CN114047613A

CN114047613A - Optical system and projection device

Info

Publication number: CN114047613A
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: 2022-02-15
Anticipated expiration: 2041-10-29
Also published as: CN114047613B; WO2023070811A1

Abstract

The invention discloses an optical system and a projection device, wherein the optical system sequentially includes an image source, a sixth lens, a fifth lens, a fourth lens, a third lens, a second lens and a first lens along a light transmission direction; a first lens The lens, the second lens and the third lens form the first lens group, the fourth lens, the fifth lens and the sixth lens form the second lens group; the first lens group has negative refractive power, and the second lens group has positive refractive power . The volume size of the optical system in the technical solution of the present invention is small.

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 standards of people, the projection devices are becoming more mature and home theater projectors become one of the people pursuing high quality living media. The dlp (digital Light processing) technology achieves the effect of reflecting Light rays at different angles by controlling a plurality of Micromirror elements in the dmd (digital Micromirror device) to reversely tilt. The angle of the micro-mirror element in the DMD is divided into two states of 'on' and 'off', the reflected light 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 state and the off state are rapidly alternated so as to realize various gray scales of the image. The projector can make the projection picture finer and smoother by using the DLP technology, thereby making people feel more vivid visually.

At present, in order to improve the imaging quality of the projection apparatus, the mirror group in the projection apparatus generally needs to be combined by a plurality of lenses with a larger number, which results in an increase in the volume of the projection apparatus.

Disclosure of Invention

The invention mainly aims to provide an optical system, aiming at ensuring the small volume size of the optical system.

In order to achieve the above object, the present invention provides an optical system, which sequentially includes an image source, a sixth lens, a fifth lens, a fourth lens, a third lens, a second lens, and a first lens along a light transmission direction; the first lens, the second lens and the third lens 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 power, and the second lens group has positive power.

Optionally, the first lens, the second lens and the fifth lens each have a negative optical power, and the third lens, the fourth lens and the sixth lens each have a 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, opposite surfaces of the fourth lens and the fifth lens are cemented to each other.

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

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<16.6 mm;

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

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

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

Optionally, the optical system further includes a diaphragm disposed between the third lens and the fourth lens.

In order to achieve the above object, the present invention further provides a projection apparatus, which includes a housing and the optical system as described in any one of the above embodiments, wherein the optical system is disposed 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, the first lens group has negative focal power, the second lens group has positive focal power, for the whole optical system, the first lens group mainly has the functions of eliminating distortion and aberration in the imaging process and converging light beams (diverging the light beams if the light beams are projected according to the actual effect), and the second lens group mainly has the functions of eliminating chromatic aberration and controlling telecentricity, so that the optical system meets the imaging requirement, and meanwhile, the number of the lenses is small, the structure is compact, the volume size of the optical system is small, and the optical system is convenient to carry 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 used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

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

FIG. 2 is a diagram of a modulation transfer function of a first embodiment of the optical system of FIG. 1;

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

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

The reference numbers illustrate:

reference numerals	Name (R)	Reference numerals	Name (R)
				100	Optical system	60	Sixth lens element
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 element	90	Vibrating mirror

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.

In addition, if there is a description of "first", "second", etc. in an embodiment 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 relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

The present invention provides 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 an enlargement 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 in the optical system 100 are sequentially disposed between the reduction side and the enlargement side along the same optical axis. Wherein, the reduction side is a side (as shown in B) where an image source 70 (such as a DMD chip) generating projection light is located in the projection process, i.e. an image side; the enlargement side is the side (as shown at a) where a projection surface (such as a projection screen) for displaying a projection image is located during projection, i.e., the object side. The transmission direction of the projection light is from the reduction side to the enlargement side.

Specifically, the projection light is emitted from the image source 70, emitted from the reduction side toward the enlargement side, 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 in this order, and is finally output onto the projection surface on the side of the first lens 10 away from the second lens 20, so as to display the projection image.

