JP5506576B2 - Viewfinder optical system and imaging apparatus having the same - Google Patents
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Description
本発明はファインダー光学系及びそれを有する撮像装置に関する。特に焦点板に形成された被写体像を接眼レンズを介して観察する観察光学系と、焦点板に形成された被写体像を撮像素子に再結像し、電子画像を得るための縮小光学系とを有する一眼レフカメラ等の撮像装置に好適なものである。 The present invention relates to a finder optical system and an imaging apparatus having the same. In particular, an observation optical system for observing a subject image formed on the focusing screen through an eyepiece lens, and a reduction optical system for re-imaging the subject image formed on the focusing screen on an image sensor to obtain an electronic image. It is suitable for an imaging apparatus such as a single-lens reflex camera.
近年、一眼レフカメラ等の撮像装置に用いられているファインダー光学系として、焦点板に形成された被写体像を観察するための観察光学系と、焦点板に形成された被写体像を再結像して電子画像を得るための縮小光学系を設けたものが知られている（特許文献１）。 In recent years, as a finder optical system used in imaging devices such as single-lens reflex cameras, an observation optical system for observing a subject image formed on a focusing screen and a subject image formed on the focusing screen are re-imaged. There is known one provided with a reduction optical system for obtaining an electronic image (Patent Document 1).
このファインダー光学系における観察光学系は、焦点板上に形成された被写体像をペンタプリズム等の像反転手段（正立光学系）で正立像とした後、接眼レンズを介して拡大して観察するように構成されている。 The observation optical system in this finder optical system converts an object image formed on a focusing screen into an erect image by an image inverting means (an erecting optical system) such as a pentaprism, and then magnifies and observes it through an eyepiece It is configured as follows.
特許文献１のファインダー光学系では、焦点板に形成された被写体像を、正立光学系を介して縮小光学系で撮像素子に再結像し、それより電子画像を得ている。そして例えば、被写体の顔を認識して、ピントや露出を調整する機能や、被写体の動きに合わせて測距点を移動させる機能や、カメラ本体の背面に設けた液晶画面にリアルタイムで被写体像を表示する機能を持つようにしている。 また特許文献１のファインダー光学系では、ペンタプリズムの光出射側に光路を分割するハーフミラーより成る光路分割手段を設け、光路分割手段で分割した一部の光束を縮小光学系を用いて、撮像素子に結像させる構成を開示している。 In the finder optical system of Patent Document 1, a subject image formed on a focusing screen is re-imaged on an image sensor by a reduction optical system via an erecting optical system, thereby obtaining an electronic image. For example, it recognizes the subject's face and adjusts the focus and exposure, moves the focus point according to the movement of the subject, and displays the subject image in real time on the LCD screen on the back of the camera body. It has a function to display. Further, in the finder optical system of Patent Document 1, an optical path splitting unit comprising a half mirror that splits an optical path is provided on the light exit side of the pentaprism, and a part of the light beam split by the optical path splitting unit is imaged using a reduction optical system. A configuration for imaging an element is disclosed.
ファインダー光学系の一部に縮小光学系を用いて被写体像を撮像素子に形成して電子画像を得る際、高画質の電子画像を得るには画素の多い大型の撮像素子を用いることが必要となる。 When using a reduction optical system as part of the viewfinder optical system to obtain an electronic image by forming a subject image on the image sensor, it is necessary to use a large image sensor with many pixels to obtain a high-quality electronic image. Become.
一方、焦点板に形成された被写体像を明るい状態で高倍率で観察するには観察光学系を構成する接眼レンズに大口径で高倍率のものを用いる必要がある。高画質の電子画像をリアルタイムで得て観察するとともに接眼レンズを介して明るい被写体像の観察を行うためには、正立光学系の光出射側、例えばペンタプリズムの光出射側に大型の撮像素子を含む縮小光学系と大口径の接眼レンズを配置しなければならない。しかしながらこのような構成の観察光学系と縮小光学系を正立光学系の光出射側に配置しようとすると、撮像素子と接眼光学系が機構的に干渉してきてしまい、双方を配置するのが困難になる。 On the other hand, in order to observe a subject image formed on the focusing screen at a high magnification in a bright state, it is necessary to use an eyepiece constituting the observation optical system with a large aperture and a high magnification. In order to obtain and observe a high-quality electronic image in real time and to observe a bright subject image via an eyepiece, a large image sensor on the light exit side of an erecting optical system, for example, the light exit side of a pentaprism A reduction optical system including a large-diameter eyepiece must be arranged. However, if the observation optical system and the reduction optical system having such a configuration are arranged on the light emitting side of the erecting optical system, the imaging device and the eyepiece optical system interfere mechanically, and it is difficult to arrange both. become.
