CN114518644B - Projection lens and projection device - Google Patents

Abstract

A projection lens comprises a first lens group, a second lens group and a diaphragm. The first lens group is arranged between the shrinking side and the enlarging side. The second lens group is arranged between the first lens group and the amplifying side. The second lens group is provided with a light incident surface, a reflecting surface and a light emergent surface, the light incident surface faces the first lens group, the light emergent surface faces the projection surface, the light incident surface, the light emergent surface and the first lens group are arranged on the same side of the reflecting surface, and at least one of the light incident surface, the reflecting surface and the light emergent surface is a free curved surface. The diaphragm is arranged between the first lens group and the second lens group. The light valve is used for providing an image light beam. In addition, a projection device comprising the projection lens is also provided. The projection lens has a common light path design, so that the image light beams reflected back to the first lens group by the reflecting surface of the second lens group are not easy to interfere, the distance between the diaphragm and the reflecting surface of the second lens group can be shortened, and the whole thickness and the volume of the projection lens can be effectively reduced.

Description

Projection lens and projection device

Technical Field

The invention relates to an optical lens and an optical device, and in particular to a projection lens and a projection device.

Background technique

Projectors have been widely used in home appliances, office equipment, game consoles, etc. The demand for projectors is gradually developing towards thinner and smaller ones. For example, compared with projectors using traditional light sources, pocket projectors using light-emitting diodes are small in size and light in weight, which can reduce space requirements and are easy to carry.

In practical applications, in order to reduce the use space of the projector, the structure of the projector needs to be modified to change the traditional vertical projection into oblique projection, so that the projection image can be turned with the help of a reflector, and the turned projection head image can be projected onto the projection surface (for example: desktop, ground, wall, screen, etc.) according to the needs. In the oblique projection architecture, the reference light of the projector's outgoing light cannot be perpendicular to the projection surface, that is, oblique incidence, which will cause trapezoidal distortion of the projection image. Traditionally, in order to improve trapezoidal distortion, software can be used to crop the distorted area of the projection image to achieve a distortion-free situation. However, this software correction method will result in reduced resolution and brightness loss. In addition, another way to improve trapezoidal distortion is hardware correction, that is, the projection lens is moved to, however, this method will cause the volume of the projector to become larger.

Summary of the invention

The invention provides a projection lens which has a small volume and can improve trapezoidal distortion.

The invention provides a projection device which has a small volume and can improve trapezoidal distortion.

The projection lens of the present invention is used to image a light valve arranged on the reduction side onto a projection surface arranged on the magnification side. The light valve and the projection surface have an angle. The projection lens includes a first lens group, a second lens group and an aperture. The first lens group is arranged between the reduction side and the magnification side and has a first optical axis. The second lens group is arranged between the first lens group and the magnification side, wherein the second lens group at least has a light incident surface, a reflection surface and a light exit surface, the light incident surface faces the first lens group, the light exit surface faces the projection surface, the light incident surface, the light exit surface and the first lens group are arranged on the same side of the reflection surface, and at least one of the light incident surface, the reflection surface and the light exit surface is a free-form surface. The aperture is arranged between the first lens group and the second lens group. The light valve is used to provide an image beam. The image beam from the light valve sequentially passes through the first lens group, passes through the aperture, passes through the light incident surface of the second lens group, is reflected by the reflection surface of the second lens group and passes through the light exit surface of the second lens group to be transmitted to the projection surface.

The projection device of the present invention comprises an illumination light source, a light valve, a projection surface and the above-mentioned projection lens. The illumination light source is used to provide an illumination beam. The light valve is arranged on the reduction side and is used to convert the illumination beam into an image beam. The projection surface is arranged on the magnification side, wherein the light valve and the projection surface have an angle.

