An integrated standard for longitudinal resolution calibration of terahertz measurement systems

Abstract

The present invention discloses an integrated standard for calibrating the longitudinal resolution of a terahertz measurement system. The standard comprises a rectangular upper interface substrate and a step standard block. The rectangular upper interface substrate is disposed above the step standard block and is larger in size than the step standard block. The upper end surface of the step standard block is machined into a plurality of steps, the step height specifications of which correspond to the longitudinal resolution of the terahertz measurement system. The upper and lower measurement interfaces are formed between the rectangular upper interface substrate and the steps of the step standard block. The terahertz measurement system measures terahertz waves reflected from the upper and lower measurement interfaces to determine whether the terahertz measurement system has a longitudinal resolution corresponding to the step height specifications. The rectangular upper interface substrate and the step standard block are made of inorganic non-metallic ceramic materials formed by forming and high-temperature sintering natural or synthetic compounds. The present invention can meet the testing and calibration requirements of the longitudinal resolution index of the terahertz measurement system, ensuring the accuracy and consistency of the measurement results.

Description

Technical Field

[0001] The invention belongs to the field of geometric parameter calibration, and in particular relates to an integrated standard device for calibrating the longitudinal resolution of a terahertz measurement system. Background Art

[0002] With the rapid development of modern manufacturing, the demand for material quality is constantly increasing. Within this process, the detection of internal material defects has become a critical step in ensuring product quality. Tiny internal defects, such as cracks, holes, and inclusions, are often difficult to detect through traditional visual inspection methods, necessitating more sophisticated detection technologies for identification and assessment. Currently, the detection of internal material defects primarily relies on a variety of techniques and equipment, including ultrasonic testing, X-ray testing, and magnetic particle testing. Each of these technologies has its advantages. For example, ultrasonic testing is sensitive to internal defects in metals, X-ray testing can penetrate a wide range of materials, and magnetic particle testing is suitable for detecting surface and near-surface defects in magnetic materials. However, they also have limitations. For example, ultrasonic testing is restricted in terms of material thickness and shape, X-ray testing poses radiation risks, and magnetic particle testing is unsuitable for non-magnetic materials. In recent years, terahertz (THz) measurement systems, as an emerging nondestructive testing technology, have attracted widespread attention due to their unique advantages. Terahertz waves have a wide frequency range, can penetrate a wide range of materials, and are highly sensitive to changes in a material's internal structure. This gives THz measurement systems enormous potential for application in nondestructive testing. Compared to traditional inspection technologies, terahertz measurement systems require no contact with the object being measured, offer rapid inspection speeds, high resolution, and pose no radiation hazards. With the widespread application of terahertz technology in fields such as materials science, biomedicine, and safety inspection, the development and application of terahertz measurement systems is increasing. To ensure the accuracy and reliability of test results, regular calibration of terahertz measurement systems is essential. Calibration of key terahertz measurement system parameters not only ensures consistent and accurate measurement results but also improves the stability and repeatability of the measurement system, thereby ensuring the accurate identification and assessment of material defects.

[0003] Currently, the calibration of terahertz measurement systems primarily refers to the provisions for the calibration of radiative terahertz power meters in the "Technical Specifications for National Metrology of the People's Republic of China," JJF1600-2016. This specification covers the calibration of radiative terahertz power meters with a frequency range of 0.1 THz to 10 THz and a power range of 0.1 mW to 3 mW, including detailed descriptions of environmental conditions, metrological characteristics, calibration items, and calibration methods. However, while this specification provides a foundation for terahertz measurement calibration, it does not include the calibration of longitudinal resolution, a geometric parameter closely related to the measurement capabilities of terahertz measurement systems. The longitudinal resolution of a terahertz measurement system refers to the system's ability to distinguish between different layers within a sample, which is crucial for nondestructive testing, materials processing, and the entire manufacturing industry. Insufficient longitudinal resolution directly affects the accuracy and reliability of test results, thereby affecting material quality and the performance of the final product. In particular, more and more terahertz measurement systems (products) have factory specifications that explicitly include (longitudinal) resolution. However, when users conduct acceptance inspections, they have neither reference acceptance standards nor corresponding test standards and calibration methods, making it impossible to verify this key indicator. This brings greater uncontrollable quality risks to the delivery of terahertz measurement systems (products). Summary of the Invention

[0004] The purpose of the present invention is to address the problem that the longitudinal resolution of existing terahertz measurement systems cannot be calibrated, and to provide an integrated standard for calibrating the longitudinal resolution of terahertz measurement systems. The standard can meet the testing and calibration requirements of the terahertz measurement system for the longitudinal resolution index, and ensure the accuracy and consistency of the measurement results.

