Low-cost miniaturized visible / infrared common-aperture athermalization optical system

Abstract

A low-cost miniaturized visible / infrared common-aperture athermalization optical system is characterized in that the system comprises a visible light optical system and a long-wave infrared optical system, and a visible light and long-wave infrared common-aperture and common-optical-axis design is achieved by taking a composite reflector with a hole formed in the center of an infrared lens as an optical hinge. Wherein the visible light optical system is sequentially provided with a common fairing, a visible light lens I, a visible light bonding lens II, a visible light bonding lens III, a visible light lens IV, a reflector and a visible light detector photosensitive surface from outside to inside in the light propagation direction; the long-wave infrared optical system is sequentially provided with a common fairing, an infrared lens I, an infrared lens II, an infrared lens III and a long-wave infrared detector photosensitive surface from outside to inside in the light propagation direction; a hole is formed in the center of the infrared lens I; the photosensitive surface of the visible light detector and the photosensitive surface of the infrared detector are arranged at an angle of 70 degrees. The system is wide in working wave band, excellent in imaging quality, low in cost, compact in structure and high in battlefield environment adaptability.

Description

Technical Field

[0001] The present invention belongs to the field of optical technology, and more particularly, relates to a low-cost miniaturized visible / infrared common-aperture athermalized optical system. Background Art

[0002] With the increasing levels and complexity of countermeasures against precision-guided weapons, in the ever-changing modern battlefield environment, single-mode guidance is difficult to meet the needs of precision strikes. Therefore, multi-band common-aperture compound optical systems have developed rapidly. A multi-band common-aperture compound optical system can achieve the fusion and focusing of two or more spectral bands within a limited aperture, obtaining more target and background information, and having the advantages of high fusion degree and high space utilization rate. The present invention designs a low-cost miniaturized visible / infrared common-aperture athermalized optical system, including a visible-light optical system and a long-wave infrared optical system. Through a compound mirror with a central opening in the infrared lens as an optical hinge, the common-aperture and co-optical-axis design of visible light and long-wave infrared is realized. The working bands of this system are 410nm - 760nm and 8μm - 14μm, and it has excellent imaging quality within the working temperature range of -40°C to +60°C. It has few optical elements, 100% domestic optical materials, low cost, a compact structure, small volume, and light weight, and has strong adaptability to the battlefield environment and anti-interference ability.

[0003] CN109975961A proposes a common-aperture compound imaging optical system for visible light and long-wave infrared. Its solution uses a prism to deflect the optical path and then a mirror to deflect it a second time. The optical axis of the visible-light optical system and the optical axis of the infrared optical system are basically parallel, occupying a relatively large space, having a relatively large number of optical elements, and a relatively long visible-light optical path, which poses relatively high alignment requirements for the visible-light image quality and the coaxial alignment of the visible-light optical axis and the infrared optical axis. The solution involved in the present invention only deflects the optical path through one mirror, and the optical axis of the visible-light optical system and the optical axis of the infrared optical system are set at an angle of 70°. Moreover, all the optical lenses of the visible-light optical system are concentrated within the opening of the infrared lens, with few elements, a simple structure, and a small occupied space, making it easier to align the visible-light image quality and the coaxial alignment of the visible-light optical axis and the infrared optical axis. There are obvious essential differences between the above two solutions. Summary of the Invention

[0004] The object of the present invention is to provide a low-cost miniaturized visible / infrared common-aperture athermalized optical system, which includes a visible-light optical system and a long-wave infrared optical system. By using a compound mirror with a central opening in the infrared lens as an optical hinge, the common-aperture and co-optical-axis design of visible light and long-wave infrared is realized. The working wavelength range of this system is 410nm - 760nm and 8μm - 14μm, and it has excellent imaging quality within the working temperature range of -40°C to +60°C. It has few optical elements, 100% of the optical materials are domestic, low cost, compact structure, small volume, light weight, and has strong adaptability to battlefield environment and anti-interference ability.

[0005] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0006] A low-cost miniaturized visible / infrared common-aperture athermalized optical system, which includes a visible-light optical system and a long-wave infrared optical system. By using a compound mirror with a central opening in the infrared lens as an optical hinge, the common-aperture and co-optical-axis design of visible light and long-wave infrared is realized.

