FPGA-based full-spectrum waveband light intensity detectable system

Abstract

The invention discloses a full-spectrum wave band light intensity detectable system based on an FPGA (Field Programmable Gate Array), and relates to a photodiode which responds to light in a certain wave band of a full spectrum, for example, the spectral response range of a silicon photodiode FDS100 is 350-1100 nm, and the spectral response range of a germanium photodiode FDG03 is 800-1800 nm. According to the light intensity detection system provided by the invention, photovoltages are sequentially input into the single-end-to-double-end circuit, the step-down circuit, the amplification circuit, the step-down circuit and the analog-to-digital conversion circuit by utilizing the characteristic that photovoltages are different due to different wavelengths and light intensities of a photodiode, and are finally input into the FPGA, so that the photovoltages generated by incident light with known wavelengths and unknown light intensities are obtained; the incident light intensity of the photodiode under the known wavelength is obtained through the linear relation between the photovoltage and the incident light intensity of the photodiode under the known wavelength. The light intensity detection system provided by the invention has the advantages of being convenient to verify, simple in used material and stable in system, the light voltages of different diodes under the same wavelength and the same light intensity are different, and the light intensity of the incident light can be obtained only by obtaining the linear relation between the light voltages and the incident light intensity under the wavelength, so that the method has universality. The light intensity detection system provided by the invention can be used for a full wavelength range or a wavelength range of a full spectrum band.

Description

Method Domain

[0001] This invention belongs to the field of optical communication technology, specifically relating to a type of photodiode that responds to light across the entire spectrum or a specific wavelength band. Background Method

[0002] Full spectrum refers to the complete spectral range covering ultraviolet, visible and infrared light. Photodetectors on the market obtain light of the target wavelength through filters and then display it on the FPGA through readout circuits. The detection range of such photodetectors is limited to a certain band of the full spectrum, and few detectors can detect light of the full spectrum.

[0003] An FPGA is a programmable logic device whose internal logic functions can be programmed using the Verilog language. FPGAs can meet the speed and stability requirements of hardware timing without the huge initial costs of ASIC design. FPGAs do not require tape-out; they can be deployed immediately after design verification. They can receive external digital signals and convert them into image frames, storing and displaying these frames using internal RAM or external SDRAM. Furthermore, the FPGA's main clock can be divided into specific frequencies and output to external modules. Because FPGAs can perform pipelined operations, they can still display images in real time even with numerous image processing algorithms. Summary of the Invention

[0004] In view of this, the present invention proposes an FPGA-based system with detectable light intensity across the entire spectrum. Taking the FDS100 silicon photodiode as an example, the FDS100 is responsive to light with wavelengths from 350nm to 1100nm.

[0005] This invention provides a system for detecting the light intensity of a silicon photodiode FDS100 across its full spectral range, comprising:

[0006] Light in the 350nm to 1100nm range is incident on the FDS100, and the resulting photocurrent is converted into photovoltage through a resistor converter. The photovoltage is adjusted by regulating the light intensity at each wavelength, and finally, the photovoltage and light power curves for each wavelength are obtained.

[0007] By adjusting the optical power at each wavelength, the photovoltage-optical power curves of FDS100 at wavelengths of 405nm, 530nm, 625nm, 730nm, 808nm, 940nm, and 1050nm were finally obtained.

[0008] The slope relationship between photovoltage and photopower is obtained by linear fitting of the curve.

[0009] When any of the seven wavelengths of light mentioned above is passed into the FDS100, the resulting photovoltage is processed by the hardware circuit and finally input into the FPGA for image display.

[0010] The FPGA obtains the photovoltage magnitude based on the displayed light intensity, and then calculates the incident light intensity based on the wavelength incident on the FDS100 silicon photodiode and the slope relationship between photovoltage and light power.

[0011] The main advantages of this invention are:

[0012] 1. This invention demonstrates that, at various wavelengths, the photovoltage of silicon photodiodes such as FDS100 has a highly linear relationship with the optical power of the incident light.

[0013] 2. This invention proves that as long as the wavelength of the light incident on such a photodiode is known, the intensity of the incident light can be determined.

[0014] 3. The method of the present invention is universal and applicable to all photodiodes in which the photocurrent and light intensity have a linear relationship. Attached Figure Description

[0015] Figure 1 The graph shows the linear fitting curve of "photovoltage-photopower" for the FDS100 silicon photodiode under 405nm incident light.

[0016] Figure 2 The graph shows the linear fitting curve of "photovoltage-photopower" for the FDS100 silicon photodiode under 530nm incident light.

[0017] Figure 3 The graph shows the linear fitting curve of "photovoltage-photopower" for the FDS100 silicon photodiode under 625nm incident light.

[0018] Figure 4 The graph shows the linear fitting curve of "photovoltage-photopower" for the FDS100 silicon photodiode under 730nm incident light.

