Three-channel panoramic imaging system based on dichroic film

Abstract

The invention discloses a three-channel panoramic imaging system based on a dichroic film. The three-channel panoramic imaging system comprises a panoramic head unit PHU, a subsequent lens group RLG and a sensor D which are sequentially arranged from an object space to an image space, the PHU is in the shape of a negative meniscus lens, the front surface of the PHU is plated with an annular reflecting film, the rear surface of the PHU is plated with an annular dichroic film, the PHU is used for collecting dual-band and large-field-of-view target light, and compression of a panoramic channel light incident angle and multi-channel fusion are achieved through the dichroic film and the reflecting film; the dichroic film can transmit near-infrared light rays with the wavelength of 800 nm to 900 nm and reflect visible light rays with the wavelength of 486 nm to 656 nm; the RLG is used for correcting aberration generated by large-view-field incident light in the PHU and transmitting the light collected by the PHU to the sensor D. Based on the dichroic film, the design of the three-channel blind-area-free panoramic imaging system is realized, and the three-channel blind-area-free panoramic imaging system has the characteristics of large field of view, low distortion, double wavebands and large relative aperture, so that high-quality and high-definition imaging of the three channels can be realized.

Description

Technical Field

[0001] The invention relates to the field of panoramic optical imaging, and in particular to a three-channel panoramic imaging system based on a dichroic film. Background Art

[0002] With the development of artificial intelligence and information processing technology, application fields such as machine vision and pipeline monitoring have put forward higher and higher requirements on the imaging field of view of optical systems. Among many wide-angle optical imaging systems, panoramic imaging systems integrate refractive and reflective surfaces in the panoramic head unit, thus having the advantages of low distortion, ultra-large field of view, and high imaging quality.

[0003] Usually, the circular reflective film on the front surface of the panoramic head unit will block the light entering its central area, causing a circular blind area in the center of the image plane, which greatly reduces the sensor utilization and the field of view detection range of the system. At the same time, the general single-sensor panoramic imaging system can only image a single-band light and cannot obtain multi-band information, which is not conducive to the development of the panoramic imaging system towards multi-dimensional information detection.

[0004] The patent with publication number CN116801107A discloses a large-field-of-view panoramic imaging system based on a multiplexed reflective surface. It introduces a backward channel without adding an additional lens group, thereby reducing the size of the central blind area of ​​the image plane. However, it still cannot completely eliminate the central blind area, and introduces a complex optical surface shape, which increases the difficulty of component processing.

[0005] The patent with publication number CN116974046A discloses a panoramic annular stereoscopic imaging lens with no blind spots, which eliminates the central blind spot of the panoramic imaging system image plane, but introduces a front lens group, which increases the structural complexity and assembly difficulty of the system, and can only obtain visible light information, and does not have multi-band detection capabilities. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a three-channel panoramic imaging system based on a dichroic film. Without adding additional lens groups and complex optical surface shapes, three-channel optical path imaging is achieved based on the dichroic film, eliminating the central blind area of ​​the image plane of the panoramic imaging system and increasing the multi-band information detection capability of the optical system.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A three-channel panoramic imaging system based on a dichroic film includes a panoramic head unit PHU, a subsequent lens group RLG and a sensor D arranged in sequence from the object side to the image side;

[0009] The panoramic head unit PHU is in the shape of a negative meniscus lens. The front surface of the panoramic head unit PHU close to the object side is coated with an annular reflective film, and the rear surface close to the image side is coated with an annular dichroic film. The panoramic head unit PHU is used to collect target light with a dual-band and a large field of view, and the incident angle compression of the panoramic channel light and the fusion of multiple channels are achieved through the dichroic film and the reflective film.

[0010] The dichroic film can transmit near-infrared light of 800nm-900nm and reflect visible light of 486nm-656nm; the coating position of the dichroic film must ensure that it can completely transmit all the light of the side channel, completely reflect all the light of the panoramic channel, and will not block the outgoing light of the three channels; the coating position of the reflective film must ensure that it can completely reflect all the light of the panoramic channel and will not block the light of the side channel and the front channel;

[0011] The panoramic channel can image visible light in an ultra-large field of view of 360°×(56°~96°), the side channel can image near-infrared light in a large field of view of 360°×(18°~56°), and the front channel can image visible light-near-infrared light in a small field of view of 360°×(0°~12°);

[0012] The subsequent lens group RLG is used to correct the aberration of the large-field incident light generated in the panoramic head unit PHU, and transmit the light collected by the panoramic head unit PHU to the sensor D; the sensor D is used to sense and image the three-channel light of the panoramic imaging system to obtain imaging spots in three areas.

