A short-wave telecentric optical system and imaging method thereof

Abstract

The present invention relates to a shortwave telecentric optical system and an imaging method thereof. The optical system comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens, arranged sequentially along the incident direction of light. The present invention provides a large relative aperture, limited-yoke object-space telecentric system, compatible with a refrigerated shortwave infrared detector (640×512@15μm). The large relative aperture system offers high energy concentration, while the refrigerated shortwave detector operates in a low-temperature environment, resulting in a high signal-to-noise ratio and enhanced detail resolution. Telecentric optical systems have a wide range of applications in precision measurement, optical metrology instruments, and other fields, particularly in applications requiring high-precision measurements.

Description

Technical Field

[0001] The invention relates to a short-wave telecentric optical system and an imaging method thereof. Background Art

[0002] Because the object-space principal rays of a telecentric system are parallel to the optical axis, the principal rays of the imaging beam at the same point on the object do not change with the object's position as the object moves forward or backward. This eliminates errors caused by inaccurate focusing, which is crucial for precision measurement systems that utilize imaging principles. Telecentric lenses are used in precision parts inspection, non-contact optical measurement, semiconductor testing, and other fields.

[0003] Shortwave infrared (SWIR) operates in the 0.9µm to 2.5µm wavelength range, between visible light and mid- and long-wave infrared. It can provide information beyond that of visible light, mid- and long-wave infrared. Currently, the mainstream SWIR lenses on the market operate in the 0.9µm to 1.7µm wavelength range, while cooled SWIR systems operating in the 1.8µm to 2.5µm wavelength range are relatively rare. Summary of the Invention

[0004] In response to the shortcomings of existing technologies, the present invention provides a shortwave telecentric optical system and imaging method. The lens operates in the 2µm to 2.5µm wavelength range and features a large relative aperture, enabling it to collect more target signal energy. The system is paired with a cooled shortwave infrared detector, which operates in low-temperature environments, resulting in a high signal-to-noise ratio and enhanced detail resolution. Object-side telecentricity eliminates errors caused by inaccurate focusing. The system utilizes a combination of three infrared materials, resulting in a simple lens optical structure, excellent manufacturability, and ease of fabrication and assembly.

[0005] The solution adopted by the present invention to solve the technical problem is a short-wave telecentric optical system, characterized in that the optical system consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens arranged in sequence along the incident direction of light.

[0006] Furthermore, the first lens is a meniscus positive lens with its convex surface facing the object plane; the second lens is a meniscus negative lens with its concave surface facing the object plane; the third lens is a meniscus positive lens with its concave surface facing the object plane; the fourth lens is a meniscus positive lens with its concave surface facing the object plane; the fifth lens is a double concave negative lens; the sixth lens is a double convex positive lens; the seventh lens is a meniscus negative lens with its concave surface facing the object plane; the eighth lens is a meniscus positive lens with its concave surface facing the object plane; the ninth lens is a double concave negative lens; and the tenth lens is a double convex positive lens.

[0007] Furthermore, the first lens, the fourth lens, the sixth lens, the eighth lens, and the tenth lens are made of silicon single crystal; the third lens, the fifth lens, the seventh lens, and the ninth lens are made of chalcogenide glass; and the second lens is made of germanium single crystal.

[0008] Furthermore, the air gap between the first lens and the second lens is 27.77 mm; the air gap between the second lens and the third lens is 1.05 mm; the air gap between the third lens and the fourth lens is 1.25 mm; the air gap between the fourth lens and the fifth lens is 89.39 mm; the air gap between the fifth lens and the sixth lens is 1.16 mm; the air gap between the sixth lens and the seventh lens is 1.61 mm; the air gap between the seventh lens and the eighth lens is 72.86 mm; the air gap between the eighth lens and the ninth lens is 27.78 mm; and the air gap between the ninth lens and the tenth lens is 1.53 mm.

[0009] Furthermore, an aperture is provided between the tenth lens and the image plane, and the air gap between the tenth lens and the aperture is 8.81 mm; the air gap between the aperture and the image plane is 20 mm.

