Small aperture large target surface lens

Abstract

The present application relates to a kind of small-bore large target surface lens, interval installation is in the protective glass before endoscope detector, including being sequentially arranged by object side to image side direction first lens, diaphragm, second lens and third lens;Wherein, first lens is the negative optical power plastic aspheric lens, 1.45<n<1.60, 50<Vd<60;Second lens is the positive optical power plastic aspheric lens, 1.45<n<1.60, 50<Vd<60;Third lens is the positive optical power plastic aspheric lens, 1.55<n<1.70, 20<Vd<35;The present application overcomes the shortcomings that existing endoscope lens cannot simultaneously have small-bore and large target surface, the present application provides a kind of small-bore large target surface lens, by specially designing material, shape, optical power and the cooperation of focal length of three lenses and diaphragm, with the advantages of simple structure, small-bore and large target surface.

Description

TECHNICAL FIELD

[0001] The present application relates to a small aperture large target surface lens, especially applied to an endoscope. BACKGROUND

[0002] The endoscope can enter into the human body through the natural orifice of the human body, and can be used to check and treat diseases, and is often applied to the examination and treatment of diseases in the digestive tract, respiratory tract, urinary tract, chest cavity, abdominal cavity and joint cavity. However, the natural orifice of the human body is narrow, and in order to reduce the discomfort, the size of the lens of the endoscope should be as small as possible, and in order to increase the clarity during the examination, the target surface should be as large as possible. However, the existing endoscope lens cannot simultaneously have a small aperture (aperture < 2.5 mm) and a large target surface (target surface ≥ 2.1 mm) at a short working distance, and the aperture will naturally increase when the target surface is larger. Therefore, it is urgent to provide a small aperture large target surface lens which has the advantages of simple structure, small aperture and large target surface. SUMMARY

[0003] In order to overcome the shortcomings of the existing endoscope lens which cannot simultaneously have a small aperture and a large target surface, the present application provides a small aperture large target surface lens which has the advantages of simple structure, small aperture and large target surface by specially designing the material, shape, optical power and focal length of three lenses and the cooperation of the diaphragm.

[0004] The technical scheme of the present application is as follows:

[0005] A small aperture large target surface lens is installed in front of the protective glass of an endoscope probe, and comprises a first lens, a diaphragm, a second lens and a third lens which are sequentially and spacedly arranged from the object side to the image side.

[0006] The first lens is a negative plastic aspherical lens, 1.45 < n < 1.60, 50 < Vd < 60.

[0007] The second lens is a positive plastic aspherical lens, 1.45 < n < 1.60, 50 < Vd < 60.

[0008] The third lens is a positive plastic aspherical lens, 1.55 < n < 1.70, 20 < Vd < 35.

[0009] The air gap between the first lens and the diaphragm is 0.15-0.35 mm,

[0010] The air gap between the diaphragm and the second lens is 0.03-0.09 mm,

[0011] The air gap between the second lens and the third lens is 0.05-0.1 mm.

[0012] The focal length of the first lens is -1.35~ -1.2mm,

[0013] The focal length of the second lens is 0.86~0.9mm,

[0014] The focal length of the third lens is 4.1~4.8mm;

[0015] The radius of curvature of the front surface of the first lens is -2.05~ -1.9mm, and the radius of curvature of the back surface is 1.05~1.2mm; the radius of curvature of the front surface of the second lens is 0.7~0.8mm, and the radius of curvature of the back surface is -2.0~ -0.5mm; the radius of curvature of the front surface of the third lens is 0.4~0.55mm, and the radius of curvature of the back surface is 0.4~0.55mm;

[0016] The central thickness of the first lens is 0.1~0.3mm; the central thickness of the second lens is 0.45~0.65mm; and the central thickness of the third lens is 0.1~0.3mm.

