EP0770224A1 - Systeme optique grande vitesse - Google Patents

Systeme optique grande vitesse

Info

Publication number
EP0770224A1
EP0770224A1 EP95922012A EP95922012A EP0770224A1 EP 0770224 A1 EP0770224 A1 EP 0770224A1 EP 95922012 A EP95922012 A EP 95922012A EP 95922012 A EP95922012 A EP 95922012A EP 0770224 A1 EP0770224 A1 EP 0770224A1
Authority
EP
European Patent Office
Prior art keywords
spherical
concentric
lens system
lens
mirrors
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95922012A
Other languages
German (de)
English (en)
Other versions
EP0770224A4 (fr
Inventor
Allan David Beach
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Industrial Research Ltd
Original Assignee
Industrial Research Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Industrial Research Ltd filed Critical Industrial Research Ltd
Publication of EP0770224A1 publication Critical patent/EP0770224A1/fr
Publication of EP0770224A4 publication Critical patent/EP0770224A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/08—Catadioptric systems
    • G02B17/0884—Catadioptric systems having a pupil corrector
    • G02B17/0888—Catadioptric systems having a pupil corrector the corrector having at least one aspheric surface, e.g. Schmidt plates
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/08—Catadioptric systems
    • G02B17/0804—Catadioptric systems using two curved mirrors
    • G02B17/0808—Catadioptric systems using two curved mirrors on-axis systems with at least one of the mirrors having a central aperture
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/08—Catadioptric systems
    • G02B17/082—Catadioptric systems using three curved mirrors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/08—Catadioptric systems
    • G02B17/0836—Catadioptric systems using more than three curved mirrors
    • G02B17/084—Catadioptric systems using more than three curved mirrors on-axis systems with at least one of the mirrors having a central aperture
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/08—Catadioptric systems
    • G02B17/0852—Catadioptric systems having a field corrector only

