Multi-reflection ultra-short-focus projection optical system

Abstract

The invention provides a multi-reflection ultra-short-focus projection optical system. The multi-reflection ultra-short-focus projection optical system comprises an image generation unit sensor, a projection optical assembly and a projection screen, the projection optical assembly comprises a refraction lens group, a reflecting mirror A and a reflecting mirror B. The refraction lens group firstly amplifies an image on the sensor and meanwhile is responsible for controlling the overall imaging quality, then a light path is folded and reversed through the reflecting mirror A and the reflecting mirror B, the view field is further expanded, a large-size image is projected in a short distance, meanwhile, the projection direction can be kept parallel to the optical axis direction, and the projection effect is improved. The system has the advantages of large field angle, good imaging effect and high projection image quality. The two reflectors are added to compress and fold a light path, so that the projection direction is the same as the optical axis direction, the installation position is more flexible, the reflectors can well correct distortion and aberration, meanwhile, due to folding of the light path, the structure is more compact, the machining and assembling difficulty is moderate, and the cost is low. And the requirements of miniaturization and portability can be met.

Description

Technical Field

[0001] The invention relates to the technical field of imaging devices, in particular to a multi-reflection ultra-short-focus projection optical system. Background Art

[0002] Ultra-short-throw projection technology refers to the technology that allows a projector to project a large-size image at an extremely short distance. It has been widely used in many fields such as education, business, and home entertainment, but the existing ultra-short-throw projection system still has the following problems. Due to the limitations of the optical system, the existing ultra-short-throw projectors have certain losses in image quality, such as distortion and uneven brightness. The manufacturing cost is high and the volume is large, which is not conducive to portability. The projection screen is in the opposite direction of the optical axis of the projection system, and the installation position is not flexible enough. In response to the above problems, it is necessary to provide a new ultra-short-throw projection optical system based on the principle of multiple reflections. By optimizing the optical path design and adopting two reflection structures, the system can compress the optical path and improve the image quality while maintaining a short focal length, and make the projection screen and the projection system have the same optical axis direction, which greatly improves the flexibility of installation during actual use. Summary of the invention

[0003] The purpose of the present invention is to provide a multi-reflection ultra-short-focus projection optical system, which can project a large-sized image at a relatively short distance while keeping the projection direction parallel to the optical axis direction. It has the advantages of a large field of view, good imaging effect, and high projection image quality, and is suitable for occasions with limited space.

[0004] In order to achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions: a multi-reflection ultra-short-focus projection optical system, comprising an image generating unit sensor, a projection optical component and a projection screen; the image generating unit sensor is used to generate an image; the projection optical component first enlarges the image generated by the image generating unit sensor, and then folds and reverses the optical path to further expand the field of view, and projects an enlarged image on the projection screen; the projection direction of the image generating unit sensor is parallel to the optical axis direction; the projection screen is parallel to the optical axis direction.

[0005] As a further improvement of the technical solution of the present invention, the projection optical component includes a refractive lens group, a reflector A and a reflector B; the refractive lens group and the image generating unit sensor are located on the same optical axis; the reflector A is arranged below the optical axis; the reflector B is arranged above the optical axis; the refractive lens group first amplifies the image of the image generating unit sensor and projects it onto the reflector, the image is reflected onto the reflector B through the reflector A, and the image is then reflected by the reflector B and projected onto the projection screen, thereby folding and reversing the light path, further expanding the field of view, and projecting a large-size image at a short distance.

[0006] As a further improvement of the technical solution of the present invention, the curved surface of the reflector A and the curved surface of the reflector B are both aspherical surfaces; the description equation of the aspherical surface is:

[0007]

[0008] Among them, z is the height from the vertex to the surface, r is the distance from the point perpendicular to the optical axis to the optical axis, c is the inverse of the radius of curvature, k is the cone coefficient, which is used to describe the surface shape, Ai is the i-th aspheric coefficient, and n is the number of coefficients.

[0009] As a further improvement of the technical solution of the present invention, the refractive lens group includes at least one lens.

[0010] As a further improvement of the technical solution of the present invention, the distance between the projection screen and the projection optical component is 500 mm.

[0011] As a further improvement of the technical solution of the present invention, the image generating unit sensor is a digital micromirror device DMD or a liquid crystal display panel LCD.

[0012] As a further improvement of the technical solution of the present invention, the positions and angles of the refractive lens group, the reflector A, the reflector B and the projection screen can be adjusted according to actual needs.

