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 technical field of display, in particular to a projection device. BACKGROUND

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

[0003] The projection device is widely used in families, offices, schools and entertainment places. The types of the projection device include CRT (Cathode Ray Tube), LCD (Liquid Crystal Display), DLP (Digital Light Processing), 3LCD (3 Liquid Crystal Display) and the like. The single-LCD projection device has simple structure and low cost, and is suitable for popularization to the middle and low consumption groups, thus having considerable growth space.

[0004] SUMMARY

[0005] The present disclosure provides a projection device, comprising: a light source assembly, a display panel, a first lens, a mirror and a projection lens, light emitted by the light source assembly is irradiated to the mirror after passing through the display panel and the first lens in sequence, and is reflected by the mirror to the projection lens and is emitted.

[0006] 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 mirror, and the first central normal line has a second intersection point with the mirror, and the first intersection point and the second intersection point have a second distance; the central axis of the projection lens and a first optical axis passing through the second intersection point 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 line; wherein the second distance is greater than the first distance.

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

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

[0009] In some embodiments, the reflector comprises a first reflecting portion and a second reflecting portion, the first reflecting portion is located at one end of the first intersection far away from the display panel, and the second reflecting portion is located at one end of the second intersection close to the display panel.

[0010] The first center normal and the second reflecting portion form a second included angle, and the first included angle and the second included angle are complementary.

[0011] The first center normal and the second reflecting portion form a second included angle, and the first included angle and the second included angle are complementary.

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

[0013] In some embodiments, the projection lens comprises a condenser lens group, a diaphragm and a diverging lens group arranged in sequence in the direction away from the display panel.

[0014] The projection lens satisfies 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 2000mm;

[0016] 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;

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

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

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

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

[0021] 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.

[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 comprises, in sequence from the direction away from the mirror, a condenser lens group, a diaphragm, and a divergent lens group; the divergent lens group comprises a plurality of lenses, and the diameters of the plurality of lenses in the divergent lens group gradually increase in the direction away from the diaphragm.

[0024] In some embodiments, the light source assembly comprises: a light source, a reflecting light cup, and a second lens.

[0025] The second lens is arranged between the light source and the polarizing component, and is configured to collimate the light rays emitted by the light source and incident on the second lens.

[0026] The reflecting light cup is arranged between the light source and the second lens, and surrounds 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 second opening has a projection on a reference surface on which the display panel is arranged, and the projection covers and exceeds the projection of the display area on the reference surface.

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

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

[0030] A lamp plate;

[0031] A light-emitting member arranged on the lamp plate, and located on the side of the lamp plate close to the display panel.

[0032] In some embodiments, the light-emitting surface of the light-emitting member 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] A lamp plate;

[0035] A light-emitting member arranged on the lamp plate, and located on the side of the lamp plate close to the display panel.

[0036] The light emitting surface of the light emitting member is rectangular; the reflecting light cup comprises a plurality of reflecting walls, and the orthographic projection of different reflecting walls on the second lens is located on different sides of the orthographic projection of the light emitting surface on the second lens; and the reflecting surface of the reflecting wall is a curved surface with a curvature of 1000-2000 mm. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and are used together with the specific embodiments described below to explain the present disclosure, but do not constitute a limitation on the present disclosure. In the drawings:

[0038] FIG. 1 is a schematic diagram of the imaging light path of the projection device in an example.

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

[0040] FIG. 3 shows embodiments with off-axis ratios of 0%, 50%, and 100%, respectively.

[0041] FIG. 4 is a schematic diagram of off-axis projection provided in some embodiments.

[0042] FIG. 5 is a schematic diagram of the projection device provided in some embodiments of the present disclosure.

[0043] FIG. 6 is a light path diagram of the projection device provided in some embodiments of the present disclosure.

[0044] FIG. 7 is a schematic diagram of the projection device provided in some other embodiments of the present disclosure.

[0045] FIG. 8 is another angle schematic diagram of the projection device provided in some other embodiments of the present disclosure.

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

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

[0048] FIG. 11 is a field of view diagram when not off-axis and when off-axis provided in some examples.

[0049] FIG. 12 is a sectional view of the first lens provided in some embodiments of the present disclosure.

[0050] FIG. 13 is a schematic diagram of the projection lens provided in some embodiments of the present disclosure.

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

[0052] FIG. 15 is a schematic diagram of the light source provided in some embodiments of the present disclosure.

[0053] FIG. 16 is a schematic diagram of a reflective light cup provided in some embodiments of the present disclosure.

[0054] FIG. 17 is a diagram of an illumination light path provided in some embodiments of the present disclosure.

[0055] FIG. 18 is a diagram of a point spread of a projection device provided in some embodiments of the present disclosure.

[0056] FIG. 19 is a diagram of an MTF of a projection lens provided in some embodiments of the present disclosure.

[0057] FIG. 20 is a diagram of a field curvature and distortion of a projection device provided in some embodiments of the present disclosure.

[0058] FIG. 21 is a diagram of on-axis aberrations of a projection device provided in some embodiments of the present disclosure.

[0059] FIG. 22 is a diagram of off-axis chromatic aberrations of a projection device provided in some embodiments of the present disclosure.

[0060] FIG. 23 is a diagram of relative illuminance of a projection device provided in some embodiments of the present disclosure.

[0061] FIG. 24 is a 9-point uniformity side view of a projection screen of a projection device provided in some embodiments of the present disclosure.

[0062] FIG. 25 is an illuminance simulation diagram of a projection screen of a projection device provided in some embodiments of the present disclosure. DETAILED DESCRIPTION

[0063] The specific embodiments of the present disclosure will be described hereinafter with reference to the accompanying drawings, but the present disclosure can be implemented in various ways and is not limited to the embodiments described herein. It should be understood that the specific embodiments described herein are illustrative only and are not intended to limit the scope of the present disclosure.

[0064] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be described clearly and completely below with reference to the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments of the present disclosure. Based on the described embodiments of the present disclosure, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present disclosure.

