CN111897115B - Continuous zooming optical system with heat dissipation and wide pressure adaptability - Google Patents
Continuous zooming optical system with heat dissipation and wide pressure adaptability Download PDFInfo
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Abstract
The invention provides a continuous zooming optical system with heat dissipation and wide-pressure adaptability, which solves the problem that the conventional optical system cannot realize passive compensation for temperature and air pressure changes at the same time. The system comprises a front fixed mirror group, a zoom mirror group, a diaphragm, a middle fixed mirror group, a compensation mirror group, a rear fixed mirror group and an optical filter which are coaxially arranged in sequence along the light propagation direction, wherein the front fixed mirror group comprises a first positive lens, a first negative lens, a second positive lens, a third positive lens, a second negative lens and a fourth positive lens which are sequentially arranged; the zoom lens group comprises a first cemented lens group and a fourth negative lens which are sequentially arranged and have negative focal power; the middle fixed lens group comprises a sixth positive lens, a seventh positive lens and a fifth negative lens which are sequentially arranged; the compensating lens group comprises a second cemented lens group with negative focal power; the rear fixed mirror group comprises a seventh negative lens and a ninth positive lens which are sequentially arranged from left to right; the zoom lens group and the compensation lens group can synchronously move back and forth along the optical axis direction to realize continuous zooming.
Description
Technical Field
The invention relates to a continuous zooming optical system, in particular to a continuous zooming optical system which is compact in size, can be adapted to a high-definition image sensor, and has an optical passive athermalization function and wide air pressure adaptability.
Background
The change of ambient temperature and air pressure can cause the optical system to generate defocusing, and the imaging quality is reduced. In order to reduce the influence of temperature and air pressure changes on the imaging quality of the optical system, the design of heat and air pressure elimination is needed, that is, through certain technologies such as mechanics, optics, electronics and the like, defocusing caused by the temperature and air pressure changes is compensated, so that the optical system can keep good imaging quality in a temperature and air pressure interval with a large change range.
At present, the optical system mainly has the following heat and air pressure influence eliminating modes: electromechanical active, mechanical passive, and optical passive. The electromechanical active mode is to drive one or more components in the imaging system through a servo mechanism to realize manual or automatic defocus compensation, is the most applied mode at present, and has the defect that real-time clear imaging on a target cannot be completed under certain specific environmental conditions, so that the use is influenced; the mechanical passive type is to realize the automatic compensation of temperature defocusing through the matching of optical machine structural materials with different expansion coefficients, and has the defects of difficult realization of the automatic compensation of air pressure defocusing, complex structure and less application at present; the optical passive type is characterized in that the focal power and the optical material are reasonably distributed, and the matching of the focal plane position and the length change of the lens barrel is realized when the temperature and the air pressure change, so that the imaging quality of the lens is ensured within a specific temperature and air pressure range, the structure is simple, and the reliability is high.
Particularly, in the continuous zooming optical system, in the process of continuously changing the focal length, the relative position between the movable groups is changed, the magnification, aberration characteristics and the like of the imaging system are changed, the heat dissipation and air pressure dissipation effects on each focal length position of the zooming system are difficult, and the large relative aperture of the optical system causes the focal depth range of the system to be narrow, so that the design of the heat dissipation and air pressure dissipation effects is more challenging. For some relevant continuous zooming optical systems disclosed in the literature, either electromechanical active focusing is adopted to eliminate the influence of heat and air pressure, or a complicated mechanical passive athermalization design is adopted, or only an optical passive athermalization function is realized.
For example: in 2012, a document entitled "aviation zoom lens passive heat dissipation design" published in journal of china, 32 nd volume of journal of optics, 9 th volume reports a mechanical passive continuous zoom optical system implementation, and a mechanical passive heat dissipation structure based on a differential principle compensates a shrinkage gap generated by a difference between expansion coefficients of a lens barrel material and an optical element material, thereby ensuring the imaging quality of the optical system. Compared with an optical passive athermalization mode, the method has the advantages that the structural design of the optical machine is more complicated, and the influence of air pressure change on the imaging performance is not considered.
In 2012, the university of harbin industry, a master academic paper entitled "athermal television guidance head zoom optical system design research," discloses a design of a sub-zoom optical system by an optical passive athermalization method. The working spectrum is visible light, the focal length range is 25-75 mm, the total optical length is 150mm, the heat dissipation temperature range is-40 ℃ to +55 ℃, but the adaptive situation of the optical system to the air pressure change is not given.
