Optical detection system

Abstract

Embodiments of the present disclosure relate to an optical detection system. The system comprises a light source configured to emit a laser beam for scanning a detection target along a scanning path such that the detection target generates an excitation light at a corresponding position. In addition, the system further comprises a light receiving assembly comprising a first photodetector and a second photodetector, each of the first photodetector and the second photodetector comprising a detection surface for receiving the excitation light, the detection surface comprising a rectangular photosensitive region, the first photodetector and the second photodetector being arranged in a spaced apart manner such that a gap is formed between the detection surfaces of the first photodetector and the second photodetector for the laser beam to pass through vertically, a length direction of the gap being consistent with the scanning path, and at least one side edge of the gap being the photosensitive region of the photodetector. The system can achieve that the illumination beam is completely vertically incident on the target and the photodetector is coaxially arranged with the illumination light path.

Description

Technical Field

[0001] The embodiments disclosed herein generally relate to the field of optical scanning and detection technology, and more specifically to an optical detection system. Background Technology

[0002] With the explosive growth in demand for large-format imaging in fields such as semiconductor packaging and testing (wafers, memory chips, advanced packaging, and MEMS processes), industrial non-destructive testing, and large-size medical radiographic imaging, wide-format IP imaging boards (width greater than 25mm), especially those greater than 100mm, have become the core carriers for large-area X-ray detection scenarios. Meeting the high-quality detection requirements of wide-format IP imaging—including high spatial resolution, high uniformity, no blind spots, high speed, and high dynamic range—has become the core direction of technological iteration in this field. Summary of the Invention

[0003] Embodiments of this disclosure provide an optical detection system designed to address one or more of the problems described above, as well as other potential problems.

[0004] According to a first aspect of this disclosure, an optical detection system is provided, comprising a light source for emitting a laser beam for detecting a target, the laser beam being used to scan the target along a scanning path, causing the target to generate excitation light at corresponding positions. Furthermore, the system includes a light receiving assembly comprising a first photodetector and a second photodetector, each including a detection surface for receiving the excitation light, the detection surface including a rectangular photosensitive area, the first and second photodetectors being spaced apart such that a slit is formed between the detection surfaces of the first and second photodetectors for the laser beam to pass through perpendicularly, the length direction of the slit being aligned with the scanning path, and at least one edge of the slit being the photosensitive area of ​​the photodetector.

[0005] In some embodiments, both the first photodetector and the second photodetector are silicon-based dynamometer phototube detectors.

[0006] In some embodiments, the detection surface further includes a non-photosensitive area located on the short side of the rectangular photosensitive area, and the gap is formed between the long side of the rectangular photosensitive area of ​​the first photodetector and the long side of the rectangular photosensitive area of ​​the second photodetector.

[0007] In some embodiments, the length of the slit is less than the sum of the lengths of the long side of the first photodetector and the long side of the second photodetector, and greater than the length of the non-photosensitive region of the first photodetector along its long side and the length of the non-photosensitive region of the second photodetector along its long side.

[0008] In some embodiments, the light receiving assembly further includes a slit width adjusting member for adjusting the width of the slit.

[0009] In some embodiments, the light receiving component includes one or more first photodetectors and one or more second photodetectors, and the first photodetectors and the second photodetectors are alternately distributed along the length direction of the slit.

[0010] In some embodiments, the angle between the detection surface and the laser beam passing perpendicularly through the slit is less than 90°.

[0011] In some embodiments, the length of the photosensitive region of the light receiving component is greater than 15 mm along the length direction of the slit.

[0012] In some embodiments, the system further includes a one-dimensional galvanometer disposed in the optical path between the light source and the detector.

[0013] In some embodiments, the system further includes a flat-field focusing lens disposed in the optical path between the one-dimensional galvanometer and the detector. Attached Figure Description

[0014] The above and other objects, features, and advantages of embodiments of the present disclosure will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the present disclosure are illustrated in the drawings by way of example and not limitation.

