An optical module, a zoom lens, and an endoscope

Abstract

The present invention relates to an optical module, a zoom lens, and an endoscope, which sequentially include a first lens group, a second lens group, an aperture stop, and a third lens group from the object side to the image side. The second lens group moves along the optical axis between the first lens group and the aperture stop to switch the optical module between a short focal length state and a long focal length state; the focal length of the first lens group is f1, the focal length of the third lens group is f3, the short focal length of the optical module is f W , the short focal field of view is FOV W , the long focal length is f T , the long focal field of view is FOV T , then #imgabs0# and #imgabs1# Compared with the prior art, the optical module of the present invention has good imaging effects in both the short focal length state and the long focal length state, the field curvature and distortion are effectively suppressed, and the aberration and coma are also low.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging, and in particular to an optical module, a zoom lens and an endoscope. Background Art

[0002] Thanks to the rapid development of smart healthcare in recent years, optical lenses have been increasingly used in the medical field, especially in the field of medical endoscopes. The pixel requirements for optical imaging lenses are getting higher and higher, which has also attracted more and more companies to invest more in research on ultra-high-definition, 4K and other endoscopes, hoping to develop products with higher pixels and smaller sizes. On this basis, the introduction of zoom lenses has greatly improved the compatibility of product usage scenarios. However, the aperture value of traditional zoom lenses is small, and the imaging quality is average. It is difficult to meet high-resolution application scenarios, and the imaging quality in the long-focus state and the short-focus state is often not taken into account. Summary of the invention

[0003] Based on this, it is necessary to provide an optical module, a zoom lens and an endoscope to address the problem of difficulty in balancing the quality of long-focus imaging and short-focus imaging.

[0004] An optical module, comprising a first lens group, a second lens group, an aperture stop and a third lens group in order from the object side to the image side, wherein the second lens group moves along the optical axis between the first lens group and the aperture stop, so that the optical module switches between a short focus state and a long focus state;

[0005] The focal length of the first lens group is f1, the focal length of the third lens group is f3, and the short focal length of the optical module is f W , the short-focus field of view is FOV W , the telephoto focal length is f T , the telephoto field of view is FOV T ,but and

[0006] The first lens group of the present invention comprises a first meniscus lens, a second meniscus lens and a third meniscus lens arranged in sequence from the object side to the image side, the first meniscus lens and the third meniscus lens are positive power lenses, the second meniscus lens is a negative power lens, the central curvature radius of the second meniscus lens on the image side is R3, the central curvature radius of the third meniscus lens on the object side is R4, then

[0007]

[0008] The focal length of the first meniscus lens of the present invention is f 11, the optical module further includes an imaging surface, the imaging surface is located on the image side of the third lens group, and the total optical length of the optical module is TTL, then

[0009]

[0010] In the present invention, the second lens group includes a first biconcave lens, a second biconcave lens, and a first biconvex lens arranged in sequence from the object side to the image side. The third lens group includes a second biconvex lens, a third biconvex lens, a fourth meniscus lens, and a third biconcave lens arranged in sequence from the object side to the image side. The first biconcave lens, the second biconcave lens, and the third biconcave lens are negative power lenses, and the first biconvex lens, the second biconvex lens, the third biconvex lens, and the fourth meniscus lens are positive power lenses. The first meniscus lens and the second meniscus lens are cemented, the second biconcave lens and the first biconvex lens are cemented, and the focal length f of the third meniscus lens 13 ≤ 46 mm, the focal length f of the second biconcave lens 22 ≥ -20.4 mm, the focal length f of the second biconvex lens 31 ≤ 31.5 mm.

[0011] In the present invention, the refractive index of the material of the first meniscus lens is Nd 11 , the refractive index of the material of the second meniscus lens is Nd 12 , the refractive index of the material of the fourth meniscus lens is Nd 33 , Nd 11 ≤ 1.81, Nd 12 ≤ 1.81, Nd 33 ≤ 1.85.

[0012] In the present invention, the optical module further includes a fourth lens group. The fourth lens group is located on the side of the third lens group away from the aperture stop. The fourth lens group includes a fourth biconvex lens, and the fourth biconvex lens is a positive power lens.

