CN117031705A - Projection lens and projection system - Google Patents

Abstract

The invention discloses a projection lens and a projection system, wherein the projection lens comprises a first transmission group, a diaphragm and a second lens group which are coaxially and sequentially arranged along the propagation direction of light; the first lens group comprises at least one lens, and the second lens group comprises at least one lens; the projection lens satisfies: f/TTL multiplied by F.NO is more than or equal to 0.5 and less than or equal to 1.5; limiting the focal length, lens length and F number of the projection lens within the above ranges can ensure that the optical system has a large aperture characteristic and effectively reduce the size of the projection lens, thereby realizing ultra-thin characteristic and miniaturization of the projection lens.

Description

Projection lens and projection system

Technical Field

The present disclosure relates to projection technology, and more particularly, to a projection lens and a projection system.

Background

The projection display technology is a technology of enlarging and displaying an image by using an optical system and a projection space. The projection system is finally used for completing the display of the image by the optical imaging system, and the application scene and the imaging quality of the projection system are greatly influenced by the projection lens. And the size of the projection lens can also affect the volume of the optical engine.

With the rapid development of projection technology, the application requirement modes are also more and more diversified, and in order to meet the requirements of different application scenes, the size of a projection lens is required to be reduced in some cases, so that the whole volume of an optical engine is reduced.

Disclosure of Invention

In a first aspect of an embodiment of the present invention, there is provided a projection lens, including: a first transmission group, a diaphragm, and a second lens group coaxially and sequentially arranged along a propagation direction of light; the first lens group includes at least one lens, and the second lens group includes at least one lens;

the projection lens satisfies the following conditions:

0.5≤f/TTL×F.NO≤1.5；

wherein f represents the focal length of the projection lens, TTL represents the length of the projection lens along the optical axis, and F.NO represents the aperture value of the projection lens.

In some embodiments of the invention, the second lens group includes: a first lens; the first lens is a negative lens.

In some embodiments of the invention, the first lens is a spherical lens.

In some embodiments of the invention, the thickness of the first lens satisfies:

3≤ct/et≤5；

wherein ct represents the center thickness of the first lens in the optical axis direction, and et represents the edge thickness of the first lens in the optical axis direction.

In some embodiments of the present invention, the first lens group includes a second lens, a third lens, a fourth lens, and a fifth lens sequentially disposed in a direction gradually away from the first lens;

the second lens is a positive lens, the third lens is a negative lens, the fourth lens is a positive lens, and the fifth lens is a positive lens.

In some embodiments of the invention, the second lens and the third lens are spherical lenses, and the fourth lens and the fifth lens are aspherical lenses.

In some embodiments of the invention, the thickness of the second lens satisfies:

2≤ct45/et45≤3；

wherein ct45 represents a center thickness of the second lens in the optical axis direction, and et45 represents an edge thickness of the second lens in the optical axis direction;

the thickness of the third lens satisfies:

1.5≤ct67/et67≤3；

wherein ct67 represents a center thickness of the third lens in the optical axis direction, and et67 represents an edge thickness of the third lens in the optical axis direction;

the thickness of the fourth lens satisfies:

4≤ct89/et89≤6；

wherein ct89 represents a center thickness of the fourth lens in the optical axis direction, and et89 represents an edge thickness of the fourth lens in the optical axis direction;

the thickness of the fifth lens satisfies:

4≤ct1011/et1011≤6；

where ct1011 denotes a center thickness of the fifth lens in the optical axis direction, and et1011 denotes an edge thickness of the fifth lens in the optical axis direction.

In some embodiments of the present invention, the focal lengths of the second lens, the third lens, the fourth lens, and the fifth lens satisfy:

f45≥4；

f67≥-5；

f89≥-69；

f1011≥4；

wherein f45 denotes a focal length of the second lens, f67 denotes a focal length of the third lens, f89 denotes a focal length of the fourth lens, and f1011 denotes a focal length of the fifth lens.

In some embodiments of the present invention, the thickness of the projection lens satisfies:

0.3≤(CT4+CT5)/∑CT≤0.6；

wherein CT4 represents the center thickness of the fourth lens in the optical axis direction, CT5 represents the center thickness of the fifth lens in the optical axis direction, and Σct represents the sum of the center thicknesses of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens in the optical axis direction.

