JP2008203054A - Far-infrared image acquisition apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable target biological information to be acquired easily and efficiently, without having to perform shutter driving control, by synchronizing a complex and high-precision synchronization between a camera and a shutter. <P>SOLUTION: The method comprises putting an object to be photographed on the shutter (S1); adjusting the distance between a biological portion and a proximal lens 2, by using a height fine adjusting mechanism 8 (S2); acquiring a biological temperature distribution as image information, after the adjusting step, by using a far-infrared camera 1 disposed at the lower section of the shutter 3 (S3); keeping the surface of the shutter 3 at a fixed temperature that is higher than that of a core component as well as not higher than 42°C, by controlling a heater 4 mounted on the surface of the shutter 3 on the far-infrared camera side (step S4); bringing the shutter temperature to reach a setting temperature (step S5); setting the closing period of the shutter 3 so that it is longer than the period for which the temperature-tracking characteristic of the far-infrared camera brings its temperature, to reach the temperature of the object to be photographed by using a shutter-camera synchronous controller 6, when step S5 is completed (step S6); and photographing the object to be photographed by using the far-infrared camera 1 (step S7). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a far-infrared image acquisition apparatus and method, and more particularly to a far-infrared image acquisition apparatus that acquires biological information such as fingerprints and sweat glands on the surface of a living body skin, dermal layers and veins inside the skin as far-infrared images. is there.

In recent years, far-infrared image acquisition devices that use the characteristics of far-infrared radiation (heated objects always radiate, and higher-temperature objects radiate more intensely) have been put into practical use. Widely used in the field and security field. With the latest thermography technology, in order to process a large number of images in a shorter period of time, the calculation of the far-infrared image and the data for each frame are continuously performed at a high frame rate exceeding 100 Hz, and the temperature changes every moment. A so-called “lock-in method” that improves temperature resolution by averaging changes is used.

  For example, FIG. 8 shows one configuration example of a conventional infrared image acquisition apparatus capable of acquiring biological information disclosed by “Yao plate: temperature difference image by infrared camera and lock-in, image lab, pp32-35, 2005.8”. 101 is an infrared camera, 102 is a chopping / lock-in amplifier, 103 is a rotating blade, 104 is a motor, and 105 is a frame rate synchronous controller. In this conventional infrared image acquisition device, by using the infrared camera 101 and the rotating blade 103 in combination, calculation for associating infrared image capturing and data for each frame is continuously performed based on an arbitrarily set frame rate. The lock-in method is realized by implementing the method, and the result is continuously created as an image.

  Further, in the technology disclosed by the re-published patent WO 00/42399 “Infrared image pickup device and vehicle equipped with the same, and infrared image adjustment device”, as a temperature calibration technology in an in-vehicle infrared image pickup device, an infrared image is more It describes the technology for easy-to-read display. Hereinafter, the main points will be briefly described.

  In FIG. 9, when the blocking means 40 is in the open state, infrared rays emitted from the subject 70 are imaged on the infrared detector 100 by the optical system 20 as an infrared image. The infrared detector 100 detects the amount of received infrared light at each pixel and outputs a signal corresponding to the detected amount. The correction means 30 collectively corrects variations in sensitivity between pixels, signal noise between pixels, so-called DC offset variations, lens shading, and the influence of infrared radiation of the optical system 20. In the correction, the temperature setting unit 51 is provided, the temperature Tc of the blocking unit 40 is set to a desired temperature, and the Tc is set in the vicinity of the temperature of a specific imaging object, so that a better result can be obtained. It states that it can be done.

Yao board: temperature difference image by infrared camera and lock-in, image lab, pp32-35, 2005.8 Republished Patent WO00 / 42399

In the infrared camera device as shown in FIG. 8, the infrared image capturing process while synchronizing with the frame rate commanded by the controller, the lock-in method arithmetic process, and the average process of the measured biological temperature change are performed at high speed. It is necessary to carry out with accuracy. That is, since the image detection accuracy is greatly influenced by the angular velocity control performance of the rotary blade, a high-performance lock-in amplifier is indispensable, and there is a problem that the overall configuration of the apparatus becomes complicated.