[0065] Unless otherwise defined, technical terms or scientific terms used in the present disclosure shall have the same meaning as commonly understood by one of ordinary skill in the art to which this present disclosure belongs. Unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have the same meaning as commonly understood by one of ordinary skill in the art to which this present disclosure belongs. The terms "first", "second", and similar terms are used herein to distinguish one element from another, and are not necessarily used in a sequence. Also, the terms "include", "comprise", and the like are used herein to indicate the presence of the stated elements or objects, but do not preclude the presence or addition of one or more other elements or objects. The terms "connected" and "coupled" and the like are used herein to indicate an electrical connection, but can include an electrical connection that is not directly connected or coupled.

[0066] As used herein, "parallel", "perpendicular" include the recited condition and conditions that are approximately the recited condition, the range of which is within an acceptable deviation range, as determined by one of ordinary skill in the art taking into account the measurement being discussed and the error associated with a particular measurement (i.e., limitations of the measurement system). For example, "parallel" includes absolute parallel and approximately parallel, where the acceptable deviation range for approximately parallel can be, for example, within 5°; "perpendicular" includes absolute perpendicular and approximately perpendicular, where the acceptable deviation range for approximately perpendicular can also be, for example, within 5°.

[0067] Exemplary embodiments are described herein with reference to cross-sectional and / or plan view illustrations that are idealized examples. In the interest of clarity, not all of the layer and regions are shown in the drawings with the same dimensions. For example, the thickness of layers and regions can be exaggerated in the drawings. Thus, the exemplary embodiments should not be construed as limited to the shapes of regions illustrated in the drawings, which are schematically represented. The same reference numerals in different drawings represent the same or similar elements unless otherwise indicated. Thus, exemplary embodiments are not intended to be limited to the shapes of the regions illustrated in the drawings, which are schematically represented. The regions illustrated in the drawings are intended to represent functionally equivalent regions to one another, and thus, the shapes of the regions illustrated in the drawings should not be construed as limiting the scope of exemplary embodiments.

[0068] Figure 1 is a schematic diagram of the imaging light path of a projection device in one example. Figure 2 is a structural diagram of a projection device in one example, which is a single-LCD projection device. As shown in Figure 2, the projection device includes a light source 11, a plano-convex lens 17, a first mirror 18, a second lens 16, a polarizing assembly 20, a display panel 30 (i.e., an LCD display panel), a first lens 60, a second mirror 41, and a projection lens 50. In Figure 2, the light rays from the light source 11 are converged by the plano-convex lens 17, and then are incident on the polarizing assembly 20 through the second lens 16. The polarizing assembly 20 can include a transparent substrate and a first polarizing sheet disposed on the transparent substrate. After the polarizing action of the polarizing assembly 20, the polarized light of a first polarization direction is incident on the display panel 30. The light rays from the display panel 30 are reflected by the second mirror 41 to the projection lens 50 after passing through the first lens 60. In Figure 2, the display panel 30 is imaged twice to form a projection image Ima on a projection screen. In the first imaging, the display panel 30 is the object, the first lens 60 is the imaging lens, and the intermediate surface Ml is the virtual image of the display panel 30. In the second imaging, the intermediate surface Ml is the object, the projection lens 50 is the imaging lens, and the projection image is the image.

[0069] The projection device must be imaged twice mainly because the display area of the display panel 30 is usually large, and the light beams need to be converged by the first lens 60 so that more light rays can pass through the projection lens. For example, when the display area 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. If there is no first lens 60, most of the light rays emitted by the display panel 30, especially those with large off-axis amounts and large aperture angles, cannot pass through the aperture of the projection lens 50. Moreover, the light rays entering the projection lens 50 will also have a serious vignetting phenomenon (the brightness in the middle of the projection image Ima is high, and the brightness at the edges is low). When the first lens 60 is used, the light rays emitted by each object point on the display panel 30, especially those parallel to the optical axis, are focused through the center of the aperture, thereby ensuring that each object point has a sufficiently high brightness.

[0070] In the first imaging, there is the object-image relationship that the display panel 30 is the object, the first lens 60 is the imaging lens, and the intermediate surface is the virtual image of the display panel 30. The thin-lens imaging formula is:

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

[0072] In the second imaging, there is the object-image relationship that the intermediate surface M1 is the object (virtual object), the projection lens 50 is the imaging lens, and the projection picture is the real image of the intermediate surface M1 (because it is the point where the actual light converges). According to the imaging formula of the ideal optical system (Newton formula):

[0073] Wherein, -l2 represents the object distance of the intermediate surface M1, and the symbol follows the sign convention; l2' represents the image distance of the projection picture Ima, and the symbol follows the sign convention; f2' represents the image-side focal length of the projection lens 50; 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, the imaging formula result similar to the thin lens can be obtained:

[0075] In order to calculate the imaging light path, the distance -l1 between the first lens 60 and the display panel is set, and the focal length f1' of the first lens 60 is set. According to the thin lens imaging formula, the image distance l1' can be calculated, so that the magnification of the first lens 60 is β1=l1' / l1, and the magnification of the projection lens 50 is β2=β / β1 according to the total magnification of the light path β. According to the projection size and the projection ratio, the width of the projection picture is determined as 2h3. According to the projection ratio R, l2' is determined. According to the magnification of the lens, l2 is determined. According to the imaging formula, the focal length of the lens can be calculated.

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

[0077] The "projection ratio" refers to the ratio of the projection distance to the width of the projection picture Ima. The smaller the projection ratio, the shorter the focal length of the imaging system.

[0078] In the art, an object-side telecentric optical path is one in which the image (i.e., "pupil") of the stop in the object space is at infinity in the object space. This means that light rays emanating from infinity in the object space (i.e., rays parallel to the optical axis) pass through the center of the stop (the chief ray of the main direction of the illumination system passes through the center of the stop, is least obstructed by the stop, has the least vignetting, and has the highest light utilization, and the projected image has the highest brightness). Generally, the stop refers to the stop of the entire imaging system (including the front Fresnel lens), but here it refers to the stop of the projection lens 50. Because the stop of the projection lens 50 primarily limits the aperture angle of the light rays, the front Fresnel lens does not limit the aperture angle of the light rays (otherwise the light utilization would be even lower).

