Optical system for terahertz beam shaping

Abstract

The utility model discloses an optical system for terahertz wave beam shaping, which comprises a light source for emitting terahertz wave beams, and a collimating lens, a first micro lens array, a second micro lens array and an integrating lens which are sequentially arranged along the beam propagation direction of the terahertz wave beams, a plurality of first micro lenses on the first micro lens array are in one-to-one correspondence with a plurality of second micro lenses on the second micro lens array, the corresponding first micro lenses and second micro lenses form a micro lens channel for splitting light beams, and the length of the micro lens channel is equal to the focal length of the first micro lenses; the optical parameters of the first micro lenses are the same as the optical parameters of the corresponding second micro lenses. The optical system for terahertz wave beam shaping can shape terahertz wave beams, so that the terahertz wave beams finally form a flat-topped uniform light field, and the uniformity of the light field is improved.

Description

Technical Field

[0001] The utility model belongs to the field, and in particular relates to an optical system for terahertz beam shaping. Background Art

[0002] The uniformity of the amplitude intensity of the terahertz light source on the surface of the sample under test will affect the accuracy of the test analysis. Therefore, the homogenization and shaping of the terahertz beam is crucial. Due to the mechanism of terahertz generation, the outgoing beam is generally distributed in the form of a Gaussian function in space, the amplitude and phase distribution are uneven, and the beam divergence angle is large. Terahertz beam shaping technology is one of the basic technologies for terahertz wave applications. Its purpose is to shape the divergent terahertz beam into a uniform light field. It plays an important role in the application of terahertz waves, especially in imaging, communication and sensing.

[0003] The existing technology of terahertz beam shaping devices is mainly based on the principle of diffraction beam shaping, that is, using diffraction gratings or optical elements to shape the divergent terahertz beam into a uniform light field. The advantage of this shaping device is that it has a simple structure and is easy to implement. The disadvantage is that the formed beam has uneven brightness or intensity distribution in spatial distribution, which seriously affects the performance of the imaging or communication system, and the required optical elements are large in size, low in optical efficiency, and large in loss.

[0004] The information disclosed in this background technology section is only intended to increase the understanding of the overall background of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to a person skilled in the art. Utility Model Content

[0005] The utility model aims to provide an optical system for terahertz beam shaping, which can shape the terahertz beam so that the terahertz beam eventually forms a flat-top uniform light field, thereby improving the uniformity of the light field.

[0006] In order to achieve the above-mentioned object, a specific embodiment of the utility model provides an optical system for terahertz beam shaping, comprising a light source for emitting a terahertz beam, and a collimating lens, a first microlens array, a second microlens array and an integrating lens sequentially arranged along the beam propagation direction of the terahertz beam;

[0007] The multiple first microlenses on the first microlens array correspond one-to-one to the multiple second microlenses on the second microlens array, and the corresponding first microlenses and second microlenses form a microlens channel for splitting light beams, the length of the microlens channel is equal to the focal length of the first microlens, and the optical parameters of the first microlens are the same as the optical parameters of the corresponding second microlens.

[0008] In one or more embodiments of the present utility model, the first microlens array is a single-sided microlens array, and the first microlens is arranged on a side of the first microlens array facing the collimating lens;

[0009] The second microlens array is a single-sided microlens array, and the second microlens is arranged on a side of the second microlens array facing the integrator lens.

[0010] In one or more embodiments of the present invention, the optical parameters of the first microlens are the same as the optical parameters of the corresponding second microlens, and the optical parameters include aperture, focal length and numerical aperture.

[0011] In one or more embodiments of the present invention, the refractive index of the collimating lens is 1.3-3.7.

[0012] In one or more embodiments of the present invention, the light source includes a terahertz source and a waveguide horn antenna connected to each other.

[0013] In one or more embodiments of the present invention, the refractive index of the integrator lens is 1.3-3.7.

[0014] In one or more embodiments of the present invention, the integrator lens is a convex lens.

[0015] In one or more embodiments of the present invention, the collimating lens is a convex lens; or,

[0016] The collimating lens includes a convex lens and a concave lens.

[0017] In one or more embodiments of the present invention, the collimating lens is a convex lens, one side of the collimating lens is a plane, and the other side of the collimating lens is a spherical surface.

[0018] In one or more embodiments of the present invention, the integrating lens is an integrating lens made of TPX material.

[0019] Compared with the prior art, the optical system for terahertz beam shaping of the utility model has the following beneficial effects:

[0020] (1) Through the combined use of the first microlens array, the second microlens array and the integral lens, the utility model realizes uniform shaping of the terahertz beam and forms a uniform light field. Compared with the traditional technology, this helps to improve the uniformity of the light field after shaping, which has obvious advantages for imaging and communication applications.