[0013] In the present invention, the Abbe number of the material of the first meniscus lens is Vd 11 , the Abbe number of the material of the second biconcave lens is Vd 22 , the Abbe number of the material of the fourth biconvex lens is Vd 41 , Vd 11 ≤ 65, Vd 22 ≤ 30, Vd 41 ≤ 69.

[0014] In the present invention, the optical module further includes a beam splitting device, and the beam splitting device is located on the side of the fourth lens group away from the third lens group.

[0015] One side of the second meniscus lens of the present invention facing the image side is a convex surface, and one side of the third meniscus lens facing the object side is a convex surface.

[0016] The fourth lens group of the present invention is movably arranged along the optical axis on the side of the third lens group away from the aperture stop. When the second lens group moves along the optical axis towards the aperture stop, the fourth lens group moves along the optical axis towards the third lens group. When the second lens group moves along the optical axis towards the first lens group, the fourth lens group moves along the optical axis in a direction away from the third lens group.

[0017] A zoom lens includes an optical module.

[0018] An endoscope includes a zoom lens.

[0019] The present invention controls the short focal length and short focal field angle of the entire optical module by adjusting the focal length of the first lens group, thereby improving the imaging quality of the optical module in the short focal state. The long focal length and long focal field angle of the entire optical module are controlled by the focal length of the third lens group, thereby improving the imaging quality of the optical module in the long focal state. The imaging quality of the optical module of the present invention can be effectively improved in both the short focal state and the long focal state.

[0020] Compared with the prior art, the present invention has good imaging effects in both the short focal state and the long focal state of the optical module. The field curvature and distortion are effectively suppressed, and the aberration and coma are also low. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the optical module in the short focal state in Embodiments 1 and 2 of the present invention;

[0022] Figure 2 It is a schematic structural diagram of the optical module in the long focal state in Embodiments 1 and 2 of the present invention;

[0023] Figure 3 It is an MTF curve graph of the optical module in Embodiment 1 of the present invention in the visible light band at normal temperature and in the short focal state;

[0024] Figure 4 It is an MTF curve graph of the optical module in Embodiment 1 of the present invention in the visible light band at normal temperature and in the long focal state;

[0025] Figure 5 It is a field curvature and distortion graph of the optical module in Embodiment 1 of the present invention in the visible light band in the short focal state;

[0026] Figure 6 It is a field curvature and distortion graph of the optical module in Embodiment 1 of the present invention in the visible light band in the long focal state;

[0027] Figure 7It is the lateral light fan diagram of the optical module in Embodiment 1 of the present invention in the visible light band under the short focal length state;

[0028] Figure 8 It is the lateral light fan diagram of the optical module in Embodiment 1 of the present invention in the visible light band under the long focal length state;

[0029] Figure 9 It is the spot diagram of the optical module in Embodiment 1 of the present invention in the visible light band under the short focal length state;

[0030] Figure 10 It is the spot diagram of the optical module in Embodiment 1 of the present invention in the visible light band under the short focal length state.

[0031] Reference numerals:

[0032] G1, the first lens group, L11, the first meniscus lens, L12, the second meniscus lens, L13, the third meniscus lens;

[0033] G2, the second lens group, L21, the first biconcave lens, L22, the second biconcave lens, L23, the first biconvex lens;

[0034] S, the aperture stop;

[0035] G3, the third lens group, L31, the second biconvex lens, L32, the third biconvex lens, L33, the fourth meniscus lens, L34, the third biconcave lens;

[0036] G4, the fourth lens group, L41, the fourth biconvex lens;

[0037] P, the beam splitter;

[0038] Q, the imaging surface. Detailed implementation manners

[0039] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation manners of the present invention with reference to the accompanying drawings. Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0040] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0041] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0042] In the present invention, unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] In the present invention, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0044] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation.

[0045] Embodiment 1:

[0046] Refer to Figure 1-2 , this embodiment provides an optical module, which sequentially includes a first lens group G1, a second lens group G2, an aperture stop S, a third lens group G3, a fourth lens group G4, a beam splitter P, a color filter, and an imaging surface Q from the object side to the image side.

[0047] Among them, the optical module has a long focal length state and a short focal length state. The first lens group G1, the aperture stop S, the third lens group G3, the beam splitter P, the color filter, and the imaging surface Q remain fixed, while the second lens group G2 can move along the optical axis between the first lens group G1 and the aperture stop S, and the fourth lens group G4 can move along the optical axis between the third lens group G3 and the beam splitter P. By moving the second lens group G2 and the fourth lens group G4, the entire optical module can be switched between the long focal length state and the short focal length state.

