CN102323671B - A telecentric off-axis three-mirror optical imaging system with a real entrance pupil - Google Patents

Abstract

A telecentric off-axis three-mirror optical imaging system with a real entrance pupil belongs to the imaging system involved in the field of space optics technology. The technical problem to be solved is to provide a telecentric off-axis three-mirror optical imaging system with a real entrance pupil. Technical solution: including primary mirror, secondary mirror, three mirrors, aperture stop, image plane and front focal plane; the secondary mirror is placed on the reflected light path of the primary mirror, and the third mirror is placed on the reflected light path of the secondary mirror; the front focal plane to The distance of the primary mirror is a negative value; the aperture stop coincides with the front focal plane; set the relevant structural parameters of the imaging system: f′ is the focal length of the image square, R ₁ , R ₂ and R ₃ are the primary mirror, secondary mirror and third mirror respectively The vertex curvature radius of the reflective surface, d ₁ , d ₂ and d ₃ are the distances from the primary mirror to the secondary mirror, from the secondary mirror to the third mirror, and from the third mirror to the image plane, l _f is the distance from the front focal plane to the primary mirror, α ₁ and α ₂ are the obscuration ratios of the secondary mirror to the primary mirror and the third mirror to the secondary mirror respectively, R ₁ , R ₂ , R ₃ , d ₁ , d ₂ , d ₃ and l _f respectively satisfy the relevant formulas, and determine the optical imaging system structure size.

Description

A kind of have the heart far away of real entrance pupil from the anti-mirror optical imaging system of axle three

Technical field

The invention belongs to a kind of heart far away for multi-spectral imager, imaging spectrometer and the preposition optical imaging system of fibre optic image transmission quasi-instrument of relating in the space optics technical field from the anti-mirror optical imaging system of axle three.

Background technology

From the anti-mirror optical imaging system of axle three have simple in structure, without blocking, the characteristics such as good, the compact conformation in wide visual field, no color differnece, picture element, can realize high resolving power and high-energy utilization factor, be applied to more and more the space to ground imaging observation fields such as space camera, imaging spectrometer, obtained development fast.

It is telecentric system that the Image-forming instrument of the imaging spectrometer that rearmounted spectrum beam splitting system is telecentric optical system and employing fibre optic image transmission all requires preposition optical imaging system; For before imaging system, having the application that has the situations such as directional mirror before optical window (space picture window) and sweep type Image-forming instrument, for guaranteeing imaging system visual field and energy demand, also require system have real entrance pupil and with its before window or reflector position and consistent size.Therefore, adopt and have the heart far away of real entrance pupil from the anti-mirror optical imaging system of axle three.

The prior art the most approaching with the present invention, the national defence patent of invention of Changchun Institute of Optics, Fine Mechanics and Physics, CAS in first to file, application number is 200910125577.4, denomination of invention is " field angle is that the heart far away of 10 ° is from the anti-mirror imaging system of axle three ", as shown in Figure 1, comprise primary mirror 1, secondary mirror 2, three mirrors 3 and aperture diaphragm 4, its primary mirror 1 is recessed hyperbolic mirror, secondary mirror 2 is protruding spherical mirror, three mirrors 3 are the concave ellipsoidal surface mirror, aperture diaphragm 4 is placed on secondary mirror 2, the distance of aperture diaphragm 4 to three mirrors 3 is half of three mirror 3 vertex curvature radius length, 5 is the image planes of imaging system.The subject matter that this system exists is: the system front focus is virtual focus, and namely the system entrance pupil is empty entrance pupil, can't meet the application needs of the space optics imaging system with real entrance pupil and heart requirement far away.

Summary of the invention

The defect existed in order to overcome prior art, the object of the invention is to: under the prerequisite that guarantees the heart far away, flattened field and diffraction limit modulation transfer function, the system front focus of making is real focus, and ad hoc meter is a kind of has the heart far away of real entrance pupil from the anti-mirror optical imaging system of axle three.

