Objective lens
By designing an objective lens composed of a multi-lens group, the problem of high NA and wide field of view in the prior art is difficult to take into account long WD, and the effect of high throughput and high-speed transport is achieved.
Patent Information
- Application Number
- CN202311095559.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-28
- Publication Date
- 2025-02-28
AI Technical Summary
The prior art is difficult to achieve a long working distance while having a high numerical aperture and a wide field of view, and to increase the conveying speed while avoiding collision between the object to be inspected and the objective lens.
An objective lens composed of a plurality of lens groups is designed, including a first lens group with positive refractive power, a second and third lens group composed of three joint lenses, and a fourth and fifth lens group with negative refractive power, satisfying specific focal length ratio conditions to achieve high NA, long WD and good aberration correction.
It achieves good aberration correction in a wide enough field of view while maintaining good field of view with high NA and long WD, improving high throughput and high-speed delivery capabilities for industrial purposes.
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Figure CN119535755A_ABST
Abstract
Description
Technical Field
[0001] The disclosure of this specification relates to an objective lens. Background Art
[0002] In objective lenses used in industrial applications such as wafer inspection, in order to achieve high throughput with high resolution, it is desirable to have both high numerical aperture (NA) and wide field of view. In addition, in order to achieve higher throughput, it is necessary to increase the conveying speed while avoiding the risk of collision between the object to be inspected and the objective lens, so a longer working distance (WD) is also desired.
[0003] A technique related to such a technical problem is described in Patent Document 1, for example.
[0004] Prior art literature
[0005] Patent Literature
[0006] Patent Document 1: Japanese Patent No. 3093835 Summary of the invention
[0007] Problems to be solved by the invention
[0008] Patent Document 1 describes a 20X objective lens that achieves a high NA, but the WD is approximately 1 mm, and an objective lens having a longer WD is desired.
[0009] In view of the above-mentioned actual situation, an object of one aspect of the present invention is to provide an objective lens having a high NA and a long WD and having aberrations well corrected within a sufficiently wide field of view.
[0010] Means for solving problems
[0011] An objective lens of one embodiment of the present invention includes the following components arranged in order from the object side: a first lens group with positive refractive power, which has a first concave-convex lens component on the side closest to the object, the first concave-convex lens component has a concave surface on the object side and has positive refractive power; a second lens group consisting of a first three-piece cemented lens, the first three-piece cemented lens consists of a positive lens, a negative lens and a positive lens; a third lens group consisting of a second three-piece cemented lens, the second three-piece cemented lens consists of a negative lens, a positive lens and a negative lens; a fourth lens group with negative refractive power, which has a second concave-convex lens component on the side closest to the image, the second concave-convex lens component has a concave surface on the image side and has negative refractive power; and a fifth lens group, which has a third concave-convex lens component on the side closest to the object, the third concave-convex lens component has a concave surface on the object side and has negative refractive power. The objective lens satisfies the following conditional formula: 0.21<|f / f2|<0.3...(1). Wherein, f is the focal length of the objective lens. f2 is the focal length of the second lens group.
[0012] Another embodiment of the objective lens of the present invention is an objective lens for a white interferometer, which includes the following components arranged in order from the object side: a beam splitter; a reference mirror; a first lens group with positive refractive power, which has a first concave-convex lens component on the side closest to the object, the first concave-convex lens component has a concave surface on the object side and has positive refractive power; a second lens group consisting of a first three-piece cemented lens, the first three-piece cemented lens consists of a positive lens, a negative lens and a positive lens; a third lens group consisting of a second three-piece cemented lens, the second three-piece cemented lens consists of a negative lens, a positive lens and a negative lens; a fourth lens group with negative refractive power, which has a second concave-convex lens component on the side closest to the image, the second concave-convex lens component has a concave surface on the image side and has negative refractive power; and a fifth lens group, which has a third concave-convex lens component on the side closest to the object, the third concave-convex lens component has a concave surface on the object side and has negative refractive power. The objective lens satisfies the following conditional formula: 0.21<|f / f2|<0.3...(1). Wherein, f is the focal length of the objective lens and f2 is the focal length of the second lens group.
[0013] Effects of the Invention
[0014] According to the above aspect, it is possible to provide an objective lens which has a high NA and a long WD and in which aberration is well corrected within a sufficiently wide field of view. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 It is a cross-sectional view of the objective lens 1 according to Example 1 of the present invention.
[0016] Figure 2 is a cross-sectional view of the imaging lens 10 .
[0017] Figure 3 1 and 2 are aberration diagrams of the optical system composed of the objective lens 1 and the imaging lens 10 .
[0018] Figure 4 It is a cross-sectional view of the objective lens 2 according to Example 2 of the present invention.
[0019] Figure 5 2 is an aberration diagram of the optical system composed of the objective lens 2 and the imaging lens 10 .
[0020] Figure 6 It is a cross-sectional view of the objective lens 3 according to Example 3 of the present invention.
[0021] Figure 7 1 and 2 are aberration diagrams of the optical system composed of the objective lens 3 and the imaging lens 10 .
[0022] Figure 8 It is a cross-sectional view of the objective lens 4 according to Example 4 of the present invention.
[0023] Fig. 91 and 2 are aberration diagrams of the optical system composed of the objective lens 4 and the imaging lens 10 .
[0024] Fig.10 It is a cross-sectional view of the objective lens 5 according to Example 5 of the present invention.
[0025] Fig.11 1 and 2 are aberration diagrams of the optical system composed of the objective lens 5 and the imaging lens 10 .
