Hyperspectral volume scattering function and attenuation coefficient fast measurement circuit

Abstract

The utility model discloses hyperspectral body scattering function and attenuation coefficient fast measurement circuit, including multiband light source module, optical detection array module, signal conditioning module, ADC array module, CPLD control module and MCU main control module, the CPLD control module with multiband light source module is connected for control multiband light source module output target wavelength's detection light, optical detection array module includes detector to respectively gather transmission light, different angle's scattering light and reference light signal, and output analog signal to signal conditioning module. Through CPLD control module generation global synchronous control signal, realize light source band switching, the accurate synchronization of ADC conversion, ensure that the time correlation of different wavelength, different angle measurement data, simultaneously can through MCU main control module configuration light source switching order, measurement period etc. parameter, adapt to different measurement scene demand.

Description

Technical Field

[0001] This utility model relates to the field of marine optical measurement technology, specifically to a rapid measurement circuit for hyperspectral volume scattering function and attenuation coefficient, suitable for rapid synchronous hyperspectral measurement of seawater volume scattering function and attenuation coefficient. Background Technology

[0002] Volume scattering function and attenuation coefficient are key parameters of the inherent optical properties of seawater, and have important applications in fields such as primary marine productivity assessment, water color remote sensing, and aquatic environment monitoring. Existing measurement techniques have the following shortcomings: First, multispectral measurements have poor synchronization, making it difficult to guarantee the temporal correlation of measurement data at different wavelengths; second, the separation of light source band switching and data acquisition control leads to increased measurement errors; and third, it is difficult to balance signal acquisition accuracy and speed, failing to meet the requirements of high-frequency profiling measurements. Utility Model Content

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-spectral volume scattering function and attenuation coefficient rapid measurement circuit, so as to realize the synchronous acquisition and processing of optical signals of different wavelengths and angles, and improve the measurement accuracy and efficiency.

[0004] To achieve the above objectives, the technical solution of this utility model is as follows:

[0005] A rapid measurement circuit for hyperspectral volume scattering function and attenuation coefficient includes a multi-band light source module, an optical detection array module, a signal conditioning module, an ADC array module, a CPLD control module, and an MCU main control module;

[0006] The CPLD control module is connected to the multi-band light source module and is used to control the multi-band light source module to output probe light of the target wavelength;

[0007] The optical detection array module includes a detector for acquiring transmitted light, scattered light at different angles, and reference light signals respectively, and outputting an analog signal to the signal conditioning module;

[0008] The signal conditioning module is used to amplify and filter the analog signal before inputting it to the ADC array module;

[0009] The ADC array module is connected to the CPLD control module to exchange information with the CPLD control module, and completes the conversion of analog signals to digital signals or digital signals to analog signals under the control of the CPLD control module.

[0010] The MCU main control module and the CPLD control module are connected and used to configure measurement parameters, read cached data and send control commands.

[0011] Optionally, the CPLD control module includes a register array, an SPI timing control unit, and a light source gating logic unit; the register array is used to buffer the conversion data of the ADC array module; the SPI timing control unit is used to generate synchronous conversion signals and time-division multiplexed SPI read / write timing; the light source gating logic unit is used to output a light source gating signal to control the multi-band light source module to output probe light of the target wavelength.

[0012] Optionally, the multi-band light source module includes multiple collimated lasers of different wavelengths and a light source driving circuit. The input terminal of the light source driving circuit is connected to the output terminal of the light source gating logic unit of the CPLD control module, so as to drive the collimated laser to output probe light of the corresponding wavelength according to the light source gating signal.

[0013] Optionally, the collimated laser is a circularly polarized laser with an output beam divergence angle of less than 0.1 mrad and a wavelength covering the range of 400 nm to 900 nm; the light source driving circuit uses a MOS transistor switching array to achieve contactless power supply control of the laser.

[0014] Optionally, the optical detection array module includes a transmitted light detector, seventeen scattered light detectors, and a reference light detector to collect transmitted light, scattered light at different angles, and light source reference signals, respectively.

