Device and method for generating object images for object recognition

Abstract

Aspects relate to a device (100) for generating one or more object images for recognizing an object (110), comprising a first emission source (120) configured to emit a first electromagnetic radiation (122) directed to pass through the object (110); a second emission source (130) configured to emit a second electromagnetic radiation (132) directed to pass through the object (110); a detector (140) arranged to receive a first modified electromagnetic radiation (124) and a second modified electromagnetic radiation (134) that have passed through the object from the first emission source (120) and the second emission source (130);a processor (150) configured to receive first spectral information of the first modified electromagnetic radiation (124) and second spectral information of the second modified electromagnetic radiation (134) from the detector (140) and to generate an object image (160); wherein the first electromagnetic radiation (122) and the second electromagnetic radiation (132) are in the frequency range of 0.1 to 10 terahertz (THz), and the second electromagnetic radiation (132) has a different frequency than the first electromagnetic radiation (122);

Description

TECHNICAL FIELD

[0001] This disclosure relates to an apparatus and method for generating object images for detecting objects such as recyclable plastic waste objects. STATE OF THE ART

[0002] Terahertz (THz)-based electromagnetic radiation is used for non-destructive testing (NDT) and quality control (QC) in various industrial applications due to its non-ionizing nature and high penetration of non-polar substances and non-conductive materials. It is used in various industries to facilitate the detection, imaging, or analysis of internal defects, prohibited or hidden objects and substances, along with the detection of materials and chemicals.

[0003] Two approaches have been proposed for imaging applications based on THz radiation: pulsed THz and continuous-wave THz (CW THz). The pulsed THz approach in spectroscopic imaging systems offers unique capabilities for NDT image processing, but may require raster scanning to form a large-area image and may not be suitable for some real-time use cases, such as those involving a moving conveyor belt application or inline scanning. CW THz approaches with a fixed emission frequency are more suitable for a conveyor belt application or inline scanning than pulsed THz approaches due to relatively faster data acquisition speeds, fast image processing, reasonable spatial resolution, and higher output powers.

[0004] However, THz images at a relatively low single emission frequency (e.g., 100 GHz) are only applicable to a limited range of plastics classification, for example, for specific waste plastics (PET and HDPE bottles). Feature extraction from obtained images based on THz radiation can be limited when using a lower single frequency source, leading to difficulties in the classification of other common waste plastics (PP, PS, PVC, etc.), engineering plastics (ABS, PE, PP, PA, PC, PC / ABS, and HIPS, etc.), reinforced engineering plastics (PA6-GF35, PA66-GF35, etc.), and mixed plastics (PC / ABS, PP / PE, HIPS / PS, HIPS / ABS, etc.).

[0005] There is a need to provide an improved solution to better detect or classify a wider range of plastic types. SUMMARY

[0006] This disclosure was developed to overcome the application limitations of linear THz scanners (single emitted THz mode) in material recovery facilities (MRFs). These MRFs typically include a conveyor system to move objects along the conveyor for detection and separation.

[0007] A new multi-source configuration with multiple higher THz emission frequencies is considered. The THz multi-source configuration can include an optical assembly such as one or more cylindrical PTFE optical lenses or concave metal mirrors to convert the divergent energy beam from the THz sources into a focal spot (collimated and narrow THz beam profile) and / or within a side scan window by adjusting the distance between multiple sources and / or adjusting the focal angle of each optical lens or mirror to adjust the position of the focal spot at the side scan window.

[0008] According to the present disclosure, a device according to claim 1 is provided. A computer-assisted method according to the invention is defined in claim 10. A computer program comprising instructions for carrying out the computer-assisted method is defined in claim 14.

[0009] The dependent claims define some examples related to the device or method. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention will be better understood by reference to the detailed description taken in conjunction with the non-limiting examples and the accompanying drawings in which: - Fig. 1A shows a schematic structural side view of an object detection device according to some embodiments; Fig. Figure 1B shows examples of object images obtained from the facility's separate radiation sources; Fig. Figure 1C shows another example of a combined object image obtained by the device; - Fig. Figure 2 shows another embodiment of an object detection device, wherein the detector / scanner includes a scanning window; - Fig. 3A and Fig. 3B shows a schematic structural side view of an object detection device with an optical assembly according to some embodiments; - Fig. 4A shows another embodiment of an object detection device including a synchronizer; Fig. 4B shows an embodiment of a TTL signal for internal synchronization; Fig. Figure 4C shows examples of object images obtained by scanning; - Fig. 5A and Fig. 5B shows a schematic structural side view of an object recognition device with a processor configured to generate the object image(s) at a predetermined frame rate; - Fig. 6 shows a schematic structural side view of an object detection device, wherein the detector / scanner includes a scanning window comprising an upper side window and a lower side window; and - Fig. 7 is a flowchart of a method for detecting an object. DETAILED DESCRIPTION

