Projection apparatus

Abstract

A projection apparatus. The projection apparatus comprises: a light source assembly (10), a display panel (30), a first lens (60), a reflective mirror (44), and a projection lens (50). Light emitted by the light source assembly (10) sequentially passes through the display panel (30) and the first lens (60), then is directed onto the reflective mirror (44), and is reflected by the reflective mirror (44) to the projection lens (50) to be emitted. A display area of the display panel (30) has a first central normal (A3), and the central axis of the first lens (60) is collinear with the first central normal (A3). The central axis (A2) of the projection lens (50) defines a first intersection point (P1') with the reflective mirror (44), and the first central normal (A3) defines a second intersection point (P2') with the reflective mirror (44). A second distance is provided between the first intersection point (P1') and the second intersection point (P2'). A first distance (D) is provided between the central axis (A2) of the projection lens (50) and a first optical axis (A1) passing through the second intersection point (P2'), and the first optical axis (A1) is parallel to the central axis (A2) of the projection lens (50) and is perpendicular to the first central normal (A3). The second distance is greater than the first distance (d).

Description

Projection device Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to a projection device. Background Art

[0002] A projection device is a device that can project images or videos onto a screen. It can be connected to computers, game consoles, televisions and other devices through different interfaces to play the corresponding video signals.

[0003] Projection devices are widely used in homes, offices, schools, and entertainment venues. Projection device types include CRT (Cathode Ray Tube), LCD (Liquid Crystal Display), DLP (Digital Light Processing), and 3LCD (3 Liquid Crystal Display). Single LCD projector devices offer a simple structure and low cost, making them suitable for middle and low-income groups, thus offering considerable growth potential.

[0004] Summary of the Invention

[0005] The present disclosure provides a projection device, which includes: a light source assembly, a display panel, a first lens, a reflector, and a projection lens. Light emitted by the light source assembly passes through the display panel and the first lens in sequence and then irradiates the reflector. The light is then reflected by the reflector to be emitted from the projection lens.

[0006] The display area of ​​the display panel has a first central normal, and the central axis of the first lens is collinear with the first central normal; the central axis of the projection lens and the reflector have a first intersection, the first central normal and the reflector have a second intersection, and a second distance exists between the first intersection and the second intersection; the central axis of the projection lens and a first optical axis passing through the second intersection have a first distance, and the first optical axis is parallel to the central axis of the projection lens and perpendicular to the first central normal; wherein the second distance is greater than the first distance.

[0007] In some embodiments, there is a first optical path distance between the center of the display area of ​​the display panel and the center of the projection lens; and a ratio of the first optical path distance to the first spacing is between 77 and 82.

[0008] In some embodiments, there is a first distance between the first intersection point and the center of the projection lens, and a second distance between the second intersection point and the center of the display panel; the first distance is greater than the second distance.

[0009] In some embodiments, the reflector includes a first reflective portion and a second reflective portion, wherein the first reflective portion is located at an end of the first intersection away from the display panel; and the second reflective portion is located at an end of the second intersection close to the display panel.

[0010] There is a first angle between the central axis of the projection lens and the first reflective portion.

[0011] A second angle is formed between the first center normal and the second reflecting portion, and the first angle and the second angle are complementary to each other.

[0012] In some embodiments, the first angle θ1 and the second angle θ2 satisfy: 0°≤|θ1-θ2|≤10°.

[0013] In some embodiments, the projection lens includes a condenser lens group, a stop lens group, and a divergent lens group sequentially arranged in a direction away from the display panel;

[0014] The projection lens meets at least one of the following conditions:

[0015] The sum of the focal length of the projection lens and the focal length of the first lens is greater than or equal to 2000 mm;

[0016] The ratio of the focal length of the projection lens to the diagonal length of the display area of ​​the display panel is 28 to 29;

[0017] The ratio of the focal length of the diverging lens group to the focal length of the condensing lens group is 2 to 3;

[0018] The center distance between the light incident surface and the light emitting surface of the projection lens is less than or equal to 100 mm.

[0019] In some embodiments, the projection lens includes a plurality of lenses coaxially arranged, and the Abbe number of the lens closest to the reflector and the lens farthest from the reflector are both less than 50.

[0020] In some embodiments, the projection lens includes a plurality of lenses coaxially arranged, the lens closest to the reflector has a first curved surface close to the reflector, the lens farthest from the reflector has a second curved surface close to the reflector and a third curved surface far from the reflector, the first curved surface and the third curved surface are convex, and the second curved surface is concave;

[0021] The curvature radius of the first curved surface and the curvature radius of the third curved surface are both greater than the curvature radius of the second curved surface.

[0022] In some embodiments, the ratio of the focal length of the projection lens to the entrance pupil diameter is between 2.8 and 3.3.

[0023] In some embodiments, the projection lens includes a focusing lens group, an aperture and a diverging lens group arranged in sequence along a direction away from the reflector; the diverging lens group includes multiple lenses, and the diameters of the multiple lenses in the diverging lens group gradually increase along the direction away from the aperture.

[0024] In some embodiments, the light source assembly includes: a light source, a reflective light cup, and a second lens;

[0025] The second lens is disposed between the light source and the polarizing assembly, and is used to collimate the light irradiated from the light source to the second lens;

[0026] The reflective light cup is located between the light source and the second lens, and is arranged around the optical axis of the second lens to form a cylindrical structure; the cylindrical structure has a first opening facing the light source and a second opening facing the second lens, and the area of ​​the first opening is smaller than the area of ​​the second opening.

[0027] In some embodiments, the orthographic projection of the second opening on the reference plane where the display panel is located covers and exceeds the orthographic projection of the display area on the reference plane.

[0028] In some embodiments, there is a distance of at least 0.1 mm between an edge of an orthographic projection of the second opening on the reference surface and an edge of an orthographic projection of the display area on the reference surface.

[0029] In some embodiments, the light source comprises:

[0030] Light board;

[0031] a light-emitting element provided on the light board, wherein the light-emitting element is located on a side of the light board close to the display panel;

[0032] The light-emitting surface of the light-emitting element and the display area of ​​the display panel are both rectangular, and the ratio of the diagonal length of the light-emitting surface to the diagonal length of the display area is between 0.05 and 0.15.

[0033] In some embodiments, the light source comprises:

[0034] Light board;

[0035] a light-emitting element provided on the light board, wherein the light-emitting element is located on a side of the light board close to the display panel;

[0036] In which, the light-emitting surface of the light-emitting component is rectangular; the reflective light cup includes multiple reflective walls, and the orthographic projections of different reflective walls on the second lens are located on different sides of the orthographic projection of the light-emitting surface on the second lens; the reflective surface of the reflective wall is a curved surface with a curvature between 1000 and 2000 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0038] FIG1 is a schematic diagram of an imaging light path of a projection device in an example.

[0039] FIG. 2 is a structural diagram of a projection device in an example.

[0040] FIG. 3 shows embodiments in which the off-axis ratios are 0%, 50%, and 100%.

[0041] FIG4 is a schematic diagram of an off-axis projection provided in some embodiments.

[0042] FIG5 is a schematic diagram of a projection device provided in some embodiments of the present disclosure.

[0043] FIG6 is a light path diagram of a projection device provided in some embodiments of the present disclosure.

[0044] FIG7 is a schematic diagram of a projection device provided in some other embodiments of the present disclosure.

[0045] FIG8 is a schematic diagram of a projection device provided in other embodiments of the present disclosure from another angle.

[0046] FIG. 9 is a schematic diagram of some parameters of the projection device in FIG. 7 .

[0047] FIG. 10 is a schematic diagram of a first optical path distance in the projection device of FIG. 7 .

[0048] FIG11 is a diagram of the field of view when the image is not off-axis and when the image is off-axis, provided in some examples.

[0049] FIG12 is a cross-sectional view of a first lens provided in some embodiments of the present disclosure.

[0050] FIG13 is a schematic diagram of a projection lens provided in some embodiments of the present disclosure.

