Imaging Device Vertical Line Noise Correction
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Solution Overview
Problem
Conventional imaging devices using solid state image sensors face challenges in reducing vertical line noise due to a small number of lines in the vertical OB region and changes in amplifier gain between frames, leading to incomplete noise reduction and residual noise.
Innovation Solution
The proposed solution involves a vertical line correction unit with an OB line selector, memory, level adjuster, multipliers, and subtractors that adjust and cycle the optical black line signal based on past frame levels and cyclic coefficients to effectively subtract noise from both the optical black and effective pixel regions, ensuring noise reduction and correction residue minimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If line integration (averaging) is performed in the vertical OB region to remove vertical line noise, then random noise is reduced, but if the number of lines in the vertical OB region is small, the averaging次数 is reduced and noise is not sufficiently reduced
Solution Approach 1:
The patent extends the noise reduction approach from spatial averaging (within one frame) to temporal averaging (across multiple frames). By accumulating and averaging vertical OB region signals over multiple frames, the patent effectively increases the number of averaging operations even when the vertical OB region has few lines, thereby reducing noise more effectively.
Solution Approach 2:
The patent implements continuous noise reduction by constantly accumulating signals from the vertical OB region across frames and continuously updating the averaged correction values. This continuous process ensures that noise reduction effectiveness improves over time with each additional frame processed.
2Object-affected harmful factors
If averaging is performed between frames to reduce noise, then noise reduction is improved, but if the amplifier gain changes between frames, residual noise and vertical lines remain
Solution Approach 1:
The patent applies preliminary correction by calculating the gain difference between frames and using this information to pre-adjust the vertical OB region signals before averaging. By anticipating and compensating for gain changes in advance, the patent prevents residual noise and vertical lines from appearing in the corrected image.
Solution Approach 2:
The patent dynamically adjusts the correction process by detecting changes in amplifier gain between frames and modifying the averaging calculation accordingly. When gain changes are detected, the patent applies appropriate scaling factors to maintain accuracy in the noise reduction process.
3Device complexity
If conventional vertical line correction is performed using a small vertical OB region, then device complexity is reduced, but noise reduction is insufficient and correction residue remains
Solution Approach 1:
The patent compensates for the limited spatial dimension (small vertical OB region) by utilizing the temporal dimension (multiple frames). Through frame-by-frame accumulation and averaging, the patent achieves effective noise reduction without requiring a larger vertical OB region, thus maintaining simple device architecture while improving correction performance.
Data Source
AI summary
Of the output signals of a solid state image sensor 101, only the signals in a vertical OB line period are selected by an OB line selector 105. A level adjuster 107 adjusts the level of a past vertical OB line signal read out from the line memory 106 during a first vertical OB line period of a frame where the amplification factor of an amplifier 102 has changed, and outputs the same. A subtractor 109 subtracts the signal whose level has been adjusted from a current vertical OB line signal. A multiplier 111 multiplies, via a selector B 111, the signal after subtraction by a cyclic coefficient K1H for the first vertical OB line period of the frame where the amplification factor has changed. A subtractor 112 subtracts the multiplication result from the current vertical OB line signal, and rewrites the subtraction result to the line memory 106.