阅读说明：本技术 一种滤光片阵列式的多光谱成像系统 (Multispectral imaging system of light filter array ) 是由 罗晓霞 孙金霞 王健 于 2021-08-19 设计创作，主要内容包括：本发明涉及一种滤光片阵列式的多光谱成像系统,该系统包括成像镜头、滤光片阵列和相机；所述的滤光片阵列位于成像镜头与相机之间并与相机靶面紧贴；所述的成像镜头包括沿光线入射方向依次设置的具有负屈光度的第一、第二透镜,具有正屈光度的第三、第四透镜,具有负屈光度的第五透镜,具有正屈光度的第六透镜,具有负屈光度的第七透镜和具有正屈光度的第八、第九透镜；各透镜表面均为球面。本发明消除了大视场应用下,边缘光线大入射角对滤光片的影响,且使光谱混叠区域最小化,具有大视场、结构简单、覆盖波段范围宽,像质好等特点。(The invention relates to a multispectral imaging system of optical filter array type, the system includes imaging lens, optical filter array and camera; the optical filter array is positioned between the imaging lens and the camera and is tightly attached to the target surface of the camera; the imaging lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens, wherein the first lens and the second lens are sequentially arranged along the light incidence direction and have negative diopter; the lens surfaces are spherical. The invention eliminates the influence of the edge light large incidence angle on the optical filter under the application of a large field of view, minimizes the spectrum aliasing area, and has the characteristics of large field of view, simple structure, wide coverage wave band range, good image quality and the like.)

1. A multispectral imaging system of the array of optical filters, the system includes imaging lens, optical filter array and camera; the optical filter array is positioned between the imaging lens and the camera and is tightly attached to the target surface of the camera; the imaging lens is characterized by comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens, wherein the first lens and the second lens are sequentially arranged along the light incidence direction and have negative diopter; the lens surfaces are spherical.

2. The system of claim 1, wherein the first lens element is a meniscus lens element, the object-side surface is a convex surface, the image-side surface is a concave surface, the second lens element is a biconcave lens element, the third lens element is a meniscus lens element, the object-side surface is a concave surface, the image-side surface is a convex surface, the fourth lens element is a biconvex lens element, the fifth lens element is a meniscus lens element, the object-side surface is a convex surface, the image-side surface is a concave surface, the sixth lens element is a biconvex lens element, the seventh lens element is a biconcave lens element, the eighth lens element is a biconvex lens element, the ninth lens element is a meniscus lens element, the object-side surface is a convex surface, and the image-side surface is a concave surface.

3. The optical filter array multispectral imaging system according to claim 1 or 2, wherein the focal length of the first lens is from-311 mm to-189 mm, the focal length of the second lens is from-30 mm to-24 mm, the focal length of the third lens is from 156mm to 310mm, the focal length of the fourth lens is from 72mm to 90mm, the focal length of the fifth lens is from-42 mm to-33 mm, the focal length of the sixth lens is from 11mm to 15mm, the focal length of the seventh lens is from-12 mm to-9 mm, the focal length of the eighth lens is from 18mm to 21mm, and the focal length of the ninth lens is from 47mm to 65 mm.

4. The system according to claim 3, wherein the first lens has a thickness of 8.1mm to 8.4mm, the second lens has a thickness of 1.7mm to 2.0mm, the third lens has a thickness of 6.1mm to 6.3mm, the fourth lens has a thickness of 3mm to 6.1mm, the fifth lens has a thickness of 1.7mm to 2.0mm, the sixth lens has a thickness of 4.9mm to 8.2mm, the seventh lens has a thickness of 1.4mm to 2.8mm, the eighth lens has a thickness of 3.8mm to 5.0mm, and the ninth lens has a thickness of 6.1mm to 6.4 mm.

5. The system according to claim 3, wherein the first lens and the second lens are spaced apart by 7-12mm, the air space between the second lens and the third lens is 5-6mm, the air space between the third lens and the fourth lens is 0.2-1.5mm, the air space between the fourth lens and the fifth lens is 26-37mm, the air space between the fifth lens and the sixth lens is 1.9-2.4mm, the air space between the sixth lens and the seventh lens is 0.6-0.8mm, the air space between the seventh lens and the eighth lens is 0.3-1.0mm, the air space between the eighth lens and the ninth lens is 26-30mm, and the air space between the ninth lens and the image plane is 8.9-12 mm.

6. The filter array-based multispectral imaging system as recited in claim 1, wherein the stop is disposed between the fourth lens and the fifth lens or between the fifth lens and the sixth lens.

7. The filter-arrayed multispectral imaging system of claim 1, wherein the filter array comprises 4-8 spectral bands.

8. The system according to claim 1, wherein each lens of the imaging lens is made of fused silica or calcium fluoride with high UV transmittance.

