A two-times liquid telecentric lens

Abstract

This invention discloses a 2x liquid telecentric lens, belonging to the field of optical design technology. Along the optical path, it sequentially comprises an optical magnification group, an aperture stop, a liquid lens, and an imaging group. Specifically: the optical magnification group includes three lenses: along the optical path, the first lens is a biconvex lens, the second lens is a biconvex lens, and the third lens is a biconcave lens; the liquid lens includes a protective glass containing an optical liquid, and a magnetic field generator for adjusting the curvature of the liquid lens is located on the protective glass; the imaging group includes three lenses: along the optical path, the fifth lens is a convex-concave lens, the sixth lens is a biconcave lens, and the seventh lens is a concave-convex lens. This invention, while maintaining the lens's magnification and resolution, effectively improves the accuracy and speed of detecting height differences, thus playing a greater role in various precision testing fields.

Description

Technical Field

[0001] This invention belongs to the field of optical design technology, specifically relating to a 2x liquid telecentric lens. Background Technology

[0002] With the rapid development of the machine vision industry, practitioners have increasingly higher requirements for the overall performance of systems. Most practitioners hope to achieve the highest possible visual accuracy and lens resolution, but this often conflicts with the height difference of the object being measured. Ultimately, they have to abandon high magnification and high resolution, or use mechanical means to change the relative position of the lens and the object being measured, which introduces new errors into the system. Liquid telecentric lenses can maintain the lens's magnification and resolution while ensuring the accuracy and speed of height difference detection. As a special lens that can provide low distortion rate and low telecentricity imaging, telecentric lenses can greatly improve the accuracy of the system and are increasingly recognized by practitioners. However, facing more and more applications, the characteristic of telecentric lenses that cannot change the working distance by adjusting the lens itself greatly limits practitioners' pursuit of higher visual accuracy.

[0003] In practical applications, existing solutions generally choose to increase the depth of field by reducing the magnification, thereby accommodating height differences within the imaging range. However, this method reduces the lens resolution and the overall visual accuracy of the system. Alternatively, methods such as motorized tracks can be used to change the relative position of the lens and the object under test to achieve imaging at different heights of the object. However, this method struggles to maintain both accuracy and speed simultaneously and places higher demands on the design of the entire system. For relatively old institutions, modification may not be possible, leaving them with no choice but to abandon the use of high-magnification telecentric lenses. Summary of the Invention

[0004] This invention addresses the technical problems existing in prior art by providing a 2x liquid telecentric lens. By adjusting the curvature of the liquid lens using a magnetic field generator, the telecentric lens can be adjusted to meet different needs and work distances. This technology means that while maintaining the lens's magnification and resolution, it can effectively improve the accuracy and speed of height difference detection, thus playing a greater role in various precision testing fields.

[0005] The purpose of this invention is to provide a 2x liquid telecentric lens, which, along the optical path, sequentially comprises an optical magnification group, an aperture stop, a liquid lens, and an imaging group; wherein:

[0006] The optical magnification group includes three lenses. Along the optical path, the first lens is a biconvex lens, the second lens is a biconvex lens, and the third lens is a biconcave lens.

[0007] The liquid lens includes a protective glass, an optical liquid is encapsulated inside the protective glass, and a magnetic field generator for adjusting the curvature of the liquid lens is provided on the protective glass.

[0008] The imaging group includes three lenses: along the optical path, the fifth lens is a convex-concave lens, the sixth lens is a biconcave lens, and the seventh lens is a concave-convex lens.

[0009] Preferably, the radius of curvature of the light-incident surface of the first lens is 24±5%, and the radius of curvature of the light-exit surface is -45±5%; the radius of curvature of the light-incident surface of the second lens is 40±5%, and the radius of curvature of the light-exit surface is -40±5%; the radius of curvature of the light-incident surface of the third lens is -23±5%, and the radius of curvature of the light-exit surface is 73±5%; the radius of curvature of the light-incident surface of the fifth lens is 11±5%, and the radius of curvature of the light-exit surface is 73±5%; the radius of curvature of the light-incident surface of the sixth lens is -80±5%, and the radius of curvature of the light-exit surface is 16±5%; the radius of curvature of the light-incident surface of the seventh lens is -13±5%, and the radius of curvature of the light-exit surface is -30±5%; the unit of radius of curvature is millimeters.

