Imaging lenses and microscopes

Abstract

To provide an imaging lens for microscopes that can effectively correct chromatic aberration. [Solution] The imaging lens IL is an imaging lens for a microscope that forms an image of light from the objective lens. It has a negative lens and a positive lens that satisfies the following condition. -0.002×(νdP-35)+0.602-θgFP<0 23 < νdP < 65 However, νdP: Abbe number of positive lens θgFP is the partial dispersion ratio of a positive lens, and is defined by the following equation, where ngP is the refractive index of the positive lens with respect to the g line, nFP is the refractive index of the positive lens with respect to the f line, and nCP is the refractive index of the positive lens with respect to the c line. θgFP = (ngP - nFP) / (nFP - nCP)

Description

Technical Field

[0004] ,

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[0001] The present invention relates to an imaging lens and a microscope apparatus.

Background Art

[0002] In recent years, various imaging lenses for microscopes that can accommodate objective lenses with a wide field of view have been proposed (see, for example, Patent Document 1). In such an imaging lens, it is required to satisfactorily correct chromatic aberration.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The imaging lens according to the first aspect of the present invention is an imaging lens for a microscope that forms an image of light from an objective lens, and includes a negative lens and a positive lens that satisfies the following conditional expression. -0.002×(νdP - 35) + 0.602 - θgFP < 0 23 < νdP < 65 However, νdP: Abbe number of the positive lens θgFP: Partial dispersion ratio of the positive lens, when the refractive index of the positive lens with respect to the g-line is ngP, the refractive index of the positive lens with respect to the F-line is nFP, and the refractive index of the positive lens with respect to the C-line is nCP, it is defined by the following formula [[ID=​​​​​​​​​​​ θgFN is the partial dispersion ratio of the negative lens, and is defined by the following equation, where ngN is the refractive index of the negative lens with respect to the g line, nFN is the refractive index of the negative lens with respect to the F line, and nCN is the refractive index of the negative lens with respect to the C line. θgFN = (ngN - nFN) / (nFN - nCN)

[0006] The microscope apparatus according to the present invention includes an objective lens that receives light from an object and converts it into parallel light, and the imaging lens described above. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional view showing the configuration of the imaging lens according to the first embodiment. [Figure 2] This is a diagram showing the various aberrations of the imaging lens according to the first embodiment. [Figure 3] This is a chromatic aberration diagram of the imaging lens according to the first embodiment. [Figure 4] This is a coma aberration diagram of the imaging lens according to the first embodiment. [Figure 5] This is a cross-sectional view showing the configuration of the imaging lens according to the second embodiment. [Figure 6] This is a diagram showing the various aberrations of the imaging lens according to the second embodiment. [Figure 7] This is a chromatic aberration diagram of the imaging lens according to the second embodiment. [Figure 8] This is a coma aberration diagram of the imaging lens according to the second embodiment. [Figure 9] This is a cross-sectional view showing the configuration of the imaging lens according to the third embodiment. [Figure 10] This is a diagram showing the various aberrations of the imaging lens according to the third embodiment. [Figure 11] This is a chromatic aberration diagram of the imaging lens according to the third embodiment. [Figure 12] This is a coma aberration diagram of the imaging lens according to the third embodiment. [Figure 13] This is a cross-sectional view showing the configuration of the imaging lens according to the fourth embodiment. [Figure 14] This is a diagram showing the aberrations of the imaging lens according to the fourth embodiment. [Figure 15] It is a chromatic aberration diagram of the imaging lens according to the fourth embodiment. [Figure 16] It is a coma aberration diagram of the imaging lens according to the fourth embodiment. [Figure 17] It is a cross-sectional view showing the configuration of the imaging lens according to the fifth embodiment. [Figure 18] It is various aberration diagrams of the imaging lens according to the fifth embodiment. [Figure 19] It is a chromatic aberration diagram of the imaging lens according to the fifth embodiment. [Figure 20] It is a coma aberration diagram of the imaging lens according to the fifth embodiment. [Figure 21] It is a schematic configuration diagram showing a confocal fluorescence microscope which is an example of a microscope device.

Mode for Carrying Out the Invention

[0008] Hereinafter, preferred embodiments according to the present invention will be described. First, a confocal fluorescence microscope (microscope device) having an imaging lens according to each embodiment will be described based on FIG. 21. As shown in FIG. 21, the confocal fluorescence microscope 1 includes an excitation light introduction unit 2 that guides illumination laser light from a light source unit 6 onto a sample SA, a scanning device 3 that deflects the laser light condensed on the sample SA and scans the sample SA, a light detection device 5 that detects a light intensity signal from the sample SA, and a condenser optical system 4 that guides the light from the sample SA to the light detection device ⑤.

[0009] The light source unit 6 may be provided in the confocal fluorescence microscope 1 or may be provided separately from the confocal fluorescence microscope 1. The light source unit 6 includes a laser light source (not shown) and a beam diameter adjustment mechanism (not shown) and the like. The light source unit 6 oscillates illumination laser light.

[0010] The excitation light introduction unit 2 is composed of a collimator lens 21, a dichroic mirror 22, and a microscope optical system 25 having an imaging lens 23 and an objective lens 24. The collimator lens 21 and the dichroic mirror 22 are arranged inside the microscope housing 12, which is located at the top of the lens barrel 11 of the microscope body 10. The light source unit 6 and the microscope housing 12 are connected by optical fibers 69 using connectors C3 and C4. The collimator lens 21 converts the laser light (light beam) emitted from the light source unit 6 into parallel light. The dichroic mirror 22 reflects the laser light from the collimator lens 21 toward the sample SA. The microscope optical system 25 focuses the laser light reflected by the dichroic mirror 22 onto the sample SA using the imaging lens 23 and the objective lens 24. The imaging lens 23 is arranged inside the lens barrel 11 of the microscope body 10. The imaging lens 23 is also called the second objective lens. The objective lens 24 is mounted on the lower part of the lens barrel 11.

