Method of detecting unknown object and apparatus therefor

• US 5,081,456 A
• Filed: 04/13/1988
• Issued: 01/14/1992
• Est. Priority Date: 04/13/1987
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Hiramoto, Kazuo, Michiguchi, Yoshihiro, Nishi, Masatsugu
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US07/180,964
• Time in Patent Office: 1,371 Days
• Field of Search: 342/21, 342/22, 342/27, 342/55, 342/181, 342/351
• US Class Current: 342/22
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/867 Combination of radar systems with cameras
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G06V 20/52 Surveillance or monitoring of activities, e.g. for recognising suspicious objects recognising microscopic objects G06V20/69
• CPC Class Codes: G06V 2201/05 Recognition of patterns representing particular kinds of hidden objects, e.g. weapons, explosives, drugs

Abstract

In visualizing an unknown object possessed by a person to be checked, a narrow pulsating radio wave beam is scanned over the whole surface of the person to observe the intensity of a reflected radio wave at each scan point. The frequency of the radio wave beam is set at a frequency easy to be transmitted by the human body to suppress the reflection from the human body and emphasize the unknown object to thereby discriminate between them. An image of the person to be checked is displayed and the portion having a strong reflection is color-displayed on the image to allow the check of the unknown object possessed by the person without contacting the person.

Claims

1. A method of detecting an unknown object comprising the steps of:

scanning and radiating a radio wave beam to a living body member to be checked, said radio wave beam having a frequency at which absorption of said radio wave beam by water exhibits substantially a peak so that the intensity of said radio wave beam reflected from said living body member becomes lower than a predetermined value;

obtaining the intensity of said reflected radio wave at each scan position of said radio wave beam; and

detecting an unknown object possessed by said living body member to be checked in accordance with said reflected radio wave intensity.

2. A method of detecting an unknown object according to claim 1, wherein a vapor amount in the air is detected, and the intensity of said radiated radio wave is controlled in accordance with the detected value of said vapor amount.

3. A method of detecting an unknown object according to claim 1, wherein the intensity of said radiated radio wave is controlled such that the intensity of a reflected radio wave from a standard reflector set near at said member to be checked becomes a predetermined value.

4. A method of detecting an unknown object according to claim 1, wherein the frequency of said radio wave beam is one of substantially 180 GHz and substantially 310 GHz.

5. A method according to claims 2, 3 or 4, wherein the unknown object detecting step includes visually displaying the distribution of the reflected radio wave intensity at each scan position of the radio wave beam.

6. A method according to claim 5, wherein the step of visually displaying includes visually displaying the distribution of the reflected wave by superposing the distribution upon an image of the living body member to be checked taken by a television camera.

7. A method according to claims 2, 3 or 4, further comprising the steps of:

using another radio wave beam at a frequency having a larger reflection intensity of the living body member to be checked than that of the frequency of the first mentioned radio wave beam;

scanning the living body member to be checked by alternately switching between both radio wave beams;

obtaining a cross sectional image of the living body member, based on a time from each radio wave transmission to reflected wave detection and based on a signal representative of said scan position; and

displaying on the cross sectional image on intensity distribution of the reflected radio wave at each frequency, using a color brightness specific to each frequency.

8. A method according to claim 7, wherein in addition to the display of the cross sectional image, a scan line of the radio wave beam is displayed by superposing it upon an image of the living body member to be checked taken by a television camera.

9. A method according to claim 1, wherein the step of scanning and radiating a radio wave beam includes radiating a focused radio wave beam to the living body member to be checked and scanning the living body member to be checked with the focused radio wave beam.

10. A method of detecting an unknown object according to claim 9, wherein said unknown object detecting step visually displays the distribution of said reflected radio wave intensity at each scan position of said radio wave beam.

11. A method of detecting an unknown object according to claim 10, wherein said visualization displays the distribution of said reflected radio wave by superposing it upon an image of said member to be checked taken by a television camera.