  In addition, the infrared imaging apparatus as shown in FIG. 9 only discloses matters for simplifying the determination of the correction coefficient even when the heat source such as a car or a person fluctuates by controlling the temperature of the blocking means. There is no description of a technique for acquiring a far-infrared image with improved temperature resolution by the lock-in method as well as the problem of the IN method.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a far-infrared image acquisition device capable of continuously acquiring infrared images synchronized with a frame rate with a simple device configuration.

  In view of the above-described problems, a far-infrared image acquisition device according to claim 1 of the present invention includes a far-infrared camera that acquires an infrared image, a shutter disposed between the far-infrared camera and the object to be imaged, and the shutter. A heater controller that controls the temperature of the heater so as to keep the temperature of the shutter constant at a temperature that is at least higher than the temperature of the object to be imaged, and the closing time of the shutter to follow the temperature of the far-infrared camera. It is characterized by comprising a shutter / camera synchronization controller whose characteristic is set longer than the time required to reach the temperature of the imaging object.

  In addition to the above-described configuration, the far-infrared image acquisition device according to claim 2 of the present invention is configured so that the shutter-camera synchronization controller indicates the closing time of the shutter, and the temperature tracking characteristic of the far-infrared camera indicates the shutter. The time is set to reach the set temperature.

  Furthermore, in the far-infrared image acquisition apparatus according to claim 3 of the present invention, the imaging object is a part or all of a human body, and the temperature of the heater is controlled so as to keep the temperature of the shutter at a constant temperature of 42 degrees or less. It is characterized by doing.

  Furthermore, the far-infrared image acquisition apparatus according to claim 4 of the present invention is characterized by comprising adjusting means for forming an image of the far-infrared ray emitted from the imaging object at a predetermined position of the far-infrared camera.

  Furthermore, the far-infrared image acquisition apparatus according to claim 5 of the present invention is characterized in that the adjusting means optically enlarges the imaging target.

  Furthermore, the far-infrared image acquisition apparatus according to claim 6 of the present invention is characterized by comprising installation means for installing the imaging object.

  Furthermore, a far-infrared image acquisition apparatus according to claim 7 of the present invention is characterized by comprising display means for displaying the imaging object thermographically.

  As described above, according to the present invention, the surface of the general-purpose shutter is set higher than the temperature of the object to be imaged by the heater, and the shutter closing time is set longer than the time for the temperature tracking characteristic of the far-infrared camera to reach the temperature of the imaged object. By shooting for a long time, a simple device configuration enables continuous far-infrared images synchronized with the frame rate without performing complicated and highly accurate synchronization between the camera and the shutter and shutter control. There is an effect of acquiring.

  FIG. 1 is a block diagram showing an example of a far-infrared image acquisition apparatus according to an embodiment of the present invention. This far-infrared image acquisition apparatus includes a far-infrared camera 1, a proximity lens 2, a shutter 3, a heater 4, a heater controller 5, a shutter / camera synchronization controller 6, a frame 7, a fine height adjustment mechanism 8, and a display monitor 9. Is done.

  The far-infrared camera 1 equipped with the proximity lens 2 is fixedly installed so that the proximity lens 2 faces upward. The imaging data of the far-infrared camera 1 is set to be continuously acquired at a predetermined time interval (frame rate). Frames 7 are erected on the left and right sides of the far-infrared camera 1 in the drawing, and height adjustment mechanisms 8 are attached to both frames 7 respectively. The height fine adjustment mechanism 8 is a mechanism that freely moves the shutter 3 spanned and supported by both frames in the vertical direction. In this embodiment, a sliding type that slides up and down using the fixed frame 7 as a slide rail is applied. However, as long as the adjustment accuracy is guaranteed, a telescopic type that locks the expanding and contracting frame at an arbitrary position. May be used.

