Lens with large target surface and large depth of field

Abstract

The utility model discloses a large-target-surface and large-depth-of-field lens. The large-target-surface and large-depth-of-field lens is sequentially arranged from an object side to an image side along an optical axis of the lens, wherein the first lens is an aspherical plastic lens with positive focal power; the second lens is an aspheric plastic lens with negative focal power; the third lens is an aspherical plastic lens with positive focal power or an aspherical plastic lens with negative focal power; the fourth lens is an aspheric plastic lens with negative focal power; according to the lens, f is larger than or equal to 5.5 mm, TTL is smaller than or equal to 6.5 mm, IC / TTL is larger than or equal to 0.52, TTL / f is smaller than or equal to 1.05, and OBFL / TTL is larger than or equal to 0.48. According to the utility model, four aspheric plastic lenses are adopted, so that the structure is simple; different lenses are mutually combined and the focal power is reasonably distributed, so that the system has the performances of low cost, total length, large depth of field, large target surface, good resolution and the like.

Description

Technical Field

[0001] The utility model relates to the field of optical lenses, and particularly to a large image plane and large depth of field lens. Background Art

[0002] In recent years, with the continuous increase in bar code information volume, more and more image scanning technologies have replaced the previous laser bar code scanning technology. In specific situations, special scanning instruments are often required to accurately and efficiently scan and identify information. With the popularization of mobile payment, more and more occasions require code scanning operations. Therefore, the demand for a code scanning lens with a large image plane and large depth of field is becoming more and more urgent. Content of the Utility Model

[0003] The purpose of the utility model is to provide a large image plane and large depth of field lens for the deficiencies in the prior art. The lens adopts 4 aspherical plastic lenses, combines different lenses and reasonably distributes the optical power. The total length of the lens TTL≤6.5mm, the aperture F#≥5.5, and it can be matched with a high-pixel chip of 1 / 2.6 inches, having the performances of low cost, short total length, large depth of field, large image plane, good resolution, etc.

[0004] The purpose of the utility model is realized through the following technical solutions:

[0005] A large image plane and large depth of field lens is arranged in sequence from the object side to the image side along the optical axis of the lens:

[0006] A diaphragm, and the diaphragm is arranged on the object side surface of the first lens;

[0007] A first lens, and the first lens is an aspherical plastic lens with positive optical power. The object side surface of the first lens is convex, and its image side surface is concave;

[0008] A second lens, and the second lens is an aspherical plastic lens with negative optical power. The object side surface of the second lens is concave, and its image side surface is concave;

[0009] A third lens, and the third lens can be either an aspherical plastic lens with negative optical power or an aspherical plastic lens with positive optical power. The object side surface of the third lens is concave, and its image side surface is convex;

[0010] A fourth lens, and the fourth lens is an aspherical plastic lens with negative optical power. The object side surface of the fourth lens can be either concave or convex, and its image side surface can be either concave or convex;

[0011] A filter, and the filter is arranged on the image side surface of the fourth lens;

[0012] A protective glass and an image acquisition element, the protective glass being integrated on the image acquisition element, and the image acquisition element being disposed on the image side of the filter.

[0013] Furthermore, the lens further satisfies the following relationship:

[0014] f ≥ 5.5 mm,

[0015] TTL ≤ 6.5 mm,

[0016] IC / TTL ≥ 0.52,

[0017] TTL / f ≤ 1.05,

[0018] OBFL / TTL ≥ 0.48,

[0019] In the relationship, f is the total focal length of the lens, TTL is the total optical length of the lens, OBFL is the optical back focal length of the lens, IC is the full image height of the chip matched with the lens system, and the maximum can match a 1 / 2.6-inch target chip.

[0020] Furthermore, the lens satisfies the following relationship:

[0021] 0.4 ≤ f1 / f ≤ 0.5

[0022] -1.3 ≤ f2 / f ≤ -1.1,

[0023] -4.0 ≤ f3 / f ≤ 27.5,

[0024] -5.8 ≤ f4 / f ≤ -1.2,

[0025] In the relationship, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens.