[0051] FIG. 14 is a light path diagram of a projection lens provided in some embodiments of the present disclosure.

[0052] FIG15 is a schematic diagram of a light source provided in some embodiments of the present disclosure.

[0053] FIG16 is a schematic diagram of a reflective light cup provided in some embodiments of the present disclosure.

[0054] FIG17 is a diagram of an illumination light path provided in some embodiments of the present disclosure.

[0055] FIG18 is a point diagram of a projection device provided in some embodiments of the present disclosure.

[0056] FIG19 is an MTF diagram of a projection lens provided in some embodiments of the present disclosure.

[0057] FIG20 is a field curvature diagram and a distortion diagram of a projection device provided in some embodiments of the present disclosure.

[0058] FIG21 is an on-axis aberration diagram of a projection device provided in some embodiments of the present disclosure.

[0059] FIG22 is a diagram of vertical axis chromatic aberration of a projection device provided in some embodiments of the present disclosure.

[0060] FIG23 is a relative illumination diagram of a projection device provided in some embodiments of the present disclosure.

[0061] FIG24 is a side view showing the 9-point uniformity of a projection screen of a projection device provided in some embodiments of the present disclosure.

[0062] FIG25 is a diagram showing an illumination simulation of a projection screen of a projection device according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0063] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0064] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0065] Unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present disclosure should have the usual meanings understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0066] As used herein, "parallel" and "perpendicular" include the conditions described and conditions similar to the conditions described, and the range of the similar conditions is within an acceptable deviation range, wherein the acceptable deviation range is determined by a person of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallelism and approximate parallelism, wherein the acceptable deviation range for approximate parallelism can be, for example, a deviation within 5°; "perpendicular" includes absolute perpendicularity and approximate perpendicularity, wherein the acceptable deviation range for approximate perpendicularity can also be, for example, a deviation within 5°.

[0067] Exemplary embodiments are described herein with reference to cross-sectional and / or plan views that are idealized exemplary drawings. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Therefore, the exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include deviations in shape due to, for example, manufacturing. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shape of regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0068] Figure 1 is a schematic diagram of the imaging optical path of a projection device in one example. Figure 2 is a structural diagram of the projection device in one example. As shown in Figure 2, the projection device is a single LCD projection device. The projection device in Figure 2 includes a light source 11, a plano-convex lens 17, a first reflector 18, a second lens 16, a polarizer 20, a display panel 30 (i.e., an LCD display panel), a first lens 60, a second reflector 41, and a projection lens 50. In Figure 2, light from the light source 11 is converged by the plano-convex lens 17 and then passes through the second lens 16 to the polarizer 20. The polarizer 20 may include a transparent substrate and a first polarizer disposed on the transparent substrate. After being polarized by the polarizer 20, polarized light in a first polarization direction is irradiated onto the display panel 30. Light emitted from the display panel 30 passes through the first lens 60 and is then reflected by the second reflector 41 to the projection lens 50. In Figure 2, the display panel 30 is imaged twice and projected onto the projection screen, forming a projection image Ima. During the first imaging, the display panel 30 serves as the object, the first lens 60 serves as the lens, and the intermediate surface M1 serves as the image. During the second imaging, the intermediate surface M1 serves as the object, the projection lens 50 serves as the imaging lens, and the projected image serves as the image.

[0069] The projection device must undergo two imaging processes, mainly because: the display area of ​​the display panel 30 is usually large in size, and the light beam needs to be converged by the first lens 60 first so that more light can pass through the projection lens. For example, when the display area size of the display panel 30 is 4.45 inches, the object height H = 4.45*25.4 / 2 = 56.515 mm, which is usually larger than the diameter of the projection lens 50. Without the first lens 60, most of the light emitted by the display panel 30, especially the light with a large off-axis amount and a large aperture angle, cannot pass through the aperture of the projection lens 50. Not only that, the light entering the projection lens 50 will also produce severe vignetting (the brightness of the projected image Ima is high in the middle and low at the edges). When the first lens 60 is used, the light emitted by each object point on the display panel 30 (especially those parallel to the optical axis) is focused through the center of the aperture, thereby ensuring that each object point has a sufficiently high brightness.

[0070] In the first imaging, the object-image relationship is as follows: the display panel 30 is the object being imaged, the first lens 60 is the imaging lens, and the intermediate surface is the virtual image of the display panel 30 (because the image point is not the point where the light rays converge, but the intersection of the reverse extension lines of the actual light rays). The thin lens imaging formula is:

[0071] Among them, -l1 represents the object distance of the display panel 30, and the sign follows the sign rule; -l1' represents the image distance of the intermediate surface M1, and the sign follows the sign rule; f1' represents the image-side focal length of the first lens 60, and the sign follows the sign rule (the lens used is a positive lens, and the image-side focal length is always positive).

[0072] In the second imaging, the object-image relationship is as follows: intermediate surface M1 is the imaged object (virtual object), projection lens 50 is the imaging lens, and the projected image is the real image of intermediate surface M1 (because it is the point where the actual light rays converge). According to the imaging formula of an ideal optical system (Newton's formula):

[0073] Wherein, -l2 represents the object distance of the intermediate surface M1, and the sign follows the sign rule; l2' represents the image distance of the projection image Ima, and the sign follows the sign rule; f2' represents the image-side focal length of the projection lens 50; and f2 represents the object-side focal length of the projection lens 50. Since both ends of the projection lens 50 are in the air medium, according to the formula of optical power: -f2=f′2 Equation 3

[0074] Therefore, we can get the imaging formula result similar to that of thin lens:

[0075] To calculate the imaging optical path, first determine the distance -l1 between the first lens 60 and the display panel, as well as the focal length f1' of the first lens 60. Based on the thin lens imaging formula, the image distance l1' can be calculated, and the magnification of the first lens 60 can be calculated as β1 = l1' / l1. Based on the total magnification β of the optical path, the magnification β2 of the projection lens 50 is determined as β / β1. Based on the projection size and projection ratio, the width of the projected image is determined to be 2h3. Determine l2' based on the throw ratio R. Determine l2 based on the lens magnification. Based on the imaging formula, the focal length of the lens can be calculated.

[0076] According to calculation, β1>0, so the first imaging is an upright image. β2<0, so the second imaging is an inverted image.

[0077] Throw ratio refers to the ratio of projection distance to the width of the projected image. The smaller the throw ratio, the shorter the focal length of the imaging system.

[0078] In this field, the object-side telecentric optical path means that the image of the aperture on the object side (i.e., the "pupil") is at object infinity. This means that light emitted from object infinity (i.e., light parallel to the optical axis) can pass through the center of the aperture (light emitted in the main direction of the illumination system passes through the center of the aperture, is less blocked by the aperture, has a slight vignetting effect, and has high light utilization efficiency and high brightness of the projected image). Generally speaking, the aperture refers to the aperture of the entire imaging system (including the front Fresnel lens), but here it refers to the aperture of the projection lens 50. This is because the aperture of the projection lens 50 mainly limits the aperture angle of the light, while the front Fresnel lens does not limit the aperture angle of the light (otherwise the light utilization efficiency would be even lower).

[0079] It should be noted that in the simulation, the object and image dimensions of the imaging optical path are reversed from reality. That is, the projected image is the object, and the display panel 30 is the image. This is done for the following reasons: the size of the display panel 30 is constant, while the size of the projected image can vary, for example, from 40 to 100 inches. This reversed optical path ensures that the image height (i.e., field of view) remains constant, eliminating the need to adjust the field of view and significantly modify the simulation model every time the projected image size changes.

[0080] Therefore, in simulation, the previous "object-space telecentric optical path" becomes a "image-space telecentric optical path," and the previous requirement of "entrance pupil center at object-space infinity" becomes "exit pupil center at object-space infinity." The "exit pupil" is the image of the aperture in image space. Because the optical path is reversible, there is no substantial change in the light before and after reversing the object-image space analysis.