[0079] It should be noted that in the simulation, the object and image spaces of the imaging optical path are reversed from the actual situation. That is, the projected image is the object, and the display panel 30 is the image. This is done primarily for the following reasons: the size of the display panel 30 is constant, but the size of the projected image can vary, such as 40-100 inches. Reversing the optical path allows the image height (i.e., the field of view) to remain constant, without having to adjust the field of view and substantially modify the simulation model each time the size of the projected image changes.

[0080] Therefore, in the simulation, the previous "object-side telecentric optical path" becomes an "image-side telecentric optical path", and the previous requirement that the center of the entrance pupil be at infinity in the object space becomes the requirement that the center of the exit pupil be at infinity in the object space. The "exit pupil" is the image of the stop in the image space. Because the optical path is reversible, the light rays do not substantially change when the object and image spaces are reversed.

[0081] Generally, single-LCD projection devices require an object-side telecentric optical path, because the object-side telecentric optical path allows the light utilization to be the highest. In the field of lens design, the object and image spaces are often reversed to become an "image-side telecentric optical path". The object-side telecentric optical path refers to the center of the entrance pupil being at infinity in the object space. The "entrance pupil" refers to the image of the stop in the object space. The "stop" refers to the stop in the optical imaging system that primarily limits the aperture angle of the on-axis object point, i.e., the stop with the smallest radius when the light beam passes through the lens. The "aperture angle" refers to the angle between the light ray and the optical axis, and generally the larger the aperture angle, the greater the aberration of the light ray.

[0082] In an optical system, the light ray passing through the center of the stop is called the "chief ray", and 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, then 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, then it is an image-side telecentric optical path.

[0083] Partial axial projection is one of the important functions of a projector. In a projection system, the center of the picture can be set as point A, and the intersection of the screen normal line and the screen cloth normal line through the optical center of the projection lens can be set as point B. When the two points A and B coincide, it is a non-partial axial projection (the partial axial ratio is 0%). When the two points A and B do not coincide, it is a partial axial projection. The distance between the two points A and B is called the "offset". In practice, the partial axial projection in the height direction is generally focused on, and the "partial axial ratio" (Par, i.e. Partial axial ratio) can be defined as the ratio of the offset to the picture half-height, i.e.

[0084] FIG. 3 shows embodiments with partial axial ratios of 0%, 50% and 100%, respectively. When the partial axial ratio is 50%, the offset is 1 / 4 of the picture height. When the partial axial ratio is 100%, the offset is 1 / 2 of the picture height.

[0085] In some examples, the partial axial projection can be achieved by changing the deflection direction of the light, and FIG. 4 is a schematic diagram of the partial axial projection provided in some embodiments. In the non-partial axial projection, the normal line of the mirror 44 and the screen normal line form an angle of 45°, the light emitted from the center of the first lens 60 passes through the mirror 44 and is reflected, and then passes through the optical axis of the projection lens 50 (at this time, the optical axis of the projection lens 50 is perpendicular to the screen), and is vertically irradiated on the screen. At this time, the two points A and B coincide, and the partial axial ratio is 0. When the mirror 44 is rotated by an angle α (e.g. counterclockwise), the light emitted from the center of the first lens 60 passes through the mirror 44 and is reflected, and then passes through the optical axis of the projection lens 50 (at this time, the optical axis of the projection lens 50 forms an angle θ with the screen normal line), and is obliquely irradiated on the screen. At this time, the two points A and B do not coincide. The projection device can also not use the mirror 44, but can set a height-adjustable support leg at the bottom of the projection device to achieve inclined projection. By rotating the whole projection device by an angle, the effect of rotating the projection lens 50 can also be achieved. In principle, the planar mirror 44 is an ideal optical imaging device, which only changes the propagation direction of the light, and does not change the magnification and image quality of the system. The overall effect of adjusting the inclination angle by using the support leg and adjusting the inclination angle by using the mirror 44 is to make the projection lens have an elevation angle, so there is no essential difference between adjusting the inclination angle by using the support leg and adjusting the inclination angle by using the mirror 44.

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

[0087] In some embodiments of the present disclosure, the projection device is configured to implement off-axis projection. As shown in FIGS. 5-7, 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 passes through the display panel 30, the first lens 60, and the projection lens 50 in sequence and exits.

[0088] In some embodiments of the present disclosure, the display area of the display panel 30 has a first central normal A3 that is collinear with a central axis of the first lens 60. The first central normal A3 is a line that passes through the center of the display area and is perpendicular to the display panel 30. The display panel 30 and the projection lens 50 are designed to be off-axis. In this case, light emitted along the first central normal A3 can enter the projection lens 50 along a first optical axis A1 that is parallel to the central axis of the projection lens 50 and has a non-zero first distance d from the central axis.

[0089] It should be noted that the first optical axis A1 is an axis that coincides with the incident light when a light ray emitted perpendicularly from the center of the display panel 30 enters the projection lens 50. For the structure shown in FIG. 5, the first optical axis A1 is the first central normal A3 of the display panel 30 because no mirror 44 is provided between the display panel 30 and the projection lens 50. For the structure shown in FIG. 7, the first optical axis A1 can be considered as an axis along which a reflected light ray is emitted when a light ray emitted perpendicularly from the center of the display panel 30 is reflected by the mirror 44 toward the projection lens 50.

[0090] For the structure of Fig. 6, in the non-axial projection, the central axis of the projection lens 50 and the central axis of the display panel 30 are coaxial, i.e. the first distance = 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 normally incident on the screen. The points A and B are coincident, and the axial deviation is 0. When the projection lens 50 is lifted by a height d > 0, the virtual image (the intermediate surface M1) of the display panel 30 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 relative to the central axis of the projection lens 50. If the magnification of the projection lens 50 is β, then at this time, there is an offset Offset = dβ between the points A and B, the point A being the center of the projection image Ima and the point B being the intersection of the normal line of the screen passing through the optical center of the projection lens 50 and the screen. Fig. 8 has the same principle as Fig. 6 and will also cause the projection image Ima to form a certain offset.

