JP2011028092A - Optical apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent that rack teeth run on a feed screw even when a strong impact is applied. <P>SOLUTION: An optical apparatus includes a multi-strip feed screw 19c rotated by an actuator 19, a rack member 7 that has the rack teeth 7a meshing with the multi-strip feed screw and moves in the axial direction of the multi-strip feed screw by meshing of the rotating multi-strip feed screw with the rack teeth, and an optical unit 2 moving in the axial direction together with the rack member. The rack member has a projection 7b formed separately from the rack teeth. The multi-strip feed screw includes a first-strip screw part 19a meshing with the rack teeth, and a second-strip screw part 19b that has a vertex angle b smaller than that of the first-strip screw part and prevents deviation in the axial direction with respect to the multi-strip feed screw of the rack member by abutting on the projection. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an optical apparatus such as a camera or an interchangeable lens that moves an optical unit by a feed mechanism including a feed screw and a rack meshing with the feed screw.

  An optical apparatus that moves an optical unit such as a lens in the optical axis direction (the axial direction of the feed screw) by the above feed mechanism is disclosed in, for example, Patent Document 1. Further, in the feed mechanism disclosed in Patent Document 1, when an impact is applied to the optical device due to dropping or the like, the rack is displaced in the axial direction with respect to the feed screw (that is, the rack teeth run on the feed screw portion). It has a shock absorbing structure for preventing this.

JP-A-10-111443

  However, in the feed mechanism disclosed in Patent Document 1, when a strong impact is applied to the optical device, the component force in the direction orthogonal to the optical axis of the impact load generated between the rack teeth and the inclined surface of the feed screw. As a result, the portion of the rack that fixes the rack teeth may be deformed. This makes it impossible to prevent the rack teeth from riding on the feed screw portion.

  The present invention provides an optical apparatus capable of preventing the rack teeth from climbing on the feed screw portion even when a strong impact is applied.

An optical apparatus according to one aspect of the present invention includes a multi-feed screw rotated by an actuator and rack teeth that mesh with the multi-feed screw. The multi-feed screw and the rack teeth mesh with each other. A rack member that moves in the axial direction of the feed screw; and an optical unit that moves in the axial direction together with the rack member. The rack member has a protrusion formed separately from the rack teeth. The multi-thread feed screw has a first thread portion that meshes with the rack teeth, and an apex angle smaller than that of the first thread portion. And a second threaded portion for preventing slippage.

  According to the present invention, the second thread portion that prevents the rack member from shifting with respect to the multi-thread feed screw has a smaller apex angle than the first thread portion that functions as the feed screw portion. Thereby, compared with the case where the second threaded portion has the same apex angle as the first threaded portion, the effect of preventing the rack member from shifting (the effect of preventing the rack teeth from climbing onto the feed screw portion) can be enhanced. it can.

1 is an exploded perspective view illustrating a configuration of a lens barrel portion of a video camera that is Embodiment 1 of the present invention. FIG. 3 is a diagram illustrating a configuration of a feed mechanism in Embodiment 1. The figure which shows the structure of the feed mechanism in Example 2 of this invention.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a lens barrel of a video camera (optical apparatus) that is Embodiment 1 of the present invention. In this embodiment, the lens barrel portion of the video camera will be described. However, the present invention can also be applied to optical devices other than the video camera such as a lens barrel portion and an interchangeable lens of a digital still camera.

  The lens barrel unit houses a rear focus type zoom optical system including four convex and concave lens units in order from the object side.

Reference numeral 1 denotes a fixed lens barrel that holds a fixed lens unit that is a first lens unit.
Reference numeral 2 denotes a second holding frame that holds a variable magnification lens unit that is a second lens unit, and includes a sleeve portion 2a and a U groove portion 2b. The zoom lens unit moves in the optical axis direction and zooms the zoom optical system. The sleeve portion 2a and the U groove portion 2b are respectively engaged with the guide bars 8 and 9 so as to be movable in the optical axis direction. Thus, the second holding frame 2 can move in the optical axis direction while being guided by the guide bars 8 and 9. The variable power lens unit and the second holding frame 2 that holds the variable power lens unit constitute an optical unit.

  A diaphragm unit 3 adjusts the light quantity by driving the diaphragm blades 3b and 3c in the opening and closing direction by the diaphragm actuator 3a.