[0081] Typically, single-LCD projection systems require an object-space telecentric optical path because it maximizes light utilization. In lens design, the object-image space is often inverted, resulting in an "image-space telecentric optical path." The so-called object-space telecentric optical path means that the center of the entrance pupil is at infinity in the object space. The entrance pupil is the image of the aperture on the object space. The aperture is the primary factor influencing the aperture angle of the on-axis object point in an optical imaging system. It is the aperture at the point where the radius is smallest when the light beam passes through the lens. The aperture angle refers to the angle between the light beam and the optical axis. Generally, larger aperture angles result in greater light aberrations.

[0082] In an optical system, the ray passing through the center of the aperture is called the "chief ray." The chief ray also passes through the center of the pupil. If the chief ray passes through the center of the entrance pupil, and the entrance pupil is at infinity, it is an object-side telecentric optical path. If the chief ray passes through the center of the exit pupil, and the exit pupil is at infinity, it is an image-side telecentric optical path.

[0083] Off-axis projection is one of the important functions of a projector. In a projection system, the center of the image can be set as point A, and the intersection of the screen normal through the optical center of the projection lens and the screen is point B. When points AB coincide, it is a non-off-axis projection (the off-axis rate is 0%). When points AB do not coincide, it is an off-axis projection. The distance between AB is called "offset". In practice, the focus is generally on the off-axis projection in the height direction, and the "off-axis rate" (Par., i.e., partial axial ratio) can be defined as the ratio of Offset to the half-height of the image, that is:

[0084] FIG3 shows embodiments with off-axis ratios of 0%, 50%, and 100% respectively; wherein, when the off-axis ratio is 50%, the off-axis amount is 1 / 4 of the picture height; and when the off-axis ratio is 100%, the off-axis amount is 1 / 2 of the picture height.

[0085] In some examples, off-axis projection can be achieved by changing the direction of light deflection. Figure 4 is a schematic diagram of off-axis projection provided in some embodiments. During non-off-axis projection, the normal of the reflector 44 forms an angle of 45° with the normal to the screen. Light emitted from the center of the first lens 60, after being reflected by the reflector, passes through the optical axis of the projection lens 50 (at this point, the optical axis of the projection lens 50 is perpendicular to the screen), and is incident perpendicularly on the screen. At this point, points AB coincide, and the off-axis ratio is 0. When the reflector 44 is rotated by an angle α (e.g., counterclockwise), light emitted from the center of the first lens 60, after being reflected by the reflector 44, passes through the optical axis of the projection lens 50 (at this point, the optical axis of the projection lens 50 forms an angle of θ with the normal to the screen), and is incident obliquely on the screen. At this point, points AB do not coincide. Alternatively, the projection device may be provided with a height-adjustable support leg at the bottom of the projection device to achieve tilted projection. The effect of rotating the projection lens 50 can also be achieved by rotating the entire projection device by an angle. In principle, the flat reflector 44 is an ideal optical imaging device that only changes the direction of light propagation without altering the system's magnification or image quality. The overall effect of adjusting the tilt angle using the support legs and the reflector 44 is to create an elevation angle for the projection lens. Therefore, there is no essential difference between adjusting the tilt angle using the support legs and the reflector 44.

[0086] Figure 5 is a schematic diagram of a projection device provided in some embodiments of the present disclosure, Figure 6 is an optical path diagram of a projection device provided in some embodiments of the present disclosure, Figure 7 is a schematic diagram of a projection device provided in other embodiments of the present disclosure, Figure 8 is a schematic diagram of another angle of the projection device provided in other embodiments of the present disclosure, Figure 9 is a schematic diagram of some parameters in the projection device of Figure 7, Figure 10 is a schematic diagram of the first optical path distance in the projection device of Figure 7, Figure 11 is a field of view diagram when not off-axis and when off-axis provided in some examples, Figure 12 is a cross-sectional view of a first lens provided in some embodiments of the present disclosure, Figure 13 is a schematic diagram of a projection lens provided in some embodiments of the present disclosure, and Figure 14 is an optical path diagram of a projection lens provided in some embodiments of the present disclosure.

[0087] The projection device in the disclosed embodiment is used to implement off-axis projection. As shown in Figures 5 to 7, the projection device includes a light source assembly 10, a display panel 30, a first lens 60, and a projection lens 50. Light emitted by the light source assembly 10 is sequentially emitted through the display panel 30, the first lens 60, and the projection lens 50.

[0088] The display area of ​​the display panel 30 has a first center normal A3, which is collinear with the central axis of the first lens 60. The first center normal A3 is a line passing through the center of the display area and perpendicular to the display panel 30. The display panel 30 and the projection lens 50 employ an off-axis design. This off-axis design means that light emitted along the first center normal A3 can enter the projection lens 50 along the first optical axis A1 shown in Figures 5 and 9. The first optical axis A1 is parallel to the central axis of the projection lens 50, and there is a non-zero first distance d between the two.

[0089] It should be noted that the first optical axis A1 is the axis along which a light ray perpendicularly emitted from the center of the display panel 30 coincides with the incident light ray when it enters the projection lens 50. For the structure of FIG5 , where no reflector 44 is disposed between the display panel 30 and the projection lens 50, the first optical axis A1 is the first center normal A3 of the display panel 30. For the structure of FIG7 , where a reflector 44 is disposed between the display panel 30 and the projection lens 50, the first optical axis A1 can be considered the axis along which a light ray perpendicularly emitted from the center of the display panel 30 is reflected by the reflector 44 toward the projection lens 50.

[0090] For the structure of Figure 6, during non-off-axis projection, the central axis of the projection lens 50 and the central axis of the display panel 30 are coaxial, that is, the first spacing = 0. At this time, the light emitted from the center of the display panel 30 passes through the central axis of the projection lens 50 and is vertically irradiated on the screen. Points AB coincide with each other, and the off-axis rate is 0. When the projection lens 50 is raised to a height d>0, the virtual image of the display panel 30 (middle surface M1) is lowered by d relative to the central axis of the projection lens 50. The object height of the virtual image center O is lowered by d compared to the central axis of the projection lens 50. If the magnification of the projection lens 50 is β, then there is an offset Offset = dβ between points A and B. Point A is the center of the projection image Ima, and point B is the intersection of the screen normal passing through the optical center of the projection lens 50 and the screen. The principle of Figure 8 is the same as that of Figure 6, and will also cause a certain offset in the projection image Ima.

[0091] In the embodiment shown in FIG7 , the projection device further includes a reflector 44, which is disposed on the side of the first lens 60 away from the display panel 30 and is configured to reflect light emitted from the first lens 60 toward the projection lens 50. The provision of the reflector 44 makes the projection device more compact. The central axis A2 of the projection lens 50 and the reflector 44 have a first intersection P1'. The first central normal A3 of the display panel 30 and the reflector 44 have a second intersection P2'. In this case, the first optical axis A1 can be considered as an axis passing through the second intersection A2 and the projection lens 50 and perpendicular to the first central normal A3. In FIG7 , the central axis A2 of the projection lens 50 is parallel to the first optical axis A1, and the first distance d is also present between the central axis A2 of the projection lens 50 and the first optical axis A1. Furthermore, a second distance exists between the first intersection P1' and the second intersection P2', which is greater than the first distance, to achieve off-axis projection.

[0092] The object-image relationship of the off-axis optical path and the coaxial optical path is the same, and the above imaging relationship (calculation) is applicable to off-axis imaging.

