JP2003090945A - Lens holding device and objective lens for microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens holding device capable of preventing the occurrence of a flaw caused by the mutual interference of lenses and being easily handled in manufacturing work, and to provide an objective lens for a microscope equipped with the lens holding device. SOLUTION: This lens holding device constituted by assembling lens frames 11 and 12 holding the lens 1 and 2 in a lens barrel 10 is constituted so that the clearance A1 of the superposed part of the lens frames in a radial direction satisfies A1 <B1 to the clearance B1 of the mutual lens surfaces adjacent to each other in the radial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens holding device suitable for a high precision objective lens and the like, and more particularly to a structure of a lens frame holding a lens to be incorporated in a lens barrel.

[0002]

2. Description of the Related Art Generally, in the case of holding a lens with high accuracy like an objective lens, a structure in which the lens is directly fitted in a lens barrel is not adopted, but as shown in FIG. A lens holding device for holding the lens is used. FIG. 6 shows a general lens holding device. In an objective lens of a microscope or the like, the eccentricity error of each lens group has a great influence on the optical performance, so that the lens groups 101, 102, 103 are shown.
Are incorporated in the lens frames 111, 112, 113 for holding the respective lenses so as to minimize the accuracy of the optical core. As a result, the optical center of each lens with respect to the lens barrel 120 can maintain a certain accuracy, and a lens holding device (objective lens) satisfying the optical performance is obtained.

[0003]

However, the conventional lens holding device described above has the following problems. That is, if the distance C on the optical axis between the lenses in FIG. 6 is small, there is a risk that the lenses may interfere with each other during assembly. Further, for example, as shown in FIG. 7, when the lens spacing is close to the optical axis as well as the optical axis, the risk of interference between the lenses increases. Figure 7
Lens 1 separated by a distance C in the thrust direction at the center of the lens
The case where 02 and 103 have almost the same radius of curvature is shown. The minimum clearance in the direction (radial direction) perpendicular to the optical axes of the lenses 102 and 103 is the clearance B.

Considering these schematically, in FIG. 8, the lens frame 112 holding the lens 102 is the lens 10
A slight movement in the radial direction indicated by the arrow with respect to the lens frame 113 holding 3 is frequently performed in handling in the manufacturing work. For example, as shown in FIG. 9, when the lens is displaced by X in the arrow direction, the lenses interfere with each other at the interference portion indicated by the broken line. In this case, unlike the metal lens frames, the lens surface is often scratched, often resulting in poor performance and appearance. In particular, in the case of a convex lens like the lens 103, a relatively soft glass material such as CaF ₂ (fluorite) is often used because of its optical design.
If there is even a small amount of interference, it often causes scratches, often resulting in defects. Moreover, even if it is not actually defective, such a handling is very inconvenient in the manufacturing work, and thus the productivity is very poor.

In particular, a microscope objective unit using a wavelength in the ultraviolet region has more lenses than a microscope objective unit using a wavelength in the visible region. The reason why the number of lenses increases is that ordinary glass does not pass light having a wavelength of 300 nm or less, and is therefore limited to glass materials such as fluorite and quartz that transmit light having a wavelength of 300 nm or less. Therefore, there is a disadvantage in correcting chromatic aberration. In addition, when the lenses are bonded to each other using a bonding agent (adhesive) for the purpose of correcting chromatic aberration, there arises a problem that the bonding agent (adhesive) is deteriorated by UV light and the transmittance is lowered. Therefore, it is preferable that the respective lenses that perform chromatic aberration correction be arranged at predetermined intervals. However, if the lens interval is widened, the effect of correcting chromatic aberration is diminished, so it is necessary to dispose a convex lens and a concave lens of different media in close proximity to each other.