[0091] In the embodiment shown in Fig. 7, the projection device further comprises a mirror 44 arranged on the side of the first lens 60 away from the display panel 30 for reflecting the light emitted by the first lens 60 to the projection lens 50. Through the arrangement of the mirror 44, the projection device as a whole can be more compact. The central axis A2 of the projection lens 50 and the mirror 44 have a first intersection point P1'. The first central normal A3 of the display panel 30 and the mirror 44 have a second intersection point P2'. At this time, the above-mentioned first optical axis A1 can be regarded as an axis passing through the second intersection A2 and the projection lens 50 and perpendicular to the first central normal A3. In Fig. 7, the central axis A2 of the projection lens 50 is parallel to the first optical axis A1, and there is also the above-mentioned first distance d between the central axis A2 of the projection lens 50 and the first optical axis A1; and there is a second distance between the first intersection point P1' and the second intersection point P2', the second distance being greater than the first distance, so as to realize the axial deviation projection.

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

[0093] In one example, the display panel 30 has a display area diagonal of 5 inches, the projection lens 50 has an off-axis ratio of 50%, a projection ratio of 1.25, a nearest distance between the projection lens 50 and the first lens 60 of 135 mm, a projection picture diagonal of 90 inches, a distance between the first lens 60 and the display panel 30 of 9 mm, and a thickness of the first lens 60 of 1.8 mm. The distance between the first central 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%. FIG. 11 is a view field diagram provided in some examples when the display panel 30 is not off-axis and when the display panel 30 is off-axis by 50%. In FIG. 11, 30a represents the position of the display panel 30 when not off-axis, and 30b represents the position of the display panel 30 after being off-axis by 50%. As shown in FIG. 11, for the display panel 30 having a display area diagonal of 5 inches, the view field IA1 has a radius of 63.5 mm when not off-axis, and the view field IA2 has a radius of 72.5 mm when off-axis by 50%. In other words, for the case when not off-axis (i.e., the first central normal of the display panel 30 is collinear with the central axis A2 of the projection lens 50, i.e., the light rays emitted perpendicularly from the center of the display panel 30 can be incident on the projection lens 50 along the central axis A2 of the projection lens 50), the projection lens 50 needs to receive light rays of a view field having a radius of 63.5 mm. For the case when off-axis (i.e., there is a non-zero first distance between the first central normal A3 of the display panel 30 and the central axis A2 of the projection lens 50), the projection lens 50 needs to receive light rays of a view field having a radius of 72.5 mm.

[0094] As can be seen, when the display panel 30 and the projection lens 50 of the projection device are designed to be off-axis, the projection lens 50 needs to receive light rays of a larger view field to meet the projection requirement.

[0095] In the embodiments of the present disclosure, there is a first optical path distance 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 of the light rays emitted from the center of the display panel 30 and capable of being incident on the center of the projection lens 50. For example, for the structure of FIG. 5, the first optical path distance is equal to or approximately equal to the straight-line distance between the center of the display panel 30 and the center of the projection lens 50. For the structure of FIG. 7, the light rays emitted from the center of the display panel 30 are incident on the M point of the mirror 44, are reflected by the mirror 44, and then enter the center of the projection lens 50. The first optical path distance is the sum of the distance L4 between the center of the display panel 30 and the M point and the distance L3 between the M point and the center of the projection lens 50.

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

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

[0098] In some embodiments, the projection device further comprises a first lens 60 located on the light exit side of the display panel 30, and the light emitted by the display panel 30 passes through the first lens 60 and the projection lens 50 in sequence. The first lens 60 is a Fresnel lens, also known as a front Fresnel lens, which is used to converge the received light. FIG. 12 is a cross-sectional view of the first lens 60 provided in some embodiments of the present disclosure. As shown in FIG. 12, the first lens 60 can be a Fresnel lens with a sawtooth surface 60s. Using a Fresnel lens can prevent large spherical aberration and aberration from occurring at the edge of the lens, thereby improving the imaging quality.

[0099] As shown in FIGS. 13 and 14, the projection lens 50 comprises a condenser lens group 5a, a diaphragm 5c, and a diverging lens group 5b arranged in sequence in a direction away from the mirror 44. The condenser lens group 5a is used to converge the light emitted by the display panel 30, the converged light is emitted to the diverging lens group 5b through the diaphragm 5c, and the diverging lens group 5b is used to diverge the received light. The condenser lens group 5a and the diverging lens group 5b can each comprise a plurality of lenses, thereby improving the modulation effect of the light and improving the imaging quality.

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

[0101] Condition one: the sum of the focal length of the projection lens 50 and the focal length of the first lens 60 is greater than or equal to 2000 mm, that is, the projection device realizes a telecentric optical path on the object side.

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

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

[0104] Condition four: the center distance between the light entrance surface and the light exit surface of the projection lens 50 is less than or equal to 100 mm.

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

[0106] In some embodiments, the projection lens 50 includes a plurality of lenses arranged coaxially, and the Abbe number of each of the lens closest to the display panel 30 and the lens farthest from the display panel 30 is less than 50. In the projection lens 50, the lens closest to the display panel 30 is the lens that receives the light from the display panel 30, and the lens farthest from the display panel 30 is the lens that finally projects the light to the projection screen. The Abbe number of each of the two lenses is less than 50, that is, the Abbe number is small, that is, the refractive index is large, so that the degree of deflection of the light can be improved, thereby facilitating the projection lens 50 to project as much light as possible from the large field of view received by the projection lens 50 to 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 a plurality of lenses arranged coaxially, and 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, and the second curved surface S2 is concave. The radius of curvature of the first curved surface S1 and the radius of curvature of the third curved surface S3 are both greater than the radius of curvature of the second curved surface S2, so that the entrance surface and the exit surface of the projection lens 50 have a large enough radius of curvature, which facilitates the projection lens 50 to project as much light as possible from the large field of view received by the projection lens 50 to the projection screen.

[0109] In some embodiments, as shown in FIGS. 7 and 9, the reflector 44 is arranged on the light exit side of the display panel 30, specifically on the side of the first lens 60 far from the display panel 30, for reflecting the light emitted by the first lens 60 to the projection lens 50. Through the arrangement of the reflector 44, the overall projection device can be more compact. Wherein, the first intersection P1’ and the center of the projection lens 50 are separated by a first distance L1, and the second intersection P2’ and the center of the display panel 30 are separated by a second distance L2. The first distance L1 is greater than the second distance L2.