Based on the above, in a projection device and a projection lens of an embodiment of the present invention, at least one of the light-entering surface, the reflecting surface, and the light-emitting surface of the second lens group of the projection lens is a free-form surface. In this way, a back-and-forth common optical path design can be realized, thereby reducing the overall thickness of the projection lens. In addition, since at least one of the light-entering surface, the reflecting surface, and the light-emitting surface of the second lens group is a free-form surface, the projection lens can also make the focal length of the image light beam corresponding to each viewing angle different, thereby improving the trapezoidal distortion phenomenon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a projection device according to an embodiment of the present invention.

2 is an enlarged schematic diagram of the light valve, the protective cover, the light combining element, the flat glass actuator and the projection lens of the projection device of FIG. 1 .

FIG. 3 is a schematic diagram of a projection device according to an embodiment of the present invention.

FIG. 4 schematically illustrates a projection screen formed by an image light beam on a projection surface according to an embodiment of the present invention.

FIG. 5 is a diagram of a modulation transfer function of the projection lens of FIG. 2 .

FIG. 6 schematically illustrates a projection picture on the projection surface of the projection device of FIG. 1 .

Detailed ways

The above and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only referenced to the directions of the accompanying drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention.

Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the accompanying drawings and the description to refer to the same or like parts.

Fig. 1 is a schematic side view of a projection device according to an embodiment of the present invention. Fig. 2 is an enlarged schematic view of a light valve, a protective cover, a light combining element, a flat glass actuator and a projection lens of the projection device of Fig. 1 .

1 and 2 , in the figures, direction z is, for example, a direction perpendicular to the projection plane PS, direction y is, for example, a direction parallel to the projection plane PS, and direction x is, for example, a direction parallel to the projection plane PS and perpendicular to direction y.

Referring to FIG. 1 , the projection device 100 includes an illumination light source ILS, a light valve LV, a projection lens PL, and a projection surface PS. The projection lens PL has a reduction side and an enlargement side. The light valve LV is disposed on the reduction side. The projection surface PS is disposed on the enlargement side. The illumination light source ILS is used to provide an illumination light beam ILB. The light valve LV is used to convert the illumination light beam ILB into an image light beam IMB. The projection lens PL is used to image the image light beam IMB from the light valve LV onto the projection surface PS located on the enlargement side. In particular, the projection surface PS and the light valve LV have an angle θ. In other words, the projection device 100 is an oblique projection device. The angle θ between the projection surface PS and the light valve LV satisfies: 0°<θ<90°. For example, the angle θ may satisfy: 25°<θ<90°, but the present invention is not limited thereto.

The projection surface PS generally refers to the surface of an object on which a projection image can be formed. For example, in this embodiment, the projection surface PS can be a desktop. However, the present invention is not limited thereto, and in other embodiments, the projection surface PS can also be the ground, a wall, a screen, etc.

In this embodiment, the light valve LV can be selectively a reflective light modulator, such as a digital micro-mirror device, a liquid-crystal-on-silicon panel (LCOS panel), etc. However, the present invention is not limited thereto, and in other embodiments, the light valve LV can also be a transmissive light modulator, such as a transparent liquid crystal panel (Transparent Liquid Crystal Panel), an electro-optical modulator (Electro-Optical Modulator), a magneto-optical modulator (Magneto-Optic modulator), an acousto-optic modulator (AOM), etc.

In the present embodiment, the projection device 100 may further selectively include a light combining element PR. The illumination system ILS emits an illumination light beam ILB to the light combining element PR, and the illumination light beam ILB is transmitted to the light valve LV via the light combining element PR. The light valve LV reflects the illumination light beam ILB into an image light beam IMB, and the image light beam IMB is transmitted to the projection lens PL via the light combining element PR. For example, in the present embodiment, the light combining element PR may be a total internal reflection prism (Total Internal Reflection Prism, TIRPrism). However, the present invention is not limited thereto, and in other embodiments, the light combining element PR may also be a beamsplitter, a polarizer beam splitter, a field lens or other optical elements, depending on the light splitting or light guiding design required by the projection device 100, and the present invention is not limited thereto.

