Focus Detection Device Aperture Adaptation
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Solution Overview
Problem
Focus detection devices using the split pupil type phase difference detection method face accuracy issues and potential disablement when focus detection light fluxes are partially blocked at the exit pupil of the imaging optical system.
Innovation Solution
Incorporating a focus detection device with micro-lenses and light-receiving elements that adjust focus detection based on full-aperture signals, including a condition judging unit to assess focus adjustment states, brightness, and contrast, to ensure accurate focus detection even at f-numbers slower than full-aperture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focus detection is performed with full-aperture light flux, then focus detection accuracy is maintained, but focus detection fails when aperture is slower than full-aperture
Solution Approach 1:
The patent dynamically switches between full-aperture focus detection and slow-aperture focus detection based on the current aperture state. When the aperture is at full-aperture, the system performs focus detection using all light flux. When the aperture is slower than full-aperture, the system switches to focus detection using only the slow-aperture light flux, ensuring continuous focus detection capability across varying aperture conditions.
Solution Approach 2:
The patent changes the detection parameter from full-aperture light flux to slow-aperture light flux based on the aperture state. By detecting which aperture state (full-aperture or slower) is currently active, the system adjusts the focus detection method accordingly, allowing accurate focus detection regardless of the aperture setting.
2Manufacturing precision
If focus detection light flux is blocked at exit pupil, then depth of field control is achieved, but focus detection accuracy deteriorates
Solution Approach 1:
The patent dynamically adapts the focus detection method based on the aperture state. When the aperture is closed (slower than full-aperture), causing blockage of focus detection light flux, the system switches to using the blocked light flux for focus detection. This ensures that focus detection remains accurate regardless of whether the aperture is open or closed, resolving the conflict between depth of field control and focus detection accuracy.
3Manufacturing precision
If focus detection is performed at slower f-numbers, then depth of field is increased, but focus detection capability is lost
Solution Approach 1:
The patent implements dynamic focus detection that adapts to the current aperture state. When the aperture is set to slower f-numbers, the system automatically switches to focus detection using the slow-aperture light flux. This dynamic adaptation ensures that focus detection capability is maintained across the entire range of aperture settings, from full-aperture to slow f-numbers, resolving the contradiction between depth of field and focus detection reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances focus detection accuracy and prevents disablement by adjusting aperture settings to maintain focus detection capability across varying f-numbers and lighting conditions, ensuring reliable image capture.
Implementation Method 1
the focus detection element includes a plurality of micro-lenses and each of the light-receiving elements is disposed in correspondence to one of the micro-lenses, which receive the light fluxes from the imaging optical system via the micro-lenses
Data Source
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AI summary
A focus detection device comprises: focus detection elements (311) includingllght-receivingelements(12,13) that generate a pair of signals corresponding to a pair of light fluxes each passing through an imaging optical system(202) that includes a lens and an aperture stop(211); and a focus detector(214) including a processor that determines a focus adjustment state of the imaging optical system(202) with an f-number slower than a full-aperture of the imaging optical system(202) when a specific condition is fulfilled.