[0011] The following detailed description refers to the accompanying drawings, which, by way of illustration, show specific details and embodiments in which the disclosure may be practiced. These embodiments are described in detail to enable those skilled in the art to practice the disclosure. Other embodiments may be utilized, and structural and logical changes may be made without departing from the scope of the disclosure. The various embodiments are not necessarily mutually exclusive, as some embodiments may be combined with one or more other embodiments to form new embodiments.

[0012] Embodiments described in the context of one of the systems or methods also apply analogously to the other systems or methods.

[0013] Features described in the context of one embodiment may be applicable accordingly to the same or similar features in the other embodiments. Features described in the context of one embodiment may be applicable accordingly to the other embodiments, even if they are not explicitly described in those other embodiments. Furthermore, additions and / or combinations and / or alternatives described for a feature in the context of one embodiment may be applicable accordingly to the same or similar feature in the other embodiments.

[0014] In the context of various embodiments, the articles “a,” “an,” and “the” used with respect to a feature or element include reference to one or more of the features or elements.

[0015] As used herein, the term “and / or” includes any combination of one or more of the listed related elements.

[0016] As used herein, the term "device for detecting an object" refers, in the broadest sense, to THz-based systems for detecting an object. THz radiation consists of electromagnetic waves in the frequency range of 0.1 to 10 THz. THz radiation can be transmitted through nonpolar and nonconductive materials, especially plastic objects, and can be used to detect various types of plastic objects.

[0017] As used herein, the term "object" includes any object, especially recyclable or reusable objects, that can be identified by type, class, or category. For example, plastic objects can be identified by whether they are made of high-density polyethylene (HDPE), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), low-density polyethylene (LDPE), or polyvinyl chloride (PVC), waste plastics (e.g., PP, PS, PVC), engineering plastics (e.g., ABS, PE, PP, PA, PC, PC / ABS, and HIPS), reinforced engineering plastics (PA6-GF35, PA66-GF35), or mixed plastics (PC / ABS, PP / PE, HIPS / PS, HIPS / ABS). Such objects can include bottles, jars, containers, plates, bowls, etc., in various shapes, shapes (distorted, flattened), and sizes.

[0018] As used herein, the term "optically aligned" refers to the positioning and alignment of the various components of a device / system to enable the device / system to operate as intended. For example, an emission source comprising an electromagnetic radiation source and an excitation assembly, a detector and a detection assembly, and an optical assembly comprising collimator(s) may be optically aligned or synchronized so that the detector receives the maximum signal of the reflected wave and the signal is in focus at a scanning point or window of the detector.

[0019] As used herein, the term "module" means, forms part of, or includes an application-specific integrated circuit (ASIC); an electronic circuit; a combinational logic circuit; a field-programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; other suitable hardware components that provide the described functionality; or a combination of some or all of the foregoing, such as in a system-on-chip. The term "module" may include memory (shared, dedicated, or group) that stores code executed by the processor.

[0020] As used herein, the terms “first” and “second” are for the purpose of clarity and do not imply any order or priority.

[0021] An embodiment of the disclosure is set forth in Fig. 1A, which illustrates a structure of a device 100 for generating one or more object images 160. The one or more object images 160 can subsequently be used for object recognition. The device 100 can form at least part of a system for object recognition in an MRF. The device 100 comprises at least two radiation sources, i.e., a first emission source 120 configured to emit a first electromagnetic radiation 122 directed to pass through an object 110, and a second emission source 130 configured to emit a second electromagnetic radiation 132 directed to pass through the object 110.A detector 140 is positioned or arranged to receive first modified electromagnetic radiation 124 and second modified electromagnetic radiation 134 that have passed through the object from the first emission source 120 and the second emission source 130. A processor 150 may be configured to obtain or receive first spectral information of the first modified electromagnetic radiation 124 and second spectral information of the second modified electromagnetic radiation 134 from the detector 140 and generate an object image 160 for object image recognition and processing. The detector 140 may be positioned in or below the platform 170, or below an upper belt of the platform 170, or at any other position that may be contemplated.It is contemplated that the object image 160 may include two separate images based on the first spectral information and the second spectral information, or a combined (e.g., overlaid) image based on the first spectral information and the second spectral information.

