JPH095622A - Inverted image lens - Google Patents

Abstract

PURPOSE: To provide an inverted image lens which is well corrected of various aberrations and more particularly curvature of field, astigmatism, etc., as an observation optical system without degrading spherical aberrations, etc., as an illumination optical system. CONSTITUTION: The first face 1a on the side of the eye to be examined of the inverted image lens 1 consisting of a single biconvex lens and the second face 1b on an inspector side are aspherical faces asymmetrical with each other. The displacements in the optical axis direction of both faces with respect to the displacement Y of the direction perpendicular to the optical axis with the vertex of the first face 1a and second face 1b as the original, respectively defined as X1 and X2 the focal length of the inverted image lens, defined as (f) and the refractive index to (d) rays, defined as (n), are -0.4<=Z<=0.2 in a range of 0<Y<=0.7×f when Z=(|X1 |-|X2 |)/(|X1 |+|X2 |)/n is set. The conditions |Zmin -Zmax |<=0.08 are satisfied when the values of Z are respectively defined as Z,, and Zmax , at Y=0.1×f and Y=0.7×f.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inversion lens.

[0002]

2. Description of the Related Art An inversion image lens has a function as a condenser lens that illuminates a fundus after once condensing a light flux from an illumination light source near a pupil of an eye to be examined, and an illuminated fundus retina part in the air. It has a function as an imaging lens that an examiner observes after forming an image as a fundus image. An example of the former will be described with reference to FIG. 7. Illumination light from the illumination light source 2 is incident on the eye 7 to be inspected through the condenser lens 3, the slit 4, the imaging lens 5, the mirror 6 and the inversion lens 1 to be irradiated. The fundus of the optometry 7 is illuminated. An example of the latter will be described with reference to FIG. 8. Light from the subject's eye 7 is formed as an aerial image 8 of the fundus by the inversion lens 1.
This aerial image 8 of the fundus of the eye is observed through the slit lamp objective lens 9. The aerial image 8 of the fundus formed by the inversion lens 1 may be observed by the naked eye.
Observation using a slit lamp biological microscope or the like is also performed. Further, in the examination of the anterior segment and the like, the inversion lens 1 may be used as a magnifying glass. As a conventionally known inversion lens, for example, there is one disclosed in US Pat. No. 5,333,017.

[0003]

In order to observe the eye to be inspected comfortably, it is necessary to correct spherical aberration, coma aberration, etc. as an illumination optical system, and further, a fundus image of the eye to be inspected in the air. In order to form an image with high accuracy, various aberrations as an observation optical system, especially field curvature aberration, astigmatism, etc. must be sufficiently corrected. However, since the inversion lens is a single lens, it is difficult to correct these aberrations at the same time. The inversion image lens disclosed in the above-mentioned U.S. Pat. No. 5,837,086 is also well corrected for spherical aberration as an illumination optical system, but it is not always necessary to correct various aberrations as an observation optical system, particularly field curvature aberration and astigmatism. It wasn't enough. Therefore, the present invention provides an inversion lens in which various aberrations as an observation optical system, in particular, field curvature, astigmatism, etc. are well corrected without causing deterioration of spherical aberration as an illumination optical system. Further, it is an object of the present invention to provide an inversion image lens in which the above-mentioned various aberrations are satisfactorily corrected when the refractive power is 55 dpt or more.

[0004]

In order to solve the above-mentioned problems, the present invention provides an inversion image lens composed of a single biconvex lens, which comprises a first surface on the eye side and a second surface on the examiner side. Are asymmetrical aspherical surfaces, and the displacement amounts in the optical axis direction of both surfaces with respect to the displacement amount Y in the direction perpendicular to the optical axis with the vertices of the first surface and the second surface as origins are X ₁ and X ₂ , respectively. When the focal length of the inversion image lens is f and the refractive index for the d-line is n, and Z = (| X ₁ | − | X ₂ |) / (| X ₁ | + | X ₂ |) / n, 0 In the range of Y ≦ 0.7 × f, −0.4 ≦ Z ≦ 0.2 (1), and Z of Y = 0.1 × f and Y = 0.7 × f is satisfied. There is provided an inversion image lens characterized by satisfying a condition of | Z _min −Z _max | ≦ 0.08 (2), where Z _min and Z _max are values.

