Small telephoto lens for portable code scanning equipment and working method of small telephoto lens

Abstract

The invention relates to a small telephoto lens for portable code scanning equipment and a working method of the small telephoto lens. The small telephoto lens is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged in the light incidence direction, and a diaphragm is arranged between the third lens and the fourth lens. The second lens and the third lens are glued to form a balsaming lens group A, and the fourth lens and the fifth lens are glued to form a balsaming lens group B. According to the invention, the design of six glass spherical lenses is adopted, and the parameters and the on-axis distance of each lens are optimized, so that the optical performance of high resolution and long focal length can be satisfied, and meanwhile, the optical system has the advantages of low distortion and high illumination; and the total length of the lens is smaller, so that the miniaturization requirement of portable code scanning equipment is met.

Description

Technical Field

[0001] This invention relates to a small telephoto lens for portable barcode scanning devices and its working method. Background Technology

[0002] With the automation and intelligence development of the retail, logistics, and warehousing industries, barcode scanning devices have become indispensable tools. Traditional barcode scanners typically use short-focal-length or standard-focal-length lenses, with a relatively short optimal working distance (usually between a few centimeters and tens of centimeters). However, in applications such as automated warehouses, large conveyor belt sorting systems, and applications requiring safe distances (such as hazardous materials warehouses), there is an urgent need for barcode scanning devices that can quickly and accurately read barcodes from greater distances.

[0003] Long-distance barcode scanning typically requires a telephoto lens. A telephoto lens provides a narrow field of view, concentrating limited pixel resources on the distant barcode target, thus improving recognition capabilities. However, applying telephoto lenses to portable or handheld barcode scanners faces significant miniaturization challenges. Traditional telephoto lenses have a long overall optical length, which is unsuitable for prolonged handheld operation and makes integration into space-constrained embedded devices difficult.

[0004] In existing technologies, some long-distance scanning solutions use modified general-purpose camera lenses. However, these lenses are not specifically optimized for scanning applications and have the following problems: First, they are usually designed for large image sensors, resulting in excessively large lens diameters; second, their optical design focuses on the visual perception of photography, resulting in certain distortions and aberrations that affect the accuracy of barcode recognition; third, cost and size are difficult to control.

[0005] Therefore, there is an urgent need in this field for a telephoto lens specifically optimized for barcode scanning applications. This lens needs to achieve extreme miniaturization of the optical system (e.g., TTL less than 20mm) while ensuring sufficient working distance and depth of field, and to strictly control optical distortion and field curvature to ensure that it can provide high-contrast, low-geometric-distortion barcode images for decoding algorithms across the entire image plane. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention provides a small telephoto lens for portable barcode scanning devices and its working method. The lens adopts a design of 6 glass lenses and has the advantages of miniaturization, high illumination, high image quality and good thermal stability while meeting specific working distance and depth of field range.

[0007] The solution adopted by the present invention to solve the technical problem is: a small telephoto lens for portable barcode scanning devices: the lens is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged sequentially along the incident direction of light, and an aperture stop is provided between the third lens and the fourth lens.

[0008] Furthermore, the second lens and the third lens are cemented together to form a cemented lens group A, and the fourth lens and the fifth lens are cemented together to form a cemented lens group B.

[0009] Furthermore, the first lens is a meniscus lens with positive optical power, its object-side surface is convex, and its image-side surface is concave; the second lens is a biconvex lens with positive optical power, its object-side surface is convex, and its image-side surface is convex; the third lens is a biconcave lens with negative optical power, its object-side surface is concave, and its image-side surface is concave; the fourth lens is a biconvex lens with positive optical power, its object-side surface is convex, and its image-side surface is convex; the fifth lens is a biconcave lens with negative optical power, its object-side surface is concave, and its image-side surface is concave; and the sixth lens is a meniscus lens with positive optical power, its object-side surface is concave, and its image-side surface is convex.

[0010] Furthermore, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass spherical lenses.

