Low-distortion micro-luminous night vision lens adapted to 1-inch target surface

Abstract

The application provides a low-distortion micro-light night vision lens suitable for a 1-inch target surface, and relates to the technical field of photoelectricity. The lens is coaxially provided with, from the object side to the image side, a first meniscus positive lens, a first cemented lens group, a meniscus negative lens, a biconvex positive lens, a second cemented lens group, a second meniscus positive lens, a detector protection light window and an image surface. The lens uses two cemented lenses, cooperates the positive and negative lenses, introduces vignetting, reduces high-order aberration, eliminates chromatic aberration and secondary spectrum, and realizes better image quality.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic technology, and in particular to a low-distortion low-light night vision lens adapted to a 1-inch target surface. Background Technology

[0002] Due to the physiological characteristics of the human eye, it cannot perceive light intensity outside the visible light band (wavelength approximately 390-770nm). Even on nights without visible stars or moon, in addition to weak visible light, there is near-infrared radiation, also known as night sky radiation. To observe and acquire target information in pitch-black environments, it is necessary to use low-light night vision equipment to convert invisible light into visible light. Low-light night vision lenses primarily operate in low-light environments such as nighttime, when the human eye can barely distinguish the observed target, but low-light night vision equipment can respond to near-infrared light intensity. Low-light night vision equipment requires an objective lens to collect light and image it onto a photosensitive surface. Therefore, the objective lens must be matched with the night sky radiation spectrum and the response band of the low-light night vision detector, which presents significant design challenges—it requires correcting chromatic aberration over a wide spectral range.

[0003] The larger the relative aperture of a low-light objective, the stronger its light-gathering ability, allowing it to collect more night sky radiation and observe weaker targets. However, a large relative aperture makes it difficult to correct system aberrations. Therefore, low-light objectives have a more complex structure than telephoto objectives and are classified as photographic objectives.

[0004] Existing technologies disclose a large depth-of-field low-light night vision device, composed of five single lenses, emphasizing a large depth of field, but with a relatively small image plane, making it unsuitable for large image plane detectors. Also disclosed is a lightweight, compact low-light night vision objective lens optical system composed of six single lenses, incorporating three aspherical surfaces, achieving an F-number of 1.2, a maximum diameter of less than 30mm, and a length of less than 40mm. This system features numerous spacing elements and stringent assembly requirements. A low-light night vision front-facing lens with a catadioptric structure is also disclosed, achieving a final focal length of 68mm and a length of 184mm; however, this system is complex to manufacture and assemble. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a low-distortion low-light night vision lens adapted to a 1-inch target surface. It primarily achieves better image quality by using a combination of positive and negative lenses and introducing vignetting, thereby reducing higher aberrations, eliminating chromatic aberration, and reducing secondary spectral distortion.

[0006] The purpose of this invention is to provide a low-distortion low-light night vision lens adapted to a 1-inch target surface, comprising: a first meniscus positive lens, a first cemented lens group, a meniscus negative lens, a biconvex positive lens, a second cemented lens group, a second meniscus positive lens, a detector protective light window, and an image surface, arranged coaxially from the object side to the image side.

[0007] Preferably, the night vision lens has an F-number of 1.1, a focal length of 24mm, a maximum distortion of less than 0.41%, a total length of less than 35.2mm, a maximum aperture of less than 24mm, and operates in the range of 0.5-1μm.

[0008] Preferably, the first meniscus lens is made of optical glass material HZLAF50E, with an optical power of approximately 0.0277, and its front surface is coated with an anti-reflective coating, while its rear surface is coated with a neutral density filter.

[0009] Preferably, the first cemented lens group is composed of a biconcave lens and a meniscus lens cemented together sequentially from the object side to the image side, and the front and rear surfaces of the cemented lens group are coated with anti-reflective coatings; the biconcave lens is made of optical glass material HZF3; and the meniscus lens is made of optical glass material HLAF3B.

