Scanning lens

Abstract

The invention provides a scanning lens. The scanning lens comprises an aperture diaphragm, a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from an object side to an image side along an optical axis, the first lens is a positive lens, the object-side surface is convex in a paraxial region, and the image-side surface is concave in a paraxial region. The second lens is a negative lens, the object side surface is a concave surface near the optical axis, and the image side surface is a convex surface near the optical axis; the third lens is a positive lens, the object side surface of the positive lens is a concave surface near the optical axis, and the image side surface of the positive lens is a convex surface near the optical axis; the fourth lens is a negative lens, the object side surface is a concave surface in a paraxial region, and the image side surface is a concave surface in a paraxial region. The scanning lens meets the requirements of high-definition imaging and high relative illumination, the total length of the lens is shortened, the production efficiency is improved, the material cost of the lens is lower, a new design framework and a brand new film system are matched, the size is small, and the mass production performance is excellent.

Description

Technical Field

[0001] The present invention relates to the field of optical equipment, and more particularly to a scanning lens. Background Art

[0002] The rapid development of information technology, the popularization of the Internet, and the widespread use of digital tools in modern society have created the code era. The emergence of the code era has made information exchange a breeze. In the code era, technology has developed rapidly, and the demand for barcode scanning lenses has gradually increased. The barcode scanning camera must have high resolution and good adaptability to the environment.

[0003] Indoor and outdoor barcode scanning cameras recognize one-dimensional / two-dimensional codes at a limited object distance. The camera must adapt to the surrounding light, humidity, temperature, object distance changes in various environments, and keep the picture clear and highly consistent with the actual one-dimensional / two-dimensional code, and recognize accurately. The camera appears as an imaging product, and its main pursuit is excellent image quality, and it must be light in size, diversified in functions, personalized in appearance and low in price. At present, the total length of conventional barcode scanning lenses is between 6 and 12 mm, and the variety is not rich enough, resulting in a limited scope of use. Based on this, the present invention provides a new scanning lens. Summary of the invention

[0004] The present invention aims at the technical problems existing in the prior art and proposes a scanning lens to supplement the types of imaging scanning lenses, so as to enrich the types of lenses and expand the scope of application.

[0005] The technical solution provided by the present invention is as follows:

[0006] A scanning lens comprises an aperture stop, a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged along an optical axis from an object side to an image side;

[0007] The first lens is a positive lens, the object side surface near the optical axis is convex, and the image side surface near the optical axis is concave;

[0008] The second lens is a negative lens, the object side surface near the optical axis is concave, and the image side surface near the optical axis is convex;

[0009] The third lens is a positive lens, which has a concave surface on the object side near the optical axis and a convex surface on the image side near the optical axis;

[0010] The fourth lens is a negative lens, and the object side surface near the optical axis is concave, and the image side surface near the optical axis is concave.

[0011] Based on the above technical solution, the present invention can also make the following improvements.

[0012] Optionally, the object-side surface radius of the first lens is R(L1S1), the image-side surface radius of the first lens is R(L1S2), the core thickness of the first lens is T(L1), and the total optical length of the lens is TTL, satisfying the following conditions:

[0013] 0.838 <R(L1S1)<1.075;

[0014] 3.542 <R(L1S2)<60.205;

[0015] 0.051 <T(L1) / TTL<0.096。

[0016] Optionally, the focal length of the second lens is f2, the focal length of the lens is f, and the following conditions are met:

[0017] -6.031 <f2 / f<-1.198。

[0018] Optionally, the combined lens focal length of the first lens and the second lens is f12, the lens focal length is f, and the following conditions are met:

[0019] 0.619 <f12 / f<0.730。

[0020] Optionally, the object-side surface radius of the third lens is R(L3S1), and the image-side surface radius of the third lens is R(L3S2), satisfying the following conditions:

[0021] -1.098 <R(L3S1)<-0.832;

[0022] -1.133 <R(L3S2)<-0.895。

[0023] Optionally, the combined lens focal length of the third lens and the fourth lens is f34, the air interval between the third lens and the fourth lens is T(L3-L4), the lens focal length is f, and the total optical length of the lens is TTL, which satisfies the following conditions:

[0024] -1.066 <f34 / f<-0.741;

[0025] 0.051 <T(L3-L4) / TTL<0.113。

[0026] The scanning lens provided by the present invention has the following beneficial effects by matching the aperture diaphragm and four lenses according to a specific surface shape and reasonable optical focal length distribution: the scanning lens reduces the total optical length of the scanning lens to within 4.2mm (miniaturization), has a large depth of field (when the object distance is 131mm, when F.NO is 6, DOF is greater than 70mm, when F.NO is 8, DOF is greater than 105mm), and is convenient for changing the object distance while still having high relative illumination (more than 60%) and high resolution (90lp / mm MTF is excellent), and the cost is lower, and other performance remains unchanged or even better. That is, the scanning lens provided by the present invention meets high-definition imaging, high relative illumination, shortens the total length of the lens (miniaturization), improves production efficiency, and has lower lens material costs. With a new design architecture and a new film system, it is lightweight and has excellent mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the structure of a scanning lens provided in the first embodiment of the present invention;