[0007] In the described low-cost miniaturized visible / infrared common-aperture athermalized optical system, the visible-light optical system is sequentially provided with a common radome, a first visible-light lens, a second visible-light cemented lens, a third visible-light cemented lens, a fourth visible-light lens, a mirror, and the photosensitive surface of the visible-light detector from outside to inside in the light propagation direction; the long-wave infrared optical system is sequentially provided with a common radome, a first infrared lens, a second infrared lens, a third infrared lens, and the photosensitive surface of the long-wave infrared detector from outside to inside in the light propagation direction, and the first infrared lens has a central opening; the photosensitive surface of the visible-light detector and the photosensitive surface of the infrared detector are placed at 70°.

[0008] In the described low-cost miniaturized visible / infrared common-aperture athermalized optical system, the common radome is a spherical concentric lens. In the visible-light optical system, a total of 4 lens elements and 1 mirror element are included. All the lenses are spherical lenses, and the mirror is a plane mirror; in the long-wave infrared optical system, a total of 3 lens elements are included, where the first infrared lens is an aspherical & diffractive lens and has a central opening, and the second infrared lens and the third infrared lens are spherical lenses.

[0009] The described low-cost miniaturized visible / infrared common-aperture athermalized optical system uses domestic Chengdu Guangming materials for all optical elements in the system, and the common radome is made of ZNS_BROAD material. In the visible-light optical system, the first visible-light lens is made of H-ZLAF52 material; the second visible-light cemented lens is made by cementing H-ZBAF50 material and H-ZLAF52 material; the third visible-light cemented lens is made by cementing H-FK61 material and H-LAF3B material; the fourth visible-light lens is made of H-ZK21 material; the mirror is made of H-K9L material; in the long-wave infrared optical system, the first infrared lens is made of IRG206 material; the second and third infrared lenses are both made of GE material.

[0010] The described low-cost miniaturized visible / infrared common-aperture athermalized optical system The total weight of the optical system (excluding the radome) < 210 g.

[0011] The described low-cost miniaturized visible / infrared common-aperture athermalized optical system, where the working band of the visible-light optical system is 410 nm to 760 nm, the focal length is 48 mm, the F number is 5.6, the field of view size is 8.2° × 6.6°, the detector uses a high-resolution visible-light detector with a resolution of 1280 × 1024 and a pixel size of 5.4 μm, the single-pixel angular subtense ≤ 112 urad, the system distortion ≤ 0.1%, the relative illuminance uniformity value of the image plane > 98%, at room temperature of 20 °C, at 90 lp / mm, the modulation transfer function value of the 0 field of view ≥ 0.55, and the transfer function values of the remaining fields of view ≥ 0.4; at low temperature of -40 °C, at 90 lp / mm, the modulation transfer function value of the 0 field of view ≥ 0.54, and the transfer function values of the remaining fields of view ≥ 0.4; at high temperature of +60 °C, at 90 lp / mm, the modulation transfer function value of the 0 field of view ≥ 0.54, and the transfer function values of the remaining fields of view ≥ 0.4.

[0012] The described low-cost miniaturized visible / infrared common-aperture athermalized optical system, where the working band of the long-wave infrared optical system is 8 μm to 14 μm, the focal length is 76 mm, the F-number is 1, the field of view size is 11.5° × 9.2°, the detector selects a high-resolution long-wave uncooled infrared detector with a resolution of 1280 × 1024 and a pixel size of 12 μm, the single-pixel angular subtense ≤ 157 urad, the system distortion ≤ 0.8%, the relative illuminance uniformity value of the image plane > 98%, at room temperature of 20 °C, at 42 lp / mm, the modulation transfer function value of the 0 field of view ≥ 0.42, and the transfer function values of the remaining fields of view ≥ 0.36; at low temperature of -40 °C, at 42 lp / mm, the modulation transfer function value of the 0 field of view ≥ 0.42, and the transfer function values of the remaining fields of view ≥ 0.35; at high temperature of +60 °C, at 42 lp / mm, the modulation transfer function value of the 0 field of view ≥ 0.42, and the transfer function values of the remaining fields of view ≥ 0.38.

[0013] The described low-cost miniaturized visible / infrared common-aperture athermalized optical system has a working band of 410 nm to 760 nm and 8 μm to 14 μm, and has excellent imaging quality within the working temperature range of -40 °C to +60 °C, with a small number of optical elements, 100% domestic optical materials, low cost, compact structure, small volume, and light weight, and has strong battlefield environment adaptability and anti-interference ability.