1 and 2, in this embodiment, the projection device 100 may further selectively include a protective cover CG (indicated in FIG. 2), which is disposed on the light receiving surface LVa (indicated in FIG. 2) of the light valve LV and is located between the light valve LV and the light combining element PR. The protective cover CG is used to protect the light valve LV. In addition, in this embodiment, the projection device 100 may further selectively include a flat glass actuator AC, which may have a light filtering function.

The projection lens PL includes a first lens group LG1, an aperture AS, and a second lens group LG2. The first lens group LG1 is disposed between the reduction side and the magnification side and has a first optical axis X1. The second lens group LG2 is disposed between the first lens group LG1 and the magnification side. The aperture AS is disposed between the first lens group LG1 and the second lens group LG2. The second lens group LG2 has at least a light incident surface RP3, a reflection surface RP2, and a light exit surface RP1, wherein the light incident surface RP3 faces the first lens group LG1, the light exit surface RP1 faces the projection surface PS, and the light incident surface RP3, the light exit surface RP1, and the first lens group LG1 are disposed on the same side of the reflection surface RP2.

2 , the first lens group LG1 includes a plurality of lenses L1, L2, L3, L4, and L5 arranged in sequence from the magnification side to the reduction side, wherein each of the lenses L1, L2, L3, L4, and L5 has a first surface L11, L21, L31, L41, and L51 facing the second lens group LG2 and a second surface L12, L22, L32, L42, and L52 facing the light valve LV.

For example, in the present embodiment, the first lens group LG1 includes a lens L1, a lens L2, a lens L3, a lens L4, and a lens L5 arranged in sequence from the magnification side to the reduction side, wherein the lens L1 has a first surface L11 facing the second lens group LG2 and a second surface L12 facing the light valve LV, the lens L2 has a first surface L21 facing the second lens group LG2 and a second surface L22 facing the light valve LV, the lens L3 has a first surface L31 facing the second lens group LG2 and a second surface L32 facing the light valve LV, the lens L4 has a first surface L41 facing the second lens group LG2 and a second surface L42 facing the light valve LV, and the lens L5 has a first surface L51 facing the second lens group LG2 and a second surface L52 facing the light valve LV. In the present embodiment, the number of the plurality of lenses L1, L2, L3, L4, and L5 of the first lens group LG1 is, for example, 5. However, the present invention is not limited thereto, and the number of lenses of the first lens group LG1 may vary according to actual needs. In other embodiments, the number of lenses of the first lens group LG1 may also be 2, 3, 4, 6, or a positive integer greater than 6. In this embodiment, the focal length of the first lens group LG1 may be a negative value, but the present invention is not limited thereto.

The aperture AS refers to an entity that limits the image beam IMB in the projection lens PL. The beam has the smallest cross-sectional area when passing through the aperture AS. It can be the edge of the lens, the frame, or a specially set perforated screen. For example, in this embodiment, the aperture AS is, for example, a perforated screen disposed between the first lens group LG1 and the second lens group LG2, but the present invention is not limited thereto. In this embodiment, the first surface L11 of the lens L1 closest to the aperture AS among the multiple lenses L1, L2, L3, L4, and L5 of the first lens group LG1 can be a free-form surface.

In this embodiment, the second lens group LG2 may include a turning prism RP, and the turning prism RP has a light incident surface RP3, a reflection surface RP2, and a light emitting surface RP1. In this embodiment, the light incident surface RP3 of the turning prism RP may be a concave surface, and the light emitting surface RP1 of the turning prism RP may be a convex surface.

It is worth noting that at least one of the light incident surface RP3, the reflection surface RP2 and the light emitting surface RP1 of the second lens group LG2 is a free-form surface, and the first optical axis X1 of the first lens group LG1 does not overlap with the center IMBc of the image beam IMB. In this way, a round-trip common optical path design can be achieved, that is, the optical path of the image beam IMB transmitted from the first lens group LG1 to the second lens group LG2 and the optical path of the image beam IMB reflected back to the first lens group LG1 by the reflection surface RP2 of the second lens group LG2 can overlap, and the image beam IMB reflected by the reflection surface RP2 of the second lens group LG2 can have enough space to be emitted from the light incident surface RP3 of the second lens group LG2. Since the projection lens PL has a common optical path design, the image beam IMB reflected back to the first lens group LG1 by the reflection surface RP2 of the second lens group LG2 is not likely to cause interference, so the maximum distance D between the aperture AS and the reflection surface RP2 of the second lens group LG2 in the direction d1 parallel to the first optical axis X1 can be shortened. When the maximum distance D is shortened, the optical effective diameter CA of the reflection surface RP2 of the second lens group LG2 will not be too large. In this way, the overall thickness H of the projection lens PL can be reduced.