[0048] In this embodiment, when the second lens group G2 moves along the optical axis towards the first lens group G1 and the fourth lens group G4 moves along the optical axis towards the beam splitter P, the optical module gradually switches from the long focal length state to the short focal length state. Conversely, when the second lens group G2 moves along the optical axis towards the aperture stop S and the fourth lens group G4 moves along the optical axis towards the third lens group G3, the optical module gradually switches from the short focal length state to the long focal length state.

[0049] The short focal length of the optical module is f W , the short focal field of view is FOV W , the focal length of the first lens group G1 is f1. In order to improve the imaging quality and clarity of the optical module in the short focal length state, it is necessary to satisfy By adjusting the focal length of the first lens group G1 to f1, the short focal length f W and the short focal field of view FOV W are optimized to improve the imaging performance of the entire optical module in the short focal length state.

[0050] The long focal length of the optical module is f T , the long focal field of view is FOV T, the focal length of the third lens group G3 is f3. To improve the imaging quality and clarity of the optical module in the telephoto state, it is necessary to satisfy By adjusting the focal length of the third lens group G3 to f3, for the telephoto focal length f T and the telephoto field of view FOV T are optimized to improve the imaging performance of the entire optical module in the telephoto state, and the influence of the first lens group G1 and the second lens group G2 on the imaging performance of the optical module in the telephoto state is reduced by the aperture stop S, especially the influence of the change of the focal length f1 of the first lens group G1 on the imaging performance of the optical module in the telephoto state.

[0051] By controlling the focal length f1 of the first lens group G1 and the focal length f3 of the third lens group G3, the optical performance parameters of the entire optical module can satisfy the requirements of clear imaging both in the short-focus state and the telephoto state, reducing the contradiction between the optical parameters required in the short-focus state and the optical parameters required in the telephoto state of the optical module, and the imaging quality of the optical module in the short-focus state and the telephoto state has been improved well.

[0052] Specifically, in this embodiment, the first lens group G1 only includes the first meniscus lens L11, the second meniscus lens L12, and the third meniscus lens L13 arranged in sequence from the object side to the image side. Among them, the first meniscus lens L11 and the third meniscus lens L13 are positive power lenses, and the second meniscus lens L12 is a negative power lens. The surfaces of the first meniscus lens L11 and the second meniscus lens L12 facing the image side are convex surfaces, and the surface of the third meniscus lens L13 facing the object side is a convex surface.

[0053] Preferably, the first meniscus lens L11 and the second meniscus lens L12 are glued together to improve the final imaging quality of the optical module and reduce chromatic aberration.

[0054] The central curvature radius of the second meniscus lens L12 on the image side is R3, and the central curvature radius of the third meniscus lens L13 on the object side is R4. To further improve the imaging quality of the optical module in the short-focus state, it is necessary to satisfy

[0055] The focal length of the first meniscus lens L11 is f 11 , and similarly, to improve the imaging quality of the optical module in the short-focus state, the total optical length of the optical module is TTL, then According to this relationship, the influence of the focal length f of the first meniscus lens L11 11 on the imaging performance of the optical module in the short-focus state is within a relatively good range.

[0056] There are two color filters and two imaging surfaces Q respectively, so that a color filter and an imaging surface Q can be sequentially arranged along the respective light-emitting directions on the two light-emitting sides of the beam splitter device P. In this embodiment, two optical paths are formed via the beam splitter device P, and finally the optical total lengths of the two optical paths are equal, both being TTL.

[0057] In this embodiment, the second lens group G2 only includes a first double concave lens L21, a second double concave lens L22, and a first double convex lens L23 arranged in sequence from the object side to the image side. When the second lens group G2 moves along the optical axis, the relative positions of the first double concave lens L21, the second double concave lens L22, and the first double convex lens L23 remain unchanged. Among them, the first double concave lens L21 and the second double concave lens L22 are negative focal length lenses, and the first double convex lens L23 is a positive focal length lens.

[0058] Similarly, in order to improve the final imaging quality of the optical module and reduce chromatic aberration, the second double concave lens L22 and the first double convex lens L23 are cemented. After the second double concave lens L22 and the first double convex lens L23 are cemented, the relative position stability between the two can also be improved, and the internal stability can be improved when the second lens group G2 moves, ensuring the imaging quality stability during the switching process between the telephoto state and the wide-angle state of the optical module.

