A large-aperture 2K resolution infrared lens

Abstract

This invention belongs to the field of infrared lens design and manufacturing technology, and relates to a large-aperture 2K resolution infrared lens. The infrared lens, along the light incident direction, sequentially comprises a first lens with negative optical power, a second lens with positive optical power, a third lens with positive optical power, a fourth lens with negative optical power, a detector protective glass, and an imaging target surface for the detector. The first, second, third, and fourth lenses are all convex surfaces in the light incident direction and concave surfaces in the opposite direction. This invention provides a large-aperture 2K resolution infrared lens with a thermal-free design, capable of normal operation within a temperature range of -40℃ to 50℃, and compatible with 1920*1080@8μm uncooled long-wave infrared detectors. It features a large aperture, simple structure, and large imaging target surface size.

Description

Technical Field

[0001] This invention belongs to the field of infrared lens design and manufacturing technology, specifically, it relates to a large-aperture 2K resolution infrared lens. Background Technology

[0002] Uncooled infrared detectors are currently developing towards higher resolution and smaller pixel size. Higher resolution allows for more detail in infrared images and better display effects, while smaller pixel size enables the overall size of the detector to be reduced, thereby lowering the cost of the detector and making it easier for products to adapt and apply.

[0003] At present, the 1024*768@17μm and 1280*1024@12μm uncooled long-wave infrared detectors are mature products and have been widely used, while the 1920*1080@8μm uncooled long-wave infrared detector has entered the prototype stage.

[0004] For uncooled infrared detectors, the smaller the pixel size, the higher the Nyquist frequency. For example, a 17μm pixel chip has a Nyquist frequency of 29.4 lp / mm, a 12μm pixel chip has a Nyquist frequency of 42 lp / mm, and an 8μm pixel chip has a Nyquist frequency of 62.5 lp / mm. Currently, most mainstream infrared lenses have a relative aperture of F#1.0, and their maximum resolution cannot reach the matching Nyquist frequency of 62.5 lp / mm. This results in a loss of high-frequency information in the image, preventing the full utilization of the uncooled infrared detector's performance and causing a waste of its potential.

[0005] For optical lenses, the larger the relative aperture (the smaller the F#), the more difficult the design and the more complex the optical system. At the same time, the more optical lenses there are, the lower the optical transmittance, which not only affects optical performance but also increases cost and size. Therefore, for infrared lenses, the number of lenses is generally controlled as much as possible.

[0006] Currently, various high-resolution infrared lenses have emerged, such as the large relative aperture, large target surface, long-wave infrared athermalized lens disclosed in Chinese patent document CN202123256454.X, the infrared athermalized lens adapted for 4K resolution assembly disclosed in Chinese patent document CN202211741003.1, the long back intercept, wide temperature athermalized infrared optical system disclosed in Chinese patent document CN202311150970.5, the 2K high-definition long-wave infrared athermalized optical system disclosed in Chinese patent document CN202320312472.5, the refractive-diffraction hybrid large relative aperture long-wave infrared optical system disclosed in Chinese patent document CN202310656988.6, and the refractive-diffraction hybrid large relative aperture long-wave infrared optical system disclosed in Chinese patent document CN202211379583.4. The relative apertures of these systems are relatively small, which will cause performance loss if adapted to small pixel detectors. The ultra-large aperture, large target surface, calorimetric long-wave infrared optical system disclosed in Chinese patent document CN202211355670.6, which is suitable for 8μm pixel cores, has a relative aperture of F#0.8, but has a large number of lenses and a complex structure.

[0007] Therefore, there is an urgent need in this field to develop a large-aperture 2K resolution infrared lens with a relatively small aperture (F#1.0) and a relatively simple structure to match a 1920*1080@8μm uncooled long-wave infrared detector. Summary of the Invention

[0008] The purpose of this invention is to provide a large-aperture 2K resolution infrared lens to improve the field of view and reduce optical distortion. Its diagonal field of view is >40° and the maximum optical distortion is ≤2.5%. It can be matched with a 1920*1080@8μm uncooled long-wave infrared detector and can be applied to island and reef defense, military reconnaissance, forest fire prevention, vehicle-mounted assisted driving, power maintenance and other fields, with broad application prospects.

