JPH08220415A - Zoom lens barrel and optical instrument using the same - Google Patents

Abstract

PURPOSE: To accurately execute focusing control by obtaining a count starting signal of a pulse at the time of moving a focusing lens group, based on a signal from a detecting means. CONSTITUTION: A cam barrel 17 is rotated from a stopping position at the time of focusing and the pulse for focusing is counted by a pulse plate and a pulse detecting means from the time of redetection by a zooming detecting switch, to detect the position of a focusing lens (first lens group 1). Then, the rotation of the cam barrel 17 is detected by the pulse plate and the pulse detecting means and the zooming detecting switch and gears for detecting first and second positions are used to periodically detect the rotation of the cam barrel 17 from a zooming position to the next position, so that a positional deviation at each zooming position, when an object is at a point at infinity is reduced and accurate focusing control is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens barrel and an optical apparatus using the same, and in particular, uses a signal from a zoom position detecting means for detecting a periodic signal generated for zooming as a focus pulse count start signal. Thus, it is suitable for a video camera, a still camera, or the like that has performed highly accurate focus control.

[0002]

2. Description of the Related Art Various zoom lens barrels having a zoom function have been proposed. For example, Japanese Patent Laid-Open No. 61-259
In Japanese Patent Laid-Open No. 237, first, the zoom lens is rotated to move the movable lens barrel in the optical axis direction to change the photographing magnification, and an initial lens group arrangement is achieved in which an object at infinity is in focus at a certain zoom position. . Then, when the zoom ring is rotated further from that position, the focusing lens group is extended at this zoom position. This proposes a zoom lens barrel in which the focus can be adjusted from an infinitely distant object to a close object at a certain zoom position by simply rotating the zoom ring. By controlling the operation at this time by providing a pulse plate, a pulse detection circuit, and a comparator in a part of the lens barrel, the rotation amount of the zoom ring is converted into the number of pulses, and the zoom position of the taking lens is detected from this. I am doing it.

[0003]

When rotating the zoom ring, if there is a mechanical error, the number of pulses may change at each zoom operation, for example, when zooming from the wide-angle end to the telephoto end. That is, the initial position of the object position at infinity at each zoom position may be displaced. When the pulse is counted from the shifted position (zoom position) as the initial position to perform focusing, there is a problem that the number of pulses increases when photographing a close-up object, so that the object is out of focus.

According to the present invention, a predetermined number of zoom positions in the zoom range are accurately detected by the detecting means, the initial position of each lens group is accurately identified, and the focus lens is based on the signal from the detecting means. An object of the present invention is to provide a zoom lens barrel that can accurately perform focus control by using a pulse count start signal when moving a group, and an optical device using the zoom lens barrel.

[0005]

[Means for Solving the Problems]

(1-1) A zoom lens barrel according to the present invention comprises a cam barrel provided with a cam for moving the zoom and focus lens groups in the optical axis direction, and the cam barrel rotated by driving means via gear means. When the moving operation is performed, a zoom position detecting means for detecting a periodic signal generated for zooming by the rotation of the cam barrel and a reference state at a predetermined position of the cam barrel are utilized by using a pulse plate connected to the gear means. Rotation detection means for detecting a rotation amount related to focus from the lens group is provided, and the lens group is moved on the optical axis using the signal from the rotation detection means to perform focusing.

(1-2) The optical device of the present invention is an optical device in which an object image is formed on a predetermined surface by using a zoom lens group and a focus lens group. And a cam cylinder provided with a cam for moving the lens group for use in the optical axis direction and a cycle generated by the rotation of the cam cylinder when the cam cylinder is rotated by the driving means through the gear means. A zoom position detecting means for detecting a specific signal, and a rotation detecting means for detecting a rotation amount of the cam cylinder with respect to focus from a reference state at a predetermined position by using a pulse plate connected to the gear means, It is characterized in that the lens group is moved along the optical axis for focusing by using a signal from the rotation detecting means.

[0007]

Embodiment 1 FIGS. 1 and 7 show a retractable lens barrel according to Embodiment 1 of the present invention,
FIG. 2, FIG. 3, FIG. 4, FIG. 5, and FIG. 6 are explanatory views of a part of FIG. 1 at the wide-angle end. In the figure, 1 is a first lens group and 7 is a second lens group, and both lens groups are moved on the optical axis to be set at a predetermined zoom position. Photoreceptor surface (not shown) by the first lens group 1 and the second lens group 7.
An object image is formed on. A first holder 2 holds the first lens group 1. A first holding member 3 holds the first holder 2. Reference numerals 4 and 5 are shutter blades.

