Large aperture terahertz-gigahertz lens system

Abstract

Lens systems used in a gigahertz/terahertz imaging system are proposed. Each proposed lens system may include two thin lens elements, spherical or aspherical, in which combined provides gigahertz-terahertz refractive power with a small f-number. The gigahertz-terahertz waves are diverted by the lens systems in such a way that it forms an image of an object, such as a human scale object, on a planar gigahertz-terahertz image sensor. The radius of curvatures, profile, sizes, spacing, and aspherical coefficients of the lens elements may be selected to achieve quality focusing performance. The spacing between the lens elements and the spacing between the lens elements and the image sensor may be adjusted to change both the focal length and the focusing distance to achieve optimum field of view and maximum imaging resolution. The size of the lens may be scaled with the size of the object or the lens aperture stop.

What is claimed is: 
     
         1 . A lens system has two lenses that form an image from the reflection or transmission of terahertz-gigahertz wave off an object. 
     
     
         2 . The lens system of  claim 1 , wherein each of the lenses is made of glass or quartz. 
     
     
         3 . The lens system of  claim 1 , wherein the object has a scale about from 80 cm to 200 cm in diameter and the object may be at a distance as close as about 0.5 meters to infinity from the lens system. 
     
     
         4 . The lens system of  claim 1 , wherein the image is detected by a two-dimensional planar terahertz-gigahertz image sensor with the size of about 10 cm 2 . 
     
     
         5 . The lens system of  claim 1 , wherein the largest diameter of the lens elements is about 32 cm, and the f-number may be as low as 0.64. 
     
     
         6 . The lens system of  claim 1 , wherein the distance of the two lens elements may be adjusted to adjust the focal length of the lens system. 
     
     
         7 . The lens system of  claim 1 , wherein one or more of the lens surfaces is spherical. 
     
     
         8 . The lens system of  claim 1 , wherein one or more of the lens surfaces is aspherical. 
     
     
         9 . The lens system of  claim 1 , wherein the gross weight of the lens system is smaller than 10 kilogram. 
     
     
         10 . The lens system of  claim 1 , wherein the size of the lens elements may be scaled with the object size. 
     
     
         11 . A large aperture terahertz-gigahertz lens system, comprising:
 a first lens element, wherein the left surface of the first lens element is a spherical surface with a radius about 477.9 to 589.1 mm and a diameter about 300 mm, wherein the right surface of the first lens element is a spherical surface with a radius about 1472.4 to 1799.6 mm and a diameter about 300 mm, wherein the thickness of the first lens element is about 17 to 37 mm; and   a second lens element, wherein the left surface of the second lens element is a spherical surface with a radius about 169.2 to 206.8 mm and a diameter about 240 mm, wherein the right surface of the second lens element is a spherical surface with a radius about 384.3 to 469.7 mm and a diameter about 240 mm, wherein the thickness of the second lens element is about 28 to 48 mm;   wherein the distance between the first lens element and second lens element is about 190 to 450 mm;   wherein the first lens element and the second lens element are positioned con-centered along an optical axis;   wherein both the first lens element and the second lens elements are made of material(s) with refractive index about 2.32 to 2.72.   
     
     
         12 . The large aperture terahertz-gigahertz lens system as claimed in claim  11 , wherein each of the lens elements is made of glass. 
     
     
         13 . The large aperture terahertz-gigahertz lens system as claimed in  claim 11 , further comprising an aperture stop positioned in front of the first lens element, the aperture stop has an infinite radius and a diameter about 290 mm, wherein the distance between the aperture stop and the left surface of the first lens element is about 0 mm. 
     
     
         14 . The large aperture terahertz-gigahertz lens system as claimed in  claim 11 , wherein the lens system has a HFOV range about 7° to 15°, wherein an object positioned on the left side of the lens elements and inside the FOV range about 14° to 30° may be sensed by an image sensor positioned on the right side of these lens elements. 
     
     
         15 . The large aperture terahertz-gigahertz lens system as claimed in  claim 14 , wherein the lens system is designed to form an image of an object with a diameter about 2000 mm and positioned on the left side of the first lens element with a separation about 4500 mm. 
     
     
         16 . The large aperture terahertz-gigahertz lens system as claimed in  claim 11 , further comprising an image senor positioned behind the second lens element, the image sensor has an infinite radius and a diameter about 100 mm, wherein the distance between the image sensor and the right surface of the second lens element is a variable based on both the distance between the object and the lens system and the distance between the two lens elements. 
     
     
         17 . The large aperture terahertz-gigahertz lens system as claimed in  claim 11 , further comprising an aperture stop positioned in front of the first lens elements, the aperture stop has an infinite radius and a finite diameter smaller than 300 mm, wherein the diameter of the first lens element may be reduced to match the diameter of the aperture stop. 
     