[0013] As a further improvement of the technical solution of the present invention, the projection screen is a flat surface or a curved surface.

[0014] The present invention has the following beneficial effects:

[0015] The present invention provides a multi-reflection ultra-short-focus projection optical system, which is provided with an image generation unit sensor, a refractive lens group, a reflector A, a reflector B, and a projection screen. In the optical system, the refractive lens group first amplifies the image on the sensor and is responsible for controlling the overall imaging quality, and then folds and reverses the optical path through the reflector A and the reflector B to further expand the field of view, so as to achieve the projection of a large-size image at a relatively short distance, and at the same time can keep the projection direction parallel to the optical axis direction, has the advantages of a large field of view, good imaging effect, and high projection image quality, and is suitable for occasions with limited space. By optimizing the optical path design and adopting two reflective structures, the system can compress the optical path and improve the image quality while maintaining a short focal length, and make the projection screen and the projection system have the same optical axis direction, which greatly improves the flexibility of installation during actual use. Compared with the traditional full-refractive projection lens, this system adds two reflectors to compress and fold the light path so that the projection direction is the same as the direction of the optical axis, which makes the installation position more flexible. The added reflectors can correct distortion and aberration well. At the same time, the folding of the light path makes the structure more compact, and the processing and assembly difficulty is moderate, which can meet the needs of miniaturization and portability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0017] Figure 1 It is a schematic diagram of a multi-reflection ultra-short-focus projection optical system;

[0018] Figure 2 It is a light path diagram of a multi-reflection ultra-short-focus projection optical system;

[0019] Figure 3 A light spot array diagram of a multi-reflection ultra-short-focus projection optical system;

[0020] Figure 4 A grid distortion diagram of a multi-reflection ultra-short-focus projection optical system;

[0021] Figure 5 It is an MTF curve diagram of a multi-reflection ultra-short-focus projection optical system;

[0022] Figure 6 It is a relative illumination curve of a multi-reflection ultra-short-focus projection optical system.

[0023] In the accompanying drawings: 1-image generating unit sensor; 2-refractive lens group; 3-reflector A; 4-reflector B; 5-projection screen. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0025] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, upper end, lower end, top, bottom...) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0026] In the present invention, unless otherwise clearly defined and limited, the term "connection" should be understood in a broad sense, for example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features; in addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0029] like Figure 1 and Figure 2 As shown, a multi-reflection ultra-short-focus projection optical system includes an image generating unit sensor 1, a projection optical component and a projection screen 5; the image generating unit sensor 1 is used to generate an image; the projection optical component first amplifies the image generated by the image generating unit sensor 1, and then folds and reverses the optical path to further expand the field of view, and projects an enlarged image on the projection screen 5; the projection direction of the image generating unit sensor 1 is parallel to the optical axis direction; the projection screen 5 is parallel to the optical axis direction.

[0030] Specifically, in the present embodiment, the projection optical assembly includes a refractive lens group 2, a reflector A3 and a reflector B4; the refractive lens group 2 and the image generating unit sensor 1 are located on the same optical axis; the reflector A3 is arranged below the optical axis; the reflector B4 is arranged above the optical axis; the refractive lens group 2 first amplifies the image of the image generating unit sensor 1 and projects it onto the reflector, the image is reflected onto the reflector B4 via the reflector A3, and the image is then reflected by the reflector B4 and projected onto the projection screen 5, thereby folding and reversing the light path, further expanding the field of view, and projecting a large-sized image at a short distance. It should be noted that the refractive lens group 2 first amplifies the image on the image generating unit sensor 1, and then folds and reverses the light path via the reflectors A3 and B4, further expanding the field of view, and projecting a large-sized image on the screen of about 2000mm. 2 The designed system parameters are as follows: focal length is 2.4mm, projection ratio (ratio of projection distance to projection size) is 0.25, magnification (ratio of sensor size to projection pattern size) is 200, MTF is greater than 0.5 at 94lp / mm, TV distortion is less than 2%, and relative illumination is greater than 80%. Compared with the traditional full-refractive projection lens, the system adds two reflectors to compress and fold the light path so that the projection direction is the same as the optical axis direction, which makes the installation position more flexible, and the added reflectors can correct distortion and aberration well. At the same time, the folding of the light path makes the structure more compact, and the difficulty of processing and assembly is moderate, which can meet the needs of miniaturization and portability.