[0013] Further, the subsequent lens group RLG includes a meniscus lens RL1, a doublet lens RL2, a meniscus lens RL3, a biconvex lens RL4, an aperture S, a doublet lens RL5 and a biconvex lens RL6, which are arranged in sequence from the object side to the image side;

[0014] Among them, the focal length of the meniscus lens RL1 is negative, the focal length of the doublet lens RL2 is negative, the focal length of the meniscus lens RL3 is negative, the focal length of the biconvex lens RL4 is positive, the focal length of the doublet lens RL5 is positive, and the focal length of the biconvex lens RL6 is positive.

[0015] Furthermore, the working focal length f of the panoramic channel is p , the working focal length f of the side channel s and the working focal length f of the front channel f Satisfies the following relationship: s >5f p >0,f f >4f p >0.

[0016] Furthermore, the F number F of the panoramic channel p , F number of the side channel s and the F number of the front channel F f They satisfy the following relations: 2 <F p <2.5, 2 <F s <2.5, 2 <F f <2.5.

[0017] Furthermore, the diameter D of the panoramic head unit PHU is PHU and the total length L of the three-channel panoramic imaging system satisfy the following relationship: PHU <0.85L.

[0018] Furthermore, the maximum f-θ distortion δ of the panoramic channel is p , the maximum f-θ distortion of the side channel δ s and the maximum f-θ distortion δ of the front channel f They satisfy the following relations: p <8%, δ s <7%, δ f <0.1%.

[0019] Furthermore, the circular imaging spot of the front channel on the sensor D, the annular imaging spot of the panoramic channel on the sensor D, and the annular imaging spot of the side channel on the sensor D do not overlap with each other, and are arranged in sequence from the center to the edge, without any central blind spot.

[0020] Furthermore, the optical parameter optimizations of the panoramic channel, the side channel and the front channel constrain each other, and the light paths of the three channels pass through all the optical elements in the panoramic imaging system.

[0021] Furthermore, the panoramic head unit PHU is made of glass with a refractive index not less than 1.7.

[0022] Furthermore, the resolution of sensor D is 1920×1080 and the pixel size is 2.9 μm.

[0023] In general, the above technical solutions provided by the present invention can achieve the following beneficial effects:

[0024] (1) Without adding additional lens groups, the central blind area on the image plane of the panoramic imaging system is eliminated, the utilization rate of the sensor is improved, and the field of view detection range of the panoramic imaging system is expanded.

[0025] (2) The dual-band information perception of the panoramic imaging system is realized. The panoramic channel, side channel and front channel respectively image visible light, near-infrared light and visible-near-infrared light.

[0026] (3) Multi-channel optical path fusion is realized. Under the condition of mutual constraints among the three channels, low distortion, large relative aperture, high definition and high resolution imaging can be achieved, and the imaging spots of the three channels on the image plane do not overlap with each other.

[0027] (4) Only a single conventional CMOS detector is needed to complete panoramic optical imaging, without the need to use two detectors or a dual-color detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 4 is a system structure diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0029] Figure 2 Schematic diagram of the imaging area of ​​the three-channel panoramic imaging system based on the dichroic film on the sensor D according to an embodiment of the present invention.

[0030] Figure 3 This is a three-dimensional ray tracing diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0031] Figure 4 1 is a panoramic channel ray tracing diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0032] Figure 5 1 is a side channel ray tracing diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0033] Figure 6 This is a front channel ray tracing diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0034] Figure 7 This is a panoramic channel imaging point diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0035] Figure 8 This is a side channel imaging point diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0036] Fig. 9 This is a front channel imaging point diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0037] Fig.10 1 is a panoramic channel MTF curve diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0038] Fig.11 1 is a side channel MTF curve diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0039] Fig.12 1 is a front channel MTF curve diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0040] Fig.13 1 is a panoramic channel field curvature distortion diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0041] Fig.14 1 is a side channel field curvature distortion diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention.

