Zoom extender lens and projection field of view switching method

Abstract

The application discloses a zoom expansion lens and a projection visual field switching method, which comprises a projection module for outputting projection light, a first optical reflection element arranged at the exit end of the projection module, and a second optical reflection element arranged at the exit end of the first optical reflection element; the first optical reflection element and the second optical reflection element form an off-axis double-reflection type optical path structure; the first optical reflection element is further connected with a switching mechanism, which is used for driving the first optical reflection element to intervene or not intervene in the projection light path of the projection module; when the first optical reflection element at least partially intervenes in the projection light path, the exit light from the projection module is reflected by the first free curved surface reflection surface and the second free curved surface reflection surface in sequence and then exits, and zoom imaging converging in the near field is realized in the exit direction; when the first optical reflection element entirely not intervenes in the projection light path, far field projection is realized by the visual field of the projection module.

Description

Technical Field

[0001] This invention relates to the field of automotive lighting technology, and more particularly to a zoom extension lens and a method for switching projection fields of view. Background Technology

[0002] In the field of projection display technology, the ability to adjust the projection field of view directly affects the scene adaptability and user experience of projection devices. To adapt to different projection distances and screen sizes, it is usually necessary to change the field of view of the projection system. Currently, the main technical solutions for achieving projection field of view variation fall into the following categories: The first type is the continuous zoom lens solution, which uses a compensation group and a zoom group for optical compensation. It achieves continuous focal length change through the relative movement between two or more groups of lenses while maintaining image plane stability. This solution can achieve a relatively smooth zoom effect, but its structure is complex, requiring precise mechanical motion mechanisms and complex control algorithms, resulting in a large system size, high cost, and extremely high assembly precision requirements, which limits its application in compact projection devices.

[0003] The second type is the switchable zoom lens solution, which introduces a rotation or switching mechanism into the optical path to allow different combinations of optical elements for different focal lengths, thereby achieving focal length switching. For example, multi-position switchable zoom lenses are already used in infrared optical systems. However, this type of solution also requires a built-in rotation or switching mechanism, occupies a large internal space, and cannot achieve optical path direction reversal, limiting its use in space-constrained applications or applications requiring changes in projection direction.

[0004] The third type is the external extension lens solution, which changes the system's focal length by attaching additional optical components to the light-emitting side of the original projection lens. For example, CN117784373A discloses an external projection lens and a projection combination lens, which includes a first group and a second group arranged from the magnification side to the reduction side. The first group contains at least two lenses with negative optical power, and the second group contains at least one lens with positive optical power. The second group is arranged off-axis relative to the first group. This external projection lens, by being mounted on the magnification side of the original lens in the projection system, can change the projection ratio, enabling switching between telephoto projection and medium-long telephoto or short telephoto projection. Furthermore, consumer products such as external lenses for mobile phones also fall into this category. However, in-depth research has revealed the following drawbacks of this technology: First, it cannot achieve light path reversal; its light path propagates along a roughly straight line and lacks the ability to directionally reverse the projected light path. In situations requiring bending the projected light path to adapt to a specific spatial layout (such as ultra-short-throw projection or concealed installation), the above solutions cannot meet the needs. Second, its zoom capability is limited and its image quality correction methods are singular. Image quality correction mainly relies on cemented lens groups or combinations of materials with different refractive indices, resulting in relatively simple correction methods that make it difficult to maintain good image quality while expanding the field of view.

[0005] In summary, given the shortcomings of existing technologies for achieving changes in the projection field of view, new lenses need to be designed to meet the usage requirements of changing the projection field of view. Summary of the Invention

[0006] The primary objective of this invention is to provide a zoom extension lens to solve the technical problem of simultaneously achieving zoom extension of the field of view and optical path refraction.

[0007] The second objective of this invention is to provide a projection field switching method to solve the technical problem of flexibly switching between far-field projection mode and near-field projection mode.

[0008] The zoom extension lens of this invention is implemented as follows: A zoom extension lens includes: a projection module for outputting projection light, a first optical reflective element disposed at the emitting end of the projection module, and a second optical reflective element disposed at the emitting end of the first optical reflective element; wherein... The first optical reflecting element and the second optical reflecting element constitute an off-axis double-reflector optical path structure; the first optical reflecting element has a first freeform reflective surface, and the second optical reflecting element has a second freeform reflective surface; and The first optical reflective element is also connected to a switching mechanism; the switching mechanism is used to drive the first optical reflective element to enter or exit the projection optical path of the projection module; When the first optical reflective element is at least partially involved in the projection optical path, the outgoing light from the projection module is reflected sequentially by the first freeform surface reflective surface and the second freeform surface reflective surface before being emitted, and the zoom imaging is converged at a close distance in the outgoing direction; When the first optical reflective element extends out of the projection optical path, far-field projection is achieved by the field of view of the projection module.

[0009] In an optional embodiment of the present invention, the switching mechanism includes a rotating shaft and a rotating motor used in conjunction; The rotating shaft is connected to the first optical reflective element so as to drive the first optical reflective element to rotate into or out of the projection light path.