     
         18 . The large aperture terahertz-gigahertz lens system as claimed in  claim 11 , wherein the lens system is designed to form an image of an object positioned on the left side of the first lens element with a finite separation and has an image sensor positioned on the right side of the second lens element with a finite separation, wherein the diameter of the second lens element and the diameter of the image sensor may be reduced proportional to the diameter of the object. 
     
     
         19 . A large aperture terahertz-gigahertz lens system, comprising:
 a first lens element, wherein the left surface of the first lens element is an aspherical surface with a radius about 208.8 to 255.2 mm and a diameter about 320 mm, wherein the right surface of the first lens element is a spherical surface with a radius about 343.8 to 420.2 mm and a diameter about 320 mm, wherein the thickness of the first lens element is about 35 to 55 mm; and   a second lens element, wherein the left surface of the second lens element is an aspherical surface with a radius about 143.1 to 174.9 mm and a diameter about 170 mm, wherein the right surface of the second lens element is a spherical surface with a radius about 154.8 to 189.2 mm and a diameter about 170 mm, wherein the thickness of the second lens element is about 22 to 42 mm;   wherein the distance between the first lens element and second lens element is about 150 to 230 mm;   wherein the first lens element and the second lens element are positioned con-centered along an optical axis;   wherein both the first lens element and the second lens elements are made of material(s) with refractive index about 2.32 to 2.72.   
     
     
         20 . The large aperture terahertz-gigahertz lens system as claimed in  claim 19 , wherein each of the lens elements is made of glass. 
     
     
         21 . The large aperture terahertz-gigahertz lens system as claimed in  claim 19 , further comprising an aperture stop positioned in front of the first lens element, the aperture stop has an infinite radius and a diameter about 300 mm, wherein the distance between the aperture stop and the left surface of the first lens element is about 0 mm. 
     
     
         22 . The large aperture terahertz-gigahertz lens system as claimed in  claim 19 , wherein the lens system has a HFOV range about 12° to 14°, wherein an object positioned on the left side of the lens elements and inside the FOV range about 24° to 28° may be sensed by an image sensor positioned on the right side of these lens elements, 
     
     
         23 . The large aperture terahertz-gigahertz lens system as claimed in  claim 22 , wherein lens system is designed to form an image of an object with a diameter about 2000 mm and positioned on the left side of the first lens element with a separation about 4500 mm. 
     
     
         24 . The large aperture terahertz-gigahertz lens system as claimed in  claim 19 , further comprising an image senor positioned behind the second lens element, the image sensor has an infinite radius and a diameter about 100 mm, wherein the distance between the image sensor and the right surface of the second lens element is a variable based on both the distance between the object and the lens system and the distance between the two lens elements. 
     
     
         25 . The large aperture terahertz-gigahertz lens system as claimed in  claim 19 , further comprising an aperture stop positioned in front of the first lens elements, the aperture stop has an infinite radius and a finite diameter smaller than 300 mm, wherein the diameter of the first lens element may be reduced to match the diameter of the aperture stop. 
     
     
         26 . The large aperture terahertz-gigahertz lens system as claimed in  claim 19 , wherein the lens system is designed to form an image of an object positioned on the left side of the first lens element with a finite separation and has an image sensor positioned on the right side of the second lens element with a finite separation, wherein the diameter of the second lens element and the diameter of the image sensor may be reduced proportional to the diameter of the object. 
     
     
         27 . A large aperture terahertz-gigahertz lens system, comprising:
 a first lens element, wherein the left surface of the first lens element is an aspherical surface with a radius about 194.4 to 237.6 mm and a diameter about 300 mm, wherein the right surface of the first lens element is a spherical surface with a radius about 1251 to 1529 mm and a diameter about 300 mm, wherein the thickness of the first lens element is about 40 to 60 mm; and   a second lens element, wherein the left surface of the second lens element is a spherical surface with a radius about 101.7 to 124.3 mm and a diameter about 150 mm, wherein the right surface of the second lens element is a spherical surface with a radius about 146.7 to 179.3 mm and a diameter about 150 mm, wherein the thickness of the second lens element is about 20 to 40 mm;   wherein the distance between the first lens element and second lens element is about 200 to 300 mm;   wherein the first lens element and the second lens element are positioned con-centered along an optical axis;   wherein both the first lens element and the second lens elements are made of material(s) with refractive index about 1.76 to 2.16.   
     
     
         28 . The large aperture terahertz-gigahertz lens system as claimed in  claim 27 , wherein each of the lens elements is made of quartz. 
     
