| 摘要 |
An aberration correction element including a diffraction plane that corrects a spherical aberration caused by the difference among a first optical recording medium, a second optical recording medium, and a third recording medium by transmitting first beams of light having a wavelength of lambda1 emitted from a first light source to read and write data on the first recording medium comprising a substrate having a thickness of t1, and diffracting second beams of light having a wavelength of lambda2 emitted from a second light source to read and write data on the second recording medium comprising a substrate having a thickness of t2, and third beams of light having a wavelength of lambda3 emitted from a third light source to read and write data on the third recording medium comprising a substrate having a thickness of t3; and a phase shifter plane including a step form having multiple steps along the optical axis direction that is formed in a ring band manner with a step height of a significant multiple integral of wavelengths of lambda1, lambda2, and lambda3 at room temperature, the phase shifter plane generating a spherical aberration -DeltaSA having a reverse direction to a spherical aberration DeltaSA generated at an objective lens optimized for the first optical recording medium according to a temperature change, wherein the aberration correction element is formed of resin material and satisfies the following relationship 1: - 3.6 x 10 - 10 ( n T ) x ( h T ) x m - 2.1 x 10 - 10 Relationship 1 where dn/dT represents a change in a refraction factor of the resin material based on 1° C., dh/dT represents a change in the step height based on 1° C., and m represents a number of the multiple steps and an integer greater than 1.
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