[0010] In an optional embodiment of the present invention, the zoom imaging is configured independently in the horizontal and vertical directions; and the zoom ratio of the zoom imaging is the horizontal zoom ratio, the vertical zoom ratio, or a combination of both.

[0011] In an optional embodiment of the present invention, the first optical reflecting element is a first reflecting mirror, and the second optical reflecting element is a second reflecting mirror.

[0012] In an optional embodiment of the present invention, when the absolute value of the zoom ratio of the zoom imaging is greater than 1, along the direction of light propagation, the first optical reflective element has a converging effect on the incident collimated beam, and the second optical reflective element has a diverging effect on the beam reflected by the first optical reflective element. When the absolute value of the zoom ratio of the zoom imaging is less than 1, along the direction of light propagation, the first optical reflective element has a diverging effect on the incident collimated beam, and the second optical reflective element has a converging effect on the beam reflected by the first optical reflective element.

[0013] In an optional embodiment of the present invention, the focusing distance in the zoom imaging state is 1m to 8m; In the far-field projection state, the focusing distance is from 6m to infinity.

[0014] In an optional embodiment of the present invention, the first optical reflecting element and / or the second optical reflecting element are catadioptric lenses; and The catadioptric lens has an incident refraction surface, a reflecting surface, and an exit refraction surface. Light enters the catadioptric lens through the incident refraction surface, is reflected by the reflecting surface, and exits through the exit refraction surface.

[0015] In an optional embodiment of the present invention, the first optical reflecting element and the second optical reflecting element are arranged off-axis in a direction perpendicular to the optical axis along the direction of light propagation, so that the outgoing direction of the light is deflected relative to the incident direction after being reflected twice by the first optical reflecting element and the second optical reflecting element.

[0016] In an optional embodiment of the present invention, the first freeform surface reflecting surface and the second freeform surface reflecting surface are characterized by an extended polynomial, and the expression for their height z is:

[0017] Where z is the elevation at coordinates (x, y), and r is the aperture of the control point. c is the curvature, and k is the conic coefficient. Let x and y be polynomials. Let be the coefficient of the i-th polynomial.

[0018] The projection field switching method of the present invention is implemented as follows: A method for switching projection fields of view, employing the aforementioned zoom extension lens; the method for switching projection fields of view includes: Step S1: Obtain the mode switching command; Step S2: According to the mode switching instruction obtained in step S1, drive the first optical reflective element to at least partially intervene in or completely exit the projection optical path of the projection module through the switching mechanism.

[0019] By adopting the above technical solution, the present invention has the following beneficial effects: The zoom extension lens and projection field of view switching method of the present invention, through the switching mechanism driving the first optical reflective element to at least partially intervene in or completely intervene in the projection optical path of the projection module, realizes dynamic and real-time switching between far-field projection mode and near-field projection mode. Compared with the static method in the prior art that requires physical installation and removal of external lenses to achieve projection ratio switching, the present invention does not require disassembly or assembly of any optical components. Mode switching can be completed by driving the switching mechanism, which is convenient to operate, responds quickly, and significantly improves the switching flexibility of the projection device in different application scenarios. By arranging the first and second optical reflective elements off-axis, the light is deflected relative to the incident direction after two reflections. By adjusting the angle of the first and second optical reflective elements, the deflection direction and angle of the light path can be flexibly controlled. This function enables the projection device to be flexibly deployed in application scenarios where space is limited or the projection direction needs to be changed, such as ultra-short-throw projection, hidden installation, multi-directional projection, etc., effectively overcoming the technical defect of existing transmissive zoom lenses that cannot fold the light path. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the zoom extension lens of the present invention; Figure 2 This is a top-view optical path diagram of the zoom extension lens of Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the optical path in the side view direction of the zoom extension lens of Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the first and second optical reflective elements of the zoom extension lens of Embodiment 1 of the present invention in an oblique view direction; Figure 5 This is a schematic diagram of the optical path in the far-field state of the zoom extension lens of the present invention. Figure 6 This is a ground projection diagram showing the zoom extension lens of the present invention compared to the non-extension lens in the prior art. Figure 7 This is a parametric representation of the zoom extension lens of Embodiment 1 of the present invention; Figure 8 This is a schematic diagram of the first and second optical reflective elements of the zoom extension lens in Embodiment 2 of the present invention, viewed from an oblique angle. Figure 9 This is a schematic diagram of the optical path in the side view direction of the zoom extension lens of Embodiment 2 of the present invention; Figure 10 This is a schematic diagram of the first and second optical reflective elements of the zoom extension lens in Embodiment 3 of the present invention, viewed from an oblique angle. Figure 11 This is a schematic diagram of the optical path in the side view direction of the zoom extension lens in Embodiment 3 of the present invention. Detailed Implementation

[0021] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0022] Example 1: Please see Figures 1 to 7 As shown, this embodiment provides a zoom extension lens including a projection module 1, a rotating shaft 2, a rotating motor 3, a first reflector 4, and a second reflector 5. The rotating shaft 2 and the rotating motor 3 constitute a switching mechanism, and the first reflector 4 and the second reflector 5 together form an off-axis switching zoom extension lens. The rotating shaft 2 and the rotating motor 3 are connected to a fixed bracket of the projection module 1. The first reflector 4 has a first freeform reflective surface S1, and the second reflector 5 has a second freeform reflective surface S2. The first reflector 4 is connected to the rotating shaft 2, and the rotating motor 3 drives the rotating shaft 2 to rotate, thereby causing the first reflector 4 to rotate into or out of the projection light path of the projection module 1.