[0026] Furthermore, the aperture of the lens is F#, and F# ≥ 5.5.

[0027] Furthermore, the focal lengths, refractive indices, and curvature radii of the first lens, second lens, third lens, and fourth lens respectively satisfy the following conditions:

[0028]

[0029]

[0030] Among them, f1 is the focal length of the first lens, ND1 is the refractive index of the first lens, R11 is the curvature radius of the object side surface of the first lens, and R12 is the curvature radius of the image side surface of the first lens; f2 is the focal length of the second lens, ND2 is the refractive index of the second lens, R21 is the curvature radius of the object side surface of the second lens, and R22 is the curvature radius of the image side surface of the second lens; f3 is the focal length of the third lens, ND3 is the refractive index of the third lens, R31 is the curvature radius of the object side surface of the third lens, and R32 is the curvature radius of the image side surface of the third lens; f4 is the focal length of the fourth lens, ND4 is the refractive index of the fourth lens, R41 is the curvature radius of the object side surface of the fourth lens, and R42 is the curvature radius of the image side surface of the fourth lens; among them, the "+" sign of the curvature radius indicates that the lens surface bends towards the image plane side, and the "-" sign indicates that the lens surface bends towards the object plane side.

[0031] Furthermore, the filter is made of H-K9L glass.

[0032] The beneficial effects of the present utility model are:

[0033] The lens of the present utility model adopts four lenses with specific optical powers. Through specific surface shape matching and reasonable optical power distribution, the structure of the lens is more compact. Compared with the existing lenses on the market, the focal length f≥5.5mm and the aperture F#≥5.5, which can ensure a larger depth of field range; it has the advantages of a total length ≤6.5mm, small volume, and easy integration; the maximum can match a 1 / 2.6-inch target surface chip and can match higher pixel chips; thus meeting the requirements of a large target surface and large depth of field lens.

[0034] In terms of manufacturability, four aspherical plastic lenses are adopted, with low manufacturing cost, uniform and reasonable thickness of each lens and insensitivity, easy manufacturing, and high yield. Description of the Drawings

[0035] Figure 1 It is a schematic optical structure diagram of Embodiment 1 of the present utility model;

[0036] Figure 2 It is a schematic optical path structure diagram of Embodiment 1 of the present utility model;

[0037] Figure 3 It is the field curvature curve graph and distortion curve graph of visible light 0.555μm of Embodiment 1 of the present utility model;

[0038] Figure 4 It is the Thought Focus MTF curve at 83lp / mm under visible light of Embodiment 1 of the present utility model;

[0039] Figure 5 It is a schematic optical structure diagram of Embodiment 2 of the present utility model;

[0040] Figure 6 Schematic diagram of the optical path structure for Embodiment 2 of the present utility model;

[0041] Figure 7 Field curvature curve graph and distortion curve graph of visible light at 0.555μm for Embodiment 2 of the present utility model;

[0042] Figure 8 Thought Focus MTF curve at 83 lp / mm under visible light for Embodiment 2 of the present utility model;

[0043] Reference numerals: 1 - first lens, 2 - second lens, 3 - third lens, 4 - fourth lens, 5 - filter, 6 – protective glass, 7 - image acquisition element, 8 - diaphragm. Detailed implementation manners

[0044] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. In this specification, the expressions such as first, second, and third are only used to distinguish one feature from another feature, and do not represent any limitation on the features. The shapes of spherical or aspherical surfaces are not limited to the spherical or aspherical shapes shown in the drawings. The drawings are only for illustration and are not drawn strictly to scale.

[0045] In the present utility model, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region; if the lens surface is not defined as convex, concave or flat, it means that the lens surface can be convex, concave or flat. The surface of each lens closest to the object to be photographed is called the object side surface of the lens, and the surface of each lens closest to the imaging surface is called the image side surface of the lens.

