A multi-reflective surface fast rotating optical delay device

Abstract

This invention discloses a multi-reflective surface fast rotating optical delay device. It comprises a circular multi-period array mirror structure formed by equidistantly arranged individual mirrors along a circumferential direction, with each period corresponding to one individual mirror. A light beam is incident from a position perpendicular to the plane of a fixed disk, and undergoes multiple reflections sequentially through an optical fiber collimator, a circular multi-period array mirror, a right-angle prism, another circular multi-period array mirror, a plane mirror, another circular multi-period array mirror, a right-angle prism, and another circular multi-period array mirror, finally returning to the optical fiber collimator. The circular multi-period array mirror can provide a high scanning frequency. By employing multiple rings of circular multi-period array mirrors with different numbers of periods from the inside out, different time delays are generated by utilizing different incident positions of the light, satisfying various delay requirements. By using right-angle prisms and plane mirrors to construct the structured optical path, the device achieves a high delay time even at high scanning frequencies.

Description

Technical Field

[0001] This invention belongs to the field of terahertz spectroscopy measurement and relates to an optical delay device, specifically a multi-reflective surface rapidly rotating optical delay device. Background Technology

[0002] With the development of terahertz technology, terahertz spectroscopy and imaging have shown great application potential in many fields such as biology, medical disease diagnosis, materials science, military, and basic chemical research. Optical delay line devices are devices that achieve precise and controllable relative time delays between coherent light pulses through optical means, and are key components for rapid spectral measurement and imaging in terahertz time-domain spectrometers.

[0003] The most commonly used optical delay line is an optical back-facing mirror controlled by a linear displacement platform. Linear displacement platforms are the most prevalent method due to their simplicity, ease of use, unlimited scan length, and relatively low cost. To ensure high displacement accuracy and stability, the speed of the displacement stage is often low, resulting in a long single scan time, typically several minutes or more. Rotating optical delay devices usually consist of multiple mirrors fixed to a rotating body. Optical delay is generated by changing the optical path length of light through changes in the angle of the rotating body. One high-speed, high-stability optical delay line device uses the involute principle, achieving optical delay by rotating mirrors to reflect light at different positions on the involute reflective surface. Its delay time can reach 167.45 ps at a scan frequency of 100 Hz. Another multi-faceted rotating optical delay device uses a 24-reflective-surface design, generating 24 delay periods with one rotation, achieving a delay time of 72 ps while maintaining over 99% linearity. In summary, rotating optical delay devices have a higher scan frequency than linear optical delay devices, but due to the structural limitations of rotating optical delay devices, the delay time decreases rapidly as the scan frequency increases. Summary of the Invention

[0004] To meet the demand for increased delay time in rotating optical delay devices at high scanning frequencies, this invention provides a multi-reflective surface fast rotating optical delay device. The rotating body of this device is a circular multi-period array of mirrors, which consists of multiple identical mirror units arranged equidistantly in a circular direction to form a multi-period structure, with each period corresponding to one mirror unit. The circular multi-period array of mirrors can provide a high scanning frequency. By using multiple circular multi-period arrays of mirrors with different numbers of periods from the inside out, different time delays can be generated by using light incident at different positions to meet various delay requirements. By using right-angle prisms and plane mirrors to build the structured optical path, the device can achieve a high delay time at high scanning frequencies.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A multi-reflection surface fast rotating optical delay device includes an optical fiber collimator, a right-angle prism, a plane mirror, a motor, a rotating disk, and at least two sets of circular multi-period array mirrors. The at least two sets of circular multi-period array mirrors are concentrically arranged on the rotating disk, which is driven to rotate by the motor. The optical fiber collimator is mounted above the circular multi-period array mirrors, and the plane mirror is mounted below the optical fiber collimator. Each circular multi-period array mirror is composed of multiple mirror units, which are evenly arranged on the rotating disk along the circumference. The reflecting surfaces of the mirror units are inclined relative to the plane of the rotating disk, and the reflecting surfaces of all mirror units in the same set of circular multi-period array mirrors are parallel to each other. A light beam is incident from a position perpendicular to the plane of the fixed disk, and passes through the optical fiber collimator, the circular multi-period array mirror, the right-angle prism, the circular multi-period array mirror, the plane mirror, the circular multi-period array mirror, the right-angle prism, and the circular multi-period array mirror multiple times before finally returning to the optical fiber collimator.

