Miniature DMS lens

Abstract

An optical system of the lens is composed of a first lens, a second lens and a third lens which are sequentially arranged from left to right along a light incident light path, the first lens is a plano-convex lens with positive focal power, the object side face of the first lens is a convex face, and the image side face of the first lens is a plane; the second lens is a meniscus lens with positive focal power, the object side surface of the second lens is a concave surface, and the image side surface of the second lens is a convex surface; the third lens is a meniscus lens with negative focal power, the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a concave surface; the first lens is a glass spherical lens, and the second lens and the third lens are plastic aspheric lenses. A glass-plastic mixed optical system is formed by one glass spherical lens and two plastic aspheric lenses, and the lenses have high resolution, low distortion and low temperature drift by reasonably distributing the focal power and the surface type of each lens, the central thickness of each lens, the axial distance between the lenses and the like, and can clearly image at the temperature of-40 DEG C to 105 DEG C; the total length of the lens is greatly shortened, and miniaturization requirements are met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lenses, and particularly relates to a small DMS lens. BACKGROUND

[0002] With the rapid development of intelligent driving technology, the driver monitoring system (DMS) has become a core component for improving driving safety, which reduces the risk of accidents by monitoring the fatigue state, distraction and dangerous behavior (such as using a mobile phone, closing eyes, etc.) of the driver in real time. At present, the DMS lens based on infrared or visible light imaging needs to meet the all-weather working requirements (such as day and night confocal, high and low temperature stability), and at the same time, the optical performance of high resolution, large aperture and low distortion needs to be considered.

[0003] However, the existing DMS technology still has the following key bottlenecks: 1. Contradiction between miniaturization and imaging quality: the traditional DMS lens adopts a full-glass spherical lens structure to pursue clear imaging, which leads to an optical total length of more than 12 mm, a large volume, and difficulty in integration in the narrow space (such as A column, steering wheel) in the vehicle; 2. Insufficient temperature adaptability: the vehicle-mounted environment temperature range is wide (-40℃ to 105℃), the refractive index of the glass lens is temperature drift, which causes defocus, and affects the high and low temperature imaging stability, while the full-plastic aspherical lens has low cost and is easy to miniaturize, but the thermal expansion coefficient is high, and the distortion and field curvature are aggravated at high temperature; 3. The full-glass lens scheme has high cost, and the full-plastic aspherical lens has high tolerance sensitivity and low assembly yield, which is difficult to meet the large-scale production demand. SUMMARY

[0004] The application improves the existing technology, and the technical problem to be solved by the application is to provide a small DMS lens.

[0005] In order to achieve the above purpose, the technical scheme adopted by the application is: a small DMS lens, the optical system of the lens is composed of a first lens, a second lens and a third lens arranged in sequence from left to right along the light incident path, the first lens is a plano-convex lens with positive focal power, the object side is a convex surface, and the image side is a plane; the second lens is a meniscus lens with positive focal power, the object side is a concave surface, and the image side is a convex surface; the third lens is a meniscus lens with negative focal power, the object side is a convex surface, and the image side is a concave surface; the first lens is a glass spherical lens, and the second lens and the third lens are plastic aspherical lenses.

[0006] Further, the on-axis distance of the optical system satisfies the following relationship, the air gap between the first lens and the second lens is: 0-0.5mm; the air gap between the second lens and the third lens is: 0-0.5mm.

[0007] Furthermore, the focal length of the optical system is f, and the focal lengths of the first lens, the second lens, and the third lens are f1, f2, and f3, respectively, where f1, f2, f3, and f satisfy the following ratio: 1.0 <f1 / f<2.0,0<f2 / f<1.0,-2.0<f3 / f<-1.0。

[0008] Furthermore, the first lens satisfies the relationship: 2.0 ≤ N d ≤2.1, V d ≤50.0; The second lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; The third lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≤50.0; where N d V is the refractive index. d Let be Abbe's constant.

