A small-caliber endoscope optical system

Abstract

The present invention provides a small-caliber endoscope optical system, which includes a filter, an aperture, a first lens with positive focal length, a second lens with negative focal length, and a chip protection glass from the object side to the image side. The optical system satisfies the following conditional formulas: 0.1<|f1 / f|<0.7; 0.6<|f2 / f|<1.3; 1.7<|R11+R12| / |R11‑R12|<2.1; wherein f1 is the focal length of the first lens, f2 is the focal length of the second lens, f is the focal length of the entire optical system, and R11 and R12 are the radii of curvature of the object side of the first lens and the image side of the first lens, respectively. The small-caliber endoscope optical system involved in the present invention has two lenses made of plastic materials, which reduces the cost and is more suitable for mass production. Compared with previous endoscopes, it not only ensures the imaging quality, but also greatly reduces the total length and caliber of the endoscope, meeting the current trend of miniaturization of endoscopes.

Description

[Technical field]

[0001] The invention relates to an endoscope optical system, in particular to a small-caliber endoscope optical system. [Background technology]

[0002] With the development of medical electronic equipment, people have higher and higher requirements for endoscopes. People hope that the size of endoscopes can be made smaller and smaller, and they also hope that the endoscope optical system has higher imaging quality. However, the size and imaging quality of endoscopes are mutually constrained. Reducing the size usually means sacrificing the imaging quality of the optical system, including field of view, illumination, and working distance. Therefore, in order to reduce the harm of endoscopes to patients, it is necessary to reduce the caliber of the endoscope as much as possible while ensuring the imaging quality of the endoscope.

[0003] The present invention is made based on this situation. [Summary of the invention]

[0004] The present invention overcomes the shortcomings of the prior art and provides a small-caliber endoscope optical system, the biggest advantage of which is that the caliber is very small, the maximum caliber is less than 1mm, and the overall length of the optical system is less than 2.6mm; the optical system has a compact structure, obvious volume advantage, and good imaging quality within a certain depth of field.

[0005] The technical solution adopted by the present invention is:

[0006] A small-caliber endoscope optical system includes, from the object side to the image side, a filter (IR), a stop (ST), a first lens (L1) with positive focal power, a second lens (L2) with negative focal power, and a chip protection glass (CG), and the optical system satisfies the following conditional formula:

[0007] 0.1<|f1 / f|<0.7;

[0008] 0.6<|f2 / f|<1.3;

[0009] 1.7<|R11+R12| / |R11-R12|<2.1;

[0010] Wherein, f1 is the focal length of the first lens (L1), f2 is the focal length of the second lens (L2), f is the focal length of the entire optical system, and R11 and R12 are the curvature radii of the object side surface (S4) of the first lens (L1) and the image side surface (S5) of the first lens (L1), respectively.

[0011] The small-diameter endoscope optical system as described above is characterized in that: the object side surface (S4) of the first lens (L1) is concave, and the image side surface (S5) is convex; the object side surface (S6) of the second lens (L2) is concave, and the image side surface (S7) is concave; both the first lens (L1) and the second lens (L2) are plastic aspherical lenses.

[0012] The small-diameter endoscope optical system as described above is characterized in that the optical system satisfies the following conditional formula:

[0013] 0.23 < f / TTL < 0.71; where f is the focal length of the entire optical system, and TTL is the axial distance from the object side surface (S1) of the filter (IR) of the optical system to the imaging surface (S10).

[0014] The small-diameter endoscope optical system as described above is characterized in that the optical system satisfies the following conditional formula:

[0015] 30 < |Vd1 - Vd2| < 40; where Vd1 is the Abbe number of the first lens (L1); Vd2 is the Abbe number of the second lens (L2).

[0016] The small-diameter endoscope optical system as described above is characterized in that the optical system satisfies the following conditional formula:

[0017] 2.7 < TTL / ImgH < 3.4; where ImgH is the maximum image height of the optical system, and TTL is the axial distance from the object side surface (S1) of the filter of the optical system to the imaging surface (S10).

[0018] The small-diameter endoscope optical system as described above is characterized in that the optical system satisfies the following conditional formula:

[0019] 0.25 < Ts1 / f < 0.41;

[0020] 0.04 < T12 / f < 0.11;

[0021] 1.1 < T2i / f < 2.3;

[0022] Where Ts1 is the axial distance from the image side surface (S2) of the filter (IR) to the object side surface (S4) of the first lens (L1), T12 is the axial distance between the image side surface (S5) of the first lens (L1) and the object side surface (S6) of the second lens (L2); T2i is the axial distance from the image side surface (S7) of the second lens (L2) to the imaging surface (S10), and f is the focal length of the entire optical system.

