Solid-State Imaging Device Reading Electrode Asymmetry
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Solution Overview
Problem
Conventional solid-state imaging devices experience variations in distance measurement results due to differing dark current levels in signal charges S0, S1, and BG, which can lower distance measurement accuracy.
Innovation Solution
The imaging device positions reading electrodes oppositely in an up-down direction for each column to unify the sources of dark currents, ensuring uniform signal levels for signal charges S0, S1, and BG, thereby reducing errors and variations in distance measurement results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixels are disposed in a checkered pattern to improve horizontal and vertical resolutions, then resolution improves, but dark current variations occur in signal charges S0, S1, and BG leading to reduced distance measurement accuracy
Solution Approach 1:
The patent applies asymmetry by positioning reading electrodes alternately on opposite sides (above or below) of photoelectric conversion units in a checkered pattern. Specifically, first reading electrodes are positioned above first photoelectric conversion units while second reading electrodes are positioned below second photoelectric conversion units, creating an asymmetric but systematic arrangement that ensures all dark currents originate from uniform sources
Solution Approach 2:
The patent achieves equipotentiality by ensuring that all reading electrodes are positioned at equivalent distances from their respective photoelectric conversion units. This symmetric positioning relative to the photoelectric conversion units ensures that dark currents generated under each reading electrode have uniform signal levels, eliminating variations that would otherwise reduce measurement accuracy
2Ease of operation
If reading electrodes are positioned to read signal charges from photoelectric conversion units, then signal charge reading is enabled, but dark current components vary across different signal charges S0, S1, and BG
Solution Approach 1:
The patent applies local quality by making the reading electrode positioning specific to each photoelectric conversion unit's location. Each reading electrode is positioned locally above or below its corresponding photoelectric conversion unit in a checkered pattern, ensuring that dark current characteristics are uniform across all local reading positions while maintaining the ability to read signal charges from all pixels
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 improves distance measurement accuracy by eliminating dark current components from the calculation, leading to more precise distance measurements.
Implementation Method 1
Each of the pixels includes a photoelectric conversion unit that converts the incident light into a signal charge
Implementation Method 2
The solid-state imaging device uses a time of flight method (TOF method) as an operation principle of a distance measuring camera. The solid-state imaging device emits pulsed infrared light, and receives reflected light of the infrared light from a subject
Data Source
AI summary
Each of pixels disposed in a matrix form on a substrate includes a photoelectric conversion unit that converts incident light into a signal charge, a reading electrode that reads the signal charge from the photoelectric conversion unit, and a vertical transfer electrode that constitutes a vertical transfer unit. A plurality of first pixels, and a plurality of second pixels disposed adjacent to the first pixels are alternately disposed for each row, and also alternately disposed for each column to form a checkered pattern. The reading electrode of each of the pixels is disposed such that a plurality of signal charges read from the identical photoelectric conversion unit contain a dark current generated under the common reading electrode.