Abstract: Provided is a lens driving unit for an optical pickup and an optical disc drive employing the lens driving unit. First and second driving coils are directly wound around a coil winding unit included in the lens frame, which is different from a conventional lens frame in which a driving coil is manufactured as a separate element and is separately attached to a lens frame.

Abstract: In one embodiment, the optical read/write apparatus includes a plurality of optical pickups arranged to cross tracks of an optical storage medium and a control section. On finding the data that has been written by any of those optical pickups inaccurate or on detecting any defect at a location where data is going to be written by any of the optical pickups, the control section instructs another one of the optical pickups to write that data on a different track from a track on which the data should have been written.

Abstract: An optical pickup apparatus including a photodetector including first to fourth quadrant light-receiving portions, a first generating unit configured to generate a focus error signal based on respective signals from the first to fourth light-receiving portions, a second generating unit configured to generate a tracking error signal based on respective signals from the first to fourth light-receiving portions, first to fourth low-pass filters configured to allow respective signals to be input thereto from the first to fourth light-receiving portions, a third generating unit configured to generate a first correction signal for correcting the focus error signal by performing subtraction on an addition signal obtained by adding respective signals from the first and fourth low-pass filters, and an addition signal obtained by adding respective signals from the second and third low-pass filters, and a correction unit configured to correct the focus error signal based on the first correction signal.

Abstract: Provided are an objective lens driving device capable of strengthening the effective magnetic fluxes of the magnets while preventing increases in size and costs of the device; and an optical pickup apparatus including the same. The objective lens driving device of the invention includes an actuator frame for movably supporting an OBL holder. Four tracking coils are attached to sidewalls of the OBL holder, and four magnets are attached to the back yokes of the actuator frame to be opposed to the tracking coils, respectively. In addition, two of the tracking coils are placed tilting to one of the sidewalls of the OBL holder.

Abstract: In one embodiment, an optical read/write apparatus includes first and second optical pickups 2a, 2b and a control section. The first optical pickup 2a includes a first lens 3a that condenses a light beam emitted from a first light source onto an optical storage medium, and a first lens actuator that can shift the first lens 3a in a track crossing section with respect to a middle position. The second optical pickup 2b includes a second lens 3b that condenses a light beam emitted from a second light source onto the optical storage medium, and a second lens actuator that can shift the second lens 3b in the track crossing section with respect to the middle position. The control section makes the lens actuators operate so that as the magnitude of shift of the first lens 3a increases, that of the second lens 3b decreases.

Abstract: Provided is an optical recording medium, including a plurality of tracks on each of which small record carriers are arranged in a wobbling manner, each of the small record carriers storing a recording state by modulation according to light irradiation, wherein the tracks are arranged adjacent to each other in a tracking direction which is a direction orthogonal to a longitudinal direction of the tracks, and there is a reflectance difference between a forming portion and a non-forming portion of the small record carrier in both of a recording state and a non-recording state of the small record carrier.

Abstract: An optical disc apparatus includes a focus controller including a first digital filter, tracking controller including a second filter, focus actuator driver, tracking actuator driver, defect detector for detecting a defect on an optical disc, and a system controller for controlling the focus controller, the tracking controller and the defect detector. The system controller holds an input and output of at least one of either the focus controller or the tracking controller on the basis of the output of the defect detector, and sets an initial value in a delay memory of the digital filter of the controller held upon awake of the hold state.

Abstract: Systems and methods for data storage on an optical medium having a plurality of tracks include splitting a light beam into a higher power main beam and at least one lower power side beam that form corresponding spots spaced along a selected one of the plurality of tracks and selectively positioning and aligning the beams/spots along the selected one of the plurality of tracks using the higher power main beam to write data while reading previously written data using the at least one lower power side beam. The systems and methods may include correlating the read signal with a time-shifted write signal to provide a direct read after write capability to verify data written to the optical medium. In one embodiment, an optical tape drive includes an optical pickup unit (OPU) that generates a lower power satellite beam to read data directly after writing by a higher power main beam.

Abstract: A reversible recording medium based on optical storage of at least one item of information within a support material, includes at least one layer of support material having: base molecules able to take, in a local zone, a first collective state of molecules able to generate a first signal of second harmonic characteristic of this first collective state of molecules when excited by electromagnetic reading radiation; the base molecules having the first collective state of molecules able to transform, at least in part, into transformed molecules so as to pass to a second collective state of molecules when excited by electromagnetic writing radiation, the molecules having the second collective state of molecules able to generate a second signal of second harmonic characteristic of this second collective state of molecules when excited by the electromagnetic reading radiation. The molecules exhibit a molecular structure based on a coumarin skeleton of Formula (I).

