An ultra-short focus scanning optical system

Abstract

The invention relates to the technical field of scanners, and discloses an ultra-short focus scanning optical system, which comprises, from an object plane to an image plane, a light emitting unit, an aperture, a DOE lens, a rotating mirror, an F-theta lens and a toner cartridge in sequence; the light emitting unit emits an elliptical laser beam; the aperture calibrates the elliptical laser beam into an aperture-shaped beam; the first lens surface of the DOE lens collimates the aperture-shaped beam into a parallel beam; the second lens surface shapes the parallel beam into a linear beam along the y-axis direction; the rotating mirror receives and changes the angle of the linear beam; the F-theta lens receives the linear beam after passing through the rotating mirror, and converges it into a circular light spot within the diffraction limit; the toner cartridge converts the circular light spot focused by the F-theta lens into a printable image; by improving the curved surface shape of the F-theta lens, the light spot printed on the toner cartridge is symmetrical about the center, which can improve the uniformity of the light spot during scanning and make the scanner miniaturized.

Description

Technical Field

[0001] The present invention relates to the technical field of scanners, and in particular to an ultra-short focus scanning optical system. Background Art

[0002] With the rise of mobile office, users are increasingly demanding lightweight and portable scanners to adapt to changing usage environments. This trend is particularly evident in professional fields, such as the medical and design industries, where users are increasingly demanding the clarity and color reproduction of scanned images. However, scanners currently on the market generally face the problems of large size and uneven light spots, mainly due to the complex mechanical structure and optical system in traditional designs.

[0003] Many scanners on the market today are bulky due to their complex mechanical structures and optical systems. These devices usually require a lot of space to accommodate internal components such as lasers, optical lenses, and moving parts. The large size not only affects the user's portability, but also limits the use of the device. For example, when working away from home or on temporary projects, users need lightweight devices that can be readily available, which is a big challenge for traditional scanners. In addition, the laser light sources used in many existing devices have a high divergence angle, which causes the beam to scatter significantly after a certain distance, thus affecting the clarity of the image. The uniformity of the beam becomes critical in the scanning process, especially in the generation of high-resolution images. The design of traditional optical systems often fails to effectively optimize the spot shape and distribution, resulting in significantly lower image quality at the edge of the scan than in the center area. This unevenness not only affects the overall quality of the image, but may also result in failure to meet professional standards in certain application scenarios. Uneven spots and low-quality scanning results directly affect the user experience. In professional fields, users usually need high-fidelity images for analysis and decision-making. For example, in the medical field, scanned images are used for diagnosis, and any quality deficiencies may lead to wrong judgments. In the design industry, color reproduction and detail presentation of images are crucial, and the performance of the scanner directly affects work efficiency and quality of results.

[0004] Therefore, there is an urgent need for an ultra-short focus scanning optical system that can achieve uniform spot scanning and effectively shorten the volume of the entire scanning system. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides an ultra-short focus scanning optical system, which can effectively improve the uniformity of the light spot, effectively reduce the distance from the light source to the center of the rotating mirror and the distance from the center of the rotating mirror to the toner drum, thereby reducing the volume of the entire scanning system.

[0006] The present invention provides an ultra-short focus scanning optical system, which includes, from the object plane to the image plane, the following components:

[0007] Light emitting unit, aperture, DOE lens, rotating mirror, F-theta lens and toner cartridge;

[0008] The light emitting unit is used to emit an elliptical laser beam;

[0009] The aperture is used to calibrate the elliptical laser beam into an aperture-shaped beam;

[0010] The DOE lens comprises a first lens surface and a second lens surface; the first lens surface is used to collimate the aperture-shaped light beam into a parallel light beam; the second lens surface is used to shape the parallel light beam into a linear light beam along the y-axis direction;

[0011] The rotating mirror is used to receive and change the angle of the linear light beam;

[0012] The F-theta lens is used to receive the line light beam after passing through the rotating mirror and converge it into a circular light spot within the diffraction limit;

[0013] The toner cartridge is a photoelectric conversion element used to convert a circular light spot focused by an F-theta lens into a printable image;

[0014] Based on the curved surface of the improved F-theta lens, the light spot formed on the toner drum through the F-theta lens is centrally symmetrical with respect to the optical axis of the F-theta lens.