2 , the image beam IMB includes a first edge ray IMB1 and a second edge ray IMB2. The first edge ray IMB1 is emitted from a point LVp on the edge LFe of the light valve LV in a direction away from the first optical axis X1. The second edge ray IMB2 is emitted from a point LVp on the edge LFe of the light valve LV in a direction pointing to the first optical axis X1. The first edge ray IMB1 in the first lens group LG1 has a maximum distance H1 from the first optical axis X1 in a direction d2 perpendicular to the first optical axis X1. The second edge ray IMB2 on the light exit surface RP1 of the second lens group LG2 has a maximum distance H2 from the first optical axis X1 in a direction d2 perpendicular to the first optical axis X1. The overall thickness H of the projection lens PL mentioned above refers to the sum of the maximum distance H1 and the maximum distance H2. For example, in this embodiment, the overall thickness H of the projection lens PL may be less than 12 mm, but the present invention is not limited thereto.

The aperture AS and the reflection surface RP2 of the second lens group LG2 have a maximum distance D in the direction d1 parallel to the first optical axis X1. In this embodiment, H/D<3. In addition, in this embodiment, the light exit surface RP1 of the second lens group LG2 has an optically effective diameter CA, and CA/D<3. In other words, the ratio of the overall thickness H of the projection lens PL to the maximum distance D between the aperture AS and the reflection surface RP2 and the ratio of the optically effective diameter CA of the light exit surface RP1 of the second lens group LG2 to the maximum distance D between the aperture AS and the reflection surface RP2 are both below an appropriate value. This design method can reduce the volume of the projection lens PL.

In addition, since at least one of the light incident surface RP3, the reflection surface RP2, and the light emitting surface RP1 of the second lens group LG2 is a free-form surface, the second lens group LG2 can also make the focal lengths of the image beams IMB corresponding to each viewing angle different, thereby improving the trapezoidal distortion phenomenon. In the present embodiment, the light incident surface RP3, the reflection surface RP2, and the light emitting surface RP1 of the second lens group LG2 can all be free-form surfaces, but the present invention is not limited thereto. In another embodiment, the light emitting surface RP1 and the reflection surface RP2 of the second lens group LG2 can be free-form surfaces, while the light incident surface RP3 can not be a free-form surface. In yet another embodiment, the reflection surface RP2 and the light incident surface RP3 of the second lens group LG2 can be free-form surfaces, while the light emitting surface RP1 can not be a free-form surface. In the present embodiment, the focal length of the second lens group LG2 is, for example, a positive value.

In this embodiment, the image beam IMB has an offset value O relative to the first optical axis X1 of the first lens group LG1 . A method for measuring the offset value O is described below with reference to FIG.

FIG3 is a schematic diagram of a projection device according to an embodiment of the present invention. Referring to FIG1 and FIG3 , the projector PJT of FIG3 at least includes the illumination light source ILS, the light valve LV and the projection lens PL of FIG1 , and the projector PJT is used to form a projection screen IM on the projection surface PS. Referring to FIG3 , in the method for measuring the offset O, first, the horizontality of the projector PJT is calibrated so that the first optical axis X1 of the projector PJT is level with the ground GD. Next, when the first optical axis X1 of the projector PJT is level with the ground GD, the projector PJT is made to project a projection screen IM on the projection surface PS. Then, the height h of the projection screen IM, the distance a from an edge IMe of the projection screen IM away from the ground GD to the ground GD, and the distance b from the first optical axis X1 of the projector PJT to the ground GD are measured. Finally, the offset value O of the image beam IMB relative to the first optical axis X1 of the first lens group LG1 is calculated using the following formula: O=[(a-b)/h]·100%. For example, in this embodiment, O may be greater than 50%, but the invention is not limited thereto.