[0110] Due to the limitation of process conditions, the edge of the first lens 60 cannot modulate the light emitted by the display panel 30 ideally, and the part of light can be regarded as 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, and for the stray light with a certain inclination angle, the farther the projection lens 50 is from the reflector, the more the incident position of the stray light on the projection lens 50 deviates from the optical axis of the projection lens 50, thereby facilitating the stray light to be absorbed by the diaphragm 5c and improving the imaging quality.

[0111] As shown in FIG. 9, the reflector 44 includes a first reflection part 441 and a second reflection part 442. The first reflection part 441 is located at one end of the first intersection P1' away from the display panel 30, and the second reflection part 442 is located at one end of the second intersection P2' close to the display panel 30. The central axis of the projection lens 50 and the first reflection part 441 form a first included angle θ1, and the first central normal A3 of the display panel 30 and the second reflection part 442 form a second included angle θ2. The first included angle θ1 and the second included angle θ2 are supplementary to each other, which facilitates the off-axis projection.

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

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

[0114] In some embodiments, the projection lens 50 includes a condenser lens group 5a, a diaphragm 5c and a divergent lens group 5b arranged in sequence in the direction away from the reflector 44; the divergent lens group 5b includes a plurality of lenses, and the diameters of the plurality of lenses in the divergent lens group 5b gradually increase in the direction away from the diaphragm 5c, so as to ensure that the projection lens 50 can project as many light rays as possible to the screen to form a large-size projection image.

[0115] Wherein, 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 F number), the better the imaging quality; but at this time, the aperture of the diaphragm 5c is low, resulting in low projection brightness; and if the ratio of the focal length to the entrance pupil diameter is smaller, the aperture of the diaphragm 5c is larger, and the projection brightness is higher, but the imaging quality is poorer. In order to improve the imaging quality and the projection brightness, the F number of the projection lens 50 in the embodiments of the present disclosure is between 2.8-3.3, so as to meet the high brightness requirement of the projection brightness reaching 500 lm. The aperture of the diaphragm 5c can be set to be between 40-50 mm.

[0116] The entrance pupil refers to the image of the diaphragm 5c in the object field.

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

[0118] In some embodiments, as shown in Figures 13 and 14, the focusing lens group 5a includes, sequentially arranged along the direction close to the diverging lens group 5b: a first lens 51, a second lens 52, a third lens 53, a fourth lens 54, and a fifth lens 55. In one example, the first lens 51 is a concave-convex mirror, with its surface away from the aperture stop 5c (i.e., the light-incident surface of the entire projection lens 50) being convex, and its surface near the aperture stop 5c being 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 the light entering the projection lens 50 from the display panel 30. The second lens 52 is a double concave mirror; the third lens 53 and the fourth lens 54 are bonded together, and the two are used to correct light residuals. The third lens 53 is a double convex mirror, the fourth lens 54 is a double concave mirror, and the fifth lens 55 is a double convex mirror, which further converges 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 mirrors, 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 mirror that initially diverges the light rays passing through the aperture 5c; the seventh lens 57 is also a concave-convex mirror and is used to diverge the light rays, although the degree of divergence between the seventh lens 57 and the sixth lens 56 may differ.

[0120] The embodiment of the present disclosure can improve the modulation effect on the light emitted by the display panel 30 by setting a large 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 can be arranged on the surface of each lens close to the mirror 44 and away from the mirror 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 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 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 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 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 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 as described above, the image quality and brightness uniformity of the projection 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, or 218.5 mm, or 219.8 mm, or 221.3 mm, or 223 mm, or 225 mm; the spherical radius of the convex surface of the first lens 51 is between 70 and 80 mm, for example, 70 mm, or 75 mm, or 77 mm, or 77.6 mm, or 80 mm; the central thickness of the first lens 51 is between 3.9 and 4.1 mm, for example, 3.9 mm, or 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, or 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 61-63mm, for example, 61mm, or 61.6mm, or 62.1mm, or 63mm. The spherical radius of the concave surface of the second lens 52 close to the first lens 51 is between 106-108mm, for example, 106mm, or 106.4mm, or 106.7mm, or 107.5mm, or 108mm. The central thickness of the second lens 52 is between 2.4-2.6mm, for example, 2.4mm, or 2.5mm, or 2.6mm. The diameter of the second lens 52 is between 50-51mm, for example, 50mm, or 50.3mm, or 50.7mm, or 51mm.

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

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

[0127] The fifth lens 55 has a spherical radius of between 87.5 and 88.5 mm, for example 87.5 mm, or 88.1 mm, or 88.5 mm, on the convex side away from the first lens 51. The fifth lens 55 has a spherical radius of between 142.5 and 144.5 mm, for example 142.5 mm, or 143.3 mm, or 143.8 mm, or 145.5 mm, on the convex side towards the first lens 51. The fifth lens 55 has a centre thickness of between 6.0 and 6.2 mm, for example 6 mm, or 6.1 mm, or 6.2 mm. The fifth lens 55 has a diameter of between 46.5 and 47.5 mm, for example 46.5 mm, or 47 mm, or 47.5 mm.

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

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

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

[0131] In some embodiments, the light emitted by the light source assembly 10 can be natural light. It should be noted that the natural light in the present disclosure refers to light that does not show polarization characteristics. Specifically, the natural light emitted by the light source assembly 10 can be white light. As shown in FIG. 7, the projection device can further include a polarizing assembly 20 disposed on the light emitting side of the light source assembly 10, configured to convert the light emitted by the light source assembly 10 into first polarized light of a first polarization direction.

