JP4915990B2 - Eyepiece - Google Patents

Description

  The present invention relates to an eyepiece used in a telescope, binoculars, a microscope, or the like.

  In telescopes, binoculars, microscopes, and the like, eyepieces are used to further enlarge and observe an image formed by an objective lens. In these eyepieces, it goes without saying that each aberration is well corrected over a wide angle of view, and an eye relief that is long enough for comfortable observation (the most observer-side lens in eyepieces). The axial distance between the surface and the eye point) is required.

  With a general eyepiece, only about 80% of the focal length of the entire lens system can be secured as an eye relief, so an eye relief with a short focal length cannot provide a sufficient eye relief. Further, if the eye relief is increased while keeping the apparent field of view constant, an increase in the diameter of the lens system on the observer side is caused. As a result, it is also well known that the aberrations of the peripheral rays of the visual field, particularly astigmatism and distortion, are abruptly deteriorated.

Therefore, in order from the object side, a first lens group having a negative refractive power as a whole and a second lens group having a positive refractive power as a whole are disposed, and a field stop (object side of the second lens group) therebetween. 2. Description of the Related Art An eyepiece having a configuration having a focal plane is known (for example, see Patent Document 1). In the eyepiece having such a configuration, a long eye relief is ensured by disposing a (first) lens group having negative refractive power on the object side. In addition, by having the (first) lens group having a strong negative refractive power, the Petzval sum can be reduced, and the field curvature aberration and the like can be favorably corrected.
Japanese Patent No. 3518704

  However, there has been a demand for further expanding the angle of view (that is, the apparent field of view) while correcting each aberration satisfactorily for the above-described eyepiece lens.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an eyepiece that has a wide angle of view (field of view) and in which each aberration is favorably corrected over a wider angle of view.

  In order to achieve such an object, the eyepiece according to the present invention includes, in order from the object side, a first lens group having a negative refractive power as a whole and a second lens group having a positive refractive power as a whole. The object-side focal plane of the second lens group is configured to be located between the first lens group and the second lens group, and the second lens group includes a first negative lens having a concave surface facing the object side. A first bonded lens having a positive refractive power as a whole formed by bonding a first positive lens having a convex surface facing the observer side, a second positive lens, and a second negative lens are bonded. A first cemented lens, a second cemented lens having a positive refractive power and a single lens having a positive refractive power with a convex surface facing the object side. The bonded lens and single lens are moved from the object side to the observer side. The focal length of the entire lens system is f, the focal length of the first lens group is f1, the focal length of the second lens group is f2, and the first lens group and the first lens group When the air space between the two lens groups is D and the radius of curvature of the surface closest to the viewer side in the first cemented lens is R6, the following conditional expressions (1) to (4) are satisfied. Each condition is satisfied.

−4.5 ≦ f1 / f ≦ −1.1 (1)
0.3 ≦ D / f ≦ 2.5 (2)
−4.0 ≦ f1 / f2 ≦ −1.3 (3)
0.7 ≦ | R6 / f2 | ≦ 2.8 (4)

In the present invention, when the focal length of the first cemented lens is f21, and the radius of curvature of the cemented surface of the first positive lens and the first negative lens in the first cemented lens is R5. The condition represented by the following conditional expression (5) is satisfied .

  0.5 ≦ | R5 / f21 | (5)

  Furthermore, in the above-described invention, it is preferable that the first lens group includes a third bonded lens formed by bonding a third positive lens and a third negative lens.

  According to the present invention, it is possible to obtain an ocular lens having a wide angle of view (field of view) and a good correction of each aberration over a wider angle of view.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1, FIG. 3, FIG. 5, FIG. 7, and FIG. 9 are block diagrams of eyepieces EL for binoculars corresponding to the first to fifth embodiments, respectively. An eyepiece EL according to the first embodiment shown in FIG. 1 includes a first lens group G1 having a negative refractive power as a whole and a second lens having a positive refractive power as a whole, which are coaxially arranged in order from the object side. The second lens group G2 is configured such that the object-side focal plane FS is located between the first lens group G1 and the second lens group G2.

  The first lens group G1 is formed by bonding a first lens component L11 (third negative lens) that is a negative lens and a second lens component L12 (third positive lens) that is a positive lens. It is comprised from the bonding lens L1 (3rd bonding lens). In the first cemented lens L1, the first lens component L11 is positioned on the object side, and the second lens component L12 is positioned on the viewer side (eye point EP side).

