Imaging Apparatus Adaptive Bias Control for Noise Reduction
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Solution Overview
Problem
Conventional imaging apparatuses face challenges in adaptively managing noise levels, particularly at varying illuminance conditions, as thermal noise and 1/f noise are influenced by current consumption, leading to increased power usage and costs, while quantization noise is tied to AD converter resolution.
Innovation Solution
An imaging apparatus with a photoelectric conversion element, a conversion unit, and a bias circuit controlled by a control unit to adjust current flow through the analog circuit based on output signals, allowing for adaptive voltage boosting during charge transfer, thereby optimizing power consumption and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the gm of the circuit is improved to reduce thermal noise, then thermal noise is reduced, but current consumed by the analog circuit increases leading to increased power
Solution Approach 1:
The patent applies dynamics by making the bias current supplied to the analog circuit variable rather than fixed. The control unit dynamically adjusts the bias current based on illuminance detection, allowing the circuit to operate at high current (low noise) when needed and low current (low power) when not needed, thus resolving the contradiction between noise reduction and power consumption
Solution Approach 2:
The patent changes the parameter of bias current from a constant value to a variable value that depends on illuminance conditions. By detecting illuminance level and adjusting the bias current parameter accordingly, the system achieves low thermal noise at low illuminance while maintaining low power consumption at high illuminance
2Object-affected harmful factors
If measures are taken to reduce 1/f noise by adjusting current, then 1/f noise is reduced, but costs increase
Solution Approach 1:
The patent uses dynamic adjustment of bias current controlled by illuminance detection to reduce 1/f noise only when necessary (at low illuminance), rather than using fixed high-current operation or expensive circuit modifications. This approach reduces noise effectively while avoiding increased manufacturing costs
Solution Approach 2:
The system uses the image sensor's own output signal to control the bias current, creating a self-regulating system that automatically adjusts noise levels based on operating conditions without requiring external expensive components or complex control mechanisms
3Object-affected harmful factors
If the resolution of the AD converter is increased to reduce quantization noise, then quantization noise is reduced, but device complexity and cost increase
Solution Approach 1:
The patent converts the harmful effect of quantization noise into a benefit by using the AD converter's output signal itself to control the bias current. The quantization noise, instead of being merely an error to be reduced by higher resolution, becomes part of the feedback mechanism that optimizes the analog circuit operation, reducing overall noise without increasing AD converter complexity
4Object-affected harmful factors
If current consumed by the analog circuit is increased to reduce random noise, then random noise is reduced, but power consumption increases
Solution Approach 1:
The patent implements dynamic control of bias current based on illuminance conditions, allowing the analog circuit to operate at high current only when random noise would otherwise dominate (at low illuminance). At high illuminance levels, the circuit operates at low current, achieving low power consumption while maintaining low random noise through intelligent timing of high-current operation
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 solution enables low power consumption at high illuminance and low noise at low illuminance by dynamically adjusting current consumption, improving image quality and reducing operational costs.
Implementation Method 1
an image sensor, for example, a charge coupled device (CCD), a complementary metal oxide semiconductor (CMOS) image sensor
Data Source
AI summary
The present technology relates to an imaging apparatus and electronic equipment that can reduce noise. A photoelectric conversion element, a conversion unit that converts a signal from the photoelectric conversion element into a digital signal, a bias circuit that supplies a bias current for controlling a current flowing through an analog circuit in the conversion unit, and a control unit that controls the bias circuit on the basis of an output signal from the conversion unit are provided, and at the start of transfer of a charge from the photoelectric conversion element, the control unit boosts a voltage at a predetermined position of the analog circuit. The conversion unit converts the signal from the photoelectric conversion element into a digital signal using a slope signal whose level monotonously decreases with time. The present technology is applicable to, for example, an imaging apparatus.