CN111579069B - Spectrum self-calibration grating and spectrometer - Google Patents

Abstract

The invention discloses a spectrum self-calibration grating and a spectrometer, wherein the spectrum self-calibration grating comprises a micro grating and a correction mark. The micro-grating and the calibration mark are irradiated by the light beam to form a diffraction pattern and a calibration pattern on the imaging surface respectively. And correcting the spectrum of the diffraction pattern according to the distance between the diffraction pattern and the correction pattern.

Description

Spectrum self-calibration grating and spectrometer

Technical Field

The present invention relates to a grating and a spectrometer, and more particularly, to a spectral self-calibration grating and a spectrometer using the same.

Background

Spectral analysis includes advantages such as non-destructive, chemical discrimination, wavelength-shift, high sensitivity, and fast analysis speed, and thus the demand for analyzing various photophysical phenomena or photochemical phenomena of materials using spectrometers has been increasing in recent years.

The spectrometer mainly performs light splitting through a light splitting element, receives light beams from the light splitting element through a light receiver, and obtains corresponding spectrums through back-end operation. In recent years, mobile devices with computing and photographing functions have become more popular, and if a spectrometer can be integrated with a mobile device, the integration of the spectrometer and the mobile device will contribute to reducing the production cost and promoting the popularization of applications, and has a great potential for market development of portable spectrometers in the future.

The prior art proposes a portable spectrometer formed by a disc grating and a mobile phone, but the spectrometer has many problems. For example, when the light intensity of the incident light is too high, the light intensity of the different color light intercepted by the light receiver may be oversaturated, resulting in too large a correction error. In addition, since the optical disc grating is too simple and cannot be accurately split, the image intercepted by the optical receiver is blurred, and the spectral position information cannot be correctly determined, so that an incorrect spectrogram is generated.

Based on the above, how to reduce the correction error and improve the accuracy of determining the spectral position information becomes a problem that researchers in this field want to solve.

Disclosure of Invention

The invention provides a spectrum self-calibration grating which is beneficial to reducing correction errors and improving the accuracy of judging spectrum position information.

The invention provides a spectrometer which can effectively correct a spectrum and judge spectral position information.

The spectrum self-calibration grating comprises a micro grating and a correction mark. The micro-grating and the calibration mark are irradiated by the light beam to form a diffraction pattern and a calibration pattern on the imaging surface respectively. And correcting the spectrum of the diffraction pattern according to the distance between the diffraction pattern and the correction pattern.

A spectrometer of the present invention includes a spectral self-calibration grating and an optical receiver. The spectral self-calibration grating comprises a micro-grating and a correction mark. The micro-grating and the calibration mark are irradiated by the light beam to form a diffraction pattern and a calibration pattern on the imaging surface of the light receiver. And correcting the spectrum of the diffraction pattern according to the distance between the diffraction pattern and the correction pattern.

In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

FIG. 1 is a schematic diagram of a spectrometer according to an embodiment of the invention;

FIG. 2 is a bottom view of the spectral self-alignment grating of FIG. 1;

FIGS. 3A-3D and 3E-3H are flow charts of the fabrication of the spectrally self-aligned grating of FIG. 2 along line A-A 'and line B-B', respectively;

FIG. 4 is a schematic cross-sectional view of a spectrometer according to another embodiment of the present invention;

FIG. 5 is a flow chart of a calibration operation of the spectrometer of FIG. 4;

FIG. 6 is a graph of wavelength versus light intensity, showing the spectra before and after calibration.

Description of the reference numerals

1. 2: a spectrometer;

10: spectrum self-calibration grating;

11: an optical receiver;

12: a housing;

13: a collimating element;

14: a focusing element;

51. 52, 53, 54, 55: a step of;

100: a micro grating;

101: correcting the mark;

102. SUB, SUB': a substrate;

103. 103': an optical layer;

104: a light-shielding layer;

110: an imaging plane;

120. 1030: a slit;

1031: a groove;

1040: opening a hole;

B. b1, B2: a light beam;

D. d11, D12, D13: a distance;

p and P': a pattern;

PC: correcting the pattern;

PD: a diffraction pattern;

PD0: a 0 th order diffraction pattern;

PD1, PD11, PD12, PD13: a 1 st order diffraction pattern;

r: calibrating the sensing region;

s1, S2: a surface;

x, Y: direction;

θ: an included angle;

A-A ', B-B': and (6) cutting the line.