これに対して特許文献１に開示されているように、正立光学系からの光束をハーフミラーによって２つに分割して、一方を観察光学系へ他方を縮小光学系へ導光する構成は光束を２つに分割しているため、接眼レンズで観察される被写体像の明るさが暗くなってくる。また縮小光学系で撮像素子に結像するときの光束の光量も少なくなり、良好なる画質の電子画像を得るのが難しい。 On the other hand, as disclosed in Patent Document 1, a configuration in which a light beam from an erecting optical system is divided into two by a half mirror and one is guided to an observation optical system and the other is guided to a reduction optical system. Since the light beam is divided into two, the brightness of the subject image observed with the eyepiece becomes darker. In addition, the amount of light flux when forming an image on the image sensor with the reduction optical system is small, and it is difficult to obtain an electronic image with good image quality.
本発明は、焦点板に形成した被写体像について、高画質の電子画像をリアルタイムで得ることができ、しかも明るいファインダー像を観察することができるファインダー光学系を提供することを目的とする。 An object of the present invention is to provide a finder optical system capable of obtaining a high-quality electronic image in real time for a subject image formed on a focusing screen and observing a bright finder image.
本発明のファインダー光学系は、撮像光学系によって焦点板に結像された被写体像を正立像とする正立光学系と、前記正立像を接眼レンズを介して観察させる観察光学系と、前記焦点板と前記観察光学系の光軸の交点を通り前記観察光学系の光軸に対して傾斜した光軸を有し、前記焦点板に結像された被写体像を前記正立光学系を介して撮像素子に縮小結像する縮小光学系と、を備えたファインダー光学系において、前記縮小光学系と、前記接眼レンズは前記正立光学系の光出射側に各々の光入射側の面が前記正立光学系の光出射面に対向するように配置されており、前記縮小光学系は前記正立光学系から順に、開口絞り、正の屈折力の第１レンズ、正の屈折力の第２レンズから構成され、前記第１レンズは光入射面から入射した光束を内面反射面で反射させて光出射面より出射するプリズム体より成り、前記第１レンズと前記第２レンズの合成焦点距離をｆ、前記第１レンズの光入射面の近軸曲率半径をＲ１とするとき、
−０．４ ＜ ｆ／Ｒ１ ＜ ０．４
なる条件式を満足することを特徴としている。
The finder optical system according to the present invention includes an erecting optical system in which an object image formed on a focusing screen by an imaging optical system is an erect image, an observation optical system for observing the erect image through an eyepiece, and the focus It has an optical axis inclined with respect to the optical axis of the plate and the observation optical system intersection as the observation optical system of the optical axis of the object image formed on the focusing plate via the erecting optical system a reduction optical system for reducing image on the imaging device, in a finder optical system and a the reduction optical system, the eyepiece each of the planes of the light incident side on the light emitting side of the erecting optical system is the positive stand are arranged so as to face the light exit plane of the optical system, the reduction optical system includes, in order from the erecting optical system, an aperture stop, a first lens having a positive refractive power, a positive second lens optical power consists, the inner surface of the light beam incident from said first lens is light incident surface Is reflected by the elevation plane made of a prism body that emits from the light emitting surface, the composite focal length of the said first lens second lens f, and paraxial radius of curvature of the light incident surface of the first lens is R1 When
−0.4 <f / R1 <0.4
It satisfies the following conditional expression.
本発明によれば、焦点板に形成した被写体像について、高画質の電子画像をリアルタイムで得ることができ、しかも明るいファインダー像の観察ができるファインダー光学系 According to the present invention, a finder optical system capable of obtaining a high-quality electronic image in real time for a subject image formed on a focusing screen and observing a bright finder image.
以下に、本発明の好ましい実施の形態を、添付の図面に基づいて詳細に説明する。本発明のファインダー光学系は、撮像光学系によって焦点板に結像された被写体像を正立像とするペンタプリズム等の正立光学系と、正立像を接眼レンズを介して観察させる観察光学系を有する。更に焦点板と観察光学系の光軸の交点を通り観察光学系の光軸に対して傾斜した光軸を有し、焦点板に結像された被写体像を正立光学系を介して撮像素子に縮小結像する縮小光学系を有する。縮小光学系と、接眼レンズは正立光学系の光出射側に各々の光入射側の面が正立光学系の光出射面に対向するように並列的に配置されている。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The finder optical system of the present invention includes an erecting optical system such as a pentaprism that uses an object image formed on a focusing screen by an imaging optical system as an erect image , and an observation optical system for observing the erect image through an eyepiece. Have. Further, the image sensor has an optical axis that passes through the intersection of the optical axis of the focusing screen and the observation optical system and is inclined with respect to the optical axis of the observation optical system, and that captures the subject image formed on the focusing screen via the erecting optical system. A reduction optical system that performs reduction image formation. The reduction optical system and the eyepiece are arranged in parallel on the light exit side of the erecting optical system so that the respective light incident side faces the light exit surface of the erecting optical system.
