CN115356837A

CN115356837A - Optical projection system and projection device

Info

Publication number: CN115356837A
Application number: CN202210918444.8A
Authority: CN
Inventors: 郭恒琳
Original assignee: Goertek Optical Technology Co Ltd
Current assignee: Goertek Optical Technology Co Ltd
Priority date: 2022-08-01
Filing date: 2022-08-01
Publication date: 2022-11-18

Abstract

The application discloses an optical projection system and a projection device, wherein the optical projection system sequentially comprises a first lens, a diaphragm and a lens group from an enlargement side to a reduction side; the lens group comprises at least three lenses; the focal power of the lens closest to the diaphragm in the lens group is opposite to that of the first lens, and the focal power of the lens group is positive; the ratio of the total length TL of the optical projection system to the caliber D of the largest lens in all lenses meets the conditions that 1 TL/D <2.3 is covered.

Description

Optical projection system and projection device

Technical Field

The present disclosure relates to the field of optical devices, and more particularly, to an optical projection system and a projection apparatus.

Background

With the rapid development of scientific technology, the projection technology has become mature day by day, and the application field of the projection device has become wider and wider, for example, the projection device is applied to the business fields such as conference explanation, tour display and sales promotion activities, the education fields such as school teaching and academic discussion, and the home field such as home theater. In recent years, digital Light Processing (DLP) projection devices have become the mainstream technology of projection devices, and are the preferred choice in projection display products in terms of lightness, durability, high brightness, high contrast, etc.

Currently, the optical design in DLP projection devices mainly includes an illumination system design and an imaging system design. The quality of the design of the imaging system directly determines the imaging definition, the picture size and the image quality of picture distortion of the projection device product. Generally, in order to improve the imaging quality of the projection apparatus, the projection apparatus usually needs to include a large number of lenses for combination, which, however, results in an increase in the volume of the projection apparatus. Therefore, how to balance the number of lenses in the projection device and the imaging quality of the projection device becomes one of the main directions of research in the industry.

Disclosure of Invention

An object of the present application is to provide a new technical solution for an optical projection system and a projection apparatus.

According to a first aspect of the present application, there is provided an optical projection system comprising, in order from an enlargement side to a reduction side:

a first lens, a diaphragm and a lens group;

the lens group comprises at least three lenses;

the focal power of the lens closest to the diaphragm in the lens group is opposite to that of the first lens, and the focal power of the lens group is positive;

the ratio of the total length TL of the optical projection system to the caliber D of the largest lens in all lenses meets the conditions that 1 TL/D <2.3 is covered.

Optionally, the optical projection system satisfies 5.80mm and effl and 6.60mm, wherein effl is an effective focal length of the optical projection system.

Alternatively, the lens group includes a second lens, a third lens, a fourth lens, and a fifth lens that are arranged in order from the magnification side to the reduction side;

the focal power of the first lens is negative, and the focal power of the second lens is positive.

Optionally, the magnifying side surface of the first lens is a convex surface, and the reducing side surface of the first lens is a concave surface; the magnifying side surface of the second lens is a convex surface; the magnifying side surface of the third lens is a concave surface, and the reducing side surface of the third lens is a concave surface; the magnifying side surface of the fourth lens is a concave surface, and the reducing side surface of the fourth lens is a convex surface; the magnifying side surface of the fifth lens is a convex surface, and the reducing side surface of the fifth lens is a convex surface.

Optionally, the effective focal length f1 of the first lens is more than or equal to-9.48mm and less than or equal to f1< -9.08mm; the effective focal length f2 of the second lens meets 4.137mm & lt/2 & gt & lt 4.637mm; the effective focal length f3 of the third lens meets the requirement that the length of the third lens is < -2.838mm and is less than or equal to f3< -2.22mm; the effective focal length f4 of the fourth lens is more than or equal to 6.26mm & lt f4 & gt & lt 6.8mm, and the effective focal length f5 of the fifth lens is more than or equal to 6.16mm & lt f5 & gt & lt 6.6mm.

Optionally, a ratio of a distance from the first lens to the diaphragm to a distance from the second lens to the diaphragm ranges from 1 to 3.

Optionally, the lens group includes a second lens, a third lens and a sixth lens which are sequentially arranged from the magnification side to the reduction side, the sixth lens being an aspherical lens; an air space is arranged between the second lens and the third lens;

Optionally, the magnifying side surface and the reducing side surface of the sixth lens element are convex surfaces.

