(19)
(11)EP 2 470 936 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
11.12.2019 Bulletin 2019/50

(21)Application number: 10757654.8

(22)Date of filing:  26.08.2010
(51)International Patent Classification (IPC): 
G02B 13/14(2006.01)
G02B 15/173(2006.01)
G02B 13/16(2006.01)
(86)International application number:
PCT/US2010/046728
(87)International publication number:
WO 2011/025850 (03.03.2011 Gazette  2011/09)

(54)

MID INFRARED SPECTRAL BAND CONTINUOUS ZOOM SYSTEM

KONTINUIERLICHES ZOOMSYSTEM AUF DER BASIS EINES SPEKTRALBANDES IM MITTLEREN INFRAROTBEREICH

SYSTÈME DE ZOOM CONTINU À BANDE SPECTRALE MOYEN INFRAROUGE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR

(30)Priority: 28.08.2009 US 549423

(43)Date of publication of application:
04.07.2012 Bulletin 2012/27

(73)Proprietor: Corning Incorporated
Corning, NY 14831 (US)

(72)Inventors:
  • CORNELL, Jim, D.
    Rochester New York 14620 (US)
  • SANSON, Mark, C.
    Macedon New York 14502 (US)

(74)Representative: Elkington and Fife LLP 
Prospect House 8 Pembroke Road
Sevenoaks, Kent TN13 1XR
Sevenoaks, Kent TN13 1XR (GB)


(56)References cited: : 
FR-A1- 2 916 862
JP-A- 2002 014 283
US-A- 5 022 724
US-A1- 2005 259 330
GB-A- 2 138 591
US-A- 4 907 867
US-A- 6 091 551
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    TECHNICAL FIELD



    [0001] The present invention relates to a mid infrared spectral band continuous zoom system for thermally imaging a distant object. The mid infrared spectral band continuous zoom system has a continuous zoom range with a focal length change that is greater than 25X.

    BACKGROUND



    [0002] The traditional mid infrared spectral band systems utilize several discrete fields of view or several discountinuous zoom ranges to thermally image a distant object in the mid infrared spectral range (3-5 µm). As such, manufacturers have been trying to design and produce a mid infrared spectral band continuous zoom system with a continuous zoom over a large zoom range (e.g., greater than 25X) to thermally image a distant object in the mid infrared spectral range (3-5 µm). One such mid infrared spectral band continuous zoom system is the subject of the present invention. US 2005 259330 teaches a zoom lens system is which a first optical unit and a second optical unit are moved to provide magnification.

    SUMMARY



    [0003] In one aspect, the present invention provides a mid infrared spectral band continuous zoom system for thermally imaging an object according to claim 1. The mid infrared spectral continuous zoom system includes: (a) a positive element that focuses incoming light from the object; (b) a negative focal length moving group that intercepts the light being focused by the positive element and creates a virtual image; (c) a positive focal length moving group that relays the virtual image created by the negative focal length moving group to an intermediate image; (d) a relay group that relays the intermediate image to a final image plane; and (e) a cooled infrared camera that thermally images the object at the final image plane. The negative focal length moving group and the positive focal length moving group are moved relative to one another while providing a continuous zoom range with a focal length change greater than 25X.

    [0004] In another aspect, the present invention provides a method for thermally imaging an object in a mid infrared spectral range (3-5 µm) according to claim 13. The method includes the steps of: (a) providing a mid infrared spectral band continuous zoom system including: (i) a positive element that focuses incoming light from the object; (ii) a negative focal length moving group that intercepts the light being focused by the positive element and creates a virtual image; (iii) a positive focal length moving group that relays the virtual image created by the negative focal length moving group to an intermediate image; (iv) a relay group that relays the intermediate image to a final image plane; and (v) a cooled infrared camera that thermally images the object at the final image plane; and (b) moving the negative focal length moving group and the positive focal length moving group relative to one another while providing a continuous zoom range with a focal length change that is greater than 25X when imaging the object.

    [0005] Additional aspects of the invention will be set forth, in part, in the detailed description, figures and any claims which follow, and in part will be derived from the detailed description, or can be learned by practice of the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as disclosed.

    Brief Description of the Drawings



    [0006] A more complete understanding of the present invention may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein:

    FIGURES 1A-1B illustrate an exemplary mid infrared spectral band continuous zoom system configured in accordance with a first embodiment of the present invention; and

    FIGURES 2A-2B illustrate an exemplary mid infrared spectral band continuous zoom system configured in accordance with a second embodiment of the present invention.


    DETAILED DESCRIPTION



    [0007] Referring to FIGURES 1A-1B, there are illustrated an exemplary mid infrared spectral band continuous zoom system 100 in accordance with a first embodiment of the present invention. The mid infrared spectral band continuous zoom system 100 includes a positive element 102, a negative focal length moving group 104, a positive focal length moving group 106, a first fold mirror 108 (optional), a relay group 110, a second fold mirror 112 (optional), and a cooled infrared camera 114. In addition, the mid infrared spectral band continuous zoom system 100 includes an enclosure 116 (e.g., gimbal enclosure 116, spotting scope enclosure 116) that protects at least the positive element 102, the negative focal length moving group 104, the positive focal length moving group 106, the first fold mirror 108, the relay group 110, the second fold mirror 112, and the cooled infrared camera 114.