[0010] Preferably, the meniscus negative lens is made of optical glass material HZPK1A, and its front and rear surfaces are coated with anti-reflective films.

[0011] Preferably, the biconvex positive lens is made of optical glass material HLAF3B, and its front and rear surfaces are coated with anti-reflective coatings.

[0012] Preferably, the second cemented lens group is composed of a positive lens and a negative lens cemented together sequentially from the object side to the image side; the front and rear surfaces of the cemented lens group are coated with anti-reflective coatings, the positive lens is made of optical glass material HZLAF55D, the negative lens is made of optical glass material HZF52, and the front surface of the positive lens is an aperture stop.

[0013] Preferably, the second meniscus lens is made of optical glass material HZK10L, and its front and rear surfaces are coated with anti-reflective coatings.

[0014] Preferably, the on-axis distance between the first meniscus positive lens and the first cemented lens group is 1.532 mm; the on-axis distance between the first cemented lens group and the meniscus negative lens is 1.65 mm; the on-axis distance between the meniscus negative lens and the biconvex positive lens is 4.34 mm; the on-axis distance between the biconvex positive lens and the second cemented lens group is 0.1 mm; and the on-axis distance between the second cemented lens group and the second meniscus positive lens is 1.7 mm.

[0015] Preferably, the distance from the detector's protective light window to the rear surface of the second meniscus lens is 4.1 mm.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention provides a low-distortion low-light night vision lens adapted to a 1-inch target surface, applicable to a wide-band low-light night vision optical system in the 0.5-1μm wavelength range. It has a focal length of 24mm, an F-number of 1.1, a maximum distortion of less than 0.41%, a total length of less than 35.2mm, and a maximum aperture of less than 24mm. The entire optical system consists of six groups of eight lenses along the light incident direction, including four single lenses and two cemented doublet lenses. The large relative aperture optical system uses ordinary optical glass and does not use aspherical surfaces, making it suitable for mass production. The almost negligible distortion value maximizes the reproduction of the actual scene and reduces visual fatigue.

[0018] The advantages of this invention are:

[0019] 1. The optical system consists of 6 groups of 8 spherical lenses, which can be mass-produced, reducing processing costs and processing cycle.

[0020] 2. The lens has an F-number of 1.1, enabling 10mm f / s. -3 Imaging under ultra-low illumination conditions in Lx;

[0021] 3. The lens operates in a wavelength range of 0.5-1μm, which is much larger than the common 0.6-0.9μm operating wavelength range, allowing it to collect more energy and achieve ultra-low light imaging;

[0022] 4. The lens is compatible with imaging detectors with a 1-inch large target surface.

[0023] 5. The lens exhibits low distortion performance of less than 0.41% across the entire field of view.

[0024] The lens provided by this invention uses two cemented lenses. By combining positive and negative lenses and introducing vignetting, it reduces higher aberrations, eliminates chromatic aberration and secondary spectrum, thereby achieving better image quality. Attached Figure Description

[0025] Figure 1 This is a structural view of the optical system of the present invention;

[0026] Figure 2 This is the optical MTF evaluation chart at room temperature (20°C) of this invention;

[0027] Figure 3 This is the distorted mesh diagram of the present invention. Detailed Implementation

[0028] The following describes several specific embodiments of the present invention in detail, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0029] This invention provides a low-distortion low-light night vision lens adapted to a 1-inch target surface. Based on a 1-inch large-area CMOS array, an ultra-wideband low-light night vision optical system for the 0.5-1μm wavelength range is designed, with a focal length of 24mm, an F-number of 1.1, a maximum distortion of less than 0.41%, a total length of less than 35.2mm, and a maximum aperture of less than 24mm. The entire optical system consists of six groups of eight spherical lenses along the light incident direction, achieving a reduction in processing costs and a shorter production cycle compared to aspherical systems. Groups 2 and 5 are negative power cemented doublet lenses, group 3 is a negative power single lens, and the rest are positive power single lenses. The system uses cemented doublet lenses to reduce higher-order aberrations and achromatic aberration; and introduces vignetting to reduce edge ray aberrations, thereby improving image quality.