[0022] Fig. 1B illustrates two separate images based on the first spectral information and the second spectral information, i.e., the generated object image 160a based on the emission source 120 (at 100 GHz) and 160b based on the emission source 130 (at 300 GHz), respectively. For comparison, an RGB example image R1 is shown on the left. In some embodiments, the two separate images may be generated based on different methods. One method is to generate two separate object images by decoupling combined spectral information obtained at the different emission source frequencies. Another method for generating the two separate object images may be to extract spectral information separately within a scan window, wherein the scan window is divided into two or more lateral sections, each section being sensitive to an emission source 120 or 130.Another method for generating the two separate object images may be to control the operating time of each emission source 120, 130 via synchronization signals so as to generate object images corresponding to the synchronized signals.

[0023] Fig. 1C illustrates the generation of the object image in the form of a combined object image 160c. The combined image 160c can be generated based on the superposition of the first spectral information and the second spectral information, so that the prominent features of an object 110 can be shown in a single object image 160c. For comparison, an RGB example image R2 is shown on the left.

[0024] In some embodiments, the first electromagnetic radiation 122 and the second electromagnetic radiation 132 are in the frequency range of 0.1 to 10 terahertz (THz). In some embodiments, the first electromagnetic radiation 122 has an operating frequency of 100 gigahertz (GHz), and the second electromagnetic radiation 132 has an operating frequency of 300 GHz.

[0025] The first modified electromagnetic radiation 124 and a second modified electromagnetic radiation 134 may be transmitted, diffracted, reflected, absorbed, scattered, or refracted electromagnetic waves that pass through the object 110 and impinge on the detector 140.

[0026] In some embodiments, the first emission source 120 and the second emission source 130 comprise a continuous-wave THz source, particularly a continuous-wave THz source operating in a transmission mode. The generated THz excitation wave 122, 132 propagates in a line of sight and is transmitted through non-conductive materials such as plastics, paper, wood, ceramics, and fabric. The THz excitation wave 122, 132 may not be able to transmit effectively through metal or liquids to produce useful spectral information because metal is relatively more reflective and liquids are relatively more absorbent.Both the first emission source 120 and the second emission source 130 may include any source configured to generate THz waves, such as, but not limited to: avalanche time-of-flight (IMPATT) diodes, gallium phosphide (GaP) nonlinear optical crystal modules with fiber lasers, Gunn diodes, heterostructure junction varactor (HBV) diodes, Schottky diode multiplier-based sources, backward wave oscillators (BWO), and tunable photonic mixer sources.

[0027] Fig. 1A further includes a platform 170 configured to support the object 110. In some embodiments, the platform 170 may be a conveyor belt that acts as the support medium for supporting the object 110. The platform 170 may be a movable / rotatable platform 170, and the object 110 may move along the platform 170 to overlap the detector 140.

[0028] Detector 140 may include any detector configured to receive THz waves, such as, but not limited to, gallium arsenide (GaAs) plasmonic array detectors, GaAs Schottky diode array detectors, and high-mobility GaAs / aluminum GaAs (AlGaAs) quantum well heterostructure array detectors. It is contemplated that detector 140 may be any other detector suitable for receiving the modified waves 124, 134 in the THz frequency range.

[0029] For some in Fig. In the embodiments shown in Figure 2, the detector 140 may include a scan window 142 configured to receive the first modified electromagnetic radiation 124 and the second modified electromagnetic radiation 134. The scan window typically depends on the specification of the detector 140. In some embodiments, the scan window may be between 0.5 millimeters (mm) and 3 mm in size to accommodate a 100 GHz and a 300 GHz emission source. In some embodiments, a narrower scan window may be preferred, providing high-speed scanning capabilities (5000 lines per second) and good spatial resolution (0.5 mm). Technically, the scan window can be increased by enlarging a corresponding pixel array. In the embodiment shown in Fig. In the embodiment shown in Figure 2, the distance between the first emission source 120 and the second emission source 130 can be adjusted to direct the first electromagnetic radiation 122 and / or the second electromagnetic radiation 132 to different positions (e.g., a center position) of an object 110. The scan window 142, the first emission source 120, and the second emission source 130 can be configured and positioned such that, for each object 110, a first half of line data (pixel data) corresponding to the scan window portion 142a is received from the emission source 120, and a second half of line data (pixel data) corresponding to the scan window portion 142b is received from the emission source 130 within the scan window.