[0026] Fig.12 It is a cross-sectional view of the objective lens 6 according to Example 6 of the present invention.
[0027] Fig.13 2 is an aberration diagram of the optical system composed of the objective lens 6 and the imaging lens 10 .
[0028] Description of Reference Numerals
[0029] 1, 2, 3, 4, 5, 6 ... objective lens
[0030] 10 ...imaging lens
[0031] G1 ...First lens group
[0032] G2...Second lens group
[0033] G3...Third lens group
[0034] G4 ... the fourth lens group
[0035] G5...Fifth lens group
[0036] L1~L11、TL1~TL4 ...Lens
[0037] CL1~CL4、CTL1、CTL2…cemented lens DETAILED DESCRIPTION
[0038] An objective lens according to one embodiment of the present application will be described. The objective lens according to one embodiment (hereinafter, simply referred to as objective lens) is an infinity-corrected microscope objective lens used in combination with an imaging lens.
[0039] The objective lens is composed of a first lens group having positive refractive power, a second lens group and a third lens group each consisting of three cemented lenses, and a fourth lens group and a fifth lens group whose concave surfaces face each other, which are arranged in order from the object side.
[0040] The first lens group has positive refractive power in order to make the divergent light from the specimen surface close to a convergent state.
[0041] The first lens group has a meniscus lens component on the side closest to the object, and the meniscus lens component has a concave surface on the object side. The meniscus lens component is the first meniscus lens component of the objective lens, and has positive refractive power. By including a positive meniscus lens component with a concave surface facing the object side on the side closest to the object, the first lens group can suppress the generation of spherical aberration and make the divergent light from the specimen surface close to a convergent state.
[0042] In addition, in this specification, the so-called lens component, whether it is a single lens or a cemented lens, refers to a lens block in which only the object side surface and the image side surface of the lens surface through which the light from the object point passes are in contact with the air. That is, one single lens is one lens component, and one cemented lens is also one lens component. On the other hand, multiple single lenses or multiple cemented lenses arranged with air between them are not called one lens component.
[0043] The second lens group has a relatively large positive refractive power to converge the incident light or make it closer to a convergent state. The second lens group is composed of three cemented lenses, which are composed of a positive lens, a negative lens, and a positive lens. The three cemented lenses are the first three cemented lenses of the objective lens. By forming the second lens group with a relatively strong positive refractive power by three cemented lenses including more positive lenses than negative lenses, it is possible to suppress the generation of chromatic aberration and well correct spherical aberration and coma.
[0044] The third lens group has positive refractive power to further converge the incident light. The third lens group is composed of three cemented lenses, and the three cemented lenses are composed of a negative lens, a positive lens and a negative lens. The three cemented lenses are the second three cemented lenses of the objective lens. The outgoing light from the second lens group is converging light or is roughly in a converging state, so the third lens group does not need too much refractive power, and preferably has a relatively weak positive refractive power. By forming a third lens group with a relatively weak positive refractive power by three cemented lenses of negative, positive and negative that include more negative lenses than positive lenses, it is possible to suppress the generation of chromatic aberration and correct spherical aberration and coma well.
[0045] The fourth lens group and the fifth lens group are so-called Gaussian (double Gaussian) structures that make the concave and convex face each other, and transform the convergent light emitted from the third lens group into parallel light. Therefore, at least the fourth lens group has negative refractive power. In addition, it is preferred that the fifth lens group also has negative refractive power.
[0046] In order to form a Gauss type, the fourth lens group has a meniscus lens component on the image side, and the meniscus lens component has a concave surface on the image side. The meniscus lens component is the second meniscus lens component of the objective lens and has negative refractive power.
[0047] Similarly, in order to form a Gaussian lens, the fifth lens group has a meniscus lens component on the object side, the meniscus lens component having a concave surface on the object side. The meniscus lens component is the third meniscus lens component of the objective lens and has negative refractive power.
[0048] The fourth lens group and the fifth lens group are configured as Gaussian lenses, so that spherical aberration, coma, and astigmatism can be corrected favorably, and the convergent light emitted from the third lens group can be converted into parallel light.
[0049] The objective lens constructed as described above is constructed to satisfy the following conditional expression (1): wherein f is the focal length of the objective lens, and f2 is the focal length of the second lens group.
[0050] 0.21<|f / f2|<0.3...(1)
[0051] Conditional expression (1) is a conditional expression that specifies the refractive power of the second lens group. By satisfying this conditional expression, spherical aberration and coma can be corrected well. If |f / f2| is above the upper limit value (0.3), the refractive power of the second lens group becomes too strong relative to the focal length of the entire system, resulting in overcorrection, and spherical aberration and coma deteriorate. When |f / f2| is below the lower limit value (0.21), the refractive power of the second lens group becomes too weak, resulting in undercorrection.
[0052] According to the objective lens configured as described above, it is possible to have a high NA and a long WD and to satisfactorily correct aberrations in a sufficiently wide field of view.
[0053] In addition, the objective lens may be configured to satisfy the following conditional expression (1-1) instead of conditional expression (1) or in addition to conditional expression (1).
[0054] 0.24<|f / f2|<0.26...(1-1)
[0055] Hereinafter, a preferred structure of the objective lens will be described.
[0056] The objective lens preferably satisfies the following conditional expression (2): wherein f3 is the focal length of the third lens group.
