CN115308131A - Photoelectric co-integration laser spectrum sensing technology and core module - Google Patents

Abstract

The invention discloses a photoelectric co-integrated laser spectrum gas sensing module, which comprises a circuit substrate, a photoelectric sensor and a sensor circuit, wherein the circuit substrate is integrated with the sensor circuit; a laser emitting unit coupled to the circuit substrate; a photoelectric detection unit coupled to the circuit substrate; the circuit substrate, the laser emission unit and the photoelectric detection unit form a sensor module with a complete detection function, and laser emitted by the laser emission unit penetrates through gas to be detected and is directly received by the photoelectric detection unit or is received by the photoelectric detection unit after being reflected. The structure of the laser emission unit and the photoelectric detection unit is simplified, complicated manual calibration is omitted, the photoelectric circuit and devices of the sensor are integrated on the circuit substrate, the integration level is higher, batch automatic production is facilitated, and the cost is effectively reduced; the core module is simplified, and the development difficulty of the laser spectrum gas sensor is reduced.

Description

Photoelectric co-integration laser spectrum sensing technology and core module

Technical Field

The invention relates to the field of laser spectrum gas sensing, in particular to a photoelectric co-integrated laser spectrum gas sensing module.

Background

Compared with the traditional gas detection methods (such as a combustion catalysis method, electrochemical detection and gas-sensitive semiconductor detection), the laser spectrum gas detection technology has the advantages of obvious advantages, higher performance and high reliability, is safe in detection process, strong in anti-interference capability, sensitive to only one gas, and widely applied to natural gas stations, pipe networks and natural gas users, especially in severe environments.

At present, the laser spectrum type gas sensor is mostly formed by integrating discrete devices of a TO-packaged DFB laser and a PIN photoelectric detector; the TO packaging DFB laser is internally provided with elements in a layering mode for mounting, a DFB laser chip is mounted on a heat sink in an eutectic way, the heat sink is pasted on the surface of a TEC by using silver glue with good heat conductivity, the TEC is pasted on the surface of a TO tube seat by using the silver glue, the chip and the TEC are connected with a TO seat pin by gold wire bonding, and a sealing cap is welded after a ball cap with an optical lens is aligned; for the TO packaged PIN photoelectric detector, firstly, a PIN photoelectric chip is attached TO a heat sink in an eutectic way, the chip is connected with a TO base PIN by adopting a gold wire bonding process, and a sealing cap is welded after a ball cap with an optical lens is aligned.

The existing laser spectrum type gas sensor generally comprises a TO packaging laser, a TO packaging PIN photoelectric detector, collimating convergence optics, a multi-reflection absorption gas chamber, a circuit part and a mechanical structure; the laser spectrum gas sensor based on the discrete photoelectric device has the defects of low integration level, complex process, difficulty in realizing automatic assembly and incapability of realizing batch production, so that the laser spectrum gas sensor is high in cost and cannot be popularized and applied in a large scale.

Based on the consideration, the system design scheme needs to be innovated, so that the integration, miniaturization and automatic assembly of the laser spectrum type gas sensor are realized, the production efficiency is improved, the cost is reduced, the wide application of the laser spectrum gas sensor is finally promoted, and the construction and production of the laser spectrum gas detection system are simplified.

Disclosure of Invention

In view of the defects of the existing laser spectrum sensing technology and modules, the invention provides a photoelectric co-integrated laser spectrum gas sensing module which can improve the integration level of a laser spectrum gas sensor, reduce the size of the sensor, reduce the power consumption, reduce the development difficulty of the laser spectrum gas sensor, facilitate batch automatic production and improve the production efficiency.

In order to achieve the above purpose, the embodiment of the invention adopts the following technical scheme:

a photoelectric co-integrated laser spectrum gas sensing module comprises a circuit substrate, a sensor circuit and a photoelectric sensor, wherein the sensor circuit is integrated on the circuit substrate; a laser emitting unit coupled to the circuit substrate; a photoelectric detection unit coupled to the circuit substrate; the circuit substrate, the laser emission unit and the photoelectric detection unit form a sensor module with a complete detection function, and laser emitted by the laser emission unit passes through a gas to be detected and is directly received by the photoelectric detection unit or is received by the photoelectric detection unit after being reflected.

