Terahertz light path calibration method based on visible light simulation

Abstract

The invention discloses a terahertz light path calibration method based on visible light simulation, and belongs to the technical field of light path calibration, and the method comprises the following steps: S1, adjusting the height and the vertical angle of visible first point laser emitted by a first point laser instrument; s2, a first laser level meter and a second laser level meter are placed on the two sides of the first parabolic mirror; s3, a first point laser instrument is placed on the side where a second laser gradienter is located, and first point laser is emitted to the center position of a first parabolic mirror and is aligned with the laser line propagation path of the second laser gradienter; s4, debugging the first working lens group by means of visible first point laser; and S5, replacing the first point light source instrument with the first terahertz source. According to the invention, the required equipment is simple, the operation is convenient and fast, the efficiency is high, the effective calibration of the light path can be realized only by means of the visible light source and the laser level meter, and the signal quality and the measurement precision are obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of optical path calibration technology, specifically relating to a terahertz optical path calibration method based on visible light simulation. Background Technology

[0002] Terahertz (THz) waves are electromagnetic waves with frequencies between 0.1 and 10 THz and wavelengths between 30 µm and 3 mm, located between the microwave and infrared bands. This band carries nearly half the energy of cosmic photons emitted from the cosmic microwave background (CMB), thus holding an irreplaceable position in astronomical research. High-sensitivity terahertz detectors are crucial for studying atmospheric structure and the origin of the universe. To effectively detect weak terahertz signals, a sophisticated optical transmission system must be designed and constructed to guide the signal radiation to the detector to the maximum extent. This process not only directly affects the signal reception efficiency but also has significant implications for the performance calibration and further optimization of the detector itself.

[0003] Optical path calibration is a key step in ensuring signal quality and measurement accuracy. Since the wavelength of terahertz waves is between infrared and microwave, it cannot be directly observed by the naked eye. Therefore, indirect control methods, special auxiliary tools and real-time signal feedback technology are needed to achieve accurate alignment during calibration. Currently, the commonly used methods for optical path calibration are: (1) Scanning spot positioning method: a two-dimensional scanning platform with a stepper motor is used to move the detector (such as a pyroelectric detector) and the center of the spot is determined by recording the THz signal intensity distribution; (2) Real-time phase monitoring: in an interferometer or coherent detection system, the optical path difference is adjusted by the phase difference feedback between the reference arm and the sample arm (such as moving the delay line), and a high-precision piezoelectric displacement stage (with a resolution of up to nm) is the key instrument for this method; (3) Coaxial visible light calibration method: a visible laser (such as 650 nm red light) coaxial with the THz beam is used as the guiding light, and the same optical path is achieved by a beam splitter or a coated mirror. After completion, remove or turn off visible light and switch to THz detection; (4) Real-time imaging with THz camera: THz camera based on microbolometer or quantum well detector (QWIP) directly images the light spot (such as TeraSense camera). The resolution is limited by wavelength (usually in the hundreds of µm range) and requires image processing algorithms. The above methods have high requirements for experimental equipment and are very complicated to operate. Therefore, how to adjust the optical path in the detection system more accurately and efficiently is still a technical problem in the research of high-sensitivity terahertz detection.

[0004] Problems with existing technology

[0005] 1. The scanning spot positioning method and the real-time phase monitoring method place extremely high demands on the accuracy and versatility of automated control equipment, which leads to high equipment costs and complex operation procedures. Therefore, their application faces high technical barriers and economic costs.

[0006] 2. Real-time imaging with THz cameras relies on sophisticated specialized instruments for spot positioning and requires complex processing algorithms to accurately calibrate the optical path. Currently, this technology is still under development and requires further advancement and refinement through lengthy, complex, and high-precision experimental research.

[0007] 3. The coaxial visible light calibration method is similar in principle to the method proposed in this paper. However, due to the significant differences in physical size and radiation characteristics between visible light instruments and non-visible light instruments such as terahertz instruments, it is difficult to keep the spatial position of the laser radiation port and the terahertz wave radiation port completely consistent when replacing the two, making it difficult to directly replace or use them interchangeably in practical applications. Summary of the Invention

[0008] In view of the above-mentioned problems in the prior art, the technical problem to be solved by the present invention is to provide a terahertz optical path calibration method based on visible light simulation, which can efficiently adjust the optical path in the detection system.

[0009] Technical Solution: To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] A terahertz optical path calibration method based on visible light simulation includes the following steps:

[0011] S1. Adjust the height and vertical angle of the first visible point laser emitted by the first point laser device to ensure the collimation of the propagation path of the first point laser.

