Imaging Device Exposure Control for Face Recognition
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Solution Overview
Problem
Conventional face recognition systems in digital cameras face challenges in maintaining stable recognition and tracking due to fluctuations in the depth of field and insufficient lighting, especially when faces move or are small, leading to degraded resolution and recognition accuracy.
Innovation Solution
An imaging device that adjusts exposure time and aperture based on the area and moving speed of the face region, extending exposure time for larger areas to increase light and depth of field, and shortening it for smaller areas to reduce motion blur, while also controlling aperture values to optimize light and noise levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the diaphragm is narrowed to increase depth of field for small faces, then the recognition range is extended, but the light amount becomes insufficient leading to degraded recognition accuracy
Solution Approach 1:
The patent dynamically adjusts the diaphragm aperture value based on the detected face size. For small faces, the diaphragm is narrowed to extend depth of field and recognition range. For large faces, the diaphragm is opened to increase light amount. This dynamic adaptation resolves the contradiction between recognition range and light amount.
Solution Approach 2:
The patent changes the diaphragm aperture parameter according to face size conditions. By adjusting this physical parameter, the system optimizes both the recognition range (through depth of field control) and light amount (through aperture size), resolving the technical contradiction.
2Illumination intensity
If the exposure time is extended to increase light amount for large faces, then the light amount is sufficient, but motion blur increases leading to degraded resolution
Solution Approach 1:
The patent dynamically adjusts exposure time based on face size. For large faces where motion blur is less critical, exposure time is extended to increase light amount. For small faces where resolution is critical, exposure time is kept short to minimize motion blur. This dynamic adjustment resolves the contradiction between light amount and resolution.
3Manufacturing precision
If the focusing position is adjusted based on immediately preceding image data, then the focusing is optimized for previous frame, but the face escapes out of depth of field when face moves
Solution Approach 1:
The patent performs preliminary action by detecting face size in advance and pre-adjusting the diaphragm aperture value before capturing the image. This ensures that when the face is captured, the depth of field is already optimized for that face size, preventing the face from escaping the depth of field during movement.
4Illumination intensity
If the lighting function is activated to improve light amount, then the illumination is sufficient, but power consumption increases and flash usage may be prohibited
Solution Approach 1:
The patent replaces the mechanical/electrical lighting system (flash) with an optical control mechanism (diaphragm adjustment). By adjusting the diaphragm aperture, the system controls light amount optically without consuming additional power for active illumination, thus avoiding the drawbacks of flash usage.
Data Source
AI summary
An imaging device for recognition (100) includes an image pickup unit (101) that sequentially generates a plurality of images by shooting an object, a face recognition unit (105) that recognizes, in each of the plurality of images, an object region in which the object is located in the image, a face tracking unit (106) that tracks the object region across the plurality of images, an area calculation unit (109) that calculates an area of the object region, and an exposure control unit (102) that sets a first exposure time for the image pickup unit (101) in the case where the area is smaller than a first threshold, and sets a second exposure time longer than the first exposure time in the case where the area is equal to or larger than the first threshold.