For the above reasons, the objective units for microscopes using wavelengths in the ultraviolet region are often constructed so that their lenses are very close to each other. It should be noted that 0.58 <Rp / Rn <1.65 is a condition for making the radii of curvature of the surfaces of the lenses facing each other substantially the same. As long as the radius of curvature of each surface of each lens facing each other satisfies the above-mentioned conditions, it becomes possible to suitably correct various aberrations including chromatic aberration. Further, if this condition is exceeded, it becomes difficult to correct chromatic aberration in particular.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the invention according to claim 1, 2 or 3 is to prevent the occurrence of scratches due to the interference between lenses, and to handle it in the manufacturing process. Another object of the present invention is to provide an easy-to-use lens holding device and an objective lens for a microscope equipped with the lens holding device.

[0008]

In order to solve the above problems, the invention according to claim 1 is a lens holding device in which a lens frame holding a lens is incorporated in a lens barrel, and two lens frames adjacent to each other are provided. Has a fitting portion for fitting with each other in the optical axis direction of the lens, a radial clearance A of the fitting portion in the radial direction orthogonal to the optical axis of the lens, and the lenses held by the two lens frames, respectively. The radial clearance B between the lens surfaces is such that A <B.

The invention according to claim 2 is a lens holding device in which a lens frame holding a lens is incorporated in a lens barrel.
Two lens frames adjacent to each other have a fitting portion that fits in the optical axis direction of the lens, a radial clearance A orthogonal to the optical axis of the lens of the fitting portion, and the two mirrors. A radial clearance B between the lens surfaces of the lenses held by the frame is A <B, the optical axis clearance between the lenses is 0.5 mm or less, and the lenses are adjacent to each other. When the radius of curvature of the positive power surface of the lens surface is Rp and the radius of curvature of the negative power surface is Rn, 0.58 <Rp / Rn <1.65.

The invention according to claim 3 is an objective lens for a microscope, comprising the lens holding device according to claim 1 or 2.

In the lens holding device according to the first aspect of the present invention, two lens frames adjacent to each other have a fitting portion that fits in the optical axis direction of the lens, and the fitting portion is provided with the light of the lens. The radial clearance A orthogonal to the axis and the radial clearance B between the lens surfaces of the lenses held by the two lens frames are configured so that A <B. Even if they are displaced in the radial direction, the clearance A of the portion of the lens frame that holds the lens that overlaps in the radial direction is smaller than the radial clearance B between the lens surfaces, so the movement of the lens is restricted by the clearance A between the lens frames. However, the lenses do not move any further, and the lenses do not interfere with each other.

In the lens holding device according to the second aspect of the present invention, two lens frames adjacent to each other have a fitting portion that fits in the optical axis direction of the lens, and the fitting portion holds the light of the lens. A radial clearance A orthogonal to the axis and a radial clearance B between the lens surfaces of the lenses held by the two lens frames are configured so that A <B, and the optical axes of the lenses are aligned with each other. Is 0.5 mm or less, and Rp is the radius of curvature of the surface of positive power among adjacent lens surfaces and Rn is the radius of curvature of the surface of negative power, 0.58 <Rp / Rn <1. By setting 65, the distance between adjacent lenses is small, the difference in radius of curvature is small, and the interference between lenses is avoided even under the condition that interference between lenses in the radial direction easily occurs.

In the objective lens for a microscope according to a third aspect of the present invention, the lens holding device according to the first or second aspect is incorporated in the objective lens for a microscope without interference between the lenses.

[0014]

DETAILED DESCRIPTION OF THE INVENTION Specific embodiments will be described below.

(Embodiment 1) FIG. 1 is a block diagram of a lens holding device having a two-group structure, and FIG. 2 is an explanatory diagram of a deviation amount between a front group frame and a rear group frame of the lens holding device. In FIG. 1, the front lens group 1 and the rear lens group 2 have radii of curvature that are close to each other, and the radius of curvature Rp of the positive power surface of the front lens group 1 is 10 mm, and the rear lens group is 1 mm. Lens 2
The radius of curvature Rn of the surface of negative power of 10.5 mm, the thrust interval C ₁ as a clearance in the optical axis direction is 0.5 m
m. Front group frame 1 as a lens frame for holding this optical system
1 and the rear group frame 12 are fitted in the lens barrel 10, but overlap each other in the optical axis direction in the radial direction (fitting portion 11).
a, 12a), which has a clearance A _{1 in the} radial direction. Further, due to the thrust distance C ₁ between the lenses, a clearance B ₁ exists in the radial direction between the lenses. At this time, the clearance A ₁ between the front group frame 11 and the rear group frame 12 is set so that A ₁ <B ₁ .

