CN107238570B - Micro spectrometer based on MEMS micro vibrating mirror, gas sensor and spectrum detection method - Google Patents
Micro spectrometer based on MEMS micro vibrating mirror, gas sensor and spectrum detection method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
- G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
- G02B26/085—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD the reflecting means being moved or deformed by electromagnetic means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
- G01N2021/0106—General arrangement of respective parts
- G01N2021/0112—Apparatus in one mechanical, optical or electronic block
Abstract
The invention provides a micro spectrometer based on an MEMS micro vibrating mirror, a gas sensor and a spectrum detection method, which comprises the following steps: a light converging module; the micro-vibration mirror module is arranged on an emergent light path of the light converging module, receives light emitted by the light converging module and reflects the light at different angles; the filtering module is arranged on the emergent light path of the micro-galvanometer module, receives the light reflected by the galvanometer module and filters the light to obtain a plurality of light signals of monochromatic light with different wavelengths; and the detection module is connected with the light filtering module and is arranged at the focal position of the light converged by the light converging module, and the light signals obtained by the light filtering module are read out to obtain a spectrogram. Through the scheme, the spectrometer provided by the invention adopts the integrated optical filter and the micro-vibrating mirror based on the MEMS technology, so that the traditional mechanical structure, the grating prism and other large devices are simplified, the spectrometer is high in integration and small in size, the light intensity and light utilization efficiency of unit pixel are improved, the signal-to-noise ratio and measurement precision and sensitivity are improved, and the overall power consumption of the spectrometer is reduced.
Description
Technical Field
The invention belongs to the technical field of optical measurement, and particularly relates to a micro spectrometer, a gas sensor and a spectrum detection method based on an MEMS micro vibrating mirror.
Background
Spectrometers have been widely used in various fields to analyze the composition and content of substances by means of spectral signals. The traditional light splitting mode mainly comprises a time decomposition method of a rotary grating, a prism and an optical filter runner, but the time decomposition method involves a mechanical transmission device, and has the advantages of low speed and complex structure; and a space decomposition method using a grating prism and a beam splitting filter is also adopted, and a corresponding instrument occupies a larger space.
At present, most spectrometers are large instruments and can be used only in relatively fixed places such as laboratories and factories, but in recent years, as the requirements of people on food quality are higher and higher, the demands of people on miniaturized and portable spectrometers are higher and higher, so in order to solve the problem of miniaturization, people are always searching for an effective solution way, and an optical filter array is a miniature space optical filter which is researched and developed in the eighties of the twentieth century, and the optical filter array is combined with a detector, so that a light splitting system can be greatly simplified. There are two main types of miniature spatial filters at this stage: an integrated narrow band filter array, the other is a graded filter. Subsequently, people begin to use the two integrated filter technologies in the preparation of a small spectrometer or integrate the small spectrometer in a mobile phone, but because the narrow-band integrated filter has low transmittance, small volume and high density, the light transmittance is very small, the obtained spectrum information has poor precision and low sensitivity, thus the resolution is low, the integrated filter can only be used in the detection of objects with very large spectrum information differences, the advantage that the spectrometer can precisely detect the material information is lost, and the current spectrometer cannot be popularized.
However, the scanning galvanometer is used as a conventional optical element in the fields of optical imaging, large-scale spectrometers, projection and the like, however, the conventional scanning galvanometer is difficult to be applied to a micro optical scanning system with limited space due to its large structure and the adoption of a stepping motor drive. In recent years, with the development of microelectromechanical systems (MEMS) technology, MEMS scanning mirrors developed by the units of Hiperscan, microvision, tokyo university, japan, and the like have successfully solved this problem. The MEMS scanning mirror has wide application prospect in the fields of optical communication, projection display, object identification, data storage, biomedicine and the like due to the remarkable advantages of small volume, light weight, low cost, low power consumption and the like, and at present, the unit for domestic research on the MEMS scanning mirror is Beijing university, northwest university of industry, tianjin university and the like and is still in a starting stage.
Therefore, the spectrometer which not only keeps the advantages of high integration level, miniaturization and high processing speed of the traditional optical filter, but also can realize good measurement precision, sensitivity and signal-to-noise ratio is necessary.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, the present invention is directed to providing a micro spectrometer, a gas sensor and a spectrum detection method based on a MEMS micro-resonator, which are used for solving the problems that an integrated narrowband filter in the prior art can only be used for detecting objects with very different spectrum information, and the existing spectrometer has low measurement precision, poor sensitivity and signal-to-noise ratio.
