An optical system

Abstract

The application provides an optical system, comprising: a first imaging unit, comprising, in sequence from an object side to an image side along an optical axis: a first lens configured as a meniscus negative lens; a second lens; a third lens mutually adhered to the second imaging second lens and forming a positive lens; a diaphragm; a fourth lens; a fifth lens mutually adhered to the second imaging fourth lens and forming a positive lens; and a sixth lens configured as a biconvex positive lens; wherein the second imaging first imaging unit is suitable for imaging an image of an object surface, and the focal length f1 of the second imaging first lens, the focal length f2 of the second imaging second lens, the focal length f3 of the second imaging third lens, the focal length f4 of the second imaging fourth lens, the focal length f5 of the second imaging fifth lens, the focal length f6 of the second imaging sixth lens and the focal length f of the second imaging optical system satisfy: -1.75 < f1 / f < -1.55, -2.45 < f2 / f < 0.75, -0.85 < f3 / f < 0.75, -0.95 < f4 / f < -0.35, 0.35 < f5 / f < 0.75, and 2.25 < f6 / f < 5.45; and the object side numerical aperture NA of the optical system and the focal length f of the optical system satisfy: 0.5 < NA / f < 1.

Description

Technical Field

[0001] This invention relates to the field of optical imaging, and in particular to an optical system. Background Technology

[0002] Through holes and blind holes are common engineering structures widely used in precision manufacturing, aerospace, and other critical fields. In recent years, with increasingly stringent technical requirements, the market demand for non-destructive testing of ultra-deep fine holes with ultra-high aspect ratios (depth / diameter > 30) has been growing. Visual endoscopy, as a mature non-contact inspection technology, has attracted widespread attention due to its advantages such as compact and flexible systems, stable imaging, and intuitive results. However, existing small-aperture endoscopes (outer diameter ≤ 4 mm) have low object-space resolution, generally below 9 line pairs / mm, making it difficult to accurately identify minute defects (such as scratches and pinholes) on the inner wall of small holes. This limitation seriously affects the effective control of the processing quality of micro-channels and poses new challenges to advanced manufacturing. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide an optical system for accurately identifying minute defects (such as scratches, pinholes, etc.) on the inner wall of a small hole.

[0004] As a first aspect of the present invention, an optical system is provided, the optical system comprising:

[0005] The first imaging unit comprises: arranged sequentially along the optical axis from the object side to the image side:

[0006] The first lens is a meniscus negative lens;

[0007] Second lens;

[0008] The third lens is attached to the second lens to form a positive lens;

[0009] Aperture;

[0010] Fourth lens;

[0011] The fifth lens, together with the fourth lens mentioned above, forms a positive lens;

[0012] The sixth lens is a biconvex positive lens;

[0013] The first imaging unit is suitable for imaging an image of an object surface. The focal lengths f1 of the first lens, f2 of the second lens, f3 of the third lens, f4 of the fourth lens, f5 of the fifth lens, f6 of the sixth lens, and the focal length f of the optical system satisfy the following relationship:

[0014] -1.75 <f1 / f<-1.55,-2.45<f2 / f<0.75,-0.85<f3 / f<0.75,-0.95<f4 / f<-0.35,0.35<f5 / f<0.75,2.25<f6 / f<5.45;

[0015] The object-side numerical aperture NA of the aforementioned optical system satisfies the following relationship with the focal length f of the aforementioned optical system:

[0016] .

[0017] According to an embodiment of the present invention, the total optical length of the first imaging unit described above is... The total optical length of the above optical system The following relationship exists between the focal length f of the aforementioned optical system and the focal length f:

[0018] .

[0019] According to embodiments of the present invention, the refractive index of the first lens, the refractive index of the second lens, the refractive index of the third lens, the refractive index of the fourth lens, and the refractive index of the sixth lens are all greater than or equal to 1.5, and the refractive index of the fifth lens is less than or equal to 1.5; and / or

[0020] The Abbe constants of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all greater than or equal to 50.

[0021] According to embodiments of the present invention, the effective optical diameter of the optical system described above is... Numerical aperture of the object The following conditions must be met: ; and / or

[0022] The outer diameter of the aforementioned optical system is less than or equal to 2.5 mm;

[0023] The optical magnification PMAG, object-side numerical aperture NA, and focal length f of the optical system described above satisfy the following relationship:

[0024] .

