Method and apparatus for modulating infrared radiation
First Claim
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1. An apparatus comprising a chopper which includes:
- a frame having a first coefficient of thermal expansion, having a space therein, and having at least one opening which allows radiation to pass through said space in a first direction;
a sheet having a second coefficient of thermal expansion different from said first coefficient of thermal expansion, said sheet being movably disposed within said space in said frame, in a manner so that said sheet can expand and contract relative to said frame in a second direction approximately parallel to said sheet and approximately perpendicular to said first direction, said frame preventing significant movement of said sheet parallel to said first direction with respect to said frame, and said sheet including structure which influences radiation that passes through said sheet in said first direction;
wherein said sheet and said frame have cooperating features that maintain said sheet in angular and radial alignment with respect to said frame.
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Abstract
A chopper for an imaging system includes a frame and a sheet that have different coefficients of thermal expansion. The frame has a space within it, and has at least one opening that allows radiation to pass through the space. The sheet has structure which influences radiation passing through the sheet, and the sheet is movably disposed within the space in the frame, in a manner so that the sheet can expand and contract relative to the frame in a direction approximately parallel to the sheet. The frame prevents any significant movement of the sheet in a direction transverse to the sheet.
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Citations
30 Claims
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1. An apparatus comprising a chopper which includes:
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a frame having a first coefficient of thermal expansion, having a space therein, and having at least one opening which allows radiation to pass through said space in a first direction; a sheet having a second coefficient of thermal expansion different from said first coefficient of thermal expansion, said sheet being movably disposed within said space in said frame, in a manner so that said sheet can expand and contract relative to said frame in a second direction approximately parallel to said sheet and approximately perpendicular to said first direction, said frame preventing significant movement of said sheet parallel to said first direction with respect to said frame, and said sheet including structure which influences radiation that passes through said sheet in said first direction; wherein said sheet and said frame have cooperating features that maintain said sheet in angular and radial alignment with respect to said frame. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method, comprising:
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providing a frame which has a first coefficient of thermal expansion, which has a space therein, and which has at least one opening that allows radiation to pass through said space in a first direction; providing a sheet which has a second coefficient of thermal expansion different from said first coefficient of thermal expansion, and which includes structure that influences radiation which passes through said sheet in said first direction; and responding to temperature changes by causing said sheet to undergo at least one of expansion and contraction relative to said frame within said space in a second direction approximately parallel to said sheet and approximately perpendicular to said first direction, said frame preventing significant movement of said sheet parallel to said first direction with respect to said frame; wherein said sheet and said frame have cooperating features that maintain said sheet in angular and radial alignment with respect to said frame; and wherein a chopper is formed by said frame and said sheet. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. An apparatus comprising a chopper which includes:
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a frame having a first coefficient of thermal expansion, having a space therein, and having at least one opening which allows radiation to pass through said space in a first direction; a sheet having a second coefficient of thermal expansion different from said first coefficient of thermal expansion, said sheet being movably disposed within said space in said frame, in a manner so that said sheet can expand and contract relative to said frame in a second direction approximately parallel to said sheet and approximately perpendicular to said first direction, said frame preventing significant movement of said sheet parallel to said first direction with respect to said frame, and said sheet including structure which influences radiation that passes through said sheet in said first direction; wherein said chopper has an axis extending approximately parallel to said first direction; wherein said sheet has a plurality of slots at angularly spaced locations around said axis, said slots each extending approximately radially of said axis; and wherein said frame has a plurality of pins extending through said space approximately parallel to said first direction, each said pin extending through a respective said slot. - View Dependent Claims (20, 21, 22, 23, 24, 30)
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25. A method, comprising:
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providing a frame which has a first coefficient of thermal expansion, which has a space therein, and which has at least one opening that allows radiation to pass through said space in a first direction; providing a sheet which has a second coefficient of thermal expansion different from said first coefficient of thermal expansion, and which includes structure that influences radiation which passes through said sheet in said first direction; and responding to temperature changes by causing said sheet to undergo at least one of expansion and contraction relative to said frame within said space in a second direction approximately parallel to said sheet and approximately perpendicular to said first direction, said frame preventing significant movement of said sheet parallel to said first direction with respect to said frame; wherein a chopper is formed, which has an axis extending approximately parallel to said first direction; said method further including configuring said sheet to have a plurality of slots at angularly spaced locations around said axis, said slots each extending approximately radially of said axis; and including configuring said frame to have a plurality of pins extending through said space approximately parallel to said first direction, each said pin extending through a respective said slot. - View Dependent Claims (26)
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27. A method, comprising:
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providing a frame which has a first coefficient of thermal expansion, which has a space therein, and which has at least one opening that allows radiation to pass through said space in a first direction; providing a sheet which has a second coefficient of thermal expansion different from said first coefficient of thermal expansion, and which includes structure that influences radiation which passes through said sheet in said first direction, said frame and said sheet forming a chopper having an axis extending approximately parallel to said first direction; rotating said chopper about said axis and maintaining said sheet in angular and radial alignment with respect to said frame; and responding to temperature changes by causing said sheet to undergo at least one of expansion and contraction relative to said frame within said space in a second direction approximately parallel to said sheet and approximately perpendicular to said first direction, said frame preventing significant movement of said sheet parallel to said first direction with respect to said frame. - View Dependent Claims (28)
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29. An apparatus comprising a chopper which includes:
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a frame having a first coefficient of thermal expansion, having a space therein, and having at least one opening which allows radiation to pass through said space in a first direction; a sheet having a second coefficient of thermal expansion different from said first coefficient of thermal expansion, said sheet being movably disposed within said space in said frame, in a manner so that said sheet can expand and contract relative to said frame in a second direction approximately parallel to said sheet and approximately perpendicular to said first direction, said frame preventing significant movement of said sheet parallel to said first direction with respect to said frame, and said sheet including structure which influences radiation that passes through said sheet in said first direction; wherein said chopper has an axis extending approximately parallel to said first direction; and wherein said chopper is configured to rotate about said axis and wherein said sheet and frame are configured so that said sheet is maintained in angular and radial alignment with respect to said frame.
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Specification