finder optical axis) X4 of the eyepiece optical system. For this reason, the light that is reflected by the reflecting member 5 and enters the eyepiece optical system includes a large decentration aberration. Therefore, in the present embodiment, among the three eyepieces 6 to 8, the eyepiece 6 closest to the reflecting member 5 is conjugate to the reflecting member side (light incident side) lens surface R1 and the concave reflecting surface 5a. Have a relationship.

  The conjugate relationship here refers to the decentering aberration caused by the concave reflecting surface 5a inclined with respect to the finder optical axes X3 and X4, on the R1 surface, R2 surface, or R1 surface and R2 surface of the eyepiece 6. This means a relationship in which the light beam that is corrected and incident on the eyepiece lens 7 is a light beam that does not include decentration aberration. Needless to say, the eyepiece 6 has the function of a lens as a finder eyepiece system and also has a correction shape. It should be noted that there is a conjugate relationship between the lens surface R1 of the eyepiece lens 6 and the lens surface R2 on the opposite side (light emission side) and the concave reflecting surface 5a, or between the lens surfaces R1 and R2 of the eyepiece lens 6. May have a conjugate relationship. With such a relationship, it is possible to satisfactorily correct (reduce) the decentration aberration generated by the reflection at the concave reflecting surface 5a.

  Thus, the light incident on the eyepieces 7 and 8 contains almost no decentering aberration. For this reason, the diopter of the eyepiece optical system can be adjusted by moving the eyepiece lens 7 in the direction of the finder optical axis X4.

  Reference numeral 10 denotes an exterior member of the imaging apparatus that houses various components such as the finder optical system and the imaging element 9.

  Next, the shapes of the concave reflecting surface 5a and the holding member 12 will be described in more detail with reference to FIGS. As described above, the holding member 12 has a roof-shaped upper surface portion and left and right side surface portions. Joining surfaces 12a and 12b that are joined to the joining surface 5b of the reflecting member 5 by bonding are configured as curved surfaces on the end surfaces on the subject side (front side in the drawing) of both side surface portions. The joining surface 5b and the joining surfaces 12a and 12b may be in contact with each other, or a very thin film of adhesive may be interposed between them.

  As shown in FIG. 4, the joint surfaces 12a, 12b, 5b and the concave reflecting surface 5a are formed of curved surfaces parallel to each other. The mutually parallel curved surfaces referred to here are a plurality of curved surfaces in which the distance between the curved surfaces in the normal direction of each curved surface is the same at any position of each curved surface. When the reference curved surface (concave reflection surface 5a) is a spherical surface, curved surfaces (joint surfaces 12a, 12b, 5b) parallel to the curved surface are also spherical surfaces.

  “Parallel” and “same” in this embodiment are not only strictly parallel or identical, but also deviate from exact parallel or identical within the range of manufacturing error, but are parallel or identical in optical performance. This includes cases where it can be considered.

  3 and 4 show an example in which the concave reflecting surface 5a protrudes from the bonding surface 5b of the reflecting member 5 so as to be intentionally convex at the time of molding in order to make the film thickness equivalent to the vapor deposition film thickness or yato during vapor deposition. Show. FIG. 4 shows a case where the joint surface 5b and the concave reflection surface 5a are spherical surfaces having the same center of curvature B in the vertical direction. If the protruding amount of the concave reflecting surface 5a is t and the radius of curvature of the joint surface 5b is C, the radius of curvature of the concave reflecting surface 5a is D (= C−t). Further, the joining surfaces 12a and 12b shown in FIG. 2 have the same center of curvature B as the joining surface 5b and the concave reflecting surface 5a, and have a curvature radius D.

  The joint surface 5b (12a, 12b) and the concave reflecting surface 5a may be configured as the same curved surface which is one of parallel curved surfaces, that is, a curved surface having a center of curvature of B and a radius of curvature of C.

  Moreover, about the left-right direction, you may comprise the concave reflective surface 5a and the joint surfaces 5b, 12a, and 12b as a spherical surface, and you may comprise as an aspherical surface.

