JP3263282B2 - Millimeter wave / infrared imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for a millimeter-wave / infrared combined seeker for a missile or a sensor of a terrestrial combined millimeter-wave / infrared monitoring system, and obtains a millimeter-wave image and an infrared image simultaneously. -It relates to an infrared imaging device.

[0002]

2. Description of the Related Art As is well known, a millimeter-wave imaging apparatus that captures a spatial view with millimeter waves as an image, as shown in FIG. The image is formed by scanning or electrically scanning a millimeter wave beam using the electronic scanning antenna 12 as shown in FIG. 7B. According to this method, it takes several seconds to scan a desired viewing space (20 ° × 10 °) in a 94 GHz band using a parabolic antenna having a diameter of 20 cm. The same applies to the electronic scanning antenna.

On the other hand, in an infrared imaging apparatus, mechanical scanning is performed by scanning an infrared incident surface of an infrared sensor, which is focused on a focal plane of a single-element infrared detector by a focal optical system, using a prism or a reflecting mirror. Image. Recently, the focal plane array sensing element has enabled imaging without mechanical scanning.

However, in order to simultaneously obtain a millimeter-wave image and an infrared image within a desired field of view in the same direction, the only way is to arrange the imaging devices 21 and 22 vertically or horizontally as shown in FIG. According to this method, parallax occurs (the image centers of the two imaging devices do not match) depending on the arrangement interval, and the entire device becomes large. In particular, it is a disadvantage that it takes too much time to extract a millimeter wave image.

[0005]

As described above, in the conventional millimeter-wave / infrared imaging apparatus, each imaging apparatus has no choice but to be arranged vertically or horizontally. Becomes a large scale. In particular, it takes too much time to extract a millimeter wave image.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a simple structure and a millimeter wave / red image capable of obtaining a millimeter wave / infrared image in a short time without causing parallax. It is an object to provide an outside imaging device.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a method for generating millimeter-wave and infrared images from the same direction.
In a millimeter-wave / infrared imaging apparatus for obtaining an image, a primary reflector for reflecting and converging the millimeter wave and a primary reflector
It is placed on the millimeter wave reflection path of
Using a compound lens, the surface facing the primary reflecting mirror is
Reflecting the millimeter wave received from the primary reflecting mirror and the primary reflecting mirror
At the same time as forming an image on one point above,
Transmits infrared light incident from the opposite surface and reflects the primary light
A secondary reflecting mirror having a shape for forming an image on the same plane as the millimeter wave image forming surface on the mirror, and a secondary reflecting mirror arranged on the image forming surface on the primary reflecting mirror;
A millimeter wave / infrared co-focal plane in which a millimeter wave two-dimensional receiving array element for current detection of an imaged millimeter wave and an infrared two-dimensional light receiving array element for photoelectrically converting an imaged infrared ray are arranged in the same plane. An array, and signal processing means for simultaneously reading the millimeter-wave detection signal and the infrared detection signal from the array, performing scan conversion, and converting the millimeter-wave image and the infrared image into image signals for displaying on separate displays. It is composed.

In the millimeter-wave / infrared imaging apparatus having the above configuration, the two-dimensional millimeter wave receiving array element and the two-dimensional infrared light receiving array element are arranged on the focal plane of the primary reflecting mirror and the secondary reflecting mirror for reflecting the millimeter wave. A millimeter-wave infrared co-focal plane array arranged in a plane is arranged, and the secondary reflecting mirror has an infrared condensing lens structure so that both millimeter-wave and infrared light can be obtained as images.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 is a perspective view showing the structure of a Cassegrain antenna system in a millimeter wave / infrared imaging apparatus according to the present invention, FIG. 2 is a sectional view showing the specific structure thereof, and FIG. 3 is a block circuit showing the structure of a signal processing system. FIG.

