Micro-projection optical system based on micro light emitting diode display

Abstract

This invention provides a micro-projection optical system based on a micro-light-emitting diode (LED) display, comprising: a first lens group, an aperture stop, a second lens group, and a light source lens group arranged sequentially; the aperture stop controls the amount of light entering the light source lens group, the light source lens group emits light and collimates the emitted light, the first lens group adjusts the projection field of view and balances the system field curvature, and the second lens group balances system aberrations and chromatic aberrations; the first lens group includes: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially, and the second lens group includes: a sixth lens, a seventh lens, and an eighth lens arranged sequentially; the light source lens group includes: a ninth lens, a tenth lens, an eleventh lens, and a micro-light-emitting diode (LED) display. This invention solves the problems of low projection brightness, image quality, and resolution, as well as high cost and design difficulty in the prior art.

Description

Technical Field

[0001] This invention relates to the field of optical projection technology, and in particular to a micro-projection optical system based on a micro-light-emitting diode display. Background Technology

[0002] Currently, the main projection technologies available on the market are DLP projection, LCD projection, 3LCD projection, ALPD projection, and LCOS projection.

[0003] MicroLED displays (English: MicroLightEmittingDiodeDisplay, abbreviated as MicroLED) are based on the principle of thinning, miniaturizing, and arraying LED structures, with their size only around 1 to 10 μm.

[0004] Since LCD screens, LCOS screens, and DMDs are not self-emissive devices, projection systems built on image generating devices such as LCD, LCOS, and DLP technologies all require a matching lighting system. The light source emits light through the lighting optics system and is incident on the image generator. The image information is then transmitted or reflected and projected onto the projection surface through the imaging optics system. The projection brightness, image quality, and resolution are relatively low, and the cost is relatively high.

[0005] Micro-light-emitting diode displays are self-emissive devices, consisting of pixel-level self-emissive screens composed of micron-level light-emitting chip arrays. Their inherent light source properties eliminate the need for an illumination optical system to provide light energy, allowing them to be directly paired with an imaging optical system to achieve reduced, same-size, and magnified projection.

[0006] LED chips all use Lambertian light sources (i.e., 180° light emission). Although collimating lenses can be added to the package of micro LED displays, high collimation cannot be achieved due to limitations in size and lens diopter. In other words, micro LED displays still have the characteristic of increasing the light emission angle, resulting in a very large light cone angle at the native screen end. The optical system needs to be adapted to a large aperture to improve system efficiency, which increases the design difficulty of the imaging optical system. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a micro projection optical system based on a micro light-emitting diode display. This invention solves the problems of low projection brightness, image quality and resolution, high cost and high design difficulty in the prior art.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] A micro-projection optical system based on a micro-light-emitting diode display includes:

[0010] The first lens group, the aperture stop, the second lens group, and the light source lens group are arranged in sequence.

[0011] The aperture is used to control the amount of light entering the light emitted by the light source lens group. The light source lens group is used to emit light and collimate the emitted light. The first lens group is used to adjust the size of the projection field of view and balance the field curvature of the system. The second lens group is used to balance the aberrations and chromatic aberrations of the system.

[0012] The first lens group includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence, wherein the first lens, the second lens, the third lens, the fourth lens, and the fifth lens all have positive optical power;

[0013] The second lens group includes a sixth lens, a seventh lens, and an eighth lens arranged in sequence, all of which have positive optical power;

[0014] The light source lens group includes a ninth lens, a tenth lens, an eleventh lens, and a micro-light-emitting diode display. The ninth lens, the tenth lens, and the eleventh lens all have positive optical power. The micro-light-emitting diode display is a pixel-level self-emissive screen composed of a micron-level light-emitting chip array.

[0015] Preferably, both the first lens and the ninth lens are aspherical lenses.

[0016] Preferably, the ratio of the focal length of the first lens group to that of the micro-projection optical system is in the range of 1.4-1.6.

[0017] Preferably, the ratio of the focal length of the second lens group to that of the micro-projection optical system is in the range of 1.5-1.7.

[0018] Preferably, the ratio of the focal length of the light source lens to that of the micro-projection optical system is in the range of 1.7-1.9.

