CN114047613B

CN114047613B - Optical system and projection device

Info

Publication number: CN114047613B
Application number: CN202111287172.8A
Authority: CN
Inventors: 程发超; 宁静; 王中亮; 郭恒琳
Original assignee: Goertek Optical Technology Co Ltd
Current assignee: Goertek Optical Technology Co Ltd
Priority date: 2021-10-29
Filing date: 2021-10-29
Publication date: 2023-07-18
Anticipated expiration: 2041-10-29
Also published as: WO2023070811A1; CN114047613A

Abstract

The invention discloses an optical system, which sequentially comprises an image source, a sixth lens, a fifth lens, a fourth lens, a third lens, a second lens and a first lens along the light transmission direction; the first lens, the second lens and the third lens group form a first lens group, and the fourth lens, the fifth lens and the sixth lens form a second lens group; the first lens group has negative focal power, and the second lens group has positive focal power. The optical system has small volume size.

Description

Optical system and projection device

Technical Field

The present invention relates to the field of projection imaging technologies, and in particular, to an optical system and a projection apparatus.

Background

With the development of technology and the improvement of living standard of people, projection devices are becoming more mature, and home cinema projectors are one of the media for people to pursue high quality life. The DLP (Digital Light Processing) technology achieves the effect of reflecting light rays at different angles by controlling the reverse inclination of the micro mirror elements in DMD (Digital Micromirror Device). The angles of the micro-mirror elements in the DMD are divided into an on state and an off state, the light reflected in the on state is imaged on a projection screen through an optical system, and the light in the off state is absorbed by an absorber. The "on" and "off" states alternate rapidly to achieve multiple gray levels for the image. The projector can make the projection picture finer by using the DLP technology, so that the visual feeling of a person is more lifelike.

Currently, in order to improve the imaging quality of a projection apparatus, a lens group in the projection apparatus is generally required to be combined with a plurality of lenses, which results in an increase in the size of the projection apparatus.

Disclosure of Invention

The invention mainly aims to provide an optical system, which aims to ensure that the volume size of the optical system is small.

In order to achieve the above object, the present invention provides an optical system comprising, in order along a light transmission direction, an image source, a sixth lens, a fifth lens, a fourth lens, a third lens, a second lens, and a first lens; the first lens, the second lens and the third lens group form a first lens group, and the fourth lens, the fifth lens and the sixth lens form a second lens group;

the first lens group has negative optical power, and the second lens group has positive optical power.

Optionally, the first lens, the second lens, and the fifth lens each have negative optical power, and the third lens, the fourth lens, and the sixth lens each have positive optical power.

Optionally, the optical system satisfies the following relationship: TL/D is more than 0.5 and less than 5.75;

wherein TL is the total length of the optical system, and D is the maximum lens aperture in the optical system.

Optionally, the surfaces of the fourth lens and the fifth lens opposite to each other are glued to each other.

Optionally, the optical system satisfies the following relationship: 5.5mm < f00<6.8mm, -65.6mm < f11< -57.6mm,10mm < f22<15.5mm;

wherein f00 is an effective focal length of the optical system, f11 is an effective focal length of the first lens group, and f22 is an effective focal length of the second lens group.

Optionally, the optical system satisfies the following relationship: -10.2mm < f1< -18.5mm, -10.6mm < f2< -20.6mm,13mm < f3<21.1mm,11.5mm < f4<17.7mm, -12.2mm < f5< -20.7mm,9.6mm < f6<16.6mm;

wherein f1 is an effective focal length of the first lens, f2 is an effective focal length of the second lens, f3 is an effective focal length of the third lens, the f4 is an effective focal length of the fourth lens, the f5 is an effective focal length of the fifth lens, and the f6 is an effective focal length of the sixth lens.

Optionally, the first lens and the sixth lens are aspheric lenses, and the second lens, the third lens, the fourth lens and the fifth lens are spherical lenses.

Optionally, the first lens is made of optical plastic, and the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are made of optical glass.