[0030] In some embodiments, the detector 140 may be positioned below the platform 170 in a manner such that the object 110 is positioned between the first emission source 120, the second emission source 130, and the detector 140.

[0031] In some embodiments, detector 140 and processor 150 may be integrated as a single unit. An example of such an integration is a terahertz imaging camera / scanner.

[0032] In some embodiments, at least one of the first emission source 120 and the second emission source 130 may include an optical assembly 202, as shown in Fig. 3A and Fig. 3B, which is arranged to collimate and focus the first electromagnetic radiation 122 and / or the second electromagnetic radiation 132.

[0033] The optical assembly 202 can be considered an excitation assembly optically aligned with the first emission source 120 and / or the second emission source 130. The electromagnetic radiation source 120 can emit divergent radiation, and the optical assembly 202 can comprise any optical device, e.g., a lens or a mirror, configured to collimate and focus the divergent radiation into a narrow wave profile. The optical assembly 202 can comprise a linear lens, such as a cylindrical lens made of polytetrafluoroethylene (PTFE), or can be a concave metal mirror. It is contemplated that the optical assembly 202 can be any optical device that collimates the divergent radiation.In some embodiments, the optical assembly 202 can be positioned to change the direction of the first electromagnetic radiation 122 and / or the second electromagnetic radiation 132. For example, the optical assembly 202 can be rotated or tilted, ie, inclined, about a pivot point (not shown) so that the direction of the first electromagnetic radiation 122 and / or the second electromagnetic radiation 132 can be changed (see rotation arrow in ). Fig. 3B).

[0034] The device 100 includes a processor 150 configured to receive spectral information about the first modified electromagnetic radiation 124 and the second modified electromagnetic radiation 134 from the detector 140. The processor 150 may be arranged in signal communication with the detector 140 such that the spectral information about the first modified electromagnetic radiation 124 and the second modified electromagnetic radiation 134 may be transmitted to the processor 150 for further processing. In some embodiments, the spectral information about the first modified electromagnetic radiation 124 and the second modified electromagnetic radiation 134 may be transmitted via wireless means according to a predefined wireless communication protocol.Examples of predefined wireless communication protocols include: Global System for Mobile Communication (GSM), Enhanced Data GSM Environment (EDGE), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Wireless Fidelity (Wi-Fi), Voice over Internet Protocol (VoIP), Worldwide Interoperability for Microwave Access (Wi-MAX), Wi-Fi Direct (WFD), Ultra Wideband (UWB), Infrared Data Association (IrDA), Bluetooth, ZigBee, SigFox, LPWan, LoRaWan, GPRS, 3G, 4G, LTE, and 5G communication systems. Alternatively, the processor 150 and the detector 140 may be in signal communication via wired means. The detector 140 and / or the processor 150 may also include memory for storing the spectral information.

[0035] The spectral information about the first modified electromagnetic radiation 124 and the second modified electromagnetic radiation 134 may include the amplitude, frequency, phase, wavelength, electric field, power intensity, and / or refractive index of the object 110. The processor 150 may be further configured to generate the object image 160 for detecting the object 110 using computer vision and image processing techniques suitable for continuous-wave terahertz imaging, for example, CW THz vector spectroscopy. In one embodiment, the object image 160 may be a THz heatmap image of the object 110 and may be the THz power intensity distribution of the object 110. Based on the object image, the object 110 may be detected.It is contemplated that the object 110 may also be detected based on the spectral information about the first modified electromagnetic radiation 124 and the second modified electromagnetic radiation 134. It is further contemplated that the processor 150 may apply pre- or post-processing image techniques to minimize noise and improve the accuracy of the object image 160. In some embodiments, the generated object image 160 may enable detection of the object 110 based on the material type, in particular, detection of the HDPE or PET plastic object 110 based on spectral information about the first modified electromagnetic radiation 124, and of waste plastics (e.g., PP, PS, PVC, etc.), engineering plastics (e.g., ABS, PE, PP, PA, PC, PC / ABS, and HIPS, etc.), reinforced engineering plastics (e.g., PA6-GF35, PA66-GF35, etc.), and mixed plastics (e.g., PC / ABS, PP / PE, HIPS / PS, HIPS / ABS, etc.).) based on spectral information about the second modified electromagnetic radiation 134. The object 110 can be further separated or sorted based on the detection.

[0036] Fig. 3A and Fig. 3B show the device 100 with the dual source configurations 120, 130, wherein the first emission source 120 and the second emission source 130 are configured to simultaneously emit the first electromagnetic radiation 122 and the second electromagnetic radiation 132, and the processor 150 is configured to receive combined spectral information of the first modified electromagnetic radiation 124 and the second modified electromagnetic radiation 134.