  The second lens group includes a second bonded lens L2 (first bonded lens), a third bonded lens L3 (second bonded lens), and a single lens L4. Are arranged on the same axis in this order from the viewer side to the viewer side (eye point EP side). The single lens L4 is disposed with the convex surface facing the object side and has a positive refractive power. The second cemented lens L2 (first cemented lens) includes a third lens component L21 (first negative lens) that is a negative lens having a concave surface facing the object side, and a positive lens having a convex surface facing the observer side. It is formed by bonding a fourth lens component L22 (first positive lens) that is a lens, and has a positive refractive power as a whole. In the second cemented lens L2, the third lens component L21 is positioned on the object side, and the fourth lens component L22 is positioned on the viewer side (eye point EP side).

  The third cemented lens L3 (second cemented lens) includes a fifth lens component L31 (second positive lens) that is a positive lens and a sixth lens component L32 (second negative lens) that is a negative lens. And have a positive refractive power as a whole. In the third cemented lens L3, the fifth lens component L31 is positioned on the object side, and the sixth lens component L32 is positioned on the viewer side (eye point EP side).

  As in the first embodiment, the eyepiece EL of the second embodiment shown in FIG. 3 has a first lens group G1 having a negative refractive power as a whole and a second lens group G2 having a positive refractive power as a whole. And is configured. Similarly to the first embodiment, the first lens group G1 includes a first lens component L11 (third negative lens) that is a negative lens and a second lens component L12 (third positive lens) that is a positive lens. It is comprised from the 1st bonding lens L1 (3rd bonding lens) formed by bonding. Similarly to the first embodiment, the second lens group includes a second bonded lens L2 (first bonded lens), a third bonded lens L3 (second bonded lens), and a single lens L4. It is comprised.

  Similarly to the first embodiment, the second cemented lens L2 (first cemented lens) includes a third lens component L21 (first negative lens) that is a negative lens having a concave surface facing the object side. The fourth lens component L22 (first positive lens), which is a positive lens having a convex surface facing the viewer, is bonded to the third lens L3 (second bonded lens). A fifth lens component L31 (second positive lens) that is a lens and a sixth lens component L32 (second negative lens) that is a negative lens are bonded together. As described above, the eyepiece lens EL of the second embodiment has the same configuration as that of the eyepiece lens EL of the first embodiment, and the same reference numerals as those of the first embodiment are given to the respective parts, and detailed description thereof is omitted. To do.

  The eyepiece EL of the third embodiment shown in FIG. 5 includes a first lens group G1 having a negative refractive power as a whole and a second lens group G2 having a positive refractive power as a whole. The first lens group G1 is formed by bonding a first lens component L11 (third positive lens) that is a positive lens and a second lens component L12 (third negative lens) that is a negative lens. It is comprised from the bonding lens L1 (3rd bonding lens). Similarly to the first embodiment, the second lens group includes a second bonded lens L2 (first bonded lens), a third bonded lens L3 (second bonded lens), and a single lens L4. It is comprised.

  Similarly to the first embodiment, the second cemented lens L2 (first cemented lens) includes a third lens component L21 (first negative lens) that is a negative lens having a concave surface facing the object side. The fourth lens component L22 (first positive lens), which is a positive lens having a convex surface facing the viewer, is bonded to the third lens L3 (second bonded lens). A fifth lens component L31 (second positive lens) that is a lens and a sixth lens component L32 (second negative lens) that is a negative lens are bonded together. Thus, the eyepiece lens EL of the third embodiment has the same configuration as the eyepiece lens EL of the first embodiment except that the configuration of the first bonded lens L1 is slightly different. The detailed description is abbreviate | omitted with the same code | symbol.

  The eyepiece lens EL of the fourth embodiment shown in FIG. 7 includes a first lens group G1 having a negative refractive power as a whole and a second lens group G2 having a positive refractive power as a whole. Similarly to the first embodiment, the first lens group G1 includes a first lens component L11 (third negative lens) that is a negative lens and a second lens component L12 (third positive lens) that is a positive lens. It is comprised from the 1st bonding lens L1 (3rd bonding lens) formed by bonding. Similarly to the first embodiment, the second lens group includes a second bonded lens L2 (first bonded lens), a third bonded lens L3 (second bonded lens), and a single lens L4. It is comprised. Similarly to the first embodiment, the second cemented lens L2 (first cemented lens) includes a third lens component L21 (first negative lens) that is a negative lens having a concave surface facing the object side. The fourth lens component L22 (first positive lens), which is a positive lens having a convex surface facing the viewer, is bonded to the viewer.