Optionally, the optical system further comprises a diaphragm, and the diaphragm is arranged between the third lens and the fourth lens.

In order to achieve the above object, the present invention also proposes a projection device including a housing and an optical system according to any one of the above embodiments, the optical system being provided in the housing.

In the technical scheme of the invention, the optical system sequentially comprises an image source, a sixth lens, a fifth lens, a fourth lens, a third lens, a second lens and a first lens along the light transmission direction, wherein the first lens group has negative focal power, the second lens group has positive focal power, the main function of the first lens group is to eliminate distortion and aberration in the imaging process and converge light beams (if the light beams are diverged according to the actual projection effect) for the whole optical system, and the main function of the second lens group is to eliminate chromatic aberration and control telecentricity, so that the optical system meets the imaging requirement, and meanwhile, the optical system has fewer lenses and compact structure, thereby ensuring small volume size and convenient carrying and use.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.

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

FIG. 2 is a graph of modulation transfer functions of a first embodiment of the optical system of FIG. 1;

FIG. 3 is a graph of field curvature and distortion of the first embodiment of the optical system of FIG. 1;

fig. 4 is a diagram of a vertical chromatic aberration diagram of the first embodiment of the optical system of fig. 1.

Reference numerals illustrate:

reference numerals	Name of the name	Reference numerals	Name of the name
				100	Optical system	60	Sixth lens
10	First lens	70	Image source
				20	Second lens	71	Transparent protective layer
30	Third lens	72	Turning prism
				40	Fourth lens	80	Diaphragm
50	Fifth lens	90	Vibrating mirror

The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all 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, if directional indications (such as up, down, left, right, front, and rear … …) are included in the embodiments of the present invention, the directional indications are merely used to explain the relative positional relationship, movement conditions, etc. between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indications are correspondingly changed.

In addition, if there is a description of "first", "second", etc. in the embodiments of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.

The present invention proposes an optical system 100.

In the embodiment of the present invention, as shown in fig. 1, the optical system 100 includes, in order along the light transmission direction, an image source 70, a sixth lens 60, a fifth lens 50, a fourth lens 40, a third lens 30, a second lens 20, and a first lens 10;

the first lens 10, the second lens 20, and the third lens 30 constitute a first lens group, and the fourth lens 40, the fifth lens 50, and the sixth lens 60 constitute a second lens group;

the first lens group has negative focal power, and the second lens group has positive focal power.

It should be noted that, the optical system 100 of the present invention is applied to a projection apparatus, and includes a reduction side and a magnification side along a light transmission direction, and the image source 70, the sixth lens 60, the fifth lens 50, the fourth lens 40, the third lens 30, the second lens 20, and the first lens 10 are disposed between the reduction side and the magnification side in order along the same optical axis. The reduction side is the side (shown as B in the figure) where the image source 70 (such as DMD chip) generating projection light is located in the projection process, i.e. the image side; the magnified side is the side (shown at a in the figure) on which a projection surface (such as a projection screen) for displaying a projection image is located during projection, that is, the object side. The transmission direction of the projection light is from the shrinking side to the enlarging side.

Specifically, the projection light is emitted from the image source 70, and emitted from the reduction side toward the enlargement side, sequentially passes through the sixth lens 60, the fifth lens 50, the fourth lens 40, the third lens 30, the second lens 20, and the first lens 10, and finally is output onto the projection surface located on the side of the first lens 10 facing away from the second lens 20, so as to display the projection image.

In an embodiment of the present invention, the image source 70 may be a digital micromirror device (Digital Micromirror Device, DMD) chip. The DMD is composed of a plurality of digital micro-mirrors arranged in a matrix, and each micro-mirror is capable of deflecting and locking in both forward and reverse directions when in operation, so that light is projected in a predetermined direction, and swings at a frequency of tens of kilohertz, and light from an illumination light source is reflected into the optical system 100 by turning the micro-mirror to be imaged on a screen. The DMD has the advantages of high resolution, no need of digital-to-analog conversion of signals and the like. The present example uses a 0.23"dmd with dimensions of 5.184mm x 2.916mm and a throw ratio in the range 1.2-1.5. Of course, the image source 70 may alternatively be a liquid crystal on silicon (Liquid Crystal On Silicon, LCOS) chip or other display device for emitting light, which is not limited by the present invention.

