Optical System and Projection Device

Abstract

The present invention discloses an optical system and a projection device. The optical system sequentially includes, from the object side to the image side, a first lens with a negative optical power, a second lens with a negative optical power, a third lens with a positive optical power, a fourth lens with a negative optical power, a fifth lens with a positive optical power, a sixth lens with a positive optical power, an equivalent TIR prism, and a photosensitive chip. The first lens and the sixth lens are aspherical lenses, and the second lens, the third lens, the fourth lens, and the fifth lens are spherical lenses. Through reasonable setting of the optical powers and shapes of the six lenses, the f-number of the optical system is F≤1.7, enabling the optical system to well control the light path, introducing more light while making the structure more compact, and controlling the total length of the optical system within 54 mm, so as to provide a large-aperture and small-sized optical system for use in combination with a TIR prism structure.

Description

Technical Field

[0001] The present invention relates to the field of optical technologies, and particularly to an optical system and a projection device. Background Art

[0002] In recent years, due to the widespread use of online teaching and home projection, people have higher and higher requirements for the miniaturization and resolution of projectors. Most projectors on the market adopt the structure of a TIR prism. This structure results in a relatively large length and volume of the optical lens. Reducing the lens volume is beneficial to the miniaturization of projectors, improving portability, and reducing costs. Summary of the Invention

[0003] The main objective of the present invention is to propose an optical system and a projection device, aiming to provide an optical system with a large aperture and small volume for use in combination with the TIR prism structure.

[0004] To achieve the above objective, an optical system proposed by the present invention has an object side and an image side disposed oppositely along the optical axis direction. The optical system includes a first lens with a negative optical power, a second lens with a negative optical power, a third lens with a positive optical power, a fourth lens with a negative optical power, a fifth lens with a positive optical power, a sixth lens with a positive optical power, an equivalent TIR prism, and a photosensitive chip arranged in sequence from the object side to the image side. The first lens and the sixth lens are aspherical lenses, and the second lens, the third lens, the fourth lens, and the fifth lens are spherical lenses, so that the total optical length TTL of the optical system is ≤ 54 mm, and the aperture number of the optical system is F ≤ 1.7.

[0005] Optionally, the optical system further satisfies the following conditions:

[0006]

[0007] Wherein, is the optical power of the optical system, is the optical power of the first lens, is the optical power of the second lens, is the optical power of the third lens, is the optical power of the fourth lens, is the optical power of the fifth lens, is the optical power of the sixth lens.

[0008] Optionally, the first lens is a plastic lens.

[0009] Optionally, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass lenses.

[0010] Optionally, the first lens and the sixth lens are aspherical lenses;

[0011] The second lens, the third lens, the fourth lens, and the fifth lens are all spherical lenses.

[0012] Optionally, the fourth lens and the fifth lens are adhesively connected to form an adhesive lens.

[0013] Optionally, the optical system further satisfies the following conditions: 40 < |T1 - T6| < 60;

[0014] where is the optical power of the first lens, is the optical power of the sixth lens, T1 is the thermal expansion coefficient of the first lens, and T6 is the thermal expansion coefficient of the sixth lens.

[0015] Optionally, the optical system further includes a diaphragm, and the diaphragm is disposed between the third lens and the fourth lens.

[0016] Optionally, the optical system further includes a protective glass, and the protective glass is disposed between the equivalent TIR prism and the photosensitive chip.

[0017] The present invention also provides a projection device, and the projection device includes the above optical system.

[0018] In the technical solution provided by the present invention, there are a first lens with a negative optical power, a second lens with a negative optical power, a third lens with a positive optical power, a fourth lens with a negative optical power, a fifth lens with a positive optical power, a sixth lens with a positive optical power, an equivalent TIR prism, and a photosensitive chip. The first lens and the sixth lens are aspherical lenses, and the second lens, the third lens, the fourth lens, and the fifth lens are spherical lenses. The distortion of large-angle light is corrected by the first lens, and at the same time, the height of the light entering the rear group of lenses is reduced. The second lens adopts a biconcave lens to turn the light, so that the third lens can further increase the height of the light entering the rear group, enabling the system to have a larger aperture. The optical system can also clearly image under low light. The fourth lens and the fifth lens correct the chromatic aberration of the system. The sixth lens can correct the residual distortion aberration of the system and make the outgoing light enter the photosensitive chip at a smaller angle. By arranging the above six lenses in the order of negative, negative, positive, negative, positive, positive from the projection surface to the photosensitive chip, a smaller total length can be achieved, and the distance between the first lens and the photosensitive chip is controlled within 54 mm, and the manufacturability is also good, so as to provide a large-aperture and small-volume optical system for use in combination with the TIR prism structure. Description of the Drawings

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the structures shown in these drawings.

