Background
The imaging spectrum chip is an important component in a spectrum imaging detection system, can perform two-dimensional imaging of a target, and can detect spectrum information of the target. At present, imaging spectrum chip development is mainly carried out by adopting methods such as a filter, quantum dots, fabry-Perot interference, photonic crystals, super-structure surface narrow-band light filtering and the like.
The filter method is, for example, as in US9466628B2, spectral imaging device and method to calibrate the same, and a plurality of filters are provided to perform light splitting and acquisition by an image sensor to obtain continuous, narrow-band spectral image data with high spectral resolution.
As described in chinese patent document CN114910165a, the quantum dot method is a method in which a spectrum chip and a spectrum device are used to obtain information and spectrum information related to the spatial distribution of the intensity of an incident light source by preparing quantum dot films with different transmission curves on a wafer of a photoelectric image sensor to perform light splitting.
The fabry-perot interferometry is described in chinese patent document CN111351573 a: in the spectrum chip, the chip packaging structure and the manufacturing method, the Fabry-Perot cavity formed by the reflecting film is developed on the photosensitive surface of the photoelectric image sensor, so that the light splitting of the incident light is realized, and the photoelectric image sensor is used for collecting the information of the incident light. To achieve modularity and miniaturization of the spectral detection.
A photonic crystal method is described in a Chinese patent document CN114279565A, and is characterized in that a non-refrigeration infrared spectrum chip, a preparation method thereof and an infrared spectrometer are disclosed, a plurality of photonic crystal plate arrays with different parameters are prepared on the photosensitive surface of a photoelectric image sensor, broadband light splitting of incident light is realized, meanwhile, the dimension of the photonic crystal can be scaled, the crosstalk of the incident light on the sensor is reduced, and the spectrum measurement precision is improved.
A hypersurface narrowband filtering method is described in Chinese patent document CN106847849A, and a multispectral chip based on hypersurface narrowband filtering and a preparation method thereof are disclosed, wherein periodic porous nanostructure arrays with different sizes are prepared on a metal dielectric film layer with the same thickness, so that narrowband filtering of a target image on a multispectral spectrum band is realized, and the preparation of a miniaturized and large-area array imaging spectrum chip can be realized.
The imaging spectrum chip technology has the practical technical problems of low energy utilization rate, low spectrum modulation degree, narrow spectrum coverage range, reduced spatial resolution, small view field angle and the like in practical application, and cannot meet the requirements of daily application scenes. Meanwhile, the preparation process is complex, the process precision requirement is high, and the mass production cannot be realized.
Disclosure of Invention
The invention aims to solve the problems existing in the practical application of the existing imaging spectrum chip technology: the wide-spectrum modulation-demodulation imaging spectrum chip based on the symmetrical C-shaped three-dimensional structure and the production method thereof are provided.
The chip is sequentially from top to bottom: the device comprises a broad spectrum modulation structure layer, a photoelectric image sensor module and a spectrum image demodulation module.
Further, a preferred scheme is provided: the wide spectrum modulation structure layer is composed of a plurality of wide spectrum modulation structure units, the plurality of wide spectrum modulation structure units form N multiplied by N channels, and each channel corresponds to a metamaterial structure unit array.
Further, a preferred scheme is provided: n is 3 or 4 or 5.
Further, a preferred scheme is provided: the planar view of the wide spectrum modulation structure unit in x-z is two C-shaped, and the two C-shaped openings are arranged in a mirror image mode.
Further, a preferred scheme is provided: the wide-spectrum modulation structure unit is a cuboid, the cuboid is square on the x-z plane, the side length L of the square is 1-10 mu m, and the width of the cuboid along the y-axis direction is 1-10 mu m.
Further, a preferred scheme is provided: the width omega of the slit between the C-shaped incident end and the emergent end is 0.3 mu m-3 mu m; the thickness of the incident end and the emergent end is t, the depth d of the C-shaped inner wall groove is 0.2 mu m to 2 mu m, the width of the C-shaped inner wall groove is h, and the C-shaped inner wall groove comprises: l=h+2t.