[0017] The small-aperture large-target lens of the present application has the advantages of simple structure, small aperture and large target by matching three lenses and diaphragms with special design of material, shape, focal power and focal length. The main parameters affecting the lens aperture are focal length, distortion, field angle, aperture size, chief ray incidence angle, etc. In order to design a small-aperture lens product, the lens of the present application matches three lenses and diaphragms with special design of material, shape, focal power and focal length, so that the focal length of the lens is 0.8±5% mm, the distortion is ≤|16.9%|, which meets an extreme acceptable distortion range, and the aperture F is controlled at 5±5%, which can meet the light amount during use and reduce the incident pupil size. The chief ray angle is designed to be relatively large, which reduces the rear optical aperture, thereby shortening the back focal length and controlling the optical size aperture of the lens. The large target is selected by matching a 2.1 mm large target chip. The 110° object side light in the object side field of view is projected to the lens, and the curvature of the front lens and the focal power of the lenses are adjusted to make the light in the 110° object side be received by the lens, which is converged to the image side after deflection of the optical system, and the converged image circle covers all the photosensitive areas of the chip to realize the design of the large target of the lens. That is, the present application optimizes a minimum optical aperture by comprehensively considering the above several main parameters, and ensures the large target at the same time. The distance between the third lens and the protective glass is 0.3-0.45 mm during use. The target of the small-aperture large-target lens can reach 2.1 mm, the lens aperture is less than 1.44 mm, the working distance is 5-70 mm, and it is applicable in the environment of 10-40℃. The full field MTF meets 125lp / mm>0.3, the F number is 5±5%, the optical total length is 2.6±0.1 mm, FOV (view angle): 0-110°, half image height: 0-1.08 mm, full field RMS radius <2um, relative luminance >56%, and it has good resolution. The distance between the filter and the object side can be 5-100 mm, and the distance between the filter and the first lens can be 0-0.1 mm.

[0018] Table 1 Optical structure parameters (the lens of the present application is applied to an endoscope)

[0019]

[0020]

[0021] The first lens, the second lens and the third lens are all odd non-spherical surfaces (i.e. aspherical lenses), which meet the following expression:

[0022]

[0023] In the formula, r is the diameter in the direction perpendicular to the optical axis, z is the distance from the vertex of the aspheric surface when the aspheric surface is at a position with a height of r along the optical axis, c represents the vertex curvature of the surface, k is the conic coefficient, and a is a high-order aspheric surface coefficient.

[0024] Table 2 aspheric surface coefficients

[0025]

[0026]

[0027]

[0028] The small-aperture large-target-surface lens further comprises a filter arranged between the object side and the first lens.

[0029] The application also optimizes the structure of the lens system, and the filter is usually applied to the rear end of the lens. In the application, the filter is arranged at the front end of the lens (i.e., between the object side and the first lens), so that the probability of ghosting of the filter is reduced, and the influence of ghosting on the detection picture is reduced.

[0030] The filter satisfies 1.45 < n < 1.55 and 55 < Vd < 65.

[0031] The preferred filter can effectively reduce the probability of ghosting of the filter and reduce the influence of ghosting on the detection picture.

[0032] The thickness of the filter is 0.1-0.3 mm.

[0033] The preferred thickness of the filter is not only good for processing but also can reduce the length of the lens, and does not affect the effect of the lens.

[0034] Compared with the prior art, the application has the following advantages:

[0035] 1) The small-aperture large-target-surface lens of the application has the advantages of simple structure, small aperture and large target surface by special design of the material, shape, optical power and focal length of the three lenses and the cooperation of the diaphragm.

[0036] 2) The application also optimizes the structure of the lens system, and the filter is usually applied to the rear end of the lens. In the application, the filter is arranged at the front end of the lens (i.e., between the object side and the first lens), so that the probability of ghosting of the filter is reduced, and the influence of ghosting on the detection picture is reduced. DETAILED DESCRIPTION

[0037] Figure 1 is a schematic diagram of the optical structure of the small-aperture large-target-surface lens of the application;

[0038] Figure 2 is a MTF graph of the small-aperture large-target-format lens embodiment 1 according to the present application;

[0039] Figure 3 is a spot diagram of the small-aperture large-target-format lens embodiment 1 according to the present application;

[0040] Figure 4 is a field curvature / distortion graph of the small-aperture large-target-format lens embodiment 1 according to the present application;

[0041] Figure 5 is an illuminance graph of the small-aperture large-target-format lens embodiment 1 according to the present application;

[0042] Figure 6 is a MTF graph of the small-aperture large-target-format lens embodiment 2 according to the present application;