[0011] The scanning device 3 comprises a scanning mechanism (scanner) 31 and a scanning optical system 32. The scanning device 3 is disposed between the dichroic mirror 22 and the imaging lens 23 inside the microscope housing 12. The scanning mechanism (scanner) 31 is configured to have, for example, a galvanometer mirror (not shown) or a resonant mirror (not shown). The scanning mechanism (scanner) 31 deflects the incident laser light. That is, the scanning mechanism (scanner) 31 deflects the laser light focused on the sample SA and scans the sample SA. The scanning optical system 32 is an optical system provided between the scanning mechanism (scanner) 31 and the imaging lens 23. Furthermore, the scanning optical system 32 is an optical system in which the focal position of the scanning optical system 32 is located on the imaging plane 13 (also called the primary image plane) which is conjugate to the sample SA (the scanning surface of the sample SA).

[0012] The focusing optical system 4 comprises an objective lens 24 and an imaging lens 23 that constitute the microscope optical system 25, a total internal reflection mirror 41, and a focusing lens 42. The objective lens 24 receives fluorescence generated by the sample SA and converts it into parallel light. The imaging lens 23 focuses the fluorescence (parallel light) emitted from the objective lens 24 onto the imaging plane 13 (primary image plane) to form an image. As a result, the fluorescence from the sample SA that has passed through the objective lens 24 and the imaging lens 23 is focused onto the imaging plane 13, passes through the scanning device 3 and the dichroic mirror 22, and reaches the total internal reflection mirror 41. The total internal reflection mirror 41 and the focusing lens 42 are arranged above the dichroic mirror 22 inside the microscope housing 12. The total internal reflection mirror 41 reflects the fluorescence from the sample SA that has passed through the objective lens 24 and the imaging lens 23. The focusing lens 42 concentrates the fluorescence reflected by the total reflection mirror 41 onto a light-shielding plate 52 having a pinhole 51 (aperture).

[0013] The photodetector 5 comprises a light-shielding plate 52 having a pinhole 51, an optical fiber 53, and a detection unit 55. The optical fiber 53 is connected to the microscope housing 12 and the detection unit 55 using connectors C1 and C2. Light (fluorescence) passing through the pinhole 51 is incident on the optical fiber 53. The detection unit 55 detects the light (fluorescence) that has passed through the pinhole 51 and the optical fiber 53. A processing unit 57 is electrically connected to the detection unit 55 via a cable 56. The processing unit 57 performs image processing (of the sample SA) based on the detection signal detected by the detection unit 55, and the observation image of the sample SA obtained by the image processing of the processing unit 57 is displayed on a monitor (not shown).

[0014] Furthermore, the laser light from the scanning device 3 is first focused onto the imaging plane 13 (primary image plane), and then focused again onto the sample SA by the imaging lens 23 and objective lens 24 of the microscope optical system 25. In other words, the scanning plane of the sample SA, the imaging plane 13, and the pinhole 51 are conjugate to each other. Therefore, by configuring the laser light to be focused onto the sample SA by the imaging lens 23 and objective lens 24, it becomes possible to pass the fluorescence generated on the scanning plane of the sample SA through the pinhole 51.

[0015] While a confocal fluorescence microscope 1 has been described as an example of a microscope apparatus according to this embodiment, the apparatus is not limited to this. For example, the microscope apparatus according to this embodiment may be a multiphoton excitation microscope or a super-resolution microscope, etc. Furthermore, the confocal fluorescence microscope 1 may be an upright microscope or an inverted microscope.

[0016] The imaging lens IL described below can be used as the imaging lens 23 provided in such a confocal fluorescence microscope 1 (microscope device). Therefore, first, the imaging lens IL according to the first embodiment will be described.

[0017] As an example of an imaging lens IL according to the first embodiment, the imaging lens IL(1) shown in Figure 1 has a negative lens and a positive lens (L13) that satisfies the following conditions (1) and (2). -0.002×(νdP-35)+0.602-θgFP<0 ···(1) 23 < νdP < 65 ···(2) However, νdP: Abbe number of positive lens θgFP is the partial dispersion ratio of a positive lens, and is defined by the following equation, where ngP is the refractive index of the positive lens with respect to the g line, nFP is the refractive index of the positive lens with respect to the f line, and nCP is the refractive index of the positive lens with respect to the c line. θgFP = (ngP - nFP) / (nFP - nCP)

[0018] According to the first embodiment, it is possible to obtain an imaging lens in which chromatic aberration is well corrected over a wide wavelength range, and a microscope apparatus having this imaging lens. The imaging lens IL according to the first embodiment may be the imaging lens IL(2) shown in Figure 5, the imaging lens IL(3) shown in Figure 9, the imaging lens IL(4) shown in Figure 13, or the imaging lens IL(5) shown in Figure 17.

[0019] Condition (1) appropriately defines the anomalous dispersion of the positive lens. By satisfying condition (1), the second-order spectrum of axial chromatic aberration can be effectively corrected.

[0020] If the corresponding value in conditional equation (1) falls outside the above range, it becomes difficult to correct the secondary spectrum of axial chromatic aberration. Setting the upper limit of conditional equation (1) to -0.002 and further to -0.004 can make the effect of this embodiment more reliable. Alternatively, the lower limit of conditional equation (1) may be set to -0.05 and further to -0.025.

[0021] Condition (2) defines an appropriate range for the Abbe number of a positive lens. By satisfying condition (2), first-order axial chromatic aberration can be effectively corrected.

[0022] If the corresponding value in conditional equation (2) falls outside the above range, it becomes difficult to correct first-order axial chromatic aberration. Setting the upper limit of conditional equation (2) to 60, 55, 50, 45, 40, and further to 35 can make the effect of this embodiment more reliable. Setting the lower limit of conditional equation (2) to 23.5, 24, and further to 24.5 can make the effect of this embodiment more reliable.

[0023] In the imaging lens IL according to the first embodiment, the positive lens may satisfy the following condition (3). 1.55 <ndP<1.79 ···(3) However, ndP: refractive index of a positive lens with respect to the d line.

[0024] Condition (3) specifies an appropriate range for the refractive index of a positive lens with respect to the d line. By satisfying condition (3), field curvature can be effectively corrected.

[0025] If the corresponding value in conditional equation (3) exceeds the upper limit, the difference in refractive index between the positive lens and the lens adjacent to the positive lens becomes large, making it difficult to correct spherical aberration. By setting the upper limit of conditional equation (3) to 1.78, and further to 1.76, the effect of this embodiment can be made more reliable.