In practical application, the circuit substrate can be fixedly connected with the air chamber housing to form an air chamber with a hollow cavity; the air chamber is of a correlation type or a reflection type.

The laser emission unit comprises a DFB laser chip, a TEC and a first heat sink; the DFB laser chip is attached to one side of the TEC through conductive adhesive eutectic with good heat conductivity; the other side of the TEC is connected to one side of the first heat sink through conductive glue; the other side of the first heat sink is adhered to the surface of the circuit substrate through conductive glue;

the laser emission unit further comprises a first transfer substrate; the TEC can be not directly bonded with the circuit substrate, but the TEC is bonded on the first transfer substrate firstly, then the first transfer substrate is bonded on the circuit substrate, laser emitted by the DFB laser chip is emitted from the side face, namely the laser is emitted in parallel to the circuit substrate, and a 45-degree reflecting prism is arranged beside the DFB laser chip, so that the side face emission is changed into vertical emission, namely the laser is emitted in perpendicular to the circuit substrate.

The photoelectric detection unit comprises a photoelectric detector chip and a second heat sink; the photoelectric detector chip is attached to one side of the second heat sink through conductive adhesive eutectic; the other side of the second heat sink is adhered to the surface of the circuit substrate through conductive glue; the photoelectric detector chip can adopt horizontal mounting or vertical mounting, and when the horizontal mounting is adopted, the detection surface of the photoelectric detector chip is parallel to the circuit substrate; when the vertical mounting is adopted, the detection surface is vertical to the circuit substrate.

The photoelectric detection unit further comprises a second switching substrate; the second heat sink may not be directly adhered to the circuit substrate, but the second heat sink is adhered to the second interposer substrate first, and then the second interposer substrate is adhered to the circuit substrate.

In order to reduce the influence of the external environment on the DFB laser chip and the photoelectric detector chip, a sealing optical window is arranged on the surfaces of the laser emission unit and the photoelectric detection unit, the sealing optical window is glued on the circuit substrate under the atmosphere of dry air or nitrogen, and the laser emission unit or the photoelectric detection unit is sealed between the sealing optical window and the circuit substrate.

When the air chamber is in a correlation type, the laser emission unit and the photoelectric detection unit are arranged at two ends of the air chamber in an opposite mode, laser emitted by a DFB laser chip of the laser emission unit is emitted from the side face, and a photoelectric detector chip is pasted and mounted vertically; the laser emitted by the laser emitting unit is directly received by the photoelectric detection unit; the receiving, sending and registering of the laser emitting unit and the photoelectric detection unit can be automatically controlled and completed by an automatic chip mounter when a chip is mounted.

When the air chamber is of a reflection type, the laser emission unit and the photoelectric detection unit are arranged on the same side of the air chamber, and a reflector is arranged on the other side of the air chamber; a 45-degree prism is arranged beside a DFB laser chip of the laser emission unit, laser emitted by the laser emission unit is vertically emitted, and a photoelectric detector chip is horizontally mounted; the emitted laser is reflected by the reflector and then received by the photoelectric detection unit.

The sensor circuit at least comprises a preamplifier circuit, a laser drive circuit, a TEC temperature control circuit, an AD signal acquisition circuit, an MCU control chip, a signal processing circuit, a temperature sensor, an air pressure sensor, a power chip and a communication interface circuit; the sensor circuit can adopt discrete devices, is attached to the circuit substrate through an automatic chip mounter, can effectively reduce the cost, improves the integration level of the laser spectrum gas sensor, and is convenient for batch and rapid production.

The circuit substrate adopts an FR4 substrate or a ceramic substrate, the bonding parts of the circuit substrate, the laser emission unit and the photoelectric detection unit are provided with copper exposure windows, tin spraying treatment is not carried out on the window-opening parts or a gold plating process is adopted, the heat of the laser emission unit and the photoelectric detection unit can be rapidly conducted to the circuit substrate, meanwhile, the smoothness of bonding points can be guaranteed, and the assembly error is reduced.

