US3794408A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical filter
Assignee: US Philips Corp
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Filing: 1972-08-14
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Granted: 1974-02-26
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Expires: 1992-08-14
Abstract
Abstract An optical filter for use in a field-sequential colour television camera, for which purpose it is rotatably arranged in front of a light-integrating camera tube. The filter partly comprises sections which produce a reduction in definition and for this purpose are provided with a plurality of diffraction gratings having different spacings. The optical filter which owing to the provision of the diffraction gratings has a discontinuous light transmission characteristic, after integration of the light has a more or less continuous light transmission characteristic which corresponds in a desirable manner to an electric filter characteristic.
Inventors
- 👤 Liong Ian Sing
- 👤 J Hofman
- 👤 G Bouwhuis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 10:44
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/10; H04N23/12
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
113 words
A filter for a field-sequential color television camera, comprising a transparent disc divided into at least two groups spanning substantially equal areas, each group being further divided into at least three substantially equal sectors, at least three diffraction gratings of different spatial frequencies in equal fractional portions of at least two sectors in each group, an optically non-diffracting region in a sector of each group spanning an area equal to at least the area covered by the gratings in one of the other sectors of the group, and an optically clear sub-sector in each of the sectors containing the diffraction gratings, the optically clear sub-sectors all covering substantially equal areas of the sectors.
Claim 2
Dependent Claim
113 words
A filter for a field-sequential color television camera, comprising a transparent disc divided into at least two groups spanning substantially equal areas, each group being further divided into at least three substantially equal sectors, at least three diffraction gratings of different spatial frequencies in equal fractional portions of at least two sectors in each group, an optically non-diffracting region in a sector of each group spanning an area equal to at least the area covered by the gratings in one of the other sectors of the group, and an optically clear sub-sector in each of the sectors containing the diffraction gratings, the optically clear sub-sectors all covering substantially equal areas of the sectors.
Claim 3
Dependent Claim
41 words
A filter as claimed in claim 1, wherein the optically non-diffracting region in the sector of each group spanning an area of at least the area covered by the gratings in one of the other sectors of the group is opaque.
Claim 4
Dependent Claim
20 words
An optical filter as claimed in claim 1, wherein the disc is divided into four groups, each containing three sectors.
Claim 5
Dependent Claim
23 words
A filter as claimed in claim 1, further comprising a different color filter in each sector of a group that contains diffraction gratings.
Claim 6
Dependent Claim
24 words
A filter as claimed in claim 1, wherein the sectors provided with diffraction gratings each comprise at least six gratings of different spatial frequencies.
Claim 7
Dependent Claim
40 words
An optical filter as claimed in claim 5, wherein the ratio between the spatial frequencies of z different diffraction gratings is 1 : 1/2 : 1/3 : 1/4 : 1/z, where z is an integer at least equal to 3.
Claim 8
Dependent Claim
22 words
An optical filter as claimed in claim 1, wherein the surface areas of the different diffraction gratings in each sector are unequal.
Claim 9
Dependent Claim
15 words
An optical filter as claimed in claim 1, wherein the diffraction gratings are phase gratings.
Claim 10
Dependent Claim
120 words
A field-sequential opto-electronic converter, comprising a field sequential color television camera having an optically sensitive member, a disc rotatably mounted proximate the optically sensitive member of the camera and equally divided into at least two groups, each of said groups being equally divided into at least two sectors, at least one of said sectors comprising an optically clear sub-sector and a second sub-sector, at least three diffraction gratings in the second sub-sector, said diffraction gratings having different spatial frequencies, and means for rotating the disc at an angular velocity sufficient to sequentially pass a sector of the disc in confronting relationship with the optically sensitive member of the color TV camera during each field period of the field sequential camera.
Claim 11
Dependent Claim
120 words
A field-sequential opto-electronic converter, comprising a field sequential color television camera having an optically sensitive member, a disc rotatably mounted proximate the optically sensitive member of the camera and equally divided into at least two groups, each of said groups being equally divided into at least two sectors, at least one of said sectors comprising an optically clear sub-sector and a second sub-sector, at least three diffraction gratings in the second sub-sector, said diffraction gratings having different spatial frequencies, and means for rotating the disc at an angular velocity sufficient to sequentially pass a sector of the disc in confronting relationship with the optically sensitive member of the color TV camera during each field period of the field sequential camera.
Claim 12
Dependent Claim
34 words
A converter as claimed in claim 9, wherein the diffraction gratings in the sectors cover a fractional portion of said sectors, the remaining area in each sector containing a diffraction grating being optically clear.
Claim 13
Dependent Claim
38 words
A converter as claimed in claim 10, wherein at least one sector in each group contains an opaque area substantially equal to the area covered by the diffraction gratings in each of the other sectors of the group.
Claim 14
Dependent Claim
13 words
A converter as claimed in claim 9, wherein the diffraction gratings are phase-gratings.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-25 | 1977-08-27 | 1978-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-25 | 1981-08-27 | 1982-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-25 | 1985-08-27 | 1986-02-26 | $7700.00 | Window Closed / Lapsed |