Metallographic microscope bright and dark field illumination system

Abstract

The invention discloses a metallographic microscope bright and dark field illumination system which comprises a light source, a first light collecting lens group, a second light collecting lens group, an aperture diaphragm, a view field diaphragm, a first light collecting lens group, a second light collecting lens group, a spectroscope, an annular dark field reflector and an objective lens. The light sequentially passes through the field diaphragm and the two condensing lens groups to reach the spectroscope, is reflected to the back focus of the objective lens by the spectroscope, and is collimated by the objective lens to irradiate the surface of an object to be measured to realize illumination; in the dark field illumination mode, light emitted by the light source is converged at the position of the aperture diaphragm through the two light collecting lens sets, then reaches the annular dark field reflector after sequentially passing through the field diaphragm and the second light collecting lens set and is reflected to the objective lens through the annular dark field reflector to achieve illumination on the surface of an object to be measured, and the aperture diaphragm is located on the object space focal plane of the second light collecting lens set. The LED lamp can be switched between bright field illumination and dark field illumination, and is compact in structure and convenient to operate.

Description

Technical Field

[0001] The present invention belongs to the technical field of microscopes, and particularly relates to a bright and dark field illumination system for a metallurgical microscope. Background Art

[0002] A metallurgical microscope uses an epi-illumination system to control and irradiate illumination light onto the surface of a test object. The reflected light or scattered light from the test object surface is imaged at the visual end or camera end through the objective lens and subsequent optical systems. A metallurgical microscope can non-contactedly observe the surface morphology and contour of opaque and translucent materials, and is widely used in the detection and analysis of the surface structure and morphology of materials such as semiconductors, integrated circuits, plastics, metals, ores, fabrics, etc.

[0003] The existing technology usually has a single bright field illumination system or dark field illumination system, and cannot achieve the switching function between the bright field or dark field illumination systems. For example, in the Chinese patent with the authorization announcement number CN11638926B, its bright field epi-illumination system images the image of the fly-eye lens at the rear focal point of the objective lens, and after being refracted by the objective lens and emitted, it uniformly irradiates the surface of the test object. This system can perform an expansion process on the optical étendue, but can only be used for bright field observation. Another example is the Chinese patent with the authorization announcement number CN21670387U, which successively adjusts the divergent light emitted by the LED lamp into parallel light through a condenser lens, a condenser lens, a condenser lens, a condenser lens, and a dark field lens, forms a circular parallel light through a circular reflector and reflects it into the dark field objective lens, and forms a large-angle irradiation light through the reflector in the dark field objective lens and obliquely irradiates the surface of the object to be detected to form dark field illumination. The above all separately achieve bright field illumination or dark field illumination, and cannot adapt to the characteristics of different observation samples to switch the illumination mode, and the applicable range is narrow. Summary of the Invention

[0004] The purpose of the present invention is to propose a bright and dark field illumination system for a metallurgical microscope in view of the above problems, which can switch between bright field and dark field illumination modes by moving a beam splitter, a first condenser lens group, and an annular dark field reflector into or out of the optical path, improving the light source utilization rate and illumination uniformity, with a compact structure and convenient operation.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A bright and dark field illumination system for a metallurgical microscope proposed by the present invention is installed on a metallurgical microscope. The bright and dark field illumination system for a metallurgical microscope includes a light source, a first condenser lens group, a second condenser lens group, an aperture stop, a field stop, a first condenser lens group, a second condenser lens group, a beam splitter, an annular dark field reflector, and an objective lens, wherein:

[0007] In the bright-field illumination mode, the light emitted by the light source is successively converged by the first condenser lens group and the second condenser lens group to form a primary image at the aperture stop, and the primary image then reaches the beam splitter after passing through the field stop, the first condenser lens group and the second condenser lens group in sequence. It is reflected by the beam splitter to form a secondary image at the rear focal plane of the objective lens, and the secondary image is collimated by the objective lens and irradiated onto the surface of the object to be measured to achieve illumination. The position of the aperture stop and the rear focal position of the objective lens are a pair of conjugate points;

[0008] In the dark-field illumination mode, the light emitted by the light source is successively converged by the first condenser lens group and the second condenser lens group to form a primary image at the aperture stop, and the primary image then reaches the annular dark-field reflector after passing through the field stop and the second condenser lens group in sequence. It is reflected by the annular dark-field reflector and irradiated onto the surface of the object to be measured after passing through the objective lens to achieve illumination. The aperture stop is located on the object-side focal plane of the second condenser lens group.

