Image Sensor Switching Between Linear and Logarithmic Response Modes
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Solution Overview
Problem
Existing image sensing apparatuses struggle to precisely control image sensing operations, particularly in automatic exposure control, as they lack the ability to effectively utilize the advantages of both linear and logarithmic operative states of image sensors, leading to suboptimal performance in dynamic range and contrast management.
Innovation Solution
An image sensing apparatus that detects evaluation values based on subject luminance information in both linear and logarithmic characteristic areas, allowing for controlled operation in conjunction with the photoelectric conversion characteristics, enabling precise image sensing control by switching between these states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the image sensor operates in a linear operative state, then high-contrast image signal with high gradation is obtained, but the dynamic range becomes narrower
Solution Approach 1:
The patent applies dynamics by enabling the image sensor to switch between linear and logarithmic operative states based on the luminance of the subject. The system dynamically adjusts its photoelectric conversion characteristics to match the lighting conditions, transitioning from linear state for high-contrast low-luminance scenes to logarithmic state for wide dynamic range high-luminance scenes, thereby resolving the contradiction between fixed contrast performance and fixed dynamic range
Solution Approach 2:
The patent changes the photoelectric conversion parameter of the image sensor by switching between linear and logarithmic characteristic areas. This parameter change allows the sensor to optimize its response curve according to the subject's luminance, achieving high contrast when needed and wide dynamic range when needed, thus resolving the technical contradiction
2Adaptability or versatility
If the image sensor operates in a logarithmic operative state, then wide dynamic range is ensured, but the contrast becomes poorer due to logarithmic compression
Solution Approach 1:
The system dynamically selects the operative state based on subject luminance detection. For high-luminance subjects, it switches to logarithmic state to ensure wide dynamic range; for low-luminance subjects, it switches to linear state to maintain high contrast. This dynamic adaptation resolves the contradiction between dynamic range and contrast by matching the operational characteristic to the specific imaging scenario
Solution Approach 2:
The patent changes the photoelectric conversion parameter according to the subject's luminance characteristics. By switching between linear and logarithmic characteristic areas, the system optimizes the output signal distribution to achieve either wide dynamic range or high contrast depending on the imaging conditions, thereby resolving the technical contradiction
3Device complexity
If automatic exposure control is carried out without distinguishing evaluation data from respective characteristic areas, then the control process is simplified, but precise control of image sensing operations is compromised
Solution Approach 1:
The patent segments the image sensor's photoelectric conversion characteristic into distinct linear and logarithmic characteristic areas, each with its own evaluation data. This segmentation allows the system to maintain precise control by using appropriate evaluation data from the relevant characteristic area while keeping the overall control process manageable through structured decision-making based on subject luminance
Solution Approach 2:
The system changes the evaluation data parameter based on the operative state. By selecting evaluation data corresponding to the active characteristic area (linear or logarithmic), the system maintains measurement precision for exposure control while managing complexity through parameter selection rather than comprehensive processing of all possible data types
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 allows for improved control of image sensing operations, optimizing dynamic range and contrast management by utilizing the advantages of both operative states, resulting in enhanced image quality and exposure control.
Implementation Method 1
an image sensor for generating an electrical signal corresponding to an amount of an incident light
Implementation Method 2
a subthreshold characteristic of the MOSFET is taken advantage of to make an output characteristic of the solid-state sensing device such that the electrical signal is logarithmically converted in relation to the amount of the incident light
Data Source
AI summary
An image sensing apparatus is provided with an image sensor having a photoelectric conversion characteristic comprised of 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 of a signal processing unit detects evaluation values concerning an image sensing control from each of the linear characteristic area and the logarithmic characteristic area upon picking up an image of a subject based on pieces of subject luminance information in the respective areas. A central control unit (image sensing controller) carries out the image sensing control based on the evaluation values corresponding to the respective areas detected by the evaluation value detector.