In the embodiment of the present invention, the image source 70 may be a Digital Micromirror Device (DMD) chip. The DMD is composed of a plurality of digital micromirrors arranged in a matrix, and each micromirror can deflect and lock in both forward and reverse directions during operation, so that light is projected in a predetermined direction, and swings at a frequency of tens of thousands of hertz, and light beams from an illumination light source enter the optical system 100 through the inverted reflection of the micromirror to be imaged on a screen. The DMD has the advantages of high resolution, no need of digital-to-analog conversion for signals and the like. This example uses a 0.23 "DMD, size 5.184mm 2.916mm, throw ratio in the range of 1.2-1.5. Of course, the image source 70 may also be a Liquid Crystal On Silicon (LCOS) chip or other display elements capable of emitting light, which is not limited in the present invention.

Wherein, for the whole optical system 100, the main function of the first lens group is to eliminate distortion and aberration during imaging and converge the light beam (or diverge the light beam if the actual projection effect is obtained); the second lens group has the main functions of eliminating chromatic aberration and controlling telecentricity, so that the optical system meets the imaging requirement, and meanwhile, the number of lenses is small, the structure is compact, and the optical system is small in size and convenient to carry and use.

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

The focal power is the difference between the convergence of the image-side light beam and the convergence of the object-side light beam, and represents the ability of the optical system 100 to deflect light. The negative focal power lens is a lens with thin middle and thick periphery, is also called as a concave lens and has the function of diverging light; the positive focal power lens is a lens with thick middle part and thin periphery, which is also called a convex lens and has the function of converging light. 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 combining 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, thereby ensuring the imaging quality.

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 largest lens aperture in the optical system 100.

Because the optical system 100 adopts six lenses, the number of the lenses is small, and meanwhile, the total length TL of the optical system 100 and the maximum lens caliber D in the optical system 100 are set to satisfy the following conditions: TL/D is more than 0.5 and less than 5.75, the total length and the radius of the optical system 100 can be controlled, so that the structure of the optical system 100 is compact, the volume size of the optical system 100 is ensured to be small to a certain extent, and the optical system 100 is convenient to carry and use. The total length of the optical system 100 is: a distance between a vertex of the light exit surface of the first lens 10 and a back surface (a surface on a side facing away from the sixth lens 60) of the image source 70 in the optical axis direction. In this embodiment, the maximum lens aperture in the optical system 100 is the aperture of the first lens 10, and in general, the projection lens has two lens apertures larger than the aperture of the middle lens, which facilitates the assembly of the lens and the design of the structure. In one embodiment, the total length TL of the optical system 100 is between 45 mm and 60 mm.

Therefore, in the technical solution of the present invention, the optical system 100 sequentially includes, along the light transmission direction, an image source 70, a positive power sixth lens 60, a negative power fifth lens 50, a positive power fourth lens 40, a positive power third lens 30, a negative power second lens 20, and a negative power first lens 10, and the total length TL of the optical system 100 and the maximum lens caliber D in the optical system 100 are set to satisfy: 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 optical system has small lens number and compact structure, thereby ensuring that the optical system 100 has small volume size and is convenient to carry and use.

Further, the light-emitting surface of the first lens 10 is a convex surface, and the light-entering surface is a concave surface;

the light-emitting surface of the second lens 20 is a concave surface, and the light-entering surface is a concave surface;

the light-emitting surface of the third lens 30 is a convex surface, and the light-entering surface is a convex surface;

the light-emitting surface of the fourth lens 40 is a concave surface, and the light-entering surface is a convex surface;

the light-emitting surface of the fifth lens 50 is a concave surface, and the light-entering surface is a convex surface;

the light-emitting surface of the sixth lens element 60 is a convex surface, and the light-entering surface is a convex surface.

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

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

Specifically, the first lens 10 is a meniscus lens having a negative refractive power, the second lens 20 is a biconcave lens having a negative refractive power, the third lens 30 is a biconvex lens having a positive refractive power, the fourth lens 40 is a meniscus lens having a positive focal length, the fifth lens 50 is a meniscus lens having a negative refractive power, the fourth lens 40 and the fifth lens 50 are cemented doublets combined together, and the sixth lens 60 is a biconvex lens having a positive refractive power. 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 field angle, and mainly plays a role of gathering light rays in optical design (when designing, a projection picture is set as an object plane, light rays are incident from the object plane side of the first lens 10, and if the light rays are diverged according to an actual projection effect), and meanwhile, the first lens 10 also plays an important role of eliminating distortion, thereby ensuring imaging quality.

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<16.6 mm;

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

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

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 both aspheric lenses, and the second lens 20, the third lens 30, the fourth lens 40, and the fifth lens 50 are all spherical lenses.

