Attached lens

Abstract

The present disclosure provides an attached lens including, from an object side, a first lens having a positive refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power, both surfaces of the first lens, the second lens, and the third lens being aspheric, respectively, and satisfying the following formulae (1), (2), (3), (4), (5), and (6), (1) 4.30 < = f1 / f < = 4.95 (2) 0.120 < = [phi] 1 / n1 < = 0.160 (3) 0.0030 < = [phi] 1 / v1 < = 0.0050 (4)-3.20 < = f2 / f < =-2.70 (5)-0.240 < = [phi] 2 / n2 < =-0.160 (6)-0.0200 < = [phi] 2 / v2 < =-0.0120.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an attachment lens, particularly an attachment lens capable of achieving microscopic and high-resolution optical characteristics by being fitted to the front of a photographing lens. BACKGROUND

[0002] As an optical element capable of changing the performance and purpose of a photographing lens by being fitted to the photographing lens, an attachment lens is known. The attachment lens has an attachment lens that changes the angle of view, an attachment lens that changes the magnification, and the like, and also has an attachment lens that is fitted to the photographing object side of a photographing lens, an attachment lens that is fitted to the image side of a photographing lens, and the like.

[0003] For example, as an attachment lens that is fitted to the photographing object side of a photographing lens, a lens having a function of expanding the angle of view is disclosed in Patent Literature 1 and Patent Literature 2.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2002-214529

[0007] Patent Literature 2: Japanese Patent Application Laid-Open No. 2020-144177 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] However, a photographing lens is mainly designed to exhibit optical performance as a single body, and generally, since an attachment lens is fitted, the aberration balance is broken, and in the optical system as a whole including the photographing lens and the attachment lens, the optical performance is deteriorated in many cases.

[0010] Therefore, an object of the present application is to provide an attachment lens that does not deteriorate the overall optical performance even when fitted to an original photographing lens, and that can observe a fine object with high resolution.

[0011] TECHNICAL SOLUTION FOR SOLVING THE PROBLEM

[0012] An embodiment of the present application provides an attachment lens that includes a first lens having a positive refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power from the object side, both surfaces of the first lens, the second lens, and the third lens are aspherical surfaces, and satisfies the following expressions (1), (2), (3), (4), (5), and (6).

[0013] (1) 4.30 ≦ f1 / f ≦ 4.95

[0014] (2) 0.120 ≦ φ1 / n1 ≦ 0.160

[0015] (3) 0.0030 ≦ φ1 / ν1 ≦ 0.0050

[0016] (4) -3.20 ≦ f2 / f ≦ -2.70

[0017] (5) -0.240 ≦ φ2 / n2 ≦ -0.160

[0018] (6) -0.0200 ≦ φ2 / ν2 ≦ -0.0120

[0019] f: total focal distance of the attached lens with respect to the d-line

[0020] f1: focal distance of the first lens with respect to the d-line

[0021] φ1: product of the refractive power of the first lens with respect to the d-line and f (f / f1)

[0022] n1: refractive index of the first lens with respect to the d-line

[0023] ν1: Abbe number of the first lens

[0024] f2: focal distance of the second lens with respect to the d-line

[0025] φ2: product of the refractive power of the second lens with respect to the d-line and f (f / f2)

[0026] n2: refractive index of the second lens with respect to the d-line

[0027] ν2: Abbe number of the second lens

[0028] The attached lens described above can suppress deterioration of flatness of an image surface of the entire optical system including the attached lens and the original camera lens by satisfying the formula (2) and (5) while satisfying the formula (1) and (4), even if it is attached to the original camera lens. In addition, the attached lens described above can suppress generation of chromatic aberration in the entire optical system including the attached lens and the original camera lens by satisfying the formula (3) and (6) while satisfying the formula (1) and (4), even if it is attached to the original camera lens.

[0029] The attached lens of the embodiment preferably further satisfies the following formula (7) and (8). According to this mode, deterioration of flatness of an image surface of the entire optical system including the attached lens and the original camera lens can be further suppressed by satisfying the following formula (7), and generation of chromatic aberration in the entire optical system including the attached lens and the original camera lens can be further suppressed by satisfying the following formula (8).

[0030] (7) 0.000 ≦ P ≦ 0.510

[0031] (8) -0.0046 ≦ Q ≦ 0.0046

[0032] P: sum of φ1 / n1, φ2 / n2, and φ3 / n3

[0033] Q: sum of φ1 / ν1, φ2 / ν2, and φ3 / ν3

[0034] φ3: product of the refractive power of the third lens with respect to the d-line and f (f / f3)

[0035] f3: focal distance of the third lens with respect to the d-line

[0036] n3: refractive index of the third lens with respect to the d-line

[0037] ν3: Abbe number of the third lens

[0038] The attachment lens of the embodiment preferably further satisfies the following equations (9), (10), and (11). According to this mode, by satisfying the following equation (10) while satisfying the following equation (9), it is possible to further suppress deterioration in flatness of an image surface of the entire optical system including the imaging lens and the attachment lens. In addition, by satisfying the following equation (11) while satisfying the following equation (9), it is possible to further suppress generation of chromatic aberration in the entire optical system including the imaging lens and the attachment lens.

[0039] (9) 1.10 ≦ f3 / f ≦ 1.40

[0040] (10) 0.000 ≦ φ3 / n3 ≦ 0.600

[0041] (11) 0.0000 ≦ φ3 / ν3 ≦ 0.0200

[0042] f3: focal distance of the third lens with respect to the d-line

[0043] φ3: product of the refractive power of the third lens with respect to the d-line and f (f / f3)

[0044] n3: refractive index of the third lens with respect to the d-line

[0045] ν3: Abbe number of the third lens

[0046] The attachment lens of the embodiment preferably is composed of a non-fluorescent material for each of the first lens, the second lens, and the third lens. According to this mode, for example, in the case of use as an attachment lens of an analysis device using ultraviolet light, it is possible to prevent generation of fluorescence in each lens by ultraviolet light, and the fluorescence becomes noise of measurement. That is, the attachment lens of this mode is suitable for use as an attachment lens of an analysis device using ultraviolet light.

[0047] The attached lens of the embodiment is preferably composed of a non-fluorescent material, and further satisfies the following formulas (1'), (2'), (3'), (4'), (5'), and (6'). According to this, not only can the attached lens be suitably used for an analysis device using ultraviolet light, but also the flatness of the image plane of the entire optical system including the photographing lens and the attached lens can be further suppressed from deteriorating, and chromatic aberration can be further suppressed from occurring.