[0005] One aspect of the present invention provides an integrated standard for calibrating the longitudinal resolution of a terahertz measurement system, comprising a rectangular upper interface substrate and a step standard block, wherein the rectangular upper interface substrate is disposed above the step standard block, and the size of the rectangular upper interface substrate is larger than that of the step standard block;

[0006] The upper end surface of the step standard block is processed into a plurality of steps, and the step height specification corresponds to the longitudinal resolution of the terahertz measurement system. The upper and lower measurement interfaces are formed between the rectangular upper interface substrate and the steps of the step standard block. The terahertz wave reflected by the upper and lower measurement interfaces is measured by the terahertz measurement system to determine whether the terahertz measurement system has the longitudinal resolution corresponding to the step height specification.

[0007] The rectangular upper interface substrate and the step standard block are made of inorganic non-metallic ceramic materials made by forming and high-temperature sintering natural or synthetic compounds;

[0008] The surface roughness of the upper and lower surfaces of the rectangular upper interface substrate is ≤0.2μm, the flatness is ≤1μm, and the parallelism is ≤3μm; the surface roughness of the upper and lower surfaces of the step standard block is ≤0.2μm, the flatness is ≤1μm, and the parallelism is ≤3μm.

[0009] Preferably, the step height specifications of the step standard block are 0.5 μm, 1 μm, 2 μm, 5 μm, and 10 μm.

[0010] Preferably, the inorganic non-metallic ceramic material is zirconia ceramic.

[0011] Preferably, the step height value of the step standard block is traced by a high-precision three-dimensional coordinate measuring machine or a step profiler.

[0012] The integrated standard for longitudinal resolution calibration of a terahertz measurement system according to the above aspects of the present invention can meet the testing and calibration requirements of the terahertz measurement system for longitudinal resolution indicators, and ensure the accuracy and consistency of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive efforts.

[0014] Figure 1 This is a front view of an integrated standard for calibrating the longitudinal resolution of a terahertz measurement system according to an embodiment of the present invention;

[0015] Figure 2 1 is a front view of an integrated standard for calibrating the longitudinal resolution of a terahertz measurement system according to an embodiment of the present invention;

[0016] Figure 3 The figure is a schematic diagram of the working principle of an integrated standard device for calibrating the longitudinal resolution of a terahertz measurement system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0018] One embodiment of the present invention provides an integrated standard for calibrating the longitudinal resolution of a terahertz measurement system, such as Figure 1 and Figure 2 As shown, the standard device includes a rectangular upper interface substrate 1 and a step standard block 2.

[0019] The upper end surface of the step standard block 2 is processed into multiple steps with a certain gradient difference. The step height corresponds to the longitudinal resolution of the terahertz measurement system. The preferred specifications are 0.5μm, 1μm, 2μm, 5μm, and 10μm. The step height value of the step standard block 2 can be traced using a high-precision three-dimensional coordinate measuring machine or a step profiler. The measurement uncertainty of the step nominal height of the step standard block 2 should be better than: U = 2nm + 6×10 -5 H, k = 2, H is the step height.

[0020] The rectangular upper interface substrate 1 is placed on the step standard block 2 to form an integrated step standard. The material of the rectangular upper interface substrate 1 can be selected from zirconia ceramics, a type of inorganic non-metallic ceramic material made by forming and sintering natural or synthetic compounds at high temperature. The material of the step standard block 2 should have a refractive index ratio of 1 as large as possible, preferably zirconia ceramics, a type of inorganic non-metallic ceramic material made by forming and sintering natural or synthetic compounds at high temperature, or metal. The material of the object being measured by the terahertz system can also be selected based on the material being measured, which should be consistent with the material being measured, or the material density (refractive index) should be close to the material.

[0021] The processing technical requirements for the upper and lower surfaces of the rectangular upper interface substrate 1 are: surface roughness Ra≤0.2μm, flatness≤1μm, parallelism≤3μm; the processing technical requirements for the step standard block 2 are: roughness Ra≤0.2μm, flatness≤1μm, parallelism≤3μm.