  In the following description, an optical path that is incident on the finder optical system through the optical axis (lens optical axis) X1 of the imaging lens 1 shown in FIG. An optical path along which the central ray reflected by the reflecting surface 4 and traveling toward the concave reflecting surface 5a follows is defined as an optical axis X3.

  In order to reflect the central ray (optical axis X3) reflected by the roof reflecting surface 4 in the direction of the finder optical axis X4 by the concave reflecting surface 5a, the normal direction A at the incident position of the central ray on the concave reflecting surface 5a is The angle formed by the finder optical axis X4 and the optical axis X3 needs to be a direction that bisects the angle. If the normal direction is tilted, the finder optical axis X4 is not parallel to the lens optical axis X1, so that a large aberration occurs and a good finder image cannot be formed.

  When using a plane mirror as a reflection member as in the past, the joint surface between the reflection member and the holding member may be set as a surface perpendicular to the normal direction A. In this case, even if the plane mirror is moved in the vertical direction, the image performance is not affected at all.

  However, when the reflecting member 5 is moved up and down with the joining surface of the reflecting member 5 and the holding member 12 formed with the concave reflecting surface 5a as in the present embodiment as a plane perpendicular to the normal direction A, FIG. As shown in FIG. 6, the normal direction A ′ at the incident position of the central ray on the concave reflecting surface 5a changes. As a result, the central ray reflected by the concave reflecting surface 5a passes through a position deviated from the finder optical axis X4 in the eyepiece optical system, so that an unfavorable finder image is formed.

  Therefore, in this embodiment, by adopting the configuration shown in FIG. 4, even if the reflecting member 5 is moved up and down along the joining surfaces 12a and 12b from the position shown in FIG. 4 as shown in FIG. The line direction A does not change. That is, regardless of the vertical position of the reflecting member 5 (concave reflecting surface 5a), the central ray from the roof reflecting surface 4 can be reflected so as to pass on the finder optical axis X4. For this reason, it is possible to adjust the position of the concave reflecting surface 5a in the vertical direction while ensuring a good finder image (image performance) with little aberration.

  Further, projections (ribs) 12c and 12d for positioning the reflecting member 5 to some extent in the left-right direction are formed outside the joint surfaces 12a and 12b of the holding member 12. That is, the position of the reflecting member 5 may be set within a range in which further movement is restricted by contact with the ribs 12c and 12d in the left-right direction. This is because the decentering aberration occurs only in the vertical direction because the reflecting member 5 is inclined with respect to the finder optical axis X4, and no decentration aberration occurs in the left-right direction.

  Furthermore, as described above, since the reflecting member 5 and the eyepiece 6 have a conjugate relationship, it is possible to satisfactorily correct the decentration aberration that occurs when the reflecting member 5 is inclined with respect to the finder optical axis X4. However, since the reflecting member 5 and the eyepiece lens 6 have a conjugate relationship, an allowable amount for decentering is reduced. In other words, if an eccentricity shift occurs due to a manufacturing error or an assembly error, the image performance deteriorates.

  Therefore, in this embodiment, the concave reflection surface 5a and the joint surfaces 5b, 12a, and 12b are formed as parallel curved surfaces having the same center of curvature, and the position of the concave reflection surface 5a can be adjusted along the joint surfaces 12a and 12b. Yes. Thereby, a manufacturing error and an assembly error can be extremely reduced, and a finder optical system having a good image performance is realized.

  The concave reflecting surface 5a may be an aspherical surface (a rotationally symmetric aspherical surface or a rotationally asymmetric aspherical surface) for aberration correction. In this case, the joining surfaces 12a, 12b and 5b can also be formed as aspherical surfaces as curved surfaces parallel to the concave reflecting surface 5a. However, even when the concave reflecting surface 5a is formed of an aspherical surface, the position adjustment amount of the reflecting member 5 is a slight amount corresponding to a manufacturing error or an assembly error, so that the joint surfaces 5b, 12a, and 12b are approximated to an aspherical surface. It may be configured as a spherical surface that can be regarded as a parallel curved surface.