To achieve the above and other related objects, the present invention provides a micro spectrometer based on a MEMS micro vibrating mirror, comprising:
the light converging module is used for converging light reflected by the object to be detected;
the micro-vibration mirror module is arranged on an emergent light path of the light converging module and is used for receiving the light emitted by the light converging module and reflecting the light at different angles;
the light filtering module is arranged on an emergent light path of the micro-vibration mirror module and is used for receiving light reflected by the micro-vibration mirror module and filtering the light so as to obtain a plurality of light signals of monochromatic light with different wavelengths; and
the detection module is connected with the light filtering module and arranged at the focal position of the light converged by the light converging module, and reads the light signals obtained by the light filtering module to obtain a spectrogram of the light signals.
As a preferable scheme of the invention, the optical filtering module comprises an integrated narrow-band optical filter, the integrated narrow-band optical filter comprises m multiplied by n resonant cavities, wherein m and n are integers greater than or equal to 1, the resonant cavities have different thicknesses, and the resonant cavities with different thicknesses are filtered to obtain the optical signals of monochromatic light with different wavelengths.
As a preferred scheme of the invention, the integrated narrowband filter comprises a lower layer film system, a spacer layer and an upper layer film system which are sequentially overlapped, wherein the spacer layer comprises m×n resonant cavities, and the upper layer film system and the lower layer film system are arranged in a mirror symmetry manner.
As a preferable mode of the present invention, the upper layer film system and the lower layer film system have the same thickness, and each includes a low refractive index film layer and a high refractive index film layer stacked in order.
As a preferable scheme of the invention, the light filtering module comprises a gradient light filter, the gradient light filter comprises a substrate and a coating layer positioned on the upper surface of the substrate, and the distance between the coating layer and the upper surface of the substrate is in linear or stepped gradient so as to filter and obtain the light signals of monochromatic lights with different wavelengths.
As a preferable scheme of the invention, the micro-vibration mirror module comprises a substrate, a torsion component arranged on the substrate and a micro-mirror component arranged on the torsion component, wherein the torsion component drives the micro-mirror component to deflect, and the micro-mirror component receives and reflects the light emitted by the light converging module.
As a preferred scheme of the invention, the micro-vibration mirror module further comprises a coil assembly and a magnetic assembly which are arranged on the substrate, wherein the magnetic force of the magnetic assembly acts on the coil assembly, the coil assembly is stressed to deflect, and the torsion assembly drives the micro-mirror assembly to deflect.
As a preferable mode of the present invention, the micromirror assembly is a mirror, and the area of the mirror is equal to or larger than the area of the light received by the mirror, and the deflection angle is 0 to 23 °.
As a preferred scheme of the invention, the micro-vibration mirror module further comprises a position sensor arranged on the substrate and used for detecting the deflection angle of the micro-mirror assembly and transmitting the detection value to an angle control system so as to realize compensation of the deflection angle of the micro-mirror assembly.
As a preferable scheme of the invention, the detection module comprises a plurality of detection pixels, and the plurality of detection pixels read out the optical signals and obtain a spectrogram thereof, wherein the preset number of detection pixels correspond to the optical signals of the monochromatic light with one wavelength generated by the filtering module.
The invention also provides an integrated gas sensor, which comprises the micro spectrometer based on the MEMS micro vibrating mirror according to any scheme.
As a preferred solution of the present invention, the filtering module includes a plurality of resonant cavities having different preset thicknesses, where the preset thicknesses are set according to characteristic peaks of the gas to be measured.
The invention also provides a spectrum detection method of the micro spectrometer based on the MEMS micro vibrating mirror, which comprises the following steps:
1) Providing a micro spectrometer based on a MEMS micro vibrating mirror according to any of the above aspects;
2) Driving the micro-vibrating mirror module to deflect in an electromagnetic driving mode so as to reflect light emitted by the light converging module received by the micro-vibrating mirror module at different angles;
3) And controlling the light reflected by the micro-vibrating mirror module to pass through the light filtering module and focus on the detection module so as to obtain spectrograms of light signals of monochromatic light with different wavelengths, thereby realizing spectrum detection.
As a preferred embodiment of the present invention, in step 2), the electromagnetic driving mode specifically includes: and driving current is introduced into a coil assembly of the micro-vibration mirror module so that the coil assembly deflects under the action of magnetic force of a magnetic assembly of the micro-vibration mirror module, and the coil assembly drives the micro-mirror assembly of the micro-vibration mirror module to deflect through a torsion assembly of the micro-vibration mirror module, wherein the magnitude and the frequency of the driving current are set according to the pixel interval and the sampling period of the detection module.
In a preferred embodiment of the present invention, in step 2), the driving current is generated by a driving circuit, wherein when the detection module starts sampling, a first pulse signal is generated to control the driving circuit to generate the driving current, and when the detection module stops sampling, a second pulse signal is generated to control the driving circuit to stop generating the driving current.
As a preferred scheme of the invention, the micro-vibration mirror module further comprises a position sensor, the position sensor detects the deflection angle of the micro-mirror assembly and transmits the detection value to the driving circuit, and the driving circuit realizes the compensation of the deflection angle according to the received position information of the deflection angle and a preset parameter value.
