An objective lens system and an optical observation device

Abstract

The application provides an objective lens system and an optical observation device. The objective lens system comprises, in order from an object side, a fourth lens with positive refractive power, a third lens with positive refractive power, a second lens with negative refractive power, and a first lens with positive refractive power. The first lens and the third lens are both double convex lenses, the second lens is a double concave lens, the fourth lens is a cemented lens, and the image side surface of the fourth lens is a convex surface. The focal length f of the objective lens system and the focal length f1 of the first lens satisfy f / f1>1. Through the application, the tolerance requirement is low during assembly, the assembly and adjustment are more convenient, the field of view is larger, the vignetting is smaller, the number of lenses is smaller, and the cost performance is higher.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, in particular to an objective lens system and an optical observation device. BACKGROUND

[0002] An endoscope is a medical device that can realize visual inspection, diagnosis or minimally invasive treatment of internal cavity organs or tissues of the human body by combining a front-end precision optical system with illumination and instrument channels. An objective lens is one of the core components of the optical system contained in the endoscope, which is located at the front end of the endoscope and is directly close to the observation site. The objective lens is responsible for capturing the initial optical information of the target region (such as human tissues, etc.), so its performance has a decisive influence on the final imaging quality of the optical observation device such as the endoscope.

[0003] Most of the existing objective lenses are finite conjugate systems, which can image alone, and the object distance and image distance are both finite values. The finite conjugate objective lens has poor adaptability and poor stability in the application of the variable working distance of the endoscope, and is not suitable for the scene with limited space such as the endoscope; and the finite conjugate lens needs to optimize the object and image surface with a limited distance of the central light path at the same time, so it also needs more lenses. Too many lenses will significantly reduce the fault tolerance of the optical system, and any small flaw (such as shape error, surface defect) of any lens will be accumulated in the objective lens, which will eventually seriously affect the imaging quality. At the same time, although the lens can correct aberration, too many lenses will introduce other difficult-to-control high-order aberration or tolerance sensitivity problems. Therefore, configuring too many lenses will increase the length of the objective lens along the optical axis (i.e., the central light path of the objective lens), thereby causing the objective lens to have the problems of increasing cost and volume, and it is difficult to achieve an ideal balance among performance, cost, volume and manufacturing difficulty.

[0004] Therefore, it is necessary to improve the objective lens in the prior art to solve the above problems.

[0005] It should be noted that the above introduction to the background technology is only for the convenience of clearly and completely describing the technical solutions of the present application, and facilitating the understanding of those skilled in the art. The above technical solutions cannot be considered as known to those skilled in the art merely because they are described in the background section of the present application. SUMMARY

[0006] The objective of the present application is to solve the problems of poor adaptability, poor stability and too many lenses increasing cost and volume of the existing objective lens which is mostly a finite conjugate system in actual application.

[0007] To achieve the above objective, the present application provides an objective lens system, comprising:

[0008] a fourth lens with positive refractive power, a third lens with positive refractive power, a second lens with negative refractive power and a first lens with positive refractive power are arranged in sequence along the optical axis from the object side;

[0009] The first lens and the third lens are both lenticular lenses, the second lens is a double-concave lens, the fourth lens is a cemented lens, and the image-side surface of the fourth lens is a convex surface;

[0010] The focal length f of the objective lens system and the focal length f1 of the first lens satisfy .

[0011] As a further improvement of the present application, the central thickness d1 of the first lens, the refractive index n1 of the first lens, the radius of curvature r1 corresponding to the image-side surface of the first lens, and the radius of curvature r2 corresponding to the object-side surface of the first lens satisfy .

[0012] As a further improvement of the present application, the central thickness d2 of the second lens, the refractive index n2 of the second lens, the radius of curvature r3 corresponding to the image-side surface of the second lens, and the radius of curvature r4 corresponding to the object-side surface of the second lens satisfy .

[0013] As a further improvement of the present application, the focal length f3 of the third lens, the refractive index n3 of the third lens, the radius of curvature r5 corresponding to the image-side surface of the third lens, and the radius of curvature r6 corresponding to the object-side surface of the third lens satisfy .

[0014] As a further improvement of the present application, the combined focal length f34 of the third lens and the fourth lens and the focal length f of the objective lens system satisfy .

