Solid-State Imaging Pixel Signal Addition for Focus Detection
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Solution Overview
Problem
Existing solid-state imaging apparatuses face challenges in achieving adequate sensitivity for focus detection due to the narrow opening in focus detection pixels, which results in lower output signals, and increasing amplification factors can amplify noise, leading to a low signal-to-noise ratio, especially in low brightness conditions, affecting focus detection performance.
Innovation Solution
A solid-state imaging apparatus with a pixel structure where multiple focus detection pixels share a floating diffusion region, allowing the addition of their signals to generate a single added focusing signal, while imaging pixels also share signals but to a lesser extent to maintain high resolution, thereby enhancing sensitivity and focus detection performance without degrading image sharpness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the opening in focus detection pixels is narrowed by a light shielding layer to selectively introduce light flux, then the phase difference detection capability is improved, but the output signal of focus detection pixels becomes smaller compared to imaging pixels, reducing sensitivity
Solution Approach 1:
Multiple focus detection pixels share a common floating diffusion region, merging their photoelectric conversion units into a single signal collection point. This combining approach increases the total light flux collected for focus detection while maintaining the phase difference detection capability provided by the light shielding layer configuration.
Solution Approach 2:
The floating diffusion region serves dual purposes: it collects signals from both imaging pixels and focus detection pixels. By making this component universal, the patent enables both high-resolution imaging and sensitive focus detection without requiring separate dedicated structures for each function.
2Reliability
If the amplification factor of AF pixels is increased to improve sensitivity, then the output signal level is improved, but noise is also amplified, resulting in a low signal-to-noise ratio especially in low brightness conditions
Solution Approach 1:
By combining signals from multiple focus detection pixels at the shared floating diffusion region before amplification, the patent achieves signal integration that improves the signal-to-noise ratio. This merging occurs at the photoelectric conversion stage rather than through post-amplification, avoiding noise amplification while maintaining sensitivity.
Solution Approach 2:
The patent performs signal integration at the floating diffusion region before the amplification stage. This preliminary combining of signals ensures that the amplification process acts on an already-integrated signal with better signal-to-noise characteristics, rather than amplifying individual weak signals that would then be noisy.
3Reliability
If multiple focus detection pixels share a floating diffusion region to increase signal addition, then focus detection sensitivity is improved, but the number of pixels available for high resolution imaging is reduced
Solution Approach 1:
The shared floating diffusion region is designed to accept signals from both imaging pixels and focus detection pixels simultaneously. This universal design allows the same hardware structure to support both high-resolution imaging and sensitive focus detection without requiring separate dedicated pixel arrays.
Solution Approach 2:
The pixel array is segmented into different functional regions: imaging pixels that maintain individual floating diffusion regions for high-resolution imaging, and focus detection pixels that share a common floating diffusion region for sensitive autofocus detection. This segmentation allows each region to be optimized for its specific function.
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 approach improves the sensitivity of focus detection pixels while maintaining high resolution for imaging pixels, especially in low brightness conditions, by selectively adding signals from multiple focus detection pixels and imaging pixels, thus enhancing the overall focus detection and imaging performance.
Implementation Method 1
a plurality of imaging pixels each configured to generate an imaging signal through photoelectric conversion; a plurality of focus detection pixels each configured to generate a focusing signal through photoelectric conversion
Data Source
AI summary
Provided is a solid-state imaging apparatus including: imaging pixels each configured to generate an imaging signal through photoelectric conversion; focus detection pixels each configured to generate a focusing signal through photoelectric conversion; and an adding unit configured to add the imaging signals generated by the imaging pixels to generate an added imaging signal, and configured to add the focusing signals generated by the focus detection pixels to generate an added focusing signal, in which a number of the focusing signals to be used by the adding unit to generate one added focusing signal is larger than a number of the imaging signals to be used by the adding unit to generate one added imaging signal, and operation for outputting the added focusing signal and operation for outputting each of the focusing signals without adding are selectively carried out.