[0057] 0.05<|f / f3|<0.2...(2)
[0058] Conditional expression (2) is a conditional expression that specifies the refractive power of the third lens group. By satisfying this conditional expression, spherical aberration and coma can be corrected well. If |f / f3| is above the upper limit value (0.2), the refractive power of the third lens group becomes too strong relative to the focal length of the entire system, resulting in overcorrection, and spherical aberration and coma deteriorate. When |f / f3| is below the lower limit value (0.05), the refractive power of the third lens group becomes too weak, resulting in undercorrection.
[0059] In addition, the objective lens may be configured to satisfy the following conditional expression (2-1) instead of conditional expression (2) or in addition to conditional expression (2).
[0060] 0.06<|f / f3|<0.17...(2-1)
[0061] The first meniscus lens component is preferably a cemented lens formed by cementing two meniscus lenses with their concave surfaces facing the object side. In this case, the objective lens preferably satisfies the following conditional expression (3).
[0062] 17<|ν1-ν2|<40...(3)
[0063] Here, ν1 is the Abbe number of the convex-convex lens arranged on the object side (i.e., the convex-convex lens arranged closest to the object side) of the two convex-convex lenses constituting the first convex-convex lens component for the d-line. ν2 is the Abbe number of the convex-convex lens arranged on the image side (i.e., the second convex-convex lens from the object side) of the first convex-convex lens component for the d-line.
[0064] Conditional expression (3) is a conditional expression for specifying the difference in Abbe numbers of the two concave-convex lenses constituting the first concave-convex lens component. By constituting the first concave-convex lens component with a cemented lens and satisfying this conditional expression, the difference in Abbe numbers of the two lenses is appropriately set, so that axial chromatic aberration and lateral chromatic aberration can be well corrected. If |ν1-ν2| is above the upper limit value (40), the axial chromatic aberration and lateral chromatic aberration are overcorrected, and if |ν1-ν2| is below the lower limit value (17), the correction is insufficient.
[0065] In addition, the objective lens may be configured to satisfy the following conditional expression (3-1) instead of conditional expression (3) or in addition to conditional expression (3).
[0066] 17.9<|ν1-ν2|<39.8...(3-1)
[0067] In addition, when the first meniscus lens component is a cemented lens formed by cementing two meniscus lenses with concave surfaces facing the object side, the objective lens preferably satisfies the following conditional expression (4).
[0068] 3.4 <n1+n2<4.0...(4)
[0069] Among them, n1 is the refractive index of the meniscus lens arranged on the object side (i.e., the meniscus lens arranged closest to the object side) of the two meniscus lenses constituting the first meniscus lens component for the e-line. n2 is the refractive index of the meniscus lens arranged on the image side (i.e., the second meniscus lens from the object side) of the first meniscus lens component for the e-line.
[0070] Conditional expression (4) is a conditional expression that specifies the sum of the refractive indices of the two concave-convex lenses that constitute the first concave-convex lens component. By satisfying this conditional expression, it is possible to mainly achieve a high NA and well correct the image curvature. When n1+n2 is above the upper limit value (4.0), the difference in refractive power between the colors in the first lens group is too large, and therefore, it is difficult to well correct the axial chromatic aberration. When n1+n2 is below the lower limit value (3.4), the refractive power required for the first lens group is obtained by reducing the radius of curvature. In this case, the Petzval sum is greatly biased toward positive in the first lens group, and therefore, the Petzval sum cannot be completely corrected in the entire optical system including the fourth lens group (and the fifth lens group) with negative refractive power.
[0071] In addition, the objective lens may be configured to satisfy the following conditional expression (4-1) instead of conditional expression (4) or in addition to conditional expression (4).
[0072] 3.5 <n1+n2<3.8...(4-1)
[0073] The first lens group may be composed of a positive meniscus lens with a concave surface facing the object side. In particular, when the second lens group and the third lens group satisfy conditional expressions (1) and (2), chromatic aberration, spherical aberration, and coma can be well corrected in the objective lens as a whole. Therefore, the first lens group may be composed of a single lens, thereby reducing the number of lenses constituting the objective lens.
[0074] The second meniscus lens component may also be a cemented lens formed by cementing two meniscus lenses with the concave surface facing the image side. Furthermore, the second meniscus lens component may be composed of a negative meniscus lens with the concave surface facing the image side, and the fourth lens group may be composed of a negative meniscus lens. In particular, when the second lens group and the third lens group satisfy conditional expressions (1) and (2), chromatic aberration, spherical aberration, and coma can be well corrected in the objective lens as a whole, so the fourth lens group may be composed of a single lens to suppress the number of lenses constituting the objective lens.
[0075] The objective lens preferably satisfies the following conditional formula (5). WD is the air-converted length of the distance from the specimen surface to the surface of the first lens group closest to the object on the optical axis. More specifically, it is the air-converted length of the distance from the specimen surface to the surface of the first lens group closest to the object on the optical axis when the specimen surface is focused. L is the distance from the surface of the first lens group closest to the object to the surface of the fifth lens group closest to the image on the optical axis.
[0076] WD / L>0.065...(5)
[0077] Conditional expression (5) is a conditional expression that specifies WD. By satisfying this conditional expression, it is possible to achieve a higher throughput when the compactly constructed object lens is used for industrial purposes. If WD / L is below the lower limit (0.065), the distance between the object under test and the object lens shortens, and the risk of collision increases. As a result, in order to avoid collision, for example, when changing the observation position, the high-speed movement of the object lens and the stage is restricted, so sufficient throughput cannot be obtained.
[0078] In addition, the objective lens may be configured to satisfy the following conditional expression (5-1) instead of conditional expression (5) or in addition to conditional expression (5).
[0079] 0.08 <WD / L<0.12...(5-1)
[0080] Hereinafter, an embodiment of the objective lens will be described in detail.
