RU2427862C1 - Large aperture ratio projection lens - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: projection lens has a first group of lenses, an aperture diaphragm and a second group of lenses, all lying in series on the path of optical radiation from the object to the image. The first group of lenses has a negative meniscus whose convex side faces the object, and a biconvex lens with another biconvex lens in between. The first lens of the second group is biconcave. The second lens of the second group is convergent and its convex side faces the image. The third lens of the second group faces the image with its concave side and comprises a biconvex and a biconcave lens glued together. A biconvex lens is placed between the second and third lenses of the second group. All lenses are spherical. The lenses are made from colourless optical glass. ^ EFFECT: operation of the lens with objects lying at a finite distance, high aperture ratio and illumination on the edge of the image field, providing the value and sign of distortion which is sufficient for correcting X-ray image converter distortion, high manufacturability. ^ 4 dwg

Description

The invention relates to optical instrumentation, specifically to projection lenses, and can be used, for example, in image transfer devices formed on the output window of an X-ray electron-optical converter (REOP) or other electron-optical converter (EOP) on a CCD matrix.

Known projection lens (patent EP 2149808, published 03.02.2010), containing the first group of lenses, the aperture diaphragm and the second group of lenses arranged sequentially along the optical radiation from the subject to the image, the first group of lenses containing three lenses, including with an aspherical surface , and the second group of lenses contains five lenses, including aspherical.

This lens has the following advantages: a significant magnitude of the field of view, a small decrease in illumination at the edge of the field of vision with respect to illumination in the center of the field of view, high image quality, sufficient image size, small size. When considering the possibility of using this lens to solve the problem, the disadvantages were: a low relative aperture (1: 1.96 with the required no worse than 1: 1.1) and the presence of two higher-order aspherical surfaces in the lens, which in this particular case is for small-scale production not economically feasible.

As a prototype, the lens according to the patent for invention US 6,600,610 was selected, published on July 29, 2003, containing the first group of lenses, the aperture diaphragm, and the second group of lenses arranged sequentially along the optical radiation from the subject to the image, the first group of lenses containing two lenses, the first of which is made in the form of a negative meniscus convex to the object, the second is made in the form of a positive meniscus convex to the object, as an option - from organic material with two aspherical iusami, first lens of the second group is made negative concavity facing the subject, as an option - an organic material with two aspheric radii, the second lens of the second group is made positive, the convex side facing to the image, and the third lens of the second group is concave to the image.

The advantages of this lens are: large image size, small size, high image quality, a small number of lenses.

The disadvantages of this lens are: low relative aperture, low ratio of illumination at the edge of the image with respect to illumination in the center of the image, the amount of negative distortion insufficient to correct the positive distortion of the REOP, the lens works with an infinitely distant object, the presence, as options, of one or two, low-tech lenses made of organic material and with aspherical radii.

The technical result of the inventive lens is to ensure that the lens works with objects located at a finite distance, increase the relative aperture, increase the illumination at the edge of the image field with respect to the center, provide a magnitude and sign of distortion sufficient to correct REOP distortion, perform all the lens radii included in lens, spherical, using optical colorless glass as the lens material to ensure manufacturability in single and small batch production TBE.

The technical result in a projection lens with a large relative aperture, containing the first group of lenses, the aperture diaphragm and the second group of lenses arranged sequentially along the optical radiation from the subject to the image, the first group of lenses containing a negative meniscus convex to the object and a positive lens, the first the lens of the second group is made negative, facing concavity to the subject, the second lens of the second group is made positive, convex side to the image and the third lens of the second group is turned concavity to the image, it is achieved by the fact that the positive lens of the first group is made biconvex and between the negative and positive lenses a biconvex lens is additionally introduced, the first lens of the second group is made biconcave, the third lens of the second group is glued from two, the first of which - biconvex, and the second - biconcave, moreover, between the second and third lenses of the second group, a biconvex lens is additionally introduced, and all the lens radii are It is spherical, and the lens material - optical flint.

The invention and the possibility of its industrial application is illustrated by an example of a specific implementation, which is shown in figures 1-4. Figure 1 shows a schematic optical diagram of the lens, figure 2 is a graph of the frequency response (frequency-contrast characteristics of this lens), figure 3 is a graph of the relative illumination of the image depending on the size of the subject, figure 4 is a graph of the distortion of the image in depending on the size of the item.