[0046] Unless otherwise defined, all terms (including technical terms and scientific terms) used in the present utility model have the same meaning as the ordinary understanding of those of ordinary skill in the art to which this application belongs. It should also be understood that terms (such as those defined in a common dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless clearly defined as such in the present utility model.

[0047] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings.

[0048] The present invention provides a large target surface and large depth of field lens. The surface of the lens adjacent to the object side is the object side surface, and the surface of the lens adjacent to the image side is the image side surface. Along the optical axis of the lens, a diaphragm 8, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a filter 5, a protective glass 6, and an image acquisition element 7 are sequentially arranged from the object side to the image side along the optical axis of the lens. The diaphragm 8 is located on the object side surface of the first lens 1; the filter 5 is arranged on the image side surface of the fourth lens 4, and the filter 5 is made of H-K9L glass. The image acquisition element 7 is arranged on the image side surface of the protective glass 6, and the protective glass 6 is integrated on the image acquisition element 7.

[0049] In the present invention, in order to make the optical system present better performance, in the design process, we should reasonably select the lens material, reasonably distribute the focal lengths of each lens, and reasonably optimize the optical system, so as to finally optimize the performance of the optical system. Usually, the existence of optical system aberrations will affect the imaging quality of the optical system. Correcting aberrations is the key to optimizing the optical system. There are many methods to correct aberrations. For example, selecting lenses with different refractive indices and large differences in Abbe numbers and using them in combination can eliminate chromatic aberration and spherical aberration to a certain extent. Reasonably distributing and optimizing the focal lengths and shapes of each lens can also correct the aberrations of the system.

[0050] In the present invention, the focal length of the first lens 1 is f1, the focal length of the second lens 2 is f2, the focal length of the third lens 3 is f3, the focal length of the fourth lens 4 is f4, the total focal length of the entire lens is f, and the ratio of the focal length of each lens to the total focal length of the lens satisfies the following conditions:

[0051] 0.4 ≤ f1 / f ≤ 0.5

[0052] -1.3 ≤ f2 / f ≤ -1.1,

[0053] -4.0 ≤ f3 / f ≤ 27.5,

[0054] -5.8 ≤ f4 / f ≤ -1.3.

[0055] In the present invention, the focal lengths, refractive indices, and curvature radii of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 respectively satisfy the following conditions:

[0056] f1 +2.7～+3.0 ND1 1.50～1.55 R11 +1.0～+1.2 R12 +3.1～+5.1 f2 -7.9～-7.2 ND2 1.60～1.68 R21 -3.6～-3.2 R22 -13.9～-9.5 f3 -24.6～+171.2 ND3 1.50～1.55 R31 -1.3～-1.0 R32 -1.5～-1.2 f4 -36.4～-7.9 ND4 1.50～1.55 R41 -85.2～-9.2 R42 +8.0～+25.5

[0057] Wherein, f1 is the focal length of the first lens 1, ND1 is the refractive index of the first lens 1, R11 is the curvature radius of the object side surface of the first lens 1, and R12 is the curvature radius of the image side surface of the first lens 1; f2 is the focal length of the second lens 2, ND2 is the refractive index of the second lens 2, R21 is the curvature radius of the object side surface of the second lens 2, and R22 is the curvature radius of the image side surface of the second lens 2; f3 is the focal length of the third lens 3, ND3 is the refractive index of the third lens 3, R31 is the curvature radius of the object side surface of the third lens 3, and R32 is the curvature radius of the image side surface of the third lens 3; f4 is the focal length of the fourth lens 4, ND4 is the refractive index of the fourth lens 4, R41 is the curvature radius of the object side surface of the fourth lens 4, and R42 is the curvature radius of the image side surface of the fourth lens 4. Among them, the "+" sign of the curvature radius indicates that the lens surface bends towards the image side, and the "-" sign indicates that the lens surface bends towards the object side.

