Solid-State Imaging Device Analog Difference Circuit
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Solution Overview
Problem
Current solid-state image sensing devices face inefficiencies in distance measurement due to the need to convert all photoelectrons into digital signals for ambient light subtraction and difficulty in achieving high integration and reducing thermal noise.
Innovation Solution
A solid-state image sensing device with separate photoelectron storage units for ambient and reflected light, using comparators and a differential circuit to calculate the difference between these signals, reducing the number of counter circuits and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all photoelectrons are converted into digital signals for ambient light subtraction, then distance measurement can be performed, but power consumption increases and noise is amplified
Solution Approach 1:
The patent extracts only the necessary differential signal (reflected light information) from the photoelectron data by performing subtraction in the analog domain before ADC conversion. This eliminates the need to convert and process all photoelectrons digitally, reducing power consumption while maintaining measurement precision for distance calculation.
Solution Approach 2:
The patent performs the subtraction operation in advance (during the analog signal processing stage) before the ADC conversion. By calculating the difference between photoelectron signals from different exposure periods prior to digital conversion, the system avoids the power-intensive operation of converting full photoelectron data to digital signals and then subtracting them digitally.
2Measurement precision
If all photoelectrons are converted into digital signals, then ambient light can be subtracted, but the number of counter circuits and noise increase
Solution Approach 1:
The patent extracts only the essential differential information needed for distance measurement by subtracting analog signals representing photoelectrons from different exposure periods. This approach obtains the reflected light signal without requiring multiple counter circuits to process full photoelectron data, thereby reducing device complexity while maintaining ambient light removal capability.
3Measurement precision
If multiple switches and capacitors are used for storing differential photoelectrons, then ambient light subtraction is enabled, but pixel integration density decreases
Solution Approach 1:
The patent replaces the mechanical/electrical system of multiple switches and capacitors for storing and processing differential photoelectrons with an analog signal processing system. By converting photoelectrons to analog signals and performing subtraction in the analog domain, the design eliminates the need for complex pixel-level switching and capacitance structures, enabling higher pixel integration density while maintaining differential measurement precision.
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 allows for efficient digital signal generation representing the difference in photoelectrons, reducing power consumption and noise, enabling higher integration and accurate distance measurement.
Implementation Method 1
a photoelectric conversion unit that converts light into photoelectrons
Data Source
AI summary
Disclosed is a solid-state imaging device capable of calculating the difference in charge obtained by photoelectric conversion, and capable of a high level of integration. A solid-state imaging device is provided with an AD converter which is provided with: a first comparator which outputs a signal corresponding to a first analog signal of a first pixel by comparing said first analog signal with a reference voltage supplied from the reference voltage generation unit which generates a reference voltage which gradually changes; a second comparator which outputs a signal corresponding to a second analog signal of a second pixel by comparing said second analog signal with the reference voltage supplied by the reference voltage generation unit; a difference circuit which finds the difference between the signal corresponding to said first analog signal and the signal corresponding to said second analog signal and outputs a difference signal; and a counter circuit which counts the number of pulses in a pulse sequence corresponding to the aforementioned difference signal and converts said difference signal into a digital signal.