  The third cemented lens L3 (second cemented lens) includes a fifth lens component L31 (second negative lens) that is a negative lens and a sixth lens component L32 (second positive lens) that is a positive lens. Lens) and has a positive refractive power as a whole. In the third bonded lens L3, the fifth lens component L31 is positioned on the object side, and the sixth lens component L32 is positioned on the viewer side. As described above, the eyepiece lens EL of the fourth embodiment has the same configuration as the eyepiece lens EL of the first embodiment except that the configuration of the third cemented lens L3 is slightly different. The same reference numerals as those in the case are attached and detailed description is omitted.

  As in the first embodiment, the eyepiece EL of the fifth embodiment shown in FIG. 9 includes a first lens group G1 having a negative refractive power as a whole and a second lens group G2 having a positive refractive power as a whole. And is configured. Similarly to the first embodiment, the first lens group G1 includes a first lens component L11 (third negative lens) that is a negative lens and a second lens component L12 (third positive lens) that is a positive lens. It is comprised from the 1st bonding lens L1 (3rd bonding lens) formed by bonding. Similarly to the first embodiment, the second lens group includes a second bonded lens L2 (first bonded lens), a third bonded lens L3 (second bonded lens), and a single lens L4. It is comprised.

  Similarly to the first embodiment, the second cemented lens L2 (first cemented lens) includes a third lens component L21 (first negative lens) that is a negative lens having a concave surface facing the object side. The fourth lens component L22 (first positive lens), which is a positive lens having a convex surface facing the viewer, is bonded to the third lens L3 (second bonded lens). A fifth lens component L31 (second positive lens) that is a lens and a sixth lens component L32 (second negative lens) that is a negative lens are bonded together. As described above, the eyepiece lens EL of the fifth embodiment has the same configuration as the eyepiece lens EL of the first embodiment, and the same reference numerals as those of the first embodiment are given to the respective parts, and detailed description thereof is omitted. To do.

  In the eyepiece lens EL of the first to fifth embodiments, the relationship between the lens groups will be described. Here, the focal length of the entire lens system is f, the focal length of the first lens group G1 is f1, the focal length of the second lens group G2 is f2, and the second cemented lens L2 (first cemented lens). ) Is f21. In addition, the (on-axis) air space between the first lens group G1 and the second lens group G2 is D, and the bonded surface of the third lens component L21 and the fourth lens component L22 in the second bonded lens L2. The curvature radius of 5 is R5, and the curvature radius of the surface 6 closest to the viewer side in the second bonded lens L2 is R6.

  First, if the (on-axis) air distance D between the first lens group G1 and the second lens group G2 is increased while the focal length f1 of the first lens group G1 is kept constant, the first focal length f1 is calculated from the formula of the combined focal length. Since the focal length f2 of the two-lens group G2 is increased, the eye relief and the Petzval sum work advantageously. However, in this case, since the positive refractive power of the second lens group G2 is weaker than the negative refractive power of the first lens group G1, the aberration due to the negative lens increases, and correction is difficult in the second lens group G2. Become. Further, as the air space D (on the axis) increases, the total length of the eyepiece lens EL increases, and the lens diameter of the second lens group G2 increases rapidly. On the other hand, if the air distance D is increased while keeping the focal length f2 of the second lens group G2 constant (on the axis), the focal length f1 of the first lens group G1 is increased from the formula of the combined focal length, so Petzval sum Increases, making it difficult to correct curvature of field and the like. Therefore, in each embodiment, the conditions represented by the following conditional expressions (1) to (5) are satisfied.