Detailed Description

Directional terms as used in the description of the embodiments, such as: "upper", "lower", "front", "rear", "left", "right", etc., refer only to the orientation of the figures. Accordingly, the directional terminology is used for purposes of illustration and is in no way limiting. In the drawings, each drawing illustrates generally the features of methods, structures, and/or materials used in certain exemplary embodiments. These drawings, however, should not be construed as limiting or restricting the scope or nature covered by these exemplary embodiments. For example, the relative dimensions, thicknesses, and locations of various layers, regions, and/or structures may be reduced or exaggerated for clarity.

In the embodiments, the same or similar elements will be denoted by the same or similar reference numerals, and the detailed description thereof will be omitted. Furthermore, the features of the different exemplary embodiments may be combined with each other without conflict and simple equivalent changes and modifications made in the present specification or claims may still fall within the scope of the present patent. In addition, the terms "first", "second", and the like in the description or the claims are only used for naming discrete (discrete) elements or distinguishing different embodiments or ranges, and are not used for limiting the upper limit or the lower limit of the number of elements, nor for limiting the manufacturing order or the arrangement order of the elements.

Fig. 1 is a schematic diagram of a spectrometer 1 according to an embodiment of the invention. Fig. 2 is a bottom view of the spectral self-alignment grating 10 of fig. 1. Referring to fig. 1 and 2, the spectrometer 1 includes a spectrum self-calibration grating 10 and an optical receiver 11. The spectral self-calibration grating 10 includes a micro-grating 100 and a correction mark 101. The micro-grating 100 and the calibration mark 101 are irradiated with the light beam B to form a diffraction pattern PD and a calibration pattern PC on the imaging surface 110 of the optical receiver 11. The spectrum of the diffraction pattern PD is corrected based on the distances (e.g., distance D11, distance D12, distance D13) between the diffraction pattern PD (e.g., the 1 st order diffraction pattern PD1 of the diffraction pattern PD) and the correction pattern PC.

In detail, the micro-gratings 100 in the spectrum self-calibration grating 10 are adapted to spread out light of different wavelengths (also referred to as different color light) in a light beam B (e.g. white light) in space (e.g. in the direction X). Specifically, each color light passes through the micro-grating 100 to form diffraction patterns from a 0 th order diffraction pattern to an nth order diffraction pattern, where n is an integer, such as ± 1, ± 2 \8230, and the larger the absolute value of n, the farther from the 0 th order diffraction pattern and the weaker the light intensity. For convenience of explanation, n =1 is given as an example, but the present invention is not limited thereto.

According to the diffraction principle, the 0 th order diffraction patterns of different color lights are imaged at the same position (in fig. 1, the 0 th order diffraction pattern PD0 represents the integration of the 0 th order diffraction patterns of different color lights), and the distance between the same order diffraction pattern of different color lights and the 0 th order diffraction pattern PD0 is positively correlated with the wavelength of the color light. In other words, the distance between the 1 st order diffraction pattern and the 0 th order diffraction pattern PD0 of the light beam with a longer wavelength is greater than the distance between the 1 st order diffraction pattern and the 0 th order diffraction pattern PD0 of the light beam with a shorter wavelength.

In fig. 1, the 1 st order diffraction pattern PD1 represents the integration of 1 st order diffraction patterns of different color lights, and fig. 1 schematically illustrates the 1 st order diffraction pattern PD11 of red light, the 1 st order diffraction pattern PD12 of green light, and the 1 st order diffraction pattern PD13 of blue light. Since the wavelength of red light is longer than that of green light, and the wavelength of green light is longer than that of blue light, the distance D11 between the 1 st-order diffraction pattern PD11 and the 0 th-order diffraction pattern PD0 is longer than the distance D12 between the 1 st-order diffraction pattern PD12 and the 0 th-order diffraction pattern PD0, and the distance D12 between the 1 st-order diffraction pattern PD12 and the 0 th-order diffraction pattern PD0 is longer than the distance D13 between the 1 st-order diffraction pattern PD13 and the 0 th-order diffraction pattern PD 0.

