Impact resistant and tempered optical elements
First Claim
1. An optical element comprising:
- a base comprising a first material having an index of refraction at 10 microns in the range of about 2.2 to 3.3, a predetermined optical transmissivity over at least portions of a band of at least about 2 μ
m to 30 μ
m and a predetermined resistance to damage caused by high velocity water droplet impact;
means optically transparent over said portion of said band and disposed over said base for increasing the resistance of the base to damage caused by water droplet impact, comprising a second material having an index of refraction less than 2.0 at 10 microns and a physical thickness related to ((2[n]N+1)λ
/4)/nc, when N is an integer, λ
is a selected wavelength in the band, and Nc is the refractive index of the second material at the wavelength λ
.
0 Assignments
0 Petitions
Accused Products
Abstract
An impact resistant anti-reflection coating for an optical element mounted on an airborne system which mitigates damage to the optical element when the airborne system is flown through a high velocity droplet impact medium is described. In a first embodiment, the coating comprises a material having a relatively high modulus of elasticity deposited to a thickness equal to an odd multiple of a quarter of a wavelength of the wavelength radiation to be transmitted through the optical element. In accordance with a further aspect of the invention, the high modulus of elasticity layer may comprise a homogeneous mixture of a pair of high modulus elasticity materials as well as a composite layer comprising a first layer of a high modulus elasticity material and a second layer of a second modulus of elasticity material. In a second embodiment, the outer surface of an infrared material is strengthened by single diamond point turning the outer surface of the material to introduce into the surface a compressive layer. The compressive layer is characterized as having a plurality of furrows or grooves being spaced by compressed regions of material and having disposed under said furrows or grooves a compressed region of material.
66 Citations
43 Claims
-
1. An optical element comprising:
-
a base comprising a first material having an index of refraction at 10 microns in the range of about 2.2 to 3.3, a predetermined optical transmissivity over at least portions of a band of at least about 2 μ
m to 30 μ
m and a predetermined resistance to damage caused by high velocity water droplet impact;means optically transparent over said portion of said band and disposed over said base for increasing the resistance of the base to damage caused by water droplet impact, comprising a second material having an index of refraction less than 2.0 at 10 microns and a physical thickness related to ((2[n]N+1)λ
/4)/nc, when N is an integer, λ
is a selected wavelength in the band, and Nc is the refractive index of the second material at the wavelength λ
. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
-
-
16. An optical element comprising
a base comprising a first material having an index of refraction between about 2.2 and 3.3 at 10 microns, a predetermined optical transmissivity over the range of 8 μ - m to 12 μ
m and a predetermined modulus of elasticity;a layer of a second, different material selected from the group consisting of yttrium oxide, scandium oxide, or homogeneous mixtures of yttrium oxide, scandium oxide and magnesium oxide disposed on said base, transparent over said optical wavelength range and having a modulus of elasticity at least about twice the modulus of the material of the base, an index of refraction less than 2.0 at 10 microns and a physical thickness related to ((2N+1)λ
/4)/nc, where λ
is a wavelength in the range of 8 λ
m to 12 λ
m, and N is an integer, and nc is the refractive index of the second material at the wavelength λ
to protect such element from water droplet impact and to anti-reflect correct the optical element. - View Dependent Claims (17, 18)
- m to 12 μ
-
19. An optical element comprising
a base comprising a material having an index of refraction between about 2.2 and 3.3 at 10 microns, a predetermined optical transmissivity over a predetermined range of wavelengths, a first predetermined modulus of elasticity; - and
a composite coating disposed over at least a portion of said base comprising; (1) a first layer comprising yttrium oxide having a modulus of elasticity of at least twice the modulus of elasticity of said base material and having an index of refraction less than the index of refraction of the material of said base; (2) a second layer comprising a second high modulus of elasticity material having a modulus of elasticity of at least twice the modulus of elasticity of said base material and having an index of refraction greater than 2.0. - View Dependent Claims (20, 21)
- and
-
22. A method of protecting a region of an optical element comprised of a first material having a first modulus of elasticity and a predetermined optical transmissivity over a wavelength range of about 8 μ
- m to 12 μ
m from impact damage encountered in a high velocity droplet environment comprises the step of;providing a layer of a second material selected from the group consisting of yttrium oxide and scandium oxide over the region to be protected having a modulus of elasticity at least twice the modulus of elasticity of said first material having a predetermined optical transmissivity over said range and which is resistant to debonding from the first material in response to sheer stress causes by radial outflow during water droplet impact. - View Dependent Claims (23, 24, 25)
- m to 12 μ
-
26. A method of bonding a layer of hard carbon to a base comprising a material selected from the group consisting of a Group II-V or Group III-V material comprising the step of:
providing a first layer comprising a material selected from the group consisting of yttrium oxide, scandium oxide and magnesium oxide between the base and the hard carbon layer. - View Dependent Claims (27, 28, 29)
-
30. An optical element comprising:
a base comprising a material having a predetermined optical transmissivity, with a surface portion of said optical material being in compression, said compressed surface portion having a plurality of furrows disposed in said surface potion having underlying said furrows and disposed between adjacent, ones of said furrows compressed regions of the material of said base. - View Dependent Claims (31, 32)
- 33. A method of providing a tempered, strengthened surface to an optical element, comprised of a first material having an initial predetermined fracture strength, comprising the step of converting a surface portion of said material into a compressed surface portion layer of said material, to provide said surface portion layer having a high fracture strength than the initial fracture strength of the material, by single point turning the outer surface of the optical element to introduce onto such outer surface the compressed surface portion of said optical element.
-
39. An optical element having an antireflection, impact resistant optical coating, comprising:
-
a base comprised of a material selected from the group consisting of zinc sulfide and zinc selenide said base having a predetermined thickness in the range of about 0.05 inches to 0.5 inches and said selected material having a predetermined percent transmissivity to optical energy having a wavelength in the range of about 2 μ
m to 12 μ
m;a coating of a material selected from the group consisting of scandium oxide and yttrium oxide having an optical thickness equal to about a quarter of a wavelength, said wavelength being selected within said wavelength range. - View Dependent Claims (40, 41)
-
-
42. An optical element, comprising
a base of optically transmissive material selected from the group consisting of zinc sulfide and zinc selenide having a surface portion of said material being disposed in compression relative to the base portion of the material and a predetermined percent transmission measured through said surface portion over the wavelength range of 2 μ - to 12 microns.
- View Dependent Claims (43)
Specification