JPS616611A - Focus detecting device - Google Patents
Focus detecting deviceInfo
- Publication number
- JPS616611A JPS616611A JP12682684A JP12682684A JPS616611A JP S616611 A JPS616611 A JP S616611A JP 12682684 A JP12682684 A JP 12682684A JP 12682684 A JP12682684 A JP 12682684A JP S616611 A JPS616611 A JP S616611A
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- Japan
- Prior art keywords
- lens
- image
- imaging
- pupil
- field
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/28—Systems for automatic generation of focusing signals
- G02B7/34—Systems for automatic generation of focusing signals using different areas in a pupil plane
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Focusing (AREA)
- Automatic Focus Adjustment (AREA)
Abstract
Description
【発明の詳細な説明】
本発明はカメラ等の焦点検出装置に関し、特にカメラの
結像レンズのｍを複数の領域に分割し、各領域を通過す
る光束により複数の第２次物体像を形成し、これらの第
２次物体像の相対的な位置関係より結像レンズの焦点位
置を検出する焦点検出装置に関するものでめる〇従来よ
り結像レンズの像面側に再結像系を配置し結像レンズの
瞳を複数に分割し、これらの瞳領域からの光束を用いて
結像レンズによって形成された第１次物体像から複数の
第２次物体像を形成し、これら複数の第２次物体像の相
対的位置関係を検出することにより結像レンズの焦点状
態を検出する再結像系を用いた焦点検出装置が例えば特
開昭５２−９５２２１号公報で捷案されている。第１図
は従来の再結像系を用いた焦点検出装置の光学系の概略
図である。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focus detection device such as a camera, and more particularly, to a focus detection device such as a camera, in which m of an imaging lens of a camera is divided into a plurality of regions, and a plurality of secondary object images are formed by a light beam passing through each region. This article relates to a focus detection device that detects the focal position of the imaging lens from the relative positional relationship of these secondary object images. Conventionally, a re-imaging system is placed on the image plane side of the imaging lens. The pupil of the imaging lens is divided into a plurality of parts, and the light beams from these pupil areas are used to form a plurality of secondary object images from the primary object image formed by the imaging lens. A focus detection device using a re-imaging system that detects the focus state of an imaging lens by detecting the relative positional relationship of secondary object images has been proposed, for example, in Japanese Patent Laid-Open No. 52-95221. FIG. 1 is a schematic diagram of an optical system of a focus detection device using a conventional reimaging system.
同図において１は結像レンズ、２は結像し／ズ１の予定
結像面近傍に配置した視野マスク、４は傾角が相互に逆
向きの２つのプリズム４−”１．４−２より成る瞳分割
手段、４′は瞳分割マスク、５は瞳分割マスク４′を瞳
とする再結像レンズ、６は結像レンズ１の予定結像面近
傍にあって再結像レンズ５の瞳を結像レンズｌの瞳近傍
に結像させるフィールドレンズであり、瞳分割手段４、
瞳分割マスク４′、再結像レンズ５そしてフィールドレ
ンズ６より再結像先金構成している。In the figure, 1 is an imaging lens, 2 is a field mask placed near the planned imaging plane of the lens 1, and 4 is two prisms 4-"1.4-2 whose inclination angles are opposite to each other. 4' is a pupil division mask; 5 is a re-imaging lens that uses the pupil division mask 4' as a pupil; and 6 is a pupil of the re-imaging lens 5 located near the planned imaging plane of the imaging lens 1. is a field lens that forms an image near the pupil of the imaging lens l, and the pupil dividing means 4,
A pupil division mask 4', a reimaging lens 5, and a field lens 6 constitute a reimaging tip.
７は２つのプリズム４−１．４−２に対応して再結像系
の像面付近に配置された２系列の光電変換素子列７−１
．７−２を有する充電変換手段セある。Reference numeral 7 denotes two series of photoelectric conversion element arrays 7-1 arranged near the image plane of the re-imaging system corresponding to the two prisms 4-1 and 4-2.
．． 7-2.