[0019] Preferably, the screen size of the micro-LED display is less than or equal to 0.6 inches.

[0020] Preferably, both the tenth lens and the eleventh lens are cemented lenses.

[0021] Preferably, the refractive index of the first lens is in the range of 1.5-1.65, and the Albe constant of the first lens is in the range of 50-70.

[0022] Preferably, the refractive index of the first lens is in the range of 1.5-1.65, and the Albe constant of the first lens is in the range of 40-60.

[0023] Preferably, the gap between the eighth lens and the ninth lens is in the range of 20-40 mm.

[0024] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0025] This invention provides a micro-projection optical system based on a micro-light-emitting diode display. By setting up a micro-light-emitting diode display and a matching lens combination, this invention improves projection brightness, image quality and resolution, and reduces the design difficulty and cost of the imaging optical system. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 An optical architecture diagram provided for an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of a single-channel optical architecture provided in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of a multi-channel optical architecture provided in an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the optical architecture dot array provided in an embodiment of the present invention;

[0031] Figure 5 A schematic diagram of the optical architecture MTF provided in an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of the relative illumination of the optical architecture provided in an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1-Aperture, 2-Micro LED display, 3-Light source lens group, GM1-First lens, G2-Second lens, G3-Third lens, G4-Fourth lens, G5-Fifth lens, G6-Sixth lens, G7-Seventh lens, G8-Eighth lens, GM9-Ninth lens, G10-Tenth lens, G11-Eleventh lens. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The purpose of this invention is to provide a micro-projection optical system based on a micro-light-emitting diode display. This invention realizes a projection scheme for a large-size micro-light-emitting diode display with a large emission angle, and provides a multi-purpose optical architecture selection scheme, solving problems such as low relative illumination of the field of view, insufficient image quality, and unstable system architecture in this type of optical system.

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] like Figure 1 As shown, the present invention provides a micro-projection optical system based on a micro-light-emitting diode display 2, comprising:

[0039] The first lens group, aperture 1, second lens group, and light source lens group 3 are arranged in sequence.

[0040] The aperture 1 is used to control the amount of light entering the light emitted by the light source lens group 3. The light source lens group 3 is used to emit light and collimate the emitted light. The first lens group is used to adjust the size of the projection field of view and balance the field curvature of the system. The second lens group is used to balance the aberrations and chromatic aberrations of the system.

[0041] The first lens group includes: a first lens GM1, a second lens G2, a third lens G3, a fourth lens G4 and a fifth lens G5 arranged in sequence, wherein the first lens GM1, the second lens G2, the third lens G3, the fourth lens G4 and the fifth lens G5 all have positive optical power;

[0042] The second lens group includes a sixth lens G6, a seventh lens G7, and an eighth lens G8 arranged in sequence, wherein the sixth lens G6, the seventh lens G7, and the eighth lens G8 all have positive optical power;

[0043] The light source lens group 3 includes: a ninth lens GM9, a tenth lens G10, an eleventh lens G11, and a micro-light-emitting diode display 2. The ninth lens GM9, the tenth lens G10, and the eleventh lens G11 all have positive optical power. The micro-light-emitting diode display 2 is a pixel-level self-emissive screen composed of a micron-level light-emitting chip array.

[0044] Furthermore, such as Figure 2-3 As shown, both the first lens GM1 and the ninth lens GM9 are aspherical lenses.

[0045] Furthermore, the ratio of the focal length of the first lens group to that of the micro-projection optical system ranges from 1.4 to 1.6.

[0046] Furthermore, the ratio of the focal length of the second lens group to that of the micro-projection optical system ranges from 1.5 to 1.7.

[0047] Furthermore, the ratio of the focal length of the light source lens to that of the micro-projection optical system ranges from 1.7 to 1.9.

[0048] Furthermore, the screen size of the micro-LED display 2 is less than or equal to 0.6 inches, and the imaging optical system is matched with an F-number greater than F / 1.0. F / 1.0 refers to the F-number at the micro-LED, which corresponds to a numerical aperture of 0.5.