Since the 1 st order diffraction patterns (e.g., the 1 st order diffraction pattern PD11, the 1 st order diffraction pattern PD12, or the 1 st order diffraction pattern PD 13) of different color lights are imaged at different positions on the light receiver 11, by setting the position of the imaging surface 110 of the light receiver 11 to overlap at least the position of the 1 st order diffraction pattern PD1, the information of the relative position-light intensity of the spectrum can be derived from the information of the position-light intensity of the light receiver 11 (including the light intensity corresponding to each position of the light receiver 11 and the distance between the 1 st order diffraction patterns of different color lights).

However, the light intensity of the 0 th order diffraction pattern PD0 (i.e., the sum of the light intensities of the 0 th order diffraction patterns of different color lights) is much higher than the light intensity of any of the 1 st order diffraction patterns (e.g., the 1 st order diffraction pattern PD11, the 1 st order diffraction pattern PD12, or the 1 st order diffraction pattern PD 13). In the structure without the calibration mark 101, if the position of the image forming surface 110 of the optical receiver 11 is set to overlap the position of the 0 th order diffraction pattern PD0 in addition to the position of the 1 st order diffraction pattern PD1, the light intensity captured by the optical receiver 11 is easily oversaturated, and the light intensity of the 1 st order diffraction pattern of different color light cannot be effectively recognized, and the spectrum cannot be calibrated. On the other hand, if the position of the imaging surface 110 of the optical receiver 11 is set so as not to overlap the position of the 0 th order diffraction pattern PD0 (for example, so as to overlap only the position of the 1 st order diffraction pattern PD 1) in order to avoid the supersaturation of the light intensity intercepted by the optical receiver 11, the information of the position-light intensity obtained by the optical receiver 11 does not include the distance between the 1 st order diffraction pattern of different color light and the 0 th order diffraction pattern PD 0. Due to the lack of the reference position, the spectrometer can only obtain relative position information of the spectrum, but cannot obtain absolute position information of the spectrum (that is, the actual wavelength corresponding to each light intensity cannot be known). As a result, when the spectrometer is affected by environmental changes and produces an erroneous (shifted) spectrogram, it is difficult to correct the spectrum correctly.

In the present embodiment, the position of the imaging surface 110 of the light receiver 11 is set to overlap with the position of the 0 th order diffraction pattern PD0 in addition to the position of the 1 st order diffraction pattern PD1 to obtain absolute position information of the spectrum. In addition, the light intensity at which the 0 th order diffraction pattern PD0 is located is reduced by the arrangement of the correction mark 101 to improve the problem of light intensity supersaturation.

In detail, the size of the calibration mark 101 is designed to prevent diffraction of the light beam B. For example, the size (e.g., width and length) of the calibration marks 101 is greater than 10 microns. In this way, the light beam B1 passes through the calibration mark 101 to form a calibration pattern PC (e.g., a shadow having a shape corresponding to the calibration mark 101) on the imaging surface 110 of the light receiver 11. Since the calibration pattern PC and the 0 th order diffraction pattern PD0 formed on the imaging surface 110 of the optical receiver 11 by the light beam B1 passing through the micro-grating 100 are located in the calibration sensing region R, the light intensity of the 0 th order diffraction pattern PD0 can be greatly reduced, so that the light intensity of the 1 st order diffraction pattern (including the 1 st order diffraction pattern PD11, the 1 st order diffraction pattern PD12, and the 1 st order diffraction pattern PD 13) of each color light can be effectively identified. Further, the center of the correction pattern PC may be used as a reference position. Since the distance D between the image plane 110 and the micro grating 100 (e.g., the distance required for the light beam to pass through the micro grating 100 and then focus on the image plane 110), the specification of the micro grating 100 (e.g., how many slits per cm, such as 200, 300, or 600 slits per cm, but not limited thereto), the angle θ between the 1 st order diffracted light beam (e.g., the light beam B2) and the light beam (the light beam B1) passing through the micro grating 100 and the calibration mark 101 have a dependency relationship, the absolute position information of the spectrum and the light intensity corresponding to each absolute position (wavelength) can be obtained by using the distances between the 1 st order diffraction patterns of different color lights and the reference position (e.g., the distance D11, the distance D12, and the distance D13).

