Abstract: A position detection device configured to detect a position of a moving member that moves back and forth in a predetermined moving direction is provided with an exciting coil arranged to extend in the moving direction along the moving member, a detection coil that, by a magnetic field generated by the exciting coil, outputs a voltage corresponding to a position of a detection object portion moving together with the moving member within a predetermined detection range in the moving direction, and a calculation unit that determines the position of the moving member by calculation based on an output voltage of the detection coil. The detection object portion has a predetermined length in the moving direction, and a voltage is generated in the detection coil due to a difference in magnetic field intensity between a portion corresponding to the detection object portion and a portion not corresponding to the detection object portion.

Abstract: A position detection device detects a position of a moving member moving backward and forward in a predetermined moving direction. The position detection device includes an exciting coil disposed along the moving member and extending in the moving direction, a detection coil that outputs a voltage corresponding to a position of a detection target portion moving with the moving member by means of a magnetic field generated by the exciting coil within a predetermined detection range in the moving direction, and a calculation unit that calculates the position of the moving member by the output voltage of the detection coil. The detection coil includes a pair of coil elements whose output voltage changes according to the position of the moving member, and phases of the output voltages of the pair of coil elements during movement of the moving member within the detection range differ from each other.

Abstract: In a process of manufacturing a disc master, a stamper, a disc substrate, and an optical disc, separation performance between the stamper and the disc substrate and maintenance of satisfactory signal characteristics after the optical disc is manufactured are taken into consideration in the step of manufacturing the disc master. In the disc master, a boundary portion between a recessed portion and a non-recessed portion includes a small protrusion which protrudes from a flat surface of the non-recessed portion. The shape of the disc master is inversely transferred to the stamper, and the shape of the stamper is inversely transferred to the disc substrate. The separation performance is improved and the signal characteristics are maintained due to the shape of the boundary portion.

Abstract: An optical disc medium and corresponding optical recording method and optical recording apparatus. The optical disc medium comprises a substrate on which a shape according to modulated information data has been formed, and a coating film formed on the substrate. Known data is recorded in a predetermined location of the information data, with the known data being rewritten as postscript information by recording a postscript portion to the coating film to alter a portion of the known data, wherein the postscript information comprises readable non-error data.

Abstract: An optical disk read only memory having an information recording surface with a concave-convex pattern formed on the basis of a first signal and a reflective film covering the surface. The disc medium includes: an additional information recording section formed on a recording track of a first data string; and a second data string including a mark of removing or reducing the reflective film. The modulation methods of the first and the second data strings are identical, and Lh(n)>Lp1(n) and Wh(n)>(Wp1(n)+Wp2(n))/2 are satisfied, where a reference clock cycle is T, a data length is nT, a length and a width of the mark are Lh(n) and Wh(n), a length and a width of a base of the pit are Lp1(n), and Wp1(n), a length and a width of a top face of the pit is Lp2(n) exceeding Lp1(n), and Wp2(n) exceeding Wp1(n).

Abstract: A molding and film forming apparatus 700 molds a disc substrate from a stamper 330 formed from an optical disc disc-master 320 and forms a coating film, for example, a reflective film onto the disc substrate, thereby forming a recorded optical disc 360. A postscript apparatus 200 writes postscript information once onto an optical disc 340 formed by the molding and film forming apparatus 700. As postscript information, a laser beam is irradiated to a predetermined interval of the optical disc 340, a portion which is detected as a pit is formed, and an optical disc 350 on which postscript information 420 has been recorded is formed. Identification information which enables each optical disc 340 to be identified can be postscribed. The postscript information is recorded in a conventional format and the postscript information can be reproduced by an existing reproducing apparatus.

Abstract: An optical disc medium and corresponding optical recording method and optical recording apparatus. The optical disc medium comprises a substrate on which a shape according to modulated information data has been formed, and a coating film formed on the substrate. Known data is recorded in a predetermined location of the information data, with the known data being rewritten as postscript information by recording a postscript portion to the coating film to alter a portion of the known data, wherein the postscript information comprises readable non-error data.

Abstract: In a process of manufacturing a disc master, a stamper, a disc substrate, and an optical disc, separation performance between the stamper and the disc substrate and maintenance of satisfactory signal characteristics after the optical disc is manufactured are taken into consideration in the step of manufacturing the disc master. In the disc master, a boundary portion between a recessed portion and a non-recessed portion includes a small protrusion which protrudes from a flat surface of the non-recessed portion. The shape of the disc master is inversely transferred to the stamper, and the shape of the stamper is inversely transferred to the disc substrate. The separation performance is improved and the signal characteristics are maintained due to the shape of the boundary portion.

Abstract: An optical disk read only memory having an information recording surface with a concave-convex pattern formed on the basis of a first signal and a reflective film covering the surface. The disc medium includes: an additional information recording section formed on a recording track of a first data string; and a second data string including a mark of removing or reducing the reflective film. The modulation methods of the first and the second data strings are identical, and Lh(n)>Lp1(n) and Wh(n)>(Wp1(n)+Wp2(n))/2 are satisfied, where a reference clock cycle is T, a data length is nT, a length and a width of the mark are Lh(n) and Wh(n), a length and a width of a base of the pit are Lp1(n), and Wp1(n), a length and a width of a top face of the pit is Lp2(n) exceeding Lp1(n), and Wp2(n) exceeding Wp1(n).

