Multi-reflecting-surface rapid rotation optical delay device

Abstract

The invention discloses a multi-reflecting-surface rapid rotation optical delay device, which is characterized in that a plurality of reflecting mirror monomers are arranged at equal intervals in the circumferential direction to form a circular multi-period array reflecting mirror structure, and each period corresponds to one reflecting mirror monomer; a light beam enters from the position perpendicular to the plane where the fixed disc is located, sequentially passes through the optical fiber collimator, the circular multi-period array reflector, the right-angle prism, the circular multi-period array reflector, the plane reflector, the circular multi-period array reflector, the right-angle prism and the circular multi-period array reflector to be reflected for multiple times, and finally returns to the optical fiber collimator. The circular multi-cycle array reflecting mirror can provide high scanning frequency, and the circular multi-cycle array reflecting mirror with multiple circles of different cycle numbers from inside to outside is adopted, so that different time delays are generated by utilizing different incident positions of light rays, and various delay requirements are met; the right-angle prism and the plane mirror are used for building a structured light path, so that the device has relatively high delay time under the condition of high scanning frequency.

Description

Technical Field

[0001] The invention belongs to the field of terahertz spectrum measurement and relates to an optical delay device, in particular to a multi-reflection surface fast-rotating optical delay device. Background Art

[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, material science, military and basic chemical research. The optical delay line device is a device that achieves precise and controllable relative time delay between coherent light pulses through optical means. It is a key component of terahertz time-domain spectrometer to achieve rapid spectrum measurement and imaging.

[0003] The commonly used optical delay line is an optical back reflector controlled by a linear displacement platform. The linear displacement platform is the most commonly used method at present because it is simple and easy to use, has no limit on the scanning length, and has a relatively low cost. In order to ensure high displacement accuracy and stability, the speed of the displacement stage is often low. Therefore, the single scanning time is long, usually reaching more than several minutes. The rotating optical delay device is usually fixed on a rotating body by a multi-faceted reflector. The change in the angle of the rotating body causes the change in the optical path of the light to produce optical delay. Among them, a high-speed and high-stability optical delay line device adopts the involute principle. The reflector rotates to make the light reflect at different positions on the involute reflection surface to achieve the optical delay effect. Its delay time can reach 167.45ps, and the scanning frequency is 100Hz; a multi-faceted rotating optical delay device adopts a 24-reflection surface design, and one rotation produces 24 delay cycles. The delay time can reach 72ps, while maintaining a linearity of more than 99%. In summary, it can be seen that the scanning frequency of the rotating optical delay device is higher than that of the linear optical delay device, but due to the constraints of the structure of the rotating optical delay device, the delay time will decrease rapidly when the scanning frequency increases. Summary of the invention

[0004] In order to meet the demand for increasing the delay time of a rotating optical delay device under a high scanning frequency, the present invention provides a multi-reflecting surface fast rotating optical delay device, wherein the rotating body of the device is a circular multi-period array reflector, that is, a multi-period structure is formed by equidistantly arranging a plurality of identical reflector monomers in a circumferential direction, and each period corresponds to a reflector monomer; the circular multi-period array reflector can provide a higher scanning frequency, and a circular multi-period array reflector with multiple circles of different period numbers from the inside to the outside is adopted, so that different time delays can be generated by utilizing light incident at different positions, thereby meeting a variety of delay requirements; by using a right-angle prism and a plane reflector to build a structured light path, the device has a higher delay time under a high scanning frequency.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A multi-reflection surface fast rotating optical delay device comprises a fiber collimator, a right angle prism, a plane reflector, a motor, a rotating disk and at least two groups of circular multi-period array reflectors; the at least two groups of circular multi-period array reflectors are concentrically arranged on the rotating disk, the rotating disk is driven to rotate by the motor, the fiber collimator is installed above the circular multi-period array reflector, and the plane reflector is installed below the fiber collimator; the circular multi-period array reflector is composed of a plurality of reflector monomers, the plurality of reflector monomers are evenly arranged on the rotating disk along the circumferential direction, the reflective surfaces of the reflector monomers are inclined relative to the plane of the rotating disk, and the reflective surfaces of all reflector monomers of the same group of circular multi-period array reflectors are parallel to each other; a light beam is incident at a position perpendicular to the plane where the fixed disk is located, and is reflected multiple times by the fiber collimator, the circular multi-period array reflector, the right angle prism, the circular multi-period array reflector, the plane reflector, the circular multi-period array reflector, the right angle prism, and the circular multi-period array reflector in sequence, and finally returns to the fiber collimator.