[0007] Furthermore, the reflector unit has a prism structure, which includes a reflective surface and a backlight surface, and the reflective surface is inclined relative to the plane of the rotating disk.

[0008] Furthermore, the angle between the reflective surface of the single reflector and the horizontal direction is 23°, and the angle between the back surface of the reflective surface of the single reflector and the horizontal direction is 44°.

[0009] Furthermore, the horizontal position of the fiber collimator is adjusted by an adjustment device so that it is located directly above a set of circular multi-period array reflectors, and ensures that the light beam is perpendicularly incident on the circular multi-period array reflectors through the fiber collimator.

[0010] Furthermore, the delay distance ΔL generated by the circular multi-period array reflector within a single period is:

[0011]

[0012] In the formula, α is the angle between the reflecting surface of the individual mirror and the horizontal direction; ω is the angular velocity of the motor; and R is the working radius of the circular multi-period array mirror.

[0013] At this time, the delay time Δt of the multi-reflective surface fast rotating optical delay device is:

[0014]

[0015] Where c is the speed of light.

[0016] Furthermore, when the circular multi-period array reflector completes a full single cycle, the resulting delay distance ΔL is:

[0017] ΔL=8Rtanαsinδ

[0018] In the formula, n is the number of periods of the circular multi-period array mirror; α is the angle between the reflecting surface of a single mirror and the horizontal direction; R is the working radius of the circular multi-period array mirror.

[0019] The scanning frequency f of the multi-reflective surface fast rotating optical delay device is:

[0020]

[0021] In the formula, ω is the angular velocity of the motor.

[0022] The present invention has the following beneficial effects:

[0023] This invention provides a multi-reflective surface fast rotating optical delay device. Compared with existing technologies, it uses a circular multi-period array of reflectors as the rotating body and employs a multi-period design. While ensuring a high delay time, the optical path of the light beam undergoes multiple periodic changes during one rotation of the motor, improving the waveform reproducibility. By using light rays incident perpendicular to the plane of the rotating disk, the working angle range of a single cycle is increased, thereby improving the delay time. The design of multiple circular multi-period array reflectors with different numbers of cycles arranged from the inside out provides a variable delay time, enabling a single device to meet the delay time requirements of different application scenarios. By constructing a structured optical path using right-angle prisms and plane reflectors, the number of reflections is increased by deflecting the optical path, thereby increasing the optical path change during light transmission and further increasing the delay time. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a multi-reflective surface fast-rotating optical delay device according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the reflected light path of a single reflector unit in an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the circular multi-period array reflector described in an embodiment of the present invention;

[0028] Figure 4This is a schematic diagram of the working parameters of the circular multi-period array reflector described in an embodiment of the present invention;

[0029] In the picture:

[0030] 1-Fiber optic collimator; 2-Right-angle prism; 3-Circular 36-period array reflector; 4-Plane reflector; 5-Motor; 6-Circular 24-period array reflector; 7-Rotating disk; 31-Reflector unit; 311-Reflecting surface; 312-Backlight surface. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0032] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] like Figures 1 to 4 As shown, this embodiment is a multi-reflection surface fast rotating optical delay device, including an optical fiber collimator 1, a right-angle prism 2, a plane mirror 4, a motor 5, a rotating disk 7, and at least two sets of circular multi-period array mirrors; the at least two sets of circular multi-period array mirrors are concentrically arranged on the rotating disk 7, which is driven to rotate by the motor 5; the optical fiber collimator 1 is installed above the circular multi-period array mirrors, and the plane mirror 4 is installed below the optical fiber collimator 1; the circular multi-period array mirror is composed of multiple mirror units, and the multiple mirrors... The individual mirrors are evenly arranged on the rotating disk 7 along the circumference. The reflecting surfaces of the individual mirrors are inclined relative to the plane of the rotating disk 7, and the reflecting surfaces of all the individual mirrors in the same group of circular multi-period array mirrors are parallel to each other. The light beam is incident from a position perpendicular to the plane where the fixed disk is located, and passes through the fiber collimator 1, the circular multi-period array mirror, the right-angle prism 2, the circular multi-period array mirror, the plane mirror 4, the circular multi-period array mirror, the right-angle prism 2, and the circular multi-period array mirror multiple times in sequence, and finally returns to the fiber collimator 1.

