Solid-State Image Pickup Device Phase-Detection Autofocus
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Solution Overview
Problem
Mirrorless cameras using contrast-detection AF systems face slow autofocus control compared to phase-detection AF systems, as they lack the ability to guide subject light to phase-detection sensors like conventional digital single-lens reflex cameras.
Innovation Solution
A solid-state image pickup device with a two-dimensional matrix of pixels, including both first and second photoelectric conversion means, and a light beam selecting means, where a first scanning circuit controls exposure operations for image signals and a second scanning circuit controls focus signals, allowing for simultaneous or separate exposure operations to enhance autofocus speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a mirrorless camera uses a contrast-detection AF system, then the device structure is simplified without a mirror, but the autofocus speed becomes slow
Solution Approach 1:
The pixel array is divided into two distinct types: first pixels for image capture and second pixels for phase-detection AF. Each pixel type has dedicated photoelectric conversion means and scanning circuits, allowing simultaneous independent operation. This segmentation enables the system to achieve fast autofocus through phase detection while maintaining the mirrorless simplified structure.
Solution Approach 2:
The solid-state image pickup device performs multiple functions simultaneously: image capture through first pixels and phase-detection autofocus through second pixels. The light beam selecting means enables the same optical path to serve both imaging and autofocus purposes, achieving multi-functionality without requiring separate optical systems.
2Speed
If phase-detection AF pixels are added to the effective pixel area, then autofocus speed is improved, but the device complexity increases
Solution Approach 1:
The first and second photoelectric conversion means are integrated within the same pixel structure and share common components including the solid-state imaging device substrate, scanning circuits, and light beam selecting means. This merging approach achieves phase-detection AF capability without adding separate dedicated hardware systems, thereby limiting the increase in device complexity.
Solution Approach 2:
The light beam selecting means acts as an intermediary component that directs incident light to either the first or second photoelectric conversion means based on operational requirements. This mediator enables a single optical path to serve dual purposes of image capture and phase-detection autofocus, reducing the need for separate optical systems.
3Adaptability or versatility
If separate scanning circuits are used for first and second pixels, then exposure operations can be controlled independently, but the circuit complexity increases
Solution Approach 1:
The first and second scanning circuits can operate dynamically and independently, allowing flexible control of exposure timing for image capture and autofocus respectively. This dynamic operation enables adaptive exposure control where each pixel type can be activated only when needed, providing versatility while the circuits share common control logic to limit complexity increase.
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 configuration enables efficient phase-detection AF signal acquisition while performing global exposure, reducing noise and improving image quality by separating exposure operations for image and focus signals, thus achieving faster and more accurate autofocus control.
Implementation Method 1
a first photoelectric conversion means that converts incident light into an electrical signal to store the electrical signal
Implementation Method 2
a second photoelectric conversion means that converts incident light into an electrical signal to store the electrical signal
Data Source
AI summary
A solid-state image pickup device includes a plurality of pixels arranged in a two-dimensional matrix, and outputs signals corresponding to the light quantity incident on each pixel. Each pixel includes: a first pixel that is equipped with a first photoelectric conversion means that converts incident light into an electrical signal to store it; and a second pixel that is equipped with a second photoelectric conversion means that converts incident light into an electrical signal to store it, and a light beam selecting means that selects a light beam that is incident on the second photoelectric conversion means. The solid-state image pickup device includes: a first scanning circuit; and a second scanning circuit. The solid-state image pickup device outputs the electrical signals stored in the first photoelectric conversion means as image signals, and outputs the electrical signals stored in the second photoelectric conversion means as focus signals.