第１図において結像レンズ１の瞳は再結像系によｆｆ瞳
領域８−１．８−２の２つに分割されている。このうち
瞳領域８−１を通過した光束は視野マスク２の近傍に第
１次物体像を形成し、その後フィールドレンズ６、プリ
ズム４−１ｔ’経て再結像レンズ５により光電変換素子
列７−１付近に第２次物体像を形成する。結像レンズｌ
の瞳領域８−２を通過した光束も同様に視野マスク２の
近傍に第１次物体像を形成し、その後フィールドレンズ
６、プリズム４−２を経て再結像レンズ５により光電変
換素子列７−２＋１近に第２次物体像を形成する。２つ
の第２次物体像の相対的位置は結像レンズ１の焦点状態
によ９異なる為、この２つの第２次物体像の相対的位置
を検出することにより結像レンズｌの焦点状態を検出し
ている。In FIG. 1, the pupil of the imaging lens 1 is divided into two ff pupil regions 8-1 and 8-2 by a re-imaging system. Among these, the light flux that has passed through the pupil area 8-1 forms a primary object image near the field mask 2, and then passes through the field lens 6, the prism 4-1t', and the re-imaging lens 5 to form the photoelectric conversion element array 7- A secondary object image is formed near 1. Imaging lens l
The light flux that has passed through the pupil area 8-2 similarly forms a primary object image near the field mask 2, and then passes through the field lens 6 and prism 4-2, and then is transferred to the photoelectric conversion element array 7 by the re-imaging lens 5. A secondary object image is formed near -2+1. Since the relative positions of the two secondary object images differ by 9 depending on the focal state of the imaging lens 1, the focal state of the imaging lens 1 can be determined by detecting the relative positions of these two secondary object images. Detected.
例えば結像レンズ１の結像面が予定結像面上にあれば２
つの第２次物体像の相対的位置は一致するが結像レンズ
１の結像面が予定結像面の前方にある前ピン状態では２
つの第２次物体像が一致した基準位置に対して各々矢印
９方向に相対的に移動する。逆に結像レンズの結像面が
予定結像面の後方にある後ビン状態では前述と逆に表る
。For example, if the imaging plane of imaging lens 1 is on the planned imaging plane, 2
The relative positions of the two secondary object images are the same, but in the front focus state where the imaging plane of the imaging lens 1 is in front of the expected imaging plane, the two secondary object images match.
Each of the two secondary object images moves in the direction of arrow 9 relative to the coincident reference position. On the other hand, in the rear bin state where the imaging surface of the imaging lens is behind the intended imaging surface, the situation is opposite to that described above.
フィールドレンズ６は再結像レンズ５の瞳會結倫レンズ
ｌの瞳近傍に結像させて結像レンズ１からの光束を効率
良く再結像レンズ５に導光させている。The field lens 6 forms an image near the pupil of the pupil connection lens l of the re-imaging lens 5, and efficiently guides the light beam from the imaging lens 1 to the re-imaging lens 5.
フィールドレンズは第２図に示す凸平若しくはこれに近
いレンズ形状で構成されている場合が多い。このフィー
ルドレンズ６は再結像系としての結像作用には全んど寄
与しないが再結像系による第２次物体偉に正の歪曲収差
を多（発生させる原因となっている。正の歪曲収差は再
結像系の中心に比べ周辺で局所的に横倍本管増大させる
仁とになる。この為一様輝度の物体の像であってもその
像は一様輝度とならず光電変換手段で検出される光量分
布は例えば第３図の如く周辺で低下する山形状となる。The field lens is often constructed with a convex-planar lens shape as shown in FIG. 2, or a lens shape similar to this. This field lens 6 does not contribute at all to the imaging action as a re-imaging system, but it causes a lot of positive distortion in the secondary object size due to the re-imaging system. Distortion aberration causes the lateral magnification to increase locally at the periphery compared to the center of the re-imaging system.For this reason, even if the image of an object has uniform brightness, the image does not have uniform brightness and is distorted by photoelectrons. The light amount distribution detected by the converting means has a mountain shape that decreases at the periphery, as shown in FIG. 3, for example.
