Image Pickup Apparatus Black Level Correction for Dark Current
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Solution Overview
Problem
Existing image pickup apparatuses face challenges in properly correcting the black level, particularly due to differences in dark current between normal rows and AF rows, leading to suboptimal image quality.
Innovation Solution
The apparatus employs a correction processing unit that generates distinct correction values for signals read in different modes from unit pixels in a pixel array, using signals from a reference pixel area to correct signals in light-receiving pixel areas, thereby addressing the black level correction across varying dark current conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single correction value is used for all unit pixels regardless of reading mode, then the device complexity is reduced, but the black level cannot be corrected properly due to different dark current characteristics between normal rows and AF rows
Solution Approach 1:
The patent segments the correction value generation into two distinct processes: one for normal rows (first row group) and another for AF rows (second row group). The correction value generating unit generates a first correction value for normal rows and a second correction value for AF rows, recognizing that these two row types have different dark current characteristics and require different correction approaches. This segmentation resolves the contradiction by maintaining separate correction mechanisms for each row type.
Solution Approach 2:
The patent applies local quality by providing different correction values tailored to specific row types. Unit pixels in normal rows receive a first correction value, while unit pixels in AF rows receive a second correction value. This localized correction approach ensures that each row type is corrected according to its specific characteristics, improving black level correction accuracy without requiring a single complex universal correction mechanism.
2Measurement precision
If separate correction values are generated for normal rows and AF rows, then the black level correction accuracy is improved, but the device complexity increases due to multiple correction value generation processes
Solution Approach 1:
The correction value generating unit is designed with multi-functionality, serving both normal rows and AF rows through a single integrated component. This unit can generate both the first correction value for normal rows and the second correction value for AF rows, eliminating the need for separate correction value generation devices. This universal approach reduces device complexity while maintaining the accuracy benefits of separate correction values.
Solution Approach 2:
The patent merges the correction value generation functions for normal rows and AF rows into a single correction value generating unit. By combining these functions, the patent avoids the complexity of having separate correction mechanisms while still providing differentiated correction values. The merging is achieved through a unified correction processing unit that handles both row types with appropriate correction strategies.
3Device complexity
If all unit pixels are read in the first mode (combined electric charges), then the image pickup process is simplified, but focus detection capability is lost
Solution Approach 1:
The patent implements dynamic reading capabilities where the reading mode can be changed based on the desired function. Unit pixels can be read in the first mode (combining electric charges from multiple photoelectric converters) for normal image pickup, or switched to the second mode (reading electric charges from individual photoelectric converters) for focus detection. This dynamic switching allows the system to adapt between different operational requirements without sacrificing either simplicity or functionality.
Solution Approach 2:
The patent employs periodic switching between different reading modes. During normal operation, unit pixels are read in the first mode for simplified image pickup. Periodically, when focus detection is required, the system switches to the second mode to read electric charges from individual photoelectric converters. This periodic action between different reading modes allows the system to maintain simplicity while periodically performing focus detection functions.
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 effectively corrects the black level in both normal and AF rows, ensuring improved image pickup by accounting for differences in dark current, resulting in enhanced image quality.
Implementation Method 1
two photodiodes are provided for one pixel associated with one microlens. The photodiodes therefore receive light fluxes that have passed through different areas of an exit pupil of a photographic lens.
Data Source
AI summary
An image pickup apparatus, including: a pixel array in which a first row group is to be read in a first mode for reading a signal corresponding to combined electric charges that are obtained by combining electric charges generated by the plurality of photoelectric converters, and a second row group is to be read in a second mode for reading a signal corresponding to electric charges that are generated by any one of the plurality of photoelectric converters; a correction value generating unit configured to generate a first and a second correction value for correcting a signal that is read in the first and the second mode, respectively, a correction unit configured to correct, by using the first correction value, the signal that is read in the first mode, and to correct, by using the second correction value, the signal that is read in the second mode.