Wherein, for the whole optical system 100, the first lens group mainly functions to eliminate distortion and aberration in the imaging process and converge the light beam (diverge the light beam if the actual projection effect is achieved); the second lens group has the main functions of eliminating chromatic aberration and controlling telecentricity, so that the optical system meets imaging requirements, and meanwhile, the lens group has a small number and a compact structure, thereby ensuring that the optical system has small volume and size and is convenient to carry and use.

Further, the first lens 10, the second lens 20, and the fifth lens 50 each have negative optical power, and the third lens 30, the fourth lens 40, and the sixth lens 60 each have positive optical power.

The optical power is the difference between the convergence of the image beam and the convergence of the object beam, and characterizes the ability of the optical system 100 to deflect light. The negative focal power lens is a lens with thin middle and thick periphery, also called concave lens, and has the function of diverging light rays; the positive focal power lens is a lens with thick middle and thin periphery, also called convex lens, and has the function of converging light rays. In the technical scheme of the invention, the first lens 10 with positive focal power, the second lens 20 with negative focal power and the third lens 30 with positive focal power can eliminate distortion and aberration in the imaging process, and the double-cemented lens formed by the combination of the fourth lens 40 with positive focal power and the fifth lens 50 with negative focal power and the sixth lens 60 with positive focal power can eliminate chromatic aberration and control telecentricity, so that the imaging quality is ensured.

Further, the optical system 100 satisfies the following relationship: TL/D is more than 0.5 and less than 5.75;

where TL is the total length of the optical system 100 and D is the maximum lens aperture in the optical system 100.

Since the optical system 100 employs six lenses, the number of lenses is small, and at the same time, by setting the total length TL of the optical system 100 and the maximum lens aperture D in the optical system 100, it is satisfied that: the total length and the radius of the optical system 100 can be controlled to ensure that the optical system 100 has a compact structure, thereby ensuring that the optical system 100 has a small size to a certain extent, and facilitating the carrying and the use of the optical system 100. The total length of the optical system 100 is: along the optical axis direction, the distance between the vertex of the light-exiting surface of the first lens 10 and the back surface (surface facing away from the sixth lens 60) of the image source 70. In the present embodiment, the maximum lens aperture of the optical system 100 is the aperture of the first lens 10, and generally, the projection lens has two lens apertures larger than the lens aperture of the middle portion, which is convenient for lens assembly and structural design. As one embodiment, the total length TL of the optical system 100 is between 45 and 60 mm.

Therefore, in the present invention, the optical system 100 includes the image source 70, the sixth lens 60 with positive power, the fifth lens 50 with negative power, the fourth lens 40 with positive power, the third lens 30 with positive power, the second lens 20 with negative power, and the first lens 10 with negative power in this order along the light transmission direction, and the total length TL of the optical system 100 and the maximum lens aperture D in the optical system 100 are set to be: the TL/D is more than 0.5 and less than 5.75, so that the optical system 100 meets the imaging requirement, and meanwhile, the lens number is small, the structure is compact, and the small size of the optical system 100 is ensured, and the optical system is convenient to carry and use.

Further, the light exit surface of the first lens 10 is a convex surface, and the light entrance surface is a concave surface;

the light emergent surface of the second lens 20 is a concave surface, and the light incident surface is a concave surface;

the light emergent surface of the third lens 30 is a convex surface, and the light incident surface is a convex surface;

the light emergent surface of the fourth lens 40 is a concave surface, and the light incident surface is a convex surface;

the light emergent surface of the fifth lens 50 is a concave surface, and the light incident surface is a convex surface;

the light exit surface of the sixth lens 60 is convex, and the light entrance surface is convex.