Further, a preferred scheme is provided: each wide spectrum modulation structure unit in the wide spectrum modulation structure layer corresponds to each pixel unit in the photoelectric image sensor module one by one and is coaxial.
Further, a preferred scheme is provided: the photoelectric image sensor module is used for acquiring and modulating the optical signals projected by the wide-spectrum modulation structure layer to obtain modulation spectrum signals, and sending the modulation spectrum signals to the spectrum image demodulation module.
Further, a preferred scheme is provided: the spectrum image demodulation module is used for demodulating the modulated spectrum signal to obtain target image information and spectrum information.
Further, a preferred scheme is provided: and preparing a layer of photosensitive surface on the surface of the photoelectric image sensor module, wherein the photosensitive surface is matched with the broad spectrum modulation structure layer.
The production method comprises the following steps: preparing a broad spectrum modulation structure layer, selecting a photoelectric image sensor module and a spectrum image demodulation module, and connecting the photoelectric image sensor module, the spectrum image demodulation module and the spectrum image demodulation module in sequence, wherein the preparation method of the broad spectrum modulation structure layer comprises the following steps: the method comprises the steps of substrate pretreatment, magnetron sputtering coating, ion beam etching structure, substrate cleaning, spin coating of photoresist, soft baking, mask preparation, alignment and exposure, photoresist removal and hard baking, alignment mark point and protective layer plating.
The invention provides a new technical thought, breaks through the restriction of the manufacturing principle and the structural principle of a plurality of imaging spectrum chips in the background technology, innovatively designs a wide-spectrum modulation-demodulation imaging spectrum chip structure based on a symmetrical C-type three-dimensional structure, autonomously develops a spectrum modulation metamaterial structure, innovatively designs a production process compatible with the photoetching production of the traditional CMOS, can realize the batch manufacturing of the spectrum chips, and has the advantages of high energy utilization rate of more than 50%, high spectrum resolution, large field angle, large information quantity, no reduction of spatial resolution, small volume, low cost and mature production process, thereby having larger social benefit and wide application value.
The invention can be applied to food detection, agricultural monitoring, medical sensing, camouflage identification, aerospace remote sensing and other scenes.
Drawings
Fig. 1 is a schematic structural diagram of a broad spectrum modulation demodulation type imaging spectrum chip according to an embodiment, wherein 1 is a broad spectrum modulation structure layer, 2 is a photoelectric image sensor module, and 3 is a spectrum image demodulation module;
fig. 2 is a physical diagram of a broad spectrum modem type imaging spectrum chip according to a fifth embodiment;
fig. 3 is a schematic diagram of a broad spectrum modem imaging spectrum chip according to the first embodiment and the fifth embodiment;
fig. 4 is a schematic structural diagram of a broad spectrum modulation unit according to the fifth embodiment, (a) a perspective view of the broad spectrum modulation unit, and (b) a schematic Au size diagram of the broad spectrum modulation unit; the wide spectrum modulation unit is characterized in that L is the side length of a square, t is the thickness of an incident end and an emergent end, h is the width of a C-shaped inner wall groove, ω is the width of a slit between the C-shaped incident end and the emergent end, and d is the depth of the C-shaped inner wall groove;
fig. 5 is a partial enlarged view of a broad spectrum modulation structure layer according to a fifth embodiment;
FIG. 6 is a diagram of a broad spectrum modulation spectrum according to a fifth embodiment;
fig. 7 is a schematic diagram of a single 1-channel gain control of an optoelectronic image sensor module according to a fifth embodiment;
fig. 8 is a schematic diagram of a single 4-channel gain control of the optoelectronic image sensor module according to the fifth embodiment;
fig. 9 is a schematic diagram of a 7-channel gain control of an optoelectronic image sensor module according to a fifth embodiment;