[0025] According to an embodiment of the present invention, the imaging area ImaH of the optical system described above satisfies the following relationship with the focal length f of the optical system: ; and / or

[0026] The focal length f and the total optical length of the aforementioned optical system satisfy:

[0027] .

[0028] Embodiments of the present invention further include:

[0029] N second imaging units are disposed on the image side of the first imaging unit, where N is an integer greater than or equal to 1;

[0030] When n=1, the first second imaging unit is suitable for imaging the image obtained by the first imaging unit described above;

[0031] When 1 < n ≤ N, the nth second imaging unit is suitable for imaging the image obtained by the (n-1)th second imaging unit.

[0032] According to an embodiment of the present invention, the nth second imaging unit includes:

[0033] The seventh lens is a biconvex positive lens;

[0034] The eighth lens is a biconcave negative lens;

[0035] The ninth lens is a biconvex positive lens, and it is attached to the eighth lens mentioned above to form a positive lens;

[0036] The tenth lens is a biconvex positive lens;

[0037] The eleventh lens is a biconcave negative lens, and together with the aforementioned tenth lens, they are attached to each other to form a positive lens;

[0038] The twelfth lens is a biconvex positive lens.

[0039] According to embodiments of the present invention, the focal length f7 of the seventh lens, the focal length f8 of the eighth lens, the focal length f9 of the ninth lens, and the focal length f of the tenth lens are... 10 The focal length f of the eleventh lens mentioned above 11 The focal length f of the aforementioned twelfth lens 12 The following relationship exists between the focal length f of the aforementioned optical system and the focal length f:

[0040] 1.25 <f7 / f<1.95,-0.55<f8 / f<-0.25,0.45<f9 / f<0.75,0.45<f 10 / f<0.85, -0.55 <f 11 / f<-0.25, 1.25 <f 12 / f<1.95.

[0041] According to an embodiment of the present invention, the total optical length of the second imaging unit described above The total optical length of the above optical system The following relationship exists between the focal length f of the aforementioned optical system and the focal length f:

[0042] .

[0043] According to embodiments of the present invention, the refractive indices of the seventh lens, the eighth lens, the eleventh lens, and the twelfth lens are all greater than or equal to 1.5, and the refractive indices of the ninth lens and the tenth lens are all less than or equal to 1.5.

[0044] The Abbe constants of the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, and the twelfth lens are all greater than or equal to 50.

[0045] According to an embodiment of the present invention, by defining the proportional relationship between the focal lengths of the first lens L1 to the sixth lens L6 in the first imaging unit and the focal length of the optical system, the optical power of each lens is rationally distributed in the system, thereby realizing the object-side numerical aperture. With system focal length The optimal match, This enables the optical system to achieve a resolution of ≤9 micrometers in the object plane, allowing for clear identification of minute defects on the inner wall of the aperture. Attached Figure Description

[0046] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0047] Figure 1 A schematic diagram of a first imaging unit of an optical system provided according to an embodiment of the present invention is shown.

[0048] Figure 2 A schematic diagram of a second imaging unit of an optical system provided according to an embodiment of the present invention is shown.

[0049] Figure 3 This is a full-field optical modulation transfer function diagram of the optical system of Embodiment 1 of the present invention.

[0050] Figure 4 This is the full field-of-view relative illumination diagram of the optical system of Embodiment 1 of the present invention.

[0051] Figure 5 A schematic diagram of a first imaging unit of an optical system provided according to another embodiment of the present invention is shown.

[0052] Figure 6 A schematic diagram of a second imaging unit of an optical system provided according to another embodiment of the present invention is shown.

[0053] Figure 7 This is a full-field optical modulation transfer function diagram of the optical system of Embodiment 2 of the present invention.

[0054] Figure 8 This is the full field-of-view relative illumination diagram of the optical system of Embodiment 2 of the present invention. Detailed Implementation

[0055] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0056] Figure 1 A schematic diagram of a first imaging unit of an optical system provided according to an embodiment of the present invention is shown.

[0057] like Figure 1 As shown, the optical system includes a first imaging unit and at least one second imaging unit. The first imaging unit is suitable for imaging an image of an object surface. The first imaging unit includes: a first lens L1, a second lens L2, a third lens L3, an aperture stop, a fourth lens L4, a fifth lens L5, and a sixth lens L6 arranged sequentially along the optical axis from the object side to the image side; the first lens L1 is a meniscus negative lens, the second lens L2 and the third lens L3 are attached together to form a positive lens, the fourth lens L4 and the fifth lens L5 are attached together to form a positive lens, and the sixth lens L6 is a biconvex positive lens.