縮小光学系は正立光学系の光出射側（正立光学系側）から順に、開口絞り、正の屈折力の第１レンズ、正の屈折力の第２レンズから構成されている。このときの第１レンズは光入射面から入射した光束を内面反射面で反射させて光出射面より出射する中実型のプリズム体（光学ブロック）より成っている。 The reduction optical system is composed of an aperture stop, a first lens having a positive refractive power, and a second lens having a positive refractive power in order from the light emitting side (the erecting optical system side) of the erecting optical system. At this time, the first lens is formed of a solid prism body (optical block) that reflects the light beam incident from the light incident surface by the inner reflection surface and emits the light from the light output surface.
図１、図４は本発明の実施例１、２のファインダー光学系１０１を有する撮像装置の要部概略図である。図２は図１の一部分の説明図、図３は実施例１の収差図である。図５は図４の一部分の説明図、図６は実施例２の収差図である。図１の撮像装置では、撮像光学系１１によって被写体像をクイックリターンミラー１２を介して焦点板１３に形成している。 1 and 4 are schematic views of a main part of an image pickup apparatus having a finder optical system 101 according to first and second embodiments of the present invention. 2 is an explanatory diagram of a part of FIG. 1, and FIG. 3 is an aberration diagram of the first embodiment. FIG. 5 is an explanatory diagram of a part of FIG. 4, and FIG. 6 is an aberration diagram of Example 2. In the imaging apparatus of FIG. 1, a subject image is formed on a focusing screen 13 via a quick return mirror 12 by an imaging optical system 11.
本実施例のファインダー光学系１０１は、撮像光学系１１により焦点板１３に形成された被写体像（ファインダー像）を、ペンタダハプリズム１５より成る正立光学系によって正立像とし、正立像を接眼レンズ１６を介して観察させる。また焦点板１３と観察光学系１の光軸Ｏａの交点を通り、観察光学系１の光軸Ｏａに対して傾斜した光軸Ｏｂを有する縮小光学系２で電子ファインダー像（電子画像）を得ている。図１では焦点板１３とペンタプリズム１５との間にコンデンサーレンズ１４が配置されている。コンデンサーレンズ１４は焦点板１３に結像された被写体像からの光束をペンタプリズム１５に導光している。縮小光学系２は絞りＳＴ、正の屈折力の第１レンズ１７と正の屈折力の第２レンズ１８を有する。第１レンズ１７の内部の光路中に反射面（裏面反射面）１７ａを設けることによって、光路を上方へ折り曲げている。ここで上方とは撮像光学系１１に対してファインダー光学系１０１側をいう。そして第１レンズ１７の光出射面１７ｃと第２レンズ１８及び撮像素子２０を上方またはカメラ本体の側面方向に退避させて配置することができるようにしている。これによって、縮小光学系２と接眼レンズ１６を配置する際の双方の機構的な干渉を防いでいる。 Finder optical system 101 of this embodiment, the object image formed on the focusing plate 13 by the imaging optical system 11 (finder image), and erected by erecting optical system composed of a pair pointer roof prism 15, the erect image eyepiece 16 Ru was observed through. Also through the intersection of the optical axis Oa of the focus plate 13 and observation optical system 1, an electronic viewfinder image with reduced small optical system 2 that have a optical axis Ob which is inclined obliquely with respect to the optical axis Oa of the observation optical system 1 (electronic Image) . In FIG. 1, a condenser lens 14 is disposed between the focusing screen 13 and the pentaprism 15. The condenser lens 14 guides the light beam from the subject image formed on the focusing screen 13 to the pentaprism 15. The reduction optical system 2 includes a stop ST, a first lens 17 having a positive refractive power, and a second lens 18 having a positive refractive power. By providing a reflection surface (back surface reflection surface) 17 a in the optical path inside the first lens 17, the optical path is bent upward. Here, the upper side refers to the viewfinder optical system 101 side with respect to the imaging optical system 11. The light exit surface 17c of the first lens 17, the second lens 18, and the image sensor 20 can be retracted upward or in the side surface direction of the camera body. This prevents mechanical interference between the reduction optical system 2 and the eyepiece 16 when they are arranged.
１９はローパスフィルタやＩＲ（近赤外）カットフィルタ等のフィルタである。２０は撮像素子である。２１は撮像素子２０で得られる被写体像（画像）を処理する画像処理手段である。縮小光学系２によって撮像素子２０に形成された像は画像処理手段２１で画像処理されてカメラ本体の背面に設けた液晶画面にリアルタイムで画像表示される。この他画像内の主被写体の移動に追従してフォーカス位置が変化して主被写体の合焦を行う自動追尾を行うこと等に用いられる。２２は撮像光学系１１によって形成される被写体像に相当する像を記録（受光）するＣＣＤ等の撮像素子である。 Reference numeral 19 denotes a filter such as a low-pass filter or an IR (near infrared) cut filter. Reference numeral 20 denotes an image sensor. Reference numeral 21 denotes image processing means for processing a subject image (image) obtained by the image sensor 20. The image formed on the image sensor 20 by the reduction optical system 2 is subjected to image processing by the image processing means 21 and displayed in real time on a liquid crystal screen provided on the back of the camera body. This is used to perform automatic tracking for focusing the main subject by changing the focus position following the movement of the main subject in the other image. Reference numeral 22 denotes an image sensor such as a CCD that records (receives) an image corresponding to a subject image formed by the imaging optical system 11.
