Radiation modulator
By configuring a radiation modulator on the X-ray detector array for energy-selective filtering, the trade-off between contrast and penetration and resolution of the detector array is resolved, thereby improving the resolution and contrast of the detector.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SMITHS DETECTION FRANCE SAS
- Filing Date
- 2024-11-15
- Publication Date
- 2026-07-14
AI Technical Summary
Existing X-ray detector arrays struggle to balance contrast and penetration with resolution. Smaller detector spacing improves resolution but reduces contrast, while larger detectors improve contrast but reduce resolution.
A radiation modulator is used to filter ionizing radiation of different energies. By configuring a radiation modulator on the detector, selective filtering of different energies can be achieved, thereby improving resolution while maintaining penetration.
This technology improves the detector's resolution without reducing its penetration, thereby enhancing its ability to distinguish the inspected object.
Smart Images
Figure CN122396938A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to, but is not limited to, arrays of multiple pulsed ionizing radiation detectors. It also relates to a matrix comprising at least two arrays. Background of the Invention The performance of X-ray cargo inspection systems, including detector arrays, is a trade-off between conflicting requirements and capabilities.
[0003] Both contrast and penetration require larger detectors to collect more X-ray signals, thus providing a better signal-to-noise ratio.
[0004] Conversely, resolution requires detectors to have a smaller pitch in order to separate objects that are close to each other.
[0005] In other words, detectors with smaller spacing produce lower contrast and lower penetration, while larger detectors have lower resolution. Summary of the Invention
[0006] Aspects and embodiments of the invention are set forth in the appended claims. These and other aspects, as well as aspects and embodiments useful for understanding the invention, are also described in this disclosure and set forth in the claims.
[0007] Any feature of one aspect of the invention may be applied to other aspects of the invention in any suitable combination. Attached Figure Description
[0008] Embodiments of this disclosure will now be described by way of example with reference to the accompanying drawings, in which: Figure 1A , 1B 1C schematically represents a first example array according to this disclosure; Figure 2 The energy spectrum of ionizing radiation is schematically shown. Figure 3A and 3B A second example array according to this disclosure is schematically shown; Figure 4A The illustration shows the different energies used as a basis for... Figure 3A and 3B The modulator results are various typical point spread functions, including the 6MeV X-ray accelerator spectral point spread function; Figure 4B The diagram schematically illustrates the modulation transfer function compared to the point spread function curve obtained without using a modulator placed on the detector. Figure 4AModulation transfer function of the spectral spread function curve of the 6MeV X-ray accelerator; Figure 5A and 5B A third example array according to this disclosure is schematically shown; Figure 6A and 6B A fourth example array according to this disclosure is schematically shown; Figure 7 The illustration shows the use of [the subject]. Figure 3A and 3B The point spread function of the modulator result is compared as used according to Figure 6A and 6B The point spread function of the modulator result; Figure 8 A fifth example array according to this disclosure is schematically shown; Figure 9 The diagram schematically illustrates the difference between the 2D modulation transfer function obtained using a point spread function and one obtained without using a modulator placed on the detector, and the modulation transfer function obtained using a modulator placed on the detector. Figure 8 The 2D modulation transfer function of the spectral spread function of the 6MeV X-ray accelerator obtained by the modulator; Figure 10A The matrix is schematically shown, in which multiple modulators are arranged in bands that are parallel to each other; Figure 10B The matrix is schematically shown, in which multiple modulators are arranged in segments configured in a zigzag pattern. Figure 10C A matrix comprising multiple arrays is schematically shown, in which the detectors are divided into four regions.
[0009] In the accompanying drawings, similar elements have the same reference numerals. Specific Implementation Overview This invention discloses a detector array that utilizes the polychromatism effect of ionizing radiation flux (such as X-ray radiation with a spectrum). The array includes radiation modulators on at least some detectors or close to some detectors relative to the ionizing radiation. The radiation modulators are configured to filter different energies associated with the polychromatism effect differently. The radiation modulators are configured to filter lower energies only in some spatial portions of the detectors and transmit the majority of higher energies.