Further, the opposite surfaces of the fourth lens 40 and the fifth lens 50 are cemented with each other.

In the optical system 100, the result obtained by non-paraxial ray tracing and the result obtained by paraxial ray tracing are not identical, and a deviation from an ideal state of gaussian optics (first order approximation theory or paraxial rays) is called an aberration. Aberrations are mainly classified into distortion, curvature of field, chromatic aberration, spherical aberration, coma, astigmatism, and the like. The aberration affects the imaging quality of the projection lens, and therefore, it is necessary to eliminate as much as possible the aberration generated when the optical system 100 is imaged when designing the projection lens.

Specifically, the first lens 10 is a meniscus lens having negative optical power, the second lens 20 is a biconcave lens having negative optical power, the third lens 30 is a biconvex lens having positive optical power, the fourth lens 40 is a meniscus lens having positive focal length, the fifth lens 50 has negative optical power, and the fourth lens 40 and the fifth lens 50 are a biconvex lens having positive optical power, and the sixth lens 60 is a biconvex lens combined together. The double-cemented lens composed of the fourth lens 40 and the fifth lens 50 can effectively reduce chromatic aberration generated in the optical imaging process; the first lens 10 of the meniscus type can realize a large angle of view, and mainly plays a role of collecting light in optical design (when the optical design is performed, a projection picture is set to be an object plane, the light is incident from the object plane side of the first lens 10, and if the actual projection effect is achieved, the light beam is diverged), and meanwhile, the first lens 10 has an important role of eliminating distortion, so that the imaging quality is ensured.

Specifically, the optical system 100 satisfies the following relationship: -10.2mm < f1< -18.5mm, -10.6mm < f2< -20.6mm,13mm < f3<21.1mm,11.5mm < f4<17.7mm, -12.2mm < f5< -20.7mm,9.6mm < f6<16.6mm;

wherein f1 is the effective focal length of the first lens 10, f2 is the effective focal length of the second lens 20, f3 is the effective focal length of the third lens 30, f4 is the effective focal length of the fourth lens 40, f5 is the effective focal length of the fifth lens 50, and f6 is the effective focal length of the sixth lens 60.

Specifically, the optical system 100 satisfies the following relationship: 5.5mm < f00<6.8mm, -65.6mm < f11< -57.6mm,10mm < f22<15.5mm;

where f00 is the effective focal length of the optical system 100, f11 is the effective focal length of the first lens group, and f22 is the effective focal length of the second lens group.

As an alternative embodiment, the first lens 10 and the sixth lens 60 are each aspherical lenses, and the second lens 20, the third lens 30, the fourth lens 40, and the fifth lens 50 are each spherical lenses.

Specifically, the light exit surface (surface facing the enlarging side) and the light entrance surface (surface facing the reducing side) of the first lens 10 are both aspheric, the light exit surface (surface facing the enlarging side) and the light entrance surface (surface facing the reducing side) of the sixth lens 60 are both aspheric, the light exit surface (surface facing the enlarging side) and the light entrance surface (surface facing the reducing side) of the second lens 20 are both spherical, the light exit surface (surface facing the enlarging side) and the light entrance surface (surface facing the reducing side) of the third lens 30 are both spherical, the light exit surface (surface facing the enlarging side) and the light entrance surface (surface facing the reducing side) of the fourth lens 40 are both spherical, and the light exit surface (surface facing the enlarging side) and the light entrance surface (surface facing the reducing side) of the fifth lens 50 are both spherical.

When the lens surface is of an aspherical structure, the edge aberration of the lens can be effectively reduced, thereby improving the performance of the optical system 100 and improving the imaging quality. By the aspherical structure, the effect of correcting aberration for a plurality of spherical lenses is effectively achieved, and miniaturization of the optical system 100 is also facilitated. The use of the spherical lens can effectively reduce the processing difficulty and the production cost of the lens, thereby reducing the cost of the optical system 100.

