A hybrid spherical and aspherical shah lens

Abstract

The application discloses a Sham lens, which realizes low distortion under the premise of ensuring high resolution. The first aspheric lens has a front aspheric surface and a rear spherical surface, and the bending directions of the two surfaces are not limited; the second positive focal length spherical lens has a front surface with a curvature radius greater than 0 and a rear surface with a curvature radius less than 0; the third negative focal length spherical lens has a front surface with an unlimited bending direction and a rear surface with a curvature radius greater than 0; the fourth positive focal length spherical lens has a front surface with a curvature radius greater than 0 and a rear surface with a curvature radius greater than 0; the stop; and the fifth positive focal length aspheric lens has a front surface with an unlimited bending direction and a rear surface with a curvature radius less than 0. The lens has reasonable focal length distribution and uses the aberration-correcting characteristics of the aspheric surface, and thus high resolution and low distortion are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, and particularly to a spherical and aspherical hybrid Schlieren lens. BACKGROUND

[0002] With the development of optical, image processing and computer technology, 3D line laser measurement technology is widely used. It uses an industrial camera to shoot corresponding image information, and processes the image in a series of ways to extract the required information, and finally achieves the purpose of measurement. 3D line laser measurement technology is a rapidly developing non-contact measurement technology, which has the advantages of good flexibility, high speed, high precision and intelligence. 3D line laser measurement technology needs a Schlieren lens to shoot a clear image of the full field of view of the target. The distortion of the Schlieren lens directly affects the difficulty of subsequent algorithm correction. The smaller the lens distortion is, the simpler the algorithm is, and the higher the measurement accuracy is. Therefore, under the premise of ensuring the resolution of the lens, low distortion is an important pursuit target of the design of the Schlieren lens. SUMMARY

[0003] The embodiment of the present application provides a spherical and aspherical hybrid Schlieren lens, which realizes low distortion under the premise of ensuring high resolution.

[0004] The embodiment of the present application provides a spherical and aspherical hybrid Schlieren lens, which realizes low distortion under the premise of ensuring high resolution.

[0005] The first aspherical lens, the front surface is aspherical, the back surface is spherical, and the bending directions of the two surfaces are not limited;

[0006] The second positive focal length spherical lens, the front surface curvature radius is greater than 0, and the back surface curvature radius is less than 0;

[0007] The third negative focal length spherical lens, the front surface bending direction is not limited, and the back surface curvature radius is greater than 0;

[0008] The fourth positive focal length spherical lens, the front surface curvature radius is greater than 0, and the back surface curvature radius is greater than 0;

[0009] The diaphragm;

[0010] The fifth positive focal length aspherical lens, the front surface bending direction is not limited, and the back surface curvature radius is less than 0;

[0011] And each lens meets the following requirements:

[0012] -0.3≤f1 / f≤1.5;

[0013] 0.4≤f2 / f≤1;

[0014] -25≤f3 / f≤0;

[0015] 1≤f4 / f≤1.8;

[0016] 0.4≤f5 / f≤1;

[0017] f is focal length of the Schlieren lens; f1 is focal length of the first aspherical lens; f2 is focal length of the second positive power spherical lens; f3 is focal length of the third negative power spherical lens; f4 is focal length of the fourth positive power spherical lens; f5 is focal length of the fifth positive power aspherical lens.

[0018] In a preferred embodiment, the front surface of the first aspherical lens and the back surface of the fifth positive power aspherical lens are both aspherical lenses, satisfying the aspherical equation:

[0019]

[0020] wherein z is surface sag, r is radial radius, c is curvature, k is conic coefficient, A, B, C, D, E, F, G, H are aspherical coefficients.

[0021] In a preferred embodiment, the imaging quality MTF of the lens is greater than 0.5 and the distortion is less than 0.01% under the full field of view.

[0022] In a preferred embodiment, the lens is arranged in a rectangular detector, and the ratio of the axial distance L from the front surface of the first aspherical lens to the image plane to the half image height R of the diagonal line of the rectangular detector on the image plane is less than or equal to 7.5. The length of the rectangular detector is H, the width is V, and the diagonal size is The half image height R of the diagonal line is D / 2.

[0023] In a preferred embodiment, a filter is arranged between the object plane and the first aspherical lens. The filter can be placed at any position between the object plane and the first aspherical lens, which can filter out the non-working light waveband, reduce stray light, and increase resolution.