Optionally, the lens group includes a third lens, a fourth lens, a fifth lens, and a seventh lens arranged in this order from the magnification side to the reduction side;

the focal power of the first lens is positive, and the focal power of the third lens is negative.

Optionally, the magnifying side surface of the first lens is a convex surface, and the reducing side surface of the first lens is a convex surface; the magnifying side surface of the third lens is a concave surface, and the reducing side surface of the third lens is a concave surface; the magnifying side surface of the fourth lens is a concave surface, and the reducing side surface of the fourth lens is a convex surface; the magnifying side surface of the fifth lens is a convex surface, and the reducing side surface of the fifth lens is a convex surface; the magnifying side surface of the seventh lens is a convex surface.

Optionally, the effective focal length f7 of the seventh lens satisfies 6.7mm or f7 or 8.6mm.

Optionally, the lens group includes a third lens, a fourth lens and a sixth lens which are sequentially arranged from the magnification side to the reduction side, the sixth lens being an aspherical lens;

According to a second aspect of the present application, there is provided a projection apparatus comprising an optical projection system as described in the first aspect.

In the optical projection system provided by the embodiment of the application, through the optimized configuration of each parameter, a better imaging effect and a smaller volume size can be achieved.

Further features of the present application and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which is to be read in connection with the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the application and together with the description, serve to explain the principles of the application.

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

FIG. 2 is a schematic diagram of an optical structure of an optical projection system according to the present application;

FIG. 3 is a schematic diagram of an optical structure of an optical projection system according to the present application;

FIG. 4 is a schematic diagram of an optical structure of an optical projection system according to the present application;

FIG. 5 is a schematic diagram showing a modulation transfer function of embodiment 1 in an optical projection system of the present application;

FIG. 6 is a schematic diagram showing a modulation transfer function of embodiment 2 in an optical projection system according to the present application.

Description of reference numerals:

1. a first lens; 2. a second lens; 3. a third lens; 4. a fourth lens; 5. a fifth lens; 6. a sixth lens; 7. a seventh lens; 8. a diaphragm; 9. an equivalent prism; 10. protecting glass; 11. and displaying the chip.

Detailed Description

Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application unless specifically stated otherwise.

The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the application, its application, or uses.

Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.

In all examples shown and discussed herein, any particular value should be construed as exemplary only and not as limiting. Thus, other examples of the exemplary embodiments may have different values.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

Referring to fig. 1 to 4, according to an embodiment of the present application, there is provided an optical projection system including a first lens 1, a diaphragm 8, and a lens group in order from an enlargement side to a reduction side; the lens group comprises at least three lenses; the focal power of the lens closest to the diaphragm 8 in the lens group is opposite to that of the first lens 1, and the focal power of the lens group is positive; the ratio of the total length TL of the optical projection system to the caliber D of the largest lens in all lenses meets the conditions that 1 TL/D <2.3 is covered.

The optical projection system provided by the embodiment of the application further comprises an equivalent prism 9, a protective glass 10 and a display chip 11; more specifically, the equivalent prism 9 is an equivalent turning prism, and the equivalent prism 9 is used for transmitting the light emitted by the display chip 11 or the reflected light to the lens; the protective glass 10 is used to protect the display chip 1 from external contaminants; the display chip 11 may be a digital micromirror device display panel (DMD), a Liquid Crystal On Silicon (LCOS) display panel, a liquid crystal display panel (LCD), or the like. It is understood that the display chip 11 is a laser light source with different wavelengths or other light source bodies capable of emitting light beams.

The optical projection system provided by the embodiment of the application is applied to a projection device; the optical projection system comprises a reduction side and an amplification side along the light transmission direction, and a display chip 11, a protective glass 10, an equivalent prism 9, a lens group, a diaphragm 8 and a first lens 1 in the optical projection system are sequentially arranged between the reduction side and the amplification side along the same optical axis. Wherein, the reduction side is the side where the image source (for example, the display chip 11) generating the projection light is located in the projection process, namely the image side; the enlargement side is the side on which 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. However, in designing an optical projection system in practice, light rays are simulated from the actual enlargement side to the reduction side based on the principle that the light path is reversible.

