1. Field of the Invention
The present invention relates to a camera having an auto-focus mechanism.
2. Description of the Related Art
These days, in a field of lens shutter type small sized camera which is so called compact camera, a high magnification zoom lens system is prevailingly used so that a lens having a focus length of about f=105 mm in the telescopic side has become to be generally and widely used in the compact camera. In accordance with the camera having such a zoom lens, the depth of field tends to become shallow in comparison to the conventional camera having a photo-taking lens of f=35 mm.
Also, there is a tendency to shorten the minimum distance to the subject to be photographed as a result of which the number of steps to move the lens to project for short-distance focusing is increased. Such a projecting motion of the lens for focusing has to be accurately controlled to obtain a clear photograph of high quality.
In accordance with the camera (AF camera) of the related art, the lens is controlled and driven to project with the use of a pulse motor. However, since the number of steps for projecting the lens is many, it takes much time as much as 200 ms to 300 ms to project the lens.
As a result, in the case where a moving subject is to be photographed, at the time when the lens motion to project for focusing the subject is ended, there often occurs a case wherein the subject is further moved out of the depth of field so that the photograph becomes blurred.
Such a problem may not be significant or may not arise if the camera is constructed as a single lens reflex auto focus camera arranged in such a way that the lens projecting operation and the distance measurement operation are conducted simultaneously. However, in accordance with the compact camera which is constructed in such a way that the distance measurement unit is driven independently from the photo-taking lens system, the above mentioned problem is often occurs so that the subject is photographed in the state where the subject is moved out of the depth of field of the camera.