Ultra-low distortion projection lens

Abstract

The utility model provides an ultra-low distortion projection lens. The ultra-low distortion projection lens sequentially comprises a first group lens with positive focal power, a diaphragm, a second group lens with positive focal power, a light splitting device, protective glass and an imaging surface from an object plane to an imaging plane along an optical axis. According to the ultra-low distortion projection lens provided by the utility model, the distortion of the lens is controlled below 0.02%, the ultra-low distortion requirement is realized, the working distance reaches 1-2m, the projection ratio of the lens reaches 1.2, the large projection format is realized, the distortion, the cost, the image quality and the resolution are reasonably balanced, and the ultra-low distortion projection lens is suitable for large-scale production. The method has a series of advantages of high imaging quality, small temperature influence, small distortion, reasonable tolerance, low cost and the like, and has very high practical application value.

Description

Technical Field

[0001] The utility model relates to the technical field of optical lenses, in particular to an ultra-low distortion projection lens. Background Art

[0002] The projection lens is the core component of the projection equipment. After the light passes through the reflective or projective light modulation device, it is projected onto the projection screen through the projection lens to form an image.

[0003] With the popularity of projection equipment, there are also diverse requirements for the technical indicators of projectors: smaller image distortion, clearer picture quality, larger projection frame, and smaller projection ratio. And in projectors. Due to the actual application scenarios, the projection lens will be required to have a higher off-axis rate. When the off-axis rate reaches 100%, the projection optical machine can be placed directly on any platform for projection without considering the lack of space under the projector. At present, projection lenses mostly adopt a medium-to-long focal length design. On the one hand, it can easily obtain a good distortion correction effect, and on the other hand, it can better ensure the compact size of the structure. But in other scenarios, such as in-vehicle assisted driving, a smaller projection object distance can better ensure a larger concentrated illumination.

[0004] Most existing consumer-grade projection lenses generally have distortion controlled above 0.5%. Although this can meet the viewing needs of ordinary consumers, 0.5% distortion is still relatively high. Under certain specific needs, lower lens distortion is required to meet usage requirements, such as some high-precision scanning lenses, 3D printing lenses, and high-demand projection scenes. Some professional-grade projection lens consumers also need lower lens distortion to improve the viewing experience. In addition, the low-distortion projection lenses on the market currently have the disadvantages of short working distance and small projection frame, and cannot meet higher quality projection requirements. Therefore, it is very necessary to design an ultra-low distortion projection lens. Utility Model Content

[0005] The purpose of the utility model is to provide an ultra-low distortion projection lens, which controls the lens distortion to below 0.02%, realizes the requirement of ultra-low distortion, and the working distance reaches 1-2 meters, the lens projection ratio reaches 1.2, realizes a large projection frame, reasonably balances distortion, cost, image quality and resolution, has a series of advantages such as high imaging quality, little influence by temperature, small distortion, reasonable tolerance, low cost, etc., and has high practical application value.

[0006] To achieve the above purpose, the utility model provides the following solutions:

[0007] An ultra-low distortion projection lens, comprising, along the optical axis from the object plane to the imaging plane, a first group of lenses with positive focal power, an aperture, a second group of lenses with positive focal power, a beam splitter, a protective glass and an imaging plane, wherein the aperture is used to control the amount of light emitted by the lens, the first group of lenses is used to adjust the projection field angle and balance the system field curvature, and the second group of lenses is used to balance the system aberration and chromatic aberration;

[0008] The first lens group includes a first lens G1, a second lens G2, a third lens G3, a fourth lens G4, a fifth lens G5 and a sixth lens G6 in sequence from the object plane to the image plane along the optical axis;

[0009] The second lens group includes a seventh lens G7, an eighth lens G8, a ninth lens G9 and a tenth lens G10 in sequence from the object plane to the image plane along the optical axis.

[0010] Optionally, the first lens group and the second lens group are made of glass material, the third lens G3 and the fourth lens G4 form a glass spherical doublet lens, and the seventh lens G7 and the eighth lens G8 form a glass spherical doublet lens.

