Solid-State Imaging Element Memory Optimization via Correlated Double Sampling
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Solution Overview
Problem
The increase in memory capacity with the number of sampling times in solid-state imaging elements performing correlated double sampling processing leads to higher costs and increased mounting area, necessitating a reduction in memory capacity.
Innovation Solution
A solid-state imaging element that includes a pixel circuit generating reset and signal levels, an analog-to-digital converter converting these levels into digital data, and an arithmetic circuit that calculates and holds the difference between reset and signal data, optimizing memory capacity by summing the base-2 logarithm of the number of signal levels and exposure times, and using stacked semiconductor substrates for efficient data processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of sampling times is increased to improve correlated double sampling processing, then the sampling accuracy is improved, but the memory capacity increases
Solution Approach 1:
The patent divides the sampling process into multiple stages, where only the necessary data from each sampling operation is stored in the memory. Instead of storing all N samples simultaneously requiring N×B bits, the system processes and stores only the essential difference information, segmenting the data storage requirement to minimize memory capacity while maintaining sampling accuracy.
2Ease of manufacture
If the memory capacity is reduced to decrease cost and mounting area, then the manufacturing cost is reduced, but the ability to perform multiple sampling operations is limited
Solution Approach 1:
The patent performs preliminary processing of the sampled data by calculating the difference between the reset level and signal level immediately after sampling. This preliminary action of computing the difference allows the system to store only the essential result rather than the raw sampled data, enabling multiple sampling operations to be performed with minimal memory capacity while maintaining full functionality.
Data Source
AI summary
An increase in memory capacity is suppressed in a solid-state imaging element that performs correlated double sampling processing. A pixel circuit sequentially generates each of a predetermined reset level and a plurality of signal levels corresponding to the exposure amount. An analog-to-digital converter converts a predetermined reset level into digital data and outputs the data as reset data, converts each of the plurality of pieces of signal data into digital data, and outputs the data as signal data. An arithmetic circuit holds a difference between the reset data and the signal data output first, as held data in a memory, and then adds the held data and the signal data output second and subsequent times together and causes the memory to hold the added data as new held data.