US4816665A
Expired / Lapsed
US
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Sensor array for focus detection
Assignee: MAXOPTIX Corp A CORP OF DE
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Filing: 1987-08-06
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Granted: 1989-03-28
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Expires: 2007-08-06
Abstract
Abstract Method and apparatus for astigmatic focusing control which is independent of intensity distribution and is implemented with a combined data/focus error sensor array is described. An objective lens is utilized to focus a laser beam for use in reading and/or writing in an optical disk storage system. An astigmatic focus control system is utilized in which a cylindrical lens is disposed in the path of light reflected from the optical disk. The light from the cylindrical lens forms an astigmatic image on a sensor array. The image shifts between a circle at the focal point and one of two ellipses disposed orthoganally to each other depending on whether the focal point of the objective lens is above or below the plane of the optical disk. In the preferred embodiment, a circular bi-cell sensor is disposed so as to receive and encompass a reflected beam through the cylindrical lens when the objective lens is "in focus". An outer array of four sensors is disposed symetrically about the central bi-cell. The sensor is such that no light is disposed on the outer four sensors except when the object lens is out of focus. By utilizing only the four outer sensors, false focus error signals are avoided, since there is only one true "zero" condition, namely when the objective lens is properly focused. Data information may be derived from the sum of the two inner elements (bi-cell) when the system is properly focused. In an alternate embodiment, a single sensor is utilized in the central region in lieu of a bi-cell.
Inventors
- 👤 Sunny K. Ksu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 20:14
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/13; G11B7/08; G11B7/09; G11B7/0908; G11B7/0909; G11B7/135; G11B7/1372; G11B7/1378
Claims Analysis
Total Claims: 36
Claim 1
Independent Claim
163 words
A focal position detecting apparatus comprising: a first optical system for providing of a first light beam onto a surface; a second optical system disposed in a path of a second light beam reflected from said surface, said second optical system producing a third light beam having a shape dependent on the distance of said first optical system from said surface; detection means disposed in a path of said third light beam, said detection means comprising first and second sensing means such that said third light beam is incident on said first sensing means when said first optical system is at a desired distance from said surface and said third beam falls on said first and second sensing means when said first optical system is at a distance from said surface other than said desired distance; signal generating means connected to said second sensing means for generating an error signal in response to the amount of light incident on said second sensing means.
Claim 2
Dependent Claim
163 words
A focal position detecting apparatus comprising: a first optical system for providing of a first light beam onto a surface; a second optical system disposed in a path of a second light beam reflected from said surface, said second optical system producing a third light beam having a shape dependent on the distance of said first optical system from said surface; detection means disposed in a path of said third light beam, said detection means comprising first and second sensing means such that said third light beam is incident on said first sensing means when said first optical system is at a desired distance from said surface and said third beam falls on said first and second sensing means when said first optical system is at a distance from said surface other than said desired distance; signal generating means connected to said second sensing means for generating an error signal in response to the amount of light incident on said second sensing means.
Claim 3
Dependent Claim
25 words
The apparatus of claim 1 wherein said second sensing means comprises first, second, third and fourth photosensitive sensors disposed symmetrically about said first sensing means.
Claim 4
Dependent Claim
15 words
The apparatus of claim 2 wherein said first sensing means comprises a fifth photosensitive sensor.
Claim 5
Dependent Claim
16 words
The apparatus of claim 2 wherein said first sensing means comprises fifth and sixth photosensitive sensors.
Claim 6
Dependent Claim
16 words
The apparatus of claim 1 wherein said surface comprises an optical disk having information encoded thereon.
Claim 7
Dependent Claim
16 words
The apparatus of claim 5 wherein said optical disk rotates with respect to said first beam.
Claim 8
Dependent Claim
20 words
The apparatus of claim 1 wherein said second optical system comprises means for introducing astigmatism to said second light beam.
Claim 9
Dependent Claim
15 words
The apparatus of claim 7 wherein said means for introducing astigmatism comprises a cylindrical lens.
Claim 10
Dependent Claim
37 words
The apparatus of claim 2 wherein said first optical system is at a distance from said surface greater than said desired distance when said third light beam is detected on one of said first and third sensors.
Claim 11
Dependent Claim
42 words
The apparatus of claim 2 wherein said first optical system is at a distance from said surface greater than said desired distance when light incident on said first and third sensors is greater than light incident on said second and fourth sensors.
Claim 12
Dependent Claim
37 words
The apparatus of claim 2 wherein said first optical system is at a distance from said surface less than said desired distance when said third light beam is detected on one of said second and fourth sensors.
Claim 13
Dependent Claim
42 words
The apparatus of claim 2 wherein said first optical system is at a distance from said surface less than said desired distance when light incident on said second and fourth sensors is greater than light incident on said first and third sensors.
Claim 14
Dependent Claim
31 words
The apparatus of claim 4 wherein light incident on said fifth and sixth sensors is dependent on a position of said first optical system relative to tracks disposed on said surface.
Claim 15
Dependent Claim
25 words
The apparatus of claim 1 wherein light incident on said first sensing means is maximum when said first optical system is at said desired distance.