As a preferable scheme of the invention, the sampling mode of the detection module is cyclic sampling, wherein when the detection module starts sampling, the generated first pulse signal is a zigzag pulse with a preset frequency, so that the micro-galvanometer module performs cyclic scanning, and cyclic sampling of the detection module is realized.
As described above, the MEMS micro-mirror-based micro spectrometer, the gas sensor and the spectrum detection method have the following beneficial effects:
1) The micro spectrometer based on the MEMS micro-vibrating mirror adopts the integrated optical filter and the micro-vibrating mirror based on the MEMS technology, so that the traditional mechanical structure and large devices such as the grating prism are simplified, and the spectrometer has the characteristics of high integration, small volume, light weight and convenience in carrying;
2) The invention adds the structure of vibrating mirror scanning, compared with the traditional spectrometer with only optical filters and CMOS, the invention improves the light intensity and light utilization efficiency of unit pixel, thereby improving the signal to noise ratio, and simultaneously, the invention greatly improves the measurement precision and sensitivity based on the characteristic of high-speed scanning of MEMS vibrating mirrors;
3) The MEMS micro-vibrating mirror adopts an electromagnetic driving mode, has smaller required voltage and current, is matched with a CMOS with low power consumption, greatly reduces the overall power consumption of a spectrometer, and is convenient to integrate on electronic equipment such as a mobile phone and the like.
Drawings
Fig. 1 shows a schematic diagram of the overall structure of a micro spectrometer based on a MEMS micro-mirror according to the present invention.
Fig. 2 is a schematic diagram of a specific structure of a micro-mirror module according to the present invention.
Fig. 3 shows a diagram of a 1×16 filter array and a 1×128CMOS pixel of the spectrometer provided by the present invention.
FIG. 4 is a schematic view of the atmospheric absorption and the atmospheric window in the gas sensor according to the present invention.
Description of element reference numerals
11. Light converging module
21. Micro-vibrating mirror module
211. Substrate and method for manufacturing the same
212. Coil assembly
213. Torsion assembly
214. Micromirror assembly
31. Filtering module
311. Resonant cavity
41. Detection module
411. Detecting pixel
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
Please refer to fig. 1 to 4. It should be noted that, the illustrations provided in the present embodiment are merely schematic illustrations of the basic concepts of the present invention, and only the components related to the present invention are shown in the illustrations, rather than being drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of each component in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.
Example 1
As shown in fig. 1 to 3, the present invention provides a micro spectrometer based on a MEMS micro-mirror, comprising:
a light converging module 11 for converging light reflected by the object to be measured;
the micro-galvanometer module 21 is arranged on an emergent light path of the light converging module 11 and is used for receiving the light emitted by the light converging module 11 and reflecting the light at different angles;
the filtering module 31 is disposed on the outgoing light path of the micro-galvanometer module 21, and is configured to receive the light reflected by the micro-galvanometer module 21 and filter the light to obtain a plurality of optical signals of monochromatic light with different wavelengths; and
the detection module 41 is connected to the filtering module 31 and disposed at a focal position of the light converged by the light converging module 11, and the detection module 41 reads out the light signal obtained by the filtering module 31 to obtain a spectrogram of the light signal.
Specifically, the light converging module 11 is a converging lens, and of course, may be any other module having a converging function, and the focal length of the converging lens is not specifically limited herein, and is preferably 100-200 mm, and is preferably 150mm, where the detecting module is disposed at the focal position of the light converged by the light converging module, that is, at the focal length of the converging lens. The light reflected by the object to be detected directly enters the converging lens, wherein the light reflected by the object to be detected is parallel light and non-parallel light, and most of the light is parallel light and can be converged on an image surface through the converging lens if the converging lens is placed opposite to the object to be detected.
It should also be noted that the working principle of the micro spectrometer based on the MEMS micro vibrating mirror provided by the invention is as follows: the light of the object to be detected is reflected by the light converging module and the micro-vibrating mirror module, is split by the light filtering module and is focused on the detection module, wherein the detection module can obtain light intensities with different wavelengths and read out the light intensities in sequence, so that a spectrogram reflecting the characteristics of the object to be detected can be obtained.
As an example, the filtering module 31 includes an integrated narrowband filter, where the integrated narrowband filter includes m×n resonant cavities 311, where m and n are integers greater than or equal to 1, and the resonant cavities 311 have different thicknesses, and the resonant cavities 311 with different thicknesses filter the optical signals of monochromatic light with different wavelengths.
As an example, the integrated narrowband filter includes a lower layer film system, a spacer layer, and an upper layer film system that are sequentially stacked, where the spacer layer includes m×n resonant cavities, and the upper layer film system and the lower layer film system are disposed in mirror symmetry.
