Image Sensor Live Calibration Using Alternating Dark Frames
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Solution Overview
Problem
Existing image sensor calibration methods require additional production steps, storage space, and logistical efforts, and do not account for varying operating environments and hardware combinations, leading to increased costs and inefficiencies.
Innovation Solution
A live calibration method using alternating bright and dark frames, where dark frames are used to estimate and subtract offsets, eliminating the need for additional production steps and storage, and adapting to the operating environment and hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration is performed in a controlled environment, then calibration data can be obtained, but additional production steps and storage space are required, increasing costs
Solution Approach 1:
The system performs self-calibration by using its own image sensor to capture dark frames during normal operation. The processing unit automatically generates calibration data from these dark frames without requiring external calibration equipment or separate production steps, making the system self-sufficient for calibration purposes
Solution Approach 2:
The system captures dark frames in advance during normal image acquisition and uses these pre-captured frames for calibration. By preparing calibration data beforehand through regular dark frame capture, the system eliminates the need for separate calibration procedures while maintaining accurate calibration
2Measurement precision
If calibration data are stored in the sensor device, then calibration can be performed, but storage space is required, increasing costs per unit
Solution Approach 1:
The calibration functionality is extracted from the image sensor itself and relocated to the processing unit. Instead of storing calibration data in the sensor, the processing unit captures dark frames directly and performs calibration calculations, eliminating the need for dedicated storage space in the sensor device
Solution Approach 2:
The processing unit acts as an intermediary between the image sensor and the calibration function. It receives image signals from the sensor, captures dark frames, generates calibration data, and applies calibration - serving as a mediating component that eliminates the need for storage space in the sensor while maintaining calibration capability
3Ease of manufacture
If calibration is performed in a controlled environment, then initial calibration data are obtained, but it does not account for varying operating environments and hardware combinations
Solution Approach 1:
The calibration system transitions from static controlled-environment calibration to dynamic real-time calibration. By continuously capturing dark frames during actual operation and updating calibration data accordingly, the system adapts to changing operating conditions, temperatures, and hardware variations dynamically
Solution Approach 2:
The system implements feedback by continuously monitoring dark frames during operation and using this information to adjust and update calibration data. The processing unit compares ongoing dark frame measurements with existing calibration data and refines calibration parameters to account for environmental changes and hardware variations
4Measurement precision
If calibration is repeated at certain time intervals, then calibration accuracy is maintained, but dedicated logistics and infrastructure are required
Solution Approach 1:
The calibration process becomes continuous rather than periodic. The system captures dark frames continuously during normal operation and performs real-time calibration updates, eliminating idle calibration intervals and ensuring continuous image quality without disrupting productivity
Solution Approach 2:
The system uses periodic dark frame capture during normal image acquisition to update calibration data. By incorporating calibration actions into the regular image capture cycle, the system maintains calibration accuracy without requiring separate dedicated calibration time or infrastructure
Data Source
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AI summary
A device comprising an offset subtraction unit; an image sensor which receives, for each of a plurality of bright frames, a respective image signal obtained during a respective exposure time of the image sensor, and transmits the same to the offset subtraction unit, and receives, for a dark frame, a respective image signal obtained during a respective exposure time of the image sensor, and transmits the same to the offset subtraction unit; a control unit which ensures that the image sensor alternately transmits a number of bright frames and one dark frame to the offset subtraction unit, wherein an amount of light by which the respective image signal for each of the bright frames is generated is larger than an amount of light by which the respective image signal for the dark frame is generated; the offset subtraction unit obtains an offset based on the image signal of the dark frame and subtracts the offset from a signal based on an image signal of one of the bright frames so as to obtain a calibrated signal, the dark frame and the number of bright frames constituting a sequence of frames directly following each other in time.