A second aspect of an embodiment of the present invention provides a projection system, including:

a projection light source;

an illumination system positioned on the light-emitting side of the projection light source; the illumination system comprises a light modulator;

the projection lens is any one of the projection lenses; the projection lens is positioned on the light emitting side of the light modulator.

The projection lens and the projection system comprise a first transmission group, a diaphragm and a second lens group which are coaxially and sequentially arranged along the propagation direction of light; the first lens group comprises at least one lens, and the second lens group comprises at least one lens; the projection lens satisfies: f/TTL multiplied by F.NO is more than or equal to 0.5 and less than or equal to 1.5; limiting the focal length, lens length and F number of the projection lens within the above ranges can ensure that the optical system has a large aperture characteristic and effectively reduce the size of the projection lens, thereby realizing ultra-thin characteristic and miniaturization of the projection lens.

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 of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a projection system according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of an imaging principle of a projection apparatus according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a projection lens according to an embodiment of the present disclosure;

fig. 4 is a light path diagram of a projection lens according to an embodiment of the present invention;

FIG. 5 is a graph of a modulation transfer function provided by an embodiment of the present invention;

FIG. 6 is a defocus plot provided by an embodiment of the present invention;

FIG. 7 is a dot column diagram provided by an embodiment of the present invention;

FIG. 8 is a schematic diagram of a field curvature curve according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of a distortion curve provided by an embodiment of the present invention;

fig. 10 is a telecentricity curve provided by an embodiment of the present invention.

Detailed Description

In order that the above objects, features and advantages of the invention will be readily understood, a further description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. However, the exemplary embodiments can be embodied in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus a repetitive description thereof will be omitted. The words expressing the positions and directions described in the present invention are described by taking the drawings as an example, but can be changed according to the needs, and all the changes are included in the protection scope of the present invention. The drawings of the present invention are merely schematic representations of relative positional relationships and are not intended to represent true proportions.

The projection display technology is a technology of enlarging and displaying an image by using an optical system and a projection space. The projection system is the final image display by the optical imaging system. With the continuous development of projection technology, laser projection systems have been widely used in the fields of large-screen display, laser televisions, digital cinema, portable projection display, and the like with unique advantages. The laser projection display can display more vivid and gorgeous dynamic images on an oversized screen, and the visual shock effect which cannot be achieved by other display technologies is achieved.

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

As shown in fig. 1, in practical application, the front projection system may include: projection device 100 and projection screen 200.

The projection screen 200 is located on the light emitting side of the projection apparatus 100, the viewer faces the projection screen 200, the projection apparatus 100 emits projection light, and the projection light is incident on the projection screen 200 and reflected toward the viewer through the projection screen 200, so that the viewer views the projection image.

The projection device is provided with a projection lens, and the size and the projection distance of the projection screen can be influenced by the specification of the projection lens. In practical application, projection lenses such as ultra-short focus, short focus or long focus are used according to different application scenes.

Fig. 2 is a schematic diagram of an imaging principle of a projection apparatus according to an embodiment of the present invention.

As shown in fig. 2, the projection apparatus includes: a projection light source 1, an illumination system 2 and a projection lens 3. The illumination system 2 is located at the light emitting side of the projection light source 1, the light modulator 21 is disposed in the illumination system 2, the light modulator 21 is used for modulating the incident light and emitting the modulated incident light, and the projection lens 3 is located at the light emitting side of the light modulator 21.

The projection light source 1 may be a light emitting diode (Light Emitting Diode, LED) light source or a laser light source. The LED light source has the advantages of small power consumption, small volume, long service life and the like, and is suitable for small-size projection and other application scenes. The laser light source has higher brightness and better color saturation, and can optimize the display effect of the projection image.

In the embodiment of the invention, the projection light source can adopt a laser light source, and the laser light source can adopt a monochromatic laser or a laser capable of emitting laser with various colors or a plurality of lasers emitting laser with different colors. When the laser light source adopts a monochromatic laser, the laser display device also needs to be provided with a color wheel which is used for color conversion, and the monochromatic laser can realize the purpose of emitting the primary color light of different colors according to time sequence by matching with the color wheel. When the laser light source adopts a laser capable of emitting laser light with multiple colors, the laser light source needs to be controlled to emit laser light with different colors as primary color light according to time sequence. The three-color laser light source is favorable for improving the color gamut of the projection image, has better color expressive force and can accurately reproduce the input image.