The implementation of the invention has the advantages that:

the structure of the laser reflection unit and the photoelectric detection unit is simplified, complex collimation and calibration are avoided, a high-precision lens group is not needed, the structure is simpler, and the receiving, transmitting and registering can be performed through automatic control of an automatic chip mounter; the sensor circuit is integrated on the circuit substrate, so that the size of the module is reduced, the power consumption is reduced, the cost is reduced, and the mass production is facilitated; the circuit substrate, the laser emission unit and the photoelectric detection unit can form a sensor module with complete functions, the development difficulty of the laser spectrum gas sensor is reduced, and the wide popularization and application of the sensor are facilitated.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of a conventional laser spectroscopy gas sensor;

fig. 2 is a schematic structural diagram of the side-emitting laser emitting unit according to the first embodiment of the present invention;

fig. 3 is a schematic structural diagram of the vertical emission laser emitting unit according to the first embodiment of the present invention;

fig. 4 is a schematic structural diagram of the horizontal mounted photodetecting unit according to the first embodiment of the present invention;

fig. 5 is a schematic structural diagram of a vertical-type mounted photodetecting unit according to a first embodiment of the present invention;

fig. 6 is a schematic structural diagram of the transceiver unit according to an embodiment of the present invention;

FIG. 7 is a schematic structural diagram of the correlation plenum according to one embodiment of the present invention;

FIG. 8 is a schematic structural diagram of the vertical single reflection type gas chamber according to one embodiment of the present invention;

FIG. 9 is a schematic structural view of a horizontal single reflection type gas chamber according to a second embodiment of the present invention;

FIG. 10 is a first logic block diagram of the sensor circuit according to one embodiment of the present invention;

fig. 11 is a logic block diagram of the sensor circuit according to the first embodiment of the invention.

Illustration of the drawings: 1. a circuit board; 11. a sensor circuit; 2. a laser emitting unit; 21. a laser chip; 22. a first heat sink; 23. a refrigerator; 24. a first transfer substrate; 25. a 45-degree reflecting prism; 3. a photodetecting unit; 31. a photodetector chip; 32. a second heat sink; 33. a second transfer substrate; 4. an air chamber housing; 5. a mirror; 6. sealing the optical window; 7. a laser transmitting and receiving spacer; 8. and a transmitting and receiving adapter plate.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example one

As shown in fig. 2, fig. 3, fig. 4 and fig. 5, a photo-voltaic co-integrated laser spectrum gas sensing module includes a circuit substrate 1 integrated with a sensor circuit 11; a laser emitting unit 2 coupled to the circuit substrate 1; a photodetection unit 3 coupled to the circuit substrate 1; the circuit substrate 1, the laser emission unit 2 and the photoelectric detection unit 3 form a sensor module with a complete detection function, and laser emitted by the laser emission unit 2 passes through gas to be detected and is directly received by the photoelectric detection unit 3 or is received by the photoelectric detection unit 3 after being reflected.

The circuit substrate 1 is fixedly connected with a gas chamber cover 4 to form a gas chamber with a hollow cavity, and the gas chamber is designed in a correlation mode or a reflection mode.

The laser emission unit 2 includes a laser chip 21, a refrigerator 23, and a first heat sink 22; in this embodiment, the laser chip 21 adopts a DFB laser chip, where DFB is an abbreviation of Distributed Feedback, that is, a Distributed Feedback laser, and belongs to a semiconductor laser, and its electro-optical conversion efficiency is higher than that of a conventional solid laser and a conventional fiber laser, but a large amount of heat is still generated during operation, and if the temperature of a chip with poor heat dissipation rises, the normal operation of the chip is affected, and the reliability and the lifetime of the chip are reduced;

in practical application, the refrigerator adopts a TEC (thermoelectric cooler), wherein the TEC is a semiconductor refrigerator and is used for radiating heat for the DFB laser chip and comprises a cold end and a hot end, and the cold end refrigerates and the hot end heats when the DFB laser chip is electrified; heat sinks are essentially micro heat sinks applied to electronic chips for fast dispersion of conductive heat, and alternative heat sink materials include, but are not limited to, molybdenum copper, tungsten copper, CMCC (copper-molybdenum copper-copper), and CMC (copper-molybdenum-copper) materials;

in practical application, the DFB laser chip is attached to one side of the first heat sink 22 through conductive adhesive with good thermal conductivity; the other side of the first heat sink 22 is connected to the cold end of the TEC through conductive glue; the hot end of the TEC is adhered to the surface of the circuit substrate 1 through conductive adhesive; the conductive adhesive may be selected from, but not limited to, silver adhesive.

