CN115356837A - Optical projection system and projection device - Google Patents

Abstract

The present application discloses an optical projection system and a projection device. The optical projection system sequentially includes a first lens, a diaphragm, and a lens group from the enlargement side to the reduction side; the lens group includes at least three lenses; The refractive power of the lens closest to the aperture is opposite to that of the first lens, and the refractive power of the lens group is positive; the total length TL of the optical projection system is the largest among all lenses The ratio between the aperture D of a lens satisfies 1<TL/D<2.3.

Description

A kind of optical projection system and projection device

technical field

The present application relates to the technical field of optical equipment, and more specifically, to an optical projection system and a projection device.

Background technique

With the vigorous development of science and technology, projection technology has become increasingly mature, and the application fields of projection equipment have become wider and wider, such as in commercial fields such as conference explanations, tour exhibitions and promotional activities, in school teaching, academic discussions, etc. The field of education, as well as the home field such as home theater. In recent years, Digital Light Processing (DLP) projection devices have become the mainstream technology of current projection devices, and they are the best choice among projection display products in terms of lightness, durability, high brightness, and high contrast.

At present, the optical design in the DLP projection device mainly includes the design of the lighting system and the design of the imaging system. Among them, the quality of the imaging system design directly determines the imaging definition, picture size and image quality of picture distortion of the projection device product. Generally speaking, in order to improve the imaging quality of the projection device, the projection device usually needs to include a large number of multiple lenses for combined use, however, this will lead to an increase in the volume of the projection device. Therefore, how to balance the number of lenses in the projection device and the imaging quality of the projection device has become one of the main research directions in the industry.

Contents of the invention

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

According to the first aspect of the present application, an optical projection system is provided, and the optical projection system sequentially includes from the enlargement side to the reduction side:

The first lens, diaphragm and lens group;

The lens group includes at least three lenses;

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

The ratio between the total length TL of the optical projection system and the diameter D of the largest lens among all the lenses satisfies 1<TL/D<2.3.

Optionally, the optical projection system satisfies 5.80mm<effl<6.60mm, where effl is the effective focal length of the optical projection system.

Optionally, the lens group includes a second lens, a third lens, a fourth lens and a fifth lens arranged sequentially from the enlargement side to the reduction side;

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

Optionally, the enlargement side of the first lens is convex, and the reduction side is concave; the enlargement side of the second lens is convex; the enlargement side of the third lens is concave, and the reduction side is concave; The enlargement side of the four lenses is concave, and the reduction side is convex; the enlargement side of the fifth lens is convex, and the reduction side is convex.

Optionally, the effective focal length f1 of the first lens satisfies -9.48mm<f1<-9.08mm; the effective focal length f2 of the second lens satisfies 4.137mm<f2<4.637mm; the effective focal length of the third lens f3 satisfies -2.838mm<f3<-2.22mm; the effective focal length f4 of the fourth lens satisfies 6.26mm<f4<6.8mm, and the effective focal length f5 of the fifth lens satisfies 6.16mm<f5<6.6mm.

Optionally, the ratio of the distance from the first lens to the diaphragm to the distance from the second lens to the diaphragm is in the range of 1-3.

Optionally, the lens group includes a second lens, a third lens, and a sixth lens arranged in sequence from the enlargement side to the reduction side, and the sixth lens is an aspherical lens; the second lens and the third lens There is an air space between the lenses;

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

Optionally, the enlargement side of the sixth lens is convex, and the reduction side is convex.

Optionally, the lens group includes a third lens, a fourth lens, a fifth lens and a seventh lens arranged in sequence from the enlargement side to the reduction side;

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

Optionally, the enlarged side of the first lens is convex, and the reduced side is convex; the enlarged side of the third lens is concave, and the reduced side is concave; the enlarged side of the fourth lens is concave, and the reduced side is Convex; the enlarged side of the fifth lens is convex, and the reduced side is convex; the enlarged side of the seventh lens is convex.

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

Optionally, the lens group includes a third lens, a fourth lens, and a sixth lens arranged in sequence from the enlargement side to the reduction side, and the sixth lens is an aspherical lens;

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

According to a second aspect of the present application, a projection device is provided, and the projection device includes the optical projection system as described in the first aspect.

In the optical projection system provided in the embodiment of the present application, by optimizing the configuration of various parameters, it can achieve a better imaging effect and a smaller volume size.