Reference numeral 6 is a second holding member, and the first holding member 3
The shutter blades 4 and 5 are held so as to be slidable between the first holding member 3 and the second holding member 6. Reference numeral 8 denotes a second holder, which holds the second lens group 7, and which is a surface cam 17 provided on the inner peripheral surface of a cam barrel 17 described later.
It has three cam pins 8a, 8b, 8c that come into contact with b. Reference numeral 9 is a linear guide member, which is attached to the second holding member 6 to prevent the second holder 8 from rotating around the optical axis.
Cam pins 8a, 8 for guiding the holder 8 in the optical axis direction
b, 8c corresponding to straight grooves 9a, 9b, 9c (9b, 9
c is not shown), and a key groove 20 provided in a fixed cylinder 21 described later.
Corresponding to c, it has a convex portion 9d for preventing the first lens group 1 from rotating around the optical axis. Reference numeral 10 denotes a mask member, which is attached to the straight-moving guide member 9 and includes the first lens group 1 and the second lens group
The light flux outside the effective screen that has passed through the lens group 7 is blocked.

Reference numeral 11 denotes a base member, which is the first holding member 3
Is attached. 12 is a motor, the base member 1
I am attached to 1. 13 is a gear train, and the base member 1
1 is attached to drive the lens barrel. A gear cover 15 is attached to the base member 11 and encloses the gear train 13. A pulse plate 14 is rotated by a gear arranged in the middle of the gear train 13. Reference numeral 14a is a pulse detecting means for detecting a pulse accompanying the rotation of the pulse plate 14. The pulse plate 14 and the pulse detecting means 14a constitute one element of the rotation detecting means. Reference numeral 16 is a gear cylinder, and an inner gear 16a connected to the gear train 13 on the inner diameter portion thereof.
Is formed and is rotatably fitted to the outer diameter portion of the linear guide member 9.

Reference numeral 17 denotes a cam cylinder, which is integrated with the gear cylinder 16 via a concave and convex portion. 16 male helicoid portions 17a that engage with the female helicoid 21a of the fixed barrel 21 are formed on the outer diameter portion of the cam barrel 17, and the cam pins 8a, 8b, 8c of the second holder 8 are engaged on the inner diameter portion. A surface cam 17b that determines the position of the second lens group 7 in the optical axis direction is formed. The inner diameter of the cam barrel 17 is rotatably fitted to the outer diameter portion of the rectilinear guide member 9. Reference numeral 18 denotes a spring member, which is sandwiched between the rectilinear guide member 9 and the cam barrel 17, and the cam barrel 17 and the gear barrel 16 which rotates integrally with the cam barrel 17.
Is urged toward the second holding member 6. A spring member 19 biases the cam pins 8a, 8b, 8c of the second holder 8 against the surface cam 17b of the cam barrel 17. A lens barrel cover 20 is attached to the base member 11.

Reference numeral 21 denotes a fixed barrel, which is attached to the camera body 22 via a mounting portion (not shown), and a female helicoid 21a which meshes with the male helicoid 17a of the cam barrel 17 is formed in the inner diameter portion thereof. Further, the V-groove 21b is formed in the entire system in the mountain portion of the female helicoid 21a. or,
A key groove 21c corresponding to the convex portion 9d of the linear guide member 9 is provided in the inner diameter portion of the fixed cylinder 21. An external member 23 is positioned and fixed by a mounting portion (not shown) of the camera body 22. Reference numeral 24 denotes a first sheet member, which is attached to the inside of the exterior member 23 to prevent foreign matter from entering from the outside of the camera. Reference numeral 25 denotes a second sheet member, which is attached to the second holding member 3 to prevent foreign matter and stray light from entering from the periphery of the first lens group 1. Reference numeral 26 denotes a third sheet member, which is located on the outer circumference of the effective diameter of the frontmost plastic lens of the second lens group 7 and is attached to the second holder 8.

27 is a first position detecting gear,
It is arranged at a position symmetrical to the final stage gear of the gear train 13 around the rotation axis of the motor 12. Reference numeral 28 denotes a second position detection gear, which forms a D-cut cam for turning on and off a position switch described later. 29
Is a first zoom detection contact piece and is attached to the base member 11. Reference numeral 30 denotes a second zoom detecting contact piece, which is attached to the base member 11. An insulating member 31 is sandwiched between the first and second zoom detecting contact pieces 29 and 30. Each element 27, 28, 29, 30, 31 constitutes one element of the zoom position detecting means.