Abstract: An acoustic hologram imaging system constructed from a machined housing having folded optics. Various surfaces of the housing are machined to provide a precise alignment to the optical members to be connected thereto, such as a mirror, a lens assembly, a light emitting laser diode, a camera, and the like. A three-part lens is described having different materials with different indexes of refraction in order to provide a desired focus of the light. In addition, an optical spatial filter is disclosed in which, according to various embodiments, all, some, or none of the light passing therethrough is attenuated for recording of the optical image of the hologram.

Abstract: The amplitude deviation of a tracking error signal in an optical disk apparatus is reliably corrected by processing signals at low costs. A servo signal generator generates a tracking error signal and a lens error signal from a photodetected signal. A lens error deviation signal memory circuit stores the lens error signal generated at the servo signal generator, and reproduces the one-turn deviation of the lens error signal. A tracking error signal corrector learns an amplitude correcting value for the tracking error signal from the tracking error signal detected in reproducing the one-turn deviation of the lens error signal, and stores the amplitude correcting value in a correcting signal generator.

Abstract: An information recording medium (11) adopting a zone CAV method is provided with: a guide layer (12) in which tracks (TR) are formed in advance; and a plurality of recording layers (13) laminated on the guide layer. On the tracks, a plurality of guide areas (22), each of which has a physical structure for carrying guide information for guidance, are arranged discretely at arrangement intervals of predetermined distance or less which is set in advance in a track direction and are shifted between a plurality of tracks throughout the plurality of tracks which are adjacent to each other in a radial direction. The plurality of guide areas are disposed in a partial plurality of slots which are not adjacent to each other in the track direction and which are not adjacent to each other throughout the plurality of tracks in the radial direction, out of a plurality of slots obtained by dividing the tracks in the track direction.

Abstract: An information recording medium (11) adopting a CLV method is provided with: a guide layer (12) in which tracks (TR) are formed in advance; and a plurality of recording layers (13) laminated on the guide layer. On the tracks, a plurality of guide areas (22), each of which has a physical structure for carrying guide information for guidance, are arranged discretely at arrangement intervals of predetermined distance or less which is set in advance in a track direction and are shifted between a plurality of tracks throughout the plurality of tracks which are adjacent to each other in a radial direction.

Abstract: An optical disk driving apparatus includes an optical head device having a laser light source, a converging optical system converging a light beam emitted by the laser light source onto an optical disk, a photo detector receiving reflected light reflected by the optical disk, and an aberration correcting optical system controlling aberration of the converging optical system; a motor rotating the optical disk; and a control section receiving a signal from the photo detector, wherein the converging optical system has an objective lens formed using resin as a main material, the aberration correcting optical system has a spherical aberration correcting element correcting spherical aberration, and the control section evaluates quality of a reproduction signal for information in the optical disk by using the reflected light received by the photo detector, and utilizes a result of the evaluation to perform closed loop control on the spherical aberration correcting element.

Abstract: An optical pickup apparatus is provided. Segmented regions included in a focus diffraction region includes focus segmented regions corresponding in number with different light emitted by a light source. Different focus segmented regions are arranged adjacent to each other alternately in a direction perpendicular to a parallel dividing line. Segmented regions included in a tracking diffraction region includes tracking segmented regions corresponding in number with different light emitted by the light source. Different tracking segmented regions are arranged adjacent to each other alternately in a direction perpendicular to the parallel dividing line.

Abstract: An optical pickup having a case made of a resin material reinforced with glass fiber, inorganic filler or the like with polyphenylene sulfide as a base material, and a metal plate formed of a material having a linear expansion coefficient within a range of a linear expansion coefficient of the case in a direction between bearings when a fiber orientation of the case is along the direction between the bearings or random. The metal plate has two rising members bended to the case side at both ends in the direction between the bearings. Two walls of the outer hull of an opening of the case at both ends in the direction between the bearings and the two rising members of the metal plate are alternately opposed, and the opposed walls of the case and the rising members of the metal plate are fixed using adhesives.