[0023] The small-diameter endoscope optical system as described above is characterized in that the optical system satisfies the following conditional formula:

[0024] 0.81 < CT1 / ∑CT < 0.84;

[0025] 0.41 < CT2 / ∑CT < 0.58;

[0026] Wherein, ∑CT is the total thickness of the filter (IR) and the second lens (L2) of the optical system on the optical axis respectively; CT1 is the thickness of the first lens (L1) of the optical system on the optical axis, and CT2 is the thickness of the second lens (L2) of the optical system on the optical axis.

[0027] The small-diameter endoscope optical system as described above is characterized in that the optical system satisfies the following conditional formula:

[0028] 11 < FNO·ImgH / β < 25; wherein, FNO is the aperture value of the optical system, ImgH is the maximum image height of the optical system, and β is the lateral magnification of the optical system.

[0029] The small-diameter endoscope optical system as described above is characterized in that the optical system satisfies the following conditional formula:

[0030] 0.6 < f·tan(ω / 2) / ImgH < 1.5; wherein, ω is the maximum field of view angle of the optical system placed in air.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The small-diameter endoscope optical system provided by the present invention, compared with the conventional endoscopes, while ensuring the imaging quality, greatly reduces the total length and diameter of the endoscope, meeting the current trend of miniaturization development of endoscopes; both of the two lenses used in the optical system are plastic lenses, reducing the cost and being more suitable for mass production.

Description of the Drawings

[0033] Figure 1 is a schematic structural diagram of the small-diameter endoscope optical system of the present invention;

[0034] Figure 2 is a distortion diagram of the small-diameter endoscope optical system of the present invention;

[0035] Figure 3 is an aberration curve diagram of the small-diameter endoscope optical system of the present invention;

Detailed Embodiments

[0036] The present invention will be further described in detail below with reference to the drawings.

[0037] A small-caliber endoscope optical system includes, from the object side to the image side, a filter (IR), a stop (ST), a first lens (L1) with positive focal length, a second lens (L2) with negative focal length, and a chip protection glass (CG), and the optical system satisfies the following conditional formula:

[0038] 0.1<|f1 / f|<0.7; (1)

[0039] 0.6<|f2 / f|<1.3; (2)

[0040] 1.7<|R11+R12| / |R11-R12|<2.1; (3)

[0041] Wherein, f1 is the focal length of the first lens (L1), f2 is the focal length of the second lens (L2), f is the focal length of the entire optical system, and R11 and R12 are the curvature radii of the object side surface (S4) of the first lens (L1) and the image side surface (S5) of the first lens (L1), respectively.

[0042] After the light enters the optical system, it is first refracted by the filter (IR), then passes through the aperture (ST), and then passes through the first lens (L1) and the second lens (L2) in sequence, and finally forms an image on a specific chip.

[0043] The small-aperture endoscope optical system as described above is characterized in that: the object side surface (S4) of the first lens (L1) is a concave surface, and the image side surface (S5) is a convex surface; the object side surface (S6) of the second lens (L2) is a concave surface, and the image side surface (S7) is a concave surface; the first lens (L1) and the second lens (L2) are both plastic aspherical lenses.

[0044] The small-aperture endoscope optical system satisfying equations (1), (2), and (3) can constrain the curvature radius and focal length of the lens, control the curvature of the lens, reduce the total length and aperture of the optical system, make the optical system structure compact, and meet the requirements of miniaturization; the object side surface (S4) of the first lens (L1) is a concave surface, and the image side surface (S5) is a convex surface, and the object side surface (S6) of the second lens (L2) is a concave surface, and the image side surface (S7) is a concave surface, which can reduce optical aberrations, reduce the sensitivity of tolerances, and effectively reduce the total length of the optical system.

[0045] The small-caliber endoscope optical system as described above satisfies the following conditional formula:

[0046] 0.23 <f / TTL<0.71; (4)

[0047] Wherein, f is the focal length of the entire optical system, and TTL is the axial distance from the object side (S1) to the imaging surface (S10) of the optical system filter (IR).

[0048] A small-aperture endoscope optical system that satisfies equation (4) can ensure a shorter working distance while having a larger field of view.

[0049] The small-caliber endoscope optical system as described above satisfies the following conditional formula:

[0050] 30<|Vd1-Vd2|<40; (5)

[0051] Wherein, Vd1 is the Abbe number of the first lens (L1); Vd2 is the Abbe number of the second lens (L2).

[0052] Formula (5) can be used to constrain the material range of the optical system and reduce the chromatic aberration of magnification.

[0053] The small-caliber endoscope optical system as described above satisfies the following conditions:

[0054] 2.7 <TTL / ImgH<3.4; (6)

[0055] Wherein, ImgH is the maximum image height of the optical system, and TTL is the axial distance from the object side (S1) of the optical filter (IR) to the imaging surface (S10) of the optical system.