[0093] In one example, the display area of ​​the display panel 30 has a diagonal of 5 inches, the projection lens 50 is designed with a 50% off-axis design, a throw ratio of 1.25, the closest distance between the projection lens 50 and the first lens 60 is 135 mm, the projection image has a 90-inch cross-section, the distance between the first lens 60 and the display panel 30 is 9 mm, and the thickness of the first lens 60 is 1.8 mm. The distance between the first center normal A3 of the display panel 30 and the central axis A2 of the projection lens 50 is 1 / 4 of the width of the display panel 30, i.e., the off-axis ratio is 50%. Figure 11 shows the field of view diagrams for non-off-axis and off-axis conditions provided in some examples. 30a in Figure 11 shows the position of the display panel 30 when not off-axis, and 30b shows the position of the display panel 30 after 50% off-axis. As shown in Figure 11, for a display panel 30 with a display area of ​​5 inches, the radius of the field of view IA1 when not off-axis is 63.5 mm, and the radius of the field of view IA2 after 50% off-axis is 72.5 mm. In other words, for the non-eccentric case (i.e., the first center normal of the display panel 30 is collinear with the center axis A2 of the projection lens 50, that is, the light emitted vertically from the center of the display panel 30 can be incident on the projection lens 50 along the center axis A2 of the projection lens 50), the projection lens 50 needs to receive light with a field of view with a radius of 63.5 mm; for the eccentric case (i.e., there is a non-zero first spacing between the first center normal A3 of the display panel 30 and the center axis A2 of the projection lens 50), the projection lens 50 needs to receive light with a field of view with a radius of 72.5 mm.

[0094] It can be seen that when the display panel 30 and the projection lens 50 of the projection device adopt an off-axis design, the projection lens 50 needs to receive light with a larger field of view in order to meet the projection requirements.

[0095] In the disclosed embodiment, a first optical path distance exists between the center of the display panel 30 and the center of the projection lens 50. The first optical path distance refers to the length of the optical path traversed by light emitted from the center of the display panel 30 and capable of entering the center of the projection lens 50. For example, for the structure of FIG5 , the first optical path distance is equal to or approximately equal to the straight-line distance from the center of the display panel 30 to the projection lens 50. For the structure of FIG7 , light emitted from the center of the display panel 30 illuminates point M of the reflector 44, is reflected by the reflector 44, and then enters the center of the projection lens 50. The first optical path distance is the sum of the distance L4 from the center of the display panel 30 to point M and the distance L3 from point M to the center of the projection lens 50.

[0096] The ratio of the first optical path distance (L4+L3) to the first spacing d is between 77 and 82, so that the projection lens 50 can receive light with a large field of view to meet the requirements of off-axis projection while preventing the projection device from being too large.

[0097] For example, the ratio of the first optical path distance (L4+L3) to the first spacing d is between 77 and 79, or between 78 and 80, or between 80 and 82.

[0098] In some embodiments, the projection device further includes a first lens 60 located on the light-emitting side of the display panel 30. Light emitted from the display panel 30 sequentially passes through the first lens 60 and the projection lens 50. The first lens 60 is a Fresnel lens, also known as a front Fresnel lens, which is used to focus the received light. FIG12 is a cross-sectional view of the first lens 60 provided in some embodiments of the present disclosure. As shown in FIG12, the first lens 60 can optionally be a Fresnel lens having a serrated surface 60s. The use of a Fresnel lens can prevent large spherical aberrations and aberrations at the lens edge, thereby improving imaging quality.

[0099] As shown in Figures 13 and 14, the projection lens 50 includes a condenser lens group 5a, an aperture 5c, and a diverging lens group 5b, which are sequentially arranged in a direction away from the reflector 44. The condenser lens group 5a is used to converge the light emitted by the display panel 30. The converged light passes through the aperture and is then directed to the diverging lens group 5b. The diverging lens group 5b is used to diverge the received light. Both the condenser lens group 5a and the diverging lens group 5b can include multiple lenses, thereby improving the light modulation effect and thereby enhancing the imaging quality.

[0100] In some embodiments, the projection lens 50 satisfies at least one of the following conditions 1 to 4, so that the projection lens 50 can better project the received light onto the screen, meeting the requirements of off-axis projection.

[0101] Condition 1: The sum of the focal lengths of the projection lens 50 and the first lens 60 is greater than or equal to 2000 mm, that is, the projection device realizes an object-side telecentric optical path.

[0102] Condition 2: The ratio of the focal length of the projection lens 50 to the diagonal length of the display area of ​​the display panel 30 is 28-29.

[0103] Condition 3: The ratio of the focal length of the diverging lens group 5b to the focal length of the condensing lens group 5a is 2-3.

[0104] Condition 4: The center distance between the light incident surface and the light emitting surface of the projection lens 50 is less than or equal to 100 mm.

[0105] In one example, the projection lens 50 satisfies the above conditions one to four simultaneously, so as to ensure that the projection lens 50 can project substantially all of the received light of a large field of view onto the screen, thus meeting the requirements of off-axis projection.

[0106] In some embodiments, the projection lens 50 includes a plurality of lenses coaxially arranged, and the Abbe numbers of the lens closest to the display panel 30 and the lens farthest from the display panel 30 are both less than 50. In the projection lens 50, the lens closest to the display panel 30 is the lens used to receive light from the display panel 30, and the lens farthest from the display panel 30 is the lens that ultimately projects light onto the projection screen. The Abbe numbers of these two lenses are both less than 50, that is, they have a smaller Abbe number, that is, a larger refractive index, which can increase the degree of light deflection, thereby facilitating the projection lens 50 to project as much light as possible from a large field of view onto the projection screen.

[0107] In one example, the Abbe number of the lens closest to the display panel 30 is 45.5-46.5, and the refractive index is 1.75-1.85; the Abbe number of the lens farthest from the display panel 30 is 35.8-36.8, and the refractive index is 1.57-1.67.

[0108] In some embodiments, the projection lens 50 includes multiple coaxially arranged lenses. The lens closest to the display panel 30 has a first curved surface S1 close to the display panel 30, and the lens farthest from the display panel 30 has a second curved surface S2 close to the display panel 30 and a third curved surface S3 far from the display panel 30. The first curved surface S1 and the third curved surface S3 are convex, while the second curved surface S2 is concave. The curvature radii of the first curved surface S1 and the third curved surface S3 are both greater than the curvature radius of the second curved surface S2. This ensures that the overall light incident and light exit surfaces of the projection lens 50 have sufficiently large curvature radii, which helps the projection lens 50 project as much light as possible across a wide field of view onto the projection screen.

[0109] In some embodiments, as shown in Figures 7 and 9, a reflector 44 is disposed on the light-emitting side of the display panel 30, specifically on the side of the first lens 60 away from the display panel 30, to reflect the light emitted by the first lens 60 toward the projection lens 50. The provision of the reflector 44 can make the projection device more compact. A first distance L1 exists between the first intersection point P1' and the center of the projection lens 50; a second distance L2 exists between the second intersection point P2' and the center of the display panel 30. The first distance L1 is greater than the second distance L2.

[0110] Due to process limitations, the edge of the first lens 60 does not ideally modulate the light emitted from the display panel 30. This light can be considered stray light. When the first distance L1 is greater than the second distance L2, the distance between the reflector and the projection lens 50 can be increased. For stray light at a certain tilt angle, the farther the projection lens 50 is from the reflector, the further the stray light's incident position on the projection lens 50 deviates from its optical axis. This facilitates absorption of this stray light by the aperture 5c, improving image quality.

[0111] As shown in FIG9 , the reflector 44 includes a first reflective portion 441 and a second reflective portion 442. The first reflective portion 441 is located at the end of the first intersection P1′ away from the display panel 30; the second reflective portion 442 is located at the end of the second intersection P2′ closer to the display panel 30. A first angle θ1 is formed between the central axis of the projection lens 50 and the first reflective portion 441, and a second angle θ2 is formed between the first central normal A3 of the display panel 30 and the second reflective portion 442. The first angle θ1 and the second angle θ2 are complementary to each other, facilitating off-axis projection.

[0112] In one example, 0°≤|θ1-θ2|≤10°, so as to reduce the difference between the first angle θ1 and the second angle θ2, thereby making the optical axis of the projection lens 50 as perpendicular as possible to the projection screen, thereby reducing the trapezoidal distortion of the projection image.

[0113] For example, θ1=θ2=45°, at which point the optical axis of the projection lens 50 is perpendicular to the projection screen.