Abstract: An optical pickup device and an optical disc apparatus including the optical pickup device are provided which can obtain a stable servo signal in the recording/reproduction of an information recording medium inexpensively fabricated with multiple information recording surfaces. The optical pickup device includes: a laser diode that emits a light beam; a grating that splits the light beam into at least a main beam, a first sub beam, and a second sub beam; and an objective lens that condenses the light beams and forms at least three spots on an optical disc, wherein the spot of the first sub beam and the spot of the second sub beam are located inside or outside the spot of the main beam on the optical disc, and a tracking error signal is generated from signals obtained by detecting the first sub beam and the second sub beam.

Abstract: An optical recording disc comprises: at least ten optical recording layers; a plurality of intermediate layers each interposed between adjacent optical recording layers; a base film configured to support the optical recording layers and the intermediate layers; a cover layer disposed opposite to the base film with the optical recording layers and the intermediate layers interposed therebetween. The optical recording disc is in the shape of a disc as a whole. The total thickness of the optical recording disc is not more than 300 micrometers, and the optical recording disc provides flexibility.

Abstract: An optical-recording-medium driving apparatus includes: a light irradiating/receiving section configured to irradiate light on a medium so as to form a first side spot, a main spot, and a second side spot, and to receive reflection light from the individual spots; a first delay section configured to delay a light reception signal on the first side spot in accordance with a disposition interval between the first and the second side spots; a second delay section configured to delay a light reception signal on the main spot in accordance with a disposition interval between the main and second side spots; and a tracking-error-signal generation section configured to generate a tracking error signal on the basis of a correlation between delayed light reception signals on the first side spot and the main spot, and a correlation between the light reception signals on the second side spot and the main spot.

Abstract: A lens surface (22) of an objective lens (20) includes an optical surface (221) formed of a plurality of annular optical surfaces (22a, 22b, 22c, and 22d) which include an approximately stair-shaped cross section and which are annularly partitioned centered around an optical axis (OA) of the objective lens (20), and a plurality of connecting surfaces (251) that connect the plurality of mutually adjacent annular optical surfaces to each other. The plurality of connecting surfaces (251) include cylindrical connecting surfaces (25b and 25c) formed of a cylindrical surface centered around the optical axis (OA) and a conical connecting surface (26a) formed of a conical surface centered around the optical axis (OA), and the conical connecting surface (26a) connects the annular optical surface (22c) and the annular optical surface (22d).

Abstract: An optical disc apparatus includes an optical pickup, a signal generation section which generates a control signal from an electrical signal, and a main control section which controls the optical pickup such that, during a spin-up operation of an optical disc, the optical disc is discriminated to be a multiple-layer disc with three or more layers and address information is successfully acquired from the optical disc, the optical pickup irradiates the optical disc with a light beam at a light emission power for a multiple-layer disc with three or more layers. However, if disc information is not successfully acquired, the main control section controls the optical pickup to try again to acquire the disc information at the light emission power for a multiple-layer disc with three or more layers.

Abstract: An optical disk device is configured such that when an optical disk including three or more recording layers on one side is inserted into the optical disk device, a movable lens position adjustment device performs adjustment using as an index a tracking error signal provided with a limit to an amount of movement of a movable lens for spherical aberration correction at start-up of the optical disk device and sets an upper limit to the number of retries of the adjustment at the recording layer farthest away from the side on which the laser beam is incident to 1 or more.

Abstract: Before tracking control is turned on, there is determined a correction formula for correcting a balance value of a tracking error signal depending on a position of a movable lens for spherical aberration correction. Then, after the tracking control has been turned on, using an RF signal as an index, the adjustment of the position of the movable lens for spherical aberration correction is performed, while the balance value of the tracking error signal is corrected by use of the correction formula. An adjustment value for adjusting the balance value of the tracking error signal at a time point of completing the adjustment of the position of the movable lens for spherical aberration correction is stored.

Abstract: The present invention accurately operates a tilt servo even if a gap servo is operated with a small gap.

Abstract: Obtain an expanded address without altering the bit number of an address which is embedded in a wobble. Generate a virtual bit which is not recorded on a disc, and which is expressed by the disparity from the rules and the presence or absence of information embedded in part or all of the wobble address.

Abstract: An optical disc for recording information with a plurality of sorts of data recording densities. The optical disc has a plurality of data recording areas for recording information with mutually different data recording densities. Information about the data recording densities in the data recording areas is recorded in management information recording areas (BCA and PIC areas) with a specific format not depending on the data recording densities of the data recording areas. In this case, the data recording areas are located to be divided in the same plane of the disc or to be divided into a plurality of recording layers.