[0015] Figure 1 An exemplary photoelectric detection system according to an embodiment of the present disclosure is shown.

[0016] Figure 2 A schematic diagram of an exemplary optical receiving component according to an embodiment of the present disclosure is shown.

[0017] Figure 3 A schematic diagram of the assembly of two silicon-based photomultiplier tube detectors according to an embodiment of the present disclosure is shown.

[0018] Figure 4 Several exemplary ways of forming a gap are shown.

[0019] Figure 5 Two photodetector combinations that cannot form gaps are shown.

[0020] Figure 6 A schematic diagram of receiving excitation light according to an embodiment of the present disclosure is shown.

[0021] In the various figures, the same or corresponding reference numerals indicate the same or corresponding parts. Detailed Implementation

[0022] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0023] The term "comprising" and its variations as used herein signify an open-ended inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "at least partially based on". The terms "one example embodiment" and "one embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". Terms such as "upper", "lower", "front", and "rear", indicating placement or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are used only for the purpose of describing the principles of this disclosure, and are not intended to indicate or imply that the elements referred to must have a specific orientation, be constructed or operated in a specific orientation, and therefore should not be construed as limiting this disclosure.

[0024] As mentioned earlier, with the explosive growth in demand for large-format imaging in fields such as semiconductor packaging and testing (wafers, memory chips, advanced packaging, and MEMS processes), industrial non-destructive testing, and large-size medical radiographic imaging, wide-format IP imaging boards, with their flexible, large-area coverage, and low-cost reusability, have broken the image size limitations of traditional small-format imaging media. They can simultaneously acquire information from large-field-of-view targets such as wafers, TSV vias, 3D chip packaging defects, MEMS device micromechanical structures, full-board weld seams, and full-frame limbs, becoming the core carrier for current large-area X-ray detection scenarios. In the readout detection stage adapted to wide-format IP boards, silicon-based photomultiplier tubes, with their unique advantages of high gain, low operating voltage, strong anti-magnetic interference, and compact size, perfectly avoid the pain points of traditional photomultiplier tubes, such as fragility, high-voltage drive, and inability to adapt to small integration spaces. They exhibit extremely high signal-to-noise ratio performance in the weak blue-violet light detection scenario of IP boards, significantly reducing the integration difficulty and usage threshold of the system. Meanwhile, constrained by the balance between semiconductor structure and performance, the effective detection area of ​​a single silicon-based photomultiplier tube detector is generally only on the order of a few millimeters. Unlike large-size photomultiplier tubes, it cannot achieve large-area coverage with a single device. When directly applied, it is prone to problems such as sampling blind spots, decreased spatial resolution, and uneven detection signal gain and response in the full-frame readout of wide-format IP boards. This contradiction has further spurred the demand for high-quality detection with high uniformity, no blind spots, and high dynamic range for wide-format IP images, becoming the core direction of current technological iteration in this field.

[0025] In view of this, according to the embodiments of the present disclosure, an optical detection system is provided, which is a high-precision optical detection system that enables the illumination beam to be incident on the target completely perpendicularly and the photodetector to be arranged coaxially with the illumination optical path.

