Projection device

Abstract

The invention provides a projection device which comprises a light source module, a display panel, a free-form surface reflector and a projection lens. The light source module comprises a light source, a first Fresnel lens and a second Fresnel lens. The first Fresnel lens and the second Fresnel lens are parallel to each other and are located between the light source and the display panel. The display panel is arranged between the light source module and the free-form surface reflector. The projection lens is used for transmitting the image light beam out of the projection device, and the direction of the optical axis of the projection lens is different from the normal direction of the first Fresnel lens. The projection device provided by the invention can improve the problem of projection picture distortion or picture edge resolution reduction.

Description

Technical Field

[0001] The present invention relates to an imaging system, and in particular to a projection device. Background Art

[0002] The existing projector architecture is that after the light source emits light, the light is converged by a focusing element, and then a Fresnel lens is used to converge the light into parallel light. The parallel light is incident on a non-self-luminous display panel (such as a liquid crystal panel) for image modulation to generate an image beam. After the image beam leaves the display panel, the second Fresnel lens (also commonly known as a field lens) collects the light into the lens module and projects it onto the screen.

[0003] However, although the Fresnel lens has the advantages of small size and low cost, the structure of the Fresnel lens in actual products will have an invalid area (such as the cross section of the Fresnel lens refractive surface) that has no refractive effect and reduces the imaging quality, and there are unavoidable defects in the process (for example, the refractive surface and the cross section of the Fresnel lens should theoretically be a sharp angle, but due to the injection molding process, it is formed into a rounded corner with a curvature radius). The above structures will further sacrifice the imaging quality. On the other hand, in the prior art, if an off-axis image is generated by tilting the projection lens, the optical axis of the incident Fresnel lens will be tilted, so that more image light beams pass through the invalid area and the rounded corner, which will cause the image to be further distorted and reduce the resolution. To reduce the curvature radius of the invalid area and the rounded corner, it is inevitable that the production cost of the component will increase and reduce the competitiveness of the product. Therefore, the above problems still need to be solved by relevant manufacturers. Summary of the invention

[0004] The projection device provided by the embodiment of the present invention can improve the problem of projection picture distortion or picture edge resolution reduction.

[0005] Other purposes and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

[0006] To achieve one or part or all of the above purposes or other purposes, a projection device is provided according to an embodiment of the present invention, which includes a light source module, a display panel, a free-form surface reflector and a projection lens. The light source module is used to provide an illumination beam, and includes a light source, a first Fresnel lens and a second Fresnel lens. The first Fresnel lens and the second Fresnel lens have a first light incident surface and a second light incident surface, respectively, the normal of the first light incident surface is parallel to the normal of the second light incident surface, and the first Fresnel lens is arranged between the light source and the second Fresnel lens. The display panel is used to convert the illumination beam into an image beam, and the first Fresnel lens and the second Fresnel lens are arranged between the light source and the display panel. The free-form surface reflector is arranged on the path of the image beam, and the display panel is arranged between the light source module and the free-form surface reflector. The projection lens is used to transmit the image beam from the free-form surface reflector out of the projection device, and the direction of the optical axis of the projection lens is different from the normal direction of the first light incident surface.

[0007] Based on the above, in the projection device provided by the embodiment of the present invention, the Fresnel lens is arranged between the light source and the display panel. After the light path of the image light beam exits the display panel, it no longer needs to pass through the Fresnel lens, thereby avoiding the Fresnel lens from reducing the quality of the image. The free-form surface reflector can improve the design freedom. The lens in the projection lens does not need to be configured off-axis to maintain the volume size, making the optical structure simple and easy to design, which can help reduce product costs and maintain good resolution without causing various distortions.

[0008] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic diagram of a projection device according to an embodiment of the present invention.

[0010] Figure 2 yes Figure 1 A schematic structural diagram of a projection device according to an embodiment.

[0011] Figure 3 It is a schematic structural diagram of a projection device according to another embodiment of the present invention.

[0012] Figure 4 is an illumination distribution diagram of a projection device according to an embodiment of the present invention.

