阅读说明：本技术 一种水下电影变焦光学系统 (Underwater film zooming optical system ) 是由 曲锐 武力 彭建伟 曹剑中 于 2020-07-31 设计创作，主要内容包括：本发明提供一种水下电影变焦光学系统,解决现有水下变焦电影光学系统要么变倍比小、要么不具备电影成像功能的问题。该系统包括沿光轴依次设的窗口、前固定镜组一、第二胶合镜组、前固定镜组二、第三胶合镜组、补偿镜组、光阑、中间固定镜组、第十正透镜、后固定镜组和滤光片；前固定镜组一包括第一负透镜、第一胶合镜组和第二正透镜；前固定镜组二包括第四正透镜和第五正透镜；变倍镜组包括第六正透镜、第四负透镜和第五负透镜；中间固定镜组包括第八正透镜、第九正透镜和第七负透镜；后固定镜组包括第四胶合镜组、第九负透镜和第十二正透镜；变倍镜组、补偿镜组和像差稳定镜组沿光轴方向移动实现连续变焦；调焦镜组实现变焦过程的对焦和跟焦。(The invention provides an underwater film zooming optical system, which solves the problems that the existing underwater zooming film optical system is small in zoom ratio or does not have a film imaging function. The system comprises a window, a first front fixed lens group, a second gluing lens group, a second front fixed lens group, a third gluing lens group, a compensation lens group, a diaphragm, a middle fixed lens group, a tenth positive lens, a rear fixed lens group and an optical filter which are sequentially arranged along an optical axis; the front fixed lens group I comprises a first negative lens, a first cemented lens group and a second positive lens; the front fixed lens group II comprises a fourth positive lens and a fifth positive lens; the zoom lens group comprises a sixth positive lens, a fourth negative lens and a fifth negative lens; the middle fixed lens group comprises an eighth positive lens, a ninth positive lens and a seventh negative lens; the rear fixed lens group comprises a fourth cemented lens group, a ninth negative lens and a twelfth positive lens; the zoom lens group, the compensation lens group and the aberration stabilizing lens group move along the optical axis direction to realize continuous zooming; the focusing lens group realizes focusing and focus following in the zooming process.)

1. An underwater film zoom optical system, comprising: the optical system comprises a window (12), a first front fixed mirror group (11), a focusing mirror group (10), a second front fixed mirror group (9), a zoom mirror group (8), a compensating mirror group (7), a diaphragm (6), a middle fixed mirror group (5), an aberration stabilizing mirror group (4), a rear fixed mirror group (3) and an optical filter (2) which are sequentially arranged from left to right along the light propagation direction, wherein the left side of the window (12) is an object plane (13) of the optical system, and the right side of the optical filter (2) is a focal plane (1) of the optical system;

the first front fixed lens group (11) comprises a first negative lens (1101), a first cemented lens group and a second positive lens (1104) which are sequentially arranged from left to right, and the first cemented lens group has negative focal power;

the focusing lens group (10) comprises a second cemented lens group with positive focal power;

the front fixed lens group II (9) comprises a fourth positive lens (901) and a fifth positive lens (902) which are sequentially arranged from left to right;

the zoom lens group (8) comprises a sixth positive lens (801), a fourth negative lens (802) and a fifth negative lens (803) which are sequentially arranged from left to right;

the compensating lens group (7) comprises a third cemented lens group with negative focal power;

the middle fixed mirror group (5) comprises an eighth positive lens (501), a ninth positive lens (502) and a seventh negative lens (503) which are sequentially arranged from left to right;

the aberration stabilizing lens group (4) comprises a tenth positive lens (401);

the rear fixed lens group (3) comprises a fourth cemented lens group, a ninth negative lens (303) and a twelfth positive lens (304) which are sequentially arranged from left to right, and the fourth cemented lens group has positive focal power;

the diaphragm (6) is fixed on the left side of the eighth positive lens (501);

the zoom lens group (8), the compensating lens group (7) and the aberration stabilizing lens group (4) can synchronously move back and forth along the optical axis direction to realize continuous zooming; the focusing lens group (10) can move back and forth along the optical axis direction, so that focusing and focus following of each focal length position and the zooming process are realized.

2. The underwater film zoom optical system of claim 1, wherein: the first cemented lens group is formed by a second negative lens (1102) and a first positive lens (1103) which are sequentially arranged from left to right;

the second cemented lens group is formed by cementing a third negative lens (1001) and a third positive lens (1002) which are sequentially arranged from left to right;

the third cemented lens group is formed by cementing a seventh positive lens (701) and a sixth negative lens (702) which are sequentially arranged from left to right;

the fourth cemented lens group is formed by cementing an eleventh positive lens (301) and an eighth negative lens (302) which are sequentially arranged from left to right.