[0037] It is contemplated that one or more THz sources with higher THz emission frequencies may be added if required. Fig. 3A shows an embodiment in which the optical assembly 202 collimates the electromagnetic radiation emitted from the emission sources 120, 130 (see dotted lines) at a focal line spot labeled "A" into a collimated and narrow first electromagnetic radiation 122 and second electromagnetic radiation 132, as shown. Fig. 3B shows an adjustable optical assembly 202. For example, the optical assembly 202 can be rotated or tilted, ie, inclined, about a pivot point (not shown) so that the direction of the first electromagnetic radiation 122 and the second electromagnetic radiation 132 can be changed (see rotation arrow in Fig. 3B) and the optical assembly 202 may not be parallel to the emission sources 120, 130. The adjustment angle may be within a range of ±30 degrees with respect to a longitudinal axis of the respective emission sources 120, 130. The optical assembly 202 may facilitate the construction of the multiple emission sources including the emission sources 120, 130, making them more compact, i.e., the emission sources 120, 130 may be mounted relatively closer to one another. The aforementioned adjustment angle of the rotatable optical assembly 202 may be individually tailored or adjusted to position the focal line spot "A" along various positions on the side scan window.

[0038] It is considered that the arrangement of Fig. 3A or Fig. 3B allows a direct comparison for any change in the penetration intensity of the THz electromagnetic radiation in a same ROI (region of interest) or at an average location of one or more objects 110 for detection. In some embodiments, the first electromagnetic radiation 122 has a frequency in a range of 100 GHz to 300 GHz; and the second electromagnetic radiation 132 has a frequency in a range of 600 GHz to 1.0 THz. In some embodiments, consecutive individual images may be acquired by the detector 140 in the form of a linear THz line scanner or a camera. In some embodiments, there may be more than two sources, for example, three or more sources.For example, in addition to the two emission sources 120, 130 for emitting the first electromagnetic radiation 122 and the second electromagnetic radiation 132, further emission sources may be added and configured to emit electromagnetic radiation at more than 600 GHz.

[0039] In the Fig. 3A and Fig. In the embodiments shown in Figure 3B, when the multiple sources 120, 130 with different frequencies are simultaneously directed at the object(s) 110 to be detected, a combination or superimposed spectral information of the responses from both sources 120, 130 can be acquired without any synchronization. In particular, the response of measurement pixels of the detector 140 in the form of a linear THz scanner (array detector) can depend on a combination of the sensitivity and measurement intensity of each source, and a combined (superimposed) signal U, which is a sum of two components, each of which is a multiple of the intensity (amplitude) "A" on a sensitivity factor "S," can be mathematically expressed as follows: U (combined intensity (amplitude)) = S(at 100 GHz)*A(at 100 GHz) + S(at 300 GHz)*A(at 300 GHz)

[0040] In some embodiments, the sensitivity factor "S" for each source having a specific frequency can be examined using multiple standard samples, i.e., the acquired sensitivity factor represents each plastic type at 100 GHz, 300 GHz, and / or other frequencies, as appropriate. In some embodiments, the standard samples can be obtained from a resin supplier for certified resin, and a standard sample can be obtained using this certified resin. In other embodiments, the plastic samples can already be assessed and evaluated for their composition and other aspects using one or more certified test methods.

[0041] In some embodiments, the decoupled THz image can be extracted from each frequency by known linear regression methods.

[0042] Fig. 4A shows a further embodiment of the device 100, wherein the first emission source 120 and the second emission source 130 are configured to emit the first electromagnetic radiation 122 and the second electromagnetic radiation 132 separately, and the device 100 further comprises a synchronizer 180 arranged in signal communication with the first emission source 120, the second emission source 130, the processor 150 and the detector 140 to control the switching on and off of the first emission source 120 and the second emission source 130.

[0043] The synchronizer 180 may be configured to enable internal or external synchronization of the emission sources 120, 130. Fig. Figure 4B shows an example of a transistor-to-transistor logic (TTL) signal used for internal and / or external synchronization of the emission sources 120, 130.

[0044] In some embodiments, synchronizer 180 may be part of processor 150 and configured to alternately switch the sources between an on and off state based on a control signal. In some embodiments, the control signal may be a TTL modulation waveform. The inverted signal of each source is interleaved, with odd frames (i.e., frames 1, 3, 5, 7) being captured with one source and even frames (i.e., 2, 4, 6, 8) being captured with another source.

