Photo Detectors

The three beams of light are reflected from the disc and returned to the optical assembly. They land on the photodetectors within these three groups.

E

F

 

 

AD

C B

G

H

 

 

KHM - 220AAA

PHOTO DETECTORS

The voltages from these detectors are matrixed by RF Amplifier IC001 that follows (on the TK-51 board) into servo correction and disc identifica- tion signals.

51

Photo Detector Manufactured Signals

Photo

Signals

Purpose

Detectors

Produced

 

 

 

 

A – D

TE (DVD only)

TE – DVD tracking error

 

FE, PI, Mirr., RF

FE – Focus error

 

(eye pattern)

PI – “Pull In” is the analog sum of A-D

 

 

 

 

detectors used to ID the disc and

 

 

create MIRR.

 

 

MIRR – mirror signal goes high (4V) if

 

 

PI is above a threshold. MIRR is used

 

 

to count tracks and ID the disc.

 

 

RF – Audio and Video Data

 

 

 

E, F *

TE +, TZC

CD Tracking error, track count.

 

 

 

G,H *

TE –, TZC

CD Tracking error, track count

 

 

 

*In CD and older DVD players, there are only two outer tracking error detectors (E & F). In this new laser assembly, two outer detectors were added but they are not used in this player.

The extra detectors are to permit this laser assembly to read DVD-R discs in future players. This DVD player cannot play DVD-Recordable discs even though the laser has the ability to do so. Detectors E & F are added together and treated as one. G & H detectors are also added in the matrix / RF amp IC001 that follows (not shown).

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Image 56
Sony S530D manual Photo Detectors, Te +, Tzc