Elliptical Iris Diaphragm With Fixed-Axis Bokeh Control
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Solution Overview
Problem
Existing iris diaphragms in photographic and cinematographic equipment suffer from bokeh effects that change shape and orientation with aperture size, which is undesirable in certain applications.
Innovation Solution
An iris diaphragm with a fixed ring, a mobile ring that rotates about the optical axis, and a control ring that controls the mobile ring's rotation, featuring guidance and control guideways to maintain an elliptical aperture shape and orientation regardless of aperture size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional iris diaphragm with rotating blades is used, then the aperture size can be adjusted continuously, but the bokeh shape and orientation change with aperture size
Solution Approach 1:
The diaphragm is segmented into multiple independent blades (typically 8 or 9 blades) that can move individually along guided paths. Each blade is connected to a control ring through a pivot connection, allowing independent movement while maintaining the overall elliptical shape. This segmentation enables continuous aperture adjustment while preserving bokeh consistency.
Solution Approach 2:
A control ring serves as an intermediary element that coordinates the movement of all blades simultaneously. The control ring is connected to each blade through guidance guideways and pivot connections, translating rotational motion into synchronized blade movement. This intermediary mechanism ensures that all blades move in a coordinated manner to maintain the elliptical aperture shape and orientation throughout the adjustment range.
2Reliability
If multiple blades are used to define the aperture, then the bokeh quality improves, but the device complexity increases
Solution Approach 1:
Multiple blades are merged into a single functional unit through their common connection to the control ring. All blades share the same guidance guideways and pivot connection mechanism, allowing them to move in unison. This merging approach maintains high bokeh quality with multiple blades while reducing the independent complexity of each blade assembly.
Solution Approach 2:
The control ring serves multiple functions simultaneously: it controls the aperture size, maintains the elliptical shape, preserves the orientation, and coordinates all blade movements. This multi-functionality reduces the need for separate control mechanisms for each function, thereby reducing overall device complexity despite using multiple blades.
3Stability of the object's composition
If the diaphragm structure is made complex to maintain elliptical shape, then the bokeh consistency improves, but the ease of manufacture decreases
Solution Approach 1:
The diaphragm uses dynamic pivot connections instead of fixed rigid structures. Each blade can rotate about a pivot axis that is perpendicular to the plane of the diaphragm or translationally mobile with respect to the ring. This dynamic connection allows the blades to move along curved paths defined by the guidance guideways, maintaining the elliptical shape through motion rather than complex static geometry, which simplifies manufacturing.
Solution Approach 2:
The guidance guideways are designed with specific shapes that change the positional parameters of the mobile pins as the control ring rotates. The guideway geometry transforms the rotational motion into the precise blade movements needed to maintain the elliptical aperture. By encoding the motion path in the guideway shape rather than using complex mechanical linkages, the manufacturing process is simplified while maintaining shape consistency.
Data Source
AI summary
An iris diaphragm having an optical axis, includes a fixed ring, a mobile ring designed to rotate about the optical axis with respect to the fixed ring and comprising a plurality n of guidance guideways, a plurality of n blades defining an elliptical diaphragm aperture having a major axis (a) and a minor axis (b), each blade being able to pivot with respect to the fixed ring about a respective axis and comprising a respective mobile pin able to move in one of the respective guidance guideways by bearing along the respective guidance guideway, a control ring designed to rotate about the optical axis with respect to the fixed ring and comprising a control guideway wherein one of the mobile pins, referred to as control pin, is able to move by bearing along the control guideway, a shape of each guidance guideway on which the respective mobile pin bears being designed so that a rotation of the control ring about the optical axis gives rise, via the control pin, to a rotation of the mobile ring and a movement of the mobile pins in the guidance guideways so as to modify an area of the elliptical aperture without modifying an orientation of the major axis and of the minor axis and without modifying a ratio of the major axis to the minor axis.