1. Field of the Invention
The present invention relates to a lens barrel which includes lens groups and accommodates a shooting lens whose focal length can be changed and which adjusts focus, which can advance and retract, and which allows the shooting lens to adjust focal length and focus. The invention also relates to an image taking apparatus which has such a lens barrel and which captures a subject light passing through the lens barrel, thereby taking an exposure.
2. Description of the Related Art
In recent years, in addition to cameras which take an exposure on a conventional silver-salt film, digital cameras have rapidly become widespread. Such a digital camera includes a solid state imaging element such as a CCD image pickup element or a CMOS image pickup element, and which forms a subject image on the solid state imaging element and produce an image signal.
In this digital camera also, it is strongly required to enhance the shooting performance and carrying-easiness. There is a digital camera having a lens barrel incorporating, therein, a shooting lens having lens groups. In this digital camera, the focal length can be changed so that it is possible to take an exposure with a desired angle of view. Further, in order to enhance the carrying-easiness, the shooting lens is retracted into a camera body such that a distance between the lens groups constituting the shooting lens becomes less than a minimum distance required for shooting when the camera is not used, and shooting lens advances from the camera body so that the distance between the lens groups becomes longer than a distance required for shooting when the camera is used (see Japanese Patent Application Laid-open 1993-34769.)
In the digital camera wherein the distance between the incorporated lens groups becomes shorter than the minimum necessary distance required for shooting when the lens barrel is retracted, a technique called blackout is employed when the lens barrel is retracted. This technique prevents non-formed image from being displayed on a liquid crystal panel provided on a back surface of the camera.
This means that the digital camera having such a lens barrel is brought into a shooting-disenable state where subject light cannot be formed on the solid state imaging element when the lens barrel is retracted irrespective whether the blackout technique is carried out or not. For example, even when it suddenly becomes necessary make an exposure while carrying a digital camera, it is necessary to wait until the distance between the incorporated lens groups becomes the minimum necessary distance required for shooting from the retracted position, and there is an adverse possibility to miss the perfect moment for a good picture.
A so-called silver-salt camera using a roll film has the same problem.