An ultra-short focal length small distortion projection lens

Abstract

The utility model discloses a kind of ultra-short focal length small distortion projection lens, including refractive lens group, fresnel lens and LCD screen in order from image side to object side along optical axis;The one side of fresnel lens close to object side is fresnel surface, the one side close to image side is spherical surface;Refractive lens group includes first lens, second lens, diaphragm, third lens, fourth lens;First lens is the convex-concave lens of negative optical power, second lens is the convex-concave lens of positive optical power, third lens is the convex-convex lens of positive optical power, fourth lens is the concave-convex lens of negative optical power, diaphragm is located between second lens, third lens;The projection distance T1 of projection lens is changed by adjusting the relative distance T2 of refractive lens group and fresnel lens.The utility model realizes small distortion, high brightness uniformity and compact structure by optimizing optical design, simultaneously, by adjusting the relative distance of refractive lens group and fresnel lens, projection distance of projection lens is flexibly changed.

Description

Technical Field

[0001] This utility model relates to the field of optical imaging technology, and in particular to an ultra-short focal length, low-distortion projection lens. Background Technology

[0002] With the development of projection technology, users have increasingly higher requirements for the performance of projection lenses, especially in ultra-short focal length applications, where lenses are needed to project large images over short distances. Traditional projection lenses typically suffer from the following problems: significant optical distortion, affecting image quality; insufficient edge illumination, leading to uneven screen brightness; long overall lens length, hindering device miniaturization; and inflexible projection distance adjustment.

[0003] In existing technologies, some projection lenses employ complex optical structures to correct distortion, but these are often costly and struggle to simultaneously meet the requirements of ultra-short focal length, low distortion, and compact size. Furthermore, using glass lenses increases the lens's weight and cost. Therefore, there is a need for a low-cost, high-performance ultra-short focal length projection lens capable of achieving low distortion, high brightness uniformity, and adjustable projection distance. Utility Model Content

[0004] The purpose of this invention is to provide an ultra-short focal length, low-distortion projection lens. By optimizing the optical design, it achieves low distortion, high brightness uniformity, and a compact structure. The use of resin lenses reduces costs, and the projection distance of the projection lens can be flexibly changed by adjusting the relative distance between the refractive lens group and the Fresnel lens.

[0005] The technical solution adopted by this utility model to solve its technical problem is as follows:

[0006] An ultra-short focal length, low-distortion projection lens comprises, along the optical axis from the image side to the object side, a refractive mirror group, a Fresnel lens, and an LCD screen. The Fresnel lens has a Fresnel surface near the object side and a spherical surface near the image side. The refractive mirror group includes a first lens, a second lens, an aperture stop, a third lens, and a fourth lens. The first lens is a negative power convex-concave lens, the second lens is a positive power convex-concave lens, the third lens is a positive power convex-convex lens, and the fourth lens is a negative power concave-convex lens. The aperture stop is located between the second and third lenses. The projection distance T1 of the projection lens is changed by adjusting the relative distance T2 between the refractive mirror group and the Fresnel lens.

[0007] Preferably, the first lens and the second lens form group one, and the third lens and the fourth lens form group two, wherein the total optical power of group one is [missing value]. The total optical power of group two is The optical power of the Fresnel lens is: The following relationship must be satisfied:

[0008]

[0009] Preferably, the effective focal length (EFL) of the projection lens satisfies the following conditions:

[0010] 21.375mm≤EFL≤23.625mm.

[0011] Preferably, the imaging circle diameter Φ of the projection lens satisfies the following condition:

[0012] Φ≤53mm.

[0013] Preferably, the total lens length (TTL) of the projection lens satisfies the following condition:

[0014] TTL<65mm.

[0015] Preferably, the projection lens adopts a telecentric structure and uses an image-side telecentric optical path.

[0016] Preferably, the optical distortion of the projection lens is less than 2%, and the TV distortion is less than 1%.

[0017] Preferably, the diagonal field of view (DFOV) of the projection lens satisfies the following condition: DFOV ≥ 95°.