−4.5 ≦ f1 / f ≦ −1.1 (1)
0.3 ≦ D / f ≦ 2.5 (2)
−4.0 ≦ f1 / f2 ≦ −1.3 (3)
0.7 ≦ | R6 / f2 | ≦ 2.8 (4)
0.5 ≦ | R5 / f21 | (5)

  Conditional expression (1) defines the ratio between the focal length f1 of the first lens group G1 and the focal length f of the entire eyepiece lens EL. When f1 / f falls below the lower limit value of conditional expression (1), the absolute value of f1 increases, and the Petzval sum in the eyepiece lens EL increases in the positive direction, so that correction of field curvature aberration and astigmatism is sufficient. It becomes impossible to do it. On the other hand, if f1 / f exceeds the upper limit value of the conditional expression (1), the absolute value of f1 decreases, the negative refractive power increases, the diverging action of the first lens group G1 becomes too strong, and the second The lens diameter of the lens group G2 increases, which is not preferable. In addition, an increase in negative refractive power leads to an increase in spherical aberration in the higher order region and an increase in coma aberration. If the lower limit value of conditional expression (1) is −4.0 and the upper limit value is −1.5, more preferably, the lower limit value of conditional expression (1) is −3.8 and the upper limit value is −1. If it is .7, better results can be obtained.

  Conditional expression (2) defines the (on-axis) air gap D between the first lens group G1 and the second lens group G2. If D / f is out of the range of the conditional expression (2), the balance for correcting various aberrations generated in the first lens group G1 by the second lens group G2 is lost, and it is difficult to perform good aberration correction. Furthermore, when D / f falls below the lower limit value of the conditional expression (2), the (on-axis) air interval D between the first lens group G1 and the second lens group G2 becomes narrow, and each lens group has an image plane. Therefore, scratches and dust on the lens surface can be seen together with the observation image, which is not preferable. On the other hand, if D / f exceeds the upper limit value of the conditional expression (2), the total length of the eyepiece lens EL is increased, the lens diameter of the second lens group G2 is increased, and the compactness is lost. If the lower limit value of conditional expression (2) is 0.4 and the upper limit value is 1.5, more preferably, the lower limit value of conditional expression (2) is 0.6 and the upper limit value is 1.1. Better results are obtained.

  Conditional expression (3) defines the ratio between the focal length f1 of the first lens group G1 and the focal length f2 of the second lens group G2. If f1 / f2 is less than the lower limit value of conditional expression (3), the absolute value of f1 increases and the Petzval sum increases in the positive direction, which makes correction of curvature of field aberration and the like difficult, which is not preferable. On the other hand, when f1 / f2 exceeds the upper limit value of the conditional expression (3), the absolute value of f1 decreases, the negative refractive power increases, and the refractive power burden on the first lens group G1 increases. As a result, the aberration generated in the first lens group G1 is too large, and it becomes difficult to correct the aberration in the second lens group G2.

  Here, if the refractive power (power) distribution is such that the focal length f1 of the first lens group G1 and the focal length f2 of the second lens group G2 are sufficiently large, the burden on the first lens group G1 will be small. It seems to be. However, in this case, the (on-axis) air interval D increases rapidly and the compactness is lost. If the lower limit value of conditional expression (3) is −3.8 and the upper limit value is −1.5, more preferably, the lower limit value of conditional expression (3) is −3.4 and the upper limit value is −1. If it is .8, a more preferable result can be obtained.

  Conditional expression (4) defines the ratio between the radius of curvature R6 of the surface 6 closest to the viewer side in the second bonded lens L2 and the focal length f2 of the second lens group G2. If | R6 / f2 | is less than the lower limit value of conditional expression (4), the field curvature aberration will be undercorrected. Further, the radius of curvature R6 is reduced, and the refractive power on this surface is increased, so that the eye relief is shortened. On the other hand, if | R6 / f2 | exceeds the upper limit value of conditional expression (4), the field curvature aberration will be overcorrected. If the lower limit value of conditional expression (4) is 0.8 and the upper limit value is 2.2, more preferably, the lower limit value of conditional expression (4) is 0.9 and the upper limit value is 1.8. More preferable results can be obtained.

  Conditional expression (5) defines the ratio between the radius of curvature R5 of the bonding surface 5 in the second bonding lens L2 and the focal length f21 of the second bonding lens L2. If | R5 / f21 | is less than the lower limit value of the conditional expression (5), the radius of curvature R5 becomes small, and the diverging action on the bonding surface 5 becomes too strong, resulting in the subsequent increase in the lens diameter. It becomes difficult to satisfactorily correct lateral chromatic aberration at the periphery of the field of view. If the lower limit value of conditional expression (5) is 0.6 and the upper limit value is 20, it is more preferable that the lower limit value of conditional expression (5) is 0.7 and the upper limit value is 10. Results are obtained.