[0028] Figure 2 A schematic diagram of the MFT performance of the scanning lens provided by the first embodiment of the present invention;

[0029] Figure 3 Ray fan diagram of the scanning lens provided by the first embodiment of the present invention;

[0030] Figure 4 A schematic diagram of the ratio of the illumination at any point of the scanning lens to the maximum illumination in the field of view provided by the first embodiment of the present invention;

[0031] Figure 5 A schematic diagram of the distortion and field curvature of light at any pupil of the scanning lens provided by the first embodiment of the present invention;

[0032] Figure 6 A schematic diagram of the structure of a scanning lens provided in a second embodiment of the present invention;

[0033] Figure 7 A schematic diagram of the MFT performance of a scanning lens provided in a second embodiment of the present invention;

[0034] Figure 8 A Ray fan diagram of a scanning lens provided in a second embodiment of the present invention;

[0035] Fig. 9 A schematic diagram of the ratio of the illumination at any point of the scanning lens to the maximum illumination in the field of view provided by the second embodiment of the present invention;

[0036] Fig.10 A schematic diagram of the distortion and field curvature of light at any pupil of a scanning lens provided in a second embodiment of the present invention;

[0037] Fig.11 A schematic diagram of the structure of a scanning lens provided in a third embodiment of the present invention;

[0038] Fig.12 A schematic diagram of the MFT performance of a scanning lens provided in a third embodiment of the present invention;

[0039] Fig.13 A Ray fan diagram of a scanning lens provided in a third embodiment of the present invention;

[0040] Fig.14 A schematic diagram of the ratio of the illumination at any point of the scanning lens to the maximum illumination in the field of view provided by the third embodiment of the present invention;

[0041] Fig.15 A schematic diagram of the distortion and field curvature of light at any pupil of a scanning lens provided in a third embodiment of the present invention;

[0042] Fig.16 A schematic diagram of the structure of a scanning lens provided in a fourth embodiment of the present invention;

[0043] Fig.17 A schematic diagram of the MFT performance of a scanning lens provided in a fourth embodiment of the present invention;

[0044] Fig.18 A Ray fan diagram of a scanning lens provided in a fourth embodiment of the present invention;

[0045] Fig.19 A schematic diagram of the ratio of the illumination at any point of the scanning lens to the maximum illumination in the field of view provided by the fourth embodiment of the present invention;

[0046] Fig. 20 A schematic diagram of the distortion and field curvature of light at any pupil of a scanning lens provided in a fourth embodiment of the present invention;

[0047] Fig.21 A schematic diagram of the structure of a scanning lens provided in a fifth embodiment of the present invention;

[0048] Fig. 22 A schematic diagram of the MFT performance of a scanning lens provided in a fifth embodiment of the present invention;

[0049] Fig.23 A Ray fan diagram of a scanning lens provided in a fifth embodiment of the present invention;

[0050] Fig.24 A schematic diagram of the ratio of the illumination at any point of the scanning lens to the maximum illumination in the field of view provided in the fifth embodiment of the present invention;

[0051] Fig.25A schematic diagram of the distortion and field curvature of light at any pupil of a scanning lens provided in a fifth embodiment of the present invention;

[0052] Fig.26 A schematic diagram of the structure of a scanning lens provided in a sixth embodiment of the present invention;

[0053] Fig. 27 A schematic diagram of the MFT performance of a scanning lens provided in a sixth embodiment of the present invention;

[0054] Fig.28 A Ray fan diagram of a scanning lens provided in a sixth embodiment of the present invention;

[0055] Fig.29 A schematic diagram of the ratio of the illumination at any point of the scanning lens to the maximum illumination in the field of view provided by the sixth embodiment of the present invention;

[0056] Fig.30 A schematic diagram of the distortion and field curvature of light at any pupil of a scanning lens provided in a sixth embodiment of the present invention;

[0057] Fig.31 A schematic diagram of the structure of a scanning lens provided for a comparative example;

[0058] Fig.32 A schematic diagram of the MFT performance of a scanning lens provided for comparative example;

[0059] Fig.33 Ray fan diagram of the scanning lens provided for comparative example;

[0060] Fig.34 A schematic diagram of the ratio of the illumination at any point of the scanning lens to the maximum illumination in the field of view provided for the comparative example;

[0061] Fig.35 A schematic diagram of the distortion and field curvature of light at any pupil of a scanning lens provided for comparative example;

[0062] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0063] STO, aperture stop, L1, first lens, L2, second lens, L3, third lens, L4, fourth lens. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0065] Description of relevant characteristic parameters in the present invention:

[0066] R(L1S1) is the radius of curvature of the object surface L1S1 of the first lens;

[0067] R(L1S2) is the radius of curvature of the image-side surface L1S2 of the first lens;

[0068] R(L3S1) is the radius of curvature of the object surface L3S1 of the third lens;

[0069] T(L1) is the core thickness of the first lens (the distance from the center point of the L1S1 surface to the center point of the L1S2 surface on the central optical axis);

[0070] T(L3-L4) is the air space between the third lens and the fourth lens (the distance from the center point of the L3S2 surface to the center point of the L4S1 surface on the central optical axis);