As an alternative embodiment, the first lens 10 is made of an optical plastic material, and the second lens 20, the third lens 30, the fourth lens 40, the fifth lens 50 and the sixth lens 60 are made of an optical glass material.

When the image source 70 is powered on, the projection light is emitted, and when the image source 70 emits the projection light, the image source 70 generates heat, so that generally, the glass lens has higher high temperature resistance, i.e. the glass lens has much lower thermal distortion rate than the plastic lens at the same temperature, and has better stability, and the plastic lens is easy to deform under the influence of high temperature and even volatilize toxic gas, therefore, the second lens 20, the third lens 30, the fourth lens 40 and the fifth lens 50, i.e. the sixth lens 60, which are close to the image source 70, can be arranged as glass, so that the imaging influence of the high Wen Duiguang optical system 100 is reduced to the greatest extent. The first lens 10 is farthest from the image source 70 and is least affected by temperature, and the cost of plastic material is lower than that of glass material, so that the cost of the first lens 10 is reduced.

As an alternative embodiment, the optical system 100 further includes a diaphragm 80, and the diaphragm 80 is disposed between the third lens 30 and the fourth lens 40.

Specifically, the diaphragm 80 is specifically an aperture diaphragm 80, and the diaphragm 80 is used for limiting the diameter of the passing projection light, adjusting the luminous flux emitted out of the optical system 100, and reducing the stray light interference generated by reflection of other lenses, so that the imaging of the projection light is clearer. In general, the aperture of the diaphragm 80 is a fixed value, however, in order to flexibly adjust the imaging definition, the projection lens can be better adapted to the switching between high resolution and low resolution, and the diaphragm 80 can be set in such a way that the aperture size can be adjusted.

As an alternative embodiment, the optical system 100 further includes a turning prism 72, the turning prism 72 being disposed between the sixth lens 60 and the image source 70.

In some embodiments, the image source 70 sometimes requires passive illumination. Thus, additional illumination needs to be provided to image source 70 by means of an external light source and turning prism 72. Specifically, the prism may be a right-angle prism, the inclined plane of the right-angle prism faces the image source 70, one of the right-angle surfaces of the right-angle prism faces the sixth lens 60, and at the same time, the light source is disposed corresponding to the inclined plane of the right-angle prism, and the inclined plane of the right-angle prism is provided with a semi-reflective semi-permeable membrane. When in use, the external light source emits illumination light to the inclined plane of the right angle prism, the illumination light is reflected by the semi-reflective and semi-permeable membrane and then emitted to the image source 70, so as to provide light for the image source 70, the light is modulated by the image source 70, transmitted by the semi-reflective and semi-permeable membrane and then emitted to the sixth lens 60, and sequentially passes through the sixth lens 60, the fifth lens 50, the fourth lens 40, the third lens 30, the second lens 20 and the first lens 10, so that a projection image is displayed on the projection screen.

As an alternative embodiment, the optical system 100 further comprises a galvanometer 90, the galvanometer 90 being arranged between the sixth lens 60 and the image source 70.

Specifically, the vibrating mirror 90 is a transparent glass plate, and the vibrating mirror 90 generally rotates around a transverse axis or a longitudinal axis (the transverse axis is an X axis and the longitudinal axis is a Y axis) of the intermediate position. When the galvanometer 90 is stationary, the projection light enters the galvanometer 90 along the optical axis direction perpendicular to the light incident surface of the galvanometer 90 and penetrates through the galvanometer 90. When the galvanometer 90 rotates, the incident angle formed by the projection light and the incident surface of the galvanometer 90 is smaller than 90 degrees, so that the projection light is refracted after passing through the galvanometer 90, and the imaging position of the projection light is changed. I.e., the projection light passes through the rotating galvanometer 90 and is displayed in an imaging manner at another location around the original imaging location. Thus, another pixel is formed around the original pixel. Due to the high frequency vibration of the vibrating mirror 90, the vibration period is on the order of microseconds, and the interval time between two pixel points is short. The human eyes have the persistence of vision, and the number of frames that the human eyes can recognize is 24 frames. In short, after the next pixel is formed, the human eye still stays on the last pixel, so that the two pixels are combined together to form a larger resolution picture.