[0048] (1') 4.33 ≦ f1 / f ≦ 4.94

[0049] (2') 0.130 ≦ φ1 / n1 ≦ 0.155

[0050] (3') 0.0035 ≦ φ1 / ν1 ≦ 0.0042

[0051] (4') -3.05 ≦ f2 / f ≦ -2.70

[0052] (5') -0.230 ≦ φ2 / n2 ≦ -0.180

[0053] (6') -0.0190 ≦ φ2 / ν2 ≦ -0.0130

[0054] The attached lens of the embodiment preferably satisfies the following formulas (7') and (8') in addition to the formulas (1'), (2'), (3'), (4'), (5'), and (6'). According to this, not only can the attached lens be suitably used for an analysis device using ultraviolet light, but also the flatness of the image plane of the entire optical system including the photographing lens and the attached lens can be further suppressed from deteriorating, and chromatic aberration can be further suppressed from occurring.

[0055] (7') 0.000 ≦ P ≦ 0.482

[0056] (8') -0.0040 ≦ Q ≦ 0.0040

[0057] P: sum of φ1 / n1, φ2 / n2, and φ3 / n3

[0058] Q: sum of φ1 / ν1, φ2 / ν2, and φ3 / ν3

[0059] φ3: product of the focal power with respect to the d-line and f of the third lens (f / f3)

[0060] f3: focal distance with respect to the d-line of the third lens

[0061] n3: refractive index with respect to the d-line of the third lens

[0062] ν3: Abbe number of the third lens

[0063] The attachment lens of the embodiment preferably satisfies the following formulas (9'), (10'), and (11'), in addition to the formulas (1'), (2'), (3'), (4'), (5'), and (6'). According to this, not only can the attachment lens be suitably used as an attachment lens for an analysis device using ultraviolet light, but it is also possible to further suppress deterioration in flatness of an image plane of the entire optical system including the photographing lens and the attachment lens, and generation of chromatic aberration.

[0064] (9') 1.20 ≦ f3 / f ≦ 1.30

[0065] (10') 0.400 ≦ φ3 / n3 ≦ 0.550

[0066] (11') 0.0100 ≦ φ3 / ν3 ≦ 0.0150

[0067] f3: focal distance of the third lens with respect to the d-line

[0068] φ3: product of the refractive power of the third lens with respect to the d-line and f (f / f3)

[0069] n3: refractive index of the third lens with respect to the d-line

[0070] ν3: Abbe number of the third lens

[0071] The attachment lens of the embodiment can be suitably used even in a case where a flat optical element is interposed between the observation object and the first lens. The attachment lens of the embodiment can suppress deterioration in flatness of an image plane of the entire optical system including the photographing lens and the attachment lens, and generation of chromatic aberration, even though the number of necessary lenses is small. That is, it is possible to thin the thickness of the entire attachment lens, and therefore, it can be suitably used in a case where there is a limit to the distance between the photographing lens and the observation object, and a flat optical element is interposed between the observation object and the first lens.

[0072] The flat optical element can be, for example, a wavelength filter.

[0073] The attachment lens of the embodiment can be connected to the lens of a camera of a mobile terminal, for example.

[0074] Effects of Invention

[0075] According to the present application, it is possible to provide an attachment lens that does not deteriorate the overall optical performance even when it is attached to an original photographing lens, and that can observe a fine object with high resolution. BRIEF DESCRIPTION OF DRAWINGS

[0076] Figure 1 is a schematic cross-sectional view showing an optical system using the attachment lens of the embodiment.

[0077] Figure 2 This is a diagram showing the surfaces R1 to R11 and the thicknesses (distances) d1 to d10 in the numerical embodiment. Detailed Implementation

[0078] Hereinafter, the embodiments for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail with reference to the accompanying drawings. However, the present invention is not limited thereto, and various modifications can be made without departing from its spirit. In the following description of the drawings, the same or similar parts are indicated by the same or similar reference numerals. The drawings are schematic diagrams and may not necessarily correspond to actual dimensions and ratios. Sometimes, the dimensional relationships and ratios between the parts in the drawings may differ from each other.

[0079] [Attached lens]

[0080] like Figure 1 As shown, the attachment lens 100 of this embodiment includes a first lens 101 with positive refractive power, a second lens 102 with negative refractive power, and a third lens 103 with positive refractive power from the observation object side. Figure 1 This indicates a camera lens that observes the object positioned on the sample stage 300 through a flat optical element 200. Figure 1 In the example shown, 400 denotes the mounting surface of the imaging lens. An example of an attachment lens 100 mounted on a sample stage 300 is also shown. The optical axes AX of the attachment lens 100, the flat optical element 200, and the imaging lens are configured to approximately coincide with the observation position of the object being observed. The object being observed is positioned on one side of the sample stage 300, either on the side of the attachment lens 100 or the opposite side.

[0081] The first lens 101, the second lens 102, and the third lens 103 each have aspherical surfaces on both sides. The attached lens 100 satisfies the following equations (1), (2), (3), (4), (5), and (6).

[0082] (1) 4.30≦f1 / f≦4.95

[0083] (2) 0.120≦φ1 / n1≦0.160

[0084] (3) 0.0030≦φ1 / ν1≦0.0050

[0085] (4) -3.20≦f² / f≦-2.70

[0086] (5) -0.240≦φ2 / n2≦-0.160

[0087] (6) -0.0200≦φ2 / ν2≦-0.0120

[0088] f: The focal distance of the attached lens relative to the d-line.

[0089] f1: focal distance of the first lens with respect to the d-line

[0090] φ1: product of the refractive power of the first lens with respect to the d-line and f (f / f1)

[0091] n1: refractive index of the first lens with respect to the d-line

[0092] ν1: Abbe number of the first lens

[0093] f2: focal distance of the second lens with respect to the d-line

[0094] φ2: product of the refractive power of the second lens with respect to the d-line and f (f / f2)

[0095] n2: refractive index of the second lens with respect to the d-line

[0096] ν2: Abbe number of the second lens

[0097] Here, in the present specification, the Abbe number is a value v defined by the refractive index nD of the Fraunhofer line with respect to the d-line (587.56 nm) d , the refractive index nF of the Fraunhofer line with respect to the F-line (486.1 nm) F , and the refractive index nC of the Fraunhofer line with respect to the C-line (656.3 nm) C . d .

