High-resolution double-view-field thermal imaging lens

Abstract

The invention relates to a high-resolution double-view-field thermal imaging lens, and belongs to the technical field of optical imaging. The lens sequentially comprises a telescope group, a reflex scanning lens and a convergence lens group along the light incidence direction, the telescope group is used for converging light of an infinite target and then converting the light into parallel light; the telescope group sequentially comprises a first lens group, a second lens group and a third lens group along a light incidence direction; the second lens group is a field-cutting lens group and can realize switching between a large view field and a small view field by cutting in and cutting out a light path; the reflex scanning lens can deflect along the central axis of the reflex scanning lens to be matched with the scanning type detector so as to scan an object space target; when the reflex scanning lens is static or deflects along the central axis of the reflex scanning lens, the reflex scanning lens can be matched with the staring type detector to track an object space target; and the converging lens group is used for re-converging the light into the detector and imaging. The high-resolution double-view-field staring and scanning type compatible thermal imaging lens is realized.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and particularly to a high-resolution dual-field-of-view thermal imaging lens. Background Art

[0002] With the continuous development of infrared technology, the demand for search and tracking of infrared targets is also increasing. Most of the current long-wave infrared scanning thermal imaging lenses on the market are designed to match detectors of 288×4. Traditional lenses with folding and scanning functions mostly adopt a single field-of-view design. This design is simple, with low difficulty in aberration correction, and has a single application scenario.

[0003] With the successful development of a 768×8 resolution scanning detector assembly, higher requirements are put forward for the supporting optical lens. Existing lenses are gradually unable to meet the market demand for infrared thermal imagers with high resolution, adaptability to complex scenarios, and light weight.

[0004] The difficulty in designing a high-resolution lens lies in that the larger the size of the detector photosensitive surface, the more difficult it is to correct the aberration within the full field of view of the optical system. When the lens material combination is unreasonable, it is extremely easy to cause problems such as more lens elements, larger lens volume, and heavier weight. Compared with general fixed lenses, lenses with folding and scanning functions not only need to focus on the imaging quality in the central area of the lens, but also need to focus on the imaging quality in the scanning state. In the scanning state of the lens, due to the deflection of the mirror, the optical axis deflects, and the optical axis is no longer at the center position of the lens, which also greatly increases the difficulty of aberration correction. Summary of the Invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a high-resolution dual-field-of-view thermal imaging lens to solve the problem that existing thermal imaging lenses cannot meet the market demand for infrared thermal imagers with high resolution, adaptability to complex scenarios, and light weight.

[0006] An embodiment of the present invention provides a high-resolution dual-field-of-view thermal imaging lens. The lens sequentially includes a telescope group, a folding and scanning lens, and a converging lens group along the light incident direction. The telescope group is used to converge the light of an infinitely distant target and convert it into parallel light. The telescope group sequentially includes a first lens group, a second lens group, and a third lens group along the light incident direction. The second lens group is a field-splitting lens group, which can realize the switching between a large field of view and a small field of view by cutting into and out of the optical path. The folding and scanning lens can deflect along its central axis to match a scanning detector to realize the scanning of the object target. When the folding and scanning lens is stationary or deflects along its central axis, it can match a staring detector to realize the tracking of the object target. The converging lens group is used to converge the light again and enter the detector for imaging.

[0007] Further, the first lens group of the telescopic lens group includes a first lens and a second lens in sequence along the light incident direction; the lens material of the first lens is germanium, and the lens material of the second lens is zinc sulfide; the front and rear surface curvature radii of the first lens and the second lens are both above 180 mm.

[0008] Further, the field cutting lens group includes a third lens and a fourth lens in sequence along the light incident direction; the third lens is a negative lens made of chalcogenide glass material, which deflects and contracts the light entering the first lens group; the fourth lens is a positive lens made of germanium material for converging the light emitted from the third lens.

