Imaging Apparatus Focus Detection With Signal Suppression
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Solution Overview
Problem
Conventional imaging techniques face distortion and incorrect focus detection due to signal saturation when increasing ISO sensitivity, leading to inaccurate phase difference calculations between pupil-divided images.
Innovation Solution
An imaging apparatus with a focus adjustment unit that includes a subtraction unit to generate a second image signal by subtracting a first image signal from an addition signal, and a suppression unit to limit the first image signal to a predetermined value, ensuring accurate focus detection even in saturated conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gain is increased to achieve higher ISO sensitivity, then sensitivity is improved, but signal waveform distortion occurs due to saturation
Solution Approach 1:
The patent applies preliminary action by suppressing the first image signal before the subtraction operation. The suppression unit limits the first image signal to a predetermined value (saturation level or half of saturation level) before it is subtracted from the addition signal by the subtraction unit. This preliminary suppression prevents saturation distortion from occurring in the final second image signal, thereby maintaining signal waveform accuracy while enabling higher ISO sensitivity operation.
2Productivity
If the first image signal is not suppressed, then the subtraction operation can be performed with full signal range, but saturation causes the second image signal to become zero or distorted
Solution Approach 1:
The patent applies preliminary anti-action by proactively suppressing the first image signal to prevent the harmful effect of saturation. The suppression unit limits the first image signal to a predetermined value before the subtraction operation, which prevents the scenario where the first signal would exceed the addition signal and cause the second image signal to become zero or distorted. This preliminary countermeasure ensures that the subtraction operation always produces valid, non-zero results with accurate phase difference information.
3Power
If both addition signal and first image signal reach saturation level, then maximum signal values are obtained, but the second image signal becomes zero making focus detection impossible
Solution Approach 1:
The patent applies preliminary action by suppressing the first image signal to a predetermined value (saturation level or half of saturation level) before the subtraction operation. This ensures that even when the addition signal reaches its maximum capacity, the first image signal is already limited to a value that guarantees the second image signal will remain positive and non-zero. This preliminary suppression preserves the dynamic range needed for accurate phase difference calculation and maintains focus detection capability.
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 suppresses image signal distortion and maintains accurate focus detection by limiting the first image signal, allowing for reliable phase difference calculations and improved focus detection accuracy at higher ISO sensitivities.
Implementation Method 1
an image sensor configured of an imaging pixel having a plurality of photoelectric conversion units
Data Source
AI summary
In a configuration in which a non-saturated readout value of a division pixel is subtracted from an addition signal of division pixels, an imaging apparatus capable of performing focus detection with respect to a saturated signal is provided. The imaging apparatus includes a subtraction unit and a suppression unit. The subtraction unit obtains the second image signal by subtracting the first image signal output from the image sensor from an addition signal acquired as a sum of the first image signal and the second image signal output from the image sensor, and the suppression unit suppresses the first image signal to a value equal to or less than a predetermined value.