The chinese patent publication No. CN104090353B discloses an optical system of an optical passive athermal continuous zooming high-resolution lens. The focal length range of the optical system is 28-230 mm, the relative aperture is 1/5, the field angle 2 omega is 3.02-24.8 degrees, the optical total length is less than or equal to 285mm, the heat dissipation temperature range is-30 ℃ to +60 ℃, but the passive compensation of air pressure change is not realized. And because the zooming kernel of the negative group zooming negative group compensation is adopted, the large aperture of the optical system is difficult to realize under the same volume.
Chinese patent publication No. CN109696740A and application No. 201910175475.7 disclose a large-target-surface high-definition zoom photographing integrated lens optical system. The focal length range of the optical system is 21-230 mm, the working spectrum section is visible-near infrared, the heat dissipation temperature range is-45 ℃ to +65 ℃, and passive compensation for air pressure change is not realized.
The Chinese patent with the publication number of CN110687668A and the application number of 201910807500.9 discloses a short-wave infrared optical passive athermal zoom optical system, the athermal temperature range is-40 ℃ to +60 ℃, and passive compensation for air pressure change is not realized.
The optical systems of the above publications only compensate for temperature changes, but not for air pressure changes, and therefore, there is a strong need to design an optical system that has a small F-number (F # is the F-number, which is the reciprocal of the ratio of the entrance pupil diameter to the focal length, i.e., F ═ F/D), a large field of view, and that can achieve continuous zoom function and has a design for eliminating heat and air pressure effects.
Disclosure of Invention
The invention provides a continuous zooming optical system with heat dissipation and wide pressure adaptability, aiming at solving the technical problem that the conventional optical system cannot realize passive compensation for temperature and pressure changes at the same time.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
a continuous zoom optical system having heat dissipation and wide-pressure adaptability, characterized in that: the optical system comprises a front fixed lens group, a zoom lens group, a diaphragm, a middle fixed lens group, a compensation lens group, a rear fixed lens group and an optical filter which are coaxially arranged from left to right along the light propagation direction, wherein the left side of the front fixed lens group 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 mirror group comprises a first positive lens, a first negative lens, a second positive lens, a third positive lens, a second negative lens and a fourth positive lens which are sequentially arranged from left to right;
the zoom lens group comprises a first cemented lens group and a fourth negative lens which are sequentially arranged from left to right, and the first cemented lens group has negative focal power;
the middle fixed lens group comprises a sixth positive lens, a seventh positive lens and a fifth negative lens which are sequentially arranged from left to right;
the compensation lens group comprises a second cemented lens group, and the second cemented lens group has negative focal power;
the rear fixed mirror group comprises a seventh negative lens and a ninth positive lens which are sequentially arranged from left to right;
the zoom lens group and the compensation lens group can synchronously move back and forth along the optical axis direction, and continuous zooming is realized.
Furthermore, the first cemented lens group is formed by a third negative lens and a fifth positive lens through cementing;
the second cemented lens group is formed by cementing an eighth positive lens and a sixth negative lens.
Further, let the abbe number of the second positive lens pair d-line be vd803, and the abbe number of the third positive lens pair d-line be vd804, and vd803 and vd804 respectively satisfy the following conditional expressions:
vd803<38；
vd804>56；
assuming that the focal length of the second positive lens element is f803, the focal length of the third positive lens element is f804, and the focal length of the front fixed lens group is f8, f8, f803, and f804 respectively satisfy the following conditional expressions:
1.4<|f803/f8|<1.58；
6.9<|f804/f8|<8.5。
further, assuming that the focal length of the front fixed lens group is f8, and the focal length of the telephoto end of the continuous zoom optical system is fL, fL and f8 satisfy the following conditional expressions:
1.58<|fL/f8|<1.85。
further, assuming that the focal length of the variable power lens group is f7, the abbe number of the fifth positive lens to the d-line is vd702, and fL, f7 and vd702 satisfy the following conditional expressions:
6.84<|fL/f7|<9.5；
vd702<26。
further, assuming that the focal length of the intermediate fixed lens group is f5, the abbe number of the sixth positive lens to the d-line is vd501, and fL, f5 and vd501 satisfy the following conditional expressions:
6.8<|fL/f5|<8.5；
vd501>80。
further, assuming that the focal length of the compensating lens group is f4, the abbe number of the eighth positive lens to the d-line is vd401, and fL, f4 and vd401 satisfy the following conditional expressions:
4.65<|fL/f4|<6.2；
vd401<22。
furthermore, the zoom lens group and the compensation lens group synchronously move back and forth along the optical axis direction through a gear-guide rail mechanism, a cam-sleeve mechanism or a cam-guide rail mechanism, so that continuous zooming is realized;
the diaphragm is fixed on the left side of the sixth positive lens;
the optical filter is matched with the working spectrum of the optical system.