[0114] In some embodiments, the projection lens 50 includes a focusing lens group 5a, an aperture 5c, and a diverging lens group 5b, which are arranged in sequence along a direction away from the reflector 44; the diverging lens group 5b includes multiple lenses, and the diameters of the multiple lenses in the diverging lens group 5b gradually increase along the direction away from the aperture 5c to ensure that the projection lens 50 can project as much light as possible onto the screen to form a large-size projection image.

[0115] The larger the ratio of the focal length of the projection lens 50 to the entrance pupil diameter (i.e., the aperture coefficient of the projection lens 50, also known as the F-number), the better the image quality; however, in this case, the aperture 5c is smaller, resulting in lower projection brightness; while if the ratio of the focal length to the entrance pupil diameter is smaller, the aperture 5c is larger, the projection brightness is higher, but the image quality is poorer. To improve image quality and projection brightness, the F-number of the projection lens 50 in the embodiment of the present disclosure is between 2.8 and 3.3 to meet the high brightness requirement of 500 lm projection brightness. The aperture 5c can be set to between 40 and 50 mm.

[0116] The so-called entrance pupil refers to the image of the aperture 5c on the object side.

[0117] In one example, according to the above formulas 1 to 4, the distance between the first lens 60 and the display panel 30 is -l1=9, and the focal length f1' of the first lens 60 is 135. According to the thin lens imaging formula, the image distance l1'=-9.64 can be calculated, so the magnification of the first lens 60 is β1=l1' / l1=1.07. The total magnification of the optical path β=-90 / 5=-18. Therefore, the magnification of the projection lens 50 is β2=β / β1=-16.8. According to the projection size of 90 inches and the projection ratio of 16:9, the width of the projected image is 2h3=1992mm. The projection ratio R is 1.25, and according to its definition, it can be obtained that: l2'=2490, R=l2' / (2h3). According to the magnification of the projection lens 50, it can be deduced that: l2=l2' / β2=-148.2. According to the imaging formula, the focal length of the projection lens 50 can be calculated: f2′=139.87. In one example, the F number of the projection lens 50 is 3.0, and the diameter of the aperture 5 c is 46 mm.

[0118] In some embodiments, as shown in Figures 13 and 14, the focusing lens group 5a includes: a first lens 51, a second lens 52, a third lens 53, a fourth lens 54, and a fifth lens 55, arranged in sequence along a direction approaching the diverging lens group 5b. In one example, the first lens 51 is a concave-convex lens. Its surface away from the aperture 5c (i.e., the light incident surface of the entire projection lens 50) is convex, and the surface of the first lens 51 near the aperture 5c is concave. Both the convex and concave surfaces of the first lens 51 are curved away from the second lens 52. The first lens 51 converges light from the display panel 30 entering the projection lens 50. The second lens 52 is a biconcave mirror; the third lens 53 and the fourth lens 54 are bonded together and are used to correct residual light aberrations. The third lens 53 is a biconvex mirror, the fourth lens 54 is a biconcave mirror, and the fifth lens 55 is a biconvex mirror, further converging the light.

[0119] In some embodiments, the diverging lens group 5b includes a sixth lens 56, a seventh lens 57, and an eighth lens 58. In one example, the sixth lens 56, the seventh lens 57, and the eighth lens 58 are all convex-concave lenses, with the convex and concave surfaces of the sixth lens 56, the seventh lens 57, and the eighth lens 58 all curved away from the fifth lens 55. The sixth lens 56 is a concave-convex lens that initially diverges light passing through the aperture 5c; the seventh lens 57 is a concave-convex lens that also diverges light. The degree of light divergence of the seventh lens 57 and the sixth lens 56 can be different.

[0120] The embodiment of the present disclosure can improve the modulation effect of the light emitted from the display panel 30 by disposing a larger number of lenses in the projection lens 50, thereby improving the imaging quality of the projection device.

[0121] In order to increase the transmittance of the projection lens 50 , an anti-reflection film may be provided on the surface of each lens close to the reflector 44 and the surface away from the reflector 44 , and the transmittance of each lens is greater than 98%.

[0122] In one example, the refractive index of the first lens 51 is between 1.75 and 1.85, and the Abbe number is between 45.5 and 46.5; the refractive index of the second lens 52 is between 1.6 and 1.7, and the Abbe number is between 32.8 and 33.8; the refractive index of the third lens 53 is between 1.64 and 1.74, and the Abbe number is between 54.0 and 55.0; The refractive index of the fourth lens element 54 is between 1.85 and 1.95, and the Abbe number is between 30.8 and 31.8. The refractive index of the fifth lens element 55 is between 1.95 and 2.05, and the Abbe number is between 24.9 and 25.9. The refractive index of the sixth lens element 56 is between 1.62 and 1.72, and the Abbe number is between 31.6 and 32.6. The refractive index of the seventh lens element 57 is between 1.86 and 1.96, and the Abbe number is between 34.7 and 35.7. The refractive index of the eighth lens element 58 is between 1.57 and 1.67, and the Abbe number is between 35.8 and 36.8. By designing the refractive index and Abbe number of each lens element as described above, the image quality and brightness uniformity of the projected image can be improved.

[0123] In one example, the spherical radius of the concave surface of the first lens 51 is between 215 and 225 mm, for example, 215 mm, 218.5 mm, 219.8 mm, 221.3 mm, 223 mm, or 225 mm; the spherical radius of the convex surface of the first lens 51 is between 70 mm and 80 mm, for example, 70 mm, 75 mm, 77 mm, 77.6 mm, or 80 mm; the center thickness of the first lens 51 is between 3.9 and 4.1 mm, for example, 3.9 mm, 4 mm, or 4.1 mm. The diameter of the first lens 51 is between 51.5 and 52.5 mm, for example, 51.5 mm, 52 mm, or 52.5 mm.

[0124] The spherical radius of the concave surface of the second lens 52 away from the first lens 51 is between 61 and 63 mm, for example, 61 mm, 61.6 mm, 62.1 mm, or 63 mm. The spherical radius of the concave surface of the second lens 52 close to the first lens 51 is between 106 mm and 108 mm, for example, 106 mm, 106.4 mm, 106.7 mm, 107.5 mm, or 108 mm. The center thickness of the second lens 52 is between 2.4 and 2.6 mm, for example, 2.4 mm, 2.5 mm, or 2.6 mm. The diameter of the second lens 52 is between 50 and 51 mm, for example, 50 mm, 50.3 mm, 50.7 mm, or 51 mm.

[0125] The spherical radius of the convex surface of the third lens 53 away from the first lens 51 is between 42.5 and 43.5 mm, for example, 42.5 mm, 43.1 mm, or 43.5 mm. The spherical radius of the convex surface of the third lens 53 close to the first lens 51 is between 47 and 48 mm, for example, 47 mm, 47.4 mm, 47.8 mm, or 48 mm. The center thickness of the third lens 53 is between 13.1 and 13.3 mm, for example, 13.1 mm, 13.2 mm, or 13.3 mm. The diameter of the third lens 53 is between 46 and 47 mm, for example, 46 mm, 46.4 mm, 46.7 mm, or 47 mm.

[0126] The spherical radius of the concave surface of the fourth lens 54 away from the first lens 51 is between 148 and 150 mm, for example, 148 mm, or 148.7 mm, or 149.2 mm, or 149.8 mm, or 150 mm. The spherical radius of the concave surface of the fourth lens 54 close to the first lens 51 is between 43 and 44 mm; wherein, the spherical radii of the two surfaces of the fourth lens 54 and the third lens 53 close to each other can be equal. The center thickness of the fourth lens 54 is between 2.4 and 2.6 mm, for example, 2.4 mm, or 2.5 mm or 2.6 mm. The diameter of the fourth lens 54 is between 46 and 47 mm. wherein, the fourth lens 54 can be equal to the diameter of the third lens 53.

