Lens and imaging device

Abstract

The invention provides a lens and an imaging device. The lens comprises a first lens group and a second lens group which are sequentially arranged from an object side to an image side, the first lens group comprises at least two first lenses which are sequentially arranged from the object side to the image side, and the second lens group comprises a second lens, a third lens and at least one fourth lens which are sequentially arranged from the object side to the image side. The first lens, the second lens and the fourth lens are respectively positive focal power lenses, and the third lens is a negative focal power lens. The lens comprises a first lens group with a visual angle correction function and a second lens group with a field curvature aberration correction function, and is suitable for optical performance detection of a display panel, especially an OLED display panel adopting an MLA technology.

Description

Technical Field

[0001] The present disclosure relates to the field of optical detection technology, and more specifically, to a lens and an imaging device. Background Art

[0002] Automated optical inspection (AOI) is an effective inspection solution for industrial automation and is currently widely used to test the optical performance of display panels. The inventors discovered that the viewing angles of the lenses in current imaging devices used for optical performance testing cannot match the viewing angle characteristics of display panels, such as OLED (Organic Light Emitting Diode) panels that use MLA (Micro Lens Array) technology. This results in low illumination at the edges of the field of view, low imaging resolution, and low inspection accuracy. Summary of the Invention

[0003] The present disclosure aims to provide a lens and an imaging device to solve at least one of the problems existing in the prior art.

[0004] To achieve the above objectives, the present disclosure adopts the following technical solutions:

[0005] In a first aspect, the present disclosure provides a lens, comprising a first lens group and a second lens group arranged sequentially from the object side to the image side, wherein the first lens group comprises at least two first lenses arranged sequentially from the object side to the image side, and the second lens group comprises a second lens, a third lens, and at least one fourth lens arranged sequentially from the object side to the image side, wherein the first lens, the second lens, and the fourth lens are respectively positive power lenses, and the third lens is a negative power lens.

[0006] Optionally, the lens further includes an aperture stop located between the first lens group and the second lens group.

[0007] Optionally, the at least two first lenses include a first first lens, a second first lens and a third first lens arranged in sequence from the object side to the image side, the optical focal length of the first first lens is greater than the optical focal length of the second first lens, the optical focal length of the second first lens is greater than the optical focal length of the third first lens, and the incident light passes through the first first lens, the second first lens and the third first lens in sequence to achieve perspective correction.

[0008] Optionally, the first first lens is a first meniscus lens, the second first lens is a first biconvex lens, and the third first lens is a doublet lens.

[0009] Optionally, the absolute value of the focal length of the third lens is greater than that of the second lens, and the focal length of the second lens is greater than that of the fourth lens; the incident light passes through the second lens, the third lens, and the fourth lens in sequence to achieve aberration correction.

[0010] Optionally, the second lens is a second meniscus lens, and the third lens is a biconcave lens.

[0011] Optionally, the at least one fourth lens includes a first fourth lens and a second fourth lens arranged sequentially from the object side to the image side.

[0012] Optionally, the first fourth lens is a third meniscus lens, and the second fourth lens is a second biconvex lens.

[0013] A second aspect of the present disclosure provides an imaging device, comprising the lens provided by the first aspect of the present disclosure and an image sensor located on the image side of the lens.

[0014] The beneficial effects of the present disclosure are as follows:

[0015] The lens disclosed herein includes a first lens group with a perspective correction function and a second lens group with a field curvature correction function. It is suitable for optical performance testing of display panels, particularly OLED display panels using MLA technology. Based on the lens disclosed herein, an imaging device can achieve high-resolution imaging across the entire field of view without the assistance of a mechanical motion device, improving the accuracy and speed of optical performance testing of display panels. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The specific embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0017] Figure 1 A schematic diagram showing a lens provided by an embodiment of the present disclosure is shown.

[0018] Figure 2 A schematic diagram showing the direction of light rays in a lens provided by an embodiment of the present disclosure is shown.

[0019] Figure 3 A relative illumination curve diagram of the lens provided by an embodiment of the present disclosure is shown.

[0020] Figure 4 The figure shows the MTF curves of the image plane corresponding to each field of view of the lens provided by the embodiment of the present disclosure.

[0021] Figure 5 A distortion curve diagram of the lens provided by an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0022] To more clearly illustrate the present disclosure, the present disclosure is further described below in conjunction with the embodiments and drawings. Similar components in the drawings are represented by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be used to limit the scope of protection of the present disclosure.

[0023] In the description of the present disclosure, it should be noted that the orientation or positional relationship indicated by the terms "upper" and "lower" is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present disclosure. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present disclosure can be understood according to the specific circumstances.

