Patent Publication Number: US-2023152565-A1

Title: Microscope objective lens, microscope device, and microscope optical system

Description:
TECHNICAL FIELD 
     The present invention relates to microscope objective lenses, microscope devices, and microscope optical systems. 
     TECHNICAL BACKGROUND 
     In recent years, various kinds of objective lenses have been proposed for microscopes having a wide field of view (for example, refer to Patent literature 1). Such objective lenses are required to have high resolution while keeping a wide field of view. 
     PRIOR ARTS LIST 
     Patent Document 
     
         
         Patent literature 1: Japanese Laid-Open Patent Publication No. 2016-85335(A) 
       
    
     SUMMARY OF THE INVENTION 
     A microscope objective lens according to the present invention comprises, in order from an object side: a first lens group that has positive refractive power and converts light flux from an object into convergent light flux; and a second lens group that has negative refractive power and receives the convergent light flux from the first lens group, wherein 
     the following conditional expressions are satisfied: 
       14.0≤ NA×f  
 
       1.0&lt; H 1/ H 0 
     where NA: the numerical aperture of the microscope objective lens, 
     f: the focal length of the microscope objective lens, 
     H1: the maximum height of a marginal ray from an on-axis object point in the first lens group, and 
     H0: the height of the marginal ray at a lens surface closest to an image in the second lens group. 
     A microscope device according to the present invention comprises the above microscope objective lens. 
     A microscope optical system according to the present invention comprises the above microscope objective lens, and an image formation lens that forms an image from light from the microscope objective lens. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a cross-sectional diagram showing the configuration of a microscope objective lens according to a first example; 
         FIG.  2    is a diagram showing several kinds of aberration of the microscope objective lens according to the first example; 
         FIG.  3    is a cross-sectional diagram showing the configuration of a microscope objective lens according to a second example; 
         FIG.  4    is a diagram showing several kinds of aberration of the microscope objective lens according to the second example; 
         FIG.  5    is a cross-sectional diagram showing the configuration of a microscope objective lens according to a third example; 
         FIG.  6    is a diagram showing several kinds of aberration of the microscope objective lens according to the third example; 
         FIG.  7    is a cross-sectional diagram showing the configuration of a microscope objective lens according to a fourth example; 
         FIG.  8    is a diagram showing several kinds of aberration of the microscope objective lens according to the fourth example; 
         FIG.  9    is a cross-sectional diagram showing the configuration of an image formation lens; 
         FIG.  10    is a schematic configuration diagram showing a microscope optical system; and 
         FIG.  11    is a schematic configuration diagram showing a fluorescence microscope which is an example of a microscope device. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, a microscope objective lens, microscope device, and microscope optical system of each embodiment will be described with reference to the figures. Each embodiment describes a microscope objective lens, microscope device, and microscope optical system having a wide field of view and high resolution. 
     First, a microscope objective lens according to a first embodiment will be described. As an example of a microscope objective lens OL according to the first embodiment, a microscope objective lens OL ( 1 ) shown in  FIG.  1    comprises, in order from the object side, a first lens group G 1  having positive refractive power and a second lens group G 2  having negative refractive power. The first lens group G 1  collects divergent light flux from an object Ob and converts it into convergent light flux. The second lens group G 2  receives the convergent light flux from the first lens group G 1 . The second lens group G 2  may be practically configured to convert the convergent light flux from the first lens group G 1  into parallel light flux. Note that in  FIGS.  1 ,  3 ,  5 ,  7 , and  10   , the object Ob is an object point on the optical axis (in other words, an on-axis object point). 
     The microscope objective lens OL according to the first embodiment satisfies the following conditional expression (1) and conditional expression (2): 
       14.0≤ NA×f   (1)
 
       1.0&lt; H 1/ H 0  (2)
 
     where NA: the numerical aperture of the microscope objective lens OL, 
     f: the focal length of the microscope objective lens OL, 
     H1: the maximum height of the marginal ray from the on-axis object point (Ob) in the first lens group G 1 , and 
     H0: the height of the marginal ray at the lens surface closest to the image in the second lens group G 2 . 
     In the first embodiment, by satisfying conditional expression (1) and conditional expression (2), it is possible to provide a microscope objective lens having a wide field of view and high resolution. The microscope objective lens OL according to the first embodiment may be a microscope objective lens OL ( 2 ) shown in  FIG.  3   , a microscope objective lens OL ( 3 ) shown in  FIG.  5   , or a microscope objective lens OL ( 4 ) shown in  FIG.  7   . 
     Conditional expression (1) defines the relationship between the numerical aperture of the microscope objective lens OL and the focal length of the microscope objective lens OL. By satisfying conditional expression (1), it is possible to increase the resolution while keeping a wide field of view. Note that the unit of the lower limit of conditional expression (1) is [mm]. 
     If the corresponding value of conditional expression (1) is smaller than the lower limit, in order to increase the numerical aperture of the microscope objective lens OL, the focal length of the microscope objective lens OL needs to be decreased, and this would narrow a field of view of the microscope objective lens OL. To ensure the effects of the present embodiment, the lower limit of conditional expression (1) may preferably be 15.0 [mm]. In addition, to ensure the effects of the present embodiment, the upper limit of conditional expression (1) may preferably be smaller than or equal to 20.0 [mm]. 
     Conditional expression (2) defines the relationship between the maximum height of the marginal ray from the on-axis object point (Ob) in the first lens group G 1  and the height of the marginal ray at the lens surface closest to the image in the second lens group G 2 . By satisfying conditional expression (2), it is possible to favorably correct the axial aberration such as the spherical aberration and the longitudinal chromatic aberration in the first lens group G 1 , and it is possible to favorably correct the off-axis aberration such as the field curves and the coma aberration in the second lens group G 2 . Note that in each embodiment, the marginal ray is the ray that is emitted from the on-axis object point (Ob) and passes through the edge of the entrance pupil (exit pupil) (in other words, the ray with which the numerical aperture is largest). 
     If the corresponding value of conditional expression (2) is smaller than the lower limit, the effect of correcting the axial aberration in the first lens group G 1  is small, and thus, the burden of the aberration correction in the second lens group G 2  is large. This makes it difficult to achieve both correction of the axial aberration and correction of the off-axis aberration. To ensure the effects of the present embodiment, the lower limit of conditional expression (2) may preferably be 1.05. In addition, to ensure the effects of the present embodiment, the upper limit of conditional expression (2) may preferably be smaller than 1.5. 
     The microscope objective lens OL according to the first embodiment may satisfy the following conditional expression (3): 
       0.45≤ L 1/ TL≤ 0.75  (3),
 
