CN109254387B

CN109254387B - Projection lens and image output apparatus

Info

Publication number: CN109254387B
Application number: CN201811485455.1A
Authority: CN
Inventors: 刘海朋
Original assignee: Shenzhen Xiaoxiang Light Display Co ltd
Current assignee: Shenzhen Xiaoxiang Light Display Co ltd
Priority date: 2018-12-04
Filing date: 2018-12-04
Publication date: 2023-04-25
Anticipated expiration: 2038-12-04
Also published as: CN109254387A

Abstract

The invention provides a projection lens and image output equipment, and relates to the field of projection lenses. The projection lens includes: a first lens which is a plano-convex lens and has positive diopter; a second lens having a negative diopter; a third lens having a negative diopter; a fourth lens having positive refractive power; a fifth lens having positive refractive power; a sixth lens which is a plano-convex lens and has positive refractive power; the first lens is close to the object plane, and the sixth lens is close to the image plane; the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are arranged in order from the first lens to the sixth lens along an optical axis; the lens assembly further comprises a prism, and the prism is arranged between the sixth lens and the image plane. The lens is easy to process, low in cost and loose in assembly tolerance, and compared with other telecentric structures, the lens size is reduced.

Description

Projection lens and image output apparatus

Technical Field

The present invention relates to the field of projection lenses, and in particular, to a projection lens and an image output apparatus.

Background

The projector is more and more widely used in teaching, life and work, the projection quality of the projector is a key factor for judging the advantages and disadvantages of the projector, the projection lens is the last part of a light path of the projector, the quality of the projection lens determines the projection quality, the quality of the projection lens is improved, and the projection quality of the projector can be directly improved.

In the prior art, the projection lens comprises a first lens group with positive refractive power and a second lens group with positive refractive power, and the projection lens with the structure comprises a plurality of aspherical mirrors, so that the process is complex, the processing is difficult, the tolerance requirement is strict during assembly, and the production cost and the process requirement are high.

Therefore, there is a need for a low cost, easy to manufacture, easy to assemble projection lens.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a projection lens and an image output device so as to solve the problems of complex lens technology, high production cost and difficult assembly.

In order to achieve the above purpose, the technical scheme adopted by the embodiment of the invention is as follows:

in a first aspect, an embodiment of the present invention provides a projection lens, including: the first lens is a plano-convex lens and has positive diopter. And a second lens having negative diopter. And a third lens having negative diopter. And a fourth lens having positive diopter. And a fifth lens having positive diopter. And a sixth lens, which is a plano-convex lens and has positive diopter. The first lens is close to the object plane, and the sixth lens is close to the image plane. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are arranged in order from the first lens to the sixth lens along the optical axis. The lens assembly further comprises a prism, wherein the prism is arranged between the sixth lens and the image plane.

Further, the object side surfaces of the first lens and the sixth lens are convex surfaces and spherical surfaces, and the image side surfaces are spherical surfaces with infinite radius.

Further, the second lens is a meniscus lens, and the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface and is a spherical surface.

Further, the third lens is a meniscus lens, and the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface and is spherical.

Further, the fourth lens is a meniscus lens, and the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface and is spherical. The object side surface of the fourth lens is attached to the image side surface of the third lens.

Further, the fifth lens is a meniscus lens, and the object side surface of the fifth lens is a concave surface, and the image side surface is a convex surface and is spherical.

Further, it also satisfies: and 0.35< BFL/TTL <0.46, wherein TTL is the total lens length and represents the distance from the object side surface of the first lens to the image plane, and BFL is the back focal length of the lens and represents the distance from the image side surface of the sixth lens to the image plane.

Optionally, the optical lens further comprises a diaphragm, and the diaphragm is arranged between the first lens and the second lens and is used for controlling the throughput of light rays.

Optionally, the optical lens further comprises a diaphragm, and the diaphragm is arranged between the second lens and the third lens and used for controlling the throughput of light rays.

In a second aspect, an embodiment of the present invention further provides an image output apparatus, including the projection lens of the first aspect.