[0031] The present invention provides a multi-reflection ultra-short-focus projection optical system, which is provided with an image generation unit sensor 1, a refractive lens group 2, a reflector A3, a reflector B4, and a projection screen 5. In the optical system, the refractive lens group 2 first amplifies the image on the sensor and is responsible for controlling the overall imaging quality, and then folds and reverses the optical path through the reflector A3 and the reflector B4 to further expand the field of view, so as to achieve the projection of a large-size image at a relatively short distance, and at the same time, the projection direction can be kept parallel to the optical axis direction, and the system has the advantages of a large field of view, good imaging effect, and high projection image quality, and is suitable for occasions with limited space. By optimizing the optical path design and adopting two reflective structures, the system can compress the optical path and improve the image quality while maintaining a short focal length, and make the projection screen 5 have the same direction as the optical axis of the projection system, which greatly improves the flexibility of installation during actual use.

[0032] Specifically, in this embodiment, the curved surface of the reflector A3 and the curved surface of the reflector B4 are both aspherical surfaces; the description equation of the aspherical surface is:

[0033]

[0034] Among them, z is the height from the vertex to the surface, r is the distance from the point perpendicular to the optical axis to the optical axis, c is the inverse of the radius of curvature, k is the cone coefficient, which is used to describe the surface shape, Ai is the i-th aspheric coefficient, and n is the number of coefficients.

[0035] Specifically, the light emitted from the image generating unit sensor first enters the refractive lens group 2. The refractive lens group 2 is composed of a plurality of carefully designed lenses, the materials, curvature radius and spacing of which are precisely calculated and optimized to achieve efficient amplification of the image on the image generating unit sensor 1 and fine control of the imaging quality. Through the refraction of the light, on the one hand, the image on the image generating unit sensor is amplified according to a predetermined ratio, so that the final projected image has a sufficient size; on the other hand, the propagation direction and intensity of the light are adjusted to ensure that the image is clear, the color is accurate, and the contrast is appropriate.

[0036] The light processed by the refractive lens group 2 then irradiates the reflector A. The position and angle of the reflector A are carefully designed so that the light can be incident at a specific angle. When the light reaches the reflector A, its propagation direction is instantly changed, achieving the first folding of the light path. This folding effect not only shortens the propagation path of the light, but also lays the foundation for the subsequent reversal of the light path. The surface of the reflector A is specially treated with high reflectivity and good optical flatness to ensure that the light will not be scattered or distorted during the reflection process.

[0037] The light then reaches reflector B. The position and angle of reflector B are also precisely calculated to coordinate with reflector A. When the light hits reflector B, it is reflected again, which not only further folds the light path, but also reverses the light path. Through this double reflection, the propagation path of the light is greatly shortened, while the field of view is further expanded. The surface of reflector B also has high reflectivity and good optical flatness to ensure the quality of the light during the reflection process.

[0038] In this process, the light undergoes multiple reflections and refractions, and its propagation direction and intensity are constantly changing, but always maintain a certain regularity. Through the precise design and adjustment of the refractive lens group 2 and the reflector, the light can be precisely controlled, so that the image finally projected on the projection screen 5 has high definition, high contrast and accurate color reproduction.

[0039] Finally, the folded and inverted light is projected onto the projection screen 5, presenting a large-size, high-quality image at a short distance, and the projection direction is always parallel to the optical axis direction, ensuring the stability and accuracy of the image. This parallel projection method makes the image more evenly distributed on the projection screen 5 without deformation or distortion.

[0040] It should be noted that in the multi-reflection ultra-short-throw projection optical system, the reflectivity of the reflector A and the reflector B has an important influence on the system performance, which is mainly reflected in the following aspects:

[0041] 1. Image Brightness

[0042] Effects of high reflectivity:

[0043] When the reflectors A and B have high reflectivity, the loss of light during the reflection process can be minimized. This means that more light can be effectively guided to the projection screen 5, thereby significantly improving the brightness of the projected image. For example, in a specific projection environment, if the reflectivity of the reflector is increased from 80% to 95%, the light flux reaching the projection screen 5 after multiple reflections will be greatly increased, making the image appear brighter and clearer.

[0044] High-brightness images are easier for viewers to clearly identify in various environments, especially in brightly lit indoor environments or large conference rooms. High-brightness projected images can effectively compete with the surrounding ambient light to ensure the readability and visibility of the projected content.