[0009] Further, the third lens group of the telescopic lens group includes a fifth lens to a seventh lens in sequence along the light incident direction; the converging lens group includes an eighth lens to an eleventh lens in sequence along the light incident direction;

[0010] Among the first to eleventh lenses of the thermal imaging lens, the lens materials of the second lens and the tenth lens are zinc sulfide, the lens material of the third lens is chalcogenide glass, and the lens materials of the remaining lenses are all germanium.

[0011] Further, the front surfaces of the second lens, the fourth lens, and the sixth lens of the thermal imaging lens, and the rear surfaces of the eighth lens and the eleventh lens adopt even aspherical surface types.

[0012] Further, the folding and scanning lens is controlled by high and low levels to swing the scanning direction and the swing period. The angle change of the folding and scanning lens is controlled by a sawtooth waveform. The scanning frequency of the folding and scanning lens is 50 Hz, and the effective integration time is 5 ms.

[0013] Further, the initial zero position of the folding and scanning lens is placed at an angle of 45° with the principal optical axis. The rotation axis of the folding and scanning lens is perpendicular to the paper surface and passes through the center point of the folding and scanning lens. When applied to a scanning type detector, the folding and scanning lens reciprocally deflects within a range of ±6° around this axis.

[0014] Further, the length of the folding and scanning lens is not less than 30 mm, the height is not less than 20 mm, and the thickness is not less than 3 mm.

[0015] Further, the F number of the thermal imaging lens is 2.0.

[0016] Further, the large and small fields of view of the scanning type thermal imaging lens are respectively achieved by the cutting in and cutting out of the field cutting lens group; the focal lengths of the large and small fields of view are 90 mm and 220 mm respectively.

[0017] Compared with the prior art, the present invention can at least achieve one of the following beneficial effects:

[0018] 1. Through optical design, the present invention reasonably corrects optical aberration and thermal aberration, has excellent imaging quality, and is compatible with a 768×8 high-resolution linear array infrared detector. It can drive the lens to cut into and out of the optical path through a motor, thereby realizing the zoom of the dual-field-of-view lens. Compared with the scanning lens of the traditional 288×4 type detector module, it has higher resolution and richer usage scenarios, significantly improving the observation ability and detection range of the infrared thermal imager.

[0019] 2. The lens of the present invention can be applied to both target search in scanning scenarios and target tracking in staring scenarios, and is compatible with long-wave cooled infrared detectors with resolutions below 768×8 and some staring detectors.

[0020] 3. The present invention optimally combines lens materials such as germanium, zinc sulfide, and chalcogenide glass, and through analysis and optimization, special aspherical designs are adopted for the lens surfaces that are more likely to generate aberration. The addition of chalcogenide glass and aspherical design in the present invention can not only reduce aberration but also achieve the purpose of reducing the volume of the optical system. With a small number of lenses, the entire optical system reaches an ideal state of high imaging quality, light weight, and low cost.

[0021] 4. Through the reasonable optimization design of the first two lenses, germanium and zinc sulfide, in the front telescopic system of the lens, their radius of curvature is larger, both above 180 mm, thereby significantly reducing the sensitivity of the entire optical system to the deflection of the optical axis, and having ideal imaging quality in both staring and scanning states.

[0022] 5. By designing a field-cutting lens group composed of an additional negative lens made of chalcogenide glass material and a positive lens made of germanium material in a single field of view, the lenses of this field-cutting lens group deflect and contract the light entering the front lens group with the negative lens; converge the light with the positive lens, enabling this group of field-cutting lenses to have a small volume, ensure the imaging quality of the large field of view, and at the same time not affect the imaging quality of the small field of view. The lens only adds two lenses to obtain an additional focal length with a large field of view angle, increasing the observer's field of view angle. Not only does the weight of the optical lens not increase significantly, but the usage scenarios also increase significantly.

[0023] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent specification, and some advantages can be made obvious from the specification or understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained through the content specifically pointed out in the specification and the drawings. Description of the Drawings

[0024] The accompanying drawings are only for the purpose of showing specific embodiments and are not considered as limitations of the present invention. Throughout the drawings, the same reference signs denote the same components.