[0026] Figure 1 An exemplary photoelectric detection system according to an embodiment of the present disclosure is shown. For example... Figure 1 As shown, the optical detection system 100 may include a light source 110, which outputs a collimated narrow-linewidth laser beam 111 as an excitation source for the latent image of the IP board, providing stable scanning illumination energy. In one or more embodiments of this disclosure, the light source may be a laser capable of emitting excitation light of a specific wavelength, such as a 635nm / 650nm / 670nm red semiconductor laser. Such light sources are small in size and have stable power, enabling precise excitation of the latent image fluorescence stored in the IP board, while avoiding direct laser beam interference into the photodetector, thus preventing environmental noise or even saturation. The photodetector system also includes a one-dimensional galvanometer 120, towards which the excitation light generated by the light source is emitted. The high-frequency oscillation of the galvanometer reflects the incident laser light into a uniformly scanning line spot. In one or more embodiments of this disclosure, the one-dimensional galvanometer may be a MEMS galvanometer, which, compared to a traditional mechanical galvanometer, is smaller in size and has higher repeatability. The optical detection system also includes a planar focusing lens 130, used to convert the dynamic scanning laser reflected by the one-dimensional galvanometer into a uniform vertical beam. In one or more embodiments of this disclosure, the planar focusing lens can be an F-theta field lens, which can ensure uniform scanning speed and consistent beam size, avoiding edge imaging distortion. The laser beam output by the planar focusing lens 130 can illuminate the IP plate (i.e., the detection target 200) to complete a unidirectional line-by-line scan of the IP plate. The optical detection system also includes a light receiving component 140. After the IP plate is exposed to X-rays, a latent image is formed. When the laser scans the IP plate as an excitation source, it excites the phosphorescent material inside the plate, releasing the stored X-ray energy in the form of blue-violet visible light. This weak light signal (i.e., excitation light 201) is accurately captured by the light receiving component 140 and converted into an electrical signal, ultimately generating a digital image.

[0027] Existing technologies often employ oblique incidence to avoid the photodetector itself blocking the incident light path. This involves the photodetector being offset to one side of the optical axis, with the illumination beam illuminating the target at a certain angle. Oblique incidence causes the illumination beam to deviate from ideal normal incidence conditions, introducing astigmatism and field curvature, reducing the quality and uniformity of the scan line spot on the target. Oblique incidence also reduces the coupling efficiency between the excitation light returning from the IP plate and the photosensitive surface of the photodetector, limiting the solid angle for collecting the target fluorescence signal. Furthermore, oblique incidence causes laser beam scan line distortion, elliptical spot degradation, and poor focusing characteristics, directly affecting system resolution and signal-to-noise ratio. Therefore, the inventors considered arranging the photodetector and illumination beam completely coaxially and perpendicularly to eliminate these drawbacks in principle. This requires creating an extremely narrow slit in the photodetector to allow the laser beam to pass vertically from directly above. However, directly hollowing out a long, narrow slit in a single large-area detector presents significant obstacles in terms of both manufacturing processes and reliability. Specifically, in common silicon-based photodetectors (such as CCD, CMOS, or APD arrays), the photosensitive layer and readout circuitry are precisely deposited layer by layer on a wafer. Etching a through-hole in the center of the chip would cut off surrounding circuit traces, disrupt the crystal lattice structure, and easily lead to microcracks and edge chipping, increasing dark current and failure risk, resulting in extremely low yields or even scrapping the entire wafer. Removing the photosensitive material would reduce the effective central photosensitive area, and large-area single-piece detectors have large junction capacitances, exhibiting significant distributed capacitance effects, which are detrimental to high-frequency response (the high-frequency response of a system corresponds to a high-resolution signal in space). Large-area silicon wafers are inherently brittle; a long slit in the middle creates a stress concentration point, making the chip highly susceptible to cracking at the slit during subsequent packaging, temperature changes, or even slight vibrations, significantly reducing reliability. Therefore, large-area single-piece detectors with slits are non-standard custom parts, costly, time-consuming, and prone to damage.

