High-definition, large depth-of-field, telephoto scanning lens

Abstract

This invention provides a high-definition, large depth-of-field, telephoto barcode scanning lens, belonging to the field of optical lens technology. The high-definition, large depth-of-field, telephoto barcode scanning lens, along the optical axis from the object side to the image side, comprises: a first lens, a second lens, a cemented lens composed of a third lens and a fourth lens, and a fifth lens. The first, second, third, fourth, and fifth lenses are all glass spherical lenses, and their focal lengths are positive, negative, negative, positive, and positive, respectively. This invention addresses the shortcomings of current barcode scanning lenses, such as short focal lengths resulting in low magnification, low resolution, and shallow depth of field, by providing a high-definition, large depth-of-field, telephoto barcode scanning lens.

Description

Technical Field

[0001] This invention belongs to the field of optical lens technology, specifically relating to a high-definition, large depth-of-field, telephoto barcode scanning lens. Background Technology

[0002] With the development of 5G technology and digital intelligence, barcode scanning lenses are rapidly developing in various fields; at the same time, new requirements are being placed on barcode scanning lenses. Currently, barcode scanning lenses suffer from short focal lengths resulting in low magnification, as well as low resolution and shallow depth of field, making it difficult to meet the new market demands.

[0003] Document CN 113376801 A discloses a large field of view, large depth of field, and low distortion scanning lens, comprising a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6 arranged sequentially along the optical axis from the object side to the image side. The second lens L2 and the third lens L3 form a first cemented lens group, and the fifth lens L5 and the sixth lens L6 form a second cemented lens group. The first lens L1 is a convex-concave lens with negative optical power, the second lens L2 is a biconcave lens, the third lens L3 is a biconvex lens, the fourth lens L4 is a convex-concave lens with positive optical power, the fifth lens L5 is a biconvex lens, and the sixth lens L6 is a concave-convex lens with negative optical power. Furthermore, it satisfies the following condition: FOV ≤ 160°, where FOV is the field of view angle of the lens. This lens has a larger scanning range and depth of field, provides clear imaging, low distortion, high image quality, and structural stability, and can cope with the high and low temperature application environments of industrial scanning lenses. The invention uses six lenses, and the shapes of the fourth lens L4 and the sixth lens L6 are very difficult to process, resulting in a low yield and hindering its widespread application.

[0004] Document CN 114721122 A discloses a scanning lens and a scanning lens module, belonging to the field of optical imaging technology. Along the optical axis, from the object side to the image side in sequence, it includes: a first lens with positive optical power; a second lens with optical power, whose image side is convex near the optical axis; a third lens with optical power, whose object side is convex near the optical axis; a fourth lens with optical power, whose image side is convex near the optical axis; and a fifth lens with negative optical power, whose image side is concave near the optical axis. The scanning lens satisfies the following conditional formula: 6.71 < f / EPD < 8.70. The first lens, the second lens, the third lens, the fourth lens and the fifth lens are configured in the above combination, which is beneficial to correcting the field curvature, distortion and high-order aberration of the scanning lens and improving the imaging quality of the scanning lens. When the lens satisfies the relational formula 6.71 < f / EPD < 8.70, it is beneficial for the scanning lens to obtain a larger aperture F number, making the depth of field range of the scanning lens larger and improving the accuracy of the scanning lens during scanning. The optical system provided by this invention consists of five plastic aspherical lenses, with relatively poor overall stability and reliability, and a small operating temperature range, reasonably speculated to be 0 - 40°C; moreover, the introduction of the aspherical surface significantly reduces its assembly tolerance, and a plastic lens barrel is required to meet the accuracy requirements. Generally, five sets of aspherical lens molding dies and one set of plastic lens barrel molding dies are required, with high initial costs; in addition, this scanning lens is a short-focus optical system.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-definition, large-depth-of-field, long-focus scanning lens in view of the deficiencies of the current scanning lens, such as short focal length resulting in small magnification, low resolution and small depth of field.

[0007] To solve the above technical problem, the technical solution adopted by the present invention is:

[0008] A high-definition, large-depth-of-field, long-focus scanning lens, which sequentially includes from the object side to the image side along the optical axis: a first lens, a second lens, a cemented lens composed of a third lens and a fourth lens, and a fifth lens. The first lens, the second lens, the third lens, the fourth lens and the fifth lens are all glass spherical lenses, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are positive, negative, negative, positive and positive in sequence.