[0058] In the present utility model, f is the total focal length of the lens; TTL is the total optical length of the lens; OBFL is the optical back focal length of the lens. The optical back focal length of the lens is defined as the distance from the point on the image side surface of the fourth lens 4 closest to the image plane to the image plane; IC is the full image height of the 1 / 2.6-inch chip matched with the lens system. They satisfy the following conditions:

[0059] f ≥ 5.5 mm,

[0060] TTL ≤ 6.5 mm,

[0061] IC / TTL ≥ 0.52,

[0062] TTL / f ≤ 1.05,

[0063] OBFL / TTL ≥ 0.48,

[0064] In the present utility model, the aperture of the lens is F#, satisfying F# ≥ 5.5; the angle of the lens is FOV, satisfying FOV ≥ 55°.

[0065] Embodiment 1

[0066] Reference Figure 1 、 Figure 2 As shown in, which are respectively the optical structure schematic diagram and the optical path structure schematic diagram of Embodiment 1 of the present invention.

[0067] In this embodiment, the field of view angle FOV = 55.1°. Defining the chief ray angle of the lens as CRA, then CRA ≤ 27°. By reasonably distributing the focal lengths and optical powers of each lens, the optical system is optimized to achieve uniform and insensitive thickness of each lens, which is easy for large-scale mass production.

[0068] The lens in this embodiment is arranged in sequence from the object side to the image side along the optical axis of the lens:

[0069] The diaphragm 8 is disposed on the object side surface of the first lens 1;

[0070] The first lens 1 is an aspherical plastic lens with positive optical power. The object side surface of the first lens 1 is convex, and its image side surface can be concave;

[0071] The second lens 2 is an aspherical plastic lens with negative optical power. The object side surface of the second lens 2 is concave, and its image side surface is concave;

[0072] The third lens 3 can be an aspherical plastic lens with negative optical power. The object side surface of the third lens 3 is concave, and its image side surface is convex;

[0073] The fourth lens 4 is an aspherical plastic lens with negative optical power. The object side surface of the fourth lens 4 is convex, and its image side surface is convex;

[0074] The filter 5 is disposed on the image side surface of the fourth lens 4;

[0075] The protective glass 6 and the image acquisition element 7. The protective glass 6 is integrated on the image acquisition element 7, and the image acquisition element 7 is disposed on the image side surface of the filter 5.

[0076] In this embodiment, the first lens 1 is an aspherical plastic lens with positive optical power. Its object side surface is convex and its image side surface is concave, forming a meniscus-shaped positive optical power lens, whose function is to quickly converge light; the second lens 2 is a high refractive index plastic aspherical lens with a refractive index greater than 1.66 and an Abbe number less than 21. Its main function is to correct the resolution so that it can match a higher pixel chip; the third lens 3 has a concave object side surface and a convex image side surface, forming a meniscus-shaped negative optical power lens. Its main function is to guide the light to expand, facilitating the realization of a larger target surface; the object side surface of the fourth lens 4 is convex and its image side surface is convex. Its main function is to control the CRA and improve the resolution.

[0077] Table 1 gives the radius of curvature R (unit: mm) of each lens, the central thickness d (unit: mm) of each lens, the refractive index (ND) of each lens, the Abbe constant (VD) of each lens, and the aspherical K value (Conic) of each lens.

[0078] Table 1

[0079]

[0080]

[0081] In Table 1, the radius of curvature R represents the degree of curvature of the lens surface. A positive value indicates that the surface is curved towards the image side, and a negative value indicates that the surface is curved towards the object side. Here, "INFINITY" represents that the surface is a plane; the central thickness D represents the central axial distance from the current surface to the next surface, the refractive index ND represents the refractive ability of the current lens material for light, and the Abbe number VD represents the dispersion characteristic of the current lens material for light; the k value represents the numerical value of the best-fit conic coefficient of the aspheric surface. 11 represents the object side surface of the first lens 1, 12 represents the image side surface of the first lens 1, and so on.

[0082] In this embodiment, the aspheric surfaces of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 can all be defined by the following equation of an even aspheric surface:

[0083]

[0084] In the formula, Z is the sagitta of the lens along the optical axis direction, k is the conic coefficient of the surface, γ is the lens height, c is the lens curvature, and A, B, C, D, E, F, G, H, I are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th order terms of the aspheric polynomial.

