| 摘要 |
PURPOSE:To set F-value graduation at equal intervals for manual aperture settlement by detecting the turning position of a blade member with hall elements, and enhancing the linearity between aperture value deflection angle with a squaring circuit consisting of Hall elements. CONSTITUTION:Hall elements H1 and H2 are arranged in the moving path of an aperture member D or a magnet member which is operated together with an electromagnetic turning device and detects the positional change of the aperture member D. The element H1 applies an output VH1 proportional to the magnetic flux density, which is changed in accordance with turning or displacement of the aperture member, to an amplifier A2, and the output of the amplifier A2 is applied to the Hall element H2, and an output VH2 of the element H2 is applied to the input terminal of an amplifier A3 through resistances R7 and R8. The amplifier A3 amplifies the output proportional to the square of the magnetic flux density by characteristics of Hall elements, and an electromagnetic turning device M is operated through an amplifier A4 in the next stage, and a variable resistance or the like concerning a reference voltage VF is graduated with F-value corresponding to individual values when the reference voltage VF inputted to the amplifier A4 through a switch terminal S2 is set, thus forming a dial having approximately equal graduations.
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