[0015] Furthermore, the expression of the curved surface shape of the improved F-theta lens is:

[0016] ;

[0017] in: , represents the curvature of the free-form surface in the y-axis direction; R y is the distance from the vertex of the surface to a point on the surface in the y-axis direction; , represents the curvature of the free-form surface in the x-axis direction; R x is the distance from the vertex of the surface to a point on the surface in the x-axis direction; x is the x-axis coordinate value; y is the y-axis coordinate value; z is the z-axis coordinate value; k y k is the cone coefficient in the y-axis direction; x A is the cone coefficient in the x-axis direction; i With B i are coefficients; n is a constant.

[0018] Furthermore, an ultra-short focus scanning optical system also includes:

[0019] The BD lens, located above the rotating mirror, has an angle ranging from 5 to 15 degrees with the first beam projection point of the F-theta lens; it is used to ensure the lateral proportionality of the print width, allowing the sensor to accurately count the light spot each time the object passes.

[0020] Furthermore, the DOE lens and the BD lens are both free-form surface lenses.

[0021] Furthermore, the focal length F of the ultra-short focus scanning optical system is ≤110 mm.

[0022] Furthermore, the distance L from the center of the rotating mirror to the toner drum is ≤120 mm.

[0023] Furthermore, the angle of the rotating mirror satisfies the condition: 26°≤θ / 2≤38°.

[0024] The embodiments of the present invention have the following technical effects:

[0025] 1. By improving the curved surface of the F-theta lens, the left-right asymmetry during scanning caused by the misalignment between the optical center of the rotating mirror and the center of the optical axis of the light beam can be effectively solved. This asymmetry usually affects the overall quality of the image, resulting in significant differences in the size and uniformity of the spot in different areas of the scanned image. Optimizing the curved surface design of the lens can ensure that the light beam maintains a more consistent optical path during transmission, thereby achieving a smaller and more uniform spot.

[0026] 2. By improving the curved surface shape, the refraction angle of the light beam can be better controlled, so that the light is straighter during transmission and the propagation distance from the light source to the rotating mirror is reduced. This improvement reduces the scattering of the light beam at the rotating mirror, thereby reducing the actual transmission distance from the rotating mirror to the toner drum. Adjusting the curved surface shape helps to simplify the structure of the optical system and make the optical path design more compact, thereby physically reducing the distance between the light source and the rotating mirror, and between the rotating mirror and the toner drum, thereby reducing the volume of the scanning system and achieving miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 is a structural schematic diagram of an ultra-short focus scanning optical system provided by an embodiment of the present invention;

[0029] Figure 2is a spot diagram of a right scanning position of an ultra-short focus scanning optical system provided by an embodiment of the present invention;

[0030] Figure 3 is a spot diagram of the left scanning position of an ultra-short focus scanning optical system provided by an embodiment of the present invention;

[0031] Figure 4 This is a light spot diagram from left to right of a toner drum position of an ultra-short focus scanning optical system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0033] Figure 1 Schematic diagram of the structure of an ultra-short focus scanning optical system provided by an embodiment of the present invention. Figure 1 , an ultra-short focus scanning optical system, comprising, from the object plane to the image plane, the following:

[0034] Light emitting unit 1, aperture 2, DOE lens 3, rotating mirror 4, F-theta lens 5 and toner cartridge 7;

[0035] The light emitting unit 1 is used to emit an elliptical laser beam;

[0036] The aperture 2 is used to calibrate the elliptical laser beam into an aperture-shaped beam; specifically, the aperture-shaped beam usually presents a shape corresponding to the aperture itself, and this shape is affected by the geometric shape and size of the aperture. The shape of the aperture directly determines the shape and characteristics of the beam, so in optical design, the selection of the aperture is very important to ensure that the beam meets specific application requirements.

[0037] The DOE lens 3 comprises a first lens surface and a second lens surface; the first lens surface is used to collimate the aperture-shaped light beam into a parallel light beam; the second lens surface is used to shape the parallel light beam into a linear light beam along the y-axis direction;

[0038] The rotating mirror 4 is used to receive and change the angle of the line light beam;

[0039] The F-theta lens 5 is used to receive the line light beam after passing through the rotating mirror and converge it into a circular light spot within the diffraction limit;

[0040] The toner cartridge 7 is a photoelectric conversion element used to convert the circular light spot focused by the F-theta lens into a printable image;

[0041] Based on the curved surface of the improved F-theta lens, the light spot formed on the toner drum through the F-theta lens is centrally symmetrical with respect to the optical axis of the F-theta lens.

