1. Field of the Invention
The present invention relates generally to a lens, and more particularly to a prism type lens.
2. Description of the Related Art
As an improvement of technology, many electronic products, such as cellular phone, videogame, PDA etc., are equipped with image capture device for people to record his/her everyday life.
A conventional lens for the image capture device is cylinder cam type lens which has a plurality of lens groups. The lens groups are adjusted for focusing. The lens groups of the cylinder cam type lens will be moved into the image capture device when people turn off the electronic product. As there may be too many lens groups to be moved, sometime the cylinder cam type lens is too big for some image capture devices.
An improved lens, a prism type lens, is provided to overcome the drawback of the cylinder cam type lens. Taiwan Utility Model Patent No. M376769 discloses a prism type lens including a plurality of lens groups received in an image capture device for reciprocation and a prism for total reflection to reflect incident light to the lens groups. The prism type lens equips the image capture device with no protruded lens that the image capture device may be smaller and lighter.
However, the prism type lens has a limitation in zoom range because the lens groups have to move along a straight path and there is insufficient distance for the lens groups to move. The zoom range may be enlarged by lengthening the optical axis. However, it will increase the size of the image capture device.