UA116225U - LENS FOR MICRO SATELLITES - Google Patents

Abstract

The lens for microsatellites contains a main concave mirror, a secondary spherical mirror, a correcting element. The main mirror has an elliptical shape and a diameter of 180 mm, the main and secondary mirrors are made of astrosital CO-115M. The correcting element consists of three lenses made of fused quartz material. The extreme lenses are positive, and the middle lens has the shape of a meniscus and is located with a concave surface to the image space.

Description

The useful model belongs to optical devices, namely to the field of observational optical devices and can be used to solve the tasks of detection, recognition and identification of objects of observation from space on the Earth's surface in the spectral range of 0.45-0.75 μm.

The ultraviolet lens (Patent

RF Mo 2154849, dated 20.08.2000, IPC 502813/14, 502817/08), containing the main concave parabolic mirror, a secondary spherical mirror and a corrective element consisting of three lenses with the same refractive index. The extreme lenses are negative and are made in the form of menisci, facing the image space with concavity, and the central one is biconvex. The disadvantages of this device are a narrow spectral range of operation, a corrective element made of a material unsuitable for use in conditions of a large temperature difference, a small diameter of the main mirror, a parabolic shape of the surface of the main mirror, which is more difficult to manufacture than an elliptical one.

The basis of a useful model is the task of creating a lens system for working in open space, providing higher technical characteristics: improving image quality and expanding the spectral range of work.

The problem is solved by the fact that a lens for microsatellites containing a main concave mirror, a secondary spherical mirror, a correction element consisting of three lenses, according to a useful model, the main mirror has an elliptical shape and a diameter of 180 mm, the main and secondary mirrors made of CO-115M astrosital, and the corrective element consists of three lenses made of fused quartz material, and the extreme lenses are positive, and the middle lens has the shape of a meniscus and is located with a concave surface to the image space.

The main mirror has a larger diameter - 180 mm, which allows you to get a resolution better than 1 second of arc and an elliptical surface shape, which is easier to manufacture than a parabolic one.

The corrective element consists of three lenses, and the extreme lenses are positive, and the central one is made in the form of a meniscus, facing the image space with its concavity. The performance of mirrors from CO-115M astrosital, and the lenses of the corrective element of the system from fused quartz - materials with an ultra-low coefficient of thermal expansion, makes it possible to obtain stable parameters

From the optical system with a significant temperature difference from -60C to 1570°C.

Making a negative corrector lens in the form of a meniscus facing the image space with a concavity, followed by a positive biconvex corrector lens makes it possible to reduce residual spherochromatic aberration in a wide range of the spectrum.

At the same time, the residual coma also decreases, as a result of which the image quality increases and the spectral range of the system's operation expands. Aberration "curvature of the field" is minimized in the calculation of the use of SSO-matrix as light receivers.

Unknown optical lens systems that have features similar to the features that distinguish the proposed system from the prototype, so this optical system has significant differences.

The proposed useful model is explained by the following graphic materials:

Fig. 1 - optical scheme of the lens.

Fig. 2 - transverse aberrations on the axis and half the angle of the field of view are 0.47 and 0.757.

Fig. C - frequency-contrast characteristic.

Fig. 4 - field curvature.

Fig. 5 - optical transmission function.

In fig. 1 shows the proposed optical lens system. The system includes the main concave elliptical mirror 1, the secondary spherical mirror 2 and the correcting element installed along the path of the beam behind the secondary mirror, consisting of three lenses Z, 4 and 5, of which the extreme lenses Z and 5 are positive, and the central lens 4 is made in in the form of a negative meniscus facing the space of images by its concavity. Corrector lenses are made of material with the same refractive index (fused quartz), which has a low coefficient of thermal expansion.

Rays of light, reflecting from the main and secondary mirrors 1 and 2, pass through the corrector lenses 3, 4 and 5, forming an image of the observation object in the image plane 6, which is located behind the main mirror 1.

The design parameters of the proposed lens are listed in the table, where: i - surface number; her - radii of curvature of surfaces; and; - lens thicknesses and air gaps; n; - refractive indices;, - light diameters of surfaces; and - eccentricity. Only the main mirror 1 has an eccentricity different from zero, all other optical surfaces are spherical. All linear parameters of the system are given in mm. (510)

Table 7717711 p | material | and | is 1 -7200 | 230 | sh-.KM- | Yu.- | l80 | -0.71363 2 | 467.64 | 186855 | - | - | 73 | 0 3 | 546,067 | 70 | 1460077 | quartz. | 40 | 0 4 | -58559 | 204 | - |! - | 4 | 0 | 144867 | 10 | 1460077 | quartz. | 32 | 0 6 | zpe98 | 3525 | - | - | with | 0 7 | 86279 | 57 | 1460077 | quartz. | 30 | 0 and 8 | 90986 | from 47th | - | - / z Y o0 |i "- Back focal segment (distance from the second surface of the lens 5 of the corrective element to the image plane)

Equivalent system focus 900mm, relative aperture 1/5. The total length of the system with a secondary mirror thickness of 8-310 mm.

In fig. 2 shows the images of the point for different angles of the field of view in angular measure m/ and in millimeters 5 Й for four wavelengths. In the upper left corner, the scale is in microns. Angles are counted from the optical axis, so the full field of view will be 2m/-1.5 degrees of arc or in linear measure 21-23.9 mm.

In fig. 3 shows a graph of the frequency-contrast characteristic. The upper line on the graph marks the theoretical limit for an optical system with the same diameter of the main mirror, luminous intensity and shielding. The upper line is almost obscured by the lines of the real system, which indicates that the calculated system is close to the theoretical limit.

In fig. 4 shows the field curvature graph. The graph shows that the depth of all sharp images deviates from the ideal plane by no more than 0.1 mm. In this way, the presented optical system is ideally suited to work together with the SCO-matrix as a light-accumulating element.

In fig. 5 shows the distribution of energy from a point source. It can be seen that the central maximum occupies in a linear measure less than 3 microns, and the energy concentration in it exceeds 90 9o (the Strehl number is greater than 0.9, X axis).

The proposed lens can be used to solve the tasks of detection, recognition and identification of observation objects in the atmosphere and beyond. When used as a microsatellite lens together with a SSO-matrix with a pixel size of 6 microns and a window of 24 x 24 mm, the resulting image will have 4000 x 4000 elements and cover an area of 10.4 x 10.4 km from an altitude of 400 km. The size of one pixel on the matrix will correspond to 2.6 m on the surface

Earth In the case of using a matrix with a pixel size of 2 microns, the resolution of the lens will double.

Claims (1)

USEFUL MODEL FORMULA ZO Lens for microsatellites, containing a main concave mirror, a secondary spherical mirror, a correcting element consisting of three lenses, characterized in that the main mirror is elliptical in shape and 180 mm in diameter, the main and secondary mirrors are made of astrosite CO- 115M, and the corrective element consists of three lenses made of fused quartz material, and the extreme lenses are positive, and the middle lens has the shape of a meniscus and is located with a concave surface to the image space.