    [0008] The mid infrared spectral band continuous zoom system 100 has a continuous zoom with a 25X or greater magnification range and a fixed focal plane array that can thermally image an object (not shown) in the 3-5 µm spectral band. In operation, the positive element 102 is positioned to receive and focus incoming light 150 (collimated light 150) from the object. The negative focal length moving group 104 intercepts the light 150 being focused by the positive element 102 and creates a virtual image (which is located to the left of the negative length moving group 104). The positive focal length moving group 106 relays the virtual image via the first fold mirror 108 to an intermediate image 156 (real image location 156). The relay group 110 relays the intermediate image 156 via the second fold mirror 112 to a final image plane 158. The relay group 110 also functions to reduce the diameter of the front positive element 102. The cooled infrared camera 114 (with a fixed diameter cold aperture stop 118) thermally images the object at the final image plane 158. The negative focal length moving group 104 and the positive focal length moving group 106 are axially moved relative to one another to provide a continuous zoom range with a focal length change greater than 25X (see FIGURES 1A and 1B). Linear actuators 120 and 122 can be used to move the negative focal length moving group 104 and the positive focal length moving group 106. The components 102, 104, 106, 108, 110, 112, and 114 can be located in cells.

    [0009] In this configuration, the size of the intermediate image 156 remains fixed while the field of view (FOV) of the incoming light 150 changes based on the magnifications of the negative focal length moving group 104 and the positive focal length moving group 106. For instance, the negative focal length moving group 104 and the positive focal length moving group 106 can be moved close to one another to enable a narrow field of view (NFOV) of the incoming light 150 to about 1.25° (see FIGURE 1A). In contrast, the negative focal length moving group 104 and the positive focal length moving group 106 are moved apart from one another to enable a wide field of view (WFOV) of the incoming light 150 to over 38° (see FIGURE 1B). Thus, the mid infrared spectral band continuous zoom system 100 has a field of view (FOV) that varies from 1.25° to over 38° which makes up the intermediate image 156. The location of the intermediate image 156 does not change with zoom.

    [0010] Although the design of the mid infrared spectral band continuous zoom system 100 presented here contains the negative and positive moving groups of elements 104 and 106, it should be appreciated that more elements could be moved axially to relay the light 150 from the front positive element 106 to the intermediate image plane 156. The creation of an intermediate image plane 156 also allows for a reticle (not shown) to be used in this location if desired. Basically, the exemplary mid infrared spectral band continuous zoom system 100 has elements 102, 104, 106 and 110 with focal lengths chosen to produce a large zoom range while using as few moving groups 104 and 106 as possible.

    [0011] If desired, the mid infrared spectral band continuous zoom system 100 may utilize a focus mechanism 124 (e.g., knob and linear actuator) to move the positive element 102 and allow a relatively close object to be in focus for the thermal imaging. In particular, the positive element 102 is fixed for zoom and then can be moved to focus a relatively close object. For instance, the mid infrared spectral band continuous zoom system 100 can have a near focus that is about 1000X the focal length so that the narrow field of view (NFOV) can handle focusing in at about 440m (1000 times a 440mm focal length).

    [0012] In this example, the mid infrared spectral band continuous zoom system 100 incorporates the positive element 102 which has surfaces S1-S2 and is made from zinc selenide (ZNSE). The negative focal length moving group 104 includes a first element 104a and a second element 104b. The first element 104a has surfaces S3-S4 and is made from Ge33As12Se55 glass (AMTIR1). The second element 104b has surfaces S5-S6 and is made from germanium. The positive focal length moving group 106 includes a first element 106a, a second element 106b and a third element 106c. The first element 106a has surfaces S7-S8 and is made from silicon. The second element 106b has surfaces S9-S10 and is made from zinc selenide (ZNSE). The third element 106c has surfaces S11-S12 and is made from germanium. The first fold mirror 108 has surface S13. The intermediate image 156 has surface S14. The relay group 110 includes a first element 110a, a second element 110b, a third element 110c, a fourth element 110d, and a fifth element 110e. The first element 110a has surfaces S15-S16 made from germanium. The second element 110b has surfaces S17-S18 and is made from silicon. The third element 110c has surfaces S19-S20 and is made from germanium. The fourth element 110d has surfaces S21-S22 and is made from zinc sulfide (CLEARTRAN). The fifth element 110e has surfaces S23-S24 and is made from a chalcogenide (IG2). The second fold mirror 112 has surface S25. The cooled infrared camera 114 includes a window 114a, the fixed diameter cold aperture stop 118, and the final image plane 158. The window 114a has surfaces S26-S27 and is made from germanium. The fixed diameter cold aperture stop 118 can be represented as STO. The final image plane 158 can be represented as IMA.

    [0013] TABLES 1A and 1B present the prescription data (in millimeters) and materials that could be used to manufacture the exemplary mid infrared spectral band continuous zoom system 100. In TABLE 1A, the radius indicates the inverse of the curvature of the surface and the thickness indicates the vertex to vertex distances of the material or airspace.
    TABLE 1A
    SurfaceRadiusThicknessMaterial
    OBJInfinityInfinity 
    1 138.808 12.5 ZNSE
    2 349.3339 VARIABLE_ 1  
    3 -80.78687 5.896031 AMTIR1
    4 43.55553 5.558385  
    5 80.12824 4 GERMANIUM
    6 110.8657 VARIABLE_ 2  
    7 43.89842 4.7 SILICON
    8 135.6469 0.4287948  
    9 56.96466 4 ZNSE
    10 113.2287 0.2623286  
    11 74.7812 4 GERMANIUM
    12 37.10342 VARIABLE_ 3  
    13 Infinity 31.35303  
    14 Infinity 9.110502  
    15 -22.69671 5 GERMANIUM
    16 -44.56803 11.56441  
    17 46.5242 4.8 SILICON
    18 -104.4219 1.02688  
    19 -137.1715 7.65 GERMANIUM
    20 102.9299 2.586301  
    21 62.84298 12 CLEARTRAN
    22 45.07646 2.909197  
    23 55.87358 4.6 IG2
    24 -51.69404 8.999785  
    25 Infinity 12.46842  
    26 Infinity 1.016 GERMANIUM
    27 Infinity 0.75438  
    STO Infinity 14.33583  
    IMA Infinity    
    TABLE 1B
     NFOVWFOV
    VARIABLE_1 106.42 21.06
    VARIABLE_2 1.50 132.00
    VARIABLE_3 53.93 8.97