[0010] Furthermore, the focal length of the optical system is f, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, and the tenth lens are f1, f2, f3, f4, f5, f6, f7, f8, f9, and f10, respectively, wherein f1, f2, f3, f4, f5, f6, f7, f8, f9, and f10 satisfy the following ratio to f: -5 <f1 / f<0;0<f2 / f<5;-5<f3 / f<0;-5<f4 / f<0;0<f5 / f<5;-5<f6 / f<0;0<f7 / f<5;-5<f8 / f<0;0<f9 / f<5;-5<f10 / f<0。

[0011] Furthermore, the object-side surface of the second lens, the image-side surface of the fourth lens, the image-side surface of the fifth lens, the object-side surface of the sixth lens, the object-side surface of the seventh lens, the object-side surface of the eighth lens, and the object-side surface of the tenth lens are aspherical surfaces, and the aspherical curve equation is expressed as follows:

[0012]

[0013] Among them, Z represents the position along the optical axis; r represents the height in the vertical direction relative to the optical axis; c is the paraxial curvature of the aspheric surface; k is the cone constant; α4, α6, α8... represent the aspheric coefficients.

[0014] A working method of a short-wave telecentric optical system: when light is incident, the light path sequentially enters the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, and the aperture, and finally forms an image on the image plane.

[0015] Compared with existing technologies, the present invention has the following advantages: The adoption of a secondary imaging structure reduces the aperture of each lens element, lightens the lens weight, and reduces the lens volume. This structure, composed of ten lenses, rationally distributes optical power and uses even-order aspheric surfaces to balance system aberrations, resulting in a sufficiently small overall optical system volume and the ability to meet the requirements of a large relative aperture and object-side telecentric design. Light height is adjusted to keep relative illumination within a reasonable range, ensuring uniform illumination across the imaging surface. Adjustments to curvature and thickness reduce the sensitivity of each optical component, making the lens easier to manufacture and assemble. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the optical structure of an embodiment of the present invention;

[0017] Figure 2 1 is an MTF function curve diagram under normal temperature environment of an embodiment of the present invention;

[0018] Figure 3 is a lens distortion curve diagram of an embodiment of the present invention;

[0019] Figure 4 2 is a relative illumination curve diagram of an embodiment of the present invention.

[0020] In the figure: A-first lens; B-second lens; C-third lens; D-fourth lens; E-fifth lens; F-sixth lens; G-seventh lens; H-eighth lens; I-ninth lens; J-tenth lens; IMA-imaging surface. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, a short-wave telecentric optical system is characterized in that: the optical system consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens arranged in sequence along the incident direction of light.

[0023] In this embodiment, the first lens is a positive meniscus lens with its convex surface facing the object plane; the second lens is a negative meniscus lens with its concave surface facing the object plane; the third lens is a positive meniscus lens with its concave surface facing the object plane; the fourth lens is a positive meniscus lens with its concave surface facing the object plane; the fifth lens is a double concave negative lens; the sixth lens is a double convex positive lens; the seventh lens is a negative meniscus lens with its concave surface facing the object plane; the eighth lens is a positive meniscus lens with its concave surface facing the object plane; the ninth lens is a double concave negative lens; and the tenth lens is a double convex positive lens.

[0024] In this embodiment, the first lens, the fourth lens, the sixth lens, the eighth lens, and the tenth lens are made of silicon single crystal; the third lens, the fifth lens, the seventh lens, and the ninth lens are made of chalcogenide glass; and the second lens is made of germanium single crystal.

[0025] In this embodiment, the air gap between the object plane and the meniscus positive lens A is 60 mm, the air gap between the first and second lenses is 27.77 mm, the air gap between the second and third lenses is 1.05 mm, the air gap between the third and fourth lenses is 1.25 mm, the air gap between the fourth and fifth lenses is 89.39 mm, the air gap between the fifth and sixth lenses is 1.16 mm, the air gap between the sixth and seventh lenses is 1.61 mm, the air gap between the seventh and eighth lenses is 72.86 mm, the air gap between the eighth and ninth lenses is 27.78 mm, and the air gap between the ninth and tenth lenses is 1.53 mm.