[0011] The spectral energies that contribute to detector resolution are different from those that contribute to radiation penetration.
[0012] The detector's resolution depends on lower energy because small objects are typically thin: thin objects absorb only lower energy.
[0013] Conversely, penetration depends on higher energy because only higher energy can penetrate thick objects and thus be detected by the detector. Furthermore, penetration measurements are performed on large objects, which typically do not require high resolution for detection by the detector. Contrast measurements on large objects hidden behind a certain amount of material benefit from both lower and higher energy, but hidden large objects do not require high-resolution detection.
[0014] Because radiation modulators transmit high energy, radiation penetration is not reduced by the modulator. The modulator's filtering has energy-dependent resolution, with higher resolution for lower energies.
[0015] Detailed description of exemplary embodiments Figure 1A , 1B Figure 1C schematically illustrates an array 1 of multiple detectors 2. Figure 1A , 1B In 1C, multiple detectors 2 are arranged along the longitudinal direction (OZ).
[0016] Each detector 2 corresponds to a pixel in the cargo inspection image after the cargo has been scanned by array 1 in the scanning direction (OX).
[0017] exist Figure 1A In this case, the scanning direction (OX) is basically perpendicular to the longitudinal direction (OZ).
[0018] like Figure 1B and 1C As shown, multiple detectors 2 are configured to detect pulsed ionizing radiation 5 (such as X-ray radiation) with an energy spectrum. Figure 1B and 1C As shown, the pulsed ionizing radiation 5 has a main propagation direction (OY), which is perpendicular to the scanning direction (OX) and the longitudinal direction (OZ).
[0019] Figure 2 The energy spectrum of ionizing radiation is schematically shown 10.
[0020] exist Figure 2 In the energy spectrum 10, there are at least a higher energy portion 12 and a lower energy portion 11.
[0021] exist Figure 1A , 1B In 1C, array 1 includes at least one radiation modulator 3 located above at least one detector 2 of array 1. In other words, modulator 3 is configured to be located between ionizing radiation source 5 (not shown in the figure) and array 1. Figure 1A , 1B In 1C, the radiation modulator 3 is positioned above all detectors 2 of array 1 in the longitudinal direction (OZ), separated from array 1 by a distance counted in a direction substantially parallel to the main propagation direction (OY). Figure 1A , 1B In 1C, modulator 3 hovers above array 1 without touching it. Figure 1A , 1B In 1C, modulator 3 is located very close to array 1, i.e., between the inspected goods (not shown) and the detector. In some examples, the modulator may also be placed between the source and the inspected goods. Embodiments where the modulator is located on array 1 are also envisioned, as discussed in more detail below. Figure 3B As shown in the image.
[0022] like Figure 1A and 1C As shown, the radiation modulator 3 is configured to filter the ionizing radiation through at least two regions 31 and 32 in a direction substantially perpendicular to the longitudinal direction (OZ). Figure 1A and 1C In this configuration, the radiation modulator 3 is configured to filter the ionizing radiation in a direction substantially perpendicular to the longitudinal direction (OZ) through three consecutive regions 31-1, 32, and 31-2 corresponding to the first region 31 and the second region 32. In other words, in... Figure 1A and 1C In the middle, the first region 31 is divided into two sub-regions 31-1 and 31-2, which are separated by the second region 32 in a direction that is substantially perpendicular to the longitudinal direction (OZ) (OX).
[0023] like Figure 1C As shown, the radiation modulator 3 is configured to filter the ionizing radiation 5 through three consecutive regions 31-1, 32, and 31-2, such that the transmission of the lower portion 11 of the spectrum 10 is suppressed through the first region 31 of the modulator 3 (i.e., Figure 1C The first region 31 includes sub-regions 31-1 and 31-2), and enables the transmission of the higher portion 12 through the first region of the modulator 3 (i.e., Figure 1C The first region 31 includes sub-regions 31-1 and 31-2), and enables the transmission of the lower portion 11 and the higher portion 12 of the spectrum 10 through the second region 32 of the modulator 3 (i.e., Figure 1C The second zone 32).
