An autologous blood transfusion system for the recovery and washing of salvaged blood collected from a surgical site of a patient, comprising a blood collection reservoir for storing the collected blood, an optical detection setup (10, 12) for periodically detecting the liquid level of the salvaged blood in said blood collection reservoir and for outputting a corresponding output signal, and a processor for determining the liquid level of the salvaged blood in said blood collection reservoir based on said output signal of said optical detection setup (10,12), said optical detection setup (10,12) comprising: a plurality of light emitters disposed on a first side of said blood collection reservoir at different height levels (L1-L9) for emitting light and a plurality of light receivers disposed on a second side of said blood collection reservoir opposite to said first side for sensing light emitted by said light emitters and transmitted through said blood collection reservoir and for outputting said output signal: characterised by said processor is further configured for identifying a conspicuous signal out of said output signals of said light receivers based on a comparison of output signals of at least two light receivers out of said plurality of light receivers, wherein a conspicuous signal is a signal that indicates abnormal transmission changes between output signals of at least two directly adjacent light receivers or sequences of at least two transmission values that might be caused by blood or lipid films on the inner surface of the storage vessel or similar effects locally perturbing the optical transmission through the storage vessel, varying a detection parameter of a light emitter and/or of a light receiver and/or of an amplifier associated with said conspicuous signal, and repeating said step of determining the liquid level of the salvaged blood in said blood collection reservoir using said varied detection parameter. a blood collection reservoir for storing the collected blood, an optical detection setup (10, 12) for periodically detecting the liquid level of the salvaged blood in said blood collection reservoir and for outputting a corresponding output signal, and a processor for determining the liquid level of the salvaged blood in said blood collection reservoir based on said output signal of said optical detection setup (10,12), said optical detection setup (10,12) comprising: a plurality of light emitters disposed on a first side of said blood collection reservoir at different height levels (L1-L9) for emitting light and a plurality of light receivers disposed on a second side of said blood collection reservoir opposite to said first side for sensing light emitted by said light emitters and transmitted through said blood collection reservoir and for outputting said output signal: characterised by said processor is further configured for identifying a conspicuous signal out of said output signals of said light receivers based on a comparison of output signals of at least two light receivers out of said plurality of light receivers, wherein a conspicuous signal is a signal that indicates abnormal transmission changes between output signals of at least two directly adjacent light receivers or sequences of at least two transmission values that might be caused by blood or lipid films on the inner surface of the storage vessel or similar effects locally perturbing the optical transmission through the storage vessel, varying a detection parameter of a light emitter and/or of a light receiver and/or of an amplifier associated with said conspicuous signal, and repeating said step of determining the liquid level of the salvaged blood in said blood collection reservoir using said varied detection parameter. a plurality of light emitters disposed on a first side of said blood collection reservoir at different height levels (L1-L9) for emitting light and a plurality of light receivers disposed on a second side of said blood collection reservoir opposite to said first side for sensing light emitted by said light emitters and transmitted through said blood collection reservoir and for outputting said output signal: characterised by said processor is further configured for identifying a conspicuous signal out of said output signals of said light receivers based on a comparison of output signals of at least two light receivers out of said plurality of light receivers, wherein a conspicuous signal is a signal that indicates abnormal transmission changes between output signals of at least two directly adjacent light receivers or sequences of at least two transmission values that might be caused by blood or lipid films on the inner surface of the storage vessel or similar effects locally perturbing the optical transmission through the storage vessel, varying a detection parameter of a light emitter and/or of a light receiver and/or of an amplifier associated with said conspicuous signal, and repeating said step of determining the liquid level of the salvaged blood in said blood collection reservoir using said varied detection parameter.