US2009161520A1PendingUtilityA1
Optical arrangement
Assignee: KONINKL PHILIPS ELECTRONICS NVPriority: Jul 9, 2003Filed: Feb 24, 2009Published: Jun 25, 2009
Est. expiryJul 9, 2023(expired)· nominal 20-yr term from priority
Inventors:Bernardus Hendrikus Wilhelmus Hendriks
G11B 7/1367G11B 7/13922
62
PatentIndex Score
0
Cited by
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References
0
Claims
Abstract
An optical system is described for scanning optical record carriers of different types. The optical system includes a compensator having a number of optical elements (NPS 1 , NPS 2 ). The optical elements (NPS 1 , NPS 2 ) are non-periodic phase structures (NPS) having annular areas separated by steps, forming a non-periodic pattern of optical paths of different lengths. By including these multiple optical elements (NPS 1 , NPS 2 ) having NPS surfaces in the lens system of an optical system, it is possible to compensate for the effect of variation of a parameters such as temperature, angle of incidence, polarisation of radiation incident on the system and wavelength of radiation, without causing sensitivity to variation of another such parameter.
Claims
exact text as granted — not AI-modified1 . An optical arrangement for interacting with a radiation beam, the optical arrangement comprising an optical system and a compensator, the compensator including a first optical element, the first optical element having a phase structure comprising stepped annular areas forming a first pattern of optical paths of different lengths, the compensator being arranged to generate:
a first wavefront deviation introduced by the variation of a first parameter during interaction of the radiation beam with the compensator, the first wavefront deviation being arranged to counteract a wavefront deviation introduced by the variation of the first parameter during interaction of the radiation beam with the optical system; and a second wavefront deviation introduced by the variation of a second, different, parameter during interaction of the radiation beam with the compensator, wherein the compensator further includes a second optical element formed from a different material than the first optical element and having a phase structure comprising stepped annular areas forming a second pattern of optical paths of different lengths, the second optical element being arranged to reduce said second wavefront deviation, wherein the compensator is made substantially independent of wavelength variations by providing a substantially constant parameter which is:
K
=
m
j
q
j
≈
-
1
λ
-
n
2
λ
n
2
-
1
1
λ
-
n
1
λ
n
1
-
1
,
where m j is an integer, q j is an integer, λ is a wavelength,
n
1
λ
is a dispersion of the first material and
n
2
λ
is a dispersion of the second material.
2 . (canceled)
3 . The optical arrangement according to claim 1 , wherein the annular areas of the first optical element are stepped by a step height of h j and the annular areas of the second optical element are stepped by a step height of b j and wherein the first optical element is arranged such that, for each said annular area, the step height h j is substantially equal to:
h
j
=
m
j
λ
n
1
-
1
where n 1 is a refractive index of a first material from which the first optical element is made, and
wherein the second optical element is arranged such that, for each said annular area, the step height b j is substantially equal to:
b
j
=
q
j
λ
n
2
-
1
where n 2 a refractive index of a second material of which the second optical element is made.
4 . The optical arrangement according to claim 3 , wherein the first optical element and the second optical element have correspondingly arranged annular areas, and wherein the step heights h j , b j are interrelated.
5 . The optical arrangement according to claim 4 , wherein the step heights h j , b j are related by way of the substantially constant parameter K, the value of the constant parameter K depending on a compensating function of the respective optical elements.
6 - 7 . (canceled)
8 . The optical arrangement according to claim 5 , wherein:
K
≈
-
(
n
1
-
1
)
α
2
+
n
2
T
(
n
1
-
1
)
α
1
+
n
1
T
where α 1 and α 2 are the thermal expansion coefficients, and
n
1
T
and
n
2
T
are the temperature coefficients of refractive index, of the materials from which the first and second optical elements are formed,
and wherein the second parameter is a temperature of the optical arrangement.
9 . The optical arrangement according to claim 5 , wherein:
K
≈
-
n
1
n
2
,
and wherein the second parameter is an angle of incidence of the radiation beam.
10 . The optical arrangement according to claim 5 , wherein:
K
≈
-
(
n
1
-
1
)
n
2
p
(
n
1
-
1
)
n
1
p
,
where
n
1
p
and
n
2
p
are the polarization coefficients of refractive index of the materials from which the first and second optical elements are formed,
and wherein the second parameter is a polarization of the radiation beam.
11 . The optical scanning device comprising the optical arrangement according to claim 1 , the device being arranged for scanning an optical record carrier having an information layer using a radiation source.
12 . The optical arrangement of claims 1 , wherein at least one of the first pattern and the second pattern is non-periodic
13 . An optical arrangement for interacting with a radiation beam, the optical arrangement comprising an optical system and a compensator, the compensator being configured to generate:
a first wavefront deviation introduced by the variation of a first parameter during interaction of the radiation beam with the compensator, the first wavefront deviation being configured to counteract a wavefront deviation introduced by the variation of the first parameter during interaction of the radiation beam with the optical system; and a second wavefront deviation introduced by the variation of a second parameter during interaction of the radiation beam with the compensator, the second parameter being different from the first parameter; the compensator comprising: a first optical element, the first optical element having a phase structure comprising stepped annular areas forming a first pattern of optical paths of different lengths; and a second optical element formed from a different material than the first optical element and having a phase structure comprising stepped annular areas forming a second pattern of optical paths of different lengths, the second optical element being configured to reduce said second wavefront deviation by reducing a root mean square optical path difference of the second wavefront deviation so that the compensator compensates for effects of variations of the first parameter without substantially causing the second wavefront deviation when the second parameter is varied; wherein the first parameter includes temperature, angle of incidence, and wavelength of the radiation beam, and the second parameter includes another one the temperature, the angle of incidence, and the wavelength of the radiation beam.
14 . The optical arrangement of claim 13 , wherein materials of the first optical element and the second optical element have different refractive indices and different temperature coefficients of refractive index.
15 . The optical arrangement of claim 13 , wherein materials of the first optical element and the second optical element have different refractive indices, different thermal expansion coefficients and different temperature coefficients of refractive index.
16 . The optical arrangement of claim 13 , wherein materials of the first optical element and the second optical element have different refractive indices and different polarization coefficients of refractive index.
17 . The optical arrangement of claim 13 , wherein the first optical element and the second optical element are configured to make the optical arrangement both achromatic and athermal simultaneously.
18 . The optical arrangement of claim 13 , wherein the first optical element and the second optical element are configured to make the optical arrangement both achromatic and having reduced field of view dependence simultaneously.
19 . The optical arrangement of claim 13 , wherein the stepped annular areas are configured to give rise to phase steps of an integral number of times 2π, when a flat wavefront having zero angle of incidence passes through the compensator.Join the waitlist — get patent alerts
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