FIG4 schematically illustrates a projection screen formed on a projection surface by an image beam according to an embodiment of the present invention. Referring to FIG1 , FIG2 and FIG4 , in this embodiment, the light valve LV converts the illumination beam ILB into an image beam IMB, which sequentially passes through the first lens group LG1, passes through the aperture AS, passes through the light incident surface RP3 of the second lens group LG2, is reflected by the reflection surface RP2 of the second lens group LG2, passes through the light exit surface RP1 of the second lens group LG2, and forms a projection screen IM on the projection surface PS (i.e., the paper surface of FIG4 ); the two opposite sides IMa and IMb of the projection screen IM are parallel to each other and have a length A and a length B respectively in a direction x, and the projection screen IM has a maximum width W in the direction x, [(B-A)/W]·100%=T, and |T|<1%. In short, in this embodiment, the trapezoidal distortion of the projection screen IM is less than 1%.

The following is an example of the projection device 100. It should be noted that the data listed in Tables 1 to 3 below are not intended to limit the present invention, and any person skilled in the art may make appropriate changes to the parameters or settings after referring to the present invention, but they should still fall within the scope of the present invention.

[Table I]

Table 1 lists various parameters of the projection device 100 of an embodiment of the present invention. Please refer to FIG. 2 and Table 1. The spacing in Table 1 refers to the linear distance between two adjacent surfaces on the optical axis X. For example, the spacing of the first surface L11 is the linear distance between the first surface L11 and the second surface L12 on the first optical axis X1. For the curvature radius, spacing, refractive index, Abbe number and material corresponding to each surface/element in Table 1, please refer to the corresponding values and contents of each curvature radius, spacing, refractive index, Abbe number and material in the same column. In addition, in Table 1, RP1 is the light exit surface of the second lens group LG2, RP2 is the reflection surface of the second lens group LG2, RP3 is the light incident surface of the second lens group LG2, L11 is the first surface of the first lens L1 facing the second lens group LG2, L12 is the second surface of the first lens L1 facing the light valve LV, ASa is the light cross section of the aperture AS, L21 is the first surface of the second lens L2 facing the second lens group LG2, L22 is the second surface of the second lens L2 facing the light valve LV, L31 is the first surface of the third lens L3 facing the second lens group LG2, L41 is the first surface of the fourth lens L4 facing the second lens group LG2, and L42 is the second surface of the fourth lens L4 facing the light valve LV. , L51 is the first surface of the fifth lens L5 facing the second lens group LG2, L52 is the second surface of the fifth lens L5 facing the light valve LV, L61 is the first surface of the sixth lens L6 facing the second lens group LG2, AC1 is the first surface of the flat glass actuator AC facing the second lens group LG2, AC2 is the second surface of the flat glass actuator AC facing the light valve LV, PR1 is the first surface of the light combining element PR facing the second lens group LG2, PR2 is the second surface of the light combining element PR facing the light valve LV, CG1 is the first surface of the protective cover CG facing the second lens group LG2, CG2 is the second surface of the protective cover CG facing the light valve LV, and LVa is the light receiving surface of the light valve LV.

Referring to FIG. 2 and Table 1, in this embodiment, the first lens L1 may be a free-form surface lens. Specifically, the first surface L11 of the first lens L1 facing the second lens group LG2 may be a free-form surface, and the second surface L12 of the first lens L1 facing the light valve LV may be an aspherical surface. In this embodiment, the second lens L2 may be a spherical lens. The first surface L21 of the second lens L2 facing the second lens group LG2 and the second surface L22 of the second lens L2 facing the light valve LV may both be spherical surfaces.