[0056] The small-caliber endoscope optical system that satisfies formula (6) can not only limit the total length of the optical system and meet the requirements of miniaturization, but also constrain the image quality of the lens within an ideal range;

[0057] The small-caliber endoscope optical system as described above satisfies the following conditional formula:

[0058] 0.25 <Ts1 / f<0.41; (7)

[0059] 0.04 <T12 / f<0.11; (8)

[0060] 1.1 <T2i / f<2.3; (9)

[0061] Wherein, Ts1 is the axial distance from the image side surface (S2) of the filter (IR) to the object side surface (S4) of the first lens (L1), T12 is the axial distance from the image side surface (S5) of the first lens (L1) and the object side surface (S6) of the second lens (L2); T2i is the axial distance from the image side surface (S7) of the second lens (L2) to the image plane (S10), and f is the focal length of the entire optical system.

[0062] A small-aperture endoscope optical system that satisfies equations (7), (8), and (9) can not only help reduce the total length of the optical system, but also ensure that the field of view and distortion of the optical system are within the required range, thus meeting the requirements of miniaturization.

[0063] The small-caliber endoscope optical system as described above satisfies the following conditional formula:

[0064] 0.81 <CT1 / ∑CT<0.84; (10)

[0065] 0.41 <CT2 / ∑CT<0.58; (11)

[0066] Wherein, ΣCT is the sum of the thicknesses of the optical system filter (IR) and the second lens (L2) on the optical axis; CT1 is the thickness of the first lens (L1) of the optical system on the optical axis; and CT2 is the thickness of the second lens (L2) of the optical system on the optical axis.

[0067] Satisfying equation (10) can constrain the aperture and distortion of the optical system.

[0068] Satisfying equation (11) can constrain the total length of the optical system.

[0069] The small-caliber endoscope optical system as described above satisfies the following conditional formula:

[0070] 11 <FNO·ImgH / β<25; (12)

[0071] Wherein, FNO is the aperture value of the optical system, ImgH is the maximum image height of the optical system, and β is the vertical axis magnification of the optical system.

[0072] The optical system that satisfies formula (12) can be used to limit the depth of field, illumination and magnification of the optical system within an appropriate range. When FNO·ImgH / β is lower than the lower limit, the depth of field of the endoscope optical system will deteriorate. When FNO·ImgH / β exceeds the upper limit, the vertical axis magnification of the endoscope optical system will be too small, which will affect the overall resolution of the lens and the lens illumination will also decrease.

[0073] The small-caliber endoscope optical system as described above satisfies the following conditional formula:

[0074] 0.6 <f·tan(ω / 2) / ImgH<1.5; (13)

[0075] Wherein, ω is the maximum field of view of the optical system placed in air.

[0076] In summary, compared with previous endoscopes, the small-caliber endoscope optical system provided by the present invention greatly reduces the total length and diameter of the endoscope while ensuring the imaging quality, meeting the current trend of miniaturization of endoscopes; the two lenses used in the optical system are both plastic lenses, which reduces the cost and is more suitable for mass production.

[0077] The following are some optical parameters of the embodiment of the small-aperture endoscope optical system. In the lens data table of this embodiment, the units of radius and thickness are mm, and S (solid line) and T (dashed line) in the aberration curve diagram represent the sagittal image plane and the meridional image plane, respectively.

[0078] Figure 1 This is the overall structure diagram of the small-caliber endoscope optical system. Figure 2 is the distortion diagram of the small-caliber endoscope optical system, Figure 3 This is the aberration curve diagram of the small-aperture endoscope optical system.

[0079] The following table is the lens data table of the embodiment

[0080] Table 1 is the structural parameters of the optical system of small-caliber endoscope

[0081] Surface Type Radius(mm) Thickness(mm) Glass Object Sphere Infinity 3.8 1 Sphere Infinity 0.2100 1.517:64.2 2 Sphere Infinity 0.2200 Stop Sphere Infinity 0.0300 4 Asphere -0.6501 0.3531 1.544:56.2 5 Asphere -0.1857 0.0600 6 Asphere -1.3752 0.2200 1.633:23.35 7 Asphere 0.8287 0.6668 8 Sphere Infinity 0.5098 1.517:64.2 9 Sphere Infinity 0.014 Image Sphere Infinity 0.2200

[0082] Table 1

[0083] Table 2 shows the ratio of the sagittal height to the radius R of the first lens L1 of the small-aperture endoscope optical system

[0084]

[0085]

[0086] Table 2

[0087] Table 3 shows the ratio of the sagittal height to the radius R of the second lens L2 of the small-aperture endoscope optical system

[0088]

[0089] Table 3.

Claims

1. A small-caliber endoscope optical system, characterized in that From the object side to the image side, it includes five parts: filter (IR), aperture (ST), first lens with positive focal power (L1), second lens with negative focal power (L2), chip protection glass (CG), where the structural parameters of the optical system are as follows: 。

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