[0021] (2) The present invention adopts a relatively simple optical structure of a first microlens array, a second microlens array and an integral lens, which simplifies the design of the system compared to complex structures such as photonic crystals and liquid crystal optical elements. This reduces the complexity of the entire system, and is expected to reduce costs and improve maintainability.

[0022] (3) Through the design and application of the first microlens array and the second microlens array, the utility model improves the collimation of the terahertz wave, making the shaped beam more stable and accurate.

[0023] (4) Through the optical system, the utility model improves the performance stability of the terahertz beam after shaping, so that the system has better stability under different environments and interference conditions. This helps to improve the reliability and applicability of the system.

[0024] (5) Through the optical system, the utility model improves the adaptability of the optical system to different beam shapes, better meets diverse application needs, and enables the utility model to be applied to a wider range of scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the utility model, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 It is a structural schematic diagram of an optical system for terahertz beam shaping in an example of the utility model;

[0027] Figure 2 The structure and principle diagram of the optical system for terahertz beam shaping in an example of the utility model;

[0028] Figure 3 This is an XY cross-sectional distribution diagram of the beam amplitude of the terahertz beam emitted by the light source in Example 1 of the utility model;

[0029] Figure 4 This is a beam amplitude X-section distribution diagram of the terahertz beam emitted by the light source in Example 1 of the utility model;

[0030] Figure 5 This is an XY cross-sectional distribution diagram of the beam amplitude of the terahertz beam after passing through the second microlens array in Example 1 of the utility model;

[0031] Figure 6 This is a beam amplitude X-section distribution diagram of the terahertz beam after passing through the second microlens array in Example 1 of the utility model;

[0032] Figure 7 This is an XY cross-sectional distribution diagram of the beam amplitude of the terahertz beam after passing through the integrating lens in Example 1 of the utility model;

[0033] Figure 8 This is a beam amplitude X-section distribution diagram of the terahertz beam after passing through the integrating lens in Example 1 of the utility model;

[0034] Figure 9a This is the amplitude distribution diagram of the light spot after being processed by the optical system in Example 1 of the utility model;

[0035] Figure 9b This is a cross-sectional diagram of the amplitude distribution of the light spot after being processed by the optical system in Example 1 of the utility model;

[0036] Fig.9c The phase distribution diagram of the light spot after being processed by the optical system in Example 1 of the utility model;

[0037] Figure 9d This is a cross-sectional diagram of the phase distribution of the light spot after being processed by the optical system in Example 1 of the utility model.

[0038] Description of main reference numerals:

[0039] 1. Light source; 11. THz source; 12. Waveguide horn antenna; 2. Collimating lens; 3. First microlens array; 31. First microlens; 4. Second microlens array; 41. Second microlens; 5. Integral lens; 6. Homogenized focal plane. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0041] like Figure 1 and 2 As shown, an optical system for terahertz beam shaping in an example of the utility model includes a light source 1 for emitting a terahertz beam, and a collimating lens 2, a first microlens array 3, a second microlens array 4 and an integrator lens 5 sequentially arranged along the beam propagation direction of the terahertz beam;

[0042] The multiple first microlenses 31 on the first microlens array 3 correspond one-to-one to the multiple second microlenses 41 on the second microlens array 4, and the corresponding first microlenses 31 and second microlenses 41 form a microlens channel for splitting light beams. The length of the microlens channel is equal to the focal length of the first microlens 31, and the optical parameters of the first microlens 31 are the same as the optical parameters of the corresponding second microlens 41.

[0043] It is understandable that when the terahertz beam is used in the detection field, the uniformity of the amplitude intensity of the terahertz beam on the surface of the sample under test will affect the accuracy of the test analysis. Therefore, the homogenization and shaping of the terahertz beam are crucial. Due to the mechanism of terahertz beam generation, the outgoing beam is generally distributed in the form of a Gaussian function in space, the amplitude and phase distribution of the beam are uneven, and the beam divergence angle is large. The utility model adopts the mutual cooperation of the first microlens array 3, the second microlens array 4 and the integral lens 5 to control the redistribution of the spot intensity of the terahertz beam at the focal plane to improve the beam uniformity.

[0044] The optical system of the present invention is mainly composed of two parts: a first microlens array 3 and a second microlens array 4 for dividing the incident light beam into a large number of fine light beams, and an integrator lens 5 for superimposing each sub-beam on the target surface. The principle is as follows: Figure 2 shown.

