A flat-field telecentric scanning lens

Abstract

The present invention discloses a flat-field telecentric scanning lens, which includes a diaphragm, a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along the optical axis from the object side to the image side. The first lens is a positive meniscus lens with positive optical power; the second lens is a negative meniscus lens with negative optical power; the third lens is a positive meniscus lens with positive optical power; the fourth lens is a positive meniscus lens with positive optical power; the fifth lens is a biconvex lens with positive optical power. The tilt angle of the chief ray on the image plane of this scanning lens is less than 0.1°, various aberrations are well corrected, the scanning field diameter is not less than 110 mm, and the structure is simple, the design is reasonable, and it is easy to manufacture.

Description

Technical Field

[0001] The present invention relates to the technical field of optical instrument equipment, and more specifically, to a flat-field telecentric scanning lens. Background Art

[0002] With the continuous development of the fields of scanning imaging or laser processing, the requirements for scanning lenses are getting higher and higher. Especially in the field of scanning imaging, a scanning lens is generally placed in front of an imaging lens. The scanning lens is equivalent to the image plane of the front scanning lens. Therefore, in order to reduce the lens size and effectively utilize the lens field of view, the scanning lens needs to be designed in a telecentric form. And assuming that the front lens has no aberration, that is, the imaging plane is flat, in order to reduce aberration, the scanning lens needs to be designed as a flat-field lens. However, few existing lenses can meet the above requirements at the same time.

[0003] Therefore, how to provide a new type of flat-field telecentric scanning lens is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a flat-field telecentric scanning lens, which can achieve large field of view, non-vignetting, flat-field telecentric scanning imaging, and has a simple structure, reasonable design and is easy to manufacture.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A flat-field telecentric scanning lens includes a diaphragm, a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along the optical axis from the object side to the image side. The first lens is a positive meniscus lens with positive optical power; the second lens is a negative meniscus lens with negative optical power; the third lens is a positive meniscus lens with positive optical power; the fourth lens is a positive meniscus lens with positive optical power; the fifth lens is a biconvex lens with positive optical power.

[0007] Preferably, both surfaces of the first lens are concave towards the object side, and the focal length is 200 mm - 210 mm.

[0008] Preferably, both surfaces of the second lens are concave towards the object side, and the focal length is -90 mm - 95 mm.

[0009] Preferably, both surfaces of the third lens are concave towards the object side, and the focal length is 370 mm - 400 mm.

[0010] Preferably, both surfaces of the fourth lens are concave towards the object side, and the focal length is 250 mm - 280 mm.

[0011] Preferably, the incident surface of the fifth lens is convex towards the object side, and the exit surface is concave towards the object side, and the focal length is 450 mm - 500 mm.

[0012] Preferably, the angle between the principal ray of the object plane and the object plane in the full field of view of the scanning lens is less than 0.1°.

[0013] Preferably, the image field diameter of the scanning lens is not less than 110 mm.

[0014] Preferably, the maximum aperture diameters of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are all no greater than 150 mm.

[0015] Through the above technical solutions, it can be known that compared with the prior art, the present invention discloses a flat-field telecentric scanning lens, with a full-field telecentricity of less than 0.1 degrees, a field curvature of less than 50 microns, and a full-field diffuse spot that is almost within the Airy disk. Moreover, the present invention uses spherical lenses, which can be fully realized under the existing processing and detection technology, and has a simple structure, reasonable design, and is easy to manufacture, meeting the requirements of mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0017] Figure 1 This is a schematic diagram of the structure of a flat-field telecentric scanning lens provided by the present invention.

[0018] Among them, 1, aperture, 2, first lens, 3, second lens, 4, third lens, 5, fourth lens, 6, fifth lens.

[0019] Figure 2 1 is a transfer function curve diagram of a flat-field telecentric scanning lens implementing the present invention. In the figure, the ordinate is the value of the optical transfer function (MTF), and the abscissa is the spatial frequency. It can be seen from the figure that the optical transfer function curve is close to the diffraction limit, indicating that the scanning lens has excellent scanning quality.

