Terahertz near-field system image definition improving method

Abstract

The invention discloses a method for improving the image definition of a terahertz near-field system, belongs to the technical field of terahertz imaging, and mainly solves the problem of poor imaging definition caused by replacement of a scanning sample during imaging of the terahertz near-field system. The method comprises the following steps: S110, carrying out primary scanning by using a terahertz near-field system under the condition of no adjustment; s120, adjusting the position of the laser spot on the probe, and carrying out secondary scanning; s130, the reference point is adjusted, and three times of scanning are carried out; and S140, adjusting a gain parameter, and carrying out four times of scanning. The method has the characteristics of obvious image definition and simple operation process.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz imaging, and in particular relates to a method for improving the image clarity of a terahertz near-field system. The method can effectively improve the clarity of terahertz near-field imaging, and becomes a means for improving the quality of near-field imaging. Background Art

[0002] Terahertz is an electromagnetic wave between microwave and infrared with a frequency range of 0.1-10THz. With the continuous development of modern science and technology, terahertz waves have attracted a lot of attention due to their wide applications and potential in biology, materials, physics, etc. In the specific applications of terahertz, terahertz imaging technology occupies an important link. As one of the important technologies of terahertz science, terahertz imaging technology has broad application prospects in biomedical imaging, non-destructive testing, etc. with its unique advantages. Among them, terahertz near-field imaging technology breaks the traditional optical diffraction limit and realizes ultra-high resolution imaging of tiny objects. The terahertz near-field imaging system is generally composed of a terahertz source, a mirror module, a probe, etc., and works in reflection mode. The specific steps are as follows: the terahertz radiation emitted from the terahertz source is focused and transmitted by the mirror module, and then converged to the probe tip, and then hits the test sample through the tip. The interaction between the tip and the sample under test realizes the modulation of the terahertz wave, and then the modulated terahertz wave is reflected back by the tip and converged to the detector through the mirror module. Finally, the received terahertz waves can be processed to obtain an imaging image.

[0003] When rescanning after replacing the sample, due to the differences in type, height, and sample preparation of different samples, the amplitude of the received terahertz signal will be significantly different, resulting in a significant impact on the signal strength and stability. For example, the Z voltage amplitude fluctuates greatly during scanning, and the voltage signal of open1 is attenuated during phase locking. These will lead to a decrease in imaging clarity, and it is necessary to adjust the corresponding parameters in the specific imaging process to improve the clarity of near-field imaging and maintain stability. A terahertz near-field system imaging process method is needed to improve the clarity of near-field imaging images, effectively adjust the signal strength and stability, and perform high-definition imaging of samples. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a method for improving the imaging clarity of a terahertz near-field system, which adopts methods such as adjusting the position of the laser spot on the probe tip, the reference point and related gain parameters to achieve high-definition imaging display of the imaging image.

[0005] A method for improving image clarity of a terahertz near-field system comprises the following steps:

[0006] S110, initial scan using the terahertz near-field system without adjustment;

[0007] S120, adjusting the position of the laser spot on the probe and performing a second scan;

[0008] S130, adjusting the reference point and performing three scans;

[0009] S140, adjust the gain parameters and perform four scans

[0010] Beneficial effects:

[0011] It is clear and effective, easy to operate, produces rapid images and clear pictures, avoiding cluttered, complicated, time-consuming, laborious and ineffective operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a flow chart of a method for improving image clarity of a terahertz near-field system according to an embodiment of the present invention;

[0013] Figure 2 It is an image without any adjustment;

[0014] Figure 3 It is the image after adjusting the laser spot to the position of the probe tip;

[0015] Figure 4 It is the image after adjusting the reference point to stabilize the feedback signal;

[0016] Figure 5 This is the image after adjusting the gain parameter. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0018] According to an embodiment of the present invention, a method for improving image clarity of a terahertz near-field system is provided, such as Figure 1 As shown, the method comprises the following steps:

[0019] S110, initial scan using the terahertz near-field system without adjustment;

[0020] S120, adjusting the position of the laser spot on the probe and performing a second scan;

[0021] S130, adjust the reference point and perform three scans; the reference point refers to the target amplitude of feedback control. Feedback control is a process of returning the output information of the system to the input end, comparing it with the input information, and using the deviation between the two for control. In this article, it refers to the process used to adjust the target amplitude so that the target amplitude is close to the actual amplitude of the probe.

[0022] S140, adjust the gain parameter and perform four scans.

[0023] In the above step S120, the position of the laser spot on the probe is adjusted so that the voltage intensity increases and the laser spot is located at the probe tip. In one embodiment, the voltage intensity increases to more than 3 V. The voltage intensity is also called SUM voltage, which reflects the magnitude of the received laser light intensity. Because the optical signal is converted into an electrical signal by the photoelectric converter, the laser light intensity is represented by voltage.

[0024] In the above step S130, the reference point is adjusted so that the feedback signal is stabilized at about 0.8 V. The feedback signal refers to the actual amplitude of the probe.