  The shutter 3 is supported by a frame 7 directly above the proximity lens 2 attached to the far-infrared camera 1. Thereby, the distance between the living body part to be imaged and the proximity lens 2 can be adjusted to 0 to an arbitrary distance by the height fine adjustment mechanism 8. The shutter 3 is a slide shutter having an outer frame having a donut-shaped perforated disk structure, and is configured so that the shielding plate of the shutter 3 can be opened and closed in a spiral manner with the living body portion placed on the shutter 3. Yes. The shutter 3 can arbitrarily set and adjust the opening time / closing time.

  An annular heater 4 having an inner diameter larger than the outer diameter of the hole is attached to the rear surface side of the outer frame of the shutter 3 so as to surround the periphery of the hole portion formed. The heater 4 can be controlled to an arbitrary temperature by the heater controller 5. That is, the surface temperature of the shutter 3 can be adjusted to an arbitrary value by the heater controller 5.

  A shutter / camera synchronization controller 6 is connected to the shutter 3 and the far infrared camera 1. The shutter 3 is controlled by the shutter / camera synchronization controller 6 so that the shutter 3 is opened / closed in an optimum opening / closing time in synchronization with the photographing operation of the far-infrared camera 1. The infrared image data (thermography) of the living body image thus taken is displayed on the display monitor 9.

  FIG. 2 is an example of the far-infrared image acquisition apparatus according to the present embodiment, and is a diagram showing an overview of a state in which biological information of the finger tip is acquired. The subject himself took a stable posture, such as sitting on a chair, placed the upper arm to the abdomen of the hand on the desk, and placed the first part of the finger so that the living body part (fingertip) to be imaged was located directly above the shutter 3 opening / closing part. One joint is placed on the shutter 3 (the edge of the donut hole). At this time, in addition to the fine height adjustment mechanism 8, the shutter 3 is a mechanism that freely adjusts the movement in the horizontal plane (e.g., a far distance) so that the position of the shutter 3 can be adjusted according to the physique (forearm length) of the subject. An XY stage to which the infrared camera 1 is attached may be provided.

  FIG. 3 is a diagram schematically illustrating the far-infrared image acquisition principle of the present embodiment using a graph with time on the horizontal axis and temperature on the vertical axis. The imaging data of the far-infrared camera 1 is continuously acquired as video frames, and gradations are relatively allocated according to the temperature range for imaging. That is, it can be expressed on the graph as a rectangle with 256 gradations, with the highest temperature set to 256, the lowest temperature set to 0, as the vertical side, and the frame time as the horizontal side. In this graph, the temperature tracking characteristic of the far-infrared camera 1 is shown by a thick solid line. This temperature tracking characteristic is inherent to the camera mainly depending on the response characteristic of the sensor built in the far-infrared camera 1.

  In the state where the shutter 3 of the far-infrared camera 1 is opened first, the detection data of the far-infrared camera 1 continuously obtains video frames having the ambient environmental temperature as the gradation center (126 in gradation expression). The Although the environmental temperature varies depending on the season, etc., it is basically lower than the optimum temperature zone (core temperature of the living body) to be imaged.

  Subsequently, when the shutter 3 is closed in order to photograph the imaging target, the temperature tracking characteristic of the far-infrared camera 1 changes. In this case, since far-infrared rays emitted from the object to be imaged are blocked by the shutter 3, the temperature tracking characteristic changes exponentially according to a temperature difference in which the initial value is the environmental temperature and the ultimate temperature is the shutter setting temperature. The detection data of the far-infrared camera 1 during the closing time of the shutter 3 is kept constant with the shutter setting temperature set to white (256 in gradation expression).