[0009] To achieve the above-mentioned objectives, this invention provides a large-aperture 2K resolution infrared lens, the technical solution of which is as follows:

[0010] A large-aperture 2K resolution infrared lens, the infrared lens comprising, in sequence along the light incident direction (from left to right):

[0011] The first lens with negative optical power is convex in the direction of light incidence and concave in the opposite direction of light incidence.

[0012] The second lens with positive optical power is convex in the direction of light incidence and concave in the opposite direction of light incidence.

[0013] A third lens with positive optical power has a convex surface in the direction of light incidence and a concave surface in the opposite direction of light incidence.

[0014] The fourth lens with negative optical power is convex in the direction of light incidence and concave in the opposite direction of light incidence.

[0015] Protective glass for the detector;

[0016] The imaging target surface of the detector.

[0017] Furthermore, the radii of curvature of the first to fourth lenses successively satisfy the following conditions:

[0018] 25mm<R1<32mm, 20mm<R1′<25mm;

[0019] 23mm<R2<40mm, 30mm<R2′<60mm;

[0020] 27mm<R3<35mm, 50mm<R3′<240mm;

[0021] 18mm<R4<25mm, 15mm<R4′<20mm;

[0022] Where R1 to R4 are the radii of curvature of the first to fourth lens glass in the direction of light incidence, and R1′ to R4′ are the radii of curvature of the first to fourth lens glass in the opposite direction of light incidence.

[0023] Furthermore, the air gap between the first lens and the second lens is 7-12 mm, the air gap between the second lens and the third lens is 12-20 mm, the air gap between the third lens and the fourth lens is 1.5-5 mm, and the air gap between the fourth lens and the detector protective glass is 5-8 mm.

[0024] Furthermore, the glass thicknesses of the first to fourth lenses are L1 to L4, respectively, and L1 to L4 satisfy the following relationship:

[0025] 2.5mm < L1 < 5mm;

[0026] 4mm < L2 < 8mm;

[0027] 4mm < L3 < 8mm;

[0028] 2.5mm < L4 < 6mm.

[0029] Furthermore, the first lens, the second lens, the third lens, and the fourth lens are all made of chalcogenide glass.

[0030] Furthermore, at least one of the eight curved surfaces of the first lens, second lens, third lens, and fourth lens is a diffraction aspherical surface, thus having multiple aspherical surfaces.

[0031] Furthermore, the large-aperture 2K resolution infrared lens operates in the 8μm-12μm band and is matched with a 1920*1080@8μm uncooled long-wave infrared detector.

[0032] Furthermore, the large-aperture 2K resolution infrared lens has an F-number of 0.8.

[0033] Furthermore, the large-aperture 2K resolution infrared lens has a diagonal field of view >40° and a maximum optical distortion <2.5%.

[0034] Furthermore, the large-aperture 2K resolution infrared lens adopts an optical passive calorimetric design, meaning that the imaging focal plane does not shift within the temperature range of -40℃ to 50℃.

[0035] The present invention also includes other devices or components that enable the large aperture 2K resolution infrared lens to function properly, all of which are conventional technical means in the field. In addition, any devices or components not limited in the present invention adopt conventional means in the prior art.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] (1) The large aperture 2K resolution infrared lens of the present invention has a relative aperture of F#0.8 and the imaging resolution can match an 8μm uncooled long-wave infrared detector.

[0038] (2) The large aperture 2K resolution infrared lens of the present invention has a large imaging target size, which can be matched with a 2K resolution uncooled long-wave infrared detector, resulting in good image display effect.