3. The underwater film zoom optical system of claim 2, wherein: let the abbe number of the first positive lens (1103) to d-line be vd1103, and vd1103 satisfies the following conditional expression:

vd1103<32；

assuming that the focal length of the first negative lens (1101) is f1101, the focal length of the first front fixed lens group (11) is f11, and f1101 and f11 satisfy the following conditional expressions:

0.68<|f11/f1101|<2。

4. the underwater movie zoom optical system according to claim 1, 2 or 3, characterized in that: setting the radial magnification of the focusing mirror group (10) as m10, wherein m10 satisfies the following conditional expression:

2<|m10|<2.5。

5. the underwater film zoom optical system of claim 4, wherein: if the focal length of the front fixed lens group two (9) is f9, the focal length of the objective lens group consisting of the front fixed lens group one (11), the focusing lens group (10) and the front fixed lens group two (9) is fF, and f9 and fF satisfy the following conditional expressions:

1.0<|fF/f9|<1.5。

6. the underwater film zoom optical system of claim 5, wherein: let the abbe number of the sixth positive lens (801) to the d-line be vd801, and vd801 satisfies the following conditional expression:

vd801<34；

the focal length of the zoom lens group (8) is f8, the focal length of the telephoto end of the underwater film zoom optical system is fL, and fL and f8 satisfy the following conditional expressions:

2.6<|fL/f8|<5.5。

7. the underwater film zoom optical system of claim 6, wherein: assuming that the focal length of the compensating lens group (7) is f7, the focal length of the intermediate fixed lens group (5) is f5, the focal length of the aberration stabilizing lens group (4) is f4, and fL and f7, f5 and f4 respectively satisfy the following conditional expressions:

0.9<|fL/f7|<1.3；

1.5<|fL/f5|<2.1；

1.9<|fL/f4|<2.8。

8. the underwater film zoom optical system of claim 7, wherein: setting the radial magnification of the rear fixed mirror group (3) as m3, wherein m3 satisfies the following conditional expression:

1<|m3|<1.5。

9. the underwater film zoom optical system of claim 1, wherein: the zoom lens group (8), the compensating lens group (7) and the aberration stabilizing lens group (4) linearly move back and forth in the optical axis direction through a cam-sleeve mechanism, a cam-guide rail mechanism or a servo-guide rail mechanism;

the optical filter (2) is matched with the working spectrum of the optical system.

10. The underwater film zoom optical system of claim 2, wherein: defining the surface close to the object plane side as a front surface and the surface close to the focal plane side as a rear surface;

the first negative lens (1101) has a thickness of 3.2mm, a radius of curvature of the front surface of 281.8mm, and a radius of curvature of the rear surface of 44.176 mm;

the thickness of the second negative lens (1102) is 3mm, and the curvature radius of the front surface is-70.99 mm;

the thickness of the first positive lens (1103) is 9.4mm, the curvature radius of the gluing surface of the first positive lens (1103) and the second negative lens (1102) is 58.61mm, and the rear surface of the first positive lens (1103) is a plane;

the thickness of the second positive lens (1104) is 5.2mm, the curvature radius of the front surface is 137.09mm, and the rear surface is a plane;

the thickness of the third negative lens (1001) is 3mm, and the curvature radius of the front surface is 146.4 mm;

the thickness of the third positive lens (1002) is 12.24mm, the curvature radius of the gluing surface of the third positive lens and the third negative lens (1001) is 75.803mm, and the curvature radius of the rear surface of the third positive lens (1002) is-66.76 mm;

the thickness of the fourth positive lens (901) is 6.8mm, the curvature radius of the front surface is 128.77mm, and the curvature radius of the rear surface is-159.76 mm;

the thickness of the fifth positive lens (902) is 8.8mm, the curvature radius of the front surface is 56.287mm, and the curvature radius of the rear surface is-186.74 mm;

the thickness of the sixth positive lens (801) is 3.6mm, the curvature radius of the front surface is 70.47mm, and the rear surface is a plane;

the thickness of the fourth negative lens (802) is 1.4mm, the curvature radius of the front surface is-107.23 mm, and the curvature radius of the rear surface is 24.59 mm;

the thickness of the fifth negative lens (803) is 1.4mm, the curvature radius of the front surface is-72.73 mm, and the curvature radius of the rear surface is 36.98 mm;

the thickness of the seventh positive lens (701) is 2.39mm, and the curvature radius of the front surface is-29.41 mm;

the thickness of the sixth negative lens (702) is 1.2mm, the curvature radius of the gluing surface of the sixth negative lens (702) and the seventh positive lens (701) is-25.66 mm, and the curvature radius of the rear surface of the sixth negative lens (702) is-103.78 mm;

the thickness of the eighth positive lens (501) is 3.57mm, the curvature radius of the front surface is 36.4mm, and the curvature radius of the rear surface is-91.03 mm;

the thickness of the ninth positive lens (502) is 3.1mm, the curvature radius of the front surface is 25.64mm, and the curvature radius of the rear surface is 62.99 mm;

the thickness of the seventh negative lens (503) is 1.4mm, the curvature radius of the front surface is-57.74 mm, and the curvature radius of the rear surface is 25.66 mm;

the thickness of the tenth positive lens (401) is 4.58mm, the curvature radius of the front surface is 36.4mm, and the curvature radius of the rear surface is-19.33 mm;

the thickness of the eleventh positive lens (301) is 5.22mm, and the curvature radius of the front surface is 13.15 mm;

the thickness of the eighth negative lens (302) is 1.2mm, the curvature radius of the gluing surface of the eighth negative lens and the eleventh positive lens (301) is-24.21 mm, and the curvature radius of the rear surface of the eighth negative lens (302) is 24.21 mm;

the thickness of the ninth negative lens (303) is 1.5mm, the curvature radius of the front surface is 94.67mm, and the curvature radius of the rear surface is 16.82 mm;

the thickness of the twelfth positive lens (304) is 4.11mm, the radius of curvature of the front surface is 19.66mm, and the radius of curvature of the rear surface is-33.03 mm.