[0098] v = (nD - 1) / (nF - nC) d d F C

[0099] Further, the lens having a positive refractive power means that the refractive power of the lens with respect to the d-line, that is, the reciprocal of the focal distance of the lens with respect to the d-line is positive, and the lens having a negative refractive power means that the refractive power of the lens with respect to the d-line, that is, the reciprocal of the focal distance of the lens with respect to the d-line is negative.

[0100] The above-described equations (1) and (4) respectively prescribe the ratio of the focal distance of the first lens 101 and the second lens 102 with respect to the total focal distance of the attached lens 100. The ratio of the focal distance of the third lens 103 with respect to the total focal distance of the attached lens 100 is described later, but it is only necessary to adjust in such a manner that the desired total focal distance f is obtained in the attached lens 100 within the range satisfying the above-described equations (1) and (4).

[0101] ​​​​f1 / f can be 4.33 or more, 4.34 or more, 4.51 or more, 4.62 or more, or 4.90 or more within the range of the above formula (1). In addition, f1 / f can be 4.94 or less, 4.63 or less, 4.52 or less, or 4.35 or less within the range of the above formula (1).

[0102] f2 / f can be -3.18 or more, -3.05 or more, -3.01 or more, -3.00 or more, -2.88 or more, or -2.76 or more within the range of the above formula (4). In addition, f2 / f can be -2.80 or less, -2.87 or less, -3.00 or less, or -3.17 or less within the range of the above formula (4).

[0103] Each value of f, f1, and f2 can be appropriately adjusted by changing the size of the optical system, so-called zoom, while maintaining the relationship of each structure of the attached lens 100, and thus is not particularly limited. f can be 1.10 mm or more and 10.0 mm or less, for example, can be 1.20 mm or more and 5.00 mm or less, or can be 1.30 mm or more and 2.00 mm or less. When f is set, f1 and f2 are designed to satisfy the above formulas (1) and (4), respectively.

[0104] f is adjusted according to the focal distance of the photographing lens and the desired magnification, and the like. The magnification of the attached lens indicates the ratio of the size of the image when the attached lens is attached to the size of the image when the attached lens is not attached. The magnification β is determined according to the focal distance f 400 of the photographing lens, the focal distance f of the attached lens, and the distance between the photographing lens and the attached lens, and the like.

[0105] The magnification β of the attached lens 100 is preferably greater than 1.00, more preferably 1.10 or more, and further preferably 1.20 or more. The focal distance f of the attached lens 100 can also be appropriately adjusted according to the focal distance f 400 of the photographing lens, and the like, so that β is within the above range.

[0106] The above-described φ1 / n1 and φ2 / n2 are values obtained by normalizing the ratio of the refractive index to the power of each lens with respect to the power (1 / f) of the attached lens 100. In an optical system including a plurality of lenses, when the sum of the ratio of the refractive index to the power of each lens is close to 0, the flatness of the image surface of the entire optical system is improved, that is, the curvature of the image surface is suppressed. The sum of the ratio of the refractive index to the power of each lens, or a value obtained by normalizing the sum with respect to the power of the entire optical system is called Petzval sum. In the attached lens 100, φ1 / n1 and φ2 / n2 are respectively defined by the above-described formula (2) and (5), and thus, by appropriately adjusting a value obtained by normalizing the ratio of the refractive index to the power of the third lens 103 with respect to the power (1 / f) of the attached lens 100, it is possible to make the Petzval sum in the attached lens 100 close to 0, and it is possible to suppress the deterioration of the flatness of the image surface of the attached lens 100. In addition, φi (i = 1, 2, 3) can be understood as the ratio of the power (1 / fi) of the ith lens with respect to the d-line to the entire system power (1 / f) of the attached lens with respect to the d-line.

[0107] φ1 / n1 can be 0.130 or more, 0.140 or more, 0.144 or more, or 0.150 or more within the range of the above-described formula (2). In addition, φ1 / n1 can be 0.155 or less, 0.145 or less, 0.142 or less, 0.140 or less, or 0.135 or less within the range of the above-described formula (2).

[0108] φ2 / n2 can be -0.230 or more, -0.220 or more, -0.210 or more, -0.205 or more, or -0.190 or more within the range of the above-described formula (5). In addition, φ2 / n2 can be -0.180 or less, -0.190 or less, -0.200 or less, or -0.210 or less within the range of the above-described formula (5).

[0109] The value of n1 is not particularly limited as long as φ1 / n1 satisfies the above-described formula (2), and can be, for example, 1.20 or more and 2.00 or less, preferably 1.20 or more and 1.80 or less, more preferably 1.40 or more and 1.70 or less, and further preferably 1.45 or more and 1.60 or less.

[0110] The value of n2 is not particularly limited as long as φ2 / n2 satisfies the above-described formula (5), and can be, for example, 1.30 or more and 2.10 or less, preferably 1.40 or more and 1.90 or less, more preferably 1.50 or more and 1.80 or less, and further preferably 1.55 or more and 1.75 or less.

[0111] The magnitude relationship between n1 and n2 is not particularly limited, but n2 is preferably larger, and more preferably n2 is larger than n1 by 0.05 or more or 0.10 or more. In this case, the upper limit of the difference between n2 and n1 is not particularly limited, and can be, for example, 0.50, 0.40, 0.30, or 0.20.

[0112] The above-described formulas (3) and (6) respectively prescribe, in the first lens 101 and the second lens 102, values obtained by normalizing the ratio of the refractive power of each lens with respect to the Abbe number to the refractive power (1 / f) of the attachment lens 100. In an optical system including a plurality of lenses, when the sum of the ratio of the refractive power of each lens with respect to the Abbe number is close to 0, chromatic aberration can be suppressed in the entire optical system. In the attachment lens 100, φ1 / ν1 and φ2 / ν2 are respectively prescribed by the above-described formulas (3) and (6), and thus, by appropriately adjusting the value obtained by normalizing the ratio of the refractive power of the third lens 103 with respect to the Abbe number to the refractive power (1 / f) of the attachment lens 100, the sum in the attachment lens 100 can be made close to 0, and chromatic aberration in the attachment lens 100 can be reduced.