[0009] Preferably, the optical axes of the first condenser lens group, the second condenser lens group, the aperture stop, the field stop and the second condenser lens group are coaxial. The beam splitter and the annular dark-field reflector are connected side by side along the first direction, the first direction is perpendicular to the optical axis direction of the second condenser lens group, and the first condenser lens group is connected to the beam splitter. The optical axis of the second condenser lens group and the optical axis of the objective lens are perpendicular to each other and are both set at 45° relative to the beam splitter or the annular dark-field reflector. The bright-field illumination mode is realized by synchronously moving the beam splitter and the first condenser lens group into the optical path to drive the annular dark-field reflector out of the optical path, or the dark-field illumination mode is realized by synchronously moving the beam splitter and the first condenser lens group out of the optical path to drive the annular dark-field reflector into the optical path.

[0010] Preferably, the annular dark-field reflector is a hollow annular reflector, and a dielectric interference film layer or a metal film layer is provided on the reflecting surface of the annular dark-field reflector for total reflection, and the objective lens is a bright-field and dark-field metallographic objective lens.

[0011] Preferably, the bright-field and dark-field illumination system of the metallurgical microscope also satisfies the following conditions:

[0012] 0.06 < f2 / L < 0.084, 0.2 < f3 / L < 0.23, 0.06 < f6 / L < 0.084, 0.25 < f7 / L < 0.28;

[0013] Wherein, f2 is the focal length of the first condenser lens group, f3 is the focal length of the second condenser lens group, f6 is the focal length of the first condenser lens group, f7 is the focal length of the second condenser lens group, and L is the length of the bright-field and dark-field illumination system of the metallurgical microscope, that is, the optical path distance from the light source to the imaging surface.

[0014] Preferably, the first condenser lens group, the second condenser lens group, the first condenser lens group and the second condenser lens group all have positive optical power and satisfy the following conditions:

[0015] f2 = 25 mm to 35 mm, f3 = 85 mm to 95 mm, f6 = 25 mm to 35 mm;

[0016] f7 = 105 mm to 115 mm, L = 405 mm to 425 mm.

[0017] Preferably, the distance d1 between the second condenser lens group and the aperture stop satisfies: 10 mm < d1 < 50 mm;

[0018] The distance d2 between the aperture stop and the field stop satisfies: 10 mm < d2 < 40 mm;

[0019] The distance d3 between the field stop and the first condenser lens group satisfies: 10 mm < d3 < 40 mm;

[0020] The distance d4 between the first condenser lens group and the second condenser lens group satisfies: 10 mm < d4 < 40 mm;

[0021] The distance d5 between the second condenser lens group and the beam splitter satisfies: 20 mm < d5 < 40 mm.

[0022] Preferably, the first condenser lens group, the second condenser lens group, the first condenser lens assembly and the second condenser lens assembly each include at least one lens.

[0023] Preferably, the first condenser lens group includes a first lens with a positive optical power, a second lens with a positive optical power, and a third lens with a positive optical power arranged in sequence along the light exit direction of the light source, the second condenser lens group includes a fourth lens with a positive optical power, a fifth lens with a negative optical power, and a sixth lens with a positive optical power arranged in sequence along the light exit direction of the light source, the first condenser lens assembly includes a seventh lens with a positive optical power, the second condenser lens assembly has a positive optical power and includes an eighth lens and a ninth lens which are arranged in sequence along the light exit direction of the light source and are glued to each other, the first lens, the second lens, the third lens, the fifth lens, the seventh lens and the ninth lens are all meniscus lenses, the fourth lens is a convexo-concave lens, and the sixth lens and the eighth lens are both double convex lenses.

[0024] Preferably, the bright and dark field illumination system of the metallurgical microscope also satisfies the following conditions:

[0025] 2.5 < fL1 / fG1 < 2.9, 2.9 < fL2 / fG1 < 3.2, 2.9 < fL3 / fG1 < 3.2,

[0026] 0.35 < fL4 / fG2 < 0.47, -0.27 < fL5 / fG2 < -0.19, 0.27 < fL6 / fG2 < 0.35,

[0027] 0.4 < fL7 / fG3 < 0.56, 1.69 < fL8 / fG3 < 1.85;

[0028] Among them, fL1, fL2, fL3, fL4, fL5, fL6, fL7, and fL8 correspond to the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the first condenser lens group, and the second condenser lens group in sequence. fG1 is the focal length of the first light collector lens group, fG2 is the focal length of the second light collector lens group, and fG3 is the total focal length of the first condenser lens group and the second condenser lens group.

[0029] Preferably, the bright and dark field illumination system of the metallurgical microscope also satisfies the following conditions:

[0030] fL1 = 70 mm to 80 mm, fL2 = 80 mm to 90 mm, fL3 = 80 mm to 90 mm, fL4 = 33 mm to 43 mm,

