CN113050255A

CN113050255A - Ultra-short-focus projection lens with large view field and small volume

Info

Publication number: CN113050255A
Application number: CN202110456630.XA
Authority: CN
Inventors: 黄国豹
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-04-26
Filing date: 2021-04-26
Publication date: 2021-06-29

Abstract

The invention discloses an ultra-short focal projection lens with large visual field and small volume, which comprises a refraction lens group and a reflection lens group, wherein the refraction lens group comprises: the first lens group at least comprises an aspheric lens and at least one cemented lens, the second lens group comprises a weak-power aspheric lens and other spherical lenses, and the refractive lens closest to the reflector group is the third lens group of the aspheric lens; the reflector group comprises an aspheric reflector. The invention has the advantages of large projection breadth, good manufacturability, low cost and no virtual coke at high temperature.

Description

Ultra-short-focus projection lens with large view field and small volume

Technical Field

The invention relates to the technical field of projection lenses, in particular to an ultra-short focus projection lens with a large view field and a small volume.

Background

With the recent rise of business, entertainment and home theater, the ultra-short focus projection lens is popular in the market because of short projection distance, small space occupation, large projection breadth and good viewing effect.

The common mode of realizing the projection effect of the short distance large breadth at present has two kinds: one is to use a conventional refractive lens, which is generally a wide-angle lens of the retrofocus type, and the lens has a large number of lenses, high cost, large distortion and limited breadth. The other type is a refraction and reflection type lens formed by combining a refraction lens and a reflector, the refraction and reflection type lens is easy to realize large breadth, the defect is that the refraction and reflection type lens contains more aspheric lenses, generally 4-5 lenses, the die sinking cost is high, the production yield is low, and in order to save the cost, the virtual focus phenomenon often exists when the plastic aspheric lens is used.

For example, in patent CN103777314A, a wide-angle projection lens is disclosed, which uses a large aperture (f/1.67) wide-angle projection lens designed by a concave hybrid architecture. The wide-angle lens comprises a refraction system and a reflection system, wherein the refraction system comprises a plurality of spherical lenses and a first lens group of at least one aspheric lens and a second lens group of at least two aspheric lenses and at least one spherical lens, the at least one spherical lens is arranged between any two of the at least two aspheric lenses, the Effective Focal Length (EFFL) of the at least one spherical lens is-2.89 mm, the Focal number (f/#) of the at least one spherical lens is 1.67, the offset (offset) of the at least one spherical lens is 122%, the resolution capability of the at least one spherical lens can reach 67lp/mm, the size of a projectable picture is 40-60 inches, the projection distance is 282-418 mm, the projection ratio is 0.274-0.278, and the projection ratio is large, so that a large projection breadth can not be realized at a short projection distance.

In order to achieve the projection effect of large projection breadth, good manufacturability, low cost and no virtual focus at high temperature, it is necessary to design an ultrashort focus projection lens with large view field and small volume.

Disclosure of Invention

Aiming at the situation and overcoming the defects of the prior art, the invention provides the ultra-short-focus projection lens with the large view field and the small volume, and in order to achieve the projection effects of large projection breadth, good manufacturability, low cost and no virtual focus at high temperature, the invention uses a plurality of three cemented lenses, converts larger assembly tolerance into smaller cemented tolerance, improves the manufacturability of assembly, has high yield of mass production, uses steps for positioning most lenses, avoids the inclination phenomenon which is easy to appear when the lenses are assembled as far as possible, and has good manufacturability.

In order to achieve the purpose, the invention provides the following technical scheme: the utility model provides a little voluminous ultrashort burnt projection lens of big visual field, includes refractor group and speculum group, and refractor group includes wherein:

a first lens group including at least one aspherical lens and at least one cemented lens;

a second lens group including a weak power aspherical lens and other spherical lenses;

a third lens group, wherein the refractive lens closest to the reflector group is an aspheric lens;

the reflector group comprises an aspheric reflector.