[0049] Furthermore, both the tenth lens G10 and the eleventh lens G11 are cemented lenses. A cemented doublet is placed behind the aperture 1 and in front of the micro-LED display 2, its combination of low-refractive-index, high-Abbe number material and high-refractive-index, low-Abbe number material effectively reducing the system's secondary spectrum; G10 is a low-refractive-index, high-Abbe number material (1.40 < n10 < 1.65, 55 < v10 < 75), and G11 is a high-refractive-index, low-Abbe number material (1.70 < n11 < 1.85, 20 < v10 < 40), where nd is the refractive index of the d-th lens, Vd is the Abbe constant of the d-th lens, and d is a positive integer greater than 0.

[0050] Furthermore, the refractive index of the first lens GM1 is in the range of 1.5-1.65, and the Albe constant of the first lens GM1 is in the range of 50-70.

[0051] Furthermore, the refractive index of the first lens GM1 is in the range of 1.5-1.65, and the Albe constant of the first lens GM1 is in the range of 40-60.

[0052] Furthermore, the gap between the eighth lens G8 and the ninth lens GM9 is preferably 20-40 mm to accommodate a beam combining / splitting device. The architecture includes a light source lens group 3 (GM9 / G10 / G11), which serves as both a component of the imaging optical system and a collimation function for the light source. Therefore, the light emitted by the micro-LED display 2 can be collimated and transmitted through the long gap between G8 and GM9 after passing through the light source lens group 3 without excessive energy loss, thereby achieving multi-channel beam combining within this gap.

[0053] The light source lens group 3 has positive optical power and includes an aspherical lens GM9, which provides the system with maximum aberration correction and ensures that the incident angle of the principal rays in each field of view is perfectly matched with the light-emitting cone angle and angular vector of the micro-LED display, thereby improving the image quality and efficiency of the entire imaging system.

[0054] Table 1 shows the specific parameters of the optical architecture.

[0055] Table 1. Specific parameters of the optical architecture

[0056]

[0057]

[0058]

[0059] Table 2 shows the coefficients of each order for the first lens GM1 and the ninth lens GM9, as shown below:

[0060]

[0061] like Figure 4 As shown, a dot plot illustrates how rays emanating from a single point, after passing through an optical system, intersect the image plane at a point different from the initial point due to aberrations, forming a diffuse pattern scattered over a certain area. Here, C is the radius of curvature, K is the conic coefficient, An is the coefficient of the higher-order term corresponding to the even-order aspherical formula, and n is an even number. Dot plots are one of the most commonly used evaluation methods in modern optical design. When using dot plots, firstly, pay attention to the values ​​in the table; smaller values ​​indicate better image quality. Secondly, the shape of the distribution pattern can also reveal the influence of geometric aberrations in the system. Figure 4 (a) is the first schematic diagram of the optical architecture dot array, where the RMS radius is 1.061 and the CEO radius is 2.460; Figure 4 (b) is a second schematic diagram of the optical architecture dot matrix, where the RMS radius is 1.129 and the CEO radius is 3.086; Figure 4 (c) is the third schematic diagram of the optical architecture dot diagram, where the RMS radius is 1.271 and the CEO radius is 3.234; Figure 4 (d) is the fourth schematic diagram of the optical architecture dot matrix, where the RMS radius is 1.384 and the CEO radius is 3.813; Figure 4 (e) is the fifth schematic diagram of the optical architecture dot matrix, where the RMS radius is 1.405 and the CEO radius is 3.911; Figure 4 (f) is the sixth schematic diagram of the optical architecture dot array, where the RMS radius is 1.338 and the CEO radius is 3.292; Figure 4(g) is the seventh schematic diagram of the optical architecture dot diagram, where the RMS radius is 1.254 and the CEO radius is 3.047; Figure 4 (h) is the eighth schematic diagram of the optical architecture dot array, where the RMS radius is 1.236 and the CEO radius is 3.150; Figure 4 (i) is the ninth schematic diagram of the optical architecture dot diagram, where the RMS radius is 1.302 and the CEO radius is 3.582; Figure 4 (j) is the tenth schematic diagram of the optical architecture dot diagram, where the RMS radius is 1.506 and the CEO radius is 4.782; Figure 4 (k) is the eleventh schematic diagram of the optical architecture dot diagram, where the RMS radius is 1.863 and the CEO radius is 6.019; Figure 4 (m) is the twelfth schematic diagram of the optical architecture dot matrix, where the RMS radius is 2.624 and the CEO radius is 7.091. Among them, Figure 4 The first row from left to right is (a) to (d), the second row from left to right is (e) to (h), and the third row from left to right is (i) to (m).