As a result, the spectrometer 1 is less susceptible to saturation of light intensity, and can measure absolute spectra in different light measurement situations, and can perform spectrum correction based on the measured absolute spectra, thereby reducing correction errors, and having advantages of high environmental adaptability, high convenience, and the like. In addition, compared with a portable spectrometer using an optical disc grating, the spectrometer 1 has better spectroscopic capability, i.e., better spectroscopic resolution (the spectroscopic resolution can be adjusted by the specification of the micro grating 100) and calibration performance, so that the accuracy of determining the spectral position information and market competitiveness can be improved. In addition, due to the improvement of the spectral resolution and the correction performance, the spectrometer 1 can be applied to the detection fields of water, oil, fluorescence and the like. Moreover, compared with the conventional spectrometer, the spectrometer 1 has the advantages of low cost, simple structure, small size, and the like, and is favorable for integration with a mobile device (such as a mobile phone, a tablet computer, and the like). For example, when the spectrometer 1 is integrated with a mobile device, a camera module of the mobile device can be used as the light receiver 11 of the spectrometer 1.

The spectrum self-alignment grating 10 may optionally include other elements or layers depending on various requirements. For example, the spectrum self-calibration grating 10 may further include a substrate 102, an optical layer 103, and a light-shielding layer 104. The optical layer 103 is disposed on a surface S1 of the substrate 102 facing the light receiver 11, and the optical layer 103 has a plurality of slits 1030 and a plurality of recesses 1031 having the same depth as the plurality of slits 1030. Referring to fig. 2, in the present embodiment, the plurality of slits 1030 are arranged along the direction X and respectively extend along the direction Y. The micro-grating 100 comprises the plurality of slits 1030; the correction mark 101 includes the plurality of recesses 1031, and the shape on the plane formed by the direction X and the direction Y is, for example, a cross shape. The substrate 102 is a light-transmitting substrate, such as a glass substrate. The optical layer 103 is a light-transmitting layer, such as polymethyl methacrylate (PMMA) or other high molecular polymer.

The light-shielding layer 104 is disposed on a surface S2 of the substrate 102 facing away from the light receiver 11, and the light-shielding layer 104 is disposed such that the diffraction pattern PD formed on the imaging plane 110 includes only the 0 th order diffraction pattern PD0 and the 1 st order diffraction pattern PD1 of the micro grating 100. In other words, the light-shielding layer 104 is disposed such that diffraction patterns of the order less than-1 (e.g., the order-1 to the order-n diffraction patterns) and diffraction patterns of the order greater than 2 (e.g., the order-2 to the order-n diffraction patterns) are not imaged on the imaging surface 110. Therefore, the subsequent computation amount and the computation power consumption can be reduced, and the computation speed is improved. For example, the light-shielding layer 104 is made of a non-transparent material, and the light-shielding layer 104 has an opening 1040, and the opening 1040 overlaps at least a portion of the calibration mark 101 and at least a portion of the micro-grating 100 (portions of the plurality of slits 1030).

It should be noted that the above-mentioned elements or layers are only examples, and the elements or layers may be added or omitted according to different requirements, and the materials and relative arrangement (including number, arrangement, shape, size, etc.) of the elements or layers may be changed according to requirements. For example, the micro-gratings 100 and the alignment marks 101 may be disposed on a surface S2 of the substrate 102 opposite to the light receiver 11, and the light shielding layer 104 may be disposed on a surface S1 of the substrate 102 facing the light receiver 11. Alternatively, the micro-gratings 100 and the calibration marks 101 may be located on the same surface (e.g., the surface S1) of the same substrate (e.g., the substrate 102) as shown in fig. 1, or may be located on different substrates. Alternatively, the shape of the correction mark 101 may be a cross shape, a circle shape, or other shapes.