Technical Field

The invention relates to an underwater imaging optical system, in particular to an underwater film zooming optical system which is suitable for underwater film imaging and is adaptive to a high-resolution image sensor.

Background

In recent years, the industries of underwater television films, geological exploration, resource exploration, environmental monitoring, photogrammetry and the like all put urgent demands on the development of underwater film zoom lenses.

Unlike photographic zoom lenses, the parfocal performance, the tracking performance and the respiration performance of the lens are three main performance manifestations of a movie zoom lens. Aiming at the same object distance, the film zoom lens has the requirement of parfocalization, namely, when the film zoom lens is zoomed, the focus is always kept, and the image is always clear; the film lens also has the requirement of focus following performance aiming at different object distances, namely the focusing process is accurate and controllable for different object distances so as to ensure the accuracy of focus following to the maximum extent; in addition, for film production, the focus tracking or focus shifting between different subjects is common, and during lens focusing, the displacement of the internal lens group will cause the optical focal length to change, which generates a respiration effect and greatly affects the film composition, thus requiring the entire film lens to have the best possible anti-respiration performance. In the three aspects, the common photographic zoom lens has no requirement or can be weakened, but the requirements all put great demands on the design of a continuous zooming optical system of a movie lens.

In addition, in general, an underwater optical imaging system separates an object space in an aqueous medium from an image space in an air medium (or other pure gas medium) through an optical window, and when light enters the air medium from the aqueous medium, a refraction phenomenon occurs. At the moment, if a common imaging objective lens is used, the simple transparent parallel flat plate is adopted for sealing and waterproofing, so that the visual angle of the imaging objective lens is reduced (the focal length is increased), the magnification is reduced, the chromatic aberration and the distortion are obviously increased, and the imaging quality is deteriorated, the image is distorted and deformed, and the definition is reduced; however, the use of a common imaging lens and the addition of a spherical protection window on the outer side is limited by the optical window and can only be used in applications with a small fixed focus or zoom ratio.

Therefore, an underwater cinematography system which has small F number (F # is an F-number and is the reciprocal of the ratio of the entrance pupil aperture to the focal length, namely F ═ F/D), large visual field and high resolution and has a continuous zooming function is designed, and the difficulty is high; for some underwater continuous zooming optical systems disclosed in the documents, the zoom ratio is small or the underwater continuous zooming optical system does not have the function of a movie zoom lens.

In 2013, a document entitled design of a deep sea detection zoom optical system, published in the 9 th of the Chinese journal laser and photoelectron development, reports a large relative aperture underwater continuous zoom optical system, which adopts a dome shell type water window, wherein a long focal field is 36 degrees, a short focal field is 66 degrees, and the relative aperture of the optical system is constant at 1/1.4 in the zooming process, but does not have the function of a video lens.

Various underwater zoom imaging optical system designs disclosed in japanese patent laid-open No. disforth 05-188290 and chinese patent laid-open No. CN108627961A and CN110109237A are designed for conventional photographing lenses and cannot be used as an electron microscope zoom lens.

The japanese patents with open numbers of extra open systems 2015-106025 and extra open systems 2017-97205 disclose two designs of underwater lens optical advanced conversion lenses, and the conversion lenses are combined with corresponding movie lenses with continuous zooming functions to form an underwater movie zoom optical system, but the mode of the conversion lenses compresses the relative aperture of the optical system, so that large magnification ratio is difficult to realize.

At present, mainstream underwater optical imaging equipment suppliers, such as companies of Kongsberg, OSIL, bowtec products ltd, deep seapower & Light, insitepacitic, Sub-imaging, and red and blue rcunderwater systems saps in the united states, can provide various underwater continuous zoom imaging equipment with resolution from standard definition, high definition to 4K level, but do not have the function of film imaging, and cannot meet the requirements of underwater film imaging.

Disclosure of Invention

The invention provides an underwater film zoom optical system, aiming at solving the technical problems that the existing underwater zoom film lens optical system is small in zoom ratio or does not have a film imaging function.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

an underwater film zooming optical system is characterized in that: the optical system comprises a window, a first front fixed lens group, a focusing lens group, a second front fixed lens group, a zoom lens group, a compensating lens group, a diaphragm, a middle fixed lens group, an aberration stabilizing lens group, a rear fixed lens group and an optical filter which are sequentially arranged from left to right along the light propagation direction, wherein the left side of the window is an object plane of the optical system, and the right side of the optical filter is a focal plane of the optical system;

the front fixed lens group I comprises a first negative lens, a first cemented lens group and a second positive lens which are sequentially arranged from left to right, and the first cemented lens group has negative focal power;

the focusing lens group comprises a second cemented lens group with positive focal power;

the front fixed lens group II comprises a fourth positive lens and a fifth positive lens which are sequentially arranged from left to right;

the zoom lens group comprises a sixth positive lens, a fourth negative lens and a fifth negative lens which are sequentially arranged from left to right;

the compensation lens group comprises a third cemented lens group with negative focal power;

the middle fixed mirror group comprises an eighth positive lens, a ninth positive lens and a seventh negative lens which are sequentially arranged from left to right;

the aberration stabilizing lens group comprises a tenth positive lens;

the rear fixed lens group comprises a fourth cemented lens group, a ninth negative lens and a twelfth positive lens which are sequentially arranged from left to right, and the fourth cemented lens group has positive focal power;

the diaphragm is fixed on the left side of the eighth positive lens;

the zoom lens group, the compensation lens group and the aberration stabilizing lens group can synchronously move back and forth along the optical axis direction to realize continuous zooming; the focusing lens group can move back and forth along the optical axis direction, so that focusing and focus following of each focal length position and the zooming process are realized.