この山形状の光量むらは複数の第２次物体儂の相対的位
置を検出して焦点検出を行う焦点検出装置においては物
体像の相対的位置を誤って検出してしまう為検出精度を
低下させる原因となる。This mountain-shaped light intensity unevenness reduces detection accuracy in a focus detection device that detects the relative positions of multiple secondary objects and detects the relative positions of the object images incorrectly. Cause.
本発明は再結像系を用いた焦点検出装置においてフィー
ルドレンズにより生ずる歪曲収差全良好に補正し高精度
の焦点検出を可能とした焦点検出装置の提供を目的とす
る。SUMMARY OF THE INVENTION An object of the present invention is to provide a focus detection device using a re-imaging system, which fully corrects distortion caused by a field lens and enables highly accurate focus detection.
本発明の目的を達成する為の焦点検出装置の主たる特徴
は結像レンズの像面１ｉ１１に前記結像レンズの瞳を複
数の領域に分割する瞳分割手段と前記結像レンズの複数
に分割された瞳領域を通過する光束から複数の第２次物
体像を形成する再結像レンズと前記結像レンズの予定結
像面近傍に前記再結像レンズの瞳を前記結像レンズの瞳
付近に結像させる単一のレンズから成るフィールドレン
ズとを有した再結像系全配置し、前記再結像系の像面近
傍に配置し九九電変換手段により前記複数の第２次物体
像の相対的位置を検出し前記結像レンズの焦点位置を検
出する焦点検出装置において前記光電変換手段の前方に
前記フィールドレンズによシ生じる歪曲収差を補正する
為の単一のレンズから成る補正レンズを配置し、前記フ
ィールドレンズの物体側と像面側のレンズ面の屈折力を
各々ψ 、ψ２、前記補正レンズの物体側と像面側のレ
ンズ面の屈折力を各々ψ 、ψ４とし几とき
なる条件を満足することである。The main features of the focus detection device for achieving the object of the present invention include: a pupil dividing means for dividing the pupil of the imaging lens into a plurality of regions; a re-imaging lens that forms a plurality of secondary object images from a light beam passing through a pupil region; and a pupil of the re-imaging lens near the intended imaging plane of the imaging lens; A re-imaging system having a field lens consisting of a single lens for image formation is disposed in the vicinity of the image plane of the re-imaging system, and the plurality of secondary object images are In a focus detection device that detects a relative position and a focal position of the imaging lens, a correction lens consisting of a single lens is provided in front of the photoelectric conversion means to correct distortion caused by the field lens. The refractive powers of the object-side and image-side lens surfaces of the field lens are ψ and ψ2, respectively, and the refractive powers of the object-side and image-side lens surfaces of the correction lens are ψ and ψ4, respectively. It is to satisfy the conditions.
このように本発明においてはフィールドレンズの２つの
レンズ面の屈折力と補正レンズの２つのレンズ面の屈折
力を前述の如く設定することによυフィールドレンズで
生じる歪曲収差を良好に補正し、光電変換手段によシ第
２次物体像の相対的位置を正しく検出し高精度の合焦検
出を可能とするものである。In this way, in the present invention, by setting the refractive powers of the two lens surfaces of the field lens and the refractive powers of the two lens surfaces of the correction lens as described above, the distortion generated in the υ field lens is well corrected. The photoelectric conversion means accurately detects the relative position of the secondary object image and enables highly accurate focus detection.
次に本発明の一実施例を各図と共に説明する。Next, one embodiment of the present invention will be described with reference to each drawing.
第４図は本発明の焦点検出装置の一実施例の一部分の光
学系の概略図である。同図において第１自と同一部材に
は同じ番号を付しである。FIG. 4 is a schematic diagram of a part of the optical system of an embodiment of the focus detection device of the present invention. In the figure, the same members as those in the first part are given the same numbers.