[0024] It should also be noted that, in the description of the present disclosure, relational terms such as first and second, etc., are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0025] In the display field, OLED display panels, compared to LCDs (Liquid Crystal Displays), have advantages such as self-luminescence, fast response, wide viewing angle, high brightness, vivid colors, and thinness, and are considered the next generation of display technology. Related technologies have proposed an OLED display panel using MLA technology. By using MLA to increase light extraction efficiency, it not only increases the brightness of the display but also increases the viewing angle of the display, thereby improving the display effect. OLED display panels using MLA technology can be applied to new display products such as AR and VR.

[0026] When testing the optical performance of OLED display panels using MLA technology, the viewing angle of conventional lenses cannot match the viewing angle characteristics of OLED display panels using MLA technology, resulting in vignetting and an imaging field of view smaller than the designed value. Therefore, the optical performance data obtained from the test cannot quantitatively reflect what the human eye actually sees. If a point-by-point scanning or angle-by-angle scanning test solution is adopted, a mechanical motion device will be required to provide assistance to increase the test field of view. However, this solution is complex, has high testing costs and low testing efficiency, which will greatly limit the production and testing speed of display products and is not conducive to mass production.

[0027] In view of this, an embodiment of the present disclosure provides a high-resolution lens that can match the viewing angle characteristics (including field of view size and viewing angle distribution) of an OLED display panel using MLA technology. The lens includes a first lens group and a second lens group arranged in sequence from the object side to the image side. The first lens group includes at least two first lenses arranged in sequence from the object side to the image side. The second lens group includes a second lens, a third lens and at least one fourth lens arranged in sequence from the object side to the image side. The first lens, the second lens and the fourth lens are respectively positive optical power lenses, and the third lens is a negative optical power lens.

[0028] Among them, a positive power lens is a converging lens used to converge light, and can also be called a positive lens. A negative power lens is a diverging lens used to diverge light, and can also be called a negative lens.

[0029] The lens provided in this embodiment includes a first lens group with a perspective correction function and a second lens group with a field curvature aberration correction function, arranged sequentially from the object side to the image side. This lens is suitable for optical performance testing of display panels, particularly OLED display panels using MLA technology. For example, optical performance testing includes testing items such as points, lines, mura defects, and brightness uniformity on the display panel, thereby providing guidance for display panel repair. Based on the lens provided in this embodiment, the imaging device can perform high-resolution imaging across the entire field of view without the assistance of a mechanical motion device, which can improve the accuracy and speed of optical performance testing of display panels.

[0030] In a possible implementation, the lens further includes a stop located between the first lens group and the second lens group.

[0031] This implementation method limits the range of light by setting an aperture, and can reduce aberrations related to the beam diameter, such as high-order spherical aberration, by changing the beam diameter, thereby further improving the imaging resolution.

[0032] In a specific example, for example Figure 1As shown, the lens includes a first lens group 200, an aperture 300, and a second lens group 400, which are arranged in sequence from the object side to the image side between the object plane 100 and the image plane 500. The second lens group 400 includes a second lens 401, a third lens 402, and at least one fourth lens, which are arranged in sequence from the object side to the image side. The aperture 300 is approximately attached to the side of the second lens 401 facing the incident direction of light (and Figure 1 In the embodiment of the present invention, the first lens group 200 and the second lens group 400 are approximately symmetrical with respect to the aperture 300. The distortion aberrations generated by the lenses in the approximately symmetrical first lens group 200 and the second lens group 400 on both sides of the aperture 300 are in opposite directions. That is to say, if a certain amount of positive distortion is generated after light passes through at least two first lenses in the first lens group 200 before the aperture 300, an equal amount of negative distortion will be generated after light passes through the second lens 401, the third lens 402, and at least one fourth lens in the second lens group 400 after the aperture 300. Ultimately, the positive and negative distortions cancel each other out at the image plane 500, thereby achieving distortion correction.

[0033] In one possible implementation, the at least two first lenses include a first first lens, a second first lens, and a third first lens arranged sequentially from the object side to the image side, the optical focal power of the first first lens is greater than the optical focal power of the second first lens, the optical focal power of the second first lens is greater than the optical focal power of the third first lens, and the incident light passes through the first first lens, the second first lens, and the third first lens in sequence to achieve perspective correction.

