Non-Rotating Elliptical Iris Diaphragm for Consistent Bokeh
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Solution Overview
Problem
Existing iris diaphragms in photographic and motion picture cameras suffer from bokeh shapes and orientations that change with aperture adjustments, which is undesirable in certain applications.
Innovation Solution
An iris diaphragm with a fixed washer, a movable washer, and a control washer, featuring guide ramps and movable pins, allows the elliptical aperture to maintain its shape and orientation regardless of the aperture setting, achieved through controlled rotation of the washers and pins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional iris diaphragm with circular blades is used, then the aperture can be adjusted continuously, but the bokeh shape and orientation change depending on the aperture setting
Solution Approach 1:
The patent applies asymmetry by using elliptical blades instead of circular blades. The elliptical shape of the blades ensures that the aperture opening maintains a consistent elliptical shape and orientation across all aperture settings. This asymmetric geometry resolves the contradiction by preserving bokeh shape consistency while still allowing continuous aperture adjustment through the movement of the elliptical blades.
Solution Approach 2:
The patent employs dynamics through the movable elliptical blades that can pivot and translate relative to the fixed washer. This dynamic mechanism allows the aperture to be adjusted continuously from fully open to fully closed while maintaining the elliptical shape and orientation of the bokeh. The controlled movement of the blades resolves the contradiction between aperture adaptability and bokeh shape stability.
2Manufacturing precision
If the number of blades is increased to improve bokeh quality, then the bokeh shape approaches a perfect disc, but the device complexity increases
Solution Approach 1:
The patent uses asymmetry with elliptical blades that have specific geometric proportions. By carefully designing the elliptical shape with appropriate axis ratios, the patent achieves high bokeh quality with fewer blades. This approach resolves the contradiction by maintaining manufacturing precision for bokeh shape while reducing the number of blades required compared to conventional circular blade designs.
Data Source
Figure 1A~1B
Figure 2
Figure 3A
AI summary
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.