Avalanche Diode Pixel Select Unit for Noise Current Reduction
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Solution Overview
Problem
Photoelectric conversion devices using avalanche diodes suffer from signal quality deterioration due to noise currents caused by carrier-capturing levels near intense electric field regions, which existing technologies have not effectively addressed.
Innovation Solution
A photoelectric conversion device is designed with a select unit that controls a pixel to have either a first or a second avalanche diode in an active state, while keeping the other in an inactive state, reducing the occurrence of noise currents by selecting the diode with a smaller noise current and applying appropriate electric potentials to prevent avalanche multiplication in the diode with a larger noise current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If avalanche multiplication is used to detect weak light at single photon level, then detection sensitivity is improved, but noise current occurs due to carrier-capturing levels near intense electric field region causing signal quality deterioration
Solution Approach 1:
The pixel is divided into multiple photoelectric conversion units (first and second avalanche diodes), each with its own intense electric field region. By segmenting the detection function across multiple units and selectively activating only one at a time through the select unit, the system maintains high detection sensitivity while avoiding noise current from simultaneously active units.
Solution Approach 2:
The select unit controls the avalanche diodes to operate in alternating periods - the first avalanche diode is activated during a first period while the second is deactivated, then vice versa. This periodic switching ensures that only one photoelectric conversion unit is in the active state at any given time, preventing noise current generation while maintaining detection capability.
2Productivity
If multiple photoelectric conversion units are operated simultaneously in active state, then detection capability is improved, but noise current increases due to multiple intense electric field regions
Solution Approach 1:
The select unit implements periodic switching control where the first photoelectric conversion unit is activated during a first period and the second unit is activated during a second period, with each unit deactivated during the other's active period. This temporal separation maintains overall detection capability while ensuring that only one intense electric field region exists at any time, thereby preventing noise current.
Solution Approach 2:
While only one photoelectric conversion unit is active at a time, the select unit ensures continuous operation by seamlessly switching between units. The detection function continues without interruption as the select unit manages the alternating activation, maintaining productivity while avoiding the harmful effect of simultaneous active units.
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 configuration significantly reduces the occurrence of noise currents, thereby improving the signal quality and reducing the sensitivity of the photoelectric conversion device.
Implementation Method 1
A Single Photon Avalanche Diode (SPAD) is known as a photo-detection device that can detect a weak light of a single photon level by using avalanche (electronic avalanche) multiplication
Implementation Method 2
an optical charge due to a single photon causes avalanche multiplication
Data Source
AI summary
Provided is a photoelectric conversion device including: a pixel including a plurality of photoelectric conversion units; and a select unit configured to control each of the plurality of photoelectric conversion units to be in an active state or an inactive state. The plurality of photoelectric conversion units has a first group including a first avalanche diode and a second group including a second avalanche diode. The select unit controls the second group to be in the inactive state in a first case of controlling the first group to be in the active state, and the select unit controls the first group to be in the inactive state in a second case of controlling the second group to be in the active state. The pixel has no photoelectric conversion unit which is in the active state in both the first case and the second case.