Abstract: An optical disc apparatus includes an optical pickup, a signal generation section which generates a total reflection signal and a focus error signal, and a servo control section which controls optical pickup. The optical disc apparatus further includes a main control section which binarizes the track cross signal by using a predetermined threshold value and, by using the binarized track cross signal, checks the tracing state of a track. The main control section controls the servo control section to check, by tracing one turn of the track of an optical disc, whether or not a tracking servo deviation occurs. When a tracking servo deviation occurs during the tracing, the main control section controls the servo control section to make the check once again. When, in the check made once again, a tracking servo deviation is found to occur again, the main control section increases the threshold value used in binarization.

Abstract: An optical disc for recording information with a plurality of sorts of data recording densities. The optical disc has a plurality of data recording areas for recording information with mutually different data recording densities. Information about the data recording densities in the data recording areas is recorded in a BCA area with a specific format not depending on the data recording densities of the data recording areas. In this case, the data recording areas are located to be divided in the same plane of the disc or to be divided into a plurality of recording layers.

Abstract: A disk drive determines, from eccentric amounts of individual prescribed rotation phases for one round of an optical disk 1, a rotation phase range in which a lens shift amount after tracking pulling-in of an object lens constituting an optical pickup 3 does not exceed a movable range of the object lens in a preset tracking direction, sets the rotation phase range as a tracking pulling-in range, and carries out tracking pulling-in of the optical pickup 3 while the rotation phase of the optical disk 1 is placed within the tracking pulling-in range.

Abstract: According to the present invention, an information reproduction device and an information reproduction method are provided, which are capable of reproducing data using temporary management information that is identified by a simple way of specification. In the present invention, the control receives temporary management information identifying information, searches for and reproduces the most suitable one of a plurality of temporary management information, and reproduces data using the temporary management information. Thus, it is possible to obtain contents of an overwritten file as of before the file was overwritten.

Abstract: An optical disc apparatus includes an optical pickup unit which reads data recorded on an optical disc and converts the data into a radio frequency (RF) signal. A defect detection unit detects a defect on the optical disc using the RF signal output from the optical pickup unit. A servo signal processing unit holds a servo control signal in a corresponding defective section when the defect is detected on the optical disc. A control unit detects the variance of the servo control signal after the defective section, and uses that as feedback so as to control a servo control signal of a subsequent defective section.

Abstract: A method for irradiating a medium with a wave which is designed to focus on a particular portion in the medium, the method includes: irradiating the medium with an electromagnetic wave which is scattered in the medium, and is not designed to focus on the particular portion in the medium; detecting a first signal caused by irradiating the medium with the electromagnetic waver; irradiating the medium with a reconstructed wave which is designed to focus on the particular portion in the medium; detecting a second signal caused by irradiating the medium with the reconstructed wave; and monitoring, based on the first and second signals, that the particular portion is irradiated by the reconstructed wave.

Abstract: An FE·FS ratio, which is a ratio of a focus error signal amplitude and a focus sum signal amplitude which are measured by using one kind of light source of at least two kinds of light sources that are compatible with different kinds of optical discs, is calculated; it is determined whether the FE·FS ratio is unusual or not by comparing the calculated FE·FS ratio with a threshold value; a focus servo is turned on in a case where the FE·FS ratio is usual; thereafter, a focus error signal amplitude adjustment value is calculated based on a focus sum signal amplitude measurement value; and in a case where the FE·FS ratio is unusual, the kind of the light source is changed and a retrial is performed to calculate the FE·FS ratio.

Abstract: Even when a first differentiation value is equal to or greater than a first threshold value, this optical disc device does not confirm “CD” to be the differentiation result, as long as a first focus error signal FE1 or a first focus sum signal FS1 is less than a second threshold value; and even when the first differentiation value is equal to or greater than a second differentiation value, this optical disc device does not confirm “CD” to be the differentiation result, as long as the signal FE1 is less than a second focus error signal FE2, or as long as the signal FS1 is less than a second focus sum signal FS2. The signals FE1 and FS1 are obtained when a CD laser beam is directed onto an optical disc. The signals FE2 and FS2 are obtained when a DVD laser beam is directed onto the disc.