     
         29 . The large aperture terahertz-gigahertz lens system as claimed in  claim 27 , further comprising an aperture stop positioned in front of the first lens element, the aperture stop has an infinite radius and a diameter about 270 mm, wherein the distance between the aperture stop and the left surface of the first lens element is about 0 mm. 
     
     
         30 . The large aperture terahertz-gigahertz lens system as claimed in  claim 27 , wherein the lens system has a HFOV range about 9° to 12°, wherein an object positioned on the left side of the lens elements and inside the FOV range about 18° to 24° may be sensed by an image sensor positioned on the right side of these lens elements, 
     
     
         31 . The large aperture terahertz-gigahertz lens system as claimed in  claim 30 , wherein lens system is designed to form an image of an object with a diameter about 2000 mm and positioned on the left side of the first lens element with a separation about 5500 mm. 
     
     
         32 . The large aperture terahertz-gigahertz lens system as claimed in  claim 27 , further comprising an image senor positioned behind the second lens element, the image sensor has an infinite radius and a diameter about 150 mm, wherein the distance between the image sensor and the right surface of the second lens element is a variable based on both the distance between the object and the lens system and the distance between the two lens elements. 
     
     
         33 . The large aperture terahertz-gigahertz lens system as claimed in  claim 27 , further comprising an aperture stop positioned in front of the first lens elements, the aperture stop has an infinite radius and a finite diameter smaller than 300 mm, wherein the diameter of the first lens element may be reduced to match the diameter of the aperture stop. 
     
     
         34 . The large aperture terahertz-gigahertz lens system as claimed in  claim 27 , wherein the lens system is designed to form an image of an object positioned on the left side of the first lens element with a finite separation and has an image sensor positioned on the right side of the second lens element with a finite separation, wherein the diameter of the second lens element and the diameter of the image sensor may be reduced proportional to the diameter of the object. 
     
     
         35 . A large aperture terahertz-gigahertz lens system, comprising:
 a first lens element, wherein the left surface of the first lens element is an spherical surface with a radius about 300.6 to 367.4 mm and a diameter about 300 mm, wherein the right surface of the first lens element is a planar surface with an infinite radius and a diameter about 300 mm, wherein the thickness of the first lens element is about 35 to 55 mm; and   a second lens element, wherein the left surface of the second lens element is a spherical surface with a radius about 119.7 to 146.3mm and a diameter about 180 mm, wherein the right surface of the second lens element is a spherical surface with a radius about 558.9 to 683.1 mm and a diameter about 180 mm, wherein the thickness of the second lens element is about 30 to 50 mm;   wherein the distance between the first lens element and second lens element is about 200 to 290 mm;   wherein the first lens element and the second lens element are positioned con-centered along an optical axis;   wherein both the first lens element and the second lens elements are made of material(s) with refractive index about 1.80 to 2.12.   
     
     
         36 . The large aperture terahertz-gigahertz lens system as claimed in  claim 35 , wherein each of the lens elements is made of quartz. 
     
     
         37 . The large aperture terahertz-gigahertz lens system as claimed in  claim 35 , further comprising an aperture stop positioned in front of the first lens element, the aperture stop has an infinite radius and a diameter about 280 mm, wherein the distance between the aperture stop and the left surface of the first lens element is about 0 mm. 
     
     
         38 . The large aperture terahertz-gigahertz lens system as claimed in  claim 35 , wherein the lens system has a HFOV range about 10° to 14.2°, wherein an object positioned on the left side of the lens elements and inside the FOV range about 20° to 28.2° may be sensed by an image sensor positioned on the right side of these lens elements, 
     
     
         39 . The large aperture terahertz-gigahertz lens system as claimed in  claim 38 , wherein lens system is designed to form an image of an object with a diameter about 2000 mm and positioned on the left side of the first lens element with a separation about 4000 mm. 
     
     
         40 . The large aperture terahertz-gigahertz lens system as claimed in  claim 35 , further comprising an image senor positioned behind the second lens element, the image sensor has an infinite radius and a diameter about 100 mm, wherein the distance between the image sensor and the right surface of the second lens element is a variable based on both the distance between the object and the lens system and the distance between the two lens elements. 
     
     
         41 . The large aperture terahertz-gigahertz lens system as claimed in  claim 35 , further comprising an aperture stop positioned in front of the first lens elements, the aperture stop has an infinite radius and a finite diameter smaller than 300 mm, wherein the diameter of the first lens element may be reduced to match the diameter of the aperture stop. 
     
     
         42 . The large aperture terahertz-gigahertz lens system as claimed in  claim 35 , wherein the lens system is designed to form an image of an object positioned on the left side of the first lens element with a finite separation and has an image sensor positioned on the right side of the second lens element with a finite separation, wherein the diameter of the second lens element and the diameter of the image sensor may be reduced proportional to the diameter of the object.