[0071] TTL is the total optical length of the lens optical system (the distance from the center point of the L1S1 surface to the center point of the image plane on the central optical axis);

[0072] BFL is the distance from the center point of the last surface of the lens optical system to the image plane (the distance from the center point of the L4S2 surface to the center point of the image plane on the central optical axis);

[0073] f2 is the focal length of the second lens;

[0074] f12 is the focal length of the combined lens of the first lens and the second lens;

[0075] f34 is the focal length of the combined lens of the third lens and the fourth lens;

[0076] f is the focal length of the lens (focal length is a measure of the convergence or divergence of light in an optical system, referring to the distance from the optical center of the lens to the focus of light when parallel light is incident);

[0077] DFOV is the field of view angle (in optical instruments, the angle formed by the two edges of the maximum range of the image of the target object that can pass through the lens is called the field of view angle).

[0078] FNO is the value obtained by dividing the focal length by the entrance pupil diameter (FNO limits the amount of light entering the lens. The larger the FNO value, the less light enters and the darker the image; the smaller the FNO value, the more light enters and the brighter the image).

[0079] RI relative illumination is the ratio of the image edge brightness to the center brightness;

[0080] The object height (MIC) is the maximum range of the image of the measured target at the object plane that can pass through the lens;

[0081] Image height (MIC) is the maximum range of the image of the measured target on the image plane;

[0082] DOF depth of field is a space of a certain length in front of the lens (in front of and behind the focus) (when the subject is located in this space, its image on the film is exactly between the same confusion circle, and the length of this space where the subject is located is called the depth of field. In other words, for the subject in this space, the image blurriness of the image presented on the film surface is within the limited range of the allowable confusion circle, and the length of this space is the depth of field).

[0083] The present invention provides a scanning lens, such as Figure 1 As shown, the perspective lens includes 4 lenses, and the components are arranged in the following order from the object side along the optical axis to the image side: aperture STO, first lens L1, second lens L2, third lens L3, and fourth lens L4.

[0084] The first lens L1 is a positive lens, with a convex surface on the object side near the optical axis and a concave surface on the image side near the optical axis. The second lens L2 is a negative lens, with a concave surface on the object side near the optical axis and a convex surface on the image side near the optical axis. The third lens L3 is a positive lens, with a concave surface on the object side near the optical axis and a convex surface on the image side near the optical axis. The fourth lens L4 is a negative lens, with a concave surface on the object side near the optical axis and a concave surface on the image side near the optical axis.

[0085] The L1S1 surface and the L1S2 surface constitute the first lens L1, the L2S1 surface and the L2S2 surface constitute the second lens L2, the L3S1 surface and the L3S2 surface constitute the third lens L3, and the L4S1 surface and the L4S2 surface constitute the fourth lens L4.

[0086] The radius of the object side surface of the first lens L1 is R(L1S1), the radius of the image side surface of the first lens L1 is R(L1S2); the core thickness of the first lens L1 is T(L1); the total optical length of the lens is TTL, and the following conditions are met:

[0087] 0.838 <R(L1S1)<1.075;

[0088] 3.542 <R(L1S2)<60.205;

[0089] 0.051 <T(L1) / TTL<0.096。

[0090] The focal length of the second lens L2 is f2, and the focal length of the lens is f, which satisfies the following conditions:

[0091] -6.031 <f2 / f<-1.198。

[0092] The combined lens focal length of the first lens L1 and the second lens L2 is f12, and the lens focal length is f, which satisfies the following conditions:

[0093] 0.619 <f12 / f<0.730。

[0094] The object side surface radius of the third lens L3 is R(L3S1), and the image side surface radius of the third lens is R(L3S2). The following conditions are met:

[0095] -1.098 <R(L3S1)<-0.832;

[0096] -1.133 <R(L3S2)<-0.895。

[0097] The focal length of the combined lens of the third lens L3 and the fourth lens L4 is f34, the air interval between the third lens L3 and the fourth lens L4 is T(L3-L4); the focal length of the lens is f, and the total optical length of the lens is TTL. The following conditions are met:

[0098] -1.066 <f34 / f<-0.741;

[0099] 0.051 <T(L3-L4) / TTL<0.113。

[0100] Example 1

[0101] This embodiment provides a scanning lens structure such as Figure 1 As shown in the figure (shown with FNO=6), it should be noted that when FNO changes from 6 to 8, the aperture of the aperture diaphragm decreases and the amount of light passing through decreases, while the other structures of the scanning lens remain unchanged. Because the larger the FNO, the greater the depth of field, objects with a wider depth of field can be seen, and the relative brightness and high resolution are still high, ensuring the image quality.

[0102] In this embodiment, the lens data of the scanning lens are shown in the following table:

[0103]

[0104] The aspheric formula is as follows:

[0105]

[0106] Wherein, z represents the point on the aspherical surface that is h away from the optical axis, and its relative distance from the vertex tangent plane on the optical axis that is tangent to the aspherical surface, R represents the radius of curvature, h represents the distance between the point on the aspherical surface and the optical axis, k represents the cone coefficient, and Ai represents the i-th order aspherical coefficient.

