WO2011074614A1 - Millimeter wave image pickup device, millimeter wave image pickup system and program - Google Patents

Abstract

A millimeter wave image pickup device is provided with a lens antenna which captures a millimeter wave radiated from a viewing region to focus a subject image, a millimeter wave sensor group which outputs a detection value corresponding to the signal level of the millimeter wave captured by the lens antenna, an image generation means which generates the subject image on the basis of detected values outputted from respective millimeter wave sensors, a correction value setting means which sets the error between the detection value of a reference millimeter wave sensor designated as a millimeter wave sensor for receiving a millimeter wave radiated from a radiator and a predetermined reference detection value as a correction value for each of the millimeter wave sensors, and a detection value correction means which corrects the detection value of each of the millimeter wave sensors by the correction value set by the correction value setting means before the generation of the subject image by the image generation means.

Description

Millimeter-wave imaging device, millimeter-wave imaging system, and program Cross-reference of related applications

This international application claims priority based on Japanese Patent Application No. 2009-284080 filed with the Japan Patent Office on December 15, 2009, and is based on Japanese Patent Application No. 2009-284080. The entire contents are incorporated into this international application.

The present invention relates to a millimeter wave imaging apparatus that receives a millimeter wave emitted from a subject and images the subject.

In recent years, it has been proposed to capture a subject by receiving millimeter waves radiated from a subject such as a person, and detect metal or non-metallic weapons or smuggled goods hidden in the subject from the captured image. (See Patent Documents 1 and 2).

This type of technology uses the fact that the signal level of the millimeter wave radiated between the person who is the subject and the other area is different, and the component (for example, hue, brightness, saturation, etc.) corresponding to the signal level is used. A captured image of a subject is generated by arranging pixels by value.

JP 2006-25896A Japanese Patent No. 2788519

As described above, in a millimeter-wave imaging device that generates a captured image of a subject using a plurality of millimeter-wave sensors, the contrast between pixels in the image cannot be properly maintained when the temperature of the observation region to be observed changes. , A clear image may not be obtained.

For example, when the temperature of the observation region rises, the signal level of the millimeter wave radiated as thermal noise increases, so the detection value from each millimeter wave sensor also increases. At this time, if the temperature rises to some extent, the detection value from each millimeter wave sensor also increases, and all the components of each pixel to be determined according to this detection value all become the maximum value (or minimum value), and the pixels in the image The contrast between them cannot be maintained.

The present invention has been made in view of these problems, and an object of the present invention is to provide a technique for generating a subject image in which contrast between pixels is appropriately maintained regardless of a temperature change in an observation region. It is.

In order to solve the above problems, a first aspect of the present invention is a millimeter-wave imaging apparatus device, which is a region to be observed, and a radiator that emits a reference millimeter-wave is disposed in a part of the region. A lens antenna that captures a millimeter wave radiated from the observation region and forms a subject image, and a millimeter wave captured by the lens antenna is disposed in the imaging region that forms the subject image A millimeter wave sensor group that includes one or more millimeter wave sensors, each of which outputs a detection value corresponding to the received millimeter wave signal level, and a detection value output from the one or more millimeter wave sensors. Based on each, image generation means for generating a subject image formed by arranging pixels of components corresponding to the detected value, and one of the one or more millimeter wave sensors that receives the millimeter wave emitted from the radiator. Correction value setting means for setting an error from a predetermined reference detection value as a correction value for each of the millimeter wave sensors, with respect to the detection value of the reference millimeter wave sensor determined as the millimeter wave sensor to perform, Detection value correction means for correcting the detection value of each millimeter wave sensor by the correction value set by the correction value setting means prior to the generation of the subject image by the image generation means.

In this configuration, when correcting the detection value of each of the one or more millimeter wave sensors, the correction value is an error between the detection value of the reference millimeter wave sensor and the reference detection value. The correction value may be added to or subtracted from the detected value.

The “reference detection value” in this configuration is preferably set to a detection value from a reference millimeter wave sensor in a state where thermal noise is sufficiently small. In this case, the contrast between pixels can be appropriately maintained. The detected value in the state of being can be set as the “reference detected value”.

