A micro-spectrometer control circuit and control method
By adopting a variable gain preamplifier circuit and an adjustable DC voltage bias circuit in a micro spectrometer, combined with FPGA automatic adjustment technology, the problem of limited adaptation range of optical signals is solved in the traditional micro spectrometer, and the intensity of optical signals is achieved sensitive adaptation and improvement of measurement efficiency.
Patent Information
- Application Number
- CN201910868846.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2019-09-16
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2039-09-16
AI Technical Summary
The fixed settings of preamplification and bias circuits in the control circuit of traditional micro spectrometers result in limited adaptation range of detection light signal intensity, weak signals require long-term integration, strong signals may be saturated, and dark current affects the output with temperature changes.
A micro spectrometer control circuit is designed, using a variable gain preamplifier circuit and an adjustable DC voltage bias circuit. Gain selection and bias adjustment are automatically achieved through a field programmable gate array (FPGA), using an operational amplifier and The digital potentiometer forms an adjustable circuit, which combines an ARM processor and a PC computer to achieve rapid adjustment.
Dynamically adjusting the gain and bias voltages expands the adaptation range of the micro spectrometer to the intensity of the light signal, eliminates the influence of dark current, and improves measurement efficiency and sensitivity.
Smart Images
Figure CN110455411B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of micro-spectral detection technology, and in particular to a control circuit and a control method capable of dynamically changing the intensity adaptation range of a micro-spectrometer to an input detection light signal. Background Art
[0002] The micro-spectrometer is the core component of the spectral measurement system. Due to its small size, it is convenient and flexible to build a spectral system. It is widely used in environmental monitoring, industrial control, chemical analysis, food quality testing, material analysis, clinical testing, aerospace remote sensing and scientific education.
[0003] The control circuit of the traditional micro-spectrometer is composed of a linear array CCD, a preamplifier and bias circuit, a CPLD drive circuit, an analog-to-digital converter, a memory, and a processor. The working process of the control circuit is that the external device transmits commands through the USB or RS232 interface of the micro-spectrometer, the processor in the control circuit parses the commands, controls the CPLD to generate the timing for reading the linear array CCD, and the CCD output signal is sent to the analog-to-digital converter through the preamplifier and bias circuit. The converted data is stored in the memory and then returned to the external device after being processed by the processor.
[0004] The preamplifier and bias circuit in the control circuit of the traditional micro-spectrometer are respectively adjusted by two potentiometers to adjust the amplification factor and bias voltage. The value of the potentiometer is fixed after factory debugging and cannot be adjusted in actual use. Therefore, the problem encountered is that when the external detection light signal is weak, the control circuit of the traditional micro-spectrometer can only obtain a spectral signal of sufficient intensity by setting the integration time of the linear array CCD. The weaker the light signal, the longer the integration time is required, which will cause the measurement time to be prolonged. In addition, when the external detection light signal is strong, the preamplifier may be saturated at the minimum integration time, resulting in the inability to obtain its spectral data. Since the voltage of the bias circuit is fixed, when the dark current of the linear array CCD changes with the ambient temperature, the output of the preamplifier circuit will also be affected. Summary of the invention
[0005] The purpose of the present invention is to overcome the deficiencies and shortcomings of the prior art and to provide a control circuit and a control method that can dynamically select a preamplifier gain and a bias voltage.
[0006] The present invention discloses a micro-spectrometer control circuit, which is composed of a linear array CCD, a gain-variable preamplifier circuit and an adjustable DC voltage bias circuit, a driver chip, an analog-to-digital converter, a field programmable gate array (FPGA), an external control circuit, an ARM processor, a PC host computer, and an external light source. Among them, the ARM processor pin is connected to the field programmable gate array (FPGA), and the driving signal generated by the field programmable gate array (FPGA) is connected to the linear array CCD via the driver chip; the output signal of the linear array CCD enters the analog-to-digital converter via the gain-variable preamplifier circuit; the analog-to-digital converter is connected to the field programmable gate array (FPGA); the adjustable DC voltage bias circuit is connected to the gain-variable preamplifier circuit to provide a DC bias signal; the control signal line of the adjustable DC voltage bias circuit is connected to the field programmable gate array (FPGA); the ARM processor is connected to the PC host computer via a USB or RS232 interface; the field programmable gate array (FPGA) is connected to the external control circuit; and the external control circuit is used to output a control signal for turning on and off the external light source. The operational amplifiers A1 and A2 and the resistors R1, R2, R5 and R6 together form a gain-variable preamplifier circuit; the digital potentiometer B and the resistors R3 and R4 form an adjustable DC voltage bias circuit. The linear array CCD output signal VIN is connected to the negative input terminal - of the operational amplifier A1 through the resistor R1; the positive input terminal + of A1 is connected to the adjustable DC voltage bias circuit, and the output of A1 is connected to the positive input terminal + of the operational amplifier A2. The output signals VO1 and VO2 of A1 and A2 enter the channels 1 and 2 of the analog-to-digital converter respectively, and the control signal of the digital potentiometer B is connected to the field programmable gate array (FPGA) through the SPI interface.