[0107] The aspheric coefficients are as follows:

[0108]

[0109] The characteristic parameter values ​​of the scanning lens in this embodiment are as follows:

[0110] R(L1S1)= 0.9632 R(L3S1)= -0.9254 R(L1S2)= 10.1105 R(L3S2)= -0.9417 TTL= 4.0144 T(L1)= 0.2475 T(L3-L4)= 0.2347 f＝ 3.9275 f2＝ -7.2231 f12＝ 2.6281 f34＝ -3.3593 T(L1) / TTL= 0.0617 T(L3-L4) / TTL= 0.0585 f2 / f= -1.8391 f12 / f= 0.6692 f34 / f= -0.8553 Optical DIS(MIC)= -1.29％ TV DIS= -0.69％ DFOV(1.0F)= 58.88 BFL= 1.155 Material height (MIC) = 77.594 Image height (MIC) = 2.403 (FNO=6)RI(1.0F)= 65.56％ (FNO=6)RI(MIC)= 64.87％ (FNO=6)DOF= 78.54 (FNO=8)RI(1.0F)= 64.21％ (FNO=8)RI(MIC)= 62.24％ (FNO=8)DOF= 111.94

[0111] The above characteristic parameters are all within the following parameter ranges:

[0112] 0.838 <R(L1S1)<1.075;

[0113] 3.542 <R(L1S2)<60.205;

[0114] 0.051 <T(L1) / TTL<0.096;

[0115] -6.031 <f2 / f<-1.198;

[0116] 0.619 <f12 / f<0.730;

[0117] -1.098 <R(L3S1)<-0.832;

[0118] -1.133 <R(L3S2)<-0.895;

[0119] -1.066 <f34 / f<-0.741;

[0120] 0.051 <T(L3-L4) / TTL<0.113。

[0121] It can be seen that: DOF is large (FNO = 6, DOF70 or more; FNO = 8, DOF105 or more); RI (above 60%), MTF is high (such as Figure 2 As shown, the MTF (90lp / mm frequency) 0-1.0F of FNO=6 can reach more than 40%; the MTF (90lp / mm frequency) 0-1.0F of F.NO=8 can reach more than 25%), indicating that the resolution / clarity of each field of view is excellent.

[0122] It should be noted that the full name of the modulation transfer function MTF is Modulation Transfer Function. MTF comprehensively reflects the contrast and resolution characteristics of the lens. It is measured by instruments and can completely eliminate the influence of objective factors such as film and the influence of subjective factors of manual interpretation.

[0123] MTF is one of the best tools for quantifying the overall imaging performance of a system in terms of resolution and contrast. The higher the MTF value, the higher the resolution of the system, and the ability to deliver smaller details. MTF is a way to combine resolution and contrast into a single specification or rule. The MTF curve shows both resolution and contrast information, which makes it possible to evaluate a lens based on the needs of a specific application and can be used to compare the performance of multiple lenses.

[0124] Figure 2 This is the MTF performance diagram of the scanning lens of the first embodiment, where the meanings of the X and Y coordinates are: the horizontal axis represents different densities 0-90lp / mm; the vertical axis ranges from 0 to 100 and represents the lens performance percentage. The higher the MTF curve, the higher the lens MTF score and the better the performance. The higher the high-density (90lp / mm) MTF curve score, the stronger the lens' ability to observe small objects.

[0125] The meaning of solid and dotted lines: The solid line represents the MTF curve parallel to the diameter, called the sagittal curve; the dotted line represents the MTF curve perpendicular to the diameter, called the meridian curve. The closer the solid and dotted lines are, the closer the MTF performance of the lens in the meridian and sagittal directions is, and the better the lens performance is.

[0126] Different groups of solid / dashed lines represent fields of view with different image heights. An image height value of 0 represents the center of the lens. The larger the image height value, the farther the field of view is from the center, and the closer the MTF performance of each line is, which means that the consistency between the center and the edge of the lens is good.

[0127] Figure 3 This is a Ray fan diagram of the scanning lens of the first embodiment. The smaller the value, the better the imaging effect.

[0128] Figure 4 It is a schematic diagram of the ratio of the illumination at any point of the scanning lens of the first embodiment to the maximum illumination in the field of view; the higher the value, the better the relative illumination.

[0129] Figure 5Schematic diagram of the distortion and field curvature of light at any pupil of the scanning lens of the first embodiment. The distortion and field curvature of light at any pupil in any field of view on the wavelength defined by Wave, where the field curvature diagram on the left shows the distance from the image plane to the paraxial image plane as the field of view coordinate changes; the distortion diagram on the right shows the difference between the real image height and the ideal image height in each field of view. The closer to the center, the better the imaging effect.

[0130] Example 2

[0131] This embodiment provides a scanning lens structure such as Figure 6 As shown (including two structures of FNO=6 and FNO=8), the specific structure is generally consistent with the above-mentioned embodiment 1, and the same contents as embodiment 1 are not repeated below. The lens parameters, aspheric coefficients, characteristic parameters and corresponding technical effects are further introduced.