    [0014] The front positive element 102 is a singular element so as to reduce Narcissus and has a diffractive surface S2 to aid with color correction in the 3-5um spectral band. At the narrow field of view (NFOV), the front positive element 102 is a pupil element (see FIGURE 1A). The use of the diffractive surface S2 in the front positive element 102 reduces the need for the other optical elements 104, 106, 110 to correct chromatic aberrations which would result from not having a color corrected front fixed element 102. In addition, many different optical materials ZNSE, AMTIR1, germanium, silicon, zinc sulfide, and chalcogenide with different amounts of dispersion are used to correct chromatic aberrations (see TABLE 1A). TABLE 2 presents diffractive data (in phase) that can be used to manufacture the front positive element 102.
    TABLE 2
    Diffractive Data
    A1A2A3Normalized Radius
    -466.56 -92.89 187.07 100.00


    [0015] The phase of the diffractive surface S2 can be defined by the following equation no. 1:

    where:
    A1, A2, A3, A4 and A5 are coefficients and p is the normalized radial coordinate at the surface S2.

    [0016] The exemplary mid infrared spectral band continuous zoom system 100 has several aspheres S1, S2, S3, S9, S12, S16, S18 and S22 (non-spherical surfaces S1, S2, S3, S9, S12, S16, S18 and S22) to aid in the correction of monochromatic aberrations. The mid infrared spectral band continuous zoom system 100 has non-spherical surfaces S1, S2, S3, S9, S12, S16, S18 and S22 located therein to balance the aberration correction throughout the entire zoom travel. TABLE 3 presents aspheric data (in sag) that could be used to manufacture the non-spherical surfaces S1, S2, S3, S9, S12, S16, S18 and S22.
    TABLE 3
    Aspheric Data
    SurfaceABCD
    1 9.91E-08 -3.28E-11 8.10E-16 7.90E-19
    2 1.38E-07 -5.94E-11 8.87E-15 0.00E+00
    3 3.95E-06 -6.08E-09 2.25E-11 -2.68E-14
    9 -1.69E-06 3.94E-08 -1.39E-10 1.40E-13
    12 1.35E-06 7.23E-08 -3.08E-10 4.15E-13
    16 4.05E-05 -1.16E-06 8.38E-09 3.28E-11
    18 -1.96E-06 1.11E-07 -6.02E-10 1.16E-12
    22 3.39E-05 -2.77E-07 1.75E-09 -4.46E-12


    [0017] The non-spherical surfaces S1, S2, S3, S9, S12, S16, S18 and S22 are defined by the following equation no. 2:

    where:

    Y= Aperture height, measured perpendicular to optical axis

    K, A, B, C, D = Coefficients

    Z= Position of surface profile for a given Y value, as measured along the optical axis from the pole (i.e. axial vertex) of the surface.



    [0018] Referring to FIGURES 2A-2B, there are illustrated an exemplary mid infrared spectral band continuous zoom system 200 in accordance with a second embodiment of the present invention. The mid infrared spectral band continuous zoom system 200 includes a positive element 202, a negative focal length moving group 204, a positive focal length moving group 206, a relay group 208, and a cooled infrared camera 210. In addition, the mid infrared spectral band continuous zoom system 200 includes an enclosure 212 (e.g., gimbal enclosure 212, spotting scope enclosure 212) that protects at least the positive element 202, the negative focal length moving group 204, the positive focal length moving group 206, the relay group 208, and the cooled infrared camera 210.

    [0019] The mid infrared spectral band continuous zoom system 200 has a continuous zoom with a 25X or greater magnification range and a fixed focal plane array that can thermally image an object (not shown) in the 3-5 µm spectral band. In operation, the positive element 202 is positioned to receive and focus incoming light 250 (collimated light 250) from the object. The negative focal length moving group 204 intercepts the light 250 being focused by the positive element 202 and creates a virtual image (which is located to the left of the negative length moving group 204). The positive focal length moving group 206 relays the virtual image to an intermediate image 256 (real image location 256). The relay group 208 relays the intermediate image 256 to a final image plane 258. The relay group 208 also functions to reduce the diameter of the front positive element 202. The cooled infrared camera 210 (with a fixed diameter cold aperture stop 214) thermally images the object at the final image plane 258. The negative focal length moving group 204 and the positive focal length moving group 206 are axially moved relative to one another to provide a continuous zoom range with a focal length change greater than 25X. Linear actuators 216 and 218 can be used to move the negative focal length moving group 204 and the positive focal length moving group 206. The components 202, 204, 206, 208, and 210 can be located in cells.

    [0020] In this configuration, the size of the intermediate image 256 remains fixed while the field of view (FOV) of the incoming light 250 changes based on the magnifications of the negative focal length moving group 204 and the positive focal length moving group 206. For instance, the negative focal length moving group 204 and the positive focal length moving group 206 can be moved close to one another to enable a narrow field of view (NFOV) of the incoming light 250 to about 1.25° (see FIGURE 2A). In contrast, the negative focal length moving group 204 and the positive focal length moving group 206 are moved apart from one another to enable a wide field of view (WFOV) of the incoming light 250 to over 38° (see FIGURE 2B). Thus, the mid infrared spectral band continuous zoom system 200 has a field of view (FOV) that varies from 1.25° to over 38° which makes up the intermediate image 256. The location of the intermediate image 256 does not change with zoom.

    [0021] Although the design of the mid infrared spectral band continuous zoom system 200 presented here contains the negative and positive moving groups of elements 204 and 206, it should be appreciated that more elements could be moved axially to relay the light 250 from the front positive element 206 to the intermediate image plane 256. The creation of an intermediate image plane 256 also allows for a reticle (not shown) to be used in this location if desired. Basically, the exemplary mid infrared spectral band continuous zoom system 200 has elements 202, 204, 206 and 208 with focal lengths chosen to produce a large zoom range while using as few moving groups 204 and 206 as possible.

