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2. SKEW Adjust
2-1. SKEW Adjust t NG (Judgement is not performed)
3. Read (CD) Adjust
3-1. Adjust FE t NG
3-2. DPP (Differential Push- Pull: One of the Tracking Error Detection Methods) Balance t NG
3-3. TE Gain Offset t NG
3-4. Focus Gain, Tracking Gain t NG
3-5. Focus Bias t NG (Judgment is not performed.)
3-6. MPP Out Adjust t NG
RepairPurpose
Adjust the skew error caused by
OP unit to minimum.
Trouble Symptom
OK is shown all the time. The OK/
NG judgement is not performed.
Cause
Purpose
Adjust the focus error amplitude
and non-uniformity of the offset
of the OP unit
Trouble Symptom
NG indication appears.
Cause
Result of the adjustment has
exceeded the non-uniformity
specifications of the OP unit.
Repair
Replace the OP unit.
Purpose
Adjust non-uniformity of the
tracking error balance of the OP
unit.
Trouble Symptom
NG indication appears.
Cause
Result of the adjustment has ex-
ceeded the non-uniformity speci-
fications of the OP unit.
Repair
Replace the OP unit.
Purpose
Adjust non-uniformity of the
tracking error amplitude and offset
due to the OP unit and IC.
Trouble Symptom
NG indication appears.
Cause
Result of the adjustment has ex-
ceeded the non-uniformity speci-
fications of the OP unit.
Repair
Replace the OP unit.
Repair
Replace the OP unit.
Purpose
Adjust non-uniformity of the
focus gain and that of the tracking
gain due to the OP unit.
Trouble Symptom
NG indication appears.
Cause
Result of the adjustment has ex-
ceeded the non-uniformity speci-
fications of the OP unit.
Purpose
Adjust non-uniformity of the fo-
cus fine adjustment against CD,
caused by OP unit and IC.
Trouble Symptom
OK is shown all the time. The OK/
NG judgment is not performed.
Cause Repair
Purpose
Adjust to minimize the variations
of MPP offset to the CD cased by
the OP and IC.
Trouble Symptom
NG indication appears.
Cause
Variation has exceeded the speci-
fication value.
Repair
Replace the OP unit.
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