JP2535027B2 - Lens barrel - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lens barrel, and more specifically, to a lens mirror in which the amount of extension of a focus lens group to the same shooting distance changes as the focal length changes due to zooming. Regarding the cylinder.

[Prior Art] Conventionally, when zooming is performed from the wide-angle side (Wide; W) to the telephoto side (Tele; T), the inner focus function or rear focus function that changes the amount of extension of the focus lens group from infinity to close-up Known lens barrels are disclosed in JP-A-57-4018 and JP-A-57-37309. These are W (wide), S1, S
At each of the (standard), S2, and T (tele) focal length positions, it is necessary to change the focus lens from infinity (∞) to the close distance as shown in the diagram in FIG.
In order to make it possible to move the lens differently depending on the focal lengths of W, S1, S, S2, and T from the infinity to the close distance, the focus lens group is formed by one compound cam having a cam curve L _C as shown in FIG. I am trying to move. The entire area of this composite cam is divided into five focus areas (∞ to near) in the five focal length states W, S1, S, S2, and T, sharing a part of the area. For example, if the cam pin is located at the wide (W) ∞ position a on the cam curve L _C of this compound cam, the tele (T)
When zooming to the state, the cam pin after zooming is ∞
Position b. After this, when focusing, the cam pin moves within the range of ∞ to the closest distance. Note that in FIG. 7, 1 / β1, 1 / β2, and 1 / β3 indicate photographing magnifications.

[Problems to be Solved by the Invention] However, since the conventional zoom lens described above uses one cam for zooming and focusing,
(1) It is not possible to display the distance from the direct drive portion to the outside, and another conversion mechanism such as a cam is required. (2) When it is desired to obtain distance information as an electrical signal by an encoder or the like by mechanical driving, it cannot be obtained from a direct driving portion. (3) A conversion mechanism such as a cam is required for the stopper mechanism of the member that moves from infinity to the closest distance. For this reason, the number of parts is increased, and a conversion mechanism is required for the functions of (1), (2), and (3), which causes a problem of a large focus error.

In view of such problems, it is an object of the present invention to provide a lens barrel that eliminates focus movement error due to zooming by forming zooming and focusing information on one stereoscopic cam surface.

[Means and Actions for Solving Problems] A lens barrel of the present invention has a rotation shaft that rotates in conjunction with zooming or focusing operation in a lens barrel in which the amount of extension of the focus lens changes due to zooming. An eccentric pin is pressed against the cam surface of the three-dimensional cam whose axial height changes around the shaft and in the radial direction by an elastic member. One is provided in the focus lens frame, and the other one is provided in the other frame. Then, when the one is rotated during the focusing operation and the other is rotated during the zooming, the focus lens frame advances and retracts in the optical axis direction to reach a predetermined focus position.

[Examples] FIG. 1 is a cross-sectional view showing a schematic configuration of a lens barrel showing an embodiment of the present invention, and FIG. 2 is a development view of a drive part when the main part thereof is further viewed from the circumferential direction. Is.

In FIG. 1, an I-group lens frame that supports the first lens group I, a II-group lens frame 2 that supports the second lens group II, a III-group lens frame 3 and a fourth lens that support the third lens group III. The IV group lens frame 4 supporting the group IV is fitted to a fixed rod 6 fixed to a mount 5 and is supported so as to be movable in the optical axis direction. The four lens groups I, II, III and IV respectively move as shown in FIG. 3 during wide-angle (W) to telephoto (T) zooming. As is clear from FIG. 3, the fourth lens group IV is a focus group, and moves from ∞ to the close range from the position indicated by the solid line to the position indicated by the chain double-dashed line. That is, as the focal length changes due to zooming, the lens group IV changes in the extension amount for the same shooting distance.

A focus shaft 7 is rotatably provided in the IV group lens frame 4 in parallel with the optical axis. A focus gear 8 is formed on the outer periphery of the large diameter portion of the focus shaft 7, and a focus solid cam 9 is formed on the front end surface of the large diameter portion of the focus shaft 7. As will be described later, the focus three-dimensional cam 9 has a three-dimensional cam surface shape whose height in the axial direction gradually increases or decreases along the radial direction and the circumferential direction.

On the other hand, the fixed frame 10 is provided with a zoom shaft 11 rotatably in parallel with the optical axis. This zoom shaft 11 has a zoom gear 12
Are coaxially integrated. An arm 13 extending in a direction perpendicular to the axial direction is integrally formed on the rear end surface of the zoom gear 12 facing the IV group lens frame 4 side (see FIG. 4).
A zoom pin 13a extending rearward in parallel with the optical axis is planted at the tip of the arm 13. The zoom pin 13a faces the focus solid cam 9. Fixed frame 10 and IV
A tension spring 14 is stretched between the group lens frame 4 and the zoom pin 13a, so that the zoom pin 13a is pressed against the four-cam solid cam 9.

