CN112327476B - Method for preparing terahertz double-telecentric lens antenna group and lens antenna group - Google Patents
Method for preparing terahertz double-telecentric lens antenna group and lens antenna group Download PDFInfo
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- CN112327476B CN112327476B CN202011262125.3A CN202011262125A CN112327476B CN 112327476 B CN112327476 B CN 112327476B CN 202011262125 A CN202011262125 A CN 202011262125A CN 112327476 B CN112327476 B CN 112327476B
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- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
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- G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
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- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/22—Telecentric objectives or lens systems
Abstract
The invention belongs to the technical field of terahertz wave imaging antennas, and particularly relates to a method for preparing a terahertz double telecentric lens antenna group, which comprises the following steps: step 1) obtaining external parameters required by a terahertz double telecentric lens antenna group; step 2) obtaining initial internal parameters of the terahertz double telecentric lens antenna group; step 3) optimizing the terahertz double telecentric lens antenna group to obtain an optimized terahertz double telecentric lens antenna; step 4) preliminarily judging the telecentricity and the image plane spot radius of the terahertz double-telecentric lens antenna group; step 5) utilizing a Monte Carlo method to perform tolerance adjustment on the terahertz double-telecentric lens antenna group obtained in the step 4); and 6) obtaining the light spot radius beam of the image plane according to the obtained near field gain curve graph, and judging whether the light spot radius beam of the image plane is qualified.
Description
Technical Field
The invention belongs to the technical field of terahertz wave imaging antennas, and particularly relates to a method for preparing a terahertz double telecentric lens antenna group and the lens antenna group.
Background
The terahertz waves have stronger penetrability than infrared rays and have the advantage of high resolution compared with millimeter waves, so that the terahertz wave imaging attracts wide attention recently, and various terahertz wave imaging systems are established. Terahertz focal plane imaging is an imaging system which is researched more. The terahertz focal plane imaging and the visible light imaging have the same principle and belong to incoherent imaging. The imaging system is characterized by high imaging speed and large field of view.
Terahertz focal plane imaging requires quasi-optical focusing of beams, and the focusing modes are reflection type, refraction type, diffraction type and the combination of the modes. However, the existing terahertz quasi-optical focusing system generally has the problems of small field of view and poor resolution of off-axis beams, and in a large field of view state, the focused beams are incident into the receiving array antenna in a large inclination, so that the polarization loss is large, the beam uniformity is poor, and the off-axis beam focusing radius is far larger than that of the near-axis beams. Therefore, the field angle half angle of the current terahertz focal plane imaging system is smaller than 15 °, which limits the imaging range of the terahertz focal plane imaging system.
The telecentric lens is a new type of lens in recent years and is divided into an object-side telecentric lens, an image-side telecentric lens and a double telecentric lens; the telecentric lens antenna of the terahertz frequency band is rarely reported at present, and has a wide application scene in consideration of the application requirement of terahertz focal plane imaging. The double telecentric lens antenna has important significance in terahertz frequency band. The double telecentric lens antenna can expand the field of view, and the emitted beam and the beam incident on the image plane are both vertically incident. Under the condition of a certain field of view, the object distance is shortened, so that the resolution of terahertz imaging is improved, and the transmission loss and the polarization loss of a terahertz focal plane imaging system in space are reduced. The telecentric lens antenna has the unique characteristics of large depth of field and unchanged variable magnification, can reduce the deformation in the imaging process, and has wide application scenes in the fields of nondestructive testing and the like.
