Column Select Circuit for Image Sensor Power Reduction
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Solution Overview
Problem
Conventional column readout circuit architectures for image sensors require complex power control and consume excessive power as they read out and process pixel voltages from all columns, even when only a subset is needed, especially when focusing on a window of interest.
Innovation Solution
The proposed solution involves an image sensor apparatus with a pixel array, N parallel column readout circuits, a horizontal shift register, and a column select circuit with N latches, allowing for selective enablement and disablement of column readout circuits using a power down digital control signal, enabling efficient processing of pixel data from specific columns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional column readout circuit architecture reads out and processes pixel voltages of all columns in the analog domain, then complete pixel data can be processed, but power consumption increases and control complexity increases when skipping columns
Solution Approach 1:
The patent divides the column readout circuits into independently controllable units, where each column readout circuit can be selectively enabled or disabled based on whether its corresponding column falls within the window of interest. This segmentation allows the system to process only the necessary columns while maintaining complete data processing capability for the selected columns, thereby reducing power consumption without sacrificing processing reliability for the required data.
Solution Approach 2:
The patent implements dynamic control of column readout circuits through a control signal that can selectively enable or disable each column readout circuit based on the window of interest. This dynamic capability allows the system to adapt its operation to different processing requirements, enabling complete data processing when needed while reducing power consumption by disabling unnecessary columns during window-based processing.
2Adaptability or versatility
If conventional column readout circuit architecture generates separate waveforms for different column readout circuits to support skipping columns, then column skipping function is achieved, but control complexity increases
Solution Approach 1:
The patent employs a universal control signal that can be applied to all column readout circuits simultaneously, eliminating the need for separate control waveforms for different columns. This single control signal provides multi-functionality by enabling the system to handle both full-column processing and window-based processing modes, thereby achieving column skipping functionality without increasing control complexity.
Solution Approach 2:
Instead of generating separate control waveforms for different columns (the conventional approach), the patent inverts the approach by using a single control signal that uniformly controls all column readout circuits. The selectivity is achieved not through different control waveforms but through the circuit architecture itself, which allows the same control signal to effectively enable or disable specific columns based on the window of interest, thereby simplifying control complexity while maintaining adaptability.
3Quantity of substance
If conventional method reads out and processes all column pixel voltages in analog domain first, then all pixel data is available for processing, but power consumption cannot be reduced when only digital pixel values of interest are needed
Solution Approach 1:
The patent extracts only the necessary column readout circuits for processing based on the window of interest, rather than activating all column readout circuits. By taking out (disabling) the unnecessary column readout circuits, the system reduces power consumption while still having all required pixel data available for processing. This extraction approach allows the system to maintain data availability for the window of interest while eliminating power consumption from unnecessary columns.
Data Source
AI summary
A method of image sensor apparatus includes: providing pixel array having pixel units arranged in M rows and N columns; providing N parallel column readout circuits each being arranged for reading out pixel data of one corresponding column; disposing a horizontal shift register in row direction coupled to the N parallel column readout circuits, to receive a pulse signal and a clock signal, sequentially shift a phase of the pulse signal according to the clock signal, and scan a corresponding column according to the shifted phase of the pulse signal; and using a column select circuit having N latches to receive a power down digital control signal transmitted from a microcontroller wherein the power down digital control signal is used to disable at least one column readout circuit to enable and select a portion of the set of N parallel column readout circuits.