Abstract: A molding and film forming apparatus 700 molds a disc substrate from a stamper 330 formed from an optical disc disc-master 320 and forms a coating film, for example, a reflective film onto the disc substrate, thereby forming a recorded optical disc 360. A postscript apparatus 200 writes postscript information once onto an optical disc 340 formed by the molding and film forming apparatus 700. As postscript information, a laser beam is irradiated to a predetermined interval of the optical disc 340, a portion which is detected as a pit is formed, and an optical disc 350 on which postscript information 420 has been recorded is formed. Identification information which enables each optical disc 340 to be identified can be postscribed. The postscript information is recorded in a conventional format and the postscript information can be reproduced by an existing reproducing apparatus.

Abstract: A molding and film forming apparatus 700 molds a disc substrate from a stamper 330 formed from an optical disc disc-master 320 and forms a coating film, for example, a reflective film onto the disc substrate, thereby forming a recorded optical disc 360. A postscript apparatus 200 writes postscript information once onto an optical disc 340 formed by the molding and film forming apparatus 700. As postscript information, a laser beam is irradiated to a predetermined interval of the optical disc 340, a portion which is detected as a pit is formed, and an optical disc 350 on which postscript information 420 has been recorded is formed. Identification information which enables each optical disc 340 to be identified can be postscribed. The postscript information is recorded in a conventional format and the postscript information can be reproduced by an existing reproducing apparatus.

Abstract: A molding and film forming apparatus 700 molds a disc substrate from a stamper 330 formed from an optical disc disc-master 320 and forms a coating film, for example, a reflective film onto the disc substrate, thereby forming a recorded optical disc 360. A postscript apparatus 200 writes postscript information once onto an optical disc 340 formed by the molding and film forming apparatus 700. As postscript information, a laser beam is irradiated to a predetermined interval of the optical disc 340, a portion which is detected as a pit is formed, and an optical disc 350 on which postscript information 420 has been recorded is formed. Identification information which enables each optical disc 340 to be identified can be postscribed. The postscript information is recorded in a conventional format and the postscript information can be reproduced by an existing reproducing apparatus.

Abstract: A disc defect inspection apparatus which can detect a defect of a disc, such as an optical disc, with high accuracy. A disc defect inspection apparatus includes a rotating portion for rotating a disc, laser radiating optical portion for radiating laser lights on the disc rotated by the rotating portion under predetermined scanning conditions, sensors for detecting reflected laser lights from the disc, and a memory in which output signals of the sensors are stored together with address data generated in unison with the scanning of laser lights. Sensor outputs indicative of address positions of the disc are stored in the memory and sensor outputs near the address positions are read out and a defect of the disc is detected on the basis of a spatial difference among the nearby sensor outputs and the sensor output of the center address position.

Abstract: An optical recording medium capable of recording and/or reproducing an information by using a laser beam, comprising: a support layer having an information signal-recording portion on one side surface thereof on which said laser beam is incident, and a transparent layer disposed over the support layer and having a thickness smaller than that of the support layer. In accordance with the present invention, there are further provided production method for optical or magneto-optical discs whereby a high density reproduction can be achieved.

Abstract: A disc defect inspection apparatus which can detect a defect of a disc, such as an optical disc, with high accuracy. A disc defect inspection apparatus includes a rotating portion for rotating a disc laser radiating optical portion for radiating laser lights on the disc rotated by the rotating portion under predetermined scanning conditions, sensors for detecting reflected laser lights from the disc, and a memory in which output signals of the sensors are stored together with address data generated in unison with the scanning of laser lights. Sensor outputs indicative of address positions of the disc are stored in the memory and sensor outputs near the address positions are read out and a defect of the disc is detected on the basis of a spatial difference among the nearby sensor outputs and the sensor output of the center address position.

Abstract: The present invention is directed to an optical data storage medium in which a reflecting layer is formed on a substrate. A dye containing layer having a reflectivity of 15 to 25% is used as the reflecting layer, and a signal modulation degree of an information signal falls within a range of from 0.3 to 0.6. Further, a real number portion n of complex index of refraction of the reflecting layer is selected so as to satisfy n.gtoreq.1.84.According to the present invention, there is provided an optical data storage medium which can be reproduced by a recording and reproducing apparatus which is designed so as to record and reproduce a medium such as a magneto-optical disc or the like having a reflectivity of about 15 to 25%. Therefore, the recording and reproducing apparatus that can record and reproduce the medium having the reflecting layer whose reflectivity is low can be made small in size and light in weight.

Abstract: An optical disc for use as a compact disc, an optical video disc, or the like has a disc substrate of a light-transmissive material such as polycarbonate, PMMA, or the like. The disc substrate has a pattern of pits and lands formed as representing an information signal on at least one surface thereof. A thin reflective layer of a-corrosion-resistant metallic material such as an alloy of Fe, Ni, and Co is deposited on the disc substrate over the pattern of pits and lands. The optical disc is relatively inexpensive to manufacture as no protective layer needs to be deposited on the reflective layer and is also highly resistant to loss of performance with aging because the reflective layer is made of a corrosion-resistant metallic material.