[0081] (Example 1)
[0082] Figure 1 : is a cross-sectional view of the objective lens 1 of this embodiment. The objective lens 1 is a microscope objective lens, and includes, from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a fifth lens group G5 with negative refractive power. The fourth lens group G4 and the fifth lens group G5 are Gauss-type lens groups composed of concave and convex lens components with concave surfaces facing each other.
[0083] The first lens group G1 is composed of a cemented lens CL1, which is a meniscus lens component with a concave surface facing the object side. The cemented lens CL1 is a meniscus lens component with positive refractive power, and is composed of two cemented lenses, which are arranged in order from the object side, namely, lens L1 is a meniscus lens with a concave surface facing the object side, and lens L2 is a meniscus lens with a concave surface facing the object side. Both lens L1 and lens L2 are positive lenses.
[0084] The second lens group G2 is composed of a cemented lens CL2 having a positive refractive power. The cemented lens CL2 is a positive-negative-positive three-piece cemented lens composed of a lens L3, a lens L4, and a lens L5 arranged in order from the object side, wherein the lens L3 is a biconvex lens, the lens L4 is a biconcave lens, and the lens L5 is a biconvex lens.
[0085] The third lens group G3 is composed of a cemented lens CL3 having a positive refractive power. The cemented lens CL3 is a negative-positive-negative three-piece cemented lens composed of lens L6, lens L7, and lens L8 arranged in order from the object side, wherein lens L6 is a meniscus lens with a concave surface facing the image side, lens L7 is a biconvex lens, and lens L8 is a meniscus lens with a concave surface facing the object side.
[0086] The fourth lens group G4 is composed of a cemented lens CL4 having a negative refractive power. The cemented lens CL4 is a meniscus lens component having a concave surface on the image side, and is composed of two cemented lenses, lens L9 and lens L10, which are arranged in sequence from the object side. The lens L9 is a meniscus lens with a concave surface facing the image side, and the lens L10 is a meniscus lens with a concave surface facing the image side.
[0087] The fifth lens group G5 is a lens L11 composed of a single negative meniscus lens having a concave surface facing the object side.
[0088] Various data of the objective lens 1 are as follows. In addition, f, f1, f2, f3, f4, and f5 are respectively the focal length of the objective lens, the focal length of the first lens group G1, the focal length of the second lens group G2, the focal length of the third lens group G3, the focal length of the fourth lens group G4, and the focal length of the fifth lens group G5. Other parameters are as described above.
[0089] f=9mm, f1=19.24mm, f2=36.18mm, f3=72.06mm, f4=-78.84mm, f5=-109.68mmNA =0.6, ν1=46.62, ν2=22.76, n1=1.82017, n2=1.81643, WD=4.689mm, L=44.93mm
[0090] The lens data of the objective lens 1 are as follows: In the lens data, INF means infinity (∞).
[0091] Objective 1
[0092]
[0093] Here, s represents the surface number, r represents the radius of curvature (mm), d represents the surface spacing (mm), ne represents the refractive index for the e-line, and νd represents the Abbe number for the d-line. These symbols are the same in the subsequent embodiments. In addition, the surface shown by the surface number s1 is the specimen surface. The surfaces shown by the surface numbers s2 and s17 are the lens surface closest to the object side and the lens surface closest to the image side of the objective lens 1, respectively. In addition, for example, the surface spacing d1 represents the distance on the optical axis from the surface shown by the surface number s1 to the surface shown by the surface number s2. In addition, the surface spacing d17 represents the distance on the optical axis from the surface shown by the surface number s17 to the surface closest to the object side of the imaging lens (56.38 mm).
[0094] As shown below, the objective lens 1 satisfies conditional expressions (1) to (5).
[0095] (1) |f / f2|=0.249
[0096] (2) |f / f3|=0.125
[0097] (3)|ν1-ν2|=23.86
[0098] (4)n1+n2=3.637
[0099] (5) WD / L = 0.104
[0100] Figure 2 It is a cross-sectional view of an imaging lens 10 used in combination with an objective lens 1. The imaging lens 10 is a microscope imaging lens that forms an image of an object by combining with an infinity-corrected objective lens. The imaging lens 10 is composed of a cemented lens CTL1 and a cemented lens CTL2. The cemented lens CTL1 is composed of a lens TL1 and a lens TL2, wherein TL1 is a biconvex lens and the lens TL2 is a concave-convex lens with the concave surface facing the object side. The cemented lens CTL2 is composed of a lens TL3 as a biconvex lens and a lens TL4 as a biconcave lens. The imaging lens 10 is configured so that the distance on the optical axis from the lens surface (surface number s17) closest to the image side of the objective lens 1 to the lens surface (surface number s1) closest to the object side of the imaging lens 10 is 56.38 mm. The focal length of the imaging lens 10 is 180 mm.
[0101] Lens data of the imaging lens 10 are as follows.
[0102] Imaging lens 10
[0103]
[0104] Figure 3 1 is an aberration diagram of the optical system composed of the objective lens 1 and the imaging lens 10 , and shows aberrations on the image plane obtained by tracing rays from the object side to the image side. Figure 3 (a) is a spherical aberration diagram. Figure 3 (b) is a graph showing the amount of violation of the sine condition. Figure 3 (c) is the astigmatism diagram. Figure 3 (d) is a coma diagram at an image height ratio of 0.8 (image height 8.80 mm). In addition, "M" in the figure represents the meridional component and "S" represents the sagittal component. Figure 3 As shown, in this embodiment, aberrations are well corrected in a wide field of view.
