Laser blood flow detector based on Doppler effect

Abstract

The laser blood flow detector based on the Doppler effect comprises a shell, an operation panel is arranged on the shell, a detection port and an operation button are arranged on the operation panel, a display screen is arranged above the shell, and a control mechanism is arranged in the shell. The control mechanism comprises a laser, a light separator and a photoelectric receiver which are arranged in the detection probe and a signal processor arranged in the shell, the output end of the laser is connected with the input end of the light separator, the output end of the light separator is connected with the input end of the photoelectric receiver, and the output end of the photoelectric receiver is connected with the input end of the signal processor; the output end of the signal processor is connected with the input end of the display screen. The system is low in cost, high in precision, stable in performance and simple to operate, improves the blood detection efficiency, and provides an important basis for cardiovascular system function evaluation and disease diagnosis by providing quantitative data of blood flow.

Description

Technical Field

[0001] This utility model relates to the field of medical equipment technology, and more specifically to a laser blood flow detector based on the Doppler effect. Background Technology

[0002] Blood flow velocity is a physiological parameter that reflects many bodily functions. It mainly refers to the flow of blood cells in the human body. Blood flow velocity has extremely high reference value for detecting various major diseases in the human body. Currently, Doppler blood flow detectors are mostly used to detect blood flow velocity.

[0003] Most existing Doppler ultrasound detectors use ultrasound for detection, but in actual use, the following problems still exist: 1) Doppler ultrasound is difficult to determine the measured distance, cannot determine the location of organs and tissues, and cannot provide accurate reference for subsequent diagnosis; 2) It cannot measure high-pressure blood vessels or high-temperature measurement environments, and needs to be kept at a normal temperature to use ultrasound measurement; 3) Ultrasound cannot be used to measure when the blood vessels are too shallow; 4) Ultrasound detection requires a relatively stable blood flow, so there are certain requirements for the location of use; 5) It cannot measure the average flow velocity across the entire cross-section of the blood vessel; 6) The sampling range of ultrasound is narrow. Even if the sampling volume is expanded to the anterior and posterior walls of the blood vessel, it is only the width of a single sound beam, and the sampling range only occupies a very small part of the blood vessel lumen. Utility Model Content

[0004] The technical problem this invention aims to solve is to provide a laser blood flow detector based on the Doppler effect, which is low in cost, high in accuracy, stable in performance, simple to operate, and improves the efficiency of blood testing.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows.

[0006] A laser blood flow detector based on the Doppler effect includes a housing with an operation panel for blood flow detection. The operation panel has a detection port for connecting a detection probe and operation buttons. A display screen for displaying detection results is located on the top of the housing. A control mechanism for blood flow detection is located inside the housing. The outputs of the detection probe and operation buttons are connected to the input of the control mechanism, and the output of the control mechanism is connected to the input of the display screen. The control mechanism includes a laser emitting a laser source within the detection probe, a light splitter separating the resonant absorption lines of the laser, a photodetector receiving signals acquired by the detection probe, and a signal processor within the housing analyzing and processing the received Doppler signals. The output of the laser is connected to the input of the light splitter, the output of the light splitter is connected to the input of the photodetector, the output of the photodetector is connected to the input of the signal processor, and the output of the signal processor is connected to the input of the display screen.

[0007] To further optimize the technical solution, the photoelectric receiver includes a signal amplification circuit for amplifying the received signal and a bandpass filter circuit for filtering the amplified signal. The output terminal of the signal amplification circuit is connected to the input terminal of the bandpass filter circuit, and the output terminal of the bandpass filter circuit is connected to the input terminal of the signal processor.