The “reference detection value” may be a preset value or a value that can be arbitrarily set. For the latter, for example, it can be considered as in the second aspect.

The millimeter wave imaging apparatus according to the second aspect of the present invention includes reference setting means for setting a detection value detected by the reference millimeter wave sensor at a predetermined timing as a reference detection value. The correction value setting means sets an error between the detection value of the reference millimeter wave sensor and the reference detection value set by the reference setting means as a correction value for each of the millimeter wave sensors.

The “predetermined timing” in this configuration may be any timing, for example, a timing at which a user performs a specific operation, a timing at which imaging is started by starting a millimeter wave imaging device, or the like. Can be considered.

In each of the above configurations, the millimeter wave sensor group may employ a millimeter wave sensor array in which a plurality of millimeter wave sensors are arranged in a matrix. A millimeter wave line sensor in which a plurality of millimeter wave sensors are arranged in a line may be employed.

In order to employ a line sensor as the millimeter wave sensor group, each of the above-described configurations may be configured as a third configuration (claim 3).
The millimeter-wave sensor group of the millimeter-wave imaging device according to the third aspect of the present invention includes a plurality of millimeter-wave sensors arranged in a row in the imaging region, and a row of millimeter waves received by the millimeter-wave sensor. The line sensor outputs a detection value corresponding to the subject image.

Furthermore, the millimeter-wave imaging device according to the third aspect of the present invention includes a reflector having a reflecting surface that reflects the millimeter wave captured by the lens antenna and guides it to the millimeter-wave sensor group, and is reflected by the reflecting surface of the reflector. The millimeter wave sensor group is formed by sequentially changing the reflection angle by the reflecting surface in order to displace the imaging region of the subject image by the millimeter wave along the direction intersecting the direction in which the millimeter wave sensor is arranged. And a reflection angle changing means for sequentially outputting a detection value group corresponding to the subject image in the row corresponding to the reflection angle of the reflecting surface as the detection value corresponding to the subject image for one row.

Then, each time a detection value group is output from the millimeter wave sensor group, the image generation unit generates a subject image for one row in which pixels of a parameter corresponding to each detection value in the detection value group are arranged in one row. To do.

In order to solve the above-mentioned problem, the fourth aspect of the present invention is a radiator that is arranged in a region (observation region) to be observed and emits a millimeter wave as a reference in a part of the observation region. A millimeter-wave imaging system comprising the millimeter-wave imaging device according to any one of the above.

In addition, the radiator in this configuration may be constituted by a thermal noise source that generates a reference thermal noise or a radio wave absorber, as in the fifth aspect of the present invention.
Moreover, in order to solve the said subject, it is good also as a program (6th aspect of this invention) for functioning as all the means in each structure mentioned above.

Note that the above-described program is composed of an ordered sequence of instructions suitable for processing by a computer system, and can be used for millimeter-wave imaging devices or users who use the same via various recording media and communication lines. It is provided.

In the millimeter wave imaging device according to each of the above configurations, the millimeter wave radiated from the radiator is received by the reference millimeter wave sensor, and an error between the detection value of the reference millimeter wave sensor and the reference detection value is used as a correction value. The detection value of the wave sensor is corrected. Since the radiator is arranged in the observation region to emit the reference millimeter wave, for example, if the temperature of the observation region rises, thermal noise as a millimeter wave also increases. The detection value also increases.

In other words, the error between the detection value of the reference millimeter wave sensor and the reference detection value fluctuates according to the temperature change of the observation region. Therefore, if the detection value of each millimeter wave sensor is corrected using this error as a correction value. The influence of the temperature change in the observation area can be removed from each detection value.

For example, even when the temperature of the observation region rises and all the pixel components that should be determined according to the detection values of each millimeter wave sensor become maximum values (or minimum values), the temperature changes from here As a result of the subtraction (or addition) of the error, the original detection value is restored.

Thus, by generating a subject image based on the corrected detection value, it is possible to obtain a clear subject image in which the contrast between pixels is appropriately maintained regardless of the temperature change in the observation region.

In the second aspect, a reference detection value that is a reference for setting a correction value can be set each time at a predetermined timing. Therefore, if the detection value of the reference millimeter wave sensor is set as the reference detection value when the temperature of the observation region is sufficiently low, the detection value when the thermal noise as millimeter waves is small is used as the reference detection value. be able to.