     where L1: the distance on an optical axis from a lens surface closest to the object in the first lens group G 1  to a lens surface at which the height of the marginal ray from the on-axis object point (Ob) largest in the first lens group G 1 , and 
     TL: the distance on the optical axis from the lens surface closest to the object in the first lens group G 1  to the lens surface closest to the image in the second lens group G 2 . 
     Conditional expression (3) defines the relationship between the distance on the optical axis from the lens surface closest to the object in the first lens group G 1  to the lens surface at which the height of the marginal ray is largest in the first lens group G 1  and the distance on the optical axis from the lens surface closest to the object in the first lens group G 1  to the lens surface closest to the image in the second lens group G 2 . By satisfying conditional expression (3), it is possible to favorably correct the axial aberration such as the spherical aberration and the longitudinal chromatic aberration in the first lens group G 1 . 
     If the corresponding value of conditional expression (3) is smaller than the lower limit, the power of lenses on the object side in the first lens group G 1  is high, and this would cause higher-order axial aberration. To ensure the effects of the present embodiment, the lower limit of conditional expression (3) may preferably be 0.5. 
     If the corresponding value of conditional expression (3) is larger than the upper limit, in order to cause the light sufficiently converged by the first lens group G 1  to enter the second lens group G 2 , the power of the lenses located closer to the image needs to be higher than the lens surface at which the height of the marginal ray is largest in the first lens group G 1 , and this would cause higher-order axial aberration. To ensure the effects of the present embodiment, the upper limit of conditional expression (3) may preferably be 0.7. 
     In the microscope objective lens OL according to the first embodiment, the second lens group G 2  may comprise, in order from the object side, a first lens component with a concave lens surface on an image side and a second lens component with a concave lens surface on the object side and satisfy the following conditional expression (4): 
       0.75≤ L 2/ TL≤ 0.90  (4),
 
     where L2: the distance on an optical axis from a lens surface closest to the object in the first lens group G 1  to one lens surface, out of the lens surface on the image side of the first lens component and the lens surface on the object side of the second lens component, the height of the marginal ray from the on-axis object point (Ob) at the one lens surface being smaller than at the other, and 
     TL: the distance on the optical axis from the lens surface closest to the object in the first lens group G 1  to the lens surface closest to the image in the second lens group G 2 . 
     Conditional expression (4) defines the relationship between the distance on the optical axis from the lens surface closest to the object in the first lens group G 1  to the one lens surface, out of the lens surface on the image side of the first lens component and the lens surface on the object side of the second lens component, at which the height of the marginal ray from the on-axis object point (Ob) is smaller than at the other and the distance on the optical axis from the lens surface closest to the object in the first lens group G 1  to the lens surface closest to the image in the second lens group G 2 . By satisfying conditional expression (4), it is possible to favorably correct the off-axis aberration such as the field curves and the coma aberration in the second lens group G 2 . Note that in each embodiment, a lens component means a simple lens or a cemented lens. The first lens component may be located closest to the object in the second lens group G 2 , and the second lens component may be located next to and on the image side of the first lens component. 
     If the corresponding value of conditional expression (4) is smaller than the lower limit, the power of the lenses located between the lens surface at which the height of the marginal ray is largest and the lens surface at which the height of the marginal ray is smallest needs to be high, and this would cause higher-order off-axis aberration. 
     If the corresponding value of conditional expression (4) is larger than the upper limit, the negative power of lenses on the image side of the second lens group G 2  needs to be higher, and this would cause higher-order off-axis aberration. To ensure the effects of the present embodiment, the upper liza it of conditional expression (4) may preferably be 0.8. 
     The microscope objective lens OL according to the first embodiment may satisfy the following conditional expression (5): 
       0.75&lt; f 1/ f&lt; 1.20  (5),
 