  Usually, when the apparent field of view becomes wider, it becomes difficult to correct lateral chromatic aberration over the entire field of view. Further, it becomes difficult to correct the difference in eye relief depending on the wavelength and the coloration of the field boundary portion in the field stop as the angle of view becomes wider. In order to correct these satisfactorily, in each embodiment, a cemented lens is employed for the first lens group G1, and two cemented lenses are also employed for the second lens group G2. In this way, it is possible to correct these chromatic aberrations well over a wide angle of view. Also, by bonding the lenses, the surface of the lens that comes into contact with air can be reduced, which is effective in suppressing a decrease in transmittance due to reflection at the lens boundary surface.

  In addition, by disposing the object-side focal plane FS of the second lens group G2 between the first lens group G1 and the second lens group G2, the field stop is set (with the first lens group G1 and the second lens group G2). Can be placed properly). For example, when the object-side focal plane FS is located closer to the object side than the first lens group G1, it is necessary to bring the first lens group G1 and the second lens group G2 closer to each other for compactness. Then, it is necessary to reduce the focal length (absolute value) of the first lens group G1, and it is necessary to make the field stop closer to the first lens group G1 because the image plane is close. Can not. Furthermore, if the image surface is too close to the first lens group G1, scratches and dust on the lens surface can be seen together with the observation image, which is not preferable.

  Hereinafter, specific examples of the eyepiece according to the present invention will be described. The five examples described below correspond to the eyepiece lenses EL of the first to fifth embodiments described above, and accordingly, a lens configuration diagram of the eyepiece lenses EL of the first to fifth embodiments (FIGS. 1 and 5). 3, FIG. 5, FIG. 7, and FIG. 9) respectively show lens configurations in the first to fifth examples.

  2, 4, 6, 8, and 10 are aberration diagrams showing spherical aberration, astigmatism, and distortion in the first to fifth examples, respectively. Each aberration is an imaging aberration when a light ray (d-line) is incident from the eye point EP side. A solid line in the astigmatism diagram represents a sagittal image plane, and a broken line represents a meridional image plane. In each aberration diagram, FN represents the F number of the eyepiece lens EL, and ω represents half of the field angle in the apparent field of view of the eyepiece lens EL.

(First embodiment)
Table 1 shows the specifications of each lens in the first example. Surface numbers 1 to 11 in Table 1 are lens surface numbers from the object side, and correspond to reference numerals 1 to 11 in FIG. In Table 1, R is the radius of curvature of the lens surface, d is the distance between the lens surfaces, nd is the refractive index with respect to the d-line (λ = 587.6 nm), νd is the Abbe number with respect to the d-line, and f is the focal length of the entire lens system. , I is the length of the eye relief. Unless otherwise specified, “mm” is generally used as the unit of length in each table, such as the radius of curvature R, the lens surface interval d, and the focal length f, but the optical system may be proportionally enlarged or reduced. Since equivalent optical performance can be obtained, the unit is not limited to “mm”, and other appropriate units can be used.

(Table 1)
Focal length of the entire lens system f = 15.2
Angle of view 2ω = 65 °
Eye relief I = 18mm
Position of object side focal plane FS (distance from plane 3): 3.7
Surface number R d nd νd
1 −172.0 1.0 1.620 60.1
2 13.0 3.3 1.795 28.6
3 23.7 11.1
4 −35.8 1.2 1.805 25.3
5 93.0 7.7 1.713 53.9
6 −20.0 0.2
7 47.5 8.2 1.713 53.9
8 −23.5 1.5 1.805 25.3
9 −74.8 0.2
10 22.0 4.8 1.620 60.1
11 116.0
(Conditional value)
f1 = −43.1
f2 = 16.1
f21 = 61.2
D = 11.1
R5 = 93.0
R6 = -20.0
(1) f1 / f = −2.8
(2) D / f = 0.73
(3) f1 / f2 = −2.7
(4) | R6 / f2 | = 1.2
(5) | R5 / f21 | = 1.52

  As can be seen from the respective aberration diagrams shown in FIG. 2, in this example, a wider field of view (angle of view: 2ω = 65) compared with a conventional eyepiece (for example, the eyepiece described in Japanese Patent No. 3518704). It can be seen that each aberration is corrected well (especially in the range of astigmatism up to about ω = 30 °). Further, since the astigmatism is the same for the d-line, C-line, and F-line, it can be said that the chromatic aberration is also improved. Thus, by satisfying each conditional expression, an eyepiece having a wide angle of view (field of view) and a good correction of each aberration over a wider angle of view can be obtained. In particular, when the conditional expression (5) is satisfied, it is possible to satisfactorily correct lateral chromatic aberration. In addition, since an aspheric lens is not used, an eyepiece that can obtain the above-described effects can be obtained at a low cost.