[0023] The first reflecting mirror 4 and the second reflecting mirror 5 are arranged off-axis in a direction perpendicular to the optical axis along the direction of light propagation, forming an off-axis double-reflector optical path structure. "Off-axis" here specifically means that the effective optical surfaces of the first reflecting mirror 4 and the second reflecting mirror 5 do not contain the rotational symmetry axis of the system; that is, the vertices of the reflecting surfaces are not located on the optical axis, and there is an offset between the optical axis and the reflecting surfaces. The advantage of this off-axis arrangement is that it avoids the obstruction of incident light by the reflecting mirrors, while providing a structural basis for realizing optical path deflection.

[0024] When the first reflecting mirror 4 is at least partially involved in the projection optical path of the projection module 1, the projection module 1 emits light rays 11 and 21 in a certain field of view. If there is no off-axis double-reflector optical path structure to modulate the light rays, they will converge at the far end. The angle F1 between light rays 11 and 21 and the optical axis Axis 1 is the input field of view angle of the projection module 1. Light rays 11 and 21 are first reflected by the reflecting surface S1 of the first reflecting mirror 4, propagating in the directions of reflected light rays 12 and 22. After being reflected again by the reflecting surface S2 of the second reflecting mirror 5, they are emitted outward as outgoing light rays 13 and 23 and converge at the near end. At this time, the angle F2 between outgoing light rays 13 and 23 and the optical axis Axis 1 is the field of view angle after zooming in this embodiment. It should be noted that the proportion of the first reflector 4 intervening in the projection light path of the projection module 1 can be, for example, but not limited to, 50%, 60%, 80%, or 100% (i.e., overall intervention). This embodiment does not impose an absolute limitation on the specific proportion of the first reflector 4 intervening in the projection light path of the projection module 1, and can be flexibly selected according to the actual situation. This embodiment is described in conjunction with the accompanying drawings with the case of the first reflector 4 being fully involved in the projection light path of the projection module 1.

[0025] In this embodiment, the reflecting surface S1 of the first reflecting mirror 4 and the reflecting surface S2 of the second reflecting mirror 5 adopt specific freeform surface shapes to ensure that light rays from each field of view can be correctly reflected during propagation, achieving the purpose of large-angle emission and converging to form an image. The freeform surface shape here is represented by an extended polynomial, and the sag z at different coordinates (x, y) is determined by the expression to ultimately determine the surface shape. The extended polynomial expression used in this embodiment is:

[0026] Where z is the elevation at coordinates (x, y), and r is the aperture of the control point. c is the curvature, and k is the conic coefficient. A polynomial for x and y, with terms from the first to the Nth: , , , , ……, Let be the coefficient of the i-th polynomial. In this polynomial, the first term... Second item These represent the tilt of the surface in the X and Y directions, respectively (i.e., the first-order terms, corresponding to the tilt angle of the mirror); the third term... and the fifth item These represent the quadratic curvature of the surface in the X and Y directions, respectively (corresponding to the optical power / radius of curvature of the mirror in the X and Y directions); the fourth term Astigmatic components representing the surface shape; higher-order terms ( (and later) represents the higher-order aspherical components of the surface shape, used to correct various higher-order aberrations.

[0027] Based on the above, it should be noted that in this embodiment, the curvature c of the reflecting surface S1 of the first reflecting mirror 4 and the reflecting surface S2 of the second reflecting mirror 5 are both 0, and the conic coefficient k is also 0, indicating that the base of the reflecting surface is a plane (without a basic spherical curvature), and all surface shape variations are contributed by polynomial terms. In other words, the non-planar characteristics of the reflecting surface are entirely determined by the non-zero coefficients of the extended polynomial, which provides a great degree of freedom for surface design. The coefficients are shown in Table 1:

[0028] As shown in Table 1, in surfaces S1 and S2, the coefficients of all odd-order terms of Y (X0Y1, X1Y1, X2Y1, X3Y1, etc.) are all 0, indicating that the two reflecting surfaces are symmetrically distributed in the Y direction, that is, the system is symmetrical about the XZ plane. The coefficients of all combinations of odd-order terms of X and even-order terms of Y (X1Y2, X1Y4, X1Y6, etc.) are also 0, further maintaining the surface symmetry.

