Electronic Focal Plane Shutter for Vibration-Free Shake Correction
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Solution Overview
Problem
Imaging apparatuses with CMOS devices face issues with camera shake correction due to vibrations from mechanical focal plane shutters, leading to erroneous shake detection and exposure unevenness, particularly when using a combination of electronic and mechanical shutters.
Innovation Solution
The implementation of a control mechanism that selectively uses an electronic focal plane shutter as the front curtain during shake correction operations and a mechanical focal plane shutter otherwise, based on criteria such as shake detection signals, tripod attachment, and shutter speed, to minimize vibration influence and exposure unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a mechanical focal plane shutter is used for the front curtain, then the shutter structure is simple and cost-effective, but vibrations from curtain travel cause erroneous shake detection signals
Solution Approach 1:
The shutter system is segmented into two independent curtains: the front curtain is effected by an electronic focal plane shutter (reset signal control) while the rear curtain is effected by a mechanical focal plane shutter. This segmentation allows the front curtain to operate without mechanical movement during exposure, eliminating vibrations that would interfere with shake detection, while the rear curtain maintains mechanical operation for exposure termination.
Solution Approach 2:
The front curtain mechanism is replaced from a mechanical system to an electronic system. Instead of using a mechanical curtain movement to control the front curtain, the patent uses an electronic focal plane shutter where reset signals are sequentially supplied to pixel lines to start exposure, eliminating mechanical vibrations at the critical exposure start phase.
2Measurement precision
If the front curtain is always effected by an electronic focal plane shutter, then shake detection precision is improved, but exposure unevenness occurs due to speed differences between electronic and mechanical shutters
Solution Approach 1:
The shutter operation is segmented into two distinct phases: front curtain control via electronic focal plane shutter for vibration-free exposure initiation and shake detection, and rear curtain control via mechanical focal plane shutter for consistent exposure termination. This segmentation resolves the contradiction by allowing each curtain type to operate in its optimal mode without causing exposure unevenness.
3Object-affected harmful factors
If curtain speed is controlled to be slow during long exposure, then impact vibration is reduced, but the mechanism becomes complex and increases device size
Solution Approach 1:
The front curtain speed control is achieved by replacing the mechanical speed control mechanism with an electronic timing system. Reset signals are sequentially supplied to pixel lines at controlled intervals, eliminating the need for complex mechanical speed regulation mechanisms while achieving the same vibration reduction effect.
4Measurement precision
If the angular velocity sensor is positioned to minimize impact vibration exposure, then shake detection precision is improved, but component layout is restricted
Solution Approach 1:
The harmful vibration source (front curtain mechanical movement) is extracted and removed from the system by replacing it with an electronic focal plane shutter. This eliminates the need to carefully position the angular velocity sensor to avoid vibrations, as the vibrations are no longer generated during the critical exposure phase, thereby restoring layout flexibility.
Data Source
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AI summary
In an imaging apparatus with shake correction function, an erroneous shake correction operation is prevented from being performed due to a front curtain shock. A shutter selecting section 625 determines that the current state is the shake-correction execution mode when a shake correction switch 313 is ON, when a tripod detection sensor 185S tripod is not mounted, when a shake amount equal to or larger than a predetermined value is detected by a shake detection sensor 171, and when a shutter speed is lower than a predetermined value. In this case, the shutter selecting section 625 selects an electronic focal plane shutter as the front curtain, and supplies an operation command signal to an electronic focal plane shutter control section 627. On the other hand, in cases other than the above-mentioned case, the shutter selecting section 625 determines that the current state is not the shake-correction execution mode, and selects a mechanical focal plane shutter as the front curtain and supplies an operation command signal to a shutter drive control section 73A.