JP2007124510A - Electromagnetic wave imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To concentrically irradiate a target with an electromagnetic wave and to converge and receive the reflected electromagnetic wave, thereby acquiring a good image. <P>SOLUTION: An electromagnetic wave transmitter 3 is equipped with an electromagnetic wave oscillator 6, an array type transmitting antenna 8, and a lens 1 for concentrating the electromagnetic wave radiated from the transmitting antenna 8 to a predetermined position. An electromagnetic wave receiver 4 is equipped with a detector 5, an array type receiving antenna 7, and a lens 2 for allowing the electromagnetic wave reflected from the predetermined position to be concentrated and incident in the receiving antenna 7. The electromagnetic wave is radiated from the transmitting antenna 8, and the lens 1 concentrates the electromagnetic wave to a focusing line (aiming point) 12. A reflected wave from a target surface 9 is concentrated to the opening of the receiving antenna 7 by the lens 2. Then, the reflected wave is detected by the detector 5 connected to the receiving antenna 7, and is converted into an electric signal to depict a two-dimensional image of the target surface 9. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electromagnetic wave imaging apparatus for drawing a two-dimensional image of a target by transmitting and receiving electromagnetic waves.

  Conventionally, electromagnetic wave imaging is intended to visualize the response of a target to electromagnetic waves with a two-dimensional image. A typical example is a commercially available digital camera. A two-dimensional image is a set of fine pixels. If the image has resolutions of m and n in the vertical and horizontal directions, the total number of pixels is m × n.

  If an image is picked up using a single light receiving element, it is necessary to move and scan the light receiving element m × n times, and even an image of about 100 × 100 pixels results in the number of moving scans as many as 10,000 times. The imaging cannot be completed within. Therefore, an array in which m × n light receiving elements are arranged in advance two-dimensionally is generally used.

  There is also a system in which m light receiving elements are arranged in a line and n times of moving scanning is performed. Even with this method, the imaging time can be significantly reduced. A typical example is a scanner device commercially available as an office device.

  In general, when imaging using electromagnetic waves in the microwave band or millimeter wave band, an active system that irradiates the target with electromagnetic waves and detects the reflected or transmitted waves, or is spontaneously emitted from the target. A passive method for detecting electromagnetic waves is used.

  When the active method is employed, the target can be directly irradiated with electromagnetic waves, and therefore there is an advantage that the signal sensitivity of the reflected or transmitted wave detected is better than that of the passive method. As an electromagnetic wave oscillator in the microwave band or millimeter wave band, a GUNN oscillator or the like is generally used. In order to irradiate the electromagnetic wave output from the GUNN oscillator toward the target, it is necessary to impart directivity to the electromagnetic wave using a transmission antenna such as a horn antenna.

Here, when electromagnetic waves are radiated by the transmitting antenna, the problem is diffusion of electromagnetic waves in free space. In general, microwaves and millimeter wave band electromagnetic waves radiated from a transmitting antenna to free space become spherical waves in the near field, and gradually diffuse to become plane waves in the far field (see Non-Patent Document 1).
Development of 3D imaging radar for concrete slab inspection, Haruyuki Ohara, Proceedings of 7th Underground Electromagnetic Measurement Workshop, 2003

  In such a conventional technique, even if an electromagnetic wave is irradiated aiming at a certain point on the target surface, it is difficult to concentrate the electromagnetic wave at one point like a laser beam.

  As a result, the intensity of the reflected / transmitted wave measured by the detector is superimposed with the intensity of the reflected / transmitted wave in the peripheral area of the target point. Such an electromagnetic wave superposition characteristic around the target point is called a PSF (Point Spread Function) and has been a main factor of so-called defocusing of an image obtained by electromagnetic wave imaging.

  In addition, although a method has been taken to repair the blur after applying an image processing algorithm or the like to such a blurred image, the image processing calculation by the computer takes time, and it is sure to repair the deterioration every time. There was no guarantee of success.

  In addition, in the electromagnetic wave imaging apparatus in the microwave band and the millimeter wave band, a technique for measuring the signal intensity by extracting the reflected / transmitted wave from only the target point of the target is required, but its realization is difficult. .