[0029] Next, we will analyze the optical characteristics of this embodiment from the perspective of surface coefficient: In the Y direction (horizontal direction, the direction with a magnification ratio of 2.22), the S1 surface... The coefficient (X0Y2) is -33.1413, and the S2 surface... The coefficient of (X0Y2) is -68.8726. Corresponding to The term represents the degree of curvature of the surface in the Y direction. The absolute value of each coefficient reflects the degree of curvature of the surface; the larger the absolute value, the more curved the basic curvature of the surface. The direction of curvature depends on the sign of the coefficient. For example, on surface S1, a negative coefficient means that the surface bends to the left, opposite to the direction of the incident light, thus converging the light. Surfaces S1 and S2 have large curvatures, realizing the basic function of beam convergence and angle expansion. At the same time, they have abundant non-zero terms (A8, A12, A14, A17, A19, A23, A25, A27, A30, A32, and A34 all contain non-zero terms in Y), which can correct aberrations of the beam at various positions, enabling it to be reflected and converged more accurately onto the imaging surface, ultimately expanding the horizontal field of view from 18° to 40°.

[0030] In the X-direction (vertical direction, where the zoom ratio is 1x), since the vertical zoom ratio is 1x (i.e., neither magnification nor reduction), the curvature of the two reflecting surfaces in the Y-direction is designed to compensate for each other. The A3 coefficients determining the basic curvature are 0.709425 and 1.13394, respectively, both relatively small values, indicating that they are relatively flat planes in the x-direction. This ensures that the divergence angle of the outgoing beam is consistent with that of the incident beam in the Y-direction. At this time, the algebraic sum of the equivalent optical power of the two reflecting surfaces in the Y-direction is extremely small, allowing it to refocus only the outgoing beam (from the original far-field imaging beyond 6m to the near-field imaging within 1~8m), resulting in an overall 1:1 imaging performance of the afocal system in the Y-direction.

[0031] In addition, the existence of higher-order Y terms such as A8, A12, A14, A17, A19, A23, A25, A27, A30, A32, and A34 in Table 1 is used to correct higher-order aberrations (such as higher-order coma and higher-order astigmatism) introduced by the large field of view expansion, ensuring that good imaging quality can still be maintained while the field of view is greatly expanded.

[0032] The system parameters for this embodiment are shown in Table 2:

[0033] As shown in Table 2, the zoom ratio of this embodiment is approximately 2.22 times in the horizontal direction (40° / 18° ≈ 2.22 times) and 9° / 9° = 1 times in the vertical direction. It is evident that this embodiment achieves significant field-of-view expansion in the horizontal direction while maintaining the same vertical direction, demonstrating the independent configuration of zoom imaging in both the horizontal and vertical directions.

[0034] Combination Figure 4 According to Lagrange's invariant conservation law, in afocal optical system (i.e., the system images an object at infinity onto infinity, or parallel light incident and parallel light emanating), Lagrange's invariant can be expressed as:

[0035] in, The refractive index of the medium, The aperture of the beam (the height of the light ray on a certain cross section). This is the aperture angle (the angle between the light beam and the optical axis, i.e., the divergence angle or convergence angle). In an ideal optical system, the Lagrange invariant remains unchanged along the light path, that is:

[0036] When the system is in air medium ( When ), we have:

[0037] Based on Lagrange's invariant conservation law, the product of the beam aperture and the divergence angle remains constant during propagation in the optical system. In this embodiment, the space between the first reflecting mirror 4 and the second reflecting mirror 5 can be considered as a focalless system. Let the aperture of the incident parallel beam be... The divergence angle is (For parallel light incident, (This discussion pertains to beam divergence at the field of view angle); the aperture of the emitted beam is... The divergence angle is (That is, the degree of divergence corresponding to the output field of view F2).

[0038] When the zoom ratio M > 1 (field of view expansion), the exit divergence angle is greater than the incident divergence angle, i.e. According to Lagrange's invariant conservation There must be This means the exit beam aperture is smaller than the incident beam aperture. To achieve this change in beam aperture from large to small, the light rays must first converge and then diverge. First stage (first reflecting mirror): The parallel beam is incident on the reflecting surface S1 of the first reflecting mirror 4. Since S1 is concave in the Y direction (equivalent to a positive power reflecting mirror), it converges the beam, causing the beam to begin to converge and the beam aperture to gradually decrease. This stage corresponds to compressing the large-aperture incident beam into a small-aperture beam.

[0039] The second stage (between the first reflecting mirror 4 and the second reflecting mirror 5): Before the converging beam propagates to the second reflecting mirror, the beam aperture has been reduced to its minimum value (the beam cross-section is smallest near the focal point).

[0040] The third stage (second reflecting mirror 5): The converging beam is incident on the reflecting surface S2 of the second reflecting mirror 5. Although S2 is also concave in the Y direction, its configuration of off-axis angle and surface curvature causes it to diverge the already converged beam (i.e., it exhibits weaker convergence relative to S1 in terms of optical power, or is practically equivalent to negative optical power). The beam begins to diverge, but the divergence angle increases upon exiting. The final exiting beam has a relatively large divergence angle ( ) and smaller caliber ( The light propagates outwards and converges closer, thus expanding the field of view.