[0045] Alternatively or additionally, the synchronizer 180 may be implemented as an external device, and the TTL modulation waveform may be an external +5 V TTL synchronization mode, which may be used to activate the sources 120, 130 via a synchronization pulse. The multiple sources 120, 130 may then be turned on and off via the synchronization pulse. The synchronizer 180 may be, or be part of, a standalone rotary encoder configured to automatically adjust to conveyor belt speed variations, or it may be used to integrate the linear scanner with additional equipment in the line.

[0046] For configurations with multiple higher THz emission frequencies and the same / common exposure rate, this can be useful for the multi-source configuration, as in Fig. 4A. In some embodiments, a longer exposure rate may be configured for the relatively higher frequency source (e.g., 300 GHz) for two reasons: (a) the relatively higher frequency source (e.g., a 300 GHz source) may produce lower output power than the relatively lower frequency source (e.g., a 100 GHz source), and the linear scanners in the camera may be approximately a factor of 2 or 3 less sensitive at the 300 GHz frequency than at 100 GHz, (b) the output power, sensitivity, and detected signal level are typically lower at 300 GHz under similar conditions of alignment and exposure rate. Therefore, to increase the output power and sensitivity of a 300 GHz source, a longer exposure rate is required, which may result in a slower frame rate (scan rate, fps) per second, e.g., E.g. 71 fps at exposure 1 at 100 GHz, but 14 fps at exposure 4 at 300 GHz.In general, an exposure scale from 1 to 10 corresponds to a shortest exposure time at scale value 1 (at 71 fps) and a longest exposure time at scale value 10 (at 0.23 fps).

[0047] In some embodiments, each THz source may comprise a different technical specification, and each THz source configuration may support the extraction of different unique features associated with object(s) 110 according to different operational scenarios, such as a waste stream scenario in an MRF context.

[0048] In some embodiments, the object image 160 obtained based on the first emission source 120 operating at 100 GHz may be useful for pre-sorting and pre-screening purposes according to different waste stream scenarios.

[0049] In some embodiments, the object image 160 obtained based on the first emission source 120 at 100 GHz may be used for self-calibration purposes, and the object image 160 obtained based on the second emission source 130 at 300 GHz may be used to further classify plastic types (including engineering plastics) thanks to its higher sensitivity to different plastics.

[0050] In some embodiments, image differences, e.g., pixel differences, from two acquired THz frames, one based on the first spectral information and the other based on the second spectral information, can be processed and used to derive other THz features. Post-signal processing of pixel differences can be used for improved THz feature extraction depending on the plastic type.

[0051] In some embodiments, an absolute value of the difference between two consecutive image frames, where one frame is based on the first emission source 120 emitting electromagnetic radiation at 100 GHz and the other frame is based on the second emission source 130 emitting electromagnetic radiation at 300 GHz, can be extracted using a standard +5 V TTL waveform with high and low level transitions that indicate the frame boundaries.

[0052] Fig. 4C shows examples of separate object images 404, 406 generated based on synchronization control using TTL modulation signals. The TTL modulation signals are used to control the on / off switching of the emission sources 120, 130. As mentioned, the inverted signal of each source is interleaved, with odd frames (i.e., frames 1, 3, 5, 7) being acquired with the source 120 and even frames (i.e., 2, 4, 6, 8) being acquired with the source 130. The object image 402 is an example image obtained using a conventional RGB camera, with the object image 404 being acquired via the emission source 120 at a frequency of 100 GHz and the object image 406 being acquired via the emission source 130 at a frequency of 300 GHz. By comparing the object image 404 and the object image 406, it can be seen that different features of the same objects are highlighted.Such different features can facilitate the extraction of different unique features according to different waste stream scenarios in an MRF.

[0053] In some embodiments, as in Fig. 5A and Fig. As shown in Figure 5B, better THz feature extraction can be obtained from a THz source with higher frequencies and the same exposure rate at a focal line spot, with the multiple sources properly aligned with the optical assembly (see Fig. 5A), and multiple sources can be easily aligned separately and independently with the scan window, the scan window including an upper side scan window further sensitive to the first emission source 120 for generating the object image 404, and a lower side scan window further sensitive to the second emission source 130 for generating the object image 406. The scan rate of the detector 140 can be 71 fps at exposure 1.

[0054] In some embodiments, as in Fig. 6, the detector 140 includes the scanning window with the upper side window and the lower side window.