[0042] Fig.15 This is a front channel field curvature distortion diagram of a three-channel panoramic imaging system based on a dichroic film according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The present invention is described in detail below according to the accompanying drawings and preferred embodiments, and the effect of the present invention will become clearer. The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but are not used to limit the present invention. In addition, the technical features involved in the embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0044] like Figure 1 As shown, the three-channel panoramic imaging system based on the dichroic film proposed in the present invention includes a panoramic head unit PHU, a subsequent lens group RLG and a sensor D arranged in sequence from the object side to the image side.

[0045] The panoramic head unit PHU is in the shape of a negative meniscus lens, with an annular reflective film on the front surface and an annular dichroic film on the rear surface. The dichroic film can transmit 800nm-900nm near-infrared light and reflect 486nm-656nm visible light. The panoramic head unit PHU is used to collect dual-band, large field of view target light, and realize the compression of the incident angle of the panoramic channel light and the fusion of multiple channels through the annular reflective film and the annular dichroic film.

[0046] In order to improve the compactness of the optical system, the diameter D of the panoramic head unit PHU PHU The total length L of the three-channel panoramic imaging system satisfies the following relationship: PHU <0.85L.

[0047] The coating position of the dichroic film must ensure that it can completely transmit all the light from the side channel, completely reflect all the light from the panoramic channel, and will not block the outgoing light from the three channels; the coating position of the reflective film must ensure that it can completely reflect all the light from the panoramic channel and will not block the light from the side channel and the front channel, so that the panoramic channel can image visible light in an ultra-large field of view of 360°×(56°~96°), the side channel can image near-infrared light in a large field of view of 360°×(18°~56°), and the front channel can image visible light-near-infrared light in a small field of view of 360°×(0°~12°).

[0048] In order to improve the ability of the panoramic head unit PHU to deflect light with a large field of view, the material of the panoramic head unit PHU should be glass with a refractive index of not less than 1.70.

[0049] like Figure 1 As shown, the subsequent lens group RLG is used to correct the aberration of the incident light with a large field of view in the panoramic head unit PHU, and transmit the light collected by the panoramic head unit PHU to the sensor D. The subsequent lens group RLG includes a meniscus lens RL1, a double cemented lens RL2, a meniscus lens RL3, a double convex lens RL4, an aperture S, a double cemented lens RL5 and a double convex lens RL6 arranged in sequence from the object side to the image side. Among them, the focal length of the meniscus lens RL1 is negative, the focal length of the double cemented lens RL2 is negative, the focal length of the meniscus lens RL3 is negative, the focal length of the double convex lens RL4 is positive, the focal length of the double cemented lens RL5 is positive, and the focal length of the double convex lens RL6 is positive.

[0050] In this embodiment, the aperture S is placed in the middle of the subsequent lens group RLG, which can reduce the negative impact of stray light to a certain extent.

[0051] The sensor D is used to sense and image the three-channel light of the panoramic imaging system to obtain imaging spots of three areas. In this embodiment, the resolution of the sensor D is 1920×1080, and the pixel size is 2.9 μm.

[0052] In order to realize the information perception of different object distances, the working focal length f of the panoramic channel is p , the working focal length f of the side channel s and the working focal length f of the front channel f Satisfies the following relationship: s >5f p >0,f f >4f p >0.

[0053] In order to achieve large relative aperture imaging, the F number of the panoramic channel is F p , F number of the side channel s and the F number of the front channel Ff They satisfy the following relations: 2 <F p <2.5, 2 <F s <2.5, 2 <F f <2.5.

[0054] In order to limit the negative impact of distortion on imaging, the maximum f-θ distortion δ of the panoramic channel is p , the maximum f-θ distortion of the side channel δ s and the maximum f-θ distortion δ of the front channel f They satisfy the following relations: p <8%, δ s <7%, δ f <0.1%.

[0055] like Figure 2 As shown in the figure, the circular imaging spot of the front channel on the sensor D, the annular imaging spot of the panoramic channel on the sensor D, and the annular imaging spot of the side channel on the sensor D should not overlap each other, and should be arranged in sequence from the center to the edge, without a central blind area. In order to ensure that the annular imaging spot is obtained, the imaging spot range of the side channel should not exceed the target surface area of ​​the sensor D.

[0056] In this embodiment, the system parameters are optimized by ray tracing. During the optimization, the optical parameters among the panoramic channel, the side channel and the front channel are mutually constrained, and the light paths of the three channels pass through all the optical elements in the panoramic imaging system.

[0057] Table 1 below lists the system structure parameters in this embodiment.