[0113] φ1 / ν1 can be 0.0035 or more, 0.0038 or more, 0.0039 or more, or 0.0040 or more within the range of the above-described formula (3). In addition, φ1 / ν1 can be 0.0045 or less, 0.0042 or less, 0.0040 or less, or 0.0039 or less within the range of the above-described formula (3).

[0114] φ2 / ν2 can be -0.0190 or more, -0.0185 or more, -0.0170 or more, -0.0160 or more, or -0.0150 or more within the range of the above-described formula (6). In addition, φ2 / ν2 can be -0.0130 or less, -0.0140 or less, -0.0150 or less, or -0.0160 or less within the range of the above-described formula (6).

[0115] The value of ν1 is not particularly limited as long as φ1 / ν1 satisfies the above-described formula (3), and can be, for example, 20 or more and 100 or less, preferably 30 or more and 90 or less, and more preferably 40 or more and 70 or less.

[0116] The value of ν2 is not particularly limited as long as φ2 / ν2 satisfies the above-described formula (6), and can be, for example, 5.0 or more and 80 or less, preferably 10 or more and 60 or less, and more preferably 15 or more and 40 or less.

[0117] The magnitude relationship between ν1 and ν2 is not particularly limited, and ν1 is preferably larger, and preferably ν1 is larger than ν2 by 10 or more or 20 or more. In this case, the upper limit of the difference between ν1 and ν2 is not particularly limited, and can be, for example, 100, 80, 60, 50, or 40.

[0118] The attached lens 100 preferably also satisfies the following equations (7) and (8).

[0119] (7) 0.000 ≦ P ≦ 0.510

[0120] (8) -0.0046 ≦ Q ≦ 0.0046

[0121] P: sum of φ1 / n1, φ2 / n2, and φ3 / n3

[0122] Q: sum of φ1 / ν1, φ2 / ν2, and φ3 / ν3

[0123] φ3: product of the optical power of the third lens with respect to the d-line and f (f / f3)

[0124] f3: focal distance of the third lens with respect to the d-line

[0125] n3: refractive index of the third lens with respect to the d-line

[0126] ν3: Abbe number of the third lens

[0127] P of the above equation (7) is a value corresponding to Petzval and. In the attached lens 100, the first lens 101, the second lens 102, and the third lens 103 are aspherical lenses, and thus, as long as the first lens 101 and the second lens satisfy the above equations (2) and (5), respectively, high flatness can be achieved as a whole optical system. By P satisfying the above equation (7), higher flatness can be achieved as a whole optical system.

[0128] P can be 0.050 or more, 0.100 or more, 0.200 or more, 0.300 or more, or 0.400 or more within the range of the above equation (7). P is preferably 0.500 or less, more preferably 0.490 or less, and further preferably 0.482 or less within the range of the above equation (7).

[0129] Q of the above equation (8) is a value mainly related to chromatic aberration of the attached lens 100. In the attached lens 100, the first lens 101, the second lens 102, and the third lens 103 are aspherical lenses, and thus, as long as the first lens 101 and the second lens satisfy the above equations (3) and (6), respectively, generation of chromatic aberration can be suppressed as a whole optical system. By Q satisfying the above equation (8), generation of chromatic aberration can be further reduced as a whole optical system.

[0130] Q is preferably -0.0040 or more, more preferably -0.0030 or more, further preferably -0.0010 or more, and still further preferably 0.0000 or more, within the range of the above formula (8). Q is preferably 0.0042 or less or 0.0040 or less, within the range of the above formula (8). Q can be 0.0038 or less, or 0.0035 or less.

[0131] The attached lens 100 can also satisfy the following formulas (2A), (3A), (5A), (6A), (7A), and (8A) instead of satisfying the above formulas (2), (3), (5), (6), (7), and (8).

[0132] (2A) 0.080 ≦ 1 / f1n1 ≦ 0.110

[0133] (3A) 0.0020 ≦ 1 / f1n1 ≦ 0.0035

[0134] (5A) -0.160 ≦ 1 / f2n2 ≦ -0.110

[0135] (6A) -0.0140 ≦ 1 / f2n2 ≦ -0.0080

[0136] (7A) 0.000 ≦ P' ≦ 0.350

[0137] (8A) -0.0031 ≦ Q' ≦ 0.0031

[0138] P': sum of 1 / f1n1, 1 / f2n2, and 1 / f3n3

[0139] Q': sum of 1 / f1n1, 1 / f2n2, and 1 / f3n3

[0140] 1 / f1n1 can be 0.090 or more, 0.094 or more, 0.095 or more, or 0.098 or more, within the range of the above formula (2A). In addition, 1 / f1n1 can be 0.105 or less, 0.98 or less, 0.095 or less, 0.093 or less, or 0.090 or less, within the range of the above formula (2A).

[0141] 1 / f1n1 can be 0.0023 or more, 0.0025 or more, 0.0026 or more, or 0.0027 or more, within the range of the above formula (3A). In addition, 1 / f1n1 can be 0.0030 or less, 0.0028 or less, 0.0026 or less, or 0.0025 or less, within the range of the above formula (3A).

[0142] 1 / f2n2may be -0.150 or more, -0.142 or more, -0.140 or more, -0.130 or more, or -0.127 or more within the range of the above-described formula (5A). In addition, 1 / f2n2may be -0.120 or less, -0.125 or less, -0.135 or less, or -0.140 or less within the range of the above-described formula (5A).

[0143] 1 / f2n2may be -0.0125 or more, -0.0110 or more, -0.0105 or more, or -0.0100 or more within the range of the above-described formula (6A). In addition, 1 / f2n2may be -0.0085 or less, -0.0090 or less, -0.0100 or less, or -0.0105 or less within the range of the above-described formula (6A).

[0144] P' and Q' are values obtained by dividing P and Q by f, respectively.

[0145] P' can be 0.030 or more, 0.070 or more, 0.130 or more, 0.200 or more, or 0.250 or more within the range of the above-described formula (7A). P' is preferably 0.340 or less, more preferably 0.330 or less, and further preferably 0.320 or less within the range of the above-described formula (7A).

[0146] Q' is preferably -0.0028 or more, more preferably -0.0020 or more, further preferably -0.0010 or more, and still further preferably 0.0000 or more within the range of the above-described formula (8A). Q' is preferably 0.0029 or less or 0.0028 or less within the range of the above-described formula (8A). Q' can be 0.0025 or less, or 0.0023 or less.