[0026] If the corresponding value in condition (3) exceeds the lower limit, the refractive index of the positive lens with respect to the d line decreases, and the term relating to the positive lens in the Petzval sum increases, making it difficult to correct the field curvature. By setting the lower limit of condition (3) to 1.58, and further to 1.60, the effect of this embodiment can be made more reliable.

[0027] In the imaging lens IL according to the first embodiment, the positive lens may satisfy the following condition (4). 0.4 <fP / f<1.2 ···(4) However, fP: focal length of the positive lens f: Focal length of the imaging lens (IL)

[0028] Condition (4) defines the appropriate relationship between the focal length of the positive lens and the focal length of the imaging lens IL. By satisfying condition (4), the secondary spectrum of axial chromatic aberration can be effectively corrected.

[0029] If the corresponding value in conditional equation (4) exceeds the upper limit, the refractive power of the positive lens decreases, making it difficult to correct the secondary spectrum of axial chromatic aberration. By setting the upper limit of conditional equation (4) to 1.15, and further to 1.1, the effect of this embodiment can be made more reliable.

[0030] If the corresponding value in conditional equation (4) falls below the lower limit, the refractive power of the positive lens increases, resulting in excessive correction of the secondary spectrum of axial chromatic aberration, making it difficult to adequately correct the secondary spectrum of axial chromatic aberration. By setting the lower limit of conditional equation (4) to 0.41, and further to 0.42, the effect of this embodiment can be made more reliable.

[0031] Next, the imaging lens IL according to the second embodiment will be described. Since the imaging lens IL according to the second embodiment has the same configuration as the imaging lens IL according to the first embodiment, it will be described using the same reference numerals as in the first embodiment.

[0032] As an example of an imaging lens IL according to the second embodiment, the imaging lens IL(1) shown in Figure 1 has a positive lens and a negative lens (L21) that satisfies the following conditions (5) and (6). -0.0033×(νdN-35)+0.593-θgFN<0 ···(5) 20 < νdN < 37 ···(6) However, νdN: Abbe number of the negative lens θgFN is the partial dispersion ratio of a negative lens, and is defined by the following equation, where ngN is the refractive index of the negative lens with respect to the g line, nFN is the refractive index of the negative lens with respect to the f line, and nCN is the refractive index of the negative lens with respect to the c line. θgFN = (ngN - nFN) / (nFN - nCN)

[0033] According to the second embodiment, it is possible to obtain an imaging lens in which chromatic aberration is well corrected over a wide wavelength range, and a microscope device having this imaging lens. The imaging lens IL according to the second embodiment may be the imaging lens IL(2) shown in Figure 5, the imaging lens IL(3) shown in Figure 9, the imaging lens IL(4) shown in Figure 13, or the imaging lens IL(5) shown in Figure 17.

[0034] Condition (5) appropriately defines the anomalous dispersion of the negative lens. By satisfying condition (5), the second-order spectrum of chromatic aberration can be well corrected.

[0035] If the corresponding value in conditional equation (5) falls outside the above range, it becomes difficult to correct the second-order spectrum of chromatic aberration. Setting the upper limit of conditional equation (5) to -0.0005 and further to -0.001 can make the effect of this embodiment more reliable. Alternatively, the lower limit of conditional equation (5) may be set to -0.05 and further to -0.025.

[0036] Condition (6) defines an appropriate range for the Abbe number of the negative lens. By satisfying condition (6), first-order chromatic aberration can be effectively corrected.

[0037] If the corresponding value in conditional equation (6) falls outside the above range, it becomes difficult to correct first-order chromatic aberration. Setting the upper limit of conditional equation (6) to 36.5, 36, and further to 35.5 makes the effect of this embodiment more reliable. Setting the lower limit of conditional equation (6) to 23.5, 24, and further to 24.5 makes the effect of this embodiment more reliable.

[0038] In the imaging lens IL according to the second embodiment, the negative lens may satisfy the following condition (7). ndN<1.78 ···(7) However, ndN: refractive index of a negative lens for the d line

[0039] Condition (7) specifies an appropriate range for the refractive index of the negative lens with respect to the d line. By satisfying condition (7), field curvature can be effectively corrected.

[0040] If the corresponding value in conditional equation (7) exceeds the upper limit, the refractive index of the negative lens with respect to the d line increases, making it difficult to sufficiently cancel out the term related to the positive lens in the Petzval sum, thus making it difficult to correct the field curvature. Setting the upper limit of conditional equation (7) to 1.77, and further to 1.76, can make the effect of this embodiment more reliable. Alternatively, the lower limit of conditional equation (7) may be set to 1.57, and further to 1.58.

[0041] In the imaging lens IL according to the second embodiment, the negative lens may satisfy the following condition (8). -1.1 <fN / f<-0.2 ···(8) However, fN: Focal length of the negative lens f: Focal length of the imaging lens (IL)

[0042] Condition (8) defines the appropriate relationship between the focal length of the negative lens and the focal length of the imaging lens IL. By satisfying condition (8), field curvature can be effectively corrected.

[0043] If the corresponding value in conditional equation (8) exceeds the upper limit, the focal length of the negative lens becomes shorter, excessively canceling out the term related to the positive lens in the Petzval sum, making it difficult to correct the field curvature. By setting the upper limit of conditional equation (8) to -0.22, and further to -0.24, the effect of this embodiment can be made more reliable.

[0044] If the corresponding value in conditional equation (8) falls below the lower limit, the focal length of the negative lens increases, and the term relating to the positive lens in the Petzval sum cannot be sufficiently canceled out, making it difficult to correct the field curvature. Setting the lower limit of conditional equation (8) to -1.05 makes the effect of this embodiment more reliable.

[0045] In the imaging lens IL according to the first embodiment, the negative lens may satisfy the aforementioned condition (5). By satisfying condition (5), the second-order spectrum of chromatic aberration can be corrected well, similar to the case of the second embodiment. Furthermore, by setting the upper limit of condition (5) to -0.0005 and further to -0.001, the effect of this embodiment can be made more reliable. In addition, the lower limit of condition (5) may be set to -0.05 and further to -0.025.