  The present invention has been made in view of the above problems, and an object of the present invention is to concentrate and receive electromagnetic waves on a target and converge and receive reflected electromagnetic waves, thereby obtaining a good image.

  In order to solve the problem, the present invention according to claim 1 is an electromagnetic wave imaging apparatus for obtaining an image of the target by receiving an electromagnetic wave radiated and reflected by the transmitting antenna toward the target by the receiving antenna. A lens for focusing the electromagnetic wave on the target is disposed at the transmission opening of the transmission antenna.

  According to a second aspect of the present invention, in the first aspect, the lens is also disposed in a reception opening of the reception antenna.

  According to a third aspect of the present invention, in the first or second aspect, the lens is a convex lens.

  According to a fourth aspect of the present invention, in the first or second aspect, the lens has a substantially cylindrical shape.

  According to the present invention, electromagnetic waves can be focused and irradiated on a target, and reflected electromagnetic waves can be converged and received, so that a good image can be obtained.

  FIG. 1 is a configuration diagram of an embodiment of an electromagnetic wave imaging apparatus. FIG. 1 shows an electromagnetic wave transmission unit 3 for transmitting an electromagnetic wave and an electromagnetic wave reception unit 4 for receiving an electromagnetic wave transmitted and reflected by the electromagnetic wave transmission unit 3.

  The electromagnetic wave transmission unit 3 is radiated from the electromagnetic wave oscillation unit 6 for oscillating the electromagnetic wave, the array type transmission antenna 8 for radiating the electromagnetic wave oscillated by the electromagnetic wave oscillation unit 6 to free space, and the array type transmission antenna 8. And a lens 1 for concentrating the electromagnetic waves at a predetermined position.

  The electromagnetic wave receiving unit 4 concentrates the electromagnetic wave reflected from a predetermined position, the detector 5 for detecting the electromagnetic wave for converting the received electromagnetic wave into an electric signal, the array type receiving antenna 7 for receiving the electromagnetic wave. And the lens 2 for making it incident on the array type receiving antenna 7.

  In the configuration of FIG. 1, the electromagnetic wave oscillating unit 6 may be a microwave / millimeter wave band GNNN oscillator, for example. The array-type transmitting antenna 8 has a configuration in which, for example, a plurality of planar slot antennas are arranged and arranged at equal intervals on a substrate. As the lens 1, for example, a Teflon (registered trademark) lens that functions as a condenser lens for microwave / millimeter wave electromagnetic waves can be applied.

  The electromagnetic wave oscillated and output by the electromagnetic wave oscillating unit 6 is branched and radiated to free space from a plurality of slot antennas arranged in alignment at the final end side of the array type transmitting antenna 8. The radiated electromagnetic wave is incident on the lens 1 disposed close to or in contact with the lens 1.

  The lens 1 refracts incident electromagnetic waves inside and irradiates the target surface 9 to concentrate the electromagnetic waves as a focal line (target point) 12. The focal line 12 is a singular point that appears when the electromagnetic wave is concentrated by the lens 1 on the target surface 9, and the electromagnetic wave intensity is higher than the surroundings.

  The wallpaper 10 is attached to the surface of the target surface 9 such as a concrete wall. The crack 11 is an example of an object to be imaged by an electromagnetic wave imaging apparatus. Since the crack 11 exists under the wallpaper 10, it is impossible to visually confirm the wallpaper 10 without peeling it off. The electromagnetic wave passes through the wallpaper 10 and reaches the target surface 9 and the crack 11.

  On the other hand, the detector 5 in the electromagnetic wave transmission part 4 can use a Schottky diode, for example. Similar to the array-type transmission antenna 8, the array-type reception antenna 7 has a configuration in which, for example, a plurality of planar slot antennas are arranged on the substrate. As the lens 2, for example, a Teflon (registered trademark) lens that functions as a condenser lens for microwave / millimeter wave electromagnetic waves can be used.

  The electromagnetic wave irradiated to the target surface 9 from the electromagnetic wave transmitting unit 3 is reflected by the target surface 9 to become a reflected wave, refracted inside the lens 2 and concentrated on the opening of the array type receiving antenna 7. In the vicinity of the opening where the reflected waves concentrate, the intensity of the reflected waves is higher than the surroundings.

