Image Sensor Exposure Control for Blinking Subject Detection
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Solution Overview
Problem
Conventional image sensing apparatuses face challenges in maintaining consistent exposure when detecting a main object, particularly when the object blinks or looks away, leading to temporary failure in detection and resulting in sharp changes in image luminance.
Innovation Solution
An image sensing apparatus with a detection unit, first and second exposure value determination units, and a selection unit that calculates and selects exposure values based on object detection results and scene changes to maintain consistent exposure, even when the main object is temporarily undetected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If automatic exposure control is based on the entire frame, then the exposure is determined automatically, but the luminance of the main object may be improper
Solution Approach 1:
The image frame is segmented into multiple regions, with the detection unit identifying the main object region (e.g., face) separately from the rest of the frame. The exposure control then prioritizes the luminance of the detected main object region over the entire frame, ensuring proper exposure of the subject while maintaining automated operation.
2Measurement precision
If the user specifies the area containing the main object, then proper luminance for the main object is achieved, but the operation becomes burdensome
Solution Approach 1:
The detection unit automatically identifies the main object (such as a face) within the frame using image processing techniques like shape analysis. This self-service mechanism eliminates the need for users to manually specify the main object area, maintaining ease of operation while achieving accurate luminance control for the detected subject.
3Measurement precision
If exposure control is adjusted when the main object is detected, then proper luminance is achieved, but sudden exposure changes occur when detection fails temporarily
Solution Approach 1:
The system maintains the previously determined exposure settings as a backup when the detection unit temporarily fails to detect the main object (e.g., during blinking or head turning). This prior cushioning prevents sudden exposure changes by smoothly transitioning between detected and non-detected states, ensuring exposure stability while maintaining proper luminance when detection is successful.
Data Source
AI summary
An image sensing apparatus that carries out image sensing continuously and inputs a plurality of images, having a digital signal processing circuit that detects, at each input image, from image data thereof, an object that satisfies a preset condition, a first exposure value determination unit that calculates a first exposure value from the image data, a second exposure value determination unit that calculates a second exposure value based on the detected object, and a selection unit that selects either the first exposure value, the second exposure value, a currently set exposure value, or an exposure value calculated based on a luminance of an area referenced when calculating a currently set exposure value as an exposure value to be used for a next image sensing based on object detection results obtained by the digital signal processing circuit.