    [0022] If desired, the mid infrared spectral band continuous zoom system 200 may utilize a focus mechanism 220 (e.g., knob and linear actuator) to move the positive element 202 and allow a relatively close object to be in focus for the thermal imaging. In particular, the positive element 202 is fixed for zoom and then can be moved to focus a relatively close object. For instance, the mid infrared spectral band continuous zoom system 200 can have a near focus that is about 1000X the focal length so that the narrow field of view (NFOV) can handle focusing in at about 440m (1000 times a 440mm focal length).

    [0023] In this example, the mid infrared spectral band continuous zoom system 200 utilizes the positive element 202 which has surfaces S1-S2 and is made from zinc selenide (ZNSE). The negative focal length moving group 204 includes a first element 204a and a second element 204b. The first element 204a has surfaces S3-S4 and is made from Ge33As12Se55 glass (AMTIR1). The second element 204b has surfaces S5-S6 and is made from germanium. The positive focal length moving group 206 includes a first element 206a, a second element 206b and a third element 206c. The first element 206a has surfaces S7-S8 and is made from silicon. The second element 206b has surfaces S9-S10 and is made from zinc selenide (ZNSE). The third element 206c has surfaces S11-S12 and is made from germanium. The intermediate image 256 has surface S13. The relay group 208 includes a first element 208a, a second element 208b, a third element 208c, a fourth element 208d, and a fifth element 208e. The first element 208a has surfaces S14-S15 made from germanium. The second element 208b has surfaces S16-S17 and is made from silicon. The third element 208c has surfaces S18-S19 and is made from germanium. The fourth element 208d has surfaces S20-S21 and is made from zinc sulfide (CLEARTRAN). The fifth element 208e has surfaces S22-S23 and is made from a chalcogenide (IG2). The cooled infrared camera 210 includes a window 210a, the fixed diameter cold aperture stop 214, and the final image plane 258. The window 210a has surfaces S24-S25 and is made from germanium. The fixed diameter cold aperture stop 214 can be represented as STO. The final image plane 258 can be represented as IMA.

    [0024] TABLES 4A and 4B present the prescription data (in millimeters) and materials that could be used to manufacture the exemplary mid infrared spectral band continuous zoom system 200. In TABLE 4A, the radius indicates the inverse of the curvature of the surface and the thickness indicates the vertex to vertex distances of the material or airspace.
    TABLE 4A
    SurfaceRadiusThicknessMaterial
    OBJInfinityInfinity 
    1 138.808 12.5 ZNSE
    2 349.3339 VARIABLE_ 1  
    3 -80.78687 5.896031 AMTIR1
    4 43.55553 5.558385  
    5 80.12824 4 GERMANIUM
    6 110.8657 VARIABLE_ 2  
    7 43.89842 4.7 SILICON
    8 135.6469 0.4287948  
    9 56.96466 4 ZNSE
    10 113.2287 0.2623286  
    11 74.7812 4 GERMANIUM
    12 37.10342 VARIABLE_ 3  
    13 Infinity 40.463532  
    14 -22.69671 5 GERMANIUM
    15 -44.56803 11.56441  
    16 46.5242 4.8 SILICON
    17 -104.4219 1.02688  
    18 -137.1715 7.65 GERMANIUM
    19 102.9299 2.586301  
    20 62.84298 12 CLEARTRAN
    21 45.07646 2.909197  
    22 55.87358 4.6 IG2
    23 -51.69404 21.468205  
    24 Infinity 1.016 GERMANIUM
    25 Infinity 0.75438  
    STO Infinity 14.33583  
    IMA Infinity    
    TABLE 4B
     NFOVWFOV
    VARIABLE_ 1 106.42 21.06
    VARIABLE_ 2 1.50 132.00
    VARIABLE_ 3 53.93 8.97


    [0025] The front positive element 202 is a singular element so as to reduce Narcissus and has a diffractive surface S2 to aid with color correction in the 3-5um spectral band. At the narrow field of view (NFOV), the front positive element 202 is a pupil element (see FIGURE 2A). The use of the diffractive surface S2 in the front positive element 202 reduces the need for the other optical elements 204, 206 and 208 to correct chromatic aberrations which would result from not having a color corrected front fixed element 202. In addition, many different optical materials ZNSE, AMTIR1, germanium, silicon, zinc sulfide, and a chalcogenide with different amounts of dispersion are used to correct chromatic aberrations (see TABLE 4A). TABLE 5 presents diffractive data (in phase) that can be used to manufacture the front positive element 202.
    TABLE 5
    Diffractive Data
    A1A2A3Normalized Radius
    -466.56 -92.89 187.07 100.00


    [0026] The phase of the diffractive surface S2 can be defined by the following equation no. 3:

    where:
    A1, A2, A3, A4 and A5 are coefficients and p is the normalized radial coordinate at the surface S2.

    [0027] The exemplary mid infrared spectral band continuous zoom system 200 has several aspheres S1, S2, S3, S9, S12, S15, S17 and S21 (non-spherical surfaces S1, S2, S3, S9, S12, S15, S17 and S21) to aid in correction of monochromatic aberrations. The mid infrared spectral band continuous zoom system 200 has non-spherical surfaces S1, S2, S3, S9, S12, S15, S17 and S21 located therein to balance the aberration correction throughout the entire zoom travel. TABLE 6 presents aspheric data (in sag) that could be used to manufacture the non-spherical surfaces S1, S2, S3, S9, S12, S15, S17 and S21.
    TABLE 6
    Aspheric Data
    SurfaceABCD
    1 9.91E-08 -3.28E-11 8.10E-16 7.90E-19
    2 1.38E-07 -5.94E-11 8.87E-15 0.00E+00
    3 3.95E-06 -6.08E-09 2.25E-11 -2.68E-14
    9 -1.69E-06 3.94E-08 -1.39E-10 1.40E-13
    12 1.35E-06 7.23E-08 -3.08E-10 4.15E-13
    15 4.05E-05 -1.16E-06 8.38E-09 3.28E-11
    17 -1.96E-06 1.11E-07 -6.02E-10 1.16E-12
    21 3.39E-05 -2.77E-07 1.75E-09 -4.46E-12


    [0028] The non-spherical surfaces S1, S2, S3, S9, S12, S15, S17 and S21 are defined by the following equation no. 4:

    where:

    Y= Aperture height, measured perpendicular to optical axis

    K, A, B, C, D = Coefficients

    Z= Position of surface profile for a given Y value, as measured along the optical axis from the pole (i.e. axial vertex) of the surface.