[0025] Figure 1 Schematic diagram of the large field of view optical system of a high-resolution dual field of view thermal imaging lens according to the present invention;

[0026] Figure 2 Schematic diagram of the small field of view optical system of a high-resolution dual field of view thermal imaging lens according to the present invention;

[0027] Figure 3 Schematic diagram of the large field of view scanning state optical system of a high-resolution dual field of view thermal imaging lens according to the present invention;

[0028] Figure 4 Schematic diagram of the small field of view scanning state optical system of a high-resolution dual field of view thermal imaging lens according to the present invention;

[0029] Figure 5 MTF curve of a high-resolution dual field of view thermal imaging lens in the small field of view staring state according to the present invention;

[0030] Figure 6 MTF curve of a high-resolution dual field of view thermal imaging lens in the large field of view staring state according to the present invention;

[0031] Figure 7 MTF curve of a high-resolution dual field of view thermal imaging lens in the small field of view scanning state according to the present invention;

[0032] Figure 8 MTF curve of a high-resolution dual field of view thermal imaging lens in the large field of view scanning state according to the present invention.

[0033] Reference signs:

[0034] 1 - First lens;

[0035] 2 - Second lens;

[0036] 3 - Third lens;

[0037] 4 - Fourth lens;

[0038] 5 - Fifth lens;

[0039] 6 - Sixth lens;

[0040] 7 - Seventh lens;

[0041] 8 - Eighth lens;

[0042] 9 - Ninth lens;

[0043] 10 - Tenth lens;

[0044] 11 - The eleventh lens;

[0045] 12 - The detector protection window;

[0046] 13 - The detector filter;

[0047] 14 - The photosensitive surface of the detector;

[0048] 15 - The folding scanning lens. Specific embodiments

[0049] The following will specifically describe the preferred embodiments of the present invention in conjunction with the accompanying drawings. Among them, the accompanying drawings form a part of this application and are used together with the embodiments of the present invention to explain the principles of the present invention, rather than to limit the scope of the present invention.

[0050] A specific embodiment of the present invention discloses a high - resolution dual - field thermal imaging lens. The lens sequentially includes a telescope group, a folding scanning lens 15, and a converging lens group along the light incident direction. The telescope group is used to converge the light of an infinitely distant target and convert it into parallel light. The telescope group sequentially includes a first lens group, a second lens group, and a third lens group along the light incident direction. The second lens group is a field - cutting lens group, which can switch between a large field of view and a small field of view by cutting into and out of the optical path. The folding scanning lens 15 can deflect along its central axis to match a scanning detector to scan the object - side target. When the folding scanning lens 15 is stationary or deflects along its central axis, it can match a staring detector to track the object - side target. The converging lens group is used to converge the light again and enter the detector for imaging.

[0051] The first lens group of the telescope group sequentially includes a first lens 1 and a second lens 2 along the light incident direction. The lens material of the first lens 1 is germanium, and the lens material of the second lens 2 is zinc sulfide. The front and rear surface curvature radii of the first lens 1 and the second lens 2 are both above 180 mm.

[0052] By reasonably optimizing the design of the first two lenses of the front - end telescope group of this lens, using germanium and zinc sulfide, the curvature radii are made larger, both above 180 mm, so that the sensitivity of the entire lens to the deflection of the optical axis is significantly reduced, and ideal imaging quality is achieved in both the staring and scanning states.

[0053] The field - cutting lens group sequentially includes a third lens 3 and a fourth lens 4 along the light incident direction. The third lens 3 is a negative lens made of chalcogenide glass, which deflects and contracts the light entering from the first lens group. The fourth lens 4 is a positive lens made of germanium and is used to converge the light emitted from the third lens 3.

[0054] The large and small fields of view of the scanning thermal imaging lens are respectively achieved by the insertion and extraction of the field cutting lens group; the focal lengths of the large and small fields of view are 90 mm and 220 mm respectively.

[0055] Specifically, driven by a motor, the field cutting lens group can be inserted into or extracted from the optical path, changing the focal length of the telescopic system to perform dual-field zoom.

