Image Sensor Readout Control for Black Level Adjustment
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Solution Overview
Problem
Conventional image capturing apparatuses with condensing optical systems and image sensors face challenges in accurately adjusting black levels due to differences in signal levels when reading out image signals, leading to degraded image quality, especially when incident light is zero.
Innovation Solution
An image capturing apparatus with a readout control circuitry that separates or adds image signals from photoelectric conversion portions, using a determination circuitry to identify the readout method and adjust the black level accordingly, ensuring accurate black level correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image signals are independently read out from multiple photoelectric conversion portions in every pixel portion, then focus detection accuracy is improved, but the number of pixels to be read out increases
Solution Approach 1:
The image sensor is divided into a focus detection area and a non-focus detection area. In the focus detection area, multiple photoelectric conversion portions are independently read out for accurate focus detection. In the non-focus detection area, signals from multiple photoelectric conversion portions are added together before readout, reducing the number of pixels to be read out while maintaining overall system efficiency.
2Productivity
If signals from multiple photoelectric conversion portions are added together in non-focus lines, then the number of readout pixels is reduced, but black level adjustment accuracy deteriorates
Solution Approach 1:
Different signal processing methods are applied to different areas: in the focus detection area, signals are independently read out, while in the non-focus detection area, signals are added together. Additionally, different black level adjustment methods are applied: first black level adjustment is performed on individual line signals, and second black level adjustment is performed on the added signal from multiple lines, ensuring accurate black level adjustment despite the addition operation.
3Device complexity
If image signals are added together before readout, then readout complexity is reduced, but signal level differences cause black level adjustment errors
Solution Approach 1:
First black level adjustment is performed on each line signal before the addition operation. This preliminary adjustment ensures that each individual line signal has its black level correctly adjusted, so that when signals are added together, the black level adjustment accuracy is maintained despite the addition operation.
Solution Approach 2:
Second black level adjustment is performed on the added signal from multiple lines. This feedback mechanism compensates for any black level adjustments that may have been affected by the addition operation, ensuring final black level accuracy in the recorded image signal.
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 corrects black level differences and improves image quality by accurately adjusting the black level of added image signals, enhancing the accuracy of black level adjustment processing.
Implementation Method 1
an image sensor including a plurality of photoelectric conversion portions for each of a plurality of microlenses
Data Source
AI summary
An image capturing apparatus comprises an image sensor including a plurality of photoelectric conversion portions for each of a plurality of microlenses, performs readout control using one of a first readout method of reading out a plurality of image signals from the plurality of photoelectric conversion portions corresponding to each of the microlenses, and a second readout method of reading out an added image signal from the plurality of photoelectric conversion portions corresponding to each of the microlenses, determines whether an image signal is read out using the first readout method or the second readout method, adds the plurality of image signals read out using the first readout method, and adjusts the added image signal obtained through the addition by an increased amount of the black level that has increased due to the addition as an adjustment value.