At present, no complete preparation method is available for preparing the terahertz double telecentric lens antenna group.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a method for preparing a terahertz double telecentric lens antenna group, which comprises the following steps:
step 1) obtaining external parameters required by a terahertz double telecentric lens antenna group; the external parameters include: the field of view, the object distance, the image distance, the object numerical aperture and the magnification factor of the double telecentric lens antenna group;
step 2) obtaining initial internal parameters of the terahertz double telecentric lens antenna group;
step 3) increasing the number of lens pieces of the terahertz double-telecentric lens antenna group, optimizing the terahertz double-telecentric lens antenna group by taking the radius of a light spot focused on an image plane as a main optimization target and taking an emergence angle and a magnification factor as a secondary optimization target, and obtaining the optimized terahertz double-telecentric lens antenna group;
step 4) preliminarily judging the telecentricity and the image plane spot radius of the terahertz double-telecentric lens antenna group obtained in the step 3), and turning to the step 5 if the terahertz double-telecentric lens antenna group meets the judgment standard;
if the terahertz double-telecentric lens antenna group does not meet the judgment standard, repeating the steps 2) -4) until the terahertz double-telecentric lens antenna group meeting the judgment standard is obtained, and turning to the step 5);
step 5) utilizing a Monte Carlo method to perform tolerance adjustment on the terahertz double-telecentric lens antenna group obtained in the step 4) so that the change rate of a focusing spot and an emergence angle both meet requirements;
step 6) obtaining a light spot radius beam of the image plane according to the obtained near field gain curve graph, and judging whether the light spot radius beam of the image plane is qualified or not;
if the light spot radius beam of the image plane is qualified, ending the operation;
and if the light spot radius beam of the image plane is not qualified, adjusting initial internal parameters of the terahertz double-telecentric lens antenna group, and then turning to the step 3).
As an improvement of the above technical solution, the step 2) specifically includes:
the terahertz double telecentric lens antenna group comprises a plurality of terahertz double telecentric lens antennas which are arranged at intervals; the terahertz double-telecentric lens antenna is a quadratic lens, and the quadratic lens comprises a spherical mirror and a quadratic aspherical mirror;
obtaining initial internal parameters of the terahertz double telecentric lens antenna group by adopting a mode of gradually expanding a field of view; wherein, the initial internal parameters of the terahertz double telecentric lens antenna group comprise: the thickness, the curvature and the aspheric surface coefficient of the terahertz double-telecentric lens.
As an improvement of the above technical solution, the step 3) specifically includes:
the front and the back of each lens in the terahertz double-telecentric lens antenna group are quadric surfaces; the expression of the quadric surface is
Wherein z isiThe direction coordinate of an optical axis passing through the ith quadric surface of the terahertz double telecentric lens; r is the distance from a point in a plane perpendicular to the optical axis to the intersection of the image plane and the optical axis; k is a radical of formulaiIs a constant value of conc; c. CiThe curvature of the ith quadric surface of the terahertz double telecentric lens antenna is shown;
and (3) optimizing initial parameters of the terahertz double-telecentric lens antenna group by using a damping least square method and combining the formula (1) and taking the radius of a focused light spot on an image plane as a main optimization target and taking an emergent angle and a magnification factor as a secondary optimization target to obtain the optimized terahertz double-telecentric lens antenna group.
As an improvement of the above technical solution, in the step 4), the determination criterion is that the telecentricity of the terahertz double telecentric lens antenna set is less than or equal to 0.01 °, and the spot radius of the image plane is less than or equal to half of the airy spot radius.
