JPH11316337A - Imaging lens - Google Patents

Abstract

[PROBLEMS] To provide an imaging lens which has been subjected to aberration correction in consideration of use in a wide wavelength range from a near ultraviolet region to a visible region and a near infrared region. In order to solve the above problem, the present invention provides an imaging lens for imaging a light beam emitted from a microscope objective lens at infinity design at a predetermined position, in order from the object side, a positive lens. A first lens component having a refracting power, a second lens component having a negative refracting power, and a third lens component having a negative refracting power. The imaging lens is characterized by satisfying the following conditional expression.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging lens for imaging a light beam emitted from a microscope objective lens designed at infinity at a predetermined position, and more particularly to a near-ultraviolet region to a visible region and a near-infrared region. The present invention relates to an imaging lens which has been subjected to aberration correction in consideration of use in a wide wavelength range up to and including the imaging lens.

[0002]

2. Description of the Related Art An image forming lens has a function of forming an image by an objective lens designed at infinity. Regarding the conventional imaging lens, Japanese Patent Publication No. 61-65050,
No. 113540, Japanese Patent No. 2,521,959.

[0003]

In the above-mentioned conventional imaging lens, the visible region (approximately 400 nm to 700 nm wavelength) is used.
In consideration of the use in d-line (567 nm) and C-line (65
6 nm), F-line (487 nm), or aberration correction in consideration of use in the wavelength range up to the g-line (435 nm) in addition to the above three wavelengths.

[0004] In recent years, however, a near-ultraviolet region or near-red region has been used, such as a confocal microscope used in a wavelength region from the near-ultraviolet region to visible light (340 to 700 nm), and focusing on a specimen by ultraviolet or infrared laser. Correction of aberrations in a wide range extending to the outer region has become extremely important. However, in the conventional imaging lens, correction of aberrations in the near-ultraviolet region or near-infrared region and transmittance of ultraviolet rays have not been considered. For this reason, when a conventional imaging lens is used in the near ultraviolet region, there is a problem that the imaging performance is significantly deteriorated due to the remaining aberration, and a sufficient light amount cannot be secured because the transmittance in the near ultraviolet region is small. Had occurred. Further, even in the near-infrared region, since the axial chromatic aberration is not corrected, the imaging position of the near-infrared light is shifted from the imaging position of the visible light, causing a problem that axial chromatic aberration occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has provided an imaging lens which has been subjected to aberration correction in consideration of use in a wide wavelength range from the near ultraviolet region to the visible region and the near infrared region. The purpose is to provide.

[0006]

In order to solve the above-mentioned problems, the present invention provides an image forming lens for forming an image of a light beam emitted from a microscope objective lens designed at infinity at a predetermined position on an object side. , In order from the first lens component having a positive refractive power, a second lens component having a negative refractive power, and a third lens component having a negative refractive power. Powerful, the following conditional expression (1)
Further, an imaging lens characterized by satisfying conditional expression (8) is constituted. (1) f1 / f <0.5 (2) | f2 |> | f1 | (3) | f3 |> | f1 | (4) n1 <n2 (5) n3 <n2 (6) ν1> 80.0 (7) ν2 <50.0 (8) ν3> 60.0 where f: focal length of the entire imaging lens f1: focal length of the first lens component f2: focal length of the second lens component f3: the above Focal length n1 of the third lens component: d-line (587.6 nm) of the first lens component
N2: d-line of the second lens component (587.6 nm)
N3: d-line of the third lens component (587.6 nm)
Ν1: Abbe number of the first lens component ν2: Abbe number of the second lens component ν3: Abbe number of the third lens component

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a first lens component having a positive refractive power, a second lens component having a negative refractive power, and a second lens component having a negative refractive power. It is desirable that the zoom lens be composed of at least three lens components of the three lens components and that the following conditional expressions (1) to (8) be satisfied.

Conditional expression (1) defines the ratio of the focal length of the first lens component to the focal length of the entire imaging lens in order to properly correct the field curvature. If the value of conditional expression (1) exceeds the upper limit, the telephoto ratio of the imaging lens is small and the refractive power of the first lens component does not become sufficiently large, so that it becomes difficult to correct the field curvature. This condition is peculiar to an imaging lens that favorably corrects aberrations up to the near ultraviolet region.

