A three-dimensional projection lens and a three-dimensional projector

Abstract

The application is suitable for the field of three-dimensional projection technology, and provides a three-dimensional projection lens and a three-dimensional projection machine, wherein the three-dimensional projection lens comprises a rear group, a middle group and a front group arranged in sequence along the optical axis direction from the object side to the image side; the rear group comprises one positive focal length lens and one positive focal length double cemented lens; the middle group comprises one tightly connected positive and negative focal length lens group and one tightly connected negative and positive focal length lens group; the front group comprises one aspheric negative focal length lens; wherein all the lenses in the rear group and the middle group are spherical lenses. According to the application, the segmented aberration correction and the reasonable layout of the focal length of the lens are adopted, and excellent imaging quality is obtained under the condition of using only one aspheric lens and strict space limitation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of three-dimensional (3D) projection, and particularly relates to a 3D projection lens and a 3D projector. BACKGROUND

[0002] In the field of 3D vision technology, the 3D information restoration process of an object is as follows: a 3D projector projects a straight-line structured light stripe onto the curved surface of a detected object, the stripe is deformed on the curved surface, and a 3D vision camera restores the 3D model of the detected object according to the deformation degree of the stripe at different angles on the curved surface.

[0003] The 3D projector and the 3D vision camera are usually encapsulated in one body to facilitate transportation and precision adjustment, which has a significant limitation on the volume of the 3D projector, especially on the length of the lens of the 3D projector. At present, multiple aspherical lenses are usually used in the lens to compress the length of the lens and improve the image quality, but the mold opening cost of the aspherical lens is high, and the tolerance of the multiple aspherical lenses is sensitive and the yield is low when they are matched. Therefore, how to layout the optical power of the lens to obtain a cost-effective aberration balance is a problem to be solved. SUMMARY

[0004] Therefore, the embodiments of the present application provide a 3D projection lens and a 3D projector, aiming to solve the problem that the existing 3D projector uses multiple aspherical lenses in the lens to compress the length of the lens and improve the image quality, but the mold opening cost of the aspherical lens is high, and the tolerance of the multiple aspherical lenses is sensitive and the yield is low when they are matched.

[0005] A first aspect of the embodiments of the present application provides a 3D projection lens, comprising a rear group, a middle group and a front group arranged in sequence along an optical axis direction from an object side to an image side;

[0006] The rear group comprises one positive-power lens and one positive-power double-glued lens;

[0007] The middle group comprises one tightly-spaced positive-negative-power lens group and one tightly-spaced negative-positive-power lens group;

[0008] The front group comprises one aspherical negative-power lens;

[0009] Among them, all the lenses in the rear group and the middle group are spherical lenses.

[0010] In one embodiment, the rear group comprises a first spherical positive-power lens, a second spherical negative-power lens and a third spherical positive-power lens;

[0011] Among them, the second spherical negative-power lens and the third spherical positive-power lens are glued to form the positive-power double-glued lens.

[0012] In one embodiment, the second spherical negative power lens has a refractive index higher than or equal to the first refractive index and an Abbe number lower than or equal to the first Abbe number.

[0013] The third spherical positive power lens has a refractive index lower than or equal to the second refractive index and an Abbe number higher than or equal to the second Abbe number.

[0014] The first refractive index is higher than the second refractive index, and the first Abbe number is lower than the second Abbe number.

[0015] In one embodiment, the intermediate group comprises a fourth spherical positive power lens, a fifth spherical negative power lens, a seventh spherical negative power lens, and an eighth spherical positive power lens.

[0016] The fourth spherical positive power lens and the fifth spherical negative power lens are in close contact to form the close-contact positive-negative power lens group, and the seventh spherical negative power lens and the eighth spherical positive power lens are in close contact to form the close-contact negative-positive power lens group.

[0017] In one embodiment, the fourth spherical positive power lens has a refractive index lower than or equal to a third refractive index and an Abbe number higher than or equal to a third Abbe number.