[0041] like Figure 4As shown, along the direction of light propagation, in the Y direction (the direction where the magnification ratio is greater than 1), the reflecting surface S1 of the first reflecting mirror 4 is concave relative to the incident light 41, and a collimated beam of light is converged when reflected from this surface. Although the reflecting surface S2 of the second reflecting mirror 5 is also concave relative to the incident light 42, its curvature configuration and off-axis angle cause it to diverge the beam of light reflected by S1. Through the optimized combination of the surface shapes of S1 and S2, the outgoing beam 43 can be converged to a nearby point, thereby achieving magnification.

[0042] When the magnification ratio M < 1 (field of view reduced), the exit divergence angle is smaller than the incident divergence angle, i.e. According to Lagrange's invariant conservation, it is necessary that... That is, the aperture of the outgoing beam is larger than the aperture of the incoming beam. At this time, the light undergoes a process of first diverging and then converging: the first reflecting mirror 4 diverges the incident beam, and the second reflecting mirror 5 converges the diverged beam. Finally, the outgoing beam propagates outward with a smaller divergence angle and a larger aperture.

[0043] When the magnification ratio M=1, the exit divergence angle is equal to the incident divergence angle, that is... ,but The first reflecting mirror 4 and the second reflecting mirror 5 are both close to the plane reflecting mirror in the corresponding directions, and the beam aperture and divergence angle do not change.

[0044] Based on the above, it can be seen that by adjusting the various coefficients in the freeform surface mirror shape (especially...) , By using the coefficients of the quadratic term and the coefficients of the higher-order term, the curvature of the surfaces S1 and S2 can be precisely controlled, and any scaling ratio within the range of 0.4 to 2.5 times can be achieved.

[0045] From the perspective of optical power distribution: When M>1, along the direction of light propagation, the equivalent optical power of the first reflecting mirror 4 is positive (converging), and the equivalent optical power of the second reflecting mirror 5 is negative (diverging). Furthermore, the absolute values ​​of both satisfy the overall afocal condition of the system (the algebraic sum of the equivalent optical powers is approximately zero), while achieving field magnification under the constraint of Lagrange invariant conservation. When M<1, along the direction of light propagation, the equivalent optical power of the first reflecting mirror 4 is negative (diverging), and the equivalent optical power of the second reflecting mirror 5 is positive (converging). When M=1, the equivalent optical power of both reflecting mirrors is zero (plane reflecting mirror).

[0046] It should also be noted that the zoom extension lens in this embodiment also has an optical path reversal function. For example... Figure 3As shown, incident ray 31 strikes the first reflecting mirror 4, and its reflected ray 32 is reflected again by the second reflecting mirror 5. Since the angle Angle 1 between the first reflecting mirror 4 and the horizontal direction is 65°, and the angle Angle 2 between the second reflecting mirror 5 and the horizontal direction is 57°, according to the law of reflection, when light is reflected on a single reflecting surface, the angle of incidence equals the angle of reflection. When two reflecting mirrors are combined, the deflection angle of the outgoing ray relative to the incident ray is twice the difference in the angles between the two reflecting mirrors. Therefore, the outgoing ray 33 here is deflected by 16° relative to the incident ray 31. By adjusting the angle Angle 1 between the first reflecting mirror 4 and the horizontal direction and the angle Angle 2 between the second reflecting mirror 5 and the horizontal direction, any deflection angle within the range of 5° to 25° can be achieved. It should also be noted that the tilt direction of the reflecting mirrors (i.e., the signs and relative sizes of Angle 1 and Angle 2) determines the direction of light path deflection.

[0047] The off-axis switching zoom extension lens of this embodiment can also achieve refocusing from the far field to the near field. The refocusing function is achieved through the surface shapes of the two mirrors in corresponding directions. For example, focusing in the X direction is determined by the non-zero order terms of X (X2Y0, X3Y0, X4Y0, X5Y0, etc., singular terms of X) in Table 1. When it is necessary to change the equivalent optical power (i.e., focal length) of the system to maintain image sharpness, this embodiment changes the equivalent optical power distribution of the reflection system in the X direction by varying the non-zero order surface shape of the freeform mirror, allowing the light rays from each field of view to reconverge on the projection surface within a near-field projection distance range of 1m to 8m. Specifically, The (X2Y0) term controls the quadratic curvature distribution of the substrate, which determines the basic optical power of the mirror in the X direction; (X3Y0) Higher-order terms such as (X4Y0) locally modulate the fundamental optical power, allowing light rays from different fields of view (i.e., different X coordinates) to converge at different points, thus achieving clear imaging across the entire field of view. In far-field projection (6m to infinity), the mirror group intervenes in the optical path, and the projection module images according to its original parameters without additional focus compensation. In near-field projection (1m to 8m), the mirror group intervenes in the optical path, and the non-zero order terms of the mirror surface provide additional focus compensation, ensuring image clarity at different projection distances. This embodiment allows for refocusing at positions from 1m to 8m by setting the freeform surface parameters.