[0039] (3) The large aperture 2K resolution infrared lens of the present invention is a 4-glass structure. By using a diffractive aspherical surface and multiple aspherical surfaces, the optical structure is simplified, thereby reducing the processing and manufacturing cost.

[0040] (4) The large-aperture 2K resolution infrared lens of the present invention adopts an optical passive calorimetric design. The spacer of the optical lens is made of titanium alloy, which can achieve no shift of the focal plane in the range of -40℃ to 50℃ and good calorimetric stability.

[0041] In summary, this invention has a simple structure, low manufacturing cost, and advantages such as large aperture and large imaging target size. It can improve the field of view and reduce optical distortion. It can be matched with a 1920*1080@8μm uncooled long-wave infrared detector and can be applied to island and reef defense, military reconnaissance, forest fire prevention, vehicle-mounted assisted driving, power maintenance and other fields, and has broad application prospects. Attached Figure Description

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] Figure 1 This is an overall structural diagram of the large-aperture 2K resolution infrared lens in Embodiment 1 of the present invention.

[0044] Figure 2 This is a light trend diagram of the large-aperture 2K resolution infrared lens in Embodiment 1 of the present invention.

[0045] Figure 3 The image shows the optical transfer function (MTF) curve of the large-aperture 2K resolution infrared lens in Embodiment 1 of the present invention (under normal temperature +20℃ conditions).

[0046] Figure 4 The image shows the optical transfer function (MTF) curve of the large-aperture 2K resolution infrared lens in Embodiment 1 of the present invention (under low temperature -40℃ conditions).

[0047] Figure 5 The image shows the optical transfer function (MTF) curve of the large-aperture 2K resolution infrared lens in Embodiment 1 of the present invention (under normal temperature +50℃ conditions).

[0048] Figure 6 This is a dot plot of the large-aperture 2K resolution infrared lens in Embodiment 1 of the present invention.

[0049] Figure 7 This is a field curvature and distortion diagram of a large-aperture 2K resolution infrared lens in Embodiment 1 of the present invention.

[0050] Figure 8 This is the energy map surrounding the large-aperture 2K resolution infrared lens in Embodiment 1 of the present invention.

[0051] Figure 9 The image shows the optical transfer function (MTF) curve of the large-aperture 2K resolution infrared lens in Embodiment 2 of the present invention (under normal temperature conditions of 20°C).

[0052] Figure 10 This is a dot plot of the large-aperture 2K resolution infrared lens in Embodiment 2 of the present invention.

[0053] Figure 11 This is a field curvature and distortion diagram of a large-aperture 2K resolution infrared lens in Embodiment 2 of the present invention.

[0054] Figure 12 This is the energy map surrounding the large-aperture 2K resolution infrared lens in Embodiment 2 of the present invention. Detailed Implementation

[0055] The present invention will now be clearly described with reference to the accompanying drawings and specific embodiments. This description is merely illustrative and is not intended to limit the scope of the invention. Any modifications, equivalent substitutions, or improvements made by those skilled in the art based on the embodiments of the present invention without inventive effort to obtain all other embodiments should be included within the scope of protection of the present invention.

[0056] Example 1

[0057] See Figures 1-2 This embodiment proposes a large aperture 2K resolution infrared lens, which is provided in sequence along the light incident direction as a first lens 1 with negative optical power, a second lens 2 with positive optical power, a third lens 3 with positive optical power, a fourth lens 4 with negative optical power, a detector protective glass 5, and an imaging target surface 6 of the detector.

[0058] In this configuration, the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 are all convex surfaces in the direction of light incidence and concave surfaces in the opposite direction of light incidence. The aperture stop is located on the convex surface of the first lens 1, and the detector protective glass 5 is located between the fourth lens 4 and the detector imaging target surface 6.