[0132] In this embodiment, the lens data of the scanning lens are shown in the following table:

[0133]

[0134]

[0135] The aspheric coefficients are as follows:

[0136]

[0137]

[0138] The characteristic parameter values ​​of the scanning lens in this embodiment are as follows:

[0139] R(L1S1)= 0.8415 R(L3S1)= -1.0979 R(L1S2)= 3.5422 R(L3S2)= -0.9822 TTL= 4.1353 T(L1)= 0.2135 T(L3-L4)= 0.3187 f＝ 4.0222 f2＝ -5.2340 f12＝ 2.9351 f34＝ -3.9715 T(L1) / TTL= 0.0516 T(L3-L4) / TTL= 0.0771 f2 / f= -1.3013 f12 / f= 0.7297 f34 / f= -0.9874 Optical DIS(MIC)= -0.71％ TV DIS= -0.33％ DFOV(1.0F)= 57.36 BFL= 1.077 Material height (MIC) = 75.117 Image height (MIC) = 2.419 (FNO=6)RI(1.0F)= 63.31％ (FNO=6)RI(MIC)= 61.78％ (FNO=6)DOF= 74.26 (FNO=8)RI(1.0F)= 63.30％ (FNO=8)RI(MIC)= 61.16％ (FNO=8)DOF= 105.12

[0140] The above characteristic parameters are all within the parameter range described above.

[0141] It can be seen that: DOF is large (FNO = 6, DOF70 or more; FNO = 8, DOF105 or more); RI (above 60%), MTF is high (such as Figure 7 As shown, the MTF (90lp / mm frequency) 0-1.0F of FNO=6 can reach more than 40%; the MTF (90lp / mm frequency) 0-1.0F of F.NO=8 can reach more than 25%), indicating that the resolution / clarity of each field of view is excellent.

[0142] Figure 8 The Ray fan diagram of the scanning lens of the second embodiment. The smaller the value, the better the imaging effect.

[0143] Fig. 9It is a schematic diagram of the ratio of the illumination at any point of the scanning lens of the second embodiment to the maximum illumination in the field of view; the higher the value, the better the relative illumination.

[0144] Fig.10 Schematic diagram of the distortion and field curvature of light at any pupil of the scanning lens of the second embodiment. The distortion and field curvature of light at any pupil in any field of view on the wavelength defined by Wave, where the field curvature diagram on the left shows the distance from the image plane to the paraxial image plane as the field of view coordinates change; the distortion diagram on the right shows the difference between the real image height and the ideal image height in each field of view. The closer to the center, the better the imaging effect.

[0145] Example 3

[0146] This embodiment provides a scanning lens structure such as Fig.11 As shown (including two structures of FNO=6 and FNO=8), the specific structure is generally consistent with the above-mentioned embodiment 1, and the same contents as embodiment 1 are not repeated below. The lens parameters, aspheric coefficients, characteristic parameters and corresponding technical effects are further introduced.

[0147] In this embodiment, the lens data of the scanning lens are shown in the following table:

[0148]

[0149] The aspheric coefficients are as follows:

[0150]

[0151]

[0152] The characteristic parameter values ​​of the scanning lens in this embodiment are as follows:

[0153] R(L1S1)= 0.8383 R(L3S1)= -1.0443 R(L1S2)= 5.0365 R(L3S2)= -0.9103 TTL= 4.0475 T(L1)= 0.3000 T(L3-L4)= 0.2976 f＝ 3.9155 f2＝ -4.6910 f12＝ 2.7800 f34＝ -3.8673 T(L1) / TTL= 0.0741 T(L3-L4) / TTL= 0.0735 f2 / f= -1.1981 f12 / f= 0.7100 f34 / f= -0.9877 Optical DIS(MIC)= -1.32％ TV DIS= -0.72％ DFOV(1.0F)= 58.91 BFL= 1.213 Material height (MIC) = 77.710 Image height (MIC) = 2.401 (FNO=6)RI(1.0F)= 63.74％ (FNO=6)RI(MIC)= 62.66％ (FNO=6)DOF= 79.11 (FNO=8)RI(1.0F)= 63.54％ (FNO=8)RI(MIC)= 62.68％ (FNO=8)DOF= 112.86

[0154] The above characteristic parameters are all within the parameter range described above.

[0155] It can be seen that: DOF is large (FNO = 6, DOF70 or more; FNO = 8, DOF105 or more); RI (above 60%), MTF is high (such as Fig.12 As shown, the MTF (90lp / mm frequency) 0-1.0F of FNO=6 can reach more than 40%; the MTF (90lp / mm frequency) 0-1.0F of F.NO=8 can reach more than 25%), indicating that the resolution / clarity of each field of view is excellent.

[0156] Fig.13 The Ray fan diagram of the scanning lens of the third embodiment. The smaller the value, the better the imaging effect.

[0157] Fig.14 It is a schematic diagram of the ratio of the illumination at any point of the scanning lens of the third embodiment to the maximum illumination in the field of view; the higher the value, the better the relative illumination.