図２は図１の実施例１による、縮小光学系２のレンズ構成を光軸に沿って展開したときの光路展開図を示している。縮小光学系２は、物体側（ペンタダハプリズム１５側）より順に、開口絞りＳＴ、第１レンズ１７、第２レンズ１８を有する。図２において１９はローパスフィルタやＩＲカットフィルタ等のフィルタである。ＩＭＧは撮像素子２０の撮像面である。なお、第１レンズ１７と第２レンズ１８はプラスチックレンズである。第１レンズ１７の光入出射面１７ｂ、１７ｃ、第２レンズ１８の光入出射面１８ａ、１８ｂは非球面形状で構成されている。 FIG. 2 shows an optical path development view when the lens configuration of the reduction optical system 2 according to the first embodiment shown in FIG. 1 is developed along the optical axis. The reduction optical system 2 includes an aperture stop ST, a first lens 17, and a second lens 18 in order from the object side (the penta roof prism 15 side). In FIG. 2, 19 is a filter such as a low-pass filter or an IR cut filter. IMG is an imaging surface of the imaging device 20. The first lens 17 and the second lens 18 are plastic lenses. The light incident / exit surfaces 17b and 17c of the first lens 17 and the light incident / exit surfaces 18a and 18b of the second lens 18 are aspherical.
図４の実施例２のファインダー光学系は図１の実施例１に比べて、焦点板１３に形成した被写体像をコンデンサーレンズを介さないで直接ペンタプリズム（正立光学系）に導光していることが異なっている。この他、接眼レンズ１６のレンズ構成や縮小光学系２の第１レンズ１７と第２レンズ１８のレンズ構成が異なっている。この他の実施例１と同じである。 The viewfinder optical system of Example 2 in FIG. 4 directly guides the subject image formed on the focusing screen 13 to the pentaprism (upright optical system) without using a condenser lens, as compared with Example 1 in FIG. Is different. In addition, the lens configuration of the eyepiece 16 and the lens configurations of the first lens 17 and the second lens 18 of the reduction optical system 2 are different. This is the same as the other embodiment 1.
図５は図４の実施例２による、縮小光学系２のレンズ構成を示す光軸に沿って光路を展開したときの光路展開図を示している。縮小光学系２は、物体側（ペンタプリズム１５側）より順に、開口絞りＳＴ、第１レンズ１７、第２レンズ１８を有する。図５において１９はローパスフィルタやＩＲカットフィルタ等のフィルタである。ＩＭＧは撮像素子２０の撮像面である。なお、第１レンズ１７と第２レンズ１８の材料はプラスチックレンズである。第１レンズ１７の両面１７ｂ、１７ｃ、第２レンズ１８の両面１８ａ、１８ｂは非球面形状である。 FIG. 5 shows an optical path development view when the optical path is developed along the optical axis showing the lens configuration of the reduction optical system 2 according to the second embodiment of FIG. The reduction optical system 2 includes an aperture stop ST, a first lens 17 and a second lens 18 in order from the object side (the pentaprism 15 side). In FIG. 5, reference numeral 19 denotes a filter such as a low-pass filter or an IR cut filter. IMG is an imaging surface of the imaging device 20. The material of the first lens 17 and the second lens 18 is a plastic lens. Both surfaces 17b and 17c of the first lens 17 and both surfaces 18a and 18b of the second lens 18 are aspherical.
図３、図６は実施例１、２のファインダー光学系の球面収差、非点収差、歪曲収差を示すものである。なお、球面収差を表す図において、実線はｄ線に対する、２点鎖線はｃ線（波長＝６５６．３ｎｍ）に対する球面収差を示す。また、非点収差図において、実線はサジタル像面、破線はメリディオナル像面における値を示すものである。ＦｎｏはＦナンバー、Ｈは像高（撮像素子２０の対角線長の１／２）である。 3 and 6 show the spherical aberration, astigmatism, and distortion of the finder optical systems of Examples 1 and 2. FIG. In the diagram showing spherical aberration, the solid line indicates the spherical aberration with respect to the d line, and the two-dot chain line indicates the spherical aberration with respect to the c line (wavelength = 656.3 nm). In the graph showing astigmatism, the solid line indicates the value on the sagittal image plane, and the broken line indicates the value on the meridional image plane. Fno is the F number, and H is the image height (1/2 of the diagonal length of the image sensor 20).