[0011] Optionally, the first lens G1, the fourth lens G4, the fifth lens G5 and the seventh lens G7 are lenses with negative power, and the second lens G2, the third lens G3, the sixth lens G6, the eighth lens G8, the ninth lens G9 and the tenth lens G10 are lenses with positive power.

[0012] Optionally, the ratio of the focal length f1 of the first group of lenses to the focal length f of the ultra-low distortion projection lens is 2.06;

[0013] The focal length f of the first lens G1 is G1 The ratio to the focal length f1 of the first lens group is -3.24;

[0014] The focal length f of the second lens G2 G2 The ratio to the focal length f1 of the first lens group is 1.94;

[0015] The focal length f of the third lens G3 G3 The ratio to the focal length f1 of the first lens group is 1.43;

[0016] The focal length f of the fourth lens G4 is G4 The ratio to the focal length f1 of the first lens group is -0.59;

[0017] The focal length f of the fifth lens G5 G5 The ratio to the focal length f1 of the first lens group is -0.81;

[0018] The focal length f of the sixth lens G6 isG6 The ratio to the focal length f1 of the first lens group is 0.53.

[0019] Optionally, the ratio of the focal length f2 of the second group of lenses to the focal length f of the ultra-low distortion projection lens is 1.33;

[0020] The focal length f of the seventh lens G7 G7 The ratio to the focal length f2 of the second lens group is -0.64;

[0021] The focal length f of the eighth lens G8 is G8 The ratio to the focal length f2 of the second lens group is 3.09;

[0022] The focal length f of the ninth lens G9 G9 The ratio to the focal length f2 of the second lens group is 2.28;

[0023] The focal length f of the tenth lens G10 is G10 The ratio to the focal length f2 of the second lens group is 1.66.

[0024] Optionally, a gap between the first lens G1 and the second lens G2 is in a range of 3-5 mm, and a gap between the fifth lens G5 and the sixth lens G6 is in a range of 4-6 mm.

[0025] Optionally, the refractive index n7 and the Abbe constant v7 of the seventh lens G7 satisfy:

[0026]

[0027] The refractive index n8 and the Abbe constant v8 of the eighth lens G8 satisfy:

[0028]

[0029] According to the specific embodiments provided by the utility model, the utility model discloses the following technical effects: the ultra-low distortion projection lens provided by the utility model comprises, in sequence from the object plane to the imaging plane along the optical axis: a first group lens with positive focal length, an aperture, a second group lens with positive focal length, a spectroscopic device, a protective glass and an imaging plane; the distortion of the lens is within 0.02%, achieving an ultra-low distortion effect, excellent distortion correction, a working distance of 1-2 meters, a relative illumination full field of view higher than 0.75%, a full field of view MTF higher than 0.5, excellent imaging quality, the lenses are all made of glass material, which can effectively avoid the problem of serious focus deviation caused by the easy heat absorption of plastic aspheric surfaces, and has good resistance to temperature influence, the first lens uses a high refractive index meniscus lens, which can effectively reduce the beam height, has a great effect on correcting distortion and reducing the aperture of subsequent lenses, and the spot radius of the spot diagram (<4um) is smaller than the pixel size (5.4 um), it has obvious advantages for projection display, which focuses on the application of spot size and energy concentration. The lens material has a high transmittance of light with a wavelength of 459-618nm, exceeding 95% / 10mm. The lens absorbs less energy, which can improve the overall brightness, reduce system heat, reduce the power and size of the heat dissipation device, and contribute to the stability of projection imaging. The design wavelengths are 459nm, 536nm, and 618nm, which include the wavelength fluctuations of actual visible light sources, making the lens design more in line with the actual situation. Only 10 spherical lenses are used. Compared with the lens design of other aspherical lenses, the lens cost is effectively reduced and the production yield is improved. The lens has a large aperture and a relative aperture F# of 1.8. The larger the aperture, the greater the amount of light entering, the higher the corresponding brightness, and the higher the light efficiency. The thickness of each piece of glass does not exceed 6.1mm, and the overall system length is small and can be controlled within 70mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0031] Figure 1 This is a schematic diagram of the structure of an ultra-low distortion projection lens according to an embodiment of the utility model;

[0032] Figure 2 This is a schematic diagram of the MTF of the ultra-low distortion projection lens;

[0033] Figure 3 This is a schematic diagram of the point array of the ultra-low distortion projection lens;

[0034] Figure 4 This is the field curvature distortion diagram of the ultra-low distortion projection lens;

[0035] Figure 5 Schematic diagram of relative illumination of ultra-low distortion projection lens.