[0105] (Example 2)
[0106] Figure 4: is a cross-sectional view of the objective lens 2 of this embodiment. The objective lens 2 is a microscope objective lens for a white interferometer, and includes, from the object side, a beam splitter BS, a reference mirror RM, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a fifth lens group G5 with negative refractive power. The fourth lens group G4 and the fifth lens group G5 are Gauss-type lens groups composed of concave and convex lens components with concave surfaces facing each other.
[0107] The first lens group G1 is composed of a cemented lens CL1, which is a meniscus lens component with a concave surface facing the object side. The cemented lens CL1 is a meniscus lens component with positive refractive power, and is composed of two cemented lenses, which are arranged in order from the object side, namely, lens L1 is a meniscus lens with a concave surface facing the object side, and lens L2 is a meniscus lens with a concave surface facing the object side. Both lens L1 and lens L2 are positive lenses.
[0108] The second lens group G2 is composed of a cemented lens CL2 having positive refractive power. The cemented lens CL2 is a positive-negative-positive three-lens cemented lens composed of a lens L3 as a biconvex lens, a lens L4 as a biconcave lens, and a lens L5 as a biconvex lens, which are arranged in order from the object side.
[0109] The third lens group G3 is composed of a cemented lens CL3 having a positive refractive power. The cemented lens CL3 is a negative-positive-negative three-piece cemented lens composed of lens L6, lens L7, and lens L8 arranged in order from the object side, wherein lens L6 is a meniscus lens with a concave surface facing the image side, lens L7 is a biconvex lens, and lens L8 is a meniscus lens with a concave surface facing the object side.
[0110] The fourth lens group G4 is composed of a cemented lens CL4 having a negative refractive power. The cemented lens CL4 is a meniscus lens component having a concave surface on the image side, and is composed of two cemented lenses, lens L9 and lens L10, which are arranged in sequence from the object side. The lens L9 is a meniscus lens with a concave surface facing the image side, and the lens L10 is a meniscus lens with a concave surface facing the image side.
[0111] The fifth lens group G5 is a lens L11 composed of a single negative meniscus lens having a concave surface facing the object side.
[0112] Various data of the objective lens 2 are as follows.
[0113] f=9mm, f1=19.14mm, f2=34.73mm, f3=79.32mm, f4=-86.13mm, f5=-111.38mmNA =0.6, ν1=46.62, ν2=22.76, n1=1.82017, n2=1.81643, WD=4.689mm, L=44.25mm
[0114] The lens data of the objective lens 2 are as follows.
[0115] Objective 2
[0116]
[0117] As shown below, the objective lens 2 satisfies conditional expressions (1) to (5). (1) |f / f2|=0.259
[0118] (2) |f / f3|=0.114
[0119] (3)|ν1-ν2|=23.86
[0120] (4)n1+n2=3.637
[0121] (5) WD / L = 0.106
[0122] Figure 5 1 is an aberration diagram of the optical system composed of the objective lens 2 and the imaging lens 10 , and shows aberrations on the image plane obtained by tracing rays from the object side to the image side. Figure 5 (a) is a spherical aberration diagram. Figure 5 (b) is a graph showing the amount of violation of the sine condition. Figure 5 (c) is the astigmatism diagram. Figure 5 (d) is the coma diagram at an image height ratio of 0.8 (image height 8.80mm). Figure 5 As shown, in this embodiment, aberrations are well corrected in a wide field of view.
[0123] (Example 3)
[0124] Figure 6 : is a cross-sectional view of the objective lens 3 of this embodiment. The objective lens 3 is a microscope objective lens, and includes, from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a fifth lens group G5 with negative refractive power. The fourth lens group G4 and the fifth lens group G5 are Gauss-type lens groups composed of concave and convex lens components with concave surfaces facing each other.
[0125] The first lens group G1 is composed of a lens L1 which is a single positive meniscus lens having a concave surface facing the object side.
[0126] The second lens group G2 is composed of a positive-negative-positive cemented lens CL1 having a positive refractive power. The cemented lens CL1 is a positive-negative-positive three-lens cemented lens composed of a biconvex lens L2, a biconcave lens L3, and a biconvex lens L4 arranged in order from the object side.
[0127] The third lens group G3 is composed of a cemented lens CL2 having a positive refractive power. The cemented lens CL2 is a negative-positive-negative three-piece cemented lens composed of a lens L5, a lens L6, and a lens L7 arranged in order from the object side, wherein the lens L5 is a meniscus lens with a concave surface facing the image side, the lens L6 is a biconvex lens, and the lens L7 is a meniscus lens with a concave surface facing the object side.
[0128] The fourth lens group G4 is composed of a lens L8, which is a negative meniscus lens having a concave surface facing the image side.
[0129] The fifth lens group G5 is composed of lens L9, which is a negative meniscus lens with a concave surface facing the object side.
[0130] Various data of the objective lens 3 are as follows.
[0131] f=9mm, f1=17.64mm, f2=35.57mm, f3=53.96mm, f4=-44.48mm, f5=-115.81mm, NA=0.6, WD=4.681mm, L=44.30mm
[0132] The lens data of the objective lens 3 are as follows.
[0133] Objective 3
[0134]
[0135]
[0136] As shown below, the objective lens 3 satisfies conditional expressions (1), (2), and (5).
