JP4621486B2 - Aperture correction mechanism - Google Patents

Description

  The present invention relates to a diaphragm aperture correction mechanism for an interchangeable lens having an optical system in which an open F value is changed by focusing in a special lens such as a macro lens.

  In an interchangeable lens focusing operation, the aperture F value of the aperture is generally constant, but the aperture F value is large in order to correct the aberration of the optical system with a large change in photographing magnification like a macro lens. Some optical systems change. In the case of such an interchangeable lens in which the open F value changes, the photographer manually corrects the exposure according to the shooting distance or increases the effective diameter of the interchangeable lens optical system to prevent the change of the open F value. Was.

  When the open F value changes due to focusing of the photographing lens, the photographer needs to correct the exposure for each photographing distance when using an external photometric camera, an external exposure meter, or flash photography.

Even in the case of an interchangeable lens having an optical system in which the open F value of the photographing lens changes due to focusing in order to eliminate the troublesome manual exposure correction, the aperture value is automatically corrected according to the focusing operation, and the open F value is set. A correction mechanism that keeps the value constant has been proposed.
JP-A-57-46220 Japanese Patent Laid-Open No. 3-251832

  As means for solving the manual exposure correction of the open F value, Japanese Patent Laid-Open No. 57-46220 discloses at least one optical member for correction control of F value change for a lens whose open F value changes due to focusing. A method for correcting the open F-number by moving the optical member for correction along with the movement of the main lens group in the optical axis direction according to focusing is proposed. For this purpose alone, interposing an optical member cannot be said to be a good method in terms of image performance, and a mechanism for interlocking the optical member with focusing is complicated and cannot be said to be an effective method.

  Japanese Patent Laid-Open No. 3-251832 proposes a method of performing correction by changing the starting position of the throttle operation in accordance with the change of the open F value in conjunction with the focusing operation. Although it is recognized that there is an effect, the aperture correction centered on the optical axis is achieved by moving along the cam shape of the interlocking pin inserted into the cam groove of the connecting plate by the straight movement of the connecting plate in the optical axis direction. The open F value is corrected by converting the rotational movement of the plate, and the interlocking pin inserted in the cam groove is inclined with respect to the connecting plate as the aperture correction plate rotates, and the groove width There were problems due to errors due to the clearance of the machine and unevenness of power for movement.

  In view of this problem, in addition to the rectilinear movement, an operating mechanism with rotation for one lens group of the rectilinear movement along the optical axis necessary for focusing among the plural lens groups constituting the interchangeable lens. The problem was solved by providing a structure that enables correction of the open F value in the aperture mechanism by transmitting the rotation operation of the lens group to the aperture correction plate.

  In the diaphragm aperture correction mechanism of the present invention, in the interchangeable lens for a single-lens reflex camera that includes a plurality of lens groups and enables focusing by linearly moving a plurality of lens groups in the lens group in the optical axis direction, Focusing is performed by making one of the plurality of linearly moving lens groups move in a rotational manner and interlocking with an aperture correction plate capable of moving the fulcrum of the diaphragm blade of the diaphragm mechanism that places the rotational operation at a fixed position. Since the opening F value that changes with the operation can be corrected, the structure is simplified and the operation cooperation in the focusing operation is smoothed, and the correct opening F value can be guaranteed.

  DESCRIPTION OF EMBODIMENTS Hereinafter, the best embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of an interchangeable lens equipped with an embodiment of a diaphragm aperture correction mechanism according to the present invention, and FIG. 2 shows an assembled configuration in a lens barrel of the second group lens and the third group lens of the lens. FIG. 3 is an exploded perspective view of a diaphragm unit that corrects the open F value.

  The example of the interchangeable lens shown in FIG. 1 has a four-group configuration in which a first group lens 2, a second group lens 3, a third group lens 4, and a fourth group lens 5 are arranged around the optical axis 1, and the first front lens is arranged in front. The group lens 2 and the rear fourth group lens 5 are fixed, and the intermediate second group lens 3 and the third group lens 4 are moved straight in the direction of the optical axis 1, thereby making it possible to adjust the focus with respect to the distance of the subject. ing.

  The lens is used for AF, and the focus is adjusted by directly rotating the rotating cylinder 7 with a ring motor 6 such as an ultrasonic motor. As will be described in detail later, A mirror chamber 3a of the second group lens 3 of the block holding the second group lens 3 and a mirror chamber 4a of the third group lens 4 of the block holding the third group lens 4 along the optical axis 1 in the fixed cylinder 8. And slide it. The movement mode of the mirror chamber 3a of the second group lens 3 and the mirror chamber 4a of the third group lens 4 is shown in FIG. 1, and the upper half centering on the optical axis 1 is the adjustment position where the subject is at infinity. The half is the adjustment position at the closest position, and the mirror chamber 3a of the second lens group 3 and the mirror chamber 4a of the third lens group 4 are closer to each other as they go closer.