(Second embodiment)
Table 2 shows the specifications of each lens in the second example. Surface numbers 1 to 11 in Table 2 are lens surface numbers from the object side, and correspond to reference numerals 1 to 11 in FIG. The parameters in Table 2 are the same as in the first embodiment.

(Table 2)
Focal length of the entire lens system f = 15.2
Angle of view 2ω = 65 °
Eye relief I = 18mm
Object-side focal plane FS position (distance from plane 3): 4.0
Surface number R d nd νd
1 500.0 1.0 1.620 60.1
2 13.8 3.3 1.795 28.6
3 21.5 11.4
4 −28.0 1.2 1.805 25.3
5 96.5 8.5 1.713 53.9
6 -18.5 0.2
7 44.3 8.2 1.713 53.9
8 −25.5 1.5 1.805 25.3
9 −94.0 0.2
10 22.0 4.8 1.620 60.1
11 100.0
(Conditional value)
f1 = -45.6
f2 = 16.3
f21 = 65.2
D = 11.4
R5 = 96.5
R6 = -18.5
(1) f1 / f = -3.0
(2) D / f = 0.75
(3) f1 / f2 = −2.8
(4) | R6 / f2 | = 1.1
(5) | R5 / f21 | = 1.48

  As can be seen from the respective aberration diagrams shown in FIG. 4, in the second embodiment, the same effects as in the first embodiment can be obtained.

(Third embodiment)
Table 3 shows the specifications of each lens in the third example. Surface numbers 1 to 11 in Table 3 are lens surface numbers from the object side, and correspond to reference numerals 1 to 11 in FIG. Each parameter in Table 3 is the same as that in the first embodiment.

(Table 3)
Focal length of the entire lens system f = 15.2
Angle of view 2ω = 65 °
Eye relief I = 18mm
Position of object side focal plane FS (distance from plane 3): 3.7
Surface number R d nd νd
1 −180.0 3.3 1.795 28.6
2 −20.0 1.0 1.620 60.1
3 27.0 11.1
4 −26.4 1.2 1.805 25.3
5 93.0 9.0 1.713 53.9
6 −17.8 0.2
7 70.0 7.0 1.713 53.9
8 −24.8 1.5 1.805 25.3
9 −81.0 0.2
10 18.6 4.8 1.620 60.1
11 61.0
(Conditional value)
f1 = -53.2
f2 = 16.6
f21 = 62.4
D = 11.1
R5 = 93.0
R6 = -17.8
(1) f1 / f = −3.5
(2) D / f = 0.73
(3) f1 / f2 = −3.2
(4) | R6 / f2 | = 1.1
(5) | R5 / f21 | = 1.49

  As can be seen from the aberration diagrams shown in FIG. 6, the third embodiment can achieve the same effects as the first embodiment.

(Fourth embodiment)
Table 4 shows the specifications of each lens in the fourth example. Surface numbers 1 to 11 in Table 4 are lens surface numbers from the object side, and correspond to reference numerals 1 to 11 in FIG. The parameters in Table 4 are the same as in the first embodiment.

(Table 4)
Focal length of the entire lens system f = 15.2
Angle of view 2ω = 65 °
Eye relief I = 18mm
Position of object side focal plane FS (distance from plane 3): 3.7
Surface number R d nd νd
1 −380.0 1.0 1.620 60.1
2 18.0 2.3 1.795 28.6
3 27.5 11.1
4 −48.0 1.2 1.805 25.3
5 50.0 8.5 1.713 53.9
6 −20.4 0.2
7 117.0 1.5 1.805 25.3
8 23.0 8.0 1.713 53.9
9 −60.7 0.2
10 19.2 5.2 1.620 60.1
11 100.0
(Conditional value)
f1 = -49.2
f2 = 16.4
f21 = 50.0
D = 11.1
R5 = 50.0
R6 = −20.4
(1) f1 / f = −3.2
(2) D / f = 0.73
(3) f1 / f2 = −3.0
(4) | R6 / f2 | = 1.2
(5) | R5 / f21 | = 1.0

  As can be seen from the respective aberration diagrams shown in FIG. 8, the same effects as in the first embodiment can be obtained in the fourth embodiment.