As an example, the upper layer film system is the same thickness as the lower layer film system, and each includes a low refractive index film layer and a high refractive index film layer stacked in order.
Specifically, the filtering module 31 may be an integrated narrowband filter, and the integrated narrowband filter is based on F-The principle of P interference, in this embodiment, consists of a lower film system, a spacer layer and an upper film system, wherein the spacer layer comprises the resonant cavity 311, preferably the upper film system has the same thickness as the lower film system, preferably has an optical thickness (nd) of lambda 0 /4，λ 0 In this embodiment, the upper layer and the lower layer are both (LH) 5 The structure, wherein L is a low refractive index film layer, H is a high refractive index film layer, the low refractive index film layer includes but is not limited to a silicon dioxide film layer, the high refractive index film layer includes but is not limited to a tantalum pentoxide film layer, and is formed through a film coating process, in this embodiment, a structure composed of 5 layers of high and low refractive index film layers is selected, and specific upper and lower positions of the low refractive index film layer and the high refractive index film layer are not limited, in other embodiments, the structure with any layer number can be adopted, depending on actual requirements.
In addition, the spacer layer is formed by a plurality of resonant cavities 311, the resonant cavities with different thicknesses are obtained through a semiconductor film plating process and the like, and an m×n array resonant cavity 311 is formed, wherein m and n are integers greater than or equal to 1, the different thicknesses refer to the heights of the resonant cavities relative to the surface of the lower film system, when the integrated optical filter is a 1×n array, the integrated optical filter corresponds to a linear array CMOS pixel of the detection module 41, and a one-dimensional MEMS micro-vibrating mirror is adopted at the moment; the integrated optical filter may also be an mxn array, which corresponds to the area array CMOS pixel of the detection module 41, and a two-dimensional MEMS micro-mirror is used at this time.
Furthermore, the resonant cavities with different heights are correspondingly filtered to obtain monochromatic light with different wavelengths, the heights of the resonant cavities can be set arbitrarily according to actual requirements, and preferably, the reflection angles of the micro-vibrating mirror modules are different, so that the resonant cavities with different thicknesses are correspondingly filtered to obtain optical signals of the monochromatic light with different wavelengths. The number of the arrays of the narrow-band filters can be arbitrarily selected, the more the number of the arrays is, the wider the wavelength range of the spectrogram is, and the thickness of each array element spacing layer is different, so that the corresponding bandpass peak positions are different. The smaller the thickness difference among array elements is, the higher the resolution of the obtained spectrogram is, and the peak transmittance is between 60% and 76%.
As an example, the filtering module 31 includes a graded filter, where the graded filter includes a substrate and a coating layer on an upper surface of the substrate, and a distance between the coating layer and the upper surface of the substrate is graded in a linear or stepped manner, so as to filter the light signals of monochromatic light with different wavelengths.
Specifically, the filtering module 31 may be a graded filter, and further may be a wedge graded filter, where the graded filter is a thin film bandpass filter based on the F-P interference principle, and the bandpass peak position of the graded filter and the thickness of the thin film of the filter are in a linear relationship, that is, the thickness of the graded filter linearly changes along with the length direction to form a wedge structure, so that the center wavelength of the filter linearly changes along with the length direction, thereby realizing the light splitting effect. The different thicknesses of the graded filter are corresponding to the monochromatic light with different wavelengths, the thickness variation of the graded filter is also corresponding to the spectrum range, the detection module 41 can be combined by linear CMOS, and the detection pixels of the detection module are corresponding to the different thicknesses of the graded filter, so as to receive the light with different wavelengths.
In addition, the graded filter comprises a substrate and a coating layer arranged on the surface of the substrate, and the coating layer can be in a conical surface shape so as to realize linear change of the astigmatic angle of the graded filter in different areas along the radial direction, wherein the coating layer is a scattering particle layer, including but not limited to a glue layer well known to those skilled in the art.
As an example, the micro-mirror module 21 includes a substrate 211, a torsion assembly 213 disposed on the substrate 211, and a micro-mirror assembly 214 disposed on the torsion assembly 213, wherein the torsion assembly 213 drives the micro-mirror assembly 214 to deflect, and the micro-mirror assembly 214 receives and reflects the light emitted from the light converging module 11.
By way of example, the micromirror assembly 214 is a mirror having an area equal to or greater than the area of light it receives and a deflection angle of 0-23 °.
Specifically, the micro-mirror module 21 mainly reflects the light of the object to be measured, which is converged by the light converging module 11, where the torsion component 213 may be, but is not limited to, a torsion bar, and the micro-mirror component 214 may be, but is not limited to, a micro-mirror, especially a micro-mirror based on MEMS technology, and in this embodiment, the mirror has a reflective crystal plane with a size of 0.5-2.5 mm, preferably 1mm, and in addition, the rotation angle of the mirror is 0-23 °, where the existing micro-mirror can meet this requirement.
