A high-temperature-resistant large-depth-of-field code scanning lens

Abstract

This invention discloses a high-temperature resistant barcode scanning lens with a large depth of field, comprising a lens barrel. Inside the lens barrel, from the object side to the image plane side, are arranged a first lens, a second lens, a third lens, a filter, and an image plane. The object side of the first lens is convex at the optical axis and concave at the optical axis of the image plane side. The object side of the second lens is concave, and the image plane side is convex. The object side and image plane side of the third lens are both convex. The filter is planar, and the image plane is the imaging surface of the photosensitive element. This invention provides a barcode scanning lens that is high-temperature resistant, has low distortion (grid distortion <0.3%), a large depth of field, fewer elements, a compact structure, and high strength. These characteristics result in a large depth of field, eliminating the need for a fixed distance during scanning, minimizing image distortion, and meeting the high-temperature scanning requirements of operations such as ferries. It also promotes the advancement and development of optical research and technology.

Description

Technical Field

[0001] This invention relates to a lens, and more particularly to a high-temperature resistant, large-depth-of-field scanning lens. Background Technology

[0002] With the continuous development of information science, barcodes, QR codes, and other similar technologies have emerged and replaced traditional information storage methods. This has stimulated the development of information code reading devices, leading to diversified demands. The lens of this invention is primarily used in barcode scanners. Barcode scanners, as products integrating mechanical, electronic, and optical technologies, are mainly used for inputting information such as product details. Currently, their components are relatively mature and can meet most daily life needs. Existing barcode scanner lens systems mostly use three plastic lenses, which, while inexpensive, are insufficient to withstand high-temperature environments. At high temperatures, the refractive index of plastic changes significantly, and since barcode scanner lenses are fixed-focus lenses, their performance degrades rapidly. Although the distortion of existing barcode scanner lenses meets the distortion requirements of conventional mobile phone lenses, interference still occurs when scanning barcodes, and the scanning distance is limited after fixing the focus. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies, expand the types of barcode scanners, and provide a lens that can meet the requirements of high-temperature environments below 90°C, has a large depth of field range, and minimal distortion.

[0004] To achieve the above objectives, the present invention is implemented according to the following technical solution:

[0005] The present invention includes a lens barrel, wherein a lens 1, a lens 2, a lens 3, a filter and an image plane are arranged sequentially from the object side to the image plane side inside the lens barrel. The object side of the lens 1 is convex at the optical axis and the image plane side is concave at the optical axis. The object side of the lens 2 is concave and the image plane side is convex. The object side and the image plane side of the lens 3 are both convex. The filter is planar and the image plane is the imaging surface of the photosensitive element.

[0006] The focal length (EFL) of the lens from the image plane is 4.2 mm, the aperture value (F / #) is 5.86, and the total length (TTL) is less than 6 mm.

[0007] Furthermore, a spacer ring 1 is provided between lens 1 and lens 2, a spacer ring 2 is provided between lens 2 and lens 3, and a spacer ring 3 is provided between lens 3 and the filter. Light-transmitting holes are provided in the middle of spacer ring 1, spacer ring 2, and spacer ring 3.

[0008] Preferably, the first lens has a refractive index nd = 1.5445, an Abbe number vd = 56.09, an outer diameter of Φ2.5mm, a middle thickness of 0.509mm, an edge thickness of 0.35mm, an object side radius of curvature of 1.178mm, an aspherical diameter of Φ1.32mm, an image side radius of curvature of 3.85mm, and an aspherical diameter of Φ0.89mm.

[0009] The refractive index of the second lens is nd = 1.64, and the Abbe number is vd = 23.5. The object side of the second lens is concave at the optical axis, and the image side is convex at the optical axis. The outer diameter of the second lens is Φ2.6mm, the middle thickness is 0.376mm, the edge thickness is 0.44mm, the radius of curvature of the object side is -0.64mm, the aspherical diameter is Φ1.05mm, the radius of curvature of the image side is -1.695mm, and the aspherical diameter is Φ1.63mm.

[0010] The refractive index of the third lens is nd = 1.744, and the Abbe number is vd = 44.9. The object-side optical axis of the third lens is convex, and the image-side optical axis is also convex. The outer diameter D3 of the third lens is Φ2.7mm, the middle thickness CT3 is 0.82mm, the edge thickness ET3 is 0.26mm, the radius of curvature of the object-side lens is 11.8mm, the effective diameter is Φ2.3mm, the radius of curvature of the image-side lens is -2.327mm, and the aspherical diameter is Φ2.6mm.

[0011] Lens 1 and Lens 2 are aspherical lenses made of plastic, while Lens 3 is a spherical lens made of glass.

[0012] The filter is made of glass with a refractive index nd = 1.517 and an Abbe number vd = 64. The lens is 0.3 mm thick.