図中１０はフィールドレンズによる歪曲収差を補正する
為に光電変換手段７の前方に配置した補正レンズであり
、同実施例では平凸レンズよ多構成されている。第５図
は歪曲収差の補正状態を示す収差図であり図中実線は補
正レンズを配置しない場合、破線は補正レンズを配置し
た場合である。同図より明らかのようにフィールドレン
ズ６で生じた歪曲収差は良好に補正されていることがわ
かる。In the figure, reference numeral 10 denotes a correction lens disposed in front of the photoelectric conversion means 7 to correct distortion caused by the field lens, and in this embodiment, it is composed of a plano-convex lens. FIG. 5 is an aberration diagram showing the state of distortion aberration correction, in which the solid line represents the case where no correction lens is provided, and the broken line represents the case where the correction lens is provided. As is clear from the figure, the distortion caused by the field lens 6 is well corrected.
第６図は第４図の補正レンズ１０の像面側のレンズ面の
屈折力金庫々に変化させたときの歪曲収差の変化を示し
た収差図であり屈折力を強くすることにより収差曲線を
破線から一点鎖線、二点鎖線へと変化させることができ
る。FIG. 6 is an aberration diagram showing the change in distortion when the refractive power of the lens surface on the image plane side of the correction lens 10 shown in FIG. The dashed line can be changed to a dashed line or a dashed double dotted line.
第７図は第４図の補正レンズ１０の全体の屈折力を一定
にして両レンズ面の屈折力を変化させたときの歪曲収差
の変化を示したものであり補正レンズ１′ｏの物体側の
レンズ面の屈折力を負から正へ変化させることＫより破
線から一点鎖線、二点鎖線へと変化させることができる
。FIG. 7 shows the change in distortion when the refractive power of both lens surfaces is changed while keeping the entire refractive power of the correction lens 10 of FIG. By changing the refractive power of the lens surface from negative to positive, it is possible to change the refractive power from the broken line to the one-dot chain line to the two-dot chain line.
以上のように本実施例においては再結像系より発生する
歪曲収差を補正レンズ１０の屈折力若しくはレンズ形状
を変えることにより良好に補正することができる。As described above, in this embodiment, the distortion generated by the re-imaging system can be favorably corrected by changing the refractive power or lens shape of the correction lens 10.
特に本発明において好ましいのはフィールドレンズと補
正レンズの物体側と像面側のレンズ面の屈折力を前述の
条件式（１）の如く設定することである。In particular, in the present invention, it is preferable to set the refractive powers of the object-side and image-side lens surfaces of the field lens and correction lens as shown in the above-mentioned conditional expression (1).
これによりフィールドレンズで生じる歪曲収差を良好に
補正ししかも再結像系全体による第２次物体像を光電変
換手段上に良好に結像させることができる。Thereby, it is possible to satisfactorily correct the distortion aberration caused by the field lens, and to form a secondary object image by the entire re-imaging system on the photoelectric conversion means.
条件式（１）を外れると歪曲収差の補正及び再結像系全
体の光学性能を良好に維持するのが困難となる。If conditional expression (1) is not satisfied, it becomes difficult to correct distortion aberration and maintain good optical performance of the entire re-imaging system.
第４図に示す実施例では補正レンズ１０を正の屈折力の
レンズで構成した場合を示したが第８図に示すように補
正レンズ１１を負の屈折力の平凹レンズで構成しても第
５図と同様に歪曲収差を補正することができる。In the embodiment shown in FIG. 4, the correction lens 10 is composed of a lens with a positive refractive power, but as shown in FIG. Distortion aberration can be corrected in the same way as in FIG.
フィールドレンズを凸子状の単レンズで構成したときは
フィールドレンズより正の歪曲収差が発生するので補正
レンズな平凸状若しくはこれに近い形状の正レンズとし
又は平凹状若しくはそれに近い形状の負レンズで構成す
るのが歪曲収差を良好に補正するのに好ましい。When the field lens is composed of a convex single lens, more positive distortion occurs than the field lens, so use a positive lens with a plano-convex or similar shape as a correction lens, or a negative lens with a plano-concave or similar shape. It is preferable to have the following configuration in order to satisfactorily correct distortion.