FIGS. 3A-3D and 3E-3H are flow charts illustrating the fabrication of the spectrally self-aligned grating 10 of FIG. 2 along line A-A 'and line B-B', respectively. In one embodiment, the spectrally self-aligned grating 10 is fabricated using semiconductor fabrication process techniques. Referring to fig. 3A to 3D (along the sectional linebase:Sub>A-base:Sub>A '), and referring to fig. 3E to 3H (along the sectional line B-B'),base:Sub>A pattern P for defining the plurality of slits 1030 and the plurality of recesses 1031 in fig. 2 is formed on the substrate SUB bybase:Sub>A photolithography process (fig. 3A and 3E). Next, an etching process is performed on the substrate SUB, for example, to form a substrate SUB '(fig. 3B and 3F) having a pattern P' corresponding to the plurality of slits 1030 and the plurality of recesses 1031. Then, the pattern P ' of the substrate SUB ' is transferred to the optical layer 103' (fig. 3C and 3G) on the substrate 102 to form the optical layer 103 having the plurality of slits 1030 and the plurality of recesses 1031 (fig. 3D and 3H). Finally, a light-shielding layer 104 shown in fig. 1 may be selectively formed on the substrate 102.

It should be noted that fig. 3A to 3H are only used to illustrate one manufacturing process of the spectrum self-calibration grating 10 of fig. 2, but the manufacturing process or the manufacturing manner of the spectrum self-calibration grating 10 is not limited thereto.

Fig. 4 is a schematic cross-sectional view of a spectrometer 2 according to another embodiment of the present invention. Referring to fig. 1 and 2, the main differences between spectrometer 2 and spectrometer 1 are as follows. In addition to the spectral self-calibration grating 10 and the optical receiver 11, the spectrometer 2 comprises a housing 12, a collimating element 13 and a focusing element 14.

A housing 12 covers the light receiver 11 and houses the collimating element 13, the spectral self-calibration grating 10 and the focusing element 14 inside. Further, the housing 12 has a slit 120 through which the light beam B passes. The collimating element 13 is disposed on a transmission path of the beam B from the slit 120 to collimate the beam B from the slit 120. For example, the collimating element 13 may include at least one collimating lens, but is not limited thereto. The light-shielding layer 104 is disposed between the collimating element 13 and the optical layer 103. The micro-grating 100 and the correction mark 101 are disposed on the transmission path of the light beam B from the collimator element 13, and the micro-grating 100 and the correction mark 101 together fall within the irradiation range of the light beam B from the collimator element 13. For example, at least part of the micro-grating 100 and at least part of the correction mark 101 together fall within the irradiation range of the beam B from the collimating element 13. The focusing element 14 is disposed on a transmission path of the light beams (such as the light beam B1 and the light beam B2) from the spectral calibration grating 10, and the focusing element 14 focuses the light beams from the spectral calibration grating 10 to the light receiver 11 to form a diffraction pattern PD and a correction pattern PC. For example, the focusing element 14 may include at least one focusing lens, but is not limited thereto.

Fig. 5 is a flow chart of a calibration operation of the spectrometer 2 of fig. 4. Referring to fig. 4 and 5, during the spectral self-correction, the light beam B enters the slit 120 (step 51) and is modified into a fan-shaped light beam transmitted from a single point to the collimating element 13. The collimating element 13 collimates the light beam B from the slit 120 (step 52) to form parallel light or near-parallel light that passes towards the spectral self-calibration grating 10. Next, the light beam B from the collimating element 13 is incident on the spectral self-calibration grating 10 (step 53), wherein a first portion (e.g., the light beam B1) of the light beam B incident on the spectral self-calibration grating 10 passes through the micro-grating 100 and the correction mark 101, and a second portion (e.g., the light beam B2) of the light beam B incident on the spectral self-calibration grating 10 forms a 1 st order diffracted light beam. The focusing element 14 focuses the light beams (including the light beam B1 and the light beam B2) from the spectrum calibration grating 10 onto the light receiver 11 (step 54) to form a diffraction pattern PD and a correction pattern PC. The light receiver 11 converts the light intensity into an image signal, and the image signal is transmitted to a processor (not shown) coupled to the light receiver 11. The spectrum is then corrected by the processor (step 55).

Specifically, the processor can capture the spectrum image and calculate the absolute position information of the spectrum and the light intensity corresponding to each absolute position (wavelength) from the distance between the calibration pattern PC and the 1 st order diffraction pattern of different color light. By this spectral correction, a spectral signal can be mapped out and a spectrogram analyzed.