[0015] Optionally, the detector of the optical detection array module is a silicon photomultiplier tube, which, together with the field-of-view limiting aperture, has an inclined slope structure on the outer side of the window glass of the transmitted light detector. The field-of-view range of the scattered light detector is set according to the direction of the detector, with a maximum field-of-view of no more than 10° and a minimum of no less than 0.4°.

[0016] Optionally, the signal conditioning module includes nineteen signal conditioning units, each of which includes a signal amplification circuit, an eighth-order low-pass filter, and a precision resistor network connected in sequence, with a narrowband filtering frequency of 1kHz and an adjustable amplification gain ranging from 1 to 100 times.

[0017] Optionally, the ADC array module includes nineteen ADC chips. The ADC chips are 24-bit ADCs that output data based on SPI. The SCK pin of the SPI interface is connected to the SPI clock line of the CPLD control module, the MOSI pin is connected to the SPI output line of the CPLD control module, and the MISO pin is independently connected to the dedicated input pin of the CPLD control module. The conversion start pins of all ADC chips synchronously receive the CONVST pulse signal output by the CPLD control module.

[0018] Optionally, the CPLD control module includes a register array, which adopts a 19×24-bit dual-port RAM structure, supports parallel writing and serial reading, and is configured with a data ready flag and a channel address pointer. The SPI timing control unit operates at a frequency of 10MHz to 20MHz, and the light source gating logic unit outputs multiple gating signals to control the wavelength switching of the multi-band light source module.

[0019] Optionally, the CPLD control module and the MCU main control module communicate using an interrupt-triggered method.

[0020] Compared with the prior art, the advantages of this utility model are as follows:

[0021] The hyperspectral volume scattering function and attenuation coefficient rapid measurement circuit provided by this utility model generates a global synchronization control signal through the CPLD control module to achieve precise synchronization of light source band switching and ADC conversion, ensuring the time correlation of measurement data at different wavelengths and angles; at the same time, parameters such as light source switching sequence and measurement cycle can be configured through the MCU main control module to adapt to different measurement scenario requirements. Attached Figure Description

[0022] Figure 1 This is an overall structural block diagram of the hyperspectral volume scattering function and attenuation coefficient rapid measurement circuit provided in the embodiments of this application;

[0023] Figure 2 This diagram illustrates the internal structure of the CPLD control module and its connection to the ADC array module, multi-band light source module, and MCU main control module.

[0024] In the diagram: 1. Multi-band light source module; 11. Collimated laser; 12. Light source driving circuit; 2. Optical detection array module; 3. Signal conditioning module; 4. ADC array module; 5. CPLD control module; 6. MCU main control module Detailed Implementation

[0025] Example:

[0026] The technical solution of this utility model will be further described below with reference to the accompanying drawings and embodiments.

[0027] See Figure 1 As shown, the high-spectral volume scattering function and attenuation coefficient fast measurement circuit provided in this embodiment includes a multi-band light source module 1, an optical detection array module 2, a signal conditioning module 3, an ADC array module 4, a CPLD control module 5, and an MCU main control module 6.

[0028] The CPLD control module 5 is connected to the multi-band light source module 1 and is used to control the multi-band light source module 1 to output the probe light of the target wavelength. The optical detection array module 2 includes a detector for collecting transmitted light, scattered light at different angles, and reference light signals, and outputs an analog signal to the signal conditioning module 3. The signal conditioning module 3 is used to amplify, filter, and range-match the analog signal to improve the signal quality before inputting it to the ADC array module 4. The ADC array module 4 is connected to the CPLD control module to exchange information with it and complete the conversion from analog signal to digital signal or from digital signal to analog signal under the control of the CPLD control module. The MCU main control module 6 is connected to the CPLD control module and is used to configure measurement parameters, read buffered data, and send control commands.

[0029] Therefore, the high-spectral volume scattering function and attenuation coefficient rapid measurement circuit provided in this embodiment generates a global synchronization control signal through the CPLD control module to achieve precise synchronization of light source band switching and ADC conversion, ensuring the time correlation of measurement data at different wavelengths and angles; at the same time, parameters such as light source switching sequence and measurement cycle can be configured through the MCU main control module to adapt to different measurement scenario requirements.