[0036] Reference numerals: 1, first group of lenses; 2, aperture; 3, second group of lenses; 4, spectrometer; 5, protective glass; 6, imaging surface. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0038] The purpose of the utility model is to provide an ultra-low distortion projection lens, which controls the lens distortion to below 0.02%, realizes the requirement of ultra-low distortion, and the working distance reaches 1-2 meters, the lens projection ratio reaches 1.2, realizes a large projection frame, reasonably balances distortion, cost, image quality and resolution, has a series of advantages such as high imaging quality, little influence by temperature, small distortion, reasonable tolerance, low cost, etc., and has high practical application value.

[0039] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0040] like Figure 1 As shown, the ultra-low distortion projection lens provided by the embodiment of the utility model comprises, in order from the object plane to the imaging plane along the optical axis: a first group lens 1 with positive focal length, an aperture 2, a second group lens 3 with positive focal length, a beam splitter 4, a protective glass 5 and an imaging plane 6, wherein the aperture 2 is used to control the amount of light emitted by the lens, the first group lens 1 is used to adjust the projection field angle and balance the system field curvature, the second group lens 3 is used to balance the system aberration and chromatic aberration, and the light source lens group is used to emit light and collimate the emitted light;

[0041] The first lens group 1 includes a first lens G1, a second lens G2, a third lens G3, a fourth lens G4, a fifth lens G5 and a sixth lens G6 in sequence from the object plane to the image plane along the optical axis;

[0042] The second lens group 3 includes a seventh lens G7, an eighth lens G8, a ninth lens G9 and a tenth lens G10 in sequence from the object plane to the image plane along the optical axis.

[0043] The first lens group 1 and the second lens group 3 are made of glass material, the third lens G3 and the fourth lens G4 form a glass spherical doublet lens, and the seventh lens G7 and the eighth lens G8 form a glass spherical doublet lens;

[0044] The light splitting device 4 is a light splitting prism.

[0045] The first lens G1, the fourth lens G4, the fifth lens G5 and the seventh lens G7 are lenses with negative refractive power, and the second lens G2, the third lens G3, the sixth lens G6, the eighth lens G8, the ninth lens G9 and the tenth lens G10 are lenses with positive refractive power.

[0046] The ratio of the focal length f1 of the first lens group 1 to the focal length f of the ultra-low distortion projection lens is 2.06;

[0047] The focal length f of the first lens G1 is G1 The ratio to the focal length f1 of the first lens group 1 is -3.24;

[0048] The focal length f of the second lens G2 G2 The ratio to the focal length f1 of the first lens group 1 is 1.94;

[0049] The focal length f of the third lens G3 G3 The ratio of the focal length f1 of the first lens group 1 is 1.43;

[0050] The focal length f of the fourth lens G4 is G4 The ratio to the focal length f1 of the first lens group 1 is -0.59;

[0051] The focal length f of the fifth lens G5 G5 The ratio to the focal length f1 of the first lens group 1 is -0.81;

[0052] The focal length f of the sixth lens G6 G6 The ratio of the focal length f1 of the first lens group 1 is 0.53.

[0053] The ratio of the focal length f2 of the second lens group 3 to the focal length f of the ultra-low distortion projection lens is 1.33;

[0054] The focal length f of the seventh lens G7 G7 The ratio to the focal length f2 of the second lens group 3 is -0.64;

[0055] The focal length f of the eighth lens G8 is G8 The ratio to the focal length f2 of the second lens group 3 is 3.09;

[0056] The focal length f of the ninth lens G9 is G9The ratio to the focal length f2 of the second lens group 3 is 2.28;

[0057] The focal length f of the tenth lens G10 is G10 The ratio to the focal length f2 of the second lens group 3 is 1.66.