[0058] The focal lengths f1 of the first lens L1, f2 of the second lens L2, f3 of the third lens L3, f4 of the fourth lens L4, f5 of the fifth lens L5, and f6 of the sixth lens L6 satisfy the following relationship with the focal length f of the optical system: -1.75 <f1 / f<-1.55,-2.45<f2 / f<0.75,-0.85<f3 / f<0.75,-0.95<f4 / f<-0.35,0.35<f5 / f<0.75,2.25<f6 / f<5.45。

[0059] According to an embodiment of the present invention, by defining the proportional relationship between the focal lengths of the first lens L1 to the sixth lens L6 in the first imaging unit and the focal length of the optical system, the optical power of each lens is rationally distributed in the system, thereby realizing the object-side numerical aperture. With system focal length The optimal match, This enables the optical system to achieve a resolution of ≤9 micrometers in the object plane, allowing for clear identification of minute defects on the inner wall of the aperture.

[0060] According to an embodiment of the present invention, the total optical length of the first imaging unit The total optical length of the optical system The following relationship exists between the focal length f of the optical system and the focal length f: .

[0061] According to an embodiment of the present invention, the refractive index of the first lens L1, the refractive index of the second lens L2, the refractive index of the third lens L3, the refractive index of the fourth lens L4, and the refractive index of the sixth lens L6 are all greater than or equal to 1.5, and the refractive index of the fifth lens L5 is less than or equal to 1.5.

[0062] According to an embodiment of the present invention, the Abbe constants of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are all greater than or equal to 50.

[0063] According to an embodiment of the present invention, the optical system further includes N second imaging units disposed on the image side of the first imaging unit, wherein, when n=1, the first second imaging unit is adapted to image the image obtained by the first imaging unit; when 1<n≤N, the nth second imaging unit is adapted to image the image obtained by the (n-1)th second imaging unit. In an embodiment of the present invention, N can be, for example, 2.

[0064] Figure 2 A schematic diagram of a second imaging unit of an optical system provided according to an embodiment of the present invention is shown.

[0065] like Figure 2 As shown, the second imaging unit includes: a seventh lens L7, an eighth lens L8, a ninth lens L9, a tenth lens L10, an eleventh lens L11, and a twelfth lens L12. The seventh lens L7 is a biconvex positive lens, the eighth lens L8 is a biconcave negative lens, the ninth lens L9 is a biconvex positive lens, the tenth lens L10 is a biconvex positive lens, the eleventh lens L11 is a biconcave negative lens, and the twelfth lens L12 is a biconvex positive lens. The eighth lens L8 and the ninth lens L9 are bonded together to form a positive lens, and the tenth lens L10 and the eleventh lens L11 are bonded together to form a positive lens.

[0066] According to an embodiment of the present invention, the focal lengths of the seventh lens L7 (f7), the eighth lens L8 (f8), the ninth lens L9 (f9), and the tenth lens L10 (f...) are... 10 The focal length f of the eleventh lens L11 11The focal length f of the twelfth lens L12 12 The following relationship is satisfied between the focal length f of the optical system and the focal length f: 1.25 <f7 / f<1.95,-0.55<f8 / f<-0.25,0.45<f9 / f<0.75,0.45<f 10 / f<0.85, -0.55 <f 11 / f<-0.25, 1.25 <f 12 / f<1.95.

[0067] According to an embodiment of the present invention, the total optical length of the second imaging unit The total optical length of the optical system The following relationship exists between the focal length f of the optical system and the focal length f of the optical system. .

[0068] According to an embodiment of the present invention, the refractive index of the seventh lens L7, the refractive index of the eighth lens L7, the refractive index of the eleventh lens L11, and the refractive index of the twelfth lens L12 are all greater than or equal to 1.5, and the refractive index of the ninth lens L9 and the refractive index of the tenth lens L10 are both less than or equal to 1.5.

[0069] According to an embodiment of the present invention, the Abbe constants of the seventh lens L7, the eighth lens L7, the ninth lens L9, the tenth lens L10, the eleventh lens L11, and the twelfth lens L12 are all greater than or equal to 50.

[0070] According to an embodiment of the present invention, the effective optical path of the optical system Numerical aperture of the object The following conditions must be met: The outer diameter of the optical system is less than or equal to 2.5 mm; the optical magnification PMAG, the object-side numerical aperture NA, and the focal length f of the optical system satisfy the following conditions: .