     where f1: the focal length of the first lens group G 1 . 
     Conditional expression (5) defines the relationship between the focal length of the first lens group G 1  and the focal length of the microscope objective lens OL. By satisfying conditional expression (5), it is possible to favorably correct the axial aberration such as the spherical aberration and the longitudinal chromatic aberration in the first lens group G 1 . 
     If the corresponding value of conditional expression (5) is smaller than the lower limit, the refractive power of the first lens group G 1  is too high, and this would cause higher-order axial aberration. 
     If the corresponding value of conditional expression (5) is larger than the upper limit, it would cause higher-order axial aberration. To ensure the effects of the present embodiment, the upper limit of conditional expression (5) may preferably be 0.9. 
     Next, a microscope objective lens according to a second embodiment will be described. As an example of a microscope objective lens OL according to the second embodiment, a microscope objective lens OL ( 1 ) shown in  FIG.  1    comprises, in order from the object side, a first lens group G 1  having positive refractive power and a second lens group G 2  having negative refractive power. The first lens group G 1  collects divergent light flux from an object Ob and converts it into convergent light flux. The second lens group G 2  receives the convergent light flux from the first lens group G 1 . The second lens group G 2  may be practically configured to convert the convergent light flux from the first lens group G 1  into parallel light flux. 
     The microscope objective lens OL according to the second embodiment satisfies the foregoing conditional expression (1) and conditional expression (3). In the second embodiment, by satisfying conditional expression (1) and conditional expression (3), it is possible to provide a microscope objective lens having a wide field of view and high resolution. The microscope objective lens OL according to the second embodiment may be the microscope objective lens OL ( 2 ) shown in  FIG.  3   , the microscope objective lens OL ( 3 ) shown in  FIG.  5   , or the microscope objective lens OL ( 4 ) shown in  FIG.  7   . The microscope objective lens OL according to the second embodiment may satisfy the foregoing conditional expression (2), may satisfy the foregoing conditional expression (4), and may satisfy the foregoing conditional expression (5). 
     Next, a microscope objective lens according to a third embodiment will be described. As an example of a microscope objective lens OL according to the third embodiment, the microscope objective lens OL ( 1 ) shown in  FIG.  1    comprises, in order from the object side, a first lens group G 1  having positive refractive power and a second lens group G 2  having negative refractive power. The first lens group G 1  collects divergent light flux from an object Ob and converts it into convergent light flux. The second lens group G 2  receives the convergent light flux from the first lens group G 1 . The second lens group G 2  comprises, in order from the object side, a first lens component having a concave lens surface on the image side and a second lens component having a concave lens surface on the object side. The second lens group G 2  may be practically configured to convert the convergent light flux from the first lens group G 1  into parallel light flux. 
     The microscope objective lens OL according to the third embodiment satisfies the foregoing conditional expression (1) and conditional expression (4). In the third embodiment, by satisfying conditional expression (1) and conditional expression (4), it is possible to provide a microscope objective lens having a wide field of view and high resolution. The microscope objective lens OL according to the third embodiment may be the microscope objective lens OL ( 2 ) shown in  FIG.  3   , the microscope objective lens OL ( 3 ) shown in  FIG.  5   , or the microscope objective lens OL ( 4 ) shown in  FIG.  7   . The microscope objective lens OL according to the third embodiment may satisfy the foregoing conditional expression (2), may satisfy the foregoing conditional expression (3), and may satisfy the foregoing conditional expression (5). 
     Next, a microscope objective lens according to a fourth embodiment will be described. As an example of a microscope objective lens OL according to the fourth embodiment, the microscope objective lens OL ( 1 ) shown in  FIG.  1    comprises, in order from the object side, a first lens group G 1  having positive refractive power and a second lens group G 2  having negative refractive power. The first lens group G 1  collects divergent light flux from an object Ob and converts it into convergent light flux. The second lens group G 2  receives the convergent light flux from the first lens group G 1 . The second lens group G 2  may be practically configured to convert the convergent light flux from the first lens group G 1  into parallel light flux. 
     The microscope objective lens OL according to the fourth embodiment satisfies the foregoing conditional expression (1) and conditional expression (5). In the fourth embodiment, by satisfying conditional expression (1) and conditional expression (5), it is possible to provide a microscope objective lens having a wide field of view and high resolution. The microscope objective lens OL according to the fourth embodiment may be the microscope objective lens OL ( 2 ) shown in  FIG.  3   , the microscope objective lens OL ( 3 ) shown in  FIG.  5   , or the microscope objective lens OL ( 4 ) shown in  FIG.  7   . The microscope objective lens OL according to the fourth embodiment may satisfy the foregoing conditional expression (2), may satisfy the foregoing conditional expression (3), or may satisfy the foregoing conditional expression (4). 
     In the microscope objective lenses OL according to the first to fourth embodiments, the first lens group G 1  may comprise at least one meniscus lens, at least one positive simple lens, and at least one cemented lens, and the cemented lens may comprise a positive lens and a negative lens. In addition, the configuration may be such that the height of the light emitted from the object point on the optical axis is largest in the first lens group G 1 . 
     In the microscope objective lenses OL according to the first to fourth embodiments, at least one of the first lens component and the second lens component included in the second lens group G 2  may be a cemented lens. The lens surface closest to the image in the second lens group G 2  may have a convex surface on the image side. 
     Next, a microscope optical system according to the present embodiments will be described. As shown in  FIG.  10   , a microscope optical system MCS according to the present embodiment comprises, in order from the object side, a microscope objective lens OL according to one of the embodiments and an image formation lens IL. The microscope objective lens OL converts light from the object Ob into parallel light. The image formation lens IL collects the light from the microscope objective lens OL and forms an image of the object on an image surface Img. The image formation lens IL collects the light from the objective lens OL and forms an image of the object Ob on the image surface Img. The image of this object Ob is observed by the observer′ eye Eye through an eyepiece EP. The image of the object Ob may be formed not only through the eyepiece EP but it may be formed again on a second image surface where an image sensor (not show) is located, for example, by using a relay lens (not shown). The microscope optical system MCS according to the present embodiment comprises a microscope objective lens OL according to one of the embodiments. This makes it possible to provide a microscope optical system having a wide field of view and high resolution. 
     Next, a microscope device according to the present embodiment will be described. As an example of a microscope device, a fluorescence microscope  100  will be described with reference to  FIG.  11   . The fluorescence microscope  100  comprises a stage  101 , a light source  111 , an illumination optical system  121 , a microscope optical system  131 , an eyepiece  141 , and an imaging device  151 . On the stage  101  is placed, for example, a sample SA held between a microscope slide (not shown) and a cover glass (not shown). The sample SA placed on the stage  101  may be contained together with immersion liquid in a sample container (not shown). The sample SA includes fluorescent substances such as a fluorescent dye. The sample SA is, for example, cells fluorescently stained in advance or the like. 
     The light source  111  generates excitation light in a specified wavelength band. The specified wavelength band is set to a wavelength band that enables excitation of the sample SA including fluorescent substances. The excitation light emitted from the light source  111  enters the illumination optical system  121 . 
     The illumination optical system  121  illuminates the sample SA on the stage  101  with the excitation light emitted from the light source  111 . The illumination optical system  121  comprises a collimator lens  122  and a dichroic mirror  124  in order from the light source  111  side toward the sample SA side. The illumination optical system  121  comprises an objective lens  132  which is also included in the microscope optical system  131 . The collimator lens  122  collimates the excitation light emitted from the light source  111 . 
     The dichroic mirror  124  has characteristics of reflecting the excitation light from the light source  111  and transmitting the fluorescence from the sample SA. The dichroic mirror  124  reflects the excitation light from the light source  111  toward the sample SA on the stage  101 . The dichroic mirror  124  transmits fluorescence generated at the sample SA toward a mirror  133  of the microscope optical system  131 . Between the dichroic mirror  124  and the collimator lens  122  is arranged an excitation filter  123  that transmits the excitation light from the light source  111 . Between the dichroic mirror  124  and the mirror  133  is arranged a fluorescence filter  125  that transmits the fluorescence from the sample SA. 
     The microscope optical system  131  comprises the objective lens  132 , the mirror  133 , a first image formation lens  134 A, and a second image formation lens  134 B. The microscope optical system  131  also comprises the dichroic mirror  129  which is also included in the illumination optical system  121 . The objective lens  132  is located above the stage  101  on which the sample SA is placed so as to face the stage  101 . The objective lens  132  condenses the excitation light from the light source  111  and illuminates the sample SA on the stage  101 . The objective lens  132  receives fluorescence generated on the sample SA and converts it into parallel light. 