Conditional expressions (2) and (3) are conditions for appropriately correcting the field curvature, similarly to conditional expression (1), and include the focal length of the first lens component and the second lens component. And the relationship between the focal length of the first lens component and the focal length of the third lens component. If either of the conditional expressions (2) and (3) is not satisfied, the refractive power of the negative lens component becomes too strong, and it becomes difficult to correct the field curvature.

Conditional expressions (4) and (5) are conditions for favorably correcting coma aberration while correcting spherical aberration. The refractive index of the first lens component and the refractive index of the second lens component And the relationship between the refractive index of the second lens component and the refractive index of the third lens component. If either of the conditional expressions (4) and (5) is not satisfied, the distribution of the refractive power of the three lenses is lost, and it becomes difficult to satisfactorily correct spherical aberration and coma.

Conditional Expressions (6), (7) and (8) show that the chromatic aberration of magnification is good while the axial chromatic aberration is well corrected from near-ultraviolet to visible to near-infrared. And defines the range in which the Abbe number of each of the first lens component, the second lens component, and the negative lens component L3 should be. Conditional expression (6), conditional expression (7)
If at least one of the conditional expressions (8) is not satisfied, it is difficult to satisfactorily correct both the axial chromatic aberration and the lateral chromatic aberration.

Next, in the present invention, it is desirable to include at least one piece of fluorite. By satisfying this condition, the anomalous dispersibility of fluorite and the high transmittance of the ultraviolet region are effectively used to reduce axial chromatic aberration and lateral chromatic aberration from the near ultraviolet region to the visible region and further to the near infrared region. Correction can be made well. Next, in the present invention, it is desirable to include at least one sheet of quartz glass. By satisfying this condition, while effectively utilizing the high transmittance of the quartz glass, it is used as a concave lens by utilizing the flint dispersion of the quartz glass, and the axial chromatic aberration and the lateral chromatic aberration are favorably corrected. be able to.

[0013]

FIG. 1 is a sectional view of an optical system according to a first embodiment of the present invention. The first embodiment of the present invention includes, in order from the object side, a biconvex first lens component, a meniscus-shaped second lens component with a concave surface facing the object side, and a meniscus-shaped second lens component with a convex surface facing the object side. This is a three-group, three-element configuration including three lens components. The focal length of the entire imaging lens is 160 mm.

Table 1 below shows specifications of the first embodiment when the focal length is normalized to 100. f is the standardized focal length of the entire imaging lens, F is the F number, r is the radius of curvature of each surface, d is the thickness and air space of each lens, nd is the refractive index of each lens, and νd is each lens Represents the Abbe number of
The d-line (587.6 nm) is the reference wavelength for the refractive index and Abbe number. D0 is the distance from the exit pupil plane of the objective lens to the most object side surface of the imaging lens. [Table 1 Example 1] f = 100, F / 10.0 Surface number rd nd νd (0) 80.00 (d0) (1) 26.123 3.44 1.4339 95.25 (2) -59.711 0.16 (3) -49.711 3.13 1.5481 45.87 ( 4) -140.481 0.19 (5) 26.498 2.12 1.4585 67.85 (6) 17.799 87.96 FIG. 2 shows various aberration diagrams at the d-line which is the reference wavelength of the first embodiment. However, a solid line in the astigmatism diagram represents a sagittal image plane, and a broken line represents a meridional image plane. Further FIG.
2 shows a spherical aberration diagram and a magnification chromatic aberration diagram at d, C, F, g, A, t, and i lines. At this time, the wavelength of the C line is 65
6.3 nm, the wavelength of the F line is 486.1 nm, the wavelength of the g line is 435.8 nm, the wavelength of the A line is 768.2 nm, the wavelength of the t line is 1014 nm, and the wavelength of the i line is 365.0 nm.