[0028] Ultimately, the inventors proposed a scheme using a combination of two photodetectors. In one or more embodiments of this disclosure, the light receiving component 140 may include a first photodetector 141 and a second photodetector 142, both of which include a detection surface 143 for receiving the excitation light. Figure 2 A schematic diagram of an exemplary optical receiving component according to an embodiment of the present disclosure is shown. Figure 2As shown, in one or more embodiments of this disclosure, the detection surface of each photodetector includes a rectangular photosensitive area 143a. In one or more embodiments of this disclosure, the first and second photodetectors of the light receiving assembly can be arranged alternately, such that a slit 144 is formed between the detection surfaces of the first and second photodetectors, allowing the laser beam 111 to pass through perpendicularly. The length direction 144c of the slit 144 should be parallel to the scanning path 112 so that the movement direction of the laser beam during dynamic scanning of the IP plate is consistent with the slit direction and will not be blocked. At least one edge of the slit is the photosensitive area of ​​the photodetector, thereby ensuring that there is a continuous photosensitive area on the detection surface to sense the excitation light 201 generated on the detection target 200. In this way, a high-precision optical detection system can be achieved where the illumination beam is completely perpendicular to the target and the photodetectors are coaxially arranged with the illumination optical path, while overcoming the detection blind zone formed by the gaps between multiple silicon-based photomultiplier tube detectors, realizing a large-area detection array without blind zones. Especially for silicon-based photomultiplier tube detectors, the embodiments of this disclosure can naturally form the required physical slits through external mechanical assembly alone, without affecting the integrity of the detector itself (no destructive processing of the photodetector is required), which can greatly improve reliability and yield. At the same time, using mass-produced standard detectors results in low cost, and individual replacement is possible in case of failure, making maintenance more economical and convenient.

[0029] In one or more embodiments of this disclosure, the first photodetector and the second photodetector may be silicon-based photomultiplier tube detectors (SiPM or MPPC). Due to limitations in semiconductor manufacturing processes, the effective detection area of ​​a single SiPM / MPPC device is generally only on the order of a few millimeters, which is much smaller than that of a 20-inch PMT. Therefore, it cannot be directly adapted to the large-area or large dynamic range detection requirements of wide-format imaging panels. Figure 3 This diagram illustrates the assembly of two silicon-based photomultiplier tube detectors according to an embodiment of the present disclosure. Figure 3As shown, in one or more embodiments of this disclosure, the first photodetector 141 and the second photodetector can be spliced ​​together 142 to achieve large-area detection. Photodetectors employing silicon-based photomultiplier tubes typically have a support on their detection surface for mounting light-collecting devices and filters. By mounting light-collecting devices, the fluorescence scattered in all directions by the excitation of the IP plate can be collected by a light-collecting mirror and enter the photosensitive area of ​​the silicon-based photomultiplier tube detector. The light-collecting effect is ensured by arranging the IP plate containing the excitation light at the focal length of the light-collecting mirror, while the red light from the light source is not reflected towards the detection surface, further reducing interference with weak fluorescence excitation light. By mounting a bandpass filter, only the characteristic fluorescence band emitted by the IP plate can be allowed to pass through, further filtering out ambient stray light and interference from reflected red laser light, improving the detection signal-to-noise ratio. However, the presence of the support will block the reception of the light beam, thus forming a non-photosensitive area 143b on the photodetector surface that cannot sense the excitation light. The support is usually placed on the shorter side of the rectangular photosensitive area 143a to minimize the impact on the photosensitive area. Therefore, in one or more embodiments of this disclosure, the slit 144 may be formed between the long side of the rectangular photosensitive area of ​​the first photodetector and the second photodetector to form a longer detection width.

[0030] The single large-area detector with a slit is designed so that the slit width is determined by the manufacturing process and cannot be adjusted later. To match different beam diameters or tolerances, the entire detector needs to be replaced. In one or more embodiments of this disclosure, the light receiving assembly may further include a slit width adjustment component for adjusting the slit width. In one or more embodiments of this disclosure, the first photodetector and the second photodetector can be mounted on the same bracket 145. The bracket may have multiple mounting positions (e.g., mounting holes, mounting tracks, etc.) for connecting and fixing the photodetectors. The mounting positions are distributed along the slit width direction. Different slit widths can be achieved by fixing the first and second photodetectors at different mounting positions. In one or more embodiments of this disclosure, the first and second photodetectors can be mounted at corresponding fixed positions on the bracket. A shim for fine-tuning the detector position can be provided between the fixed position and the photodetector. By selecting shims of different thicknesses, the distance between the two photodetectors can be adjusted, thereby adjusting the slit width. In this way, the slit width is determined by the mounting positions of the two photodetectors, and the width adjustment component can flexibly adapt to different beam diameters or tolerance requirements, reducing the difficulty of precision assembly.

