US4847480A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Focus error detecting apparatus
Assignee: Pioneer Corp
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Filing: 1988-03-11
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Granted: 1989-07-11
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Expires: 2008-03-11
Abstract
Abstract A focus error detecting apparatus is improved by splitting the light detector into three portions, with a first portion located between second and third portions and being elongated. The elongation prevents an out-of-focus condition where the detection light spot is elliptically elongated in the elongation direction from being falsely detected as the focused condition.
Inventors
- 👤 Takanori Maeda
- 👤 Susumu Nomura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 03:11
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/13; G11B7/131; G11B7/08; G11B7/09; G11B7/0908; G11B7/0909; G11B7/133
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
164 words
A focus error detecting apparatus, comprising: an astigmatism optical element for making an astigmatism aberration of a reflected light from a recording media; a light detector for receiving said light passed through said astigmatism optical element; and a signal generating circuit for generating a focus error signal on the basis of an output of said detector, said detector being divided into substantially three portions such that a first one of said portions is arranged between a second and a third one of said portions, and in which said first portion is formed substantially longer than either of said second and third portions to extend beyond the boundaries of said second and third portions, such that an amount of light received by said first portions is larger than that of each of said second and third portions when a shape of a spot of said light incident on said light detector becomes elongated in a direction substantially parallel to a length direction of said portions.
Claim 2
Dependent Claim
164 words
A focus error detecting apparatus, comprising: an astigmatism optical element for making an astigmatism aberration of a reflected light from a recording media; a light detector for receiving said light passed through said astigmatism optical element; and a signal generating circuit for generating a focus error signal on the basis of an output of said detector, said detector being divided into substantially three portions such that a first one of said portions is arranged between a second and a third one of said portions, and in which said first portion is formed substantially longer than either of said second and third portions to extend beyond the boundaries of said second and third portions, such that an amount of light received by said first portions is larger than that of each of said second and third portions when a shape of a spot of said light incident on said light detector becomes elongated in a direction substantially parallel to a length direction of said portions.
Claim 3
Dependent Claim
27 words
An apparatus as claimed in claim 1, wherein said first portion has a length L, and said second and third portions have equal lengths less than L.
Claim 4
Dependent Claim
27 words
An apparatus as claimed in claim 1, wherein said first portion has a length L, and said second and third portions have unequal lengths less than L.
Claim 5
Dependent Claim
30 words
An apparatus as claimed in claim 1, wherein said first portion is comprised of plural discontinuous segments, one of said segments being unitarily formed with said second and third portions.
Claim 6
Dependent Claim
19 words
An apparatus as claimed in claim 4, wherein said second and third portions are integrally joined to each other.
Claim 7
Dependent Claim
24 words
An apparatus as claimed in claim 1, wherein said first portion is elongated relative to said second and third portions in one direction only.
Claim 8
Dependent Claim
29 words
An apparatus as claimed in claim 1, wherein said second and third portions are formed as trapezoids having a shorter major length than a length of said first portion.
Claim 9
Dependent Claim
32 words
An apparatus as claimed in claim 1, wherein said second and third portions are formed as circular sections having diameters or chords of a shorter length than that of said first portion.
Claim 10
Dependent Claim
29 words
An apparatus as claimed in claim 1, wherein said first portion is formed so as to surround said second and third portions over more than 50% of their periphery.
Claim 11
Dependent Claim
27 words
An apparatus as claimed in claim 1, wherein said first portion is formed at its ends with enlarged portions located outboard of said second and third portions.
Claim 12
Dependent Claim
46 words
An apparatus as claimed in claim 1, wherein said signal generating circuit includes adder means coupled to outputs of said second and third portions, and differential amplifier means receiving as inputs (1) an output of said adder means, and (2) an output of said first portion.
Claim 13
Dependent Claim
38 words
An apparatus as claimed in claim 5, wherein said signal generating circuit includes differential amplifier means having inputs coupled to (1) an output of said integral second and third portions, and (2) an output of said first portion.
References Cited (Backward Citations)
US4242579A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-07-10 | 1993-01-09 | 1993-07-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-07-10 | 1997-01-09 | 1997-07-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-07-10 | 2001-01-09 | 2001-07-11 | $7700.00 | Window Closed / Lapsed |