Digital micromirror device-based echelle grating spectrometer

Abstract

The utility model discloses an echelle grating spectrometer based on a digital micromirror device, which belongs to the technical field of spectrometers and comprises an echelle grating spectrometer, a digital micromirror, a reflection focusing mirror, a photomultiplier, a data acquisition card and an upper computer. The light is spatially modulated through a digital micromirror, the light is focused on a photomultiplier, and information is received by a data acquisition card; time sequence synchronization of the digital micromirror and the data acquisition card is completed by transmitting a synchronizing signal of the digital micromirror to the data acquisition card, and meanwhile, an overturning mode of the digital micromirror is designed, so that rapid scanning imaging is realized. According to the echelle grating spectrometer based on the digital micromirror device, the cost is reduced, and the time for acquiring spectral information is shortened.

Description

Technical Field

[0001] The utility model relates to the technical field of spectrometers, in particular to an echelle grating spectrometer based on a digital micromirror device. Background Technique

[0002] The characteristic spectrum of a substance is unique like the "fingerprint" of the substance and can determine the composition and content of the substance. The spectrometer realizes the identification and classification of substances through the analysis of the spectrum and has wide applications in various fields such as quality inspection and medicine. The higher the resolution of the spectral instrument, the clearer it is when distinguishing similar substances. For spectral instruments, the spectral resolution is an extremely important indicator.

[0003] The echelle grating spectrometer has extremely high resolution, which can reach the picometer level. Its core dispersion element is a grating with a large blaze angle and a low groove density. This grating enables the spectrometer to operate at a high diffraction order, has an extremely high angular dispersion rate, and thus realizes the extremely high resolution of the spectral instrument. At the same time, serious order overlapping is brought, and another dispersion element is needed to perform secondary dispersion in a different direction to form a cross-dispersed optical path. Therefore, using a matrix detector to receive the two-dimensional dispersed spectral pattern of the echelle grating spectrometer is the key to realizing its ultra-high spectral resolution. Due to the application requirements of high dispersion rate and trace detection, the energy of the spectral pattern after cross-dispersion is generally low, and the wavelength includes ultraviolet and visible light, and the wavelength range is relatively wide. Generally, a matrix camera is required to have high detection sensitivity, a large target surface, and a wide wavelength response range. Therefore, the echelle grating spectrometer is generally equipped with a large-target cooled camera such as ICCD or SCMOS, and its price is 200,000 - 300,000 yuan, which greatly increases the cost of the echelle grating spectrometer and limits its wider application.

[0004] In view of this, the combination of using a digital micromirror device (DMD) and a photomultiplier tube (PMT) instead of a matrix camera can achieve the effect of cost reduction. The digital micromirror can modulate the reflection of light on each pixel by controlling the flipping of each pixel. The photomultiplier tube can detect weak light signals. The combination of the digital micromirror and the photomultiplier tube makes it possible to replace the costly camera in the echelle grating spectrometer.

[0005] Each flip of the digital micromirror has a time limit, which is caused by its structure and cannot be changed. The wavelength information in space of the echelle grating spectrometer occupies most of the image surface on the digital micromirror. If all the image surfaces of the digital micromirror are flipped, the time will reach more than 10 seconds, which is seriously not applicable to the application of the echelle grating spectrometer. How to reduce the flipping time of the digital micromirror and obtain all the spectral information within the fewest number of flips will be the key to applying the digital micromirror to the echelle grating spectrometer. Content of the Utility Model

[0006] The object of the utility model is to provide an echelle grating spectrometer based on a digital micromirror device to solve the problems existing in the above-mentioned background technology.

[0007] To achieve the above object, the utility model provides an echelle grating spectrometer based on a digital micromirror device, which includes an echelle grating spectrometer, a digital micromirror, a reflective focusing mirror, a photomultiplier tube, a data acquisition card and a host computer. After the light is dispersed by the echelle grating spectrometer, it is focused on the digital micromirror. By controlling the flipping of the pixels of the digital micromirror, the light containing spectral information is reflected onto the reflective focusing mirror; the reflective focusing mirror focuses the light onto the photosensitive surface of the photomultiplier tube, and the photomultiplier tube converts the optical signal into an analog voltage signal and amplifies it and transmits it to the data acquisition card. The data acquisition card converts the acquired analog voltage signal into a digital voltage signal through I / V conversion and transmits it to the host computer; the host computer transmits the flipping information of the digital micromirror to control its flipping, and at the same time the digital micromirror transmits its synchronous signal of flipping to the data acquisition card, and the data acquisition card acquires data according to the synchronous signal of the digital micromirror and transmits it to the host computer.