Furthermore, the first cemented lens group is formed by cementing a first positive lens and a second negative lens which are sequentially arranged from left to right;

the second cemented lens group is formed by cementing a third negative lens and a third positive lens which are sequentially arranged from left to right;

the third cemented lens group is formed by a seventh positive lens and a sixth negative lens which are sequentially arranged from left to right;

the fourth cemented lens group is formed by cementing an eleventh positive lens and an eighth negative lens which are sequentially arranged from left to right.

Further, let the abbe number of the first positive lens to the d-line be vd1103, and vd1103 satisfies the following conditional expression:

vd1103<32；

assuming that the focal length of the first negative lens element is f1101, the focal length of the first front fixed lens group is f11, and f1101 and f11 satisfy the following conditional expressions:

0.68<|f11/f1101|<2。

further, assuming that the radial magnification of the focusing mirror group is m10, m10 satisfies the following conditional expression:

2<|m10|<2.5。

further, the focal length of the front fixed lens group two is f9, the focal length of the objective lens group consisting of the front fixed lens group one, the focusing lens group and the front fixed lens group two is fF, and f9 and fF satisfy the following conditional expressions:

1.0<|fF/f9|<1.5。

further, let the abbe number of the sixth positive lens to the d-line be vd801, and vd801 satisfies the following conditional expression:

vd801<34；

the focal length of the zoom lens group is f8, the focal length of the telephoto end of the underwater film zoom optical system is fL, and fL and f8 satisfy the following conditional expressions:

2.6<|fL/f8|<5.5。

further, assuming that the focal length of the compensating lens group is f7, the focal length of the middle fixed lens group is f5, the focal length of the aberration stabilizing lens group is f4, and fL and f7, f5, and f4 respectively satisfy the following conditional expressions:

0.9<|fL/f7|<1.3；

1.5<|fL/f5|<2.1；

1.9<|fL/f4|<2.8。

further, assuming that the radial magnification of the rear fixed mirror group is m3, m3 satisfies the following conditional expression:

1<|m3|<1.5。

further, the zoom lens group, the compensation lens group and the aberration stabilizing lens group linearly move back and forth in the optical axis direction through a cam-sleeve mechanism, a cam-guide mechanism or a servo-guide mechanism;

the optical filter is matched with the working spectrum of the optical system.

Further, a surface close to the object plane side is defined as a front surface, and a surface close to the focal plane side is defined as a rear surface;

the thickness of the first negative lens is 3.2mm, the curvature radius of the front surface is 281.8mm, and the curvature radius of the rear surface is 44.176 mm;

the thickness of the second negative lens is 3mm, and the curvature radius of the front surface is-70.99 mm;

the thickness of the first positive lens is 9.4mm, the curvature radius of the cemented surface of the first positive lens and the second negative lens is 58.61mm, and the rear surface of the first positive lens is a plane;

the thickness of the second positive lens is 5.2mm, the curvature radius of the front surface is 137.09mm, and the rear surface is a plane;

the thickness of the third negative lens is 3mm, and the curvature radius of the front surface is 146.4 mm;

the thickness of the third positive lens is 12.24mm, the curvature radius of the cemented surface of the third positive lens and the third negative lens is 75.803mm, and the curvature radius of the rear surface of the third positive lens is-66.76 mm;

the thickness of the fourth positive lens is 6.8mm, the curvature radius of the front surface is 128.77mm, and the curvature radius of the rear surface is-159.76 mm;

the thickness of the fifth positive lens is 8.8mm, the curvature radius of the front surface is 56.287mm, and the curvature radius of the rear surface is-186.74 mm;

the thickness of the sixth positive lens is 3.6mm, the curvature radius of the front surface is 70.47mm, and the rear surface is a plane;

the thickness of the fourth negative lens is 1.4mm, the curvature radius of the front surface is-107.23 mm, and the curvature radius of the rear surface is 24.59 mm;

the thickness of the fifth negative lens is 1.4mm, the curvature radius of the front surface is-72.73 mm, and the curvature radius of the rear surface is 36.98 mm;

the thickness of the seventh positive lens is 2.39mm, and the curvature radius of the front surface is-29.41 mm;

the thickness of the sixth negative lens is 1.2mm, the curvature radius of a gluing surface of the sixth negative lens and the seventh positive lens is-25.66 mm, and the curvature radius of the rear surface of the sixth negative lens is-103.78 mm;

the thickness of the eighth positive lens is 3.57mm, the curvature radius of the front surface is 36.4mm, and the curvature radius of the rear surface is-91.03 mm;

the thickness of the ninth positive lens is 3.1mm, the curvature radius of the front surface is 25.64mm, and the curvature radius of the rear surface is 62.99 mm;

the thickness of the seventh negative lens is 1.4mm, the curvature radius of the front surface is-57.74 mm, and the curvature radius of the rear surface is 25.66 mm;

the thickness of the tenth positive lens is 4.58mm, the curvature radius of the front surface is 36.4mm, and the curvature radius of the rear surface is-19.33 mm;

the thickness of the eleventh positive lens is 5.22mm, and the curvature radius of the front surface is 13.15 mm;

the thickness of the eighth negative lens is 1.2mm, the curvature radius of a gluing surface of the eighth negative lens and the eleventh positive lens is-24.21 mm, and the curvature radius of the rear surface of the eighth negative lens is 24.21 mm;

the thickness of the ninth negative lens is 1.5mm, the curvature radius of the front surface is 94.67mm, and the curvature radius of the rear surface is 16.82 mm;

the thickness of the twelfth positive lens is 4.11mm, the radius of curvature of the front surface is 19.66mm, and the radius of curvature of the rear surface is-33.03 mm.