Preferably, the aspheric lens in the first lens group is close to the chip and is a first aspheric lens of the refraction system;

the cemented lens in the first lens group is a cemented triplet, and the power distribution of a single lens in the cemented lens triplet is as follows: positive-negative-positive;

the second lens group consists of a positive lens, a negative lens and a weak focal power aspheric lens, wherein the weak focal power aspheric lens is close to the third lens group;

the second lens group can move back and forth along the axial direction;

the aspheric lens of the third lens group is close to the reflector group.

Preferably, in the cemented lens of the first lens group, the negative lens is made of a material with high refractive index (Nd is more than or equal to 1.83) and low Abbe number (Vd is less than or equal to 32), and the positive lens is made of a material with low refractive index (Nd is less than or equal to 1.50) and high Abbe number (Vd is more than or equal to 70);

the focal power of the weak-focal-power aspheric lens of the second lens group is close to zero and is negative, and the focal power is in the range of-0.003-0;

the cemented lens of the third lens group is a triple cemented lens and is close to the second lens group, the abbe numbers Vd of the single lenses of the cemented lens are all within 40, and the refractive index Nd of the negative lens is larger than that of the positive lens.

Preferably, at least one surface of the aspherical lens in the first lens group is a convex surface;

the outline shape of the three cemented lenses in the first lens group is a drum-shaped lens with two convex sides or a thick meniscus lens which is bent to the diaphragm;

a meniscus air lens is formed between the positive single lens and the negative single lens in the second lens group;

the outer profile of the three cemented lenses in the third lens group is a drum-shaped lens with two convex sides.

Preferably, the first lens group includes, in order from an object side to an image side: the lens comprises a first aspheric lens and a first cemented lens, wherein the first cemented lens is formed by sequentially cementing a first spherical positive lens, a second spherical negative lens and a third spherical positive lens.

Preferably, the second lens group includes, in order from an object side to an image side: a fourth spherical positive lens, a fifth spherical negative lens, and a second aspheric lens.

Preferably, the third lens group includes, in order from the object side to the image side: the second cemented lens is formed by sequentially cementing a sixth spherical positive lens, a seventh spherical negative lens and an eighth spherical positive lens.

The invention has the beneficial effects that:

1. the method has the advantages of large projection breadth, good manufacturability, low cost and no virtual coke at high temperature;

2. the three cemented lenses are used, so that a large assembly tolerance is converted into a small cemented tolerance, the assembly manufacturability is improved, the yield of mass production is high, most lenses are positioned by steps, the inclination phenomenon easily occurring in the lens assembly process is avoided as much as possible, and the manufacturability is good;

3. the second aspheric lens and the third aspheric lens are made of plastic lenses, compared with a glass aspheric lens, the cost of the lenses and the cost of a mold are reduced, and the two plastic lenses realize image quality complementation at different temperatures through matching of two aspheric surface shapes, so that the lens does not generate virtual focus phenomenon at the temperature of 20-60 ℃.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic structural diagram of an ultra-short focus projection lens according to the present invention;

FIG. 2(a), FIG. 2(b) and FIG. 2(c) are schematic structural diagrams of a first lens group, a second lens group and a third lens group, respectively, according to the present invention;

FIG. 3 is a schematic view of a light path of a projection lens according to the present invention;

FIG. 4 is a schematic diagram of an actual scene with light passing through the projection lens of the present invention;

fig. 5 is a simulation diagram of the imaging quality of the present invention, in which fig. 5(a) and fig. 5(b) are vertical axis chromatic aberration diagrams at the screen when the ultra-short-focus projection lens of the present invention projects 36 inches and 63 inches pictures at 20 ℃, respectively, and the pixel size is 833um for the 36 inches projection picture size and 1458um for the 63 inches projection picture size;

