Imaging Exposure Control During Face Detection Loss
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Solution Overview
Problem
Existing face auto exposure (AE) systems in imaging apparatuses fail to maintain appropriate exposure control when faces are not detected due to subjects facing sideways or other reasons, leading to potential overexposure or underexposure.
Innovation Solution
An imaging control apparatus and method that performs exposure control based on a region-of-interest detection, using a region-of-interest exposure target value when detected, and a set region exposure target value when not detected, with an exposure correction value calculated from previous exposure target values to maintain appropriate brightness during face loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If face auto exposure control is performed based on detected face region, then appropriate brightness of face can be achieved, but exposure control fails when face is not detected
Solution Approach 1:
The system stores exposure target values and correction values in advance when the face is detected, before the face becomes undetectable. This preliminary storage of exposure parameters allows the system to maintain appropriate exposure even after face detection is lost, resolving the contradiction between precision and reliability.
Solution Approach 2:
The invention introduces an exposure correction value as an intermediary parameter that bridges the gap between face-based exposure control and general scene exposure control. This correction value is applied to maintain face brightness even when the face is no longer detected, thus improving reliability without sacrificing precision.
2Reliability
If exposure control switches to set region when face is lost, then exposure control can continue, but brightness of subject may become inappropriate
Solution Approach 1:
The system uses feedback by calculating an exposure correction value based on the difference between the face exposure target value and the set region exposure target value. This correction value is then applied to the set region exposure results to maintain accurate face brightness, ensuring both continuity and precision.
Solution Approach 2:
The invention dynamically adjusts the exposure control value by applying a correction parameter derived from previous face detection data. This parameter change allows the system to transition smoothly from face-based exposure to set region-based exposure while maintaining brightness accuracy.
3Manufacturing precision
If exposure correction value is calculated and applied during face loss period, then brightness can be maintained, but control complexity increases
Solution Approach 1:
The exposure correction value is calculated and stored in advance when the face is detected, before face loss occurs. This preliminary calculation simplifies the control process during face loss, as the system only needs to apply the pre-calculated correction value rather than performing complex real-time calculations, thus maintaining brightness consistency without excessive complexity.
Data Source
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AI summary
An imaging apparatus according to the present technology includes an exposure control unit configured to perform exposure control on the basis of information of a region of interest detected from a captured image by a region-of-interest detection unit, in which the exposure control unit is configured to: perform exposure control in which a region-of-interest exposure target value calculated on the basis of a region-of-interest photometric value obtained from a first photometric region including at least a region of interest in an input frame is set as an exposure control value, in a case where the region of interest is detected from the captured image; perform exposure control in which a set region exposure target value calculated on the basis of a set region photometric value obtained from a second photometric region determined in advance in the input frame is set as the exposure control value, in a case where the region of interest is not detected from the captured image; and obtain an exposure correction value on the basis of the region-of-interest exposure target value before a time of region-of-interest lost, and then perform exposure control with the exposure control value obtained by correcting the set region exposure target value with the exposure correction value, in a predetermined period in which the region of interest is not detected continuously from the time of the region-of-interest lost in which the region of interest is not detected from the captured image.