[0085] Table 2 gives the coefficients of each term of the aspheric surfaces of the optical surfaces of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4.

[0086] Table 2

[0087]

[0088] Reference Figure 3 As shown, the field curvature curve graph and distortion curve graph of the visible light of 0.555 μm of this lens in this embodiment are presented. Among them, in the field curvature curve graph, the vertical coordinate ASTIGMATIC FIELD CURVES represents different fields of view, and the horizontal coordinate FOCUS(MILLIMETERS) represents the field quantity (mm); it can be known from Figure 3 that the field curvature offset in the meridional direction and sagittal direction on the image plane are both controlled within ±0.03 mm, indicating that the field curvature of this lens is well corrected. Among them, in the distortion curve graph, the horizontal axis represents the F - tan(Theta) distortion (unit: %), and the vertical axis represents the semi-image height value (unit: mm). It can be known from the graph that the distortion within the full field of view of the lens is within -0.5%, indicating that the distortion is well corrected.

[0089] Reference Figure 4As shown, the Thought Focus MTF curve of the lens in this embodiment at a visible light of 0.435 - 0.656μm with a frequency of 83 lp / mm. The horizontal axis represents the defocus amount (unit: mm), and the abscissa ranges from -0.2 mm to +0.2 mm, which is relatively wide. The vertical axis represents the MTF value, from Figure 4 As can be seen from Figure 4 , the defocus amount of each field of view of the lens at a visible light of 0.435 - 0.656μm is small, and the depth of focus is wide, thus ensuring a large depth of field range.

[0090] From Figure 3 and 4 it can be seen that the field curvature, distortion, and MTF of the lens in this embodiment can all be well corrected.

[0091] In Embodiment 1, the total focal length f of the lens system is 6.2 mm, the aperture value F# is 5.5, the total length TTL of the lens is 6.5 mm, the optical back focal length OBFL of the lens is 3.17 mm, and the field of view angle DFOV of the lens matching a 1 / 2.6-inch chip is 55.1°

[0092] Embodiment 2

[0093] Referring to Figure 5 and Figure 6 shown, which are respectively the optical structure schematic diagram and the optical path structure schematic diagram of Embodiment 2.

[0094] In this embodiment, the field of view angle DFOV = 55°, and the chief ray angle of the lens is defined as CRA, then CRA ≤ 30°. By reasonably selecting the lens materials and reasonably distributing the focal lengths and optical powers of each lens, the optical system is optimized to achieve uniform and insensitive thickness of each lens, making it easy for large-scale mass production.

[0095] The lens in this embodiment is sequentially arranged along the optical axis of the lens from the object side to the image side as follows:

[0096] A diaphragm 8, and the diaphragm 8 is arranged on the object side surface of the first lens 1;

[0097] The first lens 1, and the first lens 1 is an aspherical plastic lens with a positive optical power. The object side surface of the first lens 1 is convex, and its image side surface can be concave;

[0098] The second lens 2, and the second lens 2 is an aspherical plastic lens with a negative optical power. The object side surface of the second lens 2 is concave, and its image side surface is concave;

[0099] The third lens 3, and the third lens 3 can be an aspherical plastic lens with a positive optical power. The object side surface of the third lens 3 is concave, and its image side surface is convex;

[0100] The fourth lens 4, the fourth lens 4 is an aspherical plastic lens with a negative optical power, the object side of the fourth lens 4 is concave, and its image side is concave;

[0101] A filter 5, the filter 5 is disposed on the image side of the fourth lens 4;

[0102] A protective glass 6 and an image acquisition element 7, the protective glass 6 is integrated on the image acquisition element 7, and the image acquisition element 7 is disposed on the image side of the filter 5.

