Image Sensor with Dual Linear Logarithmic Conversion for Exposure Control
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Solution Overview
Problem
Existing image sensors can only automatically switch from a linear operative state to a logarithmic operative state, failing to optimally utilize the advantages of both states for image sensing, particularly in automatic exposure control based on subject luminance.
Innovation Solution
An image sensing apparatus with an image sensor having both linear and logarithmic characteristic areas, an evaluation value detector, and an exposure controller that adjusts exposure and dynamic range based on luminance information to achieve optimal exposure and dynamic range control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the image sensor operates in linear operative state, then high-contrast image signal can be obtained, but dynamic range is narrow
Solution Approach 1:
The patent applies dynamics by enabling the image sensor to dynamically switch between linear and logarithmic operative states based on incident light intensity. The sensor adapts its photoelectric conversion characteristic in real-time, transitioning from linear conversion in low-light conditions to logarithmic conversion in high-light conditions, thereby optimizing both contrast and dynamic range across varying lighting scenarios
Solution Approach 2:
The patent implements parameter changes by modifying the photoelectric conversion characteristic of the image sensor. By changing the conversion function from linear to logarithmic based on light intensity thresholds, the system adjusts its operational parameters to resolve the contradiction between maintaining high contrast and expanding dynamic range
2Adaptability or versatility
If the image sensor operates in logarithmic operative state, then wide dynamic range is ensured, but image contrast deteriorates
Solution Approach 1:
The system dynamically selects the operative state based on incident light intensity. The image sensor transitions from logarithmic conversion in high-light conditions (where dynamic range is prioritized) to linear conversion in low-light conditions (where contrast is prioritized), thereby resolving the contradiction through adaptive state switching
Solution Approach 2:
The patent changes the photoelectric conversion parameter from logarithmic to linear conversion based on light intensity thresholds. This parameter change allows the system to maintain wide dynamic range when needed while preserving image contrast when lighting conditions require it
3Adaptability or versatility
If automatic switching from linear to logarithmic state is implemented, then operational flexibility is improved, but optimal utilization of both states for exposure control is not achieved
Solution Approach 1:
The patent implements feedback by using the detected luminance information of the subject to control the switching between linear and logarithmic operative states. The system continuously monitors incident light intensity and adjusts its photoelectric conversion characteristic accordingly, enabling optimal exposure control that fully utilizes the advantages of both operative states
Solution Approach 2:
The image sensor performs self-service by automatically selecting and switching between linear and logarithmic conversion modes based on the incident light intensity. This self-controlled switching mechanism enables the system to optimize exposure and dynamic range without external intervention, resolving the contradiction between operational flexibility and control optimization
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
Enables optimal exposure control and specified dynamic range management, enhancing image quality by effectively utilizing the advantages of both operative states for improved contrast and range in varying lighting conditions.
Implementation Method 1
an image sensor for generating an electrical signal corresponding to an amount of an incident light and having a photoelectric conversion characteristic
Data Source
AI summary
An image sensing apparatus is provided with an image sensor having a photoelectric conversion characteristic having a linear characteristic area where an electrical signal is outputted after being linearly converted in relation to an amount of an incident light and a logarithmic characteristic area where the electrical signal is outputted after being logarithmically converted in relation to the amount of the incident light; an evaluation value detector for detecting exposure evaluation values concerning an exposure control based on a luminance information of a subject; and a central control unit for controlling the exposure based on the exposure evaluation values detected by the evaluation value detector. The central control unit includes an exposure amount control parameter calculating section for controlling an exposure amount in accordance with the photoelectric conversion characteristic using the exposure evaluation values and a dynamic range control parameter calculating section for controlling a dynamic range in accordance with the photoelectric conversion characteristic using the exposure evaluation values. Accordingly, a subject image can be picked up while an optimal exposure is made for the subject and a specified dynamic range is attained.