A laser illumination lens with small divergence angle and large depth of field

Abstract

This utility model relates to a laser illumination lens with a small divergence angle and a large depth of field. It includes a lens housing and a laser source axially mounted at one end of the lens housing, with its laser emission end disposed within the lens housing. A lens group includes a first lens, a second lens, a third lens, and a fourth lens coaxially and sequentially arranged along the laser emission path. The first lens is a plano-convex aspherical lens; the second lens is a positive meniscus lens with a focal length of f2; the third lens is a positive meniscus lens with a focal length f3 satisfying 1.2 ≤ f3 / f2 ≤ 1.5; and the fourth lens is a plano-convex aspherical lens with a focal length f4 satisfying 0.95 ≤ f4 / f3 ≤ 2.16. This utility model has the advantages of balancing a small divergence angle and a large depth of field, effectively correcting aberrations, and improving the adaptability of the optical system.

Description

Technical Field

[0001] This utility model relates to the field of laser equipment technology, specifically to a laser illumination lens with a small divergence angle and a large depth of field. Background Technology

[0002] With the deep integration of intelligent manufacturing, artificial intelligence, and precision manufacturing technologies, industrial production is placing higher demands on optical imaging systems. In applications such as automated inspection and 3D measurement, traditional optical systems face numerous technical bottlenecks: the difficulty in balancing beam divergence angle and depth of field is particularly prominent. When a system strives for a small divergence angle, it often results in insufficient depth of field, making it unable to adapt to changes in the position of the object being measured; conversely, designs that increase depth of field tend to increase the beam divergence angle, affecting illumination uniformity and energy utilization.

[0003] In related technologies, laser illumination systems generally suffer from insufficient aberration correction when operating over a wide wavelength range (375nm-1550nm), especially when using combinations of ordinary spherical lenses, making it difficult to simultaneously eliminate spherical aberration and chromatic aberration, leading to a decline in image quality. However, in applications such as industrial inspection and dynamic tracking, these deficiencies directly affect the system's detection accuracy and stability. For example, in workpiece inspection on high-speed production lines, it is necessary to maintain a small divergence angle to ensure illumination uniformity, while also requiring sufficient depth of field to compensate for workpiece position fluctuations.

[0004] However, the lack of optical solutions that can simultaneously meet these requirements severely limits the effectiveness of machine vision systems in complex industrial environments. To address this, we propose a laser illumination lens with a small divergence angle and a large depth of field. Utility Model Content

[0005] This application provides a laser illumination lens with a small divergence angle and a large depth of field, which at least solves the problem that existing laser illumination systems generally have insufficient aberration correction and are unable to simultaneously meet the scene application requirements of small divergence angle and large depth of field.

[0006] In a first aspect, this application provides a laser illumination lens with a small divergence angle and a large depth of field, including a lens housing, and further comprising:

[0007] A laser source is axially mounted to one end of the lens housing, and its laser emission end is disposed inside the lens housing;

[0008] The lens group includes a first lens, a second lens, a third lens, and a fourth lens that are coaxially and sequentially arranged on the laser emission path;

[0009] The first lens is a plano-convex aspherical lens;

[0010] The second lens is a positive meniscus lens with a focal length of f2;

[0011] The third lens is a positive meniscus lens, and its focal length f3 satisfies 1.2≤f3 / f2≤1.5;

[0012] The fourth lens is a plano-convex aspherical lens, and its focal length f4 satisfies 0.95≤f4 / f3≤2.16.

[0013] Optionally, the dispersion coefficient Vd of the second, third, and fourth lenses is ≥64.

[0014] Optionally, the lens housing includes a first housing and a second housing, the laser source and the first lens are axially disposed in the inner cavity of the first housing, and the second lens, the third lens and the fourth lens are axially disposed in the inner cavity of the second housing;

[0015] The first housing is axially movably inserted into the first end of the second housing at the end opposite to the laser source to adjust the distance between the first lens and the second, third, and fourth lenses.

[0016] Optionally, the incident surface of the first lens along the laser emission path is a plane, and the emission surface is a convex surface, which can shape the incident beam, eliminate spherical aberration, orient and collimate the optical path, and facilitate control.