Compared with the prior art, the invention has the advantages that:

1. the optical system is suitable for underwater imaging, has the functions of a film zoom lens, can realize an imaging field of view of more than 66 ℃ in an underwater environment, can realize 4K ultrahigh-definition imaging in a full-focus range, and can realize a continuous zooming function of more than 10 times; in the process of continuously changing the focal length, all focal length central view fields and all focal length edge view fields have better imaging quality.

2. The invention ensures excellent focusing and focus following performance for different object distances in the full-focus range by optimally controlling the influence of the movement of the focusing lens group on the focal power of the system, and simultaneously realizes excellent control of the respiration effect of the whole underwater film zooming optical system.

3. The zoom lens group, the compensating lens group and the aberration stabilizing lens group of the optical system continuously move according to a designed given movement rule, and the zooming mode is inner zooming; in the zooming process, each lens group moves back and forth on the optical axis all the time, the F number of the aperture is constant when zooming, the total length is constant, and the mass center is small in change.

4. The optical system diaphragm is fixedly arranged at the outer side of the middle fixed lens group close to the objective side lens, and enough space is reserved for adopting different types of diaphragms, so that the relative aperture of the optical system is constant, and is manually or automatically changed, and the modularization level of the optical system is improved; on the other hand, the diaphragm is imaged at a far distance of the image surface side through the subsequent lens group to form a quasi-image-space telecentric light path, so that the whole image surface can be ensured to have uniform relative illumination distribution.

5. The optical system adopts a quasi-image-space telecentric design form and combines a design method of aberration vignetting, so that the optical system has better distortion characteristics under each field condition, and meanwhile, the illumination distribution of the image surface under each field condition is more uniform.

6. The optical system can ensure the adaptability of the whole optical system to the underwater environment by adapting to the windows with different thicknesses and different materials, realizes clear imaging of the underwater environments with different depths, and is suitable for various underwater television and movies, video monitoring, resource development and the like.

7. According to the invention, the optical filter is arranged between the focal plane and the rear fixed lens group, the optical filter can be replaced according to the working requirement, and when the optical system needs to work under the color imaging condition, the optical filter is cut into the infrared cut-off filter, so that the color information of the formed image is ensured to be uniform and rich; when the optical system needs to work in a full-color mode or other spectral bands, the optical system is cut into the optical filter of the corresponding spectral band, and then an optical image of the corresponding spectral band can be obtained.

Drawings

FIG. 1 is an optical block diagram of an underwater film zoom optical system according to the present invention;

FIG. 2 is a short focus state optical path diagram of the underwater film zoom optical system of the present invention;

FIG. 3 is a long focus state optical path diagram of the underwater film zoom optical system of the present invention;

wherein the reference numbers are as follows:

1-focal plane, 2-optical filter, 3-rear fixed lens group, 301-eleventh positive lens, 302-eighth negative lens, 303-ninth negative lens and 304-twelfth positive lens; 4-aberration stabilizing lens group, 401-tenth positive lens; 5-middle fixed mirror group, 501-eighth positive lens, 502-ninth positive lens, 503-seventh negative lens, 6-diaphragm; 7-a compensating lens group, 701-a seventh positive lens, 702-a sixth negative lens; 8-zoom lens group, 801-sixth positive lens, 802-fourth negative lens and 803-fifth negative lens; 9-a front fixed lens group II, 901-a fourth positive lens and 902-a fifth positive lens; 10-a focusing lens group, 1001-a third negative lens and 1002-a third positive lens; 11-front fixed lens group I, 1101-first negative lens, 1102-second negative lens, 1103-first positive lens, 1104-second positive lens, 12-window, 13-object plane.

Detailed Description

The invention is described in further detail below with reference to the figures and specific embodiments.

As shown in fig. 1, an underwater film zoom optical system defines that light enters from left to right, and includes a window 12, a first front fixed lens group 11, a focusing lens group 10, a second front fixed lens group 9, a zoom lens group 8, a compensating lens group 7, a diaphragm 6, a middle fixed lens group 5, an aberration stabilizing lens group 4, a rear fixed lens group 3 and an optical filter 2, which are coaxially arranged along an optical axis direction from left to right, wherein the left side of the window 12 is an object plane 13 of the optical system, and the right side of the optical filter 2 is a focal plane 1 of the optical system; the zoom lens group 8, the front fixed lens group 11, the focusing lens group 10, the front fixed lens group two 9, the compensation lens group 7, the middle fixed lens group 5, the aberration stabilizing lens group 4 and the rear fixed lens group 3 form a complete imaging system together.