[0018] The fifth spherical negative power lens has a refractive index higher than or equal to a fourth refractive index and an Abbe number lower than or equal to a fourth Abbe number.

[0019] The fourth refractive index is higher than the third refractive index, and the fourth Abbe number is lower than the third Abbe number.

[0020] In one embodiment, the lenses in at least one of the close-contact positive-negative power lens group and the close-contact negative-positive power lens group are in edge contact.

[0021] In one embodiment, the intermediate group further comprises a sixth spherical positive power lens and a diaphragm arranged in sequence between the fifth spherical negative power lens and the seventh spherical negative power lens.

[0022] In one embodiment, the aspherical negative power lens has a refractive index lower than or equal to the second refractive index or the third refractive index and an Abbe number higher than or equal to the second Abbe number or the third Abbe number.

[0023] In one embodiment, the 3D projection lens further comprises a digital micromirror device and a prism equivalent flat plate arranged in sequence on the object side.

[0024] In one embodiment, the prism equivalent flat plate is an isosceles right triangular prism.

[0025] The second aspect of the embodiments of the present application provides a 3D projector, comprising the 3D projection lens provided by the first aspect.

[0026] In the 3D projection lens provided by the first aspect of the embodiments of the present application, the rear group adopts a positive focal length lens and a positive focal length double cemented lens to share a large focal length, thereby correcting spherical aberration, wherein the positive focal length double cemented lens is used to undertake a part of positive focal length and correct chromatic aberration, and a manner similar to lens splitting is adopted to reduce the correction pressure of the positive focal length lens on spherical aberration, thereby avoiding generation of high-order aberration and compressing space and reducing the use of single lenses; the middle group adopts a roughly symmetrical arrangement of a tightly connected positive and negative focal length lens group and a tightly connected negative and positive focal length lens group in focal length, thereby realizing correction of sagittal aberration, and the combination of the positive focal length lens and the negative focal length lens realizes positive and negative cancellation of aberration, so as to correct aperture aberration including spherical aberration, coma and astigmatism in priority, to obtain residual aberration beneficial to balance of the entire optical system, thereby improving imaging quality; the front group adopts a negative focal length aspheric lens to correct field aberration mainly including field curvature and distortion.

[0027] The 3D projector provided by the second aspect of the embodiments of the present application realizes segmented aberration correction and reasonable layout of focal length of lenses by adopting the 3D projection lens provided by the first aspect, and under the condition of using only one aspheric lens and strict space limitation, excellent imaging quality is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort under the premise of the drawings.

[0029] Figure 1 FIG. 1 is a structural schematic diagram of a 3D projection lens provided by an embodiment of the present application;

[0030] Figure 2 FIG. 2 is a structural schematic diagram of a rear group provided by an embodiment of the present application;

[0031] Figure 3 FIG. 3 is a structural schematic diagram of a middle group provided by an embodiment of the present application;

[0032] Figure 4 FIG. 4 is a structural schematic diagram of a front group provided by an embodiment of the present application;

[0033] Figure 5 FIG. 5 is a light path schematic diagram of the 3D projection lens provided by an embodiment of the present application;

[0034] Figure 6 is a schematic diagram of a light path of a 3D projection lens when the prism equivalent flat plate is an isosceles right prism according to an embodiment of the present application;

[0035] Figure 7 is a schematic diagram of a 3D projection lens and a projection surface thereof according to an embodiment of the present application;

[0036] Figure 8 is a schematic diagram of a modulation transfer function at a digital micromirror device according to an embodiment of the present application;

[0037] Reference signs:

[0038] 200-3D projection lens;

[0039] 201-digital micromirror device;

[0040] 202-protection glass;

[0041] 203-prism equivalent flat plate;

[0042] 210-back group, 211-first spherical positive power lens, 212-second spherical negative power lens, 213-third spherical positive power lens;

[0043] 220-middle group, 221-fourth spherical positive power lens, 222-fifth spherical negative power lens, 223-sixth spherical positive power lens, 224-diaphragm, 225-seventh spherical negative power lens, 226-eighth spherical positive power lens;

[0044] 230-front group, 231-ninth aspherical negative power lens. DETAILED DESCRIPTION

[0045] In order to make the personnel in the art better understand the present application, the technical solutions in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor should belong to the scope of protection of the present application.