[0017] Optionally, the second and third lenses have concave incident surfaces and convex exit surfaces along the laser emission path, which can effectively correct aberrations, adapt to wide-angle light, and simultaneously achieve system compactness and reduce stray light, thus combining imaging quality and structural efficiency.

[0018] Optionally, the incident surface of the fourth lens along the laser emission path is a plane, and the emission surface is a convex surface, so as to reasonably allocate the focal length relationship of each lens, thereby achieving the effects of small divergence angle, ultra-large depth of field, and effective elimination of spherical aberration.

[0019] Optionally, the wavelength range of the laser beam emitted by the laser source is 375nm-1550nm.

[0020] Compared to related technologies, the laser illumination lens with a small divergence angle and a large depth of field provided in this application has at least the following technical advantages:

[0021] Employing an adjustable design for the lens group and lens housing, the combination of aspherical and meniscus lenses in the lens group optimizes the optical path, expanding the depth of field while ensuring a small divergence angle. Combined with the movable structure of the lens housing, the lens spacing can be adjusted, effectively solving the problems of traditional systems where it is difficult to balance divergence angle and depth of field, and where aberration correction is insufficient. It has the advantages of balancing a small divergence angle and a large depth of field, fully correcting aberrations, and improving the adaptability of the optical system.

[0022] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a perspective view of a laser illumination lens with a small divergence angle and large depth of field, according to an exemplary embodiment.

[0025] Figure 2 This is a cross-sectional view of a laser illumination lens with a small divergence angle and large depth of field, according to an exemplary embodiment.

[0026] Figure 3 This is an optical path diagram of a laser illumination lens with a small divergence angle and a large depth of field, according to an exemplary embodiment. Detailed Implementation

[0027] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0028] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and for simplifying the description, and do not 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 utility model. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0030] In related technologies, laser illumination systems generally suffer from insufficient aberration correction when operating over a wide wavelength range (375nm-1550nm), especially when using combinations of ordinary spherical lenses, making it difficult to simultaneously eliminate spherical aberration and chromatic aberration, leading to a decline in image quality. In applications such as industrial inspection and dynamic tracking, these deficiencies directly affect the system's detection accuracy and stability. For example, workpiece inspection on high-speed production lines requires maintaining a small divergence angle to ensure illumination uniformity while also needing sufficient depth of field to compensate for workpiece position fluctuations. Current technologies lack optical solutions that can simultaneously meet these requirements, severely limiting the effectiveness of machine vision systems in complex industrial environments.

[0031] Based on the above, this utility model provides a laser illumination lens with a small divergence angle and a large depth of field, which will be described in detail below with reference to specific embodiments and accompanying drawings.

[0032] This utility model embodiment provides a laser illumination lens with a small divergence angle and a large depth of field. Figure 1 This is a perspective view of a laser illumination lens with a small divergence angle and large depth of field, according to an exemplary embodiment. Figure 2 This is a cross-sectional view of a laser illumination lens with a small divergence angle and large depth of field, according to an exemplary embodiment. Figure 3 This is an optical path diagram of a laser illumination lens with a small divergence angle and large depth of field, according to an exemplary embodiment. For example... Figure 1-3 As shown, this small divergence angle, large depth-of-field laser illumination lens includes a lens housing 30, and also includes:

[0033] A laser source 10 is axially mounted at one end of the lens housing 30, and its laser emission end is disposed within the lens housing 30. In this embodiment, the wavelength range of the emitted laser beam of the laser source 10 is 375nm-1550nm. Specifically, the shortest wavelength at the 375nm wavelength boundary is located in the ultraviolet band, which can excite the fluorescence properties of specific materials, while the longest wavelength at the 1550nm wavelength boundary is located in the near-infrared band, which has low attenuation characteristics during atmospheric transmission. The wavelength range of the emitted laser beam of the laser source 10 in this application covering 375nm-1550nm represents that the emitted laser beam that the laser source 10 can output has a continuous spectrum from ultraviolet to near-infrared. Specifically, a multimode semiconductor laser source can be used, and this range covers the dual requirements of visible light imaging and infrared thermal radiation detection.

[0034] The lens group 20 includes a first lens 201, a second lens 202, a third lens 203 and a fourth lens 204 coaxially and sequentially arranged on the laser emission path;

[0035] The first lens 201 is a plano-convex aspherical lens, and its focal length f1 satisfies 20≤f1≤60. The incident surface of the first lens 201 along the laser emission path is a plane, and the emission surface is a convex surface, which can shape the incident beam, eliminate spherical aberration, and make the directional collimated optical path easy to control.