[0009] Furthermore, the equations for the aspherical curves of the second and third lenses are as follows: Where Z is the distance from the vertex of the aspherical surface to the optical axis at a position of height r; c is the paraxial curvature of the aspherical surface, r = 1 / c; k is the conic constant; a1, a2, a3, a4, a5, a6, a7, a8, a9, a 10 All are coefficients of higher-order terms.

[0010] Furthermore, the total optical length (TTL) of the optical system and the focal length (f) of the optical system satisfy the following condition: 1.5 ≤ TTL / f ≤ 2.0.

[0011] Furthermore, the image height H of the optical system and the focal length f of the optical system satisfy the following condition: H / f≥1.2.

[0012] Furthermore, the aperture of the optical system is located to the left of the first lens.

[0013] Furthermore, a filter is provided on the right side of the third lens.

[0014] Furthermore, the F-number of the optical system is ≤2.2.

[0015] Compared with the prior art, the present invention has the following advantages: The present invention uses one glass spherical lens and two plastic aspherical lenses to form a glass-plastic hybrid optical system. By rationally allocating the optical power, surface shape, center thickness of each lens, and on-axis distance between each lens, the lens has high resolution, low distortion, and low temperature drift, and can form clear images in temperatures ranging from -40℃ to 105℃. The overall length of the lens is greatly shortened to less than 6mm, which meets the requirements of miniaturization design, while also being inexpensive. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the optical structure of the present invention; Figure 2 This is the transverse chromatic aberration diagram of the entire working band of the present invention; Figure 3 This is the axial chromatic aberration diagram of the entire working band of the present invention; Figure 4 This is the field curvature distortion diagram of the entire working band of the present invention.

[0017] In the picture: STO - Aperture stop; L1 - First lens; L2 - Second lens; L3 - Third lens; L4 - Equivalent glass plate; IMA - Imaging surface. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0019] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0020] like Figure 1 As shown, this invention discloses a small DMS lens. The optical system of the lens consists of a first lens L1, a second lens L2, and a third lens L3 arranged sequentially from left to right along the incident light path. The aperture stop of the optical system is located to the left of the first lens, and a filter is located to the right of the third lens. The first lens is a plano-convex lens with positive optical power, its object-side surface is convex, and its image-side surface is flat. The second lens is a meniscus lens with positive optical power, its object-side surface is concave, and its image-side surface is convex. The third lens is a meniscus lens with negative optical power, its object-side surface is convex, and its image-side surface is concave. The first lens is a glass spherical lens, and the second and third lenses are plastic aspherical lenses. Through the reasonable combination of the three lenses and the use of plastic aspherical lenses, the optical system possesses good aberration correction and resolving capabilities, such as... Figures 2 to 4 As shown, the technical solution employing one glass spherical lens and two plastic aspherical lenses not only meets the design requirements of miniaturization and low cost, but also possesses optical properties such as high resolution, good temperature stability, and low distortion.

[0021] In this embodiment, the on-axis distances of the optical system satisfy the following relationship: the air gap between the first lens and the second lens is 0 to 0.5 mm; the air gap between the second lens and the third lens is 0 to 0.5 mm.

[0022] In this embodiment, the focal length of the optical system is f, and the focal lengths of the first lens, the second lens, and the third lens are f1, f2, and f3, respectively, wherein f1, f2, f3, and f satisfy the following ratio: 1.0 <f1 / f<2.0,0<f2 / f<1.0,-2.0<f3 / f<-1.0。

[0023] In this embodiment, the first lens satisfies the relationship: 2.0 ≤ N d ≤2.1, V d ≤50.0; The second lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; The third lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≤50.0; where N d V is the refractive index. d Let be Abbe's constant.

[0024] In this embodiment, the equations for the aspherical curves of the second and third lenses are as follows: Where Z is the distance from the vertex of the aspherical surface to the optical axis at a position of height r; c is the paraxial curvature of the aspherical surface, r = 1 / c; k is the conic constant; a1, a2, a3, a4, a5, a6, a7, a8, a9, a 10 All are coefficients of higher-order terms.

[0025] In this embodiment, the total optical length TTL of the optical system and the focal length f of the optical system satisfy the following condition: 1.5≤TTL / f≤2.0.