[0020] Figure 3 The spot diagram of a flat-field telecentric scanning lens implementing the present invention is shown above. It can be seen that most of the light in each field of view is within the range of the Airy disk.

[0021] Figure 4 This is a light fan diagram of a flat-field telecentric scanning lens implementing the present invention. The ordinate in the diagram is the distance that the light deviates from the center on the image plane, and the abscissa represents the distance of the light from the center of the aperture stop. It can be seen that the optical system has a good characteristic curve.

[0022] Figure 5 It is the field curvature curve graph of a flat-field telecentric scanning lens for implementing the present invention as described above. The ordinate is the field of view, the abscissa is the deviation amount of meridional light and sagittal light, and the field curvature is not greater than 50 microns.

[0023] Figure 6 It is the distortion curve graph of a flat-field telecentric scanning lens for implementing the present invention as described above. Its F-Theta distortion is less than 0.5%. Specific embodiments

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] The embodiments of the present invention disclose a flat-field telecentric scanning lens, as Figure 1 shown, including: a diaphragm 1, a first lens 2, a second lens 3, a third lens 4, a fourth lens 5, and a fifth lens 6 arranged in sequence along the optical axis from the object side to the image side. The first lens 2 is a positive meniscus lens with a positive optical power; the second lens 3 is a negative meniscus lens with a negative optical power; the third lens 4 is a positive meniscus lens with a positive optical power; the fourth lens 5 is a positive meniscus lens with a positive optical power; the fifth lens 6 is a biconvex lens with a positive optical power.

[0026] As a specific embodiment, the distance between the diaphragm 1 and the incident surface of the first lens 2, i.e., the S1 surface, is 28 mm ± 0.5 mm.

[0027] As a specific embodiment, the radius of curvature of the incident surface of the first lens 2, i.e., the S1 surface, is -104.2 mm ± 1.2 mm, the radius of curvature of the exit surface, i.e., the S2 surface, is -60.39 mm ± 0.2 mm, the thickness of the first lens is 12.5 mm ± 0.3 mm, that is, the distance between the centers of the S1 surface and the S2 surface, the refractive index / Abbe number of the material is 1.61 / 37, the gap between the center of the exit surface of the first lens and the center of the incident surface of the second lens is 18 mm ± 0.1 mm, the focal length is 200 mm - 210 mm, and the preferred focal length is 209.4 mm.

[0028] As a specific embodiment, the radius of curvature of the incident surface of the second lens 3, i.e., the S3 surface, is -45.3 mm ± 0.5 mm, the radius of curvature of the exit surface, i.e., the S4 surface, is -409.3 mm ± 2.8 mm, and the thickness is 15.9 mm ± 0.2 mm, which is the distance between the centers of the S3 surface and the S4 surface. The refractive index / Abbe number of the material is 1.57 / 63. The gap between the center of the exit surface of the second lens and the center of the incident surface of the third lens is 30.7 mm ± 1.1 mm, and the focal length is -90 mm to -95 mm, preferably -90.5 mm.

[0029] As a specific embodiment, the radius of curvature of the incident surface of the third lens 4, i.e., the S5 surface, is -218.8 mm ± 1.3 mm, the radius of curvature of the exit surface, i.e., the S6 surface, is -118 mm ± 1.1 mm, and the thickness is 24.5 mm ± 1 mm, which is the distance between the centers of the S5 surface and the S6 surface. The refractive index / Abbe number of the material is 1.61 / 37. The gap between the center of the exit surface of the third lens and the center of the incident surface of the fourth lens is 12.7 mm ± 0.6 mm, and the focal length is 370 mm to 400 mm, preferably 379.2 mm.

[0030] As a specific embodiment, the radius of curvature of the incident surface of the fourth lens 5, i.e., the S7 surface, is -309.1 mm ± 0.2 mm, the radius of curvature of the exit surface, i.e., the S8 surface, is -135.7 mm ± 0.2 mm, and the thickness is 16.6 mm ± 0.8 mm, which is the distance between the centers of the S7 surface and the S8 surface. The refractive index / Abbe number of the material is 1.85 / 23.8. The gap between the center of the exit surface of the fourth lens and the center of the incident surface of the fifth lens is 20.7 mm ± 1.7 mm, and the focal length is 250 mm to 280 mm, preferably 269.7 mm.

