
96-21Magnetic and Optical Recording
size on the focus plane is on the order of 1 μm (d
1
), it is two to three orders greater at the air/substrate
in
terface
(d
2
). is means that optical recording can tolerate disk surface contamination and scratches
mu
ch
be
tter
th
an
ma
gnetic
re
cording
. Ho
wever,
th
e
pe
rformance
of opt
ical
re
cording
do
es
no
t
ma
tch
ma
gnetic
re
cording
in ge
neral
. e da
ta
tr
ansfer
ra
te
of CD
-ROM
dr
ives
is ex
pressed
as mu
ltiple
(×
)
of
15
0
kB
/s
. Ev
en
fo
r
a 12
×
CD
-ROM
dr
ive,
th
e
da
ta
ac
cess
ti
me
an
d
da
ta
tr
ansfer
ra
te
ar
e
st
ill
on th
e
or
der
of 10
0
ms an
d
1.8 MB
/s,
re
spectively,
wh
ile
fo
r
a hi
gh-performance
ri
gid
di
sk
dr
ive
th
ese
va
lues ...