     The mirror  133  is, for example, configured using a half mirror having a ratio of transmittance to reflectance set to 1:1. Apart of the fluorescence incident on the mirror  133  passes through the mirror  133  and enters the first image formation lens  134 A. The fluorescence having passed through the first image formation lens  134 A forms an image on a first image surface ImgA. The observer can observe an image of the sample SA formed on the first image surface ImgA, using the eyepiece  141 . The other part of the fluorescence incident on the mirror  133  is reflected by the mirror  133  and enters the second image formation lens  134 B. The fluorescence having passed through the second image formation lens  134 B forms an image on a second image surface ImgB. At the second image surface ImgB is located an area sensor  152  of the imaging device  151 . 
     Note that the mirror  133  is not limited to a half mirror but may be configured using an optical-path switching mirror capable of selectively switching the reflection direction of light. In this case, the mirror  133  reflects the fluorescence from the sample SA alternately toward one of the first image formation lens  134 A and the second image formation lens  134 B by switching. 
     The imaging device  151  comprises an image sensor  152 . The image sensor  152  comprises an imaging device such as a COD or a CMOS. The imaging device  151  is capable of capturing an image of the sample SA formed on the second image surface ImgB by using the image sensor  152 . 
     In the fluorescence microscope  100  thus configured, the excitation light emitted from the light source  111  passes through the collimator lens  122  and becomes parallel light. The excitation light having passed through the collimator lens  122  passes through the excitation filter  123  and becomes incident on the dichroic mirror  124 . The excitation light incident on the dichroic mirror  124  is reflected on the dichroic mirror  124  and passes through the objective lens  132 . The excitation light having passed through the objective lens  132  is projected onto the sample SA on the stage  101 . With this configuration, the illumination optical system  121  illuminates the sample SA on the stage  101  with the excitation light emitted from the light source  111 . 
     The illumination with excitation light excites the fluorescent substances included in the sample SA, and fluorescence is emitted. Fluorescence from the sample SA passes through the objective lens  132  and becomes parallel light. The fluorescence having passed through the objective lens  132  becomes incident on the dichroic mirror  124 . The fluorescence incident on the dichroic mirror  124  passes through the dichroic mirror  124 , passes through the fluorescence filter  125 , and becomes incident on the mirror  133 . 
     Part of the fluorescence incident on the mirror  133  passes through the mirror  133  and enters the first image formation lens  134 A. The fluorescence having passed through the first image formation lens  134 A forms an image on the first image surface ImgA. The other part of the fluorescence incident on the mirror  133  passes through the mirror  133  and enters the second image formation lens  134 B. The fluorescence having passed through the second image formation lens  134 B forms an image on the second image surface ImgB. 
     The observer observes an image of the sample SA formed on the first image surface ImgA, using the eyepiece  141 . The imaging device  151  captures an image of the sample SA formed on the second image surface ImgB, using the image sensor  152 . This fluorescence microscope  100  comprises a microscope objective lens OL according to one of the embodiments as the objective lens  132 . This makes it possible to provide a microscope device having a wide field of view and high resolution. 
     Note that in the case in which a field of view is wide, and the resolution is high, the amount of information on an image of the sample SA obtained by the imaging device  151  is large. To deal with it, use of a time delay integration (TDI) image sensor for the image sensor  152  makes it possible to obtain an image of the sample SA in a short time. 
     The fluorescence microscope  100  has been described as an example of the microscope device according to the present embodiment, but the present disclosure is not limited to this example. For example, the microscope device according to the present embodiment may be a multiphoton excitation microscope, a light sheet microscope, a phase contrast microscope, a confocal microscope, a super resolution microscope, or the like. The fluorescence microscope  100  is not limited to an upright microscope as shown in  FIG.  11    but may be an inverted microscope. With the present embodiment, as described above, it is possible to build microscope systems having various functions. 
     EXAMPLES 
     Hereinafter, examples of the microscope objective lenses OL according to the first to fourth embodiments will be described with reference to the drawings.  FIGS.  1 ,  3 ,  5 , and  7    are cross-sectional diagrams showing the configurations of the microscope objective lenses OL (OL ( 1 ) to OL ( 4 )) according to the first to fourth examples. In  FIGS.  1 ,  3 ,  5 , and  7   , each lens group is indicated by a combination of a symbol G and a number (or an alphabet), and each lens is indicated by a combination of a symbol L and a number (or an alphabet). In this case, to avoid cumbersome situations using many kinds of symbols and numbers and using large numbers, combinations of symbols and numbers are used independently in each example to indicate lenses or others. Thus, even if a combination of the same symbol and number are used n some of the examples, it does not mean the same constituent. 
     Below are shown Tables 1 to 4, in which Table 1 shows the specification data on the first example, Table 2 on the second example, Table 3 on the third example, and Table 4 on the fourth example. In each example, to calculate aberration characteristics, d-line (wavelength λ=587.6 nm), g-line (wavelength λ=435.8 nm), C-line (wavelength λ=656.3 nm), and F-line (wavelength λ=486.1 nm) are selected. 
     In the table of [General Data], β represents the magnification, and NA represents the numerical aperture. D 0  is the working distance, which means the distance on the optical axis from the object Ob (excluding the thickness of the cover glass) to the lens surface closest to the object in the microscope objective lens OL (which is a first surface described later). The symbol f represents the focal length of the microscope objective lens OL. The symbol f1 represents the focal length of the first lens group G 1 . The symbol f2 represents the focal length of the second lens group G 2 . TL represents the distance on the optical axis from the lens surface closest to the object in the first lens group G 1  to the lens surface closest to the image in the second lens group G 2 . L1 represents the distance on the optical axis from the lens surface closest to the object in the first lens group G 1  to the lens surface at which the height of the marginal ray is largest in the first lens group G 1 . L2 represents the distance on the optical axis from the lens surface closest to the object in the first lens group G 1  to one lens surface, out of the lens surface on the image side of the first lens component and the lens surface on the object side of the second lens component in the second lens group G 2 , the height of the marginal ray being smaller at the one lens surface than at the other. H1 represents the maximum height of the marginal ray in the first lens group G 1 . H0 represents the height of the marginal ray at the lens surface closest to the image in the second lens group G 2 . 
     In the table of [Lens Data], the surface number indicates the order of the lens surface from the object side, R indicates the curvature radius corresponding to each surface number (R has a positive value if the lens surface is convex toward the object), D indicates the lens thickness or the air gap on the optical axis, corresponding to each surface number, nd indicates the refractive index of the optical material corresponding to the surface number at d-line (wavelength λ=587.6 nm), and vd indicates the Abbe number of the optical material corresponding to each surface number based on d-line. The symbol “∞” in the curvature radius indicates a flat surface or an opening. Mentioning that the refractive index of air nd=1.00000 is omitted. 
     In all the specification values below, the unit of the focal length f, curvature radius R, surface distance D, other lengths, and the like listed is generally “mm” unless otherwise specified. However, the unit is not limited to this one because the same or similar optical performance can be obtained even if an optical system is proportionally enlarged or proportionally reduced in size. 
     The explanation on the tables up to this point is common in all of the examples, and hence repetitive description will be omitted below. 
     First Example 
     A first example will be described with reference to  FIGS.  1  and  2    and Table 1.  FIG.  1    is a cross-sectional diagram showing the configuration of a microscope objective lens according to the first example. The microscope objective lens OL ( 1 ) according to the first example comprises, in order from the object side along the optical axis, a first lens group G 1  having positive refractive power and a second lens group G 2  having negative refractive power. The space between the distal end of the microscope objective lens OL ( 1 ) according to the first example and a cover glass Cv covering the object Ob is filled with air. Note that it is assumed that the refractive index of the cover glass Cv at d-line (wavelength λ=587.6 nm) is 1.52, and the thickness of the cover glass Cv is 0.17 mm. 
     The first lens group G 1  collects divergent light flux from the object Ob and converts it into convergent light flux. The first lens group G 1  comprises, in order from the object side, a negative meniscus lens L 11  with a concave surface on the object side; a positive meniscus lens L 12  with a concave surface on the object side; a first cemented lens CL 11  having a positive meniscus lens L 13  with a concave surface on the object side, a biconcave negative lens L 14 , and a biconvex positive lens L 15 , joined together; a biconvex positive lens L 16 ; and a second cemented lens CL 12  having a biconvex positive lens L 17  and a biconcave negative lens L 18  joined together. 
     The second lens group G 2  converts the convergent light flux from the first lens group G 1  into parallel light flux. The second lens group G 2  comprises, in order from the object side, a first cemented lens CL 21  having a positive meniscus lens L 21  with a convex surface on the object side and a negative meniscus lens L 22  with a convex surface on the object side, joined together; a second cemented lens CL 22  having a biconcave negative lens L 23  and a biconvex positive lens L 24  joined together; and a positive meniscus lens L 25  with a concave surface on the object side. The first cemented lens CL 21  corresponds to the first lens component in each embodiment. The second cemented lens CL 22  corresponds to the second lens component in each embodiment. 
     The following Table 1 shows the specification values of the microscope objective lens according to the first example. 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
            