[0026] In this embodiment, the image height H of the optical system and the focal length f of the optical system satisfy the following condition: H / f≥1.2.

[0027] In this embodiment, the F-number of the optical system is ≤2.2.

[0028] In this embodiment, the technical specifications achieved by the optical system are as follows: (1) Focal length: 3.0≤EFFL≤4.0mm; (2) Aperture F≤2.2; (3) Field of view: 2w ≥ 69°; (4) Operating band: Infrared band.

[0029] To achieve the above design parameters, the specific design of the optical system adopted in this embodiment is shown in the table below: .

[0030] In this embodiment, the aspherical coefficients of each aspherical lens in the optical system are shown in the following table: .

[0031] The optical system in this embodiment adopts a glass-plastic hybrid optical system. By rationally allocating the optical power, surface shape, center thickness of each lens, and on-axis distance between each lens, the lens has high resolution, low distortion, low temperature drift, and good imaging quality. The total length of the lens is less than 6mm, which meets the requirements of miniaturization design, and the lens manufacturing cost is also lower.

[0032] If this invention discloses or relates to components or structural parts that are fixedly connected to each other, then, unless otherwise stated, a fixed connection can be understood as: a fixed connection that can be detached (e.g., using bolts or screws), or a fixed connection that cannot be detached (e.g., riveting, welding). Of course, a fixed connection can also be replaced by an integral structure (e.g., manufactured in one piece using a casting process) (except where it is obviously impossible to use an integral molding process).

[0033] In addition, unless otherwise stated, the terms used in any of the technical solutions disclosed in this invention to indicate positional relationships or shapes include states or shapes that are similar to, close to, or approximate with those states or shapes.

[0034] Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A small DMS lens, characterized in that: The optical system of the lens consists of a first lens, a second lens, and a third lens arranged sequentially from left to right along the incident light path. The first lens is a plano-convex lens with positive optical power, its object side is convex, and its image side is flat. The second lens is a meniscus lens with positive optical power, its object side is concave, and its image side is convex. The third lens is a meniscus lens with negative optical power, its object side is convex, and its image side is concave. The first lens is a glass spherical lens, and the second and third lenses are plastic aspherical lenses.

2. A small DMS lens according to claim 1, characterized in that: The on-axis distances of the optical system satisfy the following relationships: the air gap between the first lens and the second lens is 0 to 0.5 mm; the air gap between the second lens and the third lens is 0 to 0.5 mm.

3. A small DMS lens according to claim 1, characterized in that: The focal length of the optical system is f, and the focal lengths of the first lens, the second lens, and the third lens are f1, f2, and f3, respectively, where f1, f2, f3, and f satisfy the following ratio: 1.0 <f1 / f<2.0,0< f2 / f<1.0,-2.0<f3 / f<-1.0。 4. A small DMS lens according to claim 1, characterized in that: The first lens satisfies the relationship: 2.0 ≤ N d ≤2.1, V d ≤50.0; The second lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; The third lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≤50.0; where N d V is the refractive index. d Let be Abbe's constant.

5. A small DMS lens according to claim 1, characterized in that: The equations for the aspherical curves of the second and third lenses are as follows: Where Z is the distance from the vertex of the aspherical surface to the optical axis at a position of height r; c is the paraxial curvature of the aspherical surface, r = 1 / c; k is the conic constant; a1, a2, a3, a4, a5, a6, a7, a8, a9, a 10 All are coefficients of higher-order terms.

6. A small DMS lens according to claim 1, characterized in that: The total optical length (TTL) of an optical system and the focal length (f) of the optical system satisfy the following condition: 1.5 ≤ TTL / f ≤ 2.

0.

7. A small DMS lens according to claim 1, characterized in that: The image height H of the optical system and the focal length f of the optical system satisfy the following condition: H / f≥1.

2.

8. A small DMS lens according to claim 1, characterized in that: The aperture of the optical system is located to the left of the first lens.

9. A small DMS lens according to claim 1, characterized in that: A filter is provided on the right side of the third lens.

10. A small DMS lens according to claim 1, characterized in that: The F-number of the optical system is ≤2.2.

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