Optionally, the TEC may also be bonded to the first interposer substrate 24 instead of being directly bonded to the circuit substrate 1, and then the first interposer substrate 24 is mounted on the circuit substrate 1, at this time, the laser emitted from the DFB laser chip is emitted from a side surface, that is, the laser is emitted parallel to the circuit substrate 1, and the 45 ° reflective prism 25 is disposed beside the DFB laser chip, so that the side surface emission is changed into a vertical emission, that is, the laser is emitted perpendicular to the circuit substrate 1.

In practical application, the photo-detection unit 3 includes a photo-detector chip 31 and a second heat sink 32; the photodetector chip 31 may be a PIN photodetector chip, and may convert an optical signal into an electrical signal; the second heat sink 32 has a similar function to the first heat sink 22, and may be made of the same material, because the heat generation amount of the photodetector chip 31 is small, the material with slightly poor heat dissipation performance but low cost may also be used; the photoelectric detector chip 31 is attached to one side of the second heat sink 32 through conductive adhesive eutectic; the other side of the second heat sink 32 is adhered to the surface of the circuit substrate 1 through conductive glue; the photoelectric detector chip 31 can adopt horizontal mounting or vertical mounting, and when the horizontal mounting is adopted, the detection surface of the photoelectric detector chip 31 is parallel to the circuit substrate 1; when the vertical mounting is adopted, the detection surface is perpendicular to the circuit substrate 1.

Alternatively, the second heat sink 32 may not be directly bonded to the circuit substrate 1, but the second heat sink 32 is now bonded to the second relay substrate 33, and the second relay substrate 33 is bonded to the circuit substrate 1.

When the air chamber is in a correlation type, the laser emission unit 2 and the photoelectric detection unit are oppositely arranged at two ends of the 3-position air chamber, laser emitted by the DFB laser chip of the laser emission unit 2 is emitted from the side surface, and the photoelectric detector chip 31 is vertically mounted; the laser emitted by the laser emitting unit 2 is directly received by the photoelectric detection unit 3; the receiving, sending and registering of the laser emitting unit 2 and the photoelectric detection unit 3 can be automatically controlled and completed by an automatic chip mounter when a chip is mounted.

When the air chamber is of a reflection type, the laser emission unit 2 and the photoelectric detection unit 3 are arranged on the same side of the air chamber, and a reflector 5 is arranged on the other side of the air chamber; a micro collimating lens and a 45-degree prism (adhered to the first heat sink 22) are arranged beside the light-emitting side surface of the DFB laser chip of the laser emission unit 2, and laser emitted by the laser emission unit 2 is emitted to a reflector after being collimated and passing through the 45-degree prism; or the emitted laser is emitted through the 45-degree prism, then enters the micro collimating lens bonded on the circuit substrate 1 to be collimated and then is emitted to the reflector, and the photoelectric detector chip 31 is horizontally mounted; the emitted laser light is reflected by the mirror 5 and then received by the photodetection unit 3.

In order to reduce the influence of the external environment on the DFB laser chip and the photoelectric detector chip 31, the surfaces of the laser emission unit 2 and the photoelectric detection unit 3 are provided with sealed optical windows 6; the sealed optical window 6 is glued on the circuit substrate 1 in the atmosphere of dry air or nitrogen, and the laser emission unit 2 or the photoelectric detection unit 3 is sealed between the sealed optical window 6 and the circuit substrate 1; in the correlation type air chamber, the laser emission unit 2 and the photoelectric detection unit 3 adopt independent optical windows; in the reflective optical window, the laser emission unit 2 and the photoelectric detection unit 3 can be closely packaged, and a laser transceiving spacer 7 (used for blocking light directly emitted from the laser emission unit 2 to the photoelectric detection unit 3) is arranged between the laser emission unit 2 and the photoelectric detection unit 3 to form a laser transceiving unit, and the laser transceiving unit is sealed by adopting the same sealed optical window 6.