As an improvement of the above technical solution, the step 5) specifically includes:
performing tolerance adjustment on the terahertz double-telecentric lens antenna group obtained in the step 4) by using a Monte Carlo method;
within the tolerance range of +/-0.2 mm, if the change rate of the focusing light spots on the image plane of the terahertz double-telecentric lens antenna group is less than or equal to 10% and the emergence angle is less than or equal to 0.01 degrees, the requirement is met, and the step 6) is carried out;
if the change rate of the focusing spots on the image plane of the terahertz double-telecentric lens antenna is more than 10%, reducing the tolerance of the terahertz double-telecentric lens antenna group until the change rate of the focusing spots on the image plane of the terahertz double-telecentric lens antenna group is less than or equal to 10% and the emergence angle is less than or equal to 0.01 degrees to meet the requirement, and turning to the step 6);
as an improvement of the above technical solution, the step 6) specifically includes:
calculating near-field gains of Gaussian beams at different positions by using a full-wave analysis method, drawing a curve graph of the relation between an image plane and the near-field gains, obtaining the maximum value of the near-field gains from the curve graph, subtracting 3dB from the maximum value to obtain a near-field gain value, and taking an interval value corresponding to an abscissa between the maximum value and the-3 dB near-field gain value as a light spot radius beam of the image plane;
wherein the spot radius beam of the image plane comprises: the central beam is focused on the central spot radius of the image plane and the plurality of edge beams are focused on the spot radius of the image plane;
if the ratio of the spot radius to the central spot radius is less than or equal to 1.2 and the central spot radius is close to the diffraction limit, the spot radius beam of the image plane is qualified, and the operation is ended;
if the ratio of the edge spot radius to the diffraction limit is greater than 1.2, repeating the steps 2) -5) until a qualified spot radius beam at the image plane is obtained, and ending the operation.
The invention also provides a lens antenna group, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged at intervals;
the curvature radiuses of the front surface and the rear surface of the first lens are 45.962mm and infinity respectively, and the aspheric surface coefficient of the front surface is-0.1;
the spacing between the first lens and the second lens is kept at 25 mm;
the curvature radiuses of the front surface and the rear surface of the second lens are respectively infinity and 37.45mm, and the aspheric surface coefficient of the rear surface is-2.0;
the spacing between the second lens and the third lens is kept at 30 mm;
the curvature radiuses of the front and rear surfaces of the third lens are 38.67mm and 30.81mm, respectively;
the spacing between the third lens and the fourth lens is kept at 30 mm;
the curvature radiuses of the front surface and the rear surface of the fourth lens are-20.45 mm and-30.76 mm respectively, and the aspheric surface coefficient of the rear surface is-3.2;
the distance between the fourth lens and the fifth lens is kept at 30 mm;
the curvature radiuses of the front surface and the rear surface of the fifth lens are respectively infinity and-50.03 mm;
the distance between the fifth lens and the sixth lens is kept at 2 mm;
the curvature radiuses of the front surface and the rear surface of the sixth lens are respectively 28.02mm and-171.22 mm, and the aspheric coefficient of the rear surface is-8.1;
the spacing between the sixth lens and the image plane is kept at 25 mm.
Compared with the prior art, the invention has the beneficial effects that:
the method of the invention completes the preparation of the double telecentric lens antenna group in the terahertz frequency band, the prepared double telecentric lens antenna group realizes large field of view and high resolution, the polarization loss is reduced by the vertical incidence and the emergence of the main beam, meanwhile, the telecentric lens has better detection performance on thick objects, the multiple distortion does not exist, the tolerance requirement of the terahertz double telecentric lens antenna group is +/-0.2 mm, and the tolerance requirement is loose compared with that of a reflector antenna; meanwhile, the telecentric lens antenna group has a broadband characteristic and a telecentric characteristic in a frequency band of 100GHz-170 GHz.
Drawings
FIG. 1 is a flow chart of a method for preparing a terahertz double telecentric lens antenna group according to the invention;
FIG. 2 is a schematic diagram of a three-dimensional structure of a terahertz double telecentric lens antenna group prepared by the preparation method of the invention;
FIG. 3 is a schematic diagram of a two-dimensional structure of a terahertz double telecentric lens antenna group prepared by the preparation method of the invention in FIG. 2;
FIG. 4 is a point array diagram of a group of terahertz double telecentric lenses manufactured by the manufacturing method of the invention in FIG. 2;
fig. 5 is an image square beam uniformity effect diagram of the terahertz double telecentric lens antenna group prepared by the preparation method of the invention in fig. 2.
Detailed Description
The invention will now be further described with reference to the accompanying drawings.