[0031] fL5 = -18 mm to -25 mm, fL6 = 25 mm to 32 mm, fL7 = 25 mm to 35 mm, fL8 = 105 mm to 115 mm.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] The bright and dark field illumination system of this metallurgical microscope enables a metallurgical microscope to simultaneously observe in the bright field illumination mode and the dark field illumination mode. Specifically, by optimizing the optical elements in combination with a linkage device (the first condenser lens group, the beam splitter, and the annular dark field reflector are linked), that is, by synchronously moving the beam splitter and the first condenser lens group into the optical path to drive the annular dark field reflector out of the optical path to achieve the bright field illumination mode, or by synchronously moving the beam splitter and the first condenser lens group out of the optical path to drive the annular dark field reflector into the optical path to achieve the dark field illumination mode. In the bright field illumination mode, the aperture stop and the rear focal plane of the objective lens are a pair of conjugate points. In the dark field illumination mode, the aperture stop is located at the object-side focal plane of the second condenser lens group. By combining the bright field and dark field structures, the metallurgical microscope can achieve the switching between bright and dark field illuminations without replacing the entire illumination system, switch the illumination method according to the characteristics of different observation samples, improve the light source utilization rate and illumination uniformity, and has a compact structure and convenient operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic structural diagram of the bright and dark field illumination system of the metallurgical microscope of the present invention in the bright field illumination mode;

[0035] Figure 2 It is a schematic structural diagram of the bright and dark field illumination system of the metallurgical microscope of the present invention in the dark field illumination mode;

[0036] Figure 3Schematic diagram (a) of the first light - collecting lens group, the second light - collecting lens group, the first condenser lens group, and the second condenser lens group in bright - field illumination mode and schematic diagram (b) in dark - field illumination mode;

[0037] Figure 4 Schematic diagram (a) of the beam splitter and schematic diagram (b) of the annular dark - field reflector of the present invention.

[0038] Explanation of reference numerals: 1, light source; 2, first light - collecting lens group; 3, second light - collecting lens group; 4, aperture stop; 5, field stop; 6, first condenser lens group; 7, second condenser lens group; 8, beam splitter; 9, annular dark - field reflector; 10, objective lens; 11, surface to be measured. Detailed implementation manners

[0039] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0040] It should be noted that unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the present application. The terms used in the specification of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0041] As Figures 1 - 4 shown, a bright - and - dark - field illumination system for a metallurgical microscope is installed on a metallurgical microscope. The bright - and - dark - field illumination system for a metallurgical microscope includes a light source 1, a first light - collecting lens group 2, a second light - collecting lens group 3, an aperture stop 4, a field stop 5, a first condenser lens group 6, a second condenser lens group 7, a beam splitter 8, an annular dark - field reflector 9, and an objective lens 10, where:

[0042] In the bright - field illumination mode, the light rays emitted by the light source 1 are successively converged at the aperture stop 4 by the first light - collecting lens group 2 and the second light - collecting lens group 3 to form a primary image. The primary image then successively passes through the field stop 5, the first condenser lens group 6, and the second condenser lens group 7 and reaches the beam splitter 8. It is reflected by the beam splitter 8 to the rear focal plane of the objective lens 10 to form a secondary image. The secondary image is collimated by the objective lens 10 and irradiated onto the surface to be measured 11 to achieve illumination. The position of the aperture stop 4 and the rear focal position of the objective lens 10 are a pair of conjugate points;

[0043] In the dark-field illumination mode, the light emitted by the light source 1 is successively converged by the first condenser lens group 2 and the second condenser lens group 3 and forms a primary image at the aperture stop 4, and the primary image then reaches the annular dark-field reflector 9 after passing through the field stop 5 and the second condenser lens group 7 in sequence. The light is reflected by the annular dark-field reflector 9 to the objective lens 10 and then illuminates the object surface 11 to be measured. The aperture stop 4 is located on the object-side focal plane of the second condenser lens group 7.

[0044] Among them, the light source 1 is a halogen lamp, an LED lamp, etc.; the first condenser lens group 2 is used to converge or collimate the light emitted by the light source 1; the second condenser lens group 3 is used to converge the light converged or collimated by the first condenser lens group 2 into a primary image, and the position of the primary image is at the aperture stop 4. The diaphragm group consists of the aperture stop 4 and the field stop 5, which respectively adjust the illumination numerical aperture and the illumination range of the bright-field and dark-field illumination systems of the metallurgical microscope. The condenser unit includes the first condenser lens group 6 and the second condenser lens group 7. The first condenser lens group 6 can be cut into or out of the optical path according to the selection of the bright-field and dark-field illumination modes, and the second condenser lens group 7 remains stationary. The beam splitter 8 corresponds to the bright-field illumination mode, and the surface close to the second condenser lens group 7 is coated with a beam-splitting film, and the ratio of the reflectivity to the transmittance can be 50%:50%. The annular dark-field reflector 9 corresponds to the dark-field illumination mode. The annular dark-field reflector 9 is a hollow annular reflector, and its annular reflecting surface close to the second condenser lens group 7 is a total reflection surface, and the reflection can be realized through a dielectric interference film layer or a metal film layer. The objective lens 10 is a bright-field and dark-field metallurgical objective lens, which is an objective lens of the prior art and can be selected according to actual needs. Specifically, it mainly consists of an intermediate optical imaging system (such as including a lens barrel and several lenses built in the lens barrel, etc.) and an outer annular hollow reflecting part (such as including a cylinder coaxially sleeved outside the lens barrel, and one end of the cylinder is a conical ring). As Figure 2 shown, a dark-field ring (i.e., the chamber formed by the cylinder and the lens barrel) and a dark-field reflecting bowl (the conical ring part) are formed.