[0048] Next, it should be noted that in this embodiment, the rotating shaft can also be rotated by a motor, thereby causing the first reflecting mirror 4 to rotate out of the projection light path (i.e., in the exposed state). At this time, the projection field of view is restored to the original field of view of the projection module, 18°×9°, and the projection direction does not change, thus realizing far-field projection 31. At this time, its focusing distance depends on the focusing position of the projection module. In far-field mode, this distance is from 6m to infinity. In this mode, since the first reflecting mirror 4 is completely exposed to the light path, the projection light is not modulated by any of the first reflecting mirror 4 and the second reflecting mirror 5, and is projected onto the far-field projection surface with the original field of view and image quality of the projection module.

[0049] like Figure 6 As shown, the left side is the ground projection pattern without the extender (far field state, input field of view 18°×9°), and the right side is the ground projection pattern with the extender (near field state, output field of view 40°×9°). It can be clearly seen from the figure that after adding the off-axis switching zoom extender lens of this embodiment, the ground projection pattern is significantly expanded in the horizontal direction (the coverage range is expanded from 18° to 40°).

[0050] Example 2: Please see Figure 8 and Figure 9 As shown, based on the zoom extension lens of Embodiment 1, the zoom extension lens provided in this embodiment is largely the same as that of Embodiment 1, except that the first optical reflecting element in this embodiment is a reflector 401, and the second optical reflecting element is a catadioptric lens 501. The catadioptric lens 501 is made of a low-dispersion optical material with an Abbe number Vd of 57.1 and a refractive index Nd of 1.49. The use of a low-dispersion material with an Abbe number of 57.1 in this embodiment can effectively reduce chromatic aberration introduced by the refractive surface and ensure the color reproduction of the projected image.

[0051] The catadioptric lens 501 has an incident refraction surface S4 (which is also the exit refraction surface, with light entering and exiting through the same physical surface) and a reflecting surface S5. Light enters the catadioptric lens through the incident refraction surface S4, propagates inside the lens, is reflected at the reflecting surface S5, and is then refracted again through S4 before exiting. In other words, the same physical surface S4 of the catadioptric lens 501 performs both incident and exit refraction functions, while the reflecting surface S5 is located on the back of the lens or on an internal reflecting surface. This design allows incident and exit refraction to occur on the same surface, reducing the total number of optical surfaces required, which simplifies the structure and lowers costs.

[0052] Reflector 401 provides a first reflecting surface S3, and catadioptric lens 501 provides a second reflecting surface S5 and an incident / outgoing refractive surface S4. Therefore, the optical system of this embodiment includes one reflecting surface S3, one refractive surface, and one reflecting surface S4 and S5, i.e., three optical modulation surfaces. In this embodiment, optical surfaces S3 (the reflecting surface of reflector 401), S4 (the incident / outgoing refractive surface of catadioptric lens 501), and S5 (the reflecting surface of catadioptric lens 501) are all freeform surfaces, and their surface shapes are also characterized by the extended polynomial in Embodiment 1. The curvature c of each optical surface is 0, and the conic coefficient k is 0. The coefficients are shown in Table 3.

[0053] In this embodiment, the introduction of the catadioptric lens 501 introduces an additional refractive surface S4. The optical power of the refractive surface is determined by Snell's law. For light of different wavelengths, the refractive index of the optical material changes with wavelength (i.e., dispersion), causing light of different wavelengths to have different deflection angles on the refractive surface, thus producing chromatic aberration. Chromatic aberration is divided into axial chromatic aberration (light of different wavelengths converges at different axial positions) and magnification chromatic aberration (light of different wavelengths has different magnification). In this embodiment, due to the use of a low-dispersion material (Abbe number 57.1), the rate of change of the material's refractive index with wavelength is small, thus effectively suppressing the chromatic aberration introduced by the refractive surface. At the same time, the reflecting surface S3 of the reflector 401 and the reflecting surface S5 of the catadioptric lens 501 are both reflection-modulated, and the reflection process does not introduce chromatic aberration (the law of reflection is independent of wavelength; all wavelengths are reflected at the same angle).

[0054] Therefore, in this embodiment, only the incident / exit refractive surface S4 of the catadioptric lens 501 introduces chromatic aberration, and due to the use of a low-dispersion material, the chromatic aberration is controlled at a low level. This allows this embodiment to obtain additional optical path modulation capabilities of the refractive surface (more flexible optical power allocation and aberration correction degrees of freedom) without significantly sacrificing color reproduction performance.

[0055] Compared to the pure reflector scheme in Example 1, this embodiment introduces a catadioptric lens 501, increasing the modulation capability of the refracting surface on the light path. This allows for further optimization of image quality while maintaining the same zoom effect. Specifically, the three freeform surfaces S3, S4, and S5 offer greater design freedom than the two reflective surfaces, enabling more precise correction of various aberrations and achieving superior image quality. The optical power of the refracting surface S4 can share some of the zoom workload, allowing the surface shapes of the two reflective surfaces S3 and S5 to be used more for aberration correction rather than bearing all the optical power, thereby improving the overall image quality. Furthermore, the fact that the refracting surface S4 shares some of the optical power allows for a reduction in the curvature of the reflective surfaces, lowering the processing difficulty and manufacturing cost. The use of a low-dispersion material (Abbe number 57.1) effectively reduces the dispersion phenomenon caused by refraction, ensuring the color reproduction of the projected image.