Specifically, in an actual projection process, projection light is emitted from the display chip 11, emitted from the reduction side toward the enlargement side, and passes through the cover glass 10, the equivalent prism 9, the lens group, the diaphragm 8, and the first lens 1 in this order, thereby displaying a projection image.

In the embodiment of the present application, the display chip 11 serving as an image source may be a Digital Micromirror Device (DMD) chip. The DMD is composed of a plurality of digital micro-mirrors arranged in a matrix, each micro-mirror can deflect and lock towards the positive direction and the negative direction during operation, so that light rays are projected in a given direction, and swing at the frequency of tens of thousands of hertz, and light beams from an illumination light source enter an optical system through the overturning reflection of the micro-mirrors 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. The DMD of 0.16' is adopted in the embodiment of the application, the size transverse-longitudinal ratio is 16. It should be noted that the image source size applicable to the imaging optical path architecture in the embodiment of the present application is not limited to the dmd of 0.16' and the offset of 100%, and the size of the holographic source allowed by the embodiment of the present application may be within 5.2mm, and the full field angle is within 64 °. Of course, the Display chip 11 as the image source may also be a Liquid Crystal On Silicon (LCOS) chip, a Liquid Crystal Display panel (LCD), or other Display elements capable of emitting light, which is not limited in this application.

In this embodiment, lenses are provided on both sides of the diaphragm 8, one of which is close to the enlargement side and the other of which is close to the reduction side. Wherein, the side close to the enlargement of the diaphragm 8 is provided with only one lens, namely the first lens 1; and a lens group including at least three lenses is disposed on the side of the stop 8 close to the reduction, wherein the power of the lens closest to the stop 8 among the lens groups is opposite to the power of the first lens 1, and the power of the lens group is positive. For example, in the case where the power of the first lens 1 is positive, the power of the lens closest to the stop 8 in the lens group is negative; for example, in the case where the power of the first lens 1 is negative, the power of the lens closest to the stop 8 in the lens group is positive. In the optical projection system of the embodiment of the application, a negative distance type optical group scheme is adopted, the optical power distribution follows a negative-positive distribution mode, the optical power of the whole optical projection system is balanced, and the requirement of the projection system on an image value is met. And, it is helpful to achieve low distortion, high resolution imaging quality of the image.

Furthermore, in the optical projection system provided by the embodiment of the application, by setting the ratio between the total length TL of the optical projection system and the aperture D of the largest one of all lenses to satisfy 1-straw TL/D <2.3, it is possible to make the structure of the optical projection system compact while ensuring the quality of the imaging picture, thereby ensuring the small volume size of the optical projection system to a certain extent and making the optical projection system convenient to carry and use. That is, in the optical projection system provided in the embodiments of the present application, the imaging effect of the optical projection system can be improved while the volume of the optical projection system is reduced. The optical projection system provided by the embodiment of the application has the advantages of small distortion of a projected image, high relative illumination and high MTF modulation function.

In one embodiment, the optical projection system satisfies 5.80mm < -effl < -6.60mm, where effl is the effective focal length of the optical projection system.

In this specific example, by setting the effective focal length effl of the optical projection system to values of 5.80mm and 6.60mm, the optical projection system can be made compact while ensuring the quality of the imaged picture, thereby ensuring the small volume size of the optical projection system to some extent and making the optical projection system convenient to carry and use.

Referring to fig. 1, in one embodiment, the lens group includes a second lens 2, a third lens 3, a fourth lens 4, and a fifth lens 5, which are disposed in order from the magnification side to the reduction side; the focal power of the first lens 1 is negative, and the focal power of the second lens 2 is positive.

In this specific example, the optical projection system employs 5 spherical mirrors, and is arranged as a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, and a fifth lens 5 in this order from the enlargement side to the reduction side. Wherein, the first lens 1 is positioned on the side close to the enlargement of the diaphragm 8, and the focal power of the first lens 1 is negative; the second lens 2, the third lens 3, the fourth lens 4, and the fifth lens 5 are positioned on the side of the aperture stop 8 closer to the reduction side, and the second lens 2 is positioned closest to the aperture stop 8 among the second lens 2, the third lens 3, the fourth lens 4, and the fifth lens 5, and the power of the second lens 2 is positive; and the focal power of the lens group consisting of the second lens 2, the third lens 3, the fourth lens 4 and the fifth lens 5 is positive. The lens arrangement design in this embodiment ensures a low cost while ensuring a small volume size of the optical projection system.