[0045] The first microlens 31 on the first microlens array 3 and the second microlens 41 at the corresponding position in the second microlens array 4 form a channel, and each channel becomes an important unit element for splitting the light beam. In each channel, the optical parameters of the first microlens 31 and the second microlens 41 are exactly the same, and the length of the channel is exactly equal to the focal length of the first microlens 31 and the second microlens 41. The first microlens array 3 splits the incident light into a series of sub-beams, each of which corresponds to the sub-lens aperture in the microlens array. These sub-beams are focused on the corresponding aperture of the second microlens 41 through the first microlens 31 and incident on the aperture of the integrator lens 5 after passing through the second microlens 41, thereby completing the transmission in their respective channels. Specifically, the first microlens array 3 is a single-sided microlens array, and the first microlens 31 is arranged on the side of the first microlens array 3 facing the collimating lens 2; the second microlens array 4 is a single-sided microlens array, and the second microlens 41 is arranged on the side of the second microlens array 4 facing the integrator lens 5.

[0046] Specifically, the optical parameters of the first microlens 31 are the same as the optical parameters of the corresponding second microlens 41 , where the optical parameters include aperture, focal length and numerical aperture.

[0047] Specifically, the refractive index of the collimating lens 2 is 1.3 to 3.7.

[0048] Specifically, the light source 1 includes a connected terahertz source 11 and a waveguide horn antenna 12. The waveguide horn antenna 12 is located on the optical path of the terahertz beam emitted by the terahertz source 11, and is used to make the terahertz beam have Gaussian characteristics, that is, a terahertz beam with Gaussian characteristics. The terahertz source 11 and the waveguide horn antenna 12 are both devices or components that can be directly purchased on the market.

[0049] The waveguide horn antenna 12 is an aperture antenna, which mainly realizes impedance matching between the waveguide port and the free space through reflection of the metal inner wall morphology. The gain and directivity required for a given application are obtained by designing the aperture and axial length of the waveguide horn antenna 12. The waveguide horn antenna 12 can be a pyramid (rectangular) horn, a conical horn, a fan-shaped horn, a horn lens, a corrugated feed horn, a probe or an omnidirectional horn. Its Gaussian characteristics are mainly affected by the phase of the propagation optical path.

[0050] Specifically, the refractive index of the integrator lens 5 is 1.3 to 3.7.

[0051] Specifically, the integrator lens 5 is a convex lens.

[0052] Specifically, the collimating lens 2 is a convex lens; or, the collimating lens 2 is a combination of a convex lens and a concave lens. Preferably, the collimating lens 2 is a convex lens, which simplifies the structure.

[0053] The utility model discloses a method for using an optical system for terahertz beam shaping, comprising the following steps:

[0054] The divergent terahertz beam emitted by the light source 1 is collimated by the collimating lens 2 to obtain a parallel terahertz beam;

[0055] Make the parallel terahertz beam pass through the first microlens array 3 and the second microlens array 4 in sequence;

[0056] The terahertz beam passing through the second microlens array 4 is focused to a focal plane using an integrator lens 5 to obtain collimated light with a flat-top uniform light field.

[0057] like Figure 2 As shown, the terahertz beam after the integrating lens 5 is irradiated onto the homogenized focal plane 6 to form a light spot (ie, a light spot of collimated light).

[0058] Figure 2 In the calculation formula of the collimated light spot size H, the formula is:

[0059]

[0060] Wherein, H is the width or height of the light spot, p is the aperture of the first microlens 31 and the second microlens 41, f is the focal length of the first microlens 31 and the second microlens 41, NA is the numerical aperture of the first microlens 31 and the second microlens 41, R NA is the numerical aperture of the first microlens array 3 and the second microlens array 4. The numerical aperture is a dimensionless value used to describe the light collection ability or resolution of an optical system. It is defined as R NA =nsin(θ), where n is the refractive index of the medium, θ is the field angle of the sub-lens (i.e., the first microlens and the second microlens), and F is the focal length of the integrating lens.

[0061] It can be seen from the formula that the spot size H is independent of the distance d between the second microlens array 4 and the integrator lens 5. The spot at the target surface is equivalent to the spot obtained by magnifying the aperture P of the first microlens 31 in the first microlens array 3 by F / f times. At the same time, the spot shape is consistent with the aperture of the first microlens 31. Therefore, the beam homogenization system based on the first microlens array 3 and the second microlens array 4 can realize a variety of centrally symmetrical spots.

[0062] The optical system for terahertz beam shaping of the present invention is described in detail below in conjunction with specific embodiments.

