Optimizing a distance between lenses of a two objective lens for minimizing wavefront aberration and offsetting focus control

An optical information recording/reproducing apparatus including an optical pickup for making a light beam emitted from a light source incident on a recording medium via a two-group objective lens and at least a third lens so as to record or reproduce optical information on or from said recording medium, said two-group objective lens including a first lens disposed in the vicinity of said recording medium and a second lens disposed at a position facing to said recording medium with said first lens put therebetween and being configured such that a distance between said first lens and said second lens is fixed, said apparatus comprising:

• a first drive means for integrally driving said first lens and said second lens in the direction of the optical axis thereof, and a second drive means for driving said third lens in the direction of the optical axis thereof;
• a moving means for cyclically moving at least one of said first and second lenses and said third lens constituting part of said optical pickup in the direction of the optical axis thereof;
• and
• a control means for performing, upon focusing operation, the positional adjustment of said first and second lenses and said third lens after start-up of focus control, on the basis of reproducing signals obtained from said recording medium at one or more points of the cyclic movement of said at least one of said first and second lenses and said third lens by said moving means.

An optical information recording/reproducing apparatus including an optical pickup for making a light beam emitted from a light source incident on a recording medium via a primary lens disposed in the vicinity of said recording medium and at least a secondary lens so as to record or reproduce optical information on or from said recording medium, said apparatus comprising:

• a first drive means for driving said primary lens in the direction of the optical axis thereof, and a second drive means for driving said secondary lens in the direction of the optical axis thereof;
• a moving means for cyclically moving at least one of said primary lens and said secondary lens constituting part of said optical pickup in the direction of the optical axis thereof;
• and
• a control means for performing, upon focusing operation, the positional adjustment of said primary lens and said secondary lens after start-up of focus control, on the basis of reproducing signals obtained from said recording medium at one or more points of the cyclic movement of said at least one of said primary lens and said secondary lens by said moving means.