[0043] Figure 7 is a spot diagram of the small-aperture large-target-format lens embodiment 2 according to the present application;

[0044] Figure 8 is a field curvature / distortion graph of the small-aperture large-target-format lens embodiment 2 according to the present application;

[0045] Figure 9 is an illuminance graph of the small-aperture large-target-format lens embodiment 2 according to the present application;

[0046] Figure 10 is a MTF graph of the small-aperture large-target-format lens embodiment 3 according to the present application;

[0047] Figure 11 is a spot diagram of the small-aperture large-target-format lens embodiment 3 according to the present application;

[0048] Figure 12 is a field curvature / distortion graph of the small-aperture large-target-format lens embodiment 3 according to the present application;

[0049] Figure 13 is an illuminance graph of the small-aperture large-target-format lens embodiment 3 according to the present application.

[0050] Figure 14 is a MTF graph of the small-aperture large-target-format lens embodiment 4 according to the present application;

[0051] Figure 15 is a spot diagram of the small-aperture large-target-format lens embodiment 4 according to the present application;

[0052] Figure 16 is a field curvature / distortion graph of the small-aperture large-target-format lens embodiment 4 according to the present application;

[0053] Figure 17 is an illuminance graph of the small-aperture large-target-format lens embodiment 4 according to the present application.

[0054] Label Explanation:

[0055] First lens 1, second lens 2, third lens 3, aperture 4, filter 5, protective glass 6, endoscope detector 7. Detailed Implementation

[0056] The following is in conjunction with the instruction manual appendix. Figures 1-13 The technical solution of the present invention will be described in detail below.

[0057] Example 1

[0058] like Figures 1-5 As shown, the small-aperture, large-target-surface lens of the present invention is installed at intervals in front of the protective glass 6 of the OmniVision OV9734: 2.056mm*1.792mm*1.008mm endoscope detector 7, and includes a first lens 1, an aperture 4, a second lens 2 and a third lens 3 arranged at intervals from the object side to the image side.

[0059] Among them, the first lens 1 is a negative optical power plastic aspherical lens, 1.45. <n<1.60、50<Vd<60;

[0060] The second lens 2 is a positive optical power plastic aspherical lens, 1.45. <n<1.60、50<Vd<60;

[0061] The third lens, 3, is a positive optical power plastic aspherical lens, 1.55. <n<1.70、20<Vd<35;

[0062] The air gap between the first lens 1 and the aperture 4 is 0.257 mm.

[0063] The air gap between aperture 4 and the second lens 2 is 0.06 mm.

[0064] The air gap between the second lens 2 and the third lens 3 is 0.081 mm;

[0065] The focal length of the first lens 1 is -1.309mm.

[0066] The second lens 2 has a focal length of 0.869mm.

[0067] The focal length of the third lens is 4.147mm;

[0068] The radius of curvature of the front surface of the first lens 1 is -1.99 mm, and the radius of curvature of the rear surface is 1.13 mm; the radius of curvature of the front surface of the second lens 2 is 0.763 mm, and the radius of curvature of the rear surface is -0.9 mm; the radius of curvature of the front surface of the third lens 3 is 0.481 mm, and the radius of curvature of the rear surface is 0.481 mm.

[0069] The central thickness of the first lens 1 is 0.22 mm; the central thickness of the second lens 2 is 0.55 mm; and the central thickness of the third lens 3 is 0.22 mm.

[0070] The small-aperture large-target-surface lens further comprises a filter 5 arranged between the object side and the first lens 1, and the filter 5 is a plane lens.

[0071] The filter 5 satisfies 1.45 < n < 1.55 and 55 < Vd < 65.

[0072] The thickness of the filter 5 is 0.21 mm.

[0073] The distance between the filter 5 and the object side is 12 mm, and the distance between the filter 5 and the first lens 1 is 0.032 mm.

[0074] In use, the distance between the third lens and the protective glass is 0.380 mm.

[0075] Table 3: Optical structure parameters (the lens is applied to an endoscope)

[0076]

[0077]

[0078] The first lens, the second lens and the third lens are all odd non-spherical surfaces (i.e. non-spherical lens), and satisfy the following expression:

[0079]

[0080] In the formula, r is the aperture in the vertical direction of the optical axis, z is the distance from the vertex of the non-spherical surface when the non-spherical surface is at a height of r along the optical axis, c represents the vertex curvature of the surface, k is the conic coefficient, and a is the high-order non-spherical surface coefficient, which is referenced to the non-spherical surface coefficient table.