The beneficial effects of the invention are as follows: the telecentric structure formed by the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens ensures that the illuminance of the image surface of the lens is uniform, the contrast is good and the energy utilization rate is high, wherein the first lens and the sixth lens are plano-convex lenses, and the plano-convex lenses are used for manufacturing the projection lens, so that the processing is easy, the cost is low, the assembly tolerance is loose, and meanwhile, the size of the lens is reduced compared with that of other telecentric structures.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic view of a projection lens according to an embodiment of the invention;

FIG. 2 is a schematic view of a projection lens according to an embodiment of the present invention;

FIG. 3 is a diagram of curvature of field and distortion aberration of a projection lens according to an embodiment of the present invention;

FIG. 4 is a graph of a projection lens modulation transfer function (Modulation Transfer Function, MTF) provided by scenario one of the present invention;

FIG. 5 is a vertical axis color difference chart of a projection lens according to a first embodiment of the present invention;

FIG. 6 is a schematic view of a projection lens according to a second embodiment of the present invention;

FIG. 7 is a diagram of curvature of field and distortion aberration of a projection lens according to a second embodiment of the present invention;

fig. 8 is a schematic view of an MTF curve of a projection lens according to a second embodiment of the present invention;

FIG. 9 is a vertical axis color difference chart of a projection lens according to a second embodiment of the present invention;

fig. 10 is a schematic structural diagram of an image output apparatus according to an embodiment of the present invention.

Icon: 1-a first lens; 2-a second lens; 3-a third lens; 4-a fourth lens; 5-a fifth lens; 6-a sixth lens; 7-prisms; 8-protecting the lens; -a digital micromirror element (Digital Micromirror Device, DMD); 10-diaphragm.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.

In the description of the present invention, it should be noted that the terms "first," "second," "third," and the like are used for distinguishing descriptions, and are not to be construed as indicating or implying relative importance, and meanwhile, the image side and the object side are in a conjugated relationship.

Fig. 1 is a schematic diagram of a projection lens according to an embodiment of the invention.

As shown in fig. 1, the projection lens includes:

the first lens 1, the first lens 1 is a plano-convex lens, and has positive diopter. The second lens 2 has negative diopter. The third lens 3 has negative diopter. The fourth lens 4 has positive diopter. The fifth lens 5 has positive diopter. The sixth lens 6, the sixth lens 6 is a plano-convex lens, and has positive diopter. Wherein the first lens 1 is close to the object plane, and the sixth lens 6 is close to the image plane S15. The first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5 and the sixth lens 6 are arranged along the optical axis in sequence from the first lens 1 to the sixth lens 6 to form a telecentric structure, and the lens further comprises a prism 7, wherein the prism 7 is arranged between the sixth lens 6 and an image surface S15.

The prism 7 is a beam splitting prism, and is used for turning an optical path, for example, in the use of a projection lens, an illumination optical path and an imaging optical path exist, and the illumination optical path and the imaging optical path are connected through the beam splitting prism to form a complete projection optical path.

It should be noted that, the telecentric structure means that after the light passes through the lens, the principal ray is approximately parallel to the optical axis, in this embodiment, the included angle between the principal ray and the optical axis after the light passes through the lens is smaller than 1 °, and the telecentric structure is used to make the image plane illuminance uniform, the contrast ratio good, and the energy utilization rate high.

Alternatively, the lens may be a lens group, for example, the first lens 1 may be a lens group formed by at least 2 lenses, the lens group has the same optical performance as the first lens 1, and the number and types of lenses in the lens group are not limited, so long as the optical performance can be achieved.

The projection lens provided by the embodiment of the invention comprises a telecentric structure formed by the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens, so that the illuminance of the image surface of the lens is uniform, the contrast is good, the energy utilization rate is high, wherein the first lens and the sixth lens are plano-convex lenses, the plano-convex lenses are used for manufacturing the projection lens, the processing is easy, the cost is low, the assembly tolerance is loose, and meanwhile, the size of the lens is reduced compared with that of other telecentric structures.