The technical problem to be solved in the present invention is: provide a kind of and have the heart far away of real entrance pupil from the anti-mirror optical imaging system of axle three.The technical scheme of technical solution problem is as shown in Figure 2: comprise primary mirror 6, secondary mirror 7, three mirrors 8, aperture diaphragm 9, image planes 10 and front focal plane 11; Secondary mirror 7 is placed on the reflected light path of primary mirror 6, and three mirrors 8 are placed on the reflected light path of secondary mirror 7; In order to realize that front focus is real focus, front focal plane 11 is negative value to the distance of primary mirror 6, before namely front focal plane 11 is positioned at primary mirror 6; In order to realize the image space heart far away, aperture diaphragm 9 overlaps with front focal plane 11 before being placed on primary mirror 6, and aperture diaphragm 9 is the system entrance pupil; In order to realize required visual field width, primary mirror 6, secondary mirror 7 and three mirrors 8 need to adopt the low order aspheric mirror that can meet that image quality requires, system from after axle by each catoptron with respect to the bias of system spindle with tilt the balanced system aberration; If away from should being from the dependency structure parameter of the anti-mirror optical imaging system of axle three: f ', the heart be from the image space focal length of the anti-mirror optical imaging system of axle three, R ₁, R ₂And R ₃Be respectively the vertex curvature radius of primary mirror 6 reflectings surface, secondary mirror 7 reflectings surface and three mirror 8 reflectings surface, d ₁, d ₂And d ₃Be respectively the distance of primary mirror 6 to secondary mirror 7, secondary mirror 7 to three mirrors 8 and three mirrors 8 to image planes 10, l _fFor the distance of front focal plane 11 to primary mirror 6, α ₁And α ₂Be respectively the ratio of obstruction of 7 pairs of primary mirrors 6 of secondary mirror and 8 pairs of secondary mirrors 7 of three mirrors, the ratio of obstruction is defined as the distance of back mirror from the front mirror focus, identical with the definition in the book of " design of optical aspherical surface, processing and check " (Pan Junhua work, publishing house of University Of Suzhou, 2004.12); General α ₁Value in 0.4～0.6 scope, corresponding arbitrary definite α ₁Value, α ₂Corresponding span is arranged, can meet telecentric system right | the applications distances requirement of lf|.R ₁, R ₂And R ₃Meet respectively formula:

$R_1=\frac{2[{\mathrm{\α}}_1{(1-{\mathrm{\α}}_2)}^2+{\mathrm{\α}}_2{(1-{\mathrm{\α}}_1)}^2]}{1-{\mathrm{\α}}_1}{f}^{\′}\·\·\·\left(1\right)$

${\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000090939210000011.png"\; state="\{\{state\}\}">R</figure-callout>}}_2=\frac{2{\mathrm{\&alpha;}}_1\mathrm{}[{\mathrm{\&alpha;}}_1{(1-{\mathrm{\&alpha;}}_2)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]}{{\mathrm{\&alpha;}}_1({\mathrm{\&alpha;}}_2-2)+1}{f}^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;\left(2\right)$

${\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000090939210000011.png"\; state="\{\{state\}\}">R</figure-callout>}}_3=\frac{2{\mathrm{\&alpha;}}_1\mathrm{}[{\mathrm{\&alpha;}}_1{(1-{\mathrm{\&alpha;}}_2)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]}{{\mathrm{\&alpha;}}_1({\mathrm{\&alpha;}}_1+{\mathrm{\&alpha;}}_2-3)+1}{f}^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;\left(3\right)$

D ₁, d ₂And d ₃Meet respectively formula:

$d_1=[{\mathrm{\&alpha;}}_1{(1-{\mathrm{\&alpha;}}_2)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]f^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;\left(4\right)$

${\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA0000090939210000011.png"\; state="\{\{state\}\}">d</figure-callout>}}_2=-[{\mathrm{\&alpha;}}_1{(1-{\mathrm{\&alpha;}}_2)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]f^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;\left(5\right)$

d ₃=α ₁α ₂f'…………………………………………………………………………（6）

L _fMeet formula:

$l_f=\frac{{\mathrm{\&alpha;}}_1-(1+{\mathrm{\&alpha;}}_1{\mathrm{\&alpha;}}_2)[{\mathrm{\&alpha;}}_1{(1-{\mathrm{\&alpha;}}_2)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]}{{{\mathrm{\&alpha;}}_1}^2{\mathrm{\&alpha;}}_2}{f}^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;\left(7\right).$

Formula (1)～(6) are to meet according to optical imaging system fundamental formular in " engineering optics " (Yu Daoyin, Tan Hengying chief editor, China Machine Press) book | d ₁|=| d ₂| and derive under the particular determination condition of flattened field, for determining the system architecture size; Formula (7) is that the geometrical optics Gauss formula according to primary mirror 6 reflectings surface, secondary mirror 7 reflectings surface and three mirror 8 reflectings surface pushes away, for determine front focal plane 11 to primary mirror 6 apart from l _f, by limiting l _fMake system have front real focus.Therefore, formula (1)～(7) are the formula that solves the actual techniques problem, possess actual practical value, rather than the formula of intellection principle.

The principle of work explanation: the radiation via hole diameter diaphragm 9 in field angle is received and reflexes on secondary mirror 7 by primary mirror 6, then, successively through the reflection of secondary mirror 7 and three mirrors 8, on image planes 10, forms the podiod picture far away of ground scenery in visual field.Under identical image quality required, the visual field width of imaging system, system focal length and each catoptron aspheric surface face type three restricted mutually.Regularly, the system focal length is longer for the aspheric surface number of times one that catoptron adopts, and the visual field width is less; Regularly, the aspheric surface number of times that catoptron adopts is higher for system focal length one, and the visual field width is larger.

Good effect of the present invention: the heart far away with real entrance pupil provided by the invention can meet in the General Spatial optical application<the field range requirement of 5 ° from the anti-mirror optical imaging system of axle three field angle, guarantee the picture width of multi-spectral imager, imaging spectrometer earth observation, can obtain abundant ground resource quantity of information; Imaging system has real entrance pupil, can meet before system the application while having the incident beam restraint devices such as optical window (space picture window) and directional mirror; Select the ratio of obstruction α of 7 pairs of primary mirrors 6 of suitable secondary mirror and 8 pairs of secondary mirrors 7 of three mirrors ₁And α ₂, can make aperture diaphragm 9(system entrance pupil) and be positioned at the position of appointment; The system tube length is slightly larger than 1/4th of burnt length, compact conformation; The position of primary mirror 6 and three mirrors 8 overlaps, and the heart far away is more prone to from debuging of the anti-mirror optical imaging system of axle three.

The accompanying drawing explanation

Fig. 1 is the structural representation of prior art;

Fig. 2 is that the heart far away of the present invention is from the anti-mirror optical imaging system of axle three structural representation.

Embodiment

The present invention implements by structure shown in Figure 2.Wherein, choose the image space focal distance f '=-720mm, relative aperture D/F=1/4, the vertex curvature radius R of primary mirror 6 reflectings surface ₁=-720mm, the vertex curvature radius R of secondary mirror 7 reflectings surface ₂=-295.92252mm, the vertex curvature radius R of three mirror 8 reflectings surface ₃=-611.20908mm, front focal plane 11 to primary mirror 6 apart from l _f=231.8451mm, primary mirror 6 to secondary mirror 7 apart from d ₁=-180mm, secondary mirror 7 to three mirrors 8 apart from d ₂=180mm, three mirrors 8 to image planes 10 apart from d ₃=-382.76315mm, the asphericity coefficient e of primary mirror 6 reflectings surface ₁ ²=-1.33744, e ₁ ⁴=1.87674e-010, the asphericity coefficient e of secondary mirror 7 reflectings surface ₂ ²The asphericity coefficient e of=-1.99425, three mirror 8 reflectings surface ₃ ²=-4.09369, e ₃ ⁴=-1.24029e-009, the offset D of primary mirror 6 reflectings surface ₁=0, the offset D of secondary mirror 7 reflectings surface ₂=42.17403mm, the offset D of three mirror 8 reflectings surface ₃=60.46779mm, the tilt quantity t of primary mirror 6 reflectings surface ₁=-10 °, the tilt quantity t of secondary mirror 7 reflectings surface ₂=-6.01998 °, the tilt quantity t of three mirror 8 reflectings surface ₃=-4.02797 °, can obtain like this 4 ° of comparatively ideal field angle and have the heart far away of real entrance pupil from the anti-mirror optical imaging system of axle three.