FIG. 6 is a simulation diagram of the imaging quality of the present invention, in which FIGS. 6(a) and 6(b) are the horizontal fan diagrams at the screen when the ultra-short-focus projection lens of the present invention projects 36 inches and 63 inches of the screen at 20 ℃, respectively, the scale bar of FIG. 6(a) is 1000um, and the scale bar of FIG. 6(b) is 2000 um;

fig. 7 is a simulation diagram of the imaging quality of the present invention, wherein fig. 7(a) and fig. 7(b) are MTF diagrams at the screen of the ultra-short focus projection lens of the present invention at 36 inches of projection screen and at 20 ℃ and 60 ℃ of ambient temperature, respectively, and the MTF observation line pair is 0.61lp/mm in 36 inches of projection screen;

FIG. 8 is a simulation diagram of the imaging quality of the present invention, in which FIG. 8(a) and FIG. 8(b) are the MTF graph at the screen of the ultra-short-focus projection lens of the present invention under a 63-inch projection image and at the ambient temperatures of 20 ℃ and 60 ℃, respectively, and the MTF observation line pair is 0.34lp/mm under the 63-inch projection image;

description of the main component symbols:

Detailed Description

While the invention as set forth herein will be described in conjunction with the following embodiments, which will be understood in detail, those skilled in the art will understand that they can make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention as defined by the appended claims. For example, the cemented surface of the cemented lens is disassembled instead of a thin air gap, and the shape of the single lens profile remains similar, which should be regarded as a proper extension of the present patent, and is within the scope of the present patent.

Referring to fig. 1-4, which are schematic structural diagrams of the ultra-short-focus projection lens of the present invention, according to the sequence of light propagation, the ultra-short-focus projection lens 100 of the present invention has an optical axis 105, and the projection lens 100 includes a chip 101, a chip protection glass 102, an equivalent prism 103, a galvanometer 104, a first lens group 110, a second lens group 120, a third lens group 130, and a reflector group 140. The first lens group 110 sequentially comprises a first aspheric lens 111, a first spherical lens 112, a second spherical lens 113 and a third spherical lens 114 according to the sequence of light propagation, wherein the first aspheric lens 111 effectively corrects spherical aberration and ensures telecentric beam at the chip side, the first spherical lens 112, the second spherical lens 113 and the third spherical lens 114 are mainly responsible for correcting chromatic aberration and secondary spectrum, and astigmatism and coma aberration can be corrected by optimizing the lens material and the gluing radius. The second lens group 120 sequentially includes a diaphragm aperture 121, a fourth spherical lens 122, a fifth spherical lens 123 and a second aspheric lens 124 according to the sequence of light propagation, the second aspheric lens 124 mainly corrects the aberration caused by different projection distances, and the fourth spherical lens 122 and the fifth spherical lens 123 can exchange the positions thereof according to the aberration; the third lens group 130 sequentially comprises a sixth spherical lens 131, a seventh spherical lens 132, an eighth spherical lens 133 and a third aspherical lens 134 according to the sequence of light propagation, the focal power of the third aspherical lens 134 is negative, and the third aspherical lens 134 mainly has the main functions of converging light beams close to parallel of each field of view into an image point to provide a real image point for the reflector group 140, and correcting astigmatism and distortion of different fields of view together with the reflector group 140, wherein the sixth spherical lens 131, the seventh spherical lens 132 and the eighth spherical lens 133 mainly use high-level aberration generated by a cemented surface to effectively correct coma aberration and astigmatism, and when the chromatic aberration of the first lens group 110 is not sufficiently corrected, the sixth spherical lens 131, the seventh spherical lens 132 and the eighth spherical lens 133 can also adjust the abbe number of the lenses to compensate the chromatic aberration; the reflector set 140 includes only one aspheric reflector, and the second aspheric lens 124 and the third aspheric lens 134 use plastic lenses, which reduces the unit price and the mold cost of the lenses and has cost advantage compared with glass aspheric lenses, and the two plastic lenses realize image quality complementation at different temperatures by matching the two aspheric surface types, so that the lens does not generate virtual focus phenomenon between 20 ℃ and 60 ℃.