[0013] Reference numerals list

[0014] 1.1a: Projection device

[0015] 10. 10a: Light source module

[0016] 20: Display Panel

[0017] 21: Display surface

[0018] 30: Free-form surface reflector

[0019] 40: Projection lens

[0020] 41: First lens

[0021] 42: Second lens

[0022] 43: The third lens

[0023] 44: The fourth lens

[0024] 100: Light source

[0025] 110: The first Fresnel lens

[0026] 110A: First light incident surface

[0027] 120: Second Fresnel lens

[0028] 120A: Second light incident surface

[0029] 130: Light collecting element

[0030] 140: Polarizing element

[0031] 141: Reflective polarizer

[0032] 142: Linear polarizer

[0033] 1000: Projection surface

[0034] A: Image beam area

[0035] A1: First optical axis

[0036] A2: Second optical axis

[0037] AC: Image beam area center

[0038] AO: Lens Optical Axis

[0039] AS: Light source axis

[0040] BL: Lighting beam

[0041] h1, h2, h3: height

[0042] IL: Image beam

[0043] N1, N2, N3: Normal

[0044] X, Y, Z: direction

[0045] θ: angle. DETAILED DESCRIPTION

[0046] The above and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the drawings. The directional terms (e.g., up, down, left, right, front or back, etc.) mentioned in the following embodiments are only the directions of the reference drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention.

[0047] Figure 1 is a schematic diagram of a projection device according to an embodiment of the present invention. Figure 1 According to an embodiment of the present invention, a projection device 1 is provided, which includes a light source module 10, a display panel 20, a free-form surface reflector 30, and a projection lens 40. The display panel 20 is disposed between the light source module 10 and the free-form surface reflector 30. The free-form surface reflector 30 is disposed on the light path of the image beam IL from the display panel 20. The image beam IL is transmitted to the projection lens 40 by reflection of the free-form surface reflector 30, and is transmitted out of the projection device 1 after passing through the projection lens 40.

[0048] The projection lens 40 of the projection device 1 has a lens optical axis AO. It is worth mentioning that the image beam IL emitted by the projection device 1 of this embodiment forms an image beam area A on a projection surface 1000 (such as a projection screen or a projection wall) perpendicular to the lens optical axis AO, and the lens optical axis AO may not pass through the image beam area center AC of the image beam area A. For example, the image beam IL is irradiated in the direction Y, and the image beam area A formed can be on the projection surface 1000 (i.e. Figure 1 A rectangular projection screen is formed on the plane formed by the direction X and the direction Z in the image beam area). The image beam area center AC of the image beam area A is, for example, the center of the rectangular projection screen. In the direction Z, the image beam area center AC has the same height from the upper and lower boundaries of the image beam area A, namely, the first height h1 and the second height h2. The position of the lens optical axis AO in the image beam area A is at a third height h3 from the lower boundary of the image beam area A, and the third height h3 is less than the second height h2. In other words, the projection device 1 can be an offset screen projector. Therefore, when using the projection device 1, there is no need to use a tripod or an angle adjustment structure to specially elevate it for use. Instead, it only needs to be placed on a plane (such as a desktop) so that the image beam area A can be presented above the horizontal plane of the plane for the user to watch. It should be noted that in Figure 1 In the illustration, the image beam region A is taken as an example of being off-axis by 80%, but the present invention is not limited thereto. In other embodiments, the off-axis effect of the projection device 1 may be between 50% and 100%.

[0049] Figure 2 yes Figure 1 Please refer to the schematic diagram of the projection device in Figure 2 The light source module 10 includes a light source 100 for providing an illumination beam BL, a first Fresnel lens 110, and a second Fresnel lens 120. The first Fresnel lens 110 and the second Fresnel lens 120 have a first light incident surface 110A and a second light incident surface 120A, respectively. The first Fresnel lens 110 and the second Fresnel lens 120 can be a single linear Fresnel lens or a single circular Fresnel lens, respectively, and correspondingly include refractive surfaces with refractive power arranged in concentric circles or linearly. The first light incident surface 110A and the second light incident surface 120A can be planes without refractive power, and are arranged on opposite sides of the refractive surfaces. It is worth mentioning that the normal N1 of the first light incident surface 110A can be parallel to the normal N2 of the second light incident surface 120A. In other words, the first Fresnel lens 110 and the second Fresnel lens 120 can be arranged in parallel, so that the illumination light beam BL can be easily converged by the first Fresnel lens 110 and the second Fresnel lens 120, and the stray light generated by unexpected refraction or reflection is reduced. On the other hand, the first Fresnel lens 110 is arranged between the light source 100 and the second Fresnel lens 120.

[0050] In order to reduce the heat generation of the projection device 1, the light source 100 can preferably use a light emitting diode (LED). The first Fresnel lens 110 and the second Fresnel lens 120 can be, for example, a plastic lens or an optical glass lens. Since the first Fresnel lens 110 and the second Fresnel lens 120 are low in cost, thin in thickness and mature in technology, the first Fresnel lens 110 and the second Fresnel lens 120 are used to converge the illumination light beam BL, which is conducive to the lightweight, miniaturization and low cost of the projection device 1. Compared with the use of a parallel dual lens array to converge light, it is often difficult to popularize the projection device that uses a lens array to converge light due to the high price and the difficulty in maintaining the yield of the microlens structure in the lens array. The use of the first Fresnel lens 110 and the second Fresnel lens 120 in this embodiment can help reduce the cost of the projection device 1 and improve the product competitiveness.