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

[0133] It should be noted that the display panel 30 can include a plurality of pixel regions, and each pixel region can adjust the polarization direction of the first polarized light to obtain second polarized light with a polarization direction between the first polarization direction and the second polarization direction. It should be further noted that "between the first polarization direction and the second polarization direction" includes the two critical directions of the first polarization direction and the second polarization direction. That is, 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 can be a liquid crystal display panel, which specifically includes an array substrate and a counter substrate disposed opposite to each other, and a liquid crystal layer between the array substrate and the counter substrate. In one example, the array substrate includes a first substrate, a plurality of gate lines and a plurality of data lines disposed on the first substrate, the plurality of gate lines and the plurality of data lines are disposed crosswise to define a plurality of pixel regions, and each pixel region is provided with a pixel electrode. The counter substrate includes a second substrate and a common electrode disposed on the second substrate. By loading a pixel voltage on the pixel electrode and a common electrode on the common electrode, an electric field is generated between the pixel electrode and the common electrode to drive the liquid crystal in the pixel region to deflect, thereby adjusting the polarization direction of the first polarized light.

[0135] In one example, the polarizing assembly 20 can include a first polarizing sheet and a transparent substrate stacked together, the first polarizing sheet being located on a side of the transparent substrate away from the display panel 30 and configured to transmit polarized light of a first polarization direction. A gap is formed between the transparent substrate and the display panel 30. That is, a gap for air flow is formed between the transparent substrate and the display panel 30. The first polarizing sheet is located on a side of the transparent substrate away from the display panel 30, so that when the light emitted by the light source 10 strikes the polarizing assembly 20, the light first passes through the first polarizing sheet, thereby improving the modulation effect of the polarizing assembly 20 on the light. Specifically, the first polarizing sheet can be fixed on the surface of the transparent substrate by adhesion. The transparent substrate can be a glass substrate, which can play a heat insulation effect.

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

[0137] A first lens 60 is arranged between the second polarizing sheet 43 and the mirror 44, and the first lens 60 is configured to converge the light emitted by the second polarizing sheet 43 and emit the converged light to the mirror 44. The converged light is reflected by the mirror 44 and then emitted by the projection lens 50 to perform projection imaging.

[0138] In some embodiments, the light source assembly 10 is a collimated light source assembly configured to emit collimated light, so that the light source assembly 10 can emit more light to the polarizing assembly 20, and thus the display panel 30 can receive more polarized light of the first polarization direction.

[0139] It should be noted that the "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 light beam and the central axis.

[0140] As shown in FIG. 7, the light source assembly 10 includes a light source 11, a reflective light cup 15, and a second lens 16. In the embodiments of the present disclosure, the light source 11, the reflective light cup 15, and the second lens 16 constitute an illumination part of the projection device, and the polarizing assembly 20, the display panel 30, the second polarizing sheet 43, the mirror 44, and the projection lens 50 constitute an imaging part of the projection device.

[0141] Fig. 15 is a schematic view of a light source provided in some embodiments of the present disclosure. Optionally, as shown in Fig. 15, the light source 11 can specifically include a lamp panel 11a and a light emitting piece 11b disposed on the lamp panel 11a. The light emitting piece 11b can adopt an LED lamp.

[0142] In some embodiments, the shape of the light emitting surface of the light emitting piece 11b is the same as the shape of the display surface of the display panel 30, thereby facilitating the improvement of the light efficiency. Here, the shape refers to the shape category, for example, the shape of the light emitting surface and the shape of the display surface of the display panel 30 are both rectangular; or both elliptical; or both circular; or both hexagonal, etc.

[0143] In some embodiments, the light emitting surface of the light emitting piece 11b and the display surface of the display panel 30 are both rectangular, and the length direction of the light emitting surface is the same as the length direction of the display surface, and the width direction of the light emitting surface is the same as the width direction of the display surface, i.e., 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 piece 11b and the display surface of the display panel 30 can both be square, at which time, the four sides of the light emitting surface are respectively parallel to the four sides of the display surface.

[0144] As shown in Fig. 7, the second lens 16 is disposed between the light source 11 and the polarizing assembly 20, for collimating the light rays emitted by the light source 11 and reaching the second lens 16. Among them, the first lens 60 and the second lens 16 can both adopt a Fresnel lens. The adoption of the Fresnel lens can prevent large spherical aberration and aberration from occurring at the edge of the lens, thereby improving the imaging quality. Since the function of the second lens 16 is to collimate the divergent light of the light source, and the function of the first lens 60 is to converge the light from the display panel 30, when the first lens 60 and the second lens 16 both adopt a Fresnel lens, the sawtooth surface of the Fresnel lens faces the display panel 30, so that a circular ring or a dark spot appears on the display picture.

[0145] The reflecting light cup 15 is located between the light source 11 and the second lens 16, and is disposed around the optical axis of the second lens 16 to form a cylindrical structure; the cylindrical structure has a first opening facing the light source 11 and a second opening facing the second lens 16, and the area of the first opening is smaller than the area of the second opening. Through the setting of the reflecting light cup 15, at least part of the light rays emitted by the light source 11 and reaching the reflecting light cup 15 can be reflected to the second lens 16, thereby improving the light utilization rate and improving the brightness of the projected picture.

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

[0147] Further, the edge of the orthographic projection of the second opening on the reference plane is spaced apart from the edge of the orthographic projection of the display area on the reference plane by at least 0.1 mm, so as to ensure that the light received by the corner positions of the display area is more uniform, and the uniformity of the four corners of the projection picture is improved. In an example, the edge of the orthographic projection of the second opening on the reference plane is spaced apart from the edge of the orthographic projection of the display area on the reference plane by 0.1 mm to 2 mm, so as to improve the light utilization rate while ensuring the uniformity of the four corners of the projection picture.

[0148] In some embodiments, the light emitting surface of the light emitting piece 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 size of the light emitting surface of the light emitting piece 11b is small, so that the light emitting piece 11b tends to be a point light source, which is conducive to improving the brightness of the projection picture. 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 an example, the diagonal length of the display area is 5 inches, and the light emitting surface is a rectangle of 11.8 mm x 7.9; the power is 130 W, and the light efficiency is greater than 120 lm / W.

