JPH10148748A - Focus torque-veriable mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a torque-variable mechanism possible to secure a focusing ring and to set the focusing torque to an optimal value, and also to set an operation torque heavy in a range where the focusing effect is strong. SOLUTION: On the side face of the focusing ring 17 turnably arranged on the outer circumference of a lens barrel 10, a torque-variable ring 30 is arranged which moves in the direction of an optical axis by the rotation, and an O-ring 32 is provided as an elastic member in the groove of this torque- variable ring 30, and is pressed on the focusing ring 17 by means of movement of the torque varying ring 30. Moreover, when the focusing ring 17 is operated in infinity or in an area of its neighborhood, a rugged part is provided for reducing a gap between this focusing ring 17 and the torque variable ring 30 for making an operation torque heavy, especially in a telescope end area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable focus torque mechanism applied to a television lens or the like of a surveillance camera and capable of changing an operating torque of a focus ring for adjusting a focus.

[0002]

2. Description of the Related Art A television lens of a surveillance camera is provided with a vari-focal lens having a variable focal length. The vari-focal lens has a focus lens group with a focus ring (ring) and a zoom lens group with a zoom lever or the like. By moving in the optical axis direction, focusing can be performed after changing the focal length.

FIG. 5 shows the structure of a focus ring portion of the television lens unit. In FIG. 5, a focus lens group 2 moves in the optical axis direction 100 together with a lens frame 3 inside a lens barrel 1. The zoom lens group 4 is also mounted movably in the optical axis direction 100. A focus ring 5 is arranged on the outer peripheral side of the lens barrel 1 so as to rotate at a predetermined angle, and a cam cylinder 6 is connected to the focus ring 5. The cam cylinder 6 is rotated by rotation.
The focus lens group 2 is configured to move in the direction of the optical axis via the lens.

The focus ring 5 is provided with a focus lock knob 7 of a screw fixing type so that the state can be locked when focus is achieved. The other zoom lens group 4 is also provided with a zoom knob 8, and according to this zoom knob 8, the zoom lens group 4 can be moved and its moving position can be fixed.

[0005]

However, in the structure of the focus ring portion, since the lock knob 7 is pressed against the lens barrel 1, a hole is formed in the pressing surface of the lens barrel 1, and the focus ring portion includes the cam barrel 6. Due to the presence of the play, a tightening stress acts immediately after locking by the lock knob 7, and the cam cylinder 6 may move and defocus. Since the finger touches the focus ring 5 while the focus ring 5 is being fixed by the focus lock knob 7, the focus ring 5
Was turned, and the focus was sometimes slightly deviated.

Further, in a shallow range of the depth of field set to the tele (telephoto) end side and the aperture open side, the focus is strong, and when in this range, the focus ring 5 is slightly moved. There is a problem in that even a slight movement affects the focus and causes a defocus.

Therefore, conventionally, the operating torque of the focus ring 5 is increased by using grease.
However, in this method, there is a disadvantage that the focus ring 5 moves gradually when placed in a situation where vibration is given, and the operating torque fluctuates due to a low-temperature or high-temperature environment or a change in temperature. There was a problem that the stable operation of No. 5 could not be secured.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to ensure that the focus ring can be securely fixed without being affected by vibration or temperature, and that the operating torque of the focus ring is optimized. It is another object of the present invention to provide a variable focus torque mechanism in which the operating torque can be set to a large value and the operating torque becomes heavy in a range where the focusing effect is strong.

[0009]

To achieve the above object, a variable focus torque mechanism according to a first aspect of the present invention includes a lens barrel for holding a focus lens movably in an optical axis direction, and a lens barrel. A focus ring that is rotatably arranged on the outer periphery of the lens and drives the focus lens;
A variable torque ring mounted on the outer periphery of the lens barrel so as to be movable in the optical axis direction, and an elastic member disposed between the variable torque torque ring and the focus ring; The operating torque of the focus ring is made variable by adjusting the pressing force of the elastic member against the focus ring. According to a second aspect of the present invention, there is provided a method for controlling the distance between the focus ring and the variable torque ring when the focus ring is rotated to an area where focus is achieved by the focus ring at or near the telephoto end. A part is provided.

According to the above construction, the operating torque of the focus ring can be increased (increased) by moving the torque variable ring and pressing the focus ring with the elastic member. It is possible to adjust the torque. Also, after focusing is completed, if the torque variable ring is moved to the end,
The focus ring is locked.