Claims (1)

1. the heart far away with real entrance pupil, from the anti-mirror optical imaging system of axle three, comprises primary mirror (6), secondary mirror (7), three mirrors (8), aperture diaphragm (9), characterized by further comprising image planes (10) and front focal plane (11); Secondary mirror (7) is placed on the reflected light path of primary mirror (6), and three mirrors (8) are placed on the reflected light path of secondary mirror (7); Front focal plane (11) is negative value to the distance of primary mirror (6), and it is front that namely front focal plane (11) is positioned at primary mirror (6); Aperture diaphragm (9) is placed on that primary mirror (6) is front to be overlapped with front focal plane (11), and aperture diaphragm (9) is the system entrance pupil; If away from should being from the dependency structure parameter of the anti-mirror optical imaging system of axle three: f ', the heart be from the image space focal length of the anti-mirror optical imaging system of axle three, R ₁, R ₂And R ₃Be respectively the vertex curvature radius of primary mirror (6) reflecting surface, secondary mirror (7) reflecting surface and three mirrors (8) reflecting surface, d ₁, d ₂And d ₃Be respectively primary mirror (6) and to three mirrors (8) and three mirrors (8), arrive the distance of image planes (10), l to secondary mirror (7), secondary mirror (7) _fFor the distance of front focal plane (11) to primary mirror (6), α ₁And α ₂Be respectively secondary mirror (7) to primary mirror (6) and three mirrors (8) the ratio of obstruction to secondary mirror (7), general α ₁Value in 0.4～0.6 scope, corresponding arbitrary definite α ₁Value, α ₂Corresponding span is arranged, can meet telecentric system right | the applications distances requirement of lf|, R ₁, R ₂And R ₃Meet respectively formula:

$R_1=\frac{2[{\mathrm{\&alpha;}}_1{(1-{\mathrm{\&alpha;}}_2)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]}{1-{\mathrm{\&alpha;}}_1}{f}^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;\left(1\right)$

$R_2=\frac{2{\mathrm{\&alpha;}}_1\mathrm{}[{\mathrm{\&alpha;}}_1{(1-{\mathrm{\&alpha;}}_2)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]}{{\mathrm{\&alpha;}}_1({\mathrm{\&alpha;}}_2-2)+1}{f}^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;\left(2\right)$

$R_3=\frac{2{\mathrm{\&alpha;}}_1\mathrm{}[{\mathrm{\&alpha;}}_1{(1-{\mathrm{\&alpha;}}_2)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]}{{\mathrm{\&alpha;}}_1({\mathrm{\&alpha;}}_1+{\mathrm{\&alpha;}}_2-3)+1}{f}^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;\left(3\right)$ D ₁, d ₂And d ₃Meet respectively formula:

$d_1=[{\mathrm{\&alpha;}}_1{(1-{\mathrm{\&alpha;}}_2)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]f^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;\left(4\right)$

$d_2=-[{\mathrm{\&alpha;}}_1{(1-{\mathrm{\&alpha;}}_2)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]f^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;$ $\left(5\right)$

d ₃=α ₁α ₂f'…………………………………………………………………………（6）

L _fMeet formula:

$l_f=\frac{{\mathrm{\&alpha;}}_1-(1+{\mathrm{\&alpha;}}_1{\mathrm{\&alpha;}}_2)[{\mathrm{\&alpha;}}_1{(1-{\mathrm{\&alpha;}}_2)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]}{{{\mathrm{\&alpha;}}_1}^2{\mathrm{\&alpha;}}_2}{f}^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;\left(7\right).$

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