CN112285888A

CN112285888A - Big light ring FA camera lens

Info

Publication number: CN112285888A
Application number: CN202011215783.7A
Authority: CN
Inventors: 刘中华
Original assignee: Guanghu Optoelectronics Technology Tianjin Co ltd
Current assignee: Guanghu Optoelectronics Technology Tianjin Co ltd
Priority date: 2020-11-04
Filing date: 2020-11-04
Publication date: 2021-01-29
Anticipated expiration: 2040-11-04
Also published as: CN112285888B

Abstract

The invention discloses a large-aperture FA lens, which belongs to the technical field of optical design and sequentially comprises a first lens, a second lens, a third lens, an aperture diaphragm, a fourth lens, a fifth lens, a sixth lens and a seventh lens along a light path; wherein: the first lens is a plano-convex lens, the second lens is a convex-concave lens, the third lens is a convex-concave lens, the fourth lens is a biconcave lens, the fifth lens is a biconvex lens, the sixth lens is a plano-convex lens, and the seventh lens is a plano-convex lens; an aperture diaphragm is arranged between the third lens and the fourth lens, and the fourth lens and the fifth lens are mutually glued; the focuses of the fourth lens and the fifth lens are on the same straight line. By adopting the technical scheme, the aperture is increased, the performance of light flux is improved, and meanwhile, the contrast and the resolution are improved as much as possible through reasonable collocation of the multiple lenses, so that the imaging quality in a low-illumination environment is improved.

Description

Big light ring FA camera lens

Technical Field

The invention belongs to the technical field of optical design, and particularly relates to a large-aperture FA lens.

Background

The large-aperture FA lens is more and more widely applied to machine vision and scientific research, and along with the development of high-sensitivity low cameras, the requirement on the performance of the large-aperture FA lens is higher and higher. For a large-aperture FA lens, satisfying clear imaging in a low-illuminance environment, it is necessary to perform the function of a low camera more greatly by reducing the F value (increasing the light flux) of the lens itself. The fixed-focus lens is mainly applied to the condition of small visual field, such as the surface detection, the shape detection, the defect detection and the like of a production line and a fixed object in the industrial manufacturing industry, and has wide application range and large application amount. The large aperture is more suitable for low-illumination environment and high-speed camera shooting. The large-aperture lens increases the light flux under the low illumination condition, plays the function of a low camera more greatly and captures a clearer image. The large-aperture FA lens can finish fast and multiple sampling of a high-speed target in a short time in application with a high-speed camera, and the change process of the recorded target is clear when the high-speed target is projected at a normal speed.

Most of the F values of the existing FA lens apertures are more than 2.0, the contrast and the resolution are relatively low, and the requirements of the market on measurement in a low-illumination environment and high-speed assembly line operation in industrial manufacturing are difficult to meet.

Disclosure of Invention

The invention provides a large-aperture FA lens for solving the technical problems in the prior art, which improves the performance of light flux by increasing the aperture and improves the contrast and resolution ratio as much as possible so as to improve the imaging quality in a low-illumination environment.

The invention aims to provide a large-aperture FA lens which sequentially comprises seven lenses along an optical path; wherein:

the first lens (1) is a plano-convex lens, the second lens (2) is a convex-concave lens, the third lens (3) is a convex-concave lens, the fourth lens (4) is a biconcave lens, the fifth lens (5) is a biconvex lens, the sixth lens (6) is a plano-convex lens, and the seventh lens (7) is a plano-convex lens; an aperture diaphragm is arranged between the third lens (3) and the fourth lens (4), and the fourth lens (4) and the fifth lens (5) are mutually glued; wherein:

the curvature radius of the light incident surface of the first lens (1) is 45.317 +/-5% mm, and the curvature radius of the light emergent surface is infinite; the center thickness is 5.528 +/-5 percent mm; the refractive index and Abbe number are 1.80/45.5 +/-5 percent;