[0014] The beneficial effects of the present invention compared with the prior art are as follows:

[0015] 1. The described low-cost miniaturized visible / infrared common-aperture athermalized optical system of the present invention, where the working band of the visible light optical system is 410 nm to 760 nm, the focal length is 48 mm, the F-number is 5.6, the field of view size is 8.2° × 6.6°, the detector selects a high-resolution visible light detector with a resolution of 1280 × 1024 and a pixel size of 5.4 μm, the single-pixel angular subtense ≤ 112 urad, the system distortion ≤ 0.1%, the relative illuminance uniformity value of the image plane > 98%, and has the technical characteristics of a wide working band, high resolution, small distortion, rich image details, and good uniformity.

[0016] 2. The described low-cost miniaturized visible / infrared common-aperture athermalized optical system of the present invention, where the working band of the long-wave infrared optical system is 8 μm to 14 μm, the focal length is 76 mm, the F-number is 1, the field of view size is 11.5° × 9.2°, the detector selects a high-resolution long-wave uncooled infrared detector with a resolution of 1280 × 1024 and a pixel size of 12 μm, the single-pixel angular subtense ≤ 157 urad, the system distortion ≤ 0.8%, the relative illuminance uniformity value of the image plane > 98%, and has the technical characteristics of a small F-number, large relative aperture, strong light-gathering ability, and can work all day long.

[0017] 3. A low-cost miniaturized visible / infrared common-aperture athermalized optical system described in the present invention uses a compound mirror with a central hole in the infrared lens as an optical hinge to achieve a common-aperture and common optical axis design for visible light and long-wave infrared. The total weight of the optical system (excluding the radome) < 210 g. To adapt to extremely harsh working conditions and considering the low cost and domestic demand of the system, domestic Chengdu Guangming glass is selected as the lens material, with excellent imaging quality in the working temperature range of -40°C to +60°C, few optical elements, 100% domestic optical materials, low cost, compact structure, small volume, light weight, and strong adaptability to the battlefield environment and anti-interference ability. Brief Description of the Drawings

[0018] Figure 1 It is a structural diagram of a low-cost miniaturized visible / infrared common-aperture athermalized optical system;

[0019] Figure 2 It is the modulation transfer function curve of the visible light optical system at a working temperature of +20°C;

[0020] Figure 3 It is the modulation transfer function curve of the visible light optical system at a working temperature of -40°C;

[0021] Figure 4 It is the modulation transfer function curve of the visible light optical system at a working temperature of +60°C;

[0022] Figure 5 It is the grid distortion diagram of the visible light optical system;

[0023] Figure 6 It is the relative illuminance uniformity curve of the image plane of the visible light optical system;

[0024] Figure 7 It is the modulation transfer function curve of the long-wave infrared optical system at a working temperature of +20°C;

[0025] Figure 8 It is the modulation transfer function curve of the long-wave infrared optical system at a working temperature of -40°C;

[0026] Figure 9 It is the modulation transfer function curve of the long-wave infrared optical system at a working temperature of +60°C;

[0027] Figure 10 It is the grid distortion diagram of the long-wave infrared optical system;

[0028] Figure 11 It is the relative illuminance uniformity curve of the image plane of the long-wave infrared optical system.

[0029] Reference Signs

[0030] 1 - Common fairing; 2 - Visible light lens one; 3 - Visible light cemented lens two; 4 - Visible light cemented lens three; 5 - Visible light lens four; 6 - Mirror; 7 - Photosensitive surface of visible light detector; 8 - Infrared lens one; 9 - Infrared lens two; 10 - Infrared lens three; 11 - Photosensitive surface of long - wave infrared detector. Detailed implementation mode

[0031] The present invention will be introduced in detail below with reference to the accompanying drawings.