Definitions

  • This invention relates to an optical lens system and, optionally, an associated optical relay.
  • Solid state imaging arrays CCDs, CTDs, etc
  • CCDs Solid state imaging arrays
  • the instrument designer's problem is to find an optical system with a matching performance, not only in exceptional resolution and distortion characteristics, but also in speed so as to achieve the highest possible information acquisition rate.
  • aperture diameters exceed 150mm
  • design solutions usually reduce to catoptric or catadioptric systems which generally require only one refractive component of the full aperture diameter. Few such systems exist which combine the characteristics of high speed
  • Maksutov camera designs also suffer from problems associated with their massive full-aperture thick meniscus corrector component; to such an extent that the advantage of smaller obliquity effects is overridden by high-order sphero- chromatism as the design speed is increased.
  • This invention relates to improvements to the system.
  • This invention is an optical design which is novel in its assembly of techniques into a format that fits a previously unoccupied area of the speed/diameter relationship and which overcomes the problems previously mentioned.
  • preferred forms of the present invention provide a high speed optical system of economic construction or which, at least, provides the public with a useful choice.
  • the present invention may broadly be said to consist in a lens system suitable for focusing substantially parallel incident light onto a detector, said system comprising (A) a concentric spherical Cassegrain-like system of two mirrors,
  • (C) a transfer lens which combines the concentricity of the Cassegrain- like system of two mirrors and of the concentric spherical focal reducer by imaging the first centre of concentricity (that of the system of two mirrors) on the second centre of concentricity (that of the focal reducer) to thereby provide a single optically concentric system which combines their advantages
  • said lens system further includes:
  • (F) image detection means at the focus of the focal reducer.
  • said concentric spherical Cassegrain-like system of two mirrors does not include any aperture stop.
  • said concentric spherical focal reducer includes at least one spherical mirror element.
  • said concentric spherical focal reducer includes at least one refractor element.
  • said transfer lens system is a refractive single lens.
  • said concentric spherical focal reducer is selected from the group comprising: i. Modified forms of Baker camera; ii. Modified form of Hawkins and Linfoot camera; iii. Derivation of Maksutov or Bouwers camera.
  • said concentric spherical focal reducer is a modified form of the Hawkins and Linfoot camera system and said means to correct the sum of the spherical aberration of all of the spherical mirrors in the entire system and said aperture stop forms part thereof.
  • said means to correct the sum of this spherical aberration of all of the spherical mirrors in the entire system is a concentric meniscus concentric with the concentric focal reducer.
  • the chromatic aberration introduced by the said concentric meniscus is compensated by a refractive component located at the aperture stop.
  • said refractive component is a zero-power chromatic lens or lens combination, for example, a doublet lens or lens combination.
  • said refractive component is a weakly positive power singlet lens.
  • said zero power refractive component includes an aspheric zonal corrector surface sufficiently weak not to introduce any substantial degree of focal difficulties when instant light is angled into the overall lens system other than axially.
  • said lens system is substantially faster than ill.
  • said lens system is about f/0.8.
  • said detector is included.
  • said detector is a solid state detector.
  • said detector has a substantially planar detection surface.
  • Figure 1 shows a speed size relationship for astrocameras including an embodiment of the invention
  • Figure 2 is a drawing of prior art concentric Cassegrain Schmidt or Maksutov cameras
  • FIG. 3 is a drawing of one preferred embodiment of the present invention.
  • Figure 4 is a perspective sectional drawing of an optical relay optionally forming part of the invention.
  • Figure 5 is a perspective sectional drawing of one preferred embodiment of the present invention.
  • Figure 6 is a profile of the asphere of a preferred embodiment of the present invention in accordance with Example 1;
  • Figure 7 is a cross-sectional, side elevation view of the system of Example
  • Figure 8 is a graphical illustration of the performance of the system of
  • Figure 9 is a cross-sectional, side elevation view of the system of Example 2.
  • Figure 10 is a graphical illustration of the performance of the system of Example 2.
  • Figure 11 is a cross-sectional, side elevation view of the system of Example
  • Figure 12 is a perspective sectioned view of an alternative form of the relay which includes a concentric window for a cryostat;
  • Figure 13 is a graphical illustration of the performance of the system of Example 3;
  • Figures 14a, 14b and 14c are illustrations of prior art Maksutov, Baker and Hawkins & Linfoot cameras which can be modified to provide concentric spherical focal reducers in a preferred form of the invention.
  • Preferred forms of the present invention is a concentric Cassegrain like system with a focal reducing relay, all critical surfaces being spherical.
  • the relay described herein is also a concentric system and provides the f/1 speed characteristic at an external focus, but it should be noted that other relays can be used to give different speedVimage-scale parameters.