Other features of the present application and advantages thereof will become apparent through the following detailed description of exemplary embodiments of the present application with reference to the accompanying drawings.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the 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 of the present application;

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

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

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

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

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

Explanation of reference signs:

1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Aperture; 9. etc. Effect prism; 10. Protective glass; 11. Display chip.

Detailed ways

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 arrangements of components and steps, 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 in no way serves as any limitation of the application, its application or uses.

Techniques, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques, methods and devices should be considered part of the description.

In all examples shown and discussed herein, any specific values should be construed as exemplary only, and not as limitations. Therefore, other instances of the exemplary embodiment may have different values.

It should be noted that like numerals and letters denote like items in the following figures, therefore, once an item is defined in one figure, it does not require further discussion in subsequent figures.

Referring to FIGS. 1-4 , according to an embodiment of the present application, an optical projection system is provided, and the optical projection system includes a first lens 1, a diaphragm 8 and a lens group sequentially from the enlargement side to the reduction side; The lens group includes at least three lenses; the refractive power of the lens closest to the diaphragm 8 in the lens group is opposite to that of the first lens 1, and the refractive power of the lens group is is positive; the ratio between the total length TL of the optical projection system and the diameter D of the largest lens among all the lenses satisfies 1<TL/D<2.3.

The optical projection system provided by the embodiment of the present application also includes an equivalent prism 9, a protective glass 10, and a display chip 11; The light or the reflected light is transmitted into the lens; the protective glass 10 is used to protect the display chip 1 from the influence of external pollutants; the display chip 11 can be a digital micromirror device display panel (DMD), a silicon-based liquid crystal display panel (LCOS), liquid crystal display panel (LCD), etc. It can be understood that the display chip 11 is a laser light source of different wavelengths or other light sources capable of emitting light beams.

The optical projection system provided by the embodiment of the present application is applied to a projection device; the optical projection system includes a reduction side and an enlargement side along the light transmission direction, and the display chip 11, protective glass 10, equivalent prism 9, lens group, The diaphragm 8 and the first lens 1 are sequentially disposed between the reduction side and the enlargement side along the same optical axis. Wherein, the zoom-out side is the side where the image source (such as the display chip 11) generating the projection light is located during the projection process, that is, the image side; the zoom-in side is the projection surface (such as a projection screen) for displaying the projected image during the projection process. ) is located on the side, that is, the object space. The transmission direction of the projection light is from the reduction side to the enlargement side. But in the actual design of the optical projection system, according to the reversible principle of the optical path, the light is simulated from the actual enlargement side to the reduction side.

Specifically, in the actual projection process, the projection light is emitted by the display chip 11, emitted from the reduction side toward the enlargement side, and passes through the protective glass 10, the equivalent prism 9, the lens group, the diaphragm 8, and the first lens 1 in sequence, thereby The projected image is displayed.

In the embodiment of the present application, a digital micromirror device (Digital Micromirror Device, DMD) chip may be used as the display chip 11 as the image source. DMD is composed of many digital micro-mirrors arranged in a matrix. When working, each micro-mirror can be deflected and locked in two directions, so that the light is projected in a predetermined direction, and at a frequency of tens of thousands of hertz Swing, the light beam from the illumination source is reflected by the flip of the micro-mirror and enters the optical system to be imaged on the screen. DMD has the advantages of high resolution and no need for digital-to-analog conversion of signals. The embodiment of the present application uses a 0.16' DMD with an aspect ratio of 16:9. The specific size can be, for example, 3.456*1.944mm. The minimum projection ratio of the matching design is 1.2, and the maximum offset is 100%. 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 0.16'DMD, 100% offset, the size of the total image source allowed by the embodiment of the present application can be within 5.2mm, and the full field of view within 64°. Of course, the display chip 11 as the image source can also be a liquid crystal on silicon (LCOS) chip, a liquid crystal display panel (liquid crystal display, LCD) or other display elements that can emit light, which is not limited in this application.

In this embodiment, lenses are provided on both sides of the diaphragm 8, one side of the two sides is close to the enlargement side, and the other side is close to the reduction side. Wherein, there is only one lens, that is, the first lens 1, near the magnification side of the diaphragm 8; and a lens group comprising at least three lenses is provided near the reduction side of the diaphragm 8, wherein the lens group closest to the diaphragm The refractive power of the lens of 8 is opposite to that of the first lens 1, and the refractive power of this lens group is positive. For example, when the refractive power of the first lens 1 is positive, the refractive power of the lens closest to the diaphragm 8 in the lens group is negative; for example, when the refractive power of the first lens 1 is negative Next, the refractive power of the lens closest to the diaphragm 8 in the lens group is positive. In the optical projection system of the embodiment of the present application, the inverse telephoto optical group scheme is adopted, and the optical power distribution follows the negative-positive distribution method, and the optical power of the entire optical projection system is balanced to meet the requirements of the projection system for image value. Moreover, it is helpful to achieve the imaging quality of low distortion and high resolution image.