The chip 101 of the present invention generally includes a digital micromirror array (DMD) and a reflective silicon substrate liquid crystal display (LCOS).

Referring to fig. 2(a), a schematic diagram of a first lens assembly of the present invention is shown, wherein the first aspheric lens 111 is located at the leftmost side of the first lens assembly, close to the chip 101, and is a first aspheric lens of a refractive system, and at least one surface of the first aspheric lens is a convex surface; the first spherical lens 112, the second spherical lens 113 and the third spherical lens 114 are cemented into a cemented triplet having a contour shape with two convex sides similar to a drum-shaped lens, wherein the first spherical lens 112 and the third spherical lens 114 are both biconvex positive lenses and have a low refractive index (Nd is less than or equal to 1.50) and a high Abbe number (Vd is greater than or equal to 70), and the second spherical lens 113 is a biconcave negative lens and has a high refractive index (Nd is greater than or equal to 1.83) and a low Abbe number (Vd is less than or equal to 32).

In the first lens group, the light beams of each field on the surface of the first aspheric lens 111 are relatively dispersed, the overlapping area is less than that of other lenses in the group, and when an aspheric surface type is used, the light angles and aberrations of different fields can be corrected more favorably, so that the system keeps an object space telecentric state, and the brightness is improved; the material of the triple cemented lens formed by the first spherical lens 112, the second spherical lens 113 and the third spherical lens 114 is selected to play an important role in correcting vertical axis chromatic aberration and secondary spectrum, and the cemented surface mainly plays a role in correcting astigmatism and coma.

Referring to fig. 2(b), it is a schematic diagram of the second lens assembly structure of the present invention, wherein the stop hole 121 is closest to the first lens assembly; the fourth spherical lens 122 is a positive lens, the fifth spherical lens 123 is a negative lens, and a meniscus air space is formed between the two lenses, wherein the air space is favorable for correcting astigmatism; the focal power of the second aspheric lens 124 is close to zero and is negative, the focal power is in the range of-0.003-0 and is close to the third lens group; the second lens group 120 can realize clear focusing of a projection picture by moving along the optical axis 105 under different projection distances; the weak focal power of the second aspheric lens 124 causes almost no influence on the total focal power of the system in the moving process, and the light rays of the middle field and the peripheral field are finely adjusted through the high-order aspheric coefficients of the surface of the second aspheric lens, so that the second aspheric lens is compatible with the subtle aberration changes brought by different projection distances.

Referring to fig. 2(c), a schematic diagram of a third lens assembly according to the present invention is shown, wherein a sixth spherical lens 131, a seventh spherical lens 132 and an eighth spherical lens 133 are cemented together to form a triple cemented lens, and an outer profile of the triple cemented lens is a drum-shaped lens with two convex sides; the sixth spherical lens 131 and the eighth spherical lens 133 are positive lenses, the seventh spherical lens 132 is a negative lens, the abbe numbers Vd of the three lenses are all within 40, and the refractive index Nd of the negative lens is greater than that of the positive lens; the third aspheric lens 134 is adjacent to the mirror group; the third aspheric lens 134 mainly focuses the light beams of each field of view into real image points at different positions, and is matched with the mirror group 140 to correct the curvature of field and distortion of the lens.

The optical parameter values of the above design examples are shown in table 1 below, and the equation of the above aspheric surface curve is as follows:

in the formula, c is the curvature corresponding to the radius, y is the radial coordinate which has the same unit as the length unit of the lens, k is the cone coefficient, r²～r¹⁶Each representing a coefficient corresponding to each radial coordinate.

