Image Forming Apparatus Exposure Segmentation for Luminance Accuracy
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Solution Overview
Problem
Conventional image forming methods fail to accurately capture luminance values when external light is strong, leading to inaccurate images due to the upper limit issue and increased complexity and cost of imaging devices.
Innovation Solution
An image forming apparatus that splits exposure time into multiple segments, acquiring images with and without illumination, and subtracts luminance values to isolate and integrate only the illumination values, ensuring accurate luminance representation even in high external light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the conventional image forming method subtracts luminance values of an image without illumination from an image with illumination, then an image without external light can be formed, but when external light is strong (exceeds upper limit), all luminance values become equal to the fixed upper limit and accurate luminance values cannot be obtained
Solution Approach 1:
The exposure time is divided into multiple segments (first exposure time for image with illumination, second exposure time for image without illumination). This segmentation allows the system to capture external light information separately from the combined illumination signal, enabling accurate subtraction even when external light is strong and would otherwise saturate the sensor.
Solution Approach 2:
The patent uses a third exposure time that is longer than both the first and second exposure times to acquire an external light image. This excessive exposure time is specifically designed to capture only the external light component, which can then be used to calculate accurate external light luminance values for subtraction from the illuminated image.
2Productivity
If a light modulation method is used to subtract luminance values at hardware level, then the image processing speed is improved, but the structure of the imaging device becomes complicated and costly
Solution Approach 1:
The patent uses the imaging device's own existing components (illuminating unit and imaging unit) to acquire multiple images under different lighting conditions. The system processes these images through software-based luminance subtraction, eliminating the need for additional dedicated hardware for light modulation or external light measurement, thus avoiding increased device complexity and cost.
3Measurement precision
If the exposure time is extended to capture sufficient light information, then the image quality is improved, but the capture of external light also increases leading to more significant subtraction errors
Solution Approach 1:
By segmenting the exposure into distinct time periods (first exposure time for illuminated image, second exposure time for external light image), the system can accumulate light information over appropriate durations for each purpose while keeping the external light capture separate. This enables optimized exposure times for each imaging goal without contamination.
Solution Approach 2:
The patent employs a third exposure time that is intentionally longer than necessary for normal imaging, specifically designed to capture only external light. This excessive exposure time ensures complete capture of external light information while the illuminating unit remains off, allowing accurate external light measurement that can be subtracted from the illuminated image.
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 the formation of images with accurate luminance values of illumination, reducing noise and enhancing process speed while avoiding the need for additional light measurement devices and complex device structures.
Implementation Method 1
an imaging unit is used to acquire a first image of a photogenic subject by illuminating the photogenic subject with external light and with light of an illuminating unit
Data Source
AI summary
An image forming apparatus causes an illuminating unit and an imaging unit to equally split a predetermined exposure time into a plurality of split exposure times, and acquire an image with illumination and an image without illumination in each of the split exposure time. A luminance difference image for a particular split exposure time is calculated by subtracting the image without illumination from the image with illumination of the exposure time. The luminance difference images of all the split exposure times are integrated.