[0059] In this embodiment, the third lens group G3 only includes a second double convex lens L31, a third double convex lens L32, a fourth meniscus lens L33, and a third double concave lens L34 arranged in sequence from the object side to the image side. Among them, the aperture stop S is always located between the first double convex lens L23 and the second double convex lens L31. At the same time, the aperture stop S can be separated from the second double convex lens L31 or fixed on the second double convex lens L31. In either case, the aperture stop S is located between the first double convex lens L23 and the second double convex lens L31.

[0060] Among them, the second double convex lens L31, the third double convex lens L32, and the fourth meniscus lens L33 are positive focal length lenses, and the third double concave lens L34 is a negative focal length lens.

[0061] It can be understood that the focal length f1 of the first lens group G1 is affected by the focal length f 13 of the third meniscus lens L13, and the focal length f2 of the second lens group G2 is affected by the focal length f 22 of the second double concave lens L22, and the focal length f3 of the third lens group G3 is affected by the focal length f 31When the optical module is in the telephoto state, the imaging quality of the optical module is affected by the first lens group G1, the second lens group G2, and the third lens group G3. Although the adverse effects of the first lens group G1 and the second lens group G2 on the imaging quality of the optical module in the telephoto state are reduced by the aperture stop S, they are not completely eliminated. Therefore, it is necessary to further optimize the optical parameters of the first lens group G1 and the second lens group G2 to further reduce their adverse effects on the imaging quality of the optical module in the telephoto state. At the same time, it is also necessary to further optimize the optical parameters of the third lens group G3 to further increase the improvement effect of the third lens group G3 on the imaging quality of the optical module in the telephoto state. Therefore, in this embodiment, f 13 ≤ 46 mm, f 22 ≥ -20.4 mm, f 31 ≤ 31.5 mm.

[0062] In this embodiment, the fourth lens group G4 only includes the fourth biconvex lens L41, and the fourth biconvex lens L41 is a positive focal length lens.

[0063] In this embodiment, if the optical module is to be in the short focal state, it needs to be controlled by the cooperation of the second lens group G2 and the fourth lens group G4. Therefore, the optical parameters of the fourth lens group G4 are also very important for the imaging quality of the optical module in the short focal state.

[0064] The refractive index of the material of the first meniscus lens L11 is Nd 11 , the refractive index of the material of the second meniscus lens L12 is Nd 12 , the refractive index of the material of the fourth meniscus lens L33 is Nd 33 , in order to further improve the imaging quality of the optical module in the short focal state, Nd 11 ≤ 1.81, Nd 12 ≤ 1.81, Nd 33 ≤ 1.85. By controlling the numerical ranges of Nd 11 and Nd 12 , the adverse effects on the imaging quality of the optical module in the telephoto state caused by the change of the optical parameters of the first lens group G1 can be reduced.

[0065] If the optical parameters of the first lens group G1, the second lens group G2, and the fourth lens group G4 are further optimized, the imaging quality of the optical module in both the telephoto state and the short focal state can be improved simultaneously. To achieve this purpose, the Abbe number of the material of the first meniscus lens L11 is Vd 11 , the Abbe number of the material of the second biconcave lens L22 is Vd 22 , the Abbe number of the material of the fourth biconvex lens L41 is Vd 41 , Vd 11 ≤ 65, Vd22 ≤30, Vd 41 ≤69.

[0066] In this embodiment, the optical parameters of each component of the entire optical module are shown in Table 1.

[0067] Table 1

[0068]

[0069]

[0070] It should be noted that the mirror serial numbers in Table 1 are Figure 1 the surface numbers of the lenses from left to right in the schematic diagram of the optical module shown; the central thickness T c represents the distance between this mirror surface and the adjacent mirror surface closer to the image side.

[0071] Among them, the variable thickness data is as shown in Parameter Table 2.