  When the shutter 3 is closed and then opened again, the detection data is gradually reproduced as a video frame of 256 gradations from the white color state. The video frame descends according to the temperature tracking characteristics of the far-infrared camera, and thereafter, the video frame having the ambient environmental temperature as the center of the gradation is continuously acquired again.

  The far-infrared camera images 256 data by assigning 256 gradations to a predetermined temperature range. Therefore, for the establishment of the present invention, it is essential that the set temperature of the shutter 3 is first set to a value higher than the optimum temperature range. If the shutter is closed and then reopened at least until the temperature tracking characteristic curve exceeds the optimum temperature range, the optimum temperature range is accommodated within the gradation of the descending video frame. I can.

  However, in order to acquire a clearer far-infrared image, it is required to continuously acquire video frames corresponding to the temperature range where the gradation center is optimal. In order to realize this, the temperature of the shutter 3 needs to be set to be somewhat higher than the optimum temperature range. However, an unnecessary temperature difference between the shutter set temperature and the optimum temperature zone is not preferable for the gradation distribution of the infrared image. Therefore, the upper limit of the shutter set temperature is set to “42 ° C.” which is the maximum value of the body temperature that can exist as a living body. In addition, the shutter closing time is lower than the time until the moment when the optimum temperature range is reached. Appear and a clearer far-infrared image is acquired.

  FIG. 4 is a flowchart of an example of the imaging operation of the far-infrared image acquisition apparatus of this embodiment.

  According to FIG. 4, the living body part to be imaged is placed on the shutter (step S <b> 1), and in this state, the distance between the living body part and the proximity lens 2 is finely adjusted according to the focal length of the proximity lens 2. (Step S2). After adjusting the distance between the living body part and the proximity lens 2, the distribution state of the biological temperature information obtained through the proximity lens 2 is acquired as image information by the far-infrared camera 1 installed under the shutter 3 (step S <b> 3). . Here, the heater controller 5 controls the heater 4 attached to the surface of the shutter 3 on the far-infrared camera side so as to keep the surface of the shutter 3 constant at an arbitrary temperature higher than the core temperature of the human body and lower than 42 ° C. (Step S4). Thereby, the temperature difference between the shutter and the living body part is emphasized. When the shutter temperature reaches the set temperature (step S5), the shutter / camera synchronization controller 6 sets the closing time of the shutter 3 so that the temperature follow-up characteristic of the far-infrared camera becomes longer than the time to reach the imaging target temperature. In step S6, the far-infrared camera 1 captures an image of the imaging target (step S7). With these operations, the sensitivity (S / N ratio) of the far-infrared camera 1 is greatly improved.

  FIG. 5 shows an example of a screen photograph taken by adjusting the fine height adjustment mechanism 8 so that the far-infrared camera 1 is focused on the surface of the right hand finger tip and displayed as an infrared thermography.

  This time, feedback control was performed by the heater controller 5 so that the surface temperature of the shutter 3 was 42 ° C. As a result, it can be confirmed in FIG. 5 that fingerprints on the fingertip surface (a plurality of thin white lines seen in the lateral direction) and sweat glands (black spots) are acquired simultaneously.

  FIG. 6 is an example of a temperature distribution data screen photograph of the far-infrared camera 1 used in the present embodiment, where the shutter temperature is 40 ° C. and the surface of the right hand fingertip is photographed and displayed. It could be confirmed.

  The imaging range can be arbitrarily set by using the height fine adjustment mechanism 8, but the resolution of the acquired image is improved by narrowing the imaging range, and the fingertip is used in order to perform more precise observation. The biometric information was acquired after setting the focus of the skin surface of the skin and adjusting the imaging range to be narrow.

  As described above, according to this embodiment, the set temperature of the shutter is set to a temperature that is at least higher than the temperature of the imaging target, and the closing time of the shutter reaches the temperature of the imaging target when the temperature tracking characteristics of the far-infrared camera. By setting the time longer than the time required, it is possible to easily and efficiently obtain the desired biological information without performing complicated and highly accurate synchronization between the camera and the shutter and performing shutter drive control. It becomes.