Reference numeral 31 is a primary reflecting mirror, and 32 is a secondary reflecting mirror. The primary reflecting mirror 31 is made of a material that reflects millimeter waves, and its reflecting surface is a paraboloid. Secondary reflector 32
Is composed of three lenses 321 to 323 made of a material that transmits infrared rays (for example, Ge). One lens 32
Reference numeral 1 designates the primary reflecting mirror 31 side as a hyperboloid, operates as a millimeter-wave secondary reflecting mirror, and further reflects the reflection as an aspherical surface.
By arranging the concave lens 322 and the convex lens 323 in combination, the center of the primary reflecting mirror 31 is set to the infrared focal plane. That is, these three types of Ge lenses 321-
The H.323 secondary reflection mirror 32 functions as an infrared transmission type condensing system.

The focal plane of the primary reflecting mirror 31 has a millimeter wave
An infrared co-focal plane array 33 is arranged. This array 3
Numeral 3 designates a two-dimensional millimeter wave receiving array element and an infrared two-dimensional light receiving array element arranged on the same plane (details will be described later). As shown in FIG. By reading the wave reception output (detection current) to the outside, and simultaneously reading the infrared light reception output (detection charge) to the outside, digitizing it by the A / D converter 35, and performing scan conversion by the scan converter 36, An image can be separately output on two general CRT displays 37 and 38, and one display 37 displays a millimeter-wave image and the other display 38 displays an infrared image.

FIG. 4 shows a specific structure of the millimeter wave / infrared co-focal plane array 33. FIG. 4 (a) is a top view of the array 33, and FIG. 4 (b) is an AA line thereof. It is sectional drawing. This array 33 has an infrared receiving array section 331 in the center.
, And a millimeter wave receiving array unit 332 is arranged therearound, and both are formed on a Si wafer substrate 333. The whole is a square of about 60 mm × 60 mm.

The Si wafer substrate 333 emits infrared light
The photoelectric conversion unit 331 is located below the arrangement part of the infrared receiving array unit 331 to be converted.
An infrared charge transfer CCD for transferring the converted output is formed, and a millimeter wave receiving array unit 332 for current detection of the millimeter wave is provided.
Millimeter-wave detection current transfer CCD335 for transferring the current detection output to the arrangement subordinates Ru is formed. These CCD
Reference numerals 334 and 335 are connected to an infrared light receiving array unit 331 and a millimeter wave receiving array unit 332 , which are respectively disposed at the top, via In metal columns 336.

The infrared light receiving array section 331 is composed of a photodiode array such as InSb or PuSe. When an infrared wavelength of 3 to 5 μm is targeted, the size of one pixel is 30 μm.
Approximately 64 × 64 pixels of m-square photodiodes are arranged. In this case, the whole becomes about 2 mm × 2 mm.
It is arranged within 8 mm x 3.8 mm.

On the other hand, the millimeter wave receiving array section 332
It is composed of an As MMIC circuit, and (15 × 15-1)
Pixels are arranged around the infrared light receiving array unit 331. FIG. 5 shows the structure of the millimeter wave receiving array unit 332. FIG. 5 (a)
5B is a top view, FIG. 5B is a top view of one pixel, and FIG. 5C is a cross-sectional view thereof.

That is, the millimeter wave receiving array section 332
Are composed of (15 × 15-1) pixels. On the upper surface of the GaAs-based substrate 3321, a patch antenna unit 3322, a low noise amplifier (HEMT / LNA) 3323, and a Schottky diode unit (millimeter) are formed by strip lines for each pixel. (This is realized by forming a wave detector and forming an n + layer below the strip line) 3324, and an MMIC circuit in which an electrode 3325 is formed by a through hole. The electrode 3325 for each pixel is an In metal column 336.
Is connected to the electrode 3331 on the Si wafer 333 via the.

On the other hand, on the side of the Si wafer 333, an injection diode 333 of an n + layer is formed below the electrode 3331.
2 is formed, a charge storage MOS capacitor (Cs) 3333 is formed on the side thereof, a MOS switch gate 3334 is formed thereon, and a transfer CCD electrode 3335 is formed on the side thereof. A detection current transfer CCD 335 is configured.