    [0029] Although two embodiments of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it should be understood that the invention is not limited to the two disclosed embodiments, but is capable of numerous rearrangements, modifications and substitutions without departing from the invention as set forth and defined by the following claims. It should also be noted that the reference to the "present invention" or "invention" used herein relates to exemplary embodiments and not necessarily to every embodiment that is encompassed by the appended claims.


    Claims

    1. A mid infrared spectral band continuous zoom system (100, 200) for thermally imaging an object, comprising:

    a positive element (102, 202) that focuses incoming light (150, 250) from the object;

    a negative focal length group (104, 204) configured to move for zooming, and that intercepts the light being focused by the positive element and creates a virtual image;

    a positive focal length group (106, 206) configured to move for zooming, that relays the virtual image created by the negative focal length moving group to an intermediate image (156, 256);

    a relay group (110, 208) that relays the intermediate image to a final image plane (158, 258); and

    a cooled infrared camera (114, 210) that thermally images the object at the final image plane,

    characterised in that the negative focal length group and the positive focal length group are moved relative to one another, and the relay group is configured to be fixed during zooming, while providing a continuous zoom range with a focal length change greater than 25X;

    the positive element is made from zinc selenide;

    the negative focal length moving group includes a first element (104a, 204a) made from Ge33As12Se55 glass, and a second element (104b, 204b) made from germanium;

    the positive focal length moving group includes a first element (106a, 206a) made from silicon, a second element (106b, 206b) made from zinc selenide, and a third element (106c, 206c) made from germanium; and

    the relay group includes a first element (110a, 208a) made from germanium, a second element (110b, 208b) made from silicon, a third element (110c, 208c) made from germanium, a fourth element (110d, 208d) made from zinc sulfide, and a fifth element made from chalcogenide.


     
    2. The mid infrared spectral band continuous zoom system of claim 1, wherein the cooled infrared camera is configured to image the object over 3-5 µm spectral band.
     
    3. The mid infrared spectral band continuous zoom system of claim 1, wherein the negative focal length moving group and the positive focal length moving group are configurable to enable a near focus of about 1000X the focal length.
     
    4. The mid infrared spectral band continuous zoom system of claim 1, wherein the positive element contains a diffractive surface (S2) for correcting chromatic aberration.
     
    5. The mid infrared spectral band continuous zoom system of claim 1, wherein the positive element is a singular element for reducing Narcissus.
     
    6. The mid infrared spectral band continuous zoom system of claim 1, wherein the positive element is moved for focusing the object.
     
    7. The mid infrared spectral band continuous zoom system of claim 1, further comprising:

    a first fold mirror (108) located between the positive focal length moving group and the relay group; and

    a second fold mirror (112) located between the relay group and the cooled infrared camera.


     
    8. The mid infrared spectral band continuous zoom system of claim 1, wherein the negative focal length moving group and the positive focal length moving group are moved close to one another to enable a narrow field of view of the incoming light to about 1.25°.
     
    9. The mid infrared spectral band of claim 1, wherein the negative focal length moving group and the positive focal length moving group are moved apart from one another to enable a wide field of view of the incoming light to about 38°.
     
    10. The mid infrared spectral band of claim 1, wherein the cooled infrared camera includes a fixed diameter cold stop (118).
     
    11. The mid infrared spectral band continuous zoom system of claim 1, wherein:

    the positive element has two aspheric surfaces (S1-S2);

    the negative focal length moving group includes a first element (104a, 204a) with an aspheric surface (S3) and a spherical surface (S4), and a second element (104b, 204b) with two spherical surfaces (S5-S6);

    the positive focal length moving group includes a first element (106a, 206a) with two spherical surfaces (S7-S8), a second element (106b, 206b) with an aspheric surface (S9) and a spherical surface (S10), and a third element (106c, 206c) with a spherical surface (S11) and an aspheric surface (S12); and

    the relay group includes a first element (110a, 208a) with a spherical surface (S15, S14) and an aspheric surface (S16, S15), a second element (110b, 208b) with a spherical surface (S17, S16) and an aspheric surface (S18, S17), a third element (110c, 208c) with two spherical surfaces (S19-S20, S18-S19), a fourth element (110d, 208d) with a spherical surface (S21, S20) and an aspheric surface (S22, S21), and a fifth element (110e, 208e) with two spherical surfaces (S23-S24, S22-S23).


     
    12. The mid infrared spectral band continuous zoom system of claim 1, further comprising a gimbal device (212) that encloses the positive element, the negative focal length moving group, the positive focal length moving group, the relay group, and the cooled infrared camera.
     