               
                   
                 [General Data] 
               
               
                   
                   
               
               
                   
                 β = 10 times 
               
               
                   
                 NA = 0.75 
               
               
                   
                 D0 = 1.70 
               
               
                   
                 f = 20.00 
               
               
                   
                 f1 = 15.25 
               
               
                   
                 f2 = −140.27 
               
               
                   
                 TL = 86.84 
               
               
                   
                 L1 = 44.56 
               
               
                   
                 L2 = 65.11 
               
               
                   
                 H1 = 16.25 
               
               
                   
                 H0 = 15.01 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Data] 
               
            
           
           
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
               
               
                   
               
               
                 1 
                 −9.455 
                 7.36 
                 1.7283 
                 28.38 
               
               
                 2 
                 −20.308 
                 0.20 
               
               
                 3 
                 −72.385 
                 9.72 
                 1.5932 
                 67.90 
               
               
                 4 
                 −14.062 
                 0.20 
               
               
                 5 
                 −621.234 
                 7.73 
                 1.4560 
                 91.36 
               
               
                 6 
                 −14.527 
                 2.38 
                 1.5530 
                 55.07 
               
               
                 7 
                 86.281 
                 8.47 
                 1.4343 
                 95.02 
               
               
                 8 
                 −26.160 
                 0.50 
               
               
                 9 
                 68.673 
                 8.00 
                 1.4978 
                 82.57 
               
               
                 10 
                 −44.093 
                 0.50 
               
               
                 11 
                 25.941 
                 9.20 
                 1.4343 
                 95.02 
               
               
                 12 
                 −33.618 
                 1.87 
                 1.5530 
                 55.07 
               
               
                 13 
                 35.321 
                 0.80 
               
               
                 14 
                 32.223 
                 5.68 
                 1.5932 
                 67.90 
               
               
                 15 
                 140.892 
                 2.49 
                 1.6127 
                 44.46 
               
               
                 16 
                 17.005 
                 8.70 
               
               
                 17 
                 −14.702 
                 1.60 
                 1.6730 
                 38.26 
               
               
                 18 
                 180.493 
                 4.74 
                 1.4875 
                 70.31 
               
               
                 19 
                 −32.520 
                 1.19 
               
               
                 20 
                 −81.976 
                 5.51 
                 1.8503 
                 32.35 
               
               
                 21 
                 −25.735 
               
               
                   
               
            
           
         
       
     