Claim 16
Dependent Claim
138 words
A focal position detecting apparatus comprising: a first optical system for providing a first light beam on to a surface; a second optical system disposed in a path of a second light beam reflected from said surface, said second optical system producing an astigmatic light beam having a shape dependent on the distance of said first optical system from said surface; detection means disposed in a path of said astigmatic light beam, said detection means comprising a central sensing means surrounded by an array of sensing means such that said astigmatic light beam is incident on said array when said first optical system is at a distance from said surface other than a desired distance; signal generating means connected to said array for generating a focus error signal proportional to the amount of light incident on said array.
Claim 17
Dependent Claim
138 words
A focal position detecting apparatus comprising: a first optical system for providing a first light beam on to a surface; a second optical system disposed in a path of a second light beam reflected from said surface, said second optical system producing an astigmatic light beam having a shape dependent on the distance of said first optical system from said surface; detection means disposed in a path of said astigmatic light beam, said detection means comprising a central sensing means surrounded by an array of sensing means such that said astigmatic light beam is incident on said array when said first optical system is at a distance from said surface other than a desired distance; signal generating means connected to said array for generating a focus error signal proportional to the amount of light incident on said array.
Claim 18
Dependent Claim
16 words
The apparatus of claim 15 wherein said surface comprises an optical disk having information stored thereon.
Claim 19
Dependent Claim
26 words
The apparatus of claim 16 wherein said array of sensing means comprises first, second, third and fourth photosensitive sensors disposed symmetrically about a central sensing means.
Claim 20
Dependent Claim
15 words
The apparatus of claim 17 wherein said central sensing means comprises a fifth photosensitive sensor.
Claim 21
Dependent Claim
16 words
The apparatus of claim 17 wherein said central sensing means comprises fifth and sixth photosensitive sensors.
Claim 22
Dependent Claim
21 words
The apparatus of claim 15 wherein said second optical system comprises a means for introducing astigmatism to said second light beam.
Claim 23
Dependent Claim
15 words
The apparatus of claim 20 wherein said means for introducing astigmatism comprises a cylindrical lens.
Claim 24
Dependent Claim
37 words
The apparatus of claim 17 wherein said first optical system is at a distance greater from said surface than said desired distance when said astigmatic light beam is detected on one of said first and third sensors.
Claim 25
Dependent Claim
42 words
The apparatus of claim 17 wherein said first optical system is at a distance from said surface greater than said desired distance when light incident on said first and third sensors is greater than light incident on said second and fourth sensors.
Claim 26
Dependent Claim
37 words
The apparatus of claim 17 wherein said first optical system is at a distance from said surface less than said desired distance when said astigmatic light beam is detected on one of said second and fourth sensors.
Claim 27
Dependent Claim
39 words
The apparatus of claim 17 wherein said first optical system is at a distance less than said desired distance when light incident on said second and fourth sensors is greater than light incident on said first and third sensors.
Claim 28
Dependent Claim
30 words
The apparatus of claim 19 wherein light incident on said fifth and sixth sensors is dependent on a position of said first optical system relative to tracks on said disk.
Claim 29
Dependent Claim
27 words
The apparatus of claim 15 wherein light incident on said first sensing means is at a maximum when said first optical system is at said desired distance.
Claim 30
Independent Claim
153 words
A method for detecting focal position of a light beam with respect to a surface comprising the steps of: passing said first light beam through a first optical system for illumination of a surface; reflecting said light beam from said surface and passing said reflected light beam through a second optical system, said second optical system producing a second light beam having a shape dependent on the distance of said first optical system from said surface; providing a sensor array for detecting said second light beam, said sensor array having a central sensing means and an outer array surrounding said central sensing means; generating a signal indicating said first optical means is at a desired distance when light is not incident on said outer array; generating a signal indicating said first optical means is at a distance other than a desired distance when said second light beam is incident on said outer array.
Claim 31
Independent Claim
153 words
A method for detecting focal position of a light beam with respect to a surface comprising the steps of: passing said first light beam through a first optical system for illumination of a surface; reflecting said light beam from said surface and passing said reflected light beam through a second optical system, said second optical system producing a second light beam having a shape dependent on the distance of said first optical system from said surface; providing a sensor array for detecting said second light beam, said sensor array having a central sensing means and an outer array surrounding said central sensing means; generating a signal indicating said first optical means is at a desired distance when light is not incident on said outer array; generating a signal indicating said first optical means is at a distance other than a desired distance when said second light beam is incident on said outer array.
Claim 32
Dependent Claim
18 words
The method of claim 28 wherein said second sensing means comprises first, second, third and fourth photosensitive sensors.
Claim 33
Dependent Claim
15 words
The method of claim 29 wherein said first sensing means comprises a fifth photosensitive sensor.
Claim 34
Dependent Claim
16 words
The method of claim 29 wherein said first sensing means comprises fifth and sixth photosensitive sensors.
Claim 35
Dependent Claim
61 words
The method of claim 29 further including the step of generating a differential signal by substracting the sum of light incident on said first and third sensors from the sum of light incident on said second and fourth sensor such that when said differential signal is positive, said first optical system is disposed at a distance greater than said desired distance.
Claim 36
Dependent Claim
23 words
The method of claim 31 including the step of detecting the light incident on said fifth and sixth sensors to determine track crossings.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1992-03-27 | 1992-09-26 | 1993-03-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-03-27 | 1996-09-26 | 1997-03-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-03-27 | 2000-09-26 | 2001-03-28 | $7700.00 | Window Closed / Lapsed |