Further, assuming that the normalized thermal difference coefficient of the ninth positive lens is T302, T302 satisfies the following conditional expression:
T302<2.2×10-5。
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 positive lens is 3.36mm, the curvature radius of the front surface is 180mm, and the curvature radius of the rear surface is-119.82 mm;
the thickness of the first negative lens is 2mm, the curvature radius of the front surface is-58.75 mm, and the curvature radius of the rear surface is-151.47 mm;
the thickness of the second positive lens is 2.93mm, the curvature radius of the front surface is 150mm, and the curvature radius of the rear surface is-282.13 mm;
the thickness of the third positive lens is 2.13mm, the curvature radius of the front surface is 186.52mm, and the curvature radius of the rear surface is 433.5 mm;
the thickness of the second negative lens is 2mm, the curvature radius of the front surface is 180mm, and the curvature radius of the rear surface is 30.95 mm;
the thickness of the fourth positive lens is 5.45mm, the curvature radius of the front surface is 29.65mm, and the curvature radius of the rear surface is-242.63 mm;
the thickness of the third negative lens is 1.4mm, and the curvature radius of the front surface is 1081.33 mm;
the thickness of the fifth positive lens is 2.55mm, the curvature radius of a surface glued with the third negative lens is 10.09mm, and the curvature radius of the rear surface of the fifth positive lens is 22.91 mm;
the thickness of the fourth negative lens is 1.4mm, the curvature radius of the front surface is-31.44 mm, and the curvature radius of the rear surface is 33.64 mm;
the thickness of the sixth positive lens is 2.65mm, the curvature radius of the front surface is 25.12mm, and the curvature radius of the rear surface is-26.98 mm;
the thickness of the seventh positive lens is 2.9mm, the curvature radius of the front surface is 17.17mm, and the curvature radius of the rear surface is-21.29 mm;
the thickness of the fifth negative lens is 1.4mm, the curvature radius of the front surface is-18.74 mm, and the curvature radius of the rear surface is 248.71 mm;
the thickness of the eighth positive lens is 4.8mm, and the curvature radius of the front surface is-28.00 mm;
the thickness of the sixth negative lens is 1.4mm, the curvature radius of a surface glued with the eighth positive lens is-9.38 mm, and the curvature radius of the rear surface is 21.34 mm;
the thickness of the seventh negative lens is 1.4mm, the curvature radius of the front surface is-17.67 mm, and the curvature radius of the rear surface is 6.67 mm;
the ninth positive lens has a thickness of 2.25mm, a radius of curvature of the front surface of 11.68mm, and a radius of curvature of the rear surface of-20.47 mm.
Compared with the prior art, the invention has the advantages that:
1. the optical system can realize the passive adaptation of wide temperature and pressure ranges, realize high-definition imaging in the full zoom segment range and realize the continuous zoom function of more than 6 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 optical system of the invention comprises a zooming core consisting of a zoom lens group and a compensating lens group, and the zooming core continuously moves according to a given movement rule by design, and the zooming form is internal zooming. In the zooming process, all the lens groups can move back and forth on the optical axis all the time, the F number of the diaphragm is constant when zooming, the total length is constant, the mass center change is small, the system volume is small, and the structure is simple and compact.
3. The optical system has the capabilities of continuous zooming and broadband detection, can effectively realize the miniaturization, light weight and integration of detection means, can also reduce the difficulty of optical debugging, can give consideration to both large-view-field search detection and small-view-field identification and recognition, and can realize the functions of optical fog penetration, multi-band imaging and the like.
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 can be reserved for adopting different types of diaphragms, so that the relative aperture of the continuous zooming optical system is constant, manual or automatic, 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 the illumination distribution of the image surface under each field condition is more uniform.
6. The optical system is suitable for various photoelectric aiming pods and turrets, civil police monitoring, searching, tracking aiming and the like, and is particularly suitable for various handheld photoelectric aiming devices.
