CN102323671A - Telecentric off-axis three-mirror optical imaging system with real entrance pupil - Google Patents

Abstract

The invention relates to a telecentric off-axis three-reflector optical imaging system with a real entrance pupil, belonging to imaging systems in the technical field of space optics. The solved technical problem is to provide a telecentric off-axis three-reflector optical imaging system with a real entrance pupil. The invention has the technical scheme that the telecentric off-axis three-reflector optical imaging system with a real entrance pupil comprises a primary mirror, a secondary mirror, a tertiary mirror, an aperture stop, an image plane and a front focal plane, wherein the secondary mirror is placed on the reflecting light path of the primary mirror, and the tertiary mirror is placed on the reflecting light path of the secondary mirror; the distance between the front focal plane and the primary mirror is a negative value; and the aperture stop coincides with the front focal plane. The imaging system has the following relevant structural parameters that f' is image focal length, R1, R2 and R3 are curvature radii at peaks of the reflecting planes of the primary mirror, the secondary mirror and the tertiary mirror respectively, d1, d2 and d3 are distances between the primary mirror and the secondary mirror, between the secondary mirror and the tertiary mirror and between the tertiary mirror and the image plane respectively; lf is the distance between the front focal plane and the primary mirror, and alpha 1 and alpha 2 are obscuration ratios of the secondary mirror to the primary mirror and the tertiary mirror to the secondary mirror respectively. R1, R2, R3, d1, d2, d3 and lf respectively conform to relevant formulas to determine the structure dimensions of the optical imaging system.

Description

A kind of heart far away with real entrance pupil is from axle three anti-mirror optical imaging systems

Technical field

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

Background technology

From axle three anti-mirror optical imaging systems have simple in structure, do not have block, characteristics such as wide visual field, no color differnece, picture element are good, compact conformation; Can realize high resolving power and high-energy utilization factor; Be applied to space to ground imaging observation fields such as space camera, imaging spectrometer more and more, obtained development fast.

It is telecentric system that the imaging spectrometer that rearmounted spectrum beam splitting system is a telecentric optical system all requires preposition optical imaging system with the Image-forming instrument that adopts fibre optic image transmission; For having the application that has situation such as directional mirror before optical window (space picture window) and the sweep type Image-forming instrument before the imaging system; Be to guarantee 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 the heart far away to leave axle three anti-mirror optical imaging systems with real entrance pupil.

The prior art the most approaching with the present invention is the national defence patent of invention of Changchun Institute of Optics, Fine Mechanics and Physics, CAS in first to file, and application number is 200910125577.4; Denomination of invention is for " field angle is that 10 ° the heart far away leaves axle three anti-mirror imaging systems ", and is as shown in Figure 1, comprises 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, and three mirrors 3 are the concave ellipsoidal surface mirror, and aperture diaphragm 4 is placed on the secondary mirror 2; The distance of aperture diaphragm 4 to three mirrors 3 is the half the of three mirrors, 3 vertex curvature radius length, and 5 is the image planes of imaging system.The subject matter that this system exists is: system's front focus is a virtual focus, and promptly system's entrance pupil is empty entrance pupil, can't satisfy the application need with real entrance pupil and space optics imaging system of heart requirement far away.

Summary of the invention

In order to overcome the defective that prior art exists; The objective 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 a real focus, and a kind of heart far away with real entrance pupil of ad hoc meter is from axle three anti-mirror optical imaging systems.

The technical matters that the present invention will solve is: provide a kind of heart far away with real entrance pupil from axle three anti-mirror optical imaging systems.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 a real focus, front focal plane 11 is a negative value to the distance of primary mirror 6, before promptly front focal plane 11 is positioned at primary mirror 6; In order to realize that as Fang Yuanxin aperture diaphragm 9 overlaps with front focal plane 11 before being placed on primary mirror 6, aperture diaphragm 9 is system's 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 satisfy that image quality requires, system from the axle back through each catoptron with respect to the off-centre of system spindle with tilt the balanced system aberration; If should be the picture side focal length of the heart far away from the dependency structure parameter of axle three anti-mirror optical imaging systems: f ' from axle three anti-mirror optical imaging systems, R ₁, R ₂And R ₃Be respectively the vertex curvature radius of primary mirror 6 reflectings surface, secondary mirror 7 reflectings surface and three mirrors, 8 reflectings surface, d ₁, d ₂And d ₃Be respectively the distance of primary mirror 6, l to secondary mirror 7, secondary mirror 7 to three mirrors 8 and three mirrors 8 to image planes 10 _fBe 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 be defined as back mirror from the distance of 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 all arranged, make from axle three anti-mirror optical imaging systems rational in infrastructure.R then ₁, R ₂And R ₃Satisfy formula respectively:

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

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

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

d ₁, d ₂And d ₃Satisfy formula respectively:

d ₁＝[α ₁(1-α ₂) ²+α ₂(1-α ₁) ²]f′……………………………………………………(4)

d ₂＝-[α ₁(1-α ₂) ²+α ₂(1-α ₁) ²]f′……………………………………………………(5)

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

l _fSatisfy 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 satisfy 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, be used for confirming 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 mirrors, 8 reflectings surface pushes away, be used for confirming front focal plane 11 to primary mirror 6 apart from l _f, through limiting l _fMake system have preceding 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 the field angle is received and reflexes on the secondary mirror 7 by primary mirror 6, 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 the visual field again.Identical image quality requires down, the visual field width of imaging system, system's focal length and each catoptron aspheric surface face type three mutual restriction.Aspheric surface number of times one timing that catoptron adopts, system's focal length is long more, and the visual field width is more little; One timing of system's focal length, the aspheric surface number of times that catoptron adopts is high more, and the visual field width is big more.

Good effect of the present invention: the heart far away with real entrance pupil provided by the invention from axle three anti-mirror optical imaging system field angle can satisfy general space optics use in＜5 ° field range requirement; Guaranteed the picture width of multi-spectral imager, imaging spectrometer earth observation, the ground resource quantity of information that can obtain to enrich; Imaging system has real entrance pupil, can satisfy the application when having incident beam restraint devices such as optical window (space picture window) and directional mirror before the system; 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's entrance pupil) be positioned at appointed positions; System's 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 axle three debuging of anti-mirror optical imaging system.

Description of drawings

Fig. 1 is the structural representation of prior art;

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

Embodiment

The present invention implements by structure shown in Figure 2.Wherein, choose picture side's 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 mirrors, 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 mirrors, 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 mirrors, 8 reflectings surface ₃=-4.02797 °, can obtain the heart far away that 4 ° of comparatively ideal field angle have a real entrance pupil like this from axle three anti-mirror optical imaging systems.

Claims (1)

1. the heart far away with real entrance pupil comprises primary mirror (6), secondary mirror (7), three mirrors (8), aperture diaphragm (9) from axle three anti-mirror optical imaging systems, it is characterized in that also 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 a negative value to the distance of primary mirror (6), and it is preceding that promptly front focal plane (11) is positioned at primary mirror (6); Aperture diaphragm (9) is placed on that primary mirror (6) is preceding to be overlapped with front focal plane (11), and aperture diaphragm (9) is system's entrance pupil; If should be the picture side focal length of the heart far away from the dependency structure parameter of axle three anti-mirror optical imaging systems: f ' from axle three anti-mirror optical imaging systems, 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 arrive the distance of image planes (10), l to secondary mirror (7), secondary mirror (7) to three mirrors (8) with three mirrors (8) _fBe 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, general α to secondary mirror (7) ₁Value in 0.4～0.6 scope, corresponding arbitrary definite α ₁Value, α ₂Corresponding span is all arranged, make from axle three anti-mirror optical imaging systems rational in infrastructure, R then ₁, R ₂And R ₃Satisfy formula respectively:

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

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

$R_3=\frac{2{\mathrm{\&alpha;}}_1[{\mathrm{\&alpha;}}_1{\left({1-\mathrm{\&alpha;}}_2\right)}^2+{\mathrm{\&alpha;}}_2{(1-{\mathrm{\&alpha;}}_1)}^2]}{{\mathrm{\&alpha;}}_1({\mathrm{\&alpha;}}_1+{\mathrm{\&alpha;}}_2-3)+1}{f}^{\&prime;}\&CenterDot;\&CenterDot;\&CenterDot;\left(3\right)$

d ₁, d ₂And d ₃Satisfy formula respectively:

d ₁＝[α ₁(1-α ₂) ²+α ₂(1-α ₁) ²]f′……………………………………………………(4)

d ₂＝-[α ₁(1-α ₂) ²+α ₂(1-α ₁) ²]f′……………………………………………………(5)

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

l _fSatisfy 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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