又フィールドレンズを平凸状の単レンズで構成した場合
はフィールドレンズより負の歪曲収差が発生するので、
このときは補正レンズを凸平状若しくはそれに近い形状
の正レンズで又は凹平状若しくはそれに近い形状の負レ
ンズで構成すれば前述と同様に歪曲収差を良好に補正す
ることができる。Also, if the field lens is composed of a plano-convex single lens, more negative distortion will occur than the field lens.
In this case, if the correction lens is constructed of a positive lens having a convex-planar shape or a shape close to that, or a negative lens having a concave-flat shape or a shape close to that, the distortion can be favorably corrected in the same way as described above.
尚本発明において補正レンズを前述の屈折力に応じた２
つ以上の複数のレンズより構成しても良い。又補正レン
ズのレンズ面を非球面にすればより良好なる収差補正が
出来るので好ましい。又光電変換手段が列状の場合には
補正レンズをシリンドリカルレンズで構成するのが光学
性能上有効である。In addition, in the present invention, the correction lens is
It may be composed of three or more lenses. Furthermore, it is preferable to make the lens surface of the correction lens an aspherical surface because better aberration correction can be achieved. Further, when the photoelectric conversion means is arranged in a row, it is effective in terms of optical performance to configure the correction lens with a cylindrical lens.
補正レンズは複数の光電変換素子列の１つ１つに設けて
も良いし又全ての光電変換素子をまとめて１つの補正レ
ンズで共用するようにしても良い。The correction lens may be provided in each of the plurality of photoelectric conversion element rows, or all the photoelectric conversion elements may be collectively used as one correction lens.
尚通常光電変換手段の前面にはガラス板のような保護部
材を設けているので補正レンズの一部をこの保護部材と
兼用して構成すれば装置が簡素化されるので好ましい。It should be noted that since a protective member such as a glass plate is usually provided in front of the photoelectric conversion means, it is preferable to configure a part of the correction lens to also serve as this protective member, since this simplifies the apparatus.
以上のように本発明によれば再結像系のフィールドレン
ズで生ずる歪曲収差を良好に補正した高精度の焦点検出
装置上達成することができる。As described above, according to the present invention, it is possible to achieve a high-precision focus detection device that satisfactorily corrects the distortion caused by the field lens of the re-imaging system.
特に本発明に係る補正レンズは再結像系の歪曲収差以外
はほとんど影響を及ぼすことがないので再結像系の光学
性能を何んら低下させることがない等の特長を有してい
る。In particular, the correction lens according to the present invention has the advantage that it hardly affects anything other than distortion of the re-imaging system, so that the optical performance of the re-imaging system is not degraded in any way.
第１図は従来の焦点検出装置の光学系の概略図、第２図
は第１図のフィールドレンズのレンズ断面図、第３図は
第１図による物体像の光量分布の説明図、第４図、第８
図は各々本発明の焦点検出装置の一部分の光学系の概略
図、第５、第６、第７圀は各々本発明による収差補正を
説明する為の収差図である。
図中１は結像レンズ、２は視野マスク、４は瞳分割手段
、５は再結像レンズ、６はフィールドレンズ、７は光電
変換手段、１０ 、１１は補正レンズである。Fig. 1 is a schematic diagram of the optical system of a conventional focus detection device, Fig. 2 is a cross-sectional view of the field lens of Fig. 1, Fig. 3 is an explanatory diagram of the light intensity distribution of the object image according to Fig. 1, and Fig. 4 is a schematic diagram of the optical system of a conventional focus detection device. Figure, 8th
Each figure is a schematic diagram of a part of the optical system of the focus detection device of the present invention, and the fifth, sixth, and seventh circles are aberration diagrams for explaining aberration correction according to the present invention. In the figure, 1 is an imaging lens, 2 is a field mask, 4 is a pupil division means, 5 is a re-imaging lens, 6 is a field lens, 7 is a photoelectric conversion means, and 10 and 11 are correction lenses.