[0030] This invention provides a low-distortion low-light night vision lens adapted to a 1-inch target surface, see [link / reference]. Figures 1-3 As shown, the lens includes: a first meniscus positive lens 1, a first cemented lens group 2, a meniscus negative lens 3, a biconvex positive lens 4, a second cemented lens group 5, a second meniscus positive lens 6, a detector protective light window 7, and an image plane 8, arranged coaxially from the object side to the image side. The night vision lens has an F-number of 1.1, a focal length of 24mm, a maximum distortion of less than 0.41%, a total length of less than 35.2mm, a maximum aperture of less than 24mm, and operates in the 0.5-1μm range.

[0031] Specifically, the first meniscus lens 1 is made of optical glass material HZLAF50E, with an optical power of approximately 0.0277. Its front surface is coated with an anti-reflective coating, and its rear surface is coated with a neutral density filter.

[0032] In this embodiment, the meniscus lens [1] is made of optical glass material HZLAF50E with an optical power of about 0.0277. The front surface of the single lens is the left side surface, and the rear surface is the right side surface near the image plane 8. It is coated with an anti-reflection film of 0.48-1.02μm with a transmittance of >98.5%, which will not be described in detail below. The rear surface is coated with a neutral density filter film of 0.5-1μm with a transmittance of >96%, and the transmittance is <1% at <0.47μm.

[0033] Specifically, the first cemented lens group 2 is composed of a biconcave lens 201 and a meniscus lens 202 cemented together sequentially from the object side to the image side. The front and rear surfaces of the cemented lens group are coated with anti-reflective coatings, and its optical power is approximately -0.0173. The biconcave lens 201 is made of optical glass material HZF3, and the meniscus lens 202 is made of optical glass material HLAF3B.

[0034] Specifically, the meniscus negative lens 3 is made of optical glass material HZPK1A, with an optical power of approximately -0.00444, and its front and rear surfaces are coated with anti-reflective coatings.

[0035] The biconvex positive lens 4 is made of optical glass material HLAF3B, with an optical power of approximately 0.0312, and its front and rear surfaces are coated with anti-reflective coatings.

[0036] The second cemented lens group 5 is composed of a positive lens 501 and a negative lens 502 cemented together sequentially from the object side to the image side; the front and rear surfaces of the cemented lens group are coated with anti-reflective coatings, and its optical power is approximately -0.000273; the positive lens 501 is made of optical glass material HZLAF55D; the negative lens 502 is made of optical glass material HZF52; the front surface of the positive lens 501 is an aperture stop.

[0037] The second meniscus lens 6 is made of HZK10L optical glass material, with an optical power of approximately 0.00985, and its front and rear surfaces are coated with anti-reflective coatings.

[0038] Specifically, the on-axis distance between the first meniscus positive lens 1 and the first cemented lens group 2 is 1.532 mm; the on-axis distance between the first cemented lens group 2 and the meniscus negative lens 3 is 1.65 mm; the on-axis distance between the meniscus negative lens 3 and the biconvex positive lens 4 is 4.34 mm; the on-axis distance between the biconvex positive lens 4 and the second cemented lens group 5 is 0.1 mm; and the on-axis distance between the second cemented lens group 5 and the second meniscus positive lens 6 is 1.7 mm.

[0039] The distance from the detector's protective light window 7 to the rear surface of the second meniscus lens 6 on the axis is 4.1 mm.

[0040] The specific parameters of the optical system of the lens provided by this invention are shown in the table below:

[0041]

[0042]

[0043] Based on this, optical imaging with smaller F-numbers can be achieved by changing the aperture stop diameter. Alternatively, further optimization can be performed to obtain optical systems with other focal lengths, all of which fall within the scope of protection declared in this invention.

