CS229830B1 - Fourier Transform Lens - Google Patents

Abstract

A lens for Fourier transformation, especially for optical signal processing, comprising two identical optical systems which are mirror images of each other with respect to the plane of symmetry and each consists of a coupler, a diffuser and a meniscus, separated from each other by air gaps, whereby, counting from the entrance surface of the lens, the lenses the first coupler with the sixth coupler, the second diffuser with the fifth diffuser and the third meniscus with the fourth meniscus are optically identical.

Description

The invention relates to a Fourier transform lens. More precisely, the subject of the invention is a lens which is suitable in particular for optical signal processing and in general for Fourier transforms in an optical manner. f

Commonly manufactured lenses, such as photographic or projection lenses, are designed and corrected for the display of distant objects and cannot be used for other display ratios. The requirement for lenses for performing the Fourier transform is that the image size Y' of an infinitely distant object be given by the relation Y' i = — f'.sin w, where í' is the focal length of the lens and aw ^; is the angle of view. Commonly manufactured lenses do not satisfy this relation, since they are constructed so as to correspond to the relation Y* — — f'.tg w. If the object under examination is placed in the object ¹ focal plane, the Fourier spectrum is formed in the image focal plane, the distance of the object from its spectrum ' being equal to twice the focal length.

Compared to the prior art, this invention represents an improvement, the subject of which is a lens for Fourier transformation, in particular for......Optical signal processing, in which the essence of the invention is a structure containing two identical optical systems, which with respect to the plane of symmetry are in a mirror position with respect to each other, and each optical system consists of a coupler, a diffuser and a meniscus, separated from each other by air gaps, whereby, counted from the entrance surface of the lens, the first and sixth lenses, the second and fifth and third and fourth lenses are optically identical.

The lens according to the invention meets the requirement that the image size be functionally dependent on the angle of the field of view according to the relationship Y' — -i- f'.sin w, where the distance of the object from the spectrum is equal to the focal length of the lens, and is therefore two times smaller than when using a conventional lens.

The invention uses the knowledge that the desired effect of the lens can be achieved if the lens is composed of six lenses based on a system of a coupler, a diffuser and a meniscus, of which two are always the same; but oppositely oriented, so that the first lens is equal to the sixth, the second to the fifth and the third to the fourth, with the second lens of each pair always being oriented oppositely to the first.

The lens according to the invention can advantageously be formed so that the refractive index of the first and sixth lenses is in the range

1.55 < ni, ne < 1.66, the refractive index of the second and fifth lenses lies within the limits

1.65. < nz, ns < 1.76, and the refractive index of the third and fourth lenses is within the limits

1.45 < Π3, 114 < 1.56, where ni to ns are the refractive indices of the glasses.

The following relations apply for the radii of curvature — Ti = ri3_,· i = i, 2, 3, 4, 5, 6 where r is the radius of curvature and ai is an integer in the range 1 to 6. For the refractive indices, n, = n ₇ „ji = 1, 2, 3 where: n is the refractive index and ai is an integer with a value in the range 1 to 3. The following values are particularly advantageous for the ratios of the individual radii of curvature:

3.6 < —rz/ri < 4.6,

3.6 < —-Γ4/Γ2 < 4.6, < rs/i'6 < 1.8.

A particularly advantageous embodiment of the lens is given in the following text:

ri = 80.16 dl = 10 not = 1.61050 Γ2 = —331.85 dz = 3.92 Π2 = 1.71281 Γ3 = —214.75 d3 = 5 U3 = 1.61585 Γ4 = 847.35 d4 = 15 n4 = 1.51585 Γ5 = 47.41 ds = 23.16 ns = 1.71281 Γ6 = 32.06 d6 = 74.31 no = 1.61050 Γ7 = —32.06 d7 - 23.16 Γ8 = —47.41 there = 15 Γ9 = —847.35 dg = 5 no = 214.75 dio = 3.92 ru = 331.85 day = 10 Π2 = —80.16

where:

Γι_ΐ2 means the radius of curvature, di_n means the axial thickness of the lens and n_ ₎₆ is the refractive index.

For vertex distances the following relation holds: φ = di ₂ _i i = 1, 2, 3, 4, 5

0.2 f' <. ds < 0.4 f'

0.02 f' < di < 0.06 f'

0.01 f' < d2 < 0.022 f'

0.015 ť < d3 < 0.025 f 0.04 ť < d4 < 0.08 f'

0.06 ѥ < ds < 0.15 f‘ where:

d, i, and í’ have the meanings given above.

The attached drawing shows an example of an embodiment of a lens for Fourier transformation, in particular for optical signal processing, shown in a horizontal position and consisting of two oppositely oriented groups of lenses i, _n , _k de _skU p _in a I consists of a ζθ coupler 1, a diffuser 2 and a meniscus 3, which are separated from each other by air gaps, _and group II, located with respect to the sculpin i γ in a mirror position according to the plane of symmetry S, consists of a meniscus 4, a diffuser 5 and a coupler fi, mutually divided by air gaps, whereby the lenses 1 and 6, diffusers 2 and 5 and meniscuses 3 _and ^P 4 are identical.

Claims (1)

SUBJECT A Fourier transform pi, particularly for optical signal processing, characterized in that it comprises θ two identical optical systems [I, II] which, in respect of the plane of symmetry (S), are in mirror position with respect to each other and each consists of a coupling (1, 6), the diffusers (2, 5] and the meniscus (3, 4), separated from each other by air gaps, counting from the input surface of the lens objective, the first clutch (1) with the sixth clutch (6) ) rozDtvlkoou the fifth (5) and the third meniscus (3), ^{characterized} thereby fourth meniscus (4) are identical.