[0051] The display panel 20 is used to convert the illumination light beam BL into the image light beam IL. For example, the display panel 20 is a liquid crystal display (LCD), and the projection device 1 can be a single-chip liquid crystal projector. In this embodiment, since the first Fresnel lens 110 and the second Fresnel lens 120 are arranged between the light source 100 and the display panel 20, the light emitting side of the display panel 20 (such as the display surface 21) does not need to be provided with a Fresnel lens. That is, the projection device 1 can be a non-telecentric system. In some embodiments, after leaving the display panel 20, the image light beam IL can be directly irradiated to the free-form surface reflector 30. That is, no optical element can be arranged between the display panel 20 and the free-form surface reflector 30, which is beneficial to the mechanism design and optical path design of the projection device 1.

[0052] In addition, the free-form surface reflector 30 is disposed on the optical path of the image beam IL, and reflects the image beam IL generated from the display panel 20 to the projection lens 40. The free-form surface reflector 30 of the present invention is an asymmetric optical element and has a free-form reflective surface, which can optimize the image quality of the projection device 1 and improve the field curvature aberration and distortion aberration at the edge of the image beam area A (please allow for description below).

[0053] The projection lens 40 is used to transmit the image beam IL from the free-form surface reflector 30 out of the projection device 1, and the direction of the lens optical axis AO (the part turned by the free-form surface reflector 30) of the projection lens 40 is different from the direction of the normal line N3 of the display surface 21, thereby achieving the off-axis effect of the projection image. The projection lens 40 includes a first lens 41, a second lens 42, a third lens 43 and a fourth lens 44, which are symmetrically arranged along the lens optical axis AO from the object side to the image side. The material of the first lens 41, the second lens 42, the third lens 43 and the fourth lens 44 can be plastic or pure glass, but the present invention is not limited to this. In some embodiments, the second lens 42 and the third lens 43 can be made of materials with different refractive indices and form a cemented lens. In this way, the two lenses with different refractive indices are glued together to effectively eliminate chromatic aberration, but it is not limited to this.

[0054] Since the projection device 1 of this embodiment does not need to be provided with a Fresnel lens on the light-emitting side of the display panel 20 (e.g., the side of the display surface 21), after the image light beam IL leaves the display panel 20, it is sequentially reflected by the free-form surface reflector 30, and the projection lens 40 collects the light and transmits it out of the projection device 1, all of which can avoid the influence of the Fresnel lens on the imaging quality of the image light beam IL, so that the projection device 1 can produce a high-resolution projection picture.

[0055] In some embodiments, the first Fresnel lens 110 and the second Fresnel lens 120 may have a first optical axis A1 and a second optical axis A2, respectively, and the first Fresnel lens 110 and the second Fresnel lens 120 are symmetrically arranged with respect to the first optical axis A1 and the second optical axis A2, respectively. In other words, the first optical axis A1 and the second optical axis A2 may overlap, so that the illumination beam BL may be effectively converged by the first Fresnel lens 110 and the second Fresnel lens 120 in sequence, and the image beam IL may enter the projection lens 40, and the generation of stray light may be reduced. In some embodiments, the optical axis AS of the light source 100 may also be further overlapped with the first optical axis A1 and the second optical axis A2. In other words, the optical axis AS of the light source 100, the first optical axis A1 of the first Fresnel lens 110, and the second optical axis A2 of the second Fresnel lens 120 may all be coaxially arranged, so as to facilitate the light pattern integration of the illumination beam BL, so as to achieve an ideal optical effect.

[0056] In some embodiments, in order to avoid unnecessary divergence of the illumination light beam BL, the diopter of the first Fresnel lens 110 may be greater than the diopter of the second Fresnel lens 120. For example, the effective focal length of the first Fresnel lens 110 may be smaller than the effective focal length of the second Fresnel lens 120, which may further reduce the divergence angle of the illumination light beam BL.

[0057] It is worth mentioning that, in some embodiments, the display surface 21 of the display panel 20 may have an angle θ with the first light incident surface 110A (or the second light incident surface 120A), and the angle θ is greater than or equal to 2 degrees and less than or equal to 10 degrees.