[0024] The Schlieren lens formed by the embodiment of the present application is a mixed Schlieren lens of spherical and aspherical surfaces. Due to the reasonable power distribution and the use of aspherical aberration correction characteristics, the Schlieren lens with high resolution and low distortion can be designed. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a schematic diagram of the imaging principle of the Schlieren law;

[0026] Figure 2 It is a schematic diagram of the Schlieren lens with mixed spherical and aspherical surfaces according to the embodiment of the present application;

[0027] Figure 3 It is a schematic diagram of the axial distance from the front surface of the first aspherical lens to the image plane according to the embodiment of the present application;

[0028] Figure 4 A schematic diagram of a spherical and aspherical hybrid Sharm lens according to an embodiment of the present application;

[0029] Figure 5 A schematic diagram of a spherical and aspherical hybrid Sharm lens according to an embodiment of the present application;

[0030] Figure 6 A schematic diagram of a spherical and aspherical hybrid Sharm lens according to an embodiment of the present application. DETAILED DESCRIPTION

[0031] As shown in the accompanying drawings, Figure 1 According to the Sharm law, when the target plane, the lens main surface and the detector plane intersect at a line, and the intersection line is unique, the entire tilted target DOF field of view can be clearly imaged. The target plane, the lens main surface and the detector plane intersect at a line, and the intersection line is unique, which satisfies the following Sharm relationship:

[0032]

[0033] Wherein, α is the angle between the target plane and the optical axis of the lens, β is the angle between the detector plane and the optical axis of the lens, a' is the object distance of point D on the optical axis, b' is the image distance of point D on the optical axis, and b' / a' is the magnification of the lens.

[0034] According to the Sharm law described above, the specific embodiments of a spherical and aspherical hybrid Sharm lens provided by the present application will be described in detail in conjunction with the accompanying drawings. Figure 2 Figure 3

[0035] A spherical and aspherical hybrid Sharm lens provided by an embodiment of the present application is in order from the object plane 8 side to the image plane 9 side:

[0036] The first aspherical lens 1 has a front surface that is aspherical and a rear surface that is spherical, and the bending direction of the two surfaces is not limited, which is used to reduce lens distortion and astigmatism;

[0037] The second positive focal length spherical lens 2 has a front surface with a curvature radius greater than 0 and a rear surface with a curvature radius less than 0, which is used to eliminate spherical aberration and coma;

[0038] The third negative focal length spherical lens 3 has a front surface with an unrestricted bending direction and a rear surface with a curvature radius greater than 0, which is used to eliminate spherical aberration, coma and astigmatism;

[0039] The fourth positive focal length spherical lens 4 has a front surface with a curvature radius greater than 0 and a rear surface with a curvature radius greater than 0, which is used to eliminate spherical aberration, coma and astigmatism;

[0040] The diaphragm 6;​​

[0041] The fifth positive power aspherical lens 5, the front surface bending direction is not limited, the back surface radius of curvature is less than 0, is used for eliminating distortion, spherical aberration, field curvature;

[0042] And each lens meets the following requirements:

[0043] -0.3≤f1 / f≤1.5;

[0044] 0.4≤f2 / f≤1;

[0045] -25≤f3 / f≤0;

[0046] 1≤f4 / f≤1.8;

[0047] 0.4≤f5 / f≤1;

[0048] F is the focal length of the Sham lens; f1 is the focal length of the first aspherical lens 1; f2 is the focal length of the second positive power spherical lens 2; f3 is the focal length of the third negative power spherical lens 3; f4 is the focal length of the fourth positive power spherical lens 4; f5 is the focal length of the fifth positive power aspherical lens 5.

[0049] The front surface of the first aspherical lens 1 and the back surface of the fifth positive power aspherical lens 5 are all aspherical lenses, which meet the aspherical equation:

[0050]

[0051] Wherein z is the surface height, r is the radial radius, c is the curvature, k is the conic coefficient, A, B, C, D, E, F, G, H are aspherical coefficients.

[0052] Since the imaging lens has reasonable power distribution and uses aspherical aberration correction characteristics, a high-resolution, low-distortion Sham lens can be designed, and the imaging quality MTF of the lens is greater than 0.5 under the full field of view, and the distortion is less than 0.01%.

[0053] The size of the lens directly affects the size of the line laser sensor, and miniaturization is also an important design goal. When the lens is arranged in a rectangular detector, the ratio of the axial distance L from the front surface of the first aspherical lens 1 to the image plane 9 to the half image height R of the diagonal line of the rectangular detector is less than or equal to 7.5, wherein the length of the rectangular detector is H, the width is V, and the diagonal size The half image height R of the diagonal line is D / 2.

[0054] A filter 7 is arranged between the object plane 8 and the first aspherical lens 1. The filter can be placed between the object plane and the first aspherical lens, which can filter out the non-working light waveband, reduce stray light and increase resolution.

[0055] The following describes specific embodiments of the spherical and aspherical hybrid Sharm lens, one by one, the structure of the Sharm lens of the three specific embodiments Figure 2 Similar, but the specific parameters of the filter, each lens and diaphragm are different, so the optical path is different.

[0056] Example one:

[0057] The specific design parameters of the spherical and aspherical hybrid Sharm lens are shown in Table 1, wherein surface numbers 3 to 13 represent the surface of each lens from the first aspherical lens to the fifth positive focal length aspherical lens, wherein the number STOP represents the diaphragm surface; the surface number OBJ represents the object, and the surface numbers 1 and 2 represent the front surface and the rear surface of the filter respectively; the aspherical coefficients of the first aspherical lens and the fifth positive focal length aspherical lens are shown in Table 2.

