Appeal No. 2005-2750
Application 09/460,221
unacceptable level of spherical aberration if used with a thicker conventional optical
disc, as explained with the aid of Figures 18A and 18B. Col. 2, ll. 3-48. As a result, the
disclosed embodiments employ N (N ≥2) different converging means for writing and
reading from discs having any of N different substrate thicknesses. In other words,
each depicted embodiment, briefly described below, includes N (N ≥2) converging
means “whose aberrations have been corrected for N (N ≥2) disc substrates having
different thicknesses, respectively.” Col. 2, ll. 56-63. In all of the eight embodiments
depicted in the figures, N equals 2.
First Embodiment – Figures 1-4
The first embodiment employs two independently movable optical heads: (a) a
first optical head 3 for use with the thicker, conventional (“first”) type of disc; and (b) a
second optical head 5 for use with the thinner, high-density (“second”) type of disc.
Each optical head is supported for radial movement by its own linear motor (4, 6), col. 4,
ll. 32-39, and includes an objective lens, a semiconductor laser, a photodetector, and a
beam splitter (not shown in Figs. 1-4B). Col. 4, ll. 12-16.
Figure 4A shows the relative positions of the conventional disc and the low NA
objective lens carried by the first optical head, while Figure 4B shows the relative
4
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