[0018] Preferably, the projection distance T1 is 0.9m to 3m, and the projection ratio TR of the projection lens is 0.45.

[0019] Preferably, the first lens, the second lens, the third lens, the fourth lens, and the Fresnel lens are all made of resin.

[0020] Compared with the prior art, the beneficial effects of this utility model are:

[0021] 1. By adopting a negative-positive-positive-negative optical power distribution and a symmetrical structure with the aperture located between the second and third lenses, the transverse aberration is reduced and optical distortion is effectively corrected.

[0022] 2. The telecentric design improves edge illumination and ensures uniform brightness of the projected image.

[0023] 3. By adjusting the relative distance between the refracting mirror group and the Fresnel lens, the projection distance can be adjusted within the range of 0.9m to 3m to adapt to different application scenarios.

[0024] 4. Using resin lenses reduces production costs, achieves lightweight projection lenses, and meets optical performance requirements.

[0025] 5. The overall length of the lens is less than 65mm, with a compact structure, which is beneficial for miniaturizing the projection lens.

[0026] It is more convenient to integrate into various projection devices. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the projection lens of this utility model;

[0028] Figure 2 This is a diagram showing the RMS spot size of the sampling field of view of the projection lens of this utility model;

[0029] Figure 3 This is a field curvature and distortion diagram of the projection lens of this utility model.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1. First lens; 2. Second lens; 3. Aperture; 4. Third lens; 5. Fourth lens; 6. Fresnel lens; 7. LCD screen. Detailed Implementation

[0032] The technical solutions in the embodiments of this utility model will now be clearly and completely described in conjunction with the accompanying drawings.

[0033] Reference Figures 1 to 3 This invention proposes an ultra-short focal length, low-distortion projection lens, which, along the optical axis from the image side to the object side, includes a refractive mirror group, a Fresnel lens 6, and an LCD screen 7. The Fresnel lens 6 has a Fresnel surface near the object side and a spherical surface near the image side. The refractive mirror group includes a first lens 1, a second lens 2, an aperture stop 3, a third lens 4, and a fourth lens 5. The first lens 1 is a negative power convex-concave lens, the second lens 2 is a positive power convex-concave lens, the third lens 4 is a positive power convex-convex lens, and the fourth lens 5 is a negative power concave-convex lens. The aperture stop 3 is located between the second lens 2 and the third lens 4. The negative-positive-positive-negative power distribution and the symmetrical structure of the aperture stop 3 between the second and third lenses 4 reduce transverse aberration and effectively correct optical distortion. By adjusting the relative distance T2 between the refractive mirror group and the Fresnel lens 6, the projection distance T1 of the projection lens can be varied, allowing the projection lens to adapt to different application scenarios. The focusing data for changing the projection distance T1 of the projection lens by adjusting the relative distance T2 between the refractive mirror group and the Fresnel lens 6 are shown in Table 1.

[0034] Table 1 Lens focusing parameters

[0035] 3000mm 20.816mm 2000mm 20.963mm 900mm 21.571mm

[0036] like Figure 1 As shown, the first lens 1 and the second lens 2 form group one, and the third lens 4 and the fourth lens 5 form group two. The total optical power of group one is... The total optical power of group two is Fresnel lens 6 has an optical power of The following relationship must be satisfied:

[0037]

[0038] In this embodiment, the effective focal length (EFL) of the projection lens satisfies the following condition:

[0039] 21.375mm≤EFL≤23.625mm.

[0040] In this embodiment, the imaging circle diameter Φ of the projection lens satisfies the following condition:

[0041] Φ≤53mm.

[0042] In this embodiment, the total lens length (TTL) of the projection lens satisfies the following condition:

[0043] TTL < 65mm. The total lens length is less than 65mm, resulting in a compact structure that facilitates device miniaturization and easier integration into various projection devices.

[0044] In this embodiment, the projection lens adopts a telecentric structure and uses an image-side telecentric optical path, which can improve edge illumination and ensure uniform brightness of the projected image.