[0030] In one specific embodiment, such as Figure 2 As shown, the CPLD control module 5 uses the ALTERA MAX II series EPM240 chip, including a register array, an SPI timing control unit, and a light source gating logic unit. The register array uses a 19×24-bit dual-port RAM structure, supporting parallel writing and serial reading, as well as single-cycle writing and random reading. It is configured with a data ready flag and a channel address pointer. The SPI timing control unit operates at a frequency of 10MHz to 20MHz, sequentially reading nineteen ADC data channels using time-division multiplexing, with a single frame data reading time ≤58μs, generating a 100μs period CONVST pulse. The light source gating logic unit outputs four gating signals to control the wavelength switching of the multi-band light source module. In other words, the CPLD control module in this application uses existing chips and related control programs, without any improvement to the control program.

[0031] In one specific embodiment, the multi-band light source module 1 includes four circularly polarized collimated lasers 11 with different wavelengths of 450nm, 532nm, 650nm, and 785nm, respectively, and an output beam divergence angle of less than 0.1mrad. The input terminal of the light source driving circuit 12 is connected to the output terminal of the light source gating logic unit of the CPLD control module to drive the collimated lasers 11 to output probe light of the corresponding wavelength according to the light source gating signal. The light source driving circuit 12 uses a MOS transistor to build a switching array, and in conjunction with a level conversion circuit, converts the 3.3V gating signal output by the CPLD into a 5V driving signal to achieve rapid switching of the lasers, with a switching time ≤10μs.

[0032] In one specific embodiment, the optical detection array module 2 includes a transmitted light detector, seventeen scattered light detectors, and a reference light detector to collect transmitted light, scattered light at different angles, and reference light signals from the light source, respectively. The seventeen scattered light detectors are distributed at 10° intervals within a range of 10° to 170°. All detectors employ high-sensitivity silicon photomultiplier tubes in conjunction with field-view limiting apertures. The outer side of the window glass of the transmitted light detector is designed with an inclined slope structure to reduce the interference of specular reflection on the measurement. The half-field-view range of the scattered light detectors is 0.4° to 2.5°.

[0033] In one specific embodiment, the signal conditioning module 3 includes nineteen signal conditioning units. Each signal conditioning unit includes an AD8221 signal amplifier circuit, an eighth-order low-pass filter, and a precision resistor network connected in sequence. The narrowband filtering frequency is 1kHz, and the amplification gain is adjustable from 1 to 100 times. The amplification factor can be configured by the MCU main control module according to the signal strength.

[0034] In one specific embodiment, the ADC array module 4 includes nineteen ADC chips. These ADC chips employ a 24-bit ADC, outputting data based on SPI. The SCK pin of the SPI interface is connected to the SPI clock line of the CPLD control module, the MOSI pin is connected to the SPI output line of the CPLD control module, and the MISO pin is independently connected to a dedicated input pin of the CPLD control module. The conversion start pins of all ADC chips synchronously receive the CONVST pulse signal output by the CPLD control module. More specifically, the ADC chip is the AD7793 chip, a 24-bit high-precision ADC with a built-in low-noise PGA and reference voltage source, achieving a maximum conversion rate of 4.8kHz. The CONVST pins of all chips are connected to the synchronous output of the CPLD, ensuring a conversion start time deviation ≤10ns, meeting synchronous measurement requirements.

[0035] In one specific embodiment, the CPLD control module 5 communicates with the MCU main control module 6 via an interrupt-triggered method. When the register array of the CPLD control module 5 is full of a frame of data, it notifies the MCU main control module to read the data via an interrupt pin. The MCU main control module 6 uses an STM32F407 chip and communicates with the CPLD control module through an SPI interface (communication rate 8MHz). It configures measurement parameters including the light source switching sequence, ADC conversion frequency, and data acquisition cycle, supporting both online measurement and fully automatic underwater measurement modes, and supporting a maximum measurement frequency of 20Hz. In other words, the MCU main control module of this application uses existing chips and related control programs, without involving any improvements to the control program.