[0046] The term "comprising," and any variations thereof, in the specification, claims, and accompanying drawings of this application are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or apparatus that comprises a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such processes, methods, products, or apparatus. Furthermore, the terms "first," "second," and "third," etc., are used to distinguish different objects, not to describe a specific order.

[0047] like Figure 1 As shown, this embodiment provides a 3D projection lens 200, including a rear group 210, a middle group 220 and a front group 230 arranged sequentially from the object side to the image side along the optical axis.

[0048] The rear group 210 includes a positive power lens and a positive power cemented doublet lens;

[0049] Group 220 includes a close-contact positive and negative power lens group and a close-contact negative and positive power lens group;

[0050] The front group 230 includes an aspherical negative power lens;

[0051] All lenses in the rear group 210 and the middle group 220 are spherical lenses.

[0052] In application, the rear group 210 uses a positive optical power lens and a positive optical power cemented doublet to share the large optical power, thereby correcting spherical aberration. The positive optical power cemented doublet is used to take on part of the positive optical power and correct chromatic aberration. It adopts a lens splitting method to reduce the pressure of the positive optical power lens on spherical aberration correction, which avoids the generation of high-order aberrations, compresses space, and reduces the use of single lenses.

[0053] In application, the Zhongzu 220 uses closely spaced positive and negative optical power lens groups and closely spaced negative and positive optical power lens groups arranged in a roughly symmetrical manner to correct transverse aberrations. At the same time, the combination of positive and negative optical power lenses achieves the cancellation of positive and negative aberrations, correcting aperture aberrations, including spherical aberration, coma, and astigmatism, and obtaining residual aberrations that are beneficial to the balance of the entire optical system, thereby improving imaging quality.

[0054] In application, the front group 230 adopts a negative aspherical lens to correct the field curvature and distortion. The correction of the field curvature is difficult to be achieved by a large ray height difference between the positive and negative surfaces, which will introduce a large amount of aperture aberration and cannot be compensated by other lens groups. In addition, the separation of the positive and negative surfaces needs to occupy a large air gap, which is not conducive to the compression of the axial length of the 3D projection lens 200. The aspherical lens of the front group 230 introduces more negative power at the aperture edge to push the focal point to a farther place to correct the field curvature, and at the same time, corrects the distortion of the chief ray of each field of view through the aspherical coefficients of the lens.

[0055] As shown in FIG. 1, in one embodiment, the rear group 210 includes a first positive spherical lens 211, a second negative spherical lens 212, and a third positive spherical lens 213. Figure 2

[0056] The second negative spherical lens 212 and the third positive spherical lens 213 are cemented to form a positive cemented lens.

[0057] In application, the first positive spherical lens 211 mainly functions to bear the power to obtain a convergent real image on a digital micromirror device (DMD) of the 3D projection lens 200. Since the illumination beam of the 3D projection lens 200 is a telecentric beam, the first positive spherical lens 211 also needs to correct the aperture aberration, mainly spherical aberration, which is increased due to telecentricity. The correction of the aperture aberration is achieved by intercepting the edge rays which are prone to generate high-order aberrations through vignetting, and by sharing the ray angle through a lens splitting-like manner to reduce the deflection angle of the rays on the refractive surface, thereby reducing the generation of aberrations. The positive cemented lens composed of the second negative spherical lens 212 and the third positive spherical lens 213 bears part of the power by keeping the total power positive, which is manifested in the double-convex profile. The main function of the positive cemented lens in the 3D projection lens 200 is to correct chromatic aberration.

[0058] In one embodiment, the positive lens and the positive cemented lens in the rear group are both double-convex.