The sensor circuit 11 at least comprises a preamplification circuit, a laser driving circuit, a refrigerator temperature control circuit, an AD signal acquisition circuit, an MCU control chip, a signal processing circuit, a temperature sensor, an air pressure sensor, a power supply chip and a communication interface circuit; the pre-amplification circuit is used for amplifying the weak signal converted by the photoelectric detector chip; the laser driving circuit is used for driving the laser chip; the temperature control circuit of the refrigerator is usually linked with the temperature sensor and is used for controlling the operation of the refrigerator (TEC in the embodiment) to achieve the temperature regulation and control, so that the sensing module is prevented from being overhigh in temperature due to the heating of the laser chip and the normal operation of the whole module is not influenced; the AD signal acquisition circuit can convert the analog signal converted by the photoelectric detection unit into a digital signal so as to facilitate the subsequent signal processing circuit to process, wherein the processing comprises but is not limited to digital filtering, frequency domain conversion, synthesis and the like; the MCU control chip is responsible for controlling the operation of the circuit or the device;

the sensor circuit 11 can adopt discrete devices, and is attached to the back surface of the circuit substrate 1 through an automatic chip mounter (the surface where the air chamber housing 4, the laser emission unit 2 and the photoelectric detection unit 3 are located is the front surface of the circuit substrate 1), so that the cost can be effectively reduced, the integration level of the laser spectrum gas sensor is improved, and the batch rapid production is facilitated;

particularly, considering that the registration of the laser emitting unit and the photoelectric detection unit 3 is realized through automatic assembly of a machine, the possibility of error is existed, considering the energy attenuation after the laser works for a long time, the possible light path pollution attenuation and other conditions, the change range of the signal received by the photoelectric detection unit 3 is enlarged, therefore, the pre-amplification circuit adopts AGC two-stage automatic gain control, and the large dynamic range fluctuation change of the laser signal is adapted.

Preferably, a TDLAS special chip integrating the functions of the front-end amplification, the laser driving, the refrigerator temperature control circuit, the AD acquisition, the MCU control and the signal processing circuit is adopted to replace the discrete devices and is attached to the back of the circuit substrate 1, so that the volume of a core module is reduced, and the power consumption is reduced; under the condition of not influencing the light paths in the laser emission unit 2, the photoelectric detection unit 3 and the air chamber, the resistance-capacitance device can also be placed on the front surface of the circuit substrate 1, so that convenience is provided for the circuit wiring design on the back surface of the circuit substrate 1.

The circuit substrate 1 adopts an FR4 substrate or a ceramic substrate, the bonding positions of the circuit substrate, the laser emission unit 2 and the photoelectric detection unit 3 are provided with copper exposure windows, tin spraying treatment is not carried out on the window opening positions or a gold plating process is adopted, the heat of the laser emission unit 2 and the photoelectric detection unit 3 can be rapidly conducted to the circuit substrate 1, meanwhile, the smoothness of bonding points can be guaranteed, and the assembly error is reduced.

Optionally, the circuit substrate 1 may not be matched with the air chamber housing 4, and the circuit substrate 1, the laser emission unit 2 and the photoelectric detection unit 3 directly form a laser spectrum gas sensor core module with a complete function.

Example two

The biggest difference between the embodiment and the embodiment is that the laser emission unit 2 and the photoelectric detection unit 3 are close to and integrated on a transceiving adapter plate 8, the transceiving adapter plate 8 is arranged perpendicular to the circuit substrate 1 to form an L-shaped structure, and the receiving and transmitting device further comprises an air chamber housing 4 arranged in an L shape; the receiving and transmitting adapter plate 8, the circuit substrate 1 and the air chamber housing 4 form an air chamber with a hollow cavity.