[0034] Continuing with the previous example, Figure 1 As shown, the at least two first lenses of the first lens group 200 include a first first lens 201, a second first lens 202, and a third first lens 203, arranged sequentially from the object side to the image side. These lenses are positive-power lenses. The focal power of the first first lens 201 is greater than that of the second first lens 202, and the focal power of the second first lens 202 is greater than that of the third first lens 203. With this design, the focal power of the first first lens 201, the second first lens 202, and the third first lens 203, all of which function to converge light, gradually decreases, resulting in a gradually weakened convergence effect. This achieves stepwise convergence with a decreasing amount of change in the incident light. This allows the first lens group 200 to achieve smoother convergence of incident light when performing perspective correction on the incident light, ensuring the perspective correction effect.

[0035] In one possible implementation, the first first lens is a first meniscus lens, the second first lens is a first biconvex lens, and the third first lens is a doublet lens. This facilitates achieving the optical power design requirements of the first first lens, the second first lens, and the third first lens at low cost and high precision.

[0036] Continuing with the previous example, for example Figure 1 As shown, the first lens element 201 is a first meniscus lens that is curved toward the incident direction of light (i.e., its concave surface faces the object plane 100). The optical power of a meniscus lens is primarily determined by the radii of curvature of its convex and concave surfaces. A smaller convex radius and a larger concave radius, i.e., a shape that is more similar to a convex lens overall, results in a higher optical power (positive optical power). The second lens element 202 is a first biconvex lens. The third lens element 203, due to the need for a very small positive optical power and the high precision required, utilizes a more complex but highly precise doublet.

[0037] In one possible implementation, the absolute value of the optical power of the third lens is greater than the optical power of the second lens, and the optical power of the second lens is greater than the optical power of the fourth lens; the incident light passes through the second lens, the third lens, and the fourth lens in sequence to achieve aberration correction. Therefore, by designing the optical power of the third lens and the second lens, it is beneficial to achieve the combination of the second lens with positive optical power and the third lens with negative optical power, and then combined with the fourth lens with positive optical power. By designing the convergence, divergence, and re-convergence of light (that is, the light height goes from high to low, then from low to high, and then from high to low twice), the light produces field curvature aberrations of opposite signs or directions during the convergence and divergence process, and finally the positive and negative field curvature aberrations cancel each other out, thereby achieving field curvature aberration correction. The optical power design of the second lens and the fourth lens is more conducive to the correction of field curvature aberration in the second lens group.

[0038] In one possible implementation, the second lens is a second meniscus lens, and the third lens is a biconcave lens, thereby facilitating low-cost and high-precision implementation of the optical power design requirements for the second and third lenses.

[0039] In a possible implementation, the at least one fourth lens includes a first fourth lens and a second fourth lens sequentially arranged from the object side to the image side.

[0040] In a possible implementation, the optical power of the first fourth lens is greater than the optical power of the second fourth lens.

[0041] Based on the above implementation, by designing the number and focal length of the fourth lens to decrease gradually, the fourth lens can help converge the light on the image plane to form an image.

[0042] In one possible implementation, the first-fourth lens is a third meniscus lens, and the second-fourth lens is a second biconvex lens, thereby facilitating low-cost and high-precision implementation of the optical power design requirements for the first-fourth lens and the second-fourth lens.

[0043] Continuing with the previous example, for example Figure 1 As shown, the second lens group 400 includes a second lens 401, a third lens 402, a first-fourth lens 403, and a second-fourth lens 404, arranged sequentially from the object side to the image side. The second lens 401 is a second meniscus lens curved away from the incident direction of the light (i.e., its convex surface faces the object plane 100), the third lens 402 is a biconcave lens, the first-fourth lens 403 is a third meniscus lens curved toward the incident direction of the light (i.e., its concave surface faces the object plane 100), and the second-fourth lens 404 is a second biconvex lens. By designing the optical power of the second lens 401, the third lens 402, the first-fourth lens 403, and the second-fourth lens 404, the incident light of the second lens group 400 is converged, diverged, and then converged again (i.e., the light level changes from high to low, then from low to high, and then again from high to low again), thereby correcting field curvature aberrations. The optical power design of the first-fourth lens 403 and the second-fourth lens 404 also enables the light to converge and form an image on the image plane 500.

[0044] In conjunction with the above examples, the lens provided by the present disclosure includes a first lens group 200 with a perspective correction function and a second lens group 400 with a field curvature correction function, arranged sequentially from the object side to the image side. This design, which performs perspective correction first and then field curvature correction, is particularly suitable for optical performance testing of OLED display panels using MLA technology. This is because the inventors discovered that the perspective characteristics of most display panels are similar to those of Lambertian radiators; however, the perspective characteristics of OLED display panels using MLA technology differ significantly from those of Lambertian radiators, necessitating correction for these perspective characteristics first. Therefore, the lens includes the first lens group 200 with perspective correction function, which is positioned relatively close to the object side. Furthermore, the image sensor on the image side of the lens has a flat, rather than curved, photosensitive surface. Therefore, the lens also includes the second lens group 400 with field curvature correction function, which is positioned relatively close to the image side. This allows field curvature correction to be performed by the second lens group 400 after perspective correction by the first lens group 200.