[0147] The attached lens 100 preferably also satisfies the following formulas (9), (10), and (11). The attached lens 100 preferably satisfies the following formulas (9), (10), and (11) in addition to the above-described formulas (1) to (6), and more preferably satisfies the following formulas (9), (10), and (11) in addition to the above-described formulas (1) to (8).

[0148] (9) 1.10 ≦ f3 / f ≦ 1.40

[0149] (10) 0.000 ≦ φ3 / n3 ≦ 0.600

[0150] (11) 0.0000 ≦ φ3 / ν3 ≦ 0.0200

[0151] f3, φ3, n3, and ν3 are as defined above.

[0152] The above-described formula (9) to (11) define the characteristics of the third lens 103. Since the first lens 101 and the second lens 102 satisfy the above-described formula (1) to (6), the attached lens 100 does not deteriorate the overall optical performance even if it is disposed in the original imaging lens, and can observe a fine subject with high resolution. By appropriately adjusting the characteristics of the third lens 103, a desired characteristic can be achieved in the attached lens 100, and by the third lens 103 satisfying the above-described formula (9) to (11), the deterioration of the flatness of the image surface of the entire optical system including the imaging lens and the attached lens and the generation of chromatic aberration can be further suppressed.

[0153] The above-described formula (9) defines the ratio of the focal length of the third lens 103 to the overall focal length of the attached lens 100.

[0154] f3 / f can be 1.15 or more, 1.20 or more, or 1.24 or more within the range of the above-described formula (9). In addition, f3 / f can be 1.35 or less, 1.30 or less, or 1.28 or less within the range of the above-described formula (9). The value of f3 can be appropriately adjusted by the zoom of the attached lens 100, and thus is not particularly limited.

[0155] The above-described formula (10) defines a value obtained by normalizing the ratio of the refractive power of the third lens 103 to the refractive index with the refractive power (1 / f) of the attached lens 100.

[0156] φ3 / n3 can be 0.100 or more, 0.300 or more, 0.400 or more, 0.450 or more, or 0.500 or more within the range of the above-described formula (10). In addition, φ3 / n3 can be 0.580 or less, 0.550 or less, or 0.530 or less within the range of the above-described formula (10).

[0157] The value of n3 is not particularly limited, and can be, for example, 1.20 or more and 2.00 or less, preferably 1.20 or more and 1.80 or less, more preferably 1.40 or more and 1.70 or less, and further preferably 1.45 or more and 1.60 or less. The magnitude relationship of n1, n2, and n3 is not particularly limited, and n3 is preferably smaller than n2. n3 can be the same as n1, or can be within the range of n1 ± 0.10.

[0158] The above-described formula (11) defines a value obtained by normalizing the ratio of the refractive power of the third lens 103 to the Abbe number with the refractive power (1 / f) of the attached lens 100.

[0159] φ3 / ν3 can be 0.0050 or more, 0.0100 or more, or 0.0140 or more within the range of the above-described formula (11). In addition, φ3 / ν3 can be 0.0190 or less, 0.0180 or less, or 0.0150 or less within the range of the above-described formula (11).

[0160] The value of v3 is not particularly limited, and for example, can be 20 or more and 100 or less, preferably 30 or more and 90 or less, and more preferably 40 or more and 70 or less. The magnitude relationship of v1, v2, and v3 is not particularly limited, and v3 is preferably greater than v2. v3 can be the same as v1, and can be in the range of v1 ± 5.0.

[0161] The attachment lens 100 can satisfy the following formulae (10A) and (11A) in addition to the above formulae (10) and (11).

[0162] (10A) 0.000 ≦ 1 / f3n3 ≦ 0.400

[0163] (11A) 0.0000 ≦ 1 / f3v3 ≦ 0.0140

[0164] 1 / f3n3 can be 0.060 or more, 0.200 or more, 0.250 or more, 0.300 or more, or 0.330 or more within the range of the above formula (10A). In addition, 1 / f3n3 can be 0.380 or less, 0.370 or less, or 0.360 or less within the range of the above formula (10A).

[0165] 1 / f3v3 can be 0.0030 or more, 0.0070 or more, or 0.0090 or more within the range of the above formula (11A). In addition, 1 / f3v3 can be 0.0130 or less, 0.0120 or less, or 0.0100 or less within the range of the above formula (11A).

[0166] The material constituting the first lens 101, the second lens 102, and the third lens 103 is not particularly limited, and for example, can be an inorganic material such as glass, can be an organic material such as resin, or can be a composite material combining an inorganic material and an organic material.

[0167] The first lens 101, the second lens 102, and the third lens 103 are not particularly limited as long as they are constituted by a material that transmits the wavelength of light for observation, but are preferably constituted by a non-fluorescent material. According to this mode, for example, in the case of use as an attachment lens of an analysis device that uses ultraviolet light, it is possible to prevent the generation of fluorescence in each lens by ultraviolet light, and the fluorescence becomes noise of the measurement. That is, when the first lens 101, the second lens 102, and the third lens 103 are formed of a non-fluorescent material, it is possible to be used as an attachment lens of an analysis device that uses ultraviolet light.

[0168] In the case where the first lens 101, the second lens 102, and the third lens 103 are made of a non-fluorescent material, the attachment lens 100 preferably satisfies the following equations (1'), (2'), (3'), (4'), (5'), and (6'), more preferably further satisfies the following equations (7') and (8'), or the following equations (9'), (10'), and (11'), further preferably further satisfies the following equations (7'), (8'), (9'), (10'), and (11'). According to this case, not only the attachment lens can be suitably used for an analysis device using ultraviolet light, but also the flatness of the image plane of the entire optical system including the photographing lens and the attachment lens can be further suppressed from deteriorating, and chromatic aberration can be further suppressed from occurring.

[0169] (1') 4.33 ≦ f1 / f ≦ 4.94

[0170] (2') 0.130 ≦ φ1 / n1 ≦ 0.155

[0171] (3') 0.0035 ≦ φ1 / ν1 ≦ 0.0042

[0172] (4') -3.05 ≦ f2 / f ≦ -2.70

[0173] (5') -0.230 ≦ φ2 / n2 ≦ -0.180

[0174] (6') -0.0190 ≦ φ2 / ν2 ≦ -0.0130

[0175] (7') 0.000 ≦ P ≦ 0.482

[0176] (8') -0.0040 ≦ Q ≦ 0.0040

[0177] (9') 1.20 ≦ f3 / f ≦ 1.30

[0178] (10') 0.400 ≦ φ3 / n3 ≦ 0.550

[0179] (11') 0.0100 ≦ φ3 / ν3 ≦ 0.0150

[0180] f, f1, f2, f3, n1, n2, n3, ν1, ν2, ν3, φ1, φ2, φ3, P, and Q are the same as defined above.