[0149] FIG. 16 is a schematic view of a reflective light cup provided in some embodiments of the present disclosure. In some embodiments, the light emitting surface of the light emitting piece 11b is rectangular; as shown in FIG. 16, the reflective light cup 15 includes a plurality of reflective walls 151, and the orthographic projection of different reflective walls 151 on the second lens 16 is located on different sides of the orthographic projection of the light emitting surface on the second lens 16. That is, the first opening includes a plurality of first sides, and the second opening includes a plurality of second sides, each first side and each second side is parallel to a side of the light emitting surface, and one reflective wall 151 of the reflective light cup 15 is connected between one first side and one second side.

[0150] In the above embodiments, the reflective surface of the reflective wall 151 is a curved surface with a curvature of 1000-2000 mm, so as to be conducive to well collecting the large-angle light emitted by the light emitting piece 11b, thereby improving the uniformity of the four corners of the projection picture.

[0151] Figure 17 is a diagram of a light path provided in some embodiments of the present disclosure, in which the height of the reflective light cup 15 is 95 mm, the first opening is a rectangle with a size of 12.2 mm x 8.3 mm, the second opening is a rectangle with a size of 112 mm x 65 mm, the reflective surface of the reflective wall is a curved surface with a curvature between 1000 mm and 2000 mm, and the focal length of the second lens 16 is 90 mm. The light emitting surface of the light emitting member 11b is spaced apart from the plane on which the first opening is located by a distance of 0.2. The light intensity distribution of the light emitting member 11b satisfies a Lambertian distribution, and light rays with a Lambertian half-angle between 0° and 50° are directly irradiated to the second lens 16, so that the light rays are better condensed and focused by the second lens 16. For light rays with a large angle, such as light rays with a Lambertian half-angle between 50° and 90°, the light rays are reflected by the reflective wall after being reflected by the curved surface, are irradiated to the second lens 16, and are condensed and focused by the second lens 16, so that the light rays are integrated into parallel light or approximately parallel light (indicated by LL in Figure 17) and are irradiated to the display panel 30.

[0152] In one example of the present disclosure, the off-axis ratio of the projected picture is 50%. FIG. 18 is a spot diagram of the projection device provided in some embodiments of the present disclosure, IMA in FIG. 18 represents an image plane, the numerical value marked after IMA is the radius of the image plane, and the two rows of data below in FIG. 18 represent the quantitative indicators of 11 fields of view, wherein the 11 data in the first row respectively represent the root mean square radii of the light ray regions formed by the object plane on 11 different sizes of image planes, and the second row of data respectively represent the geometric radii of the light ray regions formed by the object plane on 11 different sizes of image planes. Wherein, a large number of light rays emitted by one light emitting point in the light emitting assembly 10 are dispersed into a certain range after passing through the optical system due to aberration, and the intersection points with the image plane (i.e. the display panel 30) are no longer concentrated at the same point, forming a dispersed pattern scattered in 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 the imaging of the display optical system on the image plane. In other words, it is to actually draw the situation that a series of object points are imaged on the image plane after passing through the optical system by calculation. For convenience of expression, it can select a series of predetermined template forms, specifically, such as a point on the axis, the design process adopts the reverse light path to simulate a plurality of light emitting points, which are parallel to the entrance pupil, then pass through the optical system, and finally are imaged on the display panel 30. Obviously, if the optical system is a perfect optical system, the imaging points of these points are an ideal point. But for the actual optical system, it will be imaged as a diffraction spot, and the image of the diffraction spot on the display panel 30 is the spot diagram. Similarly, for the off-axis point, a series of light emitting points can also be formed according to the angle and position of the chief ray, and finally imaged on the image plane to form a diffraction spot. The quality of the optical design can be observed through the spot diagram, and the smaller the diffraction spot is, the better. If the diffraction spot is found to be small enough to meet the minimum diffraction spot requirement of the optical system (the unit of the spot diagram is microns), then the optical system is designed to be completed. In the embodiments of the present disclosure, through the design of the projection lens 50 described above, the root mean square radii of the light spots of each field of view from the central field of view to the edge field of view are all less than the size of one pixel of the 5 inch 4K LCD display panel, wherein the central field of view refers to the light emitted from the center point of the projected picture, and the edge field of view refers to the light emitted from the edge position of the projected picture.

[0153] Figure 19 is a modulation transfer function (MTF) diagram of the projection lens 50 provided in some embodiments of the present disclosure. The MTF diagram is a scientific method for analyzing the resolution of the projection lens 50. The resolution of the projection lens 50 is measured in line pairs per millimeter (lp / mm). Each line pair is composed of one black line and one white line. The resolution is the number of line pairs per millimeter that can be distinguished. The resolution of the projection lens 50 is tested by using a method of shooting a sinusoidal grating (a black and white grid in the test board). The periodic pattern of the brightness according to the sine is called a "sinusoidal grating". The density of the sinusoidal grating is called "spatial frequency". The unit of spatial frequency is lp / mm. lp / mm represents the number of periodic patterns of the brightness according to the sine per unit length (per millimeter). The clarity of the projection picture under 4K resolution is greater than 0.4. Each line in Figure 19 represents the MTF curve of the edge position of the field of view with different radii in the tangential direction and the sagittal direction. The values marked on each curve represent the radius of the field of view. As shown in Figures 18 and 19, the imaging clarity of the projection lens 50 provided in the embodiments of the present disclosure is high, and meets the design requirements of 4K resolution.

[0154] Figure 20 is a field curvature diagram and a distortion diagram of the projection device provided in some embodiments of the present disclosure. Field curvature is also called "image field curvature". When the lens has field curvature, the intersection of the entire light beam does not coincide with the ideal image point. Although a clear image point can be obtained at each specific point, the entire image plane is a curved surface. Thus, the entire image plane cannot be clearly seen at the same time during the inspection, which causes difficulty in imaging. The field curvature is less than 0.22 mm. The dispersion of the projection lens 50 for RGB three colors is small. The distortion is less than 0.85%. The barrel distortion and the pillow distortion of the projection picture are small.

