CN201845121U - Broad-band large-aperture optical lens with a central wavelength of near-infrared and visible light - Google Patents

Abstract

The utility model relates to a large-aperture optical imaging lens whose central wavelength is near-infrared while taking into account visible light. It is characterized in that the imaging surface from the object side to the imaging side includes: a first lens, a second lens, a third lens, An optical lens group composed of an aperture stop, a fourth lens, a fifth lens and a sixth lens, the focal length of the lens group is 27mm, the back focus is greater than 6mm, and the field angle is greater than 18°. The utility model has clear imaging, simple structure, all lenses are made of ordinary glass, no aspherical surface is used, and the cost is low. It can be used in various lighting conditions, especially in dark and poor visibility environments, and widely used in financial , insurance and other office monitoring systems.

Description

Broad-band large-aperture optical lens with a central wavelength of near-infrared and visible light

technical field

The utility model belongs to an optical imaging lens, in particular to a wide-band large-aperture optical lens whose central wavelength is near-infrared and visible light is also considered.

Background technique

At present, monitoring systems are installed in many places, including security systems in offices such as finance, insurance, and post and telecommunications, speed measurement and capture systems on roads, and detection systems that replace manual monitoring under harsh working conditions. Most of these monitoring systems use off-the-shelf optical imaging lenses, and commonly used optical imaging lenses use visible light imaging, and the imaging quality of these lenses is good in the case of sufficient light. However, in the case of darkness and poor visibility, the imaging is blurred, and there will be a big problem with the clarity of the surveillance camera, which will bring great difficulties to image recognition and easily cause wrong judgments.

There are not many developments and studies of infrared lenses in the prior art, and the method adopted is the improvement of ordinary optical lenses. Such a design scheme is first to purchase a high-end camera, and then add an additional lens to the front or rear of the camera lens. Infrared lens, as disclosed in patent CN00242036.8, has strict requirements on the selected camera, which not only greatly increases the cost, but also makes it difficult to achieve the purpose of enhancing the function of the lens.

Contents of the invention

The object of the present invention is to provide a wide-band large-aperture optical lens whose central wavelength is near-infrared and visible light, so as to overcome the problem of blurred imaging of existing surveillance cameras in the dark and poor visibility.

The technical scheme of the utility model is: it is characterized in that the imaging surface from the object side to the imaging side along the optical axis comprises a first lens, a second lens, a third lens, an aperture stop, a fourth lens, a fifth lens and The optical lens group composed of the sixth lens has a focal length of 27 mm, a back focal distance greater than 6 mm, and a field angle greater than 18°.

Among them, the first and fifth lenses are plano-convex lenses with positive refractive power, and have a first surface that is convex toward the object side and a second surface that is flat; the second lens is a convex-convex lens with positive refractive power, and has a convex surface. The first surface and the second surface facing the object side; the third and sixth lenses are biconcave lenses with negative refractive power; the fourth lens is a biconvex lens with positive refractive power, and all lenses adopt a spherical structure.

Because the ingenious combination of several lenses of the present invention can achieve relatively high pixels, especially because the second lens is a lens of positive refractive power, the positive refractive power of the first lens can be reduced, so that the lens does not Excessive bending will shorten the length of the entire optical lens group.

Therefore, the utility model has clear imaging, simple process structure, all lenses are made of ordinary glass, no aspheric surface is used, and the cost is low. In the case of vehicle speed measurement capture.

Description of drawings

FIG. 1 is a schematic structural view of the optical imaging lens of the present invention.

Fig. 2 is a spherical aberration diagram of the optical imaging lens of the present invention.

Wherein, 1. the first lens; 2. the second lens; 3. the third lens; 4. the aperture stop; 5. the fourth lens; 6. the fifth lens; 7. the sixth lens; 8. the imaging surface.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the utility model is described in further detail.

As shown in Figure 1, the utility model is that the imaging surface 8 from the object side to the imaging side along the optical axis includes in sequence: a first lens 1, a second lens 2, a third lens 3, an aperture stop 4, a fourth lens An optical lens group composed of lens 5, fifth lens 6, and sixth lens 7; wherein, the focal length of the lens group is 27mm, the back focus is greater than 6mm, and the field of view is greater than 18°.

The first lens 1 is a plano-convex lens with positive refractive power, and has a first surface convex to the object side and a second surface that is flat.

The second lens 2 is a convex-concave lens with positive refractive power, and has a first surface and a second surface that are convex toward the object side.

The third lens 3 is a biconcave lens of negative refractive power.

The fourth lens 5 is a biconvex lens of positive refractive power.

The fifth lens 6 is a plano-convex lens with positive refractive power, and has a first surface that is convex toward the object side and a second surface that is flat.

The sixth lens 7 is a biconcave lens with negative refractive power.

The utility model adopts CCD as the imaging device of the optical lens, selects 880nm near-infrared light as the central wavelength, and takes into account visible light at the same time, and satisfies the wide band imaging of 400nm-950nm.

The material of all lenses of the present utility model is all made of ordinary optical glass, as a specific example as shown in the following table:

The utility model is analyzed by optical analysis software, and its optical properties show that the optical transfer function (MTF) of the utility model is all higher than 30% to the MTF of various fields of view, and it can be known that the imaging quality of the optical lens from the center to the edge field of view is all higher than 30%. Very uniform, i.e. the entire image is very sharp. By analyzing the ratio between the brightness of the edge of the lens and the brightness of the center, it is shown that the brightness of the center and the edge of the utility model is relatively close, that is, the brightness of the image is uniform. Moreover, the difference between the actual image and the ideal image (that is, aberration) is small when the optical lens is imaging, and the area of the diffuse spot is small in different fields of view; in addition, the field curvature and distortion of the utility model are small.

Figure 2. The spherical aberration diagram of the lens shows the size of the optical lens’ aberration on the axis. The four lines represent the spherical aberration at four wavelengths of 486nm, 588nm, 656nm and 880nm from left to right. It can be seen that in the typical four wavelengths The time difference is small.

Apparently, the utility model has clear imaging, high definition of the monitoring camera, and low cost, and is widely used in monitoring systems including office places such as finance and insurance.

Claims (7)

1. A large-aperture optical imaging lens whose central wavelength is near-infrared and visible light, is characterized in that the imaging surface (8) from the object side to the imaging side along the optical axis comprises in sequence: the first lens (1), the second The optical lens group that two lens (2), the 3rd lens (3), aperture stop (4), the 4th lens (5), the 5th lens (6) and the 6th lens (7) constitute, the lens group The focal length is 27mm, the back focus is greater than 6mm, and the field of view is greater than 18°. 2. The optical imaging lens according to claim 1, characterized in that the first lens (1) is a plano-convex lens with positive refractive power, and has a first surface convex to the object side and a second surface that is flat . 3. The optical imaging lens according to claim 1, characterized in that the second lens (2) is a convex-concave lens with positive refractive power, and has a first surface and a second surface convex to the object side. 4. The optical imaging lens according to claim 1, characterized in that said third lens (3) is a biconcave lens with negative refractive power. 5. The optical imaging lens according to claim 1, characterized in that the fourth lens (5) is a biconvex lens with positive refractive power. 6. The optical imaging lens according to claim 1, characterized in that the fifth lens (6) is a plano-convex lens with positive refractive power, and has a first surface convex to the object side and a second surface that is flat . 7. The optical imaging lens according to claim 1, characterized in that the sixth lens (7) is a biconcave lens with negative refractive power.

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