CIS Motion Detection Circuit Using Capacitor-Based Frame Comparison
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Solution Overview
Problem
Existing motion detection circuits for CMOS image sensors require analog-to-digital conversion, limiting frame rate and increasing chip area, power consumption, and cost due to the need for additional complex detection circuits.
Innovation Solution
A motion detection circuit using comparator branches with capacitors to compare current and previous frame pixel signals directly, eliminating the need for analog-to-digital conversion and simplifying the circuit structure by reusing the comparator branch in the CIS analog-to-digital conversion circuit, with only two additional capacitors and eight switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog-to-digital conversion is used for motion detection, then motion detection accuracy is improved, but frame rate is reduced due to conversion time limitations
Solution Approach 1:
The patent performs preliminary actions by storing previous frame pixel data in capacitors before the current frame is read out. This allows the comparison to be done in parallel with the analog-to-digital conversion process, eliminating the sequential dependency that limits frame rate while maintaining detection accuracy.
Solution Approach 2:
The patent replaces the mechanical analog-to-digital conversion process with a direct analog comparison mechanism. By using capacitors to hold previous frame data and comparators to perform analog subtraction, the system bypasses the need for sequential digital conversion during the comparison operation, thereby increasing frame rate.
2Adaptability or versatility
If additional detection circuits are added for motion detection, then motion detection capability is improved, but chip area increases
Solution Approach 1:
The patent merges the motion detection function with the existing pixel structure and readout circuitry of the CMOS image sensor. By integrating capacitors into the pixel array and using the same comparator infrastructure, the system adds motion detection capability without requiring separate dedicated detection circuits, thus minimizing chip area increase.
Solution Approach 2:
The patent makes the pixel structure and comparator circuits multi-functional. The same pixels that capture image data also store previous frame data in their capacitors, and the same comparators used for analog-to-digital conversion are reused for motion detection comparisons, eliminating the need for additional specialized circuits.
3Adaptability or versatility
If additional detection circuits are added for motion detection, then motion detection capability is improved, but power consumption increases
Solution Approach 1:
The patent combines the motion detection operation with the existing analog-to-digital conversion process. By performing the comparison operation using the same comparator circuits that are already powered for conversion purposes, the system avoids activating additional power-hungry detection circuits, thereby minimizing power consumption increase.
Solution Approach 2:
The patent makes the powered circuits serve dual purposes: the pixel capacitors store both current and previous frame data, and the comparator circuits perform both analog-to-digital conversion and motion detection comparisons. This multi-functionality ensures that no additional power is required beyond what is already allocated for the standard imaging operation.
4Measurement precision
If complex detection circuits are used for motion detection, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the essential elements needed for motion detection from the complex analog-to-digital conversion process. By isolating the comparison operation and performing it in the analog domain using simple capacitor-storage and comparator circuits, the system achieves accurate motion detection without incorporating complex digital processing or additional detection circuitry.
Solution Approach 2:
The patent replaces complex digital signal processing with simple analog operations. Instead of converting both frames to digital and performing computationally intensive difference calculations, the system uses analog subtraction through capacitor discharge and comparator circuits, dramatically reducing device complexity while maintaining detection accuracy.
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 real-time motion detection without analog-to-digital conversion, shortening detection time and simplifying the circuit structure, reducing area and power consumption while maintaining effective motion detection capabilities.
Implementation Method 1
a previous frame pixel signal sampling branch, one end is connected to the pixel structure output end of the CMOS image sensor through first ends of a first capacitor and a second capacitor connected in series
Implementation Method 2
a comparator branch, which comprises a first comparator branch and a second comparator branch... a comparison result signal for the current frame pixel signal and the first error reference signal, and a comparison result signal for the current frame pixel signal and the second error reference signal are output respectively
Data Source
AI summary
The present invention discloses a motion detection circuit applied to CIS and a motion detection method. Through the current frame pixel signal sampling branch and the previous frame pixel signal sampling branch, the sampling of the current frame and the previous frame pixel signal is respectively controlled, and the previous frame pixel signal is transmitted to the first end of the first capacitor and the second capacitor connected in series, and then the first error reference signal and the second error reference signal related to the pixel signal of the previous frame, which are respectively output by the second ends of the first capacitor and the second capacitor that are not connected, are transmitted to the first comparator branch and the second comparator branch of the comparator branch respectively, by judging the high and low-state of the comparison signals of the current frame pixel signal and the first error reference signal, and the current frame pixel signal and the second error reference signal respectively output by the first comparator branch and the second comparator branch, so as to determine whether an image point reflected by the pixel points of the pixels connected with the motion detection circuit has moved or not.