the curvature radius of the light incident surface of the second lens (2) is 22.325 +/-5% mm, and the curvature radius of the light emergent surface is 49.315 +/-5% mm; the center thickness is 5.672 +/-5 percent mm; the refractive index and Abbe number are 1.80/45.5 +/-5 percent;

the curvature radius of the light incident surface of the third lens (3) is 189.485 +/-5% mm, and the curvature radius of the light emergent surface is 13.641 +/-5% mm; the center thickness is 4.715 +/-5 percent mm; the refractive index and Abbe number are 1.71/29.5 +/-5 percent;

the curvature radius of the light incident surface of the fourth lens (4) is 22.227 +/-5% mm, and the curvature radius of the light emergent surface is 50.437 +/-5% mm; the center thickness is 2.900 +/-5 percent mm; the refractive index and Abbe number are 1.69/31.2 +/-5 percent;

the curvature radius of the light incident surface of the fifth lens (5) is 50.437 +/-5% mm, and the curvature radius of the light emergent surface is-20.500 +/-5% mm; the center thickness is 5.005 +/-5 percent mm; the refractive index and Abbe number are 1.71/53.58 +/-5 percent;

the curvature radius of the light incident surface of the sixth lens (6) is infinite, and the curvature radius of the light emergent surface is-14.647 +/-5 percent mm; the center thickness is 5.557 +/-5 percent mm; the refractive index and Abbe number are 1.71/53.58 +/-5 percent;

the curvature radius of the light incident surface of the seventh lens (7) is 44.634 +/-5% mm, and the curvature radius of the light emergent surface is infinite; the center thickness is 6.896 +/-5 percent mm; the refractive index and Abbe number are 1.71/53.58 +/-5 percent;

the distance of the air space between the first lens (1) and the second lens (2) on the optical axis is 2.700 +/-5 percent mm; the distance of the air space between the second lens (2) and the third lens (3) on the optical axis is 1.500 +/-5 percent mm; the distance between the third lens (3) and the air space of the aperture diaphragm on the optical axis is 5.926 +/-5 percent mm; the distance of the air space between the aperture diaphragm and the fourth lens (4) on the optical axis is 5.115 +/-5% mm; the distance of the air space between the fifth lens (5) and the sixth lens (6) on the optical axis is 0.186 +/-5 percent mm; the distance between the six lenses (6) and the seventh lens (7) on the optical axis is 0.548 +/-5 percent mm.

Preferably, the focuses of the fourth lens (4) and the fifth lens (5) are on the same straight line.

Preferably, the fourth lens (4) and the fifth lens (5) are made of different glass materials.

Preferably, the middle point between the fourth lens (4) and the fifth lens (5) is coated with photosensitive glue.

Preferably, the fourth lens (4) and the fifth lens (5) are in a coaxial relationship.

The invention has the advantages and positive effects that:

the invention improves the performance of light flux by increasing the aperture, and simultaneously improves the contrast and resolution as much as possible by reasonably matching the multiple lenses so as to improve the imaging quality in a low-illumination environment;

the two lenses of the double-cemented lens cementing group 1 are made of two different glass materials, and positive and negative spherical aberration and positive and negative chromatic aberration generated by the positive lens and the negative lens are mutually compensated, so that the spherical aberration and the chromatic aberration of the lenses are corrected; the last two lenses (the sixth lens and the seventh lens) are formed by splitting one lens, so that the degree of freedom of optimization variables is increased, and the resolution and the relative illumination of the lens are greatly improved.

Drawings

FIG. 1 is a light path diagram of a preferred embodiment of the present invention;

FIG. 2 is an optical speckle pattern of a preferred embodiment of the present invention;

FIG. 3 is a graph of the modulation function MTF of the preferred embodiment of the present invention;

FIG. 4 is a graph of relative illumination according to a preferred embodiment of the present invention;

FIG. 5 is a graph of field curvature and astigmatism for a preferred embodiment of the present invention;

Detailed Description

In order to further understand the contents, features and effects of the present invention, the following embodiments are illustrated and described in detail with reference to the accompanying drawings:

the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art without creative efforts based on the technical solutions of the present invention belong to the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

Please refer to fig. 1.