According to the second aspect of the present invention, the distance between the concavo-convex portions provided on both side surfaces of the focus ring and the torque variable ring is turned to a telephoto (tele) end and an area in which the focus ring focuses. It becomes shorter when the moving operation is performed, and the pressing force of the focus ring by the elastic member becomes stronger. Therefore, when the operation is performed to the region where the focus is achieved, the operating torque is increased, and it is possible to prevent a focus shift in a range where the effect of focusing is strong.

[0012]

1 to 4 show the structure of a lens unit to which a variable focus torque mechanism according to an embodiment is applied. FIG. 1 is an overall sectional view showing an upper half. . First, in FIG. 1, a lens barrel (main body) 10 has a C mount 12 for connection to a camera main body side.
On its inner front side, a focus lens group 13 is mounted movably in the optical axis direction 100 together with the lens frame 14,
The lens frame 14 includes a roller shaft 1 for driving a lens.
5 is fixedly arranged. On the other hand, a cam barrel 16 and a focus ring 17 are rotatably provided on the outer peripheral side of the lens barrel 10. The cam barrel 16 and the focus ring 17 are connected by a fixing screw 18 and rotate together at a predetermined angle. It has become.

FIG. 2 shows the roller shaft 15 and the cam cylinder 16.
And the like, and as shown, the cam cylinder 1
6, an oblique guide groove G1 that is oblique to the optical axis 100 is formed, and a guide groove G2 that is parallel to the optical axis 100 is formed on the lens barrel 10 side, and these guide grooves G1 and G2 are
The roller shaft (roller portion) 15 is engaged. Therefore,
According to the direction control of the guide grooves G1 and G2, the focus lens group 13 can be moved in the optical axis direction in accordance with the turning operation of the focus ring 17.

On the rear side inside the lens barrel 10, a zoom lens group 20 is disposed together with a lens frame 21, and a roller shaft 22 is mounted on the lens frame 21. Outside the lens frame 21, a cam barrel 23 having an oblique guide groove G3 formed therein and a fixed cylinder 24 having a guide groove G4 formed parallel to the optical axis 100 are arranged. A zoom lever 26 is connected to the cam barrel 23 (not shown), and a zoom knob 27 with which a screw portion is screwed to the zoom lever 26 is provided. The zoom knob 27 rotates around the outer peripheral groove of the lens barrel 10, and an interlocking shaft 28 extending to the outer peripheral surface of the lens frame 21 is attached below the zoom knob 27.

When the zoom knob 27 is rotated by a predetermined angle in the circumferential direction of the lens barrel 10, the cam barrel 23 is rotated via the zoom lever 26, and the guide groove G3 is provided.
, G4, the zoom lens group 20 moves in the optical axis direction. Then, when the zoom knob 27 is twisted and turned, the screw portion is screwed into each portion, and the zoom lens group 20 is fixed.

In such a lens portion, a variable torque ring 30 is disposed behind the focus ring 17, and the variable torque ring 30 is screwed into a lens barrel 1 by a threaded portion 31.
0 and screwed forward and backward (1 in the optical axis direction)
00) will move. An O-ring 32 is fitted as an elastic member into a groove formed on the side surface of the torque variable ring 30, and the O-ring 32 comes into contact with the contact portion 17 </ b> A on the side surface of the focus ring 17. .

FIG. 3 shows a contact state between the focus ring 17 and the torque variable ring 30. The contact portion includes a telephoto (tele) end and a turn around an area where the focus ring focuses. An uneven portion where the operation force becomes heavy at the moving operation position is formed. That is, a convex portion 17B protruding toward the torque variable ring 30 is integrally formed with the contact portion 17A of the focus ring 17, and a concave portion 30A is formed on a side surface of a groove in which the O-ring 32 of the torque variable ring 30 is disposed. . As shown in FIG.
7B and the concave portion 30A have a contact surface between an inclined surface and a vertical surface, and are set to a telephoto end at a position shown in the drawing and a region in focus near the tele end.

The focus ring 17 is widened from the telephoto end by rotating the focus ring 17 from the telephoto end in FIG. Focusing on the edge is possible,
In this region, the convex portion 17B is arranged in the concave portion 30A. On the other hand, the direction indicated by the solid line arrow (from the upper side of the figure to the front side)
When it is turned to the upper side, the operating torque gradually increases due to the inclined surfaces of the convex portion 17B and the concave portion 30A, and becomes maximum on the vertical surface. The operating angle of the focus ring 17 is, for example, about 50 to 90 degrees, and the concave portion 30A may be provided in an angle range excluding the telephoto end and the area in the vicinity thereof from this angle.