[0031] As a specific embodiment, the fifth lens 6 is a positive lens. The radius of curvature of its incident surface, i.e., the S9 surface, is 1047.5 mm ± 15.6 mm, the radius of curvature of the exit surface, i.e., the S10 surface, is -769.7 mm ± 3.6 mm, and the thickness is 25 mm ± 0.1 mm, which is the distance between the centers of the S9 surface and the S10 surface. The refractive index / Abbe number of the material is 1.95 / 17.9, and the focal length is 450 mm to 500 mm, preferably 463.7 mm.

[0032] The other parameters of the above examples are as follows:

[0033] The focal length of the flat-field telecentric scanning lens is 168.1 mm, the incident light wavelength is 532 nm ± 0.1 nm, and the maximum entrance pupil diameter is 15.6 mm.

[0034] Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6It proves the superiority of the present invention, which can achieve large field of view, non-vignetting, flat-field scanning imaging, with a scanning field radius of 58.5 mm, a scanning angle of ±20°, and relatively small aberration.

[0035] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method section.

[0036] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A flat-field telecentric scanning lens, characterized in that, It includes a diaphragm, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence along the optical axis from the object side to the image side. The first lens is a positive meniscus lens with a positive optical power; the second lens is a negative meniscus lens with a negative optical power; the third lens is a positive meniscus lens with a positive optical power; the fourth lens is a positive meniscus lens with a positive optical power; the fifth lens is a biconvex lens with a positive optical power; The distance between the diaphragm and the incident surface of the first lens, i.e., S1 surface, is 28mm ± 0.5mm; Both surfaces of the first lens are concave towards the object side, the focal length is 200mm - 210mm, the curvature radius of the incident surface of the first lens, i.e., S1 surface, is -104.2mm ± 1.2mm, the curvature radius of the exit surface, i.e., S2 surface, is -60.39mm ± 0.2mm, and the thickness of the first lens is 12.5mm ± 0.3mm; Both surfaces of the second lens are concave towards the object side, the focal length is -95mm - -90mm, the curvature radius of the incident surface of the second lens, i.e., S3 surface, is -45.3mm ± 0.5mm, the curvature radius of the exit surface, i.e., S4 surface, is -409.3mm ± 2.8mm, and the thickness of the second lens is 15.9mm ± 0.2mm; Both surfaces of the third lens are concave towards the object side, the focal length is 370mm - 400mm, the curvature radius of the incident surface of the third lens, i.e., S5 surface, is -218.8mm ± 1.3mm, the curvature radius of the exit surface, i.e., S6 surface, is -118mm ± 1.1mm, and the thickness of the third lens is 24.5mm ± 1mm; Both surfaces of the fourth lens are concave towards the object side, the focal length is 250mm - 280mm, the curvature radius of the incident surface of the fourth lens, i.e., S7 surface, is -309.1mm ± 0.2mm, the curvature radius of the exit surface, i.e., S8 surface, is -135.7mm ± 0.2mm, and the thickness of the fourth lens is 16.6mm ± 0.8mm; The incident surface of the fifth lens is convex towards the object side, the exit surface is concave towards the object side, the focal length is 450mm - 500mm, the curvature radius of the incident surface of the fifth lens, i.e., S9 surface, is 1047.5mm ± 15.6mm, the curvature radius of the exit surface, i.e., S10 surface, is -769.7mm ± 3.6mm, and the thickness of the fifth lens is 25mm ± 0.1mm; The angle between the chief ray of the object surface and the normal of the object surface within the full field of view of the scanning lens is less than 0.1°.

2. The telecentric scanning lens with a flat field according to claim 1, wherein The image-side field of view diameter of the scanning lens is not less than 110mm.

3. The afocal telecentric scanning lens according to claim 1, characterized in that, The maximum aperture diameters of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are all not greater than 150mm.

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