[0059] In one embodiment, the index of refraction (Nd) of the second negative spherical lens 212 is higher than or equal to the first index of refraction, and the Abbe number (Vd) is lower than or equal to the first Abbe number.

[0060] The index of refraction of the third positive spherical lens 213 is lower than or equal to the second index of refraction, and the Abbe number is higher than or equal to the second Abbe number. ​

[0061] Among them, the first refractive index is higher than the second refractive index, and the first Abbe number is lower than the second Abbe number.

[0062] In applications, based on the requirement of using positive power cemented doublet lenses to correct chromatic aberration, the second spherical negative power lens 212 needs to be made of a material with high refractive index (e.g., Nd ≥ 1.8) and low Abbe number (e.g., Vd ≤ 36), while the third spherical positive power lens 213 needs to be made of a material with low refractive index (e.g., Nd ≤ 1.65) and high Abbe number (e.g., Vd ≥ 60).

[0063] In one embodiment, the first refractive index is equal to 1.83 and the second refractive index is equal to 1.65;

[0064] The first Abbe number is 36, and the second Abbe number is 60.

[0065] like Figure 3 As shown, in one embodiment, the middle group 220 includes a fourth spherical positive power lens 221, a fifth spherical negative power lens 222, a seventh spherical negative power lens 225, and an eighth spherical positive power lens 226.

[0066] Among them, the fourth spherical positive power lens 221 and the fifth spherical negative power lens 222 are closely connected to form a closely connected positive and negative power lens group, and the seventh spherical negative power lens 225 and the eighth spherical positive power lens 226 are closely connected to form a closely connected negative and positive power lens group.

[0067] In applications, the fourth spherical positive power lens 221 and the fifth spherical negative power lens 222, and the seventh spherical negative power lens 225 and the eighth spherical positive power lens 226 respectively form two pairs of closely spaced positive and negative power lens combinations to correct aberrations. The positive and negative power lenses can produce aberrations of opposite signs, most of which can be canceled out. The remaining aberrations can often be used to compensate for other component aberrations through software optimization in the 3D vision camera, thus achieving better image quality. The closely spaced positive and negative power lens combinations formed by the fourth spherical positive power lens 221 and the fifth spherical negative power lens 222 also simultaneously undertake part of the chromatic aberration correction, achieving segmented aberration correction and preventing aberration accumulation during long-path propagation.

[0068] In one embodiment, the refractive index of the fourth spherical positive power lens 221 is lower than or equal to the third refractive index, and the Abbe number is higher than or equal to the third Abbe number;

[0069] The fifth spherical negative power lens 222 has a refractive index that is higher than or equal to the fourth refractive index and an Abbe number that is lower than or equal to the fourth Abbe number;

[0070] The fourth refractive index is higher than the third refractive index, and the third Abbe number is lower than the fourth Abbe number.

[0071] In applications, based on the chromatic aberration correction requirements of the close-fitting positive and negative power lens combination, the fourth spherical positive power lens 221 needs to be made of a material with low refractive index (e.g., Nd ≤ 1.65) and high Abbe number (e.g., Vd ≥ 60), and the fifth spherical negative power lens 222 needs to be made of a material with high refractive index (e.g., Nd ≥ 1.8) and low Abbe number (e.g., Vd ≤ 36).

[0072] In one embodiment, the third refractive index is equal to 1.65 and the fourth refractive index is equal to 1.83;

[0073] The third Abbe number is 60, and the fourth Abbe number is 36.

[0074] In applications, the combination of two closely spaced positive and negative optical power lenses not only forms an aberration correction unit but also constructs a symmetrical optical power layout of "positive-negative-negative-positive" to correct transverse aberrations. The combination of positive and negative optical power lenses, through a roughly symmetrical optical power layout, creates a similar deflection of the light beam on both sides of the center of symmetry to maintain the symmetry of the beam, thereby correcting transverse aberrations such as coma.

[0075] In one embodiment, the lens contact method in at least one of the closely spaced positive and negative power lens groups and the closely spaced negative and positive power lens groups is edge contact.

