Imaging system functioning on submillimeter waves

• US 6,242,740 B1
• Filed: 09/11/1998
• Issued: 06/05/2001
• Est. Priority Date: 09/16/1997
• Status: Expired due to Term

• Current Assignee: Oxford Instruments Analytical OY (Oxford Instruments PLC)
• Original Assignee: Metorex International Oy (Oxford Instruments PLC)
• Inventors: Luukanen, Arttu, Sipila, Heikki, Viitanen, Veli-Pekka
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Gabor, Otilia
• Application Number:
  US09/151,325
• Time in Patent Office: 998 Days
• Field of Search: 250/353, 250/349, 250/250
• US Class Current: 250/353
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 5/0837 Microantennas, e.g. bow-tie
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 3/784 using a mosaic of detectors
• CPC Class Codes: G01V 8/005 operating with millimetre waves, e.g. measuring the black losey radiation
• CPC Class Codes: H04N 5/30 Transforming light or analogous information into electric information scanning details H04N3/00; cameras or camera modules comprising electronic image sensors, or control thereof H04N23/00; circuitry of solid-state image sensors [SSIS] or control thereof H04N25/00

Abstract

The invention relates to detection performed over millimeter and submillimeter wavelengths, especially to imaging solutions functioning over a submillimeter-wavelength range. The system of the invention uses detectors, comprising antenna coupled bolometers together with wavelength selective optics. The detector matrix is preferably curved for reducing the number of imaging errors. In order to provide a curved detector matrix, the detector matrix is constituted by flat submatrices, each being provided with one or more integrated antenna coupled bolometers. The detectable frequency range is preferably limited in two stages, first by means of wavelength selective optics and secondly by means of the operating band of the antenna of an antenna coupled bolometer. In order to focus the incoming radiation on bolometers, the bolometer substrate is fitted or the surface or interior of the bolometer substrate is provided with a bolometer lens or a corresponding optical element in alignment with each bolometer.

Claims

1. An imaging system comprising:

more than one detector, wherein each detector is an antenna coupled bolometer having an antenna element and a bolometer element,

at least one substantially flat bolometer substrate, wherein said detector is on said substrate,

an optical element for collecting electromagnetic radiation, wherein said element focuses collected electromagnetic radiation on aid detector, and

at least one adaptation element between said optical element and said detector for improving the coupling of the radiation directed to said detector.

2. The system of claim 1 wherein said adaptation element is an anti-reflection layer on the surface of said bolometer substrate.

3. The system of claim 1 wherein said adaptation element is a wave tube matrix.

4. The system of claim 1 wherein said adaptation element is a lens.

5. The system of claim 4 having one lens per each antenna coupled bolometer.

6. The system of claim 4 wherein said lens is produced by ion implantation.

7. The system of claim 4 wherein said lens is produced from a mixture of epoxy and powder.

8. The system of claim 1 which detects electromagnetic radiation having a wavelength of about 100 μ

m to 3 mm.

9. The system of claim 1 wherein at least one antenna coupled bolometer detects electromagnetic radiation of a first wavelength range and at least one antenna coupled bolometer detects electromagnetic radiation of a second wavelength range.

10. The system of claim 1 having more than two bolometer substrates, wherein said bolometer substrates are adapted to provide a detector surface roughly in the shape of a curved surface, said curved surface being substantially the focal plane of said optical element.

11. The system of claim 1 wherein said optical element limits the wavelength band of electromagnetic radiation applied to said bolometer substrate.

12. The system of claim 11 wherein at least one of the surfaces of said optical element is rough, the roughness of said surface being substantially equal to a predetermined value.

13. The system of claim 1 wherein said optical element is a lens.

14. The system of claim 1 wherein said optical element is a mirror.

15. The system of claim 1 further comprising a cold surface for enhancing contrast between an object to be imaged and its background.

16. The system of claim 15 wherein said cold surface is produced by means of a container of liquid nitrogen, said container having thermal insulation wherein said thermal insulation is substantially transparent over the detectable wavelength band.

17. The system of claim 1 further comprising a radiation source and a diffuser for lighting an object to be imaged.