The zoom lens group 8, the compensating lens group 7 and the aberration stabilizing lens group 4 linearly move back and forth (left and right directions in fig. 1) synchronously in the optical axis direction of the optical system through a driving mechanism to realize continuous zooming; the driving mechanism can be a gear-guide rail mechanism, a cam-sleeve mechanism or a cam-guide rail mechanism and other similar driving mechanisms; meanwhile, the focusing lens group 10 can move back and forth along the direction of the optical axis, so that focusing and focus following of a scene with different object distances in a full zoom range can be realized; the optical system of the present invention has a constant overall length during continuous zooming.

In this embodiment, the first front fixed lens group 11, the focusing lens group 10 and the second front fixed lens group 9 together form an objective lens group of the film zoom optical system.

The optical system of the present embodiment includes the following lens groups:

1. front fixed lens group I11

The front fixed lens group I11 has negative focal power and comprises a first negative lens 1101, a first cemented lens group and a second positive lens 1104 which are coaxially arranged from left to right along a central axis, wherein the first cemented lens group has negative focal power; the first cemented lens group is formed by a second negative lens 1102 and a first positive lens 1103 which are sequentially arranged from left to right; a first front fixed lens group 11 with a short focal length and negative focal power can be arranged on the side of the optical system closest to the object plane 13, so that the large field of view of the optical system is facilitated; if the focal length of the first negative lens element 1101 is f1101 and the focal length of the first front fixed lens group 11 is f11, f1101 and f11 satisfy the following conditions:

0.68<|f11/f1101|<2；(1)

the conditional expression (1) is a condition for specifying that the first negative lens 1101 in the front fixed lens group one 11 excellently corrects distortion, which is introduced from the object plane 13 side operation medium water and the window 12 across the entire range of the operation spectrum, generated with respect to the entire range of the operation spectrum. By forming the first negative lens 1101 in the front fixed mirror group one 11 with the power satisfying the conditional expression (1), it is possible to excellently correct the distortion, which is generated across the entire operating spectrum range, of the entire operating spectrum range, across the entire operating spectrum range, introduced by the object plane 13 side operating medium water and the window 12, and to secure the miniaturization of the optical system, over the entire operating spectrum range. In addition, if the lower limit of the conditional expression (1) is less, it becomes difficult to downsize the optical system; if the upper limit is exceeded, it is advantageous to increase the field of view of the optical system, but large astigmatism is introduced, which complicates the optical system;

let the abbe number of the first positive lens 1103 for d-line be vd1103, and vd1103 satisfy the condition:

vd1103<32；(2)

the conditional expression (2) is a condition for specifying that the first positive lens 1103 in the front fixed lens group one 11 favorably corrects chromatic aberration, which is introduced from the object plane 13-side operation medium water and the window 12 across the entire range of the operation spectrum, over the entire range of the operation spectrum. By forming the first positive lens 1103 in the front fixed mirror group one 11 from a high dispersion material satisfying the conditional expression (2), chromatic aberration across the entire operating spectrum range, which is introduced by the object plane 13 side operating medium water and the window 12, with respect to the entire operating spectrum range, can be corrected well over the entire operating spectrum range. In addition, if the upper limit is exceeded in conditional expression (2), it becomes difficult to correct chromatic aberration introduced by the working medium.

2. Focusing lens assembly 10

The focusing lens group 10 is of a single lens group structure and is composed of a second cemented lens group; the second cemented lens group has positive focal power and is formed by a third negative lens 1001 and a third positive lens 1002 which are sequentially arranged from left to right and have coaxial central axes; assuming that the radial magnification of the focusing lens group 10 is m10, m10 satisfies the following conditional expression:

2<|m10|<2.5；(3)

the conditional expression (3) is an expression for defining the focusing ability of the focusing mirror group 10. By satisfying the conditional expression (3), rapid focusing and tracking of the optical system can be ensured, and the respiratory effect of the optical system can be effectively reduced. In the conditional expression (3), if the upper limit is exceeded, the amount of movement of the focusing mirror group 10 is reduced, and the focusing rate is increased, but the respiratory effect becomes significant. On the other hand, if the value is lower than the lower limit in the conditional expression (3), the control of the respiration effect of the optical system is advantageous, but the amount of movement of the adjustment lens group increases, and the focusing rate decreases.

In addition, the focusing lens assembly 10 can effectively compress the light beam width increased from a large field of view, and the outer diameter of each lens of the lens assembly after the focusing lens assembly 10 is compressed.

3. Front fixed lens group two 9

The front fixed lens group two 9 is of a two-piece structure and consists of a fourth positive lens 901 and a fifth positive lens 902 which are sequentially arranged from left to right; the front second fixed mirror group 9 has positive refractive power (positive refractive power), the focal length of the front second fixed mirror group 9 is f9, the focal length of the objective lens group composed of the front first fixed mirror group 11, the focusing mirror group 10 and the front second fixed mirror group 9 is fF, and then f9 and fF satisfy the conditions:

1.0<|fF/f9|<1.5；(4)

the conditional expression (4) is a condition for defining the magnitude of the second focal power of the front fixed lens group. Through the front fixed mirror group two 9 formed by the focal power satisfying the conditional expression (4), the residual distortion of the whole variable power region relative to the whole working spectrum range can be well corrected by the front fixed mirror group one 11 and the focusing mirror group 10 in the whole variable power range, and the independent correction of each aberration in the objective lens group is ensured. In addition, in conditional expression (4), when it is lower than the lower limit thereof, coma aberration and astigmatism of the objective lens group cannot be corrected well; if the upper limit is exceeded, it is advantageous to increase the field of view of the optical system, but large curvature of field is introduced, and the image formed by the optical system is distorted.

