LED modulation bandwidth fast test system and test method

Abstract

The application discloses a kind of LED modulation bandwidth fast test system, including direct-current power supply;Biaser;Laser, for exciting LED sample to emit light, realize the transformation of optical signal-electrical signal-optical signal;Transmission component, for focusing overall light;Optical filter, for excluding the influence of laser on LED light emission;Photoelectric detector, detect the light signal emitted by LED, and change into electrical signal output;Vector network analyzer, analyze two-port signal to draw frequency response curve, so as to obtain the modulation bandwidth of LED.The application can realize the function of testing the communication performance of LED without packaging, and can realize the function of measuring the modulation bandwidth of multiple LEDs simultaneously by laser scanning.Using the device of the application can realize fast measurement, and optical excitation can achieve the effect of zero damage to LED sample.

Description

Technical Field

[0001] This invention relates to a rapid testing system and method for LED modulation bandwidth. Background Technology

[0002] LED visible light communication technology boasts numerous advantages, including high bandwidth, high speed, strong resistance to electromagnetic interference, and high security, making it a hot topic in the development of visible light communication technology. As the light source for visible light communication systems, the inherent characteristics of LEDs have a significant impact on the system's communication performance.

[0003] The modulation bandwidth of an LED directly determines the channel capacity and transmission rate of visible light communication, and is one of the important indicators for measuring system communication performance. Therefore, the ability to accurately, quickly, and efficiently measure the modulation bandwidth of an LED is of great significance for the research of visible light communication technology.

[0004] Existing research largely focuses on factors influencing modulation bandwidth and methods to improve it, with relatively simple testing systems. In 2012, Pei Yanrong et al. from the Institute of Semiconductors, Chinese Academy of Sciences, designed a device for testing the performance of light sources in visible light communication systems, which can be used to test the modulation bandwidth of LEDs. The device mainly consists of a transmitter and a receiver. The transmitter includes an electrical signal source and an LED light source, while the receiver includes a photodetector and a signal acquisition module. The modulation bandwidth is ultimately obtained through the frequency response curve of the LED. In 2018, Yang Jie et al. from the Institute of Semiconductors, Chinese Academy of Sciences, used a testing system centered on a network analyzer when studying the impact of carrier recombination mechanisms on LED modulation bandwidth. The network analyzer integrates signal generation, detection, and processing functions, thereby enabling higher frequency testing.

[0005] Both of the above testing systems use electrical injection to excite LED light emission. However, this type of testing system based on the principle of electrical excitation is prone to many problems in actual operation. First, the electrode probe needs to be in direct contact with the LED under test during testing, which is difficult to operate and has a high error rate. Furthermore, it is easy to cause destructive damage to the sample during testing. In addition, the number of pixels that can be tested per unit time is limited, resulting in low testing efficiency. Therefore, building a non-contact, non-destructive, and highly efficient LED modulation bandwidth testing system is a problem that urgently needs to be solved. Summary of the Invention

[0006] This invention provides a rapid testing system for LED modulation bandwidth. Based on the physical mechanism of LED photoluminescence, a laser is introduced as a modulation signal source. The laser signal is projected onto the LED sample, causing the LED to emit light through stimulated emission, thereby realizing a novel testing method without probe contact or soldering.

[0007] The technical solution adopted in this invention is as follows:

[0008] A rapid testing system for LED modulation bandwidth, characterized by comprising a transmitter component, a receiver component, and a testing platform;

[0009] The transmitter component is used to apply an electrical signal to the laser to generate a laser test signal with loading information, and the transmitter component includes at least:

[0010] Signal generating element, used to provide test electrical signals;

[0011] Laser;

[0012] The first lens group is used to focus the laser onto the LED sample to be tested;

[0013] The receiving component is used to receive the visible light signal generated by the LED sample under excitation, and the receiving component includes at least:

[0014] The second lens group is used to focus the visible light signal generated by the LED sample;

[0015] A filter is used to filter out the generated laser light.

[0016] A photodetector is used to receive visible light signals generated by an LED sample entering its detection window and convert them into electrical signals.

[0017] A vector network analyzer is used to analyze the electrical signals at the transmitting and receiving ends and plot the frequency response curve to obtain the modulation bandwidth of the LED.

[0018] The testing platform is used to place the LED samples to be tested.