[0007] Furthermore, the reflector monomer is 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 reflector monomer and the horizontal direction is 23°, and the angle between the backlight surface of the reflective surface of the reflector monomer and the horizontal direction is 44°.

[0009] Furthermore, the horizontal position of the fiber collimator is adjusted by an adjusting device so that it is located directly above a group of circular multi-period array reflectors, and ensures that the light beam is vertically incident on the circular multi-period array reflector 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] Where, α is the angle between the reflective surface of the reflector and the horizontal direction; ω is the angular velocity of the motor; R is the working position radius of the circular multi-period array reflector;

[0013] At this time, the delay time Δt of the multi-reflection 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 rotates through a complete single period, the delay distance ΔL generated is:

[0017] ΔL=8Rtanαsinδ

[0018] In the formula, n is the period number of the circular multi-period array reflector; α is the angle between the reflective surface of the reflector monomer and the horizontal direction; R is the working position radius of the circular multi-period array reflector;

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

[0020]

[0021] Where ω is the angular velocity of the motor.

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

[0023] The present invention provides a multi-reflection surface fast-rotating optical delay device. Compared with the prior art, a circular multi-period array reflector is used as a rotating body, and a multi-period design is adopted. On the basis of ensuring a relatively high delay time, when a motor rotates one circle, the optical path of a light beam undergoes multiple periodic changes, thereby improving the waveform repetition rate; the light is incident in a manner perpendicular to the plane where a rotating disk is located, thereby improving the working angle range of a single cycle, thereby improving the delay time; a design of arranging multiple circles of circular multi-period array reflectors with different numbers of periods from the inside to the outside is adopted, thereby providing a variable delay time, and enabling one device to meet the delay time requirements in different application scenarios; a right-angle prism and a plane reflector are used to build a structural light path, and the number of reflections is increased by turning the light path, thereby increasing the change in the optical path of the light during transmission, thereby increasing the delay time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments 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. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without paying any creative work.

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

[0026] Figure 2 Schematic diagram of the reflection light path of the reflector monomer in the embodiment of the present invention;

[0027] Figure 3 Schematic diagram of a circular multi-period array reflector according to an embodiment of the present invention;

[0028] Figure 4Schematic diagram of working parameters of the circular multi-period array reflector in an embodiment of the present invention;

[0029] In the figure:

[0030] 1-fiber 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-reflection surface; 312-backlight surface. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0032] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] like Figures 1 to 4 As shown, this embodiment is a multi-reflection surface fast rotating optical delay device, comprising a fiber collimator 1, a right angle prism 2, a plane reflector 4, a motor 5, a rotating disk 7 and at least two groups of circular multi-period array reflectors; the at least two groups of circular multi-period array reflectors are concentrically arranged on the rotating disk 7, and the rotating disk 7 is driven to rotate by the motor 5, the fiber collimator 1 is installed above the circular multi-period array reflector, and the plane reflector 4 is installed below the fiber collimator 1; the circular multi-period array reflector is composed of a plurality of reflector monomers, and the plurality of reflectors are arranged on the rotating disk 7. The reflector monomers are evenly arranged on the rotating disk 7 along the circumferential direction, and the reflective surfaces of the reflector monomers are inclined relative to the plane of the rotating disk 7, and the reflective surfaces of all the reflector monomers in the same group of circular multi-period array reflectors 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 optic collimator 1, the circular multi-period array reflector, the right-angle prism 2, the circular multi-period array reflector, the plane reflector 4, the circular multi-period array reflector, the right-angle prism 2, and multiple reflections of the circular multi-period array reflector in sequence, and finally returns to the fiber optic collimator 1.

[0034] In this embodiment, Figure 3As shown, two groups of circular multi-period array reflectors are arranged on the rotating disk 7, which are 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, the circular 36-period array reflector 3 is located in the outer circle, and the circular 24-period array reflector 6 is located in the inner circle.