[0011] Furthermore, the focal length of the lens is f, and the focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens are f1, f2, f3, f4, f5, and f6, respectively, wherein f1, f2, f3, f4, f5, and f6 satisfy the following ratio with f: 0 <f1 / f<0.5,0<f2 / f<0.5,-0.5<f3 / f<0,0<f4 / f<0.5,-0.5<f5 / f<0,0<f6 / f<0.5。

[0012] Furthermore, the first lens satisfies the relationship: 1.5 ≤ N d ≤1.8,V d ≥50; the second lens satisfies the relationship: 1.4≤N d ≤1.6,V d ≥50; The third lens satisfies the relationship: 1.8≤N d ≤2.0,V d ≤50; The fourth lens satisfies the relationship: 1.5≤N d ≤1.8,V d ≤50; The fifth lens satisfies the relationship: 1.8≤N d ≤2.0,V d ≤50; The sixth lens satisfies the relationship: 1.8≤N d≤2.0,V d ≤50; where N d V is the refractive index. d Let be Abbe's constant.

[0013] Furthermore, the air gap between the first lens and the second lens is 0 to 0.2 mm; the air gap between the third lens and the fourth lens is 1.0 to 1.5 mm; and the air gap between the fifth lens and the sixth lens is 3.0 to 3.5 mm.

[0014] Furthermore, the total optical length (TTL) of the lens and the focal length (f) of the lens satisfy the following condition: TTL / f ≤ 1.0.

[0015] Furthermore, the image height H of the lens and the focal length f of the lens satisfy the following condition: H / f ≥ 0.3.

[0016] A method for operating a small telephoto lens for a portable barcode scanning device, employing a small telephoto lens as described in any one of claims 1-9, characterized in that: when light is incident, the light path sequentially enters the first lens, the second lens, the third lens, the aperture stop, the fourth lens, the fifth lens, and the sixth lens, and finally forms an image on the image plane.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] Using only six spherical glass lenses, this optical system not only ensures long-focal-length and long-working-distance imaging performance, but also boasts a total optical length of less than 15mm, resulting in a smaller size, lower cost, and compatibility with the structural requirements of portable or handheld barcode scanning devices. Optical distortion is less than 0.5%, ensuring accurate reproduction of barcode geometry by barcode recognition software. The lens is compatible with 1 / 2.5-inch chips, achieving a relative illumination of over 80% at the edge of the field of view, resulting in bright and clear images. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the optical structure of the present invention;

[0020] Figure 2 This is the axial chromatic aberration diagram of the entire working band of the present invention;

[0021] Figure 3 This is the transverse chromatic aberration diagram of the entire working band of the present invention;

[0022] Figure 4 This is the field curvature distortion diagram of the entire working band of the present invention;

[0023] Figure 5 This is the MTF defocus curve diagram of the entire working band of the present invention;

[0024] Figure 6This is the relative illumination diagram of the present invention.

[0025] In the diagram: L1 - first lens; L2 - second lens; L3 - third lens; STO - aperture stop; L4 - fourth lens; L5 - fifth lens; L6 - sixth lens; L7 - equivalent glass plate; IMA - imaging plane. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 As shown, a small telephoto lens for a portable barcode scanning device is provided: the lens consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged sequentially along the incident direction of light, and an aperture stop is provided between the third lens and the fourth lens.

[0028] In this embodiment, the second lens and the third lens are cemented together to form a cemented lens group A, and the fourth lens and the fifth lens are cemented together to form a cemented lens group B.

[0029] In this embodiment, the first lens is a meniscus lens with positive optical power, its object-side surface is convex, and its image-side surface is concave; the second lens is a biconvex lens with positive optical power, its object-side surface is convex, and its image-side surface is convex; the third lens is a biconcave lens with negative optical power, its object-side surface is concave, and its image-side surface is concave; the fourth lens is a biconvex lens with positive optical power, its object-side surface is convex, and its image-side surface is convex; the fifth lens is a biconcave lens with negative optical power, its object-side surface is concave, and its image-side surface is concave; and the sixth lens is a meniscus lens with positive optical power, its object-side surface is concave, and its image-side surface is convex.