As shown in fig. 1, the invention provides a method for preparing a terahertz double telecentric lens antenna group, the method replaces a simple refraction type lens antenna group, and the obtained terahertz double telecentric lens antenna group can realize a larger field of view and higher resolution, and is suitable for the fields of nondestructive testing and the like.
The invention provides a method for preparing a terahertz double telecentric lens antenna group, which comprises the following steps:
step 1) obtaining external parameters required by a terahertz double telecentric lens antenna group; the external parameters include: the field of view, the object distance, the image distance, the object numerical aperture and the magnification factor of the double telecentric lens antenna group;
wherein, the field range refers to the field radius in the object plane, which can realize effective focusing; the magnification is the ratio of the radii of the object plane and the image plane; the object numerical aperture is the sine value of the incident angle alpha of the Gaussian beam, namely sin alpha;
step 2) obtaining initial internal parameters of the terahertz double telecentric lens antenna group;
specifically, the terahertz double-telecentric lens antenna group comprises a plurality of terahertz double-telecentric lens antennas arranged at intervals; the terahertz double-telecentric lens antenna is a quadratic lens, and the quadratic lens comprises a spherical mirror and a quadratic aspherical mirror;
the initial internal parameters of the terahertz double telecentric lens antenna group comprise: the thickness, curvature and aspheric surface coefficient of each terahertz double telecentric lens;
the field of view is increased from the normal incidence of the central beam to the required field of view range by adopting a mode of gradually enlarging the field of view, the field of view can be increased for a plurality of times in the process, and after the field of view is increased each time, the field of view is confirmed to be increased for further optimization until the required field of view is achieved; thereby obtaining the initial internal parameters of the terahertz double telecentric lens antenna group. When the initial parameters of the required large field of view cannot be obtained through direct optimization, the field of view is gradually expanded from the central beam which can only be incident to the edge, the initial parameters of the field of view are the parameters obtained through previous optimization, and the field of view can be kept in an optimized state after being expanded.
Step 3) increasing the number of lens pieces of the terahertz double-telecentric lens antenna group, optimizing the terahertz double-telecentric lens antenna group by taking the radius of a focusing spot on an image plane as a main optimization target and taking an emergence angle and a magnification factor as a secondary optimization target, and obtaining the optimized terahertz double-telecentric lens antenna group;
specifically, the front surface and the back surface of each lens in the terahertz double-telecentric lens antenna group are two quadric surfaces, and the expression of the quadric surface is
Wherein z isiThe direction coordinate of an optical axis passing through the ith quadric surface of the terahertz double telecentric lens; r is the distance from a point in a plane perpendicular to the optical axis to the intersection of the image plane and the optical axis; k is a radical ofiIs a constant value of conc; c. CiThe curvature of the ith quadric surface of the terahertz double telecentric lens antenna is shown; wherein the exit angle refers to the beam exiting from the last lens surface and the optical axis ziThe included angle of (c);
and (3) optimizing initial parameters of the terahertz double-telecentric lens antenna group by using a damping least square method and combining the formula (1) and taking the radius of a focused light spot on an image plane as a main optimization target and taking an emergent angle and a magnification factor as a secondary optimization target to obtain the optimized terahertz double-telecentric lens antenna group. The method comprises the steps that the spot radius, the emergence angle and the magnification factor are directly related to a lens surface type, the lens surface type is related to initial parameters, the purpose of optimizing the lens surface type is to reduce the spot radius and the emergence angle of an image plane and enable the spot radius and the emergence angle to reach the minimum value meeting the standard, the optimization method is a damping least square method, therefore, the damping least square method is adopted to optimize the initial parameters, the lens surface type is optimized by optimizing the initial parameters, the spot radius and the emergence angle further reach the minimum value meeting the requirements, and the optimized terahertz double telecentric lens antenna group is obtained.
