1. Field of the Invention
The present invention relates to an imaging apparatus with a rotatable lens barrel that receives an optical block and an imaging block, and in particular, to a technique of preventing an increase in the size of an imaging apparatus when the optical block includes a large lens.
2. Description of the Related Art
As one of imaging apparatuses having a rotatable lens barrel, there is a dome type surveillance video camera (hereinafter, referred to as “dome surveillance video camera” or “dome video camera”) mounted on a ceiling or wall of, for example, a building. The dome video cameras are disposed in hospitals, hotels, and department stores for purposes of ensuring security and improving serviceability. Captured images are used for surveillance. An optical block including a lens and an imaging block including an imaging device are received in a lens barrel. The lens barrel is attached so as to be rotatable in the horizontal direction (hereinafter, panning direction) and/or the vertical direction (hereinafter, tilting direction) and is covered with a dome-shaped cover (hereinafter, dome cover) such that the cover surrounds the outer region of a motion space for the lens barrel. An imaging signal output from the imaging block is supplied to a monitor in a monitoring room through a coaxial cable.
To set up the dome video camera, the coaxial cable is connected to the rear of the video camera and the video camera is then fixed to a ceiling or wall of a building with metal inserts. Subsequently, the lens is adjusted so as to have a predetermined orientation (direction and angle) by an angle adjustment mechanism for the lens barrel, thus controlling the focus and zoom of the lens. In this instance, the set-up is performed using a portable monitor while a monitor image is being viewed in a set-up site to confirm the imaging direction and the imaging range. Finally, the video camera is covered with the dome cover for dust protection. Thus, a series of set-up operations is completed.
As described above, the orientation of the lens is determined by adjusting the angle of the lens barrel upon set-up of the dome video camera. For the angle adjustment mechanism, a technique using a ball joint is known. In other words, a rotating ball arranged at the proximal end of the lens barrel allows the lens barrel to be movable in the panning direction and/or the tilting direction. A retainer retains the ball on a support arranged in a mount. Japanese Unexamined Patent Application Publication No. 2005-156806 (Patent Document 1) discloses an example of the above-described dome video camera.
FIGS. 7A and 7B are partially sectional views of related-art dome video cameras 100a and 100b disclosed in Patent Document 1, respectively.
Referring to FIG. 7A (7B), the dome video camera 100a (100b) includes an optical block 170a (170b) including a lens 171a (171b), and an imaging block 180a (180b) including a charge coupled device (CCD) 181a (181b). The optical block 170a (170b) and the imaging block 180a (180b) are received in a lens barrel 150a (150b). The proximal end of the lens barrel 150a (150b) is secured to a rotating spherical member (hereinafter, a rotating ball) 152.
The rotating ball 152 is disposed on a cylindrical support 142 arranged on a base 141 of a mount 140. The support 142 has a circular hole 142a having a diameter smaller than that of the rotating ball 152. The rotating ball 152 is fitted in the hole 142a. Since the rotating ball 152 is rotatable on the hole 142a, the orientation of the ball 152 is appropriately adjusted to determine the lens 171a (171b) in a predetermined orientation (direction and angle).
The rotating ball 152 is held on the mount 140 by a retainer 143 and is fixed in the predetermined orientation. In other words, the mount 140 has a cylindrical male threaded member 144 that surrounds the support 142. The retainer 143 is screwed to upper end part of the male threaded member 144. The retainer 143 has a circular opening 143a having a diameter smaller than that of the ball 152. The rotating ball 152 is arranged in the opening 143a so as to partially protrude from the opening 143a. Accordingly, the ball 152 is disposed in a space defined by the retainer 143 and the support 142 so as to be prevented from coming out of the opening 143a. Therefore, the rotating ball 152 is held on the mount 140. While the retainer 143 is loosely screwed to the male threaded member 144, the rotating ball 152 is movable.
In a state (shown in FIGS. 7A and 7B) where the retainer 143 is tightly screwed to the male threaded member 144, the rotating ball 152 in contact with the periphery of the opening 143a is pressed against the support 142. Thus, the rotating ball 152 is pressed between the opening 143a and the hole 142a. Therefore, the orientation of the rotating ball 152 is adjusted to determine the lens 171a (171b) in the predetermined orientation (direction and angle) and the retainer 143 is screwed to the male threaded member 144 while the determined state of the lens is being maintained, so that the rotating ball 152 is fixed in the determined state because the rotating ball 152 is pressed against the opening 143a. 
As described above, in the angle adjustment mechanism using such a ball joint in the related-art dome video camera 100a (100b) shown in FIG. 7A (7B), the rotating ball 152 is secured to the proximal end of the lens barrel 150a (150b) with screws and the rotating ball 152 is rotatably held by the mount 140 (specifically, the support 142, the retainer 143, and the male threaded member 144). The retainer 143 is slightly unscrewed from the male threaded member 144 so that the rotating ball 152 is movable, the lens barrel 150a (150b) is appropriately rotated in the panning direction and/or the tilting direction, and the retainer 143 is tightly screwed to the male threaded member 144. Thus, the lens 171a (171b) can be determined in a desired orientation (direction and angle). A cover 120a (120b) is attached after the lens 171a (171b) is determined in the desired orientation.