CCD TDI Readout Optimization via Partial Row Extraction
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Solution Overview
Problem
Interline CCD imagers in TDI mode face inefficiencies due to the need to read out and discard partially exposed rows, which increases readout time and slows down the scanning process, while existing solutions either fail to address this issue or impose limitations such as long minimum exposure times and fixed TDI transfers.
Innovation Solution
The method involves clocking out only the valid rows and moving the partially exposed rows from the trailing side to the leading side for readout, thereby eliminating the need to read out invalid rows and reducing readout time, allowing faster scanning by resuming TDI sequences on partially integrated rows after valid rows have been read out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the entire TOTAL_ROWS rows are transferred out during readout, then all rows including partially exposed ones are read out, but the readout time increases and scanning speed decreases
Solution Approach 1:
The patent extracts and removes the partially exposed trailing rows from the readout sequence. Instead of reading out all TOTAL_ROWS including the N partially exposed rows, the system reads out only the valid exposed rows and discards the partial rows, eliminating wasted readout time and improving scanning speed
Solution Approach 2:
The patent applies discarding by intentionally leaving N trailing rows partially exposed and not reading them out. These discarded partial rows are replaced by exposing new rows during the readout period, effectively recovering useful exposure time without increasing total scan time
2Extent of automation
If TDI transfers are controlled by an internal timebase, then the system operates autonomously, but the TDI shifts cannot be precisely controlled in response to subject motion
Solution Approach 1:
The patent introduces feedback by using an external timebase that can be synchronized with subject motion. The system monitors motion and adjusts TDI transfer timing accordingly, allowing precise control of TDI shifts in response to changing subject positions while maintaining coordinated operation
3Duration of action of stationary object
If the entire TDI shift sequence is controlled by an internal timebase, then the system operates continuously, but the readout of N partially exposed rows becomes wasted time
Solution Approach 1:
The patent extracts the N partially exposed rows from the readout sequence, reading out only the valid exposed rows. This eliminates the wasted time reading out partial rows while maintaining continuous TDI operation for the valid data
Solution Approach 2:
The patent dynamically adjusts the readout sequence to match the actual exposure pattern. By reading out only the valid rows that were fully exposed during TDI transfers and discarding the partial rows, the system optimizes the readout duration while maintaining continuous scanning operation
Data Source
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AI summary
A method for operating a focal plane array in a Time Delay Integration (TDI) mode, the method including: shifting a number of rows during TDI integration, wherein the number of rows shifted is less than a total number of rows of the focal plane array; and reading out a number of rows equal to the total number of rows of the focal plane array minus the number of rows shifted, leaving behind the partially-integrated rows.