Kenwood DP-1100 B Service Manual page 21

P-1100B II
3 BRIEF EXPLANATIONS ON CD PLAYER (See
the BLOCK DIAGRAM)
3-1 P I C K U P F O R C D A P P L I C A T I O N
A p i c k u p p a r t c o r r e s p o n d i n g t o a c a r t r i d g e for a c o n v e n t i o n a l
a n a l o g player is detailed later.
a l l o w s the laser d i o d e t o e m i t a light b e a m ( X = 7 8 0 n m ) a n d
c o n v e r t t h e intensity of t h e reflected light f r o m disc pits into
electric signals.
3 - 3 S E R V O C I R C U I T
3-3-1 F o c u s S e r v o Circuit
A f o c u s error signal is f e d into a f o c u s servo c i r c u i t t o c o n t r o l a
lens s y s t e m w i t h the use of a f o c u s servo coil (like a v o i c e coil
of a l o u d s p e a k e r ) so t h a t t h e f o c u s s p o t of the laser b e a m is
Lens
Disc
• Approx. 2 nm dia. Lader Spot
3 - 3 - 2 T r a c k i n g S e r v o Circuit
Because a c o m p a c t disc has no guide g r o o v e , it is n e e d e d t o
o p e r a t e a servo so t h a t a laser b e a m s p o t c a n a u t o m a i t c a l l y
f o l l o w a signal t r a c k . A t r a c k i n g error signal is fed into a t r a c k ­
Laser spot (approx. 2 /tm dia.
1.6 nm
Pits on disc
2 4
II. FUNDAMENTALS
Briefly s p e a k i n g , this part
Pickup
Focus coil
Signal
Processing
To Tracking Coil
Signal
Processing
Pick Up
3 - 2 S I G N A L P R O C E S S I N G C I R C U I T
A signal d e t e c t e d at a p i c k u p is delivered t o a signal process­
ing c i r c u i t , a n d split into t h e f o l l o w i n g three signals.
(1) Focus Error Signal
(2) t r a c k i n g (Radial) Error Signal
(3) Radio F r e q u e n c y (RF) S i g n a l : This signal is processed to
generate an a n a l o g signal.
a l w a y s k e p t o n a pit surface against f l u c t u a t i o n s due t o t h e
revolutions of a disc. (The s a m e as a u t o - f o c u s i n g in an EE
c a m e r a )
Focus Servo
Fig. 3.1
ing servo c i r c u i t , t h e o u t p u t of w h i c h drives a t r a c k i n g servo
coil t o operate t h e servo s y s t e m .
Tracking Servo
Fig. 3 . 2
Focus Coil
Driver
Tracking
Coil Driver