9. The system of claim 1, wherein the filter array is fabricated by using different substrates to be assembled together or by dividing different regions of the same substrate into separate coatings.

10. The filter array-based multispectral imaging system according to claim 3, wherein the transmittance of each spectral band of the filter array is greater than 90%.

Technical Field

The invention belongs to the technical field of remote sensing imaging, and particularly relates to a filter array type multispectral imaging system which can be used for carrying out multispectral imaging and information acquisition on a target in an airborne, vehicle-mounted or convenient mode.

Background

The spectral imaging technology combines spatial information and spectral information, and the information quantity of remote sensing data is greatly increased. Multispectral is less than hyperspectral spectral bands, real-time performance is higher in later-stage data processing, and by selecting spectral bands with more prominent target characteristics, the target performance is stronger, and the method is suitable for ground feature classification, disaster assessment, disclosure camouflage and the like. The light splitting technology of the system directly influences the performance, the complexity of the structure, the weight, the volume and the like of the whole system. The light filter array divides the target surface of the detector into a plurality of areas by light splitting, each area corresponds to information of different spectral bands, and the detector is simple in structure and small in size.

The multispectral imaging system comprises an imaging lens, a filter array and a camera, wherein the filter array is arranged between the lens and the camera. The optical filter is sensitive to the incident angle of light, the central wavelength can shift to the short wave direction along with the increase of the incident angle, and the imaging lens is an image space telecentric lens considering the incident angle effect of the optical filter. In the field of camouflage identification, ultraviolet bands have obvious target characteristics for snow, explosives and the like, while most of the existing imaging lenses mainly use visible light bands, and the existing imaging lenses are wide-spectrum remote sensing lenses containing ultraviolet bands. In CN202010421832.6, "an ultra-wide spectrum band imaging lens", although the band range is wide, the field angle is small, and the lens is not a telecentric structure, and when a large incident angle passes through the optical filter, a large band shift is generated, which has a certain limitation in practical use.

Disclosure of Invention

The invention aims to provide a multispectral imaging system of an optical filter array type, which solves the problem of large incident angle of light rays at the lower edge of a large view field.

In order to solve the technical problem, the multispectral imaging system with the optical filter array comprises an imaging lens, an optical filter array and a camera; the optical filter array is positioned between the imaging lens and the camera and is tightly attached to the target surface of the camera; the imaging lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens, wherein the first lens and the second lens are sequentially arranged along the light incidence direction and have negative diopter; the lens surfaces are spherical.

The first lens element is a meniscus lens, the object side surface is a convex surface, the image side surface is a concave surface, the second lens element is a biconcave lens element, the third lens element is a meniscus lens, the object side surface is a concave surface, the image side surface is a convex surface, the fourth lens element is a biconvex lens element, the fifth lens element is a meniscus lens element, the object side surface is a convex surface, the image side surface is a concave surface, the sixth lens element is a biconvex lens element, the seventh lens element is a biconcave lens element, the eighth lens element is a biconvex lens element, the ninth lens element is a meniscus lens element, the object side surface is a convex surface, and the image side surface is a concave surface.

The focal length of the first lens is-311 mm to-189 mm, the focal length of the second lens is-30 mm to-24 mm, the focal length of the third lens is 156mm to 310mm, the focal length of the fourth lens is 72mm to 90mm, the focal length of the fifth lens is-42 mm to-33 mm, the focal length of the sixth lens is 11mm to 15mm, the focal length of the seventh lens is-12 mm to-9 mm, the focal length of the eighth lens is 18mm to 21mm, and the focal length of the ninth lens is 47mm to 65 mm.

The thickness of the first lens is 8.1 mm-8.4 mm, the thickness of the second lens is 1.7 mm-2.0 mm, the thickness of the third lens is 6.1 mm-6.3 mm, the thickness of the fourth lens is 3 mm-6.1 mm, the thickness of the fifth lens is 1.7 mm-2.0 mm, the thickness of the sixth lens is 4.9 mm-8.2 mm, the thickness of the seventh lens is 1.4 mm-2.8 mm, the thickness of the eighth lens is 3.8 mm-5.0 mm, and the thickness of the ninth lens is 6.1 mm-6.4 mm.

The air space between the first lens and the second lens is 7-12mm, the air space between the second lens and the third lens is 5-6mm, the air space between the third lens and the fourth lens is 0.2-1.5mm, the air space between the fourth lens and the fifth lens is 26-37mm, the air space between the fifth lens and the sixth lens is 1.9-2.4mm, the air space between the sixth lens and the seventh lens is 0.6-0.8mm, the air space between the seventh lens and the eighth lens is 0.3-1.0mm, the air space between the eighth lens and the ninth lens is 26-30mm, and the air space between the ninth lens and the image plane is 8.9-12 mm;

the diaphragm is arranged between the fourth lens and the fifth lens or between the fifth lens and the sixth lens.