[0005]

The conditional expression (1) defines the shape of the inversion image lens according to the present invention, that is, the ratio of the displacement amount in the X direction in each Y direction of the first surface and the second surface, that is, the first surface. Face and second
It shows the balance of the surface shapes. Conditional expression (1)
If the upper limit of is exceeded, the power of the first surface becomes too large, while the power of the second surface becomes too small. With such a shape, field curvature aberration, astigmatism, etc. worsen, and spherical aberration as an illumination optical system worsens, so that the illumination light is not sufficiently condensed and it is difficult to sufficiently illuminate the fundus. Become. Conditional expression (1)
Below the lower limit, the power of the first surface becomes too small and the power of the second surface becomes too large.
With such a shape, not only the image surface tilts in the plus direction, but also the meridional image surface in particular tilts greatly, and astigmatism increases. Further, coma is also generated, which is not preferable. On the other hand, if the value is much lower than the lower limit, the spherical aberration of the illumination optical system is deteriorated, and it becomes difficult to illuminate the fundus sufficiently. If the lower limit of conditional expression (1) is set to −0.3 and the upper limit is set to 0.12, various aberrations can be corrected better. Further, if the lower limit value is -0.26 and the upper limit value is 0.08,
Aberrations can be corrected even better.

Conditional expression (2) is a comparison of the balance of the shapes of the first surface and the second surface near the optical axis and near the outermost periphery of the lens. The shape satisfying this expression means that the shape balance between the first surface and the second surface of the lens does not change much between the optical axis and the lens outermost periphery. If the conditional expression (2) is not satisfied, astigmatism will increase and spherical aberration of the illumination optical system will worsen, which is not preferable. The limit value of conditional expression (2) is set to 0.
If it is set to 072, various aberrations can be corrected more favorably, and if the limit value is set to 0.065, various aberrations can be further corrected.

Therefore, by satisfying the above conditional expressions (1) and (2), when functioning as an illumination optical system, spherical aberration is corrected so that the fundus is illuminated well, and at the same time as an observation optical system. When functioning, various aberrations, particularly field curvature and astigmatism, are well corrected. Further, in the aspherical shape of the present invention, since the curvature becomes smaller toward the periphery of the lens, chromatic aberration due to prism deflection is reduced, and the outer diameter and effective diameter of the lens can be increased,
As a result, a large field of view can be taken. Therefore, with the inversion lens of the present invention, it is possible to illuminate the fundus of the eye to be examined sufficiently evenly, and observe the fundus image of the subject's eye in which field curvature aberration, astigmatism, etc. are well corrected.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the inversion image lens according to the present invention will be described below with reference to the drawings. As shown in FIG. 1, the inversion lens 1 of each example is composed of a single biconvex lens, and the first surface 1a on the eye side and the second surface 1b on the examiner side are asymmetrical aspherical surfaces. Has been formed. The aspherical shapes of both surfaces 1a and 1b are rotationally symmetric aspherical surfaces represented by the following equation.

[0009]

[Equation 1] k: conic constant X: distance measured from the apex in the optical axis direction Y: distance measured from the apex in the direction perpendicular to the optical axis C ₀ : 1 / r (r = apex curvature radius of aspherical surface) C ₂ , C ₄ , _{C 6, C 8, C 10} : 2 -order 10-order aspherical coefficients, however, although the above equation is here may generally well known as representing the aspherical aspherical shape according to the present invention,
It is not meant to be limited to those represented by the above formula.

Tables 1 to 4 below show Examples 1 to 1, respectively.
4 shows the specifications and the value of conditional expression (2). Further, FIG. 2 illustrates the value of the conditional expression (1). In Tables 1 to 4, f is the focal length of the inversion lens, r ₁ is the radius of curvature of the apex of the first surface, r ₂ is the radius of curvature of the apex of the second surface, D is the surface spacing, k is the conic constant, and C is
₂ , C ₄ , C ₆ , C ₈ and C ₁₀ are second-order to tenth-order aspheric coefficients,
n _d and ν _d represent the refractive index and Abbe number of the optical material for the d-line, respectively.

[0011]

[Table 1] [Lens Data] f = 14 (72dpt) n d 1.517 D 11.0 ν d 64.1 [ Lens surfaces Data] second surface the first surface _{r 1 15.1 r 2 -10.3 k 1} -1.93 k 2 -0.96 C ₂ 0.00 C ₂ 0.00 C ₄ -0.34 x 10 ^-5 C ₄ -0.91 x 10 ^-5 C ₆ 0.74 x 10 ^-7 C ₆ 0.00 C ₈ 0.86 x 10 ^-10 C ₈ 0.00 C ₁₀ -0.26 x 10 ^-11 C ₁₀ 0.00 [conditional expression (2)] | Z _min −Z _max | = 0.0014

[0012]