In this embodiment, when the motor 12 rotates,
The rotation power is transmitted through the gear train 13 of the lens barrel drive system to the gear barrel 1.
6 is transmitted to the inner gear 16a, and the cam cylinder 17 that is integrally connected to the gear cylinder 16 at the concavo-convex portion rotates. Cam barrel 1
By rotation of 7, male helicoid 1 provided on its outer diameter
7a and the lead of the female helicoid 21a of the fixed barrel 21 move the first lens group 1 and the second lens group 7 in the optical axis direction. At this time, in the second lens group 7, the cam pins 8a, 8b, 8c of the second holder 8 are engaged with the surface cams 17b of the cam barrel 17, and the rectilinear grooves 9a, 9b, 9c of the rectilinear guide member 9 are formed.
Since the rotation is stopped by (9b and 9c are not shown), the cam surface 17b moves in the optical axis direction by the lift amount.

As a result, the cam barrel 17 is rotated to move the first lens group 1 and the second lens group 7 forward (to the left in FIG. 1) while changing the distance. FIG. 7 shows the state at this time (wide end).

In FIG. 1, the three cam pins 8a, 8b, 8c of the second holder 8 are present on the surface cam 17b of the cam barrel 17 at the positions shown in FIG. When the cam barrel 17 rotates in the direction of the arrow from the state of FIG. 5, the cam pins 8a, 8
b and 8c come to the position (wide-angle end) shown in FIG.

In this embodiment, the cam pin 8 within the zoom range
a, 8b, and 8c can be photographed only at four zoom positions corresponding to the positions in FIG.
That is, the shooting is performed at four focal lengths, and shooting is not performed at continuous zoom positions.

The position is a state in which an object at infinity is in focus at the wide-angle end. At this position, when the cam barrel 17 rotates to reach the position ', the close-up object is in focus at the wide-angle end.

Next, when the cam barrel 17 rotates in the direction of the arrow, for example, the cam pin 8a comes to the position via the cam portion 17c. This position is a state in which an object at infinity at the zoom position Z1 is in focus. At this position, when the cam barrel rotates and reaches the position of ', the close object is brought into focus at the zoom position Z1.

When the cam barrel 17 is further rotated in the direction of the arrow, the cam pin 8a is brought into a state of being focused on an object at infinity at the zoom position Z2. Similarly, at the zoom position (telephoto end) Z3, the object at infinity is in focus. The cam portions 17c, 17d, 17e and 17f have the same leads as the male helicoid 17a and the female helicoid 21a, and the surface cams 17b are continuously formed on the cam pins 8b and 8c in the same manner.

Therefore, when the cam barrel 17 is rotated from the respective positions ,, the first lens group 1 moves forward by the lead of the male helicoid 17a and the female helicoid 21a, but the second lens group 7 leads the lead. The position moves as much as the rearward, and the position does not change as a whole when viewed from the camera body 22, for example.

In the present embodiment, during this period (in the cam pin 8a, the area X of the cam portions 17c, 17d, 17e, 17f is X).
1, X2, X3, X4), focus operation is performed from an infinitely distant object to a close object.

In this embodiment, the surface cam 17b is continuously formed on the inner diameter portion of the cam barrel 17 by 360 degrees.
The cam surfaces of a, 8b and 8c are not 1: 1.

When the lens barrel of FIG. 1 is a retractable barrel, the rotation amount of the cam barrel 17 is increased by using the area used for zooming between the wide-angle end and the telephoto end of the adjacent cam pins. Instead, the diameter of the cam barrel 17 is reduced.

Next, the operation of detecting the zoom position in the zoom operation in this embodiment will be described. The second position detection gear 28 is set to rotate once when the gear cylinder 16 and the cam cylinder 17 rotate from position to position shown in FIG. Position: Gear cylinder 16 and cam cylinder 1
Since the rotation angles of 7 are the same, the second position detecting gear 28 rotates once for each zoom position.

The first zoom detecting contact piece 29 shown in FIG.
Contact part 29 with the movable part 30a of the second zoom detection contact piece 30
There is a.