In FIG. 2, the focus gear 8 is meshed with a focus motor gear 16 on the drive shaft of a focus motor 15 attached to the IV group lens frame 4 through a reduction gear 17, and the focus motor 15 drives the focus. The focus shaft 7 integrated with the gear 8 rotates.

The zoom gear 12 meshes with the zoom motor gear 19 on the drive shaft of the zoom motor 18 mounted on the fixed frame 10 via the zoom screw gear 20 and the reduction gear 21, and the zoom gear 12 is driven by the zoom motor 18. The arm 13 that is integral with the camera rotates, and the zoom pin 13a rotates about the axis of the zoom gear 12. The locus of a circle having a radius R formed by the rotation of the zoom pin 13a passes through the center of the focus three-dimensional cam 9 as shown in FIG.

As shown in FIG. 2, the zoom screw gear 20 is integrally provided coaxially with a zoom screw 22 rotatably attached to the fixed frame 10 in parallel with the optical axis. The zoom screw 22 is screwed into the group III lens frame 3.

 Next, the operation of the above embodiment will be described.

First, when a zoom operation button (not shown) is pressed, the zoom motor 18 starts driving, and the zoom motor gear 19 and the zoom screw gear 20 rotate the zoom screw 22 and
The group lens frame 3 moves linearly in the optical axis direction. At the same time I
The group lens frame 1 is also driven in the optical axis direction by a driving unit (not shown). The II group lens frame 2 is fixed (see FIG. 3). When this zooming is performed, the rotation of the zoom screw gear 20 is transmitted to the zoom gear 12 via the reduction gear 21, and the zoom shaft 11 rotates. Then the arm
The zoom pin 13a, which is in contact with the focus three-dimensional cam 9 at the tip of the rotary shaft 13 rotates, moves on an arc having a radius R.

Here, as shown in FIG. 4, the cam surface of the focus three-dimensional cam 9 sequentially increases in the radial direction from the inner circumference close to the axis of the focus shaft 7 to the outer circumference in accordance with W, S, and T. Cam positions with different heights are formed, and in the circumferential direction, counterclockwise with respect to this cam surface in the range of angle θ, ∞, 1/10
Cam positions having different axial heights are formed corresponding to 0, 1/50, 1/30, 1/10, 1/8, 1/5, and the closest position. It should be noted that the above numerical values between ∞ and the close range indicate the photographing magnification.

Now, in the initial state of this lens barrel, as shown in FIG.
It is assumed that the lens barrel is in contact with the W position near the center in the radial direction and the ∞ position in the circumferential direction, and that this lens barrel is focused on the ∞ subject in the wide-angle (W) state. Then, by driving the zoom motor 18 as described above, the group III lens frame 3
Is moved to perform zooming, the zoom pin 13a is rotated in conjunction with the zooming and slides on the focus three-dimensional cam 9 in the radial direction toward the outer periphery thereof. When the III group lens frame 3 reaches the S (standard) focal length position, the zoom pin 13a also reaches the S position on the focus solid cam 9 at this time, and the III group lens frame 3 reaches the T (tele) focal length position. If this happens, zoom pin 13a
Also reaches the T position on the re-outer peripheral side on the focus three-dimensional cam 9.

By changing the position of the zoom pin 13a in the radial direction of the focus solid cam 9, the zoom pin 13a shifts its cam surface by the axial height of the focus solid cam 9, so that the focus solid cam 9 itself moves in the axial direction at this time. Receive power. Therefore, together with the four-cam solid cam 9,
The IV group lens frame 4 moves in the optical axis direction by the tensile force of the tension spring 14 or against the tensile force to reach the position corresponding to the zooming.

After that, when a focus button (not shown) is pressed or the shutter button is half-pressed, the focus motor 15 is driven for focusing operation. When the driving force of the focus motor 15 is transmitted to the focus gear 8 via the focus motor gear 16 and the reduction gear 17, the focus shaft 7 rotates and the focus solid cam 9 rotates. The rotation of the four-cam stereo cam 9 itself causes the zoom pin 13a to slide on the focus stereo cam 9 in the circumferential direction at a radial position corresponding to the zooming. Since the focus three-dimensional cam 9 rotates in the clockwise direction shown by the arrow in FIG. 4, the focus three-dimensional cam 9 sequentially contacts the zoom pin 13a at positions of ∞, 1/10.
It will be changed to 0, 1/50, 1/30, 1/10, 1/8, 1/5, close to, and will receive a force in the axial direction according to its axial height, IV group lens frame 4 moves in the optical axis direction and reaches a position corresponding to the subject distance and stops.

