Nikon filed a patent application in Japan (2011-97288) for an optical low-pass filter OLPF (aka as anti-aliasing filter) that can be turned ON or OFF depending on the need of the photographer:
“The imaging device by the invention according to claim 1 receives object light via a photographing optical system, The low pass filter component which is arranged in the optical path between the imaging means which outputs image data, and a photographing optical system and an imaging means, and contains the birefringence optical member of a couple.”
"The figure showing the important section composition of the electronic camera by an embodiment of the invention"
“The switching means which carries out relative rotating of the birefringence optical member of a couple, and changes the low pass filter characteristic of a low pass filter component between the 1st characteristic and the 2nd characteristic.”
The ON/OFF implementation is mechanical – here is the detailed description of the above drawing:
“The actuator 103 is constituted including the motor 103a, the base 103b, and the transmitting part 103c. The motor 103a is driven according to the driving signal from the control circuit 111. Rear filter 102AFT mentioned above was provided, for example, the base 103b is a disc-like plate. The opening is provided in the center section of the base 103b at the form which is mostly in agreement with the rectangular shape of rear filter 102AFT. And rear filter 102AFT is embedded at this opening, and it is made and joined. The transmitting part 103c is a disc-like plate, and tells rotation of the motor 103a to the base 103b. In accordance with each circumference, the gear etc. are formed so that engagement of the base 103b and the transmitting part 103c may become possible mutually. As a result, if the transmitting part 103c rotates according to rotation of the motor 103a, it will interlock and the base 103b will rotate.”