[0022] Upper and lower measurement interfaces are formed between the rectangular upper interface substrate 1 and the steps of the step standard block 2. By measuring the terahertz waves reflected from the upper and lower measurement interfaces by the terahertz measurement system, it can be determined whether the terahertz measurement system has the longitudinal resolution corresponding to the step height specification, thereby using the step standard height value to verify and calibrate the longitudinal resolution index of the terahertz measurement system.

[0023] like Figure 3 As shown, the working principle of the integrated standard for calibrating the longitudinal resolution of a terahertz measurement system according to an embodiment of the present invention is as follows:

[0024] The terahertz wave emitted by the terahertz measurement system hits the rectangular upper interface substrate 1 vertically, reflecting terahertz wave A at the upper measurement interface (the lower surface of the rectangular upper interface substrate 1). At the same time, after passing through the rectangular upper interface substrate 1, the terahertz wave reflects terahertz wave B at the lower measurement interface (the upper surface of the step of the step standard block 2). The terahertz measurement system observes the waveforms of terahertz wave A and terahertz wave B on the time domain coordinate axis to determine whether the terahertz measurement system can normally and stably output the waveform display or whether it can normally and stably extract the flight time difference between the two, thereby confirming whether it has the longitudinal resolution capability corresponding to the standard step height specification. If the terahertz measurement system can normally and stably output the waveform display or can normally and stably extract the flight time difference between the two, it can be considered that the terahertz measurement system has the ability to normally identify the standard step height specification of the standard, and the corresponding standard step height specification is the "longitudinal resolution" of the terahertz measurement system.

[0025] Compared with the prior art, the standard device of the embodiment of the present invention has the following beneficial effects:

[0026] 1. This invention can meet the needs of longitudinal resolution testing and calibration for terahertz measurement systems with varying probe structures and sizes. The step standard block, made from zirconia, an inorganic non-metallic ceramic material, exhibits advantages such as high refractive index, uniform density, strong chemical stability, high wear resistance, and excellent optical properties. It has been proven in mature applications in fields such as optics and electronics.

[0027] 2. The present invention can form upper and lower measurement interfaces through the step standard block and the upper interface substrate. By utilizing the step standard height value, the test, verification and calibration of the longitudinal resolution index of the terahertz measurement system can be realized, and the application prospect is very adaptable.

[0028] The integrated standard device for calibrating the longitudinal resolution of the terahertz measurement system in the embodiment of the present invention is the first and only one in China. Through the development and application of this standard device, the application potential and practical value of terahertz measurement technology in the fields of non-destructive testing, material processing and manufacturing can be further enhanced.

[0029] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims.

Claims

1. An integrated standard for calibrating the longitudinal resolution of a terahertz measurement system, characterized in that: It includes a rectangular upper interface substrate and a step standard block, wherein the rectangular upper interface substrate is arranged above the step standard block, and the size of the rectangular upper interface substrate is larger than that of the step standard block; The upper end surface of the step standard block is processed into a plurality of steps, and the step height specification corresponds to the longitudinal resolution of the terahertz measurement system. The upper and lower measurement interfaces are formed between the rectangular upper interface substrate and the steps of the step standard block. The terahertz wave reflected from the upper and lower measurement interfaces is measured by the terahertz measurement system, and the difference in flight time between the two is extracted to determine whether the terahertz measurement system has the longitudinal resolution corresponding to the step height specification. The rectangular upper interface substrate and the step standard block are made of inorganic non-metallic ceramic materials made by forming and high-temperature sintering natural or synthetic compounds; The surface roughness of the upper and lower surfaces of the rectangular upper interface substrate is ≤0.2μm, the flatness is ≤1μm, and the parallelism is ≤3μm; the surface roughness of the upper and lower surfaces of the step standard block is ≤0.2μm, the flatness is ≤1μm, and the parallelism is ≤3μm.

2. The standard device according to claim 1, characterized in that The step height specifications of the step standard block are 0.5 μm, 1 μm, 2 μm, 5 μm, and 10 μm.

3. The standard device according to claim 1 or 2, characterized in that: The inorganic non-metallic ceramic material is zirconia ceramic.

4. The standard device according to claim 1 or 2, characterized in that: The step height value of the step standard block is traced by a high-precision three-dimensional coordinate measuring machine or a step gauge.

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