[0076] In applications, at least one of the pairs of closely connected positive and negative power lenses is edge-contact. Edge contact can save spacers, reduce volume, and also help to form a narrow "air lens", causing different beam deflection differences in different aperture bands, thus forming different aberration correction amounts, which has a positive effect on the correction of astigmatism and spherical aberration.

[0077] like Figure 3 As shown, the middle group 220 also includes a sixth spherical positive power lens 223 and an aperture stop 224 arranged sequentially between the fifth spherical negative power lens 222 and the seventh spherical negative power lens 225.

[0078] In application, the sixth spherical positive power lens 223, combined with two pairs of closely spaced positive and negative power lenses, constructs a symmetrical power layout of "positive-negative-positive-negative-positive" to correct transverse aberrations. The aperture stop 224 is used to confine the beam to limit the imaging field of view.

[0079] like Figure 4As shown, in one embodiment, the front group 230 includes a ninth aspherical negative power lens 231, the refractive index of which is lower than or equal to the second or third refractive index, and the Abbe number is higher than or equal to the second or third Abbe number.

[0080] In applications, the aspherical coefficient of the ninth aspherical negative power lens 231 can be modified with the radius (R) value for each aperture band to adjust the deflection of the principal rays in each field of view, providing a good basis for distortion correction. To reduce the introduction of chromatic aberration, the ninth aspherical negative power lens 231 needs to be made of a material with low refractive index (e.g., Nd ≤ 1.65) and high Abbe number (e.g., Vd ≥ 60).

[0081] In one embodiment, all lenses in the 3D projection lens are glass lenses.

[0082] In applications, using glass lenses can improve light transmission performance, thereby improving imaging results.

[0083] like Figures 1-4 As shown, in one embodiment, the rear group 210 includes, in order of arrangement from the object side to the image side along the optical axis: a first spherical positive power lens 211, a second spherical negative power lens 212, and a third spherical positive power lens 213.

[0084] The middle group 220 includes: a fourth spherical positive power lens 221, a fifth spherical negative power lens 222, a sixth spherical positive power lens 223, an aperture stop 224, a seventh spherical negative power lens 225, and an eighth spherical positive power lens 226.

[0085] The front group 230 includes: the ninth aspherical negative power lens 231.

[0086] In application, taking the correction of color difference in the front, middle and rear groups as an example, the aberrations of the entire 3D projection lens are corrected in segments in different areas to avoid excessive local correction causing advanced aberrations, and finally obtain a loose assembly tolerance, laying the groundwork for improving yield.

[0087] like Figure 1 As shown, in one embodiment, the 3D projection lens 200 further includes a DMD 201 and a prism equivalent plate 203 located on the object side and arranged in sequence.

[0088] In applications, the prism equivalent plate 203 can be an isosceles right-angled triangular prism, and the thickness of the prism equivalent plate 203 is the same as the waist length of the isosceles right-angled triangular prism.

[0089] like Figure 1As shown, in one embodiment, the 3D projection lens 200 further comprises a protective glass 202 between the DMD 201 and the prism equivalent flat 203.

[0090] In application, the DMD 201 and the protective glass 202 can be integrally arranged as a whole.

[0091] As shown, an exemplary ray path diagram of the 3D projection lens 200 is shown. Figure 5

[0092] As shown, an exemplary ray path diagram of the 3D projection lens 200 is shown. Figure 6

[0093] As shown, an exemplary ray path diagram of the 3D projection lens 200 is shown. Figure 7

[0094] In one embodiment, the DMD 201 has a size of 0.3 inch, and the 3D projection lens 200 has an aperture F# = 1.7. The type, radius of curvature, thickness and glass material from the object plane to the image plane are shown in Table 1 as follows:

[0095] Table 1

[0096]

[0097]

[0098] In one embodiment, the aspherical curve equation of the 3D projection lens 200 is represented as follows:

[0099]

[0100] wherein c is the curvature corresponding to the radius, y is the radial coordinate, the unit of the radial coordinate is the same as the length unit of the lens, k is the conic coefficient, and r2~r16 represent the coefficients corresponding to each radial coordinate.

