Multiplane information storage system with an improved record carrier

An information storage system comprising an optical record carrier having at least two information planes, and a reading device for scanning the information planes from one side of the record carrier, said device comprising a first optical system for forming a radiation spot on an information plane to be read, a second optical system for passing radiation from the record carrier to a radiation-sensitive detection system which converts the radiation into an electric detection signal, and a detection circuit electrically connected to the detection system for converting the detection signal into an information signal, wherein said detection circuit determines an interference ratio Q,

• characterized in that:
• a) the distances between the information planes, and
• b) the optical properties of the information planes each comply with the interference requirement of the information storage system, by which requirement the ratio between the sum of interference signals in the detection signal generated by the information planes not to be read and a read signal in the detection signal generated by the information plane to be read is smaller than said interference ratio Q determined by the detection circuit, and
• the interference requirement is defined by ##EQU38## in which the summation over j is over all information planes not being the information plane i to be read, the summation over f is over the frequencies present in the signal received from an information plane, E.sub.j is the power of the radiation in the zeroth diffraction order from information plane j, m.sub.j (f) is the modulation factor at frequency f of the information plane j, m.sub.j (f) for an information plane not to be read is determined with the radiation beam focused on plane j, MTF(f,d.sub.j /n) is the modulation transfer function at the frequency f of the radiation from the information plane j to the detection signal, d.sub.j is the distance between the information plane j and the information plane i to be read, and n is the refractive index of the medium between the information planes i and j.

An information storage system comprising an optical record carrier having at least two information planes, and a reading device for scanning the information planes from one side of the record carrier, said device comprising a first optical system for forming a radiation spot on an information plane to be read, a second optical system for passing radiation from the record carrier to a radiation-sensitive detection system which converts the radiation into an electric detection signal, and a detection circuit electrically connected to the detection system for converting the detection signal into an information signal, wherein said detection circuit determines an interference ratio Q,

• characterized in that:
• a) the distances between the information planes, and
• b) the optical properties of the information planes each comply with the interference requirement of the information storage system, by which requirement the ratio between the sum of interference signals in the detection signal generated by the information planes not to be read and a read signal in the detection signal generated by the information plane to be read is smaller than said interference ratio Q determined by the detection circuit, and
• the interference requirement is defined by ##EQU48## in which the summation over j is over all information planes not being the information plane i to be read, the summation over f is over the frequencies present in the signal received from an information plane, E.sub.j is the power of the radiation in the zeroth diffraction order from information plane j, m.sub.j (f) is the modulation factor at frequency f of the information plane j, m.sub.j (f) for an information plane not to be read is determined with the radiation beam focused on plane j, MTF(f,d.sub.j /n) is the modulation transfer function at the frequency f of the radiation from the information plane j to the detection signal, d.sub.j is the distance between the information plane j and the information plane i to be read, and n is the refractive index of the medium between the information planes i and j.