RU2727269C1 - Fast eyepiece with remote exit pupil - Google Patents

Abstract

FIELD: optics.SUBSTANCE: eyepiece can be used in observation devices, mainly in optical sights. Eyepiece contains three components. First component is glued from a biconcave and biconvex lens, the second component is a positive lens, and the third component is glued from a negative meniscus whose concave side faces the image space and the positive lens. All positive lenses are made of glass with refraction index 1.45≤n≤1.55 and dispersion coefficient 65≤ν≤75, negative lens of first component is made of glass with refraction index 1.75≤n≤1.91 and dispersion coefficient of 23≤ν≤26, and third component negative lens is from glass with refraction index of 1.55≤n≤1.65 and dispersion coefficient 35≤ν≤40. Following ratios are met: 1.85≤φ/φ≤1.95; 2.3≤φ/φ≤2.4; |0.95|≤φ/φ≤|1.15|, where: φ – eyepiece optical power, φ, φ, φ– optical forces of the first, second and third components, respectively.EFFECT: technical result is increased exit pupil removal, increased aperture, improved image quality and simplified eyepiece design.6 cl, 5 dwg, 1 tbl

Description

The invention relates to the field of optical instrumentation and can be used in observation devices, for example, in telescopes, or in optical sights.

Known eyepiece with an extended exit pupil according to the patent of the Republic of Belarus No. 6216 from 23.11.2001, the eyepiece consists of three components, the first component along the beam is a positive biconvex lens. The second component is made in the form of a lens glued from a biconvex lens and a negative meniscus, the convex surface of which faces the image space. The third component is made in the form of a positive double-glued lens containing a biconvex and biconcave lenses.

At a focal length of 30 mm, the specified eyepiece has an insufficient exit pupil distance of 32 mm and an exit pupil diameter of 5 mm, as well as a small relative aperture of 1: 6. In addition, this eyepiece, converted to a focal length of 24.958 mm, as in the claimed eyepiece, has insufficient image quality, because all aberrations, except for chromatic ones, are poorly corrected.

The closest in technical essence to the claimed - the prototype - is an eyepiece with a remote exit pupil according to RF patent No. 191915 dated 05/15/2019. The eyepiece contains three components, the first of which consists of glued negative biconcave and positive biconvex lenses, the second component contains a positive biconvex lens, the third is glued from two lenses, characterized in that the second component additionally contains a negative meniscus facing the concavity of the image space, glued with a positive biconvex lens, and the third glued component is made of a negative meniscus facing the concavity of the image space, and a positive lenses. The positive lenses of the first and second components and the negative lens of the third component are made of glass with a refractive index of 1.7≤n≤1.8 and a dispersion coefficient of 44≤ν≤52, and the negative lenses of the first and second components are made of glass with a refractive index of 1, 72≤n≤1.77 and a variance of 27≤ν≤30. The following conditions are met: 0.3≤φ ₁ / φ≤0.45; 0.48≤φ ₂ / φ≤0.56; | 0.17 | ≤φ ₃ / φ≤ | 0.27 |, where φ is the optical power of the entire system, φ _i is the optical power of the i-th component.

The specified eyepiece has a small exit pupil distance, which can lead to eye injury when shooting using a scope with such an eyepiece. The ratio of the exit pupil distance to the focal length of the eyepiece is 1.2f ', with a focal length of 22.36 mm, the exit pupil distance is 26.83 mm.

In addition, the eyepiece has a small 1: 4.5 aperture ratio and poor image quality. According to the example of a calculated eyepiece given in the description, its polychromatic frequency-contrast characteristic over the entire field for a frequency of 25 l / mm can be only 40%. In addition, the eyepiece has a complex design, since contains 6 lenses.

The recalculation of the eyepiece to a focal length of 24.958 mm showed that there is a sharp drop in image quality both for a point on the axis and for the entire field of view. With an aperture ratio of 1: 3.6, the eyepiece has poor image quality.

The technical problem consists in obtaining the following technical result: increasing the removal of the exit pupil, increasing the relative aperture, improving the image quality and simplifying the eyepiece design.

The specified technical result is achieved in the proposed eyepiece. The eyepiece, like the prototype, contains three optically connected components, the first of which consists of glued negative biconcave and positive biconvex lenses, and the third consists of glued negative meniscus, concavely facing the image space, and a positive lens. Unlike the prototype, the second component is made in the form of a positive lens, all positive lenses are made of glass with a refractive index (n) 1.45≤n≤1.55 and a dispersion coefficient (ν) 65≤ν≤75, the negative lens of the first component is made made of glass with a refractive index of 1.75≤n≤1.91 and a dispersion coefficient of 23≤ν≤26, and the negative lens of the third component is made of glass with a refractive index of 1.55≤n≤1.65 and a dispersion coefficient of 35≤ν≤ 40, while the following ratios are satisfied: 1.85 φ ₁ / φ ≤ 1.95; 2.3≤φ ₂ / φ≤2.4; | 0.95 | ≤φ ₃ / φ≤ | 1.15 |, where: φ is the optical power of the eyepiece, φ ₁ , φ ₂ , φ ₃ are the optical powers of the first, second and third components, respectively.

The second component can be made in the form of a biconvex or plano-convex lens. The positive lenses of the second and third components may be biconvex or plano-convex.