12. A method of detecting an unknown object according to claim 9, comprising the steps of:

using another radio wave beam at a frequency having a larger reflection intensity of said member to be checked than that of the frequency of said first mentioned radio wave beam;

scanning said member to be checked by alternately switching said both radio wave beams;

obtaining a cross sectional image of said member, based on a time from each radio wave transmission to reflected wave detection and based on a signal representative of said scan position; and

displaying on said cross sectional image an intensity distribution of the reflected radio wave at each frequency, using a color brightness specific to each frequency.

13. A method of detecting an unknown object according to claim 12 wherein in addition to the display of said cross sectional image, a scan line of said radio wave beam is displayed by superposing it upon an image of said member to be checked taken by a television camera.

14. A method of detecting an unknown object according to claim 9, wherein the frequency of the radio wave beam is one of substantially 22 GHz, substantially 180 GHz and substantially 310 GHz.

15. A method according to claim 1, further comprising the step of subsequent to detecting an unknown object, scanning and radiating another radio wave beam having a frequency higher than the radio wave beam utilized for detecting the unknown object.

16. A method according to claim 15, wherein the another radio wave beam with the higher frequency is another frequency at which absorption of said another radio wave beam by water exhibits substantially a peak.

18. An apparatus for visualizing an unknown object according to claim 7, further comprising means for controlling the frequency of a radio wave beam to make the reflection intensity of said living body smaller than a predetermined value.

20. An apparatus according to claims 18 or 19, wherein the display means includes a camera for taking an image of the living body member to be checked, and displays a superimposed image of the reflection intensity distribution of the reflected radio wave upon said image taken by said camera.

27. An apparatus according to claim 2, wherein the means for radiating a radio wave beam radiates a focused radio wave beam.

28. An apparatus for visualizing an unknown object according to claim 27, further comprising a camera for taking an image of said member to be checked, whereby a superimposed image of said image taken by said camera upon a scan line of said radio wave beam is displayed.

29. An apparatus according to claim 27, wherein the frequency of the first beam is one of substantially 22 GHz, substantially 180 GHz and substantially 310 GHz.

17. An apparatus for visualizing an unknown object comprising:

means for radiating a radio wave beam at a frequency at which absorption of said radio wave beam by water exhibits substantially a peak so as to have a small reflection intensity relative to a living body, to a living body member to be checked;

means for scanning said radio wave beam to said member to be checked;

means for receiving a reflected radio wave of said radiated radio wave beam;

means for obtaining the intensity of said received reflected radio wave at each scan position of said radio wave beam; and

means for displaying the intensity of said reflected radio wave as the distribution of said radio wave beam at each scan position.

19. An apparatus according to claim 17, wherein the frequency of said radio wave beam is one of substantially 180 GHz and substantially 310 GHz.

21. An apparatus according to claim 17, wherein the means for radiating a radio wave beam radiates a focused radio wave beam.

22. An apparatus for visualizing an unknown object according to claim 21, wherein said display means includes a camera for taking an image of said member to be checked, and displays a superimposed image of the reflection intensity distribution of said reflected radio wave upon said image taken by said camera.

23. An apparatus according to claim 21, wherein the frequency of the radio wave beam is one of substantially 22 GHz, substantially 180 GHz and substantially 310 GHz.

38. An apparatus according to claim 31, 32, 35, 19 or 27, further comprising means for radiating another radio wave beam whose frequency has a larger reflection intensity of the living body member to be checked than that of the frequency of said first mentioned radio wave beam, the scanning means scanning the living body member to be checked by alternately switching between both radio wave beams, means for obtaining a cross sectional image of the living body member based on a time from each radio wave beam transmission to reflected radio wave detection and based on a signal representative of the scan position, and means for displaying an intensity distribution of the reflected radio wave at each frequency on the cross sectional image, using a color or brightness specific to each frequency.