7. The optical filter of the optical system arranged in front of the focal plane can be replaced, 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 a schematic optical path diagram of a continuous zoom optical system with heat dissipation and wide-pressure accommodation capabilities according to the present invention;
FIG. 2 is a schematic diagram of a short-focus state optical path of a continuous zoom optical system with heat dissipation and wide-pressure adaptation capability according to the present invention;
FIG. 3 is a schematic diagram of the optical path of the continuous zoom optical system with heat dissipation and wide-pressure adaptation of the present invention in the focal state;
FIG. 4 is a schematic diagram of a telephoto-state optical path of the continuous zoom optical system with heat dissipation and wide-pressure adaptability according to the present invention;
wherein the reference numbers are as follows:
1-focal plane, 2-optical filter, 3-rear fixed mirror group, 301-seventh negative lens, 302-ninth positive lens, 4-compensation mirror group, 401-eighth positive lens, 402-sixth negative lens, 5-middle fixed mirror group, 501-sixth positive lens, 502-seventh positive lens, 503-fifth negative lens, 6-diaphragm, 7-variable-power mirror group, 701-third negative lens, 702-fifth positive lens, 703-fourth negative lens, 8-front fixed mirror group, 801-first positive lens, 802-first negative lens, 803-second positive lens, 804-third positive lens, 805-second negative lens, 806-fourth positive lens, 9-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, a continuous zooming optical system with heat dissipation and wide-pressure adaptability defines that light enters from left to right, and comprises a front fixed lens group 8, a zoom lens group 7, a diaphragm 6, a middle fixed lens group 5, a compensation lens group 4, a rear fixed lens group 3 and an optical filter 2 which are coaxially arranged from an object plane 9 to the right in sequence; the right side of the optical filter 2 is a focal plane 1 (image plane) of the continuous zooming optical system with heat dissipation and wide pressure adaptability; the zoom lens group 7, the front fixed lens group 8, the middle fixed lens group 5, the compensation lens group 4 and the rear fixed lens group 3 together form a complete imaging system.
The zoom lens group 7 and the compensation lens group 4 synchronously move linearly back and forth (left and right directions in fig. 1) in the optical axis direction of the optical system through the 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, and the total length of the system is not changed in the process of changing the focal length.
The optical system of the present embodiment includes the following lens groups:
1. front fixed lens group 8
The front fixed mirror group 8 includes a first positive lens 801, a first negative lens 802, a second positive lens 803, a third positive lens 804, a second negative lens 805, and a fourth positive lens 806 coaxially arranged from the left-to-right central axis. In this way, the front fixed mirror group 8 having a long focal length and positive refractive power (positive refractive power) can be disposed on the side of the optical system closest to the object plane 9, which contributes to downsizing of the optical system.
When the abbe number of the second positive lens 803 to the d-line is vd803 and the abbe number of the third positive lens 804 to the d-line is vd804, the following conditional expressions are satisfied by vd803 and vd 804:
vd803<38；(1)
vd804>56；(2)
the conditional expressions (1) and (2) are conditional expressions that specify that the chromatic aberration generated by the front fixed mirror group 8 with respect to the entire operating band range is corrected well across the full zoom region. By forming the second positive lens 803 in the front fixed mirror group 8 from a high dispersion material satisfying the conditional expression (1) and forming the third positive lens 804 in the front fixed mirror group 8 from a low dispersion material satisfying the conditional expression (2), chromatic aberration generated with respect to the entire operating spectrum range across the entire variable power region can be corrected well over the entire variable power range. In addition, if the upper limit of the conditional expression (1) is exceeded or the lower limit of the conditional expression (2) is fallen below, it becomes difficult to correct chromatic aberration introduced by the working medium.
Further, when the focal length of the second positive lens 803 is f803, the focal length of the third positive lens 804 is f804, and the focal length of the front fixed lens group 8 is f8, f8, f803, and f804 satisfy the following conditional expressions:
1.4<|f803/f8|<1.58； (3)
6.9<|f804/f8|<8.5； (4)
the conditional expressions (3) and (4) are expressions that specify the heat-dissipation and pressure-relief design conditions in the front fixed mirror group 8. Through the second positive lens 803 satisfying the power limit of the conditional expression (3) and the third positive lens 804 satisfying the power limit of the conditional expression (4), the defocus generated in the lens group due to the ambient temperature pressure change can be excellently corrected in the full zoom range. If the temperature is out of the range of the conditional expression (3) or (4), it becomes difficult to correct the temperature-air pressure defocus generated in the front fixed mirror group 8.
If the focal length of the front fixed lens group 8 is f8, and the focal length of the long focal length of the continuous zooming optical system with heat dissipation and wide pressure adaptability is fL, fL and f8 satisfy the following conditional expressions:
1.58<|fL/f8|<1.85； (5)
the conditional expression (5) is an expression for specifying that the front fixed mirror group 8 minimizes the influence on the defocus at the telephoto end of the optical system. Through the front fixed mirror group 8 satisfying the focal power limitation of the conditional expression (5), the defocus generated by the environmental temperature pressure variation in the full zoom range, especially the telephoto section, can be corrected well. If the temperature and pressure are out of the range of the conditional expression (5), it becomes difficult to correct the temperature and pressure defocus in the tele section of the optical system.
2. Zoom lens group 7
The zoom lens group 7 includes a first cemented lens group and a fourth negative lens 703 coaxially arranged from left to right central axis, wherein the first cemented lens group has negative focal power, and is formed by cementing a third negative lens 701 and a fifth positive lens 702 coaxially arranged from left to right in sequence.
