Patent EP0476931A2 successfully refreshed from Google Patents.
EP0476931A2
Expired / Lapsed
EP
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Phase shift device and laser apparatus utilizing the same
Assignee: Canon Inc
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Filing: 1991-09-12
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Granted: —
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Expires: 2011-09-12
Abstract
Abstract A phase shift device (4) for a laser beam has a circular first area (11) transparent to the laser beam (L) and a second area (12) provided around the first area and transparent to the laser beam. The first and second areas generate a phase difference at for example, 180° in the passing light beams. The phase shift device may be positioned at a beam waist of a laser scanning apparatus to form a beam spot of a diameter smaller than that defined by the numerical aperture of the imaging optical system. The structure of a laser apparatus employing such phase shift device is also disclosed.
Inventors
- 👤 Minoru C/O Canon Kabushiki Kaisha Yoshii
- 👤 Kenji C/O Canon Kabushiki Kaisha Saito
- 👤 Masayuki C/O Canon Kabushiki Kaisha Suzuki
- 👤 Hiroshi c/o CANON KABUSHIKI KAISHA Ohsawa
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 08:12
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/0025; G02B27/0031; G02B26/00; G02B26/08; G02B26/10; G02B26/12; G02B26/124; G02B5/00; G02B5/18; G02B5/1876
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
46 words
A phase shift device (4) comprising: a first area (11) transparent to the light of a predetermined wavelength; and a second area (12) provided around said first area and adapted to generate a predetermined phase difference with respect to the light passing through said first area.
Claim 2
Dependent Claim
15 words
A phase shift device according to claim 1, wherein said predetermined phase difference is 180°.
Claim 3
Dependent Claim
105 words
A laser apparatus employing a phase shift device, comprising: a laser light source (4); and a phase shift device (4) positioned in the vicinity of a light emitting face of said laser light source or in the vicinity of a position conjugate with said light emitting face or in the vicinity of a beam waist of the laser beam emitted from said laser light source, said device including a first area (11) transparent to said laser beam and a second area (12) provided around said first area and adapted to generate a predetermined phase difference with respect to the light passing through said first area.
Claim 4
Dependent Claim
14 words
A laser apparatus according to claim 3, wherein said predetermined phase difference is 180°.
Claim 5
Dependent Claim
31 words
A laser apparatus according to claim 3, wherein said beam waist is formed by condensing the laser beam emitted from said laser light source by means of a condensing optical system.
Claim 6
Dependent Claim
27 words
A phase shift device, comprising a parallel-faced flat glass plate with a ground surface forming a subtrate, having a thin film over an area of said subtrate.
Claim 7
Dependent Claim
41 words
A phase shift device according to claim 6, wherein the thickness of said film is numerically equal to the wavelength (W) of the light to be phase shifted divided by two times the refractive index (i) minus 1, W 2(i-1) .
Claim 8
Dependent Claim
19 words
A phase shift device according to claim 6 or claim 7, wherein the film is produced by vacuum evaporation.
Claim 9
Independent Claim
37 words
A method of shifting the phase of a light beam, wherein said beam passes through two transparent mediums, in which the optical path length through one medium is longer than the path length through the other medium.
Claim 10
Dependent Claim
28 words
A method according to claim 9, wherein said longer path length is longer by substantially half a wavelength of the light beam, producing a substantially 180° phase shift.
References Cited (Backward Citations)
No citation records indexed.
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