Pixel Circuit Pulse-Width Output for Analog Optical Sensing
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Solution Overview
Problem
Conventional optical sensors require digital frame buffers to store pixel data, necessitating a solution for performing operations on pixel data at the analog phase without initial digital conversion.
Innovation Solution
A pixel circuit that utilizes a photodiode and temporal circuits with capacitors and transistors to output pulse width signals corresponding to detected light energy, enabling pixel-wise operations such as intra-pixel and inter-pixel operations without digital conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If optical sensor outputs voltage values for digital conversion, then digital image processing can be performed, but frame buffers are required to store pixel data increasing device complexity
Solution Approach 1:
The patent extracts the frame buffer function from the digital backend and implements temporal integration directly in the pixel circuit at the analog phase. The capacitor in the pixel circuit stores charge representing light energy over time intervals, eliminating the need for separate frame buffers in the digital domain.
Solution Approach 2:
The patent performs temporal integration and pixel-wise operations on light energy data before digital conversion. The analog circuit performs subtraction operations between light energy detected in different time intervals, preparing processed data in advance before ADC conversion, thus eliminating the need for frame buffers to store raw pixel data.
2Productivity
If pixel data is converted to digital format first, then processing operations can be performed, but analog operation capability is lost
Solution Approach 1:
The patent implements periodic temporal sampling of light energy using control signals that enable the pixel circuit to detect and integrate light energy in alternating time intervals. This periodic action allows the analog circuit to perform temporal differentiation operations, comparing light energy between consecutive time intervals to detect motion or changes.
Solution Approach 2:
The pixel circuit is designed to perform multiple functions in the analog domain: temporal integration of light energy, temporal differentiation by comparing consecutive intervals, and pixel-wise operations such as summation and subtraction. This multi-functionality at the analog phase eliminates the need for separate digital processing stages.
3Reliability
If frame buffers are used to store pixel data, then digital processing can be performed, but memory resources are consumed
Solution Approach 1:
The patent replaces the mechanical/electronic frame buffer memory system with an analog charge storage system using capacitors in the pixel circuit. The light energy information is stored as electrical charge in capacitors during the integration period, eliminating the need for digital memory resources while maintaining data availability for 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
Enables analog operations on pulse width signals, reducing the need for digital conversion and frame buffers, allowing for efficient processing of light energy variations over different time intervals.
Implementation Method 1
a photodiode and a temporal circuit. The temporal circuit is coupled to the photodiode
Data Source
AI summary
There is provided a pixel circuit for performing analog operation including a photodiode, a first temporal circuit, a second temporal circuit and an operation circuit. Within a first interval, the photodiode detects first light energy to be stored in the first temporal circuit. Within a second interval, the photodiode detects second light energy to be stored in the second temporal circuit. Within an operation interval, the first temporal circuit outputs a first detection signal having a first pulse width according to the first light energy and outputs a second detection signal having a second pulse width according to the second light energy for being calculated by the operation circuit.