       FIG.  2    is a diagram showing several kinds of aberration (spherical aberration, astigmatism, chromatic aberration of magnification, and coma aberration) of a microscope objective lens according to the first example. This diagram shows the several kinds of aberration in a state in which the microscope objective lens is combined with an image formation lens. In each aberration diagram in  FIG.  2   , NA represents the numerical aperture and Y represents the image height, and d indicates the aberration at d-line (wavelength λ=587.6 nm), g at g-line (wavelength λ=435.8 nm), C at C-line (wavelength λ=656.3 nm), and F at F-line (wavelength λ=486.1 nm). In the spherical aberration diagram, the vertical axis represents the normalized value with the maximum value of the entrance pupil diameter set to 1, and the horizontal axis represents the aberration value [mm] of each ray. In the astigmatism diagram, a solid line represents the meridional image surface for each wavelength, and a dashed line represents the sagittal image surface for each wavelength. In the astigmatism diagram, the vertical axis represents the image height [mm], and the horizontal axis represents the aberration value [mm]. In the diagram of chromatic aberration of magnification, the vertical axis represents the image height [mm], and the horizontal axis represents the aberration value [mm]. The coma aberration diagram shows the aberration value [mm] in the case in which the image height Y is 12.5 mm. Note that the aberration diagrams of each example shown below use the same symbols as those in this example, and hence, repetitive description is omitted. 
     The aberration diagrams show that each aberration is favorably corrected in the microscope objective lens according to the first example even in the case of a large numerical aperture NA, and that thus the microscope objective lens according to the first example has excellent image-forming performance. 
     Second Example 
     A second example will be described with reference to  FIGS.  3  and  4    and Table 2.  FIG.  3    is a cross-sectional diagram showing the configuration of a microscope objective lens according to the second example. The microscope objective lens OL ( 2 ) according to the second example comprises, in order from the object side, a first lens group G 1  having positive refractive power and a second lens group G 2  having negative refractive power. The space between the distal end of the microscope objective lens OL ( 2 ) according to the second example and the object Ob is filled with immersion liquid IM (water). Note that it is assumed that the refractive index of the immersion liquid IM (water) at d-line (wavelength λ=587.6 nm) is 1.33. 
     The first lens group G 1  collects divergent light flux from the object Ob and converts it into convergent light flux. The first lens group G 1  comprises, in order from the object side, a first cemented lens CL 11  having a plano-convex positive lens L 11  with a flat surface on the object side and a negative meniscus lens L 12  with a concave surface on the object side, joined together; a positive meniscus lens L 13  with a concave surface on the object side; a second cemented lens CL 12  having a biconcave negative lens L 14  and a biconvex positive lens L 15  joined together; a third cemented lens CL 13  having a biconvex positive lens L 16 , a biconcave negative lens L 17 , and a biconvex positive lens L 18 , joined together; a fourth cemented lens CL 14  having a negative meniscus lens L 19  with a convex surface on the object side and a biconvex positive lens L 120  joined together; and a biconvex positive lens L 121 . 
     The second lens group G 2  converts the convergent light flux from the first lens group G 1  into parallel light flux. The second lens group G 2  comprises, in order from the object side, a first cemented lens CL 21  having a biconvex positive lens L 21  and a biconcave negative lens L 22  joined together; and a second cemented lens CL 22  having a negative meniscus lens L 23  with a concave surface on the object side and a positive meniscus lens L 24  with a concave surface on the object side, joined together. The first cemented lens CL 21  corresponds to the first lens component in each embodiment. The second cemented lens CL 22  corresponds to the second lens component in each embodiment. 
     The following Table 2 shows the specification values of the microscope objective lens according to the second example. 
     
       
         
           
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
             
            
               
                   
                 [General Data] 
               
               
                   
                   
               
               
                   
                 β = 10 times 
               
               
                   
                 NA = 0.85 
               
               
                   
                 D0 = 2.57 
               
               
                   
                 f = 20.00 
               
               
                   
                 f1 = 16.36 
               
               
                   
                 f2 = 55.47 
               
               
                   
                 TL = 94.07 
               
               
                   
                 L1 = 62.77 
               
               
                   
                 L2 = 74.57 
               
               
                   
                 H1 = 18.36 
               
               
                   
                 H0 = 17.14 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Data] 
               
            
           
           
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
               
               
                   
               
               
                 1 
                 ∞ 
                 3.00 
                 1.4585 
                 67.85 
               
               
                 2 
                 −3.310 
                 6.00 
                 2.0010 
                 29.12 
               
               
                 3 
                 −8.975 
                 0.20 
               
               
                 4 
                 −35.409 
                 4.50 
                 1.6180 
                 63.34 
               
               
                 5 
                 −22.000 
                 0.20 
               
               
                 6 
                 −40.270 
                 1.20 
                 1.7340 
                 51.51 
               
               
                 7 
                 49.596 
                 8.00 
                 1.5691 
                 71.31 
               
               
                 8 
                 −19.999 
                 0.20 
               
               
                 9 
                 66.659 
                 7.00 
                 1.4978 
                 82.57 
               
               
                 10 
                 −39.999 
                 1.20 
                 1.6230 
                 58.12 
               
               
                 11 
                 54.987 
                 7.80 
                 1.4978 
                 82.57 
               
               
                 12 
                 −70.031 
                 0.20 
               
               
                 13 
                 284.159 
                 1.50 
                 1.8160 
                 46.62 
               
               
                 14 
                 41.499 
                 10.50 
                 1.4339 
                 95.25 
               
               
                 15 
                 −36.256 
                 0.20 
               
               
                 16 
                 74.995 
                 8.50 
                 1.4978 
                 82.57 
               
               
                 17 
                 −40.229 
                 0.30 
               
               
                 18 
                 75.627 
                 8.00 
                 1.4978 
                 82.57 
               
               
                 19 
                 −31.604 
                 3.50 
                 1.8160 
                 46.59 
               
               
                 20 
                 36.639 
                 9.00 
               
               
                 21 
                 −17.876 
                 1.50 
                 1.5407 
                 46.97 
               
               
                 22 
                 −120.465 
                 9.00 
                 1.7495 
                 35.33 
               
               
                 23 
                 −26.266 
               
               
                   
               
            
           
         
       
     
       FIG.  4    is a diagram showing several kinds of aberration (spherical aberration, astigmatism, chromatic aberration of magnification, and coma aberration) of a microscope objective lens according to the second example. The aberration diagrams show that each aberration is favorably corrected in the microscope objective lens according to the second example even in the case of a large numerical aperture NA, and that thus the micro cope objective lens according to the second example has excellent image-forming performance. 
     Third Example 
     A third example will be described with reference to  FIGS.  5  and  6    and Table 3.  FIG.  5    is a cross-sectional diagram showing the configuration of a microscope objective lens according to the third example. The microscope objective lens OL ( 3 ) according to the third example comprises, in order from the object side, a first lens group G 1  having positive refractive power and a second lens group G 2  having negative refractive power. The space between the distal end of the microscope objective lens OL ( 3 ) according to the third example and the object Ob is filled with immersion liquid IM (water). Note that it is assumed that the refractive index of the immersion liquid  1 M (water) at d-line (wavelength λ=587.6 nm) is 1.33. 
     The first lens group G 1  collects divergent light flux from the object Ob and converts it into convergent light flux. The first lens group G 1  comprises, in order from the object side, a first cemented lens CL 11  having a plano-convex positive lens L 11  with a flat surface on the object side and a negative meniscus lens L 12  with a concave surface on the object side, joined together; a positive meniscus lens L 13  with a concave surface on the object side; a second cemented lens CL 12  having a negative meniscus lens L 14  with a convex surface on the object side and a biconvex positive lens L 15  joined together; a third cemented lens CL 13  having a biconvex positive lens L 16 , a biconcave negative lens L 17 , and a biconvex positive lens L 18  joined together; a biconvex positive lens L 19 ; and a fourth cemented lens CL 14  having a biconvex positive lens L 120  and a negative meniscus lens L 121  with a concave surface on the object side, joined together. 
     The second lens group G 2  converts the convergent light flux from the first lens group G 1  into parallel light flux. The second lens group G 2  comprises, in order from the object side, a first cemented lens CL 21  having a biconvex positive lens L 21  and a biconcave negative lens L 22  joined together; and a second cemented lens CL 22  having a biconcave negative lens L 23  and a biconvex positive lens L 24  joined together. The first cemented lens CL 21  corresponds to the first lens component in each embodiment. The second cemented lens CL 22  corresponds to the second lens component in each embodiment. 
     The following Table 3 shows the specification values of the microscope objective lens according to the third example. 
     