[0036] In one specific embodiment, the rapid measurement circuit for hyperspectral volume scattering function and attenuation coefficient provided in this embodiment further includes a power management module. This power management module outputs a 3.3V analog power supply, a 3.3V digital power supply, and a 5V drive power supply, respectively powering the signal conditioning module, ADC array module, CPLD control module, MCU main control module, and multi-band light source module. Each power output terminal is equipped with an LC filter circuit and a ferrite bead. Specifically, the power management module uses an LT1963 regulator to provide a 3.3V analog power supply (ripple ≤1mV), an LM1117-3.3 to provide a 3.3V digital power supply, and an LM2596 to provide a 5V drive power supply. Each power circuit is connected in series with a ferrite bead and a 0.1μF + 10μF filter capacitor to reduce cross-interference between analog and digital power supplies.

[0037] The working process of the rapid measurement circuit for hyperspectral volume scattering function and attenuation coefficient provided in this embodiment is as follows:

[0038] After power-on, the MCU main control module configures the measurement parameters of the CPLD control module via SPI, including the light source switching sequence and ADC conversion cycle.

[0039] The CPLD control module's light source gating logic unit outputs a gating signal to control the multi-band light source module to output probe light of a specific wavelength;

[0040] The detectors of the optical detection array module collect transmitted light, scattered light at different angles, and reference light signals, and output analog signals to the signal conditioning module.

[0041] The signal conditioning module amplifies and filters the analog signal before inputting it to the ADC array module;

[0042] The CPLD control module's synchronization signal generator outputs a CONVST pulse, causing all 19 ADCs to start conversion simultaneously.

[0043] After the conversion is completed, the time-division multiplexing controller of the CPLD control module sequentially selects the CS pin of each ADC chip, reads 24-bit data via SPI and writes it into the corresponding RAM unit;

[0044] After all 19 data channels are written, the CPLD control module sets the data ready flag and notifies the MCU main control module via the interrupt pin.

[0045] The MCU main control module reads the data from the RAM, performs subsequent processing and storage, and simultaneously sends the next round of light source selection instructions to complete one measurement cycle.

[0046] This embodiment can realize hyperspectral measurement of volume scattering function and attenuation coefficient at 17 angles within the range of 10° to 170°, with a measurement frequency of up to 10Hz, which is suitable for rapid profile monitoring of the optical properties of marine water bodies.

[0047] In summary, the hyperspectral volume scattering function and attenuation coefficient rapid measurement circuit provided in this embodiment has the following technical advantages compared with the prior art:

[0048] Good synchronization: A global synchronization control signal is generated by CPLD to achieve precise synchronization of light source band switching and ADC conversion, ensuring the time correlation of measurement data at different wavelengths and angles;

[0049] High integration: The CPLD centrally implements light source selection, data acquisition and caching functions, reducing control links and system complexity;

[0050] Fast measurement speed: Supports measurement frequencies up to 10Hz (4 bands), enabling rapid acquisition of profile distribution data of water body optical properties;

[0051] Highly flexible: The MCU can be configured with parameters such as light source switching sequence and measurement cycle to adapt to different measurement scenarios.

[0052] The above embodiments are merely illustrative of the technical concept and features of this utility model, and are intended to enable those skilled in the art to understand the content of this utility model and implement it accordingly. They should not be construed as limiting the scope of protection of this utility model. All equivalent changes or modifications made based on the substance of the content of this utility model should be covered within the scope of protection of this utility model.

Claims

1. A rapid measurement circuit for hyperspectral bulk scattering function and attenuation coefficient, characterized in that, It includes a multi-band light source module, an optical detection array module, a signal conditioning module, an ADC array module, a CPLD control module, and an MCU main control module; The CPLD control module is connected to the multi-band light source module and is used to control the multi-band light source module to output probe light of the target wavelength; The optical detection array module includes a detector for acquiring transmitted light, scattered light at different angles, and reference light signals respectively, and outputting an analog signal to the signal conditioning module; The signal conditioning module is used to amplify and filter the analog signal before inputting it to the ADC array module; The ADC array module is connected to the CPLD control module to exchange information with the CPLD control module, and completes the conversion of analog signals to digital signals or digital signals to analog signals under the control of the CPLD control module. The MCU main control module and the CPLD control module are connected.

