Image Sensor Overlapping Pixel Readout for Frame Rate
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Solution Overview
Problem
The frame rate of image sensors is limited by the throughput rate of the column bus and signal processing circuit, with increasing the number of parallel column lines hindered by reduced light sensitivity and dynamics due to coverage of the light-sensitive surface.
Innovation Solution
Implementing a control device that allows the selection device of one pixel to be activated during the switching process of another pixel on the same column line, enabling temporal interleaving of read-out processes to efficiently use column lines, thereby increasing the frame rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of parallel column lines is increased to increase throughput rate, then the frame rate is improved, but the light sensitivity and dynamics are reduced due to coverage of the light-sensitive surface
Solution Approach 1:
The patent applies preliminary action by performing read-out preparation steps (such as charge transfer from photodiode to floating diffusion, reset operations) before the actual read-out step. This allows the column line to be utilized more efficiently by overlapping preparation activities of one pixel with the read-out activity of another pixel, thereby increasing frame rate without adding parallel column lines that would reduce light sensitivity
Solution Approach 2:
The patent implements continuity of useful action by ensuring that the column line remains continuously utilized through temporal interleaving. While one pixel is being read out, the same column line is simultaneously used for preparation steps of other pixels, eliminating idle time and maximizing throughput without requiring additional physical column lines
2Productivity
If the throughput rate of the column bus is increased by adding parallel column lines, then the frame rate is improved, but the device complexity increases
Solution Approach 1:
By performing preparation steps before read-out, the patent enables a single column line to handle multiple pixels' data through time-division multiplexing, avoiding the need for additional parallel column lines and thus reducing device complexity while maintaining high frame rate
Solution Approach 2:
The patent transitions from spatial parallelism (multiple column lines) to temporal parallelism (overlapping operations in time). This dimensional shift allows achieving the same throughput increase without adding physical column lines, thereby reducing device complexity
3Productivity
If the throughput rate of the signal processing circuit is increased by adding parallel circuits, then the frame rate is improved, but the device complexity and area increase
Solution Approach 1:
The patent performs signal preparation and conditioning operations before the actual read-out step, allowing the signal processing circuit to work continuously without idle time. This temporal optimization increases effective throughput without requiring additional parallel processing circuits, thus reducing the required circuit area
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly enhances the frame rate of the image sensor by overlapping read-out and preparation steps across pixels, optimizing the use of column lines and maintaining high light sensitivity and dynamics.
Implementation Method 1
Each pixel includes a light-sensitive detector element to produce an electric charge from incident light
Data Source
AI summary
An image sensor for electronic cameras includes a plurality of pixels arranged in rows and columns, wherein at least one common column is associated with a plurality of pixels of a column. Each pixel includes a light-sensitive detector element to produce an electric charge from incident light, a selection device to connect the detector element directly or indirectly to the associated column line and at least one switching device. The image sensor furthermore has a control device for controlling the selection device and the at least one switching device of the respective pixel. The control device is designed such that the selection device of a first pixel is activated within a time period in which the at least one switching device is activated in a second pixel with which the same column line is associated.