Illuminated cover for electromagnetic transmitter and receiver

Abstract

An illuminated cover for an electromagnetic sensor, such as a radar sensor. The cover comprises a multilayer plate that is substantially transparent to the electromagnetic radiation emitted and/or received by the electromagnetic sensor. The plate includes a first layer of optically transparent material and a second layer on at least one surface of the first layer and having a lower refractive index than the first layer. A graphic layer is provided on the second layer. At least one light source is arranged to couple light into the first layer, which acts as a light guide. At least one surface of first layer is further provided with at least one optical element for outcoupling light from the first layer.

What is claimed is: 
     
       What is claimed is: 
     
     
         1 . A cover for an electromagnetic sensor, the cover comprising:
 a plate that is substantially transparent to electromagnetic radiation, the plate having a central portion designed to be disposed over the electromagnetic sensor and an outer rim, at least the central portion having a substantially uniform thickness, the plate further defining an upper surface arranged to face an observer and a lower surface arranged to face an electromagnetic sensor, the plate comprising:   a first layer formed of an optically transparent material;   at least one optical element disposed on at least one of an upper or lower surface of the first layer for outcoupling light at least from an upper surface of the plate;   a second layer disposed on at least one of the upper or lower surfaces of the first layer, the second layer formed of a second optically transparent material having a refractive index lower than that of the first layer and being substantially thinner than the first layer; and   a graphic layer arranged on outer surface of at least one of the second layers, the graphic layer formed of an optically opaque and/or reflective material.   
     
     
         2 . The cover as claimed in  claim 1 , wherein the first layer has a refractive index of 1.3 to 1.6 or 1.5 to 1.6, and wherein the second layer has a refractive index of 1.15 to 1.3. 
     
     
         3 . The cover as claimed in  claim 1 , wherein the second layer has a thickness of 1 to 6 μm or of 2 to 3 μm. 
     
     
         4 . The cover as claimed in  claim 1 , wherein the at least one optical element comprises a light diffusing, reflecting and/or refracting surface on the first layer. 
     
     
         5 . The cover as claimed in  claim 1 , wherein the at least one optical element comprises a light diffusing, reflecting and/or refracting material applied to or integrated with the first layer. 
     
     
         6 . The cover as claimed in  claim 1 , wherein the at least one optical element comprises a light diffusing, reflecting and/or refracting material applied to or integrated with the first layer. 
     
     
         7 . The cover as claimed in  claim 1 , further comprising at least one light source disposed adjacent to the outer rim of the first layer and being arranged to couple light into the first layer. 
     
     
         8 . The cover as claimed in  claim 1 , further comprising a frame coupled to the outer rim of the plate, the frame being of a light blocking material and adapted to accommodate at least one light source. 
     
     
         9 . The cover as claimed in  claim 8 , wherein the frame is arranged to extend under the plate to enclose a space, the frame being substantially transparent to electromagnetic radiation. 
     
     
         10 . The cover as claimed in  claim 8 , wherein the frame is arranged to extend under the plate to enclose a space adapted to accommodate an electromagnetic sensor. 
     
     
         11 . A method of fabricating a cover for an electromagnetic sensor according to  claim 1 , the method comprising:
 providing a first layer of a first refractive index;   forming at least one optical element on one of an upper or lower surface of the first layer, the optical element being adapted to outcouple light at least from an upper surface of the plate;   providing a second layer at least on an upper surface of the first layer, the second layer being of a lower refractive index than the first layer; and   at least partially covering the second layer with a graphic layer.   
     
     
         12 . The method as claimed in  claim 11 , wherein the step of providing the first layer includes moulding a plastic material, PC or PMMA. 
     
     
         13 . The method as claimed in  claim 11 , wherein the step of forming at least one optical element includes applying an optically diffusing material or by moulding a diffusing material together with the plastic material in a 2K process. 
     
     
         14 . The method as claimed in  claim 11 , wherein the step of forming at least one optical element includes forming light diffusing microstructures on a surface of the first plate. 
     
     
         15 . The method as claimed in  claim 11 , further comprising applying an optically reflective layer to a lower surface of the plate. 
     
     
         16 . The cover according to  claim 1 , wherein the electromagnetic sensor is a radar sensor.