[0045] In one embodiment, the optical axes of the first condenser lens group 2, the second condenser lens group 3, the aperture stop 4, the field stop 5, and the second condenser lens group 7 are coaxial. The beam splitter 8 and the annular dark-field reflector 9 are connected side by side along a first direction. The first direction is perpendicular to the optical axis direction of the second condenser lens group 7, and the first condenser lens group 6 is connected to the beam splitter 8. The optical axis of the second condenser lens group 7 and the optical axis of the objective lens 10 are perpendicular to each other and are both set at 45° with respect to the beam splitter 8 or the annular dark-field reflector 9. The bright-field illumination mode is realized by synchronously moving the beam splitter 8 and the first condenser lens group 6 into the optical path to drive the annular dark-field reflector 9 out of the optical path, or the dark-field illumination mode is realized by synchronously moving the beam splitter 8 and the first condenser lens group 6 out of the optical path to drive the annular dark-field reflector 9 into the optical path.

[0046] Among them, connecting the first condenser lens group 6 to the beam splitter 8 can achieve synchronous movement for switching. By synchronously moving the beam splitter 8 and the first condenser lens group 6 into the optical path, the annular dark-field reflector 9 is driven to cut out the optical path to achieve bright-field illumination mode, or by synchronously moving the beam splitter 8 and the first condenser lens group 6 to cut out the optical path and then driving the annular dark-field reflector 9 into the optical path to achieve dark-field illumination mode. For example, it is achieved by pushing and pulling movement. At this time, the beam splitter 8 and the first condenser lens group 6 are arranged along the optical path direction and connected, and the annular dark-field reflector 9 is arranged side by side with the moving beam splitter 8, and the switching can be realized by pushing and pulling.

[0047] In one embodiment, the annular dark-field reflector 9 is a hollow annular reflector, and a dielectric interference film layer or a metal film layer is provided on the reflecting surface of the annular dark-field reflector 9 for total reflection, and the objective lens 10 is a bright-field and dark-field metallographic objective lens.

[0048] Among them, the objective lens 10 is a bright-field and dark-field metallographic objective lens, that is, in the bright-field illumination mode, the objective lens 10 is used to collimate and irradiate the passing light onto the object surface 11 to be measured for illumination. In the dark-field illumination mode, the light reflected by the annular dark-field reflector 9 first passes through the dark-field ring of the objective lens 10 and then irradiates onto the dark-field reflecting bowl of the objective lens 10, and then is obliquely reflected by the dark-field reflecting bowl of the objective lens 10 onto the object surface 11 to be measured for illumination. The bright-field and dark-field metallographic objective lens is a well-known prior art structure in the art and will not be elaborated here.

[0049] In one embodiment, the bright-field and dark-field illumination system of the metallurgical microscope further satisfies the following conditions:

[0050] 0.06 < f2 / L < 0.084, 0.2 < f3 / L < 0.23, 0.06 < f6 / L < 0.084, 0.25 < f7 / L < 0.28;

[0051] Among them, f2 is the focal length of the first condenser lens group 2, f3 is the focal length of the second condenser lens group 3, f6 is the focal length of the first condenser lens group 6, f7 is the focal length of the second condenser lens group 7, and L is the length of the bright-field and dark-field illumination system of the metallurgical microscope, that is, the optical path distance from the light source 1 to the imaging surface.

[0052] In one embodiment, the first condenser lens group 2, the second condenser lens group 3, the first condenser lens group 6, and the second condenser lens group 7 all have positive optical power and satisfy the following conditions:

[0053] f2 = 25 mm to 35 mm, f3 = 85 mm to 95 mm, f6 = 25 mm to 35 mm;

[0054] f7 = 105 mm to 115 mm, L = 405 mm to 425 mm.

[0055] In one embodiment, the distance d1 between the second condenser lens group 3 and the aperture stop 4 satisfies: 10 mm < d1 < 50 mm;

[0056] The distance d2 between the aperture stop 4 and the field stop 5 satisfies: 10 mm < d2 < 40 mm;

[0057] The distance d3 between the field stop 5 and the first condenser lens group 6 satisfies: 10 mm < d3 < 40 mm;

[0058] The distance d4 between the first condenser lens group 6 and the second condenser lens group 7 satisfies: 10 mm < d4 < 40 mm;

[0059] The distance d5 between the second condenser lens group 7 and the beam splitter 8 satisfies: 20 mm < d5 < 40 mm.