4. Zoom lens group 8

The focal power of the zoom lens group 8 is negative, and the zoom lens group consists of a sixth positive lens 801, a fourth negative lens 802 and a fifth negative lens 803 which are fixedly connected and arranged from left to right in sequence; the focal length of the zoom lens group 8 is f8, the focal length of the telephoto end of the underwater large-field-of-view continuous zoom optical system is fL, the abbe number of the sixth positive lens 801 to the d-line is vd801, and fL, f8 and vd801 satisfy the following conditional expressions:

2.6<|fL/f8|<5.5；(5)

vd801<34；(6)

the conditional expression (5) is an expression for defining the focal length range of the variable power lens group 8. By satisfying the conditional expression (5), the optical system can be miniaturized while ensuring rapid zooming. If the lower limit of the conditional expression (5) is exceeded, the amount of movement of the variable power lens group 8 increases, and therefore, it becomes difficult to downsize the optical system. On the other hand, if the upper limit is exceeded in conditional expression (5), it is advantageous to miniaturize the optical system, but particularly in the short focal end, correction of astigmatism becomes difficult, optical performance deteriorates, and image quality deteriorates.

The conditional expression (6) is a conditional expression for specifying that chromatic aberration generated by the variable power mirror group 8 with respect to light in the entire operating band region is corrected well across the full variable power region. By forming the sixth positive lens element 801 in the variable power lens group 8 from a high dispersion material satisfying the conditional expression (6), chromatic aberration generated by light in the operating band can be corrected well in the full variable power range. If the value is less than the lower limit of the conditional expression (6), it becomes difficult to correct the on-axis chromatic aberration, and it is not possible to sufficiently correct the chromatic aberration generated by light over the entire operating band.

5. Compensating lens group 7

The compensating lens group 7 is of a single lens group structure and is composed of a third cemented lens group, and the third cemented lens group has negative focal power; the third cemented lens group is formed by a seventh positive lens 701 and a sixth negative lens 702 which are sequentially arranged from left to right. Assuming that the focal length of the compensating lens group 7 is f7, fL and f7 satisfy the following conditional expressions:

0.9<|fL/f7|<1.3；(7)

the conditional expression (7) is an expression for defining the focal length range of the compensation lens group 7 associated with the variable power lens group 8. By satisfying the conditional expression (7), the slow and rapid movement of the optical system compensation lens group 7 can be ensured, and the focal plane offset generated in the movement process of the zoom group can be better compensated. If the value is lower than the lower limit of the conditional expression (7), the amount of movement of the compensating mirror group 7 increases, and the compensation efficiency deteriorates. On the other hand, if the value is higher than the upper limit of the conditional expression (7), the requirement for the coaxiality of the zoom lens group 8 increases, and the assembly and adjustment workability becomes poor, which is problematic.

The compensating lens group 7 can independently correct chromatic aberration generated by each lens in its own lens group (the seventh positive lens 701 and the sixth negative lens 702).

6. Middle fixed lens group 5

The focal power of the middle fixed mirror group 5 is positive, and the middle fixed mirror group comprises an eighth positive lens 501, a ninth positive lens 502 and a seventh negative lens 503 which are sequentially arranged from left to right; assuming that the focal length of the intermediate fixed lens group 5 is f5, fL and f5 satisfy the following conditional expressions:

1.5<|fL/f5|<2.1；(8)

the conditional expression (8) is an expression for defining the focal length range of the intermediate fixed mirror group 5. By satisfying the condition (8), the outer diameters of the aberration stabilizing lens group 4 and the rear fixed lens group 3 can be compressed, the zoom stroke of the aberration stabilizing lens group 4 can be effectively shortened, and the smooth and rapid movement of the lens group is ensured. If the conditional expression (8) is less than the lower limit thereof, the outer diameter of the aberration stabilizing lens group 4 becomes large, and it becomes difficult to downsize the optical system. On the other hand, if the upper limit is exceeded in conditional expression (8), it is advantageous to miniaturize the optical system, but excessive distortion is introduced at the short focal point, and distortion occurs in the image formed by the optical system.

7. Diaphragm 6

The diaphragm 6 may be fixed to the left side of the eighth positive lens 501, and the diaphragm 6 is a clear aperture iris diaphragm or a fixed clear aperture diaphragm.

8. Aberration-stabilizing lens group 4

The aberration stabilizing lens group 4 is a single-piece structure and consists of a tenth positive lens 401; assuming that the focal length of the aberration stabilizing lens group 4 is f4, fL and f4 satisfy the following conditional expressions:

1.9<|fL/f4|<2.8；(9)

the conditional expression (9) is an expression for defining the focal length range of the aberration stabilizing lens group 4 associated with the variable power lens group 8 and the compensating lens group 7. By satisfying the conditional expression (9), it is possible to better correct the zooming process, particularly, the distortion in the short focal end. If the upper limit is exceeded in the conditional expression (9), the stroke of the compensation group is reduced, which is beneficial to improving the compensation efficiency, but excessive distortion is introduced at the short focal end, and the image is distorted. On the other hand, if the conditional expression (9) is less than the lower limit, the amount of movement of the aberration stabilizing lens group 4 increases, and an inflection point appears in the movement curve, which is problematic.

In addition, one of the surfaces of the aberration stabilizing lens group 4 adopts an aspherical structure, and spherical aberration and coma aberration accompanying with the movement of the zoom lens group 8 and the compensation lens group 7 are further corrected.