[0046] In the imaging lens IL according to the first embodiment, the negative lens may satisfy the aforementioned condition (6). By satisfying condition (6), first-order chromatic aberration can be corrected well, similar to the case of the second embodiment. Furthermore, the effect of this embodiment can be made more reliable by setting the upper limit of condition (6) to 36.5, 36, and further to 35.5. The effect of this embodiment can be made more reliable by setting the lower limit of condition (6) to 23.5, 24, and further to 24.5.

[0047] In the imaging lens IL according to the first embodiment, the negative lens may satisfy the aforementioned condition (7). By satisfying condition (7), field curvature can be corrected well, similar to the case of the second embodiment. Furthermore, by setting the upper limit of condition (7) to 1.77 and further to 1.76, the effect of this embodiment can be made more reliable. In addition, the lower limit of condition (7) may be set to 1.57 and further to 1.58.

[0048] In the imaging lens IL according to the first embodiment, the negative lens may satisfy the aforementioned condition (8). By satisfying condition (8), field curvature can be corrected well, similar to the case of the second embodiment. Furthermore, the effect of this embodiment can be made more reliable by setting the upper limit of condition (8) to -0.22 and further to -0.24. The effect of this embodiment can be made more reliable by setting the lower limit of condition (8) to -1.05.

[0049] The imaging lens IL according to the first and second embodiments may satisfy the following condition (9). 0.2 <Bf / TL<0.6 ···(9) However, Bf: Back focus of the imaging lens IL TL: Total length of the imaging lens IL

[0050] Conditional equation (9) defines an appropriate relationship between the back focus of the imaging lens IL and the total length of the imaging lens IL. In each embodiment, the total length of the imaging lens IL represents the distance along the optical axis from the lens surface closest to the image on the objective lens to the image plane I. By satisfying conditional equation (9), optical elements such as prisms and half-mirrors can be placed on the object side of the imaging lens IL, making it possible to easily switch between, for example, microscopic observation using the microscope as a confocal fluorescence microscope and microscopic observation using the microscope as a stereomicroscope.

[0051] If the corresponding value in conditional equation (9) exceeds the upper limit, it becomes necessary to increase the refractive power of the positive and negative lenses to raise the telephoto ratio, making it difficult to correct field curvature and coma aberration. By setting the upper limit of conditional equation (9) to 0.55, and further to 0.5, the effects of each embodiment can be made more reliable.

[0052] If the corresponding value in conditional equation (9) falls below the lower limit, it becomes difficult to place optical elements such as prisms or half-mirrors on the object side of the imaging lens IL. By setting the lower limit of conditional equation (9) to 0.21, and further to 0.22, the effects of each embodiment can be made more reliable.

[0053] The imaging lens IL according to the first and second embodiments comprises a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. Preferably, the second lens group G2 consists of one lens component having negative refractive power, and the third lens group G3 consists of one lens component having positive refractive power. In each embodiment, the lens components represent single lenses or cemented lenses. This results in a symmetrical arrangement of lenses, which allows for good correction of astigmatism.

[0054] The imaging lens IL according to the first and second embodiments may satisfy the following condition (10). 0.45 <f1 / f3<2.4 ···(10) However, f1: Focal length of the first lens group G1 f3: Focal length of the third lens group G3

[0055] Conditional equation (10) defines the appropriate relationship between the focal length of the first lens group G1 and the focal length of the third lens group G3. By satisfying conditional equation (10), it becomes possible to make the imaging lens IL smaller while widening the field of view and increasing the numerical aperture.

[0056] If the corresponding value in conditional equation (10) exceeds the upper limit, the refractive power of the third lens group G3 becomes too strong, making it difficult to miniaturize the imaging lens IL, which is undesirable. By setting the upper limit of conditional equation (10) to 2.35, and further to 2.3, the effects of each embodiment can be made more reliable.

[0057] If the corresponding value in conditional equation (10) falls below the lower limit, the refractive power of the first lens group G1 becomes too strong, making it difficult to correct astigmatism, off-axis coma, and distortion. By setting the lower limit of conditional equation (10) to 0.48 and further to 0.50, the effects of each embodiment can be made more reliable.

[0058] The imaging lens IL according to the first and second embodiments may satisfy the following condition (11). -2.5 <f1 / f2<-0.6 ···(11) However, f1: Focal length of the first lens group G1 f2: Focal length of the second lens group G2

[0059] Condition (11) defines the appropriate relationship between the focal length of the first lens group G1 and the focal length of the second lens group G2. By satisfying condition (11), it becomes possible to make the imaging lens IL smaller while widening the field of view and increasing the numerical aperture.

[0060] If the corresponding value in conditional equation (11) exceeds the upper limit, the refractive power of the second lens group G2 becomes too weak, making it difficult to miniaturize the imaging lens IL, which is undesirable. By setting the upper limit of conditional equation (11) to -0.7, and further to -0.8, the effects of each embodiment can be made more reliable.

[0061] If the corresponding value in conditional equation (11) falls below the lower limit, the refractive power of the second lens group G2 becomes too strong, making it difficult to correct field curvature and off-axis coma aberration. By setting the lower limit of conditional equation (11) to -2.4, and further to -2.3, the effects of each embodiment can be made more reliable.

[0062] In a microscope apparatus (confocal fluorescence microscope 1) having an imaging lens IL according to the first or second embodiment, the following condition (12) may be satisfied. 0.3 <DA / TL<0.6 ···(12) However, DA: distance along the optical axis from the image-side lens surface of the objective lens to the object-side lens surface of the imaging lens IL. TL: Total length of the imaging lens IL

[0063] Condition (12) defines an appropriate relationship between the distance along the optical axis from the image-side lens surface of the objective lens to the object-side lens surface of the imaging lens IL, and the total length of the imaging lens IL. By satisfying condition (12), optical elements such as prisms and half-mirrors can be placed on the object side of the imaging lens IL, making it possible to easily switch between, for example, microscopic observation using the microscope as a confocal fluorescence microscope and microscopic observation using the microscope as a stereomicroscope.

[0064] If the corresponding value in conditional equation (12) exceeds the upper limit, the diameter of each lens in the imaging lens IL becomes larger, and it becomes difficult to secure sufficient back focus. By setting the upper limit of conditional equation (12) to 0.55, 0.5, and further to 0.48, the effects of each embodiment can be made more reliable.

