Optical device
AssigneeAsahi Glass Company, Limited
InventorHiroaki Shimozono
Life of this patent
Estimating the term…
Abstract
An optical device for recording or reading two optical disks 6.7 in which the thickness of a transparent substrate of a first optical disk 6 is different from the thickness of a transparent substrate of a second optical disk 7 wherein the optical device has an objective lens 3 for collecting light from a first light source 1 and light from a second light source 4 onto data recording surfaces 6b, 7b by means of respective transparent substrates 6a, 7a of the optical disks 6, 7; an optical material 2 for forwarding the light from the first light surface 1 and the light from the second light source 1 and light from a second light source 4 before the lights reaches the objective lens 3, and an auxiliary lens 5 provided between the second light surface 4 and the optical material 2.
Claims11
An optical device for recording or reading data in a data recording surface of an optical disk by collecting light from a light source providing light incident to the data recording surface through an objective lens, collected light being reflected from the data recording surface and received by a light receiving element through the objective lens, the optical device comprising:
- a first light source and a second light source as the light source;
- an auxiliary lens arranged such that said second light source, said auxiliary lens and said objective lens are arranged in the optical device so that the optical axis of said second light source, the optical axis of said auxiliary lens and the optical axis of said objective lens are fixed in a line;
- and
- a first optical disk and a second optical disk as the optical disk wherein the thickness of a transparent substrate of the first optical disk is different from the thickness of a transparent substrate of the second optical disk,
- wherein when data in respective data recording surfaces of the first and second optical disks are to be recorded or read, the data in the data recording surface of the first optical disk is recorded or read by collecting light from the first light source through the objective lens and the transparent substrate of the first optical disk in this order, and the data in the data recording surface of the second optical disk is recorded or read by collecting light from the second light source through the auxiliary lens, the objective lens and the transparent substrate of the second optical disk in this order,
- in response to recording or reading of the data in the data recording surface of the first optical disk, specifications of the objective lens are determined so that the absolute value in RMS value of a spherical aberration of the third order is 0.03 λ1 or less and an off-axial coma aberration in an image height of 0.1 mm is 0.03 λ1 or less, and
- in response to recording or reading of the data in the data recording surface of the second optical disk, specifications in a combination of the auxiliary lens and the objective lens are determined so that the absolute value in RMS value of a spherical aberration of the third order is 0.03 λ2 or less and an off-axial coma aberration in an image height of 0.1 mm is 0.03 λ2 or less where λ1 represents a wavelength of the light from the first light source and λ2 represents a wavelength of the light from the second light source.
Dependencies are inferred from the claim text.