A big diaphragm FA camera lens includes a first lens 1, a second lens 2, a third lens 3, an aperture diaphragm, a fourth lens 4, a fifth lens 5, a sixth lens 6 and a seventh lens 7 in sequence along an optical path: the first lens is a plano-convex lens, the second lens is a convex-concave lens, the third lens is a convex-concave lens, and an aperture diaphragm is arranged in the middle of the third lens; the fourth lens is a biconcave lens, the fifth lens is a biconvex lens, the fourth lens is a cemented combination A, the sixth lens is a plano-convex lens, and the seventh lens is a plano-convex lens.

The bonding group A is formed by combining two lenses, and the focuses of the two lenses are on the same straight line.

The middle point between the two lenses of the bonding group A is coated with photosensitive adhesive.

The two convex-concave lenses of the cemented group A are coaxial.

Further explanation is made for each lens constituting the optical path:

curvature radius of each lens forming the optical path of the large-aperture lens: the curvature radius of the first surface of the A-1 planoconvex lens is 45.317 +/-5%, and the curvature radius of the second surface is infinite; the curvature radius of the first surface of the A-2 convex-concave lens is 22.325 +/-5%, and the curvature radius of the second surface is 49.315 +/-5%; the curvature radius of the first surface of the A-3 convex-concave lens is 189.485 +/-5%, and the curvature radius of the second surface is 13.641 +/-5%; the curvature radius of the first surface of the B-4 biconcave lens is-22.227 +/-5%, and the curvature radius of the second surface is 50.437 +/-5%; the curvature radius of the first surface of the B-5 biconvex lens is 50.437 +/-5%, and the curvature radius of the second surface is-20.500 +/-5%; the curvature radius of the first surface of the B-6 planoconvex lens is infinite, and the curvature radius of the second surface is-14.647 +/-5 percent; the curvature radius of the first surface of the B-7 planoconvex lens is 44.634 +/-5%, and the curvature radius of the second surface is infinite. All radii of curvature are in millimeters.

Center thickness of each lens constituting the lens of the large aperture: the central thickness of the A-1 plano-convex lens is 5.528 +/-5%; the center thickness of the A-2 convex-concave lens is 5.672 +/-5%; the center thickness of the A-3 convex-concave lens is 4.715 +/-5%; the center thickness of the B-4 biconcave lens is 2.900 +/-5%; the center thickness of the B-5 biconvex lens is 5.005 +/-5 percent; the central thickness of the B-6 plano-convex lens is 5.557 +/-5%; the center thickness of the B-7 convex-concave lens is 6.896 + -5%. The center thickness of all lenses is in millimeters.

The object and lens forming the lens light path of the large aperture, the lens and lens, the air space distance between the lens and the aperture diaphragm and between the lens and the image plane: the distance between the object and the air space of the A-1 plano-convex lens on the optical axis is 300 +/-5%; the distance between the air spaces of the convex-concave lens A-1 and the convex-concave lens A-2 on the optical axis is 2.700 +/-5%; the distance between the air spaces of the convex-concave lens A-2 and the convex-concave lens A-3 on the optical axis is 1.500 +/-5%; the distance between the convex-concave lens A-3 and the air space of the aperture diaphragm C on the optical axis is 5.926 +/-5%; the distance between the aperture diaphragm C and the air space of the B-4 biconcave lens on the optical axis is 5.115 +/-5 percent; the B-4 biconcave lens and the B-5 biconvex lens are in double gluing without air space; the distance between the air spaces of the B-5 biconvex lens and the B-6 convex-concave lens on the optical axis is 0.186 +/-5 percent; the distance on the optical axis between the air space of the B-6 convex-concave lens and the air space of the B-7 convex-concave lens is 0.548 +/-5%. All air spaces are in the unit of millimeters on the optical axis.