[0007] The present invention provides a control method for a micro-spectrometer control circuit, which utilizes the driving instruction part of the micro-spectrometer host computer software, and the host computer software sends the adjustment command, and the field programmable gate array (FPGA) is responsible for automatically completing the gain selection and bias adjustment. The control method is as follows:
[0008] FPGA turns off the external light source signal through the external control circuit → sets the initial value of the digital potentiometer in the DC voltage bias circuit → FPGA outputs CCD drive pulse (minimum integration time) and starts analog-to-digital converter channel 2 to sample CCD output data → FPGA internally implements sampling data one by one to judge and store the minimum value → calculates the difference between the minimum value and the target value → corrects the value of the digital potentiometer according to the difference. The difference between the measured value and the target value is less than the allowable error, and the adjustment ends.
[0009] FPGA turns on the external light source signal through the external control circuit → FPGA outputs CCD drive pulse (minimum integration time) and starts analog-to-digital converter channel 2 to sample CCD output data → FPGA internally implements sampled data judgment one by one and stores the maximum value → judges whether the maximum value reaches the maximum value of the digital-to-analog converter. If the value does not exceed, the gain selection ends. If it exceeds, the analog-to-digital converter channel is set to channel 1 and the above process is repeated.
[0010] As described above, the present invention provides a micro-spectrometer control circuit and method, which can dynamically eliminate the influence of DC bias caused by the dark current of the linear array CCD, and at the same time expand the micro-spectrometer's adaptability range to the input detection light signal. Since the gain selection and DC bias adjustment are implemented using FPGA hardware circuits, the adjustment is fast and convenient. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 This is a structural block diagram of a micro-spectrometer control circuit of the present invention;
[0012] Figure 2 A circuit diagram of an embodiment of the present invention;
[0013] Figure 3 The figure is a flowchart of a control method according to an embodiment of the present invention.
[0014] Number Description
[0015] 1: Linear array CCD;
[0016] 2: Preamplifier circuit with variable gain;
[0017] 3: Adjustable DC voltage bias circuit;
[0018] 4: Driver chip;
[0019] 5: Analog-to-digital converter;
[0020] 6: Field Programmable Gate Array;
[0021] 7: External control circuit;
[0022] 8: ARM processor;
[0023] 9: PC host computer;
[0024] 10: External light source signal. DETAILED DESCRIPTION
[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.
[0026] The present invention provides a micro-spectrometer control circuit (such as the attached Figure 1 , Figure 2 shown):
[0027] The invention is composed of a linear array CCD 1, a gain-variable preamplifier circuit 2, an adjustable DC voltage bias circuit 3, a driver chip 4, an analog-to-digital converter 5, a field programmable gate array 6, an external control circuit 7, an ARM processor 8, a PC host computer 9 and an external light source signal 10 connected in a circuit manner.
[0028] The field programmable gate array 6 is respectively connected to the pins of the analog-to-digital converter 5 and the ARM processor 8, connected to the external control circuit 7, connected to the DC voltage bias circuit 3 via the control signal line, and the other end is connected to the linear array CCD1 via the driving chip 4.
[0029] The output signal of the linear array CCD 1 is connected to the analog-to-digital converter 5 via the gain-variable preamplifier circuit 2 .
[0030] The ARM processor 8 is connected to the PC host computer 9 via a USB or RS232 interface.