[0008] To further optimize the technical solution, the signal processor includes a signal conditioning circuit for conditioning the Doppler signal received by the photodetector, an A / D conversion circuit for A / D conversion of the conditioned Doppler signal, an FPGA for data processing of the converted Doppler signal, a D / A conversion circuit for D / A conversion of the data processed by the FPGA, and a multi-cycle synchronous measurement module for measuring the data after the phase. The input terminal of the signal conditioning circuit is connected to the output terminal of the bandpass filter circuit, the output terminal of the signal conditioning circuit is connected to the input terminal of the A / D conversion circuit, the output terminal of the A / D conversion circuit is connected to the input terminal of the FPGA, the output terminal of the FPGA is connected to the input terminal of the D / A conversion circuit, and the output terminal of the D / A conversion circuit is connected to the input terminal of the multi-cycle synchronous measurement module.

[0009] To further optimize the technical solution, the bottom of the outer shell is provided with four omnidirectional wheels for easy movement, and the omnidirectional wheels are provided with locking plates for fixing the omnidirectional wheels.

[0010] To further optimize the technical solution, a push rod for moving the detector is provided at the upper rear end of the housing.

[0011] To further optimize the technical solution, the front end of the outer shell is equipped with a drawer for placing items via a damping slide rail, and the front end of the drawer is equipped with a handle for easy pulling out of the drawer.

[0012] The technological advancements achieved by this utility model are as follows, due to the adoption of the above technical solutions.

[0013] The laser blood flow detector based on the Doppler effect provided by this utility model is low in cost, high in accuracy, and stable in performance. It is also simple to operate and improves the efficiency of blood testing. By providing quantitative data on blood flow, it provides an important basis for assessing cardiovascular function and diagnosing diseases. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of this utility model;

[0015] Figure 2 This is a structural block diagram of the control mechanism of this utility model;

[0016] Figure 3 This is a reference optical system diagram of the present invention;

[0017] Figure 4 This is a diagram of the dual-beam optical system of this utility model.

[0018] Figure 5 This is a circuit diagram of the signal amplification circuit of this utility model;

[0019] Figure 6 This is a circuit diagram of the bandpass filter circuit of this utility model;

[0020] Figure 7 This is a circuit diagram of the signal conditioning circuit of this utility model;

[0021] Figure 8 This is a circuit diagram of the A / D conversion circuit of this utility model;

[0022] Figure 9 This is a block diagram of the FPGA digital logic of this utility model;

[0023] Figure 10 This is a circuit diagram of the D / A conversion circuit of this utility model;

[0024] Figure 11 This is a schematic diagram of the measurement principle of the multi-cycle synchronous measurement module of this utility model.

[0025] The components include: 1. outer shell, 2. casters, 3. control panel, 4. display screen, 5. push rod, and 6. handle. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0027] Laser blood flow detector based on the Doppler effect, combined with Figure 1As shown, the device includes a housing 1, an operation panel 3 on the housing 1, a detection port and an operation button on the operation panel 3, a detection probe connected to the detection port, a display screen 4 on the top of the housing 1 for displaying the detection results, and a control mechanism inside the housing 1 for detecting blood flow rate. The outputs of the detection probe and the operation button are respectively connected to the input of the control mechanism, and the output of the control mechanism is connected to the input of the display screen.

[0028] The bottom of the outer casing 1 is equipped with four casters 2, and each caster 2 is equipped with a locking plate. The casters facilitate the movement of the detector, and the locking plates fix the casters in place after the detector is in position, thus securing the detector.

[0029] A push rod 5 is provided at the upper rear end of the outer casing 1 to push the detector to move.

[0030] A drawer is provided at the front end of the outer casing 1 via a damping slide rail for placing the items to be tested. A handle 6 is provided at the front end of the drawer to facilitate pulling the drawer out of the outer casing.

[0031] The structural block diagram of the control mechanism is as follows: Figure 2 As shown, it includes a laser, a light splitter, a photodetector, and a signal processor. The laser, light splitter, and photodetector are all housed inside the detection probe, and the signal processor is housed inside the housing 1. The output end of the laser is connected to the input end of the light splitter, the output end of the light splitter is connected to the input end of the photodetector, the output end of the photodetector is connected to the input end of the signal processor, and the output end of the signal processor is connected to the input end of the display screen.