As shown in figure 1, along the path of optical radiation from the subject 10 to the image 11, the lens contains a first group of lenses 1, 2, 3, an aperture diaphragm 4 and a second group of lenses 5-9. Lens 1 is the negative meniscus convex to the subject. Lenses 2 and 3 are biconvex. Lens 5 is biconcave, lens 6 is the positive meniscus convex to the image, lens 7 is biconvex, the lens glued from 8 and 9 is turned concave to the image, and lens 8 is biconvex, and lens 9 is biconcave.

Figure 2 presents a graph of the frequency-contrast characteristics of the inventive lens for the spectral range from 500 nm to 600 nm with a main wavelength of 575 nm, characterizing the magnitude of the contrast coefficient (T) depending on the spatial frequency in the image for three fields of view: center, 0 , 7 maximum and maximum, and for 0.7 maximum and maximum field of view, two curves are presented — for the meridional and sagittal sections. The vertical axis T characterizes the value of the contrast coefficient (modulation), the horizontal axis N, pairs lin./mm, characterizes the spatial frequency in the image in pairs of lines per mm. The graph depicts five curves, with curve 1 representing the center of the field of view (object size 0 mm), curves 2S and 2T representing half 0.7 of the field of view (object size 7.6 mm), curves 3S and 3T representing the edge of the field of view (item size 10.85 mm), with the letter S relating the curves to the sagittal section, and the letter T to the meridional section of wide beams of rays.

Figure 3 presents a graph characterizing the lens by the parameter of relative illumination of the image depending on the size of the subject. The vertical axis RI determines the magnitude of the relative illumination, the horizontal axis determines the value of the size of the object Y in mm. It can be seen from the graph that when the size of the object Y is 10.85 mm, the illumination of the image is 0.55 from the center of the field of view (Y is 0 mm), where the relative illumination is maximum and is 1.

Figure 4 presents a graph of image distortion depending on the size of the subject for a lens embodiment according to claim 1. The vertical axis Y characterizes the size of the object in mm. The horizontal axis D characterizes the percentage distortion of the image. The graph shows that the maximum distortion of the image is 7.3% for the edge of the field of view of 10.85 mm, which allows you to compensate for the positive distortion of the REOP.

The lens works as follows: the optical radiation from the object 10 sequentially passes through the lenses 1, 2, 3, the aperture diaphragm 4, the diameter of which determines the relative aperture of the lens, the lenses 5-9 are focused in the image 11. As an image receiver, a CCD can be used matrix, film, etc.

The addition of the first group of lenses to the diaphragm 1, 3 with a biconvex lens 2 and the implementation of a positive lens 3 in the form of a biconvex lens made it possible to simplify the translation of the lens into a mode of operation from a finite distance and to improve the correction of higher order aberrations throughout the image, provided that the field of view and the relative aperture increase. The implementation of 5 biconcave lenses in shape has improved the correction of spherical aberration and astigmatism. The implementation of the lens 6 in the form of a meniscus and the introduction of an additional biconvex lens 7 made it possible to reduce higher order aberrations and increase the relative aperture of the lens. The implementation of the last lens of the lens, facing concavity to the image and glued from biconvex 8 and biconcave 9 allowed to reduce spherochromatic aberration, field curvature, and chromaticity increase. The complete lack of symmetry and proportionality with respect to the diaphragm of the first and second groups of lenses in the shape of the lenses and their number made it possible to obtain residual distortion of the negative sign of -7.3% for the edge of the field of view with a coefficient of linear magnification of -0.28. The entire combination, shape and sequence of the arrangement of the lenses made it possible to exclude lenses from the lens, from organic material and with aspherical radii while ensuring high image quality over the entire field of view.

Thanks to the inventive design of the lens, a new technical result is achieved: the absence of lenses made of organic material and with aspherical radii entering the lens, the relative aperture (1: 1.06) is increased, the illumination at the edge of the image field with respect to the center is increased (0.55), the presence of negative image distortion of the required size (-7.3%), the required image quality is ensured when the lens works with an object located at a finite distance.

Claims (1)

A projection lens with a large relative aperture, containing in series, in the direction of optical radiation from the subject, the first group of lenses, an aperture diaphragm and the second group of lenses, the first group of lenses containing a negative meniscus convex to the object and a positive lens, the first lens the second the group is made negative, facing concavity to the subject, the second lens of the second group is made positive, convex side to the image, and the third lens is second of the group is turned by a concavity to the image, characterized in that the positive lens of the first group is biconvex and an additional biconvex lens is introduced between the negative and positive lenses, the first lens of the second group is biconcave, the third lens of the second group is glued from two, the first of which is biconvex, and the second is biconcave, and a biconvex lens is additionally introduced between the second and third lenses of the second group, and all the lens radii are spherical and a lens material - optical flint.

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