[0065] If the corresponding value in conditional equation (12) falls below the lower limit, it becomes difficult to place optical elements such as prisms or half-mirrors on the object side of the imaging lens IL. By setting the lower limit of conditional equation (12) to 0.35, and further to 0.38, the effects of each embodiment can be made more reliable.

[0066] In a microscope apparatus (confocal fluorescence microscope 1) having an imaging lens IL according to the first or second embodiment, the following condition (13) may be satisfied. 0.1 <FDN / f<0.18 ···(13) However, FDN: Field of View of Microscope f: Focal length of the imaging lens (IL)

[0067] Conditional equation (13) defines the appropriate relationship between the field of view of the microscope and the focal length of the imaging lens IL. By satisfying conditional equation (13), spherical aberration and coma aberration can be well corrected over a wide field of view.

[0068] If the corresponding value in conditional equation (13) exceeds the upper limit, it becomes difficult to correct spherical aberration and coma aberration. By setting the upper limit of conditional equation (13) to 0.17, the effects of each embodiment can be made more reliable.

[0069] If the corresponding value in conditional equation (13) falls below the lower limit, sufficient magnification cannot be obtained, resulting in a narrow field of view, which is undesirable. By setting the lower limit of conditional equation (13) to 0.11, the effects of each embodiment can be made more reliable. [Examples]

[0070] The following describes embodiments of the imaging lens IL according to each embodiment, based on the drawings. Figures 1, 5, 9, 13, and 17 are cross-sectional views showing the configuration and refractive power distribution of the imaging lenses IL{IL(1) to IL(5)} according to the first to fifth embodiments. In Figures 1, 5, 9, 13, and 17, each lens group is represented by a combination of the symbol G and a number (or alphabet), and each lens is represented by a combination of the symbol L and a number (or alphabet). In this case, in order to prevent the number and types of symbols and numbers from becoming too large and complicated, the lens components, etc., are represented independently using a combination of symbols and numbers for each embodiment. Therefore, even if the same combination of symbols and numbers is used between embodiments, it does not mean that they have the same configuration.

[0071] Tables 1 to 5 are shown below. Table 1 shows the specifications for the first embodiment, Table 2 for the second embodiment, Table 3 for the third embodiment, Table 4 for the fourth embodiment, and Table 5 for the fifth embodiment. In each embodiment, the d-line (wavelength λ=587.6nm), C-line (wavelength λ=656.3nm), F-line (wavelength λ=486.1nm), g-line (wavelength λ=435.8nm), and s-line (wavelength λ=851.1nm) were selected as the targets for calculating aberration characteristics.

[0072] In the [Overall Specifications] table, f indicates the focal length of the imaging lens. FNO indicates the F-number of the imaging lens. NA indicates the numerical aperture of the imaging lens, and Bf indicates the back focus of the imaging lens. TL indicates the total length of the imaging lens (the distance along the optical axis from the image-side lens surface of the objective lens to the image plane). DA indicates the distance along the optical axis from the image-side lens surface of the objective lens to the object-side lens surface of the imaging lens. FDN indicates the field of view of the microscope.

[0073] In the [Lens Specifications] table, the surface number indicates the order of the lens surfaces from the object side. R represents the radius of curvature of each optical surface (surfaces with their center of curvature on the image plane side are given a positive value). D represents the interplanar spacing, which is the distance along the optical axis from one optical surface to the next optical surface (or image plane). νd represents the Abbe number with respect to the d-line of the optical material. nd represents the refractive index of the optical material with respect to the d-line. θgF represents the partial dispersion ratio of the optical material. "∞" for the radius of curvature indicates a plane or aperture. The refractive index of air nd = 1.00000 is omitted.

[0074] Let ng be the refractive index of the optical component material with respect to the g-line (wavelength λ = 435.8 nm), nF be the refractive index of the optical component material with respect to the F-line (wavelength λ = 486.1 nm), and nC be the refractive index of the optical component material with respect to the C-line (wavelength λ = 656.3 nm). Then, the partial dispersion ratio θgF of the optical component material is defined by the following equation (A).

[0075] θgF = (ng - nF) / (nF - nC) …(A)

[0076] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length for each lens group.

[0077] In all specifications listed below, the focal length f, radius of curvature R, interplanar spacing D, and other lengths are generally expressed in "mm" unless otherwise specified. However, since optical systems can achieve equivalent optical performance even when proportionally enlarged or reduced, this is not the only way to express them.

[0078] The explanations in the table above are common to all examples, and any redundant explanations below will be omitted.

[0079] (First embodiment) The first embodiment will be described using Figures 1 to 4 and Table 1. Figure 2 is a cross-sectional view showing the configuration of the imaging lens according to the first embodiment. The imaging lens IL(1) according to the first embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, arranged in order from the object side along the optical axis. The entrance pupil plane P of the imaging lens IL(1) corresponds to the exit pupil plane of the infinity-corrected objective lens 24. The image plane I corresponds to the imaging plane 13 described above. This is the same for all the following embodiments.

[0080] The first lens group G1 consists of a biconvex positive lens L11 arranged in order from the object side along the optical axis, and a cemented lens formed by joining a positive meniscus lens L12 with its convex surface facing the object side, a biconvex positive lens L13, and a biconcave negative lens L14. The positive lens L13 of the cemented lens in the first lens group G1 corresponds to a positive lens that satisfies the aforementioned condition (1), etc.

[0081] The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object. The negative meniscus lens L21 in the second lens group G2 corresponds to a negative lens that satisfies the aforementioned condition (5), etc.

[0082] The third lens group G3 consists of a positive meniscus lens L31 with its convex surface facing the object. The image plane I is positioned on the image side of the third lens group G3.

[0083] Table 1 below lists the specifications of the imaging lens according to the first embodiment. The first surface is the entrance pupil plane P of the imaging lens.