The illumination system 2 is located on the light-emitting side of the projection light source 1, and the illumination system 2 collimates and homogenizes the light emitted from the projection light source 1, and makes the light emitted from the projection light source 1 incident on the light modulator 21 at an appropriate angle. The illumination system 2 may include a plurality of lenses or lens groups, light pipes, diffusion sheets, diffusion wheels, etc., without limitation.

The light modulator 21 is used to modulate incident light to form an image. In the embodiment, the light modulator 21 may be a transmissive light modulator or a reflective light modulator. The optical modulator 21 shown in fig. 2 is a reflective optical modulator. The light modulator 21 receives the light reflected by the beam splitter prism P and modulates the incident light, and reflects the modulated light. Since the optical path is folded back through the reflective light modulator, the volume of the projection apparatus can be reduced.

In an embodiment of the present invention, the optical modulator 21 may employ liquid crystal on silicon (Liquid Crystal on Silicon, abbreviated as LCoS) or digital micromirror (Digital Micromirror Device, abbreviated as DMD).

LCoS is formed by bonding a complementary metal oxide semiconductor (Complementary Metal Oxide Semiconductor, abbreviated as CMOS) substrate to a glass substrate containing transparent electrodes based on semiconductor technology, and then injecting liquid crystal for encapsulation. LCoS has the characteristics of high aperture ratio of each pixel, high resolution and the like, and can form a high-resolution image.

The DMD includes a plurality of minute mirrors, each of which is individually driven to deflect, and the brightness of light incident on the projection lens 3 is controlled by controlling the deflection angle of the DMD.

The beam splitter prism P is used for separating the illumination beam and the imaging beam, and the beam emitted by the projection light source is finally reflected by the beam splitter prism P to the light modulator 21 through the processes of shaping, homogenizing and the like, and the light emitted by the light modulator 21 after being modulated is emitted through the beam splitter prism P to enter the projection lens 3.

An image shift member Z is provided between the beam splitter prism P and the light modulator 21, and the image polarization member Z may be a plate glass, and image shift may be realized by high-frequency vibration to realize high-resolution image display.

After the light modulator 21 modulates the incident light to form an image, the light is reflected toward the projection lens 3, and imaged by the projection lens 3, thereby projecting the image to a proper size for viewing.

The size of the projection lens affects the overall size of the projection device, so with the trend of miniaturization of the projection device, a small projection lens needs to be designed to have a smaller size on the premise of ensuring the imaging quality.

Fig. 3 is a schematic diagram of a projection lens according to an embodiment of the present disclosure; fig. 4 is a light path diagram of a projection lens according to an embodiment of the present invention.

As shown in fig. 3, the projection lens includes a first transmission group 31, a stop s, and a second lens group 32 coaxially disposed in this order in the propagation direction of light; wherein the first lens group 31 includes at least one lens, and the second lens group 32 includes at least one lens; and the projection lens satisfies:

0.5≤f/TTL×F.NO≤1.5；

where f denotes a focal length of the projection lens, TTL denotes a length of the projection lens along the optical axis, and f.no denotes an aperture value of the projection lens.

The projection lens provided by the embodiment of the invention only comprises two lens groups, and the focal length, the length and the F number of the projection lens are limited in the range, so that the size of the projection lens can be effectively reduced while the optical system has a large aperture characteristic, and the ultra-thin characteristic and the miniaturization of the projection lens are realized.

Specifically, as shown in fig. 3, the second lens group 32 includes: the first lens l1, the first lens l1 is a negative lens. The first lens group 31 includes a second lens l2, a third lens l3, a fourth lens l4, and a fifth lens l5, which are sequentially disposed in a direction gradually away from the first lens l 1; the second lens l2 is a positive lens, the third lens l3 is a negative lens, the fourth lens l4 is a positive lens, and the fifth lens l5 is a positive lens. The stop s is located between the first lens l1 and the second lens l2, and the first lens l1, the stop s, the second lens l2, the third lens l3, the fourth lens l4, and the fifth lens l5 are coaxially disposed.