[0015] As a further improvement of the present application, the fourth lens comprises: a second cemented lens with positive refractive power and a first cemented lens with negative refractive power arranged in sequence along the optical axis from the object side, the object-side surface of the first cemented lens is a concave surface, the image-side surface is a convex surface, the object-side surface of the second cemented lens is a plane or a concave surface, the image-side surface is a convex surface, and the object-side surface of the first cemented lens and the image-side surface of the second cemented lens are cemented to form a cemented surface.

[0016] As a further improvement of the present application, the focal length f4 of the first cemented lens, the Abbe number v4 of the first cemented lens, the focal length f5 of the second cemented lens, and the Abbe number v5 of the second cemented lens satisfy .

[0017] As a further improvement of the present application, the central thickness d5 of the second cemented lens, the corresponding curvature radius r8 of the cemented surface, and the corresponding curvature radius r9 of the object-side surface of the second cemented lens satisfy .

[0018] As a further improvement of the present application, the objective lens system further comprises a plane mirror disposed on the object side of the fourth lens.

[0019] Based on the same inventive idea, the present application further discloses an optical observation device, comprising the objective lens system according to any one of the above-mentioned inventions.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] In the objective lens system disclosed by the present application, the fourth lens with positive refractive power, the third lens with positive refractive power, the second lens with negative refractive power, and the first lens with positive refractive power are sequentially disposed on the optical axis from the object side. The first lens and the third lens are both double-convex lenses, the second lens is a double-concave lens, and the fourth lens is a cemented lens, and the image-side surface of the fourth lens is a convex surface. The focal length f of the objective lens system and the focal length f1 of the first lens satisfy The objective lens system is composed of the aforementioned four lenses (i.e., the first lens, the second lens, the third lens, and the fourth lens), which ensures that the objective lens system is of infinite conjugate. By limiting the focal length of the first lens and the focal length of the objective lens system, the imaging quality of the objective lens system is ensured. At the same time, as a whole, the object-side telecentricity is ensured by the first lens and the second lens, the aperture (i.e., the entrance pupil aperture) is controlled and the spherical aberration is corrected by the third lens, and the chromatic aberration is corrected and the numerical aperture is controlled by the fourth lens. Based on this, in actual application, compared with the existing finite conjugate objective lens, the objective lens system disclosed by the present application itself and the tolerance between the objective lens system and other optical systems are low, which is more conducive to adjustment, and the field of view of the objective lens system is larger, the vignetting is smaller, the number of lenses is also smaller, and the cost performance is higher, thereby solving the problems of poor adaptability, poor stability, and increased cost and volume caused by the large number of lenses in the existing objective lens which is mostly a finite conjugate system in actual application. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The cross-sectional structure of the objective lens system includes an optical axis A1 in one embodiment;

[0023] Figure 2 The cross-sectional structure of the objective lens system includes an optical axis A2 in another embodiment;

[0024] Figure 3 The cross-sectional structure of the objective lens system includes an optical axis A3 in yet another embodiment;

[0025] Figure 4 for Figure 1 The MTF curve of the objective system at a field of view of 0.707 is shown.

[0026] Figure 5 for Figure 1 The MTF curve of the objective lens system at the edge field of view is shown below;

[0027] Figure 6 for Figure 1 The MTF curve of the objective lens system at the center field of view is shown below;

[0028] Figure 7 for Figure 2 The MTF curve of the objective system at a field of view of 0.707 is shown.

[0029] Figure 8 for Figure 2 The MTF curve of the objective lens system at the edge field of view is shown below;

[0030] Figure 9 for Figure 2 The MTF curve of the objective lens system at the center field of view is shown below;

[0031] Figure 10 for Figure 3 The MTF curve of the objective system at a field of view of 0.707 is shown.

[0032] Figure 11 for Figure 3 The MTF curve of the objective lens system at the edge field of view is shown below;

[0033] Figure 12 for Figure 3 The MTF curve of the objective lens system in the central field of view is shown. Detailed Implementation

[0034] The present application will now be described in detail with reference to the embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not intended to limit the present application. All equivalent changes or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are within the scope of protection of the present application.