[0012] S2. Set up a first working mirror group for propagating the optical path. The first working mirror group includes a first parabolic mirror and a second parabolic mirror arranged opposite each other. Place the first laser level and the second laser level on both sides of the first parabolic mirror so that the vertical laser lines of the first laser level and the second laser level are aligned and located at the center of the first parabolic mirror.

[0013] S3. Place the first point laser instrument on the side where the second laser level is located, and direct the first point laser toward the center of the first parabolic mirror and align it with the propagation path of the laser line of the second laser level.

[0014] S4. Adjust the first working lens group using a visible first point laser to ensure that the beam of the first point laser is transmitted to the target position;

[0015] S5. Based on the vertical laser line paths of the first and second laser levels that have been calibrated, replace the first point source instrument with the first terahertz source to complete the switching and calibration of the first optical path.

[0016] Preferably, step S1 specifically includes: aligning the first point laser with two magnetic beam height scales placed at an interval, and adjusting the height and vertical angle of the first point laser to ensure that the height scales it illuminates on the two magnetic beam height scales are consistent, thereby ensuring the collimation of the propagation path of the first point laser.

[0017] Preferably, S2 specifically includes: placing a first laser level on the side where the back of the first parabolic mirror is located, with the height of the first laser level being higher than that of the first parabolic mirror; placing a second laser level on the side where the working surface of the first parabolic mirror is located, with the height of the second laser level being lower than that of the first parabolic mirror; and making the vertical laser lines of the first laser level and the second laser level coincide and located at the center of the first parabolic mirror.

[0018] Preferably, step S3 specifically includes: placing the first point laser instrument on the side where the second laser level is located, and directing the first point laser toward the first parabolic mirror and aligning it with the laser propagation path of the second laser level, so as to achieve that the first point laser is perpendicularly incident on the center of the first parabolic mirror.

[0019] Preferably, S4 specifically includes: adjusting the first working mirror group with the aid of a visible first point laser, so that the first point laser is reflected by the first parabolic mirror and the second parabolic mirror and then incident on the center position of the terahertz detector.

[0020] Preferably, the distance between the two magnetic beam height gauges is L.

[0021] Preferably, when calibration of two or more terahertz optical paths is required, the following steps are also included:

[0022] S4.2. Set up a second working group for propagating the optical path. The second working group includes a beam splitter, a second working mirror, a third laser level, a fourth laser level, and a second point laser. Place the beam splitter between the first parabolic mirror and the second parabolic mirror. The beam of the first point laser passes through the beam splitter after being reflected by the first parabolic mirror.

[0023] S4.3 Adjust the height and vertical angle of the visible second point laser emitted by the second point laser device to ensure the collimation of the propagation path of the second point laser;

[0024] S4.4. Set a second working mirror on one side of the beam splitter, and place the third laser level and the fourth laser level on both sides of the beam splitter and the second working mirror, so that the vertical laser lines of the third laser level and the fourth laser level are aligned and located at the center of the beam splitter and the second working mirror.

[0025] S4.5 Place the second point laser on the same side as the fourth laser level, and direct the second point laser toward the second working mirror and the beam splitter, aligning it with the laser propagation path of the fourth laser level.

[0026] S4.6 The second point laser beam coincides with the first point laser beam after being reflected by the beam splitter. The beam of the second point laser beam is also transmitted to the target position after being reflected by the second parabolic mirror.

[0027] Preferably, step S5 further includes the following step:

[0028] S5.2 Based on the vertical laser line paths of the calibrated third and fourth laser levels, replace the second point source instrument with the second terahertz source to complete the switching and calibration of the second optical path.

[0029] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0030] 1. This invention improves upon the coaxial visible light calibration method. Based on the use of visible light for optical path adjustment, it defines the laser radiation port in a simple and efficient way using two laser levels, which is equivalent to establishing a virtual XYZ coordinate system for it. This effectively solves the compatibility problem between visible light and non-visible light (such as terahertz) instruments caused by differences in physical size and radiation characteristics.

[0031] 2. Set up two opposing laser levels. The height of the two laser levels is different from the height of the parabolic mirror. When some objects in the light path block the illumination of one of the laser levels, the two laser levels can compensate for the blocked light.

[0032] 3. This method requires simple equipment, is easy to operate, and is highly efficient. It is especially suitable for complex optical path systems with multiple terahertz signals. By simulating different terahertz signals with different colored light sources, multi-channel calibration can be completed simultaneously.