FIG. 6 shows an equivalent circuit of a millimeter wave receiving structure per pixel, and its operation will be described. First, on the millimeter-wave MMIC circuit side, after the millimeter-wave signal received by the patch antenna unit 3321 is amplified by the low-noise amplifier 3323, current detection is performed by the Schottky diode unit 3324, and the Si 3 It is led to the electrode 3331 of the wafer 333.

On the Si wafer 333 side, the detection current supplied to the electrode 3331 is transferred to the charge storage MOS capacitor 333.
3 and the charging voltage is stored in the MOS switch gate 33
34, the transfer CCD electrode 333 is taken out at a fixed cycle and transferred.
5 and output.

In the millimeter-wave / infrared co-focal plane array 33 having the above configuration, if the millimeter wave frequency is 94.7 GHz, the focal plane distance d due to the diffraction limit is about 1.2 ×
F × λ (F = f / D: F is the brightness, f is the focal length, and D is the aperture diameter) (in the case of radio waves, the half power width).

For example, if D = 25 cm and f = 25 cm, d = 1.2 × 1 × 3.16 [mm]. Assuming that about 3.8 mm square of the millimeter wave receiving array section 332 is equivalent to one pixel, the infrared receiving array section 331 has a central area of about 64 mm × 64 pixel array of about 2 mm × 2 mm and 3.8 mm × 3 including the peripheral circuit section. .8 mm, that is, one pixel equivalent of a millimeter wave. The millimeter wave receiving array unit 332 (1
5 × 15-1) pixels, so they occupy about 57 mm square. The number of millimeter-wave pixels occupying the focal plane is determined so as not to cause spillover in consideration of the diameter of the secondary reflecting mirror of the Cassegrain antenna.

Hereinafter, the infrared light receiving array unit 331 of 64 × 64 pixels is provided at the center, and the millimeter wave receiving array unit 332 of (15 × 15-1) pixels is provided at the periphery. In order to provide the infrared detecting element (photodiode) with a predetermined sensitivity, the millimeter-wave / infrared co-focal plane array is sealed in a vacuum dewar, and a structure near the center is cooled.

As one pixel of the millimeter wave, 3.8 mm ×
Although the antenna, LNA, and Schottky diode are accommodated in the MMIC circuit within 3.8 mm, the effective wavelength λg of a microstrip line having an effective permittivity εe is generally λg = λ / (εe) ^1/2 (λ: free space Wavelength)
Since εe of GaAs is about 10, the millimeter wave frequency is 9
In the case of 4.7 GHz, λg is approximately 1 mm. Therefore, it is possible to sufficiently form an antenna and a matching circuit for an LNA within a given area.

When the imaging apparatus using the millimeter-wave / infrared co-focal plane array according to the above embodiment is used as a full-wave millimeter-wave receiver for millimeter waves (passive reception of spontaneous radiation millimeter waves), 15 × 1 compared to the scanning type
5 = 225 pixels, that is, 1/2 for forming one screen
25 times, and a millimeter-wave image with a very high data rate can be obtained. As a result, millimeter wave and infrared images can be simultaneously output with one set without parallax, and can be sufficiently used as ASM and SSM (missile diameter 300 mm) seekers.

In addition to the missile seeker, if the diameter of Cassegrain is increased and the diameter of the secondary reflecting mirror is increased to increase the number of millimeter-wave elements so as not to cause spillover, the details of infrared and millimeter waves can be obtained. An image is obtained, which is very advantageous for identifying a target under a complicated background.

When the natural radiation power is insufficient, it can be transmitted from the outside into the field of view of the millimeter wave, and the reflected wave can be output as an image. It can also be used for so-called semi-active image radar. It should be noted that the present invention is not limited to the above-described embodiment, and can be similarly implemented by various modifications without departing from the spirit of the present invention.