[0026] In this embodiment, an aperture is provided between the tenth lens and the image plane. The air gap between the tenth lens and the aperture is 8.81 mm; and the air gap between the aperture and the image plane is 20 mm.

[0027] In this embodiment, the focal length of the optical system is f, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, and the tenth lens are f1, f2, f3, f4, f5, f6, f7, f8, f9, and f10, respectively, where f1, f2, f3, f4, f5, f6, f7, f8, f9, and f10 satisfy the following ratio to f: -5 <f1 / f<0;0<f2 / f<5;-5<f3 / f<0;-5<f4 / f<0;0<f5 / f<5;-5<f6 / f<0;0<f7 / f<5;-5<f8 / f<0;0<f9 / f<5;-5<f10 / f<0。

[0028] Optical parameters of the embodiment of the invention:

[0029]

[0030]

[0031] In this embodiment, the object-side surface of the second lens, the image-side surface of the fourth lens, the image-side surface of the fifth lens, the object-side surface of the sixth lens, the object-side surface of the seventh lens, the object-side surface of the eighth lens, and the object-side surface of the tenth lens are aspherical surfaces, and the aspherical curve equation is expressed as follows:

[0032]

[0033] Among them, Z represents the position along the optical axis; r represents the height in the vertical direction relative to the optical axis; c is the paraxial curvature of the aspheric surface; k is the cone constant; α4, α6, α8... represent the aspheric coefficients.

[0034] Aspheric surface related data:

[0035]

[0036]

[0037] In aspheric surface data, En represents “×10 -n ", for example, -1.56E-07 represents -1.56×10 -7 .

[0038] The specific performance parameters of this optical structure are:

[0039] (1) Working spectrum range: 2.0um~2.5um

[0040] (2) Object-side NA: 0.15

[0041] (3) Working distance: 60mm

[0042] (4) Field of view: 2w ≥ 17°

[0043] (5) Distortion: ≤0.05%

[0044] (6) Relative illumination: ≥85%

[0045] A working method of a short-wave telecentric optical system: when light is incident, the light path sequentially enters the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, and the aperture, and finally forms an image on the image plane.

[0046] Depend on Figure 2 It can be seen that the MTF curve of this lens is close to the diffraction limit, and the full field of view is greater than 0.70 at 34lp / mm, which has a high resolution. Figure 3 It can be seen that the distortion of the lens is less than 0.05%; Figure 4 It can be seen that the edge relative illumination of the system is greater than 85%, and the system image plane illumination is relatively uniform.

[0047] Compared with other lenses, this lens has the following advantages:

[0048] a) The present invention has a large relative aperture, can collect more target signal energy, and the system is matched with a refrigerated short-wave infrared detector, which has higher detection sensitivity and higher detail resolution;

[0049] b) The lens of the present invention operates in the wavelength band of 2um to 2.5um, which has high recognition. Its imaging features are similar to those of visible light grayscale images, with high imaging contrast and clearer target details.

[0050] c) The optical system of the present invention adopts a secondary imaging structure, which effectively compresses the overall outer diameter of the optical system, reduces the weight of the lens, and realizes the miniaturization of the optical system;

[0051] d) In an object-space telecentric system, the principal rays of the object-space beam are parallel to the optical axis. When the object moves forward or backward, the principal rays of the imaging beam at the same point on the object do not change with the object's position. This eliminates errors caused by inaccurate focusing, which is very important for precision measurement systems that use imaging principles.

[0052] e) The present invention adopts a refractive optical structure, which does not require adjustment of the reflector and is easy to assemble.

[0053] Unless otherwise stated, for any of the technical solutions disclosed in the present invention, if a numerical range is disclosed, the disclosed numerical range is a preferred numerical range. Any person skilled in the art should understand that the preferred numerical range is merely a numerical range that is representative or has a more obvious technical effect among many feasible numerical values. Due to the large number of numerical values, it is impossible to enumerate them exhaustively. Therefore, the present invention discloses some numerical values ​​to illustrate the technical solutions of the present invention. Moreover, the numerical values ​​listed above should not be construed as limiting the scope of protection of the present invention.

