CMOS Image Sensor Pixel Voltage Attenuator for Dynamic Range
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CMOS image sensors face limitations in utilizing their dynamic range effectively, particularly in multi-sum modes where pixel voltages exceed the input range of comparators, leading to insufficient dynamic range utilization.
Innovation Solution
Incorporating a voltage attenuator that adjusts pixel voltages by a predetermined ratio in multi-sum modes, using a voltage division method to ensure the adjusted voltages are within the input range of comparators, thereby allowing for the full utilization of the dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel binning is used to combine charges from multiple pixels, then sensitivity is improved, but the dynamic range is reduced due to voltage overflow
Solution Approach 1:
The voltage attenuator serves as an intermediary component between the pixel circuit and the comparator. It receives the output signal from the pixel circuit and attenuates the pixel voltage by a predetermined ratio (e.g., 1/2 or 1/4) before transmitting it to the comparator. This prevents voltage overflow while preserving the signal information, allowing the system to maintain both high sensitivity through pixel binning and full dynamic range utilization.
Solution Approach 2:
The invention changes the voltage parameter by introducing a voltage attenuator that modifies the pixel voltage level. The attenuator adjusts the voltage by a predetermined ratio based on the binning mode (e.g., 2x binning uses 1/2 ratio, 4x binning uses 1/4 ratio), transforming the high-voltage overflow condition into a suitable voltage range for the comparator, thereby enabling full dynamic range utilization.
2Device complexity
If pixel voltages are directly input to comparator, then device complexity is minimized, but dynamic range utilization is insufficient due to voltage exceeding input range
Solution Approach 1:
The voltage attenuator is inserted as an intermediary component between the pixel circuit and the comparator. Although this adds one component to the circuit, it enables full dynamic range utilization by preventing voltage overflow. The attenuator's simple voltage division function (using resistors or transistor-based circuits) keeps the added complexity minimal while achieving the goal of utilizing the full comparator input range.
3Adaptability or versatility
If voltage attenuator is added to adjust pixel voltages, then dynamic range utilization is improved, but device complexity increases
Solution Approach 1:
The voltage attenuator implements parameter change by adjusting the voltage level through a predetermined ratio based on the binning mode. The attenuator can be implemented using simple resistor voltage dividers or transistor-based circuits that provide the required attenuation (1/2 for 2x binning, 1/4 for 4x binning) without requiring complex control logic or additional processing stages, thus minimizing the increase in device complexity.
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 solution enables the CMOS image sensor to effectively use its dynamic range, improving signal-to-noise ratio and image quality by ensuring pixel voltages are within the comparator's input range, even in high-sensitivity or low-illumination conditions.
Implementation Method 1
using a voltage division method to ensure the adjusted voltages are within the input range of comparators
Implementation Method 2
each pixel including photoelectric conversion element and structured to receive incident light and output an output signal having pixel voltages in response to the received incident light
Data Source
AI summary
A pixel apparatus may include a pixel circuit and a voltage attenuator. The pixel circuit includes multiple pixels, each pixel including photoelectric conversion element. The pixel circuit is structured to receive incident light and output an output signal having pixel voltages in response to the received incident light. The pixel circuit operates in at least one of a quad mode outputting the output signal based on photocharges from a single photoelectric conversion element only and a multi-sum mode outputting the output signal based on photocharges from multiple photoelectric conversion elements. The voltage attenuator is coupled to the pixel circuit. The voltage attenuator can be enabled, when the pixel circuit operates in the multi-sum mode, to receive the output signal and adjust the pixel voltages of the output signal by a predetermined ratio determined by the multi-sum mode.