US4792227A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for measuring the refractive index of a substrate for an optical recording medium and method of measuring the same
Assignee: Olympus Corp
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Filing: 1987-03-03
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Granted: 1988-12-20
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Expires: 2007-03-03
Abstract
Abstract An apparatus (31) and method for measuring the refractive index of an optical recording medium substrate (34) wherein an angle of incidence of a polarized beam (33) is set at an oblique angle of incidence with the substrate (34), the polarized direction of the polarized beam (33) is varied for the substrate (34) in this state, the transmitted or reflected light beam by the substrate is received by a light receiving means (36) through a light analyzer means (35) in the crossed Nichol state and the received light amount for the polarized angle is measured and is compared with a theoretical formula so that the refractive index in the thickness direction of the substrate can be measured.
Inventors
- 👤 Akihiko Yoshizawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 06:16
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/21; G01N21/23; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10582; G11B7/00; G11B7/24; G11B7/26
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
203 words
An apparatus for measuring a refractive index of a substrate for an optical recording medium comprising: a light source generating a light beam of a substantially single wavelength; a polarizing means linearly polarizing said light beam; an angle setting means for setting an oblique angle of incidence, wherein said linearly polarized light beam, having passed through said polarizing means, is incident at the oblique angle of incidence upon a flat plate-shaped plane of said substrate for an optical recording medium to have the refractive index measured; a light analyzing means arranged on at least one of a transmitted light side and a reflected light side of said substrate and held in a crossed Nichol state with said polarizing means; a light receiving means receiving said light beam having passed through said light analyzing means; a varying means for relatively varying the direction of said linear polarized light with said angle of incidence kept constant while maintaining the crossed Nichol state between said light analyzing means and said polarizing means; and comparing means for comparing an output of the light receiving means for the varied angle in the polarized direction with a theoretical formula in order to determine the refractive index of said substrate.
Claim 2
Independent Claim
203 words
An apparatus for measuring a refractive index of a substrate for an optical recording medium comprising: a light source generating a light beam of a substantially single wavelength; a polarizing means linearly polarizing said light beam; an angle setting means for setting an oblique angle of incidence, wherein said linearly polarized light beam, having passed through said polarizing means, is incident at the oblique angle of incidence upon a flat plate-shaped plane of said substrate for an optical recording medium to have the refractive index measured; a light analyzing means arranged on at least one of a transmitted light side and a reflected light side of said substrate and held in a crossed Nichol state with said polarizing means; a light receiving means receiving said light beam having passed through said light analyzing means; a varying means for relatively varying the direction of said linear polarized light with said angle of incidence kept constant while maintaining the crossed Nichol state between said light analyzing means and said polarizing means; and comparing means for comparing an output of the light receiving means for the varied angle in the polarized direction with a theoretical formula in order to determine the refractive index of said substrate.
Claim 3
Dependent Claim
23 words
A measuring apparatus according to claim 1 wherein said light source and polarizing means are formed of semiconductor lasers generating polarized light beams.
Claim 4
Dependent Claim
29 words
A measuring apparatus according to claim 1 wherein said varying means is so formed as to rotate the substrate side around a projected beam spot position as a center.
Claim 5
Dependent Claim
44 words
A measuring apparatus according to claim 1 wherein a Babinet-Soleil phase compensating plate is arranged in a normal direction of the transmitting light side of the substrate so as to be able to eliminate an anisotropy of the refractive index in the substrate plane.
Claim 6
Independent Claim
140 words
A method of measuring the refractive index of a substrate for an optical recording medium comprising of the steps of: linearly polarizing a light beam of a substantially single wavelength; incidenting said linear polarized light beam at an oblique angle to incidence upon a flat plate-shaped substrate plane to have the refractive index in the thickness direction measured; varying a direction of said linearly polarized light with respect to said substrate in said plane of incidence; passing transmitted or reflected light beam by said substrate through a light analyzing means in a crossed Nichol state with the direction of said linear polarized light to determine the optical output characteristic of a light receiving means; and measuring the refractive index in the thickness direction of the substrate by comparing the optical output of the light receiving means with a theoretical formula.
Claim 7
Independent Claim
140 words
A method of measuring the refractive index of a substrate for an optical recording medium comprising of the steps of: linearly polarizing a light beam of a substantially single wavelength; incidenting said linear polarized light beam at an oblique angle to incidence upon a flat plate-shaped substrate plane to have the refractive index in the thickness direction measured; varying a direction of said linearly polarized light with respect to said substrate in said plane of incidence; passing transmitted or reflected light beam by said substrate through a light analyzing means in a crossed Nichol state with the direction of said linear polarized light to determine the optical output characteristic of a light receiving means; and measuring the refractive index in the thickness direction of the substrate by comparing the optical output of the light receiving means with a theoretical formula.
References Cited (Backward Citations)
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) | 1991-12-20 | 1992-06-20 | 1992-12-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-12-20 | 1996-06-20 | 1996-12-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-12-20 | 2000-06-20 | 2000-12-20 | $7700.00 | Window Closed / Lapsed |