A device for detecting soiling of a shield, the device comprising: a housing; a shield connection body for connecting the device to the shield; a first light source for emitting light to the shield, wherein the first light source is arranged for emitting a first light beam that coincides with the shield at a first angle relative to the shield and at a first incidence area on the shield, resulting in a first reflected beam, the first reflected beam extending from the shield under the same angle as under which the first light beam is incident on the shield; a first light sensor arranged to receive light from the first light source and arranged to provide a first signal providing an indication for an amount of light received by the first light sensor, wherein the first light sensor is arranged for sensing light originating from the first incidence area, wherein the first light sensor is provided out of the path of the first light beam and the path of the first reflected beam, and wherein the shield and the housing provide a sensor space for housing the first light source and the first light sensor; a second light sensor arranged for receiving light directly from the first light beam or the first reflected beam and arranged to generate a second signal in response to receiving the light; and a processing unit, the processing unit being arranged to perform the following: compare a value of the first signal to a reference sensor value; generate a first warning signal if a difference between the sensed value of the first signal and the reference sensor value is above a first predetermined threshold; determine, based on the first signal, a transmission value related to a transmission factor of the shield for a range of electromagnetic waves and output the transmission value; determine a ratio between the value of the first signal and a value representative of the second signal; and generate a second warning signal if the ratio is above a second predetermined threshold. a housing; a shield connection body for connecting the device to the shield; a first light source for emitting light to the shield, wherein the first light source is arranged for emitting a first light beam that coincides with the shield at a first angle relative to the shield and at a first incidence area on the shield, resulting in a first reflected beam, the first reflected beam extending from the shield under the same angle as under which the first light beam is incident on the shield; a first light sensor arranged to receive light from the first light source and arranged to provide a first signal providing an indication for an amount of light received by the first light sensor, wherein the first light sensor is arranged for sensing light originating from the first incidence area, wherein the first light sensor is provided out of the path of the first light beam and the path of the first reflected beam, and wherein the shield and the housing provide a sensor space for housing the first light source and the first light sensor; a second light sensor arranged for receiving light directly from the first light beam or the first reflected beam and arranged to generate a second signal in response to receiving the light; and a processing unit, the processing unit being arranged to perform the following: compare a value of the first signal to a reference sensor value; generate a first warning signal if a difference between the sensed value of the first signal and the reference sensor value is above a first predetermined threshold; determine, based on the first signal, a transmission value related to a transmission factor of the shield for a range of electromagnetic waves and output the transmission value; determine a ratio between the value of the first signal and a value representative of the second signal; and generate a second warning signal if the ratio is above a second predetermined threshold. compare a value of the first signal to a reference sensor value; generate a first warning signal if a difference between the sensed value of the first signal and the reference sensor value is above a first predetermined threshold; determine, based on the first signal, a transmission value related to a transmission factor of the shield for a range of electromagnetic waves and output the transmission value; determine a ratio between the value of the first signal and a value representative of the second signal; and generate a second warning signal if the ratio is above a second predetermined threshold.