JPH0833510B2 - Lens structure with switchable focal length - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lens structure, and more particularly, to a lens structure whose focal length can be switched.

[Prior Art] Various types of camera lenses with variable focal lengths are known. The type is a zoom type in which the focal length is continuously variable, and several typical focal lengths are selected. It can be roughly classified into the switching type that is switched. Here, among the switching types, those that move a single lens group in the optical axis direction, those that insert a conversion lens into an optical system in a standard state, those that have a plurality of independent optical systems, etc. are known. .

[Problems to be Solved by the Invention] Of these, in an optical system of a type in which a conversion lens is inserted, a special space for retracting the conversion lens is required, and more than three types of focal lengths are set. Had to have more than one conversion lens.

In view of such a point, the present invention provides a conversion lens, in particular, a lens structure of a type using a front conversion lens, by additionally setting a single conversion lens group at three types of positions in an optical system in a standard state. It is an object of the present invention to provide a lens structure capable of setting three types of focal lengths of wide, standard and tele while being compact and lightweight, and having a more compact structure.

[Means for Solving the Problems] A lens structure of the present invention is a lens structure having a second optical system for zooming on the subject side of the first optical system capable of photographing with a single focal length, The second optical system, in which the variable magnification effect is inverted by displacing the optical axis by 180 °, is rotatably supported with respect to the fixed frame of the first optical system, and the optical axis of the second optical system is A first position coinciding with the optical axis of the first optical system,
A second position in which the optical axis of the second optical system is orthogonal to the optical axis of the first optical system and a third position in which the first position is displaced by 180 °.
There is provided a magnification changing switching means capable of stopping the second optical system at the position.

[Operation] When the second optical system is at the first position, it is wide by the variable power switching means, and when the second optical system is at the second position, the second optical system is retracted from the optical path of the first optical system. Standard and the telephoto when in the third position, the three focal length states can be set by switching.

[Embodiment] FIG. 1 is a sectional view of an embodiment in which the present invention is applied to a lens barrel for a video camera. Here, as the optical system, the lenses L ₁ and L ₂ are front conversion lens groups (hereinafter referred to as variable power groups), and the lenses L ₃ , L ₄ and L _{5 are} fixed lens groups (hereinafter referred to as fixed groups). , Lenses L ₆ , L ₇ , and L _{8 form a} focus lens group (hereinafter referred to as a focus group), of which the lens L excluding the zoom lenses L ₁ and L ₂
An optical system in a standard state is formed by 6 sheets of _{3 to} L ₈ .

Lenses L ₃ , L ₄ and L ₅ which are fixed groups are held by the support frame 10 by the spring ring 29 and positioned on the fixed frame 1 by the fitting portion 10 a formed at the flange tip of the support frame 10. It is fixed with a screw 32. The auto iris 4 is sandwiched between the fixed frame 1 and the flange of the support frame 10, and the auto iris 4 is integrally held between the fixed frame and the support frame 10 by fixing the screw 32.

Lenses L ₆ , L ₇ , and L ₈ that are the focus group are lenses L ₇ and L _8.
Focus frame 5 with spring ring 30 via spacer 26
Held in. The focus frame 5 is slidably fitted on the inner circumference of the fixed frame 1. Furthermore, the focus frame 5
The focus pin 19 is planted in the
Penetrates the moving groove 1 a of the fixed frame 1 and engages with the focus lever 20 outside the fixed frame 1.

Behind the focus group of the lenses L _{6 to} L _8, the element frame 2 is fitted into the fixed frame 1 and fixed by screws 33. A filter 18 including a crystal filter, a pressing rubber 17 having elasticity, a CCD (charge-coupled device) 3 located on the image plane, and a device holder 16 are arranged in this order from the front on the element frame 2, and the element holder 16 is It is fixed to the fixed frame 1 by a member (not shown).

The above is the configuration from the CCD ₃ which is the image pickup element to the lens L ₃ , and the optical system in the standard state is completed by this.

Next, a flat plate portion 1b that supports the variable power group of the lenses L ₁ and L ₂ is provided in the front portion of the fixed frame 1, and the flat plate portion 1b has an axis
15 is fixed, and a gear 12 is rotatably held on the shaft 15. A rotary plate 7 is provided on the gear 12, and the gear 12 and the rotary plate 7 are fixed so as to rotate integrally.

