An ultra-short-throw projection lens based on catadioptric optical lenses

Abstract

The present invention discloses an ultra-short-focus projection lens based on a catadioptric optical lens, which comprises an image source, a refractive lens group, a catadioptric optical lens and a screen arranged in sequence along the optical path direction, wherein the catadioptric optical lens comprises a refractive surface and a reflective surface, and after the light is emitted from the refractive lens group, it is refracted by the refractive surface of the catadioptric optical lens, reflected by the reflective surface, and then emitted again through the refractive surface and projected onto the screen. The present invention achieves the effect of a double refractive surface plus a reflective surface through a single catadioptric optical lens, provides more degrees of freedom for correcting system aberrations without increasing system complexity, makes system performance better, and reduces system cost.

Description

Technical Field

[0001] The invention relates to a lens, and in particular to an ultra-short-focus projection lens based on a catadioptric optical lens. Background Art

[0002] With the development of ultra-short-throw projection technology, ultra-short-throw projection lenses are widely used in education, business, military, home entertainment and other fields. At present, ultra-short-throw projection systems are gradually developing towards large screens, high definition, high resolution and low projection ratios. As the core component in the ultra-short-throw projection system, the ultra-short-throw projection lens determines the projection ratio, image quality of the projection screen and system volume of the ultra-short-throw projection system, and is gradually developing towards short focal length, large field of view and large screen.

[0003] Currently, the commonly used ultra-short-focus projection lenses mainly adopt the structure of a refractive lens group plus a single-piece reflector. However, in order to achieve a large field of view, most of the system's optical focal length and field of view expansion tasks fall on the single-piece reflector. Therefore, high requirements are placed on the reflector, and the reflector is also highly sensitive, making it difficult to achieve industrial promotion and application. If the complexity of the reflector is to be simplified, more lenses will be used, which will complicate the optical path structure of the system and will inevitably increase costs. Therefore, the structure of the system needs to be improved and has certain design difficulties. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide an ultra-short-focus projection lens based on a catadioptric optical lens. By adopting a catadioptric optical lens, the projection lens not only maximizes the optimization freedom of the system without increasing the complexity of the optical path structure, thereby improving the system performance, but also can reduce the system cost.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] An ultra-short-focus projection lens based on a catadioptric optical lens comprises an image source, a refractive lens group, a catadioptric optical lens and a screen which are sequentially arranged along the light path direction. The catadioptric optical lens comprises a refractive surface and a reflective surface. After the light is emitted from the refractive lens group, it is refracted by the refractive surface of the catadioptric optical lens, reflected by the reflective surface, and then emitted again through the refractive surface and projected onto the screen.

[0007] Preferably, the radius of curvature R1 of the refractive surface of the catadioptric optical lens satisfies: |R1|<400, and the radius of curvature R2 of the reflective surface of the catadioptric optical lens satisfies: |R2|<2|R1|.

[0008] Preferably, the surface of the catadioptric optical lens is a spherical surface, an aspherical surface or a free-form surface.

[0009] Preferably, the refractive lens group includes at least two lens groups, wherein the optical power of the lens group close to the direction of the catadioptric optical lens is negative.

[0010] Preferably, one side surface of the folding reflective optical lens is coated to form a reflective surface, and the coating material is a silver film, an aluminum film or a dielectric film.

[0011] The beneficial effect of the present invention is that compared with a catadioptric ultra-short-focus projection lens using an ordinary reflector, the catadioptric optical lens disclosed in the present invention comprises two surfaces, the first surface being a refractive surface and the second surface being a reflective surface. Light is refracted from the first surface of the lens and then reflected by the second surface, and then refracted again by the first surface and projected onto the screen. By having the light pass through the first surface twice, it is equivalent to adding a refractive surface without adding optical elements, that is, a single catadioptric lens is used to achieve the effect of a double refractive surface plus a reflective surface. This not only provides more degrees of freedom for correcting system aberrations and further improves system performance, but also reduces the number of optical elements from the perspective of lens manufacturing, thereby reducing the number of molds used. Moreover, compared with manufacturing a single reflector mold, the utilization rate of the mold is improved and the cost of the system is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic structural diagram of Embodiment 1 of the present invention;

[0013] Figure 2 is a schematic diagram of a partial structure of Example 1 of the present invention;

[0014] Figure 3 is a light path diagram of embodiment 1 of the present invention;

[0015] Figure 4 is a field curvature and distortion diagram of Example 1 of the present invention;

[0016] Figure 5 is a light path diagram of embodiment 2 of the present invention;

[0017] Figure 6 is a field curvature and distortion diagram of Example 2 of the present invention;

