Abstract: The beam reflected by the mobile carrier is picked up by an optical pickup having several photodetectors. The elementary signals respectively delivered by the photodetectors are used to formulate two secondary signals, sampled and filtered by a low-pass filter having a cutoff frequency at most equal to a quarter of the sampling frequency. The mutual phase shift of the two secondary signals is representative of the positioning error TE of the beam with respect to the track. The determination of a value of the mutual phase shift comprises the selecting, for each secondary signal, of at least one pair of samples situated outside a predetermined amplitude range around a predetermined threshold. This makes it possible to tag, respectively for the two secondary signals, two transitions of these secondary signals with respect to the threshold and corresponding to one and the same direction of crossing of the threshold.

Abstract: A process and device are provided for controlling an incident optical beam for reading a track of a dynamic medium, e.g. a digital disc, having information stored therein. The beam reflected by the disc is picked up by an optical pickup having several photodetectors and the positioning error of the beam with respect to the track is determined from elementary signals delivered respectively by the photodetectors and from an overall signal containing the information and delivered by the pickup.

Abstract: A device for calculating a time gap between successive transitions of an incident signal includes an input stage which detects and selects transitions of an incident signal and calculates the time gap between each selected transition and an edge of a sampling clock signal. An assemblage of at least three blocks is also included. Each of the blocks includes a storage cell and a counter regulated by the sampling clock signal. In response to each selected current transition, a checking circuit or processor initializes the counter of the first block of the assemblage and stores in the cell of the first block the value of the time gap corresponding to the selected current transition. The contents of a block of the assemblage may then be transferred into a next block. The time interval between two successive selected transitions is determined based upon the counter values and the time gaps.

Abstract: A device is provided for calculating mutual phase shift of first and second incident signals. The device includes a first pair of blocks associated with the first incident signal, a second pair of blocks associated with the second incident signal, checking circuit, and post-processing circuit. Each of the blocks has storage elements for storing a predetermined set of samples of the corresponding incident signal. In the presence of minimum samples or maximum samples of both incident signals, the checking circuit stores a first set of samples relating to the first incident signal in one of the blocks of the first pair and a first set of samples relating to the second incident signal in the counterpart block of the second pair, and then stores the following sets of samples of each incident signal alternately in the two blocks of each pair. The checking circuit delivers a block validation signal when a set of samples has been completely stored in the storage elements of one of the blocks.