[0008] Preferably, the flipping of the digital micromirror, the conversion of the photomultiplier tube and the acquisition of the data acquisition card are carried out synchronously.

[0009] Preferably, the digital micromirror is provided with three flipping states, namely the off state, the on state and the non-flipping state; the off state is flipping -12°, and the on state is flipping +12°.

[0010] Preferably, since the flipping of the digital micromirror is carried out with the diagonal of each square pixel as the axis, the entire digital micromirror needs to be rotated 45° and placed on the horizontal plane to ensure that the reflection of the light is within the horizontal plane; through the optical path setting, when the digital micromirror flips to the off state, the light is reflected from the digital micromirror to the reflective focusing mirror, that is, in the off state, it is the working state.

[0011] Preferably, the digital micromirror adopts a digital micromirror with 1920*1080 pixels. Among them, there are 1920 pixels in the x direction and 1080 pixels in the y direction, and the image plane of the entire digital micromirror is 2,073,600 pixels; by dividing the image plane of the digital micromirror into 900 regions, among which both the x direction and the y direction are 30 parts, each part in the x direction has 64 pixels, and each part in the y direction has 36 pixels; each divided region represents a small region of 64*36 pixels, and its order is flipped to reduce the number of flips.

[0012] Therefore, the echelle grating spectrometer based on a digital micromirror device with the above structure of the utility model has the following beneficial effects:

[0013] (1) By setting the structure of the new echelle grating spectrometer, replacing the area array camera with a digital micromirror device + photomultiplier tube, the development cost of the instrument is reduced.

[0014] (2) By dividing the digital micromirror surface, a fast scanning mode of the digital micromirror is obtained, optimizing the flipping strategy of the digital micromirror, and significantly reducing the time to obtain all spectral information.

[0015] The technical solution of the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0016] Figure 1 It is a schematic structural diagram of an embodiment of an echelle grating spectrometer based on a digital micromirror device of the present utility model;

[0017] Figure 2 It is a schematic diagram of the synchronous timing of the digital micromirror and the data acquisition card in the embodiment of the present utility model;

[0018] Figure 3 It is a schematic diagram of the flipping mode of the digital micromirror in the embodiment of the present utility model;

[0019] Figure 4 It is the large-area light intensity information in the embodiment of the present utility model;

[0020] Figure 5 It is the light intensity information of each pixel in the 191st area in the embodiment of the present utility model;

[0021] Figure 6 It is the light intensity information of each pixel in the 221st area in the embodiment of the present utility model;

[0022] Figure 7 It is a schematic diagram of the restored two-dimensional spectral map information in the embodiment of the present utility model; wherein, (a) is the overall spectral map, and (b) is the partial enlarged schematic diagram;

[0023] Reference Signs

[0024] 1. Echelle grating spectrometer; 2. Digital micromirror; 3. Reflective focusing mirror; 4. Photomultiplier tube; 5. Data acquisition card; 6. Host computer. Detailed Embodiment

[0025] The technical solution of the present utility model will be further described below with reference to the accompanying drawings and embodiments.

[0026] Unless otherwise defined, the technical terms or scientific terms used in this utility model shall have the ordinary meanings understood by those with ordinary skills in the field to which this utility model belongs. The "first", "second" and similar words used in this utility model do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "including" or "comprising" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. Words such as "connected" or "linked" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0027] Embodiment

[0028] The technical solutions in the embodiments of this utility model will be clearly and completely described below in conjunction with the accompanying drawings.