[0045] Regarding the optical components of the first lens group 200 and the second lens group 400, the inventors first defined the overall lens structure as one in which the first lens group 200 and the second lens group 400 present a nearly symmetrical structure relative to the aperture 300. This allows the distortion aberrations generated by the first lens group 200 and the second lens group 400 to cancel each other out, achieving distortion correction. Based on this definition, when designing the optical components of the first lens group 200 and the second lens group 400, the inventors designed the number of optical lenses in the first lens group 200 and the second lens group 400 to follow the principle of symmetry, taking into account the requirements for achieving perspective correction and field curvature correction without increasing the cost and complexity of assembly and debugging.

[0046] First lens group 200 includes a first lens 201, a second lens 202, and a third lens 203. If third lens 203 is a doublet, i.e., comprises two lenses, first lens group 200 comprises four lenses. Second lens group 400 includes a second lens 401, a third lens 402, a first fourth lens 403, and a second fourth lens 404. Second lens group 400 also includes four lenses. Simulation experiments have verified that if first lens group 200 and second lens group 400 each consist of two or three lenses, the adjustable variables for optimizing light are limited, insufficient to achieve the desired effects of perspective correction and field curvature correction. However, if first lens group 200 and second lens group 400 each consist of four lenses, perspective correction and field curvature correction can be achieved through lens design. If first lens group 200 and second lens group 400 each consist of five or more lenses, the cost of the lenses increases, and assembly and commissioning become more complex. Therefore, the above example adopts a symmetrical design in which the first lens group 200 and the second lens group 400 each include four lenses.

[0047] After evaluating the convergence and divergence of light, the type and focal length of each lens are designed. For example, the focal length of the lens is -0.015mm. -1 The focal lengths of the first lens 201, the second lens 202, and the third lens 203 are 0.019 mm respectively. -1 , 0.011mm -1 , 0.0007mm -1 The focal lengths of the second lens 401, the third lens 402, the first and fourth lenses 403, and the second and fourth lenses 404 are 0.033 mm respectively. -1 、-0.089mm -1 , 0.016mm -1 , 0.012mm -1After the optical powers of the seven lenses are normalized (divided by the lens optical power -0.015), the normalized optical powers of the first lens 201, the second lens 202, the third lens 203, the second lens 401, the third lens 402, the first fourth lens 403, and the second fourth lens 404 are -1.267, -0.733, -0.047, -2.200, 5.933, -1.067, and -0.800, respectively. For example, the normalized optical power Φ of the first lens 201 is 201 The value range of is [-1.4, -1.1], and the normalized optical power Φ of the second first lens 202 202 The value range of is [-0.9, -0.6], and the normalized optical power Φ of the third first lens 203 is 203 The value range of is [-0.060, -0.025], and the normalized optical power Φ of the second lens 401 is 401 The value range of is [-2.4, -2], and the normalized optical power Φ of the third lens 402 402 The value range of is [5.7, 6.1], and the normalized optical power Φ of the first and fourth lenses 403 is 403 The value range of is [-1.1, -0.95], and the normalized optical power Φ of the second and fourth lenses 404 is 404 The value range is [-0.9,-0.7].

[0048] Continuing with the above example, the working distance range of the lens provided by the embodiment of the present disclosure is L with a value range of 5mm to 10mm, the magnification β with a value range of 3≥β≥1.4, the working band range of 400nm-700nm, and the imaging field of view diameter (2Y) of 25mm.

[0049] In combination with the above examples, the direction of light in the lens provided by the embodiment of the present disclosure is as follows: Figure 2 As shown, specifically:

[0050] First, the incident light within a large viewing angle range enters the lens through the first first lens 201 (first meniscus lens), and is gradually converged by the first first lens 201 (first meniscus lens), the second first lens 202 (first biconvex lens) and the third first lens 203 (cemented lens) in the first lens group 200 to achieve viewing angle correction.

[0051] Then, the light rays converged step by step by the first lens group 200 enter the second lens group 400 after passing through the aperture 300, converge by the second lens 401 (second meniscus lens), diverge by the third lens 402 (double concave lens), converge by the first and fourth lenses 403 (third meniscus lens), and converge by the second and fourth lenses 404 (second double convex lens), so as to achieve field curvature aberration correction (and distortion aberration correction), and finally focus on the image plane 500.