[0009] The present invention uses 5 lenses, which is derived from the double-Gauss structure, inherits its advantages, and at the same time optimizes the combination of the lens materials, all using glass materials, and scientifically distributes the optical power to achieve the lens effects of high definition, large depth of field and long focus.

[0010] Preferably, the third lens is made of a material with high refractive index and low dispersion.

[0011] In this invention, the third lens is made of a high refractive index material with a refractive index of 1.84 or higher and a low dispersion material with Vd=53, which is beneficial for correcting spherical aberration and chromatic aberration. Combined with the optical power distribution, the scientific combination reduces the sensitivity of the optical system and achieves 4MP high pixel count.

[0012] Preferably, the second lens is a thick meniscus lens, with a convex surface near the object side and a concave surface near the image side.

[0013] In this invention, by optimizing the combination of spherical lens materials and selecting the material of the third lens, and by adopting a thick meniscus shape for the second lens, the introduction of field curvature is reduced, so that although the lens is a telephoto lens, it is not sensitive to changes in object distance and the resolution decays slowly, thereby ensuring a large depth of field effect.

[0014] Preferably, the focal length of the high-definition, large depth-of-field, telephoto scanning lens is 12mm.

[0015] Preferably, an aperture stop is provided between the second lens and the third lens, and the aperture stop is made of SOMA sheet.

[0016] Preferably, the first lens, the second lens, the cemented lens composed of the third lens and the fourth lens, and the fifth lens are sequentially arranged inside the lens barrel. A spacer coaxial with the optical system of the scanning lens is provided inside the lens barrel. Gaskets are provided between the first lens and the second lens, and between the fourth lens and the second lens. The gaskets are made of metal.

[0017] This invention performs anti-glare treatment on the lens barrel and spacer, such as oxidizing to black, increasing surface roughness, or setting anti-glare textures, to achieve ghosting-free and glare-free effects, ensuring the cleanliness of images captured in different environments; the spacer, which is coaxially set with the optical system in the lens barrel, gives the lens significant assembly stability and good anti-glare performance.

[0018] With the continuous development and maturation of barcode scanning technology and the expansion of its market applications, the scanning technology itself is also constantly evolving. Mainstream barcode scanning equipment has been upgraded from one-dimensional laser technology to two-dimensional imaging technology. Furthermore, the types of scanners have evolved from the simplest handheld scanners to a variety of styles, including fixed and embedded scanners, each with specialized applications. Currently, barcode scanners on the market cannot adequately meet the needs of lightweight industrial applications. Some industry professionals believe that existing scanning lenses still have the following shortcomings: scanning lenses primarily using glass spherical lenses are expensive and have poor image quality. Because they all use glass spherical lenses, their aberration control is not ideal, resulting in poor image quality. For example, the lens of a 500,000-pixel barcode scanner has an on-axis MTF value of 39%@701p / mm and an off-axis MTF value of 28%@701p / mm. The lens is sufficient for detecting ordinary 13mil retail barcodes, but it cannot be used for detecting high-resolution barcodes, such as 3mil or even higher resolutions like 2mil (Shi Hui, Huang Xiaoyan, Zhang Yanke. Design and selection of multiple schemes for a barcode scanning imaging lens [J]. Optical Instruments, 2014, 36(5). 420-425). To address this, barcode scanning lenses generally incorporate relatively inexpensive plastic lenses for structural optimization, but the optimization effect is very limited.

[0019] Furthermore, increasing the depth of field in optical imaging systems has always been a research hotspot in applied optics. For barcode scanning lenses, depth of field is one of their most important parameters. Depth of field refers to the object-space depth range corresponding to the formation of a sharp image on a fixed image plane; in other words, it's the maximum distance an object can move forward or backward in object space while ensuring a sharp image. The depth of field range of conventional optical imaging systems is limited. When the depth of field of an imaging system is increased through some method, it is called a large depth-of-field imaging system, possessing large depth-of-field characteristics. For barcode scanning lenses, the longer the depth of field, the better. The greater the depth of field, the wider the range that the scanner can "see," which is more beneficial for decoding. In practical tests, this translates to a shorter average decoding time and a wider decodeable range. However, existing barcode scanning lenses generally do not yet achieve the characteristics of a large depth of field.