[0058]

[0059]

[0060] Table 1

[0061]

[0062] Table 2

[0063] The spherical and aspherical hybrid Sharm lens designed in Example one is shown in Figure 4 The focal length of the lens f = 21.7 mm, L / R = 7.35, which can well meet the requirements of miniaturization, the angle between the target plane and the optical axis α = 37 degrees, the angle between the detector plane and the optical axis β = 15 degrees, the imaging quality MTF > 0.5 under full field of view, and the distortion is less than 0.01%. In summary, the lens of Example one has the advantages of high resolution, low distortion and miniaturization.

[0064] Example two:

[0065] The specific design parameters of the spherical and aspherical hybrid Sharm lens of this embodiment are shown in Table 3, wherein surface numbers 3 to 13 represent the surface of each lens from the first aspherical lens to the fifth positive focal length aspherical lens, wherein the number STOP represents the diaphragm surface; the surface number OBJ represents the object, and the surface numbers 1 and 2 represent the front surface and the rear surface of the filter respectively; the aspherical coefficients of the first aspherical lens and the fifth positive focal length aspherical lens are shown in Table 4.

[0066]

[0067]

[0068] Table 3

[0069]

[0070] Table 4

[0071] The spherical and aspherical hybrid Sharm lens designed in Example Two is shown in Figure 5 The lens focal length f = 21.3 mm, L / R = 7.16, which can well meet the requirements of miniaturization, the target plane and the optical axis angle α = 37 degrees, the detector plane and the optical axis angle β = 15 degrees, the imaging quality MTF > 0.5 under the full field of view, the distortion is less than 0.01%. In summary, the lens of Example Two has the advantages of high resolution, low distortion and miniaturization.

[0072] Example Three:

[0073] The specific design parameters of the spherical and aspherical hybrid Sharm lens of this example are shown in Table 5, wherein surface numbers 3 to 13 represent the surface of each lens from the first aspherical lens to the fifth positive focal length aspherical lens, wherein the number STOP represents the stop surface; the surface number OBJ represents the object, the surface numbers 1 and 2 represent the front surface and the rear surface of the filter respectively; the aspherical coefficients of the first aspherical lens and the fifth positive focal length aspherical lens are shown in Table 6.

[0074]

[0075] Table 5

[0076]

[0077] Table 6

[0078] The spherical and aspherical hybrid Sharm lens designed in Example Three is shown in Figure 6 The lens focal length f = 21.75 mm, L / R = 6.15, which can well meet the requirements of miniaturization, the target plane and the optical axis angle α = 37 degrees, the detector plane and the optical axis angle β = 15 degrees, the imaging quality MTF > 0.5 under the full field of view, the distortion is less than 0.01%. In summary, the lens of Example Two has the advantages of high resolution, low distortion and miniaturization.

[0079] The above three examples well meet the requirements of the conditions between the lenses, see Table 7

[0080]

[0081] Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A hybrid spherical and aspherical SAM lens, characterized in that: From the object plane side to the image plane side, the lenses are arranged as follows: First, an aspherical lens with an aspherical front surface and a spherical rear surface, where the curvature directions of the two surfaces are unrestricted, used to reduce lens distortion and astigmatism; Second, a positive power spherical lens with a front surface radius of curvature greater than 0 and a rear surface radius of curvature less than 0, used to eliminate spherical aberration and coma. The third negative power spherical lens has an unrestricted curvature direction on its front surface and a radius of curvature greater than 0 on its rear surface, and is used to eliminate spherical aberration, coma, and astigmatism; the fourth positive power spherical lens has a radius of curvature greater than 0 on its front surface and a radius of curvature greater than 0 on its rear surface, and is used to eliminate spherical aberration, coma, and astigmatism. Aperture; The fifth positive power aspherical lens has an unrestricted curvature direction on the front surface and a radius of curvature of less than 0 on the rear surface. It is used to eliminate distortion, spherical aberration, and field curvature. There are a total of five lenses. Furthermore, each lens must meet the following requirements: -0.3≤f1 / f≤1.5; 0.4≤f2 / f≤1; -25≤f3 / f≤0; 1≤f4 / f≤1.8; 0.4≤f5 / f≤1; f is the focal length of the Sham lens; f1 is the focal length of the first aspherical lens; f2 is the focal length of the second positive power spherical lens; f3 is the focal length of the third negative power spherical lens; f4 is the focal length of the fourth positive power spherical lens; f5 is the focal length of the fifth positive power aspherical lens; The image quality MTF under the full field of view of the lens is greater than 0.5, and the distortion is less than 0.01%; the lens is set in a rectangular detector, and the ratio of the axial distance from the front surface of the first aspherical lens to the image plane to the half-image height of the diagonal of the rectangular detector on the image plane is less than or equal to 7.

5.

2. The lens according to claim 1, characterized in that, The front surface of the first aspherical lens and the rear surface of the fifth positive power aspherical lens are both aspherical lenses, satisfying the aspherical equation: Where z is the surface elevation, r is the radial radius, c is the curvature, k is the conic coefficient, and A, B, C, D, E, F, G, and H are aspheric coefficients.

3. The lens according to claim 1, characterized in that, A filter is disposed between the object plane and the first aspherical lens.

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