In this embodiment, the third lens L3 may be a spherical lens. A first surface L31 of the third lens L3 facing the second lens group LG2 and a second surface L32 of the third lens L3 facing the light valve LV may both be spherical surfaces. In this embodiment, the fourth lens L4 may be a spherical lens. A first surface L41 of the fourth lens L4 facing the second lens group LG2 and a second surface L42 of the fourth lens L4 facing the light valve LV may both be spherical surfaces. In addition, in this embodiment, the second surface L32 of the third lens L3 and the first surface L41 of the fourth lens L4 may be bonded together, so that the third lens L3 and the fourth lens L4 form a double bonded lens.

In this embodiment, the fifth lens L5 may be an aspherical lens. Specifically, a first surface L51 of the fifth lens L5 facing the second lens group LG2 and a second surface L52 of the fifth lens L5 facing the light valve LV may both be aspherical surfaces.

The second surface L12 of the first lens L1, the first surface L51 of the fifth lens L5, and the second surface L52 of the fifth lens L5 are even-order aspheric surfaces. The even-order aspheric surfaces can be expressed by the following formula:

In the formula, Z is the offset (sag) in the direction of the optical axis X, c is the reciprocal of the radius of the osculating sphere, that is, the reciprocal of the radius of curvature close to the optical axis X (such as the radius of curvature in Table 1). k is the quadratic coefficient (conic), r is the aspheric height, that is, the height from the center of the lens to the edge of the lens, and A ₂ , A ₄ , A ₆ , A ₈ , ... are aspheric coefficients. Table 2 lists the quadratic coefficients and aspheric coefficients of the second surface L12 of the first lens L1, the first surface L51 of the fifth lens L5, and the second surface L52 of the fifth lens L5.

[Table II]

Referring to FIG. 2 and Table 1, in this embodiment, the light emitting surface RP1 of the second lens group LG2, the reflecting surface RP2 of the second lens group LG2, the light incident surface RP3 of the second lens group LG2, and the first surface L11 of the first lens L1 are free-form surfaces, and the free-form surfaces can be expressed by the following formula:

Where Z is the depth of the optical surface, r is the radius of curvature, k is the conic constant, Φ is the lens aperture, and C _mn is the coefficient of the xy polynomial. The corresponding free-form surface can be established by the curvature radius in Table 1, the coefficient of the x ^m y ⁿ polynomial in Table 3, and the corresponding expansion above.

[Table 3]

In this embodiment, the projection lens PL has a large half-viewing angle; that is, the projection lens PL has a small projection ratio and can project a wide projection image within a short projection distance. For example, in this embodiment, the half-viewing angle of the projection lens PL may be greater than 45°, but the present invention is not limited thereto.

FIG5 is a modulation transfer function diagram of the projection lens of FIG2. The modulation transfer function diagram (MTF) of FIG5 can be used to evaluate the performance of the projection lens PL, and the diagrams shown in FIG5 are all within the standard range. It can be verified that the projection lens PL of this embodiment can achieve a good imaging effect.

Fig. 6 schematically depicts a projection image on the projection surface of the projection device of Fig. 1. The shape of the projection image IM shown in Fig. 6 is close to a rectangle. It can be verified from Fig. 6 that the projection device 100 can effectively improve the keystone distortion by using the asymmetric free-form surface of the optical element of the projection lens PL (for example, at least one of the light exit surface RP1, the reflection surface RP2 and the light entrance surface RP3 of the second lens group LG2).

In summary, a projection device and a projection lens according to an embodiment of the present invention include a first lens group disposed between a reduction side and an enlargement side, a second lens group disposed between the first lens group and the enlargement side, and an aperture disposed between the first lens group and the second lens group. The second lens group has a light incident surface, a reflection surface, and a light exit surface, the light incident surface faces the first lens group, the light exit surface faces the projection surface, and the light incident surface, the light exit surface, and the first lens group are disposed on the same side of the reflection surface. The light valve is used to provide an image beam. The image beam sequentially passes through the first lens group, passes through the aperture, passes through the light incident surface of the second lens group, is reflected by the reflection surface of the second lens group, and passes through the light exit surface of the second lens group to be transmitted to the projection surface. In particular, at least one of the light incident surface, the reflection surface, and the light exit surface of the second lens group is a free-form surface, and the first optical axis of the first lens group does not overlap with the center of the image beam. In this way, the projection lens can have a common optical path design. Since the projection lens has a common optical path design, the image beam reflected by the reflection surface of the second lens group back to the first lens group is less likely to cause interference, and the distance between the aperture and the reflection surface of the second lens group can be shortened. When the distance between the aperture and the reflection surface of the second lens group is shortened, the optical effective diameter of the reflection surface of the second lens group will not be too large. In this way, the overall thickness and volume of the projection lens can be effectively reduced.