Specifically, the light emitting surface (surface facing the magnification side) and the light incident surface (surface facing the reduction side) of the first lens 10 are both aspheric structures, the light emitting surface (surface facing the magnification side) and the light incident surface (surface facing the reduction side) of the sixth lens 60 are both aspheric structures, the light emitting surface (surface facing the magnification side) and the light incident surface (surface facing the reduction side) of the second lens 20 are both spherical structures, the light emitting surface (surface facing the magnification side) and the light incident surface (surface facing the reduction side) of the third lens 30 are both spherical structures, the light emitting surface (surface facing the magnification side) and the light incident surface (surface facing the reduction side) of the fourth lens 40 are both spherical structures, and the light emitting surface (surface facing the magnification side) and the light incident surface (surface facing the reduction side) of the fifth lens 50 are both spherical structures.

When the lens surface is an aspheric 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, an effect of correcting aberration for a plurality of spherical lenses is effectively achieved, which is also advantageous for achieving miniaturization of the optical system 100. 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.

In 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 all made of an optical glass material.

Image source 70 is under the circumstances of switch on, emission projection light, under the circumstances that image source 70 emits projection light, image source 70 itself produces heat, generally speaking, glass's lens has higher high temperature resistant characteristic, that is, under the same temperature, glass's the distortion rate of being heated is far less than the plastics material, better stability has, and the lens of plastic material is out of shape easily under the influence of high temperature, volatilize toxic gas even, therefore, can be close to second lens 20 of image source 70, third lens 30, fourth lens 40, fifth lens 50 sixth lens 60 that is the sixth lens 60 sets up to the glass material, thereby reduce the influence that high temperature was like images to optical system 100 in the at utmost. The first lens element 10 is farthest from the image source 70 and is least affected by temperature, and considering that the cost of the plastic material is lower than that of the glass material, the first lens element 10 is made of the plastic material, which is beneficial to reducing the cost.

In 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 configured to limit the diameter of the passing projection light, adjust the light flux exiting the optical system 100, and reduce the stray light interference generated by the reflection of other lenses, so as to make the imaging of the projection light clearer. The aperture of the diaphragm 80 is usually a fixed value, but of course, in order to flexibly adjust the image sharpness and make the projection lens better adapt to the switching of high and low resolutions, the diaphragm 80 may be set in a manner that the aperture size can be adjusted.

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

In some embodiments, the image source 70 sometimes needs to be passively illuminated. Therefore, additional illumination of the image source 70 by an external light source and turning prism 72 is required. Specifically, the prism may be a right-angle prism, an inclined plane of the right-angle prism faces the image source 70, one of right-angle surfaces of the right-angle prism faces the sixth lens 60, and meanwhile, 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 and semi-transparent film. When the projection display device is used, an external light source emits illumination light, the illumination light is emitted to the inclined plane of the right-angle prism, is reflected by the semi-reflective and semi-transparent film and then is emitted to the image source 70, so that the light is provided for the image source 70, is modulated by the image source 70, is transmitted by the semi-reflective and semi-transparent film and then is 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 a projection screen.

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

Specifically, the galvanometer 90 is a transparent glass plate, and the vibrating of the galvanometer 90 is generally rotated about a horizontal axis or a vertical axis (in the case where the optical axis is a Z axis, the horizontal axis is an X axis, and the vertical axis is a Y axis) at an intermediate position. When the galvanometer 90 is stationary, the projection light is incident on 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 light 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 also changed. Namely, the projection light passes through the rotating galvanometer 90, and is displayed in an imaging mode at another position around the original imaging position. Therefore, another pixel point is formed at the periphery of the original pixel point. Due to the high-frequency vibration of the galvanometer 90, the vibration period is in the microsecond level, and the interval time formed by two pixel points is short. And human eyes have persistence of vision, and the number of frames of a picture that can be recognized by human eyes is 24 frames. In short, after the next pixel point is formed, the human eyes obtain the picture and stay on the previous pixel point, so that the two pixel points are combined together to form a larger resolution picture.

Therefore, through the periodic vibration of the galvanometer 90, the light emitted by the image source 70 is deflected along the vibration direction, so that the resolution ratio of the image source 70 is fixed, and the light emitted by the image source 70 can be projected to different positions through the vibration of the galvanometer 90, thereby increasing the resolution ratio of the projection device corresponding to the optical system 100 and improving the use experience of a user.