[0044] Figure 2 This is the optical MTF evaluation chart at room temperature (20°C) of this invention. The horizontal axis represents resolution, with units of lp / mm: For a 1-inch target detector, at an intermediate frequency of 14 lp / mm, the on-axis center field of view MTF > 0.87, the 0.7 field of view MTF 0.75, and the full field of view MTF > 0.48; at a high frequency of 30 lp / mm, the on-axis center field of view MTF > 0.6, the 0.7 field of view MTF 0.43, and the full field of view MTF > 0.29.

[0045] Figure 3This is the distortion grid diagram of the present invention. The horizontal and vertical axes represent the image plane size, respectively. The solid grid lines represent the ideal image height of the grid space on the image plane, and the dashed lines represent the actual image height of the same grid space on the image plane. The difference between the two is the distortion. The smaller the difference, the smaller the distortion. According to the diagram, the maximum lens distortion is <0.41%.

[0046] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A low-distortion low-light night vision lens adapted to a 1-inch target surface, characterized in that, include: The first meniscus positive lens (1), the first cemented lens group (2), the meniscus negative lens (3), the biconvex positive lens (4), the second cemented lens group (5), the second meniscus positive lens (6), the detector protection window (7), and the image plane (8) are arranged coaxially from the object side to the image side. The night vision lens has an F-number of 1.1, a focal length of 24mm, a maximum distortion of less than 0.41%, a total length of less than 35.2mm, a maximum aperture of less than 24mm, and operates in the range of 0.5-1μm. The first meniscus lens (1) is made of optical glass material HZLAF50E, with an optical power of about 0.0277. Its front surface is coated with an anti-reflective coating, and its rear surface is coated with a neutral density filter. The first cemented lens group (2) is composed of a biconcave lens (201) and a meniscus lens (202) cemented together from the object side to the image side. The front and rear surfaces of the cemented lens group are coated with anti-reflective coatings. The biconcave lens (201) is made of optical glass material HZF3. The meniscus lens (202) is made of optical glass material HLAF3B. The second cemented lens group (5) is composed of a positive lens (501) and a negative lens (502) cemented together from the object side to the image side; the front and rear surfaces of the cemented lens group are coated with anti-reflective coatings; the positive lens (501) is made of optical glass material HZLAF55D; the negative lens (502) is made of optical glass material HZF52; the front surface of the positive lens (501) is an aperture stop. The on-axis distance between the first meniscus positive lens (1) and the first cemented lens group (2) is 1.532 mm; the on-axis distance between the first cemented lens group (2) and the meniscus negative lens (3) is 1.65 mm; the on-axis distance between the meniscus negative lens (3) and the biconvex positive lens (4) is 4.34 mm; the on-axis distance between the biconvex positive lens (4) and the second cemented lens group (5) is 0.1 mm; and the on-axis distance between the second cemented lens group (5) and the second meniscus positive lens (6) is 1.7 mm.

2. The low-distortion low-light night vision lens adapted to a 1-inch target surface according to claim 1, characterized in that, The meniscus negative lens (3) is made of optical glass material HZPK1A, and its front and back surfaces are coated with anti-reflective coatings.

3. The low-distortion low-light night vision lens adapted to a 1-inch target surface according to claim 1, characterized in that, The biconvex positive lens (4) is made of optical glass material HLAF3B, and its front and back surfaces are coated with anti-reflective coatings.

4. The low-distortion low-light night vision lens adapted to a 1-inch target surface according to claim 1, characterized in that, The second meniscus lens (6) is made of optical glass material HZK10L, and its front and back surfaces are coated with anti-reflective coatings.

5. The low-distortion low-light night vision lens adapted to a 1-inch target surface according to claim 1, characterized in that, The distance from the detector's protective light window (7) to the rear surface of the second meniscus lens (6) is 4.1 mm.

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