In one embodiment, the magnifying side surface of the first lens element 1 is convex, and the reducing side surface of the first lens element is concave; the magnifying side surface of the second lens 2 is a convex surface; the magnifying side surface of the third lens 3 is a concave surface, and the reducing side surface is a concave surface; the magnifying side surface of the fourth lens 4 is a concave surface, and the reducing side surface is a convex surface; the magnifying side surface and the reducing side surface of the fifth lens 5 are convex surfaces.

In this specific example, the first lens 1 is a convex-concave lens, the magnification side surface of the second lens 2 is a convex surface, the third lens 3 is a biconcave lens, the fourth lens 4 is a convex-concave lens, and the fifth lens 5 is a biconvex lens. By the above structural design of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4 and the fifth lens 5, the whole optical projection system can meet the requirements of higher image value and light convergence capability.

In one embodiment, the effective focal length f1 of the first lens 1 satisfies-9.48mm < -f 1< -9.08mm; the effective focal length f2 of the second lens 2 satisfies 4.137mm </f 2 </4.637mm; the effective focal length f3 of the third lens 3 meets the requirement that the length of the third lens is < -2.838mm < -3 < -2.22mm; the effective focal length f4 of the fourth lens 4 satisfies 6.26mm </f 4 </6.8 mm, and the effective focal length f5 of the fifth lens 5 satisfies 6.16mm </f 5 </6.6mm. The ratio of the distance from the first lens 1 to the stop 8 to the distance from the second lens 2 to the stop 8 is in the range of 1 to 3.

In this specific example, the effective focal length f1 of the first lens 1, the effective focal length f2 of the second lens 2, the effective focal length f3 of the third lens 3, the effective focal length f4 of the fourth lens 4, and the effective focal length f5 of the fifth lens 5 are defined; and by defining a range of ratios of the distance from the first lens 1 to the diaphragm 8 to the distance from the second lens 2 to the diaphragm 8; the optical design index can be optimized, the radial size of the optical projection system is effectively reduced while the imaging quality is met, and the optical projection system is light, thin and small in design.

Referring to fig. 2, in one embodiment, the lens group includes a second lens 2, a third lens 3, and a sixth lens 6 disposed in order from an enlargement side to a reduction side, the sixth lens 6 being an aspherical lens; the second lens 2 and the third lens 3 have an air space therebetween; the focal power of the first lens 1 is negative, and the focal power of the second lens 2 is positive.

In this particular example, compared to the previous embodiment, one aspherical lens, i.e. the sixth lens 6, is used instead of the two spherical lenses closest to the equivalent prism 9. The aspheric lens can be used for one generation two because of high capability of correcting phase difference, thereby further reducing the volume of the optical projection system. Further, the sixth lens element 6 has a convex magnification side and a convex reduction side.

Referring to fig. 3, in one embodiment, the lens group includes a third lens 3, a fourth lens 4, a fifth lens 5, and a seventh lens 7, which are disposed in order from the magnification side to the reduction side; the focal power of the first lens 1 is positive, and the focal power of the third lens 3 is negative.

In this specific example, the optical projection system employs 5 spherical mirrors, and the first lens 1, the third lens 3, the fourth lens 4, the fifth lens 5, and the seventh lens 7 are arranged in this order from the enlargement side to the reduction side. Wherein, the first lens 1 is positioned on the side close to the magnification of the diaphragm 8, and the focal power of the first lens 1 is positive; the third lens 3, the fourth lens 4, the fifth lens 5 and the seventh lens 7 are positioned on the reduction side of the diaphragm 8, the third lens 3 is positioned closest to the diaphragm 8 among the third lens 3, the fourth lens 4, the fifth lens 5 and the seventh lens 7, and the focal power of the third lens 3 is negative; and the focal power of the lens group consisting of the third lens 3, the fourth lens 4, the fifth lens 5 and the seventh lens 7 is positive. The lens arrangement design in this embodiment ensures a low cost while ensuring a small volume size of the optical projection system.

In one embodiment, the magnifying side surface and the reducing side surface of the first lens 1 are convex surfaces; the magnifying side surface of the third lens 3 is a concave surface, and the reducing side surface is a concave surface; the magnifying side surface of the fourth lens element 4 is a concave surface, and the reducing side surface thereof is a convex surface; the magnifying side surface and the reducing side surface of the fifth lens 5 are convex surfaces; the magnifying side surface of the seventh lens element 7 is convex.