[0045] Effects of low reflectivity:

[0046] If the reflectivity of the reflector is low, a large amount of light will be absorbed or scattered during the reflection process. This will result in a reduction in the light flux reaching the projection screen 5, making the projected image dim. For example, when the reflectivity is reduced to below 60%, the projected image may be difficult to see details due to insufficient brightness, affecting the viewing experience.

[0047] Low-brightness images not only cause visual fatigue to viewers, but may also lead to reduced color saturation, making the colors of the image appear dull and affecting the overall quality of the image.

[0048] 2. Image Contrast

[0049] The role of high reflectivity:

[0050] Highly reflective mirrors are better able to maintain the intensity and directionality of light, which helps to increase the contrast of an image. Contrast refers to the difference between the brightest and darkest parts of an image, and high-contrast images make it easier for viewers to distinguish different objects and details.

[0051] For example, when projecting an image with a black background and white text, a highly reflective mirror ensures that the black portion is as dark as possible and the white portion is as bright as possible, making the text more clearly readable and the image more contrasty.

[0052] Consequences of low reflectivity:

[0053] A low reflectivity mirror will make the light more dispersed during the reflection process, resulting in a decrease in the contrast of the image. This is because after part of the light is absorbed or scattered by the reflector, the difference between the bright and dark parts of the image becomes less obvious, making the image appear to lack layering and three-dimensionality.

[0054] For example, when watching a movie, low-contrast images may make dark scenes in the picture blurry, making it difficult to distinguish the outlines and details of objects, affecting the viewing experience.

[0055] 3. Color Accuracy

[0056] Advantages of high reflectivity:

[0057] Highly reflective mirrors reflect the color components of light more accurately, helping to maintain the color accuracy of the projected image. In projection systems, color accuracy is critical to delivering true, vivid images.

[0058] For example, when projecting a colorful picture, a high-reflectivity mirror can ensure that color components such as red, green and blue are accurately reflected onto the projection screen 5, making the color of the picture closer to the original image and improving the color restoration.

[0059] Effects of low reflectivity:

[0060] A low reflectivity reflector may cause the color component of light to change, thus affecting the color accuracy of the image. This is because part of the light may change its wavelength when it is absorbed or scattered by the reflector, causing the color of the image to deviate.

[0061] For example, when projecting an image with blue as the main color, a low-reflectivity mirror may make the blue part dim or greenish, affecting the overall color effect of the image.

[0062] 4. System efficiency and stability

[0063] The significance of high reflectivity:

[0064] High reflectivity mirrors can improve the efficiency of the entire projection system. Since more light can be used effectively, the projection system can achieve higher brightness output at lower power, thereby reducing energy consumption.

[0065] In addition, mirrors with high reflectivity generally have better stability and are less susceptible to environmental factors. For example, they are less sensitive to temperature, humidity and dust, and can maintain stable reflective performance under different environmental conditions.

[0066] Challenges of low reflectivity:

[0067] Low reflectivity mirrors reduce the efficiency of the projection system, requiring higher power input to achieve the same brightness output. This not only increases energy consumption, but may also cause the projection system to generate more heat, affecting the stability and life of the system.

[0068] At the same time, low-reflectivity mirrors may be more susceptible to environmental factors, such as dust accumulation, surface oxidation, etc., which will further reduce the reflectivity of the mirror and affect the performance of the projection system.

[0069] In summary, the reflectivity of reflector A and reflector B has a crucial impact on the performance of the multi-reflection ultra-short-throw projection optical system. When designing and selecting reflectors, reflectors with high reflectivity and good stability should be selected as much as possible to ensure that the projection system can provide high-quality image output.

[0070] Specifically, in this embodiment, the refractive lens group 2 includes at least one lens.

[0071] Specifically, in this embodiment, the distance between the projection screen 5 and the projection optical component is 500 mm.

[0072] Specifically, in this embodiment, the image generating unit sensor is a digital micromirror device DMD or a liquid crystal display panel LCD.

[0073] Specifically, in this embodiment, the positions and angles of the refractive lens group 2, the reflector A, the reflector B and the projection screen 5 can be adjusted according to actual needs.

[0074] Specifically, in this embodiment, the projection screen 5 is a flat surface or a curved surface.

[0075] Example:

[0076] The present invention is further described below. Figure 1 .