[0036] The second lens 202 is a positive meniscus lens with a focal length of f2; the third lens 203 is a positive meniscus lens with a focal length f3 satisfying 1.2≤f3 / f2≤1.5. The incident surfaces of the second lens 202 and the third lens 203 along the laser emission path are concave and the emission surfaces are convex, which can effectively correct aberrations, adapt to wide-angle light, and at the same time achieve system compactness and reduce stray light, thus achieving both imaging quality and structural efficiency.

[0037] The fourth lens 204 is a plano-convex aspherical lens, and its focal length f4 satisfies 0.95≤f4 / f3≤2.16. The incident surface of the fourth lens 204 along the laser emission path is planar, and the emission surface is convex. The planar incident surface of the fourth lens 204 allows the light beam passing through the first three lenses to enter the fourth lens 204 in a low-distortion manner. The plano-convex aspherical lens structure of the fourth lens 204 performs secondary collimation on the laser beam through continuous curvature changes, eliminating the spherical aberration generated by the previous lenses. The lower limit of the focal length ratio of 0.95 ensures that the fourth lens 204 has sufficient light-gathering ability to suppress excessive increase in divergence angle, while the upper limit of 2.16 prevents the focal length of the lens from being too long, which would lead to a reduction in depth of field. Therefore, when the third lens 203 and the fourth lens 204 are combined in this proportion, after the front-stage beam is focused by the third lens 203, the fourth lens 204 balances the divergence angle constraint and depth of field extension of the laser beam within a specific focal length range. This allows the output laser beam to maintain a small divergence angle while covering a larger distance range for clear imaging, ultimately achieving a reasonable allocation of the focal length relationship of each lens, and realizing the effects of small divergence angle, ultra-large depth of field, and effective elimination of spherical aberration.

[0038] In this embodiment, the dispersion coefficient Vd of the second lens 202, the third lens 203, and the fourth lens 204 is ≥64. The dispersion coefficient Vd is a quantitative indicator of a material's ability to disperse light; a higher dispersion coefficient indicates a smaller difference in refractive index for different wavelengths of light, thus suppressing aberrations caused by dispersion. Specifically, firstly, the second lens 202 is a positive meniscus lens, responsible for beam collimation and primary aberration correction. Its high dispersion coefficient material can suppress the influence of its own chromatic aberration on the optical path. Secondly, the third lens 203, in full... Given the focal length ratio of the second lens 201, the high dispersion coefficient further eliminates residual chromatic aberration, preventing the separation of different wavelengths of light in subsequent optical paths. Finally, as a plano-convex aspherical lens, the high dispersion coefficient material of the fourth lens 204 works synergistically with its aspherical properties to maintain the wavefront consistency of multi-wavelength beams while controlling the divergence angle. Consequently, the dispersion coefficients of the second lens 202, the third lens 203, and the fourth lens 204 are synergistically constrained, ensuring that the entire lens group maintains low chromatic aberration characteristics over a wide wavelength range.

[0039] In the above embodiment, the laser beam emitted from the laser source 10 is incident on the plane of the first lens 201, and the initial aberration is eliminated and preliminary collimation is completed through the aspherical exit surface. The positive meniscus structure of the second lens 202 and the third lens 203 forms a compound positive optical power, which corrects field curvature and suppresses beam divergence in a compact space. The focal length ratio design of the third lens 203 allows the optical path to expand the depth of field range while maintaining collimation. Finally, the fourth lens 204 redistributes the optical path through the aspherical exit surface, ultimately controlling the laser beam divergence angle within a very small range while maintaining ultra-long depth of field coverage. In this embodiment, the effective working distance of the laser illumination lens is 5mm-500000mm, and the divergence angle of the finally emitted laser beam is less than 3mrad over a long distance.

[0040] The technical solution of this application can simultaneously control the divergence angle and depth of field of the laser beam, eliminating the influence of spherical aberration on the imaging quality. After being modulated by four lenses, the laser beam can maintain a uniform energy distribution in the near field to far field range, which is suitable for detection scenarios where the workpiece position changes dynamically. Furthermore, the improved optical path collimation also reduces stray light interference, while the expanded depth of field allows targets at different distances to obtain clear images, effectively solving the limitations of traditional lenses in the detection of high-speed moving targets.