[0181] In this case, the attachment lens 100 can satisfy the following equations (2A'), (3A'), (5A'), (6A'), (7A'), (8A'), (10A'), and (11A') instead of the above equations (2'), (3'), (5'), (6'), (7'), (8'), (10'), and (11').

[0182] (2A') 0.085 ≦ 1 / f1n1 ≦ 0.105

[0183] (3A') 0.0023 ≦ 1 / f1v1 ≦ 0.0028

[0184] (5A') -0.150 ≦ 1 / f2n2 ≦ -0.140

[0185] (6A') -0.0105 ≦ 1 / f2v2 ≦ -0.0090

[0186] (7A') 0.000 ≦ P' ≦ 0.320

[0187] (8A') -0.0028 ≦ Q' ≦ 0.0028

[0188] (10A') 0.300 ≦ 1 / f3n3 ≦ 0.370

[0189] (11A') 0.0070 ≦ 1 / f3v3 ≦ 0.0100

[0190] P' and Q' are defined as above.

[0191] In the above formulae (1') to (11'), the values of f1 / f, φ1 / n1, φ1 / v1, f2 / f, φ2 / n2, φ2 / v2, P, Q, f3 / f, φ3 / n3, φ3 / v3, f, n1, n2, n3, v1, v2, and v3 can also be set to any combination within the ranges obtained by the upper and lower limit values exemplified in the above formulae (1) to (11). In the above formulae (2A'), (3A'), (5A'), (6A'), (7A'), (8A'), (10A'), and (11A'), the values of 1 / f1n1, 1 / f1v1, 1 / f2n2, 1 / f2v2, P', Q', 1 / f3n3, and 1 / f3v3 can also be set to any combination within the ranges obtained by the upper and lower limit values exemplified in the above formulae (2A), (3A), (5A), (6A), (7A), (8A), (10A), and (11A).

[0192] The above-described formulas (1') to (11') and (2A'), (3A'), (5A'), (6A'), (7A'), (8A'), (10A'), and (11A') are formulas that further limit the numerical ranges of the above-described formulas (1) to (11) and (2A), (3A), (5A), (6A), (7A), (8A), (10A), and (11A). In a case where the first lens 101, the second lens 102, and the third lens 103 are configured using a non-fluorescent material, the refractive index, the Abbe number, and the shape of the lens of each lens are sometimes limited to some extent, and by limiting the numerical ranges of the above-described formulas (1) to (11) to the ranges of the above-described formulas (1') to (11') and (2A'), (3A'), (5A'), (6A'), (7A'), (8A'), (10A'), and (11A'), it is possible to further suppress deterioration in flatness of an image plane of the entire optical system including the imaging lens and the attachment lens and generation of chromatic aberration.

[0193] [USES]

[0194] The attachment lens 100 is used in combination with a photographing lens, and an observation object is observed through the attachment lens 100. The photographing lens is not particularly limited, and can be, for example, a photographing lens of an information processing terminal such as a smartphone or a tablet, or a photographing lens of a video camera or a microscope.

[0195] Figure 1 An example in which a flat optical element 200 is interposed between the observation object and the first lens 101 of the attachment lens 100 is shown. The flat optical element 200 is an optical element having a substantially flat shape, and can be, for example, a protective lens for protecting the attachment lens 100, a wavelength filter that transmits or blocks a specific wavelength, a polarizing plate, or a phase difference plate.

[0196] The attachment lens 100 is configured by three lenses, and does not require a plurality of lenses, and thus there is a tendency to be able to reduce the thickness of the attachment lens as a whole. Therefore, even in a case where it is necessary to reduce the focal distance f or a case where it is necessary to reduce the interval between the attachment lens 100 and the observation object, it is easy to design an optical system in which an optical element other than the attachment lens 100 is interposed between the observation object and the first lens 101. That is, the attachment lens 100 can also be applied to uses in which it is difficult to design the optical system in which the flat optical element 200 or another optical element is interposed between the observation object and the first lens 101. Of course, the attachment lens 100 can also be applied to uses in which no other optical element is interposed between the observation object and the first lens 101.

[0197] Therefore, the attached lens 100 can also be used, for example, for fluorescence analysis or luminescence analysis. In this case, the flat optical element 200 can be a wavelength filter that selectively transmits light of a wavelength emitted from a fluorescent substance contained in the observed object or from a luminescent substance. The wavelength filter can also block light of the excitation wavelength of the fluorescent substance.

[0198] The attachment lens of this embodiment, once mounted on the imaging lens, can naturally be used for purposes other than those described above. For example, the attachment lens of this embodiment can be omitted. Figure 1 The planar optical element 200 can be used in this way, or it can replace the planar optical element 200, or other optical elements can be inserted between the object being observed and the first lens 101 in addition to the planar optical element 200.

[0199] [Numerical Examples]

[0200] The following describes a numerical embodiment of the attached lens 100 described above, but the present invention is not limited thereto. Furthermore, in the following numerical embodiments, the unit of length is mm.

[0201] exist Figure 2 The parameters of the optical system are represented in the diagram. R1 to R10 refer to the first principal surface of the sample stage 300, the second principal surface of the sample stage 300, the first principal surface of the flat optical element 200, the second principal surface of the flat optical element 200, the first principal surface of the first lens 101, the second principal surface of the first lens 101, the first principal surface of the second lens 102, the second principal surface of the second lens 102, the first principal surface of the third lens 103, and the second principal surface of the third lens 103. Additionally, R11 indicates the placement position of the imaging lens. Here, the object of observation is placed on surface R1.

[0202] In addition, in each numerical embodiment, the refractive index and Abbe number of the sample stage 300 are set to 1.531 and 56.0, respectively; the refractive index and Abbe number of the flat optical element 200 are set to 1.523 and 54.5, respectively; and the refractive index and Abbe number of the first to third lenses are set to the values ​​described in Table 8 below.