It is a block diagram which shows the whole structure of a millimeter wave imaging device. It is a block diagram which shows the structure of the millimeter wave sensor which comprises a line sensor. It is a flowchart which shows the imaging process in 1st Embodiment. In 1st Embodiment, it is a figure which shows a mode that the millimeter wave radiated | emitted from a millimeter wave radiation | emission part is reflected by a reflector. It is a flowchart which shows the imaging process in 2nd Embodiment. In 2nd Embodiment, it is a figure which shows a mode that the millimeter wave radiated | emitted from a millimeter wave radiation | emission part is reflected by a reflector.

DESCRIPTION OF SYMBOLS 1 ... Millimeter wave imaging system, 2 ... Millimeter wave imaging device, 3 ... Radiator, 4 ... Millimeter wave imaging system, 5 ... Millimeter wave imaging device, 10 ... Lens antenna, 20 ... Millimeter wave sensor array, 22 ... Millimeter wave sensor , 22 ... reference millimeter wave sensor, 30 ... reflector, 32 ... reflecting surface, 34 ... displacement mechanism, 50 ... control unit, 60 ... millimeter wave line sensor, 100 ... observation region, 102 ... receiving antenna, 104 ... low noise amplifier, 108 ... detector.

Embodiments of the present invention will be described below with reference to the drawings.
(1) First Embodiment (1-1) Overall Configuration As shown in FIG. 1, the millimeter wave imaging system 1 includes a millimeter wave imaging device 2 and a radiator that emits millimeter waves in an imaging region 100 to be imaged. 3.

The millimeter wave imaging device 2 includes a lens antenna 10 that captures a millimeter wave radiated from the observation region 100 and forms a subject image, and an imaging region in which the millimeter wave captured by the lens antenna 10 forms a subject image. The arranged millimeter wave sensor array 20 and a control unit 50 that controls the operation of the entire millimeter wave imaging device 2 are provided. The millimeter wave sensor array 20 is an example of a millimeter wave sensor group.

Among these, the millimeter wave sensor array 20 has a plurality of millimeter wave sensors 22 directed in the direction of arrival of millimeter waves in a matrix along a plane intersecting with the direction of arrival of millimeter waves in the imaging region. Each of the millimeter wave sensors 22 outputs a detection value corresponding to the received millimeter wave signal level. The detection value of each millimeter wave sensor 22 is the pixel information of the subject image corresponding to the position where the millimeter wave sensor 22 is arranged in the subject image formed in the imaging region (in this embodiment, the pixel value of the corresponding pixel). Information indicating light and shade).

As shown in FIG. 2, the millimeter wave sensor 22 is amplified by a reception antenna 102 for receiving millimeter waves, a low noise amplifier (LNA) 104 for amplifying a reception signal from the reception antenna 102, and an LNA 104. And a detector 108 for detecting the received signal and detecting the signal level.

The radiator 3 is disposed in a partial region of the observation region 100 and radiates a millimeter wave serving as a reference toward the lens antenna 10 from the position thus disposed. Thus, the millimeter wave radiated from the radiator 3 is received by one of the predetermined millimeter wave sensors (hereinafter referred to as “reference millimeter wave sensor”) 22 among the millimeter wave sensors 22 in the millimeter wave sensor array 20. .

In the present embodiment, the radiator 3 is configured by a thermal noise source that generates thermal noise as a reference or a radio wave absorber.
(1-2) Imaging Process by Control Unit 50 Hereinafter, a processing procedure of an imaging process executed by the control unit 50 according to a program stored in a built-in memory will be described with reference to FIG.

In this imaging process, first, among the millimeter wave sensors 22 in the millimeter wave sensor array 20, a detection value of the reference millimeter wave sensor 22, that is, a detection value indicating a millimeter wave signal level emitted from the radiator 3 is acquired. (S120). Here, when the radiator 3 is composed of a radio wave absorber, the amount of millimeter wave radiation from here is remarkably small, and thus a detection value close to “0” is acquired as a detection value.

