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YPM-2306ZF

3. AUTOMATIC ADJUSTMENT FUNC-

TIONS

Every circuit adjustment on the CD-LSI of this system is

automated.

Every circuit adjustment is automatically implemented

when the disc is inserted or the CD mode is selected

from the source key. The following describes how the

adjustments are executed.

1) FZD Cancel Setting

This setting is used for executing the focus close opera-

tion without fail.

When power is turned on, the FE offset level is read and

a voltage opposite to this offset value is written to the

CRAM on the IC to cancel the offset. In this manner, the

FZD threshold level can be set to a constant value

(+240mV), thereby ensuring to meet one of the require-

ments for the IC to execute the focus close that "the

FZD signal is latched at high".

2) Automatic Adjustment of TE, FE and RF Offset

Using REFO as the reference, this function adjusts the

pre-amp TE, FE and RF offsets to the respective target

value when power is turned on (targets values of the

TE, FE and RF are 0, 0 and −1V, respectively).

The following is the adjustment procedure :

(1) Respective offset (LD off) is read by the microcom-

puter via the servo LSI.

(2) The microcomputer calculates the voltages to be

corrected from the read values, then sets them to

the specified field.

3) Automatic Adjustment of Tracking Balance (T.

BAL)

This adjustment is used for eliminating differences

between the pickup E and F channels outputs by adjust-

ing gain of the amplifier on the LSI. In the actual opera-

tion, the TE waveform is adjusted so that it may be ver-

tically symmetric with REFO.

The following is the adjustment procedure :

(1) Make sure the focus close is complete.

(2) Kick the lens in the radial direction to generate the

TE waveform.

(3) At this time, the microcomputer reads the TE signal

offset value (via the servo LSI) being calculated by

the LSI.

(4) The microcomputer determines if the read offset

value is positive, negative or zero.

If the offset value = 0, the adjustment is terminated.

If the offset value = A positive or negative value,

gain of the E and F channels amplifiers are modified

according the predetermined rule.

Then above steps (2) through (4) are repeated until the

"Offset value = 0" or "Specified limit count" is reached.

4) Automatic Adjustment of FE Bias

This adjustment is intended at maximizing the RFI level

by optimizing the focus point in-play. This adjustment

utilizes the phase difference between the RF waveform

3T level and the focus error signal when disturbance is

applied.

Since disturbance is applied to the focus loop, this

adjustment is designed to take place in the same timing

as the auto gain control (to be described later).

The following is the adjustment procedure :

(1) Disturbance is injected to the focus loop by the com-

mand from the microcomputer (within the servo

LSI).

(2) The LSI detects fluctuation of the RF signal 3T com-

ponent level.

(3) The LSI determines relationship between fluctuation

of the 3T component and the injected disturbance to

detect magnitude and direction of the off-focus

introduced.

(4) The microcomputer reads the detected results from

the LSI.

(5) The microcomputer calculates necessary correction,

then hands the calculated value to the bias adjust-

ment term set on the LSI.

This adjustment is repeated several times, as it is so

with the auto gain control, to ensure higher accuracy.