Dynamic Charge Accumulation for Autofocus Speed
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Solution Overview
Problem
Existing automatic focus systems in imaging apparatuses struggle to maintain focus in varying photographing environments and object speeds, particularly when the object is moving quickly or at different distances, leading to deviations from the depth of field and difficulty in maintaining a stable focus state.
Innovation Solution
An automatic focusing apparatus that includes a focus lens system with a focus motor, zoom lens, and iris motor, equipped with a spectral prism and phase difference detection sensor, which calculates the object's speed and depth of field to adjust the charge accumulation time and focus control period, ensuring the focus lens remains within the depth of field by dynamically adjusting the sensor's gain and termination of charge accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the charge accumulation time is extended to improve focus detection accuracy, then the measurement precision of defocus amount is improved, but the object moves out of depth of field during the accumulation period
Solution Approach 1:
The patent dynamically adjusts the charge accumulation time based on real-time detection of object movement speed and depth of field. When object speed is high or depth of field is small, the accumulation time is shortened to prevent the object from moving out of focus. When object speed is low and depth of field is large, the accumulation time is extended to improve detection accuracy. This dynamic adaptation resolves the contradiction between detection precision and focus maintenance.
Solution Approach 2:
The patent changes the charge accumulation time parameter according to the detected object characteristics (speed and depth of field). By adjusting this critical parameter based on real-time conditions, the system optimizes both detection accuracy and focus maintenance, preventing the object from moving out of depth of field while maintaining accurate defocus measurement.
2Speed
If the focus lens driving speed is increased to respond to fast-moving objects, then the speed of focus adjustment is improved, but the focus detection accuracy deteriorates due to insufficient charge accumulation
Solution Approach 1:
The patent implements dynamic adjustment of charge accumulation time based on object movement speed. When objects move fast, the system shortens accumulation time and increases focus lens driving speed to keep up with the object. When objects move slowly, the system extends accumulation time for accurate measurement. This dynamic coordination between detection and actuation speeds resolves the contradiction between response speed and measurement precision.
3Reliability
If the charge accumulation time is shortened to maintain focus on fast-moving objects, then the focus state maintenance is improved, but the defocus amount detection accuracy deteriorates
Solution Approach 1:
The patent changes the charge accumulation time parameter dynamically based on detected object characteristics. When object speed is high or depth of field is small, the accumulation time is shortened to maintain focus. When object speed is low and depth of field is large, the accumulation time is extended to improve detection accuracy. This parameter adaptation resolves the contradiction between focus maintenance and measurement precision.
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 solution allows for constant maintenance of focus regardless of the photographing environment and object speed, ensuring the focus lens stays within the depth of field by optimizing charge accumulation and focus control based on object speed and depth of field calculations.
Implementation Method 1
a spectral prism (113) that separates a photographing beam (103) into a plurality of beams
Implementation Method 2
a phase difference detection sensor (114) that photoelectrically converts the beam (103, 104) into a signal
Data Source
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AI summary
An automatic focusing apparatus includes: a focus detector (114) photoelectrically converting at least a part of a photographing beam; a defocus computer (118) calculating a defocus amount based on an output of the focus detector; a driver (103) driving a focus lens (101) based on the defocus amount; and a unit (121) setting a maximum time period for charge accumulation in the focus detector (114). If the accumulated charge in the focus detector (114) reaches a threshold within the period, when the accumulated charge in the focus detector (114) reaches the threshold, the defocus computer (118) calculates a defocus amount using an output of the focus detector (114) and outputs the defocus amount to the driver (103). If the accumulated charge in the focus detector (114) does not reach the threshold within the period, when the period lapses, the defocus computer (118) calculates a defocus amount using an output of the focus detector (114) and outputs the defocus amount to the driver (103).