fig. 10 is a schematic diagram of a 2-channel gain control of an optoelectronic image sensor module according to a fifth embodiment;
fig. 11 is a schematic diagram of a single 5-channel gain control of an optoelectronic image sensor module according to a fifth embodiment;
fig. 12 is a schematic diagram of an individual 8-channel gain control of the optoelectronic image sensor module according to the fifth embodiment;
fig. 13 is a schematic diagram of a 3-channel gain control of an optoelectronic image sensor module according to a fifth embodiment;
fig. 14 is a schematic diagram of a single 6-channel gain control of an optoelectronic image sensor module according to a fifth embodiment;
fig. 15 is a schematic diagram of a single 9-channel gain control of the optoelectronic image sensor module according to the fifth embodiment;
FIG. 16 is a gray scale plot and a multispectral plot of the multispectral imaging result of the spectral chip described in embodiment five;
fig. 17 is a band imaging result of the spectroscopic chip 8 according to the fifth embodiment;
FIG. 18 is a graph showing the comparison between the color lump 1 spectrometer test result and the chip spectrum inversion result in the fifth embodiment;
FIG. 19 is a graph showing the comparison between the color lump 7 spectrometer test result and the chip spectrum inversion result in the fifth embodiment;
FIG. 20 is a graph showing the comparison between the color lump 13 spectrometer test result and the chip spectrum inversion result in the fifth embodiment;
fig. 21 is a graph comparing the spectrum inversion result of the chip with the spectrum inversion result of the color lump 19 spectrometer according to the fifth embodiment.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, are intended to fall within the scope of the present invention.
Embodiment one
The present embodiment will be described with reference to fig. 1 and 3.
The wide-spectrum modulation-demodulation imaging spectrum chip of the embodiment comprises the following components in sequence from top to bottom: a broad spectrum modulation structure layer 1, a photoelectric image sensor module 2 and a spectrum image demodulation module 3.
Specifically:
the broad spectrum modulation structure layer 1 is used for modulating incident light information;
the photoelectric image sensor module 2 is matched with the broad spectrum modulation structure layer 1 and is used for collecting modulated incident light information and converting the modulated incident light information into digital electric signals;
the spectrum image demodulation module 3 is used for demodulating the digital electric signal to generate target multispectral image information.
The wide spectrum modulation structure layer 1 is a symmetrical C-shaped three-dimensional wide spectrum modulation and demodulation structure layer, and a spectrum image demodulation algorithm is stored in the spectrum image demodulation module 3.
The broad spectrum modulation structure layer 1 is composed of a plurality of broad spectrum modulation structure units, the plurality of broad spectrum modulation structure units form N multiplied by N channels (including 3 multiplied by 3, 4 multiplied by 4 or 5 multiplied by 5), each channel corresponds to a metamaterial structure unit array, 9, 16 or 25 channels of spectrum modulation can be realized, and a large field angle is ensured in principle.
Each metamaterial structure unit corresponds to a pixel unit of the photoelectric image sensor module 2, the sizes of the symmetrical C-shaped metamaterial structure units and the pixel units of the photoelectric image sensor module 2 are the same, the centers of the symmetrical C-shaped metamaterial structure units and the pixel units of the photoelectric image sensor module 2 are located on the same axis, and pixel-by-pixel spectrum modulation is achieved.
The photoelectric image sensor module 2 is designed according to each metamaterial structure unit, acquires modulation spectrum signals, adjusts gain parameters of the periodic structure units of each channel, and adapts to the modulation characteristics of each channel.
The spectrum image demodulation module 3 is arranged at the bottom end of the photoelectric image sensor module 2 and connected with the photoelectric image sensor module, and demodulates the modulated spectrum signals acquired by the photoelectric image sensor module 2 by utilizing a demodulation algorithm in the spectrum image demodulation module 3 to finally obtain target image information and spectrum information.