[0031] Figure 4 Several exemplary ways of forming a gap are shown. For example... Figure 4As shown, in combination A, the long sides of the rectangular photosensitive areas of the first photodetector 141 and the second photodetector 142 can be aligned to form a longer slit 144. In combination A, the laser passes through the slit from a direction perpendicular to the view plane, enabling the illumination beam to be completely perpendicular to the target and the photodetectors to be arranged coaxially with the illumination optical path. However, since the long sides of the rectangular photosensitive areas of the two detectors are completely aligned, the detection length of the resulting light receiving assembly is the same as the detection length L of a single photodetector. In one or more embodiments of this disclosure, the detection length of a single photodetector can be 25 mm or more, allowing the photosensitive area length of the light receiving assembly to reach 25 mm, suitable for detecting wide-format IP images. The outputs of the first and second photodetectors can be connected in parallel to increase signal strength, or they can be amplified separately and then differentially processed for signal fusion, effectively suppressing common-mode noise and improving the signal-to-noise ratio.

[0032] like Figure 4 As shown, in combination B, the long sides of the rectangular photosensitive areas of the first photodetector 141 and the second photodetector 142 can be arranged alternately and parallel to each other to form a shorter slit 144. To ensure the continuity of the photosensitive area of ​​the light receiving component in the slit direction, the length of the staggered portion of the two photodetectors (i.e., the slit length) must be greater than the length of the non-photosensitive area of ​​either photodetector at one end of the overlap on its long side. For example, in the slit 144, at part 144a formed by the non-photosensitive area of ​​the second photodetector 142, although one edge is the non-photosensitive area of ​​the second photodetector, the other edge forming this part is the photosensitive area of ​​the first photodetector, thus ensuring the photosensitive continuity of the entire light receiving component at this position. Therefore, combination B not only achieves a completely perpendicular incident illumination beam on the target and coaxial arrangement of the photodetectors and the illumination light path, but also allows the detection length of the light receiving component in combination B to be much greater than the detection length L of a single photodetector, although it is less than the sum of the lengths of the long sides of the first and second photodetectors. The optical receiver assembly cascaded in this way has a detection length that is slightly less than the sum of the detection lengths of two photodetectors. The receiving area of ​​the optical receiver assembly obtained by splicing two 10mm*10mm photodetectors is comparable to the receiving area of ​​a single 20mm*20mm photodetector before it is hollowed out. However, because the receiving area of ​​a single photodetector in the optical receiver assembly is smaller and the junction capacitance is lower, a faster response speed can be obtained.

[0033] In one or more embodiments of this disclosure, the photoelectric receiving component can repeat the combination of the first photodetector and the second photodetector to achieve the cascading of three or more photodetectors, theoretically enabling an infinite extension of the detection length of the photoelectric receiving component. For example... Figure 4As shown, combination method C illustrates a combination of a light receiving assembly comprising four photodetectors. Of the four photodetectors, two are first photodetectors, and the remaining two are second photodetectors. The first photodetectors 141 and the second photodetectors 142 are alternately distributed along the length of the slit 144. The detection length of the cascaded light receiving assembly is approximately four times the detection length L of a single photodetector, minus the length of the detection surface at the pairwise intersections of the four photodetectors. Through the cascading methods of combination B or combination C, the length of the photosensitive area of ​​the light receiving assembly can reach 25 mm or more, thus enabling high-quality detection of wide-area IP interference.