[0034] In this embodiment, as Figure 3As shown, the rotating disk 7 is provided with two sets of circular multi-period array reflectors, namely a circular 36-period array reflector 3 and a circular 24-period array reflector 6. The circular 36-period array reflector 3 and the circular 24-period array reflector 6 are arranged concentrically, with the circular 36-period array reflector 3 located on the outer ring and the circular 24-period array reflector 6 located on the inner ring.

[0035] In this embodiment, the circular 36-period array reflector 3 is composed of 36 reflector units 31 evenly distributed along the circumference.

[0036] In this embodiment, the reflector unit 31 is a prism structure, which includes a reflective surface 311 and a backlight surface 312, and the reflective surface 311 is inclined relative to the plane of the rotating disk 7.

[0037] In this embodiment, the circular 24-period array reflector 6 is composed of 24 reflector units 31 evenly distributed along the circumference.

[0038] In this embodiment, as Figure 4 As shown, taking a circular 36-period array reflector 3 as an example, the delay distance ΔL generated by the circular 36-period array reflector 3 within a single period is given by the following formula:

[0039]

[0040] In equation (1), α is the angle between the reflecting surface 311 of the reflector unit 31 and the horizontal direction; ω is the angular velocity of the motor; R is the working position radius of the circular 36-period array reflector, that is, the radial distance between the central axis of the circular 36-period array reflector and the center of the rotating disk.

[0041] At this time, the delay time Δt of the multi-reflective surface rapidly rotating optical delay device is:

[0042]

[0043] Where c is the speed of light.

[0044] When the motor drives the circular 36-period array reflector 3 to complete a full single cycle, the delay distance ΔL generated by the circular 36-period array reflector 3 is:

[0045] ΔL=8Rtanαsinδ (3)

[0046] in, n is the number of periods in the circular multi-period array mirror; in this example, the number of periods is 36.

[0047] The scanning frequency of this multi-reflective surface rapidly rotating optical delay device is:

[0048]

[0049] As can be seen from formula (1), the delay time is positively correlated with the working position radius R of the fiber collimator 1 on the circular 36-period array reflector 3. Therefore, the working position radius R can be changed by adjusting the position of the fiber collimator 1, thereby changing the delay time.

[0050] As shown in formula (3), when the working position radius R is constant, as the number of periods n decreases, the circumferential length of a single period increases, and the delay distance also increases. Therefore, the delay time of a single period is negatively correlated with the number of periods n. That is, the delay time provided by this circular multi-period array reflector is determined by the number of periods n. With a fixed working position radius, the delay time can be further increased by reducing the number of periods n. Furthermore, since the delay time is mainly determined by the circumferential length, while the radial length is to ensure that light can pass smoothly through the right-angle prism during rotation, the radial length can be compressed and the number of reflector rings increased while ensuring smooth light passage, thus providing a wider range of different delay time options.

[0051] As can be seen from formula (4), the scanning frequency of the device is positively correlated with the number of cycles n and the motor speed ω. When the motor speed is constant, a higher number of cycles determines a higher scanning frequency. Taking a standard motor of 3000rpm as an example, driving the circular 36-cycle array reflector 3 to rotate, the scanning frequency is as high as 1800Hz, which is significantly improved compared with the existing rotation delay device.