As an example, the micro-mirror module 21 further includes a coil assembly 212 and a magnetic assembly (not shown) disposed on the substrate 211, wherein a magnetic force of the magnetic assembly acts on the coil assembly 212, and the coil assembly 212 is forced to deflect and drives the micro-mirror assembly 214 to deflect through the torsion assembly 213.
Specifically, the micro-mirror module 21 further includes a coil assembly 212 and an electromagnetic assembly, where the coil assembly 212 is a coil, and the magnetic assembly is a permanent magnet, so that electromagnetic driving can be implemented by a rotation mode of the micro-mirror assembly 214, that is, a magnetic field of the magnetic assembly is perpendicular to incidence of the coil, the coil is deflected under a stress action, the micro-mirror is driven to rotate by the torsion bar, and a rotation angle and a frequency of the rotation change along with a magnitude and a frequency of a driving current flowing into the coil, and are determined according to a pixel interval and a sampling period of the detection module (such as a CMOS detector).
As an example, the micromirror module 21 further includes a position sensor (not shown) disposed on the substrate for detecting the deflection angle of the micromirror assembly 214 and transmitting the detected value to an angle control system to compensate for the deflection angle of the micromirror assembly 214.
Specifically, in this embodiment, the system further includes a position sensor, which is configured to detect a rotation angle of the micromirror, and the rotation angle information is transmitted to a driving circuit that provides a driving current for the coil, that is, the angle control system, where the driving circuit modulates an amplitude of the driving current source according to the position information, so as to implement compensation of the rotation angle.
As an example, the detection module includes a plurality of detection pixels, and the plurality of detection pixels read out a spectrogram corresponding to the optical signal, where a preset number of detection pixels correspond to the optical signal of the monochromatic light with one wavelength generated by the filtering module.
Specifically, the detection module 41 may be, but is not limited to, a CMOS detector, which includes a plurality of the detection pixels, where in this embodiment, the distance from the MEMS micro-resonator to the detection pixels is 1.2mm, and in this embodiment, the detection pixels are CMOS pixels, where one, two or more of the detection pixels correspond to the resonant cavities in the filters of the filtering unit at a height, so that monochromatic light reaching the same wavelength on the pixels is obtained. For example, in this embodiment, the resonant cavity of the narrowband filter is a 1×16 array, the CMOS pixels are in a 1×128 array, so that each 8 pixels corresponds to a filter resonant cavity, and the pixel size is 8 μm, as shown in fig. 3 (taking the first 32 pixels of the CMOS as an example), the sum of detected signals of each 8 pixels is the size of the light transmission quantity of the narrowband band, and the finally obtained spectrogram is formed by sequentially arranging the light transmission quantities of 16 narrowband bands.
The spectrometer has the characteristics of high precision and high sensitivity on the basis of miniaturization and portability, and can obtain a spectrum curve with higher resolution and detect more subtle differences of substances compared with the traditional miniature spectrometer. The method is widely used for detecting food, gas, plant growth condition, water quality and the like.
As shown in fig. 1 to 4, the present invention further provides a spectrum detection method of a micro spectrometer based on a MEMS micro-mirror, where the spectrum detection method is a method for detecting by using the micro spectrometer based on the MEMS micro-mirror according to any one of the above schemes, and the method includes the following steps:
1) Providing a micro spectrometer based on a MEMS micro vibrating mirror according to any of the above aspects;
2) Driving the micro-galvanometer module 21 to deflect in an electromagnetic driving mode so as to reflect light emitted by the light converging module 11 received by the micro-galvanometer module 21 at different angles;
3) The light reflected by the micro-oscillating mirror module 21 is controlled to pass through the filtering module 31 and focused on the detecting module 41, so as to obtain spectrograms of light signals of monochromatic light with different wavelengths, and realize spectrum detection.
As an example, in step 2), the electromagnetic driving method specifically includes: driving current is introduced into the coil assembly 212 of the micro-mirror module, so that the coil assembly 212 deflects under the action of the magnetic force of the magnetic assembly of the micro-mirror module, and the coil assembly 212 drives the micro-mirror assembly 214 of the micro-mirror module to deflect through the torsion assembly 213 of the micro-mirror module, wherein the magnitude and the frequency of the driving current are set according to the pixel interval and the sampling period of the detection module 41.
As an example, in step 2), the driving current is generated by a driving circuit, wherein when the detection module starts sampling, a first pulse signal is generated to control the driving circuit to generate the driving current, and when the detection module stops sampling, a second pulse signal is generated to control the driving circuit to stop generating the driving current.