[0071] According to an embodiment of the present invention, the object-side numerical aperture NA of the optical system and the focal length f of the optical system satisfy the following relationship: The imaging area ImaH of the optical system and the focal length f of the optical system satisfy the following relationship: The focal length f and the total optical length of the optical system. satisfy: .

[0072] Example 1

[0073] In this embodiment, the first and second imaging units of the optical system employ... Figure 1 and Figure 2In this embodiment, the number of second imaging units is two. The parameters of each lens in embodiment 1 are described below with reference to Table 1.

[0074] Table 1

[0075]

[0076] Figure 3 This is a full-field optical modulation transfer function diagram of the optical system of Embodiment 1 of the present invention.

[0077] like Figure 3 As shown in the figure, different lines represent optical modulation transfer function curves for different fields of view. The full-field optical modulation transfer function value is higher than 0.3 at 100 lp / mm, indicating that the optical system of Embodiment 1 of the present invention can retain more high-frequency spatial information, thereby achieving higher image resolution and detail representation.

[0078] Figure 4 This is the full field-of-view relative illumination diagram of the optical system of Embodiment 1 of the present invention.

[0079] like Figure 4 As shown, the optical system has a relative illuminance close to 1 across the entire field of view, resulting in good image brightness and uniform illuminance distribution.

[0080] Example 2

[0081] Figure 5 A schematic diagram of a first imaging unit of an optical system provided according to another embodiment of the present invention is shown.

[0082] Figure 6 A schematic diagram of a second imaging unit of an optical system provided according to another embodiment of the present invention is shown.

[0083] like Figure 6 and Figure 7 As shown, the first imaging unit and the second imaging unit of the optical system in this embodiment respectively employ... Figure 6 and Figure 7 In this embodiment, the number of second imaging units is also two.

[0084] The parameters of each lens in Example 2 are described below with reference to Table 2.

[0085] Table 2

[0086]

[0087] Figure 7 This is a full-field optical modulation transfer function diagram of the optical system of Embodiment 2 of the present invention.

[0088] Figure 7 The middle line represents the optical modulation transfer function curves for different fields of view. For example... Figure 8 As shown, the full-field optical modulation transfer function value of the optical system in Example 2 is higher than 0.3 at 100 lp / mm, indicating that the system can retain more high-frequency spatial information, thereby achieving higher image resolution and detail.

[0089] Figure 8 This is the full field-of-view relative illumination diagram of the optical system of Embodiment 2 of the present invention.

[0090] like Figure 8 As shown, the optical system of Example 2 has a relative illuminance close to 1 across the entire field of view, exhibiting good image brightness and uniform illuminance distribution.

[0091] The optical system of this invention exhibits excellent imaging quality. The MTF value of the optical system across the entire field of view is higher than 0.3 at 100 lp / mm, and the object-side resolution is ≤9 μm. The optical system of this invention also provides uniform imaging illumination. The relative illumination across the entire field of view is ≥95.5%, demonstrating excellent brightness consistency.

[0092] According to embodiments of the present invention, a first imaging unit collects object plane information, and multiple second imaging units are used for relay imaging to extend the working length. Because the first imaging unit possesses micrometer-level resolution and the second imaging units possess near-diffraction-limited imaging quality, the invention possesses the ability to accurately identify minute defects. The various components of the optical system cooperate to eliminate optical aberrations, increase the overall optical length, control the optical aperture and light direction, and compensate for image plane thermal drift. These effects are achieved through the precise coordination of the pupils.

[0093] The optical system of this invention features a telecentric image design. The telecentricity of the optical system across the entire field of view is ≤0.1°, maintaining high imaging quality throughout the field of view, making it suitable for high-precision industrial inspection scenarios. The optical system of this invention also features a thermal differential design. Image plane drift is ≤0.05mm within a temperature range of -40 to 100℃. The optical system of this invention also features a high yield design. The entire optical system uses common low-refractive-index glass materials, and all optical surfaces are designed with spherical glass, resulting in a low incident angle and high imaging stability. The optical system of this invention features an ultra-fine outer diameter and an ultra-long image transmission distance. The outer diameter of the optical system is ≤2.5mm, and the image transmission distance is ≥160mm, meeting the requirements for inspecting the inner walls of ultra-deep small holes with a depth-to-diameter ratio ≥40. The optical system of this invention meets the design requirements of high image quality, ultra-fine outer diameter, ultra-long image transmission distance, distortion-free operation, and telecentricity, and can meet the high-precision non-contact inspection requirements within holes in key fields such as precision manufacturing.