  Further, when the concave reflecting surface 5a is a rotationally asymmetric aspherical surface (so-called free curved surface), the joint surfaces 12a, 12b, and 5b may be configured by approximate curved surfaces of the free curved surface. Also in this case, the joint surfaces 12a, 12b, 5b and the concave reflection surface 5a are regarded as curved surfaces that are approximately parallel to each other. Thereby, the position of the concave reflecting surface 5a can be adjusted while maintaining the conjugate relationship with the eyepiece 6 with almost no change in the normal direction A.

  As described above, according to the above-described embodiment, the use of the concave reflecting surface 5a and the concave reflecting surface 5a and the joint surfaces 5b, 12a, and 12b are configured by parallel curved surfaces, thereby achieving a high finder magnification and a good image. A finder optical system having high performance can be realized.

  Further, the decentration aberration generated on the concave reflecting surface 5a is corrected by the eyepiece 6 closest to the concave reflecting surface 5a in the eyepiece optical system, and the concave reflecting surface 5a and the eyepiece 6 are in a conjugate relationship. Diopter adjustment can be easily performed without changing the aberration.

  The following manufacturing method can be derived from the above embodiment. First, as the first step, the reflecting member 5 and the holding member 12 are prepared. As a second step, the reflecting member 5 is joined to the holding member 12. At this time, the joining surfaces 5b, 12a, 12b of the reflecting member 5 and the holding member 12 and the concave reflecting surface 5a are configured by curved surfaces parallel to each other, and the reflecting member 5 is formed on the holding member 12 along the joining surfaces 12a, 12b. After the position is adjusted, it is joined to the holding member 12.

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

1 is a cross-sectional view illustrating a configuration of an imaging apparatus that is an embodiment of the present invention. FIG. 3 is a partial perspective view of a finder optical system provided in the imaging apparatus of the embodiment. The perspective view of the reflective member which comprises the said finder optical system. Sectional drawing of the said finder optical system. Sectional drawing which shows position adjustment of the reflective member in the said finder optical system. Sectional drawing which shows position adjustment of the reflection member in the case of having the same joint surface shape as before.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging lens 2 Quick return mirror 3 Focus plate 4 Dach reflective surface 5 Reflective member 6, 7, 8 Eyepiece 9 Imaging element 10 Exterior member 12 Holding member X1 Lens optical axis X2, X3 Central ray (optical axis)
X4 Viewfinder optical axis A Normal direction B Center of curvature C, D Curvature radius

Claims (6)

A reflecting member having a curved reflecting surface that reflects light from an object and directs it to the eyepiece optical system;
A holding member to which the reflecting member is joined,
A finder optical system, wherein a joining surface of the reflecting member and the holding member and the curved reflecting surface are formed by curved surfaces parallel to each other.   The lens closest to the reflecting member in the eyepiece optical system has a lens surface that reduces decentration aberration caused by reflection on the curved reflecting surface, and the curved reflecting surface and the lens have a conjugate relationship. The finder optical system according to claim 1.   The finder optical system according to claim 1, wherein the holding member has a roof reflecting surface that reflects light from the object and directs the light toward the curved reflecting surface.   An imaging apparatus comprising the finder optical system according to any one of claims 1 to 3. Providing a reflecting member having a curved reflecting surface that reflects light from an object and directs it toward the eyepiece optical system, and a holding member to which the reflecting member is joined;
Joining the reflective member to the holding member,
The joining surface of the reflecting member and the holding member and the curved reflecting surface are constituted by curved surfaces parallel to each other,
A method of manufacturing a finder optical system, wherein the position of the reflecting member is adjusted with respect to the holding member along the bonding surface, and then the reflecting member is bonded to the holding member. An imaging apparatus comprising a finder optical system manufactured by the manufacturing method according to claim 5.