Solid-State Imaging Element Self-Test Circuit
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Solution Overview
Problem
Existing test methods for solid-state imaging elements require a modulation light source and a device to control it, leading to increased system complexity and difficulty in determining abnormalities.
Innovation Solution
A test system that includes an imaging device and a test device with an abnormality determination unit and an abnormal spot identification unit, which generates a test signal and determines abnormalities without using a modulation light source by analyzing detection signals from the imaging device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a modulation light source and control device are used for testing, then abnormality determination can be performed, but system complexity increases and ease of operation deteriorates
Solution Approach 1:
The solid-state imaging element tests itself by using its own pixel circuit to generate test signals and detect abnormalities. The pixel circuit serves dual purposes: normal imaging function and self-test function, eliminating the need for external test equipment.
Solution Approach 2:
The test function is extracted from the pixel circuit by adding a separate test signal generation unit. This allows the pixel circuit to focus on its primary imaging function while the dedicated test unit handles testing, resolving the contradiction between functionality and complexity.
2Reliability
If a modulation light source and control device are used for testing, then abnormality determination can be performed, but ease of operation deteriorates
Solution Approach 1:
The system performs self-testing automatically without requiring external modulation light sources or control devices. The pixel circuit generates its own test signals and determines abnormalities internally, making the testing process simple and easy to operate.
3Device complexity
If internal test signal generation is implemented, then device complexity is reduced, but measurement precision may be affected
Solution Approach 1:
The test signal generation is implemented locally within the pixel circuit itself, with each pixel having its own test signal generation capability. This localized approach maintains measurement precision by ensuring that test signals are generated at the exact location where abnormalities need to be detected, without requiring complex external equipment.
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
Enables easy determination of abnormalities in solid-state imaging elements, reducing system complexity and improving accuracy by eliminating the need for a modulation light source.
Implementation Method 1
Each of the plurality of photodiodes 221 converts incident light into a current signal by photoelectric conversion
Data Source
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AI summary
Presence or absence of an abnormality is easily determined in a solid-state imaging element that detects an address event. The solid-state imaging element includes a photoelectric conversion element, a test signal supply unit, a selection unit, and a comparator. The photoelectric conversion element converts incident light into an electric signal by photoelectric conversion. The test signal supply unit supplies, as a test signal, a signal that fluctuates with time. The selection unit selects either the electric signal or the test signal. The comparator compares a predetermined threshold value with the signal selected by the selection unit, and outputs a result of the comparison.