Abstract: The invention provides a method and apparatus 1, for determining the quality of the optical disk read signal. Said method comprises: comparing said optical disk read signal with a preset reference signal to acquire the signal values correlated with said preset reference signal in said optical disk read signal, with said correlated signal values satisfying a preset condition; sampling said optical disk read signal to acquire a, plurality of sampled signal values; acquiring, with respect to each of said signal values, two sampled signal values that are adjacent to each of said signal values according to said signal values and said sampled signal values; and finally determining the quality of said optical disk read signal on the basis of the preset relationship between the average and the maximum values of the differences of said two adjacent sampled signal values that are corresponding to each of the signal values.

Abstract: A loss of performance of slicer adaptation at high capacities due to the mismatch between the exact bits used in the computation of the RDS for the DC-control on the one hand and the often erroneous threshold decisions that are preliminarily made based on the HF waveform on the other hand, is resolved by performing a new method of DC-control at the encoder: the RDS is modified such that it is not based on the exact channel bits, but on the threshold decisions from a synthetic HF signal waveform that is generated based on a nominal MTF (modulation transfer function) or its IRF (impulse response function) of the channel. In this way, the impact of the erroneous threshold decisions in the receiver are already taken into account at the encoder, and the slicer control is no longer negatively affected thereby.

Abstract: The invention relates to a method of providing timing error information in optical systems, especially for reading high capacity optical discs, i.e. optical discs with a capacity of about 27 GB or above. At these capacities current threshold crossing timing recovery does not perform well and even becomes unfeasible due to severe inter-symbol interference. The method suggests using an upper and/or lower secondary eye in the eye diagram of the data signal to acquire the timing error information. Hereby, threshold crossing timing recovery becomes feasible for high capacity optical systems, where the central eye is closed or nearly closed due to the inter-symbol interference.

Abstract: The invention relates to an apparatus (20) for reading data from and/or writing data onto an optical data carrier (21) is proposed. An optical source generates an incident beam (26), an objective lens assembly (28) focuses the incident beam onto the optical data carrier. A thin convex lens (32) without substantial astigmatism is used for projecting the returning beam (30) onto an optical detection assembly (33) for generating a tracking error signal. An optical data carrier has a recording layer, onto which optically readable data is written in the form of binary marks or pits (11). The binary marks are capable of causing a phase difference which lies close to 180° between reflected light which has interacted with said binary marks and reflected light which has interacted with the rest of the recording layer. The signal to noise ratio of data signal and tracking error signal are improved at the same time.

Abstract: The invention regards a new threshold crossing timing recovery scheme for use in high capacity optical disc systems. The timing error of a timing error detector is multiplied with a weighing function. This scheme effectively increases the robustness of the optical system against data-induced jitter, which is considered to be the dominant disturbance of the timing recovery as the capacity of the optical discs is high. The invention furthermore describes a number of examples of possible weighing functions.

Abstract: For (re)writable and read-only optical disc systems the data clock is recovered by a phase locked loop (PLL), where the error signal is generated by comparing the actual zero-crossing with the zero-crossing of the generated clock signal. Given an optical system with a laser wavelength ?laser and a numerical aperture NA, the cut-off wavelength of the Modulation Transfer Function is given by ?0=?laser/(2·NA). With decreasing bit length the amplitude of the minimum wavelength will decrease and is zero for wavelengths below ?0. Consequently, the phase error signals generated by zero-crossing of these signals are disturbed by noise. The idea of the invention is to use the zero-crossings with sufficient performance only in deriving phase information for the clock recovery.

Abstract: A multi-stack optical data storage medium (20) for rewritable recording using a focused radiation beam (30), entering through an entrance face (25) is described. The medium (20) has a substrate (1a, 1b) and an L0 recording stack (2) and an L1 recording stack (3) both comprising a phase-change type L0 and L1 recording layer and the recording stacks are separated by a transparent spacer layer (4). The L0 recording stack (2) is present at a position closest to the entrance face (25) and has an optical transmission of TL0a and TL0c when the phase-change layer respectively is in the amorphous phase and in the crystalline phase. The medium (20) contains pre-recorded information modulated in at least one of: an embossed pregroove (21) in the substrate (1a, 1b), embossed pits in the substrate and recorded phase-change marks in at least one of the recording layers L0 and L1 (6, 11).

Abstract: In modem optical disc systems, inter-track spacing is chosen relatively small in order to allow high storage densities. As a result, the optical spot has a radius comparable with the track pitch, and the data written on neighboring tracks appear in the target track signal in the form of inter-track interference (cross-talk). To tackle the cross-talk problem, cross-talk canceling schemes are normally employed. These schemes use three spots, one spot on the main track and two satellite spots on adjacent tracks. The read signal (C) is improved by minimizing the cross-talk between the satellite signals (S+,S?) and the read signal (C). However, due to the decreasing inter-track spacing, the decorrelation concept fails since the satellite spots read too much central track information and become strongly correlated with the read signal (C), which causes “leakage” in the decorrelation.

Abstract: The present invention relates to an optical information carrier for recording information by means of an optical beam, said optical information carrier comprising a substrate layer (S), a recording layer (P) including a thermochromic material having temperature-dependent optical characteristics or a photochromic material having light dependent optical characteristics for selectively improving the sensitivity during recording and/or read-out, and a cover layer (C). To achieve an increase reflectivity the recording layer (P) at elevated temperature or high light intensity, respectively, and a very high transmission and low reflectivity at ambient temperature or low light intensity, respectively, it is proposed to use a thermochromic or photochromic material that has an imaginary part k of the complex refractive index ñ being larger than 0 at elevated temperature or high light intensity, respectively.