[0052] The lens provided in this embodiment includes seven lenses whose surfaces are all spherical. Its relative illumination curve is as follows: Figure 3 As shown, Figure 3 Middle: The horizontal axis is the imaging field radius Y (or half field height), in millimeters; the vertical axis is the relative illumination value. Figure 3 It can be seen that the relative illumination value of the lens provided in this embodiment is greater than 90% in the entire field of view.

[0053] The MTF curves of the image plane corresponding to each field of view of the lens provided in this embodiment are as follows: Figure 4 As shown, Figure 4 Middle: The horizontal axis is the spatial frequency in cycles / mm, and the vertical axis represents the modulation transfer function (MTF). Figure 4 In the figure, the curves corresponding to the central field of view to the edge field of view are arranged from top to bottom. Figure 4 It can be seen that the modulation transfer function (MTF) of the lens provided in this embodiment is greater than 0.3@501p / mm in both the central and peripheral fields of view, and the curves are smooth and compact. This indicates that the lens provides clear and uniform imaging, with excellent imaging quality across the entire field of view.

[0054] The distortion curve of the lens provided in this embodiment is as follows Figure 5 As shown, Figure 5 Middle: The horizontal axis is the distortion value relative to the image plane, in %, and the vertical axis is the imaging field of view, in millimeters. Figure 5 It can be seen that the distortion aberration of the spectroscopic imaging of the lens provided in this embodiment has been fully corrected, and the maximum distortion is less than 0.8%.

[0055] In summary, the lens provided in this embodiment, through its viewing angle design, achieves high-resolution imaging across the entire field of view without the aid of a mechanical motion device. This makes it suitable for optical performance testing of display panels, particularly OLED display panels using MLA technology, and can improve both the accuracy and speed of such testing. Furthermore, after rational optimization, the lens provided in this embodiment features a simple and compact structure, easy assembly and adjustment, high illumination uniformity, high resolution, low distortion, and high-quality imaging, promising broad application prospects.

[0056] Another embodiment of the present disclosure provides an imaging device, comprising the lens provided in the above embodiment and an image sensor located on the image side of the lens. Figure 1 As shown, the CMOS photosensitive surface of the image sensor is Figure 1 The image plane 500 is shown.

[0057] Obviously, the above embodiments of the present disclosure are merely examples for clearly illustrating the present disclosure, and are not intended to limit the implementation methods of the present disclosure. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to enumerate all the implementation methods here. Any obvious changes or modifications derived from the technical solution of the present disclosure are still within the scope of protection of the present disclosure.

Claims

1. A lens, characterized in that: The invention comprises a first lens group and a second lens group arranged in sequence from the object side to the image side, wherein the first lens group comprises at least two first lenses arranged in sequence from the object side to the image side, and the second lens group comprises a second lens, a third lens and at least one fourth lens arranged in sequence from the object side to the image side, wherein the first lens, the second lens and the fourth lens are respectively positive power lenses, and the third lens is a negative power lens.

2. The lens according to claim 1, wherein: The lens further includes an aperture stop located between the first lens group and the second lens group.

3. The lens according to claim 1, wherein: The at least two first lenses include a first first lens, a second first lens, and a third first lens arranged in sequence from the object side to the image side. The optical focal power of the first first lens is greater than that of the second first lens, and the optical focal power of the second first lens is greater than that of the third first lens. The incident light passes through the first first lens, the second first lens, and the third first lens in sequence to achieve perspective correction.

4. The lens according to claim 3, wherein: The first first lens is a first meniscus lens, the second first lens is a first biconvex lens, and the third first lens is a doublet lens.

5. The lens according to claim 1, wherein: The absolute value of the focal length of the third lens is greater than that of the second lens, and the focal length of the second lens is greater than that of the fourth lens; the incident light is corrected by the second lens, the third lens, and the fourth lens in sequence.

6. The lens according to claim 5, wherein: The second lens is a second meniscus lens, and the third lens is a biconcave lens.

7. The lens according to claim 5, wherein: The at least one fourth lens includes a first fourth lens and a second fourth lens arranged in sequence from the object side to the image side.

8. The lens according to claim 7, wherein: The optical power of the first fourth lens is greater than that of the second fourth lens.

9. The lens according to claim 8, wherein: The first and fourth lenses are third meniscus lenses, and the second and fourth lenses are second biconvex lenses.

10. An imaging device, characterized in that: The lens comprises the lens according to any one of claims 1 to 9 and an image sensor located on the image side of the lens.

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