[0020] Figure 1 Schematic structural diagram of the optical system provided by the present invention;

[0021] Figure 2 For Figure 1 MTF schematic diagram of the optical system in at room temperature;

[0022] Figure 3 For Figure 1 MTF schematic diagram of the optical system in at high temperature;

[0023] Figure 4 For Figure 1 Field distortion / field curvature schematic diagram of the optical system in .

[0024] Explanation of the reference numerals in the drawings:

[0025] Reference numeral Name Reference numeral Name 1 First lens 6 Sixth lens 2 Second lens 7 Equivalent TIR prism 3 Third lens 8 Diaphragm 4 Fourth lens 9 Image sensor chip 5 Fifth lens

[0026] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the drawings. Detailed implementation manners

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0028] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0029] In addition, if the embodiments of the present invention involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text includes three parallel scenarios. Taking "A and / or B" as an example, it includes scenario A, or scenario B, or the scenario where both A and B are satisfied simultaneously. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or inability to implement, 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.

[0030] In recent years, due to the widespread use of online teaching and home projectors, people have increasingly higher requirements for the miniaturization and resolution of projectors. Most projectors on the market adopt the structure of a TIR prism, which results in a relatively large length and volume of the optical lens. Reducing the lens volume is beneficial to the miniaturization of the projector, improving portability, and reducing costs.

[0031] To solve the above problems, the present invention provides an optical system. Figures 1 to 4 This is a specific embodiment of the optical system provided by the present invention.

[0032] Please refer to Figure 1 As shown in the figure, the optical system has an object side and an image side that are oppositely arranged along the optical axis direction. The optical system includes a first lens 1 with a negative optical power, a second lens 2 with a negative optical power, a third lens 3 with a positive optical power, a fourth lens 4 with a negative optical power, a fifth lens 5 with a positive optical power, a sixth lens 6 with a positive optical power, an equivalent TIR prism 7, and a photosensitive chip 9 arranged in sequence from the object side to the image side. The first lens 1 and the sixth lens 6 are aspherical lenses, and the second lens 2, the third lens 3, the fourth lens 4, and the fifth lens 5 are spherical lenses, so that the total optical length TTL of the optical system is ≤ 54 mm, and the aperture number of the optical system is F ≤ 1.7.

[0033] In the technical solution provided by the present invention, there are a first lens 1 with a negative optical power, a second lens 2 with a negative optical power, a third lens 3 with a positive optical power, a fourth lens 4 with a negative optical power, a fifth lens 5 with a positive optical power, a sixth lens 6 with a positive optical power, an equivalent TIR prism 7 and an image sensor chip 9. The first lens 1 and the sixth lens 6 are aspherical lenses, and the second lens 2, the third lens 3, the fourth lens 4 and the fifth lens 5 are spherical lenses. The distortion of large-angle light is corrected by the first lens 1, and at the same time, the height of the light entering the rear lens group is reduced. The second lens 2 is a double-concave lens to deflect the light, so that the third lens 3 can further increase the height of the light entering the rear group, enabling the system to have a larger aperture. The optical system can also clearly image in low light. The fourth lens 4 and the fifth lens 5 correct the chromatic aberration of the system. The sixth lens 6 can correct the residual distortion aberration of the system and make the outgoing light enter the image sensor chip 9 at a smaller angle. Just by arranging the above six lenses in the order of negative, negative, positive, negative, positive, positive from the projection surface to the image sensor chip 9, a smaller overall length can be achieved, and the distance between the first lens 1 and the image sensor chip 9 is controlled within 54 mm, and the manufacturability is also good, so as to provide an optical system with a large aperture and small volume for use in combination with the TIR prism structure.

[0034] Specifically, in this embodiment, the optical system also satisfies the following conditions: Among them, is the optical power of the optical system, is the optical power of the first lens 1, is the optical power of the second lens 2, is the optical power of the third lens 3, is the optical power of the fourth lens 4, is the optical power of the fifth lens 5, is the optical power of the sixth lens 6. The optical power is equal to the difference between the image-space beam convergence and the object-space beam convergence, and it characterizes the ability of the optical system to deflect light. By reasonably setting the constraint range of the ratio of the optical powers of the six lenses, the light beam can be projected in the desired designed direction, and the spherical aberration, coma, astigmatism, etc. on each lens are compensated and offset from each other to achieve the effect of clear imaging.