In this specific example, the first lens 1 is a biconvex lens, the third lens 3 is a biconcave lens, the fourth lens 4 is a convex-concave lens, and the fifth lens 5 is a biconvex lens; the magnifying side surface of the seventh lens element 7 is convex. Through the above structural design of the first lens 1, the third lens 3, the fourth lens 4, the fifth lens 5 and the seventh lens 7, the whole optical projection system can achieve higher image value requirements and light convergence capability.

In one embodiment, the effective focal length f1 of the first lens 1 satisfies 9.48mm < -1 > f-t 9.08mm; the effective focal length f3 of the third lens 3 meets the requirements of-2.838mm < -f3 < -2.22mm; the effective focal length f4 of the fourth lens 4 satisfies 6.26mm or < -4 > 6.8mm, and the effective focal length f5 of the fifth lens 5 satisfies 6.16mm or < -5 > 6.6mm and the effective focal length f7 of the seventh lens 7 satisfies 6.7mm or < -7 > 8.6mm.

In this specific example, the effective focal length f1 of the first lens 1, the effective focal length f3 of the third lens 3, the effective focal length f4 of the fourth lens 4, the effective focal length f5 of the fifth lens 5, and the effective focal length f7 of the seventh lens 7 are defined; the optical design index can be optimized, the radial size of the optical projection system is effectively reduced while the imaging quality is met, and the optical projection system is favorable for light, thin and small design.

Referring to fig. 4, in one embodiment, the lens group includes a third lens 3, a fourth lens 4, and a sixth lens 6 disposed in order from the magnification side to the reduction side, the sixth lens 6 being an aspherical lens; the focal power of the first lens 1 is positive, and the focal power of the third lens 3 is negative.

In this particular example, compared to the previous embodiment, one aspherical lens, i.e. the sixth lens 6, is used instead of the two spherical lenses closest to the equivalent prism 9. Since the aspheric lens has high capability of correcting phase difference, the aspheric lens can be used for the second generation, thereby further reducing the volume of the optical projection system. Further, the magnification side surface of the sixth lens element 6 is a convex surface, and the reduction side surface is a convex surface.

The optical projection system provided by the embodiment of the application has the advantages that the distortion of a projection image is small, the relative illumination is high, and the MTF modulation function is high; through the optimal configuration of the parameters, the imaging effect with higher image definition can be achieved under each view field.

According to another embodiment of the present application, there is provided a projection apparatus including the optical projection system as described above. The projection device may be, for example, a projection device. The projection device may be, for example, a projector, an illumination light engine, or the like.

Example 1:

referring to fig. 1, the optical projection system is provided with a first lens 1, a diaphragm 8, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, an equivalent prism 9, a cover glass 10, and a display chip 11 in this order from the enlargement side to the reduction side; the optical projection system satisfies effective focal length effl =6.39mm, and the total optical length TL of the optical projection system is 8.7mm.023' DMD design target is as follows:

the projection ratio is 1.85, the projection distance is 609mm, the offset is 0%, the TV distortion is less than 0.5%, the MTF of the full field is more than 0.5@96lp/mm, the telecentricity is less than 1.5 degrees, the chromatic aberration is less than 0.5pixel, F # -1.71.

The optical projection system in this embodiment comprises 5 spherical lenses; wherein, the magnifying side S1 of the first lens element 1 is convex, and the reducing side S2 is concave; the magnifying side S3 of the second lens element 2 is convex, and the demagnifying side S4 is convex; the magnifying side surface S5 of the third lens element 3 is a concave surface, and the reducing side surface S6 is a concave surface; the magnifying side S7 of the fourth lens element 4 is a concave surface, and the demagnifying side S8 of the fourth lens element is a convex surface; the magnifying side surface S9 of the fifth lens element 5 is convex, and the reducing side surface S10 is convex.

The various parameters involved in example 1 are shown in table 1 below:

TABLE 1

The modulation transfer function diagram of the optical projection system shown in embodiment 1 is shown in fig. 5, and it can be seen from the diagram that the MTF value of each field is higher than 0.56, and it can be seen that the image definition after being imaged by the system under each field is very high, and other performances also meet the design requirements.

