阅读说明：本技术 非球面超短焦投影镜头 (Aspheric ultrashort-focus projection lens ) 是由 王仕龙 周岸迪 于 2018-06-20 设计创作，主要内容包括：本发明提供了一种非球面超短焦投影镜头,其特征在于,位于投射面和DMD芯片之间的若干同轴透镜：将广角光线偏转为近轴光束的前组镜头组、将近轴光束远心成像于DMD芯片的后组镜头组。(The invention provides an aspheric ultrashort-focus projection lens which is characterized in that a plurality of coaxial lenses are arranged between a projection surface and a DMD chip: the front lens group deflects wide-angle light rays into paraxial light beams, and the rear lens group telecentrically images the paraxial light beams on the DMD chip.)

1. The utility model provides an aspheric surface ultra short focal projection lens which characterized in that, is located a plurality of coaxial lens between plane of projection and the DMD chip: a front lens group for deflecting wide-angle light into a near-axis light beam, and a rear lens group for telecentric imaging of the near-axis light beam on the DMD chip,

the front lens group sequentially comprises from an object end to an image end: a first aspheric lens (1), a second aspheric lens (2), a plano-concave lens (3), a biconcave lens (4), a convex-concave lens (5), a convex lens (6) and a first plano-convex lens (7),

the rear lens group comprises from the object end to the image end in sequence: a convex lens (8), a plano-concave lens (9), a biconvex lens (10), a plano-concave lens (11), a biconvex lens (12), a second plano-convex lens (13), and a plano-convex lens (14).

2. The aspheric ultra-short-focus projection lens of claim 1, wherein the meniscus lens (5) and the convex lens (6) form a first cemented doublet;

the concave lens (9) and the biconvex lens (10) form a second double cemented lens;

and the plano-concave lens (11) and the biconvex lens (12) form a third double-cemented lens.

3. The aspheric ultra-short-focus projection lens of claim 1, wherein the focal length of the first aspheric lens (1) is between-100 mm and-90 mm;

the focal length of the second aspheric lens (2) is between 70mm and 80 mm;

the focal length of the plano-concave lens (3) is between-60 mm and 50 mm;

the focal length of the biconcave lens (4) is between-50 mm and 40 mm;

the focal length of the convex-concave lens (5) is between-100 and-90 mm;

the focal length of the convex lens (6) is between 30mm and 40 mm;

the focal length of the first plano-convex lens (7) is between 80mm and 90 mm;

the focal length of the convex lens (8) is between 120mm and 130 mm;

the focal length of the plano-concave lens (9) is between-20 mm and-10 mm;

the focal length of the biconvex lens (10) is between 20mm and 30 mm;

the focal length of the plano-concave lens (11) is between-25 mm and-20 mm;

the focal length of the double convex lens (12) is between 25mm and 30 mm;

the focal length of the second plano-convex lens (13) is between 65mm and 70 mm;

the focal length of the third plano-convex lens (14) is between 35mm and 45 mm.

4. The aspheric ultra-short-focus projection lens of claim 3, wherein the lens is made of glass material.

5. The aspheric ultra-short focus projection lens of claim 4, wherein the effective focal length of the aspheric ultra-short focus projection lens is: 6.5 mm.

6. The aspheric ultra-short-focus projection lens of claim 1, wherein the DMD chip is offset from the optical axis.

Technical Field

The invention relates to the field of photoelectric display, in particular to the field of projection equipment, and particularly relates to an aspheric ultra-short-focus projection lens.

Background

At present, a common projector is only provided with a standard lens, and if a 152.4cm picture is projected by the projector, the projector needs to be placed at a 2.2m far place, 203.2cm needs to be at a 2.6m far place, and a 254cm picture reaches a 3m to 4m far place. If the space for projection is not large, but a large picture needs to be displayed, especially in a small conference room, the lens cannot meet the requirement. Moreover, if the presenter inadvertently blocks the light from time to time, the person viewing under the table is greatly affected thereby. In view of these factors, in recent years, short-focus lenses have been invented, so that the high requirement for projection distance is improved, but image quality cannot be guaranteed, and the shortened projection distance is also limited. The short-focus projector appearing on the market at present is divided into two forms, one is a reflective projector, the projector adds a reflector or an aspheric surface reflector in front of a common projection lens, and projects the reflector on a screen after reflection, and the technology has the defects of complex instrument structure, higher cost and unsatisfactory imaging quality; the other is a common short-focus projection lens, which has low resolution and is usually a non-telecentric lens with serious distortion.