  • Figure 1 shows the ranges of apertures and speeds for which the named design types are appropriate. This invention is appropriate for the area named "new zone”.
  • the starting point for the concept description is the concentric Cassegrain
  • Schmidt or Maksutov camera designs shown as alternatives in Figure 2. These include an aperture stop 23, a primary mirror 24, a secondary mirror 25 and a focal surface 26. Apart from obliquity effects in the Schmidt aspheric corrector 21 or high-order spherochromatism in the Maksutov corrector 22, the image quality of these designs is uniform over the whole field.
  • the Schmidt corrector located at the common centre of curvature of the mirrors and which fills the aperture stop, has an axis of symmetry, as does the Maksutov meniscus in its achromatic forms.
  • the fabrication penalties of these designs are the need for a full-aperture aspheric or for a full-aperture thick meniscus corrector and the length of the structure or tube required to support the corrector.
  • the Cassegrain focus is relocated to a position between the two mirrors 31 and 37; the optical train is shortened overall by the small forward shift of the secondary mirror 37.
  • the corrected image is virtual and is located at 36, between the relocated "cassegrain" focus and the correcting meniscus 33, because of the net negative power of the latter.
  • To reestablish a real image requires a relay lens which should, of course, be placed with its entrance pupil coincident with the aperture stop.
  • numerous specifications could be derived for relay lenses with differing conjugate ratios; the relay to be described here can reduce the relatively large virtual image to the dimensions typical of CCD devices, and shares the concentricity philosophy of the preceding optics, thus retaining the essential independence from off-axis aberrations.
  • Fast focal reducers are well known adducts for "slow" telescopes and small detector devices, but in this invention an unusually cooperative melding is possible between the subsystem described previously and the type of focal reducing relay shown in Fig. 4.
  • the concentric meniscus 44 provides correction of the spherical aberration of the concave spherical mirror independently of field angle in the same manner as described previously for the basic inventions subsystem.
  • the doublet 45 is afocal and introduces a chromatic error equal and opposite to the chromatic error of the meniscus 44. Being located at the aperture stop, doublet 45 acts equally on all ray bundles so does not disturb the overall concentricity of the system. It should be noted that there are two physical centres of curvature in Fig. 4.
  • the centre of the aperture stop 45 is the centre of curvature of the meniscus 44, but this centre is reflected to the position 40 by the folding flat 46. This arrangement makes it possible to achieve an external focus for greater accessibility. Field curvature is inherent in concentric designs, as is well known in
  • Schmidt cameras especially, and can be corrected by the insertion of a field flattening lens 48 close to the focal surface, but, at least in the usual Schmidt geometries, only at the expense of introducing significant off-axis aberrations.
  • the numerical aperture the speed
  • this problem is at least partially offset by the smaller scale of the focal surface geometry.
  • the field flattening lenses are so weak as to add no significant degradation to the residual sphero-chromatic blur.
  • the system has a primary mirror 51 and a secondary mirror 52.
  • the system also includes a corrector group 54 and 55 (the equivalent of meniscus 44 and doublet 45 in Fig 4) and a folding flat 56.
  • a corrector group 54 and 55 the equivalent of meniscus 44 and doublet 45 in Fig 4
  • a folding flat 56 is also visible in Figure 5.
  • the small weak field flattener 58 which delineates the final flat focal surface.
  • the field flattener lens 58 is intended to be optically cemented to the otherwise uncovered silicon structure of the CCD detector. This minimises additional aberrations contributed by the field flattener 58 and serves to protect the CCD surface from contaminants. Separation of this lens from the focal surface would cause it to intrude too far into the f/1 ray cone with implicit degradation of the image sharpness.
  • the characteristics of this system can be summarised as: (a) the focal power resides in the mirrors, and so is non-chromatic.
  • the spherical mirrors are optically concentric, thus eliminating coma and astigmatism when the aperture stop is located at the centre of curvature (or at the optical equivalent).
  • spherical aberration correction is the only remaining necessary adjunct to the reflective optical elements. This is the function of the corrector group.
  • the residual aberrations are low-amplitude combinations of secondary colour with weak high-order coma and astigmatism, generated primarily at the non-concentric surfaces of the transfer lens.
  • vignetting is minimal.
  • the central obscuration is determined by the perforations in the folding and relay mirrors, provided that the design is adjusted so as to image the secondary mirror into the space between them. In Example 1 below, the central obscuration is about 31.2% on axis, increasing to 33% at the circumference of the 11mm diameter image.
  • distortion is rninimal, with an amplitude generally less than that of the blur spot dimensions.
  • the example designs make use of "Smith's List" of workshop tool radii for the radii of curvature of the optical components. Although non-optimum for residual aberration correction, the difference in performance is negligible.
  • the three following examples demonstrate very different variants of the basic design, a 200mm aperture f/0.9 visible/NIR, a 1000mm aperture f/0.8 visible/NIR and a 200mm aperture f/0.93 thermal infrared version.
