Image Sensor Diagnostic Pixels for Readout Fault Detection
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Solution Overview
Problem
Image sensors used in safety-critical systems face challenges in detecting faults in row and column readout order, row and column selection control lines, and ADCs, which can lead to inaccurate and unsafe operations.
Innovation Solution
Incorporation of diagnostic pixels within the image sensor that are coupled to reference voltages, allowing for the detection of faults by comparing diagnostic signals with predetermined reference values, enabling the identification of correct readout order and detection of errors in control and readout circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional image sensor readout circuitry is used without diagnostic pixels, then device complexity is reduced, but reliability deteriorates due to inability to detect faults in readout order and control lines
Solution Approach 1:
The patent merges diagnostic functionality with the existing image sensor pixel array by incorporating diagnostic pixels that share the same readout circuitry, control lines, and ADCs as the imaging pixels. This integration allows fault detection without adding separate diagnostic circuitry, resolving the contradiction between reliability improvement and device complexity increase.
Solution Approach 2:
The diagnostic pixels are designed to be read out using the same control and readout circuitry as the imaging pixels, making the circuitry universal for both imaging and diagnostic functions. This multi-functionality approach enables fault detection while avoiding additional dedicated diagnostic circuitry, thus improving reliability without significantly increasing device complexity.
2Reliability
If diagnostic pixels are integrated into the image sensor, then reliability improves through fault detection, but manufacturing precision requirements increase
Solution Approach 1:
The diagnostic pixels are designed with the same structure and characteristics as the imaging pixels, using identical photodetectors, control lines, and readout circuitry. This homogeneity ensures that diagnostic pixels can be manufactured using the same processes as imaging pixels, maintaining manufacturing precision standards while enabling reliability improvement through fault detection.
3Measurement precision
If no diagnostic pixels are used, then ease of manufacture is improved, but measurement precision deteriorates due to inability to verify readout accuracy
Solution Approach 1:
The diagnostic pixels enable the image sensor to self-verify its readout accuracy by comparing the readout values of diagnostic pixels (which have known reference values) against expected values. This self-diagnostic capability provides measurement precision verification without requiring external diagnostic equipment or complex manufacturing processes, thus improving measurement precision while maintaining ease of manufacture.
Data Source
AI summary
The present disclosure relates to imaging systems having functionality for detecting faults in the control and/or readout of the image sensor. In one example, there is a system comprising an image sensor having a plurality of imaging pixels and at least one diagnostic pixel coupled to a reference signal. The system also comprises control and readout circuitry configured to select one or more of the imaging pixels and, for each selected imaging pixel, readout an imaging signal that is indicative of the charge accumulated on the selected imaging pixel, select the at least one diagnostic pixel and, for each selected diagnostic pixel, readout a diagnostic signal that is indicative of the reference signal of the selected diagnostic pixel, and output the diagnostic signal for use in system diagnostics.