本発明のファインダー光学系において第１レンズ１７と第２レンズ１８の合成焦点距離をｆとする。第１レンズ１７の光入射面の近軸曲率半径をＲ１とする。このとき、
−０．４ ＜ ｆ／Ｒ１ ＜ ０．４ ・・・（１）
なる条件式を満足している。条件式（１）は第１レンズ１７の光入射面１７ｂの面の曲率半径と縮小光学系２の焦点距離ｆとの関係に関する。
In the finder optical system of the present invention, the combined focal length of the first lens 17 and the second lens 18 is assumed to be f. The paraxial radius of curvature of the light incident surface of the first lens 17 is R1. At this time,
−0.4 <f / R1 <0.4 (1)
The following conditional expression is satisfied. Conditional expression (1) relates to the relationship between the radius of curvature of the light incident surface 17 b of the first lens 17 and the focal length f of the reduction optical system 2.
本実施例において縮小光学系２の焦点距離と主点位置は焦点板１３上での観察範囲と撮像素子２０の大きさによって一義的に決まる。そのため条件式（１）の上限値を超えると縮小光学系２の主点がペンタダハプリズム１５側に偏る。このため、第２レンズ１８と撮像素子２０の間隔が狭くなりすぎてしまい、フィルタの挿入や撮像素子２０の位置調整が困難となる。また上限式（１）の下限値を超えると、絞りＳＴを通過した光束が広がるため、光出射面１７ｃ及び第２レンズ１８の有効径を大きくせねばならず、縮小光学系２が大型化する。つまり、縮小光学系２の適切な主点配置及び小型化のためには、条件式（１）に適合することが望ましい。更に好ましくは条件式（１）の数値範囲を次の如く設定するのが良い。 In this embodiment, the focal length and principal point position of the reduction optical system 2 are uniquely determined by the observation range on the focusing screen 13 and the size of the image sensor 20. Therefore, when the upper limit value of conditional expression (1) is exceeded, the principal point of the reduction optical system 2 is biased toward the penta roof prism 15 side. For this reason, the distance between the second lens 18 and the image sensor 20 becomes too narrow, and it becomes difficult to insert a filter and adjust the position of the image sensor 20. If the lower limit of the upper limit expression (1) is exceeded, the light beam that has passed through the aperture stop ST spreads, so that the effective diameters of the light exit surface 17c and the second lens 18 must be increased, and the reduction optical system 2 becomes larger. . In other words, it is desirable to satisfy the conditional expression (1) in order to appropriately arrange the principal points and reduce the size of the reduction optical system 2. More preferably, the numerical range of conditional expression (1) is set as follows.
−０．３５ ＜ ｆ／Ｒ１ ＜ ０．２０ ・・・（１ａ）
以上のように各実施例によれば高解像でコンパクトなファインダー光学系を達成することができる。
−0.35 <f / R1 <0.20 (1a)
As described above, according to each embodiment, a high-resolution and compact finder optical system can be achieved.
本発明のファインダー光学系において更に好ましくは次の諸条件のうち１以上を満足するのが良い。撮像素子２０の有効対角線長を２Ｈとする。第１レンズ１７の光入射面から光出射面までの光軸上の長さをｄ１とする。縮小光学系２の光軸Ｏｂと、第１レンズ１７の内面反射面１７ａの法線ＨＰとのなす角をθとする。第１レンズ１７と第２レンズ１８の材料のアッベ数を各々ν１、ν２とする。このとき
２．５ ＜ ｆ／Ｈ ＜ ６ ・・・（２）
０．３５ ＜ ｆ／ｄ１ ＜ ０．８０ ・・・（３）
４５° ＜ θ ＜ ６０° ・・・（４）
０．８ ＜ ν１／ν２ ＜ １．２ ・・・（５）
５０ ＜ ν１ ・・・（６）
なる条件式のうち１以上を満足するのが良い。
In the finder optical system of the present invention, it is more preferable to satisfy one or more of the following conditions. The effective diagonal length of the image sensor 20 is 2H. The length on the optical axis from the light incident surface of the first lens 17 to the light emitting surface is defined as d1. An angle formed by the optical axis Ob of the reduction optical system 2 and the normal line HP of the inner reflection surface 17a of the first lens 17 is defined as θ. The Abbe numbers of the materials of the first lens 17 and the second lens 18 are ν1 and ν2, respectively. At this time, 2.5 <f / H <6 (2)
0.35 <f / d1 <0.80 (3)
45 ° <θ <60 ° (4)
0.8 <ν1 / ν2 <1.2 (5)
50 <ν1 (6)
It is preferable to satisfy one or more of the following conditional expressions.