Step 4) preliminarily judging the telecentricity and the image plane spot radius of the terahertz double-telecentric lens antenna set, and turning to step 5 if the terahertz double-telecentric lens antenna set meets the judgment standard;
if the terahertz double-telecentric lens antenna group does not meet the judgment standard, repeating the steps 2) -4) until the terahertz double-telecentric lens antenna group meeting the judgment standard is obtained, and turning to the step 5);
specifically, in the step 4), the determination criterion is that the telecentricity is less than or equal to 0.01 °, and the spot radius of the image plane is less than or equal to half of the airy disk radius.
Calculating to obtain the telecentricity of the lens antenna group, namely the exit angle of the lens, and ensuring that the exit angle of each beam from the center to the edge is less than or equal to 0.01 degrees; and under the condition of neglecting the diffraction effect, calculating the radius of the light spot focused by the image plane, wherein the radius of the light spot is less than or equal to half of the radius of the Airy spot, so that the judgment standard is met.
Step 5) utilizing a Monte Carlo method to perform tolerance adjustment on the terahertz double-telecentric lens antenna group obtained in the step 4) so that the change rate of a focusing spot and an emergence angle both meet requirements;
specifically, performing tolerance adjustment on the terahertz double telecentric lens antenna group obtained in the step 4);
within the range of +/-0.2 mm of setting tolerance, if the change rate of focusing light spots on an image plane of the terahertz double-telecentric lens antenna group is less than or equal to 10% and the emergence angle is less than or equal to 0.01 degrees, the requirement is met, and the step 6) is carried out;
if the change rate of the focusing light spots on the image plane of the terahertz double-telecentric lens antenna group is more than 10%, reducing the tolerance of the terahertz double-telecentric lens antenna group until the change rate of the focusing light spots on the image plane of the terahertz double-telecentric lens antenna group is less than or equal to 10% and the emergence angle is less than or equal to 0.01 degrees, meeting the requirement, and turning to the step 6);
wherein, the tolerance of terahertz pair telecentric lenses antenna group includes: the curvature radius and the thickness of the terahertz double telecentric lens antenna, the distance between lenses, the eccentricity and the refractive index error;
if the tolerance is reduced to less than 50 μm and the requirement cannot be met, repeating the steps 2) -4);
step 6) obtaining a light spot radius beam of the image plane by using the obtained near field gain curve graph, and judging whether the light spot radius beam of the image plane is qualified or not;
if the light spot radius beam of the image plane is qualified, ending the operation;
and if the light spot radius beam of the image plane is not qualified, adjusting initial internal parameters of the terahertz double-telecentric lens antenna group, and turning to the step 3) until the qualified light spot radius beam of the image plane is obtained, and finishing the operation.
Specifically, calculating near-field gains of Gaussian beams at different positions by using a full-wave analysis method, thereby drawing a graph of the relation between an image plane and the near-field gains, obtaining the maximum value of the near-field gains from the graph, subtracting 3dB from the maximum value to obtain a near-field gain value, and taking an interval value corresponding to an abscissa from the maximum value to the near-gain value as a light spot radius beam of the image plane;
wherein the spot radius beam of the image plane comprises: the central beam is focused on the central spot radius of the image plane and the plurality of edge beams are focused on the spot radius of the image plane;
if the ratio of the edge light spot radius to the central light spot radius is less than or equal to 1.2 and the central light spot radius is close to the diffraction limit, the light spot radius beam of the image plane is qualified, and the operation is ended;
if the ratio of the edge spot radius to the diffraction limit is greater than 1.2, repeating steps 2) -5) until a satisfactory beam of spot radii for the image plane is obtained, and ending the operation.