[0060] In one embodiment, the first condenser lens group 2, the second condenser lens group 3, the first condenser lens group 6, and the second condenser lens group 7 each include at least one lens.

[0061] In one embodiment, the first condenser lens group 2 includes a first lens with a positive focal power, a second lens with a positive focal power, and a third lens with a positive focal power arranged in sequence along the emission direction of the light source 1. The second condenser lens group 3 includes a fourth lens with a positive focal power, a fifth lens with a negative focal power, and a sixth lens with a positive focal power arranged in sequence along the emission direction of the light source 1. The first condenser lens group 6 includes a seventh lens with a positive focal power. The second condenser lens group 7 has a positive focal power and includes an eighth lens and a ninth lens that are arranged in sequence along the emission direction of the light source 1 and are glued together. The first lens, the second lens, the third lens, the fifth lens, the seventh lens, and the ninth lens are all meniscus lenses. The fourth lens is a convex meniscus lens. The sixth lens and the eighth lens are both double convex lenses.

[0062] In one embodiment, the bright and dark field illumination system of the metallurgical microscope further satisfies the following conditions:

[0063] 2.5 < fL1 / fG1 < 2.9, 2.9 < fL2 / fG1 < 3.2, 2.9 < fL3 / fG1 < 3.2,

[0064] 0.35 < fL4 / fG2 < 0.47, -0.27 < fL5 / fG2 < -0.19, 0.27 < fL6 / fG2 < 0.35,

[0065] 0.4 < fL7 / fG3 < 0.56, 1.69 < fL8 / fG3 < 1.85;

[0066] Among them, fL1, fL2, fL3, fL4, fL5, fL6, fL7, and fL8 respectively correspond to the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the first condenser lens group 6, and the second condenser lens group 7. fG1 is the focal length of the first light collector lens group 2, fG2 is the focal length of the second light collector lens group 3, and fG3 is the total focal length of the first condenser lens group 6 and the second condenser lens group 7. In this embodiment, fL7 = f6 and fL8 = f7.

[0067] In one embodiment, the bright and dark field illumination system of the metallurgical microscope further satisfies the following conditions:

[0068] fL1 = 70 mm to 80 mm, fL2 = 80 mm to 90 mm, fL3 = 80 mm to 90 mm, fL4 = 33 mm to 43 mm,

[0069] fL5 = -18 mm to -25 mm, fL6 = 25 mm to 32 mm, fL7 = 25 mm to 35 mm, fL8 = 105 mm to 115 mm.

[0070] The total optical path of the metallurgical microscope bright and dark field illumination system corresponding to the model is about 450 mm, that is, the distance from the light source 1 to the imaging surface ( Figure 3 the distance between the surface numbers S1 to S21 in the figure). The focal lengths of the first lens fL1, the second lens fL2, and the third lens fL3 are similar, and the optical powers allocated by the three lenses are similar, evenly sharing the aberration correction of the system and avoiding the tolerance sensitivity of a single lens. The fourth lens fL4, the fifth lens fL5, and the sixth lens fL6 achieve the chromatic aberration correction function through the structural form of positive, negative, and positive optical powers, and the total focal length of the second light collector lens group 3 formed by their combination is positive to achieve the convergent imaging of the light emitted from the first light collector lens group 2 (formed by the first lens fL1, the second lens fL2, and the third lens fL3). The focal length of the second condenser lens group fL8 (i.e., the second condenser lens group 7) should be equal to the distance from the second condenser lens group 7 to the aperture stop 4 to ensure that the light emitted from the aperture stop 4 in the dark field mode is collimated after passing through the second condenser lens group 7; the combined focal length of the first condenser lens group fL7 and the second condenser lens group fL8 (i.e., the first condenser lens group 6 and the second condenser lens group 7) can satisfy that the aperture stop 4 and the rear focal point of the objective lens 10 (located on the surface numbered S21) are conjugate in the bright field mode, and at the same time, the field stop 5 and the object surface of the objective lens 10 ( Figure 1 the object surface 11 to be measured in the figure) are conjugate. The illumination mode can be switched according to the characteristics of different observation samples, improving the light source utilization rate and illumination uniformity.

[0071] Such as Figure 1As shown, in the bright-field illumination mode, after the light emitted by the light source 1 is converged or collimated by the first condenser lens group 2, it is further converged by the second condenser lens group 3 and forms a primary image at the aperture stop 4. The primary image is located at the aperture stop 4. By adjusting the size of the aperture stop 4, the size of the image participating in the subsequent imaging illumination can be controlled, thereby controlling the illumination numerical aperture of the bright and dark field illumination system of the metallurgical microscope. The primary image can continue to pass through the field stop 5. The field stop 5 controls the illumination range of the object surface 11 to be measured by adjusting its size, thereby controlling the imaging range. In the bright-field illumination mode, the first condenser lens group 6 and the beam splitter 8 are inserted into the optical path, and the annular dark-field reflector 9 is cut out of the optical path. After passing through the field stop 5, the primary image is converged by the first condenser lens group 6 and the second condenser lens group 7 to form a secondary image, and the secondary image is reflected by the beam splitter 8 to the rear focal plane of the objective lens 10. At this time, the position of the aperture stop 4 and the rear focal position of the objective lens 10 are a pair of conjugate points. The secondary image is collimated by the objective lens 10 and irradiated onto the object surface 11 to be measured. Figure 1 In the figure, d1 is the distance between the second condenser lens group 3 and the aperture stop 4; d2 is the distance between the aperture stop 4 and the field stop 5; d3 is the distance between the field stop 5 and the first condenser lens group 6; d4 is the distance between the first condenser lens group 6 and the second condenser lens group 7; d5 is the distance between the second condenser lens group 7 and the beam splitter 8.

