RU2745099C1 - Optoelectronic microscope - Google Patents

Abstract

FIELD: microscopy.

SUBSTANCE: microscope contains a television observation system with a matrix photodetector, an illumination system, a first lens, an electron-optical converter and a second lens. The first lens is made of two spherical mirrors, main one a concave and secondary a convex one, and its object surface is made in the form of a concave spherical surface facing the concavity towards the lens, and the photocathode of the image converter is aligned with the image plane. The second lens is optically coupled to the image converter screen and the matrix photodetector of the television channel and is made of two positive components. The object surface, the first lens, the image converter and the illumination system are enclosed in a vacuum volume. The ratios specified in the claims are fulfilled. EFFECT: ability to observe without the use of scanning precision mechanisms and provide a resolution value of less than 50 nm in the vacuum ultraviolet region of the spectrum at a design wavelength of ~ 30 nm.

1 cl, 3 dwg, 4 tbl

Description

The proposed invention relates to the field of optoelectronic instrumentation and can be used as a high-resolution microscope (the minimum resolvable linear dimension is of the order of the wavelength), which makes it possible to observe preparations with microscopic (including viral) objects in the vacuum ultraviolet region of the spectrum with a resolution of less than 50 nm.

Known ultraviolet microscope (Inventor's certificate No. 115024, USSR, 1955), which is a combination of a visual ultraviolet microscope and a dispersive spectral system installed in front of the object under study, allowing you to obtain in the field of view of the microscope the spectrum of the applied light source. An increase in the resolution is achieved here by decreasing the operating wavelength.

The disadvantage of the ultraviolet microscope is the high value of the minimum wavelength, equal to 248 nm and limited by the wavelength interval of 248 ÷ 689 nm, which does not allow achieving high resolution less than 200 nm.

Known is a monochromatic ultra-high resolution microscope (patent RU No. 2441291 C1, publ. 27.01.2012), containing a zone plate as a focusing element, while the micro-object is illuminated with monochromatic radiation. An increase in the resolving power is achieved here by increasing the relative aperture of the focusing element (D _p.e. / F _p.e. ) to a value of ~ 3. It is expected that when using a helium-neon laser with a wavelength of 632.8 nm as a source of monochromatic radiation and a modified zone plate (with an opaque central region) 30 mm in diameter with a focal length of less than 2 mm, a resolution of about 55 nm can be achieved.

The disadvantage of an ultrahigh-resolution monochrome microscope is the complexity of manufacturing a modified zone plate with a large darkened central region, which requires the use of modern methods of electron lithography.

Known scanning near-field optical microscope (patent for utility model RU No. 106958 U1, publ. 27.07.2011), containing a probe with a surface sensor, a probe positioning system over the sample along the z axis, a scanner that moves the sample along the x and y axes, high-aperture a mirror lens located in the far zone and transmitting the collected radiation through a multimode fiber to a photomultiplier, an electronic microscope control unit. The microscope is placed on an insert in a cryostat, operating in the temperature range from 1.8 to 300 K, the insert is located directly in the vapor of a cryogenic gas (helium, or nitrogen). An increase in the resolving power is achieved here to an optical resolution of ~ 50 nm, which became possible due to the provision in the proposed design of excitation of the sample through the probe and collection of reflected radiation through a high-aperture mirror lens located on one side of the sample. The visible light is focused onto a small aperture in front of the object, which, like a confocal microscope, determines its resolution. The ultra-small aperture is the basic principle of operation of most "near-field" microscopes.

The disadvantage of a scanning near-field optical microscope is the ability to operate only in the scanning mode, which requires rather precise mechanics; in addition, a significant decrease in the light flux that has passed through a small hole and returned back significantly increases the image processing time.

