When recordingreading information data ontofrom a recording medium by irradiating the recording medium with a first light beam, correction for decreasing the amount of spherical aberration is made just before the recording or reading. Depending on the basic conditions, undesirably strong oscillations may occur at the compressor during compressor operation at the nominal rotational frequency. In the course of the positional measurement method, a projection is produced of part of the position code on the detector element that is dependent on the position of the code carrier ; said projection is produced by at least an emission of optical radiation onto the code carrier using a laser diode having an emitter edge, and said projection is detected by the detector element. When utilized in conjunction with oxygenator stems or bare root cuttings, the material is configured as a strip folded to enclose multiple cuttingsplants spaced at periodic intervals.