The zoom lens group 7 can compress the rear group aperture, excellently correct aberration generated along with the large aperture, ensure the rapid zooming of the optical system, and better correct chromatic aberration generated by light in the whole working spectrum range across the full zoom area.
Let the focal length of the variable power lens group 7 be f7, the abbe number of the fifth positive lens 702 to the d-line be vd702, and fL, f7 and vd702 satisfy the following conditional expressions:
6.84<|fL/f7|<9.5； (6)
vd702<26； (7)
the conditional expression (6) is an expression for defining the focal length range of the variable power lens group 7. By satisfying the conditional expression (6), the optical system can be miniaturized while ensuring rapid zooming. If the lower limit of conditional expression (6) is exceeded, the amount of movement of variable power lens group 7 increases, making it difficult to downsize the optical system. On the other hand, exceeding the upper limit of conditional expression (6) is advantageous for downsizing the optical system, but particularly correction of coma aberration and astigmatism at the short focal end becomes difficult, and there is a problem that optical performance deteriorates.
The conditional expression (7) is a conditional expression for specifying that chromatic aberration generated by the variable power mirror group 7 with respect to light in the entire operating band region is corrected well across the full variable power region. By forming the fifth positive lens 702 in the variable power lens group 7 from a high dispersion material satisfying the conditional expression (7), chromatic aberration generated with respect to light in the operating band range can be corrected well in the full variable power range. If the value is less than the lower limit of the conditional expression (7), 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.
Therefore, the variable power lens group 7 can effectively compress the incident angle of light on the surface of the rear group of lenses, and the difficulty of aberration correction of the rear group of lenses is reduced.
3. Middle fixed lens group 5
The intermediate fixed mirror group 5 is composed of a sixth positive lens 501, a seventh positive lens 502 and a fifth negative lens 503 which are coaxially arranged from the left to the right central axis. Assuming that the focal length of the intermediate fixed lens group 5 is f5, the abbe number of the sixth positive lens element 501 to the d-line is vd501, fL, f5 and vd501 satisfy the following conditional expressions:
6.8<|fL/f5|<8.5； (8)
vd501>60； (9)
the conditional expression (8) is an expression for defining the focal length range of the intermediate fixed mirror group 5. By satisfying the conditional expression (8), the outer diameter of the compensating lens group 4 can be compressed, the zooming stroke of the compensating lens group 4 can be effectively shortened, and the smooth and rapid movement of the lens group is ensured. If conditional expression (8) is less than the lower limit thereof, the outer diameter of the compensating lens group 4 becomes large, and downsizing of the optical system becomes difficult. On the other hand, if the upper limit is exceeded in conditional expression (4), it is advantageous to miniaturize the optical system, but excessive distortion is introduced, and distortion occurs in an image formed by the optical system.
The conditional expression (9) is a conditional expression for correcting chromatic aberration generated when the variable power lens group is moved across the full variable power region. By forming the sixth positive lens element in the intermediate fixed lens group 5 from a low dispersion material satisfying the conditional expression (5), chromatic aberration accompanying the movement of the variable power lens group can be corrected well. In addition, in the conditional expression (5), if it is lower than the lower limit thereof, the chromatic aberration correction in the intermediate fixed mirror group 5 becomes difficult, resulting in a complicated optical structure of the subsequent mirror group.
Thus, the intermediate fixed lens group 5 can minimize chromatic aberration accompanying movement of the zoom lens group, and can compress the outer diameter of the compensation lens group 4, thereby effectively shortening the zoom stroke of the compensation lens group 45 and ensuring smooth and rapid lens group movement.
4. Compensating lens group 4
The compensation lens group 4 is of a single lens group structure and is composed of a second cemented lens group with negative focal power, and the second cemented lens group is composed of an eighth positive lens 401 and a sixth negative lens 402 which are coaxially arranged from left to right in sequence; assuming that the focal length of the compensating lens group 4 is f4, and the abbe number of the eighth positive lens element 401 to the d-line is vd401, fL, f4 and vd401 satisfy the following conditional expressions:
4.65<|fL/f4|<6.2； (10)
vd401<22； (11)
the conditional expression (10) is an expression for defining the focal length range of the compensation lens group 4 associated with the zoom lens group. By satisfying the conditional expression (10), the optical system compensating lens group 4 can be ensured to move smoothly and rapidly, and the field curvature in the telephoto end can be better corrected. If the value is less than the lower limit of the conditional expression (10), the amount of movement of the compensating lens group 4 increases, making it difficult to downsize the optical system. On the other hand, if the value is higher than the upper limit of the conditional expression (10), the correction of curvature of field at the telephoto end becomes difficult, and the optical performance deteriorates, which is problematic.