[0030] In this embodiment, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass spherical lenses.

[0031] In this embodiment, the focal length of the lens is f, and the focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens are f1, f2, f3, f4, f5, and f6, respectively. The ratios of f1, f2, f3, f4, f5, and f6 with f satisfy the following ratio: 0 <f1 / f<0.5,0<f2 / f<0.5,-0.5<f3 / f<0,0<f4 / f<0.5,-0.5<f5 / f<0,0<f6 / f<0.5。

[0032] In this embodiment, the first lens satisfies the relationship: 1.5 ≤ N d ≤1.8,V d ≥50; the second lens satisfies the relationship: 1.4≤Nd ≤1.6,V d ≥50; The third lens satisfies the relationship: 1.8≤N d ≤2.0,V d ≤50; The fourth lens satisfies the relationship: 1.5≤N d ≤1.8,V d ≤50; The fifth lens satisfies the relationship: 1.8≤N d ≤2.0,V d ≤50; The sixth lens satisfies the relationship: 1.8≤N d ≤2.0,V d ≤50; where N d V is the refractive index. d Let be Abbe's constant.

[0033] In this embodiment, the air gap between the first lens and the second lens is 0 to 0.2 mm; the air gap between the third lens and the fourth lens is 1.0 to 1.5 mm; and the air gap between the fifth lens and the sixth lens is 3.0 to 3.5 mm.

[0034] In this embodiment, the total optical length (TTL) of the lens and the focal length (f) of the lens satisfy the following condition: TTL / f ≤ 1.0.

[0035] In this embodiment, the image height H of the lens and the focal length f of the lens satisfy the following condition: H / f≥0.3.

[0036] In this embodiment, the F-number of the lens is ≤7.0.

[0037] The technical specifications achieved by the optical system in this embodiment are as follows:

[0038] (1) Focal length: 19.5≤EFFL≤20.5mm;

[0039] (2) Aperture F≤7;

[0040] (3) Field of view: 2w ≥ 21°;

[0041] (4) Operating band: Visible light band.

[0042] To achieve the above design parameters, the specific design of the optical system adopted in this embodiment is shown in the table below:

[0043]

[0044] A method for operating a small telephoto lens for a portable barcode scanning device, employing a small telephoto lens as described in any one of claims 1-9, characterized in that: when light is incident, the light path sequentially enters the first lens, the second lens, the third lens, the aperture stop, the fourth lens, the fifth lens, and the sixth lens, and finally forms an image on the image plane.

[0045] This embodiment of the optical system achieves the design requirements of short TTL, long focal length, and large depth of field by rationally allocating the optical power, center thickness of each lens, and on-axis distance between each lens. It also has advantages such as ultra-low distortion and high illumination. See the appendix of the instruction manual. Figure 2-6 .

[0046] Unless otherwise stated, if any of the technical solutions disclosed in this invention specify a numerical range, then the disclosed numerical range is a preferred numerical range. Anyone skilled in the art should understand that the preferred numerical range is merely one among many feasible numerical values ​​that has a more obvious or representative technical effect. Because there are many numerical values, it is impossible to list them all. Therefore, this invention discloses only some numerical values ​​to illustrate the technical solutions of this invention. Furthermore, the numerical values ​​listed above should not constitute a limitation on the scope of protection of this invention.

[0047] If the terms "first" or "second" are used in this document to specify components, those skilled in the art should know that the use of "first" or "second" is merely for the purpose of distinguishing components in description, and unless otherwise stated, the above terms have no special meaning.