[0031] The external control circuit 7 is connected to the external light source signal 10 .
[0032] The adjustable DC voltage bias circuit 3 is connected to the gain-variable preamplifier circuit 2 .
[0033] The variable gain preamplifier circuit 2 is composed of an operational amplifier A1, an operational amplifier A2 connected with resistors R1, R2, R5 and R6.
[0034] The DC voltage bias circuit 3 is composed of a digital potentiometer B connected with resistors R3 and R4.
[0035] The linear array CCD1 output signal VIN is connected to the negative input terminal - of the operational amplifier A1 via the resistor R1.
[0036] The positive input terminal + of the operational amplifier A1 is connected to the adjustable DC voltage bias circuit 3, and the output of the operational amplifier A1 is connected to the positive input terminal + of the operational amplifier A2.
[0037] The output signals VO1 and VO2 of the operational amplifier A1 and the operational amplifier A2 are connected to the channel 1 and the channel 2 of the analog-to-digital converter 5 respectively.
[0038] The control signal of the digital potentiometer B is connected to the field programmable gate array 6 through the SPI interface.
[0039] The operational amplifiers A1 and A2 are high-speed operational amplifiers AD8031.
[0040] The digital potentiometer B adopts MCP41010.
[0041] The present invention provides a control method for a micro-spectrometer control circuit (see attached Figure 3 shown):
[0042] The PC host computer 9 sends a control instruction to FPGA6 through the ARM processor 8 via the USB or RS232 interface. The FPGA6 pin outputs a signal to turn off the external light source. First, the channel 2 of the analog-to-digital converter 5 is selected, that is, the high-gain output is used for zeroing. After the zeroing is completed, the external light source signal 10 is turned on to obtain data and determine whether the maximum value of the digital-to-analog converter 5 is reached. If the value is not reached, the gain selection is ended, and the final gain selection is a high-gain output. If it is reached, the analog-to-digital converter 5 channel is set to channel 1 and the above process is repeated. Similarly, if the channel 1 value does not reach the maximum value of the digital-to-analog converter 5, the gain is selected as a low-gain output. If it is reached, an error is reported.
[0043] The control flow is as follows:
[0044] Step S1: the PC host computer 9 issues a gain selection instruction, the FPGA 6 pin outputs a signal 10 to turn off the external light source and selects channel 2 of the analog-to-digital converter 5, that is, a high-gain channel.
[0045] Step S2: setting the initial value of the digital potentiometer B in the DC voltage bias circuit 3.
[0046] Step S3: FPGA6 outputs CCD1 driving pulse, the linear array CCD1 is set to the minimum integration time, and the analog-to-digital converter 5 is started to sample the CCD1 output data to obtain the primary spectrum data of the linear array CCD1.
[0047] Step S4: FPGA6 internally judges and stores the minimum value of the sampled data one by one, and calculates the difference between the minimum value and the target value.
[0048] Step S5: If the difference between the measured value and the target value is less than the allowable error, the adjustment is terminated; otherwise, the value of the digital potentiometer B is corrected according to the difference, and steps S3, S4, and S5 are repeated.
[0049] Step S6: FPGA6 pin output turns on the external light source signal 10 through the external control circuit 7, and outputs the CCD1 drive pulse, the linear array CCD1 is set to the minimum integration time, and the analog-to-digital converter 5 is started to sample the CCD1 output data to obtain the primary spectrum data of the linear array CCD1.
[0050] Step S7: FPGA 6 internally judges and stores the maximum value of the sampled data one by one, and judges whether the maximum value reaches the maximum value of the digital-to-analog converter 5.
[0051] Step S8: If the value is not reached, the gain selection is terminated. If it is reached, the analog-to-digital converter channel 5 is set to channel 1, i.e., the low gain channel, and the above process is repeated.
[0052] In summary, the present invention provides a micro-spectrometer control circuit and method, which can dynamically eliminate the influence of DC bias caused by the dark current of the linear array CCD, and at the same time expand the micro-spectrometer's adaptability to the intensity of the input detection light signal. Since the gain selection and DC bias adjustment are implemented using FPGA hardware circuits, the adjustment is fast and convenient.