[0058] Table 1 Structural parameters of the panoramic imaging system in this embodiment

[0059]

[0060]

[0061] Under the parameters in Table 1, the three-dimensional ray tracing diagram of the panoramic imaging system based on the dichroic film in this embodiment is as follows: Figure 3 As shown, the ray tracing diagram of the panoramic channel, the ray tracing diagram of the side channel, and the ray tracing diagram of the front channel are shown in sequence. Figure 4 , Figure 5 , Figure 6As shown. In the panoramic channel, the visible light of 486-656nm with an ultra-large field of view is first refracted by the front surface of the panoramic head unit PHU, and then the first reflection is achieved on the dichroic film on the rear surface of the panoramic head unit PHU, and then the second reflection is achieved by the reflective film on the front surface of the panoramic head unit PHU, and finally it is emitted from the central area of ​​the rear surface of the panoramic head unit PHU, and finally reaches the sensor D for imaging. In the side channel, the near-infrared light of 800-900nm with a large field of view sequentially passes through the front and rear surfaces of the panoramic head unit PHU, and then passes through the relay lens group RLG to reach the sensor D. In the front channel, the visible-near-infrared light of 486-900nm with a small field of view sequentially passes through the central area of ​​the front and rear surfaces of the panoramic head unit PHU and the relay lens group RLG, and finally reaches the sensor D for imaging.

[0062] In the panoramic imaging system based on dichroic film in this embodiment, the spot diagram of the panoramic channel on the sensor D, the spot diagram of the side channel on the sensor D, and the spot diagram of the front channel on the sensor D are shown in sequence: Figure 7 , Figure 8 , Fig. 9 As shown. The RMS radius of the spot diagram represents the energy concentration of the optical system. In this embodiment, the maximum RMS radius of the spot diagram of the panoramic channel, the maximum RMS radius of the spot diagram of the side channel, and the maximum RMS radius of the spot diagram of the front channel are 1.222μm, 1.588μm, and 2.337μm, respectively, which are close to the radius of the Airy disk and match the pixel size of the sensor D of 2.9μm, indicating that the system has a high energy concentration.

[0063] The MTF curve can directly reflect the imaging quality of the optical system. The MTF curves of the panoramic channel, the side channel, and the front channel in the panoramic imaging system based on the dichroic film in this embodiment are shown in the following order: Fig.10 , Fig.11 , Fig.12 The MTF curves of the three channels are evenly distributed and maintained at a high level. The MTF values ​​of the panoramic channel, side channel and front channel at the cutoff spatial frequency of 172lp / mm are respectively more than 0.6, 0.38 and 0.3, reflecting that the panoramic imaging system based on the dichroic film in this embodiment has a high imaging quality.

[0064] The field curvature distortion diagram of the panoramic channel, the field curvature distortion diagram of the side channel, and the field curvature distortion diagram of the front channel in the panoramic imaging system based on the dichroic film in this embodiment are shown in sequence. Fig.13 , Fig.14 , Fig.15 As shown. The maximum f-θ distortion δ of the panoramic channel p , the maximum f-θ distortion of the side channel δ s and the maximum f-θ distortion δ of the front channelf They are 7.6780%, 6.8708% and 0.0034% respectively. Even though the panoramic channel and the side channel have a very large field of view, their maximum distortion remains at a low level, verifying the excellent ability of the panoramic imaging system to suppress system distortion.

[0065] The three-channel optical parameters of the panoramic imaging system in the embodiment of the present invention are shown in Table 2. The optical system has the characteristics of small focal length, large relative aperture and large field of view. Since the three channels share all the optical elements in the optical system, the total length of the three-channel system remains consistent. The imaging ranges of the panoramic channel, the side channel and the front channel on the image plane are 0.259-0.422 mm, 0.471-1.560 mm and 0-0.230 mm respectively, without overlapping each other.

[0066] Table 2 Three-channel optical parameters of the panoramic imaging system in this embodiment

[0067] aisle Panoramic Channel Side Channel Front channel Spectral range (nm) 486～656 800～900 486～900 Focal length(mm) 0.273 1.493 1.098 Working F number 2.47 2.49 2.48 Field of view 360°×(56°～96°) 360°×(18°～56°) 360°×(0°～12°) Total system length (mm) 98.49 98.49 98.49 Image height range(mm) 0.259～0.422 0.471～1.560 0～0.230

[0068] Compared with other panoramic imaging systems, the panoramic imaging system based on the dichroic film of this embodiment breaks the detection capability limitation caused by the central blind spot, realizes enhanced detection of the near-infrared band assisting the visible light band, and has the characteristics of large field of view, large relative aperture, low distortion, and high component utilization.