[0041] In this embodiment, we continue to refer to... Figures 1-2 The lens housing 30 includes a first housing 301 and a second housing 302. The laser source 10 and the first lens 201 are axially disposed in the inner cavity of the first housing 301, and the second lens 202, the third lens 203 and the fourth lens 204 are axially disposed in the inner cavity of the second housing 302.

[0042] The first housing 301 is axially movably inserted into the first end of the second housing 302 at one end away from the laser source 10 to adjust the distance between the first lens 201 and the second lens 202, the third lens 203 and the fourth lens 204.

[0043] In the above embodiment, the movable insertion structure of the first housing 301 and the second housing 302 forms a retractable mechanical connection. When the first housing 301 moves axially along the inner cavity of the second housing 302, the distance between the first lens 201 and the second lens 202, the third lens 203 and the fourth lens 204 changes accordingly. This distance adjustment directly affects the connection position between the collimation section and the focusing section of the beam.

[0044] Specifically, when detecting distant targets, the first housing 301 is pushed into the second housing 302 to shorten the distance between the front collimating optical path and the rear focusing optical path, thereby compressing the divergence angle and increasing the far-field energy density. When detecting near targets, the first housing 301 is pulled outward from the second housing 302 to increase the optical path spacing, expand the depth of field, and maintain near-field illumination uniformity. This application adjusts the optical parameters in real time by axially moving the housing to ensure that the beam divergence angle and depth of field always match the detection distance of the application scenario, avoiding imaging blurring or uneven energy distribution caused by changes in the target position.

[0045] In one example, the surface shape, radius of curvature, center distance, refractive index, and dispersion coefficient Vd of lens group 20 are shown in Table 1 below.

[0046]

[0047] Table 1

[0048] In summary, the small divergence angle and large depth of field laser illumination lens provided by this utility model embodiment adopts an adjustable design of lens group 20 and lens housing 30. In lens group 20, the combination of aspherical lens and meniscus lens optimizes the optical path, expanding the depth of field range while ensuring a small divergence angle. Combined with the movable structure of lens housing 30, the lens spacing can be adjusted, effectively solving the problems of difficulty in balancing divergence angle and depth of field and insufficient aberration correction in traditional systems. It has the advantages of balancing small divergence angle and large depth of field, fully correcting aberrations, and improving the adaptability of optical system.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A small divergence angle large depth of field laser illumination lens comprising a lens housing, characterized in that, Also includes: A laser source is axially mounted to one end of the lens housing, and its laser emission end is disposed inside the lens housing; The lens group includes a first lens, a second lens, a third lens, and a fourth lens that are coaxially and sequentially arranged on the laser emission path; The first lens is a plano-convex aspherical lens; The second lens is a positive meniscus lens with a focal length of f2; The third lens is a positive meniscus lens, and its focal length f3 satisfies 1.2≤f3 / f2≤1.5; The fourth lens is a plano-convex aspherical lens, and its focal length f4 satisfies 0.95≤f4 / f3≤2.

16.

2. The laser illumination lens of claim 1, wherein, The dispersion coefficients Vd of the second, third, and fourth lenses are ≥64.

3. The laser illumination lens of claim 1, wherein, The lens housing includes a first housing and a second housing. The laser source and the first lens are axially disposed in the inner cavity of the first housing, and the second lens, the third lens and the fourth lens are axially disposed in the inner cavity of the second housing. The first housing is axially movably inserted into the first end of the second housing at the end opposite to the laser source to adjust the distance between the first lens and the second, third, and fourth lenses.

4. The laser illumination lens of claim 1, wherein, The first lens has a planar incident surface and a convex exit surface along the laser emission path.

5. The laser illumination lens of claim 1, wherein, The second and third lenses have concave incident surfaces and convex exit surfaces along the laser emission path.

6. The laser illumination lens of claim 1, wherein, The fourth lens has a planar incident surface and a convex exit surface along the laser emission path.

7. The laser illumination lens of claim 1, wherein, The wavelength range of the laser beam emitted by the laser source is 375nm-1550nm.

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