[0127] The spherical radius of the convex surface of the fifth lens 55 away from the first lens 51 is between 87.5 and 88.5 mm, for example, 87.5 mm, 88.1 mm, or 88.5 mm. The spherical radius of the convex surface of the fifth lens 55 close to the first lens 51 is between 142.5 and 144.5 mm, for example, 142.5 mm, 143.3 mm, 143.8 mm, or 145.5 mm. The center thickness of the fifth lens 55 is between 6.0 and 6.2 mm, for example, 6 mm, 6.1 mm, or 6.2 mm. The diameter of the fifth lens 55 is between 46.5 and 47.5 mm, for example, 46.5 mm, 47 mm, or 47.5 mm.

[0128] The spherical radius of the convex surface of the sixth lens 56 is between 165 and 167 mm, for example, 165 mm, 165.5 mm, 166.1 mm, 166.6 mm, or 167 mm. The spherical radius of the concave surface of the sixth lens 56 is between 42 and 43 mm, for example, 42.2 mm, 42.6 mm, 42.8 mm, or 43 mm. The center thickness of the sixth lens 56 is between 11.9 and 12.1 mm, for example, 11.9 mm, 12 mm, or 12.1 mm. The diameter of the sixth lens 56 is between 57 and 58 mm, for example, 57.4 mm, 57.6 mm, 57.8 mm, or 58 mm.

[0129] The convex surface of the seventh lens 57 has a spherical radius between 54 and 55 mm, for example, 54 mm, 54.5 mm, or 55 mm. The concave surface has a spherical radius between 136 and 138 mm, for example, 136.5 mm, 136.9 mm, 137.5 mm, or 138 mm. The center thickness of the seventh lens 57 is between 9.4 and 9.6 mm, for example, 9.4 mm, 9.5 mm, or 9.6 mm. The diameter of the seventh lens 57 is between 61 and 62 mm, for example, 61.2 mm, 61.4 mm, 61.6 mm, or 61.8 mm.

[0130] The spherical radius of the convex surface of the eighth lens 58 is between 51 and 53 mm, for example, 51.5 mm, 51.9 mm, or 52.5 mm. The spherical radius of the concave surface of the eighth lens 58 is between 35 and 36 mm, for example, 35.4 mm, 35.6 mm, 35.8 mm, or 36 mm. The center thickness of the eighth lens 58 is between 3.4 and 3.6 mm, for example, 3.4 mm, 3.5 mm, or 3.6 mm. The diameter of the eighth lens 58 is between 72 and 73 mm, for example, 72.1 mm, 72.3 mm, 72.5 mm, or 72.7 mm.

[0131] In some embodiments, the light emitted by the light source assembly 10 may be natural light. It should be noted that natural light in the present disclosure refers to light that does not exhibit polarization characteristics. Specifically, the natural light emitted by the light source assembly 10 may be white light. As shown in FIG7 , the projection device may further include a polarizing assembly 20 disposed on the light-emitting side of the light source assembly 10 for converting the light emitted by the light source assembly 10 into first polarized light in a first polarization direction.

[0132] The display panel 30 is disposed on a side of the polarizing assembly 20 away from the light source assembly 10 and is configured to adjust the polarization direction of the first polarized light to emit a second polarized light. The polarization direction of the second polarized light is between the first polarization direction and the second polarization direction, wherein the first polarization direction is perpendicular to the second polarization direction.

[0133] It should be noted that the display panel 30 may include multiple pixel areas, each of which can adjust the polarization direction of the first polarized light to obtain a second polarized light having a polarization direction between the first polarization direction and the second polarization direction. It should also be noted that "between the first polarization direction and the second polarization direction" includes two critical directions, the first polarization direction and the second polarization direction. In other words, the polarization direction of the second polarized light can be the first polarization direction, the second polarization direction, or a direction between the first polarization direction and the second polarization direction and intersecting both.

[0134] The display panel 30 may be a liquid crystal display panel, specifically comprising an array substrate and a pairing substrate disposed opposite each other, and a liquid crystal layer located between the array substrate and the pairing substrate. In one example, the array substrate comprises a first base substrate, a plurality of gate lines and a plurality of data lines disposed on the first base substrate, wherein the plurality of gate lines and the plurality of data lines are intersectingly disposed to define a plurality of pixel regions, each pixel region being provided with a pixel electrode. The pairing substrate comprises a second base substrate and a common electrode disposed on the second base substrate. By applying a pixel voltage to the pixel electrode and applying a common electrode to the common electrode, an electric field is generated between the pixel electrode and the common electrode, thereby driving the deflection of the liquid crystal in the pixel region, thereby adjusting the polarization direction of the first polarized light.

[0135] In one example, the polarizing element 20 may include a stacked first polarizer and a transparent substrate. The first polarizer is located on a side of the transparent substrate away from the display panel 30 and is configured to transmit polarized light in a first polarization direction. A gap is provided between the transparent substrate and the display panel 30. In other words, a gap is provided between the transparent substrate and the display panel 30 for air flow. The first polarizer is located on a side of the transparent substrate away from the display panel 30. Thus, when light from the light source 10 is irradiated onto the polarizing element 20, it first passes through the first polarizer, thereby improving the light modulation effect of the polarizing element 20. Specifically, the first polarizer can be fixed to the surface of the transparent substrate by bonding. The transparent substrate may be a glass substrate, which provides a heat-insulating effect.

[0136] In some embodiments, the projection device may further include a second polarizer 43 , wherein the second polarizer 43 is located between the display panel 30 and the reflector 44 ; the second polarizer 43 is configured to transmit one of polarized light in the first polarization direction and polarized light in the second polarization direction, and further absorb the other of the polarized light in the first polarization direction and the polarized light in the second polarization direction. The second polarizer 43 may be attached to the surface of the display panel 30 .

[0137] The first lens 60 is disposed between the second polarizer 43 and the reflector 44. The first lens 60 is used to focus the light emitted from the second polarizer 43 and transmit the focused light to the reflector 44. The focused light is reflected by the reflector 44 into the projection lens 50 and then emitted to form a projection image.

[0138] In some embodiments, the light source assembly 10 is a collimated light source assembly for emitting collimated light, so that the light source assembly 10 can irradiate more light to the polarizing assembly 20 , thereby allowing the display panel 30 to receive more first polarized light.

[0139] It should be noted that "collimated" in the embodiments of the present disclosure refers to light with a divergence angle less than or equal to 20°. It should also be noted that the divergence angle in the embodiments of the present disclosure refers to twice the angle between the direction of the light farthest from the central axis of the emitted light beam and the central axis.

[0140] As shown in Figure 7, the light source assembly 10 includes a light source 11, a reflective cup 15, and a second lens 16. In the disclosed embodiment, the light source 11, the reflective cup 15, and the second lens 16 constitute the illumination portion of the projection device, while the polarizing element 20, the display panel 30, the second polarizer 43, the reflector 44, and the projection lens 50 constitute the imaging portion of the projection device.

[0141] FIG15 is a schematic diagram of a light source provided in some embodiments of the present disclosure. Optionally, as shown in FIG15 , the light source 11 may specifically include: a light board 11 a and a light emitting element 11 b disposed on the light board 11 a. The light emitting element 11 b may be an LED lamp.

[0142] In some embodiments, the shape of the light-emitting surface of the light-emitting element 11b is the same as the shape of the display surface of the display panel 30, thereby improving light efficiency. The so-called shape here refers to a shape category. For example, the shape of the light-emitting surface and the display surface of the display panel 30 can be rectangular, elliptical, circular, hexagonal, etc.

[0143] In some embodiments, the light-emitting surface of the light-emitting element 11b and the display surface of the display panel 30 are both rectangular, with the length of the light-emitting surface being parallel to the length of the display surface and the width of the light-emitting surface being parallel to the width of the display surface. That is, the long side of the light-emitting surface is parallel to the long side of the display surface, and the short side of the light-emitting surface is parallel to the short side of the display surface. Of course, the light-emitting surface of the light-emitting element 11b and the display surface of the display panel 30 can both be square, in which case the four sides of the light-emitting surface are parallel to the four sides of the display surface.