[0063] Example 1

[0064] An optical system for terahertz beam shaping is built. The designed terahertz shaping spot size is 20×20 mm. A Gaussian beam with a full divergence angle of 17° is emitted from the terahertz source through a waveguide horn antenna. The amplitude distribution of the output beam is as follows: Figure 3 and 4 As shown; after passing through the collimating lens (the first surface of the collimating lens is a plane, and the second surface is a spherical surface), an optical material with a refractive index n of 1.46 is used, the curvature radius of the spherical surface is -24.387mm, the cone coefficient is -1.078, the thickness is 16.701mm, the diameter is 25mm, and the focal length is 53.015mm; the first microlens array and the second microlens array both use optical materials with a refractive index n of 1.47, the aperture of the sub-lens (the first microlens and the second microlens) is 0.3mm, the curvature radius of the sub-lens is 4mm, the thickness is 3mm, and the focal length is 8.69565mm. The spacing between the first microlens array and the second microlens array is 12.696mm, and the number of arrays is 41×41 (that is, there are 41 first microlenses on the first microlens array, and there are 41 second microlenses on the second microlens array, and they correspond one to one). The beam amplitude distribution after passing through the first microlens array and the second microlens array is as follows Figure 5 and Figure 6As shown; the integrating lens (the first surface of the integrating lens is a spherical surface, and the second surface is a spherical surface) adopts TPX optical material with a refractive index n of 1.47, the curvature radius of the first surface is 275mm, the curvature radius of the second surface is -275mm, the thickness is 30mm, and the focal length is 698.913mm; the distance between the homogenized focal plane and the integrating lens is 650-710mm, which is a uniform light field (that is, the light field whose distance of the distance integral is within the above range is a uniform light field), and the amplitude distribution of the outgoing beam is as shown Figure 7 and 8 shown.

[0065] The parameters of the terahertz beam shaping lens system are shown in Table 1, and the amplitude and phase distribution results are shown in Figures 9a to 9d shown.

[0066] Table 1 Beam shaping lens design system parameters and results

[0067]

[0068] In the parameters of the first microlens array and the second microlens array in Table 1, p is the aperture of the first microlens and the second microlens, d is the distance between the first microlens array and the second microlens array, and f is the focal length of the first microlens and the second microlens.

[0069] In addition, the Fresnel number is an effective parameter for evaluating the degree of interference of the microlens diffraction effect on the uniformity of the target spot. The Fresnel number evaluation formula is:

[0070]

[0071] Further, it can be simplified to Wherein, p is the aperture of the first microlens and the second microlens, λ represents the wavelength, and f is the focal length of the microlens.

[0072] After calculation by the simplified formula above, the Fresnel of the shaped light in Example 1 is 0.029, mainly because the wavelength of the terahertz beam is relatively long, which is 0.882 mm at 340 GHz, so the Fresnel number is relatively small. The Fresnel number is the main evaluation function for improving uniformity, and the value range is greater than 5 or less than 0.5. Within the above value range, it means that the uniformity of the light spot is good.

[0073] Based on the above data, the data in Table 1 and Figure 3-9d As shown, it can be seen that the beam shaped by the optical system for terahertz beam shaping of the utility model has uniformity, which improves the collimation of the terahertz wave and makes the shaped beam more stable and uniform.

[0074] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention. Any reference numeral in a claim should not be regarded as limiting the claim to which it relates.

[0075] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An optical system for terahertz beam shaping, characterized in that: It includes a light source for emitting a terahertz beam, and a collimating lens, a first microlens array, a second microlens array and an integrating lens which are sequentially arranged along the beam propagation direction of the terahertz beam; The multiple first microlenses on the first microlens array correspond one-to-one to the multiple second microlenses on the second microlens array, and the corresponding first microlenses and second microlenses form a microlens channel for splitting light beams, the length of the microlens channel is equal to the focal length of the first microlens, and the optical parameters of the first microlens are the same as the optical parameters of the corresponding second microlens.

2. The optical system for terahertz beam shaping according to claim 1, characterized in that: The first microlens array is a single-sided microlens array, and the first microlens is arranged on a side of the first microlens array facing the collimating lens; The second microlens array is a single-sided microlens array, and the second microlens is arranged on a side of the second microlens array facing the integrator lens.

3. The optical system for terahertz beam shaping according to claim 1, characterized in that: The optical parameters of the first microlens are the same as the optical parameters of the corresponding second microlens, and the optical parameters include aperture, focal length and numerical aperture.

4. The optical system for terahertz beam shaping according to claim 1, characterized in that: The refractive index of the collimating lens is 1.3-3.

7.

5. The optical system for terahertz beam shaping according to claim 1, characterized in that: The light source includes a terahertz source and a waveguide horn antenna connected to each other.

6. The optical system for terahertz beam shaping according to claim 1, characterized in that: The refractive index of the integrator lens is 1.3 to 3.

7.

7. The optical system for terahertz beam shaping according to claim 1, characterized in that: The integrator lens is a convex lens.

8. The optical system for terahertz beam shaping according to claim 1, characterized in that: The collimating lens is a convex lens; or, The collimating lens includes a convex lens and a concave lens.

9. The optical system for terahertz beam shaping according to claim 1, characterized in that: The collimating lens is a convex lens, one side of the collimating lens is a plane, and the other side is a spherical surface.

10. The optical system for terahertz beam shaping according to claim 1, characterized in that: The integrator lens is an integrator lens made of TPX material.

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