[0072] Table 2

[0073] Focal length D5 D10 D18 D20 19.39 mm 0.39 9.17 3.32 5.77 35.00 mm 9.47 0.1 1.40 7.68

[0074] The optical module provided in this embodiment has the following optical technical indicators:

[0075] Optical total length TTL ≤ 59.4 mm;

[0076] Focal length f: 19.39 (W) mm - 35 (T) mm;

[0077] Field of view FOV: 26.4° (W) - 14.31° (T);

[0078] Optical distortion: -3.1% (W) ~ 0.25% (T);

[0079] Aperture FNO ≤ 4.5;

[0080] Image plane size: 1 / 1.8〞;

[0081] Note: W represents short focus, and T represents long focus.

[0082] In this embodiment, the focal length of the first lens group G1 is f1, and the focal length of the third lens group G3 is f3; the short - focus focal length of the optical module is f W , the short - focus field of view is FOV W ; the long - focus focal length of the optical module is f T , the long - focus field of view is FOV T , satisfying The central curvature radius R3 of the second meniscus lens L12 on the image side and the central curvature radius R4 of the third meniscus lens L13 on the object side satisfy The focal length f of the first meniscus lens L11 11 and the total optical length TTL of the optical module satisfy The focal length f of the third meniscus lens L13 13 = 45.35 mm, the focal length f of the second biconcave lens L22 22 = -20.35 mm, the focal length f of the second biconvex lens L31 31 = 15.60 mm; the Abbe number Vd of the material of the first meniscus lens L11 11 = 46.56, the Abbe number Vd of the material of the second biconcave lens L22 22 = 17.98, the Abbe number Vd of the material of the fourth biconvex lens L41 41 = 68.62; the refractive index Nd of the material of the first meniscus lens L11 11 = 1.80, the refractive index Nd of the material of the second meniscus lens L12 12 = 1.80, the refractive index Nd of the material of the fourth meniscus lens L33 33 = 1.78.

[0083] The optical transfer function (MTF) is a relatively accurate, intuitive and common way to evaluate the imaging quality of an imaging system. The higher and smoother its curve is, the better the imaging quality of the system is, and various aberrations (such as spherical aberration, coma, astigmatism, field curvature, axial chromatic aberration, lateral chromatic aberration, etc.) are well corrected. As Figure 3 shown, it is the MTF curve diagram of the optical module of this embodiment in the visible light band at normal temperature and short focal length. As Figure 4 shown, it is the MTF curve diagram of the optical module of this embodiment in the visible light band at normal temperature and long focal length. Whether in the long focal length state or the short focal length state, the optical module of this embodiment is relatively smooth, and the average value of MTF at the full field of view (half image height 4.4 mm) is above 0.4, so the imaging quality is relatively high.

[0084] Field curvature is also called "image field curvature". When there is field curvature in the lens, the intersection points of the entire light beam do not coincide with the ideal image point. Although clear image points can be obtained at each specific point, the entire image plane is a curved surface. T represents the meridional field curvature, and S represents the sagittal field curvature. The field curvature curve shows the distance from the current focal plane or image plane to the paraxial focal plane as a function of the field coordinate. The meridional field curvature data is the distance measured along the Z axis from the currently determined focal plane to the paraxial focal plane and is measured in the meridian (YZ plane). The sagittal field curvature data measures the distance measured in a plane perpendicular to the meridional plane. The baseline in the schematic diagram is on the optical axis, the top of the curve represents the maximum field of view (angle or height), and no unit is set on the vertical axis because the curve is always normalized with the maximum radial field of view.

[0085] Lens distortion is the general term for the inherent perspective distortion of optical lenses, that is, the distortion caused by perspective. This kind of distortion is very unfavorable to the imaging quality of photos. After all, the purpose of photography is to reproduce, not to exaggerate. However, because this is an inherent characteristic of the lens (convex lenses converge light and concave lenses diverge light), it cannot be eliminated, only improved.

[0086] Figure 5 This is the field curvature and distortion diagram of the optical module in this embodiment in the visible light band in the short-focus state. Figure 6 This is the field curvature and distortion diagram of the optical module in this embodiment in the visible light band in the long-focus state. The field curvature and distortion diagrams are designed with reference to multiple wavelengths (0.435μm, 0.486μm, 0.546μm, 0.587μm, and 0.656μm). From Figure 5 and Figure 6 it can be seen that the field curvature of the optical module in this embodiment in the short-focus state is controlled within ±0.03mm, the distortion is within -3.1%, the field curvature in the long-focus state is controlled within ±0.05mm, and the distortion is within +0.25%. Whether in the long-focus state or the short-focus state, the field curvature and distortion are effectively suppressed. At the same time, the distortion settings in the short-focus state and the long-focus state can also balance the focal length, the field of view angle, and the size of the corresponding camera target surface, facilitating the correction of distortion through post-processing of images.