[0052] In this embodiment, taking a circular 36-cycle array reflector 3 as an example, the working surface of a single cycle is a longer inclined reflector on the right side. The angle between this reflector surface and the horizontal direction has a non-linear relationship with the single-cycle delay time. If this angle is too small or too large, it will lead to a decrease in the delay time. Through testing, this invention uses a 23° angle between the reflector surface of a single reflector and the horizontal direction. At this angle, the working angle range and delay time provided by a single cycle achieve the best balance. Furthermore, if the angle between the other inclined surface (backlight surface) of the same cycle and the horizontal direction is too large, it will cause the reflected light from the adjacent working reflector surface to be blocked. If the angle is too small, it will cause the circumferential dimension of the working reflector surface of that cycle to decrease. Testing showed that this angle is 44°. At this angle, the circumferential dimension of the working reflector surface of the same cycle can be maximized without blocking light.

[0053] In this embodiment, the horizontal position of the fiber collimator 1 is adjusted by the adjustment device so that it is positioned directly above a certain set of circular multi-period array reflectors as required, and the beam mirror fiber collimator 1 is incident on the circular multi-period array reflectors perpendicular to the direction of the rotating disk.

[0054] The working principle of this embodiment is as follows:

[0055] The fiber collimator 1 collimates the diverging beam emitted from the fiber end face into parallel light, which is then incident on a set of circular multi-period array mirrors in a direction perpendicular to the plane of the rotating disk. Driven by the motor 5, the circular multi-period array mirrors rotate, causing the optical path of the incident light to change periodically multiple times. When the multi-reflector rapidly rotating optical delay device moves from its original position to the next angle, the optical path of the two light transmissions will change because the reflective surface of the reflector unit is placed at an angle. Within one cycle, after the beam is reflected by the circular multi-period array mirrors, the beam enters the right-angle prism 2. After the right-angle prism 2 changes the light path, it is incident on the circular multi-period array mirrors again, and then reflected by the circular multi-period array mirrors to the plane mirror 4. Finally, through the plane mirror, the beam returns to the fiber collimator. The fiber collimator couples the delayed spatial beam into the fiber. The change in optical path causes the change in the transmission time of the light during transmission, which is the generation of the delay time. The right-angle prism 2 and the plane mirror 4 cause the light rays from the circular multi-period array mirror to bend and reflect again, increasing the number of reflections of the light rays in the circular multi-period array mirror. When the optical delay device rotates to a certain angle, the optical path changes multiple times because the light rays pass through the circular multi-period array mirror multiple times. The total difference in optical path changes many times compared to a single reflection, thereby increasing the delay time of the multi-reflection surface rapidly rotating optical delay device.

[0056] Taking the incident light beam onto a circular 36-period array reflector 3 as an example, the beam sequentially passes through fiber collimator 1 - circular 36-period array reflector 3 - right-angle prism 2 - circular 36-period array reflector 3 - plane reflector 4 - circular 36-period array reflector 3 - right-angle prism 2 - circular 36-period array reflector 3 - fiber collimator 1. Specifically, fiber collimator 1 collimates the diverging beam emitted from the fiber end face into parallel light, which is then incident on the reflecting surface of circular 36-period array reflector 3. After being reflected by circular 36-period array reflector 3, the beam enters right-angle prism 2, which then bends the beam before it is incident on circular 36-period array reflector 3. After being reflected by circular 36-period array reflector 3, the beam is incident on plane reflector 4, and finally returns along the original path to fiber collimator 1. Fiber collimator 1 then couples the delayed spatial beam into the fiber. The circular 36-period array reflector 3 is placed in a horizontal position and is driven by the shaft of motor 5 to rotate at a constant speed. The incident light is incident through the fiber collimator 1 from the plane where the fixed disk is located, so that the angle between the incident light and the reflecting surface remains unchanged. The influence of the shaft rotation on the working angle range is significantly reduced. Compared with the traditional rotating optical delay device, the light is incident parallel to the fixed disk, which increases the working angle range and increases the delay time of a single period.