The filter array comprises 4-8 spectral bands.

Each lens of the imaging lens adopts fused quartz or calcium fluoride with high ultraviolet transmittance.

The optical filter array is formed by splicing different substrates or dividing different areas on the same substrate for independent coating.

The transmittance of each spectral band of the optical filter array is greater than 90%.

The imaging lens is of an image space telecentric structure, the influence of a larger incident angle at the edge on the optical filter is avoided, the spectrum aliasing area of adjacent wave bands is reduced, the imaging wave bands can cover different spectrum wave band ranges, and the maximum utilization of multispectral image information is realized.

The invention has the advantages of

The optical filter array type multispectral imaging system has the beneficial effects that the lens is of an image space telecentric structure, the influence of edge light large incidence angles on the optical filter under the application of a large field of view is eliminated, the spectrum aliasing area is minimized, the multispectral imaging system can cover an ultraviolet band, the band range is 300-680nm, the focal length of the lens is 20mm, and the diagonal field angle is 40 degrees. The wide-field wide-coverage-band high-resolution imaging device has the characteristics of large field of view, simple structure, wide coverage band range, good image quality and the like.

Drawings

FIG. 1 is a schematic diagram of a filter array multispectral imaging system according to the present invention;

FIG. 2 is a schematic structural diagram of an imaging lens;

FIG. 3(a), FIG. 3(B), FIG. 3(c), and FIG. 3(d) are MTF transfer function curves of the imaging lens of example 1 in the ultraviolet band (300-.

FIG. 4(a), FIG. 4(B), FIG. 4(c), and FIG. 4(d) are MTF transfer function curves of the comparative example imaging lens in the UV band (300-.

In the figure: 1. an imaging lens; 11. a first lens; 12. a second lens; 13. a third lens; 14. a fourth lens; 15. a fifth lens; 16. a sixth lens; 17. a seventh lens; 18. an eighth lens; 19. a ninth lens; 2. an optical filter array; 3. a camera; 4. an image plane; 5 diaphragm.

Detailed Description

The present invention will be described in further detail with reference to the following drawings and examples, it being understood that the specific embodiments described herein are illustrative of the invention only and are not limiting. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other suitable relationship. The specific meanings of the above terms in the present invention can be specifically understood in specific cases by those of ordinary skill in the art.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," or "beneath" a second feature includes the first feature being directly under or obliquely below the second feature, or simply means that the first feature is at a lesser elevation than the second feature.

In the description of the present embodiment, the terms "upper", "lower", "left", "right", and the like are used in the orientation or positional relationship shown in the drawings only for convenience of description and simplicity of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used only for descriptive purposes and are not intended to have a special meaning.

As shown in fig. 1, the optical filter array multispectral imaging system of the present invention mainly comprises an imaging lens 1, an optical filter array 2 and a camera 3. The optical filter array 2 is arranged between the imaging lens and the camera and is tightly attached to the target surface of the camera; the optical filter array 2 comprises optical filter strips with a plurality of spectral bands, and a target image acquired by the imaging lens passes through the optical filter strips with the plurality of spectral bands, is endowed with different spectral information, and is finally imaged on the camera. The arrangement direction of the optical filter strips of the optical filter array with a plurality of spectral bands is perpendicular to the flight direction of the unmanned aerial vehicle, and complete multispectral data can be obtained through forward motion of the flight platform. The filter array 2 can obtain information of a plurality of spectral bands of the target image during one exposure.

The optical filter array 2 comprises 4 spectral band optical filter strips of ultraviolet light and R, G, B, and the optical filter strips are equal in width and distributed at equal intervals. The filter array 2 may be made by splicing together a plurality of individual filter strips or by dividing a plurality of regions of the individual coatings directly on a substrate material, such as a quartz substrate.

The imaging lens is designed as an image-space telecentric lens, so that the influence of a large incident angle of marginal rays on the narrow-band filter can be eliminated, and meanwhile, the aliasing area of adjacent spectral bands is minimized. Preferably, the imaging lens is designed to be a multiple structure according to specific waveband information of the optical filter array 2.