[0059] The large-aperture 2K resolution infrared lens in this embodiment has a focal length of 23mm, a total optical length (distance from the vertex of the first lens 1 in the direction of light incidence to the target surface 6 of the imaging detector) of 55mm, an operating wavelength of 8μm-12μm, an F-number of 0.8, a diagonal field of view of 42.8°, and a maximum optical distortion of 2.5%. This lens employs a passive, thermal-free optical design, and maintains good imaging quality within a temperature range of -40℃ to 50℃.

[0060] The large-aperture 2K resolution infrared lens in this embodiment meets the following optical conditions:

[0061] Surface serial number Radius of curvature (mm) Interval (mm) Lens half-aperture Material Remark S1 29.88015 4 16.5 Chalcogenide Glass aspherical S2 22.63447 8.4635 15 aspherical S3 24.85574 4.5 16.5 Chalcogenide Glass aspherical S4 32.01731 14.8166 15 S5 27.93416 6 16.5 Chalcogenide Glass aspherical S6 54.46697 3.3737 14.5 aspherical S7 20.41957 5.2 12.5 Chalcogenide Glass Diffraction aspheric surface S8 17.24064 6.652 9.5 S9 infinity 1 10 germanium S10 infinity 1 10

[0062] The relevant data for aspherical surfaces and diffractive aspherical surfaces are shown in the table below:

[0063] <![CDATA[α4]]> <![CDATA[α6]]> <![CDATA[α8]]> <![CDATA[α 10 ]]> Aspherical S1 -3.891E-005 3.8526E-09 3.1577E-011 0 Aspherical S2 -6.169E-005 4.0715E-08 -5.008E-012 0 Aspherical S3 -6.681E-006 -3.215E-09 -5.106E-012 0 Aspherical S5 9.091E-006 7.3182E-09 8.6513E-011 0 Aspherical S6 -4.545E-005 1.6873E-07 -1.540E-010 0 Diffraction Aspheric S7 -4.848E-005 -1.300E-07 1.1625E-09 -4.929E-012

[0064] The expression for an aspherical surface is:

[0065]

[0066] In the above formula, Z is the distance sag from the vertex of the aspherical surface at a height of r along the optical axis, c is the radius of curvature, k is the conic coefficient, and α4, α6, α8, α... 10 En represents the aspherical coefficient; in aspherical data, En signifies ×10. -n.

[0067] The phase distribution function of the diffraction plane in ZEMAX software = M(B1r) 2 +B2r 4 +B3r 6 )

[0068] Where r is the normalized radius, with a value of 12.5, M is the diffraction order, and the diffraction order is 1; B1, B2, and B3 are the phase coefficients of the two-dimensional surface. The specific parameters of the diffraction surface S4 are shown in the table below:

[0069] M <![CDATA[B1]]> <![CDATA[B2]]> <![CDATA[B3]]> Diffraction surface S4 1 -29.69102 -18.92087 -6.57831

[0070] Based on the above data, we can obtain... Figures 3-8 The aforementioned technical specifications.

[0071] The optical transfer function (MTF) curve of this embodiment is as follows: Figures 3-5 As shown in the figure, the 10 curves represent the meridional and sagittal modulation transfer function curves at image plane heights of 0mm, 3mm, 4.5mm, 6mm, and 8.81mm, respectively. The horizontal axis represents the spatial frequency per line pair per millimeter (lp / mm), and the vertical axis represents the MTF value. A higher curve indicates better image quality, ideally reaching the diffraction limit. In the figure, OTF stands for optical transfer function, which in this embodiment is the optical modulation transfer function, i.e., MTF. T represents the meridional transfer function curve, and S represents the sagittal transfer function curve.

[0072] like Figure 3 As shown, these 10 curves indicate that, under the 1 / 2 frequency (Nyquist frequency in this embodiment is 62.5 lp / mm) condition, the meridional and sagittal modulation transfer function curves of the lens in this embodiment are all greater than or close to 0.3, except for the edge curve at 8.81 mm. Furthermore, the curves near the center, such as 0 mm and 3 mm, are close to the diffraction limit (TSDiff.limit), indicating that the imaging quality is good.