[0032] The laser generates a high-brightness, high-energy light source. The laser used is a He-Ne laser with a wavelength of 632.8nm.

[0033] The beam splitter consists of entrance and exit slits, a mirror, and a dispersive element. Its function is to separate the desired resonant absorption lines. One of the separated laser beams is emitted through a detection probe, while the other beam passes through a photodetector. The laser emitted from the detection probe passes through the body part being tested, is reflected by the blood, and is then received by the photodetector.

[0034] The laser Doppler velocimetry optical system employs both a reference light mode and a dual-beam mode optical system to complement each other's strengths and weaknesses.

[0035] The optical system diagram of the reference light mode is shown below. Figure 3As shown, the laser beam is split into two beams. One beam passes through the fluid and directly enters the pinhole aperture of the photodetector, becoming the reference beam. The other beam illuminates particles in the fluid to generate scattered light. The receiving lens group collimates and converges the reference beam and the scattered beam onto the pinhole aperture, then illuminates the photodetector for beat frequency generation to obtain the beat frequency electrical signal. In the reference beam mode, it is desirable for the reference beam and the scattered signal beam to have the same order of magnitude; only in this way can a relatively high signal-to-noise ratio and a good Doppler signal be obtained.

[0036] The optical system diagram for dual-beam mode is shown below. Figure 4 As shown, the scattered light from one laser beam is coherently coupled with the scattered light from another laser beam, and the Doppler signal is acquired by a photodetector via a pinhole aperture. This mode features a frequency difference between the scattered light caused by the two incident beams in any scattering direction due to the detected Doppler frequency. This frequency difference is independent of the scattering direction, so the receiving aperture can be maximized during optical path design, resulting in stronger scattered light.

[0037] In reality, because scattering particles vary in size and shape, the intensity of scattered light varies considerably. This reduces the effective signal of the reference light mode and lowers the signal-to-noise ratio. A dual-beam incident light system can integrate optical units, greatly improving the stability and ease of adjustment of the optical system. Therefore, combining these two optical systems will significantly improve the accuracy of the blood flow detector.

[0038] Based on the Doppler principle of lasers, and derived through simulation experiments, with a fixed light source, let f1 represent the frequency of its emitted monochromatic laser, and A represent the speed of movement along with the blood. The scattering particles (i.e., red blood cells), where λ1 represents the wavelength of their monochromatic light, f D Let the frequency be the frequency received by the receiver.

[0039]

[0040] Photodetector: The principle of photodetector technology is that the peripheral tissue is densely covered with blood vessels, which are filled with blood. Since blood has a certain ability to absorb light, when the amount of blood in the peripheral blood vessels changes, the light absorption / reflection characteristics of the peripheral tissue change accordingly. The above detection can be completed by measuring the periodic changes in the absorption / reflection properties of the peripheral tissue with light using an instrument.

[0041] The photoelectric receiver includes a signal amplification circuit and a bandpass filter circuit. The circuit diagram of the signal amplification circuit is shown below. Figure 5As shown, the signal amplification circuit consists of four LM318s. The signal generated by the photodetector is input through the RECE terminal, and terminal A is the output terminal. The output signal is transmitted to the bandpass filter circuit. In this circuit, the two voltage followers, U10 and U9, isolate and buffer the influence between the preceding and following stages, making the voltage signal in the circuit more stable.

[0042] After the signal passes through the preceding amplification circuit, not only the desired laser signal is amplified, but also the accompanying interference signal. At this point, a bandpass filter circuit is needed to process the noise. The circuit diagram of the bandpass filter circuit is shown below. Figure 6 As shown.

[0043] The signal processor analyzes the spectral signal in digital form. The signal processor includes a signal conditioning circuit, an A / D conversion circuit, an FPGA, a D / A conversion circuit, and a multi-cycle synchronous measurement module. The input of the signal conditioning circuit is connected to the output of the bandpass filter circuit, the output of the signal conditioning circuit is connected to the input of the A / D conversion circuit, the output of the A / D conversion circuit is connected to the input of the FPGA, the output of the FPGA is connected to the input of the D / A conversion circuit, and the output of the D / A conversion circuit is connected to the input of the multi-cycle synchronous measurement module.