条件式（２）は撮像素子２０の最大像高Ｈと縮小光学系２の焦点距離fの関係を示している。縮小光学系２の焦点距離ｆは焦点板１３上での観察範囲と撮像素子２０の大きさによって一義的に決まる。そのため条件式（２）の上限値を超えると、焦点板１３上での観察範囲が狭すぎるので良くない。また下限値を超えると、縮小光学系２の各レンズ面の曲率半径がきつくなるため、球面収差、非点収差等の諸収差が多く発生してくる。つまり、焦点板１３上の適切な範囲（ファインダー視野）を観察するためには、条件式（２）を満足することが望ましい。 Conditional expression (2) shows the relationship between the maximum image height H of the image sensor 20 and the focal length f of the reduction optical system 2. The focal length f of the reduction optical system 2 is uniquely determined by the observation range on the focusing screen 13 and the size of the image sensor 20. Therefore, if the upper limit value of conditional expression (2) is exceeded, the observation range on the focusing screen 13 is too narrow, which is not good. If the lower limit is exceeded, the radius of curvature of each lens surface of the reduction optical system 2 becomes tight, and various aberrations such as spherical aberration and astigmatism occur. That is, in order to observe an appropriate range (viewfinder field) on the focusing screen 13, it is desirable to satisfy the conditional expression (2).
条件式（３）は内面反射面を有する第１レンズ１７の光軸方向の長さに関する。条件式（３）の上限値を超えると、十分な反射面の範囲およびレンズ有効径が確保されないため、縮小光学系２で得られる像が暗くなる。さらに、条件式（３）の下限値を超えると、縮小光学系２のレンズ全長が長くなり、ファインダー光学系全体が大型化する。つまり、第１レンズ１７の十分な反射面と有効径を確保し、縮小光学系２のコンパクト化を図るには条件式（３）に適合することが望ましい。 Conditional expression (3) relates to the length in the optical axis direction of the first lens 17 having the internal reflection surface. When the upper limit of conditional expression (3) is exceeded, a sufficient range of the reflecting surface and effective lens diameter are not ensured, and the image obtained by the reduction optical system 2 becomes dark. Further, when the lower limit value of conditional expression (3) is exceeded, the total lens length of the reduction optical system 2 becomes long and the entire finder optical system becomes large. That is, it is desirable to satisfy the conditional expression (3) in order to secure a sufficient reflecting surface and effective diameter of the first lens 17 and to make the reduction optical system 2 compact.
条件式（４）は縮小光学系２の光軸Ｏｂと、第１レンズ１７内の反射面１７ａの法線ＨＰとのなす角度θに関する。条件式（４）の下限値を超えて角度θが小さくなると、第１レンズ１７内の反射面１７ａで全反射しない光線が現れるため、反射面１７ａをミラー蒸着する必要があり、製造が困難になる。条件式（４）の上限値を超えて角度θが大きくなると、縮小光学系２が、観察光学系１の接眼レンズ１６の部材と干渉するようになるため、接眼レンズ１６を小さくしなければならなくなってくる。つまり、第１レンズ１７の反射面１７ａでの光線の全反射条件を満足し、かつ接眼レンズ１６との干渉を防ぐためには、条件式（４）を満足することが望ましい。 Conditional expression (4) relates to an angle θ formed by the optical axis Ob of the reduction optical system 2 and the normal line HP of the reflecting surface 17a in the first lens 17. If the angle θ is reduced beyond the lower limit value of the conditional expression (4), a light beam that is not totally reflected by the reflection surface 17a in the first lens 17 appears, so that the reflection surface 17a needs to be mirror-deposited, making manufacture difficult. Become. Should the angle θ exceeds the upper limit of conditional expression (4) becomes larger, the reduction optical system 2, to become to interfere with a member of the observation optical system 1 of the eyepiece 16, is necessary to reduce the eyepiece 16 It will disappear. That is, in order to satisfy the total reflection condition of the light beam at the reflecting surface 17a of the first lens 17 and to prevent interference with the eyepiece lens 16, it is desirable to satisfy the conditional expression (4).
条件式（５）は、第１レンズ１７の材料のアッベ数ν１と第２レンズ１８の材料のアッベ数ν２との関係を示す。条件式（６）は第１レンズ１７の材料のアッベ数ν１に関する。本実施例の縮小光学系２ではプラスチック材料より成るレンズを使用している。第１レンズ１７、第２レンズ１８ともに正のパワー（屈折力）を持つため、色収差の発生を抑えるためには、第１レンズ１７、第２レンズ１８は条件式（５）および（６）を満足する色分散の小さな硝材を用いることが望ましい。各実施例において更に好ましくは条件式（２）乃至（６）の数値範囲を次の如く設定するのが良い。 Conditional expression (5) shows the relationship between the Abbe number ν1 of the material of the first lens 17 and the Abbe number ν2 of the material of the second lens 18. Conditional expression (6) relates to the Abbe number ν1 of the material of the first lens 17. In the reduction optical system 2 of the present embodiment, a lens made of a plastic material is used. Since both the first lens 17 and the second lens 18 have positive power (refractive power), in order to suppress the occurrence of chromatic aberration, the first lens 17 and the second lens 18 satisfy the conditional expressions (5) and (6). It is desirable to use a glass material with a satisfactory color dispersion. In each embodiment, the numerical ranges of conditional expressions (2) to (6) are more preferably set as follows.