[0103] In this embodiment, the first lens 1 is an aspherical plastic lens with a positive optical power, its object side is convex, and its image side is concave, that is, a meniscus positive optical power lens, and its function is to quickly converge light; the second lens 2 is a high refractive index plastic aspherical lens with a refractive index greater than 1.64 and an Abbe number less than 24. Its main function is to correct the resolution so that it can match a higher pixel chip, and the cost can be further reduced compared with Embodiment 1; the object side of the third lens 3 is concave, and its image side is convex, that is, a meniscus negative optical power lens, and its main function is to guide the light to expand, so as to achieve a larger target surface; the object side of the fourth lens 4 is concave, and its image side is concave, and its main function is to improve the resolution.

[0104] Table 1 gives the radius of curvature R (unit: mm) of each lens, the central thickness d (unit: mm) of each lens, the refractive index (ND) of each lens, the Abbe constant (VD), and the aspherical K value (Conic) of each lens.

[0105] Table 3

[0106]

[0107]

[0108] In Table 3, the radius of curvature R represents the degree of curvature of the lens surface. A positive value represents that the surface bends towards the image side, and a negative value represents that the surface bends towards the object side. Among them, "INFINITY" represents that the surface is a plane; the central thickness D represents the central axial distance from the current surface to the next surface, the refractive index ND represents the deflection ability of the current lens material to light, and the Abbe number VD represents the dispersion characteristic of the current lens material to light; the k value represents the numerical value of the best-fit conic coefficient of the aspherical surface. 11 represents the object side of the first lens 11, 12 represents the image side of the first lens 11, and so on.

[0109] In this embodiment, the aspherical surfaces of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 can all be defined by the following even-order aspherical equation:

[0110]

[0111] Wherein, Z is the sagittal height of the lens along the optical axis direction, k is the conic coefficient of the curved surface, γ is the lens height, c is the lens curvature, and A, B, C, D, E, F, G, H, I are the coefficient terms of the 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th orders of the aspheric polynomial.

[0112] Table 4 gives the coefficient terms of the aspheric surfaces of each optical surface of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4.

[0113] Table 4

[0114]

[0115] Reference Figure 7 As shown, the field curvature curve and distortion curve of the visible light of 0.555μm of the lens in this embodiment are presented. Among them, in the field curvature curve, the vertical coordinate ASTIGMATIC FIELD CURVES represents different fields of view, and the horizontal coordinate FOCUS(MILLIMETERS) represents the field quantity (mm); from Figure 7 it can be seen that the field curvature offset of the meridian direction and the sagittal direction on the image plane are both controlled within ±0.07mm, indicating that the field curvature of the lens is well corrected; in the distortion curve, the horizontal axis represents the F-tan(Theta) distortion (unit: %), and the vertical axis represents the semi-image height value (unit: mm). From the figure, it can be seen that the distortion within the full field of view of the lens is within -0.5%, indicating that the distortion is well corrected.

[0116] Reference Figure 8 As shown, the Thought Focus MTF curve of the visible light of 0.435 - 0.656μm with a frequency of 83lp / mm of the lens in this embodiment is presented. The horizontal axis represents the defocus amount (unit: mm), and the horizontal coordinate ranges from -0.2mm to +0.2mm, which is relatively wide. The vertical axis represents the MTF value. From Figure 8 it can be seen that the defocus amount of each field of view of the visible light of 0.435 - 0.656μm of the lens is small, and the depth of focus is wide, thus ensuring a large depth of field range.

[0117] From Figure 7 , [[ID=#31]] 8 it can be seen that the field curvature, distortion, and MTF of the lens in this embodiment can all be well corrected.

[0118] In this embodiment 2, the total focal length f of the lens system is 6.2mm, the aperture value F# is 5.6, the total length TTL of the lens is 6.4mm, the optical back focal length OBFL of the lens is 3.14mm, and the field of view angle DFOV of the lens matching a 1 / 2.6-inch chip is 55°.

[0119] As can be seen from the F-Tan(θ) distortion curve diagrams, field curvature curve diagrams, and MTF curve diagrams of the above various embodiments, it shows that the optical lens provided by the present invention is small in volume, has a large target surface, can achieve high imaging quality and high pixels, etc. It also has a large depth of focus, can be compatible with a larger depth of field range, and at the same time has good manufacturability and yield.

