Sample-and-Hold Readout Sequencing for Fixed Pattern Noise Reduction
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Solution Overview
Problem
Sample and hold systems in optical sensor applications, such as LIDAR, face challenges in reducing fixed pattern noise, which cannot be suppressed by averaging techniques, affecting the system's range and noise levels.
Innovation Solution
A sample and hold system that alters the acquisition and readout order of samples in a sample and hold array, either randomly or in predefined sequences, to smear out fixed pattern noise, allowing for reduced noise levels by averaging or accumulating samples across different unit cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a sample and hold array is used to sample traces from multiple optical sensors, then the die area and power consumption are reduced, but fixed pattern noise increases due to systematic errors in specific unit cells
Solution Approach 1:
The patent applies dynamics by making the acquisition order and readout order variable rather than fixed. The controller dynamically changes the mapping between optical sensors and unit cells across different traces, so that systematic errors in specific unit cells do not consistently affect the same sensors. This dynamic reordering smears out fixed pattern noise while maintaining the area-efficient sample and hold architecture.
Solution Approach 2:
The patent changes the parameter of ordering sequence by varying the acquisition order and readout order from trace to trace. Instead of using a fixed sequential order, the system employs different permutations of unit cell addressing, which transforms the consistent fixed pattern noise into a more random distribution that can be reduced through averaging.
2Measurement precision
If averaging techniques are used to reduce time dependent noise, then temporal noise is reduced, but fixed pattern noise remains unaffected
Solution Approach 1:
By dynamically changing the acquisition and readout orders between traces, the patent ensures that when averaging is performed, the fixed pattern noise from different unit cells is combined rather than reinforced. This dynamic reordering converts fixed pattern noise into a form that benefits from averaging, complementing the existing temporal noise reduction technique.
Solution Approach 2:
The patent creates multiple copies of the sampling process with different ordering sequences. Each trace is acquired with a unique permutation of unit cell addressing, generating varied copies of the measurement data that, when averaged, cancel out fixed pattern noise while preserving the underlying signal.
3Object-generated harmful factors
If the acquisition order and readout order are changed from trace to trace, then fixed pattern noise is smeared out and reduced, but the system complexity increases
Solution Approach 1:
The patent implements periodic action by using predetermined repeating patterns for acquisition and readout orders. Instead of requiring complex real-time optimization, the system cycles through a set of predefined ordering sequences, which simplifies the controller logic while still achieving effective noise smearing over multiple traces.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing multiple valid acquisition and readout order sequences in the controller. This allows the system to select from predetermined patterns rather than computing optimal orders in real-time, reducing the computational complexity while maintaining the noise reduction benefit.
Data Source
AI summary
A sample and hold system, for capturing and reading a sequence of traces of an input signal. The sample and hold system comprising a readout device, a controller, and a sample and hold array of unit cells. The controller is configured for controlling the sample and hold system, such that during an acquisition phase a trace of samples is taken from the input signal in an original sample order and such that the samples are held in the unit cells wherein the samples are assigned to the unit cells in an acquisition order, such that during a consecutive readout phase the samples are read out from the unit cells wherein the order in which the unit cells are read out corresponds with a readout order, and such that the acquisition order and/or the readout order differs from trace to trace.