[0034] Figure 5 Two photodetector combinations that cannot form a gap are shown. For example... Figure 5 As shown, in combination D, although the long sides of the rectangular photosensitive areas of the first photodetector 141 and the second photodetector 142 are arranged in an alternating, parallel pattern to form a shorter slit, the length of the alternating portion of the two photodetectors is too short (less than the length of the non-photosensitive area of ​​one of the photodetectors on its long side). This results in a situation where, at part 144b formed by the non-photosensitive area of ​​the second photodetector 142 in combination D, one edge is the non-photosensitive area of ​​the second photodetector, and the other edge is the non-photosensitive area of ​​the first photodetector. This prevents the entire light-receiving assembly from sensing excitation light at this location (photosensitive discontinuity), creating a detection "dead zone." Figure 5 As shown, in combination E, although the rectangular photosensitive areas of the first photodetector 141 and the second photodetector 142 are arranged side by side, and the long sides of the two photodetectors are on the same straight line, in combination D, the portion 144b formed by the non-photosensitive areas of the first photodetector 141 and the second photodetector 142 on this straight line cannot sense the excitation light (photosensitive discontinuity), forming a detection "dead zone".

[0035] Figure 6 A schematic diagram of the reception of excitation light according to an embodiment of the present disclosure is shown. Figure 6 As shown, after the target 200 (e.g., an IP board) is excited by the laser beam 111, the released excitation light 201 is fluorescence emitted in all directions. The detection surfaces of the first photodetector 141 and the second photodetector 142 are mounted facing the target, thereby sensing the excitation light and generating corresponding charged signals. In order to receive as much excitation light as possible from the target, in one or more embodiments of this disclosure, the angle A between the detection surface 143 and the optical axis of the laser beam 144 is less than 90°, which allows for the reception of more excitation light compared to a mounting method where the detection surface is perpendicular to the optical axis.

[0036] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An optical detection system (100), characterized in that, include: A light source (110) for emitting a laser beam (111) of a detection target (200), the laser beam being used to scan the detection target along a scanning path (112), causing the detection target to generate excitation light (201) at corresponding positions; and The light receiving component (140) includes a first photodetector (141) and a second photodetector (142). Both the first and second photodetectors include a detection surface (143) for receiving the excitation light. The detection surface includes a rectangular photosensitive area (143a). The first and second photodetectors are arranged at intervals such that a slit (144) is formed between the detection surfaces of the first and second photodetectors for the laser beam to pass through perpendicularly. The length direction of the slit is consistent with the scanning path, and at least one edge of the slit is the photosensitive area of ​​the photodetector.

2. The system according to claim 1, characterized in that, Both the first photodetector and the second photodetector are silicon-based dynamometer phototube detectors.

3. The system according to claim 2, characterized in that, The detection surface also includes a non-photosensitive area (143b) located on the short side of the photosensitive area, and the gap is formed between the long side of the rectangular photosensitive area of ​​the first photodetector and the long side of the rectangular photosensitive area of ​​the second photodetector.

4. The system according to claim 3, characterized in that, The length of the gap is less than the sum of the lengths of the long side of the first photodetector and the long side of the second photodetector, and greater than the length of the non-photosensitive area of ​​the first photodetector along its long side and the length of the non-photosensitive area of ​​the second photodetector along its long side.

5. The system according to any one of claims 1-4, characterized in that, The light receiving assembly also includes a slit width adjusting member for adjusting the width of the slit.

6. The system according to claim 5, characterized in that, The light receiving component includes one or more first photodetectors and one or more second photodetectors, and the first photodetectors and the second photodetectors are alternately distributed along the length direction of the slit.

7. The system according to claim 6, characterized in that, The angle between the detection surface and the laser beam passing perpendicularly through the slit is less than 90°.

8. The system according to claim 6, characterized in that, Along the length of the slit, the length of the photosensitive area of ​​the light receiving component is greater than 25 mm.

9. The system according to claim 6, characterized in that, It also includes a one-dimensional galvanometer (120) arranged in the optical path between the light source and the detector.

10. The system according to claim 9, characterized in that, It also includes a flat-field focusing lens (130) arranged in the optical path between the one-dimensional galvanometer and the detector.

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