In addition, in the optical projection system provided in the embodiment of the present application, by setting the ratio between the total length TL of the optical projection system and the diameter D of the largest lens among all the lenses to satisfy 1<TL/D<2.3, In this way, the structure of the optical projection system can be made compact while ensuring the quality of the imaging picture, thereby ensuring the small size of the optical projection system to a certain extent, and making the optical projection system easy to carry and use. That is, in the optical projection system provided in the embodiment of the present application, the imaging effect of the optical projection system can be improved while reducing the volume of the optical projection system. The optical projection system provided by the embodiment of the present application has small distortion of the projected image, high relative illuminance 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 value of the effective focal length effl of the optical projection system to 5.80mm<effl<6.60mm, the structure of the optical projection system can be made compact while ensuring the quality of the imaging picture, thus to a certain extent The size of the optical projection system is ensured to be small, so that the optical projection system is easy 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 arranged in sequence from the magnification side to the reduction side; The refractive power of the lens 1 is negative, and the refractive power of the second lens 2 is positive.

In this specific example, the optical projection system adopts five spherical mirrors, which are arranged sequentially from the enlargement side to the reduction side as the first lens 1, the second lens 2, the third lens 3, the fourth lens 4 and the fifth lens 5 . Wherein, the first lens 1 is located near the enlargement side of the diaphragm 8, and the refractive power of the first lens 1 is negative; Close to the reduction side, and the second lens 2 closest to the diaphragm 8 among the second lens 2, the third lens 3, the fourth lens 4 and the fifth lens 5 is the second lens 2, and the refractive power of the second lens 2 is positive; and The refractive power of the lens group composed 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 that the volume size of the optical projection system is small and at the same time ensures low cost.

In one embodiment, the enlarged side of the first lens 1 is convex, and the reduced side is concave; the enlarged side of the second lens 2 is convex; the enlarged side of the third lens 3 is concave, and the reduced side is Concave surface; the enlarged side of the fourth lens 4 is concave, and the reduced side is convex; the enlarged side of the fifth lens 5 is convex, and the reduced side is convex.

In this specific example, the first lens 1 is a convex-concave lens, the magnified side of the second lens 2 is convex, the third lens 3 is a bi-concave lens, the fourth lens 4 is a convex-concave lens, and the fifth lens 5 is a bi-convex lens. Through the above surface structure design of the first lens 1 , the second lens 2 , the third lens 3 , the fourth lens 4 and the fifth lens 5 , the entire optical projection system can achieve higher image value requirements and light gathering capabilities.

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

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 of the fifth lens 5 The effective focal length f5 is limited; and by limiting the ratio range of the distance from the first lens 1 to the aperture 8 and the distance from the second lens 2 to the aperture 8; the optical design index can be optimized, and the effective Reducing the radial size of the optical projection system is beneficial to the thinner and smaller design of the optical projection system.

Referring to Fig. 2, in one embodiment, the lens group includes a second lens 2, a third lens 3 and a sixth lens 6 arranged in sequence from the enlargement side to the reduction side, and the sixth lens 6 is an aspheric surface Lens; there is an air gap between the second lens 2 and the third lens 3; the refractive power of the first lens 1 is negative, and the refractive power of the second lens 2 is positive.

In this specific example, compared with the previous embodiment, an aspheric lens, that is, the sixth lens 6 is used to replace the two spherical lenses closest to the equivalent prism 9 . Since the aspheric lens has a high ability to correct aberration, it can be replaced by one generation, thereby further reducing the volume of the optical projection system. Further, the enlargement side of the sixth lens 6 is a convex surface, and the reduction side is a convex surface.

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 arranged sequentially from the magnification side to the reduction side; The refractive power of the lens 1 is positive, and the refractive power of the third lens 3 is negative.