[0032] Embodiment 1

[0033] This embodiment describes a low - cost miniaturized visible / infrared common - aperture athermalized optical system, which is characterized in that: the system includes a visible - light optical system and a long - wave infrared optical system. Through an infrared lens with a central opening and a composite mirror as an optical hinge, the common - aperture and co - optical - axis design of visible light and long - wave infrared is realized. Among them, the visible - light optical system is sequentially provided with a common fairing, a visible - light lens one, a visible - light cemented lens two, a visible - light cemented lens three, a visible - light lens four, a mirror, and a photosensitive surface of a visible - light detector from outside to inside in the light propagation direction; the long - wave infrared optical system is sequentially provided with a common fairing, an infrared lens one, an infrared lens two, an infrared lens three, and a photosensitive surface of a long - wave infrared detector from outside to inside in the light propagation direction, and the infrared lens one has a central opening; the photosensitive surface of the visible - light detector and the photosensitive surface of the infrared detector are placed at 70°. The working wavelength range of this system is 410nm - 760nm and 8μm - 14μm, and it has excellent imaging quality within the working temperature range of - 40°C to + 60°C. It has few optical elements, 100% of the optical materials are domestic, low cost, compact structure, small volume, light weight, and has strong adaptability to the battlefield environment and anti - interference ability.

[0034] Embodiment 2

[0035] This embodiment describes a low-cost miniaturized visible / infrared common-aperture athermalized optical system, characterized in that: the system includes a visible-light optical system and a long-wave infrared optical system. An infrared lens with a central aperture and a compound mirror are used as an optical hinge to achieve common-aperture and co-optical-axis design for visible light and long-wave infrared. Among them, the visible-light optical system is sequentially provided with a shared radome, a first visible-light lens, a second visible-light cemented lens, a third visible-light cemented lens, a fourth visible-light lens, a mirror, and a photosensitive surface of a visible-light detector in the light propagation direction from outside to inside; the long-wave infrared optical system is sequentially provided with a shared radome, a first infrared lens, a second infrared lens, a third infrared lens, a photosensitive surface of a long-wave infrared detector, and the first infrared lens has a central aperture in the light propagation direction from outside to inside; the photosensitive surface of the visible-light detector and the photosensitive surface of the infrared detector are placed at 70°. The working bands of this system are 410nm - 760nm and 8μm - 14μm, and it has excellent imaging quality within the working temperature range of -40°C to +60°C. It has few optical elements, 100% of the optical materials are domestic, low cost, compact structure, small size, light weight, and has strong adaptability to the battlefield environment and anti-interference ability.

[0036] For the described low-cost miniaturized visible / infrared common-aperture athermalized optical system, the shared radome is a spherical concentric circle lens. In the visible-light optical system, there are a total of 4 lens elements and 1 mirror element. All the lenses are spherical lenses, and the mirror is a plane mirror; in the long-wave infrared optical system, there are a total of 3 lens elements. The first infrared lens is an aspherical & diffractive lens and has a central aperture, and the second and third infrared lenses are spherical lenses.

[0037] For the described low-cost miniaturized visible / infrared common-aperture athermalized optical system, all the optical element materials in the system are domestic Chengdu Guangming materials, and the shared radome is made of ZNS_BROAD material. In the visible-light optical system, the first visible-light lens is made of H-ZLAF52 material; the second visible-light cemented lens is cemented by H-ZBAF50 material and H-ZLAF52 material; the third visible-light cemented lens is cemented by H-FK61 material and H-LAF3B material; the fourth visible-light lens is made of H-ZK21 material; the mirror is made of H-K9L material; in the long-wave infrared optical system, the first infrared lens is made of IRG206 material; the second and third infrared lenses are both made of GE material.

[0038] For the described low-cost miniaturized visible / infrared common-aperture athermalized optical system, The total weight of the optical system (excluding the head cover) < 210g.

[0039] This technical solution defines the materials, quantities, surface profiles, external dimensions, and weights of each lens. To adapt to extremely harsh working conditions and considering the low-cost and domestic production requirements of the system, domestic Chengdu Guangming glass is selected as the lens material, which has the characteristics of a compact structure, small size, light weight, and strong environmental adaptability.