The conditional expression (11) is a conditional expression which is defined to correct chromatic aberration generated by light of the entire operating band region across the full magnification region satisfactorily, similarly to the conditional expressions (1), (2), (7), and (9). The eighth positive lens 401 of the compensating mirror group 4 is formed by a low dispersion material satisfying the conditional expression (11), and chromatic aberration generated by light in the entire operating band across the full zoom region is further corrected well. If the conditional expression (11) is higher than the upper limit, it becomes difficult to correct the off-axis chromatic aberration in the compensating mirror group 45.
In this way, the compensating lens group 4 can independently correct chromatic aberration generated by each lens in the group, and partially compensate field curvature and distortion introduced by the variable power lens group 7 and the intermediate fixed lens group 5.
5. Rear fixed lens group 3
The rear fixed mirror group 3 includes a seventh negative lens 301 and a ninth positive lens 302 arranged in this order from left to right. Let T302 be the normalized thermal difference coefficient of the ninth positive lens element 302 in the rear fixed lens group 3
n is the refractive index of the lens material, dn/dt is the refractive index/temperature coefficient of the lens material; alpha is alphagT302 satisfies the following conditional expression in the expansion coefficient of the lens material:
T302<2.2×10-5 (12)
conditional expression (12) is an expression for correcting the thermal difference occurring with the short focal end of the optical system well. By satisfying the conditional expression (12), the defocus amount of the entire optical system in the short-focus segment can be maintained, and the environmental suitability of the short-focus segment of the optical system under different use conditions can be ensured. If the value is higher than the upper limit of the conditional expression (12), the normalized thermal difference coefficient of the ninth positive lens 302 increases, and the short-focus ambient defocus amount increases, so that it becomes difficult to reduce the heat dissipation and the pressure of the optical system.
As described above, the optical system of the present embodiment can achieve heat and pressure reduction, miniaturization, continuous zooming, and high-definition imaging by satisfying or satisfying a plurality of the above conditions at the same time, and can satisfactorily correct various aberrations occurring in light over the entire operating spectrum in the full magnification-varying region, thereby obtaining more excellent optical performance.
As shown in fig. 2 to 4, the zoom lens group 7 and the compensating lens group 4 linearly move back and forth (left and right directions in fig. 1) in the optical axis direction of the optical system of the present embodiment according to a certain rule, so as to achieve continuous zooming; when the field of view changes from a wide field of view to a narrow field of view, the zoom lens group 7 translates towards one side close to the focal plane 1 (image plane), and the compensation lens group moves adaptively, as shown in fig. 4, the compensation lens group is in a long-focus state; when the field of view changes from a narrow field of view to a wide field of view, the zoom lens group 7 moves to one side of the object plane 9, and the compensation lens group moves adaptively, as shown in fig. 2, the compensation lens group is in a short-focus state; the focal length is continuously changed during the movement, and the optical path in the intermediate focus state is shown in fig. 3.
The optical system of the present embodiment has five lens groups, and a front fixed lens group 8 having positive refractive power (refractive power), a zoom lens group 7 having negative refractive power, a middle fixed lens group 5 having positive refractive power, a compensation lens group 4 having negative refractive power, and a rear fixed lens group 3 having positive refractive power are fixedly connected in this order from an object plane 9 to a focal plane 1. A light receiving surface of an imaging element such as a CCD or CMOS is arranged on an imaging surface.
Various numerical data relating to the zoom optical system according to the embodiment are shown as follows:
diagonal angle of view: (2 ω) ═ 2.36 ° (tele end) -14.2 ° (tele end)
Clear imaging range: 8 m-INF
F/#is4, F # is the reciprocal of the ratio of the diaphragm aperture to the focal length, i.e. F is F/D
Working spectral range: 450 nm-950 nm
Heat dissipation temperature range: minus 45 ℃ to plus 70 DEG C
The air pressure adaptive range is as follows: 0.05MPa to 0.1MPa
Tables 1, 2 and 3 below show optical parameter data of the zoom optical system of the embodiment
TABLE 1 concrete parameters (unit: mm) of each lens of the optical system of this example
Table 2 variable surface interval data of the optical system of the present embodiment
| Surface interval | f＝20 | f＝50 | f＝120 |
| D12 | 2.4 | 21.4 | 36.12 |
| D17 | 35.59 | 16.59 | 1.68 |
| D24 | 4.46 | 7.00 | 2.99 |
| D27 | 4.66 | 2.12 | 6.13 |
Table 3 parameter table of the optical system of the present embodiment
The optical system of the embodiment has less total number of lenses and better tolerance characteristic; the optical materials used by the lens groups can be common optical glass materials, and have better acquirable and processable characteristics.