2. The rapid measurement circuit for hyperspectral bulk scattering function and attenuation coefficient as described in claim 1, characterized in that, The CPLD control module includes a register array, an SPI timing control unit, and a light source gating logic unit. The register array is used to buffer the conversion data of the ADC array module. The SPI timing control unit is used to generate synchronous conversion signals and time-division multiplexed SPI read / write timing. The light source gating logic unit is used to output a light source gating signal to control the multi-band light source module to output probe light of the target wavelength.

3. The rapid measurement circuit for hyperspectral bulk scattering function and attenuation coefficient as described in claim 1 or 2, characterized in that, The multi-band light source module includes multiple collimated lasers of different wavelengths and a light source driving circuit. The input terminal of the light source driving circuit is connected to the output terminal of the light source gating logic unit of the CPLD control module, so as to drive the collimated laser to output probe light of the corresponding wavelength according to the light source gating signal.

4. The rapid measurement circuit for hyperspectral bulk scattering function and attenuation coefficient as described in claim 3, characterized in that, The collimated laser is a circularly polarized laser with an output beam divergence angle of less than 0.1 mrad and a wavelength range of 400 nm to 900 nm. The light source driving circuit uses a MOS transistor switching array to achieve contactless power supply control of the laser.

5. The rapid measurement circuit for hyperspectral bulk scattering function and attenuation coefficient as described in claim 1, characterized in that, The optical detection array module includes a transmitted light detector, seventeen scattered light detectors, and a reference light detector to collect transmitted light, scattered light at different angles, and reference light signals from the light source, respectively.

6. The rapid measurement circuit for hyperspectral bulk scattering function and attenuation coefficient as described in claim 1 or 5, characterized in that, The detector of the optical detection array module is a silicon photomultiplier tube, which is used in conjunction with a field-of-view limiting aperture. The outer side of the window glass of the transmitted light detector is designed as an inclined slope structure. The field-of-view range of the scattered light detector is set according to the direction of the detector. The maximum field-of-view is set to no more than 10° and the minimum is no less than 0.4°.

7. The rapid measurement circuit for hyperspectral bulk scattering function and attenuation coefficient as described in claim 1 or 5, characterized in that, The signal conditioning module includes nineteen signal conditioning units. Each signal conditioning unit includes a signal amplification circuit, an eighth-order low-pass filter, and a precision resistor network connected in sequence. The narrowband filtering frequency is 1kHz, and the amplification gain is adjustable from 1 to 100 times.

8. The rapid measurement circuit for hyperspectral bulk scattering function and attenuation coefficient as described in claim 1 or 2, characterized in that, The ADC array module includes nineteen ADC chips, each using a 24-bit ADC that outputs data based on SPI. The SCK pin of the SPI interface is connected to the SPI clock line of the CPLD control module, the MOSI pin is connected to the SPI output line of the CPLD control module, and the MISO pin is independently connected to a dedicated input pin of the CPLD control module. The conversion start pins of all ADC chips synchronously receive the CONVST pulse signal output by the CPLD control module.

9. The rapid measurement circuit for hyperspectral bulk scattering function and attenuation coefficient as described in claim 1, characterized in that, The CPLD control module includes a register array, which adopts a 19×24-bit dual-port RAM structure, supports parallel writing and serial reading, and is configured with a data ready flag and a channel address pointer. The SPI timing control unit operates at a frequency of 10MHz to 20MHz, and the light source gating logic unit outputs multiple gating signals to control the wavelength switching of the multi-band light source module.

10. The rapid measurement circuit for hyperspectral bulk scattering function and attenuation coefficient as described in claim 1 or 9, characterized in that, The CPLD control module and the MCU main control module communicate using an interrupt-triggered method.

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