[0084] (Table 1) [Overall Specifications] f=202.00 FNO=6.73 NA=0.07 Bf=88.65 TL=350.00 DA=160.00 FDN=25.00 [Lens Specifications] Face number RD nd νd θgF 1 ∞ 160.00 2 86.109 6.00 1.45600 91.37 3 -526.020 0.20 4 56.104 4.67 1.49782 82.57 5 100.000 6.00 1.66382 27.35 0.6319 6 -200.000 8.10 1.73800 32.26 7 105.381 9.30 8 217.561 19.37 1.75575 24.71 0.6290 9 40.184 42.71 10 103.799 5.00 1.85025 30.05 11 317.656 Bf [Lens group data] Group starting plane focal length G1 2 95.68 G2 8 -68.43 G3 10 179.41

[0085] Figure 2 shows the various aberrations (spherical aberration, field curvature, and distortion) of the imaging lens according to the first embodiment. Figure 3 shows the lateral chromatic aberration (transverse chromatic aberration) of the imaging lens according to the first embodiment. Figure 4 shows the coma aberration (meridional coma aberration and sagittal coma aberration) of the imaging lens according to the first embodiment. In the aberration diagrams of Figures 2 to 4, d represents the aberrations for the d line (wavelength λ=587.6nm), C represents the aberrations for the C line (wavelength λ=656.3nm), F represents the aberrations for the F line (wavelength λ=486.1nm), g represents the aberrations for the g line (wavelength λ=435.8nm), and s represents the aberrations for the s line (wavelength λ=851.1nm). In the spherical aberration diagram, the vertical axis shows the values ​​normalized to the maximum value of the entrance pupil radius as 1, and the horizontal axis shows the aberration values ​​[mm] for each light ray. In the aberration diagram showing field curvature, the solid line represents the sagittal image plane for each wavelength, and the dashed line represents the meridional image plane for each wavelength. In the aberration diagram showing field curvature, the vertical axis represents image height [mm], and the horizontal axis represents the aberration value [mm]. In the distortion aberration diagram, the vertical axis represents image height [mm], and the horizontal axis represents the aberration percentage (%). In the aberration diagram showing chromatic aberration, the vertical axis represents image height [mm], and the horizontal axis represents the aberration value [mm]. Each coma aberration diagram shows the aberration values ​​when the relative field height (RFH) is 0.00 and 1.00. Note that the same reference numerals as in this example are used in the aberration diagrams of each embodiment shown below, and redundant explanations are omitted.

[0086] From the aberration diagrams, it can be seen that the imaging lens according to the first embodiment has excellent optical performance, with various aberrations, including chromatic aberration, being well corrected over a wide wavelength range.

[0087] (Second example) The second embodiment will be described using Figures 5 to 8 and Table 2. Figure 5 is a cross-sectional view showing the configuration of the imaging lens according to the second embodiment. The imaging lens IL(2) according to the second embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, which are arranged in order from the object side along the optical axis.

[0088] The first lens group G1 consists of a biconvex positive lens L11 arranged in order from the object side along the optical axis, a positive meniscus lens L12 with its convex surface facing the object side, and a cemented lens formed by joining a positive meniscus lens L13 with its convex surface facing the object side and a negative meniscus lens L14 with its convex surface facing the object side. The positive meniscus lens L13 of the cemented lens in the first lens group G1 corresponds to a positive lens that satisfies the aforementioned condition (1), etc.

[0089] The second lens group G2 consists of a biconcave negative lens L21. The negative lens L21 in the second lens group G2 corresponds to a negative lens that satisfies the aforementioned condition (5), etc.

[0090] The third lens group G3 consists of a biconvex positive lens L31. The image plane I is positioned on the image side of the third lens group G3.

[0091] Table 2 below lists the specifications of the imaging lens according to the second embodiment. The first surface is the entrance pupil plane P of the imaging lens.

[0092] (Table 2) [Overall Specifications] f=201.00 FNO=10.05 NA=0.05 Bf=109.11 TL=350.00 DA=150.00 FDN=32.00 [Lens Specifications] Face number RD nd νd θgF 1 ∞ 150.00 2 96.572 12.65 1.45600 91.37 3 -1109.978 26.76 4 45.609 6.61 1.45600 91.37 5 579.024 0.20 6 40.424 4.01 1.61750 30.83 0.6231 7 61.797 3.00 1.73800 32.33 8 30.170 6.82 9 -77.424 9.49 1.59270 35.27 0.5935 10 73.813 17.73 11 2014.458 3.61 1.85025 30.05 12 -114.386 Bf [Lens group data] Group starting plane focal length G1 2 103.23 G2 9 -62.30 G3 11 127.40

[0093] Figure 6 shows the various aberrations (spherical aberration, field curvature, and distortion) of the imaging lens according to the second embodiment. Figure 7 shows the lateral chromatic aberration (transverse chromatic aberration) of the imaging lens according to the second embodiment. Figure 8 shows the coma aberration (meridional coma aberration and sagittal coma aberration) of the imaging lens according to the second embodiment. From each aberration diagram, it can be seen that the imaging lens according to the second embodiment has excellent optical performance, with various aberrations, including chromatic aberration, well corrected over a wide wavelength range.

[0094] (Third embodiment) The third embodiment will be described using Figures 9 to 12 and Table 3. Figure 9 is a cross-sectional view showing the configuration of the imaging lens according to the third embodiment. The imaging lens IL(3) according to the third embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, which are arranged in order from the object side along the optical axis.

[0095] The first lens group G1 consists of a biconvex positive lens L11 arranged in order from the object side along the optical axis, a positive meniscus lens L12 with its convex surface facing the object side, and a cemented lens formed by joining a biconvex positive lens L13 and a biconcave negative lens L14. The positive lens L13 of the cemented lens in the first lens group G1 corresponds to a positive lens that satisfies the aforementioned condition (1), etc.

[0096] The second lens group G2 consists of a biconcave negative lens L21. The negative lens L21 in the second lens group G2 corresponds to a negative lens that satisfies the aforementioned condition (5), etc.

[0097] The third lens group G3 consists of a biconvex positive lens L31. The image plane I is positioned on the image side of the third lens group G3.

[0098] Table 3 below lists the specifications of the imaging lens according to the third embodiment. The first surface is the entrance pupil plane P of the imaging lens.