9. Rear fixed lens group 3

The rear fixed mirror group 3 comprises a fourth cemented mirror group, a ninth negative lens 303 and a twelfth positive lens 304 which are sequentially arranged from left to right; the fourth cemented lens group is formed by cementing an eleventh positive lens 301 and an eighth negative lens 302 which are sequentially arranged from left to right; if the radial magnification of the rear fixed mirror group 3 is m3, m3 satisfies the following conditional expression:

1<|m3|<1.5；(10)

the conditional expression (10) is an expression for defining the power range of the rear fixed lens group of the optical system. By satisfying the conditional expression (10), the simple optical structure of the rear fixed mirror group 3 can be maintained without complicating the entire rear fixed mirror group 3. If the lower limit or the upper limit of the conditional expression (10) is exceeded, the rear fixed mirror group 3 becomes complicated, and the performance of the entire optical system is deteriorated.

The optical system of the embodiment can realize large field of view, continuous zooming and high-definition imaging in an underwater environment by simultaneously meeting or satisfying a plurality of conditions, and can well correct various aberrations generated by light in the whole working spectrum range in a full zoom region to obtain better optical performance.

As shown in fig. 2 and 3, the zoom lens group 8, the compensating lens group 7 and the aberration stabilizing lens group 4 linearly move back and forth (move in the left and right directions in the figure) synchronously in the optical axis direction of the optical system of the present embodiment according to a predetermined rule, so as to achieve continuous zooming; during continuous zooming, the total length of the optical system is constant; when the field of view changes from a wide field of view to a narrow field of view, the zoom lens group 8, the compensation lens group 7 and the aberration stabilizing lens group 4 are translated on one side close to the image plane direction, as shown in fig. 2; when the field of view changes from a narrow field of view to a wide field of view, the zoom lens group 8, the compensation lens group 7, and the aberration stabilizing lens group 4 move to one side in the direction of the object plane 13, as shown in fig. 3.

The optical system of the present embodiment includes eight lens groups, a first front fixed lens group 11 having negative focal power, a focusing lens group 10 having positive focal power, a second front fixed lens group 9 having positive focal power, a zoom lens group 8 having negative focal power, a compensating lens group 7 having negative focal power, a middle fixed lens group 5 having positive focal power, an aberration stabilizing lens group 4 having positive focal power, and a rear fixed lens group 3 having positive focal power are fixedly connected in sequence from an object plane 13 to a focal plane 1, and a light receiving surface of an imaging element such as a CCD or a CMOS is disposed on an imaging surface.

In the optical system of the present embodiment, the underwater diagonal field angle: (2 ω) 5.6 ° (tele end) to 62 ° (tele end); clear imaging range under water: 0.5m to INF; f/# ═ 2.8(F # is F-number, which is the reciprocal of the ratio of entrance pupil diameter to focal length, i.e. F ═ F/D); tables 1, 2, 3 and 4 below show various values related to the underwater movie zoom optical system according to the present embodiment.

TABLE 1 concrete parameters (unit: mm) of each lens of the optical system of this example

Note: the surfaces containing the signs adopt an aspheric structure.

Table 2 focusing variable surface interval data of the optical system of the present embodiment

Surface interval	Infinite object distance	Object distance of 0.5m
			D10	3.5	7.7
D13	6.4	2.2

Table 3 zoom variable surface interval data of the optical system of the present embodiment

Surface interval	f＝5.7	f＝64
			D17	2	54.51
D23	56.4	3.92
			D26	3.03	3
D33	8.96	2.5
			D35	4.46	10.92

Table 4 parameter table of the optical system of the present embodiment

The optical system of the invention has less total number of lenses and better tolerance characteristic, and the optical materials used by each lens group can be common optical glass materials, and have better availability and processability.

In this embodiment, the total length from the surface of the front fixed mirror group one 11 close to the object plane 13 to the image plane is less than 218mm, the maximum aperture of each lens is less than 58mm, the focal length range is 5.7mm to 64mm, the zoom ratio is 11, and the adaptive imaging sensor is not less than 1/1.8 ". In the zooming process, the total length of the system is constant, the F number is fixed and constant, the F number continuously changes along with the change of the focal length position, the zoom lens belongs to inner zooming, and the mass center does not change greatly in the zooming process.

In this embodiment, the optical system diaphragm 6 may adopt an iris diaphragm design, and is located at a fixed position on the object side of the middle fixed mirror group 5, so as to ensure that when the focal length of the optical system or the illuminance of the external environment changes, by adjusting the size of the aperture, the better imaging contrast is ensured, and the dynamic range of the imaging component is widened.

In the embodiment, the optical filter 2 placed in front of the focal plane 1 can be replaced, the selection of the optical filter is matched with the working spectrum section of the optical system, and when the optical system needs to work under the color imaging condition, the infrared cut-off optical filter 2 is cut in, so that the color information of the formed image is ensured to be uniform and rich; when the optical system needs to work in a full-color mode or other spectral bands, the optical system is cut into the optical filter of the corresponding spectral band, and then an optical image of the corresponding spectral band can be obtained.

The above description is only for the purpose of describing the preferred embodiments of the present invention and does not limit the technical solutions of the present invention, and any known modifications made by those skilled in the art based on the main technical concepts of the present invention fall within the technical scope of the present invention.