  The concentrated reflected waves are detected by the detector 5 connected to the array type receiving antenna 7 and converted into an electric signal, and a two-dimensional image of the target surface 9 is drawn based on the electric signal by an image processing means (not shown). To do.

  A two-dimensional image of the target surface 9 can be acquired by directing the electromagnetic wave transmission unit 3 and the electromagnetic wave reception unit 4 having such a configuration toward the target surface 9 and scanning the focal line 12 on the target surface 9. . In the two-dimensional image acquired in this way, for example, when the crack 11 exists under the wallpaper 10, the crack 11 can be clearly depicted. That is, by concentrating (converging) the electromagnetic waves diffused in the free space with the lenses 1 and 2, it is possible to render an image with reduced so-called defocus.

  The lenses 1 and 2 are preferably convex lenses, and the cross-sectional shape of the convex lenses may be a cylindrical shape as shown in FIG. 1, a semicircular shape, an arbitrary continuous curved cross section, or the like. By using the lenses 1 and 2 at the same time, the lens effect can be exhibited in both transmission / reception of electromagnetic waves. For example, a lens (lens 1) may be disposed only on the transmission side of electromagnetic waves, or a lens (lens only on the reception side) 2) may be arranged. Further, the lenses 1 and 2 are arranged along the longitudinal direction of both the array-type transmitting antenna 8 and the array-type receiving antenna 7, but instead of the lenses 1 and 2, the transmission apertures / reception apertures constituting the array are arranged. A plurality of independent lenses may be arranged for each.

  When measuring a transmitted wave instead of a reflected wave from the target surface 9, the array-type transmitting antenna 8 and the lens 1 are combined, and the array-type receiving antenna 7 and the lens 2 with the target surface 9 interposed therebetween. May be installed so as to face each other. By doing so, the electromagnetic wave concentrated on the target surface 9 by the lens 1 can be received more concentrated by the lens 2 as in the case of the reflected wave measurement.

  Next, FIG. 2 shows an explanatory diagram for explaining convergence of electromagnetic waves by the lens.

  FIG. 2 shows an example in which a Teflon (registered trademark) lens having a dielectric constant of 9.0 is used as a lens for converging electromagnetic waves, and the electromagnetic waves are set in a 100 GHz band. The electromagnetic wave 16 before entering the dielectric lens 15 is radiated in the parallel or diffusing direction. When the electromagnetic wave 16 enters the dielectric lens 15, it is refracted at the boundary surface between the dielectric lens 15 and air. Due to the convex lens shape of the dielectric lens 15, the electromagnetic wave 16 is converged and concentrated at the focal point 17 as in the case of the condensing by the optical lens, and the electromagnetic wave intensity at the focal point 17 can be increased.

  According to the present embodiment described above, it is possible to irradiate the electromagnetic waves while concentrating them on the target, and it is possible to receive the reflected electromagnetic waves in a converged manner, thereby obtaining a good image.

The block diagram of the electromagnetic wave imaging device of this Embodiment is shown. An explanatory view for explaining convergence of electromagnetic waves by a dielectric lens is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Lens 3 Electromagnetic wave transmission part 4 Electromagnetic wave reception part 5 Detector 6 Electromagnetic wave oscillator 7 Array type receiving antenna 8 Array type transmission antenna 9 Target surface 10 Wallpaper 11 Crack 12 Focus line 15 Dielectric lens 16 Electromagnetic wave 17 Focus

Claims (4)

In the electromagnetic wave imaging apparatus for obtaining an image of the target by receiving the electromagnetic wave reflected by the transmitting antenna radiated toward the target with the receiving antenna,
An electromagnetic wave imaging apparatus, wherein a lens for focusing an electromagnetic wave on a target is disposed in a transmission opening of the transmission antenna. The lens is
The electromagnetic wave imaging apparatus according to claim 1, wherein the electromagnetic wave imaging apparatus is also disposed in a reception opening of the reception antenna. The electromagnetic wave imaging apparatus according to claim 1, wherein the lens is a convex lens. The electromagnetic wave imaging apparatus according to claim 1, wherein the lens has a substantially cylindrical shape.

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