The invention adopts a lens material combination matched with the linear expansion coefficient of the lens cone material and an optical passive heat dissipation wide pressure compensation mode in the whole temperature range of minus 45 ℃ to plus 70 ℃ to compensate the defocusing caused by the temperature change of the lens cone material and the change of the environmental air pressure.
The lens cone installed in the optical system of the invention can be made of common aluminum alloy material, and the thermal expansion coefficient of the lens cone is 23.6 multiplied by 10-6and/K, other barrel materials with lower thermal expansion coefficients are not needed.
In this embodiment, the total length from the surface of the front fixed mirror group 8 close to the object plane 9 to the image plane is less than 105mm, the maximum aperture of each lens is not more than 30mm, the focal length range is 20mm to 120mm, the zoom ratio is 6, and the adaptive imaging sensor is not less than 1/3 ". In the zooming process, the total length of the system is constant, the F number is fixed and is continuously changed along with the change of the focal length position, the system has smaller volume and lighter weight, and belongs to internal zooming, and the mass center is not greatly changed in the zooming process.
In this embodiment, the optical system diaphragm 6 is an iris diaphragm, and is located at a fixed position on the image side of the middle fixed mirror group 5, so that when the focal length of the optical system or the illuminance of the external environment changes, by adjusting the size of the aperture, a 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 optical filter is selected to be 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 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 fog-penetrating mode, a full-color mode or other spectral bands, the optical system is switched into the optical filter of the corresponding spectral band, and at the moment, 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.
Claims (9)
1. A continuous zoom optical system having heat dissipation and wide pressure adaptability, characterized by: the optical system consists of a front fixed lens group (8), a zoom lens group (7), a diaphragm (6), a middle fixed lens group (5), a compensation lens group (4), a rear fixed lens group (3) and an optical filter (2) which are coaxially arranged from left to right along the light propagation direction, the left side of the front fixed lens group (8) is an object plane (9) of the optical system, and the right side of the optical filter (2) is a focal plane (1) of the optical system;
the focal power of the front fixed mirror group (8) is positive, and the front fixed mirror group consists of a first positive lens (801), a first negative lens (802), a second positive lens (803), a third positive lens (804), a second negative lens (805) and a fourth positive lens (806) which are sequentially arranged from left to right;
assuming that the focal length of the second positive lens element (803) is f803, the focal length of the third positive lens element (804) is f804, the focal length of the front fixed lens group (8) is f8, and f8 and f803, f804 respectively satisfy the following conditional expressions:
1.4<|f803/f8|<1.58；
6.9<|f804/f8|<8.5；
the zoom lens group (7) consists of a first cemented lens group and a fourth negative lens group (703) which are sequentially arranged from left to right, and the first cemented lens group has negative focal power;
the focal power of the middle fixed lens group (5) is positive, and the middle fixed lens group consists of a sixth positive lens (501), a seventh positive lens (502) and a fifth negative lens (503) which are sequentially arranged from left to right;
the compensation lens group (4) consists of a second cemented lens group, and the second cemented lens group has negative focal power;
the focal power of the rear fixed lens group (3) is positive, and the rear fixed lens group consists of a seventh negative lens (301) and a ninth positive lens (302) which are sequentially arranged from left to right;
assuming that the normalized thermal difference coefficient of the ninth positive lens (302) is T302, the T302 satisfies the following conditional expression:
T302<2.2×10-5；
the zoom lens group (7) and the compensation lens group (4) can synchronously move back and forth along the optical axis direction, so that continuous zooming is realized.
2. A continuous zoom optical system with heat dissipation and wide-pressure adaptability according to claim 1, characterized in that: the first cemented lens group is formed by cementing a third negative lens (701) and a fifth positive lens (702);
the second cemented lens group is formed by cementing an eighth positive lens (401) and a sixth negative lens (402).