[0024] like Figure 1A and 1CAs shown, the radiation modulator 3 is configured to filter the ionizing radiation 5 through at least two regions 31 and 32 in a direction substantially perpendicular to the longitudinal direction (OZ) (OX). As explained in more detail below, in some examples, the radiation modulator may be configured to further filter the ionizing radiation through at least two regions in a direction substantially parallel to the longitudinal direction (OZ).
[0025] like Figure 1C As shown, modulator 3 is also continuous in a direction substantially perpendicular to the longitudinal direction (OZ). Figure 1C In the first region 31, a material block having a first uniform thickness H1 in the transmission direction (OY) of radiation 5 is included, and a second region 32, a material block having a uniform thickness H2 in the transmission direction (OY) of radiation 5, corresponds to a material thickness in modulator 3 that is equal to the first thickness H1. Figure 1A , 1B In 1C, the second region 32 includes a material block that is different from the material of the first region 31, but is capable of transmitting the lower part (11) and the higher part (12) of the spectrum.
[0026] Embodiments of this disclosure utilize oversampling along the scan direction (OX). For example, from... Figure 1A , 1B As can be seen in 1C, detector 2 has a width W, and is wider in the scanning direction (OX) than in the longitudinal direction (OZ). The relatively wide size W of detector 2 in the (OX) direction allows for maintaining a large interaction area with the incident ionizing radiation 5, while limiting any reduction in spatial resolution, because the displacement δ between two pulses of ionizing radiation 5 in the scanning direction (OX) of array 1 is much smaller than the detector size W in the scanning direction (OX).
[0027] In addition, such as Figure 1A As shown, the width of the second region 32 in the scanning direction (OX) substantially perpendicular to the longitudinal direction (OZ) w 2 and the width of the first zone 31 w The ratio of 1 r for: .
[0028] exist Figure 1A middle, , where w 1-1 It is the width of sub-region 31-1, w 1-2 It is the width of sub-region 31-2.
[0029] Preferably, r It's like this: .
[0030] For example Figure 1A As shown, during the scanning of cargo via the array, the width of the second zone 32 in the direction (OX) substantially perpendicular to the longitudinal direction (OZ) w 2 is greater than the array displacement δ in the scanning direction (OX) between two ionizing radiation pulses, such that: .
[0031] In some examples, the width of the second zone 32 in the direction (OX) w 2. The preferred option is: .
[0032] As mentioned above and as Figure 1B As shown, the first region 31 of the radiation modulator 3 is configured to uniformly cover each detector 2 in the longitudinal direction (OZ). As described in more detail below, this disclosure applies to embodiments in which at least one radiation modulator is located on at least one detector of the array, and embodiments in which not all detectors are at least partially covered by the modulator are also contemplated.
[0033] As shown in Figure 3, sub-regions 31-1 and 31-2 can have the same width, making .
[0034] exist Figure 3A and 3B In the first region 31, there is a material block with a uniform thickness H1 in the transmission direction (OY) of the radiation 5, and the second region 32 is configured to correspond to the gap (i.e., hole) in the modulator 3 in the transmission direction (OY) of the radiation 5.
[0035] Figure 4A This schematically illustrates the effects of two different specific energies (i.e., the first energy of 6 MeV, see [reference]). Figure 4A The lower curve in the figure, and the second energy of 300 keV, see [link to figure]. Figure 4A The upper curve in the middle) uses according to Figure 3A and 3B The modulator 3 (i.e., the first region 31 with an iron thickness H1 of 3 cm and a gap with a width W2 equal to one-quarter of the total width W of the detector 2) Figure 3A and 3B The three typical point spread functions generated by the modulator in the second region 32 corresponding to the aperture shown, and the total point spread function of the full 6MeV x-ray accelerator spectrum (see [reference]). Figure 4A (The middle curve).