The implementation of the invention has the advantages that:

the structure of the laser reflection unit and the photoelectric detection unit is simplified, complex collimation and calibration are avoided, a high-precision lens group is not needed, the structure is simpler, and the receiving, transmitting and registering can be performed through automatic control of an automatic chip mounter; the sensor circuit is integrated on the circuit substrate, so that the size of the module is reduced, the power consumption is reduced, the cost is reduced, and the mass production is facilitated; circuit substrate, laser emission unit and photoelectric detection unit can constitute the sensor module that has complete function, have reduced the development degree of difficulty of laser spectrum gas sensor, are convenient for the extensive popularization and application of this type of sensor.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed herein are intended to be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (10)

1. The gas sensing module is characterized by comprising a circuit substrate (1) integrated with a sensor circuit (11); a laser emitting unit (2) coupled to the circuit substrate (1); a photodetection unit (3) coupled to the circuit substrate (1); the laser emitted by the laser emitting unit (2) is received by the photoelectric detection unit (3) directly or after being reflected.

2. The optical-electrical co-integrated laser spectroscopy gas sensing module according to claim 1, further comprising a gas chamber housing (4); the circuit substrate (1) is fixedly connected with the air chamber housing (4) to form an air chamber with a hollow cavity; the air chamber is of a correlation type or a reflection type.

3. The optical-electrical co-integrated laser spectroscopy gas sensing module according to claim 1, wherein the laser emission unit (2) comprises a laser chip (21), a first heat sink (22) and a refrigerator (23); the laser chip (21) is attached to one side of the heat sink in an eutectic way; the other side of the heat sink is bonded to one side of the refrigerator (23); the other side of the refrigerator (23) is adhered to the surface of the circuit substrate (1).

4. The optoelectronic co-integrated laser spectroscopy gas sensing module according to claim 3, wherein the laser emission unit (2) further comprises a first adapter substrate (24); the refrigerator (23) is connected with the circuit substrate (1) through a first adapter substrate (24).

5. The optoelectronic co-integrated laser spectroscopy gas sensing module according to claim 1, wherein the photodetecting unit (3) comprises a photodetector chip (31) and a second heat sink (32); the photoelectric detector chip (31) is attached to one side of the second heat sink (32) in an eutectic way; the other side of the second heat sink (32) is adhered to the surface of the circuit substrate (1).

6. The optical-electrical co-integrated laser spectroscopy gas sensing module according to claim 5, wherein the photodetecting unit (3) further comprises a second relay substrate (33); the second heat sink (32) is connected with the circuit substrate (1) through a second adapter substrate (33).

7. The optical-electrical co-integrated laser spectrum gas sensing module according to any one of claims 1 to 6, wherein when the gas chamber is of a correlation type, the laser emission unit (2) and the photoelectric detection unit (3) are located at two ends of the gas chamber and are arranged oppositely, and the laser emitted by the laser emission unit (2) is directly received by the photoelectric detection unit (3); and sealing optical windows (6) are arranged on the surfaces of the laser emission unit (2) and the photoelectric detection unit (3).

8. The optical-electrical co-integrated laser spectrum gas sensing module according to any one of claims 1 to 6, wherein when the gas chamber is of a reflective type, the laser emission unit (2) and the photoelectric detection unit (3) are disposed on the same side of the gas chamber, and a reflector (5) is disposed on the other side of the gas chamber; the laser emitted by the laser emitting unit (2) is reflected by the reflector (5) and then received by the photoelectric detection unit (3); and sealing optical windows (6) are arranged on the surfaces of the laser emission unit (2) and the photoelectric detection unit (3).

9. The optical-electrical co-integrated laser spectroscopy gas sensing module according to claim 1, wherein the sensor circuit (11) comprises at least a pre-amplification circuit, a laser driving circuit, a refrigerator temperature control circuit, an AD signal acquisition circuit, an MCU control chip, a signal processing circuit, a temperature sensor, a pressure sensor, a power chip and a communication interface circuit.

10. The optical-electrical co-integrated laser spectroscopy gas sensing module according to claim 1, wherein the circuit substrate (1) is an FR4 substrate or a ceramic substrate, and copper-exposed windows are arranged at the bonding positions of the circuit substrate, the laser emission unit (2) and the photoelectric detection unit (3).

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