  As will be described in detail later, a diaphragm unit 9 is fixed between the mirror chamber 3a of the second group lens 3 and the mirror chamber 4a of the third group lens 4, and the diaphragm is varied by a motor (not shown). On the other hand, a mechanism for correcting the aperture diameter in conjunction with the focusing operation is installed.

  A focus ring 11 is installed in the outer cylinder 10 forming the appearance, and the rotating cylinder 7 is rotated by a manual rotation operation, and a manual focusing operation is also possible. A mount 12 is fixed to the rearmost portion of the outer cylinder 10 to form an interchangeable lens according to a system that can be attached to and detached from the camera.

  Next, the structure of the fixed barrel 8 and the rotary barrel 7 holding the mirror chamber 3a of the second group lens 3 and the mirror chamber 4a of the third group lens 4 in this lens barrel are shown in FIG. The moving state of the mirror chamber 3a of the second group lens 3 and the mirror chamber 4a of the third group lens 4 during focusing will be described in detail with reference to a perspective view showing the assembly configuration.

  As the assembly order, after inserting the mirror chamber 3a of the second group lens 3 holding the second group lens 3 on the front side of the fixed cylinder 8 having a small diameter, the diaphragm unit 9 is inserted, and the inner diameter becomes a small seat. After being pressed and fixed with a screw (not shown), the mirror chamber 4a of the third group lens 4 that holds the third group lens 4 is placed behind the notch 4ab of the mirror chamber 4a of the third group lens 4. The arm 9fb extending from the aperture correction plate 9f of the aperture unit 9 inserted in the fixed cylinder 8 is inserted into the crotch portion 17a of the guide plate 17 while being inserted in the state where the guide plate 17 is fixed with the screw 18. Let me.

  In this manner, the mirror chamber 3a of the second group lens 3 and the mirror chamber 4a of the third group lens 4 are temporarily installed inside the fixed cylinder 8, and inserted into the rotary cylinder 7, and from the tip of the rotary cylinder 7 to the fixed cylinder 8 At the position where the threaded portion tip 8c appears, the rotating tube retainer 19 is screwed into the threaded portion distal end 8c so that the rotating tube 7 can be rotated with respect to the fixed tube 8, but the structure prevents the removal. .

  In the assembled state described above, the roller A13 with the screw 15 as an axis passes from the outside of the rotating cylinder 7 through the rotating cam groove A7a formed in the rotating cylinder 7, and is further formed in the fixed cylinder 8 inside. By passing through the fixing groove A8a and screwing it into the screw hole A3aa on the side surface of the mirror chamber 3a of the second group lens 3 located inside, the mirror chamber 3a of the second group lens 3 rotates with the fixed cylinder 8. The cylinder 7 is related and connected through the roller A13. The installation state from the rotating cam groove A7a and the fixed groove A8a of the roller A13 to the screw hole A3aa of the mirror chamber 3a of the second lens group 3 is indicated by a chain line j in FIG. is there. Usually, the coupling by the roller A13 is installed at three locations on the outer periphery, but only one location is shown as a representative in the figure.

  Similarly, a roller B14 with the screw 16 as an axis passes from the outside of the rotating cylinder 7 through the rotating cam groove B7b formed in the rotating cylinder 7, and further passes through the fixing groove B8b formed in the inner fixing cylinder 8. Then, by screwing into the screw hole B4aa on the side surface of the mirror chamber 4a of the third group lens 4 located inside, the mirror chamber 4a of the third group lens 4 passes through the fixed cylinder 8 and the rotary cylinder 7 through the roller B14. Relationship combined. The installation state from the rotating cam groove B7b and the fixed groove B8b of the roller B14 to the screw hole B4aa of the mirror chamber 4a of the third lens group 4 is shown by a chain line k in FIG. 2, and is shown in a lower sectional view of FIG. is there. Also in this figure, only three joints by the roller B14 are provided on the outer periphery, but only one place is shown as a representative in the figure.

  As shown in FIG. 2, the rotating cam groove A7a in the rotating cylinder 7 is formed in a right-handed screw shape with respect to the circumference, while the rotating cam groove B7b is formed in a left-handed screw shape with respect to the circumference. The fixed groove A8a of the inner fixed cylinder 8 is formed as a linear groove parallel to the optical axis 1, while the fixed groove B8b is formed into a groove slightly inclined to the left.