[0036] Figure 4B schematically shown Figure 4A The full 6MeV X-ray accelerator spectral spread function (i.e. Figure 4A The modulation transfer function (MTF, or Fourier transform) of the intermediate curve: See [link to relevant documentation]. Figure 4B The upper curve. Figure 4B The upper curve and the MTF of the point spread function curve obtained without using a modulator placed on the detector (see [reference]). Figure 4B Compare the lower curves. Figure 4B The lower curve is the MTF of the curve obtained without using a modulator placed on the detector, which corresponds to the Nyquist frequency span. (As shown from...) Figure 4B It can be seen from this that Figure 4B The upper curve has a higher Figure 4B The lower part of the Nyquist curve has a larger frequency span. In other words, when the modulator is placed above the detector array, more frequencies are transmitted to the detectors, which provides better resolution for the inspected goods.
[0037] exist Figure 5A and 5B In this context, the first region 31 is continuous in a direction (OX) that is substantially perpendicular to the longitudinal direction (OZ), in other words, the first region 31 is not divided into sub-regions.
[0038] exist Figure 6A and 6B In the first region 31, a material block with a first uniform thickness H1 in the transmission direction (OY) of radiation 5 is included. The second region 32 includes a material block of the same material as the first region but with a second varying thickness H in the transmission direction of radiation. In the transmission direction of radiation, the second thickness H corresponds to a material thickness in the modulator that is smaller than the first thickness. Figure 6B In the process, H first decreases from H1 to essentially zero, and then increases from essentially zero back to H1. Therefore, the block in the second region 32 has a triangular notch.
[0039] With as a basis for use Figure 3A and 3B The point spread function obtained by comparing the modulator result with that of the modulator is compared. Figure 7 The illustration shows the basis for use. Figure 6A and 6B The point spread function is obtained as a result of a modulator with a triangular notch. From Figure 7 It can be clearly seen from the above that, according to Figure 6A and 6B The peak shape of the modulator allows for better transmission at higher frequencies.
[0040] Other shapes of notches can be imagined in the blocks of the second area.
[0041] In the above improvements, the modulator increases the resolution in the scanning direction (OX) while maintaining transmittance.
[0042] In the following improvements, resolution is enhanced in both directions (OX) and (OZ) by having a filtering section that is simultaneously oriented in both directions (OX) and (OZ), as explained in more detail below. In the following improvements, the displacement δ of array 1 between two pulses of ionizing radiation is less than half the width of detector 2.
[0043] In some examples and such Figure 8 As shown, the radiation modulator 3 is configured to further filter ionizing radiation passing through at least two regions 31 and 32 in the longitudinal direction (OZ). Figure 8 In this configuration, for each detector 2, the first region 31 of the modulator 3 is configured to cover the upper or lower portion of the detector 2, which is defined by at least one diagonal of the detector 2. Figure 8 In this configuration, for each detector 2, the second region 32 of the modulator 3 is configured to cover either the lower or upper portion of the detector 2. In some non-limiting examples, the thickness H1 of the first portion 31 of the modulator 3 in the principal direction (OY) of radiation propagation is such that the first portion 31 of the modulator 3 is configured to absorb half of the full-scale flux (e.g., the X-ray flux without any object).
[0044] Figure 9 The use of according to the illustration is shown. Figure 8 The 2D modulation transfer function of the full 6MeV X-ray accelerator spectral spread function obtained by modulator 3: see Figure 9 The upper curve. Figure 9 The upper curve and the 2D MTF of the point spread function curve obtained without using a modulator placed on the detector (see) Figure 9 The lower curve of the modulation transfer function is compared. By comparing the modulation transfer function, in... Figure 9 The improved resolution is demonstrated in the data.
[0045] like Figure 10A , 10B As shown in 10C, this disclosure applies to a matrix 4 comprising at least two arrays 1 according to any aspect of this disclosure. Figure 10A , 10B In 10C, matrix 4 consists of five arrays 1, but other numbers of arrays can be envisioned.
