Image Sensor Readout Control for Noise Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image capturing systems face challenges in minimizing noise differences between focus detection and image acquisition regions during on-imaging plane phase difference focus control, leading to increased system load and noise variability.
Innovation Solution
An image capturing apparatus with a control method that includes a matrix of photoelectric conversion portions, a control circuit for reading pupil-divided signals, and a signal processing circuit that adjusts read-out rows based on exposure gain to minimize noise differences between focus detection and image acquisition regions, using both first and second read-out controls to combine signals from photoelectric conversion portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signals are independently read from multiple photoelectric conversion portions for focus detection, then focus control capability is improved, but system load increases due to increased output rate
Solution Approach 1:
The image sensor output is segmented into two distinct readout paths: first readout control for focus detection signals and second readout control for image signals. This segmentation allows independent optimization of each path, reducing the overall system load by processing only necessary signals through each channel rather than reading all pixel signals at full rate.
Solution Approach 2:
The patent implements partial reading of pixel signals by selectively reading only the necessary photoelectric conversion portions for focus detection through the first readout control, while other portions are read through the second readout control. This partial action approach reduces the total output rate and system load while maintaining focus detection capability.
2Loss of time
If signals from multiple photoelectric conversion portions are combined in the image sensor, then readout time is reduced, but noise differences appear between focus detection and image acquisition regions
Solution Approach 1:
The patent applies different readout control strategies to different spatial regions: the first readout control is applied to specific regions designated for focus detection, while the second readout control is applied to regions for image acquisition. This local quality differentiation ensures that each region is processed optimally for its specific purpose, maintaining noise uniformity within each region while enabling parallel processing to reduce overall readout time.
Solution Approach 2:
The system dynamically switches between first and second readout controls based on the specific readout requirements. The control circuit can adaptively select which readout control to apply to which photoelectric conversion portions, allowing flexible optimization of both readout speed and noise characteristics depending on the operational state and requirements.
3Speed
If more pixel signals are read out within predetermined time for focus control, then focus detection speed is improved, but system load increases due to increased output rate
Solution Approach 1:
The readout system is segmented into two parallel channels with different priorities and processing modes. The first readout control channel is optimized for rapid focus detection signal extraction, while the second channel handles image signal readout. This segmentation enables accelerated focus detection without proportionally increasing the load on the entire system, as only the necessary focus detection signals are processed at high speed through the first channel.
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 effectively reduces noise differences between focus detection and image acquisition regions, enabling more efficient focus control while maintaining image quality by adjusting read-out regions and signal processing based on exposure gain levels.
Implementation Method 1
an image sensor having a plurality of photoelectric conversion portions that correspond to each of a plurality of microlenses arranged in a matrix
Data Source
AI summary
An image capturing apparatus comprising: an image sensor having a plurality of photoelectric conversion portions that correspond to each of a plurality of microlenses arranged in a matrix; a control circuit that controls read-out from the image sensor by either of first read-out control for obtaining focus detection signals and second read-out control for obtaining an image signal, a setting circuit that sets rows to be read out by the first read-out control among rows that include a focus detection area; an amplification circuit that amplifies a signal with a gain set in accordance with an exposure state; and a signal processing circuit that performs signal processing on an image signal using an image signal of neighboring rows, wherein the setting circuit sets the rows to be read out by the first read-out control according to the gain.