Reference numeral 4 denotes a third holding frame that holds an afocal lens unit that is a third lens unit, and is fixed in the optical axis direction.
Reference numeral 5 denotes a fourth holding frame that holds a focus lens unit that is a fourth lens unit, and includes a sleeve portion 5a and a U groove portion 5b. The focus lens unit moves in the direction of the optical axis to perform focusing, and corrects image plane variation due to zooming. The sleeve portion 5a and the U groove portion 5b are respectively engaged with the guide bars 9 and 8 so as to be movable in the optical axis direction. Accordingly, the fourth holding frame 5 can move in the optical axis direction while being guided by the guide bars 9 and 8.

  A rack member 7 is attached to the second holding frame 2. The rack member 7 meshes with a feed screw 19c provided as an output shaft of a stepping motor 19 that is an actuator. When the feed screw 19c rotates by energizing the stepping motor 19, the feed screw portion (described later) formed on the feed screw 19 and the rack teeth (described later) formed on the rack member 7 are engaged with each other in the optical axis direction (feed screw). 19c axial direction).

  The second holding frame 2 is provided with a light shielding portion 2c. The light shielding portion 2c enters between the light emitting portion and the light receiving portion of the photo interrupter 15, so that the second holding frame 2 is a reference position in the optical axis direction. Is detected. By counting the number of drive pulses applied to the stepping motor 19 from this reference position, the position of the second holding frame 2 (that is, the zoom position) is controlled.

  Reference numeral 6 denotes an image sensor holder, which holds an image sensor 18 constituted by a CCD sensor or a CMOS sensor, and an infrared cut / low-pass filter 17 disposed in front of the image sensor 18.

  An air core coil 10 is fixed to the fourth holding frame 5. The coil 10 forms a magnetic circuit together with the magnet 12 and the yokes 11 and 13 held by the image sensor holder 6. When the coil 10 is energized, the fourth holding frame 5 is moved in the optical axis direction by using the magnetic force generated between the coil 10 and the thrust.

  The reference position of the fourth holding frame 5 is determined by abutment between the fourth holding frame 5 and the image sensor holder 6. An encoder magnet 14 is held on the fourth holding frame 5, and an MR sensor 16 is held on the image sensor holder 6 so as to face the encoder magnet 14. As the fourth holding frame 5 moves from the reference position in the optical axis direction, the MR sensor 16 outputs a signal corresponding to a change in magnetic force received from the encoder magnet 14. Based on the signal, position detection and position control of the fourth holding frame 5 are performed.

  Next, the feed mechanism of the second holding frame 2 constituted by the feed screw 19c and the rack member 7 will be described with reference to FIG. The feed screw 19c is a multi-thread feed screw, and includes a single feed screw portion (first screw portion) 19a and a single shock absorbing screw portion (second screw portion) 19b.