[0042] Specifically, the light-emitting unit 1 first emits an elliptical laser beam, and the aperture 2 calibrates the elliptical laser beam into a standard square beam. After passing through the first surface of the DOE lens 3 (diffractive optical element), the aperture-shaped beam is collimated into a parallel beam through a specific optical design to ensure that the propagation direction of the light is consistent. Then, the parallel beam passes through the second lens surface of the DOE lens 3, and the square parallel beam is further compressed into a straight line along the y-axis direction. This process further improves the focusing ability of the beam, making the shape of the beam more suitable for subsequent optical processing. Subsequently, the line beam passes through the rotating mirror 4, which guides the line beam into the F-theta lens 5 at a specific angle. The line beam is focused by the curved surface in the F-theta lens 5, and finally forms a circular spot on the toner drum 7 that is less than the diffraction limit. Ensure that a uniform and clear laser image is presented on the toner drum. Through this series of optical processing, the shape and propagation characteristics of the beam are precisely controlled, thereby achieving high-quality laser scanning.

[0043] The curved surface of the improved F-theta lens ensures that no matter how the incident angle of the light changes, the resulting light spots on the drum are uniform and equidistant, ensuring the high quality and consistency of the scanned image.

[0044] Furthermore, the curved surface profile of the improved F-theta lens is expressed as:

[0045] ;

[0046] in: , represents the curvature of the free-form surface in the y-axis direction; R y is the distance from the vertex of the surface to a point on the surface in the y-axis direction; , represents the curvature of the free-form surface in the x-axis direction; x is the x-axis coordinate value; R x is the distance from the vertex of the surface to a point on the surface in the x-axis direction; y is the y-axis coordinate value; z is the z-axis coordinate value; k y k is the cone coefficient in the y-axis direction; x A is the cone coefficient in the x-axis direction; i With B i are coefficients; n is a constant.

[0047] Furthermore, an ultra-short focus scanning optical system also includes:

[0048] The BD lens 6, located above the rotating mirror 4, has an angle range of 5 to 15 degrees with the first light beam projection point of the F-theta lens 5, which is used for the lateral scale of the printing width, so that the sensor can accurately count the light spot each time an object passes.

[0049] Furthermore, both the DOE lens 3 and the BD lens 6 are free-form surface lenses.

[0050] Furthermore, the focal length F of the ultra-short focus scanning optical system is ≤110 mm.

[0051] Furthermore, the distance L from the center of the rotating mirror to the toner drum is ≤120 mm. Figure 1 shown.

[0052] Furthermore, the angle of the rotating mirror satisfies the condition: 26°≤θ / 2≤38°, such as Figure 1 shown.

[0053] The main purpose of this parameter design is to optimize the transmission and focusing performance of the laser beam to achieve high-precision laser scanning. Specifically, a shorter focal length can enhance the focusing ability of the light beam, ensuring that the light forms a smaller and clearer spot on the drum, thereby improving the resolution and detail of the image. Limiting the distance from the center of the rotating mirror to the drum can shorten the optical path, reduce light loss during beam transmission, improve the utilization efficiency of the laser, ensure that more laser energy reaches the target area effectively, and help solve the problem of uneven spot caused by asymmetric optical axis, making the spot size smaller and more uniform throughout the scanning range, thereby improving the imaging quality. By reasonably designing the focal length and distance, the structure of the optical system can be simplified, the complexity of manufacturing and adjustment can be reduced, and the stability and reliability of the system can be improved, making the scanning system more competitive in various high-precision applications and able to meet the needs of different scenarios.

[0054] Exemplarily, in a specific embodiment of the present invention, the scanning system structural parameters are set to an effective focal length (EFL) of 108 mm, a distance L from the center of the rotating mirror to the toner drum of 110 mm, and a rotating mirror angle θ / 2 of 30°. The effective focal length of 108 mm provides sufficient focusing capability to ensure that a clear light spot is formed on the toner drum. The distance L from the center of the rotating mirror to the toner drum is 110 mm, which shortens the optical path, reduces light loss, and improves energy utilization. In addition, the design of a rotating mirror angle θ / 2 of 30 degrees helps to achieve uniform distribution of the light beam and reduce left-right asymmetry, thereby improving the quality and consistency of the entire scanning image.

[0055] Figure 2is a spot diagram of a right scanning position of an ultra-short focus scanning optical system provided by an embodiment of the present invention; Figure 3 is a spot diagram of the left scanning position of an ultra-short focus scanning optical system provided by an embodiment of the present invention; see Figure 2 and Figure 3 The center of the light spot at the left and right scanning positions is symmetrical, which solves the problem of scanning spot difference caused by the current common left-right asymmetry and avoids image distortion or asymmetry caused by uneven light.