[0035] It should be noted that, in this application, "object side" refers to the side of the objective lens system 10 closest to the object surface, that is, the side where light enters the objective lens system 10; "image side" refers to the side of the objective lens system 10 closest to the pupil surface (i.e., the exit pupil surface), that is, the side where light leaves the objective lens system 10. The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. Figure 1An objective lens system 10a containing an optical axis A1 under a first lens structure of the present application is shown, and a flat mirror 117a can also be omitted in the objective lens system 10a; Figure 2 An objective lens system 10b containing an optical axis A2 under a second lens structure of the present application is shown, and a flat mirror 117b can also be omitted in the objective lens system 10b; Figure 3 An objective lens system 10c containing an optical axis A3 under a third lens structure of the present application is shown, and a flat mirror 117c can also be omitted in the objective lens system 10c.

[0036] Please refer to Figures 1 to 12 As shown in the figure, the present application shows a specific embodiment of an objective lens system 10. The objective lens system 10 is installed in an optical observation device (not shown, such as an endoscope, etc.) used for observing an observation object (such as living or ex vivo biological tissue, etc.), and is specifically installed at the end of the optical observation device, for capturing optical information of the observation object.

[0037] In particular, the objective lens system 10 shown in the present application is of infinite conjugate, and the observation object is located on the object focal plane (i.e. the plane passing through the object side focal point and perpendicular to the optical axis A) of the objective lens system 10, which is converted into a bundle of parallel light by the objective lens system 10. Since in practical applications, the object may not be absolutely accurate on the object focal plane, but near it, as long as the defocus amount is within the depth of field of the objective lens system 10, a clear image can still be obtained on the final image plane. The image-side outgoing light is parallel light, which needs to form a real image on the image side in practical applications by cooperating with a magnifying lens (not shown) on the image side.

[0038] The objective lens system 10 includes, in order from the object side along the optical axis A, a fourth lens 116 having positive refractive power, a third lens 113 having positive refractive power, a second lens 112 having negative refractive power, and a first lens 111 having positive refractive power. The first lens 111 and the third lens 113 are both double convex lenses, the second lens 112 is a double concave lens, and the fourth lens 116 is a cemented lens, and the image-side surface of the fourth lens 116 is convex. The focal length f of the objective lens system 10 and the focal length f1 of the first lens 111 satisfy .

[0039] More specifically, the first lens 111 is a double convex lens, i.e. the object-side surface and the image-side surface of the first lens 111 are both convex. The second lens 112 is a double concave lens, i.e. the object-side surface and the image-side surface of the second lens 112 are both concave. The third lens 113 is a double convex lens, i.e. the object-side surface and the image-side surface of the third lens 113 are both convex. The fourth lens 116 is a cemented lens, the image-side surface of the fourth lens 116 is convex, and the object-side surface of the fourth lens 116 is concave (as shown in the figure, for example). Figure 1 or Figure 3as shown) or a plane (as shown). Figure 2

[0040] In the present application, the objective lens system 10 is composed of the aforementioned four lenses (i.e., the first lens 111, the second lens 112, the third lens 113, and the fourth lens 116), which ensures that the objective lens system 10 is of infinite conjugate. By limiting the focal length of the first lens 111 and the focal length of the objective lens system 10, the imaging quality of the objective lens system 10 is ensured. At the same time, as a whole, the object side is ensured to be telecentric by the first lens 111 and the second lens 112; the aperture (i.e., the entrance pupil diameter) is controlled and the spherical aberration is corrected by the third lens 113; and the chromatic aberration is corrected and the numerical aperture is controlled by the fourth lens 116. Based on this, in actual applications, compared with the existing finite conjugate objective lens, the objective lens system 10 disclosed in the present application itself and other optical systems used in cooperation have low tolerance requirements, which is more conducive to adjustment. The aforementioned optical systems refer to the relay lens system (not shown) and the magnifying lens system (not shown) located on the image side of the objective lens system 10 in the optical observation device. Since the relay lens system and the magnifying lens system are not the points of the present application, they are not specifically shown in the present application. At the same time, the objective lens system 10 has a larger field of view, smaller vignetting, fewer lenses, and higher cost performance. Thus, the problems of poor adaptability, poor stability, and increased cost and volume caused by the large number of lenses in the existing objective lens which is mostly a finite conjugate system in actual applications are solved.