[0081] The non-spherical surface coefficient is shown in Table 2.

[0082] The focal length of the small-aperture large-target-surface lens is 0.76 mm, the F number is 5, the total optical length is 2.6 mm, the FOV is 106.5°, the half image height is 1.03 mm, the distortion is < 16.5%, and the full-field MTF satisfies 125 lp / mm > 0.3.

[0083] Example 2

[0084] As Figure 1 , 6A small-aperture large-target-surface lens is shown in FIG. 9, which is installed in front of the protective glass 6 of the HOYA OH01A10: 1.639mm*1.428mm*0.804mm endoscope probe 7, and comprises a first lens 1, a diaphragm 4, a second lens 2 and a third lens 3 which are sequentially and spacedly arranged from the object side to the image side.

[0085] The first lens 1 is a negative plastic aspherical lens, 1.45<n<1.60, 50<Vd<60.

[0086] The second lens 2 is a positive plastic aspherical lens, 1.45<n<1.60, 50<Vd<60.

[0087] The third lens 3 is a positive plastic aspherical lens, 1.55<n<1.70, 20<Vd<35.

[0088] The air gap between the first lens 1 and the diaphragm 4 is 0.257mm,

[0089] The air gap between the diaphragm 4 and the second lens 2 is 0.06mm,

[0090] The air gap between the second lens 2 and the third lens 3 is 0.081mm.

[0091] The focal length of the first lens 1 is -1.309mm,

[0092] The focal length of the second lens 2 is 0.869mm,

[0093] The focal length of the third lens 3 is 4.147mm.

[0094] The radius of curvature of the front surface of the first lens 1 is -1.99mm, and the radius of curvature of the rear surface is 1.13mm; the radius of curvature of the front surface of the second lens 2 is 0.763mm, and the radius of curvature of the rear surface is -0.9mm; the radius of curvature of the front surface of the third lens 3 is 0.481mm, and the radius of curvature of the rear surface is 0.481mm.

[0095] The center thickness of the first lens 1 is 0.22mm; the center thickness of the second lens 2 is 0.55mm; and the center thickness of the third lens 3 is 0.22mm.

[0096] The small-aperture large-target-surface lens further comprises a filter 5 which is spacedly arranged between the object side and the first lens 1, and the filter 5 is a plane lens.

[0097] The filter 5 is 1.45<n<1.55, 55<Vd<65.

[0098] The thickness of the filter 5 is 0.21mm.

[0099] The distance between the filter 5 and the object is 12mm, and the distance between the filter 5 and the first lens 1 is 0.032mm.

[0100] When in use, the distance between the third lens and the protective glass is 0.380mm.

[0101] Table 4 Optical Structure Parameters (When the lens in this case is used in an endoscope)

[0102]

[0103]

[0104] Wherein, the first lens, the second lens, and the third lens are all odd-order aspherical surfaces (i.e., aspherical lenses), satisfying the following expression:

[0105]

[0106] In the formula, r is the aperture perpendicular to the optical axis, z is the distance from the vertex of the aspherical surface to the aspherical surface at a height of r along the optical axis; c represents the vertex curvature of the surface, k is the conic coefficient, and α is the higher-order aspherical coefficient (values ​​are taken from the aspherical coefficient table).

[0107] See Table 2 for aspherical coefficients.

[0108] The focal length of this small-aperture, large-surface lens is 0.76mm, F-number is 5, total optical length is 2.6mm, FOV is 80.16°, half-image height is 0.821mm, distortion is <16.24%, and the MTF of the entire field of view meets 125lp / mm>0.3.

[0109] Example 3

[0110] like Figure 1 , 10 As shown in Figure 13, the small-aperture, large-target-surface lens of the present invention is installed at intervals in front of the protective glass 6 of the endoscope detector 7, and includes a first lens 1, an aperture 4, a second lens 2, and a third lens 3 arranged at intervals from the object side to the image side.

