A portable reader module, comprising: a housing comprising: an internal space ; a first receptacle configured to removably receive a portable device comprising an imager and a light source, the first receptacle comprising a first optical entrance comprising a first opening for the imager to the internal space of the housing and a second opening through which light from the light source can enter the internal space ; 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 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 to define an optical path between the first opening of the first optical entrance and the second optical entrance ; and an illuminating path for illuminating the cartridge defined in the housing , wherein the housing is configured to allow the internal space to be light-shielded, wherein the illuminating path comprises a reflector for reflecting light from the light source of the portable device to the cartridge , and wherein internal walls of the housing in proximity to the second receptacle are provided with a low-reflexion surface while internal walls of the housing in proximity to the second opening are provided with a diffuse reflecting surface providing the reflector and improving light distribution, or wherein the reflector is a separate reflector arranged in proximity to the second opening . a housing comprising: an internal space ; a first receptacle configured to removably receive a portable device comprising an imager and a light source, the first receptacle comprising a first optical entrance comprising a first opening for the imager to the internal space of the housing and a second opening through which light from the light source can enter the internal space ; 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 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 and a light source, the first receptacle comprising a first optical entrance comprising a first opening for the imager to the internal space of the housing and a second opening through which light from the light source can enter the internal space ; 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 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 to define an optical path between the first opening of the first optical entrance and the second optical entrance ; and an illuminating path for illuminating the cartridge defined in the housing , wherein the housing is configured to allow the internal space to be light-shielded, wherein the illuminating path comprises a reflector for reflecting light from the light source of the portable device to the cartridge , and wherein internal walls of the housing in proximity to the second receptacle are provided with a low-reflexion surface while internal walls of the housing in proximity to the second opening are provided with a diffuse reflecting surface providing the reflector and improving light distribution, or wherein the reflector is a separate reflector arranged in proximity to the second opening . <EOS>