[0041] It should be noted that the tolerance of the present application itself includes the manufacturing tolerance between each lens and the assembly tolerance of each lens included in the present application.

[0042] In one embodiment, the fourth lens 116 comprises, arranged in sequence from the object side along the optical axis A, a second cemented lens 115 with positive refractive power and a first cemented lens 114 with negative refractive power. The object side surface of the first cemented lens 114 is concave, and the image side surface is convex. The object side surface of the second cemented lens 115 is a plane or concave, and the image side surface is convex. The object side surface of the first cemented lens 114 and the image side surface of the second cemented lens 115 are cemented to form a cemented surface.

[0043] In one embodiment, the central thickness d1 of the first lens 111, the refractive index n1 of the first lens 111, the radius of curvature r1 corresponding to the image side surface of the first lens 111, and the radius of curvature r2 corresponding to the object side surface of the first lens 111 satisfy ; the central thickness d2 of the second lens 112, the refractive index n2 of the second lens 112, the radius of curvature r3 corresponding to the image side surface of the second lens 112, and the radius of curvature r4 corresponding to the object side surface of the second lens 112 satisfy ​Thus, the object side telecentricity is ensured by the first lens 111 and the second lens 112.

[0044] In an embodiment, the focal length f3 of the third lens 113, the refractive index n3 of the third lens 113, the radius of curvature r5 corresponding to the image side surface of the third lens 113, and the radius of curvature r6 corresponding to the object side surface of the third lens 113 satisfy Thus, the aperture of the objective system 10 is controlled by the third lens 113, and the spherical aberration is corrected.

[0045] In an embodiment, the combined focal length f34 of the third lens 113 and the fourth lens 116, and the focal length f of the objective system 10 satisfy Thus, the numerical aperture of the object side is ensured.

[0046] In an embodiment, the focal length f4 of the first cemented lens 114, the Abbe number v4 of the first cemented lens 114, the focal length f5 of the second cemented lens 115, and the Abbe number v5 of the second cemented lens 115 satisfy Thus, the chromatic aberration is eliminated by the fourth lens 116.

[0047] In an embodiment, the central thickness d5 of the second cemented lens 115, the radius of curvature r8 corresponding to the cemented surface, and the radius of curvature r9 corresponding to the object side surface of the second cemented lens 115 satisfy Thus, the fourth lens 116 is more easily processed.

[0048] In an alternative embodiment, as shown in Figure 1 The objective system 10 further comprises a plane mirror 117 arranged on the same optical axis A as the fourth lens 116 on the object side, for spherical aberration compensation. On the basis of the aforementioned four lenses, the plane mirror 117 is added to further ensure that both the number of lenses and the imaging quality are considered.

[0049] The following describes a numerical embodiment of the objective system 10 of the present application.

[0050] [Embodiment 1]

[0051] As shown in Figure 1As shown, the objective system 10a is formed by arranging the plane mirror 117a, the fourth lens 116a with positive refractive power (including the second cemented lens 115a with positive refractive power and the first cemented lens 114a with negative refractive power), the third lens 113a with positive refractive power, the second lens 112a with negative refractive power, and the first lens 111a with positive refractive power in order from the object side along the optical axis A1. The first lens 111a and the third lens 113a are both biconvex lenses, the second lens 112a is a biconcave lens, the object side surface of the first cemented lens 114a is concave and the image side surface is convex, the object side surface of the second cemented lens 115a is concave and the image side surface is convex, and the object side surface of the first cemented lens 114a and the image side surface of the second cemented lens 115a are cemented to form a cemented surface.

[0052] The basic parameter table of the surfaces included in the objective system 10a of Example 1 and including a pupil surface (i.e., an exit pupil surface, not shown) and an object surface (not shown) is shown in Table 1, which includes a serial number, a radius of curvature, a central thickness, a refractive index, and an Abbe number.

