Non Rotating Elliptical Iris Diaphragm

Abstract: Disclosed is an iris diaphragm (1) having an optical axis (O) and comprising: - a fixed ring (RF); - a movable ring (RM) capable of rotating about the optical axis relative to the fixed ring and comprising a plurality n of guide ramps (GG); - a plurality of n blades (L) defining an elliptical aperture (OE) of the diaphragm having a major axis (a) and a minor axis (b), each blade being pivotable relative to the fixed ring about a respective axis, and comprising a respective movable pin (PM) capable of moving in one of the respective guide ramps (GG) by lengthwise engagement therewith; - a control ring (RC) capable of rotating about the optical axis relative to the fixed ring and comprising a control ramp (GC) in which one of the movable pins, referred to as the control pin (PC), is capable of moving by lengthwise engagement with the control ramp; and wherein a shape of each guide ramp (GG) with which the respective movable pin (PM) engages is such that a rotation of said control ring (RC) about the optical axis causes, via the control pin (PC), a rotation of said movable ring (RM) and a movement of the movable pins (PM) in the guide ramps (GG), thereby modifying a surface of the elliptical aperture (OE), without modifying an orientation of the major axis and the minor axis and without changing a ratio of the major axis to the minor axis.

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