[0101] In one embodiment, based on Table 1, the surfaces S21 and S22 in the 3D projection lens 200, and the conic coefficient k and the coefficients r4, r6 and r8 in the aspherical curve equation are shown in Table 2 as follows:

[0102] Table 2

[0103] Aspherical coefficients S21 S22 Conic coefficient k -0.6524927 0.3564024 r4 0.000347763 0.00020219 r6 9.41E-06 -3.02E-07 r8 2.81E-07 3.97E-09

[0104] As shown, an exemplary ray path diagram of the 3D projection lens 200 is shown. Figure 8 ​​​As shown, an exemplary diagram showing the modulation transfer function (MTF) at the DMD 201 is shown; wherein the MTF observation line pair is 46 lp / mm, the horizontal axis represents the spatial frequency in cycles per millimeter (cycles / mm), and the vertical axis represents the numerical value of the MTF.

[0105] In application, the MTF represents the comprehensive resolving power of the optical system, and the numerical value of the MTF is used to evaluate the imaging quality of the lens, the value range is 0-1, the higher and straighter the vertical axis of the MTF curve is, the better the imaging quality of the lens is, the stronger the restoration ability of the real image is, the better the coincidence degree of the curves of each field of view is, and the better the consistency of the imaging quality is, from which Figure 8 It can be seen that, in the visible light band, when the spatial frequency is 46 lp / mm, the MTF of the full field of view is greater than or equal to 0.4, and the imaging quality is good.

[0106] The embodiments of the present application also provide a 3D projector, comprising the 3D projection lens 200 in any of the above embodiments.

[0107] In application, the 3D projector can be applied to the field of 3D vision technology, and is packaged in the same housing with the 3D vision camera, so as to facilitate transportation and precision adjustment, and by adopting the 3D projection lens 200, segmented aberration correction and reasonable layout of the power of the lens are realized, and under the condition of using only one aspherical lens and strict space limitation (i.e. requiring the volume to be as small as possible), excellent imaging quality is obtained.

[0108] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the foregoing embodiments of the present application have been described in detail, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A three-dimensional projection lens characterized by comprising: The three-dimensional projection lens comprises a total of nine lenses arranged in order from an object side to an image side along an optical axis direction to form a rear group, a middle group and a front group; The rear group comprises a first spherical positive lens, a second spherical negative lens and a third spherical positive lens arranged in order from the object side to the image side along the optical axis direction; The middle group comprises a fourth spherical positive lens, a fifth spherical negative lens, a sixth spherical positive lens, a diaphragm, a seventh spherical negative lens and an eighth spherical positive lens arranged in order from the object side to the image side along the optical axis direction; The front group comprises a ninth aspherical negative lens; The second spherical negative lens and the third spherical positive lens are glued to form a positive double-glued lens; The fourth spherical positive lens and the fifth spherical negative lens are closely arranged to form a closely-arranged positive and negative lens group, and the seventh spherical negative lens and the eighth spherical positive lens are closely arranged to form a closely-arranged negative and positive lens group; The types, the curvature radii, the thicknesses and the glass materials of the lenses of the three-dimensional projection lens from the object side to the image side are shown in the following table:

2. The three-dimensional projection lens of claim 1, wherein, The lens closely-arranged manner in at least one of the closely-arranged positive and negative lens group and the closely-arranged negative and positive lens group is edge contact.

3. The three-dimensional projection lens according to claim 1 or 2, wherein The three-dimensional projection lens further comprises a digital micromirror device and a prism equivalent flat plate arranged in order from the object side.

4. The three-dimensional projection lens of claim 3, wherein, The prism equivalent flat plate is an isosceles right triangular prism.

5. A three-dimensional projector characterized by comprising: The three-dimensional projection lens comprises the three-dimensional projection lens according to any one of claims 1-4.

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