When designing the projection lens, the display surface of the light modulator 21 is used as an image plane, the imaging with a specific position reaching a set size is used as an object plane, and the parameters of the projection lens are optimized by utilizing the property of reversibility of the light path. As shown in fig. 4, the light emitted from the light modulator 21 passes through the image shift member, passes through the beam splitter prism P, reaches the projection lens, enters from one side of the first lens group 31 of the projection lens, passes through the aperture stop s and the second lens group 32, and is imaged at the specific position to obtain an image of a predetermined size. By integrally moving the projection lens in the optical axis direction, the distance between the projection lens and the beam splitter prism P is changed to realize zoom imaging.

In the embodiment of the present invention, the first lens l1 is a spherical lens, the second lens l2 and the third lens l3 are spherical lenses, and the fourth lens l4 and the fifth lens l5 are aspherical lenses. The projection lens only comprises five lenses, and can have better imaging quality only by adopting two aspheric lenses, the optical system is simple and compact in structure, and the total length of the lens can be reduced to below 12.6 mm.

Wherein, the thickness of the first lens l1 satisfies:

3≤ct/et≤5；

where ct denotes a center thickness of the first lens l1 in the optical axis direction, and et denotes an edge thickness of the first lens l1 in the optical axis direction.

By controlling the parameters of the first lens l1 to satisfy the above ranges, the aberration and curvature of field of the projection lens can be balanced.

The second lens l2 satisfies:

2≤ct45/et45≤3；

f45≥4；

where ct45 denotes a center thickness of the second lens in the optical axis direction, et45 denotes an edge thickness of the second lens in the optical axis direction, and f45 denotes a focal length of the second lens.

The third lens l3 satisfies:

1.5≤ct67/et67≤3；

f67≥-5；

where ct67 denotes a center thickness of the third lens in the optical axis direction, et67 denotes an edge thickness of the third lens in the optical axis direction, and f67 denotes a focal length of the third lens.

The fourth lens l4 satisfies:

4≤ct89/et89≤6；

f89≥-69；

where ct89 denotes a center thickness of the fourth lens in the optical axis direction, et89 denotes an edge thickness of the fourth lens in the optical axis direction, and f89 denotes a focal length of the fourth lens.

The fifth lens l5 satisfies:

4≤ct1011/et1011≤6；

f1011≥4；

where ct1011 denotes a center thickness of the fifth lens in the optical axis direction, et1011 denotes an edge thickness of the fifth lens in the optical axis direction, and f1011 denotes a focal length of the fifth lens.

By controlling the parameters of the second lens l2, the third lens l3, the fourth lens l4 and the fifth lens l5 to meet the above ranges, the workability of the lens can be ensured, the system size can be effectively reduced, the focal power of the optical system can be reasonably distributed, the optical system is not excessively concentrated on a certain lens, and meanwhile, the aberration control of the lens is facilitated.

The thickness of the projection lens satisfies:

0.3≤(CT4+CT5)/∑CT≤0.6；

wherein CT4 denotes a center thickness of the fourth lens l4 in the optical axis direction, CT5 denotes a center thickness of the fifth lens l5 in the optical axis direction, Σct denotes a sum of center thicknesses of the first lens l1, the second lens l2, the third lens l3, the fourth lens l4, and the fifth lens l5 in the optical axis direction.

The ratio of the center thicknesses of the two aspheric lenses of the fourth lens l4 and the fifth lens l5 to the center thickness of the overall lens of the lens is reasonably controlled, so that the system focal power is reasonably distributed, the system spherical aberration and the aberration are improved, and the stability of the system structure is enhanced.

The embodiment of the invention can make the projection ratio of the projection lens be 1.2 by designing the surface type of the five lenses in the projection lens and the combination mode thereof, wherein the projection ratio is the ratio of the projection picture width of the projection lens to the projection picture distance of the projection lens. The total length of the projection lens represents the distance on the optical axis from the first lens to the fifth lens, which is less than 12.6mm, so that the projection lens has a smaller length, which is beneficial to reducing the volume of the projection device. The F.NO of the projection lens represents the light receiving capacity of the lens, and the larger the value is, the smaller the light receiving angle is; the smaller the value, the larger the light receiving angle. The F.NO of the projection lens provided by the embodiment of the invention is 2.4, and the projection lens has stronger light receiving capability and larger luminous flux.