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

Specifically, the transparent protection layer 71 is a cover glass, the thickness of the cover glass is 1.1mm, the cover glass covers the light emitting surface of the image source 70, 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, other lenses in the optical system 100 can be prevented from colliding with the image source 70 due to vibration, and the image source 70 is protected from being affected by impact of external environment or other elements.

The present invention further provides a projection apparatus, which includes an optical system 100 and a housing, and the specific structure of the optical system 100 refers to the above embodiments, and since the projection apparatus adopts all technical solutions of all the above embodiments, the projection apparatus at least has all beneficial effects brought by the technical solutions of the above embodiments, and details are not repeated herein. Wherein the optical system 100 is provided 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 proposed, and please refer to table 1, which illustrates the surface type, the curvature radius and the thickness of each lens, and the glass material (refractive index and abbe number) and the half aperture of each lens. Wherein, the thickness of the interval position between two adjacent lenses is expressed as the distance between two adjacent lenses.

Table 1:

meanwhile, referring to table 2, aspheric structures of the first lens element 10 and the sixth lens element 60 are illustrated. The light emitting surface (surface facing the enlargement side) S1 and the light incident surface (surface facing the reduction side) S2 of the first lens element 10, the light emitting surface (surface facing the enlargement side) S11 and the light incident surface (surface facing the reduction side) S12 of the sixth lens element 60 are aspheric surfaces, and the aspheric surface formula is as follows:

wherein Z represents a distance in the optical axis direction of a point on the aspherical surface from the aspherical surface vertex; r represents the distance of a point on the non-surface to the optical axis; c represents the center curvature of the aspherical surface; k represents the conicity; a4, a6, a8, and a10 represent aspheric high-order coefficient, and are specifically shown in table 2.

Table 2:

in the first embodiment, the parameters of the optical system 100 are as follows:

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

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

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

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

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

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

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

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

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

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

Based on the above parameter data, please refer to fig. 2, fig. 2 is a graph of Modulation Transfer Function (MTF) of each view field chip surface of the optical system 100 of the first embodiment, where the MTF graph is used to refer to a relationship between a modulation degree and a logarithm of lines per millimeter in an image, and is used to evaluate a detail restoring capability of a scene. And taking the projection angle as a frequency coordinate between sampling of a view field, and taking the ordinate as a transfer function MTF value.

Referring to fig. 3, fig. 3 is a graph of curvature of field and distortion of the optical system 100 according to the first embodiment, wherein the curvature of field is curvature of field, which is mainly used to indicate the misalignment between the intersection point of the whole light beam and the ideal image point in the optical assembly. The distortion refers to the aberration of different magnifications of different parts of an object when the object is imaged through an optical component, and the distortion can cause the similarity of the object image to be deteriorated without influencing the definition of the image.

Referring to fig. 4, fig. 4 is a vertical axis chromatic aberration diagram of the optical system 100 according to the first embodiment, in which the vertical axis chromatic aberration is also called magnification chromatic aberration, and mainly refers to a polychromatic main light on the image side, which is dispersed by the refractive system and becomes a plurality of light rays when the object side exits, and the difference between the focus positions of the hydrogen blue light and the hydrogen red light on the image plane.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present 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 form a first lens group, and the fourth lens, the fifth lens and the sixth lens form a second lens group;

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

3. The optical system of claim 1,

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 opposing surfaces of said fourth lens and said fifth lens are cemented to each other.

5. The optical system of claim 1, wherein the optical system satisfies the following relationship: 5.5mm < f00<6.8mm, -65.6mm < f11< -57.6mm, 10mm < f22<15.5 mm;

6. The optical system of claim 1, wherein 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<16.6 mm;

7. The optical system according to any one of claims 1 to 6, wherein the first lens and the sixth lens are each an aspherical lens, and the second lens, the third lens, the fourth lens, and the fifth lens are each a spherical lens.

8. The optical system according to any one of claims 1 to 6, wherein the first lens is made of an optical plastic material, and the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are all made of an optical glass material.

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

10. A projection device comprising a housing and an optical system as claimed in any one of claims 1 to 9, the optical system being provided in the housing.