As shown in fig. 2, the imaging lens is composed of 9 lenses, and includes a first lens and a second lens with negative diopter, a third lens and a fourth lens with positive diopter, a fifth lens with negative diopter, a sixth lens with positive diopter, a seventh lens with negative diopter, and an eighth lens and a ninth lens with positive diopter, which are sequentially arranged along the light incident direction. The diaphragm is arranged between the fourth lens and the fifth lens. The first lens element is a meniscus lens, the object side surface is a convex surface, the image side surface is a concave surface, the second lens element is a biconcave lens element, the third lens element is a meniscus lens, the object side surface is a concave surface, the image side surface is a convex surface, the fourth lens element is a biconvex lens element, the fifth lens element is a meniscus lens element, the object side surface is a convex surface, the image side surface is a concave surface, the sixth lens element is a biconvex lens element, the seventh lens element is a biconcave lens element, the eighth lens element is a biconvex lens element, the ninth lens element is a meniscus lens element, the object side surface is a convex surface, and the image side surface is a concave surface.

In this embodiment, a system of different spectral bands is constructed using a plurality of structures in the optical design software Zemax.

Examples 1-4 the basic parameters and materials for each lens are shown in tables 1-4, respectively, where f is the focal length of the lens, t is the lens thickness, and d is the distance between the rear surface of the lens and the front surface of the next lens.

TABLE 1

Lens serial number	f(mm)	t/d(mm)	Material
				1	-189.07	8.243/9.697	Fused quartz
2	-29.98	1.925/5.241	Calcium fluoride
				3	167.59	6.113/0.262	Fused quartz
4	89.06	6.012/36.985	Fused quartz
				5	-41	1.968/2.201	Fused quartz
6	14.75	8.19/0.798	Calcium fluoride
				7	-11.35	2.756/0.314	Fused quartz
8	19.39	4.923/29.098	Calcium fluoride
				9	64.31	6.335/8.956	Calcium fluoride

In this embodiment 1, the effective focal length of the imaging lens is 20mm, the full field angle is 40 °, the wavelength range is 300-.

Fig. 3(a) - (d) are modulation transfer function curves MTF of the imaging lens of embodiment 1 at half field angles of 0 °, 5 °, 11 °, 17 °, and 20 ° in ultraviolet/R/G/B, 4 different bands, respectively. In the graph, the MTFs of the B band (420-.

TABLE 2

Lens serial number	f(mm)	t/d(mm)	Material
				1	-265.33	8.239/11.892	Fused quartz
2	-28.3	1.887/5.683	Calcium fluoride
				3	251.87	6.161/0.25	Calcium fluoride
4	81.10	4.16/36.267	Fused quartz
				5	-41.17	1.918/2.302	Fused quartz
6	14.20	7.976/0.658	Calcium fluoride
				7	-11.29	2.187/0.472	Fused quartz
8	20.28	4.575/28.98	Calcium fluoride
				9	60.37	6.239/10.196	Calcium fluoride

TABLE 3

Lens serial number	f(mm)	t/d(mm)	Material
				1	-236.89	8.312/7.931	Fused quartz
2	-26.97	1.832/5.349	Calcium fluoride
				3	309.61	6.171/1.429	Calcium fluoride
4	76.08	4.223/30.649	Fused quartz
				5	-39.54	1.93/1.916	Fused quartz
6	13.66	8.031/0.64	Calcium fluoride
				7	-10.87	1.769/0.469	Fused quartz
8	19.71	4.397/28.087	Calcium fluoride
				9	55.67	6.183/10.712	Calcium fluoride

TABLE 4

The imaging effects of the above examples 2-4 are similar to those of example 1, and all have better imaging quality.

The inventors have tried to place the stop between the 5 th and 6 th lenses and by software optimization also better imaging quality can be achieved. Similar to the results of example 1, the MTFs of the B band (630-680nm) and the R band (630-680nm) were above 0.3 at 110lp/mm, and the MTFs of the modulation transfer function values of the other fields were greater than 0.4 at 110 lp/mm.

The inventor tries to reduce the number of the lenses to 8, the modulation transfer function MTF of different wave bands at a large field angle is difficult to improve at a high frequency part, and fig. 4(a) - (d) show modulation transfer function MTF curves of the imaging lens at ultraviolet R, G, B and 4 different wave bands, and the visible image quality is poor.

In the optimization of the initial structure, the inventor designs the fifth lens as a biconcave structure, and after the system is optimized for a long time, even in a low-frequency part, the system cannot obtain good imaging quality, and the final result is not ideal. The inventor tries to design the ninth lens as a double-convex lens, and the system optimizes the fourth lens as a meniscus lens under a global optimization algorithm, but the effect is poor in the high-frequency part of the R wave band (630-. The present invention is not limited to the above embodiments, and the position of the diaphragm, the material of the lens, etc. can be changed according to the design parameters of the lens, and the functional effects produced by the changes according to the technical scheme of the present invention are within the protection scope of the present invention.