Focus Detection Pixel Selection for Interchangeable Lens Exit Pupils
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Solution Overview
Problem
Existing image sensors face challenges in increasing the speed of signal reading for both focus detection and image generation, particularly in systems with interchangeable lenses where the exit pupil distance varies with image height and lens type.
Innovation Solution
A focus detection device with specific pixel configurations and timing-based signal readout methods, including a selection unit to choose between focus detection and image generation pixels, and a readout unit that reads signals at different timings to optimize focus detection and image processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If signal reading is performed simultaneously for both focus detection and image generation, then processing efficiency is improved, but signal reading speed deteriorates due to shared readout resources
Solution Approach 1:
The image sensor divides pixels into separate functional groups: first pixels dedicated to focus detection and second pixels dedicated to image generation. This segmentation allows independent readout of focus detection signals and image signals through separate readout circuits, enabling simultaneous processing without resource contention and maintaining high signal reading speed for both functions.
Solution Approach 2:
The patent introduces a temporal dimension by performing focus detection signal reading and image signal reading at different timings. The control unit coordinates the timing so that focus detection pixels are read out during periods when image pixels are being exposed, and vice versa, effectively utilizing time multiplexing to achieve simultaneous processing capability while maintaining high readout speed for each signal type.
2Device complexity
If a fixed pixel configuration is used, then device complexity is reduced, but adaptability deteriorates when dealing with different lens types and exit pupil distances
Solution Approach 1:
The patent implements a dynamic pixel configuration where the control unit can selectively activate and configure different pixel groups based on the attached lens type and shooting conditions. The system dynamically adjusts which pixels function as focus detection pixels and which function as image pixels, allowing adaptation to various exit pupil distances and lens characteristics without requiring physical hardware changes.
Solution Approach 2:
The system changes operational parameters including pixel activation patterns, readout timing sequences, and signal processing weights based on detected lens characteristics and exit pupil distance. By dynamically adjusting these parameters, the system adapts to different lens types and optical configurations while maintaining a fixed physical pixel array structure.
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 speed by adapting to varying exit pupil distances, allowing for efficient focus adjustment and high-quality image capture across different lenses and image heights.
Implementation Method 1
an imaging unit having a first pixel and a second pixel each of which receives light transmitted through an optical system and outputs signal used for focus detection, and a third pixel which receives light transmitted through the optical system and outputs signal used for image generation
Data Source
AI summary
A focus detection device includes: an imaging unit having a first and second pixel each of which receives light transmitted through an optical system and outputs signal used for focus detection, and a third pixel which receives light transmitted through the optical system and outputs signal used for image generation; an input unit to which information regarding the optical system is input; a selection unit that selects one of the first and second pixel based on the information to the input unit; a readout unit that reads out the signal from one of the first and second pixel based on a selection result at a timing different from reading out the signal from the third pixel to be read out; and a focus detection unit that performs the focus detection based on at least one of the signals of the first and second pixel read out by the readout unit.