[0203] Further, the material used in the sample stage, the flat optical element, and each lens is not particularly limited as long as it satisfies the physical property values described in each numerical example. For example, the refractive index and Abbe number of the sample stage 300, and the first lens 101 and the third lens 103 are obtained from a cyclo olefin polymer (COP) or the like. As such first lens 101 and third lens 103, ZEONEX manufactured by Zeon Corporation in Japan can be given. The refractive index and Abbe number of the flat optical element 200 are obtained from a general commercially available UV cut filter or the like. The refractive index and Abbe number of the second lens 102 are obtained from a commercially available lens or the like. As such second lens 102, Iupizeta manufactured by Mitsubishi Gas Chemical Company, Inc. can be given. Further, at least numerical examples 1 and 3 are numerical examples in which all the lenses are composed of a non-fluorescent material.

[0204] In the following table, the distances dl to d10 in each numerical example are shown.

[0205] [Table 1]

[0206]

[0207] In each numerical example, Rl, R2, R3, and R4 are set to a plane. R5, R6, R7, R8, R9, and RlO are aspherical surfaces, each of which is represented by the following aspherical function. Further, in the following formula, the optical axis direction is set to z, the direction orthogonal to the optical axis is set to y, K is set to a conic coefficient, R is set to a curvature radius, and a04, a06, a08, alO, a12, a14, and a16 are set to aspherical coefficients.

[0208] [Formula 1]

[0209]

[0210] In each numerical example, the conic coefficient K in the above formula is set to 0, and the curvature radius R of the surfaces R5 to RlO is set to the value shown in the following table. Further, a negative curvature radius means that there is a convex curvature on the right side of Figure 2

[0211] [Table 2]

[0212]

[0213] Further, the aspherical coefficients a04, a06, a08, alO, a12, a14, and a16 in each numerical example are set to the values shown in the following table. In the following table, "E±x" means "x 10 ±x

[0214] (Numerical Example 1)

[0215] [Table 3]​​

[0216]

[0217] (Numberical Example 2)

[0218] [Table 4]

[0219]

[0220] (Numberical Example 3)

[0221] [Table 5]

[0222]

[0223] (Numberical Example 4)

[0224] [Table 6]

[0225]

[0226] (Numberical Example 5)

[0227] [Table 7]

[0228]

[0229] Each parameter in each numerical example is the value indicated in the following table. In addition, the definition of the notation in the following table is as described above.

[0230] [Table 8]

[0231]

[0232] In addition, as the characteristics of the entire attachment lens composed of the first lens 101, the second lens 102, and the third lens 103 in each numerical example, the focal distance f, the effective F number, and the half viewing angle ω are the values indicated in the following table. From the above, it is known that in each numerical example, even if the original camera lens is assembled, the optical performance of the entire attachment lens does not deteriorate, and a fine object can be observed at high resolution.

[0233] [Table 9]

[0234]

[0235] [Notes]

[0236] The present application includes the following embodiments.

[0237] [1] An attachment lens having, from the object side, a first lens having a positive refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power,

[0238] Both surfaces of the first lens, the second lens, and the third lens are aspherical surfaces,

[0239] satisfy the following expressions (1), (2), (3), (4), (5), and (6).

[0240] (1) 4.30 ≦ f1 / f ≦ 4.95

[0241] (2) 0.120 ≦ φ1 / n1 ≦ 0.160

[0242] (3) 0.0030 ≦ φ1 / ν1 ≦ 0.0050

[0243] (4) -3.20 ≦ f2 / f ≦ -2.70

[0244] (5) -0.240 ≦ φ2 / n2 ≦ -0.160

[0245] (6) -0.0200 ≦ φ2 / ν2 ≦ -0.0120

[0246] f: total focal distance of the attached lens with respect to the d-line

[0247] f1: focal distance of the first lens with respect to the d-line

[0248] φ1: product of the refractive power of the first lens with respect to the d-line and f (f / f1)

[0249] n1: refractive index of the first lens with respect to the d-line

[0250] ν1: Abbe number of the first lens

[0251] f2: focal distance of the second lens with respect to the d-line

[0252] φ2: product of the refractive power of the second lens with respect to the d-line and f (f / f2)

[0253] n2: refractive index of the second lens with respect to the d-line

[0254] ν2: Abbe number of the second lens

[0255] [2] The attached lens according to [1], wherein

[0256] further satisfies the following expressions (7) and (8).

[0257] (7) 0.000 ≦ P ≦ 0.510

[0258] (8) -0.0046 ≦ Q ≦ 0.0046

[0259] P: sum of φ1 / n1, φ2 / n2, and φ3 / n3

[0260] Q: sum of φ1 / ν1, φ2 / ν2, and φ3 / ν3

[0261] φ3: product of the refractive power of the third lens with respect to the d line and f (f / f3)

[0262] f3: focal distance of the third lens with respect to the d line

[0263] n3: refractive index of the third lens with respect to the d line

[0264] ν3: Abbe number of the third lens

[0265] [3] The attachment lens according to [1] or [2], wherein

[0266] the following expressions (9), (10), and (11) are also satisfied.

[0267] (9) 1.10 ≦ f3 / f ≦ 1.40

[0268] (10) 0.000 ≦ φ3 / n3 ≦ 0.600

[0269] (11) 0.0000 ≦ φ3 / ν3 ≦ 0.0200

[0270] f3: focal distance of the third lens with respect to the d line

[0271] φ3: product of the refractive power of the third lens with respect to the d line and f (f / f3)

[0272] n3: refractive index of the third lens with respect to the d line

[0273] ν3: Abbe number of the third lens

[0274] [4] The attachment lens according to any one of [1] to [3], wherein

[0275] the first lens, the second lens, and the third lens are each composed of a non-fluorescent material.

[0276] [5] The attachment lens according to [4], wherein

[0277] the following expressions (1'), (2'), (3'), (4'), (5'), and (6') are satisfied.

[0278] (1') 4.33 ≦ f1 / f ≦ 4.94

[0279] (2') 0.130 ≦ φ1 / n1 ≦ 0.155

[0280] (3') 0.0035 ≦ φ1 / ν1 ≦ 0.0042

[0281] (4') -3.05 ≦ f2 / f ≦ -2.70

[0282] (5') -0.230 ≦ φ2 / n2 ≦ -0.180

[0283] (6') -0.0190 ≦ φ2 / ν2 ≦ -0.0130

[0284] [6] The attached lens according to [4] or [5], wherein

[0285] the following formulae (7') and (8') are also satisfied.