According to the preparation method, the invention provides a terahertz double telecentric lens antenna group, as shown in fig. 2 and 3, in this embodiment, the lens antenna group comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged at intervals;
the curvature radiuses of the front surface and the rear surface of the first lens are 45.962mm and infinity respectively, and the aspheric surface coefficient of the front surface is-0.1;
the spacing between the first lens and the second lens is kept at 25 mm;
the curvature radiuses of the front surface and the rear surface of the second lens are respectively infinity and 37.45mm, and the aspheric surface coefficient of the rear surface is-2.0;
the spacing between the second lens and the third lens is kept at 30 mm;
the curvature radiuses of the front and rear surfaces of the third lens are 38.67mm and 30.81mm, respectively;
the spacing between the third lens and the fourth lens is kept at 30 mm;
the curvature radiuses of the front surface and the rear surface of the fourth lens are-20.45 mm and-30.76 mm respectively, and the aspheric surface coefficient of the rear surface is-3.2;
the distance between the fourth lens and the fifth lens is kept at 30 mm;
the curvature radiuses of the front surface and the rear surface of the fifth lens are respectively infinity and-50.03 mm;
the distance between the fifth lens and the sixth lens is kept at 2 mm;
the curvature radiuses of the front surface and the rear surface of the sixth lens are respectively 28.02mm and-171.22 mm, and the aspheric coefficient of the rear surface is-8.1;
the spacing between the sixth lens and the image plane is kept at 25 mm.
The working object distance between the double telecentric lens antennas is 0.05m, the working frequency is 110GHz-170GHz, and the spatial resolution on the object plane is less than 5 mm;
the main work for preparing the terahertz double-telecentric lens antenna group is the selection and optimization of a lens curved surface, so that the good focusing of light spots on an image plane is ensured and the vertical entering into the image plane is realized.
The terahertz double-telecentric lens antenna group prepared by the method realizes large field of view and high resolution, reduces polarization loss through vertical incidence and emergence of the main beam, has broadband characteristics, and has telecentric characteristics at 110GHz-170 GHz.
As shown in fig. 4, in the quasi-optical design, a focusing spot array diagram of the image plane is obtained, wherein the outer circle is the airy disc radius, the solid point inside is the focusing spot array diagram, the spot array diagram is located inside the airy disc, the telecentricity is less than or equal to 0.01 °, the spot radius of the image plane is less than or equal to half of the airy disc radius, and the spot radius of the image plane is far less than the airy disc radius, so as to reach the quasi-optical design standard, the spot radius of the image plane can be calculated by adopting a quasi-optical theoretical formula, and the terahertz double-telecentric lens antenna group meeting the standard is obtained and meets the design requirements.
As shown in fig. 5, electromagnetic simulation software is used, a full-wave analysis method is used for simulation, a near-field gain curve graph on an image plane is calculated, the maximum value of a near-field gain value of a vertical coordinate is found from the curve graph, then-3 dB is subtracted from the maximum value to obtain a near-field gain value, and an interval value corresponding to an abscissa from the maximum value to the near-field gain value is used as a light spot radius beam of the image plane;
wherein the spot radius beam of the image plane comprises: a center spot radius and a plurality of edge spot radii;
the spot radius beam of the image plane is an interval value of an abscissa corresponding to the maximum value of the near field gain found in each graph minus-3 dB.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (7)
1. A method for preparing a terahertz double telecentric lens antenna group is characterized by comprising the following steps:
step 1) obtaining external parameters required by a terahertz double telecentric lens antenna group; the external parameters include: the field of view, the object distance, the image distance, the object numerical aperture and the magnification factor of the double telecentric lens antenna group;
step 2) obtaining initial internal parameters of the terahertz double telecentric lens antenna group;
step 3) increasing the number of lens pieces of the terahertz double-telecentric lens antenna group, optimizing the terahertz double-telecentric lens antenna group by taking the radius of a light spot focused on an image plane as a main optimization target and taking an emergence angle and a magnification factor as a secondary optimization target, and obtaining the optimized terahertz double-telecentric lens antenna group;
step 4) preliminarily judging the telecentricity and the image plane spot radius of the terahertz double-telecentric lens antenna group obtained in the step 3), and turning to the step 5 if the terahertz double-telecentric lens antenna group meets the judgment standard;
if the terahertz double-telecentric lens antenna group does not meet the judgment standard, repeating the steps 2) -4) until the terahertz double-telecentric lens antenna group meeting the judgment standard is obtained, and turning to the step 5);
step 5) utilizing a Monte Carlo method to perform tolerance adjustment on the terahertz double-telecentric lens antenna group obtained in the step 4) so that the change rate of a focusing spot and an emergence angle both meet requirements;
step 6) obtaining a light spot radius beam of the image plane according to the obtained near field gain curve graph, and judging whether the light spot radius beam of the image plane is qualified or not;
if the light spot radius beam of the image plane is qualified, ending the operation;
and if the light spot radius beam of the image plane is not qualified, adjusting initial internal parameters of the terahertz double-telecentric lens antenna group, and then turning to the step 3).