Known infrared microscope (Inventor's certificate No. 980043, publ. 07.12.1982), containing an optical system and a radiation receiver installed in the direction of radiation from the object, as well as a source of illumination of the object and a device for scanning and processing an electrical signal connected to the output of the radiation receiver , a cuvette installed on the stage and filled with a liquid or gaseous medium in contact with the investigated surface of the object and containing a suspension of particles inert with respect to the medium and the object, the optical properties of which are different from the optical properties of the medium, as well as a unit for measuring the broadening of the signal spectrum, the input of which is connected to the output of the radiation receiver, and the output is connected to the input of the electrical signal processing device. Instead of a cuvette, a medium with a suspension of particles can be applied to a micro-object in the form of a drop, i.e. using free flowing over the object. The introduction of a liquid or gaseous medium with a suspension of particles makes it possible to measure the temperature distribution on the surface of an object by an indirect method that provides a high resolution, since this method measures the change in the speed of Brownian motion of particles, which is proportional to the distribution of the absolute temperature on the surface of the object. The measurement of the change in the speed of the Brownian motion of the particles is carried out in the unit for measuring the broadening of the spectrum of the signal received from the radiation receiver, since the indicated change in the speed causes a corresponding broadening of the spectrum of the illumination source. Due to the use of the indirect method of measuring the temperature in the proposed device, the theoretically possible limit of resolution equal to the wavelength of the emitter, which is theoretically possible for direct methods, is exceeded, i.e. at a wavelength of 5 ÷ 10 μm it is possible to achieve a spatial resolution of ~ 2 μm.

The disadvantage of the infrared microscope is the high value of the minimum wavelength, equal to 5 microns and limited to the wavelength interval of 5-10 microns, which does not allow achieving high resolution less than 2 microns.

Known infrared microscope (Inventor's certificate No. 194356, publ. 30.III.1967), containing an illuminator, a lens, a radiation receiver, which is used as an electro-optical converter, a system for projecting an image and a system of polaroids. Here, the use of an optical system for conoscopy, which directly projects the interference pattern arising in the exit pupil of the objective, onto the photocathode of an electron-optical converter and the location of this optical system and projection eyepieces for orthoscopy on a revolver, makes it possible to simplify the optical scheme of the device for operation in normal light and during operation. in infrared rays and create maximum comfort for the observer.

The disadvantage of an infrared microscope is the resolution, determined by the capabilities of conventional visible light and observation in infrared rays.

The closest in technical essence is a microscope (patent for a useful model RU No. 126481 U1, publ. 03/27/2013), including a television observation system with a matrix photodetector, the first filter, the first lens, optically connected to the first filter and matrix photodetector in series , an illumination system including an emitting diode, a second filter and a second objective located on the optical axis of the microscope between the first filter and the array photodetector, while the emitting diode is optically connected to the first objective by means of a first filter made in the form of a first plane-parallel plate having on one surface spectral-splitting optical coating with a transmission at an angle of 45 degrees greater than or equal to 0.3 in the wavelength range of 540-700 nm and a reflection at an angle of 45 degrees greater than or equal to 0.3 in the wavelength range of 610-640 nm, the second filter is made in the form of a second plane-parallel plate with transmission along the normal to its plane-parallel working surfaces more than or equal to 0.4 in the wavelength range 550-700 nm and less than 0.01 in the wavelength range less than 500 nm, and the emitting diode has a spectral composition of radiation with a short-wavelength boundary in the range from 600 nm to 620 nm and a long-wavelength border in the range from 640 nm to 670 nm. Here, the problem of increasing the resolution of the microscope is solved by narrowing the spectral composition of the optical radiation used to form the image.

The disadvantage of the microscope is the ability to work in the wavelength range from 540 to 700 nm, the diffraction limit for which does not allow achieving high resolution less than 500 nm.

The objective of the present invention is to create an optical-electronic microscope that provides the ability to observe microscopic (including viral) preparations without using precision scanning mechanisms when the resolution value is about 50 nm.

The technical result due to the task is achieved by the fact that in an optical-electronic microscope containing a television observation system with a matrix photodetector, the first lens, the illumination system and the second lens, unlike the known one, contains an electro-optical converter, and the first lens is made of two spherical mirrors, the main concave and secondary convex, and the object surface of the first lens is made in the form of a concave spherical surface facing the concavity to the lens, and the photocathode of the image converter is aligned with the image plane, while the second lens is optically coupled with the screen of the image converter and a matrix photodetector of a television channel and is made of two positive components, each of which contains four optical elements, and the aperture diaphragm is located between the first and second components of the second lens, while the object surface, ne A single lens, an image intensifier and a backlight system are enclosed in a vacuum volume and the following ratios are fulfilled:

where λ _OB1 is the calculated wavelength for the first lens and illumination system;

V _Oб1 - linear magnification of the first lens;

ρ _e - linear resolution of the optical system of the first objective;

N EOP - resolution of the _{image intensifier;}

R _PP - radius of curvature of the object surface;

F _OB1 - focal length of the first lens;

V _OB2 - linear magnification of the second objective;

d _fp - pixel size of the matrix photodetector.

