A scanning lens

Abstract

The present invention provides a scanning lens comprising an aperture stop, a first lens, a second lens, a third lens, and a fourth lens, arranged sequentially along the optical axis from the object side to the image side. The first lens 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 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 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 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. This scanning lens meets the requirements of high-definition imaging and high relative illumination, shortens the overall lens length, improves production efficiency, and reduces lens material costs. Combined with a new design architecture and a new film system, it is lightweight and has excellent mass production capabilities.

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 ubiquity of the internet, and the widespread use of digital tools in modern society have ushered in the era of barcodes. This era has made information exchange a breeze. With the rapid advancement of technology in this era, the demand for barcode scanning cameras has also steadily increased. These cameras must possess high resolution and be adaptable to the environment.

[0003] Indoor and outdoor barcode scanning cameras recognize one-dimensional / two-dimensional codes at a limited object distance. They must adapt to ambient light, humidity, temperature, and object distance in various environments, maintaining a clear image with high consistency and accurate recognition of the actual one-dimensional / two-dimensional code. Cameras, as imaging products, primarily strive for excellent image quality, a compact size, diverse functionality, a personalized appearance, and a low price. Currently, conventional barcode scanning lenses range in length from 6 to 12 mm and lack a wide variety, resulting in a limited range of applications. Therefore, the present invention provides a new scanning lens. Summary of the Invention

[0004] The present invention addresses the technical problems existing in the prior art and proposes a scanning lens to supplement the types of imaging scanning lenses, thereby enriching the types of lenses and extending the scope of use.

[0005] The technical solutions provided by the present invention are as follows:

[0006] A scanning lens comprises an aperture stop, a first lens, a second lens, a third lens and a fourth lens arranged in sequence 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, with 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 its object side surface is concave near the optical axis, and its image side surface is concave near the optical axis.

[0011] On the basis of 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 focal length of the third lens and the fourth lens is f34, the air gap 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:

[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 achieves the following beneficial effects by combining an aperture stop and four lenses according to specific surface shapes and reasonable optical power distribution: the scanning lens reduces the total optical length of the barcode scanning lens to less than 4.2mm (miniaturization), has a large depth of field (DOF greater than 70mm at an object distance of 131mm with an F.NO of 6, and greater than 105mm at an F.NO of 8), facilitates changes in object distance while maintaining high relative illumination (above 60%) and high resolution (excellent 90lp / mm MTF), and is cost-effective, while maintaining or even improving other performance characteristics. The scanning lens provided by the present invention satisfies high-definition imaging, high relative illumination, shortens the total lens length (miniaturization), improves production efficiency, reduces lens material costs, and, with a new design architecture and a new film system, is lightweight and highly manufacturable. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 2 A schematic diagram of the MFT performance of the scanning lens provided in 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 showing 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 Schematic diagram of light distortion and field curvature at any pupil of the scanning lens provided by the first embodiment of the present invention;

[0032] Figure 6 A schematic structural diagram 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 Ray fan diagram of the scanning lens provided by the second embodiment of the present invention;

[0035] Figure 9 A schematic diagram showing 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] Figure 10 A schematic diagram of the distortion and field curvature of light at any pupil of a scanning lens provided by a second embodiment of the present invention;

[0037] Figure 11 A schematic structural diagram of a scanning lens provided in a third embodiment of the present invention;

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

[0039] Figure 13 Ray fan diagram of the scanning lens provided by the third embodiment of the present invention;

[0040] Figure 14 A schematic diagram showing 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] Figure 15 A schematic diagram of the distortion and field curvature of light at any pupil of a scanning lens provided by a third embodiment of the present invention;

[0042] Figure 16 A schematic structural diagram of a scanning lens provided in a fourth embodiment of the present invention;

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

[0044] Figure 18 Ray fan diagram of the scanning lens provided by the fourth embodiment of the present invention;

[0045] Figure 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] Figure 20 A schematic diagram of the distortion and field curvature of light at any pupil of a scanning lens provided by a fourth embodiment of the present invention;

[0047] Figure 21 A schematic structural diagram of a scanning lens provided in a fifth embodiment of the present invention;

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

[0049] Figure 23 Ray fan diagram of the scanning lens provided by the fifth embodiment of the present invention;

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

[0051] Figure 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] Figure 26 A schematic structural diagram of a scanning lens provided in a sixth embodiment of the present invention;

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

[0054] Figure 28 Ray fan diagram of the scanning lens provided by the sixth embodiment of the present invention;

[0055] Figure 29 A schematic diagram showing 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] Figure 30 A schematic diagram of the distortion and field curvature of light at any pupil of a scanning lens provided by a sixth embodiment of the present invention;

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

[0058] Figure 32 Schematic diagram of the MFT performance of the scanning lens provided for comparative example;

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

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

[0061] Figure 35 Schematic diagram of light distortion and field curvature at any pupil of a scanning lens provided for comparative example;

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

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

[0064] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only 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 making creative efforts shall fall 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 the object surface L1S1 of the first lens element;

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

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

[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 and second lenses;

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

[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, and refers 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 object image that can pass through the lens of the optical instrument is called the field of view angle);

[0078] FNO is the value obtained by dividing the focal length by the entrance pupil diameter (FNO determines 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 target being measured at the object surface that can pass through the lens;

[0081] Image height (MIC) is the maximum range of the image of the target being measured 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 located 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, the blur of the image of the subject in this space 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. Starting from the object side along the optical axis to the image side, the components are arranged in the following order: aperture STO, first lens L1, second lens L2, third lens L3, and fourth lens L4.