FIG. 6 is a graph of wavelength versus light intensity showing the spectra before and after calibration. Referring to fig. 6, fig. 6 shows spectral signals before and after the deuterium lamp light source is calibrated. The spectrum of the deuterium lamp light source shifts to the wrong location (e.g., to the left of the correct location) due to environmental effects. However, after the self-correction of the spectrum, the spectrum of the deuterium lamp light source can be corrected to the right back to the correct position.

In summary, in the embodiments of the invention, by designing the calibration marks with the micro-gratings, the problem of light intensity supersaturation can be improved, and the absolute position information of the spectrum and the light intensity corresponding to each absolute position (wavelength) can be obtained at the same time. As a result, the spectrometer is not easily affected by saturation of light intensity, and can measure absolute spectra in different light measurement situations, and can perform spectrum correction according to the measured absolute spectra, thereby reducing correction errors, and having advantages of high environmental adaptability, high convenience, and the like. In addition, the spectrometer has better light splitting capability, namely better light splitting resolution (the light splitting resolution can be adjusted by the specification of the micro grating) and correction performance, so that the accuracy of judging the spectral position information and the market competitiveness can be improved. In addition, due to the improvement of the spectral resolution and the correction performance, the spectrometer can be applied to the field of verification requiring high spectral resolution. Besides, the spectrometer has the advantages of low cost, simple structure and the like, and also has the advantage of small volume, thereby being beneficial to integration with mobile devices (such as mobile phones, tablet computers and the like). In an embodiment, the spectrum self-calibration grating may further include a light-shielding layer to reduce the subsequent computation amount and the computation power consumption, and increase the computation speed.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and these modifications or substitutions do not depart from the spirit of the corresponding technical solutions of the embodiments of the present invention.

Claims (11)

1. A spectrally self-calibrating grating, comprising:

a micro grating; and

a calibration mark, wherein the micro-grating and the calibration mark are irradiated by a light beam to form a diffraction pattern and a calibration pattern on an image plane, respectively, and the spectrum of the diffraction pattern is calibrated according to the distance between the diffraction pattern and the calibration pattern,

wherein the size of the calibration mark is designed to prevent diffraction of the light beam,

wherein, the calibration pattern and the 0 th order diffraction pattern of the diffraction pattern are both positioned in the calibration sensing region.

2. The spectrally self-aligned grating of claim 1, wherein the microscreen and the calibration mark are co-located on a surface of a substrate.

3. The spectrally self-aligned grating of claim 1 wherein the micro-grating and the calibration mark are located on different substrates.

4. The spectrally self-aligned grating of claim 1 wherein the micro-grating comprises a plurality of slits and the calibration mark comprises a groove having the same depth as each of the plurality of slits.

5. The spectrally self-calibrating grating of claim 1, further comprising:

a light shielding layer configured to make the diffraction pattern formed on the imaging surface only include the 0 th order diffraction pattern and the 1 st order diffraction pattern of the micro-grating.

6. A spectrometer, comprising:

the spectrum self-calibration grating comprises a micro grating and a correction mark; and

a light receiver, wherein the micro-grating and the calibration mark are irradiated by a light beam to form a diffraction pattern and a calibration pattern on an image plane of the light receiver, respectively, and the spectrum of the diffraction pattern is calibrated according to the distance between the diffraction pattern and the calibration pattern,

wherein the size of the calibration mark is designed to prevent diffraction of the light beam,

wherein, the calibration pattern and the 0 th order diffraction pattern of the diffraction pattern are both positioned in the calibration sensing region.

7. The spectrometer of claim 6, wherein the micro grating and the calibration mark are located on the same surface of the same substrate.

8. The spectrometer of claim 6, wherein the micro grating and the calibration mark are located on different substrates.

9. The spectrometer of claim 6, wherein the micro grating comprises a plurality of slits and the calibration mark comprises a groove having the same depth as each of the slits.

10. The spectrometer of claim 6, wherein the spectral self-calibration grating further comprises:

a light shielding layer configured to make the diffraction pattern formed on the imaging surface only include the 0 th order diffraction pattern and the 1 st order diffraction pattern of the micro-grating.

11. The spectrometer of claim 6, further comprising:

and the micro grating and the correction mark are arranged on the transmission path of the light beam from the collimation element and jointly fall within the irradiation range of the light beam from the collimation element.

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