It is also possible to perform focusing first and then perform zooming. In this case, after the focus solid cam 9 is rotated with respect to the stationary zoom pin 13a, the zoom pin 13a is moved in the radial direction with respect to the focus solid cam 9 that has stopped rotating, so that the same distance is maintained. The focal length will change while still in focus.

As described above, in this embodiment, the amount of extension of the IV group lens frame 4, which is the focus frame, during zooming and the amount of extension during focusing are performed in cooperation with one focus solid cam 9 and the same solid cam 9. Zoom pin 13 that shifts in the axial direction
Since it is given by a, there is no risk of causing a focus movement error during zooming. Since the information input during zooming is given by the rotation of the zoom shaft 11 and the information input during focusing is given by the focus shaft 7, the rotation of the focus three-dimensional cam 9 is rotated, for example, via the focus gear 8. The distance information can be displayed by transmitting it to the rotating member exposed to the outside of the cylinder. It is also easy to convert the rotation of the focus stereo cam 9 into an electric distance information signal by an encoder or the like. Further, since the rotation angle position on the focus solid cam 9 from ∞ to the closest position is the same regardless of each focal length position, the focus shaft 7 is controlled so that the rotation of the focus solid cam 9 is restricted to the range from ∞ to the closest position. Can be provided with a stopper.

The amount of extension of the IV group lens frame 4 due to the rotation of the zoom pin 13a and the rotation of the focus solid cam 9 is, for example, at the zooming position of each focal length of W, S, and T, as shown in FIG. The feeding amount of each is l _ow , l _os , l
It changes with _oT, and l
It changes as _1w , l _1s , l _1T . Therefore, the cam surface height in the axial direction due to the rotation of the focus three-dimensional cam 9 from 0 ° to θ ° is, as shown in FIG. 6, each cam based on the position of each focal length of W, S, T. It changes along the curves L _w , L _s , and L _T , and the height of the cam surface corresponds to the feeding amount.

In the above embodiment, the zoom pin 13a slides in the radial direction of the focus solid cam 9 during zooming, and the zoom pin 13a slides in the circumferential direction of the focus solid cam 9 during focusing. However, the present invention is not limited to such a configuration. For example, a solid cam is provided on the zoom gear 12 side, and a pin is provided on the focus gear 8 side that abuts the solid cam in an eccentric state. The pin may slide, and the pin may slide in the radial direction of the three-dimensional cam during focusing.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to display (1) infinity to the closest information in W to T by the external exposure member directly operated by the driving portion.
(2) The mechanical driving force can be converted into an electric signal from ∞ to the closest information in W to T by using an encoder or the like. (3) It is possible to provide a stopper for restricting from ∞ to the close range. (4) Since the focus shift during zooming of the focus group is eliminated, other electrical correction means such as a CPU is unnecessary and the calculation time for correction is also reduced. And so on.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a schematic configuration of a lens barrel showing an embodiment of the present invention, and FIG. 2 is a development view of the main part of the lens barrel shown in FIG. FIG. 3 is a diagram showing the movement of each lens group in FIG. 1, FIG. 4 is a front view showing the cam surface of the focus three-dimensional cam in FIGS. 1 and 2, and FIG. , A diagram showing the amount of extension of the IV group lens frame 4 due to the sliding of the zoom pin with respect to the focus solid cam in FIGS. 1 and 2; FIG. 6 is based on the position of each focal length of W, S, T FIG. 7 is a cam curve diagram showing the axial cam surface height due to the rotation of the focus three-dimensional cam 9, and FIG. 7 shows a focus lens in a lens barrel in which the amount of extension to the same shooting distance changes with the change of the focal length. Fig. 8 shows the movement curve of the focus lens for zooming and focusing with one compound cam. A cam curve diagram for the dynamic. 4 …… IV group lens frame (focus lens frame) 9 …… Focus 3D cam (3D cam) 11 …… Zoom shaft (rotating shaft) 13a …… Zoom pin (pin) 14 …… Tension spring (elastic member)

Claims (1)

(57) [Claims] 1. In a lens barrel in which the amount of extension of a focus lens changes by zooming, a focus lens frame for focusing by advancing and retreating in the optical axis direction, and a rotatably rotatably supported axial height. On the cam surface of the three-dimensional cam that is eccentrically provided with respect to the three-dimensional cam that rotates around the axis and in the radial direction, a rotating shaft that rotates in association with zooming or focusing operation. A pin that abuts and displaces a contact point of contact with the cam surface in the radial direction of the three-dimensional cam by the rotation of the rotation shaft; and an elastic member that abuts the pin on the three-dimensional cam. , One of the three-dimensional cam and the rotation shaft is provided in the focus lens frame and the other one of them is provided in the other frame, and the one is rotated during a focusing operation and the other is rotated during zooming. A lens barrel characterized in that the focus lens frame is moved back and forth in the optical axis direction by rotating the lens barrel.