[0019] Figure 5 The graph shows the linear fitting curve of "photovoltage-photopower" for the FDS100 silicon photodiode under 808nm incident light.

[0020] Figure 6 The graph shows the linear fitting curve of "photovoltage-photopower" for the FDS100 silicon photodiode under 940nm incident light.

[0021] Figure 7 The graph shows the linear fitting curve of "photovoltage-photopower" for the FDS100 silicon photodiode under 1050nm incident light. Detailed Implementation

[0022] For ease of understanding, the present invention will be further described below with reference to the accompanying drawings. Obviously, the described examples are only a portion, not all, of the examples in this invention. All other examples obtained by those skilled in the art based on the examples in this invention without inventive effort are within the scope of protection of this invention.

[0023] Figures 1-7 These are linear fitting curves of the photovoltage-optical power of the silicon photodiode FDS100 under incident light at 405nm, 530nm, 625nm, 730nm, 808nm, 940nm, and 1050nm. It can be observed that in this example, the photovoltage and optical power of the FDS100 are approximately linearly related, and the small sum of squared residuals indicates a good fit.

[0024] The photovoltage generated by the FDS100 is passed through a single-ended to double-ended converter, a step-down converter, an amplifier, a step-down converter, and an analog-to-digital converter before finally being input into the FPGA, where the amplified photovoltage is obtained.

[0025] Based on the wavelength of the incident light, look up the corresponding linear fitting curve of "photovoltage-photopower" and calculate the intensity of the incident light based on the slope.

Claims

1. A full-spectrum light intensity detectable system based on FPGA, characterized in that: The system includes incident light of known wavelengths, such as 405nm or 530nm incident light; photodiodes, such as silicon photodiode FDS100 or germanium photodiode FDG03; hardware circuits, such as AD8138 single-ended to dual-ended circuit, OPA333 step-down circuit, LM358N amplifier circuit, AD9240 analog-to-digital converter circuit, REF2025QDDCRQ bias circuit, AMS1117 power supply circuit, and FPGA. The wavelength of the incident light of the known wavelength is within the spectral response range of the photodiode used. By aligning the incident light with the photodiode, the wavelength and intensity of the incident light can be adjusted. The photodiode is any photodiode with a spectral response, which is connected in series at the input of the system and connected to the first stage of the hardware circuit through an output resistor. The hardware circuit includes a single-ended to dual-ended converter, a step-down converter, an amplifier, an analog-to-digital converter, a bias circuit, and a power supply circuit. These five stages are cascaded in sequence. The single-ended to dual-ended converter is the first stage of the hardware circuit. The step-down converter is the second and fourth stage, with different voltage drops. The amplifier is the third stage, amplifying the dual-ended voltage. The analog-to-digital converter is the last stage, transmitting the digital signal to the FPGA. The bias circuit provides bias voltage for the step-down converter, and the power supply circuit powers the entire system. The FPGA, as the final part of the system, uses the slope relationship between photovoltage and light intensity of photodiodes at various wavelengths and the received photovoltage to calculate the incident light intensity and display the image. The slope relationship is measured by the laser and the source meter.

2. The FPGA-based full-spectrum intensity detectable system according to claim 1, characterized in that: The configuration and sequence of each module in the hardware circuit are based on the characteristics of the photodiode. The goal is to ensure that the output photovoltage of the photodiode is undistorted and that the voltage range is within the input voltage range of the ADC, thereby reducing distortion and improving the accuracy of the calculated incident light intensity.

3. The FPGA-based full-spectrum intensity detectable system according to claim 1, characterized in that: When the FPGA obtains the photovoltage, it uses a laser and a source meter to measure the slope relationship between the photovoltage and light intensity of the photodiode at various wavelengths, so as to improve the accuracy of the calculated incident light intensity.

4. The FPGA-based full-spectrum intensity detectable system according to claim 1, characterized in that: The system also includes power supply modules such as the AMS1117 module and bias circuit modules such as the REF2025QDDCRQ, REF2030QDDCRQ, and REF35102QDBVR modules. The AMS1117 module supplies power to different components of the entire system, while the REF2025QDDCRQ, REF2030QDDCRQ, and REF35102QDBVR modules provide bias voltage to the bias circuit with a deviation within 0.05% to improve the accuracy of the calculated incident light intensity. The power supply modules and bias circuit modules are not limited to the modules mentioned above.

5. The FPGA-based full-spectrum intensity detectable system according to claim 1, characterized in that: The system calculates the intensity of incident light at a known wavelength by measuring the linear slope of the photovoltage and incident light intensity at various wavelengths. Compared with traditional detectors that use filters to obtain the average light intensity of a certain band, this system can accurately calculate the light intensity of various wavelengths in a band, resulting in a clearer image on the FPGA.

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