[0033] 4. The optical path can be effectively calibrated using only a visible light source and a laser level, which significantly improves signal quality and measurement accuracy and is of great value for the calibration and further optimization of detector performance. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of terahertz wave generation by the terahertz source in Example 1;

[0035] Figure 2 This is a schematic diagram of the optical path design of the terahertz detection system in Example 1;

[0036] Figure 3 This is a schematic diagram of the method for adjusting the height and vertical angle of the visible first point laser in step S1 of Example 1;

[0037] Figure 4 This is a schematic diagram of the first point laser beam directed toward the center of the first parabolic mirror in Example 1;

[0038] Figure 5 This is a schematic diagram showing the position of the first working lens group in Example 1;

[0039] Figure 6 This is a schematic diagram of the first point laser in Example 1 after it has been replaced with a terahertz source;

[0040] Figure 7 This is a schematic diagram showing the positions of the first working mirror group and the second working group in Embodiment 2. Detailed Implementation

[0041] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0042] like Figure 1 As shown, terahertz waves are generated by terahertz sources and radiate outwards in a divergent pattern from their emission ports, such as... Figure 2 As shown, the optical path design of the terahertz detection system is as follows: First, an off-axis parabolic mirror is used to collimate the diverging terahertz wave to form a parallel beam; then, a second off-axis parabolic mirror is used to focus the parallel beam onto the terahertz detector.

[0043] Example 1

[0044] This embodiment of a terahertz optical path calibration method based on visible light simulation includes the following steps:

[0045] S1. Adjust the height and vertical angle of the visible first point laser emitted by the first point laser (existing ordinary point laser pointer) to ensure the collimation of the first point laser propagation path; specifically, this includes: aligning the first point laser with two magnetic beam height scales placed at intervals, the distance between the two magnetic beam height scales being L, where L is equal to the propagation distance of the entire optical path from the first point laser to the preset target; by adjusting the height and vertical angle of the first point laser to ensure that the height scales it illuminates on the two magnetic beam height scales are consistent, thereby ensuring the collimation of the laser propagation path.

[0046] S2. A first working mirror group is set up for propagating the optical path. The first working mirror group includes a first parabolic mirror and a second parabolic mirror arranged opposite each other. Both the first and second parabolic mirrors are existing off-axis parabolic reflectors (focal length 10.16cm). The working surfaces of the first and second parabolic mirrors are arranged opposite each other. A first laser level and a second laser level are placed on both sides of the first parabolic mirror. The first laser level is placed on the side where the back of the first parabolic mirror is located, and the height of the first laser level is higher than that of the first parabolic mirror. The second laser level is placed on the side where the working surface of the first parabolic mirror is located, and the height of the second laser level is lower than that of the first parabolic mirror. Both the first and second laser levels emit 360° vertical laser lines, so that the 360° vertical laser lines emitted by the first and second laser levels coincide and are located at the center of the first parabolic mirror. In this embodiment, both the first and second laser levels are from Boka Optoelectronics (10100576768715), which can emit 12 lasers, four 360-degree horizontal lines, eight 360-degree vertical lines (in this embodiment, 360-degree vertical lines are used), and six crosshairs (up, down, left, and right). The laser wavelength is 532nm, with a horizontal accuracy of ±1 mm (within 5 meters), a vertical accuracy of ±1 mm (within 5 meters), and a line width of ±1 mm (within 7 meters).

[0047] S3. Place the first point laser on one side of the second laser level, with the laser radiation port of the first point laser located at the focal point of the first parabolic mirror. The first point laser is directed toward the center of the first parabolic mirror and aligned with the laser propagation path of the second laser level. Specifically, this includes placing the first point laser on one side of the second laser level, with the first point laser located outside the second laser level (since the height of the second laser level is lower than that of the first parabolic mirror, the body of the second laser level will not block the first point laser). The first point laser is directed toward the first parabolic mirror and aligned with the laser propagation path of the second laser level, thereby achieving vertical incidence of the first point laser onto the center of the working surface of the first parabolic mirror.

[0048] S4. Adjust the first working mirror group using a visible first point laser to ensure the beam of the first point laser is transmitted to the target position. Specifically, this includes adjusting the first working mirror group using a visible first point laser so that the first point laser, after being reflected by the first parabolic mirror and the second parabolic mirror, is incident on the center position of the terahertz detector. In this embodiment, the target position is the center of the terahertz detector, which is located at the focal point of the second parabolic mirror. After being reflected by the first parabolic mirror, the first point laser forms a parallel beam that propagates to the second parabolic mirror. The parallel beam, after being reflected by the second parabolic mirror, converges to the center of the terahertz detector at the focal point.

