A portable reader module, comprising: a housing (100, 101) comprising an internal space, a first receptacle configured to removably receive a portable device comprising an imager, the first receptacle comprising a first optical entrance for the imager to the internal space of the housing (100, 101), and a second receptacle configured to removably receive a cartridge, the second receptacle comprising a second optical entrance to the internal space of the housing (100, 101) so that the cartridge is visible to and from the internal space; a light-deflecting optical element arranged within the internal space of the housing (100, 101) to define an optical path between the first optical entrance and the second optical entrance; an illuminating path for illuminating the cartridge being defined in the housing (100, 101); and an adapter for holding the cartridge, wherein the adapter for holding the cartridge (500, 750) comprises a cartridge interface, which is inserted into the second receptacle, and a cartridge holder for holding the cartridge (500, 750), wherein the cartridge holder cooperates with the cartridge interface when the cartridge holder is releasably attached to the cartridge interface, wherein the cartridge interface remains inserted in the second receptacle and allows easy attachment of the cartridge holder which holds the cartridge (500, 750); wherein the housing (100, 101) is configured to allow the internal space to be light-shielded, and wherein one of the cartridge holder and cartridge interface comprises magnetic bodies and the other one of the cartridge holder and the cartridge interface comprises metal pins or discs which cooperate together with the magnetic bodies to hold the cartridge holder in place relative to the cartridge interface. a housing (100, 101) comprising an internal space, a first receptacle configured to removably receive a portable device comprising an imager, the first receptacle comprising a first optical entrance for the imager to the internal space of the housing (100, 101), and a second receptacle configured to removably receive a cartridge, the second receptacle comprising a second optical entrance to the internal space of the housing (100, 101) so that the cartridge is visible to and from the internal space; an internal space, a first receptacle configured to removably receive a portable device comprising an imager, the first receptacle comprising a first optical entrance for the imager to the internal space of the housing (100, 101), and a second receptacle configured to removably receive a cartridge, the second receptacle comprising a second optical entrance to the internal space of the housing (100, 101) so that the cartridge is visible to and from the internal space; a light-deflecting optical element arranged within the internal space of the housing (100, 101) to define an optical path between the first optical entrance and the second optical entrance; an illuminating path for illuminating the cartridge being defined in the housing (100, 101); and an adapter for holding the cartridge, wherein the adapter for holding the cartridge (500, 750) comprises a cartridge interface, which is inserted into the second receptacle, and a cartridge holder for holding the cartridge (500, 750), wherein the cartridge holder cooperates with the cartridge interface when the cartridge holder is releasably attached to the cartridge interface, wherein the cartridge interface remains inserted in the second receptacle and allows easy attachment of the cartridge holder which holds the cartridge (500, 750); wherein the housing (100, 101) is configured to allow the internal space to be light-shielded, and wherein one of the cartridge holder and cartridge interface comprises magnetic bodies and the other one of the cartridge holder and the cartridge interface comprises metal pins or discs which cooperate together with the magnetic bodies to hold the cartridge holder in place relative to the cartridge interface.