[0029] As Figure 1 shown, a echelle grating spectrometer based on a digital micromirror device includes an echelle grating spectrometer 1, a digital micromirror 2, a reflection focusing mirror 3, a photomultiplier tube 4, a data acquisition card 5 and a host computer 6. The light is dispersed by the echelle grating spectrometer 1 and then focused on the digital micromirror 2. By controlling the flipping of the pixels of the digital micromirror 2, the light containing spectral information is reflected onto the reflection focusing mirror 3; the reflection focusing mirror 3 focuses the light onto the photosensitive surface of the photomultiplier tube 4. The photomultiplier tube 4 converts the optical signal into an analog voltage signal and amplifies it for transmission to the data acquisition card 5. The data acquisition card 5 converts the collected analog voltage signal into a digital voltage signal through I / V conversion and transmits it to the host computer 6; the host computer 6 transmits the flipping information of the digital micromirror 2 to control its flipping. At the same time, the digital micromirror 2 transmits its synchronous signal of flipping to the data acquisition card 5. The data acquisition card 5 collects data according to the synchronous signal of the digital micromirror 2 and transmits it to the host computer 6; the flipping of the digital micromirror 2, the conversion of the photomultiplier tube 4, and the collection of the data acquisition card 5 are synchronized.

[0030] The digital micromirror 2 has three flipping states, namely the off state with a flip of -12°, the on state with a flip of +12°, and the non-flipping state. Since the flipping of the digital micromirror 2 is carried out with the diagonal of each square pixel as the axis. Therefore, the entire digital micromirror 2 needs to be rotated 45° and placed on a horizontal plane to ensure that the reflection of the light is within the horizontal plane. After the optical path is set, when the digital micromirror 2 flips to the off state, the light is reflected from the digital micromirror 2 to the reflection focusing mirror 3. That is to say, in the off state, it is the working state.

[0031] AsFigure 2 As shown, the black solid line represents the flipping state of the digital micromirror 2. At this time, some or a certain pixel in the digital micromirror 2 is in the off state, reflecting the optical signal above it to the reflection focusing mirror 3, and most of the remaining pixels are in the on state, reflecting the light to the opposite direction. The blank part between the black lines is the short non-flipping state. The synchronization signal of the digital micromirror 2 is a group of high and low level signals, which are transmitted from the digital micromirror 2 to the data acquisition card 5. The output at the beginning of the flipping state is high level and lasts for half a cycle. At half of each flipping cycle (when the optical signal received by the photomultiplier tube 4 is the most stable), the output is low level, waiting for the next flip of the digital micromirror 2. It becomes high level again at the beginning of the next flip of the digital micromirror 2. When the data acquisition card 5 receives the low level, it acquires data once (the data acquired at this time is the most stable electrical signal converted by the photomultiplier tube 4). Through the synchronization between the flip of the digital micromirror 2 and the acquisition of the data acquisition card 5 realized by the synchronization signal of the digital micromirror 2, the synchronization of the spatial position of the digital micromirror 2 and the time sequence of the data acquisition card 5 is achieved.

[0032] To match the spatial position of the spectral light, the digital micromirror 2 with 1920 * 1080 pixels selected in this embodiment, the size of each digital micromirror 2 is 10.8 μm, and its maximum flipping rate is 17636 fps. As Figure 3 shown, there are 1920 pixels in the x direction and 1080 pixels in the y direction, and the entire image plane has 2073600 pixels. Calculated at a flipping rate of 17636 times per second, it takes a total of 117.5 seconds to flip each pixel in the image plane in sequence, which severely limits the application of the echelle grating spectrometer 1.

[0033] This embodiment designs the flipping mode of the digital micromirror 2 to reduce the number of flips and achieve the effect of full image plane flipping. Specifically, the image plane is now divided into 900 regions, with 30 parts in the x direction, each part having 64 pixels, and 30 parts in the y direction, each part having 36 pixels. At this time Figure 3 each small square region represents a small region of 64 * 36 pixels, and its row order is flipped. When flipping for the first time, the first region in the first row is in the off state, and the remaining regions are in the on state. At this time, the data acquired by the data acquisition card 5 is the voltage value corresponding to the light intensity of the first region in the first row. Flip 900 times in row order to obtain the voltage values corresponding to the light intensities of each small region, so as to judge whether there is light intensity in each small region. If there is, it is retained; if not, it is discarded. The regions containing light intensity are flipped in order again to obtain the light intensity values of each small pixel. The obtained data is input into a 1920 * 1080 two-dimensional matrix according to its logical order, and the voltage value representing the light intensity is mapped to a gray value, thereby obtaining a two-dimensional spectrogram containing spectral information.

