1. Field of the Invention
The present invention relates to a liquid lens containing liquids for changing focus.
2. Description of the Related Art
In recent years, remarkably high performance owing to the increased number of pixels and the like in a camera mounted to a portable terminal device or the like has been attained, and there has been a demand for a highly accurate optical zooming function along with the high performance of the camera. In ordinary optical zooming, it is necessary to change a focal length between an image sensor (e.g., a charge-coupled device (CCD) sensor) in a camera and a lens, and the focal length is changed by mechanically moving the lens. Therefore, in the case of mounting the ordinary optical zooming, a space for the movement of the lens is required. However, there are demands for downsizing and thinning of a camera in portable terminal devices, and an increase in size due to the space for movement of a lens should be avoided even in the case of mounting the optical zooming function.
As a method for attaining the space saving, Japanese Patent Application Laid-Open No. 01-302301 discusses a liquid lens that does not require the space for movement of the lens.
In Japanese Patent Application Laid-Open No. 01-302301, the lens includes two phase liquids which are partitioned by an elastic transparent film, and the shape of the elastic transparent film is changed by adjusting an amount of each of the two phase liquids by an externally connected pump, thereby adjusting a lens focus. In the liquid lens, since the lens focus is changed when the shape of the liquid lens itself is changed by the liquid amount adjustment, the space for movement of the lens is no longer necessary.
Also, as another mode of the liquid lens, Japanese Patent Application Laid-Open No. 2000-249813 discusses a lens including a single phase liquid which is covered with an elastic transparent film, of which a lens focus is changed by changing the shape of the elastic film by an actuator.
However, though the space for movement of the lens is not required in the liquid lens discussed in Japanese Patent Application Laid-Open No. 01-302301, the pump for adjusting the liquid amounts and a liquid reserve tank are required. Therefore, it is difficult to attain the space saving of an entire device to which the liquid lens is to be mounted. Also, though the pump and the tank are not required in the liquid lens discussed in Japanese Patent Application Laid-Open No. 2000-249813, it is in some cases impossible to ensure satisfactory accuracy of the focus adjustment because of deflection of the elastic film due to an external cause, such as gravity or external impact, since the elastic film is exposed to the outside.