ToF Image Sensor Background Light Subtraction Circuit
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Solution Overview
Problem
Image sensing devices using time of flight (ToF) technology face challenges in effectively removing background light from depth information signals, leading to inaccurate depth measurements.
Innovation Solution
The proposed image sensing device employs a circuit configuration with specific transmission and coupling circuits to differentiate between reflected light from a subject and background light, allowing for the subtraction of background charges from stored charges during distinct time periods, thereby isolating the pixel signal from background interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ToF technology is used to capture depth information, then depth measurement capability is provided, but background light interference causes inaccurate depth measurements
Solution Approach 1:
The integration period is divided into two distinct time periods: a first time period when the light emitter is activated to capture reflected light from the subject, and a second time period when the light emitter is deactivated to capture only background light. This temporal segmentation allows separate measurement of subject-related signals and background interference, enabling subsequent subtraction to eliminate background effects and improve depth measurement accuracy.
Solution Approach 2:
The patent applies preliminary anti-action by measuring the background light level during the second time period before the final depth calculation is performed. This preliminary measurement of the harmful background light enables its subsequent subtraction from the total light signal, preventing background interference from degrading the depth measurement accuracy.
2Measurement precision
If background light subtraction is implemented to improve depth accuracy, then measurement precision improves, but circuit structure complexity increases
Solution Approach 1:
The patent merges the background light subtraction function directly into the pixel-level circuit structure. The first and second transmission circuits, along with the storage circuit, are integrated within each pixel unit to perform charge transfer and storage operations. This merging approach enables background subtraction at the pixel level without requiring complex external processing circuits, thus improving depth accuracy while maintaining relatively simple overall circuit architecture.
Solution Approach 2:
The storage circuit performs preliminary action by holding the first charges (captured during light emitter activation) until the second charges (captured during light emitter deactivation) are ready for subtraction. This preliminary storage and timing coordination enables the subtraction operation to be performed efficiently at the circuit level, achieving background light removal without requiring complex real-time processing circuits.
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 enables efficient removal of background light, resulting in a more reliable depth information signal and simplifies the circuit structure for integration into pixels, improving the accuracy of depth measurements.
Implementation Method 1
a light detection circuit coupled between a low voltage terminal and a first node
Data Source
AI summary
Disclosed is an image sensing device and an operating method thereof, and the image sensing device may include a light detection circuit coupled between a low voltage terminal and a first node, a first transmission circuit coupled between the first node and a second node, a storage circuit coupled between the second node and a third node, a first coupling circuit coupled between the third node and a high voltage terminal, a second transmission circuit coupled between the third node and the first node, and a second coupling circuit coupled between the second node and the high voltage terminal.