Abstract: The invention relates to a device and method of reducing the cross-talk between a data signal (HF) and an input push-pull signal (PP), for generating an output push-pull signal (IPP), said method comprising: -a convolution step for convoluting said data signal (HF) with a filter (F), for generating a first intermediary signal, -a multiplication step for multiplying said first intermediary signal to an adaptive scaling factor (a), for generating a second intermediary signal, -a subtracting step for subtracting said second intermediary signal to said input push-pull signal (PP), for generating said output push-pull signal (IPP).

Abstract: The invention relates to Run length Limited-codes storage systems. In modern storage systems, the inter-track spacing is chosen to be relatively small to allow for high storage densities. As a result, when reading a target track, data written on side tracks may appear in the recovered signal. This inter-track interference is called cross-talk. The invention proposes a cross-talk cancellation scheme based on the minimization of the mismatch between the actual (dm+1m) and the expected (exp) run length between two transitions (xm, xm+1) of the (dm+1,m) signal. The proposed solution significantly improves the ramp-up properties of the receiver and allows more efficient hardware implementation.

Abstract: The present invention relates to a fiber having a core of crystal fiber doped with chromium and a glass cladding. The fiber has a gain bandwidth of more than 300 nm including 1.3 mm to 1.6 mm in optical communication, and can be used as light source, optical amplifier and tunable laser when being applied for optical fiber communication. The present invention also relates to a method of making the fiber. First, a chromium doped crystal fiber is grown by laser-heated pedestal growth (LHPG). Then, the crystal fiber is cladded with a glass cladding by codrawing laser-heated pedestal growth (CDLHPG). Because it is a high temperature manufacture process, the cladding manufactured by this method is denser than that by evaporation technique, and can endure relative high damage threshold power for the pumping light.

Abstract: A light therapeutic device. The light therapeutic device comprises a flexible optical element capable of deforming corresponding to an affected part of a patient and providing a light of specific wavelength for treating the affected part. The flexible optical element comprises a flexible optical conductor coated with opaque material, and light is emitted from the flexible optical conductor by selectively removing the opaque material of a part of the optical conductors.

Abstract: The present invention relates to a fiber having a core of crystal fiber doped with chromium and a glass cladding. The fiber has a gain bandwidth of more than 300 nm including 1.3 mm to 1.6 mm in optical communication, and can be used as light source, optical amplifier and tunable laser when being applied for optical fiber communication. The present invention also relates to a method of making the fiber. First, a chromium doped crystal fiber is grown by laser-heated pedestal growth (LHPG). Then, the crystal fiber is cladded with a glass cladding by codrawing laser-heated pedestal growth (CDLHPG). Because it is a high temperature manufacture process, the cladding manufactured by this method is denser than that by evaporation technique, and can endure relative high damage threshold power for the pumping light.

Abstract: A multi-stack optical data storage medium (20) for rewritable recording using a focused radiation beam (30), entering through an entrance face (25) is described. The medium (20) has a substrate (1a, 1b) and an L0 recording stack (2) and an L1 recording stack (3) both comprising a phase-change type L0 and L1 recording layer and the recording stacks are separated by a transparent spacer layer (4). The L0 recording stack (2) is present at a position closest to the entrance face (25) and has an optical transmission of TL0a and TL0c when the phase-change layer respectively is in the amorphous phase and in the crystalline phase. The medium (20) contains pre-recorded information modulated in at least one of: an embossed pregroove (21) in the substrate (1a, 1b), embossed pits in the substrate and recorded phase-change marks in at least one of the recording layers L0 and L1 (6, 11).

Abstract: A light emitting diode. The light emitting diode comprises a lead frame, a plurality of light emitting chips in the lead frame, and a molding unit in an optical path of the light emitting chips, wherein the molding unit comprises a periodic microstructure.

Abstract: A method of fabricating micro crystal fiber lasers and frequency-doubling crystal fibers is disclosed. The micro crystal fiber laser contains gain crystal fibers, frequency-doubling crystal fibers, and a semiconductor laser. The semiconductor laser provides a laser beam. The gain crystal fibers receive the laser beam and generate a base-frequency beam. The frequency-doubling crystal fibers have a polarization alternating period. The frequency-doubling crystal fibers are coupled to the gain crystal fibers to double the frequency of the base-frequency beam and provide a double-frequency beam with the required wavelength. In addition to providing a monochromic crystal fiber laser, the crystal fiber lasers in red, green, and blue light may be combined into an array, providing a color laser. The frequency-doubling crystal fiber can be formed using the LHPG method.

Abstract: A wobble signal is generated from at least two elementary signals (A,B,C,D) detected by scanning a wobbled track of a data carrier. The invention proposes a solution for eliminating the noise of various origins in the wobble signal, notably the high frequency data leakage into the wobble signal due to radial asymmetry introduced in the diffraction pattern on the detector, whatever the reason for this radial asymmetry. According to the invention, the at least two elementary signals are filtered with at least an adaptive filter (40), and said filtered elementary signals are subtracted (44) from said wobble signal (PP) thereby generating an improved wobble signal.