[0155] Figure 21 is an on-axis aberration diagram of the projection device provided in some embodiments of the present disclosure. As shown in Figure 21, the on-axis aberration of the projection lens 50 for RGB three colors is small within 0.22 mm. Figure 22 is a perpendicular axis chromatic aberration diagram of the projection device provided in some embodiments of the present disclosure. As shown in Figure 22, the perpendicular chromatic aberration is less than half of the pixel size, and the color edge effect of the edge picture is not obvious. Figure 23 is a relative luminance diagram of the projection device provided in some embodiments of the present disclosure. The relative luminance of 0.7 field of view is greater than 80%, and the relative luminance of the edge field of view is greater than 70%. This indicates that the difference between the edge brightness and the center brightness of the projection picture is small, and the brightness uniformity is good.

[0156] FIG. 24 is a 9-point uniformity side view of a projection picture of a projection device provided in some embodiments of the present disclosure, the projection picture is adjusted to 90 inches (here, 90 inches refers to the diagonal length of the picture), wherein the 9-point uniformity refers to the average value of the ratio of the brightness of P1 to P9 points to the brightness of P5 point within 30s of the projection device being turned on. The edge four-corner uniformity includes: A-point uniformity (i.e., the ratio of the brightness of P10 point to P5 point), B-point uniformity (i.e., the ratio of the brightness of P11 point to P5 point), C-point uniformity (i.e., the ratio of the brightness of P13 point to P5 point), and D-point uniformity (i.e., the ratio of the brightness of P12 point to P5 point). FIG. 25 is an illuminance simulation diagram of a projection picture of a projection device provided in some embodiments of the present disclosure, wherein the diagonal length of the projection picture is 90 inches. Table 2 is the 9-point illuminance and edge four-corner illuminance values of the projection picture, and Table 3 is the 9-point brightness values and uniformity values of the projection picture. Wherein the power of the light emitting member 11b is 130W, the light efficiency is 120lm / W, the calculated projection brightness is 521lm, the 9-point uniformity is 77%, the edge four-corner uniformity is greater than 40%, and the display requirements of high brightness and high uniformity are met.

[0157] Table 2

[0158] Table 3

[0159] It can be understood that the above embodiments are only exemplary embodiments adopted for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Various modifications and improvements can be made by those of ordinary skill in the art without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also considered to be within the protection scope of the present disclosure.

Claims

1. A projection device, wherein, The application relates to a light source assembly, a display panel, a first lens, a reflector and a projection lens, light emitted by the light source assembly is sequentially irradiated to the reflector through the display panel and the first lens, and is reflected to the projection lens by the reflector and is emitted. The display area of the display panel has a first central normal line, 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 the first intersection point and the second intersection point have a second distance. The central axis of the projection lens and a first optical axis passing through the second intersection point have a first distance, 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. The central axis of the projection lens and a first optical axis passing through the second intersection point have a first distance, 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 apparatus according to claim 1, wherein, The first intersection point and the center of the projection lens have a first distance, and the second intersection point and the center of the display panel have a second distance; the first distance is greater than the second distance.

3. The projection apparatus according to claim 1 or 2, wherein, The reflector comprises a first reflecting part and a second reflecting part, the first reflecting part is located at one end of the first intersection point away from the display panel; the second reflecting part is located at one end of the second intersection point close to the display panel; 4. The projection apparatus according to any of claims 1 to 3, wherein, The central axis of the projection lens and the first reflecting part have a first included angle, The first central normal line and the second reflecting part form a second included angle, the first included angle and the second included angle are complementary. The first included angle theta1 and the second included angle theta2 satisfy: 0 DEG <= |theta1-theta2| <= 10 DEG. The projection lens comprises a condenser lens group, a diaphragm and a diverging lens group arranged in sequence in the direction away from the display panel; 5. The projection apparatus of claim 4, wherein, The projection lens satisfies at least one of the following conditions:

6. The projection apparatus according to any of claims 1 to 5, wherein, 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 light entrance surface and the light exit surface of the projection lens is less than or equal to 100 mm. The projection lens comprises a plurality of coaxially arranged lenses, the Abbe number of the lens closest to the reflector and the lens farthest from the reflector is less than 50. The projection lens comprises a plurality of coaxially arranged lenses, 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 away from the reflector, the first curved surface and the third curved surface are convex, and the second curved surface is concave; 7. The projection apparatus according to any one of claims 1 to 6, wherein, 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.

8. The projection apparatus according to any one of claims 1 to 7, wherein, The ratio of the focal length of the projection lens to the entrance pupil diameter is between 2.8 and 3.

3. ​ 9. The projection apparatus according to any of claims 1 to 8, wherein, ​ 10. The projection apparatus according to any one of claims 1 to 9, wherein, The projection lens comprises a condenser lens group, a diaphragm and a divergent lens group arranged in sequence in a direction away from the mirror; the divergent lens group comprises a plurality of lenses, and the diameters of the plurality of lenses in the divergent lens group gradually increase in a direction away from the diaphragm.

11. The projection apparatus according to any of claims 1 to 10, wherein, The light source assembly comprises a light source, a reflecting light cup and a second lens; The second lens is arranged between the light source and the polarizing component and is used for collimating light rays emitted by the light source and reaching the second lens; The reflecting light cup is arranged between the light source and the second lens and surrounds 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 that of the second opening.

12. The projection apparatus according to claim 11, wherein, The normal projection of the second opening on a reference plane on which the display panel is arranged covers and exceeds the normal projection of the display area on the reference plane.

13. The projection apparatus according to claim 12, wherein, An edge of the normal projection of the second opening on the reference plane is spaced apart from an edge of the normal projection of the display area on the reference plane by at least 0.1 mm.

14. The projection apparatus of claim 11, wherein, The light source comprises: a lamp plate; a light emitting member arranged on the lamp plate and located on the side of the lamp plate close to the display panel; wherein the light emitting surface of the light emitting member 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 apparatus of claim 11, wherein, The light source comprises: a lamp plate; a light emitting member arranged on the lamp plate and located on the side of the lamp plate close to the display panel; wherein the light emitting surface of the light emitting member is rectangular; the reflecting light cup comprises a plurality of reflecting walls, and the normal projections of different reflecting walls on the second lens are located on different sides of the normal projection of the light emitting surface on the second lens; and the reflecting surface of the reflecting wall is a curved surface with a curvature between 1000 and 2000 mm.

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