Next, the operation of the lens holding device having the above structure in the framework will be described. As shown in FIG. 1, the radial clearance A ₁ between the front group frame 11 and the rear group frame 12
If there is, before the front group frame 11 and the rear group frame 12 are assembled into the lens barrel 10, as shown in FIG. 2, the front group frame 11 has a maximum clearance A ₁ with respect to the rear group frame 12. Although it is movable in the radial direction, the amount of radial deviation that exceeds the clearance A ₁ is restricted. In this case, as shown in FIG. 1, the front lens group 1 and the rear lens group 2 have a margin in the radial direction by (B ₁ −A ₁ ), and the lenses do not interfere with each other.

Further, Rp = 10, Rn = 10.5, C ₁
= 0.5, Rp / Rn is 0.952, and 0.58 <Rp / Rn <1.65 in claim 2.
The condition of is satisfied. That is, among the radii of curvature of the lens surfaces that are close to each other, the radius of curvature of the convex surface is a value slightly smaller than the radius of curvature of the concave surface, which is a value close to the intermediate value of the conditions under which the lenses easily interfere with each other.

According to this embodiment, since the front group frame 11 and the rear group frame 12 regulate the amount of deviation in the radial direction by the fitting portion, the lenses having a small thrust interval and a similar radius of curvature are provided. It is possible to prevent the occurrence of scratches due to the interference of the, and facilitate the handling in the manufacturing work.

(Second Embodiment) FIG. 3 shows the second embodiment and is a structural diagram of a lens holding device having a three-group structure. In FIG. 3, the first-group lens 21, the second-group lens 22, and the third-group lens 23 are optics whose radiuses of curvature of lens surfaces that are close to each other are close to each other, and have a small thrust interval C ₂ as a clearance in the optical axis direction. It is a system. First-group frame 31, second-group frame 32, and 3 as mirror frames for holding this optical system
The group frame 33 is fitted in the lens barrel 30, but is a portion (fitting portions 31a, 32a, 32) overlapping each other in the radial direction.
b, 33a), and the fitting portions 32b, 33a of the second group frame 32 and the third group frame 33 have a clearance A _{2 in the} radial direction thereof. In addition, the second group lens 22 and the third group lens 2
3, there is a thrust interval C ₂ and, correspondingly, there is a clearance B ₂ in the radial direction between the lenses. At this time, the clearance A ₂ between the second group frame 32 and the third group frame 33 is set so that A ₂ <B ₂ .

Next, the operation of the lens holding device having the above-mentioned three-group structure in the framework is the same as that of the first embodiment, and therefore its explanation is omitted.

According to the present embodiment, even with the three-group structure, the same effect as in the first embodiment can be obtained. Further, even if the lens holding device has a large number of configurations of four or more groups, the same is true, and the above-mentioned structural dimensions may be ensured for the adjacent lens surfaces.

(Third Embodiment) FIG. 4 shows a third embodiment of the lens holding device having a two-group structure. In FIG. 4, the front lens group 41 and the rear lens group 42 have radii of curvature that are close to each other, and the radii of curvature of the positive power surfaces of the front lens group 41 are Rp ₁ =
3.0 mm, the radius of curvature of the surface of the rear lens group 42 having negative power Rn ₁ = 4.7 mm, and the thrust interval C ₃ = 0.5 mm as a clearance in the optical axis direction. The front group frame 51 and the rear group frame 52 as a lens frame for holding this optical system are fitted to the lens barrel 50, but there are portions (fitting portions 51a, 52a) overlapping each other in the radial direction, It has a clearance A ₃ in its radial direction. Further, due to the thrust distance C ₃ between the lenses, there is a clearance B ₃ in the radial direction between the lenses. At this time, the front group frame 5
The clearance A ₃ between 1 and the rear group frame 52 is set so that A ₃ <B ₃ .

