Optical head device, inclination detection apparatus using the same, and optical information processing apparatus using the same

An inclination angle detection apparatus, comprising:

• a light source for emitting a beam;
• a collection optical system for converging the beam emitted by the light source into a microscopic spot on an information memory medium;
• a light detector for receiving the beam diffracted and/or reflected by the information memory medium and outputting a signal in accordance with a light amount of the beam received by the light detector;
• and
• a signal processing section for receiving the signal output from the light detector and performing an operation of the signal,
• wherein:
• the light detector outputs a first signal and a second signal,
• the information memory medium has marks or prescribed grooves,
• the relationship of λ1/NA1/Gp1≠λ2/NA2/Gp2 and the relationship of NA1>λ1/Gp1 or NA2>λ2/Gp2 are fulfilled where Gp1 is the cycle of marks or grooves on the information memory medium for obtaining the first signal, Gp2 is the cycle of marks or grooves on the information memory medium for obtaining the second signal, λ λ1 is the wavelength of the beam emitted by the light source for obtaining the first signal, λ2 is the wavelength of the beam emitted by the light source for obtaining the second signal, NA1 is the numerical aperture of the collection optical system on the side of the information memory medium for obtaining the first signal, and NA2 is the numerical aperture of the collection optical system on the side of the information memory medium for obtaining the second signal, and
• the signal processing section detects an angle made by the beam converged by the collection optical system and the information memory medium using the first signal and the second signal.