Autofocus Controller Lens Position Compensation for IR Filter Chromatic Aberration
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Solution Overview
Problem
Conventional autofocus methods in image pickup apparatuses, such as digital cameras, take a long time to search for the in-focus position when an infrared cut filter is inserted or ejected, especially when the light source lacks significant infrared components, leading to inefficient focus lens movement.
Innovation Solution
An image pickup apparatus with a controller that determines the initial focus lens position based on the difference in in-focus positions with and without the optical filter, allowing for optimized focus lens movement before starting the search, thereby reducing the search time for the in-focus position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the focus lens is moved by a predetermined amount before searching for the in-focus position when the infrared cut filter is inserted or ejected, then the in-focus position can be found after filter insertion/ejection, but the search time becomes excessively long when the light source lacks significant infrared components
Solution Approach 1:
The patent changes the movement amount of the focus lens based on the detected luminance level. When luminance is below the threshold (indicating light sources like white LEDs or fluorescent lamps with minimal infrared components), the focus lens is not moved or moved by a smaller amount. When luminance exceeds the threshold (indicating light sources with significant infrared components), the focus lens is moved by the predetermined amount. This dynamic parameter adjustment resolves the contradiction by adapting the focus lens movement to the actual lighting conditions.
Solution Approach 2:
The patent introduces dynamic control of the focus lens movement amount based on real-time luminance detection. Instead of using a fixed predetermined movement amount, the system dynamically adjusts the movement strategy according to the detected luminance level, enabling adaptive response to different light source characteristics and optimizing both accuracy and speed.
2Adaptability or versatility
If the infrared cut filter is inserted into or ejected from the optical path, then infrared photography capability is achieved, but the focus state changes due to chromatic aberration
Solution Approach 1:
The patent performs preliminary detection of the light source luminance before the filter insertion or ejection operation. Based on this advance detection, the system determines the appropriate focus lens movement amount to compensate for the upcoming focus state change. This preliminary action allows the system to pre-position the focus lens optimally, maintaining focus stability during and after the filter operation.
Solution Approach 2:
The patent implements a feedback mechanism where the detected luminance information is used to adjust the focus lens movement amount. The system continuously monitors luminance levels and uses this feedback to dynamically control the focus compensation strategy, ensuring optimal focus maintenance during filter insertion and ejection operations under varying lighting conditions.
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
This approach significantly shortens the search time for the in-focus position by determining the necessary initial focus lens position based on luminance differences, improving autofocus efficiency, especially under light sources with minimal infrared or ultraviolet components.
Implementation Method 1
an image pickup element configured to photoelectrically convert an object image formed by an optical system including a focus lens, and to generate an image pickup signal
Data Source
AI summary
An image pickup apparatus includes an image pickup element, an optical filter, a filter driver configured to insert and to eject the optical filter into and from an optical path between the optical system and the image sensor, and a controller configured to search for an in-focus position based on the image pickup signal and to control a position of the focus lens based on a result of a search. The controller determines whether the focus lens is to move by a first amount after the optical filter moves from one of the position on the optical path and the position outside the optical path to the other, and before the search starts, based on a difference between an in-focus position when the optical filter is disposed on the optical path and an in-focus position when the optical filter is not disposed on the optical path.