[0055] The first emission source 120 and the second emission source 130 are positioned to direct the respective electromagnetic radiation onto the object 110 such that the first modified electromagnetic radiation 124 impinges on the upper side scanning window and the second modified electromagnetic radiation 134 impinges on the lower side scanning window. Furthermore, the position of each source can be precisely adjusted to align each THz penetration distribution (e.g., 50% by 50% within the scanning window) in hybrid image acquisition (Janus THz imaging) for better THz feature extraction, as shown in Fig. 6 described.

[0056] Fig. 7 is a flowchart according to a further aspect of the disclosure in the form of a computer-aided method 600 for generating an object image (160) of an object 110, comprising the steps of: emitting 602 a first electromagnetic radiation 122 directed to pass through the object 110; emitting 604 a second electromagnetic radiation 132 directed to pass through the object 110; receiving 606, at a detector, a first modified electromagnetic radiation 124 and a second modified electromagnetic radiation 134 that have passed through the object 110 from the first emission source 120 and the second emission source 130; obtaining 608 a first spectral information item and a second spectral information item based on the first modified electromagnetic radiation 124 and the second modified electromagnetic radiation 134, respectively.the second modified electromagnetic radiation 134; and generating 610 an object image 160 based on the first spectral information and the second spectral information; wherein the first electromagnetic radiation 122 and the second electromagnetic radiation 132 are in the frequency range of 0.1 to 10 terahertz (THz), and the second electromagnetic radiation 132 has a different frequency than the first electromagnetic radiation 122, i.e., the frequency of the first electromagnetic radiation differs from the frequency of the second electromagnetic radiation. It is understood that the steps can be performed by the device 100. In some embodiments, the step of generating the object image 160 can comprise generating a combined object image (see . Fig. 1C) or separate object images, as in Fig. 1B, Fig. 4C.

[0057] In some embodiments, method 600 may include a step of recognizing object 110 based on using generated object image 160 as input to a machine learning module. The machine learning module may include one or more machine learning algorithms and be configured to receive object image 160 to generate an output indicating a class of object 110 (e.g., plastic or non-plastic class). In some embodiments where object 110 belongs to the plastics class, object 110 may be further classified, for example, based on specific post-consumer plastics (PET, HDPE, PP, PS, PVC, etc.), engineering plastics (ABS, PE, PP, PA, PC, PC / ABS, and HIPS, etc.), reinforced engineering plastics (PA6-GF35, PA66-GF35, etc.), and mixed plastics (PC / ABS, PP / PE, HIPS / PS, HIPS / ABS, etc.). In some embodiments, the machine learning algorithms may include convolutional neural networks.

[0058] While the disclosure has been particularly shown and described with reference to specific embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims, and all changes which come within the spirit and range of equivalency of the claims are therefore intended to be embraced.