[0056] Schematic diagrams of the large and small field optical systems of the thermal imaging lens of the present invention are respectively as Figure 1 and 2 shown.

[0057] In this lens, a negative lens made of a chalcogenide glass material and a positive lens made of a germanium material are additionally added in a single field of view. This group of lenses deflects and contracts the light entering the front lens group with the negative lens, and converges the light with the positive lens, enabling the field cutting lens group to have a small volume and ensure the imaging quality of the large field of view without affecting the imaging quality of the small field of view. This lens only adds two lenses to obtain an additional focal length with a large field of view angle, increasing the observer's field of view angle. Not only does the weight of the optical lens not increase significantly, but the usage scenarios also increase significantly.

[0058] The insertion of the field cutting lens group is used for target search and observation in the large field of view with a 90 mm focal length, and the extraction of the field cutting lens group is used for target tracking and identification in the small field of view with a 220 mm focal length.

[0059] The third lens group of the telescope group successively includes a fifth lens 5 to a seventh lens 7 along the direction of light incidence; the converging lens group successively includes an eighth lens 8 to an eleventh lens 11 along the direction of light incidence;

[0060] Among the first to eleventh lenses 11 of the thermal imaging lens, the lens materials of the second lens 2 and the tenth lens 10 are zinc sulfide, the lens material of the third lens 3 is chalcogenide glass, and the lens materials of the remaining lenses are germanium.

[0061] Preferably, among the first lens 1 to the eleventh lens 11, the second lens 2, the third lens 3, the sixth lens 6, and the tenth lens 10 are negative lenses, and the remaining lenses are positive lenses.

[0062] Specifically, the light emitted from the eleventh lens 11 needs to pass through a detector protection window 12 and a detector filter 13 before being incident on the photosensitive surface 15 of the detector.

[0063] The detector filter 13 is used to filter out other light energies outside the response band. In a specific embodiment of the present invention, the spectral sensitivity range of a 768×8 linear array infrared detector is 7.7 μm - 10.9 μm.

[0064] The front surfaces of the second lens 2, the fourth lens 4, and the sixth lens 6 of the thermal imaging lens, and the rear surfaces of the eighth lens 8 and the eleventh lens 11 adopt even aspherical surface profiles.

[0065] Specifically, aspheres can be machined by diamond turning for chalcogenide glass, zinc sulfide material, and germanium material. The surface profiles of some lenses of this lens adopt aspherical surface profile designs, which can effectively correct spherical aberration and thermal aberration in the optical system and significantly improve the imaging quality.

[0066] The MTF curves of the thermal imaging lens of the present invention in the small field of view and large field of view staring states are respectively as Figure 5 and Figure 6 shown.

[0067] The expression of the even aspherical surface profile is as follows:

[0068]

[0069] where C0 = 1 / R, R is the radius of curvature of each aspherical surface, K is the conic coefficient, Y is the distance from the point on the aspherical surface to the optical axis, and A, B, C, D... are the coefficients of each high-order term respectively.

[0070] The lens optical data of a specific embodiment of the present invention is shown in Table 1. In Table 1, the surface number refers to the sequential numbering of each surface from the object surface to the image surface along the optical axis.

[0071] Table 1

[0072]

[0073]

[0074] Among them, the surfaces with surface numbers 25-26 form the detector protection window 12, the surfaces with surface numbers 27-28 form the detector filter 13, and the surface with surface number 29 is the detector photosensitive surface 15.

[0075] [[ID=3Z]]The aspherical surface profile parameters of each specific embodiment of the present invention are shown in Table 2.

[0076] Table 2

[0077] Plane serial number Cone coefficient Coefficient of fourth-order term Coefficient of sixth-order term 3 0 -2.4e-08 -6.5e-13 7 0 -2.12e-07 -6.52e-11 11 0 -7.92e-07 -9.52e-10 18 0 6.2e-07 1.82e-9 24 0 3.79e-06 1.38e-9

[0078] The folding and scanning lens 15 controls the swing scanning direction and swing scanning period through high and low levels. The angle change of the folding and scanning lens 15 is controlled by a sawtooth waveform. The scanning frequency of the folding and scanning lens 15 is 50 Hz, and the effective integration time is 5 ms.