Refractive index and abbe number of each lens constituting a lens optical path of a large aperture: the refractive index and Abbe number of the A-1 planoconvex lens are 1.80/45.5 +/-5%; the refractive index and Abbe number of the A-2 convex-concave lens are 1.80/45.5 +/-5 percent; the refractive index and Abbe number of the A-3 convex-concave lens are 1.71/29.5 +/-5 percent; the refractive index and Abbe number of the B-4 biconcave lens are 1.69/31.2 +/-5 percent; the refractive index and Abbe number of the B-5 biconvex lens are 1.71/53.58 +/-5 percent; the refractive index and Abbe number of the B-6 planoconvex lens are 1.71/53.58 +/-5 percent; the refractive index and Abbe number of the B-7 plano-convex lens are 1.71/53.58 +/-5%.

In the preferred embodiment described above: the fourth lens 4 and the fifth lens 5 are made of different glass materials. The closest working distance of the large-aperture FA lens is 300mm, the diameter of the entrance pupil is 35.71mm, the working wave band is 486-.

Referring to fig. 2, the optical speckle pattern shows: wherein, the OBJ is the object space view field, the IMA is the image space view field, and the unit is millimeter. RMS RADIUS represents the root mean square RADIUS of the diffuse spot, GEO RADIUS represents the Airy spot RADIUS, both in microns. As shown, the central field of view has an Airy spot radius of 3.220 μm and a root mean square radius of 2.309 μm; 1/2 field of view with radius of Airy spot 5.267 μm and root mean square radius of 2.412 μm; 2/3 field of view has 6.133 μm of Airy spot radius and 2.516 μm of root mean square radius; the radius of the Airy spots of the edge field is 7.378 mu m, the radius of the root mean square is 2.651 mu m, the design requirement standard is met, the energy concentration and aberration correction of the on-axis and off-axis points are very good, and the ideal resolution is achieved.

Referring to fig. 3, the MTF graph shows that: the abscissa is spatial resolution, in line pairs/mm, the ordinate is contrast, the range is 0-1, and TS represents the meridional and sagittal components of MTF in different fields of view. As shown, the MTF values for each field are all greater than 0.6 for contrast at 70 line pairs/mm, and the overall MTF curve is relatively compact, as can be seen in the lens performs well in terms of contrast and resolution.

Referring to fig. 4, it can be seen from the relative illuminance diagram that: the abscissa is the angle of the Y field of view, from the center market to the edge market, the ordinate is the relative illuminance, the value range is 0-1, and the lower wavelet represents the center Wavelength of the light path passing through the lens to be 0.585 μm. As shown, within 0.5 field of view, the relative illumination nearly coincides with 1, indicating that there is little loss of light from objects in the center field of view; in the marginal field, the relative illumination is still kept above 0.97, and it can be seen that the lens has a good surface line on the relative illumination.

Referring to fig. 5, from the field curvature and astigmatism diagrams: the ordinate is the field of view and the abscissa is in microns.

The distortion diagram shows that: the ordinate is the field of view and the abscissa is the distortion value. As can be seen, the distortion value of the lens in the full field of view is less than 0.02%, and the lens has an extremely low distortion value.

In summary, the following steps: the FA lens designed by the invention has high contrast and resolution and extremely low distortion rate.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications, equivalent changes and modifications made to the above embodiment according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A large-aperture FA lens is characterized by comprising seven lenses along a light path in sequence; wherein:

2. The large aperture FA lens according to claim 1, wherein the focal points of the fourth lens (4) and the fifth lens (5) are on the same straight line.

3. The large aperture FA lens according to claim 1, wherein the fourth lens (4) and the fifth lens (5) are made of different glass materials.

4. The large aperture FA lens according to claim 1, wherein a middle point between the fourth lens (4) and the fifth lens (5) is coated with a photosensitive glue.

5. The large aperture FA lens according to claim 1, wherein the fourth lens (4) and the fifth lens (5) are in a coaxial relationship.