Therefore, the light emitted by the image source 70 is deflected along the vibration direction by the periodic vibration of the vibrating mirror 90, so that the resolution of the image source 70 is fixed, and the light emitted by the image source 70 can be projected to different positions by the vibration of the vibrating mirror 90, so that the resolution of the projection device corresponding to the optical system 100 is increased, and the user experience is improved.

As an alternative embodiment, the optical system 100 further comprises a transparent protective layer 71, and the transparent protective layer 71 is arranged on the side of the image source 70 facing the sixth lens 60.

Specifically, the transparent protective layer 71 is specifically a cover slip, the thickness of the cover slip is 1.1mm, and the cover slip is covered on the light emitting surface of the image source 70, so that the image source 70 can be effectively protected on the premise of ensuring good light transmittance, external dust is prevented from entering the image source 70, and collision of other lenses in the optical system 100 on the image source 70 due to vibration can be avoided, so that the image source 70 is protected from the impact of external environment or other elements.

The invention also provides a projection device, which comprises an optical system 100 and a housing, wherein the specific structure of the optical system 100 refers to the above embodiment, and since the projection device adopts all the technical solutions of all the above embodiments, at least has all the beneficial effects brought by the technical solutions of the above embodiments, and the description thereof is omitted herein. Wherein the optical system 100 is disposed within the housing.

To further optimize the performance of the optical system 100, a first embodiment of the optical system 100 of the present invention is presented, referring to table 1, illustrating the type of face, radius of curvature and thickness of each lens, and the glass material (refractive index and abbe number), half-calibre of each lens. Wherein the thickness of the spacing between adjacent two lenses is expressed as the distance between the adjacent two lenses.

Table 1:

meanwhile, referring to table 2, the aspherical structures of the first lens 10 and the sixth lens 60 are illustrated. Here, the light exit surface (surface toward the enlargement side) S1 and the light entrance surface (surface toward the reduction side) S2 of the first lens 10, and the light exit surface (surface toward the enlargement side) S11 and the light entrance surface (surface toward the reduction side) S12 of the sixth lens 60 are all aspherical surfaces, and the aspherical surface formula is as follows:

wherein Z represents the distance between the point on the aspheric surface and the vertex of the aspheric surface in the direction of the optical axis; r represents the distance from the point on the non-surface to the optical axis; c represents the central curvature of the aspherical surface; k represents the cone rate; a4, a6, a8 and a10 represent aspherical higher order coefficients, and are specifically shown in table 2.

Table 2:

in the first embodiment, the optical system 100 has the following parameters:

the effective focal length f1= -16.964mm of the first lens 10,

the effective focal length f2= -16.654mm of the second lens 20,

the effective focal length f3= 16.128mm of the third lens 30,

the effective focal length f4= 14.747mm of the fourth lens 40,

the effective focal length f5= -17.269mm of the fifth lens 50,

the effective focal length f6= 13.635mm of the sixth lens 60;

the effective focal length f00= 6.218mm of the optical system 100,

the effective focal length f11= -61.64mm of the first lens group,

the effective focal length f22=12.205 mm of the second lens group;

the overall length TL of the optical system 100 is 52.5mm.

Based on the above parameter data, referring to fig. 2, fig. 2 is a graph of the chip surface modulation transfer function of each field of view of the optical system 100 according to the first embodiment, i.e. a graph MTF (ModulationTransferFunction), the MTF graph is used to refer to the relationship between the modulation degree and the logarithm of lines per millimeter in the image, and is used to evaluate the scene detail reduction capability. The projection angle is taken as the frequency coordinate between the field of view samples, and the ordinate is taken as the transfer function MTF value.