[0072] As Figure 2 As shown, in the dark-field illumination mode, the light emitted by the light source 1 is converged or collimated by the first condenser lens group 2, and then further converged by the second condenser lens group 3 to form a primary image at the aperture stop 4. The primary image is located at the aperture stop 4. By adjusting the size of the aperture stop 4, the number and angle of the light rays irradiated from the primary image to the annular dark-field reflector 9 through the subsequent optical system can be controlled, thereby controlling the brightness of the dark-field illumination and the angle of the light rays irradiated onto the object surface 11 to be measured. The primary image can continue to pass through the field stop 5 and then directly pass through the second condenser lens group 7. At this time, the first condenser lens group 6 is cut out of the optical path, and at the same time, the beam splitter 8 is also cut out of the optical path. The annular dark-field reflector 9 is inserted into the optical path. The aperture stop 4 is located on the object-side focal plane of the second condenser lens group 7. After the primary image irradiates the second condenser lens group 7, it is collimated. The collimated light rays irradiate onto the annular dark-field reflector 9 and are reflected by the annular dark-field reflector 9 into the dark-field ring of the objective lens 10. After passing through the dark-field ring of the objective lens 10, the light rays irradiate onto the dark-field reflecting bowl of the objective lens 10 and are obliquely irradiated onto the object surface 11 to be measured through the dark-field reflecting bowl of the objective lens 10.

[0073] Among them, the light source 1 can be a halogen lamp, an LED lamp or other light-emitting bodies. The transmission ratio of the beam splitter 8 is 50%:50%. Figure 3Among them, L1 represents the first lens and is flint glass; L2 represents the second lens and is crown glass; L3 represents the third lens and is crown glass; L4 represents the fourth lens and is crown glass; L5 represents the fifth lens and is flint glass; L6 represents the sixth lens and is crown glass; L7 represents the first condenser lens group and is crown glass; L8 represents the second condenser lens group (i.e., the second condenser lens group 7) and is a cemented lens group, where the biconvex lens is crown glass and the meniscus lens is flint glass. Figure 4 are the schematic structural diagrams of the spectroscope 8 (a) and the annular dark-field reflector 9 (b). The shaded area of the annular dark-field reflector 9 is the reflection film coating area.

[0074] For the convenience of understanding, the following will be elaborated in detail through specific embodiments.

[0075] The bright and dark field illumination system of the metallurgical microscope is optimized by the ZEMAX optical design software. The lens parameters of the first condenser lens group 2, the second condenser lens group 3, the first condenser lens group 6, and the second condenser lens group 7 are shown in Table 1, Table 2, Table 3, and Table 4 respectively.

[0076] Table 1 Lens parameters of the first condenser lens group 2

[0077] Surface number Radius of curvature / mm Thickness / mm Refractive index nd Abbe number vd S1 Infinity 15.2 S2 -15.792 5 1.804 46.574 S3 -14.2486 4 S4 -55.384 5 1.48 70.4 S5 -24.3542 4 S6 -374.2141 5 1.7292 54.685 S7 -54.0184 20

[0078] Table 2 Lens parameters of the second condenser lens group 3

[0079]

[0080]

[0081] Table 3 Lens parameters of the first condenser lens group 6

[0082] Surface number Radius of curvature / mm Thickness / mm Refractive index nd Abbe number vd S16 -96.781 5 1.4378 94.523 S17 -30.9658 28.65

[0083] Table 4 Lens parameters of the second condenser lens group 7

[0084] Surface number Radius of curvature / mm Thickness / mm Refractive index nd Abbe number vd S18 200.8134 8 1.7292 54.685 S19 -45.4193 3.5 2.0007 25.426 S20 -86.4271 150

[0085] According to the above parameters, among them, the surface number S1 is the light source 1, the surface numbers S2, S4, S6, S8, S10, S12, S16, S18, S19 are the object sides of the first to ninth lenses in sequence, the surface numbers S3, S5, S7, S9, S11, S13, S17, S19, S20 are the image sides of the first to ninth lenses in sequence, and the surface numbers S14, S15 are the aperture stop 4 and the field stop 5 respectively. And Figure 3 the surface number S21 in is the imaging surface, which is Figure 1The horizontal plane at the intersection position of the light rays reflected by the middle spectroscope 8 (i.e., the plane perpendicular to the optical axis of the objective lens 10 at the light ray intersection point). G1 is the first condenser lens group 2, including the first lens L1, the second lens L2, and the third lens L3; G2 is the second condenser lens group 3, including the fourth lens L4, the fifth lens L5, and the sixth lens L6; G3 is the condenser lens group, including the first condenser lens group 6 and the second condenser lens group 7, and the first condenser lens group 6 includes the seventh lens L7 and the cemented lens group L8.