[0087] See Figure 7-8 , Figure 7 This is the lateral fan diagram of the optical module in this embodiment in the visible light band in the short-focus state. Figure 8 This is the lateral fan diagram of the optical module in this embodiment in the visible light band in the long-focus state. It can be seen that whether in the short-focus state or the long-focus state, the curve is relatively flat, indicating that the spherical aberration and chromatic aberration of the optical module are well controlled.

[0088] See Figure 9-10 , Figure 9 This is the spot diagram of the optical module in this embodiment in the visible light band in the short-focus state. Figure 10 This is the spot diagram of the optical module in this embodiment in the visible light band in the long-focus state. Whether in the short-focus state or the long-focus state, the spot radius is relatively small, and the light spots are relatively concentrated, corresponding to relatively small aberration and coma.

[0089] The optical module of this embodiment has the characteristics of a large target surface, a large aperture, and high resolution, and the cost is low.

[0090] Embodiment 2:

[0091] The difference between this embodiment and Embodiment 1 is that the parameters of each lens in the optical module change. For details, see Table 3.

[0092] Table 3

[0093]

[0094]

[0095] It should be noted that the mirror numbers in Table 3 are Figure 1 the surface numbers of the lenses from left to right in the schematic diagram of the optical module shown; the central thickness T c represents the distance between this mirror surface and the adjacent mirror surface closer to the image side.

[0096] Among them, the variable thickness data is as shown in Parameter Table 4.

[0097] Table 4

[0098] Focal length D5 D10 D18 D20 19.2 mm 0.33 8.12 1.11 7.82 35.0 mm 8.36 0.10 8.83 0.10

[0099] The optical module provided in this embodiment has the following optical technical indicators:

[0100] Optical total length TTL ≤ 60 mm;

[0101] Focal length f: 19.2 (W) mm - 35.0 (T) mm;

[0102] Field of view angle FOV: 26.98° (W) - 14.40° (T);

[0103] Optical distortion: -4.5% (W) ~ 0.47% (T);

[0104] Aperture FNO ≤ 3.58;

[0105] Image plane size: 1 / 1.8〞;

[0106] Note: W represents the short focal length, and T represents the long focal length.

[0107] In this embodiment, the focal length of the first lens group G1 is f1, and the focal length of the third lens group G3 is f3; the short focal length of the optical module is f W , and the short focal field of view angle is FOV W ; the long focal length of the optical module is f T , and the long focal field of view angle is FOV T , satisfying The central curvature radius R3 of the second meniscus lens L12 on the image side and the central curvature radius R4 of the third meniscus lens L13 on the object side satisfy The focal length f of the first meniscus lens L11 11 and the optical total length TTL of the optical module satisfy The focal length f of the third meniscus lens L13 13 = 31.25 mm, the focal length f of the second biconcave lens L22 22 = -14.39 mm, the focal length f of the second biconvex lens L3131 = 31.41 mm; The Abbe number Vd of the material of the first meniscus lens L11 11 = 64.21, the Abbe number Vd of the material of the second biconcave lens L22 22 = 29.13, the Abbe number Vd of the material of the fourth biconvex lens L41 41 = 63.40; The refractive index Nd of the material of the first meniscus lens L11 11 = 1.51, the refractive index Nd of the material of the second meniscus lens L12 12 = 1.76, the refractive index Nd of the material of the fourth meniscus lens L33 33 = 1.84.

[0108] Examples 1 and 2 satisfy the relationships shown in Table 5.

[0109] Table 5

[0110]

[0111]

[0112] Example 3:

[0113] This example provides a zoom lens, including the optical module in Example 1. The zoom lens in this example can meet the high-resolution requirements of a 1 / 1.8-inch sensor (CCD / CMOS) camera.

[0114] Example 4:

[0115] This example provides an endoscope, including the zoom lens in Example 2.