[0084] The first lens element 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 element 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 element 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 element 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 object-side surface radius of the first lens L1 is R(L1S1), the image-side surface radius of the first lens L1 is R(L1S2), the core thickness of the first lens L1 is T(L1), and the total optical length of the lens is TTL, satisfying the following conditions:

[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 focal length of the first lens L1 and the second lens L2 is f12, and the focal length of the lens 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 combined focal length of the third lens L3 and the fourth lens L4 is f34, the air gap 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 (with FNO = 6), it should be noted that when FNO increases from 6 to 8, the aperture diaphragm decreases and the amount of light passing through decreases, while the other structures of the scanning lens remain unchanged. Because a larger FNO increases the depth of field, objects with a wider depth of field can be seen, while still maintaining high relative brightness and high resolution, ensuring 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] Where z represents the point on the aspheric surface that is h away from the optical axis, and its relative distance from the vertex tangent plane on the optical axis of the aspheric surface, R represents the radius of curvature, h represents the distance between the point on the aspheric surface and the optical axis, k represents the cone coefficient, and Ai represents the i-th order aspheric 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 (more than 60%), MTF is high (such as Figure 2 As shown, the MTF (90lp / mm frequency) 0-1.0F with FNO=6 can reach more than 40%; the MTF (90lp / mm frequency) 0-1.0F with F.NO=8 can reach more than 25%, indicating that the resolution / clarity of each field of view is excellent.

[0122] It's important to note that MTF (Modulation Transfer Function) comprehensively reflects the contrast and resolution characteristics of a lens. It's measured instrumentally, completely eliminating the influence of objective factors like film stock and subjective human interpretation.

[0123] MTF is one of the best tools for quantifying a system's overall imaging performance in terms of resolution and contrast. Higher MTF values ​​indicate a system with higher resolution, capable of delivering even smaller details. MTF is a method of combining resolution and contrast into a single specification or rule. An MTF curve displays both resolution and contrast information, making it suitable for evaluating lenses based on the needs of a specific application and allowing for comparison of the performance of multiple lenses.

[0124] Figure 2 This is the MTF performance graph of the scanning lens of the first embodiment. The X and Y coordinates represent the following: the horizontal axis represents different density levels (0-90 lp / mm); the vertical axis, from 0 to 100, represents the lens performance percentage. Higher MTF curves indicate higher MTF scores and better performance. Higher scores in the high-density (90 lp / mm) MTF curve indicate a better ability to observe small objects.

[0125] The solid and dashed lines represent the MTF curve parallel to the diameter, known as the sagittal curve; the dashed line represents the MTF curve perpendicular to the diameter, known as the meridional curve. The closer the solid and dashed lines are, the closer the lens's MTF performance in the meridional and sagittal directions is, and the better the lens performance.

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

[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 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; a higher value indicates better relative illumination.

[0129] Figure 5Schematic diagram of the distortion and field curvature of light at any pupil in the scanning lens of the first embodiment. This diagram shows the distortion and field curvature of light at any pupil in any field of view at a wavelength defined by Wave. The field curvature diagram on the left shows how the distance from the image plane to the paraxial image plane varies with the field of view coordinates; the distortion diagram on the right shows the difference between the actual image height and the ideal image height for 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. The same contents as embodiment 1 are not repeated here. 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 ranges described above.

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

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

[0143] Figure 9Schematic 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; a higher value indicates better relative illumination.

[0144] Figure 10 Schematic diagram of the distortion and field curvature of light at any pupil in the scanning lens of the second embodiment. This diagram shows the distortion and field curvature of light at any pupil in any field of view at a wavelength defined by Wave. The field curvature diagram on the left shows how the distance from the image plane to the paraxial image plane changes with the field of view coordinates; the distortion diagram on the right shows the difference between the actual image height and the ideal image height for 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 Figure 11 As shown (including two structures of FNO=6 and FNO=8), the specific structure is generally consistent with the above-mentioned embodiment 1. The same contents as embodiment 1 are not repeated here. 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 ranges described above.

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

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

[0157] Figure 14 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; a higher value indicates better relative illumination.