[0079] The schematic diagrams of the optical systems of the thermal imaging lens of the present invention in the large and small field of view scanning states are respectively as Figure 3 and 4shown.

[0080] The MTF curves of the thermal imaging lens of the present invention in the small field of view and large field of view scanning states are respectively as follows: Figure 7 and Figure 8 shown.

[0081] Specifically, the scanning direction and scanning period of the folding scanning lens 15 are controlled by the high and low levels of the digital electrical signal through the communication interface of the high-speed motor.

[0082] The initial zero position of the folding scanning lens 15 is placed at an angle of 45° to the main optical axis. The rotation axis of the folding scanning lens 15 is perpendicular to the paper surface and passes through the center point of the folding scanning lens 15. When used in a scanning detector, the folding scanning lens 15 performs reciprocating deflection within a range of ±6° around the axis.

[0083] Specifically, the folding scanning lens 15 is coated with a reflective film, which can reflect the light path.

[0084] The folding scanning lens 15 has a length of not less than 30 mm, a height of not less than 20 mm, and a thickness of not less than 3 mm.

[0085] The F number of the thermal imaging lens is 2.0.

[0086] This lens can be applied to high-speed turntables, thus adapting to more complex usage scenarios.

[0087] The scanning thermal imaging lens of the present invention can be mounted on a turntable, and the 360° environment around the scene can be monitored in real time by rotating the turntable. In order to cope with the problem that the image of some low-exposure infrared detection devices is prone to tailing when the turntable rotates at a high speed, the lens of the present invention adds a folding compensation component including a high-speed motor and a folding scanning lens 15 in the optical path. When the turntable of the fixed lens rotates at a high speed, if the turntable rotates to a new position, it will cause the optical system without the folding compensation component to produce a tailing blur problem. In this embodiment, the folding compensation component controls the folding scanning lens 15 through the high-speed motor to adjust the optical axis in real time, so that the detector can capture continuous scenes and compensate the target scene in real time, effectively avoiding image blur, greatly improving the scanning speed of the scanning lens, and better adapting to complex and changeable usage scenarios. In addition, the dual-field-of-view design can also achieve the wide-range search function of the short-focus lens and the target magnification and recognition function of the long-focus lens.

[0088] Compared with the prior art, the high-resolution dual-field-of-view lens provided in this embodiment can be used for a 768×8 high-resolution linear array infrared detector. Through reasonable optical design, optical aberrations and thermal aberrations are corrected, and it has excellent imaging quality. The lens can be driven by a motor to cut into and out of the optical path, so as to realize the zoom of the dual-field-of-view lens. Compared with the scanning lens of the traditional 288×4 type detector assembly, it has higher resolution and richer usage scenarios. The observation ability and operating range of the infrared thermal imager are significantly improved. This lens can be applied to target search in scanning scenarios and also to target tracking in staring scenarios. It is adapted to and compatible with long-wave cooled infrared detectors with resolutions below 768×8 and some staring detectors. This lens optimally combines lens materials such as germanium, zinc sulfide, and chalcogenide glass, and through analysis and optimization, special aspherical designs are adopted for the lens surfaces that are more likely to generate aberrations. The addition of chalcogenide glass and aspherical design to this lens can not only reduce aberrations but also achieve the purpose of reducing the volume of the optical system. With a small number of lenses, the entire optical system reaches an ideal state of high imaging quality, light weight, and low cost. Through reasonable optimization design of the first two lenses, germanium and zinc sulfide, of the front telescopic system of this lens, their radius of curvature is larger, both above 180 mm, so that the sensitivity of the entire optical system to the deflection of the optical axis is significantly reduced, and ideal imaging quality is achieved in both staring and scanning states. This lens is designed with a field-cutting lens group composed of an additional negative lens made of chalcogenide glass material and a positive lens made of germanium material in a single field of view. The lenses of this field-cutting lens group deflect and contract the light entering the front lens group with the negative lens; the positive lens converges the light, so that this group of field-cutting lenses can ensure the imaging quality of the large field of view while being small in volume and not affecting the imaging quality of the small field of view. This lens only adds two lenses to obtain an additional focal length with a large field of view angle, increasing the observer's field of view angle. Not only will the weight of the optical lens not increase much, but the usage scenarios are also significantly increased.