[0046] like Figure 10A and 10B As shown, this disclosure applies to cases where an array 1 according to any aspect of this disclosure includes a plurality of radiation modulators 3 located above a plurality of detectors 2 of the array 1.
[0047] like Figure 10A and10B As shown, the plurality of modulators 3 are arranged in segments that are parallel to each other. Figure 10A ) and / or in a Z-shaped configuration with each other ( Figure 10B ).
[0048] exist Figure 10A In the case where the displacement of array 1 between two ionizing radiation pulses is less than half the width of matrix 4, the modulator is configured to split detector 2 into two along its diagonal, thus increasing the resolution in the (OX) and (OZ) directions.
[0049] exist Figure 10B In the case where the displacement of array 1 between two pulses of ionizing radiation is less than half the width of the spacing of the array of matrix 4 along the scanning direction, the modulator is configured to divide detector 2 into four along its two diagonals, such as... Figure 10C As shown, this further increases the resolution in the (OX) and (OZ) directions.
[0050] exist Figure 10B In this configuration, the four arrays 1 of matrix 4 are covered by two types of filters along the two diagonals. If the displacement of matrix 4 between two pulses of ionizing radiation is less than the width of each array 1, then modulator 3 is configured to divide the pixel into four.
[0051] In this disclosure, the modulator may be made of at least one of iron, copper, and lead.
[0052] In this disclosure, the thickness H1 of the filter material in the first region 31 can be defined such that the contribution of the second region 32 (which may be an unfiltered region, such as a pore) to the signal collected by the detector 2 is at least equal to the contribution of the first filter region 31. Figure 3A , 3B In some examples of 5A and 5B, for a detector 2 with a width W of 20 mm, a modulator 3 with a second region w2 (e.g., a 5 mm aperture), and for a 6 MeV spectrum, a thickness H1 of 3 cm of iron. In such examples, the thinner second region is paired with a thicker (i.e., larger H1) filter portion of the first region, while the wider second region is paired with a thinner (i.e., smaller H1) filter portion of the first region.
[0053] In the above improvements, the modulator is aligned with the array in the scanning direction, but it is conceivable that the modulator could have a wider dimension in the scanning direction than the detector to make alignment easier.
[0054] In some examples, the modulator can also be moved relative to the array in real time. In this case (not shown in the figure), the modulator can be placed near the ionizing radiation source (to minimize the size of the modulator), and the modulator can be moved in the scanning direction by an actuator based on the scanning speed of the goods being inspected (e.g., by radar detection as a non-limiting example). Other embodiments are conceivable.
[0055] This disclosure applies to X-ray radiation, but other types of pulsed ionizing radiation are also conceivable. This disclosure applies to any type of polychromatic ionizing radiation used for transmission imaging, provided that the attenuation of the radiation is energy-dependent (or wavelength-dependent).
[0056] Other embodiments different from those shown in the figures are also conceivable. This disclosure also applies to modulators configured such that their thickness varies, for example, continuously or discontinuously, along a direction substantially perpendicular to the longitudinal direction (i.e., the thickness varies in the scanning direction). For example, the thickness of the modulator may vary sinusoidally, having a spatial period in a direction substantially perpendicular to the longitudinal direction smaller than the width of the detector (i.e., the spacing between detectors in the scanning direction), and having an amplitude that filters the spectrum of radiation substantially in the same manner as the modulator described above. Similar to the modulator described above, a radiation modulator whose thickness varies along a direction substantially perpendicular to the longitudinal direction is configured to filter ionizing radiation through at least two regions in a direction substantially perpendicular to the longitudinal direction, such that: The higher portion of the spectrum can be transmitted through the first region of the modulator, which is defined as the region of the modulator that suppresses the transmission of the lower portion of the spectrum. The second region of the modulator enables both the lower and higher portions of the spectrum to be transmitted through it.