[0158] Figure 15 Schematic diagram of the distortion and field curvature of light at any pupil of the scanning lens of the third embodiment. This diagram shows the distortion and field curvature of light at any pupil in any field of view at a wavelength defined by Wave. The field curvature diagram on the left shows how the distance from the image plane to the paraxial image plane changes with the field of view coordinates; the distortion diagram on the right shows the difference between the actual image height and the ideal image height for 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 Figure 16 The specific structure shown (including two structures of FNO=4.9 and FNO=8) is generally consistent with the above-mentioned embodiment 1. The contents that are the same as those in embodiment 1 are not repeated here. 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 ranges described above.

[0169] It can be seen that: DOF is large (FNO = 4.9, DOF70 or more; FNO = 8, DOF105 or more); RI (more than 60%), MTF is high (such as Figure 17 As shown, the MTF (90lp / mm frequency) 0-1.0F with FNO=4.9 can reach more than 40%; the MTF (90lp / mm frequency) 0-1.0F with F.NO=8 can reach more than 25%, indicating that the resolution / clarity of each field of view is excellent.

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

[0171] Figure 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; a higher value indicates better relative illumination.

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

[0173] Example 5

[0174] This embodiment provides a scanning lens structure such as Figure 16 The specific structure shown (including two structures of FNO=5.2 and FNO=8) is generally consistent with the above-mentioned embodiment 1. The contents that are the same as those in embodiment 1 are not repeated here. 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 ranges described above.

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

[0184] Figure 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] Figure 24 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; a higher value indicates better relative illumination.

[0186] Figure 25 Schematic diagram of the distortion and field curvature of light at any pupil of the scanning lens of the fifth embodiment. This diagram shows the distortion and field curvature of light at any pupil in any field of view at a wavelength defined by Wave. The field curvature diagram on the left shows how the distance from the image plane to the paraxial image plane changes with the field of view coordinates; the distortion diagram on the right shows the difference between the actual image height and the ideal image height for 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 Figure 16 The specific structure shown (including two structures of FNO=4.3 and FNO=8) is generally consistent with the above-mentioned embodiment 1. The contents that are the same as those in embodiment 1 are not repeated here. 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 ranges 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 Figure 27As shown, the MTF (90lp / mm frequency) 0-1.0F with FNO=4.3 can reach more than 40%; the MTF (90lp / mm frequency) 0-1.0F with F.NO=8 can reach more than 25%, indicating that the resolution / clarity of each field of view is excellent.

[0198] Figure 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] Figure 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; a higher value indicates better relative illumination.

[0200] Figure 30 Schematic diagram of the distortion and field curvature of light at any pupil of the scanning lens of the sixth embodiment. This diagram shows the distortion and field curvature of light at any pupil in any field of view at a wavelength defined by Wave. The field curvature diagram on the left shows how the distance from the image plane to the paraxial image plane changes with the field of view coordinates; the distortion diagram on the right shows the difference between the actual image height and the ideal image height for each field of view. 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 Figure 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 Figure 32 As shown, the MTF (90lp / mm frequency) 0.6-1.0F with FNO=6 cannot reach more than 40%; the MTF (90lp / mm frequency) 0.8-1.0F with F.NO=8 cannot reach more than 25%), indicating that compared with the above embodiment, the resolution / clarity of each field of view is poor.

[0221] Figure 33 This is a 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 this comparative example is worse than that of the embodiment.

[0222] Figure 34 A schematic diagram showing the ratio of the illumination at any point of the scanning lens to the maximum illumination in the field of view provided for comparison. A higher value indicates better relative illumination. Compared to the above embodiment, this comparison example has a lower value and poorer relative illumination.

[0223] Figure 35 Schematic diagram of the distortion and field curvature of light at any pupil of a scanning lens provided for comparison. The distortion and field curvature of light at any pupil for any field of view at a wavelength defined by Wave are shown. The field curvature diagram on the left shows the distance from the image plane to the paraxial image plane as a function of the field of view coordinates; the distortion diagram on the right shows the difference between the actual image height and the ideal image height for each field of view. The closer to the center, the better the imaging effect. However, compared to the previous example, this comparison shows a larger deviation from the center.

[0224] In summary, the scanning lens provided by the embodiments of the present invention has the following beneficial effects: it reduces the total optical length of a barcode scanning lens to less than 4.2mm (miniaturization), achieves a large depth of field, facilitates variable object distance, maintains high relative illumination (over 60%) and high resolution, and is manufactured at a lower cost, while maintaining or even improving other performance characteristics. Specifically, the scanning lens achieves high-definition imaging and high relative illumination, shortens the overall lens length (miniaturization), improves production efficiency, reduces lens material costs, and, with its novel design architecture and new film system, is lightweight and highly manufacturable.

[0225] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional 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 may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

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 arranged in sequence along the optical axis from the object side 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, 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 is a negative lens, the object side surface near the optical axis is concave, and the image side surface near the optical axis is also concave; The combined focal length of the third lens and the fourth lens is f34, the air gap 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。 2. The scanning lens according to claim 1, wherein: 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, wherein: 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, wherein: 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, wherein: The object-side curved surface radius of the third lens is R(L3S1), and the image-side curved 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。

Images