  In the embodiment of the present invention, the imaging target is a fingertip and the acquired biological information is a sweat gland or a fingerprint. However, the present invention is not limited to this, and the imaging target is the palm or the back of the hand, and the biological information is Needless to say, the present invention can be applied to imaging objects and biological information that can be acquired by known far-infrared imaging, such as a vein or dermis layer. For example, FIG. 7 shows an example of a photograph taken using the other embodiment of the present invention as the imaging target from the back of the hand to the upper limb. In this embodiment, the proximity lens 2 is replaced with a standard zoom lens for photographing. In particular, it can be understood that the vein is recognized as a black line (low temperature part) from the back of the hand to the wrist.

It is a figure which shows the structure image of the simple biological information acquisition apparatus concerning one embodiment of this invention. It is the figure which looked down at a mode that living body information is acquired with a living body information acquisition device of the present invention from the upper part. It is a flowchart which shows the biometric information acquisition method of this invention. It is the figure which showed typically the biological information imaging principle of this invention using the time-dependent change graph of temperature. It is the (photograph skin surface) screen photograph of the imaging target image | photographed with the biometric information acquisition apparatus of this invention, and displayed as an infrared thermography. It is the living body part (finger skin surface) screen photograph which image | photographed without using the biometric information acquisition apparatus of this invention, and was displayed as infrared thermography. It is the screen photograph of the imaging target (back of hand-upper limb part) image | photographed with the biometric information acquisition apparatus of this invention, and displayed as infrared thermography. It is a figure which shows an example of a prior art. It is a figure which shows another example of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Far-infrared camera 2 Proximity lens 3 Shutter 4 Heater 5 Heater controller 6 Shutter camera synchronous controller 7 Frame 8 Height fine adjustment mechanism 9 Display monitor 11 Infrared camera 12 Chopping / lock-in amplifier 13 Rotating blade 14 Motor 15 Frame rate synchronous controller DESCRIPTION OF SYMBOLS 20 Optical system 30 Correction | amendment means 40 Blocking means 50 Temperature measurement means 60 Control means 70 Subject 100 Infrared detector 101 Infrared camera 102 Chopping / lock-in amplifier 103 Rotating blade 104 Motor 105 Frame rate synchronous controller

Claims (7)

  A far-infrared camera for acquiring an infrared image; a shutter disposed between the far-infrared camera and the object to be photographed; a heater attached to the shutter; and a temperature of the shutter at least higher than a temperature of the object to be imaged. A heater controller that controls the temperature of the heater so as to be kept constant, and a shutter / camera synchronization controller that sets the closing time of the shutter longer than the time that the temperature tracking characteristic of the far-infrared camera reaches the temperature of the imaging target A far-infrared image acquisition device comprising:   The far-infrared ray according to claim 1, wherein the shutter-camera synchronization controller sets the closing time of the shutter to a time when the temperature tracking characteristic of the far-infrared camera reaches the set temperature of the shutter. Image acquisition device.   The temperature of the heater is controlled so that the imaging target is a part or all of a human body, and the temperature of the shutter is maintained at a constant temperature of 42 degrees or less. The far-infrared image acquisition apparatus described in 1. The far-infrared image acquisition apparatus according to claim 1, further comprising an adjusting unit that forms an image of the far-infrared ray emitted from the imaging target at a predetermined position of the far-infrared camera.   The far-infrared image acquisition apparatus according to claim 4, wherein the adjustment unit optically enlarges the imaging target.   The far-infrared image acquisition apparatus according to any one of claims 1 to 5, further comprising installation means for installing the imaging target.   The far-infrared image acquisition apparatus according to any one of claims 1 to 6, further comprising display means for thermographically displaying the imaging target.

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