A dispersion type oblique image lens

Abstract

The application discloses a dispersion type oblique image lens and relates to the technical field of industrial cameras. An optical axis is sequentially provided with a cut-off filter, a first spherical lens with positive focal power, a second spherical lens with positive focal power, a third spherical lens with negative focal power, a fourth spherical lens with negative focal power, a fifth spherical lens with negative focal power, a diaphragm, a sixth spherical lens with positive focal power, a seventh spherical lens with positive focal power, an eighth spherical lens with negative focal power, a ninth spherical lens with positive focal power, a tenth spherical lens with positive focal power and an eleventh spherical lens with positive focal power from the object side to the image side. The mechanism of the oblique image lens for clear imaging in a certain working distance range is that different working distances correspond to different optimal working wave bands, the switching of the working wave bands is realized by replacing the cut-off filter at the front end of the lens, and the mechanism is realized by utilizing the dispersion effect and specific design of the lens. The actual product can be directly applied to the field of 3D laser detection.

Description

Technical Field

[0001] This invention relates to the field of industrial camera technology, and in particular to a dispersive oblique image lens. Background Technology

[0002] With the continuous development of 3D laser measurement technology, the lenses used in this technology are mainly of two types: oblique-image lenses and ordinary upright-image lenses. Oblique-image lenses are mainly used in applications with short working distances, while upright-image lenses are mainly used in applications with long working distances (working distance ≥ 1000mm). The logic behind this division is that the acquisition of object-side information in 3D measurement technology generally requires a large depth of field, and only oblique-image lenses can meet this requirement at short working distances. However, the depth of field of ordinary upright lenses increases with the working distance, so at long working distances, applications requiring large depth of field can be met without tilting the image.

[0003] In this application area, the working spectrum for clear imaging within the field of view is usually maintained within a narrow range, making it easy to develop applications by combining the dispersion effect of materials.

[0004] The clear imaging of oblique images under short working distance field lenses follows Scham's Law, which states that a clear image can be obtained when the extended planes of the subject plane, the image plane, and the lens plane intersect in a straight line. Summary of the Invention

[0005] The purpose of this invention is to provide a dispersive oblique image lens to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A dispersive oblique image lens, arranged along the optical axis from the object side to the image side as follows: filters coated with a cutoff film system, numbered S1 and S2 from left to right; a first spherical lens with positive optical power, numbered S3 and S4 from left to right; a second spherical lens with positive optical power, numbered S5 and S6 from left to right; a third spherical lens with negative optical power, numbered S7 and S8 from left to right; a fourth spherical lens with negative optical power, numbered S9 and S10 from left to right; and a fifth spherical lens with negative optical power, numbered S11 from left to right. S12; Aperture, numbered S13; Sixth spherical lens with positive power, surface numbers from left to right: S14 and S15; Seventh spherical lens with positive power, surface numbers from left to right: S16 and S17; Eighth spherical lens with negative power, surface numbers from left to right: S18 and S19; Ninth spherical lens with positive power, surface numbers from left to right: S20 and S21; Tenth spherical lens with positive power, surface numbers from left to right: S22 and S23; Eleventh spherical lens with positive power, surface numbers from left to right: S24 and S25.

[0008] As a further technical solution of the present invention: the filter can be replaced with a filter element coated with different cutoff film systems.

[0009] As a further technical solution of the present invention: the material parameters of the first lens are (nd, vd), the focal length is f1, and the focal length unit is mm; nd represents the refractive index of the lens material based on the wavelength of the d-line (587nm), vd represents the dispersion coefficient of the lens material, and the first lens satisfies: 1.8 < nd < 1.89; 38 < vd < 41; 81 < f1 < 85.

[0010] As a further technical solution of the present invention: the material parameters of the second lens are (nd, vd), the focal length is f2, and the unit of focal length is mm; nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The second lens satisfies: 1.71 < nd < 1.75; 46 < vd < 54; 71 < f2 < 75.

[0011] As a further technical solution of the present invention: the material parameters of the third lens are (nd, vd), the focal length is f3, and the focal length unit is mm; nd represents the refractive index of the lens material based on the wavelength of the d-line (587nm), vd represents the dispersion coefficient of the lens material, and the third lens satisfies: 1.43 < nd < 1.47; 80 < vd < 91; -35 < f3 < -31.

