The present invention relates to a retractable lens barrel and an imaging apparatus having the lens barrel thereof.
In recent years, replacing cameras using silver salt film, there have been popularly used electronic cameras wherein an imaging element carries out photo-electric conversion of light of a photographic subject, image data is obtained by applying a predetermined processing to an output from the imaging element and stored in a storage medium. In a field of the camera industry, to realize superior portability while not in use for photographing, cameras having so called a retractable lens barrel which is retracted to be thin by reducing distances between lens groups representing optical elements which configure an imaging optical system, are popular.
On the other hand, in an electronic camera using the imaging element, if dust exists in an imaging optical path near the imaging element, there is a problem that light for a light receiving element locating in the rear is interrupted and then a defect occurs in a photographic image.
To cope with this problem, there exist a camera in which dust is prevented from being adhering on surfaces between an imaging element side surface of a rearmost end lens group and a front surface of the imaging element by sealing the optical path between the rearmost end lens group and the imaging element, and a camera in which the rearmost end lens group and the imaging element are sealed and moved away from the imaging optical path and other imaging optical systems are moved backward. (For example: Refer to Patent document 1)
Patent Document 1: Japanese Unexamined Patent
Application Open to Public Inspection No. H11-109203
The problem that the defect occurs on the photographic image caused by adhesion of even a smaller foreign matter on the optical path of the imaging element is becoming obtrusive in accordance with minimizing of pixels and reduction of pixel pitches between the pixels for a higher density pixel imaging element. Also, as a dust-adhering surface comes closer to the imaging element, the dust creates more problems even if it is small.
In recent years, the number of pixel of imaging element increases and the pixel pitch is condensed to some μm. In the structure in Patent document 1, to realize a condition where adhesion of dust does not affect the imaging element, a distance from the imaging element to the object side surface of rearmost end lens has to be extremely large. In this status, if the front lens groups are moved telescopically, it is difficult to retract the lens groups to be thin enough.
Also, as the aforesaid Patent Document 1, in case thin lens barrel at retraction is realized by moving sealed imaging element, optical filter and rearmost end lens outside the imaging optical path, when moving is repeated, it is difficult to make an imaging surface of the imaging element always perpendicular to the optical axis accurately. For example, when the imaging surface is tilted, there is occurred a problem that a partial blur occurs and an image maximizing an optical performance of the lens cannot be obtained.