RU2188444C2 - Plan-apochromatic reflection-free microobjective of small enlargement - Google Patents

Abstract

FIELD: optics. SUBSTANCE: invention can be used to design objective lenses of microscopes with plan-apochromatic correction of aberrations in absence of inherent fog exposures for making up sets of metallographic and polarization microscopes. Given microobjective has first positive component produced in the form of single lens, second negative component having form of positive and negative lenses glued together, third negative component comprising negative and positive lenses cemented together, fourth positive component coming in the form of positive lens confined between two negative lenses glued together. EFFECT: provision for plan-achromatic correction with increase of numerical aperture, reduced fog exposure. 1 dwg

Description

 The present invention relates to optics and can be used in the calculation of microscope lenses with planochromatic correction of aberrations in the absence of their own veiling flares for assembling metallographic and polarizing microscopes of the EC-Polam, EC-Metam type for observation, measurement and photographing of fine structures in bright and dark field. Such studied objects are the most critical when observed under a microscope, and therefore the use of microoptics with planochromatic type of correction is required. In addition, along with good aberration correction, in such lenses, attention is paid to reducing or eliminating the veiling stray light that occurs due to the presence of reflexes of the first and second kind [1].

 A well-known micro lens with an achromatic level of correction and a reduced aperture [2], in which the main attention is paid to the simplicity of the design while achieving a compromise image quality.

 Also known is a micro lens with a planochromatic correction level [3], which has a satisfactory quality of correction of monochromatic aberrations of axial and off-axis beams, but does not meet the criterion of planochromatic correction, which reduces the efficiency of work on a microscope.

 Known micro lens [4], which has the same disadvantages. In addition, it is distinguished by large values of the calculated illumination coefficients due to the presence of a negative component in the front of the lens, which makes it unsuitable for work as part of reflected light microscopes.

 Currently, there is a steady tendency to increase the information content and productivity of work on a microscope, for which the creators of micro-lenses follow the path of increasing resolution (aperture), improving image quality by achieving planochromatic aberration correction.

 At the same time, along with good aberration correction in lenses intended for use as part of metallographic and polarizing microscopes of reflected light, special attention is paid to reducing or eliminating veiling spurious illumination arising from the presence of reflexes of the first and second kind.

 The closest technical solution to the proposed planochromatic reflex-free micro lens of small magnification is the well-known microscope lens [5]. This lens has a high calculated image quality when reaching the input numerical aperture A = 0.13, a linear increase in V = 4 krata and planochromatic aberration correction. The micro lens contains a first positive component made in the form of a single lens sequentially located along the optical axis, a second negative component made of double-glued from the positive and negative lenses, a third negative component made of glued from the negative and positive lenses, and a fourth component made in the form of a positive lens .

 This lens does not have a sufficiently high degree of correction of chromatic aberrations (planochromatic correction has not been achieved) due to the lack of balance between negative and positive components; in addition, in this lens it was not possible to reduce the illumination coefficient. In this lens, it is impossible to further increase the input numerical aperture due to the use of a single positive lens as the fourth component.

 The main objective to which the invention is directed is to increase the consumer properties of the micro-lens by achieving planochromatic aberration correction, a significant reduction in the estimated coefficient of veiling exposure, a certain increase in the input numerical aperture.

 The problem is achieved using the inventive micro lens, which, like the prototype, contains sequentially located along the optical axis of the first positive component made in the form of a single lens, the second negative component made of double-glued from positive and negative lenses, and the third negative component made of glued from negative and positive lenses, and the fourth component, made in the form of a positive lens.

 However, unlike the prototype, in the inventive micro-lens, the fourth component is made of glued from a positive, enclosed between two negative lenses.

 The essence of the invention lies in the fact that the implementation of the fourth component in this way allows you to implement it with a larger relative aperture than in the prototype, and due to this, slightly increase the input numerical aperture while increasing the free working distance, thereby significantly reducing the coefficient of veiling exposure. In addition, the implementation of this component in this way allows you to achieve in the inventive micro-lens planochromatic correction.

 Thus, a new result has been achieved in the inventive micro-lens, consisting in the possibility of simultaneously achieving a planochromatic aberration correction with a significant decrease in the estimated coefficient of veiling exposure and a slight increase in the input numerical aperture. This allows you to increase the consumer properties of the lens when working as part of metallographic and polarizing microscopes of reflected light.

 The essence of the invention is illustrated in the drawing, which shows the optical diagram of the inventive lens, as well as the "Appendix", which shows the design parameters and aberration release of a specific embodiment of a planochromatic non-reflex micro lens of small magnification.

 The inventive micro lens contains sequentially located along the optical axis, the first positive component 1, made in the form of a single lens, the second negative component 2, made of glued from positive and negative lenses, the third negative component 3, made of glued from negative and positive lenses, the fourth positive component 4, made in the form of gluing from a positive lens, enclosed between two negative.

 In a specific embodiment, a lens with a linear magnification of V = 5 times, an aperture in the space of objects A = 0.18 (in the prototype A = 0.13), and a working field of view of 2y = 25 mm in the image space was obtained. The “Appendix” presents tables that illustrate the achievement in the proposed micro-lens of plan-chromatic aberration correction over the entire field of view. The estimated coefficient of veiling exposure is 0.3, which is 3-4 times less than in the prototype.

 The device operates as follows. The first component builds an enlarged imaginary image of the object with negative values of the aberrations of the axial point and the meridional and sagittal curvature. Component 2 builds an imaginary image with a slight increase. In this case, the aberration correction is significantly improved. The third component slightly increases the scale of the imaginary image, introducing the corrected values of the secondary spectrum and negative aberration in the image of the points of the axial beam. The fourth component builds a real image at infinity, and when the lens is working in conjunction with a tube lens, in its rear focal plane. In this case, compensation values for the aberrations of the previous components are introduced. The lens works in conjunction with an additional tube lens F'tl = 160.

Sources of information
1. Arlievsky A.G. Abstract for the degree of candidate of technical sciences. - L., 1981.

 2. AS of the USSR 586413, M. Cl. G 02 B 21/02.

 3. Japan patent 60-34736, M. Kl. G 02 B 21/02.

 4. Japanese Patent 56-41084, M. Cl. G 02 B 21/02.

 5. US patent 2.238036, M. Cl. G 02 B 21/02 - prototype.

Claims (1)

 A micro lens containing the first positive component sequentially arranged along the optical axis in the form of a single lens, the second negative component made of double-glued from positive and negative lenses, the third negative component made of glued from negative and positive lenses, and the fourth component made in the form of positive lenses, characterized in that the fourth component is glued from a positive lens enclosed between two negative ones.

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