[0012] As a further technical solution of the present invention: the material parameters of the fifth lens are (nd, vd), the focal length is f5, and the focal length unit is mm; nd represents the refractive index of the lens material based on the wavelength of the d-line (587nm), vd represents the dispersion coefficient of the lens material, and the third lens satisfies: 1.43 < nd < 1.47; 80 < vd < 91; -28 < f5 < -24.

[0013] As a further technical solution of the present invention: the material parameters of the ninth lens are (nd, vd), the focal length is f9, and the focal length unit is mm; nd represents the refractive index of the lens material based on the wavelength of the d-line (587nm), vd represents the dispersion coefficient of the lens material, and the ninth lens satisfies: 1.5 < nd < 1.53; 62 < vd < 67; 30 < f9 < 33.

[0014] As a further technical solution of the present invention: the material parameters of the tenth lens are (nd, vd), the focal length is f10, and the focal length unit is mm; nd represents the refractive index of the lens material based on the wavelength of the d-line (587nm), vd represents the dispersion coefficient of the lens material, and the tenth lens satisfies: 1.7 < nd < 1.73; 51 < vd < 56; 32 < f10 < 36.

[0015] As a further technical solution of the present invention: the material parameters of the eleventh lens are (nd, vd), the focal length is f11, and the focal length unit is mm; nd represents the refractive index of the lens material based on the wavelength of the d-line (587nm), vd represents the dispersion coefficient of the lens material, and the eleventh lens satisfies: 1.8 < nd < 1.88; 39 < vd < 47; 19 < f10 < 23.

[0016] As a further technical solution of the present invention: when the lens is tilted for imaging, the tilt angle of the object surface is in the range of 65° to 75°, and the object distance for lens tilt imaging is in the range of 150mm to 400mm.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] This invention provides a dispersive oblique image lens that, while ensuring performance, employs a spectral focusing method to switch the working distance for different working distances. This avoids the disadvantages of vibration resistance and center offset caused by traditional focusing with moving parts, thus improving the application of oblique image lenses in the 3D field. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the lens element layout for the 12mm focal length used in this invention.

[0020] Figure 2 This is a ray tracing diagram of the oblique image at a working distance of 140mm and a main wavelength of 450nm;

[0021] Figure 3 Image of the slant modulation transfer function at a working distance of 140 mm

[0022] Figure 4 This is a ray tracing diagram of the oblique image at a working distance of 250mm and a main wavelength of 640nm;

[0023] Figure 5 Image of the oblique image modulation transfer function at a working distance of 250mm;

[0024] Figure 6 The image shows the ray tracing pattern of the oblique image at a working distance of 400mm and a main wavelength of 850nm.

[0025] Figure 7 Image of the oblique image modulation transfer function at a working distance of 400mm;

[0026] Figure 8 This is a ray tracing diagram of positive imaging at a working distance of 250mm and a dominant wavelength of 640nm;

[0027] Figure 9This is a positive imaging distortion diagram at a working distance of 250mm and a main wavelength of 640nm.

[0028] Figure 10 The modulation transfer function image is shown at a working distance of 250 mm and a main wavelength of 640 nm.

[0029] Figure 11 This is a schematic diagram of Scham's Law.

[0030] In the diagram: First spherical lens - L1, Second spherical lens - L2, Third spherical lens - L3, Fourth spherical lens - L4, Fifth spherical lens - L5, Sixth spherical lens - L6, Seventh spherical lens - L7, Eighth spherical lens - L8, Ninth spherical lens - L9, Tenth spherical lens - L10, Eleventh spherical lens - L11, Filter - L12, Aperture - L13, Protective glass - L13, Image plane - L14. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1, as Figure 1 As shown, a dispersive oblique image lens has the following arrangement along the optical axis from the object side to the image side: a filter L12 coated with a cutoff film system, numbered S1 and S2 from left to right; a first spherical lens L1 with positive optical power, numbered S3 and S4 from left to right; a second spherical lens L2 with positive optical power, numbered S5 and S6 from left to right; a third spherical lens L3 with negative optical power, numbered S7 and S8 from left to right; a fourth spherical lens L4 with negative optical power, numbered S9 and S10 from left to right; and a fifth spherical lens L5 with negative optical power, numbered S1 from left to right. 1 and S12; Aperture, numbered S13; Sixth spherical lens L6 with positive power, surface numbers from left to right: S14 and S15; Seventh spherical lens L7 with positive power, surface numbers from left to right: S16 and S17; Eighth spherical lens L8 with negative power, surface numbers from left to right: S18 and S19; Ninth spherical lens L9 with positive power, surface numbers from left to right: S20 and S21; Tenth spherical lens L11 with positive power, surface numbers from left to right: S22 and S23; Eleventh spherical lens L12 with positive power, surface numbers from left to right: S24 and S25.

