RU2473932C2 - Projection lens - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: lens has series-arranged first group of lenses, an aperture diaphragm and a second group of lenses. The first group of lenses has two positive menisci glued together and facing the object with their convex side. The first lens of the second group is negative, faces the object with its concave side and is glued from two menisci, the second of which is positive. The second lens of the second group is positive and its convex side faces the image. The third lens of the second group is biconcave and is glued from a biconcave lens and a positive meniscus. Between the second and third lenses of the second group there is a biconvex lens and a positive meniscus whose concave side faces the image. All radii of the lenses are spherical and the material of the lens is optical clear glass.

EFFECT: operation of the lens with objects lying at a finite distance, high illumination on the edge of the image field, providing the value and sign of distortion which is sufficient for correcting distortion of an X-ray image converter distortion, high manufacturability.

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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.

Known projection lens (patent EP 2149808, published 02/03/2010) containing the first group of lenses, the aperture diaphragm and the second group of lenses arranged in series, along the path of optical radiation from the subject to the image, the first group of lenses containing three lenses, including aspherical surface, and the second group of lenses contains five lenses, including aspherical.

This lens has the following advantages: a sufficient magnitude of the relative aperture, a significant magnitude of the field of view, a small decrease in illumination at the edge of the field of view with respect to illumination in the center of the field of view, and high image quality. However, it does not have sufficient image size (y '= 4.8 mm with the required y' = 11.5 mm). To ensure the required image size, the focal length and the design parameters of the analog were scaled. As a result, it turned out that while maintaining the essence of the invention, there was an increase in the dimensions of the lens and a deterioration in quality indicators to values that did not allow it to be used for the required conditions. When considering the possibility of using this lens to solve the problem, a negative factor was the presence of two higher-order aspherical surfaces in it, which in this particular case is not economically feasible for small-scale production.

As a prototype, a lens was chosen according to the patent for invention US 6,600,610, published July 29, 2003, containing the first group of lenses, the aperture diaphragm and the second group of lenses arranged in series, 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 radii, the first lens of the second group is made negative, concave to the object, as an option of organic material with two aspherical radii, 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.

The advantages of this lens are: large image size, small dimensions, high image quality with a sufficient relative aperture, a small number of lenses.

The disadvantages of this lens are: a 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 work of the lens with an infinitely distant object, the presence of one or two non-technological lenses made of organic material as options 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, increasing the illumination at the edge of the image field relative to the center, providing a magnitude and sign of distortion sufficient to correct the distortion of the REOP, making all the radii of the lenses included in the lens spherical, the use of optical colorless glass as lens material to ensure manufacturability in single and small batch production.

The technical result in a projection lens containing in series, in the direction of optical radiation from an object to an image, a first group of lenses, an aperture diaphragm and a second group of lenses, the first group of lenses containing a positive lens convex to the object, the first lens of the second group 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 For example, the lenses of the first group are glued together, and the first one is made positive in strength, the first lens of the second group is glued from two menisci, the second of which is positive, the third lens of the second group is biconcave and glued from two, the first of which is biconcave and the second is a positive meniscus, moreover, two positive lenses are additionally introduced between the second and third lenses of the second group, the first of which is biconvex, the second is the meniscus facing the object with concavity moreover, all the radii of the objective lenses are made spherical, and the lens material is an optical colorless glass.

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 optical radiation from the subject 11 to the image 12, the lens contains a first group of lenses 1, 2, aperture diaphragm 3 and a second group of lenses 4-10. Lenses 1 and 2 are positive menisci, convex to the object and glued together, lenses 4 and 5 are made in the form of menisci and glued together, with lens 4 being negative facing concavity to the object, and lens 5 being positive, lenses 6 being biconvex, the last lens of the lens is biconcave in shape and glued from lenses 9 and 10, respectively made in the form of a biconcave lens and a positive meniscus facing concavity to the image, and two positive lenses are introduced between lenses 6 and 9-10: 7 - biconvex, 8 - change to facing concavity to the image.

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 , 64 maximum and maximum, and for 0.64 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 shows five curves, with curve 1 representing the center of the field of view (object size 0 mm), curves 2S and 2T representing half 0.64 field of view (object size 8 mm), curves 3S and 3T representing the edge of the field of view (size subject 12.5 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 magnitude of the size of the object Y in mm. The graph shows that when the size of the subject Y is 12.5 mm, the illumination of the image is 0.91 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 3% for the edge of the field of view of 12.5 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 lens 1, the aperture diaphragm 3, the diameter of which determines the relative aperture of the lens, the lenses 4-10 and are focused in the image 11. As the image receiver, a CCD, film and etc.

Removing the negative lens from the first group of lenses to the aperture diaphragm 3 and making the positive lens in the form of glued from two positive menisci 1 and 2 with a large difference in the Abbe coefficient allowed, provided the field of view was reduced, to simplify the translation of the lens into operation mode from a finite distance and improve correction chromatic aberration. The implementation of lenses 4 and 5 glued allowed to reduce spherochromatic and spherical aberrations, the introduction of two additional positive lenses 7, 8 allowed us to reduce higher order aberrations. The implementation of the last lens of the lens is biconcave in shape and glued from lenses 9 and 10, allowed to improve the correction of field aberrations and maintain high image quality over the entire field of view while improving the illumination of the image at the edge of the field of view. The implementation of lenses 9, 10 from glasses with a large difference in the Abbe coefficient and glued allowed to reduce the chromaticity of the increase. The complete lack of symmetry and proportionality with respect to the diaphragm of the first and second groups of lenses according to the shape of the lenses and their number made it possible, even with a linear lens enlargement coefficient of 1, to obtain residual negative sign distortion of 3% for the edge of the field of view. The entire combination, shape and sequence of the arrangement of the lenses made it possible to exclude lenses from organic material and with aspherical radii from the lens, while ensuring high image quality over the entire field of view.

Thanks to the inventive design of the lens, a new technical result was achieved: the absence of lenses made of organic material and with aspherical radii entering the lens, increased illumination at the edge of the image field relative to the center (0.91), the presence of negative image distortion of the required magnitude (-3%) , the required image quality is ensured when the lens is operated with an object located at a finite distance.

Claims (1)

A projection lens containing the first group of lenses, the aperture diaphragm and the second group of lenses arranged sequentially along the path of optical radiation from the subject to the image, the first group of lenses containing two meniscus convex to the subject, the second of which is positive in strength, the first 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 facing concavity to the image, characterized in that the lenses of the first group are glued together, and the first one is made in positive force, the first lens of the second group is glued from two menisci, the second of which is positive, the third lens of the second group is biconcave and glued from two , the first of which is biconcave, and the second is the positive meniscus, moreover, two positive lenses are additionally introduced between the second and third lenses of the second group, the first of which is biconvex, the second is the meniscus facing concavity to and siderations, all of the radii of the lens are spherical lenses, and the lens material - optical colorless glass.

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