[0018] Figure 7 is a light path diagram of embodiment 3 of the present invention;

[0019] Figure 8 3 is a field curvature and distortion diagram of Example 3 of the present invention. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0021] Referring to Figures 1 to 8 Figures 1 to 8 , the present invention proposes an ultra-short focal length projection lens based on a catadioptric optical lens 13, which includes a DMD chip 400, a protective glass 200, a coupling prism 300, a refractive lens group 100, a catadioptric optical lens 13 and a screen arranged in sequence along the optical path direction. The catadioptric optical lens 13 includes a refractive surface 13b and a reflective surface 13a. After the light exits from the refractive lens group 100, it is refracted by the refractive surface 13b of the catadioptric optical lens 13 and then reflected by the reflective surface 13a, and then exits through the refractive surface 13b again and is projected onto the screen.

[0022] Embodiment 1

[0023] For the refractive surface 13b of the catadioptric optical lens 13, that is, the curvature radius R1 of its left side surface satisfies: |R1| < 400, and for the reflective surface 13a of the catadioptric optical lens 13, that is, the curvature radius R2 of its right side surface satisfies: |R2| < 2|R1|.

[0024] The refractive index Nd of the catadioptric optical lens 13 satisfies: 1.4 < Nd < 1.9, and the Abbe number Vd of the catadioptric optical lens 13 satisfies: 55 < Vd < 60.

[0025] The optical power Φ13 of the catadioptric optical lens 13 satisfies: 0.04 < |Φ13| < 0.06.

[0026] Referring to Figure 1 Figure 1 , the refractive lens group 100 includes a first lens group 101, a second lens group 102, a third lens group 103 and a fourth lens group 104 arranged in sequence along the optical path direction. The fourth lens group 104 is the lens group closest to the catadioptric optical lens 13. The optical power Φ101 of the first lens group 101 satisfies: 0.04 < |Φ101| < 0.05, the optical power Φ102 of the second lens group 102 satisfies: 0.00005 < |Φ102| < 0.00015, the optical power Φ103 of the third lens group 103 satisfies: 0.008 < |Φ103| < 0.009, and the optical power Φ104 of the fourth lens group 104 satisfies: Φ104 < 0, and 0.007 < |Φ104| < 0.008. The first lens group 101 is a rear focal group for compensating the error of rear focal assembly; the second lens group 102 and the third lens group 103 are focusing groups for adjusting the focal length at different object distances; the fourth lens group 104 is a fixed group for correcting aberrations such as astigmatism and field curvature caused by the field of view.

[0027] As a preferred solution of this embodiment, the first lens group 101 includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6 and a seventh lens 7 which are arranged in sequence along the optical path direction. A stop 14 is arranged between the sixth lens 6 and the seventh lens 7. The optical power Φ1 of the first lens 1 satisfies: 0.01<|Φ1|<0.03. The second lens 2 and the third lens 3 are glued together to form a glued lens. The overall optical power Φ23 of the second lens 2 and the third lens 3 satisfies: 0.02<|Φ23|<0.03. The fourth lens 4 and the fifth lens 5 are glued together to form a glued lens. The overall optical power Φ45 of the fourth lens 4 and the fifth lens 5 satisfies: 0.03<|Φ45|<0.04. The optical power Φ6 of the sixth lens 6 satisfies: 0.04<|Φ6|<0.05. The optical power Φ1 of the first lens 1 satisfies: 0.06<|Φ7|<0.07.

[0028] The second lens group 102 includes an eighth lens 8 , and the optical power Φ8 of the eighth lens 8 satisfies: 0.00005<|Φ8|<0.00015.

[0029] The third lens group 103 includes a ninth lens 9 and a tenth lens 10 sequentially arranged along the optical path direction. The optical power Φ9 of the ninth lens 9 satisfies: 0.008<|Φ9|<0.01, and the optical power Φ10 of the tenth lens 10 satisfies: 0.0015<|Φ10|<0.0025.

[0030] The fourth lens group 104 includes an eleventh lens 11 and a twelfth lens 12 sequentially arranged along the optical path direction. The optical power Φ11 of the eleventh lens 11 satisfies: 0.0015<|Φ11|<0.0025, and the optical power Φ12 of the twelfth lens 12 satisfies: 0.0035<|Φ12|<0.005.

[0031] In this embodiment, one side of the folding reflective optical lens 13 is coated to form a reflective surface 13a, and the coating material is a reflective film such as a silver film, an aluminum film or a dielectric film. The lens can be cold-processed glass, or can be molded by glass molding or injection molding of plastic materials. The lens surface includes a spherical surface, an aspherical surface or a free-form surface. The projection display technology corresponding to the present invention can be LCD projection, DLP projection or LCOS projection.