[0035] In this embodiment, the circular 36-period array reflector 3 is composed of 36 reflector monomers 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, Figure 4 As shown, taking the 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 range is given by the following formula:

[0039]

[0040] In formula (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; and 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-reflection surface fast 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 rotate through a complete 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 of the circular multi-period array reflector. In this example, the number of periods is 36.

[0047] The scanning frequency of the multi-reflection surface fast rotating optical delay device is:

[0048]

[0049] It can be seen from formula (1) that 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 size of the working position radius R can be changed by adjusting the position of the fiber collimator 1, thereby changing the size of the delay time.

[0050] It can be seen from formula (3) that when the working position radius R is constant, as the number of cycles n decreases, the circumferential length of a single cycle increases, and the delay distance also increases. It can be seen that the delay time of a single cycle is negatively correlated with the number of cycles n, that is, the delay time that the circular multi-cycle array reflector can provide is determined by the number of cycles n. When the working position radius is constant, the delay time can be further increased by reducing the number of cycles n. In addition, since the delay time is mainly determined by the circumferential length, and the radial length is to ensure that the light can pass smoothly through the right-angle prism during the rotation process, it is possible to compress the radial length and increase the number of reflector circles while ensuring that the light passes smoothly, thereby providing more different delay time options.

[0051] It can be seen from formula (4) that 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 3000rpm standard motor as an example, the circular 36-period array reflector 3 is driven to rotate, and the scanning frequency is as high as 1800Hz, which is significantly improved compared with the existing rotation delay device.

[0052] In this embodiment, taking the circular 36-period array reflector 3 as an example, the single-period working surface is a long inclined reflector on the right side. The angle between the reflector surface and the horizontal direction is nonlinearly related to the single-period delay time. If the angle is too small or too large, the delay time will be reduced. After testing, the present invention uses a single reflector single reflection surface with an angle of 23° with the horizontal direction. At this angle, the working angle range and delay time that can be provided by a single cycle reach the best balance. In addition, if the angle between the inclined surface (backlight surface) on the other side of the same cycle and the horizontal direction is too large, the reflected light of the adjacent working reflection surface will be blocked. If the angle is too small, the circumferential size of the working reflection surface of the cycle will be reduced. After testing, the angle is 44°. At this angle, the circumferential size of the working reflection mirror 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 an adjustment device so that it is located directly above a group of circular multi-period array reflectors as required, and ensures that the beam mirror fiber collimator 1 is incident on the circular multi-period array reflector perpendicular to the direction of the rotating disk.

[0054] The working principle of this embodiment is:

[0055] The optical fiber collimator 1 collimates the divergent light beam emitted from the end face of the optical fiber into parallel light, and then incident on a group of circular multi-period array reflectors in a direction perpendicular to the plane of the rotating disk. Driven by the motor 5, the circular multi-period array reflectors rotate, causing the optical path of the incident light to change periodically multiple times. When the multi-reflection surface rapidly rotates the optical delay device from the original position to the next angle, since the reflection surface of the reflection monomer is tilted, the optical path of the two light transmissions will change. Within one cycle, after the light beam is reflected by the circular multi-period array reflector, the light beam enters the right-angle prism 2, and after the light path is turned by the right-angle prism 2, it is incident on the circular multi-period array reflector again, and is reflected by the circular multi-period array reflector to the plane reflector 4. Finally, through the plane reflector, the light beam returns to the optical fiber collimator, and the optical fiber collimator couples the delayed spatial light beam into the optical fiber. The change in the optical path causes the change in the transmission time of the light during the transmission process, which is the generation of the delay time. The right-angle prism 2 and the plane reflector 4 make the light of the circular multi-period array reflector turn and reflect again, increasing the number of reflections of the light in the circular multi-period array reflector. When the optical delay device is rotated to a lower angle, the optical path changes multiple times because the light passes through the circular multi-period array reflector multiple times. The total difference in the optical path changes multiple times compared to a single reflection, thereby increasing the delay time of the multi-reflection surface fast rotating optical delay device.