[0053] In the serial number column of the basic parameter table, serial number 1 corresponds to the pupil surface, serial numbers 2 to 10 correspond to the surfaces closest to the image side to the surfaces closest to the object side in the first lens 111a to the fourth lens 116a in order, and serial number 12 corresponds to the object surface. Since the image side surface and the object side surface of the plane mirror 117a are the same, only serial number 11 corresponds to the plane mirror 117a is shown.

[0054] The radius of curvature column indicates the radius of curvature corresponding to the surface of the current serial number, and the sign of the radius of curvature is positive for the case of forming a convexity to the image side and negative for the case of forming a convexity to the object side.

[0055] The central thickness column indicates the separation distance formed at the central position between the surface of the current serial number and the surface of the next serial number. Serial number 11 indicates the central thickness of the plane mirror 117a.

[0056] The refractive index column indicates the refractive index of each lens under light with a wavelength of 587 nm, and is filled in at the serial number corresponding to the image side surface of the lens. Serial number 11 indicates the refractive index of the plane mirror 117a.

[0057] The Abbe number column indicates the Abbe number corresponding to the material of each lens, and is filled in at the serial number corresponding to the image side surface of the lens. Serial number 11 indicates the Abbe number corresponding to the material of the plane mirror 117a.

[0058] The focal length of the objective lens system 10a shown in Example 1 is 5 (unit: millimeter, mm), the wavelength is 0.43 - 0.66 (unit: micrometer, μm), the semi-field angle is 4.3 (unit: degree, °), and the entrance pupil diameter is 3.2 (unit: millimeter, mm). "Millimeter" (abbreviation "mm") is used as the length unit for the values in Table 1, but it is just one column and can be scaled up or down proportionally and other appropriate units can also be used. At the same time, the values shown in Table 1 are rounded to a specified number of digits.

[0059]

[0060] Table 2 shows the calculated values of the objective lens system 10a shown in Example 1.

[0061]

[0062] Reference Figures 4 to 6 The MTF curves of Example 1 are respectively shown at the 0.707 field of view, the edge field of view, and the central field of view, and Figures 4 to 6 also shows the MTF curve under ideal conditions for comparison. In Figures 4 to 6 it, the black solid line (Diff.Limit - Tangential) and the black dashed line (Diff. Limit - Sagittal) respectively refer to the MTF curves of the objective lens system 10a in the meridional direction and the sagittal direction under ideal conditions, and the MTF curves in the meridional direction and the sagittal direction under ideal conditions coincide. Therefore, [[ID=I9]] Figures 4 to 6 the black solid line and the black dashed line contained in it coincide with each other and only the black solid line can be shown; the green solid line (3.1113 (deg) - Tangential) and the green dashed line (3.1113 (deg) - Sagittal) respectively refer to the MTF curves of the objective lens system 10a in the meridional direction and the sagittal direction at the 0.707 field of view; the red solid line (4.3000 (deg) - Tangential) and the red dashed line (4.3000 (deg) - Sagittal) respectively refer to the MTF curves of the objective lens system 10a in the meridional direction and the sagittal direction at the edge field of view; the blue solid line (0.0000 (deg) - Tangential) and the blue dashed line (0.0000 (deg) - Sagittal) respectively refer to the MTF curves of the objective lens system 10a in the meridional direction and the sagittal direction at the central field of view. Since the blue solid line and the blue dashed line overlap, only the blue solid line can be shown.

[0063] [[ID=I23]]The above - mentioned illustration method, symbols, meanings, and recording methods of various data for the objective lens system 10a of Example 1 are equally applicable to the objective lens systems 10b and 10c of Example II and Example 3 below as long as there is no special explanation. Therefore, the repeated description is omitted below.

[0064] [Example 2]

[0065] As Figure 2 shown, the objective lens system 10b is formed by arranging a plane mirror 117b, a fourth lens 116b with positive refractive power (including a second cemented lens 115b with positive refractive power and a first cemented lens 114b with negative refractive power), a third lens 113b with positive refractive power, a second lens 112b with negative refractive power, and a first lens 111b with positive refractive power on the optical axis A2 in sequence from the object side. Both the first lens 111b and the third lens 113b are biconvex lenses, the second lens 112b is a biconcave lens, the object-side surface of the first cemented lens 114b is concave and the image-side surface is convex, the object-side surface of the second cemented lens 115b is flat and the image-side surface is convex, and the object-side surface of the first cemented lens 114b and the image-side surface of the second cemented lens 115b are cemented to form a cemented surface.