[0058] Specifically, the first optical axis A1 of the first Fresnel lens 110 may form an angle θ with the normal N3 of the display surface 21 of the display panel 20. In other words, the illumination light beam BL emitted by the light source module 10 may be irradiated to the light-entering side of the display panel 20 at an incident angle of angle θ, thereby correcting the angle of the light entering the lens end to achieve better optical geometric efficiency. In this way, the display panel 20 does not need to be set off-axis (i.e., the lens optical axis AO after the turn passes through the geometric center of the display surface 21 of the display panel 20), and the projection device 1 can generate the above-mentioned Figure 1 Since the image beam IL can be effectively collected by the projection lens 40 without causing excessive brightness loss, it is also beneficial to maintain the clarity and high image quality of the display image generated by the image beam IL.

[0059] In order to reduce the problem of reduced resolution due to possible trapezoidal distortion, barrel distortion, and pincushion distortion of the off-axis image, the free-form surface reflector 30 can be used to correct the image and maintain the image quality. That is, when the projection device 1 of this embodiment is used to generate an image projected onto the projection surface 1000, the distortion of the projection image caused by the tilt of the display panel 20 relative to the light source module 10 will be compensated by the adjustment of the image beam IL by the free-form surface reflector 30. Through the above, it is possible to avoid adding redundant optical elements in the housing of the projection device 1, making it easy to assemble, reducing the volume of the projection device 1 and achieving lightweight, while maintaining the provision of a good image.

[0060] Figure 3 is another embodiment of the present invention, and Figure 2 The difference of the projection device 1 of the embodiment is that: on the basis of considering improving the utilization rate of light energy and increasing the brightness of the display screen, the light source module 10a of the projection device 1a can further include a light collecting element 130, which is arranged between the first Fresnel lens 110 and the light source 100. The light collecting element 130 can be one of a light bucket, a light collecting bowl or a lens, but the present invention is not limited thereto. The light collecting element 130 can collect the divergent illumination light beam BL emitted by the light source 100, so as to increase the light intensity irradiated to the display panel 20, so that the brightness of the generated image light beam IL is further increased. A heat dissipation element (such as a fin) and a fan (both not shown) can be arranged near the light source 100 or the light collecting element 130 to transfer the heat emitted by the light source 100 or the light collecting element 130 to the outside of the projection device 1, so as to prevent the heat energy from affecting the service life of the light source 100, the display panel 20 or the circuit board (not shown) therein.

[0061] In some embodiments, the orthographic projection areas of the first Fresnel lens 110 and the second Fresnel lens 120 on the display panel 20 may be the same. Since the first Fresnel lens 110 and the second Fresnel lens 120 are arranged in parallel, it can also be understood that the areas of the first Fresnel lens 110 and the second Fresnel lens 120 are the same, that is, the first Fresnel lens 110 and the second Fresnel lens 120 have equivalent lens areas, but the present invention is not limited thereto.

[0062] On the other hand, the light source module 10a may further include a polarizing element 140. The polarizing element 140 is further disposed between the first Fresnel lens 110 and the second Fresnel lens 120. The polarizing element 140 may be parallel to the second Fresnel lens 120. In other embodiments, the polarizing element 140 may be disposed between the second Fresnel lens 120 and the display panel 20.

[0063] In detail, the polarizing element 140 may be a linear polarizer, so that the illumination light beam BL becomes linearly polarized light after passing through the polarizing element 140, and is transmitted to the display panel 20, so as to be modulated by the display medium (e.g., liquid crystal) and the electrode layer in the display panel 20 to generate the image light beam IL. It should be particularly noted that there is an angle θ between the plane of the polarizing element 140 and the plane of the display panel 20. That is, the polarizing element 140 is not disposed inside the display panel 20 like a conventional liquid crystal display, but is disposed separately from the display panel 20. Accordingly, since the polarizing element 140 can provide a linearly polarized light beam, it is not necessary to set a linear polarizer on the light incident side in the display panel 20, and only a single linear polarizer needs to be disposed on the display surface 21.

[0064] In some embodiments, the polarizing element 140 may further include a reflective polarizer 141 and a linear polarizer 142. The reflective polarizer 141 allows light of a specific polarization state to pass through and reflects light of a non-specific polarization state back to the direction of the light source 100, while the linear polarizer 142 allows light of a specific polarization state to pass through and absorbs light of other polarization states. With the above arrangement, the reflective polarizer 141 can be used to reflect light of a non-specific polarization state back to the second Fresnel lens 120 and the first Fresnel lens 110, so that more light can be reused by the light source module 10a (such as the light source 100 and / or the light collecting element 130) and then pass through the reflective polarizer 141 and the linear polarizer 142, so that more light energy can be recycled to provide to the display panel 20, thereby improving the brightness of the display screen. In other embodiments, the light source module 10 a may further include a quarter wave plate (not shown) disposed on a side of the second Fresnel lens 120 away from the polarizing element 140 , that is, on the second light incident surface 120A of the second Fresnel lens 120 .

