A DMS optical lens and imaging method thereof

Abstract

The present invention relates to a DMS optical lens and an imaging method thereof. The optical system of the lens includes an aperture, a first lens, a second lens, a third lens, and a fourth lens, arranged in sequence from left to right along the incident light path. The first and second lenses form a cemented lens group. The first lens is a glass spherical lens with positive optical power, with its object side and image side surfaces being convex. The second lens is a glass spherical lens with negative optical power, with its object side and image side surfaces being concave. The third lens is a plastic aspherical lens with positive optical power. The fourth lens is a plastic aspherical lens with negative optical power. The lens utilizes plastic aspherical lenses, achieving high definition and low-temperature drift while maintaining a compact size.

Description

Technical Field

[0001] The invention relates to a DMS optical lens and an imaging method thereof. Background Art

[0002] A driver monitoring system (DMS) is a real-time system that uses facial images, physiological indicators, or vehicle information to determine the driver's status. It primarily performs driver identification, monitoring for fatigue, distraction, and dangerous driving behavior. It alerts the driver in dangerous situations, prompting them to improve their driving behavior and providing appropriate intervention based on their condition, thereby improving driving safety. DMS cameras are typically mounted on the steering column or A-pillar, requiring a small size for easy installation and integration. However, existing lenses are generally too large. Summary of the Invention

[0003] The object of the present invention is to provide a DMS optical lens and an imaging method thereof, wherein the lens rationally uses a plastic aspheric lens so that the lens has the advantages of small size while achieving high definition, low temperature drift and other performances.

[0004] The technical solution of the present invention is: a DMS optical lens, the optical system of which includes an aperture, a first lens, a second lens, a third lens and a fourth lens arranged in sequence from left to right along the incident optical path of light; the first lens and the second lens constitute a cemented lens group; the first lens is a glass spherical lens with positive focal power, whose object side surface is convex and whose image side surface is convex; the second lens is a glass spherical lens with negative focal power, whose object side surface is concave and whose image side surface is convex; the third lens is a plastic aspherical lens with positive focal power; and the fourth lens is a plastic aspherical lens with negative focal power.

[0005] Furthermore, the air gap between the second lens and the third lens is 1-2.0 mm, and the air gap between the third lens and the fourth lens is 0-1.0 mm.

[0006] Furthermore, the focal length of the optical system is The focal lengths of the first lens, the second lens, the third lens, and the fourth lens are 、 、 、 ,in 、 、 、 and Meet the following ratio: 0.5< / <1.0, -1.5< / <-0.5, 0.5< / <1.5, -1.5< / <-0.5.

[0007] Furthermore, the first lens satisfies the relationship: 1.5≤ ≤1.6, ≥50.0; the second lens satisfies the relationship: 1.8≤ ≤2.0, ≤50.0; the third lens satisfies the relationship: ≤1.5, ≥50.0; the fourth lens satisfies the relationship: ≤1.5, ≥50.0; among them is the refractive index, is the Abbe constant.

[0008] Furthermore, the total optical length TTL of the optical system and the focal length f of the optical system satisfy the following relationship: TTL / f≤1.5.

[0009] Furthermore, the F number of the optical system is ≤4.0.

[0010] Furthermore, the image height H of the optical system and the focal length f of the optical system satisfy: H / f≥1.0.

[0011] An imaging method of a DMS optical lens is provided, wherein light is imaged after passing through an aperture, a first lens, a second lens, a third lens, and a fourth lens in sequence from left to right.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] This DMS optical lens utilizes four optical elements: two glass spherical lenses and two plastic aspherical lenses. This rationally allocates the optical power, surface shape, and on-axis spacing of each lens element, reducing overall sensitivity and improving imaging quality. It also effectively shortens the overall lens length to less than 8mm, meeting the requirements for miniaturization of DMS lenses. This ensures the lens' effective light diameter and miniaturization. It features a larger imaging target surface, ensuring the system's image height, and exhibits minimal distortion. The use of aspherical plastic lenses offers improved curvature radius characteristics, improving aberrations and resulting in superior imaging results. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 1 is a schematic diagram of the optical structure of the first embodiment of the present invention;

[0015] Figure 2This is a full-band axial chromatic aberration diagram of Example 1 of the present invention;

[0016] Figure 3 This is a vertical axis chromatic aberration diagram for the entire working band of the first embodiment of the present invention;

[0017] Figure 4 This is a field curvature distortion diagram for the entire working band of the first embodiment of the present invention;

[0018] Figure 5 is a schematic diagram of the optical structure of embodiment 2 of the present invention;

[0019] Figure 6 This is a full-band axial chromatic aberration diagram of Example 2 of the present invention;

[0020] Figure 7 This is a vertical axis chromatic aberration diagram of the full working band of embodiment 2 of the present invention;

[0021] In the figure: STO - aperture; L1 - first lens; L2 - second lens; L3 - third lens; L4 - fourth lens; L5 - equivalent glass plate; IMA - imaging surface. DETAILED DESCRIPTION

[0022] To make the above features and advantages of the present invention more clearly understood, embodiments are given below with reference to the accompanying drawings for detailed description, but the present invention is not limited thereto.