(5th Example)
Table 5 shows the specifications of each lens in the fifth example. Surface numbers 1 to 11 in Table 5 are lens surface numbers from the object side, and correspond to reference numerals 1 to 11 in FIG. 9, respectively. Each parameter in Table 5 is the same as that in the first embodiment.

(Table 5)
Focal length of the entire lens system f = 15.2
Angle of view 2ω = 65 °
Eye relief I = 18mm
Object-side focal plane FS position (distance from plane 3): 4.0
Surface number R d nd νd
1 −48.6 1.0 1.620 60.1
2 12.7 3.8 1.795 28.6
3 28.3 12.0
4 −74.0 1.2 1.805 25.3
5 80.0 6.5 1.713 53.9
6 −25.0 0.2
7 52.8 8.5 1.713 53.9
8 −21.4 1.5 1.805 25.3
9 −55.5 0.2
10 21.8 4.8 1.620 60.1
11 80.0
(Conditional value)
f1 = -36.5
f2 = 16.6
f21 = 55.5
D = 12.0
R5 = 80.0
R6 = -25.0
(1) f1 / f = −2.4
(2) D / f = 0.79
(3) f1 / f2 = −2.2
(4) | R6 / f2 | = 1.5
(5) | R5 / f21 | = 1.44

  As can be seen from the respective aberration diagrams shown in FIG. 10, the same effect as that of the first example can be obtained also in the fifth example.

  In each of the above-described embodiments, the binocular eyepiece lens EL is described as an example. However, the present invention is not limited to this, and the present invention can also be applied to an eyepiece lens used in a telescope or a microscope. .

It is a figure which shows the structure of the eyepiece which concerns on 1st Embodiment. FIG. 5 is a diagram illustrating all aberrations of the eyepiece in the first example. It is a figure which shows the structure of the eyepiece which concerns on 2nd Embodiment. It is an aberration diagram of the eyepiece in the second example. It is a figure which shows the structure of the eyepiece which concerns on 3rd Embodiment. FIG. 12 is a diagram illustrating all aberrations of the eyepiece in the third example. It is a figure which shows the structure of the eyepiece which concerns on 4th Embodiment. FIG. 10 is a diagram illustrating all aberrations of the eyepiece in the fourth example. It is a figure which shows the structure of the eyepiece which concerns on 5th Embodiment. FIG. 10 is a diagram illustrating all aberrations of the eyepiece in the fifth example.

Explanation of symbols

EL eyepiece G1 first lens group G2 second lens group L1 first cemented lens (third cemented lens)
L2 Second bonded lens (first bonded lens)
L3 Third bonded lens (second bonded lens)
L4 Single lens FS Object side focal plane

Claims (2)

In order from the object side, a first lens group having a negative refractive power as a whole and a second lens group having a positive refractive power as a whole are provided, and the object-side focal plane of the second lens group is the first lens. A second lens group and a second lens group,
The second lens group is formed by bonding a first negative lens having a concave surface facing the object side and a first positive lens having a convex surface facing the viewer side, and has a positive refractive power as a whole. A second bonded lens having a positive refractive power as a whole, and a positive refraction with a convex surface facing the object side. A single lens having power,
The first bonded lens, the second bonded lens, and the single lens are arranged in this order from the object side to the observer side,
The focal length of the entire lens system is f, the focal length of the first lens group is f1, the focal length of the second lens group is f2, and the air between the first lens group and the second lens group. When the interval is D and the radius of curvature of the surface closest to the viewer side in the first bonded lens is R6, the following equation −4.5 ≦ f1 / f ≦ −1.1 and
0.3 ≦ D / f ≦ 2.5 and
−4.0 ≦ f1 / f2 ≦ −1.3 and
0.7 ≦ | R6 / f2 | ≦ 2.8
Respectively satisfy represented by conditions in,
When the focal length of the first bonded lens is f21 and the radius of curvature of the bonded surface of the first positive lens and the first negative lens in the first bonded lens is R5, formula
0.5 ≦ | R5 / f21 |
An eyepiece characterized by satisfying the condition represented by: Wherein the first lens group, a third positive lens and the third bonding ocular lens according to claim 1, characterized in that they are composed of a lens formed by bonding the third negative lens.

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