In order to improve the projected picture quality, the projection lens is generally designed to have a longer focal length and a small visual angle; it is known that the shorter the focal length, the larger the viewing angle, and the stronger the distortion due to optical principles. With the rapid development of electronic technology, people increasingly have strong demands on high-definition projection equipment. The traditional projection lens with long focal length and narrow visual angle is difficult to meet the requirements in terms of size and projection picture quality. Meanwhile, because a lens in a general design does not realize strict image space telecentricity, the phenomenon of uneven illumination of a relatively serious projection surface is caused.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide an aspheric ultra-short-focus projection lens.

The aspheric ultrashort-focus projection lens provided by the invention is characterized in that a plurality of coaxial lenses positioned between the projection surface and the DMD chip comprise: a front lens group for deflecting wide-angle light into a near-axis light beam, and a rear lens group for telecentric imaging of the near-axis light beam on the DMD chip,

the front lens group sequentially comprises from an object end to an image end: a first aspheric lens (1), a second aspheric lens (2), a plano-concave lens (3), a biconcave lens (4), a convex-concave lens (5), a convex lens (6) and a first plano-convex lens (7),

the rear lens group comprises from the object end to the image end in sequence: a convex lens (8), a plano-concave lens (9), a biconvex lens (10), a plano-concave lens (11), a biconvex lens (12), a second plano-convex lens (13), and a plano-convex lens (14).

Furthermore, the aspheric ultrashort-focus projection lens is characterized in that the meniscus lens (5) and the convex lens (6) form a first cemented doublet; the concave lens (9) and the biconvex lens (10) form a second double cemented lens; and the plano-concave lens (11) and the biconvex lens (12) form a third double-cemented lens.

Furthermore, the aspheric ultra-short-focus projection lens is characterized in that,

the focal length of the first aspheric lens (1) is between-100 mm and-90 mm;

the focal length of the second aspheric lens (2) is between 70mm and 80 mm;

the focal length of the plano-concave lens (3) is between-60 mm and 50 mm;

the focal length of the biconcave lens (4) is between-50 mm and 40 mm;

the focal length of the convex-concave lens (5) is between-100 and-90 mm;

the focal length of the convex lens (6) is between 30mm and 40 mm;

the focal length of the first plano-convex lens (7) is between 80mm and 90 mm;

the focal length of the convex lens (8) is between 120mm and 130 mm;

the focal length of the plano-concave lens (9) is between-20 mm and-10 mm;

the focal length of the biconvex lens (10) is between 20mm and 30 mm;

the focal length of the plano-concave lens (11) is between-25 mm and-20 mm;

the focal length of the double convex lens (12) is between 25mm and 30 mm;

the focal length of the second plano-convex lens (13) is between 65mm and 70 mm;

the focal length of the third plano-convex lens (14) is between 35mm and 45 mm.

Furthermore, the aspheric ultrashort-focus projection lens is characterized in that the lens is made of glass materials.

Further, the aspheric ultra-short-focus projection lens is characterized in that the effective focal length of the aspheric ultra-short-focus projection lens is as follows: 6.5 mm.

Further, the aspheric ultrashort-focus projection lens is characterized in that the DMD chip is placed in an offset manner with respect to the optical axis.

Compared with the prior art, the invention has the following beneficial effects:

1. the aspheric surface ultra-short focus projection lens provided by the invention has the advantages of telecentric object space, high resolution, ultra-wide angle and ultra-low distortion;

2. according to the invention, by arranging the high-refractive-index glass, the curvature radius of the lens is effectively reduced, and the manufacturing difficulty is reduced.

3. Under the condition of not adding complex free-form surface reflectors and special materials, the optical projection lens with 113 degrees of field of view, 6.5mm of focal length, 206mm of optical cylinder length, F2.6, less than 0.5% of distortion, uniform image quality and better image quality of each field of view is finally obtained.