       
         
           
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
             
            
               
                   
                 [General Data] 
               
               
                   
                   
               
               
                   
                 β = 12 times 
               
               
                   
                 NA = 1.00 
               
               
                   
                 D0 = 2.30 
               
               
                   
                 f = 16.67 
               
               
                   
                 f1 = 16.86 
               
               
                   
                 f2 = 62.06 
               
               
                   
                 TL = 95.04 
               
               
                   
                 L1 = 53.90 
               
               
                   
                 L2 = 73.55 
               
               
                   
                 H1 = 20.14 
               
               
                   
                 H0 = 16.89 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Data] 
               
            
           
           
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
               
               
                   
               
               
                 1 
                 ∞ 
                 2.00 
                 1.4585 
                 67.85 
               
               
                 2 
                 −3.501 
                 6.50 
                 1.8830 
                 40.76 
               
               
                 3 
                 −11.493 
                 0.15 
               
               
                 4 
                 −37.602 
                 5.20 
                 1.5924 
                 68.33 
               
               
                 5 
                 −13.857 
                 0.15 
               
               
                 6 
                 100.000 
                 1.50 
                 1.6935 
                 53.21 
               
               
                 7 
                 49.191 
                 7.80 
                 1.4339 
                 95.25 
               
               
                 8 
                 −26.675 
                 0.15 
               
               
                 9 
                 125.876 
                 9.20 
                 1.4978 
                 82.57 
               
               
                 10 
                 −20.736 
                 1.80 
                 1.7432 
                 49.26 
               
               
                 11 
                 63.797 
                 8.00 
                 1.4339 
                 95.25 
               
               
                 12 
                 −50.110 
                 0.15 
               
               
                 13 
                 132.395 
                 9.00 
                 1.4978 
                 82.57 
               
               
                 14 
                 −34.377 
                 0.30 
               
               
                 15 
                 44.923 
                 10.00 
                 1.4343 
                 95.02 
               
               
                 16 
                 −34.217 
                 1.20 
                 1.8160 
                 46.62 
               
               
                 17 
                 −69.507 
                 0.15 
               
               
                 18 
                 34.455 
                 6.80 
                 1.4978 
                 82.57 
               
               
                 19 
                 −66.192 
                 1.20 
                 1.7292 
                 54.61 
               
               
                 20 
                 21.128 
                 12.00 
               
               
                 21 
                 −17.007 
                 1.29 
                 1.7340 
                 51.51 
               
               
                 22 
                 434.518 
                 8.20 
                 1.8830 
                 40.76 
               
               
                 23 
                 −24.699 
               
               
                   
               
            
           
         
       
     
       FIG.  6    is a diagram showing several kinds of aberration (spherical aberration, astigmatism, chromatic aberration of magnification, and coma aberration) of a microscope objective lens according to the third example. The aberration diagrams show that each aberration is favorably corrected in the microscope objective lens according to the third example even in the case of a large numerical aperture NA, and that thus the microscope objective lens according to the third example has excellent image-forming performance. 
     Fourth Example 
     A fourth example will be described with reference to  FIGS.  7  and  8    and Table 4.  FIG.  7    is a cross-sectional diagram showing the configuration of a microscope objective lens according to the fourth example. The microscope objective lens OL ( 4 ) according to the fourth example comprises, in order from the object side, a first lens group G 1  having positive refractive power and a second lens group G 2  having negative refractive power. The space between the distal end of the microscope objective lens OL ( 4 ) according to the fourth example and the cover glass Cv covering the object Ob is filled with air. Note that it is assumed that the refractive index of the cover glass Cv at d-line (wavelength λ=587.6) is 1.52, and the thickness of the cover glass Cv is 0.17 mm. 
     The first lens group G 1  collects divergent light flux from the object Ob and converts it into convergent light flux. The first lens group G 1  comprises, in order from the object side, a negative meniscus lens L 11  with a concave surface on the object side; a positive meniscus lens L 12  with a concave surface on the object side; a first cemented lens CL 11  having a positive meniscus lens L 13  with a concave surface on the object side, a biconcave negative lens L 14 , and a biconvex positive lens L 15 , joined together; a biconvex positive lens L 16 ; and a second cemented lens CL 12  having a biconvex positive lens L 17  and a biconcave negative lens L 18  joined together. 
     The second lens group G 2  converts the convergent light flux from the first lens group G 1  into parallel light flux. The second lens group G 2  comprises, in order from the object side, a first cemented lens CL 21  having a biconvex positive lens L 21  and a biconcave negative lens L 22  joined together; a second cemented lens CL 22  having a biconcave negative lens L 23  and a biconvex positive lens L 24  joined together; and a positive meniscus lens L 25  with a concave surface on the object side. The first cemented lens CL 21  corresponds to the first lens component in each embodiment. The second cemented lens CL 22  corresponds to the second lens component in each embodiment. 
     The following Table 4 shows the specification values of the microscope objective lens according to the fourth example. 
     