[0058] The gap between the first lens G1 and the second lens G2 is in the range of 3-5 mm, and the gap between the fifth lens G5 and the sixth lens G6 is in the range of 4-6 mm.

[0059] The seventh lens G7 and the eighth lens G8 are cemented lenses. A double cemented lens is placed behind the aperture. The combination of low refractive index and high Abbe number materials and high refractive index and low Abbe number materials effectively reduces the secondary spectrum of the system. The refractive index n7 and Abbe constant v7 of the seventh lens G7 satisfy:

[0060]

[0061] The refractive index n8 and the Abbe constant v8 of the eighth lens G8 satisfy:

[0062]

[0063] The aperture range of the diaphragm is 6 to 8 mm, and the relative aperture F number reaches 1.8. The aperture of the entire objective system is large, and the amount of light entering is large;

[0064] The eighth lens G8, the ninth lens G9 and the tenth lens G10 have positive refractive power, which ensures that the incident angle of the main ray of each field of view is completely matched with the light cone angle and angular vector of the image source while correcting the aberration, thereby improving the image quality and efficiency of the entire imaging system. The CRA range is within ±2.5°, and CRA refers to the angle between the main ray and the image plane.

[0065] The parameters of the ultra-low distortion projection lens are shown in Table 1;

[0066] Table 1 Specific parameters of ultra-low distortion projection lens

[0067]

[0068]

[0069] The MTF (Modulation Transfer Function) index is the most accurate and scientific evaluation standard for lenses. The vertical axis represents contrast. The closer it is to 1, the better the lens imaging. The horizontal axis represents resolution, in units of line pairs per millimeter. The image source pixel size used in the embodiment of the present application is 5.4um, and the corresponding design resolution is 93 line pairs per millimeter. The projection lens generally requires that the MTF value of each field of view is at least 0.3 in the design. Figure 2As shown, the MTF values ​​of each field of view in the embodiment of the present application are all above 0.5.

[0070] The point diagram of this application is as follows Figure 3 As shown, after many light rays emitted from one point pass through the optical system, due to aberration, their intersection points with the image plane are no longer concentrated at the same point, but a diffuse pattern scattered in a certain range is formed. The smaller the spot radius of each field of view, the better the imaging quality it represents. Generally, the full field of view RMS is smaller than the pixel size (5.4um), which is an excellent level. The full field of view RMS of the embodiment of the present application is less than 4um, which is an excellent level.

[0071] like Figure 4 As shown, the left figure is a field curvature evaluation figure, and the right figure is a distortion evaluation figure. The ordinate represents the field angle of the lens, the abscissa of the field curvature figure represents the magnitude of the field curvature value, and the abscissa of the distortion figure represents the distortion amount. Distortion is a very important indicator of a projection lens; the system distortion of the embodiment of the present application is within 0.02%, achieving ultra-low distortion.

[0072] Relative illumination refers to the ratio of the illumination at different coordinate points on the image plane to the illumination at the center point. The ordinate represents the normalized illumination value, and the abscissa represents the field of view angle of the lens. Under the same conditions, the smooth transition of the relative illumination curve of each field of view represents uniform illumination within the projection frame. The closer the relative illumination value of each field of view is to 1, the higher the final projection brightness. For general consumer projection lenses, a relative illumination greater than 0.6 can well meet people's usage needs. The relative illumination of this application is as follows Figure 5 As shown, the edge illumination reaches 75%, which makes the projection effect uniformity of the system imaging surface very good.

[0073] The optical distortion of the ultra-low distortion projection lens is less than 0.02%. The first lens G1 adopts a meniscus lens with a refractive index of 1.95. It is made of optical glass and can effectively reduce the light beam height. It plays a great role in correcting distortion and reducing the aperture of subsequent lenses. The lens uses a 0.3-inch image source and the relative illumination of the lens is greater than 0.75, which is beneficial to improving the uniformity of the optical machine. The lens uses a lamp with a wavelength of 459-618nm as the light source. The selected lens material has a high transmittance for light with a wavelength of 459-618nm. All lenses are glass spherical lenses, which are easy to process, low in cost, and less affected by temperature changes.

