Patent ID: 7567285

Claim:
An optical device for a camera comprising: a lens array for focusing incident optical signals; a window glass positioned in front of the lens array to prevent alien substances from contacting the lens array; and a barrel for retaining the lenses of the lens array, wherein each lens of the lens array is substantially coated with multi-layered thin films to suppress respective reflection waves of incident optical signals having different wavelengths, and of such a thickness that causes a phase of reflection waves reflected through the thin films to be an inverse of a phase of reflection waves reflected at a surface of the lens; and wherein the thickness, d, is determined by the following equation: where λ 1 is a first incident wave, λ 2 is a second incident wave, θ 1 is a incident angle of the first incident wave, θ 2 is a refraction angle of the first incident wave, n 1 is a refraction ratio of air, n 2 is a refraction ratio of the coating layer, A′C is the path of the first incident wave, and ABC is the path of the second incident wave, A ′ ⁢ C = ⁢ 2 ⁢ d ⁢ ⁢ tan ⁢ ⁢ θ 2 ⁢ sin ⁢ ⁢ θ 1 ABC = ⁢ 2 ⁢ ⁢ d ⁡ ( cos ⁢ ⁢ θ 2 + tan ⁢ ⁢ θ 2 ⁢ sin ⁢ ⁢ θ 2 ) = ⁢ 2 ⁢ ⁢ d cos ⁢ ⁢ θ 2 ϕ 1 - A ′ ⁢ C λ 1 ⁢ 2 ⁢ π = ⁢ 2 ⁢ π ⁢ ⁢ 2 ⁢ ⁢ d ⁢ ⁢ tan ⁢ ⁢ θ 2 ⁢ sin ⁢ ⁢ θ 1 λ 1 = 2 ⁢ π ⁢ ⁢ f ⁢ ⁢ 2 ⁢ ⁢ d ⁢ ⁢ tan ⁢ ⁢ θ 2 ⁢ sin ⁢ ⁢ θ 1 u 1 ϕ 2 - ABC λ 2 ⁢ 2 ⁢ π = ⁢ 2 ⁢ π ⁢ ⁢ f ⁢ ⁢ 2 ⁢ ⁢ d u 3 ⁢ cos ⁢ ⁢ θ 2 Δϕ = ϕ 1 - ϕ 2 = ⁢ 2 ⁢ π ⁢ ⁢ f u 2 ⁢ 2 ⁢ ⁢ d cos ⁢ ⁢ θ 2 - 2 ⁢ π ⁢ ⁢ f ⁢ ⁢ 2 ⁢ ⁢ d ⁢ ⁢ tan ⁢ ⁢ θ 2 ⁢ sin ⁢ ⁢ θ 1 u 1 = ⁢ 2 ⁢ ⁢ d · 2 ⁢ ⁢ π ⁢ ⁢ f [ 1 u 2 ⁢ cos ⁢ ⁢ θ 2 - n 2 n 1 ⁢ sin 2 ⁢ θ 2 u 1 ⁢ cos ⁢ ⁢ θ 2 ] , sin ⁢ ⁢ θ 1 sin ⁢ ⁢ θ 2 = n 2 n 1 = n = ⁢ 2 ⁢ ⁢ d · 2 ⁢ ⁢ π ⁢ ⁢ f [ 1 - n 3 n 1 ⁢ u 2 u 1 ⁢ sin 3 ⁢ θ u 2 ⁢ cos ⁢ ⁢ θ 2 ] = ⁢ 2 ⁢ ⁢ d · 2 ⁢ π ⁢ ⁢ f ⁡ [ cos ⁢ ⁢ θ 2 u 2 ] - π ⁡ ( 2 ⁢ k + 1 ) ⁢ ⁢ k = integer ∴ 4 ⁢ d · f u 2 ⁢ cos ⁢ ⁢ θ 2 = ⁢ ( 2 ⁢ k + 1 ) 4 ⁢ ⁢ d · 1 λ 2 ⁢ cos ⁢ ⁢ θ 2 = ⁢ ( 2 ⁢ k + 1 ) ⁢ ⁢ f ⁢ ⁢ λ 1 f ⁢ ⁢ λ 2 = u 1 u 2 = n 2 n 1 4 ⁢ d · 1 λ 2 ⁢ n 1 n 2 ⁢ cos ⁢ ⁢ θ 2 = ⁢ ( 2 ⁢ k + 1 ) ⁢ ⁢ 1 λ 2 = 1 λ 1 ⁢ n 1 n 2 4 ⁢ ⁢ d ⁢ ⁢ cos ⁢ ⁢ θ 2 / n = ⁢ λ 1 ⁡ ( 2 ⁢ k + 1 ) d = ⁢ n ⁢ ⁢ λ 1 ⁡ ( 2 ⁢ k + 1 ) 4 ⁢ ⁢ cos ⁢ ⁢ θ 2 .