Next, based on the detection value acquired in s120, a reference detection value serving as a reference for calculating a correction value in the subsequent processing is determined (s130). Here, the detection value acquired in s120 is determined as the reference detection value.

Next, a correction value for correcting the detection value is determined based on the reference detection value determined in s130 (s140). Here, an error (rd) between the reference detection value r determined in s130 and the detection value d detected by the reference millimeter-wave sensor at this time is calculated, and this is calculated for each millimeter-wave sensor 22. It is determined as a correction value.

When this s140 is performed for the first time after the imaging process is started, an error between the reference detection value determined in s130 and the detection value acquired in s120 is determined as a correction value. However, since these detection values match, “0” is determined as the correction value.

Next, the correction value determined in s140 is set as a correction value for each detection value of the millimeter wave sensor 22 (s150).
Next, it is checked whether or not imaging of the subject image should be continued (s170). Here, when receiving a command (including an operation by the user) for ending imaging from the outside to the millimeter-wave imaging device 2, it is determined that imaging should be terminated, that is, imaging should not be continued.

When it is determined in s170 that the imaging should be continued (s170: YES), each detection value by the millimeter wave sensor 22 of the millimeter wave sensor array 20 is acquired (s180).
Next, each of the detection values acquired in s180 is corrected based on the correction value set at this time (s190). Here, if the set correction value is a positive value, the absolute value of the correction value is subtracted from each of the detection values acquired in s180, and if the correction value is a negative value, in s180. The absolute value of the correction value is added to each acquired detection value.

Next, each piece of pixel information indicated by the detection value corrected in s190 is set as pixel information of a pixel corresponding to the position of the millimeter wave sensor 22 that detected the detection value, and the pixel (pixel) indicated by each piece of pixel information is indicated. A subject image formed by arranging (pixels of components indicated by information) is generated (s200). The subject image generated in this way is stored in an image memory for display on a display device.

When this s200 is performed, the process returns to s140 after the detection value is acquired from the reference millimeter wave sensor 22 (s210), as in s120. In s140 in this case, an error between the detection value acquired in s210 and the reference detection value determined in s130 is determined as a correction value.

Thereafter, while it is determined that imaging should be continued (s170 “YES”), s140 to s210 are repeated, and when it is determined that imaging should be terminated in s170 (s170: NO), the main imaging process is performed. finish.

As described above, in the imaging process, the detection value of each millimeter wave sensor 22 is corrected using the detection value (reference detection value) that is initially set as a reference (s130) and the variation of the detection value in the reference millimeter wave sensor as a correction value. After that (s190), a subject image is generated (s200).
(2) Second Embodiment (2-1) Overall Configuration As shown in FIG. 4, the millimeter wave imaging system 4 in this embodiment radiates millimeter waves in the millimeter wave imaging device 5 and the imaging region to be imaged. And the radiator 3 to be configured. In the present embodiment, the same configurations as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted.

The millimeter wave imaging device 5 includes a lens antenna 10, a millimeter wave line sensor 60 in which a plurality of millimeter wave sensors 22 are arranged in a row, and a millimeter wave line sensor 60 that reflects the millimeter wave captured by the lens antenna 10. And a control unit 50 that controls the operation of the entire millimeter-wave imaging device 5. The millimeter wave line sensor 60 is a millimeter wave sensor group in the present invention.

Among these, the millimeter wave line sensor 60 causes each of the plurality of millimeter wave sensors 22 oriented in the arrival direction of the millimeter wave in one direction along a plane intersecting with the arrival direction of the millimeter wave in the imaging region. Each of the millimeter wave sensors 22 outputs a detection value corresponding to the received millimeter wave signal level.

The reflector 30 is provided with a displacement mechanism 34 for displacing the reflection angle of the millimeter wave by the reflection surface 32 along the direction intersecting the direction in which the millimeter wave sensor 22 is arranged.
(2-2) Imaging Processing by Control Unit 50 Hereinafter, a processing procedure of imaging processing executed by the control unit 50 in accordance with a program stored in a built-in memory will be described with reference to FIG.

