[0055] Example 1
[0056] See figure 1 , The microscope objective lens of embodiment 1 of the present invention includes, from the object side, a first lens L1 with positive refractive power, a first lens group G1 with positive refractive power, a second lens group G5 with positive refractive power, and a second lens group G5 with positive refractive power. The third lens group G2 with negative power, the fourth lens group G3 with negative power, and the fifth lens group G4 with negative power. The first lens group G1 is used to move along the optical axis of the objective lens to change the focal length of the objective lens.
[0057] In use, the specimen is set on the object side S1 of medium O (such as a cover glass), and the light reflected by the specimen is projected on the image side S2 of medium O, and then enters the microscope objective lens and the tube lens set on the mirror side of the microscope object enters the observer’s Eyes or image sensors (not shown). When measuring different specimens, different medium O may be used. Therefore, the refractive index or thickness of the medium O will change, which will cause the image distance of the microscope to change, which will result in blurred imaging. Especially for microscope objectives with high magnification and high numerical aperture, the impact is greater. However, since the first lens group G1 is variable, the focal length of the microscope objective lens can be changed by moving the first lens group G1, thereby compensating for changes in the thickness and refractive index of the covering medium, and obtaining clear imaging.
[0058] In Embodiment 1, the first lens L1 has a meniscus shape, and the concave surface faces the object side of the microscope objective lens. The first lens L includes an object aspect S3 and an image aspect S4.
[0059] From the object side, the first lens group G1 includes biconcave negative power lenses and biconvex positive power lenses cemented with each other. The first lens group G1 includes the object side S5, the glued surface S6 and the image side S7 from the object side.
[0060] The second lens group G5 includes at least one lens. In Embodiment 1, the second lens group G5 includes a second lens L2 and a third lens L3 from the object side. The second lens L2 includes an object aspect S8 and an image aspect S9, and the third lens L3 includes an object aspect S10 and an image aspect S11.
[0061] From the object side, the third lens group G2 includes biconvex positive power lenses and biconcave negative power lenses cemented with each other. The third lens group G2 includes the object side S12, the glued surface S13 and the image side S14 from the object side.
[0062] The fourth lens group G3 from the object side includes biconvex positive power lenses and biconcave negative power lenses cemented with each other. The fourth lens group G3 includes an object aspect S15, a glued surface S16, and an image aspect S17 from the object side.
[0063] The fifth lens group G4 includes at least one lens. In Embodiment 1, the fifth lens group G4 includes biconcave negative power lenses and biconvex positive power lenses cemented with each other from the object side. The fifth lens group G4 includes the object side S18, the glued surface S19 and the image side S20 from the object side.
[0064] The fourth lens group G3 is opposite to the concave surface of the fifth lens group G4, which can effectively correct the curvature of field and make the image plane flatter.
[0065] The microscope objective meets:
[0066] 2 <2.5.
[0067] Among them, fL1 is the focal length of the first lens L1, and fobj is the focal length of the microscope objective lens.
[0068] In this way, the first lens L1 generally does not need to share too much power. In addition, if the power is too large and the focal length is small, the tolerance sensitivity of the first lens L1 will be high and it will be difficult to process. Therefore, set 2 <2.5.
[0069] The microscope objective meets:
[0070] 10 <14.
[0071] Among them, fG1 is the focal length of the first lens group G1.
[0072] In this way, the first lens group G1 is a moving lens group. If the focal length of the first lens group G1 is too large, the focal length of the microscope objective lens will change too much when the first lens group G1 moves, that is, it is sensitive to movement. It is not easy to adjust. On the other hand, it will also cause tolerance sensitive and difficult processing, so set 10
[0073] 〡fG1/fobj〡 <14.
[0074] The microscope objective meets:
[0075] 10 <25.
[0076] Among them, fG2 is the focal length of the third lens group G2.
[0077] In this way, the third lens group G2 is mainly used to control the field curvature. If the focal length is too large or too small, the field curvature cannot be better controlled. Therefore, the control is 10 <25.
[0078] The microscope objective meets:
[0079] 1.6 <4.
[0080] Among them, fG5 is the focal length of the second lens group G5.
[0081] In this way, the second lens group G5 is generally the position with the highest image height, so it needs to share more power. Therefore, if the power is small, other lenses and lens groups will share too much power. It is difficult to process, so set 〡fG5/fobj〡 <4, on the other hand, if the focal length of the second lens group G5 is too large, it will make it difficult to process, so set 1.6
[0082] The microscope objective meets:
[0083] 3mm <5mm.