３．０ ＜ ｆ／Ｈ ＜ ５．８ ・・・（２ａ）
０．４０ ＜ ｆ／ｄ１ ＜ ０．７０ ・・・（３ａ）
４７° ＜ θ ＜ ６０° ・・・（４ａ）
０．９ ＜ ν１／ν２ ＜ １．１ ・・・（５ａ）
５５ ＜ ν１ ・・・（６ａ）
次に各実施例の数値実施例を示す。数値実施例においてｉは開口絞りＳＴを第１番目（ｒ１）とする面の順序を示す。「ｒｉ」は開口絞りＳＴを含めて第ｉ番目の面の近軸曲率半径を示す。ｄｏは開口絞りＳＴと第１レンズ１７の入射面との距離である。ｄｉは開口絞りＳＴから（ｉ＋１）番目の面と（ｉ＋２）番目の面との間の軸上面間隔を示す。さらに、Ｎｉは開口絞りＳＴから第ｉ番目の硝材のｄ線（波長＝５７８．６ｎｍ）に対する屈折率を示し、νｉは開口絞りＳＴから第ｉ番目の硝材のｄ線に対するアッベ数を示す。また、ｆは焦点距離であり、ＦＮＯ．はＦナンバーである。Ｈは撮像素子２０の最大像高であり、θは縮小光学系２の光軸Ｏｂと、第１レンズ１７の反射面１７ａの法線とのなす角をそれぞれ示す。ｒ６乃至ｒ９はフィルタ１９の各面を示し、ｒ１０は撮像面ＩＭＧである。非球面形状は、次の式によって定義されるものとする。
3.0 <f / H <5.8 (2a)
0.40 <f / d1 <0.70 (3a)
47 ° <θ <60 ° (4a)
0.9 <ν1 / ν2 <1.1 (5a)
55 <ν1 (6a)
Next, numerical examples of the respective embodiments will be shown. In the numerical examples, i indicates the order of the surfaces where the aperture stop ST is the first (r1). “Ri” indicates the paraxial radius of curvature of the i-th surface including the aperture stop ST. do is the distance between the aperture stop ST and the incident surface of the first lens 17. di represents the axial upper surface distance between the (i + 1) th surface and the (i + 2) th surface from the aperture stop ST. Further, Ni represents the refractive index with respect to the d-line (wavelength = 578.6 nm) of the i-th glass material from the aperture stop ST, and νi represents the Abbe number with respect to the d-line of the i-th glass material from the aperture stop ST. F is the focal length, and FNO. Is the F number. H is the maximum image height of the image sensor 20, and θ represents an angle formed by the optical axis Ob of the reduction optical system 2 and the normal line of the reflecting surface 17 a of the first lens 17. r6 to r9 indicate the respective surfaces of the filter 19, and r10 is an imaging surface IMG. The aspheric shape is defined by the following equation.
［数値実施例１］
f = 4.76 FNO. = 1.77 H = 1.215 θ= 49.9°
曲率半径[mm] 軸上面間隔[mm] 屈折率(Nd) アッベ数(νd)
r1=∞ d0=1.100
r2=-16.012 d1=10.400 N1=1.49171 ν1=57.40
r3=-9.259 d2=0.500
r4=4.374 d3=5.400 N2=1.52470 ν2=56.20
r5=-9.106 d4=0.800
r6=∞ d5=0.550 N3=1.52300 ν3=58.60
r7=∞ d6=0.200
r8=∞ d7=0.750 N4=1.51633 ν4=64.14
r9=∞ d8=1.190
r10=∞
［非球面係数］
面番号 k
r2 8.4565E+00
r3 7.1451E-01
r4 -6.4073E-01
r5 -2.8983E+01
[Numerical Example 1]
f = 4.76 FNO. = 1.77 H = 1.215 θ = 49.9 °
Curvature radius [mm] Axial distance [mm] Refractive index (Nd) Abbe number (νd)
r1 = ∞ d0 = 1.100
r2 = -16.012 d1 = 10.400 N1 = 1.49171 ν1 = 57.40
r3 = -9.259 d2 = 0.500
r4 = 4.374 d3 = 5.400 N2 = 1.52470 ν2 = 56.20
r5 = -9.106 d4 = 0.800
r6 = ∞ d5 = 0.550 N3 = 1.52300 ν3 = 58.60
r7 = ∞ d6 = 0.200
r8 = ∞ d7 = 0.750 N4 = 1.51633 ν4 = 64.14
r9 = ∞ d8 = 1.190
r10 = ∞
[Aspheric coefficient]
Face number k
r2 8.4565E + 00
r3 7.1451E-01
r4 -6.4073E-01
r5 -2.8983E + 01
［数値実施例２］
f = 6.81 FNO. = 1.26 H = 1.215 θ= 49.7°
曲率半径[mm] 軸上面間隔[mm] 屈折率(Nd) アッベ数(νd)
r1=∞ d0=0.900
r2=45.287 d1=10.700 N1=1.49171 ν1=57.40
r3=-14.358 d2=0.760
r4=5.406 d3=5.500 N2=1.52470 ν2=56.20
r5=-12.319 d4=1.400
r6=∞ d5=0.550 N3=1.52300 ν3=58.60
r7=∞ d6=0.200
r8=∞ d7=0.750 N4=1.51633 ν4=64.14
r9=∞ d8=1.190
r10=∞
［非球面係数］
面番号 k
r2 -4.3865E+02
r3 2.0866E+00
r4 -5.7031E-01
r5 -2.9593E+01
[Numerical Example 2]
f = 6.81 FNO. = 1.26 H = 1.215 θ = 49.7 °
Curvature radius [mm] Axial distance [mm] Refractive index (Nd) Abbe number (νd)
r1 = ∞ d0 = 0.900
r2 = 45.287 d1 = 10.700 N1 = 1.49171 ν1 = 57.40