Next, the operation of the frame of the lens holding device having the above structure will be described. As shown in FIG. 4, the radial clearance A ₃ between the front group frame 51 and the rear group frame 52.
If there is, before the front group frame 51 and the rear group frame 52 are assembled into the lens barrel 50, the front group frame 51 is movable with respect to the rear group frame 52 in the radial direction by a maximum clearance A _3. However, the amount of radial deviation of clearance A ₃ or more is restricted. In this case, as in the first embodiment, the front lens group 41 and the rear lens group 42 are moved in the radial direction by (B ₃ -A
₃ ) There is a margin, and the lenses do not interfere with each other.

In addition, Rp₁= 4.7, Rn₁= 3.0,
C_Three= 0.5, Rp ₁/ Rn₁Is 1.5
66, which is 0.58 <Rp / Rn <in claim 2.
The condition of 1.65 is satisfied. In other words,
The radius of curvature of the convex surface is the radius of curvature of the concave surface.
It is a value larger than the radius, and Rp / Rn is between lenses
Shows a value near the upper critical value under conditions where
It

According to the present embodiment, also in the lens holding device incorporating the optical system in which the value of Rp / Rn is in the vicinity of the upper limit critical value and the lenses are likely to interfere with each other, the first embodiment is also provided. The same effect as can be obtained.

(Fourth Embodiment) FIG. 5 shows a fourth embodiment.
FIG. 3 is a configuration diagram of a lens holding device having a two-group configuration. In Figure 5
The front lens group 61 and the rear lens group 62 are
The radii of curvature of adjacent lens surfaces are similar to each other.
The radius of curvature Rp of the surface of the front lens group 61 having a positive power._Two=
5.8 mm, radius of curvature of surface of negative power of rear lens group 62
Rn_Two= 8.6 mm, as the clearance in the optical axis direction
Thrust interval C_Four= 0.1 mm. On the optical axis
Thrust interval C_FourIs the dimensional most in this optical system.
It is getting narrower. Before as a lens frame to hold this optical system
The group frame 71 and the rear group frame 72 are fitted to the lens barrel 70.
Are parts that overlap each other in the radial direction (fitting parts 71a,
72a), and the clearance A in the radial direction_Four
Have. Also, the thrust distance C between the lenses_FourBy
The clearance B in the radial direction between the lenses. _Four
Exists. At this time, the front group frame 51 and the rear group frame 52 are
Realance A_FourIs A _Four<B_FourTo be set.

Next, the operation of the frame of the lens holding device having the above structure will be described. As shown in FIG. 5, the radial clearance A ₄ between the front group frame 71 and the rear group frame 72.
If there is, before the front group frame 71 and the rear group frame 72 are assembled into the lens barrel 70, the front group frame 71 can be moved in the radial direction by a maximum clearance A ₄ with respect to the rear group frame 72. However, the radial deviation amount of the clearance A ₄ or more is restricted. In this case, as in the first embodiment, the front lens group 51 and the rear lens group 52 are moved in the radial direction by (B ₄ −
There is a margin of A ₄ ), and the lenses do not interfere with each other.

In addition, Rp_Two= 5.8, Rn_Two= 8.6,
C_Four= 0.1, Rp _Two/ Rn_TwoIs 0.6
74, which is 0.58 <(Rp / R in claim 2.
n) The condition <1.65 is satisfied. Ie proximity
Of the curvature radii of the lens surface, the convex curvature radius is the concave
The value is slightly smaller than the radius of curvature of
Under conditions where interference is likely to occur, Rp / Rn is close to the lower limit critical value.
Indicates the value.

According to the present embodiment, the value of Rp / Rn is in the vicinity of the lower limit critical value, and the lens holding device incorporating the optical system under the condition where the lenses easily interfere with each other is also the first embodiment. The same effect as can be obtained.

