Image Sensor Readout Circuit Amperage Control
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Solution Overview
Problem
Image sensors with phase difference focus detection require increased readout time and energy consumption, leading to higher temperatures and reduced imaging duration due to the need to acquire signals from two photodiodes per pixel.
Innovation Solution
An image capturing apparatus with a readout unit driven by two methods: one for partial and another for multiple photoelectric conversion portions, with adjustable current supply to optimize energy usage based on operational conditions such as focus detection region, temperature, sensitivity, and frame rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If signals are read out from two photodiodes per pixel for phase difference focus detection, then focus detection capability is improved, but readout time increases twofold
Solution Approach 1:
The patent dynamically switches between two driving methods based on operational conditions: a first driving method that reads signals from only one photodiode per pixel for reduced readout time, and a second driving method that reads signals from both photodiodes for phase difference focus detection. This dynamic adaptation resolves the contradiction by selecting the appropriate readout strategy based on whether focus detection is currently needed.
2Adaptability or versatility
If signals are read out from two photodiodes per pixel, then phase difference focus detection is enabled, but energy consumption increases
Solution Approach 1:
The patent implements dynamic control of the readout circuit's driving current based on operational mode. When operating in the first driving method (reading from one photodiode), a reduced amperage is supplied to minimize energy consumption. When switching to the second driving method (reading from both photodiodes for focus detection), the amperage is increased to maintain signal quality. This dynamic current adjustment resolves the energy consumption contradiction.
3Speed
If readout time increases due to reading from two photodiodes, then frame rate is maintained, but standby time per frame decreases, increasing heat generation
Solution Approach 1:
The patent employs periodic switching between two readout strategies: using the first driving method (reading from one photodiode) during normal image capture to minimize readout time and heat generation, and periodically switching to the second driving method (reading from both photodiodes) when focus detection is required. This periodic action pattern allows the system to maintain frame rate while controlling overall heat generation by limiting the duration of high-power operations.
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
Reduces energy consumption and heat generation, extending the imaging duration while maintaining focus detection accuracy and image quality.
Implementation Method 1
a plurality of photoelectric conversion portions for each of a plurality of microlenses
Data Source
AI summary
An image capturing apparatus including a plurality of photoelectric conversion portions for each of a plurality of microlenses, the image capturing apparatus comprising: a readout unit configured to be driven using a first driving method in which a signal is read out from part of the plurality of photoelectric conversion portions, and a second driving method in which a signal is read out from a greater number of the photoelectric conversion portions than in the first driving method; and a supply unit configured to, in a case where a signal is read out using the first driving method, supply an amperage that is smaller than that in a case where a signal is read out using the second driving method, to the readout unit.