[0111] Among them, the first lens 1 is a negative optical power plastic aspherical lens, 1.45. <n<1.60、50<Vd<60;

[0112] The second lens 2 is a positive optical power plastic aspherical lens, 1.45. <n<1.60、50<Vd<60;

[0113] The third lens, 3, is a positive optical power plastic aspherical lens, 1.55. <n<1.70、20<Vd<35;

[0114] The air gap between the first lens 1 and the diaphragm 4 is 0.257mm,

[0115] The air gap between the diaphragm 4 and the second lens 2 is 0.056mm,

[0116] The air gap between the second lens 2 and the third lens 3 is 0.088mm;

[0117] The focal length of the first lens 1 is -1.271mm,

[0118] The focal length of the second lens 2 is 0.867mm,

[0119] The focal length of the third lens 3 is 4.364mm;

[0120] The radius of curvature of the front surface of the first lens 1 is -2mm, and the radius of curvature of the back surface is 1.077mm; the radius of curvature of the front surface of the second lens 2 is 0.759mm, and the radius of curvature of the back surface is -0.898mm; the radius of curvature of the front surface of the third lens 3 is 0.498mm, and the radius of curvature of the back surface is 0.485mm;

[0121] The central thickness of the first lens 1 is 0.217mm; the central thickness of the second lens 2 is 0.555mm; and the central thickness of the third lens 3 is 0.221mm.

[0122] The small-aperture large-target lens further comprises a filter 5 arranged between the object side and the first lens 1, and the filter 5 is a plane lens.

[0123] The filter 5 satisfies 1.45 < n < 1.55 and 55 < Vd < 65.

[0124] The thickness of the filter 5 is 0.21mm.

[0125] The distance between the filter 5 and the object side is 12mm, and the distance between the filter 5 and the first lens 1 is 0.031mm.

[0126] In use, the distance between the third lens and the protective glass is 0.385mm.

[0127] Table 5 Optical structure parameters (when the lens is applied to an endoscope)

[0128]

[0129]

[0130] The first lens, the second lens and the third lens are all odd non-spherical surfaces (i.e. aspherical lenses), and satisfy the following expression:

[0131]

[0132] In the formula, r is the aperture in the direction of the optical axis, z is the distance from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis, c represents the vertex curvature of the surface, k is the conic coefficient, and a is a high-order aspherical surface coefficient, which is referenced to the aspherical surface coefficient table.

[0133] The aspherical surface coefficient is shown in Table 2.

[0134] The focal length of the small-aperture large-target surface lens is 0.80 mm, the F number is 5, the total optical length is 2.6 mm, the FOV is 110°, the half image height is 1.05 mm, the distortion is < 16.9%, and the full-field MTF satisfies 125 lp / mm > 0.3.

[0135] Embodiment 4

[0136] As shown in Fig. 17, the small-aperture large-target surface lens according to the present application is arranged in front of the protective glass 6 of the endoscope detector 7, and comprises a first lens 1, a diaphragm 4, a second lens 2 and a third lens 3 arranged in sequence from the object side to the image side. Figure 1 、 14 The first lens 1 is a negative plastic aspherical lens, 1.45 < n < 1.60, 50 < Vd < 60.

[0137] The second lens 2 is a positive plastic aspherical lens, 1.45 < n < 1.60, 50 < Vd < 60.

[0138] The second lens 2 is a positive plastic aspherical lens, 1.45 < n < 1.60, 50 < Vd < 60.

[0139] The third lens 3 is a positive plastic aspherical lens, 1.55 < n < 1.70, 20 < Vd < 35.

[0140] The air gap between the first lens 1 and the diaphragm 4 is 0.218 mm,

[0141] The air gap between the diaphragm 4 and the second lens 2 is 0.078 mm,

[0142] The air gap between the second lens 2 and the third lens 3 is 0.073 mm.

[0143] The focal length of the first lens 1 is -1.329 mm,

[0144] The focal length of the second lens 2 is 0.896 mm,

[0145] The focal length of the third lens 3 is 4.729 mm.