[0094] In summary, this invention meets the design requirements of high image quality, ultra-fine outer diameter, ultra-long image transmission distance, no distortion, and telecentricity, and can meet the high-precision in-hole non-contact inspection needs of key fields such as precision manufacturing.

[0095] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of the invention is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. An optical system, characterized in that, include: The first imaging unit comprises: arranged sequentially along the optical axis from the object side to the image side: The first lens is a meniscus negative lens; Second lens; The third lens is attached to the second lens to form a positive lens; Aperture; Fourth lens; The fifth lens is attached to the fourth lens to form a positive lens; The sixth lens is a biconvex positive lens; The first imaging unit is suitable for imaging an image of an object surface. The focal lengths f1 of the first lens, f2 of the second lens, f3 of the third lens, f4 of the fourth lens, f5 of the fifth lens, f6 of the sixth lens, and the focal length f of the optical system satisfy the following relationship: -1.75 <f1 / f<-1.55,-2.45<f2 / f<0.75,-0.85<f3 / f<0.75,-0.95<f4 / f<-0.35,0.35<f5 / f<0.75,2.25<f6 / f<5.45; The object-space numerical aperture NA of the optical system satisfies the following relationship with the focal length f of the optical system: 。 2. The optical system according to claim 1, characterized in that, Total optical length of the first imaging unit The total optical length of the optical system The following relationship exists between the focal length f of the optical system and the focal length f of the optical system: 。 3. The optical system according to claim 1, characterized in that, The refractive indexes of the first lens, the second lens, the third lens, the fourth lens, and the sixth lens are all greater than or equal to 1.5, and the refractive index of the fifth lens is less than or equal to 1.5; and / or The Abbe constants of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all greater than or equal to 50.

4. The optical system according to any one of claims 1 to 3, characterized in that, The optical system's effective optical diameter Numerical aperture of the object The following conditions must be met: ; and / or The outer diameter of the optical system is less than or equal to 2.5 mm; The optical magnification PMAG, the object-space numerical aperture NA, and the focal length f of the optical system satisfy the following: 。 5. The optical system according to claim 1, characterized in that, The imaging area ImaH of the optical system and the focal length f of the optical system satisfy the following: ; and / or The focal length f and the total optical length of the optical system satisfy: 。 6. The optical system according to any one of claims 1 to 5, characterized in that, Also includes: N second imaging units are disposed on the image side of the first imaging unit, where N is an integer greater than or equal to 1; When n=1, the first second imaging unit is suitable for imaging the image obtained by the first imaging unit; When 1 < n ≤ N, the nth second imaging unit is suitable for imaging the image obtained by the (n-1)th second imaging unit.

7. The optical system according to any one of claims 1 to 6, characterized in that, The nth second imaging unit includes: The seventh lens is a biconvex positive lens; The eighth lens is a biconcave negative lens; The ninth lens is a biconvex positive lens, and it is attached to the eighth lens to form a positive lens; The tenth lens is a biconvex positive lens; The eleventh lens is a biconcave negative lens, and together with the tenth lens, they are attached to each other to form a positive lens; The twelfth lens is a biconvex positive lens.

8. The optical system according to claim 7, characterized in that, The focal length f7 of the seventh lens, the focal length f8 of the eighth lens, the focal length f9 of the ninth lens, and the focal length f of the tenth lens 10 The focal length f of the eleventh lens 11 The focal length f of the twelfth lens 12 The following relationship exists between the focal length f of the optical system and the focal length f: 1.25<f7 / f<1.95,-0.55<f8 / f<-0.25,0.45<f9 / f<0.75,0.45<f 10 / f<0.85,-0.55<f 11 / f<-0.25,1.25<f 12 / f<1.95。 9. The optical system according to claim 7 or 8, characterized in that, The total optical length of the second imaging unit The total optical length of the optical system The following relationship exists between the focal length f of the optical system and the focal length f of the optical system: 。 10. The optical system according to any one of claims 7 to 9, characterized in that, The refractive index of the seventh lens, the refractive index of the eighth lens, the refractive index of the eleventh lens, and the refractive index of the twelfth lens are all greater than or equal to 1.5, while the refractive index of the ninth lens and the refractive index of the tenth lens are both less than or equal to 1.

5. The Abbe constants of the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, and the twelfth lens are all greater than or equal to 50.

Images