[0116] The technical features of the above-described examples can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above examples are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0117] The above-described examples only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. An optical module, characterized in that, From the object side to the image side direction, it sequentially includes a first lens group (G1), a second lens group (G2), an aperture stop (S), a third lens group (G3), and a fourth lens group (G4). The number of lens groups is four. The second lens group (G2) moves along the optical axis between the first lens group (G1) and the aperture stop (S) to switch the optical module between a short focal length state and a long focal length state; The first lens group (G1) includes a first meniscus lens (L11), a second meniscus lens (L12), and a third meniscus lens (L13) sequentially arranged from the object side to the image side direction. The number of lenses in the first lens group (G1) is three. The first meniscus lens (L11) and the third meniscus lens (L13) are positive power lenses, and the second meniscus lens (L12) is a negative power lens; The second lens group (G2) includes a first biconcave lens (L21), a second biconcave lens (L22), and a first biconvex lens (L23) sequentially arranged from the object side to the image side direction. The number of lenses in the second lens group (G2) is three. The third lens group (G3) includes a second biconvex lens (L31), a third biconvex lens (L32), a fourth meniscus lens (L33), and a third biconcave lens (L34) sequentially arranged from the object side to the image side direction. The number of lenses in the third lens group (G3) is four. The first biconcave lens (L21), the second biconcave lens (L22), and the third biconcave lens (L34) are negative power lenses, and the first biconvex lens (L23), the second biconvex lens (L31), the third biconvex lens (L32), and the fourth meniscus lens (L33) are positive power lenses; The fourth lens group (G4) includes a fourth biconvex lens (L41). The number of lenses in the fourth lens group (G4) is one, and the fourth biconvex lens (L41) is a positive power lens; The focal length of the first lens group (G1) is f1, the focal length of the third lens group (G3) is f3, and the short focal length of the optical module is f W , and the short focal field of view is FOV W , the long focal length is f T , and the long focal field of view is FOV T , then and 2. The optical module according to claim 1, wherein The second meniscus lens (L12) has a central radius of curvature R3 on the image side, and the third meniscus lens (L13) has a central radius of curvature R4 on the object side. Then 3. The optical module according to claim 2, wherein, The focal length of the first meniscus lens (L11) is f 11 , the optical module further includes an imaging surface (Q), the imaging surface (Q) is located on the image side of the third lens group (G3), and the total optical length of the optical module is TTL, then 4. The optical module according to claim 2, wherein The first meniscus lens (L11) and the second meniscus lens (L12) are cemented, the second biconcave lens (L22) and the first biconvex lens (L23) are cemented, and the focal length f of the third meniscus lens (L13) 13 ≤ 46 mm, the focal length f of the second biconcave lens (L22) 22 ≥ -20.4 mm, the focal length f of the second biconvex lens (L31) 31 ≤ 31.5 mm.

5. The optical module according to claim 4, wherein The refractive index of the material of the first meniscus lens (L11) is Nd 11 , and the refractive index of the material of the second meniscus lens (L12) is Nd 12 , and the refractive index of the material of the fourth meniscus lens (L33) is Nd 33 , Nd 11 ≤1.81, Nd 12 ≤1.81, Nd 33 ≤1.

85.

6. The optical module according to claim 4, wherein, The Abbe number of the material of the first meniscus lens (L11) is Vd 11 , the Abbe number of the material of the second biconcave lens (L22) is Vd 22 , the Abbe number of the material of the fourth biconvex lens (L41) is Vd 41 , Vd 11 ≤65, Vd 22 ≤30, Vd 41 ≤69.

7. The optical module according to claim 4, wherein The optical module further includes a beam splitting device (P), and the beam splitting device (P) is located on the side of the fourth lens group (G4) away from the third lens group (G3).

8. The optical module according to claim 4, wherein The surface of the second meniscus lens (L12) facing the image side is convex, and the surface of the third meniscus lens (L13) facing the object side is convex.

9. The optical module according to claim 4, wherein The fourth lens group (G4) is movably arranged along the optical axis on the side of the third lens group (G3) away from the aperture stop (S). When the second lens group (G2) moves along the optical axis towards the aperture stop (S), the fourth lens group (G4) moves along the optical axis towards the third lens group (G3). When the second lens group (G2) moves along the optical axis towards the first lens group (G1), the fourth lens group (G4) moves along the optical axis in a direction away from the third lens group (G3).

10. A zoom lens, characterized in that, Comprising the optical module according to any one of claims 1-9.

11. An endoscope, characterized in that, Comprising the zoom lens according to claim 10.

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