[0144] As shown in FIG7 , the second lens 16 is disposed between the light source 11 and the polarizing assembly 20 and is used to collimate the light irradiated by the light source 11 to the second lens 16. Both the first lens 60 and the second lens 16 can be Fresnel lenses. Using a Fresnel lens can prevent large spherical aberrations and aberrations at the lens edges, thereby improving imaging quality. Since the second lens 16 is used to collimate the divergent light from the light source, and the first lens 60 is used to converge the light from the display panel 30, when both the first lens 60 and the second lens 16 can be Fresnel lenses, the serrated surfaces of the Fresnel lenses are both oriented toward the display panel 30, thereby allowing a ring or dark spot to appear on the display screen.

[0145] The reflective cup 15 is positioned between the light source 11 and the second lens 16 and surrounds the optical axis of the second lens 16, forming a cylindrical structure. The cylindrical structure has a first opening facing the light source 11 and a second opening facing the second lens 16. The area of ​​the first opening is smaller than that of the second opening. The reflective cup 15 reflects at least a portion of the light from the light source 11 onto the reflective cup 15 toward the second lens 16, thereby improving light utilization and enhancing the brightness of the projected image.

[0146] In some embodiments, the orthographic projection of the second opening on the reference plane where the display panel 30 is located covers and exceeds the orthographic projection of the display area on the reference plane, thereby ensuring that each position in the display area can receive light.

[0147] Furthermore, a spacing of at least 0.1 mm exists between the edge of the orthographic projection of the second opening on the reference surface and the edge of the orthographic projection of the display area on the reference surface, thereby ensuring higher uniformity of light received by the corners of the display area and improving the uniformity of the projected image in all four corners. In one example, a spacing of 0.1 mm to 2 mm exists between the edge of the orthographic projection of the second opening on the reference surface and the edge of the orthographic projection of the display area on the reference surface, thereby improving light utilization while ensuring uniformity in all four corners of the projected image.

[0148] In some embodiments, the light-emitting surface of the light-emitting element 11b and the display area of ​​the display panel 30 are both rectangular, and the ratio of the diagonal length of the light-emitting surface to the diagonal length of the display area is between 0.05 and 0.15. In this case, the light-emitting surface of the light-emitting element 11b is relatively small, so that the light-emitting element 11b is close to a point light source, which is beneficial to improving the brightness of the projected image. For example, the ratio of the diagonal length of the light-emitting surface to the diagonal length of the display area is 0.05, or 0.1, or 0.11, or 0.13, or 0.15. In one example, the diagonal length of the display area is 5 inches, the light-emitting surface is a rectangle of 11.8mm×7.9; the power is 130W, and the luminous efficiency is greater than 120lm / W.

[0149] FIG16 is a schematic diagram of a reflective light cup provided in some embodiments of the present disclosure. In some embodiments, the light-emitting surface of the light-emitting element 11b is rectangular. As shown in FIG16 , the reflective light cup 15 includes multiple reflective walls 151. The orthographic projections of different reflective walls 151 on the second lens 16 are located on different sides of the orthographic projection of the light-emitting surface on the second lens 16. In other words, the first opening includes multiple first sides, and the second opening includes multiple second sides. Each first side and each second side is parallel to a side of the light-emitting surface, and each reflective wall 151 of the reflective light cup 15 is connected between a first side and a second side.

[0150] The reflecting surface of the reflecting wall 151 is a curved surface with a curvature between 1000 mm and 2000 mm, which is conducive to effectively gathering the large-angle light emitted by the light-emitting element 11 b, thereby improving the uniformity of the four corners of the projection image.

[0151] FIG17 illustrates an illumination optical path diagram provided in some embodiments of the present disclosure. The reflective cup 15 is 95 mm tall, the first opening is a 12.2 mm × 8.3 mm rectangle, the second opening is a 112 mm × 65 mm rectangle, the reflective wall has a curvature between 1000 mm and 2000 mm, and the focal length of the second lens 16 is 90 mm. A distance of 0.2 mm is provided between the light-emitting surface of the light-emitting element 11 b and the plane of the first opening. The light intensity distribution of the light-emitting element 11 b conforms to a Lambertian distribution. Light with a Lambertian half-angle between 0° and 50° is directly incident on the second lens 16, effectively converging and focusing the light. Light with a large angle, such as light with a Lambertian half-angle between 50° and 90°, is reflected by the curved reflective wall and incident on the second lens 16, where it is converged and focused, thereby shaping the light into parallel or nearly parallel light (as indicated by LL in FIG17 ) that illuminates the display panel 30.

[0152] In one example of the present disclosure, the off-axis ratio of the projected image is 50%. Figure 18 is a spot diagram of a projection device provided in some embodiments of the present disclosure. IMA in Figure 18 represents the image plane, and the value marked after IMA is the radius of the image plane. The two rows of data at the bottom of Figure 18 represent quantitative indicators of 11 fields of view. The 11 data in the first row represent the root mean square radius of the light area formed by the object plane on the image plane of 11 different sizes, and the data in the second row represent the geometric radius of the light area formed by the object plane on the image plane of 11 different sizes. After passing through the optical system, many light rays emitted by a light-emitting point in the light-emitting assembly 10 no longer converge at the same point due to aberrations, but instead form a diffuse pattern scattered over a certain range, which is called a spot diagram. The spot diagram is one of the most commonly used evaluation methods in modern optical design. The principle of the spot diagram is to display the image formed by the optical system on the image plane. In other words, it actually depicts the image formed on the image plane after a series of object points pass through the optical system through calculation. For ease of presentation, a series of predefined templates can be selected. Specifically, for example, for an on-axis point, the design process uses a reverse light path, imaging from the screen to the display panel 30. This simulates several luminous points, which enter the entrance pupil in parallel, then pass through the optical system and are finally imaged on the display panel 30. Obviously, if the optical system is perfect, the image of these points would be an ideal point. However, in a real optical system, the image will be a diffuse spot, and the image of this diffuse spot on the display panel 30 is the spot diagram. Similarly, for non-on-axis points, the angle and position of the principal ray can be referenced to form a series of luminous points, which pass through the entrance pupil and are finally imaged on the image plane, ultimately forming a diffuse spot. The spot diagram can be used to observe the quality of the optical design; the smaller the diffuse spot, the better. If the diffuse spot is found to be small enough to meet the minimum diffuse spot requirement for the optical system (the unit of the spot diagram is micrometers), then the optical system design is complete. In the embodiment of the present disclosure, the above-mentioned design of the projection lens 50 ensures that the root mean square radius of the light spot in each field of view, from the central field of view to the edge field of view, is smaller than the size of one pixel of a 5-inch 4K LCD display panel. The central field of view refers to the light emitted from the center point of the projected image, and the edge field of view refers to the light emitted from the edge position of the projected image.

[0153] FIG19 is a diagram of the MTF (Modulation Transfer Function) of the projection lens 50 provided in some embodiments of the present disclosure. The MTF diagram is a relatively scientific method for analyzing the resolution of the projection lens 50. The unit of the resolution of the projection lens 50 is line pair / millimeter (lp / mm). Two adjacent black and white lines can be called a line pair, and the number of line pairs that can be distinguished per millimeter is the resolution. The resolution of the projection lens 50 is tested by shooting a sinusoidal grating (the black and white grid in the test target). A periodic pattern whose brightness changes sinusoidally is called a "sinusoidal grating". The density of the sinusoidal grating is called the "spatial frequency", and the unit of spatial frequency is lp / mm. lp / mm represents the number of periods of the pattern whose brightness per unit length (per millimeter) changes sinusoidally. The clarity of the projected image is above 0.4 at a resolution of 4K. The lines in Figure 19 represent MTF curves in the tangential and sagittal directions at the edges of fields of view of varying radii. The numerical values ​​on each curve represent the radius of the field of view. Figures 18 and 19 illustrate that the eight-element projection lens 50 provided in this embodiment of the present disclosure offers high image clarity, meeting 4K resolution design requirements.