[0056] Example 3: Please see Figure 10 and Figure 11 As shown, based on the zoom extension lens of Embodiment 1 or Embodiment 2, the zoom extension lens provided in this embodiment is roughly the same as that of Embodiment 1 or Embodiment 2, except that the first optical reflecting element in this embodiment adopts a first catadioptric lens 402 and the second optical reflecting element adopts a catadioptric lens 502.

[0057] The first catadioptric lens 402 has an incident refraction surface S6 and a reflecting surface S7, while the second catadioptric lens 502 has an incident refraction surface S8 and a reflecting surface S9. Light rays first enter the lens through the incident refraction surface S6 of the first catadioptric lens 402, are reflected by the reflecting surface S7, and then exit through the exit surface of the first catadioptric lens 402 (in this embodiment, S6 serves as both the incident and exit surface, meaning the light rays enter and exit through the same physical surface). Subsequently, light rays enter the lens through the incident refraction surface S8 of the second catadioptric lens 502, are reflected by the reflecting surface S9, and then exit through the exit surface of the second catadioptric lens 502 (S8 also serves as the exit surface). In this embodiment, both the first catadioptric lens 402 and the second catadioptric lens 502 are made of an optical material with an Abbe number of 30 and a refractive index of 1.585.

[0058] An Abbe number of 30 is considered a medium dispersion material (higher dispersion than 57.1 in Example 2), but because this embodiment employs a birefringent lens structure, the refractive surfaces of the two lenses can compensate for each other's chromatic aberration. Specifically, light passes sequentially through the refractive surface S6 (refraction) and reflective surface S7 (reflection) of the first birefringent lens 402, and the refractive surface S8 (refraction) and reflective surface S9 (reflection) of the second birefringent lens 502. At the refractive surfaces S6 and S8, light of different wavelengths is deflected at different angles due to material dispersion. By rationally designing the surface parameters of S6 and S8 and the material configuration of the two birefringent lenses, the chromatic aberration generated by the first birefringent lens 402 and the chromatic aberration generated by the second birefringent lens 502 are made to have opposite signs and similar magnitudes, thereby achieving overall chromatic aberration cancellation (i.e., achromatic correction).

[0059] In this embodiment, the refractive surface S6 of the first catadioptric lens 402 bears the positive optical power, and the refractive surface S8 of the second catadioptric lens 502 bears the negative optical power. The optical powers of the two are matched, thereby achieving mutual compensation of chromatic aberration. Therefore, even when using materials with a low Abbe number, good color reproduction performance can still be guaranteed.

[0060] In this embodiment, optical surfaces S6, S7, S8, and S9 are all freeform surfaces, and their surface shapes are also characterized using extended polynomials. The curvature c of each optical surface is 0, and the conic coefficient k is 0. The coefficients are shown in Table 4.

[0061] As can be seen from Table 4, the coefficients of surfaces S6 and S8 are exactly the same (A3A3 is 8.26783, A5A5 is -13.1003, A6A6 is 112.1208, and so on). This is because the incident refractive surface S6 of the first catadioptric lens 402 and the incident refractive surface S8 of the second catadioptric lens 502 perform symmetrical functions in the optical path, and both are made of the same material, thus their surface parameters are identical. However, the parameters of surfaces S7 and S9 differ (A3A3: S7 is 3.595527, S9 is -1.17902; A5A5: S7 is -27.994, S9 is -105.336), indicating that the two reflecting surfaces each bear different optical power distributions.

[0062] In summary, compared to Embodiment 1 (pure reflecting mirror) and Embodiment 2 (reflecting mirror + catadioptric lens), the four freeform surfaces (two incident refractive surfaces + two reflecting surfaces) of this embodiment provide greater design freedom than two or three optical surfaces. This allows for more flexible allocation of optical power and correction of various aberrations (spherical aberration, coma, astigmatism, field curvature, distortion), resulting in superior image quality. The refractive surfaces of the two catadioptric lenses can compensate for chromatic aberration, achieving good achromatic aberration even with materials of low Abbe number, effectively reducing material costs and selection limitations. The introduction of the refractive surfaces allows the system to utilize both reflection and refraction modulation methods simultaneously, further reducing the system's size and weight while achieving the same magnification effect. Since both catadioptric lenses employ a reflective optical path folding structure, light propagates through folded folds within the lenses, resulting in a compact overall system size, suitable for applications with high space requirements.