In the torque variable ring 30, the concave portion 30A is not provided, and an elastic body such as an elastic rubber, which is used in place of the O-ring 32, is disposed at a position 33 shown in FIG. A similar effect can be obtained also by using

The embodiment has the above-described configuration. When the torque variable ring 30 is rotated, the ring 30 is moved forward and backward in the optical axis direction 100 by screw connection with the lens barrel 10. Then, as shown in FIG. 4, when the torque variable ring 30 is moved to the front side, the O-ring 32 is pressed against the contact portion 17A of the focus ring 17, and this pressing force is applied to the torque variable ring 30. By adjusting the amount of movement, the weight of the operating torque (operating force) can be changed. And focus ring 1
After the focusing by 7 is completed, the focus ring 17 can be completely locked by moving the torque variable ring 30 to the frontmost position.

In focusing at the telephoto end and in the vicinity thereof, as understood from FIG.
Is rotated toward the front from the upper side of the figure, so that the convex portion 17B of the contact portion 17A passes through the inclined surface of the concave portion 30A of the torque variable ring 30 as shown in FIG.
It rotates to the position (A). At this time, when passing through the inclined surface, the operating torque gradually increases, so that a large operating force is required.

Then, when the focus ring 17 is turned to the position of the focused area at the telephoto end and in the vicinity thereof, the focus ring 17 is substantially fixed. Therefore, the focus shift when the focus is set at the tele end where the effect of focusing is strong and the area near the tele end is improved.

In the above embodiment, the O-ring 32 is used as the elastic member. However, a synthetic resin member having another shape or a spring member such as a leaf spring may be arranged as the elastic member. The configuration in which the elastic members are arranged on a part of the circumference of the lens barrel 10 or arranged at equal intervals can be appropriately selected. The operating torque may be further adjusted by adding grease or the like to the O-ring 32.

[0024]

As described above, according to the first aspect of the present invention, it is possible to move in the optical axis direction in the vicinity of the side of the focus ring rotatably disposed on the outer periphery of the lens barrel. The elastic member is provided at a contact portion between the variable torque ring and the focus ring, and the elastic member is pressed against the focus ring by moving the variable torque ring. A variable operating torque according to the pressing force is obtained, and the focus ring can be securely fixed without being affected by vibration or temperature.
Further, the operating torque of the focus ring can be set to an optimum value or a desired value, and it is possible to reduce the occurrence of defocus. Further, even if there is play in the cam cylinder or the like, stable focusing can be achieved without generating any tightening stress at the time of locking.

According to the second aspect of the present invention, when operating the telephoto end and the setting area in the vicinity of the telephoto end, the operating torque is reduced to another area by the uneven portion for reducing the distance between the focus ring and the torque variable ring. Because it is heavier than
In particular, it is possible to effectively prevent defocusing in a range where the effect of focusing is strong. Therefore, in this case, there is an advantage that the operation of the focus ring 17 in the other area can be performed with a light operating force.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a lens unit to which a variable focus torque mechanism according to an embodiment of the present invention is applied.

FIG. 2 is an explanatory diagram illustrating a relationship between a roller shaft, a cam barrel, and a lens barrel in FIG. 1;

3A and 3B show a configuration of a contact portion between a focus ring and a torque variable ring in FIG. 1; FIG. 3A is a side view showing a cross section of the torque variable ring side; FIG. .

FIG. 4 is a cross-sectional view showing a state where the torque variable ring in FIG. 1 is moved to a focus ring side.

FIG. 5 is a cross-sectional view of a focus ring portion in a conventional camera lens unit.

[Explanation of symbols]

 2, 13 ... focus lens group, 4, 20 ... zoom lens group, 5, 17 ... focus ring, 16 ... cam cylinder, 17A ... contact part, 17B ... convex part, 30 ... torque variable ring, 30A ... concave part, 32 ... O-ring (elastic member).

Claims (2)

[Claims] 1. A lens barrel for holding a focus lens movably in an optical axis direction, a focus ring rotatably disposed on an outer periphery of the lens barrel, for driving the focus lens, A torque variable ring attached to the outer periphery so as to be movable in the optical axis direction, and an elastic member disposed between the torque variable ring and the focus ring; and moving the torque variable ring in the optical axis direction. A focus torque variable mechanism that varies the operating torque of the focus ring by adjusting the pressing force of the elastic member on the focus ring. 2. The method according to claim 1, wherein when the focus ring is rotated to a telephoto end and a setting area near the telephoto end, an uneven portion is provided so as to reduce a distance between the focus ring and the torque variable ring. The variable focus torque mechanism according to claim 1.