[0023] Example 1 Reference Figures 1 to 4

[0024] A DMS optical lens, the optical system of which includes an aperture STO, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4, which are arranged in sequence from left to right along the incident optical path of light; the first lens and the second lens constitute a cemented lens group; the first lens is a glass spherical lens with positive focal power, whose object-side surface is convex and whose image-side surface is convex; the second lens is a glass spherical lens with negative focal power, whose object-side surface is concave and whose image-side surface is convex; the third lens is a plastic aspherical lens with positive focal power; and the fourth lens is a plastic aspherical lens with negative focal power.

[0025] In this embodiment, the air gap between the second lens L2 and the third lens L3 is 1-2.0 mm, and the air gap between the third lens L3 and the fourth lens L4 is 0-1.0 mm.

[0026] In this embodiment, the aspheric curve equations of the fourth lens and the fourth lens are expressed as follows:

[0027]

[0028] Where Z is the height of the aspheric surface from the vertex of the aspheric surface at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface; k is the conic constant; All are high-order coefficients.

[0029] In this embodiment, an equivalent glass plate is further disposed between the fourth lens and the imaging plane.

[0030] In this embodiment, the focal length of the optical system is , the focal lengths of the first lens, the second lens, the third lens, and the fourth lens are 、 、 、 ,in 、 、 、 and Meet the following ratio: 0.5< / <1.0, -1.5< / <-0.5, 0.5< / <1.5, -1.5< / <-0.5.

[0031] In this embodiment, the first lens satisfies the relationship: 1.5≤ ≤1.6, ≥50.0; the second lens satisfies the relationship: 1.8≤ ≤2.0, ≤50.0; the third lens satisfies the relationship: ≤1.5, ≥50.0; the fourth lens satisfies the relationship: ≤1.5, ≥50.0; among them is the refractive index, is the Abbe constant.

[0032] In this embodiment, the total optical length TTL of the optical system and the focal length f of the optical system satisfy the following relationship: TTL / f≤1.5.

[0033] In this embodiment, the image height H of the optical system and the focal length f of the optical system satisfy: H / f≥1.0.

[0034] In this embodiment, the technical indicators implemented by the optical system are as follows:

[0035] (1) Focal length: 5.0 ≤ EFFL ≤ 6.0 mm;

[0036] (2) Aperture F≤4.0;

[0037] (3) Field of view: 2w ≥ 60°;

[0038] (4) Working band: visible light band or infrared band.

[0039] In this embodiment, to achieve the above design parameters, the specific design adopted by the optical system is shown in the following table:

[0040] .

[0041] In this embodiment, the aspheric coefficients of the aspheric lenses of the optical system are as follows:

[0042] .

[0043] In this embodiment, the optical system achieves a small size and low distortion design, while also performing good corrections for on-axis and off-axis aberrations.

[0044] The lens uses a combination of two glass spherical lenses and two plastic aspherical lenses. The third and fourth lenses are plastic aspherical lenses. The optical power of each lens is reasonably distributed and its off-axis and on-axis aberrations are corrected, enabling the lens to produce high-definition images while controlling the overall size of the lens.

[0045] Example 2 Reference Figures 5 to 7

[0046] A DMS optical lens, the optical system of which includes an aperture STO, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4, which are arranged in sequence from left to right along the incident optical path of light; the first lens and the second lens constitute a cemented lens group; the first lens is a glass spherical lens with positive focal power, whose object-side surface is convex and whose image-side surface is convex; the second lens is a glass spherical lens with negative focal power, whose object-side surface is concave and whose image-side surface is convex; the third lens is a plastic aspherical lens with positive focal power; and the fourth lens is a plastic aspherical lens with negative focal power.

[0047] In this embodiment, the air gap between the second lens L2 and the third lens L3 is 1-2.0 mm, and the air gap between the third lens L3 and the fourth lens L4 is 0-1.0 mm.

[0048] In this embodiment, the aspheric curve equations of the fourth lens and the fourth lens are expressed as follows:

[0049]

[0050] Where Z is the height of the aspheric surface from the vertex of the aspheric surface at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface; k is the conic constant; All are high-order coefficients.