In this imaging process, first, the reflection angle by the reflecting surface 32 of the reflector 30 is changed until the region of the image formed by the millimeter wave emitted from the radiator 3 overlaps the region where the millimeter wave sensor 22 is disposed. (S110). Here, a command is given to the displacement mechanism 34 of the reflector 30 to displace the reflection angle of the millimeter wave by the reflecting surface 32 to a predetermined initial angle θ ′. The reflection angle of the millimeter wave by the reflecting surface 32 is changed to the initial angle θ ′ until the region of the image formed by the emitted millimeter wave overlaps the region where the millimeter wave sensor 22 is arranged (see FIG. 6). .

Next, at the time when the reflection angle is changed to the initial angle in s110, the detection value of the reference millimeter wave sensor among the millimeter wave sensors 22 in the millimeter wave line sensor 60, that is, the millimeter wave emitted from the radiator 3. A detection value indicating the signal level of is acquired (s120).

Next, based on the detection value acquired in s120, a reference detection value serving as a reference for calculating a correction value in the subsequent processing is determined (s130).
Next, based on the reference detection value determined in s130, a correction value for correcting the detection value is determined (s140), and this correction value is set as a correction value (s150).

Next, scanning control is started to repeatedly and continuously change the reflection angle of the reflecting surface 32 of the reflector 30 within a certain angle range θ ″ (s160). Here, the reflection mechanism 30 reflects the displacement mechanism 34 of the reflector 30. A command to continuously change the reflection angle of the millimeter wave by the surface 32 is issued, and the displacement mechanism 34 that has received this command continuously changes the reflection angle of the millimeter wave by the reflection surface 32 within a certain angle range θ ″. It will be changed repeatedly. Thereby, the observation area 100 is scanned by the millimeter wave line sensor 60.

Here, the angle range θ ″ in which the reflection angle is changed is set in advance so that the imaging area of the subject image by the millimeter wave captured by the lens antenna 10 overlaps the area where the millimeter wave sensor 22 is disposed. It has been done.

Next, it is checked whether or not imaging of the subject image should be continued (s170), and when it is determined that imaging should be continued (s170: YES), each of the detection values by the millimeter wave sensor 22 of the millimeter wave line sensor 60 is detected. Is acquired (s180).

Next, each of the detection values acquired in s180 is corrected based on the correction value set at this time (s190), and each piece of pixel information indicated by the corrected detection value is converted into the detection value. As a pixel information of the pixel corresponding to the detected position of the millimeter wave sensor 22, a subject image for one column formed by arranging pixels (pixels having a density indicated by the pixel information) indicated by each pixel information is generated (s200). ). The subject image generated in this way is stored in a storage area corresponding to the corresponding column in the image memory.

When this s200 is performed, the detection value is acquired from the reference millimeter wave sensor 22 (s210), and the process returns to s140, as in the above s120.
If it is determined in s170 that the imaging should be terminated (s170: NO), the imaging process is terminated.
(3) Action and Effect In the millimeter wave imaging devices 2 and 5 described above, the millimeter wave emitted from the radiator 3 is received by the reference millimeter wave sensor 22, and the detection value and the reference detection from the reference millimeter wave sensor 22 are received. The detection value of each millimeter wave sensor is corrected using an error from the value as a correction value (s120 to s210 in FIGS. 3 and 5).

Since the radiator 3 is arranged in the observation region 100 so as to emit the reference millimeter wave, for example, if the temperature of the observation region 100 rises, thermal noise as a millimeter wave also increases. The detection value of the wave sensor 22 also increases.

That is, the error between the detection value of the reference millimeter wave sensor 22 and the reference detection value varies according to the temperature change of the observation region 100. Therefore, the detection value of each millimeter wave sensor 22 is determined using this error as a correction value. If corrected, the influence of the temperature change of the observation region 100 can be removed from each detection value.

For example, even when the temperature of the observation region 100 rises and all the pixel components to be determined according to the detection values of the millimeter wave sensors 22 become maximum values (or minimum values), the temperature changes from here. As a result of subtracting (or adding) the corresponding error, the original detection value is restored.

Thus, by generating a subject image based on the corrected detection value, it is possible to obtain a clear subject image in which the contrast between the pixels is appropriately maintained regardless of the temperature change of the observation region 100.

