3D Head Position Estimation Using Face Direction Correction
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Solution Overview
Problem
Conventional methods for estimating the three-dimensional position of a head in a driver monitoring system are inaccurate due to fluctuations caused by changes in face direction and head movement.
Innovation Solution
A device comprising a feature point extracting unit, inter-feature-point distance calculating unit, face direction detecting unit, head position angle calculating unit, inter-feature-point distance correcting unit, and three-dimensional position estimating unit, which corrects inter-feature-point distances to improve estimation accuracy by accounting for head position angles and face direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inter-feature-point distance calculation is used, then the estimation process is simple, but the three-dimensional position estimation accuracy deteriorates due to fluctuations from face direction changes and head movement
Solution Approach 1:
The patent applies preliminary action by detecting the face direction and calculating head position angles before correcting the inter-feature-point distance. The face direction detecting unit and head position angle calculating unit prepare correction parameters in advance, which are then used by the inter-feature-point distance correcting unit to compensate for head movement and face direction changes, thereby improving estimation accuracy without excessive complexity
Solution Approach 2:
The patent changes parameters by introducing face direction angles and head position angles as correction parameters. The inter-feature-point distance is corrected using these angular parameters to account for head movement and face direction changes. This parameter transformation approach improves measurement precision while maintaining a manageable estimation process
2Measurement precision
If inter-feature-point distance is calculated without correction, then the calculation is fast, but the distance measurement precision deteriorates due to head movement and face direction changes
Solution Approach 1:
The system performs preliminary detection of face direction and calculation of head position angles before the distance correction step. This preliminary action allows the inter-feature-point distance to be corrected using pre-computed angular parameters, improving distance accuracy while minimizing additional processing time through efficient sequential computation
3Measurement precision
If no face direction detection is performed, then the system complexity is low, but the three-dimensional position estimation accuracy deteriorates
Solution Approach 1:
Face direction detection is performed as a preliminary step before three-dimensional position estimation. The detected face direction information is used to calculate head position angles, which are then applied to correct inter-feature-point distances. This preliminary detection approach improves estimation accuracy while keeping the system structure manageable through a clear sequential processing flow
Solution Approach 2:
The system transforms face direction information into head position angle parameters that can be directly used for distance correction. This parameter transformation converts complex face direction data into useful correction factors, improving measurement precision while maintaining reasonable system complexity through efficient parameter utilization
Data Source
AI summary
A three-dimensional position estimation device includes: a feature point extracting unit for detecting an area corresponding to the face of an occupant in an image captured by a camera for imaging a vehicle interior and extracting a plurality of feature points in the detected area; an inter-feature-point distance calculating unit for calculating a first inter-feature-point distance that is a distance between distance-calculating feature points among the plurality of feature points; a face direction detecting unit for detecting the face direction of the occupant; a head position angle calculating unit for calculating a head position angle indicating the position of the head of the occupant with respect to an imaging axis of the camera; an inter-feature-point distance correcting unit for correcting the first inter-feature-point distance to a second inter-feature-point distance that is a distance between distance-calculating feature points in a state where portions of the head corresponding to the distance-calculating feature points are arranged along a plane parallel to an imaging plane of the camera using a result detected by the face direction detecting unit and the head position angle; and a three-dimensional position estimating unit for estimating the three-dimensional position of the head using the head position angle, the second inter-feature-point distance, and a reference inter-feature-point distance.