[0066] Table 3 shows the basic parameter table of the surfaces included in the objective lens system 10b of Example 2, which includes the serial number, radius of curvature, central thickness, refractive index, and Abbe number.

[0067] The focal length of the objective lens system 10b shown in Example 2 is 5 mm, the wavelength is 0.43 - 0.66 μm, the semi-field of view is 4.3 degrees, and the entrance pupil diameter is 3.2 mm.

[0068] ​​​​​​​​​​​​​​​​The black solid line and the black dashed line contained respectively therein coincide with each other, and only the black solid line can be shown; the green solid line (3.1113 (deg)-Tangential) and the green dashed line (3.1113 (deg)-Sagittal) respectively refer to the MTF curves of the objective lens system 10b in the meridional direction and the sagittal direction at a 0.707 field of view; the red solid line (4.3000 (deg)-Tangential) and the red dashed line (4.3000 (deg)-Sagittal) respectively refer to the MTF curves of the objective lens system 10b in the meridional direction and the sagittal direction at the edge field of view; the blue solid line (0.0000 (deg)-Tangential) and the blue dashed line (0.0000 (deg)-Sagittal) respectively refer to the MTF curves of the objective lens system 10b in the meridional direction and the sagittal direction at the central field of view. Since the blue solid line and the blue dashed line overlap, only the blue solid line can be shown.

[0072] [Embodiment 3]

[0073] As Figure 3 shown, the objective lens system 10c is formed by sequentially arranging a plane mirror 117c, a fourth lens 116c with a positive optical power (including a second cemented lens 115c with a positive optical power and a first cemented lens 114c with a negative optical power), a third lens 113c with a positive optical power, a second lens 112c with a negative optical power, and a first lens 111c with a positive optical power on the optical axis A3 from the object side. Both the first lens 111c and the third lens 113c are biconvex lenses, the second lens 112c is a biconcave lens, the object-side surface of the first cemented lens 114c is concave and the image-side surface is convex, the object-side surface of the second cemented lens 115c is concave and the image-side surface is convex, and the object-side surface of the first cemented lens 114c and the image-side surface of the second cemented lens 115c are cemented to form a cemented surface.

[0074] Table 5 shows the basic parameter table of the surfaces included in the objective lens system 10c of Embodiment 3, which includes the serial number, radius of curvature, central thickness, refractive index, and Abbe number.

[0075] The focal length of the objective lens system 10c shown in Embodiment 3 is 5 mm, the wavelength is 0.43 - 0.66 μm, the semi-field of view is 4.3 degrees, and the entrance pupil diameter is​​​​​​​​​​​​​Fig. 1 shows the MTF curves of the embodiment 1 under the 0.707 field of view, the edge field of view and the center field of view, respectively, and Figures 10 to 12 Fig. 2 shows the MTF curves under the ideal condition for comparison. In Figures 10 to 12 In Fig. 2, the black solid line (Diff. Limit-Tangential) and the black dashed line (Diff. Limit-Sagittal) respectively refer to the MTF curves of the objective lens system 10c under the ideal condition in the tangential direction and the sagittal direction, and the MTF curves in the tangential direction and the sagittal direction under the ideal condition coincide, thus, Figures 10 to 12 In Fig. 2, the black solid line and the black dashed line contained therein coincide with each other, and only the black solid line can be shown; the green solid line (3.0406 (deg)-Tangential) and the green dashed line (3.0406 (deg)-Sagittal) respectively refer to the MTF curves of the objective lens system 10c under the 0.707 field of view in the tangential direction and the sagittal direction; the red solid line (4.3000 (deg)-Tangential) and the red dashed line (4.3000 (deg)-Sagittal) respectively refer to the MTF curves of the objective lens system 10c under the edge field of view in the tangential direction and the sagittal direction; the blue solid line (0.0000 (deg)-Tangential) and the blue dashed line (0.0000 (deg)-Sagittal) respectively refer to the MTF curves of the objective lens system 10c under the center field of view in the tangential direction and the sagittal direction, since the blue solid line and the blue dashed line overlap, and only the blue solid line can be shown.