Fig. 5(a) and 5(b) are vertical axis color difference graphs at a screen when 36-inch and 63-inch projection pictures are taken at 20 ℃. The vertical axis chromatic aberration describes the difference of the principal rays of different light waves at each view field position in the height direction of the image plane, and the smaller the difference is, the smaller the chromatic aberration of the system is, the better the imaging quality is. The pixel size is 833um for a projection screen size of 36 inches, and 1458um for a projection screen size of 63 inches. At each object plane height, it can be seen that the lateral chromatic aberration at each position does not exceed 0.6 pixel, which is characterized by low lateral chromatic aberration.

Fig. 6(a) and 6(b) are diagrams of the lateral light fan at the screen at 20 c, 36 inch and 63 inch projection screens, respectively. The abscissa represents the normalized entrance pupil and the ordinate is the value of the deviation of the ray from the chief ray at the image plane. The horizontal axis shows the scale bar of FIG. 6(a) ± 1000um, and the scale bar of FIG. 6(b) ± 2000 um. As can be seen from the transverse fan image, the curves of the small aperture and the medium aperture are closer to the transverse axis, the imaging quality is good, the light of the edge aperture is more divergent, the splicing gap between the pixels of the chip can be softened to a certain degree, and the granular sensation during the film watching is reduced.

Fig. 7(a) and 7(b) are MTF graphs at the screen at ambient temperatures of 20 ℃ and 60 ℃, respectively, in a 36-inch projection screen. The MTF observation line pair was 0.61lp/mm for a 36-inch projection screen. MTF graph represents the integrated analytical capability of the optical system, and the horizontal axis in the graph represents spatial frequency, unit: turns per millimeter (cycles/mm). The longitudinal axis represents the value of a Modulation Transfer Function (MTF), the value of the MTF is used for evaluating the imaging quality of the lens, the value range is 0-1, the straighter the MTF curve is, the better the imaging quality of the lens is, the stronger the reduction capability of a real image is, the better the curve coincidence degree of each field is, and the better the consistency of the image quality is. As can be seen from fig. 7(a) and 7(b), when the ambient temperature is 20 ℃, the MTF of the visible light band at the spatial frequency of 0.61lp/mm is >0.45 in the full field, even if the ambient temperature rises to 60 ℃, the MTF is only reduced to 0.38 in the marginal field, and the image quality of the other field areas is good.

Fig. 8(a) and 8(b) are MTF graphs at the screen at ambient temperatures of 20 ℃ and 60 ℃, respectively, under a 63-inch projection screen. The MTF observation line pair is 0.34lp/mm under a 63-inch projection picture. As can be seen from fig. 8(a) and 8(b), when the ambient temperature is 20 ℃, the MTF of the visible light band at the spatial frequency of 0.34lp/mm is >0.5 in the full field, and even when the ambient temperature rises to 60 ℃, the MTF is only the marginal field and falls to 0.4, and the image quality of other field areas is good.

The following case is an ultra-short focus projection lens suitable for a 0.23 inch DMD, where TR is 0.25, OFFSET is 140%, and F # is 1.8. The actual design parameters are referred to tables 1 to 3.

Table 1:

