Optical disk and optical disk apparatus where information is recorded having a specific track pitch and as a plurality of pit trains, each including a plurality of substantially trapezoidal pits

An optical disk apparatus comprising:

• an optical disk including a substrate having information recorded thereon with a specific track pitch, said information being recorded as a .plurality of pit trains, each of said pit trains including a plurality of pits and a reflecting layer formed on said substrate;
• an objective lens disposed so as to face said optical disk;
• means for projecting a light beam onto said optical disk via said objective lens;
• and
• means for sensing the reflected light of the light beam projected on said optical disk by said projecting means to reproduce the information recorded on said optical disk;
• wherein when the wavelength of said light beam is .lambda. .mu.m and the numerical aperture of said objective lens is NA, said track pitch is set in the range of (0.72 to 0.8).times..lambda./NA/1.14 .mu.m, and each of said pits has a substantially trapezoidal cross section whose upper width is in the range of (0.3 to 0.5).times..lambda./NA/1.14 .mu.m and whose lower width is in the range of (0.2 to 0.32).times..lambda./NA/1.14 .mu.m.

An optical disk comprising:

• a substrate having information recorded thereon at a specific track pitch, said information being in the form of a plurality of pit trains, each of said pits trains including a plurality of pits;
• and
• a reflecting layer formed on said substrate;
• wherein said information is reproduced by projecting a light beam via an objective lens, and when the wavelength of said light beam is .lambda. .mu.m and the numerical aperture of said objective lens is NA, said specific track pitch is in the range of (0.72 to 0.8).times..lambda./NA/1.14 .mu.m, and each of said pits has a substantially trapezoidal cross section whose upper width is in the range of (0.3 to 0.5).times..lambda./NA/1.14 .mu.m and whose inner wall is inclined at an angle of 30.degree. to 60.degree..

An optical disk apparatus comprising:

• an optical disk including a substrate having information recorded thereon with a specific track pitch, said information being recorded as a plurality of pit trains, each of said pit trains including a plurality of pits and a reflecting layer formed on said substrate;
• an objective lens disposed so as to face said optical disk;
• means for projecting a light beam onto said optical disk via said objective lens;
• and
• means for sensing the reflected light of the light beam projected on said optical disk by said projecting means to reproduce the information recorded on said optical disk;
• when the wavelength of said light beam is .lambda. .mu.m and the numerical aperture of said objective lens is NA, said track pitch is set in the range of (0.72 to 0.8).times..lambda./NA/1.14 .mu.m, and each of said pits has a substantially trapezoidal cross section whose upper width is in the range of (0.3 to 0.5).times..lambda./NA/1.14 .mu.m and whose inner wall is inclined at an angle of 30.degree. to 60.degree..

An optical disk comprising:

• a pair of transparent substrates with surfaces facing one another, each of said transparent substrates having information recorded thereon at a specific track pitch, said information being in the form of a plurality of pits trains, each of said pit trains including a plurality of pits, wherein said information is reproduced by projecting a light beam via an objective lens;
• a pair of reflecting layers coated on said facing surfaces of said pair of substrates, respectively;
• a pair of protective layers formed on said pair of reflecting layers, respectively;
• and
• an adhesive layer formed between said protective layers to adhere said pair of protective layers to one another;
• wherein when the wavelength of said light beam is .lambda. .mu.m and the numerical aperture of said objective lens is NA, said track pitch is set in the range of (0.72 to 0.8).times..lambda./NA/1.14 .mu.m, and each of said pits has a substantially trapezoidal cross section whose upper width is in the range of (0.3 to 0.5).times..lambda./NA/1.14 .mu.m and whose lower width is in the range of (0.2 to 0.32).times..lambda./NA/1.14 .mu.m.