Abstract: An optical pickup for picking up signals from an optical disk comprises a hologram to split a laser beam emitted from a laser light source into one 0th diffraction light beam and two 1st diffraction light beams, and also to diffract return light beams reflected from the optical disk with two grating areas formed on one surface thereof. The diffracted light beams from the hologram are detected by a 6-piece-divided photodetector. The number of parts included in the system has been greatly reduced.

Abstract: An optical pickup for picking up signals from an optical disk comprises a hologram to split a laser beam emitted from a laser light source into one 0th order diffraction light beam and two 1st order diffraction light beams, and also to diffract return light beams reflected from the optical disk with two grating areas formed on one surface thereof. The diffracted light beams from the hologram are detected by a 6-piece-divided photodetector. The number of parts included in the system has been greatly reduced.

Abstract: A segmented digital transversal filter comprising a first transversal filter 4 that eliminates all frequency components from a signal sequence above half the subsampling frequency, a second transversal filter 11 that convolutes the output of the first filter with a decimated and energy compensated lower band of filter coefficients (HI.sub.1 '), a third transversal filter 22 that convolutes the output of the first filter and a decimated and energy-compensated upper band of filter coefficients (HI.sub.2 '), and a fourth transversal filter 32 that convolutes the original signal sequence and the central band of filter coefficients (HI.sub.3). Delays 21 and 31 are added so that the outputs of the second, third and fourth filters arrive concurrently at an adder 51, the sum being the output of the invention.