Lock-in Pixel Carrier Steerer for Noise Current Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Light sensors, particularly those used in imaging applications, face challenges with noise currents due to dark current and ambient light, which affect signal quality and increase power consumption.
Innovation Solution
The optical sensing apparatus employs a carrier steerer with p-doped and n-doped regions and gates to control the flow of photo-generated holes and electrons, synchronizing operations to achieve zero-mean noise current by alternating the flow of carriers during specific time periods, thereby reducing noise accumulation in readout circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional light sensors are used to detect optical signals, then photo-generated carriers are collected, but noise current accumulates due to dark current and ambient light
Solution Approach 1:
The patent applies periodic action by alternating the polarity of gate voltages between first and second time periods. During the first time period, the first gate collects holes while the second gate collects electrons. During the second time period, the polarities are reversed. This periodic switching causes dark current and ambient light-generated carriers to produce zero-mean noise current that averages to zero over complete cycles, while signal carriers are collected during specific phases.
Solution Approach 2:
The patent converts the harmful effect of dark current and ambient light into a beneficial outcome by demonstrating that when carrier collection is alternated between holes and electrons over time, these noise sources generate equal positive and negative current contributions that cancel each other out, resulting in zero-mean noise current that does not accumulate in the readout circuit.
2Measurement precision
If noise current is reduced through conventional filtering, then signal quality improves, but power consumption increases
Solution Approach 1:
The patent reduces power consumption by using periodic action to inherently cancel noise current at the sensor level rather than requiring continuous high-power filtering or resetting operations. The alternating gate polarity scheme causes noise currents to self-cancel over complete cycles, eliminating the need for frequent readout circuit resets and reducing overall power consumption while maintaining signal quality.
3Measurement precision
If readout circuits are frequently reset to remove noise accumulation, then signal quality is maintained, but productivity decreases
Solution Approach 1:
The patent eliminates the need for frequent readout circuit resets by implementing periodic action at the carrier collection stage. The alternating gate polarity causes noise currents to accumulate equal positive and negative charges that cancel each other out over complete cycles, preventing noise accumulation in the readout circuit and allowing continuous operation without reset interruptions, thereby improving sensing efficiency.
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 approach results in reduced noise current, lower power consumption, and improved signal quality by ensuring that the average current generated by dark current and ambient light is zero, effectively eliminating the need for frequent reset of readout circuits.
Implementation Method 1
an absorption region configured to receive an optical signal and to generate, in response to the optical signal, photo-generated electrons and photo-generated holes
Implementation Method 2
a first gate configured to control a flow of holes from the absorption region to the first p-doped region, and a second gate configured to control a flow of electrons from the absorption region to the first n-doped region
Data Source
AI summary
An optical sensing apparatus includes an absorption region configured to receive an optical signal and to generate, in response to the optical signal, photo-generated electrons and photo-generated holes, a carrier steerer, and circuitry electrically coupled to the carrier steerer and a controller. The carrier steerer includes a first p-doped region, a first n-doped region electrically shorted with the first p-doped region, a first gate configured to control a flow of holes from the absorption region to the first p-doped region, and a second gate configured to control a flow of electrons from the absorption region to the first n-doped region. The circuitry is configured receive electrical signals from the controller to synchronize operation of the first and second gates so that during a first time period holes flow from the absorption region to the first p-doped region while electrons do not flow from the absorption region to the first n-doped region and during a second time period electrons flow from the absorption region to the first n-doped region while holes do not flow from the absorption region to the first p-doped region.