Such an optical-electronic microscope makes it possible to observe preparations with microscopic (including viral) objects in the vacuum ultraviolet region of the spectrum with a resolution of less than 50 nm without using precision scanning mechanisms.

The optical scheme of the optical-electronic microscope is shown in figure 1.

An optical-electronic microscope contains an object surface 1, an illumination system 2, a first objective I, consisting of a secondary convex spherical mirror 3 and a main concave spherical mirror 4, an electro-optical converter (EOC) 5, a second objective II, consisting of the first component III, consisting of optical elements 6, 7, 8 and 9, aperture diaphragm 10 and the second component IV, consisting of optical elements 11, 12, 13 and 14, protective glass 15 of the matrix photodetector 16, electronic unit 17, monitor 18 of the television channel 19 and vacuum volume 20.

The image of the object 1 is transferred to the plane of the photocathode of the electron-optical converter 5 using the first objective I. The design parameters of a possible embodiment of the first objective I of the optical-electron microscope are shown in Table 1.

The parameters of a possible version of the first objective I of the optical-electronic microscope are as follows:

- linear magnification of the first objective I, times 67; - linear field of view, mm 0.26; - numerical aperture of the first objective I 0.4; - calculated wavelength, nm thirty; - theoretical resolution, nm 45.75; - diameter of the photocathode of the image intensifier, mm 17.5; - resolution of the image intensifier, lines / mm 150; - length along the optical axis from the object to the photocathode of the image intensifier, mm 407.3.

As an illumination system 2, it is possible to use a spectral glow discharge lamp of the LGVM-0.5 type filled with a mixture of helium and hydrogen. Discharge lamps are recommended by GOST 25645.338-96 for the spectral range from 10 to 200 nm. LGVM-0.5 contains a window made of magnesium fluoride, vacuum-tightly soldered to the glass, serially produced by the State Optical Institute named after V.I. S.I. Vavilov, design parameters are given in table 2.

For operation in the region of wavelengths shorter than 105 nm, as a variant of the LGVM-0.5 entrance window, it is possible to use thin polymer films placed on a fine grid.

Electron-optical converter 5 was developed by LLC MELZ FEU under the name “EOP Co”, design parameters of the ultraviolet version of the image converter “EOP Co” are given in Table 3.

The image of the screen of the electron-optical converter 5 is transferred to the plane of the matrix photodetector 16 of the television channel 19 using the second lens II.

The design parameters of the version of the second objective II of the optical-electronic microscope are shown in Table 4.

The linear magnification of the second objective II is 1.785 krat.

The total length of the optical system from the phosphor of the image intensifier tube 5 to the sensitive area of the matrix photodetector 16 is ~ 109.2 mm.

As a matrix photodetector 16, a photodetector in a 12 megapixel format version, designated CMV12000, is used. Developed by CMOSIS and semiconductor manufacturer Tower Jazz, it has a pixel pitch of 5.5 × 5.5 µm with an active area resolution of 4096 × 3072 pixels, and can read data at 300 frames per second. Produced at Fab-2.

The principle of operation of an optical-electronic microscope is as follows.

The sample under study is placed on the object surface 1 and illuminated by the illumination system 2 with radiation with a wavelength selected from the ratio:

where λ _OB1 is the calculated wavelength for the first lens I and illumination system 2.

The fulfillment of this ratio allows to provide in the center of the field of view the theoretically achievable resolution of less than 50 nm with the corresponding numerical aperture of the first objective I. The mirror surfaces of the convex 3 and concave 4 spherical mirrors can be made in the version with a multilayer Mo-Si coating on quartz glass (fused silica KU-1), developed for the VUV range in the technique of electron lithography and in vacuum ultraviolet astronomy.

The first objective I, consisting of a secondary convex spherical mirror 3 and a main concave spherical mirror 4, transfers the image of the sample located on the object surface 1 into the plane of the photocathode of the image converter 5, while the linear magnification of the first objective I is selected from the ratio:

where V _OB1 - linear magnification of the first lens I;

ρ _e - linear resolution of the optical system of the first objective I;

Ν Image intensifier - the resolution of the _{image intensifier 5.}

Fulfillment of this ratio makes it possible to match the resolution of the image-converter 5 with the theoretically achievable resolution of the first lens I. The object surface 1 of the first lens I is made in the form of a concave spherical surface facing the concavity of the lens I, the radius of curvature of which is selected from the ratio:

where R _PP is the radius of curvature of the object plane 1;

F _about1 - focal length of the first lens I.

