An engine pre-heater system comprising a housing having a passage extending therethrough for passage of coolant through the pre-heater. A device is provided for monitoring the introduction of substitution fluids for an extra-corporeal blood processing unit with an extra-corporeal blood circuit and an extra-corporeal blood processing device with a device for monitoring the introduction of substitution fluids. The bore encloses a cartridge piercing pin therein, as part of its prior art use. The rolling bearing is constituted by a linear bearing assembly with recirculating rolling elements. A servo circuit 10 extracts a specific portion having a specific amplitude or period from the reproduced random signal in each of the objective lens moved states, finds a first amplitude value and second amplitude value in the specific portions, and controls an aberration corrector 6 so that the difference between the first amplitude value and the second amplitude value approaches zero.