[0137] (1) |f / f2|=0.253
[0138] (2) |f / f3|=0.167
[0139] (5) WD / L = 0.106
[0140] Figure 7 It is an aberration diagram of the optical system composed of the objective lens 3 and the imaging lens 10, and shows the aberration on the image plane obtained by tracing rays from the object side to the image side. Figure 7 (a) is a spherical aberration diagram. Figure 7 (b) is a graph showing the amount of violation of the sine condition. Figure 7 (c) is the astigmatism diagram. Figure 7 (d) is the coma diagram at an image height ratio of 0.8 (image height 8.80mm). Figure 7 As shown, in this embodiment, aberrations are well corrected in a wide field of view.
[0141] (Example 4)
[0142] Figure 8 : is a cross-sectional view of the objective lens 4 of this embodiment. The objective lens 4 is a microscope objective lens for a white interferometer, and includes, from the object side, a beam splitter BS, a reference mirror RM, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a fifth lens group G5 with negative refractive power. The fourth lens group G4 and the fifth lens group G5 are Gauss-type lens groups composed of concave and convex lens components with concave surfaces facing each other.
[0143] The first lens group G1 is composed of a lens L1 which is a single positive meniscus lens having a concave surface facing the object side.
[0144] The second lens group G2 is composed of a positive-negative-positive cemented lens CL1 having a positive refractive power. The cemented lens CL1 is a positive-negative-positive three-lens cemented lens composed of a biconvex lens L2, a biconcave lens L3, and a biconvex lens L4 arranged in order from the object side.
[0145] The third lens group G3 is composed of a cemented lens CL2 having a positive refractive power. The cemented lens CL2 is a negative-positive-negative three-piece cemented lens composed of a lens L5, a lens L6, and a lens L7 arranged in order from the object side, wherein the lens L5 is a meniscus lens with a concave surface facing the image side, the lens L6 is a biconvex lens, and the lens L7 is a meniscus lens with a concave surface facing the object side.
[0146] The fourth lens group G4 is composed of a lens L8, which is a negative meniscus lens having a concave surface facing the image side.
[0147] The fifth lens group G5 is composed of lens L9, which is a negative meniscus lens having a concave surface facing the object side.
[0148] Various data of the objective lens 4 are as follows.
[0149] f=9mm, f1=16.82mm, f2=37.43mm, f3=53.26mm, f4=-43.42mm, f5=-123.91mm
[0150] NA=0.6,WD=4.682mm,L=44.27mm
[0151] The lens data of the objective lens 4 are as follows.
[0152] Objective 4
[0153]
[0154]
[0155] As shown below, the objective lens 3 satisfies conditional expressions (1), (2), and (5).
[0156] (1) |f / f2|=0.240
[0157] (2) |f / f3|=0.169
[0158] (5) WD / L = 0.106
[0159] Fig. 9 It is an aberration diagram of the optical system composed of the objective lens 4 and the imaging lens 10, and shows the aberration on the image plane obtained by tracing rays from the object side to the image side. Fig. 9 (a) is a spherical aberration diagram. Fig. 9 (b) is a graph showing the amount of violation of the sine condition. Fig. 9 (c) is the astigmatism diagram. Fig. 9 (d) is the coma diagram at an image height ratio of 0.8 (image height 8.80mm). Fig. 9 As shown, in this embodiment, aberrations are well corrected in a wide field of view.
[0160] (Example 5)
[0161] Fig.10 : is a cross-sectional view of the objective lens 5 of this embodiment. The objective lens 5 is a microscope objective lens, and includes, from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a fifth lens group G5 with negative refractive power. The fourth lens group G4 and the fifth lens group G5 are Gauss-type lens groups composed of concave and convex lens components with concave surfaces facing each other.
[0162] The first lens group G1 is composed of a cemented lens CL1, which is a meniscus lens component with a concave surface facing the object side. The cemented lens CL1 is a meniscus lens component with positive refractive power, and is composed of two cemented lenses, lens L1 and lens L2, which are arranged in order from the object side, and the lens L1 is a meniscus lens with a concave surface facing the object side, and the lens L2 is a meniscus lens with a concave surface facing the object side. Both the lens L1 and the lens L2 are positive lenses.
[0163] The second lens group G2 is composed of a cemented lens CL2 having positive refractive power. The cemented lens CL2 is a positive-negative-positive three-lens cemented lens composed of a biconvex lens L3, a biconcave lens L4, and a biconvex lens L5 arranged in order from the object side.
[0164] The third lens group G3 is composed of a cemented lens CL3 having a positive refractive power. The cemented lens CL3 is a negative-positive-negative three-piece cemented lens composed of lens L6, lens L7, and lens L8 arranged in order from the object side, wherein lens L6 is a meniscus lens with a concave surface facing the image side, lens L7 is a biconvex lens, and lens L8 is a meniscus lens with a concave surface facing the object side.
[0165] The fourth lens group G4 is composed of a cemented lens CL4 having negative refractive power. The cemented lens CL4 is a meniscus lens component having a concave surface on the image side, and is composed of two cemented lenses, a biconvex lens L9 and a biconcave lens L10, arranged in order from the object side.
[0166] The fifth lens group G5 is a lens L11 composed of a single negative meniscus lens having a concave surface facing the object side.
[0167] Various data of the objective lens 5 are as follows.
[0168] f=9mm, f1=20.11mm, f2=33.14mm, f3=149.64mm, f4=-3101.38mm, f5=-105.79mm
[0169] NA=0.6, ν1=60.08, ν2=20.36, n1=1.64254, n2=1.90314, WD=4.691mm, L=44.93mm
[0170] The lens data of the objective lens 5 are as follows.
[0171] Objective 5
[0172]
[0173]
[0174] As shown below, the objective lens 5 satisfies conditional expressions (1) to (5).
