RU2426160C1 - Projection lens - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: projection lens comprises sequentially arranged first set of lenses, aperture diaphragm and second set of lenses. Fist set of lenses consists of one biconvex lens. Second set first leans is negative meniscus with concavity facing the object and made up of biconcave and biconvex lenses glued together. Second set second lens is positive meniscus with convex facing the image. Second set third lens is meniscus with concavity facing the image and made up of biconcave and biconvex lenses glued together. Positive meniscus is introduced in between said second and third lenses to face the object, as well as biconvex lens. All lenses feature spherical radii. ^ EFFECT: higher illumination of object edges, distortion sufficient for correction of X-ray electron-image amplifier distortion. ^ 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.

Known projection lens (patent EP 2149808, published 02/03/2010) containing the first group of lenses, an aperture diaphragm and a second group of lenses arranged sequentially along the path of optical radiation from an object to an 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 relative aperture, a significant field of view, a small decrease in illumination at the edge of the field of view relative to the 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, 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 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, as options, of one or two non-technological 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, increasing the illumination at the edge of the image field relative to the center, providing a magnitude and sign of distortion sufficient to correct REOP distortion, lack of lenses from organic material and with aspherical radii 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 with the positive convex side facing the image, and the third lens of the second group is the meniscus facing the concave access to the image is achieved by the fact that the first group is made of one biconvex lens, the first lens of the second group is glued from biconcave and biconvex, the second lens of the second group is made in the form of a positive meniscus, the third lens of the second group is glued from biconvex and biconcave lenses, between the second and third lenses of the second group, two positive lenses are additionally introduced, the first of which is the meniscus facing the concavity to the object, and the second is biconvex, with the entire radius The objective lenses are made spherical, and the lens material is colorless optical 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 10 to the image 11, the lens contains a first group of lenses 1, an aperture diaphragm 2 and a second group of lenses 3-9. Lens 1 is biconvex, lenses 3 and 4 are glued together, and lens 3 is biconcave, lens 4 is biconvex, lens 5 is a positive meniscus convex to the image, lens 8 is biconvex, lens 9 is biconcave, and lenses 8 and 9 glued together, and between lens 5 and 8, two positive lenses 6 and 7 are additionally introduced, the first of which 6 is the meniscus facing the concavity to the object, and the second 7 is biconvex.

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 , 6 maximum and maximum, and for 0.6 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 0.6 of the field of view (object size 9 mm), curves 3S and 3T representing the edge of the field of view (size subject 17.5 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 value of the size of the object Y in mm. The graph shows that when the size of the subject Y is equal to 17.5 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 the distortion of the image depending on the size of the subject. 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 value of the image is 5.2% for the edge of the field of view of 17.5 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 passes sequentially through 1 lens, an aperture diaphragm 2, the diameter of which determines the relative aperture of the lens, lenses 3–9 are focused in the image 11. As an image receiver, a CCD, film and etc.

Removing the negative lens from the first group of lenses to the aperture diaphragm and making the positive lens in the form of a biconvex allowed, subject to a decrease in the field of view, to simplify the translation of the lens into operation mode from a finite distance. The implementation of 3 and 4 lenses glued allowed to reduce spherochromatic and spherical aberrations, the introduction of two additional positive lenses 6, 7 allowed us to reduce higher order aberrations. The implementation of lenses 8, 9 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 in the shape of the lenses and their number made it possible, even with a linear magnification factor of -0.68, to obtain residual negative sign distortion of 5.2% 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 aspherical surfaces from the lens while ensuring high image quality over the entire field of view.

Thanks to the inventive lens design, a new technical result is 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 (0.55), the presence of negative image distortion of the required magnitude (-5.2 %), 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 a first group of lenses arranged in series along the optical radiation from an object to an image, 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 object , the second lens of the second group is made with the positive convex side facing the image, and the third lens of the second group is the meniscus, facing the concavity to the image, characterized in that the first group is made of one biconvex lens, the first lens of the second group is glued from biconcave and biconvex, the second lens is made in the form of a positive meniscus, the third lens of the second group is glued from biconvex and biconcave, and between the second and third lenses of the second the group additionally introduced two positive lenses, the first of which is the meniscus facing the concavity to the object, and the second is biconvex, with all the radii of the lenses made spherical And lens material - optical flint.

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