| 摘要 |
An object of the present invention is to obtain a gradient of a road surface without consideration of a displacement of an over-spring member. The object is achieved in a manner described below. An emitting device emits parallel light beams B1, B2. The parallel light beams B1, B2 impinge on a road surface, forming marks Pc1, Pc2. An imaging device takes an image of an image pickup object containing the marks Pc1, Pc2 to obtain a picked-up image J. A longitudinal distance e between mark images Mc1, Mc2 respectively corresponding to the marks Pc1, Pc2 is detected. A larger gradient ³ can be obtained in the case where the distance e is long than in the case where the distance e is short. While the gradient of the road surface is obtained based on the distance between the two mark images as described above, a relative positional relationship between the two mark images is not changed as long as the gradient of the road surface is the same even when the height position of an over-spring member provided with the emitting device and the imaging device is changed. Accordingly, the gradient of the road surface can be obtained without consideration of the displacement of the over-spring member. |