Claims

[1] Device (100) for generating an object image (160) for recognizing an object (110), the device (100) comprising a first emission source (120) configured to emit a first electromagnetic radiation (122) directed to pass through the object (110); a second emission source (130) configured to emit a second electromagnetic radiation (132) directed to pass through the object (110); a detector (140) arranged to receive a first modified electromagnetic radiation (124) and a second modified electromagnetic radiation (134) which have passed through the object from the first emission source (120) and the second emission source (130); a processor (150) configured to receive first spectral information of the first modified electromagnetic radiation (124) and second spectral information of the second modified electromagnetic radiation (134) from the detector (140) and to generate the object image (160); wherein the first electromagnetic radiation (122) and the second electromagnetic radiation (132) are in the frequency range from 0.1 to 10 terahertz (THz) and the second electromagnetic radiation (132) has a different frequency from the first electromagnetic radiation (122). [2] The device (100) of claim 1, further comprising a platform (170) configured to support the object (110), and wherein the detector (140) is positioned in or below the platform (170) or below an upper band of the platform (170) in a manner such that the object (110) is positioned between the first emission source (120), the second emission source (130) and the detector (140). [3] Device (100) according to claim 1 or 2, wherein at least one of the first emission source (120) and the second emission source (130) comprises an optical assembly (202) arranged to collimate and focus the first electromagnetic radiation (122) and / or the second electromagnetic radiation (132). [4] Device (100) according to one of the preceding claims, wherein the first emission source (120) and the second emission source (130) are configured to simultaneously emit the first electromagnetic radiation (122) and the second electromagnetic radiation (132), and the detector (140) is configured to generate combined spectral information, and the processor (150) is configured to receive the combined spectral information of the first modified electromagnetic radiation (124) and the second modified electromagnetic radiation (134) from the detector (140). [5] The device (100) of any one of claims 1 to 3, wherein the first emission source (120) and the second emission source (130) are configured to emit the first electromagnetic radiation (122) and the second electromagnetic radiation (132) separately, and the processor (150) further comprises a synchronizer (180) arranged in signal communication with the first emission source (120), the second emission source (130) and the detector (140) to control the switching on and off of the first emission source (120) and the second emission source (130). [6] The device (100) of claim 5, wherein the synchronizer (180) is configured to control the first emission source (120) and the second emission source (130) based on a TTL modulation signal. [7] The device (100) of claim 5 or 6, wherein the synchronizer (180) is configured to control the first emission source (120) and the second emission source (130) at a common exposure rate to the object (110). [8] Device (100) according to one of claims 5 to 7, wherein the detector (140) comprises a scanning window, the scanning window comprises an upper side window and a lower side window, and the first emission source (120) and the second emission source (130) are positioned to direct the respective electromagnetic radiation onto the object (110) such that the first modified electromagnetic radiation (124) impinges on the upper side scanning window and the second modified electromagnetic radiation (134) impinges on the lower side scanning window. [9] Device (100) according to one of claims 1 to 8, wherein the generated object image (160) comprises at least one of the following: a superimposed THz image (160c), a decoupled THz image, a first THz object image (160a, 404) based on the first emission source (120) and a second THz object image (160b, 406) based on the second emission source (130). [10] Method (600) for generating an object image (160) for recognizing an object (110), comprising the steps: Emitting (602) a first electromagnetic radiation (122) directed to pass through the object (110); emitting (604) a second electromagnetic radiation (132) directed to pass through the object (110); Receiving (606), at a detector, a first modified electromagnetic radiation (124) and a second modified electromagnetic radiation (134), which have passed through the object (110) from the first emission source (120) and the second emission source (130); Obtaining (608) first spectral information and second spectral information based on the first modified electromagnetic radiation (124) and the second modified electromagnetic radiation (134); and Generating (610) the object image (160) based on the first spectral information and the second spectral information; wherein the first electromagnetic radiation (122) and the second electromagnetic radiation (132) are in the frequency range from 0.1 to 10 terahertz (THz) and the second electromagnetic radiation (132) has a different frequency from the first electromagnetic radiation (122). [11] The method (600) of claim 10, wherein the steps of emitting the first electromagnetic radiation (122) and emitting the second electromagnetic radiation (132) are performed simultaneously, and wherein the first spectral information and the second spectral information are combined. [12] The method (600) of claim 10 or 11, wherein the steps of emitting the first electromagnetic radiation (122) and emitting the second electromagnetic radiation (132) are performed separately, and the method (600) comprises a step of synchronizing the first emission source (120), the second emission source (130), and the detector (140) to control the switching on and off of the first emission source (120) and the second emission source (130). [13] The method (600) of any one of claims 10 to 12, wherein the step of generating (610) an object image (160) comprises at least one of the following: simultaneously directing the first electromagnetic radiation (122) and the second electromagnetic radiation (132) onto the object (110) to be detected, whereby combined spectral information is obtained; and generating a superimposed object image (160c); Synchronizing the first emission source (120) and the second emission source (130) to direct the first electromagnetic radiation (122) and the second electromagnetic radiation (132) separately, thereby obtaining the first spectral information and the second spectral information; and generating a first object image (160a) corresponding to the first spectral information, and a second object image (160b) corresponding to the second spectral information; Decoupling the combined spectral information to obtain the first object image (160a), which corresponds to the first spectral information, and to generate the second object image (160b) which corresponds to the second spectral information; Providing a scanning window (142) comprising an upper side window (142a) and a lower side window (142b), directing the first electromagnetic radiation (122) onto the object (110) such that the first modified electromagnetic radiation (124) impinges on the upper side scanning window (142a) and the second modified electromagnetic radiation (134) impinges on the lower side scanning window (142b); and / or Aligning and adjusting a penetration distribution of each of the first electromagnetic radiation (122) and the second electromagnetic radiation (132) such that the first modified electromagnetic radiation (124) impinges on the upper side scanning window (142a) and the second modified electromagnetic radiation (134) impinges on the lower side scanning window (142b). [14] A computer program product comprising instructions for causing the device according to any one of claims 1 to 9 to carry out the steps of the method according to any one of claims 10 to 13. [15] A computer-readable data carrier on which the computer program product according to claim 14 is stored.

Images