公开(公告)号：EP0827908A1

公开(公告)日：1998-03-11

申请号：EP96306480.3

申请日：1996-09-06

Applicant: Robotic Vision Systems Inc.

Inventor： Schoeffler, Daniel ,  Stern, Howard ,  Costa, Pat V.

IPC: B64D15/20 ,  G08B19/02

CPC classification number: G08B19/02 ,  B64D15/20 ,  G01J4/04 ,  G01J2004/005

Abstract: An apparatus for detecting a polarization altering substance, such as ice, on a surface includes a polarizing filter on the surface between the surface and the polarization altering substance. When the polarizing filter includes alternating regions having orthogonal polarizing properties, only one viewing of the surface through a blocking filter is required. When light, either polarized or unpolarized, reflects off the surface, it passes through the polarizing filter and becomes polarized. Reflected light that additionally passes through ice after leaving the polarizer becomes unpolarized. When viewed through a blocking polarizer filter, polarized light passing through ice appears bright due to the unpolarizing effect of ice. On the other hand, polarized light not passing through ice retains its polarization and appears dark when viewed through a blocking filter. Since the polarizing filter is between the surface and the viewer, the surface can be metallic, dielectric, or painted without affecting the results. If the proper blocking orientation for the viewer is not known in advance, the Stokes coefficients can be calculated if views are taken through a series of specified polarizing filters. The ratio of polarized light returned to the viewer compared to the unpolarized light returned to the viewer can then be calculated from any arbitrary position. A retroreflective substance on the surface further enhances the effect for systems employing an active illumination source located coaxially with or adjacent to the imaging system.

Abstract translation: 用于在表面上检测诸如冰的偏振改变物质的装置包括在表面和偏振改变物质之间的表面上的偏振滤光器。 当偏振滤光器包括具有正交偏振特性的交替区域时，仅需要通过阻挡滤光器观察表面。 当偏振或非偏振的光从表面反射时，它通过偏振滤光器并变成极化的。 离开偏光片之后额外通过冰的反射光变成非偏振光。 当通过阻挡偏振器滤光器观察时，通过冰的偏振光由于冰的非偏振效应而变亮。 另一方面，当通过阻挡滤光片观察时，不通过冰的偏振光保持其偏振并且看起来暗。 由于偏振滤光片位于表面和观察者之间，因此表面可以是金属的，电介质的或涂层的，而不影响结果。 如果预先不知道观察者的正确的阻挡方位，如果通过一系列指定的偏振滤光片拍摄视图，则可以计算斯托克斯系数。 然后可以从任何任意位置计算返回观察者的偏振光与返回观察者的非偏振光相比的比率。 表面上的回射物质进一步增强了使用与成像系统同轴或相邻的有源照明源的系统的效果。