Imaging Apparatus FPN Correction Using Temperature-Matched Dark Images
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Solution Overview
Problem
Conventional imaging apparatuses struggle to effectively correct fixed pattern noise (FPN) during bulb exposure, as the temperature of the image sensor increases during live-view display, leading to uneven image density and reduced image quality due to the dark current component, which cannot be adequately corrected using existing FPN cancellation processing.
Innovation Solution
The imaging apparatus performs relatively bright or dark composition processing by comparing pixel data from continuously read-out image signals and reconstructing composite images using either larger or smaller pixel data, and uses dark image data obtained at temperatures closest to the exposure time to correct FPN in the cumulative composite images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If live-view display is performed using image sensor during bulb exposure, then the user can confirm the state of subject and exposure conditions during exposure, but the temperature of the image sensor increases leading to increased dark current and fixed pattern noise
Solution Approach 1:
The patent applies preliminary action by capturing a dark image (light-shielded image) before the actual bulb exposure begins. This dark image captures the fixed pattern noise characteristics at the initial temperature. By having this reference data prepared in advance, the system can later correct the bright image using this pre-captured dark image, thus resolving the issue of temperature-induced noise while maintaining the ability to display live view during exposure.
2Manufacturing precision
If FPN cancellation processing is performed using dark image captured before bright image, then fixed pattern noise can be corrected, but the temperature difference between dark and bright images reduces correction accuracy
Solution Approach 1:
The patent implements feedback by capturing multiple dark images at different time points (before and after the bright image) and using temperature information to select or combine the most appropriate dark image for correction. The system continuously monitors temperature and uses this feedback to determine which dark image best matches the thermal state during bright image capture, thereby improving correction accuracy despite temperature changes.
Solution Approach 2:
The patent applies parameter changes by using temperature as a selection criterion for choosing the appropriate dark image. Instead of using a single fixed dark image, the system varies the selection based on temperature parameters, choosing the dark image whose temperature most closely matches the bright image temperature. This dynamic parameter-based selection optimizes the correction accuracy across varying thermal conditions.
3Manufacturing precision
If dark image is captured after bright image in bulb exposure, then temperature matching can be improved, but the dark current characteristics may differ due to temperature change during exposure
Solution Approach 1:
The patent merges multiple dark images (captured both before and after the bright image) through addition or averaging to create a composite dark image. This composite dark image represents the average dark current characteristics over the entire exposure period, thereby compensating for temperature variations. By combining multiple measurements rather than relying on a single dark image, the system achieves both temperature matching and consistency in dark current characterization.
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 improves the correction effect of FPN cancellation, resulting in enhanced image quality by matching the temperature conditions of the dark and bright images, thereby reducing fixed pattern noise and improving the overall image quality during bulb exposure.
Implementation Method 1
image sensor that repeatedly and sequentially performs relatively bright composition processing on second image data in a second frame and after generated on the basis of image data read out of an image sensor
Implementation Method 2
a dark current component is generated in a photodiode constituting a pixel of the image sensor during the long exposure shooting
Data Source
AI summary
An imaging apparatus comprising: a dark image data imaging section that obtains dark image data in a state in which light beams entering an imaging surface of an image sensor are shielded before first image data is obtained or after second image data obtained lastly; and a correcting section that corrects a fixed pattern noise in cumulative relatively bright composite image data by using the dark image data, wherein the correcting section corrects the fixed pattern noise in the cumulative relatively bright composite image data by using the dark image data obtained at a time closest to the time in a temperature of the image sensor when the first image data or the second image data is obtained is assumed to be the highest, of the dark image data obtained before the first image data is obtained or the dark image data obtained after the second image data obtained lastly.