[0044] The optical path measurement section uses a 1550nm distributed feedback laser. When using optical heterodyne detection, the power of the optical signal received by the photodetector is only on the order of microwatts (μW), resulting in a very weak output Doppler signal with a large noise component and a significant DC bias. This signal is easily interfered with by other noise. To improve the signal-to-noise ratio and ensure the accuracy of subsequent signal processing, a signal conditioning circuit is used to debias, amplify, and filter the signal output from the photodetector. The circuit diagram of the signal conditioning circuit is shown below. Figure 7 As shown, the AD8045 operational amplifier chip is used, and the input signal is the Doppler signal containing optical difference frequency information output by the photodetector. R1 and C2 form a low-pass filter to block high-frequency noise, and R3 and C1 form a high-pass filter to block low-frequency noise. The two are connected in series at the non-inverting input of the operational amplifier, and the filtering characteristics are improved by the feedback resistor R5. The signal is output to the subsequent circuit through pin 6.

[0045] An A / D conversion circuit is used to convert the conditioned Doppler signal into a digital signal. The circuit diagram of an A / D conversion circuit is shown below. Figure 8 As shown, an 8-bit high-speed analog-to-digital converter chip ADC08200 is used. An external reference source ADR441ARZ chip generates a 2.5V voltage, which is connected to the pin 3 of the chip. The 8-bit data bus D0-D7 output from the ADC08200 is connected to the I / O of the FPGA to transmit data to the FPGA.

[0046] The FPGA performs data processing on the converted digital signal, using Altera's EP4CE15F17C8N, which has 15408 logic units. FPGA is a chip with multiple power supply requirements. According to the design requirements of this system, the system uses an external power supply of ±5V to meet the needs of the front-end signal conditioning circuit and A / D conversion circuit. Multiple voltage conversion chips are selected to provide the FPGA with the required 3.3V, 2.5V and 1.2V power supply.

[0047] FPGA digital logic block diagram as follows Figure 9 As shown, the system includes a clock module, an A / D logic module, a data processing module, a FIFO buffer module, a D / A logic module, and a Joint Test Action Group (JTAG) download module. During operation, the clock module provides the necessary operating clock for the system. The FPGA first uses the A / D control module to detect whether an enable signal indicating completion of Doppler data acquisition has been received. If received, the data is read and buffered in an asynchronous FIFO. When the FIFO is nearly full, the signal processing logic module performs frequency measurement. The calculated speed and direction signals are output through the D / A control module, thus completing the entire acquisition and processing logic control.

[0048] The D / A conversion circuit uses an FPGA to calculate the velocity and direction changes of the vibrating object's surface. These changes are then output as analog signals via two D / A conversion modules, allowing for real-time observation using an oscilloscope. Because the system is a high-speed circuit, the conversion rate of the D / A chip must be considered when selecting the appropriate converter. The circuit diagram of the D / A conversion circuit is shown below. Figure 10 As shown, an 8-bit TLC5602C analog-to-digital converter chip is selected. The two D / A data buses D0 to D7 and the clock control port are connected to the I / O of the FPGA, and the conversion result is output through Pin 6 of the chip.

[0049] The multi-cycle synchronous measurement module is used to process test data. The A / D conversion module converts the data into digital values, which are then transmitted to the FIFO module for data buffering. An asynchronous FIFO is used to simultaneously store the data and read it for signal frequency measurement. The multi-cycle synchronous frequency measurement method is based on the direct frequency measurement method. This method ensures synchronization between the gate signal and the measured signal, achieving equal-precision measurement across the entire frequency band. The measurement principle is as follows: Figure 11 As shown.