[0158] Fig.15 Schematic diagram of the distortion and field curvature of light at any pupil of the scanning lens of the third embodiment. The distortion and field curvature of light at any pupil in any field of view on the wavelength defined by Wave, where the field curvature diagram on the left shows the distance from the image plane to the paraxial image plane as the field of view coordinate changes; the distortion diagram on the right shows the difference between the real image height and the ideal image height in each field of view. The closer to the center, the better the imaging effect.

[0159] Example 4

[0160] This embodiment provides a scanning lens structure such as Fig.16 The specific structure shown (including two structures of FNO=4.9 and FNO=8) is generally consistent with the above-mentioned embodiment 1, and the same contents as embodiment 1 are not repeated below. The lens parameters, aspheric coefficients, characteristic parameters and corresponding technical effects are further introduced.

[0161] In this embodiment, the lens data of the scanning lens are shown in the following table:

[0162]

[0163]

[0164] The aspheric coefficients are as follows:

[0165]

[0166] The characteristic parameter values ​​of the scanning lens in this embodiment are as follows:

[0167] R(L1S1)= 0.8383 R(L3S1)= -1.0443 R(L1S2)= 5.0365 R(L3S2)= -0.9103 TTL= 4.0475 T(L1)= 0.3000 T(L3-L4)= 0.2976 f＝ 3.9155 f2＝ -4.6910 f12＝ 2.7800 f34＝ -3.8673 T(L1) / TTL= 0.0741 T(L3-L4) / TTL= 0.0735 f2 / f= -1.1981 f12 / f= 0.7100 f34 / f= -0.9877 Optical DIS(MIC)= -1.32％ TV DIS= -0.72％ DFOV(1.0F)= 58.91 BFL= 1.213 Material height (MIC) = 77.710 Image height (MIC) = 2.401 (FNO=6)RI(1.0F)= 63.74％ (FNO=6)RI(MIC)= 62.66％ (FNO=6)DOF= 79.11 (FNO=8)RI(1.0F)= 63.54％ (FNO=8)RI(MIC)= 62.68％ (FNO=8)DOF= 112.86

[0168] The above characteristic parameters are all within the parameter range described above.

[0169] It can be seen that: DOF is large (FNO = 4.9, DOF above 70; FNO = 8, DOF above 105); RI (above 60%), MTF is high (such as Fig.17 As shown, the MTF (90lp / mm frequency) 0-1.0F of FNO=4.9 can reach more than 40%; the MTF (90lp / mm frequency) 0-1.0F of F.NO=8 can reach more than 25%), indicating that the resolution / clarity of each field of view is excellent.

[0170] Fig.18This is a Ray fan diagram of the scanning lens of the fourth embodiment. The smaller the value, the better the imaging effect.

[0171] Fig.19 Schematic diagram of the ratio of the illumination at any point of the scanning lens of the fourth embodiment to the maximum illumination in the field of view; the higher the value, the better the relative illumination.

[0172] Fig. 20 Schematic diagram of the distortion and field curvature of light at any pupil of the scanning lens of the fourth embodiment. The distortion and field curvature of light at any pupil in any field of view on the wavelength defined by Wave, where the field curvature diagram on the left shows the curve of the distance from the image plane to the paraxial image plane changing with the field of view coordinates; the distortion diagram on the right shows the difference between the real image height and the ideal image height in each field of view, and the closer to the center, the better the imaging effect.

[0173] Example 5

[0174] This embodiment provides a scanning lens structure such as Fig.16 The specific structure shown (including two structures of FNO=5.2 and FNO=8) is generally consistent with the above-mentioned embodiment 1, and the same contents as embodiment 1 are not repeated below. The lens parameters, aspheric coefficients, characteristic parameters and corresponding technical effects are further introduced.

[0175] In this embodiment, the lens data of the scanning lens are shown in the following table:

[0176]

[0177]

[0178] The aspheric coefficients are as follows:

[0179]

[0180] The characteristic parameter values ​​of the scanning lens in this embodiment are as follows:

[0181] R(L1S1)= 1.0749 R(L3S1)= -1.0272 R(L1S2)= 60.2042 R(L3S2)= -1.1327 TTL= 4.0100 T(L1)= 0.3594 T(L3-L4)= 0.2075 f＝ 3.8740 f2＝ -6.4690 f12＝ 2.7121 f34＝ -4.1277 T(L1) / TTL= 0.0896 T(L3-L4) / TTL= 0.0518 f2 / f= -1.6699 f12 / f= 0.7001 f34 / f= -1.0655 Optical DIS(MIC)= 1.69％ TV DIS= -0.11％ DFOV(1.0F)= 58.93 BFL= 1.330 Material height (MIC) = 77.796 Image height (MIC) = 2.404 (FNO=6)RI(1.0F)= 64.11％ (FNO=5.2)RI(MIC)= 61.93％ (FNO=6)DOF= 81.14 (FNO=8)RI(1.0F)= 63.89％ (FNO=8)RI(MIC)= 61.88％ (FNO=8)DOF= 116.15

[0182] The above characteristic parameters are all within the parameter range described above.