[0086] When the first condenser lens group 6 and the spectroscope 8 are cut into the optical path (at this time, the annular dark-field reflector 9 is cut out of the optical path), the metallographic microscope bright-field illumination system is in the bright-field illumination mode. The first condenser lens group 6 and the second condenser lens group 7 image the primary image of the light rays emitted by the light source 1 on the aperture stop 4 again at the rear focal plane of the objective lens 10 to form a secondary image. The secondary image is collimated by the objective lens 10 and uniformly irradiates the object surface 11 to be measured to achieve bright-field illumination. At this time, the field stop 5 is conjugate with the object surface 11 to be measured (i.e., the front focal position of the objective lens 10), and the first condenser lens group 6 and the second condenser lens group 7 jointly correct the imaging aberration of the field stop 5. When the annular dark-field reflector 9 is cut into the optical path (at this time, the first condenser lens group 6 and the spectroscope 8 are cut out of the optical path), it is in the dark-field illumination mode. When the first condenser lens group 6 is cut out of the optical path, the aperture stop 4 is located on the object-side focal plane of the second condenser lens group 7. The primary image of the light source 1 on the aperture stop 4 is collimated by the second condenser lens group 7 and then reflected by the annular dark-field reflector 9 and irradiated into the dark-field ring of the objective lens 10 and reflected by the dark-field reflecting bowl of the objective lens 10 and irradiated onto the object surface 11 to be measured to achieve dark-field illumination. By optimizing the optical elements and driving the first condenser lens group, the spectroscope, and the annular dark-field reflector to cut into or out of the optical path through linkage, on the basis that the main body of the metallographic microscope bright-field and dark-field illumination system does not need to be replaced, the switching between the bright-field illumination mode and the dark-field illumination mode is realized, with a compact structure and convenient operation.

[0087] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0088] The above-described embodiments only express the embodiments of the present application that are described in more specific and detailed terms, but should not be construed as limiting the scope of the application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A bright and dark field illumination system for a metallurgical microscope, installed on the metallurgical microscope, characterized in that: The bright and dark field illumination system of the metallurgical microscope includes a light source (1), a first condenser lens group (2), a second condenser lens group (3), an aperture stop (4), a field stop (5), a first condenser lens group (6), a second condenser lens group (7), a beam splitter (8), an annular dark field reflector (9) and an objective lens (10), wherein: In the bright field illumination mode, the light emitted by the light source (1) is successively converged by the first condenser lens group (2) and the second condenser lens group (3) to form a primary image at the aperture stop (4), and the primary image then successively passes through the field stop (5), the first condenser lens group (6) and the second condenser lens group (7) and reaches the beam splitter (8), and is reflected by the beam splitter (8) to the rear focal plane of the objective lens (10) to form a secondary image. The secondary image is collimated by the objective lens (10) and irradiated onto the object surface to be measured (11) for illumination. The position of the aperture stop (4) and the rear focal position of the objective lens (10) are a pair of conjugate points; In the dark field illumination mode, the light emitted by the light source (1) is successively converged by the first condenser lens group (2) and the second condenser lens group (3) to form a primary image at the aperture stop (4), and the primary image then successively passes through the field stop (5) and the second condenser lens group (7) and reaches the annular dark field reflector (9), and is reflected by the annular dark field reflector (9) to the objective lens (10) and then illuminates the object surface to be measured (11). The aperture stop (4) is located on the object-side focal plane of the second condenser lens group (7).

2. The bright and dark field illumination system of the metallographic microscope according to claim 1, characterized in that: The optical axes of the first condenser lens group (2), the second condenser lens group (3), the aperture stop (4), the field stop (5) and the second condenser lens group (7) are coaxial. The beam splitter (8) and the annular dark field reflector (9) are connected side by side in the first direction. The first direction is perpendicular to the optical axis direction of the second condenser lens group (7), and the first condenser lens group (6) is connected to the beam splitter (8). The optical axis of the second condenser lens group (7) and the optical axis of the objective lens (10) are perpendicular to each other and are both set at 45° with respect to the beam splitter (8) or the annular dark field reflector (9). By synchronously moving the beam splitter (8) and the first condenser lens group (6) into the optical path, the annular dark field reflector (9) is driven to cut out of the optical path to achieve the bright field illumination mode, or by synchronously moving the beam splitter (8) and the first condenser lens group (6) out of the optical path, the annular dark field reflector (9) is driven to cut into the optical path to achieve the dark field illumination mode.