[0080] It should be noted that, under the ideal condition, the MTF curves in the tangential direction and the sagittal direction coincide to achieve the best imaging effect and the lower the distortion rate. In the actual test condition, the closer the vertical coordinates corresponding to the same horizontal coordinate, the closer the MTF curves in the tangential direction and the sagittal direction; at the same time, from the actual imaging angle, the closer the vertical coordinates corresponding to the same horizontal coordinate in the test condition and the vertical coordinates corresponding to the same horizontal coordinate under the ideal condition, the better the imaging efficiency, the closer to the real image, and the lower the distortion rate of the image. Based on this, Figures 4 to 12 It can be known that the objective lens system 10 disclosed in the present application not only has the attribute of infinite conjugate to improve the adaptability in practical application, but also has good imaging effect under the condition of fewer lenses.

[0081] Based on the same inventive idea, the present application also discloses an optical observation device, which has the objective lens system 10 disclosed above, can install the objective lens system 10 inside the end of the optical observation device, and can optically image and observe the living or excised biological tissue (i.e., a lower concept of the observation object). Details can be referred to the foregoing description, which will not be repeated here. Optionally, the optical observation device can be an endoscope.

[0082] The above detailed description set forth above in connection with the disclosure merely describes some embodiments of the present application and is not intended to limit the scope of the application. Equivalent embodiments or variations of the embodiments described herein are possible without departing from the spirit of the application.

[0083] In addition, it should be understood that although the present specification describes only a few embodiments of the application, the specification is not limited to these few embodiments, and the skilled person should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that the skilled person can understand.

Claims

1. An objective lens system mounted to an optical observation apparatus used for observing an observation object, characterized by comprising: The objective lens system is composed of a fourth lens with positive refractive power, a third lens with positive refractive power, a second lens with negative refractive power and a first lens with positive refractive power arranged in sequence from the object side along the same optical axis, the fourth lens is composed of a second cemented lens with positive refractive power and a first cemented lens with negative refractive power arranged in sequence from the object side along the same optical axis; The first lens and the third lens are both lenticular lenses, the second lens is a double-concave lens, the fourth lens is a cemented lens, and the image-side surface of the fourth lens is a convex surface, the object-side surface of the first cemented lens is a concave surface, and the image-side surface is a convex surface, the object-side surface of the second cemented lens is a plane or a concave surface, and the image-side surface is a convex surface, and the object-side surface of the first cemented lens and the image-side surface of the second cemented lens are cemented to form a cemented surface; The focal length f of the objective system and the focal length f1 of the first lens satisfy .

2. The objective system according to claim 1, characterized in that The center thickness d1 of the first lens, the refractive index n1 of the first lens, the radius of curvature r1 corresponding to the image-side surface of the first lens, and the radius of curvature r2 corresponding to the object-side surface of the first lens satisfy .

3. The objective system of claim 1, wherein The center thickness d2 of the second lens, the refractive index n2 of the second lens, the radius of curvature r3 corresponding to the image-side surface of the second lens, and the radius of curvature r4 corresponding to the object-side surface of the second lens satisfy .

4. The objective system of claim 1, wherein The focal length f3 of the third lens, the refractive index n3 of the third lens, the radius of curvature r5 corresponding to the image-side surface of the third lens, and the radius of curvature r6 corresponding to the object-side surface of the third lens satisfy .

5. The objective system of claim 1, wherein a combined focal length f34 of the third lens and the fourth lens and a focal length f of the objective system satisfy .

6. The objective system of claim 1, wherein The focal length f4 of the first cemented lens, the Abbe number v4 of the first cemented lens, the focal length f5 of the second cemented lens, and the Abbe number v5 of the second cemented lens satisfy .

7. The objective system of claim 1, wherein The central thickness d5 of the second cemented lens, the corresponding curvature radius r8 of the cemented surface, and the corresponding curvature radius r9 of the object side surface of the second cemented lens satisfy .

8. The objective system of claim 1, wherein The objective lens system further comprises a plane mirror arranged on the object side of the fourth lens along the same optical axis.

9. An optical viewing device, characterized by The objective lens system comprises: The objective lens system according to any one of claims 1 to 8.

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