Claims
1. An array of multiple detectors arranged along a longitudinal direction and configured to detect pulsed ionizing radiation having an energy spectrum comprising at least a higher energy portion and a lower energy portion, each detector corresponding to a pixel in an inspection image of the cargo after the cargo has been scanned by the array in a scanning direction substantially perpendicular to the longitudinal direction. The array includes at least one radiation modulator located above at least one detector of the array, and The radiation modulator is configured to filter the ionizing radiation through at least two zones in at least a direction substantially perpendicular to the longitudinal direction, such that: Suppressing the transmission of the lower portion of the spectrum through the first region of the modulator, and enabling the transmission of the higher portion of the spectrum through the first region of the modulator, and This enables the transmission of the lower and higher portions of the spectrum through the second region of the modulator.
2. The array according to claim 1, wherein, During the array scanning of the cargo, the width of the second zone in a direction substantially perpendicular to the longitudinal direction w 2 is greater than the displacement δ of the array in the scanning direction between two ionizing radiation pulses, such that: ， Optionally, where 。 3. The array according to claim 1 or 2, wherein the width of the second region in a direction substantially perpendicular to the longitudinal direction w 2 and the width of the first region w The ratio R of 1 makes: Preferably, the following is achieved: 。 4. The array according to any one of claims 1 to 3, wherein the first region is continuous in a direction substantially perpendicular to the longitudinal direction.
5. The array according to any one of claims 1 to 3, wherein, The first region is divided into two sub-regions separated by the second region in a direction substantially perpendicular to the longitudinal direction.
6. The array according to any one of claims 1 to 5, wherein, The first region of the radiation modulator is configured to uniformly cover the detector in the longitudinal direction.
7. The array according to any one of claims 1 to 5, wherein the radiation modulator is configured to filter the ionizing radiation through at least two regions in the longitudinal direction.
8. The array of claim 7, wherein the first region of the modulator is configured to cover the upper or lower portion of the detector, the upper and lower portions being defined by at least one diagonal of the detector, and wherein the second region of the modulator is configured to cover the lower or upper portion of the detector.
9. The array according to any one of claims 4 to 8, wherein the modulator is configured such that its thickness varies continuously or discontinuously along a direction substantially perpendicular to the longitudinal direction, and the modulator is configured to filter the ionizing radiation such that: This allows the transmission of the higher portion of the spectrum to pass through a region corresponding to a first region of the modulator, whereby the first region of the modulator is defined as a region of the modulator, wherein the transmission of the lower portion of the spectrum is suppressed. This enables the transmission of the lower and higher portions of the spectrum through the region corresponding to the second region of the modulator. Optionally, the thickness of the modulator varies sinusoidally in a direction substantially perpendicular to the longitudinal direction, with a spatial period smaller than the width of the detector.
10. The array according to any one of claims 4 to 8, wherein, The first region includes a material block having a first uniform thickness in the direction of radiation transmission, and The second region is configured to correspond to a void or include a block of material: The material block is the same as the material in the first region, but has a uniform or varying second thickness in the direction of radiation transmission. This second thickness corresponds to a smaller thickness of the material in the modulator compared to the first thickness in the direction of radiation transmission, and / or The material block is different from the material in the first region, but transmits the lower and higher portions of the spectrum and has a second uniform thickness in the direction of radiation transmission, which corresponds to the thickness of the material in the modulator in the direction of radiation transmission that is equal to the first thickness.
11. The array according to any one of claims 1 to 10, wherein the modulator is located between the ionizing radiation source and the array, and in, The modulator is configured to be located between the inspected cargo and the detector array, very close to the array but not in contact with it, or the at least one radiation modulator is located on the at least one detector of the array, or The modulator is configured to be located between the source and the inspected goods.
12. The array according to any one of claims 1 to 11, wherein, The array includes radiation modulators located above each detector in the array.
13. The array according to any one of claims 1 to 12, wherein, The modulator is configured to move relative to the array in the scanning direction.
14. The array according to any one of claims 1 to 13, wherein, The array includes multiple radiation modulators located above multiple detectors of the array, and The plurality of modulators are arranged in segments that are parallel to each other and / or in a zigzag configuration.
15. A matrix comprising an array of at least two of the preceding claims.