Claims
1. A micro-spectrometer control circuit, characterized in that: The device is composed of a linear array CCD (1), a gain-variable preamplifier circuit (2), an adjustable DC voltage bias circuit (3), a driver chip (4), an analog-to-digital converter (5), a field programmable gate array (6), an external control circuit (7), an ARM processor (8), a PC host computer (9) and an external light source signal (10) connected in a circuit manner; The field programmable gate array (6) is respectively connected to the pins of the analog-to-digital converter (5) and the ARM processor (8), connected to the external control circuit (7), connected to the DC voltage bias circuit (3) via a control signal line, and connected to the linear array CCD (1) via a drive chip (4); The output signal of the linear array CCD (1) is connected to an analog-to-digital converter (5) via a gain-variable preamplifier circuit (2); The ARM processor (8) is connected to a PC host computer (9) via a USB or RS232 interface; The external control circuit (7) is connected to the external light source signal (10); The adjustable DC voltage bias circuit (3) is connected to the gain-variable preamplifier circuit (2); The gain-variable preamplifier circuit (2) is composed of an operational amplifier A1, an operational amplifier A2, and resistors R1, R2, R5, and R6, wherein the resistor R1 is connected to the negative input terminal - of the operational amplifier A1, the resistor R2 is connected between the negative input terminal - and the output terminal of the operational amplifier A1, the resistor R5 is connected between the negative input terminal - and the output terminal of the operational amplifier A2, one end of the resistor R6 is connected to the negative input terminal - of the operational amplifier A2, and the other end is grounded; The DC voltage bias circuit (3) is composed of a digital potentiometer B connected with resistors R3 and R4; The linear array CCD (1) output signal VIN is connected to the negative input terminal - of the operational amplifier A1 via the resistor R1; The positive input terminal + of the operational amplifier A1 is connected to an adjustable DC voltage bias circuit (3), the output of the operational amplifier A1 is connected to the positive input terminal + of the operational amplifier A2, and the output signal VO1 of the operational amplifier A1 is input to the positive input terminal + of the operational amplifier A2; The output signals VO1 and VO2 of the operational amplifier A1 and the operational amplifier A2 are connected to channel 1 and channel 2 of the analog-to-digital converter (5) respectively; The control signal of digital potentiometer B is connected to the field programmable gate array (6) via the SPI interface.
2. A micro-spectrometer control circuit as claimed in claim 1, characterized in that: The operational amplifiers A1 and A2 adopt high-speed operational amplifier AD8031; the digital potentiometer B adopts MCP41010.
3. A control method for a micro-spectrometer control circuit, characterized in that: The micro-spectrometer control circuit applied to claim 1 or 2 comprises the following steps: Step S1: The PC host computer (9) issues a gain selection instruction, and the field programmable gate array (6) turns off the external light source signal (10) through the external control circuit (7) and selects the high gain channel 2 of the analog-to-digital converter (5); Step S2: setting the initial value of the digital potentiometer B in the DC voltage bias circuit (3); Step S3: the programmable gate array (6) outputs a driving pulse for the linear array CCD (1), the linear array CCD (1) is set to a minimum integration time, and the analog-to-digital converter (5) is started to sample the output data of the linear array CCD (1), thereby obtaining primary spectrum data of the linear array CCD (1); Step S4: the programmable gate array (6) internally determines and stores the minimum value of the sampled data one by one, and calculates the difference between the minimum value and the target value; Step S5: If the difference between the measured value and the target value is less than the allowable error, the adjustment is ended; otherwise, the value of the digital potentiometer is corrected according to the difference, and steps S3, S4, and S5 are repeated; Step S6: the programmable gate array (6) turns on the external light source signal (10) through the external control circuit (7) and outputs a driving pulse for the linear array CCD (1), the linear array CCD (1) is set to a minimum integration time, and the analog-to-digital converter (5) is started to sample the output data of the linear array CCD (1), thereby obtaining primary spectrum data of the linear array CCD (1); Step S7: the programmable gate array (6) internally implements the determination of the maximum value of the sampled data one by one and stores the maximum value, and determines whether the maximum value reaches the maximum value of the analog-to-digital converter (5); Step S8: If the value is not reached, the gain selection is terminated; if it is reached, the channel of the analog-to-digital converter (5) is set to low-gain channel 1, and the above steps S6 and S7 are repeated.