[0074] The ratio of the combined focal length of the first lens group to the combined focal length of the second lens group is close to 1.5, and the length of the two lens groups is 55mm;

[0075] The entire system structure uses glass spherical lenses, and the thickness of each piece of glass does not exceed 6.1mm. The overall system length is small and controlled within 70mm.

[0076] In an embodiment, the optical lens satisfies the following conditional formula:

[0077] 12<T L / IH<20

[0078] Where, T L represents the total optical length of the optical lens, and IH represents the actual half-image height of the optical lens;

[0079] When the above formula is satisfied, the relationship between the total length and resolution of the lens can be reasonably balanced, T L When the value of / IH exceeds the upper limit, the overall length of the lens is too long, or if the overall length is shortened, the image height will be insufficient, and T L When the value of / IH exceeds the lower limit, the lens aberration correction is difficult due to the excessive focal length of each lens, and the resolution capability is significantly reduced;

[0080] In an embodiment, the optical lens satisfies the following conditional formula:

[0081] 2mm<IH / tanθ<3mm

[0082] Wherein, IH represents the actual half image height of the optical lens, and θ represents the half field angle of the optical lens;

[0083] When the above formula is satisfied, the distortion of the optical lens can be reasonably limited, reducing the difficulty of distortion correction. When the value of IH / tanθ exceeds the lower limit, the distortion of the lens will increase in the negative direction. When the value of IH / tanθ exceeds the upper limit, the distortion of the lens will increase in the positive direction.

[0084] In an embodiment, the optical lens satisfies the following conditional formula

[0085] 1.8 <Nd1<1.95

[0086] 15 <Vd1<20

[0087] Wherein, Nd1 represents the refractive index of the first lens, and Vd1 represents the dispersion coefficient of the first lens;

[0088] When the above formula is satisfied, the glass material selection of the first lens can be reasonably limited, the aberrations of other optical lenses can be balanced, and the beam height can be effectively reduced, which has a great effect on correcting distortion and reducing the aperture of subsequent lenses;

[0089] In an embodiment, the optical lens satisfies the following conditional formula:

[0090] CRA<2.5°

[0091] Wherein, CRA represents the incident angle of the main light of the optical lens on the imaging surface, which can well match the image source such as DMD imaging chip or LED to achieve good projection effect.

[0092] The curvature radii of the G1 and G6 lenses are a combination of positive, positive, and negative, which can effectively control the smooth transition of light, thereby reducing the tolerance sensitivity of these two lenses and thus improving the actual production yield.

[0093] The ultra-low distortion projection lens provided by the utility model comprises, in order from the object plane to the imaging plane along the optical axis: a first group lens with positive focal power, an aperture, a second group lens with positive focal power, a beam splitter, a protective glass and an imaging plane; the distortion of the lens is within 0.02%, and an ultra-low distortion effect can be achieved, and the distortion correction is excellent. The working distance is in the range of 1-2 meters, the relative illumination of the whole field of view is higher than 0.75%, the MTF of the whole field of view is higher than 0.5, and the imaging quality is excellent. The lenses are all made of glass material, which can effectively avoid the problem of serious focus deviation caused by the easy heat absorption of plastic aspheric surfaces, and has good resistance to temperature influence. The first lens uses a high-refractive-index meniscus lens, which can effectively reduce the height of the light beam, and has a great effect on correcting distortion and reducing the aperture of subsequent lenses. The spot radius of the spot diagram (<4um) is smaller than the pixel size (5.4um), which is very suitable for projection display, which focuses on light The application advantages of spot size and energy concentration are obvious. The lens material has a high transmittance of light with a wavelength of 459-618nm, exceeding 95% / 10mm. The lens absorbs less energy, which can improve the overall brightness, reduce system heat, reduce the power and size of the heat dissipation device, and contribute to the stability of projection imaging. The design wavelengths are 459nm, 536nm, and 618nm, which include the wavelength fluctuations of actual visible light sources, making the lens design more in line with actual conditions. Only 10 spherical lenses are used, which effectively reduces the lens cost and improves the production yield compared to other aspherical lens designs. The lens has a large aperture with a relative aperture F# of 1.8. The larger the aperture, the greater the amount of light entering, the higher the corresponding brightness, and the higher the light efficiency. The thickness of each piece of glass does not exceed 6.1mm, and the overall system length is small and can be controlled within 70mm.