[0069] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A three-channel panoramic imaging system based on a dichroic film, characterized in that: It includes a panoramic head unit PHU, a subsequent lens group RLG and a sensor D arranged in sequence from the object side to the image side; The panoramic head unit PHU is in the shape of a negative meniscus lens. The front surface of the panoramic head unit PHU close to the object side is coated with an annular reflective film, and the rear surface close to the image side is coated with an annular dichroic film. The panoramic head unit PHU is used to collect target light with a dual-band and a large field of view, and the incident angle compression of the panoramic channel light and the fusion of multiple channels are achieved through the dichroic film and the reflective film. The dichroic film can transmit near-infrared light of 800nm-900nm and reflect visible light of 486nm-656nm; the coating position of the dichroic film must ensure that it can completely transmit all the light of the side channel, completely reflect all the light of the panoramic channel, and will not block the outgoing light of the three channels; the coating position of the reflective film must ensure that it can completely reflect all the light of the panoramic channel and will not block the light of the side channel and the front channel; The panoramic channel can image visible light in an ultra-large field of view of 360°×(56°~96°), the side channel can image near-infrared light in a large field of view of 360°×(18°~56°), and the front channel can image visible light-near-infrared light in a small field of view of 360°×(0°~12°); The subsequent lens group RLG is used to correct the aberration of the large-field incident light generated in the panoramic head unit PHU, and transmit the light collected by the panoramic head unit PHU to the sensor D; the sensor D is used to sense and image the three-channel light of the panoramic imaging system to obtain imaging spots in three areas.

2. The three-channel panoramic imaging system based on dichroic film according to claim 1, characterized in that: The subsequent lens group RLG includes a meniscus lens RL1, a doublet lens RL2, a meniscus lens RL3, a biconvex lens RL4, a stop S, a doublet lens RL5 and a biconvex lens RL6, which are arranged in sequence from the object side to the image side; Among them, the focal length of the meniscus lens RL1 is negative, the focal length of the doublet lens RL2 is negative, the focal length of the meniscus lens RL3 is negative, the focal length of the biconvex lens RL4 is positive, the focal length of the doublet lens RL5 is positive, and the focal length of the biconvex lens RL6 is positive.

3. The three-channel panoramic imaging system based on dichroic film according to claim 1, characterized in that: The working focal length f of the panoramic channel p , the working focal length f of the side channel s and the working focal length f of the front channel f Satisfies the following relationship: s >5f p >0,f f >4f p >0.

4. The three-channel panoramic imaging system based on dichroic film according to claim 1, characterized in that: The F number of the panoramic channel is F p , F number of the side channel s and the F number of the front channel F f They satisfy the following relations: 2 <F p <2.5, 2 <F s <2.5, 2 <F f <2.

5.

5. The three-channel panoramic imaging system based on dichroic film according to claim 1, characterized in that: The diameter D of the panoramic head unit PHU PHU and the total length L of the three-channel panoramic imaging system satisfy the following relationship: PHU <0.85L.

6. The three-channel panoramic imaging system based on dichroic film according to claim 1, characterized in that: The maximum f-θ distortion δ of the panoramic channel p , the maximum f-θ distortion of the side channel δ s and the maximum f-θ distortion δ of the front channel f They satisfy the following relations: p <8%, δ s <7%, δ f <0.1%.

7. The three-channel panoramic imaging system based on dichroic film according to claim 1, characterized in that: The circular imaging spot of the front channel on the sensor D, the annular imaging spot of the panoramic channel on the sensor D, and the annular imaging spot of the side channel on the sensor D do not overlap with each other, and are arranged in sequence from the center to the edge, without a central blind area.

8. The three-channel panoramic imaging system based on dichroic film according to claim 1, characterized in that: The optical parameter optimizations of the panoramic channel, the side channel and the front channel constrain each other, and the light paths of the three channels pass through all the optical elements in the panoramic imaging system.

9. The three-channel panoramic imaging system based on dichroic film according to claim 1, characterized in that: The panoramic head unit PHU is made of glass with a refractive index of not less than 1.

7.

10. The three-channel panoramic imaging system based on dichroic film according to claim 1, characterized in that: The resolution of sensor D is 1920×1080 and the pixel size is 2.9μm.

Images