In the above embodiment, the reference detection value that serves as a reference for setting the correction value can be set every time the imaging process is started (s120 in FIGS. 3 and 5). Therefore, if the imaging process is started when the temperature of the observation region 100 is sufficiently low, the detection value when the thermal noise as a millimeter wave is small can be set as the reference detection value.
(4) Modifications The embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment, and can take various forms as long as they belong to the technical scope of the present invention. Needless to say.

For example, in the above embodiment, the “reference detection value” is set in the imaging process. However, the detection value in a state where the contrast between the pixels can be appropriately maintained may be fixedly set as a “reference detection value” in advance.

In the above embodiment, the “reference detection value” is set at the timing immediately after the imaging process is activated (s120 in FIGS. 3 and 5). However, the timing for setting the “reference detection value” is not limited to this, and may be a timing at which the user performs a specific operation, for example.
(5) Correspondence with the Present Invention In the embodiment described above, s200 in FIGS. 3 and 5 is an example of an image forming step by the image generation unit, and s140 and s150 in the figure are an example of correction by the correction value setting unit. S190 is an example of a correction step by the detection value correction unit, and s120 and s130 are examples of acquisition of the detection value and determination of the reference detection value by the reference setting unit. In each step, s110 and s160 in FIG. 5 are examples of the reflection angle changing step by the reflection angle changing means.

Claims (6)

1. A millimeter wave imaging device,
   For an observation region that is a region to be observed and in which a radiator that emits a reference millimeter wave is arranged in a part of the region, a millimeter wave emitted from the observation region is captured to form a subject image A lens antenna,
   The millimeter wave captured by the lens antenna is composed of one or more millimeter wave sensors arranged in an imaging region where an object image is formed, and each of the millimeter wave sensors detects in accordance with the received millimeter wave signal level. A group of millimeter wave sensors that output values;
   Image generation means for generating a subject image formed by arranging pixels of components corresponding to the detection values based on the detection values output from the one or more millimeter-wave sensors;
   Among the one or more millimeter wave sensors, for a detection value of a reference millimeter wave sensor defined as a millimeter wave sensor that receives a millimeter wave emitted from the radiator, an error from a predetermined reference detection value is determined. Correction value setting means for setting as a correction value for each of the millimeter wave sensors;
   Detection value correction means for correcting the detection value of each of the one or more millimeter wave sensors with the correction value set by the correction value setting means prior to the generation of the subject image by the image generation means. The millimeter wave imaging device characterized by the above-mentioned.
2. A reference setting means for setting a detection value detected by the reference millimeter wave sensor at a predetermined timing as a reference detection value;
   The correction value setting means sets an error between a detection value of the reference millimeter wave sensor and a reference detection value set by the reference setting means as a correction value for each of the millimeter wave sensors. The millimeter-wave imaging device according to 1.
3. The millimeter wave sensor group is a line in which a plurality of millimeter wave sensors are arranged in a row in the imaging region, and a detection value corresponding to the subject image for one row is output by the millimeter wave received by the millimeter wave sensor. Configured as a sensor,
   further,
   A reflector having a reflecting surface that reflects the millimeter wave captured by the lens antenna and guides it to the millimeter wave sensor group;
   In order to displace the imaging area of the subject image by the millimeter wave reflected by the reflection surface of the reflector along the direction intersecting the direction in which the millimeter wave sensor is arranged, the reflection angle by the reflection surface is sequentially changed. Thus, the reflection angle changing means for sequentially outputting the detection value group corresponding to the subject image in the row corresponding to the reflection angle of the reflection surface as the detection value corresponding to the subject image for one row to the millimeter wave sensor group, With
   The image generation means generates a subject image for one row in which pixels of a parameter corresponding to each detection value in the detection value group are arranged in a row each time a detection value group is output from the millimeter wave sensor group. The millimeter-wave imaging device according to claim 1 or 2, wherein
4. A radiator that is arranged in an observation target region (observation region) and emits a millimeter wave as a reference in a part of the observation region;
   A millimeter-wave imaging system comprising: the millimeter-wave imaging device according to claim 1.
5. The millimeter wave imaging system according to claim 4, wherein the radiator is configured by a thermal noise source that generates thermal noise as a reference or a radio wave absorber.
6. A program for causing a computer to function as all the means according to any one of claims 1 to 3.

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