| 摘要 |
<p>An optical scanning device can scan two different types of optical record carrier (1; 25), requiring a scanning beam (15) having different numerical apertures. The device has two stops (33; 32) at different positions along the optical axis of the path followed by the radiation beam for both types of discs. The first stop (33) limits the numerical aperture of the radiation beam when scanning the first type of record carrier (1). The second stop (32) limits the numerical aperture when scanning the second type of record carrier (25).</p> |