Here, FIG. 4 corresponding to the cross section along the line IV-IV in FIG. 1 and the third cross section taken along the line III-III
Referring to the drawings, the rotary plate 7 that rotates integrally with the gear 12
Is formed in a U-shape when viewed from the side, and has a shape capable of supporting both ends of the shaft 14 and the shaft 25 as shown in FIG. That is, as shown in FIG. 1, both ends of the shaft 14 are fitted with fitting portions 7a, 7b formed at the rising portions of the rotary plate 7.
And one end surface of the shaft 14 is restricted by the end surface of the blind-shaped fitting portion 7a. The other end surface of the shaft 14 located on the fitting portion 7b side has the shaft 14
After being inserted into 7b, it is regulated by the holding plate 11. shaft
The 25 has the same configuration. In addition, the presser plate 11
Is fixed to the rotary plate 7 with screws 31.

Further, on the shafts 14 and 25, the lens L ₁
Although L ₂ is located, the magnification varying lens L ₁ is composed of a concave lens, and the magnification variation lens L ₂ is composed of a convex lens. As shown in FIG. 7, the lens frame 8 in which the variable power concave lens L ₁ is fixedly supported by the spring ring 27 is slidably fitted to the shaft 14 and is slidably fitted to the shaft 25. A fitting portion 8c that movably fits and a projection portion 8a that serves as a contact portion with a cam plate 6 described later are formed. Therefore, the variable magnification lens frame 8, that is,
The lens L ₁ is positioned by the shaft 14 and the shaft 25. The variable power lens frame 9 is also similar in structure to the variable power lens frame 8, and both variable power lens frames 8 and 9 have symmetrical shapes. The variable power lens frame 9 also fixes and supports the variable power convex lens L ₂ by the spring ring 28, and the shaft 14,
Positioned by the shaft 25. Further, a coil spring 23 is provided on the outer periphery of the shaft 14, and the elastic repellency of the spring 23 applies a biasing force to the variable power lens frame 9 of the variable power lens frame 8 in the direction in which they move away from each other. There is.

At the position where it contacts the projection 9a of the variable power lens frame 9, the fourth
A cam plate 6 having a shape as shown in the figure is provided, and the cam plate 6 is provided.
Is fixed to the support frame 10 with screws 34 as shown in FIG. 2 which is a front view.

As shown in FIG. 3, a gear 13 that meshes with the rotary plate 7 meshes with a gear 13, and a variable power pin 21 fixed to the gear 13
Is engaged with the zoom lever 22. The gear 13 is rotatably supported by a shaft 24 fixed to the fixed frame 1.

Next, the operation of the lens barrel configured as described above will be described.

The states shown in FIG. 1 to FIG. 4 show the lens barrel for a video camera in the wide / infinity state. This lens barrel can be switched between three focal length states. here,
And three focal length state of the standard state obtained by only the optical system of the lens L _1, L ₂ from the zooming group is retracted from the photographing optical axis comprising the lens L ₃ ~L _8, the variable power group 2 A wide state and a tele state obtained by adding the lenses L _{3 to} L ₈ in front of the optical system from different directions.

When focusing is performed in the lens barrel from infinity to a close range, the focus lever 20 shown in FIGS. 1 and 3 is moved forward by a member (not shown). As a result, the focus pin 19 moves in the moving groove 1a of the fixed frame 1.
Moves forward in the lens and integrates it with the focus pin 19
The focus group consisting of L ₆ , L ₇ , and L ₈ moves forward. Needless to say, the operation of the focus lever 20 from the outside at this time can correspond to both autofocus and manual operation.

Next, the operation of switching the lens barrel from wide to standard will be described. In FIG. 3, when the zoom lever 22 is moved forward by a member (not shown) indicated by an arrow a, the zoom pin 21 that is engaged with the zoom lever 22 and is regulated has a fork-shaped groove of the zoom lever 22. The gear 13 integrated with the variable power pin 21 rotates in the clockwise direction in FIG. The rotation of the gear 13 is transmitted to the gear 12, so that the rotary plate 7 integrated with the gear 12 tends to rotate. Here, as shown in FIG. 4, in the rotary plate 7, the projection 9a of the variable power lens frame 9 is recessed in the cam plate 6 by the coil spring 23.
Since the positioning in the rotation direction is performed by being biased by 6a, rotation is not performed with a rotation force of a certain value or less. That is, when the force for operating the magnification varying lever 22 becomes a certain value or more, the protrusion 9a moves on the outer periphery of the shaft 14 against the biasing force of the coil spring 23 while being restricted by the cam portion 6b of the cam plate 6, This allows the rotary plate 7 to rotate.