[0049] S5. Based on the calibrated vertical laser line paths of the first and second laser levels, replace the first point source with the first terahertz source to complete the switching and calibration of the first optical path. Since the first and second laser levels provide a simple and efficient spatial definition for the laser radiation port of the first point source, it is equivalent to establishing a virtual XYZ coordinate system (the X and Y axes are determined by the vertical laser line and the first point laser; since the first parabolic mirror has a certain focal length, and the terahertz source has a certain radiation distance and polarization angle, the forward and backward movement of the Z-axis can be initially determined according to the focal length of the first parabolic mirror, and later adjusted according to the terahertz response of the sample). Switching can be completed simply by placing the terahertz wave radiation port of the first terahertz source at the laser radiation port of the first point source. The terahertz wave radiates outward in a divergent pattern at the terahertz wave radiation port of the first terahertz source. The first parabolic mirror collimates the divergent terahertz wave, forming a parallel beam; subsequently, the second parabolic mirror focuses this parallel beam onto the terahertz detector.

[0050] Example 2

[0051] Unlike Example 1, this example requires calibration of both terahertz optical paths. In this example, step S4 further includes the following steps:

[0052] S4.2. Set up a second working group for propagating the optical path. The second working group includes a beam splitter, a second working mirror, a third laser level, a fourth laser level, and a second point laser. Place the beam splitter between the first parabolic mirror and the second parabolic mirror. The beam of the first point laser is reflected by the first parabolic mirror and then passes through the beam splitter. The beam splitter is a circular transparent quartz plate, which has a diameter of four inches in this embodiment.

[0053] S4.3 Adjust the height and vertical angle of the visible second point laser emitted by the second point laser to ensure the collimation of the second point laser propagation path; align the second point laser with two magnetic beam height scales placed at an interval, the distance between the two magnetic beam height scales being L2, and L2 being equal to the entire optical path propagation distance from the second point laser to the preset target. By adjusting the height and vertical angle of the second point laser, ensure that the height scales it illuminates on the two magnetic beam height scales are consistent, thereby ensuring the collimation of the laser propagation path;

[0054] S4.4. A second working mirror is set on one side of the beam splitter. The second working mirror is a plano-convex lens. The third laser level and the fourth laser level are placed on both sides of the beam splitter and the second working mirror. The third laser level is located on one side of the beam splitter and on the same side as the first laser level. The height of the third laser level is higher than that of the beam splitter. The beam splitter and the second working mirror are at the same height. The fourth laser level is located on one side of the second working mirror and on the same side as the second laser level. The height of the fourth laser level is lower than that of the second working mirror. The 360° vertical laser lines of the third laser level and the fourth laser level are aligned and located at the center of the beam splitter and the second working mirror.

[0055] S4.5 Place the second point laser on the same side as the fourth laser level, and direct the second point laser toward the second working mirror and the beam splitter, aligning it with the laser propagation path of the fourth laser level.

[0056] S4.6 The second point laser and the first point laser illuminate the same position of the beam splitter. After being reflected by the beam splitter, the second point laser coincides with the first point laser. By adjusting the angle of the beam splitter, the first and second point lasers illuminate the same position of the second parabolic mirror. The beam of the second point laser is also reflected by the second parabolic mirror and transmitted to the target position. In this embodiment, the target position is the center of the terahertz detector.

[0057] S5 also includes the following steps:

[0058] S5.2. Based on the vertical laser line paths of the calibrated third and fourth laser levels, replace the second point source with the second terahertz source. Since the third and fourth laser levels provide a simple and efficient spatial definition for the laser radiation port of the second point source, essentially establishing a virtual XYZ coordinate system, simply placing the terahertz wave radiation port of the second terahertz source at the laser radiation port of the second point source is sufficient to complete the switching and calibration of the second optical path. After completing the optical path calibration, replace the beam splitter with a circular, opaque, high-resistivity silicon lens of the same size (the beam splitter is fixed to the mounting base via a circular frame; the circular frame uses an existing optical lens mounting bracket, such as Hengyang Optics MLNR-4A. During replacement, loosen the fixing screws on the circular frame, remove the beam splitter, replace it with the high-resistivity silicon lens, and tighten the fixing screws to complete the replacement). The high-resistivity silicon lens can increase the transmission of terahertz waves (first terahertz source), reduce the attenuation during transmission, and reflect terahertz waves (second terahertz source). The terahertz waves radiate outward in a divergent manner at the terahertz wave radiation port of the second terahertz source. The plano-convex lens collimates the divergent terahertz waves emitted by the second terahertz source to form a parallel beam. After being reflected by the high-resistivity silicon lens, the parallel beam is then focused onto the terahertz detector by the second parabolic mirror.