24. An apparatus for visualizing an unknown object comprising:

means for radiating a radio wave beam to a living body member to be checked, said radio wave beam including a first beam having a frequency at which absorption of said radio wave beam by water exhibits substantially a peak;

means for scanning said radio wave beam to said member to be checked;

means for alternately switching the frequency of said radio wave beam radiated from said radiating means, between said first beam with a frequency having a low reflection intensity of said living body member and a second beam with a frequency having a large reflection intensity of said living body member;

means for detecting a reflected radio wave of said radio wave beam;

means for obtaining the intensity of said detected reflected radio wave at each scan position of said radio wave beam;

means for obtaining a cross sectional image of said member to be checked in accordance with a time from transmission of said radio wave beam to detection of said reflected radio wave, at each scan position of said radio wave beam; and

means for displaying on said cross sectional image the intensity of said reflected radio wave in a color or brightness specific to each frequency of said radio wave beam.

25. An apparatus according to claim 24, wherein the frequency of said first beam is one of substantially 180 GHz and substantially 310 GHz.

26. An apparatus according to claim 25, further comprising a camera for taking an image of the living body member to be checked, whereby a superimposed image of the image taken by the camera upon a scan line of the radio wave beam is displayed.

30. An apparatus for visualizing an unknown object possessed by a living body member by radiating a radio wave beam, comprising:

means for scanning a member to be checked by using a focused radio wave beam having a frequency at which absorption of said radio wave beam by water exhibits substantial a peak so that the reflection intensity of a living body is smaller than a predetermined value;

means for obtaining the intensity of a reflected radio wave at each span position; and

means for visually displaying the intensity distribution of said reflected radio wave at each scan position.

31. An apparatus for visually an unknown object according to claim 30, further comprising means for radiating another radio wave beam whose frequency has a larger reflection intensity of said member to be checked than that of the frequency of said first mentioned radio wave beam, said member to be checked is scanned by said scanning means by alternatively switching said both radio wave beams, means for obtaining a cross sectional image of said member based on a time from each radio wave beam transmission to reflected radio wave detection and based on a signal representative of said scan position, and means for displaying an intensity distribution of said reflected radio wave at each frequency on said cross sectional image, using a color or brightness specific to each frequency.

32. An apparatus for visualizing an unknown object according to claim 31, further comprising means for detecting a vapor amount in the air, and means for controlling the intensity of said radiated radio wave beam in accordance with the amount detected by said detecting means.

33. An apparatus for visualizing an unknown object according to claim 31, further comprising means for controlling the intensity of said radiated radio wave beam such that the intensity of a reflected radio wave from a standard reflector set near said member to be checked becomes a predetermined value.

34. An apparatus for visualizing an unknown object according to claim 30, further comprising means for detecting a vapor amount in the air, and means for controlling the intensity of said radiated radio wave beam in accordance with the amount detected by said detecting means.

35. An apparatus for visualizing an unknown object according to claim 30, further comprising means for controlling the intensity of said radiated radio wave beam such that the intensity of a reflected radio wave from a standard reflector set near said member to be checked becomes a predetermined value.

36. An apparatus according to claim 30, wherein the frequency of the radio wave beam is one of substantially 22 GHz, substantially 180 GHz and substantially 310 GHz.

37. An apparatus according to claim 30, wherein the frequency of said radio wave beam is one of substantially 180 GHz and substantially 310 GHz.

39. An apparatus for visualizing an unknown object comprising:

means for radiating first and second radio wave beams to a living body member to be checked;

means for scanning said first and second radio wave beams to said living body member to be checked;

means for alternately switching between said first and second radio wave beams, said first radio wave beam having a frequency providing a low reflection intensity of said living body member and said second radio wave beam having another frequency providing one of a large reflection intensity of said living body member and a low reflection intensity of said living body member;

means for detecting a reflected radio wave of each of said first and second radio wave beams;

means for obtaining the intensity of said detected reflected radio wave at each scan position of said first and second radio wave beams; and

means for displaying an indication of the intensity obtained of said received reflected radio wave.

40. An apparatus according to claim 39, wherein said another frequency is higher than the frequency of said first radio wave beam.

41. An apparatus according to claim 39, wherein the scanning means scans the first and second radio wave beams on the same scan line.

42. An apparatus according to claim 39, wherein the frequency of at least the first radio wave beam is a frequency at which absorption of said first radio wave beam by water exhibits substantially a peak.