[0025] In the above step S140, the gain parameters include: proportional gain parameter, integral gain parameter, and differential gain parameter, wherein the proportional gain parameter and the integral gain parameter represent feedback sensitivity, and the differential gain parameter represents oscillation sensitivity. The values ​​of the proportional gain parameter, the integral gain parameter, and the differential gain parameter are dynamically adjusted until the image clarity is the highest, and finally an imaging test image with obvious clarity can be obtained.

[0026] The following describes an example process of the above method:

[0027] According to the technical solution of the present invention, after replacing the sample, no adjustment is made and the sample is imaged for the first time using the terahertz near-field imaging system. The main purpose is to serve as a reference for subsequent adjustment imaging and verify the feasibility of the terahertz imaging process. Figure 2 As shown, we can see that the image clarity without any adjustment is very limited, the overall image stability is poor, and we cannot recognize the information on the image.

[0028] After the first imaging, adjust the laser spot so that it is located at the probe tip while ensuring that the voltage intensity is greater than 3V, and then perform the second imaging. Figure 3 As shown. It can be seen that the overall clarity of the image has been improved to a certain extent and the stability has also increased. This is because when the laser spot is at the tip position, it will coincide with the initial laser calibration position. At this time, the amount of terahertz waves reaching the sample will reach the highest, thereby increasing the value of the electrical signal and improving the clarity of the image. At the same time, the increase in voltage intensity will stabilize the laser spot and improve the imaging stability. The downside is that the improvement in image clarity is not large and does not play a very good role.

[0029] After the second imaging, adjust the value of the reference point so that the feedback signal reaches about 0.8V, and perform the third imaging. Figure 4 As shown in the figure, when the reference point is adjusted to maintain the feedback signal at a specific value, the overall clarity of the image is significantly improved, and more sample information is observed. This is because stable feedback will keep the interaction between the probe and the sample stable, thereby ensuring the overall imaging stability and clarity. The only drawback is that there are still many parts of the image that are blurred.

[0030] After three imagings, the final adjustment is performed by dynamically adjusting the proportional gain, integral gain, and differential gain to perform the fourth imaging. Figure 5 It can be seen that after dynamically adjusting the gain parameters, the internal situation of the sample can be easily observed, and the clarity and signal have been greatly improved, and the blurring of the sample imaging image has been resolved. In the near-field system, when the probe is in operation, the interaction between the probe and the sample will have a dynamic error with the set reference point. Among them, the proportional gain is used to control the speed of error compensation, the integral gain is used to compensate for the accumulated system error, and the differential gain is used to control stability and oscillation. According to the increase or decrease of the reference point value adjusted during the three imaging, the proportional gain, differential gain, and integral gain are adjusted to achieve a dynamic balance of feedback to obtain a high-definition imaging display. If the clarity of the image after four imaging is not greatly improved, the parameters can be corrected for subsequent scanning if necessary.

[0031] In summary, the present invention provides a method for improving the image clarity of a terahertz near-field imaging system, which mainly solves the problem of poor imaging effect caused by the replacement of scanning samples during imaging of the terahertz near-field system. It is carried out in four steps. First, the initial scan is performed without adjustment for comparison and reference; then the laser spot is adjusted so that it is located at the tip of the probe and the voltage intensity is greater than 3V for a second scan, which improves the signal and imaging stability; then the reference point is adjusted so that the feedback signal maintains a specific value and remains stable for three scans, and the imaging clarity is further improved; finally, the gain parameter is dynamically adjusted so that the set reference point and the actual adjusted reference point reach a dynamic balance for four scans, at which time the signal is maximum and the image clarity is optimal. This method has the characteristics of simple operation and high image clarity.

[0032] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving image clarity of a terahertz near-field system, characterized in that: The following steps are involved: S110, initial scan using the terahertz near-field system without adjustment; S120, adjusting the position of the laser spot on the probe and performing a second scan; S130, adjusting the reference point and performing three scans; S140, adjust the gain parameter and perform four scans.

2. The method for improving image clarity of a terahertz near-field system according to claim 1, characterized in that: In step S120, the position of the laser spot on the probe is adjusted so that the voltage intensity is increased and the laser spot is located at the tip of the probe.

3. The method for improving image clarity of a terahertz near-field system according to claim 1, characterized in that: In step S130, the reference point is adjusted so that the feedback signal is stabilized at about 0.8V.

4. The method for improving image clarity of a terahertz near-field system according to claim 1, characterized in that: In step S140, the gain parameters include: a proportional gain parameter, an integral gain parameter, and a differential gain parameter, wherein the proportional gain parameter and the integral gain parameter represent feedback sensitivity, and the differential gain parameter represents oscillation sensitivity; Adjusting the gain parameters includes: dynamically adjusting the values ​​of the proportional gain parameter, the integral gain parameter, and the differential gain parameter until the image clarity is the highest.

Images