The spectrum chip according to the present embodiment includes: the device has the advantages of high spectral resolution, high energy utilization rate, large field angle, no reduction of spatial resolution, small volume and simple and mature whole production process.
Second embodiment
The present embodiment will be described with reference to fig. 4
This embodiment is a further illustration of the broad spectrum modulation structural unit in the broad spectrum modem imaging spectrum chip according to the first embodiment.
As shown in fig. 4:
the wide spectrum modulation structure unit in the embodiment has two C-shaped planar views in x-z, and the two C-shaped openings are arranged in a mirror image mode.
Specifically:
the two C-shaped openings are opposite, the outer frame of the wide spectrum modulation structural unit is a cuboid, the cuboid is square on the x-z plane, and the side length L of the square is adjustable from 1 mu m to 10 mu m; the width of the cuboid along the y-axis direction is adjustable from 1 mu m to 10 mu m. The width w of the slit between the symmetrical C-shaped incident end and the emergent end is 0.3 mu m to 3 mu m, the depth d of the groove on the symmetrical C-shaped inner wall is 0.2 mu m to 2 mu m, the width h of the groove on the symmetrical C-shaped inner wall is 0.1 mu m to 10 mu m, the thickness t of the symmetrical C-shaped incident end and the emergent end, the width h of the groove on the C-shaped inner wall, and the device comprises: l=h+2t.
The light rays of each transmission angle of the designed symmetrical C-shaped three-dimensional structure have approximately the same analysis optical path from the microscopic angle, so that the spectral transmittance is unchanged, and a large field angle is ensured in principle.
According to the parameters, quasi-sinusoidal continuous wide-spectrum modulation line types with different frequencies in the wave bands of 300-1100nm can be realized.
The structure can generate plasma resonance phenomenon at the metal/medium interface according to the plasmon resonance characteristic, namely, when incident light enters the structure, the incident light enters the symmetrical C-shaped inner wall groove to be reflected, and according to the designed size of the symmetrical C-shaped inner wall groove. The method comprisesThe structure is designed in a groove embedded manner according to a traditional grating model, and a symmetrical C-shaped equivalent grating model aims at main parameters affecting the transmission performance of the grating model: grating period L, duty cycle、/>And performing model analysis on the metal grating height h and the equivalent medium grating refractive index n.
According to waveguide grating theory, the symmetrical C-type equivalent grating period L and refractive index n, and incident wavelengthAngle of incidence->Diffraction angle->The relationship is as follows:
peak transmittanceThe relationship with the slot geometry (entrance and exit slot width w, inner wall slot depth d) can be summarized as the following equation:
the geometrical term to the right of the equation represents the decrease in transmission peak due to reflection loss, and the exponential term represents ohmic loss related to both the entrance-end exit-end slit width w and the inner-wall groove depth d, where d corresponds to the slit width that satisfies the transmission peak output for a given slit width.
Symmetrical C-type equivalent gratingAnd->The mode of an F-P-like resonant cavity exists between the metal gratings in the direction, and the periodic structure of the single-layer metal grating is converted into a three-layer uniform medium structure through an equivalent medium theory, namely, the metal layers with heights of t, h and t in the Z direction in the figure 4 (b) are respectively formed.
The transmission rule formula of the F-P cavity formed in the symmetrical C type is as follows:
where l=h=2d+w,is the phase change generated when incident light is reflected on the surface of the grating, R 0 And T 0 Is the reflection and transmission coefficient, which can be obtained by irradiating the symmetrical C-type equivalent grating with incident light.
When the incident light resonates in the cavity, the reflected light and the incident light interfere and cancel at the exit interface, so that the grating has low transmittance, a trough appears, and most of other energy is reflected.