Specifically, the micro-mirror module 21 further includes a coil assembly 212 and an electromagnetic assembly, where the coil assembly 212 is a coil, the magnetic assembly is a permanent magnet, and electromagnetic driving is implemented by the above assembly in a rotation manner of the micro-mirror assembly 214, that is, a magnetic field of the magnetic assembly is perpendicular to incidence of the coil, the coil is forced to deflect, and the torsion bar drives the micro-mirror to rotate, and the rotation angle and frequency thereof change with the magnitude and frequency of the driving current flowing into the coil, and are determined according to the pixel interval and sampling period of the detection module (such as a CMOS detector), where the detection module is used to receive the optical signal obtained by the filtering module. The MEMS micro-vibrating mirror adopts an electromagnetic driving mode, the required voltage and current are very small, and the integrated power consumption of the spectrometer is greatly reduced by matching with a CMOS with low power consumption, so that the MEMS micro-vibrating mirror is conveniently integrated on electronic equipment such as a mobile phone.
Specifically, the torsion assembly 213 may be, but is not limited to, a torsion bar, the micromirror assembly 214 may be, but is not limited to, a micromirror, the coil assembly 212 is a coil, the magnetic assembly is a permanent magnet, and in an actual operation process, when the CMOS detector starts sampling, a trigger pulse signal is generated for a driving circuit of the MEMS micro-resonator in the micro-resonator module 21, and the driving circuit controls the MEMS micro-resonator to deflect and rotate from 0 ° to 23 ° in a sampling period; after the sampling is finished, the CMOS generates a pulse signal to trigger the vibrating mirror to stop rotating.
As an example, the micro-mirror module further includes a position sensor that detects the deflection angle of the micro-mirror assembly 214 and transmits its detection value to the driving circuit, and the driving circuit implements compensation of the deflection angle according to the received position information of the deflection angle and a preset parameter value.
Specifically, the micro-vibration mirror module further comprises a position sensor, wherein the position sensor is used for detecting the rotation angle of the micro-mirror, and the rotation angle information is transmitted to a driving circuit for providing driving current for the coil, namely the angle control system, and the driving circuit modulates the amplitude of the driving current source according to the position information, so that the compensation of the rotation angle is realized.
As an example, the sampling mode of the detection module 41 is a cyclic sampling, where when the detection module 41 starts sampling, the generated first pulse signal is a zigzag pulse with a predetermined frequency, so that the micro-mirror module 21 performs cyclic scanning, and the cyclic sampling of the detection module 41 is implemented.
Specifically, the spectrum detection method provided by the invention further comprises the step of circularly sampling, so that the CMOS detector is circularly sampled to improve the accuracy of spectrum measurement, the MEMS micro-vibrating mirror is required to generate sawtooth-shaped pulses with a certain frequency, the vibrating mirror is circularly scanned, and the CMOS detector is used for repeatedly sampling and summing to obtain a spectrogram with higher accuracy.
Example two
The invention also provides an integrated gas sensor, comprising the micro spectrometer based on the MEMS micro vibrating mirror according to any one of the above embodiments.
As an example, the filtering module includes a plurality of resonant cavities having different preset thicknesses, where the preset thicknesses are set according to characteristic peaks of the gas to be measured.
Specifically, the integrated gas sensor provided in this embodiment adopts the spectrometer according to any one of the embodiments, and takes the spectrometer with the integrated narrowband filter as an example, when designing the integrated filter array, different thicknesses of the resonant cavities are designed according to the characteristic peaks of different gases to be detected.
Since the conventional sensor often uses a chemical method, the requirement of high-precision gas detection cannot be satisfied, and the detection needs to be performed by an optical method, but the gas usually has a specific absorption peak, and the detection of the whole spectral range is not required. If the spectrometer is selected for detection, the cost is greatly increased. The gas detection is usually to detect various gases, if a special gas sensor is selected for detection, a plurality of sensors are needed to meet the requirements, so that the cost is increased, the integration rate is low, the requirements of small portability cannot be met, and the miniature spectrometer can be combined for different gas characteristic peak filter array elements to meet the requirements of simultaneous measurement of various gases, and has the advantages of high precision, small portability and low cost. For example, the micro spectrometer can be used for agricultural detection, and in some greenhouse planting or greenhouse cultivation, the requirements on factors such as carbon dioxide, temperature and humidity, nitrogen, oxygen and the like are very high; the micro spectrometer can be used for designing filter array elements corresponding to different wavelengths for different gases, and combining the filter array elements with CMOS (complementary metal oxide semiconductor) pixels or pyroelectric detectors, so that each pixel can detect characteristic peaks of different gases, and the concentration change of different gases is judged.