An example of a specific implementation of an eyepiece is shown in the drawings.

FIG. 1 shows the optical diagram of the eyepiece.

FIG. 2 shows the distortion graph.

FIG. 3 shows plots of transverse spherical aberration for the fundamental wavelength of 546 nm (δY ' _λ0 ) and chromatic aberration of position for wavelengths 480 nm (δY' _λ1 ) and for 643.8 nm (δY ' _λ2 ).

FIG. 4 shows the graphs of curvature in the meridian (Z'm) and sagittal (Z's) planes.

FIG. 5 is a graph of magnification chromatism for the difference between the wavelengths of 480 nm and 643.8 nm (δY ' _λ2-λ1 ).

The eyepiece (Fig. 1) contains three optically coupled components. The first component along the ray path consists of a glued negative biconcave lens 1 and a positive biconvex lens 2, the second component is made in the form of a positive plano-convex lens 3, the third component consists of a glued negative meniscus 4, concavely facing the image space, and a positive biconvex lens five.

The eyepiece works as follows. Diverging beams of rays emanating from the points of the object are refracted by all components of the eyepiece, converted into parallel beams and build an image of the object. The beams from the object of observation pass through the first component, introducing positive spherical aberration, astigmatism and curvature. The second component partially compensates for them, and the third component builds an image at infinity, compensating for residual aberrations.

As a specific example of implementation of the invention, an eyepiece is calculated with the design parameters shown in Table 1.

From the table it follows that in the calculated eyepiece φ ₁ / φ = 1.9; φ ₂ / φ = 2.35; φ ₃ / φ = | 0.98 |. These ratios, as well as the refractive indices and dispersion coefficients of these lens glasses are within the stated ranges.

Eyepiece optical characteristics:

Focal length 24.96 mm Angular field of view 21 ° Spectral range 480-643.8 nm Removal of the exit pupil 60 mm Exit pupil diameter 7 mm Relative hole 1: 3.6.

In this eyepiece, compared with the prototype at a focal length of 24.96 mm, the exit pupil removal is increased by 2.2 times, and the relative aperture is increased by 1.25 times. The high quality of the eyepiece image is demonstrated by the graphs in FIG. 2-5.

The distortion (FIG. 2) for a 21 ° field of view is less than 1%. Residual aberrations of the eyepiece in the return path of the beams for a point on the axis at a relative aperture of 1: 3.6 are: longitudinal spherical aberration - no more than 0.08 mm, transverse spherical aberration - no more than 0.01 mm, transverse chromatism of position - no more than 0 , 01 mm. For an angular field of view of 21 °, the meridional astigmatic segment (Z'm) is not more than 1.1 mm, the sagittal astigmatic segment (Z's) is not more than 0.28 mm, and the chromatic aberration of magnification is not more than 0.007 mm.

From the given graphs (Fig. 2, 3, 4, 5) it follows that in the proposed eyepiece aberrations are significantly corrected and a high image quality is obtained.

The specified technical results are achieved with the refractive indices and dispersion coefficients of glass of lens 1 in the ranges 1.75≤n≤1.91 and 23≤ν≤26, lenses 2, 3 and 5 - in the ranges 1.45≤n≤1.55 and 65≤ν≤75, lenses 4 - in the ranges 1.55≤n≤1.65 and 35≤ν≤40, as well as when the claimed ratios of optical powers are fulfilled: 1.85≤φ ₁ / φ≤1.95; 2.3≤φ ₂ / φ≤2.4; | 0.95 | ≤φ ₃ / φ≤ | 1.15 |.

Thus, in comparison with the prototype, in the proposed eyepiece, which has a simpler design, the distance of the exit pupil is increased to 60 mm and the relative aperture to 1: 3.6 and the image quality is improved.

Claims (11)

1. A high-aperture eyepiece with a remote exit pupil, containing three optically coupled components, the first of which consists of glued negative biconcave and positive biconvex lenses, and the third consists of glued negative meniscus, concavely facing the image space, and a positive lens, characterized in that the second component is made in the form of a positive lens, all positive lenses are made of glass with a refractive index of 1.45≤n≤1.55 and a dispersion coefficient of 65≤ν≤75, the negative lens of the first component is made of glass with a refractive index of 1.75≤n ≤1.91 and dispersion coefficient 23≤ν≤26, and the negative lens of the third component is made of glass with a refractive index 1.55≤n≤1.65 and dispersion coefficient 35≤ν≤40, while the following relations are fulfilled: 1.85≤φ ₁ / φ≤1.95; 2.3≤φ ₂ / φ≤2.4; | 0.95 | ≤φ ₃ / φ≤ | 1.15 |, where: φ is the optical power of the eyepiece; φ ₁ , φ ₂ , φ ₃ are the optical powers of the first, second and third components, respectively. 2. An eyepiece according to claim. 1, characterized in that the second component is made in the form of a biconvex lens. 3. An eyepiece according to claim 1, characterized in that the second component is made in the form of a plano-convex lens. 4. An eyepiece according to claim 1, wherein the positive lens of the third component is biconvex. 5. An eyepiece according to claim 1, wherein the positive lens of the third component is flat-convex. 6. An eyepiece according to claim 1, wherein all positive lenses are made of glass of the same brand.

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