[0033] Example 2, based on Example 1, has the following parameters for the first lens: material parameters (nd, vd), focal length f1 (mm); nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The first lens satisfies: 1.8 < nd < 1.89; 38 < vd < 41; 81 < f1 < 85. The second lens has the following parameters: material parameters (nd, vd), focal length f2 (mm); nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The second lens satisfies: 1.71 < nd < 1.75; 46 < vd < 54; 71 < f2 < 75. The material parameters of the third lens are (nd, vd), and the focal length is f3, in mm. nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The third lens satisfies the following conditions: 1.43 < nd < 1.47; 80 < vd < 91; -35 < f3 < -31. The material parameters of the fifth lens are (nd, vd), and the focal length is f5, in mm. nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The third lens satisfies the following conditions: 1.43 < nd < 1.47; 80 < vd < 91; -28 < f5 < -24. The material parameters of the ninth lens are (nd, vd), and the focal length is f9, in mm. nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The ninth lens satisfies the following conditions: 1.5 < nd < 1.53; 62 < vd < 67; 30 < f9 < 33. The material parameters of the tenth lens are (nd, vd), and the focal length is f10, in mm. nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The tenth lens satisfies the following conditions: 1.7 < nd < 1.73; 51 < vd < 56; 32 < f10 < 36. The material parameters of the eleventh lens are (nd, vd), and the focal length is f11, with the focal length in mm. nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The eleventh lens satisfies the following conditions: 1.8 < nd < 1.88; 39 < vd < 47; 19 < f10 < 23.

[0034] The working principle is as follows:

[0035] like Figure 1 As shown, in order to make full use of the dispersion characteristics of glass materials, conventional bonded components such as double-bonded or triple-bonded components are not used in the component layout.

[0036] See also Figure 1The structure and optical parameters of each optical element in the lens, as shown in the component layout diagram, are listed in Table 1 below. Along the direction of light propagation, number 1 indicates the first plane, and so on up to the image plane. Here, nd and vd values ​​represent the refractive index and dispersion coefficient based on the d-line at 487nm, respectively, while the units for radius of curvature and thickness are mm.

[0037] Table 1: Structure and optical parameter data of each optical element in the lens;

[0038]

[0039]

[0040] Combination Figure 11 The diagram shows the parameters of the lens at the three nodes, which satisfy Scham's Law.

[0041] Table 2: Lens parameters at three nodes;

[0042]

[0043] The lens has a fixed working aperture, and its aperture parameter cannot be adjusted. The working mechanism of the lens is described below with reference to the parameters in the table above. The lens's working distance range is 140mm to 400mm. Different working distances correspond to different working spectra: short working distances correspond to a working spectrum of 430nm-470nm (dominant wavelength 450nm), and long working distances correspond to a working spectrum of 830nm-870nm (dominant wavelength 850nm). The lens adjusts its working spectrum by changing the filter. After replacing the front of the lens with a cutoff filter for a specific working distance using a simple structure, the tilt angle of the camera's receiving plane and the lens's back focus do not need to be adjusted at that working distance. However, it is worth noting that since the lens plane and camera plane do not change when the working distance changes, the object plane angle will vary to a value between 65° and 75° depending on the working distance. This phenomenon is a natural consequence of Scherm's Law. This phenomenon is acceptable in the calibration and processing of image information for different object distances.

[0044] See Figure 2 , Figure 4 and Figure 6 The illustrations in this series show ray tracing diagrams at object distances corresponding to three typical dominant wavelengths in this invention. The camera target size used is 1 / 1.8 inch (H7.2mm × V5.3mm).