[0183] It can be seen that: DOF is large (FNO = 5.2, DOF70 or more; FNO = 8, DOF105 or more); RI (above 60%), MTF is high (such as Fig. 22 As shown, the MTF (90lp / mm frequency) 0-1.0F of FNO=5.2 can reach more than 40%; the MTF (90lp / mm frequency) 0-1.0F of F.NO=8 can reach more than 25%), indicating that the resolution / clarity of each field of view is excellent.

[0184] Fig.23 This is a Ray fan diagram of the scanning lens of the fifth embodiment. The smaller the value, the better the imaging effect.

[0185] Fig.24 This is a schematic diagram of the ratio of the illumination at any point of the scanning lens of the fifth embodiment to the maximum illumination in the field of view; the higher the value, the better the relative illumination.

[0186] Fig.25 Schematic diagram of the distortion and field curvature of light at any pupil of the scanning lens of the fifth embodiment. The distortion and field curvature of light at any pupil in any field of view on the wavelength defined by Wave, where the field curvature diagram on the left shows the distance from the image plane to the paraxial image plane as the field of view coordinate changes; the distortion diagram on the right shows the difference between the real image height and the ideal image height in each field of view. The closer to the center, the better the imaging effect.

[0187] Example 6

[0188] This embodiment provides a scanning lens structure such as Fig.16 The specific structure shown (including two structures of FNO=4.3 and FNO=8) is generally consistent with the above-mentioned embodiment 1, and the same contents as embodiment 1 are not repeated below. The lens parameters, aspheric coefficients, characteristic parameters and corresponding technical effects are further introduced.

[0189] In this embodiment, the lens data of the scanning lens are shown in the following table:

[0190]

[0191] The aspheric coefficients are as follows:

[0192]

[0193]

[0194] The characteristic parameter values ​​of the scanning lens in this embodiment are as follows:

[0195] R(L1S1)= 0.8691 R(L3S1)= -0.8321 R(L1S2)= 3.5741 R(L3S2)= -0.9607 TTL= 4.1255 T(L1)= 0.3922 T(L3-L4)= 0.4660 f＝ 3.9291 f2＝ -23.6960 f12＝ 2.4354 f34＝ -2.9124 T(L1) / TTL= 0.0951 T(L3-L4) / TTL= 0.1130 f2 / f= -6.0309 f12 / f= 0.6198 f34 / f= -0.7412 Optical DIS(MIC)= -1.40％ TV DIS= -0.37％ DFOV(1.0F)= 58.90 BFL= 1.219 Material height (MIC) = 77.686 Image height (MIC) = 2.402 (FNO=6)RI(1.0F)= 65.23％ (FNO=4.3)RI(MIC)= 64.34％ (FNO=6)DOF= 78.46 (FNO=8)RI(1.0F)= 63.04％ (FNO=8)RI(MIC)= 64.02％ (FNO=8)DOF= 111.82

[0196] The above characteristic parameters are all within the parameter range described above.

[0197] It can be seen that: DOF is large (FNO = 4.3, DOF70 or more; FNO = 8, DOF105 or more); RI (more than 60%), MTF is high (such as Fig. 27As shown, the MTF (90lp / mm frequency) 0-1.0F of FNO=4.3 can reach more than 40%; the MTF (90lp / mm frequency) 0-1.0F of F.NO=8 can reach more than 25%), indicating that the resolution / clarity of each field of view is excellent.

[0198] Fig.28 This is a Ray fan diagram of the scanning lens of the sixth embodiment. The smaller the value, the better the imaging effect.

[0199] Fig.29 Schematic diagram of the ratio of the illumination at any point of the scanning lens of the sixth embodiment to the maximum illumination in the field of view; the higher the value, the better the relative illumination.

[0200] Fig.30 Schematic diagram of the distortion and field curvature of light at any pupil of the scanning lens of the sixth embodiment. The distortion and field curvature of light at any pupil in any field of view on the wavelength defined by Wave, where the field curvature diagram on the left shows the distance from the image plane to the paraxial image plane as the field of view coordinate changes; the distortion diagram on the right shows the difference between the real image height and the ideal image height in each field of view, and the closer to the center, the better the imaging effect.

[0201] Comparative Example

[0202] The structure of the scanning lens provided in this comparative example is as follows Fig.31 As shown (including two structures of FNO=6 and FNO=8).

[0203] In this comparative example, the lens data of the scanning lens are shown in the following table:

[0204]

[0205]

[0206] The aspheric coefficients are as follows:

[0207]

[0208] In this comparative example, the characteristic parameter values ​​of the scanning lens are as follows:

[0209] R(L1S1)= 1.1425 R(L3S1)= -1.4396 R(L1S2)= -463.3303 R(L3S2)= -1.1973 TTL= 4.4161 T(L1)= 0.4325 T(L3-L4)= 0.5065 f＝ 4.1005 f2＝ -4.8784 f12＝ 3.2584 f34＝ -5.4075 T(L1) / TTL= 0.0979 T(L3-L4) / TTL= 0.1147 f2 / f= -1.1897 f12 / f= 0.7946 f34 / f= -1.3187 Optical DIS(MIC)= 1.43％ TV DIS= 1.07％ DFOV(1.0F)= 55.60 BFL= 1.209 Material height (MIC) = 69.129 Image height (MIC) = 2.307 (FNO=6)RI(1.0F)= 53.80％ (FNO=6)RI(MIC)= 42.31％ (FNO=6)DOF= 59.99 (FNO=8)RI(1.0F)= 49.29％ (FNO=8)RI(MIC)= 36.91％ (FNO=8)DOF= 83.22