[0057] In this embodiment, a 3000rpm standard motor is used, and the scanning frequency of the multi-reflective surface fast rotating optical delay device can reach 1800Hz (outer ring) and 1200Hz (inner ring). Compared with other rotating optical delay devices, this embodiment increases the number of light reflections by combining a right-angle prism 2 and a plane mirror 4. Even with multiple cycles, the multi-reflective surface fast rotating optical delay device can still achieve a high delay time. Taking a circular 36-cycle array mirror with a working radius of 105mm as an example, the delay time can reach more than 100ps. Based on the multiple cycles, the delay time is significantly improved compared with various existing multi-cycle rotating optical delay devices.

[0058] As an extension, if it is necessary to increase the scanning frequency and obtain a higher delay time of the multi-reflective surface fast rotating optical delay device, the number of reflecting surfaces can be increased, and the circumferential dimension and working radius of the mirrors can be increased in the circular multi-period array mirror structure to increase the scanning frequency and delay time of the multi-reflective surface fast rotating optical delay device. If more different delay time options are needed, while ensuring that the radial dimension of the mirror is sufficient to reflect light completely through the right-angle prism, the radial dimension of each revolution can be reduced, and multiple circular multi-period array mirrors with different number of cycles can be added to meet various delay time requirements.

[0059] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A multi-reflective surface rapidly rotating optical delay device, characterized in that, The system includes an optical fiber collimator, a right-angle prism, a plane mirror, a motor, a rotating disk, and at least two sets of circular multi-period array mirrors. The at least two sets of circular multi-period array mirrors are concentrically arranged on the rotating disk, which is driven to rotate by the motor. The optical fiber collimator is mounted above the circular multi-period array mirrors, and the plane mirror is mounted below the optical fiber collimator. Each circular multi-period array mirror is composed of multiple mirror units, which are evenly arranged circumferentially on the rotating disk. The reflecting surfaces of each mirror unit are inclined relative to the plane of the rotating disk, and the reflecting surfaces of all mirror units in the same set are parallel to each other. The light beam is incident from a position perpendicular to the plane of the fixed disk, and passes through the optical fiber collimator, the circular multi-period array mirror, the right-angle prism, the circular multi-period array mirror, the plane mirror, the circular multi-period array mirror, the right-angle prism, and the circular multi-period array mirror multiple times before finally returning to the optical fiber collimator. In the above optical path, the circular multi-period array mirrors through which the light beam passes are mirrors within the same set of circular multi-period arrays.

2. The multi-reflective surface fast rotating optical delay device as described in claim 1, characterized in that, The reflector unit has a prism structure, which includes a reflective surface and a backlight surface, and the reflective surface is inclined relative to the plane of the rotating disk.

3. The multi-reflective surface fast-rotating optical delay device as described in claim 2, characterized in that, The angle between the reflective surface of the single reflector and the horizontal direction is 23°, and the angle between the back surface of the reflective surface of the single reflector and the horizontal direction is 44°.

4. The multi-reflective surface fast rotating optical delay device as described in claim 1, characterized in that, The horizontal position of the fiber collimator is adjusted by an adjustment device so that it is directly above a set of circular multi-period array reflectors, and the beam is perpendicularly incident on the circular multi-period array reflectors through the fiber collimator.

5. The multi-reflective surface fast rotating optical delay device as described in claim 1, characterized in that, The delay distance ΔL generated by the circular multi-period array reflector within a single period is: In the formula, α is the angle between the reflecting surface of the individual mirror and the horizontal direction; ω is the angular velocity of the motor; and R is the working radius of the circular multi-period array mirror. At this time, the delay time Δt of the multi-reflective surface fast rotating optical delay device is: Where c is the speed of light.

6. The multi-reflective surface fast-rotating optical delay device as described in claim 5, characterized in that, When the circular multi-period array reflector completes a full single cycle, the resulting delay distance ΔL is: ΔL=8Rtanαsinδ In the formula, n is the number of periods of the circular multi-period array mirror; α is the angle between the reflecting surface of a single mirror and the horizontal direction; R is the working radius of the circular multi-period array mirror. The scanning frequency f of the multi-reflective surface fast rotating optical delay device is: In the formula, ω is the angular velocity of the motor.

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