[0045] See Figure 3 , Figure 5 and Figure 7This series of illustrations shows the optical modulation transfer function (MTF) at object distances corresponding to three typical dominant wavelengths in this invention. The series of illustrations displays information from 12 field-of-view points, including the central field of view. The field of view of the oblique-image lens is not centrally symmetric, but rather about... Figure 2 (or Figure 4 or Figure 6 Since the cross-section in the image is symmetrical, more field points are needed to represent the image quality of the entire field of view.

[0046] See Figure 8 , Figure 9 and Figure 10 These are illustrations of the lens used in this invention at a working distance of 250mm and a main wavelength of 640nm. The purpose of this series of illustrations is to examine the degree of distortion correction under the same working distance and positive imaging state, and to provide correction data for distortion calibration under oblique image state. Figure 9 The astigmatism, field curvature, and distortion aberrations of the lens were corrected, with optical distortion less than 0.3% and being negative. Figure 10 The MTF indicates that the lens meets the usage requirements even when operating in positive imaging mode.

[0047] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0048] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A dispersive oblique image lens, characterized in that, The optical path, arranged from the object side to the image side, is as follows: Filters coated with a cutoff film system, surface numbers S1 and S2 from left to right; a first spherical lens with positive optical power, surface numbers S3 and S4 from left to right; a second spherical lens with positive optical power, surface numbers S5 and S6 from left to right; a third spherical lens with negative optical power, surface numbers S7 and S8 from left to right; a fourth spherical lens with negative optical power, surface numbers S9 and S10 from left to right; a fifth spherical lens with negative optical power, surface numbers S11 and S12 from left to right; an aperture stop, numbered S13; and a positive optical... The sixth spherical lens has surface numbers S14 and S15 from left to right; the seventh spherical lens has surface numbers S16 and S17 from left to right; the eighth spherical lens has surface numbers S18 and S19 from left to right; the ninth spherical lens has surface numbers S20 and S21 from left to right; the tenth spherical lens has surface numbers S22 and S23 from left to right; and the eleventh spherical lens has surface numbers S24 and S25 from left to right. The filters can be replaced with filter elements coated with different cutoff film systems.

2. A dispersive oblique image lens according to claim 1, characterized in that, The material parameters of the first lens are (nd, vd), and the focal length is f1, with the unit of focal length being mm; nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The first lens satisfies: 1.8 <nd<1.89;38<vd<41;81<f1<85。 3. A dispersive oblique image lens according to claim 1, characterized in that, The material parameters of the second lens are (nd, vd), and the focal length is f2, with the focal length in mm; nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The second lens satisfies: 1.71 <nd<1.75;46<vd<54;71<f2<75。 4. A dispersive oblique image lens according to claim 1, characterized in that, The material parameters of the third lens are (nd, vd), and the focal length is f3, with the focal length in mm; nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The third lens satisfies: 1.43 <nd<1.47;80<vd<91;-35<f3<-31。 5. A dispersive oblique image lens according to claim 1, characterized in that, The material parameters of the fifth lens are (nd, vd), and the focal length is f5, with the focal length in mm; nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The third lens satisfies: 1.43 <nd<1.47;80<vd<91;-28<f5<-24。 6. A dispersive oblique image lens according to claim 1, characterized in that, The material parameters of the ninth lens are (nd, vd), and the focal length is f9, with the focal length in mm; nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The ninth lens satisfies: 1.5 <nd<1.53;62<vd<67;30<f9<33。 7. A dispersive oblique image lens according to claim 1, characterized in that, The material parameters of the tenth lens are (nd, vd), and the focal length is f10, with the focal length in mm; nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The tenth lens satisfies: 1.7 <nd<1.73;51<vd<56;32<f10<36。 8. A dispersive oblique image lens according to claim 1, characterized in that, The material parameters of the eleventh lens are (nd, vd), and the focal length is f11, with the unit of focal length being mm; nd represents the refractive index of the lens material based on the d-line (587nm) wavelength, and vd represents the dispersion coefficient of the lens material. The eleventh lens satisfies: 1.8 <nd<1.88;39<vd<47;19<f11<23。 9. A dispersive oblique image lens according to any one of claims 1-8, characterized in that, When the lens is tilted for imaging, the tilt angle of the object surface ranges from 65° to 75°, and the object distance ranges from 150mm to 400mm.

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