[0099] (Table 3) [Overall Specifications] f=200.25 FNO=8.01 NA=0.06 Bf=100.00 TL=321.62 DA=130.00 FDN=32.00 [Lens Specifications] Face number RD nd νd θgF 1 ∞ 130.00 2 61.153 7.64 1.43425 94.77 3 -5880.256 0.30 4 76.472 5.20 1.56908 71.34 5 198.298 0.30 6 111.442 7.19 1.66382 27.35 0.6319 7 -112.886 3.00 1.73800 32.33 8 115.027 20.21 9 -382.558 5.00 1.75575 24.71 0.6290 10 44.607 37.79 11 141.268 5.00 1.85025 30.05 12 -449.497 Bf [Lens group data] Group starting plane focal length G1 2 87.81 G2 9 -52.60 G3 11 126.91

[0100] Figure 10 shows the various aberrations (spherical aberration, field curvature, and distortion) of the imaging lens according to the third embodiment. Figure 11 shows the lateral chromatic aberration (transverse chromatic aberration) of the imaging lens according to the third embodiment. Figure 12 shows the coma aberration (meridional coma aberration and sagittal coma aberration) of the imaging lens according to the third embodiment. From each aberration diagram, it can be seen that the imaging lens according to the third embodiment has excellent optical performance, with various aberrations, including chromatic aberration, well corrected over a wide wavelength range.

[0101] (Fourth embodiment) The fourth embodiment will be described using Figures 13 to 16 and Table 4. Figure 13 is a cross-sectional view showing the configuration of the imaging lens according to the fourth embodiment. The imaging lens IL(4) according to the fourth embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, which are arranged in order from the object side along the optical axis.

[0102] The first lens group G1 consists of a biconvex positive lens L11, a positive meniscus lens L12 with its convex surface facing the object, and a cemented lens formed by joining a positive meniscus lens L13 with its concave surface facing the object and a biconcave negative lens L14, all arranged in order from the object side along the optical axis. The positive meniscus lens L13 of the cemented lens in the first lens group G1 corresponds to a positive lens that satisfies the aforementioned condition (1), etc.

[0103] The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object. The negative meniscus lens L21 in the second lens group G2 corresponds to a negative lens that satisfies the aforementioned condition (5), etc.

[0104] The third lens group G3 consists of a positive meniscus lens L31 with its convex surface facing the object. The image plane I is positioned on the image side of the third lens group G3.

[0105] Table 4 below lists the specifications of the imaging lens according to the fourth embodiment. The first surface is the entrance pupil plane P of the imaging lens.

[0106] (Table 4) [Overall Specifications] f=200.50 FNO=6.68 NA=0.07 Bf=80.00 TL=348.66 DA=160.00 FDN=25.00 [Lens Specifications] Face number RD nd νd θgF 1 ∞ 160.00 2 78.259 10.55 1.45600 91.37 3 -286.156 0.30 4 65.866 6.60 1.45600 91.37 5 286.969 6.00 6 -573.131 4.65 1.66382 27.35 0.6319 7 -114.403 10.82 1.67300 38.26 8 75.339 37.67 9 63.694 4.64 1.61750 30.83 0.6231 10 41.142 22.43 11 76.078 5.00 1.85025 30.05 12 130.046 Bf [Lens group data] Group starting plane focal length G1 2 192.28 G2 9 -204.21 G3 11 206.81

[0107] Figure 14 shows the various aberrations (spherical aberration, field curvature, and distortion) of the imaging lens according to the fourth embodiment. Figure 15 shows the lateral chromatic aberration (transverse chromatic aberration) of the imaging lens according to the fourth embodiment. Figure 16 shows the coma aberration (meridional coma aberration and sagittal coma aberration) of the imaging lens according to the fourth embodiment. From each aberration diagram, it can be seen that the imaging lens according to the fourth embodiment has excellent optical performance, with various aberrations, including chromatic aberration, well corrected over a wide wavelength range.

[0108] (Fifth example) The fifth embodiment will be described using Figures 17 to 20 and Table 5. Figure 17 is a cross-sectional view showing the configuration of the imaging lens according to the fifth embodiment. The imaging lens IL(5) according to the fifth embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, which are arranged in order from the object side along the optical axis.

[0109] The first lens group G1 consists of a biconvex positive lens L11, a positive meniscus lens L12 with its convex surface facing the object, and a cemented lens formed by joining a positive meniscus lens L13 with its concave surface facing the object and a biconcave negative lens L14, all arranged in order from the object side along the optical axis. The positive meniscus lens L13 of the cemented lens in the first lens group G1 corresponds to a positive lens that satisfies the aforementioned condition (1), etc.

[0110] The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object. The negative meniscus lens L21 in the second lens group G2 corresponds to a negative lens that satisfies the aforementioned condition (5), etc.

[0111] The third lens group G3 consists of a biconvex positive lens L31. The image plane I is positioned on the image side of the third lens group G3.

[0112] Table 5 below lists the specifications of the imaging lens according to the fifth embodiment. The first surface is the entrance pupil plane P of the imaging lens.

[0113] (Table 5) [Overall Specifications] f=200.25 FNO=8.01 NA=0.06 Bf=149.89 TL=327.69 DA=140.00 FDN=25.00 [Lens Specifications] Face number RD nd νd θgF 1 ∞ 140.00 2 50.458 7.00 1.45600 91.37 3 -1015.705 0.30 4 50.531 5.00 1.45600 91.37 5 242.282 3.00 6 -418.199 4.50 1.75575 24.71 0.6290 7 -78.557 3.00 1.67300 38.26 8 48.197 4.00 9 2824.698 4.00 1.61750 30.83 0.6231 10 56.230 3.00 11 117.967 4.00 1.85025 30.05 12 -236.827 Bf [Lens group data] Group starting plane focal length G1 2 204.84 G2 9 -92.96 G3 11 93.10

[0114] Figure 18 shows the various aberrations (spherical aberration, field curvature, and distortion) of the imaging lens according to the fifth embodiment. Figure 19 shows the lateral chromatic aberration (transverse chromatic aberration) of the imaging lens according to the fifth embodiment. Figure 20 shows the coma aberration (meridional coma aberration and sagittal coma aberration) of the imaging lens according to the fifth embodiment. From each aberration diagram, it can be seen that the imaging lens according to the fifth embodiment has excellent optical performance, with various aberrations, including chromatic aberration, well corrected over a wide wavelength range.