[0040] Embodiment 3

[0041] This embodiment describes a low-cost miniaturized visible / infrared common-aperture athermalized optical system, which is characterized in that: the system includes a visible-light optical system and a long-wave infrared optical system. Through a compound mirror with a central opening in the infrared lens as an optical hinge, common-aperture and co-optical-axis designs for visible light and long-wave infrared are realized. Among them, the visible-light optical system is sequentially provided with a common radome, a first visible-light lens, a second visible-light cemented lens, a third visible-light cemented lens, a fourth visible-light lens, a mirror, and a photosensitive surface of the visible-light detector from outside to inside in the light propagation direction; the long-wave infrared optical system is sequentially provided with a common radome, a first infrared lens, a second infrared lens, a third infrared lens, and a photosensitive surface of the long-wave infrared detector from outside to inside in the light propagation direction, and the first infrared lens has a central opening; the photosensitive surface of the visible-light detector and the photosensitive surface of the infrared detector are placed at 70°. The working bands of this system are 410nm - 760nm and 8μm - 14μm, and it has excellent imaging quality within the working temperature range of -40°C to +60°C. It has a small number of optical elements, 100% domestic optical materials, low cost, a compact structure, small volume, light weight, and strong battlefield environment adaptability and anti-interference ability.

[0042] For the described low-cost miniaturized visible / infrared common-aperture athermalized optical system, the visible-light optical system has a working band of 410nm - 760nm, a focal length of 48mm, an F-number of 5.6, a field of view size of 8.2°×6.6°, and a high-resolution visible-light detector with a resolution of 1280×1024 and a pixel size of 5.4μm is selected. The angular subtense of a single pixel ≤112urad, the system distortion ≤0.1%, the relative illuminance uniformity value of the image plane >98%. At room temperature of 20°C, at 90lp / mm, the modulation transfer function value of the 0 field of view ≥0.55, and the transfer function values of the remaining fields of view ≥0.4. At low temperature of -40°C, at 90lp / mm, the modulation transfer function value of the 0 field of view ≥0.54, and the transfer function values of the remaining fields of view ≥0.4. At high temperature of +60°C, at 90lp / mm, the modulation transfer function value of the 0 field of view ≥0.54, and the transfer function values of the remaining fields of view ≥0.4.

[0043] The described low-cost miniaturized visible / infrared common-aperture athermalized optical system, where the working band of the long-wave infrared optical system is 8μm to 14μm, the focal length is 76mm, the F number is 1, the field of view size is 11.5°×9.2°, the detector selected is a high-resolution long-wave uncooled infrared detector with a resolution of 1280×1024 and a pixel size of 12μm, the single-pixel angular resolution ≤157urad, the system distortion ≤0.8%, the relative irradiance uniformity value of the image plane >98%, at room temperature of 20°C, at 42lp / mm, the modulation transfer function value of the 0 field of view ≥0.42, and the transfer function values of the remaining fields of view ≥0.36; at low temperature of -40°C, at 42lp / mm, the modulation transfer function value of the 0 field of view ≥0.42, and the transfer function values of the remaining fields of view ≥0.35; at high temperature of +60°C, at 42lp / mm, the modulation transfer function value of the 0 field of view ≥0.42, and the transfer function values of the remaining fields of view ≥0.38.

[0044] This technical solution defines technical parameters such as the working band, focal length, F number, field of view size, detector resolution, pixel size, single-pixel angular resolution, transfer function, and relative irradiance uniformity of the image plane of the optical system, and has the technical characteristics of a wide working band, a small F number, a large relative aperture, strong light-gathering ability, high resolution, small distortion, rich image details, and the ability to work all day long.

[0045] Working principle of the optical imaging detection system

[0046] The optical imaging detection system (hereinafter referred to as the system) consists of 6 parts: a protective window, a housing cabin, an optical system, an imaging detector, an image processing and signal transmission system, and a terminal control system. Among them, the protective window and the housing cabin form a sealed space to protect the internal components of the system, and have the characteristics of high strength, high hardness, radiation resistance, high temperature resistance, and high transmittance, ensuring the normal operation of the system in complex working conditions. The optical system is used to receive the reflected information inherent in the target and the background and converge it onto the photosensitive surface of the imaging detector. The imaging detector converts the optical signal into an electrical signal to achieve optoelectronic conversion, and has high sensitivity and small spatial resolution. The image processing and signal transmission system processes the received data information and transmits it to the terminal control system. The terminal control system analyzes and judges the received data information and sends control commands to achieve the detection, identification, and precise positioning of the target. This invention only elaborates in detail on the optical system and does not specifically describe other subsystems.