FIG. 5 shows a state in which the rotary plate 7 is rotated by a certain angle and reaches a position corresponding to an intermediate position between wide and standard. In the state shown in FIG. 5, the zoom lens frame 9 is moved toward the zoom lens frame 8 by the cam plate 6 and the zoom lens is moved.
The distance between L ₁ and L ₂ is shorter than that shown in FIG. As a result, the variable magnification lens frame 9 and the variable magnification lens L ₂ and the support frame 10 can rotate without contact. Further, in the state shown in FIG. 5, the zoom lens frame 9 has the cam portion 6b.
Since it is moving against the biasing force of the coil spring 23, the rotary plate 7 returns to the state shown in FIG. 4 if the operating force of the magnification varying lever 22 is removed in the state shown in FIG. It is natural.

When the zoom lever 22 is further operated from the state shown in FIG. 5, the projection 9a of the zoom lens frame 9 goes beyond the inflection point 6d of the cam plate 6 toward the recess 6c. The state in which the protrusion 9a reaches the recess 6c and is stable is the standard state shown in FIG. In the state shown in FIG. 6, the variable magnification lens frame 8
Similarly to the projection 9a of the variable power lens frame 9, the projection 8a is also urged against the recess 6e of the cam plate 6 by the coil spring 23, so that the position of the rotary plate 7 is regulated at both ends. Here, in the state shown in FIG. 6, the lenses forming the variable power group
Since L _1, the optical axis of the L ₂ becomes perpendicular to the optical axis of the optical system of the lens L ₃ ~L _8, Henbaigun becomes a state of being retracted from the optical path by the optical system of the lens L ₃ ~L _8, The optical system of the lenses L _{3 to} L ₈ is not affected at all. Therefore, the state shown in FIG. 6 is the standard state in which the variable power group is excluded from the lens barrel.

Next, when switching from the standard state to the telescopic state, the zoom lever 22 is further operated in the same direction as when switching from the wide state to the standard state, as described above. Then, the rotary plate 7 tries to rotate further clockwise than the state shown in FIG.
As a result, the projection 9a, which was responsible for the movement of the zoom lens frame 9 when switching from the wide state to the standard state, is disengaged from the cam plate 6, but the projection 8a of the zoom lens frame 8 is cammed. The plate 6 is moved along the cam portion 6f through the inflection point 6g to move the variable power lens frame 8, and the operation similar to the operation performed by the projection 9a of the variable power lens frame 9 is performed. And the protrusion 8a
There With against urged by the coil spring 23 in the recess 6a of the cam plate 6, When this stable state, the optical axis of the optical system by the optical axis and the lens L ₃ ~L ₈ zooming group in the same state one However, as compared with the case of the wide-angle described above, the positions of the variable power concave lens L ₁ and the variable power convex lens L ₂ are completely interchanged, and the telescopic state is achieved in this lens barrel. From this state,
It goes without saying that if the variable magnification lever 22 is operated in the direction opposite to the arrow a, the rotary plate 7 rotates in the opposite direction to the above, and the telescopic state is sequentially switched to the standard state and then to the wide state. .

FIG. 8 shows a modification of the variable magnification lens frame 8. That is, instead of the variable power lens frame 8, the variable power lens frame 108 having the shape shown in FIG. 8 may be used. This variable lens frame 1
A zoom lens L ₁₀ having a barrel shape when viewed from the front as shown by the solid line in FIG. 9 is used for 08. In FIG. 9, the alternate long and short dash line L ₁₀₁ represents the outline of a normal circular lens, and the dashed line L ₁₀₂ represents a rectangle that is inscribed in the outline of the alternate long and short dash line L ₁₀₁ and is similar to the image sensor. That is, in consideration of the shape of the image pickup element, the shape of the variable power lens of this modified example has a shape in which unnecessary portions are removed to the extent that each aberration is not degraded. Further, in FIG. 8, the lens supporting portion of the variable power lens frame 108 has a shape corresponding to the shape of the variable power lens L ₁₀ shown in FIG. 9, and fixing is performed by adhesion instead of the spring ring 27. Done. Other protrusions 108a, fitting portions 108b,
Reference numerals 108c are projections of the corresponding variable magnification lens frame 8 respectively.
8a and fitting portions 8b and 8c. The variable power lens frame 108 that supports the variable power concave lens is configured in this way, but also a variable power lens frame (not shown) corresponding to the other variable power lens frame 9 that supports the variable power convex lens. The shape is similar to that of the variable power lens frame 108.