Abstract: Provided is an optical disc apparatus and an optical disc recording method, in which it is decided whether or not an optical disc recording medium is one of DVD-RW and DVD+RW when data is recorded in the medium. If it is decided that the medium is one of DVD-RW and DVD+RW, maximum length information is read out from a storage portion. The maximum length information contains a previously set maximum data length of data recorded to the medium by an optical pick-up portion in one recording operation. Data to be recorded is split into split data having a data length of the maximum data length or smaller. Further, an electric power value of a base electric power for controlling the semiconductor laser element to emit a laser beam with a bottom power is reset every recording operation of the split data.

Abstract: Information is recorded and reproduced with high quality by all of the information layers of an optical information recording medium. A recording wavelength generator (112) selects control parameters of a recording pulse sequence for forming marks, on the basis of combinations of a mark length of a mark, a first space length of a first space immediately before the mark, and a second space length of a second space immediately after the mark. A laser drive circuit (111) records the marks by the recording pulse sequence determined by the selected control parameters. The first space length is classified into m types (m is an integer) and the second space length is classified into n types (n is an integer).

Abstract: To provide a polymer compound capable of forming an alignment film which has a sufficient aligning performance to a liquid crystalline compound and which is excellent also in adhesion with an optical anisotropic film obtainable by polymerizing a liquid crystalline compound in an aligned state, and a composition containing it, as well as an alignment film obtainable by using such a composition, an optical element and an optical information writing/reading device. Provided is a polymer compound comprising polymerized units derived from a fumaric acid diester and polymerized units having a radical polymerizable group in a side chain. By using this polymer compound, an alignment film is prepared. An optical element having this alignment film and an optical anisotropic film is used as a retardation plate 4 having mechanical strength and heat resistance, and good reliability without peeling. An optical information writing/reading device is constituted by using it.

Abstract: A method for determining a phase difference of a tracking error signal is provided. The method includes: predetermining a plurality of phase differences, measuring MPP and SPP signals, establishing a phase difference curve by use of an amplitude ratio between (MPP+SPP) and (MPP?SPP), measuring MPP and SPP signals for a tracking error signal under test, calculating the amplitude ratio (MPP+SPP)/(MPP?SPP), and comparing with the phase difference curve to promptly determine the phase difference.

Abstract: A method for determining an eccentricity of an optical disc is provided. The method includes predetermining a plurality of optical disc with known eccentric distances, respectively measuring a ratio of maximum and minimum amplitudes of a tracking error signal of the optical discs, establishing an eccentric distance ratio table or curve, measuring a ratio of maximum and minimum amplitudes of the tracking error signal for an optical disc under test, and comparing the measured ratio with the table or curve to promptly determine the eccentricity distance of the optical disc under test.

Abstract: An apparatus includes a waveguide including a core layer and first and second cladding layers positioned on opposite sides of the core layer, a plurality of slots extending through the core layer and into the first and second cladding layers, a filler material in the slots, wherein the core has a first refractive index, the cladding layers have a second refractive index lower than the first refractive index, and the filler material has a third refractive index between the first and second refractive indices, and a light source positioned to direct light onto the slots. A data storage device that includes the apparatus is also provided.

Abstract: An optical pickup includes a lens moving mechanism constructed of a lens, a lens holder holding the lens, a guide member guiding the lens holder, a lead screw including a thread groove, a motor rotating the lead screw, and a rack gear including a body fixed to the lens holder and claws fitted into the thread groove of the lead screw, in which an arm connecting the body and the claws of the rack gear is formed so that the shape of a cross section perpendicular to the rotational axis direction of the lead screw is a convex shape, a recess shape or a wave-shape.

Abstract: According to one embodiment, single-sided dual-layer recordable disc 100 may be used. Information recording is performed by forming mark and space portions on data area DA using modulated laser power. Pp denotes the maximum laser power or peak power for forming the mark portion, and Pb denotes the bias power for forming the space portion. Power ratio Pb/Pp is calculated for each of recording layers L0 and L1. Information is recorded on any of the recording layers L0 and L1 based on the result of calculation. Here, the calculated power ratio Pb/Pp changes among the recording layers L0 and L1, thereby optimizing the recording condition for a multi-layer recordable optical disc within relatively short time.

