Imaging Apparatus Defocus Calculation Using Light Shielding and Photodiode Pixels
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Solution Overview
Problem
Imaging apparatuses face challenges in accurately calculating defocus amounts in dark environments due to deteriorated S/N ratio of phase difference signals.
Innovation Solution
Incorporating a defocus amount calculation unit that selectively uses output signals from light shielding pixels and photodiode division pixels based on exposure amounts, with light shielding pixels having a pupil division function and photodiode division pixels receiving light fluxes through partial regions of the exit pupil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase difference signals from light shielding pixels or photodiode division pixels are used for defocus detection, then autofocus control can be performed, but the S/N ratio deteriorates in dark environments where light amount is insufficient
Solution Approach 1:
The patent changes the parameter of pixel type selection based on exposure amount. When exposure amount is sufficient, light shielding pixels are used for phase difference detection. When exposure amount is insufficient (dark environment), photodiode division pixels are used instead. This dynamic parameter change adapts to lighting conditions to maintain measurement precision while preserving autofocus capability.
Solution Approach 2:
The patent introduces exposure amount as an intermediary parameter to mediate between the two pixel types. The exposure amount calculation unit measures the light condition, and based on this intermediary value, the system selects the appropriate pixel type for phase difference detection. This intermediary enables smooth transition between pixel types according to lighting conditions.
2Adaptability or versatility
If light shielding pixels are used for phase difference detection, then pupil division function can be achieved, but output signal level becomes smaller compared to photodiode division pixels
Solution Approach 1:
The patent changes the operational parameter (pixel type) based on the parameter (exposure amount) that reflects signal level requirements. Light shielding pixels with pupil division function are selected when exposure amount is sufficient to compensate for their lower output signal level. When exposure amount is low, photodiode division pixels are selected to maintain adequate signal levels.
3Measurement precision
If photodiode division pixels are used for phase difference detection, then higher output signal level is achieved, but pupil division function requires receiving light fluxes through partial regions of exit pupil
Solution Approach 1:
The patent changes the pixel configuration parameter based on exposure amount. When exposure amount is sufficient, the simpler light shielding pixel configuration is used. When exposure amount is low, the photodiode division pixel configuration with partial region light flux reception is employed to achieve higher output signal levels, accepting the increased structural complexity only when necessary.
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
Enables accurate defocus amount calculation and autofocus control even in low-light conditions by optimizing signal selection and pixel configuration, improving focusing accuracy and reliability.
Implementation Method 1
a pixel of a photodiode (PD) division method (a photodiode division pixel)
Implementation Method 2
a light shielding pixel and a photodiode division pixel... a light shielding portion that shields one of a pair of light fluxes
Data Source
AI summary
An imaging apparatus according to the present technology includes an imaging element including a light shielding pixel and a photodiode division pixel, and a defocus amount calculation unit that calculates a defocus amount using at least one of an output signal of the light shielding pixel and an output signal of the photodiode division pixel on the basis of an exposure amount.