[0084] Among them, D3 is the distance between the first lens group L1 and the first lens group G1, and D4 is the distance between the first lens group G1 and the second lens group G5.
[0085] In this way, D3+D4 is actually the adjustable range of the first lens group G1. If it is too small, the adjustment will be too sensitive, and if it is too large, it will cause the total length of the microscope objective lens to be too large, so the control range is 3mm <5mm. The microscope objective meets:
[0086] 1.7
[0087] 50
[0088] Among them, nd1 is the refractive index of the first lens L1 when the spectrum is at 546.07nm, and Vd is the Abbe number of the first lens L1 when the spectrum is at 546.07nm.
[0089] In this way, the ability of the first lens L1 to control aberration and control chromatic aberration can be balanced. If nd1 is too small, the aberration cannot be corrected well, and if vd1 is too small, the chromatic aberration cannot be corrected.
[0090] With this setting, the focal range of the microscope objective lens is 8-11mm, and the field of view of the image square is 22mm. The adjustable range of cover glass thickness is 0-2mm. The focal length of the tube lens used with the microscope objective lens is 160-220mm. The axial difference between the best focus point of the edge field of view of the microscope objective and the best focus point of the center field of view is less than 2λ/NA 2 , F light and C light achromatic, d light and g light axial chromatic aberration is less than 2λ/NA 2. Where λ is the central wavelength, NA is the numerical aperture of the objective lens, F represents light with a wavelength of 0.4861 μm, d represents light with a wavelength of 0.5876 μm, C represents light with a wavelength of 0.6563 μm, and g represents light with a wavelength of 0.436 μm.
[0091] In Example 1, the microscope objective meets the conditions in the following table:
[0092] Table 1
[0093]
[0094]
[0095] Among them, radius refers to the radius of curvature of the surface, and thickness refers to the axial distance from the current surface to the next surface. For example, the thickness of the surface S1 is the distance from S1 to S2, which may be the axial thickness of the medium or lens, or it may be The on-axis air gap between them. The microscope objective lens of this embodiment also satisfies:
[0096] Table 2
[0097] D1
[0098] Among them, fobj=1; NA=0.45. 〡fL1/fobj〡=2.4; 〡fG1/fobj〡=13.1; 〡fG2/fobj〡=24.8 and 〡fG5/fobj〡=2.1.
[0099] figure 2 It is a 0-field lateral aberration diagram of the microscope objective lens of Example 1, where the abscissa PY and PX represent the entrance pupil, and the ordinate EY and EX represent the lateral aberration (Y represents the meridian direction and X represents the sagittal direction). It can be seen that the aberrations are well balanced and the image quality is high. The abscissa in the figure is the normalized entrance pupil, ±5μm means that the ordinate is the maximum 5μm and the minimum is -5μm.
[0100] image 3 It is a 1-field lateral aberration diagram of the microscope objective lens of Example 1. It can be seen from the diagram that the aberration is well balanced and the image quality is high.
[0101] Figure 4 This is an axial aberration diagram of the microscope objective lens of Example 1. The ordinate in the figure represents the entrance pupil, and the abscissa represents the longitudinal aberration (in mm). From the figure, we can see that the F light and C light are achromatic, and the axial chromatic aberration of d light and g light is less than 2λ/NA. 2. Close to the semi-apochromatic level. The ordinate in the figure is the normalized entrance pupil; the abscissa represents the longitudinal aberration, the maximum is 0.005mm, and the minimum is -0.005mm.
[0102] Figure 5 For field curvature distortion diagram. The picture on the left is a field curve diagram, in which the ordinate represents the field of view, and the abscissa represents the field curvature (unit: μm). The axial difference between the best focus point of the edge field of view and the best focus point of the center field of view is less than 2λ/NA 2 , The theoretical value meets the clear field of view and the requirements of the plan objective. The ordinate in the figure is the normalized field of view; the abscissa represents the field curvature, the maximum is 2μm, and the minimum is -2μm. The picture on the right is a distortion diagram. The ordinate in the diagram represents the field of view, and the abscissa represents the distortion (percentage). It can be seen that the distortion is less than 0.3%. The ordinate in the figure is the normalized field of view; the abscissa represents the distortion, the maximum is 0.5%, and the minimum is -0.5%.