[0175] (1) |f / f2|=0.272
[0176] (2) |f / f3|=0.060
[0177] (3)|ν1-ν2|=39.72
[0178] (4)n1+n2=3.546
[0179] (5) WD / L = 0.104
[0180] Fig.11 It is an aberration diagram of the optical system composed of the objective lens 5 and the imaging lens 10, and shows the aberration on the image plane obtained by tracing rays from the object side to the image side. Fig.11 (a) is a spherical aberration diagram. Fig.11 (b) is a graph showing the amount of violation of the sine condition. Fig.11 (c) is the astigmatism diagram. Fig.11 (d) is the coma diagram at an image height ratio of 0.8 (image height 8.80mm). Fig.11 As shown, in this embodiment, aberrations are well corrected in a wide field of view.
[0181] (Example 6)
[0182] Fig.12 : is a cross-sectional view of the objective lens 6 of this embodiment. The objective lens 6 is a microscope objective lens, and includes, from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a fifth lens group G5 with negative refractive power. The fourth lens group G4 and the fifth lens group G5 are Gauss-type lens groups composed of concave and convex lens components with concave surfaces facing each other.
[0183] The first lens group G1 is composed of a cemented lens CL1, which is a meniscus lens component with a concave surface facing the object side. The cemented lens CL1 is a meniscus lens component with positive refractive power, and is composed of two cemented lenses, lens L1 and lens L2, which are arranged in order from the object side, and the lens L1 is a meniscus lens with a concave surface facing the object side, and the lens L2 is a meniscus lens with a concave surface facing the object side. Both the lens L1 and the lens L2 are positive lenses.
[0184] The second lens group G2 is composed of a cemented lens CL2 having positive refractive power. The cemented lens CL2 is a positive-negative-positive three-lens cemented lens composed of a biconvex lens L3, a biconcave lens L4, and a biconvex lens L5 arranged in order from the object side.
[0185] The third lens group G3 is composed of a cemented lens CL3 having a positive refractive power. The cemented lens CL3 is a negative-positive-negative three-piece cemented lens composed of lens L6, lens L7, and lens L8 arranged in order from the object side, wherein lens L6 is a meniscus lens with a concave surface facing the image side, lens L7 is a biconvex lens, and lens L8 is a meniscus lens with a concave surface facing the object side.
[0186] The fourth lens group G4 is composed of a cemented lens CL4 having a negative refractive power. The cemented lens CL4 is a meniscus lens component having a concave surface on the image side, and is composed of two cemented lenses, lens L9 and lens L10, which are arranged in sequence from the object side. The lens L9 is a meniscus lens with a concave surface facing the image side, and the lens L10 is a meniscus lens with a concave surface facing the image side.
[0187] The fifth lens group G5 is a lens L11 composed of a single negative meniscus lens having a concave surface facing the object side.
[0188] Various data of the objective lens 6 are as follows.
[0189] f=9mm, f1=19.21mm, f2=34.66mm, f3=81.47mm, f4=-66.84mm, f5=-120.34mm
[0190] NA=0.6, ν1=42.74, ν2=24.80, n1=1.83945, n2=1.86290, WD=4.687mm, L=44.93mm
[0191] The lens data of the objective lens 6 are as follows.
[0192] Objective 6
[0193]
[0194] As shown below, the objective lens 6 satisfies conditional expressions (1) to (5).
[0195] (1) |f / f2|=0.260
[0196] (2) |f / f3|=0.111
[0197] (3)|ν1-ν2|=17.3
[0198] (4)n1+n2=3.702
[0199] (5) WD / L = 0.104
[0200] Fig.13 1 and 2 are aberration diagrams of the optical system composed of the objective lens 6 and the imaging lens 10 , and show aberrations on the image plane obtained by tracing rays from the object side to the image side. Fig.13 (a) is a spherical aberration diagram. Fig.13 (b) is a graph showing the amount of violation of the sine condition. Fig.13 (c) is the astigmatism diagram. Fig.13 (d) is the coma diagram at an image height ratio of 0.8 (image height 8.80mm). Fig.13 As shown, in this embodiment, aberrations are well corrected in a wide field of view.
Claims
1. An objective lens, characterized in that: The objective lens includes the following components arranged in sequence from the object side: a first lens group having positive refractive power, the first lens group having a first meniscus lens component on the side closest to the object, the first meniscus lens component having a concave surface on the object side and having positive refractive power; A second lens group consisting of a first three-piece cemented lens, wherein the first three-piece cemented lens consists of a positive lens, a negative lens, and a positive lens; a third lens group consisting of a second three-element cemented lens, wherein the second three-element cemented lens consists of a negative lens, a positive lens, and a negative lens; a fourth lens group having negative refractive power, which has a second meniscus lens component on the image side, the second meniscus lens component having a concave surface on the image side and having negative refractive power; and a fifth lens group having a third meniscus lens component on the side closest to the object, the third meniscus lens component having a concave surface on the object side and having negative refractive power, The objective lens satisfies the following conditional formula: 0.21<|f / f2|<0.3...(1) Among them, f is the focal length of the objective lens, and f2 is the focal length of the second lens group.