[0020] Furthermore, the optical lens is one of the most important factors determining the quality of image formation. Various aberrations in the lens can degrade image quality and affect image sharpness. Optical design optimizes these aberrations to eliminate their impact on image quality. The double-Gaussian lens is a classic optical imaging lens that has undergone continuous improvement since its invention, and this structure is still widely used in many applications. Meanwhile, high-definition applications have penetrated all industries, and as a crucial component of barcode scanning systems, the quality of the barcode lens directly determines its ability to decode accurately.

[0021] In existing technologies, document CN212111952U discloses an F-Theta scanning lens and optical lens assembly, whose scanning lens has a field of view of only ±20°, resulting in a small scanning range and slow speed. Furthermore, other existing scanning lenses generally employ eight or more lenses or use aspherical technology, making the lens structure relatively complex. They also cannot simultaneously achieve clear imaging over a wide object distance range. Additionally, the presence of aspherical lenses makes the lens tolerance sensitive, its high and low temperature performance unstable, and its durability low, increasing the overall cost and manufacturing complexity. As for the existing technologies cited in the background section, such as documents CN 113376801 A and CN 114721122 A, these technologies all use scanning lenses with different lens combinations and have achieved certain technical results. However, they also have certain shortcomings and require further exploration and improvement.

[0022] Therefore, it is imperative to provide a high-definition, large depth-of-field, telephoto scanning lens.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. The scanning lens of this invention uses 5 lenses, derived from the double Gauss structure, inheriting its advantages. At the same time, in terms of material selection, the third lens uses a high refractive index and low dispersion material, preferably a high refractive index material with a refractive index of 1.84 or higher, and a low dispersion material with Vd=53, which is beneficial for correcting spherical aberration and chromatic aberration, and is scientifically matched with optical power to reduce the sensitivity of the optical system, achieve 4MP high pixel, and realize high-definition scanning image.

[0025] 2. Barcode scanning lenses often require a large working distance, which necessitates a large depth of field. This invention optimizes the combination of spherical lens materials, preferably using glass, and employs a high-refractive-index, low-dispersion material for the third lens. Furthermore, the design of the second lens's shape reduces the introduction of field curvature. As a result, although this invention is a telephoto lens (focal length of 12mm), it is insensitive to object distance and exhibits slow resolution decay, thus ensuring a large depth of field.

[0026] 3. Under different light sources and brightness conditions, lenses often produce significant ghosting and flare, interfering with the image quality of the scanned image and leading to recognition failure. This invention, based on prior estimation, uses targeted adjustments to the R-values ​​of the second and fifth lenses to transform the light beam reflected secondary to the image plane from a beam converging into a spot on the image plane into a beam diverging on the image plane, greatly reducing the concentration of ghosting spots. Combined with the light-reducing treatment of the lens barrel and spacers, a ghost-free and flare-free effect is achieved, ensuring the cleanliness of images captured in different environments.

[0027] 4. The scanning lens of this invention uses an all-glass lens to form an optical system, which has high reliability and dependability, and can operate at temperatures ranging from -30°C to +80°C. The initial investment cost is relatively low, which is conducive to its widespread application.

[0028] 5. The present invention tests the spherical aberration, distortion, chromatic aberration and MTF of the scanning lens. The results show that the scanning lens of the present invention has high image cleanliness and high resolution. The relative chromatic aberration of f, d and c light is within 2μm of the chromatic aberration ... Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 : A schematic diagram of the structure of the high-definition, large depth-of-field, telephoto scanning lens of this invention;

[0031] Figure 2 : A spherical aberration curve of the scanning lens in an embodiment of the present invention;

[0032] Figure 3 : Distortion curve diagram of the scanning lens in an embodiment of the present invention;

[0033] Figure 4 : A chromatic aberration curve of the scanning lens in an embodiment of the present invention;

[0034] Figure 5 MTF curve of the scanning lens in this embodiment of the invention;

[0035] Among them, 1-first lens, 2-second lens, 3-cemented lens, 4-fifth lens, 5-lens tube, 6-cap, 7-first gasket, 8-second gasket, 9-aperture. Detailed Implementation

[0036] To better understand the present invention, the following embodiments further illustrate its content, but the scope of protection of the present invention is not limited to the embodiments described below. Numerous specific details are set forth in the following description to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0037] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0038] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0039] For ease of description, the left side of the scanning lens is defined as the scene side (hereinafter also referred to as the object side), and the surface of the lens facing the object side can be called the object side surface. The object side surface can also be understood as the surface of the lens close to the object side. The right side of the scanning lens is defined as the image side (hereinafter also referred to as the image side), and the surface of the lens facing the image side can be called the image side surface. The image side surface can also be understood as the surface of the lens close to the image side.