[0035] Specifically, since the resin lens has strong impact resistance, light weight and low cost, in this embodiment, the first lens 1 is a plastic lens. By using a plastic aspherical lens, the cost can be effectively controlled, and the chromatic aberration of the lens can be well corrected by the aspherical lens. While ensuring the control of the purple fringing of the lens, the spherical aberration and sine aberration at the high magnification position are corrected at the same time.

[0036] However, due to the relatively unstable chemical properties of plastic materials affected by environmental temperature, their refractive index is weaker than that of all-glass lenses, resulting in a poorer picture restoration degree than all-glass lenses. To ensure the stability of the optical system against temperature changes, in this embodiment, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are all glass lenses. Since glass lenses are not easily affected by thermal expansion and contraction and do not experience focus shift, they can well resist the problem of lens deformation due to heat and maintain high precision of the lens for a long time. The optical system uses a combination of glass and plastic materials, which not only saves costs but also has strong impact resistance, and ensures the stability and applicability at high and low temperatures of the system.

[0037] Specifically, in this embodiment, the first lens 1 and the sixth lens 6 are aspherical lenses. The characteristics of aspherical lenses are that the curvature changes continuously from the center to the periphery of the lens. Different from spherical lenses with a constant curvature from the center to the periphery of the lens, aspherical lenses have better curvature radius characteristics and have the advantages of improving distortion aberration and astigmatism aberration. After using aspherical lenses, it is possible to eliminate the aberration that appears during imaging as much as possible, thereby improving the imaging quality of the lens. In this embodiment, the second lens 2, the third lens 3, the fourth lens 4, and the fifth lens 5 are all spherical lenses. In this way, on the premise of ensuring image quality and reliability, costs are reduced, the assembly sensitivity is lower, and the yield of finished products is improved. The present invention uses both glass aspherical and plastic aspherical lenses, which not only controls costs but also significantly reduces the volume of the lens.

[0038] Specifically, in order to enable optical components to improve the image quality of the optical system, reduce light energy loss, increase imaging clarity, protect the scale surface, and further optimize the processing process to meet the design requirements, in this embodiment, the fourth lens 4 and the fifth lens 5 are glued together to form a glued lens. By reasonably using glued components and appropriately distributing the optical power, combined with the thermal parameters of the glass material, it can well correct aberration and achieve the effect of athermalization at high and low temperatures, and at the same time achieve a clear effect.

[0039] Specifically, in this embodiment, the optical system also satisfies the following conditions: 40 < |T1 - T6| < 60; where is the optical power of the first lens 1, is the optical power of the sixth lens 6, T1 is the thermal expansion coefficient of the first lens 1, and T6 is the thermal expansion coefficient of the sixth lens 6. With such a setting, it is possible to achieve no focus shift when the projector outputs 800 lm of brightness.

[0040] Further, in this embodiment, the optical system further includes a diaphragm 8, and the diaphragm 8 is disposed between the third lens 3 and the fourth lens 4. The diaphragm 8 restricts the light passing aperture of the on-axis beam to block part of the light during the zooming process, reduces the light spot, improves the image contrast, and helps to enhance the image quality.

[0041] Further, in this embodiment, the optical system further includes a protective glass, and the protective glass is disposed between the equivalent TIR prism 7 and the photosensitive chip 9. The protective glass can provide effective protection for the photosensitive chip IMAGE. The protective glass can be set as a filter, and the filter can effectively filter out the stray light in the non-working wavelength band to reduce the optical noise, making it easier for the subsequent optoelectronic module processing part and thus improving the imaging quality.

[0042] Specifically, the imaging surface can be understood as the surface of the photosensitive chip 9 facing the object side, that is, it can be the surface of a CCD or CMOS imaging element, etc. It can be understood that the light carrying the information of the photographed object can sequentially pass through the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the equivalent TIR prism 7, and finally form an image on the imaging surface.

[0043] Specifically, the following case is the actual design parameters of a projection lens used on a 0.23-inch DMD chip platform with an aperture of the optical system of F1.7. The refractive index, radius of curvature, and thickness interval of the lens materials are shown in Table 1 below:

[0044] Table 1

[0045]

[0046] Further, in this embodiment, the aspherical surface shape of the aspherical lens satisfies the following conditions:

[0047]

[0048] Wherein, c is the curvature corresponding to the radius, y is the radial coordinate (its unit is the same as the lens length unit), k is the conic quadratic coefficient (when the k coefficient is less than -1, the surface curve is a hyperbola; when the k coefficient is equal to -1, it is a parabola; when the k coefficient is between -1 and 0, it is an ellipse; when the k coefficient is equal to 0, it is a circle; when the k coefficient is greater than 0, it is an oblate), and a1 to a8 respectively represent the coefficients corresponding to each radial coordinate. Please refer to Table 2 below. Through the above parameters, the shape dimensions of the aspherical surfaces on the object side and the image side of the lens can be set.