       
         
           
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
             
            
               
                   
                 [General Data] 
               
               
                   
                   
               
               
                   
                 β = 10 times 
               
               
                   
                 NA = 0.80 
               
               
                   
                 D0 = 1.22 
               
               
                   
                 f = 20.00 
               
               
                   
                 f1 = 15.26 
               
               
                   
                 f2 = −184.75 
               
               
                   
                 TL = 88.47 
               
               
                   
                 L1 = 45.28 
               
               
                   
                 L2 = 66.45 
               
               
                   
                 H1 = 16.99 
               
               
                   
                 H0 = 16.02 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Data] 
               
            
           
           
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
               
               
                   
               
               
                 1 
                 −9.267 
                 6.84 
                 1.7283 
                 28.38 
               
               
                 2 
                 −21.308 
                 0.20 
               
               
                 3 
                 −50.864 
                 9.45 
                 1.5932 
                 67.90 
               
               
                 4 
                 −12.620 
                 0.20 
               
               
                 5 
                 −437.617 
                 6.93 
                 1.4560 
                 91.36 
               
               
                 6 
                 −13.531 
                 3.13 
                 1.5530 
                 55.07 
               
               
                 7 
                 505.411 
                 10.04 
                 1.4343 
                 95.02 
               
               
                 8 
                 −24.935 
                 0.50 
               
               
                 9 
                 77.838 
                 8.00 
                 1.4978 
                 82.57 
               
               
                 10 
                 −44.014 
                 0.50 
               
               
                 11 
                 27.884 
                 9.67 
                 1.4343 
                 95.02 
               
               
                 12 
                 −30.538 
                 1.90 
                 1.5530 
                 55.07 
               
               
                 13 
                 35.211 
                 0.80 
               
               
                 14 
                 33.912 
                 5.00 
                 1.5932 
                 67.90 
               
               
                 15 
                 −613.951 
                 3.30 
                 1.6127 
                 44.46 
               
               
                 16 
                 18.717 
                 8.88 
               
               
                 17 
                 −15.554 
                 1.90 
                 1.6730 
                 38.26 
               
               
                 18 
                 198.283 
                 3.95 
                 1.4875 
                 70.31 
               
               
                 19 
                 −34.136 
                 1.76 
               
               
                 20 
                 −84.972 
                 5.52 
                 1.8503 
                 32.35 
               
               
                 21 
                 −26.238 
               
               
                   
               
            
           
         
       
     
       FIG.  8    is a diagram showing several kinds of aberration (spherical aberration, astigmatism, chromatic aberration of magnification, and coma aberration) of a microscope objective lens according to the fourth example. The aberration diagrams show that each aberration is favorably corrected in the microscope objective lens according to the fourth example even in the case of a large numerical aperture NA, and that thus the microscope objective lens according to the fourth example has excellent image-forming performance. 
     Because the microscope objective lens according to each example is an infinity-corrected lens, it is combined, when used, with an image formation lens that forms an image of the object. Hence, an example of an image formation lens that is used in combination with the microscope objective lens will be described with reference to  FIG.  9    and Table 5,  FIG.  9    is a cross-sectional diagram showing the configuration of an image formation lens that is used in combination with the microscope objective lens according to each example. The diagrams of several kinds of aberration of the microscope objective lens according to each example were obtained in combination with this image formation lens. The image formation lens IL shown in  FIG.  9    comprises, in order from the object side, a first cemented lens CL 31  having a biconvex positive lens L 31 , a biconcave negative lens L 32 , and a biconvex positive lens L 33 , joined together; a biconvex positive lens L 34 ; and a second cemented lens CL 32  having a biconvex positive lens L 35  and a biconcave negative lens L 36  joined together. The image formation lens IL is located on the image side of the microscope objective lens according to each example. Note that the image surface Img is located on the image side of the second cemented lens CL 32 . The entrance pupil surface Pu of the image formation lens IL corresponds to the exit pupil surface of the infinity-corrected objective lens. 
     The following Table 5 shows the specification values of the image formation lens. Note that in the table of [Lens Data], the surface number, R, D, nd, and vd are the same as those explained in the foregoing Tables 1 to 4. 
     
       
         
           
               
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 [Lens Data] 
                   
               
            
           
           
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 1 
                 143.588 
                 8.80 
                 1.4560 
                 91.36 
               
               
                 2 
                 −94.993 
                 4.00 
                 1.5638 
                 60.71 
               
               
                 3 
                 89.827 
                 7.60 
                 1.4560 
                 91.36 
               
               
                 4 
                 −309.677 
                 114.10 
               
               
                 5 
                 116.697 
                 8.50 
                 1.6477 
                 33.73 
               
               
                 6 
                 −363.426 
                 21.00 
               
               
                 7 
                 56.818 
                 9.30 
                 1.5725 
                 57.30 
               
               
                 8 
                 −208.394 
                 15.20 
                 1.7380 
                 32.33 
               
               
                 9 
                 33.862 
                 67.04 
               
               
                   
               
            
           
         
       
     
     Next, the table of [Conditional Expression Corresponding Value] is shown below. This table shows the values corresponding to the conditional expressions (1) to (5) for all examples (the first to fourth examples) together. 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Conditional Expression(1) 
                 14.0 ≤ NA × f 
               
               
                   
                 Conditional Expression(2) 
                 1.0 &lt; H1/H0 
               
               
                   
                 Conditional Expression(3) 
                 0.45 ≤ L1/TL ≤ 0.75 
               
               
                   
                 Conditional Expression(4) 
                 0.75 ≤ L2/TL ≤ 0.90 
               
               
                   
                 Conditional Expression(5) 
                 0.75 &lt; f1/f &lt; 1.20 
               
               
                   
                   
               
            
           
         
       
     
     [Conditional Expression Corresponding Value] 
       
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                 Conditional 
                 1st 
                 2nd 
                 3rd 
                 4th 
               
               
                 Expression 
                 example 
                 example 
                 example 
                 example 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 (1) 
                 15.00 
                 17.00 
                 16.67 
                 16.00 
               
               
                 (2) 
                 1.08 
                 1.07 
                 1.19 
                 1.06 
               
               
                 (3) 
                 0.51 
                 0.66 
                 0.56 
                 0.51 
               
               
                 (4) 
                 0.75 
                 0.79 
                 0.77 
                 0.75 
               
               
                 (5) 
                 0.76 
                 0.82 
                 0.84 
                 0.76 
               
               
                   
               
            
           
         
       
     
     With each of the above examples, it is possible to achieve a microscope objective lens and microscope optical system having a wide field of view and high resolution. 
     Here, the above examples are to show specific examples of the embodiments, and hence the embodiments are not limited to these examples. 
     EXPLANATION OF NUMERALS AND CHARACTERS 
     
         
         G 1  first lens group 
         G 2  second lens group