Abstract: Laser receivers are optical-electronic components. Their optical and photoelectric properties must be rigorously tested and analyzed quantitatively to ensure product quality and obtain reliable experimental data for new product research. This testing system, through advanced virtual instrument technology and LabVIEW 7.0 programming, controls traditional optical testing instruments and uses a signal source and NI PCI-6104E multifunction acquisition card to simulate laser receivers. The system can acquire and analyze relevant test data in real time and display, save, and print the final test results. Due to the use of advanced LabVIEW programming software and virtual instrument technology, this system becomes a comprehensive testing system capable of automatically detecting various parameters of the laser receiver. Actual test results prove that this method is practical, convenient, and has high measurement accuracy. Keywords: Laser receiver, LabVIEW, Virtual instrument (I) Functions of the Laser Receiver Testing System The laser receiver converts photoelectric information into encoded information of a certain frequency through a PIN photoelectric conversion element, which is then amplified and transmitted to the subsequent electronic processing system. The main and key photoelectric performance test contents are: 1. Spectral response characteristics test of the whole laser receiver When the laser receiver is working, it can not only receive the laser emitted by the laser with a wavelength of λ=1.06μm, but also receive other spectra such as sunlight. In order to improve the signal-to-noise ratio of the receiving system, its receiving optical system should make the light signal of λ=1.06μm effectively pass through, while blocking other spectral components as much as possible. The quality of this spectral signal-to-noise ratio is one of the key performance indicators of the receiver, and it is necessary to conduct quantitative testing, evaluation and research. 2. Spectral response characteristics test of the four-quadrant photoelectric detection element [1] The four-quadrant photoelectric detection element is the core component of the laser receiver and is an externally purchased product. In order to record and compare the quality of four-quadrant Si phototubes (or other phototubes) from different manufacturers and different batches, such as the spectral response curve of the phototube, the peak wavelength position, and the response sensitivity of the spectral point of interest (such as 1.06μm), etc. 3. Spectral transmittance curve testing of optical components (filters, thin films, optical glass materials, etc.): Optical filters and receiving lenses in laser receivers are all purchased components and must be inspected upon arrival to ensure product quality. Furthermore, product modifications and new product development often involve studying how to improve the signal light transmittance and spectral signal-to-noise ratio of the receiving system. Testing the spectral transmittance, reflectance, and absorptivity of optical components is a basic requirement for verifying the performance of general optical systems. 4. Simulation experiment of the receiver's received light information changing with the laser distance R: To assess the receiver's receiving sensitivity and dynamic linear range, it is necessary to simulate the change in received light signal caused by changes in laser distance in the laboratory. Currently, the laser wavelengths used in the tested receivers are mainly λ=1.06μm and λ=0.9μm. Therefore, this test system aims to simulate the emission distance characteristics of these two laser wavelengths. (II) Design Scheme of Laser Receiver Test System Based on the system's functions and main technical specifications, we designed the test system scheme and planned its architecture, as described below: 1. The laser receiver test system architecture consists of three test benches to complete the testing tasks of the entire system: ① Spectral response test bench ② Spectral transmittance and reflectance test bench ③ Distance simulation test bench The preliminary overall layout of the laboratory is planned as follows: The layout concept of the three test benches is as follows: ① Spectral response test bench This test bench will be able to complete: (a) Spectral response curve testing of the entire laser receiver; (b) Spectral response curve testing of the photoelectric four-quadrant receiver; The block diagram is as follows: ② Spectral transmittance and reflectance test bench The block diagram of the components of this test bench is shown in Figure 4. ③ Distance simulation test bench This test bench consists of six working components: power supply box, modulation signal generator box, semiconductor laser transmitter head, variable aperture, power head, and the receiver system under test. Among them, the semiconductor laser transmitter head, variable aperture, power meter, and receiver system should all be equipped with appropriate adjustment and clamping devices. The