It will be further explained that fig. 4 shows an atmospheric absorption and atmospheric window diagram, and it can be seen that different gases correspond to different absorption peaks, so that different array elements (such as the resonant cavity) can be designed according to the wavelength of absorption. For example, when gas detection such as carbon dioxide, oxygen, water vapor, methane, carbon monoxide, and nitrogen dioxide is designed, the absorption wavelength corresponding to the gas detection is selected: carbon dioxide at 4.2 μm, oxygen at 0.1 μm and 0.7 μm, water vapor at 1.4 μm, 1.8 μm and 1.9 μm, methane at about 3.4 μm, carbon monoxide at 4.64 μm, nitrogen dioxide at 4.47 μm, in this example, a wavelength of about 1 μm which is not absorbed by any gas can also be selected as an environmental reference value. And each optical filter array element is designed to have a corresponding thickness according to different wavelengths, and corresponds to different CMOS pixels, and finally the corresponding gas concentration can be obtained by subtracting the environment reference value from the luminous flux measured by the CMOS. Meanwhile, in order to make the measurement more accurate, each gas can correspond to a plurality of optical filter array elements and a plurality of pixels, and the average is removed by measuring for a plurality of times, and temperature measurement can be added, wherein the measurement temperature is generally selected to be within the spectrum range of 0.18-1.0 mu m.
In addition, the combination of different gas sensors can be used in different fields, such as integrated sensors for measuring carbon dioxide, oxygen, water vapor and temperature, and can be used in the fields of agricultural detection, greenhouse planting, greenhouse cultivation and the like; integrated sensors such as measuring carbon dioxide, oxygen, methane, temperature can be used in poultry farming and aquaculture; integrated sensors such as carbon monoxide, nitrogen dioxide, oxygen, carbon dioxide, etc. sensors may be used in flame detection, etc.
In summary, the present invention provides a micro spectrometer, a gas sensor and a spectrum detection method based on a MEMS micro vibrating mirror, where the spectrometer includes: the light converging module is used for converging light reflected by the object to be detected; the micro-vibration mirror module is arranged on an emergent light path of the light converging module and is used for receiving the light emitted by the light converging module and reflecting the light at different angles; the light filtering module is arranged on an emergent light path of the micro-vibration mirror module and is used for receiving light reflected by the micro-vibration mirror module and filtering the light so as to obtain a plurality of light signals of monochromatic light with different wavelengths; and the detection module is connected with the light filtering module and arranged at the focal position of the light converged by the light converging module, and reads the light signal obtained by the light filtering module to obtain a spectrogram of the light signal. Through the scheme, the micro spectrometer based on the MEMS micro-vibrating mirror adopts the integrated optical filter and the micro-vibrating mirror based on the MEMS technology, so that the traditional mechanical structure and large devices such as the grating prism are simplified, and the spectrometer has the characteristics of high integration, small volume, light weight and convenience in carrying; the invention adds the structure of vibrating mirror scanning, compared with the traditional spectrometer with only optical filters and CMOS, the invention improves the light intensity and light utilization efficiency of unit pixel, thereby improving the signal to noise ratio, and simultaneously, the invention greatly improves the measurement precision and sensitivity based on the characteristic of high-speed scanning of MEMS vibrating mirrors; the MEMS micro-vibrating mirror adopts an electromagnetic driving mode, has smaller required voltage and current, is matched with a CMOS with low power consumption, greatly reduces the overall power consumption of a spectrometer, and is convenient to integrate on electronic equipment such as a mobile phone and the like. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (17)
1. A micro spectrometer based on MEMS micro-mirrors, comprising:
the light converging module is used for converging light reflected by the object to be detected;
the micro-vibration mirror module is arranged on an emergent light path of the light converging module and is used for receiving the light emitted by the light converging module and reflecting the light at different angles;
the light filtering module is arranged on an emergent light path of the micro-vibration mirror module and is used for receiving light reflected by the micro-vibration mirror module and filtering the light so as to obtain a plurality of light signals of monochromatic light with different wavelengths; and
the detection module is connected with the light filtering module and arranged at the focal position of the light converged by the light converging module, and reads the light signals obtained by the light filtering module to obtain a spectrogram of the light signals.
2. The MEMS micro-mirror based micro-spectrometer of claim 1, wherein the filter module comprises an integrated narrowband filter comprising m x n resonators, wherein m and n are integers greater than or equal to 1, the resonators have different thicknesses, and the resonators of different thicknesses filter the light signals of monochromatic light of different wavelengths.
3. The MEMS micro-mirror based micro-spectrometer of claim 2, wherein the integrated narrowband filter comprises a lower layer film system, a spacer layer and an upper layer film system stacked in sequence, the spacer layer comprising m x n resonant cavities, the upper layer film system being mirror-symmetrically disposed with the lower layer film system.
4. The MEMS micro-mirror based micro-spectrometer of claim 3, wherein the upper layer of film is the same thickness as the lower layer of film and each comprises a low refractive index film and a high refractive index film stacked in sequence.