[0054] If words such as "first" and "second" are used in this document to limit components, those skilled in the art should know that the use of "first" and "second" is only for the convenience of description to distinguish between components. Unless otherwise stated, the above words have no special meaning.

[0055] If the present invention discloses or involves components or structural parts that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by integrated molding using a casting process) (except where it is obviously impossible to use an integrated molding process).

[0056] In addition, the orientations or positional relationships indicated by terms such as "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", and "outside" used in any of the technical solutions disclosed in the above invention are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing this patent, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this patent. Unless otherwise stated, the terms used to indicate shapes used in any of the technical solutions disclosed in the above invention include shapes that are approximate, similar, or close to them.

[0057] Any component provided by the present invention may be assembled from multiple separate components, or may be a separate component manufactured by an integral molding process.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention. They should all be included in the scope of the technical solution for protection of the present invention.

Claims

1. A short-wave telecentric optical system, characterized in that: The optical system consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens arranged in sequence along the incident direction of light; The first lens is a positive meniscus lens with its convex surface facing the object plane; the second lens is a negative meniscus lens with its concave surface facing the object plane; the third lens is a positive meniscus lens with its concave surface facing the object plane; the fourth lens is a positive meniscus lens with its concave surface facing the object plane; the fifth lens is a double concave negative lens; the sixth lens is a double convex positive lens; the seventh lens is a negative meniscus lens with its concave surface facing the object plane; the eighth lens is a positive meniscus lens with its concave surface facing the object plane; the ninth lens is a double concave negative lens; and the tenth lens is a double convex positive lens. The focal length of the optical system is f, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, and the tenth lens are f1, f2, f3, f4, f5, f6, f7, f8, f9, and f10, respectively, wherein f1, f2, f3, f4, f5, f6, f7, f8, f9, and f10 satisfy the following ratio to f: -5 <f1 / f<0;0<f2 / f<5;-5<f3 / f<0;-5<f4 / f<0;0<f5 / f<5;-5<f6 / f<0;0<f7 / f<5;-5<f8 / f<0;0<f9 / f<5;-5<f10 / f<0。 2. The short-wave telecentric optical system according to claim 1, characterized in that: The first lens, the fourth lens, the sixth lens, the eighth lens and the tenth lens are made of silicon single crystal; the third lens, the fifth lens, the seventh lens and the ninth lens are made of chalcogenide glass; and the second lens is made of germanium single crystal.

3. The short-wave telecentric optical system according to claim 1, characterized in that: The air gap between the first lens and the second lens is 27.77 mm; the air gap between the second lens and the third lens is 1.05 mm; the air gap between the third lens and the fourth lens is 1.25 mm; the air gap between the fourth lens and the fifth lens is 89.39 mm; the air gap between the fifth lens and the sixth lens is 1.16 mm; the air gap between the sixth lens and the seventh lens is 1.61 mm; the air gap between the seventh lens and the eighth lens is 72.86 mm; the air gap between the eighth lens and the ninth lens is 27.78 mm; and the air gap between the ninth lens and the tenth lens is 1.53 mm.

4. The short-wave telecentric optical system according to claim 1, characterized in that: An aperture is provided between the tenth lens and the image plane, and the air gap between the tenth lens and the aperture is: 8.81mm; the air gap between the aperture and the image plane is: 20mm.

5. The short-wave telecentric optical system according to claim 1, characterized in that: The object-side surface of the second lens, the image-side surface of the fourth lens, the image-side surface of the fifth lens, the object-side surface of the sixth lens, the object-side surface of the seventh lens, the object-side surface of the eighth lens, and the object-side surface of the tenth lens are aspherical surfaces, and the aspherical curve equation is expressed as follows: Among them, Z represents the position along the optical axis; r represents the height in the vertical direction relative to the optical axis; c is the paraxial curvature of the aspheric surface; k is the cone constant; α4, α6, α8... represent the aspheric coefficients.

6. A method for operating a short-wave telecentric optical system, using the short-wave telecentric optical system according to any one of claims 1 to 5, characterized in that: When light is incident, the light path enters the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, eighth lens, ninth lens, tenth lens, and aperture in sequence, and finally forms an image on the image plane.

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