Design of infrared optical lens on various infrared thermal imager
Infrared imaging is to converge the detected optical signal to the detector through the lens group, and then convert the optical signal to the electrical signal from the detector and its rear channel. Detectors and applications are different, and the lens materials used in optical systems are different. According to the characteristics of different infrared lens materials, processing methods and process equipment are also different.
Design of Infrared Optical Lens
The design of infrared lens needs to be considered comprehensively according to the pixel and size of the detector, the specific application situation, and the cost-performance ratio. Generally speaking, infrared crystals, especially Ge、ZNS raw materials, are more expensive, so in many designs, designers will use aspherical or diffraction surfaces to reduce the number of lenses and take into account the excellent imaging results. Because aspherical and binary surfaces are also expensive to process and detect, try not to use multiple aspherical or diffraction surfaces.
SWIR lens, especially the extended band SWIR short-wave infrared lens, can be used materials need to consider the wide band through the processing, transparent visible light and other factors, so ZNSE、ZNS、CaF2 and so on become a common choice, in addition, there are some rare glass. However, it should be noted that, in general, the glass is not in stock and the frequency of production is not high, so it is necessary to determine whether the materials can be delivered on time and have the possibility of continuous supply before adoption. such as schott or xiaoyuan optics, some materials are produced only once a year, and if you miss this purchasing opportunity, you have to wait another year.
MWIR lens is usually used with medium wave refrigeration detector, the light bar is placed behind the lens, so the lens is relatively large, but also consider the so-called cold bar effect (ghost, reflection, also known as cold screen effect). The size of the refrigeration lens and detector is large, but the detection distance can reach a long distance, such as focal length 150 mm、300mm, can see 10 km to 30 km distance.
LWIR design is commercialized, that is, both cheap and effective. Therefore, aspheric surface is more common. In addition, with the popularity of commercial applications, such as vehicle night vision, gun vision, mobile phones and other applications, sulfur glass began to become the darling of such applications. Because it can be molded at low temperature, the price of sulfur glass lens can be very low (if the quantity is large).
Under extremely cold and very hot conditions, especially when the temperature difference is very large, the curvature of infrared lens, the thickness of lens, the refractive index of lens tube and lens material cause lens defocusing. In order to ensure the clarity of imaging, the lens needs to be refocused by electric or manual focusing. In order to eliminate the adverse effects of temperature change, no thermochemical design is needed. Usually designers use different optical materials for optical compensation (temperature difference), or use mechanical materials and optical materials to design the opposite trend of optical materials, optical machine compensation. Also has a kind of AF automatic focusing design, is through the software technology, unceasingly approximates the focal plane, thus the electric focusing automatic focusing.
Design of Double Fields and Three Fields
A two-field-of-view, three-field-of-view design, which refers to a set of lenses in which fixed focal lengths, such as 25 mm、50mm、75mm., can be obtained at different locations The optical design of this kind of lens only needs to consider the imaging quality at three focal points, without considering the image quality change in the process of change. This is a very real design, such as in the case of a small focal length of 25 mm is easy to find the target, quickly switch to 50 mm or 75 focal length, can zoom in to see the target.
Continuous zoom lens
Continuous zoom lens (continuous zoom) is the most challenging lens, and the higher the magnification ratio, the higher the difficulty. The 20 x doubling lenses on the market come from a company called Ophir, which uses three optical paths to achieve a continuous zoom effect of 15-300 mm. In addition to the high challenge of optics, the difficulty of mechanical structure is also unusually high.
The reflective design usually appears on the lens with long focal length, which is to reduce the volume of the lens (too long) and add the reflective lens to the optical path for reentry to shorten the length. Because it is infrared wide band, the general metal film can achieve the effect of reflection.
Temperature measurement, imaging lens
The design of temperature measuring lens and imaging lens have some different considerations. Because of the need for temperature measurement, the focus of lens design is to reduce the reflection or miscellaneous light, which will properly handle the position of the light bar. Its relative illumination uniformity is one of the most important indexes to evaluate the quality of lens. A good lens design, need to consider the effect of optical machine coordination, indispensable. The market also has a very good optical machine simulation software, specially improve the effect of optical machine cooperation.
It can be said that mechanical design is very important, lightweight design in the vehicle, airborne has strict requirements, let alone in the military use. Recently, commercial use of infrared has become more and more extensive, consumers do not want to carry heavy infrared lenses, they prefer products as light as plastic, so it is very important to pay attention to the design of infrared optical lenses.
Wuhan ZIP Technology provides all kinds of infrared optical lenses with different focal length. Please contact your consultant for discount immediately. Miss Xu :+86 18502742430