3. A continuous zoom optical system with heat dissipation and wide-pressure adaptability according to claim 2, characterized in that:
let the abbe number of the second positive lens (803) to d-line be vd803, and the abbe number of the third positive lens (804) to d-line be vd804, and vd803 and vd804 respectively satisfy the following conditional expressions:
vd803<38；
vd804>56。
4. a continuous zoom optical system with heat dissipation and wide-pressure adaptability according to claim 3, characterized in that: assuming that the focal length at the telephoto end of the continuous zoom optical system is fL, fL and f8 satisfy the following conditional expression:
1.58<|fL/f8|<1.85。
5. a continuous zoom optical system with heat dissipation and wide pressure adaptation capability according to claim 2, 3 or 4, characterized in that: the focal length of the variable power lens group (7) is f7, the Abbe number of the fifth positive lens (702) to the d line is vd702, and fL, f7 and vd702 satisfy the following conditional expressions:
6.84<|fL/f7|<9.5；
vd702<26。
6. a continuous zoom optical system with heat dissipation and wide-pressure adaptability according to claim 5, characterized in that: assuming that the focal length of the intermediate fixed lens group (5) is f5, the abbe number of the sixth positive lens (501) to the d-line is vd501, and fL, f5 and vd501 satisfy the following conditional expressions:
6.8<|fL/f5|<8.5；
vd501>80。
7. a continuous zoom optical system with heat dissipation and wide-pressure adaptability according to claim 6, characterized in that: the focal length of the compensating lens group (4) is f4, the Abbe number of the eighth positive lens (401) to the d line is vd401, and the fL, f4 and vd401 satisfy the following conditional expressions:
4.65<|fL/f4|<6.2；
vd401<22。
8. a continuous zoom optical system with heat dissipation and wide-pressure adaptability according to claim 1, characterized in that: the zoom lens group (7) and the compensation lens group (4) synchronously move back and forth along the optical axis direction through a gear-guide rail mechanism, a cam-sleeve mechanism or a cam-guide rail mechanism to realize continuous zooming;
the diaphragm (6) is fixed on the left side of the sixth positive lens (501);
the optical filter (2) is matched with the working spectrum of the optical system.
9. A continuous zoom optical system with heat dissipation and wide-pressure adaptability according to claim 2, characterized in that: defining the surface close to the object plane (9) side as a front surface and the surface close to the focal plane (1) side as a rear surface;
the thickness of the first positive lens (801) is 3.36mm, the curvature radius of the front surface is 180mm, and the curvature radius of the rear surface is-119.82 mm;
the first negative lens (802) has a thickness of 2mm, a radius of curvature of the front surface of-58.75 mm, and a radius of curvature of the rear surface of-151.47 mm;
the second positive lens (803) has a thickness of 2.93mm, a radius of curvature of the front surface of 150mm, and a radius of curvature of the rear surface of-282.13 mm;
the thickness of the third positive lens (804) is 2.13mm, the curvature radius of the front surface is 186.52mm, and the curvature radius of the rear surface is 433.5 mm;
the second negative lens (805) has a thickness of 2mm, a radius of curvature of the front surface of 180mm, and a radius of curvature of the rear surface of 30.95 mm;
the thickness of the fourth positive lens (806) is 5.45mm, the curvature radius of the front surface is 29.65mm, and the curvature radius of the rear surface is-242.63 mm;
the thickness of the third negative lens (701) is 1.4mm, and the curvature radius of the front surface is 1081.33 mm;
the thickness of the fifth positive lens (702) is 2.55mm, the curvature radius of a gluing surface of the fifth positive lens and the third negative lens (701) is 10.09mm, and the curvature radius of the rear surface of the fifth positive lens is 22.91 mm;
the thickness of the fourth negative lens (703) is 1.4mm, the curvature radius of the front surface is-31.44 mm, and the curvature radius of the rear surface is 33.64 mm;
the thickness of the sixth positive lens (501) is 2.65mm, the curvature radius of the front surface is 25.12mm, and the curvature radius of the rear surface is-26.98 mm;
the thickness of the seventh positive lens (502) is 2.9mm, the curvature radius of the front surface is 17.17mm, and the curvature radius of the rear surface is-21.29 mm;
the thickness of the fifth negative lens (503) is 1.4mm, the curvature radius of the front surface is-18.74 mm, and the curvature radius of the rear surface is 248.71 mm;
the thickness of the eighth positive lens (401) is 4.8mm, and the curvature radius of the front surface is-28.00 mm;
the thickness of the sixth negative lens (402) is 1.4mm, the curvature radius of a gluing surface of the sixth negative lens and the eighth positive lens (401) is-9.38 mm, and the curvature radius of the rear surface is 21.34 mm;
the thickness of the seventh negative lens (301) is 1.4mm, the curvature radius of the front surface is-17.67 mm, and the curvature radius of the rear surface is 6.67 mm;
the thickness of the ninth positive lens (302) is 2.25mm, the curvature radius of the front surface is 11.68mm, and the curvature radius of the rear surface is-20.47 mm.
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| CN113866967B (en) * | 2021-09-07 | 2023-09-01 | 昆明物理研究所 | Low-cost light-weight small-sized medium-wave infrared continuous zooming optical system |
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| JP6323742B2 (en) * | 2013-12-06 | 2018-05-16 | コニカミノルタ株式会社 | Zoom lens, lens unit, and imaging apparatus |
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