2. An objective lens for a white interferometer, characterized in that: The objective lens includes the following components arranged in sequence from the object side: Beam splitters; Reference mirror; a first lens group having positive refractive power, the first lens group having a first meniscus lens component on the side closest to the object, the first meniscus lens component having a concave surface on the object side and having positive refractive power; A second lens group consisting of a first three-piece cemented lens, wherein the first three-piece cemented lens consists of a positive lens, a negative lens, and a positive lens; a third lens group consisting of a second three-element cemented lens, wherein the second three-element cemented lens consists of a negative lens, a positive lens, and a negative lens; a fourth lens group having negative refractive power, which has a second meniscus lens component on the image side, the second meniscus lens component having a concave surface on the image side and having negative refractive power; and a fifth lens group having a third meniscus lens component on the side closest to the object, the third meniscus lens component having a concave surface on the object side and having negative refractive power, The objective lens satisfies the following conditional formula: 0.21<|f / f2|<0.3...(1) Among them, f is the focal length of the objective lens, and f2 is the focal length of the second lens group.
3. The objective lens according to claim 1 or 2, characterized in that: The objective lens satisfies the following conditional formula: 0.05<|f / f3|<0.2...(2) Wherein, f3 is the focal length of the third lens group.
4. The objective lens according to claim 1 or 2, characterized in that: The first meniscus lens component is a cemented lens formed by cementing two meniscus lenses. The objective lens satisfies the following conditional formula: 17<|ν1-ν2|<40...(3) Here, ν1 is the Abbe number of the meniscus lens disposed on the object side of the two meniscus lenses with respect to the d-line, and ν2 is the Abbe number of the meniscus lens disposed on the image side of the two meniscus lenses with respect to the d-line.
5. The objective lens according to claim 1 or 2, characterized in that: The first meniscus lens component is a cemented lens formed by cementing two meniscus lenses. The objective lens satisfies the following conditional formula: 3.4 <n1+n2<4.0...(4) Here, n1 is the refractive index of the meniscus lens disposed on the object side of the two meniscus lenses with respect to the e-line, and n2 is the refractive index of the meniscus lens disposed on the image side of the two meniscus lenses with respect to the e-line.
6. The objective lens according to claim 1 or 2, characterized in that: The objective lens satisfies the following conditional formula: WD / L>0.065...(5) Wherein, WD is the air-converted length of the distance from the specimen surface to the surface of the first lens group closest to the object side on the optical axis, and L is the distance from the surface of the first lens group closest to the object side to the surface of the fifth lens group closest to the image side on the optical axis.
7. The objective lens according to claim 1 or 2, characterized in that: The first lens group is composed of a positive meniscus lens with a concave surface facing the object side.
8. The objective lens according to claim 1 or 2, characterized in that: The fourth lens group is composed of a negative meniscus lens with a concave surface facing the image side.
9. The objective lens according to claim 3, characterized in that The first meniscus lens component is a cemented lens formed by cementing two meniscus lenses. The objective lens satisfies the following conditional formula: 17<|ν1-ν2|<40...(3) Here, ν1 is the Abbe number of the meniscus lens disposed on the object side of the two meniscus lenses with respect to the d-line, and ν2 is the Abbe number of the meniscus lens disposed on the image side of the two meniscus lenses with respect to the d-line.
10. The objective lens according to claim 3, characterized in that The first meniscus lens component is a cemented lens formed by cementing two meniscus lenses. The objective lens satisfies the following conditional formula: 3.4 <n1+n2<4.0...(4) Here, n1 is the refractive index of the meniscus lens disposed on the object side of the two meniscus lenses with respect to the e-line, and n2 is the refractive index of the meniscus lens disposed on the image side of the two meniscus lenses with respect to the e-line.
11. The objective lens according to claim 3, characterized in that The objective lens satisfies the following conditional formula: WD / L>0.065...(5) Wherein, WD is the air-converted length of the distance from the specimen surface to the surface of the first lens group closest to the object side on the optical axis, and L is the distance from the surface of the first lens group closest to the object side to the surface of the fifth lens group closest to the image side on the optical axis.
12. The objective lens according to claim 3, characterized in that The first lens group is composed of a positive meniscus lens with a concave surface facing the object side.
13. The objective lens according to claim 3, characterized in that The fourth lens group is composed of a negative meniscus lens with a concave surface facing the image side.
14. The objective lens according to claim 9, characterized in that The objective lens satisfies the following conditional formula: 3.4 <n1+n2<4.0...(4) Here, n1 is the refractive index of the meniscus lens disposed on the object side of the two meniscus lenses with respect to the e-line, and n2 is the refractive index of the meniscus lens disposed on the image side of the two meniscus lenses with respect to the e-line.
15. The objective lens according to claim 9, characterized in that The objective lens satisfies the following conditional formula: WD / L>0.065...(5) Wherein, WD is the air-converted length of the distance from the specimen surface to the surface of the first lens group closest to the object side on the optical axis, and L is the distance from the surface of the first lens group closest to the object side to the surface of the fifth lens group closest to the image side on the optical axis.
16. The objective lens according to claim 9, characterized in that The fourth lens group is composed of a negative meniscus lens with a concave surface facing the image side.
17. The objective lens according to claim 12, characterized in that The fourth lens group is composed of a negative meniscus lens with a concave surface facing the image side.
18. The objective lens according to claim 14, characterized in that The objective lens satisfies the following conditional formula: WD / L>0.065...(5) Wherein, WD is the air-converted length of the distance from the specimen surface to the surface of the first lens group closest to the object side on the optical axis, and L is the distance from the surface of the first lens group closest to the object side to the surface of the fifth lens group closest to the image side on the optical axis.
19. The objective lens according to claim 14, characterized in that The fourth lens group is composed of a negative meniscus lens with a concave surface facing the image side.
20. The objective lens according to claim 18, characterized in that The fourth lens group is composed of a negative meniscus lens with a concave surface facing the image side.