[0056] Figure 4 is a spot diagram of the toner drum position from left to right of an ultra-short focus scanning optical system provided by an embodiment of the present invention, see Figure 4 , it can be seen that the light spots from left to right are within the diffraction limit, which means that the size and intensity of the light spots are kept in the best focusing state, ensuring high-quality image output. In this case, the light spot printed on the drum shows the characteristics of the Airy disk light spot, and this spot shape helps to improve resolution and reduce edge effects. Due to the characteristics of the Airy disk, the uniformity of the entire picture is guaranteed, avoiding image distortion caused by uneven light spots, thereby ensuring high standards for the final print quality. Such a design significantly improves the application effect of the laser scanning system in fine printing and image processing.

[0057] By improving the curved surface of the F-theta lens, the left-right asymmetry during the scanning process caused by the non-coincidence between the optical center of the rotating mirror and the center of the optical axis of the light beam can be effectively solved. That is, by improving the curved surface of the F-theta lens, although the optical centers of the two do not coincide, after the F-theta lens is improved, the light spot printed on the toner cartridge is centrally symmetrical relative to the optical axis of the F-theta lens, and the volume of the scanning system is reduced. Specifically, by accurately calculating and adjusting the geometry of the lens, the divergence of the light beam within the scanning range can be reduced to ensure that the light spot size remains consistent throughout the entire left-to-right scanning process. This improvement not only improves the clarity of the image, but also improves the ability to restore details, allowing users to obtain higher quality when printing and displaying documents. In addition, this uniformity also helps to improve the applicability of the scanner, especially in applications that require high precision, such as medical imaging and high-quality image processing. These improvements provide a stronger guarantee for the performance of the scanner and meet the market's demand for high-standard equipment.

[0058] It should be noted that the terms used in the present invention are only for describing specific embodiments, rather than limiting the scope of the present application. As shown in the present specification, unless the context clearly indicates an exception, the words "one", "a", "a kind of" and / or "the" do not specifically refer to the singular, but may also include the plural. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method or device. In the absence of more restrictions, the elements defined by the sentence "include one..." do not exclude the presence of other identical elements in the process, method or device including the elements.

[0059] It should also be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention 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 invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. 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 an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. An ultra-short focus scanning optical system, characterized in that: From the object plane to the image plane, it includes: Light emitting unit, aperture, DOE lens, rotating mirror, F-theta lens and toner cartridge; The light emitting unit is used to emit an elliptical laser beam; The aperture is used to calibrate the elliptical laser beam into an aperture-shaped beam; The DOE lens comprises a first lens surface and a second lens surface; the first lens surface is used to collimate the aperture-shaped light beam into a parallel light beam; the second lens surface is used to shape the parallel light beam into a linear light beam along the y-axis direction; The rotating mirror is used to receive and change the angle of the linear light beam; The F-theta lens is used to receive the line light beam after passing through the rotating mirror and converge it into a circular light spot within the diffraction limit; The toner cartridge is a photoelectric conversion element used to convert a circular light spot focused by an F-theta lens into a printable image; Based on the curved surface of the improved F-theta lens, the light spot formed on the toner cartridge through the F-theta lens is made centrally symmetrical with respect to the optical axis of the F-theta lens; The expression of the curved surface shape of the improved F-theta lens is: ； in: , represents the curvature of the free-form surface in the y-axis direction; R y is the distance from the vertex of the surface to a point on the surface in the y-axis direction; , represents the curvature of the free-form surface in the x-axis direction; R x is the distance from the vertex of the surface to a point on the surface in the x-axis direction; x is the x-axis coordinate value; y is the y-axis coordinate value; z is the z-axis coordinate value; k y k is the cone coefficient in the y-axis direction; x A is the cone coefficient in the x-axis direction; i With B i are coefficients; n is a constant.

2. The ultra-short focus scanning optical system according to claim 1, characterized in that: Also includes: A BD lens, located above the rotating mirror, with an angle ranging from 5 degrees to 15 degrees with respect to the first beam projection point of the F-theta lens; Used to ensure lateral scaling of the print width, allowing the sensor to accurately count the light spot each time an object passes.

3. The ultra-short focus scanning optical system according to claim 2, characterized in that: The DOE lens and the BD lens are both free-form surface lenses.

4. The ultra-short focus scanning optical system according to claim 1, characterized in that: The focal length F of the ultra-short focus scanning optical system is ≤110 mm.

5. The ultra-short focus scanning optical system according to claim 1, characterized in that: The distance L from the center of the rotating mirror to the toner drum is ≤120 mm.

6. The ultra-short focus scanning optical system according to claim 1, characterized in that: The angle of the rotating mirror satisfies the condition: 26°≤θ / 2≤38°.

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