[0115] Next, the table of [Conditional Expression Corresponding Values] is shown below. This table summarizes the values ​​corresponding to each conditional expression (1) to (13) for all examples (Examples 1 to 5). Conditional expression (1) -0.002×(νdP-35)+0.602-θgFP<0 Condition (2) 23 < νdP < 65 Condition (3) 1.55 <ndP<1.79 Conditional expression (4) 0.4 <fP / f<1.2 Conditional expression (5) -0.0033×(νdN-35)+0.593-θgFN<0 Conditional expression (6) 20<νdN<37 Conditional expression (7) ndN<1.78 Condition (8) -1.1 <fN / f<-0.2 Conditional expression (9) 0.2 <Bf / TL<0.6 Condition (10) 0.45 <f1 / f3<2.4 Conditional expression (11) -2.5 <f1 / f2<-0.6 Conditional expression (12) 0.3 <DA / TL<0.6 Conditional expression (13) 0.1 <FDN / f<0.18

[0116] [Conditional Expression Corresponding Values] (Examples 1-3) Conditional expression First example Second example Third example (1) -0.0146 -0.0128 -0.0146 (2) 27.35 30.83 27.35 (3) 1.6638 1.6175 1.6638 (4) 0.50 0.88 0.43 (5) -0.0020 -0.0014 -0.0020 (6) 24.71 35.27 24.71 (7) 1.7558 1.5927 1.7558 (8) -0.34 -0.31 -0.26 (9) 0.25 0.31 0.31 (10) 0.53 0.81 0.69 (11) -1.40 -1.66 -1.67 (12) 0.46 0.43 0.40 (13) 0.12 0.16 0.16 [Conditional Expression Corresponding Values] (Examples 4-5) Conditional expression, 4th example, 5th example (1) -0.0146 -0.0064 (2) 27.35 24.71 (3) 1.6638 1.7558 (4) 1.07 0.64 (5) -0.0163 -0.0163 (6) 30.83 30.83 (7) 1.6175 1.6175 (8) -1.02 -0.46 (9) 0.23 0.46 (10) 0.93 2.20 (11) -0.94 -2.20 (12) 0.46 0.43 (13) 0.12 0.12

[0117] According to the above embodiments, it is possible to realize an imaging lens in which chromatic aberration is well corrected over a wide wavelength range, and a microscope device having this imaging lens.

[0118] Herein, the above embodiments are merely examples of this embodiment, and this embodiment is not limited to these.

[0119] In each of the above embodiments, the second lens group G2 is composed of a single lens having negative refractive power, but is not limited to this, and may be composed of a single cemented lens having negative refractive power. The third lens group G3 is composed of a single lens having positive refractive power, but is not limited to this, and may be composed of a single cemented lens having positive refractive power.

[0120] In each of the above embodiments, one positive lens (L13) in the imaging lens IL corresponds to a positive lens that satisfies the aforementioned condition (1), etc. However, it is not limited to this, and multiple positive lenses in the imaging lens IL may correspond to positive lenses that satisfy the aforementioned condition (1), etc. [Explanation of Symbols]

[0121] G1 First lens group G2 Second lens group G3 3rd lens group I Image plane P Entrance pupil plane

Claims

1. An imaging lens for a microscope that forms an image from light from the objective lens, An imaging lens having a negative lens and a positive lens that satisfies the following condition. -0.002×(νdP-35)+0.602-θgFP<0 23 < νdP < 65 However, νdP: Abbe number of the positive lens θgFP: This is the partial dispersion ratio of the positive lens, and is defined by the following equation, where ngP is the refractive index of the positive lens with respect to the g line, nFP is the refractive index of the positive lens with respect to the F line, and nCP is the refractive index of the positive lens with respect to the C line. θgFP=(ngP-nFP) / (nFP-nCP)

2. An imaging lens for a microscope that forms an image from light from the objective lens, An imaging lens having a positive lens and a negative lens that satisfies the following condition. -0.0033×(νdN-35)+0.593-θgFN<0 20 < νdN < 37 However, νdN: Abbe number of the negative lens θgFN: This is the partial dispersion ratio of the negative lens, and is defined by the following equation, where ngN is the refractive index of the negative lens with respect to the g line, nFN is the refractive index of the negative lens with respect to the F line, and nCN is the refractive index of the negative lens with respect to the C line. θgFN=(ngN-nFN) / (nFN-nCN)

3. The imaging lens according to claim 1, wherein the positive lens is the third lens positioned from the object side.

4. The imaging lens according to claim 2, wherein the negative lens is the lens positioned furthest towards the image side among the negative lenses.

5. The imaging lens according to claim 1 or 3, wherein the positive lens satisfies the following condition. 1.55<ndP<1.79 However, ndP: refractive index of the positive lens with respect to the d line.

6. The imaging lens according to claim 2 or 4, wherein the negative lens satisfies the following condition. ndN < 1.78 However, ndN: refractive index of the negative lens with respect to the d line.

7. The imaging lens according to claim 1, wherein the positive lens satisfies the following condition. 0.4<fP / f<1.2 However, fP: focal length of the positive lens. f: Focal length of the imaging lens

8. The imaging lens according to claim 2, wherein the negative lens satisfies the following condition. -1.1<fN / f<-0.2 However, fN: focal length of the negative lens. f: Focal length of the imaging lens

9. An imaging lens according to claim 1 or 2 that satisfies the following conditional expression. 0.2<Bf / TL<0.6 However, Bf: Back focus of the imaging lens TL: Total length of the imaging lens

10. It consists of a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, arranged in order from the objective lens side. The second lens group consists of one lens component having negative refractive power, The imaging lens according to claim 1 or 2, wherein the third lens group comprises one lens component having positive refractive power.

11. The imaging lens according to claim 10, satisfying the following conditional expression. 0.45<f1 / f3<2.4 However, f1: focal length of the first lens group f3: Focal length of the third lens group

12. The imaging lens according to claim 10, satisfying the following conditional expression. -2.5<f1 / f2<-0.6 However, f1: focal length of the first lens group f2: Focal length of the second lens group

13. A microscope apparatus having an objective lens that receives light from an object and converts it into parallel light, and an imaging lens according to claim 1 or 2.

14. The microscope apparatus according to claim 13, satisfying the following conditional expression. 0.3<DA / TL<0.6 However, DA: distance along the optical axis from the image-side lens surface of the objective lens to the object-side lens surface of the imaging lens. TL: Total length of the imaging lens

15. The microscope apparatus according to claim 13, satisfying the following conditional expression. 0.1<FDN / f<0.18 However, FDN: Field of view of the microscope device. f: Focal length of the imaging lens

Images