The movable portion 30a of the second zoom detecting contact piece 30.
Is in a position apart from the contact part 29a when it is in contact with the outer peripheral part 28a of the D-cut cam of the second position detection gear 28, and when it falls into the D-cut part 28b, the contact part 2
Contact 9a. That is, each time the zoom position changes by one (every time the second position detection gear 28 makes one rotation), the zoom detection SW (zoom position detection means) is executed only once.
Turn on the SW.

That is, a periodic signal is generated. The D-cut cam is turned on slightly near the zoom position at the wide-angle end when focusing on an object at infinity at each zoom position.
I am trying to do it. The change in the zoom position is detected by the signal at this time by the zoom position detection means, and the zoom detection switch SW is returned to the slightly wide-angle side and stopped in the OFF state.

FIG. 9 shows the loci of the first lens group 1 and the second lens group 7 as seen from the camera body 22 due to the zoom position detecting operation and the rotation of the cam barrel 17 as described above.

Next, at the time of focusing, the cam barrel 17 rotates from the above-mentioned stop position, and from the time when the zoom detection switch SW detects again, the pulse for focusing is counted by the pulse plate 14 and the pulse detecting means 14a to focus. The position of the lens (first lens group 1) is detected.

In the present embodiment, the rotation of the cam barrel 17 is detected by the pulse plate 14 and the pulse detecting means 14a, and
By using the zoom detection switch SW and the first and second position detection gears 27 and 28 so that the rotation of the cam barrel 17 from the zoom position to the next position can be detected periodically, a pulse is generated for each zoom position. Is reset to reduce the displacement of each zoom position when an object is at infinity, and perform accurate focus control.

[0031]

According to the present invention, by setting each element as described above, a predetermined number of zoom positions in the zoom range can be accurately detected by the detecting means, and the initial position of each lens group can be accurately detected. A zoom lens barrel and an optical device using the same that can be accurately identified and used as a pulse count start signal when moving the focus lens group based on the signal from the detection means are achieved. be able to.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a first embodiment of the present invention when a lens barrel is used.

FIG. 2 is a perspective view of a main part of a gear cylinder and a cam cylinder of FIG.

FIG. 3 is a schematic diagram of the gear train and zoom position detection means of FIG.

FIG. 4 is an explanatory diagram of a gear train of FIG.

5 is a development view of the inner surface of the cam barrel of FIG. 1. FIG.

6 is a development view of the inner surface of the cam barrel of FIG.

FIG. 7 is a cross-sectional view of the main part at the wide-angle end according to the first embodiment of the present invention.

FIG. 8 is an explanatory view of a part of the zoom position detecting means of FIG.

9 is an explanatory view of the inner surface of the cam barrel of FIG.

[Explanation of symbols]

 1 1st lens group 2 1st holder 3 1st holding member 4 shutter blades 5 shutter blades 6 2nd holding member 7 2nd lens group 8 2nd holder 9 linear guide member 10 mask member 11 base member 12 motor 13 gear train 14 Pulse plate 15 Gear cover 16 Gear cylinder 17 Cam cylinder 18 Spring member 1 19 Spring member 2 20 Lens barrel cover 21 Fixed cylinder 22 Camera body 23 Appearance member 24 First sheet member 25 Second sheet member 26 Third sheet member 27 1st position gear 28 2nd position gear 29 1st zoom detection contact piece 30 2nd zoom detection contact piece 31 Insulation member

Claims (2)

[Claims] 1. A cam barrel provided with a cam for moving a lens group for zooming and a lens group for focusing in the optical axis direction, and the cam barrel when the cam barrel is rotationally operated by a driving means via a gear means. Using a zoom position detecting means for detecting a periodic signal generated with respect to the zoom by the rotation of the cam, and a pulse plate connected to the gear means, the amount of rotation for the focus from the reference state at the predetermined position of the cam barrel is detected. And a rotation detecting means for rotating the lens group on the optical axis to focus on the signal from the rotation detecting means. 2. An optical device in which an object image is formed on a predetermined surface using a zoom lens group and a focus lens group, and the zoom and focus lens groups are moved in the optical axis direction. And a zoom position detecting means for detecting a periodic signal generated for zooming due to the rotation of the cam cylinder when the cam cylinder is provided with a cam for driving the cam cylinder and the cam cylinder is rotated by the driving means through the gear means. And rotation detecting means for detecting a rotation amount of the cam barrel with respect to focus from a reference state at a predetermined position by using a pulse plate connected to the gear means, and using a signal from the rotation detecting means. An optical device characterized in that the lens group is moved on the optical axis for focusing.