This paper presents the design of a continuous zoom optical system operating in the long-wave infrared spectrum (8 - 12μm), compatible with an uncooled detector having a resolution of 640×480 pixels and a pixel size of 12μm. Focal length ranges from 20mm to 100mm, with corresponding aperture values varying from F/0.8 to F/1.1. In order to possess good optical performance and compactness, the optical system applied a number of diffractive and aspheric surfaces. This system consists of 5 elements with a total length of 180mm and is optimized at 8 focal positions. All configurations exhibit good optical quality, with RMS spot sizes smaller than the sensor pixel size and MTF values at Nyquist frequency close to the diffraction limit. Additionally, in order to give the system good imaging performance in the operating temperature range from -20°C to 60°C, an active mechanical compensation method was used.
This study explores the design and refinement of a Mid-Wave Infrared (MWIR) continuous zoom lens system, which is coupled with a high-definition detector. Tailored to operate within a focal length range spanning 36-550 mm and offering a resolution of 1280 x 1024 pixels, MWIR imaging serves as a cornerstone in surveillance, defense, and remote sensing applications. Leveraging advanced optical design methodologies, this research aims to achieve heightened imaging resolution, mitigate aberrations, and counteract narcissus effects throughout the zooming spectrum. Furthermore, through meticulous manufacturing optimization, the production process is streamlined, ensuring cost-effectiveness and efficiency. The resultant MWIR zoom lens system showcases remarkable performance enhancements, promising superior image quality, and positioning itself as a versatile solution for diverse MWIR imaging endeavors.
This paper presents the design of a fast aperture, high resolution, wide-angle, optically passive athermalized long-wave infrared (LWIR) lens suitable for driver vision enhancer systems. The growing demand in high resolution thermal imaging has led to the need for advanced lens designs that can deliver exceptional performance in this electromagnetic spectrum. The proposed lens design focuses on achieving a fast aperture, which is crucial for capturing object details in modern bolometer arrays with smaller pixel pitch. Additionally, the design provides a wide-angle field of view to enable comprehensive scene coverage. The use of optical passive athermalization technique also ensures that the lens maintain its performance across a wide range of operating temperatures, thereby eliminating the need for any active temperature compensation mechanisms. In order to achieve a large image diameter, the lens design incorporates aspheric and diffractive surfaces, as well as a combination between conventional and chalcogenide materials. These elements help to minimize optical aberrations and increase image sharpness. With the use of computer-aided design software and its corresponding optical simulation tools, the design was refined to meet the desired specifications, including resolution, field of view and athermalization requirements. The resulting lens design managed to achieve a horizontal field of view of 76 degrees with a fast aperture of F1.0 for an uncooled 12-micron SXGA detector. This design ensures consistent and nearly diffraction-limited performance in diverse operating conditions, making it suitable for driver vision enhancer systems, as well as the general automotive applications.
In this report, through the use of suitable power distribution, material selection, diffractive surfaces, and retro-reflective pattern monitoring, a compact MWIR continuous zoom lens was successfully designed for surveillance UAS payload applications. This is highly applicable in opto-electronic system design where small size plays a critical role.
This paper introduces a mid-wavelength infrared (MWIR) lens design which has both function of high-speed scanning and optical zooming for Infrared Search and Track (IRST) System. For scanning function, a reflecting mirror is integrated within the optical system to stabilize the light-of-sight of the optical axis in integration time. This scanning mirror is placed in front of an imager group which focus the light onto the image surface. To perform the optical zooming function, an afocal telescope is place conjugated with the scanning mirror so that the optical lens design can change the focal length without affecting the scanning function. The field of view in scanning mode is 19.0° x 23.6° for a single frame while in optical zooming mode, the field of view can be change to 5.9° x 4.8° at minimum which makes the optical zoom power of 4X. All optical configurations of the system are designed to work with a F/#2 SXGA (1280 x 1024) cooled detector having a pixel pitch of 15μm.
Infrared Search and Track (IRST) system has been widely applied to cover a wide field-of-view in surveillance systems to passively search, detect, track, classify several objects at as long ranges as possible. In order to achieve that wide area of coverage the optical system must have a relatively large field of view which ultimately limits the observation range due to the fixed size of detector and optical performance of the system. The IRST system could integrate with a Forward-Looking-Infrared (FLIR) camera with longer focal length which increases the observation distance in required situations; this solution would make the IRST system become unnecessarily complex with two separate optical cameras. This paper introduces a mid-wave infrared (MWIR) lens design which has both abilities of high-speed scanning and optical zooming for Infrared Search and Track (IRST) system. A reflecting mirror is integrated within the optical system to perform the scanning function by stabilizing light-of-sight of the optical axis. The scanning mirror is placed to be conjugated with an afocal telescope which has the function of optical magnification. In scanning mode, the field of view is 20° x 16° for a single frame at a maximum scanning angle of 4.32°. In optical zooming mode, the minimum field of view is 6.7° x 5.3° which makes the optical zoom power of 3X. All configurations of the optical system are designed to work with a F/2 SXGA (1280 x 1024) cooled detector having a pixel pitch of 15µm.
