Apparatus for recording and reading information tracks on an optical record carrier with a beam of radiation

An apparatus for recording and reading information tracks on a reflective information surface of a record carrier, said apparatus comprising a first laser which emits a write beam of radiation of a first wavelength for producing detectable changes in the information surface so as to record information thereon, a second laser which emits a read beam of radiation of a second wavelength which is different from said first wavelength for reading information recorded on the information surface, an objective system, said beams being directed through said objective system so that said objective system forms on the information surface a write spot and a read spot which is spaced from said write spot by a predetermined distance in the track direction and at least a portion of the radiation of each of said read and write beams is reflected by the information surface back along a portion of the paths traversed by the incident radiation, means for splitting off at least a portion of said reflected radiation of the write and read beams from the incident radiation of the beams which is travelling towards the information structure, said splitting off means including a wavelength sensitive means for rotating the direction of polarization of one of said write and read beams and a polarization sensitive beam splitter, said wavelength sensitive means and said beam splitter being disposed in said path portion traversed by said incident and reflected radiation, means for separating said reflected read and write radiation so that said reflected write radiation is directed along a first path and said reflected read radiation is directed along a second path, a first radiation sensitive detector disposed in said first path of the reflected write radiation which has been split off from the incident radiation, a second radiation sensitive detector disposed in said second path of the reflected read radiation which has been split off from the incident radiation, and a wavelength selective filter disposed in front of each of said first and second detectors so as to reduce the amount of radiation of said second wavelength reaching said first detector and to reduce the amount of radiation of said first wavelength reaching said second detector.

An apparatus for recording and reading information tracks on a reflective information surface of a record carrier, said apparatus comprising a first laser which emits a write beam of radiation of a first wavelength for producing detectable changes in the information surface so as to record information thereon, a second laser which emits a read beam of radiation of a second wavelength which is different from said first wavelength for reading information recorded on the information surface, said first and second lasers being arranged so that the beams emitted thereby are substantially parallel and have orthogonal directions of polarization, a polarization sensitive beam splitter disposed in the path of one of said write and read beams, means disposed in the path of the other of said beams for directing said other beam onto said beam splitter, said beam splitter being arranged to direct said orthogonally polarized beams incident thereon along a substantially common path, an objective system arranged in said common path so as to form from said beams a write spot and a read spot on the information surface, at least a portion of the radiation of said write and read beams being reflected by the information surface back through said objective system and along said common path, wavelength sensitive means for splitting off the reflected radiation from the radiation travelling towards the information structure and directing said reflected write radiation along a first path and said reflected read radiation along a second path which is different from said first path, a first radiation sensitive detector disposed in said first path and a second radiation sensitive detector disposed in said second path, said wavelength sensitive splitting off means including said polarization sensitive beam splitter disposed in said common path, first wavelength sensitive means disposed in said common path between said objective system and said beam splitter for changing the direction of polarization of the radiation of said one beam with respect to the radiation of said other beam such that said beam splitter directs the reflected radiation of said beams along a further common path which is different from said first-named common path, second wavelength sensitive means disposed in said further common path for changing the direction of polarization of one of said reflected read and write radiation with respect to that of the other, and a second polarization sensitive beam splitter arranged in said further common path so as to direct the reflected write radiation along said first path and the reflected read radiation along said second path.