    13. A method for thermally imaging an object, the method comprising the steps of:

    providing a mid infrared spectral band continuous zoom system (100, 200) including:

    a positive element (102, 202) that focuses incoming light (150, 250) from the object;

    a negative focal length moving group (104, 204) that intercepts the light being focused by the positive element and creates a virtual image;

    a positive focal length moving group (106, 206) that relays the virtual image created by the negative focal length moving group to an intermediate image (156, 256);

    a relay group (110, 208) that relays the intermediate image to a final image plane (158, 258); and

    a cooled infrared camera (114, 210) that thermally images the object at the final image plane; and

    moving the negative focal length moving group and the positive focal length moving group relative to one another while providing a continuous zoom range with a focal length change greater than 25X when imaging the object, wherein the relay group is fixed during zooming;

    wherein:

    the positive element is made from zinc selenide;

    the negative focal length moving group includes a first element (104a, 204a) made from Ge33As12Se55 glass, and a second element (104b, 204b) made from germanium;

    the positive focal length moving group includes a first element (106a, 206a) made from silicon, a second element (106b, 206b) made from zinc selenide, and a third element (106c, 206c) made from germanium; and

    the relay group includes a first element (110a, 208a) made from germanium, a second element (110b, 208b) made from silicon, a third element (110c, 208c) made from germanium, a fourth element (110d, 208d) made from zinc sulfide, and a fifth element made from chalcogenide.


     


    Ansprüche

    1. Kontinuierliches Zoomsystem im mittleren Infrarotbereich (100, 200) für die thermische Abbildung eines Objekts, umfassend:

    ein positives Element (102, 202), das vom Objekt eingehendes Licht (150, 250) fokussiert;

    eine negative Brennweitengruppe (104, 204), die konfiguriert ist, um sich zum Zoomen zu bewegen, und die das vom positiven Element fokussierte Licht abfängt und ein virtuelles Bild erzeugt;

    eine positive Brennweitengruppe (106, 206), die konfiguriert ist, um sich zum Zoomen zu bewegen, die das von der sich bewegenden negativen Brennweitengruppe erzeugte virtuelle Bild an ein Zwischenbild (156, 256) überträgt;

    eine Übertragungsgruppe (110, 208), die das Zwischenbild an eine Endbildebene (158, 258) überträgt; und

    eine gekühlte Infrarotkamera (114, 210), die das Objekt an der Endbildebene thermisch abbildet;

    dadurch gekennzeichnet, dass die negative Brennweitengruppe und die positive Brennweitengruppe relativ zueinander bewegt werden, und die Übertragungsgruppe konfiguriert ist, um während des Zoomens fixiert zu sein, während ein kontinuierlicher Zoombereich mit einer Brennweitenänderung von größer als 25X bereitgestellt wird;

    das positive Element aus Zinkselenid besteht;

    die sich bewegende negative Brennweitengruppe ein erstes Element (104a, 204a), das aus Ge33As12Se55-Glas besteht, und ein zweites Element (104b, 204b), das aus Germanium besteht, enthält;

    die sich bewegende positive Brennweitengruppe ein erstes Element (106a, 206a), das aus Silizium besteht, ein zweites Element (106b, 206b), das aus Zinkselenid besteht, und ein drittes Element (106c, 206c), das aus Germanium besteht, enthält; und

    die Übertragungsgruppe ein aus Germanium bestehendes erstes Element (110a, 208a), ein aus Silizium bestehendes zweites Element (110b, 208b), ein aus Germanium bestehendes drittes Element (110c, 208c), ein aus Zinksulfid bestehendes viertes Element (110d, 208d), ein aus Chalkogenid bestehendes fünftes Element enthält.


     
    2. Kontinuierliches Zoomsystem im mittleren Infrarotbereich nach Anspruch 1, wobei die gekühlte Infrarotkamera konfiguriert ist, das Objekt über ein Spektralband von 3-5 µm abzubilden.
     
    3. Kontinuierliches Zoomsystem im mittleren Infrarotbereich nach Anspruch 1, wobei die sich bewegende negative Brennweitengruppe und die sich bewegende positive Brennweitengruppe konfiguriert werden können, um einen nahen Brennpunkt von etwa 1000X der Brennweite zu ermöglichen.
     
    4. Kontinuierliches Zoomsystem im mittleren Infrarotbereich nach Anspruch 1, wobei das positive Element eine Beugungsfläche (S2) zur Korrektur von chromatischer Aberration enthält.
     
    5. Kontinuierliches Zoomsystem im mittleren Infrarotbereich nach Anspruch 1, wobei das positive Element ein einzelnes Element zur Verringerung des Narcissus-Effekts ist.
     
    6. Kontinuierliches Zoomsystem im mittleren Infrarotbereich nach Anspruch 1, wobei das positive Element zum Fokussieren des Objekts bewegt wird.
     
    7. Kontinuierliches Zoomsystem im mittleren Infrarotbereich nach Anspruch 1, ferner umfassend:

    einen ersten Faltspiegel (108), der sich zwischen der sich bewegenden positiven Brennweitengruppe und der Übertragungsgruppe befindet; und

    einen zweiten Faltspiegel (112), der sich zwischen der Übertragungsgruppe und der gekühlten Infrarotkamera befindet.


     
    8. Kontinuierliches Zoomsystem im mittleren Infrarotbereich nach Anspruch 1, wobei die sich bewegende negative Brennweitengruppe und die sich bewegende positive Brennweitengruppe nahe zueinander bewegt werden, um ein schmales Sichtfeld des eingehenden Lichts auf etwa 1,25° zu ermöglichen.
     
    9. Kontinuierliches Zoomsystem im mittleren Infrarotbereich nach Anspruch 1, wobei die sich bewegende negative Brennweitengruppe und die sich bewegende positive Brennweitengruppe entfernt voneinander bewegt werden, um ein breites Sichtfeld des eingehenden Lichts auf etwa 38° zu ermöglichen.
     
    10. Kontinuierliches Zoomsystem im mittleren Infrarotbereich nach Anspruch 1, wobei die gekühlte Infrarotkamera einen Kältestopp mit festem Durchmesser (118) enthält.
     