The phase difference when the incident and reflected light meet at the exit interface can be formulated as follows:
K 0 for incident light wave vector, n l The refractive index of the medium, h is the groove width of the symmetrical C-shaped inner wall,is the phase change that occurs when light is reflected. If the phase difference is pi or an odd number of piResonance occurs at times, as expressed by the following formula:
m is an integer. It is this resonance mode that causes energy to be localized in the intermediate dielectric layer, thereby degrading the grating transmission and creating a trough phenomenon.
The size of the wide-spectrum modulation structure unit is in the micron order, and can be in one-to-one correspondence with the size of the pixel unit of the photoelectric image sensor module 2. According to the pixel unit size of the photoelectric image sensor module, the unit modulation structure is arranged in an array mode, and the original spatial resolution of the photoelectric image sensor is not lost; the photoelectric image sensor can also be designed to have a single spectrum modulation structure corresponding to N pixels of the photoelectric image sensor, partial spatial resolution is lost, and the energy utilization rate of incident light corresponding to the single spectrum modulation structure is improved by N times.
Embodiment III
This embodiment is a further example of the optoelectronic image sensor module 2 in the broad spectrum modem type imaging spectrum chip according to the first embodiment.
The surface of the photoelectric image sensor module 2 in this embodiment is provided with a photosensitive surface capable of being matched with the broad spectrum modulation structure layer 1, so that the influence of the angle of incident light can be reduced, the detection view angle is increased, the modulated incident light information is converted into a digital electric signal, and the gain control function matched with the channels is arranged in the photoelectric sensor module 2, so that the gain control of each independent channel can be realized.
The pixel size of the photosensitive area of the photoelectric image sensor module 2 is matched with the size of the wide spectrum modulation structure unit, the size of the pixel size is between 1 μm and 10 μm, the photoelectric image sensor module can be matched with the size requirement of the wide spectrum modulation unit of the symmetrical C-shaped three-dimensional wide spectrum modulation structure layer according to the practical scene application requirement, and the photoelectric image sensor module has different channel gain control functions, and has the functions of automatic gain and noise floor control of N x N groups in rows and columns. The response intensity of each channel can be linearly regulated by controlling the gain, the dynamic range reduction phenomenon brought by the symmetrical C-shaped three-dimensional wide spectrum modulation structure layer in the modulation process is compensated, the dynamic range of the photoelectric image sensor is ensured to be good, the spectral modulation linear region can be regulated by controlling the gain, and the gray value of each channel is ensured to be within a reasonable dynamic range.
Fourth embodiment
This embodiment is a further example of the spectral image demodulation module 3 in the broad spectrum modem type imaging spectral chip according to the first embodiment.
The spectrum image demodulation module 3 in this embodiment includes an image signal processor and a built-in spectrum image inversion algorithm, so as to demodulate the acquired information, and finally obtain the target image information and the spectrum information.
Specifically:
the image signal processor has a spectrum correction function, and since there is a difference between the spectrum of visible light and the spectral responsivity of the semiconductor sensor and there is a deviation in the obtained spectrum due to the influence of a lens or the like, it is necessary to correct the spectrum, and it is common practice to perform spectrum correction by using an n×n spectrum change matrix.
According to the spectrum image inversion algorithm, according to the spectrum transmittance of each group of N multiplied by N channels (namely N multiplied by N symmetrical C-shaped three-dimensional wide spectrum modulation structural units), gray values on pixels of a photoelectric image sensor corresponding to the periodic structural units form an N multiplied by N element linear equation set, the equation set is solved, the whole image is traversed, N multiplied by N unknowns are obtained, the unknowns are intensity values on the N multiplied by N spectral segments, the whole image is traversed, the spectrum values of the N multiplied by N spectral segments of the target are calculated, and the spectrum information of the target to be detected can be demodulated.
Consider the firstThe output signals Oi of the individual photo-image sensor pixels are shown in the following equation.
Wherein,spectrum representing the object of measurement, +.>Indicate->The individual spectral sensors are +.>Is a light transmittance of the substrate. Multiplication term->In section->Having non-zero components therein, ">Is system noise or disturbance.