The surface type parameters of each optical component and the intervals among the optical components in the projection lens provided by the embodiment of the invention are shown in the following table:

face number

Surface type

Radius of curvature

Thickness of (L)

Material

Semi-aperture

OBJ

Spherical surface

Infinite number of cases

800

401.572

S1

Spherical surface

8.87

2.03

1.73；51.5

2.58

S2

Spherical surface

3.353

1.942

Refraction by refraction

1.708

Diaphragm

Spherical surface

Infinite number of cases

0.195

Refraction by refraction

1.275

S4

Spherical surface

16.48

1.118

1.81；22.7

Refraction by refraction

1.43

S5

Spherical surface

-6.78

1.787

Refraction by refraction

1.644

S6

Spherical surface

-3.878

1

1.92；18.9

Refraction by refraction

2.005

S7

Spherical surface

-37.095

0.2

Refraction by refraction

2.608

S8

Aspherical surface

-25.913

2.033

1.5；81.6

Refraction by refraction

2.85

S9

Aspherical surface

-107.248

0.325

Refraction by refraction

3.285

S10

Aspherical surface

3.61

1.938

1.62；63.9

Refraction by refraction

3.794

S11

Aspherical surface

-8.764

1.011

Refraction by refraction

3.828

S21

Spherical surface

Infinite number of cases

8

1.73；54.7

Refraction by refraction

3.609

S22

Spherical surface

Infinite number of cases

0.5

Refraction by refraction

2.92

S23

Spherical surface

Infinite number of cases

1.1

1.51；62.9

Refraction by refraction

2.845

S24

Spherical surface

Infinite number of cases

0.303

Refraction by refraction

2.737

S25

Spherical surface

Infinite number of cases

0

2.735

Wherein, the aspherical coefficients are shown in the following table:

surface of the body	S8	S9	S10	S11
					Conic constant	0.385	92.949	-5.382	-1.109
Coefficient of order 4	6.454E-03	-0.018	1.55E-04	6.48E-03
					Coefficient of order 6	-6.661E-04	-1.401E-03	-2.944E-04	-9.396E-04
Coefficient of 8 th order	3.305E-05	-4.936E-05	4.201E-05	7.93E-05
					Coefficient of order 10	-1.944E-06	-1.286E-06	-1.714E-06	-2.537E-06

Based on the parameters, the projection lens is a miniature tele lens, the projection ratio is 1.2, the effective focal length is 5.4mm, the resolution capability can reach 66lp/mm, and the image distance is 500-1200 mm.

The embodiment of the invention also carries out image quality evaluation on the projection lens based on the parameter optimization result.

Fig. 5 is a graph of a modulation transfer function provided by an embodiment of the present invention.

Fig. 5 shows a graph of modulation transfer functions (Modulation Transfer Function, abbreviated as MTF) of light rays of wavelengths 0.4650 μm to 0.6430 μm in different fields of view, wherein the abscissa represents spatial frequency in cycles/mm and the ordinate represents OTF modulus values, which can characterize the resolution of a projection lens. As can be seen from fig. 5, the MTF values of the light rays are all above 0.5, and the curves are relatively flat, which indicates that the imaging gap between the edge and the center of the projection lens is small, and the imaging quality reaches the design standard.

Fig. 6 is a defocus graph provided by an embodiment of the present invention.

FIG. 6 shows defocus curves for light rays of wavelengths 0.4650 μm to 0.6430 μm in different fields of view at a spatial frequency of 50.0000 cycles/mm, where the abscissa represents focal shift (defocus position) in mm and the ordinate represents OTF mode values. As can be seen from fig. 6, the MTF values of the light rays at the optical axis are all above 0.6, and the degree of image plane shift is within a reasonable range.

Fig. 7 is a dot column diagram provided in an embodiment of the present invention.

The more concentrated the points in the point column diagram show that the imaging of the projection lens is less in smear and better in sharpness, and fig. 7 shows the imaging point column diagram (Spot Size diagram) of the light rays with the wavelengths of 0.465 μm, 0.525 μm and 0.643 μm in six fields of view respectively, as can be seen from fig. 7, the imaging of the projection lens in different fields of view can be within a reasonable range.

Fig. 8 is a schematic diagram of a field curvature curve according to an embodiment of the present invention.