  Therefore, when the focal length shown in the upper half of FIG. 1 is in an infinite position and the mirror chamber 3a of the second group lens 3 and the mirror chamber 4a of the third group lens 4 are in the positions shown in the figure, the focus ring 11 is moved. When it is attempted to move in the close direction by the rotating manual or ring motor 6, the rotary cylinder 7 is rotated in the right direction in conjunction with this, but at this time, the roller A13 of the mirror chamber 3a of the second group lens 3 is Since it is constrained in the rotational direction by the fixing groove A8a of the fixed cylinder 8, a backward pushing force acts according to the right-hand thread shape of the rotating cam groove A7a of the rotating cylinder 7, and according to the straight line of the fixing groove A8a of the fixed cylinder 8. The mirror chamber 3a of the inner second group lens 3 is moved rearward, and reaches the position close to the aperture unit 9 as shown in the lower half of FIG.

  Next, since the roller B14 in the mirror chamber 4a of the third group lens 4 is also restrained by the fixing groove B8b of the fixed cylinder 8, a forward pressing force is applied according to the left-hand thread shape of the rotating cam groove B7b of the rotating cylinder 7. The mirror chamber 4a of the inner third group lens 4 is moved forward according to the fixed groove B8b of the fixed cylinder 8, but the fixed groove B8b is inclined to the left as described above. The mirror chamber 4a moves forward while rotating slightly to the left according to the shape of the fixing groove B8b, and reaches a position close to the aperture unit 9 as shown in the lower half of FIG.

  Next, in the diaphragm unit 9 shown in FIG. 3, a disc-shaped diaphragm 9b in which a plurality of diaphragm grooves 9ba are arranged on the circumference is incorporated in an annular case 9a having a notch 9aa at the lowest position, and on the back side thereof. The aperture correction plate 9f is overlapped with the pin 9d and the aperture blade 9c having the pin 9e fixed on the front side in between, and is housed in the case 9a while being pressed by the pressing plate 9g.

  In FIG. 3, a single diaphragm blade 9c is representative, but usually it has the same number as the diaphragm grooves 9ba of the diaphragm 9b and is arranged at equal intervals on the circumference, and the back side pins 9d are arranged on the diaphragm 9b. The aperture pin 9e is inserted into the aperture groove 9ba, and the front-side pin 9e is inserted into a hole 9fa in which the number of aperture blades 9c is arranged at equal intervals on the circumference of the aperture correction plate 9f. It is sandwiched between the correction plates 9f. Thus, when the aperture correction plate 9f is fixed, the diaphragm 9b is rotated by applying rotation to the interlocking plate 9bb from the outside, and the diaphragm blade 9c moves with the pin 9e as a fulcrum and the pin 9d moves according to the inclination of the diaphragm groove 9ba. Accordingly, the tip of the diaphragm blade 9c can be moved toward the optical axis 1 in accordance with this, and a change in the aperture diameter can be obtained comprehensively. In the example shown in FIG. 3, if the diaphragm 9b is rotated clockwise with respect to the left front, the tip of the diaphragm blade 9c is tilted in the direction of the optical axis 1 by the diaphragm groove 9ba having a shape close to the center direction, and the diaphragm aperture is generally small. Acts in the direction of

  On the other hand, when the aperture correction plate 9f is rotated while the diaphragm 9b is fixed, the circumferential position of the pin 9d of the diaphragm blade 9c with respect to the optical axis 1 moves, and accordingly, the diaphragm groove 9ba of the pin 9e of the diaphragm 9b. The pin 9d that is inserted in is also moved, and the tip of the diaphragm blade 9c is moved according to the inclination of the diaphragm groove 9ba, so that the aperture diameter can be changed comprehensively. According to this principle, it is understood that the aperture value determined by rotating the aperture correction plate 9f can be corrected with respect to the aperture value set by driving the interlocking plate 9bb of the diaphragm 9b from the outside. In the example of FIG. 3, when the aperture correction plate 9f is rotated leftward through the arm 9fb with respect to the determined aperture value, the aperture diameter is closed, and when it is rotated rightward, the aperture aperture is opened. It will be corrected.

  Here, the arm 9fb of the aperture correction plate 9f extends rearward through the notch 9aa of the case 9a, and as described above, the guide plate fixed to the notch 4ab of the mirror chamber 4a of the third lens group 4. 17 is inserted into the crotch portion 17a of the third group lens. Therefore, if the mirror chamber 4a of the third group lens 4 is rotated, the aperture correction plate 9f can be rotated and interlocked from the arm 9fb. The aperture value can be corrected by the rotational movement.

