Intermittent Assist Light Control for Camera Focus Detection
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Solution Overview
Problem
Existing image-capturing apparatuses face challenges in performing high-speed focus detection using assist light due to frequent failures, leading to increased emissions of assist light until successful focus detection is achieved, especially in low-light conditions.
Innovation Solution
An image-capturing apparatus with a controller that selectively performs focus detection processes with intermittent light emission, adjusting light emission amounts and focus element movement based on defocus reliability, and using multiple focus detection results to optimize light emission for subsequent detections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If focus detection is performed using assist light emission, then focus detection can be enabled in low-light conditions, but the number of assist light emissions increases due to detection failures
Solution Approach 1:
The patent performs focus detection using paired photoelectric convertors before emitting assist light, to determine whether assist light emission is actually necessary. This preliminary detection action prevents unnecessary assist light emissions and reduces energy consumption while maintaining reliable focus detection in low-light conditions.
Solution Approach 2:
The patent uses feedback from the paired photoelectric convertors to adjust focus detection strategy. When the convertors detect sufficient light, the system performs focus detection without assist light. When light is insufficient, the system uses assist light only when necessary, creating a feedback loop that optimizes energy usage while maintaining detection reliability.
2Measurement precision
If pupil-division by microlens with paired photoelectric convertors is used, then focus detection can be performed, but only small defocus amounts can be detected due to short base length
Solution Approach 1:
The patent transitions from detecting only small defocus amounts with paired photoelectric convertors to detecting large defocus amounts by utilizing the image sensor's ability to capture out-of-focus images. This dimensional change in detection capability allows the system to handle both small and large defocus scenarios, improving overall focus detection reliability.
Solution Approach 2:
The patent changes the detection parameter from relying solely on phase difference signals from paired convertors to using luminance information from the image sensor. By changing to luminance-based focus detection, the system can detect large defocus amounts that were previously undetectable, thereby improving detection success rate.
3Reliability
If multiple focus detection attempts are made with assist light emission, then focus detection success rate improves, but detection speed decreases
Solution Approach 1:
The patent implements dynamic focus detection by moving the focus element during detection. This dynamic approach allows the system to quickly scan through focus positions and identify the correct focus point in a single operation, rather than requiring multiple static detection attempts, thereby improving both speed and success rate.
Solution Approach 2:
The patent maintains continuous focus detection action by moving the focus element continuously through its range while performing detection. This continuous action eliminates the need to stop and restart detection multiple times, improving detection speed while maintaining reliability through persistent detection effort.
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
The solution enables high-speed focus detection with reduced assist light emissions by optimizing light emission strategies based on defocus reliability, improving detection accuracy and efficiency.
Implementation Method 1
a light emitter for illuminating an object
Implementation Method 2
an image sensor configured to capture an object image formed by an image-capturing optical system
Data Source
AI summary
The image-capturing apparatus (100) includes an image sensor (14), a focus detector (42) performing focus detection using output from the image sensor; and a controller (50) configured to cause the focus detector to perform the focus detection and configured to control emission of a light emitter for illuminating an object and movement of a focus element for focusing. The controller selectively performs: a first focus detection process that causes the focus detector to perform the focus detection with the focus element being stopped while causing the light emitter to intermittently emit light; and a second focus detection process that causes the focus detector to perform the focus detection with the focus element being moved while causing the light emitter to intermittently emit the light.