[0051] In this embodiment, the focal length of the optical system is , the focal lengths of the first lens, the second lens, the third lens, and the fourth lens are 、 、 、 ,in 、 、 、 and Meet the following ratio: 0.5< / <1.0, -1.5< / <-0.5, 0.5< / <1.5, -1.5< / <-0.5.

[0052] In this embodiment, the first lens satisfies the relationship: 1.5≤ ≤1.6, ≥50.0; the second lens satisfies the relationship: 1.8≤ ≤2.0, ≤50.0; the third lens satisfies the relationship: ≤1.5, ≥50.0; the fourth lens satisfies the relationship: ≤1.5, ≥50.0; among them is the refractive index, is the Abbe constant.

[0053] In this embodiment, the total optical length TTL of the optical system and the focal length f of the optical system satisfy the following relationship: TTL / f≤1.5.

[0054] In this embodiment, the image height H of the optical system and the focal length f of the optical system satisfy: H / f≥1.0.

[0055] In this embodiment, the technical indicators implemented by the optical system are as follows:

[0056] (1) Focal length: 5.0 ≤ EFFL ≤ 6.0 mm;

[0057] (2) Aperture F≤4.0;

[0058] (3) Field of view: 2w ≥ 60°;

[0059] (4) Working band: visible light band or infrared band.

[0060] In this embodiment, to achieve the above design parameters, the specific design adopted by the optical system is shown in the following table:

[0061] .

[0062] In this embodiment, the aspheric coefficients of the aspheric lenses of the optical system are as follows:

[0063] .

[0064] In this embodiment, the optical system achieves a small size and low distortion design, while also performing good corrections for on-axis and off-axis aberrations.

[0065] The lens uses a combination of two glass spherical lenses and two plastic aspherical lenses. The third and fourth lenses are plastic aspherical lenses. They rationally distribute the optical power of each lens and correct its off-axis and on-axis aberrations, enabling the lens to produce high-definition images while controlling the overall size of the lens.

[0066] An imaging method of a DMS optical lens is provided, wherein light is imaged after passing through an aperture, a first lens, a second lens, a third lens, and a fourth lens in sequence from left to right.

[0067] The above description is merely a preferred embodiment of the present invention. For those skilled in the art, designing different types of DMS optical lenses based on the teachings of the present invention does not require creative effort. All equivalent changes, modifications, substitutions, and variations made within the scope of the present invention without departing from the principles and spirit of the present invention are intended to fall within the scope of the present invention.

Claims

1. A DMS optical lens, characterized in that: The optical system of the lens includes an aperture, a first lens, a second lens, a third lens and a fourth lens arranged in sequence from left to right along the incident light path; the first lens and the second lens constitute a cemented lens group; the first lens is a glass spherical lens with positive focal length, the object side surface of which is convex and the image side surface is convex; the second lens is a glass spherical lens with negative focal length, the object side surface of which is concave and the image side surface is convex; the third lens is a plastic aspherical lens with positive focal length; the fourth lens is a plastic aspherical lens with negative focal length; the focal length of the optical system is , the focal lengths of the first lens, the second lens, the third lens, and the fourth lens are 、 、 、 ,in 、 、 、 and Meet the following ratio: 0.5< / <1.0, -1.5< / <-0.5, 0.5< / <1.5, -1.5< / <-0.

5.

2. A DMS optical lens according to claim 1, characterized in that: The air gap between the second lens and the third lens is 1-2.0 mm, and the air gap between the third lens and the fourth lens is 0-1.0 mm.

3. A DMS optical lens according to claim 1 or 2, characterized in that: The first lens satisfies the relationship: 1.5≤ ≤1.6, ≥50.0; the second lens satisfies the relationship: 1.8≤ ≤2.0, ≤50.0; the third lens satisfies the relationship: ≤1.5, ≥50.0; the fourth lens satisfies the relationship: ≤1.5, ≥50.0; among them is the refractive index, is the Abbe constant.

4. A DMS optical lens according to claim 1 or 2, characterized in that: The total optical length TTL of the optical system and the focal length f of the optical system satisfy the following: TTL / f≤1.

5.

5. A DMS optical lens according to claim 1 or 2, characterized in that: The F number of the optical system is ≤4.

0.

6. A DMS optical lens according to claim 1 or 2, characterized in that: The image height H of the optical system and the focal length f of the optical system satisfy the following relationship: H / f≥1.

0.

7. An imaging method applied to the DMS optical lens according to claim 1 or 2, characterized in that: The light passes through the aperture, the first lens, the second lens, the third lens, and the fourth lens from left to right to form an image.

Images