[0146] The first lens 1 has a front surface with a radius of curvature of -1.967 mm and a back surface with a radius of curvature of 1.166 mm; the second lens 2 has a front surface with a radius of curvature of 0.776 mm and a back surface with a radius of curvature of -0.952 mm; and the third lens 3 has a front surface with a radius of curvature of 0.529 mm and a back surface with a radius of curvature of 0.534 mm.

[0147] The first lens 1 has a central thickness of 0.225 mm; the second lens 2 has a central thickness of 0.555 mm; and the third lens 3 has a central thickness of 0.224 mm.

[0148] The small-aperture large-target-surface lens further comprises a filter 5 arranged between the object side and the first lens 1, and the filter 5 is a plane lens.

[0149] The filter 5 has a refractive index of 1.45 < n < 1.55 and 55 < Vd < 65.

[0150] The filter 5 has a thickness of 0.21 mm.

[0151] The distance between the filter 5 and the object side is 12 mm, and the distance between the filter 5 and the first lens 1 is 0.1 mm.

[0152] In use, the distance between the third lens and the protective glass is 0.437 mm.

[0153] Table 6: Optical structure parameters (when the lens is applied to an endoscope)

[0154]

[0155]

[0156] The first lens, the second lens and the third lens are all odd-order aspheric surfaces (i.e., aspheric lenses) and satisfy the following expression:

[0157]

[0158] In the formula, r is the aperture in the direction perpendicular to the optical axis, z is the distance from the vertex of the aspheric surface when the aspheric surface is at a height of r along the optical axis, c represents the vertex curvature of the surface, k is the conic coefficient, and ɑ is the high-order aspheric coefficient, which is referenced to the aspheric coefficient table.

[0159] The aspheric coefficients are shown in Table 2.

[0160] The small-aperture large-target-surface lens has a focal length of 0.84 mm, an F number of 5.2, an optical total length of 2.594 mm, a FOV of 100.4°, a half image height of 1.06 mm, a distortion of < | 15.12% |, and a full-field MTF of 100 lp / mm > 0.3.

[0161] The small-aperture large-target-surface lens described in the present application is not limited to the above-described embodiments, and any improvements or replacements based on the principle of the present application should be within the scope of protection of the present application.

Claims

1. A small aperture large target lens, which is installed in front of a protective glass (6) of an endoscope probe (7) with a spacing, characterized in that: The lens comprises a first lens (1), a diaphragm (4), a second lens (2) and a third lens (3) which are arranged in sequence in the direction from the object side to the image side. The first lens (1) is a negative plastic aspherical lens, 1.45 < n < 1.60, 50 < Vd < 60. The second lens (2) is a positive plastic aspherical lens, 1.45 < n < 1.60, 50 < Vd < 60. The third lens (3) is a positive plastic aspherical lens, 1.55 < n < 1.70, 20 < Vd < 35. The air gap between the first lens (1) and the diaphragm (4) is 0.15-0.35 mm, The air gap between the diaphragm (4) and the second lens (2) is 0.03-0.09 mm, The air gap between the second lens (2) and the third lens (3) is 0.05-0.1 mm. The focal length of the first lens (1) is -1.35--1.2 mm, The focal length of the second lens (2) is 0.86-0.9 mm, The focal length of the third lens (3) is 4.1-4.8 mm. The radius of curvature of the front surface of the first lens (1) is -2.05--1.9 mm, and the radius of curvature of the rear surface is 1.05-1.2 mm. The radius of curvature of the front surface of the second lens (2) is 0.7-0.8 mm, and the radius of curvature of the rear surface is -2.0--0.5 mm. The radius of curvature of the front surface of the third lens (3) is 0.4-0.55 mm, and the radius of curvature of the rear surface is 0.4-0.55 mm.

2. The small format, large aperture lens of claim 1, wherein: The central thickness of the first lens (1) is 0.1-0.3 mm, the central thickness of the second lens (2) is 0.45-0.65 mm, and the central thickness of the third lens (3) is 0.1-0.3 mm.

3. The small format, large aperture lens of claim 2, wherein: The small-aperture large-target lens further comprises a filter (5) which is arranged between the object side and the first lens (1) in sequence.

4. The small format, large aperture lens of claim 2, wherein: The filter (5) is a plane lens, 1.45 < n < 1.55, 55 < Vd < 65. The thickness of the filter (5) is 0.1-0.3 mm.

Images