[0019] Preferably, the transmitter assembly further includes an optoelectronic bracket, on which the laser is placed and the emission distance and angle of the laser can be adjusted.

[0020] Preferably, the signal generating element is composed of a DC signal generating section of a DC power supply and an AC signal generating section of a vector network analyzer.

[0021] Preferably, it also includes a bias unit, which is used to couple the DC signal generated by the DC power supply with the AC signal generated by the vector network analyzer, and load the coupled electrical signal onto the laser.

[0022] Preferably, the testing platform has a three-axis movable base, which controls the LED sample to perform displacement scanning.

[0023] Preferably, both the first lens group and the second lens group are optical zoom lenses.

[0024] The present invention also discloses the application of laser in testing the modulation bandwidth of LED samples.

[0025] This invention also discloses a method for rapid testing of LED modulation bandwidth, the steps of which include:

[0026] (1) Apply a voltage signal to the laser to make it emit laser light;

[0027] (2) The laser emitted by the laser is projected onto the LED sample to be tested, driving the LED sample to emit light;

[0028] (3) The visible light signal generated by the laser driving the LED sample is converted into an electrical signal by a photodetector and then input into a vector network analyzer for analysis to obtain the modulation bandwidth of the test LED.

[0029] Preferably, step (1) specifically involves the DC power supply outputting a DC signal of 3.5V-6V and the vector network analyzer outputting an AC signal of 300kHz-3GHz. The DC signal and the AC signal are coupled and applied to the laser to excite the laser to emit laser light.

[0030] Preferably, step (2) specifically involves the laser emitted by the laser being focused by a lens and then projected onto the LED sample.

[0031] Preferably, step (3) specifically involves the visible light signal generated by the LED sample being focused by a lens, then filtered to remove interference from the laser signal, and then converted into an electrical signal by a photodetector. Finally, the signal is input into a vector network analyzer for frequency response analysis to obtain the modulation bandwidth of the LED sample being tested.

[0032] The beneficial effects of this invention are as follows:

[0033] (1) Easy to operate, no need to package the sample, no strict requirements on sample size, just place the LED sample on the test platform to carry out the test;

[0034] (2) The sample is non-destructive and does not require contact with the sample using an electrode probe, thus preventing damage or destruction to the sample.

[0035] (3) High efficiency in testing: The three-axis control of the testing platform can quickly switch the laser irradiation zone, which greatly improves the testing efficiency of LED modulation bandwidth.

[0036] In summary, this invention enables the testing of the communication performance of LEDs without encapsulation, and allows for the simultaneous measurement of the modulation bandwidth of multiple LEDs via laser scanning. The device of this invention enables rapid measurement, and photoexcitation achieves zero damage to the LED sample. Attached Figure Description

[0037] Figure 1This is a structural block diagram of the LED modulation bandwidth rapid testing system in Embodiment 1 of the present invention;

[0038] Figure 2 The image shows the spectrum of the laser in Embodiment 1 of the present invention;

[0039] Figure 3 The frequency response curve of the laser in Embodiment 1 of the present invention;

[0040] Figure 4 The frequency response curve of the LED sample in Example 1 of this invention;

[0041] Figure 5 The above are the frequency response curves of the LED samples in Examples 1, 2, and 3 of this invention under the condition that the laser operating current is 200mA.

[0042] [Explanation of symbols for key components in this invention]

[0043] 1-Transmitter assembly; 2-Receiver assembly;

[0044] 11-DC power supply; 12-Bias switch;

[0045] 13-Laser; 14-Lens group;

[0046] 21-Lens group; 22-Filter;

[0047] 23 - Photodetector; 24 - Vector network analyzer;

[0048] 3-Sample to be tested; 31-Movable base;

[0049] 32-LED sample. Detailed Implementation

[0050] The present invention will be further described below with reference to the embodiments, but the description of the embodiments does not limit the scope of protection of the present invention in any way.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, while this document provides examples of parameters containing specific values, it should be understood that the parameters need not be exactly equal to the corresponding values, but can approximate the corresponding values ​​within acceptable error tolerances or design constraints. Directional terms mentioned in the embodiments, such as “up,” “down,” “front,” “back,” “left,” “right,” etc., are only for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the scope of protection of this invention.