[0045] The specific optical parameters of each lens in the projection lens are shown in Table 2.

[0046] Table 2 Lens optical parameters

[0047]

[0048]

[0049] In Table 2, / indicates that it does not participate in the refraction of light and its refractive index does not need to be calculated.

[0050] The surfaces in Table 2 that are aspherical or Fresnel surfaces satisfy the following formula:

[0051] In the formula, c is the reciprocal of the radius of curvature R, r is the radial distance from a point on the surface, k is the quadratic surface constant, and A i These are the coefficients of higher-order terms.

[0052] Figure 2 This diagram shows the RMS spot size of the projection lens in the sampling field of view of this invention. As can be seen from the diagram, the RMS spot size in each sampling field of view is less than 0.085 mm, resulting in clear imaging.

[0053] Figure 3This is a graph showing the field curvature and distortion curves of the projection lens of this utility model. As can be seen from the graph, the defocusing amount is less than 1mm and the distortion is less than 2% in each field of view. The field curvature and distortion of the projection lens are both small, resulting in high image quality and providing a clear image with minimal distortion.

[0054] The above are merely preferred embodiments of this utility model. Any technical solution that achieves the purpose of this utility model by essentially the same means shall fall within the protection scope of this utility model.

Claims

1. A projection lens with ultra-short focal length and low distortion, characterized in that: Along the optical axis from the image side to the object side, the projection lens consists of a refraction mirror group, a Fresnel lens (6), and an LCD screen (7). The Fresnel lens (6) has a Fresnel surface on the object side and a spherical surface on the image side. The refraction mirror group includes a first lens (1), a second lens (2), an aperture stop (3), a third lens (4), and a fourth lens (5). The first lens (1) is a convex-concave lens with negative optical power, the second lens (2) is a convex-concave lens with positive optical power, the third lens (4) is a convex-convex lens with positive optical power, and the fourth lens (5) is a concave-convex lens with negative optical power. The aperture stop (3) is located between the second lens (2) and the third lens (4). The projection distance T1 of the projection lens is changed by adjusting the relative distance T2 between the refraction mirror group and the Fresnel lens (6).

2. The ultra-short focal length, low-distortion projection lens according to claim 1, characterized in that: The first lens (1) and the second lens (2) form group one, and the third lens (4) and the fourth lens (5) form group two. The total optical power of group one is φ1, the total optical power of group two is φ2, and the optical power of the Fresnel lens (6) is φ3, satisfying the following relationship: -0.004<φ1<-0.003, 0.0255<φ2<0.0355, 0.0245<φ3<0.0345.

3. The ultra-short focal length, low-distortion projection lens according to claim 1, characterized in that: The effective focal length (EFL) of the projection lens satisfies the following condition: 21.375mm≤EFL≤23.625mm.

4. The ultra-short focal length, low-distortion projection lens according to claim 1, characterized in that: The imaging circle diameter Φ of the projection lens satisfies the following condition: Φ≤53mm.

5. The ultra-short focal length, low-distortion projection lens according to claim 1, characterized in that: The total length (TTL) of the projection lens satisfies the following condition: TTL<65mm.

6. The ultra-short focal length, low-distortion projection lens according to claim 1, characterized in that: The projection lens adopts a telecentric structure and uses an image-side telecentric optical path.

7. The ultra-short focal length, low-distortion projection lens according to claim 1, characterized in that: The optical distortion of the projection lens is less than 2%, and the TV distortion is less than 1%.

8. The ultra-short focal length, low-distortion projection lens according to claim 1, characterized in that: The diagonal field of view (DFOV) of the projection lens satisfies the following condition: DFOV ≥ 95°.

9. The ultra-short focal length, low-distortion projection lens according to claim 1, characterized in that: The projection distance T1 is 0.9m to 3m, and the projection ratio TR of the projection lens is 0.

45.

10. The ultra-short focal length, low-distortion projection lens according to claim 1, characterized in that: The first lens (1), the second lens (2), the third lens (4), the fourth lens (5) and the Fresnel lens (6) are all made of resin.

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