    11. Kontinuierliches Zoomsystem im mittleren Infrarotbereich nach Anspruch 1, wobei:

    das positive Element zwei asphärische Oberflächen (S1-S2) aufweist;

    die sich bewegende negative Brennweitengruppe ein erstes Element (104a, 204a) mit einer asphärischen Oberfläche (S3) und einer sphärischen Oberfläche (S4) und ein zweites Element (104b, 204b) mit zwei sphärischen Oberflächen (S5-S6) enthält;

    die sich bewegende positive Brennweitengruppe ein erstes Element (106a, 206a) mit zwei sphärischen Oberflächen (S7-S8), ein zweites Element (106b, 206b) mit einer aspährischen Oberfläche (S9) und einer sphärischen Oberfläche (S10) und ein drittes Element (106c, 206c) mit einer sphärischen Oberfläche (S11) und einer asphärischen Oberfläche (S12) enthält; und

    die Übertragungsgruppe ein erstes Element (110a, 208a) mit einer sphärischen Oberfläche (S15, S14) und einer asphärischen Oberfläche (S16, S15), ein zweites Element (110b, 208b) mit einer sphärischen Oberfläche (S17, S16) und einer asphärischen Oberfläche (S18, S17), ein drittes Element (110c, 208c) mit zwei sphärischen Oberflächen (S19-S20, S18-S19), ein viertes Element (110d, 208d) mit einer sphärischen Oberfläche (S21, S20) und einer asphärischen Oberfläche (S22, S21) und ein fünftes Element (110e, 208e) mit zwei sphärischen Oberflächen (S23-S24, S22-S23) enthält.


     
    12. Kontinuierliches Zoomsystem im mittleren Infrarotbereich nach Anspruch 1, ferner umfassend eine Kardanvorrichtung (212), die das positive Element, die sich bewegende negative Brennweitengruppe, die sich bewegende positive Brennweitengruppe und die gekühlte Infrarotkamera umschließt.
     
    13. Verfahren zum thermischen Abbilden eines Objekts, wobei das Verfahren die folgenden Schritte umfasst:

    Bereitstellen eines kontinuierlichen Zoomsystems im mittleren Infrarotbereich (100, 200), enthaltend:

    ein positives Element (102, 202), das vom Objekt eingehendes Licht (150, 250) fokussiert;

    eine sich bewegende negative Brennweitengruppe (104, 204), die das vom positiven Element fokussierte Licht abfängt und ein virtuelles Bild erzeugt;

    eine sich bewegende positive Brennweitengruppe (106, 206), die das von der sich bewegenden negativen Brennweitengruppe erzeugte virtuelle Bild an ein Zwischenbild (156, 256) überträgt;

    eine Übertragungsgruppe (110, 208), die das Zwischenbild an eine Endbildebene (158, 258) überträgt; und

    eine gekühlte Infrarotkamera (114, 210), die das Objekt an der Endbildebene thermisch abbildet; und

    Bewegen der sich bewegenden negativen Brennweitengruppe und der sich bewegenden positiven Brennweitengruppe relativ zueinander, während ein kontinuierlicher Zoombereich mit einer Brennweitenänderung von mehr als 25X bereitgestellt wird, wenn das Objekt abgebildet wird, wobei die Übertragungsgruppe während des Zoomens fixiert ist; wobei:

    das positive Element aus Zinkselenid besteht;

    die sich bewegende negative Brennweitengruppe ein erstes Element (104a, 204a), das aus Ge33As12Se55-Glas besteht, und ein zweites Element (104b, 204b), das aus Germanium besteht, enthält;

    die sich bewegende positive Brennweitengruppe ein erstes Element (106a, 206a), das aus Silizium besteht, ein zweites Element (106b, 206b), das aus Zinkselenid besteht, und ein drittes Element (106c, 206c), das aus Germanium besteht, enthält; und

    die Übertragungsgruppe ein aus Germanium bestehendes erstes Element (110a, 208a), ein aus Silizium bestehendes zweites Element (110b, 208b), ein aus Germanium bestehendes drittes Element (110c, 208c), ein aus Zinksulfid bestehendes viertes Element (110d, 208d), und ein aus Chalkogenid bestehendes fünftes Element enthält.


     


    Revendications

    1. Système de zoom continu à bande spectrale moyen infrarouge (100, 200) destiné à effectuer une imagerie thermique d'un objet, comprenant :

    un élément positif (102, 202) qui focalise la lumière entrante (150, 250) provenant de l'objet ;

    un groupe de longueurs focales négatives (104, 204) conçu pour se déplacer en vue d'un zoom et qui intercepte la lumière focalisée par l'élément positif et crée une image virtuelle ;

    un groupe de longueurs focales positives (106, 206) conçues pour se déplacer en vue d'un zoom, qui relaie l'image virtuelle créée par le groupe mobile de longueurs focales négatives vers une image intermédiaire (156, 256) ;

    un groupe relais (110, 208) qui relaie l'image intermédiaire vers un plan d'image final (158, 258) ; et

    une caméra infrarouge refroidie (114, 210) qui effectue une imagerie thermique de l'objet au niveau du plan d'image final,

    caractérisé en ce que le groupe de longueurs focales négatives et le groupe de longueurs focales positives sont déplacés l'un par rapport à l'autre, et le groupe relais est conçu pour être fixe durant le zoom, tout en fournissant une plage de zoom continue avec un changement de longueur focale supérieur à 25 fois ;

    l'élément positif est en séléniure de zinc ;

    le groupe mobile de longueur focale négative comprend un premier élément (104a, 204a) en verre Ge33As12Se55, et un deuxième élément (104b, 204b) en germanium ;

    le groupe mobile de longueur focale positive comprend un premier élément (106a, 206a) en silicium, un deuxième élément (106b, 206b) en séléniure de zinc et un troisième élément (106c, 206c) en germanium ; et

    le groupe relais comprend un premier élément (110a, 208a) en germanium, un deuxième élément (110b, 208b) en silicium, un troisième élément (110c, 208c) en germanium, un quatrième élément (110d, 208d) en sulfure de zinc et un cinquième élément en chalcogénure.