[0062] like Figure 5 As shown, MTF (Modulation Transfer Function) is currently the most accurate and scientific evaluation standard for lenses. The vertical axis represents contrast ratio; the closer it is to 1, the better the lens image quality. The horizontal axis represents resolution, measured in line pairs per millimeter. The image source pixel size used in this embodiment is 9.3µm, corresponding to a design resolution of 54 line pairs per millimeter. Projection lenses generally require an MTF value of at least 0.3 across all fields of view at the design resolution, while the MTF values ​​in the optical zoom range of this embodiment are all above 0.8, demonstrating excellent image quality.

[0063] like Figure 6 As shown, relative illuminance refers to the ratio of illuminance at different coordinate points on the image plane to the illuminance at the center point. The vertical axis represents the normalized illuminance value, and the horizontal axis represents the field of view angle of the lens. Under the same conditions, a smooth transition of the relative illuminance curves for each field of view indicates uniform illuminance within the projection frame, and the closer the relative illuminance value for each field of view is to 1, the higher the final projection brightness.

[0064] The beneficial effects of this invention are as follows:

[0065] As can be seen from the implementation case, the pixel size of the micro-LED display is 9.3 micrometers. As can be seen from the dot plot, the radius of the blur spot in each field of view is less than 2.624 micrometers. As can be seen from the MTF plot, the MTF (modulation transfer function) of the optical system at low, medium and high frequencies is very good, which indicates that it has high resolution.

[0066] As can be seen from the relative illumination diagram, it has a high uniformity of image plane illumination, which also suggests that the system has the characteristics of high efficiency and high brightness.

[0067] As shown in the schematic diagrams of single-channel and multi-channel optical architectures, this architecture can realize monochrome screens, single-color screens, or multi-color screen light combining applications. It caters to the needs of multiple application scenarios, high performance, and low cost.

[0068] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0069] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A micro-projection optical system based on a micro-light-emitting diode display, characterized in that, The miniature projection optical system consists of a first lens group, an aperture, a second lens group, and a light source lens group arranged in sequence. The aperture is used to control the amount of light entering the light emitted by the light source lens group, the light source lens group is used to emit light and collimate the emitted light, the first lens group is used to adjust the size of the projection field of view and balance the field curvature of the system, and the second lens group is used to balance the aberrations and chromatic aberrations of the system. The first lens group consists of a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence, wherein the first lens and the second lens have negative optical power, and the third lens, the fourth lens, and the fifth lens all have positive optical power; The second lens group consists of a sixth lens, a seventh lens, and an eighth lens arranged in sequence. The sixth lens has negative optical power, while the seventh and eighth lenses have positive optical power. The light source lens group consists of a ninth lens, a tenth lens, an eleventh lens, and a micro-light-emitting diode display. The ninth and tenth lenses have positive optical power, the eleventh lens has negative optical power, and the micro-light-emitting diode display is a pixel-level self-emissive screen composed of a micron-level light-emitting chip array. The ratio of the focal length of the first lens group to that of the micro-projection optical system is 1.63; The ratio of the focal length of the second lens group to that of the micro-projection optical system is -31.88; The ratio of the focal length of the light source lens group to that of the micro-projection optical system is 1.81; The sixth and seventh lenses are cemented lenses, and the tenth and eleventh lenses are cemented lenses. 2.The micro-projection optical system based on micro-LED display according to claim 1, wherein, Both the first lens and the ninth lens are aspherical lenses.

3. The micro-projection optical system based on a micro-light-emitting diode display according to claim 1, characterized in that, The screen size of the micro-LED display is less than or equal to 0.6 inches.

4. A micro-projection optical system based on a micro-light-emitting diode display according to claim 1, characterized in that, The first lens has a refractive index of 1.59 and an Albe constant of 61.

2.

5. A micro-projection optical system based on a micro-light-emitting diode display according to claim 1, characterized in that, The gap between the eighth lens and the ninth lens is 30mm.

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