Focus Detection Pixel Illuminance Correction via Pre-computed Parameters
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Solution Overview
Problem
Existing focus detection apparatuses face challenges in accurately detecting focus states due to uneven illuminance caused by the optical characteristics of imaging optical systems, which affect the performance of imaging devices.
Innovation Solution
A focus detection apparatus and method that includes an imaging element with focus detection pixels, a correction value calculation unit to calculate optical state-based correction values, and a correction unit to correct pixel signals from focus detection pixels, enabling focus detection based on corrected signals. This solution involves calculating correction values before imaging for still image capturing or focus detection and applying them simultaneously with signal reading to improve focus detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If illuminance correction is performed using optical parameters calculated before imaging, then focus detection accuracy is improved, but processing time is increased
Solution Approach 1:
The patent calculates optical parameters including illuminance correction values before the imaging operation begins. This preliminary calculation allows the correction to be applied during signal reading without adding processing time, as the correction data is already prepared in advance based on the imaging conditions.
Solution Approach 2:
The patent combines the illuminance correction process with the signal reading process from the imaging element. By merging these operations, the correction is applied simultaneously with data acquisition, eliminating separate processing steps and reducing overall processing time while maintaining focus detection accuracy.
2Manufacturing precision
If correction values are calculated based on optical state before imaging, then uneven illuminance is effectively corrected, but device complexity is increased
Solution Approach 1:
The patent changes the approach from hardware-based optical correction to parameter-based software correction. By calculating illuminance correction values as parameters based on optical state (focal length, aperture, subject distance), the system achieves uniform illuminance correction through computational methods rather than complex optical design modifications.
Solution Approach 2:
The patent introduces optical parameters as intermediary elements that mediate between the imaging optical system and the focus detection process. These parameters carry information about illuminance distribution and enable correction without requiring direct modification of the optical system structure, thus reducing overall system complexity.
3Productivity
If focus detection is performed using uncorrected pixel signals, then processing speed is maintained, but focus detection accuracy deteriorates due to uneven illuminance
Solution Approach 1:
The patent performs illuminance correction calculations in advance before focus detection is executed. By preparing correction values beforehand based on the optical state, the actual focus detection process can use these pre-computed values without additional calculation overhead, maintaining processing speed while improving accuracy.
Solution Approach 2:
The patent ensures continuous correction of pixel signals throughout the focus detection process by applying illuminance correction values during signal reading. This continuous correction maintains accurate focus detection results without interrupting or pausing the processing flow, thereby preserving processing speed.
Data Source
AI summary
A focus detection apparatus includes an imaging element includes that a plurality of focus detection pixels, a correction value calculation unit that calculates a correction value used to correct pixel signals based on an optical state before the imaging element performs imaging for still image capturing or imaging for focus detection, a correction unit that performs correction using the correction value simultaneously with reading the pixel signals from the focus detection pixels subsequent to the imaging for the still image capturing or the imaging for the focus detection by the imaging element, and a focus detection unit that performs focus detection based on the corrected pixel signals.