Portable appliance for detecting explosive materials, having an apparatus for generating and measuring emission of an indicator, wherein the indicator has a carrier and a plurality of indicator substances (125-1, 125-2) that can be impinged upon by analytes, said indicator substances being applied onto the carrier as a thin layer and being positionable in an indicator area by means of a holding apparatus, wherein the indicator substances (125-1, 125-2) are arranged in different regions of the carrier in such a way that the indicator substances in the indicator area represent a pattern of indicator substances depending on the location, wherein the apparatus comprises: a plurality of radiation sources (210-1, 210-2) for emitting quasi-monochromatic excitation radiation, wherein the radiation sources are arranged at various locations in a radiation area in such a way that the radiation area represents a pattern of radiation sources (210-1, 210-2) depending on the location; an excitation beam path with at least one first imaging system (220-1, 220-2) for imaging excitation radiation into the indicator area in such a way that emission of the indicator substances is producible at the locations at which the excitation radiation is imaged on the indicator area; an emission beam path having at least one second imaging system for imaging the indicator area into a reception area in such a way that a pattern of emissions is producible in the reception area depending on the location; a plurality of receivers (270-1, 270-2) for receiving emissions from the reception area and for converting the received emissions into electrical signals wherein the excitation beam path and the emission beam path are arranged in a backward geometry such that the excitation beam path and the emission beam path are arranged on one and the same side of the indicator area, and wherein the excitation beam path has a plurality of excitation channels, wherein each excitation channel has a first imaging system (220-1, 220-2) that defines an optical axis (222-1, 222-2) of the excitation channel, characterized in that the optical axes (222-1, 222-2, 252) of the first imaging systems (220-1, 220-2) of the excitation beam path and of one or more second imaging systems of the emission beam path cross at a distance in front of the indicator area, and so points of intersection of the optical axes (222-1, 222-2, 252) in the indicator area are laterally spaced apart. a plurality of radiation sources (210-1, 210-2) for emitting quasi-monochromatic excitation radiation, wherein the radiation sources are arranged at various locations in a radiation area in such a way that the radiation area represents a pattern of radiation sources (210-1, 210-2) depending on the location; an excitation beam path with at least one first imaging system (220-1, 220-2) for imaging excitation radiation into the indicator area in such a way that emission of the indicator substances is producible at the locations at which the excitation radiation is imaged on the indicator area; an emission beam path having at least one second imaging system for imaging the indicator area into a reception area in such a way that a pattern of emissions is producible in the reception area depending on the location; a plurality of receivers (270-1, 270-2) for receiving emissions from the reception area and for converting the received emissions into electrical signals wherein the excitation beam path and the emission beam path are arranged in a backward geometry such that the excitation beam path and the emission beam path are arranged on one and the same side of the indicator area, and wherein the excitation beam path has a plurality of excitation channels, wherein each excitation channel has a first imaging system (220-1, 220-2) that defines an optical axis (222-1, 222-2) of the excitation channel, characterized in that the optical axes (222-1, 222-2, 252) of the first imaging systems (220-1, 220-2) of the excitation beam path and of one or more second imaging systems of the emission beam path cross at a distance in front of the indicator area, and so points of intersection of the optical axes (222-1, 222-2, 252) in the indicator area are laterally spaced apart.