[0286] (7') 0.000 ≦ P ≦ 0.482

[0287] (8') -0.0040 ≦ Q ≦ 0.0040

[0288] P: sum of φ1 / n1, φ2 / n2, and φ3 / n3

[0289] Q: sum of φ1 / ν1, φ2 / ν2, and φ3 / ν3

[0290] φ3: product of power with respect to the d-line and f of the third lens (f / f3)

[0291] f3: focal distance with respect to the d-line of the third lens

[0292] n3: refractive index with respect to the d-line of the third lens

[0293] ν3: Abbe number of the third lens

[0294] [7] The attached lens according to any one of [4] to [6], wherein

[0295] the following formulae (9'), (10'), and (11') are also satisfied.

[0296] (9') 1.20 ≦ f3 / f ≦ 1.30

[0297] (10') 0.400 ≦ φ3 / n3 ≦ 0.550

[0298] (11') 0.0100 ≦ φ3 / ν3 ≦ 0.0150

[0299] f3: focal distance with respect to the d-line of the third lens

[0300] φ3: product of power with respect to the d-line and f of the third lens (f / f3)

[0301] n3: refractive index with respect to the d-line of the third lens

[0302] ν3: Abbe number of the third lens

[0303] [8] The attachment lens according to any one of [1] to [7], wherein

[0304] is used with a flat optical element interposed between the observation object and the first lens.

[0305] [9] The attachment lens according to [8], wherein

[0306] the flat optical element is a wavelength filter.

[0307]

[10] The attachment lens according to any one of [1] to [9], which is connected to a lens of a camera of a mobile terminal.

[0308] BRIEF DESCRIPTION OF DRAWINGS

[0309] 100: attachment lens, 101: first lens, 102: second lens, 103: third lens, 200: flat optical element, 300: sample stage, 400: arrangement surface of camera lens.

Claims

1. An attachment lens, wherein a first lens having a positive refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power are provided from an object side, both surfaces of the first lens, the second lens, and the third lens are aspherical surfaces, the following expressions (1), (2), (3), (4), (5), and (6) are satisfied, (1) 4.30 ≦ f1 / f ≦ 4.95 (2) 0.120 ≦ φ1 / n1 ≦ 0.160 (3) 0.0030 ≦ φ1 / ν1 ≦ 0.0050 (4) -3.20 ≦ f2 / f ≦ -2.70 (5) -0.240 ≦ φ2 / n2 ≦ -0.160 (6) -0.0200 ≦ φ2 / ν2 ≦ -0.0120 f: total focal distance of the attachment lens with respect to the d-line f1: focal distance of the first lens with respect to the d-line φ1: product of the refractive power of the first lens with respect to the d-line and f, f / f1 n1: refractive index of the first lens with respect to the d-line ν1: Abbe number of the first lens f2: focal distance of the second lens with respect to the d-line φ2: product of the refractive power of the second lens with respect to the d-line and f, f / f2 n2: refractive index of the second lens with respect to the d-line ν2: Abbe number of the second lens.

2. The attachment lens according to claim 1, wherein the following expressions (7) and (8) are also satisfied, P: sum of φ1 / n1, φ2 / n2, and φ3 / n3 （7）0.000≦P≦0.510 （8）－0.0046≦Q≦0.0046 Q: sum of φ1 / ν1, φ2 / ν2, and φ3 / ν3 φ3: product of the refractive power of the third lens with respect to the d-line and f, f / f3 f3: focal distance of the third lens with respect to the d-line n3: refractive index of the third lens with respect to the d-line ν3: Abbe number of the third lens.

3. The attachment lens according to claim 1 or 2, wherein the following expressions (9), (10), and (11) are also satisfied, (9) 1.10 ≦ f3 / f ≦ 1.40 (10) 0.000 ≦ φ3 / n3 ≦ 0.600 (11) 0.0000 ≦ φ3 / ν3 ≦ 0.0200 f3: focal distance of the third lens with respect to the d-line φ3: product of the refractive power of the third lens with respect to the d-line and f, f / f3 n3: refractive index of the third lens with respect to the d-line ν3: Abbe number of the third lens.

4. The attachment lens according to claim 1, wherein the first lens, the second lens, and the third lens are each composed of a non-fluorescent material.

5. The attachment lens according to claim 4, wherein the following expressions (1'), (2'), (3'), (4'), (5'), and (6') are satisfied, (1') 4.33 ≦ f1 / f ≦ 4.94 (2') 0.130 ≦ φ1 / n1 ≦ 0.155 (3') 0.0035 ≦ φ1 / ν1 ≦ 0.0042 (4') -3.05 ≦ f2 / f ≦ -2.70 (5') -0.230 ≦ φ2 / n2 ≦ -0.180 (6') -0.0190 ≦ φ2 / ν2 ≦ -0.0130.

6. The attachment lens according to claim 4 or 5, wherein ​ ​ Further, the following formulas (7') and (8') are satisfied, （7’）0.000≦P≦0.482 （8’）－0.0040≦Q≦0.0040 P: sum of φ1 / n1, φ2 / n2, and φ3 / n3 Q: sum of φ1 / ν1, φ2 / ν2, and φ3 / ν3 φ3: product of the optical power of the third lens with respect to the d-line and f, f / f3 f3: focal distance of the third lens with respect to the d-line n3: refractive index of the third lens with respect to the d-line ν3: Abbe number of the third lens.

7. The attachment lens according to claim 4 or 5, wherein Further, the following formulas (9'), (10'), and (11') are satisfied, (9') 1.20 ≦ f3 / f ≦ 1.30 (10') 0.400 ≦ φ3 / n3 ≦ 0.550 (11') 0.0100 ≦ φ3 / ν3 ≦ 0.0150 f3: focal distance of the third lens with respect to the d-line φ3: product of the optical power of the third lens with respect to the d-line and f, f / f3 n3: refractive index of the third lens with respect to the d-line ν3: Abbe number of the third lens.

8. The attachment lens according to claim 1 or 2, wherein A flat optical element is inserted between the observation object and the first lens.

9. The attachment lens according to claim 8, wherein The flat optical element is a wavelength filter.

10. The attachment lens according to claim 1 or 2, wherein The attachment lens is connected to the lens of a camera of a mobile terminal.

Images