Endoscope Focus Control Using Bright Spot Influence Rate
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Solution Overview
Problem
Endoscope systems face challenges in achieving accurate autofocus due to high luminance portions in images, which can lead to incorrect focus determination and blurring, especially with the use of image sensors having a large number of pixels and shallow depth of field.
Innovation Solution
A focus control device that sets areas on a captured image, calculates an autofocus evaluation value, and determines a bright spot influence rate based on the size of high luminance portions, adjusting focus control to minimize the impact of large high luminance portions and utilize the contribution of non-saturated pixel values for accurate focus determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image sensors having a large number of pixels are used, then imaging resolution is improved, but depth of field becomes shallow and high luminance portions cause focus determination errors
Solution Approach 1:
The patent divides the image into multiple regions and calculates bright spot influence rates separately for each region. By segmenting the image analysis, the system can identify and handle high luminance portions locally without letting them dominate the overall focus determination, thus resolving the contradiction between high resolution imaging and reliable focus detection.
Solution Approach 2:
The patent applies different processing strategies to different parts of the image based on local characteristics. Specifically, regions containing high luminance portions are identified and processed differently from normal regions, with the bright spot influence rate used to weight or exclude affected areas from focus evaluation, thereby maintaining accuracy despite the presence of bright spots.
2Ease of operation
If conventional contrast AF control is used, then focus determination is simple, but high luminance portions cause the largest contrast value to be achieved at incorrect lens positions
Solution Approach 1:
The patent introduces a new parameter - the bright spot influence rate - to modify the conventional contrast AF approach. By calculating this influence rate based on high luminance portion detection and incorporating it into the focus evaluation, the system adjusts the contrast calculation to account for bright spot effects, thereby improving accuracy while building upon the simple contrast AF framework.
Solution Approach 2:
The bright spot influence rate acts as an intermediary factor between the raw contrast values and the final focus determination. This intermediate calculation step allows the system to filter out the distorting effects of high luminance portions before making the final focus decision, bridging the gap between simple contrast measurement and accurate focus detection.
Data Source
AI summary
A focus control device includes a processor including hardware, the processor being configured to implement: an area setting process that sets a plurality of areas, each including a plurality of pixels, on a captured image acquired by an imaging section, an evaluation value calculation process that calculates an AF (Autofocus) evaluation value for each of the plurality of set areas, a bright spot influence rate calculation process that calculates a bright spot influence rate for each of the plurality of set areas, based on whether or not the area includes a high luminance portion determined to have a size equal to or larger than a given size, and focus control based on the AF evaluation value and the bright spot influence rate.