3. The bright and dark field illumination system of the metallographic microscope according to claim 1, characterized in that: The annular dark field reflector (9) is a hollow annular reflector, and a dielectric interference film layer or a metal film layer is provided on the reflecting surface of the annular dark field reflector (9) for total reflection. The objective lens (10) is a bright and dark field metallurgical objective lens.

4. The bright and dark field illumination system of the metallographic microscope according to claim 1, characterized in that: The bright and dark field illumination system of the metallurgical microscope also satisfies the following conditions: 0.06 < f2 / L < 0.084, 0.2 < f3 / L < 0.23, 0.06 < f6 / L < 0.084, 0.25 < f7 / L < 0.28; Wherein, f2 is the focal length of the first condenser lens group (2), f3 is the focal length of the second condenser lens group (3), f6 is the focal length of the first condenser lens group (6), f7 is the focal length of the second condenser lens group (7), and L is the length of the bright and dark field illumination system of the metallurgical microscope, that is, the optical path distance from the light source (1) to the imaging surface.

5. The bright and dark field illumination system of the metallographic microscope according to claim 4, characterized in that: The first condenser lens group (2), the second condenser lens group (3), the first condenser lens group (6), and the second condenser lens group (7) all have positive optical power and satisfy the following conditions: f2 = 25 mm to 35 mm, f3 = 85 mm to 95 mm, f6 = 25 mm to 35 mm; f7 = 105 mm to 115 mm, L = 405 mm to 425 mm.

6. The bright and dark field illumination system of the metallurgical microscope according to claim 4, wherein: The distance d1 between the second condenser lens group (3) and the aperture stop (4) satisfies: 10 mm < d1 < 50 mm; The distance d2 between the aperture stop (4) and the field stop (5) satisfies: 10 mm < d2 < 40 mm; The distance d3 between the field stop (5) and the first condenser lens group (6) satisfies: 10 mm < d3 < 40 mm; The distance d4 between the first condenser lens group (6) and the second condenser lens group (7) satisfies: 10 mm < d4 < 40 mm; The distance d5 between the second condenser lens group (7) and the beam splitter (8) satisfies: 20 mm < d5 < 40 mm.

7. The bright and dark field illumination system of the metallurgical microscope according to claim 1, characterized in that: The first condenser lens group (2), the second condenser lens group (3), the first condenser lens group (6), and the second condenser lens group (7) each include at least one lens.

8. The metallographic microscope bright and dark field illumination system according to claim 7, wherein: The first condenser lens group (2) includes a first lens with positive optical power, a second lens with positive optical power, and a third lens with positive optical power arranged in sequence along the exit direction of the light source (1). The second condenser lens group (3) includes a fourth lens with positive optical power, a fifth lens with negative optical power, and a sixth lens with positive optical power arranged in sequence along the exit direction of the light source (1). The first condenser lens group (6) includes a seventh lens with positive optical power. The second condenser lens group (7) has positive optical power and includes an eighth lens and a ninth lens that are sequentially arranged and glued together along the exit direction of the light source (1). The first lens, the second lens, the third lens, the fifth lens, the seventh lens, and the ninth lens are all meniscus lenses. The fourth lens is a convexo-concave lens. The sixth lens and the eighth lens are both biconvex lenses.

9. The metallographic microscope bright and dark field illumination system according to claim 8, wherein: The bright and dark field illumination system of the metallurgical microscope also satisfies the following conditions: 2.5 < fL1 / fG1 < 2.9, 2.9 < fL2 / fG1 < 3.2, 2.9 < fL3 / fG1 < 3.2, 0.35 < fL4 / fG2 < 0.47, -0.27 < fL5 / fG2 < -0.19, 0.27 < fL6 / fG2 < 0.35, 0.4 < fL7 / fG3 < 0.56, 1.69 < fL8 / fG3 < 1.85; Wherein, fL1, fL2, fL3, fL4, fL5, fL6, fL7, and fL8 respectively correspond to the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the first condenser lens group (6), and the second condenser lens group (7), fG1 is the focal length of the first light collector lens group (2), fG2 is the focal length of the second light collector lens group (3), and fG3 is the total focal length of the first condenser lens group (6) and the second condenser lens group (7).

10. The bright and dark field illumination system of the metallographic microscope according to claim 9, characterized in that: The bright and dark field illumination system of the metallurgical microscope further satisfies the following conditions: fL1 = 70mm to 80mm, fL2 = 80mm to 90mm, fL3 = 80mm to 90mm, fL4 = 33mm to 43mm, fL5 = -18mm to -25mm, fL6 = 25mm to 32mm, fL7 = 25mm to 35mm, fL8 = 105mm to 115mm.

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