The fulfillment of this ratio makes it possible to ensure a high quality of the image of the sample located on the object surface 1 with a diameter of ∅ 0.26 mm, built by the first objective I on the photocathode of an image intensifier 5 with a diameter of ∅ 17.5 mm, both in the center and throughout the field of view. The contrast characteristics of the image quality of the lens version I for the Nyquist frequency of 150 lines / mm, determined by the resolution Ν of the _{image intensifier tube} , are close to the diffraction limit for the entire field of view and are shown in Fig. 2.

The image of the screen of the image converter 5 is transferred to the plane of the matrix photodetector 16 of the television channel 19 using the second lens II, while the linear magnification of the second lens II is selected from the ratio:

where V _OB2 - linear magnification of the second objective II;

d _fp - pixel size of the matrix photodetector 16.

Fulfillment of this ratio makes it possible to ensure that the pixel size of the matrix photodetector 16 of the television channel 19 is matched with the theoretically achievable resolution of the first lens I without degrading the quality of the original image.

The image quality of the second lens II is ensured by its design. The lens is structurally made of two positive components III and IV, each of which contains four optical elements (6, 7, 8, 9 and 11, 12, 13, 14, respectively), while the aperture diaphragm is located between the first and second components of the second lens II ... The contrast characteristics of the image quality of objective II for the Nyquist frequency of 91 lines / mm, determined by the pixel size of the matrix photodetector d _fp (5.5 μm), are shown in Fig. 3.

The initial resolution of the microscope is determined by the parameters of the first objective I by the size of the radius of the Airy circle in the space of objects (formula II.37 of the monograph "Optics of microscopes. Calculation and design", Panov V.Y., Andreev LN, Leningrad, "Mechanical engineering", Leningrad branch, 1976):

where: λ is the calculated wavelength of the lens I (λ = λ _OB1 );

A is the numerical aperture of objective I in the object space.

where: n is the refractive index of the medium in the space of objects;

u is the front aperture angle of the lens I.

The Rayleigh criterion formula demonstrates the main ways to increase the resolution of microscopes and photolithographic systems, one of which is to decrease the wavelength λ (λ _OB1 ). Based on the calculated wavelength λ _OB1 = 30 nm and the numerical aperture of the objective equal to A = 0.4 (see Table 1), we obtain the theoretically achievable resolution of the first objective I equal to ρ _e ≈ 45.75 nm. Fulfillment of the above relations does not impair the resolution of the first objective I, thus, the obtained value of ρ _e ≈ 45.75 nm makes it possible to observe microscopic (including viral) objects with sizes of 50-200 nm. To take into account the peculiarities of the spectral range of the vacuum ultraviolet region of the spectrum with wavelengths from 20 to 40 nm, the object surface 1, the first objective I, the electron-optical converter 5 and the illumination system 2 are enclosed in a vacuum volume 20, since the absorption of this radiation sharply increases in air and to work with it, it is necessary to create a vacuum throughout the entire path where this radiation propagates.

The proposed optical-electronic microscope provides the ability to observe preparations with microscopic (including viral) objects in the vacuum ultraviolet region of the spectrum with a resolution of less than 50 nm at a design wavelength of ~ 30 nm without using precision scanning mechanisms.

Claims (10)

An optoelectronic microscope containing a television observation system with a matrix photodetector, a first lens, an illumination system and a second lens, characterized in that it contains an electro-optical converter, and the first lens is made of two spherical mirrors, the main concave and secondary convex, and the object surface of the first lens is made in the form of a concave spherical surface facing the concavity to the lens, and the photocathode of the electron-optical converter is aligned with the image plane, while the second lens is optically coupled with the screen of the image-converter and the matrix photodetector of the television channel and is made of two positive components, each of which it contains four optical elements, and the aperture diaphragm is located between the first and second components of the second lens, while the object surface, the first lens, the image converter and the illumination system are enclosed in a vacuum reasonable volume and the following ratios are met:

where λ _OB1 is the calculated wavelength for the first lens and illumination system; V _OB1 ^_ linear magnification of the first objective; ρ _e - linear resolution of the optical system of the first objective; N EOP - resolution of the _{image intensifier;} R _PP - radius of curvature of the object surface; F _OB1 - focal length of the first lens; V _OB2 - linear magnification of the second objective; d _fp - pixel size of the matrix photodetector.

Images