Claims (2)
の領域に分割する瞳分割手段と前記結像レンズの複数に
分割された瞳領域を通過する光束から複数の第２次物体
像を形成する再結像レンズと前記結像レンズの予定結像
面近傍に前記再結像レンズの瞳を前記結像レンズの瞳付
近に結像させる単一のレンズから成るフィールドレンズ
とを有した再結像系を配置し、前記再結像系の像面近傍
に配置した光電変換手段により前記複数の第２次物体像
の相対的位置を検出し前記結像レンズの焦点位置を検出
する焦点検出装置において前記光電変換手段の前方に前
記フィールドレンズにより生じる歪曲収差を補正する為
の単一のレンズから成る補正レンズを配置し、前記フィ
ールドレンズの物体側と像面側のレンズ面の屈折力を各
々ψ＿１、ψ＿２、前記補正レンズの物体側と像面側の
レンズ面の屈折力を各々ψ＿３、ψ＿４としたとき ψ＿１＞ψ＿２（但しψ＿１＞０）のときψ＿３＜｜ψ
＿４｜ψ＿１＜ψ＿２（但しψ＿２＞０）のときψ＿３
＞｜ψ＿４｜なる条件を満足することを特徴とする焦点
検出装置。(1) A pupil dividing means for dividing the pupil of the imaging lens into a plurality of regions on the image plane side of the imaging lens, and a plurality of secondary rays from the light flux passing through the plurality of divided pupil regions of the imaging lens. A field lens consisting of a re-imaging lens that forms an object image and a single lens that forms an image of the pupil of the re-imaging lens near the planned imaging plane of the imaging lens. A re-imaging system having a re-imaging system is arranged, and a photoelectric conversion means arranged near an image plane of the re-imaging system detects the relative positions of the plurality of secondary object images, and detects the focal position of the imaging lens. In the focus detection device, a correction lens consisting of a single lens for correcting distortion caused by the field lens is disposed in front of the photoelectric conversion means, and a correction lens consisting of a single lens is arranged in front of the photoelectric conversion means, and When the refractive powers are ψ_1 and ψ_2, respectively, and the refractive powers of the object-side and image-side lens surfaces of the correction lens are ψ_3 and ψ_4, respectively, when ψ_1>ψ_2 (however, ψ_1>0), ψ_3<|ψ
＿4｜When ψ_1<ψ_2 (however, ψ_2>0), ψ_3
A focus detection device characterized by satisfying the following condition: >|ψ_4|.
球面より構成したことを特徴とする特許請求の範囲第１
項記載の焦点検出装置。(2) At least one lens surface of the correction lens is an aspherical surface.
The focus detection device described in Section 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12682684A JPS616611A (en) | 1984-06-20 | 1984-06-20 | Focus detecting device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12682684A JPS616611A (en) | 1984-06-20 | 1984-06-20 | Focus detecting device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS616611A true JPS616611A (en) | 1986-01-13 |
Family
ID=14944882
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP12682684A Pending JPS616611A (en) | 1984-06-20 | 1984-06-20 | Focus detecting device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS616611A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4928650A (en) * | 1988-03-28 | 1990-05-29 | Nissan Motor Co., Ltd. | Operating arrangement for internal combustion engine poppet valves and the like |
| US4944256A (en) * | 1988-08-16 | 1990-07-31 | Nissan Motor Company, Ltd. | Rocker arm arrangement for internal combustion engine poppet valves and the like |
| US5048474A (en) * | 1989-02-22 | 1991-09-17 | Nissan Motor Co., Ltd. | Valve train for automotive engine |
| JPH04231223A (en) * | 1990-12-28 | 1992-08-20 | Kubota Corp | Forward and reverse selector construction for work vehicle |
-
1984
- 1984-06-20 JP JP12682684A patent/JPS616611A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4928650A (en) * | 1988-03-28 | 1990-05-29 | Nissan Motor Co., Ltd. | Operating arrangement for internal combustion engine poppet valves and the like |
| US4944256A (en) * | 1988-08-16 | 1990-07-31 | Nissan Motor Company, Ltd. | Rocker arm arrangement for internal combustion engine poppet valves and the like |
| US5048474A (en) * | 1989-02-22 | 1991-09-17 | Nissan Motor Co., Ltd. | Valve train for automotive engine |
| JPH04231223A (en) * | 1990-12-28 | 1992-08-20 | Kubota Corp | Forward and reverse selector construction for work vehicle |
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