Signal Extraction Circuit for Time-of-Flight Sensors
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Solution Overview
Problem
Conventional signal extraction circuits for Time of Flight ranging in image sensors face challenges with area wastage and calculation errors due to multiple capacitors, which also increase data processing demands and errors from capacitance differences.
Innovation Solution
A signal extraction circuit with reduced capacitors, utilizing a single integrating unit with two charging branches and switch units to perform forward and reverse integration, eliminating background light interference and calculating signal extraction results directly, thereby reducing pixel area usage and data processing load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple capacitors are provided to respectively receive electrical charges converted by the signal including the echo signal and the background light, then the background light interference can be eliminated, but the area in the pixel is wasted and calculation errors are caused by capacitance difference
Solution Approach 1:
The patent merges the functions of multiple capacitors into a single integrating unit. The integrating unit performs both forward integration (receiving echo signal + background light) and reverse integration (receiving only background light) that were previously done by separate capacitors. This consolidation eliminates the need for multiple capacitors, saving pixel area while maintaining the ability to eliminate background light interference through differential calculation.
Solution Approach 2:
The single integrating unit is designed to perform multiple functions: it can integrate signals in forward mode, reset to zero, and integrate signals in reverse mode. This multi-functional design replaces what previously required multiple dedicated capacitors, allowing the same hardware component to fulfill multiple roles in the signal extraction process.
2Measurement precision
If multiple capacitors are provided to respectively receive electrical charges converted by the signal including the echo signal and the background light, then the background light interference can be eliminated, but calculation errors are caused by capacitance difference between different capacitors
Solution Approach 1:
By consolidating multiple capacitors into a single integrating unit, the patent eliminates the source of capacitance difference errors. Since there is only one capacitor, there are no variations in capacitance values between different capacitors that could cause calculation errors in the differential measurement process.
3Ease of manufacture
If data obtained by the signal extraction process is transmitted to a post-processing unit for processing, then the signal can be processed, but the data processing amount increases and time is wasted
Solution Approach 1:
The integrating unit performs preliminary signal processing by directly calculating the difference between forward and reverse integration results within the pixel circuit itself. This preliminary action extracts the echo signal component before data leaves the pixel, reducing the amount of data that needs to be processed by external post-processing units and enabling faster overall processing.
4Ease of manufacture
If data obtained by the signal extraction process is transmitted to a post-processing unit for processing, then the signal can be processed, but the data processing amount increases
Solution Approach 1:
The integrating unit performs preliminary signal processing by directly calculating the difference between forward and reverse integration results within the pixel circuit itself. This preliminary action extracts the echo signal component before data leaves the pixel, reducing the amount of data that needs to be processed by external post-processing units and enabling faster overall processing.
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
The solution effectively saves pixel area, reduces calculation errors, and speeds up data processing by eliminating background light interference and calculating signal extraction results within the circuit, improving ranging accuracy and speed.
Implementation Method 1
a signal generating unit connected with a first end of the integrating unit... the signal generating unit is configured to convert a received external signal into an electrical signal
Data Source
AI summary
A signal extraction circuit, a signal extraction method, and a distance measurement method and device. The distance measurement method comprises: performing multiple signal extractions using a circuit in a sensor, so as to obtain multiple extraction results; and determining the distance to a measurement object according to the multiple extraction results. Compared with pixel circuits in the prior art, the signal extraction circuit reduces the number of capacitors by half, thereby significantly increasing effective areas in pixels, and reducing calculation errors resulting from capacitance differences between the various capacitors. Moreover, part of the calculation is completed during the signal extraction, thus reducing the pressure of subsequent data processing, and particularly improving the accuracy and speed of distance measurement during the distance measurement process.