     
    2. Système de zoom continu à bande spectrale moyen infrarouge selon la revendication 1, ladite caméra infrarouge refroidie étant conçue pour effectuer l'imagerie de l'objet sur une bande spectrale de 3 à 5 µm.
     
    3. Système de zoom continu à bande spectrale moyen infrarouge selon la revendication 1, ledit groupe mobile de longueur focale négative et ledit groupe mobile de longueur focale positive pouvant être conçus pour permettre une focalisation rapprochée d'environ 1 000 fois la longueur focale.
     
    4. Système de zoom continu à bande spectrale moyen infrarouge selon la revendication 1, ledit élément positif contenant une surface de diffraction (S2) destinée à corriger l'aberration chromatique.
     
    5. Système de zoom continu à bande spectrale moyen infrarouge selon la revendication 1, ledit élément positif étant un élément singulier destiné à réduire l'effet narcisse.
     
    6. Système de zoom continu à bande spectrale moyen infrarouge selon la revendication 1, ledit élément positif étant déplacé pour focaliser l'objet.
     
    7. Système de zoom continu à bande spectrale moyen infrarouge selon la revendication 1, comprenant en outre :

    un premier miroir de renvoi (108) situé entre le groupe mobile à longueur focale positive et le groupe relais ; et

    un second miroir de renvoi (112) situé entre le groupe relais et la caméra infrarouge refroidie.


     
    8. Système de zoom continu à bande spectrale moyen infrarouge selon la revendication 1, ledit groupe mobile de longueur focale négative et ledit groupe mobile de longueur focale positive étant rapprochés l'un de l'autre pour permettre un champ de vision étroit de la lumière entrante à environ 1,25°.
     
    9. Bande spectrale moyen infrarouge selon la revendication 1, ledit groupe mobile de longueur focale négative et ledit groupe mobile de longueur focale positive étant écartés l'un de l'autre pour permettre un champ de vision étendu de la lumière entrante à environ 38°.
     
    10. Bande spectrale moyen infrarouge selon la revendication 1, ladite caméra infrarouge refroidie comprenant un diaphragme froid de diamètre fixe (118).
     
    11. Système de zoom continu à bande spectrale moyen infrarouge selon la revendication 1,
    ledit élément positif possédant deux surfaces asphériques (S1-S2) ;
    ledit groupe mobile de longueur focale négative comprenant un premier élément (104a, 204a) avec une surface asphérique (S3) et une surface sphérique (S4), et un deuxième élément (104b, 204b) avec deux surfaces sphériques (S5-S6) ;
    ledit groupe mobile de longueur focale positive comprenant un premier élément (106a, 206a) avec deux surfaces sphériques (S7-S8), un deuxième élément (106b, 206b) avec une surface asphérique (S9) et une surface sphérique (S10), et un troisième élément (106c, 206c) avec une surface sphérique (S11) et une surface asphérique (S12) ; et
    ledit groupe relais comprenant un premier élément (110a, 208a) avec une surface sphérique (S15, S14) et une surface asphérique (S16, S15), un deuxième élément (110b, 208b) avec une surface sphérique (S17, S16) et une surface asphérique (S18, S17), un troisième élément (110c, 208c) avec deux surfaces sphériques (S19-S20, S18-S19), un quatrième élément (110d, 208d) avec une surface sphérique (S21, S20) et une surface asphérique (S22, S21) et un cinquième élément (110e, 208e) avec deux surfaces sphériques (S23-S24, S22-S23).
     
    12. Système de zoom continu à bande spectrale moyen infrarouge selon la revendication 1, comprenant en outre un dispositif à cardan (212) qui renferme l'élément positif, le groupe mobile de longueur focale négative, le groupe mobile de longueur focale positive, le groupe relais et la caméra infrarouge refroidie.
     
    13. Procédé destiné à effectuer une imagerie thermique d'un objet, le procédé comprenant les étapes de :

    fourniture d'un système de zoom continu à bande spectrale moyen infrarouge (100, 200) comprenant :

    un élément positif (102, 202) qui focalise la lumière entrante (150, 250) provenant de l'objet ;

    un groupe mobile de longueur focale négative (104, 204) qui intercepte la lumière focalisée par l'élément positif et crée une image virtuelle ;

    un groupe mobile de longueur focale positive (106, 206) qui relaie l'image virtuelle créée par le groupe mobile de longueur focale négative vers une image intermédiaire (156, 256) ;

    un groupe relais (110, 208) qui relaie l'image intermédiaire vers un plan d'image final (158, 258) ; et

    une caméra infrarouge refroidie (114, 210) qui effectue une imagerie thermique de l'objet dans le plan d'image final ; et

    déplacement du groupe mobile de longueur focale négative et du groupe mobile de longueur focale positive l'un par rapport à l'autre tout en fournissant une plage de zoom continue avec un changement de longueur focale supérieur à 25 fois lorsqu'il effectue l'imagerie de l'objet, ledit groupe relais étant fixe durant le zoom ;

    ledit élément positif étant en séléniure de zinc ;

    ledit groupe mobile de longueur focale négative comprenant un premier élément (104a, 204a) en verre Ge33As12Se55, et un deuxième élément (104b, 204b) en germanium ;

    ledit groupe mobile de longueur focale positive comprenant un premier élément (106a, 206a) en silicium, un deuxième élément (106b, 206b) en séléniure de zinc et un troisième élément (106c, 206c) en germanium ; et

    ledit groupe relais comprenant un premier élément (110a, 208a) en germanium, un deuxième élément (110b, 208b) en silicium, un troisième élément (110c, 208c) en germanium, un quatrième élément (110d, 208d) en sulfure de zinc et un cinquième élément en chalcogénure.


     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



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    Patent documents cited in the description