5. The MEMS micro-mirror based micro-spectrometer of claim 1, wherein the filter module comprises a graded filter comprising a substrate and a coating on the upper surface of the substrate, wherein the distance between the coating and the upper surface of the substrate is graded in a linear or stepped manner to filter the light signals of monochromatic light with different wavelengths.
6. The MEMS micro-mirror based micro-spectrometer of claim 1, wherein the micro-mirror module comprises a substrate, a torsion assembly disposed on the substrate, and a micro-mirror assembly disposed on the torsion assembly, the torsion assembly driving the micro-mirror assembly to deflect, the micro-mirror assembly receiving and reflecting the light emitted by the light converging module.
7. The MEMS micro-mirror based micro-spectrometer of claim 6, wherein the micro-mirror module further comprises a coil assembly and a magnetic assembly disposed on the substrate, wherein a magnetic force of the magnetic assembly acts on the coil assembly, the coil assembly is forced to deflect and the micro-mirror assembly is driven to deflect by the torsion assembly.
8. The MEMS micro-mirror based micro-spectrometer of claim 7, wherein the micro-mirror assembly is a mirror having an area greater than or equal to the area of the light it receives and a deflection angle of 0-23 °.
9. The MEMS micro-mirror based micro-spectrometer of claim 6, wherein the micro-mirror module further comprises a position sensor disposed on the substrate for detecting the deflection angle of the micro-mirror assembly and transmitting the detected value to an angle control system to compensate the deflection angle of the micro-mirror assembly.
10. The MEMS micro-mirror based micro-spectrometer of claim 1, wherein the detection module comprises a plurality of detection pixels, the plurality of detection pixels reads out the light signal and obtains a spectrogram thereof, wherein the preset number of detection pixels corresponds to the light signal of the monochromatic light with one wavelength generated by the filtering module.
11. An integrated gas sensor comprising a MEMS micro-mirror based micro-spectrometer according to any of claims 1-10.
12. The integrated gas sensor of claim 11, wherein the filter module comprises a plurality of resonant cavities having different preset thicknesses, the preset thicknesses being set according to characteristic peaks of the gas to be measured.
13. The spectrum detection method of the micro spectrometer based on the MEMS micro vibrating mirror is characterized by comprising the following steps of:
1) Providing a MEMS micro-mirror based micro-spectrometer according to any of claims 1-10;
2) Driving the micro-vibrating mirror module to deflect in an electromagnetic driving mode so as to reflect light emitted by the light converging module received by the micro-vibrating mirror module at different angles;
3) And controlling the light reflected by the micro-vibrating mirror module to pass through the light filtering module and focus on the detection module so as to obtain spectrograms of light signals of monochromatic light with different wavelengths, thereby realizing spectrum detection.
14. The method for detecting a spectrum of a micro spectrometer based on a MEMS micro vibrating mirror according to claim 13, wherein in step 2), the electromagnetic driving mode is specifically: and driving current is introduced into a coil assembly of the micro-vibration mirror module so that the coil assembly deflects under the action of magnetic force of a magnetic assembly of the micro-vibration mirror module, and the coil assembly drives the micro-mirror assembly of the micro-vibration mirror module to deflect through a torsion assembly of the micro-vibration mirror module, wherein the magnitude and the frequency of the driving current are set according to the pixel interval and the sampling period of the detection module.
15. The method of claim 14, wherein in step 2), the driving current is generated by a driving circuit, wherein when the detection module starts sampling, a first pulse signal is generated to control the driving circuit to generate the driving current, and when the detection module stops sampling, a second pulse signal is generated to control the driving circuit to stop generating the driving current.
16. The method of claim 15, wherein the micro-mirror module further comprises a position sensor, the position sensor detects a deflection angle of the micro-mirror assembly and transmits the detected value to the driving circuit, and the driving circuit compensates the deflection angle according to the received position information of the deflection angle and a preset parameter value.
17. The method for detecting a spectrum of a micro spectrometer based on a MEMS micro-mirror according to claim 15 or 16, wherein the sampling mode of the detection module is a cyclic sampling, wherein the first pulse signal generated when the detection module starts sampling is a zigzag pulse with a predetermined frequency, so that the micro-mirror module performs cyclic scanning to realize cyclic sampling of the detection module.
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| US11092727B2 (en) | 2018-06-29 | 2021-08-17 | Viavi Solutions Inc. | High-resolution single photodiode spectrometer using a narrowband optical filter |
| TWI685660B (en) * | 2018-09-20 | 2020-02-21 | 大陸商信泰光學（深圳）有限公司 | Optical detecting apparatus |
| CN111351768B (en) * | 2018-12-20 | 2022-10-18 | 中国科学院合肥物质科学研究院 | Multi-component gas laser detection device and method using scanning galvanometer |
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