The above description is only the preferred embodiment of the present invention, and it cannot be used to limit the scope of the implementation of the present invention. That is, all simple equivalent changes and modifications made according to the claims and the description of the present invention are still within the scope of the patent coverage of the present invention. In addition, any embodiment or claim of the present invention does not need to achieve all the purposes, advantages or features disclosed by the present invention. In addition, the abstract and the name of the invention are only used to assist in the retrieval of patent documents, and are not used to limit the scope of rights of the present invention. In addition, the terms "first", "second", etc. mentioned in this specification or claims are only used to name the name of the element or distinguish different embodiments or scopes, and are not used to limit the upper or lower limit of the number of elements.

Reference numerals list

100: Projection device

A, B: Length

a, b: distance

AC1, CG1, L11, L21, L31, L41, L51, PR1: First surface

AC2, CG2, L12, L22, L32, L42, L52, PR2: Second surface

AC: Flat Glass Actuator

AS: Aperture

Asa: light cross section

CG: Protective cover

CA: Optical effective diameter

D: Maximum distance

GD: Ground

H:Thickness

h: height

H1, H2: Maximum distance

IM: Projection screen

IMa, IMb: edge

IMe:Edge

IMB: Image beam

IMB1: First marginal ray

IMB2: Second marginal ray

IMBc: Center

ILB: Illumination beam

ILS: Lighting System

LG1: First mirror group

LG2: Second mirror group

LV: Light Valve

LVa: light receiving surface

LVe: Edge

LVp: point

L1, L2, L3, L4, L5: Lens

PJT: Projector

PL: Projection lens

PR: Light combining element

PS: Projection surface

RP1: light-emitting surface

RP2: Reflective surface

RP3: Light incident surface

W: Maximum width

X1: First optical axis

x, y, z, d1, d2: direction

θ: angle.

Claims (12)