2. The method for preparing the terahertz double-telecentric lens antenna group according to claim 1, wherein the step 2) specifically comprises:
the terahertz double telecentric lens antenna group comprises a plurality of terahertz double telecentric lens antennas which are arranged at intervals; the terahertz double-telecentric lens antenna is a quadratic lens, and the quadratic lens comprises a spherical mirror and a quadratic aspherical mirror;
obtaining initial internal parameters of the terahertz double telecentric lens antenna group by adopting a mode of gradually expanding a field of view; wherein, the initial internal parameters of the terahertz double telecentric lens antenna group comprise: the thickness, the curvature and the aspheric surface coefficient of the terahertz double-telecentric lens.
3. The method for preparing the terahertz double-telecentric lens antenna group according to claim 1, wherein the step 3) specifically comprises:
the front and the back of each lens in the terahertz double-telecentric lens antenna group are quadric surfaces; the expression of the quadric surface is
Wherein z isiThe direction coordinate of an optical axis passing through the ith quadric surface of the terahertz double telecentric lens; r is the distance from a point in a plane perpendicular to the optical axis to the intersection of the image plane and the optical axis; k is a radical ofiIs a constant value of conc; c. CiThe curvature of the ith quadric surface of the terahertz double telecentric lens antenna is shown;
and (3) optimizing initial parameters of the terahertz double-telecentric lens antenna group by using a damping least square method and combining the formula (1) and taking the radius of a focused light spot on an image plane as a main optimization target and taking an emergent angle and a magnification factor as a secondary optimization target to obtain the optimized terahertz double-telecentric lens antenna group.
4. The method for preparing the terahertz double-telecentric lens antenna set according to claim 1, wherein in the step 4), the judgment standard is that the telecentricity of the terahertz double-telecentric lens antenna set is less than or equal to 0.01 °, and the spot radius of the image plane is less than or equal to half of the airy disc radius.
5. The method for preparing the terahertz double-telecentric lens antenna group according to claim 1, wherein the step 5) specifically comprises:
carrying out tolerance adjustment on the terahertz double telecentric lens antenna group obtained in the step 4) by using a Monte Carlo method;
within the tolerance range of +/-0.2 mm, if the change rate of the focusing light spots on the image plane of the terahertz double-telecentric lens antenna group is less than or equal to 10% and the emergence angle is less than or equal to 0.01 degrees, the requirement is met, and the step 6) is carried out;
if the change rate of the focusing light spots on the image plane of the terahertz double-telecentric lens antenna is larger than 10%, reducing the tolerance of the terahertz double-telecentric lens antenna group until the change rate of the focusing light spots on the image plane of the terahertz double-telecentric lens antenna group is smaller than or equal to 10% and the emergence angle is smaller than or equal to 0.01 degrees, meeting the requirement, and turning to the step 6).