[Table 2] [Lens Data] f = 14 (72dpt) n d 1.589 D 10.5 ν d 61.1 [ Lens surfaces Data] second surface the first surface _{r 1 16.5 r 2 -12.4 k 1} -1.3 k 2 -1.7 C ₂ 0.00 C ₂ 0.00 C ₄ 0.57 x 10 ^-5 C ₄ -0.50 x 10 ^-5 C ₆ -0.15 x 10 ^-7 C ₆ 0.00 C ₈ 0.27 x 10 ^-9 C ₈ 0.00 C ₁₀ -0.12 x 10 ^-11 C ₁₀ 0.00 [conditional expression (2)] | Z _min −Z _max | = 0.0326

[0013]

[Table 3] [Lens Data] f = 14 (72dpt) n d 1.713 D 10.5 ν d 53.9 [ Lens surfaces Data] second surface the first surface _{r 1 28.1 r 2 -12.9 k 1} 0.16 k 2 -0.81 C ₂ 0.00 C ₂ 0.00 C ₄ 0.57 x 10 ^-5 C ₄ 0.17 x 10 ^-4 C ₆ -0.15 x 10 ^-7 C ₆ 0.11 x 10 ^-6 C ₈ 0.64 x 10 ^-9 C ₈ 0.00 C ₁₀ -0.34 x 10 ^-11 C ₁₀ -0.16 × 10 ^-11 [conditional expression (2)] | Z _min −Z _max | = 0.0589

[0014]

[Table 4] [Lens Data] f = 7.1 (140dpt) n d 1.589 D 5.5 ν d 61.1 [ Lens surfaces Data] second surface the first surface _{r 1 8.5 r 2 -6.3 k 1} -1.3 k 2 -1.7 C ₂ 0.00 C ₂ 0.00 C ₄ 0.4 x 10 ^-4 C ₄ -0.36 x 10 ^-4 C ₆ -0.4 x 10 ^-6 C ₆ 0.00 C ₈ 0.3 x 10 ^-7 C ₈ 0.00 C ₁₀ -0.5 x 10 ^-9 C ₁₀ 0.00 [conditional expression (2)] | Z _min −Z _max | = 0.0307

3 to 6 show various aberrations of Examples 1 to 4, respectively. In each figure, (A) represents spherical aberration when functioning as an illumination optical system, that is, when ray tracing is performed from the examiner side. Further, (B) and (C) represent spherical aberration and astigmatism on the observation image plane when functioning as an observation optical system, that is, when ray tracing is performed from the eye side to be examined.
In each figure, F _NO. Is the F number, ω is the angle of view, d is the d line,
F indicates the F line and C indicates the C line. In the diagram of astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each figure, by satisfying conditional expression (1), and further satisfying conditional expression (2),
It can be seen that various aberrations are well corrected.

[0016]

As described above, according to the present invention, while illuminating the fundus of the subject sufficiently, various aberrations of the observation image plane, particularly the field curvature aberration, which greatly affect the comfortable observation of the fundus. It is possible to obtain an inversion lens in which astigmatism and astigmatism are well corrected.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic aspherical shape of an inversion image lens of the present invention and a coordinate system defining the shapes of a first surface (a) and a second surface (b).

FIG. 2 is a diagram showing values of conditional expression (1) in Examples 1 to 4.

FIG. 3 is a diagram showing various aberrations of Example 1.

FIG. 4 is a diagram of various types of aberration of Example 2.

FIG. 5 is a diagram showing various types of aberration in Example 3.

FIG. 6 is a diagram showing various types of aberration in Example 4.

FIG. 7 is a schematic diagram showing an inversion image lens when it functions as one element of an illumination optical system using a slit lamp.

FIG. 8 is a schematic diagram showing an inversion lens when it functions as one element of an observation optical system.

[Explanation of symbols]

1 ... Inverting image lens 1a ... 1st surface 1
b ... Second surface

Claims (2)

[Claims] 1. An inversion lens composed of a single biconvex lens, wherein the first surface on the eye side and the second surface on the examiner side are asymmetrical aspherical surfaces, and the first surface and the second surface are asymmetrical. Let X ₁ and X ₂ be the displacements in the direction of the optical axis on both sides with respect to the displacement Y in the direction perpendicular to the optical axis with the apex of the origin as the origin, and let the focal length of the inversion lens be f and the refractive index for the d line be n. , Z = (| X ₁ | − | X ₂ |) / (| X ₁ | + | X ₂ |) / n, in the range of 0 <Y ≦ 0.7 × f, −0.4 ≦ Z ≦ 0.2 (1), and letting Z values at Y = 0.1 × f and Y = 0.7 × f be Z _min and Z _max , respectively | Z _Min- Z _max | ≦ 0.08 Inverting image lens characterized by satisfying the condition (2). 2. The image lens according to claim 1, wherein the refractive power is in the range of 55 to 150 dpt.