[0056] Taking the case where light is incident on the circular 36-period array reflector 3 as an example, the light beam passes through the 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 in sequence. Specifically, the fiber collimator 1 collimates the divergent light beam emitted from the end face of the optical fiber into parallel light, which is incident on the reflection surface of the circular 36-period array reflector 3. After being reflected by the circular 36-period array reflector 3, the light beam enters the right angle prism 2, and then the right angle prism 2 turns the light beam and incidents it on the circular 36-period array reflector 3. After being reflected by the circular 36-period array reflector 3, it is incident on the plane reflector 4, and finally returns to the fiber collimator 1 along the original path, and the fiber collimator 1 couples the delayed spatial light beam into the optical fiber. The circular 36-period array reflector 3 is placed in a horizontal position and driven by the shaft of the motor 5 to rotate at a constant speed. The incident light is incident from the plane where the vertical fixed disk is located through the fiber collimator 1, so that the angle between the incident light and the reflecting surface remains unchanged. The influence of the rotation of the shaft 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 the delay time of a single cycle.

[0057] In this embodiment, a 3000rpm standard motor is used, and the scanning frequency of the multi-reflection surface fast rotating optical delay device can reach 1800Hz (outer circle) and 1200Hz (inner circle). Compared with rotating optical delay devices of other structures, this embodiment increases the number of light reflections by combining the right-angle prism 2 and the plane reflector 4. When the multi-reflection surface fast rotating optical delay device has multiple cycles, it can still have a high delay time; taking a circular 36-cycle array reflector with a working radius of 105mm as an example, the delay time can reach more than 100ps. On the basis of having multiple cycles, the delay time has been greatly improved compared with various types of multi-cycle rotating optical delay devices currently available.

[0058] As an extension, if it is necessary to increase the scanning frequency of the multi-reflecting surface rapidly rotating optical delay device and obtain a higher delay time, the number of reflecting surfaces can be increased in the circular multi-period array reflector structure, and the circumferential size and working radius of the reflector can be increased to increase the scanning frequency and delay time of the multi-reflecting surface rapidly rotating optical delay device; if more options of different delay times are required, while ensuring that the radial size of the reflector is sufficient to reflect light completely through the right-angle prism, the radial size of each circle can be reduced, and multiple circles of circular multi-period array reflectors with different numbers of periods can be added to meet a variety of delay time requirements.

[0059] Although 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 the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-reflection surface fast rotating optical delay device, characterized in that: The invention comprises a fiber collimator, a right-angle prism, a plane reflector, a motor, a rotating disk and at least two groups of circular multi-period array reflectors; the at least two groups of circular multi-period array reflectors are concentrically arranged on the rotating disk, the rotating disk is driven to rotate by the motor, the fiber collimator is installed above the circular multi-period array reflector, and the plane reflector is installed below the fiber collimator; the circular multi-period array reflector is composed of a plurality of reflector monomers, the plurality of reflector monomers are evenly arranged on the rotating disk along the circumferential direction, the reflective surfaces of the reflector monomers are inclined relative to the plane of the rotating disk, and the reflective surfaces of all reflector monomers of the same group of circular multi-period array reflectors are parallel to each other; the light beam is incident at a position perpendicular to the plane where the fixed disk is located, and is reflected multiple times by the fiber collimator, the circular multi-period array reflector, the right-angle prism, the circular multi-period array reflector, the plane reflector, the circular multi-period array reflector, the right-angle prism, and the circular multi-period array reflector in sequence, and finally returns to the fiber collimator.

2. A multi-reflection surface fast rotating optical delay device as claimed in claim 1, characterized in that: The reflector monomer is 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. A multi-reflection surface fast rotating optical delay device as claimed in claim 2, characterized in that: The angle between the reflective surface of the reflector monomer and the horizontal direction is 23°, and the angle between the backlight surface of the reflective surface of the reflector monomer and the horizontal direction is 44°.

4. A multi-reflection surface fast rotating optical delay device as claimed in claim 1, characterized in that: The horizontal position of the fiber collimator is adjusted by an adjusting device so that it is located directly above a group of circular multi-period array reflectors, and ensures that the light beam is vertically incident on the circular multi-period array reflector through the fiber collimator.

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

6. A multi-reflection surface fast rotating optical delay device as claimed in claim 5, characterized in that: When the circular multi-period array reflector rotates through a complete single period, the delay distance ΔL generated is: ΔL=8Rtanαsinδ In the formula, n is the period number of the circular multi-period array reflector; α is the angle between the reflective surface of the reflector monomer and the horizontal direction; R is the working position radius of the circular multi-period array reflector; The scanning frequency f of the multi-reflection surface fast rotating optical delay device is: Where ω is the angular velocity of the motor.

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