[0052] Unless otherwise specified, all substances or instruments used in the following examples can be obtained from conventional commercial sources.

[0053] In Embodiment 1 of the present invention, a rapid testing system for LED modulation bandwidth is provided. For example... Figure 1 As shown, the device includes: a transmitter assembly 1, a receiver assembly 2, and a test platform 3. The transmitter assembly 1 is a signal generation and transmission device, including: a DC power supply 11, a biaser 12, a laser 13, and a lens group 14. The receiver assembly 2 is a visible light signal receiving and processing device, including: a lens group 21, a filter 22, a photodetector 23, and a vector network analyzer 24.

[0054] The following sections will provide a detailed description of each component of the LED modulation bandwidth rapid testing system in this embodiment.

[0055] DC power supply 11 outputs a DC signal, and CH1 and CH2 drive the laser and photodetector to operate normally, respectively. By controlling and changing the output voltage of DC power supply CH1, test results of samples under different current densities can be obtained.

[0056] The vector network analyzer 24 uses the GRATTEN GA3623 high-precision 3GHz vector network analyzer, which has advantages such as high sensitivity, high reliability and low noise, and is a key instrument for analyzing LED modulation bandwidth. CH1 outputs an AC signal and performs a spectrum scan in the range of 300kHz-3GHz. CH2 receives the final electrical signal transmitted through the optoelectronic circuit, and then plots the frequency response curve to obtain the corresponding -3dB frequency, i.e., the modulation bandwidth of the LED.

[0057] The DC signal output from the CH1 port of the DC power supply 11 and the AC signal output from the CH1 port of the vector network analyzer 24 are respectively input to the DC and RF ports of the bias converter 12. The electrical signal coupled by the bias converter 12 is output from the "DC & RF" port and loaded onto the laser 13.

[0058] Laser 13 uses a TO-18 packaged 405nm wavelength LD, which is soldered onto the PCB circuit board before testing. Laser 13 operates at 3.5V-6V and is fully activated when the current exceeds 20mA. Figure 2 As shown, the peak wavelength of laser 13 is 402.5 nm. Figure 3 As shown, under the extreme condition of an input voltage of 6V, the current of laser 13 is 203mA, and the modulation bandwidth can reach 994.87MHz.

[0059] Both lens group 14 and lens group 21 are optical zoom lenses. Lens group 14 focuses the light signal emitted by the laser onto the LED sample 32, and lens group 21 focuses the light signal generated by the LED so that it can be captured by the photodetector 23.

[0060] The movable base 31 is a three-axis moving platform that can move the position of the LED sample 32 it carries, so that the laser signal can accurately and quickly scan different LED array units on the chip.

[0061] In this embodiment, LED sample 32 uses a gallium nitride-based blue LED epitaxial wafer. LEDs have advantages such as high brightness, low energy consumption, long lifespan, and fast response, and can serve as both a lighting source and an information transmission source. LED array light-emitting units with different characteristics can be fabricated on the same wafer, and their modulation bandwidth can be quickly tested and compared using the system of this invention.

[0062] The function of filter 22 is to filter the laser. It needs to be placed in front of the detection window of photodetector 23 to prevent the laser from interfering with the test of the LED visible light signal during transmission in the optical path.

[0063] Photodetector 23 is an APD avalanche photodetector used to receive optical signals and convert them into electrical signals, which are then input to CH2 of vector network analyzer 24. It operates in the visible light wavelength range of 380nm-780nm, with a measurable modulation bandwidth of up to 1.5GHz. Photodetector 23 operates at 12V and requires power from DC power supply 11.

[0064] The testing process for the LED modulation bandwidth fast testing system in this embodiment is as follows:

[0065] During the emission phase: The DC power supply 11 outputs a 3.5V-6V DC signal via CH1, and CH2 provides the photodetector 23 with a 12V operating voltage. The vector network analyzer 24 outputs a 300kHz-3GHz AC signal via CH1, and the bias unit 12 couples the DC and AC signals to the laser 13. The laser emitted by the laser 13 is focused by the lens group 14 and projected onto the LED sample 32 on the test platform 3, driving the LED to emit light and communicate. The movable base 31 can support and move the LED sample 32, facilitating laser positioning and scanning of different light-emitting units of the LED chip.

