For the calibration of line structured light sensors in small fields of view, this paper proposes a light plane parameter calibration method based on unified homography estimation. By intersecting the light stripe with non-chessboard regions of the target plane to form calibration feature points for the light plane, a high-precision one-dimensional displacement device and a two-dimensional target movement are used to establish an affine coordinate system. The introduction of spatial unit vectors and movement step constraints extends the two-dimensional target feature points into three-dimensional space, fully leveraging the noise resistant advantages of three-dimensional feature points. A unified homography estimation is performed on all spatial feature points, achieving high-precision calibration of the line structured light sensor in small fields of view. Experimental results show that, compared with traditional methods, the proposed method reduces the distance measurement error by approximately 60%, and improves the calibration repeatability by about 93%.