According to these, in the first embodiment, the respective aberrations are satisfactorily corrected, and the axial chromatic aberration and the chromatic aberration of magnification are satisfactorily corrected in a wide wavelength range from the near ultraviolet region to the near infrared region. You can see that there is. Next, FIG. 4 shows a sectional view of an optical system according to a second embodiment of the present invention. Embodiment 2 of the present invention
In order from the object side, a cemented convex lens having a positive refractive power as a whole, comprising a biconvex first lens component, a meniscus-shaped second lens component with a concave surface facing the object side, and a convex surface facing the object side It has a two-element, three-element configuration consisting of a meniscus third lens component.

Table 2 below shows specifications of the second embodiment when the focal length is normalized to 100. f is the standardized focal length of the entire imaging lens, F is the F number, r is the radius of curvature of each surface, d is the thickness and air space of each lens, nd is the refractive index of each lens, and νd is each lens Represents the Abbe number of
The d-line (587.6 nm) is the reference wavelength for the refractive index and Abbe number. D0 is the distance from the exit pupil plane of the objective lens to the most object side surface of the imaging lens. [Table 2 Example 2] f = 100, F / 10.0 Surface number rd nd νd (0) 80.00 (d0) (1) 32.542 3.44 1.4339 95.25 (2) -51.334 1.88 1.5481 45.87 (4) -243.036 0.19 ( 5) 23.634 3.13 1.4585 67.85 (6) 18.589 88.39 FIG. 5 shows various aberration diagrams at the d-line which is the reference wavelength of the first embodiment. However, a solid line in the astigmatism diagram represents a sagittal image plane, and a broken line represents a meridional image plane. Further FIG.
2 shows a spherical aberration diagram and a magnification chromatic aberration diagram at d, C, F, g, A, t, and i lines. At this time, the wavelength of the C line is 65
6.3 nm, the wavelength of the F line is 486.1 nm, the wavelength of the g line is 435.8 nm, the wavelength of the A line is 768.2 nm, the wavelength of the t line is 1014 nm, and the wavelength of the i line is 365.0 nm.

According to these, in the second embodiment, each aberration is satisfactorily corrected, and axial chromatic aberration and lateral chromatic aberration are satisfactorily corrected in a wide wavelength range from the near ultraviolet region to the near infrared region. You can see that there is.

[0018]

As described above, according to the present invention, with a very simple structure, chromatic aberration is excellently corrected from the near ultraviolet region to the visible region and the near ultraviolet region, and spherical aberration, astigmatism,
It is possible to obtain an imaging lens in which distortion, coma, and field curvature are well corrected.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an optical system according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing an optical system according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating various aberrations at the reference wavelength d-line according to the first embodiment.

FIG. 4 is a diagram showing spherical aberration and chromatic aberration of magnification at d, C, F, g, A, t, and i lines in Example 1.

FIG. 5 is a diagram illustrating various aberrations at a reference wavelength d-line in Example 2.

FIG. 6 is a diagram illustrating spherical aberration and chromatic aberration of magnification at d, C, F, g, A, t, and i lines in Example 2.

[Explanation of symbols]

 L1 First lens component L2 Second lens component L3 Third lens component

Claims (3)

[Claims] 1. An imaging lens for imaging a light beam emitted from a microscope objective lens designed at infinity at a predetermined position, comprising a first lens component having a positive refractive power in order from the object side; It is composed of at least three lens components, a second lens component having a negative refractive power and a third lens component having a negative refractive power, has a positive refractive power as a whole, and has the following conditional expression (1):
And an imaging lens characterized by satisfying conditional expression (8). (1) f1 / f <0.5 (2) | f2 |> | f1 | (3) | f3 |> | f1 | (4) n1 <n2 (5) n3 <n2 (6) ν1> 80.0 (7) ν2 <50.0 (8) ν3> 60.0 where f: focal length of the entire imaging lens f1: focal length of the first lens component f2: focal length of the second lens component f3: the above Focal length n1 of the third lens component: d-line (587.6 nm) of the first lens component
N2: d-line of the second lens component (587.6 nm)
N3: d-line of the third lens component (587.6 nm)
Ν1: Abbe number of the first lens component ν2: Abbe number of the second lens component ν3: Abbe number of the third lens component 2. The imaging lens according to claim 1, wherein the imaging lens includes at least one fluorite. 3. The imaging lens according to claim 1, wherein the imaging lens includes at least one piece of quartz glass.
An imaging lens according to item 1.