[0048] If this invention discloses or relates to components or structural parts that are fixedly connected to each other, then, unless otherwise stated, a fixed connection can be understood as: a fixed connection that can be detached (e.g., using bolts or screws), or a fixed connection that cannot be detached (e.g., riveting, welding). Of course, a fixed connection can also be replaced by an integral structure (e.g., manufactured in one piece using a casting process) (except where it is obviously impossible to use an integral molding process).

[0049] Furthermore, the orientations or positional relationships used in any of the technical solutions disclosed in this invention above to indicate positional relationships, such as "longitudinal," "lateral," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing this patent. They are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this patent. In addition, unless otherwise stated, the terms used to indicate shape in any of the technical solutions disclosed in this invention above include shapes that are similar to, close to, or approximate with it.

[0050] Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A small telephoto lens for portable barcode scanning devices, characterized in that: The lens consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged sequentially along the incident direction of light, with an aperture stop provided between the third lens and the fourth lens.

2. The small telephoto lens according to claim 1, characterized in that: The second lens and the third lens are cemented together to form a cemented lens group A, and the fourth lens and the fifth lens are cemented together to form a cemented lens group B.

3. The small telephoto lens according to claim 1, characterized in that: The first lens is a meniscus lens with positive optical power, its object-side surface is convex, and its image-side surface is concave; the second lens is a biconvex lens with positive optical power, its object-side surface is convex, and its image-side surface is convex; the third lens is a biconcave lens with negative optical power, its object-side surface is concave, and its image-side surface is concave; the fourth lens is a biconvex lens with positive optical power, its object-side surface is convex, and its image-side surface is convex; the fifth lens is a biconcave lens with negative optical power, its object-side surface is concave, and its image-side surface is concave; the sixth lens is a meniscus lens with positive optical power, its object-side surface is concave, and its image-side surface is convex.

4. The small telephoto lens according to claim 1, characterized in that: The first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass spherical lenses.

5. The small telephoto lens according to claim 1, characterized in that: The focal length of the lens is f The focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens are respectively f 1 、f 2 、f 3 、f 4 、f 5 、f 6 ,in f 1 、f 2 、f 3 、f 4 、f 5 、f 6 ,and f The following ratio must be met: 0 < f 1 / f <0.5, 0< f 2 / f <0.5, -0.5< f 3 / f <0, 0< f 4 / f <0.5, -0.5< f 5 / f <0, 0< f 6 / f <0.

5.

6. The small telephoto lens according to claim 1, characterized in that: The first lens satisfies the following relationship: 1.5 ≤ N d ≤1.8, V d ≥50; the second lens satisfies the relationship: 1.4≤ N d ≤1.6, V d ≥50; The third lens satisfies the following relationship: 1.8≤ N d ≤2.0, V d ≤50; The fourth lens satisfies the relationship: 1.5≤ N d ≤1.8, V d ≤50; The fifth lens satisfies the following relationship: 1.8≤ N d ≤2.0, V d ≤50; The sixth lens satisfies the relation: 1.8≤ N d ≤2.0, V d ≤50; of which N d For refractive index, V d Let be Abbe's constant.

7. The small telephoto lens according to claim 1, characterized in that: The air gap between the first lens and the second lens is 0~0.2mm; the air gap between the third lens and the fourth lens is 1.0~1.5mm; and the air gap between the fifth lens and the sixth lens is 3.0~3.5mm.

8. The small telephoto lens according to claim 1, characterized in that: The total optical length (TTL) of the lens and the focal length (f) of the lens satisfy the following condition: TTL / f ≤ 1.

0.

9. The small telephoto lens according to claim 1, characterized in that: The image height H of the lens and the focal length f of the lens satisfy the following condition: H / f≥0.

3.

10. A method for operating a small telephoto lens for a portable barcode scanner, employing the small telephoto lens as described in any one of claims 1-9, characterized in that: When light is incident, the light path sequentially enters the first lens, the second lens, the third lens, the aperture stop, the fourth lens, the fifth lens, and the sixth lens, and finally forms an image on the image plane.

Images