In the above, the first to fourth embodiments have explained the measures for preventing the interference between the lenses whose radiuses of curvature are close to each other, the thrust intervals are small, and the lenses are close to each other. A specific example of such a lens system is a microscope objective lens that uses wavelengths in the deep ultraviolet region. The microscope objective lens for the deep ultraviolet region has a larger number of lenses than the objective lens for the visible region. In addition, it is desirable not to use a cemented lens because the adhesive that bonds the lenses together may deteriorate in transmittance due to ultraviolet rays, but it is desirable not to use a cemented lens, but in order to eliminate the cemented lens, a convex lens and a concave lens with similar radii of curvature should be used. It will be necessary to place them very close to each other. The lens holding device of the present invention can be suitably used for such a microscope objective lens for the deep ultraviolet region. Moreover, various aberrations including chromatic aberration can be suitably corrected.

[0031]

According to the first aspect of the present invention, even if the adjacent lens surfaces are displaced in the radial direction, the clearance A of the portion of the lens frame holding the lens that overlaps in the radial direction.
Is smaller than the radial clearance B between the lens surfaces, the amount of lens deviation is the clearance A between the lens frames.
The lens holding device is regulated by, and does not move any more, and the lenses do not interfere with each other. Therefore, it is possible to obtain a lens holding device which prevents scratches and is easy to handle in manufacturing work.

According to the second aspect of the present invention, even if the adjacent lens surfaces are displaced in the radial direction, the clearance A in the portion of the lens frame holding the lens overlapping in the radial direction is the clearance in the radial direction between the lens surfaces. Since it is smaller than B, the amount of lens deviation is restricted by the clearance A between the lens frames and does not move any further, and the distance between adjacent lenses is small and the difference in radius of curvature is also small. Even under such a condition that the interference between the lenses is extremely likely to occur, the lenses do not interfere with each other, and it is possible to obtain a lens holding device which prevents the occurrence of scratches and is easy to handle in the manufacturing operation.

According to the third aspect of the present invention, by incorporating the lens holding device according to the first or second aspect in which there is no interference between the lenses, the occurrence of scratches is prevented, and the microscope holding device is easy to handle in manufacturing work. An objective lens can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a lens holding device having a two-group configuration according to a first embodiment.

FIG. 2 is an explanatory diagram of a deviation amount between a front group frame and a rear group frame of the lens holding device according to the first embodiment.

FIG. 3 is a configuration diagram of a lens holding device having a three-group configuration according to a second embodiment.

FIG. 4 is a configuration diagram of a lens holding device having a two-group configuration according to a third embodiment.

FIG. 5 is a configuration diagram of a lens holding device having a two-group configuration according to a fourth embodiment.

FIG. 6 is a configuration diagram of a conventional lens holding device having a three-group configuration.

FIG. 7 is an explanatory diagram of a framework work of a lens holding device having a three-group configuration according to the related art.

FIG. 8 is an explanatory diagram of problems in the conventional technique.

FIG. 9 is an explanatory diagram of problems in the conventional technique.

[Explanation of symbols]

1 front group lens 2 rear group lens 10 lens barrel 11 front group frame 12 rear group frame A ₁ clearance B ₁ clearance

Claims (3)

[Claims] 1. A lens holding device in which a lens frame holding a lens is incorporated in a lens barrel, wherein two lens frames adjacent to each other have a fitting portion that fits in the optical axis direction of the lens, The clearance A in the radial direction of the fitting portion in the radial direction orthogonal to the optical axis of the lens and the radial clearance B between the lens surfaces of the lenses held by the two lens frames are A <B. A lens holding device characterized by being configured. 2. A lens holding device in which a lens frame holding a lens is incorporated in a lens barrel, wherein two lens frames adjacent to each other have a fitting portion that fits in the optical axis direction of the lens, The clearance A in the radial direction of the fitting portion in the radial direction orthogonal to the optical axis of the lens and the radial clearance B between the lens surfaces of the lenses held by the two lens frames are A <B. When the clearance between the lenses in the optical axis direction is 0.5 mm or less and the radius of curvature of the surface of positive power among the adjacent lens surfaces is Rp and the radius of curvature of the surface of negative power is Rn, The lens holding device is characterized in that 0.58 <Rp / Rn <1.65. 3. An objective lens for a microscope, comprising the lens holding device according to claim 1.