Short-wave telecentric optical system and imaging method thereof

Abstract

The invention relates to a short-wave telecentric optical system and an imaging method thereof. The optical system is composed 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 which are sequentially arranged in the light incidence direction. The invention relates to a large relative aperture limited yoke object space telecentric system which is matched with a refrigeration type short wave infrared detector 640 * 512 at 15 microns. The large-relative-aperture system is high in energy concentration ratio, and the refrigeration type short wave detector works in a low-temperature environment, is high in signal-to-noise ratio and has higher detail resolution. The telecentric optical path system has wide application in the fields of precision measurement, optical metrology instruments and the like, especially in occasions requiring high-precision measurement.

Description

Technical Field

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

[0002] Since the object-side principal rays of the object-side telecentric system are parallel to the optical axis, when the object moves forward and backward, the principal rays of the imaging beam at the same point on the object do not change with the position of the object, which can eliminate the error caused by inaccurate focusing, which is very important for precision measurement systems that use imaging principles. Telecentric lenses can be used in precision parts detection, non-contact optical measurement, semiconductor detection and other fields.

[0003] The working band of short-wave infrared is between 0.9um and 2.5um, which is between visible light and medium- and long-wave infrared, and can provide information beyond visible light, medium-wave infrared, and long-wave infrared. Currently, the working band of the mainstream short-wave infrared lens on the market is between 0.9um and 1.7um, while the cooling short-wave infrared system with a working band of 1.8um to 2.5um is relatively rare. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides a short-wave telecentric optical system and an imaging method thereof. The lens has a working band between 2um and 2.5um, has a large relative aperture, can collect more target signal energy, and the system matches a refrigerated short-wave infrared detector, which works in a low-temperature environment, has a high signal-to-noise ratio, and has a higher detail resolution. The object-side telecentricity can eliminate the error caused by inaccurate focusing. The system adopts a combination design of three infrared materials, and the lens has a simple optical structure, good processability, and is easy to process and assemble.

[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 lens 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 with 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] Further, 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:

[0012]

[0013] Among them, Z represents the position in the direction of 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 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, a tenth lens, and an aperture, and finally forms an image on an image plane.

[0015] Compared with the prior art, the present invention has the following beneficial effects: the use of a secondary imaging structure can reduce the aperture of each lens of the system, lighten the weight of the lens, and reduce the volume of the lens. The structure consists of ten lenses, reasonably distributes the focal length and combines the use of even-order aspheric surfaces to balance the system aberration, so that the overall volume of the optical system is small enough and can meet the design of large relative aperture and object telecentricity. The light height is adjusted to control the relative illumination within a reasonable range to make the illumination of the imaging surface uniform; the sensitivity of each optical component is reduced by adjusting the curvature and thickness, making the lens easier to process 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 is an MTF function curve diagram of an embodiment of the present invention under a normal temperature environment;

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

[0019] Figure 4 4 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 is further described below in conjunction with 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 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.

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

[0027] In this embodiment, the focal length of the optical lens 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 with 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:

[0032]

[0033] Among them, Z represents the position in the direction of 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, α0... 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 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 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, a tenth lens, and an aperture, and finally forms an image on an image plane.

[0046] Depend on Figure 2 It can be seen that the MTF curve of the 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 working band of the lens of the present invention is 2um to 2.5um, which has high recognition, and its imaging is similar to the characteristics 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) The object-side telecentric system has its object-side principal rays parallel to the optical axis. When the object moves forward and backward, the principal rays of the imaging beam at the same object point on the object do not change with the position of the object, which can eliminate the error caused by inaccurate focusing, which is very important for precision measurement systems using the imaging principle;

[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, any technical solution disclosed in the present invention disclosed above, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range, and any technician in the field should understand that the preferred numerical range is only a numerical value with a more obvious technical effect or representative value among many implementable numerical values. Since there are too many numerical values ​​to be exhaustive, the present invention discloses some numerical values ​​to illustrate the technical solution of the present invention, and the numerical values ​​listed above should not constitute a limitation on the scope of protection of the present invention.

[0054] If the words "first", "second" and so on are used in this article 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 the components. Unless otherwise stated, the above words have no special meaning.

[0055] If the present invention discloses or involves components or structures 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 one-piece molding using a casting process) (except when it is obviously impossible to use an one-piece molding process).

[0056] In addition, the orientations or positional relationships indicated by terms such as "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", and "outside" used in any of the technical solutions disclosed in the above-mentioned 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, and therefore cannot be understood as a limitation on this patent. Unless otherwise stated, the terms used to indicate shapes used in any of the technical solutions disclosed in the above-mentioned invention include shapes that are approximate, similar, or close to them.

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

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than 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, which should 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 which are sequentially arranged along the incident direction of light.

2. The short-wave telecentric optical system according to claim 1, characterized in that: The first lens is a meniscus positive lens with the convex surface facing the object plane; the second lens is a meniscus negative lens with the concave surface facing the object plane; the third lens is a meniscus positive lens with the concave surface facing the object plane; the fourth lens is a meniscus positive lens with the 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 the concave surface facing the object plane; the eighth lens is a meniscus positive lens with the 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.

3. 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.

4. 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.

5. 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 interval between the tenth lens and the aperture is: 8.81mm; the air gap between the aperture and the image plane is: 20mm.

6. The short-wave telecentric optical system according to claim 1, characterized in that: The focal length of the optical lens 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 with 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。 7. 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: Among them, Z represents the position in the direction of 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.

8. A method for operating a short-wave telecentric optical system, using the wide-angle monitoring lens as claimed in any one of claims 1 to 7, characterized in that: When light is incident, the light path 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 in sequence, and finally forms an image on the image plane.

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