[0077] The multi-reflection ultra-short-throw projection optical system includes an image generation unit sensor 1, a refractive lens group 2, a reflector A3, a reflector B4, and a projection screen 5. The refractive lens group first amplifies the image on the sensor and is responsible for controlling the overall imaging quality. Then, the light path is folded and reversed through the reflectors A and B to further expand the field of view, thereby projecting a large-size image at a relatively short distance while keeping the projection direction parallel to the optical axis direction. The light path diagram is shown in FIG. Figure 2 .

[0078] In addition, the curved surfaces of the reflector A and the reflector B are aspherical surfaces, and their description equations are:

[0079]

[0080] Among them, z is the height from the vertex to the surface, r is the distance from the point perpendicular to the optical axis to the optical axis, c is the inverse of the radius of curvature, k is the cone coefficient, which is used to describe the surface shape, Ai is the i-th aspheric coefficient, and n is the number of coefficients.

[0081] Compared with spherical surfaces, aspherical surfaces can provide higher degrees of freedom in optical optimization. Reasonable use of aspherical surfaces can improve optical performance, reduce aberrations such as spherical aberration, chromatic aberration, and distortion, and improve optical quality.

[0082] The design parameters of the two aspheric surfaces are as follows:

[0083]

[0084] Through optimized design, the light spot diagram of the system is as follows Figure 3 As shown, the RMS spot radius is less than 0.5mm, which means that the light spot can be well concentrated within one pixel, proving that the aberration is small, with small chromatic aberration and high imaging quality.

[0085] The grid distortion of the system is shown in Figure 4 , TV distortion is 0.68%, which is less than 2%. The distortion of the system cannot be detected by the naked eye, and the difference between the ideal image point and the actual image point cannot be seen, which proves that the distortion is small and has high imaging quality.

[0086] The MTF curve of the system is as follows: Figure 5 As shown, the cut-off frequency is greater than 0.2 at 92lp / mm, which can meet the use requirements.

[0087] The relative illumination curve of the system is shown in Figure 6 ,With the field of view increases, the relative illumination decreases slowly and is relatively smooth as a whole, which is greater than 80% at the maximum field of view, proving that the overall field of view is relatively uniform and has good imaging quality.

[0088] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A multi-reflection ultra-short-throw projection optical system, characterized in that: It comprises an image generating unit sensor, a projection optical component and a projection screen; the image generating unit sensor is used to generate an image; the projection optical component firstly amplifies the image generated by the image generating unit sensor, and then folds and reverses the optical path to further expand the field of view, and projects an amplified image on the projection screen; the projection direction of the image generating unit sensor is parallel to the optical axis direction; and the projection screen is parallel to the optical axis direction.

2. The multi-reflection ultra-short-focus projection optical system according to claim 1, characterized in that: The projection optical assembly includes a refractive lens group, a reflector A and a reflector B; the refractive lens group and the image generation unit sensor are located on the same optical axis; The reflector A is arranged below the optical axis; The reflector B is arranged above the optical axis; The refractive lens group first amplifies the image of the image generating unit sensor and projects it onto the reflector. The image is reflected by the reflector A onto the reflector B. The image is then reflected by the reflector B and projected onto the projection screen, thereby folding and reversing the light path, further expanding the field of view, and projecting a large-size image at a short distance.

3. The multi-reflection ultra-short-focus projection optical system according to claim 2, characterized in that: The curved surface of the reflector A and the curved surface of the reflector B are both aspherical surfaces; the description equation of the aspherical surface is: Among them, z is the height from the vertex to the surface, r is the distance from the point perpendicular to the optical axis to the optical axis, c is the inverse of the radius of curvature, k is the cone coefficient, which is used to describe the surface shape, Ai is the i-th aspheric coefficient, and n is the number of coefficients.

4. The multi-reflection ultra-short-focus projection optical system according to claim 2, characterized in that: The refractive lens group includes at least one lens.

5. The multi-reflection ultra-short-focus projection optical system according to claim 1, characterized in that: The distance between the projection screen and the projection optical component is 500 mm.

6. The multi-reflection ultra-short-focus projection optical system according to claim 2, characterized in that: The image generating unit sensor is a digital micromirror device DMD or a liquid crystal display panel LCD.

7. The multi-reflection ultra-short-focus projection optical system according to claim 2, characterized in that: The positions and angles of the refractive lens group, reflector A, reflector B and projection screen can be adjusted according to actual needs.

8. The multi-reflection ultra-short-focus projection optical system according to claim 1, characterized in that: The projection screen is a flat surface or a curved surface.

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