[0010] Preferably, the center thickness of the first lens is 3±5%, the center thickness of the second lens is 3±5%, the center thickness of the third lens is 5±5%, the total thickness of the liquid lens is 5±5%, the center thickness of the fifth lens is 3±5%, the center thickness of the sixth lens is 2±5%, and the center thickness of the seventh lens is 2±5%, with the center thickness in millimeters.

[0011] Preferably, the distance between the object and the air gap of the first lens on the optical axis is 67±5%; the distance between the air gap of the first lens and the second lens on the optical axis is 5±5%; the distance between the air gap of the second lens and the third lens on the optical axis is 1±5%; the distance between the air gap of the third lens and the aperture stop on the optical axis is 1±5%; the distance between the aperture stop and the liquid lens on the optical axis is 14±5%; the distance between the air gap of the liquid lens and the fifth lens on the optical axis is 37±5%; the distance between the air gap of the fifth lens and the sixth lens on the optical axis is 1±5%; and the distance between the air gap of the sixth lens and the seventh lens on the optical axis is 4±5%. The unit of distance is millimeters.

[0012] Preferably, the first lens has a refractive index of 1.49±5% and an Abbe number of 56±5%; the second lens has a refractive index of 1.53±5% and an Abbe number of 58±5%; the third lens has a refractive index of 1.69±5% and an Abbe number of 28±5%; the fifth lens has a refractive index of 1.57±5% and an Abbe number of 35±5%; the sixth lens has a refractive index of 1.67±5% and an Abbe number of 51±5%; and the seventh lens has a refractive index of 1.67±5% and an Abbe number of 51±5%.

[0013] Preferably, the magnetic field generator interacts with a host computer via a microcontroller.

[0014] Preferably, the working distance of the double liquid telecentric lens is 65mm, and the working wavelength is 450nm~700nm.

[0015] The advantages and positive effects of this invention are:

[0016] The technical solution of this invention mainly includes six lenses, an aperture stop, and a liquid lens made of various materials. Each lens has its own unique functional focus, ensuring that each performance parameter of the lens is handled by a corresponding lens, thus optimizing the performance parameters. Specifically, the parameters of the first lens determine the lens's field of view and initial working distance. The second lens further constricts light rays, providing space for object-side telecentricity control. The third lens, through its high refractive index, compensates for some of the aberrations caused by the first and second lenses, allowing light to enter the liquid lens more smoothly. It also works with the first and second lenses to control object-side telecentricity. The liquid lens adjusts its curvature to change the overall focal length of the optical system, thereby varying the working distance. The fifth lens manages the edge field of view and reduces system distortion and field curvature. The sixth and seventh lenses work together to control the lens's back focal length. Furthermore, the combination of the fifth and sixth lenses, along with the seventh lens, uses similar materials, has similar shapes, and faces opposite directions, thus minimizing aberrations. The seventh lens also controls the image plane size and overall magnification of the lens.

[0017] In this invention, each lens performs its own function and works together with others. The lens assembled in this way can tolerate aberrations caused by different curvatures of liquid lenses and maintain the lens's excellent performance of low telecentricity and distortion rate. Attached Figure Description

[0018] Figure 1 This is an optical path diagram of a preferred embodiment of the present invention;

[0019] Figure 2 This is an optical dispersion pattern of a preferred embodiment of the present invention;

[0020] Figure 3This is a modulation transfer function (MTF) diagram in a preferred embodiment of the present invention;

[0021] Figure 4 Field curvature and astigmatism diagrams of a preferred embodiment of the present invention; Detailed Implementation

[0022] To further understand the invention's content, features, and effects, the following embodiments are provided, and detailed descriptions are given below in conjunction with the accompanying drawings:

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the technical solutions of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and 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 invention.

[0025] Please see Figure 1 .

[0026] A 2x liquid telecentric lens mainly comprises the following four parts: a first optical magnification group, an aperture stop, liquid lenses, and an imaging group; wherein:

[0027] The optical magnification group mainly consists of three lenses, arranged along the optical path as follows: the first lens L1 is a biconvex lens, the second lens L2 is a biconvex lens, and the third lens L3 is a biconcave lens; followed by an aperture stop; the liquid lens L4 mainly consists of a protective glass, an optical liquid, and a magnetic field generator. The optical liquid is encapsulated inside the protective glass, and the magnetic field generator is controlled by a microcontroller that can communicate with a host computer; the imaging group mainly consists of three lenses: the fifth lens L5 is a convex-concave lens, the sixth lens L6 is a biconcave lens, and the seventh lens L7 is a concave-convex lens.