In the present embodiment, the case where both the feed screw portion 19a and the shock absorbing screw portion 19b are formed one by one will be described. However, at least one of the feed screw portion 19a and the shock absorbing screw portion 19b is 2 You may form more than a strip.
The feed screw portion 19a is formed as a triangular screw or a trapezoidal screw whose apex angle is a ° (for example, 60 °). The shock absorbing screw portion 19b is formed as a trapezoidal screw or a square screw whose apex angle is b ° smaller than a ° (for example, 45 ° to 0 °).
Rack teeth (feed teeth) 7a formed on the rack member 7 mesh with the feed screw portion 19a. In other words, the inclined surface of the rack tooth 7a is in contact with the inclined surface of the feed screw portion 19a. The rack member 7 is subjected to a pinching force against the feed screw 19c by the spring 7c, and the rack tooth 7a is engaged with the feed screw portion 19a by the pinching force so that no backlash occurs in the optical axis direction. It is matched.
In the following description, as shown in FIG. 2, the rack teeth 7a are normally engaged with the feed screw portion 19a, that is, the rack member 7 and the second holding frame 2 are moved along the optical axis as the feed screw 19c rotates. A state that can move smoothly in the direction is called a “normal state”. As will be described later, the “normal state” corresponds to a state before the axial displacement of the rack member 7 with respect to the feed screw 19c occurs due to an impact such as dropping.
On the side of the rack member 7 facing the rack teeth 7a, opposed teeth 7b as protrusions formed separately from the rack teeth 7a are provided. The opposing tooth 7b has a flat portion parallel to the side surface (slope or vertical surface) of the shock absorbing screw portion 19b. In the normal state, the opposing teeth 7b are arranged such that the plane portion has a gap with respect to the side surface of the shock absorbing screw portion 19b.
In the feed mechanism configured as described above, when an impact force in the optical axis direction is applied to the second holding frame 2 due to a fall of the video camera or the like, the rack member 7 acts on the lead of the feed screw portion 19a with respect to the feed screw 19c. Along the optical axis direction (and the direction perpendicular to the optical axis). However, in the state where this slight deviation occurs, the flat portion of the opposing tooth 7b abuts against the side surface of the shock absorbing screw portion 19b, thereby preventing further deviation of the rack member 7 from the feed screw 19c.
As described above, the apex angle b ° of the shock absorbing screw portion 19b is set to an acute angle than the apex angle a ° of the feed screw portion 19a. For this reason, as compared with the case where the apex angle b ° is the same as the apex angle a °, the direction orthogonal to the optical axis of the impact force acting between the flat surface portion of the opposing tooth 7b and the side surface of the impact absorbing screw portion 19b. The component force to becomes smaller. Therefore, the portion of the rack member 7 where the opposing teeth 7b are formed is deformed, and as a result, the rack member 7 is prevented from being greatly displaced with respect to the feed screw 19c. That is, it is possible to prevent the rack teeth 7a from climbing on or over the feed screw portion 19a to prevent the second holding frame 7 from being smoothly driven or highly accurately controlled.
According to the present embodiment, a feed screw portion 19a for accurately moving the rack member 7 to the feed screw 19c using a multi-thread feed screw, and an impact absorbing screw for preventing the rack member 7 from being displaced due to an impact. The part 19b was formed as a thread part of a different strip. Moreover, the apex angle of the shock absorbing screw portion 19b is made smaller than the apex angle of the feed screw portion 19a. Thereby, it is possible to improve the impact resistance of the feed mechanism while keeping the movement accuracy of the second holding frame 2 good.

FIG. 3 illustrates a feed mechanism for the second holding frame 2 in the video camera that is Embodiment 2 of the present invention. In the present embodiment, members having the same or similar functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.
In the first embodiment, in the normal state, the opposing teeth 7b of the rack member 7 are arranged such that the flat portion has a gap with respect to the side surface of the shock absorbing screw portion 19b. On the other hand, in the present embodiment, in the normal state, the flat portion of the opposed tooth 7d is in contact with the side surface of the shock absorbing screw portion 19b. Also in this embodiment, the apex angle (for example, 45 ° to 0 °) of the shock absorbing screw portion 19b is smaller than the apex angle (for example, 60 °) of the feed screw portion 19a.
Also in the present embodiment, as in the first embodiment, it is possible to improve the impact resistance of the feed mechanism while keeping the movement accuracy of the second holding frame 2 good.
Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

  An optical device with high position control accuracy of the optical unit and high impact resistance can be provided.

2 Second Holding Frame 7 Rack Member 7a Rack Teeth 7b Opposing Teeth 19 Stepping Motor 19c Feed Screw 19a Feed Screw Part 19b Shock Absorbing Screw Part

Claims (3)

A multi-thread feed screw rotated by an actuator;
A rack member that meshes with the multi-feed screw, and a rack member that moves in an axial direction of the multi-feed screw by meshing with the rotating multi-feed screw and the rack tooth;
An optical unit that moves in the axial direction together with the rack member;
The rack member has a protrusion formed separately from the rack teeth,
The multi-feed screw is
A first threaded portion meshing with the rack teeth;
A second thread portion that has a smaller apex angle than the first thread portion and prevents the rack member from shifting in the axial direction relative to the multi-feed screw by contacting the protrusion. An optical apparatus comprising:   2. The projection according to claim 1, wherein the protrusion has a gap with respect to the thread portion of the second strip in a state before the axial displacement of the rack member with respect to the multi-feed screw occurs. Optical equipment.   3. The optical apparatus according to claim 1, wherein the first thread portion is formed by a triangular screw, and the second thread portion is formed by a square screw. 4.