For spectral inversion, which can be modeled as a system of linear equations, a discretized model in matrix form can be represented by the following equation:
and solving the X in the equation to obtain the spectrum image information of the target to be detected.
Fifth embodiment
The present embodiment will be described with reference to fig. 7 to 21.
This embodiment is a further example of the broad spectrum modem type imaging spectrum chip described in the first to fourth embodiments.
The wide-spectrum modulation demodulation type spectrum imaging chip shown in fig. 3 comprises a wide-spectrum modulation structure layer 1 shown in fig. 2, a photoelectric image sensor module 2 and a spectrum image demodulation module 3. The wide-spectrum modulation structure layer is formed by a metamaterial unit structure array with 3 multiplied by 3 different structural parameters, and each symmetrical C-shaped metamaterial unit corresponds to a pixel unit of the photoelectric image sensor to realize pixel-by-pixel spectrum modulation; the photoelectric image sensor module is designed according to symmetrical C-shaped metamaterial structure units, and gain parameter adjustment is carried out on each channel periodic structure unit so as to adapt to modulation characteristics of each channel; the spectrum image demodulation algorithm module is arranged at the bottom end of the photoelectric image sensor and connected with the photoelectric image sensor, light transmitted to the symmetrical C-shaped three-dimensional wide spectrum modulation structure is collected by the photoelectric image sensor after being modulated by the structure to generate a modulation chart, the modulation chart is output to the spectrum image demodulation algorithm module, and the collected information is demodulated by the spectrum image demodulation algorithm module, so that target image information and spectrum information are finally obtained.
The wide spectrum modulation spectrum is shown in fig. 4, the photoelectric image sensor module adopts a domestic BF3005 type CMOS image sensor, the pixel size is 6 μm multiplied by 6 μm, the photoelectric image sensor module has the automatic gain control functions of 3×3 groups of rows and columns, and the gain control of the independent channels of the photoelectric image sensor module is shown in fig. 7 to 15. The gray value of each channel can be ensured to be within a reasonable dynamic range by controlling the gain to adjust the spectrum modulation linear region.
In the present embodiment, the spectrum sensors each having a group of 3×3 9 cells are integrated in 9 pixels of the photoelectric image sensor 3×3. In the context of the illustration of figure 5,spectrum representing the object of measurement, +.>Indicate->The individual spectral sensors are +.>Is a light transmittance of the substrate. Consider->The output signals of the individual spectral sensors are shown in the following equation.
Wherein the multiplication termIn section->Having non-zero components therein, ">Is system noise. For spectral inversion, which can be modeled as a system of linear equations, a discretized model in matrix form can be represented by the following equation:
and solving the X in the equation to obtain the spectrum image information of the target to be detected. Taking a 24-color card imaging result as an example, a gray level image is shown in fig. 16 (a), a multispectral image is shown in fig. 16 (b), a spectrum chip 8-band imaging result is shown in fig. 17, and a pair of a partial color block spectrometer testing result and a chip spectrum inversion result is shown in fig. 18-21, so that the spectrum matching degree is more than 80%.
Embodiment six
The method for producing the wide-spectrum modulation-demodulation type imaging spectrum chip comprises the following steps:
the preparation method of the wide-spectrum modulation structure layer comprises the steps of preparing the wide-spectrum modulation structure layer, selecting a photoelectric image sensor module and a spectrum image demodulation module, and connecting the photoelectric image sensor module, the spectrum image demodulation module and the spectrum image demodulation module in sequence, and is characterized in that the preparation method of the wide-spectrum modulation structure layer comprises the following steps: the method comprises the steps of substrate pretreatment, magnetron sputtering coating, ion beam etching of a structure, substrate cleaning, spin coating of photoresist, soft baking, mask preparation, alignment and exposure, photoresist removal and hard baking, magnetron sputtering coating, alignment mark points, ion beam etching of a structure and plating of a protective layer.