[0073] like Figure 4 and Figure 5 As shown, the 10 curves indicate that the MTF value of the lens in this embodiment is close to that at room temperature (+20℃) under high and low temperatures, which means that the imaging quality of the lens in this embodiment does not change with temperature within a certain temperature range.

[0074] like Figure 6 As shown, the size of the blur spots in the lens dot plot of this embodiment is smaller than or close to the Airy disk size, indicating that the imaging quality is good.

[0075] like Figure 7 As shown, the field curvature of the lens in this embodiment is between -0.05mm and +0.05mm, and the maximum absolute value of distortion is ≤2.5%.

[0076] like Figure 8 As shown, the lens of this embodiment has a center energy concentration of close to 0.8 and an edge energy concentration of more than 0.7 at a pixel size (8μm), indicating that the energy concentration of this embodiment is good.

[0077] Example 2

[0078] The difference between this embodiment and Embodiment 1 is as follows:

[0079] The large-aperture 2K resolution infrared lens in this embodiment has a maximum optical distortion of 2% and meets the following optical conditions:

[0080] Surface serial number Radius of curvature (mm) Interval (mm) Lens half-aperture Material Remark S1 27.13366 3.5 16.5 Chalcogenide Glass aspherical S2 21.63237 10.179 15 aspherical S3 35.20591 4.7 16.5 Chalcogenide Glass aspherical S4 59.83466 15.326 15 aspherical S5 31.92029 5.5 16.0 Chalcogenide Glass aspherical S6 212.72011 2.293 14.5 S7 22.47204 4.5 12.5 Chalcogenide Glass Diffraction aspheric surface S8 15.12056 7.00 9.5 S9 infinity 1 10 germanium S10 infinity 1 10

[0081] The relevant data for aspherical surfaces and aspherical diffraction surfaces are shown in the table below:

[0082] α4 α6 α8 α10 Aspherical S1 -4.579E-005 1.0951E-08 2.1025E-011 0 Aspherical S2 -6.449E-005 4.9090E-08 -3.053E-011 0 Aspherical S3 9.7379E-007 -5.635E-09 9.6939E-012 0 Aspherical S4 5.6156E-006 -1.198E-08 1.7148E-011 0 Aspherical S5 6.2683E-006 -9.080E-09 -1.725E-011 0 Diffraction aspheric surface S7 -2.452E-005 -1.230E-07 6.3133E-011 8.3084E-013

[0083] The specific parameters of diffraction plane S4 are shown in the table below:

[0084] M <![CDATA[B1]]> <![CDATA[B2]]> <![CDATA[B3]]> Diffraction surface S4 1 -23.454 -41.469 5.397

[0085] Based on the above data, we can obtain... Figures 9-12 The aforementioned technical specifications.

[0086] The optical transfer function (MTF) curve of this embodiment is as follows: Figure 9 As shown in the figure, the 10 curves represent the meridional and sagittal modulation transfer function curves at image plane heights of 0mm, 3mm, 4.5mm, 6mm, and 8.81mm, respectively. The horizontal axis represents the spatial frequency per line pair per millimeter (lp / mm), and the vertical axis represents the MTF value. A higher curve indicates better image quality, ideally reaching the diffraction limit. In the figure, OTF stands for optical transfer function, which in this embodiment is the optical modulation transfer function, i.e., MTF. T represents the meridional transfer function curve, and S represents the sagittal transfer function curve.

[0087] like Figure 9As shown, these 10 curves indicate that, under the 1 / 2 frequency (Nyquist frequency in this embodiment is 62.5 lp / mm) condition, the meridional and sagittal modulation transfer function curves of the lens in this embodiment are all greater than or close to 0.3, except for the edge curve at 8.81 mm. Furthermore, the curves near the center, such as 0 mm and 3 mm, are close to the diffraction limit (TSDiff.limit), indicating that the imaging quality is good.