In this specific example, the optical projection system adopts five spherical mirrors, which are arranged sequentially from the enlargement side to the reduction side as the first lens 1, the third lens 3, the fourth lens 4, the fifth lens 5 and the seventh lens 7 . Wherein, the first lens 1 is located near the enlargement side of the diaphragm 8, and the refractive power of the first lens 1 is positive; Close to the reduction side, and the third lens 3 closest to the diaphragm 8 among the third lens 3, the fourth lens 4, the fifth lens 5 and the seventh lens 7 is the third lens 3, and the refractive power of the third lens 3 is negative; and The refractive power of the lens group composed 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 that the volume size of the optical projection system is small and at the same time ensures low cost.

In one embodiment, the enlarged side of the first lens 1 is convex, and the reduced side is convex; the enlarged side of the third lens 3 is concave, and the reduced side is concave; the enlarged side of the fourth lens 4 is The concave surface and the reducing side are convex; the enlarged side of the fifth lens 5 is convex, and the reducing side is convex; the enlarged side of the seventh lens 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 enlarged side of the seventh lens 7 is a convex surface . Through the above surface structure design of the first lens 1 , the third lens 3 , the fourth lens 4 , the fifth lens 5 and the seventh lens 7 , the entire optical projection system can meet higher image value requirements and light gathering ability.

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

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 of the seventh lens 7 The effective focal length f7 is limited; the optical design index can be optimized, and the radial size of the optical projection system can be effectively reduced while satisfying the imaging quality, which is conducive to the thinning and miniaturization design of the optical projection system.

Referring to Fig. 4, in one embodiment, the lens group includes a third lens 3, a fourth lens 4 and a sixth lens 6 arranged in sequence from the enlargement side to the reduction side, and the sixth lens 6 is an aspheric surface Lens; the refractive power of the first lens 1 is positive, and the refractive power of the third lens 3 is negative.

In this specific example, compared with the previous embodiment, an aspheric lens, that is, the sixth lens 6 is used to replace the two spherical lenses closest to the equivalent prism 9 . Since the aspheric lens has a high ability to correct aberration, it can be replaced by one generation, thereby further reducing the volume of the optical projection system. Further, the enlargement side of the sixth lens 6 is a convex surface, and the reduction side is a convex surface.

The optical projection system provided by the embodiment of the present application has small distortion of the projected image, high relative illuminance and high MTF modulation function; through the optimal configuration of the above parameters, it can achieve high image definition imaging effect in each field of view.

According to another embodiment of the present application, a projection device is provided, and the projection device includes the above-mentioned optical projection system. The projection device may be, for example, a projection device. The projection device may be, for example, a projector, or an illuminating machine or the like.

Example 1:

Referring to Fig. 1, from the enlargement side to the reduction side, the optical projection system is provided with a first lens 1, a stop 8, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, etc. Effective prism 9, protective glass 10 and display chip 11; the optical projection system meets the effective focal length effl=6.39mm, and the total optical length TL of the optical projection system is 8.7mm. The design goals of 023’DMD are as follows:

Throw ratio is 1.85, projection distance is 609mm, offset 0%, TV distortion <0.5%, full field of view MTF>0.5@96lp/mm, telecentricity <1.5°, chromatic aberration <0.5pixel, F#1.71.

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

Each parameter involved in embodiment 1 is shown in table 1 below:

Table 1

The schematic diagram of the modulation transfer function of the optical projection system shown in Example 1 is shown in Figure 5. It can be seen from the diagram that the MTF values of each field of view are higher than 0.56, and it can be seen that the image formed by the system under each field of view The definition is very high, and other performances also meet the design requirements.

Example 2:

Referring to Fig. 4, from the enlargement side to the reduction side, 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 protection Glass 10 and display chip 11; the optical projection system satisfies the effective focal length effl=6.45mm, and the total optical length TL of the optical projection system is 8.6mm. The design goals of 023’DMD are as follows:

Throw ratio is 1.85, projection distance is 609mm, offset 0%, TV distortion <0.5%, full field of view MTF>0.5@96lp/mm, telecentricity <1.5°, chromatic aberration <0.5pixel, F#1.71.

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

Each parameter involved in embodiment 2 is shown in table 2 below:

The schematic diagram of the modulation transfer function of the optical projection system shown in Example 2 is shown in Figure 6. It can be seen from the diagram that the MTF values of each field of view are higher than 0.55, and it can be seen that the images imaged by the system under each field of view The definition is very high, and other performances also meet the design requirements.

Although some specific embodiments of the present application have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration, rather than limiting the scope of the present application. Those skilled in the art will appreciate that modifications can be made to the above embodiments without departing from the scope and spirit of the application. The scope of the application is defined by the appended claims.

Claims (12)

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;

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

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;

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

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

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