Image Sensor Multi-Standard Operation via Line Interpolation
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Solution Overview
Problem
Existing image sensors face challenges in supporting multiple video standards like NTSC and PAL/SECAM due to differences in frame rate and visible scan lines, leading to increased costs and complexity when trying to develop single products compatible with both standards.
Innovation Solution
A system that uses a single pixel array with NTSC frame resolution, incorporating a line buffer and digital image processor to interpolate and duplicate pixel data, allowing the image sensor to operate in both NTSC and PAL modes with reduced costs and complexity by reading out pixel data in an unconventional sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single image sensor is designed to support both NTSC and PAL video standards, then the adaptability of the sensor is improved, but the device complexity increases due to the need for additional line buffers and complex PLL circuits
Solution Approach 1:
The image sensor is designed with a pixel array and timing controller that can operate in multiple video standards (NTSC, PAL, SECAM) without requiring separate dedicated circuits for each standard. The timing controller dynamically adjusts the readout timing and line interpolation based on the selected standard, making the same hardware serve multiple functions.
Solution Approach 2:
The sensor changes operational parameters such as frame rate (29.97fps for NTSC, 25fps for PAL), lines per frame (525 for NTSC, 625 for PAL), and visible raster lines (480 for NTSC, 576 for PAL) by reconfiguring the timing controller and pixel array readout sequence, allowing adaptation to different standards without physical hardware changes.
2Adaptability or versatility
If the pixel array is designed with PAL resolution (625 lines) to support PAL standard, then the adaptability for PAL is improved, but the sensor area increases by 25% compared to NTSC-sized sensors
Solution Approach 1:
The patent segments the 625-line PAL standard into two parts: the actual pixel array reads only 480 lines (NTSC resolution), and the remaining 145 lines are generated through line interpolation using stored pixel data. This segmentation allows the physical sensor to be smaller while still producing PAL-compatible output.
Solution Approach 2:
The patent creates virtual copies of pixel data through line interpolation, where missing lines in the PAL output are synthesized by copying and interpolating data from adjacent lines stored in the line buffer. This allows PAL resolution to be achieved without physically capturing all 625 lines with sensor pixels.
3Productivity
If line interpolation is performed to generate additional lines for PAL mode, then the number of output lines is increased to comply with PAL specification, but the processing complexity increases
Solution Approach 1:
The timing controller performs preliminary actions by storing pixel data from each line in the line buffer immediately after reading, preparing the data in advance for interpolation. This preliminary storage and organization of data simplifies the subsequent interpolation process, as all necessary source data is already available and properly organized.
Data Source
AI summary
An image sensor system and associated method supporting multiple video output standards, such as NTSC and PAL, including a pixel array corresponding in size to the frame size having a smaller line number of the video standards, is described. System and method for resolving discrepancies between standards includes multiple crystal oscillators or frequency synthesis to derive a dot clock, and a standard-specific pixel read-out scheme that provides additional lines when outputting according to the frame size having a larger line number of the video standards. In an embodiment, additional line video data is derived by duplicating a line of image data, and in an alternative embodiment additional line video data is derived by digital vertical interpolation.