[0059] In this embodiment, the second point laser is a different color from the first point laser. The first point laser is red and the second point laser is green. This can simulate different terahertz signals. The second working group can set up multiple sets to calibrate multiple optical paths and can complete multi-channel calibration simultaneously.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A terahertz optical path calibration method based on visible light simulation, characterized in that, Includes the following steps: S1. Adjust the height and vertical angle of the first visible point laser emitted by the first point laser device to ensure the collimation of the propagation path of the first point laser. S2. Set up a first working mirror group for propagating the optical path. The first working mirror group includes a first parabolic mirror and a second parabolic mirror arranged opposite each other. Place the first laser level and the second laser level on both sides of the first parabolic mirror so that the vertical laser lines of the first laser level and the second laser level are aligned and located at the center of the first parabolic mirror. S3. Place the first point laser instrument on the side where the second laser level is located, and direct the first point laser toward the center of the first parabolic mirror and align it with the propagation path of the laser line of the second laser level. S4. Adjust the first working lens group using a visible first point laser to ensure that the beam of the first point laser is transmitted to the target position; S5. Based on the vertical laser line paths of the first and second laser levels that have been calibrated, replace the first point source instrument with the first terahertz source to complete the switching and calibration of the first optical path.

2. The terahertz optical path calibration method based on visible light simulation according to claim 1, characterized in that, S1 specifically includes: aligning the first point laser with two magnetic beam height scales placed at an interval, and adjusting the height and vertical angle of the first point laser to make the height scales it illuminates on the two magnetic beam height scales consistent, thereby ensuring the collimation of the propagation path of the first point laser.

3. The terahertz optical path calibration method based on visible light simulation according to claim 2, characterized in that, S2 specifically includes: placing a first laser level on the side where the back of the first parabolic mirror is located, with the height of the first laser level being higher than that of the first parabolic mirror; placing a second laser level on the side where the working surface of the first parabolic mirror is located, with the height of the second laser level being lower than that of the first parabolic mirror; and making the vertical laser lines of the first laser level and the second laser level coincide and located at the center of the first parabolic mirror.

4. The terahertz optical path calibration method based on visible light simulation according to claim 2, characterized in that, S3 specifically includes: placing the first point laser instrument on the side where the second laser level is located, the first point laser is directed toward the first parabolic mirror and aligned with the laser propagation path of the second laser level, so as to achieve the first point laser being perpendicularly incident on the center of the first parabolic mirror.

5. The terahertz optical path calibration method based on visible light simulation according to claim 1, characterized in that, S4 specifically includes: adjusting the first working mirror group with the aid of a visible first point laser, so that the first point laser is reflected by the first parabolic mirror and the second parabolic mirror and then incident on the center position of the terahertz detector.

6. The terahertz optical path calibration method based on visible light simulation according to claim 1, characterized in that, The distance between the two magnetic beam height scales is L.

7. The terahertz optical path calibration method based on visible light simulation according to claim 1, characterized in that, When calibration is required for two or more terahertz optical paths, the following steps are also included: S4.

2. Set up a second working group for propagating the optical path. The second working group includes a beam splitter, a second working mirror, a third laser level, a fourth laser level, and a second point laser. Place the beam splitter between the first parabolic mirror and the second parabolic mirror. The beam of the first point laser passes through the beam splitter after being reflected by the first parabolic mirror. S4.3 Adjust the height and vertical angle of the visible second point laser emitted by the second point laser device to ensure the collimation of the propagation path of the second point laser; S4.

4. Set a second working mirror on one side of the beam splitter, and place the third laser level and the fourth laser level on both sides of the beam splitter and the second working mirror, so that the vertical laser lines of the third laser level and the fourth laser level are aligned and located at the center of the beam splitter and the second working mirror. S4.5 Place the second point laser on the same side as the fourth laser level, and direct the second point laser toward the second working mirror and the beam splitter, aligning it with the laser propagation path of the fourth laser level. S4.6 The second point laser beam coincides with the first point laser beam after being reflected by the beam splitter. The beam of the second point laser beam is also transmitted to the target position after being reflected by the second parabolic mirror.

8. The terahertz optical path calibration method based on visible light simulation according to claim 7, characterized in that, S5 further includes the following steps: S5.2 Based on the vertical laser line paths of the calibrated third and fourth laser levels, replace the second point source instrument with the second terahertz source to complete the switching and calibration of the second optical path.

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