DP-1100B II
II.
FUNDAMENTALS
(1) C o l l i m a t o r Lens
D i f f u s e d l i g h t b e a m s are c h a n g e d t o parallel l i g h t b e a m s .
L i g h t b e a m s d i s t r i b u t e d in oval p a t t e r n is c h a n g e d t o a p
p r o x . c i r c u l a r d i s t r i b u t i o n s .
(2) Polarized Prism
L i g h t p o l a r i z e d in parallel t o a s u r f a c e is r e f l e c t e d , a n d
light p o l a r i z e d in v e r t i c a l is passed t h r o u g h t h e p r i s m .
5 - 2 F O C U S E R R O R A N D T R A C K I N G E R R O R
T o read t i n y pits ( w i d t h : 0 . 5 / i m , l e n g t h 0 . 9 # 3 . 2 / * m ) o n a
disc by m e a n s of a laser s p o t , t h e l o c a t i o n m u s t be precisely
c o n t r o l l e d t o f o l l o w s u r f a c e a n d axial d e v i a t i o n s of t h e disc
c a u s e d by r o t a t i n g t h e disc f o r p l a y b a c k . For this p u r p o s e ,
(1) F o c u s error a n d
(2) T r a c k i n g error
m u s t be d e t e c t e d . T h e d e t e c t i o n m u t h o d s f o r b o t h errors w i l l
be g i v e n b e l o w .
5-2-1 F o c u s Error D e t e c t i o n
W h e n a light b e a m is passed f r o m a h i g h r e f r a c t i o n m a t e r i a l t o
a l o w r e f r a c t i o n m a t e r i a l , a r e l a i o n , as s h o w n in Fig. 5 . 2 , is
existed b e t w e e n t h e i n c i d e n t a n g l e a n d r e f l e c i t o n ratio at t h e
b o u n d a r y of t h e m a t e r i a l s . A s c a n be seen f r o m t h e g r a p h s ,
t h e r e f l e c t i o n ratio w i l l c h a n g e rapidly as t h e i n c i d e n t light
angle c h a n g e s in t h e area w h e r e t h e i n c i d e n t a n g l e is slightly
less t h a n t h e c r i t i c a l a n g l e .
(3) 114 W a v e l e n g t h Plate
NA = Sin0
Pit surface
(5) 4 - d i v i d e d p h o t o d i o d e s
C o n v e r t s l i g h t i n t o an e l e c t r i c a l signal
Fig. 5 . 2 Refleciton c h a n g e s rapidly at a n g l e s d o s e
to critical angle.
2 8
(4) O b j e c t i v e Lens
Reflection Surface
S
P
o
l
a
" " 1 L ,
g
h
t
Critical Angle
( 4 1 . 8 ° )
Incident light angle 0
Strength
of
Reflection
(Rp-Rs)
1.5/xm
Disc
WD
NA
0 . 4 7
Summary of Contents for DP-1100 B
Page 3: ...D P 1 1 0 0 B II D P 1 1 0 0 B II I BLOCK DIAGRAM ...
Page 32: ...D P 1 1 0 0 B II 1 CIRCUIT DESCRIPTION Disc Scratch Dust RFES D C O N D O C K Fig 1 2A 3 5 ...
Page 112: ...2 IC OPERATION OF EACH CIRCUIT AND D P 1 1 0 0 B II PIN DESCRIPTION Fig 2 4 1 G 1 ...
Page 117: ...DP 1100B II I OPERATION OF MAIN MICROPROCESSOR Fig 3 1D Q data reading flow chart ...