[0032] Compared with the catadioptric ultra-short-focus projection lens using an ordinary reflector, the catadioptric optical lens 13 disclosed in the present invention includes two surfaces, the first surface is a refractive surface 13b, and the second surface is a reflective surface 13a. The light is refracted from the first surface of the lens and reflected by the second surface, and then refracted again by the first surface and projected onto the screen. The light passes through the first surface twice, which is equivalent to adding a refractive surface 13b without adding optical elements, that is, a single catadioptric lens is used to achieve the effect of a double refractive surface 13b plus a reflective surface 13a. This not only provides more degrees of freedom for correcting system aberrations and further improves system performance, but also reduces the number of optical elements from the perspective of lens manufacturing, thereby reducing the number of molds used. Moreover, compared with manufacturing a single reflector mold, the utilization rate of the mold is improved and the cost of the system is reduced.

[0033] Figure 4 is a field curvature and distortion diagram of Example 1 of the present invention. It can be seen from the diagram that this embodiment has a smaller degree of distortion.

[0034] In this embodiment, the aspheric surface equation used by the catadioptric aspheric optical lens is:

[0035]

[0036] in c is the curvature of the aspherical vertex, K is the quadratic surface coefficient, and A1, A2, A3, A4, A5, and A6 are high-order aspherical surface coefficients.

[0037] The following Tables 1 and 2 are basic data of Example 1 of the present invention:

[0038] Table 1

[0039]

[0040]

[0041] Table 2

[0042]

[0043] Example 2

[0044] Figure 5 Embodiment 2 of the present invention is shown. This embodiment has a similar structure to Embodiment 1, and the difference lies in the structure of the refractive lens group 100. In this embodiment, the refractive lens group 100 includes three lens groups. Figure 6 is a field curvature and distortion diagram of Example 2 of the present invention. It can be seen from the diagram that this embodiment has a smaller degree of distortion.

[0045] Example 3

[0046] Figure 7 Embodiment 3 of the present invention is shown. This embodiment has a similar structure to Embodiment 1, and the difference lies in the structure of the refractive lens group 100. In this embodiment, the refractive lens group 100 includes two lens groups. Figure 8 3 is a field curvature and distortion diagram of Example 3 of the present invention. It can be seen from the diagram that this embodiment has a smaller degree of distortion.

[0047] A common feature of the above three embodiments is that the refractive lens group 100 includes at least two lens groups, wherein the optical focal length of the lens group close to the catadioptric optical lens 13 is negative, and the lens group is used to correct aberrations such as astigmatism and field curvature caused by the field of view.

[0048] In summary, the catadioptric optical lens 13 disclosed in the present invention, when combined with the refractive lens assembly 100 including different numbers of groups, can achieve better optical performance and good projection imaging effect.

[0049] The above are only preferred feasible embodiments of the present invention. All equivalent changes made by applying the present invention specification and the scope of patent application should be included in the scope of the claims of the present invention.

Claims

1. An ultra-short-throw projection lens based on a catadioptric optical lens, characterized in that: It includes an image source, a refractive lens group (100), a catadioptric optical lens (13) and a screen arranged in sequence along the optical path direction. The catadioptric optical lens (13) includes a refractive surface (13b) and a reflective surface (13a). After the light exits from the refractive lens group (100), it is refracted by the refractive surface (13b) of the catadioptric optical lens (13) and then reflected by the reflective surface (13a), and then exits again through the refractive surface (13b) and is projected onto the screen. The radius of curvature R1 of the refractive surface (13b) of the catadioptric optical lens (13) satisfies: |R1| < 400, and the radius of curvature R2 of the reflective surface (13a) of the catadioptric optical lens (13) satisfies: |R2| < 2R1|. The surface type of the catadioptric optical lens (13) is spherical, aspherical or freeform surface. The refractive lens group (100) includes at least two lens groups, and the optical power of the lens group closer to the catadioptric optical lens (13) is negative. The refractive index Nd of the catadioptric optical lens (13) satisfies: 1.4 < Nd < 1.9, the Abbe number Vd of the catadioptric optical lens (13) satisfies: 55 < Vd < 60, and the optical power Φ13 of the catadioptric optical lens (13) satisfies: 0.04 < Φ13 < 0.

06.

2. The ultra-short-throw projection lens based on a catadioptric optical lens according to claim 1, characterized in that: One side of the catadioptric optical lens (13) is coated with a film to form the reflective surface (13a), and the coating material is a silver film, an aluminum film or a dielectric film.

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