4. The invention ensures that the emergent picture is upwardly biased during the orthographic projection work by placing the DMD chip in a biased way, realizes that the emergent light beam is higher than the position of the projection lens, and the projection picture can not be shielded by the projection objective.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a schematic diagram of an aspheric ultra-short-focus projection lens;

the optical lens comprises a first aspheric lens 1, a second aspheric lens 2, a plano-concave lens 3, a plano-concave lens 4, a biconcave lens 5, a convex-concave lens 6, a convex lens 7, a first plano-convex lens 8, a convex lens 9, a plano-concave lens 10, a biconvex lens 11, a plano-concave lens 12, a biconvex lens 13, a second plano-convex lens 14 and a plano-convex lens.

FIG. 2 is a light path diagram of an aspheric ultra-short-focus projection lens;

FIG. 3 is an interface form diagram of an MTF curve of an aspheric ultra-short-focus projection lens;

FIG. 4 is a diagram of an interface of field curvature and distortion map of an aspheric ultra-short-focus projection lens;

FIG. 5 is an interface form diagram of a simulated illumination of the aspheric ultra-short-focus projection lens;

FIG. 6 is a schematic diagram of an interface format of a DMD chip bias simulation.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.

As shown in FIG. 1, the invention is realized by determining the lens as a separated 'reverse-distance' type objective lens with a front negative group and a rear positive group according to the imaging characteristics of an ultra-wide angle, selecting lenses with similar structures as initial structures according to the structural types, and finally obtaining a short-focus projection objective lens with excellent image quality through proper focal length zooming and aberration optimization design. The invention is composed of 14 lenses, which specifically comprises the following components: the front lens group comprises from the object end to the image end in sequence: the optical lens comprises a first aspheric lens (1), a second aspheric lens (2), a plano-concave lens (3), a biconcave lens (4), a convex-concave lens (5), a convex lens (6) and a first plano-convex lens (7).

The rear lens group comprises from the object end to the image end in sequence: a convex lens (8), a plano-concave lens (9), a biconvex lens (10), a plano-concave lens (11), a biconvex lens (12), a second plano-convex lens (13), and a plano-convex lens (14).

The lens uses the high-refractive-index glass, so that the curvature radius of the lens is effectively reduced, and the manufacturing difficulty is reduced. The concave-convex lens (5) and the convex lens (6) form a first cemented doublet; the concave lens (9) and the biconvex lens (10) form a second double cemented lens; and the plano-concave lens (11) and the biconvex lens (12) form a third double-cemented lens.

Preferably, the lens can be selected from the following parameters:

preferably, the lens is made of high-refractive-index glass, and the refractive index of the high-refractive-index glass exceeds 1.7.

The lens can be used for placing the DMD in an offset mode, the DMD chip is placed in an offset mode relative to the optical axis, the maximum offset placement distance is plus or minus 2.0mm, and when the optical axis is offset by 2mm, the projection effect is shown in figure 5. Therefore, the emergent picture is ensured to be upwardly biased during orthographic projection work, the emergent light beam is higher than the position of the projection lens, and the projection picture cannot be shielded by the projection objective. And 3.2 m × 2.4 m high-definition pictures are projected within a distance of 1.5 m.

The effective focal length of the lens is 6.50 mm; the total length is 240 mm; f/# is 2.6; the exit pupil position is 500; the field angle is 113 °.

Fig. 2 is an optical path diagram of the projection lens of the present invention. Therefore, the light is deflected into a near-axis light beam through the front group of lenses, and the near-axis light beam is telecentric and imaged on the DMD chip through the rear group of lenses.

Fig. 3 is an interface form diagram of an MTF graph of an aspheric ultrashort-focus projection lens, in which MTF curves of each field under 70lp/mm are compacted into a bundle and have values greater than 0.4, and values greater than 0.5 except for an edge field, which shows that an imaging picture of the lens is clear and uniform and meets a requirement of a high resolution of 1920 × 1080. The pixel size of the 0.7-inch DMD chip is 7.5 microns, the corresponding MTF line pair is 66lp/mm, and the resolution requirement of the chip can be met when the MTF value is larger than 0.3 under the line pair number. As shown in the figure, the field curvature of the lens is less than 0.1mm, and the distortion is less than 0.5 percent.

As shown in fig. 4, the present invention has excellent projection surface irradiation uniformity, the full-field irradiation uniformity is greater than 93%, as shown in fig. 5, which is an interface form diagram of a projection illumination simulation diagram of an aspheric ultra-short-focus projection lens, and as shown in fig. 6, which is an interface form diagram of a DMD chip offset simulation diagram.

The design can be modified by changing the form of the lens and the distance between the lenses to apply to similar projection systems.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.