[0028] To better understand the concept of this invention, it will be described in detail below:

[0029] Further explanation of the lenses forming the optical path: Since the curvature of the liquid lens is variable and controlled by the circuit, the design scheme excludes the liquid lens from refraction, resulting in an infinite curvature. The first lens L1 has an incident light surface curvature radius of 24±5% and an exit light surface curvature radius of -45±5%; the second lens L2 has an incident light surface curvature radius of 40±5% and an exit light surface curvature radius of -40±5%; the third lens L3 has an incident light surface curvature radius of -23±5% and an exit light surface curvature radius of 73±5%; the fifth lens L5 has an incident light surface curvature radius of 11±5% and an exit light surface curvature radius of 73±5%; the sixth lens L6 has an incident light surface curvature radius of -80±5% and an exit light surface curvature radius of 16±5%; and the seventh lens L7 has an incident light surface curvature radius of -13±5% and an exit light surface curvature radius of -30±5%. All units are millimeters.

[0030] The center thicknesses of the lenses forming the dual telecentric optical path are as follows: the center thickness of the first lens L1 is 3±5%; the center thickness of the second lens L2 is 3±5%; the center thickness of the third lens L3 is 5±5%; the total thickness of the liquid lens is 5±5%; the center thickness of the fifth lens L5 is 3±5%; the center thickness of the sixth lens L6 is 2±5%; and the center thickness of the seventh lens L7 is 2±5%. All units are millimeters.

[0031] The distance on the optical axis between the object and the air gap of the first lens L1 is 67±5%; the distance on the optical axis between the first lens L1 and the second lens L2 is 5±5%; the distance on the optical axis between the second lens L2 and the third lens L3 is 1±5%; the distance on the optical axis between the third lens L3 and the aperture is 1±5%; the distance on the optical axis between the aperture and the liquid lens is 14±5%; the distance on the optical axis between the liquid lens and the fifth lens L5 is 37±5%; the distance on the optical axis between the fifth lens L5 and the sixth lens L6 is 1±5%; and the distance on the optical axis between the sixth lens L6 and the seventh lens L7 is 4±5%. All units are millimeters.

[0032] The refractive indices and Abbe numbers of the lenses forming the telecentric optical path are as follows: the first lens L1 has a refractive index of 1.49±5% and an Abbe number of 56±5%; the second lens L2 has a refractive index of 1.53±5% and an Abbe number of 58±5%; the third lens L3 has a refractive index of 1.69±5% and an Abbe number of 28±5%; the fifth lens L5 has a refractive index of 1.57±5% and an Abbe number of 35±5%; the sixth lens L6 has a refractive index of 1.67±5% and an Abbe number of 51±5%; and the seventh lens L7 has a refractive index of 1.67±5% and an Abbe number of 51±5%.

[0033] In this invention patent, when the liquid lens does not participate in refraction, the working distance of the double liquid telecentric lens is 65mm, and the working wavelength is 450nm-700nm.

[0034] Depend on Figure 2 It can be seen that the RMS radius represents the root mean square radius of the diffuse spot, and the GEO radius represents the Airy disk radius, both in micrometers. As shown in the figure, in the central field of view, the RMS radius is 8.732 μm and the Airy disk radius is 15.403 μm; in the peripheral field of view, the RMS radius is 8.865 μm and the Airy disk radius is 22.604 μm. Most of the aberrations are within the Airy disk radius, and the energy concentration and aberration correction at both on-axis and off-axis points are excellent, achieving ideal resolution.

[0035] Depend on Figure 3 As shown in the figure, although the lens resolution is slightly lower due to the influence of various materials in the liquid lens, the overall contrast and resolution of the lens can meet the theoretical requirements of the lens parameters, and the performance across the entire field of view is also roughly the same.

[0036] Depend on Figure 4 It can be seen that the vertical axis represents the field of view, and the horizontal axis is in millimeters.

[0037] The distortion graph shows that the vertical axis represents the field of view, and the horizontal axis represents the distortion value. As shown in the figure, the maximum distortion value of the lens is 0.0056%.