Fig. 8 shows curves of meridional and sagittal fields of light rays with wavelengths of 0.643 μm, 0.525 μm and 0.465 μm, where the abscissa indicates the field curvature in mm and the ordinate indicates the image height (field of view), and as can be seen from fig. 8, the field curvature of the projection lens is within ±0.1mm and the field curvature of the projection lens is within a reasonable range.

Fig. 9 is a schematic diagram of a distortion curve according to an embodiment of the present invention.

Fig. 9 shows distortion curves imaged for light rays having wavelengths of 0.643 μm, 0.525 μm, and 0.465 μm over a range of fields of view, where the abscissa represents percent distortion and the ordinate represents image height (field of view). Distortion refers to the degree of distortion of an image of an object by an optical system relative to the object itself, the thickness of the lens and its position relative to the aperture stop determining the degree of contribution to the system distortion. As can be seen from fig. 9, the maximum distortion of the projection lens is about 0.5%, and the distortion of the projection lens is within a reasonable range.

Fig. 10 is a telecentricity curve provided by an embodiment of the present invention.

Fig. 10 shows a bar graph of telecentricity of outgoing light rays of the projection lens in different fields of view, wherein the abscissa indicates the field of view size and the ordinate indicates the angular telecentricity of the principal ray deviated from the optical axis, and as can be seen from fig. 10, the telecentricity of the projection lens is less than 0.3 °, and the performance of the projection lens is better.

As can be seen from the image quality evaluation results of fig. 5 to 10, various aberrations of the projection lens provided by the embodiment of the invention are smaller in imaging, and better imaging quality can be achieved.

Based on the same inventive concept, an embodiment of the present invention also provides a projection system, as shown in fig. 1, where the projection system may include a projection device 100 and a projection screen, and the projection device includes any of the above-mentioned projection lenses. The total length of the projection lens provided by the embodiment of the invention is only below 12.6mm, so that the volume of the projection device can be effectively reduced, and the miniaturized design of the projection device is realized.

According to a first inventive concept, a projection lens includes a first transmissive group, a diaphragm, and a second lens group coaxially disposed in this order along a propagation direction of light. The projection lens satisfies: F/TTL multiplied by F.NO is not less than 0.5 and not more than 1.5. Only two lens groups are needed, and the focal length, the length and the F number of the projection lens are limited in the range, so that the optical system can ensure the large aperture characteristic and effectively reduce the size of the projection lens, and the ultra-thin characteristic and the miniaturization of the projection lens are realized.

According to a second inventive concept, the second lens group includes: and the first lens is a negative lens. The first lens group comprises a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged along the direction gradually far away from the first lens; the second lens is a positive lens, the third lens is a negative lens, the fourth lens is a positive lens, and the fifth lens is a positive lens. The diaphragm is located between the first lens and the second lens. The zoom imaging is realized by integrally moving the projection lens in the optical axis direction so that the distance between the projection lens and the beam splitter prism is changed.

According to a third inventive concept, the first lens is a spherical lens, the second and third lenses are spherical lenses, and the fourth and fifth lenses are aspherical lenses. The projection lens only comprises five lenses, and can have better imaging quality only by adopting two aspheric lenses, the optical system is simple and compact in structure, and the total length of the lens can be reduced to below 12.6 mm.

According to a fourth inventive concept, the thickness of the first lens satisfies: ct/et is more than or equal to 3 and less than or equal to 5; by controlling the parameters of the first lens to satisfy the above ranges, the aberration and curvature of field of the projection lens can be balanced.

According to a fifth inventive concept, the second lens satisfies: ct45/et45 is more than or equal to 2 and less than or equal to 3; f45 Not less than 4; by controlling the parameters of the second lens to meet the above ranges, the workability of the lens can be ensured.

According to a sixth inventive concept, the third lens satisfies: ct67/et67 is less than or equal to 1.5 and less than or equal to 3; f67 Not less than-5; by controlling the parameters of the third lens to satisfy the above ranges, the workability of the lens can be ensured.

According to a seventh inventive concept, the fourth lens satisfies: ct89/et89 is more than or equal to 4 and less than or equal to 6; f89 Not less than-69; by controlling the parameters of the fourth lens to satisfy the above range, the workability of the lens can be ensured.

According to an eighth inventive concept, the fifth lens satisfies: ct1011/et1011 is more than or equal to 4 and less than or equal to 6; f1011 Not less than 4; by controlling the parameters of the fourth lens to satisfy the above range, the workability of the lens can be ensured.