[0013] The beneficial effects of this invention are:

[0014] This invention relates to a high-temperature resistant barcode scanning lens with a large depth of field. Compared with existing technologies, this invention provides a barcode scanning lens that is resistant to high temperatures, has low distortion (grid distortion <0.3%), a large depth of field, fewer elements, a compact structure, and high strength. These characteristics result in a large depth of field, eliminating the need for a fixed distance during scanning, minimizing image distortion, and meeting the high-temperature scanning requirements of operations such as those on ferries. It also promotes the advancement and development of optical research technologies. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the optical path of the present invention;

[0016] Figure 2 This is a cross-sectional structural schematic diagram of the present invention;

[0017] Figure 3 This is a cross-sectional view of the lens of the present invention;

[0018] Figure 4 This is a two-section view of the lens of the present invention;

[0019] Figure 5 This is a three-section view of the lens of the present invention;

[0020] Figure 6 This is a front structural diagram of the present invention;

[0021] Figure 7 This is a field curvature distortion diagram of the lens of this invention;

[0022] Figure 8 This is a grid distortion diagram of the lens of the present invention;

[0023] Figure 9 This is a lateral chromatic aberration diagram of the lens of this invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions herein are used to explain the present invention, but are not intended to limit the present invention.

[0025] like Figure 1 As shown, this invention provides a high-temperature resistant, large depth-of-field barcode scanning lens. The optical system, arranged sequentially from the object side to the image plane side, includes a lens barrel 1, a first lens 2, a first spacer 3, a second lens 4, a second spacer 5, a third lens 6, a third spacer 7, a filter 8, and an image plane 9. The arrangement order is from the first lens 2 to the photosensitive surface 9, all along the optical axis. The first spacer 3 has a through-hole in the middle, which serves as an aperture stop, determining the lens's aperture size and controlling the amount of light entering the lens. The imaging lens has a focal length EFL = 4.2mm and an aperture value F / # = 5.86, which is a small aperture, allowing for a certain amount of light intake, thus ensuring a certain level of sharpness while expanding the depth of field. The imaging lens has a short overall length (TTL < 6mm), a compact structure, which is beneficial for the spatial design and layout of barcode scanners and other products, saving space. The imaging lens has a large image circle size, with a maximum image circle size of Φ4.9mm, compatible with most chips used in barcode scanning. The imaging lens exhibits minimal distortion, with optical distortion less than 0.25% and TV distortion <|-0.3%|, resulting in negligible differences in image shape. Furthermore, the imaging lens exhibits low lateral chromatic aberration; the chromatic aberration curves for all wavelengths in the system design are within 1µm, and all chromatic aberration curves fall within the Airy disk range.

[0026] A spacer ring 3 is provided between lens 1 2 and lens 2 4, a spacer ring 2 5 is provided between lens 2 4 and lens 3 6, and a spacer ring 3 7 is provided between lens 3 6 and filter 8. Light-transmitting holes are provided in the middle of spacer ring 1 3, spacer ring 2 5, and spacer ring 3 7. All three components are made of CU material to ensure strength and are oxidized to eliminate stray light.

[0027] Each lens element consists of two surfaces: the surface closer to the object plane is named R1, and the surface closer to the image plane is named R2. The distance between the vertices of the two surfaces is called the median thickness, and the distance between the two large planes at the edge of the lens is called the edge thickness. FOV refers to the field of view, which is the range that the lens can capture. EFL refers to the finite focal length of the lens. Subsequent descriptions of lens surfaces will follow this method. Figure 1 The center line indicated by the mark A is the optical axis of the lens, running from left to right, representing the light rays emitted from the object plane and propagating to the image plane.

[0028] Lens 2 is an aspherical lens made of plastic with a refractive index nd = 1.5445 and an Abbe number vd = 56.09. The R1 surface of lens 2 is convex at the optical axis, and the R2 surface is concave at the optical axis. Lens 2 has an outer diameter D1 of Φ2.5mm, a middle thickness CT1 of 0.509mm, an edge thickness ET1 of 0.35mm, a radius of curvature of 1.178mm for the R1 surface, and an aspherical diameter of Φ1.32mm. The radius of curvature of the R2 surface is 3.85mm, and the aspherical diameter is Φ0.89mm.

[0029] Lens 4 is an aspherical lens made of plastic with a refractive index nd = 1.64 and an Abbe number vd = 23.5. The R1 surface of lens 4 is concave at the optical axis, and the R2 surface is convex at the optical axis. Lens 4 has an outer diameter D2 of Φ2.6mm, a middle thickness CT2 of 0.376mm, an edge thickness ET2 of 0.44mm, a radius of curvature of -0.64mm for the R1 surface, and an aspherical diameter of Φ1.05mm. The radius of curvature of the R2 surface is -1.695mm, and the aspherical diameter is Φ1.63mm.