[0066] Receiving stage: The visible light signal generated by the laser driving the LED sample is focused by the lens group 21 in the receiving end component 2, filtered by the filter 22 to remove interference from the laser signal, and then converted into an electrical signal by the photodetector 23. Finally, it is input into CH2 of the vector network analyzer 24 for frequency response analysis to obtain the modulation bandwidth of the test LED. Figure 4 As shown, when the laser injection current reaches 200mA, the maximum modulation bandwidth of this LED sample is 4.31MHz.

[0067] The testing equipment and procedures used in Examples 2 and 3 are the same as in Example 1, except for the LED sample. In Example 2, the LED sample is a gallium nitride-based green LED epitaxial wafer, and in Example 3, the LED sample is a gallium nitride-based violet LED epitaxial wafer. Figure 5 As shown, under the condition that the laser operating current is 200mA, the modulation bandwidths of the samples measured in Examples 2 and 3 are 3.27MHz and 5.05MHz, respectively. The successful testing of different samples further verifies the feasibility and applicability of the present invention.

[0068] The embodiments of the present invention have now been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the present invention for a rapid testing system for LED modulation bandwidth.

[0069] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A rapid testing system for LED modulation bandwidth, characterized in that... This includes transmitter components, receiver components, and a test platform; The transmitter component is used to apply an electrical signal to the laser to generate a laser test signal with loading information, and the transmitter component includes at least: Signal generating element, used to provide test electrical signals to the laser; Laser; The first lens group is used to focus the laser onto the LED sample to be tested; The receiving component is used to receive the visible light signal generated by the LED sample under excitation, and the receiving component includes at least: The second lens group is used to focus the visible light signal generated by the LED sample; A filter is used to filter out the generated laser light. A photodetector is used to receive visible light signals generated by an LED sample entering its detection window and convert them into electrical signals. A vector network analyzer is used to analyze the electrical signals at the transmitting and receiving ends and plot the frequency response curve to obtain the modulation bandwidth of the LED. The testing platform is used to place the LED samples to be tested.

2. The LED modulation bandwidth rapid testing system according to claim 1, characterized in that... The transmitter assembly also includes an optoelectronic bracket, on which the laser is placed and the emission distance and angle of the laser can be adjusted.

3. The LED modulation bandwidth rapid testing system according to claim 2, characterized in that... The signal generating element is composed of a DC signal generating section of a DC power supply and an AC signal generating section of a vector network analyzer.

4. The LED modulation bandwidth rapid testing system according to claim 3, characterized in that... It also includes a bias unit, which is used to couple the DC signal generated by the DC power supply with the AC signal generated by the vector network analyzer, and load the coupled electrical signal onto the laser.

5. The LED modulation bandwidth rapid testing system according to claim 3, characterized in that... The testing platform has a three-axis movable base, which controls the displacement and scanning of LED samples.

6. The LED modulation bandwidth rapid testing system according to claim 1, characterized in that... Both the first lens group and the second lens group are optical zoom lenses.

7. A method for rapid testing of LED modulation bandwidth, characterized in that... The steps include: (1) Apply a voltage signal to the laser to make the laser emit laser light; (2) The laser emitted by the laser is projected onto the LED sample to be tested, driving the LED sample to emit light; (3) The visible light signal generated by the laser driving the LED sample is converted into an electrical signal by a photodetector and then input into a vector network analyzer for analysis to obtain the modulation bandwidth of the test LED.

8. The method for rapid testing of LED modulation bandwidth according to claim 7, characterized in that... Step (1) specifically involves the DC power supply outputting a DC signal of 3.5V-6V and the vector network analyzer outputting an AC signal of 300kHz-3GHz. The DC signal and the AC signal are coupled and applied to the laser to excite the laser to emit laser light.

9. The method for rapid testing of LED modulation bandwidth according to claim 7, characterized in that... Step (2) specifically involves the laser emitted by the laser being focused by a lens and then projected onto the LED sample.

10. The method for rapid testing of LED modulation bandwidth according to claim 7, characterized in that... Step (3) specifically involves focusing the visible light signal generated by the LED sample through a lens, filtering out interference from the laser signal, converting it into an electrical signal through a photodetector, and finally inputting it into a vector network analyzer for frequency response analysis to obtain the modulation bandwidth of the LED sample being tested.

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