[0120] According to the disclosure of the above specification, those skilled in the art to which the present invention pertains can also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A large target surface and large depth of field lens, characterized in that: They are arranged in sequence from the object side to the image side along the lens optical axis as follows: A first lens, which is an aspherical plastic lens with a positive optical power. The object side surface of the first lens is convex, and the image side surface is concave. A second lens, which is an aspherical plastic lens with a negative optical power. The object side surface of the second lens is concave, and the image side surface is concave. A third lens, which is an aspherical plastic lens with a positive optical power or an aspherical plastic lens with a negative optical power. The object side surface of the third lens is concave, and the image side surface is convex. A fourth lens, which is an aspherical plastic lens with a negative optical power. The object side surface of the fourth lens is concave or convex, and the image side surface is concave or convex. A filter, which is arranged on the image side surface of the fourth lens. A protective glass and an image acquisition element. The protective glass is integrated on the image acquisition element, and the image acquisition element is arranged on the image side surface of the filter.

2. The large target surface and large depth of field lens according to claim 1, characterized in that: A diaphragm is also arranged from the object side to the image side along the lens optical axis, and the diaphragm is arranged on the object side surface of the first lens.

3. A large target surface and large depth of field lens according to claim 1, characterized in that: The lens satisfies the following relational expressions: 0.4 ≤ f1 / f ≤ 0.5, In the relational expression, f is the total focal length of the lens, and f1 is the focal length of the first lens.

4. A large target surface and large depth of field lens according to claim 1, characterized in that: The lens satisfies the following relational expressions: -1.3 ≤ f2 / f ≤ -1.1, In the relational expression, f is the total focal length of the lens, and f2 is the focal length of the second lens.

5. A large target surface and large depth of field lens according to claim 1, characterized in that: The lens satisfies the following relational expressions: -4.0 ≤ f3 / f ≤ 27.5, In the relational expression, f is the total focal length of the lens, and f3 is the focal length of the third lens.

6. The large target surface and large depth of field lens according to claim 1, characterized in that: The lens satisfies the following relational expressions: -5.8 ≤ f4 / f ≤ -1.2, In the relational expression, f is the total focal length of the lens, and f4 is the focal length of the fourth lens.

7. A large target surface and large depth of field lens according to claim 1, characterized in that: The value ranges of the focal lengths corresponding to the first lens, the second lens, the third lens, and the fourth lens are +2.7 to +3.0, -7.9 to -7.2, -24.6 to +171.2, and -36.4 to -7.9 respectively; among them, the "+" sign indicates that the focal length of the lens is positive, and the "-" sign indicates that the focal length of the lens is negative.

8. A large target surface and large depth of field lens according to claim 1, characterized in that: The value ranges of the refractive indices corresponding to the first lens, the second lens, the third lens, and the fourth lens are 1.50 to 1.55, 1.60 to 1.68, 1.50 to 1.55, and 1.50 to 1.55 respectively.

9. A large target surface and large depth of field lens according to claim 1, characterized in that: The value ranges of the curvature radii of the object side surfaces corresponding to the first lens, the second lens, the third lens, and the fourth lens are +1.0 to +1.2, -3.6 to -3.2, -1.3 to -1.0, and -85.2 to -9.2 respectively; among them, the "+" sign indicates that the surface of the lens bends towards the image side, and the "-" sign indicates that the surface of the lens bends towards the object side.

10. A large target surface and large depth of field lens according to claim 1, characterized in that: The value ranges of the curvature radii of the image side surfaces corresponding to the first lens, the second lens, the third lens, and the fourth lens are +3.1 to +5.1, -13.9 to -9.5, -1.5 to -1.2, and +8.0 to +25.5 respectively; among them, the "+" sign indicates that the surface of the lens bends towards the image side, and the "-" sign indicates that the surface of the lens bends towards the object side.

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