[0154] Figure 20 shows a diagram of the field curvature and distortion of a projection device provided in some embodiments of the present disclosure. Field curvature, also known as "image field curvature," occurs when a lens exhibits field curvature, causing the intersection of the entire light beam to not coincide with the ideal image point. While a clear image point can be obtained at each specific point, the entire image plane is a curved surface. This prevents simultaneous visualization of the entire image plane during microscopic examination, making imaging difficult. The field curvature is within 0.22 mm, and the projection lens 50 exhibits minimal dispersion for the three RGB colors. Distortion is <0.85%, and the projected image exhibits minimal barrel and pincushion distortion.

[0155] Figure 21 is an on-axis aberration diagram of the projection device provided in some embodiments of the present disclosure. As can be seen from Figure 21, the on-axis aberration of the projection lens 50 for the RGB colors is small within 0.22 mm. Figure 22 is a vertical chromatic aberration diagram of the projection device provided in some embodiments of the present disclosure. As can be seen from Figure 22, the vertical chromatic aberration is less than half the size of a pixel, and the color fringing effect at the edge of the image is not obvious. Figure 23 is a relative illumination diagram of the projection device provided in some embodiments of the present disclosure. In particular, the relative illumination of the 0.7 field of view is greater than 80%, and the relative illumination of the edge field of view is greater than 70%, indicating that the difference between the edge brightness and the center brightness of the projected image is small, and the brightness uniformity is good.

[0156] Figure 24 is a side view of the 9-point uniformity of the projection screen of the projection device provided in some embodiments of the present disclosure. The projection screen is adjusted to 90 inches (here 90 inches refers to the diagonal length of the screen), wherein the 9-point uniformity refers to the ratio of the average brightness of the positions P1 to P9 to the brightness of the position P5 within 30 seconds after the projection device is turned on. The edge four-corner uniformity includes: point A uniformity (i.e., the ratio of the brightness of the position P10 to the position P5), point B uniformity (i.e., the ratio of the brightness of the position P11 to the position P5), point C uniformity (i.e., the ratio of the brightness of the position P13 to the position P5), and point D uniformity (i.e., the ratio of the brightness of the position P12 to the position P5). Figure 25 is an illuminance simulation diagram of the projection screen of the projection device provided in some embodiments of the present disclosure, wherein the diagonal length of the projection screen is 90 inches. Table 2 shows the 9-point illuminance and edge four-corner illuminance values ​​of the projection screen, and Table 3 shows the 9-point brightness values ​​and uniformity values ​​of the projection screen. Among them, the power of the light-emitting element 11b is 130W, the light efficiency is 120lm / W, and after calculation, the projection brightness is 521lm, the 9-point uniformity is 77%, and the uniformity of the four corners of the edge is greater than 40%, meeting the display requirements of high brightness and high uniformity.

[0157] Table 2

[0158] Table 3

[0159] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A projection device, wherein, Comprising: A light source assembly, a display panel, a first lens, a reflector, and a projection lens. The light emitted by the light source assembly sequentially passes through the display panel and the first lens and then irradiates onto the reflector, and is reflected by the reflector to be emitted from the projection lens; Wherein, the display area of the display panel has a first central normal line, and the central axis of the first lens is collinear with the first central normal line; the central axis of the projection lens has a first intersection point with the reflector, the first central normal line has a second intersection point with the reflector, and there is a second distance between the first intersection point and the second intersection point; There is a first distance between the central axis of the projection lens and a first optical axis passing through the second intersection point. The first optical axis is parallel to the central axis of the projection lens and perpendicular to the first central normal line; wherein, the second distance is greater than the first distance.

2. The projection device according to claim 1, wherein, There is a first optical path distance between the center of the display area of the display panel and the center of the projection lens; the ratio of the first optical path distance to the first distance is between 77 and 82.

3. The projection device according to claim 1 or 2, wherein There is a first distance between the first intersection point and the center of the projection lens, and there is a second distance between the second intersection point and the center of the display panel; the first distance is greater than the second distance.

4. The projection device according to any one of claims 1 to 3, wherein, The reflector includes a first reflection part and a second reflection part. The first reflection part is located at one end of the first intersection point far from the display panel; the second reflection part is located at one end of the second intersection point close to the display panel; There is a first included angle between the central axis of the projection lens and the first reflection part, A second included angle is formed between the first central normal line and the second reflection part, and the first included angle is complementary to the second included angle.

5. The projection device according to claim 4, wherein, The first included angle θ1 and the second included angle θ2 satisfy: 0° ≤ |θ1 - θ2| ≤ 10°.

6. The projection device according to any one of claims 1 to 5, wherein, The projection lens includes a condenser lens group, a diaphragm, and a diverging lens group sequentially arranged in a direction away from the display panel; The projection lens satisfies at least one of the following conditions: The sum of the focal length of the projection lens and the focal length of the first lens is greater than or equal to 2000 mm; The ratio of the focal length of the projection lens to the length of the diagonal of the display area of the display panel is 28 - 29; The ratio of the focal length of the diverging lens group to the focal length of the condenser lens group is 2 - 3; The central distance between the incident surface and the exit surface of the projection lens is less than or equal to 100 mm.

7. The projection device according to any one of claims 1 to 6, wherein, The projection lens includes a plurality of lenses arranged coaxially, and the Abbe numbers of the lens closest to the reflector and the lens farthest from the reflector are both less than 50.

8. The projection device according to any one of claims 1 to 7, wherein, The projection lens includes a plurality of lenses arranged coaxially. The lens closest to the reflector has a first curved surface close to the reflector, the lens farthest from the reflector has a second curved surface close to the reflector and a third curved surface far from the reflector. The first curved surface and the third curved surface are convex surfaces, and the second curved surface is a concave surface; The radius of curvature of the first curved surface and the radius of curvature of the third curved surface are both greater than the radius of curvature of the second curved surface.

9. The projection device according to any one of claims 1 to 8, wherein, The ratio of the focal length of the projection lens to the entrance pupil diameter is between 2.8 and 3.

3.

10. The projection device according to any one of claims 1 to 9, wherein, The projection lens includes a condenser lens group, a diaphragm, and a diverging lens group that are sequentially arranged in a direction away from the reflector; the diverging lens group includes a plurality of lenses, and in the direction away from the diaphragm, the diameters of the plurality of lenses in the diverging lens group gradually increase.

11. The projection device according to any one of claims 1 to 10, wherein, The light source assembly includes: a light source, a reflecting cup, and a second lens; The second lens is disposed between the light source and the polarizing assembly and is configured to collimate the light emitted by the light source onto the second lens; The reflecting cup is located between the light source and the second lens and is arranged around the optical axis of the second lens to form a cylindrical structure; the cylindrical structure has a first opening facing the light source and a second opening facing the second lens, and the area of the first opening is smaller than the area of the second opening.

12. The projection device according to claim 11, wherein, The orthographic projection of the second opening on the reference plane where the display panel is located covers and exceeds the orthographic projection of the display area on the reference plane.

13. The projection device according to claim 12, wherein, There is a spacing of at least 0.1 mm between the edge of the orthographic projection of the second opening on the reference plane and the edge of the orthographic projection of the display area on the reference plane.

14. The projection device according to claim 11, wherein, The light source includes: a lamp board; a light-emitting component disposed on the lamp board, and the light-emitting component is located on the side of the lamp board close to the display panel; wherein, the light-emitting surface of the light-emitting component and the display area of the display panel are both rectangular, and the ratio of the diagonal length of the light-emitting surface to the diagonal length of the display area is between 0.05 and 0.

15.

15. The projection device according to claim 11, wherein, The light source includes: a lamp board; a light-emitting component disposed on the lamp board, and the light-emitting component is located on the side of the lamp board close to the display panel; wherein, the light-emitting surface of the light-emitting component is rectangular; the reflecting cup includes a plurality of reflecting walls, and the orthographic projections of different reflecting walls on the second lens are located on different sides of the orthographic projection of the light-emitting surface on the second lens; the reflecting surface of the reflecting wall is a curved surface with a curvature between 1000 and 2000 mm.

Images