[0040] See Figure 1 The scanning lens of this embodiment of the invention contains 5 lenses, which, from the object side to the image side, are sequentially arranged along the optical axis as follows: a first lens 1, a second lens 2, a cemented lens 3 composed of a third lens and a fourth lens, and a fifth lens 4. The first lens 1, the second lens 2, the third lens, the fourth lens, and the fifth lens 4 are all glass spherical lenses, and the focal lengths of the first lens 1, the second lens 2, the third lens, the fourth lens, and the fifth lens 4 are positive, negative, negative, positive, and positive, respectively.

[0041] This invention employs five lenses, derived from the double Gauss structure, inheriting its advantages. At the same time, by optimizing the combination of lens materials, all of which are made of glass, and scientifically allocating the optical power, it achieves high-definition, large depth-of-field, and telephoto lens effects.

[0042] In one specific embodiment of the present invention, the third lens is made of a material with high refractive index and low dispersion.

[0043] In this invention, the third lens is made of a high refractive index material with a refractive index of 1.84 or higher and a low dispersion material with Vd=53, which is beneficial for correcting spherical aberration and chromatic aberration. Combined with the optical power distribution, the scientific combination reduces the sensitivity of the optical system and achieves 4MP high pixel count.

[0044] In one specific embodiment of the present invention, the second lens 2 is a thick meniscus lens, with a convex surface near the object side and a concave surface near the image side.

[0045] In this invention, by optimizing the combination of spherical lens materials and selecting the material of the third lens, and by adopting a thick meniscus shape for the second lens 2, the introduction of field curvature is reduced, so that although the lens is a telephoto lens, it is not sensitive to changes in object distance and the resolution decays slowly, thereby ensuring the effect of a large depth of field.

[0046] In one specific embodiment of the present invention, the high-definition, large depth-of-field, telephoto scanning lens has a focal length of 12mm, achieving the characteristics of telephoto.

[0047] In one specific embodiment of the present invention, an aperture stop 9 is provided between the second lens 2 and the third lens, and the aperture stop 9 is made of SOMA sheet.

[0048] In one specific embodiment of the present invention, a first lens 1, a second lens 2, a cemented lens 3 composed of a third lens and a fourth lens, and a fifth lens 4 are sequentially disposed inside a lens barrel 5; a spacer coaxial with the optical system of the barcode scanning lens is disposed inside the lens barrel 5.

[0049] In this invention, the lens barrel 5 and the spacer are treated with a matte finish, such as by oxidizing to black, increasing surface roughness, or setting matte textures, which helps to achieve ghosting-free and glare-free effects and ensures the cleanliness of images captured in different environments. The spacer, which is coaxially set with the optical system in the lens barrel 5, gives the lens significant assembly stability and good anti-glare performance.

[0050] In one specific embodiment of the present invention, pressure caps 6 are also provided at both ends of the lens barrel 5 to stabilize the lens.

[0051] In one specific embodiment of the present invention, a first spacer 7 is provided between the first lens 1 and the second lens 2, and a second spacer 8 is provided between the fourth lens and the second lens 2; both the first spacer 7 and the second spacer 8 are made of metal.

[0052] In one specific embodiment of the present invention, by adjusting the radius of curvature R of the second lens 2 and the fifth lens 4, specifically, the radius of curvature of the object side of the second lens 2 is 6.0 mm and the radius of curvature of the image side is 3.9 mm, the radius of curvature of the object side of the fifth lens 4 is -6.1 mm and the radius of curvature of the image side is 10.3 mm, the light beam reflected to the image surface is changed from a beam that converges into a spot on the image surface to a beam that diverges on the image surface, greatly reducing the degree of ghosting and achieving a ghost-free and glare-free effect, ensuring the cleanliness of the captured image in different environments.