  • the specification tables are based on a coordinate system in which the z- axis is the optical axis and the x and y-axes are mutually orthogonal to it. In these design examples the origin is the centre of curvature of the primary mirror. "Diam” and “diam” are the outside and inside diameters of annuli.
  • the bandpass for the first two of the examples given for this class of the system is intended to match the spectral sensitivity of generic silicon CCD devices, for which the highest response lies between 450 and 1 lOOnm.
  • the corresponding refractive index data for optical glass is published for the spectral lines g, e, d, C, r, s and n 10600 . amongst others, providing a good coverage for analytic purposes.
  • the initial ray-tracing process always shows some coma as the dominant residual aberration, for off-axis rays, emanating from the non-concentric components. This is largely corrected by introducing equal and opposite coma within the concentric Cassegrain subsystem, the technique chosen here being that of increasing the focal length of the transfer lens so as to make the transfer imperfectly concentric. The effect of this procedure is to displace the centre of the entrance pupil away from the classical Schmidt location (at the centre of curvature of the primary mirror), and laterally proportionate to off-axis angle, thus effecting the required compensation.
  • Ray tracing is performed thereafter by ensuring that the aperture stop, located at the aspheric surface, accurately delineates the marginal rays for each spectral line.
  • the median ray aberration graphs which follow have as their vertical axis the height of the ray in the entrance pupil and the horizontal axis gives the lateral position of the intercept with the focal plane.
  • the 2D histograms are normalised in amplitude; any significant fine structure is derived from the line-spectrum ray trace. The most relevant feature is the maximum extent of the "footprint" on the 32 X 32 ⁇ m focal patch.
  • Fig. 6 The profile of the aspheric zonal corrector surface is illustrated in Fig. 6. Note that the z-axis is expanded by a factor of 2000 relative to the (vertical) x- axis. Fig. 7 provides a side elevation of this example design, Fig. 8 gives a graphical illustration of the computed performance.
  • Example 2 describes a 1000mm aperture version. There is an extra chromatic correction element used in the transfer lens of the lm variant. This helps to trim back the outer parts of the blur spot which are caused by the extremes of the spectral bandpass.
  • Figure 9 shows the side view of the optical layout and Figure 10 gives a graphic illustration of the computer median ray and blur spot performance.
  • Germanium is a low-cost, easily worked optical medium suited to the refractive components of the fast relay, with the benefit that the high refractive index allows large reductions in the spherical curvatures of the field/transfer lens giving a corresponding significant reduction of the high-order aberrations which limit the off-axis performance of the visible/NIR version of this design.
  • Example 3 lists the optical design of a thermal version of the new system, comparable in most characteristics to those of the example given in Table 1.
  • Figure 11 shows the side view of the optical layout.
  • the significant differences in detail include the use at the aperture stop of a synthetic sapphire spectral dispersion corrector 115 which has only a singlet format, but which has a weak positive power exactly sufficient for the associated positive longitudinal chromatic aberration to correct the negative chromatic aberration of the Germanium concentric meniscus corrector over the spectral band 3.7 - 5.5 ⁇ m.
  • An essential component of a thermal camera of this type is the cryostat sub ⁇ system.
  • the cryostat window is usually made as an optical flat, but with the fast optics in this design, it is more appropriate to fabricate the window as a concentric memscus 119 with its centre of curvature coincident with the reflection of the common centre of curvature created by the folding flat.
  • a perspective view is shown in Fig. 12. This window then contributes to the corrective negative spherical aberration of the system and introduces no off-axis aberrations.
  • Figure 13 illustrates the computed performance of the median ray bundles and of the blur spot.
  • a possible advantage of at least preferred forms of the present invention over prior art designs such as provided by the Hawkins and Linfoot camera as the basis for the design of the focal reducing relay, is that the corrector meniscus is truly concentric, and the chromatic doublet has zero power, thus giving more degrees of freedom to the designer.
  • the classical Maksutov corrector is designed specifically non-concentric, so as to intrinsically compensate for its chromatic aberration for small angles off axis; however, it is believed that at least preferred forms of the present invention exceed allowable off-axis angles in this case.
  • the extra degrees of freedom mentioned above can be used to apochromatise the system, in that optical glasses can be selected for the meniscus and the chromatic doublet which permit a sharp focus for more than the usual two wavelengths implicit in the usual achromatic correction.
  • the chromatic aberration to be corrected by the doublet is minimised to the extent that the glasses KzF N2 and PK 5 la can be utilised to provide apochromatisation over the bandpass 400 to HOOnm (the entire sensitive bandpass of typical silicon-based CCD imaging devices), while retaining the zero-power specification of the doublet.
  • a triplet form allows even further gains in aberration control.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Lenses (AREA)
  • Telescopes (AREA)