Based on the above parameter data, referring to fig. 3, fig. 3 is a field curvature and distortion diagram of the optical system 100 according to the first embodiment, wherein the field curvature refers to an image field curvature, and is mainly used to represent the misalignment degree between the intersection point of the whole light beam and an ideal image point in the optical assembly. Distortion refers to aberration of different magnification of different parts of an object when the object is imaged by an optical component, and the distortion can cause deterioration of similarity of object images, but does not affect definition of the images.

Based on the above parameter data, referring to fig. 4, fig. 4 is a vertical axis chromatic aberration diagram of the optical system 100 according to the first embodiment, wherein the vertical axis chromatic aberration refers to a chromatic aberration, which is also called as a chromatic aberration of magnification, and mainly refers to a compound-color principal ray of an image side, which becomes multiple rays when exiting from an object side due to chromatic dispersion of a refraction system, and is a difference value between focal positions of hydrogen blue light and hydrogen red light on an image plane.

The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent structural changes made by the description of the present invention and the accompanying drawings or direct/indirect application in other related technical fields are included in the scope of the invention.

Claims

1. An optical system is characterized by comprising an image source, a sixth lens, a fifth lens, a fourth lens, a third lens, a second lens and a first lens in sequence along a light transmission direction; the first lens, the second lens and the third lens group form a first lens group, and the fourth lens, the fifth lens and the sixth lens form a second lens group;

for 6 lenses that the optical system has in total, the first lens group has negative optical power, and the second lens group has positive optical power; wherein the first lens and the sixth lens are aspheric lenses, and the second lens, the third lens, the fourth lens and the fifth lens are spherical lenses; the first lens is a meniscus lens with negative focal power, the second lens is a biconcave lens with negative focal power, the third lens is a biconvex lens with positive focal power, the fourth lens is a concave-convex lens with positive focal power, the fifth lens is a meniscus lens with negative focal power, the fourth lens and the fifth lens are biconvex lenses combined together, and the sixth lens is a biconvex lens with positive focal power;

the first lens is made of optical plastic, and the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are made of optical glass; wherein the optical system further comprises a galvanometer, and the galvanometer is arranged between the sixth lens and the image source; the light emergent surface of the first lens is a convex surface, and the light incident surface is a concave surface; the light emergent surface of the second lens is a concave surface, and the light incident surface is a concave surface; the light emergent surface of the third lens is a convex surface, and the light incident surface is a convex surface; the light emergent surface of the fourth lens is a concave surface, and the light incident surface is a convex surface; the light emergent surface of the fifth lens is a concave surface, and the light incident surface is a convex surface; the light emergent surface of the sixth lens is a convex surface, and the light incident surface is a convex surface; 5.5mm < f00<6.8mm, -65.6mm < f11< -57.6mm,10mm < f22<15.5mm; wherein f00 is an effective focal length of the optical system, f11 is an effective focal length of the first lens group, and f22 is an effective focal length of the second lens group.

2. The optical system of claim 1, wherein the first lens, the second lens, and the fifth lens each have negative optical power, and the third lens, the fourth lens, and the sixth lens each have positive optical power.

3. The optical system of claim 1, wherein,

the optical system satisfies the following relationship: TL/D is more than 0.5 and less than 5.75;

4. The optical system of claim 1 wherein the opposed surfaces of the fourth lens and the fifth lens are cemented with each other.

5. The optical system of claim 1, wherein the optical system satisfies the relationship: -10.2mm < f1< -18.5mm, -10.6mm < f2< -20.6mm,13mm < f3<21.1mm,11.5mm < f4<17.7mm, -12.2mm < f5< -20.7mm,9.6mm < f6<16.6mm;

6. The optical system of any one of claims 1 to 5, further comprising a stop disposed between the third lens and the fourth lens.

7. A projection device comprising a housing and an optical system according to any one of claims 1 to 6, the optical system being provided in the housing.