[0094] This article uses specific examples to illustrate the principles and implementation methods of the utility model. The above examples are only used to help understand the method and core ideas of the utility model. At the same time, for those skilled in the art, according to the ideas of the utility model, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the utility model.

Claims

1. An ultra-low distortion projection lens, characterized in that: The optical axis includes, from the object plane to the imaging plane, a first group of lenses with positive focal power, an aperture, a second group of lenses with positive focal power, a beam splitter, a protective glass, and an imaging plane. The aperture is used to control the amount of light emitted by the lens. The first group of lenses is used to adjust the projection field angle and balance the field curvature of the system. The second group of lenses is used to balance the aberration and chromatic aberration of the system. The first lens group includes a first lens G1, a second lens G2, a third lens G3, a fourth lens G4, a fifth lens G5 and a sixth lens G6 in sequence from the object plane to the image plane along the optical axis; The second lens group includes a seventh lens G7, an eighth lens G8, a ninth lens G9 and a tenth lens G10 in sequence from the object plane to the image plane along the optical axis.

2. The ultra-low distortion projection lens according to claim 1, characterized in that: The first lens group and the second lens group are made of glass material, the third lens G3 and the fourth lens G4 form a glass spherical doublet lens, and the seventh lens G7 and the eighth lens G8 form a glass spherical doublet lens.

3. The ultra-low distortion projection lens according to claim 1, wherein: The first lens G1, the fourth lens G4, the fifth lens G5 and the seventh lens G7 are lenses with negative refractive power, and the second lens G2, the third lens G3, the sixth lens G6, the eighth lens G8, the ninth lens G9 and the tenth lens G10 are lenses with positive refractive power.

4. The ultra-low distortion projection lens according to claim 1, wherein: The ratio of the focal length f1 of the first lens group to the focal length f of the ultra-low distortion projection lens is 2.06; The focal length f of the first lens G1 is G1 The ratio to the focal length f1 of the first lens group is -3.24; The focal length f of the second lens G2 G2 The ratio to the focal length f1 of the first lens group is 1.94; The focal length f of the third lens G3 G3 The ratio to the focal length f1 of the first lens group is 1.43; The focal length f of the fourth lens G4 is G4 The ratio to the focal length f1 of the first lens group is -0.59; The focal length f of the fifth lens G5 G5 The ratio to the focal length f1 of the first lens group is -0.81; The focal length f of the sixth lens G6 is G6 The ratio to the focal length f1 of the first lens group is 0.

53.

5. The ultra-low distortion projection lens according to claim 1, wherein: The ratio of the focal length f2 of the second lens group to the focal length f of the ultra-low distortion projection lens is 1.33; The focal length f of the seventh lens G7 G7 The ratio to the focal length f2 of the second lens group is -0.64; The focal length f of the eighth lens G8 is G8 The ratio to the focal length f2 of the second lens group is 3.09; The focal length f of the ninth lens G9 G9 The ratio to the focal length f2 of the second lens group is 2.28; The focal length f of the tenth lens G10 is G10 The ratio to the focal length f2 of the second lens group is 1.

66.

6. The ultra-low distortion projection lens according to claim 1, wherein: The gap between the first lens G1 and the second lens G2 is in the range of 3-5 mm, and the gap between the fifth lens G5 and the sixth lens G6 is in the range of 4-6 mm.

7. The ultra-low distortion projection lens according to claim 1, wherein: The refractive index n7 and the Abbe constant v7 of the seventh lens G7 satisfy: The refractive index n8 and the Abbe constant v8 of the eighth lens G8 satisfy:

Images