Abstract

L'invention concerne un système à lentille et/ou un procédé d'imagerie sur un détecteur d'imagerie. Le système à lentille et le procédé sont utilisés pour focaliser sur ledit détecteur la lumière incidente sensiblement parallèle. Ledit système à lentille comprend: (a) un système concentrique et sphérique du type Cassegrain à deux miroirs; (b) un réducteur de focale sphérique et concentrique; (c) un système à lentille de transfert qui combine la concentricité du système du type Cassegrain à deux miroirs et du réducteur de focale concentrique et sphérique en formant l'image du premier centre de concentricité, c'est-à-dire du système de deux miroirs, sur le second centre de concentricité, c'est-à-dire du réducteur de focale, de manière à produire un seul système optiquement concentrique combinant les avantages des deux; (d) un moyen de correction de la somme de l'aberration sphérique de tous les miroirs sphériques dans la totalité du système, et (e) un diaphragme.
EP95922012A 1994-06-07 1995-06-07 Systeme optique grande vitesse Withdrawn EP0770224A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NZ26069694 1994-06-07
NZ26069694 1994-06-07
PCT/NZ1995/000051 WO1995034013A1 (fr) 1994-06-07 1995-06-07 Systeme optique grande vitesse

Publications (2)

Publication Number Publication Date
EP0770224A1 true EP0770224A1 (fr) 1997-05-02
EP0770224A4 EP0770224A4 (fr) 1998-11-25

Family

ID=19924810

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95922012A Withdrawn EP0770224A4 (fr) 1994-06-07 1995-06-07 Systeme optique grande vitesse

Country Status (4)

Country Link
EP (1) EP0770224A4 (fr)
JP (1) JPH10505432A (fr)
CA (1) CA2192328A1 (fr)
WO (1) WO1995034013A1 (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2300392A1 (fr) * 1997-08-12 1999-02-18 Allan David Beach Camera avec systeme de relais de reduction d'image
WO1999021145A1 (fr) * 1997-10-20 1999-04-29 Industrial Research Limited Systeme de surveillance ameliore
WO2002093231A1 (fr) * 2001-05-15 2002-11-21 Industrial Research Limited Systeme imageur optique a elements de correction d'aberration
ITNA20090061A1 (it) * 2009-10-05 2011-04-06 Optimath Srl Nuova combinazione ottica per telescopi senza la limitazione del diametro dovuta alla dimensione del correttore.
CZ307952B6 (cs) * 2015-03-25 2019-09-11 Univerzita PalackĂ©ho v Olomouci Refraktivní afokální optický systém pro korekci barevné vady difraktivních zobrazovacích prvků
CN107850775B (zh) * 2015-06-15 2020-06-26 中国航空工业集团公司洛阳电光设备研究所 成像装置
CN109324403B (zh) * 2018-09-28 2020-05-19 中国科学院长春光学精密机械与物理研究所 一种面向拼接镜实验的大口径长焦距成像光学系统
CN113766218B (zh) * 2021-09-14 2024-05-14 北京集创北方科技股份有限公司 光学镜头的位置检测方法、电子设备及存储介质

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DE3121044A1 (de) * 1981-03-19 1982-09-30 Erwin Dr Ing Wiedemann Katadioptrisches objektiv hoher lichtstaerke
JPH0682699A (ja) * 1991-06-03 1994-03-25 Her Majesty The Queen In Right Of New Zealand レンズシステム

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US3711184A (en) * 1971-04-12 1973-01-16 Kollsman Instr Corp Large catadioptric objective
DE3121044A1 (de) * 1981-03-19 1982-09-30 Erwin Dr Ing Wiedemann Katadioptrisches objektiv hoher lichtstaerke
JPH0682699A (ja) * 1991-06-03 1994-03-25 Her Majesty The Queen In Right Of New Zealand レンズシステム

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See also references of WO9534013A1 *

Also Published As

Publication number Publication date
WO1995034013A1 (fr) 1995-12-14
AU2684795A (en) 1996-01-04
CA2192328A1 (fr) 1995-12-14
EP0770224A4 (fr) 1998-11-25
AU686393B2 (en) 1998-02-05
JPH10505432A (ja) 1998-05-26

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