According to the ninth inventive concept, by controlling parameters of the second lens, the third lens, the fourth lens and the fifth lens to satisfy the above ranges, workability of the lens can be ensured, system size can be effectively reduced, optical power of the optical system can be reasonably distributed, excessive concentration on a certain lens can be prevented, and aberration control of the lens can be facilitated.

According to a tenth inventive concept, the thickness of the projection lens satisfies: the (CT4+CT5) is more than or equal to 0.3 and the CT is less than or equal to 0.6; the ratio of the center thicknesses of the two aspheric lenses of the fourth lens and the fifth lens to the center thickness of the overall lens of the lens is reasonably controlled, so that the system focal power is reasonably distributed, the system spherical aberration and the aberration are improved, and meanwhile, the stability of the system structure is enhanced.

According to the eleventh inventive concept, the projection ratio of the projection lens is 1.2, the total length is less than 12.6mm, the F.NO is 2.4, and the resolving power can reach 66lp/mm.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims (10)

1. A projection lens, comprising: a first transmission group, a diaphragm, and a second lens group coaxially and sequentially arranged along a propagation direction of light; the first lens group includes at least one lens, and the second lens group includes at least one lens;

the projection lens satisfies the following conditions:

0.5≤f/TTL×F.NO≤1.5；

wherein f represents the focal length of the projection lens, TTL represents the length of the projection lens along the optical axis, and F.NO represents the aperture value of the projection lens.

2. The projection lens of claim 1 wherein the second lens group comprises: a first lens; the first lens is a negative lens.

3. The projection lens of claim 2 wherein the first lens is a spherical lens.

4. The projection lens of claim 2 wherein the thickness of the first lens satisfies:

3≤ct/et≤5；

wherein ct represents the center thickness of the first lens in the optical axis direction, and et represents the edge thickness of the first lens in the optical axis direction.

5. The projection lens of claim 2, wherein the first lens group includes a second lens, a third lens, a fourth lens, and a fifth lens disposed in this order in a direction gradually away from the first lens;

the second lens is a positive lens, the third lens is a negative lens, the fourth lens is a positive lens, and the fifth lens is a positive lens.

6. The projection lens of claim 5 wherein the second lens and the third lens are spherical lenses and the fourth lens and the fifth lens are aspherical lenses.

7. The projection lens of claim 5 wherein the thickness of the second lens satisfies:

2≤ct45/et45≤3；

wherein ct45 represents a center thickness of the second lens in the optical axis direction, and et45 represents an edge thickness of the second lens in the optical axis direction;

the thickness of the third lens satisfies:

1.5≤ct67/et67≤3；

wherein ct67 represents a center thickness of the third lens in the optical axis direction, and et67 represents an edge thickness of the third lens in the optical axis direction;

the thickness of the fourth lens satisfies:

4≤ct89/et89≤6；

wherein ct89 represents a center thickness of the fourth lens in the optical axis direction, and et89 represents an edge thickness of the fourth lens in the optical axis direction;

the thickness of the fifth lens satisfies:

4≤ct1011/et1011≤6；

where ct1011 denotes a center thickness of the fifth lens in the optical axis direction, and et1011 denotes an edge thickness of the fifth lens in the optical axis direction.

8. The projection lens of claim 7 wherein the focal lengths of the second lens, the third lens, the fourth lens, and the fifth lens satisfy:

f45≥4；

f67≥-5；

f89≥-69；

f1011≥4；

wherein f45 denotes a focal length of the second lens, f67 denotes a focal length of the third lens, f89 denotes a focal length of the fourth lens, and f1011 denotes a focal length of the fifth lens.

9. The projection lens of claim 5 wherein the thickness of the projection lens satisfies:

0.3≤(CT4+CT5)/∑CT≤0.6；

wherein CT4 represents the center thickness of the fourth lens in the optical axis direction, CT5 represents the center thickness of the fifth lens in the optical axis direction, and Σct represents the sum of the center thicknesses of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens in the optical axis direction.

10. A projection system, comprising:

a projection light source;

an illumination system positioned on the light-emitting side of the projection light source; the illumination system comprises a light modulator;

a projection lens according to any one of claims 1 to 9; the projection lens is positioned on the light emitting side of the light modulator.