Optical information apparatus and information processing apparatus

An optical information apparatus that records and/or reproduces information on and/or from a recording medium having a plurality of information recording surfaces, the optical information apparatus comprising:

• a light source that emits laser light with a wavelength of λ;
• an objective lens that causes the laser light from the light source to converge on any of the plurality of information recording surfaces of the recording medium;
• a luminous flux splitting element which is divided in a direction perpendicular to a tangent line of an information track of the information recording surface of the recording medium, which has a central region including an optical axis of the laser light and a first end portion region and a second end portion region that sandwich the central region, and which splits the laser light reflected by any of the information recording surfaces of the recording medium into a luminous flux diffracted by the central region, a luminous flux diffracted by the first end portion region, and a luminous flux diffracted by the second end portion region;
• a first light detector which receives a plurality of luminous fluxes split by the luminous flux splitting element and which outputs a plurality of signals in accordance with light intensities of the plurality of received luminous fluxes;
• a plurality of waveform equalizers which impart different gains to the plurality of signals output from the first light detector in accordance with a frequency component of each signal;
• an adder which adds up a plurality of signals output from the plurality of waveform equalizers and which outputs the added signals as an information signal;
• and
• a signal processing section which processes the information signal, wherein
• the central region is formed by a binary diffraction grating and generates ±1 order diffracted light from the laser light incident on the central region,
• the first end portion region is formed by a blazed diffraction grating and generates first +1 order diffracted light from the laser light incident on the first end portion region,
• the second end portion region is formed by a blazed diffraction grating and generates second +1 order diffracted light from the laser light incident on the second end portion region, and
• the first light detector receives both the ±1 order diffracted light generated by the central region, the first +1 order diffracted light generated by the first end portion region, and the second +1 order diffracted light generated by the second end portion region.