[0065] Figure 4 is an illumination distribution diagram of a projection device according to an embodiment of the present invention. Figure 4 In an optical simulation system (such as Zemax), it can be found that the projection device 1 of this embodiment has good performance in terms of geometric efficiency, central illumination of the screen, and illumination uniformity on the projection screen. The peak illumination can reach 4.19*10 -3 Watt / square centimeter (W / cm 2 ), and the total power of the image can reach 5.58*10 1 Watt (W). Compared with the existing technology, the peak illumination and total power are 2.83*10 -3 Watt / square centimeter (W / cm 2 ) and 3.44*10 1Watt (W), the projection device 1 of this embodiment has good performance in both the central illumination and the illumination uniformity of the picture.

[0066] In summary, in the projection device provided by the embodiment of the present invention, the Fresnel lens is arranged between the light source and the display panel. After the light path of the image light beam exits the display panel, it no longer needs to pass through the Fresnel lens, thereby avoiding the Fresnel lens from reducing the quality of the image. The free-form surface reflector can improve the design freedom. The lens in the projection lens does not need to be off-axis and can maintain the volume size, making the optical structure simple and easy to design, which can help reduce product costs and maintain good resolution without causing various distortions.

[0067] The above description is only a preferred embodiment of the present invention, and it cannot be used to limit the scope of the implementation of the present invention. That is, all simple equivalent changes and modifications made in accordance with the claims of the present invention and the specification of the present invention are still within the scope of the patent of the present invention. In addition, any embodiment or claim of the present invention is not required to achieve all the purposes, advantages or features disclosed in the present invention. In addition, the abstract of the specification and the name of the invention are only used to assist in the retrieval of patent documents, and are not used to limit the scope of rights of the present invention. In addition, the terms "first", "second", etc. mentioned in this specification or claims are only used to name the name of the element or distinguish different embodiments or scopes, and are not used to limit the upper or lower limit of the number of elements.

Claims

1. A projection device, characterized in that: The projection device comprises a light source module, a display panel, a free-form surface reflector and a projection lens, wherein: The light source module is used to provide an illumination beam, and comprises a light source, a first Fresnel lens and a second Fresnel lens, wherein the first Fresnel lens and the second Fresnel lens respectively have a first light incident surface and a second light incident surface, a normal line of the first light incident surface is parallel to a normal line of the second light incident surface, and the first Fresnel lens is disposed between the light source and the second Fresnel lens; The display panel is used to convert the illumination light beam into an image light beam, and the first Fresnel lens and the second Fresnel lens are disposed between the light source and the display panel; The free-form surface reflector is arranged on the path of the image light beam, and the display panel is arranged between the light source module and the free-form surface reflector; The projection lens is used to transmit the image light beam from the free-form surface reflector out of the projection device. The projection lens has a lens optical axis, and the direction of the lens optical axis is different from the normal direction of the first light incident surface.

2. The projection device according to claim 1, characterized in that: The first Fresnel lens and the second Fresnel lens have a first optical axis and a second optical axis respectively, and the first optical axis overlaps with the second optical axis.

3. The projection device according to claim 2, characterized in that: The optical axis of the light source overlaps with the second optical axis.

4. The projection device according to claim 1, characterized in that: The display panel has a display surface. An angle is formed between the first light incident surface and the display surface. The angle is greater than or equal to 2 degrees and less than or equal to 10 degrees.

5. The projection device according to claim 1, characterized in that: The image light beam directly irradiates the free-form surface reflector after leaving the display panel.

6. The projection device according to claim 1, characterized in that: The light source module further includes a light collecting element, and the light collecting element is arranged between the first Fresnel lens and the light source.

7. The projection device according to claim 1, characterized in that: The focal length of the first Fresnel lens is smaller than the focal length of the second Fresnel lens.

8. The projection device according to claim 1, characterized in that: The light source module further includes a polarizing element, and the polarizing element is disposed between the second Fresnel lens and the display panel, wherein the polarizing element is parallel to the second Fresnel lens.

9. The projection device according to claim 8, characterized in that: The polarizing element includes a reflective polarizer and a linear polarizer.

10. The projection device according to claim 1, characterized in that: The orthographic projection areas of the first Fresnel lens and the second Fresnel lens on the display panel are the same.

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