| 摘要 |
PURPOSE:To nearly eliminate the defect of a relative value encoder in terms of principle in practical use with comparatively simple constitution without making the constitution of a zoom encoder large by making an absolute value encoder non-contact and without causing the increase of cost. CONSTITUTION:This zoom encoder detects the turning amount and the turning direction of a cam ring which turns around the optical axis of a photographing optical system so as to change the focal distance of the photographing optical system. Then, it is provided with a non-contact type pulse generating means 2 which generates a pulse signal in accordance with the turning of the cam ring being a zoom driving means 1, a pulse counting means 3 which adds or subtracts the pulse signal in accordance with the turning direction of the cam ring, a position detecting means (zoom specified position detecting means) 4 which detects a specified position signal at least near the wide angle end and the telephoto end in the focal distance, a counted value changing means 5 which changes the counted value by the counting means 3 to a specified value in accordance with the change of the output from the means 4, and a zoom information detecting means 6 which obtains zoom information based on the output from the means 3. |