[0034] ​This device was verified using a 660 nm laser as the light source, and relatively ideal spot information was obtained.

[0035] Figures 4 to 7 This is the verification process for the two-dimensional spectrum of the entire 660 nm laser.

[0036] Figure 4 This is the light intensity information for each large area. The abscissa represents the area label, and the ordinate is the voltage value detected by the data acquisition card 5 (representing the light intensity within each area). Figure 4 It can be seen that only areas 191 and 221 contain spectral information. Figure 5 and Figure 6 are the light intensity information for each pixel in areas 191 and 221 respectively. The light intensity information in areas 191 and 221 is filled into a 1920*1080 matrix according to its flipping logic and the light intensity information is mapped to grayscale values, obtaining Figure 7 two-dimensional spectrum information. The two-dimensional spectrum presented by the spectral characteristics of the 660 nm laser is a straight line, and the spot at the top is the brightest while the light intensity decreases significantly for the rest. From Figure 7 it can be seen from (b) that the actually measured spectral information is an oblique line. This is because the digital micromirror 2 is placed rotated by 45°. Rotating a straight line by 45° exactly results in an oblique line, and the relative position of the brightest spot also conforms to the actual situation, thus indicating that the spectral information of the 660 nm laser has been successfully measured.

[0037] Therefore, the present utility model adopts a echelle grating spectrometer based on a digital micromirror device with the above structure, which solves the problems that the cost of a highly sensitive area array camera is extremely expensive and the flipping rate of the digital micromirror is limited by the hardware structure. Flipping the entire holographic surface of the digital micromirror requires a long time, severely restricting the application of the digital micromirror in the echelle grating spectrometer.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model and are not intended to limit them. Although the present utility model has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present utility model, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present utility model.

Claims

1. A digital micromirror device-based echelle grating spectrometer, characterized in that: The invention comprises a chèche grating spectrometer, a digital micromirror, a reflective focusing mirror, a photomultiplier tube, a data acquisition card and a host computer. After being split by the chèche grating spectrometer, the light is focused on the digital micromirror. The light containing spectral information is reflected on the reflective focusing mirror by controlling the flipping of the pixels of the digital micromirror. The reflective focusing mirror focuses the light on the photosensitive surface of the photomultiplier tube. The photomultiplier tube converts the light signal into an analog voltage signal and amplifies and transmits it to the data acquisition card. The data acquisition card converts the collected analog voltage signal into a digital voltage signal through I / V and transmits it to the host computer. The host computer transmits the flipping information of the digital micromirror to the digital micromirror to control its flipping. Meanwhile, the digital micromirror transmits its flipping synchronization signal to the data acquisition card. The data acquisition card collects data according to the synchronization signal of the digital micromirror and transmits it to the host computer.

2. The digital micromirror device-based echelle grating spectrometer according to claim 1, characterized in that: The flipping of the digital micromirror, the conversion of the photomultiplier tube and the acquisition of the data acquisition card are carried out synchronously.

3. The digital micromirror device-based echelle grating spectrometer according to claim 1, characterized in that: The digital micromirror is set with three flip states, namely, off state, on state and non-flip state; the off state is flipped by -12°, and the on state is flipped by +12°.

4. The digital micromirror device-based echelle grating spectrometer according to claim 3, characterized in that: Since the flipping of the digital micromirror is based on the diagonal of each square pixel, the entire digital micromirror must be rotated 45° and placed on a horizontal plane to ensure that the light is reflected within the horizontal plane; after the optical path is set, when the digital micromirror is flipped to the off state, the light is reflected by the digital micromirror to the reflective focusing mirror, that is, when it is in the off state, it is in the working state.

5. The digital micromirror device-based echelle spectrometer according to claim 1, characterized in that: The digital micromirror uses a 1920*1080 pixel digital micromirror, where the x-direction is 1920 pixels, the y-direction is 1080 pixels, and the image surface of the entire digital micromirror is 2073600 pixels; the image surface of the digital micromirror is divided into 900 areas, where the x-direction and the y-direction are 30 parts, each part in the x-direction has 64 pixels, and each part in the y-direction has 36 pixels; each divided area represents a small area of ​​64*36 pixels, and they are flipped sequentially to reduce the number of flipping times.

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