[0210] The above characteristic parameters are not within the following parameter ranges:

[0211] 0.838 <R(L1S1)<1.075;

[0212] 3.542 <R(L1S2)<60.205;

[0213] 0.051 <T(L1) / TTL<0.096;

[0214] -6.031 <f2 / f<-1.198;

[0215] 0.619 <f12 / f<0.730;

[0216] -1.098 <R(L3S1)<-0.832;

[0217] -1.133 <R(L3S2)<-0.895;

[0218] -1.066 <f34 / f<-0.741;

[0219] 0.051 <T(L3-L4) / TTL<0.113。

[0220] It can be seen that: DOF is small (FNO = 6, DOF below 70; FNO = 8, DOF below 105); RI is low (below 60%), MTF is low (such as Fig.32 As shown, the MTF (90lp / mm frequency) 0.6-1.0F of FNO=6 cannot reach more than 40%; the MTF (90lp / mm frequency) 0.8-1.0F of F.NO=8 cannot reach more than 25%), which means that compared with the above embodiments, the resolution / clarity of each field of view is poor.

[0221] Fig.33 Ray fan diagram of the scanning lens provided for the comparative example. The smaller the value, the better the imaging effect. Compared with the above embodiment, the imaging effect of the comparative example is worse than that of the embodiment.

[0222] Fig.34 A schematic diagram of the ratio of the illumination at any point of the scanning lens to the maximum illumination in the field of view provided for the comparative example; the higher the value, the better the relative illumination. Compared with the above embodiment, the value of this comparative example is lower and the relative illumination is worse.

[0223] Fig.35 Schematic diagram of the distortion and field curvature of light at any pupil of the scanning lens provided for the comparative example. The distortion and field curvature of light at any pupil in any field of view on the wavelength defined by Wave, where the field curvature diagram on the left shows the curve of the distance from the image plane to the paraxial image plane changing with the field of view coordinates; the distortion diagram on the right shows the difference between the real image height and the ideal image height of each field of view. The closer to the center, the better the imaging effect. However, compared with the above embodiment, the center deviation of this comparative example is larger.

[0224] In summary, the scanning lens provided by the embodiment of the present invention has the following beneficial effects: the scanning lens reduces the total optical length of the scanning lens to within 4.2mm (miniaturization), has a large depth of field, is convenient for changing the object distance, and still has high relative illumination (more than 60%) and high resolution, and has a lower cost, and other performance remains unchanged or even better. That is, the scanning lens meets high-definition imaging, high relative illumination, shortens the total length of the lens (miniaturization), improves production efficiency, has lower lens material costs, is equipped with a new design architecture and a new film system, is lightweight, and has excellent mass production.

[0225] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0226] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A scanning lens, characterized in that: It includes an aperture stop, a first lens, a second lens, a third lens and a fourth lens which are arranged in sequence from the object side along the optical axis to the image side; The first lens is a positive lens, the object side surface near the optical axis is convex, and the image side surface near the optical axis is concave; The second lens is a negative lens, the object side surface near the optical axis is concave, and the image side surface near the optical axis is convex; The third lens is a positive lens, which has a concave surface on the object side near the optical axis and a convex surface on the image side near the optical axis; The fourth lens is a negative lens, and the object side surface near the optical axis is concave, and the image side surface near the optical axis is concave.

2. The scanning lens according to claim 1, characterized in that: The object-side surface radius of the first lens is R(L1S1), the image-side surface radius of the first lens is R(L1S2), the core thickness of the first lens is T(L1), and the total optical length of the lens is TTL, which satisfies the following conditions: 0.838 <R(L1S1)<1.075; 3.542 <R(L1S2)<60.205; 0.051 <T(L1) / TTL<0.096。 3. The scanning lens according to claim 1, characterized in that: The focal length of the second lens is f2, and the focal length of the lens is f, which satisfies the following conditions: -6.031 <f2 / f<-1.198。 4. The scanning lens according to claim 1, characterized in that: The combined lens focal length of the first lens and the second lens is f12, and the lens focal length is f, which satisfies the following conditions: 0.619 <f12 / f<0.730。 5. The scanning lens according to claim 1, characterized in that: The object-side surface radius of the third lens is R(L3S1), and the image-side surface radius of the third lens is R(L3S2), which satisfies the following conditions: -1.098 <R(L3S1)<-0.832; -1.133 <R(L3S2)<-0.895。 6. The scanning lens according to claim 1, characterized in that: The focal length of the combined lens of the third lens and the fourth lens is f34, the air interval between the third lens and the fourth lens is T(L3-L4), the focal length of the lens is f, and the total optical length of the lens is TTL, which satisfies the following conditions: -1.066 <f34 / f<-0.741; 0.051 <T(L3-L4) / TTL<0.113。

Images