원근투영법 기반의 PTZ 카메라를 이용한 머리자세 추정 = Head Pose Estimation Based on Perspective Projection Using PTZ Camera

국문 초록 (Abstract)

본 논문에서는 PTZ 카메라를 이용한 머리자세추정 방법에 대하여 서술한다. 회전 또는 이동에 의하여 카메라의 외부인자가 변경되면, 추정된 얼굴자세도 변한다. 본 논문에는 PTZ 카메라의 회전과 위치 변화에 독립적으로 머리자세를 추정하는 새로운 방법을 제안한다. 제안하는 방법은 얼굴검출, 특징추출 그리고 자세추정으로 이루어진다. 얼굴검출은 MCT특징을 이용해 검출하고, 얼굴 특징추출은 회귀트리 방법을 이용해 추출하고, 머리자세 추정은 POSIT 알고리즘을 사용한다. 기존의 POSIT 알고리즘은 카메라의 회전을 고려하지 않지만, 카메라의 외부인자 변화에도 강건하게 머리자세를 추정하기 위하여 본 논문은 원근투영법에 기반하여 POSIT를 개선한다. 실험을 통하여 본 논문에서 제안하는 방법이 기존의 방법 보다 RMSE가 약 $0.6^{\circ}$ 개선되는 것을 확인했다.

다국어 초록 (Multilingual Abstract)

This paper describes a head pose estimation method using PTZ(Pan-Tilt-Zoom) camera. When the external parameters of a camera is changed by rotation and translation, the estimated face pose for the same head also varies. In this paper, we propose a new method to estimate the head pose independently on varying the parameters of PTZ camera. The proposed method consists of 3 steps: face detection, feature extraction, and pose estimation. For each step, we respectively use MCT(Modified Census Transform) feature, the facial regression tree method, and the POSIT(Pose from Orthography and Scaling with ITeration) algorithm. The existing POSIT algorithm does not consider the rotation of a camera, but this paper improves the POSIT based on perspective projection in order to estimate the head pose robustly even when the external parameters of a camera are changed. Through experiments, we confirmed that RMSE(Root Mean Square Error) of the proposed method improve $0.6^{\circ}$ less then the conventional method.

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