[0049] Table 2 Conic coefficients and aspherical coefficients corresponding to the aspherical lens:

[0050] S1 S2 S11 S12 k -17.69797 151.4406 -1.176391 -0.7709284 a1 0 0 0 0 a2 0.002074691 0.0057360039 -6.0215056e-005 3.2968543e-005 a3 -7.5623493e-005 -0.00038912674 5.6906072e-006 1.1642325e-006 a4 2.1459003e-006 3.2875626e-005 -5.6758045e-007 -2.7382055e-007 a5 -4.4669815e-008 -2.1630228e-006 3.7120148e-008 2.3522206e-008 a6 3.8506741e-010 8.560746e-008 -1.5742932e-009 -1.0550376e-009 a7 1.5964758e-011 -1.3099267e-009 4.0858523e-011 2.2537719e-011 a8 -7.0303699e-013 -2.9130647e-011 -6.0367148e-013 -1.2167669e-013 a9 1.1165706e-014 1.431222e-012 4.471294e-015 -2.7485595e-015 a10 -6.5429812e-017 -1.5902407e-014 -1.3353716e-017 3.1250592e-017

[0051] Figure 2 Show the MTF curve graph of the optical system at room temperature of 25°C. Figure 3 Show the MTF curve graph of the optical system at high temperature of 80°C. Figure 4 Show the distortion graph (distortion) and field curvature graph (field curvature) of the optical system.

[0052] As can be seen from the above figures, the spherical aberration, field curvature and distortion of the optical system in this embodiment can all be well corrected.

[0053] In summary, the aperture value F of the optical system satisfies F ≤ 1.7, and the overall optical length is controlled within 54 mm. When it can be used in cooperation with the equivalent TIR prism 7, the volume is small and the cost is reduced.

[0054] The present invention also provides a projection device, which includes the optical system described in the above technical solution. The specific structure of this optical system refers to the above embodiment. Since the optical system of this optical system adopts all the technical solutions of the above all embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated one by one here.

[0055] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields are all included in the patent protection scope of the present invention.

Claims

1. An optical system, characterized in that, The optical system has an object side and an image side that are oppositely arranged along the optical axis direction. The optical system includes a first lens with a negative focal power, a second lens with a negative focal power, a third lens with a positive focal power, a fourth lens with a negative focal power, a fifth lens with a positive focal power, a sixth lens with a positive focal power, an equivalent TIR prism, and an image sensor chip, which are arranged in sequence from the object side to the image side. The first lens and the sixth lens are aspherical lenses, and the second lens, the third lens, the fourth lens, and the fifth lens are spherical lenses, so that the total optical length TTL of the optical system is ≤ 54 mm, and the f-number of the optical system is F ≤ 1.7; The optical system also satisfies the following conditions: 1.2 < |φ1 / φ2| < 1.5, 0.05 < φ3 < 0.06, 0.06 < φ6 < 0.08; Wherein, φ1 is the focal power of the first lens, φ2 is the focal power of the second lens, φ3 is the focal power of the third lens, and φ6 is the focal power of the sixth lens.

2. The optical system according to claim 1, characterized in that, The first lens is a plastic lens.

3. The optical system according to claim 1, characterized in that, The second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass lenses.

4. The optical system according to claim 1, wherein The first lens and the sixth lens are aspherical lenses; The second lens, the third lens, the fourth lens, and the fifth lens are all spherical lenses.

5. The optical system according to claim 1, characterized in that, The fourth lens and the fifth lens are adhesively connected to form an adhesive lens.

6. The optical system according to claim 1, characterized in that The optical system also satisfies the following conditions: 40 < |T1 - T6| < 60; Wherein, T1 is the thermal expansion coefficient of the first lens, and T6 is the thermal expansion coefficient of the sixth lens.

7. The optical system according to claim 1, characterized in that, The optical system also includes a diaphragm, and the diaphragm is arranged between the third lens and the fourth lens.

8. The optical system according to claim 1, wherein The optical system also includes a protective glass, and the protective glass is arranged between the equivalent TIR prism and the image sensor chip.

9. A projection device, characterized in that, The optical system according to any one of claims 1 to 8.

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