r3 = -14.358 d2 = 0.760
r4 = 5.406 d3 = 5.500 N2 = 1.52470 ν2 = 56.20
r5 = -12.319 d4 = 1.400
r6 = ∞ d5 = 0.550 N3 = 1.52300 ν3 = 58.60
r7 = ∞ d6 = 0.200
r8 = ∞ d7 = 0.750 N4 = 1.51633 ν4 = 64.14
r9 = ∞ d8 = 1.190
r10 = ∞
[Aspheric coefficient]
Face number k
r2 -4.3865E + 02
r3 2.0866E + 00
r4 -5.7031E-01
r5 -2.9593E + 01
１ 観察光学系 ２ 縮小光学系 １１ 対物レンズ
１２ クイックリターンミラー １３ 焦点板 １４ コンデンサーレンズ
１５ ペンタダハプリズム １６ 接眼レンズ １７ 第１レンズ
１８ 第２レンズ １９ フィルタ ２０ センサ
DESCRIPTION OF SYMBOLS 1 Observation optical system 2 Reduction optical system 11 Objective lens 12 Quick return mirror 13 Focus plate 14 Condenser lens 15 Penta roof prism 16 Eyepiece 17 First lens 18 Second lens 19 Filter 20 Sensor
Claims (5)
−０．４ ＜ ｆ／Ｒ１ ＜ ０．４
なる条件式を満足することを特徴とするファインダー光学系。 An erecting optical system that makes an object image formed on a focusing screen by an imaging optical system an erect image, an observation optical system that observes the erecting image through an eyepiece, and light from the focusing plate and the observation optical system has an optical axis inclined with respect to the optical axis intersecting point of the street the observation optical system of the shaft, to reduction imaging an object image formed on the focusing plate an imaging element via the erecting optical system reduced an optical system, in the finder optical system and a the reduction optical system, the eyepiece lens on the light emitting surface of each of the planes of the light incident side on the light exit side of the erecting optical system of the erecting optical system are arranged so as to face, the reduction optical system includes, in order from the erecting optical system, an aperture stop, a first lens having a positive refractive power and a second lens having a positive refractive power, the first lens The light beam incident from the light incident surface is reflected by the inner reflection surface and is reflected from the light output surface. It consists prism body morphism, when the combined focal length of the said first lens second lens f, and paraxial radius of curvature of the light incident surface of the first lens and R1,
−0.4 <f / R1 <0.4
A finder optical system characterized by satisfying the following conditional expression:
２．５ ＜ ｆ／Ｈ ＜ ６
０．３５ ＜ ｆ／ｄ１ ＜ ０．８０
なる条件式を満足することを特徴とする請求項１に記載のファインダー光学系。 When the effective diagonal length of the image sensor is 2H, and the length on the optical axis from the light incident surface to the light exit surface of the first lens is d1,
2.5 <f / H <6
0.35 <f / d1 <0.80
The finder optical system according to claim 1, wherein the following conditional expression is satisfied.
４５° ＜ θ ＜ ６０°
なる条件式を満足することを特徴とする請求項１又は２に記載のファインダー光学系。 When the angle between the optical axis of the reduction optical system and the normal line of the inner reflection surface of the first lens is θ,
45 ° <θ <60 °
The finder optical system according to claim 1, wherein the following conditional expression is satisfied.
０．８ ＜ ν１／ν２ ＜ １．２
５０ ＜ ν１
なる条件式を満足することを特徴とする請求項１乃至３のいずれか１項に記載のファインダー光学系。 Each ν1 an Abbe number of the material of the second lens and the first lens, when the .nu.2,
0.8 <ν1 / ν2 <1.2
50 <ν1
The finder optical system according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
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