[0089] Those skilled in the art can understand that all or part of the processes of implementing the methods in the above embodiments can be completed by instructing relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium. Among them, the computer-readable storage medium is a magnetic disk, an optical disk, a read-only memory, or a random access memory, etc.

[0090] The above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A high-resolution dual-field-of-view thermal imaging lens, characterized in that, The lens sequentially includes a telescope group, a folding and scanning lens, and a focusing lens group along the light incident direction; the telescope group is used to converge the light of an infinitely distant target and then convert it into parallel light; the telescope group sequentially includes a first lens group, a second lens group, and a third lens group along the light incident direction; the second lens group is a field cutting lens group, and can realize the switching between a large field of view and a small field of view by cutting into and out of the optical path; the folding and scanning lens can deflect along its central axis to match a scanning detector to realize the scanning of the object target; when the folding and scanning lens is stationary or deflects along its central axis, it can match a staring detector to realize the tracking of the object target; the focusing lens group is used to converge the light again and enter the detector for imaging.

2. The thermal imaging lens according to claim 1, wherein, The first lens group of the telescope group sequentially includes a first lens and a second lens along the light incident direction; the lens material of the first lens is germanium, and the lens material of the second lens is zinc sulfide; the front and rear surface curvature radii of the first lens and the second lens are both above 180 mm.

3. The thermal imaging lens according to claim 2, wherein, The field cutting lens group sequentially includes a third lens and a fourth lens along the light incident direction; the third lens is a negative lens made of chalcogenide glass, and this negative lens deflects and contracts the light entering the first lens group; the fourth lens is a positive lens made of germanium and is used to converge the light emitted by the third lens.

4. The thermal imaging lens according to claim 3, characterized in that, The third lens group of the telescope group sequentially includes a fifth lens to a seventh lens along the light incident direction; the focusing lens group sequentially includes an eighth lens to an eleventh lens along the light incident direction; Among the first to eleventh lenses of the thermal imaging lens, the lens materials of the second lens and the tenth lens are zinc sulfide, the lens material of the third lens is chalcogenide glass, and the lens materials of the remaining lenses are germanium.

5. The thermal imaging lens according to claim 4, wherein The front surfaces of the second lens, the fourth lens, and the sixth lens, and the rear surfaces of the eighth lens and the eleventh lens of the thermal imaging lens adopt even aspherical surfaces.

6. The thermal imaging lens according to claim 1, wherein, The folding and scanning lens controls the swing scanning direction and the swing scanning period through high and low levels, the angle change of the folding and scanning lens is controlled by a sawtooth waveform, the scanning frequency of the folding and scanning lens is 50 Hz, and the effective integration time is 5 ms.

7. The thermal imaging lens according to claim 1, wherein, The initial zero position of the folding and scanning lens is placed at an angle of 45° with the principal optical axis, the rotation axis of the folding and scanning lens is perpendicular to the paper surface and passes through the center point of the folding and scanning lens, and when applied to a scanning detector, the folding and scanning lens reciprocally deflects within a range of ±6° around this axis.

8. The thermal imaging lens according to claim 7, wherein The length of the folding and scanning lens is not less than 30 mm, the height is not less than 20 mm, and the thickness is not less than 3 mm.

9. The thermal imaging lens according to claim 1, characterized in that, The F number of the thermal imaging lens is 2.

0.

10. The thermal imaging lens according to claim 3, characterized in that, The large and small fields of view of the scanning thermal imaging lens are respectively realized by cutting into and out of the field cutting lens group; the focal lengths of the large and small fields of view are 90 mm and 220 mm respectively.

Images