[0030] Lens 6 is a spherical lens made of glass with a refractive index nd = 1.744 and an Abbe number vd = 44.9. The R1 and R2 surfaces of lens 6 are convex at the optical axis. Lens 6 has an outer diameter D3 of Φ2.7mm, a middle thickness CT3 of 0.82mm, an edge thickness ET3 of 0.26mm, a radius of curvature of 11.8mm for the R1 surface, an effective diameter of Φ2.3mm, a radius of curvature of -2.327mm for the R2 surface, and an aspherical diameter of Φ2.6mm.

[0031] The filter 8 is made of glass with a refractive index nd = 1.517 and an Abbe number vd = 64.2; the filter thickness is 0.3 mm.

[0032] In this invention, two out of the three lenses in the scanning lens have aspherical surfaces. The formula for calculating the aspherical surface is as follows:

[0033]

[0034] In the formula, C refers to the curvature of the lens surface, which is the reciprocal of the radius of curvature R, i.e., C = 1 / R, K is the conic coefficient, r is the distance of the lens surface from the optical axis, a4, a6, a8, a10... are aspherical higher-order coefficients, and SAG is the position along the optical axis at a height of r with the vertex of the surface as the reference point.

[0035] The following is a first embodiment of the present invention: Lens data list

[0036]

[0037] The following are the conic coefficients and higher-order coefficients of the aspherical lens in the first embodiment:

[0038]

[0039] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A high-temperature resistant, large depth-of-field barcode scanning lens, comprising a lens barrel (1), characterized in that: The scanning lens has three lenses. The lens barrel (1) is provided with lens 1 (2), lens 2 (4), lens 3 (6), filter (8) and image plane (9) in sequence from the object side to the image plane side. The object side of lens 1 (2) is convex at the optical axis and the image plane side is concave at the optical axis. The object side of lens 2 (4) is concave and the image plane side is convex. The object side and the image plane side of lens 3 (6) are both convex. The object side and the image plane side of filter (8) are both flat. The image plane (9) is the imaging surface of the photosensitive element. The lens one (2) has positive optical power; The second lens (4) has negative optical power; The lens three (6) has positive optical power; The scanning lens has a focal length EFL=4.2mm, an aperture value F / #=5.86, and a total length TTL<6mm.

2. The high-temperature resistant, large depth-of-field barcode scanning lens according to claim 1, characterized in that: A spacer ring 1 (3) is provided between lens 1 (2) and lens 2 (4), a spacer ring 2 (5) is provided between lens 2 (4) and lens 3 (6), and a spacer ring 3 (7) is provided between lens 3 (6) and filter (8). Light-transmitting holes are provided in the middle of spacer ring 1 (3), spacer ring 2 (5), and spacer ring 3 (7).

3. The high-temperature resistant, large depth-of-field barcode scanning lens according to claim 1 or 2, characterized in that: The refractive index of the lens 1 (2) is nd=1.5445, the Abbe number is vd=56.09, the outer diameter (D1) is Φ2.5mm, the middle thickness (CT1) is 0.509mm, the edge thickness (ET1) is 0.35mm, the object side curvature radius is 1.178mm, the aspherical diameter is Φ1.32mm, the image side curvature radius is 3.85mm, and the aspherical diameter is Φ0.89mm.

4. The high-temperature resistant, large depth-of-field barcode scanning lens according to claim 1 or 2, characterized in that: The refractive index of the second lens (4) is nd=1.64, the Abbe number is vd=23.5, the object side of the second lens (4) is concave at the optical axis, and the image side is convex at the optical axis. The outer diameter (D2) of the second lens (4) is Φ2.6mm, the middle thickness (CT2) is 0.376mm, the edge thickness (ET2) is 0.44mm, the radius of curvature of the object side is -0.64mm, the aspherical diameter is Φ1.05mm, the radius of curvature of the image side is -1.695mm, and the aspherical diameter is Φ1.63mm.

5. The high-temperature resistant, large depth-of-field barcode scanning lens according to claim 1 or 2, characterized in that: The refractive index of the lens three (6) is nd=1.744, the Abbe number is vd=44.9, the object side optical axis of the lens three (6) is convex, and the image side optical axis is convex; the outer diameter (D3) of the lens three (6) is Φ2.7mm, the middle thickness (CT3) is 0.82mm, the edge thickness (ET3) is 0.26mm, the radius of curvature of the object side is 11.8mm, the effective diameter is Φ2.3mm, the radius of curvature of the image side is -2.327mm, and the aspherical diameter is Φ2.6mm.

6. The high-temperature resistant, large depth-of-field barcode scanning lens according to claim 1 or 2, characterized in that: Lens 1 (2) and Lens 2 (4) are aspherical lenses and are made of plastic, while Lens 3 (6) is a spherical lens and is made of glass.

7. The high-temperature resistant, large depth-of-field barcode scanning lens according to claim 1, characterized in that: The filter (8) is made of glass with a refractive index nd=1.517, an Abbe number vd=64.2, and a thickness of 0.3mm.

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