[0050] During system operation, the preset gate signal is first activated. The two counters do not start counting initially, waiting for the rising edge of the measured signal fx as a trigger signal. At this time, the system controls the corresponding D flip-flop circuit, which sends a signal allowing the system to start counting. Counter 1 begins counting pulses of the system frequency signal f0, and counter 2 begins counting pulses of the measured signal fx. When the gate signal is closed, the two counters in the system do not stop counting; they stop counting only when the rising edge of fx serves as a termination signal, thus completing the entire frequency measurement process.

[0051] During the process, the number of pulses counted by counter 1 is N0, and the number of pulses counted by counter 2 is Nx. From the formula N0·T0=Nx·Tx, the frequency of the measured signal is fx=Nx / N0·f0. Based on:

[0052]

[0053] f x =f D

[0054] The Doppler frequency shift f is obtained by taking the maximum value of the received amplitude-frequency signal. D Substituting these values ​​into the formula yields the blood flow velocity. The Doppler frequency shift and blood flow velocity are positively correlated and exhibit a linear relationship. Therefore, the blood flow velocity can be determined from the Doppler frequency shift of the blood.

Claims

1. A laser blood flow detector based on Doppler effect, characterized in that: The device includes a housing (1), an operation panel (3) for blood flow detection, a detection port for connecting a detection probe and an operation button on the operation panel (3), a display screen (4) for displaying detection results on the top of the housing (1), and a control mechanism for blood flow detection inside the housing (1). The output ends of the detection probe and the operation button are respectively connected to the input end of the control mechanism, and the output end of the control mechanism is connected to the input end of the display screen. The control mechanism includes a laser for emitting a laser light source, a light splitter for separating the resonant absorption lines of the laser, a photoelectric receiver for receiving signals collected by the detection probe, and a signal processor for analyzing and processing the received Doppler signals inside the housing. The output end of the laser is connected to the input end of the light splitter, the output end of the light splitter is connected to the input end of the photoelectric receiver, the output end of the photoelectric receiver is connected to the input end of the signal processor, and the output end of the signal processor is connected to the input end of the display screen.

2. The Doppler effect-based laser blood flow detector according to claim 1, characterized in that: The photoelectric receiver includes a signal amplification circuit for amplifying the received signal and a bandpass filter circuit for filtering the amplified signal. The output of the signal amplification circuit is connected to the input of the bandpass filter circuit, and the output of the bandpass filter circuit is connected to the input of the signal processor.

3. The Doppler effect based laser blood flow detector according to claim 2, characterized in that: The signal processor includes a signal conditioning circuit for conditioning the Doppler signal received by the photodetector, an A / D conversion circuit for A / D conversion of the conditioned Doppler signal, an FPGA for data processing of the converted Doppler signal, a D / A conversion circuit for D / A conversion of the data processed by the FPGA, and a multi-cycle synchronous measurement module for measuring the phased data. The input of the signal conditioning circuit is connected to the output of the bandpass filter circuit, the output of the signal conditioning circuit is connected to the input of the A / D conversion circuit, the output of the A / D conversion circuit is connected to the input of the FPGA, the output of the FPGA is connected to the input of the D / A conversion circuit, and the output of the D / A conversion circuit is connected to the input of the multi-cycle synchronous measurement module.

4. The Doppler effect-based laser blood flow detector according to claim 1, characterized in that: The bottom of the outer casing (1) is provided with four omnidirectional wheels (2) for easy movement, and the omnidirectional wheels (2) are provided with locking plates for fixing the omnidirectional wheels.

5. The Doppler effect based laser blood flow detector according to claim 1, characterized in that: The upper rear end of the outer casing (1) is provided with a push rod (5) for pushing the detector to move.

6. The laser blood flow detector based on the Doppler effect according to claim 1, characterized in that: The front end of the outer casing (1) is provided with a drawer for placing items via a damping slide rail, and the front end of the drawer is provided with a handle (6) for easy pulling out of the drawer.

Images