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EP-3822665-B1 - RADIATION DETECTOR, RADIATION INSPECTING DEVICE, AND METHOD FOR PROCESSING RADIATION DETECTION SIGNAL

EP3822665B1EP 3822665 B1EP3822665 B1EP 3822665B1EP-3822665-B1

Inventors

  • OTAKE, MAKOTO

Dates

Publication Date
20260506
Application Date
20190704

Claims (6)

  1. A radiation detector (2), comprising: a signal detecting section (21) including a scintillator constituted of a plurality of cells (211), the cells (211) adjacent each other are partitioned by optically separating separators in said scintillator (210); and a photoelectric conversion unit (212) constituted of a plurality of light receiving devices (212a-212c) that receive scintillation light, convert it into analog signals, and output the analog signals; a signal converting section (22) including signal amplification devices (221) that amplify the analog signals output from the respective light receiving devices of the photoelectric conversion unit (212), and A/D conversion devices (222) that convert the analog signals output from the signal amplification devices into digital signals and output the digital signals; and an image data generating section (23) that generates a radiation detection signal received by the light receiving devices (212a-212c) from the digital signals output by the A/D conversion devices (222) and generates radiation image data from the radiation detection signal, wherein the photoelectric conversion unit (212) is constituted of a plurality of light receiving devices (212a-212c) having different light receiving sizes that are arranged along each of the cells (211) of the scintillator (210), and the image data generating section (23) includes a signal selecting section (21) that selects a signal having a predetermined level from the output signals of the plurality of light receiving devices (212a-212c) converted into the digital signals as a radiation detection signal, and a signal generating section that generates one radiation detection signal from one signal selected by the signal selecting section or by combining a plurality of selected signals.
  2. The radiation detector according to claim 1, wherein the signal generating section has a function of averaging a plurality of signals selected by the signal selecting section and combining them into one radiation detection signal.
  3. The radiation detector according to claim 1 or 2, wherein the signal generating section of the image data generating section weights detection signals according to arrangement positions of the light receiving devices (212a-212c).
  4. The radiation detector (2) according to any one of claims 1 to 3, comprising a signal sorting section that sorts arbitrary light receiving devices (212a-212c) from the plurality of light receiving devices (212a-212c) and inputs signals output from the sorted light receiving devices to the signal amplification devices (221) of the signal converting section (22) as radiation detection signals.
  5. A radiation inspecting device (1), comprising the radiation detector (2) according to any one of claims 1 to 4, a radiation source (3) that irradiates an inspection object with radiation, and a terminal device including a display device that outputs and displays radiation image data output from the radiation detector.
  6. A method for processing a radiation detection signal, wherein in the method for processing a radiation detection signal using a radiation detector (2), the radiation detector (2) is according to any of claim 1 to 4 ; and wherein the method includes: a process in which the plurality of light receiving devices (212a-212c) arranged along each cell photoelectrically convert scintillation light emitted by each cell of the scintillator when the scintillator (211) of the signal detecting section is irradiated with radiation to output analog signals; a process of amplifying the analog signals output from the plurality of light receiving devices (212a-212c) in each cell by the signal amplification devices of the signal converting section (22), converting them into digital signals by the A/D conversion devices, and inputting them to the image data generating section; a process of selecting a signal having a predetermined level from the output signals of the plurality of light receiving devices (212a-212c) converted into the digital signals in the image data generating section; and a process of generating one radiation detection signal from the selected signal when the signal is one, or by combining the plurality of selected signals when there are multiple signals.

Description

Technical field The present invention relates to a radiation detector according to claim 1 and a radiation inspecting device for non-destructively inspecting the inside of a container, luggage, or the like which cannot be seen from the outside. Background art Many detectors using radiation such as X-rays and gamma rays use a scintillator that converts radiation into visible light or ultraviolet-infrared light having longer wavelengths in the signal detecting section. This is a method of indirectly measuring the intensity of radiation incident on a scintillator by converting the intensity of light converted by the scintillator into an electrical signal with a light receiving element such as a photodiode, which is still one of the best methods for measuring the intensity of radiation. Radiation inspecting devices are widely used in devices that handle low-energy radiation for foreign matter contamination inspection of food, small-size baggage inspection, and medical use for inspecting the human body, as well as high-energy radiation for inspecting large-size objects such as containers and the inside of housings. The design and types of members used for these devices vary depending on the application and the amount of energy. For example, a low-energy radiation inspecting device used in the medical field is described in the following patent document (see Patent Document 1). This device outputs X-ray projection data in a two-dimensional form and generates a pixel signal with high accuracy for improving a sampling rate and spatial resolution without increasing an exposure dose to a subject. EP2495585 A2, US 2017/212250 A1, US 5 144 141 A, WO 2017/086181 A1 all disclose similar radiation detectors as the invention except that none of these documents disclose that the photoelectric conversion unit is constituted of a plurality of light receiving devices having different light receiving sizes. JP 018154 A discloses a scintillator plus photodiode radiation detector for a CT image reconstruction device, wherein the photoelectric conversion unit is constituted of a plurality of light receiving devices. Citation list Patent document Patent Document 1: International Publication No. WO 2017/183481 Disclosure of the invention Problem to be solved by the invention Meanwhile, in applications for handling high-energy radiation for inspecting large-size objects such as containers, the following problems are faced. That is, when signals output from the signal detecting section are processed by an integrated circuit, the integrated circuit has a limited capacity of signals that can be input, so that when a high-energy signal exceeding the allowable input charge amount is input to the integrated circuit, the input signal is clipped due to range over, and accurate detection of the radiation cannot be performed. In the case of internally observing large-size objects such as containers using high-energy radiation, it is necessary to newly develop a dedicated integrated circuit for processing high-energy signals or to configure a complicated circuit by combining a plurality of general-purpose components in order to increase the allowable input charge amount, and thus there is a problem that the manufacturing cost of the inspecting device is inevitably high in any case. Further, in the inspecting device for containers, the case where the radiation irradiated toward the containers is incident on the detector with high energy, and the case where the radiation passes through an iron plate or the like having a thickness of about several hundred millimeters and is incident on the detector with weak energy intensity, may occur at the same time. In order to accurately detect the contents of containers, it is necessary to provide a detecting function corresponding to a wide range that can detect both high-energy radiation and low-energy radiation by minimizing the influence of noise as much as possible in accordance with the energy intensity of the radiation. In view of such problems of the prior art, the present invention has an object to configure a radiation detector suitable for applications handling high-energy radiation, and a detector capable of appropriately and highly accurately detecting radiation even under an environment where radiation of various energy intensities is irradiated. Means for solving problem The present invention employs a configuration in which a scintillator and a light receiving device such as a photodiode are used in a signal detecting section of a radiation detector as in the conventional case, and a plurality of light receiving devices are arranged in each cell of the scintillator that is divided into a plurality of cells and output signals output from the respective light receiving devices are combined to generate a radiation detection signal of each cell. That is, the present invention employs a configuration in which photoelectric conversion of scintillation light emitted by one cell is dividedly performed