6. The method for preparing the terahertz double-telecentric lens antenna group according to claim 1, wherein the step 6) specifically comprises:
calculating near-field gains of Gaussian beams at different positions by using a full-wave analysis method, drawing a curve graph of the relation between an image plane and the near-field gains, obtaining the maximum value of the near-field gains from the curve graph, subtracting 3dB from the maximum value to obtain a near-field gain value, and taking an interval value corresponding to an abscissa between the maximum value and the-3 dB near-field gain value as a light spot radius beam of the image plane;
wherein the spot radius beam of the image plane comprises: the central beam is focused on the central spot radius of the image plane and the plurality of edge beams are focused on the spot radius of the image plane;
if the ratio of the spot radius to the central spot radius is less than or equal to 1.2 and the central spot radius is close to the diffraction limit, the spot radius beam of the image plane is qualified, and the operation is ended;
if the ratio of the edge spot radius to the diffraction limit is greater than 1.2, repeating steps 2) -5) until a satisfactory beam of spot radii for the image plane is obtained, and ending the operation.
7. A lens antenna group is prepared by the method for preparing the terahertz double-telecentric lens antenna group as claimed in any one of claims 1 to 6, and the lens antenna group comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged at intervals;
the curvature radiuses of the front surface and the rear surface of the first lens are 45.962mm and infinity respectively, and the aspheric surface coefficient of the front surface is-0.1;
the spacing between the first lens and the second lens is kept at 25 mm;
the curvature radiuses of the front surface and the rear surface of the second lens are respectively infinity and 37.45mm, and the aspheric surface coefficient of the rear surface is-2.0;
the spacing between the second lens and the third lens is kept at 30 mm;
the curvature radiuses of the front and rear surfaces of the third lens are 38.67mm and 30.81mm, respectively;
the spacing between the third lens and the fourth lens is kept at 30 mm;
the curvature radiuses of the front surface and the rear surface of the fourth lens are-20.45 mm and-30.76 mm respectively, and the aspheric surface coefficient of the rear surface is-3.2;
the distance between the fourth lens and the fifth lens is kept at 30 mm;
the curvature radiuses of the front surface and the rear surface of the fifth lens are respectively infinity and-50.03 mm;
the distance between the fifth lens and the sixth lens is kept at 2 mm;
the curvature radiuses of the front surface and the rear surface of the sixth lens are respectively 28.02mm and-171.22 mm, and the aspheric coefficient of the rear surface is-8.1;
the spacing between the sixth lens and the image plane is kept at 25 mm.
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| CN107092075A (en) * | 2017-03-14 | 2017-08-25 | 中国工程物理研究院激光聚变研究中心 | A kind of big view field imaging object lens of the high relative aperture of terahertz wave band |
| WO2018059135A1 (en) * | 2016-09-27 | 2018-04-05 | 深圳市太赫兹科技创新研究院 | Method for measuring parameters of terahertz beam |
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| WO2020119107A1 (en) * | 2018-12-13 | 2020-06-18 | 北京遥测技术研究所 | Integrated research and development platform for terahertz focal plane imaging system |
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| US20100059677A1 (en) * | 2008-09-10 | 2010-03-11 | Rainer Leonhardt | Aspheric Lenses for Imaging |
| KR101316568B1 (en) * | 2012-03-14 | 2013-10-15 | 한국식품연구원 | High resolution object inspection apparatus using terahertz wave |
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| CN104035197A (en) * | 2014-06-12 | 2014-09-10 | 电子科技大学 | Refraction and reflection type THz wave imaging system |
| WO2018059135A1 (en) * | 2016-09-27 | 2018-04-05 | 深圳市太赫兹科技创新研究院 | Method for measuring parameters of terahertz beam |
| WO2018086574A1 (en) * | 2016-11-11 | 2018-05-17 | 华讯方舟科技有限公司 | Apparatus for testing water content distribution and use thereof |
| CN107092075A (en) * | 2017-03-14 | 2017-08-25 | 中国工程物理研究院激光聚变研究中心 | A kind of big view field imaging object lens of the high relative aperture of terahertz wave band |
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