CMOS Image Sensor Dual-Mode AD Conversion for Illuminance Adaptation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current CMOS image sensors using time-divisional photon counting face challenges in achieving high-precision image pickup at both low and high illuminance levels without increasing the speed of the sense circuit and power consumption, as they experience significant noise and counting errors due to the limited number of counts and compression of output at high illuminance.
Innovation Solution
The implementation of a CMOS image sensor with a sense circuit that operates in two modes: one-bit output mode for binary decision and gray-scale output mode by multi-bit resolution, allowing the AD conversion device to integrate output results from multiple exposures to determine light intensity, either per pixel or as a single light reception surface, thereby enhancing precision and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-divisional photon counting is used, then noise is reduced at low illuminance, but counting misses occur at high illuminance
Solution Approach 1:
The patent applies dynamics by making the AD conversion device operable in multiple modes (one-bit output mode and gray-scale output mode) that can be dynamically selected based on illuminance conditions. This allows the system to adapt its counting mechanism to match the photon flux level, resolving the contradiction between low-noise performance at low illuminance and accurate counting at high illuminance.
Solution Approach 2:
The patent changes the operational parameters of the AD conversion device by switching between different output modes. In the one-bit output mode, binary decision is used for low illuminance, while in the gray-scale output mode, multi-bit resolution is used for high illuminance. This parameter change enables the system to maintain high measurement precision across varying illuminance levels without suffering from counting misses.
2Measurement precision
If reading speed is increased to handle high photon counts, then counting accuracy improves, but power consumption increases
Solution Approach 1:
The patent changes the operational parameters of the AD conversion device by switching between different output modes. In the one-bit output mode, binary decision is used for low illuminance, while in the gray-scale output mode, multi-bit resolution is used for high illuminance. This parameter change enables the system to maintain high measurement precision across varying illuminance levels without suffering from counting misses.
3Measurement precision
If binary decision mode is used, then noise is reduced, but dynamic range is limited
Solution Approach 1:
The patent applies universality by designing the AD conversion device to perform multiple functions through different operational modes. The same device can operate in one-bit output mode for low illuminance conditions (achieving high S/N ratio) and in gray-scale output mode for high illuminance conditions (achieving wide dynamic range). This multi-functionality resolves the contradiction between noise reduction and dynamic range expansion.
Solution Approach 2:
The patent applies dynamics by making the AD conversion device operable in multiple modes (one-bit output mode and gray-scale output mode) that can be dynamically selected based on illuminance conditions. This allows the system to adapt its counting mechanism to match the photon flux level, resolving the contradiction between low-noise performance at low illuminance and accurate counting at high illuminance.
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 enables high-precision image pickup with reduced noise at both low and high illuminance levels without increasing the speed of the sense circuit or power consumption, by effectively managing the number of counts and output compression.
Implementation Method 1
Each pixel in a CMOS image sensor converts incident light into electrons by a photodiode as a photoelectric conversion device
Data Source
AI summary
Provided are an image pickup device and a camera system that are capable of performing high-precision image pickup with less noise both at low illuminance and high illuminance without increasing the speed of a sense circuit and power consumption. The image pickup device includes a pixel array section including a plurality of pixels arranged in an array, each of the pixels including a photoelectric conversion device, a storage section, and an amplifier device configured to output an accumulated charge as an electrical signal, each of the pixels configured to output an electrical signal to an output signal line in response to photon incidence; and a sense circuit section including a sense circuit, the sense circuit configured to perform decision as to whether or not a photon is incident on the pixel in a predetermined period, in which the sense circuit includes an AD conversion device connected to the output signal line, the AD conversion device is allowed to operate by at least two modes, i.e., a one-bit output mode by binary decision and a gray-scale output mode by multi-bit resolution, and at least when the one-bit output mode is selected, the AD conversion device integrates output results from each of the pixels by a plurality of exposures to determine intensity of light incident on each of the pixels by calculation.