[0053] The relevant parameters of each lens in the barcode scanning lens provided in this embodiment are shown in the table below.

[0054] Face number face shape radius / mm Thickness / mm Refractive index surface STANDARD infinity infinity 1 STANDARD 9.3 1.56 1.755 2 STANDARD 133.6 0.38 3 STANDARD 6.0 2.01 1.755 4 STANDARD 3.9 0.32 STOP STANDARD 1.07 6 STANDARD -4.8 1.46 1.845 7 STANDARD 6.1 2.71 1.801 8 STANDARD -6.1 0.085 9 STANDARD 10.3 1.52 1.567 10 STANDARD -100 11 STANDARD infinity

[0055] In the table: the cemented surfaces of cemented lens 3 are indicated by the same surface number.

[0056] 1 is the object-side mirror of the first lens 1, and 2 is the image-side mirror of the first lens 1;

[0057] 3 is the object-side mirror of the second lens 2, and 4 is the image-side mirror of the second lens 2;

[0058] 6 is the object-side mirror of the third lens, 7 is the cemented surface of the third lens and the fourth lens (i.e., cemented lens 3), and 8 is the image-side mirror of the fourth lens.

[0059] 9 is the object-side mirror of the fifth lens 4, and 10 is the image-side mirror of the fifth lens 4;

[0060] 11 is the image plane.

[0061] Based on the above data, the spherical aberration curve of the scanning lens in this embodiment is as follows: Figure 2 As shown, the main part of the spherical aberration is corrected to within ±0.02mm. The spherical aberration is well corrected within the spectral bandwidth, achieving a balance between the inner and outer apertures, which increases the cleanliness of the actual image captured by the lens.

[0062] like Figure 3 The distortion curve shown demonstrates that, based on the precise coordination of five spherical lenses, astigmatism and field curvature can be corrected to a suitable range, enabling the meridional resolution to be similar to the sagittal resolution.

[0063] like Figure 4 The chromatic aberration curves shown indicate that the chromatic aberrations of f-ray, d-ray, and c-ray relative to the chromatic aberration are within 2μm, which fully meets the resolution quality requirements of the barcode scanning lens.

[0064] like Figure 5 The MTF curve shown indicates that the lens of this invention has excellent resolution, high sharpness at a spatial frequency of 160 cycles / mm within the center field of view and 0.9 field of view, and the MTF curve is close to the diffraction limit.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A high-definition, large depth-of-field, telephoto barcode scanning lens, characterized by: The optical system comprises, sequentially from the object-side to the image-side along the optical axis, five lenses: a first lens, a second lens, a cemented lens composed of a third and a fourth lens, and a fifth lens. The first, second, third, fourth, and fifth lenses are all spherical glass lenses. Their focal lengths are positive, negative, negative, positive, and positive, respectively. The third lens is made of a material with a refractive index of 1.84 or higher and Vd = 53. The second lens has a radius of curvature of 6.0 mm on its object-side surface and 3.9 mm on its image-side surface. The fifth lens has a radius of curvature of 10.3 mm on its object-side surface and -100 mm on its image-side surface. The scanning lens has a focal length of 12 mm.

2. The high-definition, large depth-of-field, telephoto barcode scanning lens as described in claim 1, characterized in that: The second lens is a thick meniscus lens, with a convex surface near the object side and a concave surface near the image side.

3. The high-definition, large depth-of-field, telephoto barcode scanning lens as described in claim 1, characterized in that: An aperture stop is provided between the second lens and the third lens, and the aperture stop is made of SOMA sheet.

4. The high-definition, large depth-of-field, telephoto barcode scanning lens as described in claim 1, characterized in that: The first lens, the second lens, the cemented lens composed of the third and fourth lenses, and the fifth lens are sequentially arranged inside the lens barrel.

5. The high-definition, large depth-of-field, telephoto barcode scanning lens as described in claim 4, characterized in that: The lens barrel is equipped with a spacer ring that is coaxial with the optical system of the barcode scanning lens.

6. The high-definition, large depth-of-field, telephoto barcode scanning lens as described in claim 5, characterized in that: Spacers are provided between the first lens and the second lens, and between the fourth lens and the second lens.

7. The high-definition, large depth-of-field, telephoto barcode scanning lens as described in claim 6, characterized in that: The gasket is made of metal.

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