[0038] In summary, the telecentric lens designed in this invention achieves the theoretical standard in terms of contrast and resolution, and has low telecentricity and distortion rate.

[0039] Explanation of some related concepts and definitions:

[0040] Resolution: A measure of optical capability; the smallest distance that can be resolved.

[0041] Contrast: The contrast between black and white, light and dark lines.

[0042] Distortion rate: The change in the geometry of an object as seen when it is viewed through a material.

[0043] Telecentricity: describes the angle at which the principal ray deviates from the optical axis.

[0044] Optical magnification: The ratio of the size of the image of an object on the focal plane formed by a lens group to the actual size of the object.

[0045] Visual precision: The length of each pixel in machine vision imaging corresponds to the length in the real world.

[0046] Liquid lenses: Lenses encapsulated with optical liquids, whose curvature can be controlled by circuitry.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A double-liquid telecentric lens, characterized in that, Along the optical path, there are sequentially arranged optical magnification group, aperture stop, liquid lens, and imaging group; the total number of lenses in the 2x liquid telecentric lens is 7; among which: The optical magnification group includes three lenses. Along the optical path, the first lens is a biconvex lens, the second lens is a biconvex lens, and the third lens is a biconcave lens. The liquid lens includes a protective glass, an optical liquid is encapsulated inside the protective glass, and a magnetic field generator for adjusting the curvature of the liquid lens is provided on the protective glass. The imaging group includes three lenses. Along the optical path, the fifth lens is a convex-concave lens, the sixth lens is a biconcave lens, and the seventh lens is a concave-convex lens. The focal length of the fifth lens is positive, and the focal length of the seventh lens is negative. The first lens has a refractive index of 1.49±5% and an Abbe number of 56±5%; the second lens has a refractive index of 1.53±5% and an Abbe number of 58±5%; the third lens has a refractive index of 1.69±5% and an Abbe number of 28±5%; the fifth lens has a refractive index of 1.57±5% and an Abbe number of 35±5%; the sixth lens has a refractive index of 1.67±5% and an Abbe number of 51±5%; and the seventh lens has a refractive index of 1.67±5% and an Abbe number of 51±5%.

2. The double liquid telecentric lens according to claim 1, characterized in that: The first lens has an incident light surface radius of 24±5% and an exit light surface radius of -45±5%; the second lens has an incident light surface radius of 40±5% and an exit light surface radius of -40±5%; the third lens has an incident light surface radius of -23±5% and an exit light surface radius of 73±5%; the fifth lens has an incident light surface radius of 11±5% and an exit light surface radius of 73±5%; the sixth lens has an incident light surface radius of -80±5% and an exit light surface radius of 16±5%; and the seventh lens has an incident light surface radius of -13±5% and an exit light surface radius of -30±5%. The unit of radius of curvature is millimeters.

3. The double liquid telecentric lens according to claim 1, characterized in that: The center thickness of the first lens is 3±5%, the center thickness of the second lens is 3±5%, the center thickness of the third lens is 5±5%, the total thickness of the liquid lens is 5±5%, the center thickness of the fifth lens is 3±5%, the center thickness of the sixth lens is 2±5%, and the center thickness of the seventh lens is 2±5%. The unit of center thickness is millimeters.

4. The double liquid telecentric lens according to claim 1, characterized in that, The distance between the object and the air gap of the first lens on the optical axis is 67±5%; the distance between the air gap of the first lens and the second lens on the optical axis is 5±5%; the distance between the air gap of the second lens and the third lens on the optical axis is 1±5%; the distance between the air gap of the third lens and the aperture stop on the optical axis is 1±5%; the distance between the aperture stop and the liquid lens on the optical axis is 14±5%; the distance between the air gap of the liquid lens and the fifth lens on the optical axis is 37±5%; the distance between the air gap of the fifth lens and the sixth lens on the optical axis is 1±5%; the distance between the air gap of the sixth lens and the seventh lens on the optical axis is 4±5%; the unit of distance is millimeters.

5. The double liquid telecentric lens according to any one of claims 1-4, characterized in that, The magnetic field generator interacts with a host computer via a microcontroller.

6. The double liquid telecentric lens according to claim 5, characterized in that, The working distance of the double liquid telecentric lens is 65mm, and the working wavelength is 450nm~700nm.

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