[0047] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A low-cost miniaturized visible / infrared common-aperture athermalized optical system, characterized in that: The system includes a visible-light optical system and a long-wave infrared optical system. An infrared lens with a central opening and a compound mirror are used as an optical hinge to achieve the design of common aperture and common optical axis for visible light and long-wave infrared. The visible-light optical system is sequentially provided with a common radome (1), a first visible-light lens (2), a second visible-light cemented lens (3), a third visible-light cemented lens (4), a fourth visible-light lens (5), a mirror (6), and a photosensitive surface of a visible-light detector (7) from outside to inside in the light propagation direction; the long-wave infrared optical system is sequentially provided with a common radome (1), a first infrared lens (8), a second infrared lens (9), a third infrared lens (10), and a photosensitive surface of a long-wave infrared detector (11) from outside to inside in the light propagation direction. The first infrared lens (8) has a central opening; the photosensitive surface of the visible-light detector (7) and the photosensitive surface of the infrared detector (11) are placed at 70°. The working band of the system is 410nm - 760nm and 8μm - 14μm, and it has excellent imaging quality within the working temperature range of -40°C to +60°C, with a small number of optical elements, 100% domesticated optical and mechanical materials, low cost, compact structure, small volume, light weight, and strong adaptability to battlefield environment and anti-interference ability.

2. A low-cost miniaturized visible / infrared common-aperture athermalized optical system according to claim 1, characterized in that: The materials of the optical elements in the system are all domestic Chengdu Guangming materials. The common radome (1) is a spherical concentric circle lens. In the visible-light optical system, there are a total of 4 lens elements and 1 mirror element. All lenses are spherical lenses, and the mirror is a plane mirror. The first visible-light lens (2) is made of H-ZLAF52 material; the second visible-light cemented lens (3) is cemented by H-ZBAF50 material and H-ZLAF52 material; the third visible-light cemented lens (4) is cemented by H-FK61 material and H-LAF3B material; the fourth visible-light lens (5) is made of H-ZK21 material; the mirror (6) is made of H-K9L material. In the long-wave infrared optical system, there are a total of 3 lens elements. Among them, the first infrared lens (8) is an aspherical & diffractive lens with a central aperture, and the second infrared lens (9) and the third infrared lens (10) are spherical lenses. The first infrared lens (8) is made of IRG206 material; the second infrared lens (9) and the third infrared lens (10) are both made of GE material; the external dimensions of the optical system (excluding the hood) < The total weight of the optical system (excluding the hood) < 210 g.

3. A low-cost miniaturized visible / infrared common-aperture athermalized optical system according to claim 1, characterized in that: The system includes a visible light optical system and a long-wave infrared optical system. The working band of the visible light optical system is 410nm - 760nm, the focal length is 48mm, the F number is 5.6, the field of view size is 8.2°×6.6°, the detector selected is a high-resolution visible light detector with a resolution of 1280×1024 and a pixel size of 5.4μm, the angular subtense of a single pixel ≤112urad, the system distortion ≤0.1%, the relative illuminance uniformity value of the image plane >98%. At room temperature of 20°C, at 90lp / mm, the modulation transfer function value of the 0 field of view ≥0.55, and the transfer function values of the other fields of view ≥0.

4. At low temperature of -40°C, at 90lp / mm, the modulation transfer function value of the 0 field of view ≥0.54, and the transfer function values of the other fields of view ≥0.

4. At high temperature of +60°C, at 90lp / mm, the modulation transfer function value of the 0 field of view ≥0.54, and the transfer function values of the other fields of view ≥0.4; Among them, the working band of the long-wave infrared optical system is 8μm - 14μm, the focal length is 76mm, the F number is 1, the field of view size is 11.5°×9.2°, the detector selected is a high-resolution long-wave uncooled infrared detector with a resolution of 1280×1024 and a pixel size of 12μm, the angular subtense of a single pixel ≤157urad, the system distortion ≤0.8%, the relative illuminance uniformity value of the image plane >98%. At room temperature of 20°C, at 42lp / mm, the modulation transfer function value of the 0 field of view ≥0.42, and the transfer function values of the other fields of view ≥0.

36. At low temperature of -40°C, at 42lp / mm, the modulation transfer function value of the 0 field of view ≥0.42, and the transfer function values of the other fields of view ≥0.

35. At high temperature of +60°C, at 42lp / mm, the modulation transfer function value of the 0 field of view ≥0.42, and the transfer function values of the other fields of view ≥0.38.

Images