In order to better illustrate the structure of the projection lens shown in fig. 1 and its mirror parameters, a possible implementation is described below.

In this context, f is used to denote a focal length in millimeters; r represents the surface curvature radius of the optical lens, and the unit is millimeter; d is the on-axis distance of the corresponding optical surface to the latter optical surface in millimeters; nd is the refractive index of the corresponding optical lens for d-ray (the wavelength of light is 587 nm), and Vd is the abbe number of the optical lens corresponding to d-ray.

The object side surface S1 of the first lens 1 is a convex surface and a spherical surface, and the image side surface S2 is a spherical surface with an infinite radius.

The object side surface S10 of the sixth lens 6 is a convex surface and a spherical surface, and the image side surface S11 is a spherical surface with an infinite radius.

In the present embodiment, the material of the first lens 1 is glass, and the focal length satisfies 22< f <46; the refractive index satisfies: 1.76< nd <1.79; the Abbe number satisfies: 25< Vd <42.

Alternatively, the material of the first lens 1 may be plastic, quartz, or other materials that satisfy optical performance.

In this embodiment, the sixth lens 6 is made of glass, and the focal length satisfies: 15< f <25, the refractive index satisfies: 1.62< nd <1.74, abbe number: 50< Vd <65.

Alternatively, the sixth lens 6 may be made of plastic, quartz, or the like, which satisfies optical properties.

The first lens 1 and the sixth lens 6 are plano-convex lenses, and the plano-convex lenses are easy to process, low in cost and easy to assemble, and can effectively reduce the processing difficulty and cost of the projection lens.

The second lens 2 is a meniscus lens, and an object-side surface S3 and an image-side surface S4 of the second lens 2 are both convex and concave.

In this embodiment, the material of the second lens 2 is glass, and the focal length satisfies: -15< f < -20 > and the refractive index is such that: 1.58< nd <1.61, abbe number: 42< Vd <50.

Alternatively, the material of the second lens 2 may be plastic, quartz, or other materials that satisfy optical performance.

The third lens 3 is a meniscus lens, and an object-side surface S5 and an image-side surface S6 of the third lens 3 are both convex and concave.

In this embodiment, the material of the third lens 3 is glass, and the focal length satisfies: 8<f < -5 > and the refractive index satisfies: 1.80< Nd <1.85, abbe number satisfies: 22< Vd <32.

Alternatively, the material of the third lens 3 may be plastic, quartz, or other materials that satisfy optical performance.

The fourth lens element 4 is a meniscus lens element, and an object-side surface S6 and an image-side surface S7 of the fourth lens element 4 are both concave and convex. The object side surface S6 of the fourth lens 4 is attached to the image side surface S6 of the third lens 3.

In this embodiment, the fourth lens 4 is made of glass, and the focal length satisfies: 8< f <10, the refractive index satisfies: 1.76< nd <1.81, abbe number: 45< Vd <50.

Alternatively, the material of the fourth lens 4 may be plastic, quartz, or other materials that satisfy optical performance.

In the present embodiment, the third lens 3 and the fourth lens 4 are bonded.

The fifth lens 5 is a meniscus lens, and an object-side surface S8 and an image-side surface S9 of the fifth lens 5 are both concave and convex.

In this embodiment, the material of the fifth lens 5 is glass, and the focal length satisfies: 17< f <24, the refractive index satisfies: 1.62< nd <1.74, abbe number: 50< Vd <65.

Alternatively, the fifth lens 5 may be made of plastic, quartz, or other materials that satisfy optical performance.

In this embodiment, the first lens element 1, the second lens element 2, the third lens element 3, the fourth lens element 4, the fifth lens element 5 and the sixth lens element 6 are all made of glass, so that thermal defocus can be effectively reduced, and an image is more stable during projection.

In this embodiment, the provided projection lens further satisfies: and 0.35< BFL/TTL <0.46, wherein TTL is the total lens length, and represents the distance from the object side surface of the first lens 1 to the image surface S15, and BFL is the lens back focal length, and represents the distance from the image side surface of the sixth lens 6 to the image surface S15.