[0088] like Figure 10 As shown, the size of the blur spots in the lens dot plot of this embodiment is smaller than or close to the size of the Airy disk, indicating that the imaging quality is good.

[0089] like Figure 11 As shown, the field curvature of the lens in this embodiment is between -0.05mm and +0.05mm, and the maximum absolute value of distortion is ≤2%.

[0090] like Figure 12 As shown, the lens of this embodiment has a center energy concentration of close to 0.8 and an edge energy concentration of close to 0.7 at a pixel size (8μm), indicating that the energy concentration of this embodiment is good.

[0091] The embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A large-aperture 2K resolution infrared lens, having four lenses with optical power, characterized in that, Along the direction of light incidence, there are sequentially arranged a first lens (1) with negative optical power, a second lens (2) with positive optical power, a third lens (3) with positive optical power, a fourth lens (4) with negative optical power, a detector protective glass (5), and an imaging target surface (6) of the detector. Among them, the first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) are all convex surfaces in the direction of light incidence and concave surfaces in the opposite direction of light incidence; and the radii of curvature of the first lens (1) to the fourth lens (4) satisfy the following conditions in sequence: 25 mm<R1<32 mm, 20 mm<R1′<25mm; 23 mm<R2<40 mm, 30 mm<R2′<60 mm; 27mm<R3<35 mm, 50 mm<R3′<240 mm; 18 mm<R4<25 mm, 15 mm<R4′<20 mm; Wherein, R1~R4 are the absolute values ​​of the radii of curvature of the first lens (1) to the fourth lens (4) in the direction of light incident, and R1′~R4′ are the absolute values ​​of the radii of curvature of the first lens (1) to the fourth lens (4) in the opposite direction of light incident. The air gap between the first lens (1) and the second lens (2) is 7~12mm, the air gap between the second lens (2) and the third lens (3) is 12~20mm, the air gap between the third lens (3) and the fourth lens (4) is 1.5~5mm, and the air gap between the fourth lens (4) and the detector protective glass (5) is 5~8mm.

2. The large-aperture 2K resolution infrared lens according to claim 1, characterized in that, The glass thicknesses of the first lens (1) to the fourth lens (4) are L1 to L4, respectively, and L1 to L4 satisfy the following relationship: 2.5mm < L1 < 5mm; 4mm < L2 < 8mm; 4mm < L3 < 8mm; 2.5mm < L4 < 6mm.

3. The large-aperture 2K resolution infrared lens according to claim 1, characterized in that, The first lens (1), the second lens (2), the third lens (3), and the fourth lens (4) are all made of chalcogenide glass.

4. The large-aperture 2K resolution infrared lens according to claim 1, characterized in that, The first lens (1), the second lens (2), the third lens (3), and the fourth lens (4) have a total of 8 curved surfaces, at least one of which is a diffractive aspherical surface, and they also have multiple aspherical surfaces.

5. A large-aperture 2K resolution infrared lens according to claim 1, characterized in that, The large-aperture 2K resolution infrared lens operates in the 8μm~12μm band and is used to match a 1920*1080@8μm uncooled long-wave infrared detector.

6. A large-aperture 2K resolution infrared lens according to claim 1, characterized in that, The large-aperture 2K resolution infrared lens has an F-number of 0.

8.

7. A large-aperture 2K resolution infrared lens according to claim 1, characterized in that, The large-aperture 2K resolution infrared lens has a diagonal field of view >40° and a maximum optical distortion ≤2.5%.

8. A large-aperture 2K resolution infrared lens according to claim 1, characterized in that, The large-aperture 2K resolution infrared lens adopts an optical passive calorimetric design, meaning that the imaging focal plane does not shift within the temperature range of -40℃ to 50℃.

Images