test bench layout is as follows: The structural principle of this test system is shown in Figure 5 (III) Based on virtual instrument technology In the past 20 years, the rapid popularization of PC applications has promoted the innovation of test measurement and automation instrument systems. The most significant point is the emergence and development of the concept of virtual instruments. Virtual instruments have made great contributions to improving the productivity, measurement accuracy and system performance of engineers and scientists [2]. Virtual instruments are industrial standard computers equipped with powerful application software, low-cost hardware and driver software to complete the functions of traditional instruments. On the other hand, they can also control traditional instruments through drivers, so that they can be integrated into the entire automated test and measurement control system. This laser receiver test system adopts virtual instrument technology. Through graphical LabVIEW programming, the application software environment becomes the core of the entire system's automated control, testing and measurement. Through the software developed by LabVIEW, in terms of communication with traditional instruments, we can not only control the spectrometer to perform spectral testing, but also return spectral data and perform analysis and processing. In terms of using NI's virtual instruments, we insert the NI PCI-1407E multi-function acquisition card into the computer and control the signal source through the RS 232 serial port to realize the simulation of the laser receiver. The software interface for the laser receiver simulation section is shown in Figure 6. [align=center] Figure 6 Software interface for the laser receiver simulation section[/align] (IV) Test Results and Error Analysis Test Results: Numerous experiments and actual tests show that the laser receiver test system is easy to use, has high testing accuracy, and stable performance. Figure 7 shows the overall response curve of a laser receiver. [align=center] Figure 7 Software interface for the laser receiver simulation section[/align] As can be seen from Figure 7, the laser receiver has the maximum response value at a wavelength of 1,045 nm. The curve reflects the overall response characteristics of the laser receiver. From the distance sensitivity curve of the laser receiver, it can be concluded that when the excitation signal voltage is 0.5 V, i.e., the optical power is 25 mW, the output voltage of the laser receiver is 0.14 mV. This is the response threshold of the laser receiver. The maximum detection distance can be calculated from the minimum optical power of the response (the maximum detection distance varies under different external environments, such as atmospheric visibility, temperature, humidity, etc.). It can also be seen that when the excitation signal voltage is 19.5V, that is, the optical power is 0.9W, the output voltage of the laser receiver tends to saturate, and the receiver's response has reached saturation. Error analysis for laser receiver responsivity test, its error sources are mainly three aspects[4]: (1) When measuring the laser receiver response curve, the error caused by the sampling rate of the spectrometer can be calculated as σt caused by the deviation of the sampling point from the sampling value; (2) The error σad generated when the analog signal of the spectrometer is converted into digital signal. This error depends on the A/D bit number of the spectrometer acquisition unit, but this error can be greatly reduced when the average value is calculated after multiple measurements; (3) When performing spectral scanning, the motor drives the grating of the spectrometer to rotate, which will also cause error σd. Therefore, after considering the above four error effects, according to the error calculation theory, under the condition of multiple measurements, the total error σa of the laser receiver responsivity test is: For laser receiver distance sensitivity simulation test, its error sources are also mainly three aspects: (1) The error σs caused by the voltage fluctuation of the signal source driving the laser; (2) Since the test scheme uses an optical power meter to calibrate the light energy, there will be an error σl caused by the stability of the laser optical power meter; (3) The error σa generated when the data acquisition card converts analog signals to digital signals depends on the number of A/D bits of the acquisition card. Therefore, the total error of the laser receiver responsivity test during multiple measurements is *The program software interface in the figure cannot provide data due to the confidentiality of specific laser receiver parameters. References: 1. Lei Yutang, Wang Qingyou, He Jiaming, et al. Optoelectronic Detection Technology [M]. Beijing: China Metrology Press, 1997. 2. National Instruments, Inc. Virtual Instruments White Paper, 2002. 3. Gao Zhiyun, Gao Yue. Optoelectronic Detection Technology [M]. Beijing: National Defense Industry Press, 1995.