  As an actual operation, the mirror chamber 3a of the second group lens 3 linearly moves parallel to the optical axis 1 in accordance with the rotation of the rotary cylinder 7 during focusing, whereas the mirror chamber 4a of the third group lens 4 is shown in FIG. 2, since the fixing groove B8b of the fixed cylinder 8 is slightly inclined, it moves while rotating slightly with respect to the optical axis 1, and in conjunction with this, the aperture correction plate of the diaphragm 9f rotates and the set aperture value is corrected according to the amount of focusing. In the example shown in FIG. 2, when focusing from infinity to the closest position, the rotating cylinder 7 rotates rightward so that the mirror chamber 3a of the second lens group 3 moves straight back, and the mirror chamber 4a of the third lens group 4 rotates to the left. However, since the aperture correction plate 9f is rotated counterclockwise in conjunction with this, the aperture value can be corrected in the direction of closing the aperture, that is, in the direction of increasing the F value.

  As described above, the present invention provides a mechanism capable of accurately and precisely correcting the open F value movement in focusing that occurs in lens design with respect to each focal length by a simple mechanism. Target value is great.

  The combined operation mode of rotation and rectilinear movement has a wide range of industrial applications.

It is sectional drawing of the interchangeable lens carrying 1 Example of the aperture_diaphragm | restriction diameter correction mechanism in this invention. It is a perspective view which shows the assembly structure in the lens barrel of a 2nd group lens and a 3rd group lens. It is a disassembled perspective view of the aperture unit for correcting the open F value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical axis 2 1st group lens 3 2nd group lens 4 3rd group lens 5 4th group lens 6 Ring motor 7 Rotating cylinder 8 Fixed cylinder 9 Aperture unit 10 Outer cylinder 11 Focus ring 12 Mount 13 Roller A
14 Roller B
15 screw 16 screw 17 guide plate 18 screw 19 rotating cylinder holder

Claims (1)

A focusing mirror for adjusting the focal position;
A diaphragm unit having an aperture correction plate, a holding plate, a diaphragm, a pin X, a pin Y, and a diaphragm blade;
A fixed cylinder in which the focusing mirror chamber and the aperture unit are loosely inserted so as to be movable in the optical axis direction;
A rotating cylinder in which the fixed cylinder is loosely inserted so as to be movable in the optical axis direction;
A diaphragm aperture correction mechanism provided in a lens barrel having
The focusing mirror room is composed of a mirror room A and a mirror room B to which a guide plate is fixed,
The mirror chamber A and the mirror chamber B are arranged in order from the subject side,
A cam groove A and a cam groove B are formed in the circular curved surface portion of the rotating cylinder,
A guide groove A parallel to the optical axis and a guide groove B having an inclination with respect to the guide groove A are drilled through the circular curved surface portion of the fixed cylinder,
The mirror chamber A is supported by a roller A inserted in the cam groove A and the guide groove A so as to be movable in the optical axis direction,
The mirror chamber B is supported by a roller B inserted into the cam groove B and the guide groove B so as to be movable in the optical axis direction,
The aperture unit is disposed between the mirror chamber A and the mirror chamber B;
The aperture unit is fixed so as to be inscribed in the fixed cylinder,
The diaphragm is provided with a throttle groove,
The aperture correction plate has an arm portion toward the mirror chamber B at a peripheral portion,
The aperture blade has the pin X and the pin Y,
The pin X and the pin Y are fixed so that the axes of the pin X and the pin Y are different on different surfaces of the diaphragm blade,
The aperture blade is pivotally attached by the pin Y by the pin Y being fitted into a hole formed in the aperture correction plate,
The diaphragm blade is pivotally attached by the pin X by the pin X being disposed so as to be movable along the diaphragm groove disposed on the diaphragm.
The aperture correction plate is engaged with the mirror chamber B by inserting the arm portion into the guide plate,
The mirror chamber A moves in the optical axis direction in the fixed cylinder along the cam groove A and the guide groove A by the roller A along with the rotation of the rotating cylinder in a focusing operation.
The mirror chamber B moves in the optical axis direction while rotating in the fixed cylinder along the cam groove B and the guide groove B by the roller B along with the rotation of the rotating cylinder in a focusing operation.
The arm portion fitted into the guide plate rotates the aperture correction plate in the same direction as the mirror chamber B,
The aperture correction plate is rotated by the movement of the pin X in the aperture groove and the rotation of the pin Y in the hole, and the rotation of the aperture blade is accompanied by the rotation along the aperture groove toward the optical axis. The diaphragm aperture correction mechanism is characterized in that the movement with the rotation of the aperture blade moves the tip of the aperture blade toward the optical axis to adjust the aperture diameter and adjust the light amount. .

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