In this embodiment, in order to have enough space for placing the prism 7, a certain limitation needs to be made on the back focal length of the lens, and the BFL/TTL is limited to be between 0.35 and 0.46, so that after the prism 7 is placed between the sixth lens 6 and the image surface S15, enough space can be left for structural design and stray light processing.

Further, the projection lens further comprises a protective lens 8, wherein the protective lens 8 is arranged between the prism 7 and the image surface S15 and is used for protecting an imaging element placed on the image surface S15.

The imaging element comprises a DMD9, and the protective lens 8 and the DMD9 are integrally formed.

Optionally, when the distance between the object plane and the projection lens is changed, the distances between the first lens element 1, the second lens element 2, the third lens element 3, the fourth lens element 4, the fifth lens element 5, the sixth lens element 6 and the image plane S15 are adjusted to obtain a clear image.

In this embodiment, when the image projected by the lens irradiates the display medium, the plane of the display medium is not in the same plane as the object plane, so that the projected image is blurred, and at this time, focusing operation is required, for example, by adjusting the distances between the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the image plane S15, the position of the plane of the object plane is changed, so as to obtain a clear image, wherein the distances between the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the image plane S15 are adjusted, and the distances between the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are kept unchanged.

Alternatively, the focusing operation may be implemented by changing the distances between the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6, and how the focusing operation is implemented is not limited herein.

The projection lens provided by the invention has a plurality of possible implementation modes, and the projection lens is described by taking a scene one and a scene two as examples. The structure and parameters in scene one and scene two are merely examples of implementations of projection shots, and are not limiting in that they must be so set.

Scene one

Fig. 2 is a schematic view of a projection lens according to a first embodiment of the present invention.

As shown in fig. 2, the projection lens further comprises a diaphragm 10, wherein the diaphragm 10 is arranged between the first lens 1 and the second lens 2 and is used for controlling the throughput of light rays and simultaneously compressing the whole volume of the projection lens.

In the first scene, parameters of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the prism 7, the protective lens 8, the DMD9, and the diaphragm 10 are shown in the following table:

the projection lens has a focal length f=11.17 mm, a total length ttl=30.14 mm, and an aperture F _No. =1.7, wherein the aperture is the reciprocal of the relative aperture. The relative aperture is the ratio of the entrance pupil diameter, which is the diameter of the diaphragm 10 imaged by the optical system in front of it, to the focal length.

Fig. 3 is a diagram showing curvature of field and distortion aberration of a projection lens according to a first embodiment of the present invention.

As shown in fig. 3, the projection lens field Qu Xiao provided in the first embodiment of the present invention has a maximum distortion of 0.8% at 0.05 mm.

Fig. 4 is a graph of MTF of a projection lens according to a first embodiment of the present invention.

As shown in fig. 4, the MTF of the full field of view of the projection lens provided in scene one of the present embodiment at 93lp/mm spatial frequency is >48%.

Fig. 5 is a vertical axis color difference chart of a projection lens according to a first embodiment of the present invention.

As shown in fig. 5, the imaging system of the projection lens provided in the first embodiment has a vertical chromatic aberration of 2.4 μm at maximum.

According to the parameters, the projection lens provided by the scene one has small distortion, excellent MTF performance, small vertical axis chromatic aberration, F1.7 aperture and excellent imaging quality.

Scene two

Fig. 6 is a schematic view of a projection lens according to a second embodiment of the present invention.

As shown in fig. 6, the optical device further includes an optical stop 10, where the optical stop 10 is disposed between the second lens 2 and the third lens 3, for controlling the throughput of light.

In the second scene, the diaphragm 10 is arranged between the second lens 2 and the third lens 3, so that the overall structure of the lens is relatively symmetrical, coma and distortion can be effectively balanced, and the imaging quality of the lens is improved.