[0027]

As described above, according to the present invention, there is provided a millimeter-wave / infrared imaging apparatus which can obtain a millimeter-wave / infrared image in a short time with a simple structure without causing parallax. Can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the structure of an embodiment of a millimeter wave / infrared imaging apparatus according to the present invention.

FIG. 2 is a cross-sectional view showing a specific structure of the antenna system of the embodiment.

FIG. 3 is a block diagram showing a structure of a signal processing system of the embodiment.

FIG. 4 is a diagram showing a specific structure of a millimeter wave / infrared co-focal plane array of the embodiment.

FIG. 5 is a diagram illustrating a structure of a millimeter wave receiving array unit according to the embodiment;

FIG. 6 is a block circuit diagram showing an equivalent circuit of a millimeter wave receiving structure per pixel of the millimeter wave receiving array unit of the embodiment.

FIG. 7 is a diagram illustrating a configuration example of a conventional millimeter wave imaging device.

FIG. 8 is a diagram showing a configuration of a conventional millimeter-wave / infrared imaging device.

[Explanation of symbols]

11: parabolic antenna, 12: electronic scanning antenna, 2
DESCRIPTION OF SYMBOLS 1 ... Millimeter-wave imaging device, 22 ... Infrared imaging device, 31 ... Primary reflecting mirror, 32 ... Secondary reflecting mirror, 321-323 ... Infrared lens, 33 ... Millimeter-wave / infrared co-focal plane array, 331 ...
Infrared light receiving array section, 332 ... Millimeter wave receiving array section, 33
21: GaAs substrate, 3322: patch antenna section,
3323 ... Low noise amplifier (HEMT / LNA), 332
4: Schottky diode part, 3325: through-hole electrode, 333: Si wafer substrate, 3331: electrode, 3
332: injection diode, 3333: charge storage MOS capacitor, 3334: MOS switch gate, 3335
... Transfer CCD electrode, 334 ... Infrared charge transfer CCD, 33
5: Millimeter wave detection current transfer CCD, 336: In metal pillar,
34: Array drive circuit, 35: A / D converter, 36: Scan converter, 37, 38: CRT display.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 5/30-5/335 H04N 7/18 G01S 7/03 G01S 13/86

Claims (3)

(57) [Claims] 1. Millimeter-wave and infrared images from the same direction
In Millimeter and infrared imaging device to obtain a first order reflection mirror that focuses and reflects the millimeter wave, disposed on the millimeter wave reflection path from the primary reflector, red
The primary reflecting mirror using a compound lens made of an external light transmitting material
Reflects the millimeter wave received from the primary mirror on the surface facing
To form an image on one point on the primary reflecting mirror
The infrared rays incident from the surface opposite to the primary reflecting mirror are transmitted.
Image on the same plane as the millimeter-wave image plane on the primary reflecting mirror
A secondary reflector having a shape to be formed, and a millimeter arranged on an image plane on the primary reflector and imaged.
A millimeter-wave / infrared confocal plane array in which a millimeter-wave two-dimensional receiving array element for current detection of waves and an infrared two-dimensional light-receiving array element for photoelectrically converting an imaged infrared ray are arranged in the same plane; The millimeter-wave detection signal and the infrared detection signal are simultaneously read out from the
A millimeter-wave / infrared imaging apparatus comprising: a signal processing unit that converts an infrared image into an image signal to be displayed. Wherein said primary reflector parabolic secondary reflectors millimeter and infrared imaging apparatus according to claim 1, characterized in that it constitutes a mosquito cell Glen antenna has a hyperboloid . Wherein the millimeter-wave and infrared same focal plane array, before
A millimeter wave two-dimensional receiving array element and the infrared two-dimensional receiving element;
Charge transfer device facing each lower part of optical array element
Arrangement, and the millimeter wave-infrared imaging apparatus according to claim 1, wherein the each element to the charge transfer devices respectively arranged opposite are constituted by bumps bonded.