Abstract: A pressure-sensitive adhesive sheet 1 for an optical data recording medium D1 from which a signal with a mark length shorter than the resolution limit of an optical system of a reproducing device is capable of being reproduced by reproduction light emitted during reproducing, the pressure-sensitive adhesive sheet 1 having an adhesive transparent resin layer 11 to be disposed on an data recording layer 3 of the optical data recording medium D1, the transparent resin layer 11 having a (meth)acrylate copolymer containing no acidic group as a main component, the transparent resin layer 11 having a storage elastic modulus at 23° C. of 1.5×105 Pa or less and a gel fraction of 68 wt % or more.

Abstract: A super-resolution optical recording medium includes: a medium information region on which medium identification information is recorded; a content region on which content information is recorded; and a blank region provided between the medium information region and the content region and in which at least two tracks are provided so as to connect a train of prepits in the medium information region and a train of prepits in the content region. No information is recorded on the blank region. Thus, a super-resolution optical recording medium is provided in which a region on which medium identification information is recorded and a region on which content information is recorded are different in track pitch and in which a reproduction error hardly occurs when reproduction shifts from the region on which the medium identification information is recorded to the region on which the content information is recorded.

Abstract: The operability of an optical disc device for reading or writing data from/to a disc having a data layer and a servo layer is improved by increasing the resistance to control disturbances. An optical disc device in accordance with the present invention includes an objective lens, a relay lens, a blue-violet laser detector, a red laser detector, an objective lens focus actuator, an objective lens tracking actuator, a relay lens actuator, a pair of focus error signal generating units, a pair of focus control signal generating units, a switching unit for selecting a focus control signal, a pair of tracking error signal generating units, a pair of tracking control signal generating units, a switching unit for selecting a tracking control signal, a focus error conversion unit and a tracking error conversion unit.

Abstract: In an optical recording medium, even when a plurality of recording and reading layers are stacked, deterioration in the recording and reading signal quality thereof is suppressed. Furthermore, the transfer rate thereof can be increased. When recording or reading information by means of light irradiation on or from an optical recording medium having a plurality of recording and reading layers which are stacked in advance or formed eventually, an optical recording and reading device includes: a first optical system for irradiating a first beam to recording and reading layers to be a first target to perform recording or reading of information; and a second optical system for irradiating a second beam to recording and reading layers to be a second target to perform recording or reading of information.

Abstract: An optical head capable of recording or playing back optical discs is provided. The optical disc comprises a light source to emit a beam, an objective to focus the beam on an optical disc, a beam dividing element having a plurality of divided areas with which to divide a cross section of the beam reflected from the optical disc, and a light detector to receive the beams divided by the beam dividing element, wherein the beam dividing element has in at least one of the plurality of areas an aberration imparting function of imparting an astigmatism or defocus aberration to a beam passing through that area.

Abstract: To ensure a favorable recording characteristic for a write-once recording medium for a bluish-purple laser, an optical information recording apparatus includes ways to write power to form recording marks, a space forming power to form spaces, pulse width of a cooling pulse and ways to record information onto the optical information recording medium according to the setting of the write power, the setting of the space forming power and the setting of the pulse width of the cooling pulse. At this time, the pulse width of the cooling pulse and a ratio whose numerator is the write power and whose denominator is the space forming power have a preferable region of the recording characteristic, and information is recorded onto the optical recording medium by using values in this range.

Abstract: Method and device for generating a control voltage for a position actuator of a disk drive system for displacing a lens of a pick-up unit to a given X-position. The actuator is operated by an open loop control system. First, parameters of the control system are calibrated so that the control system produces a control voltage (Va) from an input position signal (Xact_setp). Then, the control voltage is processed in a feed forward system for generating a processed control signal (Va_p) which is fed to the position actuator for displacing said lens to the X-position. A Z-value corresponding to the axial distance of the lens from a calibrated axial position and a temperature of the pick-up unit are measured. The position actuator operates according to the formula: Xdc=Va—p*K(Temp,Z)/(R(Temp)*C(Temp,Z)).

Abstract: A reproduction signal evaluation method evaluates the quality of a reproduction signal reproduced from an information recording medium based on a binary signal generated from the reproduction signal using a PRML signal processing system. A pattern extraction step extracts, from the binary signal, a specific state transition pattern which has the possibility of causing a bit error; a step computes a differential metric based on the binary signal; an extraction step extracts the differential metric which is not greater than a predetermined signal processing threshold; a step determines a mean value of the differential metrics which are not greater than the signal processing threshold and extracted in the extraction step; a standard deviation computing step determines a standard deviation which corresponds to an error rate predicted from the mean value; and an evaluation step evaluates a quality of the reproduction signal using the standard deviation.