As described above, the cam portion 6b of the cam plate 6, 6f are provided as the variable magnification lens frame 8 does not interfere with the support frame 10 during rotation, in this modification, the variable power lens L ₁₀ The barrel shape allows the variable magnification lens frame 108 to have a narrow width as shown in FIG. 8. Therefore, the retracting amount at the time of rotation, that is, the variable magnification lens frame by the cam portions 6b and 6f of the cam plate 6 It is possible to reduce the lift amount of 108 and improve the operability.

[Effects of the Invention] As described above, according to the present invention, the front conversion lens group (variable magnification group) is rotatably provided so that the variable magnification group can be used from both directions. By providing the position of the standard state in which the effect of the state is produced and the zooming group does not interfere with the optical path of the optical system other than the zooming group at the intermediate position, one zooming group has three types of focal lengths. It is possible to switch. Further, since the zooming is performed along with the rotation of the zooming group, it is not necessary to retract the zooming group together with the unit out of the optical path. Therefore, a mechanism and a space are not required, and a compact focal length switchable lens. You can get the structure. Furthermore, when the zooming group rotates, the zooming lens and zooming lens frame on one side are retracted so that they do not interfere with the support frames of other optical systems. Does not need to be particularly wide, and a more compact configuration can be achieved.

[Brief description of drawings]

FIG. 1 is a vertical side view of a lens structure showing an embodiment of the present invention in a wide / infinity state, FIG. 2 is a front view of the lens structure shown in FIG. 1, and FIG. 1 is a bottom view taken along line III-III in FIG. 1, FIG. 4 is a cross-sectional plan view taken along line IV-IV in FIG. 1, and FIG. 5 is a view from the wide state of the lens structure to the standard state. FIG. 6 is a cross-sectional plan view corresponding to FIG. 4 during switching, FIG. 6 is a cross-sectional plan view corresponding to FIG. 4 in the standard state of the lens structure, and FIG. FIG. 8 is a perspective view of one of the variable power lens frames of the group, FIG. 8 is a perspective view showing a modified example of one of the variable power lens frames of the variable power group used in the lens structure of the present invention, and FIG. FIG. 6 is a front view showing the shape of a variable power lens used in the variable power lens frame in the figure. 6 ... Cam plate (regulating member) (magnifying power switching means) 7 ... Rotating plate (support member) (magnifying power switching means) 8,9,108 ... Variable lens frame (magnifying power switching means) 23 ... … Coil spring (elastic member) (magnification switching means) L ₁ …… Magnification concave lens (second optical system) L ₂ …… Magnification convex lens (second optical system) L _{3 to} L ₈ lens (First optical system) 12, 13 ...... Gear (magnification changing member) 21 …… Magnification pin (magnification changing member) 22 …… Magnification lever (magnification changing member)

Claims (1)

[Claims] 1. A first optical system capable of photographing at a single focal length, a concave lens and a convex lens, which are provided closer to the subject than the first optical system, and are displaced by 180 ° from the optical axis. As a result, the second optical system in which the variable magnification effect is inverted, and this second optical system are rotatably supported with respect to the fixed frame of the first optical system, and at least the second optical system A first position where the optical axis coincides with the optical axis of the first optical system, a second position where the second optical system is orthogonal to the optical axis of the first optical system and retracts from the optical path of the first optical system. Position and the first position above
In order to stop the second optical system at the third position displaced by 180 °, a variable magnification lens frame provided integrally with each lens of the second optical system is provided in the second optical system. A support member that is placed and supported movably in the optical axis direction, and a magnification switching member that rotates the support member so that the second optical system passes through the first, second, and third positions. And an elastic member provided on the support member and having an urging force in a direction to increase the distance between the lenses of the second optical system, and a sliding contact with the variable lens frame of the lenses, A restricting member that reduces the distance between the two lenses against the biasing force of the elastic member when the member is rotated by the variable power switching member to a position other than the first, second and third positions. And a switching means for zooming, which comprises: Lens structure that can be separated.