1. A projection lens, characterized in that it is used to image a light valve arranged on a reduction side onto a projection surface arranged on an enlargement side, the light valve and the projection surface have an angle, and the projection lens comprises a first lens group, a second lens group and an aperture, The first lens group is disposed between the reduction side and the magnification side and has a first optical axis; The second lens group is arranged between the first lens group and the magnifying side, wherein the second lens group at least has a light incident surface, a reflection surface and a light emitting surface, the light incident surface faces the first lens group, the light emitting surface faces the projection surface, the light incident surface, the light emitting surface and the first lens group are arranged on the same side of the reflection surface, and at least one of the light incident surface, the reflection surface and the light emitting surface is a free-form surface; The aperture is arranged between the first lens group and the second lens group, wherein the light valve is used to provide an image light beam, the image light beam from the light valve sequentially passes through the first lens group, the aperture, the light incident surface of the second lens group, is reflected by the reflection surface of the second lens group and passes through the light exit surface of the second lens group to be transmitted to the projection surface, and the first optical axis of the first lens group does not pass through the center of the light valve, the aperture and the reflection surface of the second lens group have a maximum distance D in a direction parallel to the first optical axis, the light exit surface of the second lens group has an optical effective diameter CA, and CA/D<3. 2 . The projection lens according to claim 1 , wherein the second lens group comprises a turning prism, and the turning prism has the light incident surface, the reflection surface, and the light emitting surface. 3. The projection lens according to claim 1 , wherein the first lens group comprises a plurality of lenses arranged in sequence from the magnification side to the reduction side, each of the plurality of lenses has a first surface facing the second lens group and a second surface facing the light valve, and a first surface of a lens closest to the aperture stop among the plurality of lenses is a free-form surface. 4 . The projection lens according to claim 1 , wherein the image beam has an offset value relative to the first optical axis of the first lens group. 5 . The projection lens according to claim 1 , wherein the angle is θ, and 25°<θ<90°. 6. The projection lens according to claim 1 is characterized in that the image light beam forms a projection screen on the projection surface, the opposite sides of the projection screen are parallel to each other and have a length A and a length B in one direction respectively, the projection screen has a maximum width W in the direction, [(B-A)/W]·100%=T, and |T|<1%. 7. The projection lens according to claim 1, wherein the aperture and the reflection surface of the second lens group have a maximum distance D in a direction parallel to the first optical axis, the image light beam comprises a first edge ray and a second edge ray, the first edge ray is emitted from a point on an edge of the light valve in a direction away from the first optical axis, the second edge ray is emitted from the point on the edge of the light valve in a direction pointing to the first optical axis, the first edge ray in the first lens group and the first optical axis have a maximum distance H1 in a direction perpendicular to the first optical axis, the second edge ray on the light exit surface of the second lens group and the first optical axis have a maximum distance H2 in a direction perpendicular to the first optical axis, and (H1+H2)/D<3. 8. A projection device, comprising an illumination light source, a light valve, a projection surface and a projection lens, The illumination light source is used to provide an illumination light beam; The light valve is disposed at a reduction side and is used to convert the illumination light beam into an image light beam; The projection surface is arranged at an enlarged side, wherein the light valve has an angle with the projection surface; The projection lens comprises a first lens group, a second lens group and an aperture. The first lens group is disposed between the reduction side and the magnification side and has a first optical axis; The second lens group is arranged between the first lens group and the magnifying side, wherein the second lens group at least has a light incident surface, a reflection surface and a light emitting surface, the light incident surface faces the first lens group, the light emitting surface faces the projection surface, the light incident surface, the light emitting surface and the first lens group are arranged on the same side of the reflection surface, and at least one of the light incident surface, the reflection surface and the light emitting surface is a free-form surface; The aperture is disposed between the first lens group and the second lens group, wherein the image light beam from the light valve sequentially passes through the first lens group, the aperture, the light incident surface of the second lens group, is reflected by the reflection surface of the second lens group, and passes through the light exit surface of the second lens group to be transmitted to the projection surface, and the first optical axis of the first lens group does not pass through the center of the light valve, the aperture and the reflection surface of the second lens group have a maximum distance D in a direction parallel to the first optical axis, and the light exit surface of the second lens group has an optical effective diameter CA, and CA/D<3. 9 . The projection device according to claim 8 , wherein the second lens group comprises a turning prism, and the turning prism has the light incident surface, the reflection surface, and the light emitting surface. 10. The projection device according to claim 8, wherein the first lens group comprises a plurality of lenses arranged in sequence from the magnification side to the reduction side, each of the plurality of lenses has a first surface facing the second lens group and a second surface facing the light valve, and a first surface of a lens closest to the aperture stop among the plurality of lenses is a free-form surface. 11 . The projection device according to claim 8 , wherein the image light beam has an offset value relative to the first optical axis of the first lens assembly. 12. The projection device according to claim 8, wherein the aperture and the reflecting surface of the second lens group have a maximum distance D in a direction parallel to the first optical axis, the image light beam comprises a first edge ray and a second edge ray, the first edge ray is emitted from a point on an edge of the light valve in a direction away from the first optical axis, the second edge ray is emitted from the point on the edge of the light valve in a direction pointing to the first optical axis, the first edge ray in the first lens group and the first optical axis have a maximum distance H1 in a direction perpendicular to the first optical axis, the second edge ray on the light emitting surface of the second lens group and the first optical axis have a maximum distance H2 in a direction perpendicular to the first optical axis, and (H1+H2)/D<3.