surface of	Type (B)	Radius of curvature	Thickness of	Glass	Coefficient of cone
						OBJ	Spherical surface	Infinite number of elements	0.303		0
S1	Spherical surface	Infinite number of elements	1.1	H-K5	0
						S2	Spherical surface	Infinite number of elements	0.6		0
S3	Spherical surface	Infinite number of elements	10.6	H-LAK7A	0
						S4	Spherical surface	Infinite number of elements	2		0
S5	Spherical surface	Infinite number of elements	2	H-K51	0
						S6	Spherical surface	Infinite number of elements	2		0
S7	Even aspheric surface	12.22951	6.995034	D-K9	-1.173881
						S8	Even aspheric surface	-20.90679	0.1		-14.18268
S9	Spherical surface	9.844101	4.884464	H-FK61	0
						S10	Spherical surface	-12.76586	1.2	H-ZLAF75A	0
S11	Spherical surface	6.883175	5.547932	H-FK61	0
						S12	Spherical surface	-23.88936	1.2		0
STO	Spherical surface	Infinite number of elements	0.1		0
						S14	Spherical surface	47.0414	2.8	H-ZF52TT	0
S15	Spherical surface	-13.12076	1.331021		0
						S16	Spherical surface	-25.29831	1	H-K5	0
S17	Spherical surface	12.04478	11.72236		0
						S18	Even aspheric surface	98.96484	2	ZEONEX_E48R_2017	-4.376018
S19	Even aspheric surface	70.92268	1.37227		18.39652
						S20	Spherical surface	35.06622	8.151171	H-F13	0
S21	Spherical surface	-38.26712	2	H-ZF52	0
						S22	Spherical surface	30.05439	10	H-ZF1	0
S23	Spherical surface	-22.96505	0.5		0
						S24	Even aspheric surface	-20.34062	2.5	ZEONEX_E48R_2017	0.409944
S25	Even aspheric surface	36.45425	60.9064		0.1802212
						S26	Even aspheric surface	-21.80409	-200	MIRROR	-0.963869
IMA	Spherical surface	Infinite number of elements			0

Table 2:

coefficient of aspheric surface	S7	S8	S18	S19
					r4	4.5276439E-05	-5.0653998E-05	-3.9380086E-04	-2.7768702E-04
r6	3.9904713E-07	5.2588282E-06	2.9701573E-06	4.0310948E-06
					r8	6.9676861E-09	-1.5001246E-08	-2.7797740E-08	-3.4448570E-08
r10	-1.5904927E-11	2.1064032E-11	-2.8798843E-11	1.0676089E-10

Table 3:

coefficient of aspheric surface	S24	S25	S26
				r4	3.0150050E-04	-3.2306589E-05	6.1061167E-06
r6	-7.3705723E-07	-7.4792351E-08	-5.1400698E-09
				r8	2.2381753E-09	5.4567888E-11	4.5834096E-12
r10	-5.6382295E-12	-5.8739659E-13	-1.7232386E-15

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The utility model provides an ultrashort burnt projection lens of little volume of big visual field which characterized in that: including refractor group and speculum group, wherein refractor group includes:

the reflector group comprises an aspheric reflector.

2. The ultra-short-focus projection lens with large field of view and small volume as claimed in claim 1, wherein: the aspheric lens in the first lens group is close to the chip and is a first aspheric lens of the refraction system;

the second lens group can move back and forth along the axial direction;

the aspheric lens of the third lens group is close to the reflector group.

3. The ultra-short-focus projection lens with large field of view and small volume as claimed in claim 1, wherein: in the cemented lens of the first lens group, the negative lens is made of a material with high refractive index (Nd is more than or equal to 1.83) and low Abbe number (Vd is less than or equal to 32), and the positive lens is made of a material with low refractive index (Nd is less than or equal to 1.50) and high Abbe number (Vd is more than or equal to 70);

4. The ultra-short-focus projection lens with large field of view and small volume as claimed in claim 3, wherein: at least one surface of the aspheric lens in the first lens group is a convex surface;

5. The ultra-short-focus projection lens with large field of view and small volume as claimed in claims 1-4, wherein: in order from an object side to an image side, the first lens group includes: the lens comprises a first aspheric lens and a first cemented lens, wherein the first cemented lens is formed by sequentially cementing a first spherical positive lens, a second spherical negative lens and a third spherical positive lens.

6. The ultra-short-focus projection lens with large field of view and small volume as claimed in claims 1-4, wherein: in order from an object side to an image side, the second lens group includes: a fourth spherical positive lens, a fifth spherical negative lens, and a second aspheric lens.

7. The ultra-short-focus projection lens with large field of view and small volume as claimed in claims 1-4, wherein: in order from the object side to the image side, the third lens group includes: the second cemented lens is formed by sequentially cementing a sixth spherical positive lens, a seventh spherical negative lens and an eighth spherical positive lens.