[0063] Example 4: Based on the zoom extension lens of Embodiment 1, Embodiment 2, or Embodiment 3, this embodiment provides a projection field of view switching method, which uses the zoom extension lens of Embodiment 1, Embodiment 2, or Embodiment 3; specifically, the projection field of view switching method of this embodiment includes: Step S1: Obtain the mode switching command; Step S2: According to the mode switching command obtained in step S1, drive the first optical reflective element to at least partially intervene in or completely intervene in the projection optical path of the projection module through the switching mechanism.

[0064] By using a switching mechanism (rotating shaft and rotating motor) to drive the first optical reflective element to either fully engage or disengage from the projection light path of the projection module, dynamic and real-time switching between far-field and near-field projection modes is achieved. When the reflective mirror group disengages from the light path, the projection system maintains its original field of view for far-field projection, with a focusing distance of 6m to infinity, suitable for projection scenarios at conventional distances. When the reflective mirror group engages from the light path, the projection system switches to near-field projection mode, with a focusing distance of 1m to 8m, suitable for large-screen projection scenarios at close range. This embodiment requires no disassembly or assembly of any optical components; mode switching is completed via motor drive, making operation convenient and responsive, significantly improving the flexibility of the projection device in switching between different application scenarios.

[0065] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0066] In the description of this invention, it should be understood that the terms indicating 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 invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0067] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0068] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. 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. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0069] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0070] In this invention, unless otherwise expressly specified and limited, "above or below" a first feature may include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on" the first feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the first feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

Claims

1. A zoom extension lens, characterized in that, include: A projection module for outputting projection light, a first optical reflective element disposed at the output end of the projection module, and a second optical reflective element disposed at the output end of the first optical reflective element. in The first optical reflective element and the second optical reflective element constitute an off-axis dual-reflective optical path structure; the first optical reflective element has a first freeform reflective surface, and the second optical reflective element has a second freeform reflective surface; as well as The first optical reflective element is also connected to a switching mechanism; the switching mechanism is used to drive the first optical reflective element to enter or exit the projection optical path of the projection module; When the first optical reflective element is at least partially involved in the projection optical path, the outgoing light from the projection module is reflected sequentially by the first freeform surface reflective surface and the second freeform surface reflective surface before being emitted, and the zoom imaging is converged at a close distance in the outgoing direction; When the first optical reflective element extends out of the projection optical path, far-field projection is achieved by the field of view of the projection module.

2. The zoom extension lens according to claim 1, characterized in that, The switching mechanism includes a rotating shaft and a rotating motor used in conjunction; The rotating shaft is connected to the first optical reflective element so as to drive the first optical reflective element to rotate into or out of the projection light path.

3. The zoom extension lens according to claim 1, characterized in that, The zoom imaging is configured independently in the horizontal and vertical directions; and the zoom ratio of the zoom imaging is the horizontal zoom ratio, the vertical zoom ratio, or a combination of both.

4. The zoom extension lens according to claim 3, characterized in that, The first optical reflecting element is a first reflecting mirror, and the second optical reflecting element is a second reflecting mirror.

5. The zoom extension lens according to claim 4, characterized in that, When the absolute value of the zoom ratio of the zoom imaging is greater than 1, along the direction of light propagation, the first optical reflective element has a converging effect on the incident collimated beam, and the second optical reflective element has a diverging effect on the beam reflected by the first optical reflective element. When the absolute value of the zoom ratio of the zoom imaging is less than 1, along the direction of light propagation, the first optical reflective element has a diverging effect on the incident collimated beam, and the second optical reflective element has a converging effect on the beam reflected by the first optical reflective element.

6. The zoom extension lens according to claim 1 or 3, characterized in that, In the zoom imaging mode, the focusing distance is 1m to 8m; In the far-field projection state, the focusing distance is from 6m to infinity.

7. The zoom extension lens according to claim 3, characterized in that, The first optical reflecting element and / or the second optical reflecting element are catadioptric lenses; and The catadioptric lens has an incident refraction surface, a reflecting surface, and an exit refraction surface. Light enters the catadioptric lens through the incident refraction surface, is reflected by the reflecting surface, and exits through the exit refraction surface.

8. The zoom extension lens according to claim 1, characterized in that, The first optical reflective element and the second optical reflective element are arranged off-axis in a direction perpendicular to the optical axis along the direction of light propagation, so that the light is deflected from the incident direction after being reflected twice by the first optical reflective element and the second optical reflective element.

9. The zoom extension lens according to claim 1, characterized in that, The first and second freeform surface reflectors are characterized using extended polynomials, and their elevation z is expressed as follows: Where z is the elevation at coordinates (x, y), and r is the aperture of the control point. c is the curvature, and k is the conic coefficient. Let x and y be polynomials. Let be the coefficient of the i-th polynomial.

10. A method for switching projection fields of view, characterized in that, The method employs a zoom extension lens as described in any one of claims 1 to 9; the projection field of view switching method includes: Step S1: Obtain the mode switching command; Step S2: According to the mode switching instruction obtained in step S1, drive the first optical reflective element to at least partially intervene in or completely exit the projection optical path of the projection module through the switching mechanism.

Images