This paper describes an optical design of a compact continuous zoom mid-wave infrared (MWIR) lens for use with today’s infrared detector technologies. The developed design is applicable in industries where system size becomes a critical factor, including unmanned aerial systems (UAS), unmanned aerial vehicles (UAV) and drone payloads. By applying optical design principles such as power distribution via element bending, element splitting and aberration balancing, a continuous zoom MWIR lens was successfully designed. It has a focal length range of 20–275 mm, which translates to a magnification ratio of almost 14x. The IR detector type that is compatible with the developed design is a VGA (640 x 512) high operating temperature (HOT) MWIR focal plane array (FPA) having a pixel pitch of 15 μm and an aperture of F/5.5. While a standard MWIR FPA is usually sensitive to a spectral range of 3.7–4.8 μm, a HOT MWIR FPA is responsive to a spectral range of 3.7–4.2 μm. This is also the limits which the optical design discussed in this paper was optimized for. Overall, the continuous zoom MWIR lens managed to maintain its high level of imaging performance throughout the prescription zoom range, all of which is contained within a compact package under 100 mm in length. With its long target detection range, the developed design is highly suitable for surveillance UAV payloads as well as other relevant aerial systems on the market.
Infrared Search and Track (IRST) System has become the main approach to cover a wide area with high resolution imagery of long-range targets. A fast-steering mirror (FSM) is generally integrated in the optical system to provide back scanned motion for maintaining the line-of-sight stability. However, the conventional optical designs can hold only the center of field relatively stable on the FPA during back-scanning; all other field points may wander during the exposure time due to imaging distortion characteristic of the optical system which reduces the quality of the observed images. This paper reports a lens design with implemented Non-Rotationally symmetric field mapping which can keep all field points stable on the FPA during back-scanning. This lens design covers a large Field of view (FOV) of 10° x 8° for single frame and a maximum scanning angle of 2.16°. With a F/2 SXGA (1280 x 1024) cooled detector, this optical system help scan a large number of objects in a long-range distance at a high scanning rate with diffraction limit performance.
This paper reports a design of a high magnification mid-wave infrared (MWIR) continuous zoom lens system that is compatible with a high-resolution focal plane array (FPA). The zoom lens design has been developed via a series of optimization processes, from a global search to look for potential design candidates, to different local optimization strategies to balance out optical aberrations between different zoom configurations, then comes a few minor adjustments in order to mitigate the negative effects that the optical system might encounter during its operation. By using these processes, an F/5.5 continuous zoom lens system with a magnification ratio of 22x that works with an SXGA (1280 x 1024) cooled detector having a pixel pitch of 15 μm has been successfully designed. This zoom lens system only makes use of two movable lenses to maintain its performance throughout the entire zoom range. With a maximum focal length of 1200 mm, this optical system plays a major role in extremely long-range observation and surveillance applications.
This paper reports a design process for high magnification mid-wave infrared continuous zoom lens. The process consists of algorithms for finding global paraxial solution, optimization strategies for balancing aberrations in all zoom configurations, and cam curve smoothing methods in opto-mechanical design. Using this process, a parfocal continuous zoom lens with F/4, magnification of 20× working with a 640x512 cooled 15μm pixel pitch detector array, has been successfully designed and fabricated. In principal, this design bases on a zoom and a focus group. The zoom group consisting of three separate moving lens subsets allows for a high magnification ratio of 20× and its parfocality during continuous zooming, while the focus group helps changing focal planes and ensures normal operation in a large temperature and observation range. The lens uses different optical surfaces varying from spherical to hybrid diffractiveaspheric form. This results in high optical performance with MTF approaching diffraction limit while keeping the overall system compact and light weight. For the coordination of lens movement in the zoom group, smooth cam curves having satisfactory stiffness and pressure angles were achieved by a smoothing method which maps different system focal length values with appropriate barrel rotation angles. The simulation of optical performance and experimental testing results will be presented. This zoom lens can be used in long range surveillance camera system.
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