Example 2:

referring to fig. 4, the optical projection system is provided with a first lens 1, a diaphragm 8, a third lens 3, a fourth lens 4, a sixth lens 6, an equivalent prism 9, a cover glass 10, and a display chip 11 in this order from the enlargement side to the reduction side; the optical projection system meets the requirements that the effective focal length effl =6.45mm and the optical total length TL of the optical projection system is 8.6mm.023' DMD design target is as follows:

the projection ratio is 1.85, the projection distance is 609mm, the offset is 0%, the TV distortion is less than 0.5%, the MTF of the full field is more than 0.5@96lp/mm, the telecentricity is less than 1.5 degrees, the chromatic aberration is less than 0.5pixel, F #1.71.

The optical projection system in this embodiment includes 3 spherical lenses and 1 aspherical lens; wherein, the magnifying side S1 of the first lens element 1 is convex, and the reducing side S2 is convex; the magnifying side surface S3 of the third lens element 3 is a concave surface, and the reducing side surface S4 is a concave surface; the magnifying side surface S5 of the fourth lens element 4 is a concave surface, and the reducing side surface S6 is a convex surface; the magnifying side surface S7 of the sixth lens element 6 is a convex surface, and the reducing side surface S8 is a convex surface.

The various parameters involved in example 2 are shown in table 2 below:

the schematic diagram of the modulation transfer function of the optical projection system shown in embodiment 2 is shown in fig. 6, and it can be seen from the diagram that the MTF value of each field is higher than 0.55, and it can be seen that the image definition after being imaged by the system under each field is very high, and other performances also meet the design requirements.

Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are for illustrative purposes only and are not intended to limit the scope of the present application. It will be appreciated by those skilled in the art that modifications can be made to the above embodiments without departing from the scope and spirit of the present application. The scope of the application is defined by the appended claims.

Claims

1. An optical projection system comprising, in order from an enlargement side to a reduction side:

a first lens (1), a diaphragm (8) and a lens group;

the lens group comprises at least three lenses;

the focal power of the lens closest to the diaphragm (8) in the lens group is opposite to the focal power of the first lens (1), and the focal power of the lens group is positive;

the ratio of the total length TL of the optical projection system to the aperture D of the largest lens in all the lenses meets the condition that the TL/D is less than 1 and less than 2.3.

2. The optical projection system of claim 1, wherein the optical projection system satisfies 5.80mm and effl-s-6.60mm, wherein effl is an effective focal length of the optical projection system.

3. The optical projection system according to claim 1, wherein the lens group includes a second lens (2), a third lens (3), a fourth lens (4), and a fifth lens (5) which are arranged in this order from the enlargement side to the reduction side;

the focal power of the first lens (1) is negative, and the focal power of the second lens (2) is positive.

4. The optical projection system according to claim 3, wherein the effective focal length f1 of the first lens (1) satisfies-9.48mm < -f 1< -9.08mm; the effective focal length f2 of the second lens (2) satisfies 4.137mm and < -2 < -4.637mm.

5. The optical projection system according to claim 3, characterized in that the ratio of the distance of the first lens (1) to the diaphragm (8) to the distance of the second lens (2) to the diaphragm (8) ranges from 1 to 3.

6. The optical projection system according to claim 1, wherein said lens group comprises a second lens (2), a third lens (3) and a sixth lens (6) which are arranged in order from the enlargement side to the reduction side, said sixth lens (6) being an aspherical lens; the second lens (2) and the third lens (3) have an air space therebetween;

7. The optical projection system of claim 6, characterized in that the sixth lens (6) has a convex magnification side and a convex demagnification side.

8. The optical projection system according to claim 1, wherein the lens group includes a third lens (3), a fourth lens (4), a fifth lens (5), and a seventh lens (7) which are arranged in this order from the enlargement side to the reduction side;

the focal power of the first lens (1) is positive, and the focal power of the third lens (3) is negative.

9. The optical projection system as claimed in claim 8, characterized in that the magnifying side of the seventh lens (7) is convex.

10. The optical projection system of claim 8, wherein the effective focal length f7 of the seventh lens (7) satisfies 6.7 mm/f 7/8.6 mm.

11. The optical projection system according to claim 1, wherein the lens group includes a third lens (3), a fourth lens (4), and a sixth lens (6) which are arranged in this order from the magnification side to the reduction side, the sixth lens (6) being an aspherical lens;

12. A projection device, characterized in that it comprises an optical projection system according to any one of claims 1-11.