In the second scene, parameters of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the prism 7, the protective lens 8, the DMD9, and the diaphragm 10 are shown in the following table:

the projection lens has a focal length f=10.33 mm, a total length ttl=39.93 mm, and an aperture F _No. =1.7, wherein the aperture is the reciprocal of the relative aperture. The relative aperture is the ratio of the entrance pupil diameter, which is the diameter of the diaphragm 10 imaged by the optical system in front of it, to the focal length.

Fig. 7 is a diagram of curvature of field and distortion aberration of a projection lens according to a second embodiment of the present invention.

As shown in fig. 7, the projection lens field Qu Xiao provided in the second embodiment has a maximum distortion of 0.8% at 0.05 mm.

Fig. 8 is a schematic diagram of an MTF curve of a projection lens according to a second embodiment of the present invention.

As shown in fig. 8, the MTF of the full field of view of the projection lens provided in the second embodiment at 93lp/mm spatial frequency is >50%.

Fig. 9 is a vertical axis color difference chart of a projection lens according to a second embodiment of the present invention.

As shown in FIG. 9, the imaging system has a maximum of 2.8 μm in vertical chromatic aberration.

According to the parameters, the projection lens provided by the second scene has small distortion, excellent MTF performance, small vertical axis chromatic aberration, F1.7 aperture and excellent imaging quality.

Further, with respect to the projection lens provided in the above embodiment, it may be applied to an image output apparatus, for example, a desktop projector, a writing projector, or other end products with projection functions, and a possible implementation is given below to describe the image output apparatus.

As shown in fig. 10, the apparatus includes: projection lens 901, light source 903, imaging element 902.

The light source is used for irradiating the imaging element and projecting the image on the imaging element through the projection lens.

Optionally, the apparatus may further comprise: a processor, memory, radio frequency circuitry, and other related input/output components for performing the corresponding functions of the device are not limited herein.

The image output device uses the projection lens, so that the beneficial effects are similar to those of the image output device, and the description is omitted here.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A projection lens, wherein the number of lenses with diopters in the projection lens is six, and the projection lens comprises:

a first lens which is a plano-convex lens and has positive diopter;

a second lens having a negative diopter;

a third lens having a negative diopter;

a fourth lens having positive refractive power;

a fifth lens having positive refractive power;

a sixth lens which is a plano-convex lens and has positive refractive power;

the first lens is close to the object plane, and the sixth lens is close to the image plane;

the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are arranged in order from the first lens to the sixth lens along an optical axis;

the lens system further comprises a prism, wherein the prism is arranged between the sixth lens and the image plane;

the third lens is a meniscus lens;

the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface and is spherical;

the fourth lens is a meniscus lens;

the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface and is spherical;

the object side surface of the fourth lens is attached to the image side surface of the third lens;

the prism is a beam splitter prism and is used for connecting an illumination light path and an imaging light path to form a complete projection light path;

the optical lens further comprises an optical diaphragm, wherein the optical diaphragm is arranged between the first lens and the second lens and is used for controlling the throughput of light rays;

the focal length of the third lens satisfies: 8<f < -5 > and the refractive index satisfies: 1.80< Nd <1.85, abbe number satisfies: 22< Vd <32;

the focal length of the fourth lens satisfies: 8< f <10, the refractive index satisfies: 1.76< nd <1.81, abbe number: 45< Vd <50.

2. The projection lens of claim 1 wherein the object side surfaces of the first lens and the sixth lens are convex and spherical and the image side surface is spherical with an infinite radius.

3. The projection lens of claim 1 wherein the second lens is a meniscus lens;

the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface and is spherical.

4. The projection lens of claim 1 wherein the fifth lens is a meniscus lens;

the object side surface of the fifth lens is concave, and the image side surface is convex and spherical.

5. The projection lens of any of claims 1-4 further satisfying: and 0.35< BFL/TTL <0.46, wherein TTL is total lens length and represents the distance from the object side surface of the first lens to the image plane, BFL is back focal length of the lens and represents the distance from the image side surface of the sixth lens to the image plane.

6. An image output apparatus comprising the projection lens of any one of claims 1 to 5.